Towards the Deconfinement Phase Transition in Hot Gauge Theories

化学化工英语试题及答案一、选择题（每题2分，共20分）1. Which of the following is a chemical element?A. WaterB. OxygenC. HydrogenD. Carbon答案：B, C, D2. The chemical formula for table salt is:A. NaOHB. NaClC. HClD. NaHCO3答案：B3. What is the process called when a substance changes from a solid to a liquid?A. SublimationB. VaporizationC. MeltingD. Condensation答案：C4. In the periodic table, which group contains alkali metals?A. Group 1B. Group 2C. Group 17D. Group 18答案：A5. What is the name of the process where a substance decomposes into two or more substances due to heat?A. CombustionB. OxidationC. ReductionD. Decomposition答案：D6. Which of the following is a physical property of a substance?A. ColorB. TasteC. SolubilityD. Reactivity答案：A7. What is the term for a compound that releases hydrogen ions (H+) when dissolved in water?A. BaseB. AcidC. SaltD. Neutral答案：B8. The law of conservation of mass states that in a chemical reaction:A. Mass is lostB. Mass is gainedC. Mass remains constantD. Mass can be converted into energy答案：C9. Which of the following is a type of chemical bond?A. Ionic bondB. Covalent bondC. Hydrogen bondD. All of the above答案：D10. What is the name of the process where a substance absorbs energy and changes from a liquid to a gas?A. MeltingB. VaporizationC. SublimationD. Condensation答案：B二、填空题（每题2分，共20分）1. The symbol for the element iron is ________.答案：Fe2. The pH scale ranges from ________ to ________.答案：0 to 143. A compound that produces a basic solution when dissolvedin water is called a ________.答案：base4. The smallest particle of an element that retains its chemical properties is called a ________.答案：atom5. The process of separating a mixture into its individual components is known as ________.答案：separation6. The study of the composition, structure, and properties of matter is called ________.答案：chemistry7. The process of a substance changing from a gas to a liquid is called ________.答案：condensation8. A(n) ________ reaction is a type of chemical reactionwhere two or more substances combine to form a single product. 答案：synthesis9. The volume of a gas at constant temperature and pressureis directly proportional to the number of ________.答案：moles10. The process of converting a solid directly into a gas without passing through the liquid phase is known as ________. 答案：sublimation三、简答题（每题10分，共30分）1. Explain what is meant by the term "stoichiometry" in chemistry.答案：Stoichiometry is the calculation of the relative quantities of reactants and products in a chemical reaction.It is based on the law of conservation of mass and involvesthe use of balanced chemical equations and the molar massesof substances to determine the amounts of reactants needed to produce a certain amount of product or the amounts ofproducts formed from a given amount of reactant.2. Describe the difference between a physical change and a chemical change.答案：A physical change is a change in the state or form of a substance without altering its chemical composition. Examples include melting, freezing, and boiling. A chemical change, on the other hand, involves a change in the chemical composition of a substance, resulting in the formation of new substances. Examples include combustion and rusting.3. What are the three main types of chemical bonds, and givean example of each.答案：The three main types of chemical bonds are ionic bonds, covalent bonds, and metallic bonds. An ionic bond is formed when electrons are transferred from one atom to another, resulting in the formation of oppositely charged ions. An example is the bond between sodium (Na) and chloride (Cl) in table salt (NaCl). A covalent bond is formed when two atoms share electrons, as seen in water (H2O) where hydrogen atoms share electrons with oxygen. Metallic bonds occur in metals, where a "sea" of delocalized electrons is shared among positively charged metal ions, as in sodium metal。

固态转变课程主要内容OutlinePART 1 General Introduction to Phase Transformation (相变概论)Classification of Phase Transformation (相变分类)Thermodynamics of Phase Transformation (相变热力学)Dynamics of Phase Transformation (相变动力学)Crystallography of Phase Transformation (相变晶体学)PART 2 Several Typical Phase Transformation (几种典型相变)Polymorphic Changes (多形性转变)Precipitation Transformation (脱溶转变)Eutectoidal Transformations (共析转变)Massive Transformation (块状转变)Order-Disorder Transformations (有序-无序转变)Spinodal Decomposition (调幅分解)Martensitic Transformations (马氏体转变)Bainitic Transformations (贝氏体转变)PART 3 Theory of Modern Phase Transformation (近代相变理论)Landau Theory (朗道理论)Solitons Theory (孤立子理论)Fractal Theory (分形理论)Phase Field Theory (相场理论)PART 4 Recovery and Recrystallization (回复和再结晶)Recovery (回复)Recrystallization (再结晶)Dynamic Recovery and Dynamic Recrystallization (动态回复和动态再结晶)Continuous Recrystallization (连续再结晶)Recrystallization Textures (再结晶织构)相变分类：①按相变时热力学参数变化特征分类（一级相变、二级相变）；②按相变方式分类（形核长大型转变、连续型相变）；③按相变时原子迁移特征分类（扩散型相变、无扩散型相变）。

小学下册英语第2单元测验试卷考试时间：80分钟（总分:100）A卷一、综合题(共计100题共100分)1. 听力题：The Earth is located in the Orion ______.2. 听力题：The chemical symbol for selenium is ______.3. 选择题：What do we call the force that pulls objects toward each other?A. MagnetismB. GravityC. FrictionD. Tension答案:B4. 填空题：I can ______ (灵活应变) to new challenges.5. 听力题：Chemical reactions can be classified as synthesis, decomposition, and _____.6. 选择题：What is the main ingredient in oatmeal?A. RiceB. WheatC. OatsD. Corn答案:C. Oats7. 选择题：What do we call the time when schools are closed for summer?A. HolidayB. VacationC. BreakD. Session8. 听力题：Endothermic reactions require energy, usually in the form of ______.9. 选择题：What do you call a person who helps in an emergency?A. TeacherB. ParamedicC. ChefD. Driver答案:B10. 填空题：A _____ (章鱼) can squirt ink to escape danger.11. 听力题：The Battle of Hastings took place in the year ________.12. 选择题：What do you call the part of the plant that absorbs water?A. LeafB. StemC. RootD. Flower答案:C13. 填空题：A ______ (生态系统服务) is crucial for human well-being.14. 选择题：What do we call a person who plays a musical instrument?A. MusicianB. ComposerC. ConductorD. Singer答案: A. Musician15. 填空题：The _____ (户外) is a perfect place for a picnic among the flowers.16. 填空题：The kangaroo uses its powerful legs to ______ (跳跃).17. 填空题：A monkey can _______ (爬) trees easily.18. 听力题：My favorite subject is _____ (math/science).19. 听力题：A ____ is a gentle giant that can be very friendly.20. 听力题：Planets are classified as terrestrial or ______.21. 填空题：A ____(green certification) recognizes sustainable practices.22. 填空题：The capital of the Gambia is ________ (班珠尔).23. 听力题：The __________ is a region known for its unique languages.24. 填空题：My dad enjoys cooking on the ____.25. 选择题：Which animal is known for its ability to swim fast?A. DogB. DolphinC. CatD. Elephant答案:B26. 听力题：A prism can separate light into different ______.27. 填空题：Many plants are _____ (可食用) and nutritious.28. 填空题：I enjoy _______ (喝果汁) in the summer.29. 选择题：What is the opposite of 'fast'?A. QuickB. SlowC. SpeedyD. Rapid30. 填空题：The ________ (机场) is busy with travelers.31. 选择题：What do bees make?A. MilkB. HoneyC. ButterD. Jam答案:B32. 听力题：I like to _____ in the garden. (play)33. 听力题：Matter is anything that has ______.34. 听力题：The chemical formula for beryllium oxide is ______.35. 选择题：What is the opposite of 'hot'?'热'的反义词是什么？A. ColdB. WarmC. CoolD. Boiling答案: A36. 选择题：What is the main ingredient in a salad?a. Meatb. Vegetablesc. Fruitd. Bread答案:B37. 听力题：The Titanic sank on its maiden _______.38. 听力题：Some _______ are grown for their beauty.What is the name of the popular game where you try to guess words based on clues?A. PictionaryB. CharadesC. TabooD. Scattergories答案: A40. 选择题：What do you call a young female goat?A. KidB. CalfC. LambD. Pup答案: A41. 填空题：The ________ is small and cute.42. 填空题：The ________ (历史遗迹) tell stories of the past.43. 填空题：I saw a __________ form in the sky before the storm. (乌云)44. 填空题：I hear birds singing when it’s ______ (晴天).45. 选择题：What is the capital city of Russia?A. MoscowB. St. PetersburgC. KazanD. Novosibirsk答案: A46. 选择题：What do we call a computer program that helps us to create documents?A. BrowserB. Word processorC. SpreadsheetD. Game答案:BA ______ (多样的生态系统) promotes resilience.48. 填空题：My favorite number is ______.49. 填空题：The __________ (地貌) shapes the landscape.50. 听力题：Organic chemistry is the study of ______ compounds.51. 听力题：Some _______ can be climbing or trailing.52. 选择题：Which item is used to tell time?A. CalendarB. ClockC. MapD. Book答案：B53. 听力题：The park is ___ (full/empty) of children.54. 听力题：__________ is the process of separating a mixture into its components.55. 听力题：The process of ______ can lead to the discovery of fossils.56. 填空题：A _____ (狒狒) can be quite mischievous.57. 选择题：What is the primary function of the lungs?A. To pump bloodB. To digest foodC. To absorb oxygenD. To filter waste答案: C58. 填空题：The owl has _______ (大眼睛) for night vision.Electric fields can exert ______ (forces) on charged particles.60. 填空题：The ________ (养分) in the soil is important for growth.61. 听力题：She likes to wear ________ shoes.62. 听力题：They are going to ________ a concert.63. 填空题：The ancient Greeks believed in many _____ and myths.64. 填空题：My brother loves to __________ (参加) sports tournaments.65. 填空题：A __________ (生态旅游) promotes awareness of environmental issues.66. 选择题：What is the capital of Vietnam?A. Ho Chi Minh CityB. HanoiC. Da NangD. Can Tho答案:B. Hanoi67. 听力题：The wind is ______ (blowing) gently today.68. 填空题：A horse is used for riding and ________________ (工作).69. 选择题：How many months are there in a year?A. TenB. TwelveC. ElevenD. Nine70. 填空题：The musician plays the _____ (小号) in the band.What do you call a story with animals that talk?A. Fairy taleB. FableC. BiographyD. Novel72. 选择题：What is the process of changing from liquid to gas called?A. FreezingB. MeltingC. EvaporationD. Condensation答案: C73. 选择题：How do you say "再见" in English?A. HelloB. GoodbyeC. PleaseD. Thank you74. 听力题：This is my best ____ (friend). We go to school together.75. 选择题：How many days are in a week?A. FiveB. SixC. SevenD. Eight76. 填空题：The ______ (植物的生长速度) can vary based on conditions.77. 填空题：On a sunny day, I decided to visit the ______ (1) with my family. We packed a picnic basket filled with sandwiches, fruits, and drinks. When we arrived, the park was filled with ______ (2) enjoying the beautiful weather. My little brother ran stra78. 填空题：The scientist discovered a new _____ (物种).79. 填空题：I have a new _______ (背包).We are having a ___. (picnic) this weekend.81. 填空题：The goldfish can live for several _________ (年).82. 听力题：The ______ teaches us about different countries.83. 选择题：What is the capital of Australia?A. SydneyB. CanberraC. MelbourneD. Brisbane答案: B84. 听力题：Birds have ______ to help them fly.85. 填空题：My __________ (玩具名) is very __________ (形容词) to play with.86. 填空题：I enjoy reading ______ (故事) before going to sleep.87. 填空题：My family loves to __________ on holiday. (度假)88. 选择题：How many sides does a pentagon have?A. 4B. 5C. 6D. 7答案: B89. 听力题：He is _____ (running) very fast.90. 选择题：What do we call the process of a caterpillar turning into a butterfly?A. EvolutionB. MetamorphosisC. DevelopmentD. Transformation答案:B91. 填空题：Ancient Egyptians believed in many ________.92. 听力题：The first man to reach the South Pole was _______ Amundsen.93. 填空题：My teacher encouraged us to create our own ________ (漫画). I drew a funny ________ (角色).94. 选择题：Which one is a popular sport?A. SwimmingB. EatingC. SleepingD. Writing95. 选择题：What do you call a person who writes music?A. ComposerB. MusicianC. LyricistD. All of the above答案:D96. 听力题：Vinegar is an example of an _______.97. 听力题：Reactions that happen quickly release more ______.98. 听力题：The first human to fly in space was _______ Gagarin.99. 听力题：I like to play ______ (video games) on weekends.100. 填空题：A _______ (蜥蜴) can be found on warm rocks.。

