Heat transfer in viscoplastic boundary layer flow from a vertical permeable cone with momentum and thermal wall slip : numerical study

A mathematical model is presented for the laminar free convection boundary layer flow of Casson viscoplastic non-Newtonian fluid external to a vertical penetrable circular cone in the presence of thermal and hydrodynamic slip conditions. The cone surface is maintained at non-uniform surface temperature. The boundary layer conservation equations, which are parabolic in nature, are transformed into non-dimensional form via appropriate similarity variables, and the emerging boundary value problem is solved computationally with the second order accurate implicit Keller-box finite-difference scheme. The influence of velocity (momentum) slip, thermal slip and Casson non-Newtonian parameter on velocity, temperature, skin friction and Nusselt number are illustrated graphically. Validation of solutions with earlier published work is included. The computations show that the flow near the cone surface is strongly decelerated with increasing momentum slip whereas the temperature and thermal boundary layer thickness are increased. Increasing Casson parameter generally decelerates the flow and also decreases temperatures. Both velocity and thermal boundary layer thickness are reduced with greater Prandtl number. The study is relevant to petro-chemical engineering (polymer) processing systems

Free convection heat and mass transfer of a nanofluid past a horizontal cylinder embedded in a non-Darcy porous medium

In the present paper, we analyzed the laminar boundary layer flow and heat transfer from a horizontal cylinder in a nanofluid-saturated non-Darcy porous medium in the presence of thermal radiation. This is the first paper presenting non-similar solutions for such a regime.The boundary layer conservation equations,which are parabolic in nature,are normalized into non-similar form and then solved computationally with an efficient, implicit, stable Keller-box finite difference scheme. Non-Darcy effects are simulated via a second-order Forchheimer drag force term in the momentum boundary layer equation. The model used for the nanofluid incorporates the effects of Brownian motion, buoyancy ratio, and thermophoresis. A non-similarity solution is presented that depends on the Brownian motion number (Nb), buoyancy ratio (Nr), thermophoresis number (Nt), Forchheimer parameter (Λ), and radiation parameter (F). Velocity is reduced with increasing Forchheimer parameter, whereas temperature and nanoparticle concentration are both enhanced.The model finds applications in energy systems and thermal enhancement of industrial flow processe

Numerical study of viscoelastic micropolar heat transfer from a vertical cone for thermal polymer coating

A mathematical model is developed to study laminar, nonlinear, non-isothermal, steady-state free convection boundary layer flow and heat transfer of a micropolar viscoelastic fluid from a vertical isothermal cone. The Eringen model and Jeffery’s viscoelastic model are combined to simulate the non-Newtonian characteristics of polymers, which constitutes a novelty of the present work. The transformed conservation equations for linear momentum, angular momentum and energy are solved numerically under physically viable boundary conditions using a finite difference scheme (Keller Box method). The effects of Deborah number (De), Eringen vortex viscosity parameter (R), ratio of relaxation to retardation times (λ), micro-inertia density parameter (B), Prandtl number (Pr) and dimensionless stream wise coordinate (ξ) on velocity, surface temperature and angular velocity in the boundary layer regime are evaluated. The computations show that with greater ratio of retardation to relaxation times, the linear and angular velocity are enhanced whereas temperature (and also thermal boundary layer thickness) is reduced. Greater values of the Eringen parameter decelerate both the linear velocity and micro-rotation values and enhance temperatures. Increasing Deborah number decelerates the linear flow and Nusselt number whereas it increases temperatures and boosts micro-rotation magnitudes. The study is relevant to non-Newtonian polymeric thermal coating processes

Numerical study of non-Newtonian polymeric boundary layer flow and heat transfer from a permeable horizontal isothermal cylinder

