Practical comparison of fast public-key cryptosystems
四级对比观点类型英语范文
四级对比观点类型英语范文In the realm of academic pursuits, the debate over the importance of theoretical knowledge versus practical skills is a perennial one. This discourse is particularly relevant in the context of higher education and job market readiness. On one hand, proponents of theoretical knowledge argue that it forms the foundation of understanding in any field, providing a framework within which practical skills can be developed. On the other hand, advocates for practical skills assert that in a rapidly evolving job market, the ability to apply knowledge effectively is paramount.Theoretical knowledge, often derived from textbooks, lectures, and rigorous study, is undeniably valuable. It equips students with fundamental principles and concepts that are essential for deep comprehension. For instance, in the field of science, understanding the laws of physics is crucial before one can engage in experiments and practical applications. This knowledge allows for predictions, explanations, and the development of new hypotheses. It is the bedrock upon which innovation is built.Conversely, practical skills are the tools that enable individuals to execute tasks efficiently and effectively. In many professions, such as engineering or medicine, the ability to apply theoretical knowledge to real-world scenarios is what defines success. Practical skills foster adaptability and problem-solving abilities, which are highly sought after in today's dynamic work environments. They are the means through which theoretical knowledge is translated into tangible outcomes.The interdependence of theory and practice is evident when one considers the historical advancements in various fields. Theoretical breakthroughs often precede technological leaps, yet it is the application of these theories that propels society forward. For example, the theoretical underpinnings of electricity were established long before the invention of the light bulb. However, it was the practical application of these theories that illuminated the world.In the educational sphere, this dichotomy influences curriculum design. A balanced approach that integrates both theoretical knowledge and practical skills is widelyconsidered the most effective. This hybrid model ensures that students are not only well-versed in the foundational aspects of their field but are also capable of applying their knowledge in practical settings. Such an approach prepares students for the complexities of the workforce and fosters lifelong learning.The debate extends to the evaluation of job candidates. Employers often seek a combination of deep understanding and the ability to apply knowledge. In competitive job markets, candidates who demonstrate both strong theoretical foundations and robust practical skills are more likely to excel. This duality is particularly crucial in industries that are subject to rapid change, where the capacity to learn and adapt is as important as existing knowledge and skills.In conclusion, the juxtaposition of theoretical knowledge and practical skills is not a matter of choosing one over the other but recognizing the value of both. Education systems and employers alike must acknowledge the symbiotic relationship between the two. As the world continues to evolve, the fusion of deep, theoretical understanding with the proficiency of practical application will remain the cornerstone of progress and innovation. The harmonious blend of these elements is what will drive the next generation of leaders, thinkers, and doers to achieve greatness in their respective domains. 。
对比的英语作文
对比的英语作文In the realm of English composition, the skill of comparison is a powerful tool that can enhance the quality and impact of a writer's work. It allows for a deeper exploration of ideas, the highlighting of similarities and differences, and can make complex concepts more accessible to readers. This essay will delve into the techniques of comparative writing, its benefits, and how it can be effectively employed in various types of compositions.Understanding ComparisonComparison is a method of identifying and examining the similarities and differences between two or more subjects. In English, this is often achieved through the use of comparative and superlative forms of adjectives and adverbs, as well as conjunctions and phrases that signal a comparison, such as "similarly," "in contrast," and "whereas."Techniques of Comparative Writing1. Analogies: Drawing parallels between two seemingly unrelated subjects can provide a fresh perspective and help readers understand complex ideas. For example, comparing the workings of a clock to the human heart can clarify the concept of how the heart functions.2. Contrastive Essays: These focus on the differences betweensubjects. By outlining the distinctions, a writer can emphasize the unique characteristics of each subject.3. Point-by-Point Comparison: In this method, each point of comparison is addressed separately, allowing for a clear and organized presentation of similarities and differences.4. Thematic Comparison: This involves comparing the themes or underlying messages of different texts, which can lead to a deeper understanding of the subject matter.Benefits of Comparative Writing1. Enhanced Clarity: Comparisons can simplify abstract ideas by relating them to familiar concepts or experiences.2. Improved Persuasiveness: By highlighting the similarities or differences, a writer can strengthen their argument and persuade readers to adopt a particular viewpoint.3. Greater Engagement: A well-crafted comparison can intrigue readers, prompting them to think more deeply about the subjects being compared.4. Educational Value: In academic writing, comparison can bea means to explore multiple theories or viewpoints, fostering critical thinking and analysis.Effective Use of ComparisonTo effectively use comparison in an essay, a writer should:- Choose Relevant Subjects: Ensure that the subjects being compared are relevant to the essay's purpose and can provide meaningful insights.- Be Clear and Specific: Vague comparisons can confuse readers. It's important to be explicit about what is being compared and why.- Use a Structured Approach: Organize the essay in a way that logically presents each point of comparison.- Avoid Overgeneralization: While making comparisons, it's crucial to avoid sweeping generalizations that may not hold true in all cases.ConclusionThe art of comparison in English composition is a nuancedskill that, when mastered, can significantly enhance awriter's ability to convey ideas and engage readers. By understanding the techniques, recognizing the benefits, and applying a structured approach, a writer can effectively employ comparison to illuminate, persuade, and educate.。
对比类英语作文
对比类英语作文In the modern era, where technology and urbanization are rapidly advancing, the distinction between urban and rural lifestyles has become increasingly pronounced. This essayaims to explore the key differences in various aspects oflife, including the environment, community, opportunities,and lifestyle choices.EnvironmentUrban life is characterized by skyscrapers, bustling streets, and a fast-paced environment. The city offers a vibrant atmosphere with a multitude of cultural and entertainment options. However, this comes at the cost of noise pollution,air pollution, and a higher cost of living. In contrast,rural life is often associated with tranquility, open spaces, and a closer connection to nature. The slower pace andcleaner air can be beneficial for one's health and well-being. CommunityThe sense of community in rural areas tends to be tighter-knit, with people knowing each other well and often having multi-generational ties to the same community. This can leadto strong support networks and a sense of belonging. On the other hand, urban communities are more diverse and can offera broader social network. However, the anonymity of city life can sometimes make it challenging to forge deep, lastingrelationships.OpportunitiesCities are economic hubs, providing a wealth of job opportunities across various industries. The availability of educational institutions, healthcare facilities, and entertainment options is typically higher in urban areas.Rural areas, while offering a more relaxed lifestyle, mayhave limited job prospects and fewer resources forprofessional and educational development.Lifestyle ChoicesThe lifestyle in urban areas is often more fast-paced and competitive, with a focus on career advancement and material success. The city offers a wide array of activities and amenities, from restaurants and clubs to theaters and museums. Rural life, conversely, is generally slower and more self-sufficient, with a focus on simplicity and community involvement. The rural lifestyle can be more conducive to outdoor activities and a closer relationship with the land.ConclusionBoth urban and rural lifestyles offer unique advantages and challenges. The choice between them often depends on personal preferences, career goals, and the desired quality of life. While urban living provides convenience and a wealth of opportunities, rural living offers a peaceful and close-knitcommunity experience. Ultimately, the best choice is the one that aligns with an individual's values and aspirations.。
在临床实际应用和科研工作中评价胰岛素敏感性(英文版)
December2003:397–412 Lead Review ArticleEvaluation of Insulin Sensitivity in Clinical Practice and in Research SettingsLais U.Monzillo,M.D.,and Osama Hamdy,M.D.,Ph.D.Insulin resistance is the core metabolic abnormal-ity in type2diabetes.Its high prevalence and its association with dyslipidemia,hypertension,hy-perinsulinemia,and high coronary and cerebro-vascular mortality put it in the forefront as the plausible target for aggressive intervention.Mea-surements of insulin sensitivity provide clinicians and clinical researchers with invaluable instru-ments to objectively evaluate the efficiency of both current and potentially useful interventional tools.Although several methods had been devel-oped and validated to evaluate insulin sensitivity, none of these methods can be universally used in all patients.Nonetheless,a method suitable for use in clinical or basic research may not neces-sarily be a practical method for use in clinical practice or for epidemiologic research.We re-viewed the currently used methods for assess-ment of insulin sensitivity.For each method,we summarized its procedure,normal value,cut-off value for defining insulin resistance,advantages and limitations,validity,accuracy for each patient population,and suitability for use in clinical prac-tice and in research settings.The methods re-viewed include fasting plasma insulin,homeo-static model assessment,quantitative insulin sensitivity check index,glucose-to-insulin ratio, continuous infusion of glucose with model as-sessment,indices based on oral glucose toler-ance test,insulin tolerance test,and the so called “gold standard”methods,the hyperinsulinemic euglycemic clamp and the frequently sampled–intravenous glucose tolerance test.Key words:insulin resistance,insulin sensitivity, clinical practice©2003International Life Sciences Institutedoi:10.1301/nr.2003.dec.397–412IntroductionInsulin resistance is a state in which physiologic concen-trations of insulin produce a subnormal biologic re-sponse.1It underlies abnormalities of glucose,lipid,and blood pressure homeostasis.2This cluster of metabolic abnormalities is referred to as the insulin resistance syndrome,syndrome X,or the metabolic syndrome,and is related to type2diabetes,obesity,hypertension,and dyslipidemia.3–5In fact,insulin resistance is present long before the clinical manifestations of the individual com-ponents of the syndrome.6–8Epidemiologic evidence indicates that insulin resistance is directly related to the risk of developing atherosclerosis and cardiovascular disease.9–11To clinically identify patients with the metabolic syndrome,the National Cholesterol Education Program Expert Panel on Detection,Evaluation,and Treatment of High Blood Cholesterol in Adults(Adult Treatment Panel III,ATP III)suggested that individuals having three or more of the following criteria are defined as having the metabolic syndrome:121.Abdominal obesity:waist circumferenceϾ40inchesin men andϾ35inches in women;2.Hypertriglyceridemia:Ͼ150mg/dL(1.69mmol/L);3.Low high-density lipoprotein(HDL)cholesterol:Ͻ40mg/dL(1.04mmol/L)in men andϽ50mg/dL(1.29mmol/L)in women;4.High blood pressure:Ն130/85mmHg;5.High fasting plasma glucose:Ն110mg/dL(Ն6.1mmol/L).A recent epidemiologic study among adults above age20 showed that the age-adjusted prevalence of the metabolic syndrome in the United States is23.7%,with a higher prevalence among minority populations.13Several clinical trials have shown that lifestyle mod-ification delays the progression to type2diabetes among individuals with impaired glucose tolerance;14–17how-ever,none of these studies included quantitative evalu-ation of insulin sensitivity as an integral component of the study design.It is possible that an improvement in insulin sensitivity can be achieved either through life-style modification18–21or pharmacologically with met-Drs.Monzillo and Hamdy are with the Clinical Research Center,Joslin Diabetes Center;Department of Medicine,Harvard Medical School,Boston,MA 02215,USA.formin22,23or thiazolidinediones.24–26The Food and Drug Association(FDA)has not approved either of these pharmacologic compounds for treatment of insulin resis-tance in nondiabetic individuals;however,the diagnosis of type2diabetes,hypertension,and dyslipidemia man-dates aggressive appropriate treatment with antidiabetic, blood pressure–lowering,and lipid-lowering agents aimed at reducing cardiovascular morbidity and mortal-ity.The rapidly growing epidemic of obesity and con-sequent insulin resistance has increased the interest in finding quantitative,accurate,and easy methods to eval-uate insulin sensitivity in both clinical research and clinical practice.Such a tool is not only useful for early identification of insulin resistance but also to assess the degree of success in treating this syndrome and its consequences.This review will summarize our current knowledge of the available methods used to evaluate insulin sensitivity in humans.The components of each method,its indications,and its limitations are discussed. Fasting Plasma Insulin ConcentrationOne of the most practical ways to estimate insulin resis-tance from the clinical perspective is to measure plasma insulin concentration after an overnight fast.As it is inexpensive and easy to do,it has been used in several population-based studies.27–30Very high plasma insulin values reflect the presence of insulin resistance.Despite the relatively good correlation between fasting plasma insulin and insulin sensitivity derived from the hyperin-sulinemic euglycemic