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adjoint concentration 半导体物理-回复Adjoint Concentration in Semiconductor Physics: An In-depth AnalysisIntroduction:In the field of semiconductor physics, adjoint concentration is a critical parameter that plays a significant role in understanding the electrical and optical properties of semiconductor materials. This article aims to provide a comprehensive overview of adjoint concentration, its significance, measurement techniques, and its impact on device performance. By exploring the concept step-by-step, we can develop a deeper understanding of this fundamental aspect of semiconductor physics.What is Adjoint Concentration?Adjoint concentration refers to the concentration of impurity atoms or dopant atoms in a semiconductor material. In semiconductors, impurity atoms are intentionally introduced tomodify their electrical behavior. These impurities or dopants can be either elements from Group III or Group V of the periodic table—known as p-type and n-type dopants, respectively. The concentration of these dopants directly influences the electrical conductivity and the performance of semiconductor devices.Significance of Adjoint Concentration:The adjoint concentration plays a crucial role in determining the electrical behavior of semiconductors. It fundamentally affects the concentration of charge carriers, such as electrons or holes, and their mobility within the material. By controlling the adjoint concentration, we can tailor the electrical properties of the semiconductor to suit specific applications. For instance, in designing transistors, the adjoint concentration is finely tuned to achieve the desired voltage amplification and switching characteristics.Measurement Techniques:Measuring the adjoint concentration in a semiconductor material involves several techniques, such as Hall effect measurements, secondary ion mass spectrometry (SIMS), and capacitance-voltage (C-V) measurements.Hall effect measurements involve applying a magnetic field perpendicular to the current flow across a semiconductor sample. By measuring the resulting Hall voltage, the charge carrier concentration and mobility can be determined.SIMS is a technique that uses ion bombardment to sputter a semiconductor sample's surface. This creates a stream of secondary ions that are analyzed in a mass spectrometer, providing information about the dopant concentration as a function of depth.C-V measurements utilize the variation in capacitance with voltage applied across a metal-semiconductor junction. By analyzing the change in capacitance, one can infer the dopant concentration in the semiconductor material.Impact on Device Performance:Adjoint concentration directly impacts the performance of various semiconductor devices. For example, in a bipolar junction transistor (BJT), the emitter, base, and collector regions have different adjoint concentrations to achieve proper device operation. The adjoint concentration gradient ensures efficient charge carrier injection, transport, and collection within the transistor, resulting in reliable amplification of electrical signals.Similarly, in a metal-oxide-semiconductor field-effect transistor (MOSFET), the adjoint concentration at the interface between the channel and the gate oxide significantly affects the transistor's threshold voltage and subthreshold slope. By adjusting the dopant concentration, the transistor's performance in terms of speed, power consumption, and leakage current can be optimized for specific applications.Conclusion:In conclusion, adjoint concentration is a crucial parameter in semiconductor physics that influences the electrical behavior and performance of semiconductor materials. Its precise control through various measurement techniques such as Hall effect measurements, SIMS, and C-V measurements allows for customized electrical properties in semiconductors, enabling the design and manufacture of high-performance devices. Understanding and characterizing adjoint concentration is essential in advancing semiconductor technology and meeting the demands of modern electronic devices.。
