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TwinsUK is the largest cohort of community-dwelling adult twins in the UK. The registry comprises over 14,000 volunteer twins (14,838 including mixed, single and triplets); it is predominantly female (82%) and middle-aged (mean age 59). In addition, over 1800 parents and siblings of twins are registered volunteers. During the last 27 years, TwinsUK has collected numerous questionnaire responses, physical/cognitive measures and biological measures on over 8500 subjects. Data were collected alongside four comprehensive phenotyping clinical visits to the Department of Twin Research and Genetic Epidemiology, King’s College London. Such collection methods have resulted in very detailed longitudinal clinical, biochemical, behavioral, dietary and socioeconomic cohort characterization; it provides a multidisciplinary platform for the study of complex disease during the adult life course, including the process of healthy aging. The major strength of TwinsUK is the availability of several ‘omic’ technologies for a range of sample types from participants, which includes genomewide scans of single-nucleotide variants, next-generation sequencing, metabolomic profiles, microbiomics, exome sequencing, epigenetic markers, gene expression arrays, RNA sequencing and telomere length measures. TwinsUK facilitates and actively encourages sharing the ‘TwinsUK’ resource with the scientific community — interested researchers may request data via the TwinsUK website (http://twinsuk.ac.uk/resources-for-researchers/access-our-data/) for their own use or future collaboration with the study team. In addition, further cohort data collection is planned via the Wellcome Open Research gateway (https://wellcomeopenresearch.org/gateways). The current article presents an up-to-date report on the application of technological advances, new study procedures in the cohort and future direction of TwinsUK.
Serendip II is an automated system designed to perform a real time search for narrow band radio signals in the spectra of sources in a regularly scheduled, non-Seti, astronomical observing program. Because we expect Serendip II to run continuously without requiring dedicated observing time, we hope to survey a large portion of the sky at high sensitivity and low cost. Serendip II will compute the power spectrum using a 65,536 channel fast Fourier transform processor with a real time bandwidth of 128 KHz and 2 Hz per channel resolution. After searching for peaks in a 100 KHz portion of the radio telescope's IF band, Serendip II will move to the next 100 KHz portion using a programmable frequency synthesizer; when the whole IF band has been scanned, the process will start again. Unidentified peaks in the power spectra are candidates for further study and their celestial coordinates will be recorded along with the time and power, IF and RF frequency, and bandwidth of the peak.
(1) To test the usefulness of Abell clusters for locating voids
It is well known that Abell clusters are not uniformly distributed in three-dimensional space (e.g. Bahcall and Soneira, 1983). Recently, Batuski and Bums (1985a, b) have suggested that Abell clusters tend to form filamentary structures between which there appear to be large regions (50–200 Mpc across) devoid of bright galaxies. The technique of using Abell clusters as tracers of voids is controversial because the correlation length of Abell clusters is so much larger than the galaxy-galaxy correlation length. However, compared to an all-sky magnitude-limited survey, the technique, if valid, potentially reduces the amount of telescope time required to identify significant voids and map them in redshift space. To investigate this possibility we have undertaken a redshift survey of galaxies in the direction of a nearby and relatively compact candidate void surrounded by a ring of Abell clusters.
(2) To identify a void suitable for more extensive study.
Ultimately we would like to know not only the degree to which voids are empty, but also to what extent those galaxies that may be found within a void differ from those in the surrounding shell. Some theorists (e.g. Dekel and Silk, 1986 and references therein) suggest that as a result of biased galaxy formation, galaxies within a void might be expected to be preferentially younger, fainter, more irregular, more metal-poor and more gas-rich than shell galaxies. The region we selected for study is one which forms part of the Haynes and Giovanelli (1986 and references therein) 21 cm redshift survey. It was chosen, in part, because it is of interest to compare optical results with radio data to determine whether or not the two techniques reveal the same structure.
We report on results from the Berkeley Ultraviolet Experiment (UVX), which performed 15 ± 2 Å resolution spectroscopy of the diffuse far ultraviolet background in eight directions. We have used the spectrum obtained in the direction of low H I column density to derive constraints on any extragalactic background. We find evidence that a hitherto unidentified dust component is present that accounts for most of the background in directions of low neutral hydrogen column density.
The FAUST telescope is an ultraviolet survey instrument that features a wide 8° field of view, ~1′ angular resolution, and a photon counting detector. Operating in the 1400–1800 Å band, it will be sufficiently sensitive to detect blue mv =17 objects in a single 20 minute night. The instrument is part of the ATLAS-1 shuttle mission, presently scheduled for flight in May 1991. A substantial number of high galactic latitude fields will be investigated, with particular emphasis on studies of the origin of the diffuse far UV background.
NASA's Ultraviolet Experiment (UVX) payload, which flew aboard space shuttle Columbia in January 1986, contained a spectrograph built by the Space Astrophysics Group at the University of California, Berkeley. The wavelength range is 1400–1850 Å with a FWHM resolution of ~15 ± 2 Å. A full description of the instrument can be found in Martin and Bowyer (1984). The instrument was pointed at various regions of the sky for 8 nighttime orbits. Targets spanning a wide range of galactic latitudes and neutral hydrogen column densities were observed.
