981 resultados para p–n junction
Resumo:
α型Y-CPA-PN配合物向β型配合物转化的反应对α型Yb-CPA-PN向β型转化的反应具有诱导作用。利用这一诱导反应可用来测定混合稀土中的钇。在初步研究反应机理的基础上,茯得了不同反应时期反应速率与钇浓度的定量关系,并确定了最佳反应条件。通过求算协同诱导系数、解联立方程的办法可扣除共存轻稀土的干扰。方法可能用于含钇和轻稀土样品中氧化钇的测定。
Resumo:
本文对新合成的19个O-乙基-N-异丙基(取代硫脲基)硫代磷酰胺醋进行了质谱研究。讨论了P—N键的断裂,包括简单断裂和重排反应、失HS·反应及硫脲N上不同取代基的影响等问题。在亚稳态测定和高分辨精确质量测量的基础上得到了这类化合物的断裂规律和质谱特征。
Resumo:
MEP is a member of thioester-containing protein (TEP) family found in Zhikong scallop Chlamys farreri and is involved in innate immunity against invading microbes. In the present study, the genomic DNA of CfTEP was cloned and characterized. The genomic DNA sequence of CfTEP consisted of 40 exons and 39 introns spanning 35 kb with all exon-intron junction sequences agreeing with the GT/AG consensus. The genomic organization of CfTEP was similar to human and mouse 0 rather than ciona C3-1 and Drosophila dTEP2. By RT-PCR technique, seven different cDNA variants of CfTEP (designated as CfTEP-A-CfTEP-G) were cloned from scallop gonad. CfTEP-A-CfTEP-F were produced by alternative splicing of six mutually exclusive exons (exons 19-24), respectively, which encoded the highly variable central region. While in CfTEP-G, the deletion of all the six exons introduced a new translation stop site and might trigger nonsense mediated decay (NMD). The mRNA expression and the proportion of the seven CfTEP variant transcripts were examined in the gonad of scallops after bacterial challenge. The fragments containing the highly variable central region of UTEP were amplified by RT-PCR and a 100 positive clones were sequenced randomly. The expression profiles of the seven MEP variants were different and displayed the sex and bacteria dependent manner. In the blank, sea water and Listonella anguillarum challenged subgroups of male scallops, all the transcripts detected were CfTEP-G isoform. In the Micrococcus luteus challenged subgroup, the isoforms expressed and their proportions were CfTEP-F (54%), CfTEP-B (23%), CfTEP-A (10%), CfTEP-C (7%) and CfTEP-E (6%). However, in the gonad of female scallops, only CfTEP-A were found in blank and sea water challenged subgroups. After L anguillarum or M. luteus challenge, four and five isoforms were detected, respectively, with CfTEP-F isoform being the most one in the both subgroups. These results suggested that the evolution of TEP genes was very complex, and that the diverse CfTEP transcripts generated by alternative splicing played an important role as pattern recognition receptors in the innate immune defense of scallops. (C) 2009 Elsevier Ltd. All rights reserved.
Resumo:
Cell migration is essential to direct embryonic cells to specific sites at which their developmental fates are ultimately determined. However, the mechanism by which cell motility is regulated in embryonic development is largely unknown. Cortactin, a filamentous actin binding protein, is an activator of Arp2/3 complex in the nucleation of actin cytoskeleton at the cell leading edge and acts directly on the machinery of cell motility. To determine whether cortactin and Arp2/3 mediated actin assembly plays a role in the morphogenic cell movements during the early development of zebrafish, we initiated a study of cortactin expression in zebrafish embryos at gastrulating stages when massive cell migrations occur. Western blot analysis using a cortactin specific monoclonal antibody demonstrated that cortactin protein is abundantly present in embryos at the most early developmental stages. Immunostaining of whole-mounted embryo showed that cortactin immunoreactivity was associated with the embryonic shield, predominantly at the dorsal side of the embryos during gastrulation. In addition, cortactin was detected in the convergent cells of the epiblast and hypoblast, and later in the central nervous system. Immunofluorescent staining with cortactin and Arp3 antibodies also revealed that cortactin and Arp2/3 complex colocalized at the periphery and many patches associated with the cell-to-cell junction in motile embryonic cells. Therefore, our data suggest that cortactin and Arp2/3 mediated actin polymerization is implicated in the cell movement during gastrulation and perhaps the development of the central neural system as well.
