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Hydrogeochemical Characterization of Aquifer Systems and Surface Water/Groundwater Relations in the Lower Senegal River Valley

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Journal of Geoscience and Environment Protection 2024年第6期12卷 232-254页

作者： Abibatou Camara Fatou Diop ngom Moctar Diaw Cheikh Tidiane Wade Ibrahima Mall Department of Geology Cheikh Anta Diop University Dakar Senegal Department of Applied Geosciences and Environment Amadou Mahtar Mbow University Dakar Senegal

This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed using classical geochemical interpretation diagrams (Piper, GIBBS, etc.) and multivariate geostatistical analyses, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results revealed three types of facies: Ca-Mg-HCO3-type facies, characteristic of poorly mineralized waters such as surface waters and groundwater from dune formations and the alluvial plain close to the hydraulic axis;Na-Cl type facies associated with well waters located in the alluvial plain that tap Inchirian or Nouakchottian shallow reservoirs and Maastrichtian deep borehole waters;and mixed Ca-Cl and Na-HCO3 type facies observed in certain floodplain and dune reservoirs. The results showed a strong correlation between sodium, chlorides, bromides, and electrical conductivity, indicating a significant contribution of these ions to groundwater mineralization. The various sources of water mineralization include mixing processes between surface water or rainwater, or calcite or dolomite dissolution processes (for weakly mineralized waters), basic exchanges or inverse basic exchanges between the aquifer and the water table (for moderately mineralized waters), and evaporation processes, halite dissolution, and paleosalinity during periods of marine transgression and regression (for highly mineralized waters). The study also highlighted the high vulnerability of the alluvial aquifer to pollution from intensive irrigated agriculture, as significant quantities of sulfates and nitrates were measured in some samples. These results also highlight the importance of water quality management in the Lower Senegal Valley, particularly as concerns the protection of the alluvial aquifer against pollution from irrigated agriculture.

关键词： Senegal River Valley Groundwater Pollution Agriculture Alluvial Aquifer

Numerical Modeling of Mass Transfer in the Interaction between River Biofilm and a Turbulent Boundary Layer

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Open Journal of Fluid Dynamics 2024年第1期14卷 1-23页

作者： Falilou Coundoul Evrad M. D. ngom Frédéric Y. Moulin Institut Polytechnique de Saint-Louis Université Gaston Berger Saint-Louis Senegal Institut de Mécanique des Fluides de Toulouse UMR 5502-Université de Toulouse Occitanie France

In this article dedicated to the modeling of vertical mass transfers between the biofilm and the bulk flow, we have, in the first instance, presented the methodology used, followed by the presentation of various results obtained through analyses conducted on velocity fields, different fluxes, and overall transfer coefficients. Due to numerical constraints (resolution of relevant spatial scales), we have restricted the analysis to low Schmidt numbers (Sc=0.1, Sc=1, and Sc=10) and a single roughness Reynolds number (Re*=150). The analysis of instantaneous concentration fields from various simulations revealed logarithmic concentration profiles above the canopy. In this zone, the concentration is relatively homogeneous for longer times. The analysis of results also showed that the contribution of molecular diffusion to the total flux depends on the Schmidt number. This contribution is negligible for Schmidt numbers Sc≥0.1, but nearly balances the turbulent flux for Sc=0.1. In the canopy, the local Sherwood number, given by the ratio of the total flux (within or above the canopy) to the molecular diffusion flux at the wall, also depends on the Schmidt number and varies significantly between the canopy and the region above. The exchange velocity, a purely hydrodynamic parameter, is independent of the Schmidt number and is on the order of 10% of in the present case. This study also reveals that nutrient absorption by organisms near the wall depends on the Schmidt number. Such absorption is facilitated by lower Schmidt numbers.

