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181.
Alain Billionnet 《Ecological modelling》2011,222(3):546-554
The Reserve Selection Problem consists in selecting certain sites among a set of potential sites for biodiversity protection. In many models of the literature, the species present and able to survive in each site are supposed to be known. Here, for every potential site and for every species considered, only the probability that the species survives in the site is supposed to be known. The problem to select, under a budgetary constraint, a set of sites which maximizes the expected number of species is known in the literature under the name of probabilistic reserve selection problem. In this article, this problem is studied with species weighting to deal differently with common species and rare species. A spatial constraint is also considered preventing to obtain too fragmented reserve networks. As in Polasky et al. (2000), the problem is formulated by a nonlinear mathematical program in Boolean variables. Camm et al. (2002) developed a mixed-integer linear programming approximation that may be solved with standard integer programming software. The method gives tight approximate solutions but does not allow to tell how far these solutions are from the optimum. In this paper, a slightly different approach is proposed to approximate the problem. The interesting aspect of the approach, which also uses only standard mixed-integer programming software, is that it leads, not only to an approximate solution, but also to an upper limit on the true optimal value. In other words, the method gives an approximate solution with a guarantee on its accuracy. The linear reformulation is based on an upper approximation of the logarithmic function by a piecewise-linear function. The approach is very effective on artificial instances that include up to 400 sites and 300 species. Within an average CPU time of about 12 min, near-optimal solutions are obtained with an average relative error, in comparison to the optimum, of less than 0.2%. 相似文献
182.
The influence of hydrostatic pressure on the stability and activity of glutamate dehydrogenase (GDH) from the liver of the
Antarctic fish Chaenocephalus aceratus (Notothenioidei: Channichthyidae) has been investigated using the homologous bovine enzyme for comparison. At gradually increasing
pressure, the fish GDH retains all activity up to 140 MPa, whereas in the same pressure range the bovine enzyme is slightly
inactivated. The kinetics of pressure-induced inactivation of Antarctic GDH displays an exponentially decreasing residual
activity as a function of the incubation time, whereas the bovine enzyme shows a complex pattern of behaviour in the first
20 min of incubation, attributable to the transient formation of aggregates. The coenzyme NAD increases the stability of both
enzymes. The activation volume calculated for the reaction catalysed under pressure by fish GDH is higher than that of the
bovine enzyme. These results indicate that the molecular properties of fish and bovine GDH are affected differently by hydrostatic
pressure. A common mode of inactivation under extreme conditions of pressure and temperature of the cold-adapted Antarctic
fish and mesophilic bovine GDH is deduced and discussed.
Received: 20 October 1998 / Accepted: 7 May 1999 相似文献
183.
Dispersal in coral reef fishes occurs predominantly during the larval planktonic stage of their life cycle. With relatively
brief larval stages, damselfishes (Pomacentridae) are likely to exhibit limited dispersal. This study evaluates gene flow
at three spatial scales in one species of coral reef damselfish, Dascyllus trimaculatus. Samples were collected at seven locations at Moorea, Society Islands, French Polynesia. Phylogenetic relationships and gene
flow based on mitochondrial control region DNA sequences between these locations were evaluated (first spatial scale). Although
spatial structure was not found, molecular markers showed clear temporal structure, which may be because pulses of settling
larvae have distinct genetic composition. Moorea samples were then compared with individuals from a distant island (750 km),
Rangiroa, Tuamotu Archipelago, French Polynesia (second spatial scale). Post-recruitment events (selection) and gene flow
were probably responsible for the lack of structure observed between populations from Moorea and Rangiroa. Finally, samples
from six Indo-West Pacific locations, Zanzibar, Indonesia, Japan, Christmas Island, Hawaii, and French Polynesia were compared
(third spatial scale). Strong population structure was observed between Indo-West Pacific populations.
Received: 26 May 2000 / Accepted: 10 October 2000 相似文献
184.
