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Sample records for poluprovodnikov tipa aiiibv

  1. Second-order nonlinear optical susceptibilities of AIIBVI and AIIIBV semiconductors

    NASA Astrophysics Data System (ADS)

    Kumar, V.; Sinha, Anita; Singh, B. P.; Chandra, S.

    2016-10-01

    The second-order nonlinear optical (NLO) susceptibilities χ123(2) of AIIBVI and AIIIBV groups of semiconductors with zincblende (ZB) structure have been studied. Two relations have been proposed for the calculation of χ123(2) (0) at zero frequency. One is based on bond charge model of Levine and the other is based on plasma oscillations theory of solids. Calculated values of χ123(2) (0) for all compounds are in fair agreement with the available experimental and reported values.

  2. Identification of cellular targets of a series of boron heterocycles using TIPA II-A sensitive target identification platform.

    PubMed

    Ward, Matthew S; Silva, Isba; Martinez, Walfre; Jefferson, Jameka; Rahman, Shakila; Garcia, Jeanie M; Kanichar, Divya; Roppiyakuda, Lance; Kosmowska, Ewa; Faust, Michelle A; Tran, Kim P; Chow, Felicia; Buglo, Elena; Zhou, Feimeng; Groziak, Michael P; Xu, H Howard

    2016-08-01

    One of the hurdles in the discovery of antibiotics is the difficulty of linking antibacterial compounds to their cellular targets. Our laboratory has employed a genome-wide approach of over-expressing essential genes in order to identify cellular targets of antibacterial inhibitors. Our objective in this project was to develop and validate a more sensitive disk diffusion based platform of target identification (Target Identification Platform for Antibacterials version 2; TIPA II) using a collection of cell clones in an Escherichia coli mutant (AS19) host with increased outer membrane permeability. Five known antibiotics/inhibitors and 28 boron heterocycles were tested by TIPA II assay, in conjunction with the original assay TIPA. The TIPA II was more sensitive than TIPA because eight boron heterocycles previously found to be inactive to AG1 cells in TIPA assays exhibited activity to AS19 cells. For 15 boron heterocycles, resistant colonies were observed within the zones of inhibition only on the inducing plates in TIPA II assays. DNA sequencing confirmed that resistant clones harbor plasmids with fabI gene as insert, indicating that these boron heterocycles all target enoyl ACP reductase. Additionally, cell-based assays and dose response curved obtained indicated that for two boron heterocycle inhibitors, the fabI cell clone in AG1 (wild-type) host cells exhibited at least 11 fold more resistance under induced conditions than under non-induced conditions. Moreover, TIPA II also identified cellular targets of known antibacterial inhibitors triclosan, phosphomycin, trimethoprim, diazaborine and thiolactomycin, further validating the utility of the new system.

  3. Growth and properties of AIIIBV QD structures for intermediate band solar cells

    NASA Astrophysics Data System (ADS)

    Vyskočil, J.; Gladkov, P.; Petříček, O.; Hospodková, A.; Pangrác, J.

    2015-03-01

    Intermediate band solar cells theoretically offer a promising way to significantly increase cell efficiency compared to a single-junction solar cell. We focused on the preparation of antimony containing materials as a covering of QD layers. In this article we discuss how the concentration gradient of GaAsSb strain reducing layers can influence the resulting optical properties of the solar cell structures. The main principle of the structure is that the absorption of light is achieved at QD excited states with a better overlap of electron and hole wave functions. With fast relaxation of carriers to the ground state, the electrons and holes are quickly spatially separated. Two different composition gradients of GaAsSb SRL were used for the solar cell structure. One or five quantum dot stacks were compared. The maximal PC increased approximately 17 times with increasing number of QD layers from 1 to 5. The highest PC was achieved for sample I5A with increasing concentration of Sb in the SRL, especially in the QD absorption region. The possible explanation is a better carrier separation in this type of structure suppressing the radiative recombination rate in QDs. These results suggest a high application potential of this structure for photovoltaics.

  4. Dislocation gliding and cross-hatch morphology formation in AIII-BV epitaxial heterostructures

    SciTech Connect

    Kovalskiy, V. A. Vergeles, P. S.; Eremenko, V. G.; Fokin, D. A.

    2014-12-08

    An approach for understanding the origin of cross-hatch pattern (CHP) on the surface of lattice mismatched GaMnAs/InGaAs samples grown on GaAs (001) substrates is developed. It is argued that the motion of threading dislocations in the (111) slip planes during the relaxation of InGaAs buffer layer is more complicated process and its features are similar to the ones of dislocation half-loops gliding in plastically deformed crystals. The heterostructures were characterized by atomic force microscopy and electron beam induced current (EBIC). Detailed EBIC experiments revealed contrast features, which cannot be accounted for by the electrical activity of misfit dislocations at the buffer/substrate interface. We attribute these features to specific extended defects (EDs) generated by moving threading dislocations in the partially relaxed InGaAs layers. We believe that the core topology, surface reconstruction, and elastic strains from these EDs accommodated in slip planes play an important role in the CHP formation. The study of such electrically active EDs will allow further understanding of degradation and changes in characteristics of quantum devices based on strained heterostructures.

