mtDNA control region and D-HPLC analysis: a method to evaluate the mating system in Syngnathidae (Teleostei)

Mitochondrial DNA (mtDNA) has been used extensively in animals for phylogenetic and population studies but it has been applied only occasionally to mating systems analysis, where nuclear markers are usually preferred. We used denaturing-high performance liquid chromatography (D-HPLC) to detect mitochondrial DNA polymorphisms to assess the genetic mating system in Syngnathus abaster. Our study of ten pregnant males, revealed polygyny in 30% of the males, who carried embryos originating from multiple females. In addition, 30% of the pregnant males carried embryos with the same mitochondrial haplotype. This is not sufficient to demonstrate polyandry but allows a rapid selection and a reduced sample size for further studies. In conclusion, the proposed technique is time- and cost-effective, allows the certain identification of polygyny and provides useful information to study polyandry.     

Soil profile distribution of phosphorus and other nutrients following wetland conversion to beef cattle pasture

Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands were lost in the coastal plain region of the southeastern United States, primarily as a result of drainage for agricultural activities. To better understand the chemical response of soils during wetland conversion, soil core samples were collected from the converted beef cattle pastures and from the natural wetland at Plant City, FL in the summers of 2002 and 2003. Data collected from the natural wetland sites were used as reference data to detect potential changes in soil properties associated with the conversion of wetlands to improved beef cattle (Bos taurus) pastures from 1940 to 2003. The average concentration of total phosphorus (TP) in pasture soils (284 mg kg(-1)) was significantly (p 相似文献   

Predictors of coping behavior after a layoff

In a longitudinal study of laid-off industrial workers, we examined the effects of individual differences and situational characteristics on individuals' use of six job loss coping strategies. In each case the predictors explained a significant portion of the variance (30–47 percent) although different predictors were significantly associated with each of the six coping strategies. The results also suggest that the use of problem-focused and symptom-focused coping strategies are complementary rather than mutually exclusive. The study's implications and directions for future research are discussed as well. © 1998 John Wiley & Sons, Ltd.     

Spatial relationships between lead sources and children’s blood lead levels in the urban center of Indianapolis (USA)

Urban children remain disproportionately at risk of having higher blood lead levels than their suburban counterparts. The Westside Cooperative Organization (WESCO), located in Marion County, Indianapolis, Indiana, has a history of children with high blood lead levels as well as high soil lead (Pb) values. This study aims at determining the spatial relationship between soil Pb sources and children’s blood lead levels. Soils have been identified as a source of chronic Pb exposure to children, but the spatial scale of the source–recipient relationship is not well characterized. Neighborhood-wide analysis of soil Pb distribution along with a furnace filter technique for sampling interior Pb accumulation for selected homes (n = 7) in the WESCO community was performed. Blood lead levels for children aged 0–5 years during the period 1999–2008 were collected. The study population’s mean blood lead levels were higher than national averages across all ages, race, and gender. Non-Hispanic blacks and those individuals in the Wishard advantage program had the highest proportion of elevated blood lead levels. The results show that while there is not a direct relationship between soil Pb and children’s blood lead levels at a spatial scale of ~100 m, resuspension of locally sourced soil is occurring based on the interior Pb accumulation. County-wide, the largest predictor of elevated blood lead levels is the location within the urban core. Variation in soil Pb and blood lead levels on the community level is high and not predicted by housing stock age or income. Race is a strong predictor for blood lead levels in the WESCO community.     

Assessing Spatial Variability of Ambient Nitrogen Dioxide in Montréal,Canada, with a Land-Use Regression Model

Abstract

The purpose of this study was to derive a land-use regression model to estimate on a geographical basis ambient concentrations of nitrogen dioxide (NO₂) in Montréal, Quebec, Canada. These estimates of concentrations of NO₂ will be subsequently used to assess exposure in epidemiologic studies on the health effects of traffic-related air pollution. In May 2003, NO₂ was measured for 14 consecutive days at 67 sites across the city using Ogawa passive diffusion samplers. Concentrations ranged from 4.9 to 21.2 ppb (median 11.8 ppb). Linear regression analysis was used to assess the association between logarithmic concentrations of NO₂ and land-use variables derived using the ESRI Arc 8 geographic information system. In univariate analyses, NO₂ was negatively associated with the area of open space and positively associated with traffic count on nearest highway, the length of highways within any radius from 100 to 750 m, the length of major roads within 750 m, and population density within 2000 m. Industrial land-use and the length of minor roads showed no association with NO₂. In multiple regression analyses, distance from the nearest highway, traffic count on the nearest highway, length of highways and major roads within 100 m, and population density showed significant associations with NO₂; the best-fitting regression model had a R² of 0.54. These analyses confirm the value of land-use regression modeling to assign exposures in large-scale epidemiologic studies.     

