Agenda setting and acid precipitation in the United States

The objective of this research was to analyze the retention of acid precipitation as a viable policy issue on the Congressional agenda during the 1980s. Issue maintenance (a term borrowed from Barbara Nelson's discussion of the four stages associated with agenda decision making) was examined in relation to a set of issue characteristics originally developed by Roger Cobb and Charles Elder, i.e., concreteness, social significance, temporal relevance, complexity, and categorical precedence. Each issue attribute was found to be somewhat useful in explaining the longevity of acid rain as an agenda item although the direction of influence for two factors, complexity and temporal relevance, was contrary to expectations. It was suggested that a conceptual merger of this sort could contribute to the comparative analysis of agenda policy decisions by providing a clearer and more restricted set of decision points to be explained.     

Radon-222 signatures of natural ventilation regimes in an underground quarry

Radon-222 activity concentration has been monitored since 1999 in an underground limestone quarry located in Vincennes, near Paris, France. It is homogeneous in summer, with an average value of 1700 Bq m(-3), and varies from 730 to 1450 Bq m(-3) in winter, indicating natural ventilation with a rate ranging from 0.5 to 2.4 x 10(-6) s(-1) (0.04-0.22 day(-1)). This hypothesis is supported by measurements in the vertical access pit where, in winter, a turbulent air current produces a stable radon profile, smoothly decreasing from 700 Bq m(-3) at 20 m depth to 300 Bq m(-3) at surface. In summer, a thermal stratification is maintained in the pit, but the radon-222 concentration jumps repeatedly between 100 and 2000 Bq m(-3). These jumps are due to atmospheric pressure pumping, which induces ventilation in the quarry at a rate of about 0.1 x 10(-6) s(-1) (0.009 day(-1)). Radon-222 monitoring thus provides a dynamical characterisation of ventilation regimes, which is important for the assessment of the long-term evolution of underground systems.     

Response of Organic and Inorganic Carbon and Nitrogen to Long-Term Grazing of the Shortgrass Steppe

We investigated the influence of long-term (56 years) grazing on organic and inorganic carbon (C) and nitrogen (N) contents of the plant–soil system (to 90 cm depth) in shortgrass steppe of northeastern Colorado. Grazing treatments included continuous season-long (May–October) grazing by yearling heifers at heavy (60–75% utilization) and light (20–35% utilization) stocking rates, and nongrazed exclosures. The heavy stocking rate resulted in a plant community that was dominated (75% of biomass production) by the C₄ grass blue grama (Bouteloua gracilis), whereas excluding livestock grazing increased the production of C₃ grasses and prickly pear cactus (Opuntia polycantha). Soil organic C (SOC) and organic N were not significantly different between the light grazing and nongrazed treatments, whereas the heavy grazing treatment was 7.5 Mg ha^–1 higher in SOC than the nongrazed treatment. Lower ratios of net mineralized N to total organic N in both grazed compared to nongrazed treatments suggest that long-term grazing decreased the readily mineralizable fraction of soil organic matter. Heavy grazing affected soil inorganic C (SIC) more than the SOC. The heavy grazing treatment was 23.8 Mg ha^–1 higher in total soil C (0–90 cm) than the nongrazed treatment, with 68% (16.3 Mg ha^–1) attributable to higher SIC, and 32% (7.5 Mg ha^–1) to higher SOC. These results emphasize the importance in semiarid and arid ecosystems of including inorganic C in assessments of the mass and distribution of plant–soil C and in evaluations of the impacts of grazing management on C sequestration.     

Improving older driver knowledge and self-awareness through self-assessment: the driving decisions workbook

PURPOSE: This study aims to assess whether the Driving Decisions Workbook, a self-assessment instrument for older drivers, increased self-awareness and general knowledge. This study also assessed perceptions regarding its usefulness, particularly as a tool for facilitating discussions within families of older drivers. A secondary purpose of the study was to determine if problems identified by drivers in the workbook related to problems they had with actual driving. DESIGN AND METHODS: The Driving Decisions Workbook was administered along with a questionnaire and a road test. A convenience sample of 99 licensed drivers aged 65 and above was used. RESULTS: After completing the workbook, about three fourths of the participants reported being more aware of changes that could affect driving. Fourteen percent reported that they had discovered a change in themselves of which they had not been previously aware. All respondents found the workbook to be at least a little useful and thought the workbook could help facilitate family discussions. Workbook responses were positively correlated with overall road test scores. Significant correlations were also noted between the road test and a majority of workbook subsection responses. IMPLICATIONS: This study indicates that the workbook may be a useful first-tier assessment instrument and educational tool for the older driver. It may encourage an older driver to drive more safely and/or to seek clinical assessment, and help in facilitating discussions about driving within their families.     