  5. Bibliography of Soviet Laser Developments, No. 21, July - September 1975

    DTIC Science & Technology

    1976-01-15

    198. (RZhF, 6/75, 6D1317) 175. Vlokh , O. G. , L. F. Lutsiv-Shumskiy, A. M. Popel1, and I. V. Stasyuk (114). Transverse...rav ra"g•-•’)• AN SSSR. Sibirskoye otdelemye. Institut fiziki poluprovodnikov. Preprint, no. 26, Novosibirsk, 1174, 6 p. (KLDV, 6...ng atomic and molecular transitions^. AN SSSR. Fizicheskiy institut . Trudy, no. 31, 1975, 185 p. (LC) 541. Basov, N. G. , V

  6. Thiostrepton-induced gene expression in Streptomyces lividans.

    PubMed Central

    Murakami, T; Holt, T G; Thompson, C J

    1989-01-01

    Thiostrepton induced the expression of four proteins (17, 19, 30, and 56 kilodaltons) of unknown function in Streptomyces lividans. The chromosomal gene which encoded the 19-kilodalton protein (tipA) was cloned and sequenced. Transcription of the tipA promoter was induced at least 200-fold by thiostrepton. The tipA 200-fold by thiostrepton. The tipA transcriptional start site (located by S1 mapping and primer extension experiments) was preceded by a 45-base-pair imperfect inverted-repeat sequence which included the -10 and -35 regions of the promoter. Under noninducing conditions in vivo, this might form a cruciform structure which is not recognized by RNA polymerase. A 143-base-pair fragment including this region was cloned into a promoter probe vector, pIJ486. In this plasmid, pAK114, the thiostrepton-inducible tipA promoter controlled the expression of a kanamycin resistance gene encoding an aminoglycoside phosphotransferase. As little as 1 ng of thiostrepton spotted on a lawn of S. lividans(pAK114) induced kanamycin-resistant growth. Other thiostreptonlike antibiotics also induced tipA, but structurally unrelated antibiotics which inhibit translation had no effect. In S. lividans, the promoter could be induced by thiostrepton during either growth or stationary phase. The tipA promoter should be a valuable tool for expression studies in streptomycetes. Images PMID:2537819

  7. Syntheses, structures and tunable luminescence of lanthanide metal-organic frameworks based on azole-containing carboxylic acid ligand

    SciTech Connect

    Zhao, Dian; Rao, Xingtang; Yu, Jiancan; Cui, Yuanjing Yang, Yu; Qian, Guodong

    2015-10-15

    Design and synthesis of a series of isostructural lanthanide metal-organic frameworks (LnMOFs) serving as phosphors by coordinate the H{sub 2}TIPA (5-(1H-tetrazol-5-yl)isophthalic acid) ligands and lanthanide ions is reported. The color of the luminescence can be tuned by adjusting the relative concentration of the lanthanide ions in the host framework GdTIPA, and near-pure-white light emission can be achieved. - Graphical abstract: Lanthanide metal-organic frameworks (LnMOFs) with tunable luminescence were synthesized using an azole-containing carboxylic acid as ligand. - Highlights: • A series of isostructural LnMOFs serving as phosphor is reported. • We model the GdTIPA: Tb{sup 3+}, Eu{sup 3+} which can tune color and emit white light. • The scheme and mechanism of luminescent LnMOFs are also presented and discussed.

  8. Highly selective sorption of small hydrocarbons and photocatalytic properties of three metal-organic frameworks based on tris(4-(1H-imidazol-1-yl)phenyl)amine ligand.

    PubMed

    Fu, Hong-Ru; Kang, Yao; Zhang, Jian

    2014-04-21

    By employing a tris(4-(1H-imidazol-1-yl)phenyl)amine (Tipa) ligand, three new metal-organic frameworks, [Zn2(Tipa)(4,4'-bpdc)1.5(H2O)(NO3)]·2(DMF)·H2O (1; 4,4'-bpdc = 4,4'-biphenyldicarboxylate, DMF = N,N-dimenthylformamide), [Cd(Tipa)Cl2]·2(DMF)·H2O (2), and [Co(Tipa)Cl2(H2O)]·DMF·H2O (3), have been synthesized solvothermally. Compound 1 features a three-dimensional (3D) pillared-layer structure with low band gap and interesting photocatalytic properties. Compound 2 is a 2-fold interpenetrating (3,6)-connected porous framework, and it shows highly selective adsorption of C2H2, CO2, and C2H4 over CH4. Compound 3 with honeycomb-like layers exhibits unusual 2D + 2D→ 3D polycatenation (2D = two-dimensional). The luminescent properties for these compounds were also investigated.

  9. 75 FR 43076 - 2-Propanol, 1,1′,1′′-nitrilotris-; Exemption from the Requirement of a Tolerance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-23

    ... alcohols and hydrocarbons; surfactants such as polyoxyethylene polymers and fatty acids; carriers such as... (1,000 mg/kg/day). In a 1-generation reproduction toxicity study in rats with TIPA, no adverse... lack of systemic toxicity in the 1-generation reproduction study in rats as well as a negative...

