6,404 research outputs found
The George C. Davis Site, Cherokee County, Texas: Spring 1980 Archeological Investigations
The results of archeological investigations in portions of the George C. Davis Site are presented in this report prepared by Ross Fields and J. Peter Thurmond . Stringent contract requirements and the provisions of Texas Antiquities Permit No. 237 dictate that this report be brief and descriptive in nature. Requirements such as inclusion of a detailed site investigation history and environmental data were excluded and extensive excavations were stressed in preference to detailed analyses and comparisons. Field investigations were limited by contract to 20 working days and the analysis/write-up to 10 working days. The governing research design was prepared by the Texas Antiquities Committee staff to reflect agreements between the Committee and the Texas Forest Service. Sighificant findings include the general delineation of extensive, and in places intensive, Archaic and Late Prehistoric occupations. Of primary importance is the lack of an identifiable Alto Focus occupation within the northern portion of the Davis Site. This suggests that the small left bank tributary to Bowles Creek existed during Alto Focus times and served as a natural boundary for the village area during that period of site usage. There are hints that significant variations in the selection and use of lithic resources through time are identifiable. It is indeed ! unfortunate that time limitations precluded pursuit of this line of investigation. Ross and Pete have successfully accomplished a most challenging task under less than ideal conditions. They and their field crew are commended for their outstanding work at the Davis Site
Analyses of the cloud contents of multispectral imagery from LANDSAT 2: Mesoscale assessments of cloud and rainfall over the British Isles
The author has identified the following significant results. It was demonstrated that satellites with sufficiently high resolution capability in the visible region of the electromagnetic spectrum could be used to check the accuracy of estimates of total cloud amount assessed subjectively from the ground, and to reveal areas of performance in which corrections should be made. It was also demonstrated that, in middle latitude in summer, cloud shadow may obscure at least half as much again of the land surface covered by an individual LANDSAT frame as the cloud itself. That proportion would increase with latitude and/or time of year towards the winter solstice. Analyses of sample multispectral images for six different categories of clouds in summer revealed marked differences between the reflectance characteristics of cloud fields in the visible/near infrared region of the spectrum
New aperture photometry of QSO 0957+561; application to time delay and microlensing
We present a re-reduction of archival CCD frames of the doubly imaged quasar
0957+561 using a new photometry code. Aperture photometry with corrections for
both cross contamination between the quasar images and galaxy contamination is
performed on about 2650 R-band images from a five year period (1992-1997). From
the brightness data a time delay of 424.9 +/- 1.2 days is derived using two
different statistical techniques. The amount of gravitational microlensing in
the quasar light curves is briefly investigated, and we find unambiguous
evidence of both long term and short term microlensing. We also note the
unusual circumstance regarding time delay estimates for this gravitational
lens. Estimates by different observers from different data sets or even with
the same data sets give lag estimates differing by typically 8 days, and error
bars of only a day or two. This probably indicates several complexities where
the result of each estimate depends upon the details of the calculation.Comment: 14 pages, 16 figures (several in color
The Sensitivity of the Parkes Pulsar Timing Array to Individual Sources of Gravitational Waves
We present the sensitivity of the Parkes Pulsar Timing Array to gravitational
waves emitted by individual super-massive black-hole binary systems in the
early phases of coalescing at the cores of merged galaxies. Our analysis
includes a detailed study of the effects of fitting a pulsar timing model to
non-white timing residuals. Pulsar timing is sensitive at nanoHertz frequencies
and hence complementary to LIGO and LISA. We place a sky-averaged constraint on
the merger rate of nearby () black-hole binaries in the early phases
of coalescence with a chirp mass of 10^{10}\,\rmn{M}_\odot of less than one
merger every seven years. The prospects for future gravitational-wave astronomy
of this type with the proposed Square Kilometre Array telescope are discussed.Comment: fixed error in equation (4). [13 pages, 6 figures, 1 table, published
in MNRAS
Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)
\We present the sixth catalog of Kepler candidate planets based on nearly 4
years of high precision photometry. This catalog builds on the legacy of
previous catalogs released by the Kepler project and includes 1493 new Kepler
Objects of Interest (KOIs) of which 554 are planet candidates, and 131 of these
candidates have best fit radii <1.5 R_earth. This brings the total number of
KOIs and planet candidates to 7305 and 4173 respectively. We suspect that many
of these new candidates at the low signal-to-noise limit may be false alarms
created by instrumental noise, and discuss our efforts to identify such
objects. We re-evaluate all previously published KOIs with orbital periods of
>50 days to provide a consistently vetted sample that can be used to improve
planet occurrence rate calculations. We discuss the performance of our planet
detection algorithms, and the consistency of our vetting products. The full
catalog is publicly available at the NASA Exoplanet Archive.Comment: 18 pages, to be published in the Astrophysical Journal Supplement
Serie
Evaluation of ERTS imagery for spectral geological mapping in diverse terranes of New York State
Linear anomalies dominate the new geological information derived from ERTS-1 imagery, total lengths now exceeding 6000 km. Experimentation with a variety of viewing techniques suggests that conventional photogeologic analyses of band 7 results in the location of more than 97 percent of all linears found. The maxima on rose diagrams for ERTS-1 anomalies correspond well with those for mapped faults and topographic lineaments, despite a difference in relative magnitudes of maxima thought due to solar illumination direction. A multiscale analysis of linears showed that single topographic linears at 1:2,500,000 became segmented at 1:1,000,000, aligned zones of shorter parallel, en echelon, or conjugate linears at 1:500,000, and still shorter linears lacking obvious alignment at 1:250,000. Visible glacial features include individual drumlins, best seen in winter imagery, drumlinoids, eskers, ice-marginal drainage channels, glacial lake shorelines and sand plains, and end moraines
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