Review of: Amer EI-Ahraf et al., The Impact of Public Policy on Environmental Quality and Health: The Case of Land Use Management and Planning

Review of the book The Impact of Public Policy on Environmental Quality and Health: The Case of Land Use Management and Planning by Amer El-Ahraf et al., (Quorum Books 1999). Acknowledgments, introduction, appendixes, selected bibliography, index. ISBN 1-56720-065-6 [181 pp. $59.95. Hardbound, 88 Post Road West, Westport, CT 06881]

Graphene for Antenna Applications: Opportunities and Challenges from Microwaves to THz

The use of graphene for antennas and other electromagnetic passives could bring significant benefit such as extreme miniaturization, monolithic integration with graphene RF nanoelectronics, efficient dynamic tuning, and even transparency and mechanical flexibility. Though recently different related theoretical works have been presented, relatively few applications have been proposed and realistically assessed. In this invited talk we will briefly review the main properties of graphene and the state of the art in its theoretical and experimental characterization. Then, we will discuss a number of potential antenna applications from microwave to THz, providing in each case a critical assessment of the benefits, limitations, and remaining issues towards actual real-life implementations. Here we provide a brief overview of different devices and associated developments in our group discussed in the talk, including graphene antennas and reflectarrays at microwave and THz, plasmonic switches, isotropic and anisotropic meta-surfaces, or graphene RF-NEMS

A search for solar-like oscillations in the Am star HD 209625

The goal is to test the structure of hot metallic stars, and in particular the structure of a near-surface convection zone using asteroseismic measurements. Indeed, stellar models including a detailed treatement of the radiative diffusion predict the existence of a near-surface convection zone in order to correctly reproduce the anomalies in surface abundances that are observed in Am stars. The Am star HD 209625 was observed with the Harps spectrograph mounted on the 3.6-m telescope at the ESO La Silla Observatory (Chile) during 9 nights in August 2005. This observing run allowed us to collect 1243 radial velocity (RV) measurements, with a standard deviation of 1.35 m/s. The power spectrum associated with these RV measurements does not present any excess. Therefore, either the structure of the external layers of this star does not allow excitation of solar-like oscillations, or the amplitudes of the oscillations remain below 20-30 cm/s (depending on their frequency range).Comment: 5 pages, 4 figures, A&A accepte

Optically induced free carrier light modulator

Signal carrier laser beam is optically modulated by a second laser beam of different frequency acting on a free carrier source to which the signal carrier laser is directed. The second laser beam affects the transmission characteristics of the free carrier source to light from the signal carrier laser, thus modulating it

Americans' Access to Prescription Drugs Stabilizes, 2007-2010

Examines trends in the percentage of Americans reporting difficulty affording prescription drugs by insurance status, age group, income, and health status. Considers contributing factors such as changes in the uninsured population and fewer doctor visits

Competing Ultrafast Energy Relaxation Pathways in Photoexcited Graphene

For most optoelectronic applications of graphene a thorough understanding of the processes that govern energy relaxation of photoexcited carriers is essential. The ultrafast energy relaxation in graphene occurs through two competing pathways: carrier-carrier scattering -- creating an elevated carrier temperature -- and optical phonon emission. At present, it is not clear what determines the dominating relaxation pathway. Here we reach a unifying picture of the ultrafast energy relaxation by investigating the terahertz photoconductivity, while varying the Fermi energy, photon energy, and fluence over a wide range. We find that sufficiently low fluence ($\lesssim$ 4 $\mu$J/cm$^2$) in conjunction with sufficiently high Fermi energy ($\gtrsim$ 0.1 eV) gives rise to energy relaxation that is dominated by carrier-carrier scattering, which leads to efficient carrier heating. Upon increasing the fluence or decreasing the Fermi energy, the carrier heating efficiency decreases, presumably due to energy relaxation that becomes increasingly dominated by phonon emission. Carrier heating through carrier-carrier scattering accounts for the negative photoconductivity for doped graphene observed at terahertz frequencies. We present a simple model that reproduces the data for a wide range of Fermi levels and excitation energies, and allows us to qualitatively assess how the branching ratio between the two distinct relaxation pathways depends on excitation fluence and Fermi energy.Comment: Nano Letters 201

Soil mechanics on the Moon, Mars, and Mulberry

From a soil mechanics point of view, the Moon is a relatively simple place. Without any water, organics, or clay minerals, the geotechnical properties of the lunar soil are confined to a fairly limited range. Furthermore, the major soil-forming agent is meteorite impact, which breaks the big particles into little particles; and simultaneously, cements the little particles back together again with molten glass. After about a hundred million years of exposure to meteorite impact, the distribution of particle sizes in the soil achieves a sort of steady state. The majority of the returned lunar soil samples have been found to be well-graded silty-sand to sandy-silt (SM in the Unified Soil Classification System). Each of the particle size distributions plots within a relatively narrow band, which appears to be uniform over the entire lunar surface. This further restricts the range of physical properties of the lunar surface. In contrast, Martian soils should exhibit an extremely wide range of properties. We already know that there is a small amount of water in the soil, greater than in the Martian atmosphere. Furthermore, the soil is suspected to be smectitic clay. That makes two out of the three factors that greatly affect the properties of terrestrial soils