Late survival of Neanderthals at the southernmost extreme of Europe

The late survival of archaic hominin populations and their long contemporaneity with modern humans is now clear for southeast Asia. In Europe the extinction of the Neanderthals, firmly associated with Mousterian technology, has received much attention, and evidence of their survival after 35 kyr bp has recently been put in doubt. Here we present data, based on a high-resolution record of human occupation from Gorham's Cave, Gibraltar, that establish the survival of a population of Neanderthals to 28 kyr bp. These Neanderthals survived in the southernmost point of Europe, within a particular physiographic context, and are the last currently recorded anywhere. Our results show that the Neanderthals survived in isolated refuges well after the arrival of modern humans in Europe.     

南京地区竹叶锈病病原及发生规律研究

对南京地区竹叶锈病的病原及发生规律进行了研究。结果表明：南京地区竹叶锈病的病原主要有3种,分别为刚竹柄锈菌(Puccinia phyllostachydis)、长角柄锈菌(Puccinia longicornis)和竹夏孢锈菌(Uredo ignava)。刚竹柄锈菌和长角柄锈菌主要以冬孢子堆在竹叶越冬,二者的初侵染源主要是冬孢子堆下面的菌丝产生的夏孢子,此外,刚竹柄锈菌的初侵染源还包括少量能越冬的夏孢子堆。竹叶锈病的潜育期为10~15 d,夏孢子可造成多次侵染,6月及10月为侵染高峰期。竹叶锈病的发生未发现转主寄生现象。     

No extreme bipolar glaciation during the main Eocene calcite compensation shift

Major ice sheets were permanently established on Antarctica approximately 34 million years ago, close to the Eocene/Oligocene boundary, at the same time as a permanent deepening of the calcite compensation depth in the world's oceans. Until recently, it was thought that Northern Hemisphere glaciation began much later, between 11 and 5 million years ago. This view has been challenged, however, by records of ice rafting at high northern latitudes during the Eocene epoch and by estimates of global ice volume that exceed the storage capacity of Antarctica at the same time as a temporary deepening of the calcite compensation depth approximately 41.6 million years ago. Here we test the hypothesis that large ice sheets were present in both hemispheres approximately 41.6 million years ago using marine sediment records of oxygen and carbon isotope values and of calcium carbonate content from the equatorial Atlantic Ocean. These records allow, at most, an ice budget that can easily be accommodated on Antarctica, indicating that large ice sheets were not present in the Northern Hemisphere. The records also reveal a brief interval shortly before the temporary deepening of the calcite compensation depth during which the calcite compensation depth shoaled, ocean temperatures increased and carbon isotope values decreased in the equatorial Atlantic. The nature of these changes around 41.6 million years ago implies common links, in terms of carbon cycling, with events at the Eocene/Oligocene boundary and with the 'hyperthermals' of the Early Eocene climate optimum. Our findings help to resolve the apparent discrepancy between the geological records of Northern Hemisphere glaciation and model results that indicate that the threshold for continental glaciation was crossed earlier in the Southern Hemisphere than in the Northern Hemisphere.     

A late Eemian aridity pulse in central Europe during the last glacial inception

Investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end, which has been a matter of much debate (see, for example, refs 1, 2). A recent ice core from Greenland demonstrates climate cooling from 122,000 years ago driven by orbitally controlled insolation, with glacial inception at 118,000 years ago. Here we present an annually resolved, layer-counted record of varve thickness, quartz grain size and pollen assemblages from a maar lake in the Eifel (Germany), which documents a late Eemian aridity pulse lasting 468 years with dust storms, aridity, bushfire and a decline of thermophilous trees at the time of glacial inception. We interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the North Atlantic drift, the ocean current that brings warm surface waters to the northern European region. The late Eemian aridity pulse occurred at a 65 degrees N July insolation of 416 W m(-2), close to today's value of 428 W m(-2) (ref. 9), and may therefore be relevant for the interpretation of present-day climate variability.     

No benefits from warming even for subnival vegetation in the central Himalayas

Global temperature has been increasing at unprecedented rates during the Anthropocene,impacting both natural and human sys-tems [1].Alpine biomes,among the most...     

华中地区近50年高温事件及大气环流成因分析

基于中国气象局信息中心整编的1960-2009年逐日地面最高气温的站点资料及NCEP/NCAR再分析资料,分析了华中地区85个站点的年平均高温日数和高温日平均最高气温的时间、空间变化,同时分析了高温日大气环流特征.结果表明:年平均高温日数和高温日年平均最高气温在时间分布上呈现增暖的趋势,在20世纪60-80年代中期呈降低趋势,之后呈现上升的趋势,尤其在2000年之后,表现得更加明显.年平均高温日数(＞35℃)和年平均高温日数(＞ 37℃)在空间分布上均呈现扩大趋势,部分地区年平均高温日数(＞ 35℃)增加10天,但是高温日(＞40℃)年平均气温呈弱下降趋势.从大范围高温事件的环流形势来看,7月与8月西太平洋副热带高压脊线北抬至25°～35°N之间.8月586线经向变化,西伸至90°E,100 hPa南亚高压发展强大.由此,在对流层中、上层两个高压系统相互配合,并且二者高度场均呈现强大的正距平,这便是形成华中大范围极端高温事件的大气环流形势场.     

