Resonance Effects in the Interaction of NLS Solitons with Potential Wells

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瞬变电磁英语

瞬变电磁英语Fluctuating Electromagnetic ForcesThe realm of electromagnetism is a captivating and dynamic field of study, where the interplay between electricity and magnetism gives rise to a myriad of fascinating phenomena. At the heart of this intricate tapestry lies the concept of fluctuating electromagnetic forces, a phenomenon that has profound implications in various scientific and technological domains.Electromagnetic forces are the fundamental interactions that govern the behavior of charged particles, whether they are stationary or in motion. These forces arise from the interaction between electric and magnetic fields, which are inextricably linked through Maxwell's equations. When a charged particle experiences a change in its motion or position, it creates a fluctuating electromagnetic field, which in turn exerts a force on other nearby charged particles.The study of fluctuating electromagnetic forces has been a subject of keen interest for scientists and engineers alike. In the realm of particle physics, these forces play a crucial role in the behavior of subatomic particles and the dynamics of high-energy collisions. Theability to predict and harness these forces has enabled the development of sophisticated particle accelerators and detectors, which have revolutionized our understanding of the fundamental building blocks of matter.Beyond the realm of particle physics, fluctuating electromagnetic forces have found numerous applications in various fields. In the field of materials science, these forces play a crucial role in the understanding and manipulation of the properties of materials at the nanoscale. The ability to control and engineer these forces has led to the development of novel materials with exceptional electrical, magnetic, and optical properties, opening up new avenues for technological advancements.In the realm of electronics and communications, fluctuating electromagnetic forces are of paramount importance. The design and operation of electronic devices, from simple transistors to complex integrated circuits, rely heavily on the precise control and management of these forces. The ability to mitigate the detrimental effects of electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues has been a driving force behind the continuous evolution of electronic systems, ensuring their reliability and performance.The field of energy generation and transmission is another areawhere fluctuating electromagnetic forces play a pivotal role. The generation of electricity through the use of electromagnetic induction, as seen in power generators and transformers, is a direct consequence of these forces. Similarly, the transmission of electrical power over long distances requires the careful management of electromagnetic fields to minimize energy losses and ensure grid stability.In the realm of biomedical engineering, fluctuating electromagnetic forces have found intriguing applications. The use of magnetic resonance imaging (MRI) technology, a powerful diagnostic tool, relies on the intricate interplay between electromagnetic fields and the human body. Additionally, the emerging field of bioelectromagnetics explores the potential therapeutic applications of electromagnetic fields in areas such as pain management, tissue regeneration, and the treatment of certain neurological disorders.As the world continues to evolve and technological advancements accelerate, the understanding and control of fluctuating electromagnetic forces will become increasingly crucial. Researchers and engineers across various disciplines are actively exploring new frontiers, seeking to harness the power of these forces to create innovative solutions that address the pressing challenges of our time.In conclusion, the study of fluctuating electromagnetic forces is amultifaceted and ever-evolving field of inquiry. From the fundamental principles of particle physics to the practical applications in electronics, energy, and biomedicine, these forces have shaped and continue to shape the trajectory of scientific and technological progress. As we delve deeper into the mysteries of the electromagnetic realm, we unlock new possibilities for discovery and innovation, paving the way for a future where the interplay between electricity and magnetism holds the key to unlocking the vast potential of our universe.。

高分子化学名词解释英文

高分子化合物（High Molecular Compound）：the compound which many atom or atom group mai nly conbined by covalent bond ,relative molecular weight is above 10^4.单体（Monomer）：The raw material used to form polymer.重复单元（Repeating Unit）：The smallest basic unit which repeatedly emergence and component are the same in the lagre molecular chain of polymer .单体单元（Monomer Unit）：结构单元与原料相比，除了电子结构变化外，其原子种类和各种原子的个数完全相同，这种结构单元又称为单体单元。

结构单元（Structural Unit）：The unit monomers formed in the macromolecular chain .聚合度（DP、X n）(Degree of Polymerization) the average number of repeating unit of polymer ma cromolecular.聚合物分子量（Molecular Weight of Polymer）：The molecular weight of repeating units multiplied with the number of repeating units数均分子量(Number-average Molecular Weight)：Polymer molecules with a different numberaverag e molecular weight average molecular weight of statistics.重均分子量（Weight-average Molecular Weight）：Using different molecular weight polymermolecula r weight average molecular weight ofthe statistical average.粘均分子量（Viscosity-average Molecular Weight）：Using viscosity method to measure the molecu lar weight of polymer.分子量分布（Molecular Weight Distribution, MWD ）：Because different molecular weight polymersa re generally composed of a mixture ofhomologues, it has a certain molecular weightdistribution,多分散性（Polydispersity）：Used to express the size of the polymermolecular weight does not equ al more technical terms is called dispersion.分布指数(Distribution Index) ：The ratio of Molecular Weight and Number-average Molecular Weigh t。

Fluorescence Resonance Energy Transfer (FRET)荧光共振能量转移(FRET)

(H3C)2N
• chemical attachment of synthetic dyes
O
N+(CH3)2
OCH3 O
R
Absorption / Emission (a.u.)
580
fluorescence
a typical synthetic chromophore: tetramethylrhodamine
Absorption Emission
400 450 500 550 600 650 700 wavelength (nm)
• extinction coefficient: ~100,000 Molar-1 cm-1 • fluorescence quantum yield: ~50% • triplet quantum yield <1% • available in reactive forms (to attach to amines,
fluorophore *Donor-Acceptor의 Energy transfer는 거리에 의해 효율이 결정 (~10nm)
Spectral properties of involved chromophore
FRET
Calculation
Efficiency of Energy Transfer = E = kT/(kT + kf + k’) kT = rate of transfer of excitation energy kf = rate of fluorescence k’ = sum of the rates of all other deexcitation
fluorescence experiments 4. Some applications & examples

化学基础英文17羧酸_carboxylic_acids

The following formulas are examples of other naturally occurring carboxylic acids. The molecular structures range from simple to complex, often incorporate a variety of other functional groups, and many are chiral.
As shown in the following table, tacids are usually referred to by their common names, which in most cases reflect their sources. A mnemonic phrase for the C10 to C20 natural fatty acids capric, lauric, myristic, palmitic, stearic and arachidic is: "Curly, Larry & Moe Perform Silly Antics" (note that the names of the three stooges are in alphabetical order).
Chapter 17 Carboxylic Acids 羧酸
Chapter 17 Carboxylic Acids
The carboxyl functional group that characterizes the carboxylic acids is unusual in that it is composed of two functional groups described earlier in this text. As may be seen in the formula, the carboxyl group is made up of a hydroxyl group bonded to a carbonyl group. It is often written in condensed form as –CO2H or –COOH. Other combinations of functional groups were described previously, and significant changes in chemical behavior as a result of group interactions were described (e.g. phenol & aniline). In this case, the change in chemical and physical properties resulting from the interaction of the hydroxyl and carbonyl group are so profound that the combination is customarily treated as a distinct and different functional group.

核磁共振中自旋裂分或J偶合[精心整理]

核磁共振中自旋裂分或J偶合Spin-spin splitting or J couplingCoupling in 1H NMR spectraWe have discussed how the chemical shift of an NMR absorption is affected by the magnetic field B e produced by the circulation of neighboring electrons. Now we wish to examine how the magnetic field produced by neighboring nuclei B n affects the appearance of the 1H NMR absorption. The effect occurs through the interaction of nuclear spins with bonding electron spins rather than through space. Let's first consider the absorption of a hydrogen nucleus labeled A with only one neighboring hydrogen nucleus in a vicinal position labeled X. Let's also assume that H A and H X have significantly different chemical shifts.H X will have approximately equal probability of existing in either the low energy alpha state or high energy beta state. Again because of the small energy difference between the low and high energy states, the high energy state is easily populated from thermal energy. For those molecules in which H X exists in the low energy state, about half the molecules in the sample, its magnetic field B n will subtract from the magnetic field B o-B e and for those molecules in which H X exists in the higher energy state, again about half the molecules, its magnetic field B n will add to B o-B e.Note: whether B n for a particular spin state adds to or subtracts from B o is a function of the number of intervening bonds; this phenomenon doesn't usually affect the appearance of the signal and will not be explained here but results from the mechanism of coupling involving interaction of nuclear spins with electron spins. For the example of vicinal coupling (3 intervening bonds), the B n field is negative for H X in the alpha spin state; for geminal coupling B n is positive for H X in the alpha spin state. Geminal coupling occurs between protons of different chemical shift bonded to the same carbon (2 intervening bonds); it will be discussed later.As a consequence of the B n field in a vicinal system, at fixed external magnetic field B o, a lower frequency will be required to achieveresonance for those molecules which have H X in the state than for those molecules which have H X in the state. The NMR signal for H A will appear as a two line pattern as shown in Figure 16. We say the H X splits the absorption H A into a doublet and the two protons are coupled to each other. The intensity of the two lines will be equal since the probability of H X existing in the or states is approximately equal. The chemical shift, which is defined as the position of resonance in the absence of coupling, is the center of the doublet. Just as H X splits the signal of H A into a doublet, H A splits the signal of H X into a doublet. The overall splitting pattern consisting of two doublets is call an A X pattern. The splitting of H A by H X is diagramed in Figure 16.When the molecule bears two equivalent vicinal protons, four possibilities exist for their combined magnetic fields: both are in spin states, one is in the spin state and one in the spin state, andvice versa, or both in the spin state. These four possibilities have about equal probability, and the appearance of the NMR signal is a 3-line pattern, a triplet(Figure 17), with intensities 1:2:1 because the effect of and are the same. With one adjacent proton in the spin state andthe other in the spin state, the effect of the B n field becomes zero, and the center line of the triplet is the position of the chemical shift. The two H X protons split the H A signal into a triplet and the H A proton splits the two H X protons into a doublet. The overall splitting pattern consisting of a triplet and a doublet is called an A X2 pattern.Three chemical shift equivalent vicinal protons H X split the absorption of H A into a quartet with intensity pattern 1:3:3:1 as shown in Figure 10. The chemical shift is the center of the quartet. The three H X protons split the H A signal into a quartet and the H A proton splits the signal for the three H X protons into a doublet. The overall splitting pattern consisting of a quartet and a doublet is called an A X3 pattern.The spacing between the lines of a doublet, triplet or quartet is called the coupling constant. It is given the symbol J and is measured in units of Hertz (cycles per second). The magnitude of the coupling constant can be calculated by multiplying the separation of the lines in units (ppm) by the resonance frequency of the spectrometer in megaHertz.J Hz = ppm x MHz (typically 300, 400, or 500 MHz)In general, N neighboring protons with the same coupling constant J will split the absorbance of a proton or set of equivalent protons into N+1 lines. Note that the splitting pattern observed for a particular proton or set of equivalent protons is not due to anything inherent to that nucleus but due to the influence of the neighboring protons. The relative intensity ratios are given by Pascal's triangle as shown in Figure 18.Because of the mechanism of J coupling, the magnitude is field independent: coupling constants in Hertz will be the same whether the spectrum is measured at 300 MHz or 500 MHz. Coupling constants range in magnitude from 0 to 20 Hz. Observable coupling will generally occur between hydrogen nuclei that are separated by no more than three sigma bonds.H-C-H, two sigma bonds or geminal couplingH-C-C-H, three sigma bonds or vicinal couplingCoupling is never observed between chemical shift equivalent nuclei, be it from symmetry or by accident, not because the B n field disappears but because spin transitions that would reveal the coupling are forbidden by symmetry. The role of symmetry in forbidding spectral transitions is of general importance in spectroscopy but is beyond the scope of this discussion. The magnitude of the coupling constant also provides structural information; for example, trans-alkenes show larger vicinal coupling than cis-alkenes. Sometimes, coupling is not observed betweenprotons on heteroatoms such as the OH proton of an alcohol and adjacent protons on carbon. In this case the absence of coupling results from rapid exchange of the OH protons via an acid base mechanism; because of rapid exchange the identity of the spin state, or , of the acidic proton is lost. Examples of coupling constants J are shown in Figure12.The example of geminal coupling of protons on a saturated carbon requires a structure in which the protons have different chemical shifts. This commonly occurs in a chiral molecule with a tetrahedral stereocenter adjacent to the methylene group as shown in the following compounds with stereocenters labeled with an asterisk. The geminal protons are labeled H A and H B rather than H A and H X because they have similar chemical shifts (A and B are close in the alphabet). Coupling between the geminal protons is independent of optical activity and rotation about single bonds. The hydrogens H A and H B are said to be diastereotopic hydrogens because if alternately each one is replaced with a deuterium atom, the resulting two structures are diastereomers (stereoisomers that aren't mirror images).Now let's examine the 1H NMR spectrum of methyl propanoate (methyl propionate). Notice that hydrogen atoms of the methyl group bonded to oxygen appear as a singlet at 3.6 ppm. They are chemical shift equivalent and hence, do not couple with each other. The chemical shift results from the deshielding effect of the strongly electronegative oxygen atom. The resonance for the methylene protons appear as a quartet at 2.3 ppm. Thesplitting is caused by the three chemical shift equivalent protons on the adjacent methyl group. The methylene protons do not split each other since they are also chemical shift equivalent. The methyl protons appear at 1.1 ppm and are split into a triplet by the adjacent methylene protons.The coupling constant for the methyl triplet and the methylene quartet is 7 Hz. The overall splitting pattern consisting of a three-proton triplet and a two-proton quartet is called an A3X2 pattern.next section: Spin-spin splitting and coupling - More complex 1H NMR splitting© University of Colorado, Boulder, Chemistry and Biochemistry Department, 2003Spin-spin splitting or J couplingMore complex splitting patterns1H NMR patterns are more complex than predicted by the N+1 coupling rule when coupling of one proton or set of equivalent protons occurs to two different sets of protons with different size coupling constants or when coupling occurs between protons with similar but not identical chemical shifts. The former situation can still be analyzed in terms of overlapping N+1 patterns using stick diagrams. This is shown for the spectrum of phenyloxirane which has three oxirane protons of different chemical shift all coupled to each other. The protons are labeled H A, H M, and H X to reflect that they are not close to each other in chemical shift. Each resonance appears as a doublet of doublets, and the overall pattern of three doublets of doublets is called an A M X pattern.The situation of protons with close chemical shifts coupled to each other is more complex. If only two protons are coupled to each other, the pattern still appears as two doublets but the intensities are no longer 1:1 and the chemical shifts are not the centers of the doublets; the separation between the lines of each doublet is still the coupling constant J. The chemical shifts are closer to the larger peaks of each doublet and can be calculated using a simple equation as shown below.If more than two protons of close chemical shift are coupled to each other, more complex patterns, often described as complex multiplets, are observed. Multiplets still provide useful structural information because they indicate the presence of coupled protons of similar chemical shift. The AB pattern and complex multiplet patterns result from what is called second order effects. Second order effects occur when the ratio of the chemical shift separation in Hz to the coupling constant is less than approximately 10 or /J < 10. Even when this ratio is greater than 10,slight intensity perturbation is evident in first order patterns as shown by the spectrum for 2-butanone. In fact, if we draw an arrow over the pattern showing the slight tilt (blue arrows in Figure 25), the arrowspoint toward each other. So we say the patterns for coupled protons point towards each other.Spin-spin splitting and couplingCoupling in 13C NMR spectraBecause the 13C isotope is present at only 1.1% natural abundance, the probability of finding two adjacent 13C carbons in the same molecule of a compound is very low. As a result spin-spin splitting between adjacent non-equivalent carbons is not observed. However, splitting of the carbon signal by directly bonded protons is observed, and the coupling constants are large, ranging from 125 to 250 Hz. Methyl groups appear as quartets, methylenes as triplets, methines as doublets, and unprotonated carbons as singlets. Commonly, splitting of the signal by protons is eliminated by a decoupling technique which involves simultaneous irradiation of the proton resonances at 300 MHz while observing the carbon resonances at 75 MHz. The decoupling is accomplished with a second broad band, continuous, oscillating magnetic field B2(as opposed to the pulsed B1field), and the decoupling is continued during data collection. The B2field causes rapid proton spin transitions such that the 13C nuclei lose track of the spin states of the protons. Figure 26 shows a proton decoupled 13C spectrum of ethyl acetate. The purpose of proton decoupling is to eliminate overlapping signal patterns and to increase the signal to noise ratio. Decoupling of the protons increases the signal to noise ratio by causing the collapse of quartets, triplets, and doublets to singlets and bycausing a favorable increase in the number of carbons in the -spin state relative to the -spin state. The latter effect is called the Nuclear Overhauser Effect (NOE); how it causes this change in spin state populations will not be discussed here.Integration of 1H NMR spectraThe area under each pattern is obtained from integration of the signal (or better the function that defines the signal) and is proportional to the number of hydrogen nuclei whose resonance is giving rise to the pattern. The integration is sometimes shown as a step function on top of the peak with the height of the step function proportional to the area. The integration of the patterns at 1.1, 2.4, and 3.7 ppm for methyl propanoate is approximately 3:2:3 (see figure 22). Note, the error in integration can be as high as 10% and depends upon instrument optimization. The integration of an 1H NMR spectrum gives a measure of the proton count adjusted for the molecular symmetry. Methyl propanoate has no relevant molecular symmetry and so, the integration gives the actual proton count: 3+2+3=8 protons. In contrast diethyl ether (Et-OEt) has a plane of symmetry which makes the two ethyl groups equivalent, and so, only two signal are observed, a triplet and a quartet, with integration 3:2.The areas represented by the integration step function is usually integrated by the instrument and displayed as numerical values under the scale. For instance, the normalized integration values for 2-butanoneare shown in Figure 27. Note that these values are not exact integers andneed to be rounded to the nearest integer to obtain the proper value.Integration of 13C NMR SpectraIn a 1H NMR spectrum, the area under the signals is proportional to the number of hydrogens giving rise to the signal. As a result the integration of the spectrum is a measure of the proton count. In a 13C NMR spectrum the area under the signal is not simply proportional to the number of carbons giving rise to the signal because the NOE from proton decoupling is not equal for all the carbons. In particular, unprotonated carbons receive very little NOE, and their signals are always weak, only about 10% as strong as signals from protonated carbons.Because the resolution in 13C NMR is excellent, the number of peaks in the spectrum is a measure of the carbon count adjusted for the symmetry of the molecule. For example, hexane gives three peaks: the two methyls are equivalent as are two sets of methylenes. Several examples are analyzed as follows; the chemical shifts shown are not the observed values but calculated values from empirical rules:Hexane shows three peaks, two methyls and two sets of methylenes.Acetone shows two peaks, one for the methyls and one for the carbonyl carbon.Ethyl benzoate shows 7 peaks; the benzene ring shows only 4 peaks because of two sets of equivalent carbons.Ethyl 3-chlorobenzoate, however, shows 9 peaks, a separate signal for each carbon because it has no symmetry.Cis-1,2-dimethylcyclohexane shows 4 peaks; because of rapid chair-chair interconversion, we can analyze the NMR spectrum in terms of a flat structure; hence, the methyls are equivalent, as are the methines, and there are two sets of equivalent methylenes.Solvents for NMR spectroscopyA common solvent for dissolving compounds for 1H and 13C NMR spectroscopy is deuteriochloroform, DCCl3. In 1H NMR spectra, the impurity of HCCl3 in DCCl3gives a small signal at 7.2 ppm (see spectrum of methyl propanoate). In 13C spectroscopy 1.1% of the deuteriochloroform has a 13C isotope and it is bonded to a deuterium atom. The nucleus of the deuterium atom, the deuteron, has a more complicated nuclear spin than does the proton, and it has a gyromagnetic ratio () 1/6 as large. This more complicated nuclearspin gives rise to three spin states instead of the two spin states for the proton, and the deuteron undergoes resonance at a different frequency than either the proton or 13C nucleus. These spin states are approximately all equally populated. Because the spin-spin coupling between the 13C and the deuterium is not eliminated during proton decoupling, the DCCl3shows three equal peaks of low to moderate intensity at about 77 ppm (see Figure 13). The separation is the carbon-deuterium coupling constant JCD. The intensity is low to moderate because the 13C receives no Nuclear Overhauser Enhancement from the proton decoupling.。