Resumo:
We explore the tectono-magmatic processes in the western West Philippine Basin, Philippine Sea Plate, using bathymetric data acquired in 2003 and 2004. The northwestern part of the basin formed through a series of northwestward propagating rifts. We identify at least five sequences of propagating rifts, probably triggered by mantle flow away from the mantle thermal anomaly that is responsible for the origin of the Benham and Urdenata plateaus. Gravitational forces caused by along-axis topographic gradient and a similar to 30 degrees ridge reorientation appear to also be driving the rift propagations. The along-axis mantle flow appears to be reduced and deflected along the Luzon-Okinawa fracture zone, because the spreading system remained stable west of this major fault zone. North-east of the Benham plateau, a left-lateral fracture zone has turned into a NE-SW-trending spreading axis. As a result, a microplate developed at the triple junction.
Resumo:
本论文研究了胶洲湾、东海和渤海的蓝细菌(Synechococcus)、生物量、异养细菌生物量和生产力的生态学特点。并在汇泉湾、渤海和东海用分极增减法对海洋蓝细菌在微型食物环(the microbial loop)中的作用进行了初步研究。在以上海区调查研究的时间如下:胶州湾:1993年2月、5月、9月11月,1996年5月、1999年3月、5月和12月。汇泉湾:1996年4月至1998年4月。东海:1997年2-3月,1998年7月。渤海1998年9-10月,1999年4-5月。研究结果如下:胶州湾:蓝细菌生物量的变化范围是11.4-0.03 mgC/m~3,季节变化是夏季>秋季和春季>冬季。其水平分布是除夏季蓝细菌生物量是沿岸浅水区向湾外递减外,其它三季(春、秋和冬季)是由湾外向湾内至沿岸浅水区递减。蓝细菌生物量与海水温度周年变化正相关,与季节海水温度的关系是秋、冬季分布变化一致,春、夏季分布变化相反。海水温度是影响胶州湾蓝细菌生物量分布变化的主要原因。异养细菌生物量和生产力的变化范围分别是29.8-1.62 mgC/m~3; 129.12-1.92 mgC/m~3.d。季节变化都是夏季>秋季、春季>冬季。夏季的异养细菌生物量和生产力水平分布趋势与蓝细菌生物量的分布变化相同。海水温度对异养细菌生产力的影响较对异养细菌生物量的影响大。异养细菌生产力相比(BP:PP)的变化在0.58-0.02之间,季节分布变化是夏季>秋季、春季>冬季。夏季表层的BP:PP由沿岸浅水区向湾心、湾口和湾外递减。东海:蓝细菌生物量的变化范围是46.72-0.011 mgC/m~3,夏季高平均是23.59 mgC/m~3,冬季低平均是3.61 mgC/m~3。冬季蓝细菌生物量的水平分布明显受黑潮的影响,在表面和20米层是由东南向西北方向递减。其垂直分布是冬季表层和20米层>底层,夏季是20米层>表层>底层;在连续站冬111站和410站变化都是中层>底层>表层。异养细菌生物量和生产力的变化范围分别是17.2-4.4 mgC/m~3(1997.2);376.8-7.2 mgC/m~3.d。异养细菌生产力夏季高平均是35.1 mgC/m~3.d。异养细菌生物量的水平分布是由沿岸向外海递增(1997.2),异养细菌生产力的水平分布是冬季异养细菌生产力在32度断面有由沿岸向外递减趋势,PN断面的变化与冬季相似。垂直分布,冬季和夏季的异养细菌生产力的垂直变化在2断面是底层大于表面,PN断面则是表层大于底层,32度断面大多断站是底层大于表层。在连续站冬季111站异养细菌生产力的变化是底层>中层>表层,409站的变化是中层>底层>表层,夏季111站和410站都是中>底层>表层。异养细菌生物量(1997.2)表层分布变化与海水温度分布变化相似,底层变化相反。异养细菌生产力与初级生产力相比(BP:PP),冬季在0.04-0.30之间,平均为0.17;夏季在0.20-0.43之间平均0.32。冬季在长江口附近BP:PP有一个高值区是0.30,夏季在111站附近有一个高值区是0.43。从连续站111站和409’站观测发现底层的BP:PP明显高于表层。渤海:蓝细菌生物量秋季(16.6-0.37 mgC/m~3)比春季(0.44-0.015 mgC/m~3)高。其秋季的水平分布与海水盐度水平分布相同,与海水温度水平分布相反。异养细菌生产力秋季(189-62.2 mgC/m~3.d)与春季(193.2-49.8 mgC/m~3.d)相当。但秋季捕层BP普遍小于底层,而春季是表层普遍大于底层。根据颗粒分级培养实验结果,海洋蓝图细菌在微型食物环中的作用如下:在汇泉湾的春季和秋季蓝细菌可能主要被小型浮游动物(microzooplankton 20-200 μm)捕食。在渤海的春季和秋季也是同样结果。但在东海夏季的111站和410站附近(东海大陆架中部)微型浮游动物(nanozooplankton 2-20 μm)对蓝细菌的捕食压力明显。