924 research outputs found
Electronic Structure of Three-Dimensional Superlattices Subject to Tilted Magnetic Fields
Full quantum-mechanical description of electrons moving in 3D structures with
unidirectional periodic modulation subject to tilted magnetic fields requires
an extensive numerical calculation. To understand magneto-oscillations in such
systems it is in many cases sufficient to use the quasi-classical approach, in
which the zero-magnetic-field Fermi surface is considered as a
magnetic-field-independent rigid body in k-space and periods of oscillations
are related to extremal cross-sections of the Fermi surface cut by planes
perpendicular to the magnetic-field direction. We point out cases where the
quasi-classical treatment fails and propose a simple tight-binding
fully-quantum-mechanical model of the superlattice electronic structure.Comment: 8 pages, 7 figures, RevTex, submitted to Phys. Rev.
A new technique using a rubber balloon in emergency second trimester cerclage for fetal membrane prolapse
The definitive version is available at www.blackwell-synergy.comArticleJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH. 34(6):935-940 (2008)journal articl
Highly anisotropic interlayer magnetoresistance in ZrSiS nodal-line Dirac semimetal
We instigate the angle-dependent magnetoresistance (AMR) of the layered
nodal-line Dirac semimetal ZrSiS for the in-plane and out-of-plane current
directions. This material has recently revealed an intriguing butterfly-shaped
in-plane AMR that is not well understood. Our measurements of the polar
out-of-plane AMR show a surprisingly different response with a pronounced
cusp-like feature. The maximum of the cusp-like anisotropy is reached when the
magnetic field is oriented in the - plane. Moreover, the AMR for the
azimuthal out-of-plane current direction exhibits a very strong four-fold
- plane anisotropy. Combining the Fermi surfaces calculated from first
principles with the Boltzmann's semiclassical transport theory we reproduce and
explain all the prominent features of the unusual behavior of the in-plane and
out-of-plane AMR. We are also able to clarify the origin of the strong
non-saturating transverse magnetoresistance as an effect of imperfect
charge-carrier compensation and open orbits. Finally, by combining our
theoretical model and experimental data we estimate the average relaxation time
of ~s and the mean free path of ~nm at 1.8~K in our
samples of ZrSiS.Comment: 8 pages, 4 figure
Magic angle effects of the one-dimensional axis conductivity in quasi-one dimensional conductors
In quasi-one-dimensional conductors, the conductivity in both one-dimensional
axis and interchain direction shows peaks when magnetic field is tilted at the
magic angles in the plane perpendicular to the conducting chain. Although there
are several theoretical studies to explain the magic angle effect, no
satisfactory explanation, especially for the one-dimensional conductivity, has
been obtained. We present a new theory of the magic angle effect in the
one-dimensional conductivity by taking account of the momentum-dependence of
the Fermi velocity, which should be large in the systems close to a spin
density wave instability. The magic angle effect is explained in the
semiclassical equations of motion, but neither the large corrugation of the
Fermi surface due to long-range hoppings nor hot spots, where the relaxation
time is small, on the Fermi surface are required.Comment: 4 pages, 3 figure
Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010
Anthropogenic SO<sub>2</sub> emissions increased alongside economic development in China at a rate of 12.7% yr<sup>−1</sup> from 2000 to 2005. However, under new Chinese government policy, SO<sub>2</sub> emissions declined by 3.9% yr<sup>−1</sup> between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 3–8% yr<sup>−1</sup> to a peak around 2005–2006 and subsequently decreased by 2–7% yr<sup>−1</sup>, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO<sub>2</sub> emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO<sub>2</sub> emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO<sub>2</sub> vertical column density and bottom-up SO<sub>2</sub> emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO<sub>2</sub> emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO<sub>2</sub> emissions and satellite retrieval. Satellite measurements of fine-mode AOD above the Sea of Japan marked a 4.1% yr<sup>−1</sup> decline between 2007 and 2010, which corresponded to the 9% yr<sup>−1</sup> decline in SO<sub>2</sub> emissions from China during the same period
Hofstadter butterfly and integer quantum Hall effect in three dimensions
For a three-dimensional lattice in magnetic fields we have shown that the
hopping along the third direction, which normally tends to smear out the Landau
quantization gaps, can rather give rise to a fractal energy spectram akin to
Hofstadter's butterfly when a criterion, found here by mapping the problem to
two dimensions, is fulfilled by anisotropic (quasi-one-dimensional) systems. In
3D the angle of the magnetic field plays the role of the field intensity in 2D,
so that the butterfly can occur in much smaller fields. The mapping also
enables us to calculate the Hall conductivity, in terms of the topological
invariant in the Kohmoto-Halperin-Wu's formula, where each of is found to be quantized.Comment: 4 pages, 6 figures, RevTeX, uses epsf.sty,multicol.st
Quantum interference and weak localisation effects in the interlayer magnetoresistance of layered metals
Studies of angle-dependent magnetoresistance oscillations (AMRO) in the
interlayer conductivity of layered metals have generally considered
semi-classical electron transport. We consider a quantum correction to the
semi-classical conductivity that arises from what can be described as an
interlayer Cooperon. This depends on both the disorder potential within a layer
and the correlations of the disorder potential between layers. We compare our
results with existing experimental data on organic charge transfer salts that
are not explained within the standard semi-classical transport picture. In
particular, our results may be applicable to effects that have been seen when
the applied magnetic field is almost parallel to the conducting layers. We
predict the presence of a peak in the resistivity as the field direction
approaches the plane of the layers. The peak can occur even when there is
weakly incoherent transport between layers.Comment: 11 pages, 6 figure
m7824 msb0011359c a bifunctional fusion protein targeting pd l1 and tgf β in asian patients with pretreated biliary tract cancer preliminary results from a phase i trial
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Interference Commensurate Oscillations in Q1D Conductors
We suggest an analytical theory to describe angular magnetic oscillations
recently discovered in quasi-one-dimensional conductor (TMTSF)2PF6 [see Phys.
Rev. B, 57, 7423 (1998)] and define the positions of the oscillation minima.
The origin of these oscillations is related to interference effects resulting
from an interplay of quasi-periodic and periodic ("commensurate") electron
trajectories in an inclined magnetic field. We reproduce via calculations
existing experimental data and predict some novel effects.Comment: 10 pages, 2 figure
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