Dual modes of the carbon cycle since the Last Glacial Maximum

The most conspicuous feature of the record of past climate contained in polar ice is the rapid warming which occurs after long intervals of gradual cooling. During the last four transitions from glacial to interglacial conditions, over which such abrupt warmings occur, ice records indicate that the CO2 concentration of the atmosphere increased by roughly 80 to 100 parts per million by volume. But the causes of the atmospheric CO2 concentration increases are unclear. Here we present the stable-carbon-isotope composition (delta 13 CO2) of CO2 extracted from air trapped in ice at Taylor Dome, Antarctica, from the Last Glacial Maximum to the onset of Holocene times. The global carbon cycle is shown to have operated in two distinct primary modes on the timescale of thousands of years, one when climate was changing relatively slowly and another when warming was rapid, each with a characteristic average stable-carbon-isotope composition of the net CO2 exchanged by the atmosphere with the land and oceans. delta 13 CO2 increased between 16.5 and 9 thousand years ago by slightly more than would be estimated to be caused by the physical effects of a 5 degrees C rise in global average sea surface temperature driving a CO2 efflux from the ocean, but our data do not allow specific causes to be constrained.     

Changes in plant diversity on the Chinese Loess Plateau since the Last Glacial Maximum

Changes in biodiversity during periods of glo- bal warming are of broad public concern. To study the effect of the warming process on the ecosystem, we carried out pollen analyses on samples from seven selected sections at Qingyang, Ningxian, Yangling, Binxian, Baoji, Yanshi, and Lingbao on the Chinese Loess Plateau in order systematically to evaluate changes in plant diversity since the Last Glacial Maximum （LGM）. The plant richness indices （Simpson＇s diversity index and rarefaction analysis） indicated that the plant diversity of each section increased during the process of warming from the LGM to the Holocene Optimum, especially at Baoji and Lingbao. These results are consistent with many long-timescale geological records, which show that warming can increase biodiversity; therefore, the popular viewpoint that warming leads to biodiversity loss or species extinction needs to be re-examined.     

A palynological and palaeoclimatological record from the southern Philippines since the Last Glacial Maximum

A palynological analysis of a marine sediment core in the southern Philippines,provides a detailed regional vegetation and climate history for the West Pacific Warm Pool(WPWP)since the Last Glacial Maximum(LGM).Chronology was determined by a detailed oxygen isotope record.A higher representation of pollen from tropical upper montane rainforest during the LGM indicate that this forest type moved down along elevation,probabaly due to the lowered temperature.During the last deglaciation and the early Holocene,mangroves were more expanded and tropical mid and upper montane rainforests were restricted,suggesting a rising sea-level and temperature increase.Herbaceous pollen and pteridophyte spore records indicate a much drier condition during the LGM than the Holocene.Mangrove development is controlled by conditions at the river mouth influenced by river discharge.Pteridophyte spores are abundant in wet conditions and are mainly transported by rivers.During the mid-Holocene,the reduction in mangrove pollen and pteridophyte spore appears to be a result of climate change:mainly decrease in river discharge.This may have been affected by the decreasing intensity of the Southeast Asian Monsoon,and the increasing frequency and intensity of warm ENSO events,El Ni?o,in this region.     

Spatial and temporal variations of C3/C4 relative abundance in global terrestrial ecosystem since the Last Glacial and its possible driving mechanisms

The primary factor controlling C 3 /C 4 relative abundance in terrestrial ecosystem since the Last Glacial has been widely debated. Now more and more researchers recognize that climate, rather than atmospheric CO 2 concentration, is the dominant factor. However, for a specific area, conflicting viewpoints regarding the more influential one between temperature and precipitation still exist. As temperature and precipitation in a specific area usually not only vary within limited ranges, but also covary with each other, it is difficult to get a clear understanding of the mechanism driving C 3 /C4 relative abundance. Therefore, systematic analysis on greater spatial scales may promote our understanding of the driving force. In this paper, records of C3/C4 relative abundance since the Last Glacial on a global scale have been reviewed, and we conclude that: except the Mediterranean climate zone, C3 plants predominated the high latitudes during both the Last Glacial and the Holocene; from the Last Glacial to the Holocene, C4 relative abundances increased in the middle latitudes, but decreased in the low latitudes. Combining with studies of modern process, we propose a simplified model to explain the variations of C3 /C4 relative abundance in global ecosystem since the Last Glacial. On the background of atmospheric CO2 concentration since the Last Glacial, temperature is the primary factor controlling C3/C4 relative abundance; when temperature is high enough, precipitation then exerts more influence. In detail, in low latitudes, temperature was high enough for the growth of C4 plants during both the Last Glacial and the Holocene; but increased precipitation in the Holocene inhibited the growth of C4 plants. In middle latitudes, rising temperature in the Holocene promoted the C4 expansion. In high latitudes, temperature was too low to favor the growth of C4 plants and the biomass was predominated by C3 plants since the Last Glacial. Our review would benefit interpretation of newly gained records of C3/C4 relative abundance from different areas and different periods, and has its significance in the understanding of the driving mechanisms of C3/C4 variations on longer timescales (e.g., since the late Miocene) with reliable records of temperature and atmospheric CO2 concentration.     

