Showing papers by "Hungarian Academy of Sciences published in 1993"

Common randomness in information theory and cryptography. I. Secret sharing

Abstract: As the first part of a study of problems involving common randomness at distance locations, information-theoretic models of secret sharing (generating a common random key at two terminals, without letting an eavesdropper obtain information about this key) are considered. The concept of key-capacity is defined. Single-letter formulas of key-capacity are obtained for several models, and bounds to key-capacity are derived for other models. >

The CNN paradigm

Abstract: A concise tutorial description of the cellular neural network (CNN) paradigm is given, along with a precise taxonomy. The CNN is defined, and the canonical equations are described. The importance of many independent input signal arrays, adaptive templates, and the multilayer capability is emphasized and motivated by examples. It is shown how simply a wave-type partial differential equation can be generated. >

The CNN universal machine: an analogic array computer

Abstract: A new invention, the cellular neural network (CNN) universal machine and supercomputer, is presented. This is the first algorithmically programmable analog array computer having real-time and supercomputer power on a single chip. The CNN universal machine is described, emphasizing its programmability as well as global and distributed analog memory and logic, high throughput via electromagnetic waves, and complex cells that may be used also for simulating a broad class of PDEs. Its implementation, the CNN universal chip, is also described, along with its use of a multichip supercomputer. Other types of hardware implementations are also briefly discussed. Details of the algorithmic aspects of the new type of analogic (analog logic) algorithms, as well as the analogic software (language, compiler, machine code, etc.) are explained, along with a brief description of the available CNN workstation for implementing and simulating these new concepts. A broad range of applications is reviewed, including neuromorphic computing, programmable physics, programmable chemistry, and programmable bionics. >

Random walks in a convex body and an improved volume algorithm

Abstract: We give a randomized algorithm using O(n7 log’ n) separation calls to approximate the volume of a convex body with a fixed relative error. The bound is O(n6 log4 n) for centrally symmetric bodies and for polytopes with a polynomial number of facets, and O(n5 log4 n) for centrally symmetric polytopes with a polynomial number of facets. We also give an O(n6 log n) algorithm to sample a point from the uniform distribution over a convex body. Several tools are developed that may be interesting on their own. We extend results of Sinclair-Jerrum [43] and the authors [34] on the mixing rate of Markov chains from finite to arbitrary Markov chains. We also analyze the mixing rate of various random walks on convex bodies, in particular the random walk with steps from the uniform distribution over a unit ball. @ 1993 John Wiley & Sons, Inc.

Generalized cutoff rates and Renyi's information measures

Abstract: Renyi's (1961) entropy and divergence of order a are given operational characterizations in terms of block coding and hypothesis testing, as so-called /spl beta/-cutoff rates, with /spl alpha/=(1+/spl beta/)/sup -1/ for entropy and /spl alpha/=(1-/spl beta/)/sup -1/ for divergence. Out of several possible definitions of mutual information and channel capacity of order /spl alpha/, our approach distinguishes one that admits an operational characterization as /spl beta/-cutoff rate for channel coding, with /spl alpha/=(1-/spl beta/)/sup -1/. The ordinary cutoff rate of a DMC corresponds to /spl beta/=-1. >

Hippocampal pyramidal cells excite inhibitory neurons through a single release site

Abstract: Morphologically a synapse consists of a presynaptic release site containing vesicles, a postsynaptic element with membrane specialization, and a synaptic cleft between them The number of release sites shapes the properties of synaptic transmission between neurons Although excitatory interactions between cortical neurons have been examined, the number of release sites remains unknown We have now recorded excitatory postsynaptic potentials evoked by single pyramidal cells in hippocampal interneurons and visualized both cells using biocytin injections Light and electron microscopy showed that excitatory postsynaptic potentials were mediated by a single synapse We also reconstructed the entire axon arborization of single pyramidal cells, filled in vivo, in sections counterstained for parvalbumin, which selectively marks basket and axo-axonic cells Single synaptic contacts between pyramidal cells and parvalbumin-containing neurons were dominant (> 80%), providing evidence for high convergence and divergence in hippocampal networks

