Short-range correlations in low-lying nuclear excited states

The electromagnetic transitions to various low-lying excited states of 16O, 48Ca and 208Pb are calculated within a model which considers the short-range correlations. In general the effects of the correlations are small and do not explain the required quenching to describe the data.Comment: 6 pages, 2 postscript figures, 1 tabl

Recovery and creative practices in people with severe mental illness: evaluating well-being and social inclusion

Purpose: This mixed (quantitative-qualitative) study evaluates the impact of an artistic workshop on a group of people with severe mental illness. This study focuses on the impact of creative practices on well-being and social inclusion outcomes. Method: After participating in a creative workshop, 31 people diagnosed with a severe mental illness completed pre/post-intervention measures, namely, the Warwick-Edinburgh Mental Well-Being Scale and the Social Inclusion questionnaire. It was applied in two-way repeated measures analysis of variance. The statistic Wilcoxon and Kruskal-Wallies were applied for non-parametric data to measure pre/post-test effects and workshop experience effects respectively. In addition to quantitative measures, one observer participated in each workshop that ran in parallel in order to deepen and triangulate quantitative outcomes. Results: The qualitative and quantitative results show that social inclusion improved in a significant way with an important size effect. Psychological wellbeing increased significantly with a low size effect. Conclusions: In accordance with these results, creative practices with people diagnosed with severe mental illness are recommended. In order to increase the impact of these interventions, it is recommended to utilize public space away from clinical environments and to include people without severe mental illness in creative activities together with severe mental illness patients

Effects of Short-Range Correlations in (e,e'p) reactions and nuclear overlap functions

A study of the effects of short-range correlations over the (e,e'p) reaction for low missing energy in closed shell nuclei is presented. We use correlated, quasi-hole overlap functions extracted from the asymptotic behavior of the one-body density matrix, containing central correlations of Jastrow type, up to first-order in a cluster expansion, and computed in the very high asymptotic region, up to 100 fm. The method to extract the overlap functions is checked in a simple shell model, where the exact results are known. We find that the single-particle wave functions of the valence shells are shifted to the right due to the short-range repulsion by the nuclear core. The corresponding spectroscopic factors are reduced only a few percent with respect to the shell model. However, the (e,e'p) response functions and cross sections are enhanced in the region of the maximum of the missing momentum distribution due to short-range correlations.Comment: 45 pages, 15 figure

Polarization discontinuity induced two-dimensional electron gas at ZnO/Zn(Mg)O interfaces: A first-principles study

The discovery of a high-mobility two-dimensional electron gas (2DEG) in wurtzite ZnO/Zn(Mg)O heterostructures is promising for applications due to the high mobility of the carriers. In this paper, we study the formation and properties of the 2DEG at ZnO/Zn(Mg)O interfaces using first-principles calculations based on hybrid density functional theory. The 2DEG arises from the polarization discontinuity at the interface between the two materials. The uncompensated bound charge at the interface gives rise to an electric field in the bulk of ZnO which confines free carriers close to the interface. We find that the type of the confined carriers is determined by the interface termination, while the amount of charge and the confinement width could be controlled by the Mg doping and the device dimensions

Ferromagnetic transition of a two-component Fermi gas of Hard Spheres

We use microscopic many-body theory to analyze the problem of itinerant ferromagnetism in a repulsive atomic Fermi gas of Hard Spheres. Using simple arguments, we show that the available theoretical predictions for the onset of the ferromagnetic transition predict a transition point at a density ($k_F a \sim 1$) that is too large to be compatible with the universal low-density expansion of the energy. We present new variational calculations for the hard-sphere Fermi gas, in the framework of Fermi hypperneted chain theory, that shift the transition to higher densities ($k_F a \sim 1.8$). Backflow correlations, which are mainly active in the unpolarized system, are essential for this shift

Epithermal neutron beams from the 7Li(p,n) reaction near the threshold for neutron capture therapy

Two applications for neutron capture therapy of epithermal neutron beams calculated from the 7Li(p,n) reaction are discussed. In particular, i) for a proton beam of 1920 keV of a 30 mA, a neutron beam of adequate features for BNCT is found at an angle of 80◦ from the forward direction; and ii) for a proton beam of 1910 keV, a neutron beam is obtained at the forward direction suitable for performing radiobiology experiments for the determination of the biological weighting factors of the fast dose component in neutron capture therapy

Biexciton oscillator strength

Our goal is to provide a physical understanding of the elementary coupling between photon and biexciton and to derive the physical characteristics of the biexciton oscillator strength, following the procedure we used for trion. Instead of the more standard two-photon absorption, this work concentrates on molecular biexciton created by photon absorption in an exciton gas. We first determine the appropriate set of coordinates in real and momentum spaces to describe one biexciton as two interacting excitons. We then turn to second quantization and introduce the "Fourier transform in the exciton sense" of the biexciton wave function which is the relevant quantity for oscillator strength. We find that, like for trion, the oscillator strength for the formation of one biexciton out of one photon plus a \emph{single} exciton is extremely small: it is one biexciton volume divided by one sample volume smaller than the exciton oscillator strength. However, due to their quantum nature, trion and biexciton have absorption lines which behave quite differently. Electrons and trions are fermionic particles impossible to pile up all at the same energy. This would make the weak trion line spread with electron density, the peak structure only coming from singular many-body effects. By contrast, the bosonic nature of exciton and biexciton makes the biexciton peak mainly rise with exciton density, this rise being simply linear if we forget many-body effects between the photocreated exciton and the excitons present in the sample

Two-nucleon emission in the longitudinal response

The contribution of the two-nucleon emission in the longitudinal response for inclusive electron scattering reactions is studied. The model adopted to perform the calculations is based upon Correlated Basis Function theory but it considers only first order terms in the correlation function. The proper normalization of the wave function is ensured by considering, in addition to the usually evaluated two-point diagrams, also the three-point diagrams. Results for the 12C nucleus in the quasi-elastic region are presented.Comment: 7 pages, 4 Postscript figure

Effects of state dependent correlations on nucleon density and momentum distributions

The proton momentum and density distributions of closed shell nuclei are calculated within a model treating short--range correlations up to first order in the cluster expansion. The validity of the model is verified by comparing the results obtained with purely scalar correlations with those produced by finite nuclei Fermi Hypernetted Chain calculations. State dependent correlations are used to calculate momentum and density distributions of 12C, 16O, 40Ca, and 48Ca, and the effects of their tensor components are studied.Comment: 16 pages, latex, 8 figures, accepted for publication in Phys. Rev.