嘈杂小世界网络中的随机共振现象

以双稳态振荡器耦合而成的具有小世界拓扑结构的网络为研究对象,重点研究了该体系在周期弱信号和乘性高斯白噪声的共同作用下,振荡器之间的耦合强度与网络拓扑结构的无序度对于网络动力学行为的影响．结果显示噪声可以诱导产生随机共振现象,在适中的耦合强度下增加体系拓扑的无序度可以使整个体系的随机共振现象得到加强．另外,研究表明体系中存在着一组最优的耦合强度和拓扑无序度,在它们的协同作用下体系能够最有效地检测到外界的弱信号．     

刚果红共振光散射法测定蛋白质

本文研究了生物染料刚果红(Congo red)与人血清白蛋白(HSA)作用的共振光散射光谱,pH为4．35的溶液中,刚果红与人血清白蛋白作用导致在575m处共振光散射明显增强,且共振光散射信号值与蛋白质的浓度具有线性关系。     

非恒温一氧化碳表面催化氧化体系双随机共振

以衬底(support)温度为控制参数, 研究了温度涨落对非恒温Pt(110)/CO+O₂体系反应振荡的影响. 发现反应振荡随涨落强度或相关时间的变化出现双随机共振现象; 当衬底温度稍远离振荡区时, 温度涨落对反应振荡的影响明显减弱. 这表明, 温度涨落可以有选择地多次加强反应振荡, 从而对表面反应起到积极作用.     

邻苯二酚紫-溴化十六烷基三甲铵-核酸共振光散射体系的研究及其分析应用

研究了核酸与阴离子染料邻苯二酚紫(PV)及阳离子表面活性剂溴化十六烷基三甲铵(CTMAB)体系的共振光散射光谱特性。在pH2．35的柠檬酸介质中，核酸(yRNA或fsDNA)与阳离子表面活性剂CTMAB对邻苯二酚紫的共振光散射光谱有协同增强作用，产生最大散射波长为400nm的共振光散射光信号。在最佳实验条件下，共振光散射测定yRNA和fsDNA的线性范围皆为0．02-0.75mg／L，检出限分别为1．4和8．7μg/L。据此建立了一种测定核酸的新方法。     

利用电子自旋共振(ESR)技术研究啤酒原辅料自由基及其对麦汁自由基的影响

利用电子自旋共振(ESR)技术研究了啤酒生产原辅料固有自由基含量,发现麦芽自由基量最多,大麦其次,大米中未测到;且自由基存在于皮壳中.全麦麦汁和30%大米辅料麦液都含有羟基自由基和FR1.随糖化进行,羟基自由基上升,FR1下降;但全麦麦汁羟基出现较早,且糖化终了含量较高.     

细胞内钙离子体系中的双参数内信号随机共振

自从Benzi等于1981年提出随机共振(SR)现象以来,它已经受到物理、化学和生物学等领域的关注．SR是非线性体系中弱外信号和环境扰动之间的协同作用．后来胡岗等发现外信号可以由体系的内信号所代替,此时出现的SR被称为内随机共振(ISR)．通常对SR的研究都集中在外信号和噪音扰动参数上,如电压、电流和压力等．     

动态凝胶网络中的溶质扩散

从理论和实验两方面研究了凝胶网络中溶质的扩散 .着重于凝胶网络的涨落对扩散的影响 ,以动态链渗流理论建立了凝胶动态网络中溶质扩散的数学模型 .制备了聚异丙基丙烯酰胺(PNIPA)水凝胶 ,用激光光散射法测定了凝胶网络的涨落行为 .用双室膜池法以甲基蓝为溶质测定了凝胶中的扩散 .模型与实验结果定性相符 .     

异硫氰基孔雀石绿受激拉曼光谱研究

本文报道了具有时间分辨能力的全频宽带受激拉曼（BBSRS）系统和关于异硫氰基孔雀石绿（MGITC）受激拉曼光谱（sRs）的研究．BBSRS系统的探测光为450-800nm宽带连续白光,泵浦光为280～900nm范围内连续可调谐的ps窄带可见光（带宽≈7．5cm-1,脉宽≈2．5ps）．在合适的泵浦波长下,该系统可同时获取拉曼损失和拉曼增益光谱．MGITC的SRS研究结果表明,当拉曼损失谱峰出现在最大吸收波长（≈627nm）时,共振SRS谱峰强度最大;当泵浦或增益谱峰在最大吸收波长附近时,未观察到明显的共振拉曼信号;共振峰强度随浓度增大而增大,随泵浦功率增大而迅速增大,后趋于饱和;共振和非共振峰强在延时零点附近达到最大值,并随延时绝对值的增大而减小．     

