Long-lifetime metal-ligand complexes as luminescent probes for DNA

We examined the intensity and anisotropy decays of DNA labeled with two ruthenium metalligand complexes, [Ru(bpy)₂(dppz)]²⁺ and [Ru(phe)₂(dppz)]²⁺. Both complexes display high emission anisotropies in the absence of rotational diffusion, making them suitable probes for rotational motions. When bound to DNA, these complexes display decay times as long as 294 ns, providing long-lived probes of DNA dynamics. The decay times of both complexes were rather insensitive to dissolved oxygen. We examined anisotropy decays of these complexes bound to B-form DNA. The anisotropy decays revealed correlation times near 10, 50, and several hundred nanoseconds, suggesting that these probes are sensitive to a wide range of DNA motions. The use of metalligand complexes should allow resolution of both the torsional and bending motions of DNA, the latter of which has been mostly inaccessible using shorter-lived fluorescent probes bound to DNA. Dedicated to Professor Robert F. Steiner upon his retirement     

Polarized He neutron spin filter program at the JCNS

Polarized neutron instruments will occupy about 80% of the Jülich Centre for Neutron Science (JCNS) instrument park. A successful polarized ³He program will be integral to many of these instruments. We have been focusing the developments on spin-exchange optical pumping (SEOP) to polarize the ³He gas in situ. Where possible, in situ polarization using the SEOP method will provide higher time averaged performance of the instruments. Further this allows a custom-built and independent source of polarized ³He to be developed optimized for each instruments demands. In this paper we will: present an argument for the advantages of in situ polarization; describe an in situ polarizer we have constructed, and initial tests of its performance; describe testing of polarization analysis for small angle neutron scattering on biological samples, and our plans for an in situ polarizer for this application.     

Energy transfer from a polymer host to a europium complex in light-emitting diodes

Energy transfer leading to electroluminescence of a lanthanide complex, Eu(Fod)₃MK (Fod=heptafluoro-dimethyl-octanedionate, MK=4, 4′-bis(N,N-dimethylaminobenzophenone) doped into PVK host is investigated. The optical properties of pure Eu(Fod)₃MK and its doping in PVK show that the PVK host can efficiently transfer energy to europium ions through a co-ligand of MK due to good spectrally overlap. Light-emitting diodes (LED) consisting of PVK doped with 1-5 wt% of Eu(Fod)₃MK also demonstrates this energy transfer. Organolanthanide complexes doped into a wide-gap conducting polymers would lead to efficient and pure red organic LEDs to solve the full colour conjugated polymer displays.     

Polarized neutron imaging: A spin-echo approach

Polarized neutron imaging has recently been introduced as an efficient method to three-dimensionally visualize and measure magnetic fields even in the bulk of massive objects. Here we introduce a spin-echo approach for polarized neutron imaging, which has the potential to overcome some drawbacks of the first attempts, namely to deal with strong fields, arbitrary field directions and quantification. Furthermore our novel approach increases the efficiency of quantitative studies due to relaxed monochromatisation requirements for spin-echo neutron imaging and with respect to additional information available in the recorded images, which allows for straightforward quantification in many cases.     

Polarized radiation transfer in finite binary Markovian random media

The problem of polarized radiation transfer in a finite plane-parallel binary Markovian random medium is studied. Pomraning-Eddington approximation is used for both the total intensity and the difference function of the polarized radiation. The formalism obtained by Levermore et al. and Pomraning is used to average the obtained solution in the deterministic case. The random medium is assumed to have specular-reflecting boundaries with angular-dependent externally incident flux. Numerical results of the average reflectivity and the average transmissivity are calculated for the different degrees of polarization.     

Polarized Laser Raman Spectra of the Crystal Cs3UO2F3

Abstract

Polarized Raman spectra of Cs₃UO₂F₅ in which the UO₂F₅ ^3? ion is in its statistical position have made it possible to assign definitely the Raman fundamental vibration modes as follows : v₁(A′¹) = 784, v₂(A′¹) = 423, v₈(E′²) = 325, v₈(E′²) = 219 and v₁₀(E″¹) = 259 cm^?1.     

偏振光在多层散射介质中传输的蒙特卡罗模拟研究*

基于米氏散射理论,运用斯托克斯-穆勒形式,结合子午面法和拒绝法,提出了偏振光在多层散射介质中传输的蒙特卡罗模型,并首次分析了当菲涅耳公式失效时,多层介质界面处的全反射行为.同时用该模型研究了微粒直径和介质折射率对漫反射和漫透射的影响.结果表明：无论是折射率匹配介质还是非匹配介质,当粒子浓度一致时,漫反射率都随微粒直径的增加而增加,随介质折射率的增加而减小,而漫透射率则相反.研究结果为生物组织的偏振光散射研究提供了理论验证模型.     

Quasi-simultaneous ultraviolet and infrared emission from a plasma cathode TEA laser

Quasi-simultaneous laser action in the UV (0.337 μm) and the IR (10.6 μm) was observed from a pulsed laser with a sliding discharge plasma cathode. The laser operates at atmospheric pressure, with a gas mixture of CO₂/N₂/He, at a 0.26/0.50/4.0 lmin⁻¹ flow rate. Output energies of 30 mJ in the IR and 0.35 mJ in the UV were obtained, from a laser discharge volume of 38.0×1.0×2.8 cm³. The optimum gas mixtures have been determined and the temporal behavior of the discharge parameters, the performance characteristics of the laser and the beam spatial distributions were investigated.     

