7,763 research outputs found
Free boundary regularity for harmonic measures and Poisson kernels
One of the basic aims of this paper is to study the relationship between the
geometry of ``hypersurface like'' subsets of Euclidean space and the properties
of the measures they support. In this context we show that certain doubling
properties of a measure determine the geometry of its support. A Radon measure
is said to be doubling with constant C if C times the measure of the ball of
radius r centered on the support is greater than the measure of the ball of
radius 2r and the same center. We prove that if the doubling constant of a
measure on \R^{n+1} is close to the doubling constant of the n-dimensional
Lebesgue measure then its support is well approximated by n-dimensional affine
spaces, provided that the support is relatively flat to start with. Primarily
we consider sets which are boundaries of domains in \R^{n+1}. The n-dimensional
Hausdorff measure may not be defined on the boundary of a domain in R^{n+1}.
Thus we turn our attention to the harmonic measure which is well behaved under
minor assumptions. We obtain a new characterization of locally flat domains in
terms of the doubling properties of their harmonic measure. Along these lines
we investigate how the ``weak'' regularity of the Poisson kernel of a domain
determines the geometry of its boundary.Comment: 85 pages, published version, abstract added in migratio
Boundary structure and size in terms of interior and exterior harmonic measures in higher dimensions
In this work we introduce the use of powerful tools from geometric measure theory (GMT) to study problems related to the size and structure of sets of mutual absolute continuity for the harmonic measure of a domain and the harmonic measure of , int, in dimension
Fast inactivation in Shaker K+ channels. Properties of ionic and gating currents.
Fast inactivating Shaker H4 potassium channels and nonconducting pore mutant Shaker H4 W434F channels have been used to correlate the installation and recovery of the fast inactivation of ionic current with changes in the kinetics of gating current known as "charge immobilization" (Armstrong, C.M., and F. Bezanilla. 1977. J. Gen. Physiol. 70:567-590.). Shaker H4 W434F gating currents are very similar to those of the conducting clone recorded in potassium-free solutions. This mutant channel allows the recording of the total gating charge return, even when returning from potentials that would largely inactivate conducting channels. As the depolarizing potential increased, the OFF gating currents decay phase at -90 mV return potential changed from a single fast component to at least two components, the slower requiring approximately 200 ms for a full charge return. The charge immobilization onset and the ionic current decay have an identical time course. The recoveries of gating current (Shaker H4 W434F) and ionic current (Shaker H4) in 2 mM external potassium have at least two components. Both recoveries are similar at -120 and -90 mV. In contrast, at higher potentials (-70 and -50 mV), the gating charge recovers significantly more slowly than the ionic current. A model with a single inactivated state cannot account for all our data, which strongly support the existence of "parallel" inactivated states. In this model, a fraction of the charge can be recovered upon repolarization while the channel pore is occupied by the NH2-terminus region
Medios técnico-tácticos colectivos en boloncesto en categorÃas de formación
The objectives of this study were: a) record the view of basketball coaches on how they should evolve along the different stages of training, some Basic Tactical Media Collective (MTCBs), b) recording the views of basketball coaches on how to evolve along different stages of training some Complex Tactical Media Collective (MTCC). A questionnaire was administered to 102 coaches. The most significant results indicated that: a) formation increases with age, it is necessary to devote more time to MTCBs except to pass and progression, which should hold in the infant category, b) in the category minibasket and children, only develop MTCBs Pass and Progression and Establishment of the Odd, c) blocks begin to be important in the cadet category, d) development of counter-attack, followed by individual collective defense dominated in all categories, e) in the categories minibasket and children, he devotes little importance only to the collective defense and counterattack individual f) from the cadet category, when it puts more emphasis on improving the positional attack, g) is only dedicated to the importance zonal defense, from the junior category, and g) in all