关键词： Epilithic Biofilm Passive Scalar Transport Direct Numerical Simulation Navier-Stokes

Influence of Topography on the Distribution and Structure of Woody Plants in the Senegalese Sahel (Sandy Ferlo)

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American Journal of Plant Sciences 2024年第1期15卷 14-28页

作者： Moustapha Bassimbe Sagna Aïssatou Ndong Thiam khoudia Niang Oumar Sarr Aly Diallo Sekouna Diatta Daouda ngom Aliou Guissé Department of Plant Biology Faculty of Science and Technology Cheikh Anta Diop University Dakar Senegal IRL 3189 “Environment Health Society” Tessekere Human Environment Observatory (Senegal) Dakar Senegal Department of Agronomy and Plant Production El Hadji Ibrahima Niasse University Kaolack Senegal Department of Agroforestry Assane Seck University Ziguinchor Senegal

This study describes the floristic composition and structure of a woody stand in the Senegalese Sahel, paying particular attention to the edaphic factors of its floristic composition. A stratified inventory considering the different relief units was adopted. Woody vegetation was surveyed using a dendrometric approach. The results obtained show that the flora is dominated by a few species adapted to drought, such as Balanites aegyptiaca (L.) Del., Calotropis procera Ait. and Boscia senegalensis (Pers.). The distribution of this flora and the structure of the ligneous plants are linked to the topography. In the lowlands, the flora is more diversified and the ligneous plants reach their optimum level of development compared with the higher relief areas. In the lowlands, there are a few woody species which, in the past, were indicative of better climatic conditions. These are Anogeissus leiocarpus (DC.), Commiphora africana (A. Rich.), Feretia apodanthera Del., Loeseneriella africana (A. Smith), Mitragyna inermis (Willd.) and Sclerocarya birrea (A. Rich). It is important that their reintroduction into reforestation projects takes account of their edaphic preference.

关键词： Woody Plants Distribution Topography Ferlo Senegal

Aqueous-phase reforming of hydroxyacetone solution to bio-based H_(2)over supported Pt catalysts

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Green Energy & Environment 2024年第4期9卷 777-788页

作者： A.k.k.Vikla k.koichumanova Songbo He k.Seshan Joint International Research Laboratory of Circular Carbon Nanjing Tech UniversityNanjing211816China Faculty of Science and Technology University of Twente7500 AE EnschedeThe Netherlands CoRe Pro 9723 BL GroningenThe Netherlands

Aqueous-phase reforming(APR)is an attractive process to produce bio-based hydrogen from waste biomass streams,during which the catalyst stability is often challenged due to the harsh reaction *** this work,three Pt-based catalysts supported on C,AlO(OH),and ZrO_(2)were investigated for the APR of hydroxyacetone solution in afixed bed reactor at 225℃and 35 *** them,the Pt/C catalyst showed the highest turnover frequency for H_(2)production(TOF of 8.9 molH_(2)molPt^(-1)min^(-1))and the longest catalyst *** the AlO(OH)and ZrO_(2)supported Pt catalysts,the side reactions consuming H_(2),formation of coke,and Pt sintering result in a low H_(2)production and the fast catalyst *** proposed reaction pathways suggest that a promising APR catalyst should reform all oxygenates in the aqueous phase,minimize the hydrogenation of the oxygenates,maximize the WGS reaction,and inhibit the condensation and coking reactions for maximizing the hydrogen yield and a stable catalytic performance.

关键词： APR Hydroxyacetone TOF Bio-based H_(2) Support effect

Reasons for Elective Surgery Cancellations in a Senegalese Pediatric Surgery Department

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Open Journal of Pediatrics 2024年第5期14卷 783-789页

作者： Cheikh Tidiane Mbaye Cheikh Diouf Florent Tshibwid A Zeng Faty Balla Lô Lissoune Cissé Doudou Gueye Ibrahima Bocar Wellé Souleymane Camara Papa Alassane Mbaye Oumar Ndour Gabriel ngom Department of Pediatric Surgery Aristide Le Dantec University Teaching Hospital Universit Cheikh Anta Diop Dakar Senegal Department of Pediatric Surgery Ziguinchor Regional Hospital Center Universit Cheikh Anta Diop Ziguinchor Senegal Department of Pediatric Surgery El Hadj Ibrahima Niass Regional Hospital Center Kaolack Senegal Department of Pediatric Surgery Pikine National Hospital Center Dakar Senegal Department of Pediatric Surgery Albert Royer National Childrens Hospital Center Universit Cheikh Anta Diop Dakar Senegal Unit of Pediatric Surgery Department of Pediatrics Dalal Jamm National Hospital Center Dakar Senegal

