Showing papers by "University of Ljubljana published in 1972"
TL;DR: In this paper, a pseudo-spin wave theory for order-disorder-type ferroelectrics and anti-ferro-electrics is proposed. But the pseudo-Ising model is not suitable for the case of the non-ising model.
Abstract: The dynamics of order-disorder-type ferroelectrics and anti-ferroelectrics is discussed with reference to recent theoretical and experimental investigations. Following a short review of the lattice dynamical theory of structural phase transitions the pseudo-spin formalism appropriate for order-disorder-type systems is introduced. It is shown that most dynamical properties of such systems can be described by a pseudo-Ising model in a transverse tunnelling field. Finally, the predictions of the pseudo-spin wave theory are compared with some recent experiments.
274 citations
TL;DR: In this paper, phase diagrams indicating solidus and liquidus temperatures and the extent of solid solubility for pseudobinary systems of niobium monocarbide with iron, chromium, nickel and cobalt were presented.
Abstract: Phase equilibrium relationships in the pseudobinary systems of niobium monocarbide with iron, chromium, nickel and cobalt have been investigated by metallographic, electron micro-probe and X-ray diffraction techniques. Alloys of variable compositions were arc-melted in an argon atmosphere using non-consumable electrodes and were subsequently annealed at predetermined temperatures, cooled and subjected to various examinations for phase identification. NbC was found to form simple binary eutectics with the respective metals, with partial solid solubility at both ends of the systems. Eutectic compositions and melting points have been determined and phase diagrams indicating solidus and liquidus temperatures and the extent of solid solubility for each system are presented.
49 citations
TL;DR: In this paper, the authors applied tight-binding approximation for calculation of the band structure of planar hexagonal crystal layers of graphite and boron nitride, and obtained the theoretical width of the valence band of 15.9 eV in graphite.
Abstract: The tight-binding approximation has been applied for calculation of the band structure of planar hexagonal crystal layers of graphite and boron nitride. The theoretical width of the valence band of 15.9 eV in graphite and the distance between the centers of $\ensuremath{\pi}$ and $\ensuremath{\sigma}$ band of 5.3 eV as obtained in the present calculation are in good agreement with Chalkin's experimental work yielding 15 and 5 eV, respectively. For boron nitride, the width of the energy gap and the width of the valence band were calculated to be 4.9 and 6.8 eV, respectively.
48 citations
TL;DR: A method is described for the neutron activation analysis or arsenic and antimony simultaneously in biological materials at submicrogram level, based on the differences in the extraction behaviour of the iodides from sulphuric acid-potassium iodide medium with toluene.
45 citations
TL;DR: In this article, it was shown that the mechanisms for proton spin-lattice relaxation in the nematic liquid crystalline phase in 4- n -methoxybenzylidene-4'- n -butylaniline (MBBA) is different from that in p -azoxyanisole (PAA) when the measurements of T 1 are extended to low frequencies.
37 citations
TL;DR: In this article, the solvent extraction with toluene of 17 elements as iodides from sulphuric acid-potassium iodide media has been investigated with a view to developing separation methods, particularly for neutron activation analysis.
35 citations
TL;DR: In this article, the authors used pulsed nitrogen double resonance in the rotating frame to determine the electric field gradient tensors at the 14N sites in paraelectric (NH4)2SO4.
29 citations
TL;DR: In this article, the generator coordinate method is extended to non-harmonic systems, where the many-dimensional Hill-Wheeler integral equation is reduced to a one-dimensional integral equation by expressing all independent parameters in the generator function by a single parameter.
25 citations
TL;DR: In this article, the normal coordinate analysis of the Cl3COO · H · OOCCl3 ion was made using a modified Urey-Bradley force field and the results indicated that the hydrogen bond is genuinely symmetrical in this acid salt.
22 citations
TL;DR: A histometric thyroid gland activation index has been proposed as a quotient between the mean voluminal percentage of the epithelial cells and the colloid and a positive correlation between the blood TSH level and this index is supposed.
Abstract: SUMMARY
A histometric thyroid gland activation index has been proposed as a quotient between the mean voluminal percentage of the epithelial cells and the colloid. A positive correlation between the blood TSH level and this index is supposed.
22 citations
TL;DR: The results suggest that the choline carrier has a higher affinity for the quaternary ammonium compounds which areknown as neuromuscular blocking agents than for those which are known as ganglionic blocking agents.
TL;DR: In this paper, a simple binary-eutectic type with partial solid solubility at both ends of the BaTiO3-BaGeO3 system was investigated by DTA and X-ray diffraction methods.
Abstract: The system BaTiO3-BaGeO3 has been investigated by DTA, metallographic and X-ray diffraction methods. A number of selected samples were also analysed on the electron probe micro-analyser. The system was found to be of the simple binary-eutectic type with partial solid solubility at both ends. The eutectic composition was established as 68±0.5 mol% BaGeO3 and its melting temperature as 1120±5° C. The solid solubility of BaGeO3 in BaTiO3 at 1120°C was found to be 1.8 mol % and that of BaTiO3 in BaGeO3 2.2 mol %. Additions of BaGeO3 to BaTiO3 did not appear to cause any change in the temperature of the cubic to hexagonal inversion of BaTiO3 but the temperature of the tetragonal to cubic inversion was raised slightly with such additions. The transformation temperature of 1180° C for the low- to high-temperature form of BaGe03 was not affected by additions of BaTiO3
TL;DR: The vanishing of ferroelectricity in KH 2 PO 4 at high pressures reflects the fact that the transverse tunneling field has become equal to the longitudinal dipolar field so that no "longitudinal" ordering is possibly any more as discussed by the authors.
