Prenatal diagnosis of thrombocytopenia absent radius syndrome by ultrasound and cordocentesis

The prenatal diagnosis of thrombocytopenia absent radius (TAR) syndrome, utilizing ultrasound and cordocentesis, is described. To our knowledge, this represents the first prenatal diagnosis of this condition in an index case. The diagnostic evaluation of a fetus with upper extremity limb reduction defects is discussed.     

高纬度地区的可持续发展

位于北极圈及北温带北部的八个国家,其社会和环境正经历着空前的快速变化.对于为什么有些北方国家在面临这些变化时表现出非凡的恢复力而有些却表现得很脆弱,以下的7篇文章对此进行了简明扼要的解释和说明.     

Oligohydramnios sequence in a live-born infant following chorionic villus sampling

We describe an infant born at 29 weeks' gestation with oligohydramnios sequence due to amniotic fluid leakage following chorionic villus sampling at 12 weeks. To our knowledge, this is the first such report.     

Is the OECD acute worm toxicity test environmentally relevant? The effect of mineral form on calculated lead toxicity

In a series of experiments the toxicity of lead to worms in soil was determined following the draft OECD earthworm reproduction toxicity protocol except that lead was added as solid lead nitrate, carbonate and sulphide rather than as lead nitrate solution as would normally be the case. The compounds were added to the test soil to give lead concentrations of 625-12 500 microg Pb g(-1) of soil. Calculated toxicities of the lead decreased in the order nitrate> carbonate> sulphide, the same order as the decrease in the solubility of the metal compounds used. The 7-day LC50 (lethal concentration when 50% of the population is killed) for the nitrate was 5321+/-275 microg Pb g(-1) of soil and this did not change with time. The LC50 values for carbonate and sulphide could not be determined at the concentration ranges used. The only parameter sensitive enough to distinguish the toxicities of the three compounds was cocoon (egg) production. The EC50s for cocoon production (the concentration to produce a 50% reduction in cocoon production) were 993, 8604 and 10246 pg Pb g(-1) of soil for lead nitrate, carbonate and sulphide, respectively. Standard toxicity tests need to take into account the form in which the contaminant is present in the soil to be of environmental relevance.     

Analysis of the toxic effects of physical and chemical properties of hypolimnetic waters by time series

A field experiment was conducted to identify potential causes of an existing fish kill problem and to identify useful control variables to assist in minimizing future fish kills. The experiment is described along with the mechanism deduced from earlier histological specimens and observed chemical phenomena. Time series analysis of chemical and biological variables is used to elucidate various hypothesis of the postulated fish kill mechanism.     

Price uncertainty and the exhaustive firm

In the presence of a resource constraint the risk-averse exhaustive firm reacts to price uncertainty in a manner different than its competitive counterpart. In particular: (i) some results are independent of attitudes toward risk; (ii) comparative statics results differ from the no resource constraint case; and (iii) results depend upon the relative magnitudes of the discount rate and quasi-fixed costs. An assumption crucial to the relevance of risk-aversion in an intertemporal setting is the presence of imperfections in capital markets (i.e., the absence of complete contingent commodity markets).     

Distributions of personal VOC exposures: a population-based analysis

Information regarding the distribution of volatile organic compound (VOC) concentrations and exposures is scarce, and there have been few, if any, studies using population-based samples from which representative estimates can be derived. This study characterizes distributions of personal exposures to ten different VOCs in the U.S. measured in the 1999-2000 National Health and Nutrition Examination Survey (NHANES). Personal VOC exposures were collected for 669 individuals over 2-3 days, and measurements were weighted to derive national-level statistics. Four common exposure sources were identified using factor analyses: gasoline vapor and vehicle exhaust, methyl tert-butyl ether (MBTE) as a gasoline additive, tap water disinfection products, and household cleaning products. Benzene, toluene, ethyl benzene, xylenes chloroform, and tetrachloroethene were fit to log-normal distributions with reasonably good agreement to observations. 1,4-Dichlorobenzene and trichloroethene were fit to Pareto distributions, and MTBE to Weibull distribution, but agreement was poor. However, distributions that attempt to match all of the VOC exposure data can lead to incorrect conclusions regarding the level and frequency of the higher exposures. Maximum Gumbel distributions gave generally good fits to extrema, however, they could not fully represent the highest exposures of the NHANES measurements. The analysis suggests that complete models for the distribution of VOC exposures require an approach that combines standard and extreme value distributions, and that carefully identifies outliers. This is the first study to provide national-level and representative statistics regarding the VOC exposures, and its results have important implications for risk assessment and probabilistic analyses.     

World Population Projections for Greenhouse Gas Emissions Scenarios

A survey is made of the latest world population projections issued by the United Nations, World Bank, U.S. Census Bureau, and International Institute for Applied Systems Analysis. Medium variants from all the organizations show excellent agreement with respect to many features of future world population growth. It appears that little would be gained by obtaining additional regional projections made by governments or organizations other than those listed above. In general, the new range of population projections that are candidates for forthcoming IPCC emissions scenarios are narrower and lower than the previous IPCC IS92 population range: a reflection of updated information on the decline of fertility rates in developing countries and the incorporation of a plausible correlation between mortality rates and fertility rates within the IIASA ‘rapid’ and ‘slow’ demographic transition variants. Comments are made on the schematic approach of forecasting CO2 emissions using multiplicative identities such as ‘IPAT’ (impact/emissions = population × affluence × technology). Although the unqualified IPAT model suggests that emissions should scale linearly with population, a number of caveats to this exist, the most important of which may be factor interactions. A brief review is made of conventional thinking about interactions between population growth and economic development. Correlation studies and theory suggest that population growth has a neutral or, at most, weak negative effect on economic growth. Conversely, it is well established that higher per capita incomes are well correlated with lower fertility and mortality rates in developing countries. Therefore, a plausible first-order relationship worth exploring in the next generation of IPCC scenarios is that scenarios with higher average economic growth rates in the developing world should be associated with lower fertility and mortality rates there. Calculations are presented that illustrate the effect this negative correlation could have had on the range of the older IS92 emission scenarios, assuming that all other factors are unchanged. Finally, some policy issues concerning population and global warming are reviewed in connection with the IPCC’s omission of population policy discussion in its 1995 Second Assessment Report.