  10. JPRS Report, Arms Control.

    DTIC Science & Technology

    2007-11-02

    Joint-Stock Company"] [Text] A constituent conference of the "Ural- Kosmos " closed joint-stock company [aktsionernoye obshchestvo zakrytogo tipa] has...due to be destroyed under arms cuts. Their warheads will be replaced by communications satellites. The founders of the "Ural- Kosmos " company note

  11. Structural basis and dynamics of multidrug recognition in a minimal bacterial multidrug resistance system

    PubMed Central

    Habazettl, Judith; Allan, Martin; Jensen, Pernille Rose; Sass, Hans-Jürgen; Thompson, Charles J.; Grzesiek, Stephan

    2014-01-01

    TipA is a transcriptional regulator found in diverse bacteria. It constitutes a minimal autoregulated multidrug resistance system against numerous thiopeptide antibiotics. Here we report the structures of its drug-binding domain TipAS in complexes with promothiocin A and nosiheptide, and a model of the thiostrepton complex. Drug binding induces a large transition from a partially unfolded to a globin-like structure. The structures rationalize the mechanism of promiscuous, yet specific, drug recognition: (i) a four-ring motif present in all known TipA-inducing antibiotics is recognized specifically by conserved TipAS amino acids; and (ii) the variable part of the antibiotic is accommodated within a flexible cleft that rigidifies upon drug binding. Remarkably, the identified four-ring motif is also the major interacting part of the antibiotic with the ribosome. Hence the TipA multidrug resistance mechanism is directed against the same chemical motif that inhibits protein synthesis. The observed identity of chemical motifs responsible for antibiotic function and resistance may be a general principle and could help to better define new leads for antibiotics. PMID:25489067

  12. Atomic structure of InSb(001) and GaAs(001) surfaces imaged with noncontact atomic force microscopy.

    PubMed

    Kolodziej, J J; Such, B; Szymonski, M; Krok, F

    2003-06-06

    Noncontact atomic force microscopy (NC-AFM) has been used to study the c(8x2) InSb(001) and the c(8x2) GaAs(001) surfaces prepared by sputter cleaning and annealing. Atomically resolved tip-surface interaction maps display different characteristic patterns depending on the tip front atom type. It is shown that representative AFM maps can be interpreted consistently with the most recent structural model of A(III)B(V)(001) surface, as corresponding to the A(III) sublattice, to the B(V) sublattice, or to the combination of both sublattices.

  13. Projects of High-Temperature Nuclear Reactors

    NASA Astrophysics Data System (ADS)

    Ekmanis, J.; Tomsons, E.; Zeltiņš, N.

    2013-04-01

    Part 2 of the overview gives emphasis to the projects of high-temperature NRs, whose development is an area of active engagement for the specialists from the USA, France, Japan, Russia, China, the Netherlands, and Germany. Projects of several powerful NRs of the HTGR type for commercial use had been worked out in the USA and Germany already by 1970 but not yet implemented. Augstas temperatūras ar gāzes dzesēšanu HTGR (High Temperature Gas cooled Reactor) tipa kodolreaktoru (KR) izstrādes koncepcija bija piedāvāta 1956. gadā Lielbritānijā. Apmēram tanī pašā laikā minētā tipa KR izstrādi uzsāka Vācijā un ASV. HTGR tipa KR kodoldegviela un kodoldegvielas atražošanas materiāla sīkās daļiņas ar diametru apmēram 0.5 mm pārklātas ar vairākām aizsargkārtām un atrodas grafīta neitronu palēninātājā, kas aizsargā daļiņas no neitronu palēninātāja un dzesētāja iedarbes. Augstas temperatūras KR bez hēlija gāzes siltumnesēja var izmantot šķidrus metālus (nātriju, svinu vai svina-bismuta sakausējumu) un izkausētu sāli. Pašlaik darbojās divi augstas temperatūras ar hēlija gāzi dzesēti eksperimentālie HTGR tipa KR. Viens Japānā "HTTR" no 1998. gada oktobra (sākts būvēt 1991. gada 15. martā) ar 30 MWth siltuma jaudu. Otrs Ķīnā "HTR-10" no 2000.gada decembra (sākts būvēt 1995. gada14. jūnijā) ar 10 MWth siltuma jaudu. Ķīnā Shandong provincē 2011.gada aprīlī uzsāka augstas temperatūras "HTR-PM" (High Temperature Gas-cooled Reactor - Pebble bed Module) tipa kodolreaktora celtniecību ar 250 MWth siltuma jaudu. Augstas temperatūras kodolreaktoru izstrādē pašlaik aktīvi iesaistīti ASV, Francijas, Japānas, Krievijas, Ķīnas, Nīderlandes un Vācijas speciālisti.

  14. Investigation of Shot Noise Reduction in InGaP HBTs with different Base Thickness

    NASA Astrophysics Data System (ADS)

    Sakalas, P.; Schroter, M.; Zampardi, P.

    2005-08-01

    DC, AC characteristics and Noise parameters of InGaP/GaAs HBTs with base thicknesses of wB/nm=90, 70, 50 as well as CCHBTs with wB=90 nm, were measured and modeled using advanced compact model HICUM. Very good agreement of HICUM versus measured data was observed for AC and DC data. Significant base thickness reduction only slightly increases peak transit frequency fT/GHz =(45 (90nm), 54 (50nm)) due to reduced base transit time. High speed performance is mainly controlled by nonequilibrium electrons which form minority carrier jam in B/C SCR and thus additional delay. Significant increase of fT/GHz =60 (90nm) was observed for CCHBTs, which feature lower collector internal resistance and smaller delay in B/C SCR. Therefore measured NFmin of different wB HBTs did not exhibit expected difference, in contrast to CCHBTs, which demonstrated significantly lower NFmin. Our analytical noise model clarified that strong shot noise reduction in AIIIBV is stemming not only from correlated currents, but also from Coulomb blockade by nonequilibrium electrons.

