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Showing papers by "Academy of Sciences of the Czech Republic published in 1979"


Journal ArticleDOI
TL;DR: The most debatable and discrepant viewpoints of non-isothermal kinetics are discussed in the form of twelve questions and answers as discussed by the authors, including the reputation of nonisothermal analysis when carried out by thermoanalysts, the consequences of simplified concepts transferred from the kinetics of homogeneous reactions, the physical meaning of basic kinetic parameters in solid-state processes, the kinetic compensative effect and interdependence of kinetic parameters using the Arrhenius rate constant, the mutual usefulness of differential and integral methods of kinetic data evaluation, their accuracy and correctness, the reliability of
Abstract: The most debatable and discrepant viewpoints of non-isothermal kinetics are discussed in the form of twelve questions and answers. The reputation of non-isothermal kinetics when carried out by thermoanalysts; the consequences of simplified concepts transferred from the kinetics of homogeneous reactions; the physical meaning of basic kinetic parameters in solid-state processes; the kinetic compensative effect and interdependence of kinetic parameters using the Arrhenius rate constant; the mutual usefulness of differential and integral methods of kinetic data evaluation; their accuracy and correctness; the reliability of DTA measurements; non-isothermal versus isothermal investigations; equilibrium and kinetic data and their mutual effect; the extended discussion initiated by MacCallum and Tanner; non-isothermal data publication policy; and finally the use of computers.

107 citations


Journal ArticleDOI
TL;DR: It is shown that dissociation constants can be determined even when these complicating factors are not negligible; in fact, in some cases these factors may be useful for obtaining additional information about the complex.

99 citations



Journal ArticleDOI
TL;DR: Two types of bead‐form macroporous carriers based on glycidyl methacrylate with ethylene dimethacrylated copolymers were used for the immobilization of penicillin amidase either directly or after chemical modificaton.
Abstract: Two types of bead-form macroporous carriers based on glycidyl methacrylate with ethylene dimethacrylate copolymers were used for the immobilization of penicillin amidase either directly or after chemical modification. Direct binding through oxirane groups, which is equally efficient at pH 4.2 and 7, is relatively slow and brings about an activity loss at low enzyme concentrations. The most efficient immobilization was achieved on glutaraldehyde-activated amino carrier, irrespective of whether the amino groups were formed by ammonia or 1,6-diaminohexane treatment of the original oxirane carrier. Hydrazine treatment gave lower immobilization yields. The same is true of the azide method independent of the length of the spacer. Most enzyme activity was preserved by coupling the carbodiimide-activated enzyme to the carrier with alkyl or arylamino groups at the end of a longer substituent. Immobilization on diazo-modified carrier gave average results. Rapid immobilization by a lysine-modified phosgene-treated carrier resulted in an activity loss. It is suggested that multipoint and very tight attachment of the enzyme molecule to the matrix decreased the activity. The immobilized activity is quite stable in solution and very stable upon lyophilization with sucrose.

44 citations


Journal ArticleDOI
TL;DR: The heartwood of Libocedrus yateensis has been found to contain cumic acid and several related hydroxyacids so far not reported from any conifer, a sesquiterpene (−)-cryptomerione and (E, E)-1,4-bis-(p-hydroxyphenyl)-buta-1,3-diene, both known from Taxodiaceae.

42 citations


Journal ArticleDOI
TL;DR: The kinetic theory of crosslinking by step reactions (Kuchanov 1978) may be extended beyond the gel point, and the structure and amount of sol may be described as mentioned in this paper.
Abstract: The kinetic theory of crosslinking by step reactions (Kuchanov 1978) may be extended beyond the gel point, and the structure and amount of sol may be described. For random reactions, the kinetic theory yields results identical with the theory of branching processes based on cascade substitution (Gordon 1962, 1975, Dobson 1965). The extension of the kinetic theory may be employed in order to compare deviations between the two theories expected for the dependent reactivities of functional groups.

42 citations


Journal ArticleDOI
TL;DR: In this article, the CNDO/2 method was applied in the study of the electronic structure of zeolite HY using models employing (HO)3Si.O.OH.Al(OH)−3 clusters for various types of skeletal oxygens.

