121,202 research outputs found
Contact-eutectic-lens fabrication technique
Method enables use of crystal or semiconductor materials with selective spectral-response characteristics (ultraviolet, visible, or infrared wavelengths) in fabrication of contact lenses, reading glasses, and photographic processing equipment
Frequency and Phase Synchronization in Neuromagnetic Cortical Responses to Flickering-Color Stimuli
In our earlier study dealing with the analysis of neuromagnetic responses
(magnetoencephalograms - MEG) to flickering-color stimuli for a group of
control human subjects (9 volunteers) and a patient with photosensitive
epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy
(FNS) was able to identify specific differences in the responses of each
organism. The high specificity of individual MEG responses manifested itself in
the values of FNS parameters for both chaotic and resonant components of the
original signal. The present study applies the FNS cross-correlation function
to the analysis of correlations between the MEG responses simultaneously
measured at spatially separated points of the human cortex processing the
red-blue flickering color stimulus. It is shown that the cross-correlations for
control (healthy) subjects are characterized by frequency and phase
synchronization at different points of the cortex, with the dynamics of
neuromagnetic responses being determined by the low-frequency processes that
correspond to normal physiological rhythms. But for the patient, the frequency
and phase synchronization breaks down, which is associated with the suppression
of cortical regulatory functions when the flickering-color stimulus is applied,
and higher frequencies start playing the dominating role. This suggests that
the disruption of correlations in the MEG responses is the indicator of
pathological changes leading to photosensitive epilepsy, which can be used for
developing a method of diagnosing the disease based on the analysis with the
FNS cross-correlation function.Comment: 21 pages, 14 figures; submitted to "Laser Physics", 2010, 2
Space-time symplectic extension
It is conjectured that in the origin of space-time there lies a symplectic
rather than metric structure. The complex symplectic symmetry Sp(2l,C), l\ge1
instead of the pseudo-orthogonal one SO(1,d-1), d\ge4 is proposed as the
space-time local structure group. A discrete sequence of the metric space-times
of the fixed dimensionalities d=(2l)^2 and signatures, with l(2l-1) time-like
and l(2l+1) space-like directions, defined over the set of the Hermitian
second-rank spin-tensors is considered as an alternative to the
pseudo-Euclidean extra dimensional space-times. The basic concepts of the
symplectic framework are developed in general, and the ordinary and
next-to-ordinary space-time cases with l=1,2, respectively, are elaborated in
more detail. In particular, the scheme provides the rationale for the
four-dimensionality and 1+3 signature of the ordinary space-time.Comment: 15 pp, LaTe
Lax pairs, Painlev\'e properties and exact solutions of the alogero Korteweg-de Vries equation and a new (2+1)-dimensional equation
We prove the existence of a Lax pair for the Calogero Korteweg-de Vries
(CKdV) equation. Moreover, we modify the T operator in the the Lax pair of the
CKdV equation, in the search of a (2+1)-dimensional case and thereby propose a
new equation in (2+1) dimensions. We named this the (2+1)-dimensional CKdV
equation. We show that the CKdV equation as well as the (2+1)-dimensional CKdV
equation are integrable in the sense that they possess the Painlev\'e property.
Some exact solutions are also constructed
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