Showing papers by "University of Zagreb published in 1984"

Topographical atlas of the gangliosides of the adult human brain.

Abstract: Forty different brain samples, consisting of neocortical, archicortical, and paleocortical areas; telencephalic, diencephalic, and mesencephalic subcortical nuclei; and the cerebellum as well as some of the corresponding white matter bundles were analyzed with respect to total content of ganglioside-sialic acid and the ganglioside pattern. The total content of gangliosides seems to depend mainly on the proportions of gray and white matter. Thus, neocortical areas, which are rich in gray matter, have a four- to fivefold higher ganglioside content (per milligram of protein) than white matter-rich samples such as optic chiasm, capsula interna, or corpus callosum. White matter-rich regions, although very heterogeneous in ganglioside composition, are further characterized by appreciable amounts of the myelin-enriched GM4. In the neocortex a remarkable degree of regional pattern differences was revealed. In the frontal and parietal areas there is a moderate, and in the temporal region a strong preponderance of sialic acid bound to gangliosides of the a-pathway (GD1a, GM1). In contrast, the occipital cortex favors the b-pathway of ganglioside synthesis (GQ1b, GT1b, GD1b). A predominance of “b-gangliosides” was found in all structures that are related to the visual system (optic chiasm, pulvinar-thalamus, superior colliculi, visual cortex) as well as in the cerebellum and the nucleus ruber. All diencephalic nuclei tend to favor slightly “b-gangliosides,” while the mesencephalic nuclei are very heterogeneous in their ganglioside composition. A preponderance of “a-gangliosides” was found in the periamygdalar cortex, putamen, inferior colliculi, substantia nigra, frontal white matter, internal capsule, globus pallidus, basal nucleus of Meynert, and corpus callosum as well as in the frontal, parietal, and temporal cortices. An exceptional predominance of GM1 and GD1a was revealed for the hippocampal archicortex and the amygdala, suggesting a possible functional correlation to glutaminergic synaptic transmission.

Generation of the coherent pulses by the CDW-motion. Solutions of the microscopic model equations

Abstract: The collective transport of charge density waves (CDW) converts into an ordinary current at the contacts with a normal metal. In the present work this conversion is proposed to proceed via the process of phase slippage (PS). The CDW in the quasi-one-dimensional system with a nested Fermi surface and impurities is described by the nonlinear differential equation derived earlier. This equation is solved numerically for semi-infinite samples, as well as for finite samples with both edges fixed. The analysis of solutions is carried out for electrical fields E and sample lengths L which are respectively one to two orders of magnitude larger and smaller than the actual experimental values. This leads to the following results: the PS solutions are one-periodic functions of time, with the distance of the PS centre from the fixed end behaving like E −0.284 in the limit of small E. The coherent CDW transport in the finite samples occurs above the threshold field which varies as L −1.23 . The pulses in the voltage generated by PS processes are also analysed. The results are in a good agreement with the experimental data for the length dependence of the threshold field and with some properties of the periodic noise in e.g. NbSe 3 and TaS 3 Etude theorique du transport collectif par les ondes de densite de charge (CDW), qui se transforme en un courant ordinaire dans les contacts avec un metal normal, ce processus se produisant par un glissement de phases de CDW. Analyse des solutions numeriques obtenues pour des echantillons finis et semi-infinis. Comparaison aux donnees experimentales pour NbSe 3 et TaS 3

SU(6) model for odd-odd nuclei (OTQM/IBOM) and boson-aligned phase diagram inO(6) limit

Abstract: We introduce the SU(6) model IBOM/OTQM for odd-odd nuclei and discuss the bands in O(6) limit. Bands are characterized by a particular type of phase correlations in the wave functions and exhibit splitting of the SU(3) analogs of Gallagher-Moszkowski bands.

Plant regeneration from mesocotyl callus of Hordeum vulgare L.

