Showing papers by "University of Ljubljana published in 1979"
TL;DR: In this article, the temperature dependence of the dielectric constant of Cs${\mathrm{H}}_{2}$P${O}}_{4}$ was analyzed.
Abstract: The temperature dependence of the dielectric constant of Cs${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ shows a crossover between a region ($3 \mathrm{K}l~T\ensuremath{-}{T}_{c}l~90 \mathrm{K}$) dominated by one-dimensional correlations and a region ($0 \mathrm{K}l~T\ensuremath{-}{T}_{c}l~3 \mathrm{K}$) dominated by three-dimensional correlations. A similar effect is observed as well in Cs${\mathrm{D}}_{2}$P${\mathrm{O}}_{4}$. The dielectric data allow for a quantitative determination of the ratio between the long-range interchain and the short-range intrachain coupling constants. $^{31}\mathrm{P}$ and $^{2}\mathrm{H}$ NMR data show that the ferroelectric transition is connected with an order of the H(2) hydrogens along the zig-zag chains.
94 citations
TL;DR: The methodical steps which led towards the construction of a six-channel electrical stimulator are given and a discussion of preliminary experience obtained by using the stimulator clinicaly is also presented and ideas for future work are given.
Abstract: Recent trends in the field of functional electrical stimulation (FES) of stroke patients are presented together with a short history of the development of the field. The methodical steps which led towards the construction of a six-channel electrical stimulator are given. The criteria for detennining the number of stimulation channels are highlighted and FES problems of stance phase active stimulation are discussed. The stimulator described is intended for FES assistance of a patient's gait. Stimulation is synchronized with the gait by means of a shoe-insole heel switch. A review of design principles and functions employed is presented in detail, together with a discussion emphasizing problems of multi-site FES in swing and stance phases during locomotion. A discussion of preliminary experience obtained by using the stimulator clinicaly is also presented and ideas for future work are given.
88 citations
TL;DR: Findings indicate a decreased risk of benign breast neoplasias and no relation to breast cancer risk with OC use, and the results of other studies suggesting increased risk of developing benign and malignant breast neplasms in long-term users of estrogen-containing preparations call for continued monitoring of the effects of these preparations.
86 citations
TL;DR: The MES method used is a modification of previously used similar methods of maximal stimulation with respect to reduced intensity of stimulation and reduced number of electrodes, so discomfort to the patient during treatment is considerably lessened.
71 citations
TL;DR: Urethral and bladder responses to anal electrical stimulation were evaluated by cystometry and urethral pressure profile measurements in 55 patients with different Urethral-bladder dysfunctions.
56 citations
TL;DR: The unimolecular charge separation fragmentations of doubly charged benzene and 18 derivatives containing various numbers of fluorine, chlorine and bromine atoms have been studied in this paper, in which two distinct kinds of transition state can be characterized, in one case the ring system remains intact and in the other case a linear transition state ion is formed.
Abstract: The unimolecular charge separation fragmentations of doubly charged benzene and 18 derivatives containing various numbers of fluorine, chlorine and bromine atoms have been studied. In the majority of cases two distinct kinds of transition state can be characterized, in one of which the ring system remains intact and in the other of which a linear transition state ion is formed. There is evidence for rearrangement of halogens both around the ring and along the linear chain.
45 citations
43 citations
TL;DR: In this article, two earthquakes of March 26, 1511 with different positions of foci represent some of the strongest seismic phenomena which occurred in the past in the central part of Europe.
37 citations
TL;DR: A new approach to cyanide determination based on the measurement of the diffusion current arising from the oxidation of silver to dicyanoargentate(I) is described, which is fast and linear for levels from one microgram to several grams per litre of solution.
37 citations
15 Dec 1979
TL;DR: In this paper, a discussion based on semi-empirical PPP hamiltonian explains how electronic correlation neglected in the Hartree-Fock (HF) self-consistent field (SCF) theory reduces this gap to ≈4 eV, while the excitation energy for the creation of excitons is estimated to be below 2 eV.
Abstract: Previous ab initio LCAO Hartree-Fock (HF) self-consistent field (SCF) band structure calculations predicted the alternating all trans (CH) x (polyacetylene or polyene) to be energetically more stable than the equidistant metallic chain, however, the gap of those calculations was too large (≈7 eV). The present discussion based on semi-empirical PPP hamiltonian explains how electronic correlation neglected in the HF theory reduces this gap to ≈4 eV, while the excitation energy for the creation of excitons is estimated to be below 2 eV. The formalism for this estimation is an intermediate-binding exciton theory with explicit use of numerical Wannier functions. It is concluded that the gap is not due to a spin-density-wave state of the equidistant chain, as expected by Ovchinnikov .
32 citations
TL;DR: The kinetics of AChE solubilization from intact motor endplates of mouse diaphragm, by collagenase, papain and hyaluronidase was studied in parallel with the ultrastructural localization of A ChE in treated neuromuscular junctions.