clamp,measures of fasting plasma insulin explain no more than5to50%of the variability in insulin action seen in nondiabetic subjects.31,32This is because plasma insulin levels depend not only on insulin sensitivity,but also on insulin secretion,distribution,and degradation.33Moreover,with the development of diabetes,fasting plasma insulin levels tend to decrease owing to beta cell dysfunction.Therefore,plasma insulin levels in diabetic patients are valid reflection of both target tissue insulin resistance and diminishing insulin production.34This explains why fasting plasma insulin levels may accu-rately predict insulin sensitivity among normoglycemic patients than among those with impaired glucose toler-ance(IGT)or type2diabetes.32,35,36Another limitation to using fasting plasma insulin to predict insulin resis-tance is cross-reactivity between insulin and proinsulin. Proinsulin levels are high among insulin-resistant sub-jects with type2diabetes and IGT,37,38but not in people who are insulin resistant and normoglycemic.39 The commonly used radioimmunoassay(RIA) method has a lower specificity and sensitivity,and a higher interassay coefficient of variation,when com-pared with the two-site monoclonal antibody-based in-sulin assay methods(immuno-radiometric[IRMA],im-muno-enzymometric[IEMA],and immuno-fluorimetric [IFMA])methods.40,41The presence of anti-insulin an-tibodies in type1and type2diabetic patients,who are treated with human or animal insulin,can interfere with both the RIA and two-site monoclonal assay,unless removal of anti-insulin antibodies and antibody-bound insulin is performed.41,42The normal range for insulin levels using RIA is3to 32mU/L.43,44However,there is no defined cut-off value indicating insulin resistance.This lack of consensus stems partly from the various means used to define abnormal.In a population-based study examining the association between insulin levels and cardiovascular risk,Lindahl et al.8defined insulin resistance as a plasma insulin levelϾ7.2mU/ing the hyperinsulinemic euglycemic clamp as the reference standard,McAuley et al.45found that a fasting insulinϾ12.2mU/L predicted insulin resistance among normoglycemic adults. Laakso,32also using the hyperinsulinemic clamp in nor-moglycemic adults,arrived at a cut-off of18mU/L. Finally,defining the abnormal range as the upper10% percentile,Ascaso et al.46defined insulin resistance in nondiabetic individuals when plasma insulin levels were equal or greater than16.7mU/l(Table1).While these variations illustrate how study designs influences what insulin level is determined to represent insulin resistance, the lack of established standards for insulin assay proce-dures further complicates the issue.47Another limitation for measurement of fasting plasma insulin is the pulsatile mode of insulin secretion (pulses with a periodicity of10–15minutes,and ultra-dian oscillations periods of1to3hours).The periodicity, amplitude,and ultradian oscillations of insulin pulsesparison of Fasting Plasma Insulin Values and Insulin Assays Used to Assess Insulin Sensitivity in Different StudiesStudy Year Population Insulin Assay Insulin Resist Value Lindahl et al.81993General population RIAϾ7.2mU/L McAuley et al.452001General population RIAϾ12.2mU/L Laakso et al.321992Normoglycemic RIAϾ18mU/L Ascaso et al.462001Normoglycemic RIAՆ16.7mU/L RIAϭradioimmunoassay.vary in the fasting state,and are altered in IGT and in type2diabetes.41Because of these limitations,fasting plasma insulin levels are of limited value for clinical purposes,but have some utility as a research tool in population-based studies.The Homeostasis Model Assessment(HOMA)Because fasting insulin per se does not provide an accu-rate measure of insulin sensitivity in diabetic patients, efforts have been made to incorporate fasting plasma glucose in a formula to arrive at a better estimate of insulin-sensitivity.HOMA was developed by Matthews et al.48as a method for estimating insulin sensitivity from fasting serum insulin(FI)and fasting plasma glu-cose(FG)using the following mathematic formula: HOMA Insulin Resistance(HOMA IR)ϭFIϫFG/22.5FI is measured inU/mL and FG is measured in mmol/L.Low HOMA IR indicates high insulin sensitiv-ity,whereas high HOMA IR indicates low insulin sensi-tivity.In their original report,Matthews et al.found HOMA IR ranges between1.21and1.45in normal sub-jects and between 2.61and 2.89in insulin-resistant diabetic subjects.48However,further epidemiologic studies performed in the general population reported higher HOMA IR values of2.1,442.7,31and3.8.46 Because fasting insulin is a major component of the HOMA IR calculation,all previously mentioned limita-tions should apply to this formula.Three samples for fasting plasma insulin should be drawn5minutes apart to avoid errors that may arise owing to the pulsatile nature of insulin secretion.However,most studies use only one basal insulin measurement to calculate HOMA IR.HOMA IR correlates well with the glucose disposal rate derived from the hyperinsulinemic euglycemic clamp.49–53In addition,two authors found a good cor-relation between the HOMA IR and the insulin sensitivity index(S i)derived from the frequently sampled intrave-nous glucose tolerance test(FSIVGT).54,55By contrast, Anderson et al.35failed to demonstrate a good correla-tion between the two.Furthermore,some of the studies that initially demonstrated significant correlation be-tween the HOMA IR and the clamp-derived insulin sen-sitivity used a low insulin infusion rate of20 mU⅐m2Ϫ1⅐minuteϪ1during the clamp,which might not have completely suppressed the hepatic glucose pro-duction and may have created an error in calculating theglucose uptake by peripheral tissues.51,52One of the limitations of HOMA IR is the model assumption that insulin sensitivity in the liver and pe-ripheral tissues are equivalent,whereas it is known that they can differ considerably in the same individual.50 Furthermore,some data suggest that the accuracy of HOMA IR is limited by hyperglycemia.Those studies that demonstrated good correlations between HOMA IR and the clamp-derived insulin sensitivity in diabetic patients tended to enroll patients without significant hyperglyce-mia.48–50,52,53Mari et al.56failed to show a significant correlation between HOMA IR and clamp in type2dia-betic patients with higher glucose levels(mean basal plasma glucose of205mg/dL).In addition,Anderson et al.35and Brun et al.57found that the correlation between HOMA IR and S i derived from the FSIVGT weakened as glycemia increased.These results suggest a non-linear relationship between S i and HOMA IR.The coefficient of variation(CV)for HOMA IR is as high as31%,48which limits its use in clinical practice and clinical research.47Optimizing sample size and in-sulin assay method reduceHOMA IR CV to8to12%.49,51 In conclusion,HOMA IR is mostly useful for the evaluation of insulin sensitivity in euglycemic individu-als and in persons with mild diabetes;however,this index appears to offer little or no advantage over the fasting insulin concentration alone.31,45,58In patients with severe hyperglycemia or in lean diabetic patients with beta cell dysfunction,the HOMA IR may not be accurate.Its usefulness should therefore be restricted to large population-based studies that require a simple method to assess insulin sensitivity.Quantitative Insulin Sensitivity Check Index (QUICKI)QUICKI is another mathematic model available to esti-mate insulin sensitivity.59QUICKIϭ1/[log(I0)ϩlog(G0)],where I0is the fasting plasma insulin level inU/mL, and G0is the fasting plasma glucose level in mg/dL.The mean QUICKI for lean,obese,and obese-diabetic sub-jects are0.382,0.331,and0.304,respectively.59Al-though other studies have found a similar range for a normal healthy population of0.372and0.366,60,61one study showed a wider range between0.265and0.518.62 The mathematic difference between the QUICKI and the HOMA IR is that the former uses the reciprocal of the logarithm of both glucose and insulin to account for the skewed distribution of fasting insulin values.As expected,there is very good correlation between QUICKI and HOMA IR,63especially when the HOMA IR is log-transformed.59,62,64,65Although two studies failed to demonstrate any real advantage of QUICKI when compared with log HOMA IR,62,65other studies argue that QUICKI has the advantage of being applied to wider ranges of insulin sensitivity.61,63,64QUICKI was also shown to correlate well with the FSIVGT66and the hyperinsulinemic eu-glycemic clamp.58However,the correlation is weakerwhen insulin levels were low,as seen in non-obese insulin-sensitive subjects and diabetic patients with di-minished insulin production;59,60,62,65,67,68this is be-cause low insulin levels lead to variability in determined insulin concentrations and because of the oscillatory pattern of insulin secretion in healthy individuals.Other limitations to this mathematic method include its limited applicability for type1diabetic patients owing to lack of endogenous insulin secretion,59and its inaccuracy if conducted following exercise training.67In conclusion,the QUICKI may be a useful and simple tool for assessing insulin sensitivity in epidemi-ologic settings;it may offer some advantage over the HOMA IR,especially in obese and diabetic individuals with relatively preserved beta cell function.However, the model needs validation in a wider range of subjects with different glucose tolerance patterns in order to confirm its reliability for use in clinical practice and in research settings.Fasting Plasma Glucose-to-Insulin Ratio(G/I)G/I is another mathematic method that uses fasting plasma insulin and fasting plasma glucose to estimate insulin sensitivity.The higher the ratio,the more insulin-resistant an individual is.The index generally correlates well with other indi-ces of insulin sensitivity.1,45,69–75It correlated with in-sulin sensitivity indices derived from the oral glucose tolerance test(OGTT,rϭ0.82,PϽ0.05),1,71and FSIVGT(rϭ0,76,PϽ0.001).1,69,72Vuguin et al.72 found that a fasting G/I ratioϽ7provided87%sensitiv-ity and89%specificity for identifying low insulin sen-sitivity in young girls with premature adrenarche.In another study of white nondiabetic women with polycys-tic ovarian syndrome(PCOS),Legro et al.69found the G/I ratio to be the best screening test for insulin resis-tance.The authors showed that a cut-offϽ4.5provided an87%positive predictive value and94%negative predictive value in screening for insulin resistance in PCOS.G/I ratio was found to correlate well with HOMA IR(rϭ0.83,PϽ0.01),fasting insulin(rϭ0.95, PϽ0.001),73and QUICKI(rϭ0.91,PϽ0.0001)74in healthy individuals.Data on the correlation between G/I ratio and insulin sensitivity derived from the euglycemic clamp procedure are inconsistent;whereas two studies found a significant correlation,1,45another did not.50 Adding to the previously mentioned problems that in-clude precision of insulin assay,pulsatile pattern of insulin secretion,and cross reactivity with proinsulin,the major problem with using the G/I ratio is its inaccuracy in diabetic patients owing to defects in insulin secretion and high plasma fasting glucose.1,50,70,76In subjects with normoglycemia,G/I ratio offered little advantage over the1/insulin measure76or fasting insulin.45Moreover,it provides indirect information on whole-body sensitivitybut not on the effect of insulin in peripheral tissues.1Inconclusion,this index,like the previously describedindices,should be limited to the nondiabetic population.For research purposes,its superiority over the fastinginsulin is questionable.Continuous Infusion of Glucose with Model Assessment(CIGMA)Because of the inaccuracy that may result from low basalinsulin concentrations,an alternative mathematic methodwas proposed.This method assesses insulin sensitivitythrough the evaluation of the near–steady state glucoseand insulin concentrations after a continuous infusion ofglucose with model assessment.77This procedure mim-ics postprandial glucose and insulin concentrations.CIGMA not only provides information about glucosetolerance and insulin sensitivity,but also about beta celling a mathematic model of glucose ho-meostasis,glucose and insulin values are compared withknown physiologic data of glucose and insulin kinetics inresponse to glucose infusion that are derived fromhealthy lean subjects with no family history of diabetes.The glucose and insulin values used for CIGMA areobtained during the last15minutes of the60-minutecontinuous glucose infusion(5mg glucose⅐kg idealbody weightϪ1⅐minuteϪ1).Samples are collected at five-minute intervals,to avoid the oscillatory variation ininsulin concentration.The average is then compared withpredicted values from the computer model.The medianvalue for normal subjects is1.35and for diabetic patientswith mild hyperglycemia is4.0.77Although CIGMA has been used in several studiesto evaluate insulin resistance,78–83few studies havecompared CIGMA with other insulin sensitivity indices.In elderly normoglycemic patients,CIGMA significantlycorrelated with mean fasting plasma insulin concentra-tions.84Hermans et al.55compared CIGMA,HOMA IR,FSIVGT,and the insulin tolerance test(ITT),in subjectswith glucose tolerance ranging from normal to frankdiabetes.They found that CIGMA and HOMA IR wereable to discriminate differences in insulin sensitivityamong subjects as well as the FSIVGT and better thanthe ITT.Among the four methods,CIGMA was the bestdiscriminatory test in precision analysis.It is worthmentioning that CIGMA in this study derived from a2-hour test(compared with the original1-hour CIGMA).Other studies have also reported data from2-hourCIGMA.85,86Data aiming to validate CIGMA against the clamp-derived insulin sensitivity index are scarce.In the orig-inal article,CIGMA was shown to correlate well with theeuglycemic hyperinsulinemic clamp(rϭ0.87,P Ͻ0.0001)77in normal subjects and in diabetic patientswith mild hyperglycemia.However,the relationship be-tween CIGMA and the clamp was nonlinear for diabetic patients with severe insulin resistance.Nijpels et al.70 studied90subjects,most of them with normal or im-paired glucose tolerance,and found a modest correlation between CIGMA and the clamp-derived insulin sensitiv-ity(rϭ0.66;PϽ0.05).The CV of CIGMA ranges between17%84and20%.77There are two main advantages of CIGMA over HOMA IR.First,the insulin values that are measured in CIGMA are much higher than those in HOMA IR owing to the glucose stimulus;therefore,the high insulin inter-assay CV(10–15%)41,47that is problematic at low insu-lin a concentration is avoided.55Second,higher insulin concentration in CIGMA stimulates peripheral glucose uptake producing a steady-state glucose concentration, which is a better reflection of the peripheral insulin sensitivity.Although CIGMA is more physiologic,practical, cheaper,and less invasive than the FSIVGT and clamp procedure,the