Indirect observation of phase conjugate magnons from non-degenerate four-wave mixing

A phase conjugate mirror utilising four-wave mixing in a magnetic system is experimentally realised for the first time. Indirect evidence of continuous-wave phase conjugation has been observed experimentally and is supported by simulations. The experiment utilizes a pump-probe method to excite a four-wave mixing process. Two antennae are used to pump a region of a thin-film yttrium iron garnet waveguide with magnons of frequency $f_{1}$ to create a spatio-temporally periodic potential. As the probe magnons of $f_{\mathrm{p}}$ impinge on the pumped region, a signal with frequency $f_{\mathrm{c}} = 2f_{1}-f_{\mathrm{p}}$ is observed. The amplitude of the nonlinear signal was highly dependent on the applied magnetic field $H$. Width modes of the probe magnons and standing wave modes of the pump magnons were shown to affect the amplitude of the signal at $f_{\mathrm{c}}$. Experimental data is compared with simulations and theory to suggest that $f_{\mathrm{c}}$ is a phase conjugate of $f_{\mathrm{p}}$.Comment: 6 pages, 6 figure

Online mentoring and peer support: Using learning technologies to facilitate entry into a community of practice

A vital aspect of any professional education is the opportunity for students to engage in meaningful practical experiences. In pre‐service teacher education in Australia, this vital teaching practice component has undergone challenges in recent years due to increasing student numbers (linked to the increasing demand for new teachers) and limited resources in university and school sectors. As such, initiatives to enhance the practical component of this professional degree have been sought. This paper details the methodology and outcomes associated with a pilot project that utilized asynchronous Web‐based communication tools to facilitate mentoring and peer support through the teaching practice experience. Analysis of the online discussions and interviews with participants provides an indication of the nature of the interactions and the perceived value of the intervention, and informs the potential for larger‐scale implementation

Impingement of Water Droplets on an Ellipsoid with Fineness Ratio 5 in Axisymmetric Flow

The presence of radomes and instruments that are sensitive to water films or ice formations in the nose section of all-weather aircraft and missiles necessitates a knowledge of the droplet impingement characteristics of bodies of revolution. Because it is possible to approximate many of these bodies with an ellipsoid of revolution, droplet trajectories about an ellipsoid of revolution with a fineness ratio of 5 were computed for incompressible axisymmetric air flow. From the computed droplet trajectories, the following impingement characteristics of the ellipsoid surface were obtained and are presented in terms of dimensionless parameters: (1) total rate of water impingement, (2) extent of droplet impingement zone, (3) distribution of impinging water, and (4) local rate of water impingement

Stellar Polarimetry: Where Are We and Where Are We Going?

On the final day of the Stellar Polarimetry conference, participants split up into three "breakout sessions" to discuss the future of the field in the areas of instrumentation, upcoming opportunities, and community priorities. This contribution compiles the major recommendations arising from each breakout session. We hope that the polarimetric community will find these ideas useful as we consider how to maintain the vitality of polarimetry in the coming years.Comment: 7 pages, published in proceedings of "Stellar Polarimetry: From Birth to Death" (Madison, WI, June 2011

Grass shrimp Palaemonetes pugio predation on sediment- and stem-dwelling meiofauna: Field and laboratory experiments

Field and laboratory experiments were conducted to clarify the predatory role of Palaemonetes pugio Holthius in salt-marsh benthic communities. Field experiments (cage enclosures using P. pugio as a predator) were conducted on unvegetated mudflat and vegetated-marsh sites. Neither sediment- or stem-dwelling meiofaunal abundances were significantly impacted. Laboratory experiments measured the functional response of P. pugio feeding on suspended harpacticoid copepods, tested the efficiency of P. pugio feeding on harpacticoids in sediments, and measured the predation rate of P. pugio on stem-dwelling meiofauna. Grass shrimp feeding rate on suspended copepods followed a type II functional response, increasing with increasing prey density to a maximum of 59 copepods h-1. When a sediment refuge was available, a 40% decline in the consumption of copepods by P. pugio was noted; this decreased feeding efficiency may contribute to the lack of significant declines in meiofaunal abundances in field enclosures over unvegetated sediment. P. pugio proved to be a highly effective predator on the fauna of Spartina alterniflora stems, significantly reducing abundances of stem-associated meiofauna within 24 h and consuming an estimated 35 meiofauna h-1. The greatest impact was exhibited on the lowest (0 to 6 cm) portion of the stems. These experiments suggest that laboratory experiments are an important aid to help interpret field experiments examining predation on meiofauna, and that Spartina stems, and their epiphytic algae and meiofauna, are important, but largely overlooked, resources in salt-marsh food webs

Interview of John P. Rossi, Ph.D.

Dr. John Patrick Rossi was born in Philadelphia in 1936 to Gabriel (Al) and Muriel Rossi. He was raised by two aunts, an uncle, and his grandfather in lower Olney. He attended La Salle College High School, received his B. A. in history from La Salle College in 1958, his M. A. from Notre Dame in 1960, and his Ph.D. in History from the University of Pennsylvania in 1965. His dissertation was on the British Liberal Party from 1874 to 1880. He began teaching at La Salle College in 1962; was associate editor of Four Quarters ; received the Lindback Award; developed popular classes on World War II, baseball history, and George Orwell; and served as History Department chair. He has published many works on the British Liberal Party, baseball history, Orwell, and other topics. After retiring, he received the honorable title Professor Emeritus

Hybrid bearings for turbopumps and the like

In rocket engines power is usually obtained by burning fuel and oxidizer which are mixed, pressurized, and directed to a combustion chamber by means of turbopumps. Roller bearings are generally used in these turbopumps, but because of bearing demands hydrostatic bearings were proposed. The use of such bearings is quite feasible because during flight hydrostatic lubrication can reduce roller bearing wear. A disadvantage of such proposals is that during startup, acceleration, and shutdown high pressure fluids are not available for hydrostatic bearings. The fluid lubrication film is not always present in bearings of turbopumps. During these periods a second bearing is required to carry the load. This requirement suggests the use of hybrid bearings in rocket engine turbopumps. Such duplex bearings were provided, but when their inner races are keyed to the shaft or journal two of them are required. And such duplex bearings do not wear evenly. A hybrid hydrostatic-rolling element bearing was provided wherein the rolling element bearing is locked on the stationary housing rather than on the rotating journal