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F Denes

Publications and source records attributed to F Denes.

At least 19 recordsLinked to original sources
PubMed2001

Dense medium plasma environments: a new approach for the disinfection of water.

The levels to which microbial colony forming units are permitted in various waters fit for human contact are carefully regulated. Conventional chemical and physical approaches usually are complex processes with significant limitations due to the generation of toxic side-products. In this contribution a novel plasma reactor--dense medium plasma reactor--is described, and its efficiency for the disinfection of contaminated water is discussed. It has been shown that owing to the intense stirring of the reaction medium (e.g. contaminated water), as a result of the specially designed spinning electrode and gas-flow system, a volume-character discharge is created, which can efficiently kill bacteria. It has been demonstrated that treatment times as low as 20 s are enough for the total inactivation of microorganisms for 200 mL of 10(5) bacteria/mL contaminated water.

Bacteria↗
PubMed2001

Immobilization of papain on cold-plasma functionalized polyethylene and glass surfaces.

Polyethylene and glass surfaces were functionalized under dichlorosilane-RF-cold-plasma environments and were employed as substrates for further in situ derivatization reactions and immobilization of papain. Surface functionality changes of RF-plasma-exposed surfaces were monitored under 40 kHz continuous discharge environments. The nature and morphology of derivatized substrates and the substrates bearing the immobilized enzyme were analyzed using survey and high resolution ESCA, ATR-FTIR, and fluorescence of chemical derivatization techniques. Spacer molecules intercalated between the substrates and the enzyme significantly increased the enzyme activity (comparable with the that of the free enzyme). Computer-aided conformational modeling of the substrate-spacer systems corroborated with experimental data indicated that an optimal distance might exist between the enzyme and the substrate. The activity of free and immobilized papain was monitored using benzoyl arginine ethyl ester assay. The pH data were recorded every 0.3 s over 25 min. The Michaelis-Menten kinetic constants were evaluated for immobilized enzymes. It was shown, that the immobilized papain retains most of its activity after several washing/assay cycles.

Arginine↗
PubMed2000

Immobilized biomolecules on plasma functionalized cellophane. I. Covalently attached alpha-chymotrypsin.

Surface morphology changes of hydrazine-RF-plasma-exposed cellophane surfaces were monitored under 40 kHz and 13.56 MHz CW and pulsed discharge environments and the immobilization of alpha-chymotrypsin onto plasma-modified substrates was studied. It has been shown, using SEM and AFM techniques, that significantly different cellophane topographies are generated under different frequency and pulsing parameter conditions. ESCA and ATR-FTIR analyses of plasma-modified surfaces indicated the presence of primary amide and primary amine functionalities. It was found that the relative ratios of crystalline vs amorphous zones of the nascent surface layers can also be controlled by properly selected plasma parameters, including the duty cycles of pulsed plasma environments. Enzyme immobilization reactions with alpha-chymotrypsin were accomplished both from oxygen-plasma-generated carbonyl and hydrazine-plasma-created primary amine functionalities by anchoring the biomolecules either directly to the cellophane surface or by involving spacer molecules. It was found with the cellulose substrates that fairly good enzyme activity was retained without the necessity of intercalated spacer chains. It appears that the ability of the cellulose substrate to swell in the aqueous environment allows sufficient freedom of mobility for the immobilized enzyme to retain a significant part of its activity on the cellulose. However, the activities both of the free enzyme in the presence of cellophane, and that of the immobilized enzyme molecules are significantly diminished in comparison to the activity of the free enzyme, as a result of the incorporation of these molecules into the swollen network. Potential applications of immobilized enzymes from cold-plasma-functionalized surfaces are discussed.

Argon↗
PubMed1998

Immobilization of alpha-chymotrypsin on oxygen-RF-plasma functionalized PET and PP surfaces.

In this contribution the immobilization of alpha-chymotrypsin on plasma activated PET and PP surfaces is investigated. The 'anchoring' C=O groups on polymer surfaces were created under RF-O2-plasma environments. The identity and relative concentrations of plasma-created functionalities were evaluated using survey and high resolution X-ray photoelectron spectroscopy, and differential attenuated total reflectance-FTIR spectroscopy. Surface morphology changes of plasma-exposed substrates were analyzed by atomic force microscopy. Enzyme assays were performed from both virgin and plasma modified samples which underwent the immobilization procedure. It was demonstrated that cold-plasma technique is suitable for generating functional, synthetic polymeric surfaces which can initiate enzyme coupling reactions. It also has been shown that the activity of the immobilized enzyme is lower in comparison to the free enzyme. Reduced conformational mobility resulting from multiple-point coupling process might be responsible for this behavior.

Argon↗
PubMed1994

Agreement in the clinical diagnosis of dementia: evaluation of a case series with mild cognitive impairment.

Interobserver agreement in the clinical diagnosis of dementia among four neurologists was evaluated. The physicians, masked to the original diagnoses, independently reviewed the clinical records of 50 outpatients consulting either the 1st University Neurology Department of Milan or the Neuropsychology Unit of the Medical Center of Veruno (Novara) for suspected cognitive impairment, during a 6-month period. The records contained patients' medical and neurological history, results of neuropsychological testing, laboratory tests, cerebral computed tomography and other investigations. For each patient, the raters had to provide both a diagnosis concerning the presence or absence of dementia and to assign an analytical diagnosis to all the dementia cases. The kappa statistic was used as a measure of interrater reliability. The level of agreement on the primary diagnosis of dementia was moderate (kappa = 0.49); with respect to the nosological diagnoses, the kappa values ranged from 0.16 for depression to 0.80 for multi-infarct dementia.

Aged↗
PubMed1976

Polycondensation of alpha-amino acids by pyrosulfuric acid.

The thermal polycondensation of amino acids common to protein is promoted at 80 degrees C by pyrosulfuric acid. This is in contrast to the noncondensation at 100 degrees C in the presence of concentrated sulfuric acid. These results are in accord with an anhydride mechanism, as proposed earlier for copolycondensation promoted by polyphosphoric acid. The amino acid composition, molecular weight, near-homogeneity, are infrared absorption of the polymer formed are described. The potential significance of planetary pyrosulfuric acid is discussed.

Amino Acids↗
PubMed1976

Abiotic synthesis of some polysaccharide-like and polypeptide-like structures in cold plasma.

Starting from methane, ammonia and water vapors polypeptide-like and polysaccharide-like structures have been synthesized in cold plasma conditions. By gel filtration analysis of the raw product eight fractions of different molecular weight have been separated. The partial chemical nature of each fraction and of the hydrolysis products has been determined using elementary analysis, IR spectroscopy, paper, thin-layer and gas-chromatography. It is noteworthy that higher proportions of H2O in the feed composition increase the amount of sugar and polysaccharide-like compounds in the reaction product.

Amino Acids↗
PubMed1975

Palilalia.

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Adult↗