Showing papers by "Comenius University in Bratislava published in 1980"
71 citations
TL;DR: In this paper, the authors investigated the correlation between short-term 14C variations in tree rings and the 11-yr solar cycle and found that these variations are difficult to observe because the atmosphere acts as a low-pass filter, attenuating their amplitude.
Abstract: As 14C is produced in the atmosphere by interactions between neutrons and nitrogen atoms, changes in the cosmic ray flux associated with the 11-yr solar cycle will produce variations in 14C production with the same period1 These variations are difficult to observe because the atmosphere acts as a low-pass filter, greatly attenuating their amplitude2 Previous investigations on short-term 14C variations in tree rings either reported no correlation with the 11-yr solar cycle3–5 or found a correlation with an average amplitude of 15 to 3‰ (refs 6–10) However, Baxter et al reported an average amplitude of about 10‰ in tree rings11,12 and in samples of whiskies, wines and plant seeds13, and Lavrukhina et al14 found a 10‰ correlation amplitude in wood samples However, very precise 14C tree-ring measurements reported more recently15–17 show only minor short-term 14C variations A comparison of resultsobtained by Stuiver15 and Baxter et al11 suggests that the larger 14C fluctuations found by the latter group may be due to a lower precision of their 14C measurements Here we have dated wines from the period 1909–52 and our results show 14C variations with an average amplitude of 43±11‰ during the 11-yr solar cycle
52 citations
TL;DR: In this article, it has been shown that the Pontrjagin maximum principle can be used as an assumption on a closed-loop control to generate open-loop optimal controls.
49 citations
TL;DR: In this article, it has been shown that if a certain non-degeneracy (or, as we shall say, normality) condition is satisfied then the latter problem satisfies the hypotheses of the theorem of [l] and, therefore, it admits a regular synthesis of the optimal control.
34 citations
TL;DR: In this paper, the retention indices of 60 isomers of C 15 C 18 n -alkenes in the presence of the corresponding n-alkanes in highly efficient glass capillary columns (N ≈ 0.5·10 6 effective plates for n -ALKenes with k ≈ 3), coated with C 87 hydrocarbon, Apiezon L or Carbowax 20M as stationary phase.
34 citations
TL;DR: In this paper, the 1H NMR spectra of 26 substituted chalcones (3-aryl-1 phenyl-2-propene-1-ones) were studied.
Abstract: 1H NMR spectra of 26 substituted chalcones (3-aryl-1 phenyl-2-propene-1-ones and 1-aryl-3-phenyl-2-propene-1-ones) have been studied. The chemical shifts of the α and β protons to the carbonyl group were correlated with Hammett s parameters. To gain information on the effect of the transmission of the resonance and inductive contributions of the substituents on the chemical shifts of H-α and H-β, two parameter correlations with and parameters were also perfomed. The chemical shifts of the aromatic protons of the para-disubstituted benzene ring correlated with the ai substituent increments.
25 citations
TL;DR: In this article, the transmission of electronic effects across the ferrocene analogues of chalcones, as well as the conformations of both types of analogues have been studied.
Abstract: The transmission of electronic effects across the ferrocene analogues of chalcones [3-aryl-1-ferrocenyl-2-propene-1-ones (series 1) and 1-aryl-3-ferrocenyl-2-propene-1-ones (series 2)], as well as the conformations of both types of ferrocene analogues have been studied. The ferrocene analogues of chalcones of series 1 were found to be in a non-planar conformation. Their H-α and C-α chemical shifts are more sensitive to the resonance than to the inductive effects of substituents. The C-α chemical shifts of the ferrocene analogues of chalcones of series 2 are more sensitive to the inductive than to the resonance effects of substituents. The transmission of the substituent effects to the ferrocene moiety is also briefly discussed.
25 citations
TL;DR: In this paper, DARC topological analysis (DTA) has been applied to Kovats retention indices for a series of 84 linear alkenes up to tetradecenes studied by gas-liquid chromatography on squalane at 100 °C.
24 citations
21 citations
TL;DR: The results support the notion that the nitrofuran mutagens under study induce single base substitutions.
Abstract: The mutagenic activity of 5 nitrofuran drugs (furadantin, furoxon, furacin, benzazon VII and lampit) was tested on strainsSalmonella typhimurium TA 100, TA 1535, TA 1538 andEscherichia coli WP2uvra
+ and WP2uvr A. All nitrofurans tested had a marked mutagenic effect on strain TA 100 and, partially, on strain TA 1535 except for furoxon which was strongly toxic for this strain. No significant mutagenic effects of the drugs were observed with strain TA 1538. With the exception of lympit, all drugs exerted a mutagenie action onE.coli WP2uvrA but no on WP2 uvrA+ which has an intact excision repair system. The only drug exerting a mutagenie effect on the latter strain was furoxon. All five nitrofurans exhibited a positive repair rest. The results support the notion that the nitrofuran mutagens under study induce single base substitutions.
