The effect of excess tellurium on the thermo electric properties of Bi2Te3-Sb2Te3 solid solutions

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[1527] The function of the bypass valve on the self-contained breathing apparatus is to ______.A. control the pressure of the oxygen as it enters the bodyB. allow the wearer to manually give himself oxygenC. release excess heat which would otherwise cause the bottle to explodeD. allow exhaled gases to pass outside the bottle[1577]The man directing and supervising the work of stevedores is the______．A. local agent B．watchman C．docker D．ForemanKEY: D指导和监督码头工人工作的人是工头。

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当代医学英语3

1. A 2. C 3. D 4. B 5. C
Chapter 3- The Progress of Medical Science
D. Watch a video clip “ Universal Flu Vaccine” twice and
decide whether each of the following statements is true (T) or false (F).
Chapter 3- The Progress of Medical Science
English Course of Contemporary Medicine
当代医学英语综合教程
Chapter 3- The Progress of Medical Science
Chapter 3
The Progress of
Chapter 3- The Progress of Medical Science
We're especially proud of several advances that we've made, primarily because they are advances making in (1)_________ life better for hard-to-reach populations such as the elderly, children, vulnerable populations. Some really good include examples of those (2)_________ the addition of coping skills training for teenagers with diabetes, manage which enables them to better (3)___________ their diabetic condition and yet live normal, healthy lives as teenagers. We have tested a program successfully (4)____________ with inner city African-American males—a hard-to-reach population, which has

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Ａｕꎬ ａｎｄ５０ｔｉｍｅｓｅｘｃｅｓｓ [ ｉｏｎ / Ａｕ( ｗ / ｗ) ] ｉｎｔｅｒｆｅｒｉｎｇｉｏｎｓｄｏｅｓｎｏｔｉｎｔｅｒｆｅｒｅｄｅｔｅｒｍｉｎａｔｉｏｎ. Ｔｈｅｍａｓｓｃｏｎｃｅｎｔｒａｔｉｏｎｏｆｇｏｌｄ
ｗБайду номын сангаасｓｌｉｎｅａｒｗｉｔｈｉｔｓｅｍｉｓｓｉｏｎｉｎｔｅｎｓｉｔｙｉｎｔｈｅｒａｎｇｅｏｆ０.０５ ~ ２５.００ｍｇ / Ｌ. Ｔｈｅｃａｌｉｂｒａｔｉｏｎｅｑｕａｔｉｏｎｗａｓｙ＝４６.４８７ｘ＋０.３４３ꎬ
样品１＃、样品２＃:浙江省嘉兴市某电镀企业退
镀液样品ꎬ 密封保存于纯水清洗并干燥后的塑料
等. 其中离子色谱法基
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其发射强度呈线性ꎬ线性回归方程为ｙ＝４６.４８７ｘ＋０.３４３ꎬ相关系数ｒ大于０.９９９９ꎬ检出限为０.００４４ｍｇ / Ｌ. 对实际样
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Briefly summarize the proposal then state her opinion about the proposal and explain the reasons she gives for holding that opinion.T3Frustration ToleranceWhen young children are not able to accomplish their goals, they may become frustrated and act inappropriately. However, as children mature, they can learn to manage or tolerate frustration. The development of frustration tolerance allows children to continue to work toward completing tasks, even when their initial attempts are unsuccessful. Parents can help their children develop frustration tolerance by deliberately restricting their own responses to their children’s demands for help. By gradually reducing their response time, parents can teach children to manage their frustration while they keep trying to accomplish their goals, despite any difficulties or setbacks that they may encounter.Question：Using the example from the lecture, explain how parents can help their children develop frustration tolerance.T4Question：Using the examples from the lecture, explain two types of animal social groups第二部分听力Section 11. Why does the student peak with the professor?A. To ask for assistance coming up with an idea for her assignmentB. To go over an article the professor had assignedC. To discuss an architectural concept she would like to work withD. To review her work on a project she recently submitted.2. What point do the speakers make when they discuss the materials used in the iceberg design?A. The materials are designed to help cool the buildingB. The materials are more costly than building materials typically used in urban structuresC. The thickness of materials requires that they be cut with special equipmentD. The amount of materials used reduced the impact on the environment3. Why does the professor mention retail space?A. To explain the cause of city developer’s tax problemB. To introduce the focus of the class’s next model projectC. To point out how quickly modern retail structures are builtD. To provide background on why the iceberg design was created4. What does the professor say about air beams?Click on 2 answersA. They provide support to the icebergB. They are made partly from steelC. They permit an iceberg to assume a variety of shapesD. They take a long time to manufactureListen again to part of the conversation. Then answer the question 5. What can be inferred about the student?A. She was not fully aware of the trip’s dateB. She does not intend to go on the tripC. She had already been to the Frank LIoyd Wright houseD. She would prefer to lead the tour, not be a group member.6. What is the lecture mainly about?A. The life of a famous Italian Renaissance artistB. The history of fresco painting in ItalyC. The creation of a particular work of Renaissance artD. The construction of a typical church of the Italian Renaissance7. According to the professor, what is one advantage of using the fresco technique?A. A fresco can last a long timeB. The materials for making a fresco are inexpensiveC. The fresco technique is easy to learnD. A fresco can be completed quickly8. According to the professor, why is a fresco painted before the plaster dries?A. So that mistakes can be corrected easilyB. So that the paint will sink into the plasterC. So that the colors of the paints can be blended betterD. So that human forms will appear more lifelike9. Why does the professor mention the artist who painted with a paintbrush in each hand?A. To describe how the Sistine Chapel’s ceiling was paintedB. To illustrate the ingenious creativity of Renaissance artistsC. To explain how Michelangelo learned to paintD. To emphasize the need for fresco painters to work quickly10. Why did Michelangelo choose to build footbridges rather than traditional scaffolding when he painted the chapel?A. To accommodate the curved shape of the chapel’s ceilingB. To keep the floor clear for ceremonies in the chapelC. To reach both the walls and the ceiling of the chapelD. To paint while lying on his back for long periods of time11. What does the professor imply when he says thisA. He has suggestions about how students can deal with difficult situationsB. Many people would have been uncomfortable paint ing the chapel’s ceilingC. There was one problem that Michelangelo was unable to overcomeD. Michelangelo’s reputation as a great artist may be somewhat exaggerated Section 21. Why does the woman go to see the man?A. To provide feedback on her previous housing experienceB. To find out how she can participate in a different housing programC. To reapply for housing at the Eco House next semesterD. To get information about a student assistant position2. What is t he woman’s attitude about the Eco House?A. She had hoped it would be more committed to sustainable practicesB. She believes that its program is exactly what she will needC. She thinks its program is too narrow for her academic goalsD. She regrets that residents are only permitted to live there for one year3. What are two advantages that living at the Mary Blake HouseClick on 2 answersA. It would allow her to actively engage with guest scholarsB. It would allow her to create a house theme with other studentsC. She would join a classmate who currently lives at the Mary Blake HouseD. She would have an opportunity to qualify for staff discounts4. Why does the woman mention a journalist?A. To provide background on one of the faculty living at the Mary Blake HouseB. To provide an example of a recent dinner guest at the Mary Blake HouseC. 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To explain how sunlight affects temperatures on Uranus8. According to the professor, how did astronomers deduce the composition of the planet Uranus?Click on 2 answersA. By calculating Uranus’ densityB. By measuring Uranus’ force of gravityC. By examining the strength of Uranus’ magnetic fieldD. By comparing Uranus with Jupiter9. What features of Uranus do some astronomers think were caused by the planet’s collision with another object? Click on 2 answersA. The composition of its coreB. The angle of its axis of rotationC. Its rapid rotationD. Its low internal temperature10. Why does the professor mention Uranus’ magnetic field?A. To point out a surprising similarity between Uranus and EarthB. To emphasize the limitations of remote observations in astronomyC. To point out a recent discovery about Uranus that contradicts earlier findingsD. To explain one effect of Uranus’ distance from the SunListen again to part of the lecture. Then answer the question11. 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It could not use flying to hunt because it would have been such a clumsy and inefficient flier that it could not possibly have captured enough food. The bird, therefore, probably lost the ability to fly during its evolution.独立Do you agree or disagree with the following statement: There is never a good reason to be impolite (rude) to other people.第四部分阅读Artisans in Sixteenth-Century EuropeFor centuries European artisans had operated in small, autonomous handcraft businesses, but by the sixteenth century an evolving economic system—moving toward modern capitalism, with its free-market pricing, new organization of production, investments, and so on—had started to erode their stable and relatively prosperous position. What forces contributed to the decline of the artisan?In a few industries, there appeared technological innovations that costmore to install and operate than artisans—even associations of artisans—could afford. 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In late sixteenth-century Antwerp, where a skilled worker earned 125 to 250 guilders a year, a large blast furnace alone cost 3,000 guilders, and other industrial equipment was equally or more expensive.Raw materials, not equipment, constituted artisans’ major expense in most traders, however. ■Whereas in 1583 an Antwerp silk weaver paid 12 guilders for a loom (and made small payments over many years to pay off the debt for purchasing the loom), every six weeks he or she had to lay out 24 guilders for the 2 pounds of raw silk required to make a piece of cloth. ■Thus access to cheap and plentiful primary materials was a constant preoccupation for independent producers. ■Using local materials might allow even the poorest among them to avoid reliance on merchant suppliers. ■The loss of nearby sources could therefore be devastating. As silk cultivation waned around the Spanish cities of Cordoba and Toledo, weavers in these cities were forced to becomeemployees of merchants who put out raw silk from Valencia and Murcia provinces. In the Dutch Republic, merchants who imported unprocessed salt from France, Portugal, and Spain gained control of the salt-refining industry once exploitation of local salt marshes was halted for fear that dikes (which held back the sea from the low-lying Dutch land) would be undermined.Credit was necessary for production but created additional vulnerabilities for artisans. Prices for industrial products lagged behind those of raw materials and foodstuffs, and this, coupled with rising taxes, made it difficult for many producers to repay their creditors. 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Incorrect choices change the meaning in important ways or leave out essential information.□In the sixteenth century, the European economy moved toward a system of free-market pricing, new ways of production, and investments.□ Before the sixteenth century, European makers of handcrafts enjoyed stability, autonomy, and relative prosperity.□ By the sixteenth century, the rise of capitalism began to weaken the autonomy and relative prosperity of European artisans.□European artisans operated small, autonomous businesses before modern capitalism emerged in the sixteenth century.2. According to paragraph 2, how did technological advances contribute to the economic decline of artisans?□ Artisans had no place to store or use the new machines.□Goods produced by the new technology were cheaper than those produced by artisans.□ The fixed costs of remaining in business became very high.□ Artisans did not know how to use the new machines.3. The word “preoccupation” in the passage is closest in meaning to□ necessity□ concern□ struggle□ uncertainty4. In paragraph 3, why does the author provide the information about an Antwerp silk weaver’s costs in 1583?□ To describe some typical costs in the silk-weaving industry□To support the statement that artisans’ main expense was materials, not equipment□ To argue against the view that artisans did not have to borrow money to buy equipment□ To show that materials were cheap and plentiful for most artisans5. According to paragraph 3, which of the following was sometimes an effect on artisans of the loss of local sources of their primary materials?□ They had to sell their products to merchants.□ They needed to take loans in order to buy the materials from merchants.□They could no longer afford to be independent producers. □ They imported the materials from distant sources.6. According to paragraph 4, all of the following caused economic difficulties for artisans EXCEPT□ decreasing availability of credit□ decreased demand for manufactured goods□ increased taxes□ problems caused by wars7. Paragraph 5 supports which of the following statements about artisans during the sixteenth century?□ They had difficulty transporting their goods to the best markets.□ They were at a disadvantage because the concentration of supplies and exports was in the hands of big-city merchants.□ They received higher wages as employees of big-city merchants.□ They were able to obtain raw materials from local merchants.8. All of the following are identified in paragraph 6 as concerns that urban artisans had about the growth of industry in the countryside EXCEPT□ a decrease in the supply of raw materials□ a cheaper cost of living in the countryside□ a more manageable level of competition□ less complex production processes in the countryside9. Look at the four squares [■] that indicate where the following sentence can be added to the passage.This was possible because when transportation costs were low, the price of rawmaterials was generally also low.Where would the sentence best fit? Cl ick on a square [■] to add the sentence to the passage.10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Drag your choices to the spaces where they belong. To review the passage, click on View Text.Answer choice1. Artisans’ ability to earn profits was restricted by their dependence on creditors, to whom they were forced to sell their goods, and by competition from rural areas.2. As industries came under the control of merchants, artisans lostaccess to cheap raw materials, and they had to borrow money to buy the materials they needed from merchant suppliers.3. In the new industrial system from which skilled artisans were progressively excluded, the quality of manufactured items gradually declined.4. Advances in technology in some industries increased the cost of the equipment, buildings, and facilities that artisans needed for producing and selling their goods.5. Iron production in the sixteenth century depended on new inventions such as blast furnaces, tilt hammers, wire-drawing machines, and stamping, rolling, and silting mills.6. The rising prices of food and other necessities often left artisans without enough money to pay their taxes and other business expenses.Earth’s AtmosphereEarth’s atmosphere has changed through time. Compared to the Sun, whose composition is representative of the raw materials from which Earth and other planets in our solar system formed, Earth contains less of some volatile elements, such as nitrogen, argon, hydrogen, and helium. These elements were lost when the envelope of gases, or primary atmosphere, that surrounded early Earth, was stripped away by the solar wind or by meteorite impacts, or both. Little by little, the planet generated a new, secondary atmosphere by volcanicoutgassing of volatile materials from its interior.Volcanic outgassing continues to be the main process by which volatile materials are released from Earth—although it is now going on at a much slower rate. The main chemical constituent of volcanic gases (as much as 97 percent of volume) is water vapor, with varying amounts of nitrogen, carbon dioxide, and other gases. In fact, the total volume of volcanic gases released over the past 4 billion years or so is believed to account for the present composition of the atmosphere with one important exception: oxygen. Earth had virtually no oxygen in its atmosphere more than 4 billion years ago, but the atmosphere is now approximately 21 percent oxygen.Traces of oxygen were probably generated in the early atmosphere by the breakdown of water molecules into oxygen and hydrogen by ultraviolet light (a process called photo dissociation). Although this is an important process, it cannot begin to account for the present high levels of oxygen in the atmosphere. Almost all of the free oxygen now in the atmosphere originated through photosynthesis, the process whereby plants use light energy to induce carbon dioxide to react with water, producing carbohydrates and oxygen.Oxygen is a very reactive chemical, so at first most of the free oxygen produced by photosynthesis was combined with iron in ocean water to form iron oxide-bearing minerals. The evidence of the gradual transition from oxygen-poor to oxygen-rich water is preserved in seafloor sediments. The minerals inseafloor sedimentary rocks that are more than about 2.5 billion years old contain reduced (oxygen-poor) iron compounds. In rocks that are less than 1.8 billion years old, oxidized (oxygen-rich) compounds predominate. The sediments that were precipitated during the transition contain alternating bands of red (oxidized iron) and black (reduced iron) minerals. These rocks are called banded-iron formations. Because ocean water is in constant contact with the atmosphere, and the two systems function together in a state of dynamic equilibrium, the transition from an oxygen-poor to an oxygen-rich atmosphere also must have occurred during this period.Along with the buildup of molecular oxygen (O2) came an eventual increase in ozone (O3) levels in the atmosphere. ■Because ozone filters out harmful ultraviolet radiation, this made it possible for life to flourish in shallow water and finally on land. ■This critical state in the evolution of the atmosphere was replaced between 1100 and 542 million years ago. ■Interestingly, the fossil record shows an explosion of life forms 542 million years ago.■Oxygen has continued to play a key role in the evolution and form of life. Over the last200 million years, the concentration of oxygen has risen from 10 percent to as much as 25 percent of the atmosphere, before setting (probably not permanently) at its current value of 21 percent. This increase has benefitedmammals, which are voracious oxygen consumers. Not only do we require oxygen to fuel our high-energy, warm-blooded metabolism, our unique reproductive system demands even more. An expectant mother’s used (venous) blood must still have enough oxygen in it to diffuse through the placenta into her unborn child’s bloodstream. It would be very difficult for any mammal species to survive in an atmosphere of only 10 percent oxygen.Geologists cannot yet be certain why the atmospheric oxygen levels increased, but they have a hypothesis. First, photosynthesis is only one part of the oxygen cycle. The cycle is completed by decomposition, in which organic carbon combines with oxygen and forms carbon dioxide. But if organic matter is buried as sediment before it fully decomposes, its carbon is no longer available to react with the free oxygen. Thus there will be a net accumulation of carbon in sediments and of oxygen in the atmosphere.1. In paragraph 1, why does the author state that Earth has less nitrogen, argon, hydrogen, and helium than the Sun?▢ To argue that these elements were once part of an early atmosphere, which disappeared▢To suggest that these elements were drawn into the Sun’s atmosphere▢To provide evidence that Earth’s original atmosphere came primarily from meteorites▢To support the claim that Earth’s atmosphere would have changed even moreif it had contained more volatile elements2. According to paragraph 2, the history of volcanic outgassing cannot explain which of the following?▢ The lack of oxygen in the atmosphere 4 billion years ago▢ The amount of water vapor in the atmosphere today▢ The proportions of nitrogen and carbon dioxide in the atmosphere today ▢ The present abundance of oxygen in the atmosphere3. Paragraph 3 suggests which of the following about the process of Photo dissociation?▢ It is more common today than it was in the early history of the atmosphere.▢ It is responsible for only a small amount of the oxygen in the atmosphere today.▢It removes trace amounts of oxygen from the atmosphere. ▢It produces more free oxygen than photosynthesis does.4. The word “gradual” in the passage is closest in meaning to▢ critical▢ original▢ beneficial▢ slow5. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning。

