Is Prolonged Sitting a Risk Factor in Developing Hemorrhoids and Anal Fissures?

Background: Anal fissures and hemorrhoids are common anal conditions. They cause significant morbidity, social embarrassment, and work absenteeism. In addition, they form a significant workload on the healthcare system. Nevertheless, the etiology of these conditions is still contentious. It has been observed that hemorrhoids and anal fissures are associated with prolonged sitting. This study aims to investigate this observation.Methods: This is a case–control study. We compared 81 patients with symptomatic and endoscopically proven hemorrhoids and/or anal fissures with 162 controls with no symptoms or endoscopic evidence of perianal disease. The study was conducted at Khartoum North Teaching Hospital (KNTH) endoscopy unit between January and December 2019. Demographic data, sitting hours per day, and endoscopic findings of patients and controls were recorded in a proforma. The cases and controls were matched for age, sex, and bowel habits. Data were analyzed and compared using the SPSS version 23.Results: The mean sitting hours for cases was 5.99 (SD 3.4) whereas that for controls was 4.0 (SD 3.0) with a highly significant difference (P < 0.001). Sitting for 5 hr or more per day (exposure) was associated with an increased risk of developing hemorrhoids and/or anal fissures [odds ratio 3.68, 95% CI: 2.1–6.47].Conclusion: The study showed that sitting down for 5 hr or more per day might increase the risk of developing hemorrhoids and/or anal fissures. This finding could help in the prevention and treatment of these diseases and the reduction of recurrences

Unsteady reactive magnetic radiative micropolar flow, heat and mass transfer from an inclined plate with joule heating: a model for magnetic polymer processing

Magnetic polymer materials processing involves many multi-physical and chemical effects. Motivated by such applications, in the present work a theoretical analysis is conducted of combined heat and mass transfer in unsteady mixed convection flow of micropolar fluid over an oscillatory inclined porous plate in a homogenous porous medium with heat source, radiation absorption and Joule dissipation. A first order homogenous chemical reaction model is used. The transformed non-dimensional boundary value problem is solved using a perturbation method and Runge-Kutta fourth order numerical quadrature (shooting technique). The emerging parameters dictating the transport phenomena are shown to be the gyro-viscosity micropolar material parameter, magnetic field parameter, permeability of the porous medium, Prandtl number, Schmidt number, thermal Grashof number, species Grashof number, thermal radiation-conduction parameter, heat absorption parameter, radiation absorption parameter, Eckert number, chemical reaction parameter and Eringen coupling number (vortex viscosity ratio parameter). The impact of these parameters on linear velocity, microrotation (angular velocity), temperature and concentration are evaluated in detail. Results for skin friction coefficient, couple stress coefficient, Nusselt number and Sherwood number are also included. Couple stress is observed to be reduced with stronger magnetic field. Verification of solutions is achieved with earlier published analytical results

Variable Viscosity Effect on Heat Transfer over a Continuous Moving Surface with Variable Internal Heat Generation in Micropolar Fluids

