Density dependence of electron scattering at low density

1994 ◽  
Vol 50 (16) ◽  
pp. 11583-11591 ◽  
Author(s):  
D. W. Snoke
Keyword(s):  
Density Dependence ◽  
Electron Scattering ◽  
Low Density

Density dependence of the Hanle effect of the 3s4p1P10 level of neutral magnesium

1979 ◽  
Vol 57 (6) ◽  
pp. 838-840
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Density Dependence ◽  
Excited Level ◽  
Lifetime Measurement ◽  
Oscillator Strengths ◽  
Low Density ◽  
Hanle Effect

The Hanle effect in the 3s2 1S0–3s4p1P1 (2026 Å) transition of Mg I has been studied over a range of densities. The low density observations lead to an accurate lifetime measurement of the 4p1P1 excited level. Related oscillator strengths are calculated.

Age- and Density-Dependent Bathymetric Pattern of Atlantic Cod (Gadus morhua) in the Southern Gulf of St. Lawrence

1993 ◽  
Vol 50 (6) ◽  
pp. 1255-1264 ◽  
Author(s):  
Douglas P. Swain
Keyword(s):  
Habitat Selection ◽  
Density Dependence ◽  
Shallow Water ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Age Groups ◽  
Low Density ◽  
Positive Correlation ◽  
Using Data ◽  
Trawl Surveys

I examined the bathymetric pattern of Alantic cod (Gadus morhua) in September in the southern Gulf of St. Lawrence for age groups 3–8+ over the period 1971–91 using data from annual bottom trawl surveys. Mean age of cod tended to increase with depth in all years. The age-specific bathymetric patterns underlying this relationship differed markedly between periods of low and high abundance. When abundance was high, cod densities tended to be highest at intermediate depths, and the positive correlation between age and depth reflected a tendency for density to be highest in progressively deeper water for older fish. When abundance was low, density was either unrelated to depth or highest in shallow water, and the positive correlation between age and depth reflected a tendency for older cod to be more widely distributed than younger cod (i.e., density decreased less sharply with depth for older cod). I suggest explanations for this density dependence of cod bathymetric pattern and discuss these results in relation to the factors underlying habitat selection and bathymetric segregation by age in this population.

Modelled impact of insecticide-contaminated dung on the abundance and distribution of dung fauna

2002 ◽  
Vol 92 (3) ◽  
pp. 251-263 ◽  
Author(s):  
G.A. Vale ◽  
I.F. Grant
Keyword(s):  
Population Density ◽  
Life Span ◽  
Density Dependence ◽  
Low Density ◽  
Deterministic Models ◽  
Size And Shape ◽  
Treatment Interval ◽  
Species Survival ◽  
Abundance And Distribution ◽  
The Impact

AbstractDeterministic models assessed the effects that contaminated dung from insecticide-treated cattle had on populations of three hypothetical species of dung fauna that dispersed randomly and could double their numbers every 1–28 weeks at low density. Insecticide was allowed to kill 2–98 % of adults and prevent 16–100% of breeding in pats produced immediately after cattle treatment, with toxicity declining to < 1% in pats produced 2–23 days later. Treatment intervals were 10–40 days. The modelled impact of insecticide was affected little by approximately four-fold variations in: length and density dependence of the attractive life span of pats, frequency of pat occupation by immature adults, distribution of pat toxicity during treatment interval, and changes in dispersal rates due to age and population density. Of greater importance were variations in: pat toxicity, treatment interval, frequency of pat occupation by breeding adults, density dependence of recruitment and death, natural adversity and mortality in dormancy, general rate of dispersal, and the size and shape of the area with treated cattle. Overall, it seemed that wide variations in the impact of contamination will occur in the field, but in many situations the risk to dung fauna can be substantial, especially for slow breeding beetles, and muscoids contacting insecticide on cattle. Risk extends outside the treated areas, for a distance equal to several daily displacements of the insects. Untreated refuges for species survival should be compact blocks at least 25 daily displacements wide.

scholarly journals Calibration of bottom trawls for northern shrimp

2008 ◽  
Vol 65 (6) ◽  
pp. 873-881 ◽  
Author(s):  
Michael C. S. Kingsley ◽  
Kai Wieland ◽  
Bo Bergström ◽  
Michael Rosing
Keyword(s):  
Density Dependence ◽  
Bayesian Methods ◽  
The Other ◽  
Bottom Trawl ◽  
Trawl Survey ◽  
Low Density ◽  
The West ◽  
Pandalus Borealis ◽  
Northern Shrimp ◽  
Data Calibration

Abstract Kingsley, M. C. S., Wieland, K., Bergström, B., and Rosing, M. 2008. Calibration of bottom trawls for northern shrimp. – ICES Journal of Marine Science, 65: 873–881. The Skjervøy 3000 trawl used since 1988 in the West Greenland bottom-trawl survey has been replaced by a Cosmos 2000. To be able to compare old data on the northern shrimp (Pandalus borealis) with new data, calibration experiments were carried out by trawling twice consecutively along the same track, using either the same gear twice or the two different gears in one order or the other. Catch models were fitted to the shrimp data—both size-aggregated catch weights and size-specific counts—by likelihood and Bayesian methods. The catch in the second haul relative to that in the first depended not only on the gear used in the two hauls, but also on density, the second catches being a smaller proportion of first catches when densities were high, and often larger than the first catches at low-density stations. This density-dependence of the catch ratio was larger for small shrimp than for big ones. The Cosmos trawl was estimated to fish with ∼87% of the catchability of the Skjervøy trawl after correction for its greater wingspread. Catchability ratio varied with the size of shrimp caught, but the differences were not statistically significant.

