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Search Results: 1 - 10 of 84403 matches for " W. Sekkal "
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NaCl nanodroplet on NaCl(100) at the melting point
T. Zykova-Timan,U. Tartaglino,D. Ceresoli,W. Sekkal,E. Tosatti
Physics , 2004, DOI: 10.1016/j.susc.2004.06.110
Abstract: The self-wetting properties of ionic crystal surfaces are studied, using NaCl(100) as a prototype case. The anomalously large contact angle measured long ago by Mutaftschiev is well reproduced by realistic molecular dynamics simulations. Based on these results, and on independent determinations of the liquid-vapor and the solid-vapor interface free energy, an estimate of the solid-liquid interface free energy is extracted. The solid-vapor surface free energy turns out to be small and similar to the liquid-vapor one, providing a direct thermodynamic explanation of the reduced wetting ability of the ionic melt.
STRUCTURAL STABILITY AND ELECTRONIC STRUCTURE OF YCu DUCTILE INTERMETALLIC COMPOUND BY FIRST-PRINCIPAL CALCULATION.
A. Sekkal,A. Benzair
Journal of Fundamental and Applied Sciences , 2012,
Abstract: We investigate the structural, elastic and electronic properties of cubic YCu intermetallic compound. Which crystallize in the CsCl- B2 type structure, the investigated using the first principle full potential linearized augmented plane wave method (FP-LAPW) within density functional Theory (DFT). We used generalized gradient approximation (GGA) and local density theory (LDA), which is based on exchange correlation energy optimization, are used to determinate the total energies and the electronic band structures. The latter provide us with the ground states properties such as lattice parameter, bulk modulus and its pressure derivative, elastic constants and the structural phase stability with respect to the B1, B3, and L10structures of this compound. Our results are in good agreement with numerous experimental and theoretical data where available.
Novel strain-induced low dimensional confinement structures
Nadir Sekkal,V. R. Velasco
Physics , 2008, DOI: 10.1063/1.3030981
Abstract: We propose new confinement structures similar to heterostructures and superlattices. The new heteostructures can be obtained by applying strain to a single material in a periodic or aperiodic way. The conversion of an indirect gap into an optical active direct or quasi-direct gap problem has also been investigated together with the role of zone folding in this phenomenon.
Confounders in the assessment of the renal effects associated with low-level urinary cadmium: an analysis in industrial workers
Nahida Haddam, Sekkal Samira, Xavier Dumont, Abdesselem Taleb, Dominique Lison, Vincent Haufroid, Alfred Bernard
Environmental Health , 2011, DOI: 10.1186/1476-069x-10-37
Abstract: We examined 184 healthy male workers (mean age, 39.5 years) from a zinc smelter (n = 132) or a blanket factory (n = 52). We measured the concentrations of Cd in blood (B-Cd) and the urinary excretion of Cd (U-Cd), retinol-binding protein (RBP), protein HC and albumin. Associations between biomarkers of metal exposure and urinary proteins were assessed by simple and multiple regression analyses.The medians (interquartile range) of B-Cd (μg/l) and U-Cd (μg/g creatinine) were 0.80 (0.45-1.16) and 0.70 (0.40-1.3) in smelter workers and 0.66 (0.47-0.87) and 0.55 (0.40-0.90) in blanket factory workers, respectively. Occupation had no influence on these values, which varied mainly with smoking habits. In univariate analysis, concentrations of RBP and protein HC in urine were significantly correlated with both U-Cd and B-Cd but these associations were substantially weakened by the adjustment for current smoking and the residual influence of diuresis after correction for urinary creatinine. Albumin in urine did not correlate with B-Cd but was consistently associated with U-Cd through a relationship, which was unaffected by smoking or diuresis. Further analyses showed that RBP and albumin in urine mutually distort their associations with U-Cd and that the relationship between RBP and Cd in urine was almost the replicate of that linking RBP to albuminAssociations between proteinuria and low-level urinary Cd should be interpreted with caution as they appear to be largely driven by diuresis, current smoking and probably also the co-excretion of Cd with plasma proteins.Cadmium (Cd) is a widespread pollutant that accumulates in the soil, the food chain and ultimately in the human body. Other major sources of exposure to Cd are cigarette smoking and the use or production of Cd in various industrial settings. Cd is a highly toxic metal which at high doses can cause damage on virtually all organs and biological systems. At current human exposure levels in the industry or environment,
