The cost of crop damage caused by ozone air pollution from motor vehicles

The effects of ozone air pollution on the agricultural sector are an important environmental challenge facing policy makers. Most studies of the economic impact of air pollution on agriculture have found that a 25% reduction in ambient ozone would provide benefits of at least $1–2 billion annually in the United States. This paper extends existing research by estimating the benefits of a reduction in emissions from a major source of ozone formation: motor-vehicle emissions. An agricultural production model is combined with an analysis of motor-vehicle emissions and air quality to estimate the impacts of emissions from six different motor-vehicle classes, at both the regional and national level. The benefits to the agricultural sector from completely eliminating ozone precursor emissions from motor vehicles ranges between $3·5 and $6·1 billion annually.     

Effects of two doses of methylphenidate on simulator driving performance in adults with attention deficit hyperactivity disorder

INTRODUCTION: Numerous studies have documented an increased frequency of vehicular crashes, traffic citations, driving performance deficits, and driving-related cognitive impairments in teens and adults with attention deficit hyperactivity disorder. METHOD: The present study evaluated the effects of two single, acute doses of methylphenidate (10 and 20 mg) and a placebo on the driving performance of 53 adults with ADHD (mean age=37 years, range=18-65) using a virtual reality driving simulator, examiner and self-ratings of simulator performance, and a continuous performance test (CPT) to evaluate attention and inhibition. A double-blind, drug-placebo, within-subjects crossover design was used in which all participants were tested at baseline and then experienced all three drug conditions. RESULTS: A significant beneficial effect for the high dose of medication was observed on impulsiveness on CPT, variability of steering in the standard driving course, and driving speed during the obstacle course. A beneficial effect of the low dose of medication also was evident on turn signal use during the standard driving course. An apparent practice effect was noted on some of the simulator measures between the baseline and subsequent testing sessions that may have interacted with and thereby obscured drug effects on those measures. CONCLUSIONS: The results, when placed in the context of prior studies of stimulants on driving performance, continue to recommend their clinical use as one means of reducing the driving risks in ADHD teens and adults. IMPACT ON INDUSTRY: Given the significantly higher risk of adverse driving outcomes associated with ADHD, industry needs to better screen for ADHD among employees who drive as part of employment so as to improve safety and reduce costs. Use of stimulants to treat the adult ADHD driver may reduce safety risks.     

Genetic variability and differentiation in the temperature niche component of the diatom Thalassiosira pseudonana

The acclimated reproduction rates of 14 clones of the diatom Thalassiosira pseudonana were measured at 12°, 16°, 20°, and 24°C. Reproduction rate increased monotonically with an increase in temperature in all 14 clones. Significant genetic variability in reproduction rates and electrophoretic mobility of isozymes were observed among clones within a population from a single water bottle collected in a warm core eddy overlying slope water. The major genetic differentiation was between neritic and oceanic populations, with neritic clones having higher reproduction rates at all 4 temperatures. Surprisingly small genetic differences were observed among clones from neritic waters around the world. The slopes of the temperature-reproduction rate plots of all 14 clones were quite similar.Woods Hole Oceanographic Institution Contribution No. 4679     

The use of isotope dilution mass spectrometry for the certification of standard reference materials

Isotope dilution mass spectrometry (IDMS) has been used extensively at the U.S. National Bureau of Standards as an accurate method to determine trace element concentrations in natural materials. Thermal ionization mass spectrometry is a single element technique capable of high accuracy and precision, and has been used for “definitive” measurements of trace elements in sera with 95% confidence limits less than 0.25%. Spark source mass spectrometry is a complementary multielement, high-sensitivity technique that has been used to determine up to 20 elements in a sample, with typical accuracies of 2%–5%. Together with appropriate chemical separations, such as anion and cation exchange, chelate resins, electrodeposition, and chemical extraction, IDMS has been applied to elemental concentration measurements ranging over eight orders of magnitude, from decigrams/gram to picograms/gram. Many of these applications have been used for the certification of a broad spectrum of biological and environmental Standard Reference Materials, including lead in Trace Elements in Water (SRM 1643), 15 elements in Coal Fly Ash (SRM 1633a), uranium in Bovine Liver (SRM 1577a), and mercury in water (SRM 1642).     

Employee behaviors before and after stress management

A quasi-experiment was used to compare employee behaviors before and after stress management training. Organizational records on employee absenteeism, performance ratings, equipment accidents, and work injuries were obtained for highway maintenance workers who received biofeedback (BIO=21) or muscle relaxation (MR=16) training. Similar data were gathered for a comparison group of employees who did not volunteer for training (n = 80). The pre-training period (time 1) consisted of 2 1/2 years. The post-training period was divided into the year immediately after training (time 2) and the following 1/2 year (time 3). Multiple regression analyses indicated that the MR (but not BIO) group variable explained unique variance in time 2 absenteeism (p < 0.05) but not in performance ratings, equipment accidents, nor work injuries (p > 0.05). Neither group entered predictive models for any measure at time 3 (p > 0.05). The results provide limited support for relaxation training offered as a prevention activity in work settings.     

Racketed tail of the male and female turquoise-browed motmot: male but not female tail length correlates with pairing success,performance, and reproductive success

Both males and females of many avian species maintain elaborate plumage traits, and elaborate monomorphic plumage may convey adaptive benefits to one or both sexes as inter- or intraspecific signals. Both sexes of the turquoise-browed motmot (Eumomota superciliosa) are elaborately plumed with long racket-tipped tail. I investigated whether the racketed tail functions as a sexually selected signal in one or both sexes by testing the predictions that males and/or females with the largest tails have: (1) greater pairing success, (2) greater reproductive performance (clutch-initiation date, clutch size, and hatching success), and (3) greater reproductive success. Yearling males with longer denuded rachises (wires) on the central tail feathers had greater pairing success. In addition, adult males with longer wires paired with females who laid larger clutches, had greater hatching success independent of clutch size, and fledged more young. There was no relationship between female tail plumage and pairing success, reproductive performance, or fledgling success. These results are consistent with the hypothesis that male tail plumage functions as a mate choice or status signal, but that the tail of the female does not function in a sexually selected context. I discuss alternative hypotheses for the evolutionary maintenance of the elaborate female tail plumage.