888 research outputs found
The submuscular sliding plate technique for acetabular posterior wall fractures extending to the acetabular roof
AbstractThere is extension of the Kocher-Langenbeck approach using trochanteric osteotomy for posterior wall fracture extending to acetabular roof, but it exposes to complications such as nonunion, breakage, and heterotopic ossification. The current study introduces a submuscular sliding plate technique. We retrospectively analyzed 13 patients treated with this technique. It is based on conventional method for posterior wall fracture. After reduction of roof fragment with direct visualization, a pre-contoured plate was passed through a submuscular tunnel under the gluteus medius and minimus. A small split incision was performed on the muscles, and screws were inserted with a triple trocar complex safely under fluoroscopic imaging. All patients had fracture union without complications. X-rays results showed anatomical reduction in 10 cases and imperfect reduction in 3 cases. Our results were satisfactory, particularly without heterotopic ossifications despite no prophylactic regimen of NSAID was applied and no neurological complications, so we believe that this technique is a good option for posterior wall fractures extending to the acetabular roof
Flow boiling heat transfer and pressure drop of propane in smooth horizontal minichannels
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This study examined convective boiling heat transfer and pressure drop in horizontal minichannels using propane. The local heat transfer coefficients and pressure drop were obtained for heat fluxes ranging from 5-20 kW m-2, mass fluxes ranging from 50-400 kg m-2 s-1, saturation temperatures of 10, 5, and 0°C, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm, and lengths of 1000 mm and 2000 mm, respectively. The section was heated uniformly by applying an electric current to the tubes directly. The present study showed an effect of mass flux, heat flux, inner tube diameter, and saturation temperature on heat transfer coefficient and pressure drop. The experimental results were compared against several two-phase heat transfer coefficient and pressure drop prediction methods. A new boiling heat transfer coefficient correlation based on the superposition model for propane in minichannels was developed with a mean deviation of 8.27%
Energy Spectrum of Bloch Electrons Under Checkerboard Field Modulations
Two-dimensional Bloch electrons in a uniform magnetic field exhibit complex
energy spectrum. When static electric and magnetic modulations with a
checkerboard pattern are superimposed on the uniform magnetic field, more
structures and symmetries of the spectra are found, due to the additional
adjustable parameters from the modulations. We give a comprehensive report on
these new symmetries. We have also found an electric-modulation induced energy
gap, whose magnitude is independent of the strength of either the uniform or
the modulated magnetic field. This study is applicable to experimentally
accessible systems and is related to the investigations on frustrated
antiferromagnetism.Comment: 8 pages, 6 figures (reduced in sizes), submitted to Phys. Rev.
Cost-benefit analysis of introducing next-generation sequencing (metagenomic) pathogen testing in the setting of pyrexia of unknown origin
Pyrexia of unknown origin (PUO) is defined as a temperature of >38.3°C that lasts for >3 weeks, where no cause can be found despite appropriate investigation. Existing protocols for the work-up of PUO can be extensive and costly, motivating the application of recent advances in molecular diagnostics to pathogen testing. There have been many reports describing various analytical methods and performance of metagenomic pathogen testing in clinical samples but the economics of it has been less well studied. This study pragmatically evaluates the feasibility of introducing metagenomic testing in this setting by assessing the relative cost of clinically-relevant strategies employing this investigative tool under various cost and performance scenarios using Singapore as a demonstration case, and assessing the price and performance benchmarks, which would need to be achieved for metagenomic testing to be potentially considered financially viable relative to the current diagnostic standard. This study has some important limitations: we examined only impact of introducing the metagenomic test to the overall diagnostic cost and excluded costs associated with hospitalization and makes assumptions about the performance of the routine diagnostic tests, limiting the cost of metagenomic test, and the lack of further work-up after positive pathogen detection by the metagenomic test. However, these assumptions were necessary to keep the model within reasonable limits. In spite of these, the simplified presentation lends itself to the illustration of the key insights of our paper. In general, we find the use of metagenomic testing as second-line investigation is effectively dominated, and that use of metagenomic testing at first-line would typically require higher rates of detection or lower cost than currently available in order to be justifiable purely as a cost-saving measure. We conclude that current conditions do not warrant a widespread rush to deploy metagenomic testing to resolve any and all uncertainty, but rather as a front-line technology that should be used in specific contexts, as a supplement to rather than a replacement for careful clinical judgement
Impact of infectious complications on the outcome in patients with hematopoietic stem cell transplantation
Theory of proximity effect in superconductor/ferromagnet heterostructures
We present a microscopic theory of proximity effect in the
ferromagnet/superconductor/ferromagnet (F/S/F) nanostructures where S is s-wave
low-T_c superconductor and F's are layers of 3d transition ferromagnetic metal.
