394 research outputs found
Description of the ICCAT length at age data base for bluefin tuna from the eastern Atlantic, including the Mediterranean Sea
This study aims to describe the current length at age database available for Eastern Atlantic bluefin
tuna management area. A total of 8 500 spines and 5 000 otoliths were read from specimens caught
from 1984 to 2017 in both the Atlantic Ocean and Mediterranean Sea. Obtaining ALKs for this
species is difficult, as it has a wide length range and spatial distribution, and sampling is costly.
Unfortunately, there are practically no contributions to this database from the East Atlantic and
Mediterranean Sea countries, and only thanks to the initiative of the GBYP has it been possible to
increase the number of samples in the ICCAT database in the last 10 years. As a result, the current
ICCAT length at age database has incomplete spatial, temporal and size range coverage. However,
it may be suitable as conditional age-at-length data for the Stock Synthesis model
Description of nuclear systems within the relativistic Hartree-Fock method with zero range self-interactions of the scalar field
An exact method is suggested to treat the nonlinear self-interactions (NLSI)
in the relativistic Hartree-Fock (RHF) approach for nuclear systems. We
consider here the NLSI constructed from the relativistic scalar nucleon
densities and including products of six and eight fermion fields. This type of
NLSI corresponds to the zero range limit of the standard cubic and quartic
self-interactions of the scalar field. The method to treat the NLSI uses the
Fierz transformation, which enables one to express the exchange (Fock)
components in terms of the direct (Hartree) ones. The method is applied to
nuclear matter and finite nuclei. It is shown that, in the RHF formalism, the
NLSI, which are explicitly isovector-independent, generate scalar, vector and
tensor nucleon self-energies strongly density-dependent. This strong isovector
structure of the self-energies is due to the exchange terms of the RHF method.
Calculations are carried out with a parametrization containing five free
parameters. The model allows a description of both types of systems compatible
with experimental data.Comment: 23 pages, 14 figures (v2: major quantitative changes
Overexpression of Mouse D-Type Cyclins Accelerates G(1) Phase in Rodent Fibroblasts
Mammalian D-type cyclins are growth factor-regulated, delayed early response genes that are presumed to control progression through the G1 phase of the cell cycle by governing the activity of cyclin-dependent kinases (cdks). Overexpression of mouse cyclin D1 in serum-stimulated mouse NIH-3T3 and rat-2 fibroblasts increased their rates of G0 to S- and G1- to S-phase transit by several hours, leading to an equivalent contraction of their mean cell generation times. Although such cells remained contact inhibited and anchorage dependent, they manifested a reduced serum requirement for growth and were smaller in size than their normal counterparts. Ectopic expression of cyclin D2 in rodent fibroblasts, either alone or together with exogenous cdk4, shortened their G0- to S-phase interval and reduced their serum dependency, but cyclin D2 alone did not alter cell size significantly. When cells were microinjected during the G2 interval with a monoclonal antibody specifically reactive to cyclin D1, parental rodent fibroblasts and derivatives overexpressing this cyclin were inhibited from entering S phase, but cells injected near the G1/S phase transition were refractory to antibody-induced growth suppression. Thus, cyclin D1, and most likely D2, are rate limiting for G1progression
Updated comparison of age estimates from paired calcified structures from Atlantic bluefin tuna
In this paper we present an updated comparison of age estimates from otoliths and spines
from the same specimen, with the intention to analyze whether it is possible to use both
structures in obtaining age-length keys for this species. The agreement between otolith and
spine age estimates was good for bluefin tuna younger than 14 years old with less than one
year difference. Tests of symmetry showed the asymmetrical distribution of ages. However
no significant differences were found between the growth parameters estimated from both
paired hard parts. It is suggested using both structures readings for constructing agelength
keys for bluefin tuna younger than 14 years.En prensa0,000
REPORT OF THE 2019 ICCAT WORKSHOP ON SWORDFISH BIOLOGY STUDIES FOR GROWTH, REPRODUCTION AND GENETICS
This report describes the June, 2019 ICCAT workshop on swordfish biology studies for growth,
reproduction and genetics, hosted by the Instituto Português do Mar e da Atmosfera, Olhão,
Portugal . The major objectives of the workshop were to 1) refine sampling and biological data
collection protocols, 2) develop protocols and start the sample processing and analysis, and 3)
plan for the project future steps. The biological sampling program was established by ICCAT’s
Swordfish Species Group in 2018, aiming to improve knowledge of the stock distribution, age and
gender of the catch, growth rate, age at maturation, maturation rate, spawning season and
location and diet. This work will contribute to the next major advance in the assessment of
swordfish status, by permitting the development of more spatially and biologically realistic
population models used in both Atlantic and Mediterranean populations assessments and within
the ICCAT Management Strategy Evaluation (MSE) for North Atlantic swordfish.En prens
NEK2 induces osteoclast differentiation and bone destruction via heparanase in multiple myeloma
Spin symmetry in Dirac negative energy spectrum in density-dependent relativistic Hartree-Fock theory
The spin symmetry in the Dirac negative energy spectrum and its origin are
investigated for the first time within the density-dependent relativistic
Hartree-Fock (DDRHF) theory. Taking the nucleus O as an example, the
spin symmetry in the negative energy spectrum is found to be a good
approximation and the dominant components of the Dirac wave functions for the
spin doublets are nearly identical. In comparison with the relativistic Hartree
approximation where the origin of spin symmetry lies in the equality of the
scalar and vector potentials, in DDRHF the cancellation between the Hartree and
Fock terms is responsible for the better spin symmetry properties and
determines the subtle spin-orbit splitting. These conclusions hold even in the
case when significant deviations from the G-parity values of the
meson-antinucleon couplings occur.Comment: 13 pages, 7 figures, 1 table, accepted by Eur. Phys. J.
