Isothermal section of ternary Sn ? Zn?Ni phase equilibria at 250 °C

Ternary Sn ?Zn? Ni alloys were prepared and equilibrated at 250 °C for 4? 15 weeks. The phases formed in these equilibrated alloys were determined experimentally. The isothermal section of Sn ?Zn? Ni system was constructed, based on the phase diagrams of the three constituent binary sy stems and the ternary phase equilibria data, determined in this study and referenced in literatures. 12 single-phase regions were identified in the Sn? Zn?Ni ternary system at 250 °C, including the three ternary compounds, δ , τ1 and τ2. There were 13 ternary phase regions and 23 binary phase regions in the 250 °C Sn ? Zn? Ni isothermal section. The solubility of Zn in the binary Sn ?Ni compounds is significant, and is 15.1% (mole fraction) in the Ni3Sn phase.     

Three-dimensional reconstruction of mature dengue virus cultured in neutral medium

Dengue virus (DEN), a single positively stranded RNA virus, is a family member of Flaviviridae; it uses the mosquito Aeodes aegypti as its principle vector to cause what is known as Dengue fever. Its genome is -10.8-kb in size and has one open reading frame encoding three structural proteins: capsid (C), precursor of the membrane (prM) and envelope (E), as well as seven non-structural proteins from a single polypeptide. The immature DEN particles are assembled on the inner surface of the endoplasmic reticulum(ER) and budded into the lumen of the ER.     

Sparsity analysis of signals

In this paper, the signals with generalized Gaussian distribution are considered. A mathematical formula is given to illustrate the sparsity of the signals. According to this formula, the measure of the Laplacian signal is 1, and Gaussian signal is 2. Given a signal, compared with Laplacian signal and Gaussian signal, we can intuitively know how sparse the signal is via its measure. Some examples demonstrate that, if there are no sufficient observed signals (e.g. only three observed signals), one can achieve underdetermined blind source separation (BSS) only for the sufficiently sparse source signals (e.g. much sparser than Laplacian signals) by the measure we defined.     

Effects of doping in 25-atom bimetallic nanocluster catalysts for carbon–carbon coupling reaction of iodoanisole and phenylacetylene

We here report the catalytic effects of foreign atoms (Cu, Ag, and Pt) doped into well-defined 25-gold-atom nanoclusters. Using the carbon-carbon coupling reaction of p-iodoanisole and phenylacetylene as a model reaction, the gold-based bimetallic MxAu25?x(SR)18 (–SR=–SCH2CH2Ph) nanoclusters (supported on titania) were found to exhibit distinct effects on the conversion of p-iodoanisole as well as the selectivity for the Sonogashira cross-coupling product, 1-methoxy-4-(2-phenylethynyl)benzene). Compared to Au25(SR)18, the centrally doped Pt1Au24(SR)18 causes a drop in catalytic activity but with the selectivity retained, while the AgxAu25?x(SR)18 nanoclusters gave an overall performance comparable to Au25(SR)18. Interestingly, CuxAu25?x(SR)18 nanoclusters prefer the Ullmann homo-coupling pathway and give rise to product 4,4′-dimethoxy-1,1′-biphenyl, which is in opposite to the other three nanocluster catalysts. Our overall conclusion is that the conversion of p-iodoanisole is largely affected by the electronic effect in the bimetallic nanoclusters’ 13-atom core (i.e., Pt1Au12, CuxAu13?x, and Au13, with the exception of Ag doping), and that the selectivity is primarily determined by the type of atoms on the MxAu12?x shell (M=Ag, Cu, and Au) in the nanocluster catalysts.     

Recent advances in the iron-catalyzed C-C bond formation via polar reactions of alcohols with carbon-centered nucleophiles

We summarized here the recent developments in the iron-catalyzed C-C bond formation via the polar reactions of alcohols with various carbon-centered nucleophiles. It is composed of three sections according to the categories of the C-centered nucleophiles such as C(sp3), C(sp2), and C(sp).     

Influence of Manufacturing Process of Warp-knitted Vascular Prosthesis on the Wall Homogeneity

This paper reports the evolution of textile structure and mechanical properties of vascular prosthesis in the level of the whole prosthesis and the constituent filaments with respect to the manufacturing process. The tubular wall of the prosthesis is divided circumferentially into three zones; basic line (BL), remeshing line ( RL) and guide line ( GL). Some heterogeneity has been observed on the tubular wall in terms of stitch structure of the prosthesis and linear density of the constituent filaments. The breaking position of the prosthesis under circumferential tensile localizes preferentially in remeshing line that is the weakest zone by warp knitting with double needle bed. Furthermore, the statistical differences of the mechanical properties of the filaments of zone RL, GL and BL have been confirmed too. It is predictable that the deterioration of prosthesis, under physiological loads (periodical pulse blood pressure etc.), could happen firstly in the weaker zone in vivo.     