  15. Penicillium antifungal protein (PAF) is involved in the apoptotic and autophagic processes of the producer Penicillium chrysogenum.

    PubMed

    Kovács, Barbara; Hegedűs, Nikoletta; Bálint, Mihály; Szabó, Zsuzsa; Emri, Tamás; Kiss, Gréta; Antal, Miklós; Pócsi, István; Leiter, Eva

    2014-09-01

    PAF, which is produced by the filamentous fungus Pencicillium chrysogenum, is a small antifungal protein, triggering ROS-mediated apoptotic cell death in Aspergillus nidulans. In this work, we provide information on the function of PAF in the host P. chrysogenum considering that carbon-starving cultures of the Δpaf mutant strain showed significantly reduced apoptosis rates in comparison to the wild-type (wt) strain. Moreover, the addition of PAF to the Δpaf strain resulted in a twofold increase in the apoptosis rate. PAF was also involved in the regulation of the autophagy machinery of this fungus, since several Saccharomyces cerevisiae autophagy-related ortholog genes, e.g. those of atg7, atg22 and tipA, were repressed in the deletion strain. This phenomenon was accompanied by the absence of autophagosomes in the Δpaf strain, even in old hyphae.

  16. An inducible expression system of histidine-tagged proteins in Streptomyces lividans for one-step purification by Ni2+ affinity chromatography.

    PubMed

    Enguita, F J; de la Fuente, J L; Martín, J F; Liras, P

    1996-04-01

    An expression and purification cassette containing the aminoglycoside phosphotransferase gene (aph) as selective marker has been constructed in the Escherichia coli vector pULHis2. DNA fragments inserted in the cassette can be easily subcloned in pIJ699 to give vectors for overexpression of genes in Streptomyces and purification of proteins by a one-step procedure. The expression system uses the thiostrepton-inducible promoter tipA for expression and a six histidine coding nucleotide sequence that is fused in frame to the foreign gene inserted in the polylinker. The pULHis2-derived expression vector has been used satisfactorily to express and to purify the P7 and P8 proteins of Nocardia lactamdurans which carry out the methoxylation of cephalosporin C to 7-methoxycephalosporin C.

  17. Development of drift-diffusion numerical models of high-speed on-chip photodetectors with heterojunctions

    NASA Astrophysics Data System (ADS)

    Pisarenko, I. V.; Ryndin, E. A.

    2016-12-01

    In this paper, we consider the issue of research and development of on-chip optoelectronic devices designed for the optical interconnecting of integrated circuit elements. We address the conceptual on-chip optical interconnections based on AIIIBV nanoheterostructure lasers with functionally integrated modulators of optical radiation. According to the estimations, these optoelectronic devices can generate subpicosecond optical pulses. The paper is aimed at the development of numerical models, simulation methods, and specialized software. These aids are intended for the research of physical processes taking place in high-speed heterostructure photodetectors suitable for operation as parts of on-chip optical interconnections together with the lasers-modulators. We propose to utilize the drift-diffusion approximation of the semiclassical approach for the numerical simulation of charge carrier transport and accumulation in semiconductor photosensitive heterostructures. The drift-diffusion numerical simulation technique was developed. This technique is based on the application of the Newton method, implicit difference scheme, and Slotboom drift-diffusion formulation in terms of electron and hole imref exponents and electrostatic potential. We researched p+-Al0.3Ga0.7As/i-GaAs/n+-Al0.3Ga0.7As and metal/n-Al0.3Ga0.7As/n+-GaAs heterostructures. Rise and fall times of the devices being considered are approximately equal and amount to about 1.6 ps for the p-i-n structure and 1.7 ps for the Schottky-barrier photodiode. We concluded that it is reasonable to develop the methods directed at the improvement of photodetector response speed.

  18. The Positron as a Probe for Studying Bulk and Defect Properties in Semiconductors

    NASA Astrophysics Data System (ADS)

    Dlubek, G.; Brümmer, O.

    Positron lifetime measurements are used to study various doped and undoped III-V compound semiconductors like GaAs, GaP, InAs and InP. In some as-grown crystals native vacancies (V, V) or their complexes with dopants (TeAsV, VPZnInV) are detected with maximum concentrations of a few 1018 cm-3. In undoped GaAs neutral As vacancies V are identified, the concentration of which varies locally. The vacancies have their origin in deviations from the stoichiometrie composition of the compound. They disappear at 500°C. At this temperature defects created by irradiation with fast neutrons anneal also out. The relation between the bulk positron lifetime and the density and polarization of valence electrons is analyzed. Further, the potential of the positron annihilation method in identifying and characterizing vacancy-type defects in semiconductors is discussed.Translated AbstractDas Positron als Sonde zur Untersuchung der Volumen- und Fehlstelleneigenschaften in HalbleiternPositronenlebensdauermessungen werden angewandt, um verschiedene dotierte und undotierte AIIIBV-Verbindungshalbleiter, wie GaAs, GaP, InAs und InP, zu untersuchen. In einigen Kristallen werden Leerstellen (V, V) oder ihre Komplexe mit Dotierungen (TeAsV, VPZnInV) mit maximalen Konzentrationen von einigen 1018 cm-3 nachgewiesen. In undotierten GaAs werden neutrale As-Leerstellen V identifiziert, deren Konzentration lokal variiert. Die Leerstellen haben ihren Ursprung in Abweichungen von der stöchiometrischen Zusammensetzung der Verbindung. Sie verschwinden bei 500°C. Bei dieser Temperatur heilen auch Defekte aus, welche durch Bestrahlung mit schnellen Neutronen erzeugt wurden. Die Beziehung zwischen der Positronenlebensdauer im Kristall und der Dichte und Polarisierung der Valenzelektronen wird analysiert. Weiterhin wird das Potential der Methode der Positronenannihilation zur Identifizierung und Charakterisierung leerstellenartiger Defekte in Halbleitern diskutiert.

