432 research outputs found
Extragenic suppressor mutations in ΔripA disrupt stability and function of LpxA
Background: Francisella tularensis is a Gram-negative bacterium that infects hundreds of species including humans, and has evolved to grow efficiently within a plethora of cell types. RipA is a conserved membrane protein of F. tularensis, which is required for growth inside host cells. As a means to determine RipA function we isolated and mapped independent extragenic suppressor mutants in ΔripA that restored growth in host cells. Each suppressor mutation mapped to one of two essential genes, lpxA or glmU, which are involved in lipid A synthesis. We repaired the suppressor mutation in lpxA (S102, LpxA T36N) and the mutation in glmU (S103, GlmU E57D), and demonstrated that each mutation was responsible for the suppressor phenotype in their respective strains. We hypothesize that the mutation in S102 altered the stability of LpxA, which can provide a clue to RipA function. LpxA is an UDP-N-acetylglucosamine acyltransferase that catalyzes the transfer of an acyl chain from acyl carrier protein (ACP) to UDP-N-acetylglucosamine (UDP-GlcNAc) to begin lipid A synthesis. Results: LpxA was more abundant in the presence of RipA. Induced expression of lpxA in the ΔripA strain stopped bacterial division. The LpxA T36N S102 protein was less stable and therefore less abundant than wild type LpxA protein. Conclusion: These data suggest RipA functions to modulate lipid A synthesis in F. tularensis as a way to adapt to the host cell environment by interacting with LpxA
Astroparticle Physics with a Customized Low-Background Broad Energy Germanium Detector
The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg
array of high purity germanium detectors housed in an ultra-low background
shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA
DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while
demonstrating the feasibility of a tonne-scale experiment. It may also carry
out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that
customized Broad Energy Germanium (BEGe) detectors produced by Canberra have
several desirable features for a neutrinoless double-beta decay experiment,
including low electronic noise, excellent pulse shape analysis capabilities,
and simple fabrication. We have deployed a customized BEGe, the MAJORANA
Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and
shield at the Kimballton Underground Research Facility in Virginia. This paper
will focus on the detector characteristics and measurements that can be
performed with such a radiation detector in a low-background environment.Comment: Submitted to NIMA Proceedings, SORMA XII. 9 pages, 4 figure
Review debate: we need human rights not nationalism 'lite': globalization and British solidarity
The article explores the relationship of multiculturalism to social solidarity. The multicultural nature of Britain is accepted as a welcome reality but certain problems in relation to the development of multiculturalism in Britain are acknowledged. Various approaches to buttress or replace multiculturalism are reviewed. These are: a strengthened and/or reconstituted nationalism (`Britishness'); human rights; and social equality. The issue of citizenship recurs throughout. It is argued that a combined emphasis on human rights and greater social equality offer a better basis than nationalism for strengthening solidarity in Britain, especially in the longer term. Sociological theory offers a fruitful if strangely neglected starting point for understanding social solidarity. I draw critically on Durkheim and Marx to obtain some objective perspective on this controversial matter. Copyright 2007 SAGE Publications. All rights reserved. Not for commercial use or unauthorized distribution
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Search for W' bosons decaying to an electron and a neutrino with the D0 detector
This Letter describes the search for a new heavy charged gauge boson W'
decaying into an electron and a neutrino. The data were collected with the D0
detector at the Fermilab Tevatron proton-antiproton Collider at a
center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity
of about 1 inverse femtobarn. Lacking any significant excess in the data in
comparison with known processes, an upper limit is set on the production cross
section times branching fraction, and a W' boson with mass below 1.00 TeV can
be excluded at the 95% C.L., assuming standard-model-like couplings to
fermions. This result significantly improves upon previous limits, and is the
most stringent to date.Comment: submitted to Phys. Rev. Let
Search for a scalar or vector particle decaying into Zgamma in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for a narrow scalar or vector resonance decaying into
Zgamma with a subsequent Z decay into a pair of electrons or muons. The data
for this search were collected with the D0 detector at the Fermilab Tevatron
ppbar collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0)
fb-1 of data, we observe 49 (50) candidate events in the electron (muon)
channel, in good agreement with the standard model prediction. From the
combination of both channels, we derive 95% C.L. upper limits on the cross
section times branching fraction (sigma x B) into Zgamma. These limits range
from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c^2 to 2.5
(3.1) pb for a mass of 140 GeV/c^2.Comment: Published by Phys. Lett.
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
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