2,838 research outputs found
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Magmatic Intrusions into the Sulfur-Rich Carmel Formation on the Colorado Plateau, USA: Implications for the Mars 2020 Mission
We report on basaltic dikes in the Colorado Plateau, which crosscut sulfate bearing sediments and compare this to Martian basalts and basaltic sediments in contact with sulfate mineralizations
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Alteration and Oxidiation of an Olivine Lamprophyre Dike from Southern Utah, USA: An Analog for Mars
We report on oxidized basaltic dike intrusions on the Colorado Plateau as analog for Martian basalt oxidation
An overview of Viscosity Solutions of Path-Dependent PDEs
This paper provides an overview of the recently developed notion of viscosity
solutions of path-dependent partial di erential equations. We start by a quick
review of the Crandall- Ishii notion of viscosity solutions, so as to motivate
the relevance of our de nition in the path-dependent case. We focus on the
wellposedness theory of such equations. In partic- ular, we provide a simple
presentation of the current existence and uniqueness arguments in the
semilinear case. We also review the stability property of this notion of
solutions, in- cluding the adaptation of the Barles-Souganidis monotonic scheme
approximation method. Our results rely crucially on the theory of optimal
stopping under nonlinear expectation. In the dominated case, we provide a
self-contained presentation of all required results. The fully nonlinear case
is more involved and is addressed in [12]
A new representation for non--local operators and path integrals
We derive an alternative representation for the relativistic non--local
kinetic energy operator and we apply it to solve the relativistic Salpeter
equation using the variational sinc collocation method. Our representation is
analytical and does not depend on an expansion in terms of local operators. We
have used the relativistic harmonic oscillator problem to test our formula and
we have found that arbitrarily precise results are obtained, simply increasing
the number of grid points. More difficult problems have also been considered,
observing in all cases the convergence of the numerical results. Using these
results we have also derived a new representation for the quantum mechanical
Green's function and for the corresponding path integral. We have tested this
representation for a free particle in a box, recovering the exact result after
taking the proper limits, and we have also found that the application of the
Feynman--Kac formula to our Green's function yields the correct ground state
energy. Our path integral representation allows to treat hamiltonians
containing non--local operators and it could provide to the community a new
tool to deal with such class of problems.Comment: 9 pages ; 1 figure ; refs added ; title modifie
Impacts of Recent Mill Closures and Potential Biofuels Development on Maine’s Forest Products Industry
The economic contributions of a sector (i.e., employment, output, value added) are a measure of how money from that sector moves about a regional economy. Using 2014 estimates of economic contributions from the forest product industry in Maine, we estimate the 2016 contribution by considering the impacts from several recent mill closures (five pulp/paper, two bioelectric). The loss of these mills, particularly paper mills, reduces the economic contributions of the forest products industry relative to the state economy and distorts markets for low-value wood. We also explore a prospective opportunity to revive low-value wood markets by modeling the economic impacts from a hypothetical colocated biorefinery, where wood chips are turned into advanced fuels and chemical coproducts. The dollar value of economic impacts from such an investment are small relative to the total industry, but they may prove significant for some rural communities
Toddler-Inspired Visual Object Learning
Real-world learning systems have practical limitations on the quality and quantity of the training datasets that they can collect and consider. How should a system go about choosing a subset of the possible training examples that still allows for learning accurate, generalizable models? To help address this question, we draw inspiration from a highly efficient practical learning system: the human child. Using head-mounted cameras, eye gaze trackers, and a model of foveated vision, we collected first-person (egocentric) images that represents a highly accurate approximation of the "training data" that toddlers' visual systems collect in everyday, naturalistic learning contexts. We used state-of-the-art computer vision learning models (convolutional neural networks) to help characterize the structure of these data, and found that child data produce significantly better object models than egocentric data experienced by adults in exactly the same environment. By using the CNNs as a modeling tool to investigate the properties of the child data that may enable this rapid learning, we found that child data exhibit a unique combination of quality and diversity, with not only many similar large, high-quality object views but also a greater number and diversity of rare views. This novel methodology of analyzing the visual "training data" used by children may not only reveal insights to improve machine learning, but also may suggest new experimental tools to better understand infant learning in developmental psychology
