[1,3]oxazines: green synthesis by sonication using a magnetically-separable basic nano-catalyst and investigation of its activity against the toxic effect of a pesticide on the morphology of blood cells

Environmental Chemistry Letters - The demand for a cleaner environment has led chemists to develop greener protocols, notably by using catalysts. Encapsulation of an active substance on a solid...     

What does team–member exchange bring to the party? A meta‐analytic review of team and leader social exchange

Both leader–member exchange (LMX) and team–member exchange (TMX) measure the quality of reciprocal exchange among employees in the workplace. Although LMX focuses on supervisor–subordinate relationships while TMX examines the relationships among team members, both have theory‐based and empirically proven relations with workplace outcomes such as job performance, organizational commitment, job satisfaction, and turnover intentions. However, it is not yet known which has more of an impact on such workplace outcomes—specifically, it is not clear if an employee's time is best spent developing vertical relationships among supervisors and subordinates (LMX) or on the horizontal relationships among team members (TMX). Accordingly, this meta‐analysis explores the incremental validity and relative importance of these two social exchange‐based constructs. The theoretical logic underlying LMX and TMX is clarified, and the parameter estimates between LMX, TMX, and work outcomes are reported. Results demonstrate that TMX shows incremental validity above and beyond LMX for some outcomes (organizational commitment and job satisfaction), but not others (job performance and turnover intentions). Also, LMX shows greater relative importance across all four outcomes. In sum, the clarification of the theoretical and empirical landscape lays a foundation for recommendations for future research. Copyright © 2013 John Wiley & Sons, Ltd.     

A state of the science review of the potential health hazards associated with asbestos in shielded metal arc welding rods in the United States

Due to its unique chemical properties, chrysotile asbestos was historically incorporated into a wide variety of products, including the outer covering, or “flux” of certain classifications of general arc mild steel welding electrodes. The purpose of this analysis is to review the historical engineering, toxicology, regulatory, and epidemiology information relevant to asbestos in mild steel welding rods in order to assess whether mild steel welders are at increased risk of developing asbestos-related diseases as a result of welding rod use. We divided our analysis into four distinct time periods, based on what we perceived to be seminal events in welding technology or in the evolution of knowledge regarding asbestos and asbestos-related diseases. These time periods are as follows: late 1800s to 1929, 1930–1955, 1956–1970, and 1971–2006. We found that studies that attempted to measure airborne asbestos directly in welding rod fumes found no measurable fibers; this is likely due to the fact that the fibers degrade at high temperatures present in the welding arc. In addition, “worst-case” use simulation studies, specifically intended to generate airborne flux particles, reported that airborne asbestos concentrations were either undetectable or very low. The airborne concentrations generated were always below the current OSHA permissible exposure limit (0.1 f/cc TWA), and the lifetime doses associated with “worst-case” use were found to be far below the plausible thresholds for mesothelioma and lung cancer. The epidemiology of mild steel welders is difficult to interpret due to confounding exposures such as (1) possible exposure to nickel and hexavalent chromium in stainless steel welding fumes (lung cancer), (2) smoking (lung cancer), and (3) bystander exposure to amphibole asbestos (lung cancer and mesothelioma). None of the published welder studies controlled for all three factors, yet when any single source of bias was controlled for, the majority of the studies reported no significant risk in either asbestos-related disease. Furthermore, none of the investigators in any of the welder studies suggested that asbestos in welding rods might be a risk factor for lung cancer or mesothelioma, and there is not a single case report in the medical literature that attempts to link welding rod use to an asbestos-related disease. We conclude that the weight of evidence indicates that welders were not historically at risk of developing asbestos-related diseases as a result of welding rod use.     

Inorganic and organic contaminants in sediments from an urban playa and associated toxicity among Hyalella azteca

Playa wetlands are important components of the Southern High Plains (USA) landscape as they are the major aquatic surface feature. Chemical contaminants associated with playas have been documented, particularly for grassland and agricultural watersheds, but not for playas in urban settings. The objectives of this study were to determine concentrations of inorganic and organic contaminants in sediments from an urban playa within the I-20 Wildlife Preserve and Jenna Welch Nature Study Center in Midland, TX, and evaluate toxicity of these sediments to Hyalella azteca. Concentrations of most trace elements were below sediment quality guidelines with exceptions of lead, cadmium, and arsenic. Concentrations of organic contaminants, particularly PAHs, DDT, DDE, and malathion, were above sediment quality guidelines at various locations within the playa. Decreased survival was observed among H. azteca exposed to sediment from a single location when compared those exposed to reference sediments. This location also produced maximum observed concentrations for five of seven trace elements, potentially due to its location at the lowest elevation within the playa. This study documented concentrations of contaminants in sediments of an urban playa associated with past and present land uses in its urban setting, including those from automotive emissions and historical pesticide use.     

