Safe Design Suggestions for Vegetated Roofs

Rooftop vegetation is becoming increasingly popular because of its environmental benefits and its ability to earn green-building certification credits. With the exception of one international guideline, there is little mention of worker safety and health in vegetated-roof codes and literature. Observations and field investigations of 19 vegetated roofs in the United States revealed unsafe access for workers and equipment, a lack of fall-protection measures, and other site-specific hazards. Design for safety strategies and the integration of life-cycle safety thinking with green-building credits systems are the preferred methods to reduce risk to workers on vegetated roofs. Design suggestions have been developed to add to the body of knowledge. The findings complement several National Institute for Occupational Safety and Health (NIOSH) construction and prevention through design (PtD) goals and are congruent with NIOSH’s Safe Green Jobs initiative. Organizations that install and maintain vegetated roofs can utilize the findings to understand hazards, take precautions, and incorporate safety into their bids The published version of this article is available here: 10.1061/(ASCE)CO.1943-7862.0000500Support from the the Virginia Tech Occupational Safety and Health Research Center through the Kevin P. Granata Pilot Program funded by the Institute for Critical Technology and Applied Sciences

Excitonic recombination dynamics in shallow quantum wells

We report a comprehensive study of carrier-recombination dynamics in shallow AlxGa1-xAs/GaAs quantum wells. At low crystal temperature (2 K), the excitonic radiative recombination time is shown to be strongly enhanced in shallow quantum wells with x>0.01, consistently with a model that takes into account the thermal equilibrium between the three-dimensional exciton gas of the barrier and the two-dimensional exciton gas, which are closer in energy as x decreases. Furthermore, we demonstrate the existence of a thermally activated escape mechanism due to the low effective barrier height in these structures. The nonradiative recombination is shown to dominate the carrier dynamics for temperatures as low as 10 K for x≈0.01. Our experimental observations are analyzed using three different variational exciton calculations. In particular, we study the crossover from the two-dimensional to the three-dimensional behavior of the exciton, which occurs for x as low as 0.01 and affects mainly the oscillator strength, whereas the transition energies in shallow quantum wells can be calculated, to a large extent, using the same approximations as for conventional quantum wells. The peculiar behavior of the oscillator strength at the crossover to the weak confinement regime is obtained by expansion in a large basis

Financial wellbeing of Asian Americans

The Asian American population in the United States has been increasing. Research on the economic wellbeing of this minority group is far from being adequate. It is generally found that Asian Americans are more highly educated and have more wealth. Although the homeownership rate of this population is lower than the national average rate, the gap is gradually narrowing. Asian Americans are found to have more confidence in their financial future and have better management in their financial lives. In addition, Asian-owned businesses have been an important part of the U.S. economy and, as such, the self-employment status of Asian Americans has stimulated great interest for research. Large differences in financial behaviors exist among different groups in Asian Americans. This chapter serves the purpose to summarize past research on Asian American consumer finances and provide directions for future research.Includes bibliographical references

Strawberry fields forever? Urban agriculture in developed countries: a review

International audienceFood production in cities has long been a tradition in many countries around the world and a mainstream activity for many developed countries. While urban agriculture plays an important role in increasing food security and social well-being, it comes with significant costs and constraints. Here, we review the growth of urban agriculture throughout the developed world in order to clarify the different benefits, risks, and hindrances associated with the practice. Through this analysis, we identify the need for better understanding of the following five aspects if urban agriculture is to make a meaningful contribution to food security and social well-being in the future: (1) the impacts of continued urban sprawl and loss of peri-urban agricultural land; (2) appropriate government and institutional support at local, regional, and country levels; (3) the role of urban agriculture in self-sufficiency of cities; (4) the risks posed by pollutants from agriculture to urban ecosystems and from urban ecosystems to agriculture; and (5) the carbon footprint of urban agriculture and use of “food miles.” If urban agriculture is to have a legitimate place in resolving the global food crisis as advocates claim, then it is time to take urban agriculture seriously and assess more rigorously both the positive and negative impacts, especially carbon emissions. Only then can the world’s limited resources be properly allocated to the development of urban agriculture

Ecology And Survival Of The Key Silverside, Menidia Conchorum, An Atherinid Fish Endemic To The Florida Keys

