1,721,138 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
REM sleep alterations in primary insomnia
No full textObjectives: We previously (2008) found an association between
REM sleep duration and perceived wakefulness in 81 patients with primary insomnia (PI) in addition to a clearly increased arousal index in REM sleep. The current study aimed to replicate and extend the previous findings.
Methods: Polysomnogram (PSG) and subjective sleep quality
questionnaire (Schlaffragebogen A, SFA) data of PI patients and
matched good sleeper controls (GSC) were evaluated for group
differences.
Results: One hundred and fifty-six new PI patients could be
matched to the same number of GSC (GSC; 60M, 96F; Mean age PI: 42.6 ± 12.4 years, GSC: 42.2 ± 13.4 years). PI patients had a higher wake time within bed time as well as lower REM and sleep stage 2 time. The association between perceived wake time and REM sleep time could be replicated in this new and larger group, as well as a clearly increased arousal index in REM sleep, while the arousal index in NREM sleep was significantly but less strongly increased.
Conclusion: We postulate that the psychophysiological hyperarousal characteristic for primary insomnia is particularly expressed as a REM sleep alteration. REM sleep appears to be particularly vulnerable to pre-sleep worries, leading to increased retrospective recall of this time as wake time and a lower restorative sleep quality
Significance of REM sleep dysregulation in depression: State of the art (In press.)
No full textDisturbances of sleep are typical for most depressed patients and belong to the core symptoms of the disorder. Since the 1960ies polysomnographic sleep research has demonstrated that besides disturbances of sleep continuity, depression is associated with altered sleep architecture, i.e. a decrease in slow wave sleep (SWS) production and disturbed REM sleep regulation. Shortened REM latency (i.e. the interval between sleep onset and the occurrence of the first REM period), increased REM sleep duration and increased REM density (i.e. the frequency of rapid eye movements per REM period) have been considered as biological markers of depression which might predict relapse and recurrence. High risk studies including healthy relatives of patients with depression demonstrate that REM sleep alterations may precede the clinical expression of depression and may thus be useful in identifying subjects at high risk for the illness. Several models have been developed to explain REM sleep abnormalities in depression, like the cholinergic-aminergic imbalance model or chronobiologically inspired theories, which are reviewed in this overview. Moreover, REM sleep alterations have been recently considered not only as biological "scars" but as true endophenotypes of depression. This review discusses the genetic, neurochemical and neurobiological factors that have been implicated to play a role in the complex relationships between REM sleep and depression. We hypothesize on the one hand that REM sleep dysregulation in depression may be linked to a genetic predisposition/vulnerability to develop the illness; on the other hand it is conceivable that REM sleep disinhibition in itself is a part of a maladaptive stress reaction with increased allostatic load. We also discuss whether the REM sleep changes in depression may contribute themselves to the development of central symptoms of depression such as cognitive distortions including negative self-esteem and the overnight consolidation of negatively toned emotional memories
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
Schlafmangel und Insomnie
No full textDie Begriffe „Schlafmangel“ und „Insomnie“
sollten nicht synonym verwendet und nicht
verwechselt werden. Als Schlafmangel wird
eine Verkürzung der üblichen Schlafdauer
eines Menschen bezeichnet, die durch äußere
Umstände oder motivationale Faktoren bedingt
ist. Bei einer Insomnie liegt hingegen
eine für die Betroffenen nicht erklärbare und
mit einem Leidensdruck verbundene Störung
des Schlafs vor, obwohl die äußeren Umstände
nicht gegen einen ausreichend langen
Schlaf sprechen. Die meisten Studien zum
Thema Schlafmangel untersuchten den Zusammenhang
zwischen der Schlafdauer sowie
körperlicher und psychischer Gesundheit.
Die Längsschnittstudien zeigten dabei, dass
Menschen mit einer verkürzten Schlafdauer
(< 6 Stunden) ein erhöhtes Risiko für das Auftreten
eines metabolischen Syndroms und für
kardiovaskuläre Erkrankungen aufweisen. Zudem
zeigte sich ein U-förmiger Zusammenhang
zwischen der Schlafdauer und Mortalität,
das heißt, die Mortalität ist sowohl bei
einer verkürzten (< 6 Stunden) als auch bei
einer verlängerten Schlafdauer (> 8 Stunden)
erhöht. In Bezug auf Insomnien konnten ähnliche,
allerdings schwächer ausgeprägte Zusammenhänge
gezeigt werden. Zudem sind
Insomnien Risikofaktoren für psychische Erkrankungen,
insbesondere für Depressionen.
Die Befunde legen nahe, dem Thema Schlaf
und Schlafstörungen in der ärztlichen Praxis
mehr Zeit einzuräumen und diesbezügliche
Präventionsmaßnahmen zu stärken
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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