Showing papers by "Hungarian Academy of Sciences published in 1992"
TL;DR: In this article, the applicability of the density functional theory to systems containing hydrogen bonds was evaluated using a linear combination of Gaussian type orbitals-local density calculations on two intermolecular and two intramolecular hydrogen-bonded systems.
Abstract: As a test of the applicability of the density functional theory to systems containing hydrogen bonds, linear combination of Gaussian type orbitals-local density calculations have been performed on two intermolecular and two intramolecular hydrogen-bonded systems. A comparison is made of results using the local density approximation (LDA) and those including nonlocal density gradient type corrections, using two different nonlocal functionals. The calculated minimum energy structures for the water dimer and the formamid-water complex are presented
440 citations
TL;DR: Various theorems have been derived from the axiom system to ensure that this approach is mathematically rigorous, thereby rendering it possible to develop efficient process synthesis methods on the basis of a rigorous mathematical foundation.
354 citations
TL;DR: It is proposed that a mechanism by which the numerically small ascending pathways can exert a powerful global effect in the neocortex is by the selective innervation of gamma-aminobutyric acid-releasing interneurons, which, in turn, control the activity of large populations of pyramidal cells through their extensive axon arborizations.
Abstract: The basal forebrain-neocortex pathway--involved in higher cognitive processing, selective attention, and arousal--is considered one of the functionally most important ascending subcortical projections. The mechanism by which this relatively sparse subcortical pathway can control neuronal activity patterns in the entire cortical mantle is still unknown. The present study in the cat provides evidence that gamma-aminobutyric acid-containing basal forebrain neurons participate in the neocortical projection and establish multiple synaptic connections with gamma-aminobutyric acid-releasing interneurons containing somatostatin or parvalbumin. We propose that a mechanism by which the numerically small ascending pathways can exert a powerful global effect in the neocortex is by the selective innervation of gamma-aminobutyric acid-releasing interneurons, which, in turn, control the activity of large populations of pyramidal cells through their extensive axon arborizations. Finally, these results demonstrate a direct anatomical link between two cell populations implicated in Alzheimer disease pathology: basal forebrain neurons and cortical somatostatin cells.
282 citations
TL;DR: The results suggest that the calbindin D28k-containing and apparently GABA-immunonegative non-pyramidal cells in stratum oriens of the CA1-CA3 regions may also be GABAergic, but have a distant projection, that is, to the medial septum.
265 citations
TL;DR: The layer-specific location of these cells and their processes suggested that the majority of their input may derive from mossy fibres, and this presumption has been confirmed by electron microscopic examination.
258 citations
TL;DR: It is suggested that the production of a series of active signal molecules with different degrees of specificity might be important in controlling the symbiosis of R. meliloti with several different host plants or under different environmental conditions.
Abstract: We have shown that a Rhizobium meliloti strain overexpressing nodulation genes excreted high amounts of a family of N-acylated and 6-O-sulfated N-acetyl-beta-1,4-D-glucosamine penta-, tetra-, and trisaccharide Nod factors. Either a C(16:2) or a C(16:3) acyl chain is attached to the nonreducing end subunit, whereas the sulfate group is bound to the reducing glucosamine. One of the tetrasaccharides is identical to the previously described NodRm-1 factor. The two pentasaccharides as well as NodRm-1 were purified and tested for biological activity. In the root hair deformation assay the pentasaccharides show similar activities on the host plants Medicago sativa and Melilotus albus and on the non-host plant Vicia sativa at a dilution of up to 0.01-0.001 microM, in contrast to NodRm-1, which displays a much higher specific activity for Medicago and Melilotus than for Vicia. The active concentration range of the pentasaccharides is more narrow on Medicago than on Melilotus and Vicia. In addition to root hair deformation, the different Nod factors were shown to induce nodule formation on M. sativa. We suggest that the production of a series of active signal molecules with different degrees of specificity might be important in controlling the symbiosis of R. meliloti with several different host plants or under different environmental conditions.
239 citations
TL;DR: In this paper, the number of light neutrino species is found to be Nv=3.30% CL with the constraints of the standard electroweak model, which rules out the possibility of a fourth type of LN at 98% CL.
