2''-脱氧鸟苷在水溶液中激发态氢键动力学的密度泛函理论研究

用密度泛函理论和含时密度泛函理论研究了2'-脱氧鸟苷在水溶液中形成的一水和二水复合物在基态和激发态的氢键性质．计算了两种复合物的稳定构型、红外光谱、前沿分子轨道以及密里根电荷等光物理参数．结果表明,两种水合物的分子内氢键在光激发下变化不一致,分子间氢键变化相似．一水复合物的分子内氢键N3···H4-O2 在激发态是加强的,二水复合物的是减弱的．两种水合物的分子间氢键N2-H2···O3和O3-H5···O2及O3···H7-O4和H5···O1-C1在激发态全是减弱的．两种复合物红外光谱的计算结果与实验值一致．二水复合物中分子间氢键O4···H1-N1在激发态断裂,形成了新的分子间氢键O4···H3-N2,这种变化可能与鸟嘌呤部分的结构弯曲有关．最后分析了一水和二水复合物分子的分子内电子转移特性．     

基于分子对接的类二恶英类多氯联苯的拉曼光谱增强

为了从分子结构角度找到可以增强类二恶英类多氯联苯（PCBs）的拉曼光谱振动强度的结构变量,利用密度泛函理论（DFT）在B3LYP/6-31G（d）水平下对13种类PCBs结构进行优化,通过分子对接技术提取13种PCBs与联苯双加氧酶（Bpha,PDB：3GZX）对接后的PCBs分子结构,并计算了气态环境下对接前后PCBs分子的拉曼光谱振动强度和频率。研究结果表明：13种PCBs的拉曼振动归属为苯环变形、C-C伸缩、C-H摇摆、C-H伸缩以及各种形式的耦合,其中拉曼光谱频率在1 632.77~1 652.06 cm^-1之间的振动最强,苯环变形为特征振动;对接后PCBs的二面角大小有明显的改变,导致拉曼振动强度提高2.9%~213.98%,频率在1 631.57~1 651.94 cm^-1之间的拉曼峰整体发生蓝移,二面角大小与拉曼振动强度呈现一定程度的线性关系,随二面角逐渐减小,拉曼振动增强。实验结果表明,可通过调整PCBs的二面角大小达到提升PCBs辨识灵敏度的目的,并为PCBs拉曼光谱检测提供理论依据。     

基于二值化图像结合像元统计法的扑尔敏片剂近红外成像检测参数优化研究

研究药物领域中近红外成像检测参数对高光谱数据质量的影响,建立检测参数优化方法。以扑尔敏片剂为研究对象,采用近红外化学成像技术,考察光谱分辨率、空间分辨率、扫描次数和扫描高度等因素,采用L9 (34) 正交表设计,优化近红外成像检测参数;采用二值化图像法和像元统计法对高光谱数据进行定量分析,测定扑尔敏片剂表面马来酸氯苯那敏含量。以高效液相色谱法作为参考方法,精密测定片剂中马来酸氯苯那敏含量。两种方法测定的含量差值绝对值为考察指标,优化最佳检测条件。结果表明, 扑尔敏片剂的高光谱数据最佳检测条件：空间分辨率25 μm×25 μm,扫描高度-5340(Z值,精确聚焦),光谱分辨率16 cm-1,扫描次数16次。该研究首次优化近红外成像扫描高度参数对高光谱数据质量的影响,优化近红外成像扫描高度等检测参数可用于指导扑尔敏片及其他药物近红外成像数据采集和方法建立。     

2-（甲苯-4-磺酰胺基）-苯甲酸的结构、光谱与热力学性质的理论研究

在B3LYP/6-31++G^**水平对2-（甲苯-4-磺酰胺基）-苯甲酸分子进行几何构型优化和频率的计算,得到红外光谱,拉曼光谱和不同温度下的热力学性质.结果显示,该分子羧基的碳氧原子、磺酰胺基的氮原子与苯环形成不同的离域大π键,空间位阻效应和共轭效应使两个苯环不在同一平面,二面角为63.2°.使用含时密度泛函理论方法计算第一激发态的电子垂直跃迁能,得到最大吸收波长为312.7?nm,属于近紫外区,这与该分子在二氯甲烷溶剂中的实验测得值307?nm一致. 关键词： 2-（甲苯-4-磺酰胺基）-苯甲酸 光谱 热力学性质 密度泛函理论     

