Transport in the metallic regime of Mn doped III-V Semiconductors

The standard model of Mn doping in GaAs is subjected to a coherent potential approximation (CPA) treatment. Transport coefficients are evaluated within the linear response Kubo formalism. Both normal (NHE) and anomalous contributions (AHE) to the Hall effect are examined. We use a simple model density of states to describe the undoped valence band. The CPA bandstructure evolves into a spin split band caused by the $p-d$ exchange scattering with Mn dopants. This gives rise to a strong magnetoresistance, which decreases sharply with temperature. The temperature ($T$) dependence of the resistance is due to spin disorder scattering (increasing with $T$), CPA bandstructure renormalization and charged impurity scattering (decreasing with $T$). The calculated transport coefficients are discussed in relation to experiment, with a view of assessing the overall trends and deciding whether the model describes the right physics. This does indeed appear to be case, bearing in mind that the hopping limit needs to be treated separately, as it cannot be described within the band CPA.Comment: submitted to Phys. Rev.

Four dimensional observations of clouds from geosynchronous orbit using stereo display and measurement techniques on an interactive information processing system

Simultaneous Geosynchronous Operational Environmental Satellite (GOES) 1 km resolution visible image pairs can provide quantitative three dimensional measurements of clouds. These data have great potential for severe storms research and as a basic parameter measurement source for other areas of meteorology (e.g. climate). These stereo cloud height measurements are not subject to the errors and ambiguities caused by unknown cloud emissivity and temperature profiles that are associated with infrared techniques. This effort describes the display and measurement of stereo data using digital processing techniques

Land Preservation in British Columbia: An Empirical Analysis of the Factors Underlying Public Support and Willingness to Pay

This study extends previous empirical research on land preservation by considering an actual land preservation scheme, the agricultural land reserve in British Columbia, Canada. The reserve was established in 1973 to ensure that development did not occur on the province’s most productive agricultural land. ‘To ensure that local food production is maintained,’ ‘the economic importance of British Columbia’s agricultural sector,’ and ‘to protect the environment’ are the most important factors that underlie support for the reserve. Aggregate, provincewide willingness to pay to maintain the land reserve is substantial, with our most conservative estimate being Can$91.18 million per year.agriculture, contingent, land, preservation, valuation, Agribusiness, Agricultural Finance, International Development, Resource /Energy Economics and Policy, Q15, Q24, Q28, Q51,

The Effects of Interrupted Enrollment on Graduation from College: Racial, Income, and Ability Differences

We present a multiple spells-competing risks model of stopout, dropout, reenrollment, and graduation behavior. We find that students who experience an initial stopout are more likely to experience subsequent stopouts (occurrence dependence) and be less likely to graduate. We also find evidence of the impact of the length of an initial spell on the probability of subsequent events (lagged duration dependence). We simulate the impacts of race, family income, and high school performance on student behavior and show that there are often very large differences between unadjusted rates of student outcomes and adjusted rates. Differences in student performance often ascribed to race are shown to be the result of income, age at entry, and high school performance.

Neo-Inuit strategies for ensuring food security during the Little Ice Age climate change episode, Foxe Basin, Arctic Canada

This paper examines Neo-Inuit (ca. AD 1250 to present) responses to the decreased temperatures of the Little Ice Age (LIA) climate change episode (ca. AD 1300–1900) in the Foxe Basin region of central Nunavut, Arctic Canada. Cooler temperatures (and increased sea ice) would be expected to have reduced both bowhead whale (Balaena mysticetus) and Atlantic walrus (Odobenus rosmarus rosmarus) habitats, forcing Neo-Inuit to refocus their hunting activities on landfast-ice-dwelling small seals (e.g., Pusa hispida) during winter months. However, an analysis of faunal remains from Foxe Basin's largest-known Neo-Inuit (Thule, historic and modern Inuit) archaeological site, Pingiqqalik (NgHd-1), reveals a long-term subsistence economy based largely on multi-seasonal walrus hunting. Two interrelated factors may explain these results: (1) a system of recurring polynyas provided a degree of ecological stability for local walrus populations, and (2) the development of a distinctive walrus caching regime—a form of which continues among the region's contemporary Inuit—allowed residents to adeptly exploit an ecological niche, thereby ensuring food security. Together, these factors likely insulated northern Foxe Basin Neo-Inuit from the worst effects of the LIA

Dissecting the Workforce and Workplace for Clinical Endocrinology, and the Work of Endocrinologists Early in Their Careers

[Excerpt] No national mechanism is in place for an informed, penetrating, and systematic assessment of the physician workforce such as that achieved by the National Science Foundation (NSF) for the periodic evaluation of the nation’s scientists and engineers. Likewise, knowledge of the workforce for clinical research is enigmatic and fragmentary despite the serial recommendations of “blue-ribbon” panels to establish a protocol for the recurrent assessment of clinical investigators early in their careers. Failure to adopt a national system for producing timely, high-quality data on the professional activities of physicians limits the application of improvement tools for advancing clinical investigation and ultimately improving clinical practice. The present study was designed as a pilot project to test the feasibility of using Web-based surveys to estimate the administrative, clinical, didactic, and research work of subspecialty physicians employed in academic, clinical, federal, and pharmaceutical workplaces. Physician members of The Endocrine Society (TES) were used as surrogate prototypes of a subspecialty workforce because of their manageable number and investigative tradition. The results establish that Web-based surveys provide a tool to assess the activities of a decentralized workforce employed in disparate workplaces and underscore the value of focusing on physician work within the context of particular workplaces within a subspecialty. Our report also provides a new and timely snapshot of the amount and types of research performed by clinically trained endocrinologists and offers an evidenced-based framework for improving the investigative workforce in this medical subspecialty

High School Achievement in Maine: Where You Come From Matters More Than School Size and Expenditures

Fern Desjardins and Gordon Donaldson report on their research examining the relationship between academic achievement in Maine’s public high schools and school size, per-pupil operating costs, and socioeconomic status. Using aggregated Maine Educational Assessment (MEA) scores, their study confirmed previous research that socioeconomic status (using both family and community measures) is the most important factor associated with achievement, while school size is not a critical factor. Additionally, the authors found that per-pupil operating costs are higher in the state’s largest and smallest high schools. The authors suggest that the creation of larger districts and larger schools, as supported by recent state policies, will not necessarily mitigate inequities in student achievement resulting from family and community socioeconomic status, and may not yield the desired cost savings