234 citations
TL;DR: The morphology of the extensively arborizing aminergic neurons described suggests that they have modulatory functions in the brain and subesophageal ganglion of the blowflies.
Abstract: The distribution and morphology of neurons reacting with antisera against dopamine (DA), tyrosine hydroxylase (TH) and histamine (HA) were analyzed in the blowflies Calliphora erythrocephala and Phormia terraenovae. TH-immunoreactive (THIR) and HA-immunoreactive (HAIR) neurons were also mapped in the fruitfly Drosophila melanogaster. The antisera against DA and TH specifically labeled the same neurons in the blowflies. About 300 neurons displayed DA immunoreactivity (DAIR) and THIR in the brain and subesophageal ganglion of the blowflies. Most of these neurons were located in bilateral clusters; some were distributed as bilateral pairs, and two ventral unpaired median (VUM) neurons were seen in the subesophageal ganglion. Immunoreactive processes were found in all compartments of the mushroom bodies except the calyces, in all divisions of the central body complex, in the medulla, lobula and lobula plate of the optic lobe, and in non-glomerular neuropil of protocerebrum, tritocerebrum and the subesophageal ganglion. No DA or TH immunoreactivity was seen in the antennal lobes. In Drosophila, neurons homologous to the blowfly neurons were detected with the TH antiserum. In Phormia and Drosophila, 18 HA-immunoreactive neurons were located in the protocerebrum and 2 in the subesophageal ganglion. The HAIR neurons arborized extensively, but except for processes in the lobula, all HAIR processes were seen in non-glomerular neuropil. The deuto- and tritocerebrum was devoid of HAIR processes. Double labeling experiments demonstrated that TH and HA immunoreactivity was not colocalized in any neuron. In some regions there wasm however, substantial superposition between the two systems. The morphology of the extensively arborizing aminergic neurons described suggests that they have modulatory functions in the brain and subesophageal ganglion.
229 citations
TL;DR: In this article, an acid-catalized parasitic pathway was found to operate in competition with the glucose production pathway in the presence of acid, and kinetic modeling of the measured, temperature-dependent rates of glucose evolution indictaes that an acidated, catalized, parasitic pathway operates in competition.
Abstract: Cellulose hydrolysis experiments were conducted in a percolating reactor at 34.5 MPa. A glucose yield of 71% of the theorical maximum was obtained at 215°C with 0.05% by weigth of sulfuric acid in percolating solution. The classical model of glucose formation from cellulose followed by secondary sugar degradation did not describe the reaction chemistry under these conditions. A parasitic pathway which leads to the formation of nonhydrolysable oligomer was discovered in the absence of acid. In the presence of acid, kinetic modeling of the measured, temperature-dependent rates of glucose evolution indictaes that an acid-catalized parasitic pathway operates in competition with the glucose production pathway. No chemical change were detecte in the solid phase during the course of reaction
221 citations
TL;DR: The results demonstrate that the majority of calretinin-immunoreactive neurons are GABAergic and represent a subpopulation of non-pyramidal cells with no or only a negligible overlap with the subpopulations containing the other calcium binding proteins, parvalbumin and calbindin.
216 citations
TL;DR: It is shown that cyclically permutable codes provide a natural solution to the problem of constructing protocol-sequence sets for the M-active-out-of-T-users collision channel without feedback.
Abstract: A general theorem is proved showing how to obtain a constant-weight binary cyclic code from a p-ary linear cyclic code, where p is a prime, by using a representation of GF(p) as cyclic shifts of a binary p-tuple. Based on this theorem, constructions are given for four classes of binary constant-weight codes. The first two classes are shown to achieve the Johnson upper bound on minimum distance asymptotically for long block lengths. The other two classes are shown similarly to meet asymptotically the low-rate Plotkin upper bound on minimum distance. A simple method is given for selecting virtually the maximum number of cyclically distinct codewords with full cyclic order from Reed-Solomon codes and from Berlekamp-Justesen maximum-distance-separable codes. Two correspondingly optimum classes of constant-weight cyclically permutable codes are constructed. It is shown that cyclically permutable codes provide a natural solution to the problem of constructing protocol-sequence sets for the M-active-out-of-T-users collision channel without feedback. >
TL;DR: This work has reproduced the absolute width of the α decay of the ground state of 212Po in a model in which the shell model is combined with a 208Pb+α cluster model, and found that the amount of core+α clustering in the parent state is ~30%.
