348 research outputs found
Bleaching of sol-gel glass film with embedded gold nanoparticles by thermal poling
Gold clusters embedded in glass are expected to be hard to dissolve in the form of ions since gold is essentially a nonreactive metal. In spite of that, bleaching of Au-doped nanocomposite sol-gel glass film on a soda-lime glass substrate is demonstrated in which electric-field thermal poling is employed to effectively dissolve randomly distributed gold nanoparticles (15 nm in diameter) embedded in a low conductivity sol-gel glass film with a volume filling factor as small as 2.3%. The surface plasmon absorption band at 520 nm is suppressed in the region covered by the anodic electrode. The phenomenon is explained by the ionization of the gold nanoparticles and the redistribution of gold ions in the glass matrix due to the action of the extremely high electrostatic field locally developed during poling
Persistence of a particle in the Matheron-de Marsily velocity field
We show that the longitudinal position of a particle in a
-dimensional layered random velocity field (the Matheron-de Marsily
model) can be identified as a fractional Brownian motion (fBm) characterized by
a variable Hurst exponent for . The
fBm becomes marginal at . Moreover, using the known first-passage
properties of fBm we prove analytically that the disorder averaged persistence
(the probability of no zero crossing of the process upto time ) has a
power law decay for large with an exponent for and
for (with logarithmic correction at ), results that
were earlier derived by Redner based on heuristic arguments and supported by
numerical simulations (S. Redner, Phys. Rev. E {\bf 56}, 4967 (1997)).Comment: 4 pages Revtex, 1 .eps figure included, to appear in PRE Rapid
Communicatio
Exact Asymptotic Results for Persistence in the Sinai Model with Arbitrary Drift
We obtain exact asymptotic results for the disorder averaged persistence of a
Brownian particle moving in a biased Sinai landscape. We employ a new method
that maps the problem of computing the persistence to the problem of finding
the energy spectrum of a single particle quantum Hamiltonian, which can be
subsequently found. Our method allows us analytical access to arbitrary values
of the drift (bias), thus going beyond the previous methods which provide
results only in the limit of vanishing drift. We show that on varying the
drift, the persistence displays a variety of rich asymptotic behaviors
including, in particular, interesting qualitative changes at some special
values of the drift.Comment: 17 pages, two eps figures (included
細胞毒性化合物、DeoxypodophyllotoxinのJuniperus chinensis 茎葉からの単離と同定
Deoxypodophyllotoxin was isolated as a cytotoxic constituent from ethanol extract of the leaves of Juniperus chinensis by assay-guided fractionation.マレーシアなど熱帯地方において、庭木としてよく植栽されているJuniperus chinensisの茎葉のエタノール抽出物から HeLa細胞に対する毒性を指標として、細胞毒性化合物Deoxypodophyllotoxinを単離した。この化合物のHeLa細胞に対するMECは、0.004μg/mlであった
Short Communication Functional characterization of carrier-mediated transport of pravastatin across the blood-retinal barrier in rats
Abstract: 248 words Introduction: 432 word
Boundary driven zero-range processes in random media
The stationary states of boundary driven zero-range processes in random media
with quenched disorder are examined, and the motion of a tagged particle is
analyzed. For symmetric transition rates, also known as the random barrier
model, the stationary state is found to be trivial in absence of boundary
drive. Out of equilibrium, two further cases are distinguished according to the
tail of the disorder distribution. For strong disorder, the fugacity profiles
are found to be governed by the paths of normalized -stable
subordinators. The expectations of integrated functions of the tagged particle
position are calculated for three types of routes.Comment: 23 page
The maximum of the local time of a diffusion process in a drifted Brownian potential
We consider a one-dimensional diffusion process in a
-drifted Brownian potential for . We are interested
in the maximum of its local time, and study its almost sure asymptotic
behaviour, which is proved to be different from the behaviour of the maximum
local time of the transient random walk in random environment. We also obtain
the convergence in law of the maximum local time of under the annealed law
after suitable renormalization when . Moreover, we characterize
all the upper and lower classes for the hitting times of , in the sense of