Ag-CV的表面增强共振散射光谱研究

采用共振散射光谱和紫外可见光谱研究了银胶与结晶紫的相互作用。在ＰＨ为４．０的ＨＡｃ－ＮａＡｃ缓冲溶液中,奶胶在３４５ｎｍ和７００ｎｍ有两个共振散射峰;当加入带下辈民的阳离子染料结晶紫后,产生表面增强效应,３４５ｎｍ和７００ｎｍ处的共振散身信号大为增强,从而获得灵敏的表面增强共振散射光谱。     

液相卤化银纳米微粒的界面荧光和共振散射光谱特性

液相卤化银纳米微粒的共振散射光谱和发射光谱表明,AgCl和AgBr纳米微粒均在330,400,470和680nm处产生4个共振散射峰,在340,400和470nm处产生三个荧光峰．Ad纳米微粒在340,400,437,470和680nm处产生5个共振散射峰;除在340,400和470nm处产生3个荧光峰外,在434nm处有一最强的荧光峰．卤化银纳米微粒体系的浓度对共振散射信号的影响与浓度对荧光强度的影响一致,Aga,AgBr和AgI体系的共振散射光信号强度分别约为荧光信号的110,130和80倍,即荧光与共振散射之间存在相关性．提出了液相AgX纳米微粒荧光产生机理,解释了荧光与共振散射之间存在相关性的原因．     

Infrared spectra of heterocumulenes—VII: Correlations of infrared gruop wavenumbers and integrated absorption intensities in some heterocumulenes with substituent constants

A statistical evaluation of the empirical linear relations of the ν_as(X=Y=Z) integrated absorption intensities (A) in forty various heterocumulenes with substituent constants σ and σ⁺ has been carried out. The correlations of log A with substituent constants show that the positive sign of the slopes and ⁺ has been observed, suggesting that with all heterocumulenes studied the structure of the X=Y=Z group with cumulative bonds is dominant.     

葡萄糖激酶Y214C活性突变的理论研究

葡萄糖激酶(GK)催化葡萄糖转变为6-磷酸葡萄糖,这是糖代谢的第一步.正因为如此,GK活性异常在糖代谢紊乱的发生发展中起着重要作用.对青年型早发糖尿病(MODY2)和高胰岛素性低血糖症(PHHI)的深入研究证实GK活性改变与糖尿病的发生有关.为了研究GK活性改变的机理,利用分子动力学模拟和隐性溶剂的自由能计算对GK的单点突变Y214C(Tyr214→Cys)进行了理论研究.通过GK的Cα原子均方根浮动变化(RMSF)和动态相关性矩阵(DCCM)分析发现,Y214C突变导致处于活化状态的GK的构象更加稳定;通过包结自由能分析发现,Y214C突变可增加GK对葡萄糖的包结亲合性.相关研究结果有助于从原子水平理解Y214C活性突变的机制,并为糖尿病的治疗提供一定的理论参考.     

Investigation of the neighboring residue effects on protein chemical shifts

In this study, we report nearest neighbor residue effects statistically determined from a chemical shift database. For an amino acid sequence XYZ, we define two correction factors, Delta((X)Y)n,s and Delta(Y(Z))n,s, representing the effects on Y's chemical shifts from the preceding residue (X) and the following residue (Z), respectively, where X, Y, and Z are any of the 20 naturally occurring amino acids, n stands for (1)H(N), (15)N, (1)H(alpha), (13)C(alpha), (13)C(beta), and (13)C' nuclei, and s represents the three secondary structural types beta-strand, random coil, and alpha-helix. A total of approximately 14400 Delta((X)Y)n,s and Delta(Y(Z))n,s, representing nearly all combinations of X, Y, Z, n, and s, have been quantitatively determined. Our approach overcomes the limits of earlier experimental methods using short model peptides, and the resulting correction factors have important applications such as chemical shift prediction for the folded proteins. More importantly, we have found, for the first time, a linear correlation between the Delta((X)Y)n,s (n = (15)N) and the (13)C(alpha) chemical shifts of the preceding residue X. Since (13)C(alpha) chemical shifts of the 20 amino acids, which span a wide range of 40-70 ppm, are largely dominated by one property, the electron density of the side chain, the correlation indicates that the same property is responsible for the effect on the following residue. The influence of the secondary structure on both the chemical shifts and the nearest neighbor residue effect are also investigated.     

