129 research outputs found
Alfalfa Leaf-Cutter Bee: Management for Alfalfa Pollination in South Dakota
The alfalfa leaf-cutter bee, Megachile rotundata (Fabricius), was introduced into South D a k o t a from Utah in 1962 for alfalfa pollination testing. This leaf-cutting bee, because of its pollen collecting activmes, has shown considerable promise as a means of increasing yields of alfalfa seed. A native of Eurasia, it was introduced into eastern United States in the mid-thirties and by 1958 had moved across the country into Oregon. There is some indication that the alfalfa leaf-cutter bee may have become established in isolated locations in South Dakota during this initial cross-country movement
Why Are Students Not Majoring in Information Systems?
The purpose of this study was to examine some of the factors that influence and impact business students when they select their major and, more particularly, to examine why students are not majoring in information systems. Students in an entry level business class responded that they were more knowledgeable about careers in management, marketing, accounting, and finance than they were about careers in information systems. These business students indicated that they are looking for majors that will be interesting, provide them with job security initially and over their careers, and pay them well. The most important information sources used by these students in their major selection decision were information on college/department websites, brochures about the major, and information on the Internet. When asked why they were not majoring in information systems, the top two reasons given were not what I wanted to do and subject not of interest
Polarization of superfluid turbulence
We show that normal fluid eddies in turbulent helium II polarize the tangle
of quantized vortex lines present in the flow, thus inducing superfluid
vorticity patterns similar to the driving normal fluid eddies. We also show
that the polarization is effective over the entire inertial range. The results
help explain the surprising analogies between classical and superfluid
turbulence which have been observed recently.Comment: 3 figure
A proposed measurement of the ß asymmetry in neutron decay with the Los Alamos Ultra-Cold Neutron Source
This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002
A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)
A new boron-coated CCD camera is described for direct detection of ultracold
neutrons (UCN) through the capture reactions B
(n,0)Li (6%) and B(n,1)Li (94%).
The experiments, which extend earlier works using a boron-coated ZnS:Ag
scintillator, are based on direct detections of the neutron-capture byproducts
in silicon. The high position resolution, energy resolution and particle ID
performance of a scientific CCD allows for observation and identification of
all the byproducts , Li and (electron recoils). A
signal-to-noise improvement on the order of 10 over the indirect method has
been achieved. Sub-pixel position resolution of a few microns is demonstrated.
The technology can also be used to build UCN detectors with an area on the
order of 1 m. The combination of micrometer scale spatial resolution, few
electrons ionization thresholds and large area paves the way to new research
avenues including quantum physics of UCN and high-resolution neutron imaging
and spectroscopy.Comment: 10 pages, 8 figure
Measurement of the neutron lifetime using an asymmetric magneto- gravitational trap and in situ detection
The precise value of the mean neutron lifetime, , plays an important
role in nuclear and particle physics and cosmology. It is a key input for
predicting the ratio of protons to helium atoms in the primordial universe and
is used to search for new physics beyond the Standard Model of particle
physics. There is a 3.9 standard deviation discrepancy between
measured by counting the decay rate of free neutrons in a beam (887.7 2.2
s) and by counting surviving ultracold neutrons stored for different storage
times in a material trap (878.50.8 s). The experiment described here
eliminates loss mechanisms present in previous trap experiments by levitating
polarized ultracold neutrons above the surface of an asymmetric storage trap
using a repulsive magnetic field gradient so that the stored neutrons do not
interact with material trap walls and neutrons in quasi-stable orbits rapidly
exit the trap. As a result of this approach and the use of a new in situ
neutron detector, the lifetime reported here (877.7 0.7 (stat) +0.4/-0.2
(sys) s) is the first modern measurement of that does not require
corrections larger than the quoted uncertainties.Comment: 9 pages, 3 figures, 2 table
Status of the UCNÏ„ experiment
The neutron is the simplest nuclear system that can be used to probe the structure of the weak interaction and search for physics beyond the standard model. Measurements of neutron lifetime and β-decay correlation coefficients with precisions of 0.02% and 0.1%, respectively, would allow for stringent constraints on new physics. The UCNτ experiment uses an asymmetric magneto-gravitational UCN trap with in situ counting of surviving neutrons to measure the neutron lifetime, τ_n = 877.7s (0.7s)_(stat) (+0.4/−0.2s)_(sys). We discuss the recent result from UCNτ, the status of ongoing data collection and analysis, and the path toward a 0.25 s measurement of the neutron lifetime with UCNτ
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