8,601 research outputs found
Local spin and charge properties of beta-Ag0.33V2O5 studied by 51V NMR
Local spin and charge properties were studied on beta-Ag0.33V2O5, a
pressure-induced superconductor, at ambient pressure using 51V-NMR and
zero-field-resonance (ZFR) techniques. Three inequivalent Vi sites (i=1, 2, and
3) were identified from 51V-NMR spectra and the principal axes of the
electric-field-gradient (EFG) tensor were determined in a metallic phase and
the following charge-ordering phase. We found from the EFG analysis that the V1
sites are in a similar local environment to the V3 sites. This was also
observed in ZFR spectra as pairs of signals closely located with each other.
These results are well explained by a charge-sharing model where a 3d1 electron
is shared within a rung in both V1-V3 and V2-V2 two-leg ladders.Comment: 12pages, 16figure
Exploration of Finite 2D Square Grid by a Metamorphic Robotic System
We consider exploration of finite 2D square grid by a metamorphic robotic
system consisting of anonymous oblivious modules. The number of possible shapes
of a metamorphic robotic system grows as the number of modules increases. The
shape of the system serves as its memory and shows its functionality. We
consider the effect of global compass on the minimum number of modules
necessary to explore a finite 2D square grid. We show that if the modules agree
on the directions (north, south, east, and west), three modules are necessary
and sufficient for exploration from an arbitrary initial configuration,
otherwise five modules are necessary and sufficient for restricted initial
configurations
Preparation in Assessment for Early Childhood Educators in Hawai‘i
Report to the Hawai‘i State Executive Office on Early LearningThe purpose of this study was to investigate the extent to which programs that prepared early childhood educators in Hawai‘i included various aspects of early childhood assessment. It was an attempt to establish a baseline of what existed with regard to instruction in early childhood assessment among preparation programs. Participants included 9 program coordinators and 43 faculty members from 12 of the 14 preparation programs in the State. The programs included four associate, three bachelor, and five post-baccalaureate degree programs. Participants completed online surveys. Program coordinators responded to questions about whether candidates in their programs were required to learn about and how to conduct assessment in various areas, and how assessment content was delivered. They also reported on more general information about their programs, such as enrollment, target student populations, and numbers of faculty. Faculty members responded to questions about whether they taught candidates about and how to conduct assessment in various areas and whether they would find it helpful to have professional development opportunities in these areas. Results indicated that all faculty members reported teaching candidates about and how to conduct assessments in the areas of different developmental domains and using authentic assessment tools. There were a number of discrepancies regarding what coordinators reported was required and what faculty members suggested that they taught. The greatest discrepancies were in the areas of formal assessment, particularly regarding readiness and achievement tests and using assessment data to inform local programming and policy. Compared to the other types of programs, there appeared to be the most alignment across coordinators and faculty members in the associate degree programs.The Hawai‘i State Executie Office on Early Learning and the University of Hawai‘i System Office of the Vice President for Academic Affair
Theoretical investigation of magnetoelectric effects in Ba2CoGe2O7
A joint theoretical approach, combining macroscopic symmetry analysis with
microscopic methods (density functional theory and model cluster Hamiltonian),
is employed to shed light on magnetoelectricity in Ba2CoGe2O7. We show that the
recently reported experimental trend of polarization guided by magnetic field
can be predicted on the basis of phenomenological Landau theory. From the
microscopic side, Ba2CoGe2O7 emerges as a prototype of a class of
magnetoelectrics, where the cross coupling between magnetic and dipolar degrees
of freedom needs, as main ingredients, the on-site spin-orbit coupling and the
spin-dependent O p - Co d hybridization, along with structural constraints
related to the noncentrosymmetric structural symmetry and the peculiar
configuration of CoO4 tetrahedrons.Comment: 5 pages, 4 figures, submitted for publicatio
Chandra deep X-ray observation on the Galactic plane
Using the Chandra ACIS-I instruments, we have carried out the deepest X-ray
observation on a typical Galactic plane region at l 28.5 deg, where no discrete
X-ray sources have been known previously. We have detected, as well as strong
diffuse emission, 275 new point X-ray sources (4 sigma confidence) within two
partially overlapping fields (~250 arcmin^2 in total) down to ~3 x 10^{-15} erg
s^{-1} cm^{-2} (2 -- 10 keV) or ~ 7 x 10^{-16} erg s^{-1} cm^{-2} (0.5 -- 2
keV). We have studied spectral distribution of these point sources, and found
that very soft sources detected only below ~ 3 keV are more numerous than hard
sources detected only above ~ 3 keV. Only small number of sources are detected
both in the soft and hard bands. Surface density of the hard sources is almost
consistent with that at high Galactic regions, thus most of the hard sources
are considered to be Active Galactic Nuclei seen through the milky way. On the
other hand, some of the bright hard X-ray sources which show extremely flat
spectra and iron line or edge features are considered to be Galactic,
presumably quiescent dwarf novae. The soft sources show thermal spectra and
small interstellar hydrogen column densities, and some of them exhibit X-ray
flares. Therefore, most of the soft sources are probably X-ray active nearby
late type stars.Comment: Contribution to the proceedings of the "New Visions of the X-Ray
Universe in the XMM-Newton and Chandra Era" symposium at ESTEC, The
Netherlands. 26-30 Nov. 200
Positions of Point-Nodes in Borocarbide Superconductor YNi2B2C
To determine the superconducting gap function of YNi2B2C, we calculate the
local density of states (LDOS) around a single vortex core with the use of
Eilenberger theory and the band structure calculated by local density
approximation assuming various gap structures with point-nodes at different
positions. We also calculate the angular-dependent heat capacity in the vortex
state on the basis of the Doppler-Shift method. Comparing our results with the
STM/STS experiment, the angular-dependent heat capacity and thermal
conductivity, we propose the gap-structure of YNi2B2C, which has the
point-nodes and gap minima along . Our gap-structure is consistent with
all results of angular-resolved experiments.Comment: 7 pages, 5 figure
Open inflation in the landscape
Open inflation scenario is attracting a renewed interest in the context of
string landscape. Since there are a large number of metastable de Sitter vacua
in string landscape, tunneling transitions to lower metastable vacua through
the bubble nucleation occur quite naturally. Although the deviation of Omega_0
from unity is small by the observational bound, we argue that the effect of
this small deviation on the large angle CMB anisotropies can be significant for
tensor-type perturbation in open inflation scenario. We consider the situation
in which there is a large hierarchy between the energy scale of the quantum
tunneling and that of the slow-roll inflation in the nucleated bubble. If the
potential just after tunneling is steep enough, a rapid-roll phase appears
before the slow-roll inflation. In this case the power spectrum is basically
determined by the Hubble rate during the slow-roll inflation. If such
rapid-roll phase is absent, the power spectrum keeps the memory of the high
energy density there in the large angular components. The amplitude of large
angular components can be enhanced due to the effects of the wall fluctuation
mode if the bubble wall tension is small. Therefore, one can construct some
models in which the deviation of Omega_0 from unity is large enough to produce
measurable effects. We also consider a more general class of models, where the
false vacuum decay may occur due to Hawking-Moss tunneling, as well as the
models involving more than one scalar field. We discuss scalar perturbations in
these models and point out that a large set of such models is already ruled out
by observational data, unless there was a very long stage of slow-roll
inflation after the tunneling. These results show that observational data allow
us to test various assumptions concerning the structure of the string theory
potentials and the duration of the last stage of inflation.Comment: 14 pages, 11 figures, v2:minor corrections and a reference added,
v3:accepted for publication in PR
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