Showing papers by "Bulgarian Academy of Sciences published in 1984"
TL;DR: A new organic material for polarization holographic recording--azo-dye methyl-orange, introduced in polyvinyl alcohol (PVA)--is fabricated and investigated, which makes possible the recording of reversible polarization gratings with diffraction efficiency over 30%.
Abstract: A new organic material for polarization holographic recording--azo-dye methyl-orange, introduced in polyvinyl alcohol (PVA)--is fabricated and investigated. It possesses all the good characteristics of the known polarization-sensitive materials--high sensitivity, reversibility, etc.--but excels them substantially in the magnitude of the photoinduced birefringence: delta n > 10(-3). This makes possible the recording of reversible polarization gratings with diffraction efficiency over 30%. Depending on the conditions of production and subsequent mechanical and thermal treatments the layers of methyl orange/PVA may also have intrinsic birefringence. In this paper the results of experimental investigations into the properties of this new material are reported.
789 citations
TL;DR: In this paper, the coordination polyhedra in 43 double salt structures are examined and the differences in the environment around the metal ions are explained using the HSAB concept, and the values of hardness for 25 cations are calculated according to Klopman.
400 citations
TL;DR: Polarization holographic recording, based on photoinducing optical anisotropy in the recording material, is examined in this paper, where the properties (diffraction efficiency and selectivity) are discussed for two t
Abstract: Polarization holographic recording, based on photoinducing optical anisotropy in the recording material, is examined. The properties (diffraction efficiency and selectivity) are discussed for two t...
318 citations
TL;DR: Results are reported of experimental investigations on the diffraction efficiency and its polarization dependence of holographic phase polarization gratings in a photoanisotropic medium methyl orange/PVA with intrinsic birefringence, in agreement with the theoretical considerations on such gratings.
Abstract: Results are reported of experimental investigations on the diffraction efficiency and its polarization dependence of holographic phase polarization gratings in a photoanisotropic medium methyl orange/PVA with intrinsic birefringence. A comparative study of layers with different intrinsic birefringence was conducted. The conditions—initial birefringence and a type of polarization recording—were found to have high diffraction efficiency (>30%) and strong dependence on the direction of polarization of the linearly polarized readout beam. The results are in agreement with the theoretical considerations on such gratings.
211 citations
TL;DR: In this paper, the curvature elasticity and flexoelectricity of a pure lipid bilayer in a liquid crystal state were investigated, and the influence of out-of-plane fluctuations on surface interactions and cell-cell contact of flexible biomembranes was considered.
134 citations
TL;DR: A system was established for achieving plant regeneration from mesophyll protoplasts and cotyledon-derived cell suspension cultures of alfalfa, Medicago sativa L. Citation, Answer and Regen S, the latter two produced embryos from which plants could be regenerated.
Abstract: A system was established for achieving plant regeneration from mesophyll protoplasts and cotyledon-derived cell suspension cultures of alfalfa, Medicago sativa L. Peeled leaflets or cells from 6-day-old cell suspensions were incubated in an enzyme mixture containing 1% Driselase, 1% Rhozyme, 0.1% Cellulase and 72 gl-1 mannitol at pH 5.8 for 2–16 h to liberate protoplasts. A complex Kao medium supported cell division and colony formation, whereas a high auxin/low cytokinin treatment on Schenk and Hildebrandt medium followed by culture on growth regulator-free Blaydes or Linsmaier and Skoog medium resulted in somatic embryo formation. Of the three varieties tested. Citation, Answer and Regen S, the latter two produced embryos from which plants could be regenerated.
124 citations
123 citations
TL;DR: In this paper, the work function changes, Δφ, surface conductivity, Δσ, and electron energy loss spectra (ELS) have been obtained as a function of relative hydrogen coverage, θ, determined by thermal desorption (TD) measurements.
121 citations
TL;DR: In this article, Li/Li1+xV3O8 cells have been examined and shown that up to 3 eq Li+ could be accepted both chemically and electrochemically by one mole of active material.
114 citations
TL;DR: The sequences of the nontranscribed spacers (NTS) of cloned ribosomal DNA (rDNA) units from both Saccharomyces cerevisiae and Saccharocyces carlsbergensis were determined and revealed a remarkable bias of G and C-residues.
