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Showing papers by "University of Ljubljana published in 1989"


Journal ArticleDOI
TL;DR: The upper bound is a strong discrete version of the wellknown Cheeger inequality bounding the first eigenvalue of a Riemannian manifold.

363 citations


Journal ArticleDOI
TL;DR: A procedure is developed to calculate red blood cell and phospholipid vesicle shapes within the bilayer couple model of the membrane and the spontaneous membrane curvature (C0) and compressibility of membrane leaflest can be incorporated into the model.
Abstract: A procedure is developed to calculate red blood cell and phospholipid vesicle shapes within the bilayer couple model of the membrane. The membrane is assumed to consist of two laterally incompressible leaflets which are in close contact but unconnected. Shapes are determined by minimizing the membrane bending energy at a given volume of a cell (V), given average membrane area (A) and given difference of the areas of two leaflets (ΔA). Different classes of shapes exist in parts of the v/Δa phase diagram, where v and Δa are the volume and the leaflet area difference relative to the sphere with area A. The limiting shapes are composed of sections of spheres with only two values allowed for their radii. Two low energy axisymmetrical classes, which include discocyte and stomatocyte shapes are studied and their phase diagrams are analyzed. For v=0.6, the discocyte is the lowest energy shape, which transforms by decreasing Δa continuously into a stomatocyte. The spontaneous membrane curvature (C 0) and compressibility of membrane leaflest can be incorporated into the model. A model, where ΔA is free and C 0 determines the shapes at given V and A, is also studied. In this case, by decreasing C 0, a discocyte transforms discontinuously into an almost closed stomatocyte.

324 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a survey on the applications of grapheme in chimie and in physique applications, with a focus on the use of graphes in chimies.
Abstract: Introduction. Operateurs lineaires associes a un graphe. Resultats fondamentaux. Rayon spectral, fonctions generatrices de marche et mesures spectrales. Croissance et nombre isoperimetrique d'un graphe. Fonctions propres positives. Graphes de groupes, arbres et graphes reguliers en distance. Quelques remarques sur les applications en chimie et en physique

321 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe the development and psychometric properties of a 56 item self report altruism scale, which was administered to university student subjects in Australia, Egypt, Korea, the Republic of China (Taiwan), the United States (Hawaii and Missouri) and Yugoslavia.

126 citations


Journal ArticleDOI
TL;DR: In this paper, the ARGUS detector at the e+e− storage ring DORIS II at DESY was used to study the γγ→ϱ+ϱ−→π+π−π 0π0π0 reaction.

91 citations


Journal ArticleDOI
Tadej Bajd1, A. Kralj, R Turk, H Benko, J. Šega 
TL;DR: A two-channel peroneal stimulator was found to be a useful approach in order to inhibit this tone and thereby help the patients to initiate a step.

83 citations


Journal ArticleDOI
TL;DR: The distribution, behaviour, and trophic ecology of the jellyfish Pelagia noctiluca were studied in coastal waters of the Adriatic Sea, both in situ and in the laboratory, indicating a substantial predatory impact when found in aggregations.

79 citations


Journal ArticleDOI
TL;DR: Pair-binding-energy and hole-density correlation functions indicate that two holes bind for moderate exchange interactions, even in the case of the extreme anisotropic-Ising limit.
Abstract: The effective single-band Hamiltonian for holes in the two-dimensional quantum antiferromagnet, relevant for the ${\mathrm{CuO}}_{2}$ layers in copper-oxide superconductors, is studied by the exact diagonalization of a finite-size system with 16 cells. Single- and two-hole ground-state properties are calculated. Pair-binding-energy and hole-density correlation functions indicate that two holes bind for moderate exchange interactions, even in the case of the extreme anisotropic-Ising limit.

73 citations


Journal ArticleDOI
TL;DR: Application de la resonance magnetique nucleaire a perturbation quadripolaire a la determination de the distribution de polarisation locale et son second moment, dans des verres renfermant de l'hydrogene ou du deuterium.
Abstract: Application de la resonance magnetique nucleaire a perturbation quadripolaire a la determination de la distribution de polarisation locale et son second moment, dans des verres renfermant de l'hydrogene ou du deuterium. Les resultats experimentaux correspondent a ceux prevus par un modele de verre deutere au grand nombre de liaisons aleatoires en interaction, en presence de champs aleatoires geles

63 citations


Proceedings ArticleDOI
25 Jul 1989
TL;DR: In this paper, the response times and operating voltages for light shutters made from polymer dispersed liquid crystals' are studied and compared with calculations based on simplified models for ellipsoidal shaped droplets with major and minor axes a and b respectively.
Abstract: The response times and operating voltages for light shutters made from polymer dispersed liquid crystals' are studied. Alterations in the resistivity of the polymer binder are made by varying the degree of cross-linking to demonstrate and quantitize the strong effect of resistivity on the switching voltage. The voltage response from transitions in the nematic director configuration is studied in radially configured droplets and the molecular anchoring energy at the droplet wall is measured. Measurements of the relaxation time, response time, and voltage response are also reported on uniformly elongated and aligned droplets to study the effect of droplet shape. The results of these measurements are compared with calculations based on simplified models for ellipsoidal shaped droplets with major and minor axes a and b respectively. Response equations in terms of the aspect ratio e = a/b are experimentally examined.