model incorrectly assumes that levels of insulin resistance at the liver and peripheral tissues are equal.Furthermore,in insulin-deficient subjects,where the insulin response is insufficient to stimulate glucose uptake,the interpretation of CIGMA is difficult.33As CIGMA is a procedure and not a simple test such as fasting insulin or the HOMA IR,its use in clinical practice is limited.Moreover,due to insufficient data comparing CIGMA against the“gold standard”euglycemic hyper-insulinemic clamp,its use in research settings should also be viewed with caution.The Oral Glucose Tolerance Test(OGTT) Because oral glucose tolerance is in part determined by sensitivity of peripheral tissues to insulin,the OGTT has been used to evaluate insulin release and the sensitivity of the peripheral tissue to the insulin action.Being a less costly and less labor-intensive procedure compared with the FSIVGT and the euglycemic clamp,the OGTT has been considered a practical method for epidemiologic studies,58for population screening,and for large-scale intervention trials.50,63,87Several indices to estimate in-sulin sensitivity have been derived from the four samples of insulin and glucose(0,30,60,and120minutes)taken after ingestion of75grams of glucose(Table2). Insulin Sensitivity Indices Based on the OGTT Levine et al.88was one of thefirst authors to use the product of the area under the curve for glucose(AUC G) and the area under the curve for insulin(AUC I)during the OGTT to derive an estimate of insulin sensitivity. Later,AUC I was used alone as an estimate.31,36,89Cederholm and Wibell Index90SIϭM/G⅐log I,where Mϭglucose load/120ϩ(0-h plasma glucose concentration–2-h plasma glucose concentration)ϫ1.15ϫ180ϫ0.19ϫbody weight/120;where Gϭmean plasma glucose concentration,and Iϭmean serum insulin.A normal reference value is79Ϯ14.Gutt et al.Index91ISI0,120ϭMCR/log MSI(mean serum insulin),uses the fasting(0min)and120min post-load insulin and glucose concentrations,where MCR(metabolic clear-ance rate)is m/MPG(mean plasma glucose),where mϭ(75000mgϩ[0min glucose–120min glucose]ϫ0.19ϫbody weight)/120min.The reference range for lean controls was89Ϯ39,for obese58Ϯ23,for IGT 46Ϯ12,and for diabetic patients23Ϯ19.Avignon et al.Index92Sibϭ108/(IϫGϫVD)⅐(normal rangeϭ11.99Ϯ1.43)Si2hϭ108/(I2hϫG2hϫVD)⅐(normal rangeϭ1.79Ϯ0.33), where Iϭfasting insulin,Gϭfasting plasma glucose, G2h and I2hϭplasma glucose and insulin at the second hour of the OGTT,and VDϭvolume distribution(150 mL/kg of body weight).An additional insulin sensitivity index(S i M)was derived by the average of the2,after multiplying S i b by a correcting factor:SiMϭ[(0.137ϫSib)ϩSi2h]/2(normal rangeϭ1.71Ϯ0.24). Matsuda et al.Index50ISI(composite)ϭ10,000/͙(FPGϫFPI)ϫ(GϫI), where FPGϭfasting plasma glucose,FPIϭfasting plasma insulin,and Gϭmean plasma glucose,and Iϭmean plasma insulin concentration.Belfiore et al.Index93ISIϭ2/(INSpϫGLYp)ϩ1,where INSp and GLYp are the insulinemic and glycemic areas of the person under study recorded during OGTT. Reference value in normal controls was around1,butmarkedly reduced in the obese and obese-diabetic sub-groups.Stumvoll et al.Index94MCR est(OGTT)ϭ18.8Ϫ0.271BMIϪ0.0052ϫI120Ϫ0.27ϫG90, where MCR est stands for metabolic clearance rate estimate derived from the OGTT,BMIϭbody mass index,I120ϭplasma insulin at120minutes OGTT,and G90ϭplasma glucose at90minutes OGTT.Mari et al.Index56OGIS180ϭ[637106(G(120)Ϫ90)ϩ1]Cl ogtt, where OGIS180ϭoral glucose insulin sensitivity,G120ϭplasma glucose at2h OGTT,andCl ogttϭ289DoϪ104[G(180)ϪG(120)/60]G(120)ϩ14.0103G(0)440I(120)ϪI(0)ϩ270, where Clϭglucose clearance in mL⅐minϪ1⅐mϪ2, Doϭoral glucose dose in g/m2,G(120)ϭplasmaTable2.OGTT-derived Indices to Estimate Insulin Sensitivity and their Correlation with the Euglycemic Hyperinsulinemic Clamp or Frequently Sampled Intravenous Glucose Tolerance Test(FSIVGT)in Various PopulationsFormulae Subjects Correlation with 1.AUC I NGT Euglycemic clamp89rϭ0.61,Pϭ0.001IST31rϭ0.79,PϽ0.001AUC II30min I2hrG30min G2hr NGT,IGT ITT36rϭϪ0.51,PϽ0.001rϭϪ0.43,PϽ0.001rϭϪ0.39,PϽ0.001rϭϪ0.28,Pϭ0.01rϭϪ0.38,PϽ0.0012.SIϭMGϫlog INGT,IGT,DMEuglycemic clamp90rϭ0.62,PϽ0.00013.ISI0,120ϭMCR/log MSI NGT,IGT,DM Euglycemic clamp91rϭ0.63,PϽ0.001 4.Sibϭ108/(f Iϫf GϫVD)NGT,IGT,DM FSIVGT92Si2hϭ108(I2hϫG2hϫVD)rϭ0.90,PϽ0.0001 SiMϭ[(0.137ϫSib)ϩSi2h]/25.ISI(Comp)ϭ10,000͙(FPGϫFPI)ϫ(GϫI)NGT,IGT,DMEuglycemic clamp50rϭ0.73,PϽ0.00016.ISIϭ2(INSpϫGLYp)ϩ1NGT,O,ODMEuglycemic clamp93rϭ0.96,PϽ0.0017.MCRestϭ18.8Ϫ0.271BMIϪ0.0052ϫI120Ϫ0.27ϫG90NGT,IGT Euglycemic clamp94rϭ0.80;PϽ0.000058.OGIS180ϭ[637106(G{120}Ϫ90)ϩ1]Cl ogtt L,O,IGT,DM Euglycemic clamp56rϭ0.73;PϽ0.0001 AUC Iϭarea under the insulin curve,NGTϭnormal glucose tolerance,IGTϭimpaired glucose tolerance,I30minϭ30minutes post-load insulin,I2hrϭ2hours post-load insulin,G30minϭ30minutes post-load glucose,G2hrϭ2hour post-load glucose, ITTϭinsulin tolerance test,SIϭinsulin sensitivity,Mϭglucose uptake rate in mg⅐minϪ1,Gϭmean glucose concentration,Iϭmean insulin concentration,DMϭtype2diabetes,ISI0,120ϭindex of insulin sensitivity from fasting and120minutes post OGTT insulin and glucose concentrations,MCRϭmetabolic clearance rate,MSIϭmean serum insulin,Sibϭinsulin sensitivity in the basal state,Si2hϭinsulin sensitivity at the second hour,f Iϭfasting insulin concentration,f Gϭfasting glucose concentration,VDϭ150mL/kg of body weight,SiMϭinsulin sensitivity index,ISI(Comp)ϭcomposite whole-body insulin sensitivity index,FPGϭfasting plasma g glucose,FPIϭfasting plasma insulin,Gϭglucose,Iϭinsulin,ISIϭinsulin sensitivity index,INSpϭinsulinemic area,GLYpϭglycemic area,MCRestϭmetabolic clearance rate estimate,OGISϭoral glucose insulin sensitivity,Doϭoral dose glucose,Cl ogttϭglucose clearance.glucose at120minutes OGTT,G(180)ϭplasma glucose at180minutes OGTT,G(0)ϭfasting plasma glucose, I(120)ϭinsulin levels at120minutes,and I(0)ϭfasting insulin.Reference values in lean controls ranged300–600mL⅐minϪ1⅐mϪ2.As shown in Table2,the insulin sensitivity mea-sures derived from these formulas correlate well with insulin sensitivity determined by the euglycemic clamp50,89,90,93and FSIVGT.93However,the correlation was weaker in type2diabetic patients50,92,94and in the IGT group.36,58Belfiore et al.93advocate that their for-mula should not be used in type2diabetic patients with significant insulin deficiency.On the other hand,Mari et al.formula(OGIS),56showed a positive correlation with the clamp data in type2diabetic patients(rϭ0.49,P Ͻ0.002).In addition to the inadequacy of this method in insulin deficient states,other problems should be consid-ered.First,during the oral glucose tolerance test suppres-sion of hepatic glucose production is minimal,confound-ing interpretation of the plasma glucose level.Thus,it is impossible to differentiate among whole-body,periph-eral,or hepatic insulin sensitivity separately using data from the OGTT.49Second,the insulin level achieved in response to an oral glucose load involves gut hormones, neural stimulation,and of course the integrity of the pancreatic beta cells.68For example it has been shown that after75grams of glucose,obese subjects exhibit insulin hypersecretion,95while type2diabetes patients show a blunted response.96Third,glucose homeostasis in the postprandial state depends partly on the suppression of glucagon secretion and partly on the rate of entry of ingested glucose into the circulation.This rate is deter-mined by the rate of gastric emptying and splanchnic glucose uptake.60,61Fourth,the OGTT is poorly repro-ducible.Several studies show only about50to65% reproducibility of the results of an OGTT.63,97,98 Despite these limitations,the OGTT may be used in clinical settings to assess insulin action and in large-scale clinical and epidemiologic studies.However,the glucose and insulin excursions in the OGTT should be inter-preted with caution in populations with varying glucose tolerance.The Insulin Tolerance Test(ITT)ITT was one of thefirst methods developed to assess insulin sensitivity in vivo.99In this method,afixed bolus of regular insulin(0.1U/kg body weight)is given intra-venously after an8-to10-hour fast.The plasma glucose decrement over60minutes is then measured.The faster the decline in glucose concentration,the more insulin sensitive the subject is.The slope of the linear decline in plasma glucose(K ITT)can be calculated by dividing 0.693by the plasma glucose half-time(50%from base-line,Figure1).100K ITTϭ0.693/t1/2ϫ100,where t1/2represents the half-life of plasma glucose decrease.Normal K ITT isϾ2.0%/minute and values Ͻ1.5are considered abnormal.This method gives an indirect estimate of overall insulin sensitivity.It has been shown to correlate with the euglycemic clamp(rϭ0.811,PϽ0.001)101in several studies.101–104Some of the drawbacks of this method include the supraphysi-ologic insulin dose used,102and also the fact that the test does not differentiate peripheral versus hepatic insulin resistance.A major limitation of this test is the risk of hypo-glycemia,particularly in normoglycemic subjects and in elderly diabetic patients.Moreover,hypoglycemia trig-gers counterregulatory hormonal responses,which may interfere with insulin sensitivity.A lower insulin dose method of0.05units/kg,or shortening the test to15 minutes was suggested as an attempt to decrease the risk of hypoglycemia.105–107The lower dose ITT has also been shown to correlate well with the clamp.105How-ever,some studies failed to demonstrate reduction of the risk of hypoglycemia in insulin sensitive sub-jects.55,108,109They also showed a higher CV(16and 31%)in comparison to the conventional dose ITT(6–9% CV).101,103,104,110The shorter version101,103evolved from the notion that the counterregulatory hormone re-sponse occurs only after20minutes of the insulin infu-sion.111–113The short ITT yielded a good correlation with the euglycemic clamp101,103,105and has been used in most of the recent studies.114–117In conclusion,the ITT should be used with great caution in insulin sensitive individuals because of the increased risk of hypoglycemia,even when thesmallerFigure1.Calculation of the KITT(percentage decline in plasma glucose concentration per minute)in nondiabetic subjects.100 The time(t1⁄2)required for the plasma glucose concentration to decline by50%(i.e.,from90to45mg/dL)was25minutes.From the equation,KITTϭ0.693/t1⁄2ϫ100,the K rate was determined to be2.77%.。
2024版Fast and accurate reading for the College Eng
•Overview of Readingcomprehension question typesand problem solving skills 目录•Discussion on Quick Positioningof Key Information Methods•Exploring Strategies forImproving Reading Speed andAccuracy目录•Practical exercises and detailedexplanations of real problems•Recommendation of readingmaterials and suggestions forexpanding reading•Exam preparation experiencesharing and interactivecommunication session目录01Overview of Readingcomprehensionquestion types andproblem solving skillsIntroduction to question types and score distributionQuestion TypesScore DistributionSteps and Strategies for Solving ProblemsNotes and Miscellaneous Tips02Discussion on QuickPositioning of KeyInformation MethodsSkimmingScanning for key wordsReading the first and last attentionScanning method: Quickly find the paragraph where the answer is locatedBrief reading method: Grasp the central idea of the articleAs you read, think about how each paragraph relates to the main idea of thearticle This helps you form a clear understanding of the author's argument orperspectiveMaking connections Look for the central theme or main point of the article This can be found inthe introduction or conclusionIdentifying the main ideaQuickly read each paragraph and try to summarize the main point in your ownwords This helps you understand the overall structure and content of thearticleSummarizing each paragraphReading method: Find relevant information for the problemUnderstanding the problemLocation relevant informationAnalyzing and synthesizing information03Exploring Strategiesfor ImprovingReading Speed andAccuracyExpand vocabulary and improve guiding abilityMaster the skills of analyzing long and diverse sensesStrengthening then awareness of course structure and grasping the context of the article04Practical exercises and detailed explanationsof real problems010203Analysis of frequently occurring question types and themesIdentification ofcommon misses andpitfalls to avoidDiscussion of effectivestrategies forapproaching differentquestion typesReview and summary of past real problemsSimulated question training and explanation 010203Student self directed practice and feedback01020305Recommendation ofreading materials andsuggestions forexpanding reading01 02 03The Great Gatsby by F. Scott Fitzgerald To Kill a Mockingbird by Harper Lee "1984" by George OrwellSelected Readings of Classic English Original WorksThe Economist The New YorkTimes BBC NewsFollow current affairs news and hot topicsNetwork resource utilization and recommendation of self-learning platformsCoursera Duolingo TED Ed06experience sharingand interactivecommunicationsessionSuccess Experience SharingQ&A sessionAnswering questions about exam techniquesClarifying misunderstandings about the examWATCHING。
快餐的利与弊英语作文
快餐的利与弊英语作文The Pros and Cons of Fast Food。
Fast food has become a popular choice for many people due to its convenience and affordability. However, there are both advantages and disadvantages to consuming fast food on a regular basis.One of the main advantages of fast food is the convenience it offers. With busy schedules and hectic lifestyles, many people find it difficult to prepare and cook meals at home. Fast food restaurants provide a quick and easy solution for those who are on the go and need a quick meal. In addition, fast food is often readily available in many locations, making it a convenient option for those who are traveling or on the road.Another advantage of fast food is its affordability. In comparison to dining at a sit-down restaurant or preparing a meal at home, fast food is often much cheaper. This makesit an attractive option for individuals and families on a budget, as well as for those who are looking for a quickand inexpensive meal option.However, despite its convenience and affordability,fast food also has its drawbacks. One of the main disadvantages of fast food is its negative impact on health. Many fast food items are high in calories, fat, and sodium, which can contribute to weight gain, high cholesterol, and other health issues. In addition, fast food is often processed and contains additives and preservatives, which can have long-term health effects.Another disadvantage of fast food is its impact on the environment. The production and consumption of fast food contribute to environmental issues such as deforestation, water pollution, and greenhouse gas emissions. In addition, the packaging and waste generated by fast food restaurants can contribute to litter and pollution.In conclusion, while fast food offers convenience and affordability, it also has its drawbacks in terms of healthand environmental impact. It is important for individuals to be mindful of their fast food consumption and to make informed choices about their diet and lifestyle. By balancing the benefits and drawbacks of fast food, individuals can make healthier choices for themselves and for the environment.。
