131,546 research outputs found
Michel de L’Hospital chancelier-poète, sous la direction de Perrine Galand-Willemen et Loris Petris
No full textRecensione del volume Michel de L’Hospital chancelier-poète, sous la direction de Perrine Galand-Willemen et Loris Petri
Charles D. Perrine y el “gran debate” de la astronomía a comienzos del siglo XX
No full textEn 1920, en la Academia de Ciencias de los Estados Unidos, se presentó un debate público en torno a las escalas del universo entre Heber D. Curtis del Observatorio Lick y Harlow Shapley del Observatorio de Mount Wilson. En este debate participaron numerosos astrónomos quienes adoptaron diversas posiciones al respecto. La presente investigación se halla en curso y se centra en dilucidar cuál era la postura de Charles D. Perrine, director del Observatorio Nacional Argentino (1909-1936). Precisamente, se intenta mostrar algunas influencias epistémicas de tal controversia en ciertas investigaciones astrofísicas de Perrine en Córdoba. Como fuentes importantes para esta investigación histórica, se ha considerado la correspondencia de 1920 y de 1921, entre Perrine, Curtis y William W. Campbell (director del Observatorio Lick). Asimismo, se ha analizado documentación existente en los archivos del Museo del Observatorio Astronómico (MOA) de la Universidad Nacional de Córdoba (UNC).In 1920, a public debate on the scales of the universe was held, at the Academy of Sciences of the United States of America, between Heber D. Curtis of Lick Observatory and Harlow Shapley of Mount Wilson Observatory. Many astronomers participated in this debate and adopted different positions in relation to that matter. The present research is being carried out and focuses on elucidating the position of Charles D. Perrine, director of the Argentine National Observatory (1909-1936). Precisely, an attempt is made to show some epistemic influences of such controversy in certain astrophysical investigations of Perrine in Córdoba. As important sources for this historical research, the letters of 1920 and 1921 among Perrine, Curtis and William W. Campbell (director of the Lick Observatory) have been considered. Several documents, available within the files of the Museum of the Astronomical Observatory (MOA) of the National University of Córdoba (UNC), have been analysed.Asociación Argentina de Astronomí
Lick Observatory Belletin, n° 102. — Preliminary note on some simplifications in the reduction of stellar photographs, by C.-D. Perrine
No full textLick Observatory Belletin, n° 102. — Preliminary note on some simplifications in the reduction of stellar photographs, by C.-D. Perrine. In: Bulletin astronomique, tome 24, 1907. p. 199
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Embriogênese somática em Agave sisalana Perrine: indução, caracterização anatômica e regeneração
No full textSisal (Agave sisalana Perrine) is used for the extraction of fibers present in their leaves, being considered the main hard fiber produced in the world. However, a decline has been observed for this crop, due to a disease caused by the soil fungus Aspergillus niger. Biotechnology, particularly tissue culture techniques, represents a viable alternative for propagating this species. Among these techniques, the somatic embryogenesis can be pointed out. Thus, this study aimed to characterize the in vitro morphogenesis, during somatic embryogenesis, in A. sisalana Perrine. In all experiments, bulblets were used as explants and also ½ MS medium plus sucrose (30.0 g L-1), solidified with agar (7.0 g L-1) supplemented with different concentrations of auxin and cytokinin. The explants formed callus with compact and semi-compact aspects, pointing out the embryogenic cells converted into somatic embryos with the use of 2,4-D and BAP. The anatomic analyzes showed embryos in globular and torpedo stages and no connection with the mother callus.O sisal (Agave sisalana Perrine) é utilizado para a extração das fibras contidas em suas folhas, sendo a principal fibra dura produzida no mundo. Entretanto, tem sido observado um declínio dessa cultura, devido a uma doença causada pelo fungo de solo Aspergilus niger. A biotecnologia, em especial as técnicas de cultura de tecidos, representa uma alternativa viável para a propagação dessa espécie. Dentre essas técnicas, está a embriogênese somática e, nesse sentido, este estudo objetivou caracterizar a morfogênese in vitro, durante a embriogênese somática, em A. sisalana Perrine. Em todos os experimentos, utilizaram-se bulbilhos como explantes e meio de cultura MS½ acrescido de sacarose (30,0 g L-1), solidificado com ágar (7,0 g L -1) suplementado com diferentes concentrações de auxinas e citocininas. Os explantes formaram calos com aspectos compactos e semicompactos, evidenciando células embriogênicas que se converteram em embriões somáticos, com o uso de 2,4-D e BAP. Por meio das análises anatômicas, pôde-se observar embriões em estádios globular e torpedo e a não conexão com o calo mãe
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
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