Studies of the surface species formed from nitric oxide on copper zeolites

Abstract: The surface chemistries of CuZSM-5 and of CuY preparations have been compared, using spectra of adsorbed NO taken under dynamic flow conditions at various temperatures between 173 and 723 K. Flow microbalance experiments were made with NO/He mixtures. At NO decomposition temperatures, a curious time dependence was observed where adsorption on the fresh catalyst increased rapidly, passed through a maximum, and then decreased again as it reached a steady state. In the steady state, the weight of CuZSM-5 was greater than its initial weight. Under favorable circumstances this increment was sufficiently large to permit observation of surface species present by IR

Postsynaptic targets of GABAergic hippocampal neurons in the medial septum-diagonal band of broca complex

Abstract: The termination pattern of hippocamposeptal nonpyramidal cells was investigated by injecting Phaseolus vulgaris leucoagglutinin (PHAL) into stratum oriens of the CA1 region. Electron microscopic analysis showed that the majority of the anterogradely labeled boutons formed symmetric synapses with dendrites and occasionally with cell bodies located in the medial septum-diagonal band of Broca complex. We have demonstrated with postembedding GABA immunocytochemistry that the majority of PHAL-labeled axon terminals were GABAergic. The neurochemical character of the postsynaptic target cells was also investigated using immunocytochemical double staining. Our data showed that the majority of the labeled hippocamposeptal axons innervated parvalbumin-immunoreactive cells representing GABAergic projection neurons, and a smaller number of contacts were found on ChAT-positive neurons. Septohippocampal neurons identified by retrograde HRP transport were also shown to reactive direct hippocamposeptal input. According to recent results, the lateral septum is unlikely to relay the hippocampal feedback to the medial septum; therefore, the direct hippocampal projection to the medial septum, arising from GABAergic nonpyramidal cells, seems to be the only feedback pathway to the area containing septohippocampal neurons. A novel circuit diagram, based on our recent morphological-immunocytochemical findings, is shown for the synaptic organization of the septo-hippocampo-septal loop. We suggest that the GABAergic hippocamposeptal feedback controls the activity of septal (mostly GABAergic) projection neurons as a function of hippocampal synchrony. The newly discovered reciprocal interactions may give a better insight into septohippocampal physiology.

The primary signal in the biological perception of temperature: Pd-catalyzed hydrogenation of membrane lipids stimulated the expression of the desA gene in Synechocystis PCC6803

Abstract: One of the well-characterized phenomena associated with the acclimation of organisms to changes in ambient temperature is the regulation of the molecular motion or "fluidity" of membrane lipids via changes in the extent of unsaturation of the fatty acids of membrane lipids. The enzymes responsible for this process when the temperature is decreased are the desaturases, the activities of which are enhanced at low temperature. To examine whether the change in the fluidity of membrane lipids is the first event that signals a change in temperature, we studied the effect of the Pd-catalyzed hydrogenation of membrane lipids on the expression of the desA gene, which is responsible for the desaturation of fatty acids of membrane lipids in the cyanobacterium Synechocystis PCC6803. The Pd-catalyzed hydrogenation of plasma membrane lipids stimulated the expression of the desA gene. We also found that, for unexplained reasons, the hydrogenation was much more specific to a minor phospholipid, phosphatidylglycerol, than to members of other lipid classes. These results suggest that the organism perceives a decrease in the fluidity of plasma membrane lipids when it is exposed to a decrease in temperature.

