Bound and unbound nuclear systems at the drip lines: A one-dimensional model

22 págs.; 13 figs.; 1 tab.; 1 app.We construct a one-dimensional toy model to describe the main features of Borromean nuclei at the continuum threshold. The model consists of a core and two valence neutrons, unbound in the mean potential, that are bound by a residual point contact density-dependent interaction. Different discretization procedures are used (harmonic oscillator and transformed harmonic oscillator bases, or use of large rigid wall box). Resulting energies and wave functions, as well as inelastic transition intensities, are compared within the different discretization techniques, as well as with the exact results in the case of one particle and with the results of the di-neutron cluster model in the two particles case. Despite its simplicity, this model includes the main physical features of the structure of Borromean nuclei in an intuitive and computationally affordable framework, and will be extended to direct reaction calculations. © 2016 IOP Publishing Ltd Printed in the UKPart of this work was funded by MINECO grant FIS2014-53448-C2-2-P. LM thanks the University of Huelva, where part of this work was done with the finantial support of the Erasmus Placement program.Peer Reviewe

Cyanobacteria and Cyanotoxin in the Billings Reservoir (Sâo Paulo, SP, Brazil)

The Billings Complex and the Guarapiranga System are important strategic reservoirs for the city of Sâo Paulo and surrounding areas because the water is used, among other things, for the public water supply. They produce 19,000 liters of water per second and supply water to 5.4 million people. Crude water is transferred from the Taquacetuba branch of the Billings Complex to the Guarapiranga Reservoir to regulate the water level of the reservoir. The objective of this study was to evaluate the water quality in the Taquacetuba branch, focusing on cyanobacteria and cyanotoxins. Surface water samples were collected in February (summer) and July (winter) of 2007. Analyses were conducted of physical, chemical, and biological variables of the water, cyanobacteria richness and density, and the presence of cyanotoxins. The water was classified as eutrophic-hypereutrophic. Cyanobacteria blooms were observed in both collection periods. The cyanobacteria bloom was most significant in July, reflecting lower water transparency and higher levels of total solids, suspended organic matter, chlorophyll-a, and cyanobacteria density in the surface water. Low richness and elevated dominance of the cyanobacteria were found in both periods. Cylindrospermopsis raciborskii was dominant in February, with 352 661.0 cel mL−1, and Microcystis panniformis was dominant in July, with 1 866 725.0 cel mL−1. Three variants of microcystin were found in February (MC-RR, MC-LR, MC-YR), as well as saxitoxin. The same variants of microcystin were found in July, but no saxitoxin was detected. Anatoxin-a and cylindropermopsin were not detected in either period. These findings are of great concern because the water in the Taquacetuba branch, which is transferred into the Guarapiranga Reservoir, is not treated nor managed. It is recommended that monitoring be intensified and more effective measures be taken by the responsible agencies to prevent the process of eutrophication and the consequent development of the cyanobacteria and their toxinsEl Complejo Billings y el Sistema Guarapiranga son embalses estratégicos importantes para la ciudad de Sâo Paulo (Brasil) y áreas circundantes porque, entre otras cosas, el agua es utilizada para el abastecimiento público. Este sistema produce 19 mil litros de agua por segundo, que es suministrado a 5.4 millones de personas. El agua bruta es transferida por el afluente Taquacetuba desde el Complejo Billings hacia el Embalse Guarapiranga, para regular el nivel de agua del embalse. El objetivo de este estudio fue evaluar la calidad del agua en el tramo del Taquacetuba, teniendo como foco las cianobacterias y cianotoxinas. El muestreo de agua bruta superficial fue realizado en febrero (verano) y julio (invierno 2007). Fueron analizadas variables físicas, químicas y biológicas, cianobacteria, riqueza, densidad y la presencia de cianotoxinas. El tramo fue clasificado como eutrófico-hipereutrófico. Las cianobacterias fueron observadas en ambos periodos de colecta. El crecimiento más significativo de algas fue observado en julio, reflejando baja transparencia del agua y niveles más altos en el agua superficial de sólidos totales, materia orgánica, clorofila-a y densidad de cianobacterias en el agua superficial. Una baja riqueza y un elevado dominio de cianobacteria fueron encontrados en ambos períodos. Cylindrospermopsis raciborskii fue dominante en febrero, con 352 661.0 cel mL�1, y Microcystis panniformis fue dominante en julio, con 1 866 725.0 cel mL�1. Tres variedades de microcistina fueron encontradas en febrero (MC-RR, MC-LR, MC- YR), as� como saxitoxina. Las mismas variedades de microcistina fueron encontradas en julio, pero ninguna saxitoxina fue observada. Anatoxina-a y cylindropermopsina no fueron observadas en ningún período. Estas conclusiones son preocupantes porque el agua del tramo del Taquacetuba, que es transferida al Embalse Guarapiranga, no es tratada o manejada. Se recomienda intensificar el monitoreo y medidas más eficaces deben ser tomadas por parte de las agencias responsables para prevenir el proceso de eutrofización y el desarrollo consiguiente de cianobacterias y sus toxina

Sharp two-sided heat kernel estimates for critical Schr\"odinger operators on bounded domains

