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121.
M. V. Senat J. P. Bernard A. Delezoide P. Saugier-Veber Y. Hillion J. Roume Y. Ville 《黑龙江环境通报》2001,21(13):1129-1132
Hydrocephalus-stenosis of the acqueduct of Sylvius sequence (HSAS) is characterized by hydrocephalus, macrocephaly, adducted thumbs, spasticity, agenesis of the corpus callosum and mental retardation. X-linked hydrocephalus is known to be due to mutations in the gene coding for the neural cell adhesion molecule L1 (L1-CAM) and diagnosis is made by identification of a mutation in the L1-CAM gene. Prenatal diagnosis of HSAS is usually suggested on ultrasound examination showing hydrocephalus in a male fetus associated with bilateral adducted thumbs. Mutation screening of the L1-CAM gene is indicated when neuropathological examination shows hypoplasia of the corticospinal tract associated with aqueductal stenosis. We report here two cases of HSAS diagnosed within the same family by ultrasound examination in the first trimester of pregnancy when bilateral adducted thumbs were the only early ultrasound marker. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
122.
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124.
Seventeen different wastewater sludges were characterized using both chemical and organic matter fractionation methods (water extraction, Van Soest method, and acid hydrolysis) and 6-mo incubation studies to assess their decomposition in soil. Simple correlation and multiple factor analysis (MFA) were then performed to establish relationships between composition and C and N mineralization of sludges. Carbon and N concentrations covered a wide range of values, but organic carbon (C(o)) to organic nitrogen (N(o)) ratios were relatively low (from 5 to 19). Carbon and N were mainly distributed in the most soluble fractions of the Van Soest method and in the water-insoluble fraction at 100 degrees C. Carbon mineralization varied from 180 to 661 g C kg(-1) organic C added during the 168-d incubation. The addition of sludges led to different inorganic N dynamics: from -3.3 to +120.0 g N kg(-1) sludge organic C mineralized after the 168-d incubation. Fractionation studies showed that the most discriminating method was acid hydrolysis. Carbon mineralization was linked with the proportion of sludge N and C present in the lignin-like fraction (r = -0.68 and -0.65, respectively). Significant relationships were established between N mineralization and N(o) to C(o) ratio (0.88 < r < 0.95) and the C(o) to N(o) ratio of sludges, the C to N ratio of the soluble fraction obtained by the Van Soest method, the water-soluble fraction at 100 degrees C, and the C and N present in the acid-hydrolyzable fraction. Finally, multiple factor analysis also enabled establishing a sludge typology using five clusters based on composition and mineralization characteristics. 相似文献
125.
Faith A. Fitzpatrick Barbara C. Scudder Bernard N. Lenz Daniel J. Sullivan 《Journal of the American Water Resources Association》2001,37(6):1489-1507
ABSTRACT: The U.S. Geological Survey examined 25 agricultural streams in eastern Wisconsin the determine relations between fish, invertebrate, and algal metrics and multiple spatial scales of land cover, geologic setting, hydrologic, aquatic habitat, and water chemistry data. Spearman correlation and redundancy analyses were used to examine relations among biotic metrics and environmental characteristics. Riparian vegetation, geologic, and hydrologic conditions affected the response of biotic metrics to watershed agricultural land cover but the relations were aquatic assemblage dependent. It was difficult to separate the interrelated effects of geologic setting, watershed and buffer land cover, and base flow. Watershed and buffer land cover, geologic setting, reach riparian vegetation width, and stream size affected the fish IBI, invertebrate diversity, diatom IBI, and number of algal taxa; however, the invertebrate FBI, percentage of EPT, and the diatom pollution index were more influenced by nutrient concentrations and flow variability. Fish IBI scores seemed most sensitive to land cover in the entire stream network buffer, more so than watershed‐scale land cover and segment or reach riparian vegetation width. All but one stream with more than approximately 10 percent buffer agriculture had fish IBI scores of fair or poor. In general, the invertebrate and algal metrics used in this study were not as sensitive to land cover effects as fish metrics. Some of the reach‐scale characteristics, such as width/depth ratios, velocity, and bank stability, could be related to watershed influences of both land cover and geologic setting. The Wisconsin habitat index was related to watershed geologic setting, watershed and buffer land cover, riparian vegetation width, and base flow, and appeared to be a good indicator of stream quality Results from this study emphasize the value of using more than one or two biotic metrics to assess water quality and the importance of environmental characteristics at multiple scales. 相似文献
126.
Facultative joint colony founding by social insects provides opportunities to analyze the roles of genetic and ecological
factors in the evolution of cooperation. Although cooperative nesting is observed in range of social insect taxa, the most
detailed studies of this behavior have been conducted with Hymenoptera (ants, bees, and wasps). Here, we show that foundress
associations in the haplodiploid social thrips Dunatothrips aneurae (Insecta: Thysanoptera) are most often comprised of close relatives (sisters), though groups with unrelated foundresses are
also found. Associations among relatives appear to be facilitated by limited female dispersal, which results in viscous population
structure. In addition, we found that per capita productivity declined with increasing group size, sex ratios were female-biased,
and some female offspring apparently remained in their natal domicile for some time following eclosion. D. aneurae thus exhibits a suite of similarities with eusocial Hymenoptera, providing evidence for the convergent evolution of associated
social and life-history traits in Hymenoptera and Thysanoptera. 相似文献
127.