Abstract: The sequences of the nontranscribed spacers (NTS) of cloned ribosomal DNA (rDNA) units from both Saccharomyces cerevisiae and Saccharomyces carlsbergensis were determined. The NTS sequences of both species were found to be 93% homologous. The major disparities comprise different frequencies of reiteration of short tracts of six to sixteen basepairs. Most of these reiterations are found within the 1100 basepairs long NTS between the 3'-ends of 26S and 5S rRNA (NTS1). The NTS between the starts of 5S rRNA and 37S pre-rRNA (NTS2) comprises about 1250 basepairs. The first 800 basepairs of NTS NTS2 (adjacent to the 5S rRNA gene) are virtually identical in both strains whereas a variable region is present at about 250 basepairs upstream of the RNA polymerase A transcription start. In contrast to the situation in Drosophila and Xenopus no reiterations of the putative RNA polymerase A promoter are present within the yeast NTS. The strands of the yeast NTS reveal a remarkable bias of G and C-residues. Yeast rDNA was previously shown to contain a sequence capable of autonomous replication (ARS) (Szostak, J.W. and Wu, R (1979), Plasmid 2, 536-554). This ARS, which may correspond to a chromosomal origin of replication, was located on a fragment of 570 basepairs within NTS2.
111 citations
TL;DR: An anatomical model for streaming potentials in osteons is developed to characterize the electromechanical effect in bone and the cusp-like behavior of intra-osteonal potentials is explained and insight is gained relative to the time dependence of stress generated potentials.
TL;DR: Although investigations into human sensory information processing are numerous and have a long history, comparably fewer studies have been devoted to the analysis of human cortical motor functions.
Abstract: The entirety of human behavior is based on motor acts. Without some kind of motor expression no reasoning or tradition could be retained in the culture. Man's capacity for acting on and interacting with the environment is dependent on his voluntary movements. Although investigations into human sensory information processing are numerous and have a long history, comparably fewer studies have been devoted to the analysis of human cortical motor functions. Previous views of human cortical motor control, determined by the sequelae of cerebral stroke and cortical stimulation experiments, envisaged an exclusively contralateral organization. However, the processes underlying early preparation for voluntary movement are different. Readiness for movement is accompanied by a widespread slow negativity over both hemispheres, the Bereitschaftspotential (BP, Kornhuber and Deecke, 1964, 1965). There are basically two major categories of movements, the distinction being made by how the movements are initiated. Movements can occur in response to an external stimulus. Movements of this kind are reactions to our environment. But we can also move spontaneously, i.e. of our own volition. Movements of this kind are our free actions on the environment. Although we also need motivation to react to an external
TL;DR: Results point to the physiological role of the embryonic axes during natural or accelerated aging of seeds, notwithstanding that the axis is a small part as compared to the cotyledonary material, and it is suggested that lipid peroxidation in embryonic axes may play an important role in the seed deterioration during aging.
Abstract: Embryonic axes and cotyledons of three soybean (Glycine max L. cv. Gudzon) seed lots designated as “normal”, “naturally aged” and “acceleratedly aged” were analyzed for their organic free radical contents. No signals of free radicals were found in ESR spectra from cotyledonary material of the three samples investigated. High levels of organic free radicals were observed in the embryonic axes. There were significant differences in the free radical contents of the embryonic axes: the relative values of free radicals were 100, 190 and 170% for samples aged normally, naturally and in an accelerated manner, respectively. These results point to the physiological role of the embryonic axes during natural or accelerated aging of seeds, notwithstanding that the axis is a small part as compared to the cotyledons. It is suggested that lipid peroxidation in embryonic axes may play an important role in the seed deterioration during aging.
TL;DR: An efficient computational algorithm for pole assignment of linear multiinput systems is proposed, which works equally well with real and complex, distinct, and multiple poles and is applicable to ill-conditioned and high-order problems.
Abstract: An efficient computational algorithm for pole assignment of linear multiinput systems is proposed. A preliminary stage of the algorithm is a reduction of the system matrices into orthogonal canonical form. The gain matrix elements are then found by orthogonal transformation of the closed-loop system matrix into upper quasi-triangular form whose diagonal blocks correspond to the desired poles. The algorithm is numerically stable, the computed gain matrix being exact for a system with slightly perturbed matrices. It works equally well with real and complex, distinct, and multiple poles and is applicable to ill-conditioned and high-order problems.
TL;DR: In this paper, the authors used the Bonati-Ugo (BU) criterion for discerning the dithiocarbamate (dtc) bonding type from its ν as (CS) band ( ca. 1000 cm −1 ), by comparing these bands for dtc complexes containing different N-substituted ligands.
TL;DR: In this paper, the structure of thin ZnO films was investigated by X-ray diffraction and it was found that the preferred orientation in ZnOs is determined in the growth process and that there is a transition region at the interface in which the texture evolves.
TL;DR: In this article, the interaction of oxygen with Pd(111) has been studied by means of AES, ELS, thermal desorption (TD), electron stimulated desorptions (ESD), and work function measurements.
TL;DR: In this article, the double emulsion method and creeping film pertraction are applied to dephenolization of low-concentration waste waters, and their characteristics are compared.
