CO2 enrichment inhibits shoot nitrate assimilation in C3 but not C4 plants and slows growth under nitrate in C3 plants

The CO2 concentration in Earth's atmosphere may double during this century. Plant responses to such an increase depend strongly on their nitrogen status, but the reasons have been uncertain. Here, we assessed shoot nitrate assimilation into amino acids via the shift in shoot CO2 and O2 fluxes when plants received nitrate instead of ammonium as a nitrogen source (deltaAQ). Shoot nitrate assimilation became negligible with increasing CO2 in a taxonomically diverse group of eight C3 plant species, was relatively insensitive to CO2 in three C4 species, and showed an intermediate sensitivity in two C3-C4 intermediate species. We then examined the influence of CO2 level and ammonium vs. nitrate nutrition on growth, assessed in terms of changes in fresh mass, of several C3 species and a Crassulacean acid metabolism (CAM) species. Elevated CO2 (720 micromol CO2/mol of all gases present) stimulated growth or had no effect in the five C3 species tested when they received ammonium as a nitrogen source but inhibited growth or had no effect if they received nitrate. Under nitrate, two C3 species grew faster at sub-ambient (approximately 310 micromol/mol) than elevated CO2. A CAM species grew faster at ambient than elevated or sub-ambient CO2 under either ammonium or nitrate nutrition. This study establishes that CO2 enrichment inhibits shoot nitrate assimilation in a wide variety of C3 plants and that this phenomenon can have a profound effect on their growth. This indicates that shoot nitrate assimilation provides an important contribution to the nitrate assimilation of an entire C3 plant. Thus, rising CO2 and its effects on shoot nitrate assimilation may influence the distribution of C3 plant species.     

Song dialects do not restrict gene flow in an urban population of the orange-tufted sunbird, <Emphasis Type="Italic">Nectarinia osea</Emphasis>

Geographic variation in vocalizations is widespread in passerine birds, but its origins and maintenance remain unclear. In this study, we test the hypothesis that song dialect, a culturally transmitted trait, is related to the population genetic structure of the orange-tufted sunbird, Nectarinia osea. To address this, we compared mitochondrial DNA (mtDNA) sequence variation together with allele frequencies at five microsatellite loci from an urban population of sunbirds exhibiting two distinct song dialects on a microgeographic scale. Our findings reveal no association between dialect membership and genetic composition. All genetic measures, from both mitochondrial and nuclear DNA, indicate high levels of gene flow between both dialect populations. The low F _ST values obtained from mtDNA and microsatellite analysis imply that the variation among dialects does not account for more than 2%, at best, of the overall genetic variation found in the entire population. These measures fall well within the range of similar measures obtained in other studies of species exhibiting vocal dialects, most of which fail to detect any dialect-based genetic differentiation. The persistence of dialects in the orange-tufted sunbird may thus best be explained by dispersal of individuals across dialect boundaries and possibly from surrounding areas, followed by postdispersal vocal matching. Because genetic structuring appears weaker than cultural structure in this species, we discuss the behavioral mechanisms underlying dialect maintenance in the presence of apparent gene flow.     

沙漠公路驾驶员心理、生理特性初探

针对沙漠公路交通安全现状,采用动体视力、速度估计、复杂(选择)反应、处置判断、血压脉搏检测仪等驾驶适宜性检测仪器,就长期从事沙漠公路运输活动的驾驶员群体进行了包括视觉、速度估计、反应、判断等在内的心理、生理特性的实地测试。检测结果初步表明,沙漠公路特殊的线形布设和修筑技术特征以及沿线的自然环境条件,使得驾驶员表现出有别于一般绿洲公路的驾驶心理和行为特性,其主要表现在在沙漠环境中,驾驶员的动体视力要较静体视力受到更大的影响;急躁心理影响,沙漠公路驾驶员的速度估计和复杂反应时间相应指标值均小于全国平均水平;沙漠公路驾驶员复杂反应错误次数和处置判断错误次数均高于绿洲公路。     