变温过程中二甲基亚砜与水之间氢键行为的拉曼光谱研究

测量了在降温过程中体积比为1∶1的二甲基亚砜(DMSO)水溶液的拉曼光谱,并对DMSO水溶液的拉曼光谱进行了归属。对实验数据进行分析发现: 在降温过程中DMSO分子与水分子的分子间氢键、DMSO分子与DMSO分子和水分子与水分子间氢键的作用行为引起了DMSO的SO双键和水分子的O—H键的拉曼谱带的变化。进一步分析表明：在27～-30 ℃降温过程DMSO与水之间氢键加强,-30～-60 ℃降温过程水与水之间氢键代替DMSO与水之间的氢键。这为丰富水溶液的氢键理论提供了实验依据。     

N-(4-硝基苯基)马来酰亚胺分子结构、光谱和热力学性质的理论研究

N-(4-硝基苯基)马来酰亚胺是一种新合成的NPMI类化合物,在B3LYP/6-311++G~(**)水平对N-(4-硝基苯基)马来酰亚胺分子进行几何结构优化和频率、热力学性质计算,得到它的红外光谱、拉曼光谱和不同温度下的热力学性质.结果显示,该分子中两个C=O与五元环在同一个平面内,苯环上硝基中的N—O与六元环也在同一个平面内,五元环与六元环呈129.6°的二面角,整个分子不具有对称性;热容、熵、焓等热力学性质与温度之间存在很好的函数关系式.     

基于密度泛函理论的肾上腺素分子的光谱分析

肾上腺素是一种神经和激素的传送体,研究肾上腺素分子的光谱和能级有助于了解其化学稳定性和药理作用。基于密度泛函理论（DFT）,利用Gaussian 09软件在B3LYP/6-311G（d,p）基组水平上对肾上腺素分子进行结构优化,采用含时密度泛函理论（TD-DFT）的PBE方法在def2tzvp基组水平上计算肾上腺素分子在气相中的前20个激发态,利用Multiwfn3.7（dev）软件绘制出其紫外光谱图并对激发性质进行分析。肾上腺素分子紫外光谱对应的主要跃迁是从基态分别到第1,2,4,8,15和16激发态的跃迁,其他的激发态的振子强度低于阈值0.03。理论计算得出肾上腺素的紫外光谱有两个吸收峰,分别位于206.23和273.92 nm,206.23 nm峰主要由基态跃迁到第16激发态形成,273.92 nm峰主要是基态跃迁到第2、4激发态形成,主要是由苯环上π→π*跃迁所产生,并与实验光谱吻合较好。对肾上腺素分子的激发态性质分析可知,上述吸收峰都是在最高占据轨道和最低空轨道的临近轨道跃迁产生的。利用密度泛函的PBE方法在6-311G（d, p）的基组水平上计算肾上腺素分子频率并绘制红外光谱,由振动分析可知,3 738和3 662 cm-1峰是由酚羟基O-H伸缩振动产生的特征吸收峰,3 715 cm-1峰是由醇羟基O-H伸缩振动产生的特征吸收峰,2 854 cm-1峰是由甲基的C18-H20键的伸缩振动产生的特征吸收峰,1 516和1 439 cm-1峰是苯环骨架的伸缩振动的特征吸收峰,1 279与1 057 cm-1峰分别是由C6-O10和C12-O23键伸缩振动产生的特征吸收峰,620 cm-1峰是N22-H17键摇摆振动的特征吸收峰。对比肾上腺素的实验红外光谱,发现理论光谱与实验光谱中各基团的特征吸收峰都较为明显且总体吻合较好。由于肾上腺素分子二聚体和多聚体之间形成氢键,分子间氢键的形成削弱了O-H键的强度,降低了能形成分子间氢键的羟基O-H的伸缩振动频率,从而导致实验光谱在3 500～2 500 cm-1之间呈现出一个宽峰。     

C1对称C20分子结构与光谱特性的密度泛函方法研究

利用密度泛函方法研究了富勒烯C20分子的结构、光谱和分子轨道分布特性.在B3LYP/6.31G*基组下完成了在C1群对称性下C20分子的几何结构优化,并通过计算得出了C20分子的能态、轨道密度和基振光谱.结果说明C20分子轨道具有明显的离域特性,能隙小于2 ev,具有半导体特性.红外与拉曼光谱分别对应两个强特征峰.     

