12,424 research outputs found
Comparing the correlation length of grain markets in China and France
In economics comparative analysis plays the same role as experimental
research in physics. In this paper we closely examine several methodological
problems related to comparative analysis by investigating the specific example
of grain markets in China and France respectively. This enables us to answer a
question in economic history which has so far remained pending, namely whether
or not market integration progressed in the 18th century. In economics as in
physics, before being accepted any new result has to be checked and re-checked
by different researchers. This is what we call the replication and comparison
procedures. We show how these procedures should (and can) be implemented.Comment: 16 pages, 7 figures, to appear in International Journal of Modern
Physics
A Non-Algebraic Patchwork
Itenberg and Shustin's pseudoholomorphic curve patchworking is in principle
more flexible than Viro's original algebraic one. It was natural to wonder if
the former method allows one to construct non-algebraic objects. In this paper
we construct the first examples of patchworked real pseudoholomorphic curves in
whose position with respect to the pencil of lines cannot be
realised by any homologous real algebraic curve.Comment: 6 pages, 1 figur
Mach-Zehnder Interferometric device for spin filtering in a GaAs/AlGaAs electron gas
A spin filtering device using quantum spin interference is theoretically
proposed in a GaAs/AlGaAs electron gas that has both Rashba and Dresselhaus
spin-orbit couplings. The device achieves polarized electron currents by
separating spin up and spin down components without a magnetic field gradient.
We find two broad spin filtering regimes, one where the interferometer has
symmetrical arms, where a small magnetic flux is needed to achieve spin
separation, and the other with asymmetric arms where the change in path length
renders an extra phase emulating the effects of a magnetic field. We identify
operating points for the device where optimal electron polarization is achieved
within value ranges found in a 2D electron gas. Both device setups apply for
arbitrary incoming electron polarization and operate at broad energy ranges
within the incoming electron band
Superintegrability in a two-dimensional space of nonconstant curvature
A Hamiltonian with two degrees of freedom is said to be superintegrable if it admits three functionally independent integrals of the motion. This property has been extensively studied in the case of two-dimensional spaces of constant (possibly zero) curvature when all the independent integrals are either quadratic or linear in the canonical momenta. In this article the first steps are taken to solve the problem of superintegrability of this type on an arbitrary curved manifold in two dimensions. This is done by examining in detail one of the spaces of revolution found by G. Koenigs. We determine that there are essentially three distinct potentials which when added to the free Hamiltonian of this space have this type of superintegrability. Separation of variables for the associated HamiltonâJacobi and Schrödinger equations is discussed. The classical and quantum quadratic algebras associated with each of these potentials are determined
Satellite material contaminant optical properties
The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K geranium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future
Probably Safe or Live
This paper presents a formal characterisation of safety and liveness
properties \`a la Alpern and Schneider for fully probabilistic systems. As for
the classical setting, it is established that any (probabilistic tree) property
is equivalent to a conjunction of a safety and liveness property. A simple
algorithm is provided to obtain such property decomposition for flat
probabilistic CTL (PCTL). A safe fragment of PCTL is identified that provides a
sound and complete characterisation of safety properties. For liveness
properties, we provide two PCTL fragments, a sound and a complete one. We show
that safety properties only have finite counterexamples, whereas liveness
properties have none. We compare our characterisation for qualitative
properties with the one for branching time properties by Manolios and Trefler,
and present sound and complete PCTL fragments for characterising the notions of
strong safety and absolute liveness coined by Sistla
Conductivity tensor of striped quantum Hall phases
We study the transport properties of pinned striped quantum Hall phases. We
show that under quite general assumptions, the macroscopic conductivity tensor
satisfies a semicircle law. In particular, this result is valid for both
smectic and nematic stripe phases, independent of the presence of topological
defects such as dislocations and grain boundaries. As a special case, our
results explain the experimental validity of a product rule for the dissipative
part of the resistivity tensor, which was previously derived by MacDonald and
Fisher for a perfect stripe structure.Comment: 5 pages, 2 figure
Stimulation of tPA-dependent provisional extracellular fibrin matrix degradation by human recombinant soluble melanotransferrin
AbstractTissue-type plasminogen activator (tPA) and its substrate plasminogen (Plg) are key components in the fibrinolytic system. We have recently demonstrated, that truncated human recombinant soluble melanotransferrin (sMTf) could stimulate the activation of Plg by urokinase plasminogen activator and inhibit angiogenesis. Since various angiogenesis inhibitors were shown to stimulate tPA-mediated plasminogen activation, we examined the effects of sMTf on tPA-dependent fibrinolysis. This study demonstrated that sMTf enhanced tPA-activation of Plg by 6-fold. sMTf also increased the release of [125I]-fibrin fragments by tPA-activated plasmin. Moreover, we observed that the interaction of sMTf with Plg provoked a change in the fibrin clot structure by cleaving the fibrin α and ÎČ chains. Overall, the present study shows that sMTf modulates tPA-dependent fibrinolysis by modifying the clot structure. These results also suggest that sMTf properties could involve enhanced dissolution of the provisional extracellular fibrin matrix
On calculating the mean values of quantum observables in the optical tomography representation
Given a density operator the optical tomography map defines a
one-parameter set of probability distributions on the real line allowing to reconstruct . We
introduce a dual map from the special class of quantum observables
to a special class of generalized functions such that the
mean value is given by the formula
. The class
includes all the symmetrized polynomials of canonical variables
and .Comment: 8 page
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