  19. Influence of ferrite phase in alite-calcium sulfoaluminate cements

    NASA Astrophysics Data System (ADS)

    Duvallet, Tristana Yvonne Francoise

    Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition

  20. Self-assembled copper(II) coordination polymers derived from aminopolyalcohols and benzenepolycarboxylates: structural and magnetic properties.

    PubMed

    Kirillov, Alexander M; Karabach, Yauhen Y; Haukka, Matti; Guedes da Silva, M Fatima C; Sanchiz, Joaquin; Kopylovich, Maximilian N; Pombeiro, Armando J L

    2008-01-07

    The new copper(II) or copper(II)/sodium(I) 1D coordination polymers [Cu2(Hmdea)2(mu-H2O)(mu2-tpa)]n.2nH2O (1), [Cu2(H2tipa)2(mu2-ipa)]n.4nH2O (2), [Cu2(H2tea)2Na(H2O)2(mu2-tma)]n.6nH2O (3), [Cu2(H2tea)2(mu2-ipa)]n.nH2O (4a), and [Cu2(H2tea)2{mu3-Na(H2O)3}(mu3-ipa)]n(NO3)n.0.5nH2O (4b) have been prepared in aqueous medium by self-assembly from copper(II) nitrate, aminopolyalcohols [methyldiethanolamine (H2mdea), triisopropanolamine (H3tipa), and triethanolamine (H3tea)] as main chelating ligands and benzenepolycarboxylic acids [terephthalic (H2tpa), isophthalic (H2ipa), and trimesic (H3tma) acid] as spacers. They have been characterized by IR spectroscopy, elemental and single-crystal X-ray diffraction analyses, the latter indicating the formation of unusual multinuclear metal cores interconnected by various benzenepolycarboxylate spacers, leading to distinct wavelike, zigzag, or linear 1D polymeric metal-organic chains. These are further extended to 2D or 3D hydrogen-bonded supramolecular networks via extensive interactions with the intercalated crystallization water molecules. The latter are associated, also with aqua ligands, by hydrogen bonds resulting in acyclic (H2O)3 clusters in 1, (H2O)8 clusters in 2, infinite 1D water chains in 3, and disordered water-nitrate associates in 4b, all playing a key role in the structure stabilization and its extension to further dimensions. Variable-temperature magnetic susceptibility measurements have shown that 1-4 exhibit a moderately strong ferromagnetic coupling through the alkoxo bridge. The small Cu-O-Cu bridging angle and the large out-of-plane displacement of the carbon atom of the alkoxo group accounts for this behavior. The magnetic data have been analyzed by means of a dinuclear and a 1D chain model, and the magnetic parameters have been determined. The magnetic exchange coupling in 3, to our knowledge, is the highest found in alkoxo-bridged copper(II) complexes.

  1. TipC and the chorea-acanthocytosis protein VPS13A regulate autophagy in Dictyostelium and human HeLa cells.

    PubMed

    Muñoz-Braceras, Sandra; Calvo, Rosa; Escalante, Ricardo

    2015-01-01

    Deficient autophagy causes a distinct phenotype in Dictyostelium discoideum, characterized by the formation of multitips at the mound stage. This led us to analyze autophagy in a number of multitipped mutants described previously (tipA(-), tipB(-), tipC(-), and tipD(-)). We found a clear autophagic dysfunction in tipC(-) and tipD(-) while the others showed no defects. tipD codes for a homolog of Atg16, which confirms the role of this protein in Dictyostelium autophagy and validates our approach. The tipC-encoded protein is highly similar to human VPS13A (also known as chorein), whose mutations cause the chorea-acanthocytosis syndrome. No member of the VPS13 protein family has been previously related to autophagy despite the presence of a region of similarity to Atg2 at the C terminus. This region also contains the conserved domain of unknown function DUF1162. Of interest, the expression of the TipC C-terminal coding sequence containing these 2 motifs largely complemented the mutant phenotype. Dictyostelium cells lacking TipC displayed a reduced number of autophagosomes visualized with the markers GFP-Atg18 and GFP-Atg8 and an impaired autophagic degradation as determined by a proteolytic cleavage assay. Downregulation of human VPS13A in HeLa cells by RNA interference confirmed the participation of the human protein in autophagy. VPS13A-depleted cells showed accumulation of autophagic markers and impaired autophagic flux.

