Magneto-elastic oscillations modulating the emission of magnetars

Magneto-elastic oscillations of neutron stars are believed to explain observed quasi-periodic oscillations (QPOs) in the decaying tail of the giant flares of highly magnetized neutron stars (magnetars). Strong efforts of the theoretical modelling from different groups have increased our understanding of this phenomenon significantly. Here, we discuss some constraints on the matter in neutron stars that arise if the interpretation of the observations in terms of superfluid, magneto-elastic oscillations is correct. To explain the observed modulation of the light curve of the giant flare, we describe a model that allows the QPOs to couple to the stellar exterior through the magnetic field. In this magnetosphere, the shaking magnetic field induces currents that provide scattering targets for resonant cyclotron scattering of photons, which is calculated with a Monte-Carlo approach and coupled to a code that calculates the momentum distribution of the charge carriers as a one-dimensional accelerator problem. We show first results of a simplified, but self-consistent momentum distribution, i.e. a waterbag distribution, and of the corresponding spectra.Comment: 7 pages, 4 figures, proceedings of stars2017 and 2017smfn

Elastic alpha-scattering of 112Sn and 124Sn at astrophysically relevant energies

The cross sections for the elastic scattering reactions {112,124}Sn(a,a){112,124}Sn at energies above and below the Coulomb barrier are presented and compared to predictions for global alpha-nucleus potentials. The high precision of the new data allows a study of the global alpha-nucleus potentials at both the proton and neutron-rich sides of an isotopic chain. In addition, local alpha-nucleus potentials have been extracted for both nuclei, and used to reproduce elastic scattering data at higher energies. Predictions from the capture cross section of the reaction 112Sn(a,g)116Te at astrophysically relevant energies are presented and compared to experimental data.Comment: 20 pages, 10 figures, accepted for publication in Phys. Rev.

Reversible magnetomechanical collapse: virtual touching and detachment of rigid inclusions in a soft elastic matrix

Soft elastic composite materials containing particulate rigid inclusions in a soft elastic matrix are candidates for developing soft actuators or tunable damping devices. The possibility to reversibly drive the rigid inclusions within such a composite together to a close-to-touching state by an external stimulus would offer important benefits. Then, a significant tuning of the mechanical properties could be achieved due to the resulting mechanical hardening. For a long time, it has been argued whether a virtual touching of the embedded magnetic particles with subsequent detachment can actually be observed in real materials, and if so, whether the process is reversible. Here, we present experimental results that demonstrate this phenomenon in reality. Our system consists of two paramagnetic nickel particles embedded at finite initial distance in a soft elastic polymeric gel matrix. Magnetization in an external magnetic field tunes the magnetic attraction between the particles and drives the process. We quantify the scenario by different theoretical tools, i.e., explicit analytical calculations in the framework of linear elasticity theory, a projection onto simplified dipole-spring models, as well as detailed finite-element simulations. From these different approaches, we conclude that in our case the cycle of virtual touching and detachment shows hysteretic behavior due to the mutual magnetization between the paramagnetic particles. Our results are important for the design and construction of reversibly tunable mechanical damping devices. Moreover, our projection on dipole-spring models allows the formal connection of our description to various related systems, e.g., magnetosome filaments in magnetotactic bacteria.Comment: 14 pages, 7 figure

How important is the Family? : Alpha nuclear potentials and p-process nucleosynthesis

Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike LicenceIn this work we present the results from the analysis of the experimentally measured angular distributions of the reaction 106Cd(α , α )106 Cd at several different energies around the Coulomb barrier. The difficulties that arise in the study of 106Cd-α -nuclear potential and the so called Family Problem are addressed in this work

La gestion communautaire des ressources naturelles à l’Est de la R.D.Congo : expérience de l’UGADEC

Les provinces du Nord Kivu et du Maniema, à l’est de la R.D.Congo sont confrontés à la destruction de l’environnement, particulièrement dans les parties des territoires de Walikale, Lubero, Punia et Lubutu. Alors que les forêts riches en biodiversité sont importantes tant pour l’Etat du fait de leur valeur économique que pour les communautés locales pour leur développement, les menaces qui pèsent sur ces dernières sont légions. Les plus importantes sont les mines, les guerres, le foncier, la légitimité et la légalité, etc. Face à cette situation, en 1998 les communautés locales de ces territoires ont décidé d’initier un nouveau modèle de gestion communautaire des ressources naturelles par la création de réserves gérées par les populations locales. L’objectif de ce modèle est la gestion de biodiversité associée au développement endogène, conduite par une l’Union des Associations de Conservation de Gorilles pour le Développement Communautaire à l’Est de la R.D.Congo (UGADEC). Quinze ans après le début de cette initiative les résultats sont prometteurs. Des actions de conservation ont été mises en place et un développement rural amorcé. Cependant, pour que la gestion communautaire devienne une réalité, il importe qu’un partenariat durable soit établi entre les différents acteurs liés à la gestion des réserves communautaires de l’est

Schistosoma haematobium co-infection with soil-transmitted helminthes: prevalence and risk factors from two communities in the central region of Ghana

Background: Schistosoma haematobium co-infection with S. mansoni and  soil-transmitted helminthes afflict most-at-risk populations in endemic communities in the developing world. Aim: This study investigated S. haematobium co-infection with soil-transmitted helminthes, and host risk factors in two communities in the central region of Ghana. Methods: Schools and children were selected by stratified cluster and random sampling methods respectively. A total of 250 school children (aged 5 - > 20 years) were recruited. Teachers issued questionnaires to obtain information on host risk factors, water-contact activities and knowledge of S.  haematobium infection. Urine and stool samples were examined for S. haematobium infection and S. mansoni and soil-transmitted helminthes using sedimentation quantitative and direct smear/formol-ether sedimentation concentration techniques respectively.Results: S. haematobium infection (1 - 50 eggs/10 ml urine)  prevalence at Apewosika and Putubiw were 27.5 % and 17 % respectively. Males were more at risk of S. haematobium infection than females. S. haematobium co-infection with soil-transmitted helminthes (A. lumbricoides, E. histolytica, and T. trichuria) was recorded in Putubiw, with females more at risk than males. Children aged 16-19 and 10-15 were more at risk of S. haematobium infection and  helminthic co-infection respectively. Haematuria and proteinuria were predictive of S. haematobium infection. School children had poor knowledge of S. haematobium infection. Water-contact activity was common.Conclusion: S. haematobium prevalence and its co-infection with soil-transmitted helminthes were common in Putubiw. Watercontact activity and poor knowledge about S. haematobium infection were major risk factors. Increased education on preventive and control measures especially in schools is recommended.Key words: Haematuria, proteinuria, Schistosoma haematobium, S. mansoni, helminthes, Bulinus globosu