Showing papers by "Bulgarian Academy of Sciences published in 1991"
TL;DR: In this article, the general properties of neutrino transitions in matter induced by neutrinos flavour changing neutral current (FCNC) interactions are analyzed and it is shown that matter-enhanced transitions can take place even with zero mass.
248 citations
TL;DR: It is suggested that the parameter in the BADD family, the distinction between different defuzzification methods, is related to the confidence the authors have in the rest of the controller, and the use of these BADD transformations form the basis of a learning scheme to obtain the optimaldefuzzification method in a given application.
Abstract: Defuzzification in fuzzy logic controllers concerns itself with the issue of selecting an appropriate crisp value from the fuzzy output of the controller. We provide a parametized family of defuzzification operations. We call this family BAsic Defuzzification Distributions (BADD). We show that the commonly used methods. Mean of Maximum and Center of Area are special cases of this family. We suggest the use of these BADD transformations form the basis of a learning scheme to obtain the optimal defuzzification method in a given application. We suggest that the parameter in the BADD family, the distinction between different defuzzification methods, is related to the confidence we have in the rest of the controller.
240 citations
TL;DR: In this paper, a slab model is proposed for developing the height of the mixed layer capped by stable air aloft, which is closed by relating the consumption of energy (potential and kinetic) at the top of a mixed layer to the production of convective and mechanical turbulent kinetic energy within the mixed layers.
Abstract: A slab model is proposed for developing the height of the mixed layer capped by stable air aloft. The model equations are closed by relating the consumption of energy (potential and kinetic) at the top of the mixed layer to the production of convective and mechanical turbulent kinetic energy within the mixed layer. By assuming that the temperature difference at the top of the mixed layer instantaneously adjusts to the actual meteorological conditions without regard to the initial temperature difference that prevailed, the model is reduced to a single differential equation which easily can be solved numerically. When the mixed layer is shallow or the atmosphere nearly neutrally stratified, the growth is controlled mainly by mechanical turbulence. When the layer is deep, its growth is controlled mainly by convective turbulence. The model is applied on a data set of the evolution of the height of the mixed layer in the morning hours, when both mechanical and convective turbulence contribute to the growth process. Realistic mixed-layer developments are obtained.
192 citations
TL;DR: In this article, a general formula for ti is proposed which is valid for any number of nuclei appearing and growing in the parent phase and which unites the known expressions for ti only applicable when either one or a large number of cells are involved in the process.
186 citations
TL;DR: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Immunomodulatory action of propolis. Influence on anti-infectious protection and macrophage function V Dimov, N Ivanovska, N Manolova, V Bankova, N Nikolov, S Popov
156 citations
TL;DR: The use of phthalic anhydride is one of the most important products of large-scale organic synthesis, and it has a wide application in various branches of chemical industry as discussed by the authors.
Abstract: Phthalic anhydride is one of the most important products of modem large-scale organic synthesis, and it has a wide application in various branches of chemical industry. It is mostly used (60% of the world production) for preparation plasticizers for PVC. The rapid development of the industrial production of polymeric materials during the last two decades increased the need of phthalic anhydride, which resulted in an increase of its production [1, 2].
143 citations
TL;DR: The concept of the quasilinear fuzzy model (QLFM) of a dynamic nonlinear system is introduced, and the problem of its identification, state-space, and transfer function representation is discussed.
138 citations
TL;DR: The findings suggest that the nervous system relies on the purposeful coupling of elbow and wrist flexors to counter the inertial effects during the unrestricted voluntary movement, even though the coupling does not appear to be purposeful during the perturbation or with the wrist immobilized.
Abstract: To examine the coordination of muscles during multijoint movement, we compared the response of wrist muscles to perturbations about the elbow joint with their activation during a volitional elbow movement. The purpose was to test the following two predictions: (a) Responses can occur in muscles not stretched by the perturbation, as has been reported for other multijoint systems; and (b) the motor pattern in response to a perturbation mimics an opposing volitional motor pattern across the two joints. We recorded the electromyographic (EMG) activity of elbow and wrist muscles as well as the flexion/extension motions at the elbow and wrist joints during individual trials that either involved a response to a torque perturbation that extended the elbow or required volitional elbow flexion. The results of this study confirmed that responses were elicited in the nonstretched wrist muscles when the elbow joint was perturbed. The same motor sequence of elbow and wrist flexors was present for both the voli...