34 citations


Journal ArticleDOI
TL;DR: In this article, the relative protonation cross-sections of β-amino alcohols appear to be independent of their relative affinities, and the interfunctional distance between functional groups is not a significant determinant of dehydration.
Abstract: Dehydration of β-amino alcohols after chemical ionization with iso-butane as reagent gas is dependent upon the interfunctional distance. Relative protonation cross-sections of both functional groups appear to be essentially independent of their relative proton affinities.

34 citations


Journal ArticleDOI
31 May 1979-Nature
TL;DR: The life cycles of two members of this group, Stylodinium sphaera and Cystodinedria inermis, include a parasitic amoeboid stage which brings about vegetative reproduction and also possibly sexual reproduction.
Abstract: SEXUAL reproduction has so far been unknown among the Dinococcales, unicellular brown algae belonging to the Dinophyceae (dinoflagellates). As we report here, however, the life cycles of two members of this group, Stylodinium sphaera and Cystodinedria inermis, include a parasitic amoeboid stage which brings about vegetative reproduction and also possibly sexual reproduction. We believe that the two amoeboid forms have previously been identified mistakenly as a separate taxon of protozoon.

33 citations


Journal ArticleDOI
TL;DR: The basic principles of the description and processing of thermal analysis (TA) curves are examined in this article, where a rational approach is used to investigate the limits of the validity of phenomenological thermodynamics under non-isothermal conditions.

31 citations


Journal ArticleDOI
TL;DR: In this paper, the ionization energy of the deep donor states due to oxygen and of the acceptor levels due to compensating VA1 vacancies were determined from the optical properties of AlN:O.
Abstract: The ionization energy of the deep donor states due to oxygen and of the acceptor levels due to compensating VA1 vacancies were determined from the optical properties of AlN:O. The theoretical calculations together with the experimental data (the emission spectra, the excitation of luminescence spectra and EPR data) indicate that the deepest donor level belongs to the ion O−.

Journal ArticleDOI
TL;DR: In this article, two mechanisms are proposed for the release of charges due to thermal ionization of the centres and migration of charges on the impurity centres, and the probability of the occurrence of impurity migration is discussed.
Abstract: Thermoluminescence of AlN: O in the 80–420 K temperature range is described. Two mechanisms are proposed for its explanation: the release of charges due to thermal ionization of the centres and migration of charges on the impurity centres. The probability of the occurrence of impurity migration is discussed.

Journal ArticleDOI
TL;DR: The effects of several types of vasopressin analogs that are considered to be resistant to some of the physiologically significant enzymatic systems were investigated utilizing rats trained in a passive avoidance task.


Journal ArticleDOI
TL;DR: This study determined the 7 values of the early and late pig anti-Dnp antibodies with precipitating and non-precipitating properties and found the rotational correlation times i of immunoglobulin molecules and their fragments to be in fair agreement with the results of fluorescence polarization experiments.

Book ChapterDOI
01 Jan 1979
TL;DR: In this article, a global heat flow map, derived from existing observations supplemented in areas without data by an empirical predictor based on tectonic setting and age, is discussed, along with a generalized map of European heat flow derived from the global parameters.
Abstract: A global heat flow map, derived from existing observations supplemented in areas without data by an empirical predictor based on tectonic setting and age, is discussed, along with a generalized map of European heat flow derived from the global parameters. High heat flow in the southern Europe-Mediterranean and North Atlantic regions and low heat flow in the East European platform dominate the long wavelength pattern of heat flow for the European region. The observation that continental and oceanic geotherm families parametric in surface heat flow intersect the mantle solidus at a depth coincident with the top of the seismic low velocity zone, enables surface heat flow variations to be used to infer lithospheric thickness over the European region. Thick lithosphere is projected for the shields and platform of northern and eastern Europe, while thin lithosphere is projected for the North Atlantic and southern European high heat flow zones. No simple relationship appears to exist relating heat flow to crustal thickness.

Journal ArticleDOI
TL;DR: In this paper, single and dual substituent parameter analysis was performed for a series of meta and para substituted phenoxytrimethylsilanes and the results showed that the increased silicon shift sensitivity to substituents in phenoxysilanes is due to higher sensitivity of silicon shielding (ϱ shield ) to electron density in these compounds rather than to a bettr transmission of electronic effects.

Journal ArticleDOI
TL;DR: In this article, the conversion of a reactive, micro-grained limestone to sulfate was studied in terms of exposure time and concentration of sulfur dioxide in the flue gas.