科技使交流更方便更容易的英语作文

科技使交流更方便更容易的英语作文全文共3篇示例，供读者参考篇1Technology and Communication: A Gateway to ConvenienceAs a student living in the digital age, technology has become an integral part of my daily life, intertwined with almost every aspect of my routine. Among the myriad of ways technology has impacted our world, one area that stands out is its profound influence on communication. The advent of various technological advancements has reshaped the way we interact, making communication more convenient, efficient, andfar-reaching than ever before.Looking back just a few decades ago, communication was a considerably more arduous task. Staying in touch with friends and family required lengthy phone calls, handwritten letters, or even face-to-face meetings. While these methods fostered meaningful connections, they were often time-consuming and subject to geographical limitations. Fast forward to the present day, and the landscape of communication has been transformed beyond recognition.One of the most significant innovations that have revolutionized communication is the rise of instant messaging and social media platforms. Applications like WhatsApp, Facebook Messenger, and Snapchat have become ubiquitous, enabling us to instantly connect with our loved ones, regardless of their physical location. With just a few taps on our smartphones or keyboards, we can share updates, exchange messages, and even engage in video calls, bridging the distance that once seemed insurmountable.The convenience of instant messaging extends beyond personal relationships; it has also streamlined communication in academic and professional settings. Group chats and collaborative platforms like Google Docs and Slack have become indispensable tools for teamwork and project coordination. As a student, I have experienced firsthand how these technologies have facilitated seamless collaboration with classmates, allowing us to share ideas, discuss assignments, and work together in real-time, regardless of our individual schedules or locations.Moreover, the rise of social media has revolutionized the way we consume and share information. Platforms like Twitter, Instagram, and Reddit have become virtual hubs where news, ideas, and perspectives from around the globe converge. With afew clicks, I can access a wealth of knowledge and stay informed about current events, academic research, and diverse viewpoints from people across the world. This unprecedented access to information has not only enriched my learning experience but has also fostered a broader understanding and appreciation for different cultures and perspectives.However, the impact of technology on communication extends far beyond the realm of personal interactions and information exchange. The advent of video conferencing solutions, such as Zoom and Microsoft Teams, has transformed the way we conduct meetings, attend classes, and participate in conferences. During the COVID-19 pandemic, these platforms became a lifeline, enabling students like myself to continue our education and maintain connections with our peers and instructors, despite the physical barriers imposed by lockdowns and social distancing measures.While the convenience and efficiency of digital communication are undeniable, it is essential to acknowledge the potential drawbacks and challenges that accompany this technological revolution. The abundance of communication channels and the constant influx of information can lead to information overload and disrupt our ability to focus andprioritize. Additionally, the reliance on digital platforms has raised concerns about online privacy, cybersecurity, and the potential for miscommunication due to the lack of non-verbal cues.Despite these challenges, the benefits of technology-driven communication cannot be overstated. As a student navigating the demands of academic life and maintaining connections with loved ones, the convenience and accessibility offered by these technological advancements have been invaluable. From collaborating on group projects to staying in touch with family members across the globe, technology has opened doors to a world of seamless communication and interconnectedness.Looking ahead, it is clear that the symbiotic relationship between technology and communication will continue to evolve, presenting us with new opportunities and challenges. As we embrace these advancements, it is crucial to strike a balance between embracing the convenience they offer and maintaining meaningful, authentic connections with those around us. By approaching technology with mindfulness and moderation, we can harness its power to enhance our communication while preserving the essence of human interaction.In conclusion, the impact of technology on communication has been nothing short of transformative. From instant messaging and social media to video conferencing and collaborative platforms, these advancements have reshaped the way we interact, making communication more convenient, efficient, and far-reaching than ever before. As students navigating the complexities of academic life and personal relationships, we have witnessed firsthand the profound impact of these technologies on our ability to connect, collaborate, and stay informed. While acknowledging the potential drawbacks, it is undeniable that technology has paved the way for a future where communication transcends boundaries, fostering a more interconnected and informed global community.篇2Technology Makes Communication Easier and More ConvenientAs a student in today's world, I can't imagine life without modern technology and all the ways it has revolutionized how we communicate. From texting and video calls to social media and instant messaging, technology has truly transformed communication, making it easier and more convenient than ever before.One of the biggest game-changers has been the rise of smartphones and mobile devices. Having a powerful computer and communication tool in my pocket at all times is something previous generations could never have dreamed of. I remember my parents telling me stories about having to find a payphone or wait until they got home to make calls. Now, I can easily keep in touch with friends and family anywhere, anytime just by pulling out my smartphone.Texting has become one of the primary ways my friends and I communicate. We have group chats going constantly, sharing memes, making plans, or just random banter throughout the day. While some argue that texting has made communication more impersonal, I find it to be incredibly convenient. I can fire off a quick text whenever I have a free moment, rather than having to coordinate schedules for a call. Plus, with things like emoji, GIFs, and video texting, texting can actually be a very personal and expressive way to chat.Video calling has also been a game-changer, especially during the pandemic when many of us were stuck at home. Apps like FaceTime, Skype, and Zoom allowed me to easily video chat with far-away friends and family, which was a lifeline during those isolating times. While audio-only calls are great, there'ssomething about being able to see someone's face that makes the interaction feel so much more personal and meaningful. Video calling has also been hugely beneficial for remote learning and virtual office hours with teachers and professors.Social media has revolutionized how we interact as well. I'm constantly keeping up with friends and what's happening in their lives through apps like Instagram, Snapchat, and Twitter. While some criticize social media for being a time-waster or contributing to feelings of isolation, I actually find it helps me feel more connected, especially to friends who live far away. It's a simple way to stay present in each other's lives. Group chats and pages on apps like Facebook also allow me to easily communicate with clubs, organizations, and classmates.Messaging apps like WhatsApp have made it incredibly easy to communicate with anyone around the world. Between texting, voice notes, video calls, and multimedia messaging, these apps provide an all-in-one communication solution that bridges geographic barriers. I have friends and relatives living abroad, and WhatsApp keeps us feeling connected across continents. It's also handy for coordinating group projects and communicating with study groups.Even traditional email, while perhaps less flashy than some newer communication tech, has become a powerful communication tool thanks to modern innovations. I can easily attach and share all sorts of documents, photos, and files. Video or audio recordings can be embedded right into emails. And with browser extensions and apps, email is more integrated than ever across all my devices so I can communicate on-the-go.And of course, we can't forget about how the internet and technology have completely transformed how we communicate for things like research, work, creative projects, and education. Video tutorials, online collaboration tools, cloud storage, virtual learning environments – the possibilities enabled by the internet are truly mind-boggling. Complex group assignments that may have been logistical nightmares in the past can now be efficiently coordinated using tools like Google Docs and Dropbox.At the same time, I try to be thoughtful about balancing all this technology in my life. As convenient as things like texting and instant messaging are, there's still an importance toin-person, face-to-face communication that I don't want to lose. Some conversations are better had in the same room, with all the nuances and emotional resonance that brings. And there's a beautiful simplicity to picking up the phone and hearingsomeone's voice directly in your ear, with no screens or technology mediating the interaction.I'm also wary of the ways some communication technology can enable unhealthy behaviors like cyberbullying, toxic communication, and a lack of personal boundaries and privacy. As powerful as social media can be for building communities, it can also be a breeding ground for negativity, misinformation, and feelings of inadequacy. Like most things, moderation and thoughtfulness are required to use communication tech in a truly positive way.Overall though, there's no denying that technology has radically changed how we communicate for the better. Geography is no longer the barrier it once was. We can connect with anyone, anywhere, instantly through texts, calls, video, or any other digital means. At the same time, communication itself is richer and more dynamic, integrating multimedia experiences in addition to just voice or text.As a student, this technology is invaluable. I can more easily collaborate with classmates, communicate with teachers and mentors, stay connected to family and friends, and simply express myself through all these different communication channels. Technology hasn't made communication perfect, but ithas made it more convenient and enriching than ever before. I can't wait to see how communication continues to evolve in my lifetime as new technologies emerge. For now, I'll keep taking advantage of all the amazing communication tools at my fingertips as I navigate my studies and life as a student in this digital age.篇3Technology Making Communication Easier and More ConvenientAs a student in today's world, technology has become an integral part of my daily life. From the moment I wake up to the time I go to bed, I find myself constantly relying on various technological devices and platforms to communicate, learn, and stay connected with the world around me. One of the most significant impacts of technology has been on the way we communicate, making it more convenient and easier than ever before.Let's start with the most obvious example – our smartphones. These handheld devices have revolutionized the way we communicate, enabling us to stay in touch with friends, family, and classmates at all times. Gone are the days when we had towait for someone to be home to make a call or rely on snail mail to send a letter. With just a few taps on our smartphones, we can instantly send text messages, make video calls, or even share our location with others.But smartphones are just the tip of the iceberg when it comes to the ways technology has transformed communication. Social media platforms like Facebook, Twitter, and Instagram have created virtual communities where we can share our thoughts, experiences, and ideas with people from all corners of the globe. These platforms have also made it easier for us to connect with like-minded individuals, form study groups, and collaborate on projects, regardless of our physical locations.Online messaging apps like WhatsApp, Telegram, and Discord have further simplified communication by allowing us to create group chats, share files, and even make calls without incurring additional costs. These apps have become indispensable tools for coordinating group projects, discussing assignments, and seeking help from classmates or teachers.Moreover, video conferencing platforms like Zoom, Google Meet, and Microsoft Teams have revolutionized the way we attend classes and participate in online discussions. During the COVID-19 pandemic, these platforms played a crucial role inensuring the continuity of our education, allowing us to attend virtual classes and interact with our teachers and peers from the comfort of our homes.Technology has also made communication more accessible for those with disabilities or special needs. Text-to-speech and speech-to-text software, along with assistive technologies like screen readers and braille displays, have helped break down barriers and enable individuals with visual or hearing impairments to communicate effectively.Beyond interpersonal communication, technology has also transformed the way we access information and acquire knowledge. Online libraries, educational websites, and digital learning platforms have made it possible for us to access a wealth of information at our fingertips. We can easily research topics, watch educational videos, and even take online courses from renowned universities and institutions around the world.However, with all these advantages, it's important to acknowledge the potential downsides of technology-driven communication. The constant bombardment of notifications and the temptation to multitask can lead to divided attention and diminished focus during important conversations or lectures. Additionally, the ease of communication through digitalchannels can sometimes lead to miscommunication or misunderstandings due to the lack of non-verbal cues and context.Furthermore, the widespread use of technology has raised concerns about privacy and security. We must be cautious about the information we share online and take necessary precautions to protect our personal data from potential breaches or misuse.Despite these challenges, it's undeniable that technology has made communication more convenient and easier for us as students. It has opened up new avenues for collaboration, learning, and staying connected with our peers and educators. However, as we embrace these technological advancements, it's crucial to strike a balance and ensure that we use them responsibly and ethically.In conclusion, the impact of technology on communication has been nothing short of transformative. From instant messaging to video conferencing, from social media to online learning platforms, technology has enabled us to communicate more efficiently, collaborate more effectively, and access knowledge more readily. As students, we must continue to adapt to these ever-evolving technologies while being mindful of their potential drawbacks and limitations. By using technologyjudiciously and responsibly, we can harness its power to enhance our communication, learning, and overall educational experience.。

