24,724 research outputs found
Water-resource records of Brevard County, Florida
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
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 =-0.50.1 (S),
typical of a shell-type SNR. The remnant's flux density at 1420 MHz is
6.60.7 Jy, and at 408 MHz is 11.51.2 Jy. Both of these are corrected
for compact sources. An integrated spectral index of 0.13 is
determined. This new SNR has among the lowest surface brightness of any known
remnant (=2.4 W m Hz
sr). 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 G108.20.6 in the radial
velocity range 53 to 58 km s, and indicate it is located in the
Perseus arm shock at a distance of 3.20.6 kpc. At this distance the
diameter of G108.20.6 is 58 pc. IRAS maps (12, 25, 60 and 100\mu m) of the
new SNR show rich infrared emission surrounding G108.20.6.Comment: 10 pages, 6 figs, accepted by A&
Recommended from our members
Effects of urbanisation and landscape heterogeneity mediated by feeding guild and body size in a community of coprophilous beetles
Although the impacts of urbanisation on biodiversity are well studied, the precise response of some invertebrate groups remains poorly known. Dung-associated beetles are little studied in an urban context, especially in temperate regions. We considered how landscape heterogeneity, assessed at three spatial scales (250, 500 and 1000 metre radius), mediates the community composition of coprophilous beetles on a broad urban gradient. Beetles were sampled using simple dung-baited traps, placed at 48 sites stratified across three distance bands around a large urban centre in England. The most urban sites hosted the lowest abundance of saprophagous beetles, with a lower mean body length relative to the least urban sites. Predicted overall species richness and the richness of saprophagous species were also lowest at the most urban sites. Ordination analyses followed by variation partitioning revealed that landscape heterogeneity across the urban gradient explained a small but significant proportion of community composition. Heterogeneity data for a 500-metre radius around each site provided the best fit with beetle community data. Larger saprophagous species were associated with lower amounts of manmade surface and improved grassland. Some individual species, particularly predators, appeared to be positively associated with urban or urban fringe sites. This study is probably the first to examine the response of the whole coprophilous beetle community to urbanisation. Our results suggest that the response of this community to urbanisation matches expectations based on other taxonomic groups, whilst emphasising the complex nature of this response, with some smaller-bodied species potentially benefitting from urbanisation
G181.1+9.5, a new high-latitude low-surface brightness supernova remnant
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^{-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)
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
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 ,
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
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
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
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
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