1,721,076 research outputs found
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
Single-electronic cleavage of a carbon-sulphur bond in the cathodic reduction of 2,3-bis(phenylsulphonyl)-1,4-dimethylbenzene in dimethyl sulphoxide
No full text2,3-Bis(phenylsulphonyl)-1,4-dimethylbenzene, dissolved in dimethyl sulphoxide, undergoes a one-electron single reduction wave at -1.6 V with respect to Ag-Ag+ (0.01 M). The reduction was studied by differential pulse polarography, cyclic voltammetry, and controlled-potential electrolysis. Fast chemical steps follow the initial reduction and the isolated products are 1,4-dimethyldibenzothiophene 5,5-dioxide and 1,4-dimethyl-2-(phenylsulphonyl) benzene. In some experiments small percentages of 5a,9a-dihydro-1,4- dimethyldibenzothiophene 5,5-dioxide are also obtained. The results argue in support of the electron-transfer mechanism previously proposed for the photoinduced reactions of the same substrate with sodium arenethiolates in dimethyl sulphoxide
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
Differential expression of synapsin genes during early zebrafish development
No full textSynapsins are a family of synaptic vesicle (SV)-associated phosphoproteins that have been identified in several vertebrates and invertebrates. We report here the cloning and expression of synapsin family genes in the zebrafish Danio rerio. We identified the complete coding sequence of synapsin 3, which is not present in the currently available genome, and characterized and annotated the synapsin gene family in the zebrafish D.rerio. By means of whole-mount in situ hybridization, we showed the spatiotemporal expression of synapsin genes at three different time points during early embryonic development: 20-24h postfertilization (hpf), 30-33hpf, and 3days postfertilization (dpf). As very few data are available describing the expression of synapsin family genes during CNS development in vertebrate models, our results may help to achieve a better understanding of the complex functions of these molecules. Finally, new interesting evidence from our temporal gene expression studies suggests that synapsins have also maternal functions
Ni-based catalysts for the steam reforming of ethanol: surface acidity and catalytic activity
No full textConcept
A series of Ni-based catalysts supported on TiO2, SiO2 and ZrO2 (10 wt% Ni) were prepared by an innovative flame pyrolysis (FP) method to achieve proper thermal resistance and to tune metal dispersion. Every sample was characterised by various techniques, in among which infrared spectroscopy (FT-IR). The latter allowed to assess samples acidity and to define the nature of the Ni species present on catalyst surface. Catalytic activity for the steam reforming of ethanol was tested on a bench scale continuous plant under atmospheric pressure at different temperatures, i.e. 500, 625 and 750°C, with 3:1 mol/mol water/ethanol ratio.
Motivations and Objectives
The steam reforming of biofuels such as ethanol represents a hot research topic in the last few years. Different metals have been proposed as active phase, e.g. Ni, Co and Cu, to restrict the field to the less expensive non-noble metals. The most interesting results have been obtained with Co and Ni [1-3]. The latter seems very promising, though some drawbacks remain unsolved due to sintering and coking [1,4,5], especially when Ni particles are very dispersed [6].
From what above reported it seems that the thermal resistance of the sample is one of the key points for these catalytic materials and that another important feature is Ni dispersion and its interaction with the support. The aim of the work was then the design, the synthesis and the characterisation of heterogeneous catalysts to be used for the steam reforming of ethanol.
Results and Discussion
The FP technique proved an interesting method for the preparation of steam reforming catalysts, especially for use at high temperature (≥625°C). The titania supported catalyst showed higher activity and, above all, superior stability, with respect to similar samples prepared by coprecipitation. The advantages of the FP synthesis were less evident when dealing with silica and zirconia supported samples. Medium Lewis acidity due to exposed support ions was detected over the titania and zirconia based catalysts, whereas over the Ni/SiO2 catalyst, Lewis acidity could be induced by the metal phase itself. However, catalyst acidity did not seem really connected to coking. Based on H2 productivity and on the selected operating conditions, the best results were obtained with the silica-supported sample at 625°C, a temperature sufficient to achieve full ethanol conversion and 100% C balance. By contrast, coke formation was usually observed at 500°C, though in general not related to irreversible catalyst deactivation. An optimization of the reaction conditions is therefore required to further decrease the operating temperature, e.g. a higher water/ethanol ratio. Supposing to use such catalyst for the production of 7 Nm3/h of H2, suitable to feed a 5 kWel+5 kWth fuel cell, ca. 1.5 kg of catalyst would be needed, working at 625°C.
References
[1] V. A. Kirillov, V. D. Meshcheryakov, V. A. Sobyanin, V. D. Belyaev, Yu. I. Amosov, N. A. Kuzin, A. S. Bobrin, Theoretical Foundations of Chemical Engineering, 42 (2008) 1
[2] M. Benito, R. Padilla, A. Serrano-Lotina, L. Rodríguez, J.J. Brey, L. Daza, J. Power Sourc., 192 (2009) 158
[3] L.J.I. Coleman, W. Epling, R.R. Hudgins, E. Croiset, Appl. Catal. A: General, 363 (2009) 52
[4] A.J. Vizcaíno, A. Carrero, J.A. Calles, Int. J. Hydrogen Energy, 32 (2007) 1450
[5] J. Xuan, M.K.H. Leung, D.Y.C. Leung, M. Ni, Renewable and Sustainable Energy Reviews, 13 (2009) 1301
[6] S.Q. Chen, Y. Liu, Int. J. Hydrogen Energy, 34 (2009) 473
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
Geochemical features of the kaolin deposits from Sardinia (Italy) and genetic implications
No full textEquation of state of Fe3+-bearing phase-X
No full textWe investigated the high-pressure behaviour of Fe3+-bearing hydrous phase-X, (K1.307Na0.015)(Mg1.504Fe3+0.373
Al0.053Ti0.0044 )Si2O7H0.36, up to 34 GPa at room temperature by synchrotron X-ray powder diffraction. The lattice parameters behave anisotropically, with the [001] direction stiffer than [100]. In the 10-4 to 22 GPa pressure range, the axial bulk moduli are K0a = 112(3) GPa and K0 = 4, and K0c = 158(2) GPa and K0 = 4, and the anisotropy of the lattice parameters is b0c:b0a = 0.71:1.The cell volumes are fitted by a second-order Birch–Murnaghan equation of state giving a bulk modulus of K0 = 127(1) GPa and K0 = 4 in the same pressure range. After 22 GPa, a discontinuity in volume and lattice parameters can be recognized. Sample did not become amorphous up to 34 GPa. The coupled substitution K , Mg = [] , Fe3+ has only a limited influence on the bulk modulus and structural stability of phase-X
Scissione monoelettrica del legame C-S nella riduzione catodica del 2,3-bis(fenilsolfonil)-1,4-dimetilbenzene.
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