1000 resultados para 24-232A


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东海陆架是世界上最宽阔的陆架之一,面积达770 000 km2左右。在末次冰盛期(LGM),东海海平面下降120~130 m左右,绝大部分陆架暴露出海面。而冲绳海槽是第四纪以来一直保持海洋环境的东海深海区。本文以冲绳海槽北部PC-1岩芯为材料,通过分析该孔的孢粉,加上详细的AMS 14C测年,恢复了周边地区24 cal.kaBP以来的古植被,并推测古环境和古气候变化,重点讨论了LGM时期出露大陆架上发育的植被。 PC-1孔(31°27.5′N,128°24.8′E)位于黑潮支流对马暖流东侧,水深590 m,柱长812 cm。孢粉分析按间隔8 cm取样,个别为4~6 cm,共分析了103个孢粉样品。利用9个AMS 14C数据建立年龄标尺,用Calib5.1.0软件进行年龄校正。通过相邻样品深度的线性内插获得每个样品的年龄,采用外延法得到顶部和底部的校正年龄分别为351cal aBP、24 280 cal aBP,孢粉样品的时间分辨率平均为230 a。 根据孢粉百分比和沉积率的变化,可划分出四个带:Ⅰ带(812~715 cm,24.2~21.1 cal. kaBP)、Ⅱ带(715~451 cm,21.1~15.2 cal. kaBP)、Ⅲ带(451~251 cm,15.2~10.8 cal. kaBP)、Ⅳ带(251~0 cm,10.8~0.3 cal. kaBP),分别对应MIS 3末期、末次冰盛期、冰消期和全新世。末次冰盛期草本植物花粉占优势,孢粉沉积率较高,此时草本花粉主要来源于出露的大陆架,其上发育了以蒿属为主的草地植被,气候比较寒冷干燥;冰消期海平面开始回升,松属花粉含量升高,草本植物花粉含量下降;全新世以木本植物花粉占绝对优势,栗属-栲属花粉迅速增加,蕨类孢子含量升高,草本植物花粉含量锐减,孢粉沉积率降低,由于海平面回升,大陆架被淹没,此时孢粉主要来源于日本岛,九州地区生长了以栲属、栎属为主的常绿阔叶与落叶阔叶林,气候温暖湿润。 叶枝杉属花粉在整个岩芯中零星出现。叶枝杉属植物分布于菲律宾吕宋北部至塔斯马尼亚和新西兰气候潮湿的山地林中,该属花粉在岩芯中的出现,可能暗示了黑潮的影响或者是较强的夏季风。 草本植物与松属花粉百分比变化很好的反映了海平面的升降,松属花粉含量较高指示海平面较高。对岩芯中主要类型的花粉百分比进行了频谱分析,显示存在千年尺度的准周期变化,有明显的6.8,3.8,2.2,1.6 ka的周期。 孢粉样品中的炭屑统计表明,末次冰消期炭屑含量最高,可能因为末次冰消期降雨量增加,炭屑可被降水带到沉积地点沉积下来;全新世的炭屑浓度较高,尤其在晚全新世,出现了一个峰值,究其原因可能与气候变化和人类活动有关。

