The impact of job demands and behavioral control on experienced job stress

The present study examines the impact of behavioral control on the experience of work strain under conditions of work overload. Extending experimental laboratory findings that suggest that control can lessen the impact of aversive stimuli on psychological and physiological strain responses, we hypothesized an interaction between control and workload such that the effects of high demands on strain would be less if the worker had behavioral control over the task. This hypothesis is also consistent with Karasek's job demands-job decision latitude model of work strain and health. The hypothesis was tested in a laboratory experiment in which 125 subjects worked on a mail sorting task with either a high or moderate level of workload and either a high or low level of behavioral control. Strain responses were assessed with measures of job satisfaction, anxiety, and physiological arousal. The hypothesis was only partially supported in that high control lessened the impact that work overload had on anxiety. While not fully supportive of the model, the results are seen as conservative given the constraints on the manipulation of work overload inherent in the laboratory environment.     

The transtheoretical model of change in adolescents: implications for injury prevention

INTRODUCTION: Many injury prevention interventions require changes in human behavior to reduce self-risk or risk to others. Promising injury prevention interventions may be discarded if they lack power to create a significant difference in outcomes when judging their ability to "move a person from nonaction or negative action to positive action (safety)." The transtheoretical model of change (TMC) allows greater sensitivity in detecting along the change process where an intervention may be effective. The stages of change consist of precontemplation, contemplation, preparation, action, maintenance, and termination. Change is not viewed as an "all or none phenomenon." METHOD: Use of the TMC was examined using a quasiexperimental, cross-over design involving high school agriculture students enrolled in 21 schools in Kentucky (n=9), Iowa (n=7), and Mississippi (n=5). A series of physical and narrative simulations (safety training exercises) were developed with a focus on preventing amputation, spinal cord injury, hypersensitivity pneumonitis, and noise-induced hearing loss. Contemplation and action, as part of the TMC, were measured using a 10-item, Likert-type, stages of change (SOC) instrument comprised of two subscales (reliability coefficients were.88 and.81, respectively). The final sample consisted of 790 students (373 treatment and 417 control). RESULTS: There was a significant group effect for both contemplation, F(1,732)=197.4; p<.0001, and action, F(1,730)=106.1; p<.0001. A convenience sample of 29 of the participating students was selected for follow-up farm visits 1 year postparticipation. Of these students, 25 (86%) had made safety behavior changes in their farm work. IMPACT ON INDUSTRY: The use of the TMC model can provide researchers with greater precision in examining intervention effectiveness in promoting change.     

Forests and competing land uses in Kenya

Indigenous forests in Kenya, as in other developing countries, are under heavy pressure from competing agricultural land uses and from unsustainable cutting. The problem in Kenya is compounded by high population growth rates and an agriculturally based economy, which, even with efforts to control birth rates and industrialize, will persist into the next century. Both ecological and economic consequences of these pressures need to be considered in land-use decision making for land and forest management to be effective. This paper presents one way to combine ecological and economic considerations. The status of principal forest areas in Kenya is summarized and competing land uses compared on the basis of ecological functions and economic analysis. Replacement uses do not match the ecological functions of forest, although established stands of tree crops (forest plantations, fuel wood, tea) can have roughly comparable effects on soil and water resources. Indigenous forests have high, although difficult to estimate, economic benefits from tourism and protection of downstream agricultural productivity. Economic returns from competing land uses range widely, with tea having the highest and fuel wood plantations having returns comparable to some annual crops and dairying. Consideration of ecological and economic factors together suggests some trade-offs for improving land allocation decisions and several management opportunities for increasing benefits or reducing costs from particular land uses. The evaluation also suggests a general strategy for forest land management in Kenya.The views and interpretations expressed in this article are those of the authors and should not be attributed to the World Bank, its affiliated organizations, or any individual acting on their behalf.     