Study on the bulk wave radiation of finite-length SAW devices using FEMBEM

Based on the distributions of stress and free charge on the interface of the surface acoustic wave (SAW) device calculated with the combination of boundary element method and finite element method(FEMBEM), the power of each of the three possible bulk waves radiated by the SAW device is calculated, and their contributions to the overall input conductance are separated respectively. Moreover, the formula of angular distributions of their power radiation into the substrate is derived. Consider the effect of mass loading, the resistance density，defined as a scalar, is extended to generalized resistance densities which can be written as three 4×4 tensors and for which the formulas are derived. The bulk wave radiations for a synchronous one-port resonator on 42°Y-rotated LiTaO3 are simulated. It is found that the radiated energy by slow shear wave contributes a very high proportion to input electrical energy in some frequency range.     

The role of cupric in maintaining the structure of CopC

The CopC protein from pseudomonas syringae pathovar tomato is expressed as one of four proteins encoded by the operon CopABCD that is responsible for copper resistance. And there are one trypto-phan (83), one tyrosine (79), and three phenylalanines (35, 43, 99) in apoCopC. The fluorescence peak of apoCopC is located near 320 nm, and the peak shifts toward 353 nm in the presence of 10 mmol·L~(-1) urea with excitation at 280 nm. Using urea as a chemical agent, the conformational stabilities of apoCopC and Cu_N~(2 ) -CopC were monitored by fluorescence spectrum in 20 mmol·L~(-1) phosphate buffer and 100 mmol·L~(-1) sodium chloride at pH 6.0. The free energy of stabilization for apoCopC and Cu_N~(2 )-CopC is 16.29±0.65 kJ·mol~(-1) and 26.26±0.35 kJ·mol~(-1), respectively. The distance between the tryptophan residue and the Cu~(2 ) in Cu_N~(2 ) -CopC has been studied by observing Frster type nonradia-tive energy transfer. And it is calculated to be 11.6 .     

Toxicity of Diphenyl-pentenone Against Three Aphids （Homoptera： Aphididae） and Its Effects on the Esterases and Glutathione S-transferase

The most provocative aspect of this study is its original findings on the toxicity of diphenyl-pentenone (1,5-diphenyl-2-penten-l-one, DP) against the three kinds of aphids (Maerosiphum granarium Kirby, Lipaphis erysimi (kaltenbaeh), Schizaphis aurantiae (Fosc.) and the inhibitory effects of DP againstdetoxification enzyme system of the aphid (S aurantiae). The result of bioassay in the laboratory shows that the product has strong contact activity and very good antifeeding activity, with higher efficacy than anabasine and nicotine, two botanical aphidicides. The median lethal concentrations of the three products against the apterous adult (Mgranarium) are 175.85, 217.23 and 245.22 mg/L, respectively, at 24h of pest treatment. DP is inferior to methomyl in contact assay but superior in antifeeding activity assay against the three aphides. DP has strong inhibitory effects on nonspecific esterases, carboxylesterase of aphid (S aurantiae), but it can not inhibit AchE. DP also has strong inhibitory effects on glutathione Stransferase of the aphid.     

Effects of Phenolic Antioxidants on Ultra - high Molecular Weight Poly-ethylene/Decalin Solution

The degradation of ultra - high molecular weight polyethylene (UHMW- PE) during its dissolution into deca-lin is discussed. Also is discussed the stabilization of thesolution by three phenolic antioxidants, octadecyl β - (3, 5 - di - tert - butyl - 4 - hydroxyphenyl) propionate(1076), tetrakis[methylene β-(3,5-di-t-butyl-4- hydroxyphenyl) - propionate] methane(1010), 1,1,3-tris(2-methyl- 4- hydroxy- 5- tert-butylphe-nyl)butane (CA), and an auxiliary antioxidant.dilauryl-thio- dipropionate(DLTP). Among the three phenolic antioxidants, the effect of 1076 is the greatest) and the auxiliary antioxidant is effective in the stabilizing the solution when combined with one of the three phenolic antioxidants.     

