835 resultados para 816


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推导并验证了新型阶跃伏安技术──常规二脉冲叠加四阶跃微分伏安法准可逆电极过程的理论电流方程式,同时研究了各项参数如扫描增量(E_s)、脉冲高度(△E)、传递系数(α)对峰电流函数(ψp)、峰电流(i_p)、峰电位(E_p)和半峰宽(W_(1/2))的影响.运用理论ψp-lgk_s图和单纯形优化计算测量了及Zn(Ⅱ)/Zn(Hg)-NaNO3体系的K_s及α值,结果与文献值一致。

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合成了标题络合物的晶体,在四圆衍射仪上测得其晶体结构。晶体Eu(TTA)_4Epy属三斜晶系,P(?)空间群,中心离子Eu(Ⅲ)和4个TTA~-通过8个氧原子螯合配位,Epy为外界阳离子。晶胞参数如下:a=12.437(5),b=17.816(3),c=10,706(3)(?),α=90.92(2)°,β=102.01(3)°,γ=87.10(2)°,Z=2。此外,还对该化合物的热稳定性、红外及紫外可见光谱以及荧光性质进行了研究。

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Transfer behaviors across the water/nitrobenzene interface were studied for five choline derivatives by chronopotentiometry with linear current scanning, cyclic voltammetry and differential pulse voltammetry. The irreversible hydrolysis reactions coupled to the phase transfer of ions across the water/nitrobenzene interface were observed. The Gibbs energies of the transfer of choline derivatives show the effects of an additive constitution on hydrophobic property of the medicine.

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用循环线性电流扫描计时电位法(CLC)、循环伏安法(CV)和微分脉冲伏安法(DPV)研究了五种胆碱类药物在水/硝基苯界面(W/NB)上的转移行为.在水相溶液呈碱性时,观察到了伴有不可逆水解反应的相转移过程.讨论了药物结构中的取代基效应,并依据离子转移的标准 Gibbs 能△_o~wG_(tr)~o 度量了取代基的疏水性效应及药物的脂溶性.

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Porphyra haitanensis T. J. Chang et B. F. Zheng (Bangiales, Rhodophyta) is cultivated in China and widely consumed in Asia. To gain more insight into its physiological and biochemical properties, we generated 5318 expressed sequence tags (ESTs) from the sporophyte of P. haitanensis, and upon assembling into a nonredundant set, 2535 sequences were obtained, among which only 32.2% (816) shared certain similarity with published sequences (Nr and KOG). Functional classification of such ESTs revealed that most of the transcripts were related to its conservative biological metabolism, and P. haitanensis most likely possesses cyanide-resistant respiration and a C4-like carbon-fixation pathway, both of which have never been reported in a rhodophyte before. Twenty-eight percent of the nonredundant gene clusters exhibited significant similarity to those from P. yezoensis Ueda sporophytes, and 16 genes up-regulated in P. yezoensis sporophytes were also expressed abundantly in P. haitanensis. Codon usage analysis indicated that exposure to high GC pressure might occur during evolution of P. haitanensis. These findings represent the most extensive collection of ESTs from P. haitanensis to date, and all the ESTs in this study have been submitted to GenBank (accession nos. DN604790-DN608469, EG016226-EG018540).

