2,048 research outputs found
Renal tubule necrosis and apoptosis modulation by A1 adenosine receptor expression
We have shown that A1 adenosine receptors (A1ARs) are cytoprotective against renal tubular necrosis and apoptosis both in vivo and in vitro. To study the role of A1AR numbers on renal epithelial cell survival, we stably overexpressed the human A1 receptor in a porcine renal tubule cell line and utilized primary cultures of proximal tubules obtained from A1AR knockout mice. Receptor-overexpressing cells were protected against peroxide-induced necrosis and tumor necrosis factor-α/cycloheximide-induced apoptosis. Conversely, cultured proximal tubule cells from receptor knockout mice showed more necrotic and apoptotic cell loss than corresponding cells from wild-type mice. Overexpression of the receptor resulted in a significantly higher baseline expression of both total and phosphorylated heat-shock protein (HSP)27; the latter due to A1 receptor enhancement of p38 and AP2 mitogen-activated protein kinase activities. The resistance to cell death in the porcine cells was reversed by selective A1 receptor antagonism and by a selective inhibitor of HSP synthesis. Receptor activation in wild-type mice in vivo led to increased total and phosphorylated HSP27, whereas receptor knockout mice showed decreased baseline and adenosine-mediated HSP phosphorylation. These studies show that endogenous A1AR activation produces cytoprotective effects in renal proximal tubules by modulating HSP27 signaling pathways
Exactly soluble model for self-gravitating D-particles with the wormhole
We consider D-particles coupled to the CGHS dilaton gravity and obtain the
exact wormhole geometry and trajectories of D-particles by introducing the
exotic matter. The initial static wormhole background is not stable after
infalling D-particles due to the classical backreaction of the geometry so that
the additional exotic matter source should be introduced for the stability.
Then, the traversable wormhole geometry naturally appears and the D-particles
can travel through it safely. Finally, we discuss the dynamical evolution of
the wormhole throat and the massless limit of D-particles.Comment: 16 pages, 3 figures, revte
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Cooperative Fabrication Methodology for Embedding Wireon Corved Surfaces
In conventional additive manufacturing (AM), an object is fabricated by depositing material in a
layer by layer fashion. Typically, this process is retained so that deposition can occur on flat
surfaces and motion can be constrained to requiring only three degrees of freedom (DOF) in a
Cartesian coordinate system. When incorporating wire in three-dimensional (3D) objects, there is
sometimes a need for placement along curved surfaces on which positions are defined not only
by 3D Cartesian coordinates but also angular ones. Therefore, a minimum of two additional
DOFs are required allowing movement to be generated at the build platform as well as of the
extrusion head. This paper addresses a method for trajectory planning of both systems, that is,
the extrusion head and the movable build platform, allowing for cooperative and harmonic
motion between the two.Mechanical Engineerin
On the effects of using CO2 and F2 lasers to modify the wettability of a polymeric biomaterial.
Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 ÎĽm spaced (with depths between 1 and 10 ÎĽm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy analysis and showed that the O2 increased by up to 1.5% At. and decreased by up to 1.6% At. for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser induced trench-like topographical patterns
Scalar wave propagation in topological black hole backgrounds
We consider the evolution of a scalar field coupled to curvature in
topological black hole spacetimes. We solve numerically the scalar wave
equation with different curvature-coupling constant and show that a rich
spectrum of wave propagation is revealed when is introduced. Relations
between quasinormal modes and the size of different topological black holes
have also been investigated.Comment: 26 pages, 18 figure
Nanoparticle-regulated phase behavior of ordered block copolymers
This document is the accepted manuscript version of a published article. Published by The Royal Society of Chemistry in the journal "Soft Matter" issue 8, DOI: 10.1039/b805540hAlthough block copolymer motifs have received considerable
attention as supramolecular templates for inorganic nanoparticles,
experimental observations of a nanostructured diblock copolymer
containing inorganic nanoparticles—supported by theoretical trends
predicted from a hybrid self-consistent field/density functional
theory—confirm that nanoparticle size and selectivity can likewise
stabilize the copolymer nanostructure by increasing its order–
disorder transition temperature.Research Council of Norway under the NANOMAT Program
Los Alamos National Laboratory || Contract No. DE-AC52-06NA25396
NSERC of Canada
GEM Fellowship and a NOBCChE Procter and Gamble Fellowship
Spin-charge separation in the single hole doped Mott antiferromagnet
The motion of a single hole in a Mott antiferromagnet is investigated based
on the t-J model. An exact expression of the energy spectrum is obtained, in
which the irreparable phase string effect [Phys. Rev. Lett. 77, 5102 (1996)] is
explicitly present. By identifying the phase string effect with spin backflow,
we point out that spin-charge separation must exist in such a system: the doped
hole has to decay into a neutral spinon and a spinless holon, together with the
phase string. We show that while the spinon remains coherent, the holon motion
is deterred by the phase string, resulting in its localization in space. We
calculate the electron spectral function which explains the line shape of the
spectral function as well as the ``quasiparticle'' spectrum observed in
angle-resolved photoemission experiments. Other analytic and numerical
approaches are discussed based on the present framework.Comment: 16 pages, 9 figures; references updated; to appear in Phys. Rev.
Photonic band structure of highly deformable, self-assembling systems
We calculate the photonic band structure at normal incidence of highly
deformable, self-assembling systems - cholesteric elastomers subjected to
external stress. Cholesterics display brilliant reflection and lasing owing to
gaps in their photonic band structure. The band structure of cholesteric
elastomers varies sensitively with strain, showing new gaps opening up and
shifting in frequency. A novel prediction of a total band gap is made, and is
expected to occur in the vicinity of the previously observed de Vries bandgap,
which is only for one polarisation
Quantum phase transitions and thermodynamic properties in highly anisotropic magnets
The systems exhibiting quantum phase transitions (QPT) are investigated
within the Ising model in the transverse field and Heisenberg model with
easy-plane single-site anisotropy. Near QPT a correspondence between parameters
of these models and of quantum phi^4 model is established. A scaling analysis
is performed for the ground-state properties. The influence of the external
longitudinal magnetic field on the ground-state properties is investigated, and
the corresponding magnetic susceptibility is calculated. Finite-temperature
properties are considered with the use of the scaling analysis for the
effective classical model proposed by Sachdev. Analytical results for the
ordering temperature and temperature dependences of the magnetization and
energy gap are obtained in the case of a small ground-state moment. The forms
of dependences of observable quantities on the bare splitting (or magnetic
field) and renormalized splitting turn out to be different. A comparison with
numerical calculations and experimental data on systems demonstrating magnetic
and structural transitions (e.g., into singlet state) is performed.Comment: 46 pages, RevTeX, 6 figure
Angular dependence of novel magnetic quantum oscillations in a quasi-two-dimensional multiband Fermi liquid with impurities
The semiclassical Lifshitz-Kosevich-type description is given for the angular
dependence of quantum oscillations with combination frequencies in a multiband
quasi-two-dimensional Fermi liquid with a constant number of electrons. The
analytical expressions are found for the Dingle, thermal, spin, and amplitude
(Yamaji) reduction factors of the novel combination harmonics, where the latter
two strongly oscillate with the direction of the field. At the "magic" angles
those factors reduce to the purely two-dimensional expressions given earlier.
The combination harmonics are suppressed in the presence of the non-quantized
("background") states, and they decay exponentially faster with temperature
and/or disorder compared to the standard harmonics, providing an additional
tool for electronic structure determination. The theory is applied to
SrRuO.Comment: 5 pages, 2 figures, minor typos correcte
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