溶剂和外电场下N-羟乙酰神经氨酸的理论光谱研究

通过密度泛函理论对非人源性的红肉危害因子N-羟乙酰神经氨酸(Neu5Gc)在溶剂和外电场下的分子光谱性质进行研究.以M062X/6-311+G(d,p)水平在不同介电常数溶剂(苯ε=2.27，乙酸ε=6.2528，乙醇ε=24.85，甲酸ε=51.10，水ε=78.35)和气相条件下完成几何结构优化、红外、拉曼光谱模拟，相应的，在M062X/6-311G (d,p)水平进行笛卡尔坐标X轴正方向不同强度外电场(0,0.005,0.01,0.015,0.02,0.025 a.u．)下的对比计算.基于各自优化后结构在PBE1PBE/TZVP水平模拟了Neu5Gc在溶剂和外电场下的紫外光谱.结果表明，溶剂下Neu5Gc因溶液极性和与溶质分子间相互作用使其结构稳定性降低，红外和拉曼光谱均产生一定蓝移，在乙醇、甲酸、水相下O-H红外收缩振动频率增高;紫外最大吸收波长为乙酸时183.26 nm，其主要是HOMO到LUMO+1轨道的跃迁.电场下Neu5Gc的红外和拉曼光谱因诱导偶极效应差异较大，在0.025 a.u．时C-H键拉曼活性达到最大，伴随红外光谱蓝移; 0.025a.u．时，紫外激发能最低，紫外最大吸收波长为189.63 nm，主要是HOMO-4和HOMO-1到LUMO+1轨道的跃迁.     

GaN在辐射场中的物理特性和光谱研究

采用密度泛函理论的B3LYP方法, 在6-311G++(d,p)基组水平上优化了不同外电场(0～0.025 a.u.)下氮化镓分子的基态稳定构型, 在此基础上利用同样的方法计算了氮化镓分子的分子结构、偶极矩、总能量、能隙以及红外光谱, 拉曼光谱, 紫外-可见吸收光谱强度。结果表明, 分子的结构的变化与电场大小呈现强烈的依赖关系。随着正向外加电场的增加, GaN分子键长不断减小, 电偶极距不断减小, 分子总能量不断增大, 分子能隙不断减小, 红外光谱吸收峰出现蓝移现象, 拉曼光谱出现蓝移现象。随着外电场的加强, 分子紫外-可见吸收光谱振子强度出现先减小后增大再减小的反复变化, 其波峰则出现红移现象。     

外电场下L-茶氨酸分子的结构特征与光谱性质

L-茶氨酸(N-乙基-L-谷氨酰胺)是一类具有降压、抗氧化的非蛋白氨基酸,研究外场下它的结构和光谱特征有助于人们更好地认识L-茶氨酸分子的性质.基于密度泛函理论,利用B3LYP方法,在6-311g(d,p)基组水平上对L-茶氨酸分子进行几何构型优化,在此基础上计算L-茶氨酸分子在不同外电场下(0～0.0125 a.u.)的分子各键长与振动频率,得到对应的红外光谱.同时,在相同的基组下采用含时密度泛函方法(TD-DFT)计算外电场对分子的激发态、前线轨道和能隙的影响.结果表明:分子结构及其紫外、红外光谱都随外电场强度发生变化.随外电场的增加,伸缩振动频率红移,弯曲振动频率蓝移;最高占据轨道的能量(E_(HOMO))与最低空轨道的能量(E_(LUMO))发生改变,前线轨道能隙先小幅增加后随电场减小,分子活性先减小后增强;紫外吸收光谱先蓝移后红移.本研究对L-茶氨酸分子的检测、合成及其生物活性的研究可提供理论依据.     

外电场下L-茶氨酸分子的结构特征与光谱性质

L-茶氨酸(N-乙基-L-谷氨酰胺)是一类具有降压、抗氧化的非蛋白氨基酸,研究外场下它的结构和光谱特征有助于人们更好地认识L-茶氨酸分子的性质.基于密度泛函理论,利用B3LYP方法,在6-311g(d,p)基组水平上对L-茶氨酸分子进行几何构型优化,在此基础上计算L-茶氨酸分子在不同外电场下(0～0.0125 a.u.)的分子各键长与振动频率,得到对应的红外光谱.同时,在相同的基组下采用含时密度泛函方法(TD-DFT)计算外电场对分子的激发态、前线轨道和能隙的影响.结果表明:分子结构及其紫外、红外光谱都随外电场强度发生变化.随外电场的增加,伸缩振动频率红移,弯曲振动频率蓝移;最高占据轨道的能量(E_(HOMO))与最低空轨道的能量(E_(LUMO))发生改变,前线轨道能隙先小幅增加后随电场减小,分子活性先减小后增强;紫外吸收光谱先蓝移后红移.本研究对L-茶氨酸分子的检测、合成及其生物活性的研究可提供理论依据.     

