Orbital Decay and Tidal Disruption of a Star Cluster: Analytical Calculation

The orbital decay and tidal disruption of a star cluster in a galaxy is studied in an analytical manner. Owing to dynamical friction, the star cluster spirals in toward the center of the galaxy. Simultaneously, the galactic tidal field strips stars from the outskirts of the star cluster. Under an assumption that the star cluster undergoes a self-similar evolution, we obtain the condition and timescale for the star cluster to reach the galaxy center before its disruption. The result is used to discuss the fate of so-called intermediate-mass black holes with >10^3 M(sun) found recently in young star clusters of starburst galaxies and also the mass function of globular clusters in galaxies.Comment: 12 pages, 1 PS file for 2 figures, to appear in The Astrophysical Journa

A Hopf lemma for the regional fractional Laplacian

We provide a Hopf boundary lemma for the regional fractional Laplacian (-Delta)(Omega)(s), with Omega subset of R-N a bounded open set. More precisely, given u a pointwise or weak super-solution of the equation (-Delta)(Omega)(s)u = c(x)u in Omega, we show that the ratio u(x)/(dist(x, partial derivative Omega))(2s-1) is strictly positive as x approaches the boundary partial derivative Omega of Omega. We also prove a strong maximum principle for distributional super-solutions

Salinisation-acidification des sols et riziculture dans la commune de mlomp, Oussouye (Bassecasamance, Senegal)

Les conditions pluviométriques déficitaires des années 1970 en Basse-Casamance ont accéléré et intensifié le processus de salinisation et d’acidification des rizières de la commune de Mlomp, département d’Oussouye. L‘objectif de ce travail est d’analyser les impacts de la salinisationacidification des rizières sur la production rizicole dans la commune de Mlomp. Dix localités (Samatite, Ebrouaye, Bouhimbane, Djicomol, Haer, Kadjifolong, Hasuka, Kafone, Cagnao et Djiramaite) ont été choisies. Ce choix est motivé par l’ampleur de la dégradation des rizières par salinisation-acidification. La méthodologie comprend des enquêtes de terrain, des analyses  pédologiques et une cartographie de l’occupation du sol. Les résultats montrent une salinisation-acidification généralisée des sols de rizières dans la commune de Mlomp, avec une conductivité électrique comprise entre 0,99 et 10,01 mS/cm et un pH entre à 4,4 et 5,9. L’intrusion marine et l’oxydation de la pyrite sont, respectivement, les principaux facteurs responsables de la salinisation et de  l’acidification des rizières de Mlomp. La baisse de la production rizicole et l’abandon des rizières en sont aujourd’hui les impacts les  plus visibles. Mots clés : Rizières – Salinization – Acidification - Mlomp – Oussouye - Sénégal   The rainfall decrease of the 1970s in Lower Casamance have accelerated and intensified the process of salinization and acidification of rice fields in the locality of Mlomp, department of Oussouye. The objective of this work is to analyze the causes and impacts of the salinization-acidification of rice fields on rice production in Mlomp. Ten localities (Samatite, Ebrouaye, Bouhimbane, Djicomol, Haer, Kadjifolong, Hasuka, Kafone, Cagnao and Djiramaite) were selected. This choice is motivated by the extent of the degradation of the rice fields by salinization and acidification. The methodology includes field surveys, soil sample analysis and land cover mapping. The results show a general salinization and acidification of rice-field soils in the locality of Mlomp, with an electrical conductivity between 0.99 and 10.01 mS / cm and a pH between 4.4 and 5.9. Marine intrusions and pyrite oxidation are, respectively, the main factors  responsible for the salinization and acidification of the rice fields of Mlomp. The drop in rice production and the abandonment of rice fields are today the most visible impacts. Keywords: Rice fields - Salinization – Acidification - Mlomp – Oussouye – Senega

Expected Number and Flux Distribution of Gamma-Ray-Burst Afterglows with High Redshifts

