1,198 research outputs found
Using airborne LiDAR Survey to explore historic-era archaeological landscapes of Montserrat in the eastern Caribbean
This article describes what appears to be the first archaeological application of airborne LiDAR survey to historic-era landscapes in the Caribbean archipelago, on the island of Montserrat. LiDAR is proving invaluable in extending the reach of traditional pedestrian survey into less favorable areas, such as those covered by dense neotropical forest and by ashfall from the past two decades of active eruptions by the Soufrière Hills volcano, and to sites in localities that are inaccessible on account of volcanic dangers. Emphasis is placed on two aspects of the research: first, the importance of ongoing, real-time interaction between the LiDAR analyst and the archaeological team in the field; and second, the advantages of exploiting the full potential of the three-dimensional LiDAR point cloud data for purposes of the visualization of archaeological sites and features
Field Studies of Crater Gradation in Gusev Crater and Meridiani Planum Using the Mars Exploration Rovers
The Mars Exploration Rovers Spirit and Opportunity investigated numerous craters since landing in Gusev crater (14.569degS, 175.473degE) and Meridiani Planum (1.946degS, 354.473degE) over the first 400 sols of their missions [1-4]. Craters at both sites are simple structures and vary in size and preservation state. Comparing observed and expected pristine morphology and using process-specific gradational signatures around terrestrial craters as a template [5-7] allows distinguishing gradation processes whose relative importance fundamentally differs from those responsible for most crater modification on the Earth
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Insights into the subsurface structure of the Caloris basin, Mercury, from assessments of mechanical layering and changes in long-wavelength topography
The volcanic plains that fill the Caloris basin, the largest recognized impact basin on Mercury, are deformed by many graben and wrinkle ridges, among which the multitude of radial graben of Pantheon Fossae allow us to resolve variations in the depth extent of associated faulting. Displacement profiles and displacement-to-length scaling both indicate that faults near the basin center are confined to a ~ 4-km-thick mechanical layer, whereas faults far from the center penetrate more deeply. The fault scaling also indicates that the graben formed in mechanically strong material, which we identify with dry basalt-like plains. These plains were also affected by changes in long-wavelength topography, including undulations with wavelengths of up to 1300 km and amplitudes of 2.5 to 3 km. Geographic correlation of the depth extent of faulting with topographic variations allows a first-order interpretation of the subsurface structure and mechanical stratigraphy in the basin. Further, crosscutting and superposition relationships among plains, faults, craters, and topography indicate that development of long-wavelength topographic variations followed plains emplacement, faulting, and much of the cratering within the Caloris basin. As several examples of these topographic undulations are also found outside the basin, our results on the scale, structural style, and relative timing of the topographic changes have regional applicability and may be the surface expression of global-scale interior processes on Mercury
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Insights into the subsurface structure of the Caloris basin, Mercury, from assessments of mechanical layering and changes in long-wavelength topography
The volcanic plains that fill the Caloris basin, the largest recognized impact basin on Mercury, are deformed by many graben and wrinkle ridges, among which the multitude of radial graben of Pantheon Fossae allow us to resolve variations in the depth extent of associated faulting. Displacement profiles and displacement-to-length scaling both indicate that faults near the basin center are confined to a ~ 4-km-thick mechanical layer, whereas faults far from the center penetrate more deeply. The fault scaling also indicates that the graben formed in mechanically strong material, which we identify with dry basalt-like plains. These plains were also affected by changes in long-wavelength topography, including undulations with wavelengths of up to 1300 km and amplitudes of 2.5 to 3 km. Geographic correlation of the depth extent of faulting with topographic variations allows a first-order interpretation of the subsurface structure and mechanical stratigraphy in the basin. Further, crosscutting and superposition relationships among plains, faults, craters, and topography indicate that development of long-wavelength topographic variations followed plains emplacement, faulting, and much of the cratering within the Caloris basin. As several examples of these topographic undulations are also found outside the basin, our results on the scale, structural style, and relative timing of the topographic changes have regional applicability and may be the surface expression of global-scale interior processes on Mercury
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Deployment of Innovative Characterization Technologies and Implementation of the Marssim Process at Radiologically Contaminated Sites.