大学英语阅读精选25篇

Passage 1No one prior to World War II more trenchantly analyzed the philosophical differences between utopians and realists than did E.H.Carr in his celebrated work, which, although published in 1939, did not have its impact in America until after World War II. Carr used the term utopians for idealists who placed emphasis on international law and organization and on the influence of morality and public opinion in the affairs of nations. He probably did not intend the more pejorative connotation that attached to the term utopians after World War II as naïve opponents of power politics expounded by realists. Indeed, since the end of the Cold War, the idealist concept of the harmony of national interests in peace has received new attention in a more recent neoliberal-neorealist debate.The failures of the League of Nations in the 1930s cast doubt on the harmony of interest in peace, which appeared to accord with the interests of satisfied, status-quo powers with democratic governments, but not with the perceived needs of revisionists, totalitarians, authoritarian states seeking boundary changes, enhanced status, greater power, and, especially in the case of Nazi Germany, revenge for the humiliation of the post-World War I settlement imposed by the Versailles treaty. Contrary to the utopian assumption, national self-determination did not always produce representative governments. Instead, the overthrow of the old monarchical order gave rise in many places, including Russia, to a more pervasive and oppressive totalitarian states. The Molotov-Ribbentrop Pact of August 1939 between the Soviet Union and Nazi Germany set the stage for Adolph Hitler’s invasion of Poland, the outbreak of World War II, the partition of Poland, and the absorption of Baltic states into the Soviet Union, all in flagrant contravention of the standards of international conduct set forth in utopian theory.1.Who took a strong analysis of the philosophical differences between utopians and realists?A.Adolph Hitler didB. E.H.Carr didC.Neorealist didD.Molotov did2.What did utopian mean in Carr’s opinion?A.Idealists who placed emphasis on international law and organization and on the influenceof morality and public opinion in the affairs of nations.B.Naïve opponents of power politics.C.Status-quo powersD.Revisionists.3.What is the consequence of national self-determination?A.Producing representative governments.B.Giving rise to a more pervasive and oppressive totalitarian states.C.Both A and BD.Sometimes A, sometimes B.4.What was the influence of the Molotov-Ribbentrop Pact of August 1939?A.to set the stage for Adolph Hitler’s invasion of PolandB.leading to the outbreak of World War IIC. a cause of the partition of PolandD.all of A,B and C5.Which one can serve as the title of this passage?A.Post-World War II RealismB.Post-World War II UtopiansC. E.H.Carr and the Crisis of World PoliticsD.The Influence of Versailles Treatypassage 2Beyond marking the seasons, the chief interests that actuated the Babylonian astronomer in his observations were astrological. After quoting Diodorus to the effect that the Babylonian priests observed the position of certain stars in order to cast horoscopes, Thompson tells us that from a very early day the very name Chaldean became synonymous with magician. He adds that "from Mesopotamia, by way of Greece and Rome, a certain amount of Babylonian astrology made its way among the nations of the west, and it is quite probable that many superstitions which we commonly record as the peculiar product of western civilization took their origin from those of the early dwellers on the alluvial lands of Mesopotamia. One Assurbanipal, king of Assyria B.C. 668-626, added to the royal library at Nineveh his contribution of tablets, which included many series of documents which related exclusively to the astrology of the ancient Babylonians, who in turn had borrowed it with modifications from the Sumerian invaders of the country. Among these must be mentioned the series which was commonly called 'the Day of Bel,' and which was decreed by the learned to have been written in the time of the great Sargon I., king of Agade, 3800 B.C. With such ancient works as these to guide them, the profession of deducing omens from daily events reached such a pitch of importance in the last Assyrian Empire that a system of making periodical reports came into being. By these the king was informed of all the occurrences in the heavens and on earth, and the results of astrological studies in respect to after events. The heads of the astrological profession were men of high rank and position, and their office was hereditary. The variety of information contained in these reports is best gathered from the fact that they were sent from cities as far removed from each other as Assur in the north and Erech in the south, and it can only be assumed that they were despatched by runners, or men mounted on swift horses. As reports also came from Dilbat, Kutba, Nippur, and Bursippa, all cities of ancient foundation, the king was probably well acquainted with the general course of events in his empire."1.What actuated the Babylonian astronomer?A.Marking the seasonsB.AstrologyC.Both A and BD.Neither of A and B2.Where, according to Thompson , did many superstitions of western civilization originatefrom?A.NinevehB.BabyloniaC.AssurD.Erech3.How was the social status of an astrologer at that time?A.Of high social statusB.Of middle social statusC.Of low social statusD.It wasn’t mentioned in the passage.4.How was the king acquainted with the general course of events in his empire?A.By periodical reports of astrology from the cities of the empire.B.By scientific reports from specialists.C.By rumorsD.By making a tour in disguise5.What does the author mainly talk about in this passage?A.astronomyB.physicsC.meteorologyD.astrologypassage 3Mr Malthus very correctly defines, "the rent of land to be that portion of the value of the whole produce which remains to the owner, after all the outgoings belonging to its cultivation, of whatever kind, have been paid, including the profits of the capital employed, estimated according to the usual and ordinary rate of the profits of agricultural stock at the time being."Whenever, then, the usual and ordinary rate of the profits of agricultural stock, and all the outgoings belonging to the cultivation of land, are together equal to the value of the whole produce, there can be no rent.And when the whole produce is only equal in value to the outgoings necessary to cultivation, there can neither be rent nor profit.In the first settling of a country rich in fertile land, and which may be had by any one who chooses to take it, the whole produce, after deducting the outgoings belonging to cultivation, will be the profits of capital, and will belong to the owner of such capital, without any deduction whatever for rent.Thus, if the capital employed by an individual on such land were of the value of two hundred quarters of wheat, of which half consisted of fixed capital, such as buildings, implements, &c. and the other half of circulating capital, -- if, after replacing the fixed and circulating capital, the value of the remaining produce were one hundred quarters of wheat, or of equal value with one hundred quarters of wheat, the neat profit to the owner of capital would be fifty per cent or one hundred profit on two hundred capital.For a period of some duration, the profits of agricultural stock might continue at the same rate, because land equally fertile, and equally well situated, might be abundant, and therefore, might be cultivated on the same advantageous terms, in proportion as the capital of the first, and subsequent settlers augmented.1.In Mr Malthus’ opinion, the rent of land and profits of the capital employed in cultivation__________________?A.have not been paid.B.have been paid.C.have been partially paidD.ought to be paid.2.What, according to Mr Malthus, is the correlation between the four parties: rent of land,outgoings necessary to cultivation, profit of capital and value of the whole produceA.outgoings necessary to cultivation = rent of land + profit of capital +value of thewhole produceB.profit of capital = value of the whole produce – rent of land – outgoings necessary tocultivationC.value of the whole produce = land of the rent + outgoings necessary to cultivation –profit of capitalD.profit of capital = value of the whole produce + rent of land – outgoings necessary tocultivation3.When does a cultivator have no profit under the following circumstances?A.The usual and ordinary rate of the profits of agricultural stock is together equal to thevalue of the whole produce.B.The whole produce is only equal in value to the outgoings necessary to cultivation.C. A cultivator takes first settling of a country rich in fertile landD.The land is not free.4.In the fifth paragraph, if, after replacing the fixed and circulating capital, the value of theremaining produce were fifty quarters of wheat, the neat profit to the owner of capital would be___?A.50%B.100%C.75%D.25%5.The author believes the profits of agricultural stock are ____?A.unsustainableB.sustainableC.sometimes sustainableD.depending on the weatherpassage 4While the laborer is confined to the culture of the soil on his own -account, because it is in that manner alone that he can obtain access to the wages on which he is to subsist, the form and amount of the Rents he pays are determined by a direct contract between himself and the proprietor. The provisions of these contracts are influenced sometimes by the laws, and almost always by the long established usages, of the countries in which they are made. The main object in all is, to secure a revenue to the proprietors with the least practicable amount of trouble or risk on their part.Though governed in common by some important principles, the variety in the minuter details of this class of Rents is of course almost infinite. But men will be driven in similar situations to very similar expedients, and the general mass of peasant rents may be separated into four great divisions, comprising 1st, Labor Rents, 2dly, Metayer Rents, 3dly, Ryot Rents (borrowing the last term from the country in which we are most familiar with them, India).These three will be found occupying in contiguous masses the breadth of the old world, from the Canary Islands to the shores of China and the Pacific, and deciding, each in its own sphere, not merely the economical relations of the landlords and tenants, but the political and social conditionof the mass of the people.To these must be added a fourth division, that of Cottier Rents, or Rents paid by a laborer extracting his own wages from the land, but paying his rent in money, as in Ireland and part of Scotland. This class is small, but peculiarly interesting to Englishmen, from the fact of its prevalence in the sister island, and from the influence it has exercised, and seems likely for some time yet to exercise, over the progress and circumstances of the Irish people.1.Why is the laborer confined to the culture of the soil?A.Only by that can he/she obtain access to wages for survival.B.Only by that can he/she obtain control over the proprietor.C.Only by that can he/she obtain profits of agricultural stock.D.Only by that can he/she get freedom.2. Which factors will influence the form and amount of the Rents a laborer pays?ws, long established usages and personal viewsws and long established usagesC.long established usages, personal views and advices from othersD.None of the above is correct.3. Why, according to the author, may the general mass of peasant rents be separated into four great divisions?A.Men will be driven in similar situations to very similar expedients.B.Men will be driven in similar situations to very different expedients.C.The general mass of peasant rents is not of one mind.D.The author likes to do so.4.Which of the four divisions is the smallest?A.Class of Labor RentsB.Class of Metayer RentsC.Class of Ryot RentsD.Class of Cottier Rents5.How do laborers pay their rents in class of Cottier Rents?A.in cerealsB.in moneyC.in laborD.All of the above mentioned.Passage 5Tea drinking was common in China for nearly one thousand years before anyone in Europe had ever heard about tea. People in Britain were much slower in finding out what tea was like, mainly because tea was very expensive. It could not be bought in shops and even those people who could afford to have it sent from Holland did so only because it was a fashionable curiosity. Some of them were not sure how to use it. They thought it was a vegetable and tried cooking the leaves. Then they served them mixed with butter and salt. They soon discovered their mistake but many people used to spread the used tea leaves on bread and give them to their children as sandwiches.Tea remained scarce and very expensive in England until the ships of the East India Company began to bring it direct from China early in the seventeenth century. During thenext few years so much tea came into the country that the price fell and many people could afford to buy it.At the same time people on the Continent were becoming more and more fond of tea. Until then tea had been drunk without milk in it, but one day a famous French lady named Madame de Sevigne decided to see what tea tasted like when milk was added. She found it so pleasant that she would never again drink it without milk. Because she was such a great lady her friends thought they must copy everything she did, so they also drank their tea with milk in it. Slowly this habit spread until it reached England and today only very few Britons drink tea without milk.At first, tea was usually drunk after dinner in the evening No one ever thought of drinking tea in the afternoon until a duchess found that a cup of tea and a piece of cake at three or four o’clock stopped her getting“a sinking feeling〞as she called it. She invited her friends to have this new meal with her, so tea-time was born.1. Which of the following introductions of tea into Britain is true?A) The Britons got expensive tea from India.B) Tea reached Britain from Holland.C) The Britons were the first people in Europe who drank tea.D) It was not until the 17th century that the Britons had tea.2. This passage mainly discusses.A)the history of tea drinking in BritainB) how tea became a popular drink in BritainC)how the Britons got the habit of drinking teaD)how tea-time was born3. Tea became a popular drink in Britain.A) in eighteenth centuryB) in sixteenth centuryC) in seventeenth centuryD) in the late seventeenth century4. People in Europe began to drink tea with milk becauseA)it tasted like milkB) it tasted more pleasantC)it became a popular drinkD)Madame de Sevinge was such a lady with great social influence that people tried to copy the way she drank tea5. We may infer from the passage that the habit of drinking tea in Britain was mostly due to the influence of.A)a famous French lady named Madame de SevigneB)the ancient ChineseC)the upper social classD)people in HollandPassage 6In a family where the roles of men and women are not sharply separated and where many household tasks are shared to a greater or lesser extent, notions of male superiority arehard to maintain. The pattern of sharing in tasks and in decisions makes for equality, and this in turn leads to further sharing. In such a home, the growing boy and girl learn to accept that equality more easily than did their parents and to prepare more fully for participation in a world characterized by cooperation rather than by the “battle of the sexes〞.If the process goes too far and man’s role is regarded as less important - and that has happened in some cases–we are as badly of as before, only in reverse.It is time to reassess the role of the man in the American family. We are getting a little tired of “momism〞, - but we don’t want to exchange it for a“neo-popism 〞. What we need, rather, is the recognition that bringing up children involves a partnership of equals.There are signs that psychiatrists, psychologists, social workers, and specialists on the family are becoming more aware of the part men play and that they have decided that women should not receive all the credit–not all the blame. We have almost given up saying that a woman’s place is the home. We are beginning, however, to analyze men’s place in the home and to insist that he does have a place in it. Nor is that place irrelevant to the healthy development of the child.The family is a cooperative enterprise for which it is difficult to lay down rules, because each family needs to work out its own ways for solving its own problems.Excessive authoritarianism has unhappy consequences, whether it wears skirts or trousers, and the ideal of equal rights and equal responsibilities is connected not only with a healthy democracy, but also with a healthy family.1. From the passage we know that the author is very concerned with the role that.A)parents play in bringing up their childrenB)men play in a familyC)women play in a familyD)equality plays in a family2. The author means to tell us that.A)a man’s place is in the homeB)a woman’s place is in the homeC)a woman should be equal to a manD)a man should have an equal share in family matters3. According to the author, a healthy family should be based on.A) cooperationC) momismB)authoritarianismD) neo-popism4. Who will benefit most from a family pattern of sharing in tasks and decisions?A)The children.C) The man.B)The woman D) The psychologist.5. We may safely conclude from the passage that.A)male superiority maintains a healthy familyB)equal rights and equal responsibilities are very essential to a healthy familyC)authoritarianism does no good to a healthy familyD)women should be equal to men.Passage 7As the pace of life continues to increase, we are fast losing the art of relaxation. Once you are in the habit of rushing through lift, being on the go from morning till night, it is hard to slow down. But relaxation is essential for a healthy mind and body.Stress is a natural part of everyday lift and there is no way to avoid it. In fact, it is not the bad thing it is often supposed to be .A certain amount of stress is vital to provide motivation and give purpose to life. It is only when the stress gets out of control that it can lead to poor performance and ill health.The amount of stress a person can withstand depends very much on the individual. Some people are not afraid of stress, and such characters are obviously prime material for managerial responsibilities. Others lose heart at the first signs of unusual difficulties. When exposed to stress, in whatever form, we react both chemically and physically. In fact we make choice between "fight" or "flight" and in more primitive days the choice made the difference between life or death. The crises we meet today are unlikely to be so extreme, but however little the stress is, it involves the same response. It is when such a reaction lasts long, through continued exposure to stress, that health becomes endangered. Such serious conditions as high blood pressure and heart disease have established links with stress. Since we cannot remove stress from our lives (it would be unwise to do so even if we could), we need to find ways to deal with it.1.People are finding less and less time for relaxing themselves because_____.a. they do not know how to enjoy themselvesb. they do not believe that relaxation is important for healthc. they are traveling fast all the timed. they are becoming busier with their work2.According to the writer ,the most important character for a good manager is his ________.a. not fearing stressb. knowing the art of relaxationc. high sense of responsibilityd. having control over performance3.Which of the following statements is true?a. We can find some ways to avoid stressb. Stress is always harmful to peoplec. It is easy to change the habit of keeping oneself busy with work.d. Different people can withstand different amounts of stress4.In Paragraph 3, "such a reaction" refers back to_______.a. "making a choice between 'flight' or 'fight'"b. "reaction to stress both chemically and physically"c. "responding to crises quickly"d. "losing heart at the signs of difficulties"5.In the last sentence of the passage, "do so " refers to ______.a. "expose ourselves to stress"b. "find ways to deal with stress"c. "remove stress from our lives"d. "established links between diseases and stress"Passage 8Manners nowadays in metropolitan cities like London are practically nonexistent. It is nothing for a big, strong schoolboy to elbow an elderly woman aside in the dash for the last remaining seat on the tube or bus, much less stand up and offer his seat to her.This question of giving up seats in public transport is much argued about by young men, who say that, since women have claimed equality, they no longer deserve to be treated with courtesy and that those who go out to work should take their turn in the rat race like anyone else. Women have never claimed to be physically as strong as men. Even if it is not agreed, however, that young men should stand up for younger women, the fact remains that courtesy should be shown to the old, the sick and the burdened. Are we really so lost to all ideals of unselfishness that we can sit there indifferently reading the paper or a book, saying to ourselves `First come, first served', while a grey-haired woman, a mother with a young child stands? Yet this is all too often seen.Older people, tired and irritable from a day's work, are not angels, either far from it. Many a brisk argument or an insulting quarrel breaks out as the weary queues push and shove each other to get on buses and tubes. One cannot commend this, of course, but one does feel there is just a little more excuse.If cities are to remain pleasant places to live in at all, however, it seems imperative, not only that communications in transport should be improved, but also that communication between human beings should be kept smooth and polite. All over cities, it seems that people are too tired and too rushed to be polite. Shop assistants won't bother to assist, taxi drivers growl at each other as they dash dangerously round corners, bus conductors pull the bell before their desperate passengers have had time to get on or off the bus, and so on and so on. It seems to us that it is up to the young and strong to do their small part to stop such deterioration.1.From what you have read, who are expected to improve their manners?A) who are physically weak or crippledB) who once lived in a prison-camp during the WarC) who live in big modern citiesD) who live only in small towns2.What is the writer's opinion concerning courteous manners towards women?A) Now that women have claimed equality, they no longer need to be treated differently from men.B) It is generally considered old-fashioned for young men to give up their seats to young women.C) "Lady First" should be universally practiced.D) Special consideration ought to be shown to them.3.On tubes or buses, according to the author, older people___ .A) often offer their seats to othersB) are treated better than younger people areC) are no more considerate to each otherD) from the Continent are more irritablemunication between human beings would be smoother if __.A) people were more considerate to each otherB) people were not so tired and irritableC) women were treated with more courtesyD) public transport could be improved.5.What is the possible meaning of the word "deterioration" in the last paragraph?A) Worsening of general situation.B) Lowering of moral standards.C) Declining of physical constitution.D) Spreading of evil conduct.Passage 9A study of art history might be a good way to learn more about a culture than is possible to learn in general history classes. Most typical history courses concentrate on polities, economies, and war, but art history focuses on much more than this because art reflects not only the political values of a people, but also religious beliefs, emotions, and psychology. In addition, information about the daily activities of our ancestors-or of people very different from our own-can be provided by art. In short, art expresses the essential qualities of a time and a place, and a study of it clearly offers us a deeper understanding than can be found in most history books.In history books, objective information about the political life of a country is presented; that is, facts about politics are given, but opinions are not expressed. Art, on the other hand, is subjective: it reflects emotions and opinions. The great Spanish painter Francisco Goya was perhaps the first truly "political" artist. In his well-known painting The Third of May 1080, he criticized the Spanish government for its misuse of power over people. Over a hundred years later, symbolic images were used in Pablo Picasso's Guernica to express the horror of war. Meanwhile, on another continent, the powerful paintings of Diego Rivera, Jose Clemente Orozco, and David Alfaro Siqueiros-as well as the works of Alfredo Ramos Martinze-depicted these Mexican artists' deep anger and sadness about social problems.In the same way, art can reflect a culture's religious beliefs. For hundreds of years in Europe, religious art was almost the only type of art that existed. Churches and other religious buildings were filled with paintings that depicted people and stories from the Bible. Although most people couldn't read, they could still understand biblical stories in the pictures on church walls. By contrast, one of the main characteristics of art in the Middle East was (and still is) its absence of human and animal images. This reflects the Islamic (伊斯兰教的) belief that statues are unholy. 1.More can be learned about a culture from a study of art history than from general history classes because art history_______ .A) shows us the religious and emotions of a people in addition to political valuesB) provides us with information about the daily activities of people in the pastC) gives us an insight into the essential qualities of a time and a placeD) all of the above2.Art is subjective in that__________ .A) a personal and emotional view of history is presented through itB) it can easily arouse our anger or sadness about social problemsC) it will find a ready echo in our heartsD) both B and C3.Which of the following statements is true according to the passage?A) Unlike Francisco Goya, Pablo Picasso and several Mexican artists expressed their political opinions in their paintings.B) History books often reveal the compilers' political views.C) Religious art remained in Europe for centuries the only type of art because most people regarded the Bible as the Holy Book.D) In the Middle East even today you can hardly find any human and animal images on church walls or religious buildings.4.The passage is mainly discussing __________.A) the difference between general history and art historyB) the making of art historyC) what we can learn from artD) the influence of artists on art history5.It may be concluded from this passage that_______ .A) Islamic artists had to create architectural decoration with images of flowers or geometric formsB) history teachers are more objective than artistsC) it is more difficult to study art history than general historyD) people and stories from the Bible were painted on churches and other buildings in order to popularize the BiblePassage 10If women are mercilessly exploited year-round, they have only themselves to blame. Because they tremble at the thought of being seen in public in clothes that are out of fashion, they are always taken advantage of by the designers and the big stores. Clothes which have been worn only a few times have to be put aside because of the change of fashion. When you come to think of it, only a woman is capable of standing in front of a wardrobe packed full of clothes and announcing sadly that she has nothing to wear.Changing fashions are nothing more than the intentional creation of waste. Many women spend vast sums of money each year to replace clothes that have hardly been worn. Women who cannot afford to throw away clothing in this way, waste hours of their time altering the dresses they have. Skirts are lengthened or shortened; necklines are lowered or raised, and so on.No one can claim that the fashion industry contributes anything really important to society. Fashion designers are rarely concerned with vital things like warmth, comfort and durability. They are only interested in outward appearance and they take advantage of the fact that women will put up with any amount of discomfort, as long as they look right. There can hardly be a man who hasn’t at some time in his life smile at the sight of a woman shaking in a thin dress on a winter day, or delicately picking her way through deep snow in high-heeled shoes.When comparing men and women in the matter of fashion, the conclusions to be drawn are obvious. Do the constantly changing fashions of women’s clothes, one wonders, reflect basic qualities of inconstancy and instability? Men are too clever to let themselves be cheated by。