HLA-A*0201限制性CTL表位肽的分子力场分析

运用比较分子力场(CoMFA)和比较相似性指数分析(CoMSIA)方法研究了50个HLA-A* 0201限制性CTL表位九肽结构与亲和性间的关系,另外15个表位九肽作为预测集用于检验模型的预测能力。结果表明,采用CoMSIA得到的构效关系模型(q2 =0.608,r2 =0.987,F=440.4,SD=0. 111)要明显优于采用CoMFA得到的构效关系模型。在CoMSIA计算中,当引入疏水场时,三维构效关系模型得到明显改善,通过该三维构效关系模型,可较精确地估算预测集中15个CTL表位肽与HLA-A* 0201间的亲和力(r2pred=0. 703,SD=0. 368)。通过分析分子场等势面图在空间的分布,可以观察到表位肽分子周围的立体及疏水特征对表位肽与HLA-A* 0201间结合亲和力的影响,从而为进一步对CTL表位肽进行结构改造并基于此进行治疗性疫苗分子设计提供理论基础。     

芳香氨基酸及其肽光电离、SO*-4氧化与光敏化过程的比较研究

运用激光闪光光解瞬态吸收光谱研究了色氨酸 (Trp)、酪氨酸 (Tyr) ,苯丙氨酸 (Phe)和二肽 (Trp Tyr)光电离和被SO· - 4单电子氧化的过程 ,表征了反应过程中生成的自由基 ,并与丙酮光敏化生成的自由基进行了比较。三者不同之处是 ,Trp和Tyr光电离分别生成氮中心的吲哚自由基和酚氧自由基 ;丙酮光敏化除生成上述自由基外 ,在敏化Trp光解体系还观察到Trp激发三重态 ,丙酮三重态与Phe没有作用 ;在SO· - 4单电子氧化体系 ,分别在Trp的吲哚环、Tyr的苯环上加成生成加成产物 ,其中Trp尤为显著 ;Phe的光电离与SO· - 4氧化体系结果一致。在二肽Trp Tyr的光电离和光敏化体系中观察到自由基的转变过程 ,Trp/N· Tyr→Trp Tyr/O·即分子内的电子转移过程 ;而SO· - 4单电子氧化体系没有观察到这种转变     

表达肿瘤抗原HPV-58 E7的HLA-A*0201阳性宫颈癌细胞模型的构建和鉴定

为建立内源性表达58型人乳头瘤病毒(Huamn papillomavirus type 58,HPV-58)重要癌抗原E7蛋白的HLA-A*0201阳性人宫颈癌细胞模型.以HPV-58全基因组为模板,采用PCR法扩增E7蛋白的编码基因,构建真核表达载体pEGFP-N2-HPV58E7;转化大肠杆菌DH5α,通过DNA测序鉴定质粒载体;经除内毒素纯化后,将大量制备的重组质粒瞬时转染293T细胞,采用RT-PCR和细胞免疫荧光方法研究重组质粒在人源细胞中的表达情况;最后,选择HPV检出阴性的HLA-A*0201阳性人宫颈癌C33A细胞株为宿主细胞,采用脂质体转染、G418抗性加压筛选和细胞克隆化培养技术,建立能够稳定表达HPV-58 E7的恒定转染细胞株.采用RT-PCR、Western-blot和细胞增殖测定等方法从转录、翻译和表型等3个层次对所建细胞株进行鉴定研究.研究结果显示:克隆制备了HPV-58 E7蛋白的编码基因;构建获得了能够在人源细胞中表达HPV58E7-EGFP融合蛋白的真核表达质粒;并成功建立了能够稳定表达HPV-58 E7的HLA-A*0201阳性人宫颈癌细胞模型;核酸和蛋白水平的鉴定结果表明所建模型细胞能够表达HPV-58 E7癌抗原,宿主细胞本身表达的Ⅰ类组织相容性抗原HLA-A*0201有望通过内源性抗原加工途径将E7抗原的细胞毒性T细胞(Cytotoxic lyphocyte,CTL)表位提呈到细胞表面;另外,细胞增殖试验结果亦表明该细胞模型体现出E7蛋白显著的诱导细胞增殖的生物学特征.总之,能够稳定表达HPV-58 E7癌蛋白的HLA-A*0201阳性人宫颈癌细胞模型的建立为后续即将展开的以HPV-58 E7为靶标的宫颈癌治疗性疫苗和药物的寻找和研究奠定基础.     

