73 research outputs found
Levinson's Theorem for Non-local Interactions in Two Dimensions
In the light of the Sturm-Liouville theorem, the Levinson theorem for the
Schr\"{o}dinger equation with both local and non-local cylindrically symmetric
potentials is studied. It is proved that the two-dimensional Levinson theorem
holds for the case with both local and non-local cylindrically symmetric cutoff
potentials, which is not necessarily separable. In addition, the problems
related to the positive-energy bound states and the physically redundant state
are also discussed in this paper.Comment: Latex 11 pages, no figure, submitted to J. Phys. A Email:
[email protected], [email protected]
The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model
We study the short-range nucleon-nucleon interaction in a chiral constituent
quark model by diagonalizing a Hamiltonian comprising a linear confinement and
a Goldstone boson exchange interaction between quarks. The six-quark harmonic
oscillator basis contains up to two excitation quanta. We show that the highly
dominant configuration is due to its specific
flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a
strong effective repulsion at zero separation between nucleons in both
and channels. The symmetry structure of the highly dominant
configuration implies the existence of a node in the S-wave relative motion
wave function at short distances. The amplitude of the oscillation of the wave
function at short range will be however strongly suppressed. We discuss the
mechanism leading to the effective short-range repulsion within the chiral
constituent quark model as compared to that related with the one-gluon exchange
interaction.Comment: 31 pages, LaTe
Phase structures of strong coupling lattice QCD with finite baryon and isospin density
Quantum chromodynamics (QCD) at finite temperature (T), baryon chemical
potential (\muB) and isospin chemical potential (\muI) is studied in the strong
coupling limit on a lattice with staggered fermions. With the use of large
dimensional expansion and the mean field approximation, we derive an effective
action written in terms of the chiral condensate and pion condensate as a
function of T, \muB and \muI. The phase structure in the space of T and \muB is
elucidated, and simple analytical formulas for the critical line of the chiral
phase transition and the tricritical point are derived. The effects of a finite
quark mass (m) and finite \muI on the phase diagram are discussed. We also
investigate the phase structure in the space of T, \muI and m, and clarify the
correspondence between color SU(3) QCD with finite isospin density and color
SU(2) QCD with finite baryon density. Comparisons of our results with those
from recent Monte Carlo lattice simulations on finite density QCD are given.Comment: 18 pages, 6 figures, revtex4; some discussions are clarified, version
to appear in Phys. Rev.
Infective endocarditis caused by Salmonella enteritidis in a dialysis patient: a case report and literature review
BackgroundInfective endocarditis is significantly more common in haemodialysis patients as compared with the general population, the causative pathogen is generally Staphylococcus aureus; there have been no previously reported cases of infective endocarditis caused by a Salmonella species in haemodialysis patients.Case presentationWe report the case of a 68 year-old woman on haemodialysis who developed infective endocarditis as a result of Salmonella enteritidis. Although we treated the patient with ceftriaxone combined with ciprofloxacin, infective endocarditis was not detected early enough and unfortunately developed into cerebral septic emboli, which ultimately resulted in death.ConclusionAlthough there are several reports that Salmonella endocarditis without cardiac failure can be successfully treated with antibiotics alone, early surgical intervention is essential for some cases to prevent life-threatening complications. Transesophageal echocardiography should be performed in any patient with high clinical suspicion of infective endocarditis. To the best of our knowledge, this is the first case-report of Salmonella endocarditis in a haemodialysis patient
Morphological correlates to cognitive dysfunction in schizophrenia as studied with Bayesian regression
BACKGROUND: Relationships between cognitive deficits and brain morphological changes observed in schizophrenia are alternately explained by less gray matter in the brain cerebral cortex, by alterations in neural circuitry involving the basal ganglia, and by alteration in cerebellar structures and related neural circuitry. This work explored a model encompassing all of these possibilities to identify the strongest morphological relationships to cognitive skill in schizophrenia. METHODS: Seventy-one patients with schizophrenia and sixty-five healthy control subjects were characterized by neuropsychological tests covering six functional domains. Measures of sixteen brain morphological structures were taken using semi-automatic and fully manual tracing of MRI images, with the full set of measures completed on thirty of the patients and twenty controls. Group differences were calculated. A Bayesian decision-theoretic method identified those morphological features, which best explained neuropsychological test scores in the context of a multivariate response linear model with interactions. RESULTS: Patients performed significantly worse on all neuropsychological tests except some regarding executive function. The most prominent morphological observations were enlarged ventricles, reduced posterior superior vermis gray matter volumes, and increased putamen gray matter volumes in the patients. The Bayesian method associated putamen volumes with verbal