1,720,961 research outputs found
Liquid-phase oxidation of organic feedstock in a compact multichannel reactor
No full textA millimeter-scale compact multifunctional reactor has been developed and tested for the selective oxidation of benzyl alcohol, using molecular oxygen as the oxidant. The reactor consists of parallel reaction channels that are packed with catalyst particles. Within the structured assembly are an integrated heat-exchange system, a gas/liquid mixing zone, and a provision for reactant injection. Experiments were performed in square channels that are 10 cm long with a cross-sectional area of 9 mm2. These were packed either with Ru/Al2O3 (0.9 wt % of Ru) or Ru/TiO2 (2 wt % of Rt) catalysts. Hydrodynamic characteristics of the system were evaluated to establish pressure drop and effectiveness of gas/liquid mixing and to confirm the nature of the gas-liquid flow regime. Operating the reactor at 8 bar and 388 K with a liquid flow L = 3.2 kg m-2 s-1 and gas flows G > 2.5 × 10-2 kg m-2 s-1, it was shown that, even in a short 10 cm length of channel, a product yield of up to 55% (with 99.7% selectivity) could be obtained. Although the adiabatic temperature rise at 55% yield is estimated to be ca. 180 K, the reactor was shown to operate isothermally, because of the efficient removal of heat through the integrated micro-heat-exchange system. It was concluded that this structured design of a reactor showed considerable promise for the development of cleaner oxidation processes
Selective oxidation of alcohols in a continuous multifunctional reactor: ruthenium oxide catalysed oxidation of benzyl alcohol
No full textA multifunctional compact reactor was designed, built, and tested, using as a model reaction the selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen. The reactor contains static mixers, heat-transfer channels and mm-scale packed-bed reaction channels, i.e., integrating mixing, heat transfer and reaction functionalities. Integrated compact reactor technology should be particularly attractive to the fine chemistry and pharmaceutical industries. The reactor was shown to operate in the kinetic regime over a broad range of operating conditions due to intensified mass transfer. The reactor was also shown to operate isothermally despite high reaction rate, an appreciable heat effect and high reactant concentration (TOF = 300 h-1, ΔH°r = -183.7 kJ mol-1). Staged injection of oxygen along the length of the reactor was investigated as a method of increasing the selectivity of oxidation reactions. Staged injection was shown to be beneficial; however, this was likely to be due to the development of a more uniform hydrodynamic regime of two-phase flow along the packed reaction channel. Experiments were performed with the ruthenium(III) hydrated oxide catalyst supported on alumina (0.9 wt% Ru/Al2O3). High activity and selectivity were observed even when working with reactant concentrations approaching industrial conditions (1 mol L-1)
Application of a structured multifunctional reactor for the oxidation of a liquid organic feedstock
No full textExperiments are performed in a structured packed bed reactor that has been developed for the selective oxidation of organic liquids to produce pharmaceutical products. Molecular oxygen is used as the oxidant, providing a “cleaner processing route”, than in established methods. The structured assembly consists of an integrated heat exchange system, a gas/liquid mixing zone, and provision for reactant injection. To illustrate the application, the selective oxidation of benzyl alcohol to benzaldehyde was studied. The reactor consisted of parallel reaction channels (10 cm long and square shaped) that were packed with Ru/Al2O3 (0.9 wt% Ru) catalyst particles. From experiments in three different sizes of channel: 2 mm × 2 mm, 3 mm × 3 mm, and 5 mm × 5 mm (at P = 8 bar, T = 388 K, with liquid and gas flows L = 3.2 kg m?2 s?1, G = 1.35 × 10?2 kg m?2 s?1), it was shown that in a short 10 cm length of channel, a product yield up to ca. 29% (with minimum 99.5% selectivity) could be obtained. Conversions were highest in the 3 mm × 3 mm channel. From the experiments with the reactor mounted both in horizontal and vertical planes, it was shown that gravitational influences are minor.The choice of solvent was shown to affect the yield of benzaldehyde. The highest yield was with toluene; the application of dioxane/water mixture (70/30 by vol.) and N-methyl pyrrolidone (NMP) not only decreased the yield by factor 2, but NMP also caused deactivation of the catalyst.Preliminary results are presented of work with Pt/C (Pt 3 wt%) catalyst
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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