325,696 research outputs found
Edwin Henry Spanier (1921-1996)
No full textThis paper presents a major and difficult decidability result in grammar form theory. It is proved that, given two arbitrary context-free grammar forms, it is decidable whether or not the family of one is contained in the other. This leads immediately to the decidability of the equality of two context-free grammar forms." This result is based on an earlier paper, "A prime decomposition theorem for grammatical families ", in which the same authors obtained a prime decomposition for formal language families, closely analogous in form to the decomposition of whole numbers into prime factors. Spanier's publications, as were his lectures, are characterized by unusual lucidity and precision and an even rarer quality of naturalness and simplicity. No matter how complex the subject, at the end the reader feels the theorems are the right ones, the hypotheses natural, and the methods as simple as possible. Ed Spanier will be remembered as a gifted researcher, an inspiring teacher, an able administrator, and as a modest, friendly, wise, and helpful colleague
A numerical model of parsec-scale SSC morphologies and their radio emission
No full textIn current models for jets of active galactic nuclei and their emission a shortcoming in the description and understanding of the connection between the largest and smallest scales exists. In this work we present a spatially resolved synchrotron self-Compton model extended to parsec scales, which opens the possibility of probing the connections between the radio and high-energy properties. We simulate an environment that leads to Fermi-I acceleration of leptonic particles and includes the full time dependence of this process. Omitting the restriction of a finite downstream region, we find that the spectral energy distribution produced by the accelerated particles strongly depends on their radial confinement behind the shock. The requirement, for both the restriction of high-energy emission to a small region around the shock and the production of a flat radio spectrum, is an initial linear increase of the radius immediately behind the shock, which then slows down with increasing distance from the shock. A good representation of the data for the blazar Mrk 501 is achieved by a parameterized log function. The prediction for the shape of the radio blob is given by the flux distribution with respect to shock distanc
AGN neutrino flux estimates for a realistic hybrid model
No full textRecent reports of possible correlations between high energy neutrinos observed by IceCube and Active Galactic Nuclei (AGN) activity sparked a burst of publications that attempt to predict the neutrino flux of these sources. However, often rather crude estimates are used to derive the neutrino rate from the observed photon spectra. In this work neutrino fluxes were computed in a wide parameter space. The starting point of the model was a representation of the full spectral energy density (SED) of 3C 279. The time-dependent hybrid model that was used for this study takes into account the full pγ reaction chain as well as proton synchrotron, electron-positron-pair cascades and the full SSC scheme. We compare our results to estimates frequently used in the literature. This allows to identify regions in the parameter space for which such estimates are still valid and those in which they can produce significant errors. Furthermore, if estimates for the Doppler factor, magnetic field, proton and electron densities of a source exist, the expected IceCube detection rate is readily availabl
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Considering Gay Penguins: Gender and Sexuality Politics in the Zoo
No full textEbeling S, Spanier B. Considering Gay Penguins: Gender and Sexuality Politics in the Zoo. In: Ernst W, ed. Internationale Frauen- und Genderforschung in Niedersachsen. Teilband 6: Ethik – Geschlecht – Medizin. Körpergeschichten in politischer Reflexion. Focus gender. Vol 14. Berlin: Lit; 2010: 187-205
What made those Penguins Gay? Gender and Sexuality Politics in the Zoo
No full textEbeling S, Spanier B. What made those Penguins Gay? Gender and Sexuality Politics in the Zoo . In: Fisher JA, ed. Gender and the Science of Difference. Cultural Politics of Contemporary Science and Medicine. Studies in modern science, technology, and the environment. New Brunswick, NJ: Rutgers Univ. Press; 2011: 126-144
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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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