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Acta Geochimica 2020年第2期39卷 226-235页

作者： Maha ahmed mohamed Abdallah ahmed mohamed Badr-ElDin Marine Pollution Lab National Institute of Oceanography and FisheriesAlexandriaEgypt Oceanography Department Faculty of ScienceAlexandria UniversityAlexandriaEgypt

A protected semi-enclosed embayment,the Eastern Harbor(EH),is situated in the central sector of the Mediterranean coast of Alexandria,*** is a famous fishing dock and water-sport center and its importance arose after the discovery of the Ptolemaic royal quarter of ancient *** protect this national treasure and improve its environmental health,the untreated anthropogenic effluents,which continued for decades into the EH since 1992,must be totally ***,it is an important issue to continually monitor and asses the environmental status of the *** sediment texture,total organic carbon,and the accumulation,distribution,and ecological risks of Cd,Cr,Pb,As,Hg and A1 were determined with a total of 14 surficial sediments samples collected in the EH during *** contents were compared to the literature data to assess the pollution status of *** factors,Degree of contamination(mCd)and potential ecological risk were calculated as a criterion of possible *** mCd calculation produces an overall average value for a range of pollutants,in the present study the contamination factor that provides a measure of the degree of overall contamination in the surface layers in a particular sampling site may provide a better indication of the state of pollution in the EH sediments than other indicators.

关键词： Heavy metals Eastern harbor Enrichment factors Degree of contamination Potential ecological risk

Friction and wear of sand-contaminated lubricated sliding

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Friction 2018年第4期6卷 457-463页

作者： mohamed ahmed RAMADAN Faculty of Engineering at Helwan Helwan University

This paper reports a test investigation of friction and wear responses from sand contaminated lubricated sliding. The influence of sand contaminants on wear and friction is characterized. Analyses are completed utilizing segments of piston ring sliding against the cylinder liner. Paraffin oil, with and without sand contaminants, is utilized. The effects of the concentration and particle size of sand are examined. Based on the observations in the present work, we found that friction and wear increase with sand concentration in the lube. Solid proposals ought to be considered, in order to enlighten the general population on the importance of changing a car engine's oil filter regularly.

关键词： sand contamination lubrication oil abrasive wear lubricated sliding

Developing Check-Point Mechanism to Protect Mobile Agent Free-Roaming Against Untrusted Hosts

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Computers, Materials & Continua 2022年第8期72卷 3849-3862页

作者： Tarig mohamed ahmed Department of Information Technology FCITKing Abdulaziz UniversityJeddahSaudi Arabia

Mobile Agent has many benefits over traditional distributed systems such as reducing latency,bandwidth,and *** Agent Systems are not fully utilized due to security *** paper focuses on mobile agent protection against malicious hosts.A new security mechanism called Checkpoints has been *** Mechanism(CPM)aims to protect Mobile Agent against malicious hosts in case of Capturing and Integrity *** assumes using a free-roaming mobility mechanism by Mobile agent *** main idea behind CPM is to generate multiple versions of Mobile *** multiple version is used to recover Mobile Agent from Capturing and Integrity attacks by untrusted *** versions are kept in Recovery Host(RH).RH plays a key role in CPM by controlling and monitoring MAs’recovery processes.A prototype method has been used to prove the feasibility of *** p https://***/Default-305-ARrototype was implemented by using *** framework and C#.full discussion for several scenarios has been done to analyze the feasibility and performance for *** found from this research,CPM has a strong ability to protect Mobile Agents from Capturing and Integrity attacks *** addition,there is no negative impact on the overall performance of the mobile agent system.

