用四氨基铝酞菁共振光散射技术测定纳克级核酸

痕量核酸对四氨基铝酞菁的共振散射光产生增强作用,且增强程度与核酸浓度之间有良好的线性关系.据此建立了测定核酸的高灵敏共振散射光增强分析方法.在pH=6.0、最大散射波长400nm处,测定小牛胸腺DNA(CTDNA)、鲑鱼精子DNA(SMDNA)和酵母RNA(YeastRNA)的线性范围分别是0～250ng/mL,0～200ng/mL和0～400ng/mL,检测限分别为1.4ng/mL,1.4ng/mL和2.7ng/mL.该法简单,灵敏度高,用于实际样品中核酸含量的测定,所得结果与紫外吸收法一致.     

Calculation of scanning tunnelling microscopy images for Kr/graphite system

The scanning-tunnelling-microscopy (STM) images of Kr atoms adsorbed on a monolayer graphite sheet (Kr/graphite system) are calculated using the first-principle total-energy electronic structure calculations within the density functional theory in the local density approximation. The results obtained agree well with the observations. It is found that the optimal site of the adsorbed Kr atom is at the top of the centre of the carbon hexagon, and its equilibrium distance from monolayer graphite surface is about 0.335nm. It is shown that the hybridization of C 2p electronic states (π-electronic states) and Kr 4p and 5s electronic states is the main origin of the Fermi-level local density of state.     

D-D结合型金刚石聚晶的高压合成研究

 为了探索功能金刚石聚晶的高压合成，使其具有优异的透红外和散热性能，我们采取了提高合成压力、温度和尽量减少结合剂的办法进行试验。首先探索如何使合成的金刚石聚晶具有D-D型结合，然后尽量减少结合剂，以合成出高密度的D-D型金刚石聚晶。为了尽量减少结合剂含量，不用粉末混合法，而是分别采用7~14 μm和63~80 μm粒度的金刚石为原料，与纯Ni或Ni₇₀Mn₂₅Co₅合金为基底积层组装，通过高温高压下触媒金属向金刚石晶粒间渗透进行烧结生长。在6.3 GPa的压力和1 440~1 650 ℃的不同温度下分别保持3~40 min。所得到的金刚石聚晶在触媒金属渗透得充分的区域形成了D-D结合型结构，而没有发现碳化物生成及金刚石表面石墨化等现象。     

天然Alboatisin电子结构和圆二色谱的密度泛函理论研究

采用蒙特卡罗MMFF94分子力学力场方法搜索一类新发现的生物活性分子Alboatisin A～C的稳定构象,用梯度校正的B3LYP方法,计算其稳定构象的旋光度、振动圆二色谱(VCD)、电子圆二色谱(ECD)等光学活性,并从微观的角度对VCD谱和ECD谱中强或弱的正或负康登效应进行归属．从分子结构、电子结构和分子振动分析了分子手性的微观起源．结果表明,计算与实验的旋光度值相吻合,OH的取代位置与数目可调控旋光度发生在手性骨架上的振动或电子跃迁转移是手性光谱产生的重要原因．Alboatisin的圆二色谱是手性骨架变形振动的光谱响应,是不对称电子跃迁的光谱响应结果．     

THE EXCESS HEAT EXPERIMENTS ON COLD FUSION IN TITANIUM LATTICE

ＴＨＥ　ＥＸＣＥＳＳ　ＨＥＡＴ　ＥＸＰＥＲＩＭＥＮＴＳ　ＯＮ　ＣＯＬＤ　ＦＵＳＩＯＮ　ＩＮ　ＴＩＴＡＮＩＵＭ　ＬＡＴＴＩＣＥＴＨＥＥＸＣＥＳＳＨＥＡＴＥＸＰＥＲＩＭＥＮＴＳＯＮＣＯＬＤＦＵＳＩＯＮＩＮＴＩＴＡＮＩＵＭＬＡＴＴＩＣＥ￥ＺｈａｎｇＱｉｎｇ...     

Electron spectrometry study of associative and penning ionization in laser excited sodium vapor

The first observation, by electron spectrometry, is reported in laser-excited sodium vapor of the primary low energy electrons produced by associative ionization and by Penning ionization of sodium atoms in highly excited n1 states. The sequential heating of these primary electrons has been observed in 1, 2 or 3 superelastic collisions with Na(3p) atoms. The variation of associative ionization was measured as a function of the excited state density by using inner-shell photoionization produced by synchrotron radiation. Finally, an associative ionization cross section of 3.8 X 10^-17 cm² and a Penning ionization cross section for the 5s state of 1.1 X 10^-12 cm² were found (within 50% uncertainty) for an oven temperature of 520 K.     

The structures of physisorbed and chemisorbed formic acid on Si(1 1 1)-7 × 7

The reaction of formic acid on Si(1 1 1)-7 × 7 was investigated using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and high-resolution electron energy loss spectroscopy (HREELS). The hydroxyl and carbonyl O 1s core levels of chemisorbed formic acid display chemical shifts of 2.4 and 0.2 eV respectively, compared with those of physisorbed molecules. The HREELS spectra of chemisorbed formic acid show the absence of stretching and bending modes of the O-H bond, the appearance of Si-H (2089 cm⁻¹) and the Si-O (680 cm⁻¹) stretching modes and the retained stretching mode of CO at 1703 cm⁻¹. Our results clearly suggest that formic acid dissociates to form monodentate formate species and H-atom on the adatom-rest atom pair of Si(1 1 1)-7 × 7.     

碳团簇型微波隐身功能材料的研究

本文简要报道了制备温度，试样厚度，材料层数和掺杂等因素对碳团簇型功能材料的微波身性能影响的实验结果。     

带轴向引导磁场自由电子激光的工作参数选择

利用电子能量守恒定律、轨道稳定性条件和静电模稳定性条件,给出了能使轴向引导磁场对增益起放大作用的自由电子激光器件的参数取值范围。     

Synthesis and pyrolysis of a novel preceramic polymer PZMS from PMS to fabricate high‐temperature‐resistant ZrC/SiC ceramic composite

As a valuable ultra‐high‐temperature ceramic (UHTC), ZrC was introduced to SiC ceramic for the preparation of high‐temperature‐resistant ZrC/SiC composite by a polymer‐derived method through the reaction between Cp₂Zr(CH=CH₂)₂ and polymethylsilane (PMS). The composition, structure, element distribution and pyrolysis process of the preceramic polymer polyzirconomethylsilane (PZMS) were investigated by nuclear magnetic resonance, infrared, gel permeation chromatography, X‐ray photoelectron spectroscopy, energy‐dispersive X‐ray spectroscopy, scanning electron microscopy and thermogravimetric analysis. The obtained ZrC/SiC ceramic composites had very good high‐temperature resistance with a weight loss of 7.1% after being subjected to temperatures ranging from 1200 to 2200°C, as the introduction of ZrC prevented the fast growth of crystalline β‐SiC. The ceramic composites prepared by this method were homogeneous with well‐distributed element components, and the ceramic yield reached as high as 78.4%. Copyright © 2013 John Wiley & Sons, Ltd.