24,840 research outputs found

    Water-resource records of Brevard County, Florida

    Get PDF
    The U. S. Geological Survey made a comprehensive investigation of the water resources of Brevard County from 1954 to 1958. The purposes of this investigation were: (1) to determine the occurrence and chemical quality of water in the streams and lakes, (2) to determine the location and the thickness of aquifers, and (3) to determine the occurrence and chemical quality of the ground water. During the period from 1933 to 1954, water records were collected from a few stream-gaging stations and a few observation wells. The purpose of this report is to present basic data collected during these investigations. (Document has 188 pages.

    Discovery of A New Faint Radio SNR G108.2-0.6

    Full text link
    A new faint and large shell-type radio Supernova Remnant (SNR) G108.2-0.6 has been discovered in the Canadian Galactic Plane Survey (CGPS). The SNR shows an elliptical shell-type structure at 1420 MHz, and has a 408-1420 MHz TT-plot spectral index of α\alpha=-0.5±\pm0.1 (Sν_{\nu}\proptoν\nuα^{\alpha}), typical of a shell-type SNR. The remnant's flux density at 1420 MHz is 6.6±\pm0.7 Jy, and at 408 MHz is 11.5±\pm1.2 Jy. Both of these are corrected for compact sources. An integrated spectral index of 0.45±-0.45\pm0.13 is determined. This new SNR has among the lowest surface brightness of any known remnant (Σ\Sigma1GHz_{1 GHz}=2.4×1022\times10^{-22} W m2^{-2} Hz1^{-1} sr1^{-1}). 21 cm Stokes Q and U CGPS data (plus preliminary Effelsberg Q and U maps) show some suggestive features that correlate with total power. \ion{H}{i} observations show structures associated with G108.2-0.6 in the radial velocity range -53 to -58 km s1^{-1}, and indicate it is located in the Perseus arm shock at a distance of 3.2±\pm0.6 kpc. At this distance the diameter of G108.2-0.6 is 58 pc. IRAS maps (12, 25, 60 and 100\mu m) of the new SNR show rich infrared emission surrounding G108.2-0.6.Comment: 10 pages, 6 figs, accepted by A&

    G181.1+9.5, a new high-latitude low-surface brightness supernova remnant

    Full text link
    More than 90% of the known Milky Way supernova remnants are within 5 degrees of the Galactic Plane. We present the discovery of the supernova remnant G181.1+9.5, a new high-latitude SNR, serendipitously discovered in an ongoing survey of the Galactic Anti-centre High-Velocity Cloud complex, observed with the DRAO Synthesis Telescope in the 21~cm radio continuum and HI spectral line. We use radio continuum observations (including the linearly polarized component) at 1420~MHz (observed with the DRAO ST) and 4850~MHz (observed with the Effelsberg 100-m radio telescope) to map G181.1+9.5 and determine its nature as a SNR. High-resolution 21~cm HI line observations and HI emission and absorption spectra reveal the physical characteristics of its local interstellar environment. Finally, we estimate the basic physical parameters of G181.1+9.5 using models for highly-evolved SNRs. G181.1+9.5 has a circular shell-like morphology with a radius of about 16~pc at a distance of 1.5 kpc some 250 pc above the mid-plane. The radio observations reveal highly linearly polarized emission with a non-thermal spectrum. Archival ROSAT X-ray data reveal high-energy emission from the interior of G181.1+9.5 indicative of the presence of shock-heated ejecta. The SNR is in the advanced radiative phase of SNR evolution, expanding into the HVC inter-cloud medium with a density of 1 cm~cm^{-3}$. Basic physical attributes of G181.1+9.5 calculated with radiative SNR models show an upper-limit age of 16,000 years, a swept-up mass of more than 300 solar masses, and an ambient density in agreement with that estimated from HI observations. G181.1+9.5 shows all characteristics of a typical mature shell-type SNR, but its observed faintness is unusual and requires further study.Comment: A&A accepted, 11 pages, 13 figure

    Clonal mixing in the soldier-producing aphid <i>Pemphigus spyrothecae</i> (Hemiptera: Aphididae)

    Get PDF
    Illuminating the genetic relationships within soldier-producing aphid colonies is an essential element of any attempt to explain the evolution of the altruistic soldier caste. Pemphigus spyrothecae is a soldier-producing aphid that induces galls on the leaf petioles of its host (trees of the genus Populus). At least a quarter of the aphids within the clonally produced gall population are morphologically and behaviourally distinct first-instar soldiers that defend the gall population from predation. Using field trapping and microsatellites, we investigated the degree of clonal mixing within natural gall populations. Field trapping in the UK showed that all the migrants of P. spyrothecae and of two other Pemphigus species were wingless first-instar soldiers. The average degree of mixing estimated from trapping P. spyrothecae migrants was 0.68% (range = 0–15%). Microsatellite genotyping of 277 aphids from 13 galls collected in Italy revealed an average mixing level of 10.4% (range = 0–59%). Six galls contained more than one clone (range = 2–5 clones). Non-kin aphids were not restricted to the soldier caste but were evenly distributed across instars. An additional gall, from which 527 occupants were genotyped, contained 12 non-kin aphids distributed among nine clones, showing that clonal diversity can be high even when mixing is very low. These observations suggest that although soldiers migrate regularly and can moult and reproduce within foreign galls, clonal mixing in this species is generally low and is unlikely to provide a barrier to the evolution of investment by the aphid clones in an altruistic soldier caste

    Universality of collapsing two-dimensional self-avoiding trails

    Full text link
    Results of a numerically exact transfer matrix calculation for the model of Interacting Self-Avoiding Trails are presented. The results lead to the conclusion that, at the collapse transition, Self-Avoiding Trails are in the same universality class as the O(n=0) model of Blote and Nienhuis (or vertex-interacting self-avoiding walk), which has thermal exponent ν=12/23\nu=12/23, contrary to previous conjectures.Comment: Final version, accepted for publication in Journal of Physics A; 9 pages; 3 figure

    Solar/hydrogen systems assessment. Volume 1: Solar/hydrogen systems for the 1985 - 2000 time frame

    Get PDF
    Opportunities for commercialization of systems capable of producing hydrogen from solar energy were studied. The hydrogen product costs that might be achieved by the four selected candidate systems was compared with the pricing structure and practices of the commodity gas market. Subsequently, product cost and market price match was noted to exist in the small user sector of the hydrogen marketplace. Barriers to and historical time lags in, commercialization of new technologies are reviewed. Recommendations for development and demonstration programs designed to accelerate the commercialization of the candidate systems are presented

    Optical implementation of systolic array processing

    Get PDF
    Algorithms for matrix vector multiplication are implemented using acousto-optic cells for multiplication and input data transfer and using charge coupled devices detector arrays for accumulation and output of the results. No two dimensional matrix mask is required; matrix changes are implemented electronically. A system for multiplying a 50 component nonnegative real vector by a 50 by 50 nonnegative real matrix is described. Modifications for bipolar real and complex valued processing are possible, as are extensions to matrix-matrix multiplication and multiplication of a vector by multiple matrices

    Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations

    Get PDF
    Abstract On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (\u3e2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased \u3e90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Key Points Substorm dynamics are important for highly relativistic electron energization Cold plasma preconditioning is significant for rapid relativistic energization Relativistic / highly relativistic electron energization can occur in \u3c 5 hrs
    corecore