15 research outputs found

    Comparative effectiveness of methods of transformation of the pig embrio kidney cells (pekc, pekc tc"-) by genes pis- alpha _2 of the man interferon, psv_2-neo, pago tc

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    The work is aimed at development of the technique of calculating radionuclide precipitation in reactor facilities with different heat carriers. A physical model of precipitation is developed, conditions of precipitation simulation are determined; calculated dependences are received for radionuclide concentration fields and precipitation coefficients. A technique of calculating radionuclide precipitation is developed, RADON computation program is created. Radionuclide precipitation is calculated for reactor plant AST-200 using RADON program. An increase of APP radiation sefety was observed. The field of application covers design and use of APP with different heat carriersAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

    Methods for preparation and characterisation of heterogeneous catalysts

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    Whilst much research effort was spent on optimisation of catalyst performance, less attention has been drawn to problems concerning catalyst preparation. It is commonly known that catalyst research is facing two problems: the Materials gap and the Pressure gap. The “Materials gap” describes the discrepancy between commercial catalyst material that is often too complex to be successfully characterised and (single crystal) model catalysts that are often not able to achieve good product rates. The “Pressure gap” addresses the problem that surface investigations are commonly performed under UHV conditions whereas commercial processes are carried out at ambient or high pressure. As a consequence information of reaction mechanisms or the “real structure” under reaction conditions is very limited. Although catalysis experiments on single crystals led to new information about catalyst behaviour, it is now commonly believed that the main catalytic processes happen on centres with a high- but often unidentified- number of defects. A major task for catalyst preparation is therefore to produce highly defective metastable material. New syntheses have to be developed that fulfil many more requirements such as to ensure high reproducibility and products easy to characterise. Whilst the former can be achieved by monitoring each reaction step in-situ, the latter is taken care of by preparing thin films on a substrate. These new preparation methods will be demonstrated on the example of MoVW supported catalysts, which are used in industry for the synthesis of acrylic acid [1-5]. Despite this industrial importance, there is still a lack of information concerning structure formation during synthesis and the atomic arrangements with respect to different preparation routes and element ratios. Earlier work [6-9] showed a significant increase in selectivity for partial oxidation products in the presence of a Mo5O14 type structure. This structure, which was first identified by Kihlborg et.al. [10], is built up by pentagonal bipyramids and octahedrally coordinated metal centres [Figure 1]. It is metastable until crystallisation and oxidative decomposition into binary oxide phases occurs under high oxygen partial pressure (air and above). The element ratio is (Mo0.68V0.23W0.09)5O14. At the same time binary molybdenum based oxides doped with different elements such as Nb, W and Ta have been synthesised and their structure was identified as that of the Mo5O14-type [11, 12]. These phases were found to be stable at a wide temperature range. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried and subsequently calcined in air and helium. The Mo5O14 structure is an idealised endpoint that is formed under reduced oxygen partial pressure during the organisation process of a mixture of oligo anions, which are generated in solution. It is therefore necessary to characterise not only the structure itself but also the full preparation process with all intermediates. It seems plausible that different thermal treatments of the precursor solutions affect a) the composition of the usually mixed phase catalysts and b) the crystallite sizes of the different constituting phases. Thus, the understanding of the aqueous precursor chemistry is required to control the preparation of such mixed oxide catalysts. Furthermore, subsequent drying and activation procedures from the liquid precursor to the active and selective catalyst are of paramount importance for the development of the optimal catalytic performance. A preparation that is based on understanding of the system would allow precise control of the phase composition of the mixed oxide catalyst, the crystallite size, the crystallinity, and the morphology of the active phase. A developed synthesis routine thus could lead to defined crystallite sizes or even nano-crystalline (MoVW)5O14 mixed oxide catalysts. Moreover, it offers a versatile path to control its elementary composition. Effects of crystallite size / morphology and elemental composition could be studied separately on the catalytic performance. To this end, some steps of the developed aqueous preparation procedure are characterised by in situ micro Raman spectroscopy. The important, subsequent drying process as well as further activation and formation procedures are investigated by in situ Raman spectroscopy, HREM and XRD. Comparison with Raman spectra of well defined, single-crystalline reference oxides [13] can be used to assign the obtained spectra during these catalyst preparation routes to certain oxides, such as MoO2, Mo4O11, Mo8O23, MoO3, or Mo5O14. A different approach is currently carried out to synthesize the MoVW oxide by a Sol gel method. The Sol-gel chemistry is widely used to synthesize metal oxides by inorganic polymerisation of molecular precursors in organic media (alcohols, hydrocarbons). The low synthesis temperatures often lead to the formation of oxides with amorphous or metastable phases, which are not observed using other synthesis routes. The sol-gel synthesis of molybdenum oxides has received little attention, especially in comparison with transition metal oxides such as TiO2, V2O5 and WO3. The overall aim of this work is the rational preparation of molybdenum-based oxides via sol-gel synthesis of alkoxide precursors. The work concentrates on the mechanisms of solid formation from solution by in-situ measurements (Raman and UV-vis) in order to find new synthesis methods for high surface molybdenum oxides

