Out of Africa again and again

The publication of a haplotype tree of human mitochondrial DNA variation in 1987 provoked a controversy about the details of recent human evolution that continues to this day. Now many haplotype trees are available, and new analytical techniques exist for testing hypotheses about recent evolutionary history using haplotype trees. Here I present formal statistical analysis of human haplotype trees for mitochondrial DNA, Y-chromosomal DNA, two X-linked regions and six autosomal regions. A coherent picture of recent human evolution emerges with two major themes. First is the dominant role that Africa has played in shaping the modern human gene pool through at least two--not one--major expansions after the original range extension of Homo erectus out of Africa. Second is the ubiquity of genetic interchange between human populations, both in terms of recurrent gene flow constrained by geographical distance and of major population expansion events resulting in interbreeding, not replacement.     

解决中国粮食问题的战略对策选择

我国粮食由1949年的1．13亿吨增加到1998年4．91亿吨,提高3．35倍,解决了12．6亿人的吃饭问题,取得了举世眠目的成绩,但随着人口的增加,粮食生产,供给不容乐观,预计2000年人口达到13亿,2030年达到16亿,粮食需求量分别为5．2亿吨和7．34亿吨,这是经济发展面临的重大难题,根据建国50年来粮食发展的情况,从粮食地位,深度开发,科技兴粮,开源节流,人口控制五个方面作了系统分析,提出了综合解决中国粮食问题的基本思路,为实现“中国人解决中国的粮食问题”的宏伟目标提供科学依据。     

Rethinking schizophrenia

How will we view schizophrenia in 2030? Schizophrenia today is a chronic, frequently disabling mental disorder that affects about one per cent of the world's population. After a century of studying schizophrenia, the cause of the disorder remains unknown. Treatments, especially pharmacological treatments, have been in wide use for nearly half a century, yet there is little evidence that these treatments have substantially improved outcomes for most people with schizophrenia. These current unsatisfactory outcomes may change as we approach schizophrenia as a neurodevelopmental disorder with psychosis as a late, potentially preventable stage of the illness. This 'rethinking' of schizophrenia as a neurodevelopmental disorder, which is profoundly different from the way we have seen this illness for the past century, yields new hope for prevention and cure over the next two decades.     

再论党的学风

党的学风问题是一个事关党的兴衰和事业成败的重大政治问题。无产阶级的革命导师们都一贯强调和重视理论学习。今天，党内学风方面还存在着诸多问题，给党的建设带来了一些消极影响。为迎接二十一世纪可能经受的各种风险考验，必须继续加强党的理论学习和思想建设，进一步端正党的学风，以科学的态度对待马克思主义。     

The coming acceleration of global population ageing

The future paths of population ageing result from specific combinations of declining fertility and increasing life expectancies in different parts of the world. Here we measure the speed of population ageing by using conventional measures and new ones that take changes in longevity into account for the world as a whole and for 13 major regions. We report on future levels of indicators of ageing and the speed at which they change. We show how these depend on whether changes in life expectancy are taken into account. We also show that the speed of ageing is likely to increase over the coming decades and to decelerate in most regions by mid-century. All our measures indicate a continuous ageing of the world's population throughout the century. The median age of the world's population increases from 26.6 years in 2000 to 37.3 years in 2050 and then to 45.6 years in 2100, when it is not adjusted for longevity increase. When increases in life expectancy are taken into account, the adjusted median age rises from 26.6 in 2000 to 31.1 in 2050 and only to 32.9 in 2100, slightly less than what it was in the China region in 2005. There are large differences in the regional patterns of ageing. In North America, the median age adjusted for life expectancy change falls throughout almost the entire century, whereas the conventional median age increases significantly. Our assessment of trends in ageing is based on new probabilistic population forecasts. The probability that growth in the world's population will end during this century is 88%, somewhat higher than previously assessed. After mid-century, lower rates of population growth are likely to coincide with slower rates of ageing.     

