740 research outputs found
The role of the serotonin transporter in prefrontal cortex glutamatergic signaling following short- and long-access cocaine self-administration
n/
Ground state properties of exotic nuclei near Z=40 in the relativistic mean-field theory,
Study of the ground-state properties of Kr, Sr and Zr isotopes has been
performed in the framework of the relativistic mean field (RMF) theory using
the recently proposed relativistic parameter set NL-SH. It is shown that the
RMF theory provides an unified and excellent description of the binding
energies, isotope shifts and deformation properties of nuclei over a large
range of isospin in the Z=40 region. It is observed that the RMF theory with
the force NL-SH is able to describe the anomalous kinks in isotope shifts in Kr
and Sr nuclei, the problem which has hitherto remained unresolved. This is in
contrast with the density-dependent Skyrme Hartree-Fock approach which does not
reproduce the behaviour of the isotope shifts about shell closure. On the Zr
chain we predict that the isotope shifts exhibit a trend similar to that of the
Kr and Sr nuclei. The RMF theory also predicts shape coexistence in heavy Sr
isotopes. Several dramatic shape transitions in the isotopic chains are shown
to be a general feature of nuclei in this region. A comparison of the
properties with the available mass models shows that the results of the RMF
theory are generally in accord with the predictions of the finite-range droplet
model.Comment: 24 pages Latex, 7 figures (available upon request), Nuclear Physics A
(in press)
An approach to construct wave packets with complete classical-quantum correspondence in non-relativistic quantum mechanics
We introduce a method to construct wave packets with complete classical and
quantum correspondence in one-dimensional non-relativistic quantum mechanics.
First, we consider two similar oscillators with equal total energy. In
classical domain, we can easily solve this model and obtain the trajectories in
the space of variables. This picture in the quantum level is equivalent with a
hyperbolic partial differential equation which gives us a freedom for choosing
the initial wave function and its initial slope. By taking advantage of this
freedom, we propose a method to choose an appropriate initial condition which
is independent from the form of the oscillators. We then construct the wave
packets for some cases and show that these wave packets closely follow the
whole classical trajectories and peak on them. Moreover, we use de-Broglie Bohm
interpretation of quantum mechanics to quantify this correspondence and show
that the resulting Bohmian trajectories are also in a complete agreement with
their classical counterparts.Comment: 15 pages, 13 figures, to appear in International Journal of
Theoretical Physic
Using social network sites in Higher Education: An experience in business studies
In the past 5 years the impact of Web 2.0 in new generations has been remarkably significant (Pew Research Center, 2010). This paper reports on an experience in the use of Social Network Sites (SNS) to support student involvement with the subject and to develop basic skills.
According to students’ opinion, the experience was deemed as positive. They considered that the experience contributed to a higher engagement with the subject and a deeper collaboration with other students and teaching staff. As a result, the majority of students would prefer the use of SNS as a first option if they had to enrol again in the subject.
