3,632 research outputs found
Transferable Rights of Recreational Fishery: An Application to Red Snapper Fishery in the Gulf of Mexico
Transferable rights (TRs) programs are being increasingly considered in fisheries to overcome current overfishing situation. This paper will focus on developing a conceptual foundation, investigating advantages of the TRs program in fishery management, and answering critical issues to implement recreational TRs programs. Implication is to the Gulf of Mexico red snapper fishery.Transferable Rights, Individual Transferable Quota, Recreational Fishery, Resource /Energy Economics and Policy, Q22,
The pharmacokinetics of anthocyanins and their metabolites in humans
Background and Purpose: Anthocyanins are phytochemicals with reported vasoactive bioactivity. However, given their instability at neutral pH, they are presumed to undergo significant degradation and subsequent biotransformation. The aim of the present study was to establish the pharmacokinetics of the metabolites of cyanidin-3-glucoside (C3G), a widely consumed dietary phytochemical with potential cardioprotective properties. Experimental Approach: A 500 mg oral bolus dose of 6,8,10,3′,5′-13C5-C3G was fed to eight healthy male participants, followed by a 48 h collection (0, 0.5, 1, 2, 4, 6, 24, 48 h) of blood, urine and faecal samples. Samples were analysed by HPLC-ESI-MS/MS with elimination kinetics established using non-compartmental pharmacokinetic modelling. Key Results: Seventeen 13C-labelled compounds were identified in the serum, including 13C5-C3G, its degradation products, protocatechuic acid (PCA) and phloroglucinaldehyde (PGA), 13 metabolites of PCA and 1 metabolite derived from PGA. The maximal concentrations of the phenolic metabolites (Cmax) ranged from 10 to 2000 nM, between 2 and 30 h (tmax) post-consumption, with half-lives of elimination observed between 0.5 and 96 h. The major phenolic metabolites identified were hippuric acid and ferulic acid, which peaked in the serum at approximately 16 and 8 h respectively. Conclusions and Implications: Anthocyanins are metabolized to a structurally diverse range of metabolites that exhibit dynamic kinetic profiles. Understanding the elimination kinetics of these metabolites is key to the design of future studies examining their utility in dietary interventions or as therapeutics for disease risk reduction
Structurally frustrated polar nanoregions in BaTaO₂N and the relationship between its high dielectric permittivity and that of BaTiO₃
This letter presents direct evidence for the existence of the same inherently polar one-dimensional (1D), displacive disorder in BaTaO₂N as occurs in paraelectric BaTiO₃ as well as in doped BaTiO₃relaxor ferroelectric systems. The inherently polar, off-center and oppositely directed displacements of Ta and neighboring O∕N ions along give rise to 1D polar nanoregions (PNRs) and are responsible for the dielectric properties of BaTaO₂N. A bond valence sum analysis of the underlying crystal chemistry of BaTaO₂N shows clearly that O∕N ordering is not directly responsible for inducing the observed 1D PNRs.R.L.W. and Y.L. acknowledge the financial support from
the Australian Research Council ARC in the form of an
ARC Discovery Grant. P.M.W. and Y.I.K. acknowledge
funding from the National Science Foundation through their
support of the Centre for the Design of Materials CHE-
043567
Role of local disorder in the dielectric response of BaTaO_2N
Short-range structural disorder of the high-κ dielectric BaTaO_2N is revealed by the analysis of the extended x-ray-absorption fine-structure (EXAFS) spectroscopy measured at the Ta L_III edge. Although previous neutron, x-ray, and electron diffraction studies have shown BaTaO_2N to crystallize in a centrosymmetric, cubic structure, these EXAFS spectra show a wide distribution of first shell Ta-(O,N) distances with further implications to nonuniformity of the existing octahedral distortions. A distortion model based upon a density functional theory energy minimization for a 4×4×4 supercell of BaTaO_2N was used to successfully interpret these EXAFS data. We find that structural distortions with very short correlation lengths exist in this material and that these distortions are consistent with the large dielectric permitivity of BaTaO_2N
Low Mach number effect in simulation of high Mach number flow
In this note, we relate the two well-known difficulties of Godunov schemes:
the carbuncle phenomena in simulating high Mach number flow, and the inaccurate
pressure profile in simulating low Mach number flow. We introduced two simple
low-Mach-number modifications for the classical Roe flux to decrease the
difference between the acoustic and advection contributions of the numerical
dissipation. While the first modification increases the local numerical
dissipation, the second decreases it. The numerical tests on the double-Mach
reflection problem show that both modifications eliminate the kinked Mach stem
suffered by the original flux. These results suggest that, other than
insufficient numerical dissipation near the shock front, the carbuncle
phenomena is strongly relevant to the non-comparable acoustic and advection
contributions of the numerical dissipation produced by Godunov schemes due to
the low Mach number effect.Comment: 9 pages, 1 figur
Magnetic fields and the dynamics of spiral galaxies
We investigate the dynamics of magnetic fields in spiral galaxies by
performing 3D MHD simulations of galactic discs subject to a spiral potential.