满城县土地生产力及人口承载力初探

本文采用联合国粮农组织的农业生态区域法计算了满城县的土地生产力及人口承载力。然后结合该县未来耕地投入的增加和耕作技术水平提高的可能性,以及人口数量和消费水平变化趋势,计算了1995年与2000年的土地生产力及其承载人口的能力。最后通过分析,提出本世纪末要实现小康生活水平所应采取的主要措施。     

水稻新株型——超级水稻的评价

随着人口的不断增长,目前的水稻高产品种将越来越赶不上人类对粮食需求的增长。国际水稻研究所已培育出一种水稻新株型,即“超级水稻”。新型超级水稻的增产潜力比现有的高产品种高２５％,达到每公顷１３ｔ。这超级水稻育种计划始于１９８８年,将在本世纪末下世纪初可得到适当的推广。这项计划被认为是有效地解决人类特别是亚洲消费稻米国家粮食短缺问题的重要措施。     

钙化合物在煤热解过程中的作用

煤热解联产焦炭、焦油和煤气,是煤化工的重要分支。为了提高焦油和煤气的品质及产率,国内外研究了多种催化剂对煤热解过程的影响,大量文献表明,含钙化合物可以催化焦油裂解、提高焦油品质和煤气中高附加值组分(如H2和CO)的产率。本文基于近30年来的文献数据,从钙化合物对煤热解产物的收率、组成以及性质的影响方面展开评述,分析了钙化合物对煤热解过程的作用机理、对S和N迁移的影响,最后提出了需要进一步解决的问题。     

基于地理加权回归的江南市镇发展动力机制分析(1736-1949年)

为揭示18世纪中叶至20世纪中叶江南市镇分布演变的驱动力并展现其时空演变过程,分别以1736—1850年和1851—1949年的市镇数量为因变量,以其所对应的人口数量、人口密度、河流密度和海拔中位数为自变量,建立了江南市镇数量演变的时空模型(GWR模型);再将市镇核密度图和产业区图进行叠加,以观察产业因素对市镇发展的影响.研究结果表明:(1)1736—1850年,江南地区市镇分布存在空间集聚性;1851—1949年,集聚性有所降低. (2)江南人口增长较为稳定地驱动全局市镇数量增长. (3)1736—1850年,河流密度显著地驱动了江南东部地区的市镇增长. (4)1851—1949年, 江南东部部分地区河流密度与本地市镇数量增长之间转为负相关关系. (5)1851—1949年,环太湖地区及江南西北地区的河流密度显著地驱动市镇数量增长. (6)未能纳入GWR模型分析的区域中所出现的市镇数量爆发性增长现象与当地植棉业密切相关.     

Variation of Antarctic seal population in response to human activities in 20th century

A sediment core was collected from the Fildes Peninsula of Antarctica, which contained numerous seal hairs and was identified to be seal excrement deposition. By analyzing its total organic carbon (TOC) and concentrations of bio-elements, the seal population changes of the past century were reconstructed. The variation of seal population in the last century on the Fildes Peninsula is primarily controlled by human activities. The sealing industry in the early 20th century caused the dramatic decline of seal ...     

未来五年我国学龄人口变化与师范教育改革的探讨与实践

21世纪初期我国人口增长率基本控制在6‰左右,有关专家预测我国人口总数的高峰将出现在2050年。可是本世纪初期我国学龄人口的不稳定变化,及由此引起的对教师需求量的影响不容忽视,师范生的就业问题又是困扰师范教育发展的首要问题。本文的工作就是以我国的学龄人口变化为依据,对师范教育的改革进行了探讨。     

基于GIS的南宁市城市内部人口时空分布特征研究

为了解21世纪近10年南宁市城市人口空间结构的变化和发展,借助Geographic Information System(GIS)技术和SPSS统计分析软件,对2000年和2010年南宁市城市内部人口分布进行分析。结果表明,南宁市城市内部人口空间结构总体表现为集聚。2000年和2010年南宁市人口密度均以西乡塘街道办事处范围内最高,兴宁区内各街道人口密度增长较快;2000—2010年人口重心向西北移动约1.2km;2000年人口密度函数和2010年人口密度函数分别以反函数模型和二次函数模型拟合最优。随着距市中心的距离增加,人口密度递减;在市中心附近具有较大的向心效应,带来周边邻近区域人口的增长。     

The end of world population growth

There has been enormous concern about the consequences of human population growth for the environment and for social and economic development. But this growth is likely to come to an end in the foreseeable future. Improving on earlier methods of probabilistic forecasting, here we show that there is around an 85 per cent chance that the world's population will stop growing before the end of the century. There is a 60 per cent probability that the world's population will not exceed 10 billion people before 2100, and around a 15 per cent probability that the world's population at the end of the century will be lower than it is today. For different regions, the date and size of the peak population will vary considerably.     