关键词： Mobile agent security capturing integrity attacks

Immunovirological Discordance and Associated Factors among People Living with HIV under Antiretroviral Treatment at Hôpital de Jour de Donka, Guinea

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Open Journal of Medical Microbiology 2024年第2期14卷 93-104页

作者： Mariama Sadjo Diallo Djiba Kaba Charles Tchibinda Delicat Issiaga Diallo Boh Fanta Diane Doufin Traore Ousmane Niabaly Oumar Mouctar Diallo Ouo-Ouo Yaramon Kolie Aly Patrice Kamano Pascal Koivogui ahmed Sékou Keita mohamed Macire Soumah Thierno Mamadou Tounkara mohamed Cisse Facult des Sciences et Techniques de la Sant Universit Gamal Abdel Nasser de Conakry Conakry Guine Laboratoire de Biologie Molculaire Nestor Bangoura/Helene Labrousse Hpital de Jour Donka CHU Donka Conakry Guine Centre dExcellence Africain Pour la Prvention et le Contrle des Maladies Transmissibles Conakry Guine Service de Dermatologie-Vnrologie CHU Donka Conakry Guine

The antiretroviral treatment (ART) has significantly reduced the number of new HIV/AIDS infections and related deaths. However, cases of immunovirological discordance (IVD) are found in various locations. The objective of this study was to determine the profile of People living with HIV (PLHIV) with IVD and to identify associated factors. We conducted a cross-sectional study based on the records of PLHIV under ART for at least 6 months, followed at Hpital de Jour Donka from 2015 to 2017, and having both viral load (CV) and CD4 T-cell count. Prevalence of IVD was 34.57%, with 23.87% for immunological discordance (ID) and 10.7% for virological discordance (VD). Females were predominant (66.26%), and male gender influenced IVD with a statistically significant difference (p = 0.006) and was associated with VD (p = 0.007). The average age was 38.77 11.30 years. PLHIV were classified at WHO stages 3 and 4 (86.01%). The median initial haemoglobin level was 11.5 g/L [3.2 - 12]. The mean initial CD4 T-cell count was 272.84 cells/mm3 201.6. The median initial viral load (VL) was 147,337 copies/mL [1092 - 31,675,000]. The initial CD4 T-cell count 3 was associated with IVD with a statistically significant difference (p = 0.0009) and correlated with ID (p = 0.000). Prurigo was associated with IVD with a statistically significant difference (p = 0.003). Cerebral toxoplasmosis was not associated with IVD but was associated with ID (p = 0.04). This study allowed us to describe the profile of PLHIV with IVD. The main associated factors were male gender, initial CD4 T-cell count 3, toxoplasmosis, prurigo, and herpes zoster.

关键词： HIV Antiretroviral Treatment (ART) Immunovirological Discordance Donka Guinea

Static and dynamic stability responses of multilayer functionally graded carbon nanotubes reinforced composite nanoplates via quasi 3D nonlocal strain gradient theory

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Defence Technology（防务技术） 2022年第10期18卷 1778-1809页

作者： ahmed Amine Daikh mohamed Sid ahmed Houari mohamed Ouejdi Belarbi Salwa A.mohamed mohamed A.Eltaher Laboratoire D'Etude des Structures et de Mecanique des Materiaux Departement de Genie CivilFacultedes Sciences et de La TechnologieUniversite Mustapha Stambouli B.P.305R.P.29000MascaraAlgeria Laboratoire de Genie Energetique et Materiaux LGEMUniversite de BiskraB.P.145R.P07000BiskraAlgeria Department of Engineering Mathematics Zagazig UniversityP.O.Box 44519ZagazigEgypt Faculty of Engineering Mechanical Engineering DepartmentKing Abdulaziz UniversityP.O.Box 80204JeddahSaudi Arabia Faculty of Engineering Mechanical Design and Production DepartmentZagazig UniversityP.O.Box 44519ZagazigEgypt