Recent hydrodynamic simulations have demonstrated the formation of inter-arm
spurs as well as spiral arm molecular clouds provided the ISM model includes a
cold HI phase. We find that the main effect of adding a magnetic field to these
calculations is to inhibit the formation of structure in the disc. However,
provided a cold phase is included, spurs and spiral arm clumps are still
present if in the cold gas. A caveat to two phase
calculations though is that by assuming a uniform initial distribution, in the warm gas, emphasizing that models with more consistent
initial conditions and thermodynamics are required. Our simulations with only
warm gas do not show such structure, irrespective of the magnetic field
strength. Furthermore, we find that the introduction of a cold HI phase
naturally produces the observed degree of disorder in the magnetic field, which
is again absent from simulations using only warm gas. Whilst the global
magnetic field follows the large scale gas flow, the magnetic field also
contains a substantial random component that is produced by the velocity
dispersion induced in the cold gas during the passage through a spiral shock.
Without any cold gas, the magnetic field in the warm phase remains relatively
well ordered apart from becoming compressed in the spiral shocks. Our results
provide a natural explanation for the observed high proportions of disordered
magnetic field in spiral galaxies and we thus predict that the relative
strengths of the random and ordered components of the magnetic field observed
in spiral galaxies will depend on the dynamics of spiral shocks.Comment: 17 pages, 14 figures, accepted by MNRA
Instabilities of Spiral Shocks I: Onset of Wiggle Instability and its Mechanism
We found that loosely wound spiral shocks in an isothermal gas disk caused by
a non-axisymmetric potential are hydrodynamically unstable, if the shocks are
strong enough. High resolution, global hydrodynamical simulations using three
different numerical schemes, i.e. AUSM, CIP, and SPH, show similarly that
trailing spiral shocks with the pitch angle of larger than ~10 deg wiggle, and
clumps are developed in the shock-compressed layer. The numerical simulations
also show clear wave crests that are associated with ripples of the spiral
shocks. The spiral shocks tend to be more unstable in a rigidly rotating disk
than in a flat rotation. This instability could be an origin of the secondary
structures of spiral arms, i.e. the spurs/fins, observed in spiral galaxies. In
spite of this local instability, the global spiral morphology of the gas is
maintained over many rotational periods. The Kelvin-Helmholtz (K-H) instability
in a shear layer behind the shock is a possible mechanism for the wiggle
instability. The Richardson criterion for the K-H stability is expressed as a
function of the Mach number, the pitch angle, and strength of the background
spiral potential. The criterion suggests that spiral shocks with smaller pitch
angles and smaller Mach numbers would be more stable, and this is consistent
with the numerical results.Comment: 11 pages, 14 figures, to be published in MNRAS, high quality figures
can be downloaded from http://th.nao.ac.jp/~wada/paperlist.htm
Collimation and asymmetry of the hot blast wave from the recurrent nova V745 Scorpii
The recurrent symbiotic nova V745 Sco exploded on 2014 February 6 and was
observed on February 22 and 23 by the Chandra X-ray Observatory Transmission
Grating Spectrometers. By that time the supersoft source phase had already
ended and Chandra spectra are consistent with emission from a hot, shock-heated
circumstellar medium with temperatures exceeding 10^7K. X-ray line profiles are
more sharply peaked than expected for a spherically-symmetric blast wave, with
a full width at zero intensity of approximately 2400 km/s, a full width at half
maximum of 1200 +/- 30 km/s and an average net blueshift of 165 +/- 10 km/s.
The red wings of lines are increasingly absorbed toward longer wavelengths by
material within the remnant. We conclude that the blast wave was sculpted by an
aspherical circumstellar medium in which an equatorial density enhancement
plays a role, as in earlier symbiotic nova explosions. Expansion of the
dominant X-ray emitting material is aligned close to the plane of the sky and
most consistent with an orbit seen close to face-on. Comparison of an
analytical blast wave model with the X-ray spectra, Swift observations and
near-infrared line widths indicates the explosion energy was approximately
10^43 erg, and confirms an ejected mass of approximately 10^-7 Msun. The total
mass lost is an order of magnitude lower than the accreted mass required to
have initiated the explosion, indicating the white dwarf is gaining mass and is
a supernova Type 1a progenitor candidate.Comment: To appear in the Astrophysical Journa
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