An example of active circulation control of the unsteady separated flow past a semi-infinite plate

Active circulation control of the two-dimensional unsteady separated flow past a semiinfinite plate with transverse motion is considered. The rolling-up of the separated shear layer is modelled by a point vortex whose time-dependent circulation is predicted by an unsteady Kutta condition. A suitable vortex shedding mechanism introduced. A control strategy able to maintain constant circulation when a vortex is present is derived. An exact solution for the nonlinear controller is then obtained. Dynamical systems analysis is used to explore the performance of the controlled system. The control strategy is applied to a class of flows and the results are discussed. A procedure to determine the position and the circulation of the vortex, knowing the velocity signature on the plate, is derived. Finally, a physical explanation of the control mechanism is presented

Using the Hawthorne Effect to Examine the Gap Between a Doctor's Best Possible Practice and Actual Performance

Many doctors in developing countries provide considerably lower levels of quality to their patients than they have been trained to provide. The gap between best practice and actual performance is difficult to measure for individual doctors who differ in levels of training and experience and who face very different types of patients. We exploit the Hawthorne effect—in which doctors change their behavior when a researcher comes to observe their practices—to measure the gap between best and actual performance. We analyze this gap for a sample of doctors, examining the impact of the organization for which doctors work on the performance of doctors, after controlling for their ability. We find that some organizations succeed in motivating doctors to work at levels of performance that are close to their best possible practice. This paper adds to recent evidence that motivation is at least as important to health care quality as training and knowledge.motivation, practice quality, health care, Tanzania, Hawthorne effect, Health Economics and Policy, Institutional and Behavioral Economics, International Development, I1, O1, O2,

Auger electron emission due to incident particle in Ar(+), Ne(+) and Na(+) collisions with different solid targets

The L23 Auger spectra of Ar, Ne and Na from Ar(+)-Ti, Ne(+)-Mg, Ne-A1, Na(+)-Be, Na(+)-Mg and Na(+)-A1 collisions were obtained. For Ar, L23 MM Auger electrons are emitted from the fast moving incident projectiles and a Doppler broadened structure is observed. The Ne and Na Auger spectra are due to Auger transitions with single or double 2p vancancies in the initial state of the implanted Ne atoms or surface trapped Na atoms

Antimicrobial peptides: agents of border protection for companion animals.

Over the past 20 years, there have been significant inroads into understanding the roles of antimicrobial peptides in homeostatic functions and their involvement in disease pathogenesis. In addition to direct antimicrobial activity, these peptides participate in many cellular functions, including chemotaxis, wound healing and even determination of canine coat colour. Various biological and genetic approaches have helped to elucidate the role of antimicrobial peptides with respect to innate immunity and host defense. Associations of antimicrobial peptides with various skin diseases, including psoriasis, rosacea and atopic dermatitis, have been documented in humans. In the longer term, therapeutic modulation of antimicrobial peptide expression may provide effective new treatments for disease. This review highlights current knowledge about antimicrobial peptides of the skin and circulating leukocytes, with particular focus on relevance to physiology and disease in companion animals

A novel laser ranging system for measurement of ground-to-satellite distances

A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid

Perfection of materials technology for producing improved Gunn-effect devices Interim scientific report

Chemical vapor deposition of epitaxial gallium arsenid

Measurement of exciton correlations using electrostatic lattices

We present a method for determining correlations in a gas of indirect excitons in a semiconductor quantum well structure. The method involves subjecting the excitons to a periodic electrostatic potential that causes modulations of the exciton density and photoluminescence (PL). Experimentally measured amplitudes of energy and intensity modulations of exciton PL serve as an input to a theoretical estimate of the exciton correlation parameter and temperature. We also present a proof-of-principle demonstration of the method for determining the correlation parameter and discuss how its accuracy can be improved.Comment: 10 pages, 11 figure