The key silverside, Menidia conchorum, is studied as an indicator of adaptations to environmental conditions in lagoonal and ponded water habitats of the lower Florida Keys. Evidence is presented to support the current view of ichthyologists that M. conchorum is a valid species. It occurs in lagoons from Grassy Key to Key West, Florida. This lagoonal habitat is shared by a distinct community. Such lagoons are characterized by rapid fluctuations and broad ranges of physico-chemical parameters. M. conchorum feeds on planktonic crustaceans and terrestrial insects. Maximum size for females is about 58 mm (SL) and 50.1 mm for males. Maturation appears to take place at about 40 mm. The species appears to live one year or less in nature. Reproduction continues year-round with peaks in fertility in the spring and fall. Its population size is seasonal, with a low point in late summer and fall. Nearly all populations inhabit lagoons altered by man and the species is judged as threatened with extinction

Ecology And Survival Of The Key Silverside, Menidia Conchorum, An Atherinid Fish Endemic To The Florida Keys

The key silverside, Menidia conchorum, is studied as an indicator of adaptations to environmental conditions in lagoonal and ponded water habitats of the lower Florida Keys. Evidence is presented to support the current view of ichthyologists that M. conchorum is a valid species. It occurs in lagoons from Grassy Key to Key West, Florida. This lagoonal habitat is shared by a distinct community. Such lagoons are characterized by rapid fluctuations and broad ranges of physico-chemical parameters. M. conchorum feeds on planktonic crustaceans and terrestrial insects. Maximum size for females is about 58 mm (SL) and 50.1 mm for males. Maturation appears to take place at about 40 mm. The species appears to live one year or less in nature. Reproduction continues year-round with peaks in fertility in the spring and fall. Its population size is seasonal, with a low point in late summer and fall. Nearly all populations inhabit lagoons altered by man and the species is judged as threatened with extinction

MAPPING THE DISTRIBUTION OF PROTECTED AND VALUABLE, OIL-SENSITIVE COASTAL FISH AND WILDLIFE

ABSTRACT An approach has been developed to produce a map series that displays known, pertinent information concerning the distribution, seasonality, and habits of protected and valuable coastal fish and wildlife that are sensitive to oil spill impacts. This involves a compilation of all literature on the protected and oil-sensitive fish and wildlife for a region. Distribution and abundance data are then evaluated for each species, and all point localities, aggregations, and home ranges are shown on maps. These data include marine mammal haul-out and pupping areas, terrestrial mammal feeding areas, marine bird rookeries, salmon and herring streams and intertidal spawning sites, marine turtle nesting beaches, and intertidal shellfish beds. Aerial surveys are then made of the sites located during the literature search to verify the mapped literature data, as well as to add new wildlife localities. Information on the species, their distribution and ecological type, their habits, and seasonality is color coded on the maps. This approach has been applied to coastal areas in Shelikof Strait (Alaska), Puget Sound (Washington), southeastern Florida, and Massachusetts, and is underway for South Carolina and Norton Sound (Alaska).</jats:p

Effect of Substrate Depth and Planting Season on Sedum Plug Survival on Green Roofs

Abstract Green roofs, a roofing technology that entails growing plants on rooftops, provide many benefits such as improved stormwater management, energy conservation, mitigation of the urban heat island effect, increased longevity of roofing membranes, reduction in noise and air pollution, and improved aesthetics. Plants on rooftops are more susceptible to extremes in temperature and drought due to their shallow substrate and elevation above ground. Because of these unfavorable growing conditions, plant selection and season of establishment are critical. The major objective of this study was to quantify the effect of substrate depth and planting season on successful establishment of plugs of Sedum species on green roofs. Plugs of nine species of Sedum were planted in East Lansing, MI, in autumn (September 20, 2004) or spring (June 8, 2005) and then evaluated for survival on June 1, 2005, and June 1, 2006, respectively. Overall, spring planting exhibited superior survival rates (81%) compared to autumn (23%) across substrate depths. Sedum cauticola ‘Lidakense’, S. floriferum, and S. sexangulare were not affected by season of planting. Sedum cauticola barely survived at any substrate depth or planting season, whereas the latter two exhibited nearly 100% survival regardless of planting season. All other species had superior survival percentages when planted during spring.</jats:p