Galactic and solar radiation exposure to aircrew during a solar cycle

An on-going investigation using a tissue-equivalent proportional counter (TEPC) has been carried out to measure the ambient dose equivalent rate of the cosmic radiation exposure of aircrew during a solar cycle. A semi-empirical model has been derived from these data to allow for the interpolation of the dose rate for any global position. The model has been extended to an altitude of up to 32 km with further measurements made on board aircraft and several balloon flights. The effects of changing solar modulation during the solar cycle are characterised by correlating the dose rate data to different solar potential models. Through integration of the dose-rate function over a great circle flight path or between given waypoints, a Predictive Code for Aircrew Radiation Exposure (PCAIRE) has been further developed for estimation of the route dose from galactic cosmic radiation exposure. This estimate is provided in units of ambient dose equivalent as well as effective dose, based on E/H x (10) scaling functions as determined from transport code calculations with LUIN and FLUKA. This experimentally based treatment has also been compared with the CARI-6 and EPCARD codes that are derived solely from theoretical transport calculations. Using TEPC measurements taken aboard the International Space Station, ground based neutron monitoring, GOES satellite data and transport code analysis, an empirical model has been further proposed for estimation of aircrew exposure during solar particle events. This model has been compared to results obtained during recent solar flare events.     

Diffraction loss in radiometry

Diffraction loss in radiometry has gained in importance recently because of an increased interest in longer wavelengths and the continuous improvement in experimental accuracy. The deviation from geometrical optics now contributes significantly to the errors of experiments. Previous research has concentrated on geometries classified as F1 and F2, leaving an intermediate case yet to be investigated. This intermediate case has some interesting behavior, as it is in this envelope of geometries that it is possible to have zero diffraction loss. We designate this intermediate geometric regime as F3. We introduce a numerical regime to calculate diffraction loss for intermediate geometries, which is also highly efficient for the F1 and F2 regimes.     

Resonantly enhanced two-wave mixing via population pulsations insemiconductor laser amplifiers

Demonstrates theoretically the existence of enhanced probe gain via population pulsations in nearly degenerate two-wave mixing in a semiconductor amplifier. The enhancement arises from the injection current modulation frequency coinciding with the pump/probe detuning. Probe saturation is shown to occur in less than 10 μm cavity length     

Growth periodization in mental test performance.

Epstein proposed that the brain and mental ability grow in spurts, specifically at 3–20 months and 2–4, 6–8, 10–22 or 13, and 14–26 or 17 years of age, and that new concepts and skills should be taught primarily during the spurts, not during the plateaus. The mental test data cited by Epstein to support his theory are reanalyzed in this article. Only two studies provided any statistically significant relation with the theory. In one, the age changes were partly confounded with differences in test forms. In the other study, the pattern of means ran counter to theoretical predictions. A summary of the age distribution of increments and decrements in mental growth rates across studies did not reveal consistent or substantial age changes, and the age period that most consistently contained accelerated growth across studies had been hypothesized to be a period of slow, not rapid, growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sediment Mixing by Lampsilis Radiata Siliquoidea (Mollusca) from Western Lake Erie

The sediment reworking activities of an abundant Lake Erie unionid bivalve, Lampsilis radiata siliquoidea, have been studied by field observations and laboratory experiments. Unionid burrowing in laboratory microcosms increased sediment water content 10-20%, decreased water content variability, homogenized sedimentary structures, and increased tenfold the volume of oxidized sediment over that in microcosms with no unionids. Incomplete mixing of sediment took place to a depth of 10 cm during burrowing by L. r. siliquoidea. Burrowing by other unionids may extend the depth of maximum reworking to 20 cm. Unionid burrowing, feeding, and respiratory activities may alter the profiles of various elements and radionuclides associated with sediment particles and alter the location and intensity of microbial activity in sediments.     

The mechanism of the hammerhead ribozyme

The rate of cleavage of a 13-mer substrate by an all-RNA ribozyme with 2 10-mer hybridising arms (TAT RA), appears to be limited by a conformational change involving the longer than necessary arms. The same limitation does not apply to a similar ribozyme with DNA arms (TAT RB) or to an all-RNA ribozyme with only 6 hybridising bases on each arm (TAT RA 6x2). The limitation does not arise in the hybridisation step nor in the dissociation of products. An extra step involving a conformational change of the pre-formed ribozyme-substrate prior to cleavage is introduced to explain the observed kinetics.     

Communicating developmental research results to the general public through television.

Describes a project in which developmental psychologists worked cooperatively with producers to create a series of 20 news features (60–250 sec episodes) that were broadcast on the local news of TV stations across the US. Topics included divorce, adolescent abuse, parent–infant attachment, and the visual capabilities of babies. Public relations specialists, an interviewer, and 2 developmental psychologists experienced in TV appearances provided suggestions for developmental psychologists on how to be more effective as sources for news programs, talk shows, and documentaries. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)