learning, vigilance, and (to a lesser extent) executive function, while caudate volumes were associated with working memory. Vermis regions were associated with vigilance, executive function, and, less strongly, visuo-motor speed. Ventricular volume was strongly associated with visuo-motor speed, vocabulary, and executive function. Those neuropsychological tests, which were strongly associated to ventricular volume, showed only weak association to diagnosis, possibly because ventricular volume was regarded a proxy for diagnosis. Diagnosis was strongly associated with the other neuropsychological tests, implying that the morphological associations for these tasks reflected morphological effects and not merely group volumetric differences. Interaction effects were rarely associated, indicating that volumetric relationships to neuropsychological performance were similar for both patients and controls. CONCLUSION: The association of subcortical and cerebellar structures to verbal learning, vigilance, and working memory supports the importance of neural connectivity to these functions. The finding that a morphological indicator of diagnosis (ventricular volume) provided more explanatory power than diagnosis itself for visuo-motor speed, vocabulary, and executive function suggests that volumetric abnormalities in the disease are more important for cognition than non-morphological features
Pairing in nuclear systems: from neutron stars to finite nuclei
We discuss several pairing-related phenomena in nuclear systems, ranging from
superfluidity in neutron stars to the gradual breaking of pairs in finite
nuclei. We focus on the links between many-body pairing as it evolves from the
underlying nucleon-nucleon interaction and the eventual experimental and
theoretical manifestations of superfluidity in infinite nuclear matter and of
pairing in finite nuclei. We analyse the nature of pair correlations in nuclei
and their potential impact on nuclear structure experiments. We also describe
recent experimental evidence that points to a relation between pairing and
phase transitions (or transformations) in finite nuclear systems. Finally, we
discuss recent investigations of ground-state properties of random two-body
interactions where pairing plays little role although the interactions yield
interesting nuclear properties such as 0+ ground states in even-even nuclei.Comment: 74 pages, 33 figs, uses revtex4. Submitted to Reviews of Modern
Physic
Mineral bone disorder in chronic kidney disease: head-to-head comparison of the 5/6 nephrectomy and adenine models
Constraints to Coupling Constants of the Omega- and Sigma-Mesons with Dibaryons
The effect of narrow dibaryon resonances to nuclear matter and structure of
neutron stars is investigated in the mean-field theory (MFT) and in the
relativistic Hartree approximation (RHA). The existence of massive neutron
stars imposes constraints to the coupling constants of the omega- and
sigma-mesons with dibaryons. We conclude that the experimental candidates to
dibaryons d1(1920) and d'(2060) if exist form in nuclear matter a Bose
condensate stable against compression. This proves stability of the ground
state for nuclear matter with a Bose condensate of the light dibaryons.Comment: 10 pages, 6 figure
Four-nucleon scattering with a correlated Gaussian basis method
Elastic-scattering phase shifts for four-nucleon systems are studied in an
- type cluster model in order to clarify the role of the tensor
force and to investigate cluster distortions in low energy and
scattering. In the present method, the description of the cluster wave function
is extended from a simple (0) harmonic-oscillator shell model to a few-body
model with a realistic interaction, in which the wave function of the
subsystems are determined with the Stochastic Variational Method. In order to
calculate the matrix elements of the four-body system, we have developed a
Triple Global Vector Representation method for the correlated Gaussian basis
functions. To compare effects of the cluster distortion with realistic and
effective interactions, we employ the AV8 potential as a realistic
interaction and the Minnesota potential as an effective interaction. Especially
for , the calculated phase shifts show that the and channels
are strongly coupled to the channel for the case of the realistic
interaction. On the contrary, the coupling of these channels plays a relatively
minor role for the case of the effective interaction. This difference between
both potentials originates from the tensor term in the realistic interaction.
Furthermore, the tensor interaction makes the energy splitting of the negative
parity states of He consistent with experiments. No such splitting is
however reproduced with the effective interaction
The Observed Correlations for the Strange Multibaryon States in Systems with -Hyperon from pa Collision at Momentum of 10 Gev/
he observed well-known resonances (1385) and
(892) from PDG are good tests of this method. Exotic strange
multibaryon states have been observed in the effective mass spectra of:
,, , subsystems.
The mean value of mass for resonance is shifted till mass
of 1370 MeV/ and width is two times larger than the same value from PDG.
Such kind of behavior for width and invariant mass of
resonance is interpreted as extensive contribution from stopped
and medium effect with invariant mass. The mean value of
mass for from secondary interactions is also shifted till
mass of 1370 MeV/. The width of is 2 times larger
than the experimental error. There are enhancement production for all observed
hyperons.Comment: 4 pages, 6 figures, XXIst Rencontres de Blois "Windows on the
Universe " Blois, France June 21st - June 26th, 200
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