专题21 黑巨人因环境变化而灭绝-2024届高中英语时文阅读外刊精选精练(原卷版)

高中英语时文阅读外刊精选精练专题21黑巨人因环境变化而灭绝【原文·外刊阅读】Gigantopithecus blacki extinct after failure to adapt to environmental changes（文章来源：Global Times）Chinese, Australian and US researchers have revealed more about the extinction of the Gigantopithecus blacki great ape in their latest joint study, which was published in Nature on Thursday. The study found that Gigantopithecus blacki became extinct between 295,000 and 215,000 years ago due to being unable to adapt its food preferences and behavior, as well as being vulnerable to the changing climate, the Global Times learned from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and the Chinese Academy of Sciences (CAS).With a height of about three meters and weight of about 250 kilograms, Gigantopithecus blacki is the largest primate that has ever existed on the Earth. It is a very distant human ancestor. Gigantopithecus blacki once roamed the karst plains of southern China and became extinct before humans arrived in the region, leaving around 2,000 fossilized teeth and four jawbones among the only signs of their existence. "The story of Gigantopithecus blacki is an enigma in paleontology - how could such a mighty creature go extinct at a time when other primates were adapting and surviving? The unresolved cause of its disappearance has become a mystery in the field," said Zhang Yingqi, a Chinese paleontologist from the IVPP and co-lead author of the study.According to Zhang, the IVPP has been excavating for Gigantopithecus blacki remains in southern China for more than 10 years, but could figure out the cause of its extinction through consistent environmental analysis. Definitive evidence revealing the story of the giant ape's extinction came from a large-scale evidence collecting project on 22 cave sites spread across a wide region of South China's Guangxi Zhuang Autonomous Region. "It's a major challenge to present a defined cause for the extinction of a species. At first, we should figure out the exact time when a species disappears from the fossil record so that we can conduct an environmental reconstruction and behavior assessment," said Kira Westaway, a geochronologist associate professor from Macquarie University whois another co-lead author of the study. "Without robust dating, you are simply looking for clues in the wrong places," Westaway said.Six different dating techniques were applied to analyze the cave sediments and fossils. Luminescence dating, which measures a light-sensitive signal found in the burial sediments that encased the Gigantopithecus blacki fossils, was the primary technique, supported by uranium series (US) and electron-spin resonance (US-ESR) dating of the Gigantopithecus blacki teeth themselves. By direct-dating the fossil remains, the scientists confirmed the fossils' age aligns with the luminescence sequence in the sediments where they were found, providing a comprehensive and reliable chronology for the extinction of Gigantopithecus blacki.Using detailed pollen analysis, fauna reconstructions, stable isotope analysis of the teeth and a detailed analysis of the cave sediments at a micro level, the team established the environmental conditions when Gigantopithecus blacki went extinct. Then, using trace element and dental microwear mark textural analysis (DMTA) of the ape's teeth, the team built a comparison model between when it was flourishing and when it was close to extinction. According to scientists, tooth tissue contains rich information related to species' feeding behavior that can be used to interpret in depth whether they are facing survival pressure, the diversity of their food, the regularity of their feeding behavior and their activity range.The findings show Gigantopithecus blacki went extinct between 295,000 and 215,000 years ago, much earlier than previously assumed. Before that time, Gigantopithecus blacki flourished in a rich and diverse forest environment. However, by 700,000 to 600,000 years ago, the increased seasonality in the forest led to diversification of the environment and change in the structure of the forest communities. Orangutans (genus Pongo) - a close relative of Gigantopithecus blacki - adapted in size, behavior and habitat preferences as conditions changed. However, Gigantopithecus blacki relied on a less nutritious food source when its preferences were unavailable. At the same time, they grew larger and bulkier, and their geographical range for feeding was greatly reduced. Therefore, its population faced long-term survival pressure and continued to shrink, eventually becoming extinct.It was Gigantopithecus blacki's stubbornness and conservatism that led to its demise, Zhang noted. As the specter of a sixth mass extinction looms over us, we urgently need to understand why species become extinct. As with the story of the extinction of Gigantopithecus blacki, exploring unresolved extinction events in the past will help us to understand the resilience of primates and the fate of other large animals in the past and into the future, Westaway noted.【原创·阅读理解】1.According to the joint study published in Nature, what were the primary factors that led to the extinction of Gigantopithecus blacki?A. Lack of suitable habitats.B. Inability to adapt food preferences and behavior.C. Competition with other primate species.D. Overhunting by humans.2.How did the researchers determine the age of Gigantopithecus blacki fossils?A. By analyzing the size and weight of the fossils.B. Through detailed pollen analysis.C. Using luminescence dating and other dating techniques.D. By studying the geographical range of Gigantopithecus blacki.3.What environmental changes contributed to Gigantopithecus blacki's extinction?A. Increase in seasonality in the forest.B. Adaptation of orangutans in size, behavior, and habitat preferences.C. Availability of a less nutritious food source.D. Growth of Gigantopithecus blacki population.【精选·名校好题】Ⅰ（2024·河南模拟预测）Most of us have an unclear memory of learning about the Pythagorean Theorem (勾股定理) many years ago in math class.If you’re anything like us writer-types, that 2,000-year-old theorem went in one ear, and immediately out the other! But for two students at St. Mary’s Academy in New Orleans, Louisiana, the theorem presented a challenge they simply couldn’t resist taking on. As a reminder for those of us who aren’t potential mathematicians, the Pythagorean Theorem is the basis of trigonometry (三角学). For over 2,000 years, math scholars have stated it’s impossible to use trigonometry to prove the Pythagorean Theorem because doing so would be circular logic. In other words, an idea cannot prove itself.Calcea Johnson and Ne’Kiya Jackson have challenged that concept in their new abstract. The two high school seniors recently presented their abstract in front of the American Mathematical Society (AMS) at their annual southeastern conference. Unsurprisingly, they were the only teenagers there in a sea of math scholars! Their abstract states, “We present a new proof of the Pythagorean Theorem which is based on a fundamental result in trigonometry.” In plain English, that means Calcea and Ne’Kiya proved the theorem using trigonometry after all, and without using circular reasoning.How did a pair of teenagers solve a riddle that has stumped so many mathematicians before them? Countless math scholars can do nothing facing this theorem. According to Calcea and Ne’Kiya, they have their teachers to thank!The St. Mary’s school slogan is “No Excellence Without Hard Labor”, and they mean it! Both girls say their teachers push them to think outside the box and encourage them to discover new concepts. “We have really great teachers,” Ne’Kiya said with a smile. Calcea is proud of herself and her friend for doing something no other high school students have ever done.1．What does the author think of the Pythagorean Theorem in paragraph 2?A．It has too short a history.B．It’s unattractive to writers.C．It’s too academic to understand.D．It needs to be proved once more.2．What did Calcea and Ne’Kiya do about the theorem in front of the AMS?A．They proved it using trigonometry.B．They showed it was based on trigonometry.C．They said circular reasoning couldn’t prove it.D．They introduced a kind of theory similar to it.3．What does the underlined word “stumped” in paragraph 4 mean?A．Helped.B．Excited.C．Puzzled.D．Changed.4．What do Calcea and Ne’Kiya’s teachers ask them to do?A．Think creatively.B．Act independently.C．Study curiously.D．Live thankfully.Ⅱ（2023·黑龙江期末联考）Researchers at the University of Washington created a new web app, Self-Talk with Superhero Zip, aimed to help children develop skills like self-awareness and emotional management.At first, some parents were wary: In a world of Siri and Alexa, they are skeptical that the makers of such technologies are putting children’s welfare first.In Self-Talk with Superhero Zip, a chatbot guided pairs of siblings through lessons. The UW team found that, after speaking with the app for a week, most children could explain the concept of supportive self-talk and apply it in their daily lives. And kids who’d engaged in negative self-talk before the study were able to turn that habit positive.The UW team published its findings in June at the 2023 Interaction Design and Children conference. The app is still a prototype (雏形) and is not yet publicly available. Previous studies have shown children can learn various tasks and abilities from chatbots. Yet little research explores how chatbots can help kids effectively acquire socioemotional skills.“There is room to design child-centric experiences with a chatbot that provide fun and educational practice opportunities,” said senior author Alexis Hiniker, an associate professor in the UW Information School. “Over the last few decades, television programs like ‘Sesame Street,’ ‘Mister Rogers,’ and ‘Daniel Tiger’s Neighborhood’ have shown that it is possible for TV to help kids cultivate socioemotional skills. We asked: Can we make a space where kids can practice these skills in an interactive app? We wanted to create something useful and fun— a‘Sesame Street’ experience for a smart speaker.”The length of these effects isn’t clear, researchers note. The study spanned just one week and the tendency for survey participants to respond in ways that make them look good could lead kids to speak positively about the app’s effects.“Our goal is to make the app accessible to a wider audience in the future,” said lead author Chris (Yue) Fu, a UW doctoral student in the iSchool. “We’re exploring the integration of large language models — the systems that power tech like ChatGPT — into our prototype and we plan to work with content creators to adapt existing socioemotional learning materials into our system. The hope is that these will facilitate more prolonged and effective interventions.”。

