铜-铝扩散焊及拉伸的分子动力学模拟

采用分子动力学方法模拟了铜-铝扩散焊过程，分析了理想平面铜-铝试件(001)晶面间扩散焊的过渡层厚度，并利用径向分布、键对分析方法分析了在不同的降温速率下过渡层的结构变化.降温速率大时，过渡层保持原有无序结构，降温速率小时，过渡层从无序结构向面心立方结构转变.还对扩散焊后的铜-铝试件进行了拉伸模拟，并与尺寸大小相近的单晶铜和单晶铝的拉伸模拟结果进行比较.结果发现焊接后的强度比单晶铝和单晶铜的强度都要小，最大应变值也小.     

光腔中两原子共振荧光的相干性质

研究了置于光腔中的两个二能级原子，在强相干场驱动下的共振荧光光场的辐射场相干性质，发现在坏腔条件下，可以通过调节光腔与相干场的频率来提高一阶可见度和减小二阶关联函数.这是因为改变光腔与相干场的频率会引起原子修饰态布居数的改变，导致一阶可见度和二阶关联函数发生显著变化. 关键词： 光腔 两个二能级原子 一阶可见度 二阶关联函数     

Helicity-dependent time delays in multiphoton ionization by two-color circularly polarized laser fields

By numerically solving the three-dimensional time-dependent Schrödinger equation, we have invest-tigated multiphoton ionization of hydrogen atom in the two-color circularly polarized (TCCP) laser fields consisting of a strong 400 nm and a much weaker 800 nm pulses. Due to the presence of perturb-bative 800 nm laser pulse, sideband peaks emerge between the above-threshold ionization rings in the photoelectron momentum distributions. Our numerical results show that the sideband peaks exhibit one-lobe structure in the co-rotating TCCP laser fields, while it displays the three-lobe structure in the counter-rotating TCCP laser fields. Moreover, the photoelectron yield of sidebands in the co-rotating TCCP fields is much higher than those of the counter-rotating TCCP fields. These phenomena could be well explained from the perspective of the photon-absorption channels via the selection rules. In-terestingly, an obvious phase shift between the sidebands of different orders from the co-rotating and counter-rotating TCCP fields is observed. This shift indicates the helicity-dependent time delay in the one-photon continuum-continuum transition process.     

White-light-emitting diodes using GaN-excited CdSe/CdS/ZnS quantum dots

Fluorescence-based white-light-emitting diodes （WLEDs） were fabricated using blue GaN chips and green- and red-emitting CdSe/CdS/ZnS quantum dots （QDs）. The coordinate and color temperature of the WLEDs could be varied because of the size-tunable emission of CdSe QDs from 510 to 620 nm. Warm and cold white emissions were confirmed with the color temperature ranging from 4000 to 9000 K. Color coordinates were analyzed at different bias. The fast enhancement of blue emission resulted in the shift of color coordinates to the cold side. The stability of white emission during operation was analyzed; stable spectra were achieved within 90 min.     

Directed evolution of high-affinity antibody mimics using mRNA display

We constructed a library of >10(12) unique, covalently coupled mRNA-protein molecules by randomizing three exposed loops of an immunoglobulin-like protein, the tenth fibronectin type III domain (10Fn3). The antibody mimics that bound TNF-alpha were isolated from the library using mRNA display. Ten rounds of selection produced 10Fn3 variants that bound TNF-alpha with dissociation constants (K(d)) between 1 and 24 nM. After affinity maturation, the lowest K(d) measured was 20 pM. Selected antibody mimics were shown to capture TNF-alpha when immobilized in a protein microarray. 10Fn3-based scaffold libraries and mRNA-display allow the isolation of high-affinity, specific antigen binding proteins; potential applications of such binding proteins include diagnostic protein microarrays and protein therapeutics.     

Studies on Carbohydrates ⅩⅩⅧ. Synthesis of Key Intermediates of Oligosaccharides Related to Serratia marcescens O10 Antigen

TheO-antigenofbacteriacanbeusedasahaptenandvaccine.Preparationofanantigeninv0lvesthesynthesisofacorrespondinghaPtenbearingeithernarrow0rwiderspeci-ficity.Generally,fragmentsofcarbohydratechainsbearingthes0-calledcompleterepeatingunitareemployedashaPtens.Synthesis0foligosaccharides,whichareveryspecificfragments,isatpresentoneoftheimP0rtantaspectsofcarb0hydratechemistry.TheS.marcescensOlOantigenhasbeenisolatedfromtheLPSofthereferencesKain(C.D.C.l287-54)ofS.marcescens.Itsbiol0gicalrepeatun…     

冲击载荷下分支交错层状仿生复合材料动态断裂行为的实验研究和数值模拟

通过三点弯动态冲击实验和数值模拟方法,研究了分支交错层状仿生复合材料的动态断裂韧性。首先设计并制备了分支交错层状仿贝壳复合材料试样,即将一种脆性刚性材料和一种橡胶类材料分别作为复合材料的硬质层和软胶层;随后采用改进的分离式Hopkinson压杆装置进行了三点弯冲击实验;接着讨论了初始冲击速度、硬质材料长宽比、软质材料层厚度对复合材料试样动态断裂行为的影响;最后采用ABAQUS有限元数值模拟,研究了不同宽度和不同冲击方向对复合材料试样动态断裂韧性和裂纹扩展的影响。结果表明:随着冲击速度和硬质材料长宽比增加、软胶层厚度减小,裂纹越倾向于沿直线扩展,反之,裂纹越倾向于绕过硬质材料沿着软胶层呈折线扩展;试样的峰值动载荷和起裂时间也随之增大。有限元模拟结果表明:随着结构总宽度的增大,试样断裂韧性增加,裂纹倾向于绕过硬质材料沿着软胶层扩展;采用实验设计的冲击方向时,试样的断裂韧性高于其他方向。     

Brain-like synaptic memristor based on lithium-doped silicate for neuromorphic computing

Artificial synapse is one of the potential electronics for constructing neural network hardware. In this work, Pt/LiSiO_x/TiN analog artificial synapse memristor is designed and investigated. With the increase of compliance current (C. C.) under 0.6 mA, 1 mA, and 3 mA, the current in the high resistance state (HRS) presents an increasing variation, which indicates lithium ions participates in the operation process for Pt/LiSiO_x/TiN memristor. Moreover, depending on the movement of lithium ions in the functional layer, the memristor illustrates excellent conduction modulation property, so the long-term potentiation (LTP) or depression (LTD) and paired-pulse facilitation (PPF) synaptic functions are successfully achieved. The neural network simulation for pattern recognition is proposed with the recognition accuracy of 91.4%. These findings suggest the potential application of the LiSiO_x memristor in the neuromorphic computing.     

A CuAAC/Ullmann C-C coupling tandem reaction: copper-catalyzed reactions of organic azides with N-(2-iodoaryl)propiolamides or 2-iodo-N-(prop-2-ynyl)benzenamines

A novel copper-catalyzed tandem reaction was developed by utilizing two famous copper-catalyzed reactions, CuAAC and Ullmann coupling. The trapping of the C-Cu intermediate produced in CuAAC led to further formation of an aryl C-C bond through intramolecular Ullmann C-C coupling.