138 citations
TL;DR: A beam of monochromatic UV light from a laser has been used to initiate crosslinking in nano- and picosecond time intervals and the applications of this method are explored.
101 citations
TL;DR: In this paper, the fundamental questions about how the nuclei form on a foreign substrate are addressed. But the fundamental question is not addressed in this paper, but rather why and how they form on the substrate.
Abstract: Electrochemical phase formation is a typical example of a first-order phase transition. The precursor of the overall phase change is nucleation—the appearance of small clusters of atoms or molecules carrying the basic properties of the new phase. Why and how the nuclei form on a foreign substrate are the fundamental questions addressed by this article.
98 citations
TL;DR: In this paper, the effect of water vapour on the yield and composition of the products obtained by low temperature thermal destruction of solid fuels at atmospheric pressure, before and after complete extraction with ethanol-benzene, is investigated.
Book•
12 Sep 1991TL;DR: The Universal Nuclear Energy Density Functional (UNEDF) project as discussed by the authors was developed to optimize the energy density functional for atomic nuclei using state-of-the-art computational infrastructure.
Abstract: An understanding of atomic nuclei is crucial for a complete nuclear theory, for the nuclear astrophysics, for performing new experimental tasks, and for various other applications. Within a density functional theory, the total binding energy of the nucleus is given by a functional of the nuclear density matrices and their derivatives. The variation of the energy density functional with respect to particle and pairing densities leads to the Hartree-Fock-Bogoliubov equations. The “Universal Nuclear Energy Density Functional” (UNEDF) SciDAC project to develop and optimize the energy density functional for atomic nuclei using state-of-the-art computational infrastructure, is briefly described. The ultimate goal is to replace current phenomenological models of the nucleus with a well-founded microscopic theory with minimal uncertainties, capable of describing nuclear data and extrapolating to unknown regions.
TL;DR: In this article, the authors investigated possible T-violating effects in three-neutrino oscillations in matter and derived a simple analytical expression for the experimentally measurable quantity P(n, l) √ n √ l √ t √ left( t \right) -P(n, l' \to n, l' √ m √ right) -n √ T √ √ (t, l') √ N √ 1.
Abstract: We continue the investigation of possible T-violating effects in three-neutrino oscillations in matter. Intriguingly simple analytical expression for the experimentally measurable quantity $P_{
u _l \to
u _{l'} }^m \left( t \right) - P_{
u _{l'} \to
u _l }^m $ (t) is derived.
TL;DR: In this article, a pulse potentiostatic method (PPM) was used for the electrochemical formation of polyaniline films and an enhanced mode of growth of the polymer films was observed.
TL;DR: It appears that the truly metastable ripple phase is expressed by the second ripple structure although in the course of the actual cooling transition both the secondary and primary ripple structures form and coexist.
TL;DR: It is suggested that melatonin release is affected by stress and, possibly, under these circumstances, interacts with adrenal steroid secretion.
Abstract: Plasma and pineal melatonin and plasma corticosterone and progesterone concentrations have been shown to be altered by several types of stressors. This study was designed to define the circadian patterns of the hormones mentioned above in rats subjected to chronic stress and to investigate the influence of constant illumination. The results revealed that melatonin and corticosterone circadian patterns deteriorated and their plasma concentrations were significantly elevated. The constant illumination (2,500 lux) during the dark period (from 2000 to 0600) was not able to suppress melatonin production in stressed animals, while the plasma content of corticosterone was decreased at the end of experimental period compared to control rats. Plasma levels of progesterone were increased in stressed animals as well. Constant illumination, however, provoked also an increase of progesterone secretion in controls. Statistical comparisons between hormonal secretory patterns showed that melatonin and corticosterone correlated negatively in controls (r = -0.58, P less than 0.05) during the nighttime. However, in stressed animals correlation was observed only between melatonin and progesterone secretion during the light and dark period (r = -0.43, P less than 0.05). Surprisingly, the correlation during the nighttime in rats subjected to constant illumination was negative (r = -0.60, P less than 0.02) compared to positive correlation (r = 0.60, P less than 0.02) in rats kept under normal lighting regimen. These results suggest that melatonin release is affected by stress and, possibly, under these circumstances, interacts with adrenal steroid secretion.
