Group-level organizational citizenship behavior: Effects of demographic faultlines and conflict in small work groups

Organizational scholars have recently shifted their attention to examining organizational citizenship behavior (OCB) as a group-level phenomenon. Adopting the input-mediator-outcome model of group performance, we examined antecedents and intermediate processes that predict group-level OCB (GOCB) in small work groups. The results, based on data from 62 work groups representing a variety of industries, revealed that demographic faultlines based on relation-oriented attributes (gender, age, and race) and a task-related attribute (tenure) had differentiated relationships with task and relationship conflict, which mediated the relationships between faultlines and group outcomes (GOCB and group performance). Both task and relationship conflict were negative predictors of group performance. However, task conflict increased GOCB, whereas relationship conflict decreased it. The present study offers evidence of the relationship between demographic faultlines and various group processes and outcome variables in natural work groups. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of reactive media composition and co-contaminants on sulfur-based autotrophic denitrification

As a part of a study developing a biological reactive barrier system to treat nitrate-contaminated groundwater, the effects of reactive media composition and co-contaminants on sulfur-oxidizing autotrophic denitrification were investigated. The size of sulfur granules affected the denitrification rates; kinetic constants of 2.883, 2.949, and 0.677 mg-N(1/2)/L(1/2)/day were obtained when the granule sizes were below 2 mm, between 2 and 5 mm, and over 5 mm, respectively. When the volume ratios of sulfur to limestone were 1:1, 2:1, 3:1, and 4:1, kinetic constants of 5.490, 3.903, 4.072, and 2.984 mg-N(1/2)/L(1/2)/day were obtained, respectively. The presence of TCE up to 20 mg/L didn't significantly affect nitrate removal efficiency. At the TCE concentration of 80 mg/L, however, nitrate removal was markedly inhibited. Also, Zn and Cu inhibited the denitrification activity at more than 0.5 mg/L of concentration whereas Cr (VI) did not significantly affect the nitrate removal efficiency at all levels tested.     

Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.     

Maternal serum activin A and inhibin A in trisomy 18 pregnancies at 10–14 weeks

In 45 cases of trisomy 18 and 493 control pregnancies at 10–14 weeks of gestation, maternal serum inhibin A, total activin A, free β-hCG and PAPP-A were measured. In the trisomy 18 pregnancies the median values were 0.74 MoM for inhibin A, 1.23 MoM for activin A, 0.38 MoM for free β-hCG and 0.16 MoM for PAPP-A. The degree of deviation from normal in the levels of inhibin and activin is small in comparison with free β-hCG and PAPP-A and they are therefore unlikely to be of value in improving the sensitivity of 90% for a 1% false-positive rate achieved by screening with fetal nuchal translucency and maternal serum free β-hCG and PAPP-A. Copyright © 2001 John Wiley & Sons, Ltd.     

Remediation of nutrient-rich waters using the terrestrial plant, Pandanus amaryllifolius Roxb.

Effective control of eutrophication is generally established through the reduction of nutrient loading into waterways and water bodies. An economically viable and ecologically sustainable approach to nutrient pollution control could involve the integration of retention ponds, wetlands and greenways into water management systems. Plants not only play an invaluable role in the assimilation and removal of nutrients, but they also support fauna richness and can be aesthetically pleasing. Pandanus amaryllifolius, a tropical terrestrial plant, was found to establish well in hydrophytic conditions and was highly effective in remediating high nutrient levels in an aquatic environment showing 100% removal of NO~-N up to 200 mg/L in 14 days. Phosphate uptake by the plant was less efficient with 64% of the PO4-P removed at the maximum concentration of 100 mg/L at the end of 6 weeks. With its high NO~-N and PO43--P removal efficiency, P. amaryllifolius depleted the nutrient-rich media and markedly contained the natural colonization of algae. The impediment of algal growth led to improvements in the water quality with significant decreases in turbidity, pH and electrical conductivity. In addition, the plants did not show stress symptoms when grown in high nutrient levels as shown by the changes in their biomass, total soluble proteins and chlorophyll accumulation as well as photochemical efficiency. Thus, P. amaryUifolius is a potential candidate for the mitigation of nutrient pollution in phytoremediation systems in the tropics as the plant requires low maintenance, is tolerant to the natural variability of weather conditions and fluctuating hydro-periods, and exhibit good nutrient removal capabilities.     