Analysis of the Structure-Properties Relationships of Different Multiphase Systems Based on Plasticized Poly(Lactic Acid) 总被引:2,自引:0,他引:2
Cécile Courgneau Sandra Domenek Alain Guinault Luc Avérous Violette Ducruet 《Journal of Polymers and the Environment》2011,19(2):362-371
Poly(lactic acid) is one of the most promising biobased and biodegradable polymers for food packaging, an application which
requires good mechanical and barrier properties. In order to improve the mechanical properties, in particular the flexibility,
PLA plasticization is required. However, plasticization induces generally a decrease in the barrier properties. Acetyl tributyl
citrate (ATBC) and poly(ethylene glycol) 300 (PEG), highly recommended as plasticizers for PLA, were added up to 17 wt% in
P(D,L)LA. In the case of PEG, a phase separation was observed for plasticizer contents higher than 5 wt%. Contrary to PEG,
the Tg decrease due to ATBC addition, modelled with Fox’s law, and the absence of phase separation, up to 17 wt% of plasticizer,
confirm the miscibility of PLA and ATBC. Contents equal or higher than 13 wt% of ATBC yielded a substantial improvement of
the elongation at break, becoming higher than 300%. The effect of PLA plasticization on the barrier properties was assessed
by different molecules, with increasing interaction with the formulated material, such as helium, an inert gas, and oxygen
and water vapour. In comparison to the neat sample, barrier properties against helium were maintained when PLA was plasticized
with up to 17 wt% of ATBC. The oxygen permeability coefficient and the water vapour transmission rate doubled for mixtures
with 17 wt% ATBC in PLA, but increased five-fold in the PEG plasticized samples. This result is most likely caused by increased
solubility of oxygen and water in the PEG phase due to their mutual miscibility. To conclude, ATBC increases efficiently the
elongation at break of PLA while maintaining the permeability coefficient of helium and keeping the barrier properties against
oxygen and water vapour in the same order of magnitude. 相似文献
185.
The cytokinesis-blocked micronucleus (CBMN) assay, in combination with fluorescent in situ hybridization (FISH) of human pan-centromeric DNA probes, or with CREST antibodies that specifically stain kinetochore proteins, is widely used on several cell types. It distinguishes micronuclei containing one or several whole chromosomes, which are positively labeled (centromere positive micronucleus, C+MN, due to aneugenic effect), or acentric chromosome fragments, which are unlabeled due to the absence of centromere (centromere negative micronucleus, C−MN, due to clastogenic effect). However, the very slight level of the centromeric signals obtained with the FISH technique on primary human fibroblasts, a cell type commonly used in environmental genetic toxicology, leads to great difficulties in distinguishing C+MN and C−MN. Furthermore, the CREST technique may lead to inappropriate results particularly with regards to variations in antibody composition between patient sera. Our results show that the in vitro CBMN, in combination with immunofluorescence staining of CENP-A (centromere protein A), efficiently screens genotoxicants for their ability to induce clastogenic and/or aneugenic effects. We propose the in vitro CBMN assay in combination with immunofluorescence staining of CENP-A as a suitable tool in environmental genotoxicity testing of primary human fibroblasts. 相似文献
186.
Lindahl P Maquet A Hult M Gasparro J Marissens G González de Orduña R 《Journal of environmental radioactivity》2011,102(2):163-169
The distribution of natural radionuclides was studied in winter wheat plants collected from three sites in Belgium during 2004-2007. Activity concentrations of 40K, 226Ra, 228Ra and 228Th in organically and conventionally grown wheat, and in the corresponding soil samples, were determined using ultra low-level gamma-ray spectrometry. The observed soil-to-wheat concentration ratios were calculated for the different parts of the wheat plant (root, stem and grain) in the two agricultural systems (organic and conventional). There were large variations in radionuclide activity concentrations between the sites and fields, but no significant difference between conventionally and organically grown wheat plants was observed. 相似文献
187.