Europe-wide reduction in primary productivity caused by the heat and drought in 2003

Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate, their impact on terrestrial carbon cycling is unclear. Here we report measurements of ecosystem carbon dioxide fluxes, remotely sensed radiation absorbed by plants, and country-level crop yields taken during the European heatwave in 2003. We use a terrestrial biosphere simulation model to assess continental-scale changes in primary productivity during 2003, and their consequences for the net carbon balance. We estimate a 30 per cent reduction in gross primary productivity over Europe, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg C yr(-1)) to the atmosphere and reversed the effect of four years of net ecosystem carbon sequestration. Our results suggest that productivity reduction in eastern and western Europe can be explained by rainfall deficit and extreme summer heat, respectively. We also find that ecosystem respiration decreased together with gross primary productivity, rather than accelerating with the temperature rise. Model results, corroborated by historical records of crop yields, suggest that such a reduction in Europe's primary productivity is unprecedented during the last century. An increase in future drought events could turn temperate ecosystems into carbon sources, contributing to positive carbon-climate feedbacks already anticipated in the tropics and at high latitudes.     

新世纪初期中国城市化与经济增长关系的定量分析

城市化与经济发展之间是一种相互促进、互为因果的关系。以往的研究多以经济发展水平为自变量来研究相应的城市化水平,而以城市化水平为自变量反向研究他们的关系则不多,这种研究具有更积极的实际意义,模型也更为简单。从人口城市化和空间城市化两个方面,用统计数据的时间序列和空间序列进行相关分析和回归分析,结果表明:中国单位人口城市化率增量对应的人均产值增量在350～1 600元/人之间,且新世纪以来逐年提高,中国人口城市化的经济效益越来越好;单位空间城市化率增量对应的地均产值增量在2.7～12.5万元/KM2之间,新世纪以来先降后升,存在波动,2003年后城市土地利用的经济效益逐年提高。     

全球气候变化对中国自然灾害的可能影响

随着人口增多和社会经济的发展，全球CO2、CH4、N2O等气体的排放增加所引起的温室效应，预期本世纪的全球变暖较20世纪更为强烈．讨论了全球气候变化及其对中国自然灾害的可能影响．结果表明，本世纪全球气候进一步变暖将可能导致我国北方干旱趋势仍将延续．南方雨量增加特别是暴雨和台风的增加，会使洪涝灾害扩大加剧．沿海地区由于海平面上升，海岸带灾害主要是风暴潮呈现加剧趋势、农林病虫害、滑坡与泥石流、水土流失与土壤侵蚀灾害也将发展，唯寒冻灾害可能大幅度减轻．面对全球气候变化，我国政府及科学界应加强科学研究，积极参与国际合作，采取减轻、防范和适应措施，以减少经济损失．     

小麦不同密度和田间配置对套作玉米苗期素质和产量的影响

试验研究不同小麦密度和田间配置对套作群体质量和产量的影响.结果表明:小麦密度过大,套作群体内透光率低,群体质量差,虽然以穗多可获得较高小麦产量,但玉米单产低,致使套作群体产量偏低.小麦密度低,通风透光好,以争取较多分蘖、穗大、粒多也能获取高产,并且还有利于玉米生长,套作群体产量较高.行数不同播种量一致的处理在4行150万/hm2的田间配置下,套作群体质量优,产量较高;行数和播种量均不同处理中以3行90万/hm2的田间配置较好.相关分析表明麦/玉套作群体产量的高低主要取决于玉米单产.     

Three centuries of alcohol in the British diet.

Alcoholic drinks were consumed in larger quantities in the eighteenth and nineteenth centuries than in the twentieth century, although there has been a recent increase from the historical low of 1930-60. Beer, spirits and wines once provided at least 2 MJ (nearly 500 kcal) per person per day compared with 0.67 MJ (160 kcal) in 1975, towards an average energy requirement of the total population little different from that needed now. Beer has always contributed most to the alcohol, energy and nutrient content of the diet, although its importance relative to spirits and wine has declined.     

韶关市人口与经济社会协调发展问题初探

进入21世纪，人口与发展进一步成为人们广泛关注的重大问题。结合韶关市第五次人口普查资料，对本市人口现状、发展趋势及促进人口与经济社会协调发展的问题进行了初步的研究和探讨，并提出相应的对策和措施。     

浙江海域曼氏无针乌贼资源演变及修复路径探讨

就我国浙江海域曼氏无针乌贼种群分布、生命周期、洄游、近海生长等资源特征以及从20世纪50-60年代的盛产,经历了80-90年代的衰竭,到本世纪初有恢复迹象这段时间内的各种变化及其产生原因展开综述,并探讨了曼氏无针乌贼资源修复路径——加大曼氏无针乌贼增殖放流工作力度;产卵场的修复和保护;洄游路径上禁止捕捞作业;严格控制年捕捞量,以及拟定了资源保护和修复方面相关渔政措施及建议。