1,721,137 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
Chronic cigarette smoke exposure induces microbial and inflammatory shifts and mucin changes in the murine gut
No full textInflammatory Bowel Diseases (IBD) are complex multifactorial diseases characterized by an inappropriate host response to an altered commensal microbiome and dysfunctional mucus barrier. Cigarette smoking is the best known environmental risk factor in IBD. Here, we studied the influence of chronic smoke exposure on the gut microbiome and mucus layer composition in conventional mice. We compared smoke-exposed to air-exposed mice (n = 12) after a smoke exposure of 24 weeks. Both Illumina sequencing (n = 6) and denaturing gradient gel electrophoresis (DGGE) (n = 12) showed that bacterial activity and community structure were significantly altered in the colon due to smoke exposure. Interestingly, an increase of Lachnospiraceae sp. activity in the colon was observed. Also, changes in the mRNA expression Muc2 and Muc3 increased in the ileum, whereas Muc4 increased in the distal colon of smoke-exposed mice (n = 6). Furthermore, we observed increased Cxcl2 and decreased Ifn-γ in the ileum, and increased Il-6 and decreased Tgf-β in the proximal colon. Tight junction gene expression remained unchanged. We infer that the modulating role of chronic smoke exposure as a latently present risk factor in the gut may be driven by the altered epithelial mucus profiles and changes in microbiome composition and immune factors
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
Mikroben-Wirtsinteraktion: Extrazelluläre Metabolite mit immunmodulatorischem Potential, gebildet von Escherichia coli als Reaktion auf humanes Defensin
No full textHost-microbial interactions in the human gut can influence the development and course of several pathologies, including inflammatory bowel diseases (IBD). Inflammation in IBD represents a complex scenario where the inducible epithelial defensins are shown to play an important role. The present study investigated the hypothesis that Escherichia coli responds to human beta-defensin-2 (hBD-2), generating extracellular compounds which could have an effect on the host. Using HPLC-MS, supernatants from E. coli cultures challenged with hBD-2 were analyzed compared to unchallenged controls. Molecules present specifically in challenged cultures were identified and quantified by MS/MS. The general physiological state of challenged bacteria was addressed by microscopic and biochemical tools, and the mechanisms leading to the observed response were investigated. Additionally, the effects of extracellular compounds from hBD-challenged E. coli upon human intestinal epithelial cell line were evaluated by assessing the activity of the NF-kB pathway. The major compounds identified in E. coli supernatants after hBD challenge were the purine nucleosides adenosine (Ado) and guanosine (Guo). The response was dependent upon hBD-2 dose and cell density, each compound presented distinct variation. Other tested defensins and bacterial strains presented variable outcomes. Interaction of hBD-2 with E. coli membrane and intracellular nucleic acids, rather than absolute cell lysis, was found to be the mechanism generating extracellular Ado, and the involvement of a AMP-degrading activity was demonstrated. Experiments with the human cell line indicated that NF-kB pathway activation is enhanced in the presence of Ado and supernatants from hBD-challenged E. coli containing Ado. Thus, hBD-2 may alter local levels of Ado as a consequence of its interaction with gut bacteria, which in turn can affect the inflammatory process, mediating host-microbial interactions in the intestinal mucosa.Die Mikroben-Wirtsinteraktion im menschlichen Darm kann die Entwicklung und den Verlauf zahlreicher Krankheiten, u. a. auch von entzündlichen Darmerkrankungen (IBD), beeinflussen. Entzündungen in IBD bilden ein komplexes Szenario, in denen die induzierbaren Defensine des Epithels eine wichtige Rolle spielen. Die vorliegende Studie untersucht die Hypothese, dass Escherichia coli auf humanes beta-Defensin-2 (hBD-2) mit der Bildung extrazellulärer Substanzen reagiert, welche den Wirt beeinflussen. Mittels HPLC-MS wurden Kulturbrühen von E. coli Kulturen nach hBD-2-Zugabe untersucht und mit Kontrollen verglichen. Substanzen, welche nur bei den mit hBD-2 behandelten Kulturen auftraten, wurden mittels MS/MS identifiziert und quantifiziert. Der physiologische Zustand der behandelten