Case report - Ectopic molar pregnancy: A case report
N Bousfiha, S Erarhay, A Louba, H Saadi, C Bouchikhi, A Banani, H El Fatemi, M Sekkal, A Laamarti
Pan African Medical Journal , 2012,
Abstract: The incidence of hydatidiform moles is 1 per 1,000 pregnancies. Ectopic pregnancy occurs in 20 per 1,000 pregnancies. Thus, the incidence of the ectopic molar gestation is very rare. We report a case of tubal molar pregnancy diagnosed at the systematic histology exam of an ectopic pregnancy. We report the case of 32 years old nulliparus women who presented a vaginal bleeding, lower abdominal pain and 6 weeks amenorrhea corresponding to the last menstrual period. At the clinical examination, the arterial pressure was 100/60 mmHG. The gynecological examination was difficult because of lower abdominal pain. Serum gonadotropin activity was 3454 ui/l. Pelvic ultrasound revealed an irregular echogenic mass in the left adnexa. Diagnostic laparoscopy revealed a left-sided unruptured ampullary ectopic pregnancy. A left laparoscopic salpingectomy was performed. The systematic histologic test identified an ectopic partial molar pregnancy, which was confirmed by DNA ploidy image analysis. The patient was followed with weekly quantitative ;-hCG titers until three successive ;-hCG levels were negative. It is pertinent that clinicians take routine histological examination of tubal specimens in ectopic pregnancy very seriously in order to diagnose cases of ectopic molar gestations early and mount appropriate post treatment surveillance.
Changes in Intestinal Glucocorticoid Sensitivity in Early Life Shape the Risk of Epithelial Barrier Defect in Maternal-Deprived Rats
Nabila Moussaoui, Viorica Braniste, Afifa Ait-Belgnaoui, Mélissa Gabanou, Soraya Sekkal, Maiwenn Olier, Vassilia Théodorou, Pascal G. P. Martin, Eric Houdeau
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088382
Abstract: Glucocorticoids (GC) contribute to human intestine ontogeny and accelerate gut barrier development in preparation to birth. Rat gut is immature at birth, and high intestinal GC sensitivity during the first two weeks of life resembles that of premature infants. This makes suckling rats a model to investigate postpartum impact of maternal separation (MS)-associated GC release in preterm babies, and whether GC sensitivity may shape MS effects in immature gut. A 4 hours-MS applied once at postnatal day (PND)10 enhanced plasma corticosterone in male and female pups, increased by two times the total in vivo intestinal permeability (IP) to oral FITC-Dextran 4 kDa (FD4) immediately after the end of MS, and induced bacterial translocation (BT) to liver and spleen. Ussing chamber experiments demonstrated a 2-fold increase of permeability to FD4 in the colon immediately after the end of MS, but not in the ileum. Colonic permeability was not only increased for FD4 but also to intact horseradish peroxidase 44 kDa in MS pups. In vivo, the glucocorticoid receptor (GR) antagonist RU486 or ML7 blockade of myosin light chain kinase controlling epithelial cytoskeleton contraction prevented MS-induced IP increase to oral FD4 and BT. In addition, the GR agonist dexamethasone dose-dependently mimicked MS-increase of IP to oral FD4. In contrast, MS effects on IP to oral FD4 and BT were absent at PND20, a model for full-term infant, characterized by a marked drop of IP to FD4 in response to dexamethasone, and decreased GR expression in the colon only compared to PND10 pups. These results show that high intestinal GC responsiveness in a rat model of prematurity defines a vulnerable window for a post-delivery MS, evoking immediate disruption of epithelial integrity in the large intestine, and increasing susceptibility to macromolecule passage and bacteremia.
Bauxit
. W.