英文文献(金属salen配合物)14

Journal of Molecular Catalysis A:Chemical203(2003)9–19Oxidation of veratryl alcohol by molecular oxygen in aqueous solution catalyzed by cobalt salen-type complexes:the effect of reaction conditionsKaisa Kervinen,Heikki Korpi,Markku Leskelä,Timo Repo∗Laboratory of Inorganic Chemistry,Department of Chemistry,University of Helsinki,P.O.Box55,FIN-00014Helsinki,Finland Received18October2002;received in revised form19February2003;accepted22February2003AbstractA series of Schiff-base salen-type cobalt complexes Co(salen)(1)[salen=N,N -bis(salicylidene)ethylenediamine], Co(␣-CH3salen)(2)[␣-CH3salen=N,N -bis(␣-methylsalicylidene)ethylenediamine],Co(4-OHsalen)(3)[4-OHsalen= N,N -bis(4-hydroxosalicylidene)ethylenediamine],Co(sulfosalen)(4)[sulfosalen=N,N -bis(5-sulfonatosalicylidene)ethyl-enediamine],Co(acacen)(5)[acacen=N,N -bis(acetylacetone)ethylenediamine)]and Co(N-Me-salpr)(6)[N-Me-salpr= bis(salicylideniminato-3-propyl)methylamine]were studied as catalysts for dioxygen activation in the oxidation of3,4-dime-thoxy benzylalcohol(veratryl alcohol)in basic aqueous conditions.The oxidation occurs selectively at benzylic position as in all experiments veratraldehyde was the only observed product.The highest catalytic activity was reached with the unsub-stituted complex(1),which was used for further studies on the effect of temperature,pressure,time and pH.The effect of pH was noted to be critical and the reaction proceeds up to72h if the pH is kept at about12.5.The need for higher temperatures (over60◦C)was also conﬁrmed.Reactivity of the catalyst increase linearly with increased O2pressure,the best turnover numbers(TON=moles of veratryl aldehyde produced per mole of complex)reached in similar conditions were58for ambient pressure and103for oxygen pressure of10bar.The catalytic activity can be further enhanced if the catalyst:substrate ratio is increased.Turnover numbers as high as330were detected with catalyst:substrate ratio1:5950at ambient pressure.©2003Elsevier Science B.V.All rights reserved.Keywords:Catalytic oxidation;Oxygen;Aqueous solution;Cobalt complexes1.IntroductionResearch under the theme“green chemistry”is challenged by the development of environmentally and economically sustainable processes for industrial applications.Selective oxidation of organic com-pounds with simple oxidants,such as cheap,abundant, and non-toxic dioxygen,would be an example of an ∗Corresponding author.Tel.:+358-9-19150236;fax:+358-9-19150198.E-mail address:timo.repo@helsinki.ﬁ(T.Repo).attractive approach for high variety of ecologically sustainable chemical processes.The proper activa-tion of dioxygen under moderate reaction conditions requires a suitable catalyst and in many industrial processes simple transition metal complexes are used as catalytic species[1].With these catalysts it is of-ten difﬁcult to combine high activity together with high selectivity,while in nature enzymes are able to do so.The structures of the active sites in these enzymes are,therefore,widely studied and synthetic equals to mimic their catalytic behavior are prepared [2–7].1381-1169/03/$–see front matter©2003Elsevier Science B.V.All rights reserved. doi:10.1016/S1381-1169(03)00156-010K.Kervinen et al./Journal of Molecular Catalysis A:Chemical 203(2003)9–19The pulp and paper industry has searched for alter-natives for chlorine-based bleaching since the begin-ning of 1980’s.In the totally chlorine-free bleaching,the main drawback is the damaging of the cellulose ﬁbers during the multistage deligniﬁcation [8].More active oxygen stages are,therefore,looked for and catalytic activation of molecular oxygen is an very attempting approach.Catalytic bleaching would al-low the production of paper of good quality with fewer stages and lower chemical consumption.All together,this would make the bleaching of pulp more economical and less harmful to the environment.Water as a preferred medium for pulp and paper industry limits the number of catalyst alternatives (most of the other studies published about aerobic oxidation of alcohols have been performed in organic solvents,especially the ones with ruthenium or pal-ladium catalysts)[9–15].In the present study,cobalt salen-type complexes 1–6were chosen as catalysts for their known ability to activate oxygen [16–21],and because they are easy to prepare,cheap,stable in water and small in size.Cobalt(salen)complexes are also known to catalyze the oxidation of pheno-lic substrates [17,22–25],but examples of oxidation of benzylic type substrates are fewer [26].Veratryl alcohol was chosen as the model substrate for this study because it can be considered as a model com-pound for lignin substructures [27]and it is often used in studies of lignin degradation by enzymes as it is the most probable substrate for lignin peroxidase [28,29].These model reactions are important as the catalyst behavior needs to be monitored well before tests with more complicated substrates,e.g.pulp,can be performed.Careful study of the model reactions might also enlighten the mechanism of the catalyticreaction.Fig.1.The schematic structures of cobalt complexes 1–6.Reaction conditions and ligand structure are known to have a inﬂuence in the equilibrium between a su-peroxo complex (Co:O 2ratio 1:1)and a dimeric per-oxo complex (Co:O 2ratio 2:1)[16–18,30],of which the superoxo complex is thought to be catalytically more active.It is also plausible that other Co–oxygen complexes can be present than the ones mentioned above.By careful choice of the ligand,solvent,tem-perature,pH and other parameters,the equilibrium can be shifted towards the catalytically more active species.We have previously reported the oxidation of veratryl alcohol by molecular oxygen and Co(salen)complexes in basic aqueous media [31].In this paper,more detailed study on the inﬂuence of reaction pa-rameters on the oxidation activity of the Co(salen)/O 2system in water is reported.The variables studied in-clude the added axial base,temperature,pH,time,oxygen pressure and the catalyst:substrate ratio.2.ExperimentalThe complexes 2–5were prepared according to the literature methods [32–40]and the complexes 1and 6were purchased from Aldrich and used without further puriﬁcation.The substrate veratryl alcohol (3,4-dimethoxybenzyl alcohol)was purchased from ACROS and used as received (Fig.1).2.1.The oxidation experiments at ambient pressureExperiments in ambient pressure were performed mainly in 25ml two-neck ﬂasks under oxygen gas.De-ionized water,the chosen cobalt complex and axial base (usually pyridine)were added ﬁrst and stirred forK.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–1911about10min prior to the addition of other reagents. Sodium hydroxide was then added followed by vera-tryl alcohol and at this point pH of the solution was recorded.(Experiments were also performed by re-placing NaOH with KOH,LiOH or Ca(OH)2.Systems with NaOH and KOH reach similar turnover numbers at pH12.5for veratryl alcohol oxidation,while re-sults for systems with LiOH or Ca(OH)2are much poorer.The TON reached with LiOH system is about one-half of those for NaOH,with Ca(OH)2system it is about one-fourth.Additional information upon re-quest).Oxygen atmosphere was set after evacuation of the reaction system and the reaction mixture was heated to the chosen temperature and the reaction was let to proceed for the desired time.The reaction was stopped by cooling to ambient temperature and then theﬁnal pH was measured.The pH of the reaction mix-ture was adjusted to6–7with2M HCl and soluble or-ganic products were extracted with ethyl acetate.The organic phase was separated,dried with sodium sul-fate,ﬁltered andﬁnally the solvent was removed.The recovery of the extracted product was between92and 97%.The reaction conditions(time,pH,axial base, amount of solvent,temperature and catalyst:substrate ratio)were varied.The oxidation products were iden-tiﬁed with IR spectroscopy(Perkin-Elmer,Spectrum One)and/or1H NMR(Varian Gemini2000)spec-troscopy and by chromatographic methods(GC–MS, HP5890/HP5972MSD).The results are expressed as TONs(TON=turnover number,the number of moles of aldehyde produced per one mole of catalyst).2.2.High-pressure oxidationsExperiments at higher oxygen pressures were made in100ml steel autoclave with a glass vessel inside.The autoclave was loaded with10ml H2O, catalyst(Co(salen)(1),0.15mmol)and pyridine(cat-alyst:pyridine1:1)and stirred for0.5h.Veratryl alco-hol was then added,pH adjusted to12.5with0.2ml of2M NaOH and the desired oxygen pressure was set from a gas cylinder.The autoclave was placed in an oil bath and the reaction mixture was stirred at elevated temperatures for5–80h.Afterwards the reac-tion mixture was neutralized with2M HCl,extracted with ethyl acetate and the organic phase was sepa-rated and dried with NaSO4.Results were analyzed by1H NMR and conﬁrmed with GC–MS(see above).3.Results and discussionA series of salen complexes1–6(Fig.1)was cho-sen to study the inﬂuence of the ligand structure on their catalytic performance in aqueous solutions.Pre-viously it has been shown that ligand substituents do not have any effect on the oxidation behavior of salen-type cobalt complexes,because the differences in the electronic effects caused by substituents are compensated by the change in the donating proper-ties of the axial base.Thus,when the donor proper-ties of the Schiff-base ligand decrease,the axial base binds more efﬁciently and the overall effects of the substituents are mitigated[41].The differences that can be reached with varying ligand structures can thus arise from steric effects or from better solubility or stability of the complex.The unsubstituted salen complex1can be consid-ered as a standard when compared to the catalytic performance of the substituted plex2has sulfonyl groups at3,3 -positions,which make the com-plex highly water soluble and therefore an attractive candidate for pulp bleaching processes.In complex3, the labile imine protons have been replaced by methyl groups,which should stabilize the complex against nucleophilic plex4is otherwise similar as3but the aromaticity of the ligand is removed while the conjugation in the ligand framework is remained. Complex5was selected to observe the inﬂuence of the OH-groups at4,4 -position,which should im-prove water solubility of the plex6 resembles complex1,but it has an additional amine functionality on the bridge between the imido groups. In alkaline aqueous media,the oxidation of veratryl alcohol with the Co(salen)complexes seems to pro-ceed selectively and in1H NMR only the appearance of veratraldehyde can be detected(Fig.2).Therefore, the determination of the extent of the oxidationis Fig.2.The overall reaction scheme of veratryl alcohol oxidation with complexes1–6as catalysts.12K.Kervinen et al./Journal of Molecular Catalysis A:Chemical 203(2003)9–19Fig.3.The effect of temperature on the oxidation of veratryl alcohol.Reaction conditions:10ml of distilled water,0.15mmol of complex and pyridine,5mmol of veratryl alcohol,0.2ml of 2M NaOH and time 24h.relatively easy and results are expressed as TONs (TON =turnover number,the number of moles of aldehyde produced per one mole of catalyst).In spite of the basic reaction conditions,further oxidation of the veratraldehyde and the formation of e.g.corre-sponding carboxylic acid have not been observed.One explanation might be that veratraldehyde precipitates during the oxidation,because it is not water soluble,and this prevents further oxidation to occur.Experi-ments,where dioxan was added to dissolve veratralde-hyde,were also performed but similar results were obtained.This suggests that the reaction mechanism does not facilitate over-oxidations at higher extent.3.1.The effect of temperatureAll complexes 1–6were examined at different temperatures but otherwise constant conditions at pH 12.5(Fig.3).At ambient temperature the conversion of veratryl alcohol to corresponding aldehyde is very slow and for a moderate oxidation activity the reac-tion temperature needs to be over 60◦C.The catalytic productivity increases with increasing temperature and activity of complexes 1–4more than doubles from 70to 80◦C while highest activity was observed at the temperature range of 80–90◦C (TON =25).At 100◦C,complexes 1–4exhibit declined -plex 5is the only one with which the activity increases steadily with the increasing temperature,while the ox-idation capability of 6remains low at the whole tem-perature scale.Also simple cobalt chloride or acetate complexes were investigated,but they are not able to catalyze the oxidation under the studied conditions.The increased activity at higher temperatures might be connected with enhanced solubility of different Co-species into alkaline water solution,but as the same phenomenon was seen with highly soluble com-plex 2,other reasons have to exist,too.Temperature is known to have a strong inﬂuence on which type of oxygen–Co complex dominates in the solution;the bimetallic peroxo-bridged complex is usually favored at higher temperatures [41,43,44],while the oxidation activity is thought to be due to a reactive superoxo complex [17,44].The higher temperatures needed for the reaction to proceed suggests that actually the bridged species should be dominating in the solution.As mentioned below,other reaction conditions have also strong effect on the equilibrium between the superoxo and the dimeric peroxo complexes and by careful reaction setup the domination of the bridged species at higher temperatures can be avoided.We assume that high temperatures are needed for an an-other step in the catalytic oxidation rather than the formation of an active Co–oxygen complex.K.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–1913Fig.4.The effect of pH on activity.In these experiments,temperature was kept at80◦C,other conditions as in Fig.2.The observation that most of the complexes loose their catalytic activity at high temperatures is connected to the thermal stability of the Co(salen) complexes in the basic aqueous conditions.The tem-perature where the catalysts begin to decompose can be detected from appearance of the color of the cobalt–aqua complex(greenish blue)in remains of the water-phase from extraction and the presence of the free salen-ligand in the ethylacetate-phase.The increasing activity of complex5with increasing tem-perature may be,therefore,due to better stability obtained with–OH substituents in the aromatic ring of the ligand.3.2.The effect of pHVariations in hydroxide concentrations have a strong inﬂuence on the oxidation capability of the studied systems.With pH values below7no oxidation activ-ity was observed.When pH is gradually raised from 7to12.5the activity of Co complexes1–5increases dramatically as enlightened clearly with the unsub-stituted complex1(TON:at pH7=3and at pH 12.5=30)[31].About four-fold activity increase can be observed in the pH range from11to12.5but,on the other hand,higher pH values than12.5seem to have only marginal effect on the catalytic productiv-ity(Fig.4).Therefore,presence of sufﬁcient amount of OH−seems to be more important than the actual pH value for the reaction to proceed.This is also sup-ported by the fact that there is no signiﬁcant difference in the observed turnover numbers,when pH has been adjusted to12at the beginning of the reaction or if the same amount of NaOH is added as small portions during the reaction time(24h)(Table1,entries6and 11).Complex6shows low activity in all pH values [31]and thus it was not used for further experiments. Without NaOH in the solution,the complex1does not dissolve properly into water even at70◦C,but it can be separated as an unchanged solid.By adding NaOH,the solubility of the salen complex is consider-ably improved and it is transferred into water-soluble form,probably a hydroxo-or bishydroxo-species. During the oxidation reaction some dark-red solid is precipitating from the solution.If this solid is sep-arated and used as such as a catalyst for oxidation, it does not dissolve well and no further reaction is observed.MS-and IR-spectra of the separated solid show that it is indeed Co(salen).In the IR-spectra, a strong additional band at981cm−1is appearing, which is the region often designed for O–O bonds [44,45].It has been shown earlier,that at pH region of14K.