电池正极材料中Li~+运动特性的~7Li NMR研究

利用变温７ＬｉＮＭＲ实验对Ｌｉ电池正极材料ＬｉＭｎ２Ｏ４和ＬｉＣｏＯ２中Ｌｉ＋的运动特性进行了研究，结果表明，随实验温度的提高，ＬｉＭｎ２Ｏ４的７ＬｉＮＭＲ谱线窄化，表明其中Ｌｉ＋迁移能力增加，而ＬｉＣｏＯ２的谱线无变化．此外随温度提高，ＬｉＭｎ２Ｏ４的７Ｌｉ的Ｔ１变短，而ＬｉＣｏＯ２的Ｔ１变长，产生这种不同变化趋势的原因在于ＬｉＭｎ２Ｏ４和ＬｉＣｏＯ２晶相结构的差异造成其中Ｌｉ＋迁移能力的差别，它们各自的相关时间τｃ使７Ｌｉ核的Ｔ１分别位于Ｔ１－τｃ曲线极小点两侧     

氨基酸共聚物修饰的生物相容性MRI造影剂

通过天门冬氨酸(Asp)、异亮氨酸(Ile)热缩聚反应,制备了天门冬氨酸-异亮氨酸共聚物(AI),通过乙二胺(EDA)胺化,并与1,4,7,10-四氮杂环十二烷-1,4,7,10-四羧酸(DOTA)连接,再与钆离子(Gd3+)络合,合成了生物相容性大分子磁共振成像(MRI)造影剂——AI-EDA-DOTA-Gd.运用红外光谱(IR)、核磁共振(NMR)、电感耦合等离子谱(ICP)等方法对其进行结构表征,并通过弛豫性能、溶血性质、急性毒性及动物体内成像对其进行综合评价.体外弛豫结果表明,AI-EDA-DOTA-Gd的纵向弛豫效率(r_1=12.6mmol~(–1)×L×s~(–1))是商用造影剂Gd-DOTA(r_1=5.8 mmol~(–1)×L×s~(–1))的2.2倍.动物组织生理切片和溶血性实验结果说明其具有良好的生物相容性和较低的毒性.动物体内成像结果显示,AI-EDA-DOTA-Gd的最佳成像时间为30~70 min,注射AI-EDA-DOTA-Gd后的肝脏组织信号相比于未注射造影剂时增强了约(55.1±5.7)%.     

超声造影剂研究进展

本文综述超声造影剂的现状及新进展，在简要介绍造影剂物理原理的基础上，对超声造影剂在医学超声领域尤其是低速血流测量与组织灌注成像中的应用进行了总结与讨论，并介绍了用于实验研究和第二期临床试验的国际上最新的超声造影剂的特点，制备技术与评价方法。     

ESR方法研究高TC氧化物的超导电性

用电子顺磁共振方法研究了一些高温超导氧化物样品的零场非共振吸收信号和正常的ＥＳＲ共振信号。认为这种方法可以作为鉴别样品进入超导态的实验判据之一。利用零场非共振吸收实验给出的下临界磁场Ｈｃ１（Ｔ）很好地遵多Ｈｃ１（Ｔ）＝Ｈｃ１（０）（１－Ｔ＆＾２／Ｔｃ＾２）。     

基于调频信号发射的超声造影剂谐波成像方法

提出了一种能够提取超声造影剂回波中二次谐波的非线性成像方法,从数学原理、仿真计算和声学实验三个方面对造影剂血流灌注成像方法进行了研究。首次将调频信号发射技术用于医学超声造影剂谐波成像领域,仿真计算和声学实验结果表明:为了获得较好的图像质量,发射调频信号应该具有合适的包络;发射信号带宽与解码匹配滤波器带宽之间必须有一个带宽间隔;适当降低发射声压能够降低生物组织的谐波。应用编码发射方法和解码滤波器,得到了造影剂二次谐波图像,此图像具有较好的信号噪声比和造影剂组织比。声学实验结果和理论计算结果完全吻合。     

DTPA双芳酰胺钆配合物作为肝胆磁共振成象造影剂

对三种DTPA双芳酰胺钆配合物用作肝胆磁共振成象造影剂进行了研究.配合物的亲脂性通过正辛醇-水分配比进行表征,结果表明实验值与理论值有很好的线性关系.蛋白结合实验表明亲脂性较强的配合物具有较强的蛋白结合能力.家兔的活体磁共振成象表明,将芳香环引入配合物中可以实现肝细胞对配合物的特异性摄取.     

Eu（TTA）3.2H2O的分子内能量转移机制及其中心离子Eu（Ⅲ）的发？…

利用时间分辨光谱，讨论了铕与噻吩甲酰三氟丙酮（ＴＴＡ）配合物Ｅｕ（ＴＴＡ）３．２Ｈ２Ｏ分子同能量转移机制，结果表明分子内能量转移途径主要为Ｔ１→＾５Ｄ１→＾５Ｄ０，即＾５Ｄ１作为传能的中间能级，讨论了并提出了中心离子Ｅｕ（Ⅲ）的发光动力学方程，且与实验结果相自洽。     

生物激活磁共振成像造影剂的研究进展

介绍了磁共振成像新一代造影剂--生物激活造影剂（亦称之为“酶激活”、“生物应答”或“智能型”造影剂）的研究进展.主要讲述了这类造影剂的设计原理、性能与作用. 它们主要分别对生物体内的酶、金属离子浓度、pH等敏感.     

T1系超导体中T1含量的控制

Ｔ１－２２２３和Ｔ１－２２１２相超导样品经Ｔｌ２Ｏ３蒸气处理超导转变温度发生明显的变化，Ｔｃ的变化来源于样品中Ｔ１含量的变化，Ｔｌ２Ｏ３蒸气能有效地阻止Ｔ１基超导体中Ｔ１的损失，随着Ｔｌ２Ｏ３蒸气压的增加Ｔ１损失明显减少，这是一种控制Ｔ１浓度的有效方法。     

对连接体间作用力问题的讨论

对连接体间作用力问题的讨论周洪颖（安徽省轻工业学校合肥２３００５１）在教学中，发现有的教师把连接体（如图１和图２）中绳子分别对两物体的拉力Ｔ１和Ｔ２说成是一对作用力和反作用力．笔者认为这种说法不妥．作用力和反作用力是指两个相互作用的物体之间发生的相互...     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.