Abstract: Callus tissue was induced on barley mesocotyl explants of germinated seven-day-old seedlings on MS medium supplemented with 2,4-D or 2,4,5-T in high concentrations. Two morphologically different tissue cultures were maintained in vitro for a long time: a callus tissue without organogenesis and a culture with high rhizogenic capacity. Shoots and plantlets were generated when the auxin-media induced callus was transferred to medium supplemented with 3 μM TIBA. In 62% of cultures, during the first five subcultures, four to twentyeight plants per single mesocotyl were obtained. Some cultures produced shoots even in the 9th subculture, being in culture for nearly 14 months. The largest number of plants obtained per one mesocotyl was forty. Plantlets rooted well on MS with 5.7 μM IAA and survived transplantation to soil in high percentages.

Hall effect and electronic structure of glassy Zr 3d alloys

Abstract: Accurate Hall coefficients of glassy Zr1-xFex, Zr1-xCox, Zr1-xNix and Zr1-xCux alloys are reported. In Zr-rich alloys the Hall coefficient is positive and changes sign (except for ZrFe alloys) at progressively higher concentrations (x) in going from ZrCo to ZrCu alloys. A correlation is found between the cross-over concentration and the concentration at which the nature of the states at the Fermi level changes from being predominantly of Zr d character to being predominantly of solute d character.

The Relationship between Electrode Area and Sensory Qualities in Electrical Human Tongue Stimulation

Abstract: The relationship between the size of the stimulated human tongue area, the stimulating electric current intensity and the provoked sensory qualities was examined. Five different electrode areas and four anodal current intensities were used. The observed sensations were of three kinds: sour taste, somatosensory, and undefined ones. At a given current intensity level the proportion of taste increases with the increase in the stimulation area, while somatosensory sensations decrease. These results imply that at the suprathreshold level there is a certain interdependence between the area, current intensity and sensory effects. In order to achieve optimal activation of the taste system alone, it is more effective to use a larger electrode and stronger current, than to use smaller areas and weaker stimuli: in this case the electrical sour taste is satisfactorily clear, since the somatosensory system is still not activated. These findings may have implications in clinical electrogustometry.

Prenatal and perinatal development of radial cell columns in the human auditory cortex.

Abstract: The aim of this study was to analyse cytoarchitectonic development of radial cell columns in the human auditory cortex and to correlate these ‘ontogenetic’ cell columns with the ‘adult’ pattern of radial cell arrangement. For this cytoarchitectonic analysis, brains were obtained from human fetuses and infants ranging between 9 weeks of gestation and third postnatal month. Plastic and celloidin sections containing prospective auditory areas TC, TB and TA of Economo & Koskinas were stained by Nissl method. In youngest fetuses (8–13 weeks) radially oriented cell columns (1–3 cell wide ‘ontogenetic’ columns) were found in the whole thickness of the developing cortical plate. During the next developmental stage (13–26 weeks of gestation), radial cell columns were present in the superficial part of the cortical plate, while the deep part of the cortical plate showed a variable cell arrangement due to the formation of the subplate layer (13–15 weeks), The appearance of the pale bands, and development of the pros...

