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Search Results: 1 - 10 of 69195 matches for " 罗学才 "
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从观赏动物五爪龙的粪便中分离出三种肠道病原菌
明义,秦庆,单建青,王海燕,李生
微生物学通报 , 1991,
Abstract: 本文报道从稀有爬行动物五爪龙(Varanus salvator)的体内同时分离出三种肠道病原菌,伦敦沙门氏菌(Salmonella london)、德比沙门氏菌(S.derby)和一株类志贺邻单胞菌(Plesiomomas shigelloides)。并提出应注意经常监测各类动物的带菌状况,加强对带菌动物的管理。
模式识别法在化工调优中的应用
程兆年,汤锋潮,,张未名,陈念贻
化工学报 , 1990,
Abstract: 模式识别调优的基本出发点是,以工艺参数为特征变量构筑模式空间,按调优目标划分样本的类别.采用模式特征抽提方法压缩工艺参数,找出影响目标的主要因素.分别对两类调优问题,即最优指标问题和最优方向问题,提出了寻找最优工况的具体处理方法.对多目标调优也作了简单的讨论.
微机实理非线性映照
, 程兆年, 汤锋潮, 缪强, 陈念贻
自动化学报 , 1989,
Abstract: ?本文提出了在微机上实现非线性映照的下山法和逐步松弛法相结合的计算方法.编制了在IBM-PC机上运行的程序.双倍精度计算,最大允许样本集250个.程序结构采用积木块式,结合菜单选择,使用方便灵活.
陕西秦岭东段南坡繁殖鸟类群落组成的30年变化
赵洪峰,,侯玉宝,许长生,,王树
动物学杂志 , 2012,
Abstract: 于2008和2010年每年5~7月在秦岭东段南坡的商洛地区商南、山阳、柞水和洛南4县根据海拔和植被类型选择样点,并采用样线法和网捕法相结合的方法对繁殖鸟类群落进行了调查。共观察记述鸟类159种,农田和栽培植物带(215~650m)有鸟类96种,其中优势种是山麻雀(Passerrutilans),低山阔叶林带(650~1200m)鸟类种数最多,有135种,其中优势种是绿背山雀(Parusmonticolus),针阔混交林带(1200~2200m)有73种,其中优势种是橙翅噪鹛(Garrulaxelliotii);秦岭东段南坡鸟类群落与中段南坡以及西段南坡和巴山北坡鸟类群落有较高的相似性,但是和秦岭北坡、巴山南坡的鸟类群落相似性较小,反映出秦岭和巴山对鸟类物种组成的阻隔作用和该地区鸟类区系组成的过渡性。和30年前相比,秦岭东段南坡鸟类物种增加了64种,但是有8种鸟类在2008和2010年的调查中未见到。总体上,秦岭东段南坡的繁殖鸟类群落组成在过去的30年里已经发生了明显的变化。
分子动力学模拟研究熔盐中的局部结构
程兆年,,马剑鹏,邵俊,陈念贻
物理化学学报 , 1989,
Abstract:
分子动力学模拟研究licl急冷非晶形成过程中的局部结构
程兆年,,马剑鹏,邵俊,陈念贻
物理化学学报 , 1989,
Abstract:
漆酶催化邻苯二酚开环的自由基反应机制
Radical Mechanism of Laccase-Catalyzed Catechol Ring-Opening