Introduction: Cancellation of elective surgery is common in developing countries. This decision is difficult to make as it generates economic and organizational consequences for the healthcare facility and an additional source of stress for patients and their caregivers. This study aimed to analyze the various aspects of this medical problem. Patients and Methods: We conducted a prospective and descriptive study over six months (from January 1st, 2017, to June 30th, 2017) at the pediatric surgery department of Aristide Le Dantec University Teaching Hospital in Senegal. Results: Ninety-one cases were collected. The cancellation rate was 20.8%. Infants were affected in 36.3% of cases. Among anesthesiologists, 83.5% were residents, and 16.5% were specialists. Cancellation in nephroblastoma children with an indication for extended nephrectomy represented 15.4% of cases. Concerning reasons for cancellation, comorbidities, dominated by respiratory infections, accounted for 28.5% of cases, patient absences for 24.2%, and issues related to the anesthesiologist for 17.6%. Cancellations were avoidable in 33% of cases. Patients were responsible for cancellation in 37.4% of cases, the healthcare system in 33%, and medical reasons in 29.7%. Conclusion: Our findings suggest that one-third of cancellations could have been avoided with improvements in the healthcare system. Actions should be taken to reduce the cancellation rate in our context.

关键词： Cancellation Elective Surgery Pediatric Surgery LMICs Senegal

Frailty in People Living with Human Immunodeficiency Virus Aged 50 Years and Older: Prevalence and Predictors

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World Journal of AIDS 2024年第1期14卷 18-34页

作者： Alassane Ndiaye Ndèye Fatou ngom kiné Ndiaye Assiétou Gaye Elhadji Bara Diop Ahmadou Mboup Houlèye Saou Bessoume Sy Ababacar Niang Betty Fall Mame Awa Faye Outpatient Treatment Clinic (CTA) Dakar Senegal Medicine Department of Health and Sustainable Development/Research and Training Unit (UFRSDD) Alioune Diop University of Bambey Diourbel Senegal Health and Development Institute (ISED) Cheikh Anta Diop University Dakar Senegal Geriatrics and Gerontology Department Fann National Teaching Hospital Center Dakar Senegal

Introduction: Life expectancy improvement for people living with Human Immunodeficiency Virus (HIV) is coming up against the problems associated with aging and chronic diseases. Frailty is a concern affecting a growing number of patients, particularly the elderly in this population. Our study aimed to determine the prevalence of frailty and its predictors on people living with HIV aged 50 years and older followed at the Outpatient Treatment Clinic (CTA) in Dakar. Methodology: We conducted a cross-sectional study of descriptive and analytic purposes ranging from November 2022 to August 2023, in CTA, Dakar (Senegal). We included people living with HIV aged 50 years and older under antiretroviral therapy for at least 6 months (≥6 months). Frailty was considered according to Fried criteria with a score ≥3. To identify the predictors of frailty, we performed a multivariate logistic regression analysis using STATA software version 18. Results: We included 199 patients. The median age at the moment of the study was 58 years old [50 - 91] with a sex ratio (M/F) of 0.58. The most representative age group was that of [50 - 59] years (59.3%). HIV-1 profile was most common in 89.45%. The median duration under antiretroviral therapy was 180 months [6 - 284] and 94% of patients received a Tenofovir Disoproxil Fumarate (TDF)-containing regimen with 43% of them for at least 10 years. Viral load was undetectable (≤40 copies/ml) in 98% of cases. WHO Stage III was more common at inclusion and 55.78% had nadir TCD4+ Lymphocyte counts Conclusion: Our study confirms the high prevalence of frailty among older people living with HIV. Its prevention should consider the management of comorbidities and the implementation of non-pharmacological interventions such as nutrition.