If Gamma-Ray-Bursts (GRBs) occur at high redshifts, then their bright afterglow emission can be used to probe the ionization and metal enrichment histories of the intervening intergalactic medium during the epoch of reionization. In contrast to other sources, such as galaxies or quasars, which fade rapidly with increasing redshift, the observed infrared flux from a GRB afterglow at a fixed observed age is only a weak function of its redshift. This results from a combination of the spectral slope of GRB afterglows and the time-stretching of their evolution in the observer's frame. Assuming that the GRB rate is proportional to the star formation rate and that the characteristic energy output of GRBs is ~10^{52} ergs, we predict that there are always ~15 GRBs from redshifts z>5 across the sky which are brighter than ~100 nJy at an observed wavelength of ~2 \mu m. The infrared spectrum of these sources could be taken with the future Next Generation Space Telescope, as a follow-up on their early X-ray localization with the Swift satellite.Comment: 29 pages, 14 figures; submitted to Ap

Urètrocèle post-traumatique chez l’homme: A propos de 2 cas

RésuméAffection rare chez l’homme, le diverticule urétral est souvent d’origine acquise. Nous rapportons deux cas d’urètrocèle post-traumatique chez des sujets jeunes qui ont été traités avec succès par chirurgie ouverte et nous en discutons les aspects cliniques para cliniques et thérapeutiques.AbstractUrethral diverticulum is unusual in male where it is often acquired. We report two cases of post-traumatic urethrocele in young male managed successfully by open surgery. We describe herein, the clinical, paraclinical and therapeutic features

Direct evidence for an early reionization of the Universe?

We examine the possible reionization of the intergalactic medium (IGM) by the source UDF033238.7-274839.8 (hereafter HUDF-JD2), which was discovered in deep {\it HST}/VLT/{\it Spitzer} images obtained as part of the Great Observatory Origins Deep Survey and {\it Hubble} Ultra-Deep Field projects. Mobasher et al (2005) have identified HUDF-JD2 as a massive ($\sim6\times10^{11}M_\odot$) post-starburst galaxy at redshift z$\gtrsim6.5$. We find that HUDF-JD2 may be capable of reionizing its surrounding region of the Universe, starting the process at a redshift as high as z$\approx 15 \pm5$.Comment: 6 pages, 2 figures. Accepted for publication in ApJ Letter

Influence of gravel and adjuvant on the compressive strength and water absorption of concrete.

Concrete is the most commonly used material in civil engineering, given its economic cost and ease of manufacture. Its strength depends on the characteristics of its constituents. A good mix makes it possible to build solid, durable and economical structures. The present work aims to characterize the gravel of the Eastern region (quarry of eastern Morocco) by granulometric analysis and water absorption. Then, the studied gravel is used to produce three types of concrete (B20, B25 and B30), which were assessed in terms of water absorption and compressive strength. The last step is to study the effect of an adjuvant, more specifically a water reducer, on mechanical characteristics of local concrete. B25 concrete was chosen for the last step since it is the most used type in the region. Results show that adding a water reducer adjuvant, in this case 'Chrysoplast', can improve the compressive strength of concrete if the percentage added is accurately determined

La lithotripsie extracorporelle: expérience d’un centre Sénégalais

No Abstrac

Angular momentum distribution of hot gas and implications for disk galaxy formation

We study the angular momentum profiles both for dark matter and for gas within virialized halos, using a statistical sample of halos drawn from cosmological hydrodynamics simulations. Three simulations have been analyzed, one is the ``non-radiative'' simulation, and the other two have radiative cooling. We find that the gas component on average has a larger spin and contains a smaller fraction of mass with negative angular momentum than its dark matter counterpart in the non-radiative model. As to the cooling models, the gas component shares approximately the same spin parameter as its dark matter counterpart, but the hot gas has a higher spin and is more aligned in angular momentum than dark matter, while the opposite holds for the cold gas. After the mass of negative angular momentum is excluded, the angular momentum profile of the hot gas component approximately follows the universal function originally proposed by Bullock et al. for dark matter, though the shape parameter $\mu$ is much larger for hot gas and is comfortably in the range required by observations of disk galaxies. Since disk formation is related to the distribution of hot gas that will cool, our study may explain the fact that the disk component of observed galaxies contains a smaller fraction of low angular momentum material than dark matter in halos.Comment: 30 pages, 12 figures, 4 tables, accepted for publication in Ap