International Journal of Heat and Mass Transfer, 2013
A linear stability analysis is performed to study the effect of a vertical alternating current (A... more A linear stability analysis is performed to study the effect of a vertical alternating current (AC) electric field on the criterion for the onset of convection in a horizontal couple stress dielectric fluid layer heated uniformly either from below or from above. The lower and upper isothermal boundaries of the fluid layer are considered to be either rigid or free. The principle of exchange of stability is shown to be valid irrespective of the nature of velocity boundary conditions. The resulting eigenvalue problem is solved exactly for free-free boundaries and numerically using the Galerkin method for rigid-rigid boundaries. The stability characteristics of the system have been analyzed when the electric and buoyancy forces are acting together as well as in isolation and their coupling effects are highlighted in the presence of couple stresses. It is noted that there is a qualitative agreement between the results of free-free and rigid-rigid boundaries. The effect of increasing AC electric Rayleigh number is to increase the transfer of heat more effectively and hence to hasten the onset of convection. To the contrary, the effect of increasing couple stress parameter is to delay the onset of electrothermal convection. Moreover, the influence of couple stress on the stability characteristics of the system is found to be more pronounced for the case with rigid boundaries compared to the free boundaries case.
The present paper is aimed at studying the effect of gravity o n the general model of the equatio... more The present paper is aimed at studying the effect of gravity o n the general model of the equations of the generalized therm omicrostretch for a homogeneous isotropic elastic half-spa ce solid whose surface is subjected to a Mode-I crack problem . The problem is in the context of the Green and Naghdi theory (GN). The norm al ode analysis is used to obtain the exact expressions for t he displacement components, the force stresses, the temperat ure, the couple stresses and the microstress distribution. The variations of the considered variables through the horizontal distance are i llustrated graphically. Comparisons are made with the resu lts in the presence and absence of gravity with two cases: Case (1) for the genera lized micropolar thermoelasticity elastic medium (withou t microstretch constants) between the both types (II, III). Case (2) for the generalized micropolar thermoelasticity elastic medium ( without micropolar constants) between the both types II and III.
The aim of this paper is to introduce the Green-Naghdi (G-N) theory of type III (with energy diss... more The aim of this paper is to introduce the Green-Naghdi (G-N) theory of type III (with energy dissipation) to study the effect of thermal loading due to laser pulse on generalized micropolar thermoelastic homogeneous isotropic medium in three dimensions. The normal mode analysis technique is used to solve the resulting non-dimensional equations of the problem. Numerical results for the displacement, thermal stress, strain, temperature, couple stresses and micro-rotation distributions are represented graphically to display the effect of the laser pulse on the resulting quantities. Comparisons are made within the theory in the presence and absence of the laser pulse.
An effect of three factors-the order of fractional derivative, the hydrostatic initial stress, an... more An effect of three factors-the order of fractional derivative, the hydrostatic initial stress, and parameter of magnetic field-on the plane waves in the half-space made of fiber-reinforced material, that is described by the theory of generalized magnetothermoelasticity, is studied. The problem is solved numerically using the normal mode analysis. The results correspond to the Lord-Shulman model and the model, that uses the fractional derivatives and are presented in the form of graphs. The findings show pronounced effect of mentioned three factors. The results are compared with the case, when the initial stress and magnetic field are absent.
Journal of Computational and Theoretical Nanoscience, 2015
The present chapter is concerned with the investigation of disturbances in a homogeneous, isotrop... more The present chapter is concerned with the investigation of disturbances in a homogeneous, isotropic, generalized thermo-viscoelastic material with voids and two-temperature under the effect of moving loads. The problem formulated in the context of Green-Naghdi theories (G-N II without energy dissipation and G-N III with energy dissipation). The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by G-N II and G-N III theories in the presence and absence of moving initial stress
Journal of Computational and Theoretical Nanoscience, 2015
Three-phase-lag theory of thermoelasticity is employed to study the deformation of thermoelastic ... more Three-phase-lag theory of thermoelasticity is employed to study the deformation of thermoelastic solid half-space under hydrostatic initial stress and rotation with two-temperature. The normal mode analysis is used to obtain the analytical expressions of the displacement components, force stress, thermodynamic temperature and conductive temperature. The numerical results are given and presented graphically when mechanical and thermal force is applied. Comparisons are made with the results predicted by three phase lag, Green-Naghdi III and Lord-Shulman in the presence and absence of initial stress as well as rotation.