Measurements of the far ultraviolet background are reviewed. A major turning point occurred in the study of this field in the early 1980s, when evidence was first presented that this flux was primarily galactic in origin rather than extragalactic, as had been generally believed. A number of experiments have confirmed this result, and it has been established that the flux is the result of scattering of starlight by dust. However, the detailed scattering properties of dust in the far ultraviolet are uncertain; a wide range of albedos and scattering phase functions have been reported. Very recent evidence indicates that ultraviolet scattering grains are different from grains that scatter in the visible in that they have a low albedo and scatter isotropically. There is evidence that this dust is present at some level in all view directions in the galaxy. Spectral emission features have been detected recently in the diffuse background. Lines of C IV and O III] have been observed and lines of O IV/Si IV and N III have probably been observed. It has been established that the 105 K gas producing these lines is 2–3 kpc above the galactic plane. Overall mass flux rates of 5 to 25 M⊙ yr−1 for this gas are indicated, which provides strong support for the galactic fountain model for this material. Emission from molecular hydrogen has been detected in directions of high and low neutral hydrogen column density. This emission emanates from low density molecular clouds and indicates clumping of the emitting material in the clouds. Our knowledge of the sources of the far ultraviolet background has increased dramatically in the past 10 years. The results obtained have yielded surprising new insights on a variety of astrophysical topics.
Nearly simultaneous FUV and optical spectrophotometry of X-ray selected Seyfert galaxies has revealed an average Ly α/H β ratio of 22, a positive correlation between the ratio Ly α/H β and the width of the lines, and additional Ly α emission in the wings of one source which is not matched by emission in the Balmer line wings. However, we find no distinguishing features in the continuum emission from these X-ray selected objects compared with other samples. If the correlation between Ly α/H β and the width of the lines is found to apply to larger samples of Seyferts, it may be that our objects appear Ly α bright because they are also broad-lined compared with other samples.
We have studied the first extreme ultraviolet spectroscopic data and a high accuracy light curve for the BL Lac object PKS 2155–304 observed with the Extreme Ultraviolet Explorer (EUVE) on July 21–22, 1992. This target was observed with the Deep Survey Spectrometer telescope for approximateley 30,000 sec during the in-orbit-calibration phase of the mission, allowing to obtain simultaneous image and spectrum.
The radiative decay of massive relic 30eV neutrinos could explain several observational puzzles including the missing dark matter in the universe and the anomalous degree of ionization of interstellar matter in the Galaxy. We note that various non-standard particle physics models with extended scalar sector or minimal supersymmetry have sufficient freedom to accommodate such neutrinos. We discuss observational constraints in the immediate Solar neighborhood, in nearby regions of low interstellar absorption, in the Galactic halo, in clusters of galaxies, and in extragalactic space. Although some observations have been interpreted as ruling out this picture, we note that this is true only for models in which extreme concentrations of neutrinos occur in clusters of galaxies. An instrument is under development to measure the cosmic diffuse EUV background in the local Solar neighborhood, for flight on the Spanish Minisat satellite platform. This instrument will have the capability of providing a definitive test of the radiative neutrino decay hypothesis.
Diffuse EUV emission has been detected in five clusters of galaxies: Virgo(Lieu et al., 1996a), Coma (Lieu et al., 1996b), Abell 1795, Abell 2199, and Abell 4038. These results were 'obtained with the Deep Survey Telescope of the Extreme Ultraviolet Explorer (Bowyer and Malina, 1991) using a Lex/B filter which covers the 60 to 170 A band. The extent of this diffuse emission from these clusters r_anges from 20' to 40' in diameter. The statistical significance of these results varies from 8 to 50 standard deviations. Some EUV emission would be expected fromthe low-energy tail of the wellstudied X-ray cluster emission, However, the EUV emission detected is far greater than the expected emission from the X-ray-emitting gas. Marginal sigatures of this “soft excess” are often present in the lowest energy resolution band of the ROSAT PSPC where it is typically less than a 20% effect. In the case of Abell 2199, no low energy excess is present in the ROSAT data. In the data taken with EUVE, however, the excesses range from 70% to 600%.
The extragalactic background at ultraviolet, X-ray and gamma ray energies is reviewed. Early work on the diffuse backgrounds in each of these bands was motivated, at least in part, by the idea that these fluxes were the result of processes which produced a truly diffuse flux with profound cosmological implications. As we will see, these processes were not observed. However, the study of this background has led to the discovery of unexpected processes at work in the Universe. Our current understanding of these backgrounds is presented.
Because the division consists of many very active commissions, most activities are included in the reports of the individual commissions. This report highlights a small subset of the major achievements that are covered in detail in the reports by the commissions. Some administrative activities of the division and reports of the divisional working groups and committees are also included as subsequent sections of this divisional report.
It has been known that non spherical silicate particles of a size comparable to the wavelength of light, and aggregates of such particles, produce negative polarization in the backscattering region (e.g. Xing & Hanner 1997, Yanamandra-Fisher & Hanner, 1999). It has now been shown that large aggregates of small absorbing particles of fractal dimension about 2 produce a slightly negative polarization at small phase angles (Levasseur-Regourd et al., 1997). The phase-curves strongly differ from those of Mie spheroidal particles. They are likely to be due to scattering by irregular dust particles and/or fluffy aggregates of numerous submicronic absorbing particles (Levasseur-Regourd et al., 1997; Lumme et al., 1997).