偏振光在多层散射介质中传输的蒙特卡罗模拟研究

基于米氏散射理论,运用斯托克斯-穆勒形式,结合子午面法和拒绝法,提出了偏振光在多层散射介质中传输的蒙特卡罗模型,并首次分析了当菲涅耳公式失效时,多层介质界面处的全反射行为.同时用该模型研究了微粒直径和介质折射率对漫反射和漫透射的影响.结果表明:无论是折射率匹配介质还是非匹配介质,当粒子浓度一致时,漫反射率都随微粒直径的增加而增加,随介质折射率的增加而减小,而漫透射率则相反.研究结果为生物组织的偏振光散射研究提供了理论验证模型.     

偏振全息光栅衍射光场的理论分析

利用介质的光致各向异性和可记录偏振全息光栅,从偏振全息的透射琼斯矩阵出发,运用傅里叶展开法,对记录光不同的偏振态组合情况下,衍射光场的可能出现的衍射级次及其偏振特性进行了理论分析.并以甲基橙掺杂聚乙烯醇膜为例,对各阶衍射光的衍射效率进行了理论计算.     

用偏光织构及透射光谱分析液晶器件的老化

对一组台式计算器液晶显示器进行了光辐照,研究了光辐照对液晶显示器件显示品质的影响。采用偏光显微镜观察到了辐照后液晶的偏光织构的变化,液晶中出现了平行的条纹状织构和失去消光作用的黑洞,随着接受光辐照时间的增加,黑洞数量越来越多,面积越来越大。通过由计算机控制的双光束紫外-可见分光光度计测试了透射光谱的变化,发现其透射率随着接受光辐照时间的增加而降低。分析结果表明,条纹状织构和黑洞的出现是由于液晶分子结构在紫外线的照射下发生了变化所致,失去消光作用的黑洞是导致液晶器件透射率持续下降的主要原因。     

星载多角度偏振成像仪偏振辐射测量的理论误差分析

星载多角度偏振成像仪可以获取目标的多角度偏振辐射信息,探测精度是重要的技术指标。为研究仪器的测量精度及相关的误差因素,以Stokes-Mueller为数学描述方法,分析仪器的原理和光路结构特点,从理论上推导了仪器的偏振辐射测量模型,并通过实验初步验证了镜头Mueller模型的正确性。在考虑目标光各种偏振态的情况下,分析了非理想光学器件重要参数对目标光偏振度测量结果的影响,得到了偏振度测量误差与通道相对透射率、空间高频相对透射率/响应率、线偏振片振透轴方位角、镜头线性双向衰减这四种参数偏差之间的关系。按照仪器探测精度要求,结合各参数偏差对应误差最敏感的目标光偏振态,从理论上提出了各重要参数的误差容限。该研究为整个仪器的研制、定标及后期数据处理提供了理论依据。     

偏振全息光栅衍射光场的理论分析

利用介质的光致各向异性和可记录偏振全息光栅,从偏振全息的透射琼斯矩阵出发,运用傅里叶展开法,对记录光不同的偏振态组合情况下,衍射光场的可能出现的衍射级次及其偏振特性进行了理论分析.并以甲基橙掺杂聚乙烯醇膜为例,对各阶衍射光的衍射效率进行了理论计算.     

复合阴极材料发射特性分析

 基于对爆炸发射点火机制的分析,提出了介质增强场致爆炸发射的设想,研制并实验研究了金属-介质复合阴极的电子发射特性;同时,基于对表面闪络爆炸发射机制的分析,研制出了石墨-碳纤维复合阴极并进行了初步实验研究。研究结果表明,金属-介质复合阴极与石墨 碳纤维复合阴极电子发射密度均超过17 kA/cm²,使用寿命预计超过10⁵次。     

傅里叶变换红外偏振光谱在涤纶工业丝结构表征中的应用

应用傅里叶变换红外偏振光谱对涤纶工业丝样品的反式构象含量、非晶取向、整体取向等结构参数进行了表征，对制备涤纶工业丝各阶段中结构变化规律进行了初步探索。     

牛奶水溶液的偏振三维荧光光谱研究

测得由伊利、蒙牛公司生产的纯牛奶、高钙奶、高钙低脂奶的偏振三维荧光光谱,发现在激发偏振片和发射偏振片取向平行时,偏振荧光强度高于取向垂直时的值。通过一个简单的模型估算了各种牛奶样品等效荧光团的激发偶极子和发射偶极子之间的夹角,均小于40°,且高钙低脂奶对应荧光团激发偶极子和发射偶极子之间的夹角略小于纯牛奶和高钙奶。实验还发现,在激发偏振片和发射偏振片取向平行时,高钙低脂奶的偏振荧光强度明显高于纯牛奶和高钙奶,与理论计算相符。     

氧化锌纳米棒场发射性能研究

采用简单物理气相沉积法制备出取向和非取向的氧化锌纳米棒，他们的场致电子发射性能测量结果表明，ZnO纳米棒具有较好的场发射性能，但是高度取向的ZnO纳米棒阵列并不利于获得高的场致电子发射电流密度.这可能是由于高密度ZnO纳米棒之间具有较高的屏蔽效应，降低了ZnO纳米棒阵列的场放大因子，从而影响了其场发射性能.相反，非取向ZnO纳米棒由于相互之间的屏蔽效应比较弱，而且表面存在容易成为发射中心的微小突起，表现出较好的场发射效果.这些结果不仅有助于加深我们对准一维纳米材料场致电子发射性能的理解，也为未来场发射电子器件的实际应用提供了可靠的依据. 关键词： 氧化锌 场发射 非取向