厌氧微生物对新疆六中区稠油的降解特性

厌氧微生物作为油藏中微生物的重要组成部分,受到人们越来越多的关注,但是关于对原油的降解效果和降解机制的研究报道较少.对发酵菌富集培养物和产甲烷菌富集培养物作用前后的原油进行色质联用分析,结果表明:产甲烷菌富集培养物作用后的原油,其原油族组成变化明显,饱和烃和胶质相对含量降低,而芳香烃和沥青质相对含量上升,其中正构烷烃的含量有所增加,尤其是大于C22的正构烷烃的含量增加明显,藿烷及其同系物的含量也都有所上升.而发酵菌富集培养物作用后,饱和烃、芳烃以及胶质含量都略有上升,变化最明显的沥青质作用后下降了2%,发酵菌富集培养物降解了原油中的杂环芳烃二苯并噻吩和二苯并呋喃.同时两种富集培养物对二环芳烃的降解作用明显.产甲烷菌富集培养物和发酵菌富集培养物作用后,新疆六中区原油中短链正构烷烃含量相对增加,而长链正构烷烃含量则相对减少,∑nC21-/∑nC22+值由作用前1.033分别下降到1.023和1.015,Pr/Ph的值基本都保持在0.945左右,但是Pr/nC17和Ph/nC18都有所增大.总的来说,产甲烷菌富集培养物对原油的降解作用更明显,两种不同厌氧微生物的富集培养物对原油的作用表现出了一定的选择性.     

Increasing risk of great floods in a changing climate

Radiative effects of anthropogenic changes in atmospheric composition are expected to cause climate changes, in particular an intensification of the global water cycle with a consequent increase in flood risk. But the detection of anthropogenically forced changes in flooding is difficult because of the substantial natural variability; the dependence of streamflow trends on flow regime further complicates the issue. Here we investigate the changes in risk of great floods--that is, floods with discharges exceeding 100-year levels from basins larger than 200,000 km(2)--using both streamflow measurements and numerical simulations of the anthropogenic climate change associated with greenhouse gases and direct radiative effects of sulphate aerosols. We find that the frequency of great floods increased substantially during the twentieth century. The recent emergence of a statistically significant positive trend in risk of great floods is consistent with results from the climate model, and the model suggests that the trend will continue.     

Nonlinear optics in the extreme ultraviolet

Nonlinear responses to an optical field are universal in nature but have been difficult to observe in the extreme ultraviolet (XUV) and soft X-ray regions owing to a lack of coherent intense light sources. High harmonic generation is a well-known nonlinear optical phenomenon and is now drawing much attention in attosecond pulse generation. For the application of high harmonics to nonlinear optics in the XUV and soft X-ray regime, optical pulses should have both large pulse energy and short pulse duration to achieve a high optical electric field. Here we show the generation of intense isolated pulses from a single harmonic (photon energy 27.9 eV) by using a sub-10-femtosecond blue laser pulse, producing a large dipole moment at the relatively low (ninth) harmonic order nonadiabatically. The XUV pulses with pulse durations of 950 attoseconds and 1.3 femtoseconds were characterized by an autocorrelation technique, based on two-photon above-threshold ionization of helium atoms. Because of the small cross-section for above-threshold ionization, such an autocorrelation measurement of XUV pulses with photon energy larger than the ionization energy of helium has not hitherto been demonstrated. The technique can be extended to the characterization of higher harmonics at shorter wavelengths.     

重庆直辖以来旅游业发展走势分析

以重庆市旅游业1997~2004年的统计资料为基础,以Excel软件为工具,运用理性分析法、比较分析法分析了重庆直辖以来旅游业的发展趋势及发展原因,提出了完善管理体制,强化政府主导等建议。     

400Oa前中国洪水与文化的探讨

从环境演变及环境考古等方面给其一个较为精确的定位,从气候、地质学角度分析了4 000 a前洪水的形成原因.同时,在史前时期,古文化的分布在很大程度上依赖环境条件,极端的水文事件或许会导致文化格局的重大调整,4 000 a的洪水对当时的文化造成了很大的冲击.     