Dissipation of atrazine, enrofloxacin, and sulfamethazine in wood chip bioreactors and impact on denitrification

Wood chip bioreactors are receiving increasing attention as a means of reducing nitrate in subsurface tile drainage systems. Agrochemicals in tile drainage water entering wood chip bioreactors can be retained or degraded and may affect denitrification. The degradation of 5 mg L atrazine, enrofloxacin, and sulfamethazine under denitrifying conditions in wood chips from an in situ reactor was determined. The impact of these chemicals on denitrifying microorganisms was assessed using the denitrification potential assay, most probable number (MPN), and quantitative polymerase chain reaction targeting the gene of the denitrifiers. Initial half-lives for these chemicals in the aqueous phase were 0.98 d for atrazine, 0.17 d for enrofloxacin, and 6.2 d for sulfamethazine. Similar rates of disappearance in autoclaved and nonautoclaved wood chip solutions during the first 48 h suggested sorption was the dominant mechanism. The presence of atrazine did not impair denitrification potential, the MPN, or the copy number. The denitrifier MPN and copy number in sulfamethazine- and enrofloxacin-treated microcosms were less than the control within the first 5 d after chemical addition, whereas the denitrification potentials were not affected. However, after 45 d the denitrification rate, MPN and gene copy numbers for sulfamethazine and enrofloxacin were similar to that of the no-chemical control, indicating that acclimation of the denitrifier population to the antibiotic or reduced bioavailability over time allowed recovery of the denitrifier population.     

The effects of self‐emotion,counterpart emotion,and counterpart behavior on negotiator behavior: a comparison of individual‐level and dyad‐level dynamics

This study expands the negotiation literature by examining how negotiator behavior is predicted by various emotions felt by the negotiators and their counterparts and by counterpart negotiation behavior. Using hierarchical linear modeling, we also compare individual‐ and dyad‐level processes that lead to negotiator behavior and outcomes. The results from a dyadic negotiation simulation showed that both the valence and agency of negotiator and counterpart emotions need to be considered to understand the roles of emotion in negotiator behavior. Negotiators tend to reciprocate counterparts' integrating, compromising, and dominating behaviors, but they also offer complementary (or matching) responses to the counterparts' dominating and yielding behaviors. Integrating behavior was more dependent on dyad‐level interpersonal dynamics than were the other behaviors. The comparison of negotiator‐level and dyad‐level results suggests that negotiation needs to be understood in the context of collective exchanges as well as individual‐level cognitive processes. Copyright © 2005 John Wiley & Sons, Ltd.     

Modeling of air sparging of VOC-contaminated soil columns

Air sparging is a remediation technology currently being applied for the restoration of sites contaminated with volatile organic compounds (VOCs). Attempts have been made by various researchers to model the fate of VOCs in the gas and liquid phase during air sparging. In this study, a radial diffusion model with an air–water mass transfer boundary condition was developed and applied for the prediction of VOC volatilization from air sparging of contaminated soil columns. The approach taken was to use various parameters such as mass transfer coefficients and tortuosity factors determined previously in separate experiments using a single air channel apparatus and applying these parameters to a complex system with many air channels. Incorporated in the model, is the concept of mass transfer zone (MTZ) where diffusion of VOCs in this zone was impacted by the volatilization of VOCs at the air–water interface but with negligible impact outside the zone. The model predicted fairly well the change in the VOC concentrations in the exhaust air, the final average aqueous VOC concentration, and the total mass removed. The predicted mass removal was within 1% to 20% of the actual experimental mass removed. The results of the model seemed to suggest that air-sparged soil columns may be modeled as a composite of individual air channels surrounded by a MTZ. For a given air flow rate and air saturation, the VOC removal was found to be inversely proportional to the radius of the air channel. The approach taken provided conceptual insights on mass transfer processes during air sparging operations.     

Carrying capacity of an uninhabited island off the southwestern coast of Korea

An emergy evaluation was carried out to assess the carrying capacity of a small, uninhabited island (Woosedo) off the southwestern coast of Korea. The sea area within 1 km from the high tide level of the island was included in the evaluation. The total environmental emergy input to Woosedo was 1.66E19 sej/yr, with the most emergy contribution from the tidal energy. The land and marine ecosystems of Woosedo contributed 4.97 million Em$ (7600 Em$/ha/yr) to the Korean economy annually. If Woosedo was developed to the national average at the emergy investment ratio of 2.86, its carrying capacity was estimated at 1034 people at the current living standard of Korea. With this population, the island system would not be sustainable with a very low emergy sustainability index of 0.36. At the same living standard used in the developed scenario, the carrying capacity of the island would be 370 people for a sustainable development scenario and 270 people if the renewable emergy were the only source to support the population. The emergy contribution of the marine ecosystem of the island was the major source of support in determining the level of carrying capacity of the island.