快与慢的二元作文素材
快与慢的二元作文素材英文回答：Fast and Slow: A Comparison.When it comes to the concept of fast and slow, there are many aspects to consider. In terms of speed, fastrefers to something that moves or happens quickly, while slow refers to the opposite, something that moves or happens at a leisurely pace. However, fast and slow can also be used to describe various other aspects of life, such as decision-making, learning, and even personal relationships. In this essay, I will explore the differences between fast and slow in various contexts.Firstly, let's talk about the advantages of being fast. When it comes to decision-making, being fast can be beneficial in certain situations. For example, in a business setting, making quick decisions can give you a competitive edge. If you are able to analyze informationand make decisions swiftly, you can respond to market changes faster than your competitors. This can lead to increased profits and success in the business world. Additionally, in emergency situations, being fast can be a matter of life and death. For instance, if someone is choking, performing the Heimlich maneuver quickly can save their life.On the other hand, there are also advantages to being slow. When it comes to learning, taking things slow can lead to better understanding and retention of information. For example, when studying a new language, it is important to take the time to practice and review the material thoroughly. By doing so, you can ensure that you truly understand the concepts and are able to apply them in real-life situations. Similarly, in personal relationships, taking things slow can lead to stronger connections. Rushing into a relationship without truly getting to know the other person can lead to misunderstandings and conflicts down the line. By taking the time to build a solid foundation, you can establish a deeper and more meaningful connection with your partner.In addition to decision-making and learning, theconcept of fast and slow can also be applied to variousother aspects of life. For example, in terms of technology, fast internet speeds enable us to access information and communicate with others instantly. On the other hand, slow internet speeds can be frustrating and hinder our productivity. Similarly, in terms of food, fast food isoften associated with convenience and quick meals on the go. However, slow-cooked meals are often considered to be more flavorful and satisfying. These examples demonstrate thatthe concept of fast and slow can be applied to various aspects of our daily lives.中文回答：快与慢，一种比较。
科技类对比英语作文模板
科技类对比英语作文模板Title: Technology Comparison English Essay Template。
With the rapid development of technology, various electronic products have emerged, and people's lives have become more and more convenient. In this essay, we will compare and contrast different types of technology, including smartphones, computers, and tablets, to explore their similarities and differences.Firstly, let's compare smartphones and computers. Smartphones are portable devices that can make phone calls, send text messages, and access the internet. They are small and lightweight, making them easy to carry around. On the other hand, computers are larger and more powerful, with the ability to run complex programs and perform tasks that smartphones cannot. While smartphones are great for staying connected on the go, computers are better suited for tasks that require more processing power, such as video editing or gaming.Next, let's compare computers and tablets. Computers are versatile machines that can be used for a wide range of tasks, from word processing to graphic design. They typically have a keyboard and mouse for input, and a large monitor for display. Tablets, on the other hand, are more portable and have a touchscreen interface. They are great for consuming media, such as watching videos or reading e-books, but may not be as suitable for tasks that require a lot of typing or precise mouse control.Finally, let's compare tablets and smartphones. Both devices are portable and can access the internet, but they have different form factors and use cases. Tablets have larger screens, making them better for tasks that require more screen real estate, such as watching movies or playing games. Smartphones, on the other hand, are more compact and are better suited for tasks that require mobility, such as making phone calls or taking photos on the go.In conclusion, while smartphones, computers, and tablets all have their own strengths and weaknesses, they each serve different purposes and cater to different needs.Smartphones are great for staying connected on the go, computers are powerful machines for complex tasks, and tablets are versatile for media consumption. As technology continues to evolve, it will be interesting to see how these devices continue to adapt and improve to meet the needs of users.。
对比的话英文作文
对比的话英文作文Title: A Comparative Analysis: Contrasting Perspectives in English Composition。
Introduction:In the realm of academic writing, comparative analysis serves as a valuable tool for exploring contrasting perspectives, ideologies, or methodologies. This essay embarks on a journey of comparison, delving into the nuances of various subjects to highlight their differences and similarities.Literature Review:Comparative analysis has long been a cornerstone of scholarly discourse, facilitating deeper understanding through juxtaposition. By examining disparate viewpoints side by side, researchers gain insights into the complexities of human thought and behavior. In Englishcomposition, this approach is particularly illuminating, as it allows writers to explore diverse themes, styles, and literary devices.Contrasting Perspectives in English Composition:English composition encompasses a vast array of genres, from narrative prose to poetic verse, each offering unique opportunities for expression. When comparing different forms of writing, one often encounters contrasting perspectives on elements such as structure, tone, and thematic focus.For instance, in comparing classical literature with contemporary fiction, one may observe divergent approaches to character development. While classical works often prioritize archetypal characters and moral dilemmas, contemporary fiction tends to emphasize psychological depth and nuanced interpersonal relationships.Similarly, the use of language varies across different genres and time periods. Whereas Shakespearean sonnetsemploy intricate rhyme schemes and poetic diction to convey complex emotions, modernist poetry often experiments with free verse and fragmented syntax to evoke a sense of dislocation and alienation.Moreover, the role of the author in shaping narrative voice and point of view can vary significantly between works. In autobiographical writing, such as memoirs or personal essays, the author's subjective perspective is foregrounded, inviting readers to empathize with theirlived experiences. In contrast, omniscient narrators in fiction may adopt a more detached stance, allowing for broader social commentary or philosophical reflection.Implications and Applications:By critically analyzing these contrasting perspectives in English composition, scholars can gain a deeper appreciation for the dynamic nature of literary expression. Moreover, educators can leverage comparative analysis as a pedagogical tool to foster critical thinking and cultural awareness among students.For example, by pairing canonical texts with contemporary counterparts, instructors can encourage students to examine how societal values and literary conventions have evolved over time. Through guided discussions and writing assignments, students can develop their analytical skills while gaining insight into the complexities of human experience.Conclusion:In conclusion, comparative analysis offers a valuable framework for exploring contrasting perspectives in English composition. By examining diverse genres, styles, and thematic concerns, scholars can gain a deeper understanding of the complexities of literary expression. Moreover, educators can harness the power of comparative analysis to cultivate critical thinking skills and cultural literacy among students. As we continue to navigate the ever-changing landscape of literature, comparative analysis remains a vital tool for uncovering the rich tapestry of human creativity.。
出行选择私家车还是公交车观点对比英语作文
出行选择私家车还是公交车观点对比英语作文全文共3篇示例，供读者参考篇1Traveling is an essential part of our daily lives, and we often face the dilemma of whether to use a private car or public transportation. Both options have their own advantages and disadvantages, and the decision usually depends on various factors such as convenience, cost, comfort, and environmental impact. In this essay, I will compare the two modes of transportation and provide my perspective on which one is the better choice.Firstly, let's consider the convenience of using a private car. One of the biggest advantages of a private car is the flexibility it offers. You can travel at your own pace, choose your own route, and stop whenever and wherever you want. This is especially beneficial if you have a tight schedule or need to make multiple stops during your journey. Additionally, having a car of your own means you don't have to wait for public transportation schedules or worry about missing a bus or train.On the other hand, public transportation also has its own set of advantages. One of the main benefits of using public transportation is the cost savings. Taking a bus or train is usually much cheaper than using a private car, especially when you factor in expenses such as fuel, maintenance, insurance, and parking fees. Public transportation also helps reduce traffic congestion and environmental pollution, as it can carry a large number of passengers at once, thereby reducing the number of cars on the road.Another factor to consider when deciding between a private car and public transportation is comfort. Private cars offer a more personalized and comfortable travel experience, as you have the freedom to control the temperature, music, and seating arrangements. You can also avoid crowded buses or trains and enjoy a quieter and more relaxing journey. However, public transportation is often more convenient for short distances or commuting to work, as you don't have to worry about finding parking or dealing with traffic jams.In terms of environmental impact, public transportation is generally considered to be more sustainable and eco-friendly than using a private car. Buses and trains produce fewer carbon emissions per passenger than individual cars, and they helpreduce air pollution and greenhouse gas emissions. By choosing public transportation over a private car, you can contribute to a cleaner and healthier environment for future generations.In conclusion, both private cars and public transportation have their own advantages and disadvantages. The decision of which mode of transportation to use ultimately depends on your individual needs and preferences. If you value convenience, flexibility, and comfort, a private car may be the better choice for you. However, if you prioritize cost savings, environmental sustainability, and reducing traffic congestion, public transportation may be the more practical option. Ultimately, it is important to consider all factors before making your decision and choose the mode of transportation that best suits your needs.篇2Private Car vs Public Transport: A ComparisonWhen it comes to getting around in today's fast-paced world, the question of whether to use a private car or public transport is a common dilemma for many people. Both options have their own advantages and disadvantages, and choosing between them can be a difficult decision. In this article, we will comparethe two modes of transportation and explore which might be the better choice for different situations.Private CarOne of the main advantages of using a private car is the convenience and flexibility it provides. With a car, you can come and go as you please, without having to stick to a set schedule or wait for public transport. This can be especially useful for those who have busy lifestyles or need to travel to multiple destinations in a short amount of time.Another benefit of using a private car is the comfort and privacy it offers. You can listen to your favourite music, adjust the temperature to your liking, and enjoy the privacy of your own space. This can be particularly appealing for those who value their personal space and want to avoid the crowds and noise of public transport.However, there are also some drawbacks to using a private car. One of the biggest disadvantages is the cost. Owning and maintaining a car can be expensive, with costs including petrol, insurance, maintenance, and parking fees. In addition, the environmental impact of driving a car can be significant, with emissions contributing to air pollution and climate change.Public TransportPublic transport, on the other hand, offers a more economical and environmentally friendly alternative to using a private car. Buses, trains, and trams are often cheaper than driving a car, and many cities offer discounted fares for students, seniors, and regular commuters. In addition, public transport can help reduce traffic congestion and air pollution by encouraging more people to use shared modes of transportation.One of the main advantages of public transport is the convenience of not having to worry about parking or navigating through traffic. Many public transport systems operate on regular schedules and routes, making it easy to plan your journey and avoid getting stuck in traffic jams. Public transport can also be a safer option for those who are not comfortable driving or navigating unfamiliar areas.However, there are also some drawbacks to using public transport. One of the main disadvantages is the lack of flexibility and limited options for getting to certain destinations. Public transport can be less convenient for those who need to travel to remote locations or have strict time constraints. In addition, overcrowding and delays can be common on public transport, especially during peak hours.ConclusionIn conclusion, both private cars and public transport have their own advantages and disadvantages, and the best choice will depend on your individual needs and preferences. Private cars offer convenience, flexibility, and privacy, but can be expensive and have a negative environmental impact. Public transport is more economical, environmentally friendly, and safe, but may be less convenient and reliable for some travellers.Ultimately, the decision of whether to use a private car or public transport will depend on factors such as your budget, lifestyle, and travel habits. Some people may find that a combination of both modes of transportation works best for them, depending on the circumstances. Whichever option you choose, it is important to consider the impact of your decision on the environment, your finances, and your overall well-being.