Radiometric phenomena: From the 19th to the 21st century

Many of the major scientists of the late 19th and early 20th century have weighed in on the mechanisms that influence the forces produced in the Crookes radiometer. However, even today, there is still some uncertainty, and in fact confusion, about the order of magnitudes of forces produced by these mechanisms and the dominant mechanisms in various operational regimes and configurations. The development of a better understanding of the radiometric force, aimed at resolving that confusion, has been helped by modern computational techniques. In the transitional flow regime, where the radiometric force is observed, kinetic approaches are necessary for valid results. These modern kinetic approaches, coupled with significant increases in computational speed, have qualitatively improved the level of understanding of radiometric flows. For the first time, flowfields near the vanes of a radiometer can be fully investigated in an attempt to quantify the importance of various mechanisms involved in the production of the radiometric force. In many cases, the computational techniques have been validated by highly accurate experiments. Various operational regimes and geometric configurations have been studied in an attempt to maximize the force. This review looks at the historic context of three types of radiometers, most notably the Crookes radiometer, develops a modern understanding of the mechanisms behind the radiometric force, and documents recent applications.     

Adolescent to emerging adulthood smoking trajectories: when do smoking trajectories diverge, and do they predict early adulthood nicotine dependence?

This study evaluated the adolescent tobacco-use trajectories that predict nicotine dependence in early adulthood and when these trajectories start to diverge. As part of a follow-up to a large prevention trial, the present study evaluated 1,017 individuals from early adolescence (age 12) to early adulthood (age 28). Participants were recruited from eight middle schools in Kansas City, Missouri. Students were entering 6th grade or 7th grade at baseline. Smoking was evaluated at baseline, 6 months, at annual follow-ups through high school, and every 18 months thereafter until age 28. The study goals were to determine (a) whether distinct weekly tobacco-use trajectories could be identified between early adolescence and emerging adulthood (ages 12-24); (b) when during development these trajectories diverged; and (c) which trajectories could predict nicotine dependence in early adulthood (ages 26-28). A four-trajectory mixed model (abstainers, low users, late stable users, and early stable users) demonstrated the best fit to the data. Membership in increasingly high-use trajectories placed participants at greater relative risk for becoming nicotine dependent than did membership in lower-use trajectories. General linear models showed greater weekly cigarette consumption for early stable users as early as the first wave of data collection (age 12) and significant differences among all other trajectories by age 15. The findings support the implementation of smoking prevention programs early in middle or junior high school and suggest that adolescents who are already smoking at least two cigarettes per week by age 12 may benefit from additional addiction prevention efforts.     

Lateral, Ge, nanowire growth on SiO2

Vapor-liquid-solid (VLS) nanowires (NWs) typically grow in [111] directions. Previously, the authors have demonstrated guided Si NW growth, engineering the VLS NWs to grow in a [110] direction against a SiO(2) surface. In this work, the authors demonstrate guided high-quality Ge nanowire growth against a SiO(2) surface in the substrate plane to bridge between two Si mesas. The authors explore the interfaces between a Ge NW and the two Si device-layer mesas and report high-quality, epitaxial interfaces between the Ge NW and both Si mesas.     

Going Green at West Point: Is It Economically Beneficial? A Cost-Benefit Analysis of Installing a Wind Farm at the United States Military Academy

Abstract:

In 2007, BQ Energy communicated an idea to the United States Military Academy (USMA) at West Point, NY, about the construction of a 12.5 MW wind farm for electricity production on the western edge of its property in the training grounds near Camp Buckner. Such a project would bring educational, strategic, and potentially economic benefits to USMA, in addition to the obvious environmental benefits that would be realized by the Hudson Valley region. This article describes a quantitative approach to answer why it is financially beneficial for West Point to allow the installation of a wind farm on its property.