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A meeting was convened on February 22-24, 2005 in Charleston, South Carolina to bring together researchers collaborating on the Bottlenose Dolphin Health and Risk Assessment (HERA) Project to review and discuss preliminary health-related findings from captured dolphins during 2003 and 2004 in the Indian River Lagoon (IRL), FL and Charleston (CHS), SC. Over 30 researchers with diverse research expertise representing government, academic and marine institutions participated in the 2-1/2 day meeting. The Bottlenose Dolphin HERA Project is a comprehensive, integrated, multi-disciplinary research program designed to assess environmental and anthropogenic stressors, as well as the health and long-term viability of Atlantic bottlenose dolphins (Tursiops truncatus). Standardized and comprehensive protocols are being used to evaluate dolphin health in the coastal ecosystems in the IRL and CHS. The Bottlenose Dolphin Health and Risk Assessment (HERA) Project was initiated in 2003 by Dr. Patricia Fair at the National Oceanic and Atmospheric Administration/National Ocean Service/Center for Coastal Environmental Health and Biomolecular Research and Dr. Gregory Bossart at the Harbor Branch Oceanographic Institution under NMFS Scientific Research Permit No. 998-1678-00 issued to Dr. Bossart. Towards this end, this study focuses on developing tools and techniques to better identify health threats to these dolphins, and to develop links to possible environmental stressors. Thus, the primary objective of the Dolphin HERA Project is to measure the overall health and as well as the potential health hazards for dolphin populations in the two sites by performing screening-level risk assessments using standardized methods. The screening-level assessment involves capture, sampling and release activities during which physical examinations are performed on dolphins and a suite of nonlethal morphologic and clinicopathologic parameters, to be used to develop indices of dolphin health, are collected. Thus far, standardized health assessments have been performed on 155 dolphins during capture-release studies conducted in Years 2003 and 2004 at the two sites. A major collaboration has been established involving numerous individuals and institutions, which provide the project with a broad assessment capability toward accomplishing the goals and objectives of this project.

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EXTRACT (SEE PDF FOR FULL ABSTRACT): Pluvial Lake Estancia in central New Mexico experienced large and rapid fluctuations in surface area and elevation during the build-up to and termination of the last glacial maximum (LGM). Due to continuous groundwater discharge, a minimum pool covering about 400 square kilometers was maintained in the central basin until about 12,000 years ago, ensuring a continuous depositional sequence even during low stands of the lake. ... The sensitive response to fluctuations in climate by several independent proxies at Estancia show that transport of Pacific moisture over western North America changed dramatically during the last Ice Age, perhaps comparable to the large and rapid changes in climate documented from high-latitude ice and North Atlantic marine sediments for the LCM and its transitions.

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This publication is a report of the proceedings of the ICSF Pondy Workshop, which focused on the FAO’s Voluntary Guidelines for Securing Sustainable Small-scale Fisheries in the Context of Food Security and Poverty Eradication (SSF Guidelines). The workshop brought together 71 participants from 20 countries representing civil society organizations, governments, FAO, academia and fishworker organizations from both the marine and inland fisheries sectors. This report will be found useful for fishworker organizations, researchers, policymakers, members of civil society and anyone interested in small-scale fisheries, food security and poverty eradication.

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 p 24 是H IV 的主要结构蛋白, 在病毒的包装和成熟过程中起重要作用。p 24 蛋白的氨基酸序列在 H IV 各毒株之间高度保守。H IV p 24 抗原的检测在早期诊断、预测病程、胎儿感染确诊和基础研究等方面具有重要 意义。本文主要介绍了H IV p 24 抗原的生物学特性、检测意义, 评述了各种检测方法的主要优缺点和发展趋势。

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Participants consisted of 25 middle and junior level personnel from BOBLME countries. Modules included: Integrated Coastal Management (ICM) concept and principles; ICM development and implementation; indicators of good practice; and action planning.

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以1981~2004年间捕获的中华鲟(AcipensersinensisGray)亲鲟样本为研究材料,研究葛洲坝截流24年来中华鲟繁殖季节中坝下30km范围内产卵群体结构的变化情况。测定与统计结果显示,中华鲟雌雄性比由1981~1983年的1.10∶1降低到1987~1989年的0.63∶1,而后上升到2003~2004年的5.86∶1。雌鲟平均体长由1990~1992年的263.1cm增加到1999~2001年的276.7cm,升幅为5.2%(差异极显著);平均体重由1990~1992年的202.4kg

