287 research outputs found
Magnetotransport study of the charged stripes in high-T_c cuprates
We present a study of the in-plane and out-of-plane magnetoresistance (MR) in
heavily-underdoped, antiferromagnetic YBa_{2}Cu_{3}O_{6+x}, which reveals a
variety of striking features. The in-plane MR demonstrates a "d-wave"-like
anisotropy upon rotating the magnetic field H within the ab plane. With
decreasing temperature below 20-25 K, the system acquires memory: exposing a
crystal to the magnetic field results in a persistent in-plane resistivity
anisotropy. The overall features can be explained by assuming that the CuO_2
planes contain a developed array of stripes accommodating the doped holes, and
that the MR is associated with the field-induced topological ordering of the
stripes.Comment: 4 pages, 5 figures, invited paper at M2S-HTSC-VI, to be published in
Physics C (Proceedings of the International Conference on Materials and
Mechanisms of Superconductivity, High Temperature Superconductors VI
(M2S-HTSC-VI), Houston, Feb 20-25, 2000
Aureobasidin A, an antifungal cyclic depsipeptide antibiotic, is a substrate for both human MDR1 and MDR2/P-glycoproteins
AbstractThe human MDR1 gene encodes the multidrug transporter P-glycoprotein (Pgp). Although the MDR2/Pgp shares about 80% identity at the amino acid level with the MDRI/Pgp, the MDR2/Pgp cannot act as a multidrug transporter. We examined the drug sensitivity of Saccharomyces cerevisiae expressing either the human MDR1/Pgp or MDR2/Pgp. The human MDR1/Pgp conferred about 4-fold resistance to aureobasidin A, a cyclic depsipeptide antifungal antibiotic, on the drug-sensitive yeast strains. Interestingly the human MDR2/Pgp also conferred about 2.5-fold resistance to aureobasidin A. The resistance to aureobasidin A conferred by the MDR2/Pgp as well as by the MDR1/Pgp was overcome by vinblastine, verapamil, and cyclosporin A, depending on their concentrations, but not by colchicine. Aureobasidin A probably interacts directly with Pgps, because it overcame multidrug resistance of human cells and inhibited azidopine photoaffinity labeling of MDRI/Pgp in human cell membranes. These results suggest the possibility that the human MDR1 and MDR2/Pgps have conserved domain(s) for drug recognition
An Adaptive Node Relocation Procedure in FEM with Its Application to Deformation Analysis of Ground
Laboratory Study on the Effect of Walls for preventing Offshore Sediment Movement around a Submarine Canyon
Clustering of red Galaxies near the Radio-loud Quasar 1335.8+2834 at z=1.1
We have obtained new deep optical and near-infrared images of the field of
the radio-loud quasar 1335.8+2834 at where an excess in the surface
number density of galaxies was reported by Hutchings et al. [AJ, 106, 1324]
from optical data. We found a significant clustering of objects with very red
optical-near infrared colors, and near the quasar. The colors and magnitudes of the reddest objects
are consistent with those of old (12 Gyr old at z=0) passively-evolving
elliptical galaxies seen at , clearly defining a `red envelope' like
that found in galaxy clusters at similar or lower redshifts. This evidence
strongly suggests that the quasar resides in a moderately-rich cluster of
galaxies (richness-class ). There is also a relatively large fraction
of objects with moderately red colors () which have a
distribution on the sky similar to that of the reddest objects. They may be
interpreted as cluster galaxies with some recent or on-going star formation.Comment: 14 pages text, 5 PostScript figures, 1 GIF figure, and 1 combined PS
file. Accepted for ApJ, Letter
Large-scale Filamentary Structure around the Protocluster at Redshift z=3.1
We report the discovery of a large-scale coherent filamentary structure of
Lyman alpha emitters in a redshift space at z=3.1. We carried out spectroscopic
observations to map the three dimensional structure of the belt-like feature of
the Lyman alpha emitters discovered by our previous narrow-band imaging
observations centered on the protocluster at z=3.1. The feature was found to
consist of at least three physical filaments connecting with each other. The
result is in qualitative agreement with the prediction of the 'biased'