This manuscript presents the comprehensive study of thickness stretching effects on the free vibration,static stability and bending of multilayer functionally graded(FG)carbon nanotubes reinforced composite(CNTRC)*** nanoscale and microstructure influences are considered through a modified nonlocal strain gradient continuum *** on power-law functions,four different patterns of CNTs distribution are considered in this analysis,a uniform distribution UD,FG-V CNTRC,FG-X CNTRC,and FG-O CNTRC.A 3D kinematic shear deformation theory is proposed to include the stretching influence,which is neglected in classical ***'s principle is applied to derive the governing equations of motion and associated boundary *** solutions are developed based on Galerkin method to solve the governing equilibrium equations based on the generalized higher-order shear deformation theory and the nonlocal strain gradient theory and get the static bending,buckling loads,and natural frequencies of *** with previous works is presented.A detailed parametric analysis is carried out to highlight the impact of thickness stretching,length scale parameter(nonlocal),material scale parameter(gradient),CNTs distribution pattern,geometry of the plate,various boundary conditions and the total number of layers on the stresses,deformation,critical buckling loads and vibration *** new results are also reported in the current study,which will serve as a benchmark for future research.

关键词： 3D shear deformation theory Free vibration Buckling Bending Galerkin method Functionally graded nanotube Nonlocal strain gradient theory

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiberreinforced concrete railway sleepers

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Frontiers of Structural and Civil Engineering 2023年第3期17卷 411-428页

作者： Sayed ahmed Hossam ATEF mohamed HUSAIN Department of Structural Engineering Faculty of EngineeringZagazig UniversityZagazig 44519Egypt Track Work Department National Authority for TunnelsCairo 11522Egypt

In this study,ultrahigh-performance fiber-reinforced concrete(UHPFRC)used in a type B70 concrete sleeper is investigated experimentally and *** main parameters investigated are the steel fiber volume fractions(0%,0.5%,1%,and 1.5%).Under European standards,35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections,and the screw on the fastening system is pulled *** first cracking load,failure load,failure mode,crack propagation,load–deflection curve,load–crack width,and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete *** accuracy of the parametric study is verified ***,the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their *** and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is *** manufactured using UHPFRC with a steel fiber volume fraction of 1%and a concrete volume less than 25%that of standard sleeper B70 can be used under the same loads and requirements,which contributes positively to the cost and surrounding environment.

关键词： pre-stressed concrete sleeper ultrahigh performance fiber-reinforced concrete pull-out test static bending test steel fiber aspect ratio volume fraction

A hydromechanical approach for anisotropic elasto-viscoplastic geomaterials:Application to underground excavations in sedimentary rocks

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Underground Space 2019年第2期4卷 109-120页

作者： mohamed Mahjoub ahmed Rouabhi Mines ParisTech PSL Research UniversityCentre de Ge´osciencesFontainebleauFrance

To better describe excavation operations in deep geological formations,several aspects should be considered,especially the material anisotropy,time-dependent behavior,and hydromechanical *** the present paper,a hydromechanical model based on the framework of continuous porous media was *** mechanical elasto-viscoplastic constitutive model accounted for the material elastic and non-elastic anisotropies,using a transformation between the real transversely isotropic material and a fictitious isotropic *** the hydraulic behavior,the permeability was expressed as a function of the volumetric viscoplastic *** model was applied to a case study of two tunnel excavations in an anisotropic rock under an initial anisotropic stress *** results of the numerical simulations using a finite element code were in good agreement with the field convergence and permeability data.

关键词： Hydromechanical behavior Transverse isotropy Tunnel excavation Viscoplasticity Permeability

Nonalcoholic fatty liver disease and COVID-19:An epidemic that begets pandemic

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World Journal of Clinical Cases 2021年第17期9卷 4133-4142页

作者： Musaab ahmed mohamed H ahmed College of Medicine Ajman UniversityAjman 346United Arab Emirates Department of Medicine and HIV Metabolic Clinic Milton Keynes University Hospital NHS Foundation TrustMilton Keynes MK56LDUnited Kingdom

Coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has become a global pandemic,affecting all the individuals across the ***-19 has gained significant attention due to its high prevalence among individuals with diabetes,nonalcoholic fatty liver disease(NAFLD),and metabolic *** is the hepatic manifestation of metabolic syndrome and can be associated with a high risk of developing type 2 *** association of COVID-19 and NAFLD has also gained more attention because NAFLD is highly associated with the epidemic of *** is a potential risk factor for SARS-CoV-2 infection and severe COVID-19,independent of metabolic ***,it is not yet clear whether the epidemics of obesity and NAFLD have perpetuated the current pandemic of *** research is urgently needed to assess the following:(1)Whether NAFLD is a high risk factor for SARS-CoV-2 infection;(2)Whether NAFLD is associated with the severe form of COVID-19;and(3)Whether the presence of NAFLD can explain the racial variation in the morbidity and mortality associated with *** review summarizes the interactions between COVID-19 and NAFLD,mechanism of liver injury by COVID-19,and effect of lockdown due to COVID-19 on patients with NAFLD.