19 citations
TL;DR: In this article, second and third order contributions to the correlation energy were computed for the basis sets of the double zeta and double zero plus polarization quality for a series of elementary chemical reactions and compared with the experimental data and the results of best-ab initio calculations reported in the literature.
Abstract: The title technique was applied to a series of elementary chemical reactions. Second and third order contributions to the correlation energy were computed for the basis sets of the double zeta and double zeta plus polarization quality. Calculated heats of reaction and energies of activation were compared with the experimental data and the results of the bestab initio calculations reported in the literature.
TL;DR: The multi-wire proportional chambers and drift chambers together with multichannel electronics operating on-line with a minicomputer open up new possibilities in low-level counting of several radioisotopes as discussed by the authors.
01 Dec 1980
TL;DR: In this paper, the chromosome numbers for 38 species of the Mongolian Flora were given, including Allium anisopodium, Caltha membranacea, Carex macroura, carex redowskiana, Gastrolychnis brachypetala and Vicia multicaulis.
Abstract: The paper gives the chromosome numbers for 38 species of the Mongolian Flora. Some of the counts appear to be the first findings for the species. They are:Allium anisopodium 2n = 16, Caltha membranacea 2n = 32, Carex macroura 2n = 50, Carex redowskiana 2n = 26, Gastrolychnis brachypetala 2n = 72, Iris biglumis 2n = 40, Iris flavissima 2n = 28 andVicia multicaulis 2n = 24.
TL;DR: In this article, the correlation energies obtained by the fourth-order diagrammatic perturbation theory were analyzed for three diatomic molecules: N2, CO, and F2, and it was shown that these contributions are considerably larger than for the ten-electron hydrides not only in absolute value but also in percentage.
Abstract: The correlation energies obtained by the fourth-order diagrammatic perturbation theory were analyzed for three diatomic molecules: N2, CO, and F2. The results were compared with correlation energies obtained previously for the ten-electron hydrides HF, H2O, and NH3. The relative importance of contributions which arise from the double excitations, from the quadruple excitations, as well as from the renormalization term was investigated. It is shown that for the diatomic molecules under study these contributions are considerably larger than for the ten-electron hydrides not only in absolute value but also in percentage: they represent about 3, 3, and 5%, respectively, of the valence shell correlation energy obtained by the perturbation theory up to the fourth order. A careful analysis of the fourth-order correlation effects is also presented for the reaction energy of the process ½H2 + ½F2 = HF.
TL;DR: The complexes K[VO(O2)2H2O], K3[VO[O2]2CO3] and K3 [VO[C2O4] have been prepared as discussed by the authors, where the anions are monomeric with the pentagonal pyramidal or pentagonal bipyramidal structure.
Abstract: Die Komplexe K[VO(O2)2H2O], K3[VO(O2)2CO3], K3[VO(O2)2C2O4] und K3[VO(O2)(C2O4)2] · H2O wurden dargestellt. Zusammensetzung und IR-Spektren der Verbindungen lassen auf eine monomere, pentagonal-pyramidale oder pentagonal-bipyramidale Konfiguration der Anionen schliesen.
Oxo-peroxocomplexes of Vanadium(V)
The complexes K[VO(O2)2H2O], K3[VO(O2)2CO3], K3[VO(O2)2C2O4], and K3[VO(O2)(C2O4)2] · H2O have been prepared. On the basis of the composition and the IR spectra it is supposed, that the anions are monomeric with the pentagonal pyramidal or pentagonal bipyramidal structure.
TL;DR: A 200m long glass capillary column coated with C87 hydrocarbon stationary phase was applied to the analysis of 13 possible positional and structural isomers of linear pentadecenes as discussed by the authors.
TL;DR: In the Late Cenozoic West Carpatian alkali olivine basalts spinel peridotite xenoliths have been found as discussed by the authors, their mineral composition corresponds to those found in this type of Xenoliths in alkali basalts throughout the world.
Abstract: In the Late Cenozoic West Carpatian alkali olivine basalts spinel peridotite xenoliths have been found. Their mineral composition corresponds to those found in this type of xenoliths in alkali basalts throughout the world (Mg-rich olivine, Cr-diopside, clinopyroxene, spinel). For the studied West Carpathian alkali olivine basalts kaersutite amphibole and clinopyroxene magacrysts are characteristic. The presence of the xenoliths under consideration in the boundary zone between Tatra and Pannonian blocks is the consequence of tectonic conditions (thickness of the Crust) in the area mentioned as distinct from the other West Carpathian areas of alkali olivine basalt occurrences.
TL;DR: In this paper, a new method of simultaneous low level counting of 3H and 14C is described, which involves the use of doubly-labeled methane, i.e. a CH4 molecule is labelled both with C and H from the sample to be measured.
