Characterization and Antioxidant Properties of Six Algerian Propolis Extracts: Ethyl Acetate Extracts Inhibit Myeloperoxidase Activity

Because propolis contains many types of antioxidant compounds such as polyphenols and flavonoids, it can be useful in preventing oxidative damages. Ethyl acetate extracts of propolis from several Algerian regions show high activity by scavenging free radicals, preventing lipid peroxidation and inhibiting myeloperoxidase (MPO). By fractioning and assaying ethyl acetate extracts, it was observed that both polyphenols and flavonoids contribute to these activities. A correlation was observed between the polyphenol content and the MPO inhibition. However, it seems that kaempferol, a flavonoid, contributes mainly to the MPO inhibition. This molecule is in a high amount in the ethyl acetate extract and demonstrates the best efficiency towards the enzyme with an inhibiting concentration at 50% of 4 ± 2 μM.     

Illumination d’un réseau de lignes ou de câbles par une onde de foudre Modélisation par des générateurs de courant

In this paper we propose a new formalism for the analysis of electromagnetic coupling between the lightning wave and a network of lines or cables. This approach allows obtaining currents and induced voltages directly on the set of lines or cables extremities. For this objective we use the current generators representation of the lightning wave. Then by a mathematical formulation based on the topological analysis of the network, we deduce a linear equation system which resolution leads directly to the currents and induced voltages. In order to confirm our theoretical work, we present a set of applications that allows validating this formalism.     

Research on planar antennas and arrays: `structures Rayonnantes'

The basic research on radiowave systems dealing with electromagnetism, electronics, and signal processing at the University of Rennes is discussed. The fusion of these different domains occurs for studies concerning systems where radiating structures, active devices and interfaces, and signal processing play a fundamental role and cannot be separated. Different geometries and methods developed for various types of patches, dipoles, and slot antennas, including patch antennas with coaxial or microstrip feeds, printed slot antennas, slot-fed patches, slot-loaded patches, and electromagnetic coupled dipoles and patches, are described. Different kinds of arrays have been designed with active or passive feed networks. The analysis includes mutual-coupling effects, especially when beam steering is considered with small element spacing. Arrays considered include planar phased arrays, planar passive arrays, dual-beam printed antennas, and arrays of microstrip dipoles     

Analysis of coplanar waveguide radiating end effects using theintegral equation technique

An integral equation technique solved by the moment method associated with the single one-port model is used to analyze radiating end effects of coplanar waveguides (CPWs). This analysis has the advantage of being performed in the space domain, which allows the electric and magnetic field distributions in the whole space to be determined directly without the use of an inverse Fourier transform. An experimental method is given for the measurement of the reactance of a CPW short circuit end that allows its radiation resistance to be determined. It is shown that this resistance increases with frequency. Two examples of calculated results that give the electric field distribution in the two slots are given. The first one represents a CPW mode (odd mode), while the second represent an even coupled slots mode. The normalized reactance obtained by the present theory is compared with previously obtained measurements. The comparison shows a very good agreement. The results of a comparative study of the short-end equivalent impedance for a slotline and a CPW having the same slot width operating once in the odd mode (coplanar mode) and another time in the even mode are given. The results clearly show that the CPW operating in the odd mode has very low radiation properties when compared with the slotline and coupled slotlines operating in the even mode     

Theoretical Investigation of Phase Diagrams and Compensation Behaviors of a Ferrimagnetic Mixed-Spin (3/2,2) Ising Nanowire with Cylindrical Core-Shell Structure

Journal of Superconductivity and Novel Magnetism - In this work, we use effective field theory (EFT) based on the probability distribution technique to study the magnetic properties (phase diagrams...     

Effects of symmetric distribution laws on spectral power density in randomized PWM

The effects on the spectral power density (SPD) of randomized pulse width modulation (RPWM) waveforms by the choice of different probability distribution laws are investigated. The distribution laws under studied are symmetric uniform, normal, laplace, and parabolic. A comparison method, based on a normalized deviation with respect to the uniform distribution law, is devised. It is shown, by way of analytical derivation and simulations, that uniform distribution produces power spectrum comparable to those generated by other relatively more complex distributions under studied. Significantly, it means that uniform distribution, which is the simplest to implement, is the preferred probability law for randomization in a RPWM scheme.     

Simplified dipole concept for the assessment of transient electromagnetic field in the vicinity of grounding grid

The objective of this work is to provide a simplified model to analyse the electromagnetic emission of the grounding grid thus enabling engineers to perform parametric studies rapidly without greater loss of accuracy. The proposed approach is based on the use of the transmission line theory and the concept of dipole radiation in the presence of a lossy half‐space including the Sommerfeld integral approach. The model proposes to determine the electromagnetic fields (soil and air) and current distribution in a grounding system. The proposed model is described and illustrated with applications. The limitations and advantages are also discussed and compared against antenna theory counter parts. Copyright © 2014 John Wiley & Sons, Ltd.     

Analyse de Circuits Passifs en Technologie Microruban Suspendu

Simple and complex suspended stripline uniaxial discontinuities are precisely characterized using the modal analysis combined with the spectral domain approach. Frequency dependent equivalent circuits for the studied discontinuities are derived. They can be used as data base for microwave cad programs. A directional coupler and different resonators are realized in this suspended stripline technology using the results of this study. Experimental performance of these components validates our theoretical results. An integral equations technique solved by the method of moments is used to characterize suspended stripline multiaxial junctions. Examples of the results are given for a bend, a T or a meander. A good agreement is observed between theoretical results and experimental ones.