The purpose of this paper is to study the thermoviscoelastic interactions in a homogeneous, isotr... more The purpose of this paper is to study the thermoviscoelastic interactions in a homogeneous, isotropic semi-infinite solid under two-temperature theory with heat source. The Kelvin-Voigt model of linear viscoelasticity which describes the viscoelastic nature of the material is used. The bounding plane surface of the medium is subjected to a non-Gaussian laser pulse. The generalized thermoelasticity theory with dual phase lags model is used to solve this problem. Laplace transform technique is used to obtain the general solution for a suitable set of boundary conditions. Some comparisons have been shown in figures to estimate the effects of the phase lags, viscosity, temperature discrepancy, laser-pulse and the laser intensity parameters on all the studied fields. A comparison was also made with the results obtained in the case of one temperature thermoelasticity theory.
The dual-phase-lag (DPL) model is applied to study the influence of rotation on a two-dimensional... more The dual-phase-lag (DPL) model is applied to study the influence of rotation on a two-dimensional micro-elongated thermoelastic medium problem. Mechanical force along with the layer of the elastic half-space interface and micro-elongated thermoelastic half-space is applied. The analytic expressions for displacement component, temperature distribution, micro-elongational scalar and stress components have been derived and represented graphically. The rotation has been studied in the presence DPL model and Lord-Shulman theory.
This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with v... more This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with voids problem. The problem is assessed according to three-phase-lag model. The normal mode analysis used to obtain the analytical expressions of the considered variables. The non-dimensional displacement, temperature, Micro rotation, the change in the volume fraction field, and stress of the material are obtained and illustrated graphically. Comparisons are made with the results predicted by two theories; namely three- phase-lag model (3PHL) and Green-Naghdi theory of type III (G-N III). The considered variables were plotted for different values of the rotation parameter, the phase-lag of heat flux and the phase-lag of temperature. The numerical results reveal that the rotation and the phase-lag times significantly influence the distribution of the field quantities. Some particular cases of interest are deduced from the present investigation.
A new model of equations of generalized thermoelasticity for an isotropic medium with mechanical ... more A new model of equations of generalized thermoelasticity for an isotropic medium with mechanical properties that are dependent on temperature is established. The present problem is a generalization of the three-phase-lag model, Lord and Shulman's coupled theory. The elasticity modulus is a reference temperature function which is linear. Analytical expressions of the considered variables are obtained by using the Laplace–Fourier transforms technique. The results are analysed in a deeper manner by comparing them with unique cases of absence of the magnetic field, temperature-dependent properties of the body, and two types of mechanical loads. The most significant points are highlighted.
Female, 82 FINAL DIAGNOSIS: Achalasia Symptoms: Nocturnal regurgtation • weight loss - Clinical P... more Female, 82 FINAL DIAGNOSIS: Achalasia Symptoms: Nocturnal regurgtation • weight loss - Clinical Procedure: Esophageal stenting Specialty: Gastroenterology • Hepatology Objective: Unusual or unexpected effect of treatment. Pneumatic dilatation is one of the most effective methods for treating achalasia. Esophageal perforation is the most serious complication after pneumatic dilatation and has been reported to occur in the range of 1 to 4.3%. The appropriate management of esophageal perforation can range from conservative medical treatment to surgical intervention. We report a case of an 82-year-old male who had an 8 month history of dysphagia for solid and liquids, a 10 lb weight loss and nocturnal regurgitation. The diagnosis of achalasia was established by endoscopic; barium and manometric criteria. He underwent a pneumatic dilation with a 30 mm Rigiflex balloon. A confined or limited esophageal perforation projecting into the mediastinum and located 1-2 cm above the diaphragm was ...
