1,720,979 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
The influence of hypoxia in erythropoiesis and morphology of red blood cells in sickle cell disease and hereditary spherocytosis.
Full text linkDie Lebensfahigkeit menschlicher Zellen h ¨ angt in hohem Maße vom Sauerstoff ab, der von den roten ¨
Blutkorperchen transportiert und zur Verf ¨ ugung gestellt wird. In dieser Arbeit wird untersucht, wie ¨
Sauerstoff die Physiologie und Pathophysiologie jener roten Blutkorperchen beeinflusst. Die Arbeit ¨
ist in zwei wesentliche Teile gegliedert.
Zunachst werden Ergebnisse einer gr ¨ oßeren Studie mit Probanden vorgestellt, die in großer H ¨ ohe ¨
(3450 m) durchgefuhrt wurde. In dieser H ¨ ohe sorgt der reduzierte Luftdruck f ¨ ur eine Abnahme ¨
der Sauerstoffsattigung im Blut und f ¨ uhrt so zu einer erh ¨ ohten Produktion an roten Blutk ¨ orperchen ¨
(Erythropoese). Nach der Ruckkehr aus großer H ¨ ohe f ¨ allt die Zahl an roten Blutk ¨ orperchen nach ¨
kurzer Zeit wieder auf das vorherige Niveau Es ist bislang nicht verstanden, ob die neugebildeten
roten Blutzellen dazu abgebaut werden. Der hyptothetische Mechanismus der Neozytolyse (engl.
Neocytolisis) geht davon aus, dass ausgerechnet die neu gebildeten, roten Blutzellen als erste wieder
abgebaut werden, wenn die Ruckkehr auf Meeresniveau erfolgt. Die wissenschaftliche Fragestellung, ¨
die im Rahmen dieser Studie beantwortet wurde, ist, ob und in welchem Maß Neocytolyse nach einem
3-wochigen Aufenthalt in großer H ¨ ohe stattfindet. Dazu wurden zun ¨ achst Untersuchungen an aller ¨
Probanden mittels in-vitro Zellkulturen durchgefuhrt, um sowohl die Erythropoese als auch (neu ent- ¨
standende) Retikulozyten zu charakterisieren. Die Ergebnisse zeigen eine beschleunigte Reifung der
Vorlauferzellen in Zellkulturen bei niedrigerem Sauerstoffgehalt (3%) verglichen mit normaler Atmo- ¨
sphare (20%) und eine unerwartet verbesserte ¨ Uberlebensrate der Retikulozyten. Dies stimmt mit dem ¨
Ergebnis der Studie uberein, dass nach der R ¨ uckkehr von der gew ¨ ahlten H ¨ ohe keine Neozytolyse, d.h. ¨
kein bevorzugter Abbau von neu gebildeten roten Blutzellen, auftrat, was die Hypothese eines selektiven, vorzeitigen Abbaus von unreifen roten Blutzellen widerlegt. Weiterhin wurde in der Zellkultur
unter verringerter Sauerstoffgabe eine erhohte Zahl bikonkaver Zellen beobachtet, was eine typische ¨
Gestalt fur einen fortgeschrittenen Reifegrad ist. Diese Beobachtung k ¨ onnte ein Anhaltspunkt daf ¨ ur¨
sein, dass der Reifeprozess von roten Blutzellen durch die Reduzierung des atmospharischen Sauer- ¨
stoffgehaltes begunstigt werden kann. Im Rahmen dieser Arbeit wurde zus ¨ atzlich ein Protokoll zur ¨
Isolation der Retikulozyten vom Vollblut der Probanden entwickelt, um die pure Zell-RNA jeweils
vor und in großer Hohe zu sequenzieren. Jedoch muss die Ausbeute an RNA weiter optimiert werden, ¨
um einen detaillierten Vergleich der Gen-Expressions-Niveaus anstellen zu konnen. ¨
Der zweite Teil der Arbeit konzentriert sich auf die Untersuchung der Morphologie der roten Blutkor- ¨
perchen bei zwei Arten von Anamie. Aufgrund der hohen Empfindlichkeit der roten Blutk ¨ orperchen ¨
gegenuber Formvariationen, mussten die Proben vor jeder experimentellen Manipulation fixiert wer- ¨
den. Dazu musste ein angemessenes Verfahren entwicklelt werden, das im Rahmen dieser Arbeit
vorgestellt wird. Zunachst wird auf die Sichelzellenan ¨ amie eingegangen, bei der es unter Desoxy- ¨
genierung des Hamoglobins zur starken Verformung der roten Blutk ¨ orperchen (Sichelzellen) kommt. ¨
Dies beintrachtigt sowohl deren Funktion als auch Lebensdauer. Eine quantitative Analyse von Zell- ¨
Projektionsbildern aus konfokalen Mikroskopieaufnahmen wurde mit Hilfe eines maßgeschneiderten
Computerprogramms im Rahmen einer klinischen Pilotstudie der Phase II zur Therapie der Sichelzellanamie durchgef ¨ uhrt. Es konnte gezeigt werden, dass diese Methode in Kombination mit anderen ¨
experimentellen Verfahren ein wirkungsvolles Instrument zur Beurteilung des Zellhydratationszustands von Sichelzellenpatienten ist. Daher kann diese Technik zur Beurteilung der Wirksamkeit
von Sichelzellen-Therapien oder zur Beurteilung des Zustands der roten Blutkorperchen eines Pa- ¨
tienten verwendet werden. Da die roten Blutkorperchen bei verschiedenen Arten von An ¨ amie auch ¨
verschiedene Formvariationen aufweisen, wurde eine weitere Blutkrankheit, die hereditare Sph ¨ arozy- ¨
tose, untersucht. In diesem Fall lag der Schwerpunkt auf der automatisierten Formerkennung der roten
Blutkorperchen, die in der Regel manuell durchgef ¨ uhrt wird und daher einer Bewertungsinkonsistenz ¨
unterliegt. Die Untersuchung nutzt die 3D-Rekonstruktion der Zellen aus konfokalen Mikroskopieaufnahmen und die anschließende Formerkennung mittels kunstlicher neuronaler Netze. Die Beurteilung ¨
dieses Systems zeigte sowohl eine sehr gute Erkennungsrate, hohe Prazision, eine schnelle Prozesszeit, ¨
als auch ein objektives Ergebnis verglichen mit der manuellen Klassifikation. Verglichen mit der
Analyse von 2D Mikroskopieaufnahmen von Blutabstrichen, konnten durch die Auswertung korrespondierender 3D Aufnahmen außerdem andere Formspektren abgeleitet werden. Dies legt die
Empfehlung nahe, die manuelle Klassifizierung von Zellformen (Stand der Technik) im Kontext von
hereditarer Sph ¨ arozytose zu ¨ uberdenken.Human cell viability highly depends on oxygen, which is carried and provided by red blood cells.
