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Effects of free surface and heterogeneous residual internal stress on stress-driven grain growth in nanocrystalline metals
By reevaluating the experimental study of Zhang et al. (2005), here we demonstrate that the extent of grain growth, previously proposed to be solely driven by external stress, may have been significantly overestimated. A new physical mechanism, termed as free surface assisted stress-driven grain growth (or self-mechanical annealing), is proposed and discussed in detail. Representing the cooperative effect of free surface and heterogeneous residual internal stress, the proposed mechanism is considered more favorable than the traditional pure stress-driven mechanism for interpreting the abnormal grain growth widely observed in deforming nanocrystalline metals at room temperature
Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal
The synthesis of nanocomposite materials combining titanate nanofibers (TNF)
with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work.
The TNF were produced via hydrothermal synthesis and sensitized with the
semiconductor nanoparticles, through a single-source precursor decomposition
method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's
surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts were
obtained using either a layer-by-layer or a co-sensitization approach. The
samples' photocatalytic performance was first evaluated through the production
of the hydroxyl radical using terephthalic acid as probe molecule. All the
tested samples show photocatalytic ability for the production of this oxidizing
species. Afterwards, the samples were investigated for the removal of methylene
blue. The nanocomposite materials with best adsorption ability for the organic
dye were the ZnS/TNF and Bi2S3ZnS/TNF. The removal of the methylene blue was
systematically studied, and the most promising results were obtained
considering a sequential combination of an adsorption-photocatalytic
degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and
photocatalyst material.Comment: 26 pages, 10 figure
Current Helicity and Twist as Two Indicators of The Mirror Asymmetry of solar Magnetic Fields
A comparison between the two tracers of magnetic field mirror asymmetry in
solar active regions, twist and current helicity, is presented. It is shown
that for individual active regions these tracers do not possess visible
similarity while averaging by time over the solar cycle, or by latitude,
reveals similarities in their behaviour. The main property of the dataset is
anti-symmetry over the solar equator. Considering the evolution of helical
properties over the solar cycle we find signatures of a possible sign change at
the beginning of the cycle, though more systematic observational data are
required for a definite confirmation. We discuss the role of both tracers in
the context of the solar dynamo theory.Comment: 14 pages, 6 figure
Plasma lipoproteins are required for both basal and stress-induced adrenal glucocorticoid synthesis and protection against endotoxemia in mice
Lipoprotein-associated cholesterol has been suggested to make a significant contribution to adrenal steroidogenesis in vivo. To determine whether lipoproteins indeed contribute to optimal adrenal steroidogenesis in mice, in the current study we have determined the effect of relative lipoprotein deficiency on adrenal steroidogenesis in C57BL/6 wild-type mice. Feeding C57BL/6 mice the lipid-lowering drug probucol (0.25% wt/wt) for 2 wk induced a 90% decrease in plasma high-density lipoprotein (HDL) cholesterol levels and a 77% reduction in low-density lipoprotein (LDL) cholesterol levels. Neutral lipid stores were depleted upon probucol treatment specifically in the glucocorticoid-producing zona fasciculata of the adrenal, leading to a 44% decreased plasma corticosterone level under basal conditions. Exposure to lipopolysaccharide (LPS) induced a 37% increase in the adrenal uptake of HDL cholesteryl esters. Probucol-treated mice could induce only a relatively minor corticosterone response upon a LPS challenge compared with controls, which coincided with an approximately twofold increased hepatic expression level of interleukin-6 and tumor necrosis factor (TNF)α and an 89% higher TNFα response in plasma. Furthermore, a compensatory two- to fivefold upregulation of LDL receptor (cholesterol uptake) and HMG-CoA reductase (cholesterol synthesis) expression was noticed in the adrenals of probucol-treated mice. In conclusion, we have shown that lipoprotein deficiency in mice as a result of probucol feeding is associated with decreased adrenal cortex cholesterol levels, a lower basal and stress-induced plasma glucocorticoid level, and an increased susceptibility to LPS-induced inflammation. Therefore, it is suggested that plasma lipoproteins are required for optimal adrenal steroidogenesis and protection against endotoxemia in mice.Biopharmaceutic
Dirac-harmonic maps from degenerating spin surfaces I: the Neveu-Schwarz case
We study Dirac-harmonic maps from degenerating spin surfaces with uniformly
bounded energy and show the so-called generalized energy identity in the case
that the domain converges to a spin surface with only Neveu-Schwarz type nodes.
