脂环多硫化物香料的研究进展

脂环多硫化物是一种新型香料，具有浓郁的特征香味和良好的生物活性．为了寻找更简单高效的合成方法，推动此类香料的研究，详尽探讨了其研究现状、合成进展及生物活性。     

主链含脂环的聚酰亚胺的制备

采用酯化和催化氢化的方法合成一种含有脂环结构的新型二胺单体1,4-双(4-氨基苯甲酰氧亚甲基)环己烷,并以此单体分别与两种二酐ODPA(二苯醚四羧二酐)、PMDA(均苯四酸二酐),经两步法化学环化制得聚酰亚胺.通过红外光谱表征、热失重分析、溶解性能测试探讨其结构与性能的关系.     

以CBTDA为单体的脂环族聚酰亚胺的合成及其性能

通过Diels—Alder及[2＋2]环加成反应,合成了1,2;3,4-环丁烷-对称（3,6-氧桥-1,2,3,6-四氢苯-1,2-二甲基甲酸酐）（CBTDA）,然后与4,4’-二氨基-3,3’-二甲基二苯基甲烷（DADMDPM）、4,4’-二氨基二苯基醚（DADPE）,通过化学亚胺化和热亚胺化法合成了两种脂环族聚酰亚胺．所合成的聚酰亚胺具有较好的溶解性,高的玻璃化转变温度（Ta〉290℃）及热稳定性（分解温度Td〉490℃）,所合成的聚酰亚胺薄膜在可见光区域具有较高的透明性,介电系数在2．8～2．9．     

心肌桥模拟装置

从装置研制背景、基本要求、主要参数与指标、结构与功能以及性能评价等5个方面，介绍了心肌桥模拟装置．心肌桥模拟装置的实际使用证明，它能够在相当程度上复现心肌桥压迫壁冠状动脉，并导致血流动力学特性异常的现象，模拟实验大部分结论与临床研究和动物实验的结果相一致。     

A neuronal analogue of state-dependent learning

State-dependent learning is a phenomenon in which the retrieval of newly acquired information is possible only if the subject is in the same sensory context and physiological state as during the encoding phase. In spite of extensive behavioural and pharmacological characterization, no cellular counterpart of this phenomenon has been reported. Here we describe a neuronal analogue of state-dependent learning in which cortical neurons show an acetylcholine-dependent expression of an acetylcholine-induced functional plasticity. This was demonstrated on neurons of rat somatosensory 'barrel' cortex, whose tunings to the temporal frequency of whisker deflections were modified by cellular conditioning. Pairing whisker stimulation with acetylcholine applied iontophoretically yielded selective lasting modification of responses, the expression of which depended on the presence of exogenous acetylcholine. Administration of acetylcholine during testing revealed frequency-specific changes in response that were not expressed when tested without acetylcholine or when the muscarinic antagonist, atropine, was applied concomitantly. Our results suggest that both acquisition and recall can be controlled by the cortical release of acetylcholine.     

Autocatalytic synthesis of a tetranucleotide analogue

As an approach to the study of the kind of chemical process that might have contributed to the origin of life, attempts have been made to develop purely chemical systems in which oligonucleotides self-replicate. Although performed oligonucleotides have been shown to facilitate the formation of their complements from activated mononucleotides, only a restricted range of oligomers are efficient templates and it will clearly be difficult to find a pair of complementary oligomers each of which will facilitate the formation of the other. Many of the difficulties facing the development of a self-replicating system could be overcome by using a pair of complementary substrate molecules that condense together more easily than ribonucleotides. It would also be helpful if each substrate molecule contained equal numbers of purine and pyrimidine bases as, otherwise, there is a tendency for purines to be overrepresented in the products. We have therefore explored the chemistry of 3'-amino-3'-deoxynucleotides and their dimers. We report here that the tetranucleoside triphosphoramidate GNHpCNHpGNHpCN3 acts as a template to catalyse the condensation of GNHpCNH2 and pGNHpCN3, forming further molecules of the template. The system is therefore autocatalytic, and in accordance with elementary theory the amount of product made increases with the square root of the template concentration.     

A cellular analogue of visual cortical plasticity

Neuronal activity plays an important role in the development of the visual pathway. The modulation of synaptic transmission by temporal correlation between pre- and postsynaptic activity is one mechanism which could underly visual cortical plasticity. We report here that functional changes in single neurons of area 17, analogous to those known to take place during epigenesis of visual cortex, can be induced experimentally during the time of recording. This was done by a differential pairing procedure, during which iontophoresis was used to artificially increase the visual response for a given stimulus, and to decrease (or block) the response for a second stimulus which differed in ocularity or orientation. Long-term modifications in ocular dominance and orientation selectivity were produced in 33% and 43% of recorded cells respectively. Neuronal selectivity was nearly always displaced towards the stimulus paired with the reinforced visual response. The largest changes were obtained at the peak of the critical period in normally reared and visually deprived kittens, but changes were also observed in adults. Our findings support the role of temporal correlation between pre- and postsynaptic activity in the induction of long-lasting modifications of synaptic transmission during development, and in associative learning.     

集成模拟乘法器工作原理的一种分析方法

通用电子线路教材对模拟乘法器的工作原理未作严格的理论推导.以集成模拟乘法器XFC 1596电路原理图为例,根据电路理论,运用数学方法,建立了模拟乘法器的调试数学分析模型.该方法的提出对理论教学及模拟乘法器的调试和研究必有益处.     

数字化时代的模拟集成电路

模拟集成电路是微电子技术的核心技术之一,在国防科技、工业生产和日常生活中有着广泛应用,在数字化时代也进入了一个前所未有的发展阶段。本文概述了模拟集成电路的应用和发展趋势,并展望中国模拟集成电路的发展。     

数字化时代的模拟集成电路

模拟集成电路是微电子技术的核心技术之一,在国防科技、工业生产和日常生活中有着广泛应用,在数字化时代也进入了一个前所未有的发展阶段.本文概述了模拟集成电路的应用和发展趋势,并展望中国模拟集成电路的发展.     

Rodrigues线性积分不等式的离散模拟

Roldrigues积分不等式在泛函微分方程周期轨道的研究中有重要应用，本给出它的离散模拟，作为证明主要结果的引理，还对Pachpatte建立的一个积分不等式给出离散模拟。     

谈模拟电路的设计与实现

随着高校教学改革的进一步深入,各高校更加重视学生的素质和能力的培养,对教师的教育教学提出了更高的要求.模拟电路的设计与实现是培养高校学生综合能力的一个重要手段,在教学实践中要重视这一教学过程.因此提出模拟电路设计的步骤和方法,对设计题目的设定、单元电路的设计、元件的选取分别进行讨论,同时介绍电路的实现途径,以及如何对电路设计过程进行总结与考核.