1,155 research outputs found
The Synthesis and Characterization of LiFeAs and NaFeAs
The newest homologous series of superconducting As-pnictides, LiFeAs (Li111)
and NaFeAs (Na111) have been synthesized and investigated. Both crystallize
with the layered tetragonal anti-PbFCl-type structure in P4/nmm space group.
Polycrystalline samples and single-crystals of Li111 and Na111 display
superconducting transitions at ~ 18 K and 12-25 K, respectively. No magnetic
order has been found in either compound, although a weak magnetic background is
clearly in evidence. The origin of the carriers and the stoichiometric
compositions of Li111 and Na111 were explored.Comment: submitted for publication in Physica C special issue on Fe-pnictide
Gastric cancer and Helicobacter pylori: a combined analysis of 12 case control studies nested within prospective cohorts
BACKGROUND: The magnitude of the association
between Helicobacter pylori and
incidence of gastric cancer is unclear. H
pylori infection and the circulating antibody
response can be lost with development
of cancer; thus retrospective studies
are subject to bias resulting from classifi-
cation of cases as H pylori negative when
they were infected in the past.
AIMS: To combine data from all case control
studies nested within prospective
cohorts to assess more reliably the relative
risk of gastric cancer associated with H
pylori infection.To investigate variation in
relative risk by age, sex, cancer type and
subsite, and interval between blood sampling
and cancer diagnosis.
METHODS: Studies were eligible if blood
samples for H pylori serology were collected
before diagnosis of gastric cancer in
cases. Identified published studies and two
unpublished studies were included. Individual
subject data were obtained for
each. Matched odds ratios (ORs) and 95%
confidence intervals (95% CI) were calculated
for the association between H pylori
and gastric cancer.
RESULTS: Twelve studies with 1228 gastric
cancer cases were considered. The association
with H pylori was restricted to noncardia
cancers (OR 3.0; 95% CI 2.3–3.8)
and was stronger when blood samples for
H pylori serology were collected 10+ years
before cancer diagnosis (5.9; 3.4–10.3). H
pylori infection was not associated with an
altered overall risk of cardia cancer (1.0;
0.7–1.4).
CONCLUSIONS: These results suggest that
5.9 is the best estimate of the relative risk
of non-cardia cancer associated with H
pylori infection and that H pylori does not
increase the risk of cardia cancer. They
also support the idea that when H pylori
status is assessed close to cancer diagnosis,
the magnitude of the non-cardia
association may be underestimated
Experimental Critical Current Patterns in Josephson Junction Ladders
We present an experimental and theoretical study of the magnetic field
dependence of the critical current of Josephson junction ladders. At variance
with the well-known case of a one-dimensional (1D) parallel array of Josephson
junctions the magnetic field patterns display a single minimum even for very
low values of the self-inductance parameter . Experiments
performed changing both the geometrical value of the inductance and the
critical current of the junctions show a good agreement with numerical
simulations. We argue that the observed magnetic field patterns are due to a
peculiar mapping between the isotropic Josephson ladder and the 1D parallel
array with the self-inductance parameter .Comment: 4 pages, 4 picture
Isobutyl acetate: electronic state spectroscopy by high-resolution vacuum ultraviolet photoabsorption, He(I) photoelectron spectroscopy and ab initio calculations
The high-resolution vacuum ultraviolet photoabsorption spectrum of isobutyl acetate, C6H12O2, is presented here and was measured over the energy range 4.3–10.8 eV (290–115 nm). Valence and Rydberg transitions with their associated vibronic series have been observed in the photoabsorption spectrum and are assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. The measured photoabsorption cross sections have been used to calculate the photolysis lifetime of this ester in the Earth’s upper atmosphere (20–50 km). Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of isobutyl acetate and are compared with a photoelectron spectrum (from 9.5 to 16.7 eV), recorded for the first time. Vibrational structure is observed in the first photoelectron band of this molecule
Measurement of the decay width of He
We have precisely measured decay width of \5LHe and
demonstrated significantly larger - overlap than expected
from the central repulsion - potential, which is derived from
YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure
Proton asymmetry in non-mesonic weak decay of light hypernuclei
We have obtained the decay asymmetry parameters in non-mesonic weak decay of
polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized
Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in
high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward
angles. Preliminary analysis shows that the decay asymmetry parameters are very
small for these s-shell and p-shell hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and
Strange Particle Physics (HYP2003
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