Abstract: We have reproduced the absolute width of the α decay of the ground state of 212Po in a model in which the shell model is combined with a 208Pb+α cluster model, and found that the amount of core+α clustering in the parent state is ~30%.
TL;DR: The pH dependencies of the rate constants in the photocycles of recombinant D96N and D115N/D96N bacteriorhodopsins were determined and indicated that the overall M1----M2 reaction includes a second kinetic step in addition to proton release; this is probably the earlier postulated extracellular-to-cytoplasmic reorientation switch in the proton pump.
Abstract: The pH dependencies of the rate constants in the photocycles of recombinant D96N and D115N/D96N bacteriorhodopsins were determined from time-resolved difference spectra between 70 ns and 420 ms after photoexcitation. The results were consistent with the model suggested earlier for proteins containing D96N substitution: BR hv----K----L----M1----M2----BR. Only the M2----M1 back-reaction was pH-dependent: its rate increased with increasing [H+] between pH 5 and 8. We conclude from quantitative analysis of this pH dependency that its reverse, the M1----M2 reaction, is linked to the release of a proton from a group with a pKa = 5.8. This suggests a model for wild-type bacteriorhodopsin in which at pH greater than 5.8 the transported proton is released on the extracellular side from this as yet unknown group and on the 100-microseconds time scale, but at pH less than 5.8, the proton release occurs from another residue and later in the photocycle most likely directly from D85 during the O----BR reaction. We postulate, on the other hand, that proton uptake on the cytoplasmic side will be by D96 and during the N----O reaction regardless of pH. The proton kinetics as measured with indicator dyes confirmed the unique prediction of this model: at pH greater than 6, proton release preceded proton uptake, but at pH less than 6, the release was delayed until after the uptake. The results indicated further that the overall M1----M2 reaction includes a second kinetic step in addition to proton release; this is probably the earlier postulated extracellular-to-cytoplasmic reorientation switch in the proton pump.
TL;DR: This brief outlook intends to give a practical insight into current problems and future applications of T-DNA tagging by underlining the potential of the genetic approach in studies of plant development.
Abstract: T-DNA insertion mutagenesis is one of those recently developed genetic techniques which can be expected to have a major impact in plant molecular biology [17, 50, 87]. Unlike conventional reviews, this brief outlook intends to give a practical insight into current problems and future applications of T-DNA tagging by underlining the potential of the genetic approach in studies of plant development.
TL;DR: No simple relationship exists between vulnerability in status epilepticus and neuronal calcium binding protein content, and that local and/or systemic hypoxia during status epileptus may be responsible for the ischemic pattern of cell death.
TL;DR: Among other results it is proved that f ( n ; 1 1 11 1 ) = Θ ( α ( n ) n ), where α( n ) is the inverse of the Ackermann function.
TL;DR: In this article, samples o cellulose, hemicellulose, lignin, and nine species of whole biomass are pyrolyzed in sealed reactors, and very high charcoal yields (e.g., 40% from cellulose and 48% from Eucalyptus gummifera) were obtained.
Abstract: In this paper, samples o cellulose, hemicellulose, lignin, and nine species of whole biomass are pyrolyzed in sealed reactors. Very high charcoal yields (e.g., 40% from cellulose, 48% from Eucalyptus gummifera) were obtained. Higher sample loading (sample mass per unit reactor volume) increased charcoal yield and the associated exothermic heat release and lowered the reaction onset temperature. These effects were induced by the vapor-phase concentrations of the volatile products, and not the system pressure. Addition of water catalyzed the reaction and increased the char yield. These observations suggest that charcoal formation is autocatalyzed by water, an initial pyrolysis product. When whole biomass was used as a feedstock, higher charcoal yields were obtained from species with high lignin and/or low hemicellulose content.
TL;DR: This question was motivated by practical problems in scheduling and VLSI theory and its complexity status for interval graphs and for graphs with a bounded treewidth is investigated.
