93 research outputs found
Alternative Linear Chiral Models for Nuclear Matter
The equation of state of a family of alternative linear chiral models in the
mean field approximation is discussed. We investigate the analogy between some
of these models with current models in the literature, and we show that it is
possible to reproduce very well the saturation properties of nuclear matter.Comment: 11 pages in Latex, 4 ps figures include
Hadronic Entropy Enhancement and Low Density QGP
Recent studies show that for central collisions the rising of the incident
energy from AGS to RHIC decreases the value of the chemical potential in the
Hadron-QGP phase diagram. Thus, the formation of QGP at RHIC energies in
central collisions may be expected to occur at very small values of the
chemical potential. Using many different relativistic mean-field hadronic
models (RMF) at this regime we show that the critical temperature for the
Hadron-QGP transition is hadronic model independent. We have traced back the
reason for this and conclude that it comes from the fact that the QGP entropy
is much larger than the hadronic entropy obtained in all the RMF models. We
also find that almost all of these models present a strong entropy enhancement
in the hadronic sector coming from the baryonic phase transition to a
nucleon-antinucleon plasma. This result is in agreement with the recent data
obtained in the STAR collaboration at RHIC where it was found a rich
proton-antiproton matter
Neutron Star Constraints on the H Dibaryon
We study the influence of a possible H dibaryon condensate on the equation of
state and the overall properties of neutron stars whose population otherwise
contains nucleons and hyperons. In particular, we are interested in the
question of whether neutron stars and their masses can be used to say anything
about the existence and properties of the H dibaryon. We find that the equation
of state is softened by the appearance of a dibaryon condensate and can result
in a mass plateau for neutron stars. If the limiting neutron star mass is about
that of the Hulse-Taylor pulsar a condensate of H dibaryons of vacuum mass 2.2
GeV and a moderately attractive potential in the medium could not be ruled out.
On the other hand, if the medium potential were even moderately repulsive, the
H, would not likely exist in neutron stars. If neutron stars of about 1.6 solar
mass were known to exist, attractive medium effects for the H could be ruled
out. Certain ranges of dibaryon mass and potential can be excluded by the mass
of the Hulse-Taylor pulsar which we illustrate graphically.Comment: Revised by the addition of a figure showing the region of dibaryon
mass and potential excluded by the Hulse-Taylor pulsar. 18 pages, 11 figures,
latex (submitted to Phys. Rev. C
QCD Sum Rules for Hyperons in Nuclear Matter
Within finite-density QCD sum-rule approach we investigate the self-energies
of hyperons propagating in nuclear matter from a correlator of
interpolating fields evaluated in the nuclear matter ground state. We
find that the Lorentz vector self-energy of the is similar to the
nucleon vector self-energy. The magnitude of Lorentz scalar self-energy of the
is also close to the corresponding value for nucleon; however, this
prediction is sensitive to the strangeness content of the nucleon and to the
assumed density dependence of certain four-quark condensate. The scalar and
vector self-energies tend to cancel, but not completely. The implications for
the couplings of to the scalar and vector mesons in nuclear matter and
for the spin-orbit force in a finite nucleus are discussed.Comment: 20 pages in revtex, 6 figures available under request as ps files,
UMD preprint #94--11
MYORG-related disease is associated with central pontine calcifications and atypical parkinsonism
Objective: To identify the phenotypic, neuroimaging, and genotype-phenotype expression of MYORG mutations. Methods: Using next-generation sequencing, we screened 86 patients with primary familial brain calcification (PFBC) from 60 families with autosomal recessive or absent family history that were negative for mutations in SLC20A2, PDGFRB, PDGBB, and XPR1. In-depth phenotyping and neuroimaging investigations were performed in all cases reported here. Results: We identified 12 distinct deleterious MYORG variants in 7 of the 60 families with PFBC. Overall, biallelic MYORG mutations accounted for 11.6% of PFBC families in our cohort. A heterogeneous phenotypic expression was identified within and between families with a median age at onset of 56.4 years, a variable combination of parkinsonism, cerebellar signs, and cognitive decline. Psychiatric disturbances were not a prominent feature. Cognitive assessment showed impaired cognitive function in 62.5% of cases. Parkinsonism associated with vertical nuclear gaze palsy was the initial clinical presentation in 1/3 of cases and was associated with central pontine calcifications. Cerebral cortical atrophy was present in 37% of cases. Conclusions: This large, multicentric study shows that biallelic MYORG mutations represent a significant proportion of autosomal recessive PFBC. We recommend screening MYORG mutations in all patients with primary brain calcifications and autosomal recessive or negative family history, especially when presenting clinically as atypical parkinsonism and with pontine calcification on brain CT
- …