Multimodal signals increase active space of communication by wolf spiders in a complex litter environment

Multimodal signals may compensate for environmental constraints on communication, as signals in different modalities vary in efficacy. We examined the influence of complex microhabitats on transmission of vibratory and visual signals of courting male Schizocosa ocreata wolf spiders (Araneae: Lycosidae) with laser Doppler vibrometry (LDV) and behavioral observations in lab and field. We measured maximum potential detection distance of visual and vibratory signals by females in laboratory mesocosms, recorded vibration signal attenuation on different substrates, and estimated transmission distances for male vibration signals in the field. We also determined effective line-of-sight visual detection distances in the field with laser distance measures. Together, these data were used to estimate the potential and effective active space of multimodal signals. LDV measures show leaves are highly conductive substrates for wolf spider vibratory signals compared to others (soil, wood, rock). For both visual and vibratory modes, lab estimates of maximum potential distance for signal transmission and detection (behavior studies) exceeded estimates of effective active space (signal attenuation, “vanishing point,” and “line-of-sight” measures). Field estimates of transmission distance for signal modes overlap, such that in close range (<20 cm), vibratory signals are more likely to be detected, while farther away, visual signals are more likely to be seen. These findings thus support current hypotheses regarding how multimodal communication might extend the range of overall signal active space or compensate for environmental constraints.     

Influence of planform geometry and momentum ratio on thermal mixing at a stream confluence with a concordant bed

The effects of planform geometry and momentum flux ratio on thermal mixing at a stream confluence with concordant bed morphology are investigated based on numerical simulations that can capture the dynamics of large-scale turbulence. In two simulations, the bathymetry and asymmetrical planform geometry are obtained from field experiments and the momentum flux ratio is set at values of one and four. These two conditions provide the basis for studying differences in thermal mixing processes at this confluence when the wake mode and the Kelvin–Helmholtz mode dominate the development of coherent structures within the mixing interface (MI). The effects of channel curvature and angle between the two incoming streams on thermal mixing processes are investigated based on simulations conducted with modified planform geometries. Two additional simulations are conducted for the case where the upstream channels are parallel but not aligned with the downstream channel and for the zero-curvature case where the upstream channels are parallel and aligned with the downstream channel. The simulations highlight the influence of large-scale coherent structures within the MI and of streamwise-oriented vortical (SOV) cells on thermal mixing processes within the confluence hydrodynamics zone. Simulation results demonstrate the critical role played by the SOV cells in promoting large-scale thermal mixing for cases when such cells form in the immediate vicinity of the MI and in modifying the shape of the thermal MI within cross sections of the downstream channel—predictions consistent with empirical measurements of thermal mixing at the confluence. The set of numerical simulations reveal that the degree of thermal mixing occurring within the confluence hydrodynamic zone varies dramatically with planform geometry and incoming flow conditions. In some cases thermal mixing at the downstream end of the confluence hydrodynamic zone is limited to the MI and its immediate vicinity, whereas in others substantial thermal mixing has occurred over most of the cross-sectional area of the flow. Overall, the simulations highlight the flow conditions and the controls of these conditions that influence mixing within the immediate vicinity of a confluence.     

Impact of photocatalytic remediation of pollutants on urban air quality

In the recent years, photocatalytic self-cleaning and “depolluting” materials have been suggested as a remediation technology mainly for NO _x and aromatic VOCs in urban areas. A number of products incorporating the aforementioned technology have been made commercially available with the aim to improve urban air quality. These commercial products are based on the photocatalytic properties of a thin layer of TiO₂ at the surface of the material (such as glass, pavement, etc.) or embedded in paints or concrete. The use of TiO₂ photocatalysts as an emerging air pollution control technology has been reported in many locations worldwide. However, up to now, the effectiveness measured in situ and the expected positive impact on air quality of this relatively new technology has only been demonstrated in a limited manner. Assessing and demonstrating the effectiveness of these depolluting techniques in real scale applications aims to create a real added value, in terms of policy making (i.e., implementing air quality strategies) and economics (by providing a demonstration of the actual performance of a new technique).

