13,606 research outputs found
Concatenation of convolutional and block codes Final report
Comparison of concatenated and sequential decoding systems and convolutional code structural propertie
A comparison of spectral element and finite difference methods using statically refined nonconforming grids for the MHD island coalescence instability problem
A recently developed spectral-element adaptive refinement incompressible
magnetohydrodynamic (MHD) code [Rosenberg, Fournier, Fischer, Pouquet, J. Comp.
Phys. 215, 59-80 (2006)] is applied to simulate the problem of MHD island
coalescence instability (MICI) in two dimensions. MICI is a fundamental MHD
process that can produce sharp current layers and subsequent reconnection and
heating in a high-Lundquist number plasma such as the solar corona [Ng and
Bhattacharjee, Phys. Plasmas, 5, 4028 (1998)]. Due to the formation of thin
current layers, it is highly desirable to use adaptively or statically refined
grids to resolve them, and to maintain accuracy at the same time. The output of
the spectral-element static adaptive refinement simulations are compared with
simulations using a finite difference method on the same refinement grids, and
both methods are compared to pseudo-spectral simulations with uniform grids as
baselines. It is shown that with the statically refined grids roughly scaling
linearly with effective resolution, spectral element runs can maintain accuracy
significantly higher than that of the finite difference runs, in some cases
achieving close to full spectral accuracy.Comment: 19 pages, 17 figures, submitted to Astrophys. J. Supp
A review of the clinical utility of the Enhanced Liver Fibrosis test in multiple aetiologies of chronic liver disease
The rising incidence of chronic liver disease continues to be an increasing health burden. The morbidity and mortality associated with chronic liver disease typically occur in patients with advanced fibrosis. Hence, early identification of those at-risk is of vital importance to ensure appropriate ongoing management. Currently, tools for appropriate risk stratification remain limited. Increasing awareness of the limitations of liver biopsy has driven research into alternative non-invasive methods of fibrosis assessment including serological markers assessing functional changes. One such biomarker, the Enhanced Liver Fibrosis test, was initially validated in a cohort of 1021 patients with mixed aetiology chronic liver disease and shown to perform well. Since this pathfinder study, it has been independently validated in cohorts of hepatitis C, non-alcoholic fatty liver disease, alcoholic liver disease, primary biliary cirrhosis and primary sclerosing cholangitis. In addition to performing well as a diagnostic tool, the Enhanced Liver Fibrosis test has been shown to outperform liver biopsy in prognostic studies and is the only non-invasive marker to do so. However, questions remain regarding the use of this test, particularly regarding the possible effect age and alcohol may have on test scores. This review examines the current literature published in relation to the Enhanced Liver Fibrosis test and its clinical utility and highlights areas requiring further study
The Arecibo L-band Feed Array Zone of Avoidance Survey I: Precursor Observations through the Inner and Outer Galaxy
The Arecibo L-band Feed Array (ALFA) is being used to conduct a low-Galactic
latitude survey, to map the distribution of galaxies and large-scale structures
behind the Milky Way through detection of galaxies' neutral hydrogen (HI) 21-cm
emission. This Zone of Avoidance (ZOA) survey finds new HI galaxies which lie
hidden behind the Milky Way, and also provides redshifts for partially-obscured
galaxies known at other wavelengths. Before the commencement of the full
survey, two low-latitude precursor regions were observed, totalling 138 square
degrees, with 72 HI galaxies detected. Detections through the inner Galaxy
generally have no cataloged counterparts in any other waveband, due to the
heavy extinction and stellar confusion. Detections through the outer Galaxy are
more likely to have 2MASS counterparts. We present the results of these
precursor observations, including a catalog of the detected galaxies, with
their HI parameters. The survey sensitivity is well described by a flux- and
linewidth-dependent signal-to-noise ratio of 6.5. ALFA ZOA galaxies which also
have HI measurements in the literature show good agreement between our
measurements and previous work. The inner Galaxy precursor region was chosen to
overlap the HI Parkes Zone of Avoidance Survey so ALFA performance could be
quickly assessed. The outer Galaxy precursor region lies north of the Parkes
sky. Low-latitude large-scale structure in this region is revealed, including
an overdensity of galaxies near l = 183 deg and between 5000 - 6000 km/s in the
ZOA. The full ALFA ZOA survey will be conducted in two phases: a shallow survey