应用与环境生物学报 1999,5(6):638~639C hin.J.A ppl.Environ.Biol.1999 12 25简报收稿日期:1998 11 09 修回日期:1999 02 03 接受日期:1998 05 17不同条件下水杨酸对蚕豆气孔开度的影响刘 新 张蜀秋 孟繁霞(中国农业大学生物学院 北京 100094)关键词 水杨酸;气孔运动;蚕豆中图法分类号 Q945.1 S643.6EFFECT OF SALICYLIC ACID ON STO MATAL APERTURE OF VICICA FABA L.UNDER DIFFERENT CONDITIONSLI U Xin ,ZHANG Shuqiu &MENG Fanxia(Colle ge o f Biological Sc ie nce s ,China Agricultural Universit y ,Beijing 100094)Abstract The effect of salicylic acid (SA)on stomatal aperture of 3~4weeks Viciaf aba L.under different conditions was investigated.It was shown that stomatal closure responded to S A after 3hours treatment.The concentration and pH of SA solution at different media affeeted SA to different exten ts.The degree of effects was concentration-dependent.With increasing SA concentration,the p romotion effect on stomatal closure was en hanced.At 10-3mol L -1SA exerted the most effect.The effect of SA was dependent on the p H of the solution.In the range of 10-6~10-3mol L -1as pH decreased,the effect of S A on stomatal closure was enhanced.SA 10-4mol L -1in distilled water at p H 4the percentage of inhibiti on on the stomatal aperture was 67%,while at pH 7the percentage of inhibiti on was only 20%.The degrees of SA effect on stomatal aperture in distilled wa ter 、MES buffer solution and citric acid buffer solution were differen t.In MES buffer the effect of SA was lower than that in distilled water,or in citric acid buffer.Keywords salicylic acid;stomatal aperture;Vic ia faba L.水杨酸(SA)被认为是一种在植物体内广泛存在的新的植物生长调节物质[1],能够调节植物体内的许多生理过程,如产热、开花、性别分化、离子吸收、乙烯的合成、气孔开闭等等,并与植物的抗病性密切相关,可能作为植物的防御信号[2].有报道,蚕豆表皮条细胞对SA 高度敏感,10-6mol L -1SA 就可使气孔关闭[3],S A 能降低菜豆和鸭趾草的蒸腾[4],但也有SA 逆转ABA 诱导的气孔关闭的报道[5].因此,有必要对SA 和气孔运动的关系进行研究,以探索SA 是否作为一种信号,参与对气孔运动的调节,进而影响其他生理活动.1 材料与方法1.1 材料蚕豆(Vicia faba L.)种子HgCl 2灭菌后,浸种12h,25 催芽24h,播种于生长室营养土中.培养条件为12h/d 光照、光强200 mol m -2S -1、昼夜温差24 /18 、相对湿度50%.培养3~4周后供试验用.1.2 方法1.2.1 SA 处理方法 c (SA)分设10-3、10-4、10-5、10-6mol L -14个水平.S A 的介质:蒸馏水(p H 4,5,6,7)、MES 缓冲液(c (MES/KOH)=10mmol L -1,c (KCl)=50mmol L -1,c (CaCl 2)=100 mol L -1,pH 6.1)、柠檬酸缓冲液(p H 4,5,6,7).1.2.2 气孔开度测定 取3~4周令蚕豆幼苗刚完全展开的第4叶片,放入盛有蒸馏水的培养皿中,光诱导2h 使气孔完全张开.小心撕取其下表皮,并用毛笔刷除去上面粘附的叶肉细胞.用显微测微尺测量气孔的初始孔径,测量时随机选取5个视野,每个视野内随机选取10个气孔.然后,用不同浓度、不同p H 、不同介质的S A 处理表皮3h.记录终态孔径.每个处理重复5次以上.2 结果与分析2.1 不同介质和不同SA 浓度对蚕豆气孔开度的影响表1表明,在p H 为6的不同介质中SA 对气孔开度的影响是不同的.S A 在蒸馏水和柠檬酸缓冲液中对气孔的作用相似,当SA 在蒸馏水溶液的浓度为10-6、10-5、10-4、10-3mol L -1时,它对表皮条上气孔孔径的抑制百分率分别为12%、28%、38%、52%,在同样浓度下S A 在柠檬酸缓冲液中对表皮上气孔孔径的抑制百分率分别为19%、28%、36%、42%.而在同样浓度下SA 在MES 缓冲液中对蚕豆气孔的抑制率为19%、24%、30%、37%,这种差异可能与缓冲液的成分有关.表1 不同介质中SA 对气孔开度的影响(d / m)Table 1 Effects of different media and concentrations of SA on s tomatal aperture处理(pH 6)TreatmentCK初始态Ini tial s tate 终止态Terminal s tate c (SA)/mol L -110-610-310-410-3蒸馏水Di stilled water 7.25 0.407.25 0.40 6.35 0.20 5.25 0.55 4.50 0.60 3.50 0.53M ES 缓冲液MES buffer 7.68 0.537.25 0.55 6.25 0.35 5.83 0.33 5.33 0.53 4.83 0.63柠檬酸缓冲液Citric acid buffer8.08 0.437.91 0.306.54 0.235.80 0.305.20 0.134.65 0.132.2 不同pH 条件下SA 对气孔开度的影响表2显示,当气孔的初始孔径已达到最大时,不同p H 梯度(p H 4,5,6,7)的蒸馏水溶液和柠檬酸缓冲溶液对气孔开度几乎没有影响,但SA 在不同p H 梯度(p H 4,5,6,7)的蒸馏水溶液和柠檬酸缓冲溶液中对气孔开度的作用存在显著差异.SA 在酸性环境中(p H 4)能明显促进气孔关闭,甚至会使气孔完全关闭,并且在酸性介质中10-4mol L -1与10-3mol L -1的作用效果相当.这表明SA 介质的p H 大小与S A 的生理作用密切相关.表2 不同p H 条件下SA 对气孔开度的作用(d / m)T able 2 Effect of medium p H of SA on stomatal aperture处理Treatment4567CK蒸馏水Dis tilled water 7.33 0.757.00 0.207.00 0.407.83 0.23柠檬酸缓冲液Ci tric aci d buffer8.75 0.328.83 0.319.08 0.139.08 0.13SA/柠檬酸SA/Citric10-3mol L -1 1.25 0.73 4.00 0.83 5.08 0.73 6.50 0.70acid buffer10-4mol L-11.50 0.934.00 1.435.83 1.156.83 0.65参考文献1 Raski n I.Role of salicylic acid i n plants.Annu Re v Plant Physiol .1992,43:439~4632 原永兵.水杨酸在植物体内的作用.植物学通报.1994,11:1~93 Mathe B,Schulz M,Schnabl H.Effects of s alicylic acid on growth and s tomatal move ments of Vicia faba L:evidece for s alicylic acidmetaboli zati on.J Che m Ecol .1992,18:1525~15394 Larque Saavedra A.Stomatal clos ure in response to ac tysalicylic acid treatment.Z P flanzenphysiol .1979,93:371~3755 Rai V K,Sharma SS,Sharaa S.Revers al of ABA i nduced stomatal clos ure by phenolic co mpounds.J Exp Bot .1986,37:129~1346396期刘 新等:不同条件下水杨酸对蚕豆气孔开度的影响。
机械工程英语试题及答案一、单项选择题（每题2分，共20分）1. The term "mechanical engineering" refers to the field of study that involves the application of principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems.A. TrueB. False答案：A2. Which of the following is not a sub-discipline of mechanical engineering?A. RoboticsB. ThermodynamicsC. Civil EngineeringD. Materials Science答案：C3. The process of converting a design into a physical object is known as:A. PrototypingB. DesignC. AnalysisD. Manufacturing答案：D4. In mechanical engineering, what does the acronym "CAD" stand for?A. Computer Aided DesignB. Computer Aided DraftingC. Computer Aided DevelopmentD. Computer Aided Drawing答案：A5. What is the primary function of a bearing in a mechanical system?A. To reduce frictionB. To increase frictionC. To absorb shockD. To generate heat答案：A6. The study of heat