Radical reactions initiated by chelate complexes of transition metals, 12. Decomposition of cumene hydroperoxide by the system copper acetate-aminoalcohol

This paper presents an investigation of the kinetics of the decomposition of cumene hydroperoxide (1-methyl-1-phenylethyl hydroperoxide) (CHP) in benzene/methanol (95:5, by vol.) in the presence of copper(II) acetate (A) and different aminoalcohols (L), such as 2-aminoethanol, 2-(2-hydroxyethylamino)ethanol, 2-[bis(2-hydroxyethyl)amino]ethanol, 1-amino-2-propanol, and 2-(diethylamino)ethanol. It has been found that the decomposition of CHP takes place via a complex formed from the components of the reaction system. The individual components of the catalytic system (i. e. A or L), when applied separately, do not contribute to an acceleration of the decomposition reaction. Under the given conditions the initial rate of the CHP decomposition v_o is expressed formally by the equation where [A₂]₀, [L]₀, and [CHP]₀ are the initial concentrations of the above mentioned compounds; k is the monomolecular rate constant for the decomposition of the complex between metal compound and CHP, and K_L, K_c and K_A are the equilibrium constants for the formation of the adduct from aminoalcohol and copper(II) acetate, the formation of the complex consisting of this adduct and CHP and for the dimerisation of copper(II) acetate, resp.     

On the interaction of styrene-maleic anhydride copolymer with styrene

The interaction between alternating styrene/maleic anhydride copolymer as polymeric acceptor and styrene as low molecular weight donor in acetone and/or tetrahydrofuran was investigated by UV spectroscopy and polymerization technique. The equilibrium constant for the complex formation between styrene and the maleic anhydride structural unit of the styrene/maleic anhydride copolymer at 20°C was found to be 0,02 ± 0,001 dm³·mol^?1 in acetone and 0,06 ± 0,003 dm³·mol^?1 in tetrahydrofuran. The results of the thermally initiated polymerization of styrene in acetone in the presence of the alternating styrene/maleic anhydride copolymer indicate that the copolymer or the products of the interaction between the monomeric units of maleic anhydride in the copolymer and styrene do not initiate a radical polymerization of styrene.     

Localization,structure and polymorphism of two paralogous <Emphasis Type="Italic">Xenopus laevis</Emphasis> mitochondrial malate dehydrogenase genes

Two paralogous mitochondrial malate dehydrogenase 2 (Mdh2) genes of Xenopus laevis have been cloned and sequenced, revealing 95% identity. Fluorescence in-situ hybridization (FISH) combined with tyramide amplification discriminates both genes; Mdh2a was localized into chromosome q3 and Mdh2b into chromosome q8. One kb cDNA probes detect both genes with 85% accuracy. The remaining signals were on the paralogous counterpart. Introns interrupt coding sequences at the same nucleotide as defined for mouse. Restriction polymorphism has been detected in the first intron of Mdh2a, while the individual variability in intron 6 of Mdh2b gene is represented by an insertion of incomplete retrotransposon L1Xl. Rates of nucleotide substitutions indicate that both genes are under similar evolutionary constraints. X. laevis Mdh2 genes can be used as markers for physical mapping and linkage analysis.     

Emulsion polymerization of butyl methacrylate initiated by 2,2′-azoisobutyronitrile, 1. Kinetics and mechanism

The effect of 2,2′-azoisobutyronitrile (AIBN) on the kinetics and mechanism of emulsion polymerization of butyl methacrylate was studied in the presence of anionic emulsifier disodium dodecylphenoxybenzene disulfonate (Dowfax® 2A1) at 60°C. The ratio between the proportion of the polymerization in monomer droplets and that of the polymerization in the aqueous phase was determined for the overall initial rate of butyl methacrylate polymerization in the region of the increasing polymerization rate (interval I). Using the model of polymerization in discrete particles, the portion of the polymerization in monomer droplets with a diameter of 100 nm in the overall polymerization rate is 24,4%; the portion of the polymerization in the water phase is only 0,022% for a concentration of Dowfax® 2A1 of 5 · 10^?2 mol · dm^?3, and 60,4% and 0,054% for a Dowfax® 2A1 concentration of 1 · 10^?2 mol · dm^?3. The exponent of the emulsifier concentration in the equation for the polymerization rate is 0,56 for interval I and 0,36 for interval II; the exponent for the concentration of AIBN over the conversion range between 0 and 30% is 0,34. For the proposed reaction mechanism it is assumed that 2-cyanoisopropyl radicals, generated from AIBN in the water phase, are responsible for the initiation of polymerization in micelles swollen by monomer and in polymer/monomer particles. Polymer/monomer particles are formed also by co-precipitation of oligomer radicals, which in turn are formed by polymerization of monomer molecules present in the water phase. Polymerization within monomer droplets has no significant influence on the course of emulsion polymerization.     

