Instrumental requirements for the detection of electron beam-induced object excitations at the single atom level in high-resolution transmission electron microscopy

This contribution touches on essential requirements for instrument stability and resolution that allows operating advanced electron microscopes at the edge to technological capabilities. They enable the detection of single atoms and their dynamic behavior on a length scale of picometers in real time. It is understood that the observed atom dynamic is intimately linked to the relaxation and thermalization of electron beam-induced sample excitation. Resulting contrast fluctuations are beam current dependent and largely contribute to a contrast mismatch between experiments and theory if not considered. If explored, they open the possibility to study functional behavior of nanocrystals and single molecules at the atomic level in real time.     

Pretreatment of garlic powder using sweep frequency ultrasound and single frequency countercurrent ultrasound: Optimization and comparison for ACE inhibitory activities

The sweep frequency ultrasound (SFU) and single frequency countercurrent ultrasound (SFCU) pretreatments were modeled and compared based on production of angiotensin I-converting enzyme (ACE) inhibitory peptides from garlic hydrolysates. Two mathematical models were developed to show the effect of each variable and their combinatorial interactions on ACE inhibitory activity. The optimum levels of the parameters in SFU were determined using uniform design, which revealed these as follows: total ultrasonic time 1.5 h, on-time of pulse 18 s and off-time of pulse 3 s. Under optimized conditions, the experimental values of SFU and SFCU were 65.88% and 67.78%, which agreed closely with the predicted values of 63.44% and 67.33%. The SFU and SFCU pretreatments both resulted in higher ACE inhibitory activity compared with untreated garlic (p < 0.05). However, there were no significant differences in the ACE inhibitory activities and IC₅₀ values obtained from SFCU and SFU pretreatments under optimum conditions (p > 0.05).     

Analysis of plant genomic DNAs and the genetic relationship among plants by using surface-enhanced Raman spectroscopy

The study aimed to distinguish genomic DNAs from nine species of plants belonging to six families and analyze their genetic relationship by using surface-enhanced Raman scattering (SERS). The silver nano-colloid and excitation wavelength of 785 nm used in this study yielded excellent quality of the SERS spectra. Raman signals were remarkably enhanced. Although the spectra for the nine species of plants appeared very similar, there were significant differences according to the analysis of variance analysis. There were three strong characteristic peaks. The peak at 625 cm⁻¹ was due to the vibration overlap of C3′-endo/anti deoxyribose, cytosine, and guanine; the one at 715 cm⁻¹ was due to the scissoring vibrations of C2N1C6 of adenine; and that at 1011 cm⁻¹ was due to the stretching vibration of the CO bond of deoxyribose and vibrations of cytosine. The SERS data were smoothed and standardized and evaluated using second derivative analysis, principal component analysis, and hierarchical cluster analysis. A model was established using the data from hierarchical cluster analysis and principal components of the second derivative. The clustering result of this model was highly consistent with the traditional classification of plants; all plant species investigated were correctly clustered into classes according to the cluster distance coefficient among them; the accuracy of clustering was 100%. Chinese cabbage (Brassica pekinensis Rupr.) and green cabbage (Brassica chinensis L.) belonging to Cruciferae, maize (Zea mays L.) and bamboo (Sinocalamus affinis McClure) belonging to Gramineae, and magnolia (Magnolia delavayi Franch.) and champaca (Michelia alba DC.) belonging to Magnoliaceae were clustered into three separate classes, and fern (Nephrolepis auriculata L., Nephrolepidaceae), garlic (Allium sativum L., Amaryllidaceae), and ginkgo (Ginkgo biloba L., Ginkgoaceae) were each clustered into separate classes. These findings suggest that the SERS spectra of plant genomic DNAs can be used to classify species and analyze their genetic relationship. It is an effective and perfect supplement to traditional classification and can form the basis for genetic analysis.     