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气候变化和异常是当今地球科学研究的重大课题之一,与人类的生存、发展密切相关。南海作为我国最大的边缘海, 位于夏季风气流上游, 同时,作为热带太平洋的边缘海,具有显著的年际变异特征。近年来,随着卫星资料的积累和产品化使得我们有机会对南海的上层海洋要素进行全面的直接的观察,并进行南海气候异常变异及其可预报性的研究。 本文的研究内容就是利用近年来卫星资料产品,对南海主要海面要素,包括海面风场(SW)、表层温度场(SST)、海面高度场(SSH)的气候变化趋势以及南海表层温度变异的可预测性进行细致的探讨,并且利用较新的分析方法对南海上层海洋要素在近年来的非线性变异特点进行了分析。主要工作包括: 1. 采用南海卫星高度计及具有高精度模式输出结果通过联合经验正交函数分解(EOF)得到空间分辨率为1/3°×1/3°的南海绝对动力地形及地转流的季节变化(1-12个月)。从地转流场可以看到南海内部的表层流场主要有3种流系:西边界流、离岸流及南海多涡涡旋结构。 2. 通过南海海表大气和海洋要素(SW、风应力、SST、SSH)的气候变化趋势分析计算得到南海SST平均增暖0.5K/decade,海面高度升高6.7cm/decade,表层风场东分量和北分量的变化趋势分别为0.5m/s/decade、-0.04m/s/decade。其中南海SST增暖趋势和海面抬升速率远大于全球增暖和海面抬升速率。 3. 对南海SW、SSH和SST的异常场的EOF分析揭示南海SW、SSH及SST的年际尺度变化均表现出与ENSO变异现象一定的相关性:其中南海SW的第一模态特征表现为海盆尺度的反气旋,是西太平洋反气旋的最西南的一部分。对应的时间系数函数(TCF)滞后Nino3.4指数3个月,相关系数较高为0.90。南海SW的第二模态特征表现为均一化的西南风,TCF与印度洋偶极子(IOD)指数有一定相关性:TCF超前IOD指数4个月,相关系数达到0.58,表明南海SW第二模态似乎可以用来作印度洋偶极子现象的一个前兆。南海SSH的EOF第一模态特征为沿着南海东边界低水位,对应的TCF滞后Nino3.4指数2个月时间,二者相关系数为0.94;南海SST的EOF第一模态特征表现为整个海盆的增暖,对应的TCF与滞后Nino3.4指数8个月,相关系数等于0.62。 4. 基于典型相关分析(CCA),利用南海SSTA滞后热带太平洋Nino指数及印度洋IOD指数的关系建立南海SSTA的统计预报模式。通过对南海SSTA后报试验(1993/1994-2004年10月)与持续性预报值的预报效果进行比较分析,表明基于CCA统计方法对南海SSTA后期预报在预报时效超过3个月以上时具有更好的稳定性,提前1~12个月的后期预报水平平均值为0.60左右,误差均方根大约0.2个标准差。综合热带太平洋Nino指数为预报因子作南海SSTA统计预报的平均水平为0.55左右,亦具有较好的稳定性。 5. 基于前馈型神经网络,对南海近年的表层要素场(SW、SSH、SST)作非线性EOF分析。其中非线性EOF第一模态方差贡献与线性EOF相比均相应提高:海面风场、海面高度场的非线性作用较强,非线性EOF第一模态对变量场的方差贡献与线性EOF方法相比分别从54.75%提高到67.26%和50.43%提高至60.24%,非线性曲率强的空间范围占据绝大部分南海海域;相比较而言,南海SSTA场的非线性EOF第一模态的方差贡献提高不明显,非线性特征明显的区域仅在南海北部和南部靠近大陆的海区。对南海SSTA场1982-2003年时间长度的数据进行非线性与线性EOF分析比较,发现南海SSTA在近20年的非线性EOF分析中得到的非线性特征更不明显,表明与前10年相比,南海近10年的南海SSTA场的非线性成分有所增强。

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在扫描电镜下观察了獐牙菜属Swertia L.10组30种植物花蜜腺的数目,位置,形态和附属物等特征;同时还利用光镜对各组代表种的蜜腺结构进行了解剖学观察。结果表明獐牙菜属花蜜腺外部形态多种多,但在组与组之间无明显间断,演化序列呈梯度变化;内部结构基本相同,为不具维管束的结构蜜腺,且均为淀粉型蜜腺。因此,从花蜜腺的角度不支持将獐牙菜属划分为小属的观点,同时,还结合其它证据讨论了花蜜腺特征的演化趋势。

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本文叙述了某种水中机动目标(被试品)运动性能评价决策支持系统的设计和功能。根据被试品考核项目,本系统将提供灵活的评价结构。评价结构的生成既可采用自动生成方式,亦可通过交互由人工选择完成。知识库和推理机制的引入为被试品的定性评价提供了进一步的可能。该系统能及时、准确地对被试品性能进行在线的准实对评估,为使用者掌握本次试验情况和后续试验进度提供有力的辅助支持。

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采用动力学通量箱法(Dynamic Flux Chamber) 与高时间分辨率大气测汞仪联用技术对贵州红枫湖地区土壤- 大气界面间汞交换通量进行了初步研究。结果显示,红枫湖地区土壤- 大气界面间汞交换通量变化范围为- 816 ng21513 ng·m- 2·h - 1 ,平均2714 ±4011 ng/ m2·h ( n = 255) ;且土壤与大气界面间的汞交换是双向的:既有土壤汞的释放,又有大气汞的沉降,主要以土壤汞的释放为主( n释放= 253 , n沉降= 2n) 。土壤汞的释放通量与土壤温度、气温、光照强度有强相关关系,相关系数分别为0180 、0183 、0174 。