Review and assessment of models used to predict the fate of radionuclides in lakes

A variety of models for predicting the behaviour of radionuclides in fresh water ecosystems have been developed and tested during recent decades within the framework of many international research projects. These models have been implemented in Computerised Decision Support Systems (CDSS) for assisting the appropriate management of fresh water bodies contaminated by radionuclides. The assessment of the state-of-the-art and the consolidation of these CDSSs has been envisaged, by the scientific community, as a primary necessity for the rationalisation of the sector. The classification of the approaches of the various models, the determination of their essential features, the identification of similarities and differences among them and the definition of their application domains are all essential for the harmonisation of the existing CDSSs and for the possible development and improvement of reference models that can be widely applied in different environmental conditions. The present paper summarises the results of the assessment and evaluation of models for predicting the behaviour of radionuclides in lacustrine ecosystems. Such models were developed and tested within major projects financed by the European Commission during its 4th Framework Programme (1994-1998). The work done during the recent decades by many modellers at an international level has produced some consolidated results that are widely accepted by most experts. Nevertheless, some new results have arisen from recent studies and certain model improvements are still necessary.     

Evaluation of Rio Grande Management Alternatives Using a Surface‐Water/Ground‐Water Model1

Abstract: Previous investigations observed significant seepage losses from the Rio Grande to the shallow aquifer between Socorro and San Antonio, New Mexico. High‐resolution telescopic modeling was used along a 10‐km reach of the Rio Grande and associated drains and canals to evaluate several management alternatives aimed at improving river conveyance efficiency. Observed data consisted of ground‐water and surface‐water elevations, seepage rates along the Rio Grande and associated canals and drains, and borehole geology. Model calibration was achieved by adjusting hydraulic conductivity and specific storage until the output matched observed data. Sensitivity analyses indicated that the system was responsive to changes in hydrogeologic properties, especially when such alterations increased vertical connectivity between layers. The calibrated model predicted that removal of the low flow conveyance channel, a major channel draining the valley, would not only decrease river seepage by 67%, but also decrease total flow through the reach by 75%. The decreased flow through the reach would result in increased water logging and an average increase in ground‐water elevations of 1.21 meter. Simulations of the system with reduced riparian evapotranspiration rates or a relocated river channel also predicted decreased river seepage, but to a much lesser degree.     

Flexibility of X-Ray Emission Spectrography as Adapted to Microanalysis of Air Pollutants

Methods previously published by this laboratory for analyzing thin dust coatings of airborne particulates have been further evaluated, as applied to vast air pollution surveys. It was demonstrated that choice of glass fiber filters adapted to high-volume samplers restricts the analysis to a limited number of elements, such as lead. More flexibility and versatility are attained through the use of organic membrane filters mounted in small plastic monitors which permit multi-elemental analysis at least as accurately as with other popular but time-consuming techniques. These qualities of speed and accuracy allow shorter intervals of sampling which are normally required for better statistical assessment of broad air pollution surveys. Sensitivity of the technique reaches a value close to 0.05 μg/m³, while time of analysis required is about five minutes per element after receipt of the sample.     

Demographic performance predicts invasiveness of species in the Commelinaceae under high-nutrient conditions.

Demographic models are powerful tools for making predictions about the relative importance of transitions from one life stage (e.g., seeds) to another (e.g., nonreproductives); however, they have never been used to compare the relative performance of invasive and noninvasive taxa. I use demographic models parameterized from common garden experiments to develop hypotheses about the role of different life stage transitions in determining differences in performance in invasive and noninvasive congeners in the Commelinaceae. I also extended nested life table response experiment (LTRE) analyses to accommodate interactions between nested and unnested factors. Invasive species outperformed their noninvasive congeners, especially under high-nutrient conditions. This difference in performance did not appear to be due to differences in elasticities of vital rates, but rather to differences in the magnitude of stage transitions. Self-compatible invasive species had greater fecundity in high-nutrient environments and a shorter time to first reproduction, and all invasive species had greater vegetative reproduction than their noninvasive congeners. Thus greater opportunism in sexual and asexual reproduction explained the greater performance of invasive species under high-nutrient conditions. Similar common garden experiments could become a useful tool to predict potential invaders from pools of potential introductions. I show that short-term and controlled experiments considering multiple nutrient environments may accurately predict invasiveness of nonnative plant species.     

Variety of technological trajectories in low emission vehicles (LEVs): A patent data analysis

This paper focuses on the diversity of engine technologies for low emission vehicles (LEVs) that are developed by car manufacturers in order to substitute for the conventional internal combustion engine vehicle (ICEV). Our purpose is to analyse the competition between the various technologies for LEVs as well as the innovative strategy of car manufacturers. We first propose to define and to represent these technological trajectories in order to compare their performances and to identify their strengths and weaknesses. The technological bottlenecks, the barriers to the adoption of these alternative engine technologies as well as the features of this technological competition are underlined. We then use a patent data analysis to study the patent portfolios of the main car manufacturers in these technologies over the period [1990–2005]. The dynamics of patent applications by car manufacturers gives insight on the competition among technologies and on the strategy of firms. This analysis emphasises the progressive diversification of firms' patent portfolios over the whole set of engine technologies and the differentiated strategic positioning of car manufacturers according to countries.