SiC在辐射场中的物理特性和光谱研究

本文采用密度泛函理论的B3LYP方法,在6-311G++(d,p)基组水平上优化了不同外电场(0-0.04a.u.)下碳化硅分子的基态稳定构型,在此基础上利用同样的方法计算了碳化硅分子的分子结构、偶极矩、总能量、能隙以及红外光谱、拉曼光谱、紫外-可见吸收光谱强度.结果表明,在外电场的作用下,分子结构变化明显,与电场呈现强烈的依赖关系.碳化硅分子键长一直在增大,电偶极矩先减小后增大,分子总能量先增大后减小,能隙E_G先减小后增大再减小再增大,红外光谱吸收峰出现红移现象,拉曼光谱出现蓝移现象.随着外电场的加强,分子紫外可见吸收光谱振子强度出现先增大后减小的反复变化,其波峰也出现蓝移现象.     

不同外电场下对二甲苯结构和光谱特性研究

本文采用密度泛函B3LYP方法在6-311G++(d,p)基组上优化了不同外电场下(-0.025~0.025 a.u)的对二甲苯分子,得到了不同外电场下的键长,能量,电偶极矩和前线轨道等构型参数,并分析了上述参数随外电场的变化情况.之后在优化后基态的基础上,采用TDDFT/B3LYP/6-311++G(d,p)方法得出了不同外电场下(0~0.02 a.u.)对二甲苯分子的紫外可见吸收光谱,并探讨了外电场变化对对二甲苯分子前9个激发态的激发能,波长和振子强度的影响规律.这些计算结果为利用强电场降解有毒物质对二甲苯提供理论依据.     

不同外电场下对二甲苯结构和光谱特性研究

本文采用密度泛函B3LYP 方法在 6-311G++(d, p)基组上优化了不同外电场下（-0.025～0.025a.u）的对二甲苯分子,得到了不同外电场下的键长,能量,电偶极矩,前线轨道等构型参数并分析了上述参数随外电场的变化情况。之后在优化后基态的基础上,采用TDDFT/B3LYP/6-311++G(d, p)方法得出了不同外电场下（0～0.02a.u.）对二甲苯分子的紫外可见吸收光谱,并探讨了外电场变化对对二甲苯分子前9个激发态的激发能,波长和振子强度的影响规律。这些计算结果为利用强电场降解有毒物质对二甲苯提供理论依据。     

硼球烯B_(40)在外电场下的基态性质和光谱特性

以6-31G*为基组,采用密度泛函PBE0方法研究了不同外电场(0—0.060 a.u.)对硼球烯B_(40)的基态几何结构、电荷分布、能量、电偶极矩、能隙、红外及拉曼光谱特性的影响;继而采用含时的TD-PBE0方法研究了硼球烯B_(40)在外电场下的电子光谱.研究结果表明:外电场的加入导致分子对称性降低,当电场从0 a.u.变化到0.060 a.u.时,偶极矩逐渐增加,体系总能量和能隙一直减小;外电场的加入将改变红外和拉曼光谱特征,如谐振频率的移动以及红外和拉曼峰的增强或减弱;外电场对硼球烯B_(40)的电子光谱影响较大,当电场从0 a.u.变化到0.060 a.u.时,电子光谱发生红移,同时对振子强度有很大影响,原来振子强度最强的激发态变弱或成为禁阻跃迁,而原来振子强度很弱或禁阻的激发态变得最强.可以通过改变外电场来改变B_(40)的基态性质,以及控制B_(40)的光谱特性.     

二溴甲烷分子在外电场下物理性质及逐步解离特性研究

二溴甲烷在太阳光辐射下分解成破坏臭氧的溴自由基,严重危害自然环境和人类健康,研究对二溴甲烷的降解很有必要.利用密度泛函理论在B3LYP/6-311G(d, p)基组水平上研究了不同外电场(0～0.025a.u.)作用下二溴甲烷分子的物理性质,包括总能量、键长、电偶极矩、能级、能隙、红外光谱等.采用含时密度泛函理论在同样基组水平下研究了外电场对分子激发态的影响.此外,外电场下扫描两个C-Br键的势能曲线,发现外电场强度分别为0.025a.u.和0.04a.u.时两个C-Br键依次断裂分子发生逐步解离,该结果为保护环境即对二溴甲烷进行电场降解提供重要的参考依据.     

外电场作用下N2O分子的结构与光谱特性

采用密度泛函B3LYP方法,在6-311+g(d)基组水平上研究了不同外电场对直线型分子N₂O的基态结构、偶极矩、轨道能级、红外和拉曼光谱特性的影响,并采用杂化CIS方法研究了N₂O分子在外电场作用下前9个激发态的激发特性.结果表明:外电场导致分子键长变化,但并没有改变分子的直线特征,偶极矩和分子总能量随外电场的增加先减小后增大,而能隙随外电场的增加先增大后减小,外电场的增加使LUMO(lowest unoccupied molecular orbital)组成由π~*轨道变为σ~*轨道,外电场使红外光谱发生移动,峰的强度增强或减弱.外电场的增加显著影响了N₂O分子的激发特性.激发能、激发波长受外电场影响发生了变化,同时,振子强度受外电场影响明显,禁阻跃迁变为可允许的跃迁,允许的跃迁在电场作用下变为禁阻跃迁或者跃迁变弱.紫外光谱在电场的作用下吸收峰发生了明显的移动,而且有新的吸收峰产生.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.