篇3When it comes to choosing between private cars and public transportation for traveling, people often have different opinions. Some prefer the convenience and comfort of driving their own cars, while others appreciate the affordability and environmental friendliness of taking public transit. In this essay, we will discussthe pros and cons of each option to help you make an informed decision.First and foremost, let's talk about private cars. Driving a car offers a sense of independence and flexibility that public transportation cannot match. You can go wherever you want, whenever you want, without having to rely on timetables or schedules. This is especially convenient for people with busy schedules or those who live in areas with limited public transportation options. Additionally, having a car allows you to carry more luggage or travel with pets, which may not be allowed on public transit.However, owning a car comes with its own set of challenges. The cost of purchasing and maintaining a vehicle can be quite high, including expenses for fuel, insurance, maintenance, and parking. Traffic congestion and the stress of driving in crowded cities can also take a toll on your mental well-being. In addition, cars contribute to air pollution and greenhouse gas emissions, which are harmful to the environment.On the other hand, public transportation offers several benefits for travelers. It is generally more affordable than owning a car, as you only need to pay for tickets or passes. Public transit systems are also more environmentally friendly, as they cantransport a large number of people in a single trip, reducing the overall carbon footprint. Moreover, taking public transportation can help reduce traffic congestion and ease the strain on infrastructure in urban areas.However, public transportation may not always be the most convenient option. Buses and trains operate on fixed schedules, so you may need to plan your trips around their timetables. This can be limiting for people who need to travel at odd hours or to destinations that are not well-served by public transit. Additionally, crowded buses and trains can be uncomfortable, especially during peak hours.In conclusion, both private cars and public transportation have their own advantages and disadvantages. The choice between the two ultimately depends on your individual needs and preferences. If you prioritize convenience and independence, a private car may be the better option for you. On the other hand, if you value affordability and sustainability, public transportation could be the way to go. Ultimately, the most important thing is to consider the costs, benefits, and environmental impacts of each mode of transportation before making your decision.。
对比论证英文作文
对比论证英文作文下载温馨提示:该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。
文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by theeditor. I hope that after you download them,they can help yousolve practical problems. The document can be customized andmodified after downloading,please adjust and use it according toactual needs, thank you!In addition, our shop provides you with various types ofpractical materials,such as educational essays, diaryappreciation,sentence excerpts,ancient poems,classic articles,topic composition,work summary,word parsing,copyexcerpts,other materials and so on,want to know different data formats andwriting methods,please pay attention!Some people think that going to university is the best way to get a good job. They believe that universities provide students with professional knowledge and skills.But there are also people who think that practical experience is more important. They say that through working, one can gain real-world skills and understand the needs of the workplace better.Another thing to consider is that some people are very talented in certain areas and don't necessarily need a university degree. For example, a person with a naturalgift for music or art might be able to succeed withoutgoing to university. However, for many other careers, a degree can be a big advantage.Then there are those who focus on personal growth and development. University can offer a rich and diverse environment for students to explore different interests and expand their horizons. But on the other hand, traveling orengaging in various activities outside of school can also have a huge impact on personal growth.In different cultures, people have different views on success. In some cultures, having a lot of money and material possessions is seen as the ultimate goal. While in others, having a happy family and good relationships is more important. It really depends on individual values and beliefs.。
衣服对比过去和现在英语作文
衣服对比过去和现在英语作文Here is an English essay on the topic of "Comparing Clothing of the Past and Present", with the content exceeding 1000 words as requested.Clothing has always been an integral part of human civilization, serving both practical and cultural purposes. Over the centuries, the styles and materials used in clothing have undergone significant transformations, reflecting the changing socio-economic conditions, technological advancements, and evolving cultural preferences. When comparing the clothing of the past and present, one can observe a remarkable contrast in terms of design, functionality, and the overall approach to fashion.In the past, clothing was primarily utilitarian in nature, designed to provide protection from the elements and serve the practical needs of the wearer. The materials used were often locally sourced and relatively simple, such as animal hides, woven fabrics, and natural fibers. The styles were typically more modest and conservative, with an emphasis on functionality over aesthetics. For instance, traditional garments like the toga in ancient Rome or the kimono in feudal Japan were designed to cover the body and keep the wearer warmor cool, depending on the climate.As societies progressed and industrialization took hold, the manufacturing of clothing underwent a significant transformation. The advent of mass production and the use of synthetic materials revolutionized the fashion industry. Clothing became more accessible, affordable, and diverse in terms of styles and designs. The focus shifted from pure functionality to a greater emphasis on aesthetics, self-expression, and the creation of personal identity through fashion.One of the most notable differences between past and present clothing is the speed at which fashion trends change. In the past, fashion cycles were relatively slow, and clothing styles often remained popular for decades or even centuries. The introduction of new styles was a gradual process, influenced by cultural exchange, social hierarchies, and the availability of resources. In contrast, the modern fashion industry is characterized by a rapid turnover of trends, with new styles emerging and fading away at an unprecedented pace.This accelerated fashion cycle has been driven by several factors, including the rise of global communication, the influence of media and celebrity culture, and the increasing demand for novelty and individuality. The advent of fast fashion retailers has furthercontributed to this phenomenon, offering affordable and trendy clothing options that cater to the constantly changing desires of consumers.Another significant difference between past and present clothing is the level of sustainability and environmental consciousness. In the past, clothing was often made from natural materials that were biodegradable and had a relatively low environmental impact. However, the mass production and widespread use of synthetic fabrics, such as polyester and nylon, have raised concerns about the environmental consequences of the fashion industry. The industry is now facing increasing pressure to adopt more sustainable practices, including the use of eco-friendly materials, ethical manufacturing processes, and the promotion of circular fashion models.Despite these challenges, the fashion industry has also seen a resurgence of interest in traditional and heritage-inspired clothing. Many consumers are seeking authenticity and a connection to the past, leading to a renewed appreciation for handcrafted garments, artisanal techniques, and the preservation of cultural textile traditions. This trend has not only revived traditional styles but has also inspired contemporary designers to incorporate elements of the past into their creations, blending the old and the new.Furthermore, the democratization of fashion has allowed individualsto express their personal style and identity through clothing in unprecedented ways. The rise of subcultures, street fashion, and the empowerment of marginalized communities have all contributed to a more diverse and inclusive fashion landscape. Individuals can now curate their wardrobes to reflect their unique personalities, social affiliations, and political or cultural beliefs.In conclusion, the comparison of clothing from the past and present reveals a profound transformation in the way we approach fashion. While the past was characterized by a more practical and conservative approach to clothing, the present is marked by a rapid pace of change, a greater emphasis on aesthetics and self-expression, and a growing awareness of the environmental impact of the fashion industry. As we move forward, it will be interesting to see how the fashion industry continues to evolve, balancing the desire for innovation and individuality with the need for sustainability and cultural preservation.。
快餐的好处英语作文
快餐的好处英语作文The Advantages of Fast Food。
Fast food has become an integral part of modern life. It is convenient, affordable, and delicious. In recent years, the popularity of fast food has soared, and it has become a staple in the diets of many people. Despite the criticisms it often receives, fast food has numerous advantages that make it a popular choice for millions of people around the world.First and foremost, fast food is incredibly convenient. In today's fast-paced world, people are constantly on the go, and they often don't have the time to sit down for a leisurely meal. Fast food restaurants provide a quick and easy solution to this problem. With drive-thru options and speedy service, people can grab a meal on the go and continue with their busy schedules. This convenience is especially valuable for those who work long hours or have hectic lifestyles.Additionally, fast food is also very affordable. In comparison to sit-down restaurants, fast food is significantly cheaper, making it an attractive option for people on a budget. For many individuals and families, fast food is a cost-effective way to enjoy a meal without breaking the bank. This affordability allows people totreat themselves to a meal out without feeling guilty about the cost.Furthermore, fast food is undeniably delicious. With a wide range of options to choose from, there is somethingfor everyone to enjoy. Whether it's a juicy burger, crispy fries, or a refreshing milkshake, fast food offers avariety of tasty treats that satisfy cravings and indulge the taste buds. The appeal of these mouthwatering optionsis a major reason why fast food remains so popular.In addition to its convenience, affordability, and deliciousness, fast food also offers a sense of familiarity and comfort. For many people, visiting a fast food restaurant is a nostalgic experience that brings back fondmemories of family outings, road trips, and special occasions. The familiar tastes and smells of fast food can evoke feelings of happiness and contentment, making it a comforting choice for many.Despite these advantages, it is important to acknowledge that fast food should be consumed in moderation. While it is convenient, affordable, and delicious, it isalso often high in calories, fat, and sodium, which canhave negative effects on health if consumed excessively. It is essential to balance fast food with healthier optionsand to make informed choices about what and how much to eat.In conclusion, fast food offers numerous advantagesthat make it a popular choice for many people. Its convenience, affordability, deliciousness, and comfort make it an appealing option for those with busy lifestyles or limited budgets. However, it is important to consume fast food in moderation and to be mindful of its potentialimpact on health. By doing so, people can enjoy thebenefits of fast food while maintaining a balanced and healthy diet.。
快餐的流行英语作文
快餐的流行英语作文The Popularity of Fast Food。
Fast food has become a popular choice for many people around the world. It is convenient, affordable, and offers a wide variety of options. In this essay, we will explore the reasons behind the popularity of fast food and its impact on our lives.One of the main reasons why fast food is so popular is its convenience. In today's fast-paced world, people are constantly on the go and don't always have the time to prepare a meal at home. Fast food restaurants provide a quick and easy solution for those who are looking for a meal on the run. With drive-thru options and mobile ordering, fast food has become even more accessible to consumers.Another reason for the popularity of fast food is its affordability. In comparison to dining at a sit-downrestaurant, fast food is often much cheaper. This makes it an attractive option for those on a tight budget or for families looking to save money on meals. Many fast food restaurants also offer value menus and combo deals, makingit even more appealing to cost-conscious consumers.Furthermore, fast food offers a wide variety of options to choose from. Whether you're in the mood for a burger, pizza, tacos, or fried chicken, there is a fast food restaurant that can satisfy your cravings. This variety makes it easy for people with different tastes and dietary preferences to find something they enjoy.However, the popularity of fast food also comes withits drawbacks. One of the main concerns is the impact ithas on our health. Fast food is often high in calories, fat, and sodium, which can contribute to obesity, heart disease, and other health problems. Additionally, the large portion sizes and frequent consumption of fast food can lead to overeating and unhealthy eating habits.In addition to its impact on health, fast food also hasenvironmental implications. The production and distribution of fast food contribute to greenhouse gas emissions, deforestation, and water pollution. The excessive use of packaging and single-use plastics also adds to the environmental impact of fast food.Despite these concerns, the popularity of fast food continues to grow. It has become a staple in many people's diets and a part of their daily routine. As a result, it is important for consumers to be mindful of their fast food consumption and make healthier choices when possible.In conclusion, the popularity of fast food can be attributed to its convenience, affordability, and variety. However, it is important to be aware of the impact it has on our health and the environment. By making informed choices and seeking out healthier alternatives, we can enjoy the convenience of fast food without sacrificing our well-being.。
