6,778 research outputs found
Magnetic ordering and fluctuation in kagome lattice antiferromagnets, Fe and Cr jarosites
Jarosite family compounds, KFe_3(OH)_6(SO_4)_2, (abbreviate Fe jarosite), and
KCr_3(OH)_6(SO_4)_2, (Cr jarosite), are typical examples of the Heisenberg
antiferromagnet on the kagome lattice and have been investigated by means of
magnetization and NMR experiments. The susceptibility of Cr jarosite deviates
from Curie-Weiss law due to the short-range spin correlation below about 150 K
and shows the magnetic transition at 4.2 K, while Fe jarosite has the
transition at 65 K. The susceptibility data fit well with the calculated one on
the high temperature expansion for the Heisenberg antiferromagnet on the kagome
lattice. The values of exchange interaction of Cr jarosite and Fe jarosite are
derived to be J_Cr = 4.9 K and J_Fe = 23 K, respectively. The 1H-NMR spectra of
Fe jarosite suggest that the ordered spin structure is the q = 0 type with
positive chirality of the 120 degrees configuration. The transition is caused
by a weak single-ion type anisotropy. The spin-lattice relaxation rate, 1/T_1,
of Fe jarosite in the ordered phase decreases sharply with lowering the
temperature and can be well explained by the two-magnon process of spin wave
with the anisotropy.Comment: REVTeX, 14 pages with 5 figures. Submitted to Canadian Journal of
Physic
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Tracking surface photovoltage dipole geometry in bi2se3 with time-resolved photoemission
Topological insulators have been shown to exhibit strong and long-lived surface photovoltages when excited by an infrared pump. The ability to generate long-lived potentials on these surfaces provides opportunities to manipulate the spin-momentum locked topological surface states. Moreover, the photo-induced nature of this effect allows for localized excitation of arbitrary geometries. Knowing precisely how these potentials form and evolve is critical in understanding how to manage the effect in applications. The uniqueness of the photoemission experimental geometry, in which the photoelectron must traverse the induced surface field in vacuum, provides an interesting probe of the electric dipole shape generated by the surface photovoltage. In this study, we are able to match the observed decay of the geometric effect on the photoelectron to an essential electrodynamics model of the light-induced dipole thereby tracking the fluence-dependent evolution of the dipole geometry. By utilizing a standard time-resolved angle-resolved photoemission experiment, we are able to determine real-space information of the dipole while simultaneously recovering time-resolved band structure
Cyclotron radiation and emission in graphene
Peculiarity in the cyclotron radiation and emission in graphene is
theoretically examined in terms of the optical conductivity and relaxation
rates to propose that graphene in magnetic fields can be a candidate to realize
the Landau level laser, proposed decades ago [H. Aoki, Appl. Phys. Lett. {\bf
48}, 559 (1986)].Comment: 4 pages, 3 figure
Epigenomes in Cardiovascular Disease.
If unifying principles could be revealed for how the same genome encodes different eukaryotic cells and for how genetic variability and environmental input are integrated to impact cardiovascular health, grand challenges in basic cell biology and translational medicine may succumb to experimental dissection. A rich body of work in model systems has implicated chromatin-modifying enzymes, DNA methylation, noncoding RNAs, and other transcriptome-shaping factors in adult health and in the development, progression, and mitigation of cardiovascular disease. Meanwhile, deployment of epigenomic tools, powered by next-generation sequencing technologies in cardiovascular models and human populations, has enabled description of epigenomic landscapes underpinning cellular function in the cardiovascular system. This essay aims to unpack the conceptual framework in which epigenomes are studied and to stimulate discussion on how principles of chromatin function may inform investigations of cardiovascular disease and the development of new therapies
Bending and springback prediction method based on multi-scale finite element analyses for high bendability and low springback sheet generation
In this study, a sheet bendability and springback property evaluation technology through bending test simulations is newly developed using our multi-scale finite element analysis code, which is based on the crystallographic homogenization method
Effect of the atmosphere on the classification of LANDSAT data
The author has identified the following significant results. In conjunction with Turner's model for the correction of satellite data for atmospheric interference, the LOWTRAN-3 computer was used to calculate the atmospheric interference. Use of the program improved the contrast between different natural targets in the MSS LANDSAT data of Brasilia, Brazil. The classification accuracy of sugar canes was improved by about 9% in the multispectral data of Ribeirao Preto, Sao Paulo
The Boltzmann equation without angular cutoff in the whole space: II, Global existence for hard potential
As a continuation of our series works on the Boltzmann equation without
angular cutoff assumption, in this part, the global existence of solution to
the Cauchy problem in the whole space is proved in some suitable weighted
Sobolev spaces for hard potential when the solution is a small perturbation of
a global equilibrium
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