929 research outputs found
A review of IATTC research on the early life history and reproductive biology of scombrids conducted at the Achotines Laboratory from 1985 to 2005
English:
For nearly a century, fisheries scientists have studied marine fish stocks in an effort to understand how the
abundances of fish populations are determined. During the early lives of marine fishes, survival is
variable, and the numbers of individuals surviving to transitional stages or recruitment are difficult to
predict.
The egg, larval, and juvenile stages of marine fishes are characterized by high rates of mortality and
growth. Most marine fishes, particularly pelagic species, are highly fecund, produce small eggs and
larvae, and feed and grow in complex aquatic ecosystems. The identification of environmental or
biological factors that are most important in controlling survival during the early life stages of marine
fishes is a potentially powerful tool in stock assessment.
Because vital rates (mortality and growth) during the early life stages of marine fishes are high and
variable, small changes in those rates can have profound effects on the properties of survivors and
recruitment potential (Houde 1989). Understanding and predicting the factors that most strongly
influence pre-recruit survival are key goals of fisheries research programs.
Spanish:
Desde hace casi un siglo, los científicos pesqueros han estudiado las poblaciones de peces marinos en un
intento por entender cómo se determina la abundancia de las mismas. Durante la vida temprana de los
peces marinos, la supervivencia es variable, y el número de individuos que sobrevive hasta las etapas
transicionales o el reclutamiento es difícil de predecir.
Las etapas de huevo, larval, y juvenil de los peces marinos son caracterizadas por tasas altas de
mortalidad y crecimiento. La mayoría de los peces marinos, particularmente las especies pelágicas, son
muy fecundos, producen huevos y larvas pequeños, y se alimentan y crecen en ecosistemas acuáticos complejos. La identificación los factores ambientales o biológicos más importantes en el control de la
supervivencia durante las etapas tempranas de vida de los peces marinos es una herramienta
potencialmente potente en la evaluación de las poblaciones.
Ya que las tasas vitales (mortalidad y crecimiento) durante las etapas tempranas de vida de los peces
marinos son altas y variables, cambios pequeños en esas tasas pueden ejercer efectos importantes sobre
las propiedades de los supervivientes y el potencial de reclutamiento (Houde 1989). Comprender y
predecir los factores que más afectan la supervivencia antes del reclutamiento son objetivos clave de los
programas de investigación pesquera
Positive solutions of Schr\"odinger equations and fine regularity of boundary points
Given a Lipschitz domain in and a nonnegative
potential in such that is bounded
in we study the fine regularity of boundary points with respect to
the Schr\"odinger operator in . Using potential
theoretic methods, several conditions equivalent to the fine regularity of are established. The main result is a simple (explicit if
is smooth) necessary and sufficient condition involving the size of
for to be finely regular. An essential intermediate result consists in
a majorization of for
positive harmonic in and . Conditions for
almost everywhere regularity in a subset of are also
given as well as an extension of the main results to a notion of fine
-regularity, if , being two potentials, with and a second order elliptic operator.Comment: version 1. 23 pages version 3. 28 pages. Mainly a typo in Theorem 1.1
is correcte
A Weighted Estimate for the Square Function on the Unit Ball in \C^n
We show that the Lusin area integral or the square function on the unit ball
of \C^n, regarded as an operator in weighted space has a linear
bound in terms of the invariant characteristic of the weight. We show a
dimension-free estimate for the ``area-integral'' associated to the weighted
norm of the square function. We prove the equivalence of the classical
and the invariant classes.Comment: 11 pages, to appear in Arkiv for Matemati
Testing the Void against Cosmological data: fitting CMB, BAO, SN and H0
In this paper, instead of invoking Dark Energy, we try and fit various
cosmological observations with a large Gpc scale under-dense region (Void)
which is modeled by a Lemaitre-Tolman-Bondi metric that at large distances
becomes a homogeneous FLRW metric. We improve on previous analyses by allowing
for nonzero overall curvature, accurately computing the distance to the
last-scattering surface and the observed scale of the Baryon Acoustic peaks,
and investigating important effects that could arise from having nontrivial
Void density profiles. We mainly focus on the WMAP 7-yr data (TT and TE),
Supernova data (SDSS SN), Hubble constant measurements (HST) and Baryon
Acoustic Oscillation data (SDSS and LRG). We find that the inclusion of a
nonzero overall curvature drastically improves the goodness of fit of the Void
model, bringing it very close to that of a homogeneous universe containing Dark
Energy, while by varying the profile one can increase the value of the local
