1,721,046 research outputs found
Laser Ablation: An Easy Route To Obtain Gold And Silver Nanomaterials
No full textGold and silver nanoparticles (AuNP and AgNP) have a very important role in nanotechnolgy and nanoscience, due to their physical, chemical and biochemical properties. We produced colloidal solution of Au and Ag nanoparticles in a fast and inexpensive way by laser ablation of the bulk metals in a liquid buffer using the 1064 nm line of a Q -switched Nd – YAG laser. On one hand these solutions are stable without any external chemical reagent, so nanoparticles can be obtained free in solution. On the other hand we succesfully performed the laser ablation synthesis (LAS) in water and in organic solvents, so it is possible to functionalize these particles during as well as after the LAS, simply solubilizing the ligands in the appropriate solvent.[1,2] Furthermore we found that in toluene, LAS of AuNP produces a graphite – gold nanocomposite. The graphitic matrix determined the quenching of the characteristic surface plasmon absorption (SPA) of the AuNP, that can be restored by the matrix removal.[3]
The characterization of AuNP and AgNP solutions is easily achieved by UV – vis spectroscopy using the Mie Theory to fit the SPA. For free particles in solution we conveniently fitted the SPA with the Mie Model for compact spheres and the Gans model for spheroids. We verified that one can account for the isolated nanoparticles fraction using the Mie model for simple spheres and for the aggregated nanoparticles fraction using the Gans model for spheroids.[2] In the case of the graphite – AuNP composite we reproduced the SPA quenching using the Mie model extension for core@shell particles.[3] HRTEM images confirmed the results obtained with the UV-vis spectroscopy.
Finally we were able to obtain a certain control on the average size and aggregation of nanoparticles by laser treatment at 532 nm of AuNP solution.
[1] V. Amendola, G. Mattei, C. Cusan, M. Prato and M. Meneghetti; Synthetic Metals 2005; 155; 283–286
[2] Vincenzo Amendola, Stefano Polizzi and Moreno Meneghetti; J Phys Chem B 2006; 110; 7232-7237
[3] Vincenzo Amendola, Gian Andrea Rizzi, Stefano Polizzi and Moreno Meneghetti; J Phys Chem B 2005; 109; 23125-2312
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
Nuove sintesi di ossidi nanostrutturati [New syntheses of nanostructured oxides]
No full textNuove sintesi di ossidi nanostrutturat
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
Morphological, Microstructural and Electrochemical Properties of RuO2-SnO2 Film Electrodes
No full textThe electrochemical devices based on conductive RuO2 stabilized by ceramic oxides are the most employed in chlorine-alkali cells.
Their efficiency is influenced by many variables, among which the chemical nature of the stabilizer oxide plays a considerable role.
In this paper, morphology, microstructure, and electrocatalytic properties of supported RuO2-SnO2 thin films, prepared in a wide
compositional range, were investigated by X-ray diffraction (XRD), scanning tunneling microscopy (STM), and cyclic voltammetry (CV). X-ray analysis indicates an immiscibility zone for the two oxides approximately in the range 20-70 atom % of Sn nominal amounts. In both solubility regions, a tetragonal phase (rutile-type) is formed. Peak profile analysis indicates a nonequiaxial crystal growth and shows that in solid solutions where RuO2 is the major component larger crystallites (about 100-160 Å) are formed than in those where SnO2 is the major component (about 30 Å). STM characterization reveals a rough surface with a complex microstructure: very large agglomerates, which seems to be made up of a large number of smaller units with sizes of the same order of magnitude found by XRD. Only in the sample with 70 atom % of Sn (nominal amounts) there exists regions where the small units are clearly visible as distinct particles. The CV analysis shows that the highest electrocatalytic activity is exhibited by the latter sample, which has the highest possible content of RuO2 before it forms a solid solution in SnO2 and where particles tend not to form aggregates
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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