Journal ArticleDOI
TL;DR: In this paper, the optical properties of magnetite and iron-excess manganese ferrites are analyzed in terms of both, the Drude-Zener model of the free electron gas and the small polaron theory applied to the hopping of the electrons (Fe2+ ions) in the octahedral positions of the spinel lattice.
Abstract: The optical properties of magnetite and iron-excess manganese ferrites are analyzed in terms of both, the Drude-Zener model of the free electron gas and the small polaron theory applied to the hopping of the electrons (Fe2+ ions) in the octahedral positions of the spinel lattice. Several characteristic parameters of the charge carriers are deduced and a comparison with the dc electrical conductivities is made. Die optischen Eigenschaften von Magnetit und eisenreichen Manganferriten werden mit Hilfe des Drude-Zener-Modells des freien Elektronengases und der Polaronentheorie des Elektronenhoppings (Fe2+ Ionen) in Oktaederplatzen des Spinellgitters analysiert. Einige charakteristische Parameter der Ladungstrager werden bestimmt und ein Vergleich mit der Gleichstromleitfahigkeit durchgefuhrt.

Journal ArticleDOI
TL;DR: In this article, the exact formulae for the strain and displacement field, which changes near the surface due to relaxation of the internal concentration stresses, can be used for determination of the distribution of the solute atoms by X-ray diffraction techniques.
Abstract: Deformation caused by a modulated distribution of solute atoms, periodic in one dimension, in a plate-like crystal is studied within the framework of the isotropic theory of elasticity. The exact formulae for the strain and displacement field, which changes near the surface due to relaxation of the internal concentration stresses, can be used for determination of the distribution of the solute atoms by X-ray diffraction techniques.

Journal ArticleDOI
TL;DR: The level of the γ-carboxyglutamic acid containing protein in atherogenic diet fed rat aortae exceeds that found normally in bone or in tissues predisposed for physiological calcification.

Journal ArticleDOI
TL;DR: In this article, the radial electron density distribution curves of samples of bulk amorphous material were prepared in the range from TlSe2 to Se and it was shown that Tl atoms are embedded either ionically or in isolated Tl[Se4] tetrahedrons between Se-rings and/or chains.
Abstract: Samples of bulk amorphous material were prepared in the range from TlSe2 to Se. Analysis of radial electron density distribution curves of samples TlSe2, TlSe2.7, TlSe9 and Se indicates that selenium rings and/or chains are responsible for the existence of the amorphous phase in a relatively broad interval of compositions. Increasing the Tl content we observe in the first stage (for TlSe9) that Tl atoms are embedded either ionically or in isolated Tl[Se4] tetrahedrons between Se-rings and/or chains. Further increasing the Tl content (for TlSe2.7 and TlSe2) chains of Tl[Se4]-tetrahedra (probably edge-bound) are formed on behalf of selenium rings and/or chains. When a critical amount of these tetrahedra is reached crystallization processes hinder the formation of the amorphous phase.

Journal ArticleDOI
TL;DR: In this article, the positive column in a dc oxygen glow discharge was analyzed and the particle concentrations in a dependence on discharge parameters were obtained and the mechanism of the discharge was discussed, where the discharge plasma as a mixture of electrons, positive molecular ions, negative atomic ions, metastable molecules O2* (a1Δg), atoms and molecules particle balance equations were solved.
Abstract: Computational analysis of the positive column in a dc oxygen glow discharge was performed. Considering the discharge plasma as a mixture of electrons, positive molecular ions, negative atomic ions, metastable molecules O2* (a1Δg), atoms and molecules particle balance equations were solved. As a result the particle concentrations in a dependence on discharge parameters were obtained and the mechanism of the discharge was discussed.

Journal ArticleDOI
TL;DR: In this paper, single crystal films of Y3Fe5−x−yCoxGeyO12 garnets (0 ≦ x ≦ 0.05) were prepared by LPE method on the Gd3Ga5O12 (001) plane.
Abstract: Single crystal films of Y3Fe5−x−yCoxGeyO12 garnets (0 ≦ x ≦ 0.05) are prepared by LPE method on the Gd3Ga5O12 (001) plane. The first cubic anisotropy constant and the effective magnetization are measured and the influence of the Co-substitution is discussed. Depending on the growth rates of the films different types of the remanent domain structure are observed including even a close packed lattice of rectangular bubbles.

