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751.
Patrick Safran 《Marine Biology》1992,112(4):545-551
The weight-length relationship in fish juveniles was investigated theoretically, to assess the significance of the allometric factor and the validity of the condition factor; these biological factors often remain undetermined, because most fishery studies have been conducted for commercial-sized and/or adult populations. The exponent b (allometric factor) seemed to be the main parameter, performing a key role in the equation W=aL
b
, where W=weight, a is a constant and L=length. The parameters a (condition factor) and K (ponderal index; K=103
W/L
3) were judged to be less important in comparative studies, since these parameters were closely correlated with b. It is recommended that the assumed theoretical value of b=3 not be used in applied ichthyological surveys, since this value was rarely obtained in the studies, and since a much wider range is usually seen. These analyses led to a new working hypothesis — not yet verified — which opens a new approach to understanding the biological significance of the allometric factor. This approach involves the fractal theory (where b may be considered as a fractal dimension equivalent) linked to the theory of saltatory ontogeny [where b is a threshold characteristic in the (early) life history of fishes]. 相似文献
752.
753.
We examined variation in aggressive responses within and among individuals in the green frog, Rana clamitans. We tested the hypothesis that resident males respond in a graded fashion to changes in perceived intruder proximity (stimulus intensity). We also investigated how response level varied with responder body size. We found that green frogs differentially alter aggressive responses (increasing movement and calling rates while decreasing the duration and dominant frequency of their calls) with an increase in stimulus intensity. Body size did not appear to be a significant influence on most response levels. We suggest that aggressive responses are graded, and advertisement and aggressive calls represent opposite ends of a continuum. Green frogs do not exhibit clearly defined thresholds for responses like those reported for some other frogs. By using graded responses rather than discrete all-or-nothing responses, males may reduce the potential costs of aggressive encounters. 相似文献
754.
Summary We present the first experiment to assess band color effects in a natural bird population. 38 territorial male red-winged blackbirds (Agelaius phoeniceus) were randomly assigned to 1 of 2 banding treatments. They received either all red bands (to match their epaulets) or all black bands (controls). Over half the red-banded males lost their territories while all black-banded males retained their territories. Red and black-banded males did not differ morphologically. However, among red-banded males, those that lost their territories had larger epaulets and were in poorer condition than those retaining their territories. Red-banded males suffered much higher intrusion rates, particularly by neighbors, than black-banded males. We propose that red color bands exaggerated the males' natural aggressive signal beyond the point where the signal was reliable. Our results suggest that signal reliability is maintained by regular testing, particularly of those males most likely to be signalling dishonestly.
Offprint requests to: K.J. Metz 相似文献
755.
Patrick W. Corrigan E. Paul Holmes Daniel Luchins Brett Buican Abdul Basit Joseph J. Parks 《组织行为杂志》1994,15(1):65-74
Previous research has shown that burnout in staff members at psychiatric hospitals is significantly associated with state anxiety and collegial support. The directionality of these relationships may be inferred using a cross-lagged panel design. To do this, 35 staff members representing various clinical disciplines completed measures of burnout, support, and anxiety twice, eight months apart. Burnout comprised three factors: emotional exhaustion, depersonalization, and personal accomplishment. Findings from one cross-lagged panel suggested that emotional exhaustion causes state anxiety. The second panel showed that lack of collegial support caused depersonalization. Understanding causes and effects of burnout for inpatient psychiatric staff may lead to training and resource development that will improve the quality of their work environment. 相似文献
756.
Dr Patrick H. Armstrong 《The Environmentalist》1994,14(3):215-231
Summary A historic analysis of human-initiated influences on the Falkland Islands ecologies is presented. Ecosystems were extensively altered by the destruction of seal and penguin communities in the late eighteenth and nineteenth centuries; and by the introduction of domesticated animals and exotic plants, the proliferation of fires, and the hunting to extinction, or near extinction, of certain animals. The harsh Falklands climate has permitted only limited recovery from some of these ravages. No island ecosystems, however remote, are spared the effects of economic and political changes influencing the rest of the world.He has published a previous article on island ecologies inThe Environmentalist (1992). 相似文献
757.
