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561.
Isabelle Amat Emmanuel Desouhant Carlos Bernstein 《Behavioral ecology and sociobiology》2009,63(4):563-572
When foraging partially depleted patches (i.e., a fraction of hosts are already parasitized), female parasitoids must decide:
1—whether to superparasitize, and 2—whether to stay in their current patch (thus missing the opportunity of finding a better
patch elsewhere). To make these decisions, parasitoids may rely on different cues, produced both by the environment and by
conspecifics. Animals thriving in different environments may differ in cues they use. In the solitary parasitoid Venturia canescens, thelytokous (asexual) and arrhenotokous (sexual) individuals are found in two contrasting environments. Thelytokous females,
from anthropogenic conditions, are known to cope with superparasitism in an adaptive way. On the other hand, little is known
about superparasitism by arrhenotokous females. We compared the host exploitation strategies of thelytokous and arrhenotokous
females in partially depleted patches. Hosts parasitized by thelytokous females were more frequently avoided than those parasitized
by arrhenotokous females, suggesting a stronger chemical marking of the former. Only thelytokous females used information
from conspecifics for patch-leaving decisions. The conformity of the differences in the behavior of thelytokous and arrhenotokous
females with the environmental conditions they experience in their habitat is discussed. 相似文献
562.
Gene Whelan John P. McDonald Randal Y. Taira Emmanuel K. Gnanapragasam Charley Yu Christine S. Lew William B. Mills 《Journal of contaminant hydrology》2000,41(3-4)
Multimedia modelers from the US Environmental Protection Agency (EPA) and US Department of Energy (DOE) are collaborating to conduct a comprehensive and quantitative benchmarking analysis of four intermedia models: MEPAS, MMSOILS, PRESTO, and RESRAD. These models represent typical analytically based tools that are used in human-risk and endangerment assessments at installations containing radioactive and hazardous contaminants. The objective is to demonstrate an approach for developing an adequate source term by simplifying an existing, real-world, 90Sr plume at DOE's Hanford installation in Richland, WA, for use in a multimedia benchmarking exercise between MEPAS, MMSOILS, PRESTO, and RESRAD. Source characteristics and a release mechanism are developed and described; also described is a typical process and procedure that an analyst would follow in developing a source term for using this class of analytical tool in a preliminary assessment. 相似文献
563.
The objective of the present study was to investigate seasonal variations in the oxidative metabolism of the sea urchin Loxechinus albus gonads. The reported spawning period for this species is from September to November. Lipid radical content showed non-significant
changes upon the seasons. Ascorbyl radical content and the content of α-tocopherol were lower in samples collected in spring
and summer as compared to the values in winter-collected animals. Ascorbate content decreased in samples collected in fall
as compared to those collected in winter. For the lipophilic compartment, the lipid radical content/α-tocopherol content ratio
is an indicator of oxidative stress. This index increased significantly in tissues during spawning as compared to the values
in samples collected during winter. The ascorbyl content/ascorbate content ratio is an indicator of oxidative stress for the
hydrophilic milieu. A significant decrease by 66% was determined in tissues from gonads of animals collected in summer as
compared to values in animals collected in winter. The data reported here suggest a different profile of response against
oxidative stress at the lipophilic and hydrophilic milieus in L. albus gonads. 相似文献
564.
Gómez-Aracena J Riemersma RA Gutiérrez-Bedmar M Bode P Kark JD Garcia-Rodríguez A Gorgojo L Van't Veer P Fernández-Crehuet J Kok FJ Martin-Moreno JM;Heavy Metals Myocardial Infarction Study Group 《Chemosphere》2006,64(1):112-120
The association between cerium status and risk of first acute myocardial infarction (AMI) was examined in a case-control study in 10 centres from Europe and Israel. Cerium in toenails was assessed by neutron activation analysis in 684 cases and 724 controls aged 70 years or younger. Mean concentrations of cerium were 186 and 173 microg/kg in cases and controls, respectively. Cerium was positively associated with low socio-economic status, smoking, mercury, zinc and scandium (p0.001). Cases had significantly higher levels of cerium than controls after adjustment for age and centre (case-control ratio 1.074; 95% CI 1.002-1.151) and increased in further adjustment for other cardiovascular risk factors 1.085; 95% CI 1.025-1.149. The risk after adjustment for age and centre was higher with increasing cerium levels (p for trend=0.02). After adjustment for BMI, history of hypertension, smoking, alcohol intake, diabetes, family history of CHD, beta-carotene, lycopene, alpha-tocopherol, selenium, mercury and scandium, the OR for the highest quintile was 1.43 (95% CI 0.85-2.41; p-trend 0.08). When we applied this same model in non-smokers the odds ratios in the 4th and 5th quintiles of cerium as compared with the lowest were 2.09 (95% CI 1.05-4.16) and 2.81 (95% CI 1.21-6.52), respectively, p-trend 0.011. Our results suggest that toenail cerium levels may be associated with an increased risk of AMI, but more research is warranted to shed further light and fully understand the plausibility and public health implications of these findings. 相似文献
565.
Duringer P Schuster M Genise JF Likius A Mackaye HT Vignaud P Brunet M 《Die Naturwissenschaften》2006,93(12):610-615
Higher termites of the subfamily Macrotermitinae (fungus-growing termites) are known to build fungus gardens where a symbiotic fungus (Termitomyces sp.) is cultivated. The fungus grows on a substrate called fungus comb, a structure built with the termites’ own faeces. Here we present the first fossil fungus combs ever found in the world. They were extracted from 7-million-year-old continental sandstone (Chad basin). Fossilized fungus combs have an ovoid morphology with a more or less flattened concave base and a characteristic general alveolar aspect. Under lens, they display a typical millimetre-scale pelletal structure. The latter, as well as the general shape and alveolar aspect, are similar to the morphology of fungus combs from extant fungus-growing termites. 相似文献
566.