Metacommunity models predict the local-regional species richness relationship in a natural system 总被引:1,自引:0,他引:1
Many natural communities exhibit positive relationships between local and regional species richness (LSR-RSR relationships), which can be either linear or curvilinear. Previous models have shown that the form of this relationship depends on the relative rates of colonization and extinction and the sensitivity of these rates to competition. We use simple models to show that the LSR-RSR relationship also depends on the type of metacommunity structure (Levins-like or mainland-island), and our models generate a wider range of realistic forms than do most previous models. We parameterize and test our models with two independent data sets for Daphnia in rock pools on islands in Finland and Sweden. We find that the Levins-like model with competition correctly predicts the observed LSR-RSR relationship and provides the best fit to the average local species richness per island. Simulations show that our models are robust to relaxing our assumption of identical species properties. Our study is one of the first to make and successfully test quantitative predictions for how a widely studied community pattern, the LSR-RSR relationship, arises from metacommunity dynamics. 相似文献
128.
Jedediah F. Brodie Anthony J. Giordano Elise F. Zipkin Henry Bernard Jayasilan Mohd‐Azlan Laurentius Ambu 《Conservation biology》2015,29(1):110-121
Humans influence tropical rainforest animals directly via exploitation and indirectly via habitat disturbance. Bushmeat hunting and logging occur extensively in tropical forests and have large effects on particular species. But how they alter animal diversity across landscape scales and whether their impacts are correlated across species remain less known. We used spatially widespread measurements of mammal occurrence across Malaysian Borneo and recently developed multispecies hierarchical models to assess the species richness of medium‐ to large‐bodied terrestrial mammals while accounting for imperfect detection of all species. Hunting was associated with 31% lower species richness. Moreover, hunting remained high even where richness was very low, highlighting that hunting pressure persisted even in chronically overhunted areas. Newly logged sites had 11% lower species richness than unlogged sites, but sites logged >10 years previously had richness levels similar to those in old‐growth forest. Hunting was a more serious long‐term threat than logging for 91% of primate and ungulate species. Hunting and logging impacts across species were not correlated across taxa. Negative impacts of hunting were the greatest for common mammalian species, but commonness versus rarity was not related to species‐specific impacts of logging. Direct human impacts appeared highly persistent and lead to defaunation of certain areas. These impacts were particularly severe for species of ecological importance as seed dispersers and herbivores. Indirect impacts were also strong but appeared to attenuate more rapidly than previously thought. The lack of correlation between direct and indirect impacts across species highlights that multifaceted conservation strategies may be needed for mammal conservation in tropical rainforests, Earth's most biodiverse ecosystems. Correlación y Persistencia de los Impactos de la Caza y la Tala sobre los Mamíferos de los Bosques Tropicales 相似文献
129.
Mathieu B. Hounsou Bernard Ahamide Euloge K. Agbossou Thomas Gaiser 《The Environmentalist》2011,31(4):407-415
Water is an essential element for humankind, animals, and plants. It is also an important element of the aquatic environment
(the natural habitat of multiple species), where its quality plays a determining role in their protection and conservation.
Unfortunately, the water quality of natural environments has worsened in the last decades. In sub-Saharan Africa and particularly
in Bénin, in contrast to river discharges, monitoring the quality of surface water is a very rare activity. Thus, knowledge
about physical and chemical properties as a basis for evaluation of the state of the environment and protection measures needed
is almost absent. This article presents the results of the first structured, regular monitoring campaign on surface waters
in the whole basin of the Ouémé River in Bénin Republic. With 510 km, the Ouémé River’s water quality fluctuates from upstream
(Taneka Koko mountains in the north) to downstream (gauging station Bonou in the south) sources. This is due to soil erosion,
lack of water treatment plants, and the use of significant quantities of fertilizer in the cotton zone. The present research
was initiated to study the resource degradation of this area through chemical and physical water analysis. The monitoring
of water quality has been followed for 5 years on twenty physicochemical parameters, from samples taken at four gauging stations
on the main channel of the Ouémé River. Means and standard deviations of water analysis results were compared to both the
recommendations of the World Health Organization (WHO) and the Maximum Permissible Concentrations (MPC) for drinking water
(WHO 1987). Thus, high values were observed for physical parameters, i.e., color and turbidity had peaks of 697.5 uC and 129 FTU at
Bétérou station in the wet season, although certain parameters, such as total hardness, present low values compared to the
recommended standards. Moreover, excluding the concentrations of NO2
− and NH4
+ with values above the MPC, nutrient concentrations posed no direct risk for human consumption. However, together with phosphate
concentrations (which are up to ten times higher than permissible ecological thresholds), they can cause eutrophication of
the aquatic ecosystem. Due to the current flow regime, which has very low discharge rates in the dry season and torrential
rainfall and high sediment loads in the wet season, the risk of eutrophication, i.e., excessive concentrations of ammonium
and phosphates, is present throughout the year. Accumulation of ammonium and the distribution of nitrate and nitrites in the
river water suggest that nitrification is impeded due to a lack of oxygen in both dry and wet seasons. Finally, the investigations
show that the risk of water pollution exists and it is necessary to take measures of sanitation and water treatment to prevent
the further degradation of water along the Ouémé River. 相似文献
130.
Sophie Bernard 《Journal of Environmental Economics and Management》2011,62(3):337-351
This paper presents a theoretical model of remanufacturing where a duopoly of original manufacturers produces a component of a final good. The specific component that needs to be replaced during the lifetime of the final good creates a secondary market where independent remanufacturers enter the competition. An environmental regulation imposing a minimum level of remanufacturability is also introduced. The main results establish that, while collusion of the firms on the level of remanufacturability increases both profit and consumer surplus, a social planner could use collusion as a substitute for an environmental regulation. However, if an environmental regulation is to be implemented, collusion should be repressed since competition supports the public intervention better. Under certain circumstances, the environmental regulation can increase both profit and consumer surplus. Part of this result supports the Porter Hypothesis, which stipulates that industries respecting environmental regulations can see their profits increase. 相似文献