81 research outputs found
Nuclear medium modifications of the NN interaction via quasielastic () and () scattering
Within the relativistic PWIA, spin observables have been recalculated for
quasielastic () and () reactions on a Ca
target. The incident proton energy ranges from 135 to 300 MeV while the
transferred momentum is kept fixed at 1.97 fm^{-1}. In the present
calculations, new Horowitz-Love--Franey relativistic NN amplitudes have been
generated in order to yield improved and more quantitative spin observable
values than before. The sensitivities of the various spin observables to the NN
interaction parameters, such as (1) the presence of the surrounding nuclear
medium, (2) a pseudoscalar versus a pseudovector interaction term, and (3)
exchange effects, point to spin observables which should preferably be measured
at certain laboratory proton energies, in order to test current nuclear models.
This study also shows that nuclear medium effects become more important at
lower proton energies ( 200 MeV). A comparison to the limited available
data indicates that the relativistic parametrization of the NN scattering
amplitudes in terms of only the five Fermi invariants (the SVPAT form) is
questionable.Comment: 10 pages, 6 Postscript figures, uses psfig.sty and article.sty,
submitted to Phys. Rev.
Gamma ray production cross sections in proton induced reactions on natural Mg, Si and Fe targets over the proton energy range 30 up to 66 MeV
Gamma-ray excitation functions have been measured for 30, 42, 54 and 66 MeV
proton beams accelerated onto C + O (Mylar), Mg, Si, and Fe targets of
astrophysical interest at the separate-sector cyclotron of iThemba LABS in
Somerset West (Cape Town, South Africa). A large solid angle, high energy
resolution detection system of the Eurogam type was used to record Gamma-ray
energy spectra. Derived preliminary results of Gamma-ray line production cross
sections for the Mg, Si and Fe target nuclei are reported and discussed. The
current cross section data for known, intense Gamma-ray lines from these nuclei
consistently extend to higher proton energies previous experimental data
measured up to Ep ~ 25 MeV at the Orsay and Washington tandem accelerators.
Data for new Gamma-ray lines observed for the first time in this work are also
reported.Comment: 11 pages, 6 figures. IOP Institute of Physics Conference Nuclear
Physics in Astrophysics VII, 28th EPF Nuclear Physics Divisional Conference,
May 18-22 2015, York, U
Structural insight into African horsesickness virus infection
African horsesickness (AHS) is a devastating disease of horses. The disease is caused by the double-stranded RNA-containing African horsesickness virus (AHSV). Using electron cryomicroscopy and three-dimensional image reconstruction, we determined the architecture of an AHSV serotype 4 (AHSV-4) reference strain. The structure revealed triple-layered AHS virions enclosing the segmented genome and transcriptase complex. The innermost protein layer contains 120 copies of VP3, with the viral polymerase, capping enzyme, and helicase attached to the inner surface of the VP3 layer on the 5-fold axis, surrounded by double-stranded RNA. VP7 trimers form a second, T 13 layer on top of VP3. Comparative analyses of the structures of bluetongue virus and AHSV-4 confirmed that VP5 trimers form globular domains and VP2 trimers form triskelions, on the virion surface. We also identified an AHSV-7 strain with a truncated VP2 protein (AHSV-7 tVP2) which outgrows AHSV-4 in culture. Comparison of AHSV-7 tVP2 to bluetongue virus and AHSV-4 allowed mapping of two domains in AHSV-4 VP2, and one in bluetongue virus VP2, that are important in infection. We also revealed a protein plugging the 5-fold vertices in AHSV-4. These results shed light on virus-host interactions in an economically important orbivirus to help the informed design of new vaccines
Comparison of double-folding effective interactions within the cluster model
CITATION: Kaya, B. D. C. K., et al. 2018. Comparison of double-folding effective interactions within the cluster model. Physical Review C, 98(4):044308, doi:10.1103/PhysRevC.98.044308.The original publication is available at https://journals.aps.org/prcCluster-core hybrid potentials with Woods-Saxon plus cubic terms have been constructed to account for both
the decay properties and positive-parity ground-state bands in 212Po, 218Rn, 222Ra, and 228Th. The hybrid potential
parameters have been extracted from the real part of the double-folding interaction using the realistic Michigan-
3-Yukawa (M3Y) and a complex Gaussian effective interactions. We find that both the effective interactions
exhibit similar behavior in the internal region, and the agreement between our estimated results with the existing
experimental data is satisfactory.https://journals.aps.org/prc/abstract/10.1103/PhysRevC.98.044308Publisher's versio
Relativistic predictions of spin observables for exclusive proton knockout reactions
Within the framework of the relativistic distorted wave impulse approximation
(DWIA), we investigate the sensitivity of complete sets of polarization
transfer observables for exclusive proton knockout from the 3s,
2d and 2d states in Pb, at an incident laboratory
kinetic energy of 202 MeV, and for coincident coplanar scattering angles
(, ), to different distorting optical potentials,
finite-range (FR) versus zero-range (ZR) approximations to the DWIA, as well as
medium-modified meson-nucleon coupling constants and meson masses. Results are
also compared to the nonrelativistic DWIA predictions based on the
Schr\"{o}dinger equation.Comment: Submitted for publication to Physicical Review C, 23 pages, 7 figure
The detection and isolation of a paralysis toxin present in Argas (Persicargas) walkerae
One-day-old leghorn chickens were used in a laboratory assay to determine the toxicity of crude extracts of the tick Argas (Persicargas) walkerae and of fractions obtained during the isolation procedure. Extracts of unfed and engorged larvae, nymphae and females were tested using this in vivo test system. Only extracts of replete A. (P.) walkerae larvae produced paralysis.
