1,722,768 research outputs found
Bessel-like functional distributions in brain average evoked potentials
No full textAverage evoked potential data recorded as impulse responses of brains to electric shocks show Bessel-like functional distributions which we analyze in terms of couples of damped/amplified oscillators.
This reproduces results obtained in terms of ordinary differential equations (Freeman K-sets) and offers the possibility of a direct connection with the dissipative model of brain in the quantum gauge field theory paradigm. We study the control mechanism by fine tuning the model parameters and the brain property
of discriminating between two similar behaviors or perceptions. We suggest that a similar control
mechanism may be useful in security communication protocols. Finally, brain activity and mental activity is considered in the light of our results
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
Protocolli di stimolazione ovarica per cicli di inseminazione intrauterina: efficacia degli antagonisti del GnRH
No full textCapture probe conjugated to paramagnetic nanoparticles for purification of Alexandrium spp. (dinoflagellate) DNA from environmental samples
No full textNon-Hermitian Hamiltonian deformations in quantum mechanics
Full text linkThe construction of exactly-solvable models has recently been advanced by considering integrable TTbar deformations and related Hamiltonian deformations in quantum mechanics. We introduce a broader class of non-Hermitian Hamiltonian deformations in a nonrelativistic setting, to account for the description of a large class of open quantum systems, which includes, e.g., arbitrary Markovian evolutions conditioned to the absence of quantum jumps. We relate the time evolution operator and the time-evolving density matrix in the undeformed and deformed theories in terms of integral transforms with a specific kernel. Non-Hermitian Hamiltonian deformations naturally arise in the description of energy diffusion that emerges in quantum systems from time-keeping errors in a real clock used to track time evolution. We show that the latter can be related to an inverse TTbar deformation with a purely imaginary deformation parameter. In this case, the integral transforms take a particularly simple form when the initial state is a coherent Gibbs state or a thermofield double state, as we illustrate by characterizing the purity, Rényi entropies, logarithmic negativity, and the spectral form factor. As the dissipative evolution of a quantum system can be conveniently described in Liouville space, we further study the spectral properties of the Liouvillians, i.e., the dynamical generators associated with the deformed theories. As an application, we discuss the interplay between decoherence and quantum chaos in non-Hermitian deformations of random matrix Hamiltonians and the Sachdev-Ye-Kitaev model
Brain Dynamics, Chaos and Bessel Functions
Full text linkBy resorting to Freeman’s observations showing that the distribution functions
of impulse responses of cortex to sensory stimuli resemble Bessel functions, we study brain
dynamics by considering the equivalence of spherical Bessel equation, in a given parametrization,
to two oscillator equations, one damped and one amplified oscillator. The study of such a couple
of equations, which are at the basis of the formulation of the dissipative many-body model,
reveals the structure of the root loci of poles and zeros of solutions of Bessel equations, which
are consistent with results obtained using ordinary differential equation techniques. We analyze
stable and unstable limit cycles and consider thermodynamic features of brain functioning,
which in this way may be described in terms of transitions between chaotic gas-like and ordered
liquid-like behaviors. Nonlinearity dominates the dynamical critical transition regimes. Linear
behavior, on the other hand, characterizes superpositions within self-organized neuronal domains
in each dynamical phase. The formalism is consistent with the observed coexistence in circular
causality of pulse density fields and wave density fields
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