Synthesis, Characterization and Catalysis of Nanostructured Vanadia Model Catalysts for Partial Oxidation of Propane

Nanostrukturierte Vanadiumoxidmodellkatalysatoren, geträgert auf Siliziumdioxid, wurden sowohl mit einem mehrstufigen Verfahren als auch mit herkömmlicher Imprägnierung(incipient wetness impregnation) synthetisiert, charakterisiert und in der oxidativen Dehydrierung von Propan getestet. Als Siliziumdioxidträgermaterial wurde zum einen mesoporöses SBA-15 und zum anderen Aerosil 300 eingesetzt. Das mehrstufige Syntheseverfahren beinhaltet eine Funktionalisierung der SiO2-Oberfläche und einen Ionenaustausch mit Decavanadationen. Ein Ziel war es die Unterschiede zwischen den beiden Trägermaterialien und den Synthesemethoden hinsichtlich der Vanadiumstruktur und dem katalytischen Verhaltens zu untersuchen und einen Zusammenhang herauszuarbeiten. Um möglichst vergleichbare hochdisperse Vanadiumoxidspezies zu erhalten, wurde eine Vanadiumdichte von 0,7 V-atome/nm2 eingestellt. Die Proben wurden mit Stickstoff-Adsorption-Desorption, Kleinwinkel XRD, TEM, XPS, Raman- und UV-vis Spektroskopie charakterisiert. Die Reaktivität wurde zusätzlich mit TPR untersucht. Dabei konnte gezeigt werden, dass die mehrstufige Synthesemethode einen Stabilisierungseffekt auf das mesoporösen Material hat. Nach mechanischer, thermischer und hydrothermischer Belastung zeigte das Material nach der Oberflächenfunktionalisierung durch diese Methode eine höhere Stabilität als das reine SBA-15. Während das reine SBA-15 schon bei 75 MPa mechanischen Druckbehandlung einen deutlichen Rückgang der BET-Oberfläche aufweist, ändern sich die Proben, die mit dem mehrstufigen Verfahren hergestellt wurden, bis zu einem Druck von 376 MPa nur geringfügig. Nach einer mechanischen Druckbehandlung von 752 MPa lässt sich bei reinem SBA-15 keine mesoporöse Struktur mehr erkennen, bei den Proben des mehrstufuigen Verfahrens sind dahingegen noch Strukturen sichtbar. Die imprägnierten Proben zeigen die gleichen Stabilitätseigenschaften wie das reine SBA-15. Diese erhöhte Stabilität hat einen positiven Einfluss auf die Testreaktion. Die mit 752 MPa gepresste mehrstufig hergestellte Probe zeigt in der ODH von Propan eine höhere Selektivität zu Propen, als die imprägnierte Probe. Das ist auf die Erreichbarkeit der aktiven Zentren zurückzuführen, von denen in der imprägnierten Probe ein größerer Anteil nicht erreichbar ist. Beim Vergleich der verschieden präparierten Proben auf den unterschiedlichen Trägermaterialien kann eine Erhöhung des Polymerisierungsgrades in folgender Reihenfolge beobachtet werden: VxOy/SBA-15 mehrstufig - VxOy/SBA-15 imprägniert - VxOy/A300 mehrstufig - VxOy/A300 imprägniert. Dabei zeigen die spektroskopischen Daten einen deutlichen Einfluss der unterschiedlichen Trägermaterialien auf den Polymerisationsgrad, während die TPR Ergebnisse klare Unterschiede zwischen den Synthesemethoden aufweisen. Diese Unterschiede haben jedoch keinen signifikanten Einfluss in der oxidativen Dehydrierung (ODH) von Propan bzgl. der Selektivitäten (bei gleichen Umsätzen). Das führt zu der Annahme, dass die Zusammensetzung der Gasphase einen starken Einfluss auf die Reaktivität des Vanadiumoxids hat. Ein weiteres Thema dieser Arbeit waren erste Untersuchungen zu einem SBA-15 - Titansystem, das als Trägermaterial für Vanadiumoxid dienen kann. Dafür wurden verschiedene Beladungen von Titanoxid auf SBA-15 aufgebracht und harakterisiert. Zusätzlich wurde eine Probe Ti/SBA-15 mit Vanadium hergestellt, spektroskopisch untersucht und in der oxidativen Dehydrierung von Propan gestestet. Die Ergebnisse hier zeigen bezüglich Umsatz und Selektivität ein ähnliches Verhalten wie