15,089 research outputs found
ASCA Slew Survey
We are systematically analyzing ASCA GIS data taken during the satellite
attitude maneuver operation. Our motivation is to search for serendipitous hard
X-ray sources and make the ASCA Slew Survey catalog.
During its operational life from 1993 February to 2000 July, ASCA carried out
more than 2,500 maneuver operations, and total exposure time during the
maneuver was ~415 ksec after data screening. Preliminary results are briefly
reported.Comment: Proceedings for "X-ray surveys in the light of new observations",
Santander (Spain), 2002 September. 1 pag
Staggered magnetism in LiVO at low temperatures probed by the muon Knight shift
We report on the muon Knight shift measurement in single crystals of LiV2O4.
Contrary to what is anticipated for the heavy-fermion state based on the Kondo
mechanism, the presence of inhomogeneous local magnetic moments is demonstrated
by the broad distribution of the Knight shift at temperatures well below the
presumed "Kondo temperature" ( K). Moreover, a significant
fraction ( %) of the specimen gives rise to a second component which
is virtually non-magnetic. These observations strongly suggest that the
anomalous properties of LiV2O4 originates from frustration of local magnetic
moments.Comment: 11 pages, 5 figures, sbmitted to J. Phys.: Cond. Mat
Growth of ZnO nanostructures on Si by means of plasma immersion ion implantation and deposition
Crystalline zinc oxide (ZnO) nanostructures have been grown on Si substrates by means of Plasma Based Ion Implantation and Deposition (PIII&D) at temperature of about 300 0C and in the presence of an argon glow discharge. In the process a crucible filled with small pieces of metallic zinc plays the role of the anode of the discharge itself, being polarized by positive DC voltage of about 400V. Electrons produced by thermionic emission by an oxide cathode (Ba, Sr, Ca)O impact this crucible, causing its heating and vaporization of Zn. Partial ionization of Zn atoms takes place due to collisions with plasma particles. High negative voltage pulses (7 kv/40μs/250Hz) applied to the sample holder cause the implantation of metallic zinc into Si surface, while Zn deposition happens between pulses. After annealing at 700 0C, strong UV and various visible photoluminescence bands are observed at room temperature, as well as the presence of ZnO nanoparticles. The coated surface was characterized in detail using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. XRD indicated the presence of only ZnO peaks after annealing. The composition analysis by EDS revealed distinct Zn/O stoichiometry relation depending on the conditions of the process. AFM images showed the formation of columns in the nanoscale range. Topography viewed by SEM showed the formation of structures similar to cactus with nanothorns. Depth analysis performed by XPS indicated an increase of concentration of metallic Zn with increasing depth and the exclusive presence of ZnO for outer regions. PIII&D allowed to growing nanostructures of ZnO on Si without the need of a buffer layer
Evolutionary origin of power-laws in Biochemical Reaction Network; embedding abundance distribution into topology
The evolutionary origin of universal statistics in biochemical reaction
network is studied, to explain the power-law distribution of reaction links and
the power-law distributions of chemical abundances. Using cell models with
catalytic reaction network, we find evidence that the power-law distribution in
abundances of chemicals emerges by the selection of cells with higher growth
speeds. Through the further evolution, this inhomogeneity in chemical
abundances is shown to be embedded in the distribution of links, leading to the
power-law distribution. These findings provide novel insights into the nature
of network evolution in living cells.Comment: 11 pages, 3 figure
Bose-Einstein droplet in free space
We show that a droplet of a Bose-Einstein condensate can be dynamically
stabilized in free space by rapid oscillations of interatomic interactions
between attractive and repulsive through, e.g., the Feshbach resonance. Energy
dissipation, which is present in realistic situations, is found to play a
crucial role to suppress dynamical instabilities inherent in nonlinear
nonequilibrium systems.Comment: 5 pages, 5 figure
Electronic energy spectra and wave functions on the square Fibonacci tiling
We study the electronic energy spectra and wave functions on the square
Fibonacci tiling, using an off-diagonal tight-binding model, in order to
determine the exact nature of the transitions between different spectral
behaviors, as well as the scaling of the total bandwidth as it becomes finite.
The macroscopic degeneracy of certain energy values in the spectrum is invoked
as a possible mechanism for the emergence of extended electronic Bloch wave
functions as the dimension changes from one to two
Hyperbolic Deformation Applied to S = 1 Spin Chains - Scaling Relation in Excitation Energy -
We investigate excitation energies of hyperbolically deformed S = 1 spin
chains, which are specified by the local energy scale f_j^{~} = \cosh j
\lambda, where j is the lattice index and \lambda is the deformation parameter.
The elementary excitation is well described by a quasiparticle hopping model,
which is also expressed in the form of hyperbolic deformation. It is possible
to estimate the excitation gap \Delta in the uniform limit \lambda \rightarrow
0, by means of a finite size scaling with respect to the system size N and the
deformation parameter \lambda.Comment: 5 pages, 4 figure
Symmetry of the Gap in Bi2212 from Photoemission Spectroscopy
In a recent Letter, Shen et al have detected a large anisotropy of the
superconducting gap in Bi2212, consistent with d-wave symmetry, from
photoemission spectroscopy. Moreover, they claim that the change in their
spectra as a function of aging is also consistent with such an intrepretation.
In this Comment, I show that the latter statement is not entirely correct, in
that the data as a function of aging are inconsistent with a d-wave gap but are
consistent with an anisotropic s-wave gap.Comment: 3 pages (Plain TeX with macros), plus 1 postscript figur
Energy gaps and roton structure above the nu=1/2 Laughlin state of a rotating dilute Bose-Einstein condensate
Exact diagonalization study of a rotating dilute Bose-Einstein condensate
reveals that as the first vortex enters the system the degeneracy of the
low-energy yrast spectrum is lifted and a large energy gap emerges. As more
vortices enter with faster rotation, the energy gap decreases towards zero, but
eventually the spectrum exhibits a rotonlike structure above the nu=1/2
Laughlin state without having a phonon branch despite the short-range nature of
the interaction.Comment: 4 pages, 4 figures, 1 tabl
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