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1.
Puritjarra rock shelter provides a long record of late Quaternary vegetation in the Australian arid zone. Analysis of the sedimentary history of this rock shelter is combined with reanalysis of charcoal and phytolith records to provide a first‐order picture of changing landscapes in western Central Australia. These show a landscape responding to increasing aridity from 45 ka with deflation of clay‐rich red palaeosols (<45 ka) and sharp declines in grassland and other vegetation at 40–36 ka, and at the beginning of the Last Glacial Maximum (LGM) (24 ka). Vegetation in the catchment of the rock shelter recovered after 15 ka with expansion of both acacia woodland and spinifex grasslands, registering stronger summer rainfall in the interior of the continent. By 8.3 ka re‐vegetation of local palaeosols and dunes had choked off sediment supply to the rock shelter and the character of the sediments changed abruptly. Poaceae values peaked at 5.8 ka, suggesting the early–mid Holocene climatic optimum in Central Australia is bracketed between 8.3 and 5.8 ka. Local vegetation was disrupted in the late Holocene with a sharp decline in Poaceae at 3.8 ka, coinciding with an abrupt intensification of ENSO. Local grasslands recovered over the next two millennia and by 1.5 ka the modern vegetation appears to have become established. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
2.
Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
3.
目的:基于生物信息学探讨骨质疏松症与 2 型糖尿病的关系。方法:通过基因表达汇编(GEO)数据库检索骨质疏松症和2型糖尿病的相关数据集,并筛选骨质疏松症-2型糖尿病共同差异表达基因,将数据导入STRING数据库找寻关键基因,以一个单细胞测序数据集作为检验集验证关键基因细胞层面的表达水平,对筛选结果进行基因本体(GO)功能及京都基因与基因组百科全书(KEGG)通路富集分析,并对关键靶点、相关中药进行频数统计及功效分类。结果:骨质疏松症与 2 型糖尿病相关通路集中在 ErbB信号通路、丝活化蛋白激酶(MAPK)信号通路、神经营养素信号通路、NOD样受体信号通路。频数统计结果显示,与骨质疏松症-2型糖尿病关键基因相关的中药有51味,以功效分类,可分为清热解毒药、止痛药、祛风药、补虚药、止呕药。结论:骨质疏松症和2型糖尿病都是复杂的代谢性疾病,涉及众多基因表达网络和信号通路。尽管两种疾病存在复杂的基因网络背景,但是分析结果表明两种疾病之间仍存在高度重合的差异基因表达和信号通路。这表明两种疾病的分子机制密切相关,可能存在共同调控的靶点,因此这些靶点可能成为药物同时干预两种疾病的治疗靶点。  相似文献   
4.
Abstract. Ecology and Global Ecology (GE) are terms by which the relations between the organism (or living matter as a whole) and the environment (or Earth as a whole) have been treated for almost a century. Geophysiology and Parahistology (PH) are terms slowly replacing older scientific thoughts jointly with an increasing number of modifications and alterations of the Darwinian Evolution (DE) concept. Somehow Geophysiology and Parahistology seem to describe evolution in a non-Darwinian domain. According to V.I. Vernadsky (1929,1930,1988) - the great Russian naturalist and biogeochemist - the biogeochemical processes on Earth are controlled by the force of living matter rather than by species associations developing in and with individual ecosystems as expressed by darwinian evolutionary terms. He also claimed that Goethe was incorrectly regarded as a predecessor of DE by some authors (including Darwin) and that “Natur” (nature) and “Lebendige Natur” (the totality of creatures) are two very different things for Goethe. Detailed analyses of microbial mat systems in the German Wadden Sea and in artificial hypersaline WInogradsky columns have shown that the totality of creatures and matter around them i.e., the “lebendige Natur”sensu Goethe or “living matter”sensu Vernadsky of such environments control to a considerable extent the structure, stability. and (geo-)morphology of sediments and thereby the geological structure of the living Earth. These structures do not follow the rules of sedimentation formulated by the laws of Stokes They represent growth structures (Aufwuchs), whose physics and dynamics are controlled by complex fractal systems. The factors controlling the ultimate shape and stabilisation potential of the eventually resulting rocks and fossils are comparable to tissue development in macroorganisms. Also, certain microbial associations in the sub-recent and in the fossil record may be compared to metazoan tissues. Chemical gradients in the sedimentary column, regulated by the interplay of living matter and sluggish (slow-reactive to non-reactive) compounds, combine to create a pattern of porosity and structure of the resulting deposits that clearly indicates microbial influences and especially those of extracellular polymeric substances on the morphology and texture. The combined effects of microbiota or living matter on the sedimentary record are described as parahistology of sediments in analogy of the histology of tissue on a geological scale. This conceptual living tissue made up of microbially generated rocks and ore deposits cycled through metabolic processes and forced into tissue-like structures by microbial biofilms and mats may extend down to the upper mantle of Earth and far up into the stratosphere when Earth is regarded as a living entity over geological periods. We may have to conceive Earth as a living specimen, which is breathing at a frequency of thousands of years instead of the normal physiological breathing rate of man or an insect. Macroorganisms in all terrestrial systems represent the transport and logistic media, which, however, utterly depend on myriads of intra-, inter-, and extracellular microbial symbiotic partners.  相似文献   
5.