Skeletal structures of hexa-organo substituted triatomics R3XYZR3: A rationalisation using the second-order Jahn—Teller effect

In compounds of type R₃XYZR₃ (R  phenyl, methyl, benzyl; X, Z  Al, Si, P, Ge, Sn; Y  C, N, O, F) linearity of the XYZ skeleton is predicted by the second-order Jahn—Teller effect in those examples where the valence orbitals of X and Z are much less tightly bound than those of Y. When the X and Z orbitals are bound more tightly than those of Y, the XYZ skeleton is predicted to be non linear at Y. The effects of varying R, X and Z, and the contribution of π-interactions are discussed.     

基于对苯二甲酸配体的含二维铅无机层的三维无机-有机杂化材料的合成及晶体结构(英文)

以对苯二甲酸作为配体,利用水热法合成了含二维(2D)铅无机层的三维(3D)无机-有机杂化材料[Pb2Cl(1,4-BDC)1.5]n(1);利用红外光谱、电感耦合等离子体原子发射光谱、X-射线衍射表征了产物的结构,利用热重分析测定了其热稳定性.结果表明,[Pb2Cl(1,4-BDC)1.5]n属于单斜晶系,P21/c空间群,其晶格参数为:a=0.599 000(10)nm,b=1.185 29(2)nm,c=1.847 37(3)nm,β=91.778 0(10)°,V=1.310 98(4)nm3,Z=4,R1=0.032 0,wR2=0.089 4,Rint=0.043 6.就化合物1的分子结构而言,由Pb—X—Pb(X=O或Cl)链接形成的2D无机层通过对苯二甲酸配体连接,构筑成具有3D骨架的无机-有机杂化材料.     

A New Route to Phosphoryl Thiocarbonyl Mixed Imides - Structure Limitations

Abstract

The rearrangement of N-methyl thiophosphoryl carbonyl mixed imides (I, XYP(S)N(Me)C(O)Z) to N-methyl phosphoryl thiocarbonyl mixed imides (II, XYP(O)N(Me)C(S)Z) was studied as a function of substitution on phosphorus (Ia: X = Y = MeO; Ib: X = Ph, Y = MeO; and Ic: X = Y = Ph) with Z = Ph and as a function of substitution on carbon (Ia: Z = Ph; Id: Z = Me; and Ie: Z = OiBu) with X = Y = MeO. For Ia, Ib, and Id, rearrangement is complete and quantitative. In contrast, Ic rearranges to a 10/90 equilibrium mixture of IIc/Ic and Ie gives no evidence for rearrangement to the phosphoryl thiocarbonyl mixed imide IIe. A relative reactivity order for Ia, Ib, Ic, and Id of 1.00, 0.15, 0.036, and 0.11 respectively, was observed in the rearrangements.     

Computational methods to calculate accurate activation and reaction energies of 1,3-dipolar cycloadditions of 24 1,3-dipoles

Theoretical calculations were performed on the 1,3-dipolar cycloaddition reactions of 24 1,3-dipoles with ethylene and acetylene. The 24 1,3-dipoles are of the formula X≡Y(+)-Z(-) (where X is HC or N, Y is N, and Z is CH(2), NH, or O) or X═Y(+)-Z(-) (where X and Z are CH(2), NH, or O and Y is NH, O, or S). The high-accuracy G3B3 method was employed as the reference. CBS-QB3, CCSD(T)//B3LYP, SCS-MP2//B3LYP, B3LYP, M06-2X, and B97-D methods were benchmarked to assess their accuracies and to determine an accurate method that is practical for large systems. Several basis sets were also evaluated. Compared to the G3B3 method, CBS-QB3 and CCSD(T)/maug-cc-pV(T+d)Z//B3LYP methods give similar results for both activation and reaction enthalpies (mean average deviation, MAD, < 1.5 kcal/mol). SCS-MP2//B3LYP and M06-2X give small errors for the activation enthalpies (MAD < 1.5 kcal/mol), while B3LYP has MAD = 2.3 kcal/mol. SCS-MP2//B3LYP and B3LYP give the reasonable reaction enthalpies (MAD < 5.0 kcal/mol). The B3LYP functional also gives good results for most 1,3-dipoles (MAD = 1.9 kcal/mol for 17 common 1,3-dipoles), but the activation and reaction enthalpies for ozone and sulfur dioxide are difficult to calculate by any of the density functional methods.     

