Circularly Polarized Rectangular Ring-Slot Antenna with Chamfered Corners for Off-Body Communication at 5.8 GHz ISM Band

This paper deals with a substrate integrated waveguide (SIW) circularly polarized rectangular ring-slot antenna with chamfered corners designed for 5.8 GHz ISM frequency band for off-body communication. The antenna consists of a substrate integrated waveguide, which operates in the fundamental mode TE10, and the rectangular ring-slot radiator with chamfered corners etched in the top wall of the SIW. It radiates a right-handed circularly polarized (RHCP) wave in the boresight direction. Experimental results prove that the proposed antenna located in free space achieves the impedance bandwidth of 2.41 % (for the reflection coefficient less than -10 dB) and the RHCP gain of 6.57 dBi, and the impedance bandwidth of 2.6 % and the RHCP gain of 6.98 dBi for its location on the phantom. The axial ratio (AR) bandwidth (for the AR less than 3 dB) is 0.9 % for both configurations

An accurate simplified data treatment for the initial adsorption kinetics in conditions of laminar convection in a slit: Application to protein adsorption

We present the derivation of a simple approximation for the original expression of the adsorption rate [Langmuir 10 (1994) 3898] in conditions of laminar flow in a slit, to relate the measured initial kinetic constant k with the interfacial kinetic constant ka and the transport-limited Lévêque constant kLev. The same method of derivation is applied here to get a simple approximation of the average kinetic constant 〈k〉 [Biomaterials 20 (1999) 1621]. For the local value, at distance x from the entrance of the slit, we propose k(x)/ka=(u-1)(au-1)/(bu+1), where u=k(x)/kLev, a=0.452, b=-0.625, with a maximal error of 1% in comparison with the exact solution. For the average value over the length of the slit, we propose 〈k〉/ka=(U-1)(AU-1)/(BU+1), where U=〈k〉/〈kLev〉, A=0.203, B=-0.273, with a maximal error of 0.03%. These approximations lead to an easy determination of the adsorption constant and diffusion coefficient D of the solute, as appropriate plots of experimental data provide ka and D2/3 as the intercepts of the curve with the ordinate and abscissa axes, respectively. It is pointed out that the linear approximation k-1=ka -1+kLev -1 would lead to the overestimation of both the diffusion coefficient and adsorption kinetic constant. As an example, the application to the analysis of experimental data for adsorption of α-chymotrypsin onto mica plates is provided. © 2003 Elsevier B.V. All rights reserved

Adsorption of α-chymotrypsin onto mica in laminar flow conditions. Adsorption kinetic constant as a function of tris buffer concentration at pH 8.6

We examined the adsorption kinetics of α-chymotrypsin (pH 8.6,10 -2 to 0.5 M Tris buffer) on muscovite mica in conditions of laminar flow through a slit. The range of buffer concentrations is between two limits: (i) no adsorption in 1 M Tris and (ii) no desorption in 10-3 M Tris. Studying the dependence of adsorption kinetics on the wall shear rate leads to the determination of the interfacial adsorption kinetic constant ka. and the diffusion coefficient. The obtained value for the diffusion coefficient is close to the one expected from the molecular size of α-chymotrypsin. The interfacial adsorption kinetic constant of a-chymotrypsin decreases when ionic strength increases, while the initial desorption constant (over a part of all the adsorbed population) shows the contrary. Although α-chymotrypsin is almost at its isoelectric point, the effect of ionic strength on the adsorption kinetics suggests the importance of electrostatic interactions between the protein and mica. We observed an increase in the adsorption rate, at a surface coverage near 0.14 ug cm-2, for adsorption in 10-2 M Tris and the low wall shear rates (300 s-1). This change in the adsorption rate suggests a structural transition, that we assume again to be due to electrostatic interactions, but between proteins. The large dipole moment of the protein may induce this transition, illustrated here by the ferroelectric/antiferroelectric pattern. The variation of the ζ potential with interfacial concentration seems to be in agreement with such a model

Kinetics of adsorption, desorption, and exchange of α-chymotrypsin and lysozyme on poly(ethyleneterephthalate) tracked film and track-etched membrane

Adsorption kinetics of 125I-radiolabeled α-chymotrypsin at pH 8.6 was studied in a laminar regime between two walls of poly(ethyleneterephthalate) tracked films and membranes. Adsorption kinetics in the presence of solution (10 μg/mL), desorption by rinsing with buffer, and the following exchange of proteins by flowing unlabeled solution were measured. At pH 8.6, α-chymotrypsin is almost neutral and can be mostly removed from the film surface, contrary to positive lysozyme adsorbed at pH 7.4. Results suggest that α-chymotrypsin is irreversibly adsorbed in pores, while desorption and exchange occur on membrane flat faces. A method is proposed to determine adsorption kinetics in the pores. Kinetics of desorption and exchange of α-chymotrypsin from the film surface can be described by stretched exponential functions in the examined time domain with the same exponent, β ≈ 0.62, which does not depend also on the former adsorption duration. However, the mean residence time at the interface is about 2.5 times greater in the presence of only the buffer than that in the presence of solution. This effect could be explained by a fast exchange at the arrival of unlabeled solution for a part of the adsorbed population

Barrier effect of Esoxx® on esophageal mucosal damage: experimental study on ex-vivo swine model

The aim of the present study was to assess the potential barrier effect of Esoxx®, a new nonprescription medication under development for the relief of gastroesophageal reflux symptoms. Esoxx is based on a mixture of hyaluronic acid and chondroitin sulfate in a bioadhesive suspension of Lutrol® F 127 polymer (poloxamer 407) which facilitates the product adhesion on the esophageal mucosa. The mucosal damage was induced by 15 to 90 minutes of perfusion with an acidic solution (HCl, pH 1.47) with or without pepsin (2000 U/mL, acidified to pH 2; Sigma-Aldrich). Mucosal esophageal specimens were histologically evaluated and Evans blue dye solution was used to assess the permeability of the swine mucosa after the chemical injury. The results show that: (1) esophageal mucosal damage is related to the perfusion time and to the presence of pepsin, (2) mucosal damage is associated with an increased permeability, documented by an evident Evans blue staining, (3) perfusion with Esoxx is able to reduce the permeability of the injured mucosa, even after saline washing of the swine esophagus. These preliminary results support further clinical studies of Esoxx in the topical treatment of gastroesophageal reflux symptoms

Argon plasma irradiation of polypropylene

a b s t r a c t Polypropylene samples were exposed to argon plasma discharge and the changes of the PP surface properties were studied by different methods. Surface wettability was derived from contact angle measured by standard goniometry and chemical structure of the plasma modified PP was studied using X-ray photoelectron spectroscopy (XPS) and by Rutherford backscattering spectroscopy (RBS), surface morphology and roughness of samples using AFM. Zeta potential of pristine and modified PP was determined with the SurPASS. The presence of incorporated oxygen in the PP surface layer, about 60 nm thick, was observed in RBS spectra. Oxygen concentration is a decreasing function of the depth. With progressing aging time the oxygen concentration on the PP surface decreases. Plasma treatment results in a rapid decrease of the contact angle, which increases again with increasing aging time. In XPS measurement the oxygen containing structures, created by the plasma treatment, were found on the very surface of the modified PP and the zeta potential being changed too. The significant difference in zeta potential between pristine and plasma treated PP clearly indicates that the plasma treatment leads to a more hydrophilic PP surface

Advanced database mining integrating sequence and structure bioinformatics with microfluidics challenges enzyme engineering

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