Local field distribution near corrugated interfaces: Green's function formulation

We have developed a Green's function formalism to compute the local field distribution near an interface separating two media of different dielectric constants. The Maxwell's equations are converted into a surface integral equation; thus it greatly simplifies the solutions and yields accurate results for interfaces of arbitrary shape. The integral equation is solved and the local field distribution is obtained for a periodic interface.Comment: Presented at the Conference on Computational Physics (CCP2000), held at Gold Coast, Australia from 3 - 8, December 2000. To be published in Proceedings of CCP200

Nonlinear ER effects in an ac applied field

The electric field used in most electrorheological (ER) experiments is usually quite high, and nonlinear ER effects have been theoretically predicted and experimentally measured recently. A direct method of measuring the nonlinear ER effects is to examine the frequency dependence of the same effects. For a sinusoidal applied field, we calculate the ac response which generally includes higher harmonics. In is work, we develop a multiple image formula, and calculate the total dipole moments of a pair of dielectric spheres, embedded in a nonlinear host. The higher harmonics due to the nonlinearity are calculated systematically.Comment: Presented at Conference on Computational Physics (CCP2000), held at Gold Coast, Australia from 3-8, December 200

Analysis of Solar Two Heliostat Tracking Error Sources

This paper explores the geometrical errors that reduce heliostat tracking accuracy at Solar Two. The basic heliostat control architecture is described. Then, the three dominant error sources are described and their effect on heliostat tracking is visually illustrated. The strategy currently used to minimize, but not truly correct, these error sources is also shown. Finally, a novel approach to minimizing error is presented

Depinning of a superfluid vortex line by Kelvin waves

We measure the interaction of a single superfluid vortex with surface irregularities. While vortex pinning in superconductors usually becomes weaker at higher temperatures, we find the opposite behavior. The pinning steadily increases throughout our measurement range, from 0.15Tc to over 0.5Tc. We also find that moving the other end of the vortex decreases the pinning, so we propose Kelvin waves along the vortex as a depinning mechanism.Comment: 5 figures; substantial revision including 2 new figure

Effects of a Structured Exercise Programme on Functional Balance in Visually Impaired Elderly Living in a Residential Setting

AbstractOne major priority for health care professionals is to minimize the risk of fall in the elderly population. While the quality of life of an individual is affected by fall accidents, management of post-fall disability in the elderly could be a huge economic burden to the society. Visually impaired elderly are at a higher risk of fall, because “vision”, an important component contributing to balance, is disturbed. The aim of this study was to examine the effects of an exercise programme, which focused on improvement of the functional balance of visually impaired elderly. Visually impaired elderly residents were randomly assigned to either the exercise training or control group. A multidimensional, individually tailored exercise programme was introduced by physiotherapists to the exercise group for 12 weeks. Functional balance status reflected by the Berg Balance Scale, chair stand test, and timed up-and-go test assessed before and after the 12-week training programme was compared between the two groups. Results demonstrated a significant improvement in balance outcomes in the exercise group (p < 0.05) but not in the control group. The results of this study suggest that a physiotherapist-designed strengthening and balance-training programme can improve the functional balance status of visually impaired elderly

Characterization of the Muscles within the Beef Forequarter

Thirty - four muscles/muscle groups, each greater than .1 kg, were dissected from 16 forequarters to establish a data base of individual muscle yields, palatability profiles and chemical composition. Carcass data from the 16 steers revealed the following averages: carcass weight - 288.4 kg, yield grade - 3.2, and quality grade – low choice. Individual muscle yields, tenderness profiles and chemical analyses indicated that the muscles within the forequarter are extremely variable. However, several of the larger muscles within the forequarter possess tenderness profiles comparable to the longissimus dorsi, the major muscle within rib steaks. This study suggests that maximum utilization of the beef forequarter may best be achieved when individual muscles are fabricated and marketed according to their size and tenderness potential

Effects of rapid prey evolution on predator-prey cycles

We study the qualitative properties of population cycles in a predator-prey system where genetic variability allows contemporary rapid evolution of the prey. Previous numerical studies have found that prey evolution in response to changing predation risk can have major quantitative and qualitative effects on predator-prey cycles, including: (i) large increases in cycle period, (ii) changes in phase relations (so that predator and prey are cycling exactly out of phase, rather than the classical quarter-period phase lag), and (iii) "cryptic" cycles in which total prey density remains nearly constant while predator density and prey traits cycle. Here we focus on a chemostat model motivated by our experimental system [Fussmann et al. 2000,Yoshida et al. 2003] with algae (prey) and rotifers (predators), in which the prey exhibit rapid evolution in their level of defense against predation. We show that the effects of rapid prey evolution are robust and general, and furthermore that they occur in a specific but biologically relevant region of parameter space: when traits that greatly reduce predation risk are relatively cheap (in terms of reductions in other fitness components), when there is coexistence between the two prey types and the predator, and when the interaction between predators and undefended prey alone would produce cycles. Because defense has been shown to be inexpensive, even cost-free, in a number of systems [Andersson and Levin 1999, Gagneux et al. 2006,Yoshida et al. 2004], our discoveries may well be reproduced in other model systems, and in nature. Finally, some of our key results are extended to a general model in which functional forms for the predation rate and prey birth rate are not specified.Comment: 35 pages, 8 figure