Hubble parameter which has been a challenge for these models. We also try to
gauge how well our model can fit the large-scale-structure data, but a
comprehensive analysis will require the knowledge of perturbations on LTB
metrics. The model is consistent with the CMB dipole if the observer is about
15 Mpc off the centre of the Void. Remarkably, such an off-center position may
be able to account for the recent anomalous measurements of a large bulk flow
from kSZ data. Finally we provide several analytical approximations in
different regimes for the LTB metric, and a numerical module for CosmoMC, thus
allowing for a MCMC exploration of the full parameter space.Comment: 70 pages, 12 figures, matches version accepted for publication in
JCAP. References added, numerical values in tables changed due to minor bug,
conclusions unaltered. Numerical module available at
http://web.physik.rwth-aachen.de/download/valkenburg
Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences
Based on Luttinger's formulation the complex optical conductivity tensor is
calculated within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker method for layered systems by means of a contour
integration technique. For polar geometry and normal incidence ab-initio Kerr
spectra of multilayer systems are then obtained by including via a 2x2 matrix
technique all multiple reflections between layers and optical interferences in
the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite
fcc-Pt(111) bulk substrate show good qualitative agreement with the
experimental spectra, but differ from those obtained by applying the commonly
used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to
Phys. Rev.
Relationship between dynamical heterogeneities and stretched exponential relaxation
We identify the dynamical heterogeneities as an essential prerequisite for
stretched exponential relaxation in dynamically frustrated systems. This
heterogeneity takes the form of ordered domains of finite but diverging
lifetime for particles in atomic or molecular systems, or spin states in
magnetic materials. At the onset of the dynamical heterogeneity, the
distribution of time intervals spent in such domains or traps becomes stretched
exponential at long time. We rigorously show that once this is the case, the
autocorrelation function of the renewal process formed by these time intervals
is also stretched exponential at long time.Comment: 8 pages, 4 figures, submitted to PR
The Intentional Use of Service Recovery Strategies to Influence Consumer Emotion, Cognition and Behaviour
Service recovery strategies have been identified as a critical factor in the success of. service organizations. This study develops a conceptual frame work to investigate how specific service recovery strategies influence the emotional, cognitive and negative behavioural responses of . consumers., as well as how emotion and cognition influence negative behavior. Understanding the impact of specific service recovery strategies will allow service providers' to more deliberately and intentionally engage in strategies that result in positive organizational outcomes. This study was conducted using a 2 x 2 between-subjects quasi-experimental design. The results suggest that service recovery has a significant impact on emotion, cognition and negative behavior. Similarly, satisfaction, negative emotion and positive emotion all influence negative behavior but distributive justice has no effect
Five blood pressure loci identified by an updated genome-wide linkage scan: meta-analysis of the Family Blood Pressure Program.
BACKGROUND: A preliminary genome-wide linkage analysis of blood pressure in the Family Blood Pressure Program (FBPP) was reported previously. We harnessed the power and ethnic diversity of the final pooled FBPP dataset to identify novel loci for blood pressure thereby enhancing localization of genes containing less common variants with large effects on blood pressure levels and hypertension.
METHODS: We performed one overall and 4 race-specific meta-analyses of genome-wide blood pressure linkage scans using data on 4,226 African-American, 2,154 Asian, 4,229 Caucasian, and 2,435 Mexican-American participants (total N = 13,044). Variance components models were fit to measured (raw) blood pressure levels and two types of antihypertensive medication adjusted blood pressure phenotypes within each of 10 subgroups defined by race and network. A modified Fisher's method was used to combine the P values for each linkage marker across the 10 subgroups.
RESULTS: Five quantitative trait loci (QTLs) were detected on chromosomes 6p22.3, 8q23.1, 20q13.12, 21q21.1, and 21q21.3 based on significant linkage evidence (defined by logarithm of odds (lod) score ≥3) in at least one meta-analysis and lod scores ≥1 in at least 2 subgroups defined by network and race. The chromosome 8q23.1 locus was supported by Asian-, Caucasian-, and Mexican-American-specific meta-analyses.
CONCLUSIONS: The new QTLs reported justify new candidate gene studies. They may help support results from genome-wide association studies (GWAS) that fall in these QTL regions but fail to achieve the genome-wide significance
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