126 research outputs found
Electric fields in plasmas under pulsed currents
Electric fields in a plasma that conducts a high-current pulse are measured
as a function of time and space. The experiment is performed using a coaxial
configuration, in which a current rising to 160 kA in 100 ns is conducted
through a plasma that prefills the region between two coaxial electrodes. The
electric field is determined using laser spectroscopy and line-shape analysis.
Plasma doping allows for 3D spatially resolved measurements. The measured peak
magnitude and propagation velocity of the electric field is found to match
those of the Hall electric field, inferred from the magnetic-field front
propagation measured previously.Comment: 13 pages, 13 figures, submitted to PR
Status of COLDDIAG: A Cold Vacuum Chamber for Diagnostics
One of the still open issues for the development of superconducting insertion
devices is the understanding of the beam heat load. With the aim of measuring
the beam heat load to a cold bore and the hope to gain a deeper understanding
in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is
under construction. The following diagnostics will be implemented: i) retarding
field analyzers to measure the electron energy and flux, ii) temperature
sensors to measure the total heat load, iii) pressure gauges, iv) and mass
spectrometers to measure the gas content. The inner vacuum chamber will be
removable in order to test different geometries and materials. This will allow
the installation of the cryostat in different synchrotron light sources.
COLDDIAG will be built to fit in a short straight section at ANKA. A first
installation at the synchrotron light source Diamond is foreseen in June 2011.
Here we describe the technical design report of this device and the planned
measurements with beam.Comment: Presented at First International Particle Accelerator Conference,
IPAC'10, Kyoto, Japan, from 23 to 28 May 201
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2
Among the most fundamental observables of nucleon structure, electromagnetic
form factors are a crucial benchmark for modern calculations describing the
strong interaction dynamics of the nucleon's quark constituents; indeed, recent
proton data have attracted intense theoretical interest. In this letter, we
report new measurements of the proton electromagnetic form factor ratio using
the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5
GeV2. By extending the range of Q2 for which GEp is accurately determined by
more than 50%, these measurements will provide significant constraints on
models of nucleon structure in the non-perturbative regime
One-carbon metabolism in cancer
Cells require one-carbon units for nucleotide synthesis, methylation and reductive metabolism, and these pathways support the high proliferative rate of cancer cells. As such, anti-folates, drugs that target one-carbon metabolism, have long been used in the treatment of cancer. Amino acids, such as serine are a major one-carbon source, and cancer cells are particularly susceptible to deprivation of one-carbon units by serine restriction or inhibition of de novo serine synthesis. Recent work has also begun to decipher the specific pathways and sub-cellular compartments that are important for one-carbon metabolism in cancer cells. In this review we summarise the historical understanding of one-carbon metabolism in cancer, describe the recent findings regarding the generation and usage of one-carbon units and explore possible future therapeutics that could exploit the dependency of cancer cells on one-carbon metabolism
Measurements of Non-Singlet Moments of the Nucleon Structure Functions and Comparison to Predictions from Lattice QCD for
We present extractions of the nucleon non-singlet moments utilizing new
precision data on the deuteron structure function at large Bjorken-
determined via the Rosenbluth separation technique at Jefferson Lab
Experimental Hall C. These new data are combined with a complementary set of
data on the proton previously measured in Hall C at similar kinematics and
world data sets on the proton and deuteron at lower measured at SLAC and
CERN. The new Jefferson Lab data provide coverage of the upper third of the
range, crucial for precision determination of the higher moments. In contrast
to previous extractions, these moments have been corrected for nuclear effects
in the deuteron using a new global fit to the deuteron and proton data. The
