7,490 research outputs found
Facilitating the exploitation of ERTS-1 imagery using snow enhancement techniques
The author has identified the following significant results. The applications of ERTS-1 imagery for geological fracture mapping regardless of season has been repeatedly confirmed. The enhancement provided by a differential cover of snow increases the number and length of fracture-lineaments which can be detected with ERTS-1 data and accelerates the fracture mapping process for a variety of practical applications. The geological mapping benefits of the program will be realized in geographic areas where data are most needed - complex glaciated terrain and areas of deep residual soils. ERTS-1 derived fracture-lineament maps which provide detail well in excess of existing geological maps are not available in the Massachusetts-Connecticut area. The large quantity of new data provided by ERTS-1 may accelerate and improve field mapping now in progress in the area. Numerous other user groups have requested data on the techniques. This represents a major change in operating philosophy for groups who to data judged that snow obscured geological detail
Application of EREP imagery to fracture-related mine safety hazards and environmental problems in mining
The author has identified the following significant results. All Skylab 2 imagery received to date has been analyzed manually and data related to fracture analysis and mined land inventories has been summarized on map-overlays. A comparison of the relative utility of the Skylab image products for fracture detection, soil tone/vegetation contrast mapping, and mined land mapping has been completed. Numerous fracture traces were detected on both color and black and white transparencies. Unique fracture trace data which will contribute to the investigator's mining hazards analysis were noted on the EREP imagery; these data could not be detected on ERTS-1 imagery or high altitude aircraft color infrared photography. Stream segments controlled by fractures or joint systems could be identified in more detail than with ERTS-1 imagery of comparable scale. ERTS-1 mine hazards products will be modified to demonstrate the value of this additional data. Skylab images were used successfully to update a mined land map of Indiana made in 1972. Changes in mined area as small as two acres can be identified. As the Energy Crisis increases the demand for coal, such demonstrations of the application of Skylab data to coal resources will take on new importance
Fracture mapping and strip mine inventory in the Midwest by using ERTS-1 imagery
Analysis of the ERTS-1 imagery and high-altitude infrared photography indicates that useful fracture data can be obtained in Indiana and Illinois despite a glacial till cover. ERTS MSS bands 5 and 7 have proven most useful for fracture mapping in coal-bearing rocks in this region. Preliminary results suggest a reasonable correlation between image-detected fractures and mine roof-fall accidents. Information related to surface mined land, such as disturbed area, water bodies, and kind of reclamation, has been derived from the analysis of ERTS imagery
Relationship of roof falls in underground coal mines to fractures mapped on ERTS-1 imagery
ERTS imagery is of unique value for mapping of certain fractures that are not identifiable on aircraft imagery. Because color infrared and ERTS imagery complement each other both sources of data were used to map fractures in western Indiana and eastern Illinois. In the Kings Station Mine, Gibson County, Indiana, most roof falls reported had occurred in areas where mapped fractures were closely spaced and intersecting. Using this information as a basis for extrapolation, roof fall hazard maps were prepared for other mine sites. Various coal resources programs related to energy and environment also were conducted
Magnetism in heavy-fermion U(Pt,Pd)3 studied by mSR
We report mSR experiments carried out on a series of heavy-electron
pseudobinary compounds U(Pt1-xPdx)3 (x<=0.05). For x<=0.005 the zero-field muon
depolarisation is described by the Kubo-Toyabe function. However the
temperature variation of the Kubo-Toyabe relaxation rate does not show any sign
of the small-moment antiferromagnetic phase with TN~6 K (signalled by neutron
diffraction), in contrast to previous reports. The failure to detect the small
ordered moment suggests it has a fluctuating (> 10 MHz) nature, which is
consistent with the interpretation of NMR data. For 0.01<=x<=0.05 the muon
depolarisation in the ordered state is described by two terms of equal
amplitude: an exponentially damped spontaneous oscillation and a Lorentzian
Kubo-Toyabe function. These terms are associated with antiferromagnetic order
with substantial moments. The Knight-shift measured in a magnetic field of 0.6
T on single-crystalline U(Pt0.95Pd0.05)3 in the paramagnetic state shows two
signals for B perpendicular to c, while only one signal is observed for B||c.
