22,252 research outputs found
Monte Carlo calculation of the linear resistance of a three dimensional lattice Superconductor model in the London limit
We have studied the linear resistance of a three dimensional lattice
Superconductor model in the London limit London lattice model by Monte Carlo
simulation of the vortex loop dynamics. We find excellent finite size scaling
at the phase transition. We determine the dynamical exponent for the
isotropic London lattice model.Comment: 4 pages, RevTeX with 3 postscript figures include
Spontaneous Charging of Drops on Lubricant-Infused Surfaces
[Image: see text] When a drop of a polar liquid slides over a hydrophobic surface, it acquires a charge. As a result, the surface charges oppositely. For applications such as the generation of electric energy, lubricant-infused surfaces (LIS) may be important because they show a low friction for drops. However, slide electrification on LIS has not been studied yet. Here, slide electrification on lubricant-infused surfaces was studied by measuring the charge generated by series of water drops sliding down inclined surfaces. As LIS, we used PDMS-coated glass with micrometer-thick silicone oil films on top. For PDMS-coated glass without lubricant, the charge for the first drop is highest. Then it decreases and saturates at a steady state charge per drop. With lubricant, the drop charge starts from 0, then it increases and reaches a maximum charge per drop. Afterward, it decreases again before reaching its steady-state value. This dependency is not a unique phenomenon for lubricant-infused PDMS; it also occurs on lubricant-infused micropillar surfaces. We attribute this dependency of charge on drop numbers to a change in surface conductivity and depletion of lubricant. These findings are helpful for understanding the charge process and optimizing solidâliquid nanogenerator devices in applications
Nuclear symmetry energy effects on neutron stars properties
We construct a class of nuclear equations of state based on a schematic
potential model, that originates from the work of Prakash et. al.
\cite{Prakash-88}, which reproduce the results of most microscopic
calculations. The equations of state are used as input for solving the
Tolman-Oppenheimer-Volkov equations for corresponding neutron stars. The
potential part contribution of the symmetry energy to the total energy is
parameterized in a generalized form both for low and high values of the baryon
density. Special attention is devoted to the construction of the symmetry
energy in order to reproduce the results of most microscopic calculations of
dense nuclear matter. The obtained nuclear equations of state are applied for
the systematic study of the global properties of a neutron star (masses, radii
and composition). The calculated masses and radii of the neutron stars are
plotted as a function of the potential part parameters of the symmetry energy.
A linear relation between these parameters, the radius and the maximum mass of
the neutron star is obtained. In addition, a linear relation between the radius
and the derivative of the symmetry energy near the saturation density is found.
We also address on the problem of the existence of correlation between the
pressure near the saturation density and the radius.Comment: 17 pages, 25 figure
Correlated electron emission in laser-induced nonsequence double ionization of Helium
In this paper, we have investigated the correlated electron emission of the
nonsequence double ionization (NSDI) in an intense linearly polarized field.
The theoretical model we employed is the semiclassical rescattering model, the
model atom we used is the helium. We find a significant correlation between
magnitude and direction of the momentum of two emission electrons, and give a
good explanation for this striking phenomenon by observing the classical
collisional trajectories. We argue that this correlation phenomenon is
universal in NSDI process, as revealed by the recent experiment on the argon.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev.
Baryon Current Matrix Elements in a Light-Front Framework
Current matrix elements and observables for electro- and photo-excitation of
baryons from the nucleon are studied in a light-front framework. Relativistic
effects are estimated by comparison to a nonrelativistic model, where we use
simple basis states to represent the baryon wavefunctions. Sizeable
relativistic effects are found for certain transitions, for example, to radial
excitations such as that conventionally used to describe to the Roper
resonance. A systematic study shows that the violation of rotational covariance
of the baryon transition matrix elements stemming from the use of one-body
currents is generally small.Comment: 32 pages, LaTeX, 10 postscript figures, uses epsf.sty; figures
uuencoded with uufiles (or available by request in .ps or hardcopy form
Probing nuclear expansion dynamics with -spectra
We study the dynamics of charged pions in the nuclear medium via the ratio of
differential - and -spectra in a coupled-channel BUU (CBUU)
approach. The relative energy shift of the charged pions is found to correlate
with the pion freeze-out time in nucleus-nucleus collisions as well as with the
impact parameter of the heavy-ion reaction. Furthermore, the long-range Coulomb
force provides a 'clock' for the expansion of the hot nuclear system. Detailed
comparisons with experimental data for at 1 GeV/A and at
2.0 GeV/A are presented.Comment: 21 pages, latex, figures include
Exploring isospin, strangeness charm distillation in heavy ion collisions
The isospin and strangeness dimensions of the Equation of State are explored.
RIA and the SIS200 accelerator at GSI will allow to explore these regions in
compressed baryonic matter. Sn+Sn and Sn+Sn
collisions as well as the excitation functions of , and
the centrality dependence of charmonium suppression from the UrQMD and HSD
transport models are presented and compared to data. Unambiguous proof for the
creation of a 'novel phase of matter' from strangeness and charm yields is not
in sight.Comment: Proceedings of the ISPUN 02. 8 pp, 6 fig
Neutron star properties with relativistic equations of state
We study the properties of neutron stars adopting relativistic equations of
state of neutron star matter, calculated in the framework of the relativistic
Brueckner-Hartree-Fock approximation for electrically charge neutral neutron
star matter in beta-equilibrium. For higher densities more baryons (hyperons
etc.) are included by means of the relativistic Hartree- or Hartree-Fock
approximation. The special features of the different approximations and
compositions are discussed in detail. Besides standard neutron star properties
special emphasis is put on the limiting periods of neutron stars, for which the
Kepler criterion and gravitation-reaction instabilities are considered.
Furthermore the cooling behaviour of neutron stars is investigated, too. For
comparison we give also the outcome for some nonrelativistic equations of
state.Comment: 43 pages, 22 ps-figures, to be published in the International Journal
of Modern Physics
Effect of different rhBMP-2 and TG-VEGF ratios on the formation of heterotopic bone and neovessels
Bioengineered bone substitutes might represent alternatives to autologous bone grafts in medically compromised patients due to reduced operation time and comorbidity. Due to the lack of an inherent vascular system their dimension is limited to the size of critical bone size defect. To overcome this shortcoming, the experiment tried to create heterotopic bone around vessels. In vivo, a two-component fibrin and thrombin gel containing recombinant bone morphogenic protein (rhBMP-2) and transglutamate vascular endothelial growth factor (TG-VEGF) in different ratios, respectively, was injected into a dimensionally stable membrane tube, wrapped around the femoral vessel bundle in twelve New Zealand white rabbits. Sacrifice occurred eight weeks postoperatively. Microcomputed tomography of the specimens showed significantly increased bone volume in the rhBMP-2 to TG-VEGF ratio of 10 to 1 group. Histology showed new bone formation in close proximity to the vessel bundle. Immunohistochemistry detected increased angiogenesis within the newly formed bone in the rhBMP-2 to TG-VEGF ratios of 3 to 1 and 5 to 1. Heterotopic bone was engineered in vivo around vessels using different rhBMP-2 and TG-VEGF ratios in a fibrin matrix injected into a dimensionally stable membrane tube which prevented direct contact with skeletal muscles.published_or_final_versio
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