Toward a Science of Translating Nida AbstractThe purpose of this paper is to explore the potential of a science of translating according to the model proposed by Eugene Nida. Nida proposed a model of translation based on the scientific study of language and its use. This paper will discuss the implications of Nida’s model for the field of translation, and the potential for a science of translatingto be developed. It will also discuss the challenges and obstacles that must be overcome in order to develop such a science.IntroductionTranslating is a complex process that involves the transfer of meaning between two languages. It is a process that is both creative and analytical, and requires a deep understanding of the source and target languages. Translators must be able to interpret the source language accurately, while alsoconveying the same meaning in the target language. The challenge of translating can be daunting, and there is a need for a more scientific approach to the process.Eugene Nida proposed a model of translation based on the scientific study of language and its use. He argued that translation should be based on a scientific approach to language, and that this approach should be used to inform the process of translation. This paper will explore the implications of Nida’s model for the field of translation, andthe potential for a science of translating to be developed.Nida’s Model of TranslationNida proposed a model of translation that was based on the scientific study of language and its use. He argued that translation should be based on a scientific approach to language, and that this approach should be used to inform the process of translation. This model is based on the idea that language is a system, and that the meaning of a text can be determined by analyzing thestructure of the language. Nida argued that the meaning of a text can be determined by analyzing the structure of the language, and that the translator should use this analysis to inform their translation.Nida’s model of translation is based on the idea that language is a system, and that the meaning of a text can be determined by analyzing the structure of the language. This model is based on the idea that language is a system, and that the meaning of a text can be determined by analyzing the structure ofthe language. Nida argued that the meaning of a text can be determined by analyzing the structure of the language, and that the translator should use this analysis to inform their translation.Nida’s model of translation also includes the idea of equivalence. He argued that translation should strive for equivalence between the source and target languages. This means that the translator should strive to convey the same meaning in the target language as is expressed in the source language. Nida argued that this could be achievedby analyzing the structure of the language, and by using the same linguistic structures in the target language.Nida’s model of translation also includes the idea of dynamic equivalence. He argued that translation should strive for dynamic equivalence, which is the ability to convey the same meaning in the target language as is expressed in the source language, but in a different form. This means that the translator should be able to adapt the source language to the target language,while still conveying the same meaning. ConclusionIn conclusion, Nida’s model of translation is based on the scientific study of language and its use. This model is based on the idea that language is a system, and that the meaning of a text can be determined by analyzing the structure of the language. Nida argued that the meaning of a text can be determined by analyzing the structure of the language, and that the translator should use this analysis toinform their translation. Nida also argued that translation should strive for equivalence and dynamic equivalence between the source and target languages.The implications of Nida’s model for the field of translation are clear. If his model is followed, then it is possible to develop a science of translating. This science would be based on the scientific study of language and its use, and would provide a more systematic approach to the process of translation. Such a science would also provide amore reliable and consistent approach to the process of translation, and would help to ensure that translations are accurate and meaningful.The development of a science of translating would require the development of new tools and techniques for analyzing language, and for translating texts. It would also require the development of new theories and models for the process of translation. The development of such a science would be a complex and challenging task, but one that couldToward a science of translating Nidapotentially revolutionize the field of translation.。