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雪鸡坪斑岩铜矿位于西南三江构造火成岩带义敦岛孤带,其成矿斑岩为印支期石英闪长玢岩和石英二长宽岩。研究对该矿区安山岩、矿化斑岩和矿石矿物系统进行S,Pb同位素分析结果表明:金属硫化物的δ34S值为-3.1‰~+0.7‰,平均值为-1.1‰,与矿化斑岩的硫同位素组成(-1.4‰和-1.5‰)一致,均落入幔源硫范围,表明硫主要来自岩浆;δ34S黄铁矿(-1.8‰~+0.7‰,平均0.5‰)〉δ34S黄铜矿(-2.2‰~0.0‰,平均-1.2‰)〉δ34S方铅矿(-3.1‰~1.3‰,平均-2.4‰),硫同位素分馏基本达到平衡。矿石矿物(208Pb/204Pb=37.917~38.230,平均值38.075;207Pb/204Pb-15.528~15.614,平均值15.571;206Pb/204Pb=17.929~18.082,平均值17.981)与矿化斑岩(208Pb/204Pb=37.832、37.883,207Pb/204Pb=15.529、15.538,206Pb/204Pb=17.906、17.910)以及安山岩(208Pb/204Pb=37.816~37.884,207Pb/204Pb-15.549~15.562,206Pb/204Pb=17.845~17.919)的初始铅组成基本一致,变化范围较小,表明三者具有相同的来源;在铅构造模式图上,所有样品铅同位素均位于造山带演化线上或附近,在铅同位素源区判别图中,均落入造山带和下地壳区域,这表明Pb主要来源于壳幔混合。雪鸡坪铜矿S,Pb同位素组成共同指示成矿物质主要来自于深部岩浆,这种岩浆可能主要起源于俯冲洋壳板片的部分熔融并受到少量地壳物质的混染。

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The p16 tumor suppressor gene is inactivated by promoter region hypermethylation in many types of tumor. Recent studies showed that aberrant methylation of the p16 gene is an early event in many tumors, especially in lung cancer, and may constitute a new biomarker for early detection and monitoring of prevention trials. We detected tumor-associated aberrant hypermethylation of the p16 gene in plasma and tissue DNA from 153 specimens using a modified semi-nested methylation-specific PCR (MSP) combining plastic microchip electrophoresis or slab gel electrophoresis, respectively. Specimens were from 79 lung cancer patients, 15 abdominal tumor patients, 30 positive controls and 30 negative controls. The results showed that the positive rate obtained by microchip electrophoresis was more than 26.6% higher and the same speciticity was kept when compared with slab gel electrophoresis. The microchip electrophoresis can rapidly and accurately analyze the PCR products of methylated DNA and obviously improve the positive rate of diagnosis of cancer patients when compared with gel electrophoresis. This method with the high assay sensitivity might be used for detection of methylation of p16 gene and even to facilitate early diagnosis of cancer patients. (C) 2004 Elsevier B.V. All rights reserved.

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Scott, Len, and Peter Jackson, 'The Study of Intelligence in Theory and Practice', Intelligence and National Security, (2004) 19(2) pp.139-169 RAE2008

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Limited data are available regarding the molecular epidemiology of Mycobacterium tuberculosis (Mtb) strains circulating in Guatemala. Beijing-lineage Mtb strains have gained prevalence worldwide and are associated with increased virulence and drug resistance, but there have been only a few cases reported in Central America. Here we report the first whole genome sequencing of Central American Beijing-lineage strains of Mtb. We find that multiple Beijing-lineage strains, derived from independent founding events, are currently circulating in Guatemala, but overall still represent a relatively small proportion of disease burden. Finally, we identify a specific Beijing-lineage outbreak centered on a poor neighborhood in Guatemala City.

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En esta comunicación breve quiero compartir con las personas interesadas en escuchar una propuesta de Evaluación para algunos de los procesos que se trabajan en Combinatoria. Manejando el discurso de la evaluación como un proceso que debe: Ser formativo, constructivo, Ser continuo, Ser sistematizado, Ser flexible. Además que inicia desde una actividad diagnóstica, pasando por una actividad formativa y finalizando en una evaluación sumatoria (resultado de la actividad formativa). Teniendo en cuenta que la evaluación nos debe permitir visualizar de manera clara y consistente los aspectos que estemos trabajando, sin olvidar que la evaluación debe permitir ser interpretada en todos los sentidos y direcciones: las respuestas de los estudiantes también están evaluando los currículos, los docentes y las estrategias de trabajo o sus ejecuciones (lineamientos curriculares del área de Matemáticas, MEN, 1998, p. 107/108). Veremos algunas características de la evaluación específicamente para el trabajo en Estadística y Probabilidad, extrayendo las que nos funcionan específicamente para nuestro tema Razonamiento Combinatorio. Todo enfocado a que el estudiante al final pueda: Plantear y resolver problemas, Formular y comunicar sus soluciones, Validar las soluciones de otros.