Three-block bi-focal PLS (3BIF-PLS) and its application in QSAR

When X and Y are multivariate, the two-block partial least squares (PLS) method is often used. In this paper, we outline an extension addressing a special case of the three-block (X/Y/Z) problem, where Z sits "under" Y. We have called this approach three-block bi-focal PLS (3BIF-PLS). It views the X/Y relationship as the dominant problem, and seeks to use the additional information in Z in order to improve the interpretation of the Y-part of the X/Y association. Two data sets are used to illustrate 3BIF-PLS. Example I relates to single point mutants of haloalkane dehalogenase from Sphingomonas paucimobilis UT26 and their ability to transform halogenated hydrocarbons, some of which are found as organic pollutants in soil. Example II deals with soil remediation capability of bacteria. Whole bacterial communities are monitored over time using "DNA-fingerprinting" technology to see how pollution affects population composition. Since the data sets are large, hierarchical multivariate modelling is invoked to compress data prior to 3BIF-PLS analysis. It is concluded that the 3BIF-PLS approach works well. The paper contains a discussion of pros and cons of the method, and hints at further developmental opportunities.     

Binuclear copper(I) macrocycles synthesized via the weak-link approach

The weak-link approach has been employed to synthesize a series of bimetallic Cu(I) macrocycles in high yield. Addition of phosphinoalkylether or -thioether ligands to [Cu(MeCN)4]PF6 produces "condensed" intermediates, [mu-(1,4-(PPh2CH2CH2X)2Y)2Cu2][PF6]2 (X = S, O; Y = C6H4, C6F4), containing strong P-Cu bonds and weaker O-Cu or S-Cu bonds. The weak bonds of these intermediates can be cleaved through ligand substitution reactions to generate macrocyclic structures, [mu-(1,4-(PPh2CH2CH2X)2Y)2(Z)nCu2][PF6]2 (X = S, O; Y = C6H4, C6F4; Z = pyridine, acetonitrile, diimines, isocyanide) in nearly quantitative yields. The incorporation of tetrahedral Cu(I) metal centers into these macrocycles provides a pathway to complexes that differ from analogous d8 square planar macrocycles generated via this approach in their increased air stability, small molecule reactivity, and ability to form multiple structural isomers. Solid-state structures, as determined by single-crystal X-ray diffraction studies, are presented for condensed intermediates and an open macrocycle     

13C NMR study of halogen bonding of haloarenes: measurements of solvent effects and theoretical analysis

Solvent effects on the NMR spectra of symmetrical (X = F (1), X = Cl (2), X = Br (3), X = I (4), X = NO2 (5), X = CN (6)) and unsymmetrical (X = I, Y = MeO (7), Y = PhO (8)) para-disubstituted acetophenone azines X-C6H4-CMe=N-N=CMe-C6H4-Y and of models X-C6H4-CMe=N-Z (X = I, Z = H (9), Z = NH2 (10)), 4-iodoacetophenone (11), and iodobenzene (12) were measured in CDCl(3), DMSO, THF, pyridine, and benzene to address one intramolecular and one intermolecular issue. Solvent effects on the (13)C NMR spectra are generally small, and this finding firmly establishes that the azine bridge indeed functions as a "conjugation stopper," an important design concept in our polar materials research. Since intermolecular halogen bonding of haloarenes do occur in polar organic crystalline materials, the NMR solution data pose the question as to whether the absence of solvent shifts indicates the absence of strong halogen bonding in solution. This question was studied by the theoretical analysis of the DMSO complexes of iodoarenes 4, 9-12, and of iodoacetylene. DFT and MP2 computations show iodine bonding, and characteristic structural and electronic features are described. The nonrelativistic complexation shifts and the change in the spin-orbit induced heavy atom effect of iodine compensate each other, and iodine bonding thus has no apparent effect on Ci in the iodoarenes. For iodides, complexation by DMSO occurs and may or may not manifest itself in the NMR spectra. The absence of complexation shifts in the NMR spectra of halides does not exclude the occurrence of halogen bonding in solution.