1,721,051 research outputs found
Biofilm formation upon virus infection in Sulfolobus solfataricus.
No full textThe hyperthermophilic crenarchaeote Sulfolobus solfataricus is a facultative autotroph with the ability to grow under aerobic conditions. The genome of several Sulfolobus species has been sequenced making Sulfolobus spp. model organisms for studying molecular and physiological processes in Archaea.
Information about biofilm formation in Archaea is still at the stage of infancy. Recently, it has been shown that S. solfataricus forms a biofilm mainly made of polysaccharides upon attachment to various surfaces, such as glass, mica etc. The genes possibly involved in the production of the extracellular polysaccharides have been identified (1).
We have investigated the ability of S. solfataricus to form biofilm as a stress response to the infection with the Spindle-shaped virus 2 (SSV2) (2). After prolonged growth on solid medium of a lawn of S. solfataricus cells spotted with SSV2, production of a white and dense material was observed. Formation of a white matrix was also observed in cells non-infected but grown at high density. The protein fraction of the white matrix was found to be very low and, although not confirmed, it is likely that the white matrix is an exopolysaccharide. We therefore suggest that the formation of the white matrix could be controlled by quorum sensing and cellular stress responses in order to protect cells from external factors.
The physiology of the process as well as the chemical composition of the biolfilm-like white matrix, is under way
Characterization of the Sulfolobus host-SSV2 virus interaction.
No full textThe Sulfolobus spindle virus, SSV2, encodes a
tyrosine integrase which furthers provirus formation in
host chromosomes. Consistently with the prediction
made during sequence analysis, integration was found to
occur in the downstream half of the tRNAGly (CCC)
gene. In this paper we report the findings of a comparative
study of SSV2 physiology in the natural host,
Sulfolobus islandicus REY15/4, versus the foreign host,
Sulfolobus solfataricus, and provide evidence of differently
regulated SSV2 life cycles in the two hosts. In fact,
whereas a significant induction of SSV2 replication takes
place during the growth of the natural host REY15/4,
the cellular content of SSV2 DNA remains fairly low
throughout the incubation of the foreign host. The
accumulation of episomal DNA in the former case
cannot be traced to decreased packaging activity because
of a simultaneous increase in the virus titre in the medium.
In addition, the interaction between SSV2 and its
natural host is characterized by the concurrence of host
growth inhibition and the induction of viral DNA replication.
When this virus–host interaction was investigated
using S. islandicus REY15A, a strain which is
closely related to the natural host, it was found that the
SSV2 replication process was induced in the same way as
in the natural host REY15/4
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
Catalytic glycerol dehydration-oxidation to acrylic acid
No full textThis article provides a comprehensive and critical review of the latest studies on catalytic glycerol dehydration-oxidation to acrylic acid. The two-bed catalytic system in one or two reactors involves glycerol dehydration to acrolein and subsequent oxidation of acrolein to acrylic acid. Zeolites, metal oxides, heteropoly acids, and phosphates are effective in the dehydration of glycerol to acrolein. Mo–V–O catalysts appear active in the acrolein oxidation to acrylic acid. The glycerol can be completely converted to acrolein with 98% selectivity. In such a two-step process, the step of catalytic dehydration is thought to be critical. A few recent studies reveal that the conversion of glycerol to acrylic acid in two reactors can be also achieved via allyl alcohol as intermediate. For the one-bed catalytic glycerol oxydehydration to acrylic acid, a single catalyst must possess both active acid sites and active redox sites. Mo–V–O, W–V–O, Mo–V–W–O, W–V–Nb–O oxide catalysts, and heteropoly acid catalysts are particularly promising. Currently, a 60% yield of acrylic acid can be achieved over H0.1Cs2.5(VO)0.2(PMo12O40)0.25(PW12O40)0.75 at 340°C. However, all the catalysts rapidly deactivate due to coking. Coking usually occurs during the glycerol oxydehydration step. Optimizing reaction conditions such as increasing water and oxygen feeding, lowering reaction temperature, tuning the catalysts by finely doping, adjusting the surface acidity and enlarging pores of the solid catalysts can inhibit coking to some extent by slowing the deactivation of catalyst. Yet coking over catalysts is a major obstacle when conducting glycerol oxydehydration on a large scale. We suggest that future work should place an emphasis on revealing the essence of coking, further designing coking-resisting catalysts, and developing an efficient reaction and separation system
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
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
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