A Survey of Methods for Measuring Thermally Induced Distortions of Test Articles Undergoing Solar Thermal Vacuum Test

Various methods of measuring the small thermally induced distortions experienced either by various points on the space vehicles or by deviations of surfaces from a known shape during solar thermal vacuum tests are examined. State-of-the-art application of both photographic and real time observation are discussed. The relative merits of each of the methods are compared and evaluated in their applications to different types of test articles and situations. Magnitudes of thermally induced distortions which may be expected to be routinely measurable by the various methods are presented and compared

Detection of Deep Flaws in Aluminum Structure with Magneto-Resistive Sensors

It is well known that using progressively lower frequencies in eddy current detection permits deeper penetration into conductive samples since the skin depth increases as the inverse square root of the frequency. Since the signal of interest is produced by Faraday’s Law, the amplitude of the signal voltage is proportional to the excitation frequency. This fact limits the use of normal eddy current techniques as frequency decreases. This paper presents a method of detecting the field due to the induced eddy currents rather than its time derivative, so that at least the “return” portion of the signal is not proportional to frequency

A case study of bovine tuberculosis in an area of County Donegal, Ireland

A descriptive analysis, to investigate the potential risk factors that might have contributed to the increased incidence of bovine tuberculosis (BTB) herd-breakdowns in the reference area of Co. Donegal during the fifth year of the four-area project (FAP), was performed. Seventy two different herds were restricted for BTB during the FAP; 10 of these herds were restricted twice, resulting in a total of 82 BTB breakdowns. During the first four years of the FAP, the number of BTB herd breakdowns in the area varied from a lowest of nine to a maximum of 18 per year, and were geographically dispersed. In the fifth year of the study a considerable increase in the number of BTB breakdowns (n = 32) was observed, and there was a spatial 'cluster' of infected herds in the eastern part of the study area. The increased number of BTB breakdowns during the fifth year most likely occurred because of the recrudescence of infection, herd-to-herd transmission and, to a lesser extent, purchase of infected cattle. Infected badgers remain as a possible but less likely source of infection, especially as an explanation for the cluster of infected herds. The analysis supports the hypothesis that BTB in herds is a problem that cannot be addressed successfully by dedicating our efforts to the elimination of single risk factors. Neither is it a problem that needs to be investigated only at the herd level, but rather at the area level, including groups of contiguous herds

Influence of Age on Peripheral Refraction

To investigate how age affects peripheral refraction we measured objective peripheral refraction for 55 young subjects (24 ± 4 years) and 41 older subjects (59 ± 3 years) out to 35 eccentricity in temporal and nasal visual fields. Subjects were compared in 1D subgroups based on central spherical equivalent refractions (low hypermetropes +0.54D to +1.51D, emmetropes +0.50D to 0.49D, low myopes 0.50D to 1.49D, moderate myopes 1.50D to 2.58 D). Overall, young and older subjects with similar refractive corrections had similar peripheral refraction components. Both age groups showed relative hypermetropic shifts in the peripheral fields as myopia increased and also decreases in peripheral astigmatism J180 as myopia increased. J45 varied little across the visual field with linear relationships occurring between J45 and visual field angle for all but one subgroup (older emmetropes). Peripheral refraction in emmetropes to moderate myopes is relatively unaffected by age for healthy eyes of similar refractive errors

Metabolomics enables the structure elucidation of a diatom sex pheromone

Finding a mate: Diatoms use chemical signals to sense the presence of and find their mating partners. When the metabolic profiles of sexually active and inactive cells were compared, a highly up-regulated metabolite generated in the attracting mating type was identified as di-L-prolyl diketopiperazine, the first diatom pheromone