菌紫质分子膜图象信息存储的实验研究

本文讨论了新型细菌视紫红质基因变种材料的光循环过程及其光致变色特性。利用B态P态之间的光致变色实现信息的存储与读出，建立了细菌视紫红持生物分子膜高分辨图参信息读写实验系统，并在菌紫质分子膜器件上实现了400L／mm高分辨的图象信息存储。     

基于细菌视紫红质光子逻辑门的实验研究

研究了基于细菌视紫红质(简称BR或菌紫质)变种材料D96N的3种光逻辑操作.在633nm激发光照射下，菌紫质分子会被激发到M态，处于M态的菌紫质对412nm的紫光呈较大吸收，会抑制同时入射的紫光.选择合适的紫光强度，通过CCD观测被抑制的412nm检测光透射强度分布，模拟了“非”、“或非”、“与非”几种基本的光子逻辑操作. 关键词： 细菌视紫红质 光子逻辑门 互补抑制     

基于菌紫质的光开关原型器件研究

本文分析和讨论了细菌视紫红质的饱和吸收特性及互补抑制特性,在此基础上进行了细菌视紫红质光开关的实验研究。研究证明了被激发到M态的细菌视紫红质分子对紫光有较大的吸收,而处于基态的分子则对黄光有较大吸收。随着入射黄光强度的增加,菌紫质对黄光的吸收呈饱和吸收特必,时菌紫质对紫光呈较大吸收,而较强的紫光照射将会使此饱和吸收阈值增加,使得菌紫质对黄光的吸收又增大,从而黄光和紫光表现出互补透射特性。利用紫光和黄光控制菌紫质分子在M态和基态上的分布,我们实现了对不同的波长光和选通或者关闭,即光开关模型。     

非均匀输入图像对基于细菌视紫红质膜的新事物滤波器输出特性的数值模拟

研究了基于细菌视紫红质(bR)膜的新事物滤波器的非均匀输入图像对输出图像特性的影响.与具有均匀光强分布的输入图像相比，在正弦分布的输入图像情况下，输出图像的光强分布不再呈现单调变化，而是出现两个峰值，其中间有较小的光强.bR膜的M态寿命和物体运动速度对输出图像上蓝光光强的分布有一定影响.M态寿命越大，透过的蓝光光强越小，减小的幅度是随着M态寿命的增加而减小，当M态寿命τ>50s时，减小的幅度几乎为零.在相同的入射光情况下，对于输出图像的相同位置，输入图像的运动速度越大，其输出的蓝光光强越大. 关键词： 细菌视紫红质膜 新事物滤波器 非均匀输入图像 输出特性     

细菌视紫红质膜快速光开关的实验研究

建立了“脉冲激光－连续探测光－连续擦除光”的实验系统。在532nm的调Q脉冲激发光和不同波长的连续探测光作用下，研究了细菌视紫红质（BR）膜的光循环过程中的快速响应特性及各中间态的快速光吸收特性。观察到了微秒量级的快速光开关现象，并分析了激发光脉冲作用结束时，各中间态上细菌视紫红质分子的分布。     

基于细菌视紫红质薄膜的空间光调制器实验研究

阐述了利用细菌视紫红质薄膜（BR薄膜）优良的非线性光学特性作为光寻址的空间光调制器的实验研究.BR有两个重要的光敏中间态（B态和M态），其吸收带（B态吸收峰为570nm，M态吸收峰为412nm）重叠区域较少，利用其正向（B→M）和逆向（M→B）光反应之间转化关系和B态与M态的差异吸收实现了相干光学图像到非相干光学图像的转换实验.采用经基因改性的细菌视紫红质薄膜（BRD96N）材料，使用670nm相干光作为写入光，530nm非相干光作为读出光，得到了分辨率约为200 lines/mm，对比度约为2.1∶1的 关键词： 光寻址空间光调制器 细菌视紫红质薄膜（BR薄膜） 非线性光学特性 相干光与非相干光图像相互转换     

电场作用下高分子中自陷束缚激了的极化

用同时计入电场、对称破损项ｔｅ和电子－晶格相互作用的紧束缚模型研究了电场作用下高分子中的自陷束缚激子，发现电场使高分子中自吵缚激子内电荷发生转移，出现极化，极化程度随场强增加，也与ｔｅ有关，并发现ｔｅ≤０．１ｅＶ时，双激子态表现出反向极化特性，这一特性可根据极化的量子力学化理论得到理解：对高分子的自陷束缚激子，其禁带中央附近存在两上靠得很近的定域电子态即上定域态和下定域态，用微扰论说明限上定域态是     

电场作用下紫膜中细菌视紫红质的圆二色性研究

垂直于测量光束的外电场对紫膜水悬浮液中的细菌视紫红质的圆二色性有很大影响。５０Ｈｚ正弦交流电场作用下产生５６８ｎｍ的正的差圆二色性峰，反向电脉冲串作用下产生５５６ｎｍ左右的负的差圆二色性峰，两峰峰位均未显示有随电压的变化而移动；但是，强度随外加电压的半加而增强；撤去电场后该两峰均即该消失。分析认为，电场下细菌视紫红质中存在柔性结构变化，这种结构变化也可用于存储信息。     