In this article, we investigate the nonlinear steady state boundary layer flow and heat transfer of an incompressible Jeffery non-Newtonian fluid from a permeable horizontal isothermal cylinder. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a versatile, implicit, finite-difference technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely with Deborah number (De), surface suction parameter (S), Prandtl number (Pr), ratio of relaxation to retardation times (λ) and dimensionless tangential coordinate (ξ) on velocity and temperature evolution in the boundary layer regime are examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate and local skin friction are also investigated. It is found that the velocity is reduced with increasing Deborah number whereas temperature is enhanced. Increasing λ enhances the velocity but reduces the temperature. The heat transfer rates is found to be depressed with increasing Deborah number, De, and enhanced with increasing λ. Local skin friction is found to be decreased with a rise in Deborah number whereas it is elevated with increasing values of relaxation to retardation time ratio (λ). Increasing suction decelerates the flow and cools the boundary layer i.e. reduces temperatures. With increasing tangential coordinate, the flow is also decelerated whereas the temperatures are enhanced. The simulation is relevant to polymer coating thermal processing. Polymeric enrobing flows are important in industrial manufacturing technology and process systems. Such flows are non-Newtonian. Motivated by such applications, we did the present problem

Open Problems on Central Simple Algebras

We provide a survey of past research and a list of open problems regarding central simple algebras and the Brauer group over a field, intended both for experts and for beginners.Comment: v2 has some small revisions to the text. Some items are re-numbered, compared to v

Effect of Zinc Supplementation on Growth of Low Birth Weight Infants Aged 1–6 Mo in Ardabil, Iran

Objective To assess the effect of zinc supplementation on growth of low birth weight (LBW) infants aged 1–6 mo. Methods LBW infants were enrolled at birth and randomly assigned to receive 5 mg elemental Zn per day (n=45) or placebo (n=45) until 6 mo of age. They were followed monthly for information on compliance; anthropometric measurements were performed monthly. Results After randomization, 5 infants from zinc group and 9 from placebo group were excluded. At 6 mo of age, significantly greater weight gains were observed in the zinc than in the placebo group (4995±741g in zinc group vs. 3896±865 g in placebo group, p = 0.036). Length gain during the study period improved in zinc group (16.9±8.2 cm vs. 15.1±4.1 cm, p = 0.039); after zinc supplementation head circumference were increased (8.7±1.4 cm vs.7.4± 1.5 cm p<0.001). In male infants, total weight gain and height and head circumference gain were higher in the zinc than in the placebo group. However, only head circumference change was statistically significant. A similar trend was observed among female infants, but these differences were not statistically significant. There was no significant relation between breast-feeding status and the main outcome variables. Conclusions Infants in the present study showed improve¬ments in growth rate, but more studies are required in this field to confirm this fact

Counting and effective rigidity in algebra and geometry

The purpose of this article is to produce effective versions of some rigidity results in algebra and geometry. On the geometric side, we focus on the spectrum of primitive geodesic lengths (resp., complex lengths) for arithmetic hyperbolic 2-manifolds (resp., 3-manifolds). By work of Reid, this spectrum determines the commensurability class of the 2-manifold (resp., 3-manifold). We establish effective versions of these rigidity results by ensuring that, for two incommensurable arithmetic manifolds of bounded volume, the length sets (resp., the complex length sets) must disagree for a length that can be explicitly bounded as a function of volume. We also prove an effective version of a similar rigidity result established by the second author with Reid on a surface analog of the length spectrum for hyperbolic 3-manifolds. These effective results have corresponding algebraic analogs involving maximal subfields and quaternion subalgebras of quaternion algebras. To prove these effective rigidity results, we establish results on the asymptotic behavior of certain algebraic and geometric counting functions which are of independent interest.Comment: v.2, 39 pages. To appear in Invent. Mat

In vitro effects of zinc on the cytokine production from peripheral blood mononuclear cells in patients with zinc allergy.