We find condition that is both necessary and sufficient for the modulo bubbles compactness of a sequence of such maps.Comment: 24 page
Leukocyte ABCA1 remains atheroprotective in splenectomized LDL receptor knockout mice
Biopharmaceutic
State transfer in dissipative and dephasing environments
By diagonalization of a generalized superoperator for solving the master
equation, we investigated effects of dissipative and dephasing environments on
quantum state transfer, as well as entanglement distribution and creation in
spin networks. Our results revealed that under the condition of the same
decoherence rate , the detrimental effects of the dissipative
environment are more severe than that of the dephasing environment. Beside
this, the critical time at which the transfer fidelity and the
concurrence attain their maxima arrives at the asymptotic value
quickly as the spin chain length increases. The transfer
fidelity of an excitation at time is independent of when the system
subjects to dissipative environment, while it decreases as increases when
the system subjects to dephasing environment. The average fidelity displays
three different patterns corresponding to , and . For
each pattern, the average fidelity at time is independent of when the
system subjects to dissipative environment, and decreases as increases when
the system subjects to dephasing environment. The maximum concurrence also
decreases as increases, and when , it arrives at an
asymptotic value determined by the decoherence rate and the structure
of the spin network.Comment: 12 pages, 6 figure
Helioseismology of Sunspots: A Case Study of NOAA Region 9787
Various methods of helioseismology are used to study the subsurface
properties of the sunspot in NOAA Active Region 9787. This sunspot was chosen
because it is axisymmetric, shows little evolution during 20-28 January 2002,
and was observed continuously by the MDI/SOHO instrument. (...) Wave travel
times and mode frequencies are affected by the sunspot. In most cases, wave
packets that propagate through the sunspot have reduced travel times. At short
travel distances, however, the sign of the travel-time shifts appears to depend
sensitively on how the data are processed and, in particular, on filtering in
frequency-wavenumber space. We carry out two linear inversions for wave speed:
one using travel-times and phase-speed filters and the other one using mode
frequencies from ring analysis. These two inversions give subsurface wave-speed
profiles with opposite signs and different amplitudes. (...) From this study of
AR9787, we conclude that we are currently unable to provide a unified
description of the subsurface structure and dynamics of the sunspot.Comment: 28 pages, 18 figure
Surface-focused Seismic Holography of Sunspots: I. Observations
We present a comprehensive set of observations of the interaction of p-mode
oscillations with sunspots using surface-focused seismic holography. Maps of
travel-time shifts, relative to quiet-Sun travel times, are shown for incoming
and outgoing p modes as well as their mean and difference. We compare results
using phase-speed filters with results obtained with filters that isolate
single p-mode ridges, and further divide the data into multiple temporal
frequency bandpasses. The f mode is removed from the data. The variations of
the resulting travel-time shifts with magnetic-field strength and with the
filter parameters are explored. We find that spatial averages of these shifts
within sunspot umbrae, penumbrae, and surrounding plage often show strong
frequency variations at fixed phase speed. In addition, we find that positive
values of the mean and difference travel-time shifts appear exclusively in
waves observed with phase-speed filters that are dominated by power in the
low-frequency wing of the p1 ridge. We assess the ratio of incoming to outgoing
p-mode power using the ridge filters and compare surface-focused holography
measurements with the results of earlier published p-mode scattering
measurements using Fourier-Hankel decomposition.Comment: Solar Physics, accepte
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