3,427 research outputs found
Test-Hole Exploration for Light-Firing Clay in Cloud and Ellsworth Counties, Kansas
In two areas in Kansas (Ellsworth County, sec. 25, T. 15 S., R. 7 W., and Cloud County, sec. 12, T. 8 S., R. 2 W.) the Dakota Formation was systematically drilled to determine the availability of light-color-burning clay. Beds of light-burning clay lack continuity in Cloud County in the upper part of the Dakota; however, in the Ellsworth County area the lower part of the formation contains well-defined, continuous layers of light-burning clay. The lack of continuity of one and the well-defined continuity of the other is not confined to the test localities but extends over areas of several square miles. These conditions are not typical of clays in these two stratigraphic positions, but they illustrate the extreme variations in extent and continuity of beds that can be expected in the commercial exploitation of clays in either the upper or lower beds of the formation. Both test areas have clay deposits suitable for structural clay products
Newtonian and General Relativistic Models of Spherical Shells
A family of spherical shells with varying thickness is derived by using a
simple Newtonian potential-density pair. Then, a particular isotropic form of a
metric in spherical coordinates is used to construct a General Relativistic
version of the Newtonian family of shells. The matter of these relativistic
shells presents equal azimuthal and polar pressures, while the radial pressure
is a constant times the tangential pressure. We also make a first study of
stability of both the Newtonian and relativistic families of shells.Comment: 13 pages, 5 figures, accepted for publication in MNRA
Test-Hole Exploration for Light-Firing Clay in Cloud and Ellsworth Counties, Kansas
In two areas in Kansas (Ellsworth County, sec. 25, T. 15 S., R. 7 W., and Cloud County, sec. 12, T. 8 S., R. 2 W.) the Dakota Formation was systematically drilled to determine the availability of light-color-burning clay. Beds of light-burning clay lack continuity in Cloud County in the upper part of the Dakota; however, in the Ellsworth County area the lower part of the formation contains well-defined, continuous layers of light-burning clay. The lack of continuity of one and the well-defined continuity of the other is not confined to the test localities but extends over areas of several square miles. These conditions are not typical of clays in these two stratigraphic positions, but they illustrate the extreme variations in extent and continuity of beds that can be expected in the commercial exploitation of clays in either the upper or lower beds of the formation. Both test areas have clay deposits suitable for structural clay products
Collisional dynamics around binary black holes in galactic centers
We follow the sinking of two massive black holes in a spherical stellar
system where the black holes become bound under the influence of dynamical
friction. Once bound, the binary hardens by three-body encounters with
surrounding stars. We find that the binary wanders inside the core, providing
an enhanced supply of reaction partners for the hardening. The binary evolves
into a highly eccentric orbit leading to coalescence well beyond a Hubble time.
These are the first results from a hybrid ``self consistent field'' (SCF) and
direct Aarseth N-body integrator (NBODY6), which combines the advantages of the
direct force calculation with the efficiency of the field method. The code is
designed for use on parallel architectures and is therefore applicable to
collisional N-body integrations with extraordinarily large particle numbers (>
10^5). This creates the possibility of simulating the dynamics of both globular
clusters with realistic collisional relaxation and stellar systems surrounding
supermassive black holes in galactic nuclei.Comment: 38 pages, 13 figures, submitted to ApJ, accepted, revised text and
added figure
The possible origin of the faint fuzzy star clusters in NGC 1023
In the lenticular galaxy NGC 1023 a new population of star clusters (``faint
fuzzies'') was recently discovered by Larsen & Brodie. These clusters are found
inside the disc and are faint (23 < V < 24 mag) and extended with effective
radii of r_eff approx. 7 to 15 pc. We present here N-body calculations of a
likely formation-scenario through merging star clusters in clusters of star
clusters (super-clusters). Such super-clusters are observed to form in
interacting galaxies. The resulting merger objects have masses comparable to
the ``faint fuzzies'' and show large effective radii (r_eff > 7 pc). Even
though these objects are suffering from strong tidal forces they are able to
survive and reach the estimated ages of the extended star clusters in NGC 1023.Comment: 19 pages, 12 figures, accepted by A
The Orbiter Stability Experiment on STS-40
The Orbiter Stability Experiment (OSE) was developed to evaluate the steadiness of the STS Orbiter as a potential platform for instrumentation that would image the Sun in its extreme ultraviolet and soft X-ray radiations. We were interested in any high frequency motions of the Orbiter's orientation due to normal operations and manned activities. Preliminary results are presented of the observations. Other than the expected slow motion of the Orbiter within the specified angular deadband of 0.1 degrees during the observations, it was found that high frequency (above 1 Hz) angular motions (jitter) were not detectable at the 0.25 arc sec detection limit of the most sensitive detector, for most of the period of observation. No high frequency motions were recorded during intervals that were identified with vernier thruster firings. However, one short interval with detectable spectral power to a frequency of 10 Hz has been found to date. It has not yet been correlated with a particular activity going on at the time. The results of the observations may also be of value in assessing perturbations to the Orbiter's micro-gravity environment produced by normal operations
Electron-phonon interaction at the Be(0001) surface
We present a first principle study of the electron-phonon (e-p) interaction
at the Be(0001) surface. The real and imaginary part of the e-p self energy are
calculated for the surface state in the binding energy range from the
point to the Fermi level. Our calculation shows an overall good
agreement with several photoemission data measured at high and low
temperatures. Additionally, we show that the energy derivative of real part of
the self-energy presents a strong temperature and energy variation close to
, making it difficult to measure its value just at .Comment: Accepted in Phys. Rev. Lett., 5 figure
Understanding uncertainty in temperature effects on vector-borne disease: A Bayesian approach
Extrinsic environmental factors influence the distribution and population
dynamics of many organisms, including insects that are of concern for human
health and agriculture. This is particularly true for vector-borne infectious
diseases, like malaria, which is a major source of morbidity and mortality in
humans. Understanding the mechanistic links between environment and population
processes for these diseases is key to predicting the consequences of climate
change on transmission and for developing effective interventions. An important
measure of the intensity of disease transmission is the reproductive number
. However, understanding the mechanisms linking and temperature, an
environmental factor driving disease risk, can be challenging because the data
available for parameterization are often poor. To address this we show how a
Bayesian approach can help identify critical uncertainties in components of
and how this uncertainty is propagated into the estimate of . Most
notably, we find that different parameters dominate the uncertainty at
different temperature regimes: bite rate from 15-25 C; fecundity across
all temperatures, but especially 25-32 C; mortality from
20-30 C; parasite development rate at 15-16C and again at
33-35C. Focusing empirical studies on these parameters and
corresponding temperature ranges would be the most efficient way to improve
estimates of . While we focus on malaria, our methods apply to improving
process-based models more generally, including epidemiological, physiological
niche, and species distribution models.Comment: 27 pages, including 1 table and 3 figure
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