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–19Table1Results of oxidations performed with complex1as the catalyst,veratryl alcohol as the substrate and pyridine as the axial baseEntry n substrate(mmol)n complex(mmol)V solvent(ml)n NaOH(mmol)pH start pH end t(h)%(ald.)TON 150.13151drop,2M10.87.62414.56 250.13150.0511.37.7242510 350.13150.1011.67.8243012 450.13150.15127.8244517 550.13150.312.28.92466.426 650.13150.4512.410.42476.830 750.13150.612.410.92477.330 850.13150.7512.711.5248031 911.40.15350.812.411.62440.131 1050.095300.412.310.62470.236 11a50.13150.4511.511247930 12b2×30.09100.412.57.94843.729 135+2.140.13150.4512.69.37243.729 14c2×50.13152×0.412.5–486550 15c3×50.13153×0.412.5–724956 16c6×30.17306×0.412.5–1445558 17d 2.140.015150.412.611.5248158 18 2.140.015150.412.611.6247251 The experiments were performed in water at80◦C under oxygen atmosphere.a NaOH was added as small portions at intervals of2h.b Another portion of veratryl alcohol was added after24h of reaction.c An additional portion of veratryl alcohol and NaOH was added after each24h of reaction.d In this reaction no pyridine was used.10–11Co(salen)exists as a peroxo-bridged bimetallic species[30].This could thus explain the solid formed when most of the OH−is consumed during the oxi-dation.The deactivation of the catalysis could thus be related to the formation of the bimetallic species.In the presence of additional NaOH the solid dissolves and activates the catalytic system again.The necessity of the pH values above7for the re-action to proceed can also be related to the activation of the substrate.Actually,when substrate is stirred in 80◦C and at pH12.5a slight but notable decrease in pH can be observed.This,and the need of certain amount of NaOH to start the reaction(poor activity at pH values lower than11),suggest that one step in the reaction is the deprotonation of OH-group of the substrate by a hydroxide-ion.Similar step is ob-served in the oxidation of benzylic alcohols catalysed by the copper enzyme Galactose Oxidase[42].These observations above suggest that NaOH is needed for two independent roles in the catalytic cycle of ve-ratryl alcohol oxidation by Co(salen)and molecular oxygen.Careful balancing of the amount of NaOH is important because at very high OH−concentrations the Co(salen)will start decomposing while at low ones the Co(salen)complex can exist as an inactive species.One explanation for the observed decrease in pH during the reaction would be a formation of car-boxylic acid.Due to good recovery of the oxidation product by extraction(92–97%)and the absence of signals of carboxylic acid in1H NMR the amount of carboxylic acid could be at highest only a few percent. This would be anyhow just enough to explain the observed decline in pH values because of high con-centration of veratryl alcohol used in the oxidations (substrate:OH−ratio varies from100to6.67).By paying careful attention to the observed drop in pH and the amount of aldehyde produced(Table1),an interesting correlation can be observed.The amount of OH−consumed in the reaction is nearly linearly depending on the initial OH−concentration.More than99%of the available OH−ions are consumed when the initial pH of the reaction is low(entries1–4) and even in the case of highest initial pH(12.7)94% of the OH−ions disappear during the oxidation.If the conversion of veratryl alcohol is plotted as a functionK.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–1915Fig.5.Conversion of veratryl alcohol as a function of consumed OH−ions.The mmol values are calculated from the measured pH values in Table1by subtracting the[OH−]after the reaction from the initial concentrations.Numbers in parentheses correspond the entry numbers in Table1.The line is to guide eye only.of consumed hydroxide ions a clear relationship can be distinguished(Fig.5).Extent of oxidation is lim-ited by the nearly stoichiometric consumption of OH−ions(Fig.5,points1–5).At higher[OH−]the reaction seems to be saturated because of the substrate conver-sions are only marginally enhanced while the OH−ions are still present and steadily consumed(Fig.5, points6–8).The reason why conversions rarely ex-ceed80%under these oxidation conditions remains unclear.3.3.The effect of timeThe time dependence of the oxidation reactions was investigated for complexes1–5and the reaction time was expanded from24to48,72and144h.The extent of oxidation does not increase with time unless hydroxide-ion is added during reaction(Table1,en-tries6,12and14–16).If sufﬁcient amount of NaOH is present,the reaction proceeds up to72h(Fig.6). After this the catalyst seems to be deactivated because the conversion of veratryl alcohol after144h was practically the same as it was after72h.The need of additional NaOH must be due to keeping OH−concentration high enough for the sufﬁcient depro-tonation of the substrate and to prevent formation of the above mentioned peroxo-species.3.4.The effect of the axial baseAt lower pH,the need for an axial base,such as pyridine for an efﬁcient oxidation has been noted in lit-erature[16,18,40]and also in our earlier experiments [31].At pH11bases such as pyridine,4-picoline and diethylenamine gave similar conversions of veratry-laldehyde while bases such as ethylenediamine and imidazole blocked the reaction.The effect of the axial base depends,anyhow,on the pH.We have now noted, that at higher pH values there is no need for an added axial base,as it seems OH−can act as one.In fact, when similar experiments are performed with systems containing pyridine and systems without it,the latter yields slightly better conversions(Table1,entries17 and18).3.5.The effect of pressureHigh pressure is usually used in oxidation reactions to improve the yield by increasing the oxygen con-centration in the solvent which is usually in water or16K.Kervinen et al./Journal of Molecular Catalysis A:Chemical 203(2003)9–19Fig.6.The effect of additional portion of NaOH on the extent of oxidation by complexes 1–5after initial 24h of reaction.Reaction conditions:0.09mmol of complex and pyridine,10ml water,3mmol of substrate,0.4mmol of NaOH,80◦C and atmospheric oxygen pressure:(a)3mmol of substrate added after initial 24h;(b)3mmol of substrate and 0.4mmol of NaOH added after initial 24h.basic NaOH solutions moderately low [46–48].In our experiments,the results of high-pressure oxidations follow the same trends as the oxidations in ambient pressure where the increased reaction temperature in-creases the catalytic activity (Table 2,entries 19–22).The reactions were performed at 80◦C and pH 12.5as it was found to be an optimum for the complexes 1–4.Increasing the oxygen pressure gradually from 3to 10bar increases the conversion of veratryl alcohol toTable 2The effect of temperature,pressure and reaction time on oxidation of veratryl alcohol by complex 1under elevated O 2pressure Entry T (◦C)P (bar)t (h)%(ald .)TON 19a 405174220a 60517402021a 80517763822a 100517804023b 80370798324b 80570858925b 80870949926b 8010709910427a 805 3.5281528a 80540945029b805908792Standard conditions:10ml of water at pH 12.5and at 80◦C,0.075mmol (a)or 0.038mmol (b)of complex 1and pyridine and 4mmol of veratryl alcohol.The results are expressed as turnover numbers.aldehyde almost linearly about 20%(Table 2,entries 23–26,Fig.7).Complexes seem to survive the reac-tion conditions for 3days similarly to oxidations at ambient pressure (Table 2,entries 21,24,27–29).At 10bar,the oxidation seems to proceed with a rate of about 30cycles per day.The remarkable difference in high-pressure reaction is that the additional NaOH is not needed while it was an elementary factor in ambi-ent pressure reactions.By replacing oxygen with air the reaction is signiﬁcantly slowed down (TON =7at pH 12.5and ambient pressure)and by excluding oxy-gen by argon atmosphere the formation of aldehyde simply does not occur.3.6.The effect of concentrationIn few experiments,the amount of catalyst was re-duced compared to the amount of solvent and of the substrate.In these experiments better turnover num-bers can be reached (Table 3).The reason for better oxidation results could be to enhance the coordina-tion of the substrate to the cobalt complex when more substrate is present.To ensure that cobalt(salen)complex does not act only as an initiator of an auto-oxidation reaction,experiments were performed with several catalyst concentrations,while the amount of substrate,solventK.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–1917Fig.7.The effect of pressure on oxidation of veratryl alcohol by complex1.Reactions were performed in water at pH12.5,temperature 80◦C,reaction time70h and pyridine as the axial base.Table3Results of oxidation experiments performed with varied concentrations of Co(salen)1Entry n substrate(mmol)n complex(mmol)Catalyst:substrate ratio V solvent(ml)t(h)%(ald.)TON 3050.31:16.715248414 3150.151:33.315248127 3250.0451:111152460.567 3350.031:167152458.898 3450.0151:333152437.5125 3550.0061:833152422.4187 3660.0061:1000102421.8218 37500.061:8331502424.6205 3835.70.0061:5950024 5.5330 The experiments were performed in water at80◦C and pH12.5.and base were kept constant.In these experiments,the decreased catalyst concentration enhances the oxida-tion activity remarkably,while in an auto-oxidation reaction results should be independent on the catalyst concentration.The inﬂuence of catalyst:substrate ratio was further studied by varying substrate and catalyst concentrations.Regardless of absolute concentrations, as in solutions where the catalyst:substrate ratio was 1:833,similar turnover numbers(about200)were achieved(Table3,entries35and37).This implicates that the substrate:catalyst ratio plays a role in the re-action and as a consequence of this the highest TONs were observed in neat conditions.We assume that the increased substrate concentration emphasizes the replacement of a coordinated pyridine or hydroxide molecule by the substrate molecule in the coordina-tion sphere of the cobalt,which might be prerequisite for the efﬁcient oxidation to occur.4.ConclusionsThe substituents on the salen ligand seem to have an important role in oxidation,although the differences18K.Kervinen et al./Journal of Molecular Catalysis A:Chemical203(2003)9–19observed among the complexes1–5can be mostly due to stability of the complexes in the basic and oxidizing reaction conditions.The unsubstituted complex1is much more efﬁcient catalyst than most of the substi-tuted ones,the only exception being complex2with the sulfonyl substituents.The modest performance of6 is most probably caused by the additional amine in the bridge.This suggests that the axial base used for en-hancing the oxygen binding to the cobalt-center needs to be mobile and not attached to the rigid ligand frame. Each change in the reaction conditions brings along differences in catalytic activity.For an efﬁcient ox-idation of veratryl alcohol,higher temperatures than 60◦C are needed and highest activities were observed at the temperature range between80and90◦C.The decrease of catalytic activity at temperatures above 90◦C or at very high NaOH concentrations is most probably caused by accelerated decomposition of the complexes.In this context,the stability of5,the one having OH-groups at4-position,at high temperatures is worth of notice.The catalytic activity of the stud-ied system is also linearly depending on the applied oxygen pressure;the best turnover numbers reached in similar conditions were58for ambient pressure and103at10bar.The catalytic performance of the salen complexes can be further enhanced if the sub-strate concentration is increased.Turnover numbers as high as330were detected with catalyst:substrate ratio 1:5950at ambient pressure.The exact role of NaOH in the present reaction is complicated and still not yet clear.The oxidation does not occur without NaOH and best activities were reached at pH level12.5.The decrease in pH during the oxidation clearly suggests that hydroxide is con-sumed in the ambient pressure reactions and apparent relationship between the consumption of OH−and the extent of oxidation is observed.Therefore,the pres-ence of sufﬁcient amount of OH−seems to be more important than the initial pH level of the reaction.The reason why conversions rarely exceed80%under these oxidations remains unclear.The remarkable difference in high-pressure reaction is that the additional NaOH is not needed while it was an elementary factor in ambient pressure oxidations. This implies that consumption of OH−ions is not sig-niﬁcant and,therefore,kinetics of the oxidation under ambient and high pressures are different.This is also supported by the fact that at higher oxygen pressures conversions up to99%can be reached.If the reason for NaOH consumption in ambient pressure oxidation is the formation of carboxylic acid a possibility for auto-oxidation of aldehyde can be excluded.In high oxygen pressures over-oxidation should be more fa-vored but as this is not the case,the reason for the for-mation of acid must lay on the catalytic reaction itself. The observed variations in catalytic activity can be caused by a shift in equilibrium between dif-ferent Co–oxygen-species most probably between a superoxo complex(Co:O2ratio1:1)and a dimeric peroxo complex(Co:O2ratio2:1).When the pH level of the reaction decreases the formation of the non-soluble,peroxo-bridged cobalt complex was observed.This peroxo bridge complex can be sepa-rated but it is not able to catalyze oxidations further on.Anyhow,by adding NaOH deactivated catalytic species can be regenerated back to the soluble and active form.These results suggest that the formation of the peroxo-bridged bimetallic species is the main reason for catalyst deactivation in the ambient pres-sure reactions.The oxidations can go on for extended period of time only,if supplementary NaOH is added during the reaction or if higher oxygen pressures are applied.It is very plausible that NaOH has also a major role as a proton abstractor from the hydroxyl group of veratryl alcohol,which could be an initial step in the catalytic cycle as observed for Galactose Oxidase [42].Therefore,it seems to be that NaOH has two independent roles in the catalytic cycle of veratryl al-cohol oxidation by Co(salen)and molecular oxygen. Careful balancing of the amount of NaOH is impor-tant because at very high OH−concentrations the Co(salen)will start decomposing while at low ones the deprotonation is not sufﬁcient and the Co(salen) complex can exist as an inactive species.Our fu-ture work will center on elucidating the mechanistic details of Co(salen)catalyzed oxidation of benzylic alcohols.AcknowledgementsTheﬁnancial support of this research by Finnish National Technology Development Agency(TEKES) and Acta Chemica Scandinavica is gratefully ac-knowledged.。