Magnetic field effects for the asymmetric Anderson Hamiltonian

Abstract: Perturbation expansion for the asymmetric single-orbital Anderson Hamiltonian is extended to the case with finite magnetic field, and the self-energy part of the $d$-electron Green function is calculated up to the second order in $u=\frac{U }{\ensuremath{\pi}\ensuremath{\Delta}}$ for arbitrary asymmetry $\ensuremath{\eta}=\frac{1}{2}+\frac{{\ensuremath{\epsilon}}_{d}}{U}$ and magnetic field $h$. Zero-temperature density of localized states ${\ensuremath{\rho}}_{d\ensuremath{\sigma}}(\ensuremath{\omega})$, magnetic moment $m$ and static spin susceptibility $\ensuremath{\chi}$, and low-temperature specific heat ${C}_{v}=\ensuremath{\gamma}T$ and magnetoresistance $D$ of a dilute alloy are evaluated within the ${u}^{2}$ approximation. Plausible arguments are given (which become exact in the symmetric case) that the higher-order terms do not change the qualitative features of our results. For large enough $u$ the many-body (MB) effects give rise to three different types of behavior, depending on the value of asymmetry: (i) spin-fluctuation behavior for $\ensuremath{\eta}l\frac{1}{2}$, with large fluctuations of the $d$-level magnetization; (ii) mixed-valence behavior for $\ensuremath{\eta}\ensuremath{\simeq}\frac{1}{2}$, with large fluctuations of the $d$-level occupation; (iii) essentially mean-field behavior for $\ensuremath{\eta}g\frac{1}{2}$, where the MB effects are negligible even for $u\ensuremath{\gg}1$. Thus both $\ensuremath{\chi}$ and $\ensuremath{\gamma}$ at $h=0$ are enhanced by the increase of $u$ for $\ensuremath{\eta}l\frac{1}{2}$, reduced for $\ensuremath{\eta}g\frac{1}{2}$, and practically unaffected at $\ensuremath{\eta}\ensuremath{\simeq}\frac{1}{2}$. As functions of $\ensuremath{\eta}$ for a fixed $u$, $\ensuremath{\chi}$ and $\ensuremath{\gamma}$ have a maximum at $\ensuremath{\eta}=0$ and decrease monotonously with increasing $\ensuremath{\eta}$, and do so more steeply the higher the $u$. For $h\ensuremath{ e}0$ and $\ensuremath{\eta}\ensuremath{\le}\frac{1}{2}$, $\ensuremath{\chi}$ and $\ensuremath{\gamma}$ decrease monotonously with increasing $h$, the decrease being quicker for higher $u$ and slower for higher $\ensuremath{\eta}$. For $\ensuremath{\eta}g\frac{1}{2}$, both $\ensuremath{\chi}$ and $\ensuremath{\gamma}$ exhibit a broad maximum at medium $h$ values, which becomes better pronounced with increasing $u$. The low-T magnetoresistance $D={\ensuremath{-}D}_{0}[1\ensuremath{-}\frac{1}{3}{D}_{2}{(\frac{\ensuremath{\pi}{k}_{B}T}{\ensuremath{\Delta}})}^{2}]$ is negative, with ${D}_{0}\ensuremath{\propto}{h}^{2}$ for small $h$ and ${D}_{0}\ensuremath{\rightarrow}1$ for large $h$. ${D}_{2}$ has a maximum at $h=0$ and drops down quickly with increasing $h$. Both ${D}_{0}$ and ${D}_{2}$ are enhanced by $u$ for $\ensuremath{\eta}l\frac{1}{2}$ and reduced for $\ensuremath{\eta}g\frac{1}{2}$. In the low-$h$ limit and for $\ensuremath{\eta}l\frac{1}{2}$, $D$ assumes a universal form for $u\ensuremath{\gg}{u}_{c}$, with both low-$T$ and low-$h$ behavior scaled by the same characteristic temperature ${\ensuremath{\Theta}}_{m}$. The density of localized states at $T=h=0$ is single peaked for $u\ensuremath{\lesssim}{u}_{c}$ and triple peaked for $u\ensuremath{\gg}{u}_{c}$ if $\ensuremath{\eta}l\frac{1}{2}$, with ${u}_{c}$ increasing with $\ensuremath{\eta}$. For $\ensuremath{\eta}\ensuremath{\ge}\frac{1}{2}$ it is single peaked for any finite $u$. For $\ensuremath{\eta}l\frac{1}{2}$ and $u\ensuremath{\gg}{u}_{c}$ the increasing $h$ splits ${\ensuremath{\rho}}_{d\ensuremath{\uparrow}}$ and ${\ensuremath{\rho}}_{d\ensuremath{\downarrow}}$, suppresses the narrow MB central peak above ${T}_{h}$, and restores the "magnetic" Hartree-Fock situation above ${h}_{0}$. Both ${T}_{h}$ and ${h}_{0}$ increase with increasing $\ensuremath{\eta}$. For $u\ensuremath{\lesssim}{u}_{c}$, ${T}_{h}\ensuremath{\sim}{h}_{0}\ensuremath{\sim}\ensuremath{\Delta}$.

The oscillating loop prominence of July 17, 1981

Abstract: Oscillatory motions of a loop prominence observed on July 17, 1981 are analysed. The oscillations were mainly horizontal, with a period of 8 min. Restoring force was a result of magnetic tension, and assuming a simplified magnetic field configuration the expression for frequencies of oscillations is derived and compared with the observations. Taking the observed period, the strength of the magnetic field permeating the prominence is estimated as 45 G. Finally, the stability of the prominence is discussed.

Poly(lactic acid) microencapsulated oxytetracycline: in vitro and in vivo evaluation.