Introduction. Colorectal anastomotic leak or stricture is a dreaded complication leading to signi... more Introduction. Colorectal anastomotic leak or stricture is a dreaded complication leading to significant morbidity and mortality. The novel use of self-expandable metal stents (SEMS) in the management of postoperative colorectal anastomotic leaks or strictures can avoid surgical reintervention. Methods. Retrospective study with particular attention to the indications, operative or postoperative complications, and clinical outcomes of SEMS placement for patients with either a colorectal anastomotic stricture or leak. Results. Eight patients had SEMS (WallFlex stent) for the management of postoperative colorectal anastomotic leak or stricture. Five had a colorectal anastomotic stricture and 3 had a colorectal anastomotic leak. Complete resolution of the anastomotic stricture or leak was achieved in all patients. Three had recurrence of the anastomotic stricture on 3-month flexible sigmoidoscopy follow-up after the initial stent was removed. Two of these patients had a stricture that wa...
Calculating the adenoma detection rate (ADR) is a complex process in contrast to the polyp detect... more Calculating the adenoma detection rate (ADR) is a complex process in contrast to the polyp detection rate (PDR) that can be easily calculated. The average adenoma to polyp detection rate quotient (APDRQ) was proposed as a conversion factor to estimate the ADR for individual endoscopists from the endoscopist's PDR. However, this conversion factor was not validated in different practice settings. To validate the use of the proposed conversion factor in a practice setting with a predominantly Hispanic population. We conducted a retrospective, cross-sectional study (December 2007 to November 2012) of screening colonoscopies at a university practice setting with an 86.9% Hispanic population. The actual ADR and PDR were calculated for all endoscopists. The weighted average of ADR to PDR ratio for each endoscopist was used to obtain APDRQ. The APDRQ was used as a conversion multiplier to estimate each endoscopist's ADR using the single endoscopist's PDR. A total of 2148 screening colonoscopies were included. The average PDR for the whole group was 36.9% (range, 11% to 49%). The actual ADR was estimated as 25.5% (range, 11% to 37%). The average APDRQ for our group was 0.68. The estimated ADR was 25.48% (range, 8% to 33%). There was a high correlation between actual ADR and the estimated ADR (Pearson correlation=0.92). In a practice setting with a predominantly Hispanic population, a conversion factor can be used to estimate ADR from PDR providing a high degree of correlation with the actual ADR.
A model of the equations of two-dimensional problems is studied in a half space, whose surface in... more A model of the equations of two-dimensional problems is studied in a half space, whose surface in a medium free of micropolar thermoelastic possesses cubic symmetry as a result of inclined load. There acts an initial magnetic parallel to the plane boundary of the half-space. The inclined load is assumed to be a linear combination of a normal load and a tangential load. The formulation is performed in the context of the Lord-Shulman and Green-Lindsay theories, as well as the classical dynamical coupled theory. Comparisons are made with the results in the presence of a magnetic.
A model of the equations of two-dimensional problems is studied in a half space, whose surface in... more A model of the equations of two-dimensional problems is studied in a half space, whose surface in a medium free of micropolar thermoelastic possesses cubic symmetry as a result of inclined load. There acts an initial magnetic parallel to the plane boundary of the half-space. The inclined load is assumed to be a linear combination of a normal load and a tangential load. The formulation is performed in the context of the Lord-Shulman and Green-Lindsay theories, as well as the classical dynamical coupled theory. Comparisons are made with the results in the presence of a magnetic.
A new simple well-behaved definition of the fractional derivative termed as conformable fractiona... more A new simple well-behaved definition of the fractional derivative termed as conformable fractional derivative and introducing a geometrical approach of fractional derivatives, non-integral order initial value problems are an attempt to solve in this article. Based on the geometrical interpretation of the fractional derivatives, the solution curve is approximated numerically. Two special phenomena are employed for concave upward and downward curves. In order to obtain the solution of fractional order differential equation (FDE) with the integer-order initial condition, some new criteria on fractional derivatives are proposed.
In this chapter, we will compare the differential transform method (DTM) and variational iteratio... more In this chapter, we will compare the differential transform method (DTM) and variational iteration method (VIM) for solving the one-dimensional, time dependent reaction-diffusion equations. Different cases of the equation are discussed and analytical solution in series form can be derived. The results obtained by the proposed method (DTM) are compared with the results obtained by (VIM). Some examples are presented to show the ability of the methods for such problems.
