105,563 research outputs found
Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes
No full textRhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium - the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened
Gerhard Borrmann (1908-2006) and Gerhard Hildebrandt (1922-2005) : their life stories and their contribution to the revival of dynamical theory in the 1950’s
No full textInternational audienceG. Borrmann and his former student and co-worker G. Hildebrandt passed way a few months ago. Both have given major contributions to the development of the dynamical theory of diffraction and to X-ray imaging topography. Their career and their scientific achievements are reviewed briefly, with emphasis on Borrmann's very early work (Kossel lines, the discovery of anomalous absorption and of the Borrmann fan)
Biphasic hydroformylation of olefins using a novel water soluble rhodium polyethylene glycolate catalyst
No full textThe highly reactive water-soluble hydroformylation catalyst, rhodium polyethylene glycolate (Rh(PEG),), prepared by the reaction of polyethylene glycol and rhodium trichloride hydrate, was used as a catalyst for hydroformylation reactions of olefins, such as dodec-1-ene, 2.4.4-trimethylpent-1-ene and styrene, in biphasic systems. The reactions were done in a broad temperature range and at a pressure range from 7 to 12 MPa. Turnover frequency for the catalytic reaction of the low reactive 2.4.4-trimethylpent-1-ene is 450 (mol aldehyde/mol Rh x h), which is 3 times higher than in comparable homogeneous rhodium systems. The selectivity for aldehydes is excellent(> 98%). The dependence of the conversion vs. time was monitored for different partial pressures, pH values, temperatures and catalyst concentrations. Activation parameters have been calculated for the hydroformylation of the olefins in water and polyethylene glycol with rhodium polyethylene glycolate as a precatalyst. The activation energy in water is calculated for the hydroformylation of various olefins (dodec-1-ene E-a 95 kJ/mol, 2.3.3-trimethylpent-1-ene E-a 30 kJ/mol and styrene E-a 33.1 kJ/mol). The hydroformylation reaction with rhodium polyethylene glycolate as a precatalyst is first-order for dodec-1-ene and 2,4,4-trimethylpent-1-ene and zero-order for styrene. (C) 2000 Elsevier Science B.V. All rights reserved
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
Soziale Arbeit – Kerncurriculum
No full textThiessen B, Borrmann S, Köttig M, et al. Soziale Arbeit – Kerncurriculum. In: Bassarak H, ed. Lexikon der Schulsozialarbeit. Baden-Baden: Nomos; 2018
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Modeling Cities and Landscapes in 3D with CityGML
No full textCityGML is the most important international standard used to model cities and landscapes in 3D with extensive semantics. Compared to BIM standards such as IFC, CityGML models are usually less detailed but they cover a much greater spatial extent. They are also available in any of five standardized levels of detail. CityGML serves as an exchange format and as a data source for visualizations, either in dedicated applications or in a web browser. It can also be used for a wide range of spatial analyses, such as visibility studies and solar potential. Ongoing research will improve the integration of BIM standards with CityGML, making improved data exchange possible throughout the life-cycle of urban and environmental processes.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Urban Data Scienc
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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Contribution of Information and Communication Technology (ICT) in Country’S H-Index
No full textThe aim of this study is to examine the effect of Information and Communication Technology (ICT) development on country’s scientific ranking as measured by H-index. Moreover, this study applies ICT development sub-indices including ICT Use, ICT Access and ICT skill to find the distinct effect of these sub-indices on country’s H-index. To this purpose, required data for the panel of 14 Middle East countries over the period 1995 to 2009 is collected. Findings of the current study show that ICT development increases the H-index of the sample countries. The results also indicate that ICT Use and ICT Skill sub-indices positively contribute to higher H-index but the effect of ICT access on country’s H-index is not clear
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