A toxic fraction was isolated from replete larval extracts by gel-permeation and ion-exchange chromatography. This fraction with a pI of 4,5 showed 2 major bands corresponding to a Mᵣ of 32 kDa and 60 kDa after SDS-polyacrylamide gel electrophoresis.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
System size and centrality dependence of charged hadron transverse momentum spectra in Au+Au and Cu+Cu collisions at sqrt(s) = 62.4 and 200 GeV
We present transverse momentum distributions of charged hadrons produced in
Cu+Cu collisions at sqrt(s) = 62.4 and 200 GeV. The spectra are measured for
transverse momenta of 0.25 < p_T < 5.0 GeV/c at sqrt(s) = 62.4 GeV and 0.25 <
p_T < 7.0 GeV/c at sqrt(s) = 200 GeV, in a pseudo-rapidity range of 0.2 < eta <
1.4. The nuclear modification factor R_AA is calculated relative to p+p data at
both collision energies as a function of collision centrality. At a given
collision energy and fractional cross-section, R_AA is observed to be
systematically larger in Cu+Cu collisions compared to Au+Au. However, for the
same number of participating nucleons, R_AA is essentially the same in both
systems over the measured range of p_T, in spite of the significantly different
geometries of the Cu+Cu and Au+Au systems.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
System Size, Energy and Centrality Dependence of Pseudorapidity Distributions of Charged Particles in Relativistic Heavy Ion Collisions
We present the first measurements of the pseudorapidity distribution of
primary charged particles in Cu+Cu collisions as a function of collision
centrality and energy, \sqrtsnn = 22.4, 62.4 and 200 GeV, over a wide range of
pseudorapidity, using the PHOBOS detector. Making a global comparison of Cu+Cu
and Au+Au results, we find that the total number of produced charged particles
and the rough shape (height and width) of the pseudorapidity distributions are
determined by the number of nucleon participants. More detailed studies reveal
that a more precise matching of the shape of the Cu+Cu and Au+Au pseudorapidity
distributions over the full range of pseudorapidity occurs for the same
Npart/2A value rather than the same Npart value. In other words, it is the
collision geometry rather than just the number of nucleon participants that
drives the detailed shape of the pseudorapidity distribution and its centrality
dependence at RHIC energies.Comment: Submitted to Physical Review Letter
Identified charged antiparticle to particle ratios near midrapidity in Cu+Cu collisions at sqrt(s) = 62.4 and 200 GeV
Antiparticle to particle ratios for identified protons, kaons and pions at
sqrt(s) = 62.4 and 200 GeV in Cu+Cu collisions are presented as a function of
centrality for the midrapidity region of 0.2 < eta < 1.4. No strong dependence
on centrality is observed. For the / ratio at ~ 0.51 GeV/c, we
observe an average value of 0.50 +/- 0.003_(stat) +/- 0.04_(syst) and 0.77 +/-
0.008_(stat) +/- 0.05_(syst) for the 10% most central collisions of 62.4 and
200 GeV Cu+Cu, respectively. The values for all three particle species measured
at sqrt(s) = 200 GeV are in agreement within systematic uncertainties with that
seen in both heavier and lighter systems measured at the same RHIC energy. This
indicates that system size does not appear to play a strong role in determining
the midrapidity chemical freeze-out properties affecting the antiparticle to
particle ratios of the three most abundant particle species produced in these
collisions.Comment: 5 Pages, 4 figures Made changes to the figures to include the panel
numbers. Slight changes to the text. Updated data points from other
experiment
Cluster properties from two-particle angular correlations in p+p collisions at = 200 and 410 GeV
We present results on two-particle angular correlations in proton-proton
collisions at center of mass energies of 200 and 410 GeV. The PHOBOS experiment
at the Relativistic Heavy Ion Collider has a uniquely large coverage for
charged particles, giving the opportunity to explore the correlations at both
short- and long-range scales. At both energies, a complex two-dimensional
correlation structure in and is observed. In the
context of an independent cluster model of short-range correlations, the
cluster size and its decay width are extracted from the two-particle
pseudorapidity correlation function and compared with previous measurements in
proton-proton and proton-antiproton collisions, as well as PYTHIA and HIJING
predictions.Comment: 10 pages, 10 figures, submitted to Phys. Rev.
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