积水在上倾输油管中运动状态研究

应用试验和数值模拟两种方法对积水在管道中的分布以及表观油速、管道倾角对积水运动的影响进行研究。在内径为0.1 m的环道上进行试验,用高速摄像的方法对积水在5°～30°上倾管道中的运动状况进行分析,在管道入口增加微小波动,对试验工况下积水的运动状况进行数值模拟。结果表明:表观油速对积水运动的影响较大,管道中剩余积水量随着表观油速的增大而减小,当表观油速达到临界值时积水能被完全清除;管道倾角对积水运动的影响较小,在4种试验倾角下清除积水所需的临界油速均相同;数值模拟结果与试验结果吻合较好,由于多相流模型的局限性,不能精确地模拟水滴的聚结与破碎。     

Interpreting grain-size trends associated with bedload transport on the intertidal flats at Dafeng, central Jiangsu coast

IN THE MARINE ENVIRONMENT, IT IS OFTEN DIFFICULT TO IDENTIFY THE NET SEDIMENT TRANSPORT PATHWAY BECAUSE OF THE COMPLICATED HYDRODYNAMICS AND SEDIMENT SOURCES. GAO AND COLLINS HAVE RE-EXAMINED A 1-D MODEL ORIGI- NALLY DERIVED BY MCLAREN AND BOWLES AND DEVE…     

A frequency comb in the extreme ultraviolet

Since 1998, the interaction of precision spectroscopy and ultrafast laser science has led to several notable accomplishments. Femtosecond laser optical frequency 'combs' (evenly spaced spectral lines) have revolutionized the measurement of optical frequencies and enabled optical atomic clocks. The same comb techniques have been used to control the waveform of ultrafast laser pulses, which permitted the generation of single attosecond pulses, and have been used in a recently demonstrated 'oscilloscope' for light waves. Here we demonstrate intra-cavity high harmonic generation in the extreme ultraviolet, which promises to lead to another joint frontier of precision spectroscopy and ultrafast science. We have generated coherent extreme ultraviolet radiation at a repetition frequency of more than 100 MHz, a 1,000-fold improvement over previous experiments. At such a repetition rate, the mode spacing of the frequency comb, which is expected to survive the high harmonic generation process, is large enough for high resolution spectroscopy. Additionally, there may be many other applications of such a quasi-continuous compact and coherent extreme ultraviolet source, including extreme ultraviolet holography, microscopy, nanolithography and X-ray atomic clocks.     

The trend and fluctuation of historical floods in the middle reaches of the Yangtze River

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Numerical simulation of Urumqi Glacier No. 1 in the eastern Tianshan, central Asia from 2005 to 2070

Due to climate changes, most of the alpine glaciers have retreated dramatically during the past decades. Thus it is significant to predict the alpine glacier variability in the future for a better understanding of the impact of climate changes on water resource. In this paper, we perform the numerical simulation on Urumqi Glacier No.1 in the eastern Tianshan, central Asia (hereafter Glacier No.1 for short) by considering both the mass balance and ice flow. Given the shape of the Glacier No.1, the velocity of the glacier is obtained by solving a two-dimensional nonlinear Stokes equation and simulated result is in agreement with the observation. In order to predict the variability of Glacier No.1 in the next decades, a climatic scenario is constructed with a temperature rise rate as 0.17°C/10 a and precipitation as constant during the period of 2005-2070. The simulation shows that, the glacier terminus will retreat slowly and the glacier will thin dramatically before 2040, while after year 2040, the glacier terminus retreat will accelerate. This study confirms the increasing retreat rate of alpine glaciers under global warming.     

明末浙江水旱灾害分布规律与成因分析

明代末年的崇祯时期是浙江水旱灾害频繁发生的时期.史料分析表明,①崇祯年间浙江省水旱灾害频繁发生,崇祯中后期为浙江省的旱灾高发期;②水旱灾害空间分布差异明显,旱灾和水灾的分布与地貌类型密切相关,山区、丘陵多旱灾,平原多水灾;③与同时期北方旱灾相比,浙江旱灾具有滞后现象,反映灾害与气候变化类似具有穿时性.     

孤岛油田中一区馆6砂组隔夹层分布研究

隔夹层是形成陆相储层流体流动非均质的主要原因之一,是控制厚油层复杂水淹形式的主要地质因素.孤岛油田自1990年进入特高含水期后,油层水淹严重,剩余油分布零散,因此隔夹层研究对于剩余油挖潜和提高最终采收率具有重要的意义.以孤岛中一区馆6砂组为例,利用岩心标定测井资料,提出不同类型夹层识别方法,并结合灰色理论对隔夹层进行综合判别.     

4000a前中国洪水与文化的探讨

从环境演变及环境考古等方面给其一个较为精确的定位，从气候、地质学角度分析了4000a前洪水的形成原因．同时，在史前时期，古文化的分布在很大程度上依赖环境条件，极端的水文事件或许会导致文化格局的重大调整，4000a的洪水对当时的文化造成了很大的冲击．