A high-resolution clay mineralogical record in the northern South China Sea since the Last Glacial Maximum,and its time series provenance analysis

High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea (SCS) covering the period since the Last Glacial Maximum shows that illite (29%–48%), smectite (14%–45%), chlorite (17%–28%), and minor kaolinite (6%–14%) comprise the clay mineral assemblage, and that time series variation does not present glacial-interglacial cyclicity. Provenance analysis indicates three end-member sources: almost all smectite derives from Luzon, all kaolinite is sourced from the Pearl River, and illite and chlorite originate from both the Pearl River and Taiwan. By comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS, we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity. There were three stages of provenance change. (1) During 24.1–17.5 ka BP, contributions from Taiwan and Luzon were similar (30%–40%), while that from the Pearl River was only 25%. (2) During 17.5–14.0 ka BP, the contribution from Luzon decreased rapidly to 20%–25%, while that from Taiwan increased to 35% from an average of 25% at 18 ka BP, and that from the Pearl River increased largely to 40%. (3) During the Holocene, differences in contributions from the three major provenances increased: the contribution from Luzon increased slightly and then remained at 27%–35%, that from Taiwan increased rapidly and then remained at 55%–60%, and that from the Pearl River decreased to 15%. The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production, monsoon rainfall denudation, oceanic current transport, and sea-level change.     

青藏高原湖泊湖面变迁及影响因素

 湖泊对气候波动有敏感记录。以地理信息系统（GIS）和遥感（RS）技术为基础,从20世纪70年代、90年代、2000年前后和2010年前后4期Landsat遥感影像中,提取青藏高原所有湖泊边界信息,建立青藏高原湖泊空间数据库,并收集了青藏高原47个气象台站的年平均气温和年降雨量资料（1961-2010）,研究青藏高原湖泊湖面变迁及其影响因素。结果表明,1973-2010年,青藏高原湖泊个数和总面积呈显著增加的趋势;青藏高原湖泊湖面变迁主要受气温升高、降雨量增加和蒸发量减少的影响;此外,影响青藏高原湖泊湖面动态变化的因素还有冰川分布、人类活动、湖盆形状、补给和排泄区等。     

近54年华北平原干旱时空变化特征及其影响因素

利用帕尔默干旱指数(The Palmer Drought Severity Index,PDSI),辅以经验正交分解(Empirical Orthogonal Function,EOF)、趋势分析和相关分析等方法,全面分析了1960—2013年华北平原干旱时空变化特征,并对其影响因素进行了研究.结果表明:1)近54a华北平原PDSI并无显著变化趋势,而呈阶段性变化特征.分区研究表明,海河平原PDSI呈下降趋势,而淮河平原PDSI呈上升趋势;2)华北平原PDSI具有显著的空间差异特征,整体呈由东南向西北逐渐减小的趋势.EOF分析显示,研究区PDSI最主要的空间分布型为南北反向型分布,且干旱变化具有持续性;3)在趋势上,华北平原呈现显著的"南涝北旱"格局特征,其中北部海河平原PDSI呈下降趋势,而南部淮河平原PDSI则呈增加趋势;4)华北平原和黄河平原PDSI与南方涛动指数(SOI)和西太平洋副高北界(WPSHNB)关系显著,而淮河平原与东亚夏季风指数(EASMI)和西太平洋副高强度(WPSHS)具有显著相关性,海河平原仅与SOI达到显著的正相关关系,且随着时间尺度的变长,PDSI与各环流指数的相关性提高.年代际尺度上,华北平原PDSI主要与SOI关系显著.     

