1,128 research outputs found

    Infrared and Reflected Solar Radiation Measurements from the TIROS 2 Meteorological Satellite

    Get PDF
    TIROS II contains instrumentation for measuring infrared and reflected solar radiation from the earth and its atmosphere. A medium resolution scanning radiometer and a low resolution non-scanning radiometer are employed. The satellite's spin provides the scan line of the medium resolution radiometer which is then advanced by the orbital motion. The spatial resolution is about 40 miles square when the earth directly beneath the satellite is viewed. The five channels employ bolometer detectors and filters to limit the spectral responses to five bands: 6 to 6.5 microns, 8 to 12 microns, 0.2 to 6 microns, 8 to 30 microns, and 0.55 to 0.75 microns. These five bands study, respectively: radiation in the water vapor absorption band; day and nighttime cloud cover; albedo; thermal radiation; and visual maps for comparison with satellite vidicon pictures. The low resolution non-scanning radiometer measures the earth's black-body temperature and albedo. Its field when viewing directly below is a circle of 450 miles diameter, covering part of each frame from the wide-field television camera. This radiometer consists of two thermistors, each in the apex of a reflective cone which provides optical gain. One thermistor is black and responds to both thermal and reflected solar radiation. The second responds to thermal but reflects solar radiation. The design, calibration, performance, and data reduction for both systems are discussed herein

    Rapid Evolution of Testis Size Relative to Sperm Morphology Suggests that Post-Copulatory Selection Targets Sperm Number in \u3cem\u3eAnolis\u3c/em\u3e Lizards

    Get PDF
    Post-copulatory sexual selection is thought to be responsible for much of the extraordinary diversity in sperm morphology across metazoans. However, the extent to which post-copulatory selection targets sperm morphology versus sperm production is generally unknown. To address this issue, we simultaneously characterized the evolution of sperm morphology (length of the sperm head, midpiece and flagellum) and testis size (a proxy for sperm production) across 26 species of Anolis lizards, a group in which sperm competition is likely. We found that the length of the sperm midpiece has evolved 2–3 times faster than that of the sperm head or flagellum, suggesting that midpiece size may be the most important aspect of sperm morphology with respect to post-copulatory sexual selection. However, testis size has evolved faster than any aspect of sperm morphology or body size, supporting the hypothesis that post-copulatory sexual selection acts more strongly upon sperm production than upon sperm morphology. Likewise, evolutionary increases in testis size, which typically indicate increased sperm competition, are not associated with predictable changes in sperm morphology, suggesting that any effects of post-copulatory selection on sperm morphology are either weak or variable in direction across anoles. Collectively, our results suggest that sperm production is the primary target of post-copulatory sexual selection in this lineage

    Warm-based basal sediment entrainment and far-field Pleistocene origin evidenced in central Transantarctic blue ice through stable isotopes and internal structures

    Get PDF
    Stable isotopes of water (δ18O and δ2H) were measured in the debris-laden ice underlying an Antarctic blue ice moraine, and in adjoining Law Glacier in the central Transantarctic Mountains. Air bubble content and morphology were assessed in shallow ice core samples. Stable isotope measurements plot either on the meteoric waterline or are enriched from it. The data cluster in two groups: the ice underlying the moraine has a δ2H:δ18O slope of 5.35 ± 0.92; ice from adjoining portions of Law Glacier has a slope of 6.69 ± 1.39. This enrichment pattern suggests the moraine's underlying blue ice entrained sediment through refreezing processes acting in an open system. Glaciological conditions favorable to warm-based sediment entrainment occur 30–50 km upstream. Basal melting and refreezing are further evidenced by abundant vapor figures formed from internal melting of the ice crystals. Both the moraine ice and Law Glacier are sufficiently depleted of heavy isotopes that their ice cannot be sourced locally, but instead must be derived from far-field interior regions of the higher polar plateau. Modeled ice flow speeds suggest the ice must be at least 80 ka old, with Law Glacier's ice possibly dating to OIS 5 and moraine ice older still