A phenomenological equation of state for isospin asymmetric nuclear matter
A phenomenological momentum-independent (MID) model is constructed to
describe the equation of state (EOS) for isospin asymmetric nuclear matter,
especially the density dependence of the nuclear symmetry energy
. This model can reasonably describe the general
properties of the EOS for symmetric nuclear matter and the symmetry energy
predicted by both the sophisticated isospin and momentum dependent MDI model
and the Skyrme-Hartree-Fock approach. We find that there exists a nicely linear
correlation between and as well as between and , where and represent, respectively, the
slope and curvature parameters of the symmetry energy at the normal nuclear
density while and are, respectively, the
incompressibility and the third-order derivative parameter of symmetric nuclear
matter at . These correlations together with the empirical
constraints on , and lead to an
estimation of -477 MeV MeV for the
second-order isospin asymmetry expansion coefficient for the incompressibility
of asymmetric nuclear matter at the saturation point.Comment: 9 pages, 4 figures, contribution to Special Topic on Large-Scale
Scientific Facilities (LSSF) in Science in China Series G: Physics, Mechanics
& Astronom
Isospin Physics in Heavy-Ion Collisions at Intermediate Energies
In nuclear collisions induced by stable or radioactive neutron-rich nuclei a
transient state of nuclear matter with an appreciable isospin asymmetry as well
as thermal and compressional excitation can be created. This offers the
possibility to study the properties of nuclear matter in the region between
symmetric nuclear matter and pure neutron matter. In this review, we discuss
recent theoretical studies of the equation of state of isospin-asymmetric
nuclear matter and its relations to the properties of neutron stars and
radioactive nuclei. Chemical and mechanical instabilities as well as the
liquid-gas phase transition in asymmetric nuclear matter are investigated. The
in-medium nucleon-nucleon cross sections at different isospin states are
reviewed as they affect significantly the dynamics of heavy ion collisions
induced by radioactive beams. We then discuss an isospin-dependent transport
model, which includes different mean-field potentials and cross sections for
the proton and neutron, and its application to these reactions. Furthermore, we
review the comparisons between theoretical predictions and available
experimental data. In particular, we discuss the study of nuclear stopping in
terms of isospin equilibration, the dependence of nuclear collective flow and
balance energy on the isospin-dependent nuclear equation of state and cross
sections, the isospin dependence of total nuclear reaction cross sections, and
the role of isospin in preequilibrium nucleon emissions and subthreshold pion
production.Comment: 101 pages with embedded epsf figures, review article for
"International Journal of Modern Physics E: Nuclear Physics". Send request
for a hard copy to 1/author
Report of the ICCAT GBYP international workshop on Atlantic bluefin tuna growth
In the last Atlantic bluefin tuna assessment, an age-length database coming from direct ageing
was presented for the first time. It was observed that otolith age estimates for fish younger than
8 years old had a smaller size at age compared to spine (first dorsal fin radius) age estimates.
This difference, although small, was enough to misallocate the year class. This misallocation
was solved when introducing a vector of bias corrected aged otoliths based on paired otolithspine samples. We have identified two possible causes for over-estimating age in the otolith agelength data: the current age adjustment criterion (to convert the bands counting into ages) and
a reading bias in age estimations from some laboratories. Otolith preparation and reading
protocols have been reviewed. The edge type and marginal increment analysis showed that the
formation of opaque zones would seem likely to occur primarily between December through to
June, contrary to what was thought until now, for which a new criterion for age adjustment has
been proposed
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