第三纪动物的洲际迁徙

第三纪动物的洲际迁徙李雅轩在北美,欧洲和南亚的哺乳动物区系有许多相同的生物类型都经过了新生代。现在的亚洲与北美也仅有白令海峡相隔。在新生代的某一时期,白令海峡曾作为哺乳动物迁徙的通道。在新生代的早期,欧洲与北美之间亦有大陆相连,哺乳动物可以自由地周游...     

殷商文明的东迁与美洲奥尔梅克文明的兴起——最早移民至美洲的印第安人来自何处?(二)

印第安人从亚洲迁徙到美洲 ,除从考古学方面能够证明外 ,还有些什么证据呢？从地理学来看 ,关于古代从亚洲向美洲移民的路线 ,现在基本上也形成了一致的看法 ,就是经西伯利亚跨越白令海峡或白令陆桥到达阿拉斯加 ,再扩散到整个美洲大陆。目前在亚洲和美洲大陆之间隔着白令海峡 ,其最窄处仅８５公里 ,最深处５９米 ,每年１０月至翌年７月封冻 ,从冰上跨越是很可能的。另在第四纪冰期内白令海峡四次露出海底 ,成为一道陆桥 ,最宽时达１０００多公里 ,从而为从亚洲向美洲移民提供了一条坦途。１９９１年 ,我国著名古人类学家贾兰坡先生在《大自…     

澳大利亚土著来源之谜——从考古看最早的移民来自中国或亚洲(二)

一从考古成果来看 ,澳大利亚土著不是来自南北美洲 ,而是来自北边的中国和亚洲。在研究美洲印第安人由中国和亚洲向美洲迁徙的过程中 ,很多学者主张美洲印第安人是从白令海峡移民美洲的 ,但是 ,也有部分学者主张亚洲蒙古人种是分南北两路到达美洲的。北路即前面说的经白令海峡 ,南路经太平洋东南部诸岛或由澳大利亚经南极洲再转向南美地区。葡萄牙人类学家罗思杰斯·柯莱阿提出 ,在亚洲的更南面可能也存在过一条通往美洲的“陆桥” :澳大利亚—塔斯马尼亚岛—南极地带诸岛及南极大陆—火地岛—美洲大陆。法国人类学家波利·利维通过澳大利亚…     

MASTIGOPROCTUS在亚洲首次记录和一新种记述及其生物地理学讨论(蛛形纲 :有鞭目 :鞭蝎科 )(英文)

描述了Mastigoproctus的一个新种 ,Mastigoproctustransoceaniciussp nov 。新种是Mastigoproctus在亚洲的首次记录 ,与其美国佛罗里达州的M giganteus近似 ,但新种个体较小 ,胫节和跗节较为退化 ,以至触肢收缩时 ,3个指尖相互靠近和接触。新种的生殖腹板亦较为简单。文中还讨论了Uropygida目跨越白令海峡分布在生物地理学上的意义     

西伯利亚嵩草及其相关类群的植物分类学及植物地理学研究

研究了产于西伯利亚的西伯利亚嵩草Kobresia sibirica (Turcz.ex Ledeb.) Boeck.,产于北美的K.hyperborea Porsild和K.macrocarpa Clokey。三者之间无显著差异,并且它们的雌花都具有由一至三枚小鳞片组成的花被。因此,它们为同种植物, K.hyperborea包括其变种var.alaskana Duman和var.lepagei Duman及K.macrocarpa被降为西伯利亚嵩草的异名。西伯利亚嵩草分布于亚洲和北美洲的北极和亚北极地区,可能起源于亚洲,由东西伯利亚通过白令海峡散布到北美。     

棕白点象Trichalophus rubripes Zherikhinet Nazarov

正体长1 cm左右,体黑色被覆红棕色或者棕绿色的鳞片,具金属光泽。鞘翅有2对白色斑点,是该虫重要的识别特征。成虫翅短,无飞行能力。该属象虫分布横贯白令海峡,在亚洲和北美的太平洋沿岸分布。照片2015年6月19日拍摄于吉林延边自治州老里克湖。     

几种石耳科地衣生物地理学关系的分子评估(英文)

对具有北美东部和亚洲东部近缘生物地理学关系的大型地衣种类进行系统发育检测较少。笔者获得了石耳科中8个种10个样本nrDNA的ITS完整序列,并对本科中在分布上具有重要意义的4个种的生物地理学关系进行了分析和评估。通过对细胞核核糖体DNA变异性较强的ITS段碱基序列的比较分析,支持放射盘石耳(Umbilicaria muehlenbergii)、宾州疱脐衣(Lasallia pennsylvanica)为同种型间断分布,美味石耳(U.escu-lenta)和大叶石耳(U.mammulata)间已经达到了相当高的分化程度,为异种型间断分布。地理学分析显示该两种石耳的分化可能是由于太平洋的扩展和隔离所造成的结果。同种型间断分布种类的不同地区的样本之间的差异较小。推测了不同类型间断分布种类的分化时间,美味石耳与大叶石耳的分化发生在中新世(23～5.33 Mya)中期,白令海峡形成期间。     

古人类是怎样进入美洲的

亚洲大陆上的古人类,最初于何时、以何种方式进入美洲?对这一问题,长期以来人们乐于接受的解释是所谓“白令陆桥说”。这种科学假说的基本内容是:在晚更新世,地球经历了最后一次冰期。因大量水分以巨大冰川的形式聚集在陆地上,于是造成全球性海平面下降,原来就较浅的白令海峡干涸,水下台地露出海面形成宽达一千多公里的陆桥,使西伯利亚与阿拉斯加     

东北航道

正近年来,随着全球气候变化,北极浮冰减少,使北极航道通航成为可能。有消息说,中国到欧洲的路线随着北极航道的开通也将大大缩短。看来有必要说说这个"东北航道"。"东北航道"西起西欧或者北欧港口,穿过西伯利亚与北冰洋毗邻海域,穿过白令海峡到达东亚日本、韩国、中国等国港口。这条航     

我国医院医疗质量综合评估现状研究

文章对国内当前的医疗质量综合评估的背景及现状进行了简单探讨,表明国内在医院医疗质量评估的理论基础研究、评估体系研究、实证研究等方面均已取得丰硕成果。对文献中存在的主要综合评估方法进行了回顾和分析,并提出了医疗质量综合评估下一步几个可能的研究方向：建立通用、全面的医疗质量综合评估模型,研究能够处理定性、定量混合的、综合的医疗质量评估方法,进行基于定性定量混合指标的、能够考虑多种不确定情况的、多层次多指标的医疗质量综合评估实证研究。
     

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.