1,720,956 research outputs found
Quasi-frozen orbits around a slowly rotating asteroid
No full textThe purpose of this study is to identify orbits with quasi-constant orbital elements around a slowly rotating asteroid. To this end, a recurrence approach has been developed to formulate the high-order averaged disturbing potential. The order of the model can be determined based on the irregularity of the asteroid and the required accuracy. The proposed approach presents significant advantages in studying long-term behaviors around asteroids where the second degree and order gravity model fails or does not work well. The averaged model has been applied to an ellipsoid-shaped asteroid, and families of nearly circular orbits with constant inclination and longitude of the ascending node in the body-fixed frame have been determined, as functions of semimajor axis, inclination, and rotation period of the asteroid. Finally, by transforming the mean elements into the corresponding osculating elements, the obtained frozen solutions have been propagated in the full model, where they become quasi-frozen
Stable orbits for lunar landing assistance
No full textTo improve lunar landing performances in terms of mission costs, trajectory determination and visibility the use of a single probe located over an assistance orbit around the Moon has been taken into consideration. To this end, the properties of two quasi-circular orbits characterised by a stable behaviour of semi-major axis, eccentricity and inclination have been investigated. The analysis has demonstrated the possibility of using an assistance probe, located over one of these orbits, as a relay satellite between lander and Earth, even in the case of landings on the far side of the Moon. A comparison about the accuracy in retrieving the lander's state with respect to the use of a probe located in the Lagrangian point L2 of the Earth-Moon system has also been carried out
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
Emergency reversal of anticoagulation with vitamin K antagonists with 3-factor prothrombin complex concentrates in patients with major bleeding
No full textMajor bleeding is a serious and potentially fatal complication of treatment with vitamin K antagonists (VKAs). Prothrombin complex concentrates (PCCs) can substantially shorten the time needed to reverse VKA effects. To determine the efficacy and safety of 3-factor PCCs for the rapid reversal of VKAs in patients with major bleeding. Patients receiving VKAs and suffering from acute major bleeding were eligible for this prospective cohort study if their international normalized ratio (INR) was higher than or equal to 2.0. Stratified 35-50 IU kg(-1) PCC doses were infused based on initial INR. A total of 126 patients (62 males; mean age: 74 years, range 37-96 years) were enrolled. The mean INR at presentation was 3.3 (range 2-11). At 30 min after PCC administration the mean INR was 1.4 (range: 0.9-3.1), declining to less than or equal to 1.5 in 75 % of patients. The benefit of PCC was maintained for a long time, since in 97 % of all post-infusion time points through 96 h the mean INR remained lower than or equal to 1.5 (mean: 1.19; range: 0.9-2.3). During hospitalization neither thrombotic complications nor significant adverse events were observed and 12 patients died (10 %); none of the deaths was judged to be related to PCC administration. 3-factor PCC administration is an effective, rapid ad safe treatment for the urgent reversal of VKAs in patients with acute major bleeding. Broader use of PCC in this clinical setting appears to be appropriate
Emergency reversal of anticoagulation with vitamin K antagonists with 3-factor prothrombin complex concentrates in patients with major bleeding
No full textMajor bleeding is a serious and potentially fatal complication of treatment with vitamin K antagonists (VKAs). Prothrombin complex concentrates (PCCs) can substantially shorten the time needed to reverse VKA effects. To determine the efficacy and safety of 3-factor PCCs for the rapid reversal of VKAs in patients with major bleeding. Patients receiving VKAs and suffering from acute major bleeding were eligible for this prospective cohort study if their international normalized ratio (INR) was higher than or equal to 2.0. Stratified 35-50 IU kg-1 PCC doses were infused based on initial INR. A total of 126 patients (62 males; mean age: 74 years, range 37-96 years) were enrolled. The mean INR at presentation was 3.3 (range 2-11). At 30 min after PCC administration the mean INR was 1.4 (range: 0.9-3.1), declining to less than or equal to 1.5 in 75 % of patients. The benefit of PCC was maintained for a long time, since in 97 % of all post-infusion time points through 96 h the mean INR remained lower than or equal to 1.5 (mean: 1.19; range: 0.9-2.3). During hospitalization neither thrombotic complications nor significant adverse events were observed and 12 patients died (10 %); none of the deaths was judged to be related to PCC administration. 3-factor PCC administration is an effective, rapid ad safe treatment for the urgent reversal of VKAs in patients with acute major bleeding. Broader use of PCC in this clinical setting appears to be appropriate
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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