The phase coherence of light from extragalactic sources - direct evidence against first order Planck scale fluctuations in time and space

We present a method of directly testing whether time continues to have its usual meaning on scales of <= t_P = sqrt(hbar G/c^5) ~ 5.4E-44 s, the Planck time. According to quantum gravity, the time t of an event cannot be determined more accurately than a standard deviation of the form sigma_t/t = a_o (t_P/t)^a, where a_o and a are positive constants ~1; likewise distances are subject to an ultimate uncertainty c \sigma_t, where c is the speed of light. As a consequence, the period and wavelength of light cannot be specified precisely; rather, they are independently subject to the same intrinsic limitations in our knowledge of time and space, so that even the most monochromatic plane wave must in reality be a superposition of waves with varying omega and {\bf k}, each having a different phase velcocity omega/k. For the entire accessible range of the electromagnetic spectrum this effect is extremely small, but can cumulatively lead to a complete loss of phase information if the emitted radiation propagated a sufficiently large distance. Since, at optical frequencies, the phase coherence of light from a distant point source is a necessary condition for the presence of diffraction patterns when the source is viewed through a telescope, such observations offer by far the most sensitive and uncontroversial test. We show that the HST detection of Airy rings from the active galaxy PKS1413+135, located at a distance of 1.2 Gpc, secures the exclusion of all first order (a=1) quantum gravity fluctuations with an amplitude a_o > 0.003. The same result may be used to deduce that the speed of light in vacuo is exact to a few parts in 10^32.Comment: Title change. One reference added. Final version accepted by ApJ

Characterization of the Engineering Properties and Economic Potential of the Transitional Clay Unit of the Ripley Formation, Northeast Mississippi

Expansive soils, throughout Mississippi and the U.S., have long been a source of problems within the engineering and construction industries, leading to billions of dollars in damage annually. Along with being a source of problems, the clays throughout Mississippi are also of economic importance, being mined for a variety of uses. In this study, the engineering properties of the transitional clay facies of the Ripley Formation are studied, to characterize the swell potential of the transitional clay, and to assist with the evaluation of the possible commercial uses of the soil. The transitional clay is an Upper Cretaceous unit characterized as being, medium to dark gray, fossiliferous, laminated to bedded, and micaceous. The unit was sampled across areas of Chickasaw, Pontotoc, and Union Counties of Mississippi. Sample sites across the three counties were included in the study so that the spatial and stratigraphic variability at different scales within the sampled site were investigated. Various laboratory tests were performed to document the extent of the soils engineering properties and swell potential. Atterberg limits and potential volume change tests were the main testing methods, along with the use of published empirical methods of predicting swell potential. To assess the economic potential of the unit, the Atterberg limit values of the samples were compared against other clays within Mississippi that have been mined for a variety of uses. The results of the testing show that the engineering properties of transitional clay facies, within the study area, to be highly variable. A large majority of the samples, however, are classified as having high to very high swell potential. Any construction projects within the outcrop belt of the transitional clay facies should have localized, site-specific, shrink-swell investigations performed to assess the need for mitigation of swelling soils. The high variability of the properties of the transitional clay also leads to a wide range of potential economic uses. Further investigations must to be performed, along manufacturer specific guidelines, to be able to fully assess the economic potential of these clays

Environmental pressures as they affect the acceptance of treatment by fifteen alcoholic patients in the Washingtonian Hospital 1942 to 1950

Thesis (M.S.)--Boston Universit

STEADY STATE PERFORMANCE OF ELITE CYCLISTS IN RECORD ATTEMPTS

The majority of world, Olympic and national records attempted by elite amateur .or professional cyclists may be considered as endurance events. The conditions undbr which these records are attempted suggest that the cyclist should be able to perform at a steady state at their physiological and biomechanical maximum. This paper considers this suggestion and demonstrates that the steady state condition is not achieved and therefore that certain assumptions may need review. The world records recognized by the UCI until recently were the SOOm, Ikm, 3km (women and juniors only), 4km, 5km, 1 Okm, 20km, IOOkm and the 1 Hour records, all from a standing (stationary) start. Three additional records are permitted a flying (rolling) start over 200m, 500m and lkm. Separate records existed for amateur and professional cyclists (also women and juniors) under a variety of circumstances; indoor or outdoor tracks and sea-level or altitude conditions. It is permissible to break records at the intermediate distances. Most of these records are unusual in comparison with most other sports as only the 200m flying start, 3km, 4km and 5km standing start records are directly comparable with competition performances. As a result most of these records are attempted simply because they exist and success tends to favour a dedicated attempt under ideal conditions, accordingly the majority of successful attempts have been made by professional road riders. Actual performances by top professionals and amateur riders have been examined and show that steady state performance is not achieved. Intermediate velocities show a variation of typically 5% about the mean velocity ultimately achieved. The degree of psychological and neuromuscular control exercised by such cyclists appears to indicate that better performances may be produced by improvements in "control skills" than "strength and endurance" for cyclists at such elite levels