Membrane adhesion and domain formation Thomas R.Weikl and Reinhard Lipowsky Max Planck Institute of Colloids and Interfaces Department of Theory and Bio-Systems 14424Potsdam,Germany Contents 1Introduction 31.1Membrane adhesion via sticker molecules .............31.2Stickers and repellers in biomimetic membranes ..........41.3Specific adhesion of biological membranes .............51.4Outline of review ...........................52Modelling of membranes 72.1Homogeneous or uniform membranes ................82.1.1Membrane configurations and effective Hamiltonian ...82.1.2Classification of effective membrane potentials ......92.2Discretized models for uniform membranes .............102.3Lattice gas models:General form ..................112.4Membranes with sticker molecules .................122.5Two types of membrane-anchored molecules ............143Theoretical methods 153.1Monte Carlo simulations .......................153.1.1Simple sampling and importance sampling .........153.1.2Membrane simulations ....................173.2Free energies of adhesion for homogeneous membranes ......193.3Effective potential in the absence of cis-interactions ........203.4Variational (mean-field)theory for cis-interactions ........224Entropic mechanisms for domain formation 244.1Entropic interactions between bound stickers (24)4.2Small flexible stickers without cis-interactions (27)4.3Stickers with cis-interactions (27)4.4Large stickers (30)4.5Rigid stickers (33)4.5.1Tensionless membranes (33)4.5.2Effect of tension (35)1a r Xi v:79.3759v1[c ond-ma t.s oft]23Se p275Barrier mechanisms for domain formation385.1Membranes with stickers and mobile repellers (38)5.2Membranes with stickers and generic repulsive interactions (40)5.2.1Stickers with square-well potential (41)5.2.2Stickers with linear potential (41)6Dynamics of domain formation during adhesion466.1Adhesion of vesicles with stickers and repellers (47)6.2Adhesion of T cells (51)6.2.1Model (51)6.2.2Adhesion dynamics without cytoskeletal transport (53)6.2.3Adhesion dynamics with active transport of TCRs (56)Appendices59A Continuum model for homogeneous membranes (59)21IntroductionThe molecular structure of biological and biomimetic membranes is provided by bilayers of amphiphilic molecules such as lipids and proteins.Lipid bilayers are rather thin with a thickness between4and5nm.At physiological temperatures, these membranes arefluid in the sense that they have no in-plane shear modulus. On the nanometer scale,the molecules have nofixed neighborhoods since two adjacent molecules can easily exchange their position within the membrane. This local exchange leads to rapid lateral diffusion of the molecules along the membrane.In this way,a typical lipid molecule is displaced by about one micrometer in one second.Therefore,biomembranes1represent multicomponent liquids in two dimensions.1.1Membrane adhesion via sticker moleculesNow,consider such a multicomponent membrane that forms a giant vesicle which adheres to another membrane or,more generally,to a substrate surface. Within the contact area of the vesicle,the membrane molecules can still diffuse, at least to some extent,which implies that the different molecular components may attain many different spatial patterns.In particular,some of these com-ponents may form clusters or extended domains within the contact area.In this article,we will review recent work on these patterns and their formation processes.We will focus on situations in which the membrane contains certain types of membrane-anchored molecules,so-called stickers and repellers.[1-6]Sticker molecules mediate attractive interactions between the membrane and the adja-cent surface whereas repeller molecules act as repulsive spacers between these two surfaces.Within the contact area,sticker molecules have a strong tendency to form clusters or intramembrane domains.In fact,there are several distinct mechanism for these pattern formation processes as explained in the main part of this review.There are many different types of stickers which can vary greatly in their size.The smallest stickers are presumably charged head groups of lipids which are attracted towards an oppositely charged surface.Likewise,lipids may have large sticky head groups containing,e.g.,polysaccharides.Much larger stick-ers mediate the specific adhesion of biological membranes which governs both cell-cell adhesion and the signalling between cells of the immune system.[7,8] Cell adhesion molecules,which govern the binding of two cells,and receptor molecules,which are expressed on the surface of immune cells,are usually rel-atively stiffrodlike molecules which are anchored in the bilayer membrane and have a linear extension of10-30nm.1Here and below,the term‘biomembrane’is used as an abbreviation for‘biological or biomimetic membrane’.It is always assumed implicitly that biomembranes have two charac-teristic features:(i)they contain several molecular components and(ii)they are in afluid phase.3Presumably thefirst theoretical models for the adhesion of membranes via mobile stickers were introduced by Bell et al.in Refs.[9,10]as reviewed in [11]and by Evans in Refs.[12,13].In these models,the membrane is divided up into a bound segment,which represents the contact area,and an unbound segment which acts as a reservoir for the mobile sticker molecules which can diffuse in and out of the contact area.The repellers are taken to be more or less immobile and the separation of the two interacting surfaces is taken to be constant within the contact area.If the repeller molecules are longer than the sticker molecules,the competing action of these two types of molecules should lead to a modulation of this separation:sticker–rich membrane segments should have a relatively small separation whereas repeller–rich segments should have a relatively large one as discussed in the context of gap junctions[14,15,16].Since the membrane-anchored stickers gain energy when they enter the con-tact area and bind to the second surface,these molecules will be‘recruited’by this surface and,thus,will be enriched within the contact area.Therefore, the bound and unbound segments of multicomponent membranes will usually differ in their molecular compositions[17].2In the following,we will focus on the bound membrane segment,i.e.,on the contact area of the multicomponent membrane,and view its unbound segment as a reservoir for the sticker and repeller molecules.It is then convenient to use a grand-canonical description and to replace this reservoir by chemical potentials for the sticker and repeller molecules.In this way,one arrives at lattice gas models onflexible surfaces. [1,2,3]These lattice gas models provide a general theoretical framework by which one can study the interplay of membrane adhesion and domain formation in a systematic manner.The problem of adhesion-induced domain formation has also been addressed using somewhat different theoretical models in Refs.[18,19,20,21].In addition, this process has also been observed experimentally both in biomimetic and in biological membranes.The next two subsections contain a short summary of these observations.1.2Stickers and repellers in biomimetic membranes Adhesion-induced lateral phase separation into domains with small and large membrane separations has been found to occur in several biomimetic systems. The formation of blisters has been observed in membranes containing cationic lipids in contact with a negatively charged surface[22],and between membranes containing both negatively and positively charged lipids[23].The coexistence of tightly and weakly bound membrane segments has been found for mem-branes with biotinylated lipids bound to another biotinylated surface via strep-tavidin[24],membranes with homophilic csA-receptors from the slime mold Dictyostelium discoideum[25],and membranes containing specific ligands of in-tegrin molecules adsorbed on a substrate[26].Attractive membrane-mediated 2This difference in composition has apparently been overlooked by Bell since he says on page242of Ref.[11]”that at equilibrium the number of receptors per unit area will be the same in the contact area and outside of it.”4interactions between bound csA-receptors of adhering vesicles have been inferred from membrane tension jumps induced by the micropipet aspiration technique [27].In addition to the receptors,the membranes studied in[24,25,26,27]also contain repulsive lipopolymers to prevent non-specific adhesion.1.3Specific adhesion of biological membranesThe adhesion of cells plays a key role in important biological processes such as tissue development and immune response.The highly selective interactions leading to cell adhesion are mediated by a variety of specific receptors which are embedded in the cell membranes.Two prominent examples for domain for-mation within the contact area of biomembranes are provided by focal contacts [7,28],which are formed during cell adhesion at substrate surfaces,and by the so-called‘immunological synapses’which are formed during the adhesion of helper T cells and antigen-presenting cells as part of the immune response. Within the contact area of these two cells,several groups have recently observed distinct domain patterns of membrane-anchored receptors and ligands.The antigen-presenting cells(APCs)display foreign peptide fragments on their surfaces.These peptide fragments are presented by MHC molecules on the APC surfaces,and recognized by the highly specific T cell receptors(TCR). At the cell-cell contact zone,the bound receptor-ligand pairs are arranged in characteristic supramolecular patterns[29,30,31,32,33],for reviews see[34, 35,36,37,38,39].Thefinal,‘mature’pattern of an adhering T cell consists of a central domain in which the TCRs are bound to the MHC-peptides(MHCp), surrounded by a ring-shaped domain in which the integrin receptors LFA-1 of the T cell are bound to their ligands ICAM-1of the APC.Intriguingly, the characteristic intermediate pattern formed earlier during T cell adhesion is inverted,with a TCR/MHCp ring surrounding a central LFA-1/ICAM-1domain in the contact zone[30,40,33].This pattern inversion has beenfirst observed for T cells adhering to a supported lipid bilayer with embedded MHCp and ICAM-1, [30,40],more recently also in a cell-cell system[33].A significantly different type of pattern evolution has been found for immature T cells or thymozytes,which form multifocal synapses with several nearly circular clusters of TCR/MHC-peptide complexes in the contact zone[41,42].1.4Outline of reviewThis review article is organized as follows.In section2,we describe the the-oretical framework used to study the interplay of membrane adhesion and do-main formation.Wefirst review the behavior of interacting membranes that have a homogeneous or uniform composition.We then describe general lattice gas models for multicomponent membranes with anchored sticker and repeller molecules.Section3summarizes the different theoretical methods used to elu-cidate the membrane behavior.The remaining sections4–6represent the main part of this review and discuss the interplay of adhesion and domain formation for several membrane systems.5In section4,we consider multicomponent membranes with one species of sticker molecules and describe several entropic mechanisms that enhance or induce the formation of sticker-rich domains within the contact area.These mechanisms reflect the large configuration space which the membranes and the sticker molecules can explore because of their mobility.In order to elucidate these mechanisms,one must distinguish two types of molecular interactions: (i)trans-interactions between the sticker molecules and the second membrane or substrate surface;and(ii)cis-interactions between two stickers which are anchored to the same membrane.If the cis-interactions between the stickers are repulsive and short-ranged,the thermally excited shapefluctuations of the membrane induce small clusters of stickers but are not able to initiate the for-mation of sticker-rich domains within a sticker-poor membrane matrix.In fact, in the latter case,sticker-mediated adhesion occurs only if the sticker concentra-tion exceeds a certain threshold value.Sticker-rich and sticker-poor domains are formed if the stickers experience attractive cis-interactions and these attractive interactions are effectively enhanced by the thermally excited shapefluctuations of the membranes.Furthermore,purely entropic mechanisms for the formation of sticker-rich domains arise if the stickers are large compared to the smallest wavelength of the bending modes or if the stickers increase the local bending rigidity of the membrane.Another class of mechanisms for adhesion-induced domain formation is dis-cussed in section5where we consider the adhesion of multicomponent mem-branes which contain both sticker and repeller molecules.If the length of the repellers,say l r,exceeds the length of the stickers,say l s,the size mismatch be-tween these two species of molecules favors the formation and growth of sticker-rich domains.This can be understood in terms of effective membrane potentials with a potential well arising from the stickers and a potential barrier arising from the repellers.Phase separation into sticker-rich and sticker-poor(or repeller-rich)domains occurs if the potential barrier is sufficiently high.Similar barrier mechanisms are also effective if the membranes contains two species of stickers, long and short ones.Finally,section6addresses the time evolution of domains in multicomponent membranes which contain(i)stickers and repellers,(ii)short and long stickers, or(iii)short stickers,long stickers as well as repellers.In all cases,the effective membrane potential exhibits a potential barrier which implies that the initial dynamics of the domain formation represents a nucleation process.Thus,in the presence of repellers,adhesion