1,721,083 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
Studies on Anaplasma phagocytophilum in dogs: clinical presentation of granulocytic anaplasmosis and significance for transfusion medicine
No full textA. phagocytophilum ist ein gram negatives, obligat intrazelluläres Bakterium, welches hauptsächlich von Zecken der Gattung Ixodes übertragen wird. Es befällt vor allem neutrophile Granulozyten und ist unter anderem Auslöser der caninen granulozytären Anaplasmose.
Ziele der vorliegenden retrospektiven Studien waren 1) die Beschreibung der klinischen Symptome, der Laborwertveränderungen, der Therapie und der Verlaufes der CGA und 2) die Ermittlung des Vorkommens von A. phagocytophilum bei gesunden Blutspenderhunden und die Bedeutung des Erregers für die Transfusionsmedizin.
1) Im Untersuchungszeitraum 2006 bis 2012 wurden 974 Hunde mit in der Literatur beschriebenen Symptomen einer CGA in der Klinik für kleine Haustiere der FU Berlin vorstellig, von denen 72 Hunde ein positives PCR-Ergebnis für A. phagocytophilum-DNA hatten. 63 Hunde erfüllten die Einschlusskriterien und gingen in die Studie ein. Die Hauptsymptome der an CGA akut erkrankten Hunde waren Apathie und reduziertes Allgemeinbefinden (83 %), Fieber (67 %) und Inappetenz (63 %). Die häufigste Laborwertveränderung war Thrombozytopenie (86 %) gefolgt von erhöhten Leberenzymaktivitäten und Hyperbilirubinämie (77 %), Anämie (70 %), Hypoalbuminämie (62 %) und Leukozytose (27 %). 44 % von 36 getesteten Hunden mit Thrombozytopenie waren positiv für thrombozytengebundene Antikörper. 59 von 61 Hunden erholten sich, zwei Hunde verstarben (ein Hund an epileptischen Anfällen, ein weiterer an den Folgen einer immunhämolytischen Anämie), zwei Hunde konnten nicht nachuntersucht werden. Bei Hunden, bei denen eine Zeckenexposition nicht ausgeschlossen werden kann, und die mit unspezifischen Symptomen wie Lethargie und Fieber und/oder Anzeichen einer immunmediierten Erkrankung vorstellig werden, sollte in endemischen Gebieten die CGA als Ursache in Betracht gezogen werden.
2) Insgesamt 917 EDTA-Blutproben von 517 Blutspenderhunden wurden im Untersuchungszeitraum 2006 bis 2012 mittels real-time PCR auf das Vorkommen von A. phagocytophilum-DNA getestet. 158 der Hunde spendeten mehrmals Blut und wurden somit mehrmals getestet (2 - 11 mal, Median 3). Bei 21 der 917 (2,3 %) Blutproben von 21 Blutspenderhunden war die PCR positiv, bezogen auf die Anzahl der Blutspenderhunde betrug die Prävalenz 4,06 %. Die positiven Ergebnisse fielen hauptsächlich in die Monate Juni (n=8), Mai (n=5) und Juli (n=3), kamen aber auch in fünf weiteren Monaten vor. Keiner der getesteten Hunde war mehrfach positiv. Eine leicht erhöhte Rektaltemperatur (=39,0 °C) lag bei drei Hunden vor. Bei elf Hunden fielen geringgradige Laborwertveränderungen auf: Thrombozytopenie (n=3), Leukozytose (n=2), Leukopenie (n=2), Anämie (n=1), Hyperproteinämie (6 von 18 getesteten Hunden). Im Hinblick auf die Laborwertveränderungen gab es keine statistisch signifikanten Unterschiede zwischen den PCR positiven und PCR negativen Blutproben.
Da 2,3 % der Blutproben gesunder Blutspenderhunde PCR-positiv für A. phagocytophilum waren, sollten alle Blutspender in endemischen Gebieten vor jeder Blutspende das ganze Jahr über auf das Vorkommen von A. phagocytophilum-DNA im Blut getestet werden.A. phagocytophilum is an obligatory intracellular bacterium transmitted by various genera of Ixodes ticks. It infects neutrophils and is the causative agent of canine granulocytic anaplasmosis. The goals of the current retrospective studies were 1) to perform analysis of medical records of dogs naturally infected with A. phagocytophilum, focusing on clinical signs, laboratory results, therapy and course of disease and 2) to evaluate the occurrence A. phagocytophilum in healthy blood donor dogs and to estimate the significance for transfusion medicine.
1) Between 2006–2012 974 dogs with clinical signs suggestive for CGA were presented in the Clinic for Small Animals, Faculty of Veterinary Medicine, Freie Universität Berlin. A total of 72 dogs were PCR-positive, 63 of them fulfilled the inclusion criteria. The most common clinical signs were lethargy and reduced activity (83 %), fever (67 %), and inappetence (63 %). Thrombocytopenia was the most common laboratory abnormality (86 %), followed by increased liver enzymes activities and hyperbilirubinaemia (77 %), anaemia (70 %), hypoalbuminaemia (62 %) and leukocytosis (27 %). 44 % of 36 thrombocytopenic dogs tested for platelet-bound antibodies were positive. 59 of 61 dogs recovered, two dogs died (epileptic seizures, immune-mediated haemolytic anaemia) and two were lost for follow-up. In dogs presented with acute nonspecific clinical signs and/or immune – mediated disease, where tick exposure cannot be excluded, canine granulocytic anaplasmosis should be considered as a potential cause in areas where it is endemic.