2-巯基-5-硝基苯并咪唑振动光谱的密度泛函理论研究

选用密度泛函理论中的B3LYP杂化泛函,在B3LYP/6-31++g(d,p)（C,H,N,S）水平下,优化了2-巯基-5-硝基苯并咪唑分子（MNBMZ）的结构,优化结果表明,2-巯基-5-硝基苯并咪唑分子是一个近平面结构。通过频率计算,获得了2-巯基-5-硝基苯并咪唑分子（MNBMZ）的拉曼光谱,并和实验获得的拉曼光谱图进行了对比,200～800 cm-1波数段实验获得的拉曼谱带波数和理论计算波数相比,有一定程度的蓝移,800～1 800 cm-1波数段实验获得的拉曼谱带波数和理论计算波数相比,发生了一定的红移。对实验和理论计算光谱主要振动峰进行线性回归拟合,相关系数r=0.998,标准偏差14.98。实验和理论计算获得的拉曼光谱图基本上是一致的,表明本文选取的DFT理论计算方法是可靠的。结合VEDA4软件对2-巯基-5-硝基苯并咪唑分子的拉曼谱带简正振动模式进行了指认。此外,分析并讨论了2-巯基-5-硝基苯并咪唑分子（MNBMZ）前线轨道及HOMO,LUMO轨道的组成,HOMO和LUMO轨道能级差为3.31 eV,电子有从HOMO跃迁到LUMO的趋势。HOMO轨道中S原子的贡献是52.53%,LUMO轨道中硝基N和O原子的贡献分别为23.03%,19.97%和19.36%。采用含时密度泛函理论（time dependent density functional theory,TDDFT）对2-巯基-5-硝基苯并咪唑分子（MNBMZ）的激发态进行了计算分析,计算结果表明甲醇溶剂中2-巯基-5-硝基苯并咪唑分子（MNBMZ）理论计算的吸收波长为213,281和437 nm;实验获得的吸收波长223,272和353 nm。对研究2-巯基-5-硝基苯并咪唑分子的性质,提供了理论基础。     

非水体系中镍表面Ramam光谱研究新进展

本文利用共焦显微拉曼系统,获得有机乙醇溶剂中吡啶分子吸附在硝酸刻蚀镍电极表面的拉曼光谱,与水体系相比谱峰强度有所降低。根据表面拉曼光谱中吡啶分子环呼吸振动峰ｖ１向高波数方向移动（与液态吡啶屡原子以垂直（或略微倾斜）方式作用于镍电极表面,且随电位移其与镍表面的作用逐渐减弱。     

Speckle characteristics of a broad-area VCSEL in the incoherent emission regime

We present a technique to reduce the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can be obtained when using the proper driving conditions. We evaluate the efficiency of this technique to reduce the speckle contrast by comparing it with the speckle characteristics in multimode emission under cw operation. Depending on the illumination setup, the incoherent emission regime can lead to a strongly reduced speckle contrast down to 1.3%. This is in agreement with estimates of the expected speckle contrast reduction when three contrast reducing effects are taken into account. These low contrast values make the investigated sources attractive for several applications that suffer from speckle noise.     

XYZ particles at Belle

In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X(3872), X(3915),Y(4140), X(4350), and the charged Z states.     

Optical transmission through an interface between subwavelength slits

This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers.     