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本文叙述了2.4-二甲基戊二烯基稀土金属有机化合物的合成并通过元素分析,红外光谱、核磁共振谱及质谱的鉴定。测定了Gd(2.4-GH_(11))_3的单晶结构,此外还合成了(2.4-GH_(11)K.TMEDA及K_2C_8H_8·3THF并也测定了它们的晶体结构。在所合成化合物的红外光谱中,没有属于C=C双键的吸收峰,表明分子中配位体以η~5形式的大π键体系与稀土金属离子结合,在Ln(2.4-GH_(11))_2Cl·TMF和Ln(2.4-GH_(11))Cl_2·GH_THF的红外光谱中,于1060波数附近出现一强而宽的吸收峰,即化合物中有四氢呋喃分子络合。化合物的室温NMR谱有四个吸收峰,2.4-二甲基戊二烯配位体可能为η~5平面∪或W构型。化合物的水解'H-NMR谱与质谱都证实水解产物为2.4-二甲基-1.3-戊二烯。它是-2.4二甲基戊二烯阴离子水解所得的唯一产物,它表明化合物中的配位体确为2.4-二甲基戊二烯阴离子。(2.4-GH_(11))_2Cl·TMDA配合物晶体结构是应用低温X-射线衍射技术用Nicolet R_3 M/E型四园衍射仪LT-1低温装置并利用重原子法测定的最小二乘法精修至收敛时的一致性因子R=0.055. Rw=0.057。晶体属单斜晶系P21/n空间群。晶胞参数a=11.322(4)A, b=9.242(3)A, c=15.956(5)A. β=106.70(3)分子中2.4-二甲基戊二烯阴离子呈平面∪构型。钾离子与四甲基乙二胺二啮体结合形成的络合阳离子和2.4-二甲基戊二烯阴离子相间排列形成无限链状结构分子。2.4-二甲基戊二烯阴离子的C-C键长明显分为中间与外端C-C键两组。外端组C-C键双性质较强键长较短。表明C3具有负电荷的共振杂化体贡献较大。分子中K-C键最短的是K-C(1.5)。而不是具有较多负电荷的C3-K键。这可能是由于几何因素造成的。K_2C_8H_8·3THF的晶体结构是采用与前者相同的方法测定的。它属三斜晶系,PT空间群,晶胞参数a=10.263(3)A, b=13.157(4)A, c=9.443A, α=87.51(2)°, β=114.93(2)°, γ=76.81(2)°. V=1111.6A, R=0.051. 晶体中负二价的环辛四烯阴离呈平面构型,具有中心对称性,两侧与两中心对称相关的钾离子连接,相邻的非等效的钾离子间通过两四氢呋喃分子的氧原子相连接,从而形成了无限链状结构的分子。环辛四烯反映了Huckel的4n+2芳香性规则。该结构的特别之处在于四氢呋喃分子的氧原子以桥键形式与两个钾离子同时连接。而这种形式的桥键在其它化合物中似还未发现。Go(2.4-GH_(11))_3的晶体结构亦是采用与前述相同的方法测定的。其晶体为三斜晶系,PT空间群,晶胞参数a=12.541A, b=12.853A, c=8.432A, α=91.44°, β=108.61°, γ=117.97°, V=112.54A~3. 结构测定表明,Gd(2.4-GH_(11))_3分子具有C_3h对称性。三个配位体阴离了的九个带负电荷的碳原子近似以三帽三角棱柱形式与钆离子配位。分子中2.4-二甲基戊二烯阴离子的C-C键长-亦分为而组。外端C-C键较中间C-C键强,键长较短,亦表明C3具有较多的负电荷。2.4-二甲基戊二烯阴离子本身近似呈平面∪构型。C2,C4偏离由C1 C3 C5三碳原子构成的平面0.067A。方向上远离中心钆离子。可能在此以离子性为主的化合物中,钆离子与不带电荷的C2 C4间的相互作用有些排斥性质。与Nd(2.4-GH_(11))_3不同的是,在Gd(2.4-GH_(11))_3分子中,Gd-(C(1,5)键最短,而不是Gd-C(3)键。这可能是由于钆离子的半径较小,化合物的空间位阻效应较大所致。