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601.
Lokesh Padhye Ken Rainwater W Andrew Jackson Audra Morse 《Water environment research》2007,79(2):140-146
The major objectives of this work were to operate and construct an autohydrogenotrophic reactor and estimate perchlorate degradation kinetics. The results show that autohydrogenotrophic bacteria were cultured in the reactor and capable of removing 3.6 mg/d of perchlorate in the presence of excess hydrogen (99% removal). The reactor was successful in treating the average influent perchlorate concentration of 532 microg/L to the level of 3 microg/L. A first-order relationship was obtained between the concentration of active biomass in the reactor and the hydraulic retention time for the given amount of substrate. During the kinetic loading study, perchlorate removal ranged from 100 to 50%. The kinetic rate of perchlorate degradation observed in this study was 1.62 hr(-1). The significant degradation of perchlorate in these samples indicates the ubiquity of perchlorate-reducing organisms. Additionally, nitrate was simultaneously removed during water treatment (greater than 90% removal). Because of the excess levels of hydrogen, simultaneous removal of nitrate was not believed to significantly affect perchlorate removal. The area of concern was the lack of complete control over biological treatment. The growth of sulfate-reducing organisms in the reactor negatively affected perchlorate removal efficiency. There were no significant effects observed on the dissolved organic carbon and total suspended solids concentration of the effluent, suggesting that the treatment did not produce a large amount of biomass washout. 相似文献
602.
Pathogenic diseases and environmental contaminants are two of the leading hypotheses for global amphibian declines, yet few studies have examined the influence of contaminants on disease susceptibility. In this study, we examined effects of ecologically relevant doses of atrazine (0, 1.6, 16, and 160 microg/L), sodium nitrate (0, 6.8, 68 mg/L), and their interactions on susceptibility of four laboratory-bred tiger salamander families to Ambystoma tigrinum virus (ATV), a pathogen implicated in global amphibian die-offs. Salamanders were from Arizona populations where a coevolutionary history with ATV is supported, and thus cofactors rather than recent introduction may contribute to disease epizootics. Use of atrazine and nitrogenous fertilizers are ubiquitous; therefore, the impact of these cofactors on disease susceptibility is an important consideration. Atrazine and sodium nitrate significantly decreased peripheral leukocyte levels, suggesting an impact of these contaminants on the immune system. As expected from this result, atrazine significantly increased susceptibility of larvae to ATV infection. In contrast, nitrate had a marginally significant main effect and significantly decreased infection rate at the highest level. However, neither atrazine nor sodium nitrate had significant effects on viral copy number per individual. These results suggest that ecologically relevant concentrations of atrazine and nitrates have immunosuppressive effects, and atrazine may contribute to ATV epizootics, raising concerns about the influence of contaminants on diseases in general. 相似文献
603.
Designing the Ark: Setting Priorities for Captive Breeding 总被引:2,自引:0,他引:2
Zoos can help conserve only a small minority of the species threatened with extinction. Clear and rational criteria for identifying which threatened taxa zoos should focus on are therefore essential. Current priorities for ex situ conservation stress the importance of large vertebrates. We show that this hampers the efficient use of resources because such species are less likely to breed well in captivity than smaller-bodied taxa and, despite longer generation lengths, are more costly to maintain in long-term breeding programs. Moreover, although reintroduction to the wild frees zoo space for other species and is the ultimate aim of captive breeding, zoos show no tendency to target species for which continued habitat availability makes reintroduction a realistic prospect. We suggest that zoos adopt selection criteria that reflect the economic and biological realities of captive breeding and reintroduction if they are to maximize their contribution to species conservation, and we present data on the preferences of zoo visitors indicating that doing so need not adversely affect zoo attendance. 相似文献
604.
Goodstein identified and discussed a "Saturday effect" in data on the timing of tanker oil spills. This comment describes two ways in which the validity of the statistical analysis used to identify and confirm this effect can be strengthened. 相似文献
605.
Amphibian Phenology and Climate Change 总被引:3,自引:0,他引:3
606.
Knowledge of the investment rules adopted by breeders and non-breeders, and the factors that affect them, is essential to
understanding cooperative breeding as part of a life-history tactic. Although the factors that affect relative contributions
to care of young have been studied in some cooperative bird species, there is little data on mammals, making coherent generalisations
within mammals and across taxa difficult. In this study, we investigate individual contributions to pup escorting, a strong
predictor of offspring provisioning, in the banded mongoose (Mungos mungo), a cooperatively breeding mammal in which reproductive skew is low. Contributions by those under a year old (which virtually
never breed) increased with age and body weight but were generally low. Among older age classes (yearlings and adults), individuals
that had not bred in the current litter generally contributed less to escorting than those that had bred (with the exception
of yearling males). In addition, females that did not breed reduced their investment if they were heavy presumably because
such females are more likely to breed in the following event and benefit from saving resources for this. The generally greater
contributions by breeders in banded mongooses contrast with the recent findings in meerkats (Suricata suricatta), another obligatorily cooperative mongoose with similar group size but wherein reproductive skew is high. Our results suggest
that relative contributions by breeders vs non-breeders are not dependent on group size but on the ratio of breeders to carers
and the probability that non-breeders will breed in the near future. 相似文献
607.
Measuring biological diversity 总被引:2,自引:0,他引:2
The diversity of a set of species refers to the joint dissimilarity of the species in the set. This paper discusses the measurement
of diversity from the set of pairwise distances between the species in the set. A measure called the effective number of species
is developed from a non-parametric probability inequality and is shown to have a simple interpretation in terms of comparing
linear experiments. 相似文献
608.
Andrew S. Cohen Roger Bills Christine Z. Cocquyt A.G. Caljon 《Conservation biology》1993,7(3):667-677
609.
610.
MD.?Monir.?HossainEmail author Andrew?B.?Lawson 《Environmental and Ecological Statistics》2005,12(3):259-273
This paper illustrates a method based on local likelihood (LL) for detecting disease clusters. The approach is based on estimating
a lasso distance for each region: within which regions are considered to be clustered. An important advantage in implementing
this approach is that it does not require any special Monte Carlo Markov Chain (MCMC) algorithm, e.g., reversible jump MCMC,
which is essential in hidden Markov model approach. Another advantage is that extending the model to incorporate covariates
is straightforward. We illustrate three ways of doing this by using Eastern Germany lip cancer data. By using simulated data,
we have made a comparison with the BYM model [Besag et al. (1991) Annals of the Institute of Statistical Mathematics, 43, 1–59] and the mixture model [Lawson and Clark (2002) Disease Mapping and Risk Assessment for Public Health, Chapman and Hall]. We also did a limited examination of the ability of the LL model to recover true relative risk under
different priors for lasso parameter. In order to check the edge effects, which has been overlooked in many spatial clustering
models for disease mapping but deserves special attention as it lacks observable neighbors, we have adapted here a simple
approach to observe the changes in relative risks when the edge regions are omitted.
An erratum to this article is available at . 相似文献