21,264 research outputs found
Use of infrared imagery in study of the San Andreas fault system, California
Airborne infrared imagery of San Andreas fault, Californi
Weight change across the start of three consecutive pregnancies and the risk of maternal morbidity and SGA birth at the second and third pregnancy
Funding: This work was funded by the Scottish Government's Rural and Environmental Science and Analytical Services Division (RESAS, Theme 7: Diet and Health). The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.Peer reviewedPublisher PD
Indefinitely Oscillating Martingales
We construct a class of nonnegative martingale processes that oscillate
indefinitely with high probability. For these processes, we state a uniform
rate of the number of oscillations and show that this rate is asymptotically
close to the theoretical upper bound. These bounds on probability and
expectation of the number of upcrossings are compared to classical bounds from
the martingale literature. We discuss two applications. First, our results
imply that the limit of the minimum description length operator may not exist.
Second, we give bounds on how often one can change one's belief in a given
hypothesis when observing a stream of data.Comment: ALT 2014, extended technical repor
Molecular astronomy of cool stars and sub-stellar objects
The optical and infrared spectra of a wide variety of `cool' astronomical
objects including the Sun, sunspots, K-, M- and S-type stars, carbon stars,
brown dwarfs and extrasolar planets are reviewed. The review provides the
necessary astronomical background for chemical physicists to understand and
appreciate the unique molecular environments found in astronomy. The
calculation of molecular opacities needed to simulate the observed spectral
energy distributions is discussed
Current research in oxidation-resistant carbon-carbon composites at NASA. Langley Research Center
The significant potential of carbon-carbon composites for high-temperature structural applications is well established. For hypersonic vehicle applications, desirable properties include low density, high specific strength and stiffness, low coefficients of thermal expansion, and retention of mechanical properties above 3000 F. A significant problem associated with carbon materials, however, is that they oxidize rapidly in air at temperatures above about 800 F, and therefore must be protected from oxidation. Successful development of effective methods of oxidation protection is key to the eventual utilization of carbon-carbon composites on hypersonic vehicles such as NASP. In this presentation, the basic elements of an oxidation-protection system are described. Results from oxidation-performance evaluations of state-of-the-art ACC-4 type material in simulated airframe vehicle environments (temperature, pressure, and time) conducted at NASA Langley are also presented. NASA Langley has an active research effort to improve the oxidation resistance of carbon-carbon materials for airframe structural and vehicle thermal protection applications. Conversion coating and sealant development research is highlighted
The Acraman impact and its widespread ejecta, South Australia
Discovery of a widespread horizon of shock-deformed volcaniclastic ejecta preserved in Late Proterozoic (approx. 600 Ma) shales in South Australia and its probable link to the Acraman impact structure in the Middle Proterozoic Gawler Range. Volcanics provide a rare opportunity to study the effects of a major terrestrial impact, including the sedimentology and distribution of an ejecta blanket and its precious-metal signature. The ejecta horizon occurs in the Bunyeroo Formation at many localities within the Adelaide Geosyncline, including the Wearing Hills, which are approx. 350 km northeast of the Acraman impact site. Following a search at the same stratigraphic level in other basins in South Australia, the ejecta has been located within the Lower Rodda beds of the Officer Basin, extending the limits of the ejecta to approx. 470 km northwest of the Acraman impact structure. The ejecta is therefore widely dispersed, and provides an important chronostratigraphic marker enabling precise correlation of Late Proterozoic sequences in southern Australia. In summary, the Bunyeroo ejecta is unique as the only known example of a widely dispersed, coarse-grained ejecta blanket that is, moreover, strongly linked to a known major impact structure. The marked Ir-PGE anomalies in the ejecta horizon provide support for the hypothesis that meteorite impact events can produce Ir anomalies interrestrial sediments. The findings also indicate that Ir can be mobilized and concentrated in sediments by low-temperature diagenetic processes. The identification of ejecta horizons in sedimentary rocks therefore should be based on the coincidence of shock-metamorphic features in the detritus and clear Ir anomalies
Adiabatic and Non-Adiabatic Contributions to the Free Energy from the Electron-Phonon Interaction for Na, K, Al, and Pb
We calculate the adiabatic contributions to the free energy due to the
electron--phonon interaction at intermediate temperatures, for the elemental metals Na, K, Al, and Pb. Using our
previously published results for the nonadiabatic contributions we show that
the adiabatic contribution, which is proportional to at low
temperatures and goes as at high temperatures, dominates the
nonadiabatic contribution for temperatures above a cross--over temperature,
, which is between 0.5 and 0.8 , where is the melting
temperature of the metal. The nonadiabatic contribution falls as for
temperatures roughly above the average phonon frequency.Comment: Updated versio
Effects of Negative Energy Components in the Constituent Quark Model
Relativistic covariance requires that in the constituent quark model for
mesons the positive energy states as well as the negative energy states are
included. Using relativistic quasi-potential equations the contribution of the
negative energy states is studied for the light and charmonium mesons. It is
found that these states change the meson mass spectrum significantly but leave
its global structure untouched.Comment: 14 pages revtex 3.0, 4 figures uudecoded attached in postscript
format, THU-93/1
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