3,006 research outputs found
Construction of Parseval wavelets from redundant filter systems
We consider wavelets in L^2(R^d) which have generalized multiresolutions.
This means that the initial resolution subspace V_0 in L^2(R^d) is not singly
generated. As a result, the representation of the integer lattice Z^d
restricted to V_0 has a nontrivial multiplicity function. We show how the
corresponding analysis and synthesis for these wavelets can be understood in
terms of unitary-matrix-valued functions on a torus acting on a certain vector
bundle. Specifically, we show how the wavelet functions on R^d can be
constructed directly from the generalized wavelet filters.Comment: 34 pages, AMS-LaTeX ("amsproc" document class) v2 changes minor typos
in Sections 1 and 4, v3 adds a number of references on GMRA theory and
wavelet multiplicity analysis; v4 adds material on pages 2, 3, 5 and 10, and
two more reference
Language processing within the human medial temporal lobe
Although the hippocampal formation is essential for verbal memory, it is not fully understood how it contributes to language comprehension. We recorded event-related potentials (ERPs) directly from two substructures of the medial temporal lobe (MTL), the rhinal cortex and the hippocampus proper, while epilepsy patients listened to sentences that either were correct or contained semantic or syntactic violations. Semantic violations elicited a large negative ERP response peaking at approximately 400 ms in the rhinal cortex. In contrast, syntactically incorrect sentences elicited a negative deflection of 500-800 ms in the hippocampus proper. The results suggest that functionally distinct aspects of integration in language comprehension are supported by different MTL structures: the rhinal cortex is involved in semantic integration, whereas the hippocampus proper subserves processes of syntactic integration. An analysis of phase synchronization within the gamma band between rhinal and hippocampal recording sites showed that both of the above-mentioned ERP components were preceded by an increase of phase synchronization. In contrast to these short phasic increases of phase synchronization in both violation conditions, correct sentences were associated with a long-lasting synchronization in a late time window, possibly reflecting the integration of semantic and syntactic information as required for normal comprehension
Scale-invariance of human EEG signals in sleep
We investigate the dynamical properties of electroencephalogram (EEG) signals
of human in sleep. By using a modified random walk method, We demonstrate that
the scale-invariance is embedded in EEG signals after a detrending procedure.
Further more, we study the dynamical evolution of probability density function
(PDF) of the detrended EEG signals by nonextensive statistical modeling. It
displays scale-independent property, which is markedly different from the
turbulent-like scale-dependent PDF evolution.Comment: 4 pages and 6 figure
Sigmoid-colonic motility in health and irritable bowel syndrome: A role for 5-hydroxytryptamine
General Framework for phase synchronization through localized sets
We present an approach which enables to identify phase synchronization in
coupled chaotic oscillators without having to explicitly measure the phase. We
show that if one defines a typical event in one oscillator and then observes
another one whenever this event occurs, these observations give rise to a
localized set. Our result provides a general and easy way to identify PS, which
can also be used to oscillators that possess multiple time scales. We
illustrate our approach in networks of chemically coupled neurons. We show that
clusters of phase synchronous neurons may emerge before the onset of phase
synchronization in the whole network, producing a suitable environment for
information exchanging. Furthermore, we show the relation between the localized
sets and the amount of information that coupled chaotic oscillator can
exchange
Positronium S state spectrum: analytic results at O(m alpha^6)
We present an analytic calculation of the O(m alpha^6) recoil and radiative
recoil corrections to energy levels of positronium nS states and their
hyperfine splitting. A complete analytic formula valid to O(m alpha^6) is given
for the spectrum of S states. Technical aspects of the calculation are
discussed in detail. Theoretical predictions are given for various energy
intervals and compared with experimental results.Comment: 29 pages, revte
A new intracellular serine protease inhibitor expressed in the rat pituitary gland complexes with granzyme B
AbstractWe have cloned a novel serpin (raPIT5a) from a rat pituitary cDNA library which is structurally related to members of the ovalbumin subfamily of serine protease inhibitors. This new cDNA encodes a 374-amino acid protein, designated raPIT5a. raPIT5a was expressed in specific cells in the intermediate and anterior lobes of the pituitary. Recombinant raPIT5a was not secreted suggesting raPIT5a functions to inhibit intracellular proteases. Recombinant raPIT5a formed an SDS-stable complex with human granzyme B, a serine protease which induces apoptosis by activating members of the caspase enzyme family. These data suggest raPIT5a may have a role in regulating granzyme B or related enzymes and apoptosis in the pituitary gland
Statistical Origin of Pseudo-Hermitian Supersymmetry and Pseudo-Hermitian Fermions
We show that the metric operator for a pseudo-supersymmetric Hamiltonian that
has at least one negative real eigenvalue is necessarily indefinite. We
introduce pseudo-Hermitian fermion (phermion) and abnormal phermion algebras
and provide a pair of basic realizations of the algebra of N=2
pseudo-supersymmetric quantum mechanics in which pseudo-supersymmetry is
identified with either a boson-phermion or a boson-abnormal-phermion exchange
symmetry. We further establish the physical equivalence (non-equivalence) of
phermions (abnormal phermions) with ordinary fermions, describe the underlying
Lie algebras, and study multi-particle systems of abnormal phermions. The
latter provides a certain bosonization of multi-fermion systems.Comment: 20 pages, to appear in J.Phys.
How model sets can be determined by their two-point and three-point correlations
We show that real model sets with real internal spaces are determined, up to
translation and changes of density zero by their two- and three-point
correlations. We also show that there exist pairs of real (even one
dimensional) aperiodic model sets with internal spaces that are products of
real spaces and finite cyclic groups whose two- and three-point correlations
are identical but which are not related by either translation or inversion of
their windows. All these examples are pure point diffractive.
Placed in the context of ergodic uniformly discrete point processes, the
result is that real point processes of model sets based on real internal
windows are determined by their second and third moments.Comment: 19 page
Edge overload breakdown in evolving networks
We investigate growing networks based on Barabasi and Albert's algorithm for
generating scale-free networks, but with edges sensitive to overload breakdown.
the load is defined through edge betweenness centrality. We focus on the
situation where the average number of connections per vertex is, as the number
of vertices, linearly increasing in time. After an initial stage of growth, the
network undergoes avalanching breakdowns to a fragmented state from which it
never recovers. This breakdown is much less violent if the growth is by random
rather than preferential attachment (as defines the Barabasi and Albert model).
We briefly discuss the case where the average number of connections per vertex
is constant. In this case no breakdown avalanches occur. Implications to the
growth of real-world communication networks are discussed.Comment: To appear in Phys. Rev.
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