21 resultados para Pratt, Josiah, 1768-1844.

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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用动态光散射法研究了不同浓度NaCl对液—液扩散法生长溶菌酶晶体的影响,并测量了晶体生长前后体系的Zeta电势.结果表明,NaCl浓度较高时,在溶菌酶溶液—凝胶界面处会发生液液分层现象,溶液中一直存在较大的聚集体,生长出的晶体质量较差.而在合适的NaCl浓度下,随着溶液Zeta电势降低,溶液中溶菌酶的大的聚集体发生解聚集,生长出的晶体质量较高.

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This paper presents a summary of cellular and dendritic morphologies resulting from the upward directional solidification of Al - Ni alloys in a cylindrical crucible. We analysed the coupling of solid-liquid interface morphology with natural and forced convection. The influence of natural convection was first analyzed as a function of growth parameters (solute concentration, growth rate and thermal gradient). In a second step, the influence of axial vibrations on solidification microstructure was investigated by varying vibration parameters (amplitude and frequency). Experimental results were compared to preliminary numerical simulations and a good agreement is found for natural convection. In this study, the critical role of the mushy zone in the interaction between fluid flow and solidification microstructure is pointed out.

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The dependences of the recording properties of LiNbO3:Fe:Mn crystals on an external electric field (applied in the recording or fixing phase of the nonvolatile holographic recording process) are numerically investigated and the optimal conditions for applying an external electric field in this two-step process of nonvolatile holographic recording are discussed in detail. Significant improvement of the photorefractive performance has been found and experimental verifications using a small external electric field are described. Moreover, direct measures relating to the dominant photovoltaic mechanism in the doubly doped LiNbO3 crystals and the unconventional grating-enhanced fixing are revealed by applying an external electric field in the recording and the fixing phases, respectively.

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The original scanner for tilting orthogonal double prisms is studied to test the tracking performance in intersatellite laser communications. With a reduction ratio of more than 100 times from the change rate of the angle of beam deviation to that of the tilting angle of each prism, the theoretical analysis performed, as well as the verification experiment, indicates that the scanner can meet the requirements of the scanning accuracy superior to 0.5 mu rad with the scanning range greater than 500 mu rad and can facilitate the mechanical structure design. (c) 2006 Optical Society of America.

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从靶场反射镜架模块的机械结构设计布局所需几何空间的角度出发,根据大口径、列阵器件的特殊要求,给出符合“神光Ⅲ”装置总体技术要求的ICF靶场光束口径与列阵间隔之间的关系,得出靶场△纵、△横应满足的公式.

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探讨了3种不同自成像腔,即Talbot腔、自傅里叶变换腔(SF)和傅里叶变换自成像腔实现相干组束的机理和技术难点。介绍了利用光纤激光器,采用傅里叶变换自成像方法,实现1维2路和2维4路激光相干组束的实验情况,功率分别达到122W以及26W。

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本发明涉及抗HIV-1病毒活性的化合物,具体地说是一种多皱软磺酸在抗HIV-1病毒中的应用,多皱软磺酸的结构式为,以所述多皱软磺酸为抑制HIV-1病毒活性的有效成分,该化合物在细胞水平的活性检测中,对1型人类免疫缺陷病毒 (Human Immunodeficiency Virustype I,HIV-1)表现出很好的抑制活性,而对宿主细胞的毒性非常小,作为药物先导化合物具有良好的应用前景。

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6-环己甲基取代S-DABO类化合物、其合成方法和用途,属药物技术领域。本发明涉及一种5-烷基-6-环己甲基-2-(烷基、环烷基、环烷基甲基、取代苯乙酮)硫尿嘧啶类化合物,该类化合物具有如(Ⅰ)通式:其中: R1为C1-3的烷基; R2=C1-8的烷基、环烷基、环烷基甲基,如(Ⅱ)式:(其中,X=OCH3,H, OH,卤素)。分别以氯甲基环己烷或环己基乙酸为原料制备β-酮酯,再与硫脲在醇钠催化下缩合关环制得关键中间体5-烷基-6-环己甲基硫尿嘧啶,最后通过S-烷基化反应引入C2-位侧链制备目标分子,合成方法简便易行,产物具有极其显著的抗HIV病毒活性和抗耐药性,可作为抗HIV药物候选物。

