Showing papers by "Comenius University in Bratislava published in 1986"
01 Jan 1986
257 citations
01 Dec 1986
TL;DR: In this article, the effect of structure changes of 4 series of bisammonium salts of N,N′-bis(alkyldimethyl)-3-X-1.5-pentanediammonium dibromides type, where the alkyl chain (R) had 6 to 18 carbon atoms and X = CH2, NCH3, O, or S upon the surface active and aggregation characteristics of their aqueous solutions was examined.
Abstract: The effect of the structure changes of 4 series of bisammonium salts of N,N′-bis(alkyldimethyl)-3-X-1.5-pentanediammonium dibromides type, where the alkyl chain (R) had 6 to 18 carbon atoms and X = CH2, NCH3, O, or S upon the surface active and aggregation characteristics of their aqueous solutions was examined. The critical micelle concentration (CMC) was investigated by the tensiometric and conductometric methods. The concentration of surface saturation (Γmax) and surface area per molecule (F) were calculated from the slope - ( d γ d log c ) T of the decreasing parts of surface tension lines vs log c. The change of standard Gibbs' energy of micellization (−ΔGm) was established from CMC data. From log CMC = A - B(nCH2) relationships the equivalent chain lengths (nCH2)eq and hydrophobicity indexes (I) were calculated for each series of compounds. It was found that the CMC does not reflect the fine changes in sufficient measure in comparison of molecules with the similar structure, while I represents a convenient parameter which can include the electronic and spatial changes appearing as a consequence of structural change. The anomalous courses of some relationships were elucidated in terms of spatial arrangements and weak intermolecular interactions. The isosteric exchange of the CH2 group in position 3 of the joining bridge by sulfur results in the most lipophilic molecules, followed by the reference series of 1,5-pentanediammonium derivatives; the series with NCH3 group differs from it only slightly. Most hydrophilic are the 3-oxa derivatives. Such lipophility sequence was determined from I, but also from F and surface tension at CMC (γCMC) values and from regression equations.
144 citations
TL;DR: On considere l'equation a une dimension u t =u xx +f(x,u), t>0, 0
Abstract: On considere l'equation a une dimension u t =u xx +f(x,u), t>0, 0
60 citations
TL;DR: In this article, several problems in voltage graph theory such as equivalence and regularity of coverings generated by (permutation) voltage graphs, automorphism groups and some other things are discussed.
40 citations
TL;DR: In this article, Komornik proved the asymptotic periodicity of the iterates of Markov operators with weakly constrictive Frobenius-Perron operators.
Abstract: JOZEF KOMORNIK (Received September 22, 1984) Introduction. The asymptotic periodicity of the iterates of Markov operators has been studied in [3], [4] and [5]. It has been proved to hold for (i) strongly constrictive Markov operators (ii) weakly constrictive Frobenius-Perron operators. This paper is devoted to the proof of the conjecture formulated (in the invited address at the International Congress of Mathematicians in 1983) by Lasota. We extend the results mentioned above to the case of an arbitrary weakly constrictive Markov operator P.
34 citations
TL;DR: The Bratislava 14C laboratory has been measuring 14C in atmospheric 14002 and in a variety of biospheric samples in densely populated areas and in areas close to nuclear power plants.
Abstract: 14C is one of the most important anthropogenic radionuclides released to the environment by human activities. Weapon testing raised the 14C concentration in the atmosphere and biosphere to + 100% above the natural level. This excess of atmospheric '4C at present decreases with a half-life of ca 7 years. Recently, a new source of artificially produced 14C in nuclear reactors has become important. Since 1967, the Bratislava 14C laboratory has been measuring 14C in atmospheric 14002 and in a variety of biospheric samples in densely populated areas and in areas close to nuclear power plants. We have been able to identify a heavy-water reactor and the pressurized water reactors as sources of anthropogenic 14C 14C concentrations show typical seasonal variations. These data are supported by measurements of 8H and 85Kr in the same locations. Results of calculations of future levels of anthropogenic 14C in the environment due to increasing nuclear reactor installations are presented.
32 citations
TL;DR: In this article, the conditions under which a permanganate chemical oscillator functions in a continuous-flow tank reactor (CTR) were described, where the only oscillator known has been a bromate one containing permanganates, Mn2+ ions and oxalate as a subtrate.
Abstract: Although a kinetic bistability in the reduction of permanganate by hydrogen peroxide1 as well as in the reduction of permanganate by oxalate2,3 in a continuous-flow tank reactor (CTR) has recently been observed, a permanganate chemical oscillator has not yet been described. So far, the only oscillator known has been a bromate one containing permanganate, Mn2+ ions and oxalate as a subtrate4. The discovery of new chemical oscillators which are essentially different from those described previously is of great importance, as it supplies further information concerning the exact mechanistic requirements for chemical oscillations to occur. We report here the conditions under which a permanganate chemical oscillator functions in a CTR.