Journal ArticleDOI
TL;DR: In this article, a method of estimating hot and cold plasma parameters using ground Pc 1 observations is proposed, where the authors show that the most appropriate (effective) indicator of the L -shell, where Pc1 are generated, is the group delay of wave packets.

Journal ArticleDOI
TL;DR: In this paper, the spectral dependences of real and imaginary parts of the diagonal elements of the dielectric function of the single crystal series MnxFe3−xO4 for 0 ≦ x ≦ 1.6 were obtained.
Abstract: The near normal reflectance spectrum together with the data on the index of refraction and the extinction coefficient are combined in a Kramers-Kronig analysis to obtain the spectral dependences of the real and the imaginary parts of the diagonal elements of the dielectric function of the single crystal series MnxFe3−xO4 for 0 ≦ x ≦ 1.6. One-oscillator fit to optical constants is used to show that the main rise in absorption at about 2 eV is due to the 3d-crystal field transitions of the Fe3+ and/or Mn2+ ions in tetrahedral sites. The anomalous behaviour of optical constants below 1 eV in iron rich Mn-ferrites is ascribed to the presence of charge carriers (Fe2+) in octahedral sites. Das bei fast normalem Lichteinfall gemessene Reflexionsspektrum wird zusammen mit den Werten des Brechungsindex und des Extinktionskoeffizienten fur die Kramers-Kronig-Analyse benutzt, um die Spektralabhangigkeit der Real- und Imaginarteile der Diagonalelemente der Dielektrizitatsfunktion von MnxFe3−xO4-Einkristallen (0 ≦ x ≦ 1,6) zu erhalten. Die Anpassung der optischen Konstanten an das Ein-Oszillator-Modell zeigt, das fur den Hauptanstieg der Absorption um etwa 2 eV die 3d-Kristallfeldubergange der Fe3+- und/oder Mn2+-Kationen in den Tetraederplatzen verantwortlich sind. Das anomale Vehalten der optischen Konstanten unterhalb 1 eV in eisenreichen Manganferriten wird der Anwesenheit von Ladungstragern (Fe2+) in Oktaederplatzen zugeschrieben.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the Faraday rotation in the X-ray region (1.54 A) on the following materials: Ni, Co, and MgFe2O4.
Abstract: The Faraday rotation in the X-ray region (1.54 A) is measured on the following materials: Ni, Co, and MgFe2O4. The measurements are carried out with high precision by means of two-crystal polarimeter in the case of Ni and with lower precision by means of a three-crystal-polarimeter in the case of Co and MgFe2O4. It is found that the specific Faraday rotation, if any, does not exceed 3 deg cm−1 for Ni, 800 deg cm−1 for Co, and 200 deg cm−1 for MgFe2O4. Die Faraday-Rotation im Rontgenbereich (1,54 A) wird an folgenden Materialien gemessen: Ni, Co und MgFe2O4. Die Messungen werden mit hoher Prazision an Ni mit einem Zweikristall-Polarimeter durchgefuhrt und an Co und MgFe2O4 mit einem Dreikristall-Polarimeter mit geringerer Prazision. Die spezifische Faraday-Rotation ubersteigt nicht die Werte: 3 grd cm−1 fur Ni, 800 grd cm−1 fur Co und 200 grd cm−1 fur MgFe2O4.

Journal ArticleDOI
TL;DR: In this article, the effect of internal structure on the chromatographic properties of macroporous copolymers was studied using four types of macromers of methyl methacrylate, 2-hydroxyethyl methACrylate and acrylonitrile crosslinke with ethylenedimethacrylated as an example.

Journal ArticleDOI
TL;DR: RelRelativistic equations in which the fields cotransform under the direct sum of ordinary indecomposable representations of the Lorentz group are derived and discussed in this article.
Abstract: Relativistic equations in which the fields cotransform under the direct sum of ordinary indecomposable representations of the Lorentz group are derived and discussed.

Journal ArticleDOI
TL;DR: Magnetic domain patterns observed at 150 K on (110) and (211) surfaces of a U3As4 single crystal using a low temperature colloid technique are described in this paper.
Abstract: Magnetic domain patterns observed at 150 K on (110) and (211) surfaces of a U3As4 single crystal using a low temperature colloid technique are described. Magnetische Bereichsstrukturen bei 150 K an den (110)- und (211)-Oberflachen eines U3As4-Einkristalles werden mit Hilfe der Tieftemperatur-Bitter-Technik beobachtet.