Ultrasound emission after cycles of water stress in Picea abies

The relationships among rate of ultrasound acoustic emission (AE), xylem water potential and transpiration rate were investigated in 5-year-old potted saplings of Picea abies Karst. after cycles of water stress. Water-stressed plants displayed minimum xylem water potentials of -3.9 MPa, near-zero transpiration rates and up to 45 AE counts per minute. After rewatering, water-stressed plants no longer produced AEs. Well-watered control plants produced only a small number of ultrasonic AEs. After three cycles of water stress (lasting 24 days in total), it was estimated that about two-thirds of the functional tracheids were embolized. The concomitant reduction in hydraulic conductance was about 70%.     

Giant radiation-induced color halos in quartz: solution to a riddle

The radii of radiation-induced color halos(RICHs) surrounding radioactive mineral inclusions in mica generally correspond closely to the calculated range of common uranogenic and thorogenic alpha particles in mica. Many exceptions are known, however, and these variants have led investigators to some rather exotic interpretations. Three RICHs found in quartz are identified as aluminum hole-trapping centers. Whereas the inner radii of these RICHs closely match the predicted range of the most energetic common alphas(39 micrometers), the color centers observed extend to 100 micrometers. Migration of valence-band holes down a radiation-induced charge potential might account for enigmatic RICHs. Such RICHs provide natural experiments in ultraslow charge diffusion.     

Combining cognitive and statistical approaches to survey design

Sample surveys provide data for academic research, government policy-making, the media, and business. Statistical research aims to improve survey data by reducing extraneous sources of variability and thus increasing accuracy. Researchers have begun to use paradigms adapted from the cognitive sciences to study those sources of variability associated with the processes that the respondent undertakes in understanding questions, remembering, judging and estimating, and formulating answers. To generalize laboratory-based findings, researchers must begin to embed designed experiments that vary the questionnaire content into sample surveys of broad population. Issues associated with the design of and statistical inference from such embedded experiments are examined and illustrated with an example on the effects of context questions on responses in attitude surveys.