关键词： Frailty HIV Senior Dakar

Direct scaling of residual displacements for bilinear and pinching oscillators

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 129-149页

作者： Mohammad Saifullah Vinay k.Gupta Department of Civil Engineering Indian Institute of Technology KanpurKanpur 208016India

The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the *** attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5%initial damping,directly in terms of easily available seismological,site,and model *** of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not *** statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude,epicentral distance,site geology parameter,and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models,as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model *** proposed scaling model is applicable to horizontal ground motions in the western *** earthquake magnitudes less than 7 or epicentral distances greater than 20 km.

关键词： residual displacement spectrum bilinear hysteresis model pinching hysteresis model nonlinear analysis scaling model

Analysis of the Oscillatory Flows of Multiple Shock Waves in a Constant Area Duct

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Journal of Thermal Science 2024年第3期33卷 794-806页

作者： k JAMES Jintu kIM Heuy Dong Department of Mechanical Engineering Andong National UniversityAndong36729Republic of Korea CAD-IT korea Co. Ltd.Seoul08591Republic of Korea

The oscillatory response of multiple shock waves to downstream perturbations in a supersonic flow is studied numerically in a rectangular *** shock waves are formed inside the duct at a shock Mach number of *** duct has an exit height of H,and the effect of duct resonance on multiple shock oscillations is investigated by attaching exit ducts of lengths 0H,50H,and *** downstream disturbance frequency varied from 10 Hz to 200 Hz to explore the oscillation characteristics of the multiple shock *** oscillatory response of shock waves under self-excited and forced oscillation conditions are analyzed in terms of wall static pressure,shock train leading-edge location,shock train length,and the size of the separation *** extent of the initial shock location increases with an increase in exit duct length for the self-excited oscillation *** analysis of the shock train leading edge and the spectral analysis of wall static pressure variations are *** variation in the shock train length is analyzed using the pressure ratio method for self-excited as well as forced *** RMS amplitude of the normalized shock train length(ζ_(ST))increases with an increase in the exit duct length for the self-excited oscillation *** the downstream perturbation frequency is increased,ζ_(ST)is decreased for exit duct *** all exit duct designs and downstream forcing frequencies,the size of the separation bubble grows and shrinks during the shock oscillations,demonstrating the dependence on duct resonance and forced oscillations.

关键词： shock train downstream disturbance supersonic flow shock wave boundary layer interaction duct resonance flow separation

Impact of Fin Arrangement on Heat Transfer and Melting Characteristics of Phase Change Material

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Journal of Thermal Science 2024年第2期33卷 435-456页

作者： Arun UNIYAL Yogesh k.PRAJAPATI Department of Mechanical Engineering National Institute of Technology UttarakhandSrinagar(Garhwal)246174India Department of Mechanical Engineering BIT SindriDhanbadJharkhand828123India

Present work investigates the heat transfer and melting behaviour of phase change material(PCM) in six enclosures(enclosure-1 to 6) filled with paraffin *** enclosures are equipped with distinct arrangements of the fins while keeping the fin's surface area equal in each *** analysis has been presented to recognize the suitable fin arrangements that facilitate improved heat transfer and melting rate of the *** wall of the enclosure is maintained isothermal for the temperature values 335 k,350 k and 365 *** length of the enclosure including fins is ranging between 0 and *** have been illustrated through the estimation of important performance parameters such as energy absorbing capacity,melting rate,enhancement ratio,and Nusselt *** has been found that melting time(to melt 100% of the PCM) is 60.5%less in enclosure-2(with two fins of equal length) as compared to the enclosure-1,having no *** the fin surface area equal,if the longer fin is placed below the shorter fin(enclosure-3),melting time is further decreased by 14.1% as compared to ***,among all the configurations,enclosure-6 with wire-mesh fin structure exhibits minimum melting time which is 68.4% less as compared to the *** on the findings,it may be concluded that fins are the main driving agent in the enclosure to transfer the heat from heated wall to the *** design and positioning of the fins improve the heat transfer rate followed by melting of the PCM in the entire area of the *** of the favourable vortices and natural convection current in the enclosure accelerate the melting phenomenon and help to reduce charging time.

关键词： phase change material enclosure fin melting fraction energy storage heat transfer