obtained experimental moments represent an order of magnitude improvement in
precision over previous extractions using high data. Moreover, recent
exciting developments in Lattice QCD calculations provide a first ever
comparison of these new experimental results with calculations of moments
carried out at the physical pion mass, as well as a new approach which first
calculates the quark distributions directly before determining moments
Non-typeable Haemophilus influenzae and Streptococcus pneumoniae as primary causes of acute otitis media in colombian children: a prospective study
<p>Abstract</p> <p>Background</p> <p>Acute otitis media (AOM) is one of the most frequently encountered bacterial infections in children aged < 5 years; <it>Streptococcus pneumoniae </it>(<it>S. pneumoniae</it>) and non-typeable <it>Haemophilus influenzae </it>(NTHi) are historically identified as primary AOM causes. Nevertheless, recent data on bacterial pathogens causing AOM in Latin America are limited. This prospective study aimed to identify and characterize bacterial etiology and serotypes of AOM cases including antimicrobial susceptibility in < 5 year old Colombian children.</p> <p>Methods</p> <p>From February 2008 to January 2009, children ≥3 months and < 5 years of age presenting with AOM and for whom a middle ear fluid (MEF) sample was available were enrolled in two medical centers in Cali, Colombia. MEF samples were collected either by tympanocentesis procedure or spontaneous otorrhea swab sampling. Bacteria were identified using standard laboratory methods, and antimicrobial resistance testing was performed based on the 2009 Clinical and Laboratory Standards Institute (CLSI) criteria. Most of the cases included in the study were sporadic in nature.</p> <p>Results</p> <p>Of the 106 enrolled children, 99 were included in the analysis. Bacteria were cultured from 62/99 (63%) of samples with <it>S. pneumoniae, H. influenzae, or S. pyogenes</it>. The most commonly isolated bacteria were <it>H. influenzae </it>in 31/99 (31%) and <it>S. pneumoniae </it>in 30/99 (30%) of samples. The majority of <it>H. influenzae </it>episodes were NTHi (27/31; 87%). 19F was the most frequently isolated pneumococcal serotype (10/30; 33%). Of the 30 <it>S. pneumoniae </it>positive samples, 8/30 (27%) were resistant to tetracycline, 5/30 (17%) to erythromycin and 8/30 (27%) had intermediate resistance to penicillin. All <it>H. influenzae </it>isolates tested were negative to beta-lactamase.</p> <p>Conclusions</p> <p>NTHi and <it>S. pneumoniae </it>are the leading causes of AOM in Colombian children. A pneumococcal conjugate vaccine that prevents both pathogens could be useful in maximizing protection against AOM.</p
Lysosomal protease deficiency or substrate overload induces an oxidative-stress mediated STAT3-dependent pathway of lysosomal homeostasis
How cells regulate their lysosomal proteolytic capacity is only partly understood. Here, the authors show that lysosomal protease deficiency or substrate overload induces lysosomal stress leading to activation of a STAT3-dependent, TFEB-independent pathway of lysosomal hydrolase expression
Search for effects beyond the Born approximation in polarization transfer observables in elastic scattering
Intensive theoretical and experimental efforts over the past decade have
aimed at explaining the discrepancy between data for the proton electric to
magnetic form factor ratio, , obtained separately from cross
section and polarization transfer measurements. One possible explanation for
this difference is a two-photon-exchange (TPEX) contribution. In an effort to
search for effects beyond the one-photon-exchange or Born approximation, we
report measurements of polarization transfer observables in the elastic
reaction for three different beam energies at a fixed
squared momentum transfer GeV, spanning a wide range of the
virtual photon polarization parameter, . From these measured
polarization observables, we have obtained separately the ratio , which
equals in the Born approximation, and the longitudinal
polarization transfer component , with statistical and systematic
uncertainties of \Delta R \approx \pm 0.01 \mbox{(stat)} \pm 0.013
\mbox{(syst)} and \Delta P_\ell/P^{Born}_{\ell} \approx \pm 0.006
\mbox{(stat)}\pm 0.01 \mbox{(syst)}. The ratio is found to be independent
of at the 1.5% level, while the dependence of
shows an enhancement of relative to the Born approximation at
large
- …