【原文】The Tyranny of Metrics.doc

The Tyranny of MetricsEvery step you takeIn a world where everything is quantified,power will accrue to whoever is keeping score.Measurements pervade life and society.Infants are weighed the moment they blink into the world.Pupils are graded.Schools are judged on their students’performance, universities on graduates’job panies monitor the productivity of employees while CEOs watch the share price.Countries tabulate their GDP, credit-rating agencies assess their economies,investors eye bond yields.The modern world relies on such data.It would cease to function without them.The numbers are proliferating.As ever-greater swathes of human activity are subsumed by the digital revolution,so they too can be calibrated.Uber riders earn stars for their back-seat behaviour.Social-media posts attract“likes”.Users of dating sites are assigned desirability scores.Apple’s iPhones tell their owners how many hours they have spent peering into their screens.Wristbands measure footsteps;apps can track sleep patterns and sex.As recently as the start of this decade,people who voluntarily observed themselves in this way had a cultish name,the“quantified-self movement”.That urge is now the premise of one of Apple’s latest products,a watch that keeps tabs on the wearer’s heart rate.If everything people do and every step they take is tracked,they lose the freedom to act independently of such oversight,writes Steffen Mau,a German sociologist,in “The Metric Society”.Published in German in2017and now in Sharon Howe’s English translation,Mr Mau’s book is a wide-ranging tour through rankings and ratings,stars and points,charts and graphs.When these technologies become embedded in society,he argues,life is reduced to checkboxes.Faith in experts is replaced by devotion to figures.Meanwhile,power is transferred from individuals to those who create and maintain the scoring systems.These in turn can be gamed and their purposes perverted.The numbers gameTake the World Bank’s annual comparison of business regulations around the world. One country stood out in its latest ranking:China,which had languished in78th place the previous year,jumped to46th.India seemed to have improved,too,rising23spots, to77th.Those remarkable ascents have less to do with the ease of doing business in those places than with their governments’determination to achieve good grades. Some40people work in a Chinese government unit dedicated to improving its World Bank score;perhaps200toil in India’s.At least60countries have teams that focus onthe index.Conversely,a change in methodology can lead to precipitous falls.In2016 Chile’s performance slumped after one such rejig,which some attributed to political machinations.These days,though,it is not only technocrats who have cause to fret about skewed metrics.Consider the role played by misinformation on Facebook in the American presidential election of2016.For a relatively small sum of money by the standards of American political campaigns—about$1.25m a month—Russian propaganda reached 126m people.How did the Kremlin get such a bang for its buck?“They tracked the size of the online US audiences reached through posts,different types of engagement with the posts(such as likes,comments,and reposts),changes in audience size,and other metrics,”according to an indictment by Robert Mueller,the special counsel investigating Russian interference in the vote.The algorithms that power Facebook’s news feed are opaque,but it doesn’t take a state-backed operation to work out part of the method.From around2013,media companies across the world began to pander to Facebook’s tastes,turning out increasingly emotional pieces to entice readers to click on links.Publishers monitored emerging trends using an online service called CrowdTangle(later bought by Facebook);they tracked traffic to their own websites using Chartbeat,another measurement tool.Some rewarded staff on the basis of these numbers.Some websites cynically exploited touchy issues of social justice to bring in traffic from Facebook.It became a self-fulfilling prophecy.A piece would appear on a website,attract attention from others through Facebook,be re-written and re-posted on Facebook,and soon it was all over the internet,morphing into a genuine news event.At the same time readers were being tracked by Facebook,CrowdTangle,Chartbeat and dozens of other outfits as they idly clicked entertaining-looking links.The position of the cursor, the amount of time spent on the page,the depth to which they scrolled—all were recorded,analysed,packaged and sold.Did these articles fulfil the basic journalistic function of informing their readers?Or,on the contrary,did readers’clicks determine what was written?To judge from the hysterical,hyperpartisan tone of much of the ensuing coverage,it was the clicks.If such techniques can change how countries design regulatory regimes and what the media publish,the direct effects on individuals are even greater.“In the age of the metric society,”writes Mr Mau,“individuals constitute bundles of data in which their personal worth is encoded.”When different sources of data are linked together,it becomes possible to paint an eerily complete picture of a person,and to predict with some accuracy both their net worth and their future behaviour.This is already the case in car insurance,where some drivers voluntarily attach devices to their vehicles that transmit reports to their insurers.American health insurers reduce premiums for non-smokers and exercise fanatics.All-roundsurveillance is coming to the workplace,too.In2015BP gave25,000fitness trackers to staff as part of a health-insurance scheme.The next year the Daily Telegraph,a British newspaper,installed heat-and motion-sensors under employees’desks.(They were removed after protests.)Elsewhere,score-keepers have begun to appraise people in the round.In China,for example,Zhima Credit,a popular private service,measures “personal characteristics”,“online behaviour”and“interpersonal relationships”, among other things.A high rating entitles people to a fast-track visa for Singapore. For good drivers,hard workers,athletes and the financially prudent,all this might seem an unalloyed good.For everyone else—and few people tick every virtuous box—the metric society may prove a means for faraway data overlords to capture power and entrench inequality in the guise of efficiency.It risks descending into a 21st-century dystopia that is almost as bleak,in its impersonal way,as those imagined in the darkest novels of the20th.。

高考英语总复习真题研练Week2Monday含解析word版本

Week 2MondayTask 1 ：阅读以下短文，从每题所给的四个选项( A、 B、 C 和 D) 中，选出最正确选项。

(2016 ·江苏， C)El Ni? o，a Spanish term for“ the Christ child，” was named by South American fishermen who noticed that the global weather pattern， which happens every two to seven years， reduced the amount of fishes caught around Christmas.El Ni?o sees warm wate r ， collected over several years in the westernPacific ，flow back eastwards when winds that normally blow westwards weaken， or sometimes the other way round.The weather effects both good and bad， are felt in many places.Rich countries gain more from powerful Ni?o s，on balance ，than they lose.A study found that a strong Ni?o in 1997— 98 helped America ’ s economy grow by $15 billion ， partly because of better agricultural harvests：farmers in the Midwest gained from extra rain.Thetotal rise in agricultural incomes in rich countries is greater than the fall inpoor ones.But in Indonesia extremely dry forests are in flames.A multi－ year drought ( 干旱 ) in south －east Brazil is becoming worse.Though heavy rains brought about by El Ni?o may relieve the drought in Californi a， they are likely to cause surfaceflooding and other disasters .The most recent powerful Ni?o， in 1997—98， killed around 21， 000 people and caused damage worth $36 billion around the globe.But such Ni?os com e with months of warning，and so much is known about how they happen that governments canprepare.According to the Overseas DevelopmentInstitute(ODI) ， however ， just12% of disaster－ relief funding in the past two decades has gone on reducing risks in advance ， rather than recovery and rebuilding afterwards.This is despite evidencethat a dollar spent on risk－ reduction saves at least two on reconstruction.Simple improvements to infrastructure (基础设备 ) can reduce the spread of disease.Better sewers (下水道 ) make it less likely that heavy rain is followed byan outbreak of the disease of bad stomach.Stronger bridges mean villages are less likely to be left without food and medicine after floods.According to a paper in2011 by Mr Hsiang and co－ authors ， civil conflict is related to El Ni? o’s harmful effects—and the poorer the country， the stronger the link.Though the relationship may not be causal ，helping divided communities to prepare for disasters would atleast reduce the risk that those disasters are followed by killing and woundingpeople.Since the poorest are least likely to make up for their losses from disasters linked to El Ni?o， reducing their losses needs to be the priority .【语篇解读】本文是一篇说明文。

工作日天气差的原因

很多人都有这样的经验，周一早晨上班时常常乌云密布，而到周五回家时，或圣诞节这样的假日，才会云开日霁。
But new research by two American scientists has found that bad weather - or at least thunderstorms and hail - does seem to happen midweek far more often than it does at weekends, at least in summer.
人类活动对天气产生的这种影响在美国西海岸并不适用，也许这种效应仅限于比较潮湿的气候。
The researchers said, 'This study shows for the first time statistical evidence that when man-made aerosol releases during summer time are at their weekly mid-week peak, tornado and hailstorm activity there is also near its weekly maximum.'
废气排放会影响大气的湿度，人们工作时，废气排放量会达到峰值。到周末，人们休息时，废气排放量就会下降。
The effect doesn't seem to be reproduced on the West Coast of America - so it may be limited to moister climates.
研究人员分析了美国东海岸夏季的气候，发现龙卷风和冰雹多发生在一周中间时段。这一现象不是孤立事件，也不是天气预报出现了失误。

2024年雅思真题大作文题目

2024年雅思真题大作文题目You should spend about 40 minutes on this task.Write an essay on the following topic:Some people think that the best way to improve the quality of education is to increase the amount of money spent on it. Others believe that spending more money on education will not necessarily improve its quality.Discuss both views and give your own opinion.Which of the following statements is NOT mentioned in the essay topic?A. Improving the quality of education is important.B. Increasing the amount of money spent on education will definitely improve its quality.C. Some people disagree with the view that spending more money will improve education quality.D. The writer is required to express their own opinion.You should spend about 40 minutes on this task.Write an essay on the following topic:The rise of social media has had a significant impact on people's lives. Some people believe that it has had a positive impact, while others argue that it has had a negative effect.Discuss both views and give your own opinion.Which of the following is NOT a possible argument for the negative impact of social media?A. It can lead to addiction and excessive use.B. It can damage personal relationships.C. It provides a platform for free expression and connection.D. It can lead to privacy concerns and cyberbullying.You should spend about 40 minutes on this task.Write an essay on the following topic:The use of technology in education has become increasingly common. Some people believe that this is a positive development, while others argue that it has negative consequences.Discuss both views and give your own opinion.Which of the following is NOT a possible argument for the positive development of technology in education?A. It can provide more resources and materials for students.B. It can personalize learning and cater to individual needs.C. It can replace teachers and make education more efficient.D. It can enhance learning experiences and engage students more actively.You should spend about 40 minutes on this task.Write an essay on the following topic:The importance of physical exercise for maintaining good health is widely recognized. However, some people argue that excessive exercise can be harmful.Discuss both views and give your own opinion.Which of the following is NOT mentioned in the essay topic?A. The benefits of physical exercise for health.B. The harmful effects of excessive exercise.C. The lack of importance of physical exercise.D. The writer's personal opinion on the topic.You should spend about 40 minutes on this task.Write an essay on the following topic:The rise of remote work has led to changes in the way people live and work. Some people believe that this is a positive trend, while others argue that it has negative consequences.Discuss both views and give your own opinion.Which of the following is NOT a possible argument for the negative consequences of remote work?A. It can lead to isolation and a lack of social interaction.B. It can make it difficult to separate work and personal life.C. It reduces the need for commuting and saves time.D. It can affect team dynamics and communication.You should spend about 40 minutes on this task.Write an essay on the following topic:The use of plastic has become a major environmental issue. Some people believe that the best solution is to reduce the use of plastic, while others argue that recycling is more effective.Discuss both views and give your own opinion.Which of the following is NOT mentioned as a possible solution to the environmental issue of plastic use?A. Reducing the use of plastic.B. Improving recycling methods.C. Increasing the production of plastic.D. Encouraging the development of alternative materials.You should spend about 40 minutes on this task.Write an essay on the following topic:The impact of tourism on local communities can be both positive and negative. Some people believe that the benefits outweigh the costs, while others argue that the costs are too high.Discuss both views and give your own opinion.Which of the following is NOT a possible argument for the positive impact of tourism on local communities?A. It can generate economic growth and create jobs.B. It can promote cultural exchange and understanding.C. It can damage the environment and local culture.D。

