667 research outputs found
Large-Scale CO Maps of the Lupus Molecular Cloud Complex
Fully sampled degree-scale maps of the 13CO 2-1 and CO 4-3 transitions toward
three members of the Lupus Molecular Cloud Complex - Lupus I, III, and IV -
trace the column density and temperature of the molecular gas. Comparison with
IR extinction maps from the c2d project requires most of the gas to have a
temperature of 8-10 K. Estimates of the cloud mass from 13CO emission are
roughly consistent with most previous estimates, while the line widths are
higher, around 2 km/s. CO 4-3 emission is found throughout Lupus I, indicating
widespread dense gas, and toward Lupus III and IV. Enhanced line widths at the
NW end and along the edge of the B228 ridge in Lupus I, and a coherent velocity
gradient across the ridge, are consistent with interaction between the
molecular cloud and an expanding HI shell from the Upper-Scorpius subgroup of
the Sco-Cen OB Association. Lupus III is dominated by the effects of two HAe/Be
stars, and shows no sign of external influence. Slightly warmer gas around the
core of Lupus IV and a low line width suggest heating by the
Upper-Centaurus-Lupus subgroup of Sco-Cen, without the effects of an HI shell.Comment: 54 pages, 27 figures, 5 tables. To appear in ApJS. Preprint also
available (with full-size figures) from
http://www.astro.ex.ac.uk/people/nfht/publications.html Datacubes available
from http://www.astro.ex.ac.uk/people/nfht/resources.htm
Emergence and rapid global dissemination of CTX-M-15-associated Klebsiella pneumoniae strain ST307
Abstract Recent reports indicate the emergence of a new carbapenemase producing Klebsiella pneumoniae clone, ST307. Here we show that ST307 emerged in the mid-1990s (nearly 20 years prior to its first report), is already globally distributed and is intimately associated with a conserved plasmid harbouring the bla CTX-M-15 extended-spectrum beta-lactamase (ESBL) gene plus other antimicrobial resistance determinants. Our findings support the need for enhanced surveillance of this widespread ESBL clone in which carbapenem resistance is now emerging
Crystal Structure of a PCP/Sfp Complex Reveals the Structural Basis for Carrier Protein Posttranslational Modification
SummaryPhosphopantetheine transferases represent a class of enzymes found throughout all forms of life. From a structural point of view, they are subdivided into three groups, with transferases from group II being the most widespread. They are required for the posttranslational modification of carrier proteins involved in diverse metabolic pathways. We determined the crystal structure of the group II phosphopantetheine transferase Sfp from Bacillus in complex with a substrate carrier protein in the presence of coenzyme A and magnesium, and observed two protein-protein interaction sites. Mutational analysis showed that only the hydrophobic contacts between the carrier protein’s second helix and the C-terminal domain of Sfp are essential for their productive interaction. Comparison with a similar structure of a complex of human proteins suggests that the mode of interaction is highly conserved in all domains of life
The ZEUS Forward Plug Calorimeter with Lead-Scintillator Plates and WLS Fiber Readout
A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built
as a shashlik lead-scintillator calorimeter with wave length shifter fiber
readout. Before installation it was tested and calibrated using the X5 test
beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in
the momentum range of 10 to 100 GeV/c were used. Results of these measurements
are presented as well as a calibration monitoring system based on a Co
source.Comment: 38 pages (Latex); 26 figures (ps
The Role of Regulated mRNA Stability in Establishing Bicoid Morphogen Gradient in Drosophila Embryonic Development
The Bicoid morphogen is amongst the earliest triggers of differential spatial pattern of gene expression and subsequent cell fate determination in the embryonic development of Drosophila. This maternally deposited morphogen is thought to diffuse in the embryo, establishing a concentration gradient which is sensed by downstream genes. In most model based analyses of this process, the translation of the bicoid mRNA is thought to take place at a fixed rate from the anterior pole of the embryo and a supply of the resulting protein at a constant rate is assumed. Is this process of morphogen generation a passive one as assumed in the modelling literature so far, or would available data support an alternate hypothesis that the stability of the mRNA is regulated by active processes? We introduce a model in which the stability of the maternal mRNA is regulated by being held constant for a length of time, followed by rapid degradation. With this more realistic model of the source, we have analysed three computational models of spatial morphogen propagation along the anterior-posterior axis: (a) passive diffusion modelled as a deterministic differential equation, (b) diffusion enhanced by a cytoplasmic flow term; and (c) diffusion modelled by stochastic simulation of the corresponding chemical reactions. Parameter estimation on these models by matching to publicly available data on spatio-temporal Bicoid profiles suggests strong support for regulated stability over either a constant supply rate or one where the maternal mRNA is permitted to degrade in a passive manner
Measurement of the cross-section ratio sigma_{psi(2S)}/sigma_{J/psi(1S)} in deep inelastic exclusive ep scattering at HERA
The exclusive deep inelastic electroproduction of and
at an centre-of-mass energy of 317 GeV has been studied with the ZEUS
detector at HERA in the kinematic range GeV,
GeV and GeV, where is the photon virtuality, is the
photon-proton centre-of-mass energy and is the squared four-momentum
transfer at the proton vertex. The data for GeV were taken in
the HERA I running period and correspond to an integrated luminosity of 114
pb. The data for GeV are from both HERA I and HERA II
periods and correspond to an integrated luminosity of 468 pb. The decay
modes analysed were and for the
and for the . The cross-section ratio
has been measured as a function of
and . The results are compared to predictions of QCD-inspired
models of exclusive vector-meson production.Comment: 24 pages, 8 figure
Detection of the 205 um [NII] Line from the Carina Nebula
We report the first detection of the 205 um 3P1 - 3P0 [NII] line from a
ground-based observatory using a direct detection spectrometer. The line was
detected from the Carina star formation region using the South Pole Imaging
Fabry-Perot Interferometer (SPIFI) on the Antarctic Submillimeter Telescope and
Remote Observatory (AST/RO) at South Pole. The [NII] 205 um line strength
indicates a low-density (n ~ 32 cm^-3 ionized medium, similar to the
low-density ionized halo reported previously in its [OIII] 52 and 88 um line
emission. When compared with the ISO [CII] observations of this region, we find
that ~27% of the [CII] line emission arises from this low-density ionized gas,
but the large majority ~ 73% of the observed [CII] line emission arises from
the neutral interstellar medium. This result supports and underpins prior
conclusions that most of the observed [CII] 158 um line emission from Galactic
and extragalactic sources arises from the warm, dense photodissociated surfaces
of molecular clouds. The detection of the [NII] line demonstrates the utility
of Antarctic sites for THz spectroscopy.Comment: 8 pages, 2 figures. To appear in the Astrophysical Journal Letter
Limits on the effective quark radius from inclusive scattering at HERA
The high-precision HERA data allows searches up to TeV scales for Beyond the
Standard Model contributions to electron-quark scattering. Combined
measurements of the inclusive deep inelastic cross sections in neutral and
charged current scattering corresponding to a luminosity of around 1
fb have been used in this analysis. A new approach to the beyond the
Standard Model analysis of the inclusive data is presented; simultaneous
fits of parton distribution functions together with contributions of "new
physics" processes were performed. Results are presented considering a finite
radius of quarks within the quark form-factor model. The resulting 95% C.L.
upper limit on the effective quark radius is cm.Comment: 10 pages, 4 figures, accepted by Phys. Lett.
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