is governed by the nucleation of sticker clusters or islands.The diffusion and coalescence of these clusters leads to the formation of distinct domain patterns at intermediate times.This provides a simple and generic mechanism for the observed time evolution within the immunological synapse between helper T cells and antigen-presenting cells.62Modelling of membranesIn this section,we discuss the theoretical models that will be used in order to describe and understand the interplay between membrane adhesion and domain formation.This interplay arises from two degrees of freedom:the elastic de-formations of the membranes and the spatial patterns of membrane-anchored molecules.As mentioned in the introduction,we will focus on the contact area of adher-ing vesicles or cells and view their unbound segments as reservoirs for the sticker and repeller molecules.It is then convenient to use a grand-canonical descrip-tion and to describe these reservoirs by chemical potentials for the membrane-anchored molecules.In general,the membranes may contain several species of such molecules which will be distinguished by the index k with k=1,...K. The membrane concentration of species k is then determined by the chemical potentialµk.Because of theflexibility of the membranes and the lateral mobility of the anchored molecules,the membranes can attain many microscopic states within the contact area.Each of these states can be characterized by its configurational energy or effective Hamiltonian,H.3At temperature T,the statistical weight of a certain configuration,i.e.,the probability to observe this configuration,is then proportional to the Boltzmann factor∼exp(−H/k B T)with Boltzmann constant k B.The elastic deformations of an adhering membrane will be described by the separationfield l.The spatial patterns of anchored molecules will be repre-sented by the composition variables n.These composition variables are defined with respect to an underlying lattice of membrane patches.In this way,the well-known theoretical framework of lattice gas models is extended toflexible surfaces.[1,2,3]In general,the membrane-anchored molecules may experience a variety of intermolecular forces.We will distinguish between cis-and trans-interactions of these molecules.[1]Since two molecules that are anchored to the same membrane cannot occupy the same membrane patch,these molecules always experience hardcore cis-interactions which are repulsive and short-ranged.In addition,these molecules may stick to each another,which corresponds to short-ranged attractive cis-interactions,or they may carry electric charges,which can lead to long-ranged cis-interactions.In addition,the membrane-anchored molecules mediate the trans-interactions between the membrane and the second surface.By definition,stickers mediate attractive trans-interactions whereas repellers mediate repulsive ones.The lattice gas models considered here have two rather useful features:(i)3Here and below,the term‘effective Hamiltonian’is equivalent to the term‘configurational energy’which is standard practise in statistical mechanics even though the configurations are described in terms of classical,i.e.,commuting variables and,thus,do not involve any quantum-mechanical degrees of freedom.The Hamiltonians used in this article are‘effective’in the sense that they do not describe all molecular details of the biomembranes but focus on the relevant degrees of freedom.7The hardcore cis-interaction between the anchored molecules,which leads to their mutual exclusion within the membrane,is automatically incorporated; and(ii)If this hardcore interaction is the dominant cis-interaction,one can perform the partial summation over the composition variables in the partition function.As a result,one obtains effective membrane models that depend only on the separationfield l.2.1Homogeneous or uniform membranes2.1.1Membrane configurations and effective HamiltonianOur theoretical description starts with a homogeneous or uniform membrane in contact with another,planar surface with Cartesian coordinates x≡(x1,x2). This membrane will be viewed as a thin elastic sheet that exhibits an average orientation parallel to this planar surface.If we ignore overhangs,the membrane shape can be parametrized by the separationfield l(x)which describes the local separation of the membrane from the planar reference state with l(x)≡0.The elastic deformations of the membrane are governed by two parameters: (i)the membrane tensionσ,which is conjugate to the total membrane area,and (ii)the bending rigidityκthat governs the bending energy of the membrane.In addition,the membrane experiences direct interactions with the second surface that will be described by the interaction energy per unit area or effective mem-brane potential V me(l).The membrane configurations are then governed by the effective Hamiltonian[43]H{l}=H el{l}+H in{l}(1) which consists of the elastic term H el{l}and the interaction term H in{l}.Theelastic term has the formH el{l}=d2x12σ(∇l)2+12κ(∇2l)2(2)where theσ–term is proportional to the excess area of the deformed membrane and theκ–term is proportional to the squared mean curvature of the membrane, see Appendix A.The interaction term represents an integral over the effectivemembrane potential as given byH in{l}=d2x V me(l).(3)The effective Hamiltonian as given by(1)–(3)also applies to two inter-acting membranes which are characterized by bending rigiditiesκ1andκ2and membrane tensionsσ1andσ2,respectively.In this case,the separationfield l describes the local distance between the two membranes which can both exhibit bending deformations and,thus,attain a nonplanar shape,see Appendix A.For two interacting membranes,the paramatersσandκin the elastic part(2)now represent the effective tension[44]σ≡σ1σ2/(σ1+σ2)(4)8and the effective bending rigidity[45]κ≡κ1κ2/(κ1+κ2).(5) The interaction potential between the two surfaces always contains a repul-sive hardwall potential which ensures that the two surfaces cannot penetrate each other and that the separationfield l satisfies l≥0.This hardwall poten-tial can be implemented in two ways:(i)It may be included into the definition of the effective membrane potential via V me(l)≡∞for l<0;or(ii)it may be embodied by restricting the l–integration in the partition function to positive values.In the following,we will use the second implementation and,thus,define the partition function viaZ=l>0D{l}exp[−H{l}/k B T].(6) 2.1.2Classification of effective membrane potentialsThe effective membrane potential V me(l)describes the interaction free energy of two planar surfaces at uniform separation l=const.In general,the functional dependence of V on l will reflect various intermolecular forces such as van der Waals,electrostatic,or hydrophobic interactions.[46]In addition,the effective membrane potential also depends on external forces or constraints such as an applied osmotic pressure or the confinement via another wall that provides an upper bound for the separationfield l.It is useful to distinguish two different classes of membrane potentials cor-responding to membrane confinement and membrane adhesion,respectively.Membrane confinement is described by potentials V me(l)that do not attain afinite value in the limit of large l.Simple examples are provided by(i)a confining wall at l≡L which implies V me=∞for l>L;(ii)a harmonicpotential as given by12G(l−l∗)2;and(iii)an osmotic pressure P which impliesthat V(l)contains the linear term P l for l>0.Membrane adhesion,on the other hand,corresponds to potentials V me(l) that(i)have at least one attractive potential well and(ii)attain afinite value in the limit of large l.Since we may always replace V me by V me(l)−V me(∞), it is sufficient to consider potentials that decay to zero for large l.All effective potentials that arise from intermolecular forces have this latter property.A confined membrane exhibits critical behavior as one reduces the strength of the confining potential.If this potential is symmetric,i.e.,if we can define a shifted separationfield l ≡l−l o in such a way that V me(−l )=V me(l ), the average value l is always zero but the variance (l − l )2 diverges as one reduces the confining potential.This delocalization behavior is obtained (i)for a confining wall as one moves this wall to larger values of l=L and (ii)for a harmonic potential as one decreases the strength G of this potential. For an asymmetric potential,on the other hand,the confined membrane also unbinds from the second surface at l=0as one decreases the strength of the confining potential.One example is provided by an external osmotic pressure P:9in the limit of small pressure P ,one obtains the complete unbinding behavior l ∼1/P 1/3.[43]An adhering membrane,on the other hand,exhibits critical behavior as one effectively reduces the attractive part of the effective membrane potential V me (l ).Since the membrane configurations are governed by V me (l )/k B T ,this reduction can be most easily obtained by raising the temperature T .In the absence of any confining potential,the membranes then undergo an unbinding transition at a characteristic temperature T =T u .The nature of this transition depends on the functional dependence of the effective membrane potential V me on the separation field l .The unbinding transition is continuous if V me (l )has a single potential well but no potential barrier.[43,47]Such an effective membrane potential arises,e.g.,from the interplay of van der Waals and hydration forces.If V me (l )contains both a potential well and a potential barrier,this transition is continuous for sufficiently low potential barriers but discontinous for sufficiently high barriers.[48,49]Unbinding transitions have been observed experimentally by Mutz and Hel-frich [50]for glycolipid bilayers and by Pozo-Navas et al.[51]for bilayers com-posed of two phospholipids.In both cases,the composition of the bilayer mem-branes was presumably uniform.2.2Discretized models for uniform membranesIn order to include the anchored molecules in the theoretical description,we will first discretize the uniform membrane.A convenient discretization is pro-vided by a square lattice within the planar reference plane,see Fig.1.The corresponding lattice parameter is denoted by a .In this way,the 2–dimensional coordinate x is replaced by a discrete set of lattice sites labeled by the index i .The membrane configurations are now described in terms of separation fields l i associated with the lattice sites i ,and the membrane is divided up into discrete membrane patches,each of which has projected area a 2,see Fig.1.Since the elastic part of the effective Hamiltonian depends on the derivatives of l with respect to the coordinates x 1and x 2,we have to discretize these deriva-tives as well.For the excess area term ∼(∇l )2,we will use the discretization(∇d l i )2≡[l (x 1+a,x 2)−l (x 1,x 2)]2+[l (x 1,x 2+a )−l (x 1,x 2)]2(7)where x 1and x 2denote the Cartesian coordinates of the lattice site i .Likewise,the discrete Laplacian is taken to be [47]∇2d l i ≡l (x 1+a,x 2)+l (x 1−a,x 2)+l (x 1,x 2+a )+l (x 1,x 2−a )−4l (x 1,x 2)(8)The elastic Hamiltonian now has the form H el {l }= i [12σ(∇d l i )2+12a 2κ(∆d l i )2](9)and the interaction Hamiltonian becomes H in {l }= i V (l i )(10)10which represents a summation over all membrane patches i with potential en-ergiesV(l i)≡a2V me(l(x1,x2))(11) where x1and x2denote again the Cartesian coordinates of the lattice site i. Note that V(l i)and V me(l)have the dimensions of energy and energy per area, respectively.Realistic estimates of the entropy and free energy of the membranes require that the lattice constant a is equivalent to the smallest possible wavelength for bendingfluctuations of the puter simulations with molecular membrane models indicate that this size is somewhat larger than the thickness of the lipid bilayer and of the order of6nm[52,53].2.3Lattice gas models:General formNext,we include the membrane-anchored molecules,that may act as stickers or repellers,into the theoretical modelling.In general,the membrane may contain K different types of such molecules which will be distinguished by the index k=1,...,K.Since all membrane-anchored molecules undergo lateral diffusion along the membrane,these molecules can form many different spatial patterns.In order to describe these patterns,we now introduce composition variables n i for all lattice sites i.Each composition variable can attain the values n i=0,1,...,K.If the membrane patch i contains the membrane-anchored molecule of type k,this patch is characterized by n i=k.If the patch does not contain any of the K membrane-anchored components,the composition variable n i has the special value n i=0.In the absence of the second membrane or surface,the concentrations of the K species of membrane-anchored molecules are governed by K chemical potentialsµk with k=1,2,...,K.In addition,the cis-interaction between one molecule of species k located at lattice site i and another molecule of species klocated at site j is described by the pair-potential W k,kij which is negative forattractive cis-interactions.Thus,the configurations of the composition variables n i are governed by the cis-interaction part of the effective Hamiltonian as given byH ci{n}=−iKk=1µkδk,ni+ijKk=1Kk =1δk,niδk ,njW k,kij(12)with the Kronecker symbolδk,n which is defined byδk,n=1for k=n andδk,n= 0otherwise.The symbol ij indicates a summation over all pairs of lattice sites i and j.Note that the chemical potential term alone already embodies the hardcore interactions between two neighboring membrane-anchored molecules because of the underlying lattice.The configuration of the adhering membrane is now described both by its separationfield l i and by its composition variables n i.These two degrees of freedom are governed by the effective HamiltonianH{l,n}=H el{l,n}+H in{l,n}(13)11。

