Showing papers by "Bulgarian Academy of Sciences published in 2000"
TL;DR: In this article, the effect of simulated acid rain (AR) on H2O2 and malonyldialdehyde (MDA) levels and activities of peroxidase and catalase in bean plants were investigated.
3,370 citations
TL;DR: In this article, the infrared spectral performance of N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, n2O4, N 2O5, NO2 and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered.
Abstract: The infrared spectral performance of the N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, N2O4, N2O5, NO2, and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N2, H-, and C-containing nitrogen oxo species, C─N species, NH x species) are also briefly discussed. Some guidelines for spectral identification of N x O y adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.
1,367 citations
TL;DR: The plant sources of bee glue are discussed, taking into consideration data based on reliable chemical evidence including comparisons between propolis samples and plant material.
Abstract: New information published since 1995 about propolis constituents is reviewed. The available information on the biological action of new found components is presented. Recent publi- cations are reviewed on propolis of native South American stingless bees. The plant sources of bee glue are discussed, taking into consideration data based on reliable chemical evidence including comparisons between propolis samples and plant material. Some aspects of the chemical standard- ization of propolis are discussed.
1,178 citations
TL;DR: The analysed literature shows that plants have evolved a number of adaptive mechanisms that allow the photochemical and biochemical systems to cope with negative changes in environment, including increased water deficit.
Abstract: At the whole plant level, the effect of stress is usually perceived as a decrease in photosynthesis and growth. That is why this review is focused mainly on the effect of drought on photosynthesis, its injury, and mechanisms of adaptation. The analysed literature shows that plants have evolved a number of adaptive mechanisms that allow the photochemical and biochemical systems to cope with negative changes in environment, including increased water deficit. In addition, the acquisition of tolerance to drought includes both phenotypic and genotypic changes. The approaches were made to identify those metabolic steps that are most sensitive to drought. Some studies also examined the mechanisms controlling gene expression and putative regulatory pathways.
699 citations
TL;DR: There was no significant difference with regards to the seasonal effect on the survival curve of Staphylococcus aureus and Escherichia coli; after incubation with propolis, there was an efficient antimicrobial action, mainly towards Gram-positive bacteria.
470 citations
TL;DR: A review of the present status of the problem of metal deposition and electrochemical phase formation and growth is made in this paper, with an overview of the major contributions of different electrochemical schools.
407 citations
TL;DR: These results are readily explained by 1) the lateral phase separation of ceramide enriched domains, 2) the area difference between the adjacent monolayers, 3) the negative spontaneous curvature, and 4) the augmented bending rigidity of the ceramide-containing domains, leading to membrane invagination and vesiculation of the bilayer.
281 citations
TL;DR: In this paper, the most intensive band in the Raman spectra at approximately 570 cm−1 has been assigned to electric field-induced Raman scattering on longitudinal optical phonons.
232 citations
TL;DR: In this paper, the adaption of NO and its co-adsorption with oxygen on TiO2 (Degussa P-25) were studied by FTIR spectroscopy.
Abstract: Adsorption of NO and its co-adsorption with oxygen on TiO2 (Degussa P-25) were studied by FTIR spectroscopy It was found that NO adsorption results in its disproportionation to NO− (1170 cm−1), N2O22−
(1335 cm−1) and nitrates (1650–1550 and 1240–1220 cm−1) The nitrate bands develop with time and coordinated NO (ca 1900 cm−1) is formed Addition of oxygen to NO results in a strong increase in concentration
of the nitrates and formation of NO+
(2206 cm−1) In addition, species assigned to nitrocomplexes (1520 and 1284 cm−1) are found The stability and reactivity of the different surface compounds as
well as their interconversion are studied and discussed
216 citations
TL;DR: In this article, the Mittag{Leer (M{L) functions have been compared with generalized operators of integration and dierention of the so-called Gelfond{Leontiev-type and Borel{Laplace-type integral transforms.
191 citations
TL;DR: Two theorems related to the relations between some of the operators, defined over the intuitionistic fuzzy sets, are formulated and proved.
TL;DR: A series of highly fluorescent 1,8-naphthalimide derivatives having an N-allylamino group at position 4 of the aromatic structure have been synthesized, and some of their properties for application in liquid crystal displays have been determined.
