Self-similar impulsive capillary waves on a ligament

We study the short-time dynamics of a liquid ligament, held between two solid cylinders, when one is impulsively accelerated along its axis. A set of one-dimensional equations in the slender-slope approximation is used to describe the dynamics, including surface tension and viscous effects. An exact self-similar solution to the linearized equations is successfully compared to experiments made with millimetric ligaments. Another non-linear self-similar solution of the full set of equations is found numerically. Both the linear and non-linear solutions show that the axial depth at which the liquid is affected by the motion of the cylinder scales like $\sqrt{t}$. The non-linear solution presents the peculiar feature that there exists a maximum driving velocity $U^\star$ above which the solution disappears, a phenomenon probably related to the de-pinning of the contact line observed in experiments for large pulling velocities

Responsibility without legal authority? Tackling alcohol-related health harms through licensing and planning policy in local government.

BACKGROUND: The power to influence many social determinants of health lies within local government sectors that are outside public health's traditional remit. We analyse the challenges of achieving health gains through local government alcohol control policies, where legal and professional practice frameworks appear to conflict with public health action. METHODS: Current legislation governing local alcohol control in England and Wales is reviewed and analysed for barriers and opportunities to implement effective population-level health interventions. Case studies of local government alcohol control practices are described. RESULTS: Addressing alcohol-related health harms is constrained by the absence of a specific legal health licensing objective and differences between public health and legal assessments of the relevance of health evidence to a specific place. Local governments can, however, implement health-relevant policies by developing local evidence for alcohol-related health harms; addressing cumulative impact in licensing policy statements and through other non-legislative approaches such as health and non-health sector partnerships. Innovative local initiatives-for example, minimum unit pricing licensing conditions-can serve as test cases for wider national implementation. CONCLUSIONS: By combining the powers available to the many local government sectors involved in alcohol control, alcohol-related health and social harms can be tackled through existing local mechanisms

Direct Detection of Giant Close-In Planets Around the Source Stars of Caustic-Crossing Microlensing Events

We propose a direct method to detect close-in giant planets orbiting stars in the Galactic bulge. This method uses caustic-crossing binary microlensing events discovered by survey teams monitoring the bulge to measure light from a planet orbiting the source star. When the planet crosses the caustic, it is more magnified than the source star; its light is magnified by two orders of magnitude for Jupiter size planets. If the planet is a giant close to the star, it may be bright enough to make a significant deviation in the light curve of the star. Detection of this deviation requires intensive monitoring of the microlensing light curve using a 10-meter class telescope for a few hours after the caustic. This is the only method yet proposed to directly detect close-in planets around stars outside the solar neighborhood.Comment: 4 pages, 2 figures. Submitted to ApJ Letter

Wannier-Stark ladders in one-dimensional elastic systems

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this paper we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let

Power systems research at MSFC

Power systems research reviews at Marshall Space Flight Cente

Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir force

A so far not considered energy loss mechanism in suspended micro- and nanoresonators due to noncontact acoustical energy loss is investigated theoretically. The mechanism consists on the conversion of the mechanical energy from the vibratory motion of the resonator into acoustic waves on large nearby structures, such as the substrate, due to the coupling between the resonator and those structures resulting from the Casimir force acting over the separation gaps. Analytical expressions for the resulting quality factor Q for cantilever and bridge micro- and nanoresonators in close proximity to an underlying substrate are derived and the relevance of the mechanism is investigated, demonstrating its importance when nanometric gaps are involved

Asymptotic equivalence of homogenisation procedures and fine-tuning of continuum theories

Long-wave models obtained in the process of asymptotic homogenisation of structures with a characteristic length scale are known to be non-unique. The term non-uniqueness is used here in the sense that various homogenisation strategies may lead to distinct governing equations that usually, for a given order of the governing equation, approximate the original problem with the same asymptotic accuracy. A constructive procedure presented in this paper generates a class of asymptotically equivalent long-wave models from an original homogenised theory. The described non-uniqueness manifests itself in the occurrence of additional parameters characterising the model. A simple problem of long-wave propagation in a regular one-dimensional lattice structure is used to illustrate important criteria for selecting these parameters. The procedure is then applied to derive a class of continuum theories for a two-dimensional square array of particles. Applications to asymptotic structural theories are also discussed. In particular, we demonstrate how to improve the governing equation for the Rayleigh-Love rod and explain the reasons for the well-known numerical accuracy of the Mindlin plate theory