1,721,122 research outputs found
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
Water in protoplanetary disks: Line flux modeling and disk structure
Full text linkProtoplanetary disks are the places in which planets form around young stars. These environments consist of dust and gas mainly in forms of molecules. Simple and abundant molecules such as water, carbon monoxide, ammonia, play an important role in the disk thermal balance, and allow also observers to study these objects. Water is an abundant molecule with a rich spectroscopy in the entire IR spectral regime. It can be used to probe local gas physical conditions from the inner through the outer disk. Observations of water show often non-detections for still unclear reasons. With this thesis we suggest an explanation based on the physical properties of individual protoplanetary disks, their central star and mid-IR dust spectral features. Finally we investigate the hidden reservoirs of water and other volatile species frozen in the coldest regions of the disk. We conclude that opacity due to the dust is one of the main causes for the suppression of both mid-IR and far-IR water lines in disks. Disks around more luminous central stars from modeling, should have stronger mid-IR water lines, but the stronger continuum produced by the warmer dust buries the lines. We also found that the presence of stronger mid-IR water line fluxes can be consistent with disks depleted in dust or enhanced in gas abundance in the innermost regions. Finally, time-dependent chemistry is not important in the evolution for the two-dimensional distribution of water and other ices in disks after 100.000 yrs
CO ro-vibrational emission: tracing the geometry of the inner protoplanetary disc
Full text linkBij de geboorte van een ster wordt deze omhuld door een schijf van stof en gas. Omdat we verwachten dat planeten hierin vormen, worden ze protoplanetaire schijven genoemd. Wanneer een planeet zich vormt verwachten we dat, door dynamische effecten, het materiaal dichtbij de baan van de planeet geleidelijk wordt weggeveegd. Dit zou tot gaten en kloven in de schijf kunnen leiden. CO (koolstofmonoxide) is het op één na meest voorkomende molecuul in het universum en is daarom ook veelvuldig aanwezig in deze schijven. De vibratie-rotatie lijn transities van het CO-molecuul worden regelmatig in de warme binnenste gebieden van protoplanetaire schijven geobserveerd. CO emissielijnen zouden dus uitermate geschikt zijn voor het vinden van gaten/kloven die zijn ontstaan door de vorming van een planeet. Met behulp van spectra geobserveerd met de VLT (Very Large Telescope) in Chili, en gedetailleerde computermodellen van zulke schijven, hebben we onderzocht hoe de CO vibratie-rotatie emissielijnen afkomstig van protoplanetaire schijven het beste gebruikt kunnen worden om de formatieprocessen van planeten te volgen. We hebben ontdekt dat CO vibratie-rotatie lijnprofielen met hoge resolutie en nabij-infrarood spectra met een hoge signaal/ruis verhouding de locatie van kloven in protoplanetaire schijven kunnen onthullen. Door de flux, breedte en vorm van deze lijnprofielen te bestuderen kunnen we kloven in het stof, kloven in het stof en gas, of ongebruikelijk ver uitgestrekte gebieden identificeren. Als de geometrie van het binnenste deel van de schijf onduidelijk is bij observaties van alleen het stof, kunnen we deze gebieden veel gedetailleerder kenmerken met de analyse van CO vibratie-rotatie lijnprofielen. Toekomstige instrumenten van de ELT, zoals METIS, zouden uitermate geschikt zijn om te gebruiken voor dit soort studies
High energy irradiated protoplanetary disks : the X-rays and FUV role in thermo-chemical modeling
Full text linkIn de laatste twee decennia hebben sterrenkundigen een enorme hoeveelheid informatie kunnen vergaren over het scenario waarin leven kan ontstaan. Onderzoek naar de vorming van planeten speelt daarin een belangrijke rol.
Het proces van stervorming begint in donkere wolken (Dark Clouds) waar gravitationele ineenstorting leidt tot de formatie van een schijf die de ster omgeeft, de zogenaamde circumstellar schijf. Die kan materiaal (gas en stof) bevatten waaruit planeten ontstaan. Er is dan sprake van een protoplanetaire schijf. Giambattista Aresu onderzocht de impact van hoog energetische straling (röntgenstraling en ver-uv) van de centrale ster op de chemische en thermische structuur van dergelijk omringende protoplanetaire schijven.
Since the dawn of time, men has directed his sight to the sky, addressing there his very first existential questions. Among the fundamental dilemmas, the one that is most closely related to the human kind is: where does life come from? As never before, we might be fully equipped to answer this question.
In the last two decades we have indeed been able to collect an enormous amount of information about the scenario where life similar to ours is supposed to sprout: the planets.
The star formation process starts in dark clouds, where gravitational collapse leads to the formation of a circumstellar disk.
In the still ongoing infrared (IR) satellites era, we do observe these disks of gas and dust in orbit around pre-main sequence stars (PMS), the so called protoplanetary disks: these are the birth places of the planets.
The study of newly discovered disks and extrasolar systems provides otherwise inaccessible data on the conditions that probably led to the formation of our own planetary system.
In this thesis I studied the impact that high energy radiation (X-rays and FUV) from the central star has on the chemistry and thermal structure of the surrounding protoplanetary disk.
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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