Abstract: A series of highly fluorescent 1,8-naphthalimide derivatives having an N-allylamino group at position 4 of the aromatic structure have been synthesised, and some of their properties for application in liquid crystal displays have been determined. The optical properties of the new substances are studied both in organic solvents and in the nematic liquid crystal ZLI 1840. The utility of the dyes for colouring liquid crystal displays of the 'guest–host' type is discussed on the basis of their spectral properties (absorption and emission) and the effect that the dyes have upon the orientation order parameter 〈P2〉 and upon the phase-transition behaviour of the liquid crystal in surface-stabilised display cells.
TL;DR: A new method for constructing minimal, deterministic, acyclic finite-state automata from a set of strings by adding new strings one by one and minimizing the resulting automaton on-the-fly.
Abstract: In this paper, we describe a new method for constructing minimal, deterministic, acyclic finite-state automata from a set of strings. Traditional methods consist of two phases: the first to construct a trie, the second one to minimize it. Our approach is to construct a minimal automaton in a single phase by adding new strings one by one and minimizing the resulting automaton on-the-fly. We present a general algorithm as well as a specialization that relies upon the lexicographical ordering of the input strings. Our method is fast and significantly lowers memory requirements in comparison to other methods.
TL;DR: In this article, it was shown that the catalytic activity of the gold/metal oxide catalysts depends strongly on the dispersion of gold particles but also on the state and the structure of the supports.
Abstract: It has been established that the gold catalysts on well crystallized supports, Au/Fe2O3 and Au/ZrO2, display higher catalytic activity in the water gas shift (WGS) reaction in comparison with the samples on amorphous and not well crystallized supports — Au/ZnO, Au/ZrO2, Au/Fe2O3–ZnO and Au/Fe2O3–ZrO2. It could be concluded that the catalytic activity of the gold/metal oxide catalysts depends strongly not only on the dispersion of the gold particles but also on the state and the structure of the supports.
TL;DR: In this article, the axisymmetric buckling of elastic-plastic cylindrical shells subjected to axial impact is studied using a finite element analysis, which reveals that shells are both velocity and mass sensitive, so that larger energies can be absorbed by a shell for high-velocity impacts when decreasing the striking mass.
TL;DR: In this article, a kinematic analysis of a new type of hybrid (parallel-serial) robot manipulator is presented, which consists of two serially connected parallel mechanisms, each having three degrees of freedom.
TL;DR: In this article, the heat storage capacity and structural stability at multiple thermal cycling of the composite PCM concrete system that consists of sodium thiosulphate pentahydrate absorbed into porous concrete are investigated.
TL;DR: Using whole mount in situ hybridization, it was shown that a similar subpopulation of cells expressed the Somatic Embryogenesis Receptor-like Kinase (SERK) gene during the induction of embryogenic cell formation.
Abstract: Single mesophyll cells in leaf explants of Dactylis glomerata L. (Dactylis) that were competent to form somatic embryos directly or through callus were identified by semi-automatic cell tracking. These competent cells were a subpopulation of small, isodiametric, cytoplasm-rich cells located close to the vascular bundles. Using whole mount in situ hybridization, we showed that a similar subpopulation of cells expressed the Somatic Embryogenesis Receptor-like Kinase (SERK) gene during the induction of embryogenic cell formation. In both leaf explants and suspension cultures, a transient pattern of SERK gene expression was found during early embryo development, up to the globular stage. In later embryo stages, SERK mRNA was present in the shoot apical meristem, scutellum, coleoptile and coleorhiza.
TL;DR: In this article, the authors proposed a model in which the viscosity η is related to the entropy of the system, and a master equation was developed that allows a comparison of data obtained at different temperatures.
Abstract: We suggest a model in which the viscosity η is related to the entropy of the system. The model successfully describes the dependence of viscosity on pressure. A master equation is developed that allows a comparison of data obtained at different temperatures. Earlier, in the framework of the same model we described the dependence of viscosity on temperature. The present treatment gives a simple interpretation of T g , the glass transition temperature, which takes places when the disorder in the amorphous system decreases to an extent that the dispersion σ is only 3.5% of maximum value of the activation energy E max .
TL;DR: Evaluated propolis effect on macrophage activation by oxygen (H2O2) and nitrogen (NO) metabolite determination suggests that propolis acts on host non-specific immunity by macrophages activation, and co-stimulant action of propolis associated with IFN-g on Macrophages is investigated.