transfer, thermal energy storage, and the effects of temperature on materials is known as:A. ThermodynamicsB. Fluid MechanicsC. Heat TransferD. Materials Science答案：C7. What is the SI unit for power?A. WattB. JouleC. NewtonD. Pascal答案：A8. A gear system that uses two or more gears to transmit motion and force is called:A. GearboxB. Pulley systemC. Cam mechanismD. Lever system答案：A9. In mechanical engineering, what does the term "stress" refer to?A. Force per unit areaB. Strain per unit forceC. Force per unit volumeD. Strain per unit volume答案：A10. Which of the following is a type of energy storage device used in mechanical systems?A. SpringB. BatteryC. CapacitorD. Inductor答案：A二、填空题（每题2分，共20分）1. The ________ of a material is its ability to resist deformation under applied force.答案：stiffness2. The ________ of a material is its ability to resist breaking under stress.答案：strength3. In a four-stroke internal combustion engine, the ________ stroke is where the fuel-air mixture is compressed.答案：compression4. A ________ is a mechanical device that converts rotational motion into linear motion.答案：screw5. The ________ of a system is the total energy required to produce the system.答案：embodied energy6. A ________ is a type of simple machine consisting of a wheel and a rope wrapped around it.答案：pulley7. The ________ of a system is the energy required to operate the system over its lifetime.答案：operational energy8. A ________ is a type of energy storage device that uses the elastic properties of materials to store energy.答案：spring9. The ________ of a material is its ability to resist deformation under stress.答案：ductility10. A ________ is a type of energy storage device that uses the potential energy of a raised mass to store energy.答案：gravity storage system三、简答题（每题10分，共40分）1. Explain the difference between static and dynamic equilibrium in mechanical systems.答案：Static equilibrium refers to a state where all forces and moments acting on a system are balanced, resulting in no acceleration. Dynamic equilibrium occurs when the net force and net moment on a system are zero, allowing the system to move with constant velocity.2. Describe the function of a flywheel in a mechanical system. 答案：A flywheel is a rotating mechanical device that stores rotational kinetic energy. It smooths out fluctuations in the power delivery of an engine or motor, providing a moreconstant output.3. What is the purpose of a heat exchanger in a mechanical system?答案：A heat exchanger is a device used to transfer heat between two or more fluids without mixing them. Its purposeis to either cool a hot fluid or heat a cold fluid, improving the efficiency of the system.4. Explain the concept of a control system in mechanical engineering.答案：A control system in mechanical engineering is a system that regulates the behavior of other systems or processes. It uses feedback to compare the actual output with the desired output and makes adjustments to minimize the difference, ensuring the system operates as intended.。
张晓冰，张羽师，王雨，等. 欧李果渣原花青素提取工艺优化及其体外抗氧化和降糖活性评价[J]. 食品工业科技，2024，45（1）：178−184. doi: 10.13386/j.issn1002-0306.2023030017ZHANG Xiaobing, ZHANG Yushi, WANG Yu, et al. Optimization of Proanthocyanidin Extraction from Cerasus humilis Pomace and Evaluation of Its in Vitro Antioxidant and Hypoglycemic Activity[J]. Science and Technology of Food Industry, 2024, 45(1): 178−184.(in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2023030017· 工艺技术 ·欧李果渣原花青素提取工艺优化及其体外抗氧化和降糖活性评价张晓冰，张羽师，王 雨，赵锦江，王笑雪，刘舒鹏，李卫东*（北京中医药大学中药学院，北京 102488）摘 要：本研究以欧李果渣为原料，采用单因素结合正交试验对超声波辅助提取欧李果渣原花青素工艺进行优化，采用DPPH 自由基清除实验、ABTS +自由基清除实验、FRAP 法测定铁离子还原能力实验对纯化后的欧李果渣原花青素抗氧化活性进行评价，并采用α-葡萄糖苷酶活性抑制试验对其降糖活性进行评价。
结果表明，各因素对欧李果渣中原花青素提取得率的影响程度排序为：超声温度>料液比>超声时间>乙醇浓度；最佳提取工艺为乙醇浓度70%，超声温度60 ℃，超声时间40 min ，料液比1:30 g/mL ，在此条件下欧李果渣中原花青素得率为15.37 mg/g 。
The effects of temperature on enzymeactivityIntroductionEnzymes are protein molecules that catalyze different chemical reactions in living organisms. They control the chemistry of life by speeding up metabolic processes in cells. Enzymes are highly sensitive to changes in temperature, and even a small change in temperature can affect their activity. In this article, we will explore the effects of temperature on enzyme activity.Temperature and Enzyme ActivityEnzymes work best within a specific range of temperature. This range is called the optimum temperature range. The optimum temperature range differs according to the type of enzyme and the organism in which it functions. The optimum temperature for human enzymes is 37 degrees Celsius, which is