聚乙炔激子单线态和三线态的稳态性质与零磁场判据

在Su-Schrieffer-Heeger(SSH)模型基础上,计入弱电子关联的影响,研究聚乙炔单线态和三线态两类激子的行为.与单线态相比,三线态激子能级自旋简并丧失,能隙增大,电荷密度振荡局域分布以及自旋密度波产生,三线态激子吸收谱的相应特征峰发生~0.1 eV蓝移并且强度增加~40%.这些差异为区分两类激子提供了磁共振实验之外的判据.     

细菌视紫红质膜非线性吸收特性及其光子学应用

对细菌视紫红质膜在两束非同频光照射下的非线性吸收特性进行了详细的理论分析,并讨论了细菌视紫红质膜非线性吸收特性有光子学方面的一些新应用。     

强耦合表面激子内部激发态的性质

采用线性组合算符和幺正变换方法,研究极性晶体中强耦合表面激子内部激发态的性质.计算了表面激子的激发态能量、激发能量和平均声子数.     

Acousto-exciton interaction in a gas of 2D indirect dipolar excitons in the presence of disorder

A theory for the linear and quadratic responses of a 2D gas of indirect dipolar excitons to an external surface acoustic wave perturbation in the presence of a static random potential is considered. The theory is constructed both for high temperatures, definitely greater than the exciton gas condensation temperature, and at zero temperature by taking into account the Bose–Einstein condensation effects. The particle Green functions, the density–density correlation function, and the quadratic response function are calculated by the “cross” diagram technique. The results obtained are used to calculate the absorption of Rayleigh surface waves and the acoustic exciton gas drag by a Rayleigh wave. The damping of Bogoliubov excitations in an exciton condensate due to theirs scattering by a random potential has also been determined.     

Fluorescence resonance energy transfer: FRET studies of ligand binding to cell surface receptors

We describe a simple optical system employing fluorescence resonance energy transfer (FRET) to identify potential binding domains on the macrophage scavenger receptor for the ligand maleylated bovine serum albumin (mal-BSA). Using a plasma membrane vesicle system, we placed donor probes on the ligand and acceptor probes in the membrane to determine the distance of bound ligand from the cell surface. Two donors and three acceptors were employed. Transfer between ligand covalently modified with multiple dansyl molecules and hexadecanoylaminoeosin in the membrane yielded a distance of 46.5 ± 7.5 å; transfer from the same type of donors to octadecylrhodamine B in the membrane gave a distance of 58.5 ± 3.0 å. No transfer was observed between ligand mono-labeled with fluorescein and l,l′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanineperchlorate in the membrane. This suggests that the orientation of mal-BSA bound to the receptor places the fluorescein probe too far from the lipid surface to experience energy transfer. The distance information identifies a potential location for the binding site, which can be compared to structural information about the receptor and used to extract a binding sequence.     

应用荧光探针研究菠菜叶绿体膜对低强度电磁场的辐射敏感性

应用ANS渗入菠菜叶绿体膜后的ANS荧光光谱和光合细胞Chla荧光参数的变化研究了菠菜叶绿体膜对辐射功率密度为5 mW·cm-2以下的300 MHz低强度电磁场的辐射敏感性。研究发现,在1～5 mW·cm-2的低强度电磁场作用下,菠菜叶绿体ANS荧光光谱的位置没有明显变化,但ANS荧光强度明显增大,表明低强度电磁场使菠菜叶绿体膜流动性变小。1～5 mW·cm-2低强度电磁场的作用还使菠菜叶绿体发出的Chla荧光参数F₀减小,f_V／F₀,F_V／F_m和ΔF_V／T增大,F_VI／F_V减小,表明低强度电磁场使菠菜叶绿体膜发生了光系统Ⅱ(PSⅡ)无活性中心向有活性中心的转变,PSⅡ潜在活性提高、光合电子传递过程加快,原初光能转换效率增强。菠菜叶绿体膜ANS荧光和Chla荧光对低强度电磁场的这种辐射敏感性说明了低强度电磁场能对菠菜光合作用系统产生非热效应,并且,菠菜光合细胞有可能通过PSⅡ活性中心异质性的转变来适应电磁辐射增强的环境。     

Exciton-plasma transition in GaAs

In this work, we study the stability of excitons at high density, i.e. we calculate the reduction of the exciton binding energy due to exciton-exciton interactions in a high-density exciton gas. We derive first the effective electron-hole interaction in the presence of free carriers and excitons. We use the static approximation. The exciton binding energy is calculated by the variational technique. The computations are specialized to GaAs. We investigate the critical density when the exciton binding disappears, which corresponds to the exciton plasma transition. We conclude that this transition occurs at higher density than the reverse plasma exciton transition, determined by the standard criteria a₀q_D =1.19 [Rogers F. J., Graboske H. C., Jr. and Harword D. J., Phys. Rev.A1, 1577 (1970)].     

