5,273 research outputs found
An archaeological survey of the phase I Riverpark development, Chattanooga, Tennessee
In August and September, 1986, the Jeffrey L. Brown Institute of Archaeology, University of Tennessee at Chattanooga, conducted a systematic subsurface archaeological survey of a 2.5 km (1.5 mile) corridor along the left bank of the Tennessee River, Chattanooga, Hamilton County, Tennessee. The survey was funded by the RiverCity Company, Chattanooga, a non-profit corporation overseeing the implementation of a plan to create a public recreation facility known as the Tennessee Riverpark. As part of the final planning of the Phase I area of the Riverpark, environmental impact studies of the project area were commissioned. The project area extends from the C. B. Robinson Bridge off Amnicola Highway to the Tennessee Valley Authority\u27s Chickamauga Dam. The archaeological survey of the Riverpark Phase I project area was conducted by using a power soil auger to drill test cores at 80° (25 meter) intervals in grid and linear patterns to a depth not exceeding 5.5\u27. The fill from the auger tests was sifted using 1/4 inch mesh screens for standardized artifact recovery. Testing was confined to the proposed project area. Excepting modern debris, the cultural materials recovered from subsurface contexts consisted of prehistoric artifacts from the Late Archaic, Woodland and Mississippian periods. A thin scatter of artifacts is present along the entire length of the project area but two concentrations of debris were noted and tested by hand-excavated test units 3\u27 by 6° in size. One concentration represented a Woodland period occupation superimposed on a Late Archaic component; this site has been designated 40HA233 in the Tennessee archaeological site file. The second concentration was a Woodland occupation previously recorded as site 40HA102 by the Tennessee Department of Transportation in 1979. Mississippian ceramics were present above the Woodland midden. A second previously-recorded site in the project area, 40HA83, situated behind Chattanooga State Technical Community College, was not sampled in the auger survey. It is recommended that the sites noted on each side of the C. B. Robinson Bridge be preserved and protected from construction impacts during development of the Tennessee Riverpark. If preservation of the sites is not feasible, further evaluation in the form of a secondary archaeological testing program is recommended. Since the project area landforms consist of alluvially-aggrading river terraces, there exists the possibility of deeply-buried Archaic occupations not detected by the auger survey. Monitoring of any deep excavations undertaken in the course of construction is recommended.https://scholar.utc.edu/archaeology-reports/1052/thumbnail.jp
A Fractal Analysis of the HI Emission from the Large Magellanic Cloud
A composite map of HI in the LMC using the ATCA interferometer and the Parkes
multibeam telescope was analyzed in several ways in an attempt to characterize
the structure of the neutral gas and to find an origin for it. Fourier
transform power spectra in 1D, 2D, and in the azimuthal direction were found to
be approximate power laws over 2 decades in length. Delta-variance methods also
showed the same power-law structure. Detailed models of these data were made
using line-of-sight integrals over fractals that are analogous to those
generated by simulations of turbulence with and without phase transitions. The
results suggested a way to measure directly for the first time the
line-of-sight thickness of the cool component of the HI disk of a nearly
face-on galaxy. The signature of this thickness was found to be present in all
of the measured power spectra.
The character of the HI structure in the LMC was also viewed by comparing
positive and negative images of the integrated emission. The geometric
structure of the high-emission regions was found to be filamentary, whereas the
geometric structure of the low-emission (intercloud) regions was found to be
patchy and round. This result suggests that compressive events formed the
high-emission regions, and expansion events, whether from explosions or
turbulence, formed the low-emission regions. The character of the structure was
also investigated as a function of scale using unsharp masks.
All of these results suggest that most of the ISM in the LMC is fractal,
presumably the result of pervasive turbulence, self-gravity, and self-similar
stirring.Comment: 30 pages, 21 figures, scheduled for ApJ Vol 548n1, Feb 10, 200
Comparative population structure of <i>Plasmodium malariae</i> and <i>Plasmodium falciparum</i> under different transmission settings in Malawi
<b>Background:</b> Described here is the first population genetic study of Plasmodium malariae, the causative agent of quartan malaria. Although not as deadly as Plasmodium falciparum, P. malariae is more common than previously thought, and is frequently in sympatry and co-infection with P. falciparum, making its study increasingly important. This study compares the population parameters of the two species in two districts of Malawi with different malaria transmission patterns - one seasonal, one perennial - to explore the effects of transmission on population structures.
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<b>Methods:</b> Six species-specific microsatellite markers were used to analyse 257 P. malariae samples and 257 P. falciparum samples matched for age, gender and village of residence. Allele sizes were scored to within 2 bp for each locus and haplotypes were constructed from dominant alleles in multiple infections. Analysis of multiplicity of infection (MOI), population differentiation, clustering of haplotypes and linkage disequilibrium was performed for both species. Regression analyses were used to determine association of MOI measurements with clinical malaria parameters.