6.
Abstract. Three triplefin blennies occur sympatrically in the Mediterranean Sea; Tripterygion tripteronotus and T. melanurus are endemic, whereas T. delaisi is also found in the Eastern Atlantic. Although very similar in morphology, ecology and behaviour, some striking differences exist among reproductive strategies. Several authors proposed hypotheses on the evolution of these species. In order to enhance insight into the genetic structure of this genus, an enzyme electrophoretic survey was performed. Samples of 40 to 45 specimens of each species were collected near Calvi (Corsica, France). Twenty-four enzyme loci were analysed, of which 17 appeared polymorphic. T. delaisi showed a high level of average observed heterozygosity (Ho) of 0.140, as opposed to very low levels of 0.009 and 0.021 in T. tripteronotus and T. melanurus , respectively. Nei's genetic distance was 0.21 between T. delaisi and T. tripteronotus , 0.35 between T. delaisi and T. melanurus and 0.45 between T. tripteronotus and T. melanurus . We hypothesise that divergence of these species started before the Pleistocene and that the endemic species survived the Pleistocene glaciations in refugia within the Mediterranean. The possibility that T. tripteronotus and T. delaisi diverged through sympatric speciation is discussed.  相似文献   
7.
青岛文昌鱼的生活史──年龄、生长和死亡研究   总被引:17,自引:1,他引:17  
于1989年8月-1990年7月对青岛文昌鱼的生活史进行研究。结果表明:(1)青岛文昌鱼种群由4个齿组组成,它至少生产4a以上,甚至可达6a左右。(2)在Ⅰ、Ⅱ齿时生长较快,平均年生长13-15mm,Ⅲ龄后生长速度减慢,即使同一年龄组的文晶鱼,在不同季节其生长速度也不同。(3)在冬春采集的文昌鱼中Ⅲ龄组的峰值较小。(4)繁殖季节过后,老龄文昌鱼因衰老而死亡。  相似文献   
8.
南海西沙西南海域表层沉积物特征   总被引:3,自引:1,他引:3  
西沙西南海域表层沉积物样品矿物成分,地球化学,微体古生物分析测试结果表明:沉积物可分为7种类型,沉积环境主要是陆坡,部分为深海平原,海洋生物,海洋化学以及火山物质的沉积起到了积极的作用,陆源物质的影响较小,它们主要来源于北部大陆和南部岛礁等物源区。  相似文献   
9.
TYSC-3Q与PSJ-2型数字测井仪是目前煤田测井中常用的二种测井仪器,在使用过程中难免发生诸如测井控制故障、声速探管故障、密度三侧向探管故障、井温、井液电阻率探管故障、电法面板故障、数字测井面板故障、电测井故障等常见故障类型。通过对各类故障因素进行剖析,指出了故障易发生的部位,并详细的介绍了检查的方法及故障的排除步骤。  相似文献   
10.
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