1,720,977 research outputs found
Evaluation of the antimicrobial activity of disinfectants Evaluation of the antimicrobial activity of disinfectants
No full textHow do bats maintain infections? Mathematical modelling to disentangle mechanisms driving the temporal cycles of infection in Australian bats
Full text linkZoonotic pathogens, (pathogens that can be transmitted from animals to humans), repre-sent an increasing public health concern. Cross-species transmission can only occur when particular conditions of reservoir host ecology, infection dynamics and species distribu-tions align, making spillovers (the transmission of a pathogen from a vertebrate animal to a human) at the same time a global public health concern and a complex and poorly under-stood phenomenon. Pathogen circulation in reservoir host populations is one of the fac-tors contributing to spillover risk, therefore, understanding the mechanisms driving infec-tion dynamics can help us in preventing spillovers to occur.
In Australia, the recent changes in land use caused a rapid modification in bat behaviour that coincided with the emergence of Hendra virus (HeV). HeV is maintained in wildlife by bats of the Pteropus genus (flying foxes) and can be transmitted from bats to horses and from horses to humans. Bats do not show marked signs of infection, but in humans and horses the symptomatology is very severe, with a high fatality rate (57% and 80% re-spectively), pointing out the need to avoid HeV spillovers. HeV spillovers usually occur in winter and often coincide with an increase in viral shedding in urines from bats, sug-gesting a temporal trend in pathogen circulation in reservoir host populations. Several fac-tors can contribute to drive the observed temporal dynamics, and different maintenance routes have been theoretically hypothesized to explain the cyclicity of infection.
To disentangle the mechanisms driving the pathogen dynamics in reservoir host, we ap-plied a set of mathematical models to an historical dataset collected in Boonah (Queens-land, Australia) between July 2013 and June 2014. We used a system of four differential equations (SEIR model type) to simulate infection dynamics in the host population, and we included time dependent parameters to simulate the seasonality of infection and perio-dicity of births.
We showed that the sole population dynamic of bats, with the introduction in the system of susceptible new-borns, can not explain the annual cycles of HeV shedding, and either a waning of the immunity in adult bats or the development of a chronic infection with cyclic viral reactivation must be hypothesized to explain the observed infection dynamics.
Our results support the hypothesis that cyclicity in HeV shedding can be driven by envi-ronmental stressors, like winter food shortages, that can affect bat immune response to pathogens. These findings evidence the need to reduce anthropogenic stressors that might exacerbate HeV shedding from bats. Furthermore, given the adaptability of the modelling framework, the method proposed can be applied to other infections/bat species
Valutazione dell’efficacia delle strategie di intervento per il controllo delle malattie infettive attraverso la simulazione matematica della dinamica di infezione
No full textIntroduzione
Le strategie di gestione sanitaria delle infezioni sono disparate, variano tra loro per efficacia, costo e realizzabilità, ma in molti casi manca un’analisi comparativa e sistematica della loro efficacia e questa mancanza rende controversa la scelta della migliore strategia per la gestione sanitaria di un’infezione. L’utilizzo di modelli matematici, permettendo la simulazione a priori della dinamica delle infezioni in diversi scenari, consente un’analisi sistematica degli effetti degli interventi sulle popolazioni di interesse, e rappresenta uno strumento efficace per le scelte di gestione sanitaria. Un esempio di infezione la cui gestione sanitaria è ancora dibattuta è Baylisascaris procyonis, un elminta il cui ospite definitivo è il procione (Procyon lotor). L’ingestione delle forme infettanti di B. procyonis da parte dell’uomo può essere causa di sindrome da larva migrans, ad esito anche fatale, ma ad oggi non esiste una strategia d’intervento d’elezione per questa infezione. Le strategie attualmente prese in considerazione spaziano dalla rimozione dei procioni infetti, alla rimozione delle feci dall’ambiente, al trattamento antiparassitario degli animali.
Obiettivi
Per effettuare una corretta valutazione a priori dell'efficacia delle suddette strategie, è stato sviluppato un modello matematico per lo studio della dinamica di B. procyonis, simulando l'effetto dei diversi interventi.
Metodi
È stato innanzitutto elaborato un modello deterministico di tre equazioni differenziali, adattato all’interazione tra le popolazioni ospite (procione) e parassita (adulti e fase infettante di B. procyonis). Sono stati poi simulati i tre tipi di intervento gestionale (depopolamento, somministrazione di antielmintici e rimozione di feci dall’ambiente), dei quali è stato valutato l’effetto sull'infestazione ambientale delle forme infettanti. Le simulazioni sono state adattate a due diversi scenari, il caso di una popolazione parassitaria stabilizzata, e quello di una popolazione parassitaria in espansione.
Risultati
Le simulazioni hanno evidenziato come il metodo più rapido per l'eliminazione delle forme infettanti dall’ambiente sia la rimozione delle feci, ma come questo metodo necessiti di un grande sforzo di intervento per ottenere il risultato desiderato. La somministrazione di antielmintici e la rimozione dei procioni dall’area di intervento risultano invece più lenti nell’eliminare le forme infettanti, ma quest'ultima strategia permette il conseguimento del risultato con un minor sforzo, risultando quindi l'intervento più idoneo.
Conclusioni
I risultati ottenuti evidenziano come l’utilizzo di un modello matematico rappresenti un valido strumento per la valutazione a priori dell'efficacia e dell'applicabilità delle strategie di gestione sanitaria delle infezioni, permettendo l'individuazione della tipologia di intervento più adatta in base alle risorse disponibili e alle tempistiche desiderate
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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