4,530 research outputs found
An assessment of scup (Stenotomus chrysops) and black sea bass (Centropristas striata) discards in the directed otter trawl fisheries in the Mid-Atlantic Bight
This study was undertaken to re-assess the level of scup (Stenotomus chrysops) discards by weight and to evaluate the effect of various codend mesh sizes on the level of
scup discards in the winter-trawl scup fishery. Scup discards were high in directed scup tows regardless of
codend mesh â typically one to five times the weight of landings. The weight of scup discards in the present study did not differ significantly from that recorded in scup-targeted tows in the NMFS observer database. Most discards were required as such by the 22.86 cm TL (total length) fish-size limit for catches. Mesh sizes â€12.7 cm, including the current legal mesh size (11.43 cm) did not adequately filter out scup smaller than 22.86 cm. The median length of scup discards was about 19.83 cm TL. Lowering the legal size for scup from 22.86 to 19.83 cm TL would greatly reduce discard mortality. Scup discards were a small fraction (0.4%) of black sea bass (Centropristis striata) landings in blacksea-bassâtargeted tows. The black sea
bass fishery is currently regulated under the small-mesh fishery gearrestricted area plan in which fishing
is prohibited in some areas to reduce scup mortality. Our study found no evidence to support the efficacy of this management approach. The expectations that discarding would
increase disproportionately as the trip limit (limit [in kilograms] on catch for a species) was reached towards
the end of the trip and that discards would increase when the trip limit was reduced from 4536 kg to 454 kg at the end of the directed fishing season were not supported. Trip limits did not significantly affect discard mortality
Emerging Roles of Glycogen Synthase Kinase 3 in the Treatment of Brain Tumors
The constitutively active protein glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, acts paradoxically as a tumor suppressor in some cancers while potentiates growth in others. Deciphering what governs its actions is vital for understanding many pathological conditions, including brain cancer. What are seemingly disparate roles of GSK3 stems from the complex regulation of many cellular functions by GSK3. This review focuses on the regulation of GSK3, its role in survival, apoptosis and DNA damage, and finally its potential therapeutic impact in brain cancer. A thorough understanding of this versatile protein is critical for improving the outcome of various diseases, especially cancer
Recommended from our members
Absorption corrections for x-ray fluorescence analysis of environmental samples
The discovery of a very simple and useful relationship between the absorption coefficient of a particular element and the ratio of incoherent to coherent scattering by the sample containing the element is discussed. By measuring the absorption coefficients for a few elements in a few samples, absorption coefficients for many elements in an entire set of similar samples can be obtained. (auth
Proportion Regulation in Globally Coupled Nonlinear Systems
As a model of proportion regulation in differentiation process of biological
system, globally coupled activator-inhibitor systems are studied. Formation and
destabilization of one and two cluster state are predicted analytically.
Numerical simulations show that the proportion of units of clusters is chosen
within a finite range and it is selected depend on the initial condition.Comment: 11 pages (revtex format) and 5 figures (PostScript)
The Double-Time Green's Function Approach to the Two-Dimensional Heisenberg Antiferromagnet with Broken Bonds
We improved the decoupling approximation of the double-time Green's function
theory, and applied it to study the spin- two-dimensional
antiferromagnetic Heisenberg model with broken bonds at finite temperature. Our
decoupling approximation is applicable to the spin systems with spatial
inhomogeneity, introduced by the local defects, over the whole temperature
region. At low temperatures, we observed that the quantum fluctuation is
reduced in the neighborhood of broken bond, which is in agreement with previous
theoretical expectations. At high temperatures our results showed that the
quantum fluctuation close to the broken bond is enhanced. For the two parallel
broken bonds cases, we found that there exists a repulsive interaction between
the two parallel broken bonds at low temperatures.Comment: Revtex, 6 pages, 5 Postscript figures (include
Susceptibility calculations for alternating antiferromagnetic chains
Earlier work of Duffy and Barr consisting of exact calculations on alternating antiferromagnetic Heisenberg spinâ1/2 chains is extended to longer chains of up to 12 spins, and subsequent extrapolations of thermodynamic properties, particularly the susceptibility, are extended to the weak alternation region close to the uniform limit. This is the region of interest in connection with the recent experimental discovery of spinâPeierls systems. The extrapolated susceptibility curves are compared with corresponding curves calculated from the model of Bulaevskii, which has been used extensively in approximate theoretical treatments of a variety of phenomena. Qualitative agreement is observed in the uniform limit and persists for all degrees of alternation, but quantitative differences of about 10% are present over the whole range, including the isolated dimer limit. Potential application of the new susceptibility calculations to experiment is discussed
Magnetic properties of NaV2O5, a one-dimensional spin 1/2 antiferromagnet with finite chains
We have performed measurements of the magnetic susceptibility of NaVO
between 2 and 400 K. The high temperature part is typical of spin 1/2 chains
with a nearest--neighbour antiferromagnetic exchange integral of 529 K. We
develop a model for the susceptibility of a system with finite chains to
account for the low temperature part of the data, which cannot be fitted by a
standard Curie-Weiss term. These results suggest that the next
nearest--neighbour exchange integral in CaVO should be of the
order of 500 K because, like in NaVO, it corresponds to corner
sharing VO square pyramids.Comment: An early version of the manuscript was mistakenly submitted. Although
relatively minor, the changes concern the list of authors, the main text, the
references and the figure captions. 10 pages of latex, 2 figure
Pyrochlore Antiferromagnet: A Three-Dimensional Quantum Spin Liquid
The quantum pyrochlore antiferromagnet is studied by perturbative expansions
and exact diagonalization of small clusters. We find that the ground state is a
spin-liquid state: The spin-spin correlation functions decay exponentially with
distance and the correlation length never exceeds the interatomic distance. The
calculated magnetic neutron diffraction cross section is in very good agreement
with experiments performed on Y(Sc)Mn2. The low energy excitations are
singlet-singlet ones, with a finite spin gap.Comment: 4 pages, 4 figure
A Model Study of the Low-Energy Charge Dynamics of NaV_2O_5
An exact-diagonalization technique on small clusters is used to calculate the
dynamical density correlation functions of the dimerized t-J chain and coupled
anisotropic t-J ladders (trellis lattice) at quarter filling, i.e., the systems
regarded as a network of pairs (dimers or rungs) of sites coupled weakly via
the hopping and exchange interactions. We thereby demonstrate that the
intersite Coulomb repulsions between the pairs induce a low-energy collective
mode in the charge excitations of the systems where the internal charge degrees
of freedom of the pairs play an essential role. Implications to the electronic
states of NaV_2O_5, i.e., fluctuations of the valence state of V ions and phase
transition as a charge ordering, are discussed.Comment: 4 pages, 4 gif figures. Hardcopies of figures (or the entire
manuscript) can be obtained by e-mail request to [email protected]
- âŠ