The observation of two signals for B perpendicular to c, while there is only
one muon localisation site (0,0,0), points to the presence of two spatially
distinct regions of different magnetic response.Comment: 25 pages including 12 figures (PS), J. Phys.: Condens. Matter, in
prin
Oocytes prevent cumulus cell apoptosis by maintaining a morphogenic paracrine gradient of bone morphogenetic proteins
© The Company of Biologists Ltd 2005Paracrine factors secreted by the oocyte regulate a broad range of cumulus cell functions. Characteristically, cumulus cells have a low incidence of apoptosis and we proposed that this is due to oocyte-secreted factors acting in an anti-apoptotic manner. Bovine cumulus-oocyte complexes (COC) were aspirated from abattoir-derived ovaries and oocytectomized (OOX) by microsurgical removal of the oocyte. OOX were treated with doses of either denuded oocytes (DO) or various growth factors for 24 hours (± rFSH; 0.1 IU/ml). Proportions of apoptotic cumulus cells were assessed using TUNEL and laser confocal scanning microscopy followed by image analysis. Quantification of Bcl-2 and Bax proteins in OOX was undertaken by western analysis. Oocyte removal led to a significant increase in cumulus cell apoptosis compared with COC controls (35% versus 9% TUNEL positive, respectively; P<0.001). Levels of OOX apoptosis were significantly reversed (P<0.001) in a dose-dependent manner when co-cultured with oocytes. Furthermore, the anti-apoptotic effect of oocyte-secreted factors followed a gradient from the site of the oocyte(s). Growth differentiation factor 9 (GDF9) had no significant effect on cumulus cell apoptosis. By contrast, cumulus cell apoptosis was significantly (P<0.001) reduced by bone morphogenetic proteins (BMP) 15, 6 or 7. Accordingly, levels of antiapoptotic Bcl-2 were high in OOX+DO and OOX+BMP15 and low with OOX+GDF9 or OOX alone, whereas the reverse was observed for pro-apoptotic Bax. DO, BMP15 and BMP6 were also able to protect cumulus cells from undergoing apoptosis induced by staurosporine. FSH partially prevented apoptosis in all treatment groups (P<0.001). Follistatin and a BMP6 neutralizing antibody, which antagonized the anti-apoptotic effects of BMP15 and BMP6, respectively, whether alone or combined, blocked ~50% of the anti-apoptotic actions of oocytes. These results are the first to demonstrate that oocyte-secreted factors, and particularly BMP15 and BMP6, maintain the low incidence of cumulus cell apoptosis by establishing a localized gradient of bone morphogenetic proteins.Tamer S. Hussein, David A. Froiland, Fred Amato, Jeremy G. Thompson and Robert B
The Anti-Coincidence Detector for the GLAST Large Area Telescope
This paper describes the design, fabrication and testing of the
Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope
(GLAST) Large Area Telescope (LAT). The ACD is LAT first-level defense against
the charged cosmic ray background that outnumbers the gamma rays by 3-5 orders
of magnitude. The ACD covers the top and 4 sides of the LAT tracking detector,
requiring a total active area of ~8.3 square meters. The ACD detector utilizes
plastic scintillator tiles with wave-length shifting fiber readout. In order to
suppress self-veto by shower particles at high gamma-ray energies, the ACD is
segmented into 89 tiles of different sizes. The overall ACD efficiency for
detection of singly charged relativistic particles entering the tracking
detector from the top or sides of the LAT exceeds the required 0.9997.Comment: 33 pages, 19 figure
Nonlinear Diffusive Shock Acceleration with Magnetic Field Amplification
We introduce a Monte Carlo model of nonlinear diffusive shock acceleration
allowing for the generation of large-amplitude magnetic turbulence. The model
is the first to include strong wave generation, efficient particle acceleration
to relativistic energies in nonrelativistic shocks, and thermal particle
injection in an internally self-consistent manner. We find that the upstream
magnetic field can be amplified by large factors and show that this
amplification depends strongly on the ambient Alfven Mach number. We also show
that in the nonlinear model large increases in the magnetic field do not
necessarily translate into a large increase in the maximum particle momentum a
particular shock can produce, a consequence of high momentum particles
diffusing in the shock precursor where the large amplified field converges to
the low ambient value. To deal with the field growth rate in the regime of
strong fluctuations, we extend to strong turbulence a parameterization that is
consistent with the resonant quasi-linear growth rate in the weak turbulence
limit. We believe our parameterization spans the maximum and minimum range of
the fluctuation growth and, within these limits, we show that the nonlinear
shock structure, acceleration efficiency, and thermal particle injection rates
depend strongly on the yet to be determined details of wave growth in strongly
turbulent fields. The most direct application of our results will be to
estimate magnetic fields amplified by strong cosmic-ray modified shocks in
supernova remnants.Comment: Accepted in ApJ July 2006, typos corrected in this versio
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