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.

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.

The density dependence of the Hanle effect in the resonance line of atomic barium

1977 ◽  
Vol 55 (1) ◽  
pp. 83-91 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Cross Sections ◽  
Resonance Line ◽  
Excited Level ◽  
Ground Level ◽  
Multipole Moment ◽  
Low Density ◽  
Density Region ◽  
Hanle Effect ◽  
Wide Range ◽  
Theoretical Predictions

The change in the Hanle effect of the singlet resonance line of neutral barium has been studied over a wide range of density. The low density region has been used to confirm a lifetime of 8.37 ± 0.08 ns for the 6s6p1P1 level. We have determined the cross sections for the relaxation of the multipole moment of order 2 for collisions of the excited level with the ground level and with the metastable 6s5d1D2 level, and comparisons are made with the measured value of [Formula: see text] for the ground level with theoretical predictions.

Hanle effect in the singlet excited states of the alkaline earths

1980 ◽  
Vol 58 (10) ◽  
pp. 1416-1419 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Excited States ◽  
Cross Sections ◽  
Ground Level ◽  
High Density ◽  
Oscillator Strengths ◽  
Low Density ◽  
Density Data ◽  
Hanle Effect ◽  
Singlet States ◽  
Alkaline Earths

The Hanle effect in the singlet states of Sr, Ba, Mg, and Ca has been studied over a range of densities. The low density observations lead to an accurate lifetime measurement of the singlet excited levels, and calculation of the related oscillator strengths. The depolarization cross sections, [Formula: see text], for collision with ground level neutral atoms have been obtained from the high density data.

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.

Complete Line Shape for the Impact, Static, and the Intermediate Regions

1975 ◽  
Vol 53 (1) ◽  
pp. 84-92 ◽  
Author(s):  
R. P. Srivastava ◽  
H. R. Zaidi
Keyword(s):  
Density Dependence ◽  
Line Width ◽  
Line Shape ◽  
Translational Motion ◽  
Excited Level ◽  
Dipole Interaction ◽  
Line Shapes ◽  
Classical Path ◽  
The Impact ◽  
Resonance Broadening

Line shapes are calculated for the resonance broadening of an excited level through the dipole–dipole interaction. The calculations are based on two main approximations: (1) two body collisions and (2) straight classical path for the translational motion. The results are valid over the complete region extending from the impact to the static regimes. It is shown that, under suitable conditions, the incomplete collisions can give rise to (a) a splitting of the line at the center and (b) nonlinear density dependence of the line width.

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.

The density dependence of the Hanle effect in the resonance line of atomic magnesium

1978 ◽  
Vol 56 (11) ◽  
pp. 1422-1425 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Density Dependence ◽  
Cross Section ◽  
Resonance Line ◽  
Neutral Atom ◽  
Ground Level ◽  
Hanle Effect ◽  
Wide Range

The Hanle width and hence the lifetime of the first excited 1P1 level of neutral magnesium have been measured over a wide range of densities. The natural lifetime of the 3s3p1P1 level is 2.00 ns. The depolarization cross section for collisions with the ground level neutral atom has been measured and [Formula: see text].

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