Experimental investigation of fast flame propagation in stratified hydrogen–air mixtures in semi-confined flat layers

This paper presents results of an experimental investigation on fast flame propagation and the deflagration-to-detonation transition (DDT) and following detonation propagation in a semi-confined flat layer filled with stratified hydrogen–air mixtures. The experiments were performed in a transparent, rectangular channel open from below. The combustion channel has a width of 0.3 m and a length of 2.5 m. The effective layer thickness in the channel was varied by using different linear hydrogen concentration gradients. The method to create quasi-linear hydrogen concentration gradients that differ in the range and slope is also presented. The ignited mixtures were accelerated quickly to sonic flame speed in the first obstructed part of the channel. The interaction of the fast flame propagation with different obstacle set-ups was studied in the second part of the channel. The experimental results show an initiation of DDT by one additional metal grid in the obstructed semi-confined flat layer. Detonation propagation and failed detonation propagation were observed in obstructed and unobstructed parts of the channel.     

Benefits and Challenges of Linking Green Infrastructure and Highway Planning in the United States

Landscape-level green infrastructure creates a network of natural and semi-natural areas that protects and enhances ecosystem services, regenerative capacities, and ecological dynamism over long timeframes. It can also enhance quality of life and certain economic activity. Highways create a network for moving goods and services efficiently, enabling commerce, and improving mobility. A fundamentally profound conflict exists between transportation planning and green infrastructure planning because they both seek to create connected, functioning networks across the same landscapes and regions, but transportation networks, especially in the form of highways, fragment and disconnect green infrastructure networks. A key opportunity has emerged in the United States during the last ten years with the promotion of measures to link transportation and environmental concerns. In this article we examined the potential benefits and challenges of linking landscape-level green infrastructure planning and implementation with integrated transportation planning and highway project development in the United States policy context. This was done by establishing a conceptual model that identified logical flow lines from planning to implementation as well as the potential interconnectors between green infrastructure and highway infrastructure. We analyzed the relationship of these activities through literature review, policy analysis, and a case study of a suburban Maryland, USA landscape. We found that regionally developed and adopted green infrastructure plans can be instrumental in creating more responsive regional transportation plans and streamlining the project environmental review process while enabling better outcomes by enabling more targeted mitigation. In order for benefits to occur, however, landscape-scale green infrastructure assessments and plans must be in place before integrated transportation planning and highway project development occurs. It is in the transportation community’s interests to actively facilitate green infrastructure planning because it creates a more predictable environmental review context. On the other hand, for landscape-level green infrastructure, transportation planning and development is much more established and better funded and can provide a means of supporting green infrastructure planning and implementation, thereby enhancing conservation of ecological function.     

Ecological Settings and State Economies as Factor Inputs in the Provision of Outdoor Recreation

State parks play a substantial role in the provision of outdoor recreation opportunities within the United States. Park operators must make crucial decisions in how they allocate capital expenditures, labor, and parkland to maintain recreation opportunities. Their decisions are influenced, in part, by the ecological characteristics of their state’s park system as well as the vitality of their state’s economy. In this research, we incorporate the characteristics of states’ ecosystems and their local economies into a formal production analysis of the states’ park systems from the years 1986 to 2011. Our analysis revealed all three factors of production were positive and inelastic. Expenditures on labor had the largest effect on both park utilization and operational expenditures. Our analysis also found a large degree of variability in the effects of ecological characteristics on both utilization and operating expenditures. Parkland utilization and operational expenditures were more elastic in areas such as Oceania and Mediterranean California relative to other ecological regions. These findings lead us to conclude that state park operators will experience variable levels of difficulty in both accommodating increasing demands for recreation from state parks and maintaining the existing quality of outdoor recreation provided within their system.     