陈明,王林,谭天,,郑在,尹若春,苏吉虎,(),杜江峰
- , 2017, DOI: 10.3866/PKU.WHXB201612011
Abstract: 酶催化反应是绿色化学领域中的研究热点之一.在常用的酶中,漆酶是一种多铜氧化酶.在此,漆酶被用来研究邻苯二酚的氧化和芳香环开环的自由基过程.实验表明,邻苯二酚的初始氧化产物是一个半醌自由基,再发生分子间加成反应而生成二聚体和三聚体(通过质谱鉴定),和分子内加成而生成可被5, 5-二甲基-1-氧化吡咯啉(DMPO)所捕获的含有支链烷基自由基的呋喃衍生物.后者经核磁共振氢谱(1H-NMR)加以分析.同时,通过17O同位素标记追踪方法,我们发现水直接参与该分子内加成反应,并释放出17O标记的羟基自由基(·17OH).此外,除了3-甲基邻苯二酚和4-甲基邻苯二酚两种类似物,此自由基过程在间苯二酚、对苯二酚、萘二酚、3-硝基邻苯二酚和4-硝基邻苯二酚等底物中均未发生.据此,我们对C4-C5位点的选择性活化与开环的机理展开分析和讨论,并将该机理与邻苯二酚双加氧酶导致的邻苯二酚双氧中间位置和相邻位置的开环过程相比较.这些结果将有益于漆酶的改造和仿生.
Enzyme-catalyzed reactions are a prominent field of research in green chemistry. Laccase is a multicopper oxidase, which we used to study the oxidation of catechol. A mechanism for this ring-opening reaction is also proposed. A o-benzosemiquinone radical was the initial nascent product of catechol oxidation during the catalytic reaction. This radical underwent two reaction pathways:(1) formation of an intramolecular adduct, which gave a carbon-centered furan-derived radical trapped by 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO); (2) formation of an intermolecular adduct producing dimeric and trimeric oligomers, as resolved by mass spectrometry. Products of the furan-like intermediate were also characterized by 1H-NMR. Simultaneously, a hydroxyl radical (·OH) originating from the water solvent was identified by 17O-isotope tracing. The kinetics of this radical were also evident with substrates including 3-and 4-methyl catechol, but not with resorcinol and hydroquinone isomers, 3-and 4-nitro catechol, and 2, 3-dihydroxynaphthalene. The mechanism of selective activation and ring-opening at the C4-C5 site is discussed. This reaction is distinct from intra-and extra-diol ringcleavages catalyzed by catechol dioxygenase. These results are meaningful for mimicking laccase catalysis to further protein design
The Application of Pattern Recognition to the Formability of Quasicrystal Formation in Al-alloys
LUO Xuecai,CHENG Zhaonian,CHEN Nianyi,PAN Yugang,
,程兆年,陈念贻,潘毓刚

材料科学技术学报 , 1989,
Abstract: Four parameters of chemical bond havebeen used to span a feature space to classifyquasicrystal-forming Al-alloys from thatalloys without quasicrystal formationwith good result. Since the first quasicrystal-formingsystem, Al-Mn system, discovered by She-chtman in 19841], a series of quasicrystal-forming binary alloy systems have beenfound. Most of these systems are Al-contain-ing systems. Bancel has indicated thatthere are three factors affecting theformability of quasicrystals 2]: (1) ele-ctrochemical factor (this factor can be
The Realization of Nonlinear Mapping on Microcomputer
微机实理非线性映照

Luo Xuecai,Cheng Zhaonian,Tang Fengchao,Miao Qiang,Chen Nianyi,
,程兆年,汤锋潮,缪强,陈念贻

自动化学报 , 1989,
Abstract: In this paper, we suggest a new algorithm in which the steepestdescent procedure is combined with the relaxation procedure for nonlinear mapping on microcomputer. Based on this algorithm we have written a program run on microcomputer. The allowed number of samples is extended to 250 with double precision. Using modular construction, the program contains a set of optional menus and can be used flexibly and conveniently.
大鼠杏仁核内注射异丙肾上腺素引起血压降低心率加速

科学通报 , 1985,
Abstract: 情绪活动可以影响心率和血压,这是生理学中熟知的事实。情绪活动受边缘系统控制。许多电生理工作证明,电刺激大脑边缘系统某些结构可产生多种植物性反应,特别是引起心血管活动的改变。最近有实验指出,给大鼠杏仁核较弱的电刺激(4—5V,80Hz),可引起心血管活动的明显抑制。但关于杏仁核内调节心血管活动的神经元受何种神经递质的支配,尚缺乏具体资料。本工作应用脑内微量注射的方法向大鼠杏仁核内注射β受体激动剂异丙肾上腺素(ISO),观察其对血压和心率的影响。并进一步观察ISO的效应是否能为β拮抗剂心得安所阻断。
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