TL;DR: In this article, the diffraction efficiency curves of multicoated dielectric gratings are measured as a function of wavelength and angle of incidence for S and P polarization in the visible region.
TL;DR: In this paper, a general model for the organization of the positive active mass is proposed based on SEM observations of samples, obtained from PAM and pastes with different phase compositions and crystal morphology.
Abstract: A general model for the organization of the structure of the positive active mass is proposed based on SEM observations of samples, obtained from PAM and pastes with different phase compositions and crystal morphology. The structure is built up of two levels: a first-level microstructure, which consists of small crystals with the form of grains, prisms, plates, and needles organized in porous agglomerate, and a second-level macrostructure. The individual agglomerates (with a screw-like, spherical, prismatic or rock-like shape) are linked in a macroporous skeleton, which supports mechanically the active material, conducts the electric current, and serves as memory, where the conditions for the preparation of the paste, the curing, and the formation of the active material are coded. For convenience, two limiting structures are designated: the ''agglomerate type'', when the agglomerate structure determines the properties and the cycle life of the plate; and the crystalline type'', when the microstructure determines the energy performance and the stability of the plate. The ''agglomerate-type'' structure is obtained from low sulfatized and dense pastes. During cycling, some irreversible processes occur, whereby the ''agglomerate'' structure is transformed into the ''crystalline-type'' structure, which in turn is dispersed to individual crystallites. This leads to softening and sheddingmore » of the active material and finally to cell failure. The proposed general model reveals the relationships between the performance of the positive plate and the technology of its production.« less
TL;DR: The data suggest that the enrichment in actively transcribed genes of matrices from nuclei treated with high salt does not reflect a localization of these genes close to the attachment sites of the chromatin loops but rather their artefactual association with some high salt-insoluble proteins of the transcriptional complexes.
TL;DR: It is shown that HMG1 is needed for the action of the replicative DNA polymerase and not for the reparative one, supported by the fact that the addition of exogenous H MG1 to the nuclei enhances the replication process.
TL;DR: In this paper, l'approche cinetique de la germination is discussed, which en collaboration with l'apprche thermodynamique statistique, a grandement contribue au progres de la theorie de the germination.
Abstract: Cet article souligne l'approche cinetique de la germination qui en collaboration avec l'apprche thermodynamique statistique a grandement contribue au progres de la theorie de la germination
TL;DR: In this paper, the necessary and sufficient condition for the presence of k massless and (n − k ) massive non-degenerate Majorana neutrinos in a theory with n neutrino flavors and a neutrer mass term of Majorana type is the existence of k standard and no other conserved lepton charges.
TL;DR: A large difference in the nucleophile reactivity is observed which is attributed to the S'2-P'2 interaction.
01 Mar 1984
TL;DR: Calculations on membrane rupture are consistent with previously unexplained observations by Sato and Suzuki relating cancer cell deformability to death on transpulmonary passage, and constitute a novel mechanism for “metastatic inefficiency” in terms of intravascular cancer cell death.
Abstract: Metastasis, a multistep process by which cancer disseminates through the body, mainly by intravascular routes, constitutes a major problem in cancer. When cancer cells are injected directly into the veins of animals, they are apparently arrested in the vascular bed of the first organ encountered and gradually released over the next 24 h. These interactions with the microvasculature are often associated in some manner with the death of many cancer cells, and are thought to contribute to the inefficiency of the metastatic process. We have made a theoretical analysis of cancer cells deformed into capillaries with respect to their intravascular velocity, adhesion to the vascular endothelium and intravascular destruction, in terms of the dynamics of the thin liquid film separating the surfaces of the blood vessels and cancer cells. Our calculations, which are based on previously reported experimental observations, indicate that the transit of cancer cells through the microvasculature is discontinuous, being interrupted by adhesions between the two. In addition, in some cases cell membrane rupture (and cell death) will occur when the critical membrane tension of the cancer cells is exceeded by the sum of their initial equilibrium membrane tension and the increased tension in the cancer cell membranes caused by friction generated as they move over the intraluminal surfaces of the capillaries. Our calculations on membrane rupture are consistent with previously unexplained observations by Sato and Suzuki relating cancer cell deformability to death on transpulmonary passage, and constitute a novel mechanism for "metastatic inefficiency" in terms of intravascular cancer cell death.
TL;DR: In this paper, the authors used the Mott-Schottky plots to determine the donor concentration (ND = 5.5 × 1019 cm−3) and electron affinity (EA = 4.6 eV).
