571 research outputs found

    Ecological Sampling of Gaze Shifts

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    A statistical mechanical problem?

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    The problem of deriving the processes of perception and cognition or the modes of behaviour from states of the brain appears to be unsolvablein view of the huge numbers of units involved. However, neural activities are not random, but, rather, form spatio-temporal patterns, and thank to these restrictions, which in turn are due to connections among neurons, the problem can at least be approached.The situation is similar to what happens in large physical ensembles, whereglobal behaviour is derived by microscopic properties. Despite the obvious differences between neural and physical systems a statistical mechanics approach is almost inescapable, since dynamics of the brain as a whole are clearly determined by the outputs of single neurons. In this paper it will be shown how, starting from very simple systems, connectivity engenders levels of increasing complexity in thefunctions of the brain depending on specific constraints.Correspondingly levels of explanations must take into account the fundamental role of constraints and assign at each level proper model structures and variables, that, on one hand, emerge from outputs of the lower levels, and yet are specific, in that they ignore irrelevant details

    Nonlinear beam self-imaging and self-focusing dynamics in a GRIN multimode optical fiber: theory and experiments

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    Beam self-imaging in nonlinear graded-index multimode optical fibers is of interest for many applications, such as implementing a fast saturable absorber mechanism in fiber lasers via multimode interference. We obtain an exact solution for the nonlinear evolution of first and second order moments of a laser beam carried by a graded-index multimode fiber, predicting that the spatial self-imaging period does not vary with power. Whereas the amplitude of the oscillation of the beam width is power-dependent. We have experimentally studied the longitudinal evolution of beam self-imaging by means of femtosecond laser pulse propagation in both the anomalous and the normal dispersion regime of a standard telecom graded-index multimode optical fiber. Light scattering out of the fiber core via visible fluorescence emission and harmonic wave generation permits us to directly confirm that the self-imaging period is invariant with power. Spatial shift and splitting of the self-imaging process under the action of self-focusing are also emphasized

    Theoretical and experimental analysis of the performances of a heat sink with vertical orientation in natural convection

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    In the various areas in which electrical components are used, the problem of heat dissipation generated due to the absorption of electrical energy assumes great interest and is worthy of an in-depth study. In steady state conditions, the thermal power generated can equal the electrical power absorbed and leads to an alteration in the physical properties of electrical components compromising their performance and correct functioning. One of the most frequently adopted solutions consists in the application of a heat sink on the surface to be cooled. Experimental tests were conducted using an infrared thermal camera, an internal climate control unit for the recording of the thermo hygrometric conditions of the environment and a finite element software (ProENGINEER) to simulate the thermal behaviour of the heat sink in order to analyse the modalities of thermal exchange of the heat sink. The results obtained were subsequently compared with the heat sink properties provided by the manufacturer. The main objective of the work is that of providing a methodology that blends the use of thermographic and simulation techniques with finite elements, in order to render the development of a theoretical–experimental correlation possible for any physical condition and geometrical configuration taken into consideration. This methodology is confirmed in the field of technological development of electrical components, where at each stage of the planning process exists a marked intertwining of computing, electronics, mechanics and heat transmission

    Coexistence of three EGFR mutations in an NSCLC patient: A brief report

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    The epidermal growth factor receptor (EGFR) represents a molecular target for tyrosine kinase inhibitors for non-small cell lung cancer (NSCLC) patients with a mutation in the EGFR gene. Mutations of the EGFR gene that occur at a single position in NSCLC tissue are found as single, whereas two or more mutations on the same allele are poorly detected and investigated

    Algumas considerações sobre o sanitarismo no meio rural paulista no início do século XX

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    Resumo: O objetivo deste artigo é apresentar e discutir algumas medidas higienistas implantadas no meio rural paulistano no início do século XX, com ênfase no controvertido papel do eucalipto no combate às doenças tropicais. No início do processo de modernização da agricultura paulista, no governo Jorge Tibiriçá, em 1906, o higienismo começou a ganhar espaço, enquanto política pública, também no meio rural. Algumas dessas medidas serão analisadas neste artigo: a plantação de arroz no Vale do Paraíba; a produção e publicação pela Escola Agrícola de Piracicaba do Abc do Agricultor e o discurso sobre a importância de se plantar eucalipto para a saúde humana. As fontes consultadas foram a Revista Agrícola, editada pela SPA – Sociedade Paulista de Agricultura - veículo de divulgação da agricultura moderna desde sua fundação, em 1896, Boletim da Agricultura, publicação da Secretaria da Indústria e Comércio do Estado de São Paulo e O Fazendeiro, também publicada pela SPA, após o encerramento da Revista Agrícola, em 1911. Palavras-chave: Higienismo no campo; agricultura moderna; destruição ambiental

    Fibroblast growth factor 23: translating analytical improvement into clinical effectiveness for tertiary prevention in chronic kidney disease

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    Fibroblast growth factor 23 (FGF23) plays a key role in the pathophysiology of chronic kidney disease (CKD) and of the associated cardiovascular diseases, ranking on the crossroads of several evolving areas with a relevant impact on the health-care system (ageing, treatment of CKD and prevention from cardiovascular and renal events). In this review, we will critically appraise the overall issues concerning the clinical usefulness of FGF23 determination in CKD, focusing on the analytical performances of the methods, aiming to assess whether and how the clinical introduction of FGF23 may promote cost-effective health care policies in these patients
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