剑6阅读test4精讲

第一篇题型一•i Not all doctors are persuaded•ii Choosing the best offers•iii Who is responsible for the increase in promotions?•iv Fighting the drug companies•v An example of what doctors expect from drug companies•vi Gifts include financial incentives•vii Research shows that promotion works•viii The high costs of research•ix The positive side of drugs promotion•x Who really pays for doctors‟ free gifts?第一篇题型二•8 Sales representatives like Kim Schaefer work to a very limited budget.•9 Kim Schaefer‟s marketing technique may be open to criticism on moral grounds.•10 The information provided by drug companies is of little use to doctors.•11 Evidence of drug promotion is clearly visible in the healthcare environment.•12 The drug companies may give free drug samples to patients without doctors’ prescriptions.•13It is legitimate for drug companies to make money.B段•正数第一行“But on any given day, what Schaefer can offer is typical for today‟s drugs rep- a car trunk full of promotional gifts and gadgets, a budget that could buy lunches and dinner for a small country, hundreds of free drug samples and the freedom to give a physician $200 to prescribe her new product to the next six patients who fit the drug‟s profile ”，对应第八题。

国际贸易双语教案问题答案Pugel_14_SG_AKEY (17)

CHAPTER 17THE FOREIGN EXCHANGE MARKETObjectives of the ChapterThis chapter deals with the nature and organization of the foreign exchange market. At its most basic, the equilibrium exchange rate can be thought of as the price that equates the international supply of and demand for a country’s money. For example, the exchange rate on the British pound (expressed as American dollars per British pound) would be determined by the supply of pounds arising from British purchases of American goods, services, and assets, and by the demand for British pounds arising from American purchases of British goods, services, and assets.You might want to track a few of the major currencies and related commentaries in the daily listings in the financial press.After studying Chapter 17 you should be able to identify1. what an exchange rate is.2. what the reciprocal of the exchange rate means.3. the organization of the modern foreign exchange market.4. the distinction between spot and forward exchange rates.5. determinants of demand and supply for foreign exchange.6. how a system of flexible foreign exchange rates works.7. how a system of fixed foreign exchange rates works.Important ConceptsAppreciation (depreciation): An increase (decrease) in the market price of a currency under afloating exchange rate system.Fixed exchange rate: A rate whose officially declared value is maintained by central bankintervention. (Also referred to as a pegged exchange rate.)Floating exchange rate: A rate whose value is determined purely by the market forces ofsupply and demand, with no direct intervention by central banks.(Also referred to as a flexible exchange rate.)Foreign exchange market: A computerized communications network embracing all the majorfinancial centers in the globe, where sellers and buyers of anynational money can quickly and efficiently carry out any desiredcurrency exchange.Foreign exchange market When a central bank buys or sells foreign exchange in order to intervention:manipulate or peg the exchange rate.(Foreign) exchange rate:The price of one country’s currency expressed in terms of anothercountry’s currency. (Note that, in this text, the exchange rate isexpressed in terms of domestic currency units required to purchaseone unit of a foreign currency.)Foreign exchange swap: A “package trade”in which a spot purchase of a currency isaccompanied by a forward sale of that currency, or a spot sale of acurrency is accompanied by a forward purchase of that currency andpayment. This transaction allows for temporary foreign exchangeneeds and is free of exchange risk.Forward exchange rate: The exchange rate applicable to foreign exchange transactionsagreed upon today for later delivery (usually in 30, 90, or 180 days). Revaluation (devaluation): A revaluation is an official increase in the par value of a currencyunder a fixed exchange rate system; a devaluation is an officialdecrease in the par value.Spot exchange rate: The rate applicable to foreign exchange transactions requiringcontemporaneous delivery and payment.Triangular arbitrage: The process that ensures consistency among the sets of bilateral“cross rates” of the world’s traded currencies. For example, if theBritish pound trades for US$2, and 100 Japanese yen trade for US$1,the exchange rate between the yen and the pound must be 200 yenper pound. Otherwise, there is an opportunity for an arbitrageur tobuy a currency cheaply in one market and sell it for a higher price inanother market.Vehicle currency: A currency used to facilitate an indirect trade between two othercurrencies. The U.S. dollar is often used as a vehicle currency.Warm-up QuestionsTrue or False? Explain.1. T / F An increase in U.S. imports from France will give rise to a supply of euros in exchangefor dollars.2. T / F Central bank intervention is more prevalent under a floating exchange rate system thanunder a pegged exchange rate system.3. T / F If Americans suddenly refuse to lend money to Mexico, we would expect the dollar toappreciate relative to the peso.4. T / F Art appreciation courses have nothing to do with exchange rates.5. T / F If a currency is undervalued in a fixed exchange rate system, officials from that country’scentral bank will have to sell their currency to keep it pegged.Multiple Choice1. Suppose the exchange rate between the Canadian dollar (C$) and the American dollar (US$)changes from C$1.340/US$ to C$1.325/US$, but the Canadian government wants to maintain a fixed exchange rate of C$1.340/US$. What should the Bank of Canada do?A. Stop trading with the U.S. so that fewer U.S. dollars will flow into Canada.B. Sell U.S. dollars (buy Canadian dollars).C. Sell Canadian dollars (buy U.S. dollars).D. Purchase British pounds and sell French francs.2. If a dollar equals 400 Mexican pesos in the foreign exchange market, what is the value of onepeso?A. $250B. $0.0025C. $0.04D. $1.25E. None of the above.3. Which of the following statements is false?A. British imports of Florida oranges will create a demand for U.S. dollars.B. If all Americans buy Japanese cars, the dollar will appreciate relative to the yen.C. The American dollar is often used as a vehicle currency.D. Australia, Canada, New Zealand and Taiwan all use currencies called “dollars.”4. When American residents buy bonds from Her Majesty’s Treasury in London, in the foreignexchange market this will give rise toA. a demand for American dollars.B. a supply of British pounds.C. a supply of American dollars.D. another Boston Tea Party.5. The demand curve for a foreign currency slopes downward becauseA. at lower exchange rates, foreign goods look cheaper to home country residents.B. at higher exchange rates, the home currency can buy more foreign goods.C. the quantity supplied of the foreign currency rises as the exchange rate falls.D. marginal utility theory says that individuals substitute into any commodity whose price hasfallen.Problems1.The currency of Leinster is the Leinster lira (Ll); the currency of Saxony is the Saxon scudo (Ss). Consider the following diagram of the foreign exchange market in Saxony:Figure 17.1a. What is the equilibrium price of one Leinster lira in Saxony?b. Can you also determine what the equilibrium price of the Saxon scudo is in Leinster?c. Suppose a doctor in Leinster shows that eating Saxon bread can reduce the level ofcholesterol in one’s blood. What would you expect to happen to the exchange rate between lira and scudos in a floating exchange rate system?d. If the Saxon finance minister wants to peg the exchange rate at the value you determined in(a), what must she do to counteract the impact on the exchange rate of the event described in (c)?Ll 20 (billions)E x c h a n g e r a t e r S (S s p e r L l )2. Suppose that the Saxon scudo appreciates relative to the Leinster lira. Determine whether theeconomic agents listed below would see that appreciation as a good thing or a bad thing.a. A Leinster resident who imports goods priced in scudos.b. A Saxon who exports goods priced in scudos.c. A Leinster resident who exports goods priced in lira.d. A Saxon who has a retirement account denominated in scudos.e. Anyone who expected the lira to depreciate.3. For the most part, the exchange rate between the U.S. dollar and the euro is floating. What effectwill each of the following events have on the $/€ exchange rate?a. The French government bans the import of American movies.b. Americans learn that drinking French red wine will prevent heart disease.c. An American mutual fund purchases stock in Renault.d. Parisian perfume makers buy chemicals from a company in New Jersey.e. New York foreign exchange speculators believe the euro is going to depreciate in the nextfew hours.4. Assume that U.S. government officials are trying to keep the exchange rate between the dollarand the euro pegged. For each of the events described in Problem 3, what actions must theseofficials take to return the exchange rate to its previous level?5. You have been given one million yen to play with. Use the following exchange rates to show howyou can make a riskless profit in terms of yen:1 euro = 70 yen in Munich1 yen = 1 American penny in Tokyo1 American dollar = 3 euro in New York CityDiscussion Topics1. What do you see as the benefits and costs of each country having its own currency?2. What problems would you foresee in a world where some countries have floating exchange rateswhile others try to keep their exchange rates fixed?。

济南2024年03版小学6年级下册第三次英语第6单元测验卷[有答案]

济南2024年03版小学6年级下册英语第6单元测验卷[有答案]考试时间：80分钟（总分:100）A卷一、综合题(共计100题)1、填空题：The ______ (物种) diversity is crucial for a healthy ecosystem.2、填空题：The _____ (火烈鸟) is pink and stands on one leg.3、How many hours are there in a day?A. 12B. 24C. 36D. 48答案：B4、填空题：The ______ (阳光照射) plays a role in photosynthesis.5、填空题：I want to _______ (学会) playing the piano.6、What is 20 + 30?a. 40b. 50c. 60d. 70答案:b7、听力题：The Earth’s ______ is responsible for its magnetic f ield.8、What do you call a person who repairs computers?A. TechnicianB. EngineerC. BuilderD. Designer答案:A9、What is the capital of Russia?A. St. PetersburgB. MoscowC. KievD. Minsk答案: B10、听力题：We have a _____ (活动) for Earth Day.11、What is the name of the famous rock band known for hits like "Hey Jude"?A. The Rolling StonesB. The BeatlesC. QueenD. Pink Floyd答案：B12、填空题：I have a toy _____ that can dance.13、听力题：The capital of Senegal is __________.14、听力题：Saltwater is an example of a ______.15、填空题：We have a ______ (愉快的) celebration for achievements.16、填空题：The ancient Egyptians created beautiful _____ for their gods.17、What do we call the melting of snow and ice?A. PrecipitationB. EvaporationC. RunoffD. Thawing答案:D18、填空题：A __________ day is perfect for going to the zoo. (温暖的)19、听力题：A reaction that produces a gas and a solid is called a ______ reaction.20、填空题：The _______ (Peasants’ Revolt) occurred in England in 1381.21、填空题：The ______ (鲸鱼) is known for its size and beauty.22、听力题：The chemical symbol for technetium is ______.23、填空题：Birds can ______ (飞) in the sky.24、听力题：Space exploration began in the ______ century.25、填空题：My uncle is a __________ (音乐家).26、听力题：My dad likes to go on ____ (hiking) trips.27、填空题：________ (果醋) is made from fruit.28、填空题：I enjoy playing ________ (棋类) with my friends.29、听力题：A solution is a mixture where one substance ______ in another.30、What do we call the act of trying out new things?A. ExperimentingB. TestingC. SamplingD. All of the Above答案：D31、What is the term for a person who studies the oceans?A. OceanographerB. Marine BiologistC. GeologistD. Environmentalist答案:A32、What do you call a person who works with wood?A. CarpenterB. ElectricianC. PlumberD. Mason答案: A33、What is the capital of Italy?A. RomeB. VeniceC. FlorenceD. Milan答案: A. Rome34、What do we call the effect of the Earth's rotation on weather patterns?A. Coriolis EffectB. Trade WindsC. Jet StreamD. Ocean Currents35、听力题：The ________ (strategy) guides our actions.36、What is the main ingredient in salad?A. MeatB. VegetablesC. FruitsD. Grains答案：B37、What do we call a group of dolphins?A. SchoolB. PodC. FlockD. Colony答案:B. Pod38、听力题：A _______ is a large area of land that is covered with trees.39、听力题：In chemistry, we use ______ to represent elements.40、What is the color of milk?A. WhiteB. YellowC. BlueD. Green41、What is the main ingredient in a Caesar salad?A. LettuceB. SpinachC. KaleD. Arugula答案:A. Lettuce42、Which of these is a primary color?A. PurpleB. GreenC. BlueD. Orange答案:C43、What color is a ripe strawberry?A. BlueB. YellowC. RedD. Green答案:C44、What is the opposite of ‘easy’?A. SimpleB. DifficultC. HardD. Challenging45、听力题：The ______ helps us learn about social studies.46、选择题：What is 8 + 2?A. 10B. 11C. 12D. 1347、填空题：I enjoy making ______ (贺卡) for my friends on their birthdays. It’s a personal touch they appreciate.What do we call the time of year when it’s very cold?A. SpringB. SummerC. WinterD. Autumn49、听力题：The __________ is essential for protecting water sources.50、听力题：My ______ is an expert in technology.51、What is the name of the fairy tale character who had a magic mirror?A. CinderellaB. Snow WhiteC. RapunzelD. Belle52、听力题：The snowman has a ______ (carrot) nose.53、填空题：I love to have tea parties with my ________ (玩具名) and pretend we are all friends.54、填空题：The _____ (水果收成) happens in late summer.55、听力题：My brother likes to play _____ (basketball/football).56、听力题：She is good at ______. (dancing)57、填空题：A _____ (小马) can be very gentle around children.58、What is the capital city of El Salvador?A. San SalvadorB. Santa AnaC. San MiguelD. Sonsonate59、听力题：A __________ is a small furry animal that often lives in burrows.The Age of Exploration began in the _______ century.61、填空题：I want to help protect the _______ (环境). It’s important for future _______ (世代).62、听力题：A saturated solution contains the maximum amount of ______.63、听力题：The chemical formula for magnesium sulfate is ______.64、What do we call a young deer?A. FawnB. CalfC. KidD. Pony65、What is the main gas in the atmosphere?A. OxygenB. NitrogenC. Carbon DioxideD. Hydrogen答案：B66、填空题：The discovery of ________ led to significant advances in medicine.67、填空题：I enjoy doing puzzles and brain teasers to challenge my ________ (思维).68、填空题：The ______ (金鱼) swims in circles, looking for food.69、听力题：He plays _____ (football/basketball) on the team.70、填空题：A _____ (植物园) showcases different species.71、听力题：My uncle is very ________.72、填空题：I enjoy visiting the __________ with my family. (博物馆)My friend has a ___ (小宠物), which is a cute rabbit.74、What is the name of the famous scientist known for his work on gravity?A. Isaac NewtonB. Albert EinsteinC. Galileo GalileiD. Johannes Kepler答案: A75、填空题：A _____ is a piece of land that juts out into the sea.76、ts are ________ (药用) and help heal. 填空题：Some pla77、Which animal is known for its ability to change color?A. ChameleonB. ElephantC. GiraffeD. Zebra78、填空题：Understanding the role of plants in our environment is crucial for ______. (了解植物在环境中的作用对保护至关重要。

普鲁斯特效应英语作文

普鲁斯特效应英语作文The Proust Effect: A Journey through Time and Memory。

Introduction。

The Proust Effect, also known as the "Proust phenomenon," refers to the sudden and vivid recollection of past memories triggered by a sensory stimulus. This phenomenon takes its name from the renowned French writer Marcel Proust, whose novel "In Search of Lost Time" explores the intricate relationship between memory, time, and sensory experiences. In this essay, we will delve into the Proust Effect, its significance, and the ways in which it can be applied in our daily lives.The Proust Effect: A Dive into the Past。

The Proust Effect is a powerful mechanism that allows individuals to access forgotten memories by engaging their senses. It demonstrates the profound impact sensory stimulihave on our memory recall. For instance, the smell of freshly baked bread may transport someone back to their childhood kitchen, evoking a cascade of memories associated with that particular moment in time. This phenomenon suggests that our sensory experiences are deeplyintertwined with our memories, acting as a portal to our past.The Role of Memory in Shaping Our Identity。

