3,587 research outputs found
Automation of Analysis of Thermographic Images in Diagnostics of Honeycomb Core Structure States
A method for converting the results of an active thermal imaging control of products made of polymer composite materials, using the Theil-Sen estimator, is described. Approbation of the described translation algorithm operation on a sample made in accordance with the technology of manufacturing the aircraft plane part is carried out
The String Calculation of QCD Wilson Loops on Arbitrary Surfaces
Compact string expressions are found for non-intersecting Wilson loops in
SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a
weighted sum over covers of the surface. All terms from the coupled chiral
sectors of the 1/N expansion of the Wilson loop expectation values are
included.Comment: 10 pages, LaTeX, no figure
A quantum group version of quantum gauge theories in two dimensions
For the special case of the quantum group we present an alternative approach to quantum gauge theories in
two dimensions. We exhibit the similarities to Witten's combinatorial approach
which is based on ideas of Migdal. The main ingredient is the Turaev-Viro
combinatorial construction of topological invariants of closed, compact
3-manifolds and its extension to arbitrary compact 3-manifolds as given by the
authors in collaboration with W. Mueller.Comment: 6 pages (plain TeX
Astrocytes mediate neurovascular signaling to capillary pericytes but not to arterioles
Active neurons increase their energy supply by dilating nearby arterioles and capillaries. This neurovascular coupling underlies blood oxygen level-dependent functional imaging signals, but its mechanism is controversial. Canonically, neurons release glutamate to activate metabotropic glutamate receptor 5 (mGluR5) on astrocytes, evoking Ca(2+) release from internal stores, activating phospholipase A2 and generating vasodilatory arachidonic acid derivatives. However, adult astrocytes lack mGluR5, and knockout of the inositol 1,4,5-trisphosphate receptors that release Ca(2+) from stores does not affect neurovascular coupling. We now show that buffering astrocyte Ca(2+) inhibits neuronally evoked capillary dilation, that astrocyte [Ca(2+)]i is raised not by release from stores but by entry through ATP-gated channels, and that Ca(2+) generates arachidonic acid via phospholipase D2 and diacylglycerol kinase rather than phospholipase A2. In contrast, dilation of arterioles depends on NMDA receptor activation and Ca(2+)-dependent NO generation by interneurons. These results reveal that different signaling cascades regulate cerebral blood flow at the capillary and arteriole levels
Asymptotic Learning Curve and Renormalizable Condition in Statistical Learning Theory
Bayes statistics and statistical physics have the common mathematical
structure, where the log likelihood function corresponds to the random
Hamiltonian. Recently, it was discovered that the asymptotic learning curves in
Bayes estimation are subject to a universal law, even if the log likelihood
function can not be approximated by any quadratic form. However, it is left
unknown what mathematical property ensures such a universal law. In this paper,
we define a renormalizable condition of the statistical estimation problem, and
show that, under such a condition, the asymptotic learning curves are ensured
to be subject to the universal law, even if the true distribution is
unrealizable and singular for a statistical model. Also we study a
nonrenormalizable case, in which the learning curves have the different
asymptotic behaviors from the universal law
Some New/Old Approaches to QCD
This is a talk delivered at the Meeting on Integrable Quantum Field Theories,
Villa Olmo and at STRINGS 1992, Rome, September 1992. I discuss some recent
attempts to revive two old ideas regarding an analytic approach to QCD-the
development of a string representation of the theory and the large N limit of
QCD.Comment: 20 page
Density Correlation Functions in Calogero Sutherland Models
Using arguments from two dimensional Yang-Mills theory and the collective
coordinate formulation of the Calogero-Sutherland model, we conjecture the
dynamical density correlation function for coupling and , where is
an integer. We present overwhelming evidence that the conjecture is indeed
correct.Comment: 12 pages phyzzx, CERN-TH/94.7243 One reference change
Summing Over Inequivalent Maps in the String Theory Interpretation of Two Dimensional QCD
Following some recent work by Gross, we consider the partition function for
QCD on a two dimensional torus and study its stringiness. We present strong
evidence that the free energy corresponds to a sum over branched surfaces with
small handles mapped into the target space. The sum is modded out by all
diffeomorphisms on the world-sheet. This leaves a sum over disconnected classes
of maps. We prove that the free energy gives a consistent result for all smooth
maps of the torus into the torus which cover the target space times, where
is prime, and conjecture that this is true for all coverings. Each class
can also contain integrations over the positions of branch points and small
handles which act as ``moduli'' on the surface. We show that the free energy is
consistent for any number of handles and that the first few leading terms are
consistent with contributions from maps with branch points.Comment: 17 pages, 5 eps figures contained in a uuencoded file, UVA-HET-92-1
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