94 research outputs found
A nucleonic NJL model for finite nuclei: dynamic mass generation and ground-state observables
We test the compatibility of chiral symmetry, dynamic mass generation of the
nucleon due to spontaneous breaking of chiral symmetry, and the description of
finite nuclear systems by employing an NJL model understood as a chiral
invariant effective theory for nucleons. We apply the model to nuclear matter
as well as to finite nuclei. In the latter case, the model is adjusted to
nuclear ground-state observables. We treat the case of a pure chiral theory and
the physically more realistic case where a portion of the nucleon mass (160
MeV) explicitly breaks chiral symmetry. The best version of this current model
is found to deliver reasonably good results simultaneously for both finite
nuclei and the nucleon mass, which supports our motivation of probing a link
between low-momentum QCD and the nuclear many-body problem. However, the
observables calculated for finite nuclei are not as good as those coming from
existing relativistic mean field models without explicit chiral symmetry.Comment: 19 pages, 3 eps figures, accepted for publication in Nucl. Phys.
Isotope effects in the harmonic response from hydrogenlike muonic atoms in strong laser fields
High-harmonic generation from hydrogenlike muonic atoms exposed to
ultraintense high-frequency laser fields is calculated. Systems of low nuclear
charge number Z are considered where a nonrelativistic description applies. By
comparing the radiative response for different isotopes we demonstrate
characteristic signatures of the finite nuclear mass and size in the harmonic
spectra. In particular, for Z>1, an effective muon charge appears in the
Schr\"odinger equation for the relative particle motion, which influences the
position of the harmonic cutoff. Cutoff energies in the MeV domain can be
achieved, offering prospects for the generation of ultrashort coherent
gamma-ray pulses.Comment: 11 pages, 5 figure
Criteria for nonlinear parameters of relativistic mean field models
Based on the properties of the critical and the actual effective masses of
sigma and omega mesons, criteria to estimate the values of the isoscalar
nonlinear terms of the standard relativistic mean field model that reproduce
stable equations of state in respect to particle hole excitation at high
densities are derived. The relation between nuclear matter stability and the
symmetric nuclear matter properties are shown. The criteria are used to analyze
in a more systematic way the high-density longitudinal and transverse
instabilities of some parameter sets of relativistic mean field models. The
critical role of the vector and vector-scalar nonlinear terms is also discussed
quantitatively.Comment: 21 pages, 10 figures, 4 tables. Accepted for Publication in Physical
review
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Vacuum, matter, antimatter and the problem of cold compression
We discuss the possibility of producing a new kind of nuclear system by putting a few antibaryons inside ordinary nuclei. The structure of such systems is calculated within the relativistic mean-field model assuming that the nucleon and antinucleon potentials are related by the G-parity transformation. The presence of antinucleons leads to decreasing vector potential and increasing scalar potential for the nucleons. As a result, a strongly bound system of high density is formed. Due to the significant reduction of the available phase space the annihilation probability might be strongly suppressed in such systems
Collective modes of asymmetric nuclear matter in Quantum HadroDynamics
We discuss a fully relativistic Landau Fermi liquid theory based on the
Quantum Hadro-Dynamics () effective field picture of Nuclear Matter
({\it NM}).
From the linearized kinetic equations we get the dispersion relations of the
propagating collective modes. We focus our attention on the dynamical effects
of the interplay between scalar and vector channel contributions. A beautiful
``mirror'' structure in the form of the dynamical response in the
isoscalar/isovector degree of freedom is revealed, with a complete parallelism
in the role respectively played by the compressibility and the symmetry energy.
All that strongly supports the introduction of an explicit coupling to the
scalar-isovector channel of the nucleon-nucleon interaction. In particular we
study the influence of this coupling (to a -meson-like effective field)
on the collective response of asymmetric nuclear matter (). Interesting
contributions are found on the propagation of isovector-like modes at normal
density and on an expected smooth transition to isoscalar-like oscillations at
high baryon density. Important ``chemical'' effects on the neutron-proton
structure of the mode are shown. For dilute we have the isospin
distillation mechanism of the unstable isoscalar-like oscillations, while at
high baryon density we predict an almost pure neutron wave structure of the
propagating sounds.Comment: 18 pages (LATEX), 8 Postscript figures, uses "epsfig
Effect of tensor couplings in a relativistic Hartree approach for finite nuclei
The relativistic Hartree approach describing the bound states of both
nucleons and anti-nucleons in finite nuclei has been extended to include tensor
couplings for the - and -meson. After readjusting the parameters
of the model to the properties of spherical nuclei, the effect of
tensor-coupling terms rises the spin-orbit force by a factor of 2, while a
large effective nucleon mass sustains. The overall
nucleon spectra of shell-model states are improved evidently. The predicted
anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.Comment: 31 pages, 4 postscript figures include
The HDAC inhibitor SAHA improves depressive-like behavior of CRTC1-deficient mice: Possible relevance for treatment-resistant depression.
