11,392 research outputs found
Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia
The time series of abundance indices for many groundfish
populations, as determined from trawl surveys, are often imprecise and short, causing stock assessment estimates
of abundance to be imprecise. To improve precision, prior probability distributions (priors) have been developed
for parameters in stock assessment models by using meta-analysis, expert judgment on catchability, and empirically based modeling. This article presents a synthetic approach for formulating priors for rockfish trawl survey catchability (qgross). A multivariate prior for qgross for different surveys is formulated by using 1) a correction factor for bias in estimating fish density between trawlable and untrawlable areas, 2) expert judgment on trawl net catchability, 3) observations from trawl survey experiments, and 4) data on the fraction of population
biomass in each of the areas surveyed. The method is illustrated by using bocaccio (Sebastes paucipinis) in British Columbia. Results indicate that expert judgment can be updated markedly by observing the catch-rate ratio from different trawl gears in the same areas. The marginal priors
for qgross are consistent with empirical estimates obtained by fitting a stock assessment model to the survey data under a noninformative prior for qgross. Despite high prior uncertainty (prior coefficients of variation ā„0.8) and high prior correlation between qgross, the prior for qgross still enhances the precision of key stock assessment
quantities
A Generalized Preferential Attachment Model for Business Firms Growth Rates: II. Mathematical Treatment
We present a preferential attachment growth model to obtain the distribution
of number of units in the classes which may represent business firms
or other socio-economic entities. We found that is described in its
central part by a power law with an exponent which depends on
the probability of entry of new classes, . In a particular problem of city
population this distribution is equivalent to the well known Zipf law. In the
absence of the new classes entry, the distribution is exponential. Using
analytical form of and assuming proportional growth for units, we derive
, the distribution of business firm growth rates. The model predicts that
has a Laplacian cusp in the central part and asymptotic power-law tails
with an exponent . We test the analytical expressions derived using
heuristic arguments by simulations. The model might also explain the
size-variance relationship of the firm growth rates.Comment: 19 pages 6 figures Applications of Physics in Financial Analysis,
APFA
Long-Term Performance of Old Dominion Technology Graduates
The long-term career patterns of Old Dominion University\u27s engineering technology baccalaureate graduates have been studied extensively. Results from approximately 400 alumni have been analyzed. The results of the analysis are presented and conclusions are drawn from the trends. The results indicate that the career progress of engineering technology graduates over a nearly twenty-year period is substantial and that they are performing effectively in a variety of career patterns
Analysing co-evolution among artificial 3D creatures
This paper is concerned with the analysis of coevolutionary dynamics among 3D artificial creatures, similar to those introduced by Sims (1). Coevolution is subject to complex dynamics which are notoriously difficult to analyse. We introduce an improved analysis method based on Master Tournament matrices [2], which we argue is both less costly to compute and more informative than the original method. Based on visible features of the resulting graphs, we can identify particular trends and incidents in the dynamics of coevolution and look for their causes. Finally, considering that coevolutionary progress is not necessarily identical to global overall progress, we extend this analysis by cross-validating individuals from different evolutionary runs, which we argue is more appropriate than single-record analysis method for evaluating the global performance of individuals
Earthquake networks based on similar activity patterns
Earthquakes are a complex spatiotemporal phenomenon, the underlying mechanism
for which is still not fully understood despite decades of research and
analysis. We propose and develop a network approach to earthquake events. In
this network, a node represents a spatial location while a link between two
nodes represents similar activity patterns in the two different locations. The
strength of a link is proportional to the strength of the cross-correlation in
activities of two nodes joined by the link. We apply our network approach to a
Japanese earthquake catalog spanning the 14-year period 1985-1998. We find
strong links representing large correlations between patterns in locations
separated by more than 1000 km, corroborating prior observations that
earthquake interactions have no characteristic length scale. We find network
characteristics not attributable to chance alone, including a large number of
network links, high node assortativity, and strong stability over time.Comment: 8 pages text, 9 figures. Updated from previous versio
Mapping functions and critical behavior of percolation on rectangular domains
The existence probability and the percolation probability of the
bond percolation on rectangular domains with different aspect ratios are
studied via the mapping functions between systems with different aspect ratios.
The superscaling behavior of and for such systems with exponents
and , respectively, found by Watanabe, Yukawa, Ito, and Hu in [Phys. Rev.
Lett. \textbf{93}, 190601 (2004)] can be understood from the lower order
approximation of the mapping functions and for and ,
respectively; the exponents and can be obtained from numerically
determined mapping functions and , respectively.Comment: 17 pages with 6 figure
The male of the species: a profile of men in nursing
Aim: To establish a profile of men in nursing in Western Australia and explore the perception of men in nursing from the perspective of male and female nurses.
Background: A project team, including some of the current authors, produced a YouTube video and DVD about men in nursing which led to further inquiry on this topic.
Design: The study employed a non-experimental, comparative, descriptive research design focused on a quantitative methodology, using an online survey in early 2014.
Method: A convenience sample incorporated registered and enrolled nurses and midwives in Western Australia.
Findings: The range of data included demographic information and the respondentsā perceptions of men in nursing were collected. Findings indicated that the main reasons for choosing a career in nursing or midwifery were similar for both genders. Common mis-perceptions of men in nursing included: most male nurses are gay; men are not suited to nursing and men are less caring and compassionate than women. Suggestions to promote nursing to men included: nurses are highly skilled professionals; there is the potential to make a difference for patients; nursing offers stable employment, professional diversity and opportunities for team work. There is a diminished awareness of opportunities for men in nursing and negative stereotypes related to men in nursing persist.
Conclusion: The study produced recommendations which included: using the right message to target the recruitment for men and promoting a more realistic understanding of the profile and perception of men in nursing
SiGe HBT X-Band LNAs for Ultra-Low-Noise Cryogenic Receivers
We report results on the cryogenic operation of two
different monolithic X-band silicon-germanium (SiGe) heterojunction bipolar transistor low noise amplifiers (LNAs) implemented in a commercially-available 130 nm SiGe BiCMOS platform. These SiGe LNAs exhibit a dramatic reduction in noise temperature with cooling, yielding Teff of less than 21 K (0.3 dB noise figure) across X-band at a 15 K operating temperature. To the authorsā knowledge, these SiGe LNAs exhibit the lowest broadband noise of any
Si-based LNA reported to date
Regulation of caveolin and caveolae by cholesterol in MDCK cells
We have examined the expression of caveolin in MDCK cells under conditions that vary cellular cholesterol concentration. Caveolin mRNA levels dropped to one-sixth of control levels after treatment with simvastatin, an inhibitor of cholesterol synthesis, or beta-trimethyl cyclodextrin (CD), a cholesterol sequestering drug. Both simvastatin and CD treatment decreased total cellular cholesterol levels to about 50% of control values. The potent activator of the sterol regulatory element, 25-hydroxycholesterol, showed no direct regulation of caveolin mRNA levels. Caveolin protein concentration was also decreased to 50% of control values in cholesterol-depleted cells, giving rise to a severe attenuation of caveolin expression detected by indirect immunofluorescence labeling. Quantitative electron microscopy showed a total loss of morphologically recognizable invaginated caveolae after these cholesterol depletion treatments. When the number of invaginated caveolae per cell was expressed as a function of the cellular cholesterol content, a threshold phenomenon was observed, suggesting that caveolae only form when the steady state cellular cholesterol is above 50% of control values. These findings indicate that caveolins, and caveolae, may play an important part in cellular cholesterol homeostasis
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