Properties of visual evoked potentials to onset of movement on a television screen

In 80 subjects the dependence of movement-onset visual evoked potentials on some measures of stimulation was examined, and these responses were compared with pattern-reversal visual evoked potentials to verify the effectiveness of pattern movement application for visual evoked potential acquisition. Horizontally moving vertical gratings were generated on a television screen. The typical movement-onset reactions were characterized by one marked negative peak only, with a peak time between 140 and 200ms. In all subjects the sufficient stimulus duration for acquisition of movement-onset-related visual evoked potentials was 100ms; in some cases it was only 20ms. Higher velocity (5.6°/s) produced higher amplitudes of movement-onset visual evoked potentials than did the lower velocity (2.8°/s). In 80% of subjects, the more distinct reactions were found in the leads from lateral occipital areas (in 60% from the right hemisphere), with no correlation to handedness of subjects. Unlike pattern-reversal visual evoked potentials, the movement-onset responses tended to be larger to extramacular stimulation (annular target of 5°–9°) than to macular stimulation (circular target of 5° diameter).Abbreviation PREP pattern-reversal visual evoked potentials     

Acute effects of using a mobile phone on CNS functions

Twenty volunteers participated in two experiments exploring the acute effects of using the mobile phone Motorola GSM 8700 on the functions of the CNS. When speaking (5 minutes reading a text from daily newspapers) the electromagnetic fields from the mobile apparatus did not affect the visual evoked potentials. Also a 6-min exposure did not reveal any effect of electromagnetic fields on the results in two tests (memory and attention) performed while speaking into the mobile. On the other hand the phone call itself strongly influenced the performance in a secondary task applying a test of switching attention which is a good model for driving a car. The response and decision speed were significantly worse. This is a proof that even a slight psychological stress involved in calling while driving can be a great risk.     

Birth weight of neonates as an indicator of morbidity and mortality in adult age and factors which influence it

In 28 neonates born by spontaneous delivery to healthy mothers with a normal course of gestation venous umbilical blood was examined to assess the immunoreactive insulin concentration. Moreover, the birth weight of the neonates was recorded, the weight increment of the mother during pregnancy and the body mass index at the end of gestation. By means of a questionnaire and the computer programme Progana the dietary intake of the mothers at the end of pregnancy was assessed and compared with recommended allowances. The assembled data were evaluated statistically by assessment of the correlation coefficient. The investigation revealed that the birth weight of the neonates in the group does not correlate with the immunoreactive insulin concentration in umbilical venous blood. Although the dietary intake of the mothers at the end of pregnancy is not ideal (fat and cholesterol intake predominates over carbohydrate and protein intake), it does not correlate with the birth weight of the neonates nor with the immunoreactive insulin concentration in umbilical venous blood. From these results the conclusion is drawn that neonates with a low birth weight do not have a higher plasma insulin concentration after delivery and that the mother's diet at the end of pregnancy does not influence the birth weight and insulin level in neonates.     

Malignant melanoma in dermatoscopical picture

Dermatological investigation offers a more precise clinical diagnosis of malignant melanoma in 20-30% of cases. It gives a correct visualization of melanocytic structures up to dermatoepidermal junction in ten fold magnification. A less distinct picture can be obtained from medium corial structures. Lentigo maligna melanoma and superficially spreading melanoma can be well distinguished from other pigmented lesions. Dermatoscopy offers an inspirative view between a clinical and microscopical picture plane.