660 research outputs found
Periodically driven Taylor-Couette turbulence
We study periodically driven Taylor-Couette turbulence, i.e. the flow
confined between two concentric, independently rotating cylinders. Here, the
inner cylinder is driven sinusoidally while the outer cylinder is kept at rest
(time-averaged Reynolds number is ). Using particle image
velocimetry (PIV), we measure the velocity over a wide range of modulation
periods, corresponding to a change in Womersley number in the range . To understand how the flow responds to a given modulation, we
calculate the phase delay and amplitude response of the azimuthal velocity.
In agreement with earlier theoretical and numerical work, we find that for
large modulation periods the system follows the given modulation of the
driving, i.e. the system behaves quasi-stationary. For smaller modulation
periods, the flow cannot follow the modulation, and the flow velocity responds
with a phase delay and a smaller amplitude response to the given modulation. If
we compare our results with numerical and theoretical results for the laminar
case, we find that the scalings of the phase delay and the amplitude response
are similar. However, the local response in the bulk of the flow is independent
of the distance to the modulated boundary. Apparently, the turbulent mixing is
strong enough to prevent the flow from having radius-dependent responses to the
given modulation.Comment: 12 pages, 6 figure
Generalized Lenard Chains, Separation of Variables and Superintegrability
We show that the notion of generalized Lenard chains naturally allows
formulation of the theory of multi-separable and superintegrable systems in the
context of bi-Hamiltonian geometry. We prove that the existence of generalized
Lenard chains generated by a Hamiltonian function defined on a four-dimensional
\omega N manifold guarantees the separation of variables. As an application, we
construct such chains for the H\'enon-Heiles systems and for the classical
Smorodinsky-Winternitz systems. New bi-Hamiltonian structures for the Kepler
potential are found.Comment: 14 pages Revte
Alternative linear structures for classical and quantum systems
The possibility of deforming the (associative or Lie) product to obtain
alternative descriptions for a given classical or quantum system has been
considered in many papers. Here we discuss the possibility of obtaining some
novel alternative descriptions by changing the linear structure instead. In
particular we show how it is possible to construct alternative linear
structures on the tangent bundle TQ of some classical configuration space Q
that can be considered as "adapted" to the given dynamical system. This fact
opens the possibility to use the Weyl scheme to quantize the system in
different non equivalent ways, "evading", so to speak, the von Neumann
uniqueness theorem.Comment: 32 pages, two figures, to be published in IJMP
Invariant classification of orthogonally separable Hamiltonian systems in Euclidean space
The problem of the invariant classification of the orthogonal coordinate webs
defined in Euclidean space is solved within the framework of Felix Klein's
Erlangen Program. The results are applied to the problem of integrability of
the Calogero-Moser model
The Stabilized Poincare-Heisenberg algebra: a Clifford algebra viewpoint
The stabilized Poincare-Heisenberg algebra (SPHA) is the Lie algebra of
quantum relativistic kinematics generated by fifteen generators. It is obtained
from imposing stability conditions after attempting to combine the Lie algebras
of quantum mechanics and relativity which by themselves are stable, however not
when combined. In this paper we show how the sixteen dimensional Clifford
algebra CL(1,3) can be used to generate the SPHA. The Clifford algebra path to
the SPHA avoids the traditional stability considerations, relying instead on
the fact that CL(1,3) is a semi-simple algebra and therefore stable. It is
therefore conceptually easier and more straightforward to work with a Clifford
algebra. The Clifford algebra path suggests the next evolutionary step toward a
theory of physics at the interface of GR and QM might be to depart from working
in space-time and instead to work in space-time-momentum.Comment: 14 page
The local structure of n-Poisson and n-Jacobi manifolds
N-Lie algebra structures on smooth function algebras given by means of
multi-differential operators, are studied. Necessary and sufficient conditions
for the sum and the wedge product of two -Poisson sructures to be again a
multi-Poisson are found. It is proven that the canonical -vector on the dual
of an n-Lie algebra g is n-Poisson iff dim(g) are not greater than n+1. The
problem of compatibility of two n-Lie algebra structures is analyzed and the
compatibility relations connecting hereditary structures of a given n-Lie
algebra are obtained. (n+1)-dimensional n-Lie algebras are classified and their
"elementary particle-like" structure is discovered. Some simple applications to
dynamics are discussed.Comment: 45 pages, latex, no figure
Keratinocyte footprint assay discriminates antilaminin-332 pemphigoid from all other forms of pemphigoid diseases
Background Antilaminin-332 mucous membrane pemphigoid is a chronic severe pemphigoid disease characterized by autoantibodies to laminin-332. At present no commercial assay is available to demonstrate antilaminin-332 antibodies, and diagnosis relies on in-house techniques with limited sensitivities. Objectives In order to move, keratinocytes cultured in vitro secrete laminin-332 to attach to the culture dish. In that way, they leave behind a unique footprint trail of laminin-332. We aimed to develop a sensitive and specific laboratory assay to determine antilaminin-332 autoantibodies in patient serum based on binding of patient IgG to these unique footprints. Methods Normal human keratinocytes were grown on glass coverslips and incubated with patient or control serum for 1 h. The binding of IgG was then investigated by immunofluorescence. After validating the test for its ability to identify antilaminin-332 autoantibodies it was converted into a daily available test based on binding of IgG to dried coverslips that can be stored frozen. The staining patterns of sera from patients with antilaminin-332 pemphigoid were then compared with those of sera from patients with other autoimmune bullous diseases and normal human sera. Results IgG of all antilaminin-332 pemphigoid sera (n = 16) bound to laminin-332 footprints, while all normal human controls (n = 55) were negative. From the sera of patients with other diseases (n = 72) four sera tested positive. The footprint assay was also positive for sera that were negative by salt-split skin analysis, demonstrating that it is a very sensitive technique. Conclusions The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin-332 autoantibodies. What's already known about this topic? Antilaminin-332 mucous membrane pemphigoid is a severe form of pemphigoid, and patients may have an increased risk of malignancies. The diagnosis of antilaminin-332 mucous membrane pemphigoid is complicated by the lack of specific commercial tests for antilaminin-332 antibodies and can be confirmed only in specialized laboratories. Keratinocytes in culture need laminin-332 for adhesion and migration and therefore deposit it on the bottom of the culture dish. What does this study add? The keratinocyte footprint assay detects antilaminin-332 autoantibodies in patient serum using the native laminin-332 produced by cultured keratinocytes. What is the translational message? The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin-332 autoantibodies
The Myth of the Stupid Believer: The Negative ReligiousnessâIQ Nexus is Not on General Intelligence (g) and is Likely a Product of the Relations Between IQ and Autism Spectrum Traits
Numerous studies have found a negative relationship between religiousness and IQ.
It is in the region of â0.2, according to meta-analyses. The reasons for this relationship are, however, unknown. It has been suggested that higher intelligence leads
to greater attraction to science, or that it helps to override evolved cognitive dispositions such as for religiousness. Either way, such explanations assume that the
religionâIQ nexus is on general intelligence (g), rather than some subset of specialized cognitive abilities. In other words, they assume it is a Jensen efect. Two large
datasets comparing groups with diferent levels of religiousness show that their IQ
diferences are not on g and must, therefore, be attributed to specialized abilities. An
analysis of the specialized abilities on which the religious and non-religious groups
difer reveals no clear pattern. We cautiously suggest that this may be explicable in
terms of autism spectrum disorder traits among people with high IQ scores, because
such traits are negatively associated with religiousness
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