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以滇池围湖试验区海东湾和马村湾的沉积物为研究对象,对沉积物柱状样按每3cm分层,测试有机质、总磷及赋存形态磷(包括不稳定性磷、铁铝结合态磷、钙结合态磷、残渣磷)、总氮、亚硝酸盐氮、硝酸盐氮和氨氮等指标.结果表明:近些年来,2湾遭受的氮、磷内源负荷比以前大;铁铝结合态磷在磷的各形态中含量最高,氨氮所占总氮的比例较其它湖泊偏低;也发现海东湾和马村湾这2个湖湾在9~12cm层总磷、总氮呈现污染减轻的趋势,同时在24~39cm的深度上,总磷、总氮指标再次出现转折,考虑可行性和经济制约,24~39cm处可作为疏浚层

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记述了中国产连珠藻属SirodotiaKylin的6个种,即黄山连珠藻S.huangshanensisZ.X.ShietS.L.Xie,威拉连珠藻S.huillensis(WelwitschexW.etG.S.West)Skuja,中华连珠藻S.sinicaJao,纤细连珠藻S.delicatulaSkuja,瑞典连珠藻S.suecicaKylin和细连珠藻S.tenuissima(Collins)SkujaexFlint。其中,黄山连珠藻S.huangshanensisZ.X.ShietS.L.Xie为

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<正> 鳊鱼是很名贵的经济鱼类,亦称(鱼边)角,东北地区称鳊花。在我国的江河中分布很广,长江及松花江流域中最为丰盛。这种鱼最初的记载是在1844年,学名为Leuciscus bramula,是Cuvier和Valencienes两氏订立的。后来在1846及1855年中,Richardson和Basilewsky两氏又先后记述了这种鱼类;并分别订为Abramis bramula和Abramis pekinensis。到1865年,Bleeker氏才确定这种鱼的属名为Parabramis,借以和只有一行咽喉齿

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We investigated the dynamics of spontaneous emission from a photonic crystal etched into a SiN slab. After fitting the decay curves of the emission to double exponential functions, we divided the dynamic process of the spontaneous emission into a fast process and a slow process. It was observed that the presence of the photonic crystal increased the proportion of the fast decay component, and consequently, the emission rate and time-integrated emission intensity were also enhanced. These enhancements were a result of the coupling of the guide modes to the leaky modes of the photonic crystal slab waveguide. (C) 2008 Optical Society of America.

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随着实时系统越来越多地应用于各种快速更新系统,尤其是各种片上系统,如PDA(personal digital assistant),PSP(play station portable)等,性价比已成为系统设计者的主要关注点.实际应用中,实时系统通常仅支持较少的优先级,常出现系统优先级数小于任务数的情况(称为有限优先级),此时,需将多个任务分配到同一系统优先级,RM(rate monotonic),DM(deadline monotonic)等静态优先级分配算法不再适用.为此,静态有限优先级分配是研究在任务集合静态优先级可调度的情况下,可否以及如何用较少或最少的系统优先级保持任务集合可调度.已有静态有限优先级分配可分为两类:固定数目优先级分配和最少优先级分配.给出了任意截止期模型下任务静态有限优先级可调度的充要条件以及不同静态有限优先级分配间转换时的几个重要性质,指出了系统优先级从低到高分配策略的优越性,定义了饱和任务组与饱和分配的概念,证明了在任务集合静态优先级可调度的情况下,最少优先级分配比固定数目优先级分配更具一般性.最后提出一种最少优先级分配算法LNPA(least-number priority assignment).与现有算法相比,LNPA适用范围更广,且复杂度较低.

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通过对Hybrid-Maize玉米高产模型进行田间验证,应用该模型对黄土旱塬春玉米生产潜力进行初步估算。结果表明,Hybrid-Maize模型在黄土旱塬表现出较好模拟效果,总生物量、秸秆生物量和籽粒产量模拟值与实测值间具有极显著线性相关性,其决定系数分别为0.9469、0.8164和0.9650,回归系数分别为1.0198、0.9787和1.1844,接近于1。黄土旱塬区多年光温生产潜力和气候生产潜力因品种不同有所差别,对多年平均光温籽粒和总生物量生产潜力,紧凑型玉米品种分别为13.25和22.45t/hm2,平展型玉米品种分别为12.32和20.62t/hm2,年际变化小;对多年平均气候籽粒和总生物量生产潜力,紧凑型玉米品种分别为11.97和19.94t/hm2,平展型玉米品种分别为11.37和18.63t/hm2,年际波动大。在黄土旱塬区,玉米产量潜力挖掘的主要途径应集中在提高密度和水分限制条件下,Hybrid-Maize玉米模型在指导玉米高产栽培上具有较好应用。