    A chiral bag model approach to delta electroproduction

    Get PDF
    Helicity amplitudes for the γNΔ\gamma^* N \to \Delta transition are calculated using the cloudy bag model. A correction for center-of-mass motion is carried out using a modified Peierls-Thouless projection method. This reduces the magnitude of the transition amplitudes at small momentum transfer and enhances them at modest momentum transfers. Our calculation shows that the pion cloud contributes substantially to the transition helicity amplitudes, with the final result giving reasonable agreement with the corresponding experimental values.Comment: 16 pages, 6 ps figures, revte

    Outcome of depression in later life in primary care: longitudinal cohort study with three years’ follow-up

    Get PDF
    Objectives To study the duration of depression, recovery over time, and predictors of prognosis in an older cohort (≥55 years) in primary care

    Unstable states in QED of strong magnetic fields

    Get PDF
    We question the use of stable asymptotic scattering states in QED of strong magnetic fields. To correctly describe excited Landau states and photons above the pair creation threshold the asymptotic fields are chosen as generalized Licht fields. In this way the off-shell behavior of unstable particles is automatically taken into account, and the resonant divergences that occur in scattering cross sections in the presence of a strong external magnetic field are avoided. While in a limiting case the conventional electron propagator with Breit-Wigner form is obtained, in this formalism it is also possible to calculate SS-matrix elements with external unstable particles.Comment: Revtex, 7 pages. To appear in Phys. Rev. D53(2

    Electromagnetic Form Factors of the Nucleon in an Improved Quark Model

    Get PDF
    Nucleon electromagnetic form factors are studied in the cloudy bag model (CBM) with center-of-mass and recoil corrections. This is the first presentation of a full set of nucleon form factors using the CBM. The center of mass motion is eliminated via several different momentum projection techniques and the results are compared. It is found that the shapes of these form factors are significantly improved with respect to the experimental data if the Lorentz contraction of the internal structure of the baryon is also appropriately taken into account.Comment: revtex, 28 pages, 8 ps figs include

    Neuropsychological intervention in kindergarten children with subtyped risks of reading retardation

    Get PDF
    Kindergarten children at risk of developing language problems were administered the Florida Kindergarten Screening Battery. A principal components analysis revealed a verbal and a visual-spatial component and subsequent discriminant function analyses a high verbal/low visual-spatial group (LAL: Latent L) and a high visual-spatial/low verbal group (LAP: Latent P). LAL- and LAP-children were considered at risk for developing an L- or P-type of dyslexia, respectively. As is common practice with children suffering from manifest L- or Pdyslexia, the LAL- and LAP-kindergartners received right and left hemisphere stimulation, respectively. The outcomes were compared with those of bilateral hemispheric stimulation and no intervention. Reading tests were administered in primary school Grades 1 and 5/6; teachers' evaluation of reading took place in Grade 5/6. Overall, the LAL- and LAP- groups showed significant backwardness in word and text reading, both at early and late primary school. Types of intervention made a difference though: not significantly backward in early word, late word, and late text reading were the LAL-children who had received right hemisphere stimulation. Nonintervened LAP-children did not show significant backwardness in early word reading and late text reading, nor did LAP-children who had received left hemisphere or bilateral stimulation. Early text reading was not affected by any treatment. Teacher's evaluations were in support of these findings. Copyright © 2005 by The International Dyslexia Association®

    GeantV: Results from the prototype of concurrent vector particle transport simulation in HEP

    Full text link
    Full detector simulation was among the largest CPU consumer in all CERN experiment software stacks for the first two runs of the Large Hadron Collider (LHC). In the early 2010's, the projections were that simulation demands would scale linearly with luminosity increase, compensated only partially by an increase of computing resources. The extension of fast simulation approaches to more use cases, covering a larger fraction of the simulation budget, is only part of the solution due to intrinsic precision limitations. The remainder corresponds to speeding-up the simulation software by several factors, which is out of reach using simple optimizations on the current code base. In this context, the GeantV R&D project was launched, aiming to redesign the legacy particle transport codes in order to make them benefit from fine-grained parallelism features such as vectorization, but also from increased code and data locality. This paper presents extensively the results and achievements of this R&D, as well as the conclusions and lessons learnt from the beta prototype.Comment: 34 pages, 26 figures, 24 table
    corecore