带有碳杂质的钨中氢稳定性的第一性原理研究

应用第一性原理计算方法研究了碳(C)原子对钨(W)中氢(H)原子稳定性的影响. 本征W中, 当C-H间距离为～2.5 Å时, H的溶解能出现最低值, 此时为H最稳定的位置. W中存在空位时, 由于C的影响, H占据的最佳电子密度面值为0.10 Å^-3. 研究发现, W中单空位最多能容纳10个H原子, 且不能形成H分子, 不同于没有C存在的情况, 表明C对W中H稳定性存在很大影响. 此外, 当两个C原子存在于空位中时, H占据的最佳电子密度面值变为0.13 Å^-3.     

Beyond the LAN: Ethernet’s Evolution into the Public Network

This article details the evolution of Ethernet into Gigabit Ethernet and how this LAN-based technology has undergone major transformations over time. From its data rates and distances to supported media and functionality, Ethernet has greatly improved, enabling it to surmount many of its former limitations and in so doing to expand beyond the LAN into the MAN and now even the WAN. In this article, Pioneer Consulting explores the evolution further by focusing on some of the major technological directions in the Ethernet equipment industry.     

Effect of swift heavy ion irradiation on photoluminescence properties of ZnO/PMMA nanocomposite films

We report a study on the SHI induced modifications on structural and optical properties of ZnO/PMMA nanocomposite films. The ZnO nanoparticles were synthesized by the chemical route using 2-mercaptoethanol as a capping agent. The structure of ZnO nanoparticles was confirmed by XRD, SEM and TEM. These ZnO nanoparticles were dispersed in the PMMA matrix to form ZnO/PMMA nanocomposite films by the solution cast method. These ZnO/PMMA nanocomposite films were then irradiated by swift heavy ion irradiation (Ni⁸⁺ ion beam, 100 MeV) at a fluence of 1×10¹¹ ions/cm². The nanocomposite films were then characterized by XRD, UV-vis absorption spectroscopy and photoluminescence spectroscopy. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. Enhanced green luminescence at about 527 nm and a less intense blue emission peak around 460 nm were observed after irradiation with respect to the pristine ZnO/PMMA nanocomposite film.     

Grain boundary potential and charge density at grain boundaries of chemically prepared thin silver sulfide films

The grain boundary potential and interface state charge density at the grain boundaries of silver sulfide (Ag₂S) thin films prepared by chemical conversion of cadmium sulfide (CdS) films have been determined from the dc resistance of the material and are found to be sensitive to annealing. A reduction in the grain boundary potential and the grain boundary charge density of the film has been noticed when the source CdS film is annealed at different temperatures prior to chemical conversion. The variation in the grain boundary charge density of the grown Ag₂S film with source annealing temperature has been found to be similar to that of thin cadmium sulfide film, reported earlier. An additional low temperature heat treatment of the sample results in an enhancement in the charge density at the grain boundaries. The change in the silver vacancy and/or oxygen and sulfur content of the films as revealed from the energy dispersive spectra of the films suggests possible role of film composition on the grain boundary charge density.     

Reflections from polished single mode fiber ends

Abstract

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

The Effects of Polarization and Non-Linearity on the Performance of WDM System with Optical Cross-Connects

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

化学发光法测定巯嘌呤的含量

在流动注射系统中,利用巯嘌呤在碱性Luminol-K₃Fe(CN)₆化学发光体系中发光信号强的特点,建立了一种测定巯嘌呤的新方法。在优化条件下,方法的线性范围是1.02×10-7～1.02×10-9mol·L-1, 回归方程是Y=36.315c+140.72(Y是相对发光强度,c是巯嘌呤浓度与10-8 mol·L-1的乘积), 相关系数是0.998 2,检出限(S/N=3)是6.33×10-10mol·L-1,RSD为3.54%（c_i=2.0×10-9mol·L-1, n=12）。该法用于合成样品的测定,简便、灵敏、快速,结果令人满意。文章简要地探讨了巯嘌呤在碱性Luminol-K₃Fe(CN)₆化学发光体系中的化学发光机理：在反应过程中,产生大量的过氧自由基和羟基自由基,自由基与鲁米诺反应,形成激发态的鲁米诺分子,鲁米诺分子由激发态回到基态产生化学发光现象。