关键词： Fatty liver COVID-19 Diabetes Obesity Pandemic

Anti-wear properties evaluation of frictional sliding interfaces in automobile engines lubricated by copper/graphene nanolubricants

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Friction 2020年第5期8卷 905-916页

作者： mohamed Kamal ahmed ALI Xianjun HOU mohamed AAABDELKAREEM Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070China Automotive and Tractors Engineering Department Faculty of EngineeringMinia UniversityEl-Minia 61111Egypt Hubei Collaborative Innovation Center for Automotive Components Technology Wuhan 430070China

Owing to the significance of improving fuel economy, reducing emissions, and extending the durability of engine components, this study focused on the tribological performance of nano-additives. In this study, copper (Cu) and graphene (Gr) nanomaterials were dispersed in a fully formulated engine oil (5W-30) with different concentrations. The tribological trials were investigated under various speeds and loads, utilizing a reciprocating tribometer to mimic the ring/liner interfaces in the engine. The frictional surface morphologies were com-prehensively analyzed using electron probe X-ray microanalysis (EPMA), field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), and three dimensional (3D) surface profilometry to explore the mechanisms responsible for improving the tribological performance of the frictional sliding parts in the engine. The tribological test results illustrated that lubrication by nano-additives reduced the wear rate (WR) and friction coefficient (COF) by 25%–30% and 26.5%–32.6%, respectively, as compared with 5W-30. The results showed that this is a promising approach for increasing the durability and lifespan of frictional sliding components and fuel economy in automobile engines.

关键词： engine tribology nanomaterial nanolubricant friction wear tribofilm

SYNTHESIS,CHARACTERIZATION AND ENHANCED ELECTRICAL PROPERTIES OF CTAB-DIRECTED POLYANILINE NANOPARTICLES

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Chinese Journal of Polymer Science 2011年第2期29卷 181-190页

作者： Lal Said Jan mohamed ahmed Siddig Department of Physics Postgraduate College Mardan23200Khyber PakhtunkhwaPakistan School of Physics and Applied Physics Faculty of Science and TechnologyEL Neelain UniversityKhartoumSudan

Inverse microemulsion system of cetyltrimethylammonium bromide（CTAB） molecules is utilized for virtually monodispersed and controlled growth of HCl polyaniline（PANI） nanoparticles at room temperature（ca.300 K）.The templated electroconductive polymer reveals lamellar crystalline structure under X-ray diffraction signifying marked sub-chain alignment of the polymerized *** nanostructured polymer has spherically symmetric morphology in a size range of 2.0 nm to 6.0 nm under electron microscope *** permeation chromatography gives polydispersity index of 1.02 for nanostructured polymer in agreement with the size monodispersity transpired by electron *** *** conductivityσ_（dc） of PANI at room temperature is 10.11 S/cm whereas the variation of conductivity with temperature in the range 227-303 *** that the conducting mechanism can be considered as three-dimensional variable-range-hopping（3D-VRH）.UV-Vis spectrum indicates two broad absorption bands due to polaron formation that contributes to enhanced electrical conductivity of the *** fundamental absorption edge in the polymer is formed by direct allowed transitions to the extent that the optical band gap value was found to be 2.35 *** crystalline nanostructure and homogeneous doping attained in the cationic template of amphiphile are argued as contributing factors to the enhanced conductivity of the polymer.

关键词： Polyaniline Nanostructured Band gap energy Electrical conductivity