1,721,147 research outputs found
Safety and quality of fish products : a methodological polyphasic approach to study contaminating emerging pathogens
No full textThis PhD thesis research project aims to improve the current systems of manaement and control of food safety, focusing the attention on the study of two bacterial species, Lactococcus garvieae and Morganella morganii that represent valid models of contaminating emerging pathogens in fish products
Lactococcus garvieae and Morganella morganii : two bacterial models to study quality and safety of fish products
No full textThis paper reports the results obtained for two bacterial species, Lactococcus garvieae and Morganella morganii, that represent models of contaminating fish pathogens in fish products: i) molecular characterization and genetic polymorphism of L. garvieae strains coming from different food niches; ii) detection of the histamine forming M. morganii in tuna fish samples and its quantification through the development of a new real-time PCR assay
Oltrepò partigiano : documenti della resistenza armata nell’oltrepò pavese, luglio 1944-aprile 1945
No full textLACTOCOCCUS GARVIEAE AND MORGANELLA MORGANII: TWO BACTERIAL MODELS TO STUDY QUALITY AND SAFETY OF FISH PRODUCTS
Full text linkThis PhD thesis research project aims to improve the current systems of management and control of food safety, focusing the attention on the study of two contaminating emerging pathogens in fish products: Lactococcus garvieae, the etiological agent of a hemorrhagic septicemia in aquaculture sector, and Morganella morganii, the most active histamine-producing species.
In the first part of the research the molecular characterization and genetic polymorphism of L. garvieae strains coming from different food niches were carried out revealing an early separation of L. garvieae population into two independent genetic lineages. Subsequent phylogenetic analyses through a MLST approach confirms the significant genetic heterogeneity in this species, the separation into two principal evolution lineages, and the presence of a third lineage totally separated from the others, that could be the ancestor branch of the main lineages. Genome sequencing of representative selected strains and the comparison with other L. garvieae sequences already present in databases, confirmed the subdivision in the three different subgroups. Within each subgroup the nucleotide similarity was 99%, while comparing subgroups the similarity decreased (94-95%). Moreover, this preliminary comparison reveals that the core genome of L. garvieae contains, in additions to genes codifying for the main metabolic pathways, genes encoding putative virulence factors, such as hemolysins and adhesin. Genes related to carbohydrate fermentation (such as lactose and sucrose) seemed part of the dispensable genome, as well as the gene cluster related to the capsule formation. Experiments carried out to evaluate the expression of virulence-related genes in representative L garvieae strains, indicated an adaptive response to different environmental conditions, specific at the strain-level.
Regarding the second part of the research, we started exploring the bacterial population of fresh tuna samples and evaluated the histamine content. Despite low levels of histamine were detected (<10 ppm), many samples showed high total viable counts after temperature abuse. The 10% of the 141 enteric bacteria isolated from samples were identified by 16S rDNA sequence analysis, as M. morganii, the most active histamine-producing species. Subsequently a new quantitative PCR assay for the detection of M. morganii in potentially contaminated fish products before histamine accumulates was developed, with a detection limit of 0.563 pg of pure DNA, corresponding to DNA extracted from approximately nine cells. To improve the knowledge at genome level of the histidine decarboxylase of M. morganii (hdc gene), a region of 7681 bp was sequenced. Results showed the presence of genes encoding two putative histidine/histamine antiporters upstream and downstream the hdc gene, followed by an histidyl-tRNA synthetase. Gene expression analysis indicates that in M. morganii hdc was inducible, showing the highest expression under acidic conditions, mainly in presence of histidine supplementation. Finally, with the aim to prepare a significant collection of different M. morganii strains from different ecological niches, we compared several clinical biotypes, in addition to strains isolated from fish through REP and RAPD PCR analysis. The cluster analysis confirmed the existence of two main branches related to the habitat of isolation, which were separated at a level of similarity of 19%
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
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