1,721,168 research outputs found
Tax Sensitivity and Home State Preferences in Internet Purchasing
Full text linkData on memory modules sales are used to explore aspects of e-retail demand. Aggregate sales are examined in state-level regressions. Discrete choice techniques are used to examine (incomplete) hourly sales data from a price comparison site. We find a strong relationship between e-retail sales to a given state and sales tax rates that apply to purchases from offline retailers, suggesting substantial online-offline substitution and the importance of tax avoidance motives. Geography matters in two ways: consumers prefer purchasing from firms in nearby states and appear to have a separate preference for buying from in-state firms.Center for Advanced Study in the Behavioral Sciences (Stanford, Calif.)Hoover Institution on War, Revolution, and PeaceInstitute for Advanced Study (Princeton, N.J.)Toulouse Network for Information TechnologyNational Science Foundation (U.S.) (SES-0219205)National Science Foundation (U.S.) (SES-0550897
Interacting galaxies in the IllustrisTNG simulations -- IV: Enhanced Supermassive Black Hole Accretion Rates in Post-Merger Galaxies
Full text linkWe present an analysis of the instantaneous supermassive black hole (SMBH)
accretion rates in a collection of 1563 post-merger galaxies drawn from the
IllustrisTNG simulation. Our sample consists of galaxies that have experienced
a merger in the last simulation snapshot (within ~160 Myrs of coalescence) in
the redshift range 01:10 and post-merger
stellar masses > . We find that, on average, the accretion
rates of the post-mergers are ~1.7 times higher than in a control sample and
that post-mergers are 3-4 times more likely to experience a luminous active
galactic nuclei (AGN) phase than isolated galaxies. SMBH accretion rate
enhancements persist for ~2 Gyrs after coalescence, significantly exceeding the
~500 Myr lifetime of star formation rate enhancements. We find that the
presence of simultaneous enhancements in both the star formation and SMBH
accretion rates depends on both the mass ratio of the merger and on the gas
mass of the post-merger galaxy. Despite these accretion rate enhancements, only
~35% of post-mergers experience a luminous AGN ( erg/s) within
500 Myrs after coalescence, and fewer than 10\% achieve a luminosity in excess
of erg/s. Moreover, only ~10\% of the highest luminosity
( erg/s) AGN in the IllustrisTNG galaxy sample are recent
mergers. Our results are therefore consistent with a picture in which mergers
can (but don't always) trigger AGN activity, but where the majority of galaxies
hosting high luminosity AGN are not recent mergers.Comment: This article has been accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Strategic Entry Deterrence and the Behavior of Pharmaceutical Incumbents Prior to Patent Expiration
Full text linkThis paper develops a new approach to testing for strategic entry deterrence and applies it to the behavior of pharmaceutical incumbents before patent expiration. It examines a cross section of markets, determining whether behavior is nonmonotonic in market size. Under some conditions, investment levels will be monotone in market size if firms do not invest to deter entry. Strategic investments to deter entry, however, may result in nonmonotonic investment because they are unnecessary in small markets, and impossible in large ones. Consistent with an entry-deterrence motivation is the finding that incumbents in medium-sized markets advertise less prior to patent expiration. (JEL D92, G31, L11, L21, L65)Hoover Institution on War, Revolution, and PeaceAlfred P. Sloan FoundationNational Science Foundation (U.S.) (grant SES-0550897)National Science Foundation (U.S.) (grant SES-0219205)National Science Foundation (U.S.) (grant SES-9818534
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
Interacting galaxies in the IllustrisTNG simulations - III. (The rarity of) quenching in post-merger galaxies
Full text linkGalaxy mergers are traditionally one of the favoured mechanisms for the transformation of spiral galaxies to spheroids and for quenching star formation. To test this paradigm in the context of modern cosmological simulations, we use the IllustrisTNG simulation to investigate the impact of individual merger events on quenching star formation [i.e. star formation rate (SFR) at least 3σ below the star-forming main sequence] within 500 Myr after the coalescence phase. The rate of quenching amongst recently merged galaxies is compared with a control sample that is matched in redshift, stellar mass, SFR, black hole mass, and environment. We find quenching to be uncommon among the descendants of post-merger galaxies, with only ∼5 per cent of galaxies quenching within 500 Myr after the merger. Despite this low absolute rate, we find that quenching occurs in post-mergers at twice the rate of the control galaxies. The fraction of quenched post-merger descendants 1.5 Gyr after the merger become statistically indistinguishable from that of non-post-mergers, suggesting that mergers could speed up the quenching process in those post-mergers whose progenitors had physical conditions able to sustain effective active galactic nuclei (AGN) kinetic feedback, thus capable of removing gas from galaxies. Our results indicate that although quenching does not commonly occur promptly after coalescence, mergers none the less do promote the cessation of star formation in some post-mergers. We find that, in IllustrisTNG, it is the implementation of the AGN kinetic feedback that is responsible for quenching post-mergers, as well as non-post-merger controls. As a result of the released kinetic energy, galaxies experience gas loss and eventually they will quench. Galaxies with an initially low gas fraction show a preferable pre-disposition towards quenching. The primary distinguishing factor between quenched and star-forming galaxies is gas fraction, with a sharp boundary at fgas ~ 0.1 in TNG
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