25,479 research outputs found
\u3ci\u3eUrophora Affinis\u3c/i\u3e and \u3ci\u3eU. Quadrifasciata\u3c/i\u3e (Diptera: Tephritidae) Released and Monitored by USDA, APHIS, PPQ as Biological Control Agents of Spotted and Diffuse Knapweed
USDA, APHIS, PPQ has distributed the seedhead gall flies Urophora affinis and U. quadrifasciata (Diptera: Tephritidae) as classical biological agents of the introduced weeds spotted and diffuse knapweed (Centaurea maculosa and C. diffusa, respectively) (Asteraceae) in the United States. From 1987 to 1996, Urophora spp. have been released in 97 counties in 14 midwestern and western states. Established populations of U. affinis and U. quadrifasciata are confirmed in 85 and 95 counties, respectively, among all 14 states. These include the first reports of successful establishment of Urophora spp. in Arizona (two counties), Colorado (eight counties), Michigan (one county), Minnesota (six counties), Nebraska (four counties), Nevada (two counties), North Dakota (one county), South Dakota (four counÂties), Utah (three counties), and Wisconsin (two counties). The first confirmed establishment of U. quadrifasciata in Indiana and Michigan is also reported
VLA-Max '91 tests of high energy flare physics
The potential for the Very Large Array (VLA) contributions during the coming maximum in solar activity is illustrated by unpublished observations of solar flares on 28 May, 8 June, 24 June, and 30 September 1988. Some of this data appears in the two papers by Willson et al., referenced in this article. The VLA can be used to spatially resolve flaring active regions and their magnetic fields. These results can be compared with simultaneous x ray and gamma ray observations from space. Examples are provided in which spatially separated radio sources are resolved for the pre-burst, impulsive and decay phases of solar flares. The emergence of precursor coronal loops probably triggers the release of stored magnetic energy in adjacent coronal loops. Noise storm enhancements can originate in large-scale coronal loops on opposite sides of the visible solar disk. An interactive feedback mechanism may exist between activity in high-lying 90 cm coronal loops and lower-lying 20 cm ones
Compact, variable, moving sources observed on the sun at 2 centimeters wavelength
The Very Large Array (VLA) was used to observe the active region AT 4508 in the C-configuration between 1530 and 2330 UT on June 4, 1984. The position of this region was N06 E57 at 1300 UT on this day. Followup observations were made between 1500 and 2300 UT on January 17, 1986 in the D-configuration. Observations were compared with Mt. Wilson magnetograms. Results are discussed
Balloon tank skin strain measurements at liquid-hydrogen temperature on centaur flight vehicle
Balloon tank skin strain measurements at liquid hydrogen temperature on Centaur flight vehicl
Cleaning the USNO-B Catalog through automatic detection of optical artifacts
The USNO-B Catalog contains spurious entries that are caused by diffraction
spikes and circular reflection halos around bright stars in the original
imaging data. These spurious entries appear in the Catalog as if they were real
stars; they are confusing for some scientific tasks. The spurious entries can
be identified by simple computer vision techniques because they produce
repeatable patterns on the sky. Some techniques employed here are variants of
the Hough transform, one of which is sensitive to (two-dimensional)
overdensities of faint stars in thin right-angle cross patterns centered on
bright (<13 \mag) stars, and one of which is sensitive to thin annular
overdensities centered on very bright (<7 \mag) stars. After enforcing
conservative statistical requirements on spurious-entry identifications, we
find that of the 1,042,618,261 entries in the USNO-B Catalog, 24,148,382 of
them (2.3 \percent) are identified as spurious by diffraction-spike criteria
and 196,133 (0.02 \percent) are identified as spurious by reflection-halo
criteria. The spurious entries are often detected in more than 2 bands and are
not overwhelmingly outliers in any photometric properties; they therefore
cannot be rejected easily on other grounds, i.e., without the use of computer
vision techniques. We demonstrate our method, and return to the community in
electronic form a table of spurious entries in the Catalog.Comment: published in A
Precision CW laser automatic tracking system investigated
Precision laser tracker capable of tracking a low acceleration target to an accuracy of about 20 microradians rms is being constructed and tested. This laser tracking has the advantage of discriminating against other optical sources and the capability of simultaneously measuring range
Diffusion in simple fluids
Computed self diffusion coefficients for the Lennard-Jones and hard sphere fluids are related by
