1,401 research outputs found
SU(2) approach to the pseudogap phase of high-temperature superconductors: electronic spectral functions
We use an SU(2) mean-field theory approach with input from variational
wavefunctions of the t-J model to study the electronic spectra in the pseudogap
phase of cuprates. In our model, the high-temperature state of underdoped
cuprates is realized by classical fluctuations of the order parameter between
the d-wave superconductor and the staggered-flux state. Spectral functions of
the intermediate and the averaged states are computed and analyzed. Our model
predicts a photoemission spectrum with an asymmetric gap structure
interpolating between the superconducting gap centered at the Fermi energy and
the asymmetric staggered-flux gap. This asymmetry of the gap changes sign at
the point where the Fermi surface crosses the diagonal (\pi,0)-(0,\pi).Comment: 7 pages, 10 figures; estimate of applicable temperature range
corrected and refs. added, ref. to ARPES paper added; minor changes to
published versio
Carotenoids and Antioxidant Nutrients following Burn Injury a
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72213/1/j.1749-6632.1993.tb26193.x.pd
Haydeeite: a spin-1/2 kagome ferromagnet
The mineral haydeeite, alpha-MgCu3(OD)6Cl2, is a S=1/2 kagome ferromagnet
that displays long-range magnetic order below TC=4.2 K with a strongly reduced
moment. Our inelastic neutron scattering data show clear spin-wave excitations
that are well described by a Heisenberg Hamiltonian with ferromagnetic
nearest-neighbor exchange J1=-38 K and antiferromagnetic exchange Jd=+11 K
across the hexagons of the kagome lattice. These values place haydeeite very
close to the quantum phase transition between ferromagnetic order and
non-coplanar twelve-sublattice cuboc2 antiferromagnetic order. Diffuse dynamic
short-range ferromagnetic correlations observed above TC persist well into the
ferromagnetically ordered phase with a behavior distinct from critical
scattering
An experimental investigation of microresistor laser printing with gold nanoparticle-laden inks
This paper presents an experimental investigation of the novel thermal manufacturing process of printing and laser curing of nanoparticle-laden inks that can produce functional microstructures such as electronic microresistors and interconnections for semiconductors and other devices. Of specific interest are the complex and interweaved transport phenomena involved, focusing on the absorption and diffusion processes of irradiated laser energy influencing solvent vaporization, the nanoparticle curing process, the substrate, and the final quality of the produced resistor. Parametric studies of the thermal process together with extensive microscopy analysis of the topography and resistivity measurements piece together a better understanding of the underlying physics and aid the development of the technolog
The effect of magnetic fields on properties of the circumgalactic medium
We study the effect of magnetic fields on a simulated galaxy and its surrounding gaseous halo, or circumgalactic medium (CGM), within cosmological 'zoom-in' simulations of a Milky Way-mass galaxy as part of the Simulating the Universe with Refined Galaxy Environments (SURGE) project. We use three different galaxy formation models, each with and without magnetic fields, and include additional spatial refinement in the CGM to improve its resolution. The central galaxy's star formation rate and stellar mass are not strongly affected by the presence of magnetic fields, but the galaxy is more disc dominated and its central black hole is more massive when B > 0. The physical properties of the CGM change significantly. With magnetic fields, the circumgalactic gas flows are slower, the atomic hydrogen-dominated extended discs around the galaxy are more massive and the densities in the inner CGM are therefore higher, the temperatures in the outer CGM are higher, and the pressure in the halo is higher and smoother. The total gas fraction and metal mass fraction in the halo are also higher when magnetic fields are included, because less gas escapes the halo. Additionally, we find that the CGM properties depend on azimuthal angle and that magnetic fields reduce the scatter in radial velocity, whilst enhancing the scatter in metallicity at fixed azimuthal angle. The metals are thus less well-mixed throughout the halo, resulting in more metal-poor halo gas. These results together show that magnetic fields in the CGM change the flow of gas in galaxy haloes, making it more difficult for metal-rich outflows to mix with the metal-poor CGM and to escape the halo, and therefore should be included in simulations of galaxy formation
Combined concomitant boost radiotherapy and chemotherapy in stage III-IV head and neck carcinomas: A comparison of toxicity and treatment results with those observed after radiotherapy alone
