768 research outputs found
2001 Field Crop Scout Schools
The Integrated Pest Management Field Crop Scout Schools are designed for those who have no previous scouting experience and plan to work as crop scouts. Sessions will cover identification and scouting methods for weeds, insects, and diseases; crop growth and development of corn, soybean, and alfalfa; how to use soil surveys and some general information about soil profiles; discussion of common crop problems; and scouting goals. Many of the sessions will include hands-on diagnostic activities to help in recognizing field crop problems
Worker Protection Standard Update
The Worker Protection Standard is a Federal regulation designed to protect agricultural workers (people involved in the production of agricultural plants) and pesticide handlers (people involved in mixing, loading or applying pesticides or doing other tasks involving direct contact with pesticides.) The Standard will impact farms, agricultural dealerships, nurseries, forests and greenhouses who hire employees to do tasks related to agricultural plant production. The Worker Protection Standard goes into effect on April 15, 1994. After this date, applicators that use a pesticide which refers to the Worker Protection Standard on its label, must comply with requirements under the Worker Protection Standard. The employer is responsible for seeing that their employees comply with this new regulation. The following information is a brief overview of the Worker Protection Standard. The complete details of the Standard are presented in the Federal Register or in the How to Comply manual, PAT-12, available from ISU Extension Distribution
Simultaneous NIR/sub-mm observation of flare emission from SgrA*
We report on a successful, simultaneous observation and modeling of the
sub-millimeter to near-infrared flare emission of the Sgr A* counterpart
associated with the super-massive black hole at the Galactic center. Our
modeling is based on simultaneous observations that have been carried out on 03
June, 2008 using the NACO adaptive optics (AO) instrument at the ESO VLT and
the LABOCA bolometer at the APEX telescope. Inspection and modeling of the
light curves show that the sub-mm follows the NIR emission with a delay of
1.5+/-0.5 hours. We explain the flare emission delay by an adiabatic expansion
of the source components.Comment: 12 pages, 9 figures, 3 tables, in press with A&
Recommended from our members
An XâRay, Infrared, and Submillimeter Flare of Sagittarius A*
Energetic flares are observed in the Galactic supermassive black hole Sagittarius A* from radio to X-ray wavelengths. On a few occasions, simultaneous flares have been detected in IR and X-ray observations, but clear counterparts at longer wavelengths have not been seen. We present a flare observed over several hours on 2006 July 17 with the Chandra X-Ray Observatory, the Keck II telescope, the Caltech Submillimeter Observatory, and the Submillimeter Array. All telescopes observed strong flare events, but the submillimeter peak is found to occur nearly 100 minutes after the X-ray peak. Submillimeter polarization data show linear polarization in the excess flare emission, increasing from 9% to 17% as the flare passes through its peak, consistent with a transition from optically thick to thin synchrotron emission. The temporal and spectral behavior of the flare require that the energetic electrons responsible for the emission cool faster than expected from their radiative output. This is consistent with adiabatic cooling in an expanding emission region, with X-rays produced through self-Compton scattering, although not consistent with the simplest model of such expansion. We also present a submillimeter flare that followed a bright IR flare on 2005 July 31. Compared to 2006, this event had a larger peak IR flux and similar submillimeter flux, but it lacked measurable X-ray emission. It also showed a shorter delay between the IR and submillimeter peaks. Based on these events we propose a synchrotron and self-Compton model to relate the submillimeter lag and the variable IR/X-ray luminosity ratio.Astronom
A contemporaneous infrared flash from a long gamma-ray burst: an echo from the central engine
The explosion that results in a cosmic gamma-ray burst (GRB) is thought to
produce emission from two physical processes -- the activity of the central
engine gives rise to the high-energy emission of the burst through internal
shocking and the subsequent interaction of the flow with the external
environment produces long-wavelength afterglow. While afterglow observations
continue to refine our understanding of GRB progenitors and relativistic