the normal body temperature.When enzymes are exposed to temperatures outside their optimum range, their activity decreases. If the temperature is too high, the enzyme molecule can be denatured, which means that its three-dimensional shape is altered. This can lead to a loss of enzyme activity. When the temperature is too cold, the enzymes can freeze, which can also cause a loss of activity.Effect of High Temperature on Enzyme ActivityAt high temperatures, enzymes become denatured, and their activity is greatly reduced. This happens because the high temperature disrupts the weak bonds that hold the enzyme in its three-dimensional shape. Once these bonds are disrupted, the protein loses its shape, and the active site that binds to the substrate also changes. The enzyme molecule becomes permanently altered, and it cannot function again.This can be demonstrated by doing an experiment with hydrogen peroxide and catalase, an enzyme found in living organisms that breaks down hydrogen peroxide. In the experiment, we can measure the time it takes for the enzyme catalase to break down hydrogen peroxide at different temperatures. If we raise the temperature above the optimum temperature, the reaction rate will decrease because the enzyme will lose its structure and function less effectively.Effect of Low Temperature on Enzyme ActivityAt low temperatures, enzymes become less active. This is because the low temperature decreases the rate of diffusion and slows down the collision rate between the substrate and the enzyme. The enzyme activity will increase as the temperature is raised, but only up to the optimum range.This can be demonstrated by doing an experiment with amylase, an enzyme that breaks down starch into simpler sugars. In the experiment, we can measure the time it takes for the amylase to break down starch at different temperatures. If we lower the temperature below the optimum temperature, the reaction rate will decrease because the enzyme will not have enough kinetic energy to bind with the substrate effectively.ConclusionEnzymes are essential to life, and they play a vital role in metabolic processes in living organisms. Temperature greatly affects enzyme activity, and enzymes work best within an optimum temperature range. When enzymes are exposed to temperatures above or below their optimum range, their activity decreases. Understanding the effects of temperature on enzyme activity can help us better understand how enzymes work in living organisms and how they can be used in industry and medicine.。
Technical reportEffect of Si content on the dry sliding wear propertiesof spray-deposited Al–Si alloyFeng Wanga,*,Huimin Liu b ,Yajun Ma a ,Yuansheng JinaaState Key Laboratory of Tribology,Tsinghua University,Beijing 100084,ChinabState Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,ChinaReceived 31March 2003;accepted 11August 2003AbstractIn the present investigation,Al–12Si,Al–20Si and Al–25Si (wt%)alloys were synthesized by spray atomization and deposition technique.The wear resistance of the alloys was studied using a pin-on-disc machine under four loads,namely 8.9,17.8,26.7and 35.6N.The microstructures,worn surfaces and the debris were analyzed in a scanning electron microscope.It has been found that the effect of Si content on dry sliding wear of spray-deposited Al–Si alloy was associated with applied loads.At lower load (8.9N),with increasing Si content,the wear rate of the alloy was decreased.At higher load (35.6N),spray-deposited Al–20Si alloy exhibited superior wear resistance to the Al–12Si and Al–25Si alloys.Ó2003Elsevier Ltd.All rights reserved.Keywords:Dry sliding wear;Spray deposition;Al–Si alloy1.IntroductionAl–Si base alloys have been investigated for auto-motive applications because of attractive combinations of low coefficient of thermal expansion,high elastic modulus,excellent wear resistance and good thermal stability [1,2].However,the conventional ingot metal-lurgy leads to coarse primary Si phase which limits the further improvement of the properties of hypereutectic Al–Si alloy.One approach that has been utilized to suppress the formation of the coarse,brittle,primary Si phase and eutectic phases is rapid solidification [3].Spray deposition process has an obvious modification in size,morphology and distribution of the primary Si phase in matrix as well as reduce of segregation.In this process,droplets are first atomized from a molten metal stream,quickly cooled by an inert gas,then deposited on a substrate,and finally built up to form a deposit with a