558 research outputs found
Sensitivity to temporal structure facilitates perceptual analysis of complex auditory scenes
The notion that sensitivity to the statistical structure of the environment is pivotal to perception has recently garnered considerable attention. Here we investigated this issue in the context of hearing. Building on previous work (Sohoglu and Chait, 2016a; elife), stimuli were artificial 'soundscapes' populated by multiple (up to 14) simultaneous streams ('auditory objects') comprised of tone-pip sequences, each with a distinct frequency and pattern of amplitude modulation. Sequences were either temporally regular or random. We show that listeners' ability to detect abrupt appearance or disappearance of a stream is facilitated when scene streams were characterized by a temporally regular fluctuation pattern. The regularity of the changing stream as well as that of the background (non-changing) streams contribute independently to this effect. Remarkably, listeners benefit from regularity even when they are not consciously aware of it. These findings establish that perception of complex acoustic scenes relies on the availability of detailed representations of the regularities automatically extracted from multiple concurrent streams
On invariants of almost symplectic connections
We study the irreducible decomposition under Sp(2n, R) of the space of
torsion tensors of almost symplectic connections. Then a description of all
symplectic quadratic invariants of torsion-like tensors is given. When applied
to a manifold M with an almost symplectic structure, these instruments give
preliminary insight for finding a preferred linear almost symplectic connection
on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections.
Properties of torsion of the vectorial kind are deduced
Molecular Subtyping of Borrelia burgdorferi sensu lato Isolates from Five Patients with Solitary Lymphocytoma
Solitary lymphocytoma is a rare cutaneous manifestation of Lyme borreliosis that has been reported almost exclusively from Europe. This suggests that its etiologic agent may be absent or extremely rare on the North American continent. All three species of B. burgdorferi sensu lato known to be associated with human Lyme borreliosis (B. burgdorferi sensu stricto, B. garinii and B. afzelii) have been isolated in Europe, whereas only B. burgdorferi sensu stricto has been found in North America. This suggests that either B. garinii or B. afzelii might be the etiologic agent of borrelial lymphocytoma. To investigate this hypothesis we characterized five strains of B. burgdorferi sensu lato isolated from lymphocytoma lesions of patients residing in Slovenia. The methods used included: large restriction fragment pattern analysis of restriction enzyme MlnI-digested genomic DNA, plasmid profiling, protein profiling, ribotyping using 5S, 16S and 23S rDNA probes and polymerase chain reaction amplification of the rrf (5S)-rrl (23S) inter-genic spacer region. Molecular subtyping showed that four of the five isolates belonged to the species B. afzelii; however, this species is the predominant patient isolate in Slovenia and therefore, may not represent a preferential association with lymphocytoma. The fifth isolate appeared to be most closely related to the DN127 genomic group of organisms. Further characterization of the isolate revealed that it possessed a unique molecular âfingerprint.â The results not only show that borrelial lymphocytoma can be caused by B. afzelii but also demonstrate an association with another genomic group of B. burgdoiferi sensu lato that is present in North America as well
Topological excitations in 2D spin system with high spin
We construct a class of topological excitations of a mean field in a
two-dimensional spin system represented by a quantum Heisenberg model with high
powers of exchange interaction. The quantum model is associated with a
classical one (the continuous classical analogue) that is based on a
Landau-Lifshitz like equation, and describes large-scale fluctuations of the
mean field. On the other hand, the classical model is a Hamiltonian system on a
coadjoint orbit of the unitary group SU() in the case of spin . We
have found a class of mean field configurations that can be interpreted as
topological excitations, because they have fixed topological charges. Such
excitations change their shapes and grow preserving an energy.Comment: 10 pages, 1 figur
Abelian gerbes as a gauge theory of quantum mechanics on phase space
We construct a U(1) gerbe with a connection over a finite-dimensional,
classical phase space P. The connection is given by a triple of forms A,B,H: a
potential 1-form A, a Neveu-Schwarz potential 2-form B, and a field-strength
3-form H=dB. All three of them are defined exclusively in terms of elements
already present in P, the only external input being Planck's constant h. U(1)
gauge transformations acting on the triple A,B,H are also defined, parametrised
either by a 0-form or by a 1-form. While H remains gauge invariant in all
cases, quantumness vs. classicality appears as a choice of 0-form gauge for the
1-form A. The fact that [H]/2i\pi is an integral class in de Rham cohomology is
related with the discretisation of symplectic area on P. This is an equivalent,
coordinate-free reexpression of Heisenberg's uncertainty principle. A choice of
1-form gauge for the 2-form B relates our construction with generalised complex
structures on classical phase space. Altogether this allows one to interpret
the quantum mechanics corresponding to P as an Abelian gauge theory.Comment: 18 pages, 1 figure available from the authors upon reques
Case Report Gouty Panniculitis with Ulcerations in a Patient with Multiple Organ Dysfunctions
Gouty panniculitis is a rare manifestation of gout. Clinically, it is characterized by indurated subcutaneous nodules in nonjoint areas. Pathologically, typical characteristic gouty tophi can be seen in subcutaneous tissue. It is postulated that gouty panniculitis develops as a consequence of uric acid accumulation in the body and localized inflammatory changes in subcutaneous tissue. We report a case of a 46-year-old man with 20-year history of gout, who developed multiple subcutaneous nodules over the abdomen and right groin/thigh area over a 2-year period. After a recent episode of congestive heart failure and acute renal failure, the nodules increased in size and the overlying skin became erythematous and ulcerated. Pathologic examination demonstrated typical tophi in the dermis and subcutaneous tissue. A review of the literature yielded fifteen similar cases that had been previously reported. We conclude that gouty panniculitis may be a manifestation of undertreated gout and may be exacerbated by the deterioration of other systemic functions
Nonperturbative 2D Gravity, Punctured Spheres and -Vacua in String Theories
We consider a model of 2D gravity with the coefficient of the
Einstein-Hilbert action having an imaginary part . This is equivalent to
introduce a -vacuum structure in the genus expansion whose effect is to
convert the expansion into a series of alternating signs, presumably Borel
summable. We show that the specific heat of the model has a physical behaviour.
It can be represented nonperturbatively as a series in terms of integrals over
moduli spaces of punctured spheres and the sum of the series can be rewritten
as a unique integral over a suitable moduli space of infinitely punctured
spheres. This is an explicit realization \`a la Friedan-Shenker of 2D quantum
gravity. We conjecture that the expansion in terms of punctures and the genus
expansion can be derived using the Duistermaat-Heckman theorem. We briefly
analyze expansions in terms of punctured spheres also for multicritical models.Comment: 12 pages + 2 figures available upon request. LaTeX Fil
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