Our approach is based on the solution of Gor'kov equations for the normal and
anomalous Green's functions together with a self-consistent evaluation of the
superconducting order parameter. We take into account the elastic
spin-conserving scattering of the electrons assuming s-wave scattering in the S
layer and s-d scattering in the F layers. In accordance with the previous
quasiclassical theories, we found that due to exchange field in the ferromagnet
the anomalous Green's function F(z) exhibits the damping oscillations in the
F-layer as a function of distance z from the S/F interface. In the given model
a half of period of oscillations is determined by the length \xi_m^0 = \pi
v_F/E_ex, where v_F is the Fermi velocity and E_ex is the exchange field, while
damping is governed by the length l_0 = (1/l_{\uparrow} +
1/l_{\downarrow})^{-1} with l_{\uparrow} and l_{\downarrow} being
spin-dependent mean free paths in the ferromagnet. The superconducting
transition temperature T_c(d_F) of the F/S/F trilayer shows the damping
oscillations as a function of the F-layer thickness d_F with period \xi_F =
\pi/\sqrt{m E_ex}, where m is the effective electron mass. We show that strong
spin-conserving scattering either in the superconductor or in the ferromagnet
significantly suppresses these oscillations. The calculated T_c(d_F)
dependences are compared with existing experimental data for Fe/Nb/Fe trilayers
and Nb/Co multilayers.Comment: 13 pages, REVTeX4, 8 PS-figures; improved version, submitted to PR
From Tetraquark to Hexaquark: A Systematic Study of Heavy Exotics in the Large Limit
A systematic study of multiquark exotics with one or heavy quarks in
the large limit is presented. By binding a chiral soliton to a heavy
meson, either a normal -quark baryon or an exotic -quark baryon
is obtained. By replacing the heavy quark with heavy antiquarks, exotic
-quark and -quark mesons are obtained. When , they are
just the normal triquark baryon , the exotic pentaquark baryon , tetraquark di-meson and the hexaquark
di-baryon respectively. Their
stabilities and decays are also discussed. In particular, it is shown that the
``heavy to heavy'' semileptonic decays are described by the Isgur--Wise form
factors of the normal baryons.Comment: 14 pages in REVTeX, no Figure
Inhomogeneous magnetism induced in a superconductor at superconductor-ferromagnet interface
We study a magnetic proximity effect at superconductor (S) - ferromagnet (F)
interface. It is shown that due to an exchange of electrons between the F and S
metals ferromagnetic correlations extend into the superconductor, being
dependent on interface parameters. We show that ferromagnetic exchange field
pair breaking effect leads to a formation of subgap bands in the S layer local
density of states, that accommodate only one spin-polarized quasiparticles.
Equilibrium magnetization leakage into the S layer as function of SF interface
quality and a value of ferromagnetic interaction have also been calculated. We
show that a damped-oscillatory behavior versus distance from SF interface is a
distinguished feature of the exchange-induced magnetization of the S layer.Comment: 10 pages, 7 Postscript figure
Do Cosmological Perturbations Have Zero Mean?
A central assumption in our analysis of cosmic structure is that cosmological
perturbations have zero ensemble mean. This property is one of the consequences
of statistically homogeneity, the invariance of correlation functions under
spatial translations. In this article we explore whether cosmological
perturbations indeed have zero mean, and thus test one aspect of statistical
homogeneity. We carry out a classical test of the zero mean hypothesis against
a class of alternatives in which perturbations have non-vanishing means, but
homogeneous and isotropic covariances. Apart from Gaussianity, our test does
not make any additional assumptions about the nature of the perturbations and
is thus rather generic and model-independent. The test statistic we employ is
essentially Student's t statistic, applied to appropriately masked,
foreground-cleaned cosmic microwave background anisotropy maps produced by the
WMAP mission. We find evidence for a non-zero mean in a particular range of
multipoles, but the evidence against the zero mean hypothesis goes away when we
correct for multiple testing. We also place constraints on the mean of the
temperature multipoles as a function of angular scale. On angular scales
smaller than four degrees, a non-zero mean has to be at least an order of
magnitude smaller than the standard deviation of the temperature anisotropies.Comment: 31 pages, 4 tables, 6 figure
Spontaneous Spin Polarized Currents in Superconductor-Ferromagnetic Metal Heterostructures
We study a simple microscopic model for thin, ferromagnetic, metallic layers
on semi-infinite bulk superconductor. We find that for certain values of the
exchange spliting, on the ferromagnetic side, the ground states of such
structures feature spontaneously induced spin polarized currents. Using a
mean-field theory, which is selfconsistent with respect to the pairing
amplitude , spin polarization and the spontaneous current
, we show that not only there are Andreev bound states in the
ferromagnet but when their energies are near zero they support
spontaneous currents parallel to the ferromagnetic-superconducting interface.
Moreover, we demonstrate that the spin-polarization of these currents depends
sensitively on the band filling.Comment: 4 pages, 5 Postscript figures (included
- …