Quantifying phosphorus levels in soils, plants, surface water, and shallow groundwater associated with bahiagrass-based pastures

Background, aim, and scope  

Recent assessments of water quality status have identified eutrophication as one of the major causes of water quality ‘impairment’ not only in the USA but also around the world. In most cases, eutrophication has accelerated by increased inputs of phosphorus due to intensification of crop and animal production systems since the early 1990s. Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal variability of phosphorus dynamics across landscapes, especially in agricultural landscapes with cow-calf operations. Critical to determining environmental balance and accountability is an understanding of phosphorus excreted by animals, phosphorus removal by plants, acceptable losses of phosphorus within the manure management and crop production systems into soil and waters, and export of phosphorus off-farm. Further research effort on optimizing forage-based cow-calf operations to improve pasture sustainability and protect water quality is therefore warranted. We hypothesized that properly managed cow-calf operations in subtropical agroecosystem would not be major contributors to excess loads of phosphorus in surface and ground water. To verify our hypothesis, we examined the comparative concentrations of total phosphorus among soils, forage, surface water, and groundwater beneath bahiagrass-based pastures with cow-calf operations in central Florida, USA.     

Magnetic fields of induction heaters in the framework of directive 2004/40/EC of the European Parliament and of the Council.

The spectrum and the polarization of the magnetic flux density (B-field) of 6 induction heaters and 1 arc oven were measured by means of a PMM (Italy) spectrum analyser. The spectrum analysis showed that no substantial harmonics were observed while the polarization analysis revealed that the operator's exposure was non-homogeneous within a distance of 1.5 m from the heater. When the distance was larger, the body was homogeneously exposed. In general we can state that the B-field strongly varied between heaters and that exposure exceeded the occupational reference levels recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (1998) and European Directive 2004/40/EC in 5 of the 7 heaters. Within the framework of the Directive some protection actions should be taken. Whereas mitigation of existing/old induction ovens is difficult, the design of new induction heaters and their housing should be based, among others, on electromagnetic reducing engineering concepts.     

Methane–air detonation experiments at NIOSH Lake Lynn Laboratory

The methane–air detonation experiments are performed to characterize high pressure explosion processes that may occur in sealed areas of underground coal mines. The detonation tube used for these studies is 73 m long, 105 cm internal diameter, and closed at one end. The test gas is 97.5% methane with about 1.5% ethane, and the methane–air test mixtures varied between 4% and 19% methane by volume. Detonations were successfully initiated for mixtures containing between 5.3% and 15.5% methane. The detonations propagated with an average velocity between 1512 and 1863 m/s. Average overpressures recorded behind the first shock pressure peak varied between 1.2 and 1.7 MPa. The measured detonation velocities and pressures are close to their corresponding theoretical Chapman-Jouguet (CJ) detonation velocity (D_CJ) and detonation pressure (P_CJ). Outside of these detonability limits, failed detonations produced decaying detached shocks and flames propagating with velocities of approximately 1/2 D_CJ. Cell patterns on smokefoils during detonations were very irregular and showed secondary cell structures inside primary cells. The measured width of primary cells varied between 20 cm near the stoichiometry and 105 cm (tube diameter) near the limits. The largest detonation cell (105 cm wide and 170 cm long) was recorded for the mixture containing 15.3% methane.     

Porous media grain size distribution and hydrodynamic forces effects on transport and deposition of suspended particles

The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles(2–30 μm) and Fluorescein(dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand,Coarse sand, and a third sand(Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection–dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance.A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining.     

Electrolytic transformation of ordinance related compounds (ORCs) in groundwater: laboratory mass balance studies

Electrolytic reactive barriers (e(-) barriers) consist of closely spaced permeable electrodes installed across a groundwater contaminant plume in a permeable reactive barrier format. Application of sufficient potential to the electrodes results in sequential oxidation and reduction of the target contaminant. The objective of this study was to quantify the mass distribution of compounds produced during sequential electrolytic oxidation and reduction of ordinance related compounds (ORCs) in a laboratory analog to an e(-) barrier. In this study, a series of column tests were conducted using RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and TNT (2,4,6-trinitrotoluene) as representative ORCs. The experimental setup consisted of a plexiglass column packed with quartz-feldspar sand to simulate aquifer conditions. A single set of porous electrodes consisting of expanded titanium-mixed metal oxide mesh was placed at the midpoint of the sand column as a one-dimensional analog to an e(-) barrier. Constant current of 20mA (variable voltage) was applied to the electrode set. Initial studies involved quantification of reaction products using unlabeled RDX and TNT. Approximately 70% of the influent concentration was transformed, in one pass, through sequential oxidation-reduction for both contaminants. Following the unlabeled studies, (14)C labeled RDX and TNT were introduced to determine the mass balance. An activity balance of up to 96% was achieved for both (14)C-RDX and (14)C-TNT. For both contaminants, approximately 21% of the influent activity was mineralized to (14)CO(2). The proportion of the initial activity in the dissolved fraction was different for the two test contaminants. Approximately 30% of the initial (14)C-RDX was recovered as unreacted in the dissolved phase. The balance of the (14)C-RDX was recovered as non-volatile, non-nitroso transformation products. None of the (14)C-RDX was sorbed to the column sand packing. For (14)C-TNT approximately 51% of the initial activity was recovered in the dissolved phase, the majority was unreacted TNT. The balance of the (14)C-TNT was either sorbed to the sand packing (approximately 24%) or dissolved/mineralized as unidentified ring cleavage products ( approximately 4%).