Preparation and characterisation of single phase (MoVW)₅O₁₄-type catalyst material

MoVW based materials are highly effective catalysts for partial oxidation reactions such as conversion of acrolein to acrylic acid. They offer a high selectivity, high yields and a good long term stability. Preceding work has identified the catalytically active phase of the MoVW catalyst and characterised it by Raman spectroscopy. The current work has been carried out to synthesise and characterise this active (MoVW)5O14 type structure

Impact of diabetes duration and cardiovascular risk factors on mortality in type 2 diabetes: the Hoorn Study

Background. Several studies have reported differences in the mortality risk between diabetic subjects detected by screening and known diabetic patients. We studied mortality in relation to diabetes duration, and the contribution of other cardiovascular risk factors to the elevated risk. Materials and methods. Participants were type 2 diabetic subjects (n = 174) of a population-based cohort study. Of these, 95 were diagnosed by screening. Known diabetic subjects were grouped into two categories of diabetes duration, with a median duration of 2.4 and 11.2 years, respectively. We assessed the contribution of classical cardiovascular risk factors (dyslipidaemia, hypertension, and prior myocardial infarction), and of new cardiovascular risk factors (microalbuminuria, von Willebrand factor, sVCAM-1 and C-reactive protein) to the mortality risk during nearly 10 years of follow up. Cox's proportional hazards model was used to study the association of diabetes duration and mortality. Results. The age- and sex-adjusted relative risks of mortality were 2.06 (95% C.I. 1.04-4.10) and 3.19 (1.64-6.20) for the patients with short- and long-term diabetes compared with the screening-detected diabetic subjects, respectively. Adjustment for cardiovascular risk factors resulted in a reduction of mortality risk in both groups: 1.13 (0.51-2.50) and 2.39 (1.18-4.83), respectively. Mortality risk significantly increased with increasing diabetes duration, even after multiple adjustment (P-value for trend ranged from < 0.001-0.018). Conclusions. Mortality risk increased with increasing diabetes duration. In subjects with short diabetes duration the mortality risk could largely be attributed to other risk factors. In subjects with a longer diabetes duration, however, the elevated mortality risk was independent of these cardiovascular risk factors

Analysis of the Virulence of an Atypical Enteropathogenic Escherichia coli Strain In Vitro and In Vivo and the Influence of Type Three Secretion System

Atypical enteropathogenic Escherichia coli (aEPEC) inject various effectors into intestinal cells through a type three secretion system (T3SS), causing attaching and effacing (A/E) lesions. We investigated the role of T3SS in the ability of the aEPEC 1711-4 strain to interact with enterocytes in vitro (Caco-2 cells) and in vivo (rabbit ileal loops) and to translocate the rat intestinal mucosa in vivo. A T3SS isogenic mutant strain was constructed, which showed marked reduction in the ability to associate and invade but not to persist inside Caco-2 cells. After rabbit infection, only aEPEC 1711-4 was detected inside enterocytes at 8 and 24 hours pointing to a T3SS-dependent invasive potential in vivo. In contrast to aEPEC 1711-4, the T3SS-deficient strain no longer produced A/E lesions or induced macrophage infiltration. We also demonstrated that the ability of aEPEC 1711-4 to translocate through mesenteric lymph nodes to spleen and liver in a rat model depends on a functional T3SS, since a decreased number of T3SS mutant bacteria were recovered from extraintestinal sites. These findings indicate that the full virulence potential of aEPEC 1711-4 depends on a functional T3SS, which contributes to efficient adhesion/invasion in vitro and in vivo and to bacterial translocation to extraintestinal sites