48 citations


Journal ArticleDOI
TL;DR: In this article, the average polarization of D∗+ mesons originating from exclusive decays B 0 → D ∗+ l − ν was measured using the ARGUS detector at the e+e− storage ring DORIS II.

Journal ArticleDOI
TL;DR: Analysis of the far-ultraviolet CD spectra reveals that with increasing temperature the mean residue ellipticity becomes less negative, which reflects unfolding of the native protein, and conformational changes are to a large extent reversible.

Journal ArticleDOI
TL;DR: Using the ARGUS detector at the DORIS II storage ring at DESY, a charmed meson of mass (2455±3±5) MeV/c2, decaying to D+π− was observed in this paper.

Journal ArticleDOI
TL;DR: The least dimension d necessary for vector representations of graphs is studied as a function of G and of various restrictions placed upon the coordinates of the vectors and the values of the inner products.

Journal ArticleDOI
TL;DR: The ordering in bipolar liquid-crystal droplets close to the nematic-paranematic phase translation is studied and the temperature-radius phase diagram shows the first-order coexistence curve terminating in the critical point and a pronounced decrease of the coexistence temperature on approaching the critical radius.
Abstract: The ordering in bipolar liquid-crystal droplets close to the nematic-paranematic phase translation is studied. Here, ``paranematic'' refers to the phase above the nematic-isotropic transition temperature. The structure of spherical droplets is obtained after the minimization of the Landau\char21{}de Gennes-type free energy assuming a constant value of the surface order parameter and strong anchoring of the molecules parallel to the surface. Disordered defect regions caused by elastic deformations are found close to the poles. The defect regions grow into the droplet as the coexistence temperature between the paranematic and nematic phases is approached from below. The temperature-radius phase diagram shows the first-order coexistence curve terminating in the critical point and a pronounced decrease of the coexistence temperature on approaching the critical radius.

Journal ArticleDOI
TL;DR: In this article, a rigid point particle, an analogue of the rigid string or membrane, has been considered and its action containing an extrinsic curvature term has been cast into an equivalent form in which there occurs a one-dimensional vielbein.

Journal ArticleDOI
TL;DR: In this paper, the first time that the cross section has been measured so close to threshold is presented, and the results of cross section measurements for the reaction π − p → π− π + n are presented.

Journal ArticleDOI
TL;DR: Xenon difluoride and caesium fluoroxysulphate have been used to yield α-fluorocycloalkanones in high yield.

Journal ArticleDOI
TL;DR: In this paper, a decay angular analysis of the D∗ (2420), seen in the final state D ∗(2010)+π−, was performed using data collected with the ARGUS detector.

Journal ArticleDOI
TL;DR: Using the ARGUS detector at the e + e − storage ring DORIS II, this article investigated the decay B 0 → D − l + ν, where l + is e + or μ +.

Journal ArticleDOI
TL;DR: In this paper, a simple yet accurate direct integration procedure is proposed for the ECPSSR cross section calculation and different approximations for the energy loss correction are shown to differ up to few percent in the low velocity region.
Abstract: Methods for the ECPSSR cross section calculation are examined. Direct integration procedures of the electronic form factor and the methods using the tabulated universal functions are reviewed and compared. A simple yet accurate direct integration procedure is proposed. Different approximations for the energy loss correction are shown to differ up to few percent in the low velocity region.

Journal ArticleDOI
TL;DR: Using the ARGUS detector at the storage ring DORIS II, this article investigated the inclusive production of π±,K€�€£€�£££ £££▬▬▬▬▬▬▬ in multihadron events at 9.98 GeV and in direct decays of the ϒ(1S) meson from quark and gluon fragmentation.
Abstract: Using the ARGUS detector at thee + e − storage ring DORIS II, we have investigated inclusive production of π±,K ±,K and $$\bar p$$ in multihadron events at 9.98 GeV and in direct decays of the ϒ(1S) meson, i.e. from quark and gluon fragmentation. The most pronounced difference is the rate of baryon production. The Lund Monte Carlo program gives a reasonable qualitative description, although it cannot reproduce our data in detail.

Journal ArticleDOI
TL;DR: In this article, several effective models, derived from a general two-band Hubbard model for CuO2 layers in oxide superconductors, are studied and compared with the hole-spin models and a generalized effectice single-band (t-J) model.
Abstract: Several effective models, as derived from a general two-band Hubbard model for CuO2 layers in oxide superconductors are studied. In particular we compare the Hubbard model with the hole-spin models (unsymmetrized and symmetrized) and a generalized effectice single-band (t-J) model.1 Our exact diagonalization results for a finite CuO2 chain of 4 cells show that spectral properties of a single mobile quasiparticle in a general Hubbard model can be well reproduced by reduced effective models. This remains valid even in the mixed valence regime, where the straightforward derivation of the hole-spin model is not possible due to the breakdown of the perturbation expression using hopping parameter in the Hubbard model as a small parameter.