Ruhul A. Khan Stephane Salmieri Dominic Dussault Nathalie Tufenkji Jorge Uribe-Calderon Musa R. Kamal Agnes Safrany Monique Lacroix 《Journal of Polymers and the Environment》2012,20(1):43-52
Chitosan (0.1–1%, w/w), dissolved in 2% acetic acid solution, was added into 1% methylcellulose (MC)-based formulation containing
0.5% vegetable oil, 0.25% glycerol and 0.025% Tween?80. Films were prepared by casting. Puncture strength (PS), puncture deformation (PD), viscoelasticity coefficient and water
vapour permeability (WVP) of the films were measured. The PS value of 312 N/mm was observed for MC-based films containing
0.25% chitosan. Values of PD, viscoelasticity coefficient and WVP of these films were 5.0 mm, 44.1%, and 6.0 g mm/m2 day kPa, respectively. The MC-based films containing 0.25% chitosan were also exposed to gamma radiation (0.5–50 kGy). The
PS of the treated films decreased significantly from 312 at 0 kGy to 201 N/mm when treated at a dose of 50 kGy. However, WVP
values were not affected by increasing irradiation the dose used. The Fourier Transform Infrared spectroscopy supported the
molecular interactions due to addition of chitosan in MC-based films. Thermo gravimetric analysis and differential scanning
calorimetric experiments showed that thermal properties of the films were significantly improved by chitosan loading. Surface
topography of the films was studied by scanning electron microscopy and found rougher due to chitosan addition. 相似文献
567.
Maria Clara Pessoa Amorim José Miguel Simões Paulo Jorge Fonseca Vitor C. Almada 《Marine Biology》2010,157(3):495-503
In some marine fishes, males migrate from deeper to littoral water to breed, where they defend nests and provide parental
care. In this study, we describe seasonal patterns of shelter occupation in estuarine shallow waters and assess social aggregation
in the Lusitanian toadfish (Batrachoididae), a vocal species with male parental care. Occupation of intertidal shelters was
restricted to the breeding season but adult fish remained in subtidal regions during the non-reproductive season and they
produced sounds throughout the year. Intertidal shelters were aggregated with up to five shelters found per 2-m segment of
an 80-m transect. This aggregation probably resulted from social attraction since many segments were found unoccupied. Moreover,
shelters contained on average two fish (maximum of nine). Based on size, shelters with multiple fish seemed to contain females,
or possibly sneakers, but also more than one type I male inside, indicating a high social tolerance for conspecifics. 相似文献
568.
Wilson Y. Fantong Hiroshi Satake Samuel N. Ayonghe Emmanuel C. Suh Segun M. A. Adelana Emilia Bi S. Fantong Hycinth S. Banseka Cletus D. Gwanfogbe Leonard N. Woincham Yoshitoshi Uehara Jing Zhang 《Environmental geochemistry and health》2010,32(2):147-163
The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO3 signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO3 type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods. 相似文献
569.
Investigation of trace element sources from an industrialized area (Avilés, northern Spain) using multivariate statistical methods 总被引:2,自引:0,他引:2
In the industrialized urban area of Avilés (Spain), pooled soil samples from grassland sites were taken after careful sampling design and then investigated for their content of trace elements. A combination of statistic and geostatistic techniques proved to be a reliable tool in the interpretation of the analytical results. Geochemical groups and areas influenced mainly by anthropogenic activities were distinguished by means of classic multivariate methods (factor analysis and cluster analysis) and innovative geostatistical tools (Fourier spectral analysis). The constitution of the groups is supported by the linked results of methods sequentially distributed in order to extract as much information as possible from the original data. 相似文献
570.
Incorporating soil structure and root distribution into plant uptake models for radionuclides: toward a more physically based transfer model 总被引:1,自引:0,他引:1
Albrecht A Schultze U Liedgens M Flühler H Frossard E 《Journal of environmental radioactivity》2002,59(3):329-350
Most biosphere and contamination assessment models are based on uniform soil conditions, since single coefficients are used to describe the transfer of contaminants to the plant. Indeed, physical and chemical characteristics and root distribution are highly variable in the soil profile. These parameters have to be considered in the formulation of a more realistic soil-plant transfer model for naturally structured soils. The impact of monolith soil structure (repacked and structured) on Zn and Mn uptake by wheat was studied in a controlled tracer application (dye and radioactive) experiment. We used Brilliant Blue and Sulforhodamine B to dye flow lines and 65Zn and 54Mn to trace soil distribution and plant uptake of surface-applied particle-reactive contaminants. Spatial variation of the soil water content during irrigation and plant growth informs indirectly about tracer and root location in the soil profile. In the structured monolith, a till pan at a depth of 30 cm limited vertical water flow and root penetration into deeper soil layers and restricted tracers to the upper third of the monolith. In the repacked monolith, roots were observed at all depths and fingering flow allowed for the fast appearance of all tracers in the outflow. These differences between the two monoliths are reflected by significantly higher 54Mn and 65Zn uptake in wheat grown on the structured monolith. The higher uptake of Mn can be modelled on the basis of radionuclide and root distribution as a function of depth and using a combination of preferential flow and rooting. The considerably higher uptake of Zn requires transfer factors which account for variable biochemical uptake as a function of location. 相似文献