1,428 research outputs found
Discovery of a New Quadruple Lens HST 1411+5211
Gravitational lensing is an important tool for probing the mass distribution
of galaxies. In this letter we report the discovery of a new quadruple lens HST
1411+5211 found in archived WFPC2 images of the galaxy cluster CL140933+5226.
If the galaxy is a cluster member then its redshift is . The images of
the source appear unresolved in the WFC implying that the source is a quasar.
We have modeled the lens as both a single galaxy and a galaxy plus a cluster.
The latter model yields excellent fits to the image positions along with
reasonable parameters for the galaxy and cluster making HST 1411+5211 a likely
gravitational lens. Determination of the source redshift and confirmation of
the lens redshift would allow us to put strong constraints on the mass
distribution of the lensing galaxy.Comment: 11 pages including 1 postscript figure, aastex. Accepted to the ApJL.
Also available from:
http://www.astro.lsa.umich.edu:80/users/philf/www/papers/list.htm
Unusual Behavior of Antiferromagnetic Superconductors in Low Magnetic Fields
In this article, we examine the superconducting properties of low- and
high- magnetic superconductors in magnetic fields close to the first
penetration field. Attention is paid to the properties that relate to the
interactions between antiferromagnetism and superconductivity. It is suggested
that several features characterizing the interplay between magnetic and
superconducting subsystems in low- superconductors can also be present in
high- materials, however, they have not been observed for any
non-substituted antiferromagnetic superconductors of the Y123 type. For the
GdBaCuO compound, a peak in the temperature
dependence of the ac susceptibility has been found for near the
N\'{e}el temperature of the Gd sublattice. This peak is attributed to the
suppression of superconducting persistent currents due to the pair breaking
effect that results from the enhanced magnetic fluctuations in the vicinity of
the phase transition temperature. This observation indicates that the
interaction between magnetic and conducting electrons is present for the
composition with , where magnetism is enhanced and superconductivity
diminished.Comment: To be published in Physica C; 14 pages, 7 figure
Computationally motivated synthesis and enzyme kinetic evaluation of N-(β-d-glucopyranosyl)-1,2,4-triazolecarboxamides as glycogen phosphorylase inhibitors
Following our recent study of N-(β-D-glucopyranosyl)-oxadiazole-carboxamides (Polyák et al., Biorg. Med. Chem. 2013, 21, 5738) revealed as moderate inhibitors of glycogen phosphorylase (GP), in silico docking calculations using Glide have been performed on N-(β-D-glucopyranosyl)-1,2,4-triazolecarboxamides with different aryl substituents predicting more favorable binding at GP. The ligands were subsequently synthesized in moderate yields using N-(2,3,4,6-terta-O-acetyl-β-D-glucopyranosyl)-tetrazole-5-carboxamide as starting material. Kinetics experiments against rabbit muscle glycogen phosphorylase b (RMGPb) revealed the ligands to be low µM GP inhibitors; the phenyl analogue (Ki = 1 µM) is one of the most potent N-(β-D-glucopyranosyl)-heteroaryl-carboxamide-type inhibitors of the GP catalytic site discovered to date. Based on QM and QM/MM calculations, the potency of the ligands is predicted to arise from favorable intra- and intermolecular hydrogen bonds formed by the most stable solution phase tautomeric (t2) state of the 1,2,4-triazole in a conformationally dynamic system. ADMET property predictions revealed the compounds to have promising pharmacokinetic properties without any toxicity. This study highlights the benefits of a computationally lead approach to GP inhibitor design
Constraining the Chemical Signatures and the Outburst Mechanism of the Class 0 Protostar HOPS 383
We present observations toward HOPS 383, the first known outbursting Class 0
protostar located within the Orion molecular cloud using ALMA, VLA, and SMA.
