Effect of heat and mass transfer and rotation on peristaltic flow through a porous medium with compliant walls

Purpose: The purpose of this paper is to investigate the peristaltic flow of an incompressible Newtonian fluid in a channel with compliant walls. The effects of rotation and heat and mass transfer are also taken into account. The governing equations of two dimensional fluid have been simplified under long wavelength and low Reynolds number approximation. An exact solutions is presented for the stream function, temperature, concentration field, velocity and heat transfer coefficient. Design/methodology/approach: The effect of the concentration distribution, heat and mass transfer and rotation on the wave frame are analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and heat and mass transfer. Findings: The results indicate that the effect of the permeability and rotation are very pronounced in the phenomena. Originality/value: The objective of the present analysis is to analyze the effects of rotation, heat and mass transfer and compliant walls on the peristaltic flow of a viscous fluid

Thermal Radiation and MHD Effects on Free Convective Flow of a Polar Fluid through a Porous Medium in the Presence of Internal Heat Generation and Chemical Reaction

An analysis is presented to study the MHD free convection with thermal radiation and mass transfer of polar fluid through a porous medium occupying a semi-infinite region of the space bounded by an infinite vertical porous plate with constant suction velocity in the presence of chemical reaction, internal heat source, viscous and Darcy's dissipation. The highly nonlinear coupled differential equations governing the boundary layer flow, heat, and mass transfer are solved by using a two-term perturbation method with Eckert number as a perturbation parameter. The results are obtained for velocity, angular velocity, temperature, concentration, skin friction, Nusselt number, and Sherwood number. The effect of various material parameters on flow, heat, and mass transfer variables is discussed and illustrated graphically

Effects of Rotation and Gravity Field on Surface Waves in Fibre-Reinforced Thermoelastic Media under Four Theories

Estimation is done to investigate the gravitational and rotational parameters effects on surface waves in fibre-reinforced thermoelastic media. The theory of generalized surface waves has been firstly developed and then it has been employed to investigate particular cases of waves, namely, Stoneley waves, Rayleigh waves, and Love waves. The analytical expressions for surface waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations and four thermoelastic theories. The wave velocity equations have been obtained in different cases. The numerical results are given for equation of coupled thermoelastic theory (C-T), Lord-Shulman theory (L-S), Green-Lindsay theory (G-L), and the linearized (G-N) theory of type II. Comparison was made with the results obtained in the presence and absence of gravity, rotation, and parameters for fibre-reinforced of the material media. The results obtained are displayed by graphs to clear the phenomena physical meaning. The results indicate that the effect of gravity, rotation, relaxation times, and parameters of fibre-reinforced of the material medium is very pronounced

Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field

Inflation and late time acceleration in braneworld cosmological models with varying brane tension

Braneworld models with variable brane tension $\lambda$ introduce a new degree of freedom that allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We consider a thermodynamic interpretation of the varying brane tension models, by showing that the field equations with variable $\lambda$ can be interpreted as describing matter creation in a cosmological framework. The particle creation rate is determined by the variation rate of the brane tension, as well as by the brane-bulk energy-matter transfer rate. We investigate the effect of a variable brane tension on the cosmological evolution of the Universe, in the framework of a particular model in which the brane tension is an exponentially dependent function of the scale factor. The resulting cosmology shows the presence of an initial inflationary expansion, followed by a decelerating phase, and by a smooth transition towards a late accelerated de Sitter type expansion. The varying brane tension is also responsible for the generation of the matter in the Universe (reheating period). The physical constraints on the model parameters, resulted from the observational cosmological data, are also investigated.Comment: 25 pages, 8 figures, accepted for publication in European Physical Journal

Reheating the Universe in Braneworld Cosmological Models with bulk-brane energy transfer

The emergence of the cosmological composition (the reheating era) after the inflationary period is analyzed in the framework of the braneworld models, in which our Universe is a three-brane embedded in a five-dimensional bulk, by assuming the possibility of the brane-bulk energy exchange. The inflaton field is assumed to decay into normal matter only, while the dark matter is injected into the brane from the bulk. To describe the reheating process we adopt a phenomenological approach, by describing the decay of the inflaton field by a friction term proportional to the energy density of the field. After the radiation dominated epoch the model reduces to the standard four dimensional cosmological model. The modified field equations are analyzed analytically and numerically in both the extra-dimensions dominate reheating phase (when the quadratic terms in energy density dominate the dynamics), and in the general case. The evolution profiles of the matter, of the scalar field and of the scale factor of the universe are obtained for different values of the parameters of the model, and of the equations of state of the normal and dark matter, respectively. The equation describing the time evolution of the ratio of the energy density of the dark and of the normal matter is also obtained. The ratio depends on the rate of the energy flow between the bulk and the brane. The observational constraint of an approximately constant ratio of the dark and of the baryonic matter requires that the dark matter must be non-relativistic (cold). The model predicts a reheating temperature of the order of $3\times 10^6$ GeV, a brane tension of the order of $10^{25}$ GeV$^4$, and the obtained composition of the universe is consistent with the observational data.Comment: 29 pages, 9 figures, accepted for publication in JCA

Mortality of Patients Lost to Follow-Up in Antiretroviral Treatment Programmes in Resource-Limited Settings: Systematic Review and Meta-Analysis

BACKGROUND: The retention of patients in antiretroviral therapy (ART) programmes is an important issue in resource-limited settings. Loss to follow up can be substantial, but it is unclear what the outcomes are in patients who are lost to programmes. METHODS AND FINDINGS: We searched the PubMed, EMBASE, Latin American and Caribbean Health Sciences Literature (LILACS), Indian Medlars Centre (IndMed) and African Index Medicus (AIM) databases and the abstracts of three conferences for studies that traced patients lost to follow up to ascertain their vital status. Main outcomes were the proportion of patients traced, the proportion found to be alive and the proportion that had died. Where available, we also examined the reasons why some patients could not be traced, why patients found to be alive did not return to the clinic, and the causes of death. We combined mortality data from several studies using random-effects meta-analysis. Seventeen studies were eligible. All were from sub-Saharan Africa, except one study from India, and none were conducted in children. A total of 6420 patients (range 44 to 1343 patients) were included. Patients were traced using telephone calls, home visits and through social networks. Overall the vital status of 4021 patients could be ascertained (63%, range across studies: 45% to 86%); 1602 patients had died. The combined mortality was 40% (95% confidence interval 33%-48%), with substantial heterogeneity between studies (P<0.0001). Mortality in African programmes ranged from 12% to 87% of patients lost to follow-up. Mortality was inversely associated with the rate of loss to follow up in the programme: it declined from around 60% to 20% as the percentage of patients lost to the programme increased from 5% to 50%. Among patients not found, telephone numbers and addresses were frequently incorrect or missing. Common reasons for not returning to the clinic were transfer to another programme, financial problems and improving or deteriorating health. Causes of death were available for 47 deaths: 29 (62%) died of an AIDS defining illness. CONCLUSIONS: In ART programmes in resource-limited settings a substantial minority of adults lost to follow up cannot be traced, and among those traced 20% to 60% had died. Our findings have implications both for patient care and the monitoring and evaluation of programmes

Correlates of Syphilis Seroreactivity Among Pregnant Women: The HIVNET 024 Trial in Malawi, Tanzania, and Zambia

The objectives of this cross-sectional study were to determine correlates of syphilis seroprevalence among HIV-infected and -uninfected antenatal attendees in an African multisite clinical trial, and to improve strategies for maternal syphilis prevention