Showing papers by "Academy of Sciences of the Czech Republic published in 1976"
TL;DR: In this paper, a mathematical model including intraparticle transport and chemical reaction within the particles (grain theory) has been developed to simulate this sulfur dioxide sorption reaction, and the model has been applied to simulate the reaction of sulfur dioxide and oxygen with limestones.
Abstract: Experimental measurements of the reaction of sulfur dioxide and oxygen with limestones have demonstrated substantial influence of the geologic origin of the stone, its porosity and particle size, gaseous concentration of sulfur dioxide, and temperature on the course of reaction and the conversion (that is, the degree of utilization of the limestone content of the particles as a sorbent for sulfur dioxide). A mathematical model including intraparticle transport and chemical reaction within the particles (grain theory) has been developed to simulate this sulfur dioxide sorption reaction.
207 citations
TL;DR: In this paper, the authors defined the Landau-Lifshitz damping coefficient in terms of spin-orbital torque correlations in the one-electron model and estimated as a function of the orbital collision frequency.
Abstract: The Landau-Lifshitz damping coefficient is defined in terms of spin-orbital torque correlations in the one-electron model and estimated as a function of the orbital collision frequency. The formal results are compared with previous studies and the results of a numerical calculation for nickel are compared with known experimental data.
193 citations
49 citations
TL;DR: In this paper, a class of solutions of the Peierls-Nabarro equation using the method of residua in the complex plane is found for complicated force laws leading to dissociation of dislocations.
Abstract: A class of solutions of the Peierls-Nabarro equation is found using the method of residua in the complex plane. These solutions are suitable for investigation of the planar dislocation cores within the Peierls-Nabarro model for complicated force laws leading to dissociation of dislocations.
27 citations
TL;DR: In this paper, the Peierls-Nabarro model was modified to describe the cores of screw dislocations extended along two or three intersecting slip planes, under the action of external stress.
Abstract: The Peierls-Nabarro model originally developed for dislocations with planar cores is modified to describe the cores of screw dislocations extended along two or three intersecting slip planes, under the action of external stress. This concept generalizes the simplified concept of sessile splitting of screw dislocations into singular partials and enables an instructive interpretation of fully atomistic models of screw dislocation cores developed recently for b.c.c. metals. As an example, a numerical solution of the modified Peierls-Nabarro equation is given for the equilibrium configuration of a 1/2 [111] screw dislocation core in α-Fe extended along three {110} planes.
22 citations
TL;DR: In this paper, the energies of generalized stacking faults lying on {110} and {112} planes are calculated for Fe-Si alloys with the DO3 long-range order for concentrations 10−25 at % Si.
Abstract: The energies of the generalized stacking faults lying on {110} and {112} planes are calculated for Fe-Si alloys with the DO3 long-range order for concentrations 10–25 at. % Si. In the used model, the interaction between atoms is described by the series of three central interatomic potentials fitted to experimental data. The lattice relaxations perpendicular to the stacking fault plane are considered. The displacement vectors corresponding to stable antiphase boundaries are found and some consequences for the structure of superdislocations in the DO3 superlattice are mentioned.
21 citations
TL;DR: Work-hardening curves of single crystals of iron and its alloys with 0·5 and 0·9 wt.% Si and paths of the tensile axis of specimens during deformation were investigated as mentioned in this paper.
Abstract: Work-hardening curves of single crystals of iron and its alloys with 0·5 and 0·9 wt.% Si and paths of the tensile axis of specimens during deformation were investigated. Single crystals oriented for single glide were deformed in tension at temperatures 113, 201, 295 and 403 K at a nominal strain rate of 5·5×10−5 sec−1. It appears that with increasing silicon content (a) the transition between the high-temperature regime of plastic deformation (characterized by three-stage work-hardening) and the low-temperature regime is shifted to lower temperatures, (b) stage I-hardening is enhanced and (c) the flow stress level increases. These observations are explained by strong solution hardening of iron by silicon atoms which suppresses the differences between mobilities of screw and non-screw dislocations, increases the flow stress level and consequently the density of primary dislocations. As a result of this the latent hardening in the secondary slip system increases and stage I extends to a large strain.
