Elastic moduli approximation of higher symmetry for the acoustical properties of an anisotropic material

The issue of how to define and determine an optimal acoustical fit to a set of anisotropic elastic constants is addressed. The optimal moduli are defined as those which minimize the mean squared difference in the acoustical tensors between the given moduli and all possible moduli of a chosen higher material symmetry. The solution is shown to be identical to minimizing a Euclidean distance function, or equivalently, projecting the tensor of elastic stiffness onto the appropriate symmetry. This has implications for how to best select anisotropic constants to acoustically model complex materials.Comment: 20 page

Development of welding techniques and filler metals for high strength aluminum alloys Annual summary report, 27 Jun. 1964 - 27 Jun. 1965

Welding techniques and filler metals for high strength aluminum alloy

Radio galaxies and their magnetic fields out to z <= 3

We present polarisation properties at $1.4\,$GHz of two separate extragalactic source populations: passive quiescent galaxies and luminous quasar-like galaxies. We use data from the {\it Wide-Field Infrared Survey Explorer} data to determine the host galaxy population of the polarised extragalactic radio sources. The quiescent galaxies have higher percentage polarisation, smaller radio linear size, and $1.4\,$GHz luminosity of $6\times10^{21}<L_{\rm 1.4}<7\times10^{25}\,$W Hz$^{-1}$, while the quasar-like galaxies have smaller percentage polarisation, larger radio linear size at radio wavelengths, and a $1.4\,$GHz luminosity of $9\times10^{23}<L_{\rm 1.4}<7\times10^{28}\,$W Hz$^{-1}$, suggesting that the environment of the quasar-like galaxies is responsible for the lower percentage polarisation. Our results confirm previous studies that found an inverse correlation between percentage polarisation and total flux density at $1.4\,$GHz. We suggest that the population change between the polarised extragalactic radio sources is the origin of this inverse correlation and suggest a cosmic evolution of the space density of quiescent galaxies. Finally, we find that the extragalactic contributions to the rotation measures (RMs) of the nearby passive galaxies and the distant quasar-like galaxies are different. After accounting for the RM contributions by cosmological large-scale structure and intervening Mg\,{II} absorbers we show that the distribution of intrinsic RMs of the distant quasar-like sources is at most four times as wide as the RM distribution of the nearby quiescent galaxies, if the distribution of intrinsic RMs of the WISE-Star sources itself is at least several rad m$^{-2}$ wide.Comment: 12 pages, 8 figures, accepted for publication into MNRA

Twenty eight years of ICP Vegetation: an overview of its activities

Here we look back at the activities and achievements in the 28 years of the International Cooperative Programme on the Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation). The ICP Vegetation is a subsidiary body of the Working Group on Effects of the UNECE Convention on Long-range Transboundary Air Pollution (LTRAP), established in 1979. An important role of the ICP Vegetation is to provide evidence for air pollution impacts on vegetation in support of policy development and review of the LRTAP Convention and its Protocols. The activities and participation in the ICP Vegetation have grown over the years. The main activities include: • Collate evidence of ozone impacts on vegetation, assess spatial patterns and temporal trends across Europe; • Develop dose-response relationships, establish critical levels for vegetation and provide European risk maps of ozone impacts; • Reviewing the literature on ozone impacts on vegetation and produce thematic scientific reports and policy-relevant brochures; • Determine spatial patterns and temporal trends of heavy metals, nitrogen and persistent organic pollutants concentrations in mosses as a biomonitoring tool of atmospheric deposition of these compounds

Proton endor study of the photoexcited triplet state PT in Rps. sphaeroides R-26 photosynthetic reaction centres

The photoexcited triplet state PT of Rhodopseudomonas sphaeroides R-26 has been investigated by ENDOR measurements performed on frozen photosynthetic reaction centre solutions. For the first time hyperfine data could be obtained for PT. These data indicate a delocalisation of the triplet state over two bacteriochlorophyll a molecules

Infrared-Faint Radio Sources: A New Population of High-redshift Radio Galaxies

We present a sample of 1317 Infrared-Faint Radio Sources (IFRSs) that, for the first time, are reliably detected in the infrared, generated by cross-correlating the Wide-Field Infrared Survey Explorer (WISE) all-sky survey with major radio surveys. Our IFRSs are brighter in both radio and infrared than the first generation IFRSs that were undetected in the infrared by the Spitzer Space Telescope. We present the first spectroscopic redshifts of IFRSs, and find that all but one of the IFRSs with spectroscopy has z > 2. We also report the first X-ray counterparts of IFRSs, and present an analysis of radio spectra and polarization, and show that they include Gigahertz-Peaked Spectrum, Compact Steep Spectrum, and Ultra-Steep Spectrum sources. These results, together with their WISE infrared colours and radio morphologies, imply that our sample of IFRSs represents a population of radio-loud Active Galactic Nuclei at z > 2. We conclude that our sample consists of lower-redshift counterparts of the extreme first generation IFRSs, suggesting that the fainter IFRSs are at even higher redshift.Comment: 23 pages, 17 figures. Submitted to MNRA

Conditional control of quantum beats in a cavity QED system

We probe a ground-state superposition that produces a quantum beat in the intensity correlation of a two-mode cavity QED system. We mix drive with scattered light from an atomic beam traversing the cavity, and effectively measure the interference between the drive and the light from the atom. When a photon escapes the cavity, and upon detection, it triggers our feedback which modulates the drive at the same beat frequency but opposite phase for a given time window. This results in a partial interruption of the beat oscillation in the correlation function, that then returns to oscillate.Comment: 9 pages, 5 figures, XVII Reuni\'on Iberoamericana de \'Optica, X Encuentro de \'Optica, L\'aseres y Aplicaciones (RIAO-OPTILAS-2010