2022年考研考博-考博英语-厦门大学考试全真模拟易错、难点剖析AB卷（带答案）一.综合题(共15题)1.单选题Changing from solid to liquid, water takes in heat from all substances near it and this_______produces artificial cold surrounding it.问题1选项A.absorptionB.transitionC.consumptionD.interaction【答案】A【解析】absorption吸收; transition过渡, 转变; consumption消费, 消耗; interaction相互作用。

句意：水从固体变成液体, 会吸收附近所有物质的热量, 这种吸收会在周围产生人工寒潮。

选项A符合句意。

2.单选题The British historian Niall Ferguson speculated that the end of American_______might not fuel an orderly shift to a multipolar system.问题1选项A.domainB.hegemonyC.sovereigntyD.preference【答案】B【解析】domain领地,领域; hegemony霸权; sovereignty主权,君主; preference偏爱, 优先权。

句意：英国历史学家Niall Ferguson推测, 美国霸权主义的终结可能不会推动美国向多极体系的有序转变。

选项B符合句意。

3.翻译题(1). When we talk about the danger of romantic love, we don't mean danger in the obvious heartbreak way—the cheap betrayals, the broken promises—we mean the dark danger that lurks when sensible, educated women fall for the dogmatic idea that romantic love is the ultimate goal for the modern female. Every day, thousands of films, books, articles and TV programs hammer home this message—that without romance, life is somehow barren.However, there are women who entertain the subversive notion, like an intellectual mouse scratching behind the skirting board, that perhaps this higher love is not necessarily the celestial highway to absolute happiness. (2). Their empirical side kicks in. and they observe that couples who marry in a haze of adoration and sex are, ten years later, throwing china and fight bitterly over who gets the dog.(3). But the women who notice these contradictions are often afraid to speak them in case they should be labeled cynics. Surely only the most jaded and damaged would challenge the orthodoxy of romantic love. The received wisdom that there is not something wrong with the modern idea of sexual love as ultimate panacea, but (hat if you don't get it, there is something wrong with you. You freak, go back and read the label. (4).We say the privileging of romantic love over all others, the insistence that it is the one essential, incontrovertible element of human happiness, traced all the way back to the caves, is a trap and a snare. The idea that every human heart, since the invention of the wheel, was yearning for its other half is a myth.(5). Love is a human constant: it is the interpretation of it that changes. The way that love has been expressed, its significance in daily life, have never been immutable or constant. The different kinds of love and what they signify are not fixed, whatever the traditionalists may like to tell you.So the modern idea that romantic love is a woman's highest calling, that she is somehow only half a person without it, that if she questions it she is going against all human history, does not stand up to scrutiny. It is not an imperative carved in stone; it is a human idea, and human beings are frail and suggestible, and sometimes get the wrong end of the stick.Read the passage carefully and translate the underlined sentences into Chinese.【答案】1.当说到浪漫爱情的危险时, 我们并不是指显而易见令人心碎的危险一可耻的背叛、破碎的誓言——而是指当明智的知识女性对教条主义思想信以为真, 即浪漫的爱情是现代女性的终极目标时, 潜伏着的隐秘危险。

Trois dimensions：3D技术Trois dimensions ou tridimensionnel ou 3D sont des expressions qui caractérisent l'espace qui nous entoure, tel que perçu par notre vision, en termes de largeur, hauteur et profondeur.Tache solaire : 太阳黑子Une tache solaire est une région sur la surface du Soleil qui est marqueépar une température inférieure à son environement et a une intense activité magnétique(磁性的),qui inhibe（抑制）la convection（对流）,formant des zones où la température de surface est réduite.ADN acide désoxyribonucléique：脱氧核苷酸C’est une molécule（分子）, retrouvée dans toutes les cellules（细胞）vivantes, qui renferm（comprend）l'ensemble des informations nécessaires au développement et au fonctionnement d'un organisme（机体）.Le microprocesseur : 微处理器Un microprocesseur est un processeur dont les composants ont étésuffisamment miniaturisés (小型化) pour être regroupés dans un unique circuit intégré. Fonctionnellement, le pro cesseur est la partie d’un ordinateur qui exécute les instructions et traite les données des programmes.Le Réseau informatique: 计算机网络Un réseau informatique est un ensemble d'équipements reliés entre eux pour échanger des informations.Ozone : 臭氧corps simple gazeux, à l’odeur forte,au pouvoir très oxydant（氧化性）,dont la molécule （分子）est formée de trois atomes （原子）d’oxygène.Le vaisseau spatial: 宇宙飞船Astronef de grandes dimensions destiné aux vols humains dans l’espace.3G（3G手机）：troisième génération de portableLa vitesse de la transmission est plus grande, et il peut offrir un meilleur service de données(数据业务).le clonage : 克隆La manipulation génétique （基因的）permettant d'obtenir, à partir d'un organisme original, un ou plusieurs organismes possédant le même patrimoine génétique que celui-ci。

