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61.
Marc?Le Lann Catherine?ElleouetEmail author Fran?ois?Quentel Christian?Louis?Madec 《Environmental Chemistry Letters》2003,1(1):98-102
Cathodic adsorptive stripping voltammetry is one of the most sensitive analytical methods for ultratrace analysis. The detection
limit is usually lower than 10−9 mol/L. Most adsorptive stripping procedures have been focused on the one ligand/one analyte approach. In order to reduce
analysis time and sample volume, the possibility of simultaneously determining several metals by cathodic stripping voltammetry
using a mixture of ligands was explored, e.g., by Colombo and van den Berg (1997). Here, we describe a new procedure for quantifying
chromium and copper using 2,2′-bipyridine and 8-hydroxyquinoline (oxine). The effect of various operational parameters such
as buffer type, ligand concentration, potential and time collection were assessed and optimized. Possible interferences by
trace metals and organic matter were also investigated. Applicability for fresh water is illustrated.
Electronic Publication 相似文献
62.
A test of the producer-scrounger foraging game in captive flocks of spice finches,Loncbura punctulata 总被引:2,自引:0,他引:2
Luc-Alain Giraldeau Catherine Soos Guy Beauchamp 《Behavioral ecology and sociobiology》1994,34(4):251-256
Group foraging allows the co-existence of a strategy (producer) that involves searching for food, and its alternative (scrounger) exploiting the food of the producer. The use of producer and scrounger strategies has been modelled as an alternative-option scramble which assumes strong negative frequency-dependence of the scrounger's pay-offs. We tested this assumption in a flock feeding situation by manipulating the proportion of scroungers in flocks of spice finches, Lonchura punctulata. In a first experiment we found that: (1) the food intake of scroungers, and to a lesser extent producers, was negatively affected by an increase in the proportion of scroungers; (2) the food intake of producers and scroungers was equal when the proportion of scroungers was small, suggesting that producers, who exploited 35.4% of their patches by scrounging were opportunistically adjusting their use of the strategies until the pay-offs equalized. In a second experiment we tested whether finches could vary their use of the two strategies in response to changes in foraging conditions brought about by an increase in the cost of producing. As predicted by the game, finches reduced their use of the producer strategy and increased their use of the scrounger strategy when the cost of producing increased. These results suggest that spice finches can alter their allocation to each foraging alternative by experience and that the producer-scrounger game is a realistic model for predicting group foraging decisions.
Correspondence to: L.-A. Giraldeau 相似文献
63.
Potential allelopathic effect of Pinus halepensis in the secondary succession: an experimental approach 总被引:1,自引:0,他引:1
Catherine Fernandez Benjamin Lelong Bruno Vila Jean-Philippe Mévy Christine Robles Stéphane Greff Sylvie Dupouyet Anne Bousquet-Mélou 《Chemoecology》2006,16(2):97-105
Summary. Recent economic and social changes in north Mediterranean regions have led to an important rural depopulation. Consequently,
meadows developed on abandoned agricultural lands (characterized by high species richness) undergo reforestation. These former
fields are mainly colonized by Pinus halepensis Miller, which is known to synthetize a wide range of secondary metabolites, among these, some could influence plant succession
through allelopathy. The allelopathic potential of P. halepensis, was tested against two target species (Lactuca sativa L. and Linum strictum L.) with aqueous extracts obtained from different organs (root and needle) taking into account the individual age (±10, ±30
and > 60 years old). Root and needle extracts affected differently germination and growth of the two target species, the responses
varying with concentration of extracts, age and organs tested. The strongest inhibitory effect was observed on the germination
and growth of L. strictum, exposed to needle extracts of young P. halepensis (±10 years old), and root extracts of older P. halepensis (> 30 years old). These extracts contained several phenolic acids (e.g. 4-hydroxybenzoic acid and p-coumaric acid), which are known as allelochemicals and their concentrations vary with age and
organ tested. Hence, P. halepensis could influence secondary succession through the release of potential allelochemicals in the environment by leaf leachates
or root exudates. 相似文献
64.
Observations of 2,4,6-trichlorophenol degradation by ozone 总被引:7,自引:0,他引:7
The aqueous reactivity of 2,4,6-trichlorophenol (TCP) with ozone has been studied at laboratory-scale using a simple gas bubble/liquid contacting system. Degradation rate constants were measured directly and found to be 7.6 and 77.2 M(-1)s(-1) at pH 2 and 7.5, respectively. At pH 7.5, 10 min of ozonation ( identical with 15 mM ozone consumption) achieved a 90% degradation of TCP, which corresponded to the release of approximately 2 mol Cl(-) per mol TCP. The presence of hydrogen peroxide in solution did not significantly increase the TCP degradation but increased the overall dechlorination to 2.7 mol Cl(-) per mol TCP. The presence of humic acid (HA) in solution was found to enhance the degradation rate of TCP at low relative HA concentrations (<0.6 g/g HA:TCP), but to reduce the rate at higher HA concentrations. 相似文献
65.
66.
