249 research outputs found
Magnetic Effects on Dielectric and Polarization Behavior of Multiferroic Hetrostructures
PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3(PZT/LSMO) bilayer with surface roughness ~
1.8 nm thin films have been grown by pulsed laser deposition on LaAlO3(LAO)
substrates. High remnant polarization (30-54 micro C/cm2), dielectric
constant(400-1700), and well saturated magnetization were observed depending
upon the deposition temperature of the ferromagnetic layer and applied
frequencies. Giant frequency-dependent change in dielectric constant and loss
were observed above the ferromagnetic-paramagnetic temperature. The frequency
dependent dielectric anomalies are attributed to the change in metallic and
magnetic nature of LSMO and also the interfacial effect across the bilayer; an
enhanced magnetoelectric interaction may be due to the Parish-Littlewood
mechanism of inhomogeneity near the metal-dielectric interface.Comment: 9 pages, 4 figure
Fusion of neutron rich oxygen isotopes in the crust of accreting neutron stars
Fusion reactions in the crust of an accreting neutron star are an important
source of heat, and the depth at which these reactions occur is important for
determining the temperature profile of the star. Fusion reactions depend
strongly on the nuclear charge . Nuclei with can fuse at low
densities in a liquid ocean. However, nuclei with Z=8 or 10 may not burn until
higher densities where the crust is solid and electron capture has made the
nuclei neutron rich. We calculate the factor for fusion reactions of
neutron rich nuclei including O + O and Ne + Ne. We
use a simple barrier penetration model. The factor could be further
enhanced by dynamical effects involving the neutron rich skin. This possible
enhancement in should be studied in the laboratory with neutron rich
radioactive beams. We model the structure of the crust with molecular dynamics
simulations. We find that the crust of accreting neutron stars may contain
micro-crystals or regions of phase separation. Nevertheless, the screening
factors that we determine for the enhancement of the rate of thermonuclear
reactions are insensitive to these features. Finally, we calculate the rate of
thermonuclear O + O fusion and find that O should burn at
densities near g/cm. The energy released from this and similar
reactions may be important for the temperature profile of the star.Comment: 7 pages, 4 figs, minor changes, to be published in Phys. Rev.
Enhancing the conversion of D-xylose into furfural at low temperatures using chloride salts as co-catalysts: Catalytic combination of AlCl3 and formic acid
peer-reviewedThe full text of this article will not be available on ULIR until the embargo expires on the 26/4/2019Furfural is a potential platform chemical derived from biomass, which has gained increased attention as a
potential substitute for the displacement of petrochemicals and the production of biofuels. The catalytic
effect of different metal tri-chlorides (FeCl3, AlCl3 and CrCl3) with formic acid (FA) was investigated for
the selective conversion of D-xylose to furfural in aqueous solutions. Reactions were carried out at various
temperatures (100–170 C), FA concentrations (0–65 wt%), and metal chloride concentrations (0.2–
0.8 M). Lyxose was identified as primary intermediate of the conversion of xylose at low temperatures
and FA concentrations. A mixture containing 0.4 M AlCl3 and 55 wt% FA was the most selective and active
system for the production of furfural at low temperatures (130 C, selectivity 70–90%). A simplified
kinetic model was developed to describe the overall xylose conversion and furfural formation under
the selected conditions, offering a valuable tool for process optimisation and design.ACCEPTEDpeer-reviewe
Disjoining Potential and Spreading of Thin Liquid Layers in the Diffuse Interface Model Coupled to Hydrodynamics
The hydrodynamic phase field model is applied to the problem of film
spreading on a solid surface. The disjoining potential, responsible for
modification of the fluid properties near a three-phase contact line, is
computed from the solvability conditions of the density field equation with
appropriate boundary conditions imposed on the solid support. The equation
describing the motion of a spreading film are derived in the lubrication
approximation. In the case of quasi-equilibrium spreading, is shown that the
correct sharp-interface limit is obtained, and sample solutions are obtained by
numerical integration. It is further shown that evaporation or condensation may
strongly affect the dynamics near the contact line, and accounting for kinetic
retardation of the interphase transport is necessary to build up a consistent
theory.Comment: 14 pages, 5 figures, to appear in PR
On the Interface Formation Model for Dynamic Triple Lines
This paper revisits the theory of Y. Shikhmurzaev on forming interfaces as a
continuum thermodynamical model for dynamic triple lines. We start with the
derivation of the balances for mass, momentum, energy and entropy in a
three-phase fluid system with full interfacial physics, including a brief
review of the relevant transport theorems on interfaces and triple lines.
Employing the entropy principle in the form given in [Bothe & Dreyer, Acta
Mechanica, doi:10.1007/s00707-014-1275-1] but extended to this more general
case, we arrive at the entropy production and perform a linear closure, except
for a nonlinear closure for the sorption processes. Specialized to the
isothermal case, we obtain a thermodynamically consistent mathematical model
for dynamic triple lines and show that the total available energy is a strict
Lyapunov function for this system
Pairing in high-density neutron matter including short- and long-range correlations
Pairing gaps in neutron matter need to be computed in a wide range of densities to address open questions in neutron-star phenomenology. Traditionally, the Bardeen-Cooper-Schrieffer approach has been used to compute gaps from bare nucleon-nucleon interactions. Here we incorporate the influence of short-and long-range correlations in the pairing gaps. Short-range correlations are treated, including the appropriate fragmentation of single-particle states, and substantially suppress the gaps. Long-range correlations dress the pairing interaction via density and spin modes and provide a relatively small correction. We use different interactions, some with three-body forces, as a starting point to control for any systematic effects. Results are relevant for neutron-star cooling scenarios, in particular in view of the recent observational data on Cassiopeia A
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