Density dependence of the Hanle effect of the 4s4p1P1 level of neutral calcium

1980 ◽  
Vol 58 (7) ◽  
pp. 1004-1009 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Density Dependence ◽  
High Density ◽  
Low Density ◽  
Density Region ◽  
Hanle Effect ◽  
Wide Range ◽  
High Density Region

The Hanle effect in the 4s21S0–4s4p1P1 (4226.7 Å) transition in Ca I has been observed over a wide range of densities. The low density observations determine the lifetime of the 1P1 level to be 4.49 ns. Collision parameters are obtained from observations in the high density region.

Theory of electron-electron scattering at low density

1993 ◽  
Vol 47 (20) ◽  
pp. 13346-13352 ◽  
Author(s):  
D. W. Snoke
Keyword(s):  
Electron Scattering ◽  
Low Density

NMR Theory of Gaseous CX3Y Molecules: High Frequency Effects of CF3H

1975 ◽  
Vol 53 (7) ◽  
pp. 739-755 ◽  
Author(s):  
B. C. Sanctuary ◽  
R. F. Snider
Keyword(s):  
General Theory ◽  
Density Dependence ◽  
High Frequency ◽  
Nuclear Spin Relaxation ◽  
Low Density ◽  
Frequency Effects ◽  
Dramatic Effect ◽  
Large Step ◽  
High Frequency Effects ◽  
Intramolecular Mechanism

A general theory of nuclear spin relaxation is applied to gaseous CX3Y molecules and the effects of high frequency terms studied theoretically. Although there is experimental disagreement as to what the correct high density dependence is for CF3H, it is demonstrated that rotational high frequency contributions can have a dramatic effect on the density dependence of T1. Moreover, for 'reasonable' values of the linewidth, shift, and collisional overlap parameters, the density dependence is limited in variation when the parameters are changed, making it impossible to fit Courtney's initial large 'step'. A reasonable fit to Waugh's data and the higher density dependence of Courtney can be obtained with a low density T1/n value of 0.8 s/amagat. Only a dipolar intramolecular mechanism is considered for the high frequency contributions.

scholarly journals The influence of context-dependent maternal effects on population dynamics: an experimental test

2009 ◽  
Vol 364 (1520) ◽  
pp. 1049-1058 ◽  
Author(s):  
S.J Plaistow ◽  
T.G Benton
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Maternal Effects ◽  
Maternal Effect ◽  
Population Growth Rate ◽  
High Density ◽  
Parental Effects ◽  
Low Density

Parental effects arise when either the maternal or paternal phenotype influences the phenotypes of subsequent generations. Simple analytical models assume maternal effects are a mechanism creating delayed density dependence. Such models predict that maternal effects can very easily lead to population cycles. Despite this, unambiguous maternal-effect mediated cycles have not been demonstrated in any system. Additionally, much evidence has arisen to invalidate the underlying assumption that there is a simple positive correlation between maternal performance and offspring performance. A key issue in understanding how maternal effects may affect population dynamics is determining how the expression of parental effects changes in different environments. In this study, we tested the hypothesis that maternal effects influence population dynamics in a context-dependent way. Populations of the soil mite, Sancassania berlesei , were set up at high density (500 eggs) or low density (50 eggs), with eggs that were either laid by young mothers or old mothers (a previously documented maternal effect in this system). The influence of maternal age on both population and egg and body-size dynamics was only observed in the populations initiated under low density rather than high density. This difference was attributable to the context-dependence of maternal effects at the individual level. In low-density (high food) conditions, maternal effects have an impact on offspring reproductive performance, creating an impact on the population growth rate. In high density (low food), maternal effects impact more on juvenile survival (not adult size or reproduction), creating a smaller impact on the population growth rate. This context dependence of effects at the population level means that, in fluctuating populations, maternal effects cause intermittent delayed density dependence that does not lead to persistent cycles.

Carrier density dependence of hot-electron scattering rates in quasi-equilibrium electron-hole plasmas

1991 ◽  
Vol 78 (5) ◽  
pp. 343-346 ◽  
Author(s):  
Jeff F. Young ◽  
Paul J. Kelly ◽  
Norm L. Henry ◽  
M.W.C. Dharma-wardana
Keyword(s):  
Density Dependence ◽  
Electron Scattering ◽  
Carrier Density ◽  
Quasi Equilibrium ◽  
Hot Electron ◽  
Electron Hole ◽  
Scattering Rates
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