required shape [4].The spray-deposited Al–Si alloys have been considered as potential application inthe tribological field,and are becoming a favorite ma-terial as rotor brake,bearing sleeve,cylinder liner and compressor scroll.Wear properties of these alloys have been studied mainly under dry sliding conditions against a steel counterface.The present work is aimed at un-derstanding the effect of Si content on dry sliding wear property of spray-deposited Al–Si alloy.With observa-tion and analyses of worn surfaces and wear debris,the wear mechanism of the alloys has been discussed.2.Experimental proceduresThe spray deposition experiments were conducted in an environmental chamber (manufactured by Osprey company,Swansea,UK).During spray-deposited pro-cess,the melting metal was atomized by N 2and the atomizing temperature is 1073K,the distance of at-omizing deposition was kept constant at 400mm.Wear test was carried out using a FALEX-6type pin-on-disc machine (Falex corporation,Sugar Grove,Illi-nois,USA).The wear specimens were machined in the form of cylinders with 4.8mm diameter and 12.7mm length.The counterpart discs were made of aquenchedMaterials and Design 25(2004)163–166/locate/matdesMaterials &Design*Corresponding author.Tel.:+86-10-62783968;fax:+86-10-6278-1379.E-mail address:wfbs@ (F.Wang).0261-3069/$-see front matter Ó2003Elsevier Ltd.All rights reserved.doi:10.1016/j.matdes.2003.08.005and tempered T8tool steel with a nominal chemical composition (mass percent):Fe–0.8%C–0.35%Mn–0.3%Si,surface hardness of 64HRC and surface rough-ness of Ra ¼1l m.The applied load was varied from 8.9to 35.6N (8.9,17.8,26.7and 35.6N).Sliding speed and distance were kept constant at 0.48m/s and 1.7km.The weight loss during wear test was measured using a photoelectric balance with the resolution of Æ0.1mg.Three pins were used during each test.The specimens were thoroughly cleaned with acetone in ultrasonic cleaner before and after the wear test.Wear rate was calculated by dividing weight loss by sliding distance.Microstructure,worn surface and debris were charac-terized using a CSM-950type scanning electron micro-scope (SEM)(Opton corporation,Germany)attached with energy dispersive X-ray analyses (EDX).The mi-crostructures of the alloys were revealed by etching with Keller Õs reagent.3.Results3.1.MicrostructureFig.1show the typical SEM microstructures of the spray-deposited Al–Si alloys,which is composed of the Al matrix and the Si phase with a particle shape.The presence of eutectic Al–Si alloy phase and coarse,block primary Si phase in the conventionally processed ingot metallurgy counterpart was suppressed.The presence of particulate-like Si dispersoids was attributed to the high cooling rate,associated with the rapid solidification processes [5].Meanwhile,it can be seen that the volumefraction of primary Si phase was increased with in-creasing of Si content.3.2.Wear3.2.1.Wear testFig.2shows the wear test results,which represent the wear rate as a function of the applied load.Obvi-ously,the wear rate of the alloys increases with in-creasing load.It may also be noted that the tendency of the wear rate variation with the applied load is not consistent for three materials.At low load of 8.9N,the wear resistance of spray-deposited Al–25Si alloy was superior to the Al–12Si and Al–20Si alloys.With an increase in load of up to approximately 18N,the wear rates of the three materials are comparable.Beyond 20Nomenclature Ra Surface roughnessSEM Scanning electron microscope EDXEnergy dispersive X-ray analyseswt%Weight percentT8tool steelFe–0.8%C–0.35%Mn–0.3%SiFig.1.Microstructures of spray-deposited Al–Si alloys:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.Fig.2.Variations in the wear rates of spray-deposited Al–Si alloys with load.164 F.Wang et al./Materials and Design 25(2004)163–166N,the spray-deposited Al–20Si alloy exhibited best wear resistance.3.2.2.Worn surfaces and wear debrisIn order to investigate the wear mechanism,the surfaces of the worn samples were examined under SEM.Figs.3and4show typical worn surfaces of the three materials at the applied load of8.9,35.6N,re-spectively.At low load of8.9N,large dimples are easily found on the worn surface of spray-deposited Al–12Si alloy,it indicates that hard primary Si phases have stronger abrasive wear to the soft Al matrix during wear test.Some small dimples are also seen in the surfaces of spray-deposited Al–20Si,Al–25Si alloys. At high load of35.6N,the worn surfaces of the alloys have a rather smooth appearance as a result of ho-mogeneous