Showing papers by "Hungarian Academy of Sciences published in 1991"

The Proper Formula for Relative Entropy and its Asymptotics in Quantum Probability

Abstract: Umegaki's relative entropyS(ω,ϕ)=TrDω(logDω−logDϕ) (of states ω and ϕ with density operatorsDω andDϕ, respectively) is shown to be an asymptotic exponent considered from the quantum hypothesis testing viewpoint. It is also proved that some other versions of the relative entropy give rise to the same asymptotics as Umegaki's one. As a byproduct, the inequality TrA logAB ≧TrA(logA+logB) is obtained for positive definite matricesA andB.

Al induced crystallization of a‐Si

Abstract: The crystallization of amorphous Si induced by Al during heat treatment has been investigated by cross section and plan view transmission electron microscopy. The lowest temperature of Al induced crystallization of amorphous Si was found to be 440 K. The crystallization temperature, however, depends on the thickness of Al layers in layered structures and on the concentration of Al in co‐deposited layers below 1‐nm‐layer thickness and 15 at.% of Al concentration, respectively. Al‐induced crystallization in layered structures starts at the Al/amorphous Si interfaces and is located close to them. The amount of crystallized Si depends on the quantity of Al and on the temperature and increases with them. The mechanism of crystallization involves intermixing of Al with Si and the formation of an alloy of high metal concentration in the amorphous/crystalline interface. When the formation of this alloy is not assured due to low Al concentration, then crystallization does not start or the process of crystallization stops. In Al induced crystallization the nucleation of polycrystalline Si grains rather than their crystal growth is affected.

Subpopulations of GABAergic neurons containing parvalbumin, calbindin D28k, and cholecystokinin in the rat hippocampus.

Abstract: The possible coexistence of calbindin D28k with parvalbumin and of calbindin D28k with cholecystokinin was studied in nonpyramidal cells of the rat dorsal hippocampal formation. Neighbouring Vibratome sections were immunostained either for calbindin D28k and parvalbumin or for calbindin D28k and cholecystokinin. The cells, halved during sectioning, were identified in both sections immunostained for different antigens. The coexistence of calbindin D28k and parvalbumin in the same neuron was rare throughout the hippocampal formation with the exception of stratum oriens of the CA1 region, where 9.6% of the parvalbumin-immunoreactive cells also contained calbindin D28k. In stratum radiatum of the CA3 region, calbindin D28k and cholecystokinin coexisted in 12.5% and 21.2% of the calbindin D28k and cholecystokinin-immunoreactive cells, respectively. In other regions of the hippocampal formation, the two markers coexisted in less than 5% of the cells of either type. The present results demonstrate that calbindin D28k-, parvalbumin- and cholecystokinin-containing nonpyramidal cells represent largely nonoverlapping cell populations and may thus be involved in different inhibitory circuits.

Complementation of a yeast cell cycle mutant by an alfalfa cDNA encoding a protein kinase homologous to p34cdc2

Abstract: The cdc2 protein kinase plays a central role in control of the eukaryotic cell cycle of animals and yeasts. We have isolated a cDNA clone (cdc2Ms) from alfalfa (Medicago sativa L.) that is homologous to the yeast cdc2/CDC28 genes. The encoded protein is 64% identical to the yeast and mammalian counterparts and shows all the prominent structural features known from these organisms. Antibody raised against a 16-amino acid synthetic peptide with crossreactivity against p34 proteins recognized a 34-kilodalton protein in extracts of alfalfa cells. When transferred into a fission yeast, the plant cdc2 homolog can complement a temperature-sensitive cdc2 mutant. Northern analysis revealed higher transcript levels in shoots and suspension cultures than in roots. In addition to the dominant transcript of 1.4 kilobases detected in the poly(A)+fraction, 2.5- and 1.2-kilobase transcripts were detected in total RNA preparations from shoots or somatic embryos. Suspension cultures that were induced to form somatic embryos by an auxin (2,4-dichlorophenoxyacetic acid) showed fluctuations in transcription pattern during the induction period and embryogenesis.