人类乙型肝炎样病毒核心蛋白中第7位疏水性氨基酸重复肚段区域的突变可以抑制病毒核衣壳的组装

人类乙型肝炎病毒的核衣壳由核心蛋白的二聚体所组成．但是,核心蛋白亚单位与亚单位之间相互作用的机制至今尚不清楚．研究发现,在人类乙型肝炎样病毒──土拨鼠肝炎病毒（WHV）核心蛋白的氨基端,存在着4个保守的疏水氨基酸残基（氨基酸位置101～102）．它们分别是亮氨酸101,亮氨酸108,缬氨酸115和苯丙氨酸122．这4个疏水氨基酸残基以每隔6个氨基酸残基而重复出现1次．它们被称为“第7位疏水性氨基酸重复肽段（hhr）”．由于蛋白质中的疏水键往往在蛋白质的相互作用中起重要作用,因此就在培养细胞系统中研究WHV核心蛋白的hhr区域在…     

银杏叶黄酮类化合物水提工艺的响应面优化

研究水浸提银杏叶中总黄酮类物质的最佳工艺条件.以银杏粉碎叶为试验材料,以水为提取溶剂,采用响应面设计方法,对影响黄酮提取效果的提取温度、提取时间和料液比等3个因素先后进行了部分因子试验和中心组合设计试验,并建立数学模型,研究这些因素对黄酮提取率的影响.部分因子试验结果表明:提取时间和料液比是影响仙人掌黄酮提取效果的主要因子;中心组合设计试验建立的黄酮提取率(Y1)与提取温度(X1)、提取时间(X2)、料液比(X3)间的数学模型为Y1=6.423 667+0.161*X1+0.684 25*X2-0.523 75*X3-0.660 083*X1*X1+0.174 5*X1*X2-0.657 5*X1*X3-0.534 583*X2*X2-0.013 5*X2*X3-1.527 583*X3*X3;最佳的提取工艺条件为料液比1∶13.76,提取时间3.70 h,提取温度93.37℃,该条件下模型预测的最大提取率为6.75%.结果表明应用响应面方法对黄酮类物质的提取条件进行优化是非常有效的.     

Quantitative structure-retention relationship for polychlorinated dibenzofurans based on molecular interaction field analysis

A new quantitative structure-retention relationship （QSRR） model is developed for polychlorinated dibenzofurans （PCDFs） based on molecular interaction field （MIF） analysis. The MIF of all 135 PCDFs is calculated using DRY, C1= and C3 probe, characterizing the hydrophobic and steric interaction between PCDFs and different groups of stationary phase. Then QSRR model is constructed by multiblock partial least squares （MBPLS）, and the significance of each block is evaluated by the block importance in the prediction （BIP） method. The model used for prediction is statistically significant, with calibration and cross-validation correlation coefficients 0.9990 and 0.9980 respectively, and relative error less than 1.0%. The results of MBPLS and BIP show that the steric properties have dominant influence on the retention behavior of PCDFs, and then the hydrophobic effects.     

天花粉蛋白诱发人体免疫抑制中DQA1和DQB1等位基因的顺式互补受邻近DQ基因的调变

人类白细胞抗原HLA－DQ等位基因DQA1*0501和DQB1*0201以顺式和反式两种互补格局决定中药提取物天花粉蛋白诱发人体免疫抑制中CDS介导型性状的表达．研究工作进一步揭示其中的顺式互补受另一单元型上DQB1等位基因的调变．其中起正向调变作用的等位基因是DQB1*0302，0303，0401，0601；发挥负向调变作用的等位基因是DQB1*0201，0501，0602．以上现象表明天花粉蛋白诱发人体免疫应答的遗传控制呈现十分复杂的格局．     

对甲基苯胺与溴化铜配位反应的热化学研究

用新型的具有恒定温度环境的反应热量计,以溶解量热法及根据配位反应所设计的热化学循环,得到了配位反应的反应焓ΔrH     

单L-苯丙氨酸衍生物对乙醇/水混合溶剂的凝胶化研究

考察了单L-苯丙氨酸衍生物——L-3-[(3-硬脂胺酰基)-3-苯基-丙酰基]丁酸(SPAB)在乙醇/水混合溶剂中的凝胶行为,结果表明SPAB在乙醇/水的体积比从9:1到2:3的乙醇/水混合溶剂中能形成稳定的、热可逆的超分子凝胶。而在乙醇/水(V/V=1)溶液中的最低凝胶化浓度(MGC)低至1.2 mg/m L。凝胶的相转变温度(TGS)随凝胶因子浓度增加而升高。扫描电镜(SEM)观察到SPAB在乙醇/水混合溶剂中形成了相互交联的带状纤维聚集体。红外光谱(FTIR)结果表明SPAB分子中酰胺基团间的氢键、烷基的疏水作用以及水与SPAB分子中的羧基间的氢键是分子自组装的主要驱动力。     

一种运用灰色预测模型预测蛋白质一级结构的方法

将氨基酸残基的疏水值与氨基酸残基一一对应，得到代表氨基酸残基序列的疏水值序列，再对此疏水值序列运用灰色预测模型预测未知的氨基酸残基疏水值，从而达到间接预测氨基酸残基的目的。