    Die Genese von (MoVW)5O14 Precursoren in wÀsseriger Lösung

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    Motivation MolybdĂ€n-, Vanadium- und Wolframhaltige Suboxide finden vielfĂ€ltigen Einsatz als Partialoxidationskatalysatoren. Beispielsweise wird die Partialoxidation von Acrolein zu AcrylsĂ€ure an einem solchen System durchgefĂŒhrt. KĂŒrzlich wurde (MoVW)5O14 phasenrein dargestellt. Verbindungen mit identischem Röntgenbeugungsmustern zeigten allerdings unterschiedliche katalytische AktivitĂ€t. Dies ist auf die unterschiedliche "Realstruktur" der Katalysatoren zurĂŒckzufĂŒhren [1]. Diese Arbeit soll den Reaktionsmechanismus in Lösung verdeutlichen, der zu einem Precursor fĂŒhrt, der dann beim Kalzinieren die Einphasigkeit des Systems gewĂ€hrleistet. Ferner wird untersucht welche Parameter auf die Defekte im Festkörper Einfluss haben und damit die "Realstruktur" mitbestimmen. Experimentelles Eine detailierte PrĂ€parationsvorschrift findet sich in der Literatur [1]. Zur Synthese des Suboxides werden entsprechende Mengen von AHM, AMT und Vanadyloxalat gelöst, gemischt, sprĂŒhgetrocknet und anschließend kalziniert. Die Strukturen in Lösung werden mit UV/Vis, Raman und ESR Spektroskopie untersucht. Ergebnisse Eine Erniedrigung des pH-Wertes von pH=5,5 auf pH=3 fĂŒhrt zu einem starken Ansteigen der Absorption im Bereich von 30000 cm-1 bis 50000 cm-1. Diese signifikante VerĂ€nderung im Metall-Ligand Charge Transfer wird durch eine Protonierung der Sauerstoffatome verursacht. Durch die Zugabe von AMT wird dieser Effekt noch verstĂ€rkt. ZusĂ€tzlich zu diesem Effekt zeigt sich bei der portionsweisen Zugabe von Vanadyloxalat eine Bande zwischen 18000 cm-1 und 19000 cm-1. Die Blauverschiebung bei höheren Vanadiumkonzentrationen ist durch die fortschreitende Vernetzung bzw. Polymerisation zu erklĂ€ren. Die Lage der Bande lĂ€sst auf einen Intervalence Charge Transfer Übergang schließen. Dieser Befund wird durch das ESR Experiment bestĂ€tigt. Je höher die Vanadyloxalatkonzentration, desto weniger isolierte Vanadyleinheiten liegen vor. Außerdem macht das ESR Spektrum deutlich, dass eine Vernetzung zu grĂ¶ĂŸeren oligomeren oder polymeren Einheiten stattfindet. Diese Spezies werden durch VanadylbrĂŒcken miteinander verknĂŒpft und können somit eine oligomere oder polymere Spezies in Lösung bilden (Schema 1). Ein Literaturvergleich zeigt, dass im vorliegenden pH-Bereich die Existenz von [HMo7O24]5- und [Mo8O26]4- sehr wahrscheinlich ist. FĂŒr [Mo36O112(H2O)16]8- spricht allerdings, dass dieses Ion eine pentagonale Bipyramide enthĂ€lt, also genau die Struktureinheit die in Mo5O14 auftaucht