Paul L\'evy, and provide laws of the iterated logarithm for the diffusion
itself. To this aim, we use annealed technics.Comment: 38 pages, new version, merged with hal-00013040 (arXiv:math/0511053),
with some additional result
DIFFUSION IN ONE DIMENSIONAL RANDOM MEDIUM AND HYPERBOLIC BROWNIAN MOTION
Classical diffusion in a random medium involves an exponential functional of
Brownian motion. This functional also appears in the study of Brownian
diffusion on a Riemann surface of constant negative curvature. We analyse in
detail this relationship and study various distributions using stochastic
calculus and functional integration.Comment: 18 page
Identification of Proteins Targeted by the Thioredoxin Superfamily in Plasmodium falciparum
The malarial parasite Plasmodium falciparum possesses a functional thioredoxin and glutathione system comprising the dithiol-containing redox proteins thioredoxin (Trx) and glutaredoxin (Grx), as well as plasmoredoxin (Plrx), which is exclusively found in Plasmodium species. All three proteins belong to the thioredoxin superfamily and share a conserved Cys-X-X-Cys motif at the active site. Only a few of their target proteins, which are likely to be involved in redox reactions, are currently known. The aim of the present study was to extend our knowledge of the Trx-, Grx-, and Plrx-interactome in Plasmodium. Based on the reaction mechanism, we generated active site mutants of Trx and Grx lacking the resolving cysteine residue. These mutants were bound to affinity columns to trap target proteins from P. falciparum cell extracts after formation of intermolecular disulfide bonds. Covalently linked proteins were eluted with dithiothreitol and analyzed by mass spectrometry. For Trx and Grx, we were able to isolate 17 putatively redox-regulated proteins each. Furthermore, the approach was successfully established for Plrx, leading to the identification of 21 potential target proteins. In addition to confirming known interaction partners, we captured potential target proteins involved in various processes including protein biosynthesis, energy metabolism, and signal transduction. The identification of three enzymes involved in S-adenosylmethionine (SAM) metabolism furthermore suggests that redox control is required to balance the metabolic fluxes of SAM between methyl-group transfer reactions and polyamine synthesis. To substantiate our data, the binding of the redoxins to S-adenosyl-L-homocysteine hydrolase and ornithine aminotransferase (OAT) were verified using BIAcore surface plasmon resonance. In enzymatic assays, Trx was furthermore shown to enhance the activity of OAT. Our approach led to the discovery of several putatively redox-regulated proteins, thereby contributing to our understanding of the redox interactome in malarial parasites
Emergence of new types of Theileria orientalis in Australian cattle and possible cause of theileriosis outbreaks
Theileria parasites cause a benign infection of cattle in parts of Australia where they are endemic, but have, in recent years, been suspected of being responsible for a number of outbreaks of disease in cattle near the coast of New South Wales. The objective of this study was to identify and characterize the species of Theileria in cattle on six farms in New South Wales where disease outbreaks have occurred, and compare with Theileria from three disease-free farms in Queensland that is endemic for Theileria. Special reference was made to sub-typing of T. orientalis by type-specific PCR and sequencing of the small subunit (SSU) rRNA gene, and sequence analysis of the gene encoding a polymorphic merozoite/piroplasm surface protein (MPSP) that may be under immune selection. Nucleotide sequencing of SSU rRNA and MPSP genes revealed the presence of four Theileria genotypes: T. orientalis (buffeli), T. orientalis (ikeda), T. orientalis (chitose) and T. orientalis type 4 (MPSP) or type C (SSU rRNA). The majority of animals showed mixed infections while a few showed single infection. When MPSP nucleotide sequences were translated into amino acids, base transition did not change amino acid composition of the protein product, suggesting possible silent polymorphism. The occurrence of ikeda and type 4 (type C) previously not reported to occur and silent mutation is thought to have enhanced parasite evasion of the host immune response causing the outbreak
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