The success of this Accelerated Site Technology Deployment (ASTD) project is measured on several levels. First, the deployment of this innovative approach using in situ characterization, portable field laboratory measurements, and implementation of MARSSIM was successfully established for all three phases of D and D characterization, i.e., pre-job scoping, on-going disposition of waste, and final status surveys upon completion of the activity. Unlike traditional D and D projects, since the Brookhaven Graphite Research Reactor Decommissioning Project (BGRR-DP) is operating on an accelerated schedule, much of the work is being carried out simultaneously. Rather than complete a full characterization of the facility before D and D work begins, specific removal actions require characterization as the activity progresses. Thus, the need for rapid and cost-effective techniques for characterization is heightened. Secondly, since the approach used for this ASTD project was not thoroughly proven prior to deployment, a large effort was devoted to demonstrating technical comparability to project managers, regulators and stakeholders. During the initial phases, large numbers of replicate samples were taken and analyzed by conventional baseline techniques to ensure that BGRR-DP quality assurance standards were met. ASTD project staff prepared comparisons of data gathered using ISOCS and BetaScint with traditional laboratory methods and presented this information to BGRR-DP staff and regulators from EPA Region II, NYS Department of Environmental Conservation, and the Suffolk County Board of Health. As the results of comparability evaluations became available, approval for these methods was received and the techniques associated with in situ characterization, portable field laboratory measurements, and implementation of MARSSIM were gradually integrated into BGRR-DP procedures
PSRs J0248+6021 and J2240+5832: Young Pulsars in the Northern Galactic Plane. Discovery, Timing, and Gamma-ray observations
Pulsars PSR J0248+6021 (rotation period P=217 ms and spin-down power Edot =
2.13E35 erg/s) and PSR J2240+5832 (P=140 ms, Edot = 2.12E35 erg/s) were
discovered in 1997 with the Nancay radio telescope during a northern Galactic
plane survey, using the Navy-Berkeley Pulsar Processor (NBPP) filter bank. GeV
gamma-ray pulsations from both were discovered using the Fermi Large Area
Telescope. Twelve years of radio and polarization data allow detailed
investigations. The two pulsars resemble each other both in radio and in
gamma-ray data. Both are rare in having a single gamma-ray pulse offset far
from the radio peak. The high dispersion measure for PSR J0248+6021 (DM = 370
pc cm^-3) is most likely due to its being within the dense, giant HII region W5
in the Perseus arm at a distance of 2 kpc, not beyond the edge of the Galaxy as
obtained from models of average electron distributions. Its high transverse
velocity and the low magnetic field along the line-of-sight favor this small
distance. Neither gamma-ray, X-ray, nor optical data yield evidence for a
pulsar wind nebula surrounding PSR J0248+6021. The gamma-ray luminosity for PSR
J0248+6021 is L_ gamma = (1.4 \pm 0.3)\times 10^34 erg/s. For PSR J2240+5832,
we find either L_gamma = (7.9 \pm 5.2) \times 10^34 erg/s if the pulsar is in
the Outer arm, or L_gamma = (2.2 \pm 1.7) \times 10^34 erg/s for the Perseus
arm. These luminosities are consistent with an L_gamma ~ sqrt(Edot) rule.
Comparison of the gamma-ray pulse profiles with model predictions, including
the constraints obtained from radio polarization data, favor emission in the
far magnetosphere. These two pulsars differ mainly in their inclination angles
and acceleration gap widths, which in turn explains the observed differences in
the gamma-ray peak widths.Comment: 13 pages, Accepted to Astronomy & Astrophysic
Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. I. Crowded Field Photometry and Cluster Fiducial Sequences in ugriz
We present photometry for globular and open cluster stars observed with the
Sloan Digital Sky Survey (SDSS). In order to exploit over 100 million stellar
objects with r < 22.5 mag observed by SDSS, we need to understand the
characteristics of stars in the SDSS ugriz filters. While star clusters provide
important calibration samples for stellar colors, the regions close to globular
clusters, where the fraction of field stars is smallest, are too crowded for
the standard SDSS photometric pipeline to process. To complement the SDSS
imaging survey, we reduce the SDSS imaging data for crowded cluster fields
using the DAOPHOT/ALLFRAME suite of programs and present photometry for 17
globular clusters and 3 open clusters in a SDSS value-added catalog. Our
photometry and cluster fiducial sequences are on the native SDSS 2.5-meter
ugriz photometric system, and the fiducial sequences can be directly applied to
the SDSS photometry without relying upon any transformations. Model photometry
for red giant branch and main-sequence stars obtained by Girardi et al. cannot
be matched simultaneously to fiducial sequences; their colors differ by
~0.02-0.05 mag. Good agreement (< ~0.02 mag in colors) is found with Clem et
al. empirical fiducial sequences in u'g'r'i'z' when using the transformation
equations in Tucker et al.Comment: 30 pages, 25 figures. Accepted for publication in ApJS. Version with
high resolution figures available at
http://www.astronomy.ohio-state.edu/~deokkeun/AnJohnson.pd
Uwe boxed: Empowering students in the ‘real world’-providing responsible research and innovation opportunities through the boxed project
© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. The Faculty of Health and Applied Sciences at the University of the West of England, Bristol has been piloting a schools outreach project entitled BoxED (EDucation in a Box) since 2015. School activities are inspired from the research and teaching of our academics, and the BoxED team have developed a series of hour long activities, linked to the national curriculum, which are delivered in schools across the south-west region. Alongside the somewhat obvious benefits to school pupils, this project presents numerous opportunities and benefits for our students to develop ‘real-world’ skills, enabling them to successfully enter the employment market on graduating from their studies. The challenge now is to ensure the success can be built upon by securing future funding to enable a greater number of students the opportunity to engage with the project and they themselves to then develop those necessary enterprise and entrepreneurial skills appropriately, alongside their chosen subject of study-ready for the ‘real-world’
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