单重工作休假M/M/c排队驱动的流体模型分析

该文在M/M/c排队驱动系统中加入工作休假策略,研究了单重工作休假多服务台排队驱动的流体模型.利用拟生灭过程和矩阵几何解法得到驱动系统稳态队长分布.构建净输入率结构,导出流体模型的稳态联合分布函数满足的的矩阵微分方程组,进而利用Laplace-Stieltjes变换(LST)方法得到稳态下缓冲器库存量的空库概率及均值表...     

光斜入射时偏振器作用的表述

对偏振器特性的分析表明,当光斜入射时,振动方向与偏振器透光轴不平行的光也能通过偏振器,只要该方向与系统光轴与透光轴构成的平面平行。提出了透光平面的概念。利用欧拉角表示光波坐标系和偏振器坐标系之间的变换,得到透过偏振器后偏振光的振动方向及其大小的数学表述,给出了简化表达式及其使用条件。表达式具有一般性,可以直接使用。     

Multiple bright and dark soliton solutions in three component spinor Bose-Einstein condensates

We investigate a quasi one dimensional spin-1 Bose-Einstein Condensates (BEC) in the absence of an external confinement governed by a system of three coupled Gross-Pitaevskii (GP) equation. Based on the Lax-pair, we construct one soliton solution employing gauge transformation method. In addition, the multiple bright and dark soliton solutions are obtained by properly choosing amplitude dependent parameter in the Lax-pair. The results of the paper emphasizes the richness in the structure of soliton solutions admitted by the spin components, a phenomenon which has never been brought out to the fore. We have also extended the gauge transformation method to generate two soliton solutions.     

正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法, 在这个方法中,正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上,且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面,计算结果和实验数据很好的符合.     

单链和寡链等规聚苯乙烯聚集体的结晶行为

自1960年Hoffman等提出聚合物结晶成核理论以来,人们对聚合物结晶生长速率、片晶的侧向尺寸随过冷度的变化等现象成功地进行了理论描述．1997年,Hoffman等对聚合物结晶成核理论进行修正,将de Gennes的聚合物“蛇行”概念。引入表面成核理论,通过对单根分子链从过冷熔体“卷绕”到晶体前沿所需的时间进行估算,其结果远远低于Flory预言时间约3～5个数量级,据此,Hoff-man认为,在聚合物结晶过程中,分子链在强迫稳态下的“蛇行”运动有足够的时间解缠结和结晶。     

Das Pyren und der Einfluß von Substitution oder Komplexie-rung auf seine Geometrie und Packung im kristallinen Zustand

The crystal structures of pyrene and substituted and complexed derivatives of pyrene have been investigated by X-ray and neutron diffraction. The geometry of the pyrene skeleton has been determined experimentally with high accuracy and calculated by quantum chemical methods. In the cases reported in the literature and cited here the pyrene skeleton has the molecular symmetry mmm or mm2 with values for the bond lengths of the six symmetrically independent bondsa, b, c, d, e, f differing significantly in the limits of error. Mean values of a number of experimental and theoretical bond lengths are given and can be considered as standard values for the mm2 symmetric pyrene skeleton. In the case of substitution of the pyrene in 3-position with a polar heterocyclic molecule of the azomethine-imine type the mm2 symmetry vanishes, a C–H ... N intramolecular hydrogen bond arises and the directly neighbouring pyrene units are not packed parallel with their planes to each other, but they are considerably tilted. Relatively narrow intermolekular C-C contacts, 3.314 and 3.368 Å, have been observed. The conclusion is drawn that the asymmetry of the pyrene molecule and a tilt of directly neighbouring pyrene units in the crystal packing can be induced by substitution e. g. with suitable polar heterocycles.

Juli 1985.     

钙调蛋白抑制剂预测模型研究

选用30个结构多样的caM抑制剂分子作为数据集,采用多元线性回归(MLR)方法及主成分回归分析(PCA)方法对每个化合物的194个分子参数进行回归分析,分别建立了各自的最优预测模型.结果表明:多元线性回归分析方法所建模型与主成分回归所建模型相对比,发现逐步筛选法为最优建模方法?该方法所建模型统计结果良好(R2=0.952,SEE为0.289),应用于检验集时结果也比较令人满意(R2=0.941,SEP为0.295),模型表现出较强的可靠性和预测性.