TL;DR: In this article, simple methods of calculation of the diffusion coefficient by using the model and experimental interaction potentials are discussed, and an applicability of such calculations for diffusion of metals in inert gases is analyzed.
Abstract: In the present work some simple methods of calculation of the diffusion coefficient by using the model and experimental interaction potentials are discussed. An applicability of such calculations for diffusion of metals in inert gases is analyzed.
TL;DR: In this paper, the authors investigated the effect of superimposed dc and noise in aluminum thin film conductors subjected to high current densities and found that the mean lifetime of conductors is decreased by about 22 to 38 times in comparison to the corresponding dc loading.
Abstract: Electromigration phenomena in aluminum thin film conductors subjected to high current densities are studied. The conductors are tested under superimposed dc and noise powering at temperatures of 195 and 235°C and dc density of ≈ 1.4 × 106 A/cm2. The frequency range of the noise signal with the Gaussian distribution of amplitudes is 5 Hz to 20 kHz. The results indicate that due to the superimposed dc and noise powering the electromigration failure process is accelerated and the mean lifetime of conductors is decreased by about 22 to 38 times in comparison to the corresponding dc loading. The observed effect is partly ascribed to the fluctuations of the current and, consequently, also of the temperature in the conductors. Further, it is shown that due to the noiseproduced random driving force the electromigration transport along interfaces in the polycrystalline films can be enhanced remarkably. Both these phenomena are considered to occur within the samples investigated.
Es werden Elektromigrationseffekte in dunnschichtigen Aluminiumleitbahnen untersucht, die mit hohen Stromdichten belastet werden. Die Leitbahnen werden bei superponierter Gleichstrom- und Rausch-Belastung bei Temperaturen von 195 und 235°C getestet. Die Dichte des Gleichstromes betragt ≈ 1.4 × 106 A/cm2, der Frequenzbereich des Rauschsignals mit Gaus-Verteilung fur die Amplituden 5 Hz bis 20 kHz. Die Ergebnisse zeigen, das der Ausfall der Leitbahnen durch Elektromigrationsprozesse infolge der Superposition des Gleichstromes und des Rauschens beschleunigt wird und die mittlere Lebensdauer der Leitbahnen ungefahr (22 bis 38)-mal im Verhaltnis zu der entsprechenden alleinigen Gleichstrombelastung erniedrigt wird. Der beobachtete Effekt wird teilweise den Stromschwankungen – und den entsprechenden Temperaturschwankungen in den Leitbahnen – zugeschrieben. Es wird weiter gezeigt, das infolge der rauschbedingten statistischen Triebkraft der Elektromigrationstransport entlang der Grenzflachen in polykristallinen Schichten wesentlich ansteigen kann. Beide Phanomene treten voraussichtlich bei den untersuchten Proben auf.
TL;DR: In this article, the optimal separation properties of Carbowax 20M as a stationary phase in 300m glass capillary columns at temeperatures below its lower temperature limit (60°) in terms of the selectivity, efficiency and speed of the gas chromatographic analysis of isomeric C1013n-alkenes were investigated.
TL;DR: The fowl tickArgas (Persicargas) persicus occurs in warm areas of Slovakia, where its distribution is limited by the 650–700 mm annual average isohyet and the +8° C annualaverage isotherm.
Abstract: The fowl tickArgas (Persicargas) persicus occurs in warm areas of Slovakia, where its distribution is limited by the 650–700 mm annual average isohyet and the +8° C annual average isotherm. In Slovakia, larvae hatch from spring to autumn, and nymphal and adult moultings occur chiefly in July and August. Larvae feed for four days, nymphs and adults for less than one hour. The tick develops and reproduces during the warm season in the wild but throughout the year under favourable laboratory conditions in which the life cycle requires 17 months.
TL;DR: A Stereotactic approach for transtentorial implantation of deep wire electrodes directly into the anterior lobe of cerebellum has been shown as a beneficial method for the treatment of cerebral palsy in 9 patients, with its favourable effect particularly on axial musculature stimulation.
Abstract: A Stereotactic approach for transtentorial implantation of deep wire electrodes directly into the anterior lobe of cerebellum has been shown as a beneficial method for the treatment of cerebral palsy in 9 patients. Proper placement of the electrodes especially into the central lobule were checked by evoked potentials and by choosing an optimal program of therapeutic Stimulation which appears to be essential. With its favourable effect particularly on axial musculature Stimulation seems to promote physiologic maturation of functional mechanisms in the brain, which were delayed in the course of development.
TL;DR: In this paper, a potential curve with a single minimum was found in the 1:1 complex of acetic acid - pyridine, and the effect of specific solvation (within the so-called supermolecule approach) on the potential curves for proton transfer was studied in the systems.
TL;DR: A distinct circadian rhythm of parietal cells, especially as to their fine cell structures involved in acid production was demonstrated, and further evidence of the rhythmicity of gastric acid production in rats is rendered.