  2. Autogenous transcriptional activation of a thiostrepton-induced gene in Streptomyces lividans.

    PubMed Central

    Holmes, D J; Caso, J L; Thompson, C J

    1993-01-01

    Although the antibiotic thiostrepton is best known as an inhibitor of protein synthesis, it also, at extremely low concentrations (< 10(-9) M), induces the expression of a regulon of unknown function in certain Streptomyces species. Here, we report the purification of a Streptomyces lividans thiostrepton-induced transcriptional activator protein, TipAL, whose N-terminus is similar to a family of eubacterial regulatory proteins represented by MerR. TipAL was first purified from induced cultures of S.lividans as a factor which bound to and activated transcription from its own promoter. The tipAL gene was overexpressed in Escherichia coli and TipAL protein purified in a single step using a thiostrepton affinity column. Thiostrepton enhanced binding of TipAL to the promoter and catalysed specific transcription in vitro. TipAS, a second gene product of the same open reading frame consisting of the C-terminal domain of TipAL, is apparently translated using its own in-frame initiation site. Since it is produced in large molar excess relative to TipAL after induction and also binds thiostrepton, it may competitively modulate transcriptional activation. Images PMID:7688297

  3. Autoclavable highly cross-linked polyurethane networks in ophthalmology.

    PubMed

    Bruin, P; Meeuwsen, E A; van Andel, M V; Worst, J G; Pennings, A J

    1993-11-01

    Highly cross-linked aliphatic polyurethane networks have been prepared by the bulk step reaction of low molecular weight polyols and hexamethylenediisocyanate (HDI). These polyurethane networks are optically transparent, colourless and autoclavable amorphous glassy thermosets, which are suited for use in ophthalmic applications such as intraocular lenses and keratoprostheses. The properties of these glassy polyurethanes, obtained from the reaction of the low molecular weight polyols triisopropanolamine (TIPA) or tetrakis (2-hydroxypropyl)ethylenediamine (Quadrol) and HDI in stoichiometric proportions, have been investigated in more detail. The glassy Quadrol/HDI-based polyurethane exhibits a reduction in ultimate glass transition temperature from 85 to 48 degrees C by uptake of 1% of water, and good ultimate mechanical properties (tensile strength 80-85 MPa, elongation at break ca 15%, modulus ca 1.5 GPa). IR spectra of these hydrophobic polyurethane networks revealed the absence of an isocyanate absorption, indicating that all isocyanates, apparently, had reacted during the cross-linking reaction. The biocompatibility could be increased by grafting tethered polyacrylamide chains onto the surface during network formation. These transparent cross-linked polyurethanes did not transmit UV light up to 400 nm, by incorporation of a small amount of the UV absorbing chromophore Coumarin 102, and could be sterilized simply by autoclaving. They were implanted in rabbit eyes, either in the form of small circular disks or in the form of a keratoprosthesis (artificial cornea). It was shown that the material was well tolerated by the rabbit eyes. Serious opacification of the cornea, a direct result of an adverse reaction to the implant, was never seen. Even 1 yr after implantation of a polyurethane keratoprosthesis the eye was still 'quiet'.

  4. bldA-dependent expression of the Streptomyces exfoliatus M11 lipase gene (lipA) is mediated by the product of a contiguous gene, lipR, encoding a putative transcriptional activator.

    PubMed Central

    Servín-González, L; Castro, C; Pérez, C; Rubio, M; Valdez, F

    1997-01-01

    Extracellular lipase synthesis by Streptomyces lividans 66 carrying the cloned lipase gene (lipA) from Streptomyces exfoliatus M11 was found to be growth phase dependent, since lipase was secreted into the medium mainly during the stationary phase; S1 nuclease protection experiments revealed abundant lipA transcripts in RNA preparations obtained during the stationary phase but not in those obtained during exponential growth. Transcription from the lipA promoter was dependent on the presence of lipR, a contiguous downstream gene with a very high guanine-plus-cytosine content (80.2%). The deduced lipR product consists of a protein of 934 amino acids that shows similarity to known transcriptional activators and has a strong helix-turn-helix motif at its C terminus; this motif is part of a domain homologous to DNA-binding domains of bacterial regulators of the UhpA/LuxR superfamily. The lipR sequence revealed the presence of a leucine residue, encoded by the rare TTA codon, which caused bldA dependence of lipA transcription in Streptomyces coelicolor A3(2); replacement of the TTA codon by the alternate CTC leucine codon alleviated bidA dependence but not the apparent growth phase-dependent regulation of lipA transcription. When lipR expression was induced in a controlled fashion during the exponential growth phase, by placing it under the inducible tipA promoter, lipase synthesis was shifted to the exponential growth phase, indicating that the timing of lipR expression, and not its bldA dependence, is the main cause for stationary-phase transcription of lipA. PMID:9401043