基于文献计量的中国家庭能源消费的地理格局及影响因素分析

家庭能源消费格局研究已成为全球能源地理和可持续发展的重要课题。通过文献计量分析,从空间特征、影响要素以及环境效应等视角开展中国家庭能源消费的综合评述,发现中国家庭能源消费结构存在显著空间区位差异,但在环境-经济地理特征相似区域呈现趋同性;家庭能源消费的影响因素包含家庭属性、社会文化、政治经济、地理环境以及能源可得性和能源价格等;家庭能源消费模式变化后产生了新的环境-经济-社会问题。目前研究以单一要素为主而相对缺乏集成和综合性分析,未来需要开展区域家庭能源结构、时空过程及其驱动机制和效应的能源可持续发展领域研究,探索家庭能源消费的空间-社会格局特征及其时空交互作用。     

黑色素的合成与美白产品的研究进展

随着环境污染对大气臭氧层的不断破坏,越来越多的紫外线照射到地球表面,加重了人类皮肤色素沉积异常.本文将介绍黑色素的合成过程,并综述黑色素合成过程中的关键限速酶——酪氨酸酶(TYR)的调控方式和相关信号通路的最新研究进展,还介绍了影响黑色素合成的重要因素,为黑色素抑制剂的研发提供理论依据.此外,本文还综述了目前市场上常见的几类美白产品及其特点,旨在让人们重视肌肤色素沉着问题,并关注对皮肤黑色素产生进行科学护理.     

Spatiotemporal variations of Zr/Rb ratio in three last interglacial paleosol profiles across the Chinese Loess Plateau and its implications for climatic interpretation

The ratio of Zirconium to Rubidium （Zr/Rb） is suggested to be a better proxy for the East Asian winter monsoon strength than the widely-used grain size distribution. The rationale for the Zr/Rb proxy relies on the following assumptions： （1） Grain size fractionating characteristics during eolian dust transport should be archived in the Zr/Rb ratio records and this assumption is based on the premise that Zr is preferentially enriched in coarser grain size fraction while Rb tend to be enriched in finer grain size fraction; and （2） post-depositional weathering does not change the Zr/Rb ratio due to the immobility of these two elements. To examine these two assumptions, three last interglacial paleosols （S1） from Dingxi, Tianshui and Lantian, along a NW-SE transect across the Chinese Loess Plateau, were geo- chemically investigated. Our results show that the Rb concentration exhibits an increasing trend along the NW-SE transect both in the paleosol （S1） and the measured portions of the loess units （L1 and L2）, being supportive to the assumption that Rb is enriched in the fine particles. But we also found that Rb loss did occur to some extent in the three profiles, contradicting to the presumption of Rb immobility during pedogenic processes. The Zr concentration exhibits an expected decreasing trend in the measured portions of the loess units and an unexpected increasing trend in the paleosol along the NW-SE transect. Moreover, the ratios of Zirconium to Hafnium （Zr/Hf） show different variation patterns between interglacial and glacial, implying that Zr-bearing minerals and their resident grain size fractions are probably not identical during interglacial and glacial. Thus, the assumption that Zr is enriched in coarse grain size fraction can no longer hold. We conclude that the final Zr/Rb value is not only dependent on grain size sorting processes but also on post-depositional alteration and source prove- nance. Under enhanced chemical weathering, especially when chemical index of alterat     

硝酸盐介导底泥硫自养反硝化的过程、效应和应用

底泥黑臭是当前我国城市河道水环境污染中亟待解决的问题.近年来利用硝酸钙促生底泥土著微生物以修复底泥黑臭的原位处理技术受到了不少关注,然而对于该过程中关键的硫自养反硝化反应的研究较为少见.文章介绍了硫自养反硝化反应在环境治理领域的基础研究和相关技术应用情况,论述了硝酸盐介导的底泥硫自养反硝化反应的特点、产生过程、该反应过程中普遍存在的副产物(N2O、NO-2)累积现象,以及底泥硫自养反硝化相关功能菌群及其生态关系等方面的研究进展,提出了在这些研究领域中尚不清楚的一些科学问题.最后指出,对黑臭底泥修复过程中硫自养反硝化反应的脱氮过程、脱氮贡献率,以及该过程中功能菌种群生态特征变化的研究,可进一步促进我国城市河道黑臭治理研究工作的深入和发展.     