18 citations
TL;DR: A review of theoretical treatment of the measurement of crystallinity in crystallized glasses is given in this article in order to show the assumptions and limitations of the method, and a formula for the determination of the crystallinity enables necessary corrections to be made separately, especially when large-scale measurements are undertaken.
Abstract: A review of theoretical treatment of the measurement of crystallinity in crystallized glasses is given in order to show the assumptions and limitations of the method. This consists of the measurement of non-crystalline scattering in a relatively narrow interval of the diffracted intensity spectrum, and is particularly convenient where crystalline phases developed during crystallization have unknown composition or are not preparable in pure form. A formula given for the determination of crystallinity enables necessary corrections to be made separately, especially when large-scale measurements are undertaken. Finally, crystallinity was measured on several samples of glassceramic material from the system SiO2Al2O3MgOZrO2TiO2.
15 citations
TL;DR: In this article, it was shown that the operator Hi of the two-dimensional isotropic harmonic oscillator is unitary equivalent to a direct sum of the operator Hl = − 1 2 d2/dϱ2 + 1 2 m2 ϱ2+ g(l)ϱ 2 where l = (4l2 − 1)/8 and l = 0, ±1, ±2,
13 citations
TL;DR: Ferromagnetic resonance of amorphous Gd 1− x Co x films was studied at 36 GHz in order to obtain the dependence of effective anisotropy field, g -factor and relaxation parameters on chemical composiiton in the interval 0.8 x.
12 citations
TL;DR: The study of atherosclerosis yielded the finding that the changes in the activity of some enzymes of basic metabolic cycles accompany, or even precede, the pathologic changes inThe vessel that lead to the development of atherosc1erosis.
Abstract: The problem of atherosclerosis is undoubtedly one of the most pressing in modern medicine. Because the target organ of this disease, namely, the vessel wall, has a relatively intensive metabolism, the relationship of this metabolism to the initiation and development of atherosclerosis has been studied. As stressed by the results of studies performed over many years, the problem associated with the development and therapy of atherosclerosis cannot be tackled without taking into account the metabolic processes of the vascular wall. Whatever the pathogenesis of the disease, the participation of the vascular wall and, above all, its metabolism in the formation of t h e pathologic changes currently appear to be the most important factors. Our study of the problem yielded the finding that the changes in the activity of some enzymes of basic metabolic cycles accompany, or even precede, the pathologic changes in the vessel that lead to the development of atherosc1erosis.l A lowered activity of Krebs cycle enzymes and enhanced activity of some phosphomonoesterases were found to be characteristic for the processes that lead to the deposition of lipids, alterations of connective tissue reactions, and the formation of atherosclerotic lesions in the vessel wall. This finding was true both in experimental animals under artificial conditions, wherein the dominant factor was a lesion of the vessel wall, and in human vessels or vessel segments with a predilection for the development of atherosclerosis, for example, abdominal aorta as compared with thoracic aorta, pulmonary artery versus aorta, and so ~ n . ~ . ~ These metabolic conditions, which are deleterious for the resistance of the vessel to the disease, were found to evolve gradually during the animal’s Iifetime.‘J The study of these problems has so far been entirely confined to investigation of experimental lesions of the vessel wall in animals or, with human vessels, of material obtained by dissection. A considerable step forward was therefore made by breeding a strain of spontaneously hypertensive rats .2R.”
TL;DR: In this paper, the energies and the relative intensities of the lines of the optical absorption spectra of a certain class of TCNQ salts are calculated within a strong coupling approximation.
Abstract: The energies and the relative intensities of the lines of the optical absorption spectra of a certain class of TCNQ salts are calculated within a strong coupling approximation. The unpaired electrons are supposed to interact strongly with the intramolecular excitons and with several modes of intramolecular vibrations. The agreement of the theory and experiment is satisfactory. The ways of possible improvements of the theory and the interpretation of the experimental data are discussed.
TL;DR: In eight wife-husband pairs during the whole pregnancy the reactivity of lymphocytes to PHA, to lymphocytes of unrelated donor and to lymphocyte of husband was studied, and in eleven women at delivery a statistically significant decline of MLC reaction to lymph cells of own and unrelated newborn was found.
Abstract: In eight wife-husband pairs during the whole pregnancy the reactivity of lymphocytes to PHA, to lymphocytes of unrelated donor and to lymphocytes of husband was studied. No statistically significant differences were found in reactivity of wife's and husband's lymphocytes.
