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排序方式: 共有668条查询结果,搜索用时 343 毫秒
271.
Walter Pribil Peter Gehringer Helmut Eschweiler Alexander Cabaj Thomas Haider Regina Sommer 《Water environment research》2007,79(7):720-724
Gamma and electron-beam irradiation of Bacillus subtilis spores suspended in different types of water was studied to evaluate the inactivation of the spores and assess their possible use as a bioindicator for radiation processing. We found that the inactivation proceeded endogenously, being dose-rate-dependent and affected by oxygen. The radiation resistance of the suspended spores was found to be rather high; therefore, B. subtilis spores used as a bioindicator for efficiency of water treatment by radiation under practical conditions might result in the spores being overly conservative surrogates for pathogenic microorganisms. Moreover, the doserate dependency impedes the use of the spores as a bioindicator. Thus, B. subtilis spores cannot be recommended as a bioindicator for evaluation of the microbicidal efficacy of ionizing radiation processing of water. 相似文献
272.
Eight tertiary nonanols were synthesized via Grignard reaction and coupled by Friedel–Crafts alkylation with phenol to the corresponding nonylphenols. Six branched para-nonylphenols (NP) were obtained: 4-(3′-methyl-3′-octyl)phenol (33NP), 4-(2′-methyl-2′-octyl)phenol (22NP), 4-(2′,5′-dimethyl-2′-heptyl)phenol (252NP), 4-(2′,5′,5′-trimethyl-2′-hexyl)phenol (2552NP), 4-(2′,4′-dimethyl-2′-heptyl)phenol (242NP) and 4-(4′-ethyl-2′-methyl-2′-hexyl)phenol (4E22NP). Their structures were confirmed by GC–MS and NMR spectroscopy. These six isomers as well as the earlier synthesized 4-(3′,5′-dimethyl-3′-heptyl)phenol (353NP), 4-(3′,6′-dimethyl-3′-heptyl)phenol (363NP) and 4-(2′,6′-dimethyl-2′-heptyl)phenol (262NP) were compared with commercial NP mixtures purchased from Acros and Fluka by GC–MS (equipped with a 100 m polysiloxane column). The analyses revealed that all obtained isomers are occurring in different quantities in both commercial NP mixtures. 相似文献
273.
Atmospheric concentrations of gaseous NH3 and HNO3 and of particulate NH4+ and NO3- were measured during various seasons at a forest ecosystem research site in the "Fichtelgebirge" mountains in Central Europe. Air masses arriving at this site were highly variable with respect to trace compound concentration levels and their concentration ratios. However, the distributions of NH4+ and NO3- within the aerosol particle size spectra exhibited some very consistent patterns, with the former dominating the fine particle concentrations, and the latter dominating the coarse particles range, respectively. Overall, the particulate phase (NH4+ + NO3-) dominated the atmospheric nitrogen budget (particulate and gas phase, NH4+ + NO3- + NH3 + HNO3) by more than 90% of the median total mixing ratio in winter, and by more than 60% in summer. The phase partitioning varied significantly between the winter and summer seasons, with higher relative importance of the gaseous species during summer, when air temperatures were higher and relative humidities lower as compared to the winter season. Reduced nitrogen dominated over oxidized nitrogen, indicating the prevailing influence of emissions from agricultural activity as compared to traffic emissions at this mountainous site. A model has been successfully applied in order to test the hypothesis of thermodynamic equilibrium between the particulate and gas phases. 相似文献
274.
J.R. Ginsberg K.A. Alexander S. Creel P.W. Kat J.W. Mcnutt M.G.L. Mills 《Conservation biology》1995,9(3):665-674
Populations of the African wild dog, Lycaon pictus have declined throughout their range in sub-Saharan Africa during the last 20 years. It has been hypothesized that handling of wild dogs led to local extinction of a study population in the Serengeti-Masai Mara ecosystem. In this paper we compare rates of mortality and disappearance in handled ( n = 305) versus unhandled ( n = 135) dogs to test the hypothesis that handling leads to increased mortality of Lycaon . We examine data from five ecosystems in which Lycaon have been handled. Our data show that there is no effect of handling on the longevity of Lycaon in any ecosystem studied. Given these data, a more parsimonious explanation of the decimation of the Serengeti-Mara Lycaon population would be that disease alone was responsible for the population collapse and that researcher handling of Lycaon was correlated with, but not causal to, this mortality. 相似文献
275.
Joseph Alcamo Lilibeth Acosta-Michlik Alexander Carius Frank Eierdanz Richard Klein Dörthe Krömker Dennis Tänzler 《Regional Environmental Change》2008,8(4):137-149
In this study we develop an “inference modeling” approach to compare and analyze how different disciplines (economics, political
science, and behavioral science/environmental psychology) estimate vulnerability to drought. It is thought that a better understanding
of these differences can lead to a synthesis of insights from the different disciplines and eventually to more comprehensive
assessments of vulnerability. The new methodology consists of (1) developing inference models whose variables and assertions
incorporate qualitative knowledge about vulnerability, (2) converting qualitative model variables into quantitative indicators
by using fuzzy set theory, (3) collecting data on the values of the indicators from case study regions, (4) inputting the
regional data to the models and computing quantitative values for susceptibility. The methodology was applied to three case
study regions (in India, Portugal and Russia) having a range of socio-economic and water stress conditions. In some cases
the estimates of susceptibility were surprisingly similar, in others not, depending on the factors included in the disciplinary
models and their relative weights. A new approach was also taken to testing vulnerability parameters by comparing estimated
water stress against a data set of drought occurrences based on media analysis. The new methodologies developed in this paper
provide a consistent basis for comparing differences between disciplinary perspectives, and for identifying the importance
of the differences.
相似文献
Joseph AlcamoEmail: |
276.
277.
Surrogate compounds for dioxins in incineration. A review 总被引:1,自引:0,他引:1
Dioxins, formed in any combustion process where carbon, oxygen and chlorine are present, are a subject of major interest due to their toxicity. Their measurement is very expensive and time consuming. In order to optimize the combustion process, on-line measurements of pollutants must be done. The use of surrogate compounds instead of dioxins seems to be a convenient method to overcome the aforementioned drawback. This work is a review of the literature dedicated to the possible surrogate compounds for dioxins; the relationships found were systematized and, in some cases, the available experimental data were used and original correlations were found. Correlation of surrogate compounds was found to be: incinerator, feedstock, process and sample point location specific. Amongst the possible surrogates, chlorobenzenes show real possibilities to be good indicators for toxic equivalent factors. 相似文献
278.
Lerchl A 《Die Naturwissenschaften》2005,92(12):592-594
In 5-year intervals, data from 722,306 individuals born between 1988 and 2003 in North Rhine Westphalia, Germany's largest
state, were analyzed for the weekday of birth. In contrast to data from 1900 to 1950 (n=149,267), serving as historical controls, a very marked nonrandom distribution was discovered, with decreasing numbers of
births on weekends, especially on Sundays, reaching deviations from the expected distribution of −17.8% in 2003, while births
on weekdays are more frequent than expected (Fridays: +8.1% in 2003). The increasing avoidance of births during weekends by
elective labor induction on weekdays is discussed as a consequence of practical and increasing financial constraints of hospitals. 相似文献
279.
280.