This paper examined the effects of work and family stressors and conflicts on Air Force women's mental health and functioning. We analyzed data from a 1993 survey of representative stratified samples of 525 Air Force women from the active duty reserve and guard forces. The analyses of the data are guided by the comprehensive model of work–family conflict that has been tested by Frone, Russell, and Cooper (1992) using a large representative community sample. Structural equation modeling analyses provided support for the work–family conflict model. The analyses also provided support for an extension of the model, which included the separate effects of marital and parental roles on mental health. The extended model demonstrated that job and parental stresses had direct effects on work–family conflicts and that job and marital distress and family–work conflict had an independent adverse effect on mental health. Whereas job and parental involvement had a beneficial effect on distress, they had an adverse effect on work–family conflicts. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
67.
Joana Garrido Nogueira Ronaldo Sousa Hassan Benaissa Geert De Knijf Sónia Ferreira Mohamed Ghamizi Duarte V. Gonçalves Richard Lansdown Catherine Numa Vincent Prié Nicoletta Riccardi Mary Seddon Maria Urbańska Alice Valentini Ilya Vikhrev Simone Varandas Amílcar Teixeira Manuel Lopes-Lima 《Conservation biology》2021,35(5):1367-1379
Theidentification of key biodiversity areas (KBA) was initiated by the International Union for Conservation of Nature in 2004 to overcome taxonomic biases in the selection of important areas for conservation, including freshwater ecosystems. Since then, several KBAs have been identified mainly based on the presence of trigger species (i.e., species that trigger either the vulnerability and or the irreplaceability criterion and thus identify a site as a KBA). However, to our knowledge, many of these KBAs have not been validated. Therefore, classical surveys of the taxa used to identify freshwater KBAs (fishes, molluscs, odonates, and aquatic plants) were conducted in Douro (Iberian Peninsula) and Sebou (Morocco) River basins in the Mediterranean Biodiversity Hotspot. Environmental DNA analyses were undertaken in the Moroccan KBAs. There was a mismatch between the supposed and actual presence of trigger species. None of the trigger species were found in 43% and 50% of all KBAs surveyed in the Douro and Sebou basins, respectively. Shortcomings of freshwater KBA identification relate to flawed or lack of distribution data for trigger species. This situation results from a misleading initial identification of KBAs based on poor (or even inaccurate) ecological information or due to increased human disturbance between initial KBA identification and the present. To improve identification of future freshwater KBAs, we suggest selecting trigger species with a more conservative approach; use of local expert knowledge and digital data (to assess habitat quality, species distribution, and potential threats); consideration of the subcatchment when delineating KBAs boundaries; thoughtful consideration of terrestrial special areas for conservation limits; and periodic field validation. 相似文献
68.
François Mialhe Yanni Gunnell Catherine Mering Jean-Christophe Gaillard June Gonzales Coloma Lionel Dabbadie 《Journal of Land Use Science》2016,11(2):236-256
This study documents the event chronology and causes of land-use change in a deltaic region of the Philippines since the beginnings of aquaculture in the late nineteenth century. Satellite images and topographic maps spanning the period 1972–2013 were processed to map fishponds and the natural habitats over which they have encroached. Historical archives were consulted and interviews were conducted to understand the historical exploitation of local natural resources and the reasons behind the recorded land changes. Results showed that aquaculture developed in the late nineteenth century and expanded subsequently across the landscape under a succession of forcing factors. The global market, for example, played an early role but a number of land-use changes were also a direct response to changing environmental constraints and natural hazards. These cumulative events have promoted continuous gain in favor of aquaculture, to the detriment of other land-use options. 相似文献
69.
Juliana M. Harding Michael A. Unger Roger Mann E. Alex Jestel Catherine Kilduff 《Marine Biology》2013,160(12):3027-3042
Imposex and decline in reproductive output in marine gastropods have been linked to tributyltin (TBT) exposure. This study describes Chesapeake Bay, USA, veined rapa whelk Rapana venosa imposex incidence and sex ratios from 1998 to 2009. Tissue TBT concentrations (ng g?1) were examined with respect to whelk sex, size, and water temperature at the time of collection, and also to egg case size, hatching success, and veliger diameter. Imposex incidence declined and population sex ratios moved closer to parity from 1998 to 2009. Observed TBT concentrations (ng g?1) were higher in James River than in Ocean View whelks with higher TBT concentrations observed in males than in females. Exponential declines in TBT concentrations from female-specific first to last clutches within a reproductive season were observed, indicating that whelks depurate TBT through egg case deposition. Egg capsule hatching success and veliger size were similar for female and imposex whelks. The R. venosa imposex levels observed in Chesapeake Bay apparently do not affect the production, release, or viability of larvae. 相似文献
70.
Bethann Mangel Pflugeisen Catherine A. Calder 《Environmental and Ecological Statistics》2013,20(2):179-190
The field of fisheries research commonly uses classical statistical classification methods to estimate the proportion of fish that return to natal spawning grounds to spawn. With the advent of otolith microchemical analysis, researchers are able to extract information from fish ear stones (otoliths) about the chemical composition of water in which fish have spent distinct periods of their lives. Here we present a method of analysis set in the Bayesian statistical paradigm which enables explicit incorporation of habitat information into the analysis. The ecological system is seen as arising from a mixture of disparate fish populations and information from the biological relationships inherent in otolith formation is exploited through the hierarchical model structure. We present the model and motivation, demonstrate the validity of the model through simulation studies, and conclude with an analysis of a data set from Lake Erie. 相似文献