若尔盖地区25万年以来的植被与气候

本文根据ＲＭ孔上部６０ｍ２１０个样品的花粉分析结果,探讨了若尔盖地区２５万年以来的植被演替和气候变化。研究结果表明,若尔盖地区过去２５万年的植被演替和气候变化可划分为７个阶段。在约２５０－１９５ＫａＢ．Ｐ．（７阶段）,植被以亚高山莎草草甸为主,气温和降水与现在接近。在１９５－１２８ＫａＢ．Ｐ．（６阶段）和３２－１１ＫａＢ．Ｐ．（２阶段）,植被主要是荒漠草原,反映寒冷干旱的冰期气候,年平均气温比现在低５－６℃,年降水量仅为现在的６０－８０％左右。１２８－７１ＫａＢ．Ｐ．（５阶段）是过去２５万年中水热条件最好的时期,植被主要是亚高山暗针叶林和亚高山草甸,大部分时间的气温比现在高１℃左右,降水量稍高于现在;但在此阶段的气温和降水仍有较大的波动,５ｅ、５ｃ和５ａ阶段的气温和降水高于５ｂ和５ｄ阶段。７１－５８ＫａＢ．Ｐ．（４阶段）的植被主要是高山草甸为主,年平均气温比今低３－５℃,年降水量约为现在的８０％,在５８－３２ＫａＢ．Ｐ．（３阶段）,早期植被以亚高山暗针叶林和草甸为主,晚期主要是亚高山禾草草甸,气温和降水均明显高于４阶段,在晚期气温呈非线性逐渐下降的趋势。     

晚更新世晚期以来昆仑山垭口区的植被与环境

昆仑山垭口区小南川剖面和雪水河热水剖面的孢粉分析揭示了该区４４０００ａＢ．Ｐ．以来的植被演替和气候变化。４００００ａＢ．Ｐ．前,推测昆仑山垭口区为典型的灌木荒漠植被,气候极端干燥。４００００－３００００ａＢ．Ｐ．,气候稍有好转。３００００－２４０００ａＢ．Ｐ．为草原荒漠,降水增加。２４０００－１８０００ａＢ．Ｐ．为末次冰期极盛期,气候干冷。１８０００－１３０００ａＢ．Ｐ．气候凉偏干。１３０００－８０００ａＢ．Ｐ．气候凉干。８０００－６０００ａＢ．Ｐ．为全新世温暖期,但由于植被的滞后现象,本区仍为草原荒漠景观。６０００－５０００ａＢ．Ｐ．,本区可能也存在着中全新世的降温事件。５０００－３０００ａＢ．Ｐ．在全新世大暖期的影响下,小南川附近的植被演变成温性草原植被,并有人类的放牧活动。３０００ａＢ．Ｐ．以后,气候变凉,草原迅速地演变为灌木和小乔木荒漠植被,其中３０００－１０００ａＢ．Ｐ．为凉干时期,１０００ａＢ．Ｐ．以后,可能有过一段凉湿时期。     

11000年以来太湖地区的植被气候变化

根据太湖盆地３个钻孔,约自１１０００年以来的孢粉分析结果将其划分为３个阶段;１）１１０００－９０００ａＢ．Ｐ．该段虽以Ｐｉｎｕｓ为主的针叶植物占有一定的优势,但起主导作用的仍以壳斗科为主的阔叶乔木种类,尤其是其间尚含有不少的亚热带成分,推测当时该区地带性植被已为亚热带落叶常绿阔叶林,鉴于植被中尚含有少量耐寒的Ａｂｉｅｓ和Ｐｉｃｅａ,推测当时气温可能较今略低;２）９０００－５０００（５４００）ａＢ．     

11000年以来太湖地区的植被与气候变化

根据太湖盆地３个钻孔、约自１１０００年以来的孢粉分析结果将其划分为３个阶段：１）１１０００—９０００ａＢ．Ｐ,该段虽以Ｐｉｎｕｓ为主的针叶植物占有一定的优势,但起主导作用的仍以壳斗科为主的阔叶乔木种类,尤其是其间尚含有不少的亚热带成分,推测当时该区地带性植被已为亚热带落叶常绿阔叶林,鉴于植被中尚含有少量耐寒的Ａｂｉｅｓ和Ｐｉｃｅａ,推测当时气温可能较今略低;２）９０００—５０００（５４００）ａＢ．Ｐ,该段为常绿阔叶林大发展时期,气候温暖适宜,为全新世最佳期,气温约较今高１—２Ｃ;３）５０００？ａＢ．Ｐ．－现在,孢粉组合特征显示,阔叶木本植物就总的来说呈下降趋势,尤其是亚热带成分,与其相反,针叶和一些暖温带成分的含量则略有上升,表明该段气温较前一阶段有所下降,但该阶段的植被受人类活动的影响较大。     