Vanadium auf reinem SBA-15 bei 450 °C aber ein deutlich anderes Verhalten bei 500 °C. Bei der V-Ti/SBA-15 Probe ist bei einer Reaktionstemperatur von 500 °C ein deutlicher Anstieg des Propanumsatzes zu beobachten.Nanostructured vanadia model catalysts supported by silica were synthesized in a multi-step procedure as well as through incipient wetness impregnation. Afterwards, the samples were characterized and tested in the oxidative dehydrogenation (ODH)of propane. Silica supports used were mesoporous SBA-15 and Aerosil 300. The multi-step synthesis includes a surface functionalization and an ion exchange with decavanadate ions. One aim of this study was the investigation of the in uence between two support materials and between different synthesis methods concerning the vanadia structure and to find a correlation to their catalytic behavior. Therefore, highly dispersed vanadia species with a similar vanadium density of 0.7 V atoms/nm2 were prepared. The samples were thoroughly characterized by nitrogen adsorption-desorption, small-angle XRD, TEM, XPS, Raman- and UV-vis spectroscopy. Furthermore, reactivity was tested with TPR besides catalytic test. It could be shown that the multi-step procedure has a stabilizing effect on the mesoporous material. After mechanical, thermal and hydrothermal treatment, the sample treated with surface functionalization shows a higher stability than blank SBA-15. The blank SBA-15 shows a signiffcant decrease of the BET surface area already at a mechanical treatment already at 75 MPa, whereas a significant change of the surface area in the multi-step samples appears not until at 376 MPa. After pressure treatment at 752 MPa no mesoporous structure can be observed anymore for blank SBA-15, but for the multi-step sample it is in parts still observable. The impregnated samples show the same behavior as blank SBA-15. The enhanced stability has a positive influence on reaction behavior. The multi-step sample pressed at 752 MPa shows in the ODH of propane a higher selectivity towards propene than the impregnated sample treated in the same way. This can be explained by accessibility of active sites within the samples. In the impregnated sample are more active sites blocked than in the multi-step sample, due to the complete loss of mesoporous structure. When comparing both support materials and the different synthesis methods, an increase of the degree of polymerization can be observed in the following order: VxOy/SBA-15 multi-step - VxOy/SBA-15 impregnated - VxOy/A300 multi-step - VxOy/A300 impregnated. It can be said that the spectroscopic data show a more distinct influence on the degree of polymerization of the support materials, whereas TPR data show clear differences among the synthesis methods. In the oxidative dehydrogenation of propane, no differences could be observed concerning the selectivities at similar conversions. This leads to the assumption that the reactivity is highly influenced by the composition of the gas phase. Another issue in this study were first investigations on an SBA-15/titanium system, which can be applied as a support material for vanadia. For this purpose, several loadings of titania were impregnated on SBA-15 and characterized. Additionally, a Ti/SBA-15 sample with vanadium was synthesized, spectroscopically characterized and tested in the oxidative dehydrogenation of propane. The results show for conversion and selectivity a similar behavior at a reaction temperature of 450 °C as vanadium on blank SBA-15, but clear differences at a reaction temperature of 500 °C. For V-Ti/SBA-15 at a reaction temperature of 500 °C a signiffcant increase of conversion of propane can be observe