categories, it gives more importance to collective defense, which improved positional attack.Los objetivos del presente estudio fueron: a) registrar la opinión de entrenadores de baloncesto sobre cómo deben evolucionar a lo largo de las diferentes etapas de formación, algunos Medios Técnico-tácticos Colectivos Básicos (MTCBs); b) registrar la opinión de entrenadores de baloncesto sobre cómo deben evolucionar a lo largo de las diferentes etapas de formación algunos Medios Técnico-tácticos Colectivos Complejos (MTCC). Se administró un cuestionario a 102 entrenadores. Los resultados más significativos indicaron que: a) con forme incrementa la edad, es necesario dedicar más tiempo a los MTCBs, salvo al pase y progresión, que debe estar afianzando en la categorÃa infantil; b) en la categorÃa minibasket e infantil, únicamente se desarrollan los MTCBs de Pase y Progresión y Fijación del Impar; c) los bloqueos empiezan a tener importancia en la categorÃa cadete; d) el desarrollo del contraataque, seguido de la defensa colectiva individual, predomina en todas las categorÃas; e) en las categorÃas minibasket e infantil, apenas se le dedica importancia solo al contraataque y a la defensa colectiva individual; f) a partir de la categorÃa cadete, es cuando se le dedica más importancia a la mejora del ataque posicional; g) sólo se le dedica importancia a la defensa colectiva zonal, a partir de la categorÃa júnior; y g) en todas las categorÃas, se le aporta más importancia a la defensas colectivas, que a la mejora del ataque posicional
Fast nucleon emission as a probe of the isospin momentum dependence
In this article we investigate the structure of the non-local part of the
symmetry term, that leads to a splitting of the effective masses of protons and
neutrons in asymmetric matter. Based on microscopic transport simulations we
suggest some rather sensitive observables in collisions of neutron-rich
(unstable) ions at intermediate () energies. In particular we focus the
attention on pre-equilibrium nucleon emissions. We discuss interesting
correlations between the N/Z content of the fast emitted particles and their
rapidity or transverse momentum, that show a nice dependence on the
prescription used for the effective mass splitting.Comment: 5 pages, 6 figures, revtex
Comparative Analysis of Two Cryogenic Force Balance Calibration Systems
Cryogenic wind-tunnel facilities face unique challenges in the calibration and operation of various measurement systems and instrumentation. Instruments that are subjected to the cryogenic conditions of the test plenum require careful design and calibration procedures to maintain instrument performance. NASAs National Transonic Facility (NTF) and the European Transonic Windtunnel (ETW) are two cryogenic wind-tunnel facilities, each with the ability to calibrate force measurement systems (FMS) at cryogenic conditions. These facilities have different methodologies and processes for calibrating these systems. This paper discusses differences in the methodologies and processes and compares the results of two separate cryogenic calibrations of the NTF-118A force balance that were completed at both wind-tunnel facilities
Numerical simulation of liquid sloshing in a partially filled container with inclusion of compressibility effects
A numerical scheme of study is developed to model compressible two-fluid flows simulating liquid sloshing in a partially filled tank. For a two-fluid system separated by an interface as in the case of sloshing, not only a Mach-uniform scheme is required, but also an effective way to eliminate unphysical numerical oscillations near the interface. By introducing a preconditioner, the governing equations expressed in terms of primitive variables are solved for both fluids (i.e. water, air, gas etc.) in a unified manner. In order to keep the interface sharp and to eliminate unphysical numerical oscillations in unsteady fluid flows, the non-conservative implicit Split Coefficient Matrix Method (SCMM) is modified to construct a flux difference splitting scheme in the dual time formulation. The proposed numerical model is evaluated by comparisons between numerical results and measured data for sloshing in an 80% filled rectangular tank excited at resonance frequency. Through similar comparisons, the investigation is further extended by examining sloshing flows excited by forced sway motions in two different rectangular tanks with 20% and 83% filling ratios. These examples demonstrate that the proposed method is suitable to capture induced free surface waves and to evaluate sloshing pressure loads acting on the tank walls and ceiling
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