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Journal of Central South University 2016年第4期23卷 991-999页

作者： ahmed M.Megahed Department of Mathematics Faculty of Science Benha University (13518)

This study examines theoretically and computationally the non-Newtonian boundary layer flow and heat transfer for a viscoelastic fluid over a stretching continuous sheet embedded in a porous medium with variable fluid properties, slip velocity, and internal heat generation/absorption. The flow in boundary layer is considered to be generated solely by the stretching of the sheet adjacent to porous medium with boundary wall slip condition. Highly nonlinear momentum and thermal boundary layer equations governing the flow and heat transfer are reduced to set of nonlinear ordinary differential equations by appropriate transformation. The resulting ODEs are successfully solved numerically with the help of shooting method. Graphical results are shown for non-dimensional velocities and temperature. The effects of heat generation/absorption parameter, the porous parameter, the viscoelastic parameter, velocity slip parameter, variable thermal conductivity and the Prandtl number on the flow and temperature profiles are presented. Moreover, the local skin-friction coefficient and Nusselt number are presented. Comparison of numerical results is made with the earlier published results under limiting cases.

关键词： viscoelastic fluid variable fluid properties slip velocity

Variable fluid properties and variable heat flux effects on the flow and heat transfer in a non-Newtonian Maxwell fluid over an unsteady stretching sheet with slip velocity

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Chinese Physics B 2013年第9期22卷 480-485页

作者： ahmed M. Megahed Department of Mathematics Faculty of ScienceBenha University

The effects of variable fluid properties and variable heat flux on the flow and heat transfer of a non-Newtonian Maxwell fluid over an unsteady stretching sheet in the presence of slip velocity have been studied. The governing differential equations are transformed into a set of coupled non-linear ordinary differential equations and then solved with a numerical technique using appropriate boundary conditions for various physical parameters. The numerical solution for the governing non-linear boundary value problem is based on applying the fourth-order Runge-Kutta method coupled with the shooting technique over the entire range of physical parameters. The effects of various parameters like the viscosity parameter, thermal conductivity parameter, unsteadiness parameter, slip velocity parameter, the Deborah number, and the Prandtl number on the flow and temperature profiles as well as on the local skin-friction coefficient and the local Nusselt number are presented and discussed. Comparison of numerical results is made with the earlier published results under limiting cases.

关键词： Maxwell fluid unsteady stretching sheet variable fluid properties variable heat flux

Modeling natural convection boundary layer flow of micropolar nanofluid over vertical permeable cone with variable wall temperature

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Applied Mathematics and Mechanics(English Edition) 2017年第8期38卷 1171-1180页

作者： S.E.ahmed Department of Mathematics Faculty of ScienceSouth Valley UniversityQena 83523Egypt

This paper discusses the natural convection boundary layer flow of a micropo- lax nanofluid over a vertical permeable cone with variable wall temperatures. Non-similax solutions are obtained. The nonlineaxly coupled differential equations under the boundary layer approximations governing the flow axe solved numerically using an efficient, itera- tive, tri-diagonal, implicit finite difference method. Different experimental correlations for both nanofluid effective viscosity and nanofluid thermal conductivity are considered. It is found that as the vortex-viscosity parameter increases, both the velocity profiles and the local Nusselt number decrease. Also, among all the nanoparticles considered in this investigation, Cu gives a good convection.

关键词： micropolar nanofluid non-similar solution cone finite difference method,non-uniform heating

Mutations in Plasmodium knowlesi Kelch protein 13 and the dihydropteroate synthase gene in clinical samples

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Asian Pacific Journal of Tropical Medicine 2023年第2期16卷 72-79,I0004,I0005,I0006,I0007页

作者： ahmed Saif Department of Clinical Laboratory Sciences Faculty of Applied Medical SciencesNajran UniversityP.O.Box 1988Najran 61441Saudi Arabia

