99,413 research outputs found
Electrospinning of poly(ethylene-co-vinyl alcohol) nanofibres encapsulated with Ag nanoparticles for skin wound healing
Copyright © 2011 Chao Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Skin wound healing is an urgent problem in clinics and military activities. Although significant advances have been made in its treatment, there are several challenges associated with traditional methods, for example, limited donor skin tissue for transplantation and inflammation during long-term healing time. To address these challenges, in this study we present a method to fabricate Poly(ethylene-co-vinyl alcohol) (EVOH) nanofibres encapsulated with Ag nanoparticle using electrospinning technique. The fibres were fabricated with controlled diameters (59nm-3m) by regulating three main parameters, that is, EVOH solution concentration, the electric voltage, and the distance between the injection needle tip (high-voltage point) and the fibre collector. Ag was added to the nanofibres to offer long-term anti-inflammation effect by slow release of Ag nanoparticles through gradual degradation of EVOH nanofibre. The method developed here could lead to new dressing materials for treatment of skin wounds. © 2011 Chao Xu et al.The work was partially supported by the National Natural Science Foundation of China (nos. 10825210, 10872157, and 31050110125) and the National 111 Project of China (no. B06024)
Barkhausen noise in the Random Field Ising Magnet NdFeB
With sintered needles aligned and a magnetic field applied transverse to its
easy axis, the rare-earth ferromagnet NdFeB becomes a
room-temperature realization of the Random Field Ising Model. The transverse
field tunes the pinning potential of the magnetic domains in a continuous
fashion. We study the magnetic domain reversal and avalanche dynamics between
liquid helium and room temperatures at a series of transverse fields using a
Barkhausen noise technique. The avalanche size and energy distributions follow
power-law behavior with a cutoff dependent on the pinning strength dialed in by
the transverse field, consistent with theoretical predictions for Barkhausen
avalanches in disordered materials. A scaling analysis reveals two regimes of
behavior: one at low temperature and high transverse field, where the dynamics
are governed by the randomness, and the second at high temperature and low
transverse field where thermal fluctuations dominate the dynamics.Comment: 16 pages, 7 figures. Under review at Phys. Rev.
Planar Harmonic Polynomials of Type B
The hyperoctahedral group is the Weyl group of type B and is associated with
a two-parameter family of differential-difference operators T_i, i=1,..,N (the
dimension of the underlying Euclidean space). These operators are analogous to
partial derivative operators. This paper finds all the polynomials in N
variables which are annihilated by the sum of the squares (T_1)^2+(T_2)^2 and
by all T_i for i>2 (harmonic). They are given explicitly in terms of a novel
basis of polynomials, defined by generating functions. The harmonic polynomials
can be used to find wave functions for the quantum many-body spin Calogero
model.Comment: 17 pages, LaTe
Examining the crossover from hadronic to partonic phase in QCD
It is argued that, due to the existence of two vacua -- perturbative and
physical -- in QCD, the mechanism for the crossover from hadronic to partonic
phase is hard to construct. The challenge is: how to realize the transition
between the two vacua during the gradual crossover of the two phases. A
possible solution of this problem is proposed and a mechanism for crossover,
consistent with the principle of QCD, is constructed. The essence of this
mechanism is the appearance and growing up of a kind of grape-shape
perturbative vacuum inside the physical one. A dynamical percolation model
based on a simple dynamics for the delocalization of partons is constructed to
exhibit this mechanism. The crossover from hadronic matter to sQGP as well as
the transition from sQGP to wQGP in the increasing of temperature is
successfully described by using this model with a temperature dependent
parameter.Comment: 4 pages, 4 figure
Level-rank duality via tensor categories
We give a new way to derive branching rules for the conformal embedding
(\asl_n)_m\oplus(\asl_m)_n\subset(\asl_{nm})_1. In addition, we show that
the category \Cc(\asl_n)_m^0 of degree zero integrable highest weight
(\asl_n)_m-representations is braided equivalent to \Cc(\asl_m)_n^0 with
the reversed braiding.Comment: 16 pages, to appear in Communications in Mathematical Physics.
Version 2 changes: Proof of main theorem made explicit, example 4.11 removed,
references update
Density distributions of superheavy nuclei
We employed the Skyrme-Hartree-Fock model to investigate the density
distributions and their dependence on nuclear shapes and isospins in the
superheavy mass region. Different Skyrme forces were used for the calculations
with a special comparison to the experimental data in Pb. The
ground-state deformations, nuclear radii, neutron skin thicknesses and
-decay energies were also calculated. Density distributions were
discussed with the calculations of single-particle wavefunctions and shell
fillings. Calculations show that deformations have considerable effects on the
density distributions, with a detailed discussion on the 120 nucleus.
Earlier predictions of remarkably low central density are not supported when
deformation is allowed for.Comment: 7 pages, 10 figure
Unified Band Theoretic Description of Electronic and Magnetic Properties of Vanadium Dioxide Phases
The debate about whether the insulating phases of vanadium dioxide (VO2) can
be described by band theory or must be described by a theory of strong electron
correlations remains unresolved even after decades of research. Energy-band
calculations using hybrid exchange functionals or including self-energy
corrections account for the insulating or metallic nature of different phases,
but have not yet successfully accounted for the observed magnetic orderings.
Strongly-correlated theories have had limited quantitative success. Here we
report that, by using hard pseudopotentials and an optimized hybrid exchange
functional, the energy gaps and magnetic orderings of both monoclinic VO2
phases and the metallic nature of the high-temperature rutile phase are
consistent with available experimental data, obviating an explicit role for
strong correlations. We also report a potential candidate for the newly-found
metallic monoclinic phase and present a detailed magnetic structure of the M2
monoclinic phase
- …