Rock Slopes from Mechanics to Decision Making

http://lmrwww.epfl.ch/Eurock/Eurock2010/files/papers%20grouped.pdfRock slope instabilities are discussed in the context of decision making for risk assessment and management. Hence, the state of the slope and possible failure mechanism need to be defined first. This is done with geometrical and mechanical models for which recent developments are presented. This leads with appropriate consideration of uncertainties to risk determination and to the description of tools for risk management through active and passive countermeasures, including warning systems. The need for sensitivity analysis is then demonstrated, and final comments address updating through information collection.National Science Foundation (U.S.)MIT-Portugal ProgramPortuguese Science and Technology FoundationNorwegian Geotechnical Institute (International Centre for Geohazards)United States. Dept. of Energ

Association between central sensitization and gait in chronic low back pain:Insights from a machine learning approach

BACKGROUND: Central sensitization (CS) is often present in patients with chronic low back pain (CLBP). Gait impairments due to CLBP have been extensively reported; however, the association between CS and gait is unknown. The present study examined the association between CS and CLBP on gait during activities of daily living. METHOD: Forty-two patients with CLBP were included. CS was assessed through the Central Sensitization Inventory (CSI), and patients were divided in a low and high CS group (23 CLBP- and 19 CLBP+, respectively). Patients wore a tri-axial accelerometer device for one week. From the acceleration signals, gait cycles were extracted and 36 gait outcomes representing quantitative and qualitative characteristics of gait were calculated. A Random Forest was trained to classify CLBP- and CLBP + based on the gait outcomes. The maximum Youden index was computed to measure the diagnostic test's ability and SHapley Additive exPlanations (SHAP) indexed the gait outcomes' importance to the classification model. RESULTS: The Random Forest accurately (84.4%) classified the CLBP- and CLBP+. Youden index was 0.65, and SHAP revealed that the gait outcomes' important to the classification model were related to gait smoothness, stride frequency variability, stride length variability, stride regularity, predictability, and stability. CONCLUSIONS: CLBP- and CLBP + patients had different motor control strategies. Patients in the CLBP- group presented with a more "loose control", with higher gait smoothness and stability, while CLBP + patients presented with a "tight control", with a more regular, less variable, and more predictable gait pattern

Epistemologias miúdas: acessando conhecimentos produzidos por crianças

Researches involving children require a different methodological approach from those who carry them out, as it is necessary for the person who will carry out the research to understand that children are subjects, with their languages, who intervene directly in the social groups they are part of. Based on the Sociology of Childhood, this article aims to highlight the debate on the importance of research involving children considering them as producers of knowledge and cultures with a direct impact on the territories they inhabit. Also because children influence and are influenced by society, not being passive in their environment, but agents. For this, a qualitative bibliographical research was carried out that covered the theme. Thus, from the discussions presented in the text, we intend to present how relevant it is to carry out research with and among children, in a methodological change of rupture with adultcentrism, which is limited to their reflections on children. It is important to carry out research that takes into account the knowledge produced by children from active listening to their voices and their many languages so that we do not speak for them, but with them. For this, we weave a debate about childhood and children, in order to understand the singularities and pluralities that their conceptualizations carry. We also present listening as a way of materializing this other epistemological practice: the construction of knowledge produced by young people, small people who need to be recognized for their power.As pesquisas que envolvem crianças requerem outra postura metodológica de quem as fazem, pois é necessário que a pessoa que realizará a pesquisa compreenda que as crianças são sujeitos, com suas linguagens, que intervém diretamente nos grupos sociais que estão inseridas. Pautada na Sociologia da Infância, este artigo tem por objetivo evidenciar o debate sobre a importância das pesquisas que envolvem crianças considerarem-nas como produtoras de conhecimentos e culturas com impacto direto nos territórios que habitam. Ainda porque, crianças influenciam e são influenciadas pela sociedade, não sendo passivas ao seu meio e, sim, agentes. Para isso, foi realizada uma pesquisa qualitativa de caráter bibliográfico que abarcou a temática. Assim, a partir das discussões apresentadas no texto, pretendemos apresentar o quão é relevante realizarmos pesquisas com e entre as crianças, numa mudança metodológica de ruptura com o adultocentrismo, que se limita às suas reflexões sobre as crianças. É importante realizar pesquisas que considerem os saberes produzidos pelas crianças a partir de escuta ativa das suas vozes e de suas muitas linguagens para não falarmos por elas e sim com elas. Para isso, tecemos um debate sobre infância e criança, no intuito de compreender as singularidades e as pluralidades que suas conceituações carregam. Também, apresentamos a escuta como forma de materialização desse outro fazer epistemológico: a construção de conhecimentos produzidos por gente de pouca idade, gente miúda que precisa ser reconhecida na sua potência

SchussenAktivplus: reduction of micropollutants and of potentially pathogenic bacteria for further water quality improvement of the river Schussen, a tributary of Lake Constance, Germany

The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities

Global transcriptome analysis of murine embryonic stem cell-derived cardiomyocytes

Microarray analysis reveals that the specific pattern of gene expression in cardiomyocytes derived from embryonic stem cells reflects the biological, physiological and functional processes occurring in mature cardiomyocytes