6,129 research outputs found
On the dispersionless Kadomtsev-Petviashvili equation with arbitrary nonlinearity and dimensionality: exact solutions, longtime asymptotics of the Cauchy problem, wave breaking and discontinuous shocks
We study the generalization of the dispersionless Kadomtsev - Petviashvili
(dKP) equation in n+1 dimensions and with nonlinearity of degree m+1, a model
equation describing the propagation of weakly nonlinear, quasi one dimensional
waves in the absence of dispersion and dissipation, and arising in several
physical contexts, like acoustics, plasma physics, hydrodynamics and nonlinear
optics. In 2+1 dimensions and with quadratic nonlinearity, this equation is
integrable through a novel IST, and it has been recently shown to be a
prototype model equation in the description of the two dimensional wave
breaking of localized initial data. In higher dimensions and with higher
nonlinearity, the generalized dKP equations are not integrable, but their
invariance under motions on the paraboloid allows one to construct in this
paper a family of exact solutions describing waves constant on their
paraboloidal wave front and breaking simultaneously in all points of it,
developing after breaking either multivaluedness or single valued discontinuous
shocks. Then such exact solutions are used to build the longtime behavior of
the solutions of the Cauchy problem, for small and localized initial data,
showing that wave breaking of small initial data takes place in the longtime
regime if and only if . At last, the analytic aspects of such a
wave breaking are investigated in detail in terms of the small initial data, in
both cases in which the solution becomes multivalued after breaking or it
develops a discontinuous shock. These results, contained in the 2012 master
thesis of one of the authors (FS), generalize those obtained by one of the
authors (PMS) and S.V.Manakov for the dKP equation in n+1 dimensions with
quadratic nonlinearity, and are obtained following the same strategy.Comment: 31 pages, 11 figure
Detection of entanglement between collective spins
Entanglement between individual spins can be detected by using thermodynamics
quantities as entanglement witnesses. This applies to collective spins also,
provided that their internal degrees of freedom are frozen, as in the limit of
weakly-coupled nanomagnets. Here, we extend such approach to the detection of
entanglement between subsystems of a spin cluster, beyond such weak-coupling
limit. The resulting inequalities are violated in spin clusters with different
geometries, thus allowing the detection of zero- and finite-temperature
entanglement. Under relevant and experimentally verifiable conditions, all the
required expectation values can be traced back to correlation functions of
individual spins, that are now made selectively available by four-dimensional
inelastic neutron scattering
Quantum-gate implementation in permanently coupled AF spin rings without need of local fields
We propose a scheme for the implementation of quantum gates which is based on
the qubit encoding in antiferromagnetic molecular rings. We show that a proper
engineering of the intercluster link would result in an effective coupling that
vanishes as far as the system is kept in the computational space, while it is
turned on by a selective excitation of specific auxiliary states. These are
also shown to allow the performing of single- and two-qubit gates without an
individual addressing of the rings by means of local magnetic fields.Comment: To appear in Physical Review Letter
Preference and Similarity-based Behavioral Discovery of Services
We extend Constraint Automata by replacing boolean constraints with semiring-based soft constraints. The obtained general formal tool can be used to represent preference-based and similarity-based queries, which allow a user more freedom in choosing the behavior of the service to finally use, among all possible choices. A user states his preferences through a “soft” query, and obtains results that satisfy this query with different levels of preference. The soft requirements may involve a parameter data of the service operations, or the (names of the) operations themselves. Moreover, we introduce a first implementation of the search procedure by using declarative (Soft) Constraint Programming
Diagnosis and treatment of lipodystrophy: a step‑by‑step approach
Aim : Lipodystrophy syndromes are rare heterogeneous disorders characterized by defciency of adipose tissue, usually a decrease in leptin levels and, frequently, severe metabolic abnormalities including diabetes mellitus and dyslipidemia.
Purpose : To describe the clinical presentation of known types of lipodystrophy, and suggest specifc steps to recognize, diagnose and treat lipodystrophy in the clinical setting.
Methods : Based on literature and in our own experience, we propose a stepwise approach for diagnosis of the diferent subtypes of rare lipodystrophy syndromes, describing its more frequent co-morbidities and establishing the therapeutical
approach.
Results : Lipodystrophy is classifed as genetic or acquired and by the distribution of fat loss, which can be generalized or partial. Genes associated with many congenital forms of lipodystrophy have been identifed that may assist in diagnosis. Because
of its rarity and heterogeneity, lipodystrophy may frequently be unrecognized or misdiagnosed, which is concerning because it is progressive and its complications are potentially life threatening. A basic diagnostic algorithm is proposed. Efective
management of lipodystrophy includes lifestyle changes and aggressive, evidence-based treatment of comorbidities. Leptin replacement therapy (metreleptin) has been found to improve metabolic parameters in many patients with lipodystrophy.
Metreleptin is approved in the United States as replacement therapy to treat the complications of leptin defciency in patients with congenital or acquired generalized lipodystrophy and has been submitted for approval in Europe.
Conclusions : Here, we describe the clinical presentation of known types of lipodystrophy, present an algorithm for diferential diagnosis of lipodystrophy, and suggest specifc steps to recognize and diagnose lipodystrophy in the clinical setting.S
A Bell-Evans-Polanyi principle for molecular dynamics trajectories and its implications for global optimization
The Bell-Evans-Polanyi principle that is valid for a chemical reaction that
proceeds along the reaction coordinate over the transition state is extended to
molecular dynamics trajectories that in general do not cross the dividing
surface between the initial and the final local minima at the exact transition
state. Our molecular dynamics Bell-Evans-Polanyi principle states that low
energy molecular dynamics trajectories are more likely to lead into the basin
of attraction of a low energy local minimum than high energy trajectories. In
the context of global optimization schemes based on molecular dynamics our
molecular dynamics Bell-Evans-Polanyi principle implies that using low energy
trajectories one needs to visit a smaller number of distinguishable local
minima before finding the global minimum than when using high energy
trajectories
Comparison of energy consumption and costs of different HEVs and PHEVs in European and American context
This paper will analyse on the one hand the potential of Plug in Hybrid electric Vehicles to significantly reduce fuel consumption and displace it torward various primary energies thanks to the electricity sector. On the other hand the total cost of ownership of two different PHEV architectures will be compared to a conventional cehicle and a HEV without external charging
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