International Journal of Heat and Mass Transfer, 2013
A linear stability analysis is performed to study the effect of a vertical alternating current (A... more A linear stability analysis is performed to study the effect of a vertical alternating current (AC) electric field on the criterion for the onset of convection in a horizontal couple stress dielectric fluid layer heated uniformly either from below or from above. The lower and upper isothermal boundaries of the fluid layer are considered to be either rigid or free. The principle of exchange of stability is shown to be valid irrespective of the nature of velocity boundary conditions. The resulting eigenvalue problem is solved exactly for free-free boundaries and numerically using the Galerkin method for rigid-rigid boundaries. The stability characteristics of the system have been analyzed when the electric and buoyancy forces are acting together as well as in isolation and their coupling effects are highlighted in the presence of couple stresses. It is noted that there is a qualitative agreement between the results of free-free and rigid-rigid boundaries. The effect of increasing AC electric Rayleigh number is to increase the transfer of heat more effectively and hence to hasten the onset of convection. To the contrary, the effect of increasing couple stress parameter is to delay the onset of electrothermal convection. Moreover, the influence of couple stress on the stability characteristics of the system is found to be more pronounced for the case with rigid boundaries compared to the free boundaries case.
The present paper is aimed at studying the effect of gravity o n the general model of the equatio... more The present paper is aimed at studying the effect of gravity o n the general model of the equations of the generalized therm omicrostretch for a homogeneous isotropic elastic half-spa ce solid whose surface is subjected to a Mode-I crack problem . The problem is in the context of the Green and Naghdi theory (GN). The norm al ode analysis is used to obtain the exact expressions for t he displacement components, the force stresses, the temperat ure, the couple stresses and the microstress distribution. The variations of the considered variables through the horizontal distance are i llustrated graphically. Comparisons are made with the resu lts in the presence and absence of gravity with two cases: Case (1) for the genera lized micropolar thermoelasticity elastic medium (withou t microstretch constants) between the both types (II, III). Case (2) for the generalized micropolar thermoelasticity elastic medium ( without micropolar constants) between the both types II and III.
The aim of this paper is to introduce the Green-Naghdi (G-N) theory of type III (with energy diss... more The aim of this paper is to introduce the Green-Naghdi (G-N) theory of type III (with energy dissipation) to study the effect of thermal loading due to laser pulse on generalized micropolar thermoelastic homogeneous isotropic medium in three dimensions. The normal mode analysis technique is used to solve the resulting non-dimensional equations of the problem. Numerical results for the displacement, thermal stress, strain, temperature, couple stresses and micro-rotation distributions are represented graphically to display the effect of the laser pulse on the resulting quantities. Comparisons are made within the theory in the presence and absence of the laser pulse.
An effect of three factors-the order of fractional derivative, the hydrostatic initial stress, an... more An effect of three factors-the order of fractional derivative, the hydrostatic initial stress, and parameter of magnetic field-on the plane waves in the half-space made of fiber-reinforced material, that is described by the theory of generalized magnetothermoelasticity, is studied. The problem is solved numerically using the normal mode analysis. The results correspond to the Lord-Shulman model and the model, that uses the fractional derivatives and are presented in the form of graphs. The findings show pronounced effect of mentioned three factors. The results are compared with the case, when the initial stress and magnetic field are absent.
Journal of Computational and Theoretical Nanoscience, 2015
The present chapter is concerned with the investigation of disturbances in a homogeneous, isotrop... more The present chapter is concerned with the investigation of disturbances in a homogeneous, isotropic, generalized thermo-viscoelastic material with voids and two-temperature under the effect of moving loads. The problem formulated in the context of Green-Naghdi theories (G-N II without energy dissipation and G-N III with energy dissipation). The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by G-N II and G-N III theories in the presence and absence of moving initial stress
Journal of Computational and Theoretical Nanoscience, 2015
Three-phase-lag theory of thermoelasticity is employed to study the deformation of thermoelastic ... more Three-phase-lag theory of thermoelasticity is employed to study the deformation of thermoelastic solid half-space under hydrostatic initial stress and rotation with two-temperature. The normal mode analysis is used to obtain the analytical expressions of the displacement components, force stress, thermodynamic temperature and conductive temperature. The numerical results are given and presented graphically when mechanical and thermal force is applied. Comparisons are made with the results predicted by three phase lag, Green-Naghdi III and Lord-Shulman in the presence and absence of initial stress as well as rotation.
