193 research outputs found
LES BIO-ESSAIS DANS LâĂVALUATION DâIMPACT DES POLLUANTS SUR LES ĂCOSYSTĂMES DULĂAQUICOLES
Les bioessais Ă©cotoxicologiques constituent un outil de choix dans le domaine de lâĂ©valuation des effets des polluants sur la composante biologique des Ă©cosystĂšmes, ils traduisent les teneurs analysĂ©s par des outils de la chimie conventionnelle en effets mesurables sur des variables biologiques chez des populations des organismes tests. Plusieurs espĂšces, reprĂ©sentatives des Ă©cosystĂšmes aquatiques ou terrestres, ont fait lâobjet de normalisation pour lâĂ©valuation de la toxicitĂ© aiguĂ« et/ou chronique. A cet Ă©gard, le cladocĂšre Daphnia magna Straus est un organisme test qui occupe une place confirmĂ©e pour lâĂ©valuation de la toxicitĂ© aiguĂ« et chronique de polluants sur les Ă©cosystĂšmes dâeau douce. Cette espĂšce est choisie en raison de son rĂŽle clĂ© dans la chaĂźne trophique, sa sensibilitĂ©, sa facilitĂ© dâĂ©levage et son cycle de vie qui est mis Ă profit pour le test de reproduction de 21 jours. Outre la dĂ©termination des CE50 dans des essais de toxicitĂ© aiguĂ« (24 ou 48 H), lâĂ©tude de la toxicitĂ© chronique permet la dĂ©termination de la LOEC (Lowest effect concentration) et de la NOEC (No effect concentration) qui sont des valeurs remarquables adoptĂ©es dans les Ă©tudes dâĂ©valuation de risque de nouvelles molĂ©cules par les instances de rĂ©glementation internationales
Gravitational Waves from Preheating in Gauss-Bonnet Inflation
We study gravitational wave production in an expanding Universe during the
first stages following inflation, and investigate the consequences of the
Gauss-Bonnet term on the inflationary parameters for a power-law inflation
model with a GB coupling term. Moreover, we perform the analyses on the
preheating parameters involving the number of e-folds , and the
temperature of thermalization and show that it's sensitive to the
parameters , and , the parameter is proposed to connect the
density energy at the end of inflation to the preheating energy density. We set
a correlation of gravitational wave energy density spectrum with the spectral
index detected by the cosmic microwave background experiments The
density spectrum shows good consistency with observation for
and . Our findings suggest that the generation of
gravitational waves (GWs) during preheating can satisfy the constraints from
Planck's data
Dark matter via Baryogenesis: Affleck-Dine Mechanism in the Minimal Supersymmetric Standard Model
We conducted an investigation into Affleck-Dine baryogenesis within the
context of D-term inflation, specifically focusing on its relationship with a
recent reheating formalism. It was found that by considering a specific
reheating temperature, the observed baryon asymmetry can be accounted through
Affleck-Dine baryogenesis. Additionally, the majority of gravitinos are
inferred to be generated from the decay of the next-to-lightest supersymmetric
particle, with Q-balls potentially serving as a source of gravitinos via NSP
decay. The temperature at which decay occurs depends on the charge of the
Q-balls, which is determined by the fragmentation of the Affleck-Dine
condensate. Remarkably, the gravitino mass required for dark matter aligns
naturally with the theoretical gravitino mass.Comment: 11 pages, 4 figure
Contribution to the Optimization of the Radiation Performance of Patch Array Antenna for WiMAX Applications
The aim of this paper is to increase the operating distance of the WiMAX implementation by increasing the gain and the directivity using microstrip array antenna. We present the design of simple 2X2 microstrip array antenna operating at 5.38 GHz for WiMAX applications. The design is based on a single layer FR4 substrate, having a loss tangent o
Parametric Study of a Single Effect Lithium Bromide-Water Absorption Chiller Powered by a Renewable Heat Source
This work investigates the performance of a single-effect absorption chiller utilizing an aqueous lithium bromide solution as the working fluid and driven by hot fluid rejected from either a geothermal power plant or the outlet of a thermal solar collector. This relatively low enthalpy return fluid, which will otherwise be reinjected back into the
earth, will be utilized as the thermal energy source of the chiller. Although such chillers are considered low-grade energy refrigeration cycles, the one proposed here has an advantage in terms of economy and efficiency. A parametric analysis is performed using Engineering Equation Solver software and is used to highlight the effect of the heat
exchanger size on the coefficient of performance of the chiller. The analysis proved that the proposed device can operate with excellent cooling capacity, reaching 16 kW, and a relatively high coefficient of performance (~ 0.7) while being driven by the low-grade energy. The heat source temperature, solution heat exchanger effectiveness and the size of the absorber were shown to be key parameters for the design and operation of absorption chillers. Moreover, increasing the heat source mass flow rate has a significant impact on both cooling capacity and coefficient of performance at low values (< 10 kg/s)
and unnoticeable impact at higher values (> 10 kg/s)
