Safety on stairs: influence of a tread edge highlighter and its position

BACKGROUND: Falls sustained when descending stairs are the leading cause of accidental death in older adults. Highly visible edge highlighters/friction strips (often set back from the tread edge) are sometimes used to improve stair safety, but there is no evidence for the usefulness of either

Undocumented Worker Employment and Firm Survival

Do firms employing undocumented workers have a competitive advantage? Using administrative data from the state of Georgia, this paper investigates the incidence of undocumented worker employment across firms and how it affects firm survival. Firms are found to engage in herding behavior, being more likely to employ undocumented workers if competitors do. Rivals' undocumented employment harms firms' ability to survive, while firms' own undocumented employment strongly enhances their survival prospects. This suggests that firms enjoy cost savings from employing lower-paid undocumented workers at wages less than their marginal revenue product. The herding behavior and competitive effects are found to be much weaker in geographically broad product markets, where firms have the option to shift labor-intensive production out of state or abroad.undocumented workers, firm dynamics, monopsony, immigration policy

Undocumented worker employment and firm survivability

Do firms employing undocumented workers have a competitive advantage? Using administrative data from the state of Georgia, this paper investigates the incidence of undocumented worker employment across firms and how it affects firm survival. Firms are found to engage in herding behavior, being more likely to employ undocumented workers if competitors do. Rivals' undocumented employment harms firms' ability to survive while firms' own undocumented employment strongly enhances their survival prospects. This finding suggests that firms enjoy cost savings from employing lower-paid undocumented at workers wages less than their marginal revenue product. The herding behavior and competitive effects are found to be much weaker in geographically broad product markets, where firms have the option to shift labor-intensive production out of state or abroad.Competition

3-O-Benzhydryl-2,5-dide­oxy-2,5-imino-2-C-methyl-l-lyxono-1,4-lactone

The title bicyclic lactone, C19H19NO3, is an inter­mediate in the synthesis of chiral α-methyl­prolines and branched C-methyl pyrrolidines; the absolute configuration was determined by the use of d-erythronolactone as the starting material. It exhibits no unusual crystal packing features, and each mol­ecule acts as a donor and acceptor for one C—H⋯O hydrogen bond

(S)-3-Dimethyl­amino-2-{(4S,5R)-5-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2,2-dimethyl-1,3-dioxolan-4-yl}-2-hydroxy­propanoic acid

The Kiliani reaction on 1-de­oxy-(N,N-dimethyl­amino)-d-fructose, itself readily available from reaction of dimethyl­amine and d-glucose, proceeded to give access to the title β-sugar amino acid, C15H27NO7. X-ray crystallography determined the stereochemistry at the newly formed chiral center. There are two mol­ecules in the asymmetric unit; they are related by a pseudo-twofold rotation axis and have very similar geometries, differing only in the conformation of one of the acetonide rings. All the acetonide rings adopt envelope conformations; the flap atom is oxygen in three of the rings, but carbon in one of them. There are two strong hydrogen bonds between the two independent mol­ecules, and further weak hydrogen bonds link the mol­ecules to form infinite chains running parallel to the a axis

Management of the Hydrologic System in Areas Subject to Coal Mining Activities

Publicity given to the detrimental effects of mining activities on the environment has tended to overshadow somewhat the hydrologic opportunities and benfits that could be associated with these activities. For example, many areas disturbed by surface mining have proved to be excellent recharge areas for groundwater aquifers. The degree to which mine sites can be exploited to improve management of the hydrologic system depends on both the local geology and the mining techniques used. The report examines the effects of present mining activities on the associated hydrology system, and identifies specific mining procedures and management techniques which not only minimize negative hydrologic impacts of mining operations, but which also enhance the values of the hydrologic system in terms of existing and potential social uses. Thus, the results of the research contribute to the solution of present and future hydrologic problems (both quanitty and quality) associated with coal mining in the western U.S. Emphasis is placed on sites which are representative of both existing and future coal mining areas. The specific objectives of the study are to: 1. Evaluate the potential for using underground coal mines to: a. Tap previously inaccessible groundwater supplies. b. Reduce the salt load to the Colorado River by decreasing the contact of groundwater with salt-bearing geologic formations. c. Store water in abondoned mines. 2. Consider the potential effects of underground coal mines on water resources. 3. Evaluate the potential of using surface mined areas to collect surface runoffs and thus: a. Reduce the sediment loads to the Colorado River. b. Enhance water storage in the basin. Each of the preceding objectives is addressed and discussed by the report in terms of actual coal mines in central Utah. The study suggests not only ways of reducing negative hydrologic impacts of mining operations, but also operational and management mining techniques which will enhance the social use value of the hydrologic systems, and thus, in fact, create hydrologic opportunities