Major depression is a highly complex disabling psychiatric disorder affecting millions of people worldwide. Despite the availability of several classes of antidepressants, a substantial percentage of patients are unresponsive to these medications. A better understanding of the neurobiology of depression and the mechanisms underlying antidepressant response is thus critically needed. We previously reported that mice lacking CREB-regulated transcription coactivator 1 (CRTC1) exhibit a depressive-like phenotype and a blunted antidepressant response to the selective serotonin reuptake inhibitor fluoxetine. In this study, we similarly show that Crtc1(-/-) mice are resistant to the antidepressant effect of chronic desipramine in a behavioral despair paradigm. Supporting the blunted response to this tricyclic antidepressant, we found that desipramine does not significantly increase the expression of Bdnf and Nr4a1-3 in the hippocampus and prefrontal cortex of Crtc1(-/-) mice. Epigenetic regulation of neuroplasticity gene expression has been associated with depression and antidepressant response, and histone deacetylase (HDAC) inhibitors have been shown to have antidepressant-like properties. Here, we show that unlike conventional antidepressants, chronic systemic administration of the HDAC inhibitor SAHA partially rescues the depressive-like behavior of Crtc1(-/-) mice. This behavioral effect is accompanied by an increased expression of Bdnf, but not Nr4a1-3, in the prefrontal cortex of these mice, suggesting that this epigenetic intervention restores the expression of a subset of genes by acting downstream of CRTC1. These findings suggest that CRTC1 alterations may be associated with treatment-resistant depression, and support the interesting possibility that targeting HDACs may be a useful therapeutic strategy in antidepressant development
Alcohol drinking and risk of Parkinson's disease: a case-control study in Japan
<p>Abstract</p> <p>Background</p> <p>Although some epidemiologic studies found inverse associations between alcohol drinking and Parkinson's disease (PD), the majority of studies found no such significant associations. Additionally, there is only limited research into the possible interactions of alcohol intake with aldehyde dehydrogenase (ALDH) 2 activity with respect to PD risk. We examined the relationship between alcohol intake and PD among Japanese subjects using data from a case-control study.</p> <p>Methods</p> <p>From 214 cases within 6 years of PD onset and 327 controls without neurodegenerative disease, we collected information on "peak", as opposed to average, alcohol drinking frequency and peak drinking amounts during a subject's lifetime. Alcohol flushing status was evaluated via questions, as a means of detecting inactive ALHD2. The multivariate model included adjustments for sex, age, region of residence, smoking, years of education, body mass index, alcohol flushing status, presence of selected medication histories, and several dietary factors.</p> <p>Results</p> <p>Alcohol intake during peak drinking periods, regardless of frequency or amount, was not associated with PD. However, when we assessed daily ethanol intake separately for each type of alcohol, only Japanese sake (rice wine) was significantly associated with PD (adjusted odds ratio of â„66.0 g ethanol per day: 3.39, 95% confidence interval: 1.10-11.0, <it>P </it>for trend = 0.001). There was no significant interaction of alcohol intake with flushing status in relation to PD risk.</p> <p>Conclusions</p> <p>We did not find significant associations between alcohol intake and PD, except for the daily amount of Japanese sake. Effect modifications by alcohol flushing status were not observed.</p
Statistical approach for supernova matter
We formulate a statistical model for description of nuclear composition and
equation of state of stellar matter at subnuclear densities and temperature up
to 20 MeV, which are expected during the collapse and explosion of massive
stars. The model includes nuclear, electromagnetic and weak interactions
between all kinds of particles, under condition of statistical equilibrium. We
emphasize importance of realistic description of the nuclear composition for
understanding stellar dynamics and nucleosynthesis. It is demonstrated that the
experience accumulated in studies of nuclear multifragmentation reactions can
be used for better modelling properties of stellar medium.Comment: 35 pages including 23 figures, submitted to Nuclear Physics
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