Precision and variability in postsynaptic target selection of inhibitory cells in the hippocampal CA3 region

Abstract: Non-pyramidal cells were filled intracellularly with biocytin in the CA3 region of the guinea-pig hippocampus in vitro, within or close to stratum pyramidale. On the basis of camera lucida reconstructions and electron microscopy, six different cell types with distinct laminar distribution of axon terminals could be distinguished. The axon of three axo-axonic cells, three typical basket cells, and atypical basket cells of two types arborized in the perisomatic and proximal dendritic region of CA3 pyramidal cells. Two cells with axons innervating the distal dendritic segments of pyramidal cells were also found; one terminated in stratum radiatum and the other in stratum lacunosum-moleculare. Electron microscopy demonstrated that symmetrical synapses were formed by the labelled boutons on axon initial segments, somata, and proximal or distal dendrites of mostly pyramidal neurons. Axo-axonic cells showed absolute target selectivity for axon initial segments, whereas for the other cells the distribution of contacted elements was determined by the laminar distribution of axon terminals. In two cases, where additional cells were labelled with biocytin, multiple (up to nine) light microscopically identified contacts (presumed synaptic contacts) were established by the interneurons on several pyramidal cells and on an axo-axonic cell. Our results show that a restricted set of inhibitory cells, with somata within or close to CA3 stratum pyramidale, possess variable patterns of axonal arborization. Various types of postsynaptic elements are contacted, but precision in selecting certain targets and ignoring others is maintained within a particular cell type and layer. In contrast to the diversity of axonal arbors the structure of the dendritic trees shows no consistent differences, suggesting that the cells may be activated by a similar set of afferents. It seems probable that the innervation of precise regions of postsynaptic pyramidal cells by different types of interneurons--often in conjunction with particular excitatory afferents (Han et al., Eur. J. Neurosci., 5, 395-410, 1993)--underlies functional differences in inhibitory synaptic actions.

Classification of the isostructurality of organic molecules in the crystalline state

Abstract: Since its discovery by Mitscherlich in 1819, the isomorphism of crystals has been interpreted in various, sometimes controversial ways. This can be attributed to the fact that the word isomorphous refers only to the external similarities between crystalline substances. Identical or quasi-identical packing motifs of related organic substances should therefore be distinguished by a more appropriate terminology. For organic substances, in contrast with inorganic crystals, where the recommended term is isotypic, the term isostructural is unambiguous. The present work attempts to classify the main forms as isostructural and homeostructural. Within the former class, there are two subclasses distinguished by the degree of isostructurality

P-lacW insertional mutagenesis on the second chromosome of Drosophila melanogaster: isolation of lethals with different overgrowth phenotypes.

Abstract: A single P-element insertional mutagenesis experiment was carried out for the second chromosome of Drosophila melanogaster using the P-lacW transposon. Out of 15,475 insertions on the second chromosome, 2,308 lethal and 403 semilethal mutants (altogether 2,711) were recovered. After eliminating clusters, 72% of the mutants represent independent insertions. Some of the mutants with larval, prepupal or pupal lethal phases have a prolonged larval period and show gradual overgrowth of the imaginal discs, brain and/or the hematopoietic organs (lymph glands). In this paper, 16 overgrowth mutants are described. As revealed by in situ hybridization, none of the mutations corresponds to any of the previously known overgrowth mutations on the second chromosome.

Activity of a chimeric promoter with the doubled CaMV 35S enhancer element in protoplast-derived cells and transgenic plants in maize

Abstract: A reproducible and efficient transformation system has been developed for maize that is based on direct DNA uptake into embryogenic protoplasts and regeneration of fertile plants from protoplast-derived transgenic callus tissues. Plasmid DNA, containing the β-glucuronidase (GUS) gene, under the control of the doubled enhancer element (the −208 to −46 bp upstream fragment) from CaMV 35S promoter, linked to the truncated (up to −389 bp from ATG) promoter of wheat, α-amylase gene was introduced into protoplasts from suspension culture of HE/89 genotype. The constructed transformation vectors carried either the neomycin phosphotransferase (NPTII) or phosphinothricin acetyltransferase (PAT) gene as selective marker. The applied DNA uptake protocol has resulted at least in 10–20 resistant calli, or GUS-expressing colonies after treatment of 106 protoplasts. Vital GUS staining of microcalli has made possible the shoot regeneration from the GUS-stained tissues. 80–90% of kanamycin or PPT resistant calli showed GUS activity, and transgenic plants were regenerated from more than 140 clones. Both Southern hybridization and PCR analysis showed the presence of introduced foreign genes in the genomic DNA of the transformants. The chimeric promoter, composed of a tissue specific monocot promoter, and the viral enhancer element specified similar expression pattern in maize plants, as it was determined by the full CaMV 35S promoter in dicot and other monocot plants. The highest GUS specific activity was found in older leaves with progressively less activity in young leaves, stem and root. Histochemical localization of GUS revealed promoter function in leaf epidermis, mesophyll and vascular bundles, in the cortex and vascular cylinder of the root. In roots, the meristematic tip region and vascular tissues stained intensively. Selected transformants were grown up to maturity, and second-generation seedlings with segregation for GUS activity were obtained after outcrossing. The GUS-expressing segregants carried also the NPTII gene as shown by Southern hybridization.

