试论清代宁夏地区灾荒发生的社会成因

清代宁夏地区是全国灾荒最严重的地区之一,灾荒的发生有其自然成因,但社会成因更为重要.环境破坏、粮储不足、吏治腐败、战乱频发等社会因素使人民丧失了抵抗灾荒的能力,人民饥馑潦倒,政府财政窘困,最终导致灾荒频发.     

The diagnostic performance of cytogenetic investigation in amniotic fluid cells and chorionic villi

First-trimester chorionic villus sampling has not reached the popularity of second-trimester amniocentesis in prenatal cytogenetic diagnosis, in contrast to initial expectations. We investigated whether a difference inthe diagnostic performances of cytogenetic investigation in amniotic fluid (AF) cells and chorionic villi in favour of AF-cells might justify this. Diagnostic performance was measured as laboratory failure rate, karyotype quality (G-band score, rate of follow-up samples, rate of wrong diagnoses), and karyotype representativity (rate of follow-up samples, rate of wrong diagnoses). From 1993–1999, 11 883 AF-samples were investigated (AF-cells). In chorionic villi, short term culture preparations solely were karyotyped from 1993–1996 (n=3499) (STC-villi), short and long-term culture preparations simultaneously provided a sufficient amount of tissue being available from 1997 onwards (n=1829) ((STC+LTC)-villi). Laboratory failure rates were the same after amniocentesis (0.40%) and chorionic villus sampling (0.50%). G-band scores (mean±SD) were equal in AF-cells (373±38.1) and LTC-villi (364±32.6) but significantly lower in STC-villi (311±34.6) (p=0.001). Follow-up sampling rates because of quality reasons were the same in AF-cells (0.14%), STC- villi (0.13%) and (STC+LTC)-villi (0.11%). Two wrong diagnoses turned up among AF-cells. Follow-up sampling rates because of representativity reasons differed significantly between AF-cells (0.10%), (STC+LTC)-villi (1.31%), and STC-villi (1.99%) (p<0.001). However, the ratios of the total numbers of follow-up samples and uncertain or abnormal cytogenetic results in STC, and (STC+LTC)-villi at cytogenetic risks ⩾3% (0.132 and 0.160, respectively) were equal to that in AF-cells at risks <3% (0.155). Two wrong diagnoses were made in STC-villi. Diagnostic performance improved in the rank order of STC-villi, (STC+LTC)-villi and AF-cells. At cytogenetic risks ⩾3%, (STC+LTC)-villi showed a diagnostic performance equal to that in AF-cells. This might justify a selective use of chorionic villus sampling. Copyright © 2001 John Wiley & Sons, Ltd.     

Soft and sour: The challenge of setting environmental quality standards for bioavailable metal concentration in Fennoscandinavian freshwaters

The European Union Water Framework Directive (WFD) requires member states to ensure that all inland and coastal waters achieve ‘good’ water quality status. To this end, the WFD has set environmental quality standards (EQS) or Water quality criteria (WQC) for priority pollutants that include the four metals Cd, Ni, Pb and Hg. Many states have also chosen to set EQS for Cu and Zn. The use of bioavailability models to set EQS, paves the way for accepting higher local metal concentrations in waters where metal bioavailability is deemed low. The Biotic Ligand Model (BLM) concept has been proposed as a tool for estimating metal bioavailability and for calculating local EQS in the EU guidance document. The BLM estimates metal bioavailability based on the dissolved metal concentration and key ancillary water chemistry parameters (acidity, hardness and organic carbon content). The BLMs developed so far, have only been validated for water chemistry input parameters typical of Central Europe. However, the pH, alkalinity and dissolved organic carbon levels of a significant fraction of Fennoscandinavian (Finland, Norway and Sweden) freshwaters are outside the calibration range of currently available BLMs. The levels of Ca²⁺, alkalinity and pH in 75%, 29% and 22%, respectively, of the ca. 2500 Fennoscandinavian freshwater bodies investigated in this survey were outside the calibration range of tested BLMs. Moreover, a comparison of the ability of the tested BLMs to predict the acute and chronic copper toxicity to Daphnia magna and Rainbow trout indicated that the BLMs should be used with caution outside their current validation range. We conclude that more work is needed to extend the application of BLMs in the practical risk assessment to encompass a broader range of European freshwater bodies.     

油田污染土壤残油组成与特征参数分析

为揭示石油在土壤中的降解规律、残油组分特征,筛选土壤残油的生物降解性评价参数,选取大庆、胜利、百色3个油田区共18个深度降解的石油污染土样,利用气相色谱-质谱联用仪(GC-MS)分析了土壤残油中链烷烃(正烷烃+姥鲛烷+植烷)、多环芳烃(PAHs)、萜烷、甾烷及三芳甾烃等5类超过100种石油烃单体.结果表明,经长期降解后残留在土壤残油中总烷烃残留率低于10%,总PAHs残留率低于30%,而萜烷、甾烷及三芳甾烃等生物标志物较难降解.正烷烃降解性随碳数增加有下降的趋势,但碳数<37的正烷烃降解率平均值>80%;PAHs中2～4环PAHs降解率平均值>70%,5～6环PAHs较难生物降解;萘系列、菲系列、系列及苯并[e]芘系列中随烷基取代数增多而残留率增高.残油中可被GC-MS识别的组分<3%,主要为碳数高于20的正烷烃、烷基取代萘和菲、萜烷、甾烷及三芳甾烃等生物标志物.基于烷烃及多环芳烃组成特征,筛选出6个由易降解组分含量与总油或难降解组分含量的比值构成的标准残油的特征参数,可用于判断污染土壤中石油污染物的生物降解性.     