  5. Comparison of biological and molecular characterization of Iranian lettuce mosaic virus isolates.

    PubMed

    Ormaz, B; Winter, S; Koohi-Habibi, M; Mosahebi, Gh; Izadpanah, K

    2006-01-01

    Lettuce mosaic virus (LMV) is one of the most damaging viruses in lettuce and endive cultivating regions. In order to review the characteristics of different LMV isolates of Iran during 2004-2005 samples were collected from lettuce fields in Esfahan, Ghom, Khorasan, Khuzestan and Tehran provinces. All of the isolates were detected by LMV polyclonal antiserum (AS-0155, DSMZ Germany) in ELISA and TIPA tests. Biological purification was done for the LMV isolates and then they were maintained and propagated on Chenopodium quinoa. A range of plant species such as C. amaranticolor, C. album, Carthamus tinctorius, Gazania sp., Gomphrena globosa, Pisum sativum, Spinacia oleracea were inoculated with these isolates using potassium phosphate buffer (0/05M). Molecular weight of coat protein was determined by Polyacrylamid gel electrophoresis (PAGE). Immunocapture reverse transcription polymerase chain reaction (IC-RT-PCR) was performed using LMV polyclonal antiserum and specific primer pairs of LMV as described by Zerbini et al. (1995). The amplified fragments were included the whole CP and 3'UTR regions and the nucleotide sequences of them determined. All isolates induced chlorotic local lesions on C. amaranticolor and chlorotic local lesions with symptoms of systemic infection (vein clearing) on C. album. Tehran isolate in addition, caused local lesions on Gomphrena globosa with red border and white centre. This isolate infected Pisum sativum without any symptoms. Back inoculation on C. quinoa and DAS-ELISA confirmed the latent infection. None of these isolates infected Carthamus tinctorius, Gazania sp. and Spinacia oleracea. The molecular weight of coat protein was determined 30.33 kDa. Western-blot proved this band as the coat protein of the virus. IC-RT-PCR amplification of LMV isolates produced the expected size IC-RT-PCR product of 1300 bps. The comparison of nucleotide sequences showed that there were 98% identities.

  6. Reduction of Electric Breakdown Voltage in LC Switching Shutters / Elektriskās Caursites Sprieguma Samazināšana Šķidro Kristālu Šūnās

    NASA Astrophysics Data System (ADS)

    Mozolevskis, G.; Ozols, A.; Nitiss, E.; Linina, E.; Tokmakov, A.; Rutkis, M.

    2015-10-01

    Liquid crystal display (LCD) industry is among the most rapidly growing and innovating industries in the world. Here continuously much effort is devoted towards developing and implementing new types of LCDs for various applications. Some types of LCDs require relatively high voltages for their operation. For example, bistable displays, in which an altering field at different frequencies is used for switching from clear to scattering states and vice versa, require electric fields at around 10 V/μm for operation. When operated at such high voltages an electrical breakdown is very likely to occur in the liquid crystal (LC) cell. This has been one of the limiting factors for such displays to reach market. In the present paper, we will report on the results of electrical breakdown investigations in high-voltage LC cells. An electrical breakdown in the cell is observed when current in the liquid crystal layer is above a specific threshold value. The threshold current is determined by conductivity of the liquid crystal as well as point defects, such as dust particles in LC layer, pinholes in coatings and electrode hillocks. In order to reduce the currents flowing through the liquid crystal layer several approaches, such as electrode patterning and adding of various buffer layers in the series with LC layer, have been tested. We demonstrate that the breakdown voltages can be significantly improved by means of adding insulating thin films. Šķidro kristālu ekrānu (LCD) industrija ir viena no visstraujāk augošajām industrijām pasaulē. Daudz pūļu un resursu tiek veltīti jauna tipa LCD izstrādē dažādiem pielietojumiem. Atsevišķa tipa LCD funkcionēšanai nepieciešami augsti spriegumi. Piemēram, bistabilos LCD, kuros izkliedējošs (ieslēgts) un dzidrs (izslēgts) stāvoklis tiek iegūts ar dažādu frekvenču maiņsprieguma palīdzību, elektriskā lauka intensitāte šķidrā kristāla slānī var sasniegt pat 10 V/μm. Augstās elektriskā lauka intensit

  7. Multi-Objective Optimization of Transmission Lines / Elektropārvades Līnijas Daudzkriteriālā Optimizācija

    NASA Astrophysics Data System (ADS)

    Berjozkina, S.; Sauhats, A.; Neimane, V.

    2013-10-01

    Introduction of new advanced electrical connections into a transmission grid reduces the capacity of existing overhead lines (OHLs). At the same time, designing & building of new OHLs and substations involves considerable technical, environmental and economical problems. The authors propose a concept of the multi-objective optimization for selection of transmission line routes, towers (their type, placement and geometry), of conductors, insulators, dampers, earthing and lightning protection systems, span lengths, etc.. The optimization is organized in five stages. At the first and second stages a search for optimum solutions is performed along with determination of the main impacting factors. The next two stages present a two-objective optimization based on Pareto's approach. At the last stage (exemplified by a case study), the probability of the restriction removal conditions is assessed, and preventive measures are identified. The presented approach uses a real line design and is intended for minimizing the total invested capital and maximizing the net present value. In the framework of this approach 20 alternatives have been elaborated, which can successfully be applied in the cases described in the paper. Elektropārvades tīklam rodas nepieciešamība pēc jauniem elektriskajiem pieslēgumiem, kas noved pie esošo gaisvadu līniju jaudas nepietiekamības. Viens no iespējamajiem pastāvošās problēmas risinājumiem ir jaunu gaisvadu līniju un apakšstacijas būvniecība. Gaisvadu līniju projektēšana ir saistīta ar ievērojamām tehniskām, vides un ekonomiskām problēmām. Darbā aprakstīta elektropārvades līnijas optimālās trases izvēles daudzkritēriju optimizācijas koncepcija, ieskaitot balstu tipa, balstu izvietojuma koordināšu, balstu ģeometrijas, vadu tipu un parametru, izolatoru tipu, vibroslāpētāju tipu, zibensaizsardzības un zemēšanas sistēmu, kā arī laidumu garumu izvēles optimizāciju. Optimizācijas uzdevums tiek organiz

  8. Investigation Into the Accuracy of 3D Surface Roughness Characteristics

    NASA Astrophysics Data System (ADS)

    Kumermanis, M.; Rudzitis, J.; Mozga, N.; Ancans, A.; Grislis, A.

