1,721,884 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
Short-term patency of 1 mm diameter PTFE prosthesis: an angiographic, Doppler-flowmetric and morphological experimental study
No full textExpanded polytetrafluoroethylene (PTFE) prostheses may be used in peripheral
vascular surgery. Due to contradictory results on patency rate and neointimal
formation, the effectiveness of this kind of prosthesis in small caliber artery
reconstruction is still under discussion. In order to evaluate the effectiveness
of this technique 1 mm internal diameter PTFE prosthesis (fibril length 35
microm) interposed in rabbit femoral artery, for 15 and 30 days, were studied
functionally and morphologically. Doppler was performed during surgery, at day 2,
15 and 30. Arteriography was carried out at day 1. Light microscopy and scanning
electron microscopy were performed on prosthesis sampled at day 15 and 30.
Doppler flowmetry showed the full patency in all PTFE prosthesis. Angiography
confirmed that all PTFE grafts were patent after 24 h. Doppler flowmetry,
performed after 15 and 30 days, showed a reducing patency rate respectively at
70% (21 grafts) and 60% (18 grafts). Morphological studies showed that
endothelial lining was not present at 15 day. After 30 days proliferation of
blood cells occurred in the graft wall. Lumina presented a fibrous lining and did
not show significant endothelial cell growths. These results confirm that PTFE
prosthesis represents a suitable alternative to biological graft for the repair
of small caliber artery when the latter are not available. Autologous vein is the
vascular substitute of choice for peripheral vascular reconstruction, and PTFE
prosthesis may be quite successfully used as a secondary choice, when multiple
reconstruction are needed and biological grafts are not sufficien
"Il costo della modernità urbana afroamericana. Mammy (1940) di Dorothy West”
No full textDorothy West (1907-1998), Helene Johnson (1905-1995) e Zora Neale Hurston (1890-1960) si incontrano a New York nel 1926, dando inizio a una lunga amicizia e a una comunità letteraria che durano nel tempo. Hurston, ancora oggi la più nota e rappresentativa autrice del Rinascimento di Harlem, viene di solito considerata in splendido isolamento, o in opposizione a talenti della giovana avanguardia urbana come Johnson. Nina Miller ha per esempio sostenuto l’utilità di mettere da parte Hurston a favore di poetesse come Johnson o Gwendolyn Brooks, per avere un quadro più vero della letteratura femminile e modernista del Rinascimento di Harlem. Il motivo che aveva reso Hurston protagonista di una riscoperta negli anni Ottanta – la creazione di un’arte nera autentica perché derivata dal folclore afroamericano del Sud – è ciò che nei più recenti lavori critici la esclude dal modernismo urbano nero. Quel che invece ha finora reso West poco appetibile come scrittrice afroamericana – la moderata presenza di motivi folclorici – è l’aspetto tematico che le ha regalato una certa attenzione da parte della critica più recente. La riscoperta di West è avvenuta cioè trascurando alcuni dati (la famiglia benestante in cui nasce a Boston, i personaggi borghesi, lo stile attento), ed enfatizzando la presenza sotterranea di una vena popolare e folclorica, ereditata dalla madre, che colloca la scrittrice al margine dell’autentica tradizione letteraria nera statunitense.
L’incontro casuale a New York di West, Johnson e Hurston, tre donne e artiste diversissime tra loro, durante il Rinascimento di Harlem, rappresenta l’inizio simbolico di un lavoro comune su ciò che il critico afroamericano Houston Baker Jr. ha definito il contributo della modernità nera statunitense: il contatto tra la cultura folclorica del Sud e il contesto urbano del Nord. E se Hurston è fondamentale dal punto di vista teorico e ideologico – per l’elaborazione di una cornice interpretativa del folclore tratta da quello stesso materiale “grezzo” – e dal punto di vista pratico (l’uso letterario del Black English), Johnson riveste un interesse limitato dal fatto che ha pubblicato pochissimo, West racconta le storie di quel contatto, sottolineando quanto rimane fuori, inassimilato dal processo centripeto della modernizzazione. Il residuo che resta a margine, la mammy del racconto omonimo di West, riporta sulla scena della modernità urbana americana la schiavitù e il tabù nazionale su cui il sistema si fondava: il divieto di attraversare la linea del colore che divide i bianchi dai neri
Ultrastructural characteristics of human granulosa cells in a coculture system for in vitro fertilization
No full textThe use of somatic cells for cocultures during in vitro fertilization (IVF) is
currently finalized to obtain a higher number of healthy and viable embryos with
a high potential of implantation. Among the different cell lines that can be used
as feeder cells for cocultures, granulosa cells (GCs) are autologous cells, safe
and easy to recover. The aim of the present study was to analyze the fine
structure of human GCs used in a coculture system to evaluate, from a
morphodynamic point of view, their role in supporting embryo development. GCs
were collected during oocyte pick-up, 36 h after human chorionic gonadotropin
administration, from patients undergoing IVF procedures, who had given their
informed consent to be included in this protocol. After coculture, GCs were fixed
and processed for light microscopy (LM) and transmission electron microscopy
(TEM). By LM, GCs appeared as clusters of loosely packed cells, irregularly
rounded or polyhedral in shape, varying in diameter from 18 to 25 microm. Mitotic
cells, as well as regressing elements (with pyknotic nuclei or dense cytoplasm)
and cell fragments were occasionally observed. By TEM, the plasma membrane was
irregular due to the presence of cytoplasmic evaginations. Linear and annular gap
junctions between neighboring GCs were found. GC nuclei, rounded and
eccentrically located, contained finely dispersed chromatin, one (often two)
prominent nucleoli and, infrequently, peripheral patches of heterochromatin.
Numerous organelles populated the GC cytoplasm, among them, mitochondria were
rod-shaped or elongated, usually provided with tubular-vesicular cristae but
occasionally showing atypical, longitudinally oriented cristae. Membranes of
smooth endoplasmic reticulum, Golgi stacks and vesicles, secretory-like granules,
cisternae of rough endoplasmic reticulum (RER), free ribosomes and polysomes,
lysosomal-like bodies, microfilaments, and lipid droplets were also seen in the
GC cytoplasm. In most cells, RER was scarcely represented and numerous lipid
droplets filled the perinuclear space. On the contrary, some GCs contained an
abundant RER and rare lipid droplets scattered in the cytoplasm. In conclusion,
our data demonstrated the presence, in a coculture system, of GCs provided with
ultrastructural characteristics typical of healthy, metabolically active, mostly
steroidogenic cells. Protein-synthetic cells have also been detected. These data,
evaluated at the light of biochemical and clinical studies, sustain the
capability of human GCs cocultures to positively affect early embryo development
in vitro by the secretion of steroids and proteins, putative "embryotrophic"
factor
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