305,498 research outputs found
THERAPEUTIC EFFICACY OF MAGNESIUM VALPROATE IN SUCCINIC SEMIALDEHYDE DEHYDROGENASE DEFICIENCY
No full textSuccinic semialdehyde dehydrogenase deficiency (SSADHD or gammahydroxybutyric
aciduria), a disorder of γ-aminobutyric acid (GABA)
metabolism, manifests as a slowly progressive or static encephalopathy.
The latter encompasses prominent cognitive dysfunction, neuropsychiatric
morbidity and epilepsy.We report safe and effective treatment with MgVPA
in an adolescent female with SSADHD and seizures refractory to a broad
spectrum of antiepileptics. MgVPA therapy (20 mg/Kg/day) was introduced
at 7 years based upon behavioural difficulties and EEG alterations without
adverse effects. Therapy was halted at age 13 years, and reintroduced at
14 years, due to new onset complex partial seizures. EEG demonstrated
improvement in epileptiform activity, associated with behavioural improvement
in disinhibition, aggression and coprolalia. Though typically avoided
in SSADHD due to inhibitory effects on any residual enzymatic activity,
valproate was effective and safe in our patient. Sodium valproate has
previously demonstrated therapeutic utility in SSADHD, but the use of
the magnesium conjugate has not been reported. Epilepsy remains well
controlled in our patient, with concomitant improvements in behavioural
symptoms . Our results suggest that MgVPA intervention may have utility
in selected cases of SSADH
Optimization of thermochromic multilayers for weather-resistant smart windows
No full textreservedLo sviluppo delle tecnologie nel settore delle finestre intelligenti ha introdotto nuove sfide e
opportunità nell'ottimizzazione delle loro prestazioni. In questo contesto, la vanadia, o ossido
di vanadio, emerge come un materiale promettente, grazie alle sue proprietà
fotoelettrocromiche. Questa tesi si propone di esplorare i test di durabilità della VO2,
focalizzandosi sulla ricerca di soluzioni che migliorino la resistenza e l'efficacia, ad esempio,
nel contesto delle finestre smart
Methanol oxidation over vanadia-based catalysts
No full textThe literature data on the behavior of vanadia-based catalysts in the oxidation of methanol are briefly reviewed. The potential of vanadia-titania catalysts for the production of methyl formate through methanol oxidation is outlined, and mechanistic and technical features of this process are discussed
Oxidation of ethane and cyclohexane over vanadia-niobia-silica catalysts
No full textThe conversion of ethane and cyclohexane in the presence of oxygen has been investigated on vanadia-silica (VS), niobia-silica (NS) and 1:1 vanadia-niobia-silica (VNS) catalysts. Vanadia-silica is an active catalyst for the production of ethylene from ethane and of benzene from cyclohexane. Selectivity to ethylene near 60% is obtained at near 10% ethane conversion near 820 K. Selectivity to benzene declines from above 70 to 40% when conversion of cyclohexane grows up to 40%. Cyclohexene is produced only after total oxygen conversion. Niobia-silica is much less active than vanadia-silica, and the selectivities to ethylene and to benzene grow by increasing conversion up to approach those obtained in the empty reactor at very high temperatures (above 900–1000 K). The vanadia-niobia-silica catalyst behaves quite like the vanadia-silica catalyst.