收稿日期:2005203224基金项目:国家自然科学基金项目(50231040)作者简介:刘建同(19522),男,高级工程师,主要研究方向为液态金属粘度.E 2mail :liujiantong @　文章编号:167223961(2005)0620005204熔体的粘度,亚稳相,相变和相图Ⅰ.熔体的粘度理论和亚稳相刘建同1,王玉青1,2,王　丽1,边秀房1,裘南畹1(1.山东大学　材料科学与工程学院　材料液态结构及其遗传性教育部重点实验室,　山东　济南　250061;2.济南铁道职业技术学院,　山东　济南　250013)摘要:用E instein 2Debye 粘度的流团扩散理论和流团振动的量子理论给出了熔体粘度的微观公式,并用熔体的结构模型和流团的扩散模型分析了熔体粘度的微观本质是分子间相互作用.发现熔体中存在多个亚稳相相区,指出了表征熔体亚稳相特征的有宏观相参数η0,ε和微观相参数d f .关键词:熔体;粘度;亚稳相中图分类号:TG 037 文献标识码:AViscosity ,metastable phase ,phase transition and phase diagram of meltsⅠ.The theory on viscosity and metastable phase for meltsLI U Jian 2tong 1,　W ANG Y u 2qing1,2,　W ANGLi 1,　BI AN X iu 2fang 1,　QI U Nan 2wan1(1.The K ey Laboratory of Liquid Structure and Heredity of Materials of Ministry of Education ,School of Materials Science and Engineering ,　Shandong University ,　Jinan 250061,　China ;2.Jinan Railway P olytechnic Institute ,　Jinan 250013,　China )Abstract :Based on the viscosity theory on the fluid cluster diffusion proposed by Einstein 2Debye and quantum theory on the fluid cluster vibration ,the formula of viscosity is presented.The micro nature of viscosity for melts is proved to be the interaction between m olecules by the investigation of the structure m odel for m olten alloys and the diffusion m odel for fluid clusters.S ome metastable phase regions existing in the melts are found.The metastable phase in melts is distinguished by both macro 2phase parameters (η0,ε)and micro 2phase pa 2rameter (d f ).K ey w ords :melts ;viscosity ;metastable phase0　引言P oole ,G rarde ,Angell ,McMillian 等【1】指出:“液体粘度的性质和本质在凝聚态物理中是一个重要而难解的课题”.我们通过实验和理论研究表明“液态金属和合金熔体的粘度的性质和本质是一个重要而复杂的问题.”近20年来,在凝聚态物理中研究的热点之一是Liquid 2Liquid Phase Transition (LLPT ).围绕液体中相　第35卷　第6期V ol.35　N o.6 山　东　大　学　学　报　(工　学　版)JOURNA L OF SH ANDONG UNIVERSITY (E NGINEERING SCIE NCE )2005年12月　Dec.2005　特征,LLPT的特征和普遍性,用不同方法(实验或理论)不同手段(压力诱发或温度诱发)对各类材料开展了广泛的研究.人们从实验中发现了LLPT的迹象【2～4】,其中最感兴趣的是可用肉眼观察到两相共存的多成分材料Y2O32Al2O3和用X线观测到结构转变的单质材料磷光体(P).1994,Aasland& McMillan【3】对组分为24～32%Y2O3的Y2O32Al2O3,在液线下几百度以300～400℃Πs的速率将过冷熔体冷却为玻璃体,在玻璃体中用hot2stage显微镜观察到两相分离现象;并通过电子探针等方法确定这两个相的化学组成相同而有不同的密度.2000, K atayama等【4】在温度约1050℃,压强为1G pa左右下的纯物质磷光物P用X线分析给出了存在一个突变的、由压力驱动的、可逆的、在低压为分子液体与在高压为聚合物之间的结构转变;2001,M orish2 ita【5】通过分子动力学模拟给出了磷光物P转变的机制为P4∴n P4.人们又从理论研究中提出了LLPT的普遍性【6,7】;作为一个典型例子是T anaka(2000)【6】用一个简单的物理图象———“协作中程键序”研究并提出了LLPT的普遍性.在大量实验事实和理论模型前面,迫使人们提出有关液体中存在亚稳相和LLPT的一些概念:认为在有流动性的宏观均匀的液体中存在不同的局域有序结构,在普遍的分子间相互作用中存在紧密结合的有序团簇———流团,LLPT就在这些不同局域有序结构的态之间在压力或在温度诱发下产生的转变.在液体中的这类态被称之为P olym orphous或P olyam orphous【1,8】.然而这类态要被装扮成为一类Phase的Candidate还需要有明确的相参数和序参数.组成均一,宏观物理化学性质相同的物质的态被称为这种物质的相.相变,首先是宏观物理化学性质的转变,于是研究和表征相变要有一个(或一组)能明确地表征和反映相变敏感的好物理量.反映气———液相变的好物理量是密度,反映铁磁相变的好物理量是磁化率,但对不同类型和性质的相变应有不同的物理量.从我们实验和理论研究表明反映金属及其合金熔体中相变的一个好物理量是熔体的粘度η.它能明确地表征和反映熔体中亚稳相的存在和特征,它又能明确地表征和反映亚稳相之间转变的特征:是不连续结构相变,并有两类结构转变的形式:热缩(吸收蒸发热),热胀(放出凝结热).1　熔体粘度的理论和微观本质流体的粘度η是一种宏观的力学性能,它由牛顿定律τ=ηdυΠdχ定义并表明其宏观本质是阻止“流体内作相对运动的阻力”,所以又叫“内摩擦”.在理论研究中公认气体的粘度的微观本质是分子动量的输运,并有一个可以验证的理论公式η= 13ρ v λ.对于液体,一般认为粘度的微观本质是分子间的相互作用.对于熔体,还没有一个研究和反映其微观本质的公式和理论.1.1　粘度的宏观规律和亚稳相的存在我们曾用日本产T oky o Industries OS VM高温粘度仪(振荡杯法)在0.1MPa Ar压下测得数10种金属和合金熔体在不同温度T时的粘度η,实验装置和测试方法见文献【9】,图1所示为其中10种金属和合金的Arrhenius(lgη～1ΠT)图.6　山　东　大　学　学　报　(工　学　版)第35卷　图1　lgη-1ΠT图Fig.1　T emperature dependence of viscosity从图1可见,粘度η的Arrhenius图由一些间断的直线构成,于是对于每条直线的温区,粘度服从Arrhenius定律:η=ηexp(εΠkT)(1)其中的η,ε同一直线温区内为与温度无关的常数.由此可见,在这个温区内粘度的物理性质相同,是一个相区,于是从粘度分析中发现在金属和合金熔体中存在多个亚稳相相区.而(1)中的η,ε就是亚稳相的宏观相参数.1.2　熔体粘度的流团扩散理论和流团振动的量子理论对于高温熔体,可以用Einstein2Debye流团扩散理论【8】来研究粘度:η=a kTΠd f D(2a)其中D和df为流团的扩散系数和直径;a为参数,a=3πΠ2,ξ=4～6;k:Boltzmann常数.根据扩散系数的公式和扩散的布朗运动理论【10】D=vd2exp(-εΠkT)(2b)v:流团在势阱中振动的频率;ε:势阱高度或扩散激活能;d:流团一次迁移的平均距离.于是将(2b)代入(2a)则:η=akTd f vd2exp(εΠkT)=η0exp(εΠkT)η=kTd f vd2(2c)根据振动的量子理论:hv=bkT.对于原子或离子b=1,而对于流团(大量原子构成的团簇),b<1于是hv=bkT　(b<1)(2d)将(2d)代入(2c),并令d=df+δ,则η=ηexp(εΠkT)η=chπ6(df)3=chΠV f　(V f:流团体积)C=[(6baΠπ)(1+δΠd f)2](-1)(3)这样我们得到了一个结论:η与扩散流团尺寸d f有关,且有η0∝(d f)-3的关系.这说明了表征熔体中的亚稳相,不仅要用宏观参量η,ε,还要用微观参量d f一流团尺寸.1.3　熔体的显微结构模型和流团的扩散模型上世纪60年代,Adam和G ibbs【11】曾经指出:对于密堆的液体,以单原子热激活为基础的传统输运理论已经不适用.70年代末C ohen等用自由体积模7　第6期刘建同,等:熔体的粘度,亚稳相,相变和相图　型在讨论低温液体中输运(扩散)提出的扩散模型是“分子”不断跃迁填补真空体(Void)的同时并不断改变自由体积的分布.上世纪80年代中,为了探索在非晶固体中广泛存在的中程有序结构(MRO),人们开始了对液态金属结构的深入研究,并逐步提出和认定了液体的结构是:中程尺寸的真空体和液体原子的混合物.在X线和中子线对液体结构的分析中给出的对分布函数g(r)都有一个在r=r1处的高峰,它标志着液体中存在紧密结合的直径为2r1的团簇,因此它常被用来计算配位数Z.于是溶体中扩散流团应为直径df=2r1的团簇.由此给出了熔体的结构模型为“团簇+真空体+熔体介质”,同时流动团簇的扩散模型:“振动的团簇逸出势阱,在介质中扩散移动中不断消灭真空体的同时不断产生新的真空体”.1.4　熔体粘度的微观本质由于η=ηexp(εΠkT),于是可以从η0和ε来理介粘度微观本质是“分子间相互作用”其中ε是流团逸出势阱克服周围熔体介质中分子作用力所做的功,而η=η|ε=0=η0exp(εΠkT)|ε=0是流团在熔体介质中运动时受周围分子的阻力.2　结论a,熔体粘度的微观本质是分子间相互作用.b,熔体中存在多个亚稳相,表征这些亚稳相的参数既有宏观参量η,ε;又有微观参量d f.参考文献:[1]POO LE P H,G RANDE T,ANGE LL C A,et al.P olym orphicphase transition in liquids and glasses[J].Science,1997, 275(17):3222323.[2]Z U Fang2qiu,ZH U Zhen2gang,G AO Li2jun,et al.Observa2tion of an anomalous discontinuous liquid2structure change with temperature[J].Phys Rev Lett,2002,89:1210.[3]ASE LAND S,MC MI LLAN P F.Density drive phase separationin the system Al2O32Y2O3[J].Nature,1994,369(13):6332 636.[4]K AT AY AM A Y,MIZ AT AN L T,UTS UM L W,et al.A first2order liquid2liquid transition in phasphoras[J].Nature,2000, 403(13):1702173.[5]M ORISHIT A T.Liquid2liquid phase transition of phosphorusvia constant2presure first2prinples m olecular dynamics simula2 tions[J].Phys Rev Lett,2001,87:1210.[6]T ANAK A H.G eneral view of a liquid2liquid phase transition[J].Phys Rev,2000,62:696826976.[7]MIT AS A C,PAT ASHI NSKI A Z,SH UMI LO B I.The liquid2liquid phase transition[J].Phys Lett,1985,113:41244. [8]ANGE LL C A,NG CI KL,MCKE NNA GB,et al.Relaxationin glass forming liquids and am orphous s olids[J].J Appl Phys, 2000,88(6):311323157.[9]刘建同,刘广荣,孙民华.液态A L(862x)Cu(10+x)Ce4的高温粘度及结构变化[J].山东大学学报(工学报),2004,34(1):22224.LI U Jian2tong,LI U G uang2rong,S UN Min2hua.The viscosity of liquid and structure trans oformation of A L(862x)Cu(10+x)Ce4 for high temperature[J].Journal of Shandong University(Engi2 neering science),2004,34(1):22225.[10]KIT LET C.Intraduction to s oeid state physics[M].Beijing:Science Press,1976.1210.[11]ADAM G,GI BBS J H.On the temperature dependence of co2orperative relaxation properties in glass forming liquilds[J].J Chem Phys,1965,43(1):1392146.(编辑:孙广增)8　山　东　大　学　学　报　(工　学　版)第35卷　。