Retrospective monitoring and inventory of soil contamination in relation to systematic monitoring

Retrospective monitoring of soil contamination has been performed in the Czech Republic. This kind of monitoring is based on the comparison of the heavy metals content in soil samples taken during a systematic soil survey (1960–1970) and in samples taken at the present time. The anticipated high degree of soil pollution in the Czech Republic has not been proved. Most of the contaminated soils were found to be loaded just 20–35 years ago. Retrospective monitoring is considered to be an accelerating tool for determining the strategy of the systematic monitoring of soil contamination. This procedure stimulated the development of the multi-step system of soil loading limits.     

DVR的下一代--NVRS

在去年年中的时候,著名的分析机构Frost & Sullivan公司发表了一项报告,他们认为2002年基于CCTV的数字系统应用会首次超过模拟系统的应用,并且预测这个转换过程可能在2008年之前就会完成.目前世界上有超过400家的DVR制造厂商,他们都宣称DVR将会成为数字CCTV系统中占据主导地位的技术.那么事实究竟如何呢?让我们近距离观察一下DVR技术的本质吧.     

Airborne exposure to chemical substances in hairdresser salons

Several studies indicate health problems among hairdressers to be related to their chemical exposure at work. The purpose of this study was to describe the exposure of chemical compounds in the air of Spanish hairdresser salons, and to study differences between salons in central and suburban areas. Ten hairdresser salons were examined for two days, by recording number and type of customers, ventilation and size of salon. Both stationary and personal borne samples for organic compounds were collected, as well as stationary samples of ammonia. TVOC was calculated. Air temperature, relative humidity, CO and CO2 were logged for 48 h in each salon. Fifty-six personal and 28 stationary samples were analysed for organic compounds. Thirty-five different air-borne compounds were found in the working environment of the hairdressers. All levels were well below the limit values in Spain and USA, both for ammonia and organic compounds. TVOC ranged from 48.37 mg/m3 to 237.60 mg/m3, meaning that many salons had levels above suggested comfort values of 25. There were only minor differences in exposure between central and suburban salons. No salons had ventilation systems, and the CO2 was increasing during the day. The exposure was higher for several chemical compounds when hair dying was performed. Hairdressers were exposed to low air levels of a large number of chemical substances mostly related to work related to hair dying. There were no differences between exposure levels in salons in central and suburban areas.     

塔克拉玛干沙漠公路交通事故趋势预测分析

应用塔克拉玛干沙漠干线公路建成通车以来的交通事故统计数据,在分析交通事故主要指标发展变化特征和分布特征的基础上,建立了适用于沙漠公路交通事故特点的GM(1,1)预测模型,对未来几年内交通事故发展趋势进行了预测。预测结果表明,未来几年沙漠公路交通事故次数、死亡人数、受伤人数以及直接经济损失等4项指数将分别以15.9%,10%,4.5%和5%的年平均增长率快速增长。同时针对预测结果提出了相应的对策。     

Implementation of US Surface Mine and Reclamation Act

The US Congress is currently studying various ways through which legislation similar to that of the Surface Mining Control and Reclamation Act of 1977— which is concerned mainly with coal, can be applied to all minerals other than coal. This study analyses three US mineral industries—copper, iron ore, and phosphate rock - and identifies a number of areas which Congress and other decision makers ought to consider in arriving at such legislation. The author concludes that reclamation costs may affect the economic and financial performance of each of these industries in a different manner; furthermore, their economic behaviour is significantly different from that of coal. The author's main recommendation is that if surface mining regulations are to be legislated, they should be industry- and commodity-specific rather than umbrella legislation for all non-coal minerals.     

Mineral investment valuation and the cost of capital

The author discusses some of the mineral investment modes used. He outlines the theoretical foundations of the cost of capital concept and derives models for determining the cost of capital from specific sources of financing. THe use of the weighted average cost of capital appears to have advantages and is illustrated with an example.