This thesis aimed to investigate how oxygen influences physiology and pathophysiology of red blood
cells and is divided in two main parts.
The first one presents results that are part of a larger study performed at high altitude (3450 m).
Here, the reduced air pressure causes a decrease in blood oxygenation, which is balanced by an increase in red blood cells production (erythropoiesis). Upon return from high altitude, the amount of
red blood cells is restored to the original levels within a few days, which is in contrast with the average
red blood cell lifespan of 120 days. The reasons leading to such red blood cells premature clearance
are not well understood. A hypothetical mechanism previously proposed is defined as neocytolisis,
i.e. the selective clearance of the red blood cells formed at high altitude upon return to sea level. The
scientific question of the study was therefore to assess if and how neocytolisis occurs after a 3-week
stay at high altitude. The investigations performed in this thesis involved in vitro culture of erythroid
precursors of the donors participating in the study to characterize both erythropoiesis and the obtained immature red blood cells, namely reticulocytes. Results highlighted an accelerated maturation
of erythroid precursors in cultures performed at lower oxygen (3%) compared to atmospheric oxygen
(20%) ones and an unexpected improved cell survival of the obtained reticulocytes. This was in accordance with the finding that after the stay at the chosen altitude no neocytolisis occurred, denying
the hypothesis of a higher fragility of cells formed at low oxygen causing their selective premature
clearance upon return from high altitude. Moreover, cultures performed at low oxygen resulted in the
formation of more biconcave cells, the typical shape of mature red blood cells. This suggests that
reducing oxygen levels in cultures may contribute to advance their maturation in vitro. In addition to
cell cultures, another objective was to perform RNA sequencing of isolated reticulocytes from whole
blood of the donors to compare pre- and high altitude conditions. A protocol for the isolation of a
pure fraction of reticulocytes and their RNA was developed. However, total RNA yield needs to be
increased to perform an accurate comparison of gene expression levels.
The second part of the thesis focused on studying red blood cell morphology in two types of anemia. Because of the high sensitivity of red blood cells to shape variation, samples were always fixed
before any experimental manipulation. A thorough study describing how to perform red blood cell
fixation is presented. The first blood disease of study was sickle cell anemia. In this pathology, deoxygenation of hemoglobin causes the deformation of red blood cells to the shape of a sickle that
impairs their functions and lifespan. The quantitative analysis of cell projections from confocal images by means of a customized computer program was employed within a pilot phase II clinical trial
for the therapy of sickle cell disease. The obtained results combined with other experimental evaluations showed that red blood cell shape analysis of sickle cell disease patients is a simple but powerful
tool to evaluate cell hydration state. Therefore, this technique may be used for the assessment of
the efficacy of sickle cell disease therapies or to evaluate the state of red blood cells of a patient.
Since red blood cells display shape variations in different types of anemia, a second blood disease
was investigated, namely hereditary spherocytosis. In this case, the focus was the automation of red
blood cells shape recognition, which is usually performed manually and therefore subjected to evaluation inconsistency. The investigation made use of 3D cell reconstructions from confocal images and
automated shape recognition by means of artificial neural networks. System benchmarks showed a
good recognition performance, high accuracy, fast processing time as well unbiased results compared
to the manual classification. Moreover, the application of 3D imaging in contrast to the traditional
2D-microscopy typically employed in blood smear analysis revealed a different red blood cell shapes
spectrum. These results therefore suggest to revise the state-of-the art manual shape classification
applied in hereditary spherocytosis
The development of prejudice in preschool age
No full textreservedLa tesi affronta il tema della nascita e dello sviluppo del pregiudizio nei bambini di età prescolare, includendo teorie a favore che sia causato da motivazioni ambientali/sociali e teorie che ipotizzano invece che ci sia influenza da parte dei caregiversThe thesis addresses the issue of birth and the development of prejudice in preschool children, including theories in favor of it being caused by environmental/social reasons and theories that assume instead that there is influence from caregiver
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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