1,721,129 research outputs found
Anti-Kondo resonance in transport through a quantum wire with a side-coupled quantum dot
No full textAn interacting quantum dot side-coupled to a perfect quantum wire is studied. Transport through the quantum wire is investigated by using an exact sum rule and the slave-boson mean field treatment. It is shown that the Kondo effect provides a suppression of the transmission due to the destructive interference of the ballistic channel and the Kondo channel. At finite temperatures, antiresonance behavior is found as a function of the quantum dot level position, which is interpreted as a crossover from the high temperature Kondo phase to the low temperature charge fluctuation phase.This work was supported by Grant No. 1999-2-11400-
005-5 from the Basic Research Program of the KOSEF, and
by the electron Spin Science Center at POSTECH
Low optical loss perfluorinated methacrylates for a single-mode polymer waveguide
No full textPerfluoroalkyleneoxy methacrylate containing polar functional carbonate (-O-C(= O)-O-) or carbamate (-NH-C(= O)-O-) groups were synthesized to improve optical and adhesion properties of optical waveguide materials. Transparent polymer films were prepared by photocuring of a solution containing methacryloyl perfluoroalkyleneoxy carbonate and a photoinitiator. Optical loss of 0.35 dB/ cm at 1550 nm was determined from the photocured film, for TE polarization by measuring the transmitted power along the slab waveguide length. The refractive indices at 1550 rim were determined as 1.4337 and 1.4334 for TE and TM modes, respectively, indicating low birefringence of Deltan = 0.0003 +/- 0.0002. Adhesion between the substrate and the polymer layer was enhanced by introducing carbonates and carbamates as determined from a SEM cross section and low surface energy of the photocured polymer film. Low-loss optical waveguides have been fabricated from a solution containing methacryloyl perfluoroalkyleneoxy carbonate by photo-cross-linking and then reactive ion etching to produce high-quality channel waveguides with very smooth surfaces. The propagation loss of the channel waveguides was 0.50 and 0.70 dB/cm at the monitoring light of 1550 nm for TE and TM polarizations, respectively
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
Quantum waveguide theory for triply connected Aharonov-Bohm rings
No full textQuantum interference effects for a mesoscopic loop with three leads are investigated by using a one-dimensional quantum waveguide theory. The transmission and reflection probabilities are analytically obtained in terms of the magnetic flux, arm length, and wave vector. Oscillation of the magnetoconductance is explicitly demonstrated. Magnetoconductance is found to be sharply peaked for certain localized values of flux and kl. In addition, it is noticed that the periodicity of the transmission probability with respect to kl depends more sensitively on the lead position, compared to the case of the two-lead loop
Isolation of neuronal precursors from differentiating P19 embryonal carcinoma cells by neuronal T alpha 1-promoter-driven GFP
No full textThe induction of pluripotent P19 embryonal carcinoma (EC) cells with retinoic acid results in their differentiation into cells that resemble neurons, glia, and fibroblasts. To isolate and enrich the developing neurons from heterogeneously differentiating P19 EC cells, we used a recently introduced protocol combining the expression of green fluorescent protein (GFP) driven by a tissue-specific promoter and fluorescence-activated cell sorting. Cells were transfected with the gene for GFP, which is under the control of the neuronal Tal tubulin promoter. After four days of retinoic acid treatment, GFP was specifically detected in cells undergoing neuronal differentiation. Sorting of fluorescent differentiating P19 EC transfectants yielded populations highly enriched in neuronal precursors and neurons. Immunoreactivity for nestin and neurofilament was observed in 80 and 25% of the sorted cell population, respectively. These results demonstrate that differentiated neuronal precursor cells can be efficiently isolated from differentiating pluripotent embryonic cells in vitro, suggesting that this method can reproducibly provide homogeneous materials for further studies on neurogenesis. (C) 2001 ISDN. Published by Elsevier Science Ltd. All rights reserved
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
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