    The Genesis of a single Phase (MoVW)5O14-Type Solid Precursor Formation in aqueous solution

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    Motivation Molybdenum, vanadium and tungsten containing suboxides are widely used as partial oxidation catalysts [1-3] e.g. the partial oxidation of acrolein to acrylic acid is performed on such a system [4, 5]. Recently (MoVW)5O14 was synthesised as a single phase. Compounds with identical XRD patterns however, show different catalytic activity. This is due to different “real structures” of the active catalyst. The aim of this work is to suggest a reaction mechanism in solution leading to a precursor. Due to his molecular structure this precursor is vital to give the Mo5O14 type structure single phase after calcination [6]. Further, the generation of defects in the solid, which might be important for the catalytic process could be monitored and finally controlled. Experimental A detailed calcination procedure is described in the literature [6]. Respective amounts of AHM, AMT and vanadyl oxalate are dissolved. mixed and spray-dried. This is followed by the calcination procedure. The structural changes in solution are followed by UV/Vis, Raman and ESR spectroscopy. Results A significant increase in the absorption is monitored in the region between 30000 cm-1 and 50000 cm-1 when the pH is lowered from pH = 5.5 to pH = 3. This change in the metal ligand charge transfer region is caused by a protonation of oxygen atoms. The addition of AMT enhances this effect. Additionally, a band in the region between 18000 cm-1 and 19000 cm-1 emerges when vanadyl oxalate is added stepwise. The blue shift of this band at higher vanadyl concentrations can be explained by an increasing degree of polymerisation. The band position speaks for a intervalence charge transfer transition [7]. This result is corroborated by EPR experiments. The higher the vanadyl concentration the less isolated vanadyl species are present. Further, EPR shows that oligomeric or polymeric units are present. Discussion Reaction pathways of transition metal compounds such as molybdenum, vanadium or tungsten have recently been reviewed by Cruywagen [8]. Depending on the pH Mo7O246-, [HMo7O24]5-, and Mo8O264- species prevail. In strongly acidic media [Mo36O112(H2O)16] is found. The replacement of molybdenum by tungsten in hepta molybdenum species has been reported as well [9]. These species can be interlinked by vanadyl bridges and form a polymeric network. Comparison with the literature shows that in the respective pH range [HMo7O24]5- and Mo8O264- species are very likely. A good reason for the [Mo36O112(H2O)16] species would be the pentagonal bipyramide as a structural element which also appears in Mo5O14

    Phase Stability and Transport Properties of (ZrO2)0.91−x(Sc2O3)0.09(Yb2O3)x Crystals (x = 0–0.01)

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    Phase stability and transport properties of (ZrO2)0.91−x(Sc2O3)0.09(Yb2O3)x crystals (x = 0–0.01) have been studied before and after air annealing at 1000 °C for 400 h. The crystals have been grown by radio frequency (RF) heating in a cold crucible. The microstructure, phase composition, and electrical conductivity of the crystals have been studied using optical microscopy, X-ray diffraction, Raman spectroscopy, and impedance spectroscopy. Phase stability and degradation of ionic conductivity of the crystals upon long-term high-temperature heat treatment have been discussed. We show that the stabilization of ZrO2 co-doped with 9 mol.% Sc2O3 and 1 mol.% Yb2O3 provides transparent uniform crystals with the pseudocubic t″ phase structure having high phase stability. Crystals of this composition had the highest conductivity in the entire temperature range. Long-term high-temperature annealing of these crystals did not lead to conductivity degradation