TL;DR: Tomatidine (tomatanin-3β-ol) was dehydrogenated by Nocardia restrictus to tamatanin -3-one, 1,4-tomatadien-3- one, 4-tomatenin- 3-one and 1,2- tomatidien-1-one to achieve degradation.
TL;DR: In this article, a cylinder-type sputtering apparatus enables 3 to 6 times larger sputtering rates to be achieved compared with the standard diode d.c. sputtering system, and an element for the open-ended in-line continuous deposition of protective layers on low quality steel wires was designed.
TL;DR: The hydration constants for the TOPO HOH associate have been determined in the solvents n -hexane, cyclo hexane, m -xylene, carbon tetrachloride, benzene, toluene, carbon disulphide, chloro benzene and 1,2-dichloro ethane as discussed by the authors.
TL;DR: It was concluded that the cholinoreceptor and AChE must be two different macromolecules8,9 and whether α-Bgt really is an exception in this respect was reinvestigated.
Abstract: IT has been shown that α-bungarotoxin (α-Bgt) irreversibly blocks cholinoreceptors1–10, and that D-(+)tubocurarine (TC) protects these receptors from the toxin4–7. On the other hand, it has been emphasized that α-Bgt has no effect on the catalytic activity of acetylcholinesterase (AChE)4,6,9, and it was concluded that the cholinoreceptor and AChE must be two different macromolecules8,9. Because typical cholinolytics, including TC and gallamine, characteristically influence the kinetics of a membrane-bound AChE11,12, it seemed justified to reinvestigate whether α-Bgt really is an exception in this respect.
TL;DR: In this paper, a comparison of NMR and neutron data shows a large difference in the values of the diffusion coefficients, indicating that rotational as well as translational diffusion contribute to the self-diffusion coefficient observed by the neutrons.
Abstract: Self-diffusion in the nematic and isotropic liquid phase of 4-n-methoxybenzylidene-4′-n-butylaniline (MBBA) has been studied by incoherent quasielastic neutron scattering. A comparison of NMR and neutron data shows a large difference in the values of the diffusion coefficients, D, indicating that rotational as well as translational diffusion contribute to the self-diffusion coefficient observed by the neutrons. These measurements are contrasted with those of PAA where translational diffusion is dominant.
Es wird die Selbstdiffusion in der nematischen und isotropen flussigen Phase von 4-n-Methoxybenzyliden-4′-n-Betylanilin (MBBA) durch inkoharente, quasielastische Neutronenstreuung untersucht. Ein Vergleich von NMR und Nentronenwerten zeigt eine grose Differenz in den Werten der Diffusionskoeffizienten D, was zeigt, das sowohl Rotations- als auch Translationsdiffusion zum Selbstdiffusionskoeffizienten beitragt, der durch Neutronen beobachtet wird. Diese Messnngen werden denen von PAA gegenubergestellt, wo Translationsdiffusion vorherrscht.
TL;DR: In this article, the i.r. spectra of solid hydrazinium( 1 +) fluoride and of its completely deuterated analogue have been examined over the region from 4000 to 250 cm −1.
TL;DR: A magnetic diver microgasometer operated at the constant pressure is described and by the aid of a thin quartz fiber which supports the ampulla the stable equilibrium between bouyancy and magnetic forces is maintained.
TL;DR: In this paper, the simulation of stimulated condensation of supercooled liquid is discussed and the results of the calculations show that in the initial period, after an external potential is switched on, the sytem responds with relaxation even below the stability limit.
TL;DR: In this paper, some characteristic properties of nonlinear interaction between p and s ionization waves in the positive column of a neon glow discharge are represented. But, at a neutral gas pressure of 0,3 torr and discharge current of 10 mA, the interaction appears to be nonresonat.
Abstract: Some characteristic properties of nonlinear interaction between p and s ionization waves in the positive column of a neon glow discharge are represented. At a neutral gas pressure of 0,3 torr and discharge current of 10 mA this interaction appears to be nonresonat.
TL;DR: In this paper, the temperature dependence of the "ferroelectric" contribution to the specific heat in Rochelle salt has been calculated for the two sublattice model and it is found that the heat anomaly has the same sign at the lower and at the upper Curie point.
TL;DR: In this paper, the phase equilibrium relationship in the ternary system U-Ni-N have been investigated by heat treating various mixtures at temperatures between 1200 °C and 1600 °C in 1 atm argon and nitrogen and identifying the phases present by metallographic and X-ray methods.
TL;DR: In this paper, the phase lag is found to behave like s log s for small widths of the gap between transmitter and detector, assuming no intermolecular collisions and for arbitrary gas-surface scattering kernels, disregarding any interference from the detector and with full account of the interreflections.
Abstract: The sound problem in plane geometry is solved under the assumption of no intermolecular collisions and for arbitrary gas-surface scattering kernels, first disregarding any interference from the detector and then with full account of the interreflections. In the latter case the phase lag is found to behave like s log s for small widths of the gap between transmitter and detector. Expansions derived for idealized cases show that measurements of transmitted sound hold little promise of yielding significant information about the gas-surface interaction. Such a goal is better approached by studying the reaction to the transmitter (e.g., by observing the damping of a freely vibrating elastic reed), whereby the normal-momentum accommodation coefficient could be determined.
TL;DR: In this paper, the use of hydrazinium(+2) fluoride as fluorinating agent was investigated in the N 2 H 6 F 2 Al system, where ammonium fluoroaluminates were isolated and characterised as intermediate products, formed during the thermal treatment.