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Magmatic intrusions into sulfur-rich sediments on the Colorado Plateau: an analog for Mars exploration
Mafic magmatism is a prevalent geologic process on Earth, and is a principal source of subsurface geologic change and energy influx on postNoachian Mars. While rare on Earth, the intrusion of mafic magmas into sulfur-rich soils and rocks is expected on Mars due to the observation of widespread high sulfur concentrations in Martian soils. On Mars, soils have been found to be rich in sulfur. Respectively, soil samples from Gusev Crater and Gale Crater contain between 4-8 weight percent, and 4-7 weight percent SO3, though ammounts[sic] as high as 31 weight percent have been measured in Gusev crater. With widespread sulfur-rich sediments and evidence of magmatism both ancient and young, mafic intrusions into rocks and sediments bearing significant quantities of sulfur species is expected on Mars. Processes associated with the magmatic intrusion of a sulfur-rich host, including degassing and alteration, may provide the requisite energy and nutrients for biological activity.On Earth, well exposed mafic dikes intrude the sulfur-rich sedimentary formations of the Jurassic San Rafael Group. Approximately 200 dikes, sills, and breccias can be found in proximity to the San Rafael Swell in Utah, and represent an Earth analog for a scenario of mafic magma intruding sulfur-rich sediments. Here we will investigate such an analog; a mafic dike intruding the sulfur-rich Jurassic Carmel Formation of the San Rafael Group
Dynamical response of the "GGG" rotor to test the Equivalence Principle: theory, simulation and experiment. Part I: the normal modes
Recent theoretical work suggests that violation of the Equivalence Principle
might be revealed in a measurement of the fractional differential acceleration
between two test bodies -of different composition, falling in the
gravitational field of a source mass- if the measurement is made to the level
of or better. This being within the reach of ground based
experiments, gives them a new impetus. However, while slowly rotating torsion
balances in ground laboratories are close to reaching this level, only an
experiment performed in low orbit around the Earth is likely to provide a much
better accuracy.
We report on the progress made with the "Galileo Galilei on the Ground" (GGG)
experiment, which aims to compete with torsion balances using an instrument
design also capable of being converted into a much higher sensitivity space
test.
In the present and following paper (Part I and Part II), we demonstrate that
the dynamical response of the GGG differential accelerometer set into
supercritical rotation -in particular its normal modes (Part I) and rejection
of common mode effects (Part II)- can be predicted by means of a simple but
effective model that embodies all the relevant physics. Analytical solutions
are obtained under special limits, which provide the theoretical understanding.
A simulation environment is set up, obtaining quantitative agreement with the
available experimental data on the frequencies of the normal modes, and on the
whirling behavior. This is a needed and reliable tool for controlling and
separating perturbative effects from the expected signal, as well as for
planning the optimization of the apparatus.Comment: Accepted for publication by "Review of Scientific Instruments" on Jan
16, 2006. 16 2-column pages, 9 figure
The Cosmological Time Function
Let be a time oriented Lorentzian manifold and the Lorentzian
distance on . The function is the cosmological
time function of , where as usual means that is in the causal
past of . This function is called regular iff for all
and also along every past inextendible causal curve. If the
cosmological time function of a space time is regular it has
several pleasant consequences: (1) It forces to be globally hyperbolic,
(2) every point of can be connected to the initial singularity by a
rest curve (i.e., a timelike geodesic ray that maximizes the distance to the
singularity), (3) the function is a time function in the usual sense, in
particular (4) is continuous, in fact locally Lipschitz and the second
derivatives of exist almost everywhere.Comment: 19 pages, AEI preprint, latex2e with amsmath and amsth
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