Comparative and statistical analysis of nAChR sequences: An <Emphasis Type="Italic">ab initio</Emphasis> approach to the origin of molecular discrimination

Compared with traditional structure-based approaches for the identification of species-specific ligands, the ab initio approach, based on large-scale protein sequences from different species, has been used to locate specific sites that may be important to the molecular selectivity of species. Statistically significant differences in the distribution of residues in different species and differences in the physicochemical properties of residue-specific sites may largely account for species selectivity. The nicotinic acetylcholine receptor (nAChR), an important neuro-receptor with significantly different ligand selectivity in different species, was used to test our method. Because of the lack of nAChR structural information, the mechanism of ligand discrimination is unclear which hinders attempts at novel molecular design. In this study, the specific site residues 186 and 189 in the principal subunits and residues 34, 55, 56, 57, 106 and 112 in complementary subunits of nAChR were identified by applying our method with stringent statistical cutoffs. These sites were predicted to contribute to ligand selectivity and this result coincides well with the known experimental data.     

卡托普利和肾切除对肾性高血压大鼠左室心肌MHC基因转录变化的影响

用二肾一夹（２ＫＩＣ）肾性高血压大鼠模型，探讨心肌肥厚发生和逆转以及肌球蛋白重链（ｍｙｏｓｉｎｈｅａｖｙｃｈａｉｎ，ＭＨＣ）基因表达的改变。结果表明：１）２ＫＩＣ肾性高血压大鼠术后第２～１２周，动脉血压持续升高、左室重量／体重（ＬＶＷ／ＢＷ）明显升高、左心室α－ＭＨＣ基因表达明显减弱、β－ＭＨＣ基因表达明显增强；２）在术后第４周给予血管紧张素转换酶抑制剂卡托普利和术后第８周切除肾动脉狭窄侧肾脏可使２ＫＩＣ肾性高血压大鼠动脉血压下降、左心室肥厚发生逆转、抑制左心室α－ＭＨＣ基因表达减弱和β－ＮＨＣ基因表达增强。这些结果提示在２Ｋ１Ｃ肾性高血压中，动脉血压升高是左心室肥厚、左心室肌球蛋白ＭＨＣ基因表型转换的重要因素；肾素———血管紧张素系统可能参与２ＫＩＣ肾性高血压过程中的心肌肥厚和ＭＨＣ基因表型的转移。     

数字信号处理CAI系统——采样定理与卷积

介绍数字信号处理ＣＡＩ系统中的采样定理和卷积部分，课件用文字说明及动态图形的方式演示时域、频域的采样和内插恢复，以及卷积的全过程，课件可用于课堂演示和实验教学。     

清洁Nb（100）面的结构

采用低能电子衍射(LEED)动力学计算法,计算了Nb(100)面的各种弛豫结构的Ⅰ—Ⅴ曲线,使之与实验曲线拟合,用R 因子对这些可能的结构进行搜寻和分析.结果表明清洁Nb(100)面最顶层层间距为1.46(?),与体内相比向内收缩了11%,次层层间距为1.72(?),向外膨胀了5%,与清洁的Ta(100)面的结构相似.     

微机化流动时库仑分析仪及其应用

流动时库仑分析法克服了电容电流及电极表面性质改变等噪声干扰。10 s内完成一次测定点。在“海水中溶解氧测定仪”的基础上,改为通用型仪器,使之微机化,进行数理统计处理,仪器的可靠性、再现性及灵敏度得到进一步提高,可测0.01 mg/l浓度,相应偏差±0.5～1.0％,进行了水中 Cr~(6+)、Cu~(2+)、O_2、Br~- 等测定,获得良好效果。     

我国轿车工业面临的若干选择

本文参考了世界各国轿车工业发展的经验，在分析我国轿车工业现状的基础上，对我国轿车工业所面临的若干选择作了探索性的研究。     

连铸机结晶器振动机构动力学

本文以某钢厂连铸机结晶器振动机构为研究对象,通过建立集中参数混合系统动力学分析模型,采用QR方法对系统模态参数—固有频率及振型作了数值求解计算,并采用系统仿真方法计算了机构的振动响应。为确保分析结果的准确性,利用有限元结构分析程序SAP6,通过建立机构动力有限元模型,对系统的模态参数作了进一步的分析计算。本文分析计算结果将为某钢厂现有连铸机结晶器振动频率的提高及设计新的高频振动机构提供重要依据。     

模拟熔喷纤网的孔径分布及其对过滤性能的影响

首先根据纤维过滤介质的理论假设,对分布密度不同的熔喷纤网进行计算机模拟,然后利用图像分析方法,计算了其孔径大小及其分布并与实际情况对比;在模拟纤网基础上又从理论上计算了占全部孔数10％的大孔对过滤性能产生的影响,并发现经过这10％大孔的流量比例与当量孔径标准差成线性增加的关系。     

Tax Evasion: Models with Self-Audit

Different from traditional tax audit, supervision with self-audit is a combination of audit by the taxpayer himself and audit by the tax authority. This paper mainly studies a taxpayer＇s optimal policy of tax evasion under supervision with self-audit and its related properties, in order to deduce some effective suggestions and theoretical bases to restrain tax evasion. Assuming that only a certain proportion of evaded tax can be discovered when the audit is executed, the authors first formulate a static model with self-audit. This model is divided into two stages. At the first stage, taxpayers declare their taxes, then the tax authority chooses audit objects, based on a known probability, and announces the result; if the taxpayer is chosen, he will enter the second stage, during which he has a chance to pay the evaded tax and the corresponding late fees and then is audited by the tax authority. The authors show the existence and uniqueness of the optimal amount of tax evasion at the first stage and the optimal proportion to self-expose at the second stage. The authors also discuss the related properties of the interior solution, and do elasticity analyses on some parameters. Besides, the authors extend the static model into the corresponding two-period model, and study the existence and uniqueness of the solution of the extended model. Finally, under the assumption that tax evasion can only be discovered with a certain probability when the audit is executed, the authors formulate another static model with self-audit and investigate its properties.     

一个多媒介数据库系统原型

本文从应用的角度提出一个多媒介数据库系统的功能设计原型。文章首先对经典的面向对象的方法进行了扩充使之适应于多媒介信息系统环境的要求。在此基础上,针对很大一类应用环境定义了一组内容寻址的基本模式和一组施于对象的基本操作,并设计了一个肖像型的视觉化用户接口。