Chloroplast transformation in plants: polyethylene glycol (PEG) treatment of protoplasts is an alternative to biolistic delivery systems.

Abstract: Nicotiana plumbaginifolia protoplasts were directly transformed by PEG treatment with a cloned 16S rRNA gene isolated from a double antibiotic-resistant Nicotiana tabacum plastid mutant. Putative plastid transformants were selected in cell culture by their spectinomycin resistance and identified by their unselected streptomycin resistance. Alternatively, cell lines were selected in the presence of both antibiotics. The cell line (and its regenerated plants) selected solely for spectinomycin resistance demonstrated an extensive segregation of streptomycin resistance in subsequent tests, while the double-selected line showed stable resistance for both antibiotics. The resistance markers were inherited maternally. In the putative plastid transformants the origin of the resistance mutations was identified by the absence of an AatII site, missing in the donor N. tabacum plastid gene (spectinomycin resistance site) but present in that of wild-type N. plumbaginifolia, and a sequence analysis of the particular nucleotide changes in both resistance sites. Restriction enzyme analysis of total plastid DNA (ptDNA), and the recloning and full sequencing of the fragment introduced, investigated in one of the plastid transformants, showed no DNA rearrangements accompanied with the integration process. Sequence analysis indicated a targeted, homologous integration of the DNA fragment introduced but an unexpectedly complete homology of the parental ptDNA sequences in this region prevented the location of borders. Although the frequency of plastid transformant colonies (2 x 10(-5)) should still be improved, this method for stable chloroplast DNA transformation is comparable with or more efficient than the particle bombardment techniques.

Monoselenophosphate: synthesis, characterization, and identity with the prokaryotic biological selenium donor, compound SePX.

Abstract: A labile, selenium donor compound required for synthesis of selenium-dependent enzymes and seleno-tRNAs is formed from ATP and selenide by the SELD enzyme This compound, tentatively identified as a selenophosphate [Veres, Z, Tsai, L, Scholz, T D, Politino, M, Balaban, R S, & Stadtman, T C (1992) Proc Natl Acad Sci USA 89, 2975-2979], is indistinguishable from chemically prepared monoselenophosphate by 31P NMR spectroscopy and ion pairing HPLC Furthermore, addition of chemically prepared monoselenophosphate caused a dose-dependent decrease in the amount of 75Se incorporated into tRNAs from 75SePX generated in situ by SELD enzyme A procedure is described for the chemical synthesis of monoselenophosphate in which the readily prepared (MeO)3PSe is converted in quantitative yield to (TMSO)3PSe followed by complete cleavage of the latter to monoselenophosphate in oxygen-free aqueous buffer The chemical properties of chemically synthesized monoselenophosphate are described

The Petrogenesis of Pliocene Alkaline Volcanic Rocks from the Pannonian Basin, Eastern Central Europe

Abstract: A machine is provided for practicing the method of forming a comestible in one of a variety of shapes from a foodstuff slurry. The slurry includes a gel-forming material and is supplied in predetermined amounts to a cavity which has been washed with a combination release and gellation agent. Apparatus is provided for contacting the exposed surface of the slurry in the cavity with a gellation agent to gel the gelforming material at the outer surface of the formed product. Further apparatus is provided for transporting the cavity filled with the foodstuff to a product removal station. Punch apparatus is aligned with the cavity at the product removal station and is actuated to extend into and extrude the product from the cavity onto a conveyor belt to be removed for further processing. Control means are provided for ensuring operation of the punch apparatus only when the cavity is aligned therewith and, further, the control apparatus ensures that the cavity is not transported back to the filling station until the punch has been fully retracted from the cavity.