Journal ArticleDOI
TL;DR: In this article, the influence of bias electric field on the temperature and frequency dependence of the soft mode part of the complex dielectric constant of the chiral smectic A* phase has been studied experimentally It was found that only close to T S*CS*A does the bias field have any influence on the experimentally determined quantities.
Abstract: The influence of a bias electric field on the temperature and frequency dependence of the soft mode part of the complex dielectric constant of the chiral smectic A* phase has been studied experimentally It was found that only close to T S*CS*A does the bias field have any influence on the experimentally determined quantities Here the relaxation frequency increased with increasing bias field, while the corresponding dielectric strength decreases We also present a theoretical calculation of the influence of a bias field on the complex dielectric constant of the chiral smectic A* phase which, apart from minor details, is in accordance with the observed behaviour Finally we discuss how the nature of the electroclinic effect can be correlated with the influence of the bias field on the smectic A* dielectric constant

Journal ArticleDOI
TL;DR: The data indicate that kainic acid‐induced limbic seizures result in a loss of cholinergic cells in the nucleus basalis that is paralleled by degeneration of cholinesterase fibers and choli‐noceptive structures in the piriform cortex and amygdala, a finding emphasizing the important role of Cholinergic mechanisms in generating and/or maintaining seizure activity.
Abstract: Three days after systemic administration of kainic acid (15 mg/kg, s.c.), selected cholinergic markers (choline acetyltransferase, acetylcholinesterase, muscarinic acetylcholine receptor, and high-affinity choline uptake) and GABAergic parameters [benzodiazepine and gamma-aminobutyric acid (GABA) receptors] were studied in the frontal and piriform cortex, dorsal hippocampus, amygdaloid complex, and nucleus basalis. Kainic acid treatment resulted in a significant reduction of choline acetyltransferase activity in the piriform cortex (by 20%), amygdala (by 19%), and nucleus basalis (by 31%) in comparison with vehicle-injected control rats. A lower activity of acetylcholinesterase was also determined in the piriform cortex following parenteral kainic acid administration. [3H]Quinuclidinyl benzilate binding to muscarinic acetylcholine receptors was significantly decreased in the piriform cortex (by 33%), amygdala (by 39%), and nucleus basalis (by 33%) in the group treated with kainic acid, whereas such binding in the hippocampus and frontal cortex was not affected by kainic acid. Sodium-dependent high-affinity choline uptake into cholinergic nerve terminals was decreased in the piriform cortex (by 25%) and amygdala (by 24%) after kainic acid treatment. In contrast, [3H]flunitrazepam binding to benzodiazepine receptors and [3H]muscimol binding to GABA receptors were not affected 3 days after parenteral kainic acid application in any of the brain regions studied. The data indicate that kainic acid-induced limbic seizures result in a loss of cholinergic cells in the nucleus basalis that is paralleled by degeneration of cholinergic fibers and cholinoceptive structures in the piriform cortex and amygdala, a finding emphasizing the important role of cholinergic mechanisms in generating and/or maintaining seizure activity.

Journal ArticleDOI
TL;DR: In this article, crosslinked co-poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes 1 or 2 respectively, and their reactivity studied in reactions with various aromatic molecules.

Journal ArticleDOI
TL;DR: In this article, a measurement of the π − p→π − p π 0 reaction was performed with the OMICRON spectrometer at the CERN synchrocyclotron.

Journal ArticleDOI
TL;DR: In this article, the Borgnakke-Larsen model was used to solve the Boltzmann equation for polyatomic gases, where the redistribution of rotational energy was modeled as a continous Markov process.
Abstract: Numerical methods for solving the Boltzmann equation must rely upon simplified models of the differential scattering cross-section. Whereas a variety of useful models are known for monatomic gases, little else is available for polyatomic gases than the traditional rough spheres and various smooth exisymmetric bodies. Kinematic models with only one new variable - the rotational energy - seem preferable. However, blind mathematical construction runs the risk of violating the detailed-balance symmetry. The Borgnakke-Larsen model avoids this trouble, as does a new model where the redistribution of rotational energy is pictured as resulting from a continous Markov process. Both models are easily adjusted so as to reproduce the known values of viscosity, volume viscosity and thermal conductivity. With some modification the temperature dependence of viscosity can also be incorporated.

Journal ArticleDOI
01 Jan 1989-Toxicon
TL;DR: It is concluded that tyrosine residues are involved in both lethal and cytolytic activity, while the role of arginine residues is not evident because of the non-specific alteration of tyosine residues with 2,3 butanedione.

Journal ArticleDOI
TL;DR: In this article, the intrinsic electrical resistivity-humidity characteristics of MgCr2O4 material used for humidity sensors are varied by choosing a particle size fraction of the starting powders with a radius less than or equal to 1 μm.