Oxygen Permeability and Its Role in Governing Life of YbDS Environmental Barrier Coatings

The growth kinetics of thermally grown oxide (TGO) silica in Yb-disilicate (YbDS) environmental barrier coatings (EBCs) significantly affects the durability of EBCs. The oxygen permeability can control the TGO growth kinetics and thus could play an essential role in determining EBCs life. Therefore; the oxygen permeability constant of YbDS and TGO is systematically evaluated and quantified in terms of thermodynamics using defect reactions and the parabolic rate constant (kp); respectively. Dry oxygen and wet oxygen conditions as well as different temperatures; partial pressures and top coat modifiers are investigated. The results offer evidence that the oxygen permeability constant for the YbDS top coat is an order of magnitude higher than for the TGO. As such; the TGO hinders the oxidant diffusion stronger; proving to be the diffusion rate controlling layer. Moreover; water vapor strongly increases the oxygen permeability with defect reactions playing a key role. It is suggested that the mass transfer through the top coat is primarily by outward ytterbium ion diffusion and inward oxygen ion movement; with the latter being dominant; particularly in wet environments. The effect of top coat modifiers on oxidant permeation is composition sensitive and seems to be related to their interaction with oxygen ions and their mobility.

Air permeability and sound absorption coefficient changes from ultrasonic treatment in a cross section of Malas (Homalium foetidum)

We investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.

Flow of non-Newtonian fluid through a permeable artery having non-uniform cross section with multiple stenosis

In this paper, the effect of slip on Micropolar fluid in a circular tube of non-uniform cross-section with multiple stenosis have been studied. The coupled equations governing to the flow are calculated by using Homotopy Perturbation Method. The effects of various parameters with heights of the stenosis on the resistance to the flow and wall shear stress have been studied by deriving the expressions for the flow characteristics and their solutions have been obtained. It is found that the resistance to the flow increases with the heights of the stenosis, inclination, Thermophoresis parameter, local temperature Grashof number, local nanoparticle Grashof number, inclination and permeability constant and decreases with Brownian motion parameter. It is found that the shear stress at the wall increases with heights of the stenosis, Brownian motion parameter but decreases with local nanoparticle Grashof number, Thermophoresis parameter and permeability constant. Also, it is observed that the volume of the bolus increases with the increase of permeability constant.

Mathematical Modelling on an Electrically Conducting Fluid Flow in an Inclined Permeable Tube with Multiple Stenoses

The effect of electrically conducting fluid flow in an inclined tube with permeable walls and having multiple stenosis through porous medium was studied. The Homotopy Perturbation Method is used to calculate the phenomena of Nanoparticle and temperature of the coupled equations. The solutions have been analyzed on the basis of pressure drop, resistance to the flow and wall shear stress. It is identified that the heights of the stenosis, Thermophoresis parameter, local temperature Grashof number, local nanoparticle Grashof number, Magnetic parameter increases with the resistance to the flow and Brownian motion number, permeability constant decreases with resistance to the flow. It is remarkable that, the resistance to the flow is found increasing for the values of inclination and decreases for the values of . The observation also notes that, the shear stress at the wall is found increasing with the height of the stenosis, Inclination, Thermophoresis parameter, local nanoparticle Grashof number and Permeability constant, but found decreasing with Brownian motion parameter and Magnetic Parameter

Formation and remediation simulation of an in-situ reactive zone with nanoiron for a nitrobenzene-contaminated aquifer

A two-dimensional simulated sand box was built to investigate the formation and remediation of an in-situ reactive zone (IRZ) of nanoscale zero-valent iron (NZVI) for a nitrobenzene-contaminated aquifer, and the permeability change of the zone was calculated through the loss of waterhead. The experimental results demonstrated that the remediation area in coarse sand was obviously larger than that in fine sand. The nitrobenzene concentration reached a stable level of 87.24 and 170.24 mg/L in coarse and fine sand by 50 d and 40 d, respectively; after 60 d, the concentration of aniline as the reduction end-product of nitrobenzene was 97.02 and 49.40 mg/L, corresponding to a mean production rate of 40.1% and 20.8%, respectively. This indicated that a wider zone will be formed in the media with a larger size, which is beneficial for pollution remediation. The water yield of the aquifer declined by 13.8% and 11.9% in coarse and fine sand after 60 d, and the final permeability constant was 22.94 and 1.82 m/d (declining by 60.9% and 70.6%), respectively. The reactive zone remained stable and the injection of NZVI slurry could not cause any dramatic changes in the aquifer permeability.

Complex permittivity, permeability and microwave absorbing properties of Co–Ti substituted strontium hexaferrite

M-type strontium ferrite with compositions SrFe(12-2x)CoxTixO19 (x = 0.0, 0.3, 0.5, 0.7, 1.0), were prepared by two route ceramic method. The effects of Co–Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The complex permittivity (∊′-j∊″) and complex permeability (μ′-jμ″) have been measured from 8.2 to 12.4 GHz using a network analyzer. Scanning electron microscope was used to analyze the grain size distribution and porosity of the ferrite. X-ray diffraction confirmed the M-type structure of the doped strontium ferrite. Vibrating sample magnetometer was used to study hysteresis loop of the ferrite. This study suggests that the control of grain size, decrease in coercivity and enhanced values of dielectric constant and loss are effective means to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range.

DNA, histones and neutrophil extracellular traps exert anti-fibrinolytic effects in a plasma environment

SummaryIn response to various inflammatory stimuli, neutrophils secrete neutrophil extracellular traps (NETs), web-like meshworks of DNA, histones and granular components forming supplementary scaffolds in venous and arterial thrombi. Isolated DNA and histones are known to promote thrombus formation and render fibrin clots more resistant to mechanical forces and tissue-type plasminogen activator (tPA)-induced enzymatic digestion. The present study extends our earlier observations to a physiologically more relevant environment including plasma clots and NET-forming neutrophils. A range of techniques was employed including imaging (scanning electron microscopy (SEM), confocal laser microscopy, and photoscanning of macroscopic lysis fronts), clot permeability measurements, turbidimetric lysis and enzyme inactivation assays. Addition of DNA and histones increased the median fibre diameter of plasma clots formed with 16 nM thrombin from 108 to 121 and 119 nm, respectively, and decreased their permeability constant from 6.4 to 3.1 and 3.7×10−9 cm2. Histones effectively protected thrombin from antithrombin-induced inactivation, while DNA inhibited plasminogen activation on the surface of plasma clots and their plasmin-induced resolution by 20 and 40 %, respectively. DNA and histones, as well as NETs secreted by phorbol-myristate-acetate-activated neutrophils, slowed down the tPA-driven lysis of plasma clots and the latter effect could be reversed by the addition of DNase (streptodornase). SEM images taken after complete digestion of fibrin in NET-containing plasma clots evidenced retained NET scaffold that was absent in DNase-treated clots. Our results show that DNA and histones alter the fibrin architecture in plasma clots, while NETs contribute to a decreased lytic susceptibility that can be overcome by DNase.