TL;DR: This review summarizes and discusses the data on different aspects of the interaction between the linker histone and naked DNA, including cooperativity of binding, preference for supercoiled DNA, selectivity with respect to base composition and nucleotide sequence, and effect of H1 binding on the conformation of the underlying DNA.
Abstract: The belief that histone H1 interacts primarily with DNA in chromatin and much less with the protein component has led to numerous studies of artificial H1-DNA complexes. This review summarizes and discusses the data on different aspects of the interaction between the linker histone and naked DNA, including cooperativity of binding, preference for supercoiled DNA, selectivity with respect to base composition and nucleotide sequence, and effect of H1 binding on the conformation of the underlying DNA. The nature of the interaction, the structure of the complexes, and the role histone H1 exerts in chromatin are also discussed.
TL;DR: Changes in relative stability of the different phases are discussed in terms of a possible membrane Hofmeister effect and their relevance to the mode of action of cryoprotectants is explored.
TL;DR: In this article, the steady velocity dependence of the dynamic capillary height was studied by photographing the profile of the meridian section of the meniscus and the critical contact angle at which transition from steady wetting to film entrainment was calculated from the static L/θ relationship.
TL;DR: Kutzarova et al. as discussed by the authors introduced k-β and k-nearly uniform convexity of Banach spaces, which is a special case of fully k-convex spaces.
Book•
01 Jan 1991TL;DR: In this paper, the V-cycle and V-fold algebraic multilevel BEPS preconditioners were studied for solving discrete elliptic problems on grids with local refinement.
Abstract: Algebraic multilevel analogues of the BEPS preconditioner designed for solving discrete elliptic problems on grids with local refinement are formulated, and bounds on their relative condition numbers, with respect to the composite-grid matrix, are derived. TheV-cycle and, more generally,v-foldV-cycle multilevel BEPS preconditioners are presented and studied. It is proved that for 2-D problems theV-cycle multilevel BEPS is almost optimal, whereas thev-foldV-cycle algebraic multilevel BEPS is optimal under a mild restriction on the composite cell-centered grid. For thev-fold multilevel BEPS, the variational relation between the finite difference matrix and the corresponding matrix on the next-coarser level is not necessarily required. Since they are purely algebraically derived, thev-fold (v>1) multilevel BEPS preconditioners perform without any restrictionson the shape of subregions, unless the refinement is too fast. For theV-cycle BEPS preconditioner (2-D problem), a variational relation between the matrices on two consecutive grids is required, but there is no restriction on the method of refinement on the shape, or on the size of the subdomains.
Journal Article•
TL;DR: The findings suggest that nicotinic receptors located on noradrenergic axon terminals are different from those located postsynaptically in striated muscle or ganglia but seem similar to those present on cholinergic axons terminals at the neuromuscular junction.
Abstract: In guinea-pig prostatic vas deferens loaded with [3H]-noradrenaline ([3H]-NA), nicotinic receptor agonists, nicotine and dimethylphenylpiperazinium (DMPP) enhanced the resting and facilitated the stimulation-evoked release of [3H]-NA in a concentration-dependent fashion. The effect of nicotine on both contraction of vas deferens and release of NA in response to field stimulation was stereospecific in favour of the naturally occurring (-)-enantiomer. Prolonged (15 min) exposure to (-)-nicotine resulted in a cessation of the facilitatory effect on NA release and on responses of the vas deferens to field stimulation. 2 The rank order of agonist potency in facilitating NA release was DMPP = (-)-nicotine greater than (+)-nicotine. Cytisine had no agonistic activity. The dissociation constants (KD) of antagonists were 9.3 +/- 0.6 and 31.4 +/- 2.4 microM for (+)-tubocurarine and hexamethonium, respectively, when (-)-nicotine was used as agonist. alpha-Bungarotoxin had no antagonistic activity. These findings suggest that nicotinic receptors located on noradrenergic axon terminals are different from those located postsynaptically in striated muscle or ganglia but seem similar to those present on cholinergic axon terminals at the neuromuscular junction. 3. Cotinine, the breakdown product of nicotine failed to have any agonistic activity indicating that nicotine itself is responsible for the effects observed on axon terminals. 4 Stimulation of presynaptic muscarinic receptors by oxotremorine prevented the nicotine-induced facilitation of [3H]-NA release, indicating the presence of both inhibitory muscarinic and facilitatory nicotinic receptors on noradrenergic axon terminals.