Bulking sludge for PHA production:Energy saving and comparative storage capacity with well-settled sludge

Two acetate-fed sequencing batch reactors (SBR) were operated under an aerobic dynamic feeding (ADF) model (SBR #2) and with anaerobic phase before aerobic phase (SBR #1) to select mixed cultures with a high polyhydroxyalkanoates (PHA) storage response. Although kinetic selection based on storage response should bring about a predominance of floc-formers, a bulking sludge with storage response comparable to well-settled sludge was steadily established. An anaerobic phase was introduced before the aerobic phase in the ADF model to improve the sludge settleability (SBR #1), however, due to the consequent increased feast/famine ratio, the performance of SBR #1, in terms of both the maximum PHB (polyhydroxybutyrate) cell content and ΔPHB, was lower than that of SBR #2. SBR #2 gradually reached a steady state while SBR #1 failed suddenly after 50 days of operation. The maximum specific substrate uptake rate and storage rate for the selected bulking sludge were 0.4 Cmol Ac/(Cmol X.hr) and 0.18 Cmol Ac/(Cmol PHB.hr), respectively, resulting a yield of 0.45 Cmol PHB/(Cmol Ac) in SBR #2 in the culture enrichment phase. A maximum PHB content of 53% of total suspended solids and PHB storage rate of 1.36 Cmol Ac/(Cmol PHB.hr) was achieved at 10.2 hr in batch accumulation tests under nitrogen starvation. The results indicated that it was feasible to utilize filamentous bacteria to accumulate PHA with a rate comparable to well-settled sludge. Furthermore, the lower dissolved oxygen demand of filamentous bacteria would save energy required for aeration in the culture enrichment stage.     

建筑与建筑拆除废弃物的回收：基础工具

本文主要讲述了建筑与建筑拆除废弃物回收的基础工具,包括建筑废弃物管理的基本元素、废弃物材料的重新使用、回收的团队管理、回收培训和管理方案、循环材料的运输几个方面的内容。     

矿井采掘系统安全生产诊断评价

采掘系统作为矿井生产的重要场所,其安全性和稳定性是保障矿井安全生产的前提。根据事故调查统计,结合现场实际情况,建立了包括顶板风险、瓦斯风险、火灾风险、水灾风险、有毒有害风险和其他风险6个类别、36项指标的多因素多级诊断评价指标体系。利用层次分析法确定各因素权重,在此基础上构建模糊综合评判模型,对采掘系统的本质安全状况进行评价。对漳村矿诊断评价结果表明:所建立的诊断评价指标体系较全面包含了矿井采掘系统的主要影响因素,能够辨识系统存在的安全隐患;模糊综合评判法作为采掘系统安全评价方法是实用有效的。     

Use of Multicriteria Decision Analysis to Address Conservation Conflicts

Conservation conflicts are increasing on a global scale and instruments for reconciling competing interests are urgently needed. Multicriteria decision analysis (MCDA) is a structured, decision‐support process that can facilitate dialogue between groups with differing interests and incorporate human and environmental dimensions of conflict. MCDA is a structured and transparent method of breaking down complex problems and incorporating multiple objectives. The value of this process for addressing major challenges in conservation conflict management is that MCDA helps in setting realistic goals; entails a transparent decision‐making process; and addresses mistrust, differing world views, cross‐scale issues, patchy or contested information, and inflexible legislative tools. Overall we believe MCDA provides a valuable decision‐support tool, particularly for increasing awareness of the effects of particular values and choices for working toward negotiated compromise, although an awareness of the effect of methodological choices and the limitations of the method is vital before applying it in conflict situations. Uso de Análisis de Decisiones Multicriterio para Abordar Conflictos de Conservación     

A lagrangian dispersion model for calculating concentration distribution within a built-up domain

A Lagrangian model to study the dispersion of pollutants between urban buildings is described. The flow field is supplied by an objective analysis (Rockle (1990) Ph.D. thesis, Vom Fachbereich Mechanik, der Technischen Hochschule Darmstadt, Germany) and is adjusted to satisfy the continuity equation. From the resulting; mass consistent field the Lagrangian diffusion parameters are eliminated. A 3-D Lagrangian diffusion model in a nonhomogeneous field is applied to calculate the pollutant distribution between the buildings. Several examples are studied and compared to wind tunnel measurements.