Abstract: Single crystals of CuWO, are grown by the flux method using Na2W2O7 as a flux. Semiconducting n-type behaviour, with an activation energy for the electrical conductivity of ΔE = 0.28 eV is obtained by heating under argon flow. The analysis of the spectral response gives two indirect interband transitions at 2.15 and 2.34 eV. The choice of appropriate equivalent circuit for the CuWO4/0.1 N H2SO4, + 0.5 M KCl interface and of appropriate frequency range enables the determination of the space charge capacity. The corresponding Mott-Schottky plots are used to determine the donor concentration (ND = 5.5 × 1019 cm−3) and electron affinity (EA = 4.6 eV) Photon absorption responsible for the electronic transition at 2.34 eV is probably due to a Cu2+ W6+ charge transfer, although a competing hypothesis involving a O2- . Cu2+ charge transfer cannot by absolutely ruled out.
Des monocristaux de CuWO4, ont ete obtenus par une methode de flux utilisant Na2W2O7 comme solvant. Un traitement thermique sous courant d'argon a permis de leur confbrer un comportement semi-conducteur de type n, caracterise par la variation thermique de la conductivite electrique et du pouvoir thermoelectrique. Les electrodes ont ete etudiees dans une solution 0,1 NH2SO4, + 0,5 M KCl. Le trace des courbes de Mott-Schottky a permis de determiner la concentration en donneurs ND = 5.5 × 1019 cm−3) et l'affinite electronique (EA = 4.6 eV). L'etude de la reponse spectrale met en evidence au moins deux transitions, a 2,15 et 2,34 eV. La deuxieme correspond tres probablement au transfert de charge Cu2+ W6+ bien que le rǒle du transfert O2- Cu2+ ne puisse ětre totalement ecarte.
TL;DR: In this paper, it was shown that the unitary group of a real or complex Hilbert space provided with the strong operator topology is a totally minimal topological group, which is the first example of a (totally) minimal group which is not precompact.
Abstract: Dierolf and Schwanengel ([-7]) showed that if X is an infinite diescrete space, then the group F(X) of all bijections f : X ~ X provided with the topology of pointwise convergence is a totally minimal topological group. That was the first example of a (totally) minimal group which is not precompact. Other examples of such groups can be found in [8] (see also [21, w 2]). Infinite groups which does not admit non-discrete Hausdorff group topologies were constructed first by Shelah ([22], assuming CH), and then by Hesse ([14]), and A. Ol'ghanski~ (who noted that a quotient of the Adian's group A(m,n) has the property in question, cf. [1, w Note that all the examples mentioned above are examples of non-Abelian groups. Prodanov ([19]) established the totally minimal Abelian groups are precompact, and recently Prodanov and the author ([20]) proved that all minimal Abelian groups are precompact. The main purpose of the present paper is to show that the unitary group of every real or complex Hilbert space provided with the strong operator topology is a totally minimal topological group. This result gives an affirmative answer to a question posed by I. Prodanov. In Sects. 2 and 3 we study the equivariant (with respect to the action of the unitary group) compactifications of the unit sphere S of an infinite-dimensional Hilbert space. It is shown in Sect. 2 that the unit ball endowed with the weak topology is the greatest equivariant compactification of S. This fact is used in Sect. 3 to describe all equivariant compactification of S. The main theorem is proved in Sect. 4. The proof uses the scheme of the proof of [7, (1)], a generalization of which is discussed in Proposition 4.6.
TL;DR: Under a wide range of initial conditions, experimental results are adequately described by a new kinetic model with simple first‐ and second‐order, or Michaelian‐type, rate expressions for the reversible hydrolysis of maltotriose, maltose, and isomaltose.
Abstract: Kinetic results on the glucomylase-catalysed hydrolysis of maltose and maltotriose, and glucose polymerization into maltose and isomaltose up to 450 g/L total sugar concentration are presented. Whereas the enzyme has a faster hydrolytic and synthetic activity on alpha-(1-->4) than on alpha-(1-->6) linkages, at equilibrium, on the contrary, the isomaltose level which represents 15% (w/w) of the total sugar concentration at the highest investigated concentrations is much higher than the corresponding maltose level. Under a wide range of initial conditions, experimental results are adequately described by a new kinetic model with simple first- and second-order, or Michaelian-type, rate expressions for the reversible hydrolysis of maltotriose, maltose, and isomaltose. The model also accounts for the inhibition of hydrolysis by glucose, but does not consider the concentration of water which, under the present conditions, was not found kinetically limiting.
TL;DR: In this paper, the influence of anharmonicity on the equilibrium structure of thin epitaxial films is studied in the framework of the theoretical model, introduced in Part I. The Frank and van der Merwe model is used as a reference basis, which leads to qualitatively new effects, such as: (i) a significant asymmetry of dislocation length, strains in the deposit, activation energy for surface diffusion, with respect to the sign of natural misfit between substrate and deposit; (ii) a split of the critical stability limits for pseudomorphic growth as well as for