Os livros brancos da defesa da República Popular da China 1998-2010

Este estudo é uma análise da evolução das perceções de (in)segurança da República Popular da China (RPC), através da aferição quantitativa e qualitativa de expressões idiomáticas caracterizadoras da evolução do sistema internacional, as quais foram selecionadas e associadas a tais perceções, e que constam das sete edições do Livro Branco da Defesa publicadas pelo Conselho de Estado entre 1998 e 2010. Procura-se através de um enquadramento conceptual e metodológico derivado da análise crítica do discurso baseado nas teorias de Michel Foucault e de Norman Fairclough, bem como do da perceção de ameaças por parte dos Estados no sistema internacional formulado por Robert Jervis, identificar e justificar variações nas perceções de (in)segurança da RPC entre 1998 e 2010, concluindo-se que estas refletem uma visão de natureza essencialmente realista estrutural e Lockeana quanto à evolução do sistema internacional

Herstellung eines einphasigen (MoVW)5O14-Mischoxidkatalysators

Motivation Mixed oxide catalysts containing molybdenum, vanadium and tungsten are widely used in industry for partial oxidation reactions [1, 2, 3]. Previous work revealed (MoVW)5O14 to be the active phase of the catalyst. The partial oxidation from acrolein to acrylic acid is performed on such a system [4, 5]. This catalytic system is characterised by high long term stability, excellent turn-over rates and high selectivity. Different preparation steps are necessary to form a single phase, crystalline, ternary oxide (MoVW)5O14 as a model catalyst. In a previous paper [6] it was suggested that a precursor of this oxide is already formed in solution. Therefore this poster is dedicated to propose a structure of the dissolved species and a reaction mechanism leading to the formation of this structure in solution. Experimental For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed in solution were studied using UV/Vis Raman and ESR spectroscopy. Results It is suggested from this data that a molecular structure is already formed in solution which seems to be closely related to that of the final crystalline Mo5O14-type oxide. Raman spectroscopy shows bands at 964, 943, 912, 821, 792, 709 and 682 cm-1. The bands at 943 and 792 cm-1 could be assigned to AHM. Bands at 964, 879, 821, 709, und 682 cm-1 do not belong to AHM and point to a polymeric species This result could be corroborated by UV/Vis and ESR spectroscopy. Moreover ESR shows that the state of oxidation of molybdenum and tungsten is +6. The state of oxidation of vanadium is +4. Vanadium exists as vanadyl type. The spray-dried sample shows bands at 943, 872, and 818 cm-1. A higher degree of polymerisation in the dried sample could be responsible for the shift of the band at 872 cm-1 compared to the spectrum in solution 879 cm-1. Literature [1] Hibst, H.,Unverricht, S. (BASF), DE 19815281 A 1. [2] Tanimoto, M., Himeji-shi, H., Mihara, I., Aboshi-ku, H., H., Kawajiri, T., Himeji-shi, H., (Nippon Shokubai), EP 0 711 745 B1. [3] Tenten, A., Hibst, H., Martin, F-G., Marosi, L., Kohl, V., (BASF), DE 4405514 A1. [4] Mestl, G., Linsmeier, C., Gottschall, R., Dieterle, M., Find, J., Herein, D., Jäger, J., Uchida, Y., Schlögl, R., J. Mol. Catal. A 162 (2000) 455-484. [5] Dieterle, M., Mestl, G., Jäger, J., Hibst, H., Schlögl, R., J. Mol. Catal. A 174 (2001) 169-185. [6] Knobl, S., Zenkovets, G. A., Kryukova, G. N., Ovsitser, O., Dieterle, M., Mestl, G. , Schlögl, R., J. Catal, submitted

Die kontrollierte Herstellung einer molybdänhaltigen Katalysator Prekursors durch Prezipitation verfolgt mit Hilfe der insitu UV/Vis Spektroskopie

