150 research outputs found
Combined sterno-clavicular approach as an alternative technique in hybrid exclusion of aortic arch aneurysm
<p>Abstract</p> <p>Background</p> <p>We describe a modified access technique for the proximal (open) part of single stage hybrid exclusion of aneurysm of the aortic arch.</p> <p>Case presentation</p> <p>3 patients had a bifurcated Dacron graft for the innominate and left subclavian arteries and an additional end-to-side anastomosis of the left common carotid artery on the limb to the left subclavian artery. With our modification, access to the left subclavian artery is by left subclavicular incision and creation of an anterior tunnel via the left thoracic outlet from the origin of the left subclavian artery along its anatomical course to the subclavicular plane.</p> <p>Discussion</p> <p>Advantages and disadvantages of this technique in relation to anatomy and pathology.</p
Hybridization in parasites: consequences for adaptive evolution, pathogenesis and public health in a changing world
[No abstract available
Exclusive Photoproduction of the Cascade (Xi) Hyperons
We report on the first measurement of exclusive Xi-(1321) hyperon
photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The
final state is identified by the missing mass in p(gamma,K+ K+)X measured with
the CLAS detector at Jefferson Laboratory. We have detected a significant
number of the ground-state Xi-(1321)1/2+, and have estimated the total cross
section for its production. We have also observed the first excited state
Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss
the possibilities of a search for the recently proposed Xi5-- and Xi5+
pentaquarks.Comment: submitted to Phys. Rev.
A Powerful Test of Parent-of-Origin Effects for Quantitative Traits Using Haplotypes
Imprinting is an epigenetic phenomenon where the same alleles have unequal transcriptions and thus contribute differently to a trait depending on their parent of origin. This mechanism has been found to affect a variety of human disorders. Although various methods for testing parent-of-origin effects have been proposed in linkage analysis settings, only a few are available for association analysis and they are usually restricted to small families and particular study designs. In this study, we develop a powerful maximum likelihood test to evaluate the parent-of-origin effects of SNPs on quantitative phenotypes in general family studies. Our method incorporates haplotype distribution to take advantage of inter-marker LD information in genome-wide association studies (GWAS). Our method also accommodates missing genotypes that often occur in genetic studies. Our simulation studies with various minor allele frequencies, LD structures, family sizes, and missing schemes have uniformly shown that using the new method significantly improves the power of detecting imprinted genes compared with the method using the SNP at the testing locus only. Our simulations suggest that the most efficient strategy to investigate parent-of-origin effects is to recruit one parent and as many offspring as possible under practical constraints. As a demonstration, we applied our method to a dataset from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) to test the parent-of-origin effects of the SNPs within the PPARGC1A, MTP and FABP2 genes on diabetes-related phenotypes, and found that several SNPs in the MTP gene show parent-of-origin effects on insulin and glucose levels
Search for the pentaquark in the reaction
A search for the \thp in the reaction was completed
using the CLAS detector at Jefferson Lab. A study of the same reaction,
published earlier, reported the observation of a narrow \thp resonance. The
present experiment, with more than 30 times the integrated luminosity of our
earlier measurement, does not show any evidence for a narrow pentaquark
resonance. The angle-integrated upper limit on \thp production in the mass
range of 1.52 to 1.56 GeV/c for the reaction is
0.3 nb (95% CL). This upper limit depends on assumptions made for the mass and
angular distribution of \thp production. Using \lamstar production as an
empirical measure of rescattering in the deuteron, the cross section upper
limit for the elementary reaction is estimated to be
a factor of 10 higher, {\it i.e.}, nb (95% CL).Comment: 5 figures, submitted to PRL, revised for referee comment
Onset of asymptotic scaling in deuteron photodisintegration
We investigate the transition from the nucleon-meson to quark-gluon
description of the strong interaction using the photon energy dependence of the
differential cross section for photon energies above 0.5 GeV and
center-of-mass proton angles between and . A possible
signature for this transition is the onset of cross section scaling
with the total energy squared, , at some proton transverse momentum, .
The results show that the scaling has been reached for proton transverse
momentum above about 1.1 GeV/c. This may indicate that the quark-gluon regime
is reached above this momentum.Comment: Accepted by PRL; 5 pages, 2 figure
Observation of an Exotic Baryon with S=+1 in Photoproduction from the Proton
The reaction was studied at Jefferson Lab using a
tagged photon beam with an energy range of 3-5.47 GeV. A narrow baryon state
with strangeness S=+1 and mass MeV/c was observed in the
invariant mass spectrum. The peak's width is consistent with the CLAS
resolution (FWHM=26 MeV/c), and its statistical significance is 7.8
1.0 ~. A baryon with positive strangeness has exotic structure and
cannot be described in the framework of the naive constituent quark model. The
mass of the observed state is consistent with the mass predicted by a chiral
soliton model for the baryon. In addition, the invariant mass
distribution was analyzed in the reaction with high
statistics in search of doubly-charged exotic baryon states. No resonance
structures were found in this spectrum.Comment: 5 pages, 5 figures, add reference
Photodisintegration of He into p+t
The two-body photodisintegration of He into a proton and a triton has
been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson
Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system
in the energy range from 0.35 to 1.55 GeV were incident on a liquid He
target. This is the first measurement of the photodisintegration of He
above 0.4 GeV. The differential cross sections for the He
reaction have been measured as a function of photon-beam energy and
proton-scattering angle, and are compared with the latest model calculations by
J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the
calculations that include three-body mechanisms, thus confirming their
importance. These results reinforce the conclusion of our previous study of the
three-body breakup of He that demonstrated the great importance of
three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22
postscrip figure
Hyperon Photoproduction in the Nucleon Resonance Region
Cross-sections and recoil polarizations for the reactions gamma + p --> K^+ +
Lambda and gamma + p --> K^+ + Sigma^0 have been measured with high statistics
and with good angular coverage for center-of-mass energies between 1.6 and 2.3
GeV. In the K^+Lambda channel we confirm a structure near W=1.9 GeV at backward
kaon angles, but our data shows a more complex s- and u- channel resonance
structure than previously seen. This structure is present at forward and
backward angles but not central angles, and its position and width change with
angle, indicating that more than one resonance is playing a role. Rising
back-angle cross sections at higher energies and large positive polarization at
backward angles are consistent with sizable s- or u-channel contributions. None
of the model calculations we present can consistently explain these aspects of
the data.Comment: 5 pages, 3 figures, submitted to Physical Review Letter
photoproduction on the proton for photon energies from 0.675 to 2.875 GeV
Differential cross sections for the reaction have been
measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged
photon beam with energies from 0.675 to 2.875 GeV. The results reported here
possess greater accuracy in the absolute normalization than previous
measurements. They disagree with recent CB-ELSA measurements for the process at
forward scattering angles. Agreement with the SAID and MAID fits is found below
1 GeV. The present set of cross sections has been incorporated into the SAID
database, and exploratory fits have been extended to 3 GeV. Resonance couplings
have been extracted and compared to previous determinations.Comment: 18 pages, 48 figure
- …