1,720,971 research outputs found
Development of a nanowire-based test bed device for molecular electronics applications
No full textIn this paper, we present a novel test bed system which we believe addresses several key challenges in molecular electronics, i.e., the need to fabricate metal-molecule-metal junctions that have the potential to facilitate single-molecule measurements, are easily characterized, and are reproducible. The system is based upon template-electrodeposited metal nanowires incorporating a self-assembled monolayer spacer that are fabricated into electrical devices using direct-write photolithography. Removal of the spacer leaves a nanometer-sized, characterizable gap to which nanoparticles or a test molecule of interest can be attached postfabrication. Here we report the fabrication procedure together with results showing the application of these devices to the study of the i/V characteristics of Au nanoparticles at cryogenic temperatures. These data demonstrate that the performance of these easily produced, inexpensive, novel devices compares favorably to that of devices made using preexisting methods
The oxidation of ascorbate at copolymeric sulfonated poly(aniline) coated on glassy carbon electrodes
No full textSelf-doped poly(aniline)s as electrode coatings to catalyze ascorbate oxidation are revisited in this article. Sulfonated poly(aniline) (SPAN) was deposited on glassy carbon electrodes as a copolymer of aniline and its sulfonated derivative, 2-aminobenzenesulfonic acid (2-ABSA). The resulting deposits are reproducible and show good stability and electroactivity at pH > 7, enabling studies at typical physiological pH values. Calibration curves were obtained using a rotating disc electrode at a sampling potential of 0.2 V, displaying linear dependence in the region 0–20 mM ascorbate. A kinetic model based on the Michaelis–Menten reaction mechanism, previously validated for poly(aniline) composites, was used to analyse the form of the calibration curve leading to values of the effective reaction constants KME and k?ME. New calibration curves constructed for different sampling potentials were used to elucidate the rate limiting step at saturated kinetics. Rotating disc voltammetry performed at increasing pH (from pH 2 to 9) showed a dramatic decrease in the limiting current, without any evidence for a change in the reaction mechanism.<br/
Ordered sub-micron magnetic dot arrays using self-assembly template method
Full text linkUsing a self-assembly double template method, we have prepared highly ordered magnetic dot arrays of Ni on sub-micron scales. For the template preparation we have used colloidal suspensions of polystyrene latex spheres with different diameters ranging from 200 to 700 nm combined with secondary templates of the conducting polymer polypyrrole. By variation of the template parameters and the deposition charge the material shape can be modified significantly from isolated dots to connected 3D networks. Samples have been characterized by magnetometry. Magnetic properties were found to depend strongly on dot size and connectivity leading to a rich variety of magnetic behaviors
Superconducting anti-dot arrays from self-assembly template methods
No full textWe present results of electrochemical deposition of superconducting Pb in the pores of templates prepared by self-assembly from colloidal suspensions of polystyrene latex spheres. This technique enables us to create highly ordered superconducting nanostructures with 3D architectures on length scales ranging from 50 to 1000 nm. The prepared samples show pronounced Little-Parks oscillations in T-c and matching effects in magnetization and magnetic susceptibility. Real and imaginary parts of susceptibility follow a universal Cole-Cole curve. Self-field effects play an important role in commensurability behaviour of magnetic moment at low temperatures
Confined Plasmons in Metallic Nanocavities
No full textWe investigate the properties of gold surfaces patterned using a nanoscale "lost wax" technique by electrochemical deposition through a self-assembled latex template. Near-spherical gold nanocavities within the resulting porous films support localized surface plasmons which couple strongly to incident light, appearing as sharp spectral features in reflectivity measurements. The energy of the resonances is easily tunable from ultraviolet to near infrared by controlling the diameter and height of the nanocavities. The energies of these features agree well with the Mie resonances of a perfect spherical void
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
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
- …
