Rapid body size decline in Alaskan Pleistocene horses before extinction

About 70% of North American large mammal species were lost at the end of the Pleistocene epoch. The causes of this extinction--the role of humans versus that of climate--have been the focus of much controversy. Horses have figured centrally in that debate, because equid species dominated North American late Pleistocene faunas in terms of abundance, geographical distribution, and species variety, yet none survived into the Holocene epoch. The timing of these equid regional extinctions and accompanying evolutionary changes are poorly known. In an attempt to document better the decline and demise of two Alaskan Pleistocene equids, I selected a large number of fossils from the latest Pleistocene for radiocarbon dating. Here I show that horses underwent a rapid decline in body size before extinction, and I propose that the size decline and subsequent regional extinction at 12,500 radiocarbon years before present are best attributed to a coincident climatic/vegetational shift. The present data do not support human overkill and several other proposed extinction causes, and also show that large mammal species responded somewhat individualistically to climate changes at the end of the Pleistocene.     

Late Pleistocene／Holocene wetland events recorded in southeast Tengger Desert lake sediments, NW China

The area along the eastern and southeastern margins of the Tengger Desert, NW China, which is sensitive to the summer monsoon variations, was selected for studying the environmental conditions surrounding the transition between Paleolithic foragers and Neolithic farmer/pastoral-ists. Short cores were obtained from four lake basins in the southwestern Tengger using a hand-driven piston coringdevice. Proxies from these cores were supplemented by ra-diocarbon ages obtained from lake sediment cores, shoreline features and spring mound deposits. Together these records provide evidence of millennial-scale climate change eventsfrom the Pleistocene-Holocene transition to the present.Lake/wetland events, representing periods of more intensive summer monsoon, occur in the records at-12.7-11.6,-10.1, -9.3, -8.0, -5.4, -1.5, and -0.8 ka BP. They do suggest that century- to miliennial-seale climatic cycles are characteristic of the Holocene in the southeastern Tengger Desert although the chronology must be considered extremely tentative.     

Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history

Rapid warming over the past 50?years on the Antarctic Peninsula is associated with the collapse of a number of ice shelves and accelerating glacier mass loss. In contrast, warming has been comparatively modest over West Antarctica and significant changes have not been observed over most of East Antarctica, suggesting that the ice-core palaeoclimate records available from these areas may not be representative of the climate history of the Antarctic Peninsula. Here we show that the Antarctic Peninsula experienced an early-Holocene warm period followed by stable temperatures, from about 9,200 to 2,500?years ago, that were similar to modern-day levels. Our temperature estimates are based on an ice-core record of deuterium variations from James Ross Island, off the northeastern tip of the Antarctic Peninsula. We find that the late-Holocene development of ice shelves near James Ross Island was coincident with pronounced cooling from 2,500 to 600?years ago. This cooling was part of a millennial-scale climate excursion with opposing anomalies on the eastern and western sides of the Antarctic Peninsula. Although warming of the northeastern Antarctic Peninsula began around 600 years ago, the high rate of warming over the past century is unusual (but not unprecedented) in the context of natural climate variability over the past two millennia. The connection shown here between past temperature and ice-shelf stability suggests that warming for several centuries rendered ice shelves on the northeastern Antarctic Peninsula vulnerable to collapse. Continued warming to temperatures that now exceed the stable conditions of most of the Holocene epoch is likely to cause ice-shelf instability to encroach farther southward along the Antarctic Peninsula.     

火焰在微细圆管中传播及其熄火现象

采用单步化学反应机理，假定流场满足Poiseuille分布，用热传导-组分扩散模型研究圆管中预混火焰传播特征和熄火条件。通过计算不同的壁面对流散热和气体流动速度下的火焰，得到火焰面形状的变化规律、火焰传播速度的曲线，分析出了微细圆管中熄火的规律：管道越细，熄火越容易；进口气流速度为0时的燃料消耗速率最小，但只有正的进口速度才有利于防止熄火。     

Model-data divergence in global seasonal temperature response to astronomical insolation during the Holocene

Insolation change is a primary driver for climate variation at orbital scales [1,2].During the Holocene (ca.11.7 ka BP to present),orbitally induced seasonal va...     

