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991.
Across animal taxa, exclusive female offspring care has evolved repeatedly from biparental care, suggesting that the latter
becomes evolutionarily unstable under certain conditions. Both the attributes of a species and the environment it experiences
can help to predict shifts from one particular care mode to another. Nevertheless, factors inducing differences in care strategies
among closely related species, or seasonal variation within species, have been subject to surprisingly little empirical testing.
Here, we report the results of a field-based study that examined both among and within species variation in mate desertion
in five species of closely related Nicaraguan cichlid fish in the genera Amphilophus and Amatitlania. The results show a link between female body size and male involvement in offspring care. Specifically, the larger the species
the less often males were found to provide extended care. Furthermore, we found that solitary females became more common towards
the end of the breeding season. We discuss the implications of this finding in the context of previous theoretical and empirical
contributions regarding the frequency of offspring desertion by males. 相似文献
992.
Subbiah Seenivasan NarayananNair Muraleedharan 《Environmental monitoring and assessment》2011,176(1-4):365-371
Tea is considered as a ‘health beverage’ due its antioxidant properties and resultant beneficial effects on human health. Such a beverage should be free from toxic elements such as pesticide residues and heavy metals. A large scale survey of teas produced in the tea factories of south India had been carried out for a period of three years from 2006 to 2008 and 912 tea samples were analysed for the residues of certain pesticides such as dicofol, ethion, quinalphos, hexaconazole, fenpropathrin, fenvalerate and propargite which are used for pest and disease control in tea in this part of the country. The analytical data proved that only less than 0.5 percentage of tea samples had residues of these pesticides. However, residues of pesticides were below their maximum limits in tea, stipulated by the European Union, Codex Alimentarius Commission of FAO/WHO and Prevention of Food Adulteration Act of Govt. of India. 相似文献
993.
Harshinie Karunarathna 《Journal of Coastal Conservation》2011,15(4):499-507
The long-term morphodynamic response of the Clyde Estuary to any possible change in environmental forcing associated with
global climate change and human interference is examined here using a model based on a systems approach. The model, which
uses Boolean Algebra as its formal mathematical language, provides a qualitative insight into the long term morphodynamic
behaviour of the estuarine system, at this level without the need for detailed and quantitative hydrodynamic and morphodynamic
process knowledge or extensive data resources. The model predictions suggest that the long-term morphological changes in the
Clyde Estuary largely depend on the fluvial flow of the River Clyde. Salt marshes in the upper reaches of the estuary were
found to be the most vulnerable morphological feature of the estuary. In the event of increased river flow in the future,
a likely situation according to climate change scenarios, saltmarshes will deplete or disappear altogether, irrespective of
the sediment influx into the estuary. Changes to waves and tides will also contribute to the evolution by taking the estuary
through significantly different intermediate morphological states whilst evolving towards a stable end state. 相似文献
994.
An open channel flow with a flow depth close to the critical depth is characterised by a curvilinear streamline flow field
that results in steady free surface undulations. Near critical flows of practical relevance encompass the undular hydraulic
jump when the flow changes from supercritical (F > 1) to subcritical (F < 1), and the undular weir flow over broad-crested
weirs where the flow changes from subcritical (F < 1) to supercritical (F > 1). So far these flows were mainly studied based
on ideal fluid flow computations, for which the flow is assumed irrotational and, thus, shear forces are absent. While the
approach is accurate for critical flow conditions (F = 1) in weir and flumes, near-critical flows involve long distances reaches,
and the effect of friction on the flow properties cannot be neglected. In the present study the characteristics of near-critical
free-surface flows are reanalysed based on a model accounting for both the streamline curvature and friction effects. Based
on the improved model, some better agreement with experimental results is found, thereby highlighting the main frictional
features of the flow profiles. 相似文献
995.
Jorge Alberto Achcar Josmar Mazucheli Emílio Augusto Coelho-Barros 《Environmental and Ecological Statistics》2011,18(2):315-329
In this paper we present a hierarchical Bayesian analysis for a predator–prey model applied to ecology considering the use
of Markov Chain Monte Carlo methods. We consider the introduction of a random effect in the model and the presence of a covariate
vector. An application to ecology is considered using a data set related to the plankton dynamics of lake Geneva for the year
1990. We also discuss some aspects of discrimination of the proposed models. 相似文献
996.
Armando A. Rodriguez Oguzhan Cifdaloz John Martin Anderies Marco A. Janssen Jeffrey Dickeson 《Environmental Modeling and Assessment》2011,16(1):15-36
This paper presents a framework for the study of policy implementation in highly uncertain natural resource systems in which
uncertainty cannot be characterized by probability distributions. We apply the framework to parametric uncertainty in the
traditional Gordon–Schaefer model of a fishery to illustrate how performance can be sacrificed (traded-off) for reduced sensitivity
and hence increased robustness, with respect to model parameter uncertainty. With sufficient data, our robustness–vulnerability
analysis provides tools to discuss policy options. When less data are available, it can be used to inform the early stages
of a learning process. Several key insights emerge from this analysis: (1) the classic optimal control policy can be very
sensitive to parametric uncertainty, (2) even mild robustness properties are difficult to achieve for the simple Gordon–Schaefer
model, and (3) achieving increased robustness with respect to some parameters (e.g., biological parameters) necessarily results
in increased sensitivity (decreased robustness) with respect to other parameters (e.g., economic parameters). We thus illustrate
fundamental robustness–vulnerability trade-offs and the limits to robust natural resource management. Finally, we use the
framework to explore the effects of infrequent sampling and delays on policy performance. 相似文献
997.