近藤效应

Tunable Kondo eﬀect in a single donor atomnsbergen 1,G.C.Tettamanzi 1,J.Verduijn 1,N.Collaert 2,S.Biesemans 2,M.Blaauboer 1,and S.Rogge 11Kavli Institute of Nanoscience,Delft University of Technology,Lorentzweg 1,2628CJ Delft,The Netherlands and2InterUniversity Microelectronics Center (IMEC),Kapeldreef 75,3001Leuven,Belgium(Dated:September 30,2009)The Kondo eﬀect has been observed in a single gate-tunable atom.The measurement device consists of a single As dopant incorporated in a Silicon nanostructure.The atomic orbitals of the dopant are tunable by the gate electric ﬁeld.When they are tuned such that the ground state of the atomic system becomes a (nearly)degenerate superposition of two of the Silicon valleys,an exotic and hitherto unobserved valley Kondo eﬀect appears.Together with the “regular”spin Kondo,the tunable valley Kondo eﬀect allows for reversible electrical control over the symmetry of the Kondo ground state from an SU(2)-to an SU(4)-conﬁguration.The addition of magnetic impurities to a metal leads to an anomalous increase of their resistance at low tem-perature.Although discovered in the 1930’s,it took until the 1960’s before this observation was satisfactorily ex-plained in the context of exchange interaction between the localized spin of the magnetic impurity and the de-localized conduction electrons in the metal [1].This so-called Kondo eﬀect is now one of the most widely stud-ied phenomena in condensed-matter physics [2]and plays a mayor role in the ﬁeld of nanotechnology.Kondo ef-fects on single atoms have ﬁrst been observed by STM-spectroscopy and were later discovered in a variety of mesoscopic devices ranging from quantum dots and car-bon nanotubes to single molecules [3].Kondo eﬀects,however,do not only arise from local-ized spins:in principle,the role of the electron spin can be replaced by another degree of freedom,for example or-bital momentum [4].The simultaneous presence of both a spin-and an orbital degeneracy gives rise to an exotic SU(4)-Kondo eﬀect,where ”SU(4)”refers to the sym-metry of the corresponding Kondo ground state [5,6].SU(4)Kondo eﬀects have received quite a lot of theoret-ical attention [6,7],but so far little experimental work exists [8].The atomic orbitals of a gated donor in Si consist of linear combinations of the sixfold degenerate valleys of the Si conduction band.The orbital-(or more speciﬁ-cally valley)-degeneracy of the atomic ground state is tunable by the gate electric ﬁeld.The valley splitting ranges from ∼1meV at high ﬁelds (where the electron is pulled towards the gate interface)to being equal to the donors valley-orbit splitting (∼10-20meV)at low ﬁelds [9,10].This tunability essentially originates from a gate-induced quantum conﬁnement transition [10],namely from Coulombic conﬁnement at the donor site to 2D-conﬁnement at the gate interface.In this article we study Kondo eﬀects on a novel exper-imental system,a single donor atom in a Silicon nano-MOSFET.The charge state of this single dopant can be tuned by the gate electrode such that a single electron (spin)is localized on the pared to quantum dots (or artiﬁcial atoms)in Silicon [11,12,13],gated dopants have a large charging energy compared to the level spac-ing due to their typically much smaller size.As a result,the orbital degree of freedom of the atom starts to play an important role in the Kondo interaction.As we will argue in this article,at high gate ﬁeld,where a (near)de-generacy is created,the valley index forms a good quan-tum number and Valley Kondo [14]eﬀects,which have not been observed before,appear.Moreover,the Valley Kondo resonance in a gated donor can be switched on and oﬀby the gate electrode,which provides for an electri-cally controllable quantum phase transition [15]between the regular SU(2)spin-and the SU(4)-Kondo ground states.In our experiment we use wrap-around gate (FinFET)devices,see Fig.1(a),with a single Arsenic donor in the channel dominating the sub-threshold transport charac-teristics [16].Several recent experiments have shown that the ﬁngerprint of a single dopant can be identiﬁed in low-temperature transport through small CMOS devices [16,17,18].We perform transport spectroscopy (at 4K)on a large ensemble of FinFET devices and select the few that show this ﬁngerprint,which essentially consists of a pair of characteristic transport resonances associ-ated with the one-electron (D 0)-and two-electron (D −)-charge states of the single donor [16].From previous research we know that the valley splitting in our Fin-FET devices is typically on the order of a few meV’s.In this Report,we present several such devices that are in addition characterized by strong tunnel coupling to the source/drain contacts which allows for suﬃcient ex-change processes between the metallic contacts and the atom to observe Kondo eﬀects.Fig.1b shows a zero bias diﬀerential conductance (dI SD /dV SD )trace at 4.2K as a function of gate volt-age (V G )of one of the strongly coupled FinFETs (J17).At the V G such that a donor level in the barrier is aligned with the Fermi energy in the source-drain con-tacts (E F ),electrons can tunnel via the level from source to drain (and vice versa)and we observe an increase in the dI SD /dV SD .The conductance peaks indicated bya r X i v :0909.5602v 1 [c o n d -m a t .m e s -h a l l ] 30 S e p 2009FIG.1:Coulomb blocked transport through a single donor in FinFET devices(a)Colored Scanning Electron Micrograph of a typical FinFET device.(b)Diﬀerential conductance (dI SD/dV SD)versus gate voltage at V SD=0.(D0)and(D−) indicate respectively the transport resonances of the one-and two-electron state of a single As donor located in the Fin-FET channel.Inset:Band diagram of the FinFET along the x-axis,with the(D0)charge state on resonance.(c)and(d) Colormap of the diﬀerential conductance(dI SD/dV SD)as a function of V SD and V G of samples J17and H64.The red dots indicate the(D0)resonances and data were taken at1.6 K.All the features inside the Coulomb diamonds are due to second-order chargeﬂuctuations(see text).(D0)and(D−)are the transport resonances via the one-electron and two-electron charge states respectively.At high gate voltages(V G>450mV),the conduction band in the channel is pushed below E F and the FET channel starts to open.The D−resonance has a peculiar double peak shape which we attribute to capacitive coupling of the D−state to surrounding As atoms[19].The current between the D0and the D−charge state is suppressed by Coulomb blockade.The dI SD/dV SD around the(D0)and(D−)resonances of sample J17and sample H64are depicted in Fig.1c and Fig.1d respectively.The red dots indicate the po-sitions of the(D0)resonance and the solid black lines crossing the red dots mark the outline of its conducting region.Sample J17shows aﬁrst excited state at inside the conducting region(+/-2mV),indicated by a solid black line,associated with the valley splitting(∆=2 mV)of the ground state[10].The black dashed lines indicate V SD=0.Inside the Coulomb diamond there is one electron localized on the single As donor and all the observable transport in this regionﬁnds its origin in second-order exchange processes,i.e.transport via a vir-tual state of the As atom.Sample J17exhibits three clear resonances(indicated by the dashed and dashed-dotted black lines)starting from the(D0)conducting region and running through the Coulomb diamond at-2,0and2mV. The-2mV and2mV resonances are due to a second or-der transition where an electron from the source enters one valley state,an the donor-bound electron leaves from another valley state(see Fig.2(b)).The zero bias reso-nance,however,is typically associated with spin Kondo eﬀects,which happen within the same valley state.In sample H64,the pattern of the resonances looks much more complicated.We observe a resonance around0mV and(interrupted)resonances that shift in V SD as a func-tion of V G,indicating a gradual change of the internal level spectrum as a function of V G.We see a large in-crease in conductance where one of the resonances crosses V SD=0(at V G∼445mV,indicated by the red dashed elipsoid).Here the ground state has a full valley degen-eracy,as we will show in theﬁnal paragraph.There is a similar feature in sample J17at V G∼414mV in Fig.1c (see also the red cross in Fig.1b),although that is prob-ably related to a nearby defect.Because of the relative simplicity of its diﬀerential conductance pattern,we will mainly use data obtained from sample J17.In order to investigate the behavior at the degeneracy point of two valley states we use sample H64.In the following paragraphs we investigate the second-order transport in more detail,in particular its temper-ature dependence,ﬁne-structure,magneticﬁeld depen-dence and dependence on∆.We start by analyzing the temperature(T)dependence of sample J17.Fig.2a shows dI SD/dV SD as a function of V SD inside the Coulomb diamond(at V G=395mV) for a range of temperatures.As can be readily observed from Fig.2a,both the zero bias resonance and the two resonances at V SD=+/-∆mV are suppressed with increasing T.The inset of Fig.2a shows the maxima (dI/dV)MAX of the-2mV and0mV resonances as a function of T.We observe a logarithmic dependence on T(a hallmark sign of Kondo correlations)at both resonances,as indicated by the red line.To investigate this point further we analyze another sample(H67)which has sharper resonances and of which more temperature-dependent data were obtained,see Fig.2c.This sample also exhibits the three resonances,now at∼-1,0and +1mV,and the same strong suppression by tempera-ture.A linear background was removed for clarity.We extracted the(dI/dV)MAX of all three resonances forFIG.2:Electrical transport through a single donor atom in the Coulomb blocked region(a)Diﬀerential conductance of sample J17as a function of V SD in the Kondo regime(at V G=395mV).For clarity,the temperature traces have been oﬀset by50nS with respect to each other.Both the resonances with-and without valley-stateﬂip scale similarly with increasing temperature. Inset:Conductance maxima of the resonances at V SD=-2mV and0mV as a function of temperature.(b)Schematic depiction of three(out of several)second-order processes underlying the zero bias and±∆resonances.(c)Diﬀerential conductance of sample H67as a function of V SD in the Kondo regime between0.3K and6K.A linear(and temperature independent) background on the order of1µS was removed and the traces have been oﬀset by90nS with respect to each other for clarity.(d)The conductance maxima of the three resonances of(c)normalized to their0.3K value.The red line is aﬁt of the data by Eq.1.all temperatures and normalized them to their respective(dI/dV)MAX at300mK.The result is plotted in Fig.2d.We again observe that all three peaks have the same(log-arithmic)dependence on temperature.This dependenceis described well by the following phenomenological rela-tionship[20](dI SD/dV SD)max (T)=(dI SD/dV SD)T 2KT2+TKs+g0(1)where TK =T K/√21/s−1,(dI SD/dV SD)is the zero-temperature conductance,s is a constant equal to0.22 [21]and g0is a constant.Here T K is the Kondo tem-perature.The red curve in Fig.2d is aﬁt of Eq.(1)to the data.We readily observe that the dataﬁt well and extract a T K of2.7K.The temperature scaling demon-strates that both the no valley-stateﬂip resonance at zero bias voltage and the valley-stateﬂip-resonance atﬁnite bias are due to Kondo-type processes.Although a few examples ofﬁnite-bias Kondo have been reported[15,22,23],the corresponding resonances (such as our±∆resonances)are typically associated with in-elastic cotunneling.Aﬁnite bias between the leads breaks the coherence due to dissipative transitions in which electrons are transmitted from the high-potential-lead to the low-potential lead[24].These dissipative4transitions limit the lifetime of the Kondo-type processes and,if strong enough,would only allow for in-elastic events.In the supporting online text we estimate the Kondo lifetime in our system and show it is large enough to sustain theﬁnite-bias Kondo eﬀects.The Kondo nature of the+/-∆mV resonances points strongly towards a Valley Kondo eﬀect[14],where co-herent(second-order)exchange between the delocalized electrons in the contacts and the localized electron on the dopant forms a many-body singlet state that screens the valley index.Together with the more familiar spin Kondo eﬀect,where a many-body state screens the spin index, this leads to an SU(4)-Kondo eﬀect,where the spin and charge degree of freedom are fully entangled[8].The ob-served scaling of the+/-∆-and zero bias-resonances in our samples by a single T K is an indication that such a fourfold degenerate SU(4)-Kondo ground state has been formed.To investigate the Kondo nature of the transport fur-ther,we analyze the substructure of the resonances of sample J17,see Fig.2a.The central resonance and the V SD=-2mV each consist of three separate peaks.A sim-ilar substructure can be observed in sample H67,albeit less clear(see Fig.2c).The substructure can be explained in the context of SU(4)-Kondo in combination with a small diﬀerence between the coupling of the ground state (ΓGS)-and theﬁrst excited state(ΓE1)-to the leads.It has been theoretically predicted that even a small asym-metry(ϕ≡ΓE1/ΓGS∼=1)splits the Valley Kondo den-sity of states into an SU(2)-and an SU(4)-part[25].Thiswill cause both the valley-stateﬂip-and the no valley-stateﬂip resonances to split in three,where the middle peak is the SU(2)-part and the side-peaks are the SU(4)-parts.A more detailed description of the substructure can be found in the supporting online text.The split-ting between middle and side-peaks should be roughly on the order of T K[25].The measured splitting between the SU(2)-and SU(4)-parts equals about0.5meV for sample J17and0.25meV for sample H67,which thus corresponds to T K∼=6K and T K∼=3K respectively,for the latter in line with the Kondo temperature obtained from the temperature dependence.We further note that dI SD/dV SD is smaller than what we would expect for the Kondo conductance at T<T K.However,the only other study of the Kondo eﬀect in Silicon where T K could be determined showed a similar magnitude of the Kondo signal[12].The presence of this substructure in both the valley-stateﬂip-,and the no valley-stateﬂip-Kondo resonance thus also points at a Valley Kondo eﬀect.As a third step,we