TL;DR: The dye-induced optical torque exceeds significantly the normal optical torque for all anthraquinone dyes investigated and with one of the dyes, optical Freedericksz transition in a planar layer is demonstrated.
Abstract: Optical reorientation measurements in dye-doped nematic liquid crystals are reported. The dye-induced optical torque exceeds significantly the normal optical torque for all anthraquinone dyes investigated. With one of the dyes, optical Freedericksz transition in a planar layer is demonstrated.
TL;DR: Any community-dynamical theory intended to be predictive should not omit the spatial aspects of plant population dynamics, because these may radically change the conditions of persistence and coexistence.
Abstract: The idea of relating spatial patterns and temporal processes in plant community dynamics is not new, but its transformation into realistic spatiotemporal models is the result of quite recent methodological developments. There are now two classes of analytical model and a broad class of simulation models pertaining to the role of spatial structure in vegetation dynamics. They indicate that any community-dynamical theory intended to be predictive should not omit the spatial aspects of plant population dynamics, because these may radically change the conditions of persistence and coexistence.
TL;DR: The results suggest that serotonergic median raphe fibres influence the firing of dentate granule cells via local inhibitory interneurons, and may explain the great efficacy of this pathway in the control of hippocampal electrical activity.
Abstract: The termination pattern of median raphe axons was studied in the rat dentate gyrus using Phaseolus vulgaris leucoagglutinin as an anterograde tracer, in combination with postembedding immunostaining for gamma-amino-butyric acid (GABA), and pre-embedding immunostaining for calbindin D28k, parvalbumin and GABA. Postembedding immunogold staining for GABA revealed that the majority (73.7%) of anterogradely labelled median raphe boutons make synaptic contacts with GABA-immunoreactive postsynaptic targets, mainly with dendritic shafts and perikarya. Pre-embedding immunocytochemical double staining for the anterograde tracer and GABA confirmed the electron microscopic results and showed that varicose median raphe axons establish multiple contacts with fusiform interneurons in the hilus and different types of basket cells in the granule cell layer. Some of the innervated cells were shown to contain calbindin D28k, whereas GABAergic interneurons containing another calcium-binding protein, parvalbumin, were never seen to receive multiple contacts from axons of raphe origin. Our results suggest that serotonergic median raphe fibres influence the firing of dentate granule cells via local inhibitory interneurons. The mechanism of using these interneurons with extensive local connections as monosynaptic targets may explain the great efficacy of this pathway in the control of hippocampal electrical activity.
TL;DR: The in vitro approach has been and should remain an excellent model of the blood–brain barrier to help unravel the complex molecular interactions underlying and regulating the permeability of the cerebral endothelium.
Abstract: Recent advances in our knowledge of the blood–brain barrier (BBB) have in part been made by studying the properties and function of cerebral endothelial cells in vitro. After an era of working with a fraction, enriched in cerebral microvessels by centrifugation, the next generation of in vitro BBB model systems was introduced, when the conditions for routinely culturing the endothelial cells were established. This review summarizes the results obtained from this rapidly growing field. It can be stated with certainty that, in addition to providing a better insight into the chemical composition of cerebral endothelial cells, much has been learned from these studies about the characteristics of transport processes and cell-to-cell interactions during the last 12 years. With the application of new technologies, the approach offers a new means of investigation, applicable not only to biochemistry and physiology but also to the drug research, and may improve the transport of substances through the BBB. The in vitro approach has been and should remain an excellent model of the BBB to help unravel the complex molecular interactions underlying and regulating the permeability of the cerebral endothelium.
TL;DR: In the younger group, at the two shorter ISIs, the MMN was followed by a positive wave (P3a) which is an indication of the increased activity of the orienting system in the younger subjects, in comparison to the older age group.
TL;DR: This paper presents a probabilistic procedure for calculating the maximum number of straight line segments in a convex polygon using a convolutional model.
TL;DR: It is shown that a set of n points in the plane determine O(n2 log n) triples that define the same angle α, and that for many angles α (including π 2 ) this bound is tight in the worst case.