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<b>Results:</b> Multiple-genotype infections within each species were common in both districts, accounting for 86.0% of P. falciparum and 73.2% of P. malariae infections and did not differ significantly with transmission setting. Mean MOI of P. falciparum was increased under perennial transmission compared with seasonal (3.14 vs 2.59, p = 0.008) and was greater in children compared with adults. In contrast, P. malariae mean MOI was similar between transmission settings (2.12 vs 2.11) and there was no difference between children and adults. Population differentiation showed no significant differences between villages or districts for either species. There was no evidence of geographical clustering of haplotypes. Linkage disequilibrium amongst loci was found only for P. falciparum samples from the seasonal transmission setting.
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<b>Conclusions:</b> The extent of similarity between P. falciparum and P. malariae population structure described by the high level of multiple infection, the lack of significant population differentiation or haplotype clustering and lack of linkage disequilibrium is surprising given the differences in the biological features of these species that suggest a reduced potential for out-crossing and transmission in P. malariae. The absence of a rise in P. malariae MOI with increased transmission or a reduction in MOI with age could be explained by differences in the duration of infection or degree of immunity compared to P. falciparum
Freezing by Monte Carlo Phase-Switch
We describe a Monte Carlo procedure which allows sampling of the disjoint
configuration spaces associated with crystalline and fluid phases, within a
single simulation. The method utilises biased sampling techniques to enhance
the probabilities of gateway states (in each phase) which are such that a
global switch (to the other phase) can be implemented. Equilibrium
freezing-point parameters can be determined directly; statistical uncertainties
prescribed transparently; and finite-size effects quantified systematically.
The method is potentially quite general; we apply it to the freezing of hard
spheres.Comment: 5 pages, 2 figure
Measuring Transit Signal Recovery in the Kepler Pipeline II: Detection Efficiency as Calculated in One Year of Data
The Kepler planet sample can only be used to reconstruct the underlying
planet occurrence rate if the detection efficiency of the Kepler pipeline is
known, here we present the results of a second experiment aimed at
characterising this detection efficiency. We inject simulated transiting planet
signals into the pixel data of ~10,000 targets, spanning one year of
observations, and process the pixels as normal. We compare the set of
detections made by the pipeline with the expectation from the set of simulated
planets, and construct a sensitivity curve of signal recovery as a function of
the signal-to-noise of the simulated transit signal train. The sensitivity
curve does not meet the hypothetical maximum detection efficiency, however it
is not as pessimistic as some of the published estimates of the detection
efficiency. For the FGK stars in our sample, the sensitivity curve is well fit
by a gamma function with the coefficients a = 4.35 and b = 1.05. We also find
that the pipeline algorithms recover the depths and periods of the injected
signals with very high fidelity, especially for periods longer than 10 days. We
perform a simplified occurrence rate calculation using the measured detection
efficiency compared to previous assumptions of the detection efficiency found
in the literature to demonstrate the systematic error introduced into the
resulting occurrence rates. The discrepancies in the calculated occurrence
rates may go some way towards reconciling some of the inconsistencies found in
the literature.Comment: 13 pages, 7 figures, 1 electronic table, accepted by Ap
Measuring Transit Signal Recovery in the Kepler Pipeline. III. Completeness of the Q1-Q17 DR24 Planet Candidate Catalogue, with Important Caveats for Occurrence Rate Calculations
With each new version of the Kepler pipeline and resulting planet candidate
catalogue, an updated measurement of the underlying planet population can only
be recovered with an corresponding measurement of the Kepler pipeline detection
efficiency. Here, we present measurements of the sensitivity of the pipeline
(version 9.2) used to generate the Q1-Q17 DR24 planet candidate catalog
(Coughlin et al. 2016). We measure this by injecting simulated transiting
planets into the pixel-level data of 159,013 targets across the entire Kepler
focal plane, and examining the recovery rate. Unlike previous versions of the
Kepler pipeline, we find a strong period dependence in the measured detection
efficiency, with longer (>40 day) periods having a significantly lower
detectability than shorter periods, introduced in part by an incorrectly
implemented veto. Consequently, the sensitivity of the 9.2 pipeline cannot be
cast as a simple one-dimensional function of the signal strength of the
candidate planet signal as was possible for previous versions of the pipeline.