turn our attention to the magnetic ﬁeld(B)dependence of the resonances.Fig.3shows a colormap plot of dI SD/dV SD for samples J17and H64 both as a function of V SD and B at300mK.The traces were again taken within the Coulomb diamond.Atﬁnite magneticﬁeld,the central Kondo resonances of both de-vices split in two with a splitting of2.2-2.4mV at B=FIG.3:Colormap plot of the conductance as a function of V SD and B of sample J17at V G=395mV(a)and H64at V G=464mV(b).The central Kondo resonances split in two lines which are separated by2g∗µB B.The resonances with a valley-stateﬂip do not seem to split in magneticﬁeld,a feature we associate with the diﬀerent decay-time of parallel and anti-parallel spin-conﬁgurations of the doubly-occupied virtual state(see text).10T.From theoretical considerations we expect the cen-tral Valley Kondo resonance to split in two by∆B= 2g∗µB B if there is no mixing of valley index(this typical 2g∗µB B-splitting of the resonances is one of the hall-marks of the Kondo eﬀect[24]),and to split in three (each separated by g∗µB B)if there is a certain degree of valley index mixing[14].Here,g∗is the g-factor(1.998 for As in Si)andµB is the Bohr magneton.In the case of full mixing of valley index,the valley Kondo eﬀect is expected to vanish and only spin Kondo will remain [25].By comparing our measured magneticﬁeld splitting (∆B)with2g∗µB B,weﬁnd a g-factor between2.1and 2.4for all three devices.This is comparable to the result of Klein et al.who found a g-factor for electrons in SiGe quantum dots in the Kondo regime of around2.2-2.3[13]. The magneticﬁeld dependence of the central resonance5indicates that there is no signiﬁcant mixing of valley in-dex.This is an important observation as the occurrence of Valley Kondo in Si depends on the absence of mix-ing(and thus the valley index being a good quantum number in the process).The conservation of valley in-dex can be attributed to the symmetry of our system. The large2D-conﬁnement provided by the electricﬁeld gives strong reason to believe that the ground-andﬁrst excited-states,E GS and E1,consist of(linear combi-nations of)the k=(0,0,±kz)valleys(with z in the electricﬁeld direction)[10,26].As momentum perpen-dicular to the tunneling direction(k x,see Fig.1)is con-served,also valley index is conserved in tunneling[27]. The k=(0,0,±k z)-nature of E GS and E1should be as-sociated with the absence of signiﬁcant exchange interac-tion between the two states which puts them in the non-interacting limit,and thus not in the correlated Heitler-London limit where singlets and triplets are formed.We further observe that the Valley Kondo resonances with a valley-stateﬂip do not split in magneticﬁeld,see Fig.3.This behavior is seen in both samples,as indicated by the black straight solid lines,and is most easily ob-served in sample J17.These valley-stateﬂip resonances are associated with diﬀerent processes based on their evo-lution with magneticﬁeld.The processes which involve both a valleyﬂip and a spinﬂip are expected to shift to energies±∆±g∗µB B,while those without a spin-ﬂip stay at energies±∆[14,25].We only seem to observe the resonances at±∆,i.e.the valley-stateﬂip resonances without spinﬂip.In Ref[8],the processes with both an orbital and a spinﬂip also could not be observed.The authors attribute this to the broadening of the orbital-ﬂip resonances.Here,we attribute the absence of the processes with spinﬂip to the diﬀerence in life-time be-tween the virtual valley state where two spins in seperate valleys are parallel(τ↑↑)and the virtual state where two spins in seperate valleys are anti-parallel(τ↑↓).In con-trast to the latter,in the parallel spin conﬁguration the electron occupying the valley state with energy E1,can-not decay to the other valley state at E GS due to Pauli spin blockade.It wouldﬁrst needs toﬂip its spin[28].We have estimatedτ↑↑andτ↑↓in our system(see supporting online text)andﬁnd thatτ↑↑>>h/k b T K>τ↑↓,where h/k b T K is the characteristic time-scale of the Kondo pro-cesses.Thus,the antiparallel spin conﬁguration will have relaxed before it has a change to build up a Kondo res-onance.Based on these lifetimes,we do not expect to observe the Kondo resonances associated with both an valley-state-and a spin-ﬂip.Finally,we investigate the degeneracy point of valley states in the Coulomb diamond of sample H64.This degeneracy point is indicated in Fig.1d by the red dashed ellipsoid.By means of the gate electrode,we can tune our system onto-or oﬀthis degeneracy point.The gate-tunability in this sample is created by a reconﬁguration of the level spectrum between the D0and D−-charge states,FIG.4:Colormap plot of I SD at V SD=0as a function of V G and B.For increasing B,a conductance peak develops around V G∼450mV at the valley degeneracy point(∆= 0),indicated by the dashed black line.Inset:Magneticﬁeld dependence of the valley degeneracy point.The resonance is ﬁxed at zero bias and its magnitude does not depend on the magneticﬁeld.probably due to Coulomb interactions in the D−-states. Figure4shows a colormap plot of I SD at V SD=0as a function of V G and B(at0.3K).Note that we are thus looking at the current associated with the central Kondo resonance.At B=0,we observe an increasing I SD for higher V G as the atom’s D−-level is pushed toward E F. As B is increased,the central Kondo resonance splits and moves away from V SD=0,see Fig.3.This leads to a general decrease in I SD.However,at around V G= 450mV a peak in I SD develops,indicated by the dashed black line.The applied B-ﬁeld splits oﬀthe resonances with spin-ﬂip,but it is the valley Kondo resonance here that stays at zero bias voltage giving rise to the local current peak.The inset of Fig.4shows the single Kondo resonance in dI SD/dV SD as a function of V SD and B.We observe that the magnitude of the resonance does not decrease signiﬁcantly with magneticﬁeld in contrast to the situation at∆=0(Fig.3b).This insensitivity of the Kondo eﬀect to magneticﬁeld which occurs only at∆= 0indicates the profound role of valley Kondo processes in our structure.It is noteworthy to mention that at this speciﬁc combination of V SD and V G the device can potentially work as a spin-ﬁlter[6].We acknowledge fruitful discussions with Yu.V. Nazarov,R.Joynt and S.Shiau.This project is sup-ported by the Dutch Foundation for Fundamental Re-search on Matter(FOM).6[1]Kondo,J.,Resistance Minimum in Dilute Magnetic Al-loys,Prog.Theor.Phys.3237-49(1964)[2]Hewson,A.C.,The Kondo Problem to Heavy Fermions(Cambridge Univ.Press,Cambridge,1993).[3]Wingreen N.S.,The Kondo eﬀect in novel systems,Mat.Science Eng.B842225(2001)and references therein.[4]Cox,D.L.,Zawadowski,A.,Exotic Kondo eﬀects in met-als:magnetic ions in a crystalline electricﬁeld and tun-neling centers,Adv.Phys.47,599-942(1998)[5]Inoshita,T.,Shimizu, A.,Kuramoto,Y.,Sakaki,H.,Correlated electron transport through a quantum dot: the multiple-level eﬀect.Phys.Rev.B48,14725-14728 (1993)[6]Borda,L.Zar´a nd,G.,Hofstetter,W.,Halperin,B.I.andvon Delft,J.,SU(4)Fermi Liquid State and Spin Filter-ing in a Double Quantum Dot System,Phys.Rev.Lett.90,026602(2003)[7]Zar´a nd,G.,Orbitalﬂuctuations and strong correlationsin quantum dots,Philosophical Magazine,86,2043-2072 (2006)[8]Jarillo-Herrero,P.,Kong,J.,van der Zant H.S.J.,Dekker,C.,Kouwenhoven,L.P.,De Franceschi,S.,Or-bital Kondo eﬀect in carbon nanotubes,Nature434,484 (2005)[9]Martins,A.S.,Capaz,R.B.and Koiller,B.,Electric-ﬁeldcontrol and adiabatic evolution of shallow donor impuri-ties in silicon,Phys.Rev.B69,085320(2004)[10]Lansbergen,G.P.et al.,Gate induced quantum conﬁne-ment transition of a single dopant atom in a Si FinFET, Nature Physics4,656(2008)[11]Rokhinson,L.P.,Guo,L.J.,Chou,S.Y.,Tsui, D.C.,Kondo-like zero-bias anomaly in electronic transport through an ultrasmall Si quantum dot,Phys.Rev.B60, R16319-R16321(1999)[12]Specht,M.,Sanquer,M.,Deleonibus,S.,Gullegan G.,Signature of Kondo eﬀect in silicon quantum dots,Eur.Phys.J.B26,503-508(2002)[13]Klein,L.J.,Savage, D.E.,Eriksson,M.A.,Coulombblockade and Kondo eﬀect in a few-electron silicon/silicon-germanium quantum dot,Appl.Phys.Lett.90,033103(2007)[14]Shiau,S.,Chutia,S.and Joynt,R.,Valley Kondo eﬀectin silicon quantum dots,Phys.Rev.B75,195345(2007) [15]Roch,N.,Florens,S.,Bouchiat,V.,Wernsdirfer,W.,Balestro, F.,Quantum phase transistion in a single molecule quantum dot,Nature453,633(2008)[16]Sellier,H.et al.,Transport Spectroscopy of a SingleDopant in a Gated Silicon Nanowire,Phys.Rev.Lett.97,206805(2006)[17]Calvet,L.E.,Wheeler,R.G.and Reed,M.A.,Observa-tion of the Linear Stark Eﬀect in a Single Acceptor in Si, Phys.Rev.Lett.98,096805(2007)[18]Hofheinz,M.et al.,Individual charge traps in siliconnanowires,Eur.Phys.J.B54,299307(2006)[19]Pierre,M.,Hofheinz,M.,Jehl,X.,Sanquer,M.,Molas,G.,Vinet,M.,Deleonibus S.,Oﬀset charges acting as ex-cited states in quantum dots spectroscopy,Eur.Phys.J.B70,475-481(2009)[20]Goldhaber-Gordon,D.,Gres,J.,Kastner,M.A.,Shtrik-man,H.,Mahalu, D.,Meirav,U.,From the Kondo Regime to the Mixed-Valence Regime in a Single-Electron Transistor,Phys.Rev.Lett.81,5225(1998) [21]Although the value of s=0.22stems from SU(2)spinKondo processes,it is valid for SU(4)-Kondo systems as well[8,25].[22]Paaske,J.,Rosch,A.,W¨o lﬂe,P.,Mason,N.,Marcus,C.M.,Nyg˙ard,Non-equilibrium singlet-triplet Kondo ef-fect in carbon nanotubes,Nature Physics2,460(2006) [23]Osorio, E.A.et al.,Electronic Excitations of a SingleMolecule Contacted in a Three-Terminal Conﬁguration, Nanoletters7,3336-3342(2007)[24]Meir,Y.,Wingreen,N.S.,Lee,P.A.,Low-TemperatureTransport Through a Quantum Dot:The Anderson Model Out of Equilibrium,Phys.Rev.Lett.70,2601 (1993)[25]Lim,J.S.,Choi,M-S,Choi,M.Y.,L´o pez,R.,Aguado,R.,Kondo eﬀects in carbon nanotubes:From SU(4)to SU(2)symmetry,Phys.Rev.B74,205119(2006) [26]Hada,Y.,Eto,M.,Electronic states in silicon quan-tum dots:Multivalley artiﬁcial atoms,Phys.Rev.B68, 155322(2003)[27]Eto,M.,Hada,Y.,Kondo Eﬀect in Silicon QuantumDots with Valley Degeneracy,AIP Conf.Proc.850,1382-1383(2006)[28]A comparable process in the direct transport throughSi/SiGe double dots(Lifetime Enhanced Transport)has been recently proposed[29].[29]Shaji,N.et.al.,Spin blockade and lifetime-enhancedtransport in a few-electron Si/SiGe double quantum dot, Nature Physics4,540(2008)7Supporting InformationFinFET DevicesThe FinFETs used in this study consist of a silicon nanowire connected to large contacts etched in a60nm layer of p-type Silicon On Insulator.The wire is covered with a nitrided oxide(1.4nm equivalent SiO2thickness) and a narrow poly-crystalline silicon wire is deposited perpendicularly on top to form a gate on three faces.Ion implantation over the entire surface forms n-type degen-erate source,drain,and gate electrodes while the channel protected by the gate remains p-type,see Fig.1a of the main article.The conventional operation of this n-p-n ﬁeld eﬀect transistor is to apply a positive gate voltage to create an inversion in the channel and allow a current toﬂow.Unintentionally,there are As donors present be-low the Si/SiO2interface that show up in the transport characteristics[1].Relation between∆and T KThe information obtained on T K in the main article allows us to investigate the relation between the splitting (∆)of the ground(E GS)-andﬁrst excited(E1)-state and T K.It is expected that T K decreases as∆increases, since a high∆freezes out valley-stateﬂuctuations.The relationship between T K of an SU(4)system and∆was calculated by Eto[2]in a poor mans scaling approach ask B T K(∆) B K =k B T K(∆=0)ϕ(2)whereϕ=ΓE1/ΓGS,withΓE1andΓGS the lifetimes of E1and E GS respectively.Due to the small∆com-pared to the barrier height between the atom and the source/drain contact,we expectϕ∼1.Together with ∆=1meV and T K∼2.7K(for sample H67)and∆=2meV and T K∼6K(for sample J17),Eq.2yields k B T K(∆)/k B T K(∆=0)=0.4and k B T K(∆)/k B T K(∆= 0)=0.3respectively.We can thus conclude that the rela-tively high∆,which separates E GS and E1well in energy, will certainly quench valley-stateﬂuctuations to a certain degree but is not expected to reduce T K to a level that Valley eﬀects become obscured.Valley Kondo density of statesHere,we explain in some more detail the relation be-tween the density of states induced by the Kondo eﬀects and the resulting current.The Kondo density of states (DOS)has three main peaks,see Fig.1a.A central peak at E F=0due to processes without valley-stateﬂip and two peaks at E F=±∆due to processes with valley-state ﬂip,as explained in the main text.Even a small asym-metry(ϕclose to1)will split the Valley Kondo DOS into an SU(2)-and an SU(4)-part[3],indicated in Fig1b in black and red respectively.The SU(2)-part is positioned at E F=0or E F=±∆,while the SU(4)-part will be shifted to slightly higher positive energy(on the order of T K).A voltage bias applied between the source and FIG.1:(a)dI SD/dV SD as a function of V SD in the Kondo regime(at395mV G)of sample J17.The substructure in the Kondo resonances is the result of a small diﬀerence between ΓE1andΓGS.This splits the peaks into a(central)SU(2)-part (black arrows)and two SU(4)-peaks(red arrows).(b)Density of states in the channel as a result ofϕ(=ΓE1/ΓGS)<1and applied V SD.drain leads results in the Kondo peaks to split,leaving a copy of the original structure in the DOS now at the E F of each lead,which is schematically indicated in Fig.1b by a separate DOS associated with each contact.The current density depends directly on the density of states present within the bias window deﬁned by source/drain (indicated by the gray area in Fig1b)[4].The splitting between SU(2)-and SU(4)-processes will thus lead to a three-peak structure as a function of V SD.Figure.1a has a few more noteworthy features.The zero-bias resonance is not positioned exactly at V SD=0, as can also be observed in the transport data(Fig1c of the main article)where it is a few hundredµeV above the Fermi energy near the D0charge state and a few hundredµeV below the Fermi energy near the D−charge state.This feature is also known to arise in the Kondo strong coupling limit[5,6].We further observe that the resonances at V SD=+/-2mV diﬀer substantially in magnitude.This asymmetry between the two side-peaks can actually be expected from SU(4)Kondo sys-tems where∆is of the same order as(but of course al-ways smaller than)the energy spacing between E GS and。