TL;DR: In this paper, a theory explaining the positive column constriction in terms of a thermal effect is presented, where the neutral gas becomes more rarified near the tube axis and a locally increased molecular ion production ensues.
Abstract: A theory explaining the positive column constriction in terms of a thermal effect is presented. As a consequence of the heating the neutral gas becomes more rarified near the tube axis and a locally increased molecular ion production ensues. If this is balanced by the dissociative (volume) recombination a constriction results at higher currents and pressures. The density profiles and other physical quantities are computed and compared with the available experimental data. All computations are performed for a non-Maxwellian plasma with the electron Coulomb interaction neglected. In contrast to the theories based on an ionization mechanism the thermal theory predicts also a constriction of the density profile.
TL;DR: In this paper, a phenomenological description of the optical properties of the ferroelectric phase is given, which takes into account the improper nature of the phase transition, and two possible types of phase changes, an improper and pseudoproper phase transition are discussed.
Abstract: Experimental data are presented on the spontaneous birefringence and the linear electrooptical effect in the ferroelectric phase. A phenomenological description of these optical properties is given, which takes into account the improper nature of the ferroelectric transition. Two possible types of the ferroelectric phase changes, an improper and pseudoproper phase transition, are discussed. Satisfactory agreement is found between the theory of an improper ferroelectric phase transition and experimental data given here and by other authors. The pseudoproper model leads in our opinion to a fundamental inconsistence with our optical experiments.
TL;DR: Although short-day photoperiod inhibits the activation at warm temperatures, it enables diapause development under cold temperatures and promotes future reproduction, apparently also due toPhotoperiod changes.
Abstract: To reveal the effect of photoperiod on insects under low temperatures, dormant females of Chrysopa carnea were exposed for 3 months (November–January) to cold (7°±2.5°C) and to long- or short-day conditions (18L:6D or 12L:12D). They were thereafter activated under short-day conditions at 25°C. The samples differed considerably in the incidence of ovipositing females, duration of pre- and post-oviposition period, and fecundity. All parameters evidenced a considerably higher reproductive activity of insects chilled under short-day conditions. It was thus confirmed that adults of C. carnea perceive photoperiod at cold. The action of short photoperiod at cold does not impair the subsequent oviposition; by contrast it promotes future reproduction, apparently also due to photoperiod changes. Although short-day photoperiod inhibits the activation at warm temperatures, it enables diapause development under cold temperatures.
TL;DR: The normal human epidermis fixed with glutaraldehyde and embedded in glycolmethacrylate was investigated by means of ultrastructural cytochemistry to provide more information on the morphology and composition of nuclear inclusions of keratinocytes in the uppermost granular layer.
TL;DR: In this paper, the charge transfer part of the optical spectra is interpreted in terms of the theory of optical transitions when the interaction of the electrons with the intramolecular vibrations is strong and the intermolecular interactions are neglected.
Abstract: The charge-transfer part of the optical spectra is interpreted in terms of the theory of the optical transitions when the interaction of the electrons with the intramolecular vibrations is strong and the intermolecular interactions are neglected. The theory is applied to the complex TCNQ salts and the high conductivity simple TCNQ salts.
TL;DR: In this paper, the influence of the skine effect on the kinematic properties of disaccommodation measurements in metals has been calculated in higher approximations and it is shown that the influence depends not only on the frequency of the measuring field and on the diameter and material constants of the cylindrical specimen but also on the relaxation strength, i.e., on the concentration of relaxators.
Abstract: The very sensitive and convenient ac techniques of the disaccommodation measurements in metals are substantially influenced by the skineffect. This influence has been calculated in higher approximations and it is shown that the influence of the skineffect depends not only on the frequency of the measuring field and on the diameter and material constants of the cylindrical specimen but also on the relaxation strength, i.e., on the concentration of relaxators. The second approximation is relatively simple and it can be used for the correction of ac experimental data in most cases, whereas the first approximation which has been used till the present day is applicable only for very small relaxation strength up to about 1%.
TL;DR: In this paper, the double-step chronocoulometry has been verified for the e.c. electrode reaction type, a reversible electron transfer being followed by a chemical reaction in solution leading to inactivation of the primary product.