26 citations
TL;DR: In this paper, the dependence of the mean number of low mass dileptons per event on the multiplicity of charged hadrons can disentangle various mechanisms contributing to the low-mass dilepton production.
Abstract: It is pointed out that the dependence of the mean number of low mass dileptons per event on the multiplicity of charged hadrons can disentangle various mechanisms contributing to the low mass dilepton production. Specific predictions are presented for the contribution due to annihilations of quarks and antiquarks created during the collision.
22 citations
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the contribution of excited levels with energy above 2 mec2 to internal pair production is negligible because intensities of only about 10−7% have been found.
Abstract: The measurement of internal pair production accompanying the alpha-decay of 210Po, 239Pu and 241Am has confirmed that this process occurs with probability of about 10−9. The investigation of gamma-rays of 241Am has shown that the contribution of excited levels with energy above 2 mec2 to internal pair production is negligible because intensities of only about 10−7% have been found. Several non-identified gamma-rays with energies above 900 keV have been observed which might be due to new high excited levels of 237Np.
18 citations
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, seasonal 14C variations in atmospheric CO2 caused by nuclear bomb tests and by fossil fuel combustion are discussed and a strong correlation between the 14C concentration and the temperature during a year has been found.
Abstract: Seasonal 14C variations in atmospheric CO2 caused by nuclear bomb tests and by fossil-fuel combustion are discussed. The investigated time interval is from 1968 to 1980. A comparison of Bratislava and Tbilisi 14C data shows that both are influenced by the Suess effect. Summer-winter 14C variations observed in these data are predominantly due to the fossil-fuel CO2 increase during winter months. A strong correlation between the 14C concentration and the temperature during a year has been found. In contrast to the 14C variations in CO2 from urban areas the clean air 14C data have shown that the bomb effect is responsible for the seasonal 14C variations in non-industrialized areas.
17 citations
TL;DR: Many natural and synthetic compounds used in studying the relationships between semiautonomous cellular organelles and nueleocytoplasm constitute a firm basis for adoption of the endosymbiotic origin of plastids and mitochondria.
Abstract: Many natural and synthetic compounds are used in studying the relationships between semiautonomous cellular organelles and nueleocytoplasm. These studies, together with analyses of the organelle macromolecules by methods of molecular biology, constitute a firm basis for adoption of the endosymbiotic origin of plastids and mitochondria.
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, a method of simultaneous measurement of 3H, 14C, 85Kr, and 133Xe concentration in the atmosphere around the nuclear power station is described and compared.
Abstract: 3H, 14C, 85Kr, and 133Xe, produced by nuclear power reactors, are the most important gaseous contaminants of the atmosphere. A method of simultaneous measurement of 3H, 14C, 85Kr, and 133Xe concentration in the atmosphere around the nuclear power station is described. A comparison of results shows that 3H, 14C and 85Kr are typical global contaminants, while 133Xe may be important only in the vicinity of the nuclear power station.
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the triple coincidence method and a Ge(Li)-NaI(Tl)-NIC-NIC spectrometer were used for measurement of EC/β+ ratios of 22Na, 26Al, 44Sc and 88Y.
Abstract: The triple coincidence method and a Ge(Li)-NaI(Tl)-NaI(Tl) spectrometer were used for measurement of EC/β+ ratios of 22Na, 26Al, 44Sc and 88Y. A comparison of theoretical and experimental results shows a good agreement for 26Al and 44Sc and disagreement for 22Na and 88Y.
TL;DR: In this article, the effect of well storage on the course of drawdown during a pumping test and recovery is discussed, and a method for adjusting for well diameter in the interpretation of pumping tests is described.
TL;DR: Soit le systeme u t =u xx +f(x,u), x∈(0, 1), u(t, 0) =u 0 (x), x ∈( 0, 1) =x ∈ (0, 2), u t, 0 =u x +f (x, u), u x, 0, x =x 0, 0 as discussed by the authors.
TL;DR: In this article, the effect of electron correlation on the energy profile of an S N 2 gas-phase reaction was studied within Brauman's double-well model, and correlation contributions to the well depth, intrinsic and overall barriers and the heat of reaction were calculated using complete fourth-order MBPT.
TL;DR: In this article, the selective separation ability of cyclic crowns, known for liquid-liquid extraction, is found to be effective for emulsion membrane extraction, and the co-transport of the ionic pair SrL2+. 2A through the membrane has been studied.
Abstract: The selective separation ability of the cyclic crowns, known for liquid-liquid extraction, e.g. alkali metals, is found to be effective for emulsion membrane extraction. 18-C-6, DB-18-C-6, DC-18-C-6 crowns were used as carriers. The co-transport of the ionic pair SrL2+. 2A through the membrane has been studied. Calcium was considered as a main competing ion. Even in the case of 20-fold preconcentration, there have been found conditions under which the pertraction process can reach Sr/Ca separation factors of about 500 and the yield of strontium is high (95–98%). The presence of calcium up to 1000-fold excess has no influence on the yield of strontium (1.10−5M). The calcium content in the isolated emulsion was caused by second emulsification of the outer solution. The influence of potassium on strontium pertraction has been studied and some transport data of Cs and Y have been obtained.