DOI:10.1007/s00339-006-3613-1Appl.Phys.A 84,335–339(2006)Materials Science &ProcessingApplied Physics Af.qin 1y.q.cai 1x.yao 1,2,u x.h.zeng 1q.l.rao 1g.li 1y.jiang 1y.r.li 3b.w.tao 3LPE growth of PZNT film usingsuperheating YBCO thin film as seed layer1Department of Physics,Shanghai Jiao Tong University,800Dongchuan Road,Shanghai 200240,P.R.China2State Key Laboratory for Metal Matrix Composites,Shanghai Jiao Tong University,1954Huashan Road,Shanghai 200030,P.R.China3Institute of Microelectronics and Solid State Electronics,University of Electronic Science and Technology of China,Chengdu 610054,P.R.ChinaReceived:30September 2005/Accepted version:22April 2006Published online:24May 2006•©Springer-Verlag 2006ABSTRACT A superheating YBa 2Cu 3O 7−δ(YBCO or Y123)thin film was applied as a seed layer to grow Pb [(Zn 1/3Nb 2/3)0.91Ti 0.09]O 3(PZNT)films by a liquid phase epitaxy (LPE)process.In the present work,the YBCO thin film underwent a growth temperature of 1050◦C,which was about 40◦C higher than its peritectic temperature.It is very inter-esting that the superheated YBCO seed film could be used to grow not only Nd 1+x Ba 2−x Cu 3O 7−δ(NBCO)films with simi-lar compositions but also PZNT films with completely different compositions.The XRD analysis confirmed that the PZNT film grown on the YBCO seeded MgO substrate had a good epi-taxial relationship of [100](001)PZNT //[100](001)YBCO //[100](001)MgO .Compared with the PZNT films directly grown on MgO substrates,the LPE PZNT film on YBCO /MgO presented a better surface morphology.It was found that the superheating YBCO seed film plays a crucial role for the LPE growth of PZNT in the process.Furthermore,the superheating mechanism was discussed in terms of thermodynamic theories as well.PACS 77.84.-s;;68.37.Hk;81.15.Lm;82.45.Mp1IntroductionSince the superheating phenomenon was first re-ported by Daeges in 1986,many scientists have gained new interest in this field of such an interesting phenomenon [1–4].Most of the superheating phenomena have been observed in the embedded and low-dimensional systems,such as nanopar-ticles,nanowires and thin films.It was found that when the nanoparticles are properly embedded in a high-T m metal,the melting point can be elevated to some degree above the equi-librium T m for bulk solids.For example,Ag particles can be superheated up to 25K above T 0for 1min without melting when they are coated by Cu [4].Other analogues such as In,Pd,Cd and Ti embedded in Al and Pd in Zn,Cu were observed to superheat in the same way [5–9].However,most of them are restricted to the metals or their alloys.In our previous work,we reported a novel superheat-ing phenomenon in the YBa 2Cu 3O 7−δ(YBCO or Y123)superconducting thin film,which is an oxide material and in-volves a peritectic melting.Firstly,from the successful YBCOu Fax:+86-21-54741040,E-mail:xyao@seeded Nd 1+x Ba 2−x Cu 3O 7−δ(NdBCO)thick film growth (YSNG),we found that YBCO film can endure a heating pro-cess up to the temperature 1055◦C ,which is 45◦C above its melting point (T p )[10].Later,by using a high tempera-ture optical microscope (HTOM)for in situ observation,we studied and clarified the superheating mechanism [11–13].Further,we utilized the superheating property of YBCO thin film for other seed-required RE 1+x Ba 2−x Cu 3O δ(REBCO,RE =rare earth element )processes,e.g.,the melt-textured growth of YBCO bulks [14].In that process,YBCO showed the intrinsic superheating property by withstanding a high temperature over its T p as well.Such a seed-film with a low-peritectic-temperature for the growth materials at a high processing temperature is very promising for its extensive application of YBCO seeded REBCO growth.For the YBCO film seeded REBCO growth,YBCO and REBCO not only have the same crystal structure,but also share similar elements or bondings.The question addressed in the present work is whether the superheating effect still works when most elements of YBCO film are different from those in LPE film materials.In order to prove this point,Pb [(Zn 1/3Nb 2/3)0.91Ti 0.09]O 3(PZNT),which is completely different from YBCO in chemical composition,is firstly taken into consideration due to its similar crystal structure,small misfit to the YBCO and its proper processing temperature (about 1050◦C ),which is in the range of YBCO superheating temperature.PZNT is a relaxor ferroelectric material with high di-electric constants,low dielectric loss,extremely large piezo-electric strain (>1%)and electromechanical coupling factor (k 33>90%).Such single crystals are expected to find appli-cations in piezoelectric devices,such as medical ultrasonic transducers,actuators,and sonars [15–20].Conventionally,PZNT crystals are grown by a flux method or modified Bridg-man technique [21,22].Recently,we obtained PZNT thick films on STO substrates by the liquid phase epitaxy (LPE)growth method.The PZNT films grown by LPE may be an al-ternative to the single crystals for the application as wafers.In this work,we expect to realize heteroepitaxial growth of a PZNT thick film by utilizing YBCO thin film as a seed layer.2Experimental procedureYBCO thin films were deposited on MgO sin-gle crystalline substrates by pulsed laser deposition (PLD)336Applied Physics A –Materials Science &Processingand subsequently used as seed crystals.X-ray diffraction (XRD)patterns show a highly c -axis oriented YBCO thin film with the relationship of [100](001)YBCO //[100](001)MgO .The preparation of PZNT precursor and the mixed powder has been reported by X.H.Zeng et al.[23].The LPE pro-cess consists of:(1)The powder in the crucible was heated up to 1150◦C in 2h and held for 2h ;(2)After achieving com-plete melting,the molten solution was cooled down to the temperature for the growth;(3)During the LPE growth,the temperature was maintained constant at 1050◦C for the melt surface;(4)The MgO substrate with the YBCO seed film was vertically dipped into the melt at a rate of 2mm /s ;(5)After immersing for 3s ,it was quickly pulled up while ro-tating to throw away the flux.The surface morphology of the dipped sample was observed by an OLYMPUS BX51M opti-cal microscopy (OM).Semi-quantitative microanalysis of the composition was determined by a PHILIPS515scanning elec-tron microscope (SEM)using an energy dispersive analysis of X-rays (EDAX)detecting unit.The orientation relation-ship between the LPE PZNT film and the MgO substrate was analyzed by X-ray diffraction (XRD).3Results and discussionsFigure 1is a typical optical micrograph showingthe PZNT film grown on the YBCO seeded MgO substrate with a high magnification SEM image inset on the upper right side.Some square-shaped PZNT crystals can be easily ob-served on the surface of the MgO substrate.Although there are some residual flux droplets,it is clear that the surface of the substrate was almost covered by PZNT grains.SEM image with a higher magnification of the surface morphology shows that the average PZNT grain size is about 6µm .These square-shaped grains have a good alignment on the MgO sub-strate,suggesting a good orientation relationship between the as-grown film and the substrate.In order to make a compar-ison,we prepared PZNT films directly on MgO crystal sub-strates.As shown in Fig.2,the squared-shaped PZNT grains are distributed randomly on the surface of the substrate,i.e.,FIGURE 1OM photograph showing surface morphology of the as-grownPZNT film on YBCO seeded (001)MgO substrates with a higher magnifica-tion SEM image on the upper rightsideFIGURE 2OM photograph showing surface morphology of the PNZT film grown directly on MgO substratethey show no epitaxial relationship with the substrate.No dis-tinct change happened when the temperature was varied from 1050◦C to 1080◦C .Clearly,by introducing YBCO thin film as the seed layer,the PZNT film has been successfully grown on the MgO substrate.This is the first report on the application of superheating YBCO thin film in the LPE growth of PZNT film,indicating that superheating effect still plays a role even in the case that most elements are different between YBCO seed and LPE materials.The potential benefits of the use of this film are very promising.On the one hand,it means more candidates can act as seeds for LPE or other seed-required processes.On the other hand,for device applications,by tak-ing advantage of the superheating property of YBCO thin film,the approach of hetero-seed LPE growth may be applied to the growth of other kind of oxide functional materials,lead-ing to a heterostructures,e.g.,ferroelectric /superconductor structure [24].Taking the lattice constant into consideration,MgO (a =4.216Å)and YBCO (a =3.834Å)[25]has almost the same lattice mismatch to the PZNT (a =4.047Å)[26].However,introducing a YBCO seed film may avoid the abrupt change in the thermal expansion coefficient [27,28].Therefore,the strains caused by the large thermal mismatch between the PZNT epilayer and MgO substrate were reduced efficiently.Moreover,the YBCO polycrystalline film with a thickness of 100nm may play a key role in minimizing the tensile strain in the MgO single crystal substrate.In brief,compared with the PZNT /MgO system,the lower interface energy of PZNT /YBCO makes it possible for the epitaxial growth of PZNT on MgO substrate.Table 1shows the composition of the as-grown PZNT film detected by pared with the nominal com-position of PZNT91/9,the semi-quantitative microanalysisElements Experimental composition (%)Nominal composition (%)Pb 55.0850.00Nb 28.3730.33Zn 11.5815.17Ti4.964.50TABLE 1Compositions of the as-grown PZNT filmQIN et al.LPE growth of PZNT film using superheating YBCO thin film as seed layer337FIGURE 3X-ray diffraction (Cu,K α)of the PZNT LPE filmidentifies the formation of the perovskite PZNT phase with an acceptable uncertainty.For further verification,the X-ray diffraction pattern of the LPE PZNT film (Cu,K α)was con-ducted,as shown in Fig.3.Although there are some unex-pected phases and PbO,three strong peaks correspond to the (100)PZNT,(200)MgO and (200)PZNT,respectively.It is evident that the LPE film has a regular epitaxial orientation with (001)PZNT //(001)MgO .It is worthy noting that thepeakFIGURE 4X-ray diffraction (Cu,K α)pole pat-terns (a)of the as-grown PZNT film;(b)MgOsubstrateFIGURE 5X-ray diffraction (Cu,K α)of theYBCO seed filmintensity of PZNT film is about threefold stronger than that of the MgO pared with the relatively weak peak intensity of PZNT directly grown on the STO substrate [23],it suggests that the whole surface of the MgO substrate is almost covered by the PZNT grains,i.e.,these grains coalesce into a continuous film.It can be concluded that the YBCO seed film has improved the crystallinity of the PZNT film.In order to study the orientation relationship between the as-grown PZNT film,and MgO substrates,the X-ray diffrac-tion pole figures (Cr,K α)was performed.Figure 4a and b show the pole figures of the as-grown PZNT film and MgO substrate,respectively.No distinctive difference has been found between a and b except for the little deviation along the [110],which deduces the conclusion that the PZNT film and the MgO substrate have a good epitaxial relationship of [100](001)PZNT //[100](001)MgO .The XRD pole figures of the {103}diffraction of the seed film before and after LPE growth are shown in Fig.5a and b,respectively.The pole figure in Fig.5a reveals an eightfold symmetry of seed film before LPE process,indicates coexistence of two kinds of in-plane orientation grains,whose [100]directions have an-gles of 0◦and 45◦with respect to the [100]direction of the MgO substrate.Whereas,the fourfold symmetry,as shown in Fig.6b,implies that only the 0◦oriented YBCO grains re-tained after the LPE growth.In analogy with the REBCO LPE growth on YBCO seeded MgO substrates,the partly melt-ing of YBCO seed film could be clarified by the coarsening model [29,30].338Applied Physics A –Materials Science &ProcessingFIGURE 6X-ray diffraction (Cu,K α)pole patterns of the YBCO seed film(a)before the LPE growth;(b)after the LPE growthFurthermore,the mechanism of superheating on YBCO seed film is concerned since the LPE process of PZNT film is considerably dependent on such a seed layer.In general,the origin of superheating is various,which is always related to the confinement at the interface between the superheating substance and the matrix material [31].In our case,the super-heating of YBCO seed film arose from both thermodynamic and kinetic factors.Firstly,the semi-coherent interface be-tween YBCO film and MgO substrate should be taken into account.As shown in Fig.6,the YBCO seed filmexhibitsFIGURE 7Optical pictures show-ing the evolution of the Ba-Cu-O molten droplets on the YBCO thin film when the temperature was hold at 1060◦C (a)0s;(b)after 6s;(c)after 9sa high c -axis orientation indicated by the XRD data.As is well-known,the deposition temperature of the substrate (T s )varies in a range when preparing different oriented YBCO films.The film with c -axis orientation is achieved at higher T s than one with a -axis orientation [32,33].It should be noted that during the processing of the film,the high substrate temperature corresponds to a high binding energy between YBCO film and substrate.Accordingly,the high c -axis ori-ented YBCO (c -phase)seed utilized in our LPE PZNT growth has a greatly stable film /substrate interface,which mainly contributes to the overheating behavior.Besides the interfa-cial factor,the c -phase preferential growth at the higher T s can be attributed to its lower surface energy than other oriented phase [34].The low surface energy enhances the stability of high c -axis oriented YBCO film which can also interpret its superheating behavior.Another kind of superheating model concerning the sup-pression of growth of the melting growth has been well es-tablished.In the work of L.Zhang et al.,the evident su-perheating was observed in a 2D Pb thin film confined by Al layers,which is by virtue of the suppression of molten droplets from epitaxial semi-coherent Pb /Al interfaces [35].Similarly,the suppression of melting growth occurred in the YBCO seed film.The straightforward evidence of this sup-pression of Ba-Cu-O melting growth was found in a series of microscopy graphs from YBCO melting observation,as shown in Fig.7.Two Ba-Cu-O molten droplets indicated by arrows exhibit an evolution within 9s at a temperature of 1060◦C .In Fig.7a,droplets were formed on the surface of the thin film due to the peritectic reaction of ter,instead of further melting along the melting direction,QIN et al.LPE growth of PZNTfilm using superheating YBCO thinfilm as seed layer339the Ba-Cu-O melts moved away from the melting interface of Y123immediately because molten liquid is not wettable to the MgO substrate,as illustrated in Fig.7b and c.Meanwhile,an extra driving force is required for melting because the molten liquid carries migrating from the solid and cannot promote the melting advance[13].All of above-mentioned evidences give rise to the elevation of the melting point of YBCO seed film.4ConclusionsBy taking advantage of the superheating phe-nomenon,wefirstly reported liquid epitaxy growth of the PZNTfilm on the(001)MgO substrate by using the YBCO seedfilm,which has a totally different composition from the growingfilm materials.According to the morphological in-vestigations and XRD analysis,a nearly continuous PZNT film with a good epitaxial relationship between the MgO substrate and the PZNTfilm was confirmed.The origin of su-perheating in YBCO seedfilm was ascribed to the influence of the interface and surface energy as well as the suppression of the Ba-Cu-O melting growth.ACKNOWLEDGEMENTS Authors are grateful forfinan-cial support from the Ministry of Education(grants No.20030248010 and K0293003),Shanghai Science and Technology Committee(grant No. 02DJ14041,055207077and055211003),and NSFC(grant No.50572065).REFERENCES1R.W.Cahn,Nature323,668(1986)2J.W.Herman,H.E.Elsayed-Ali,Phys.Rev.Lett.69,1228(1992)3H.W.Sheng,G.Ren,L.M.Peng,Z.Q.Hu,K.Lu,Philos.Mag.Lett.73, 179(1996)4J.Daeges,H.Gleiter,J.H.Perepezko,Phys.Lett.A119,79(1986)5P.Buffat,J.P.Borel,Phys.Rev.A13,2287(1976)6D.L.Zhang,B.Cantor,Acta Metall.Mater.39,1595(1991)7L.Grabak,J.Bohr,Phys.Rev.Lett.64,934(1990)8K.Chattopadhyay,R.Goswami,Prog.Mater.Sci.42,287(1997)9K.Lu,Y.Li,Phys.Rev.Lett.80,4474(1998)10J.Hu,X.Yao,Q.L.Rao,J.Phys.:Condens.Matter15,7149(2003)11X.Yao,K.Nomura,Y.Nakamura,T.Izumi,Y.Shiohara,J.Cryst.Growth234,611(2002)12X.Yao,K.Nomura,D.X.Huang,T.Izumi,N.Hobara,Y.Nakamura, Y.Shiohara,Physica C378–381,1209(2002)13X.Yao,J.Hu,T.Izumi,Y.Shiohara,J.Phys.:Condens.Matter16,3819 (2004)14C.Y.Tang,X.Yao,J.Hu,Q.L.Rao,Y.R.Li,B.W.Tao,Supercond.Sci.Technol.18,31(2005)15S.E.Park,T.R.Shrout,J.Mater.Res.Innovat.1,20(1997)16B.J.Kim,S.M.Cho,T.Y.Kim,H.M.Jang,Phys.Rev.Lett.86,3404 (2001)17K.Harada,S.Shimanuki,T.Kobayashi,S.Saitoh,Y.Yamashita,J.Am.Ceram.Soc.81,2785(1998)18J.Y.Xu,J.Tong,M.L.Shi,A.H.Wu,S.J.Fan,J.Cryst.Growth253,274 (2003)19H.S.Luo,G.S.Xu,Z.W.Yin,Jpn.J.Appl.Phys.39,5581(2000)20W.Chen,Z.G.Ye,J.Cryst.Growth233,503(2001)21M.Dong,Z.G.Ye,J.Cryst.Growth209,81(2000)22B.J.Fang,H.Q.Xu,Y.J.Wu,H.S.Luo,Z.W.Yin,Mater.Lett.52,423 (2002)23X.H.Zeng,X.Yao,Q.L.Rao,Y.L.Zhang,J.Hu,J.Y.Xu,J.Cryst.Growth26,251(2004)24L.Li,Mater.Sci.Eng.29,153(2000)25Y.Nishimura,Y.Yasuhara,S.Miyashita,H.Komatsu,J.Cryst.Growth 158,255(1996)26L.Zhang,M.Dong,Z.G.Ye,Mater.Sci.Eng.B78,96(2000)27R.Roy,D.K.Agrawal,H.A.McKinstry,Ann.Rev.Mater.Sci.19,59 (1989)28M.Zeisberger,tka,W.Ecke,T.Habisreuther, D.Litzkendorf, W.Gawalek,Supercond.Sci.Technol.18,S202(2005)29T.Izumi,K.Kakimoto,K.Nomura,Y.Shiohara,J.Cryst.Growth219, 228(2000)30K.Nomura,S.Hoshi,X.Yao,K.Kakimoto,Y.Nakamura,T.Izumi, Y.Shiohara,J.Mater.Res.16,979(2001)31K.Lu,Z.H.Jin,Curr.Opin.Solid State Mater.Sci.5,39(2001)32A.Inam,C.T.Rogers,R.Ramesh,K.Remschnig,L.Farrow,D.Hart, T.Venkatesan,B.Wilkins,Appl.Phys.Lett.57,2484(1990)33E.Sodtke,H.Munder,Appl.Phys.Lett.60,1360(1992)34T.Endo,K.-I.Itoh,M.Horie,K.Itoh,N.Hirate,S.Yamada,M.Tada, S.Sano,Physica C333,181(2000)35L.Zhang,Z.H.Jin,L.H.Zhang,M.-L.Sui,K.Lu,Phys.Rev.Lett.85, 1484(2000)。

