3,310 research outputs found
A Portfolio Approach for the New Zealand Multi-Species Fisheries Management
Marine species are reproducible resource. Maintaining the stock level of marine species and the sustainability of fisheries development become critical issues in current scientific research areas due to the explosion of human population and exacerbation of natural environment. The traditional method that protects the marine species is the single species approach which set maximum sustainable yield (MSY) to prevent over-harvest. However, with the development of technology and comprehension of marine science, the single species approach has been found obsolete and incapable of dealing with problems of severe depletion of fish stocks and escalation of fisheries confliction. Studies show that when regulations are species specific and species are part of a multi-species fisheries, the catch levels of different species are correlated which result in correlation of net return from each species. This paper employ financial portfolio into fisheries, treat fish stocks as assets, model the fishersâ behaviour who face multiple targeting options to predict the optimal targeting strategies. This methodology is applied to New Zealand fisheries that are managed in Quota Management System (QMS) introduced in 1986. Species considered in this research are selected carefully based on two criteria. Efficient risk-return frontier will be generated that provides a combination of optimal strategies. Comparison between results and actual data will be presented. Potential explanations will be given so that further suggestions to fisheries can be made.Agribusiness, Environmental Economics and Policy, Production Economics, Productivity Analysis, Risk and Uncertainty,
Structural and molecular basis of the assembly of the TRPP2/PKD1 complex
Mutations in PKD1 and TRPP2 account for nearly all cases of autosomal dominant polycystic kidney disease (ADPKD). These 2 proteins form a receptor/ion channel complex on the cell surface. Using a combination of biochemistry, crystallography, and a single-molecule method to determine the subunit composition of proteins in the plasma membrane of live cells, we find that this complex contains 3 TRPP2 and 1 PKD1. A newly identified coiled-coil domain in the C terminus of TRPP2 is critical for the formation of this complex. This coiled-coil domain forms a homotrimer, in both solution and crystal structure, and binds to a single coiled-coil domain in the C terminus of PKD1. Mutations that disrupt the TRPP2 coiled-coil domain trimer abolish the assembly of both the full-length TRPP2 trimer and the TRPP2/PKD1 complex and diminish the surface expression of both proteins. These results have significant implications for the assembly, regulation, and function of the TRPP2/PKD1 complex and the pathogenic mechanism of some ADPKD-producing mutations
An fMRI study of error monitoring in Montessori and traditionally-schooled children.
The development of error monitoring is central to learning and academic achievement. However, few studies exist on the neural correlates of children's error monitoring, and no studies have examined its susceptibility to educational influences. Pedagogical methods differ on how they teach children to learn from errors. Here, 32 students (aged 8-12 years) from high-quality Swiss traditional or Montessori schools performed a math task with feedback during fMRI. Although the groups' accuracies were similar, Montessori students skipped fewer trials, responded faster and showed more neural activity in right parietal and frontal regions involved in math processing. While traditionally-schooled students showed greater functional connectivity between the ACC, involved in error monitoring, and hippocampus following correct trials, Montessori students showed greater functional connectivity between the ACC and frontal regions following incorrect trials. The findings suggest that pedagogical experience influences the development of error monitoring and its neural correlates, with implications for neurodevelopment and education
Slowly rotating charged black holes in anti-de Sitter third order Lovelock gravity
In this paper, we study slowly rotating black hole solutions in Lovelock
gravity (n=3). These exact slowly rotating black hole solutions are obtained in
uncharged and charged cases, respectively. Up to the linear order of the
rotating parameter a, the mass, Hawking temperature and entropy of the
uncharged black holes get no corrections from rotation. In charged case, we
compute magnetic dipole moment and gyromagnetic ratio of the black holes. It is
shown that the gyromagnetic ratio keeps invariant after introducing the
Gauss-Bonnet and third order Lovelock interactions.Comment: 14 pages, no figur
Quantum escape of the phase in a strongly driven Josephson junction
A quantum mechanical analysis of the Josephson phase escape in the presence
of both dc and ac bias currents is presented. We find that the potential
barrier for the escape of the phase is effectively suppressed as the resonant
condition occurs, i.e. when the frequency of the ac bias matches the
Josephson junction energy level separation. This effect manifests itself by a
pronounced drop in the dependence of the switching current on the power
of the applied microwave radiation and by a peculiar double-peak structure
in the switching current distribution . The developed theory is in a
good accord with an experiment which we also report in this paper. The obtained
features can be used to characterize certain aspects of the quantum-mechanical
behavior of the Josephson phase, such as the energy level quantization, the
Rabi frequency of coherent oscillations and the effect of damping.Comment: 4 pages, 3 figures, to be published in Physical Review B (Rapid
Communication
Submergence of the Sidebands in the Photon-assisted Tunneling through a Quantum Dot Weakly Coupled to Luttinger Liquid Leads
We study theoretically the photon-assisted tunneling through a quantum dot
weakly coupled to Luttinger liquids (LL) leads, and find that the zero bias dc
conductance is strongly affected by the interactions in the LL leads. In
comparison with the system with Fermi liquid (FL) leads, the sideband peaks of
the dc conductance become blurring for 1/2<g<1, and finally merge into the
central peak for g<1/2, (g is the interaction parameter in the LL leads). The
sidebands are suppressed for LL leads with Coulomb interactions strong enough,
and the conductance always appears as a single peak for any strength and
frequency of the external time-dependent field. Furthermore, the quenching
effect of the central peak for the FL case does not exist for g<1/2.Comment: 9 pages, 4 figure
Ferromagnetic phase transition and Bose-Einstein condensation in spinor Bose gases
Phase transitions in spinor Bose gases with ferromagnetic (FM) couplings are
studied via mean-field theory. We show that an infinitesimal value of the
coupling can induce a FM phase transition at a finite temperature always above
the critical temperature of Bose-Einstein condensation. This contrasts sharply
with the case of Fermi gases, in which the Stoner coupling can not lead
to a FM phase transition unless it is larger than a threshold value . The
FM coupling also increases the critical temperatures of both the ferromagnetic
transition and the Bose-Einstein condensation.Comment: 4 pages, 4 figure
Magnetic field and pressure effects on charge density wave, superconducting, and magnetic states in LuIrSi and ErIrSi
We have studied the charge-density-wave (CDW) state for the superconducting
LuIrSi and the antiferromagnetic ErIrSi as
variables of temperature, magnetic field, and hydrostatic pressure. For
LuIrSi, the application of pressure strongly suppresses the CDW
phase but weakly enhances the superconducting phase. For ErIrSi,
the incommensurate CDW state is pressure independent and the commensurate CDW
state strongly depends on the pressure, whereas the antiferromagnetic ordering
is slightly depressed by applying pressure. In addition, ErIrSi
shows negative magnetoresistance at low temperatures, compared with the
positive magnetoresistance of LuIrSi.Comment: 12 pages, including 6 figure
Dashen's phenomenon in gauge theories with spontaneously broken chiral symmetries
We examine Dashenâs phenomenon in the Leutwyler-Smilga regime of QCD with any number of colors and quarks in either the fundamental or adjoint representations of the gauge group. In this limit, the theories only depend on simple combinations of quark masses, the volume, chiral condensate and vacuum angle. Based upon this observation, we derive simple expressions for the chiral condensate and the topological density and show that they are in fact related. By examining the zeros of the various partition functions, we elucidate the mechanism leading to Dashenâs phenomena in QCD
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