2) Between 2006 - 2012 altogether 917 EDTA blood samples from 517 dogs were submitted for A. phagocytophilum real-time PCR testing. 158 dogs were tested several times (2 – 11 times, median 3). The PCR test was positive for 21 of the 917 blood samples (2.3 %). Referred to the number of blood donor dogs, the prevalence was 4.06 %. Positive results were most often detected in June (n=8), May (n=5), and July (n=3), but also in five other months. None of the dogs tested PCR positive more than once. In three of 21 dogs a mild increase in rectal temperature (= 39.0 °C) was documented. Mild laboratory abnormalities were noted in eleven dogs: thrombocytopenia (n=3), leukocytosis (n=2), leukopenia (n=2), anemia (n=1) and hyperproteinemia (6 of 18 tested dogs). There was no significant difference between the PCR negative and positive blood samples with regard to laboratory abnormalities.
As altogether 2.3 % of blood samples from healthy canine blood donors were PCR positive for A. phagocytophilum, blood donors in endemic areas should be screened for A. phagocytophilum-DNA by PCR in blood samples all year round
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
Metabolism of macrocyclic lactones and benzimidazoles in parasitic nematodes
Full text linkAnthelmintic resistance is an accompaniment to modern livestock industry, which heavily relies on chemotherapy and chemoprophylaxis for maintaining animal health and productivity. While anthelmintic resistance is already established in horses and is a growing issue in cattle, it is, by far, the most severe and most prevalent in the sheep industry. To combat the spread of resistance, researchers are investigating alternative ways of nematode control and formulate recommendations to move towards more sustainable patterns of chemotherapeutic control. A further pillar in the management of nematodes is the understanding of the mechanisms underlying anthelmintic resistance. This knowledge is necessary to implement resistance diagnosis tests and might offer potential new drug targets. Macrocyclic lactones (MLs) and benzimidazoles (BZs) are the most frequently used anthelmintics in the sheep industry and resistance against them has been reported worldwide. Target-site related mechanisms usually are investigated first. For BZs, mutations in the ß-tubulin isotype 1 gene leading to amino acid changes at the drug target site have been found to confer resistance in trichostrongyloid nematodes, which are among the most pathogenic parasites of small ruminants. These mutations have been exploited to set up several tests capable of diagnosing BZ resistance even at very low frequencies of resistance alleles in nematode populations. So far, no target-site related mechanisms have been identified in case of MLs and diagnosis of ML resistance is limited to in vivo and in vitro tests. Drug efflux by P-glycoproteins is a non-target-site related mechanism that has been proposed to play a role in ML resistance particularly. A third possibility that has come to receive more attention in recent years is bioinactivation of MLs and BZs by cytochrome P450 monooxygenases (CYPs). In cancer drug resistance research as well as in the field of insecticide and acaricide resistance CYPs and their contribution to drug resistance are well established concepts.
Reasons to assume that CYPs might also be involved in anthelmintic resistance include, for instance, the metabolism of thiabendazole, a BZ representative, by CYP35D1 in the free-living nematode Caenorhabditis elegans and the detection of BZ metabolites, consistent with CYP activity in the parasitic nematode Haemonchus contortus. Despite these and many other indications, the role of CYPs in anthelmintic resistance is not fully clear.
The present cumulative doctoral thesis elaborates on the likelihood of an involvement of CYPs in ML metabolism in C. elegans and BZ metabolism in H. contortus. The first part was primarily processed by an in vitro approach whereby the larval development of mutant strains was compared to that of the wild-type N2 strain under different ML exposures. In particular, a strain with a temperature-sensitive mutation in the cytochrome reductase gene emb-8 was compared at a non-permissive temperature to the wild-type regarding ivermectin (IVM) and moxidectin (MOX) susceptibility. The second part focused on expression patterns of CYPs in in vitro cultured fourth larvae of H. contortus. Here, constitutive and TBZ-inducible expression was investigated in five different H. contortus isolates with varying levels of phenotypic BZ resistance.