Regarding the relationships between academic performance and use of the SNS, two different student profiles were identified based on usage patterns of the platform. Students with a more intensive use of the site showed a significantly better performance than students with a low usage profile.This work was partially supported by the Junta de Andalucía – FEDER (Proyectos de Excelencia: SEJ-02670
Surprises in the Orbital Magnetic Moment and g-Factor of the Dynamic Jahn-Teller Ion C_{60}^-
We calculate the magnetic susceptibility and g-factor of the isolated
C_{60}^- ion at zero temperature, with a proper treatment of the dynamical
Jahn-Teller effect, and of the associated orbital angular momentum, Ham-reduced
gyromagnetic ratio, and molecular spin-orbit coupling. A number of surprises
emerge. First, the predicted molecular spin-orbit splitting is two orders of
magnitude smaller than in the bare carbon atom, due to the large radius of
curvature of the molecule. Second, this reduced spin-orbit splitting is
comparable to Zeeman energies, for instance, in X-band EPR at 3.39KGauss, and a
field dependence of the g-factor is predicted. Third, the orbital gyromagnetic
factor is strongly reduced by vibron coupling, and so therefore are the
effective weak-field g-factors of all low-lying states. In particular, the
ground-state doublet of C_{60}^- is predicted to show a negative g-factor of
\sim -0.1.Comment: 19 pages RevTex, 2 postscript figures include
Quantum Computing and Quantum Simulation with Group-II Atoms
Recent experimental progress in controlling neutral group-II atoms for
optical clocks, and in the production of degenerate gases with group-II atoms
has given rise to novel opportunities to address challenges in quantum
computing and quantum simulation. In these systems, it is possible to encode
qubits in nuclear spin states, which are decoupled from the electronic state in
the S ground state and the long-lived P metastable state on the
clock transition. This leads to quantum computing scenarios where qubits are
stored in long lived nuclear spin states, while electronic states can be
accessed independently, for cooling of the atoms, as well as manipulation and
readout of the qubits. The high nuclear spin in some fermionic isotopes also
offers opportunities for the encoding of multiple qubits on a single atom, as
well as providing an opportunity for studying many-body physics in systems with
a high spin symmetry. Here we review recent experimental and theoretical
progress in these areas, and summarise the advantages and challenges for
quantum computing and quantum simulation with group-II atoms.Comment: 11 pages, 7 figures, review for special issue of "Quantum Information
Processing" on "Quantum Information with Neutral Particles
Many body physics from a quantum information perspective
The quantum information approach to many body physics has been very
successful in giving new insight and novel numerical methods. In these lecture
notes we take a vertical view of the subject, starting from general concepts
and at each step delving into applications or consequences of a particular
topic. We first review some general quantum information concepts like
entanglement and entanglement measures, which leads us to entanglement area
laws. We then continue with one of the most famous examples of area-law abiding
states: matrix product states, and tensor product states in general. Of these,
we choose one example (classical superposition states) to introduce recent
developments on a novel quantum many body approach: quantum kinetic Ising
models. We conclude with a brief outlook of the field.Comment: Lectures from the Les Houches School on "Modern theories of
correlated electron systems". Improved version new references adde
Search for heavy neutrinos mixing with tau neutrinos
We report on a search for heavy neutrinos (\nus) produced in the decay
D_s\to \tau \nus at the SPS proton target followed by the decay \nudecay in
the NOMAD detector. Both decays are expected to occur if \nus is a component
of .\
From the analysis of the data collected during the 1996-1998 runs with
protons on target, a single candidate event consistent with
background expectations was found. This allows to derive an upper limit on the
mixing strength between the heavy neutrino and the tau neutrino in the \nus
mass range from 10 to 190 . Windows between the SN1987a and Big Bang
Nucleosynthesis lower limits and our result are still open for future
experimental searches. The results obtained are used to constrain an
interpretation of the time anomaly observed in the KARMEN1 detector.\Comment: 20 pages, 7 figures, a few comments adde
Feeding strategies and energy to protein ratio on tambaqui performance and physiology
The objective of this work was to evaluate the effect of feed deprivation and refeeding with diets containing different energy to protein ratios (E/P) on the performance and physiology of juvenile tambaqui (Colossoma macropomum). A 4x2 factorial arrangement with three replicates was used, with four E/P ratios (11.5, 10.5, 9.5, and 8.5 kcal g-1 digestible energy per protein) and two feeding regimens (with and without deprivation), during 60 days. Fish from the food-deprived group were fasted for 14 days and refed from the fifteenth to the sixtieth day, whereas the remaining fish were fed for 60 days. At the end of the experimental period, weight of fish subjected to food deprivation was lower than that of those continuously fed; however, this condition did not influence the physiological parameters analyzed. Tambaqui fed 11.5 kcal g-1 achieved lower final weight than those fed with the other diets, in both regimens. Among the physiological parameters, only plasma protein presented significant increase in fish fed 8.5 kcal g-1, in both feeding regimens, probably due to the higher dietary protein concentration. These results indicate that fish show a partial compensatory growth, and that 10.5 kcal g-1 can be recommended for the diet of juvenile tambaqui
- …