改革开放下的中国女性主义批评30年

改革开放30年以来,中国女性主义批评经历了三个发展阶段,即20世纪80年代是为女性文学批评正名以及女性文学批评与女性创作互为动力,初显蓬勃发展态势的阶段;90年代是女性主义文学批评作为一个有价值的学科开始确立独立学术地位的阶段;2000年以来,女性主义批评打破文学的限制,呈现文化化、多样化的走向。     

拓展国际科技交流渠道构建开放信任合作格局——中国科协九大以来的国际民间科技交流

开展国际民间科技交流是中国科协的重要任务之一,也是国家创新战略的重要支撑和国家外交工作的组成部分.5年来,中国科协充分发挥民间对外科技交流主渠道的优势,完善民间对外科技交流开放战略布局,在复杂多变的国际形势和突如其来的疫情影响下,努力拓展工作思路,解决工作中遇到的问题和挑战,在积极搭建合作平台、充分利用国际科技资源、服...     

水下软体机器人柔性驱动方式及其仿生运动机理研究进展

 随着水下作业要求的增加以及软体机器人技术的发展,水下软体机器人的研究成为水下机器人的一个前沿方向。用人工肌肉实现驱动控制并能实现仿生运动的水下软体机器人成为相关领域的研究热点。本文介绍现有水下软体机器人中7类人工肌肉驱动方式,再根据水下软体机器人推进形式,按5种仿生运动形式介绍了现有的水下软体机器人,最后展望了水下软体机器人未来在水下勘探的应用前景。     

石墨烯基墨水的制备及其在印刷电子中的应用

 石墨烯材料具有优异的导电性、柔性、化学稳定性等特征,在印刷电子领域中具有广阔的应用前景。概述了石墨烯材料的宏量制备方法,结合喷墨打印、丝网印刷和3D打印等方法介绍了石墨烯墨水制备的技术特点和要求,展示了石墨烯在印刷电子功能器件中的应用,主要类型包括透明导电薄膜、柔性电路、超级电容器和可穿戴传感器等。总结了该领域当前研究进展中存在的问题和挑战,从材料设计、加工制备和器件应用方面进行了展望。在未来发展中可通过丰富石墨烯打印线路的结构形式,并注重利用组装的策略增强结构有序性,实现多功能、高性能的器件制备和应用。     

A review of the synthesis and application of zeolites from coal-based solid wastes

Zeolite derived from coal-based solid wastes(coal gangue and coal fly ash) can overcome the environmental problems caused by coal-based solid wastes and achieve valuable utilization. In this paper, the physicochemical properties of coal gangue and coal fly ash are introduced. The mechanism and application characteristics of the pretreatment processes for zeolite synthesis from coal-based solid wastes are also introduced. The synthesis processes of coal-based solid waste zeolite and their advanta...     

Seasonal variations of carboxylic acids and their contributions to the rainwater acidity: A case study of Guiyang and Shangzhong,China

Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chromatography from April 2006 to April 2007.Formic, acetic and oxalic acids were found to be the predominant carboxylic acids.Their volume weighted average concentration (VWA) in the rainwater of Guiyang were 14.24 μmol/L, 9.35 μmol/L and 2.79 μmol/L, respectively;as compared to 4.95 μmol/L, 1.35 μm...     

回眸百年再启程:中国科技社团发展的历史进程与主要贡献

 19世纪末20世纪初在中华大地上兴起学会热潮,尤其是“五四”新文化运动以来,现代意义上的科技社团在中国已经走过了百年历程,构成世界科技社团发展史上波澜壮阔的画卷之一。在纪念“五四”运动100周年之际,回顾科技社团百年来发展历程,研究分析科技社团在中国科学文化启蒙、科学技术发展和经济社会建设中的重要作用,对于探寻新时代中国科技社团发展道路,具有重要的理论和现实意义。     

20世纪90年代汉字结构理论述评

20世纪90年代以来的汉字结构理论,即詹鄞鑫、苏培成的“新六书”理论;张玉金的“六种汉字结构类型”理论;王宁的“十一种汉字构形”理论,同中有异,异中有同。可以在此基础上提出相关的研究建议。