    Specific structural features of LnZrOx (Ln: La, Sm) mixed oxides prepared by different methods

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    LnZrOx (Ln: La, Sm) mixed oxides of Ln: Zr = 1 were prepared by different methods (complex polymerized method, sorption of cations on starch from aqueous salt solution and conventional co-precipitation with additional redispersion of precipitate by ultra sound) and calcined at 700–1300 °C. Their specific structural features and changes were studied and discussed. Various characterization methods were used such as X-ray diffraction, Electron microscopy, Fourier-transform infrared and Raman spectroscopy, UV–Vis spectroscopy, X-Ray absorption fine structure and X-ray photoelectron spectroscopy.The formation of pyrochlore structure occurred at 1100–1300 °C from fluorite-like pseudocubic phase ZrO2 regardless the method of preparation. This phase had a block-like structure consisting of ZrO2 nanocrystals stabilized by Ln cations and residual anions such as hydroxyls and carbonates. The desorption of such anions with heating already started at 900 °C and lead to local changes of Zr cations coordination to octahedral and to the formation of pyrochlore nanodomains inclusions within fluorite-like phase. The increased cation mobility and further elimination of anions caused by further heating was accompanied by the formation of bulk pyrochlore phase at 1100–1300 °C. Even after calcination at 1300 °C the local microheterogeneity as well as defects were identified at domains boundaries or sintered microstructure. These specific features of the formed pyrochlores depend on the method of preparation. Keywords: Fluorites, Pyrochlores, Synthesis, Powders, Structur

    Structure and Physical Properties of Ceramic Materials Based on ZrO<sub>2</sub>-Sc<sub>2</sub>O<sub>3</sub> for SOFC Electrolytic Membranes Obtained from Powders of Melted Solid Solutions with a Similar Composition

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    This paper presents the results of studying the phase composition, luminescent characteristics, and ionic conductivity of ceramic scandium-stabilized solid solutions of zirconium dioxide containing 9 and 10 mol% Sc2O3. Ceramic samples were prepared by sintering powders obtained by grinding melted solid solutions of the same composition. A comparative analysis of the obtained data with similar characteristics of single crystals has been carried out. Differences in the phase composition of ceramics and initial single crystals were found. The effect of the structure and properties of grain boundaries on the ionic conductivity of ceramic samples is discussed. It is shown that the differences in the ionic conductivity of ceramic samples and crystals are mainly due to changes in the structure and phase composition

    Applying of Hierarchical Clustering to Analysis of Protein Patterns in the Human Cancer-Associated Liver

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    <div><p>Background</p><p>There are two ways that statistical methods can learn from biomedical data. One way is to learn classifiers to identify diseases and to predict outcomes using the training dataset with established diagnosis for each sample. When the training dataset is not available the task can be to mine for presence of meaningful groups (clusters) of samples and to explore underlying data structure (unsupervised learning).</p><p>Results</p><p>We investigated the proteomic profiles of the cytosolic fraction of human liver samples using two-dimensional electrophoresis (2DE). Samples were resected upon surgical treatment of hepatic metastases in colorectal cancer. Unsupervised hierarchical clustering of 2DE gel images (n = 18) revealed a pair of clusters, containing 11 and 7 samples. Previously we used the same specimens to measure biochemical profiles based on cytochrome P450-dependent enzymatic activities and also found that samples were clearly divided into two well-separated groups by cluster analysis. It turned out that groups by enzyme activity almost perfectly match to the groups identified from proteomic data. Of the 271 reproducible spots on our 2DE gels, we selected 15 to distinguish the human liver cytosolic clusters. Using MALDI-TOF peptide mass fingerprinting, we identified 12 proteins for the selected spots, including known cancer-associated species.</p><p>Conclusions/Significance</p><p>Our results highlight the importance of hierarchical cluster analysis of proteomic data, and showed concordance between results of biochemical and proteomic approaches. Grouping of the human liver samples and/or patients into differing clusters may provide insights into possible molecular mechanism of drug metabolism and creates a rationale for personalized treatment.</p></div
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