1,152 research outputs found
Carrier doping to a partially disordered state in the periodic Anderson model on a triangular lattice
We investigate the effect of hole and electron doping to half-filling in the
periodic Anderson model on a triangular lattice by the Hartree-Fock
approximation at zero temperature. At half-filling, the system exhibits a
partially disordered insulating state, in which a collinear antiferromagnetic
order on an unfrustrated honeycomb subnetwork coexists with nonmagnetic state
at the remaining sites. We find that the carrier doping destabilizes the
partially disordered state, resulting in a phase separation to a doped metallic
state with different magnetic order. The partially disordered state is
restricted to the half-filled insulating case, while its metallic counterpart
is obtained as a metastable state in a narrow electron doped region.Comment: 4 pages, 2 figure
Integrated Modeling of Negative Hydrogen (H?/D?) Ion Production, Extraction and Acceleration in a Large Negative Ion Source for Neutral Beam Injection System
Partial Disorder and Metal-Insulator Transition in the Periodic Anderson Model on a Triangular Lattice
Ground state of the periodic Anderson model on a triangular lattice is
systematically investigated by the mean-field approximation. We found that the
model exhibits two different types of partially disordered states: one is at
half filling and the other is at other commensurate fillings. In the latter
case, the kinetic energy is lowered by forming an extensive network involving
both magnetic and nonmagnetic sites, in sharp contrast to the former case in
which the nonmagnetic sites are rather isolated. This spatially extended nature
of nonmagnetic sites yields a metallic partially-disordered state by hole
doping. We discuss the mechanism of the metal-insulator transition by the
change of electronic structure.Comment: 4 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp
Effect of transfusion, leukocyte-depleted blood product on onset of new septic shock and mortality in septic shock
Synthesis and coordination chemistry of 2-(di-2-pyridylamino)pyrimidine; structural aspects of spin crossover in an Fe(II) complex
This paper was accepted on February 26 20122-(Di-2-pyridylamino)pyrimidine (L), a potentially ditopic tetradentate ligand, was synthesized from commercially available di-2-pyridylamine and 2-chloropyrimidine. Despite being capable of bridging two metal atoms with bidentate chelation of both metal centres, L prefers to chelate or bridge through the more basic pyridyl donors of the di-2-pyridylamine moiety. Mononuclear trans-[Fe(NCS)2(L)2] and [Cu(L)2(H2O)](BF4)2•H2O complexes, and a discrete [Ag2(L)4](PF6)2 metallomacrocycle were isolated and structurally characterized by X-ray crystallography. A mononuclear palladium complex [PdCl2(L)]•(solvate), where solvate = ½H2O or CH2Cl2, was also readily obtained in 71% yield. One example of the ligand acting as a bis(bidentate) bridging ligand was observed in a dinuclear [(PdCl2)2(L)]•¾H2O complex that was obtained only in very low yield (ca. 3%) from the reaction that produced [PdCl2(L)]•½H2O. trans-[Fe(NCS)2(L)2] undergoes a temperature dependent HS-LS (HS = high spin; LS = low spin) crossover at ca. 205 K that was 2 observed by X-ray crystallography and magnetic measurements and attempts were made to understand the structural basis of this process. Despite efforts to isolate examples of L bridging two iron(II) centres, only the mononuclear trans-[Fe(NCS)2(L)2] species could be obtained.Rachel S. Crees, Boujemma Moubaraki, Keith S. Murray, and Christopher J. Sumb
Methamphetamine use and correlates in two villages of the highland ethnic Karen minority in northern Thailand: a cross sectional study
Detection of Gamma Rays of Up to 50 TeV From the Crab Nebula
Gamma rays with energies greater than 7 TeV from the Crab pulsar/nebula have
been observed at large zenith angles, using the Imaging Atmospheric Technique
from Woomera, South Australia. CANGAROO data taken in 1992, 1993 and 1995
indicate that the energy spectrum extends up to at least 50 TeV, without a
change of the index of the power law spectrum. The observed differential
spectrum is \noindent between 7 TeV and 50 TeV. There is no apparent
cut-off. The spectrum for photon energies above 10 TeV allows the maximum
particle acceleration energy to be inferred, and implies that this unpulsed
emission does not originate near the light cylinder of the pulsar, but in the
nebula where the magnetic field is not strong enough to allow pair creation
from the TeV photons. The hard gamma-ray energy spectrum above 10 TeV also
provides information about the varying role of seed photons for the inverse
Compton process at these high energies, as well as a possible contribution of
-gamma rays from proton collisions.Comment: 19 pages, 4 figures, LaTeX2.09 with AASTeX 4.0 maros, to appear in
Astrophys. J. Let
TeV Gamma Ray Emission from Southern Sky Objects and CANGAROO Project
We report recent results of the CANGAROO Collaboration on very high energy
gamma ray emission from pulsars, their nebulae, SNR and AGN in the southern
sky. Observations are made in South Australia using the imaging technique of
detecting atmospheric Cerenkov light from gamma rays higher than about 1 TeV.
The detected gamma rays are most likely produced by the inverse Compton process
by electrons which also radiate synchrotron X-rays. Together with information
from longer wavelengths, our results can be used to infer the strength of
magnetic field in the emission region of gamma rays as well as the energy of
the progenitor electrons. A description of the CANGAROO project is also given,
as well as details of the new telescope of 7 m diameter which is scheduled to
be in operation within two years.Comment: 5 pages, 1 figure, LaTeX 2.09 with aipproc.sty & epsfig.sty, to
appear in proceedings of the 4th Compton Symposium, Williamsburg, 199
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