132 research outputs found
Realizzazione di un sistema qualitativo in Real-Time PCR per l'identificazione di Escherichia Coli patogeni
Get PDFShiga toxin-producing E. coli (STEC-VTEC) are foodborne pathogens that have been associated with gastroenteric diseases in humans. Infections are often caused by ingestion of contaminated food. For this purpose, the report ‘Technical specifications for the monitoring and reporting of verotoxigenic Escherichia coli (VTEC o STEC) on animals and food (VTEC surveys on animals and food)’ was proposed by EFSA (European Food Safety Authority) in order to harmonize STEC research methods in EU Member States. Moreover, the reference method ISO 13136:2012 describes the molecular identification of Shiga toxin-producing E. coli through the detection of stx and eae virulence genes and serogroup assignment through the detection of the genes associated with O157, O111, O26, O103, O145 serogroups. The genes aggR and aaiC, distinctive for Enteroaggregative E. coli (EAEC) strains, should be also taken into account considering that the large outbreak occurred in Germany in 2011 (750 cases of HUS of which 44 deaths) was due to the consumption of sprouts contaminated by a O104 strain, which was found both STEC and EAEC (stx2, aggR and aaiC) positive.
The aim of this study was to develop a multiplex real-time PCR assay for the rapid detection of pathogenic E.coli strains in food, in particular an assay for the detection of stx1, stx2, and eae genes, which identifies STEC; other three assays specifically formulated for the identification of the six main pathogenic serogroups (O157, O111, O26, O103, O145, and O104), and , lastly, another assay for the detection of aggR and aaiC genes, specific for EAEC. Furthermore, the assays were compared with official methods used in USA (USDA-FSIS, FDA/BAM) for the identification of E.coli in foodstuffs.
The results obtained show that the assays for the sensitive, specific and rapid detection of STEC (stx-eae) and serogroups (O26-O103-O111-O145-O157-O104) were developed, in compliance with the reference method ISO 13136:2012. These assays were able to identify pathogenic E. coli in the main foodstuff implicated in epidemic outbreaks. Moreover, this work demonstrates that the performance of the assays is reliant on the enrichment process that remain a critical step in assay development. Since the contamination level of STEC in food is usually low, the selection of an appropriate medium is a key element of STEC detection protocol, to reduce the risk of false negative results. Therefore, alternative enrichment condition, like mBPWp + CV at 42°C, should be taken into consideration.
Furthermore, colony tests carried out with EAEC E.coli detection assay showed optimal results, with 100% of exclusivity and efficiency.
The comparison between molecular assays developed in this study and USDA-FSIS and FDA/BAM official methods showed equivalent results of performance and sensitivity, providing in some cases better results with our method
Dall’integrale di Riemann all’integrale di Itô
No full textIl libro è un trattato avanzato che riassume la teoria matematica dell'integrazione partendo dagli integrali di funzioni continue fino ad arrivare all'integrale stocastico. E' utile per i giovani ricercatori e per coloro che si avvicinano alla Finanza proveniendo da altre discipline (Matematica, Fisica).The book is sums up -at an advanced level - the mathematical theory of integration, starting from the integrals of continuous functions, till to the stochastic integral. It is useful for early stage researchers, as well to researchers that approach Finance coming from other disciplines (Mathematics, Physics)
Black-Scholes-Schrödinger-Zipf-Mandelbrot model framework for improving a study of the coauthor core score
No full textThe data and findings by Miskiewicz (2013) on the relationship between the number (J) of publications ranked according to their decreasing importance, for some scientist with her/his coauthors (CA), i.e. J α 1/r α, as found in Ausloos (2013), when specific types of publications, i.e. proceedings (in a generalized sense) and peer-review journals, are considered, are reexamined along the Zipf-Mandelbrot law Mandelbrot (1977), i.e. J α 1/(ν+r)ζ. The statistics are much improved. The exponent α and ζ are compared. The m a core value, i.e. the core number of CAs [1] is unaffected, of course. A Black-Scholes-Schrödinger model framework is proposed to describe the findings. © 2014 Elsevier B.V. All rights reserved
Complex-valued information entropy measure for networks with directed links (digraphs). Application to citations by community agents with opposite opinions