A Method for Ensemble Wildland Fire Simulation 总被引:1,自引:0,他引:1
Mark A. Finney Isaac C. Grenfell Charles W. McHugh Robert C. Seli Diane Trethewey Richard D. Stratton Stuart Brittain 《Environmental Modeling and Assessment》2011,16(2):153-167
An ensemble simulation system that accounts for uncertainty in long-range weather conditions and two-dimensional wildland
fire spread is described. Fuel moisture is expressed based on the energy release component, a US fire danger rating index,
and its variation throughout the fire season is modeled using time series analysis of historical weather data. This analysis
is used to characterize the seasonal trend in ERC, autocorrelation of residuals, and daily standard deviation and stochastically
generate artificial time series of afternoon fuel moisture. Daily wind speed and direction are sampled stochastically from
joint probabilities of historical wind speed and direction for the date range of the fire simulation period. Hundreds or thousands
of fire growth simulations are then performed using the synthetic fire weather sequences. The performance of these methods
is evaluated in terms of the number of ensemble member simulations, one- versus two-dimensional fire spread simulations, and
comparison with results from 91 fires occurring from 2007 to 2009. Simulations were found to be in consistent agreement with
observations, but trends indicate that the ensemble average of simulated fire sizes were consistently larger than actual fires
whereas the farthest extent burned by fires was underestimated. 相似文献
998.
Matjaž Hriberšek Niko Samec Jure Ravnik Matej Zadravec 《Environmental Modeling and Assessment》2011,16(5):479-489
The contribution presents numerical simulation of gypsum particles, lifting from a gypsum landfill. First, particle characteristics
are presented, resulting from different technologies of gypsum depositing. Next, a laboratory experiment parameter validation
tests are described, which served as a means of determination of mass flow of particles from the landfill. The background
of the numerical simulations, used in the assessment of landfill impact on the environment, is also described. Simulations
consist of two parts: simulation of a long term impact of the particles on the surrounding area, performed by implementation
of the Gaussian dispersion model based computer code ISC3, and second, a CFD based simulation for assessing the flow and mass
concentration fields in the vicinity of the landfill for several pre-selected flow cases. The results of both computational
approaches are presented and compared. In the conclusions, a relation of the simulation results with existing environmental
pollution levels is made, and recommendations for landfill management are drawn. 相似文献
999.
Groundwater flow modelling is an important tool in simulating and predicting hydraulic behaviour of groundwater transporting
in the domain consisted of groundwater flow zone (aquifer) and permeable reactive barriers (PRBs). The aquifer regime is modelled
using the Darcy equation, whereas PRBs are simulated by the Brinkman equation. By combining the above equations, the present
paper is devoted to analyse the effect of permeability of aquifer (K
aq
) and reactive media (K
p
), groundwater flow velocity, and barrier size as well as assembled style of barriers on key barrier design parameter, such
as the hydraulic capture zone width. The simulations indicate that the capture zone width generally decreases with a decrease
in K
p
at a given K
aq
; however, there is relatively little decrease in capture zone width when the K
p
of freshly installed reactive media is roughly 10 times higher than the K
aq
. For a given barrier system, the absolute capture zone width increases with an increase in barrier size, whereas the increment
of relative capture zone width decreases dramatically. Although the capture zone width remains relatively unchanged as groundwater
flow velocity increases, it results in a shorter residence time in the reactive media that may require greater barrier thickness
so that contaminant levels can be reduced to regulatory limits. In addition, the effect of parallel barriers interaction on
the capture zone width should be incorporated into the design. The present paper is based on the continuous reactive barrier
and homogeneous barrier system. Similar methods can be used to analyse the hydrodynamics of funnel-and-gate system and heterogeneous
settings by the appropriate modification. 相似文献
1000.
Ivonne Bedei Karl-Philipp Gloning Luc Joyeux Matthias Meyer-Wittkopf Daria Willner Martin Krapp Alexander Scharf Jan Degenhardt Kai-Sven Heling Peter Kozlowski Kathrin Trautmann Kai M. Jahns Annegret Geipel Ismail Tekesin Michael Elsässer Lucas Wilhelm Ingo Gottschalk Jan-Erik Baumüller Cahit Birdir Andreas Schröer Felix Zöllner Aline Wolter Johanna Schenk Tascha Gehrke Alicia Spaeth Roland Axt-Fliedner 《黑龙江环境通报》2023,43(2):183-191