1,721,360 research outputs found
Plasmid-mediated antimicrobial resistance in Gram-negative bacteria
Full text linkL’epidemiologia dei plasmidi di resistenza è il principale mezzo per descrivere la diffusione
delle resistenze agli antimicrobici. L’identificazione di plasmidi correlati associati a specifici geni di
resistenza può aiutare a tracciare la disseminazione di plasmidi epidemici, aprendo nuovi scenari
epidemiologici sui meccanismi di diffusione delle resistenze agli antimicrobici. Questo aspetto è
particolarmente evidente quando si considerano plasmidi che sono associati alla diffusione delle
Beta Lattamasi a Spettro Esteso (ESBL) come gli enzimi CTX-M, SHV, TEM.
Lo scopo di questa tesi è stato quello di caratterizzare plasmidi che conferiscono resistenza
a farmaci rilevanti per la terapia umana in differenti collezioni di Enterobacteriaceae di origine
umana e animale. Verranno discussi diversi esempi di plasmidi epidemici quali: i plasmidi
IncHI2 che trasportano i geni blaCTX-M-9 o blaCTX-M-2 provenienti da isolati di origine
umana e animale di Escherichia coli e Salmonella dalla Spagna, Belgio e Inghilterra; i plasmidi
IncI1 caratterizzati da specifici fattori di virulenza, che trasportano i geni blaTEM-52 e
blaCTX-M-1 derivanti da isolati di Salmonella e E. coli di origine umana e animale; i plasmidi
IncN che trasportano i geni codificanti la metallo-β-lattamasi VIM-1 da isolati umani di
Klebsiella pneumoniae and E. coli dalla Grecia; plasmidi IncA/C2 associati a specifici geni di
resistenza come blaCMY-2, blaCMY-4, blaVIM-4 e blaVEB-1 provenienti da diverse
Enterobacteriaceae isolate in differenti parti del mondo, ed infine, i plasmidi associati all’enzima
SHV-12 isolati in diverse Enterobacteriaceae di origine umana e animale.
L’analisi mediante comparazione della struttura plasmidica ha permesso di rilevare la diffusione
di plasmidi emergenti e consente di tracciare i percorsi evolutivi e di diffusione attraverso l’acquisizione
di una vastità di elementi genetici mobili associati ai geni di resistenza.The epidemiology of resistance plasmids is a major issue for the description of antimicrobial resistance
diffusion. The identification of related plasmids associated to specific resistance genes may
help to follow the spread of epidemic plasmids, opening new epidemiological scenarios on the
mechanism of diffusion of antimicrobial resistance. This aspect is particularly interesting when
applied to collections of plasmids that are playing a major role in the diffusions of Extended
Spectrum Beta Lactamases (ESBLs) such as CTX-M, SHV, TEM.
The aim of this thesis is the molecular characterization of plasmids conferring drug resistances
in different collections of Enterobacteriaceae of human and animal origin. Several example
of epidemic plasmids will be discussed: the IncHI2 plasmids carrying blaCTX-M-9 or blaCTX-M-2
genes identified from human and animal isolates of Escherichia coli and Salmonella from Spain,
Belgium and UK; the IncI1 family of plasmids characterized by specific virulence factors, carrying
the blaCMY-2, blaTEM-52 and blaCTX-M-1 genes from Salmonella and E. coli of human and animal
origin; the IncN plasmids carrying the gene codifying the metallo-β-lacatamase VIM-1 from
human isolates of Klebsiella pneumoniae and E. coli in Greece; the IncA/C2 plasmids carrying
specific resistance genes such as blaCMY-2, blaCMY-4, blaVIM-4 and blaVEB-1 from different
Enterobacteriaceae isolated worldwide; different plasmid replicons (IncFII, IncA/C1, IncI1) carrying
the ESBL SHV-12 from human and animal origin.
The comparative analysis of plasmid backbones allowed to ascertain the diffusion of common,
emerging plasmids and helped to determine the evolution of these plasmids by acquisition
of relevant resistance genes by a panoply of mobile genetic elements and illegitimate recombination
events
A three-dimensional phenomenological model describing cyclic behavior of shape memory alloys
Full text linkNowadays, shape memory alloys, in particular Nickel–Titanium alloys (NiTi), are widely adopted in many fields (biomedical, aerospace, automotive, civil ...) for producing devices exploiting pseudo-elasticity or shape memory effect. These devices are often subjected to cyclic loadings and sometimes to large deformations that modify the material response inducing functional fatigue and/or plastic strains. Accordingly, the device effectiveness is limited or even completely compromised. In this paper, a model able to take into account both the phenomena is presented. Aiming to propose this model for the design and assessment of cyclically loaded devices by finite element simulations, a phenomenological approach was used, introducing internal variables able to describe the accumulation of inelastic strains due to fatigue and plasticity and assuming that their evolution law affects also the phase transformation domain amplitude. Two limit functions was introduced for defining the phase transformation domain and plastic region. The discrete formulation of the model is also presented. Peculiar attention is posed on the material model parameters and the procedure to calibrate them. Initially, a driver code was written in MATLAB for verifying the algorithm correctness and effectiveness; successively, the model was implemented by a user subroutine in a commercial finite element code. The results of several numerical tests are reported in order to show the model functionality and stability under different loading conditions. Finally, the model capability of reproducing 1D and 3D experimental tests is shown by comparison of numerical results with experimental tests published in the literature
Il record pollinico in sedimenti marini e continentali italiani per la ricostruzione paleoclimatica e paleombientale a partire da 1.25 Ma
No full textL’enregistrement pollinique des cycles de 100 ka en Italie: reconstitution des paléoenvironnements et valeur stratigraphique des taxons exotiques
No full textGoing 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
- …