The SMA observations reveal envelope scale continuum and molecular line
emission surrounding HOPS 383 at 0.85 mm, 1.1 mm, and 1.3 mm. The images show
that HCO and HCO peaks on or near the continuum, while
NH is reduced at the same position. This reflects the underlying
chemistry where CO evaporating close to the protostar destroys NH while
forming HCO. We also observe the molecular outflow traced by CO () and (). A disk is resolved in the ALMA
0.87 mm dust continuum, orthogonal to the outflow direction, with an apparent
radius of 62 AU. Radiative transfer modeling of the continuum gives disk
masses of 0.02 M when fit to the ALMA visibilities. The models
including VLA 8 mm data indicate that the disk mass could be up to a factor of
10 larger due to lower dust opacity at longer wavelengths. The disk temperature
and surface density profiles from the modeling, and an assumed protostar mass
of 0.5 M suggest that the Toomre parameter before the
outburst, making gravitational instability a viable mechanism to explain
outbursts at an early age if the disk is sufficiently massive.Comment: Accepted by Ap
Learning object relationships which determine the outcome of actions
Peer reviewedPublisher PD
AEGIS at CERN: Measuring Antihydrogen Fall
The main goal of the AEGIS experiment at the CERN Antiproton Decelerator is
the test of fundamental laws such as the Weak Equivalence Principle (WEP) and
CPT symmetry. In the first phase of AEGIS, a beam of antihydrogen will be
formed whose fall in the gravitational field is measured in a Moire'
deflectometer; this will constitute the first test of the WEP with antimatter.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
iGentifier: indexing and large-scale profiling of unknown transcriptomes
Development and refinement of methods to analyse differential gene expression has been essential in the progress of molecular biology. A novel approach called iGentifier is presented for profiling known and unknown transcriptomes, thus bypassing a major limitation in microarray analysis. The iGentifier technology combines elements of fragment display (e.g. Differential Display or RMDD) and tag sequencing (e.g. SAGE, MPSS) and allows for analysis of samples in high throughput using current capillary electrophoresis equipment. Application to epidermal tissue of wild-type and mlo5 barley (Hordeum vulgare) plants, infected with powdery mildew [Blumeria graminis (DC.) E.O. Speer f.sp.hordei], led to the identification of several 100 genes induced or repressed upon infection with many well known for their response to fungal pathogens or other stressors. Ten of these genes are suggested to be classified as marker genes for durable resistance mediated by the mlo5 resistance gene
Combining habitat loss and agricultural intensification improves our understanding of drivers of change in avian abundance in a North American cropland anthrome
Shear-Induced Unfolding Activates von Willebrand Factor A2 Domain for Proteolysis
To avoid pathological platelet aggregation by von Willebrand factor (VWF),
VWF multimers are regulated in size and reactivity for adhesion by
ADAMTS13-mediated proteolysis in a shear flow dependent manner. We examined if
tensile stress in VWF under shear flow activates the VWF A2 domain for cleavage
by ADAMTS13 using molecular dynamics simulations. We indeed observed stepwise
unfolding of A2 and exposure of its deeply buried ADAMTS13 cleavage site.
Interestingly, disulfide bonds in the adjacent and highly homologous VWF A1 and
A3 domains obstruct their mechanical unfolding. We generated a full length
mutant VWF featuring a homologous disulfide bond in A2 (N1493C and C1670S), in
an attempt to lock A2 against unfolding. We find this mutant to feature
ADAMTS13-resistant behavior in vitro. Our results yield molecular-detail
evidence for the force-sensoring function of VWF A2, by revealing how tension
in VWF due to shear flow selectively exposes the A2 proteolysis site to
ADAMTS13 for cleavage while keeping the folded remainder of A2 intact and
functional. We find the unconventional knotted Rossman fold of A2 to be the key
to this mechanical response, tailored for regulating VWF size and activity.
Based on our model we can explain the pathomechanism of some natural mutations
in the VWF A2 domain that significantly increase the cleavage by ADAMTS13
without shearing or chemical denaturation, and provide with the
cleavage-activated A2 conformation a structural basis for the design of
inhibitors for VWF type 2 diseases
Socially Meaningful Vocal Plasticity in Adult Campbell's Monkeys (Cercopithecus campbelli).
- …