光谱学英语

光谱学英语一、单词1. spectrum（复数：spectra）- 英语释义：A band of colors, as seen in a rainbow, produced by separation of theponents of light by their different degrees of refraction according to wavelength.- 用法：可以用作名词，如“The spectrum of light includes colors f rom red to violet.”（光谱包括从红色到紫色的颜色。

） - 双语例句：The visible spectrum is just a small part of the electromagnetic spectrum.（可见光谱只是电磁光谱的一小部分。

）2. spectroscopy- 英语释义：The study of the interaction between matter and radiated energy, especially in terms of the frequencies present in a spectrum of the radiation.- 用法：作名词，例如“Spectroscopy is widely used in chemical analysis.”（光谱学在化学分析中被广泛应用。

）- 双语例句：Infrared spectroscopy can be used to identify different chemicalpounds.（红外光谱学可用于识别不同的化合物。

）3. wavelength- 英语释义：The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.- 用法：名词，如“Each color has a different wavelength.”（每种颜色都有不同的波长。

表面等离子体共振英文

表面等离子体共振英文Surface plasmon resonance (SPR) is a phenomenon that occurs when polarized light hits a metal-dielectric interface at a specific angle, causing the electrons on the metal surface to oscillate in resonance with the light wave. This interaction leads to the generation of surface plasmons, which are coherent delocalized electron oscillations that exist at the interface between two materials where the real part of the dielectric function changes sign across the interface.The significance of SPR lies in its sensitivity to changes in the refractive index of the material close to the metal surface. This sensitivity makes SPR an invaluable tool in various fields, particularly in biosensing, where it is used to detect the binding of molecules to the metal surface. The binding event causes a change in the refractive index at the surface, which in turn alters the resonance condition. By measuring this change, one can infer details about the molecular interaction, such as the binding kinetics and affinity.In a typical SPR experiment, a thin metal film, usually gold or silver, is deposited on a glass substrate. The metal film is then exposed to a polarized light source, and the angle of incidence is varied until the resonance condition is met. At resonance, there is a significant reduction in the reflected light intensity, which is detected by a photodetector. The angle at which this dip in reflectivity occurs is referred to as the resonance angle and is highly sensitive to the refractive index of the material in contact with the metal film.The applications of SPR are vast and diverse. In the field of biochemistry, it is used to study protein-protein interactions, DNA hybridization, and the binding of small molecules to proteins. In environmental monitoring, SPR sensors can detect the presence of pollutants and pathogens. The technology is also employed in the pharmaceutical industry for drug discovery and the characterization of biomolecular interactions.One of the key advantages of SPR is that it allows for real-time monitoring of binding events without the need for labeling the interacting molecules. This non-invasivenature preserves the biological activity of the molecules and provides a more accurate representation of the interaction as it occurs in vivo.Recent advancements in SPR technology have led to the development of localized SPR (LSPR), which operates on the same principles but at a much smaller scale. LSPR is associated with nanostructures, such as nanoparticles, and offers enhanced sensitivity and spatial resolution. This miniaturization has opened up new possibilities for the integration of SPR sensors into microfluidic systems and the potential for high-throughput analysis.In conclusion, surface plasmon resonance is a powerful analytical technique that has revolutionized the way we study and understand molecular interactions. Its ability to provide real-time, label-free analysis makes it an indispensable tool in scientific research and various industries. As technology continues to advance, we can expect SPR to play an even more significant role in the fields of biosensing, environmental monitoring, and beyond.。

识别度与存在感的英语作文例子

识别度与存在感的英语作文例子Recognition and Presence: The Art of Leaving an Unforgettable Mark.In the vast tapestry of life, recognition is the thread that connects our existence to the fabric of the world. It is the acknowledgment of our impact, the affirmation of our significance. Alongside recognition, presence emerges as an equally potent force, shaping our perception and influence. The interplay of these two concepts defines how we navigate the social landscape, leaving an enduring legacy that transcends the boundaries of time.Recognition, in its myriad forms, serves as a catalyst for growth and self-discovery. When our accomplishments are acknowledged, we gain a sense of validation and purpose. This recognition fuels our aspirations, propelling us to strive for greater heights. It is in the eyes of those who witness our triumphs that we truly glimpse our own worth, fostering a belief in our abilities that empowers us toovercome challenges and embrace opportunities.Recognition is not merely an external accolade; it is an internal compass that guides our actions. It reminds us of the impact we have on others, instilling a sense of responsibility and accountability. When we recognize the power we possess, we become conscious of the ethical implications of our choices and strive to use our influence for the greater good.However, recognition is a double-edged sword. In its pursuit, we may sacrifice authenticity and creativity, conforming to societal expectations rather than forging our own paths. It is crucial to balance the desire for recognition with a deep sense of self-awareness, ensuring that our actions align with our values and aspirations.In the realm of human interaction, presence transcends recognition. It is the ability to fully engage in the present moment, connecting with others on a meaningful level. Presence is not about outward appearances or grand gestures but rather about authenticity, vulnerability, andgenuine engagement. It is in the subtle nuances of body language, the warmth of a smile, and the depth of our listening that we truly make our presence felt.Like a ripple effect, our presence extends beyond the immediate moment, creating lasting impressions that shape our relationships and influence our surroundings. When we are truly present, we create an atmosphere of trust and safety, inviting others to share their innermost thoughts and feelings. It is in these moments of genuine connection that we build bridges, foster understanding, and leave an imprint on the hearts of those we encounter.Presence is not limited to interpersonal interactions; it can also be cultivated within ourselves. By practicing mindfulness, meditation, or simply taking time to reflect on our thoughts and emotions, we cultivate a deeper connection with our inner selves. This self-awareness enhances our ability to be present and authentic in all aspects of our lives.Recognition and presence, while distinct concepts, areinextricably intertwined. Recognition affirms our existence, while presence allows us to fully inhabit it. By embracing both, we create a legacy that extends far beyondsuperficial achievements. We become beacons of inspiration, leaving an enduring mark on the world through our actions, our relationships, and the indelible presence we imprint upon the hearts and minds of others.In the words of the renowned author and activist, Maya Angelou, "I've learned that people will forget what you said, people will forget what you did, but people willnever forget how you made them feel." It is in the tapestry of emotions, the resonance within the depths of the human experience, that our true presence and enduring recognition are established.。

尊重选择心灵共鸣的英语作文

Respecting choices is a fundamental aspect of human interaction and personal growth.In an essay about the importance of respecting choices that resonate with the soul, one might explore several key points.Firstly,the essay could discuss the concept of individuality.Each person is unique,with their own set of values,beliefs,and aspirations.Respecting someones choices means acknowledging their right to make decisions that align with their personal identity,even if those choices differ from our own.Secondly,the essay might delve into the idea of autonomy.Autonomy is the ability to make choices free from external control or coercion.When we respect someones choices, we are allowing them to exercise their autonomy,fostering a sense of independence and selfassuredness.Thirdly,the essay could explore the role of empathy in respecting choices.Empathy involves understanding and sharing the feelings of others.By empathizing with someone, we can better appreciate the reasons behind their choices,even if we do not personally agree with them.Additionally,the essay might touch on the topic of personal growth.Making choices, especially those that resonate deeply with ones soul,can lead to significant personal development.Respecting these choices supports the individuals journey of selfdiscovery and selfimprovement.The essay could also address the potential for conflict that arises when choices are not respected.Disagreements and misunderstandings can occur when people feel that their choices are being dismissed or undermined.By respecting choices,we can promote harmony and reduce conflict.Furthermore,the essay might consider the broader societal implications of respecting choices.In a diverse and pluralistic society,respecting the choices of others is essential for fostering tolerance and inclusivity.It encourages a culture of openmindedness and mutual respect.Lastly,the essay could conclude by emphasizing the importance of selfrespect.When we respect our own choices,we demonstrate selfconfidence and selfworth.This selfrespect can then extend to respecting the choices of others,creating a positive cycle of mutual respect and understanding.In summary,an essay on respecting choices that resonate with the soul would explore theconcepts of individuality,autonomy,empathy,personal growth,conflict resolution, societal harmony,and selfrespect.By examining these themes,the essay would highlight the significance of respecting choices in fostering personal and societal wellbeing.。

光子晶体谐振腔英文

光子晶体谐振腔英文Photonic Crystal ResonatorPhotonic crystals are materials with periodic variations in their refractive indices, which can manipulate thebehavior of light. One of the key components of photoniccrystal devices is the photonic crystal resonator.A photonic crystal resonator is a cavity within the photonic crystal structure that can confine and enhance the light within its boundaries. The cavity is created by introducing defects, such as missing or displaced dielectric elements, into the periodic lattice of the photonic crystal. The defect acts as a local variation of the refractive index, causing the light to be trapped and resonant within the cavity.The confinement and enhancement of light in the photonic crystal resonator make it an ideal platform for various applications, such as lasing, sensing, and nonlinear optics.Lasing in the Photonic Crystal ResonatorA photonic crystal resonator can serve as a laser cavity by introducing a gain medium into the cavity. The confinement of light in the cavity can greatly enhance the interaction between the gain medium and the light, resulting in efficient lasing.The lasing in the photonic crystal resonator has several advantages over traditional Fabry-Perot laser cavities. First, the photonic crystal resonator can provide a much higherquality factor (Q factor), which is a measure of theefficiency of energy storage in the cavity. The high Q factorresults in a narrower linewidth and a higher coherence of the laser emission.Second, the photonic crystal resonator can provide a directional emission due to the efficient coupling of thelight out of the cavity through the photonic crystal waveguide. The directional emission can simplify the laser device design and improve its performance.Sensing with the Photonic Crystal ResonatorThe photonic crystal resonator can also be used as a sensor by exploiting the changes in the resonance conditionof the cavity due to the presence of the analyte. The analyte can change the refractive index of the cavity, causing ashift in the resonance wavelength or a change in the Q factor.The sensitivity of the photonic crystal resonator sensor can be greatly enhanced by using the slow light effect, which can increase the interaction between the light and theanalyte. The slow light effect is achieved by designing the photonic crystal structure to have a narrow bandgap, which slows down the group velocity of the light near the band edge.Nonlinear Optics in the Photonic Crystal ResonatorThe confinement and enhancement of light in the photonic crystal resonator can also result in strong nonlinear optical effects. The high intensity of the light in the cavity can induce various nonlinear optical phenomena, such as second harmonic generation, parametric amplification, and four-wave mixing.The nonlinear optical effects in the photonic crystal resonator can be further enhanced by exploiting the slowlight effect, which can increase the effective nonlinear coefficient and the phase matching condition.In summary, the photonic crystal resonator is aversatile platform for various photonic applications, including lasing, sensing, and nonlinear optics. Its unique properties, such as high Q factor, directional emission, and slow light effect, make it an attractive candidate for the next generation of photonic devices.。

金的等离子共振等综述

a b s t r a c t
This review describes the fundamental aspects of laser–gold nanoparticle (Au NP) interaction that leads to nanoscale energy deposition to the surroundings through light ampliﬁcation and heat generation. Besides the importance of the primary process in physics and chemistry, application of the light–NP interaction has attracted signiﬁcant interest from various areas ranging from analytical chemistry to material chemistry and biomedicine. Here we consider both mechanistic and application aspects. Our attention is focused on pulsed-laser-induced fast processes that revealed the heating–cooling dynamics of electrons, lattice (particle), and particle’s environment. On the application side, we focus on material fabrication and processing that beat diffraction-limited resolution. Together, we will shed a light on the essence of research activities carried out in the past 10 years. In addition to an abundance of latest information obtained from currently available literature, this review includes ﬁgures obtained by our own calculations to provide readers with a better understanding of the basics of the optical properties and energy and heat-transfer processes of Au NPs, which are not familiar to photochemists. © 2012 Elsevier B.V. All rights reserved.

