4,584 research outputs found
Novel Ambiguities in the Seiberg-Witten Map and the Emergent Gravity
A homogeneous part of the Seiberg-Witten gauge equivalence relation for gauge
fields can lead to solutions that involve matter fields in such a way that the
gauge equivalence and the dimensional and index structures are preserved. In
particular, we consider scalar fields coupled to U(1) gauge fields. The matter
fields appear non-linearly in the map. As an application, we analyze the
implication of this ambiguity to emergent gravity at the first order in
noncommutative parameter and show that the new ambiguity restores the
possibility of conformal coupling of real scalar density field that is coupled
non-minimally to the emergent gravity induced by gauge fields -- a possibility
that is strictly not allowed if we consider only the already known ambiguity in
the Seiberg-Witten map.Comment: JHEP style, 10 pages, minor corrections, a version published in JHE
GIANT CYSTIC HYGROMA COLLI IN AN ADULT- A RARE CASE REPORT
Cystic hygroma (lymphangioma) is often a benign congenital malformation of the lymphatic system that occurs as a result of sequestration or obstruction of lymphatic vessels. Theselesions are usually discovered in infant or children younger than two years of age.Occurrence in adults is uncommon, and fewer than 100 cases of adult lymphangioma have been reported in the literature (1,2) . The objectives of this case report are to present theclinical history and surgical findings, review of literature and the unique problems encountered in the surgical management of this particular patient
Dynamics of Diblock Copolymers in Dilute Solutions
We consider the dynamics of freely translating and rotating diblock (A-B),
Gaussian copolymers, in dilute solutions. Using the multiple scattering
technique, we have computed the diffusion and the friction coefficients D_AB
and Zeta_AB, and the change Eta_AB in the viscosity of the solution as
functions of x = N_A/N and t = l_B/l_A, where N_A, N are the number of segments
of the A block and of the whole copolymer, respectively, and l_A, l_B are the
Kuhn lengths of the A and B blocks. Specific regimes that maximize the
efficiency of separation of copolymers with distinct "t" values, have been
identified.Comment: 20 pages Revtex, 7 eps figures, needs epsf.tex and amssymb.sty,
submitted to Macromolecule
Origin of translocation barriers for polyelectrolyte chains
For single-file translocations of a charged macromolecule through a narrow
pore, the crucial step of arrival of an end at the pore suffers from free
energy barriers, arising from changes in intrachain electrostatic interaction,
distribution of ionic clouds and solvent molecules, and conformational entropy
of the chain. All contributing factors to the barrier in the initial stage of
translocation are evaluated by using the self-consistent field theory for the
polyelectrolyte and the coupled Poisson-Boltzmann description for ions, without
radial symmetry. The barrier is found to be essentially entropic, due to
conformational changes. For moderate and high salt concentrations, the barriers
for the polyelectrolyte chain are quantitatively equivalent to that of
uncharged self-avoiding walks. Electrostatic effects are shown to increase the
free energy barriers, but only slightly. The degree of ionization,
electrostatic interaction strength, decreasing salt concentration and the
solvent quality all result in increases in the barrier.Comment: J.Chem. Phys. 131, 21 (2009) - to be appeare
Complete and efficient methods for supporting side effects in independent/restricted and-parallelism
It has been shown that it is possible to exploit Independent/Restricted And-parallelism in logic programs while retaining the conventional "don't know" semantics of such programs. In particular, it is possible to parallelize
pure Prolog programs while maintaining the semantics of the
language. However, when builtin side-effects (such as write or assert) appear in the program, if an identical observable behaviour to that of sequential Prolog implementations is to be preserved, such side-effects have
to be properly sequenced. Previously proposed solutions to this problem are either incomplete (lacking, for example, backtracking semantics) or they force sequentialization of significant portions of the execution graph which could otherwise run in parallel. In this paper a series of side-effect synchronization methods are proposed which incur lower overhead and allow more parallelism than those previously proposed. Most importantly, and unlike previous proposals, they have well-defined backward execution behaviour and require only a small modification to a given
(And-parallel) Prolog implementation
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