Objective:To determine the genetic diversity,natural selection and mutations in Plasmodium(P.)knowlesi drug resistant molecular markers Kelch 13 and dhps gene in clinical samples of ***:*** full-length gene sequences Kelch 13 gene(PkK13)from 40 samples and dhps gene from 30 samples originating from Malaysian Borneo were retrieved from public *** diversity,natural selection,and phylogenetic analysis of gene sequences were analysed using DNAsp v5.10 and MEGA ***:Seventy-two single nucleotide polymorphic sites(SNPs)across the full-length PkK13 gene(63 synonymous substitutions and 9 non-synonymous substitutions)with nucleotide diversity ofπ~0.005 was *** of the full-length Pkdhps gene revealed 73 SNPs andπ~0.006(44 synonymous substitutions and 29 non-synonymous substitutions).A high number of haplotypes(PkK13;H=37 and Pkdhps;H=29)with haplotype diversity of Hd~0.99 were found in both genes,indicating population *** mutant alleles were identified in PkK13 amino acid alignment of which,7(Asp3Glu,Lys50Gln,Lys53Glu,Ser123Thr,Ser127Pro,Ser149Thr and Ala169Thr)were within the Plasmodium specific domain,2(Val372Ile and Lys424Asn)were in the BTB/POZ domain and no mutation was observed within the kelch propeller *** 29 non-synonymous mutations in the Pkdhps gene were novel and only presented in exon 1 and ***:Monitoring the mutations from clinical samples collected from all states of Malaysia along with clinical efficacy studies will be necessary to determine the drug resistance in ***.

关键词： Plasmodium knowlesi Kelch 13 dhps Dihydropteroate synthase Drug resistance Mutation

Roll-pitch-yaw autopilot design for nonlinear time-varying missile using partial state observer based global fast terminal sliding mode control

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Chinese Journal of Aeronautics 2016年第5期29卷 1302-1312页

作者： ahmed Awad Wang Haoping Sino-French International Joint Laboratory of Automatic Control and Signal Processing (LaFCAS) School of AutomationNanjing University of Science & Technology

The acceleration autopilot design for skid-to-turn （STT） missile faces a great challenge owing to coupling effect among planes, variation of missile velocity and its parameters, inexistence of a complete state vector, and nonlinear aerodynamics. Moreover, the autopilot should be designed for the entire flight envelope where fast variations exist. In this paper, a design of integrated roll-pitch-yaw autopilot based on global fast terminal sliding mode control （GFTSMC） with a partial state nonlinear observer （PSNLO） for STT nonlinear time-varying missile model, is employed to address these issues. GFTSMC with a novel sliding surface is proposed to nullify the integral error and the singularity problem without application of the sign function. The proposed autopilot consisting of two-loop structure, controls STT maneuver and stabilizes the rolling with a PSNLO in order to estimate the immeasurable states as an output while its inputs are missile measurable states and control signals. The missile model considers the velocity variation, gravity effect and parameters＇ variation. Furthermore, the environmental conditions＇ dynamics are mod- eled. PSNLO stability and the closed loop system stability are studied. Finally, numerical simulation is established to evaluate the proposed autopilot performance and to compare it with existing approaches in the literature.

关键词： Flight control system Global fast terminal slidingmode control Integrated autopilot Nonlinear state observer Skid-to-turn missile

Closed Timelike Curves in Type Ⅱ Non-Vacuum Spacetime

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Communications in Theoretical Physics 2017年第2期67卷 189-191页

作者： Faizuddin ahmed Hindustani Kendriya Vidyalaya Bhangagarh Guwahati-781005 Assam Affiliated by CBSE New Delhi India

Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.

关键词： closed timelike curves Misner space pure radiation

Biomathematical study of time-dependent flow of a Carreau nanofluid through inclined catheterized arteries with overlapping stenosis

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Journal of Central South University 2017年第11期24卷 2725-2744页

作者： Ashfaq ahmed Sohail Nadeem Department of Mathematics Quaid-I-Azam UniversityIslamabad 45320Pakistan

This work is concerned with the analysis of blood flow through inclined catheterized arteries having a balloon(angioplasty) with time-variant overlapping stenosis. The nature of blood in small arteries is analyzed mathematically by considering it as a Carreau nanofluid. The highly nonlinear momentum equations of nanofluid model are simplified by considering the mild stenosis case. The formulated problem is solved by a homotopy perturbation expansion in terms of a variant of the Weissenberg number to obtain explicit forms for the axial velocity, the stream function, the pressure gradient, the resistance impedance and the wall shear stress distribution. These solutions depend on the Brownian motion number, thermophoresis number, local temperature Grashof number G_r and local nanoparticle Grash of number B_r. The results were also studied for various values of the physical parameters, such as the Weissenberg number W_i, the power law index n, the taper angle φ, the maximum height of stenosis δ~*, the angle of inclination α, the maximum height of balloon σ~*, the axial displacement of the balloon z_d~*,the flow rate F and the Froud number Fr. The obtained results show that the transmission of axial velocity curves through a Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) is substantially lower than that through a Carreau nanofluid near the wall of balloon while the inverse occurs in the region between the balloon and stenosis. The streamlines have a clearly distinguished shifting toward the stenotic region and this shifting appears near the wall of the balloon, while it has almost disappeared near the stenotic wall and the trapping bolus in the case of horizontal arteries and Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) does not appear but for the case of Carreau nanofluid bolus appears.