wear,it indicates that wear process mainly took place by plastic deformation,as can be seen in Fig.4.Fig.5shows SEM micrographs of the wear debris generated at load of35.6N.For spray-deposited Al–12Si alloy,the wear debris is in form of irregular shaped platelets.The wear debris of spray-deposited Al–20Si, Al–25Si alloys is composed offine powders and irregu-lar shaped platelets orflakes.4.DiscussionOne of the important parameters which greatly affects the wear property of the Al–Si alloys is the primary Si phases in the matrix[6].However,the primary Si phases play an important role in the wear process.At low load of8.9N,the good wear resistance of spray-deposited Al–25Si alloy can be attributed to the presence of high volume fraction of the primary Si phases that act as load-supporting elements.In order to remain as effective load-bearing elements,the particle-like Si phases should maintain their structural integrity during wear.In this case,the local stresses generated beneath the slider are lower than the fracture strength of the Si particles,the primary Si particles without fracture on the worn sur-face can scratch the counterpart surface and act as load-supporting elements.The initial surface topographies of spray-deposited Al–Si alloys are suitable to facilitate the transfer of the applied load onto the primary Si parti-cles.The primary Si particles stand proud of the pol-ished contact surfaces,this is considered to be useful to prevent the softer Al matrix becoming directly involved in the wear process.During this process,the wear pro-ceeds mainly by the formation of oxidation layer in the worn surface and its spalling[7].EDX was used tocheck Fig.3.SEM morphologies of worn surfaces of spray-deposited alloys at the load of8.9N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.Fig.4.SEM morphologies of worn surfaces of spray-deposited alloys at the load of35.6N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.F.Wang et al./Materials and Design25(2004)163–166165the composition of worn surfaces of the pins,it showed that worn surfaces contain a certain amount of Fe and O,which indicates a typical oxidative wear [8].With in-creasing load,the primary Si particles fracture above a certain load,and the fragmented Si particles lose their ability to support the load.In this case,the Al matrix be-comes in direct contact with the counterfaces.At high load of 35.6N,concurrent with the primary Si particle fracture,large strain were generated within the Al matrix adjacent to contact surfaces.This led to the subsurface crack growth and delamination.The broken,hard Si particles entrapped between the counterface and the alloys may act as third-body abraders and be responsible for the pro-duction longitudinal grooves on the worn surfaces,as can be seen in Fig.4.The fractured primary Si particles pro-mote the worn surface damage and act as third-body abrasives,thus,the spray-deposited Al–20Si alloy pro-vided better wear resistance than Al–25Si alloy.The SEM photographs indicate that the wear debris contain a lot of shiny metallic flakes,together with some small powder.This is an indication of delamination [9].It is also possible that the hard dispersoid particles or fractured pieces thereof are mechanically dislodged during wear.The de-lamination and third-body abrasion are identified as the two major mechanisms at high load of 35.6N.5.ConclusionIn a range of applied load of 8.9–35.6N,the dry sliding wear behaviors of spray-deposited Al–Si alloys have been studied.The effect of Si content on the dry sliding wear of spray-deposited Al–Si alloy was associ-ated with applied loads.(1)At low load (8.9N),the wear rate of spray-de-posited Al–Si alloy was decreased with increasing Si content,the dominant wear mechanism was oxidative mechanism.(2)At high load (35.6N),spray-deposited Al–20Si alloy displayed superior wear resistance to the Al–12Si and Al–25Si alloys,the dominant wear mechanism was delamination and third-body abrasion.References[1]Anand S,Srivatsan TS,Wu Y,Lavernia EJ.Processing,microstructure and fracture behaviour of a spray atomized and deposited aluminum–silicon alloy.J Mater Sci 1997;32:2835–48.[2]Zhou J,Duszczyk J,Korevaar BM.As-spray-deposited structure of an Al–20Si–5Fe Osprey perform and its development during subsequent processing.J Mater Sci 1991;26:5275–91.[3]Lim SC,Gupta M,Leng YF,Lavernia EJ.Wear of a spray-deposited aluminum–silicon alloy.J Mater Process Technol 1997;63:865–70.[4]Lavernia EJ,Wu Y.Spray atomization and deposition.England Wiley press;1996.pp.487–9.