全球健康智慧树知到课后章节答案2023年下浙江大学

全球健康智慧树知到课后章节答案2023年下浙江大学浙江大学第一章测试1.Which of the following are true of Disability Adjusted Life Years or DALYs? ( )答案:DALYs help policy-makers to compare diseases and decide priorities.;DALYs enable us to compare the disease burden between, for example, depression and breast cancer.;A DALY combines years of life lost because of early death and years oflife lived with disability or illness.2.Which of the following are true? ( )答案:The GBD studies have provided trends about mortality and morbidityby cause and risk factor over time.;The countries with the highest burden of disease are mostly located in Sub-Saharan Africa3.Regarding SDGs, which are true? （）答案:Eradication of extreme poverty is one of the SDGs.;Covid-19 will slow progress towards the SDGs in many countries.;There are 17 SDGs and 169 separate targets.4.Which of the following are health targets of the SDGs, (SDG 3) but notincluded of the MDGs? （）答案:Achieve Universal Health Coverage.;Reduce mortality from NCDs.5.Which statements are true about the social determinants of health? ( )答案:Well-educated mothers have healthier children;Access to quality healthcare is fundamental to health equity.;Loneliness is strongly associated with physical and mental health第二章测试1.What type of healthcare financing is regarded as most efficient, (best valuefor money)? ( )答案:Taxation2.Which of these countries have among the lowest out-of-pocket expenditureon health? （）答案:South Africa;Japan3.Which are true? （）答案:Most African countries have included a goal of UHC in their nationalhealth strategies4.Which of these will help countries to progress towards UHC? ( )答案:Maximise use of tertiary care;Reducing corruption5.Which of the following statements are right? （）答案:WHO defines health systems as all organisations, institutions andresources which work to improve health through treatment andprevention;Cost is the major barrier to the delivery of quality healthcare;Healthcare is much more expensive than it was mainly because of an ageing population with chronic disease and multimorbidites第三章测试1.What are factors contributing to the growth of drug resistance? （）答案:inappropriate use of antibiotics in animals;failure by patients to take all their medicines;Inappropriate prescribing practices;Counterfeiting of drugs2.What are key measures to reduce the development of infectious diseases? ( )答案:strengthen implementation of the International Health Regulations;Share information on such diseases across countries;improve public education about these diseases;Improve land use planning3.Which of the following best represents the new global goals for treatment ofHIV announced by UN in 2014: （）答案:95/95/95 by 2030 - 95% of the population will know their HIV status, 95% will receive anti-retroviral therapy, and 95% will have asuppressed viral load4.The socio-economic consequences of Covid-19 in most countries include: ( )答案:Increased inequalities;Loss of education for the majority of the world’s children;Increased debt5.Regarding the situation in Africa, which are true? ( )答案:Economic effects have been greater in countries which rely on tourism ;There has been a reversal of progress towards poverty reduction goals第四章测试1.How many people die every year from noncommunicable diseases (NCDs),including cancer, heart diseases and stroke, diabetes, and chronic respiratory diseases? （）答案:40 million people2.Of the following, which disease causes most death worldwide? （）答案:Cardiovascular disease3.Women around the world are most likely to die from: （）答案:Heart disease4.What proportion of cancers can be prevented? （）答案:30%-50%ernments have agreed to reduce premature NCD deaths by the year 2030.（）答案:对第五章测试1.What is the direct effect of conflict on population health ( )答案:Mortality;Morbidity;Mental health2.What are the existing approaches to address food security? ( )答案:Diversification of crop production;Laws regulating food production and quality control3.Exposure to ambient air pollution can cause . ( )答案:respiratory diseases;cancers;cardiovascular diseasesmon health problems in cities result from: （）答案:Poor diets;Limited exercise opportunities.5.Measures to improve living conditions in big cities include: （）答案:Convenient affordable comfortable public transport;Safe neighbourhoods;Access to fresh food第六章测试1.What are the top 3 causes of death in under-5 children? ( )答案:pneumonia;injuries;diarrhea2.MDG 4 requires care for newborns and their mothers; infant and young childfeeding; vaccines; prevention and case management of various diseases. ( )答案:对3.Physical or sexual violence has a profound impact on women, including . ( )答案:sexual health;physical health;mental health;reproductive health4.Which of these are important reasons for high mortality and injury fromRTAs in low income countries? ( )答案:Poor quality old cars with no safety features;Increase in car use without matching improvement in infrastructure5.Which measures have been shown to reduce injury and death from RTAs? ( )答案:Speed cameras;Banning use of mobile phones while driving第七章测试1.China has been engaged in health diplomacy in Africa since ( )答案:19632.The criticisms of UN organization include: ( )答案:Resources often don’t reach the people most in need.;There is poor accountability;They are independent of each other, and often don’t collaborate witheach other even on the same problems3.There are many organisations involved in global health. What are the some ofthe consequences of this? ( )答案:Competition, especially for funding;Unnecessary duplication of activities;Good collaboration;Organisations may focus on their own priorities, and not necessarily the priority needs of the recipient country4.Relatively poor countries face a triple burden of disease from which of thefollowing:（）答案:Communicable diseases, injuries, non-communicable diseasespared with high income countries, which of these is true of most low-income countries? ( )答案:There is higher private healthcare spending第八章测试1.According to a Mali an doctor in Mali it’s easy to buy antibiotics just likebuying peanuts.（）答案:对2.Technologies in global health cannot be applied to use in low- and middle-income countries to address high burden disease. ( )答案:错3.What technologies below can be applied in health? ( )答案:Machine learning;AI;Deep learning;Big data4.Which of the following is not considered a middle-income country? ( ）答案:Belgium5.Which of the following are risk factors for road traffic injuries? （）答案:Increasing use of vehicles。

小学上册第7次英语第3单元真题试卷

小学上册英语第3单元真题试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The _____ (树) is tall and strong.2.The chemical symbol for gallium is ______.3. A ____(hot spring) is a natural pool of warm water.4.The atomic structure of an atom consists of protons, neutrons, and _____ (electrons).5.The teacher _____ the students' questions. (answers)6.I see a rainbow after the ______ (storm).7.In which month do we celebrate Christmas?A. NovemberB. DecemberC. JanuaryD. October8.The dog is ______ to the park. (going)9.The flowers bloom in _____ (spring/winter).10. A diverging lens spreads out light rays, making objects appear ______ (smaller).11.I want to _______ (认识) new people.12.I want to _______ (参加) a dance class.13.The country of Norway is famous for its ________ (挪威以其________而闻名).14.The process of separating mixtures based on their boiling points is called _______.15.I tell my __________ about my day. (父母)16. A _______ can symbolize growth and renewal.17.What do we call a person who repairs cars?A. DoctorB. MechanicC. EngineerD. ElectricianB18.What is the square root of 9?A. 2B. 3C. 4D. 5B19.The ______ is the energy source for plants.20.I believe everyone should try to be __________. It helps create a friendly environment. When I see someone in need, I try to __________ to help them.21.The __________ (历史研究) can influence current events.22.Which instrument has 88 keys?A. OrganB. HarpC. PianoD. Accordion答案:C23.The butterfly's bright colors help it attract ______ (配偶).24.What is the capital of South Korea?A. SeoulB. TokyoC. BeijingD. PyongyangA25.What is the name of the famous natural wonder located in Arizona?A. Grand CanyonB. Niagara FallsC. Mount RushmoreD. YosemiteA26.I love to explore ________ (村庄) during vacations.27.Flowers bloom in ______ (春天).28.I can _______ (说) three languages.29.The _____ of a solution tells us how much solute is dissolved in a given amount of solvent.30.Herbs like basil and mint are often used in _______.31.She is a great ________.32.The _____ (sky/ground) is clear.33.What is the name of the famous mountain range in North America?A. Rocky MountainsB. Appalachian MountainsC. Sierra NevadaD. Cascade RangeA34.What is the name of the famous ancient ruin in Peru?A. Machu PicchuB. TikalC. PetraD. StonehengeA Machu Picchu35. A saturated fat is solid at ______ temperature.36. A _______ can help to visualize the forces acting on an object.37.I can ______ (提高) my skills through practice.38.My birthday is in ___. (April)39. A saturated solution is in ______ equilibrium.40.My brother is good at ____.41. A ____ is a playful animal that chases after friends.42.What is the name of the layer of atmosphere closest to Earth's surface?A. TroposphereB. StratosphereC. MesosphereD. Thermosphere43.The _____ can affect the tides on Earth.44.The chemical symbol for neptunium is _____.45.The __________ (历史的回响) echoes through time.46.Catalysts are not consumed in a ______.47.What is the name of the largest volcano in the solar system, found on Mars?A. Olympus MonsB. Mauna KeaC. Mount EverestD. K248.What is the main ingredient in an omelet?A. RiceB. EggsC. BreadD. MilkB49. A __________ is formed when water evaporates and leaves minerals behind.50.Which fruit has seeds on the outside?A. KiwiB. StrawberryC. BananaD. CherryB51.Which animal is known for its ability to change colors?A. ChameleonB. LionC. EagleD. SharkA52.We have ___ (history/math) class today.53.What do we call a young eagle?A. EagletB. ChickC. CalfD. Pup54.What is the capital of France?A. RomeB. ParisC. LondonD. BerlinB55.My ______ loves to help people in need.56.I enjoy playing ______ (足球) with my team on Saturdays.57.The _______ (小海马) swims in the sea among the coral.58.I like to sing ______ songs with my friends.59. A parrot can live for many ______ (年).60.What is the capital of Angola?A. LuandaB. BenguelaC. HuamboD. LubangoA61.plate tectonics) theory explains earthquakes. The ____62.What do we call a young female sheep?A. EweB. LambC. KidD. Calf63.I can ______ (jump) really far.64.The pizza is ___ (delicious/yummy).65. A crab can hide in the _______ (沙子).66.Plants bring ______ (快乐) to our lives.67. A __________ is a chemical change that produces light and heat.68. A seismograph measures the ______ (intensity) of an earthquake.69.What do we call a scientist who studies the weather?A. MeteorologistB. ClimatologistC. Environmental ScientistD. Geochemist70.We will visit the _____ (museum/park) this weekend.71.What do we call a person who studies the history of literature?A. Literary ScholarB. HistorianC. CriticD. AuthorA72.小羊) follows its mother in the field. The ___73.The __________ (种子的发芽) is an exciting process.74. A _______ is a small particle made up of atoms.75.The __________ (历史的构成要素) shape our narratives.76.I enjoy listening to ________ (民谣音乐) at home.77.The sunflowers reach for the _______ every day.78.What do you call a short story that teaches a lesson?A. TaleB. FableC. MythD. Legend79.The clock shows _____ (three/four) o'clock.80.The __________ (奥林匹克运动会) originated in ancient Greece.81.What is the name of the famous artist known for his paintings of sunflowers?A. Vincent van GoghB. Pablo PicassoC. Claude MonetD. Salvador Dalí82.The _______ (小鸟) sings beautifully.83.What do you call the line that separates two countries?A. BoundaryB. BorderC. FrontierD. Division84.What do you call a large animal that lives in the ocean and has fins?A. SharkB. DolphinC. WhaleD. All of the aboveD85.I think it’s important to ________ (保持友好).86.They are _______ (taking) a trip this summer.87.The first African American to serve in the U.S. Senate was _______.88.The first American flag was sewn by _______ Ross.89.The chemical formula for dodecanoic acid is ______.90.What is the capital city of Mexico?A. CancunB. GuadalajaraC. Mexico CityD. Tijuana91.I love to read ______ (书) about animals. They teach me a lot of ______ (知识).92.What is the largest planet in our solar system?A. EarthB. MarsC. JupiterD. Saturn93.What do we call a group of penguins?A. ColonyB. GaggleC. PackD. FlockA Colony94.What fruit is known for having seeds on the outside?A. StrawberryB. BlackberryC. RaspberryD. BlueberryA95.The ________ (baby) is crawling on the floor.96.She is _______ (sharing) her snacks with friends.97.What do you call a person who studies the brain?A. NeurologistB. PsychologistC. PsychiatristD. BiologistA98.What insect makes honey?A. AntB. BeeC. FlyD. MosquitoB Bee99. A reduction reaction involves the gain of ______.100.Please tell your _____ (老师) about the project.。