Raman, UV-Vis and XRD characterization experiments show that V2O5 particles are present both in vanadia-silica and in niobia-vanadia-silica. On the contrary niobium oxide is present as amorphous phase and traces of V-Nb mixed oxide are found in the V-Nb-silica catalyst
Vanadia Promoted Co-AI20 3 Fischer-Tropsch Catalysts
No full textBibliography: leaves 117-124.The primary aim of this work was to study systematically V20 5 promotion on yAI203 supported cobalt-based Fischer-Tropsch catalysts. The y-Ah03 support was modified by addition of varying amounts of vanadia and was subsequently loaded with the same Co content (10 wt-%). The modified supports and catalysts were characterised using conventional characterisation methods. The physio-chemical properties of the vanadia promoted supports and catalysts were characterised using Atomic Adsorption Spectroscopy (AAS), zeta-potential measurements, and BET measurements, X-ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Transmission Electron Microscopy (TEM), and CO chemisorption. Catalyst performance in the Fischer-Tropsch synthesis was tested in fixed bed reactor. A catalysts synthesised from plain y-A1203 was used as a base catalyst. Characterization results show that modification of y-Ab03 support to obtain V205 loadings beyond 1-monolayer vanadia coverage was difficult when using ion exchange. Ion-exchange equilibrium limitations might have caused the poor vanadia loadings beyond 1-monolayer coverage. The supports net surface charge as measured using zeta potential, was decreased by vanadia content in the supports. CO chemisorption results were complex and could only be modelled using dual site Langmuir model assuming the presence of two different sites absorbing CO on the Co-V-AI catalyst system. This made extraction of physical properties from this method rather difficult. Fischer Tropsch synthesis reaction was carried out at typical industrial conditions (T=220°C, P=20 bar (a), H2/CO=2 Xco-60 mol-%) for cobalt catalysts. Vanadia promoted catalysts showed a marked decrease in initial activity. However, the overall deactivation rate was lower with increasing vanadia content. The vanadia content did not affect the chain growth kinetic behavior of the catalyst in the Fischer-Tropsch synthesis hence C5+ selectivity in the Fischer-Tropsch synthesis was unperturbed by vanadia content. Increasing the vanadia content in the catalyst resulted in high n-olefin content and high 1-olefin content. The observed increase in olefin content might be due to the low catalytic activity observed for the catalysts with high vanadia loadings. The most pronounced effect of vanadia promotion on Fischer Tropsch synthesis was in the oxygenate content in the Fischer-Tropsch product. Catalysts with high vanadia loading yielded high amounts of oxygenate products; mainly alcohols and aldehydes
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
New supported vanadia catalysts for oxidation reactions prepared by sputter deposition
No full textModel vanadia catalysts were synthesised using magnetron sputtering of the active species for precisely controlled and clean catalyst design. Two series of supported vanadia catalysts were produced on inert beads with silica surface: vanadia/silica through single vanadia coating and vanadia/titania/silica by subsequent deposition of titania and vanadia. Loadings were varied by changing deposition time. All catalysts were characterised for structure and reducibility. Catalytic performance was tested by steady-state and transient experiments with propane oxidative dehydrogenation. Both supports yielded similar vanadia structures and equal dispersion. The vanadia loading strongly influenced structure and chemical behaviour. Shorter depositions gave surface vanadia monomers and polymers, whereas for longer depositions, crystalline species developed on either support. In propane oxidative dehydrogenation, very high turnover frequencies were obtained, especially for thinner depositions. An intermediate titania layer strongly influenced the vanadia activity. Maximum activity was obtained for a few vanadia layers supported on titania. (c) 2006 Elsevier Inc. All rights reserved
Electronic Transition-Related Optical Absorption in Vanadia Films
No full textABSTRACTVanadium pentoxide (vanadia) is a wide band gap semiconductor. Its layered orthorhombic structure consists of alternating sublayers of V+O atoms and O atoms (vanadyl O) alone aligned perpendicular to the b-axis. This unique structure makes vanadia a useful host for alkali atom intercalation for electrochromic applications, and therefore, an understanding of its optical properties is important. Here, we study the optical absorption characteristics of vanadia in the incident photon energy range E=2.5–6.0 eV (λ=490–200 nm). The material is in the form of 0.1μm thick films sputter deposited in Ne/O2 discharges. Two types of films were studied: single-oriented films with the b-axis perpendicular to the substrate, and amorphous films with an oxygen deficiency. The optical absorption coefficient, α(E), was determined and interpreted in terms of the structure of the V 3d conduction band. Amorphous, O-deficient vanadia were examined for room temperature aging and were found to oxidize and increase in transmittance in the photon energy range studied.</jats:p
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