TL;DR: In this article, the authors applied the projected form of the Liouville-von Neumann equation to the study of proton motion in an asymmetric double-well potential interacting with a heat bath.
TL;DR: The 2-Benzylidene structure was solved using Patterson and Fourier syntheses and refined by the full-matrix least-squares method to a final R value of 0.036 for 2190 reflections.
TL;DR: The findings indicate the possibility of endo/para/crine activity of the female prostate Homologue and urethra and support the opinion on the non-vestigial role of the prostate homologue in woman.
15 Jul 1986
TL;DR: The alternating machine having a separate input tape with k two-way, read-only heads, and a certain number of internal configurations — AM(k) is considered as a parallel computing model and the optimal lower bounds ω(n2) and ω (n3/2) resp.
Abstract: The alternating machine having a separate input tape with k two-way, read-only heads, and a certain number of internal configurations — AM(k) is considered as a parallel computing model. For the complexity measure TIME·SPACE·PARALLELISM (TSP), the optimal lower bounds ω(n2) and ω (n3/2) resp. are proved for the recognition of specific languages on AM (1), and AM(k) respectively. For the complexity measure REVERSALS·SPACE·PARALLELISM (RSP), the lower bound ω(n1/3/log2n) is established for the recognition of a specific language on AM(k). This result implies a polynomial lower bound on PTIME·HARDWARE of parallel RAM's. All lower bounds obtained are substantially improved for the case that SPACE ≥nɛ, for 0 < ɛ < 1. Several strongest lower bounds for two-way (and one-way) alternating (deterministic, and nondeterministic) multihead finite automata are obtained as direct consequences of these results.
TL;DR: On montre l'effet des equilibres acide-base sur la constante de vitesse et les parametres thermodynamiques as mentioned in this paper ; role de la solvatation pendant l'oxydation des complexes
Abstract: On montre l'effet des equilibres acide-base sur la constante de vitesse et les parametres thermodynamiques. Role de la solvatation pendant l'oxydation des complexes
TL;DR: In this paper, the preliminary data on large transverse-energy proton-Pb collisions at 200 GeV c obtained by the HELIOS collaboration at CERN are reproduced by a simple model in which the transverse energy is built up by a large amount of soft final-state hadrons.
TL;DR: SOS-inducing potency of n-alkyl congeners decreases with increasing lipophilicity, and derivatives with positive effect on SOS-function in E. coli show mutagenic activity on Salmonella typhimurium TA98 in Ames test.
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the characteristics of one cell of the high pressure multielement proportional counter are presented, where the cell cathode of hexagonal form with a side of 11.8 mm is made of tungsten wires and the counter filled with pure xenon at a pressure of 20 atm has a resolution of 12.2, 8.7% and 7.1% for energies of 29.8, 58.8 and 88 keV.
Abstract: Characteristics of one cell of the high pressure multielement proportional counter are presented. The cell cathode of hexagonal form with a side of 11.8 mm is made of tungsten wires. The counter filled with pure xenon at a pressure of 20 atm has a resolution of 12.2%, 8.7% and 7.1% for energies of 29.8 keV, 58.8 keV and 88 keV, respectively.
TL;DR: In this paper, Membrane extraction is treated as an analogue of solvent extraction in three-phase distribution systems and its advantages and drawbacks are discussed with respect to separation and preconcentration of radionuclides, fission products of uranium and uranium itself.
Abstract: Membrane extraction is treated as an analogue of solvent extraction in three-phase distribution systems. Its advantages and drawbacks are discussed with respect to separation and preconcentration of radionuclides, fission products of uranium and uranium itself.
TL;DR: Le compose du titre cristallise dans le systeme monoclinique, groupe d'espace C2 et sa structure est affinee jusqu'a R=0,083 as discussed by the authors.
Abstract: Le compose du titre cristallise dans le systeme monoclinique, groupe d'espace C2 et sa structure est affinee jusqu'a R=0,083
02 Nov 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a method for calculation of absolute production rates of cosmogenic nuclides, based on the Monte Carlo simulation of hadron cascade process in matter, is presented, and the experimental depth profiles of 22 Na, 26 Al and 53 Mn in lunar samples are compared with results of computations.
Abstract: A method for calculation of absolute production rates of cosmogenic nuclides, based on the Monte Carlo simulation of hadron cascade process in matter is presented. The experimental depth profiles of 22 Na, 26 Al and 53 Mn in lunar samples are compared with results of computations. A disagreement between theoretical and experimental results for 26 Al and 53 Mn has been found.
TL;DR: Starch starts to be formed in plastids precisely after the cessation of mitotic activity and at the beginning of endomitotic growth, and during secondary wall formation, the starch is gradually lost.