英文科普读物对比作文
英文科普读物对比作文The burgeoning realm of scientific literature offers a kaleidoscope of informative and thought-provoking reads. Each genre boasts its unique style and approach to knowledge dissemination, captivating readers in different ways.Scientific articles, the bedrock of academic discourse, delve into the intricate complexities of their subjects. Their formal language and meticulous structure provide a rigorous framework for understanding intricate concepts. Research papers often present novel findings and hypotheses, sparking further inquiry and scientific advancement.Popular science magazines, on the other hand, adopt a more accessible tone, making complex concepts digestiblefor a broader audience. Their engaging narratives and vivid illustrations capture the public's imagination, fostering a deeper appreciation for scientific breakthroughs. Articlesin these magazines often highlight the real-worldapplications and implications of scientific discoveries, making science relatable and relevant to everyday lives.Science books, a literary masterpiece in their own right, offer in-depth exploration of scientific ideas. Authored by scientists or science writers, these books delve into the history, theory, and applications of scientific concepts. Their comprehensive nature and meticulous research provide readers with a holistic understanding of the subject matter.Scientific journals, a domain of peer-reviewed publications, serve as the primary vehicles for disseminating original research findings. Their stringent criteria for publication ensure the accuracy andreliability of the information presented. Researchers from diverse fields contribute to these journals, fostering collaboration and advancing scientific progress.Finally, science blogs and podcasts offer a more informal and interactive platform for exploring scientific concepts. Written by scientists or enthusiasts, theseplatforms provide accessible explanations of complex topics and foster a sense of community among science aficionados. Their conversational tone and engaging content make science more approachable and enjoyable for a wider audience.。
对比类的英文作文
对比类的英文作文Title: A Comparative Analysis Essay。
In today's discourse, comparing and contrasting plays a crucial role in understanding various subjects, from literature to science to societal phenomena. This essay delves into the art of comparative analysis, exploring its significance, methodologies, and applications across different disciplines.To begin with, comparative analysis involves examining two or more items to identify similarities and differences between them. It serves as a tool for deeper understanding, enabling individuals to uncover insights that might not be apparent through individual examination. This approach fosters critical thinking and facilitates informeddecision-making.In literature, comparative analysis allows readers to delve into the themes, characters, and writing styles ofdifferent authors or works. By juxtaposing two pieces of literature, one can discern unique narrative techniques, cultural influences, and underlying messages. For example, comparing Shakespeare's "Romeo and Juliet" with Emily Bronte's "Wuthering Heights" unveils contrasting portrayals of love, societal norms, and tragic fate.In scientific research, comparative analysis is instrumental in identifying patterns, trends, and relationships between variables. Researchers often conduct comparative studies to evaluate the efficacy of treatments, the impact of environmental factors, or the evolutionary adaptations of species. Through meticulous data analysis, scientists can draw meaningful conclusions and contribute to advancements in their respective fields.Moreover, comparative analysis extends beyond academic realms and finds application in everyday life. Consumers frequently compare products before making purchasing decisions, weighing factors such as price, quality, and brand reputation. Similarly, policymakers rely on comparative analysis to assess the effectiveness of publicpolicies implemented in different regions or countries, informing future strategies and initiatives.When conducting a comparative analysis, several methodologies can be employed, depending on the nature of the subject matter. Quantitative approaches involve numerical data analysis, statistical tests, and mathematical models to identify patterns and correlations. Qualitative methods, on the other hand, focus on subjective interpretations, textual analysis, and in-depth interviews to uncover underlying meanings and perspectives.Regardless of the methodology chosen, thorough research and critical thinking are essential components of a successful comparative analysis. It requires attention to detail, open-mindedness, and a willingness to explore diverse viewpoints. By embracing complexity and ambiguity, individuals can extract valuable insights and contribute to knowledge advancement.In conclusion, comparative analysis serves as a powerful tool for gaining deeper insights into diversesubjects, from literature to science to everyday phenomena. By examining similarities and differences, researchers, scholars, and individuals alike can uncover hidden patterns, make informed decisions, and foster innovation. Through rigorous methodology and critical inquiry, comparative analysis continues to enrich our understanding of the world around us.。
对比式作文
对比式作文英文回答：The comparative analysis of these two perspectives reveals stark contrasts in their attitudes towards the role of government and individual responsibility. The first perspective, which advocates for limited government intervention, emphasizes the importance of personal autonomy and free markets. It argues that individuals are best equipped to make decisions about their own lives and that government should refrain from interfering in their affairs. By contrast, the second perspective supports a more active role for government, maintaining that the state has a responsibility to protect the well-being of its citizens. It advocates for government policies that promote social justice and economic equality, arguing that these policies are necessary to ensure a fair and prosperous society for all.In terms of economic policy, the first perspectivefavors free market principles, believing that they foster innovation, efficiency, and economic growth. It argues that government intervention in the form of regulations and taxes stifles economic activity and leads to lower living standards. The second perspective, on the other hand, supports government intervention in the economy to address market failures and promote social welfare. It argues that regulations are necessary to protect consumers, workers, and the environment, and that taxes can be used to fund public services and social programs that benefit all citizens.Regarding social policy, the first perspective emphasizes individual responsibility and self-reliance. It believes that individuals should be responsible for their own well-being and that government assistance should be limited to those who are truly unable to help themselves. The second perspective, on the other hand, advocates for a more comprehensive social safety net, arguing that government has a responsibility to provide assistance to those in need. It supports social programs such as healthcare, education, and housing assistance, believingthat these programs are essential for ensuring the well-being of all citizens.中文回答：通过对比两种观点，我们发现其在政府作用与个人责任方面的态度存在显著差异。
对比英文作文话题
对比英文作文话题Title: Comparison of English Essay Topics。
When it comes to composing English essays, the choice of topic plays a pivotal role in shaping the direction and quality of the piece. In this discourse, we will compare and contrast two distinct essay topics to discern their unique characteristics and challenges. 。
Topic 1: The Impact of Technology on Modern Society。
In the contemporary era, technology has permeated every facet of human existence, revolutionizing the way we live, work, and communicate. From the proliferation of smartphones to the advent of artificial intelligence, the influence of technology is undeniable. This topic offers a vast canvas for exploration, allowing writers to delve into various subtopics such as the effects of social media on interpersonal relationships, the ethical implications of emerging technologies, and the role of technology inexacerbating or alleviating societal inequalities. However, navigating this expansive subject requires a nuanced understanding of technological advancements, socio-cultural dynamics, and ethical considerations. Moreover, the abundance of existing literature on this topic necessitates a rigorous approach to research and analysis to produce original insights.Topic 2: Exploring the Themes of Identity and Belonging in Literature。
英语比较级作文讲
英语比较级作文讲In today's fast-paced world, the concept of comparison has become an integral part of our daily lives. Whether we are comparing products, services, or even personal achievements, the idea of evaluating and determining which is better has become second nature to us. One common way we engage in comparison is through the use of comparatives, specifically in the English language. Comparatives are used to compare two things, showing the superiority, inferiority, or equality between them. This essay will delve into the intricacies of English comparatives, exploring their historical background, different perspectives, case studies, benefits, drawbacks, and future implications.The use of comparatives in the English language dates back to the early stages of its development. As English evolved over centuries, comparatives emerged as a crucial linguistic tool to express differences in degree. The comparative form typically adds '-er' to adjectives or adverbs to indicate a higher degree of a particular quality. For example, 'faster' is the comparative form of 'fast,' indicating a higher speed. This linguistic feature has been essential in facilitating clear communication and providing a structured way to convey comparisons effectively.From a historical perspective, the development of comparatives in English can be traced back to Old English and Middle English periods. During these times, the language underwent significant changes, leading to the establishment of grammatical rules and structures that included comparatives. As English continued to evolve, comparatives became more standardized, allowing for a more systematic comparison of different entities. This historical background highlights the importance of comparatives in shaping the English language and enabling concise and accurate comparisons.When examining different perspectives on English comparatives, various opinions and approaches come to light. Some linguists argue that comparatives play a vital role in enhancing the precision and clarity of communication. By usingcomparatives, individuals can convey nuanced differences and make informed decisions based on comparative analysis. On the other hand, some critics suggest that an overreliance on comparatives may lead to oversimplification or superficial judgments. They caution against reducing complex issues to mere comparisonswithout considering the broader context.To illustrate the significance of English comparatives, let us consider a case study involving two smartphone models: Model A and Model B. When comparing the battery life of both models, consumers may use comparatives to determine which device offers better performance. By stating that 'Model A lasts longer than Model B,' individuals can make an informed choice based on a clear comparison. This case study exemplifies how comparatives are utilized in everyday scenarios to evaluate and differentiate between options.Despite the benefits of using comparatives in English, there are also drawbacks to consider. One potential downside is the risk of oversimplification, where complex issues are reduced to binary comparisons without considering the nuances involved. Additionally, the overemphasis on comparatives may lead to a competitive mindset that prioritizes winning over collaboration and mutual understanding. It is essential to strike a balance between using comparatives effectively and recognizing the limitations of this linguistic tool.Looking ahead, the future implications of English comparatives suggest a continued reliance on comparative analysis in various fields, including marketing, education, and decision-making processes. As technology advances and communication becomes more globalized, the need for clear and precise comparisons will only grow. It is crucial for individuals to develop critical thinking skills to evaluate comparisons critically and discern the underlying factors that influence comparative judgments.In conclusion, English comparatives serve as a valuable tool for expressing differences in degree and facilitating comparisons in various contexts. While they have a rich historical background and offer numerous benefits, it is essential toapproach comparatives with a critical mindset and consider the broader implications of using them. By understanding the nuances of English comparatives and their impact on communication, individuals can navigate the complexities of comparison more effectively and make informed decisions based on thoughtful analysis.。
对比类型的英语作文