The mixing rate of Markov chains, an isoperimetric inequality, and computing the volume

Abstract: A. Sinclair and M. Jerrum (1988) derived a bound on the mixing rate of time-reversible Markov chains in terms of their conductance. The authors generalize this result by not assuming time reversibility and using a weaker notion of conductance. They prove an isoperimetric inequality for subsets of a convex body. These results are combined to simplify an algorithm of M. Dyer et al. (1989) for approximating the volume of a convex body and to improve running-time bounds. >

Limits on neutral light scalar and pseudoscalar particles in a proton beam dump experiment

Abstract: A search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton beam dump experiment. No positive signal is observed. Limits on the mass and life-time of these particles are set in the frame of the Standard Model and its minimal supersymmetric extension. The Higgs particle of theSU2L×U1 Standard Theory is excluded for masses in the range 1 MeV

GABAergic interneurons containing calbindin D28K or somatostatin are major targets of GABAergic basal forebrain afferents in the rat neocortex

Abstract: The arborization pattern and postsynaptic targets of the GABAergic component of the basal forebrain projection to neo- and mesocortical areas have been studied by the combination of anterograde tracing and pre- and postembedding immunocytochemistry. Phaseolus vulgaris leucoagglutinin (PHAL) was iontophoretically delivered into the region of the diagonal band of Broca, with some spread of the tracer into the substantia innominata and ventral pallidum. A large number of anterogradely labelled varicose fibres were visualized in the cingulate and retrosplenial cortices, and a relatively sparse innervation was observed in frontal and occipital cortical areas. Most of the labelled axons were studded with large en passant varicosities (Type 1), whereas the others (Type 2) had smaller boutons often of the drumstick type. Type 1 axons were distributed in all layers of the mesocortex with slightly lower frequency in layers 1 and 4. In the neocortex, layer 4, and to a smaller extent upper layer 5 and layer 6 contained the largest number of labelled fibres, whereas only a few fibres were seen in the supragranular layers. Characteristic type 2 axons were very sparse but could be found in all layers. Most if not all boutons of PHAL-labelled type 1 axons were shown to be GABA-immunoreactive by immunogold staining for GABA, Altogether 73 boutons were serially sectioned and found to make symmetrical synaptic contacts mostly with dendritic shafts (66, 90% of total targets), cell bodies (6, 8.2% of total), and with one spine. All postsynaptic cell bodies, and the majority of the dendritic shafts (44, 60.3% of total targets) were immunoreactive for GABA. Thus at least 68.5% of the total targets were GABA-positive, but the majority of the dendrites not characterized immunocytochemically for technical reasons (15.1%) also showed the fine structural characteristics of nonpyramidal neurons. The target interneurons included some of the somatostatin- and calbindin-containing subpopulations, and a small number of parvalbumin-containing neurons, as shown by double immunostaining for PHAL and calcium-binding proteins or neuropeptides. We suggest that the innervation of inhibitory interneurons having extensive local axon arborizations may be a mechanism by which basal forebrain neurons–most notably those containing GABA–have a powerful global effect on the majority of principal cells in the entire cortical mantle.

Chlorite crystallinity: an empirical approach and correlation with illite crystallinity, coal rank and mineral facies as exemplified by Palaeozoic and Mesozoic rocks of northeast Hungary

Abstract: Fairly strong (r= 0.75–0.85) positive linear correlations were found between crystallinity indices (peak widths) measured on the first two basal reflections of chlorite and those of illite–muscovite in <2-μm fractions of a representative shale–slate–phyllite series from Palaeozoic and Mesozoic formations of northeast Hungary. The metamorphic grade ranges from late or deep diagenesis through anchizone to epizone conditions. Chlorite crystallinity values measured on air-dried and ethylene-glycol-solvated samples suggest that the effects of expandable interlayers are negligable, especially in the higher grade (∼temperature) part of the series. However, the greater scattering of crystallinity values for the chlorite 001 reflection compared to those of the 002 reflection may be related to the effects of minor amounts of interlayered and/or discrete smectite and/or vermiculite. With increasing metamorphic grade and advancing equilibrium recrystallization, the chlorite compositions in different samples become more homogenous. No correlation exists between crystallinity and changes in chlorite composition as estimated from the intensity ratios of basal reflections. Hence an increase of domain size and a decrease of lattice distortion with increasing grade (∼temperature) may be decisive factors affecting chlorite crystallinity. Chlorite crystallinity can be applied as a reliable regional, statistical technique complementary with, or instead of, the illite crystallinity method. The illite and chlorite crystallinity scales used here are related to Kubler's epi-, anchi- and diagenetic zones and correlated with coal rank, conodont colour alteration and mineral facies data. As the effects of the detrital white mica can be observed even in the <2-μm fractions of anchizonal metapelites, the anchizone boundaries determined solely on the base of ‘fixed’illite crystallinity values may vary with amounts of detrital and newly formed muscovite–illite. Hence a complex approach utilizing more than one method for determination of grade is preferred for petrogenetic purposes, even if relationships between crystallinity scales, coal rank and mineral facies also vary strongly in different tectonic settings and lithologies.