The stability of comparative referent choice and feelings of inequity: A longitudinal field study

This study examined the stability of comparative referent choice and feelings of inequity, and the effects of changes in feelings of inequity on employee reactions. At two points in time, 24 months apart, employees' choices of comparative referents and feelings of inequity with regard to four job facets (compensation, security, job complexity, and supervisory behavior) were assessed. Results indicated that many employees used the same comparative referents at both times, especially for the compensation facet. For three of the facets (security, job complexity, and supervisory behavior), employees tended to either change from a disadvantaged status at T1 to an advantaged or equitable status at T2 or to maintain at T2 the advantaged/equitable status they experienced at T1. However, for the compensation facet a different picture emerged: employees who felt disadvantaged at T1 also felt disadvantaged at T2. Finally, employees who changed to or maintained an equitable or an advantaged status with regard to the job complexity and supervisory behavior facets generally reacted more positively (i.e. were more satisfied and productive and attended more frequently) than employees who changed to or maintained a disadvantaged status. Implications of these results for future research on equity theory were discussed.     

The globalization of nitrogen deposition: consequences for terrestrial ecosystems

The sources and distribution of anthropogenic nitrogen (N), including N fertilization and N fixed during fossil-fuel combustion, are rapidly becoming globally distributed. Responses of terrestrial ecosystems to anthropogenic N inputs are likely to vary geographically. In the temperate zone, long-term N inputs can lead to increases in plant growth and also can result in over-enrichment with N, eventually leading to increased losses of N via solution leaching and trace-gas emissions, and in some cases, to changes in species composition and to ecosystem decline. However, not all ecosystems respond to N deposition similarly; their response depends on factors such as successional state, ecosystem type, N demand or retention capacity, land-use history, soils, topography, climate, and the rate, timing, and type of N deposition. We point to some of the conditions under which anthropogenic impacts can be significant, some of the factors that control variations in response, and some areas where uncertainty is large due to limited information.     

Rapidly locating and characterizing pollutant releases in buildings

Releases of airborne contaminants in or near a building can lead to significant human exposures unless prompt response measures are taken. However, possible responses can include conflicting strategies, such as shutting the ventilation system off versus running it in a purge mode or having occupants evacuate versus sheltering in place. The proper choice depends in part on knowing the source locations, the amounts released, and the likely future dispersion routes of the pollutants. We present an approach that estimates this information in real time. It applies Bayesian statistics to interpret measurements of airborne pollutant concentrations from multiple sensors placed in the building and computes best estimates and uncertainties of the release conditions. The algorithm is fast, capable of continuously updating the estimates as measurements stream in from sensors. We demonstrate the approach using a hypothetical pollutant release in a five-room building. Unknowns to the interpretation algorithm include location, duration, and strength of the source, and some building and weather conditions. Two sensor sampling plans and three levels of data quality are examined. Data interpretation in all examples is rapid; however, locating and characterizing the source with high probability depends on the amount and quality of data and the sampling plan.     

Effect of Forest Fragmentation on Genetic Diversity and Mating System in a Tropical Tree, Pithecellobium elegans

Genetic diversity, population differentiation, and temporal variation in outcrossing rates were examined for Pithecellobium elegans , a Neotropical rain forest canopy tree. Several forest fragments and a large reserve (1500 ha) were compared for several population genetic parameters. For eight populations sampled on the Atlantic coastal plain of Costa Rica, allozyme heterozygosity (0.13), polymorphism (35%), and effective number of alleles (1.24) were similar to values reported for other tropical tree species that occur at similar densities of less than one individual per hectare. These measures of genetic variation were lowest in populations of the smallest size, farthest from the reserve, and more isolated from other populations. Differentiation among samples collected in small forest fragments and the reserve population accounted for 10% of the total genetic variation observed. There was a positive relationship between the level of differentiation of populations from the reserve population and their distance from the reserve. Though predominantly an annually flowering species, the number of trees in flower at any one time varied from 80% of observed trees to only 6%. Outcrossing rates did not differ for two episodes in which the proportions of flowering trees were 33% and 80%. But periods of low density of flowering adults resulted in poor seed crops or failure to set fruit for many individuals. Population size at many sites will be effectively decreased because of the variation in flowering. Fragmentation of what was once a large, continuous forested area is resulting in genetic erosion of small, isolated populations of Pithecellobium elegans .     