Metals, such as nickel, cobalt, chromium and zinc, are ubiquitous in the environment. Systemic reactions, including hand dermatitis and generalized eczematous reactions, can be caused by the dietary ingestion of metals. In this study, we aimed to determine whether the cytokine production from peripheral blood mononuclear cells (PBMCs) obtained from zinc allergy patients can be used as a sensitive marker to investigate zinc-allergic contact dermatitis. The diagnosis of sensitivity to metal was made based on the results of a metal patch test. The PBMCs were stimulated with various concentrations (5-100 μM) of zinc sulfate (ZnSO4) for 24 h. The culture supernatants were collected and analyzed using ELISA for measurement of the cytokine production. The levels of IFN-γ, TNF-α, IL-1β, IL-5, IL-13 and MIF were significantly higher in the zinc-allergic patients (n = 5) than in the healthy controls (n = 5) at 100 μM of ZnSO4 stimulation. Although, patch testing is considered as standard test to diagnose metal allergy but false-positive and -negative reactions may limit its use in conditions of existing dermatitis. Therefore, this study suggest that in support of patch testing the determination of cytokine production using PBMCs cultures would be helpful for making an early diagnosis of such conditions

A study on wear failure analysis of tungsten carbide hardfacing on carbon steel blade in a digester tank

This paper addresses wear failure analysis of tungsten carbide (WC) hardfacing on a carbon steel blade known as the continuous digester blade (CD blade). The CD blade was placed in a digester tank to mix ilmenite ore with sulphuric acid as part of a production process. Tungsten carbide hardfacing was applied on the CD blade to improve its wear resistance while the CD blade was exposed to an abrasive and acidic environment. Failure analysis was car-ried out on the hardfaced CD blade in order to improve its wear resistance and lifetime. A thickness and hardness comparison study was conducted on worn and unworn specimens from the CD blades. The carbide distribution along with elemental composition analysis of the hardfaced CD blade specimens was examined using scanning electron microscopy and energy-dispersive spectroscopy. The investigation revealed that an inconsistent hardfacing thickness was welded around the CD blade. Minimum coating thickness was found at the edges of the blade surfaces causing failure to the blades as the bare carbon steel blades were exposed to the mixed environment. The wear resistance of the CD blade can be improved by distributing the carbide uniformly on the hardfaced coating. Applying extra coating coverage at the critical edge will prevent the exposure of bare carbon steel blade, thus increasing the CD blade lifetime

Moderators, Mediators, and Other Predictors of Risperidone Response in Children with Autistic Disorder and Irritability

Objective/Background: The National Institute of Mental Health (NIMH) Research Units on Pediatric Psychopharmacology (RUPP) Autism Network found an effect size of d = 1.2 in favor of risperidone on the main outcome measure in an 8-week double-blind, placebo-controlled trial for irritabilityin autistic disorder. This paper explores moderators and mediators of this effect. Method: Intention-to-treat (ITT) analyses were conducted with suspected moderators and mediators entered into the regression equations. MacArthur Foundation Network subgroup guidelines were followed in the evaluation of the results. Results: Only baseline severity moderated treatment response: Higher severity showed greater improvement for risperidone but not for placebo. Weight gain mediated treatment response negatively: Those who gained more weight improved less with risperidone and more with placebo. Compliance correlated with outcome for risperidone but not placebo. Higher dose correlated with worse outcome for placebo, but not risperidone. Of nonspecific predictors, parent education, family income, and low baseline prolactin positively predicted outcome; anxiety, bipolar symptoms, oppositional-defiant symptoms, stereotypy, and hyperactivity negatively predicted outcome. Risperidone moderated the effect of change in 5'-nucleotidase, a marker of zinc status, for which decrease was associated with improvement only with risperidone, not with placebo. Conclusion: The benefit–risk ratio of risperidone is better with greater symptom severity. Risperidone can be individually titrated to optimal dosage for excellent response in the majority of children. Weight gain is not necessary for risperidone benefit and may even detract from it. Socioeconomic advantage, low prolactin, and absence of co-morbid problems non-specifically predict better outcome. Mineral interactions with risperidone deserve further study