TL;DR: In this paper, a Fokker-Planck-type partial differential equation for the time evolution of the cluster size distribution is formulated, and the numerical solution of this equation leads to a general scenario of first order phase transitions in systems with molecule conservation proceeding via nucleation and growth.
Abstract: Based on classical nucleation theory, a Fokker-Planck-type partial differential equation for the time evolution of the cluster size distribution is formulated. The numerical solution of this equation leads to a general scenario of first order phase transitions in systems with molecule conservation proceeding via nucleation and growth. For the initial stage of nearly constant supersaturation, the proportionality of the mean cluster radius, 〈R〉, to the square root of time, t, is verified. The following transition to the stage of Ostwald ripening may proceed either by a continuous decrease of the growth rate or via a transient stage of 〈R〉-growth considerable slower than t 1 3 . The explanation of such different possibilities is given detail. The analysis shows that, for growth processes proceeding via an attachment of single monomers and non-overlapping diffusion zones of the clusters, only one population of clusters with an unimodal size distribution should evolve. The small-angle-X-ray scattering (SAXS) experiment data from the present study show, however, the existence of two cluster populations with significantly different mean radii. Additional physical assumptions are deduced from which an explanation of a bimodal size distribution is proposed. To support this general scenario, a series of experimental results from electron microscopic, SAXS and other measurements are given for the case of silver halide precipitation from glass-forming sodium borate melts. They show the time evolution of characteristic kinetic quantities such as relative supersaturation, mean cluster size and total cluster number.
TL;DR: Cobalt(II) 2,9,16,23-tetracarboxyphthalocyanine and cobalt(III) 2.9, 16,23tetraamino-phthalocynine were covalently bonded to two different species of modified silica with low surface area.
01 Jun 1991
TL;DR: Efficient sequential and parallel solutions to the problem of answer on-line queries requesting the shortest distance between any two vertices in G, based on the hammock decomposition of a planar digraph and the use of separators for computing quickly internal distances in the graph.
Abstract: We provide here efficient sequential and parallel solutions to the following problem: given a planar digraph G (with real edge weights but no negative cycles) for preprocessing, answer on-line queries requesting the shortest distance (or path) between any two vertices in G. Our algorithms for preprocessing need O(n log n + q2) space and O(n log n + q2) sequential time. (Here q is the cardinality of a set of faces of a planar embedding of G that cover all vertices.)A parallel implementation on a CREW PRAM needs also O(n log n + q2) space and runs in O(log2n) time using O(n + M(q)) processors (where M(q) is the number of processors required to multiply two q × q matrices in O(log q) time), provided that the q faces are given by the input.This enables us to achieve O(log n) time using a single processor for a “distance” query, or O(L + log n) time for a “path” query (where L is the length of the path). Note that this is a considerable improvement over previous results in the case where q = o(n). Our techniques are based on the hammock decomposition of a planar digraph and the use of separators for computing quickly internal distances in the graph. Several other results are achieved. For outerplanar graphs, our algorithms preprocess the graph in O(n logn) space and run either in O(n log n) sequential time, or in O(log2n) time using O(n) processors on a CREW PRAM. A “distance” query can be answered in O(log n) time using a single processor. A “path” query is answered in O(L + log n) time. An optimal solution is given in the case of trees. We achieve O(1) time per “distance” query andwe need O(n) sequential time, or O(log n) time and O(n/log n) processors (on an EREW PRAM) for preprocessing. A “path” query is answered in O(L) time.
TL;DR: In this article, the formation of a new Ga active site after the hydrogen treatment of Ga/HZSM-5 catalysts prepared by different techniques such as ball-milling, impregnation and substitution in the zeolite framework was investigated.
TL;DR: In this article, a disparity in the degree of reduction of gallium was determined, and it was shown that catalytic activity differences in the two materials may be associated with the extent of reduction.
TL;DR: In this paper, the interaction of solid W3S7Br4 with Et4NBr under vibrational mill conditions followed by extraction with acetonitrile has been studied.
TL;DR: In this paper, the corrosion processes at open circuit conditions and in the active dissolution region of antimony, at low anodic overpotentials, have been studied in sulphuric acid solutions.