The purpose of this paper is to study the thermoviscoelastic interactions in a homogeneous, isotr... more The purpose of this paper is to study the thermoviscoelastic interactions in a homogeneous, isotropic semi-infinite solid under two-temperature theory with heat source. The Kelvin-Voigt model of linear viscoelasticity which describes the viscoelastic nature of the material is used. The bounding plane surface of the medium is subjected to a non-Gaussian laser pulse. The generalized thermoelasticity theory with dual phase lags model is used to solve this problem. Laplace transform technique is used to obtain the general solution for a suitable set of boundary conditions. Some comparisons have been shown in figures to estimate the effects of the phase lags, viscosity, temperature discrepancy, laser-pulse and the laser intensity parameters on all the studied fields. A comparison was also made with the results obtained in the case of one temperature thermoelasticity theory.
The dual-phase-lag (DPL) model is applied to study the influence of rotation on a two-dimensional... more The dual-phase-lag (DPL) model is applied to study the influence of rotation on a two-dimensional micro-elongated thermoelastic medium problem. Mechanical force along with the layer of the elastic half-space interface and micro-elongated thermoelastic half-space is applied. The analytic expressions for displacement component, temperature distribution, micro-elongational scalar and stress components have been derived and represented graphically. The rotation has been studied in the presence DPL model and Lord-Shulman theory.
This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with v... more This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with voids problem. The problem is assessed according to three-phase-lag model. The normal mode analysis used to obtain the analytical expressions of the considered variables. The non-dimensional displacement, temperature, Micro rotation, the change in the volume fraction field, and stress of the material are obtained and illustrated graphically. Comparisons are made with the results predicted by two theories; namely three- phase-lag model (3PHL) and Green-Naghdi theory of type III (G-N III). The considered variables were plotted for different values of the rotation parameter, the phase-lag of heat flux and the phase-lag of temperature. The numerical results reveal that the rotation and the phase-lag times significantly influence the distribution of the field quantities. Some particular cases of interest are deduced from the present investigation.
A new model of equations of generalized thermoelasticity for an isotropic medium with mechanical ... more A new model of equations of generalized thermoelasticity for an isotropic medium with mechanical properties that are dependent on temperature is established. The present problem is a generalization of the three-phase-lag model, Lord and Shulman's coupled theory. The elasticity modulus is a reference temperature function which is linear. Analytical expressions of the considered variables are obtained by using the Laplace–Fourier transforms technique. The results are analysed in a deeper manner by comparing them with unique cases of absence of the magnetic field, temperature-dependent properties of the body, and two types of mechanical loads. The most significant points are highlighted.
Female, 82 FINAL DIAGNOSIS: Achalasia Symptoms: Nocturnal regurgtation • weight loss - Clinical P... more Female, 82 FINAL DIAGNOSIS: Achalasia Symptoms: Nocturnal regurgtation • weight loss - Clinical Procedure: Esophageal stenting Specialty: Gastroenterology • Hepatology Objective: Unusual or unexpected effect of treatment. Pneumatic dilatation is one of the most effective methods for treating achalasia. Esophageal perforation is the most serious complication after pneumatic dilatation and has been reported to occur in the range of 1 to 4.3%. The appropriate management of esophageal perforation can range from conservative medical treatment to surgical intervention. We report a case of an 82-year-old male who had an 8 month history of dysphagia for solid and liquids, a 10 lb weight loss and nocturnal regurgitation. The diagnosis of achalasia was established by endoscopic; barium and manometric criteria. He underwent a pneumatic dilation with a 30 mm Rigiflex balloon. A confined or limited esophageal perforation projecting into the mediastinum and located 1-2 cm above the diaphragm was ...