[5]Zhou J,Duszczyk J,Korevaar BM.Structural development during the extrusion of rapidly solidified Al–20Si–5Fe–3Cu–1Mg alloy.J Mater Sci 1991;26:824–34.[6]Prased BK,Venkateswarlu K,Modi OP,Jha AK,Das S,Dasgupta R,Yegneswaran AH.Sliding wear behavior of some Al–Si alloys:role of shape and size of Si particles and test conditions.Metall Mater Trans A 1998;29A:2747–52.[7]Saheb N,Laoui T,Daud AR,Harun M,Radiman S,Yahaya R.Influence of Ti addition on wear properties of Al–Si eutectic alloys.Wear 2001;249:656–62.[8]Gui M,Kang SB,Lee JM.Wear of spray deposited Al–6Cu–Mn alloy under dry sliding conditions.Wear 2000;240:186–98.[9]Sahoo KL,Krishnan CSS,Chakrabarti AK.Studies on wear characteristics of Al–Fe–V–Si alloys.Wear2000;239:211–8.Fig.5.SEM micrographs showing wear debris generated at the load of 35.6N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.166 F.Wang et al./Materials and Design 25(2004)163–166。
让零极限效果增强的方法English: One method to enhance the zero limit effect is to improve the accuracy and precision of measurements and calculations. As the value of a certain variable approaches zero, small errors in measurement or calculation can have a significant impact on the result. Therefore, by using more advanced and accurate instruments for measurements, and employing more precise mathematical techniques for calculations, the accuracy of the results can be improved, leading to a stronger zero limit effect. Additionally, another method is to analyze and understand the underlying mathematical and physical principles that govern the behavior of the system as it approaches zero. By gaining a deeper understanding of the system, it becomes possible to manipulate and optimize certain parameters or factors to enhance the zero limit effect. Furthermore, using limit theorems and mathematical tools such as L'Hôpital's rule, Taylor series, or epsilon-delta definition of limits can help to further enhance the zero limit effect by providing a more rigorous and systematic approach to analyzing and manipulating the behavior of functions or variables as they approach zero.中文翻译: 提升零极限效果的方法之一是提高测量和计算的准确性和精度。
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水稻成熟胚愈伤组织诱导及其植株再生新疆农业科学2007,44(6):889—891XinjiangAgriculturalSciences水稻成熟胚愈伤组织诱导及其植株再生危晓薇,王冬梅,祖木热木?吐尔逊(新疆农科院核生所,鸟鲁木齐830091)摘要:利用水稻成熟胚为外植体,接种在NB培养基上,分别附加不同的外源激素,以诱导愈伤组织并促其分化,最终获得水稻再生植株.结果表明:2,4一D对愈伤组织诱导起决定性作用,当它与低浓度的6一BA配比时更有利于前期愈伤组织的诱导,而高浓度的6一BA则有利于后期芽丛的分化.关键词:水稻;成熟胚;愈伤组织;再生植株中图分类号:$511文献标识码:A文章编号:1001—4330(2O0r7)o6—889—03 CallusInductionandPlantRegenerationofMatureEmbryosinRiceWEIXiao—wei,W ANGDong—mei,Zhumuremu?Tuerxun (InstituteofNuclearandBiologicalTechnologies,XinjiangAcademyofAgriculturalScienc es,Urumqi830091,China)Abstract:ThematureembryoswerecultivatedonNBmediawithdifferenthormones,byusin gthematureembryosinriceasexplants,andregenerationplantswereobtainedsuccessfully.Theresultssh owedthat2,4一DWasimportantfactorincallusinduction.Whenitisproportionaltolowconcentration6一BA,itisusefultocallusinduction,andwhenithasproportionalhighconcentration6一BA,itisnecessarytodi Ⅱ.eI℃ntiategreenbud.Keywords:rice;matureembryos;callusinduction;regenerationplant水稻体细胞组织培养作为水稻基因工程的基础技术,在水稻遗传改良中具有重要的作用.因此,建立一个高效再生体系是实现基因转化的先决条件.1965年,Amemiya等开始水稻组织培养,几十年来,研究者先后从水稻各部位诱导出愈伤组织和再生植株.虽然,幼穗,幼胚,花粉粒,花药愈伤组织诱导率高,愈伤组织质量好而受到青睐被广泛用于水稻的遗传转化,品种培育中.但上述材料多受季节限制,取材不便,阻碍了水稻组织培养的进一步发展.实验利用水稻成熟种胚作为外植体[1'引,通过不同培养基,不同激素类型及浓度对水稻成熟种胚愈伤组织诱导,分化进行了相关研究L2,4,5】,为提高水稻成熟种胚愈伤组织的质量和高效再生频率提供有效依据.1材料与方法1.1材料供试材料为早锦1号,秋田小町[6~8]两个水稻品种.1.2方法1.2.1愈伤组织诱导培养基基本培养基为N6大量元素,B5微量元素及有机成分,辅加水解乳蛋白300mg/L,谷氨酰胺250mg/L,蔗糖3Og/L,pH5.8.表11.2.2愈伤组织分化培养基以N6培养基为基本培养基,辅以水解乳蛋白O.5—1.0g/L,6一BA0.5—3.5mg/L,NAA1.0mg/L,硫酸铜1.5mg/L,蔗糖30g/L,pH5.8.1.2.3生根培养基以MS为基本培养基,蔗糖3Og/L,pH5.8.收稿日期:2007—08—29基金项目:新疆农作物生物技术重点实验室作者简介:危晓薇(1956一),女,湖南人,副研究员,研究方向为基因工程890?新疆农业科学44卷表1添加不同激素的诱导培养基Table1InductivesubsWatmnaddedwititdifferenthormones1.2.4外植体消毒以及培养方法选择饱满成熟的种子,手工剥去颖壳.在超净工作台上,用70%的乙醇浸泡种子30s.0.1%的Hl2溶液表面消毒8～10min,无菌水漂洗3～4次,浸泡过夜.用镊子,解剖刀取出灭菌种子的成熟胚,将其接种于愈伤组织诱导培养基中,26～28~C暗培养.诱导培养7d后,将初始愈伤组织从萌发的种胚上剥离后转到新鲜诱导培养基上,继续培养30d,统计出愈情况.经继代生长60d左右,挑选生长旺盛,自然分散,质地紧密,呈淡黄色颗粒状的愈伤组织接种于分化培养基上,26～28~C光照培养(14h光/10h暗,1500～20001)()诱导芽的分化.绿芽分化后,把绿芽转人生根培养基中,直至成为完整小植株.2结果与分析2.1不同培养基及激素种类与浓度对愈伤组织诱导分化的影响比较Ms,N6,B5三种培养基的无机盐及有机成分,发现用N6培养基的无机盐,B5有成分和微量元素对诱导水稻成熟种胚愈伤组织较适宜.比较6一BA,2,4一D,KT等激素,发现分裂素6一BA0.2—3.5mg/L与生长素,NAA,2,4一D2mg/L进行配比有利于愈伤组织诱导和芽分化.另外,在培养基中适当加入水解乳蛋白,谷氨酰胺和硫酸铜对愈伤组织的诱导和芽丛分化都有一定促进作用.表2表2不同激素浓度配比对愈伤组织诱导的影响(以秋田小町为例)Table2Effectofdifferenthormoneconcentrationoncallusinduction (TakingAkitakaomaqiasanexample)2.2愈伤组织的获得和芽的分化按上述条件和方法进行愈伤组织的诱导,接种7d后即可看到种胚上有初始愈伤出现.15d后愈伤组织形成.