Nieuwe West-Indische Gids , 1951,
Abstract:
Creation of High Energy/Intensity Bremsstrahlung by a Multi-Target and Focusing of the Scattered Electrons by Small-Angle Backscatter at a Cone Wall and a Magnetic Field—Enhancement of the Outcome of Linear Accelerators in Radiotherapy  [PDF]
W. Ulmer
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2013, DOI: 10.4236/ijmpcero.2013.24020
Abstract: The yield of bremsstrahlung (BS) from collisions of fast electrons (energy at least 6 MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. A simplified version of a previously developed principle is also able to focus on small angle scattered electrons by a Tungsten wall. It is necessary that the thickness of each Tungsten layer does not exceed 0.04 mm—a thickness of 0.03 mm is suitable for accelerators in medical physics. Further focusing of electrons results from suitable magnetic fields with field strength between 0.5 Tesla and 1.2 Tesla (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need to be focused by wall scatter without further magnetic fields (a standard case: 31 plates with 0.03 mm thickness and 1 mm distance between the plates). We considered three cases with importance in medical physics: A very small cone with an additional magnetic field for focusing (the field diameter at 90 cm depth: 6 cm), a medium cone with an optional magnetic field (field diameter at 90 cm depth: 13 cm) and a broad cone without a magnetic field (
Social Issues of Urban Road Rehabilitation  [PDF]
W. Supul
Current Urban Studies (CUS) , 2018, DOI: 10.4236/cus.2018.63022
Abstract:
This study highlights the social issues of an urban road confronted after the recent rehabilitation works. The study reveals that the road has facilitated faster travel with rider comfort but does not provide a very safe place for residents, children of the kindergarten and school and, walkers. The study has identified several social impacts caused by rehabilitation such as walker and resident un-comfort, inconvenience for businesses, not abating environmental pollution, absence of facilities for disable people and several more. Because the road platform is devoid of trees, the motorists, residents and pedestrians are stripped off of an array of benefits. Nor the road design has considered the comfort of walkers especially disable, elderly, sick and children by not providing a fully connected road walkway and not providing any tree shade and benches to have a rest on a hot and sunny day. The road has also not addressed environmental concerns especially the mechanisms for reduction of impacts of particle and other noxious gases emanating from motor vehicle movement on inhabitants. A method to analyze road impacts is included that serves as an aid for future rehabilitation of urban roads.
On the Origin of Mass and Angular Momentum of Stellar Objects  [PDF]
Peter C. W. Fung, K. W. Wong
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.615235
Abstract: The consequence of the 5D projection theory [1] is extended beyond the Gell-Mann Standard Model for hadrons to cover astronomical objects and galaxies. The proof of Poincare conjecture by Pe-relman’s differential geometrical techniques led us to the consequence that charged massless spinors reside in a 5D void of a galactic core, represented by either an open 5D core or a closed, time frozen, 3D × 1D space structure, embedded in massive structural stellar objects such as stars and planets. The open galactic core is obtained from Ricci Flow mapping. There exist in phase, in plane rotating massless spinors within these void cores, and are responsible for 1) the outward spiral motion of stars in the galaxy in the open core, and 2) self rotations of the massive stellar objects. It is noted that another set of eigen states pertaining to the massless charged spinor pairs rotating out of phase in 1D (out of the 5D manifold) also exist and will generate a relatively weak magnetic field out of the void core. For stars and planets, it forms the intrinsic dipole field. Due to the existence of a homogeneous 5D manifold from which we believe the universe evolves, the angular momentum arising from the rotation of the in-phase spinor pairs is proposed to be counter-balanced by the rotation of the matter in the surrounding Lorentz domain, so as to conserve net zero angular momentum. Explicit expression for this total angular momentum in terms of a number of convergent series is derived for the totally enclosed void case/core, forming in general the structure of a star or a planet. It is shown that the variables/parameters in the Lorentz space-time domain for these stellar objects involve the object’s mass M, the object’s Radius R, period of rotation P, and the 5D void radius Ro, together with the Fermi energy Ef and temperature T of the massless charged spinors residing in the void. We discovered three laws governing the relationships between Ro/R, T, Ef and the angular momentum Iω of such astronomical object of interest, from which we established two distinct regions, which we define as the First and Second Laws for the evolution of the stellar object. The Fermi energy Ef was found to be that of the electron mass, as it is the lightest massive elementary particle that could be created from pure energy in the core. In fact the mid-temperature of the transition region between the
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