4,190 research outputs found

    Preliminary design characteristics of a subsonic business jet concept employing an aspect ratio 25 strut braced wing

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    The advantages of replacing the conventional wing on a transatlantic business jet with a larger, strut braced wing of aspect ratio 25 were evaluated. The lifting struts reduce both the induced drag and structural weight of the heavier, high aspect ratio wing. Compared to the conventional airplane, the strut braced wing design offers significantly higher lift to drag ratios achieved at higher lift coefficients and, consequently, a combination of lower speeds and higher altitudes. The strut braced wing airplane provides fuel savings with an attendant increase in construction costs

    Observations of Intrahour Variable Quasars: Scattering in our Galactic Neighbourhood

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    Interstellar scintillation (ISS) has been established as the cause of the random variations seen at centimetre wavelengths in many compact radio sources on timescales of a day or less. Observations of ISS can be used to probe structure both in the ionized insterstellar medium of the Galaxy, and in the extragalactic sources themselves, down to microarcsecond scales. A few quasars have been found to show large amplitude scintillations on unusually rapid, intrahour timescales. This has been shown to be due to weak scattering in very local Galactic ``screens'', within a few tens of parsec of the Sun. The short variability timescales allow detailed study of the scintillation properties in relatively short observing periods with compact interferometric arrays. The three best-studied ``intrahour variable'' quasars, PKS 0405-385, J1819+3845 and PKS 1257-326, have been instrumental in establishing ISS as the principal cause of intraday variability at centimetre wavelengths. Here we review the relevant results from observations of these three sources.Comment: 10 pages, 4 figures, to appear in Astronomical and Astrophysical Transaction

    The relationship between objectification theory and muscle dysmorphia characteristics in men

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    Objectification theory has yielded mixed results when utilized to explain male’s body image concerns. This study investigated whether a revised model of objectification theory would represent the processes associated with male’s engagement in muscle dysmorphia characteristics. Specifically the mediating role of body shame, which has previously been used to explain the psychological consequences of self-objectification among women, was substituted for muscular dissatisfaction to capture the male experience. A sample of 257 male (Mage = 29.7, SD = 11.2), the majority from Australia, completed an online questionnaire assessing measures of internalization of the mesomorphic ideal, body surveillance, self-objectification, muscular dissatisfaction, and muscle dysmorphia characteristics. Path analyses were used to investigate the relationships among these variables. Results indicated that internalization of the mesomorphic ideal mediated body surveillance through self-objectification; consistent with previous research on objectification theory. Muscular dissatisfaction mediated the link of body surveillance with muscle dysmorphia characteristics. Additionally, muscular dissatisfaction mediated the link between internalization of the mesomorphic ideal and muscle dysmorphia characteristics. Taken together, these findings support the utility of objectification theory in understanding the processes under which muscle dysmorphia characteristics are likely to emerge

    Protein Interactions from Complexes: A Structural Perspective

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    By combining crystallographic information with protein-interaction data obtained through traditional experimental means, this paper determines the most appropriate method for generating protein-interaction networks that incorporate data derived from protein complexes. We propose that a combined method should be considered; in which complexes composed of five chains or less are decomposed using the matrix model, whereas the spoke model is used to derive pairwise interactions for those with six chains or more. The results presented here should improve the accuracy and relevance of studies investigating the topology of protein-interaction networks

    Confirmation of two extended objects along the line of sight to PKS1830-211 with ESO-VLT adaptive optics imaging

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    We report on new high-resolution near-infrared images of the gravitationally lensed radio source PKS1830-211, a quasar at z=2.507. These adaptive optics observations, taken with the Very Large Telescope (VLT), are further improved through image deconvolution. They confirm the presence of a second object along the line of sight to the quasar, in addition to the previously known spiral galaxy. This additional object is clearly extended in our images. However, its faint luminosity does not allow to infer any photometric redshift. If this galaxy is located in the foreground of PKS1830-211, it complicates the modeling of this system and decreases the interest in using PKS1830-211 as a means to determine H0 via the time delay between the two lensed images of the quasar.Comment: Accepted in A&A Letter

    A Multi-Wavelength Study of the Jet, Lobes and Core of the Quasar PKS 2101-490

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    We present a detailed study of the X-ray, optical and radio emission from the jet, lobes and core of the quasar PKS 2101-490 as revealed by new Chandra, HST and ATCA images. We extract the radio to X-ray spectral energy distributions from seven regions of the 13 arcsecond jet, and model the jet X-ray emission in terms of Doppler beamed inverse Compton scattering of the cosmic microwave background (IC/CMB) for a jet in a state of equipartition between particle and magnetic field energy densities. This model implies that the jet remains highly relativistic hundreds of kpc from the nucleus, with a bulk Lorentz factor Gamma ~ 6 and magnetic field of order 30 microGauss. We detect an apparent radiative cooling break in the synchrotron spectrum of one of the jet knots, and are able to interpret this in terms of a standard one-zone continuous injection model, based on jet parameters derived from the IC/CMB model. However, we note apparent substructure in the bright optical knot in one of the HST bands. We confront the IC/CMB model with independent estimates of the jet power, and find that the IC/CMB model jet power is consistent with the independent estimates, provided that the minimum electron Lorentz factor gamma_min > 50, and the knots are significantly longer than the jet width, as implied by de-projection of the observed knot lengths.Comment: 16 pages, 10 figures, 6 table
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