继代40d后两个供试材料都诱导出大量的愈伤组织.其中,在2,4一D2mg/L,6一BA0.5mg/L组合中诱导的愈伤质地较硬,淡黄色颗粒状,分散性好.实验表明,这类愈伤组织通过在分化培养基上继代培养30d左右就可以观察到绿芽点的出现,继代培养30～40d就可见小苗生长.图1～32.3再生植株的获得一将生长长度1cm左右的芽丛切下后,接种在生根培养基中,20d左右逐渐生根,30d 后形成根系,此时,地上部分生长迅速,获得完整再生小植株.图4.6期危晓薇等:水稻成熟胚愈伤组织诱导及其植株再生?89l?图1秋田小町的初始愈伤组织Fig.1Imtialcallusof.4ddmlmomaqi图3秋田小町的绿色丛芽Fig.3GreenclumpingbudsofAkitakaomaqi3小结图2秋田小町的大量胚状体组织Fig.2GreatnumberofembryoidofAkitakaomaqi图4秋田小町的完整植株Fig.4WholeplantofAldta~omaqi3.1水稻由于其基因组小,通过组织培养易获得再生植株等特点而在基因克隆,基因功能验证以及遗传转化等研究方面成为模式植物.在实验中,选取了两个水稻品种,查阅国内大量水稻遗传转化的相关文章,对培养基做了适当调节,早锦1号和秋田小町均获得再生植株.在水稻组织培养过程中,发现外源激素是愈伤组织诱导和绿苗分化的关键因素,尤其是2,4一D和6一BA的适宜配比对水稻成熟胚愈伤组织诱导起着决定性作用.3.2新疆水稻种植面积少,主要集中在阿克苏和米泉等地.实验所用秋田小町是新疆当前水稻生产上的主栽品种之一,种植面积约占全疆水稻总面积的1/3.通过组织培养,已经得到了秋ftt4,町的再生植株,现正在对新疆其它水稻栽培品种进行再生植株的培养,这为新疆水稻的遗传转化,功能基因验证等研究贮备了前期条件.参考文献:[1]郑贵朝,胡事君.提高水稻愈伤组织植株再生能力几种方法的评价[J].杂交水稻,2005,2o(2):54—57.【2]李玉静,陈彦龙.2,4一D和6一BA对水稻愈伤组织培养力的影响[J].河北师范大学(自然科学版),2005,29(4):395—403.[3]周玲艳,秦华明.提高水稻愈伤组织再生频率的研究[J].种子,2006,25(7):28—31.[4]陈兴春,牛蓓.水稻愈伤组织分化与不同激素配比关系的研究[J].四川大学(自然科学版),2006,43(1):222—227.[5]姜华,陈静.ABA对水稻愈伤组织,不定胚发育及其植株再生的影响[J].作物,2006,32(9):1379—1383.[6]梁乃亭,魏玉波.优质水稻秋田町及其栽培技术[J].新疆农业科学1997,(2):51—52.[7]魏玉波,布哈丽且木,粱乃亭.新疆水稻优质栽培技术[J].新疆农业科学,2002,39(5):307—309.[8]魏玉波,梁乃亭,布哈丽且木,等.优质水稻品种39及栽培技术[J].新疆农业科学.2004.41(6):448—449.。
小学下册英语第二单元测验卷(有答案)英语试题一、综合题(本题有50小题，每小题1分，共100分.每小题不选、错误，均不给分)1 The ancient Greeks believed in many ________ (神祇).2 What do you call a story that teaches a lesson?A. FableB. MythC. NovelD. Biography3 My friend plays the ____ (trumpet) in the marching band.4 What do we call the act of making decisions?A. JudgmentB. EvaluationC. AnalysisD. All of the above答案: D5 A chemical that reacts with water to produce a gas is called a ______ agent.6 What is the name of the famous American author who wrote "The Adventures of Tom Sawyer"?A. Mark TwainB. Ernest HemingwayC. F. Scott FitzgeraldD. John Steinbeck答案:A7 _____ (oak) trees are strong and sturdy.8 The leaves change color in __________ (秋天).9 The capital city of Angola is __________.10 I believe every child should have a ________ (名词) to play with. It makes childhood special.11 I like to ______ (参与) in student councils.12 The flowers in the garden are _______ and vibrant.13 A crab can be found on the _______ (海滩).14 The chemical formula for propanoic acid is ______.15 My favorite subject in school is ______.16 The __________ is known for its wildlife and savannahs.17 Which instrument has keys?A. GuitarB. DrumsC. PianoD. Flute18 What is the sum of 2 + 2?A. 3B. 4C. 5D. 619 我的朋友喜欢 _______ (活动). 她觉得这很 _______ (形容词)20 What is the capital of Brazil?A. Rio de JaneiroB. BrasiliaC. Sao PauloD. Salvador答案: B21 What is the capital of Ghana?A. AccraB. KumasiC. TamaleD. Takoradi22 The symbol for zirconium is _____.23 A _______ is a charged particle that has gained or lost electrons.24 My dad tells me ______ stories.25 The chemical symbol for cadmium is _______.26 A __________ is an area of land rich in resources.27 The bee is busy collecting ______.28 I like to smell the ________.29 We have a ______ (丰富的) menu for lunch.30 soil) is crucial for agriculture. The ____31 I like to ride my ______ (skateboard).32 A wave can be described using its frequency and ______.33 The dog is barking ___. (loudly)34 I love my __________ (玩具名) because it is __________ (形容词).35 My cat loves to _______ (探索) the house.36 The __________ is a famous mountain in Japan.37 What is the name of the famous painting by Leonardo da Vinci?A. Starry NightB. The ScreamC. Mona LisaD. Girl with a Pearl Earring答案: C. Mona Lisa38 I want to learn how to ________.39 The ________ (乡村风光) is picturesque.40 What do you call the area where you can see nature and animals?A. ParkB. GardenC. ForestD. Jungle答案: A41 What type of animal is a frog?A. MammalB. ReptileC. BirdD. Amphibian答案: D. Amphibian42 A _____ is a region of space with a lot of stars.43 What is the name of the bear species that lives in the Arctic?A. Grizzly BearB. Polar BearC. Black BearD. Brown Bear答案:B. Polar Bear44 What do you call a young female kangaroo?A. JoeyB. CalfC. PupD. Kit答案: A45 A neutron has a ______ charge.46 A reaction that releases energy is called an ______ reaction.47 The __________ is a major river system in Africa. (尼日尔河)48 The ________ was a key document in the founding of the United States.49 A _______ (蜗牛) moves very slowly.50 He has a new ___. (bike)51 Which fruit is yellow and curved?A. AppleB. BananaC. GrapeD. Orange52 What is the name of the famous mouse created by Walt Disney?A. Donald DuckB. GoofyC. Mickey MouseD. Pluto53 We should _______ (保持)我们的环境干净。