鲁南地区全新世环境变化与文化响应

山东鲁南地区是我国暖温带向亚热带过渡的半湿润区,全新世以来该地演绎了多起古文化兴替.试图利用野外考古资料和已有的考古成果,系统梳理本地区全新世自然环境演变过程,探讨该地区全新世环境演变与古文化发展的关系.研究结果表明:全新世期间鲁南地区经历了多次环境变迁,同期的古文化发展明显受环境变化影响.     

Intensified deep Pacific inflow and ventilation in Pleistocene glacial times

The production of cold, deep waters in the Southern Ocean is an important factor in the Earth's heat budget. The supply of deep water to the Pacific Ocean is presently dominated by a single source, the deep western boundary current east of New Zealand. Here we use sediment records deposited under the influence of this deep western boundary current to reconstruct deep-water properties and speed changes during the Pleistocene epoch. In physical and isotope proxies we find evidence for intensified deep Pacific Ocean inflow and ventilation during the glacial periods of the past 1.2 million years. The changes in throughflow may be directly related to an increased production of Antarctic Bottom Water during glacial times. Possible causes for such an increased bottom-water production include increasing wind strengths in the Southern Ocean or an increase in annual sea-ice formation, leaving dense water after brine rejection and thereby enhancing deep convection. We infer also that the global thermohaline circulation was perturbed significantly during the mid-Pleistocene climate transition between 0.86 and 0.45 million years ago.     

大熊猫电刺激采精及精液冷冻保存研究

对卧龙自然保护区大熊猫研究中心的９只５．５－１６．５岁的雄性大熊猫进行了１７次电刺激采精,其中３只是能进行自然交配并繁殖了后代的种公兽,比较研究了精液离心、不同稀释液和冷冻方法对大熊猫精液超低温冷冻保存后的活力、运动状态、精子和顶体形态的影响。细冷冻是１种较好的超低温冷冻精液的方法。     

平潭岛全新世孢粉组合及其地质意义

选择平潭岛芦洋埔平原南部和北部两个钻孔岩芯,作为该地区全新世沉积地层代表,进行系统的孢粉研究,得出孢粉组合,从而恢复了平潭岛全新世古植被及古环境,探讨了平潭岛全新世地层时代的划分与对比及海平面变化。     

美国迈阿密地区更新世鲕粒滩发育特征及控制因素

通过对迈阿密鲕粒滩与现代鲕粒滩的类比,将高分辨率的卫星激光雷达绘图与露头信息结合起来,可视化了迈阿密鲕粒滩的整体形态以及其中的沉积特征,潮汐通道的分布直接影响鲕粒滩的形态,迈阿密鲕粒滩的形成与潮汐作用有密不可分的联系;在迈阿密鲕粒滩中的沉积相主要发育交错层理的鲕粒相和生物潜穴型泥质鲕粒灰岩相,其中可见羽状交错层理以及大量的生物遗迹化石,证实迈阿密鲕粒滩的形成受到潮汐作用的影响;迈阿密鲕粒滩经历了胶结作用和溶蚀作用等多种成岩作用,其中胶结作用会破坏其孔渗性,而在溶蚀作用的影响下会增加其孔渗性。在对迈阿密鲕粒滩中的典型露头进行了实地考察后,进一步确认了迈阿密鲕粒滩是受到潮汐作用而形成的现代鲕粒滩。     

Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean

During the last ice age, the Indian Ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial-scale climate events in the North Atlantic region, suggesting a mechanistic link. In the Holocene epoch, which had a more stable climate, the amplitude of abrupt changes in North Atlantic climate was much smaller, and it has been unclear whether these changes are related to monsoon variability. Here we present a continuous record of centennial-scale monsoon variability throughout the Holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic Arabian Sea. Our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the North Atlantic region--including the most recent climate changes from the Medieval Warm Period to the Little Ice Age and then to the present. We therefore suggest that the link between North Atlantic climate and the Asian monsoon is a persistent aspect of global climate.     