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Mercury source zone identification using soil vapor sampling and analysis

Development and demonstration of reliable measurement techniques that can detect and help quantify the nature and extent of elemental mercury (Hg(0)) in the subsurface are needed to reduce uncertainties in the decision-making process and increase the effectiveness of remedial actions. We conducted field tests at the Y-12 National Security Complex in Oak Ridge, Tennessee, USA, to determine if sampling and analysis of Hg(0) vapors in the shallow subsurface (<0.3 m depth) can be used to as an indicator of the location and extent of Hg(0) releases in the subsurface. We constructed a rigid polyvinyl chloride push probe assembly, which was driven into the ground. Soil gas samples were collected through a sealed inner tube of the assembly and were analyzed immediately in the field with a Lumex and/or Jerome Hg(0) analyzer. Time-series sampling showed that Hg vapor concentrations were fairly stable over time, suggesting that the vapor phase Hg(0) was not being depleted and that sampling results were not sensitive to the soil gas purge volume. Hg(0) vapor data collected at over 200 push probe locations at 3 different release sites correlated very well to areas of known Hg(0) contamination. Vertical profiling of Hg(0) vapor concentrations conducted at two locations provided information on the vertical distribution of Hg(0) contamination in the subsurface. We conclude from our studies that soil gas sampling and analysis can be conducted rapidly and inexpensively at large scales to help identify areas contaminated with Hg(0).     

Oceanographic influences on the dive behavior of juvenile loggerhead turtles (Caretta caretta) in the North Pacific Ocean

Satellite telemetry data from 17 juvenile loggerhead turtles (43.5–66.5 cm straight carapace length) were used in conjunction with oceanographic data to analyze the influence of regional and seasonal oceanography on dive behavior in the North Pacific Ocean. Combined dive behavior for all individuals showed that turtles spent more than 80% of their time at depths <5 m, and more than 90% of their time at depths <15 m. Multivariate classifications of dive data revealed four major dive types, three representing deeper, longer dives, and one representing shallower dives shorter in duration. Turtles exhibited variability in these dive types across oceanographic regions, with deeper, longer dives in the Hawaii longline swordfish fishing grounds during the first quarter of the year, as well as in the Kuroshio Extension Bifurcation Region and the region near the Baja California Peninsula, Mexico. Turtles in the Kuroshio Extension Bifurcation Region also exhibited dive variability associated with mesoscale eddy features, with turtles making deeper, longer dives while associated with the strongest total kinetic energy. Turtles in the central North Pacific exhibited seasonality in dive behavior that appeared to reflect synchronous latitudinal movements with the North Pacific Subtropical Front and the associated seasonal, large-scale oceanography. Turtles made deeper, longer dives during the first quarter of the year within this region, the reported time and area where the highest loggerhead bycatch occurs by the longline fishery. These results represent the first comprehensive study of dive data for this species in this region. The increased understanding of juvenile loggerhead dive behavior and the influences of oceanography on dive variability should provide further insight into why interactions with longline fisheries occur and suggest methods for reducing the bycatch of this threatened species.     

Spatial distribution of lead concentrations in urban surface soils of New Orleans, Louisiana USA

Immediately following hurricane Katrina concern was raised over the environmental impact of floodwaters on the city of New Orleans, especially in regard to human health. Several studies were conducted to determine the actual contaminant distribution throughout the city and surrounding wetlands by analyzing soil, sediment, and water for a variety of contaminants including organics, inorganics, and biologics. Preliminary investigations by The Institute of Environmental and Human Health at Texas Tech University concluded that soils and sediments contained pesticides, semi-volatiles, and metals, specifically arsenic, iron, and lead, at concentrations that could pose a significant risk to human health. Additional studies on New Orleans floodwaters revealed similar constituents as well as compounds commonly found in gasoline. More recently, it has been revealed that lead (Pb), arsenic, and vanadium are found intermittently throughout the city at concentrations greater than the human health soil screening levels (HHSSLs) of 400, 22 (non-cancer endpoint) and 390 μg/g, respectively. Of these, Pb appears to present the greatest exposure hazard to humans as a result of its extensive distribution in city soils. In this study, we spatially evaluated Pb concentrations across greater New Orleans surface soils. We established 128 sampling sites throughout New Orleans at approximately half-mile intervals. A soil sample was collected at each site and analyzed for Pb by ICP-AES. Soils from 19 (15%) of the sites had Pb concentrations exceeding the HHSSL threshold of 400 μg/g. It was determined that the highest concentrations of Pb were found in the south and west portions of the city. Pb concentrations found throughout New Orleans in this study were then incorporated into a geographic information system to create a spatial distribution model that can be further used to predict Pb exposure to humans in the city.