shocks, gamma-ray observations alone have not yielded a clear picture of the
origin of the prompt emission nor details of the central engine. Only one
concurrent visible-light transient has been found and was associated with
emission from an external shock. Here we report the discovery of infrared (IR)
emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of
GRB 041219a. Our robotic telescope acquired 21 images during the active phase
of the burst, yielding the earliest multi-colour observations of any
long-wavelength emission associated with a GRB. Analysis of an initial IR pulse
suggests an origin consistent with internal shocks. This opens a new
possibility to study the central engine of GRBs with ground-based observations
at long wavelengths.Comment: Accepted to Nature on March 1, 2005. 9 pages, 4 figures, nature12.cls
and nature1.cls files included. This paper is under press embargo until print
publicatio
A Remarkable Low-Mass X-ray Binary within 0.1 pc of the Galactic Center
Recent X-ray and radio observations have identified a transient low-mass
X-ray binary (LMXB) located only 0.1 pc in projection from the Galactic center,
CXOGC J174540.0-290031. In this paper, we report the detailed analysis of X-ray
and infrared observations of the transient and its surroundings. Chandra
bservations detect the source at a flux of F_X = 2e-12 erg cm^-2 s^-1 (2-8
keV). After accounting for absorption both in the interstellar medium and in
material local to the source, the implied luminosity of the source is only L_X
= 4e34 erg/s (2-8 keV; D=8 kpc). However, the diffuse X-ray emission near the
source also brightened by a factor of 2. The enhanced diffuse X-ray emission
lies on top of a known ridge of dust and ionized gas that is visible infrared
images. We interpret the X-ray emission as scattered flux from the outburst,
and determine that the peak luminosity of CXOGC J174540.0-290031 was >2e36
erg/s. We suggest that the relatively small observed flux results from the fact
that the system is observed nearly edge-on, so that the accretion disk
intercepts most of the flux emitted along our line of sight. We compare the
inferred peak X-ray luminosity to that of the radio jet. The ratio of the X-ray
to radio luminosities, L_X/L_R<1e4, is considerably smaller than in other known
LMXBs (> 1e5). This is probably because the jets are radiating with unusually
high efficiency at the point where they impact the surrounding interstellar
medium. This hypothesis is supported by a comparison with mid-infrared images
of the surrounding dust. Finally, we find that the minimum power required to
produce the jet, L_jet~1e37 erg/s, is comparable to the inferred peak X-ray
luminosity. This is the most direct evidence yet obtained that LMXBs accreting
at low rates release about half of their energy as jets.Comment: 11 pages, including 9 figures (6 color). submitted to Ap
An X-ray, infrared, and submillimeter flare of Sagittarius A
Energetic flares are observed in the Galactic supermassive black hole Sagittarius A* from radio to X-ray wavelengths. On a few occasions, simultaneous flares have been detected in IR and X-ray observations, but clear counterparts at longer wavelengths have not been seen. We present a flare observed over several hours on 2006 July 17 with the Chandra X-Ray Observatory, the Keck II telescope, the Caltech Submillimeter Observatory, and the Submillimeter Array. All telescopes observed strong flare events, but the submillimeter peak is found to occur nearly 100 minutes after the X-ray peak. Submillimeter polarization data show linear polarization in the excess flare emission, increasing from 9% to 17% as the flare passes through its peak, consistent with a transition from optically thick to thin synchrotron emission. The temporal and spectral behavior of the flare require that the energetic electrons responsible for the emission cool faster than expected from their radiative output. This is consistent with adiabatic cooling in an expanding emission region, with X-rays produced through self-Compton scattering, although not consistent with the simplest model of such expansion. We also present a submillimeter flare that followed a bright IR flare on 2005 July 31. Compared to 2006, this event had a larger peak IR flux and similar submillimeter flux, but it lacked measurable X-ray emission. It also showed a shorter delay between the IR and submillimeter peaks. Based on these events we propose a synchrotron and self-Compton model to relate the submillimeter lag and the variable IR/X-ray luminosity ratio
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