TL;DR: Theoretical results which show that up to six different propagation paths are possible at the same frequency between a pair of satellites at an equal height below the peak of a biparabolic concentric model ionosphere are presented in this paper.
TL;DR: In this article, a coupling between the ordinary sound wave and the F - ionization wave is presented as a possible explanation of the straightening of the free F ionisation wave dispersion relation.
TL;DR: In this article, a novel dilution technique was applied to the kinetic study of the inhibited radical polymerization of vinyl acetate and experimental evidence for the following conclusions were provided: (i) the title reaction proceeds via simultaneous pathways owing to hydrogen bonding between phenols and vinyl acetates.
Abstract: Application of a novel dilution technique to the kinetic study of the inhibited radical polymerisation of vinyl acetate provided experimental evidence for the following conclusions. (i) The title reaction proceeds via simultaneous pathways owing to hydrogen bonding between phenols and vinyl acetate. (ii) The influence of hydrogen bonding on the reactivity at 50 °C depends on the type of substitution. The free phenol is more reactive than the bonded form if at least one of the ortho-positions is unsubstituted. The hydrogen bonded species is more reactive than the free form for 2,6-dialkylphenols. (iii) The individual reaction paths are associated with significantly differing Arrhenius parameters.
TL;DR: In this article, the properties of Ag2H3IO6 and (NH4)2H 3IO6 have been investigated using NMR-NQR-spectroscopy.
Abstract: The investigation of thermal, optical and dielectric properties of Ag2H3IO6 and (NH4)2H3IO6 revealed phase transitions in two steps with unknown intermediate phases. Reflectivity measurements in the far infrared region confirm that the main step is caused by a freezing in of the proton tunnelling modes. From the results of NMR-NQR-spectroscopy the low temperature structures for both compounds are deduced. The complete group analysis of lattice vibrations and proton ordering modes of the room temperature phases is performed. In the case of Ag2H3IO6 the transitions can be discussed in the frame-work of the Landau theory, starting with a condensation of an antiphase vibration of the silver atoms in theF point of the trigonal Brillouin zone, whereas in the case of (NH4)2H3IO6 a simultaneous ordering of protons inZ, F, andL-points of the Brillouin zone is proposed for the first step. A new definition of antiferroelectric transitions is suggested which is based on symmetry arguments only. The proton-ordering transitions in both compounds can then be classified as antiferroelectric.
TL;DR: In this paper, the magnitude of intermolecular charge transfer interaction inside dimers in the Alkali TCNQ salts is deduced from the knowledge of the experimental triplet exciton energy and the constants characterizing the electronic, excitonic and vibrational properties of TCNsQ molecules.
Abstract: The optical absorption spectra of several crystalline anion radiacal salts have been analyzed recently within the frame of the model Hamiltonian of electrons and intramolecular excitons and vibrations in the limit of strong interaction of the excitonic and vibrational motions with the unpaired electrons. In the present work the magnitude of the intermolecular charge transfer interaction inside dimers in the Alkali TCNQ salts is deduced from the knowledge of the experimental triplet exciton energy and the constants characterizing the electronic, excitonic and vibrational properties of TCNQ molecules. Perturbation calculation is used to derive a formula for the triplet exciton energy.
TL;DR: In this paper, new experimental results on the coherent K L 0 C → K S 0 C regeneration in the momentum range 10≦p≦30 GeV/c are presented.
Abstract: New experimental results on the coherentK L 0 C →K S 0 C regeneration in the momentum range 10≦p≦30 GeV/c are presented. For the quantity (f0−¯f0/k (where f0 and¯f0 are theK‡C and¯K0C forward scattering amplitudes andk is the wave number) we have obtained: arg (f0−¯f0)/k=−126‡±14‡ and ¦(f0−¯f0/k¦∼ ∼p−0.62±0.14 These results are well described by a simple Regge pole model including only the (Ω-trajectory exchange in thet-channel with the intercept αω(0) close to 0.4.
TL;DR: In this paper, the results on hadron-hadron total cross-sections and the real parts of forward scattering amplitudes are discussed on the basis of rigorous model-independent theory.
Abstract: Recent experimental results on hadron-hadron total cross-sections and on the real parts of forward scattering amplitudes are discussed on the basis of rigorous model-independent theory. Some consequences of the asymptotic theorems obtained recently by the authors are presented.