using the observing techniques of the precursor observations, and also a deep
phase with much longer integration time, with thousands of galaxies predicted
for the final catalog.Comment: 26 pages, 7 figures, 2 tables, Astronomical Journal accepte
Distinct expression pattern of the full set of secreted phospholipases A2 in human colorectal adenocarcinomas: sPLA2-III as a biomarker candidate
Recent studies suggest that secreted phospholipases A2 (sPLA2s) represent attractive potential tumour biomarkers and therapeutic targets for various cancers. As a first step to address this issue in human colorectal cancer, we examined the expression of the full set of sPLA2s in sporadic adenocarcinomas and normal matched mucosa from 21 patients by quantitative PCR and immunohistochemistry. In normal colon, PLA2G2A and PLA2G12A were expressed at high levels, PLA2G2D, PLA2G5, PLA2G10 and PLA2G12B at moderate levels, and PLA2G1B, PLA2G2F and PLA2G3 at low levels. In adenocarcinomas from left and right colon, the expression of PLA2G3 was increased by up to 40-fold, while that of PLA2G2D and PLA2G5 was decreased by up to 23- and 14-fold. The variations of expression for sPLA2-IID, sPLA2-III and sPLA2-V were confirmed at the protein level. The expression pattern of these sPLA2s appeared to be linked respectively to the overexpression of interleukin-8, defensin α6, survivin and matrilysin, and downregulation of SFRP-1 and RLPA-1, all these genes being associated to colon cancer. This original sPLA2 profile observed in adenocarcinomas highlights the potential role of certain sPLA2s in colon cancer and suggests that sPLA2-III might be a good candidate as a novel biomarker for both left and right colon cancers
Dynamics of the Destruction and Rebuilding of a Dipole Gap in Glasses
After a strong electric bias field was applied to a glass sample at
temperatures in the millikelvin range its AC-dielectric constant increases and
then decays logarithmically with time. For the polyester glass mylar we have
observed the relaxation of the dielectric constant back to its initial value
for several temperatures and histories of the bias field. Starting from the
dipole gap theory we have developed a model suggesting that the change of the
dielectric constant after transient application of a bias field is only partly
due to relaxational processes. In addition, non-adiabatic driving of tunneling
states (TSs) by applied electric fields causes long lasting changes in the
dielectric constant. Moreover, our observations indicate that at temperatures
below 50 mK the relaxation of TSs is caused primarily by interactions between
TSs.Comment: 4 pages, 4 figures, submitted to PR
3D integrated superconducting qubits
As the field of superconducting quantum computing advances from the few-qubit
stage to larger-scale processors, qubit addressability and extensibility will
necessitate the use of 3D integration and packaging. While 3D integration is
well-developed for commercial electronics, relatively little work has been
performed to determine its compatibility with high-coherence solid-state
qubits. Of particular concern, qubit coherence times can be suppressed by the
requisite processing steps and close proximity of another chip. In this work,
we use a flip-chip process to bond a chip with superconducting flux qubits to
another chip containing structures for qubit readout and control. We
demonstrate that high qubit coherence (, s) is
maintained in a flip-chip geometry in the presence of galvanic, capacitive, and
inductive coupling between the chips
Structural and electronic properties of Pb1-xCdxTe and Pb1-xMnxTe ternary alloys
A systematic theoretical study of two PbTe-based ternary alloys, Pb1-xCdxTe
and Pb1-xMnxTe, is reported. First, using ab initio methods we study the
stability of the crystal structure of CdTe - PbTe solid solutions, to predict
the composition for which rock-salt structure of PbTe changes into zinc-blende
structure of CdTe. The dependence of the lattice parameter on Cd (Mn) content x
in the mixed crystals is studied by the same methods. The obtained decrease of
the lattice constant with x agrees with what is observed in both alloys. The
band structures of PbTe-based ternary compounds are calculated within a
tight-binding approach. To describe correctly the constituent materials new
tight-binding parameterizations for PbTe and MnTe bulk crystals as well as a
tight-binding description of rock-salt CdTe are proposed. For both studied
ternary alloys, the calculated band gap in the L point increases with x, in
qualitative agreement with photoluminescence measurements in the infrared. The
results show also that in p-type Pb1-xCdxTe and Pb1-xMnxTe mixed crystals an
enhancement of thermoelectrical power can be expected.Comment: 10 pages, 13 figures, submitted to Physical Review
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