On a smooth bounded domain \Omega \subset R^N we consider the Schr\"odinger operators -\Delta -V, with V being either the critical borderline potential V(x)=(N-2)^2/4 |x|^{-2} or V(x)=(1/4) dist (x,\partial\Omega)^{-2}, under Dirichlet boundary conditions. In this work we obtain sharp two-sided estimates on the corresponding heat kernels. To this end we transform the Scr\"odinger operators into suitable degenerate operators, for which we prove a new parabolic Harnack inequality up to the boundary. To derive the Harnack inequality we have established a serier of new inequalities such as improved Hardy, logarithmic Hardy Sobolev, Hardy-Moser and weighted Poincar\'e. As a byproduct of our technique we are able to answer positively to a conjecture of E.B.Davies.Comment: 40 page

Knockout of proton-neutron pairs from 16^{16}O with electromagnetic probes

After recent improvements to the Pavia model of two-nucleon knockout from $^{16}$O with electromagnetic probes the calculated cross sections are compared to experimental data from such reactions. Comparison with data from a measurement of the $^{16}$O(e,e$'$pn) reaction show much better agreement between experiment and theory than was previously observed. In a comparison with recent data from a measurement of the $^{16}$O($\gamma$,pn) reaction the model over-predicts the measured cross section at low missing momentum.Comment: 6 pages, 5 figure

First measurements of the ^16O(e,e'pn)^14N reaction

This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce the shape or the magnitude of the data.Comment: 10 pages, 11 figures, 2 tables, Accepted for publication in EPJ

Sharp Trace Hardy-Sobolev-Maz'ya Inequalities and the Fractional Laplacian

In this work we establish trace Hardy and trace Hardy-Sobolev-Maz'ya inequalities with best Hardy constants, for domains satisfying suitable geometric assumptions such as mean convexity or convexity. We then use them to produce fractional Hardy-Sobolev-Maz'ya inequalities with best Hardy constants for various fractional Laplacians. In the case where the domain is the half space our results cover the full range of the exponent $s \in (0,1)$ of the fractional Laplacians. We answer in particular an open problem raised by Frank and Seiringer \cite{FS}.Comment: 42 page

Strengths and weaknesses of different italian fish indices under the water framework directive guidelines

The ISECI (or F index) has been the first fish index to be recommended by the Italian Ministry of the Environment to assess the rivers ecological status with regard to fish communities, in accordance with the Water Framework Directive 2000/60 EC. In addition to ISECI, other fish indices have been developed such as the Forneris Ichthyic Index (I.I.) and a revised version of ISECI, the so-called NISECI. The latter is nowadays the reference Italian index in the framework of the Water Framework Directive. In this work, we analyzed 30 sampling sites along 18 watercourses in Northern Italy and computed the results of fish monitoring to evaluate the strength of ISECI and NISECI, as well as to assess weak points limiting their application. We detected several issues that undermine the ISECI effectiveness. The weakest point regarded the mismatch between the expected reference fish community and the sampled ones, which decreased the overall algorithm efficiency in the evaluation process. On the other hand, the results confirm the improvements introduced by NISECI. Although with some advancement, all three proposed indices revealed their weaknesses in the overall assessment of the ecological status of the water course, as also highlighted by a pioneering comparison with three expert-based blind judgements

A Fast, Memory-Efficient Alpha-Tree Algorithm using Flooding and Tree Size Estimation

The alpha-tree represents an image as hierarchical set of alpha-connected components. Computation of alpha-trees suffers from high computational and memory requirements compared with similar component tree algorithms such as max-tree. Here we introduce a novel alpha-tree algorithm using 1) a flooding algorithm for computational efficiency and 2) tree size estimation (TSE) for memory efficiency. In TSE, an exponential decay model was fitted to normalized tree sizes as a function of the normalized root mean squared deviation (NRMSD) of edge-dissimilarity distributions, and the model was used to estimate the optimum memory allocation size for alpha-tree construction. An experiment on 1256 images shows that our algorithm runs 2.27 times faster than Ouzounis and Soille's thanks to the flooding algorithm, and TSE reduced the average memory allocation of the proposed algorithm by 40.4%, eliminating unused allocated memory by 86.0% with a negligible computational cost

Fear avoidance beliefs are associated with reduced lumbar spine flexion during object lifting in pain-free adults

There is a long-held belief that physical activities such as lifting with a flexed spine is generally harmful for the back and can cause low back pain (LBP), potentially reinforcing fear avoidance beliefs underlying pain-related fear. In chronic LBP patients, pain-related fear has been shown to be associated with reduced lumbar range of motion during lifting, suggesting a protective response to pain. However, despite short term beneficial effects for tissue health, recent evidence suggests that maintaining a protective trunk movement strategy may also pose a risk for (persistent) LBP due to possible pro-nociceptive consequences of altered spinal motion, potentially leading to increased loading on lumbar tissues. Yet, it is unknown if similar protective movement strategies already exist in pain-free individuals which would yield potential insights into the role of fear avoidance beliefs in motor behavior in the absence of pain. Therefore, the aim of this study is to test whether fear avoidance beliefs influence spinal motion during lifting in a healthy cohort of pain-free adults without a history of chronic pain. The study subjects (N=57) filled out several pain-related fear questionnaires and were asked to perform a lifting task (5kg-box). High-resolution spinal kinematics were assessed using an optical motion capturing system. Time-sensitive analyses were performed based on statistical parametric mapping. The results demonstrated time-specific and negative relationships between self-report measures of pain-related fear and lumbar spine flexion angles during lifting, indicating potential unfavorable interactions between psychological factors and spinal motion during lifting in pain-free subjects