galaxy-formation theories that galaxies preferentially formed in large-scale
filamentary or sheet-like mass overdensities in the early Universe. We also
found that the two known giant Lyman alpha emission-line nebulae showing high
star-formation activities are located near the intersection of these filaments,
which presumably evolves into a massive cluster of galaxies in the local
Universe. This may suggest that massive galaxy formation occurs at the
characteristic place in the surrounding large-scale structure at high redshift.Comment: 11 pages, 3 figures, accepted for publication in ApJ Letter
Implications for the Cosmic Reionization from the Optical Afterglow Spectrum of the Gamma-Ray Burst 050904 at z = 6.3
The gamma-ray burst (GRB) 050904 at z = 6.3 provides the first opportunity of
probing the intergalactic medium (IGM) by GRBs at the epoch of the
reionization. Here we present a spectral modeling analysis of the optical
afterglow spectrum taken by the Subaru Telescope, aiming to constrain the
reionization history. The spectrum shows a clear damping wing at wavelengths
redward of the Lyman break, and the wing shape can be fit either by a damped Ly
alpha system with a column density of log (N_HI/cm^{-2}) ~ 21.6 at a redshift
close to the detected metal absorption lines (z_metal = 6.295), or by almost
neutral IGM extending to a slightly higher redshift of z_{IGM,u} ~ 6.36. In the
latter case, the difference from z_metal may be explained by acceleration of
metal absorbing shells by the activities of the GRB or its progenitor. However,
we exclude this possibility by using the light transmission feature around the
Ly beta resonance, leading to a firm upper limit of z_{IGM,u} < 6.314. We then
show an evidence that the IGM was largely ionized already at z=6.3, with the
best-fit neutral fraction of IGM, x_HI = N_HI/N_H = 0.00, and upper limits of
x_HI < 0.17 and 0.60 at 68 and 95% C.L., respectively. This is the first direct
and quantitative upper limit on x_HI at z > 6. Various systematic uncertainties
are examined, but none of them appears large enough to change this conclusion.
To get further information on the reionization, it is important to increase the
sample size of z >~ 6 GRBs, in order to find GRBs with low column densities
(log N_HI <~ 20) within their host galaxies, and for statistical studies of Ly
alpha line emission from host galaxies.Comment: Matches the published version in PASJ. The version with full
resolution figures is available upon request to Totani or at
http://www.kusastro.kyoto-u.ac.jp/~totani/up/grb050904-paper2-astroph-v3.pd
DNA secondary structure is influenced by genetic variation and alters susceptibility to de novo translocation
<p>Abstract</p> <p><b>Background</b></p> <p>Cumulative evidence suggests that DNA secondary structures impact DNA replication, transcription and genomic rearrangements. One of the best studied examples is the recurrent constitutional t(11;22) in humans that is mediated by potentially cruciform-forming sequences at the breakpoints, palindromic AT-rich repeats (PATRRs). We previously demonstrated that polymorphisms of PATRR sequences affect the frequency of <it>de novo </it>t(11;22)s in sperm samples from normal healthy males. These studies were designed to determine whether PATRR polymorphisms affect DNA secondary structure, thus leading to variation in translocation frequency.</p> <p><b>Methods</b></p> <p>We studied the potential for DNA cruciform formation for several PATRR11 polymorphic alleles using mobility shift analysis in gel electrophoresis as well as by direct visualization of the DNA by atomic force microscopy. The structural data for various alleles were compared with the frequency of <it>de novo </it>t(11;22)s the allele produced.</p> <p><b>Results</b></p> <p>The data indicate that the propensity for DNA cruciform structure of each polymorphic allele correlates with the frequency of <it>de novo </it>t(11;22)s produced (r = 0.77, <it>P </it>= 0.01).</p> <p><b>Conclusions</b></p> <p>Although indirect, our results strongly suggest that the PATRR adopts unstable cruciform structures during spermatogenesis that act as translocation hotspots in humans.</p
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