Dej = DNs(aB) exp (--e/2kB T)
where σB=σLJ(2/[1+ii(1+2kBT/ε)])1/6, the effective hard sphere diameter, is the (average) distance of closest approach in collisions between molecules which interact with the positive part of the LJ potential, and the Arrhenius term reflects the influence of the negative part. σLJ and ε are the size and well depth parameters. Measured diffusion coefficients of the halomethane liquids are reproduced by the equation over wide ranges of temperature and density and do not reveal any influence of the inelastic effects associated with molecular anisotropy
The Chandra Detection of Galactic Center X-ray Features G359.89-0.08 and G359.54+0.18
We report on the detection of two elongated X-ray features G359.89-0.08 and
G359.54+0.18 in the Galactic center (GC) region using the Chandra X-ray
Observatory. G359.89-0.08 is an elongated X-ray feature located 2\arcmin
in projection south of the center of the Galaxy, SgrA. This X-ray feature
source is partially coincident with a slightly curved (``wisp''-like)
non-thermal radio source. The X-ray spectrum of G359.89-0.08 can be best
characterized as non-thermal, with a photon index of 2. The morphological and
spectral characteristics of the X-ray and radio emission associated with
G359.89-0.08 are best interpreted as the synchrotron emission from a
ram-pressure confined pulsar wind nebula. G359.54+0.18 is one of the most
prominent radio non-thermal filaments (NTFs) in the GC region, located
30\arcmin in projection from SgrA. A narrow (10\arcsec)
filament of X-ray emission appears to arise from one of the two strands that
comprise the radio NTF. Although the photon statistics are poor for this
source, the X-ray emission is also likely to be non-thermal in nature. Several
models for the production of X-ray emission in G359.54+0.18 are discussed.Comment: 19 pages with 6 figures included, accepted by A
Smart Materials as Intelligent Insulation
In order to provide a robust infrastructure for the transmission and distribution of electrical power, understanding and monitoring equipment ageing and failure is of paramount importance. Commonly, failure is associated with degradation of the dielectric material; therefore the introduction of a smart moiety into the material is a potentially attractive means of continual condition monitoring. It is important that any introduction of smart groups into the dielectric does not have any detrimental effect on the desirable electrical and mechanical properties of the bulk material. Initial work focussed on the introduction of fluorophores into a model dielectric system. Fluorescence is known to be a visible effect even at very low concentrations of active fluorophores and therefore was thought well suited to such an application. It was necessary both to optimise the active fluorophore itself and to determine the most appropriate manner in which to introduce the fluorophores into the insulating system. This presentation will describe the effect of introducing fluorophores into polymeric systems on the dielectric properties of the material and the findings thus far [1]. Alternative smart material systems will also be discussed along with the benefits and limitations of smart materials as electric field sensors
Signatures of Dark Matter Scattering Inelastically Off Nuclei
Direct dark matter detection focuses on elastic scattering of dark matter
particles off nuclei. In this study, we explore inelastic scattering where the
nucleus is excited to a low-lying state of 10-100 keV, with subsequent prompt
de-excitation. We calculate the inelastic structure factors for the odd-mass
xenon isotopes based on state-of-the-art large-scale shell-model calculations
with chiral effective field theory WIMP-nucleon currents. For these cases, we
find that the inelastic channel is comparable to or can dominate the elastic
channel for momentum transfers around 150 MeV. We calculate the inelastic
recoil spectra in the standard halo model, compare these to the elastic case,
and discuss the expected signatures in a xenon detector, along with
implications for existing and future experiments. The combined information from
elastic and inelastic scattering will allow to determine the dominant
interaction channel within one experiment. In addition, the two channels probe
different regions of the dark matter velocity distribution and can provide
insight into the dark halo structure. The allowed recoil energy domain and the
recoil energy at which the integrated inelastic rates start to dominate the
elastic channel depend on the mass of the dark matter particle, thus providing
a potential handle to constrain its mass.Comment: 9 pages, 7 figures. Matches resubmitted version to Phys. Rev. D. One
figure added; supplemental material (fits to the structure functions) added
as an Appendi
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