关键词： overlapping stenosed artery nanofluid Grashof number Brownian motion thermophoresis pharmacology

Isolation of Cr(Ⅵ) reducing bacteria from industrial effuents and their potential use in bioremediation of chromium containing wastewater

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Journal of Environmental Sciences 2009年第6期21卷 814-820页

作者： ahmed Zahoor Abdul Rehman Department of Microbiology and Molecular Genetics University of the PunjabNew Campus

The present study was aimed to assess the ability of Bacillus ***-2-1 and Staphylococcus capitis to reduce hexavalent chromium into its trivalent *** ***-2-1 could tolerate Cr（Ⅵ）（4800 μg/mL） and *** could tolerate Cr（Ⅵ）（2800 μg/mL）.Both organisms were able to resist Cd^2＋（50 μg/mL）,Cu^2＋（200 μg/mL）,Pb^2＋（800 μg/mL）,Hg^2＋（50 μg/mL） and Ni2＋（4000 μg/mL）.*** resisted Zn^2＋ at 700 μg/mL while Bacillus ***-2-1 only showed resistance up to 50 μg/*** ***-2-1 and *** showed optimum growth at pH 6 and 7,respectively,while both bacteria showed optimum growth at 37°*** ***-2-1 and *** could reduce 85% and 81% of hexavalent chromium from the medium after 96 h and were also capable of reducing hexavalent chromium 86% and 89%,respectively,from the industrial effuents after 144 *** free extracts of Bacillus ***-2-1 and *** showed reduction of 83% and 70% at concentration of 10 μg Cr（Ⅵ）/mL,*** presence of an induced protein having molecular weight around 25 kDa in the presence of chromium points out a possible role of this protein in chromium *** bacterial isolates can be exploited for the bioremediation of hexavalent chromium containing wastes,since they seem to have a potential to reduce the toxic hexavalent form to its nontoxic trivalent form.

关键词： Cr(Ⅵ) reducing bacteria bioremediation Bacillus sp. JDM-2-1 Staphylococcus capitis

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

Chandelier-assisted scleral buckling using wide angle viewing contact lens for pseudophakic retinal detachment repair

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International Journal of Ophthalmology(English edition) 2019年第4期12卷 627-633页

作者： Ashraf ahmed Nossair Wael ahmed Ewais Sherif ahmed Eissa Department of Ophthalmology Faculty of Medicine Cairo University Dar El Oyoun Hospital

AIM: To evaluate a modified technique for scleral buckling(SB) in pseudophakic retinal detachment(RD).METHODS: A retrospective non-comparative study included 21 consecutive eyes with uncomplicated pseudophakic RD that was repaired by chandelier assisted SB using wide angle viewing(WAV) contact lens. Segmental tire alone was used in 5 eyes(23.81%), and combined with encircling band in 7 eyes(33.33%). Radial sponge alone was used in 3 eyes(14.29%) and combined with encircling band in 6 eyes(28.57%).RESULTS: Primary success rate was(90.48%). External drainage of subretinal fluid was performed in 8 eyes(38.1%). Intraoperative complications included vitreous prolapse at chandelier sclerotomy site in 4 eyes(19.05%) and localized subretinal hemorrhage at drainage site in one eye(4.76%). No case of intraocular lens(IOL) displacement, retinal incarceration or iatrogenic retinal tear was detected. Postoperative complications included choroidal detachment in one eye(4.76%), elevated intraocular pressure in 2 eyes(9.52%), epiretinal membrane formation in one eye(4.76%) and proliferative vitreoretinopathy in 3 eyes(14.29%). Mean postoperative corrected distance visual acuity was 0.7±0.3 logMAR units. CONCLUSION: Chandelier-assisted SB using WAV contact lens is a reliable technique for repairing selected cases of simple pseudophakic RD.

关键词： buckling pseudophakia rhegmatogenous detachment