Introduction. Colorectal anastomotic leak or stricture is a dreaded complication leading to signi... more Introduction. Colorectal anastomotic leak or stricture is a dreaded complication leading to significant morbidity and mortality. The novel use of self-expandable metal stents (SEMS) in the management of postoperative colorectal anastomotic leaks or strictures can avoid surgical reintervention. Methods. Retrospective study with particular attention to the indications, operative or postoperative complications, and clinical outcomes of SEMS placement for patients with either a colorectal anastomotic stricture or leak. Results. Eight patients had SEMS (WallFlex stent) for the management of postoperative colorectal anastomotic leak or stricture. Five had a colorectal anastomotic stricture and 3 had a colorectal anastomotic leak. Complete resolution of the anastomotic stricture or leak was achieved in all patients. Three had recurrence of the anastomotic stricture on 3-month flexible sigmoidoscopy follow-up after the initial stent was removed. Two of these patients had a stricture that wa...
Calculating the adenoma detection rate (ADR) is a complex process in contrast to the polyp detect... more Calculating the adenoma detection rate (ADR) is a complex process in contrast to the polyp detection rate (PDR) that can be easily calculated. The average adenoma to polyp detection rate quotient (APDRQ) was proposed as a conversion factor to estimate the ADR for individual endoscopists from the endoscopist's PDR. However, this conversion factor was not validated in different practice settings. To validate the use of the proposed conversion factor in a practice setting with a predominantly Hispanic population. We conducted a retrospective, cross-sectional study (December 2007 to November 2012) of screening colonoscopies at a university practice setting with an 86.9% Hispanic population. The actual ADR and PDR were calculated for all endoscopists. The weighted average of ADR to PDR ratio for each endoscopist was used to obtain APDRQ. The APDRQ was used as a conversion multiplier to estimate each endoscopist's ADR using the single endoscopist's PDR. A total of 2148 screening colonoscopies were included. The average PDR for the whole group was 36.9% (range, 11% to 49%). The actual ADR was estimated as 25.5% (range, 11% to 37%). The average APDRQ for our group was 0.68. The estimated ADR was 25.48% (range, 8% to 33%). There was a high correlation between actual ADR and the estimated ADR (Pearson correlation=0.92). In a practice setting with a predominantly Hispanic population, a conversion factor can be used to estimate ADR from PDR providing a high degree of correlation with the actual ADR.
A model of the equations of two-dimensional problems is studied in a half space, whose surface in... more A model of the equations of two-dimensional problems is studied in a half space, whose surface in a medium free of micropolar thermoelastic possesses cubic symmetry as a result of inclined load. There acts an initial magnetic parallel to the plane boundary of the half-space. The inclined load is assumed to be a linear combination of a normal load and a tangential load. The formulation is performed in the context of the Lord-Shulman and Green-Lindsay theories, as well as the classical dynamical coupled theory. Comparisons are made with the results in the presence of a magnetic.
A model of the equations of two-dimensional problems is studied in a half space, whose surface in... more A model of the equations of two-dimensional problems is studied in a half space, whose surface in a medium free of micropolar thermoelastic possesses cubic symmetry as a result of inclined load. There acts an initial magnetic parallel to the plane boundary of the half-space. The inclined load is assumed to be a linear combination of a normal load and a tangential load. The formulation is performed in the context of the Lord-Shulman and Green-Lindsay theories, as well as the classical dynamical coupled theory. Comparisons are made with the results in the presence of a magnetic.
A new simple well-behaved definition of the fractional derivative termed as conformable fractiona... more A new simple well-behaved definition of the fractional derivative termed as conformable fractional derivative and introducing a geometrical approach of fractional derivatives, non-integral order initial value problems are an attempt to solve in this article. Based on the geometrical interpretation of the fractional derivatives, the solution curve is approximated numerically. Two special phenomena are employed for concave upward and downward curves. In order to obtain the solution of fractional order differential equation (FDE) with the integer-order initial condition, some new criteria on fractional derivatives are proposed.
In this chapter, we will compare the differential transform method (DTM) and variational iteratio... more In this chapter, we will compare the differential transform method (DTM) and variational iteration method (VIM) for solving the one-dimensional, time dependent reaction-diffusion equations. Different cases of the equation are discussed and analytical solution in series form can be derived. The results obtained by the proposed method (DTM) are compared with the results obtained by (VIM). Some examples are presented to show the ability of the methods for such problems.
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Papers by Mohamed I.A. Othman