Abstract: Propolis has been the subject of several recent studies, with the aim of elucidating its biological and pharmacological properties. Propolis has a well-known antimicrobial activity as well as antioxidant, antitumoral, antiinflammatory, and regenerative properties, but literature about its effects on the immune response is scarce. The goal of this work was to evaluate the propolis effect on macrophage activation by oxygen (H2O2) and nitrogen (NO) metabolite determination. Propolis was produced by africanized honeybees and hydroalcoholic solutions were prepared at different concentrations. Peritoneal macrophages were obtained from male BALB/c mice and culture cells were stimulated in vitro with propolis or interferon-gamma (IFN-g). In the in vivo assay, the animals were sacrificed after propolis treatment and cells were stimulated with IFN-g. We also investigated the co-stimulant action of propolis associated with IFN-g on macrophages. The results show that propolis induces a discreet elevation in H2O2 release and a mild inhibition of NO generation, depending on concentration. Propolis had no co-stimulant activity, diminishing IFN-g action on H2O2 and NO production. Data suggest that propolis acts on host non-specific immunity by macrophage activation.
TL;DR: In this paper, X-ray and electron diffraction, proton magnetic resonance (PMR), Fourier transform infrared spectroscopy (FTIR), and electron paramagnetic resonance (EPR) were used to characterize mesocarbon microbeads.
TL;DR: In this paper, a number of criterial specific parameters of the electrodes in five commercial Li ion batteries of leading producers are derived on the basis of the recently published data by Johnson and White [B.A. Johnson, R.E. White, J.
TL;DR: In this article, the authors solved the critical exponent problem for the nonlinear wave equation with damping and showed that this critical exponent coincides with the famous Fujita critical exponent for the heat equation.
Abstract: In this study we solve the critical exponent problem for the nonlinear wave equation with damping. We show that this critical exponent coincides with the famous Fujita critical exponent for the heat equation. We also observe a futher interesting phenomenon due to the presence of the damping term. The “real” support of the solution is strongly suppressed by the damping and is concentrated in the ball |x| 0 the solution decays exponentially.
TL;DR: Simultaneous pyrolysis and gasification of biomass samples of different origin is performed in a flow of steam or in a mixture of steam and carbon dioxide as mentioned in this paper, and the results show that the resulting biomass samples can be used in a variety of applications.
TL;DR: In this paper, the authors proposed alternative concepts and measures: knowledge of the workings of scientific institutions and attitudes to the nature of science, and demonstrated the viability, reliability, and validity of the new measures on British and Bulgarian data.
Abstract: Research on the public understanding of science has measured knowledge as acquaintance with scientific facts and methods and attitudes as evaluations of societal consequences of science and technology. The authors propose alternative concepts and measures: knowledge of the workings of scientific institutions and attitudes to the nature of science. The viability, reliability, and validity of the new measures are demonstrated on British and Bulgarian data. The instrument consists of twenty items and takes ten to fifteen minutes to apply. Differences in the representation of science are reported between the British and Bulgarian young elite, between the elite and the public in Bulgaria, between natural and social science students, and between beginners and advanced students in Britain. The use of these measures will extend the scope of science indicator measures used by the European Commission and the National Science Foundation, help the assessment of the socialization in university training, and may even c...
TL;DR: In this paper, modes of occurrence and origin of Cl and Br in individual coal samples from 34 deposits worldwide (Bulgaria, Australia, the United States, Japan, Canada, South Africa, China, and Ukraine) were studied.
TL;DR: In this article, a method based on the use of anion exchange resins as shape-directing macro-templates was proposed for shape-directed microspheres, and spherical beads of the ion exchange resin were prepared by a first step.
TL;DR: Three ent-kaurene diterpenoids, not previously described as constituents of propolis, were isolated from a sample collected by Brazilian native bees Melipona quadrifasciata anthidioides and displayed moderate antibacterial activity.
TL;DR: In this article, a carbon aerogel with controlled porosity can be obtained by doping the resorcinol-formaldehyde reaction mixture with Ce and/or Zr.
Abstract: Carbon aerogels with controlled porosity can be obtained by doping the resorcinol–formaldehyde reaction mixture with Ce and/or Zr. As highlighted here, the concentration of metal dopant and the pH of the initial reaction mixture can have a profound effect on the structure, porosity, and physical properties of the resulting aerogel. The Figure shows the morphology of a Ce,Zr-doped carbon aerogel synthesized at pH 7.
TL;DR: The paper reports on 73 medicinal plants of 30 families, traditionally used in Bulgarian phytotherapy, which are applied in practice for the treatment of cardiovascular, gastrointestinal, respiratory, urogenital and other disorders.