Distributions and determinants of mercury concentrations in toenails among American young adults: the CARDIA Trace Element Study

Since data on mercury (Hg) levels in Caucasians and African Americans (AAs) of both genders are lacking, this study aims to present toenail Hg distributions and explore the potential determinants using data from the Coronary Artery Risk Development in Young Adults Trace Element Study. Data from 4,344 Americans, aged 20–32 in 1987, recruited from Oakland, Chicago, Minneapolis, and Birmingham were used to measure toenail Hg levels by instrumental neutron-activation method. The Hg distribution was described with selected percentiles and geometric means. Multivariable linear regression (MLR) was used to examine potential determinants of Hg levels within ethnicity–gender subgroups. The geometric mean of toenail Hg was 0.212 (95 % CI?=?0.207–0.218)?μg/g. Hg levels varied geographically with Oakland the highest [0.381 (0.367–0.395) μg/g] and Minneapolis the lowest [0.140 (0.134–0.147) μg/g]. MLR analyses showed that male gender and AA ethnicity were negatively associated with toenail Hg levels, and that age, living in Oakland city, education level, alcohol consumption, and total fish intake were positively associated with toenail Hg concentrations within each ethnicity–gender subgroup. Current smokers were found to have higher Hg only in AA men. This study suggested age, gender, ethnicity, study center, alcohol, education level, and fish consumption consistently predict toenail Hg levels. As fish consumption was the key determinant, avoiding certain types of fish that have relatively high Hg levels may be crucial in reducing Hg intake.     

MODELING WATER UTILITY FINANCIAL PERFORMANCE1

ABSTRACT: The purpose of this paper is to present a theory and model for assessing the financial health of public water systems. Using financial information from 25 water utilities in Georgia, the paper seeks to identify the causal relationships between the financial performance of a water utility and its fiscal position. The need for a theoretical understanding of water utility financial health is the result of the increasingly stringent performance requirements under the Safe Drinking Water Act (SDWA). The issue has become particularly important for small water systems that will be exposed to significant financial demands. A set of financial ratios were developed and tested in a model that was based on liquid asset theory. The model contained five variables designed to account for the size of liquid assets, current debt, cash-flow, and the level of expenses. The variables fit the need of water utilities: to provide an adequate level of operation and maintenance to meet current and future system needs as well as SDWA standards.     

Influence of environmental parameters on intraspecific variation in Fucus vesiculosus

The vesiculation and branching of Fucus vesiculosus L. were examined on plants from three different locations on the Maine Coast, USA. These localities varied in exposure to wave action and salinity. Statistical analysis of population differences was computed for 10 morphometric characteristics. It was found that decreased salinity correlated with increased vesiculation and branching. Increased wave action correlated with decreased vesiculation. Position within vertical range was not a factor in either vesiculation or branching.     

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY1

ABSTRACT: We measured annual discharges of water, sediments, and nutrients from 10 watersheds with differing proportions of agricultural lands in the Piedmont physiographic province of the Chesapeake Bay drainage. Flow-weighted mean concentrations of total N, nitrate, and dissolved silicate in watershed discharges were correlated with the proportion of cropland in the watershed. In contrast, concentrations of P species did not correlate with cropland. Organic P and C correlated with the concentration of suspended particles, which differed among watersheds. Thus, the ratio of N:P:Si in discharges differed greatly among watersheds, potentially affecting N, P or Si limitation of phytoplankton growth in the receiving waters. Simple regression models of N discharge versus the percentage of cropland suggest that croplands discharge 29–42 kg N ha^-1 yr^-1 and other lands discharge 1.2–5.8 kg N ha^-1 yr^-1. We estimated net anthropogenic input of N to croplands and other lands using county level data on agriculture and N deposition from the atmosphere. For most of the study watersheds, N discharge amounted to less than half of the net anthropogenic N.     

Comparison between direct microscopy and flow cytometry for rRNA-based quantification of Candidatus Accumulibacter phosphatis in activated sludge.

A comparison of the quantification of a specific microbial group in activated sludge by fluorescent in-situ hybridization, coupled with either direct microscopic counting or flow cytometry, was performed using an enhanced-biological-phosphorus-removal, sequencing-batch reactor. The population dynamics of Candidatus Accumulibacter phosphatis (Cand. A. phosphatis) was evaluated during two separate runs of the reactor. With the operational conditions used, Cand. A. phosphatis was enriched until a failure in the pH controller eliminated its ecological advantage. As a result, the comparison of quantification techniques included Cand. A. phosphatis concentrations as low as 11% and as high as 96% of the total cells in the samples. The analysis demonstrated that, regardless of the particular limitations of each technique, both provided similar results when the activated-sludge flocs were easily dispersed. However, when the activated-sludge samples contained flocs that were difficult to disperse, flow cytometry failed to provide quantitative results.