The kinetic aspects are not usually tackled when mimicking the soil trace metal mobilization. In this work, a simple procedure is developed for measuring the kinetics of Pb, Cu and Cd transfer from the soil solid phase towards a resin sink. A ternary system of Soil/EDTA/Chelex was employed for mimicking the metal transfer from two agricultural soil samples into the Chelex. Two different kinetic regimes (P1 and P2) were observed. The kinetic profile of Pb was distinctly different from those of Cd and Cu. Basing on kinetic principles, two kinetic models were proposed for estimating the apparent rate constants of leaching and removal processes in, respectively, two binary mixtures of soil/EDTA and EDTA extracts/Chelex. Contrary to Pb, solid phase pools of Cd and Cu exchanged with the solution on short time scales. The kinetic rate of desorption occurred in following order: Pb < Cu ? Cd. Comparing the kinetics of binary systems, the desorption process was hypothesized to control the metal transfer. The parameters related to the desorption process were extended to the kinetic regimes of Soil/EDTA/Chelex and revealed that the soil to Chelex transfer of Pb is under kinetics control whereas the bulk concentration (affected by the size of particulate reservoir) is likely to control the Cd transfer. Cu presents an intermediate case. 相似文献
188.
Hinck JE Norstrom RJ Orazio CE Schmitt CJ Tillitt DE 《Environmental pollution (Barking, Essex : 1987)》2009,157(2):582-591
Organochlorine pesticide and total polychlorinated biphenyl (PCB) concentrations were measured in largemouth bass from the Tombigbee River near a former DDT manufacturing facility at McIntosh, Alabama. Evaluation of mean p,p′- and o,p′-DDT isomer concentrations and o,p′- versus p,p′-isomer proportions in McIntosh bass indicated that DDT is moving off site from the facility and into the Tombigbee River. Concentrations of p,p′-DDT isomers in McIntosh bass remained unchanged from 1974 to 2004 and were four times greater than contemporary concentrations from a national program. Total DDT in McIntosh bass exceeded dietary effect concentrations developed for bald eagle and osprey. Hexachlorobenzene, PCBs, and toxaphene concentrations in bass from McIntosh also exceeded thresholds to protect fish and piscivorous wildlife. Whereas concentrations of DDT and most other organochlorine chemicals in fish have generally declined in the U.S. since their ban, concentrations of DDT in fish from McIntosh remain elevated and represent a threat to wildlife. 相似文献
189.
Effect directed analysis and mixture effects of estrogenic compounds in a sediment of the river Elbe
Schmitt S Reifferscheid G Claus E Schlüsener M Buchinger S 《Environmental science and pollution research international》2012,19(8):3350-3361
INTRODUCTION: Endocrine disrupting chemicals (EDCs) are present in the environment and can have serious effects on humans and wildlife. For the establishment of environmental quality guidelines and regulation of EDCs, a better understanding and knowledge of the occurrence and the behavior of environmental EDCs is necessary. The aim of the present study was to comprehensively identify substances that are responsible for the estrogenic effect of an environmental sediment sample taken from the river Elbe/Germany. DISCUSSION: The estrogenic effect of the organic sediment extract was determined using the yeast-estrogen-screen (YES). The sample was fractionated by liquid chromatography (LC) for effect directed analysis. The composition of estrogen-active fractions was further investigated by gas chromatography-mass spectrometry and high-resolution LC-MS analysis. The composition of the environmental sample was rebuilt with pure compounds in order to assess the partition of estrogenic activity caused by the identified compounds. The organic sediment extract showed an estrogenic potential of 1.9?±?0.4 ng/g ethinylestradiol equivalents in the sediment. The most prominent contaminants with an estrogenic potential were 17β-estradiol, estrone, and 4-iso-nonylphenols, but other xenoestrogens like bisphenol A and stigmasterol could be found as well. A rebuild of the sample was measured in the YES in order to investigate mixture effects. About 67 % of the observed estrogenic effect in the sediment extract could be explained by a mixture which contained all identified compounds. Chlorophene (o-benzyl-p-chlorophenol)-a widely used antiseptic that was also identified in the sediment extract-has xenoestrogenic properties in the YES that are in the range of other xenoestrogens like 4-n-nonylphenol. This is the first report on chlorophene acting as a xenoestrogen. 相似文献
190.
Carly Schmitt 《The Environmentalist》2012,32(3):332-338
Sustainability as an increasingly popular theme in Contemporary Public Art. The three pillar model of sustainability is used to examine works that deal specifically with the topic of economic, social and environmental sustainability. Viewing these contemporary art works through the lens of sustainability gives new meaning and significance to what many of these contemporary artist are trying to achieve. 相似文献