Abstract: Poly(lactic acid) microcapsules of oxytetracycline hydrochloride were prepared by precipitation of the polymer from a solution when a non-solvent was added to a polymer solution in which the drug had been dispersed. Three types of microcapsules were prepared by varying the amount of drug encapsulated, as well as by using two samples of polymer with different molecular weights. The product obtained was of a matrix character consisting of agglomerated capsules. The drug release in vitro, for the best batch, was completed within 12 hours. Serum levels of the drug in rabbits treated by intramuscular injection were prolonged maximally up to 24 hours depending upon the type of microcapsules.

Distribution of moulds on stored grains in households in an area affected by endemic nephropathy in Yugoslavia.

Abstract: The distribution of moulds on stored maize, wheat and beans in families affected and unaffected by nephropathy in the endemic area (Endemic nephrophaty — Balkan kidney disease) of middle Posavinain Yugoslavia was studied. Among 3 700 samples of stored grains, no significant difference was noted in the contamination by moulds of samples taken from affected and unaffected families. The predominant moulds on all the samples were ‘storage moulds’ from the genera Penicillium and Aspergillus, ‘field moulds’ among which Alternaria and Fusarium were encountered most frequently, and the ‘spoilage moulds’ Absidia, Mucor, Rhizopus, Trichoderma and Trichothecium.

A comparative study of bent-bond vs. Walsh model in strained systems. Bicyclo(1.1.0)butane

Abstract: Bent bond and Walsh models for the electronic structure of the highly strained bicyclo(1.1.0)butane were critically examined and compared with the available PE spectrum. It is found that the bent bond scheme is by far more superior to the widely used Walsh semilocalized molecular orbitals. Hence the local hybrid orbitals provide a useful aid in assigning and interpreting of PE spectra. Present results lend support to the hybrid model in bicyclo(1.1.0)butane proposed by Schulman.

Metal-metalloid exchange in the Zr1−xMxMo2 (M ≡; Ge, Si, Al) system

Abstract: An extensive study of the possibility of substituting zirconium in ZrMo2 by germanium, silicon or aluminium was carried out using X-ray diffractometry and metallography. In the Zr1−xGexMo2 system the crystal structure of the prototype compound ZrMo2 (cubic Friauf-Laves phase; space group, Fd3m) was retained up to the composition Zr0.8Ge0.2Mo2. Substitution in the Zr1−xSixMo2 and Zr1−xAlxMo2 systems was possible up to the compositions Zr0.75Si0.25Mo2 and Zr0.3A1{0.7}Mo2, respectively, but the cubic crystal structure transformed into a hexagonal MgZn2-type structure (space group, P6 3 mmc ). This structure was stabilized if the substituent contents were in excess of 5 at.% Si or 6.7 at.% Al. A high temperature b.c.c. ternary solid solution was also observed in all the systems investigated. The unit cell parameters, cell volumes and interatomic distances were determined for the observed phases of all three systems. Some semiquantitative correlations of these phases with those found in the related Hf1−xMxMo2 (M ≡; Ti, Ge, Si, Al), Zr1−xTixMo2, Zr1−xMxW2 and Hf1−xMxW2 (M ≡; Ti, Si, Al) systems were also made.

Three dynamical boson-fermion symmetries for odd-odd nuclei

Abstract: For odd-odd nuclei we introduce three dynamical boson-fermion symnetries associated with jπ=3/2, jυ=3/2 and UB(5) symmetry of the boson core. The corresponding energy formulas and quantum numbers for low-lying states are explicitly given.

Formation of lyotropic liquid crystals of metal dodecyl benzene sulphonates

Abstract: The formation of uni-, bi-, and trivalent metal ion dodecyl benzene sulphonate (DBS) precipitates was investigated using light scattering, low angle X-ray diffraction and polarizing microscopy at 293 K. The thermodynamic equilibrium constants were calculated, improving some of our previous experimental results and applying a fitting program to the theoretical curve for association and solubility product equilibrium involving ionic strengths. The appearene of liquid crystals formed in a particular precipitation region is characterized by relationships of the reacting components. The question of the structural model of the metal ion — DBS liquid crystalline mesophase remains to be solved in future investigations.