Motivation Molybdenum containing suboxides are widely used as partial oxidation catalysts e.g. the partial oxidation of acrolein to acrylic acid is performed on such a system. These systems usually contain additional elements such as V, W, Nb etc. The role of these elements is quite unclear. Their intrinsic properties could be either important for the catalytic process, or they are structural promoters leading to a certain defect structure which is vital for catalysis [1]. To clarify this a precipitation method was chosen, leading to a controlled variation of solid precursors for catalysts without having to change the chemical composition. In this work the pH dependency of a mixed ammonium heptamolybdate (AHM) and ammonium metavanadate (AMV) solution is investigated. Chemical transformations are monitored as well as the precipitation. This will offer a detailed insight in the processes occurring in solution. The aim is to control as many parameters as possible to ensure a reproducible preparation. Further, a profound understanding of the process should lead to a rational preparation of defects, which are important for catalysis. Experimental Respective amounts of either ammonia, sodium or lithium tungstates or molybdates were dissolved in bi-distilled water. Nitric acid was added at a controlled rate. the pH values were monitored online by a calibrated glass electrode and in situ UV/Vis spectroscopy was performed with a fibre (configuration 8 around one). Results The chemical transformations occurring in solutions can by followed by the changes of the spectra in between 380 nm and 420 nm (Fig. 1). The counter cations present in the solution are involved in the nucleation and the precipitation process. The larger the cation, the easier the precipitation. Starting from AHM and K2MoO4, spontaneous precipitation is observed at about pH 2, with Na2MoO4 precipitation sets in within 2 hours at elevated temperature. Solutions of Li2MoO4 stay stable at pH=2 without any precipitation over weeks. The spectra reveal: Þ a continuing alteration of the freshly generated precipitate dispersed in the solution with time; Þ a continuing (red) shift for the absorption of the fresh precipitate with increasing V content; Þ the occurrence of a transient intermediate state just before the precipitation sets on; Þ the nature of oligomeric species formed in the acidified solutions depends on the V-concentration

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

Motivation Molybdän-, Vanadium- und Wolframhaltige Suboxide finden vielfältigen Einsatz als Partialoxidationskatalysatoren. Beispielsweise wird die Partialoxidation von Acrolein zu Acrylsäure an einem solchen System durchgeführt. Kürzlich wurde (MoVW)5O14 phasenrein dargestellt. Verbindungen mit identischem Röntgenbeugungsmustern zeigten allerdings unterschiedliche katalytische Aktivität. Dies ist auf die unterschiedliche "Realstruktur" der Katalysatoren zurückzuführen [1]. Diese Arbeit soll den Reaktionsmechanismus in Lösung verdeutlichen, der zu einem Precursor führt, der dann beim Kalzinieren die Einphasigkeit des Systems gewährleistet. Ferner wird untersucht welche Parameter auf die Defekte im Festkörper Einfluss haben und damit die "Realstruktur" mitbestimmen. Experimentelles Eine detailierte Präparationsvorschrift findet sich in der Literatur [1]. Zur Synthese des Suboxides werden entsprechende Mengen von AHM, AMT und Vanadyloxalat gelöst, gemischt, sprühgetrocknet 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 führt zu einem starken Ansteigen der Absorption im Bereich von 30000 cm-1 bis 50000 cm-1. Diese signifikante Veränderung im Metall-Ligand Charge Transfer wird durch eine Protonierung der Sauerstoffatome verursacht. Durch die Zugabe von AMT wird dieser Effekt noch verstärkt. Zusätzlich 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 erklären. Die Lage der Bande lässt auf einen Intervalence Charge Transfer Übergang schließen. Dieser Befund wird durch das ESR Experiment bestätigt. Je höher die Vanadyloxalatkonzentration, desto weniger isolierte Vanadyleinheiten liegen vor. Außerdem macht das ESR Spektrum deutlich, dass eine Vernetzung zu größeren oligomeren oder polymeren Einheiten stattfindet. Diese Spezies werden durch Vanadylbrücken miteinander verknüpft 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. Für [Mo36O112(H2O)16]8- spricht allerdings, dass dieses Ion eine pentagonale Bipyramide enthält, also genau die Struktureinheit die in Mo5O14 auftaucht