Alfalfa heat shock genes are differentially expressed during somatic embryogenesis.

Abstract: We have isolated two cDNA clones (Mshsp18-1; Mshsp18-2) from alfalfa (Medicago sativa L.) which encode for small heat shock proteins (HSPs) belonging to the hsp17 subfamily. The predicted amino acid sequences of the two alfalfa proteins are 92% identical and a similar degree of homology (90%) can be detected between Mshsp 18-2 and the pea hsp 17. In comparison to various members of small HSPs from soybean amino acid sequence similarities of 80–86% were identified. The alfalfa HSPs share a homologous stretch of amino acids in the carboxy terminal region with hsp22, 23, 26 from Drosophila. This region contains the GVLTV motif which is characteristic of several members of small HSPs. At room temperature alfalfa hsp 18 mRNAs were not detectable in root and leaf tissues but northern analysis showed a low level of expression in microcallus suspension (MCS). The transcription of Mshsp 18 genes is induced by elevated temperature, CdCl2 treatment and osmotic shock in cultured cells. In alfalfa somatic embryos derived from MCS a considerable amount of hsp 18 mRNA can be detected during the early embryogenic stages under normal culture conditions. The differential expression of these genes during embryo development suggests a specific functional role for HSPs in plant cells at the time of the developmental switch in vitro.

Algebraization of quantifier logics, an introductory overview

Abstract: This paper is an introduction: in particular, to algebras of relations of various ranks, and in general, to the part of algebraic logic algebraizing quantifier logics. The paper has a survey character, too. The most frequently used algebras like cylindric-, relation-, polyadic-, and quasi-polyadic algebras are carefully introduced and intuitively explained for the nonspecialist. Their variants, connections with logic, abstract model theory, and further algebraic logics are also reviewed. Efforts were made to make the review part relatively comprehensive. In some directions we tried to give an overview of the most recent results and research trends, too.

Characterization of multiple [3H]ryanodine binding sites on the Ca2+ release channel of sarcoplasmic reticulum from skeletal and cardiac muscle: evidence for a sequential mechanism in ryanodine action.

Abstract: Kinetic and equilibrium measurements of [3H]ryanodine binding to the Ca2+ release channel of rabbit skeletal and rat cardiac sarcoplasmic reticulum (SR) are examined to ascertain the nature of cooperative interactions among high and low affinity binding sites and to quantitate their distribution. Equilibrium studies reveal affinities of 1-4 nM for the highest affinity binding site and of 30-50 nM, 500-800 nM, and 2-4 microM for the lower affinity sites in both preparations, with Hill coefficients of significantly less than 1, and initial rates of association and dissociation increase with increasing concentrations of ryanodine. SR vesicles are actively loaded in the presence of pyrophosphate, and fluctuations in extravesicular Ca2+ are measured by the absorbance change of antipyrylazo III. The data demonstrate a biphasic, time- and concentration-dependent action of ryanodine on the release of Ca2+, with an initial activation and a subsequent inactivation phase. Kinetic analysis of the activation of Ca2+ release by ryanodine, in consonance with the binding data, demonstrates the existence of multiple binding sites for the alkaloid on the channel complex, with nanomolar to micromolar affinities. Based on the present findings obtained by receptor binding analysis and Ca2+ transport measurements, we suggest a model that describes four, most plausibly negatively cooperative, binding sites on the Ca2+ release channel. Occupation of ryanodine binding sites produces sequential activation followed by inactivation of the SR channel, revealing the strong possibility of an irreversible uncoupling of the native function of the receptor/channel complex by high concentrations of ryanodine. A model relating ryanodine receptor occupancy with SR Ca2+ release stresses two important new findings regarding the interaction of ryanodine with its receptor. First, ryanodine binds to four sites on the oligomeric channel complex with decreasing affinities, which can be best described by allosteric negative cooperativity. Second, binding of ryanodine to its receptor activates the Ca2+ release channel in a concentration-dependent and saturable manner in the range of 20 nM to 1 mM and produces a kinetically limited and sequential inactivation of the Ca2+ channel, with the concomitant attainment of full negative cooperativity. The results presented suggest that driving of the complex toward full negative cooperativity with high concentrations of ryanodine promotes a long-lived conformational state in which ryanodine is physically occluded and hindered from free diffusion from its binding site.