TL;DR: In this article, the external heavy atom induced phosphorescence of C{sub 60} and C {sub 70} was obtained at 77 K in a glass containing ethyl iodide and gave 12 690 {plus_minus} 30 cm{sup {minus}1} as a precise lower limit for the energy of triplet C{ sub 60.
Abstract: The external heavy atom induced phosphorescence of C{sub 60} and C{sub 70} is obtained at 77 K in a glass containing ethyl iodide and gives 12 690 {plus_minus} 30 cm{sup {minus}1} as a precise lower limit for the energy of triplet C{sub 60}. Triplet lifetime measurements show that the heavy atom effect is relatively much greater on the S{sub 1} {yields} T{sub 1} than on the T{sub 1} {yields} S{sub 0} radiationless transitions, as expected from the smaller Franck-Condon constraints in the former process. 26 refs., 2 figs.
TL;DR: In this article, a generalization of the Boys-Bernardi counterpoise correction scheme to the case of relaxed monomer geometries is discussed, and it is emphasized that the monomer relaxation energy should be calculated in the basis of free monomers.
TL;DR: For transitive permutation groups G of degree n, the bound diam(G) ≤ exp(c log3 n)diam(Ak), where Ak is the largest alternating composition factor of G, is obtained.
Abstract: For a set S of generators of the finite group G, let diam(G, S) denote the maximum over g ∈ G of the minimal word length expressing g in terms of S ∪ S−1. We define the diameter of G as diam(G) = maxs diam(G, S) (‘worst case’ generators). For permutation groups G of degree n, we prove that diam(G) ≤ exp((n ln n)½(1 + o(1))). (This bound is asymptotically best possible.) For transitive permutation groups G of degree n, we obtain the bound diam(G) ≤ exp(c log3 n)diam(Ak), where Ak is the largest alternating composition factor of G. We conjecture that diam(An)
TL;DR: In this article, continuous energy distribution x-rays obtained from a high-voltage (20-30 kV) source with an Mo anode were used for exciting Si KLL, S KLL and Ag LMM transitions in the 1.5-5.5 keV kinetic energy range.
Abstract: Continuous energy distribution x-rays obtained from a high-voltage (20–30 kV) source with an Mo anode were used for exciting Si KLL, S KLL, Ag LMM and Mn KLL Auger transitions in the 1.5–5.5 keV kinetic energy range. X-ray-induced AES measurements were performed by a new, high-energy electron spectrometer demonstrating the obtainable resolution and the considerable gain in intensity in comparison with previous results.
TL;DR: This paper presents a method for semi-automatic bug localization, generalized algorithmic debugging, which has been integrated with the category partition method for functional testing, and believes that this is the first generalization of algorithmic Debugging for programs with side-effects written in imperative languages such as Pascal.
Abstract: This paper presents a method for semi-automatic bug localization, generalized algorithmic debugging, which has been integrated with the category partition method for functional testing. In this way the efficiency of the algorithmic debugging method for bug localization can be improved by using test specifications and test results. The long-range goal of this work is a semi-automatic debugging and testing system which can be used during large-scale program development of nontrivial programs.The method is generally applicable to procedural langua ges and is not dependent on any ad hoc assumptions regarding the subject program. The original form of algorithmic debugging, introduced by Shapiro, was however limited to small Prolog programs without side-effects, but has later been generalized to concurrent logic programming languages. Another drawback of the original method is the large number of interactions with the user during bug localization.To our knowledge, this is the first method which uses category partition testing to improve the bug localization properties of algorithmic debugging. The method can avoid irrelevant questions to the programmer by categorizing input parameters and then match these against test cases in the test database. Additionally, we use program slicing, a data flow analysis technique, to dynamically compute which parts of the program are relevant for the search, thus further improving bug localization.We believe that this is the first generalization of algorithmic debugging for programs with side-effects written in imperative languages such as Pascal. These improvements together makes it more feasible to debug larger programs. However, additional improvements are needed to make it handle pointer-related side-effects and concurrent Pascal programs.A prototype generalized algorithmic debugger for a Pascal subset without pointer side-effects and a test case generator for application programs in Pascal, C, dBase, and LOTUS have been implemented.