Abstract: The kinetics of AChE solubilization from intact motor endplates of mouse diaphragm, by collagenase, papain and hyaluronidase, was studied in parallel with the ultrastructural localization of AChE in treated neuromuscular junctions. Hyaluronidase did not solubilize more AChE from isolated motor endplate regions than Ringer's solution itself. Residual AChE activity could be demonstrated histochemically in motor endplates even after the plateau of solubilization by collagenase or papain was reached. Less than 35% of junctional AChE is left after collagenase, and less than 20% after papain treatment, as estimated by the percentage of AChE activity left in the isolated endplate region of the diaphragm after protease treatment. Cytochemically, both proteases had a similar effect on postsynaptic AChE. Residual AChE activity was distributed randomly, adhering to the sarcolemma of junctional clefts. Presynaptic AChE localized in the gap between axon terminal and Schwann cell appears to be resistant to collagenase but not to papain treatment. The mode of AChE attachment or the composition of the intercellular material in this gap may differ from that of the primary and secondary clefts.
01 Mar 1979
TL;DR: In this paper, the necking of a cylindrical, elastic-plastic, strain-hardening bar in axisymmetric tension was analyzed using the Lagrangian formulation.
TL;DR: Permeative properties of the red blood cell membrane are utilized for an introduction of three osmotic states of the model cell with respect to equilibration of certain cell solution constituents across the membrane and it is shown how cells are expected to behave if exposed to conditions with different Osmotic pressure, composition of external solutions, or temperature.
TL;DR: In this article, the synthesis, reactivity, uses, physical and spectral properties, biological properties, and crystal structures and molecular complexes of pyridazine are discussed, and the experimental dipole moment, Kerr constant, and molar Cotton-Mouton constant are obtained at 298°K and 633 nm, respectively.
Abstract: Publisher Summary This chapter reviews the synthesis, reactivity, uses, physical and spectral properties, biological properties, and crystal structures and molecular complexes of pyridazine. The standard synthesis of pyridazines from γ -keto acids or esters has been applied to the preparation of many derivatives. They can be synthesized using carbonyl compounds, acids, lactones, anhydrides, and related compounds. They can also be synthesized using cycloaddition reactions, heterocycles, carbohydrates, pyridazine 1,2-dioxides, pyridazine glycosides, and several miscellaneous methods. The reactions of pyridazines described are protonation, N -alkylation, N -oxidation, N -amination, substitutions at the pyridazine ring, oxidations and reductions, ring opening reactions, isomerizations, rearrangements, ring contractions, and photoreactions. Several calculations on the electronic structure of pyridazine are also presented. The physical and spectral properties of pyridazine and its derivatives are discussed in the chapter. Ionization constants of hydroxy- and mercaptopyridazines, of amino- and diaminopyridazines and their quaternization products, of methylsulfinylpyridazines, and of pyridazinium ylides are presented. The basicities of a series of pyridazines are determined and correlated with substituent constants using the Hammett free-energy relationship. The magnetic susceptibility of pyridazine is measured, and the rate constant for the reaction of hydrogen atoms with pyridazine is determined. The experimental dipole moment, Kerr constant, and molar Cotton–Mouton constant, obtained at 298°K and 633 nm, are presented.
TL;DR: In this article, it was shown that the coupling between the tunneling motion of one proton and the tunnel motion of another to the Ising model in a transverse field Hamiltonian can lead to large isotope shifts in deuteration even for small values of tunneling intergal.
Abstract: The addition of a ${B}_{\mathrm{ij}}{S}_{i}^{x}{S}_{j}^{x}$-type coupling between the tunneling motion of one proton and the tunneling motion of another to the Ising model in a transverse-field Hamiltonian, or the addition of the probably larger ${S}_{i}^{x}{F}_{i}^{x}{Q}_{i}$-type pseudospin phonon coupling (describing the modulation of the distance between the two equilibrium sites in an O-H \ifmmode\cdot\else\textperiodcentered\fi{} \ifmmode\cdot\else\textperiodcentered\fi{} \ifmmode\cdot\else\textperiodcentered\fi{} O bond by nonpolar phonons), results in a temperature-dependent renormalization of the proton tunneling integral. This is important close to ${T}_{C}$, where the soft-mode frequency vanishes, ${\ensuremath{\omega}}_{\mathrm{crit}}\ensuremath{\rightarrow}0$. This may lead to large isotope shifts in ${T}_{C}$ on deuteration even for small values of the tunneling intergal and may explain some phenomena recently observed in PbHP${\mathrm{O}}_{4}$ and squaric acid as well as the dependence of the effective proton-lattice interaction constant on hydrostatic pressure in K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$-type systems. This last effect may be also due to the presence of a ${S}_{i}^{x}{D}_{i}^{x}{{Q}_{i}}^{2}$ term in addition to the Kobayashi ${S}_{i}^{z}{F}_{i}^{z}{Q}_{i}$ term when coupling with polar optic phonons is taken into account. When the lattice motion is so anharmonic that the lattice ions move in a double-well potential, and the proton-lattice coupling so strong that the protons can tunnel in only one out of the two possible lattice configurations, two Curie temperatures may appear.
