8,173 research outputs found
Collinear-to-Spiral Spin Transformation without Changing Modulation Wavelength upon Ferroelectric Transition in Tb1-xDyxMnO3
Lattice modulation and magnetic structures in magnetoelectric compounds
Tb1-xDyxMnO3 have been studied around the ferroelectric (FE) Curie temperature
T_C by x-ray and neutron diffraction. Temperature-independent modulation
vectors through T_C are observed for the compounds with 0.50< x < 0.68. This
indicates that ferroelectricity with a polarization (P) along the c axis in the
RMnO3 series cannot be ascribed to such an incommensurate-commensurate
transition of an antiferromagnetic order as was previously anticipated. Neutron
diffraction study of a single crystal with x=0.59 shows that the FE transition
is accompanied by the transformation of the Mn-spin alignment from sinusoidal
(collinear) antiferromagnetism into a transverse spiral structure. The observed
spiral structure below T_C is expected to produce P along the c axis with the
`inverse' Dzialoshinski-Moriya interaction, which is consistent with the
observation.Comment: 9 pages, 4 figure
The Suppression of Diversity
Is it a systematic strategy or a mutation of millennial ferver that drives the escalating challenges to the civil rights of this nation\u27s racial, linguistic, and national origin minorities? Increasing juridical, legislative, and popular assaults on affirmative action policies coupled with the sometimes less heralded emergence of a de facto U.S. language policy are sweeping through the states. These activities draw on a consistent repertoire of approaches from the invocation of the very language and concepts of the civil rights movement to the isolationist buzz-words of early twentieth century advocates of Americanization. In an effort to legitimize their efforts this new breed of assailants has lifted the terms equality of opportunity, color blind, and merit directly from the lips of civil rights heroes of the past, retrofitting concepts that resonate from the very core of the civil rights movement into an arsenal of weapons that threaten the extinction of that movement. In that same vein opponents of bilingual education have reached further back into our history dredging up de-contextualized quotations from icons of American history to evoke nostalgia and patriotism and to resuscitate the fear of the dissolution of national unity in the wake of the infusion of diverse languages and cultures. The introductory portion of this article treats the failure of anti-civil rights movements to acknowledge either the rich cultural legacy of people of color or the deeply engrained cultural and political limitations that this nation has imposed on their civil rights. We discuss the re-packaged language of equality and equity used by these movements and their success and attempts at success in reversing the progress of civil rights at the polls and in legislatures across the nation. We next examine the anti-affirmative action and anti-bilingual movements sweeping the U.S. today, analyzing qualitative and quantitative data from multiple sources including data from the the 2000 U.S. Census to track current anti-affirmative action and anti-bilingual/English only developments among the states to demonstrate the coexistence of these developments in those areas where people of color are concentrated
Spatial deconvolution of spectropolarimetric data: an application to quiet Sun magnetic elements
Observations of the Sun from the Earth are always limited by the presence of
the atmosphere, which strongly disturbs the images. A solution to this problem
is to place the telescopes in space satellites, which produce observations
without any (or limited) atmospheric aberrations. However, even though the
images from space are not affected by atmospheric seeing, the optical
properties of the instruments still limit the observations. In the case of
diffraction limited observations, the PSF establishes the maximum allowed
spatial resolution, defined as the distance between two nearby structures that
can be properly distinguished. In addition, the shape of the PSF induce a
dispersion of the light from different parts of the image, leading to what is
commonly termed as stray light or dispersed light. This effect produces that
light observed in a spatial location at the focal plane is a combination of the
light emitted in the object at relatively distant spatial locations. We aim to
correct the effect produced by the telescope's PSF using a deconvolution
method, and we decided to apply the code on Hinode/SP quiet Sun observations.
We analyze the validity of the deconvolution process with noisy data and we
infer the physical properties of quiet Sun magnetic elements after the
deconvolution process.Comment: 14 pages, 9 figure
Antiproton Production in p+d Reaction at Subthreshold Energies
An enhancement of antiprotons produced in p+d reaction in comparison with
ones in p+p elementary reaction is investigated.
In the neighborhood of subthreshold energy the enhancement is caused by the
difference of available energies for antiproton production. The cross section
in p+d reaction, on the other hand, becomes just twice of the one in elementary
p+p reaction at the incident energy far from the threshold energy when
non-nucleonic components in deuteron target are not considered.Comment: LaTeX,7 pages with 5 eps figure
Volume, Coulomb, and volume-symmetry coefficients of nucleus incompressibility in the relativistic mean field theory with the excluded volume effects
The relation among the volume coefficient (=incompressibility of the
nuclear matter), the Coulomb coefficient , and the volume-symmetry
coefficient of the nucleus incompressibility are studied in the
framework of the relativistic mean field theory with the excluded volume
effects of the nucleons, under the assumption of the scaling model. It is found
that MeV is necessary to account for the empirical values of ,
, and , simultaneously, as is in the case of the point-like
nucleons. The result is independent on the detail descriptions of the potential
of the -meson self-interaction and is almost independent on the
excluded volume of the nucleons.Comment: PACS numbers, 21.65.+f, 21.30.+
Compressional properties of nuclear matter in the relativistic mean field theory with the excluded volume effects
Compressional properties of nuclear matter are studied by using the mean
field theory with the excluded volume effects of the nucleons. It is found that
the excluded volume effects make it possible to fit the empirical data of the
Coulomb coefficient of nucleus incompressibility, even if the volume
coefficient is small(MeV). However, the symmetry properties favor
MeV as in the cases of the mean field theory of point-like
nucleons.Comment: PACS numbers, 21.65.+f, 21.30.+
Partially-disordered photonic-crystal thin films for enhanced and robust photovoltaics
We present a general framework for the design of thin-film photovoltaics
based on a partially-disordered photonic crystal that has both enhanced
absorption for light trapping and reduced sensitivity to the angle and
polarization of incident radiation. The absorption characteristics of different
lattice structures are investigated as an initial periodic structure is
gradually perturbed. We find that an optimal amount of disorder controllably
introduced into a multi-lattice photonic crystal causes the characteristic
narrow-band, resonant peaks to be broadened resulting in a device with enhanced
and robust performance ideal for typical operating conditions of photovoltaic
applications.Comment: 5 pages, 4 figure
Ferromagnetism of cold fermions loaded into a decorated square lattice
We investigate two-component ultracold fermions loaded into a decorated
square lattice, which are described by the Hubbard model with repulsive
interactions and nearest neighbor hoppings. By combining the real-space
dynamical mean-field theory with the numerical renormalization group method, we
discuss how a ferromagnetically ordered ground state in the weak coupling
regime, which originates from the existence of a dispersionless band, is
adiabatically connected to a Heisenberg ferrimagnetic state in the strong
coupling limit. The effects of level splitting and hopping imbalance are also
addressed.Comment: 8 pages, 7 figure
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