1,721,104 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
IL-assisted synthesis of V2O5 nanocomposites and VO2 nanosheets
No full textLamellar structures of alternating sheets of crystalline V2O5 (shcherbinaite) and cations from certain imidazolium-based ionic liquids (IL) (e.g. 1-ethyl-3-methyl-imidazolium tetrafluoroborate) were obtained starting from VOCl3. Surprisingly, growth along the [100] direction of shcherbinaite is suppressed due to the intercalation of the IL cations, which can be attributed to the higher charge density perpendicular to this plane compared to other crystallographic planes. In the lamellar nanostructure, V2O5 consists of sheets with just one single unit cell in the [100] direction (i.e. perpendicular to the sheets). Owing to the strong interaction with the imidazolium rings, crystallization of vanadium oxide occurs at relatively moderate temperature of ca. 100 °C. Depending on the heat treatment, diverse vanadium oxide nanostructures can be obtained from the lamellar IL-V2O5 nanocomposite, namely V2O5, V2O3 and VO2. The structure of the materials was characterized by X-ray scattering, scanning (SEM) and transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS)
Photocatalytic performance of mesoporous TiO2 films doped with gold clusters
No full textWe report on the single-pot fabrication of ordered mesoporous crystallized titania films doped with gold. Au is incorporated in TiO2 films by adding to the coating solution precursors such as AuCl3 or monodisperse Au113+ nanoclusters, and Au nanoparticles are formed by calcination. A systematic study is performed to correlate structure, Au doping and photocatalytic activity of such films. Two-dimensional small angle X-ray scattering (2D-SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM) and porosimetry–ellipsometry show that the films retain their mesoporous order even for doping levels as high as 1% Au : Ti atomic ratio. Wide angle X-ray scattering (WAXS), and cyclovoltammetry (CV) show that Au113+ nanoclusters promote the formation of the TiO2 (B) phase in competition with the anatase phase. AuCl3 stabilizes instead only the anatase phase. The highest photocatalytic activity is exhibited by films where Au113+ is employed as a precursor, which we attribute to the combination of the mixed anatase/TiO2 (B) phase, of Au nanoparticle doping and of a well-ordered mesoporous TiO2 matrix
H2S Dosimetry by CuO: Towards Stable Sensors by Unravelling the Underlying Solid-State Chemistry
No full textThe precise detection of the toxic gas H2S requires reliable sensitivity and specificity of sensors even at minute concentrations of as low as 10 ppm, the value corresponding to typical exposure limits. CuO can be used for H2S dosimetry, based on the formation of conductive CuS and the concomitant significant increase in conductance. In theory, at elevated temperature the reaction is reversed and CuO is formed, ideally enabling repeated and long-term use of one sensor. Yet, the performance of CuO tends to drop upon cycling. Utilizing defined CuO nanorods we thoroughly elucidated the associated detrimental chemical changes directly on the sensors, by Raman and electron microscopy analysis of each step during sensing (CuO→CuS) and regeneration (CuS→CuO) cycles. We find the decrease in the sensing performance is mainly caused by the irreversible formation of CuSO4 during regeneration. The findings allowed us to develop strategies to reduce CuSO4 formation and thus to substantially maintain the sensing stability even for repeated cycles. We achieved CuO-based dosimeters possessing a response time of a few minutes only, even for 10 ppm H2S, and prolonged life-time
Variations on the Author
Get PDF“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
Get PDFWe 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
Ordered mesoporous thin films of rutile TiO2 nanocrystals mixed with amorphous Ta2O5
No full textOrdered mesoporous thin films of composites of rutile TiO2 nanocrystals with amorphous Ta2O5 are fabricated by evaporation-induced self-assembly followed by subsequent heat treatment beyond 780 °C. Incorporation of selected amounts of Ta2O5 (20 mol %) in the mesoporous TiO2 film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block-copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in-depth composition analysis by X-ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X-ray absorption fine structure measurement on the composite film containing 20 mol % Ta2O5 and heated to 800 °C confirms the amorphous nature of the Ta2O5 phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light
Combined use of XAFS, XRD and TEM to unravel the microstructural evolution of nanostructured ZrO2-SiO2 binary oxides: from nanometers down to molecular domain
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
