95 research outputs found
Microscopic description of d-wave superconductivity by Van Hove nesting in the Hubbard model
We devise a computational approach to the Hubbard model that captures the
strong coupling dynamics arising when the Fermi level is at a Van Hove
singularity in the density of states. We rely on an approximate degeneracy
among the many-body states accounting for the main instabilities of the system
(antiferromagnetism, d-wave superconductivity). The Fermi line turns out to be
deformed in a manner consistent with the pinning of the Fermi level to the Van
Hove singularity. For a doping rate , the ground state is
characterized by d-wave symmetry, quasiparticles gapped only at the
saddle-points of the band, and a large peak at zero momentum in the d-wave
pairing correlations.Comment: 4 pages, 2 Postscript figure
The ALPS project release 1.3: open source software for strongly correlated systems
We present release 1.3 of the ALPS (Algorithms and Libraries for Physics
Simulations) project, an international open source software project to develop
libraries and application programs for the simulation of strongly correlated
quantum lattice models such as quantum magnets, lattice bosons, and strongly
correlated fermion systems. Development is centered on common XML and binary
data formats, on libraries to simplify and speed up code development, and on
full-featured simulation programs. The programs enable non-experts to start
carrying out numerical simulations by providing basic implementations of the
important algorithms for quantum lattice models: classical and quantum Monte
Carlo (QMC) using non-local updates, extended ensemble simulations, exact and
full diagonalization (ED), as well as the density matrix renormalization group
(DMRG). Changes in the new release include a DMRG program for interacting
models, support for translation symmetries in the diagonalization programs, the
ability to define custom measurement operators, and support for inhomogeneous
systems, such as lattice models with traps. The software is available from our
web server at http://alps.comp-phys.org/
Langerhans cell histiocytosis (histiocytosis X)
There has been a renewed interest in Langerhans cell histiocytosis in recent years due both to advances in basic research and to improvements in diagnostic and treatment approaches. In this article, we review the various aspects of the disease and the potential implications of these recent scientific researches for our understanding and management of the disorder.published_or_final_versio
AHA scientific statement: Summary of the scientific conference on dietary fatty acids and cardiovascular health
Conference Planning and Writing Committee:Penny Kris-Etherton, PhD, Stephen R. Daniels, MD, PhD, Robert H. Eckel, MD, Marguerite Engler, PhD, RN, Barbara V. Howard, PhD, Ronald M. Krauss, MD, Alice H. Lichtenstein, DSc, Frank Sacks, MD, Sachiko St. Jeor, PhD, Meir Stampfer, MD, DrPH, For the American Heart Association Nutrition Committee Speakers and Discussants:, Robert H. Eckel, MD, Scott M. Grundy, MD, PhD, Lawrence J. Appel, MD, MPH, Tim Byers, MD, Hannia Campos, PhD, Greg Cooney, PhD, Margo A. Denke, MD, Barbara V. Howard, PhD, Eileen Kennedy, DSc, Ronald M. Krauss, MD, Penny Kris-Etherton, PhD, Alice H. Lichtenstein, DSc, Peter Marckmann, MD, DSc, Thomas A. Pearson, MD, PhD, Gabriele Riccardi, MD, Lawrence L. Rudel, PhD, Mike Rudrum, PhD, Frank Sacks, MD, Daniel T. Stein, MD, Russell P. Tracy, PhD, Virginia Ursin, PhD, Robert A. Vogel, MD, Peter L. Zock, PhD, AHA Members:, Terry L. Bazzarre, PhD and Julie Clark, AHA Staf
Diffusion-Weighted MRI: Distinction of Skull Base Chordoma from Chondrosarcoma
BACKGROUND AND PURPOSE: Chordoma and chondrosarcoma of the skull base are rare tumors with overlapping presentations and anatomic imaging features but different prognoses. We hypothesized that these tumors might be distinguished by using diffusion-weighted MR imaging. MATERIALS AND METHODS: We retrospectively reviewed 19 patients with pathologically confirmed chordoma or chondrosarcoma who underwent both conventional and diffusion-weighted MR imaging. Differences in distributions of ADC were assessed by the Kruskal-Wallis test. Associations between histopathologic diagnosis and conventional MR imaging features (T2 signal intensity, contrast enhancement, and tumor location) were assessed with the Fisher exact test. RESULTS: Chondrosarcoma was associated with the highest mean ADC value (2051 ± 261 × 10−6 mm2/s) and was significantly different from classic chordoma (1474 ± 117 × 10−6 mm2/s) and poorly differentiated chordoma (875 ± 100 × 10−6 mm2/s) (P CONCLUSIONS: Diffusion-weighted MR imaging may be useful in assessing clival tumors, particularly in differentiating chordoma from chondrosarcoma. A prospective study of a larger cohort will be required to determine the value of ADC in predicting histopathologic diagnosis
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