Effects of Transcendental Meditation versus resting on physiological and subjective arousal.

On 4 successive days, 10 highly trained and experienced meditators (aged 26–54 yrs) were asked to relax for 5 min, meditate for 20 min, and then relax for 5 min. In contrast, 10 other Ss (aged 22–32 yrs) who had no training or experience with meditation were asked to relax for 5 min, rest for 20 min, and then relax for 5 min. Physiological arousal (heart and respiration rates, skin resistance, and blood pressure) and subjective arousal (cognitive, somatic, and relaxation) were measured throughout the experiment. Prior to meditating or resting, meditators tended to have higher heart rates and diastolic blood pressure than did nonmeditators. Meditation was associated with generally reduced arousal; but while meditating, meditators did not evidence lower levels of arousal than nonmeditators did while resting. Results place qualifications on previous studies of the effects of meditation on arousal. Implications for the study of personality functioning, stress management, and psychotherapy are discussed. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Field tests of a radon progeny sampler for the determination of effective dose

A two-screen sampler (an effective dosimeter), with a collection efficiency matched to the particle size response of the radon progeny dose conversion factors (DCF), obtained from the ICRP respiratory tract model as implemented in the computer code RADEP, has been developed to assess the inhalation dose from exposure to radon progeny. In order to evaluate the performance of this sampler, the second stage of a six-stage wire screen diffusion battery was designed to operate as an Effective Dosimeter. This hybrid system allowed two methods for the determination of the radon progeny DCF. For the first method, the activity size distributions, measured using the diffusion battery, were used to obtain a size-weighted DCF. A second determination of DCF was obtained directly from the fraction collected by the Effective Dosimeter. The hybrid diffusion battery was used to measure radon progeny in the Fairy Cave, Buchan, Victoria at 20-min intervals over a 30-h period. This cave had radon concentrations exceeding 2000 Bq m(-3), with low aerosol concentration and low ventilation rates. The measurements were analysed for the radon progeny PAEC, the activity size distribution, the size-weighted DCF and the effective dosimeter collected fraction. The Effective Dosimeter DCFs were determined from the collected fraction using firstly a simple linear function and then using a more complex polynomial function to correct for residual errors. For the linear factor alone, the calculated Effective Dosimeter DCFs were on average 11% lower than the equivalent size-weighted DCF values. The agreement using the polynomial function was improved markedly, with a linear regression of the DCF yielding a fitted ratio of 0.965, with an R value of 0.99. For this study, the use of the ICRP conversion convention to estimate the occupational exposure to the tour guides working in the Fairy Cave would under estimate the effective dose by up to a factor of 2.     

Neurocognitive signs in prodromal Huntington disease.

Objective: PREDICT-HD is a large-scale international study of people with the Huntington disease (HD) CAG-repeat expansion who are not yet diagnosed with HD. The objective of this study was to determine the stage in the HD prodrome at which cognitive differences from CAG-normal controls can be reliably detected. Method: For each of 738 HD CAG-expanded participants, we computed estimated years to clinical diagnosis and probability of diagnosis in 5 years based on age and CAG-repeat expansion number (Langbehn, Brinkman, Falush, Paulsen, & Hayden, 2004). We then stratified the sample into groups: NEAR, estimated to be ≤9 years; MID, between 9 and 15 years; and FAR, ≥15 years. The control sample included 168 CAG-normal participants. Nineteen cognitive tasks were used to assess attention, working memory, psychomotor functions, episodic memory, language, recognition of facial emotion, sensory–perceptual functions, and executive functions. Results: Compared with the controls, the NEAR group showed significantly poorer performance on nearly all of the cognitive tests and the MID group on about half of the cognitive tests (p = .05, Cohen's d NEAR as large as ?1.17, MID as large as ?0.61). One test even revealed significantly poorer performance in the FAR group (Cohen's d = ?0.26). Individual tasks accounted for 0.2% to 9.7% of the variance in estimated proximity to diagnosis. Overall, the cognitive battery accounted for 34% of the variance; in comparison, the Unified Huntington's Disease Rating Scale motor score accounted for 11.7%. Conclusions: Neurocognitive tests are robust clinical indicators of the disease process prior to reaching criteria for motor diagnosis of HD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mapping subsurface conditions within the near-shore zone of an Arctic delta using ground penetrating radar

This paper demonstrates the capabilities of ground penetrating radar (GPR) to map and resolve shallow subsurface features in the near-shore zone: (i) ice conditions (floating or bottom fast); (ii) water bathymetry; (iii) sedimentary structures; and (iv) interfaces between frozen and unfrozen sediment. These features were resolved in the near-shore zone of the Mackenzie Delta, N.W.T., Canada, using multi-frequency (50, 100 and 250 MHz) GPR data collected in winter (2005 and 2006). The capability of GPR to resolve subsurface features in the near-shore zone was strongly controlled by bottom-fast and floating ice conditions. The latter were discriminated using a novel approach involving the energy return from the base of ice and the presence of ice-bottom multiples. Beneath zones of bottom-fast ice, sedimentary structures and interfaces between frozen and unfrozen sediment were discriminated by reflection geometry and amplitude. Beneath floating ice, water depths were measured to depths greater than 5 m using a multi-layer depth calculation. Overall, this research demonstrates that baseline information for geotechnical investigations and climate change research in Arctic coastal zones can be greatly enhanced with GPR data.     

Rice Straw Smoke Generation System for Controlled Human Inhalation Exposures

A unique burner system was designed for the purposes of exposing human subjects to rice straw smoke under highly controlled conditions. The system burns individual straws and has produced particle concentrations up to 900 w g m m 3 in a temperature- and humidity-controlled exposure chamber. Burner operation is fully automatic and programmable. Ignition is by radiant heating in a manner similar to the field. Particle concentration is controlled by the firing interval between straws and by the ratio of burner outlet flow mixing with the main purified air supplied to the exposure chamber. Steady-state particle concentrations are achieved within 5 min from start. Repeatability of particle concentration is excellent at the two exposure levels used, 200 and 500 w g m m 3 . Measurements of particle size distributions suggest that approximately 80% of mass is in the size fraction below 1 w m. Although particle concentrations are controlled at target levels with good precision, emission factors are higher than achieved with similar material in wind tunnel and field experiments. Further characterization of particulate matter is needed to determine if higher emission factors are associated with changes in particle composition and morphology that may influence exposure results.