1,720,975 research outputs found
Positron Impact Electronic Excitation Of N2
No full textWe present the results of scattering cross sections for positron impact excitation of electronic states of nitrogen molecule (N2) using the Schwinger multichannel method (SMC). All calculated cross sections took three collision channels into account (X1Σg and degenerate a1Πg states). Present theoretical results for excitation to the a1Πg states failed to reproduce the near-threshold structure observed in the recent and the only available experimental data [Sullivan et al., Phys. Rev. Lett. 87 (2001) 073201-1]. Scattering calculations from the a1Πg states (elastic and superelastic) are also reported. A spurious resonant structure found in the excitation to the a1Πg states was detected in a square integrable basis set calculation designed to reproduce the first Born approximation (FBA). Such spurious structure was removed by taking out the trial configuration state functions in which the positron was weakly coupled to the target. This may be a promising technique to separate unphysical resonances from the physical ones. We also observe that a combination between SMC scattering amplitudes (l≤2) with FBA ones (l≥3) significantly improved the cross sections at higher energies. © 2004 Elsevier B.V. All rights reserved.2211-46975Gilbert, S.J., Sullivan, J.P., Greaves, R., Surko, C.M., (2000) Nucl. Instr. and Meth. B, 171, p. 81Sullivan, J.P., Marler, J.P., Gilbert, S.J., Buckman, S.J., Surko, C.M., (2001) Phys. Rev. Lett., 87, pp. 073201-073211Sullivan, J.P., Gilbert, S.J., Surko, C.M., (2001) Phys. Rev. Lett., 86, p. 1494Surko, C.M., (2001) New Directions in Antimatter Chemistry and Physics, p. 345. , Kluwar Academic PublishersMurphy, T.J., Surko, C.M., (1992) Phys. Rev. A, 46, p. 5695Greaves, R.G., Tinkle, M.D., Surko, C.M., (1994) Phys. Plasmas, 1, p. 1439Germano, J.S.E., Lima, M.A.P., (1993) Phys. Rev. A, 47, p. 3976Da Silva, E.P., Germano, J.S.E., Lima, M.A.P., (1994) Phys. Rev. A, 49, pp. R1527Da Silva, E.P., Germano, J.S.E., Lima, M.A.P., (1996) Phys. Rev. Lett., 77, p. 1028Da Silva, E.P., Germano, J.S.E., Lino, J.L.S., De Carvalho, C.R.C., Natalense, A.P.P., Lima, M.A.P., (1998) Nucl. Instr. and Meth. B, 143, p. 140De Carvalho, C.R.C., Varella, M.T.D.N., Da Silva, E.P., Germano, J.S.E., Lima, M.A.P., (2000) Nucl. Instr. and Meth. B, 171, p. 33Hunt, W.J., Goddard III, W.A., (1974) Chem. Phys. Lett., 24, p. 464Sullivan, J.P., Gilbert, S.J., Buckman, S.J., Surko, C.M., (2001) J. Phys. B, 34, pp. L467Bromley, M.W.J., Mitroy, J., (2003) Phys. Rev. A, 67, p. 062709Rescigno, T.N., (2003), private communicationSzabo, A., Ostlund, N.S., (1989) Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory, , New York: McGraw-Hil
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
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
The Buffer-Gas Positron Accumulator and Resonances in Positron-Molecule Interactions
Get PDFThis is a personal account of the development of our buffer-gas positron trap and the new generation of cold beams that these traps enabled. Dick Drachman provided much appreciated advice to us from the time we started the project. The physics underlying trap operation is related to resonances (or apparent resonances) in positron-molecule interactions. Amusingly, experiments enabled by the trap allowed us to understand these processes. The positron-resonance "box score" to date is one resounding "yes," namely vibrational Feshbach resonances in positron annihilation on hydrocarbons; a "probably" for positron-impact electronic excitation of CO and NZ;an d a "maybe" for vibrational excitation of selected molecules. Two of these processes enabled the efficient operation of the trap, and one almost killed it in infancy. We conclude with a brief overview of further applications of the trapping technology discussed here, such as "massive" positron storage and beams with meV energy resolution
Dispelling 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
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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