958 resultados para Classical conditioning


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A proportion of Hodgkin lymphoma (HL) cases are causally associated with the Epstein-Barr virus (EBV) but the aetiology of the remaining cases remains obscure. Over the last 3 decades several studies have found an association between HL and measles virus (MV) including a recent cohort study describing the detection of MV antigens in Hodgkin and Reed-Sternberg cells, the tumour cells in HL. In the present study we looked at the relationship between history of MV infection and risk of developing HL in a population-based, case/control study of HL. In addition we used immunohistochemistry and RT-PCR to look for direct evidence of MV in HL biopsies. There was no significant difference in the proportion of cases reporting previous measles compared to controls in the entire data set or when young adults were considered separately. Using a robust immunohistochemical assay for MV infection, we failed to find evidence of MV in biopsies from 97 cases of HL and RT-PCR studies similarly gave negative results. This study therefore provides no evidence that MV is directly involved in the development of HL. However, when age at first reported MV infection was investigated, significant differences emerged with children infected before school-age having higher risk, especially of EBV-ve HL, when compared with children infected at older ages; the interpretation of these latter results is unclear.

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It is remarkable how the classical Volterra integral operator, which was one of the first operators which attracted mathematicians' attention, is still worth of being studied. In this essentially survey work, by collecting some of the very recent results related to the Volterra operator, we show that there are new (and not so new) concepts that are becoming known only at the present days. Discovering whether the Volterra operator satisfies or not a given operator property leads to new methods and ideas that are useful in the setting of Concrete Operator Theory as well as the one of General Operator Theory. In particular, a wide variety of techniques like summability kernels, theory of entire functions, Gaussian cylindrical measures, approximation theory, Laguerre and Legendre polynomials are needed to analyze different properties of the Volterra operator. We also include a characterization of the commutator of the Volterra operator acting on L-P[0, 1], 1

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Factors relating to identity and to economics have been shown to be important predictors of attitudes towards the European Union (EU). In this article, we show that the impact of identity is conditional on economic context. First, living in a member state that receives relatively high levels of EU funding acts as a 'buffer', diluting the impact of an exclusive national identity on Euroscepticism. Second, living in a relatively wealthy member state, with its associated attractiveness for economic migrants, increases the salience of economic xenophobia as a driver of sceptical attitudes. These results highlight the importance of seeing theories of attitude formation (such as economic and identity theories) not as competitors but rather as complementary, with the predictive strength of one theoretical approach (identity) being a function of system-level variation in factors relating to the other theoretical approach (macro-level economic conditions).