对比类型的英语作文英文回答：In the realm of human experience, we often find ourselves confronted with the task of making comparisons. Whether it be weighing the pros and cons of two different career paths or contemplating the relative merits of competing political ideologies, our ability to engage in comparative analysis is an essential cognitive skill.At its core, comparison involves identifyingsimilarities and differences between two or more subjects. It allows us to discern patterns, draw inferences, and make informed judgments. By comparing and contrasting, we gain a deeper understanding of the world around us and our place within it.One of the most fundamental applications of comparison is in the field of science. Scientific inquiry relies heavily on the systematic comparison of experimentalresults to establish hypotheses and theories. By comparing the behavior of different substances under controlled conditions, scientists can deduce the underlying mechanisms responsible for observed phenomena.In the social sciences, comparison plays an equally vital role. Anthropologists compare different cultures to identify universal patterns of human behavior and cultural variation. Psychologists compare different psychological profiles to understand the factors that influenceindividual development and behavior. Historians compare past events to gain insights into the present and project future outcomes.Comparison is also a powerful tool in the arts and literature. Writers and artists often use comparative techniques to create contrast, reveal hidden meanings, and provoke emotional responses from their audiences. By juxtaposing different characters, themes, or aesthetic styles, artists can highlight the complexities of human nature and explore the multifaceted nature of experience.In language, comparison is essential for expressing relationships and conveying nuanced meanings. Figurative language devices such as metaphors, similes, and analogies rely on comparison to evoke vivid imagery and create deeper connections between words and ideas.Furthermore, comparison is fundamental to the process of decision-making. By comparing the potential outcomes of different choices, we can evaluate risks and benefits and make informed decisions that are aligned with our values and goals. It allows us to weigh the pros and cons of various alternatives and choose the course of action thatis most likely to lead to a desired outcome.In conclusion, the ability to compare and contrast is a cognitive skill of paramount importance. It enables us to make sense of the world, gain deeper insights into our own thoughts and actions, and make informed decisions about our lives. From science to art, from the social sciences to language, comparison is a versatile tool that empowers us to understand, appreciate, and shape the world around us.中文回答：比较作为一种思维活动，在人们的认知和理解中扮演着重要的角色。
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Practical Comparison of Fast Public-key CryptosystemsPriit KaruTelecommunications Software and Multimedia Laboratory,Helsinki University of Technologypk@tml.hut.fiJonne LoikkanenLaboratory of Information Processing Science,Helsinki University of Technologyjloikkan@cc.hut.fiAbstractThe need to implement public key cryptography primitives in very limited envi-ronments like smart cards,PDA’s and mobile phones demands new and faster cryp-tosystems.This paper gives an overview of the proposed NTRU and braid groupbased cryptosystems.It also describes our implementation details and gives the speedcomparison of NTRU,braid group cryptosystem and currently the most used cryp-tosystem in limited environments,elliptic curve cryptosystem.The paper comes to aconclusion that NTRU is one to two orders of magnitude faster than ECC,while theefficiency of Braid groups based cryptosystem is between ECC and NTRU.Keywords:Public key cryptosystems,implementation,NTRU Cryptosystem,Ellip-tic Curve Cryptosystem,Optimal Extension Fields,Braid group cryptosystem,com-parison.1IntroductionA public key cryptosystem is an asymmetric cryptosystem where the key is constructed of a public key and a private key.The public key,known to all,can be used to encrypt messages.Only a person that has the corresponding private key can decrypt the message. One of the most widely used public key cryptosystem is RSA.In RSA a public key is constructed by multiplication of two very large primes.To completely break RSA one needs tofind the prime factors.In practice,RSA has proved to be quite slow,especially the key generation algorithm.RSA is not well suited for limited environments like PDA’s, mobile phones and smart cards without RSA co-processors,because it is hard to implement large integer modular arithmetic on such environments.RSA also requires longer keys in order to be secure compared to some other cryptosystems like elliptic curve cryptosystems (ECC).There is a need of faster asymmetric cryptosystems.This need has been the greatest with mobile devices,where not so much memory or computing resources are available.Also with traditional hardware,cryptosystems that use less resources are needed.ECC is onepublic key cryptosystem,that has proven to be faster than RSA.It is based on a discrete logarithm problem in elliptic curve groups.ECC has been around for some time and has some existing implementations.Although there seems to be not as much security analysis done for ECC as for RSA,the ECC is well known and there are also some well respected standards available(see[7]and[8]).Recently some new,allegedly even faster public key cryptosystems,have been developed. This includes NTRU[12]and braid groups based cryptosystems[2].The principal object-s used by the NTRU cryptosystem are so called truncated polynomial rings,while braid cryptosystem uses braid groups.Braid public key cryptosystem has no known public im-plementations.NTRU has been available for longer period than braid cryptosystem and is better documented.The aim of this study is to analyze and implement one traditional public key cryptosystem (ECC)and two recently proposed cryptosystems(braid group based and NTRU).Based on analysis and implementations a comparison between the cryptosystems can be made.This paper gives an overview of these two proposed cryptosystems and a rough comparison of the speed of these cryptosystems.This study can also serve as an independent verification of the claims since,for now,most of the analysis done on these new cryptosystems is done by the proposers of the cryptosystems themselves and that may not be truly objective. The role of RSA here is to function as a reference to compare the security levels of these asymmetric cryptosystems.Our implementations are done using C++as a programming language.We have optimized the implementations for-bit Intel family processors and have tried to keep the code portable to other platforms.In order to keep the memory requirements low,so it would be possible to port the code to limited environments(PDA’s),we do not use large look-up tables.This paper is organized in the following manner.Section2gives a brief description of the commonly used public key cryptosystems RSA and ECC.Section3describes the new fast public key cryptosystems:NTRU and braid cryptosystem.In this section we also describe our NTRU and braid cryptosystems implementations details.In section4we give the results of the comparison of the cryptosystems.Section6describes how this study may be taken further.2Commonly used public-key cryptosystemsThis section describes two public-key cryptosystems which are extensively used today and for which some standards have been published.Both RSA and ECC are covered by the IEEE P1363Standard Specifications for Public-key Cryptography1[7].We also briefly describe some details about our ECC implementation and state ECC security level assumptions.2.1RSAIn1977Shamir,Rivest and Adelman proposed thefirst public-key cryptosystem calledRSA as a principal object for public-key cryptography.RSA cryptosystem is defined asfollows.Let us consider that plaintext and ciphertext are both taken from the set.Let ,where and are primes,and define,.For,the encryption function is defined asand decryption function is.The values and are public,and the values are secret.The RSA cryptosystem is explained in almost any bookabout cryptography,for example in[10].Because RSA is based on modular arithmetic with very long operands,the performance ofRSA is quite slow on limited environments with low memory and processor power.Also,because there has been some progress on the factorization problem,the key sizes that areconsidered to be secure today are relatively monly used key size for RSA is1024-bits.For comparison it is widely believed that the same level of security can beachieved using ECC and only160-bit keys.Better overview about the security of ECC andRSA can be found from[9].These two facts(the long key size and slow performance onlimited environments)are the main factors why people have started to look for alternativesolutions.In this paper we look at three alternatives to RSA:ECC over optimal extensionfields,NTRU and braid group based cryptography.2.2ECCSince the introduction of the concept of public-key cryptography by Whitfield Diffie andMartin Hellman in1976,the cryptographic importance of apparent intractability of thewell-studied discrete logarithm problem has been recognized.Diffie and Hellman em-ployed the discrete logarithm in the group but the same concepts can be extended to arbitrary groups.The Elliptic Curve Cryptography is based on the intractability of the Elliptic Curve Discrete Logarithm Problem(ECDLP).There are two primary reasons for using ECDLP as an alternative to the discrete logarithm problem in the group.First of all,thefield over which elliptic curve is defined can be chosen so that it would be easier to implement ECC on limited environments.Secondly,at the time being the discrete log-arithm problem in Elliptic Curve group seems harder than the discrete logarithm problem in.Consequently,one could use a group that is smaller than while maintaining the same level of security.This results smaller key sizes,bandwidth savings,and faster imple-mentations.The security levels of the ECC are briefly described in section2.2.1.General overview of ECC can be found in[11].Elliptic Curve group is always defined over some underlyingfield.The choice of thefinitefield affects quite dramatically the performance of the cryptosystem.There is a smalloverview of thefinitefields that have been used and a description of the optimal extensionfields(OEFs)our implementation uses in section2.2.2.The OEF promise specially goodperformance on limited environments.Because OEFs have been proposed quite recently[1]there are no standards available concerning elliptic curve over OEF parameter choosing. The implementation described in section2.2.2uses ElGamal scheme to construct a cryp-tosystem using elliptic curve group.The ElGamal scheme for elliptic curves is the follow-ing.Atfirst we have to choose the base elliptic curve point with order divisible by a large prime.This point can be agreed fore-hand and can be made publicly available.Key generation.Bob chooses a large random integer.Then he calculates the value.Note that the last operation is performed on an elliptic curve group by adding point times to itself.Bob’s private key is the value and Bob’s public key is the elliptic curve point.Encryption.If Alice wants to send a message,which is an elliptic curve point,to Bob she does the following.She chooses a random number.Next she calculates the values and.The encrypted message is the pair of elliptic curve points.Decryption.When Bob receives the encrypted message he can calculate the message using his private key as.Note that when we encrypt one elliptic curve point we obtain two elliptic curve points as ciphertext.In other words,the message expansion is2-1when this ElGamal scheme is used.The actual formulas of elliptic curve arithmetic are beyond this paper.Elliptic curve arith-metic is explained in[11].The most time consuming operation in this scheme is scalar multiplication,where is an large integer and is an elliptic curve point.Because of that it can be expected that the key generation and decryption will take approximately the same amount of time,and encryption will be about two times slower.The performance tests confirm this as will be shown in section4.1.2.2.1Security level of ECCCurrently the best way to attack ECDLP is Pollard’s parallelizable rho method,with an expected running time ofandfinally Optimal Extension Fields(OEFs).As binaryfields are most suit-able for hardware implementation,primefields arithmetic is slow to implement in limited environments and for even compositefields the ECDLP can be easily solved(recent result of Gaudry,Hess,and Smart[19]),our implementation uses OEFs.OEF arefields in the form,where and for which there exists an irreducible binomial.The integer is chosen so that the value would fit into one processor register.It is also wise to choose and to be small values(usually ,or),so that we could use addition instead of multiplications in implementations.The key performance advantage of using OEFs comes from the fact that the modular reductions can be done fast using the following equivalence.Also the same idea can be used to speed up the operations modulo polynomial,using the polynomial equivalence.Our implementation uses afixed OEF in the form of with an irreducible polynomial.OEF in this form is chosen because is small enough tofit into-bit register and also because[13]states that the largest prime order of elliptic curve group over this OEF is2.For the ECC to be secure one has to choose the elliptic curve parameters so that the order of the curve would be divisible by a large prime.However,the interest of this paper is only the speed comparison,so we overlook the curve parameter choosing because curve parameters affect the performance only with neglible factor.This paper relies on the fact stated in[13] that the largest possible prime order for the elliptic curve over thefield is a168-bit integer,so we can be sure that there exists a cryptography suitable elliptic curve over thatfield.The implementation consists of two classes:class Oef which implementsfield operations and class Ec which implements elliptic curve operations.The speed of the implementation is tested using popular ElGamal scheme(the ElGamal scheme is briefly described in sec-tion2.2)for elliptic curve groups.The speed of ECC mostly depends on the speed offield operations in class Oef.Two most time consumingfield operations arefield inversions andfield multiplications.Our implementation uses the accumulation-and-then-reduction technique described in[13]forfield multiplication and polynomial version of Extended Euclidean algorithm forfield inversion which is also described in[13].The last algorithm uses also the binary extended gcd algorithm to calculate the inversions modulo. Description of the binary extended gcd algorithm can be found from[14],page608.As stated in section2.2,the ElGamal scheme assumes that the message is an ellip-tic curve point.Thus,to implement a fully working cryptosystem using elliptic curve group,we also need a quick way to decode and encode plaintext messages to elliptic curve points.The encoding and decoding process can be done using a algorithms4.3.6and4.3.7 described in[8].The current version of our ECC implementation does not have an im-plementation for encoding and decoding.The performance tests can be done without the encoding and decoding algorithms,as these routines add only a small constant factor to the overall encrypting and decrypting time.3New public-key cryptosystems3.1NTRUNTRU was originally presented by Jeffrey Hoffstein in the rump session at CRYPTO’96,and was published in[12]in1998.NTRU cryptosystem was patented by NTRU Cryp-tosystems,Inc(U.S.Patent No.6,801,597)on July24,2000.NTRU is based on the algebraic structures of certain polynomial rings.The“hard prob-lem”,on which NTRU is based,is the problem offinding a short vector in a given lattice.The NTRU encryption procedure uses a mixing system based on polynomial algebra andreduction modulo two numbers and,while the decryption procedure uses an unmixingsystem whose validity depends on elementary probability theory.The security of the poly-nomial mixing system comes from the interaction of the polynomial mixing system withthe independence of reduction modulo and.Let stand for the polynomial ring with an irreducible polynomial.That means.The key creation,encryption and decryption routines are the following.Key Creation.To create a NTRU key,Bob randomly chooses2polynomials. The polynomial must satisfy the additional requirement that it has inverses modulo and modulo.Lets denote these inverses as and.Next we can compute the public key as.The private key is the polynomial.In practise we may also want to store the inverse.Encryption.Suppose that Alice wants to send a message(with coefficients reduced modulo)to Bob.She begins by randomly choosing a polynomial and uses Bob’s public key to compute the encrypted message as. Decryption.Suppose Bob has received a message from Alice and wants to decrypt it using his private key.In order to decrypt,Bobfirst computes,where he chooses the coefficients of in the interval from to.Now Bob can recover the message by computing.The NTRU cryptosystem is a probabilistic cryptosystem,so it may also give wrong decryp-tion with some values of,and.In practice,the probability of the cryptosystem failure is very small,when the parameters have been chosen carefully.