Chinese deserts and sand fields in Last Glacial Maximum and Holocene Optimum

The Last Glacial Maximum (LGM, c. 26-16 ka) and the Holocene Optimum (HO, c. 9-5 ka) were characterized by cold-dry and warm-wet climates respectively in the recently geological Earth. How Chinese deserts and sand fields responded to these distinctive climatic changes is still not clear, however. To reconstruct environments of the deserts and sand fields during the LGM and HO is helpful to understand the forcing mechanisms of environment change in this arid region, and to test paleoclimatic modeling results. Through our long-term field and laboratory investigations, 400 optically stimulated luminescence (OSL) ages and more than 100 depositional records in the Chinese deserts and sand fields were obtained; on the basis of these data, we reconstruct spatial distributions of the deserts and sand fields during the LGM and HO. Our results show that the sand fields of Mu Us, Hunshandake, Horqin and Hulun Buir in northern and northeastern China had expanded 25%, 37%, 38% and 270%, respectively, during the LGM; the sand fields of Gonghe in the northeastern Qinghai-Tibetan Plateau had expanded 20%, and the deserts of Badain Jaran, Tengger in central northern China had expanded 39% and 29% separately during the LGM; the deserts of Taklimakan, Gurbantünggüt and Kumtag in northwestern China had expanded 10%-20% respectively, compared to their modern areas. On the other hand, all of the sand fields were nearly completely covered by vegetation during the HO; the deserts in northwestern and central northern China were reduced by around 5%-20% in area during this time. Lakes in this arid region were probably expanded during the HO but this conclusion needs more investigation. Compared with the geological distributions of deserts and sand fields, human activity has clearly changed (expanded) the area of active sand dunes at the present time. Our observations show that environmental conditions of Chinese deserts and sand fields are controlled by regional climate together with human activity.     

Holocene palynological records and their responses to the controversies of climate system in the Shiyang River drainage basin

The Shiyang River drainage basin is located in the northwest margin of the Asian monsoon region. Previous studies reached different conclusions about Holocene climatic changes in the basin. Some studies suggested the Holocene climatic changes were mainly controlled by the Asian monsoon and that the climate was relatively humid during the early Holocene (11.6-7.1 cal ka BP). Other studies found the mid-Holocene Climatic Optimum (7.0-5.0 cal ka BP), and this climate condition was similar to the Holocene westerly wind pattern in arid Central Asia. The modern climate is affected by the Asian monsoon and westerly wind in the drainage basin, and the Holocene climatic records showed two different Holocene climatic patterns-a westerly wind pattern and monsoonal pattern. However, it remains unclear what caused the two different Holocene climatic patterns to co-exist in the region. The palynological records are the main evidence for the Holocene climatic changes in the basin. This paper focuses on palynological records for different parts of the drainage basin. Among them, QTH02, QTL-03 and Sanjiaocheng records are located in the terminal lake, and the Hongshuihe record is located in the middle reaches of the basin. In the terminal lake, the palynological records of QTH02 and QTL-03 are similar, but the Sanjiaocheng record differs. The difference is mainly affected by the variable pollen assemblages in the different locations of the lake basin. From comparison and synthesis of the four palynological records, we concluded that the millennial-scale Holocene climatic changes were affected by the combined effects of the Asian monsoon and westerly wind in the drainage basin, which show the complicated Holocene climatic pattern in the northwest margin of the Asian monsoon.     

Climatic changes from the late Pliocene to middle Pleistocene in and around central Japan reconstructed from plant macrofossil assemblages

We used composition of plant macrofossil assemblages obtained mainly from the Osaka Group in central Japan to reconstruct the palaeoclimate between the late Pliocene (about 3.3 m.y. B.P.) and the middle Pleistocene (about 0.4 m.y. B.P.). The warmest climate of the period was before 3.0 m.y. B.P. Cool-temperate elements increased and subtropical elements decreased between 3 m.y. B.P. and 2.7 m.y. B.P., indicating the first climatic deterioration. The first occurrence of subarctic elements characterizes the Plio-Pleistocene boundary as a severe cold stage. After 1.1 m.y. B.P., climatic fluctuation occurred at less than 100,000 year intervals. A severe cold stage occurred just after the Jaramillo event (about 0.8 m.y. B.P.). The warmest stage in the middle Pleistocene occurred at about 0.5 m.y. B.P. With it evergreen broad-leaved forest expanded into central Japan. The climatic curves reconstructed from plant macrofossils parallel the climatic changes reconstructed from loess - paleosol stratigraphy in Central China, radiolarian faunal stratigraphy in the north Pacific deep sea drilling core, oxygen-isotope data in the North Pacific, and pollen spectra in western Europe.     