The endemic Chamaecytisus albidus is nodulated by symbiovar genistearum of Bradyrhizobium in the Moroccan Maamora Forest
Out of 54 isolates from root nodules of the Moroccan-endemic Chamaecytisus albidus plants growing in soils from the Maamora cork oak forest, 44 isolates formed nodules when used to infect their original host plant. A phenotypic analysis showed the metabolic diversity of the strains that used different carbohydrates and amino acids as sole carbon and nitrogen sources. The isolates grew on media with pH values ranging from 6 to 8. However, they did not tolerate high temperatures or drought and they did not grow on media with salt concentrations higher than 85 mM. REP-PCR fingerprinting grouped the strains into 12 clusters, of which representative strains were selected for ARDRA and rrs analyses. The rrs gene sequence analysis indicated that all 12 strains were members of the genus Bradyrhizobium and their phylogeny showed that they were grouped into two different clusters. Two strains from each group were selected for multilocus sequence analysis (MLSA) using atpD, recA, gyrB and glnII housekeeping genes. The inferred phylogenetic trees confirmed that the strains clustered into two divergent clusters. Strains CM55 and CM57 were affiliated to the B. canariense/B. lupini group, whereas strains CM61 and CM64 were regrouped within the B. cytisi/B. rifense lineage. The analysis of the nodC symbiotic gene affiliated the strains to the symbiovar genistearum. The strains were also able to nodulate Retama monosperma, Lupinus luteus and Cytisus monspessulanus, but not Phaseolus vulgaris or Glycine max. Inoculation tests with C. albidus showed that some strains could be exploited as efficient inocula that could be used to improve plant growth in the Maamora forest.The authors want to thank all the people who contributed to theachievement of this study. Financial support was obtained fromââAcadĂ©mie Hassan II des Sciences et Techniquesâ (Morocco). MrOmar Bouhnik received a grant from the Hassan II Academy of Science and Technology. The authors also thank the Ministerio de EconomĂa, Industria y Competitividad (Spain) for the granting ofthe ERDF-cofinanced project AGL2017â85676R
Numerical Study of the Bond Strength Evolution of Corroded Reinforcement in Concrete in PullâOut Tests
The corrosion of rebars in reinforced concrete structures impacts their geometry (diameter and ribs) and mass, damages the concrete at the interface between the two materials, deteriorates the bond strength, and causes the cracking of the concrete cover. In the following study, a 2D numerical model of the pullâout test is presented in order to study the impact of corrosion on the bond strength. Several parameters are investigated: the embedment depth, the rebarâs diameter, and the width of the concrete cover. The model reproduces the slip of the rebar and the failure through the splitting of concrete. It integrates an interface between the two materials and a concrete damage model that simulate the deterioration of concrete in compression and tension. The results obtained are validated with experimental data from the literature. Moreover, a parametric study is carried out to determine the impact of the embedment depth, the diameter of the rebar, and the concrete cover on the bond strength. The present study confirms that a greater embedment depth increases the pulling load. The study also confirms that the rebarâs diameter impacts highly the loss of bond between the rebar and the concrete cover. Lastly, the final main result of this paper is that the width of the concrete cover slows the loss of bond strength between the two materials
Péritonite primitive: entité réelle mais de diagnostic difficile
Les pĂ©ritonites primitives sont rares chez des patients sans facteurs de risques. Elles simulent les pĂ©ritonites secondaires. Câest pourquoi leurdiagnostic ne peut ĂȘtre que peropĂ©ratoire. Nous rapportons deux cas de pĂ©ritonites primitives dans le but de discuter leurs aspects diagnostique etthĂ©rapeutiques.Key words: Diagnostic, pĂ©ritonite primitive, traitemen
The epidemiology of HIV infection in Morocco: systematic review and data synthesis.
Morocco has made significant strides in building its HIV research capacity. Based on a wealth of empirical data, the objective of this study was to conduct a comprehensive and systematic literature review and analytical synthesis of HIV epidemiological evidence in this country. Data were retrieved using three major sources of literature and data. HIV transmission dynamics were found to be focused in high-risk populations, with female sex workers (FSWs) and clients contributing the largest share of new HIV infections. There is a pattern of emerging epidemics among some high-risk populations, and some epidemics, particularly among FSWs, appear to be established and stable. The scale of the local HIV epidemics and populations affected show highly heterogeneous geographical distribution. To optimize the national HIV response, surveillance and prevention efforts need to be expanded among high-risk populations and in geographic settings where low intensity and possibly concentrated HIV epidemics are emerging or are already endemic
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