A Fluorescence Analysis of ANS Bound to Bovine Serum Albumin: Binding Properties Revisited by Using Energy Transfer

Determination of binding parameters such as the number of ligands and the respective binding constants require a considerable number of experiments to be performed. These involve accurate determination of either free and/or bound ligand concentration irrespective of the measurement technique applied. Then, an appropriate theoretical model is used to fit the experimental data, and to extract the binding parameters. In this work, the interaction between bovine serum albumin (BSA) and 1-anilino-8-naphthalene sulphonate (ANS) is revisited. Using steady state fluorescence spectroscopy, the binding isotherm of BSA/ANS was obtained applying the Halfman-Nishida approach. The binding parameters, site number, and binding site association constants, were determined from the stoichiometric Adair model and Job's plot. The binding parameters obtained were then correlated to the distance of the respective binding site to the tryptophan residues using the energy transfer technique. This approach, that uses both tryptophans independently from each other, is presented as a tool to help understand the binding mechanism of the albumin fluorescent complex. The results show that ANS molecules bind to BSA in up to five different binding sites. Energy transfer from the tryptophan residues to the BSA/ANS complex shows that the four highest affinity binding sites (>10(4) M(-1)) are located at a reasonably close distance (18-27 A) to at least one of two tryptophan residues, while the lowest affinity binding site (approximately 10(4) M(-1)) is located over 34 A away from the both tryptophans.     

Pressure-induced threshold optical pump intensity in a CdTe/ZnTe quantum dot

Pressure-induced binding energies of an exciton and a biexciton are studied taking into account the geometrical confinement effect in a CdTe/ZnTe quantum dot. Coulomb interaction energy is obtained using Hartree potential. The energy eigenvalue and wave functions of exciton and the biexciton are obtained using the self-consistent technique. The effective mass approximation and BenDaniel-Duke boundary conditions are used in the self-consistent calculations. The pressure-induced nonlinear optical absorption coefficients for the heavy hole exciton and the biexciton as a function of incident photon energy for CdTe/ZnTe quantum dot are investigated. The optical gain coefficient with the injection current density, in the presence of various hydrostatic pressure values, is studied in a CdTe/ZnTe spherical quantum dot. The pressure-induced threshold optical pump intensity with the dot radius is investigated. The results show that the pressure-induced electronic and optical properties strongly depend on the spatial confinement effect.     

Exciton condensation in semiconductor quantum wells with a periodical modulation of potential

The appearance and properties of a structure in the density distribution of indirect excitons in coupled quantum wells in semiconductor alloys upon periodical field modulation are studied. Calculations showed that besides periodical dependence of density distribution, caused by the potential modulation, a stratification of the exciton density shafts into separate islands in the cross direction arises. Appearance of islands is the result of exciton condensed phase formation and a nonequilibrium state of the system due to the finite exciton lifetime and pumping presence. The dependence of the structure on system parameters (the pumping value, the modulated field depth and period) is investigated. Also the influence of the exciton–exciton annihilation is taken into account.     

Polaronic exciton in quantum wells wires and nanotubes

We investigate the effect of the longitudinal-optical phonon field on the binding energies of excitons in quantum wells, well-wires and nanotubes based on ionic semiconductors. We take into account the exciton-phonon interaction by using the Aldrich-Bajaj effective potential for Wannier excitons in a polarizable medium. We extend the fractional-dimensional method developed previously for neutral and negatively charged donors to calculate the exciton binding energies in these heterostructures. In this method, the exciton wave function is taken as a product of the ground state functions of the electron polaron and hole polaron with a correlation function that depends only on the electron-hole separation. Starting from the variational principle we derive a one-dimensional differential equation, which is solved numerically by using the trigonometric sweep method. We find that the potential that takes into account polaronic effects always give rise to larger exciton binding energies than those obtained using a Coulomb potential screened by a static dielectric constant. This enhancement of the binding energy is more considerable in quantum wires and nanotubes than in quantum wells. Our results for quantum wells are in a good agreement with previous variational calculations. Also, we present novel curves of the exciton binding energies as a function of the wire and nanotubes radii for different models of the confinement potential.     

Dendrimer Interactions with Hydrophobic Fluorescent Probes and Human Serum Albumin

The interactions between three types of polyamidoamine dendrimers (with anionic, cationic, and neutral charge on a surface) and fluorescent dye 1-anilinonaphthalene-8-sulfonate (ANS) were studied. Double fluorimetric titration method was employed to estimate a binding constant and the number of binding centers. As fluorescent probes can serve as models of toxin molecules, dendrimers, and human serum albumin (HSA) abilities to bind ANS were compared. In the presence of HSA and dendrimers, ANS located both in HSA and in dendrimers, but the interactions between ANS and HSA were stronger.