1,720,963 research outputs found
Submicron machining and biomolecule immobilization on porous silicon by electron beam
No full textThree-dimensional submicrometric structures and biomolecular patterns have been fabricated on a porous silicon film by an electron beam-based functionalization method. The immobilized proteins act as a passivation layer against material corrosion in aqueous solutions. The effects' dependence on the main parameters of the process (i.e., the electron beam dose, the biomolecule concentration, and the incubation time) has been demonstrated
Nanometrology
No full textIn the present paper an overview of metrology at the nanometric scale is given. After an introductory part on terminology and definitions concerning generic objects at the nanoscale, nanoparticles are taken as example to describe the overall features of these systems and typical characterization issues occurring from a metrological point of view. The case of nanoparticles is then further examined in depth with reference to gold nanoparticles, whose peculiar properties deriving from nano-scaled effects, like surface plasmon resonance, are discussed in detail, along with the state of the art on the main fabrication methods and applications in different sectors. Finally, a case study on the detection, by gold nanoparticles, of a contaminant used for food adulteration, namely melamine, is presented and analyzed
Photoconductivity effects in mixed-phase BSCCO whiskers
Full text linkWe report on combined photoconductivity and annealing experiments in whisker-like crystals of the Bi-Sr-Ca-Cu-O (BSCCO) high-T-c superconductor. Both single-phase Bi2Sr2CaCu2O8+delta (Bi-2212) samples and crystals of the mixed phases Bi2Sr2Ca2Cu3O10+x (Bi-2223)/Bi-2212 have been subjected to annealing treatments at 90 degrees C in air in a few hours steps, up to a maximum total annealing time of 47 h. At every step, samples have been characterized by means of electrical resistance versus temperature (R versus T) and resistance versus time at fixed temperature (R versus t) measurements, both in the dark and under illumination with a UV-Vis halogen arc lamp. A careful comparison of the results from the two techniques has shown that, while for single-phase samples no effect is recorded, for mixed-phase samples an enhancement in the conductivity that increases with increasing annealing time is induced by the light at the nominal temperature T = 100 K, i.e. at an intermediate temperature between the critical temperatures of the two phases. A simple pseudo-1D model based on the Kudinov's scheme (Kudinov et al, 1993 Phys. Rev. B 47 9017-28) has been developed to account for the observed effects, which is based on the existence of Bi-2223 filaments embedded in the Bi-2212 matrix and on the presence of electronically active defects at their interfaces. This model reproduces fairly well the photoconductive experimental results and shows that the length of the Bi-2223 filaments decreases and the number of defects increases with increasing annealing time
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
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
Determination of the thermodynamic temperature between 236 K and 430 K from speed of sound measurements in helium
Full text linkWe report speed of sound measurements in helium at 273.16 K and at eight temperatures in the range between 236 K and 430 K. These results determine the difference (T − T 90) between the thermodynamic temperature T and its approximation T 90 by the International Temperature Scale of 1990 (ITS-90). The uncertainty of our measurements of (T − T 90) spans between a minimum of 0.25 mK near 247 K and a maximum of 0.89 mK at the freezing point of indium (429.75 K) with comparable contributions from the uncertainty of our acoustic determination of T and from the uncertainty of our laboratory realization of ITS-90. On the overlapping temperature ranges these results are consistent with other recent acoustic determinations of (T − T 90). We also present evidence that (T − T 90) can be determined with comparably small uncertainties by the alternative, time-saving procedure of measuring the speed-of-sound in helium using only a single, judiciously-chosen, pressure on each isotherm
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
- …
