Power-Law Behavior of Power Spectra in Low Prandtl Number Rayleigh-Benard Convection

The origin of the power-law decay measured in the power spectra of low Prandtl number Rayleigh-Benard convection near the onset of chaos is addressed using long time numerical simulations of the three-dimensional Boussinesq equations in cylindrical domains. The power-law is found to arise from quasi-discontinuous changes in the slope of the time series of the heat transport associated with the nucleation of dislocation pairs and roll pinch-off events. For larger frequencies, the power spectra decay exponentially as expected for time continuous deterministic dynamics.Comment: (10 pages, 6 figures

Which sexual abuse victims receive a forensic medical examination? : The impact of Children\u27s Advocacy Centers

Abstract Objective This study examines the impact of Children\u27s Advocacy Centers (CAC) and other factors, such as the child\u27s age, alleged penetration, and injury on the use of forensic medical examinations as part of the response to reported child sexual abuse. Methods This analysis is part of a quasi-experimental study, the Multi-Site Evaluation of Children\u27s Advocacy Centers, which evaluated four CACs relative to within-state non-CAC comparison communities. Case abstractors collected data on forensic medical exams in 1,220 child sexual abuse cases through review of case records. Results Suspected sexual abuse victims at CACs were two times more likely to have forensic medical examinations than those seen at comparison communities, controlling for other variables. Girls, children with reported penetration, victims who were physically injured while being abused, White victims, and younger children were more likely to have exams, controlling for other variables. Non-penetration cases at CACs were four times more likely to receive exams as compared to those in comparison communities. About half of exams were conducted the same day as the reported abuse in both CAC and comparison communities. The majority of caregivers were very satisfied with the medical professional. Receipt of a medical exam was not associated with offenders being charged. Conclusions Results of this study suggest that CACs are an effective tool for furthering access to forensic medical examinations for child sexual abuse victims

Grain boundary motion in layered phases

We study the motion of a grain boundary that separates two sets of mutually perpendicular rolls in Rayleigh-B\'enard convection above onset. The problem is treated either analytically from the corresponding amplitude equations, or numerically by solving the Swift-Hohenberg equation. We find that if the rolls are curved by a slow transversal modulation, a net translation of the boundary follows. We show analytically that although this motion is a nonlinear effect, it occurs in a time scale much shorter than that of the linear relaxation of the curved rolls. The total distance traveled by the boundary scales as $\epsilon^{-1/2}$, where $\epsilon$ is the reduced Rayleigh number. We obtain analytical expressions for the relaxation rate of the modulation and for the time dependent traveling velocity of the boundary, and especially their dependence on wavenumber. The results agree well with direct numerical solutions of the Swift-Hohenberg equation. We finally discuss the implications of our results on the coarsening rate of an ensemble of differently oriented domains in which grain boundary motion through curved rolls is the dominant coarsening mechanism.Comment: 16 pages, 5 figure

Full scale visualization of the wing tip vortices generated by a typical agricultural aircraft

The trajectories of the wing tip vortices of a typical agricultural aircraft were experimentally determined by flight test. A flow visualization method, similar to the vapor screen method used in wind tunnels, was used to obtain trajectory data for a range of flight speeds, airplane configurations, and wing loadings. Detailed measurements of the spanwise surface pressure distribution were made for all test points. Further, a powered 1/8 scale model of the aircraft was designed, built, and used to obtain tip vortex trajectory data under conditions similar to that of the full-scale test. The effects of light wind on the vortices were demonstrated, and the interaction of the flap vortex and the tip vortex was clearly shown in photographs and plotted trajectory data

Three-dimensional cell to tissue assembly process

The present invention relates a 3-dimensional cell to tissue and maintenance process, more particularly to methods of culturing cells in a culture environment, either in space or in a gravity field, with minimum fluid shear stress, freedom for 3-dimensional spatial orientation of the suspended particles and localization of particles with differing or similar sedimentation properties in a similar spatial region

Low cost laboratory micro-grid hardware and control for electrical power systems teaching

There is a growing trend within education establishments to teach electrical power system theory within lectures and back this up with software simulation laboratory sessions. This allows the courses to be taught at a lower cost than if real hardware was implemented. However, the students that are graduating from these programs are missing out on the opportunity to learn about real equipment and issues such as health and safety of voltages above 50V, mismatching component sizes and accuracy. Bespoke electrical power systems teaching equipment is expensive to buy. This paper details a low cost hardware setup that can be used to enforce electrical power system theory. The proposed equipment employs real off-the shelf equipment with some interfacing units which can be reproduced by laboratory technicians to enhance the student learning experience by offering students experience of real machines operating on an electrical power systems network

Full scale visualization of the wing tip vortices generated by a typical agricultural aircraft

The trajectories of the wing tip vortices of a typical agricultural aircraft were experimentally determined by flight test. A flow visualization method, similar to the vapor screen method used in wind tunnels, was used to obtain trajectory data for a range of flight speeds, airplane configurations, and wing loadings. Detailed measurements of the spanwise surface pressure distribution were made for all test points. Further, a powered 1/8 scale model of the aircraft was designed, built, and used to obtain tip vortex trajectory data under conditions similar to that of the full scale test. The effects of light wind on the vortices were demonstrated, and the interaction of the flap vortex and the tip vortex was clearly shown in photographs and plotted trajectory data

Stability of Quasicrystals Composed of Soft Isotropic Particles

Quasicrystals whose building blocks are of mesoscopic rather than atomic scale have recently been discovered in several soft-matter systems. Contrary to metallurgic quasicrystals whose source of stability remains a question of great debate to this day, we argue that the stability of certain soft-matter quasicrystals can be directly explained by examining a coarse-grained free energy for a system of soft isotropic particles. We show, both theoretically and numerically, that the stability can be attributed to the existence of two natural length scales in the pair potential, combined with effective three-body interactions arising from entropy. Our newly gained understanding of the stability of soft quasicrystals allows us to point at their region of stability in the phase diagram, and thereby may help control the self-assembly of quasicrystals and a variety of other desired structures in future experimental realizations.Comment: Revised abstract, more detailed explanations, and better images of the numerical minimization of the free energ