    2014-04-01

    The existing standards for surface roughness cover only two dimensions, while in reality this is three-dimensional (3D). In particular, the 3D surface roughness parameters are important for solving the contact surface mechanics problems as related to the accuracy of 3D surface roughness characteristics. One of the most important factors for determination of 3D characteristics is the number of data points (NDP) on the x- and y-axes (i.e. in cut-off length). The NDP has a profound effect on the accuracy of measurement results, measuring time and volume of the output data (especially along the y-axis, where the NDP is identical to the number of parallel profiles). At a too small NDP the results will be incorrect and with too broad scatter, while a too large NDP - though not enlarging the range of basic information - considerably increases the measuring time. Therefore, the aim of the work was to find the optimal NDP for such surface processing methods as grinding, spark erosion and shot methods of surface treatment. Eksistējošie virsmas raupjuma standarti apskata virsmas raupjumu tikai divās dimensijās. Tomēr reālais virsmas raupjums pēc savas dabas ir trīsdimensiju (3D) objekts. Līdz ar to virsmas raupjums ir jāraksturo ar 3D parametriem. Un no šo parametru noteikšanas precizitātes ir atkarīgi tālākie virsmas aprēķini, piemēram, virsmu kontaktēšanās process. Viens no svarīgākajiem faktoriem, raksturojot virsmas raupjumu 3D, pielietojot kontakta tipa mēriekārtas, ir datu punktu skaits pa abām mērīšanas asīm x un y. Ar datu punktu skaitu mēs saprotam to skaitu mērīšanas bāzes garumā. Datu punktu skaits būtiski ietekmē sagaidāmo mērījumu rezultātu precizitāti, mērīšanai nepieciešamo laiku un izejas datu faila izmērus (sevišķi y-ass virzienā, kur katrs datu punkts ir paralēls profils). Datu punktu skaitam ir jābūt optimālam. Pārāk mazs punktu skaits noved pie neprecīziem rezultātiem un lielas to izkliedes, savuk

  9. Sail-Type Wind Turbine for Autonomous Power Supplay: Possible Use in Latvia

    NASA Astrophysics Data System (ADS)

    Sakipova, S.; Jakovics, A.

    2014-12-01

    Under the conditions of continuous increase in the energy consumption, sharply rising prices of basic energy products (gas, oil, coal), deterioration of environment, etc., it is of vital importance to develop methods and techniques for heat and power generation from renewables. The paper considers the possibility to use a sail-type wind turbine for autonomous power supply in Latvia, taking into account its climatic conditions. The authors discuss the problems of developing a turbine of the type that would operate efficiently at low winds, being primarily designed to supply power to small buildings and farms distant from centralized electricity networks. The authors consider aerodynamic characteristics of such a turbine and the dependence of the thrust moment of its pilot model on the airflow rate at different angles of attack. The pilot model with a changeable blade shape has been tested and shows a good performance. Darbs veltīts vienam no atjaunojamo enerģiju veidiem - vēja enerģijai, analizētas tās izmantošanas iespējas. Vispirms īsi raksturota vēja enerģijas izmantošana pasaulē, kā arī vērtētas izmantošanas perspektīvas no inženiertehniskā un klimatisko apstākļu viedokļa. Turpinājumā raksturota situācija Latvijā, t. sk., arī vēja potenciāla pieejamība dažādos reģionos, kā arī vēja enerģijas izmantošanas efektivitāti raksturojošie lielumi. Konstatējot problēmu, rast vēja turbīnu risinājumus Latvijas apstākļiem ar maziem vidējiem vēja ātrumiem, izveidots buras tipa turbīnas modelis. Šī modeļa raksturlielumu izpēte veikta vēja tunelī Karagandas universitātē, konstatējot relatīvi labus efektivitātes rādītājus tiešai un pretējai vēja plūsmai. Izmantojot mērījumu rezultātus, ierosināti sistēmas uzlabojumi, kurus plānots pētīt turpmāk. Šādas sistēmas potenciāli var rast lietojumu tur, kur nepieciešami autonomi enerģijas avoti.

  10. Power Generation Investment Planning in a Modern Power System With High Share of Renewables

    NASA Astrophysics Data System (ADS)

    Oleinikova, I.; Ruksans, O.; Turcik, M.

    2014-04-01

    enerācijas tehnoloģijas izmaksu novērtēšana; - elektrostaciju ģenerācijas īstermiņa un ilgtermiņa izmaksu novērtēšana; - elektrostaciju ģenerācijas investīciju un vadības izmaksu novērtēšana; - dažādu ģenerācijas tehnoloģiju izmaksu skaitliskie aprēķini un analīze. Īpaša uzmanība veltīta investīciju plānošanai elektroenerģijas ražošanas nozarē liberalizēta tirgus apstākļos; tika izanalizēti efektīvie instrumenti, izmaksu metodes un ekonomiskās efektivitātes novērtēšanas nozīme dažāda tipa ģenerējošām jaudām un tās atbilstība mūsdienu elektroapgādes sistēmas prasībām