946 research outputs found
Hypothalamic Integration of Metabolic, Endocrine, and Circadian Signals in Fish: Involvement in the Control of Food Intake
The regulation of food intake in fish is a complex process carried out through several different mechanisms in the central nervous system (CNS) with hypothalamus being the main regulatory center. As in mammals, a complex hypothalamic circuit including two populations of neurons: one co-expressing neuropeptide Y (NPY) and Agouti-related peptide (AgRP) and the second one population co-expressing pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) is involved in the integration of information relating to food intake control. The production and release of these peptides control food intake, and the production results from the integration of information of different nature such as levels of nutrients and hormones as well as circadian signals. The present review summarizes the knowledge and recent findings about the presence and functioning of these mechanisms in fish and their differences vs. the known mammalian model
Shine bright or live long: substituent effects in [Cu(N^N)(P^P)]+-based light-emitting electrochemical cells where N^N is a 6-substituted 2,2'-bipyridine
We report [Cu(P^P)(N^N)][PF6] complexes with P^P = bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) and N^N = 6-methyl-2,2′-bipyridine (Mebpy), 6-ethyl-2,2′-bipyridine (Etbpy), 6,6′-dimethyl-2,2′-bipyridine (Me2bpy) or 6-phenyl-2,2′-bipyridine (Phbpy). The crystal structures of [Cu(POP)(Phbpy)][PF6]·Et2O, [Cu(POP)(Etbpy)][PF6]·Et2O, [Cu(xantphos)(Me2bpy)][PF6], [Cu(xantphos)(Mebpy)][PF6]·CH2Cl2·0.4Et2O, [Cu(xantphos)(Etbpy)][PF6]·CH2Cl2·1.5H2O and [Cu(xantphos)(Phbpy)][PF6] are described; each copper(I) centre is distorted tetrahedral. In the crystallographically determined structures, the N^N domain in [Cu(xantphos)(Phbpy)]+ and [Cu(POP)(Phbpy)]+ is rotated ∼180° with respect to its orientation in [Cu(xantphos)(Mebpy)]+, [Cu(POP)(Etbpy)]+ and [Cu(xantphos)(Etbpy)]+; in each complex containing xantphos, the xanthene ‘bowl’ retains the same conformation in the solid-state structures. The two conformers resulting from the 180° rotation of the N^N ligand were optimized at the B3LYP-D3/(6-31G**+LANL2DZ) level and are close in energy for each complex. Variable temperature NMR spectroscopy evidences the presence of two conformers of [Cu(xantphos)(Phbpy)]+ in solution which are related by inversion of the xanthene unit. The complexes exhibit MLCT absorption bands in the range 378 to 388 nm, and excitation into each MLCT band leads to yellow emissions. Photoluminescence quantum yields (PLQYs) increase from solution to thin-film and powder; the highest PLQYs are observed for powdered [Cu(xantphos)(Mebpy)][PF6] (34%), [Cu(xantphos)(Etbpy)][PF6] (37%) and [Cu(xantphos)(Me2bpy)][PF6] (37%) with lifetimes of 9.6–11 μs. Density functional theory calculations predict that the emitting triplet (T1) involves an electron transfer from the Cu–P^P environment to the N^N ligand and therefore shows a 3MLCT character. T1 is calculated to be ∼0.20 eV lower in energy than the first singlet excited state (S1). The [Cu(P^P)(N^N)][PF6] ionic transition-metal (iTMC) complexes were tested in light-emitting electrochemical cells (LECs). Turn-on times are fast, and the LEC with [Cu(xantphos)(Me2bpy)][PF6] achieves a maximum efficacy of 3.0 cd A−1 (luminance = 145 cd m−2) with a lifetime of 1 h; on going to the [Cu(xantphos)(Mebpy)][PF6]-based LEC, the lifetime exceeds 15 h but at the expense of the efficacy (1.9 cd A−1). The lifetimes of LECs containing [Cu(xantphos)(Etbpy)][PF6] and [Cu(POP)(Etbpy)][PF6] exceed 40 and 80 h respectively
Magneto-elastic torsional oscillations of magnetars
We extend a general-relativistic ideal magneto-hydrodynamical code to include
the effects of elasticity. Using this numerical tool we analyse the
magneto-elastic oscillations of highly magnetised neutron stars (magnetars). In
simulations without magnetic field we are able to recover the purely crustal
shear oscillations within an accuracy of about a few per cent. For dipole
magnetic fields between 5 x 10^13 and 10^15 G the Alfv\'en oscillations become
modified substantially by the presence of the crust. Those quasi-periodic
oscillations (QPOs) split into three families: Lower QPOs near the equator,
Edge QPOs related to the last open field line and Upper QPOs at larger distance
from the equator. Edge QPOs are called so because they are related to an edge
in the corresponding Alfv\'en continuum. The Upper QPOs are of the same kind,
while the Lower QPOs are turning-point QPOs, related to a turning point in the
continuous spectrum.Comment: 6 pages, 1 figure, 1 table, Proceedings of NEB14, to appear in J.