Background Alteration of radiation therapy (RT) fractionation and the combination of chemotherapy (CT) with RT represent two predominant fields of current research in the treatment of head and neck carcinomas. To assess the potential integration of these two fields, a retrospective comparison of toxicity and treatment outcome was carried out in stage III-IV patients treated with a concomitant boost RT schedule with or without CT. Patients and methods Fifty-two patients were treated by RT alone and 35 by RT and CT. In the RT group, there were significantly fewer T3-4 tumors (56% vs. 88%, P=0.002) and higher proportion of planned neck dissections (35% vs. 14%, P=0.047). The planned total dose was 69.9 Gy delivered over 5.5 weeks. In 10 cases CT was given before RT and in 25 concomitantly with RT, either alone or with neoadjuvant and/or adjuvant CT. All patients but two had cisplatin-based (CDDP, 100 mg/m2) CT, associated in 28 patients with 5-fluorouracil (5-FU, 1000 mg/m2/24 h Ă— 5). The median follow-up for the surviving patients was 21 and 31 months for the RT and RT-CT groups respectively. Results Grade 3-4 acute toxicity (RTOG) was observed in 73% and 86% of patients, and grade 3 dysphagia in 31% and 57% (P=0.02) respectively in the RT and RT-CT groups. The rates of grade 3-4 late complications were similar in the two groups (5% vs. 12%). At three years, actuarial loco-regional control (LRC) was 57% and 66% (P%0.66) and overall survival was 56% and 47% (P=0.99) in the RT and RT-CT groups respectively. Conclusion While acute toxicity was higher compared with RT alone, this accelerated RT schedule was feasible in association with 5-FU/CDDP, even administered concomitantly. Despite the significant proportion of more advanced disease in the RT-CT group, LRC was similar to that obtained by RT alone. Combinations of concomitant boost RT and chemotherapy merit further investigation in prospective trial
Finding largest small polygons with GloptiPoly
A small polygon is a convex polygon of unit diameter. We are interested in
small polygons which have the largest area for a given number of vertices .
Many instances are already solved in the literature, namely for all odd ,
and for and 8. Thus, for even , instances of this problem
remain open. Finding those largest small polygons can be formulated as
nonconvex quadratic programming problems which can challenge state-of-the-art
global optimization algorithms. We show that a recently developed technique for
global polynomial optimization, based on a semidefinite programming approach to
the generalized problem of moments and implemented in the public-domain Matlab
package GloptiPoly, can successfully find largest small polygons for and
. Therefore this significantly improves existing results in the domain.
When coupled with accurate convex conic solvers, GloptiPoly can provide
numerical guarantees of global optimality, as well as rigorous guarantees
relying on interval arithmetic
Ultrastructural changes in chemically induced preneoplastic focal lesions in the rat liver: a stereological study
Ultrastructural changes were investigated and quantified, using a stereological approach, in early gamma-glutamyl transpeptidase (GGT)-positive focal lesions, induced in the rat liver by treatment with a single initiating dose of diethylnitrosamine (DENA) followed by promotion with phenobarbitone (PB) for 30 weeks. Within the extra-hepato cyte environment of focal tissue, the mean volume occupied by Ito cells was markedly decreased, whilst that occupied by endothelial and Kupffer cells was increased, when compared to uninvolved tissue from the same rat livers. The bile canalicull were dilated, but nosignificant differences in the mean volume occupkd by the sinusoidal and Disse spaces were noted. In focal hepatocytes there was a striking overproduction of lipid droplets and proliferation of smooth endoplasmic reticulum (sER). Whorls of concentrically arranged, parallel ER membranes were found only in the hepatocytes of preneoplastic foci, in association with the proliferated sER, and never in the surrounding, uninvolved tissue. The Increase In mean volume of the sER, lipid droplet and cytoplasmic matrix compartments, together with the appearance of whorls, were the major contributing factors to the marked hypertrophy seen in focal hepatocytes. The mean volume of the rough endoplasmic reticulum, mitochondrial, lysosomal, peroxisomal and nuclear compartments per hepatocyte also Increased, but contributed to a lesser extent to the cellular hypertrophy. It is speculated that whorls may be structural adaptations, resulting from a possible alteration in the normalfeedback control of cholesterol synthesis, for the production of sterols and the biogenesis of sER in eosinophilic-type focal cells. The significance of changes observed in focal tissue, and the high biological variation noted between foci, is discussed in relation to the hepatocarcinogenic proces
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