527 research outputs found
Multiple Quantum Well AlGaAs Nanowires
This letter reports on the growth, structure and luminescent properties of
individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition
modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga
during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B
substrates. Transmission electron microscopy and energy dispersive X-ray
spectroscopy performed on individual NWs are consistent with a configuration
composed of conical segments stacked along the NW axis. Micro-photoluminescence
measurements and confocal microscopy showed enhanced light emission from the
MQW NWs as compared to non-segmented NWs due to carrier confinement and
sidewall passivation
Microscopic measurement of the linear compressibilities of two-dimensional fatty acid mesophases
The linear compressibility of two-dimensional fatty acid mesophases has
determined by grazing incidence x-ray diffraction. Surface pressure vs
molecular area isotherms were reconstructed from these measurements, and the
linear compressibility (relative distortion along a given direction for
isotropic applied stress) was determined both in the sample plane and in a
plane normal to the aliphatic chain director (transverse plane). The linear
compressibilities range over two orders of magnitude from 0.1 to 10 m/N and are
distributed depending on their magnitude in 4 different sets which we are able
to associate with different molecular mechanisms. The largest compressibilities
(10m/N) are observed in the tilted phases. They are apparently independent of
the chain length and could be related to the reorganization of the headgroup
hydrogen-bounded network, whose role should be revalued. Intermediate
compressibilities are observed in phases with quasi long-range order
(directions normal to the molecular tilt in L_2 or L_2' phases, S phase), and
could be related to the ordering of these phases. The lowest compressibilities
are observed in the solid untilted CS phase and for 1 direction of the S and
L_2'' phases. They are similar to the compressibility of crystalline polymers
and correspond to the interactions between methyl groups in the crystal.
Finally, negative compressibilities are observed in the transverse plane for
L_2' and L_2'' phases and can be traced to subtle reorganizations upon
untilting.Comment: 24 pages, 17 figure
Efficacy of cyclosporin A in psoriasis: a summary of the United States’ experience
Since its discovery in 1972, cyclosporin A (CyA) has been widely used in the experimental treatment of multiple inflammatory diseases considered to be of immune-mediated aetiology. In dermatology, oral CyA is most effective in the treatment of psoriasis and has been used successfully for plaque-type, pustular and erythrodermic forms of the disease. While dosages ranging from 1 to 14 mg/kg/day have been used, a starting dose of 4 mg/kg/day gives a rapid response with few side-effects. Nephrotoxicity remains the greatest concern in long-term use of the drug. Although intralesional CyA has proven effective in psoriasis, topical preparations have not. It is hoped that future research will provide effective topical formulations of CyA which are efficacious without the risks inherent in systemic administration.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72330/1/j.1365-2133.1990.tb02878.x.pd
Coulomb-U and magnetic moment collapse in -Pu
The around-the-mean-field version of the LDA+U method is applied to
investigate electron correlation effects in -Pu. It yields a
non-magnetic ground state of Pu, and provides a good agreement with
experimental equilibrium volume, bulk modulus and explains important features
of the photoelectron spectra
Effects of agonists of peroxisome proliferator-activated receptor γ on proteoglycan degradation and matrix metalloproteinase production in rat cartilage in vitro
AbstractObjective To examine the effects of agonists of peroxisome proliferator-activated receptor (PPAR) γ on proteoglycan degradation induced by interleukin (IL)-1β or tumor necrosis factor (TNF)α in cartilage in vitro.Design Proteoglycan degradation was measured as release of radioactivity from rat cartilage explants previously labeled with 35SO2−4. Western blots were used to examine tissue levels of aggrecan neoepitopes NITEGE and VDIPEN, generated by aggrecanases and matrix metalloproteinases (MMP), respectively. Production of MMP-2, -3 and -9 by cultured rat chondrocytes was measured by zymography and by fluorimetric assay.Results IL-1β-induced proteoglycan degradation was likely due to aggrecanase, since it was associated with a strong increase of NITEGE signal. MMP-dependent VDIPEN signal increased only after further incubation with pro-MMP activator APMA. PPAR agonists 15d-PGJ2 and GI262570 (10μM) inhibited IL-1β- and TNFα-induced proteoglycan degradation measured both before and after addition of APMA. The agonists also inhibited cytokine-induced MMP production by isolated chondrocytes.Conclusion This study shows that PPARγ agonists inhibit cytokine-induced proteoglycan degradation mediated by both aggrecanase and MMP. This effect is associated with inhibition of production of MMP-3 and -9. These results support the interest for PPARγ agonists as candidate inhibitors of pathological cartilage degradation. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved
A Single-Nucleotide Polymorphism in a Methylatable Foxa2 Binding Site of the G6PC2 Promoter Is Associated With Insulin Secretion In Vivo and Increased Promoter Activity In Vitro
OBJECTIVE—The G6PC2 gene encoding islet-specific glucose-6-phosphatase related protein (IGRP) has a common promoter variant, rs573225 (−231G/A), located within a Foxa binding site. We tested the cis-regulatory effects of rs573225 on promoter activity and its association with insulin response to oral glucose
Molecular Dynamics Study of the Nematic-Isotropic Interface
We present large-scale molecular dynamics simulations of a nematic-isotropic
interface in a system of repulsive ellipsoidal molecules, focusing in
particular on the capillary wave fluctuations of the interfacial position. The
interface anchors the nematic phase in a planar way, i.e., the director aligns
parallel to the interface. Capillary waves in the direction parallel and
perpendicular to the director are considered separately. We find that the
spectrum is anisotropic, the amplitudes of capillary waves being larger in the
direction perpendicular to the director. In the long wavelength limit, however,
the spectrum becomes isotropic and compares well with the predictions of a
simple capillary wave theory.Comment: to appear in Phys. Rev.
Glycosylation status of the C. albicans cell wall affects the efficiency of neutrophil phagocytosis and killing but not cytokine signaling
The cell wall of the opportunistic human fungal pathogen, Candida albicans is a complex, layered network of rigid structural polysaccharides composed of β-glucans and chitin that is covered with a fibrillar matrix of highly glycosylated mannoproteins. Poly-morphonuclear cells (PMNs, neutrophils) are the most prevalent circulating phagocytic leukocyte in peripheral blood and they are pivotal in the clearance of invading fungal cells from tissues. The importance of cell-wall mannans for the recognition and uptake of C. albicans by human PMNs was therefore investigated. N- and O-glycosylation-deficient mutants were attenuated in binding and phagocytosis by PMNs and this was associated with reduced killing of C. albicans yeast cells. No differences were found in the production of the respiratory burst enzyme myeloperoxidase (MPO) and the neutrophil chemokine IL-8 in PMNs exposed to control and glycosylation-deficient C. albicans strains. Thus, the significant decrease in killing of glycan-deficient C. albicans strains by PMNs is a consequence of a marked reduction in phagocytosis rather than changes in the release of inflammatory mediators by PMNs
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