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- Author or Editor: V. Benić x
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Abstract
By the method of synthetic geometry, we define a seemingly new transformation of a three-dimensional projective space where the corresponding points lie on the rays of the first order, nth class congruence C n 1 and are conjugate with respect to a proper quadric Ψ. We prove that this transformation maps a straight line onto an n + 2 order space curve and a plane onto an n + 2 order surface which contains an n-ple (i.e. n-multiple) straight line. It is shown that in the Euclidean space the pedal surfaces of the congruences C n 1 can be obtained by this transformation. The analytical approach enables new visualizations of the resulting curves and surfaces with the program Mathematica. They are shown in four examples.
Abstract
Emanation thermal analysis was used to characterize the thermal behaviour of alumina coatings as deposited on EUROFER 97 steel surface by filtered vacuum arc technique. Temperature ranges of the healing of cracks and structure irregularities observed by SEM were determined from the ETA results. Transport properties of the alumina coatings were assessed from the ETA results by the evaluation of radon diffusion parameters in the temperature range from 50 to 300°C. Healing microstructure irregularities of the alumina coatings can be expected in the range 300–700°C as indicated by the decrease of the radon release rate. From the ETA results it followed that the onset of healing the cracks observed by the SEM on the surface of one alumina coating sample can be expected at 430°C.
Abstract
Simple and rapid extraction method for quantitative and selective isolation of the new local anesthetic pentacaine from biological materials is proposed. The technique of ion-pair formation was found to be more effective than usual access using the extraction of the nonionized species. The extraction yield of the unchanged molecule3H-pentacaine after double extraction and single scrubbing was found to be more than 90%. The radiochemical purity was over 90%. The method appears suitable for pharmacokinetic studies in the animal body.
Abstract
Pentacaine, heptacaine and carbisocaine, new local anaesthetics of Czechoslovak origin, are weak bases of the carbanilate type. Their pKA values are 8.6, 8.9 and 8.8, respectively. The technique of ion-pair extraction was found to be more effective than usual access using the extraction of nonionized species. The counter-ion ClO4 was chosen as the most efficient. The extraction yield of pentacaine into benzene from strongly acidic media (IN HClO4) of biological matrix after subsequent scrubbing of coextracted metabolites into a buffer of pH 9.6 is over 90%. The radiochemical purity is better than 92%.
Abstract
Thermogravimetry (TG/DTG) coupled with evolved gas analysis (MS detection) of volatiles was used to characterize the thermal behavior of commercial PVC cable insulation material during heating in the range 20-800C in air and nitrogen, respectively. In addition, simultaneous TG/FTIR was used to elucidate chemical processes that caused the thermal degradation of the sample. A good agreement between results of the methods was found. The thermal degradation of the sample took place in three temperature ranges, namely 200-340, 360-530 and 530-770C. The degradation of PVC backbone started in the range 200-340C accompanied by the release of HCl, H2O, CO2 and benzene. The non-isothermal kinetics of thermal degradation of the PVC cable insulation in the temperature range 200-340C was determined from TG results measured at heating rates of 1.5, 5, 10, 15 and 20 K min-1 in nitrogen and air, respectively. The activation energy values of the thermal degradation process in the range 200-340C of the PVC cable insulation sample were determined from TG results by ASTM method.
Abstract
A set of new materials with general formula [M(H2O)]X(VO)1−XPO4·2H2O (M 3+=Al, Cr, Ga, Mn), isomorphous with layered tetragonal VOPO4·2H2O and having potential catalytic properties, have been characterized by TG and DTA, X-ray diffraction and surface acid strength. During heating the compounds transform in the monohydrated and anhydrous phases, all maintaining a layered structure, with a proper interlayer spacing. Catalytic tests performed with 1-butene show that theM 3+-vanadyl phosphates greatly improve the conversion of the olefine with respect to pure vanadyl phosphate.
Abstract
Emanation thermal analysis (ETA) and thermogravimetry measured in the range 20–1000C was used to characterize the thermal behaviour of Na-montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite samples prepared by saturation with cations Li+ , Mg2+ , Al3+ , respectively. It was confirmed that the presence of cations used for montmorillonite saturation (Li+ , Mg2+ , Al3+ ) influenced the thermal behaviour of the samples. The results that indicated the decrease of radon release rate corresponding to a collapse of the interlayer space between the silicate sheets after water release and the crystallization of meta-montmorillonite in the respective temperature intervals were compared. From the ETA results it followed that the thermal stability of intermediate microstructure depends on the type of exchanged cation. A mathematical model was used to evaluate the ETA data.
Abstract
Thermal behavior of talc samples (from locality Puebla de Lillo, Spain) were characterized by emanation thermal analysis (ETA), DTA and TG. The ETA, based on the measurement of radon release rate from samples, revealed a closing up of surface micro-cracks and annealing of microstructure irregularities of the talc samples on heating in the range 200–500°C. For ground talc sample a crystallization of non-crystalline phase formed by grinding, into orthorhombic enstatite was characterized as a decrease of radon mobility in the range 785–825°C and by a DTA exothermal effect with the maximum at 830°C. ETA results characterized the microstructure development of the talc samples on heating and served to evaluate their radon mobility and transport properties on heating and cooling. Transport properties of the talc samples were evaluated by using ETA experimental data measured during heating to 600 and 1300°C, respectively, and subsequent cooling to room temperature.
Summary
Thermal behavior of commercial PVC cable insulation both before and after extraction of plasticizers, fillers and other agents were tested by TG/DTG and DSC during heating in the range 20-800C in air. The ultrasound enhanced hexane extraction and dissolution in THF with subsequent precipitation of PVC were used to prepare 'extracted' and 'precipitated' samples. The total mass loss measured for the 'non-treated', 'extracted' and 'precipitated' PVC samples was 71.6, 66.6 and 97%, respectively. In the temperature range 200-340C the release of dioctylphthalate, HCl and CO2was observed by simultaneous TG/FTIR. From TG results measured at different heating rates (1.5, 5, 10, 15 K min-1) in the range 200-340C the non-isothermal kinetics of the PVC samples degradation was determined. Activation energy values of the thermal degradation processes calculated by ASTM E 698 method, for 'non-treated', 'extracted' and 'precipitated' PVC samples were 174.617 kJ min-1, 192.819 kJ min-1, 217.120 kJ min-1, respectively. These kinetic parameters were used for the lifetime simulation of the materials.