未来社交于现在的不同英语作文

未来社交于现在的不同英语作文The world of social interaction has undergone a profound transformation in recent years, as the rapid advancements in technology have significantly altered the way we connect and communicate with one another. As we look towards the future, it becomes increasingly evident that the landscape of social interaction will continue to evolve, presenting both challenges and opportunities.One of the most significant changes in the realm of social interaction is the increasing reliance on digital platforms and virtual environments. The advent of social media, messaging apps, and video conferencing tools has revolutionized the way we engage with our peers, family, and acquaintances. These digital platforms have provided us with unprecedented access to a vast network of individuals, allowing us to maintain and cultivate relationships across vast geographical distances.However, this shift towards digital social interaction has also given rise to a new set of concerns and considerations. The lack of physical proximity and the mediated nature of these interactions can sometimes lead to a sense of disconnect and a perceived loss of authenticity. The ease with which we can curate and present ouronline personas can also contribute to a distorted perception of reality, as individuals may feel the need to project an idealized version of themselves.Moreover, the ubiquity of digital devices and the constant connectivity they provide have led to a phenomenon known as "social media fatigue." Individuals may find themselves overwhelmed by the constant stream of information, updates, and notifications, leading to feelings of anxiety, distraction, and a diminished ability to truly engage in meaningful conversations.As we look towards the future, it is clear that the integration of technology into our social lives will only continue to deepen. The rise of virtual and augmented reality technologies, for instance, may offer new avenues for social interaction, where individuals can engage in immersive, shared experiences without the limitations of physical distance.Furthermore, the increasing use of artificial intelligence and machine learning in social platforms may lead to more personalized and tailored social experiences. Algorithms could potentially analyze our preferences, interests, and communication patterns to suggest relevant connections, curate content, and facilitate more meaningful interactions.However, the reliance on such technologies also raises concerns about privacy, data security, and the potential for manipulation or exploitation. As we navigate this evolving landscape, it will be crucial for individuals, policymakers, and technology companies to work collaboratively to ensure that the benefits of technological advancements in social interaction are balanced with the preservation of human connection, empathy, and ethical considerations.Another significant aspect of the future of social interaction is the potential impact of demographic shifts and changing societal norms. As the global population continues to age, the needs and preferences of older adults may become more prominent in the design and development of social technologies. Similarly, the increasing diversity and inclusivity of our societies may necessitate the creation of more inclusive and accessible social platforms that cater to the needs of individuals from diverse backgrounds.Moreover, the COVID-19 pandemic has accelerated the adoption of remote and virtual social interactions, as physical distancing measures have become a necessity. This shift has highlighted the importance of developing robust and user-friendly digital tools that can facilitate meaningful connections, support mental health, and foster a sense of community, even in the absence of physical proximity.As we look towards the future, it is clear that the landscape of social interaction will continue to evolve, presenting both challenges and opportunities. While the integration of technology into our social lives may offer new avenues for connection and engagement, it will be crucial to strike a balance between the convenience and efficiency of digital platforms and the preservation of the human elements of social interaction, such as empathy, trust, and emotional resonance.By embracing the potential of technological advancements while also prioritizing the well-being and authentic connections of individuals, we can work towards a future where social interaction is enriched, rather than diminished, by the ever-changing digital landscape.。

关于理解他人的英文单词

关于理解他人的英文单词Empathy is the cornerstone of human interaction, and the English language is rich with words that encapsulate the essence of understanding others. The word "compassion" speaks to a deep sense of sympathy and concern for the sufferings of others, often accompanied by a desire to alleviate their pain. "Empathy" itself is the ability to share and understand the feelings of another, to put oneself in someone else's shoes."Understanding" is a broad term that encompasses the cognitive process of comprehending and being aware of the feelings, thoughts, and experiences of others. "Sympathy," on the other hand, is a feeling of pity or sorrow for someoneelse's misfortune, but it does not necessarily imply the same level of emotional resonance as empathy.The term "appreciation" can also be used to express a recognition of the value or worth of someone's feelings or experiences. When we "appreciate" someone, we acknowledgetheir perspective and the validity of their emotions."Tolerance" is the capacity to endure or accept behavior, opinions, or beliefs that differ from one's own. It is a form of understanding that allows for diversity and coexistence."Acknowledgment" is the act of recognizing or expressing recognition of the existence or validity of someone'sfeelings or experiences. It is an important step in showingthat we understand and respect the other person's point of view."Support" is not just a word for physical or emotional assistance; it also conveys the understanding that someone needs help and is willing to provide it.Finally, "validation" is the act of confirming or corroborating the truth of someone's feelings or experiences. It is a powerful form of understanding that can affirm a person's reality and give them a sense of being heard and believed.These words are not just parts of speech; they are tools for building bridges between people, fostering connections, and creating a more empathetic world.。

resonance词根

resonance词根Resonance: Understanding the Essence of a Powerful WordResonance, derived from the Latin 'resonantia', holds within it the power to create a harmonious connection between individuals, ideas, and even objects. This extraordinary word originates from the root 'reson-', meaning to resound or vibrate in harmony. Within the realms of physics, music, and personal relationships, resonance plays an essential role in generating understanding, empathy, and a sense of unity. In this article, we will explore the various dimensions in which resonance manifests and how it influences our lives.In the domain of physics, resonance refers to the phenomenon when an object vibrates at its natural frequency as a result of being exposed to external vibrations of the same frequency. This interaction leads to an amplification of the original vibrations, causing an intensified effect. The concept of resonance is crucial in various aspects of our daily lives, such as acoustic instruments that produce sound through vibrations and electronic circuits that rely on resonance for amplification and filtering. Without resonance, our world would lack the richness and depth of sound and communications.Beyond the physical realm, resonance extends to our interpersonal connections. People resonate with each other when there is a fundamental alignment of ideas, values, or emotions. This resonance is characterized by an effortless understanding, empathy, and mutual respect that facilitates effective communication and deepens relationships. The experience of sharing a resonate connection can be profound, creating a sense of belonging and unity. Such resonance can occur between friends, romantic partners, or even in a larger societal context, where it facilitates the formation of communities and networks based on shared beliefs or goals.Resonance in music is perhaps one of the most palpable examples of the power of this word. Musical resonance occurs when vibrations from one instrument or voice are transmitted to another instrument, resulting in a sympathetic vibration. This creates a harmonious blend of sounds, enhancing the overall musical experience. The concept ofresonance is not limited to musical instruments but also applies to the human voice. Certain voices have the ability to resonate deeply within us, evoking strong emotions and leaving lasting impressions. This resonance can transcend language and cultural barriers, uniting people through the universal language of music.Resonance goes beyond simply vibrating in unison; it encompasses the idea of a shared energy or frequency. It is the recognition of a common thread that connects individuals and allows them to bond. When we resonate with someone or something, we are attuned to their essence, sensing their authenticity and integrity. This shared resonance forms the foundation for trust and deep connections. It enables us to truly understand and connect with others, transcending differences and creating a sense of unity in an increasingly diverse world.In summary, resonance is a powerful word that encapsulates the essence of harmonious vibrations and connections. From the physical realm of physics to the interpersonal domain of relationships and the enchanting world of music, resonance permeates various aspects of our lives. It amplifies vibrations, creates unity, and enables understanding and empathy. Resonance manifests as a guiding force, helping us navigate the complexities of our world and forging lasting connections. As we strive for resonance in our interactions and embrace the resonant connections we encounter, we unlock the transformative power of this remarkable word.。

论振动体电动力学(Ⅳ)——共振场规范变换与对称性

论振动体电动力学(Ⅳ)——共振场规范变换与对称性王鼎聪【摘要】The resonance point lattice concept was put forward to explain the symmetry of the microscopic particles, atoms, molecules and macroscopic objects. The resonance point of the lattice is the electromagnetic gauge transformation of the cumulative resonance point and has a gauge transformation, showing the Ul symmetry. The resonance point of the lattice is the angular momentum conservation movement, is the circumference of inertial motion. Electronic angular momentum causes the direction of the resonance field, the electric field to produce a centripetal force, the magnetic field generated tangent eccentric exercise. Electrons in different energy level transition probability of the different resonance lattice resonance radiation has the symmetry. The difference between the center of mass balance produces a symmetry breaking of the resonance radiation, electrons release energy to produce a non-gauge transformations, asymmetric radiation. Atomic and molecular crystals are determined by the resonance point lattice between the resonance point of the lattice will produce nuclear resonance precession of the nuclear role model. Resonance radiation - photons in the dissemination process of fermion aggregates (planet) to produce the weak interaction, this function of photon energy attenuation, the attenuation constant for the Hubble constant Ho .%提出了共振点点阵概念来解释微观粒子、原子、分子和宏观物体的对称性.共振点点阵是电磁规范变换,累加的共振点之和具有规范变换,呈U1对称性.共振点点阵是角动量守恒运动,是圆周惯性运动.电子角动量产生的原因是共振场方向决定的,电场产生了向心力,磁场产生了切线离心运动.电子在不同能级跃迁是不同共振点阵的几率,共振辐射具有对称性.质心平衡差较大产生了共振辐射的对称性破缺,电子所释放能量产生了非规范变换,非对称性的辐射.原子和分子晶体是共振点点阵所决定的,核子之间共振点点阵将产生共振进动核子作用模型.共振辐射—光子在传播的过程与费米子聚集体(星球)产生弱相互作用,这个作用使光子能量发生衰减,衰减常数为哈勃常数H0.【期刊名称】《石油化工高等学校学报》【年(卷),期】2012(025)004【总页数】10页(P29-37,41)【关键词】共振点;点阵;规范变换;对称性;角动量;共振辐射;光子【作者】王鼎聪【作者单位】中国石油化工股份有限公司抚顺石油化工研究院,辽宁抚顺113001【正文语种】中文【中图分类】TE621;O4411 研究背景薛定谔方程是类比出来的，即分析力学和光学类比得到方程［1］。

玩手机减少交流的坏处的英语作文

玩手机减少交流的坏处的英语作文全文共3篇示例，供读者参考篇1The Advantages of Reducing Cell Phone Usage on CommunicationIn today's modern world, cell phones have become an integral part of our daily lives. We use them for communication, entertainment, and productivity. However, excessive cell phone usage can have negative effects on our ability to communicate effectively with others. In this essay, we will explore the benefits of reducing cell phone usage on communication.One of the main ways that cell phones can interfere with communication is by distracting us from the people we are with. When we are constantly checking our phones for messages or notifications, we are not fully present in the moment. This can lead to misunderstandings, miscommunication, and a lack of connection with those around us. By reducing our cell phone usage, we can be more attentive and engaged in our interactions with others.Another way that cell phones can hinder communication is by replacing face-to-face interactions with digital communication. While texting and messaging can be convenient, they lack the nuances of in-person communication, such as tone of voice, body language, and facial expressions. By relying too heavily on digital communication, we may miss out on the deeper connections that can be formed through face-to-face interactions.Furthermore, excessive cell phone usage can lead to a decline in our social skills. When we spend more time interacting with screens than with people, we may struggle to engage in meaningful conversations, make eye contact, or interpret social cues. This can make it difficult to build and maintain relationships, both in personal and professional settings.On the other hand, reducing cell phone usage can have a number of benefits for communication. By unplugging from our devices and being more present in the moment, we can improve our listening skills, show more empathy towards others, and cultivate stronger relationships. Face-to-face interactions allow us to connect on a deeper level, share experiences, and build trust and understanding.In conclusion, while cell phones have many useful functions, they can also have negative impacts on our ability to communicate effectively. By reducing our cell phone usage, we can improve our relationships, enhance our social skills, and deepen our connections with others. It is important to strike a balance between technology and human interaction in order to thrive in today's digital age.篇2Playing on the phone is a common activity for people of all ages in today's society. With the rise of smartphones, it has become easier than ever to access games, social media, and other forms of entertainment on the go. While smartphones can be a great tool for staying connected and informed, they also have the potential to decrease face-to-face communication and interpersonal relationships.One of the main drawbacks of spending too much time on your phone is that it can lead to a decrease in meaningful conversations and relationships with others. When people are constantly scrolling through their phones or playing games, they may miss out on opportunities to connect with those around them. This can be especially harmful in relationships with friends and family, as it can lead to feelings of neglect and isolation.In addition to impacting personal relationships, excessive phone use can also have negative effects on communication skills. When individuals are constantly communicating through screens, they may struggle to effectively communicate in person. This can lead to misunderstandings, conflicts, and a lack of empathy towards others.Furthermore, spending too much time on the phone can also have negative effects on mental health. Studies have shown that excessive use of smartphones is associated with higher levels of stress, anxiety, and depression. This is likely due to the fact that spending too much time on the phone can lead to feelings of isolation and disconnection from the real world.In conclusion, while smartphones can be a useful tool for staying connected and entertained, it is important to be mindful of the potential drawbacks of excessive phone use. By making an effort to limit screen time and prioritize face-to-face communication, we can foster stronger relationships and improve our overall well-being. Remember, it's important to put down the phone and engage in meaningful interactions with those around you.篇3The advancement of technology has revolutionized the way we communicate. With the widespread use of smartphones, people have become increasingly reliant on their devices for social interaction. While smartphones have made it easier for us to connect with others, they have also resulted in a decrease in face-to-face communication. This trend of excessive phone usage has had detrimental effects on our ability to engage in meaningful conversations and build strong relationships.One of the main downsides of excessive phone usage is the lack of genuine communication. When people spend too much time on their phones, they tend to prioritize virtual interactions over real-life conversations. This can lead to a decline in social skills as individuals become less adept at reading body language, tone of voice, and other non-verbal cues. As a result, meaningful connections are often replaced by shallow interactions that lack depth and emotional resonance.Moreover, excessive phone usage can also lead to feelings of isolation and loneliness. While social media platforms allow us to stay connected with a large network of friends and acquaintances, these virtual relationships can never fully replace the sense of belonging that comes from genuine human interaction. When we prioritize our phones over face-to-faceconversations, we miss out on the opportunity to form meaningful connections and build strong, supportive relationships.Another negative consequence of excessive phone usage is the impact it can have on our mental health. Studies have shown that excessive screen time can lead to feelings of anxiety, depression, and low self-esteem. Constantly comparing ourselves to others on social media can create unrealistic expectations and a sense of inadequacy. Additionally, the constant barrage of notifications and messages can be overwhelming and contribute to feelings of stress and overwhelm.In conclusion, while smartphones have undoubtedly revolutionized the way we communicate, it is important to be mindful of the negative effects of excessive phone usage. By prioritizing real-life conversations and connections over virtual interactions, we can cultivate strong relationships, improve our social skills, and safeguard our mental health. It is important to strike a balance between technology use and face-to-face communication in order to maintain healthy and fulfilling relationships in today's digital age.。