Essentially, the ablation of CYP enzymatic activity by use of an inhibitor and a genetic approach was found to minimally alter the susceptibility to IVM in C. elegans, but not to MOX, both of which are MLs but belong to different groups. CYP14-A5, initially suspected to be involved in ML resistance in C. elegans, is most likely not involved, as its loss of activity was not shown to modulate IVM susceptibility and inducibility of gene expression by IVM or MOX was not observed. Therefore, CYPs can be expected to play no major role in ML resistance in C. elegans. As for BZ resistance in H. contortus, exposure to TBZ did not induce expression of selected CYPs in any of the isolates. However, the highly resistant WR isolate showed a 2.4- 3.7- fold higher constitutive expression of CYP HCOI100383400 in comparison to BZ susceptible isolates. In a previously published study, this CYP has been shown to have elevated transcript levels in the gut – the hypothesized major site of detoxification in nematodes. This is a first hint towards a possible involvement of CYPs in BZ resistance in a parasitic nematode. The WR isolate was also shown to be considerably more resistant than known resistant field isolates while having similar frequencies of the F200Y single nucleotide polymorphism (SNP) in the β-tubulin isotype 1 gene which along with E198A and F167Y is the primary cause for BZ resistance. The comparison of the frequency of F200Y and phenotypic resistance levels corroborates the long-held assumption of a multi-genic context for BZ resistance. Whether a co-governance of BZ resistance by several mechanisms in general and by the involvement of CYPs in particular is true, cannot be guaranteed with absolute certainty at the present state of research. However, the possibility of such should not be thoughtlessly abandoned, particularly in case of high resistance phenotypes as suggested by the present thesis. There is no question that further experimental investigations are necessary to improve our understanding of metabolism-based detoxification in nematodes
Molecular typing of Toxoplasma gondii isolates from cats and humans in Germany
Full text linkToxoplasma gondii weist eine weltweite Verbreitung auf und kann fast alle Wirbeltiere, vor allem Vögel und Menschen infizieren. Felide sind Endwirte von T. gondii, welche das infektiöse und umweltresistente Oozysten-Stadium ausscheiden können. T. gondii kann auch ohne sexuelle Vermehrung unterschiedlichste Zwischenwirte und Zwischenwirtspezies infizieren. Obwohl eine sexuelle Phase ein Teil des Lebenszyklus ist, werden rekombinierte Genotypen nur selten beobachtet. Dies ist ein Grund dafür, warum T. gondii eine klonale Populationsstruktur erkennen lässt. Während in Nordamerika und Europa drei klonale Genotypen (Typ I, II und III) dominieren, werden in Südamerika und Asien, neben den drei bekannten auch atypische und andere Genotypen beobachtet. Auch innerhalb der atypischen Genotypen lässt sich eine klonale Populationsstruktur erkennen. Die Linien I, II und III weisen Unterschiede in ihrer Virulenz für Mäuse auf. Typ-I-Stämme sind hochvirulent. Die Infektion mit nur einem Organismus führt bereits zum Tod. Klonale Typ-II- und Typ-III-Stämme sind avirulent für Mäuse. Nur Infektionen mit mehr als 103 Organismen führen zum Tod. In dieser Studie zeige ich, dass die Mehrzahl isolierter T. gondii-Oozysten dem Typ II zuzuordnen ist. Es wurde keine Typ-I-, dafür aber eine Typ-III-Infektion und vereinzelte Hinweise auf Mischinfektionen und nicht-kanonische T. gondii Genotypen beobachtet. Erstmalig kann gezeigt werden, dass aus einer Rekombination zwischen den Typen II und III genetisch unterschiedliche T. gondii in einer natürlich infizierten Katze entstanden sind. Die identifizierten nicht-kanonischen T. gondii Klone weisen unterschiedliche, meist hohe Virulenz im Mausmodell auf. Eine geringe Anzahl von T. gondii-DNA Proben von humanen Toxoplasmose-Fällen deutet auf eine Infektion mit T. gondii des Typs II hin. Ich zeige mit dieser Studie, dass sexuelle Rekombination von T. gondii in Deutschland möglich ist, und diese zur Entstehung von hochvirulenten T. gondii führen kann.Toxoplasma gondii is a protozoan parasite that can infect almost all warm-blooded animals, including birds and humans. The definitive host is the cat which excretes the highly infectious and environmental resistant oocyst stage. Equally important for the spread of T. gondii is the transmission of T. gondii by ingestion of contaminated food (prey) between host species. Sexual recombination is a rare event observed in T. gondii. This is one of the reasons why a clonal population structure of T. gondii is observed. In Europe and North America the majority of genotypes (types) of T. gondii are members of only three clonal types, designated type I, type II and type III. In South America and Asia, T. gondii is shown to have an increased genetic diversity with a high prevalence of atypical genotypes. However, even within those atypical genotypes, a clonal population structure can be observed. More importantly, mouse virulence of types I, II and III differ markedly. While infection with T. gondii type I is always lethal in mice, infections with 104–106 parasites of type II or type III are needed to have the same effect in mice. This study shows that the majority of cats in Germany excrete T. gondii oocysts of type II. We have not observed any type I T. gondii, but show that type III and, importantly, mixed type infection as well as non-canonical T. gondii are present in Germany. For the first time we demonstrate that a sexual cross between T. gondii type II and type III in a single, naturally infected cat occurred in Germany resulting in excretion of many genetically different non-canonical T. gondii. Most of the identified non-canonical T. gondii show a high virulence in mice. The RFLP-typing analysis of a limited number of T. gondii-DNA isolated from human samples revealed only alleles of T. gondii type II. I show that genetic recombination of different T. gondii types in Germany can lead to a higher genetic diversity and generation of highly mouse-virulent T. gondii
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