Biomedical subjects

A Charef

Publications and source records attributed to A Charef.

4 recordsLinked to original sources

PubMed2001

Reductive degradation of carbaryl in water by zero-valent iron.

Reduction of carbaryl solution by zero-valent iron powder (ZVIP) was studied in a rotator batch system (70 rpm) in order to evaluate the utility of this reaction in remediation of carbamate contaminated water. Degradation with different amount of ZVIP: 0.01, 0.02, 0.03, 0.04 g/ml at pH 6.6 and at ambient temperature was investigated. The results show that the process exhibits a degradation rate appearing to be directly proportional to the surface contact area of ZVIP (325-mesh) with the carbaryl molecules. Three analytical techniques were used to monitor carbaryl degradation: (1) A UV-Vis diode array spectrophotometer was used to record all spectra. (2) A high performance liquid chromatography was used to separate by-products and examine the evolution of breakdown products. (3) A home-built spectrophosphorimeter that uses the solid surface room temperature phosphorescence (SSRTP) was employed to observe selectively the decline of the carbaryl concentration at different amount of ZVIP on Whatman no. 1 filter paper. Results show that the reducing degradation of carbaryl with ZVIP as the source of electrons is effective with a half-life close to several minutes.

Absorption↗

PubMed2000

Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water.

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka-Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A(R) vs log of the mol l(-1) concentration. Limits of detection at the 10(-4) M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.

Cations↗

PubMed1992

Analysis of polarization dynamics by singularity decomposition method.

The driving point immittance (impedance or admittance) function is commonly used in electrical characterization of polarized materials and interfaces. The immittance function typically attenuates following a power function dependence on frequency. This fact has been recognized as a macroscopic dynamical property manifested by strongly interacting dielectric, viscoelastic and magnetic materials and interfaces between different conducting substances. Linear interfacial polarization processes which occur at metal electrode-electrolyte interfaces have been represented by the Fractional Power Pole [FPP] function in single or multiple stages. The FPP function is referred to as the Davidson-Cole function in the dielectrics literature. A related function widely used in mathematical modeling of dielectric and viscoelastic polarization dynamics is the Cole-Cole function. The fractional power factor which parametrizes the FPP or the Davidson-Cole function has been shown earlier to equal the logarithmic ratio of the locations of the pole-zero singularities. In this paper we first review a modified form of the singularity decomposition of the FPP function accomplished within a prescribed error range. The distribution spectrum and the corresponding simulation by a cascade R-C network, as opposed to the synthesis by a ladder R-C network, are readily obtained as the next step in the simulation. The method is then applied to decompose the Cole-Cole function; the pole-zero placement of the singularity function is determined and the equivalent cascade R-C network is synthesized.

Electric Conductivity↗

PubMed1990

Fractal system--a time domain approach.

A method to analyze the fractal system in the time domain is presented so that the dynamic behavior of the system can be studied. The fractal system is represented by a set of linear time-varying differential equations whose order depends on the order of the system under non-fractal condition. Four different types of fractal system are considered and their solutions in the time domain are presented. These analyses show that the fractal system is dynamically more stable with smooth changes of magnitude and less oscillatory than the non-fractal system. Examples of the physiological system of the conduction pathways in the heart and also the polarization phenomena of noble metal are presented to illustrate the phenomena.

Bundle of His↗