Molecular and structural composition of phospholipid membranes in livers of marine and freshwater fish in relation to temperature.

Abstract: The compositions and physical states of the liver phospholipids of marine and freshwater fish adapted to relatively constant but radically different temperatures were investigated. Fish adapted to low temperature (5-10 degrees C) accumulated more unsaturated fatty acids than those in a warm (25-27 degrees C) environment. There were no measurable differences in the gross fatty acid compositions of the total liver phospholipids from identical thermal environments. Docosahexaenoic acid (22:6) did not seem to participate in the process of adaptation. Cold adaptation was coincidental with oleic acid (18:1) accumulation, preferentially in the phosphatidylethanolamine. Determination of the molecular species composition of phosphatidylethanolamine revealed a 2- to 3-fold and 10-fold increase in the level of 18:1/22:6 and 18:1/20:5 species, respectively. ESR spectroscopy revealed a 7-10% compensation in the ordering state of native phospholipids with temperature. Combination of 16:0/22:6 phosphatidylcholine with phosphatidylethanolamines of cold-adapted marine fish showed a drastic fluidization near the C-2 segment of the bilayer, but not in the deeper regions. An appropriate combination (75:25) of phosphatidylcholines from warmth-adapted marine fish with phosphatidylethanolamines from cold-adapted marine fish mimicked a 100% adaptational efficacy in the C-2 segment as compared with the phosphatidylethanolamines of warmth-adapted marine fish. A specific role of 18:1/22:6 phosphatidylethanolamine in controlling membrane structure and physical state with thermal adaptation is proposed.

Coulomb dissociation of 11Li.

Abstract: Kinematically complete measurements for Coulomb dissociation of $^{11}\mathrm{Li}$ into $^{9}\mathrm{Li}$+2n were made at 28 MeV/nucleon The n-n correlation function suggests a large source size for the two-neutron emission The electromagnetic excitation spectrum of $^{11}\mathrm{Li}$ has a peak, as anticipated in low-energy dipole resonance models, but a large post-breakup Coulomb acceleration of the $^{9}\mathrm{Li}$ fragment is observed, indicating a very short lifetime of the excited state and favoring direct breakup as the dissociation mechanism

Electromagnetic excitation of Li 11

Abstract: We have performed a kinematically complete measurement of the Coulomb dissociation of 28 MeV/nucleon $^{11}\mathrm{Li}$ into $^{9}\mathrm{Li}$ and two neutrons by a Pb target. From the energies and angles of the emitted neutrons and of $^{9}\mathrm{Li}$, the excitation energy E of $^{11}\mathrm{Li}$ was determined on an event-by-event basis, and the Coulomb dissociation cross section as a function of excitation energy was constructed. The photonuclear cross section ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) and the dipole strength function dB(E1)/dE were determined from the Coulomb dissociation cross section. ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) has a peak at E=1.0 MeV and a width \ensuremath{\Gamma}=0.8 MeV. These parameters are consistent with the picture of a soft dipole mode. However, a significant post-breakup Coulomb acceleration of $^{9}\mathrm{Li}$ suggests instead a direct breakup. The complete kinematical measurement also allowed neutron and $^{9}\mathrm{Li}$ momentum distributions to be constructed in the rest frame of the $^{11}\mathrm{Li}$. The momentum distributions were fitted with Gaussian functions, yielding width parameters ${\mathrm{\ensuremath{\sigma}}}_{9}$=18\ifmmode\pm\else\textpm\fi{}4 MeV/c and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{n}}$=13\ifmmode\pm\else\textpm\fi{}3 MeV/c. A more general feature of the breakup mechanism of $^{11}\mathrm{Li}$ could be deduced from these measurements. It was found that the $^{9}\mathrm{Li}$ and neutron momentum distributions and the neutron-neutron relative momentum distribution could be reproduced if the $^{11}\mathrm{Li}$ excitation energy was partitioned between the $^{9}\mathrm{Li}$ and the neutrons by a three-body phase space distribution. This indicates there is no directional correlation between the halo neutrons, and shows that the halo neutrons do not exist as a dineutron bound to a $^{9}\mathrm{Li}$ core.