[12]proposes to choose, and with afixed number of small nonzero coefficients.The actual description of how to choose,and and a longer explanation of the NTRU cryptosystem can be found in [12].3.1.1Security level of NTRUSome security analysis of NTRU can be found in[12].The reference contains a brief description of four attacks to NTRU(brute force attacks,meet-in-the-middle attacks,mul-tiple transmission attacks and lattice based attacks).The same paper also gives three sets of NTRU parameters(NTRU167,NTRU263and NTRU503).Our paper assumes that NTRU167has roughly the same security level as RSA512,NTRU263can be compared to RSA1024and NTRU503to RSA2048.These assumptions are taken from NTRU FAQ[18],which maybe is not truly objective.3.1.2NTRU implementationsThe implementation of NTRU cryptosystem consists of two classes:Polyn which imple-ments the arithmetic of the truncated polynomial ring and Ntru which implements the actual cryptosystem.As the NTRU cryptosystem is based on polynomial rings,the main speed improvements can be made by optimizing polynomial ring operations in class Polyn.The most time con-suming operation is the ring inversion.Our implementation uses a polynomial version of Almost Inverse Algorithm described in[17]for calculating the inverses.The ring inver-sion operations are used only in the key generating part of NTRU(see3.1),so the good performance of the ring inversion algorithm does not affect the speed of NTRU encryption and decryption.The other key part of the polynomial ring arithmetic is the ring multiplication operation. Our implementation uses a naive multiplication algorithm(star multiplication)from[15], with a running time of,where is the degree of the polynomial.Some possible improvements to multiplication algorithm are described in[16],where it is explained how to reduce the running time of polynomial multiplication toa bFigure1:a.A braid before word-algorithm,b.A braid after word-algorithm meaning that when two strings cross the string running from left to right is above the other. If a fundamental braid has negative exponents the crossings are negative.A-braid group,denoted as,is set a set of-braids.Each braid within the braid group can be transformed into any other braid in the braid group using generating equations, which are:,if,if.Two-braids are said to be equivalent if they reside in the same braid group.Each braid group can be presented with a canonical form,which is unique for each[2].A canonical from of a braid group can be presented with fundamental braid following with a number of permutations.Permutation is a representation of one possible ordering of a set.The number of permutations in canonical form representation is denoted as canonical length.The permutations are in leftweighted form,which means that if a crossing would be passed from one permutation to the next,the permutation couldn’t present the generated braid anymore.Thefigure1illustrates the canonical form.Word problem is the problem for converting a braid in braid group to its unique pre-sentation,canonical form.The multiplication of two braids is the braid obtained by positioning on top of[2].3.2.2Public Key cryptosystem using braidsA cryptosystem using braids as the mathematical basis is described in[2].This cryp-tosystem is a specialized version of a general methodfirst introduced in[3].The key factor behind the cryptosystem is the word problem.There are algorithms that can solve the word problem in polynomial time.The product of the word algorithm is the canonical form of a -braid.This canonical form corresponds to an unique braid group.If we obtain a productof three braids and transform the product into its canonical form,the original braid-factors are hard tofind.In fact all the known algorithms to produce the factors require exponential time.We can thus use braids to implement a fast asymmetric cryptosystem. Another mathematical key feature of the braid cryptosystem is the commutative property of the braids constructed in,group of-braids generated using only generators smaller than some integer,and,group of-braids constructed using only generators larger than.The cryptosystem is as follows(from[2]):Key generation.Choose a sufficiently complicated-braid.Next choose a braid.Public key is,where.Private key is. Encryption.Given a message and the public key.Choose a braid at random.Ciphertext is,where and. Decryption.Given a ciphertext and private key,compute. Note that the hash function is applied to the same braid in both encryption and decryption, because of the commutative property of and:.The following operating characteristics are promised in[2]:(=canonical length,= braid index)plaintext block bits;ciphertext block bits;encryption speed operation;decryption speed operation;message expansion;private key length.The security level of the braid public key cryptosystem is analyzed in the next section. 3.2.3Our implementation of the braid public key cryptosystemThis chapter relies on theory presented at3.2.2.For now the implementation only deals with braids made up from positive generators.The implementation consists of a few C++ classes.In the bottom is the Permutation-class,that serves for presenting permutations and offers operations to manipulate permutations.A-permutation is presented in an array of integers.In paper[4]it is suggested that a-permutation(different permutations) could be presented as an integer and different transitions and could be pre-calculated inlook up tables for each permutation.This kind of an implementation would clearly be toodemanding for PDA’s(or any present computers).The storage space for left multiplicationtable would be integers.For example would require storage space of million integers!(for32-bit processor,130megabytes!).For considerable(secure)lengthsof the storage space becomes a number of astronomical proportions.A braid of any kind can be presented with a fundamental braid and a list of permutations.ListElement-class handles the chaining of the permutations into braids.The next level of the implementation is the WordAlgorithm-class that has operations forcalculating the canonical form of a braid,inversing a braid in canonical form and calculat-ing the canonical form of the product of two braids in canonical forms.The calculating of an inverse braid[2]requires going through all permutations of the braidto be inverted(canonical length=)and calculating their inverses.Calculating an inverseof a permutation has(=braid index)complexity.Inverting a braid,therefore,hascomplexity.The key algorithm for the braid cryptosystem performance is the algorithm that calculatesthe canonical form of product of two braids in canonical forms.The algorithm is imple-mented as the word-algorithm presented in[4].The calculating of the product is done byinserting the permutations of the other braid from the left in to the left canonical form ofthe other braid.In[5]it is shown that by doing the construction this way,the adding ofa permutation has limited effects:The cascading propagates to one direction only and thematerial exchanged from one permutation to the next is at mostAs a permutation is cascaded into braid,we must calculate what chunkfits into the currentpermutation and what chunk must be passed on to the next permutation.This calculationcorresponds tofinding the maximal tail[5].For now this operation is done at methodfindTail and the operation takes complexity in the worst case.So,the whole productcalculating algorithm takes(and are the canonical lengths of the braids).This is somewhat slower than the theoretical promised[2].The next level of the implementation is the BraidCryptoSystem-class.This class has op-erations for creating the public key,encrypting and decrypting.The operations are doneaccording to braid presentation in3.2.2using the above described classes and operations. The actual decryption and encryption are done using a hash function,that has the same parameters from both encryption and decryption.Note,that unlike some other public key cryptosystems(ECC,RSA)the length of the plaintext has no significant effect on the decryption and encryption speeds of the braid cryptosystem(see3.2.2).The calculation of the braids for hash function has greater complexity than calculating the hash itself,which can be calculated in time proportional to message length.The space requirements for the implementation are as follows:One permutation can bepresented with an array of elements.A braid with canonical length will requirepermutations.The space requirement is therefore.While computing a product,copiesof participating braids are made.No additional look up tables or data structures are usedin computation.The braid PKC requires the memorization of a few braids.Therefore thecomplete space requirement is,where is a small integer.If,and(symbols refer to section3.2.2)have the same canonical length,the public key has at most the key-size of integers(one for,three for.For and,this would mean bits bits.This seem quite a lot,but for reasons given at the beginning of this section the implementation wastes a little space in presenting the braids to avoid using extremely large look-up tables.However, for transferring purposes the permutations may be converted into into a more economical form using the’factorial coordinate’method[6].The number of permutations inis,a number that can be presented with bits.Therefore the storage of the public key for and would take only bits.3.2.4The security analysis of braid public key cryptosystemNot much research has been done on breaking of the braid cryptosystem.In[2]it is implied that with most choices of parameters and the breaking of braid cryptosystem would mean solving the generalized conjugacy search problem(find from if ).This problem is known to be hard.For the sake of comparison let us assume that breaking braid cryptosystem indeed requires the solving of the generalized conjugacy search problem and that the problem can only be solved by brute force methods.The assumption is,of course,not certain,but even a nearly sufficient security analysis would be a topic of another paper.Let’s assume that the and(see definitions in section3.2.2)division is,he must go through all the braids in braid area.The key factor of this approach is to determine how much work must be done to verify that one particular choice is/is not the privateKey.This work is at most proportional to the amount of work to calculate the canonical form of the product,,where is the canonical length of one candidate and is the canonical length of(see3.2.2).To discard a choice one must at least take into account all the data that makes up the braid. This means at least the complexity.One could,for instance calculate one permuta-tion from candidates permutations and compare this with permutation calculated from the result.If these wouldn’t match a choice could be discarded.This would eliminate most choices,leaving only:th fraction of choices left.For the choices left we can try the conver-sion algorithm,total work proportional to,while we should actually count3The elliptic curve order of bits also shows that-bit keys are used.Key generation speed(ms)60140255Decryption speed(ms)NTRU167NTRU263NTRU5038.319.871.2Encryption speed(ms)1.4 3.512.7Table2:The performance of our NTRU implementation on a500MHz Celeron processor about decoding and encoding are covered by the ANSI standard[8].This paper assumes that-bit message can be decoded as an elliptic curve point on an elliptic curve with the order of-bit ing this assumption we can state that it takes milliseconds to encrypt a-bit plaintext and milliseconds to decrypt the same message using ECC with the security level comparable to RSA1024.A private key of the ECC with a group order of-bit is a-bit integer,the public key (elliptic curve point)can be coded to a-bit integer.4.1.1Test results for NTRU cryptosystemThe test were run on a workstation with500MHz Intel Celeron processor running Linux. Each test was repeated several times and the average time was used.The table2shows the test results of key generating,encrypting and decrypting messages using the NTRU cryptosystem.It takes milliseconds to encrypt one ring element using NTRU263.The decryption takes milliseconds.The performance of encryption and decryption can be increased by using a better multiplication algorithm,see3.1.2. Decoding and encoding plaintext messages as polynomial ring elements can be done fast. In general-bit plaintext can be coded as a truncated polynomial ring elements of degree,with coefficients modulo(see paragraph5.2in[12]).Thus,-bit plaintext can be coded as a truncated polynomial ring element with a degree of.To encrypt the same plaintext using NTRU cryptosystem with the security level roughly the same as RSA1024it takes about milliseconds.The decryption ciphertext obtained takes milliseconds.The public key of NTRU263can be coded to a bit integer.The private key length is two times bigger,because we store also the inverse of polynomial(see also section3.1).。