1,720,992 research outputs found
SILICA-SUPPORTED RUTHENIUM AND OSMIUM CARBONYLS AS CATALYSTS FOR CYCLOOCTA-1,5-DIENE ISOMERIZATION
No full textHEXAGONAL CLOSE PACKED NICKEL POWDER - SYNTHESIS, STRUCTURAL CHARACTERIZATION AND THERMAL-BEHAVIOR
No full textSTRUCTURAL STUDIES OF AL-BASED POWDERS PREPARED BY CHEMICAL METHODS
No full textFinely dispersed metal powders have been obtained after chemical reduction of Ni and Co acetylacetonate by lithium aluminum hydride in tetrahydrofuran at low temperature. The Al/Ni and Al/Co stoichiometry of the as-reduced powders was 1.1 and 1.2, respectively. The structure and thermal stability of the as-reduced powders were affected by the temperature of reduction. For the NiAl powders it was found that the thermal treatment initially induces a separation of highly unstable Ni(Al) and Al(Ni) solid solutions, which subsequently react to give a single NiAl phase of cubic structure not reported in the equilibrium phase diagram. Conversely, the reduction of cobalt acetylacetonate directly gives a cubic metastable phase, from which precipitates some hexagonal form of Co after treatment at 450-degrees-C
How traces of pollutants in the environment modify bioremediation efficiency performed with Desulfovibrio vulgaris, and the advantage of an optimization protocol using soft chemicals
No full textIn recent years, Desulfovibrio vulgaris has been used to clean marble statues affected by gypsum black crusts. Many studies showed that “biocleaning” is very selective: chemical-cleaning products cannot distinguish the decay product, which has to be eliminated, from the original stone that must be fully preserved. Besides, they may cause direct and indirect damage to limestone artefacts. Instead, Sulphate Reducing Bacteria (SRB), as D. vulgaris, are able to remove just the decay matter. D. vulgaris uses SO42− ions (gypsum constituent) in its own respiratory chain; while, it does not interact with the calcium carbonate layer underneath because it does not need carbonate ions for its catabolism. However, “biocleaning” shows a large variability in the efficiency depending on the environment. If the cleaning results are not consistent, “biocleaning” cannot become an alternative cleaning method. Therefore, it is extremely important to uncover the reasons behind these differences, and to identify possible strategies to overcome the problem. The large variability of efficiency of “biocleaning” can be explained by the close relationship between the bacterial community and pollutants previously entrapped in the substrate. The aim of this work is to ascertain this hypothesis and identify how the toxic effects of the inorganic pollutants could be mitigated to improve the efficiency of this new cleaning method. In order to identify which kinds of pollutants were present and how they interact with the bacterial community during “biocleaning”, two different steps have been carried out. The first step consists in an environmental/ecotoxicological study that characterized the substrate and proves if inorganic pollutants could affect the bacterial survival. Toxic heavy metals (i.e. Pb > Zn > Cu) were found into the chalky matrix by ICP-AES and ICP-MS analyses and the followed toxicological kinetic studies demonstrated that they reduced the bacterial growth and activity. The second step consists of an optimization of the in situ bioremediation protocol, to create a better condition for the “biocleaning” application. A soft chemical pre-treatment was performed before the bacterial application using Tween 20 surfactant. Tween 20 (non-ionic surfactant) was able to reduce the adverse effects of pollutants, decreasing their superficial amount. Moreover, the method did not influence bacterial growth and activity since it did not have superficial charges and it did not change the pH value of the surroundings. This work proves that inorganic pollutants present in the gypsum decay layer can drastically reduce the bacterial growth and, at the same time, they decrease heavily the bioremediation efficiency. This study provides a soft chemical optimization strategy, helping to overcome the problem and to improve the “biocleaning” efficiency
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
BIFUNCTIONAL CATALYSTS FROM PILLARED CLAYS - VAPOR-PHASE CONVERSION OF PROPENE TO ACETONE CATALYZED BY IRON AND RUTHENIUM CONTAINING ALUMINUM PILLARED BENTONITES
No full textA natural bentonite was pillared with aluminum, aluminum-iron and aluminum-ruthenium polyoxocations. The alkali cations of some clays were successively exchanged with iron. The prepared pillared clays were characterized by X-ray diffraction, DTA, TGA, ESCA and N2 adsorption. The relative amount of Lewis and Bronsted acid sites was estimated from FR-IR spectra of adsorbed pyridine. All the clays resulted active catalysts for the vapour phase conversion of propene to acetone in the 150-350-degrees-C temperature range. The reaction appeared to occur via acid catalyzed propene hydration to isopropanol and successive oxidative dehydrogenation of the alcohol to acetone. The reactivity of all the prepared samples was correlated to the nature and number of the redox and acid sites
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
- …