从高分子构象与动力学到蛋白质折叠

针对作用在聚合物刷上的键拉力研究表明作用在接枝基面上的力随着聚合物刷接枝密度的增大反而减小,然而尾端单体上的拉伸张力并没有消失.高分子的构象和动力学转变决定了其物性和多种多样的应用,而生物大分子蛋白质作为由二十种不同属性的氨基酸构成的序列,更是具有由其序列所决定的特别的三维自然结构.本文就聚合物刷、聚合物纳米复合材料、聚合物网络等几种高分子体系的构象与动力学过程,及蛋白质构象和其折叠与去折叠的动力学过程做了介绍.特别是蛋白质的折叠与去折叠速率在单分子操纵实验中受到拉力的调控,通过测量这种拉力依赖的动力学过程、蛋白质的自由能曲面和折叠去折叠路径可以得到系统全面的研究.本文以肌肉蛋白titin的免疫球蛋白结构域I27为例对蛋白质折叠研究进行了阐述.     

长江三角洲地区新石器遗址文化间歇层与全新世埋藏古树研究

在长江三角洲多年考古发掘中发现 ,在文化层之间经常出现由自然淤积的泥炭和沼铁构成的不含任何文化器物的文化间歇层。这些文化间歇层主要分布于 3个时间段 :( 1)崧泽文化晚期—良渚文化早期 ( 530 0～ 4 70 0yrBP) ;( 2 )良渚文化晚期—马桥文化早期 ( 4 2 0 0～ 4 0 0 0yrBP) ;( 3)马桥文化晚期—商周文化早期 ( 330 0～ 30 0 0yrBP)。此外 ,在本区第四纪地质调查和市政工程建设中还发现大量全新世埋藏古树和泥炭沉积。这些埋藏古树和泥炭层主要出现在 4个时间段地层中 :( 1)大西洋气候期早期 ( 70 0 0～60 0 0yrBP) ;( 2 )大西洋气候期晚期 ( 550 0～ 50 0 0yrBP) ;( 3)亚北方气候期中期 ( 4 40 0～ 4 10 0yrBP)以及 ( 4 )亚北方气候期晚期 ( 360 0～ 310 0yrBP)。上述现象反映了本区全新世气候和海面中低频的波动特征。大量研究揭示 ,上述灾变沉积地层主要起因于高温高海面条件下夏季风活动增强引发的 4次大规模陆地洪水事件 ,但并非由海侵所致。     

渭河阶地全新世成壤过程及人类因素研究

通过对陕西眉县清湫村全新世黄土剖面的野外考察研究、粒度分析和磁化率测定，揭示了在渭河阶地自然地带性土壤褐土的形成过程中，由于气候恶化和风尘堆积，以及仰韶文化期人类农业耕垦和聚落建设活动的影响，造成了某些区域全新世古土壤分裂为两层的现象．根据清湫村全新世黄土剖面层序模式，论证了全新世时期风尘堆积仍在继续，古土壤覆盖层亦具有风尘堆积的性质，但是它们受到历史时期人类耕作活动的改造     

Sex differences in emigration and mortality affect optimal management of deer populations

Populations of red deer that are limited by food, like those of many other ungulates, commonly include more females than males. We assessed the contribution of variation in sex- and age-specific rates of mortality and emigration to density-dependent changes in the adult sex ratio, using long-term observations and demographic experiments involving the red deer population on Rum, Scotland. We incorporated these effects in a stochastic model of local populations under different management regimes to show here that, when female numbers are allowed to increase to more than 60% of the ecological carrying capacity, the sustainable annual harvest of males from local deer populations will fall. Because males are typically culled by fee-paying hunters and generate more income than females, income will decrease as the male harvest falls. Because numbers of female deer throughout much of the Highlands probably exceed the threshold at which male density starts to be affected, many managers might be able to raise income from local deer populations by reducing female numbers, with potential benefits to the vegetation of Scottish Highland environments.