Bakterien wurde mittels mikroskopischer und biochemischer Methoden bestimmt und die dazu führenden Mechanismen untersucht. Außerdem wurden die Effekte der von E. coli nach hBD-2-Behandlung gebildeten, extrazellulären Verbindungen auf humane Darmepithelzellen über den NF-kB Signalweg quantifiziert. Adenosine (Ado) und Guanosin (Guo) wurden als Hauptverbindungen der mit hBD-2 behandelten E. coli-Kulturen identifiziert. Die Bildung hing von der hBD-2-Dosis und der Zelldichte ab, wobei sich Ado und Guo unterschiedlich verhielten und war Defensin- und Bakterien-spezifisch. Die Wechselwirkung von hBD-2 mit der E. coli-Membran und intrazellulären Nukleinsäuren und nicht bloße Zelllysis wurde als Mechanismus der Bildung von extrazellulärem Ado identifiziert und eine AMP-abbauende Aktivität nachgewiesen. Experimente mit einer humanen Zelllinie zeigten eine Aktivierung des NF-kB-Signalweges in Gegenwart von Ado oder von mit hBD-2-behandelten E. coli-Kulturüberständen. Daraus folgt, dass hBD-2 die lokale Konzentration von Ado durch seine Interaktion mit Darmbakterien beeinflussen kann, was wiederum den Entzündungsprozess in einer Wirts-Mikroben-Interaktion in der Darmschleimhaut modulieren kann
Biochemische und molekularbiologische Untersuchungen zum 3,6-Dichlor-2-methoxybenzoat-Abbau durch Sphingomonas sp. RW5
Full text linkDer Stamm RW5 wurde mit 3,6-Dichlor-2-methoxybenzoat (36DC2MBA) als alleiniger Kohlenstoff- und Energiequelle aus aeroben Sedimenten des Flusses Elbe isoliert und durch Analyse der 16S rDNA als Sphingomonas sp. identifiziert. Der Stamm RW5 konnte 36DC2MBA und 3,6-Dichlorsalicylat vollständig mineralisieren und bildete während der exponentiellen Wachstumsphase mit beiden Verbindungen jeweils einen Metaboliten, der als 3,6-Dichlorgentisat identifiziert werden konnte. Außerdem konnte der Stamm 3,6-Dichlorgentisat, nicht aber 3,6-Dichlorbrenzkatechin als Kohlenstoff- und Energiequelle verwerten. Sauerstoffaufnahmeraten 36DC2MBA-gewachsener Zellen zeigten dementsprechend signifikante Aktivitäten für 36DC2MBA, 3,6-Dichlorsalicylat und 3,6-Dichlorgentisat, dagegen nur sehr geringe Aktivitäten für 3,6-Dichlorbrenzkatechin und keine für Brenzkatechin. In zellfreien Extrakten des Stammes war eine hohe spezifische Aktivität für eine Gentisinsäure-1,2-Dioxygenase nachzuweisen, die auch 3,6-Dichlorgentisat umsetzen konnte, wogegen Aktivitäten für eine Salicylat-5-Hydroxylase und eine der Brenzkatechin-Dioxygenasen nicht nachweisbar waren. Maleylpyruvat wurde von zellfreien Extrakten des Stammes RW5 in einer Glutathion-abhängigen Reaktion vollständig umgesetzt. Diese Ergebnisse lassen den Schluß zu, daß der Stamm RW5 36DC2MBA über einen (Chlor)-Gentisat-Weg abbaut. Das Gen, das für eine Gentisinsäure-1,2-Dioxygenase (GDO) kodiert, sollte identifiziert und charakterisiert werden. Dazu wurde ein 4.103 bp großes, daß GDO-Gen enthaltende DNA-Fragment aus einer Plasmidbank von Sphingomonas sp. RW5 kloniert und sequenziert. Das Gen gtdA kodiert für ein 350 Aminosäuren großes Protein mit einer berechneten Größe von 38,85 kDa. Sequenzvergleiche der vorhergesagten Aminosäuresequenz von gtdA zeigten keine signifikanten Homologien (jeweils <13) zu bisher bekannten Proteinsequenzen ringspaltenender Dioxygenasen des intradiolen- und extradiolen Typs.The bacterial strain RW5 was isolated from aerob sediments of the Elbe river by using 3,6-dichloro-2-methoxybenzoate (36DC2MBA) as sole source of carbon and energy. The strain was identified by 16S rDNA analysis as a Sphingomonas sp. Strain RW 5 mineralised 36DC2MBA and 3,6-dichlorosalicylate by producing 3,6-dichlorogentisate as a growth-metabolite during growth with these compounds. The strain used 3,6-dichlorogentisate as sole source of carbon and energy but not 3,6-dichlorocatechol. Oxygen uptake rates with 36DC2MBA-grown cells showed significant activities for 36DC2MBA, 3,6-dichlorosalicylate and 3,6-dichlorogentisate but no activity for 3,6-dichlorocatechol and catechol. Cell free extracts showed a high specific activity for a gentisate 1,2-dioxygenase which could also catalyse 3,6-dichlorogentisate. Enzyme acitivities of an active salicylate 5-hydroxylase or a catechol-dioxygenase were not present in cell free extracts. Maleylpyruvate was transformed with cell free extracts in a glutathion-dependend reaction completely. Therefor 36DC2MBA is degraded in strain RW5 by a (chloro-)gentisate pathway. A 4.103 bp long DNA fragment containing the structural gene of a gentisate 1,2-dioxygenase (E.C.1.13.11.4), gtdA, from Sphingomonas sp. strain RW5 was cloned and sequenced. The gtdA gene encodes a 350 amino acid polypeptide with a predicted size of 38.85 kDa. Comparison of the gtdA gene product with protein sequences in databases, including those of intradiol or extradiol ring-cleaving dioxygenases, revealed no significant. This gentisate 1,2-dioxygenase is thus a member of a new class of ring-cleaving dioxygenases. The gene was subcloned and hyperexpressed in E. coli. The resulting product was purified to homogeneity and partially characterised. Under denaturing conditions the polypeptide exhibited an approximate size of 38.5 kDa and migrated on gel filtration as a species with a molecular mass of 177 kDa
Polyphasische Analyse der mikrobiellen Populationen des Spittelwassersediments
Full text linkDie mikrobiellen Populationen des oberen Sediments (0,5 cm) der Spittelwasser wurden untersucht. Dieser Fluß wurde durch die Abwässer der Chemiewerke in Bitterfeld-Wolfen (Sachsen-Anhalt) extrem belastet. Sediment-Extrakt-Agar [SA] ermöglichte eine belastungsspezifische Anreicherung der „Gesamtpopulation“. Das Selbstreinigungspotential kennzeichneten Minimalmedien mit den folgenden Xenobiotika: 4-Chlor-, 5-Chlorsalizylsäure [4CS, 5CS], 3-Chlorbenzoesäure [3CB], 2,4-Dichlorphenoxyessigsäure [24D], Biphenyl [Bip], Anthrazen [Ant], Naphthalin [Nap], ß-Hydroxynaphthalin [ßHN], Toluol [Tol], Ethylbenzol [Etb], o-, m-, p-Xylol [oXy, mXy, pXy]. Zusätzlich wurden das Wachstum der SA-Isolate auf den 13 Xenobiotika-Medien bestimmt. Insgesamt 504 Isolate wurden in einem polyphasischen Ansatz charakterisiert. Analysiert wurde die Verwertung verschiedener Kohlenstoffquellen (BIOLOG), die Gesamt-fettsäuren (FAME) und die PCR-amplifizierte 16S rDNA (TGGE, Sequenzierung). Die in dieser Form neue Anwendung der TGGE (Temperaturgradienten-Gelelektrophorese) ermöglichte eine Sortierung der Isolate auf phylogenetischer Basis. Die Anreicherung auf dem naturnahen Sedimentextrakt-Medium ergab eine heterogene, artenreiche Gemeinschaft. Es wurden diverse bekannte und unbekannte Arten detektiert. Die Agrobacterium-Gruppe und Acidovorax dominierten die Proteobakterien. Das Xenobiotika-Screening zeigte hohe Variabilität der SA-Stämme, konnte aber kein taxonspezifisches Wachstum nachweisen. Mit den Xenobiotika wurden relativ artenarme Gesellschaften selektioniert. Zum Beispiel wurden Flavobacterium johnsonae (oXy), Serratia (Nap, Ant), Stenotrophomonas (3CB, Nap, oXy), Ochrobactrum (Ant, 4CS, oXy) und auch Gram-positive Bakterien (4CS, 24D, Nap, oXy) Xenobiotika-spezifisch isoliert. Die häufig genannten Degradierer waren nur schwach vertreten.The microbial populations of the upper fraction of Spittelwasser sediment have been examined. This small river was extremely polluted by the refuse from the chemical industry in Bitterfeld-Wolfen (Sachsen-Anhalt). Sediment-Extract-Agar [SA] allowed a pollution-specific enrichment of the 'total population'. The degrading potential was characterized by Minimal media with the following xenobiotics: 4-chloro-, 5-chlorosalicylic acid [4CS, 5CS], 3-chlorobenzoic acid [3CB], 2,4-dichlorophenoxy acetic acid [24D], biphenyl [Bip], anthracene [Ant], naphthalene [Nap], ß-hydroxynaphthalene [ßHN], toluene [Tol], ethylbenzene [Etb], o-, m-, p-xylene [oXy, mXy, pXy]. Additionally, the SA-isolates were screened on the 13 xenobiotic-media. 504 isolates were characterized using a polyphasic approach. The respiration patterns for different carbon-sources (BIOLOG), fatty acids (FAME) and PCR-amplified 16S rDNA (TGGE, Sequencing) were analyzed. The TGGE (Temperature Gradient Gel Elektrophoresis) was used as a new method for screening the isolates on the basis of their phylogenetic relationships. A heterogenous, species-rich community was characterized with the in situ-like sediment-extract-medium. A diverse spectrum of known and unknown species was detected. The Agrobacterium-group and Acidovorax dominated the Proteobacteria. Xenobiotic-screening showed high variability among SA-isolates, although taxon-specific growth could not be demonstrated. The xenobiotic-media revealed communities with low diversity. For example Flavobacterium johnsonae (oXy), Serratia (Nap, Ant), Stenotro-phomonas (3CB, Nap, oXy) and Ochrobactrum (Ant, 4CS, oXy) as well as gram-positive bacteria (4CS, 24D, Nap, oXy) were xenobitic-specifically selected. Known xenobiotic-degraders were only weakly represented
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