TL;DR: Vanadium and tin contents of total diet samples collected in five Italian towns are given, and discussed in relation to literature data, their status as essential elements and their levels in human blood.
TL;DR: In this article, a Landau theory describing the melting of bilayer membranes in terms of order parameters used in the theory of liquid crystals has been constructed to explain the obtained results.
Abstract: The hydrocarbon part of (${\mathrm{C}}_{10}$${\mathrm{H}}_{21}$N${\mathrm{H}}_{3}$)$_{2}\mathrm{Cd}$${\mathrm{Cl}}_{4}$ represents a smectic lipid bilayer exhibiting two structural phase transitions in analogy to biomembranes. Single-crystal $^{13}\mathrm{C}$ NMR and $^{14}\mathrm{N}$ nuclear quadrupole resonance and x-ray data show that the first transition is connected with a disordering of the polar heads whereas the second represents a partial melting of the lipid chains. A Landau theory describing the melting of bilayer membranes in terms of order parameters used in the theory of liquid crystals has been constructed to explain the obtained results.
TL;DR: In this paper, a mechanism was proposed which serves to explain the effects of some important variables on the electrochemical behavior of technetium, on the basis of diagnostic criteria, which served to explain how important variables can affect the performance of the reduction process.
TL;DR: In this article, a method is suggested for the kinetic consideration of a differential thermal analysis (DTA) or thermogravimetric (TG) curve which is based on a relation for the first-order reaction rate and Arrhenius's equation.
TL;DR: Permeative properties of the red blood cell membrane are utilized for an introduction of three osmotic states of the model cell with respect to equilibration of certain cell solution constituents across the membrane and it is shown how cells are expected to behave if exposed to conditions with different Osmotic pressure, composition of external solutions, or temperature.
TL;DR: WCl4Py2 (Py = Pyridine) as discussed by the authors has 2/m symmetry requiring trans position of the ligands and is isostructural with WBr4Pyridin.
Abstract: WCl4Py2 (Py = Pyridine) crystallizes in the monoclinic space group: I2/m, with a = 7.237(1), b = 7.278(2), c = 12.865(4) A, β = 94.60(2)°, and Z = 2. WCl4Py2 has 2/m crystallographic symmetry requiring trans position of the ligands. WCl and WN bond lengths are 2.347(1) and 2.181(4) A. WCl4Py2 is isostructural with WBr4Py2.
WX4Pic2 (Pic = 4-methylpyridine) can be obtained from WX4Py2 and 4-methylpyridine at room temperature. Chemical and physical evidence speaks for the trans structure of WX4Pic2.
Praparative und strukturelle Untersuchungen an WX4L2 (X = Cl, Br; L = Pyridin, 4-methylpyridin) und Kristallstruktur von WCl4Py2
WCl4Py2 (Py = Pyridin) kristallisiert in der monoklinen Raumgruppe I2/m mit Z = 2 und a = 7,237(1), b = 7,278(2), c = 12,865(4) A, β = 94,60(2)°. WCl4Py2 hat 2/m Lagesymmetrie mit Trans-Konfiguration der Liganden. WCl und WN-Abstande sind 2,347(1) und 2,181(4) A. WCl4Py2 ist isostrukturell mit WBr4Py2.
WX4Pic2 (Pic = 4-methylpyridin) wurde aus WX4Py2 und 4-methylpyridin bei Zimmertemperatur hergestellt. Chemische und physikalische Beweise sprechen fur die Trans-Konfiguration von WX4Pic2.
TL;DR: In the tissue of Planaria, cholinesterase, cholineacetyltransferase and acetylcholine were demonstrated, which permits the assumption that cholinergic system is one of the mediator systems in turbellaria.
TL;DR: In this article, Pappa proposed a six-dimensional space-time, which is made up of three equivalent two-dimensional spaces, and tested the relationship between co-ordinate and proper time.
Abstract: In a letter PAPPAS has considered a six-dimensional space-time (1). I t is not the first proposal of this kind since symmetric space-time is appealing, particularly from the standpoint of extended relativity (2). Attempts to generalize the experimental accessible one temporal dimension to three abstract dimensions are interesting per se. But a viable scheme must meet a severe condition: it has to incorporate the wellknown four-dimensional equations at least to the accuracy to which they have been verified experimentally. In Pappa 's scheme space-time exhibits an attractive novel feature: it is made up of three equivalent two-dimensional spaces. So it appears worthwhile, put t ing aside possible flaws and internal inconsistencies of the scheme, to confront it with experimental evidence. A convenient test (3) is the relationship between co-ordinate and proper time, t and t ~, respectively:
TL;DR: In this study, two spinlabelled isocyanides with different chain lengths are studied to obtain a deeper insight into stereochemical properties of the active sites of enzymes.