6,657 research outputs found
Circadian Disruption and Metabolic Disease: Findings from Animal Models
Social opportunities and work demands have caused humans to become increasingly active during the late evening hours, leading to a shift from the predominantly diurnal lifestyle of our ancestors to a more nocturnal one. This voluntarily decision to stay awake long into the evening hours leads to circadian disruption at the system, tissue, and cellular levels. These derangements are in turn associated with clinical impairments in metabolic processes and physiology. The use of animal models for circadian disruption provides an important opportunity to determine mechanisms by which disorganization in the circadian system can lead to metabolic dysfunction in response to genetic, environmental, and behavioral perturbations. Here we review recent key animal studies involving circadian disruption and discuss the possible translational implications of these studies for human health and particularly for the development of metabolic disease
Can Momentum Correlations Proof Kinetic Equilibration in Heavy Ion Collisions at 160 AGeV?
We perform an event-by-event analysis of the transverse momentum distribution
of final state particles in central Pb(160AGeV)+Pb collisions within a
microscopic non-equilibrium transport model (UrQMD). Strong influence of
rescattering is found. The extracted momentum distributions show less
fluctuations in A+A collisions than in p+p reactions. This is in contrast to
simplified p+p extrapolations and random walk models.Comment: 9 pages, 3 eps figures, submitted to Phys. Lett.
Heavy-quark axial charges to non-leading order
We combine Witten's renormalization group with the matching conditions of
Bernreuther and Wetzel to calculate at next-to-leading order the complete
heavy-quark contribution to the neutral-current axial-charge measurable in
neutrino-proton elastic scattering. Our results are manifestly renormalization
group invariant.Comment: 5 pages, revtex styl
Polyenamines from aromatic diacetylenic diketones and diamines
The synthesis and characterization of several polyenamine ketones are discussed wherein conjugated diacetylenic diketones and aromatic diamines are used as a route to the formation of high molecular weight polyenamine ketones which exhibit good mechanical properties and can be cast into creasible films. Typical polymerization conditions involved the reaction of stoichiometric amounts of 1,4- or 1,3-PPPO and a diamine at 60 to 130 C in m-cresol at (w/w) solids content of 8 to 26% for a specified period of time under a nitrogen atmosphere. Novel polyenamine ketones were prepared with inherent viscosities as high as 1.99 dl/g and tough, clear amber films with tensile strengths of 12,400 psi and tensile moduli of 397,000 psi were cast from solutions of the polymers in chloroform. In most cases, the elemental analyses for the polyenamine ketones agree within + or - 0.3% of the theoretical values
Ultraviolet atomic emission detector
A device and method are provided for performing qualitative and quantitative elemental analysis through the utilization of a vacuum UV chromatographic detector. The method involves the use of a carrier gas at low pressure. The gas carries a sample to a gas chromatograph column; the column output is directed to a microwave cavity. In this cavity, a low pressure microwave discharge produces fragmentation of the compounds present and generates intense atomic emissions in the vacuum ultraviolet. These emissions are isolated by a monochromator and measured by photometer to establish absolute concentration for the elements
Direct Emission of multiple strange baryons in ultrarelativistic heavy-ion collisions from the phase boundary
We discuss a model for the space-time evolution of ultrarelativistic
heavy-ion collisions which employs relativistic hydrodynamics within one region
of the forward light-cone, and microscopic transport theory (i.e. UrQMD) in the
complement. Our initial condition consists of a quark-gluon plasma which
expands hydrodynamically and hadronizes. After hadronization the solution
eventually changes from expansion in local equilibrium to free streaming, as
determined selfconsistently by the interaction rates between the hadrons and
the local expansion rate. We show that in such a scenario the inverse slopes of
the -spectra of multiple strange baryons (, ) are practically
unaffected by the purely hadronic stage of the reaction, while the flow of
's and 's increases. Moreover, we find that the rather ``soft''
transverse expansion at RHIC energies (due to a first-order phase transition)
is not washed out by strong rescattering in the hadronic stage. The earlier
kinetic freeze-out as compared to SPS-energies results in similar inverse
slopes (of the -spectra of the hadrons in the final state) at RHIC and SPS
energies.Comment: 4 pages, 3 figures, statistics for Omegas improved, slight revision
of the manuscript (expansion of hadronization volume more emphasized,
pi-Omega scattering is discussed very briefly
An absorption spectrum amplifier for determining gas composition
Compositions of gas samples are frequently studied by laser absorption spectroscopy. Sensitivity is improved by two orders of magnitude when absorption cell is placed inside an organic-dye laser cavity
Possibility of synthesizing doubly closed superheavy nucleus
The possibility of synthesizing a doubly magic superheavy nucleus,
, is investigated on the basis of fluctuation-dissipation
dynamics. In order to synthesize this nucleus, we must generate more
neutron-rich compound nuclei because of the neutron emissions from excited
compound nuclei. The compound nucleus has two advantages to
achieving a high survival probability. First, because of small neutron
separation energy and rapid cooling, the shell correction energy recovers
quickly. Secondly, owing to neutron emissions, the neutron number of the
nucleus approaches that of the double closed shell and the nucleus obtains a
large fission barrier. Because of these two effects, the survival probability
of does not decrease until the excitation energy MeV.
These properties lead to a rather high evaporation reside cross section.Comment: 5 pages, 6 figure
Strangeness Enhancement in Heavy Ion Collisions - Evidence for Quark-Gluon-Matter ?
The centrality dependence of (multi-)strange hadron abundances is studied for
Pb(158 AGeV)Pb reactions and compared to p(158 GeV)Pb collisions. The
microscopic transport model UrQMD is used for this analysis. The predicted
Lambda/pi-, Xi-/pi- and Omega-/pi- ratios are enhanced due to rescattering in
central Pb-Pb collisions as compared to peripheral Pb-Pb or p-Pb collisions. A
reduction of the constituent quark masses to the current quark masses m_s \sim
230 MeV, m_q \sim 10 MeV, as motivated by chiral symmetry restoration, enhances
the hyperon yields to the experimentally observed high values. Similar results
are obtained by an ad hoc overall increase of the color electric field strength
(effective string tension of kappa=3 GeV/fm). The enhancement depends strongly
on the kinematical cuts. The maximum enhancement is predicted around
midrapidity. For Lambda's, strangeness suppression is predicted at
projectile/target rapidity. For Omega's, the predicted enhancement can be as
large as one order of magnitude. Comparisons of Pb-Pb data to proton induced
asymmetric (p-A) collisions are hampered due to the predicted strong asymmetry
in the various rapidity distributions of the different (strange) particle
species. In p-Pb collisions, strangeness is locally (in rapidity) not
conserved. The present comparison to the data of the WA97 and NA49
collaborations clearly supports the suggestion that conventional (free)
hadronic scenarios are unable to describe the observed high (anti-)hyperon
yields in central collisions. The doubling of the strangeness to nonstrange
suppression factor, gamma_s \approx 0.65, might be interpreted as a signal of a
phase of nearly massless particles.Comment: published version, discussion on strange mesons and new table added,
extended discussion on strange baryon yields. Latex, 20 pages, including 5
eps-figure
Manipulating Current-Induced Magnetization Switching
We summarize our recent findings on how current-driven magnetization
switching and magnetoresistance in nanofabricated magnetic multilayers are
affected by varying the spin-scattering properties of the non-magnetic spacers,
the relative orientations of the magnetic layers, and spin-dependent scattering
properties of the interfaces and the bulk of the magnetic layers. We show how
our data are explained in terms of current-dependent effective magnetic
temperature.Comment: 6 pages, 6 figures, submitted to MMM'04 proceeding
- …