Complete axon arborization of a single CA3 pyramidal cell in the rat hippocampus, and its relationship with postsynaptic parvalbumin-containing interneurons.

Abstract: The complete axon arborization of a single CA3 pyramidal cell has been reconstructed from 32 (60 microns thick) sections from the rat hippocampus following in vivo intracellular injection of neurobiotin. The same sections were double-immunostained for parvalbumin--a calcium-binding protein selectively present in two types of GABAergic interneurons, the basket and chandelier cells--in order to map boutons of the pyramidal cell in contact with dendrites and somata of these specific subsets of interneurons visualized in a Golgi-like manner. The axon of the pyramidal cell formed 15,295 boutons, 63.8% of which were in stratum oriens, 15.4% in stratum pyramidale and 20.8% in stratum radiatum. Only 2.1% of the axon terminals contacted parvalbumin-positive neurons. Most of these were single contacts (84.7%), but double or triple contacts (15.3%) were also found. The majority of the boutons terminated on dendrites (84.1%) of parvalbumin-positive cells, less frequently on cell bodies (15.9%). In order to estimate the proportion of contacts representing synapses, 16 light microscopically identified contacts between boutons of the filled pyramidal cell axon and the parvalbumin-positive targets were examined by correlated electron microscopy. Thirteen of them were found to be asymmetrical synapses, and in the remaining three cases synapses between the labelled profiles could not be confirmed. We conclude that the physiologically effective excitatory connections between single pyramidal cells and postsynaptic inhibitory neurons are mediated by a small number of contacts, mostly by a single synapse. This results in a high degree of convergence and divergence in hippocampal networks.

Effects of low-dose dopamine infusion on cardiovascular and renal functions, cerebral blood flow, and plasma catecholamine levels in sick preterm neonates.

Abstract: Effects of 2 and 4 μg/kg/min dopamine infusion on cardiovascular and renal functions, cerebral blood flow (CBF) and plasma catecholamine levels were studied in sick preterm neonates during the first four days of life. Preterm infants were found to have an enhanced responsiveness to the pressor effects of dopamine during this period. Comparison of the renal effects of 2 and 4 μg/kg/ min dopamine in 61 preterm infants indicate that 2 μg/kg/ min dopamine induces maximum diuresis and natriuresis during the first day of life provided that systemic blood pressure is within the predicted normal range. Although administration of 4 μg/kg/min dopamine induces further increases in blood pressure and glomerular filtration rate, urine output and sodium excretion remain similar to that on 2 μg/kg/min of the drug. These findings demonstrate that the direct tubular effects of dopamine play an important role in the diuretic and natriuretic action of the drug in the one-day old preterm infant. In five preterm neonates, changes in CBF transiently paralleled the dopamine-induced alterations in systemic blood pressure indicating that autoregulation of CBF is impaired but not completely ineffective in the one-day old preterm infant. In eight term neonates, increases in blood pressure had no effect on CBF. Measurements of plasma dopamine and norepinephrine levels in 14 preterm neonates and five children suggest that decreased metabolism of dopamine may contribute to the enhanced pressor responsiveness to dopamine in sick preterm infants. Based on these findings, we propose that dopamine should be started at 2 μg/kg/min in the hypotensive and/or oliguric preterm infant, and that the dose should be increased in a step-wise manner tailored to the cardiovascular and renal response to the patient.