Simulation and measurement of hts josephson heterodyne oscillator

We report continuing investigations into practical applications of the ac Josephson effect as the basis for a voltage-tunable radio-frequency oscillator. We have previously demonstrated experimentally that useful power levels (10 s of nW) and linewidths of a few kHz can be achieved in the heterodyne output from a High-Temperature-Superconducting Resistive SQUID (HTS-RSQUID) operating in the frequency range 1-50 MHz. Those results were achieved with 2-junction R-SQUIDs incorporating current-biased shunt resistors of a few micro-ohms. We have now modified the fabrication procedures, and adjusted the shunt resistors and bias current values so that higher frequencies can be achieved. The Josephson junctions are of step-edge type, rather than the bi-crystal type used in our earlier work. The step-edge technique permits much more flexibility in the geometrical lay-out and utilizes the more cost-effective single-crystal MgO substrates. In the present paper, we report numerical simulations and experimental measurements on these devices in the frequency range up to 2 GHz

THE VALUE OF SPORT FISHING IN THE SNAKE RIVER BASIN OF CENTRAL IDAHO

The value of sportfishing in the Snake River Basin in Central Idaho was measured using a two-stage/disequilibrium travel model. The two-stage/disequilibrium model does not require monetization of recreationists? travel time as required of traditional equilibrium labor market travel cost models. The model was estimated using Poisson regression, appropriate for count data when over-dispersion is absent, and adjusted for endogenous stratification (self selection bias) . Contrary to expectations that anglers living close to the sites with low values would be over represented in the sample, the endogenous stratification adjustment caused estimated consumers surplus to decline from $42 per person per trip before adjustment for endogenous stratification to$35 after adjustment. The average number of sportfishing trips per year was 6.72, resulting in an average annual willingness-to-pay of $236 per year per angler.Resource /Energy Economics and Policy,

Measuring the Location Value of a Recreation Site

The demand for sport fishing on the Snake River reservoirs was estimated using the travel cost method. A short-run demand model was specified with location value for anglers who have the option to access a follow-on site if fishing conditions are poor. Willingness to pay for a fishing trip to the site was $18.52 for anglers who did not have a follow-on site and$43.48 for anglers who did. A location value of $24.96 accrued only to anglers with a follow-on site. Total annual site value was understated by as much as 40$0.78 million) if location value for anglers with a follow-on site was excluded from the benefit estimate.contingent behavior, count data, endogenous stratification, follow-on site, location value, multiple destination, option value, short-run demand, travel cost method, Resource /Energy Economics and Policy,

Current Management of Parkinsonism

In the management of Parkinson’s disease, one must be reasonably certain of the diagnosis. In spite of the foregoing sophisticated biochemistry, there is really no laboratory test for the disease, so it becomes an entity that must be recognized on purely clinical grounds. While the differential diagnosis can be quite extensive and includes such rare entities as manganese poisoning, as well as such usually apparent causes as phenothiazine intoxication or carbon monoxide sequelae, several disorders and etiologies account for most of our diagnostic problems. Although we think of Parkinsonism as a triad of rest tremor, rigidity, and akinesia, the onset may be with any one of these, and if it is with tremor, the distinction from essential tremor may be difficult

Introduction

We conclude our two-part issue on Neurology for Primary Care Physicians with both the new and the old. Attempting to avoid repetition, our authors address themselves to the overlooked, under-emphasized, and sometimes new area of familiar subjects. Our guest speakers, Dr. Millikan and Dr. Horenstein discuss acute cerebral infarction and the perennial problem of dementia. Exciting new fronts are explored by Drs. Isaacs and Sakalas as they expand on their ideas on neuromuscular disease and surgical techniques for extra-intracranial oscular anastomoses, respectively. Dr. Selhorst contributes some interesting views on low back problems

Introduction

This issue of the MCV Quarterly is devoted to a review of some of the problems in clinical neurology that present soon after onset and often require urgent evaluation and care. Problems such as seizures and headache are regular features of many types of practice. Others such as acute ophthalmoplegias are infrequently seen outside the field of neurology. Still others, for instance, head injury, are commonly seen but often require the attention of physicians with specialized training, such as Dr. Miller of the MCV Division of Neurosurgery. While every acute neurologic problem cannot be reviewed in a single issue, the selection here is designed to provide readers with information useful not only in their own practices but also valuable for all physicians to know

Interferometric experiments towards advanced gravitational wave detectors

In 1905, Einstein postulated that the speed of light is not only finite, but that its speed in vacuum is a universal limit that no process can exceed. The Theory of General Relativity later extended this concept to include gravitational interactions, and Eddington's timely measurements of stellar positions during a solar eclipse in 1919 confirmed that gravity's effect on spacetime is both real and entirely physical -- not merely a mathematical curiosity. With the death of Newton's notions of universal time and instantaneous gravity came the idea of gravitational waves as distortions in space-time that propagate the gravitational interaction at the speed of light. These gravitational waves are emitted from any object undergoing a non-axi-symmetric acceleration of mass, but -- due to the exceptionally weak coupling between gravitational waves and matter -- are expected to induce displacements of the order of 10^-18 m in kilometre-scale detectors: the extraordinary diminutiveness of this effect has thus far precluded any direct detection of the phenomenon. Numerous gravitational wave detectors have been built since the 1960s, in the form of both interferometric detectors and resonant mass devices. Interferometric detectors currently represent the most promising form of detector, due to their relatively wide-band response to gravitational wave signals and promising levels of sensitivity. In recent years a worldwide network of these interferometric detectors (LIGO, GEO600, Virgo and TAMA300) have begun to approach (or indeed reach) their design sensitivities. Although these detectors have started to provide upper limit results for gravitational wave emission that are of astrophysical significance, there have as yet been no direct detections. As such, work is underway to upgrade and improve these detectors. However, increasing the signal sensitivity necessarily leads to an increase in their sensitivity to their limiting noise sources. Two critical noise limits that must be characterised, understood, and hopefully reduced for the benefit of future detectors, are thermal noise (from mirror substrates, reflective coatings and suspension systems) and photon noise -- associated with the intrinsic shot noise of light and the noise due to light's radiation pressure. Two interferometric experiments designed to help inform on these phenomena were constructed at the University of Glasgow's Institute for Gravitational Research. The first experiment compared the relative displacement noise spectra of two specially constructed optical cavities, to extract the thermal noise spectrum of a single test mirror. In future experiments, this optic could be changed and the thermal noise spectrum for any suitable combination of mirror substrate and reflective coating evaluated. The second experiment involved the investigation of suitable control schemes for a three-mirror coupled optical cavity. As the resonant light power in interferometers increases in future devices (in order to decrease the photon shot noise) the need to de-couple the control schemes that govern the respective cavities so that they can be controlled independently, becomes more important. As a three-mirror cavity effectively represents a simple coupled system, it provides a suitable test-bed for characterising suitable control schemes for more advanced interferometers. Together, these experiments may provide information useful to the design of future gravitational wave interferometers