No full textThe notion of complex-valued information entropy measure is presented. It applies in particular to directed networks (digraphs). The corresponding statistical physics notions are outlined. The studied network, serving as a case study, in view of illustrating the discussion, concerns citations by agents belonging to two distinct communities which have markedly different opinions: the Neocreationist and Intelligent Design Proponents, on one hand, and the Darwinian Evolution Defenders, on the other hand. The whole, intra-and inter-community adjacency matrices, resulting from quotations of published work by the community agents, are elaborated and eigenvalues calculated. Since eigenvalues can be complex numbers, the information entropy may become also complex-valued. It is calculated for the illustrating case. The role of the imaginary part finiteness is discussed in particular and given some physical sense interpretation through local interaction range consideration. It is concluded that such generalizations are not only interesting and necessary for discussing directed networks, but also may give new insight into conceptual ideas about directed or other networks. Notes on extending the above to Tsallis entropy measure are found in an Appendix
Physics of Competition and Conflicts
No full textThe issue gathers the papers delivered at the 1st annual meeting of the COST Action Physics of Competition and Conflicts, held in Rome, 2009
An investigation of computational complexity of the method of symbolic images
No full textThe widespread presence of maps in discrete dynamical mo,dels needs the usage of efficient algorithms for their investigagtion. The method of symbolic images is more efficient that exhaustive numerical simulation of trajectories because it transforms a map into a graph through a discretization of the state space, so it opens the way to the usage of graph algorithms and it provides a unified framework for the detection of system features. In this framework, a modification of the algorithm deascribed by Osipenko et al. is proposed and its efficiency is analysed Issues on the convergence of the method raise when the dynamical system is described by a not-Lischitzian nonlinear map in the plane. As case study it is sbhown the application of the method on an evolutionary model of boundedly rational consumer characterized by the presence of a denominator that can vanish
The Hurst’s exponent in technical analysis signals
No full textThe fractal nature of financial data has been investigated through literature.
The aim of this paper is to use the information given by the detection of the
fractal measure of data in order to provide support for trading decisions when
dealing with technical analysis signals that can be used to trigger buy/sell orders.
Trendlines are considered as a case study
Companies' decisions for profit maximization: A structural model
No full textHuge analyses on firms data selected from public available databases
accomplished the task to describe the size and growth of firms through
interpolating functions. The structure and internal firms organization
that lead to the optimal profit is a main matter of business studies
and must take carefully into account internal work distribution and
the subsequent productivity. Moreover factors external to firms, like
as the evolution of markets and the availability of new technologies
show their immediate bias on the wealth of the firms. In this paper
a model is developed for a set of firms producing a single commodity.
The shape of the productivity that leads to profit optimization is drawn
and discussed. Furthermore the optimal time for the firm to renew
its technology is established and consequences on the productivity are
examined
Organization of networks with tagged nodes and biased links: A priori distinct communities The case of intelligent design proponents and Darwinian evolution defenders
No full textpeer reviewedAmong the topics of opinion formation it is of interest to observe the characteristics of networks with a priori distinct communities. The citation network(s) between selected members of the Neocreationist and Intelligent Design and the Darwinian Evolution communities are unfolded through the available internet citations. The resulting adjacency matrix is not symmetric. A generalization of considerations pertaining to the case of networks with tagged nodes and biased links, directed or undirected, is presented. The main characteristic coefficients describing the structure of such networks are outlined. The structural features are discussed searching for statistical aspects of the communities. The degree distributions, each network's assortativity, specific global and local clustering coefficients and the Average Overlap Indices are especially calculated since the distribution of elements in the rectangular submatrices represent inter-community connections. The various closed and open triangles made from nodes, distinguishing the community, are listed. The z-scores of patterns are calculated. One can distinguish between opinion leaders, followers and main rivals and briefly interpret their relationships through intuitively expected behavior in defence of an opinion. Suggestions for more elaborate models describing such communities and their subsequent structures are found in conclusions. (C) 2010 Elsevier B.V. All rights reserved
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