The importance of considering spatial attributes in evaluating estuarine habitat condition: the South Carolina experience

The South Carolina Estuarine and Coastal Assessment Program (SCECAP) was initiated in 1999 to assess the condition of the state's coastal habitats using multiple measures of water quality, sediment quality, and biological condition. Sampling was subsequently expanded to include components required for the National Coastal Assessment (Coastal 2000) Program. Habitats are classified as either tidal creeks (<#60; 100 meters in width) or larger open water bodies. Approximately 30 sites are sampled within each habitat during the summer months using a probability-based random sampling design. Results obtained from the first two years of sampling documented significant differences in several water quality parameters (DO, salinity, pH, turbidity, fecal coliform bacteria, total nitrogen, TKN, total phosphorus) and biological measures (chlorophyll-a, finfish and crustacean abundance and biomass and a number of benthic species) between the tidal creek and open water habitats. These differences highlight the value of partitioning shallow water habitats separately from the larger open water bodies traditionally sampled in estuarine monitoring programs, especially since tidal creeks serve as critical nursery areas for many species. Based on the differences observed, there is a clear need to identify different physical and biological thresholds for evaluating the condition of each habitat type.     

Estimating Lag to Peak between Rainfall and Peak Streamflow with a Mixed‐Effects Model

We test the use of a mixed‐effects model for estimating lag to peak for small basins in Maine (drainage areas from 0.8 to 78 km²). Lag to peak is defined as the time between the center of volume of the excess rainfall during a storm event and the resulting peak streamflow. A mixed‐effects model allows for multiple observations at sites without violating model assumptions inherent in traditional ordinary least squares models, which assume each observation is independent. The mixed model includes basin drainage area and maximum 15‐min rainfall depth for individual storms as explanatory features. Based on a remove‐one‐site cross‐validation analysis, the prediction errors of this model ranged from ?42% to +73%. The mixed model substantially outperformed three published models for lag to peak and one published model for centroid lag for estimating lag to peak for small basins in Maine. Lag to peak estimates are a key input to rainfall–runoff models used to design hydraulic infrastructure. The improved accuracy and consistency with model assumptions indicates that mixed models may provide increased data utilization that could enhance models and estimates of lag to peak in other regions.     

Organoclays for Aquifer Bioremediation: Adsorption of Chlorobenzene on Organoclays and its Degradation by RHODOCOCCUS B528

The adsorption and degradation of chlorobenzene on partially modified organoclays and by the autochthonous microorganism Rhodococcus B528 were studied by means of the batch technique. Organoclays were prepared from Na-montmorillonite (MM) by using dodecyltrimethylammonium (C₁₂) and dioctadecyldimethylammonium (2C₁₈) bromides. The degree of modification was 35 (2C₁₈-35-MM) and 89% (C₁₂-89-MM) of the cation exchange capacity of MM. The adsorption experiments were carried out using headspace GC. The intercalation of chlorobenzene into the interlayers of organo-MM was detected by X-ray diffraction. The adsorption isotherms found were of the S1 type indicating a cooperative effect. Chlorobenzene showed a higher affinity for 2C₁₈-35-MM than C₁₂-89-MM, which could not only be explained by the organic carbon content. The comparison with 2,4-dichlorophenol adsorption has implied that for the studied systems the different adsorption mechanisms are primarily governed by the different molecular properties and not by the type of absorbent. The presence of 2C₁₈-35-MM caused no negative effect on the investigated microorganisms and complete biodegradation of chlorobenzene was achieved without desorption limitation for growth, demonstrating the applicability of partially modified organoclays for bioremediation.