Carbon nano-materials were applied to the gas Diffusion layers of PEMFC. Gas Diffusion layers consist of gas Diffusion medium (carbon cloth or carbon paper) and micro-layers. Carbon actives have been widely used for the micro-layers. Main functions of gas Diffusion layers are distribution of reactants to the active site of electrode, management of water supplied and/or generated and enhancement of electrical contact between the electrode and the bipolar plates. In this work, nano-tubes are adopted to the micro-layer of gas Diffusion layers. The micro-porous layer of the GDLs as seen under scanning electron microscope showed excellent surface morphology showing the reinforcement with nano-tubes and the surface homogeneity without any cracks. In this work, the 50% of carbon nano tube and 50% of carbon active contained micro-layer case showed the best I-V performance. By applying nano-materials, thinner micro-layers can be fabricated. This newly made micro-layer showed higher gas permeability and good electric conductivity with similar degree of water management as well as enhanced performance.

Arterial drug concentration distribution determines local toxicity. The safety issues dealing with Drug-Eluting Stents reveal the needs for investigation on the effective factors contributing to fluctuations in arterial drug uptake. The current study focuses on the importance of hypertension as an important and controversial risk factor among researchers on the efficacy of Heparin-Eluting Stents. For this purpose, the effect of blood pressure is systematically investigated in certain cardiac cycle modes. A comprehensive study is conducted on two classes, pulsatile (time-dependent), to have a more realistic simulation, and non-pulsatile (time-independent) blood flow, each one in four modes. The governing equations applied to drug release dynamics are obtained based on porous media theory. The equations are solved numerically using the Finite Volume Method. Results reveal that there is a significant difference when the plasma flow considered, and when it is neglected (regardless of time dependency). Moreover, the concentration level is more decreased in pulsatile blood flow rather than the non-pulsatile blood flow, although the penetration depth for pressure and concentration are nearly 20% and 5% of the wall thickness, respectively. In other words, the mass experienced by the arterial wall is lower in pulsatile blood flow in comparison to non-pulsatile blood flow. As a consequence, the risk of toxicity is declined as the blood pressure increases. Also, it can be seen that the polymer is Diffusion-dominated so that no significant changes in the release characteristics are observed in the presence of the plasma filtration.

Aim: The aim of this study was to compare the effects of Ethylen glycol tetra acetic acid (EGTA) and EDTA for their smear layer removal capability using scanning electron microscopy technique.Material and Methods: A group of 28 single rooted teeth were instrumented to size 60 master file. Four teeth were also kept as control while the remaining teeth were divided into two groups. Group A: in which 12teeth were irrigated with 10 ml of 17% EGTA for 2 minutes? Group B: consisted of 12teeth irrigated with 10 ml of 17% EDTA for 2 minutes. Both groups were then irrigated with 10 ml of 5% Naocl. the control group were just irrigated with 10 ml of 5 % Naocl. All teeth in then the control group were only irrigated with 10 ml of 5% Nacl. Specimeus were then sectioned longitudinally. A scanning electrone microscope was wsed to in vetig ate the intenal surfaces of the canal.Results: EGTA chelated dentin surface more conservatively than EDTA without causing erosion.Conclusion: It seems that EGTA can be used safely to remove smear layer from the canal surfaces.

Gas Diffusion layers are essential components of proton exchange membrane fuel cell since the reactants should pass through these layers. Mass transport in these layers is highly dependent on porosity. Many of simulations have assumed, for simplicity, the porosity of GDL is constant, but in practice, there is a considerable variation in porosity along gas Diffusion layers. In the present study the porosity variation in GDL is calculated by considering the applied pressure and the amount of water generated in the cell. A two dimensional mathematical model is developed to investigate the effect of stack compression and water generation on porosity of GDL and cell performance. The validity of the model is assessed by comparing the computed results with experimental data. The results show that when the electrical current density is low, the porosity variation in the gas Diffusion layer has no significant influence on the level of polarization whereas at higher current density the influence is very significant. It is also shown that, the electrical current has a sharp gradient across the catalyst layer. Therefore, the better cell performance could be achieved by adding a certain amount of catalyst loading to each electrode, with respect to the reactant concentration.

In Polymer Electrolyte Membrane Fuel Cell (PEMFC), heat and water are generated as a side-production. The accumulated water leads to a decrease in PEMFCs efficiency; therefore, water has to be removed and flooding has to be prevented. In this study, by an experimental model and implementation of transparent Gas-Diffusion layer (GDL), water transport in PEMFC is visualized and the fingering mechanisms in GDL are studied. The effect of added Micro Porous layer (MPL) on water flooding in GDL has been also examined. Results show the characteristics of the two-phase regime in GDL are similar to the capillary fingering. Moreover; the fingers inside the GDL are generated by the capillary forces. In addition, it is observed that lateral flow on the Catalyst layer (CL) leads to an increase in water flooding in GDL in which PEMFC efficiency is decreased.

In this article, unsteady boundary layer flow formed over a vertical surface due to impulsive mo-tion and buoyancy is investigated. The mathematical model which properly accounts for space and temperature-dependent internal heat source in a flowing fluid is incorporated into the energy equa-tion. This model is presented in this study as a term which accounts for two different forms of internal heat generation during the short time period and long time period. Due to the fluid flow under consideration, the influence of thermal-Diffusion and Diffusion-thermo are incorporated into the governing equation since it may not be realistic to assume that both effects are of smaller order of magnitude than the effects described by Fourier’s or Fick’s law. The corresponding effect of in-ternal heat source on viscosity is considered, the viscosity is assumed to vary as a linear function of temperature. The flow model is described in terms of a highly coupled and nonlinear system of partial differential equations. The governing equations are nondimensionalized by using suitable similarity transformation which unraveled the behavior of the fluid flow at short time and long time periods. The dimensionless system of non-linear coupled partial differential equations (PDEs) is solved using Bivariate Spectral Relaxation Method (BSRM). A parametric study of selected parameters is conducted and results of the surface shear stress, heat transfer and mass transfer at the wall are illustrated graphically and physical aspects of the problem are discussed.

Background: Prostate cancer is the third leading cause of death and is the most common cause of cancer in elderly men. Regarding to the low accuracy of screening methods such as prostate-specific antigen (PSA), Digital Rectal Examination (DRE) and trans rectal ultrasound (TRUS) in detection and localization of tumor, Magnetic Resonance Imaging (MRI) and Diffusion Weighted Imaging (DWI) attracted many attentions in the past years. DWI reveals micro-molecular Diffusion, which is the Brownian motion of the spins in biologic tissues. This technique can delineate pathologic lesions with high tissue contrast against generally suppressed background signal. In this paper, the value of DWI in detection of prostate cancer is studied.Methods: In this cross-sectional study, the studied population are suspicious patients to prostate cancer based on high Prostatic Specific Antigen level or abnormal Digital Rectal Examination who refered for prostate biopsy to radiology department of Hazrate- Rasoul Hospital during the year 2011. The results of DWI are compared to biopsy results for all patients.Results: Eighty five patients are selected. The DWI sensitivity in detecting of prostate cancer is 100%, specificity 97.1% and positive and negative predictive values are 89.5% and 100%, respectively. The results showed that if DWI reports the prostate cancer as negative, the result was highly reliable and if it reports as positive, although the report was not 100% reliable, but it still had high reliability, more than 90%.Conclusion: DWI had high accuracy in detecting prostate cancer for patients with cancer. Also the accuracy of this method for patients without prostate cancer was acceptable compared to the other common methods.