化学反应中的相变实验Phase Change Experiments in Chemical ReactionsAs a chemist, I am always fascinated by the intricate dance of atoms and molecules during chemical reactions. Among these delicate choreographies, phase change experiments offer an especially captivating display, transforming substances from one state to another with breathtaking transformations.Phase changes are the amazing transitions matter undergoes as it shifts between solid, liquid, gas, or plasma states. In chemistry labs, we create controlled environments to observe these transitions up close, gaining insights into their fundamental mechanisms.Consider the simple yet profound experiment of melting ice cubes. As the frigid blocks of water crystal warm under the gentle heat of a Bunsen burner, they gradually lose their rigid form, softening and liquefying into pools of clear liquid. This melting process, while seemingly ordinary, is actually a complex interaction between thermal energy and intermolecular forces. It's a reminder that even the most commonplace occurrences hide wonders waiting to be discovered.Then there are evaporation experiments where liquids slowly vanish into thin air. Watching droplets gracefully ascend into vaporous clouds is akin to witnessing nature's ballet, each molecule dancing its way out of the liquidphase into freedom. These experiments not only teach us about latent heat but also remind us of how fluids can escape our grasp, leaving behind nothing but memory. The beauty of phase change experiments lies in their ability to visualize abstract concepts like enthalpy and entropy, bringing them down to earth for all to see. They demonstrate how temperature and pressure —two seemingly mundane variables — can have profound effects on matter's behavior. Moreover, these experiments kindle curiosity, pushing us to delve deeper into the mysteries of matter itself.In conclusion, phase change experiments are more than just scientific demonstrations; they are poetic explorations of nature's secrets. They invite us to marvel at the transformative power inherent in every chemical reaction, revealing the inner workings of the universe through vivid displays of matter's dynamic dances.。