20,009 research outputs found

    A study of the temporal changes recorded by ERTS and their geological significance

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    The temporal changes that are recorded by ERTS were evaluated for an area around Bathurst Inlet in the North West Territories. The seasons represented by the images included: early winter, spring, early summer, summer, and fall. Numerous surface characteristics (vegetation, drainage patterns, surface texture, lineament systems and topographic relief, etc.) were used to relate the change in observable features with the different seasons. It was found that the time of year when an observation is made has a strong control over the amount and type of information that can be derived by an experienced interpreter. It was concluded that a detailed study of temporal changes is an important part of any ERTS interpretation for geology

    Upper Bound on the Dark Matter Total Annihilation Cross Section

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    We consider dark matter annihilation into Standard Model particles and show that the least detectable final states, namely neutrinos, define an upper bound on the total cross section. Calculating the cosmic diffuse neutrino signal, and comparing it to the measured terrestrial atmospheric neutrino background, we derive a strong and general bound. This can be evaded if the annihilation products are dominantly new and truly invisible particles. Our bound is much stronger than the unitarity bound at the most interesting masses, shows that dark matter halos cannot be significantly modified by annihilations, and can be improved by a factor of 10--100 with existing neutrino experiments.Comment: 4 pages, 3 figures; version accepted for publication in PR

    Do People Make the Place?: An Examination of the Attraction-Selection-Attrition Hypothesis

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    This study tests the hypotheses that (1) congruence between internal need states and external environments drives the organizational-choice process, and (2) those attracted to particular organizations are more homogeneous than the applicant pool in general. Subjects were evaluated on fourteen needs using the Jackson Personality Research Form. They then viewed two video-taped segments of simulated campus interviews to gain information about two distinct organizational types. The interview segments entered the discussion in-progress to avoid any reference to a particular job which might introduce an occupational confound. Subjects received job offers from both organizations and were asked to indicate which of the two organizations they found more attractive by accepting one of the offers. Analysis of variance results indicated only weak support for the congruency hypothesis. Differences were observed in n Ach between the groups of subjects attracted to each organization. No differences were found for any of the other need strength measures. This suggests that the subjects attracted to the ifferent organizations are substantially similar. Implications for the homogeneity hypothesis are discussed and suggestions for further study of this concept are offered

    Universal aging properties at a disordered critical point

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    We investigate, analytically near the dimension duc=4d_{uc}=4 and numerically in d=3d=3, the non equilibrium relaxational dynamics of the randomly diluted Ising model at criticality. Using the Exact Renormalization Group Method to one loop, we compute the two times t,twt,t_w correlation function and Fluctuation Dissipation Ratio (FDR) for any Fourier mode of the order parameter, of finite wave vector qq. In the large time separation limit, the FDR is found to reach a non trivial value X∞X^{\infty} independently of (small) qq and coincide with the FDR associated to the the {\it total} magnetization obtained previously. Explicit calculations in real space show that the FDR associated to the {\it local} magnetization converges, in the asymptotic limit, to this same value X∞X^{\infty}. Through a Monte Carlo simulation, we compute the autocorrelation function in three dimensions, for different values of the dilution fraction pp at Tc(p)T_c(p). Taking properly into account the corrections to scaling, we find, according to the Renormalization Group predictions, that the autocorrelation exponent λc\lambda_c is independent on pp. The analysis is complemented by a study of the non equilibrium critical dynamics following a quench from a completely ordered state.Comment: 8 pages, 5 figure

    On General Off-Shell Representations of Worldline (1D) Supersymmetry

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    Every finite-dimensional unitary representation of the N-extended worldline supersymmetry without central charges may be obtained by a sequence of differential transformations from a direct sum of minimal Adinkras, simple supermultiplets that are identifiable with representations of the Clifford algebra. The data specifying this procedure is a sequence of subspaces of the direct sum of Adinkras, which then opens an avenue for classification of the continuum of so constructed off-shell supermultiplets.Comment: 21 pages, 5 illustrations; references update

    The beginnings of geography teaching and research in the University of Glasgow: the impact of J.W. Gregory

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    J.W. Gregory arrived in Glasgow from Melbourne in 1904 to take up the post of foundation Professor of Geology in the University of Glasgow. Soon after his arrival in Glasgow he began to push for the setting up of teaching in Geography in Glasgow, which came to pass in 1909 with the appointment of a Lecturer in Geography. This lecturer was based in the Department of Geology in the University's East Quad. Gregory's active promotion of Geography in the University was matched by his extensive writing in the area, in textbooks, journal articles and popular books. His prodigious output across a wide range of subject areas is variably accepted today, with much of his geomorphological work being judged as misguided to varying degrees. His 'social science' publications - in the areas of race, migration, colonisation and economic development of Africa and Australia - espouse a viewpoint that is unacceptable in the twenty-first century. Nonetheless, that viewpoint sits squarely within the social and economic traditions of Gregory's era, and he was clearly a key 'Establishment' figure in natural and social sciences research in the first half of the twentieth century. The establishment of Geography in the University of Glasgow remains enduring testimony of J.W. Gregory's energy, dedication and foresight

    The level and duration of RSV-specific maternal IgG in infants in Kilifi Kenya

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    Background Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in infants. The rate of decay of RSV-specific maternal antibodies (RSV-matAb), the factors affecting cord blood levels, and the relationship between these levels and protection from infection are poorly defined. Methods A birth cohort (n = 635) in rural Kenya, was studied intensively to monitor infections and describe age-related serological characteristics. RSV specific IgG antibody (Ab) in serum was measured by the enzyme linked immunosorbent assay (ELISA) in cord blood, consecutive samples taken 3 monthly, and in paired acute and convalescent samples. A linear regression model was used to calculate the rate of RSV-matAb decline. The effect of risk factors on cord blood titres was investigated. Results The half-life of matAb in the Kenyan cohort was calculated to be 79 days (95% confidence limits (CL): 76–81 days). Ninety seven percent of infants were born with RSV-matAb. Infants who subsequently experienced an infection in early life had significantly lower cord titres of anti-RSV Ab in comparison to infants who did not have any incident infection in the first 6 months (P = 0.011). RSV infections were shown to have no effect on the rate of decay of RSV-matAb. Conclusion Maternal-specific RSV Ab decline rapidly following birth. However, we provide evidence of protection against severe disease by RSV-matAb during the first 6–7 months. This suggests that boosting maternal-specific Ab by RSV vaccination may be a useful strategy to consider

    Geometry acquisition and grid generation: Recent experiences with complex aircraft configurations

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    Important issues involved in working with complex geometries are discussed. Approaches taken to address complex geometry issues in the McDonnell Aircraft Computational Grid System and related geometry processing tools are discussed. The efficiency of acquiring a suitable geometry definition, the need to manipulate the geometry, and the time and skill level required to generate the grid while preserving geometric fidelity are discussed
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