Phys.: Conf. Se
Local convergence of quasi-Newton methods under metric regularity
We consider quasi-Newton methods for generalized equations in Banach spaces under metric regularity and give a sufficient condition for q-linear convergence. Then we show that the well-known Broyden update satisfies this sufficient condition in Hilbert spaces. We also establish various modes of q-superlinear convergence of the Broyden update under strong metric subregularity, metric regularity and strong metric regularity. In particular, we show that the Broyden update applied to a generalized equation in Hilbert spaces satisfies the Dennis–Moré condition for q-superlinear convergence. Simple numerical examples illustrate the results.A. Belyakov was supported by the Austrian Science Foundation (FWF) under grant No P 24125-N13. A.L. Dontchev was supported by NSF Grant DMS 1008341 through the University of Michigan. M. López was supported by MINECO of Spain, Grant MTM2011-29064-C03-02
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Nonmedical Prescription Opioid Use in Childhood and Early Adolescence Predicts Transitions to Heroin Use in Young Adulthood: A National Study
Objectives: To examine the relationship between nonmedical use of prescription opioids and heroin initiation from childhood to young adulthood, and to test whether certain ages, racial/ethnic, and income groups were at higher risk for this transition. Study design: Among a nationally representative sample of US adolescents assessed in the 2004-2011 National Surveys on Drug Use and Health cross-sectional surveys (n = 223 534 respondents aged 12-21 years), discrete-time hazard models were used to estimate the age-specific hazards of heroin initiation associated with prior history of nonmedical use of prescription opioids. Interactions were estimated between prior history of nonmedical use of prescription opioids and age of nonmedical use of prescription opioid initiation, race/ethnicity, and income. Results: A prior history of nonmedical use of prescription opioids was strongly associated with heroin initiation (hazard ratio 13.12, 95% CI 10.73, 16.04). Those initiating nonmedical use of prescription opioids at ages 10-12 years had the highest risk of transitioning to heroin use; the association did not vary by race/ethnicity or income group. Conclusions: Prior use of nonmedical use of prescription opioids is a strong predictor of heroin use onset in adolescence and young adulthood, regardless of the user's race/ethnicity or income group. Primary prevention of nonmedical use of prescription opioids in late childhood may prevent the onset of more severe types of drug use such as heroin at later ages. Moreover, because the peak period of heroin initiation occurs at ages 17-18 years, secondary efforts to prevent heroin use may be most effective if they focus on young adolescents who already initiated nonmedical use of prescription opioids
Gravitational waves in dynamical spacetimes with matter content in the Fully Constrained Formulation
The Fully Constrained Formulation (FCF) of General Relativity is a novel
framework introduced as an alternative to the hyperbolic formulations
traditionally used in numerical relativity. The FCF equations form a hybrid
elliptic-hyperbolic system of equations including explicitly the constraints.
We present an implicit-explicit numerical algorithm to solve the hyperbolic
part, whereas the elliptic sector shares the form and properties with the well
known Conformally Flat Condition (CFC) approximation. We show the stability
andconvergence properties of the numerical scheme with numerical simulations of
vacuum solutions. We have performed the first numerical evolutions of the
coupled system of hydrodynamics and Einstein equations within FCF. As a proof
of principle of the viability of the formalism, we present 2D axisymmetric
simulations of an oscillating neutron star. In order to simplify the analysis
we have neglected the back-reaction of the gravitational waves into the
dynamics, which is small (<2 %) for the system considered in this work. We use
spherical coordinates grids which are well adapted for simulations of stars and
allow for extended grids that marginally reach the wave zone. We have extracted
the gravitational wave signature and compared to the Newtonian quadrupole and
hexadecapole formulae. Both extraction methods show agreement within the
numerical errors and the approximations used (~30 %).Comment: 17 pages, 9 figures, 2 tables, accepted for publication in PR
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