西藏扎布耶盐湖晚第四纪孢粉植物群的初步研究

扎布耶盐湖位于西藏青藏高原腹地。通过该湖ＺＫ２钻孔的孢粉分析,揭示了约３６０００ａＢ．Ｐ．以来扎布耶地区的气候和湖盆演变。约在３６０００－３３０００ａＢ．Ｐ．,扎布耶地区为森林草原,气候冷、湿;约３３０００－３００００ａＢ．Ｐ．,为灌丛草原,气候温、干;约３００００－２７５００ａＢ,Ｐ．为干旱草原,气候偏暖、湿;约１８０００－１２０００ａＢ．Ｐ．,为干旱草原,环境寒冷,干燥;约１２０００－４０００ａＢ．Ｐ．,扎布耶地区各类草本植物繁茂,气候偏温、干。另外,根据水生藻类化石群的分析,自３６０００ａＢ．Ｐ以来,扎布耶盐湖有三次湖进、淡水湖期,同时也有三次湖退事件。     

太湖全新世沉积物有机碳同位素的分布及其古气候意义

通过太湖两个钻孔岩芯有机碳同位素（＾１３Ｃ／＾１２Ｃ）的分析,发现δ＾１３Ｃ的垂直分布与太湖地区１６０００ａＢ．Ｐ．以来古气候波动相关。根据δ＾１３Ｃ垂直分布曲线可推测,大约在１１０００－６０００ａＢ．Ｐ．,太湖地区处于温暖湿润期,气温高于现在平均温度,另一方面,根据太湖两岩芯沉积物的δ＾１３Ｃ值的对比发现,大约在１１０００－６０００ａＢ．Ｐ．,西太湖（Ｗ１Ｂ）岩芯沉积物的δ＾１３Ｃ平均值明显高于     

河北卢龙饮马河流域全新世冲积物孢粉分析及对植被时空变化 …

依据河北省卢龙县闫深港４．６ｍ厚的冲积物剖百,揭示了较高时间分辨率的孢粉分析,参照现代冲积物孢粉与植被的对应关系,探讨了距今１１０００年以来饮马河流域植被的时空变化。１１０００～９０００ａＢＰ的森林覆盖率约１０％,９０００～７０００ａＢＰ约３０％～４０％,７０００～４０００ａＢＰ约２０％～４０％,３０００～２５００ａＢＰ约１０％～２０％。在９０００ａＢＰ左右出现了云杉、冷杉花粉的高峰值,表明饮马河     

根据孢粉资料推论长江三角洲地区1200年以来的环境变迁

根据长江三角洲地区全新世９个具代表性钻孔的孢粉分析结果讨论了本区约自１２０００年以来的环境变迁。孢粉序列表明：本区约在距今１２０００年前就已发育了亚热带性质的落叶常绿阔叶林,约在９０００—５０００ａＢ．Ｐ．常绿阔叶林获得大发展。孢粉序列良好地记录了古季风盛衰的历史,表现在：１２０００—１０８００ａＢ．Ｐ．较温湿,东南季风强度加强;１０８００（或１１０００－１００００（或１０３００）ａＢ．Ｐ．偏闵干,东南季风强度减弱,对应于新仙女木期;约自１００００ａ．Ｐ．起,气候好转,气温明显上升,东南季风强度再次增强,约在９０００—５０００ａＢ．Ｐ．温暖湿润,为东南季风强盛期。此外．还讨论了约在距今１１０００年前的海侵,全新世下限和哥德堡事件的年代问题,并确定哥德堡事件的年限为１１０００—１０００ａＢ。Ｐ。     

西藏两个小湖高分辨率的花粉记录

西藏东南部封闭湖泊高分辨率的花粉记录反映,在１６ ｋａ ＢＰ以前花粉组合以藜科（Ｃｈｅｎｏｐｏｄｉａｃｅａｅ） 和蒿属（Ａｒｔｅｍｉｓｉａ） 为主,花粉浓度很低,应为荒漠草原植被。当时气候寒冷干燥,１ 、７ 月份和年均温分别低于现在当地７ ～１０ ℃,０．５～１．５ ℃和４～６ ℃。年降水量仅２５０ ｍｍ 是现今当地年降水量的４０ ％ ;１２ ｋａ ＢＰ以后气温和降水逐渐增加,出现木本植物花粉,桦属（ Ｂｅｔｕｌａ） 和松属（ Ｐｉｎｕｓ）等,在９ ．２～５ ｋａ ＢＰ发育森林或森林草甸;８～６ ｋａ ＢＰ是研究区气候最适宜期,１、７ 月份气温均高于现在２～３ ℃,年降水量比现在当地高１００ ｍｍ 左右;５．５ ｋａ ＢＰ以后气温和降水呈非线性下降,主要发育草原植被,直至现在     

太湖全新世沉积物有机联同位素的分布及其古气侯意义

通过太湖两个钻孔岩芯有机碳同位素（１３Ｃ／１２Ｃ）的分析,发现δ１３Ｃ的垂直分布与太湖地区１６０００ａＢ．Ｐ．以来古气候波动相关。根据δ１３Ｃ垂直分布曲线可推测,大约在１１０００—６０００ａＢ．Ｐ,太湖地区处于温暖湿润期,气温高于现在平均温度。另一方面,根据太湖两岩芯沉积物的δ１３Ｃ值的对比发现,大约在１１０００—６０００ａＢ．Ｐ,西太湖（Ｗ１Ｂ）岩芯沉积物的δ１３Ｃ平均值明显高于东太湖（Ｅ２Ｂ）。据此可认为,在这一期间西太湖很可能有过海水侵入。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.