Low-Power Optical Reorientation in Dyed Nematics

Abstract: The optical reorientation process in nematic guest-host mixtures is investigated. It is found that for certain dyes the optical Freedericksz threshold is two orders of magnitude lower as in the pure host. The observations can be interpreted in terms of an enhanced optical torque which increases with the dye concentration.

Phytoplankton biomass and chlorophyll-a in some shallow lakes in central Europe

Abstract: Based on 388 parallel data of phytoplankton biomass and chlorophyll-a of two shallow lakes and two ponds, the following results were obtained: 1) Relative chlorophyll-a content of phytoplankton biomass varied between 0.08–1.88%; chlorophyll-a concentration showed great differences among lakes. 2) Significant correlations (r = 0.68–0.92) were established between phytoplankton biomass and chlorophyll-a concentration. The regression in the artificial ponds was non-linear. 3) In parallel with the increase of average cell volume, a decrease in relative chlorophyll-a content was observed. A significant correlation (r = + 0.83) between the two variables was found. Relative chlorophyll-a content of phytoplankton is a log-function of average cell volume.

Underpotential deposition of metals on foreign metal substrates

Abstract: The underpotential deposition of metals on foreign metal substrates has been reviewed, but this term is used in a wider sense in this monograph All the redox processes resulting in adsorbed metal atoms on foreign metal substrates are included in this term Based on the source of electrons taking part in the underpotential deposition, the classification of the processes leading to adsorbed metal atoms is also given

Geodesic convexity in nonlinear optimization

Abstract: The properties of geodesic convex functions defined on a connected RiemannianC2k-manifold are investigated in order to extend some results of convex optimization problems to nonlinear ones, whose feasible region is given by equalities and by inequalities and is a subset of a nonlinear space.

Temperature dependence of the optical Fréedericksz transition in dyed nematic liquid crystals

Abstract: We investigated the temperature dependence of the optical Fr\'eedericksz threshold in nematic liquid crystals doped with anthraquinone dyes. In the presence of these dyes, the Fr\'eedericksz threshold is anomalously low and exhibits an unusual temperature dependence. A microscopic model is proposed, according to which the anisotropic orientational distribution and the rotational dynamics of the excited dye molecules play an important role in the observed phenomena.

Capacity of the Gaussian arbitrarily varying channel

Abstract: The Gaussian arbitrarily varying channel with input constraint Gamma and state constraint Lambda admits input sequences x=(x/sub 1/,---,X/sub n/) of real numbers with Sigma x/sub i//sup 2/ >

Six nodulation genes of nod box locus 4 in Rhizobium meliloti are involved in nodulation signal production: nodM codes for D-glucosamine synthetase.

Abstract: The nucleotide sequence of the nod box locus n4 in Rhizobium meliloti was determined and revealed six genes organized in a single transcriptional unit, which are induced in response to a plant signal such as luteolin. Mutations in these genes influence the early steps of nodule development on Medicago, but have no detectable effect on Melilotus, another host for R. meliloti. Based on sequence homology, the first open reading frame (ORF) corresponds to the nodM gene and the last to the nodN gene of Rhizobium leguminosarum. The others do not exhibit similarity to any genes sequenced so far, so we designated them as nolF, nolG, nolH and nolI, respectively. We found that the n4 locus, and especially the nodM and nodN genes, are involved in the production of the root hair deformation (Had) factor. NodM exhibits homology to amidotransferases, primarily to the d-glucosamine synthetase encoded by the glmS gene of Escherichia coli. We demonstrated that in E. coli the regulatory gene nodD together with luteolin can activate nod genes. On this basis we showed that nodM complemented an E. coli glmS−mutation, indicating that nodM can be considered as a glmS gene under plant signal control. Moreover, exogenously supplied d-glucosamine restored nodulation of Medicago by nodM mutants. Our data suggest that in addition to the housekeeping glmS gene of R. meliloti, nodM as a second glmS copy provides glucosamine in sufficient amounts for the synthesis of the Had factor.