Paul E. Flathman Bryon J. Krupp Paul Zottola Jason R. Trausch John H. Carson Ruji Yao Gregory J. Laird Patrick M. Woodhull Douglas E. Jerger Paul R. Lear 《补救:环境净化治理成本、技术与工艺杂志》1996,6(2):57-79
In-situ biological solid-phase (or land) treatment was cost-effectively used to remediate 1,500 cubic yards (1,100 m3) of contaminated soil within three months of field operation following spillage of an estimated 12,000 gallons (45,000 L) of vinyl acetate from a railroad tank car onto surface soil. The vinyl acetate rapidly hydrolyzed to acetate and acetaldehyde with concentrations ranging up to 22,000 and 3,000 mg/kg, respectively. Ethanol, a metabolic intermediate, was found to accumulate in soil to concentrations as high as 280 mg/kg. The estimate for excavation, transportation, and disposal of the contaminated soil as a special waste, and for backfilling of the excavated area, was $850,000. The cost for biological remediation of the contaminated soil was $400,000, which was less than half the cost of excavation. In-situ biological treatments have been used to readily remove contaminants, such as acrylonitrile, styrene, butylcellosolve, ethylacrylate, and n-butylacrylate, at other sites involving railroad incidents. 相似文献
758.
Venkata Srinivas Challa Jayakumar Indrcanti Julius M. Baham Chuck Patrick Monika K. Rabarison John H. Young Robert Hughes Shelton J. Swanier Mark G. Hardy Anjaneyulu Yerramilli 《Environmental Fluid Mechanics》2008,8(4):367-387
Mesoscale transport and dispersion of air pollutants from a few major point sources in the Mississippi Gulf coastal region
is calculated using a coupled modeling system consisting of the atmospheric dynamical model WRF and the lagrangian particle
model HYSPLIT. The sensitivity of the dispersion model results to the meteorological fields is studied by conducting an ensemble
of simulations using the WRF model for the same dispersion case. Several parameterization schemes for the physical processes
of boundary layer turbulence and land surface temperature/moisture prediction in WRF are used in various combinations to produce
different meteorological members which are then used for dispersion simulation. The uncertainty in the simulated concentration
probabilities to the meteorological model configurations and the ensemble mean are presented. The parameters used for determining
the uncertainties include the wind fields, temperature, area of concentration and the levels of concentration. The results
indicate that dispersion model results are influenced by the choices made in respect of the planetary boundary layer and land
surface schemes in the mesoscale model to produce the meteorological forecast thereby leading to certain amount of uncertainty
in the resultant concentrations. Results show that the specific choices made about the atmospheric model configuration can
significantly after the simulated concentrations. 相似文献
759.
Joshua J. Traylor Ray T. Alisauskas F. Patrick Kehoe 《Behavioral ecology and sociobiology》2008,62(7):1085-1097
Young waterfowl can frequently join foster females shortly after hatch, resulting in post-hatch brood amalgamation. Much uncertainty
remains about physiological or ecological factors that motivate adoption including potential costs and benefits to fostered
offspring as well as to females that either lose or accept young. Several hypotheses have been put forth to explain adoption.
In this paper, we examine the salvage strategy (SSH) and accidental-mixing (AMH) hypotheses. According to the SSH, females
abandon or lose their young due to substantial energetic constraints from incubation and brood rearing. The AMH posits that
adoption results from local ecological conditions on breeding areas (i.e., adverse weather conditions, high brood densities)
which act to separate offspring and mothers. We used multistate modeling to estimate relationships between probabilities of
adoption by white-winged scoter (Melanitta fusca) ducklings from natal to foster females and a set of hypothesized ecological covariates. Results showed that most adoption
occurred within 6 days of hatch; additionally, likelihood of adoption was positively related to inclement weather and negatively
related to hatch date, size, and condition of natal females, and duckling condition. We conclude that adoption in this population
is consistent with both the salvage strategy and accidental-mixing hypotheses. Ultimately, we suggest that adoption in our
study population was foremost an outcome of intense gull predation but also of local environmental conditions. 相似文献
760.
Drissa Bamba Patrick Atheba Didier Robert Albert Trokourey Bini Dongui 《Environmental Chemistry Letters》2008,6(3):163-167
The occurrence of chlorinated pesticides in wellwaters is a major problem of public health in Ivory Coast and other African
countries. Here, we studied the photocatalytic degradation of the pesticide diuron in aqueous solution in presence of two
commercial TiO2 catalysts, P25 and PC500. The capacity of diuron adsorption at the TiO2 surface is lower for both photocatalysts. The efficiency of photocatalytic degradation of diuron, it is higher using P25
Degussa than PC500 Millenium TiO2 catalyst. 相似文献