757 research outputs found
Effect of moisture and bulk density sampling on neutron moisture gauge calibration
Three moisture and bulk density sampling methods were evaluated for use in
neutron gauge calibration. Each of the methods was comprised of a single
core or portions of a core taken during installation of a neutron access tube.
In addition to direct measurement of bulk density, the effect of using
"smoothed", "probable" and gamma-probe measured bulk density profiles was
evaluated. The use of these three alternative bulk density profiles in the
computation of volumetric moisture generally had insignificant effect on the
resulting neutron gauge calibration equation. The use of a depth-weighted
volumetric moisture profile generally improved calibration statistics, but reduced
slopes of neutron calibration equations (% moisture per count ratio). Overall,
a total core method which used a tractor-mounted, hydraulically operated
coring tool provided the most consistent calibrations with lowest standard errors
of estimate, although compression of soil along the perimeter of the cored hole
increased subsequent neutron count ratios. A "Madera" down-hole sampler
generally provided good calibrations, also. A third, small-volume, down-hole
sampler provided valid moisture and bulk density samples; however, the smaller
representative volume of the sampler relative to the sampling volume of neutron
gauges adversely affected slopes of some calibration equations
Measuring soil bulk density profiles with a single probe gamma density gauge
Calibrating neutron depth gauges for measuring soil water content profiles requires
soil bulk density data. In this study, the feasibility of using a single probe gamma
density gauge to measure the soil wet bulk density was investigated for use in neutron
gauge calibration. The same sites, access tubes, and conventional gravimetric soil data
used for the ASCE Neutron Gauge Calibration Study were used for the Gamma Gauge
Study. Iterative procedures were successfully developed to calibrate the gamma
density gauge, and then to convert wet bulk density to dry bulk density data for the
three soil sites studied
Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity
Recent application of ultrafast pump/probe optical techniques to
superconductors has renewed interest in nonequilibrium superconductivity and
the predictions that would be available for novel superconductors, such as the
high-Tc cuprates. We have reexamined two of the classical models which have
been used in the past to interpret nonequilibrium experiments with some
success: the mu* model of Owen and Scalapino and the T* model of Parker.
Predictions depend on pairing symmetry. For instance, the gap suppression due
to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave
as opposed to n for s-wave. Finally, we consider these models in the context of
S-I-N tunneling and optical excitation experiments. While we confirm that
recent pump/probe experiments in YBCO, as presently interpreted, are in
conflict with d-wave pairing, we refute the further claim that they agree with
s-wave.Comment: 14 pages, 11 figure
Soil bulk density sampling for neutron gauge calibration
The ASCE Task Committee on Neutron Gauge Calibration met in Logan, Utah in July
1992 to investigate the various methods of soil sampling, installation of access tubes,
effect of various parameters on gauge readings, methods of developing field calibration
curves and comparison of neutron gauge characteristics. Details of the overall objectives
of the study are covered by Stone (1993, this volume). This paper discusses the soil
sampling methods and presents a comparative result based on bulk density, time required
for sampling and cost of sampling equipment Other papers developed from this study
describe the soils, the three sites investigated and the problems related to the tube
installation process
Neutron gauge calibration comparison of methods
Several methods for obtaining soil samples for determining soil water content were used
for field calibration of neutron gauges. This paper compares the results of calibration
curves obtained from the study data by comparing intercepts, slopes and correlation
coefficients ("r" values). The study found differences in characteristics between gauges
of the same brand, differences between brands and a great effect by access tube
materials on the calibration curve
The ASCE neutron probe calibration study: overview
A workshop was held at Logan, Utah to gather field information on
neutron probe calibration and operation. Several techniques and instruments
were compared. This paper serves to establish the background information for
the work and describe the overall approaches, conditions, and equipment. Other
papers presented at this conference provide detailed procedures and results
Citizen Science 2.0 : Data Management Principles to Harness the Power of the Crowd
Citizen science refers to voluntary participation by the general public in scientific endeavors. Although citizen science has a long tradition, the rise of online communities and user-generated web content has the potential to greatly expand its scope and contributions. Citizens spread across a large area will collect more information than an individual researcher can. Because citizen scientists tend to make observations about areas they know well, data are likely to be very detailed. Although the potential for engaging citizen scientists is extensive, there are challenges as well. In this paper we consider one such challenge – creating an environment in which non-experts in a scientific domain can provide appropriate and accurate data regarding their observations. We describe the problem in the context of a research project that includes the development of a website to collect citizen-generated data on the distribution of plants and animals in a geographic region. We propose an approach that can improve the quantity and quality of data collected in such projects by organizing data using instance-based data structures. Potential implications of this approach are discussed and plans for future research to validate the design are described
Use of viral pathogens and indicators to differentiate between human and non-human fecal contamination in a microbial source tracking comparison study
Assays for the detection and typing of adenoviruses, enteroviruses and F+ specific coliphages were performed on samples created as part of a national microbial source tracking methods comparison study. The samples were created blind to the researchers, and were inoculated with a variety of types of fecal contamination source (human, sewage, dog, seagull and cow) and mixtures of sources. Viral tracer and pathogen assays demonstrated a general ability to discriminate human from non-human fecal contamination. For example, samples inoculated with sewage were correctly identified as containing human fecal contamination because they contained human adenovirus or human enterovirus. In samples containing fecal material from individual humans, human pathogen analysis yielded negative results probably because the stool samples were taken from healthy individuals. False positive rates for the virus-based methods (0-8%) were among the lowest observed during the methods comparison study. It is suggested that virus-based source tracking methods are useful for identification of sewage contamination, and that these methods may also be useful as an indication of the public health risk associated with viral pathogens. Overall, virus-based source tracking methods are an important approach to include in the microbial source tracking 'toolbox'
Reaction and Axial Vector Coupling
The reaction is studied in the region of low
to investigate the effect of deuteron structure and width of the
resonance on the differential cross section. The results are used to extract
the axial vector coupling from the experimental data on
this reaction. The possibility to determine this coupling from electroweak
interaction experiments with high intensity electron accelerators is discussed.Comment: 14 pages, REVTEX, 5 figure
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