Abstract The effect of temperature-dependent viscosity on heat transfer over a continuous moving surface with variable internal heat generation in micropolar fluids is studied. The fluid viscosity is assumed to vary as inverse linear function of temperature. The governing equations are transformed into dimensionless forms using the stream function and suitable variables then solved numerically using the Runge-Kutta numerical integration, procedure in conjunction with shooting technique. A parametric study illustrating the influence of the viscosity parameter, heat source generation and micropolar parameter on the velocity, microrotation and temperature profiles skin friction, couple stress as well as the Nusselt are investigated. The results of the parametric study are shown in graphic and tabulated. Keywords: micropolar fluids, internal heat generation, heat transfer, temperature dependent viscosity 6366 M. Modather M. Abdou and E. Roshdy EL-Zahar 1-Introduction Most studies of the problems of heat transfer are based on the constant physical properties of the ambient fluid. However, it is known that these properties may change with temperature, especially for fluid viscosity. To accurately predict the flow and heat transfer rates, it is necessary to take account of this variation of viscosity. The flow over a stretching surface is an important problem in many engineering processes with applications in industries such as extrusion, melt-spinning, the hot rolling, wire drawing, glass fiber production, manufacture of plastic and rubber sheets, cooling of a large metallic plate in a bath, which may be an electrolyte, etc. In industry, polymer sheets and filaments are manufactured by continuous extrusion of the polymer from a die to a windup roller, which is located at a finite distance away. has reported flow and heat characteristics on a stretched surface subject to power-law velocity and temperature distributions. The flow field of a stretching wall with a power-law velocity variation was discussed by Banks [6]. Heat transfer over a stretching surface with internal heat generation or absorption is examined by Elbashbeshy and Bazid [7]. In all of the above mentioned studies the viscosity of the fluid was assumed to be constant. However it is known that this physical property may change significantly with temperature. To accurately predict the flow behavior, it is necessary to take into account this variation of viscosity. Elbashbeshy and Bazid In the present work we study the effect of temperature-dependent viscosity on heat transfer over a continuous moving surface with variable internal heat generation in micropolar fluids. The fluid viscosity is assumed to vary as inverse linear function of temperature. The governing equations are transformed into dimensionless forms using the stream function and suitable variables then solved numerically using the Runge-Kutta numerical integration, procedure in conjunction with shooting technique. Numerical result are presented in terms of local skin friction coefficient, rate of heat transfer and wall couple stress for various values of heat source generation λ, variable viscosity θ r parameters against micropolar parameter Δ. The effect of variation in λ, θ r and Δ on the dimensionless velocity, temperature and microrotation distribution are also depicted graphically. 2-Mathematical Formulation Consider a steady, two-dimensional laminar flow of a viscous incompressible micropolar fluid on a continuous, stretching surface with uniform surface temperature T w and velocity U w moving axially through a stationary fluid. The xaxis runs along the continuous surface in the direction of the motion and y-axis is perpendicular to it. According to the assumption, the two-dimensional boundary layer equations for the flow of the fluid over a continuous moving surface are as flows: Mass: Momentum: Angular momentum: Energy: Variable viscosity effect on heat transfer 6369 In the above equations u and v are the components of fluid velocity in the x and y directions respectively, ρ ∞ is the density away from the hot plate, N is the component of microrotation, T is the fluid temperature in the boundary layer region. μ and k are respectively the dynamic viscosity and the thermal conductivity, c p is the specific heat at constant pressure, T ∞ is the free stream temperature and Q is the volumetric rate of heat generation. With the associated boundary conditions: The case 1 N -2 u y ∂ = ∂ results in the vanishing of the anti-symmetric part of the stress tensor and represents weak concentrations [16]. Ahmadi suggested that the particle spin is equal to the fluid vorticity at the boundary for fine particle suspensions. [ ] So that viscosity is an inverse linear function of temperature T. Equation (6) can be written as: ( ) The corresponding boundary conditions transform to: Where Where B is dimensionless parameter, Δ is a micropolar parameter, λ is the heat source or sink parameters, Pr is the Prandtl number and the primes denote differentiation with respect to η. The quantities of physical interested, namely, the local skin friction C f ,the wall couple stress, m w and the rate of heat transfer in terms of local Nusselt number Nu x are prescribed by: where τ w is the skin friction and q w is the heat transfer from the sheet are given by: 3-Results and Discussion Equations Since θ varies from zero at the edge of the boundary layer to one at the surface, the largest change in the fluid viscosity from its free-stream value μ ∞ , occurs at the wall, where Then cannot take values between zero and one and that the constraints, θ r > 1 for gases and θ r < 0, for liquids. These tables indicate that as heat source or sink parameter λ increases leads to a significant change in Nusselt number but slight change in the value of skin friction factor and wall couple stress. We also notice from these tables that the viscosity variation parameter θ r has a significant effect on skin friction factor, local Nusselt number and wall couple stress. In cases gases (Pr=0.78) and liquids (Pr=7.0), as the viscosity variation and heat source or sink parameters increase, the thermal boundary layer thickness decreases and thus the rate of the heat transfer increases. The viscosity variation parameter also has a noticeable effect 6372 M. Modather M. Abdou and E. Roshdy EL-Zahar on the local skin friction coefficient and wall couple stress, increasing the viscosity within the boundary layer leads to decreasing in the velocity within the layer and thus decrease the local skin friction coefficient and wall couple stress decreases for both gases (Pr=0.78) and liquids (Pr=7.0). The results indicate also, as the micropolar parameter Δ increases both Nusselt number and local skin friction coefficient increase while the value of wall couple stress decrease for gases and increases for liquids. The effect of heat source or sink parameter, λ=0.0,0.2,0.4,0.6. on velocity, temperature and microrotation fields against η at θ r =2.0, -2.0 for the fluid with Pr=0.78, 7.0 and Δ=3.0 is shown in 4-Concluding Remarks In the present work we introduced theoretically study the effect of temperaturedependent viscosity on heat transfer over a continuous moving surface with variable internal heat generation in micropolar fluids is studied. These results indicate that as heat source or sink parameter λ increases leads to a significant change in Nusselt number but slight change in the value of skin friction factor and wall couple stress. In cases gases (Pr=0.78) and liquids (Pr=7.0), as the viscosity variation and heat source or sink parameters increase, the thermal boundary layer thickness decreases and thus the rate of the heat transfer increases. The viscosity variation parameter also has a noticeable effect on the local skin friction coefficient and wall couple stress, increasing the viscosity within the boundary layer leads to decreasing in the velocity within the layer and thus decrease the local skin friction coefficient and wall couple stress decreases for both gases and liquids. The results indicate also that as the micropolar parameter Δ increases both Variable viscosity effect on heat transfer 6373 Nusselt number and local skin friction coefficient increase while the value of wall couple stress decrease for gases and increases for liquids. Acknowledgements The authors gratefully acknowledge Research Centre, Salman Bin Abdul Aziz University, Kingdom of Saudi Arabia, for supporting and encouragement during this work