We report on the implications for occurrence rate calculations based on the
Q1-Q17 DR24 planet candidate catalog and offer important caveats and
recommendations for performing such calculations. As before, we make available
the entire table of injected planet parameters and whether they were recovered
by the pipeline, enabling readers to derive the pipeline detection sensitivity
in the planet and/or stellar parameter space of their choice.Comment: 8 pages, 5 figures, full electronic version of Table 1 available at
the NASA Exoplanet Archive; accepted by ApJ May 2nd, 201
Free energies of crystalline solids: a lattice-switch Monte Carlo method
We present a method for the direct evaluation of the difference between the
free energies of two crystalline structures, of different symmetry. The method
rests on a Monte Carlo procedure which allows one to sample along a path,
through atomic-displacement-space, leading from one structure to the other by
way of an intervening transformation that switches one set of lattice vectors
for another. The configurations of both structures can thus be sampled within a
single Monte Carlo process, and the difference between their free energies
evaluated directly from the ratio of the measured probabilities of each. The
method is used to determine the difference between the free energies of the fcc
and hcp crystalline phases of a system of hard spheres.Comment: 5 pages Revtex, 3 figure
A Circuit Approach to Model Narrow Slot Structures in a Power Bus
A coupled transmission line model for narrow slot structures in DC power planes is proposed. This approach, combined with SPICE-based cavity models and a segmentation method, provides an easy and fast way to model relatively complex structures of power planes with narrow slots often used for isolation purposes. This approach is used to achieve isolation using gapping. The cavity model formulations for rectangular and isosceles right triangular segments are reviewed. The rationale of modeling the narrow slot as a three-conductor transmission line is described. The modeling results are shown and compared with the output of a full wave simulation tool, HFSS, and with experimental measurements
Alexandrium fundyense cysts in the Gulf of Maine : long-term time series of abundance and distribution, and linkages to past and future blooms
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 6-26, doi:10.1016/j.dsr2.2013.10.002.Here we document Alexandrium fundyense cyst abundance and distribution patterns over
nine years (1997 and 2004-2011) in the coastal waters of the Gulf of Maine (GOM) and identify
linkages between those patterns and several metrics of the severity or magnitude of blooms
occurring before and after each autumn cyst survey. We also explore the relative utility of two
measures of cyst abundance and demonstrate that GOM cyst counts can be normalized to
sediment volume, revealing meaningful patterns equivalent to those determined with dry weight
normalization.Cyst concentrations were highly variable spatially. Two distinct 1 seedbeds (defined here as
accumulation zones with > 300 cysts cm-3) are evident, one in the Bay of Fundy (BOF) and one
in mid-coast Maine. Overall, seedbed locations remained relatively constant through time, but
their area varied 3-4 fold, and total cyst abundance more than 10 fold among years. A major
expansion of the mid-coast Maine seedbed occurred in 2009 following an unusually intense A.
fundyense bloom with visible red-water conditions, but that feature disappeared by late 2010.
The regional system thus has only two seedbeds with the bathymetry, sediment characteristics,
currents, biology, and environmental conditions necessary to persist for decades or longer.
Strong positive correlations were confirmed between the abundance of cysts in both the 0-1 and
the 0-3 cm layers of sediments in autumn and geographic measures of the extent of the bloom
that occurred the next year (i.e., cysts → blooms), such as the length of coastline closed due to
shellfish toxicity or the southernmost latitude of shellfish closures. In general, these metrics of
bloom geographic extent did not correlate with the number of cysts in sediments following the
blooms (blooms → cysts). There are, however, significant positive correlations between 0-3 cm
cyst abundances and metrics of the preceding bloom that are indicative of bloom intensity or
vegetative cell abundance (e.g., cumulative shellfish toxicity, duration of detectable toxicity in
shellfish, and bloom termination date). These data suggest that it may be possible to use cyst
abundance to empirically forecast the geographic extent of the forthcoming bloom and,
conversely, to use other metrics from bloom and toxicity events to forecast the size of the
subsequent cyst population as the inoculum for the next year’s bloom. This is an important step
towards understanding the excystment/encystment cycle in A. fundyense bloom dynamics while
also augmenting our predictive capability for this HAB-forming species in the GOM.Research support provided by the ECOHAB
Grant program through NOAA Grants NA06NOS4780245 and NA09NOS4780193, and through the Woods Hole Center for Oceans and Human Health, National 1 Science Foundation (NSF)
Grants OCE-0430724, OCE-0911031, and OCE-1314642; and National Institute of
Environmental Health Sciences (NIEHS) Grants 1-P50-ES012742-01 and 1-P01-ES021923-01,
and funding through the states of ME, NH, and MA. We are also grateful for event response
funding provided for many of the cruises. Funding for J.L. Martin was provided by Fisheries and
Oceans Canada
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