职称英语理工类阅读判断真题

职称英语理工类阅读判断真题考试的阅读判断题型，要求考生判断题目所给出的句子。

下面是的理工类阅读判断真题，欢送欣赏!Scientists have long speculated as to why animalspecies didn’t flourish sooner, once sufficient oxygen covered the Earth’s surface. Animals began to prosper at the end of the Proterozoic period, about 800 million years ago — but what about the billion-year stretch before that, when most researchers think there also was plenty of oxygen?Well, it seems the air wasn’t so great then, after all.In a study published Oct. 31 in Science, Yaleresearcher Noah Planavsky and his colleagues found that oxygen levels during the “boring billion” period wereonly 0.1% of what they are today. In other words, Earth’s atmosphere couldn’t have supported a diversity of creatures, no matter what geic advancements were poised to our.“There is no question that geic and ecological innovation must ultimately be behind the rise of animals, but it is equally unavoidable that animals need a certain level of oxygen,” said Planavsky, co-lead author of the research along with Christopher Reinhard of the Georgia Institute of Technology. “We’re providing the first evidence that oxygen levels were low enough during this period to potentially prevent the rise of animals.”The scientists found their evidence by analyzing chromium (Cr) isotopes in ancient sediments from China, Australia, Canada, and the United States. Chromium is found in the Earth’s continental crust, and chromium oxidationis directly linked to the presence of free oxygen in the atmosphere.Specifically, the team studied samples deposited in shallow, iron-rich ocean areas, near the shore. They pared their data with other samples taken from younger locales known to have higher levels of oxygen.Oxygen’s role in controlling the first appearance of animals has long vexed scientists. “We were missing the right approach until now,” Planavsky said. “Chromium gave us the proxy.” Previous estimates put the oxygen level at 40% of today’s conditions during pre-animal times, leaving open the possibility that oxygen was already plentiful enough to support animal life.In the new study, the researchers acknowledged that oxygen levels were “highly dynamic” in the early atmosphere, with the potential for oasional spikes. However, they said, “It seems clear th at there is a first-order difference in the nature of Earth surface Cr cycling” before and after the rise of animals.“If we are right, our results will really change how people view the origins of animals and other plex life, andtheir relationships to the co-evolving environment,” said co-author Tim Lyons of the University of California-Riverside. “This could be a game changer.”“There’s a lot of interest right now in a broader discussion surrounding the role that environmentalstability played in the evolution of plex life, and wethink our results are a significant contribution to that,” Reinhard said.16. The study discovered the rise of animals ourred earlier than the Proterozoic period.A. RightB. WrongC. Not mentioned17. Many researchers believe the oxygen level was high during pre-animal times.A. RightB. WrongC. Not mentioned18. The team was funded by several research institutes.A. RightB. WrongC. Not mentioned19. Geic advancements triggered the rise of animals.A. RightB. WrongC. Not mentioned20. The samples studied in the research were collected in ocean areas.A. RightB. WrongC. Not mentioned21. The study revealed that chromium found in Earth’s continental crust remained stable before and after the rise of animals.A. RightB. WrongC. Not mentioned22. Tim Lyons liked to play puter games in his spare time.A. RightB. WrongC. Not mentionedChildren have an increased of attention problems, seen as early as grade school. If their noses inhaled(吸入)a certain type of air pollution when they were pregnant.That's the finding of a new study. Released when things aren't burned pletely, this pollution is known aspolycyclic aromatic hydrocarbons, or PAHs. The biggest sources of these PAHs: the burning of fossil fuels, wood and trash.Frederica Perera works at Columbia University's Mailman School of Public Health is New York City. She researches how exposure to things in the environment affectschildren's health in a new study, she and her team studied the exposure to air pollution of 233 nonsmoking pregnant women in New York City. Because burning tobao can spew(排放)PAHs into the air and lungs, Perera's team focused on nonsmokers. The researchers wanted to probe(探查)other sources of PAHs, ones that's would have been hard for an individual to avoid.The team started by testing the blood of each woman during pregnancy. The reason Any PAHs in a woman's blood would also be available to the baby in her womb. Nine years later, the researchers investigated signs of attentionproblems in those children, now age 9. They asked eachchild's mother a series of questions. These included whatever her child had problems doing things that needed sustained(长期的)mental effort, such as homework or games with friends. The scientists also asked if the kids had trouble following instructions or made frequent, careless mistakes. All of these can be symptoms of a disorder called Attention Deficit Hyperactivity Disorder, or ADHD. About one in U.S. children has ADHD.Among the women studied, traffic and home heating were the primary sources of air pollution exposure, Perera and her team suspect. Some of these women had low levels of PAHs in their blood. Ohters had high levels. Those with high levels were five times as likely to have children who showed attention problems by age 9. The new findings were published November 5 in the journal PLOS ONE.16. Perera and her team chose nonsmoking pregnant women all over America.A. RightB. WrongC. Not mentioned17. The main purpose of the research was to find out how exposure to PAHs played a role in harming the subjects' physical health.A. RightB. WrongC. Not mentioned18. Nonsmoking mothers were selected because the effect of smoking on PAHs was unclear.A. RightB. WrongC. Not mentioned19. The blood of each woman was tested once a month during pregnancy.A. RightB. WrongC. Not mentioned20 Kids with ADHD monly fail in school.A. RightB. WrongC. Not mentioned21. The women with high levels of PAHs in their blood were more likely to have kids with ADHD.A. RightB. WrongC. Not mentioned22. Traffic and home heating were considered to be the biggest sources of PAHs for the subjects in the research.A. RightB. WrongC. Not mentionedChildren have an increased risk of attention problems，seen as early as grade school , if their moms inhaled(吸入)a certain type of air pollution when they were pregnant. That's the finding of a new study. Released when thingsaren't burned pletely, this pollution is known aspolycyclic aromatic hydrocarbons, or PAHs. The biggest sources of these PAHs: the burning of fossil fuels, woodand trash.Frederica Perera works at Columbia University's Mailman School of Public Health in New York City. She researcheshow exposure to things in the environment affectschildren's health. In a new study , she and her teamstudied the exposure to air pollution of 233 nonsmoking pregnant women in New York City. Because burning tobao can spew(排放) PAHs into the air and lungs, Perera's team focused on nonsmokers. The researchers wanted to probe(探查) other sources of PAHs, ones that would have been hard foran individual to avoid.The team started by testing the blood of each woman during pregnancy. The reason: Any PAHs in a woman's blood would also be available to the baby in her womb. Nine years later, the researchers investigated signs of attention problems in these children, now age 9. They asked eachchild's mother a series of questions. These includedwhether her child had problems doing things that needed sustained(长期的) mental effort, such as homework or games with friends. The scientists also asked if the kids had trouble following instructions or made frequent, careless mistakes. All of these can be symptoms of a disorder called Attention Deficit Hyperactivity Disorder, or ADHD. About one in 10 U.S. children has ADHD.Among the women studied, traffic and home heating were the primary sources of air pollution exposure, Perera and her team suspect. Some of these women had low levels of PAHs in their blood. Others had high levels. Those with high levels were five times as likely to have children who showed attention problems by age 9. The new findings were published November 5 in the journal PLOS ONE.16. Perera and her team chose nonsmoking pregnant women all over AmericaA. RightB. WrongC. Not mentioned17. The main purpose of the research was to find out how exposure to PAHs played a role in harming the subjects' physical health.A. RightB. WrongC. Not mentioned18. Nonsmoking mothers were selected because the effect of smoking on PAHs was unclear.A. RightB. WrongC. Not mentioned19. The blood of each women was tested once a month during pregnancy.A. RightB. WrongC. Not mentioned20. Kids with ADHD monly fail in school.A. RightB. WrongC. Not mentioned21. The women with high levels of PAHs in their blood were more likely to have kids with ADHDA. RightB. WrongC. Not mentioned22. Traffic and home heating were considered to be the biggest sources of PAHs for the subjects in the research.A. RightB. WrongC. Not mentioned。

九江2024年01版小学6年级下册第十四次英语第1单元真题试卷

九江2024年01版小学6年级下册英语第1单元真题试卷考试时间：90分钟（总分:140）B卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、听力题：My grandma loves to make ____ (sauces).2、What is the capital of Italy?A. RomeB. MilanC. VeniceD. Florence答案:A3、听力题：A flammable substance can easily catch _______.4、填空题：I love to create new __________ (名词) with my __________ (玩具名).5、听力填空题：I love discovering new hobbies. Recently, I started __________, and it has been an exciting adventure. Trying new things helps me learn more about myself.6、听力题：The Moon's gravitational pull causes ______ on Earth.7、填空题：I have a green ______ (植物) in my room. It makes the air feel ______ (清新).8、填空题：Many fruits come from flowering ________ (植物).9、填空题：In the zoo, I saw a ________ (大象). It was so ________ (大) and friendly.10、听力题：We have _____ (two/four) eyes.11、听力题：Metals are usually ______ and can be shaped easily.12、听力题：The first human to journey into space was _______ Gagarin.13、听力题：The concept of climate resilience prepares communities for ______ impacts.14、填空题：My favorite activity is ______ (骑行).15、听力题：A river can shape the land through ______ over time.16、填空题：The turtle is very ______.17、What is the name of the famous mountain range in Europe?A. HimalayasB. AndesC. AlpsD. Rockies答案: C18、What do you call a person who studies the history of the Earth?A. GeologistB. HistorianC. BiologistD. Chemist答案: A19、填空题：The ______ (植物的维护) requires consistent effort.20、填空题：The __________ (生态研究) informs public policy.21、填空题：I like to ______ (参与) in artistic activities.22、What is the term for a young male horse?A. ColtC. FillyD. Foal答案：A23、What do we call a person who studies the effects of climate on biodiversity?A. EcologistB. BiologistC. ConservationistD. Environmental Scientist答案: A24、听力题：The most abundant gas in the Earth's atmosphere is _______.25、听力题：My dad likes to go cycling in the ____ (park).26、填空题：I find ________ (宇宙) fascinating and mysterious.27、What is the color of grass?A. BlueB. GreenC. PurpleD. Orange答案:B28、What is the term for a person who studies animals?A. ZoologistB. BotanistC. EcologistD. Biologist答案:A29、填空题：I love _____ (planting) flowers in the spring.30、填空题：A chameleon can shift its color to communicate or ______ (伪装).31、What do bees produce?A. MilkB. HoneyC. Butter答案:B32、选择题：What is the capital of Uzbekistan?A. TashkentB. SamarkandC. BukharaD. Andijan33、听力题：She is planting a ___. (tree)34、填空题：A snail carries its home on its ______ (背上).35、听力题：The boy plays ________.36、填空题：The discovery of ________ has drastically changed our approach to agriculture.37、听力题：The process of mixing two liquids to create a solid is called ______.38、填空题：My sister loves to dance. She takes ________ (舞蹈课) every week and performs at ________ (表演).39、填空题：A fish lives in _________ (水).40、How many sides does a triangle have?A. TwoB. ThreeC. FourD. Five答案:B41、听力题：When ice melts, it turns into __________.42、选择题：What do we call a person who plays the piano?A. PianistB. KeyboardistC. MusicianD. All of the above43、填空题：The stars are _______ (璀璨的).44、填空题：The tortoise is slow but very _______ (坚韧).45、填空题：I enjoy showing my friends my newest ____. (玩具名称)46、填空题：In conclusion, my best friend is ______ because they make my life better. I am so grateful to have them by my side!47、填空题：The blue color of copper sulfate is an example of a _______. (化合物)48、听力题：The ______ teaches us about environmental issues.49、 (Japanese) feudal system included samurai warriors. 填空题：The ____50、填空题：My sister loves to __________ (跳舞) at parties.51、听力题：The ______ works with computers.52、听力题：The kids are _____ (laughing/crying) at the park.53、选择题：What is the freezing point of water?A. 0 degrees CelsiusB. 100 degrees CelsiusC. 50 degrees CelsiusD. 25 degrees Celsius54、填空题：The ferret is very playful and likes to ______ (打滚).55、填空题：The __________ (三藩市) earthquake happened in 1906.56、What do you call a person who teaches others?A. EducatorB. InstructorC. MentorD. All of the above答案:D57、听力题：A pulley can help lift heavy ______.58、填空题：I enjoy going to the ______ (咖啡馆) with my friends to chat and relax. It’s a cozy place.59、听力题：He ___ to school every day. (walk, walks, walking)60、填空题：Every night, I look up at the ______ (星星) and make a wish. It feels magical to see them twinkle.61、填空题：_____ (保湿) is required for some tropical plants.62、填空题：My uncle is a __________ (社会学家).63、restoration ecology) aims to rehabilitate ecosystems. 填空题：The ____64、听力题：The ______ is the smallest unit of matter.65、What is the square root of 9?A. 2B. 3C. 4D. 5答案:B66、How many hours are in a day?A. 24B. 12C. 48D. 36答案:AThe __________ is a large lake located in North America. (五大湖)68、填空题：The wind makes the trees ______ (摇摆).69、听力题：I want to ______ how to skateboard. (learn)70、填空题：The vulture cleans up ______ (尸体) in nature.71、听力题：A rocket uses thrust to move _______.72、填空题：The ______ (果汁) of some fruits is refreshing and tasty.73、填空题：A ________ (植物研究中心) promotes innovation.74、What is the capital of Georgia (the country)?a. Tbilisib. Batumic. Kutaisid. Rustavi答案:a75、听力题：A _______ is a chemical property that describes how a substance reacts with oxygen.76、听力题：I have a red ___. (balloon)77、填空题：The __________ (历史的多重解读) enrich our knowledge.78、听力题：Many _______ produce seeds for future generations.79、填空题：A _______ (小鸽子) coos softly on the ledge.80、填空题：A porcupine can defend itself with its ________________ (刺).I need to _______ (practice) my speech.82、选择题：What is the opposite of rich?A. PoorB. WealthyC. AffluentD. Abundant83、填空题：I enjoy ________ (看书) before bedtime.84、听力题：The _______ of an object can change when it is moved.85、填空题：The ________ is one of the Seven Wonders of the Ancient World.86、听力题：The land beneath our feet is called the ______.87、听力题：A chemical reaction can occur at different _____.88、What is the capital of Canada?A. TorontoB. OttawaC. VancouverD. Montreal答案: B. Ottawa89、What is the capital city of Norway?A. OsloB. BergenC. StavangerD. Trondheim90、听力题：The chemical formula for linoleic acid is ______.91、What do we call the brightness of a star as seen from Earth?A. MagnitudeB. LuminosityC. IntensityD. Brightness92、What is the largest land animal?A. HorseB. RhinoC. ElephantD. Giraffe答案: C93、填空题：The ________ was a pivotal moment in the narrative of national identity.94、What is the color of an orange?A. GreenB. YellowC. OrangeD. Purple答案:C95、How many points is a touchdown worth in American football?A. 3B. 5C. 6D. 7答案: C96、填空题：The _______ (The Berlin Wall) fell in 1989, signaling the end of the Cold War.97、听力填空题：I think kindness is essential in our daily lives. Simple acts of kindness can brighten someone’s day. I try to spread kindness by __________ whenever I can.98、What do we call a young elephant?A. CalfB. FawnC. KidD. Cub答案: A99、听力题：A ____ hops around and has long ears.100、听力题：The chameleon has a long _______ to catch insects.。

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conductivity.
INTRODUCTION
The figure of merit of thermoelectric materials depends on the value of (m */mo)3/2 * h/K, where m *, b and K are the effective mass, mobility of the charge carriers, and lattice thermal conductivity, respectively. Therefore, the emphasis of studies of these materials has been to find the composition which has the largest value of (m */rn,,)‘j2. p,,/K, and then to optimize the carrier concentration by doping so as to give the largest figure of merit. In our previous paper [l], we confirmed the result of Yim et al. (21 that the figure of merit of p-type bismuth telluride-based solid solutions has the largest value around the composition 25%Bi2Te3-75%Sb2Te3, which is widely used as a room temperature thermoelectric material. There were, however, too many positive holes at this composition to optimize the figure of merit, and it is a well known fact [3] that these holes are created by antistructure defects. Therefore, the hole concentration is usually reduced by compensation of the antistructure defects by the addition of excess Te to the melt. However, the thermoelectric properties of this p-type material vary considerably with radial and longitudinal directions of the ingot owing to the complex behavior of excess Te under different growth conditions. There have been several reports [2,4-g] on the effects of various process parameters on the thermoelectric properties of Bi,Te,-Sb2Te3 solid sol-
thermoelectric properties of Bi,Te,-Sb,Te, solid solutions are closely related to excess Te in the melt during growth of ingots. The role of excess Te in connection with various process parameters which affect the thermoelectric properties ofp-type Bi,Te,-Sb*Te, solid solutions have been studied using the zone melting and Bridgman methods. The growth speed and amount of excess Te are important in optimizing the figure of merit. When the process parameters were optimized, a maximum figure of merit of 2.95 x IO-’ K-’ was obtained by the zone melting method at a rate of 0. I mm min-’ for a composition 22.5%Bi,Te,-77S%Sb,Te, with 5 wt% excess Te in the melt. The effect of annealing of as-grown ingots
(2)
ach-a,,’
(3) T
(a,-ac(p,)z.I. AV, and AL’? were measured by a scanning multimeter controlled by a personal computer. The absolute Seebeck coefficients of alumel (a,,) and chrome1 (a,,) wires were obtained by measuring the differential Seebeck coefficient of a,, _ r, and ach_ p, and using the absolute Seebeck coefficient of Pt (ap,) measured by Cusack et al. [I I]. 2.2. Electrical resistivity, thermal conductivity and figure of merit. The figure of merit was measured by a z-meter according to the Harman method [l2]. Four Pt wires of 40 pm diameter were spot-welded to a rectangular specimen, two for current flow and the other two for voltage measurement. The resistance of the specimen was obtained by measuring the voltages with a.c. and d.c. currents provided by a 120 Hz square wave generator. The electrical resistivity p, thermal conductivity K and figure of merit Z can be calculated from the following eqns (3)-(S) using the
THE EFFECT OF EXCESS TELLURIUM ON THE THERM0 ELECTRIC PROPERTIES OF Bi, Te,-Sb, Te, SOLID SOLUTIONS
HEON PHIL HA, YOUNG WHAN CHO, JI YOUNG BYUN
and
JAE DONG SHIM
Korean Institute of Science and Technology, P.O. Box 131. Cheongryang, Seoul, South Korea
(Received 3 February 1994; accepted 12 May 1994) Abstract-The
qf thermoelectric
properties
2.1. Seebeck coe@cient. The Seebeck coefficient was measured by the heat pulse method [IO]. Ktype thermocouples were attached to both sides of the rectangular sample by a compression-loading method. After a certain temperature difference between the two ends of the sample had been established with a miniature heater, the differential Seebeck voltages A V, = (a,, - a,)AT and AVz = (tl,, - a,)AT were measured. The Seebeck coefficient of the sample (c(,) was calculated from eqns (I) and (2).
1233
1234
HEON PHIL HA et a/. properties parallel to the growth
300 0
l
of thermoelectric direction.
.
,
,
0.1 mtNmln
, 22.5%El21.3
, - 77.5%Sb2T+
1
I
0.5mmtmln
2. Characterization
J. P/tqx Chr.
Pergnmon
. .
So/ids Vol. 55. No. I I. pp. 1233-12311. 1994 Copyright (’ 1994 Elscvier Science Lid Prinml in GIWI Britain. All rights rearmed 0022-3697/W f7.00 + 0.00