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a r X i v :n l i n /0310016v 1 [n l i n .P S ] 14 O c t 2003Resonance Eﬀects in the Interaction of NLS Solitons withPotential WellsK.T.Stoychev,M.T.Primatarowa and R.S.KamburovaInstitute of Solid State PhysicsBulgarian Academy of Sciences,1784Soﬁa,Bulgaria Abstract The interaction of nonlinear Schr¨o dinger (NLS)solitons with potential wells with variable shapes is investigated numerically.For ﬁxed initial velocities below the threshold for transmission,the outcome pattern as a function of the width of the potential yields periodically repeating regions of trapping,transmission and reﬂection.The observed eﬀects are explained by an excitation and a following resonant deexcitation of amplitude (shape)oscillations of the solitons at the boundaries of the well,associated with radiation modes.Self-localized nonlinear waves(solitons)have been studied in many areas of physics in-cluding optics,solid state,molecular,plasma,elementary particles etc.Within integrable models,solitons exhibit remarkable stability-they propagate with constant velocities and shapes and emerge from collisions unchanged except for phase and space shifts.Real physi-cal systems are often described by nonintegrable equations or such containing nonintegrable perturbations.This leads to inelastic soliton interactions with a variety of outcomes.As solitons provide an important mechanism for energy and information transport in nonlinear systems,such interactions have attracted considerable attention(see i.e.Ref.1for a review of earlier works on soliton dynamics in nearly integrable systems).Investigations have been focussed on collisions between solitons in nonintegrable models and interactions of solitons with defects and inhomogeneities.In both cases,due to the inelasticity of the interactions, solitons can change their velocities,break into a number of localized and dispersive waves and/or be trapped into bound states.In addition,interesting resonance phenomena have been observed.Resonace eﬀects in kink-antikink collisions have been studied numerically in some nonin-tegrable equations includingφ4,double and modiﬁed sine-Gordon and others[2,3,4].For initial velocities below the threshold for trapping,a sequence of narrow regions of reﬂection have been obtained.These reﬂection windows have been explained by a”two-bounce”res-onance mechanism involving excitation of an internal shape mode during theﬁrst collision, temporal trapping of the solitons due to loss of kinetic energy,deexcitation of the shape mode during the second(backward)collision and escape of the kinks to inﬁnity(reﬂection). The resonance condition requires that the time between the two collisions is commensurate with the period of the shape mode.Fine three-and four-bounce resonance structures have also been obtained[5].Collisions of vector NLS solitons have been investigated in[6]where fractal resonant patterns have been obtained.Similar eﬀects have been observed in the interactions of solitons with impurities.The latter break the translational symmetry of the unperturbed system and create an eﬀective potential for scattering or capture of the solitons[1].Resonance eﬀects in the kink-impurity interaction have been investigated in[7,8,9].It has been shown in particular that kinks can be reﬂected by an attractive impurity via a”two-bounce”resonance mechanism,analogous to that of kink-antikink interaction involving the excitation and deexcitation of a localized impurity mode[8],or an impurity and a shape mode[9].Scattering of NLS solitons frompoint defects has been studied in[10,11,12]involving a variety of nonresonant outcomes.A problem of considerable theoretical and practical importance is the interaction of soli-tons with extended defects[13,14,15,16].Trapping of solitons in potential wells and nonclassical behavior for kinetic energies close to the height of potential step have been ob-tained in[16],but no resonance phenomena have been observed.The investigations however have been restricted to potential widths comparable to the soliton width.In the present work we investigate in detail the dynamics of bright NLS solitons impinging on potential wells with variable shapes.Forﬁxed initial velocities slightly below the threshold for transmission, the increase of the width of the well yields alternating regions of capture and transmission, and occasionally-narrow reﬂection windows.The regions of transmission,capture and reﬂection follow a remarkable periodicity.The observed eﬀects are explained by excitation and a following resonant deexcitation of amplitude(shape)oscilations of the soliton at the boundaries of the well.These oscillations are not associated with true internal shape modes of the soliton,but with dispersive radiation modes.As a model in our numerical simulations we used the discrete nonlinear Schr¨o dinger equa-tion which describes the dynamics of nonlinear Bose-type excitations in atomic or molecular chains in the presence of defects which change locally the energy:i∂αn∂t +∂2αL sechx−vt−x04−1checked numerically the stability of(3)with L≥4for very long time intervals.Thus(3) was input as initial condition in the simulations,placed50sites away from the defect region to avoid radiation losses due to overlapping.A predictor-corrector method[17]was used, periodic boundary conditions and chains much longer than the defect region in order to eliminate boundary eﬀects.The accuracy of the calculations was controlled through the conservation of the norm(number of particles),which is better than10−6.The total energy associated with the solution(3)on an ideal lattice is:E s= ∞−∞(|∂α2L−2(7)L2When E kin≫|E d|,the solitons are not inﬂuenced considerably by the defect,and for E kin≪|E d|the solitons are reﬂected even by an attractive defect.The possible outcomesin the case of slow solitons(E kin∼|E d|)and moderate defect strengths are transmission or capture.No resonance reﬂection windows have been obtained.A natural question arises as to what happens when the defect spreads over several lattice sites.The energy of interaction with N consecutive defects when the soliton is in the middle of the defect region is:E d=d N/2−N/2|α|2dx=2d2L(8)One can expect,that for a small number of defects,(N≤L),the evolution should be similar to this of a soliton interacting with a single defect with N-times greater strength. This turns out to be true only for kinetic energies much smaller than the interaction energy. In the case of comparable energies,the delocalization of the defect(which decreases the interaction energy)can change the evolution from capture to transmission(Fig.1).It is worth noting that the sharper the defect-the stronger the radiation accompanying the interaction.The focus of the present study lies in the interaction of NLS solitons with potential wells considerably wider than the soliton width.We modelled rectangular potential wells by N equal consecutive defects with d=−0.007and used solitons in the form(3)with widths L=5.75,which are stable on an ideal lattice.For initial velocities v<0.04the solitons are trapped inside the well and for v>0.06they pass through it and escape to inﬁnity. For initial velocities in the intermediate region,the outcome pattern as a function of the width of the well exhibits periodically alternating regions of transmission and capture,and occasionally,at the boundaries between them-narrow reﬂection windows.This is shown on Fig.2where we have plotted theﬁnal velocity of the soliton as a function of the width of the well for diﬀerent values of the initial velocity.When trapped,the soliton oscillates back and forth inside the well with zero average velocity which we have plotted asﬁnal.The sharp minima with negativeﬁnal velocity(v f<0)correspond to reﬂection.These reﬂection ”windows”are extremely sensitive to the initial velocity.The relative widths of the regions of transmission and capture depend on the initial velocity and can be quite diﬀerent,but the period of repeat remains constant and depends weakly on the velocity.Fig.3illustrates the evolutionary patterns corresponding to capture,transmission and reﬂection.It is clearly seen,that amplitude(shape)oscillations are excited when the soliton enters the potential well and persist while the soliton is inside the well.Whenever the soliton leaves the defect region,the shape oscillations are almost totally extinguished.This bringsforward the explanation of the observed resonance phenomena:when the soliton reaches the defect region it interacts inelastically with the sharp boundary and looses part of its kinetic energy exciting additional modes.These can be internal shape modes of the soliton and/or dispersive modes(radiation).We can distinguish between them by examining the frequency of the shape oscillations.The frequencies of the true internal shape modes can be obtained by adding small perturbationα1(x,t)=ϕ1(x)e−iΩt to the unperturb solution(3) and solving the linearized Schr¨o dinger equation for it:∂2ϕ1)ϕ1=0.(9)L2cosh2(x/L)The frequencies of the shape mode determined from(9)areΩ1=−0.0735andΩ2=−0.00094.The period of the amplitude oscillations obtained from the numerical data on Fig.3is T=208which yields a frequency ofΩ=−2π/T=0.030.It practically coincides with the internal frequency of the unperturbed soliton(3)ω=−0.0296.Shape oscillations with the internal soliton frequency have been reported in[18]and are explained by interfer-ence of the soliton with radiation modes with twice the soliton frequency.This shows that similarly to the case of collision of vector solitons[6],the amplitude oscillations which we observe are due to radiation,emitted during the inelastic interaction of the soliton with the boundary,and not to true internal shape modes.The soliton crosses the defect region ac-companied by the radiation and this conﬁguration is stable and weakly damped.When the soliton meets the second boundary,diﬀerent outcomes are possible depending on the timing. In the general case,as the initial velocities are very small,the reduced kinetic energy of the soliton is not suﬃcient to overcome the potential barrier of the second boundary,the soliton is reﬂected from it and eventually gets trapped.However,the interaction of the soliton with the boundary is phase-sensitive and if the time for which the soliton crosses the defect region is commensurate with the period of the shape oscillations,the inelastic interaction with the second boundary can extinguish the shape oscillations,adding their energy back to the kinetic energy of the translational motion and allowing the soliton to overcome the barrier and escape to inﬁnity which leads to transmission.The higher the initial velocity of the soliton-the wider the transmission regions(Fig.2).In some cases the resonant condition for escape is achieved after the soliton has crossed the defect region twice-in the forward and backward directions.This yields the observed narrow reﬂection windows which are analogous to the three-bounce resonances observed in[5].Due to the radiation lossesaccompanying the propagation of the soliton inside the well,these higher-order resonances are very sharp,extremely sensitive to the initial velocity and diﬃcult to observe.The interaction energy when the soliton is at the boundary of the defect region is:E d=d N0|α|2dx=d L(10) For narrow potential wells,comparable to the soliton width,the interaction energy is smaller, leading to weaker shape oscillations and a narrower region of trapping.For suﬃciently wide potential wells(N≫L,tanh(N/L)∼1),when the soliton does not”feel”the second boundary,the interaction energy and the excited shape oscillations are constant,which results in the observed periodic outcome pattern.For very wide potential wells,due to the radiation losses accompanying the oscillating soliton,the regions of transmission get narrower and eventually close down.An increase of the depth of the well leads to wider regions of trapping and narrower regions of transmission(Fig.4),while the total period remains unchanged.The inelastic interaction of the soliton with the boundary is stronger in this case and a larger portion of the kinetic energy of the soliton is transformed into radiation.A more exact resonance condition is required at the second boundary for the escape of the soliton,which yields narrower regions of transmission.Contrarily,the change of the shape of the potential well from rectangular to trapezoid leads to wider transmission regions and narrower regions of capture(Fig.5).The potential in this case is smoother and the perturbation it induces is weaker.Hence a smaller portion of the kinetic energy is transformed into radiation and the resonance condition at the second boundary is more relaxed.We also checked the dependence of the evolutionary pattern on the initial position of the soliton with respect to the boundary of the defect region.For an initial soliton in the form(3)and aﬁxed velocity v=0.05we obtain a threshold initial distance of15lattice sites,above which the soliton passes through the defect region and below it gets trapped. This can be explained by the radiation losses when the initial unperturbed soliton overlaps with the defect region.The chaotic behavior of the outcome with the initial soliton position obtained in[16]can be attributed to the diﬀerent type of coupling between the soliton and the shape mode.AcknowledgmentsThis work is supported in part by the National Science Foundation of Bulgaria under Grant No.F911.[1]Yu.S.Kivshar and B.A.Malomed,Rev.Mod.Phys.61,763(1989).[2]M.J.Ablowitz,M.D.Kruskal and dik,SIAM J.Appl.Math.36,478(1979).[3] D.K.Campbell,J.F.Schonfeld and C.A.Wingate,Physica9D,1(1983).[4]M.Peyrard and D.K.Campbell,Physica9D,33(1983).[5] D.K.Campbell and M.Peyrard,Physica18D,47(1986).[6]J.Yang and Yu Tan,Phys.Rev.Lett.85,3624(2000).[7]Yu.S.Kivshar,Zhang Fei and L.V´a zquez,Phys.Rev.Lett.67,1177(1991).[8]Zhang Fei,Yu.S.Kivshar and L.V´a zquez,Phys.Rev.A45,6019(1992).[9]Zhang Fei,Yu.S.Kivshar and L.V´a zquez,Phys.Rev.A46,5214(1992).[10]Yu.S.Kivshar,A.M.Kosevich and O.A.Chubykalo,Zh.Eksp.Teor.Fiz.93,968(1987)[Sov.Phys.JETP66,545(1987).[11]Yu.S.Kivshar,A.M.Kosevich and O.A.Chubykalo,Phys.Lett.A125,35(1987).[12]X.D.Cao and B.A.Malomed,Phys.Lett.A206,177(1995).[13]R.Sharf and A.R.Bishop,Phys.Rev.A46,R2973(1992).[14]J.J.-L.Ting and M.Peyrard,Phys.Rev.E53,1011(1996).[15]H.Frauenkron and P.Grassberger,Phys.Rev.E53,2823(1996).[16]G.K¨a lbermann,Phys.Lett.A252,37(1999).[17]L.F.Shampine and M.K.Gordon,Computer Solution of Ordinary Diﬀerential Equations(Free-man,San Francisco,1975).[18]M.W.Chbat,J.P.Prucnal,M.N.Islam,C.E.Soccolich and J.P.Gordon,J.Opt.Soc.Am.B10,1386(1993).FIG.2:Final soliton velocity v f for d=−0.007and diﬀerent initial velocities v.Curves1to4 correspond to v=0.0440;0.0476;0.0502and0.0580respectively._D3_ _D3_ DEF_D3_FIG.3:Outcome patterns for v=0.05,d=−0.007and diﬀerent number N of defects.(a)N=95 -transmission,(b)N=110-trapping and(c)N=33-reﬂection.Only a portion of the chain around the defect region is presented,while the the total length of the chain exceeds10potential widths(to avoid boundary eﬀects).FIG.5:Final soliton velocity v f for v=0.05,d=−0.007and trapezoidal potential wells with diﬀerent slope(s is the extension of the slope).。