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Sample records for excursion set model

  1. Excursion set peaks: a self-consistent model of dark halo abundances and clustering

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Sheth, Ravi K.; Desjacques, Vincent

    2013-05-01

    We describe how to extend the excursion set peaks framework so that its predictions of dark halo abundances and clustering can be compared directly with simulations. These extensions include: a halo mass definition which uses the TopHat filter in real space; the mean dependence of the critical density for collapse δc on halo mass m; and the scatter around this mean value. All three of these are motivated by the physics of triaxial rather than spherical collapse. A comparison of the resulting mass function with N-body results shows that, if one uses δc(m) and its scatter as determined from simulations, then all three are necessary ingredients for obtaining ˜10 per cent accuracy. For example, assuming a constant value of δc with no scatter, as motivated by the physics of spherical collapse, leads to many more massive haloes than seen in simulations. The same model is also in excellent agreement with N-body results for the linear halo bias, especially at the high mass end where the traditional peak-background split argument applied to the mass function fit is known to underpredict the measured bias by ˜10 per cent. In the excursion set language, our model is about walks centred on special positions (peaks) in the initial conditions - we discuss what it implies for the usual calculation in which all walks contribute to the statistics.

  2. Excursion-Set-Mediated Genetic Algorithm

    NASA Technical Reports Server (NTRS)

    Noever, David; Baskaran, Subbiah

    1995-01-01

    Excursion-set-mediated genetic algorithm (ESMGA) is embodiment of method of searching for and optimizing computerized mathematical models. Incorporates powerful search and optimization techniques based on concepts analogous to natural selection and laws of genetics. In comparison with other genetic algorithms, this one achieves stronger condition for implicit parallelism. Includes three stages of operations in each cycle, analogous to biological generation.

  3. Peaks theory and the excursion set approach

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Sheth, Ravi K.

    2012-11-01

    We describe a model of dark matter halo abundances and clustering which combines the two most widely used approaches to this problem: that based on peaks and the other based on excursion sets. Our approach can be thought of as addressing the cloud-in-cloud problem for peaks and/or modifying the excursion set approach so that it averages over a special subset, rather than all possible walks. In this respect, it seeks to account for correlations between steps in the walk as well as correlations between walks. We first show how the excursion set and peaks models can be written in the same formalism, and then use this correspondence to write our combined excursion set peaks model. We then give simple expressions for the mass function and bias, showing that even the linear halo bias factor is predicted to be k-dependent as a consequence of the non-locality associated with the peak constraint. At large masses, our model has little or no need to rescale the variable δc from the value associated with spherical collapse, and suggests a simple explanation for why the linear halo bias factor appears to lie above that based on the peak-background split at high masses when such a rescaling is assumed. Although we have concentrated on peaks, our analysis is more generally applicable to other traditionally single-scale analyses of large-scale structure.

  4. An Excursion Set Model of the Cosmic Web: the Abundance of Sheets, Filaments And Halos

    SciTech Connect

    Shen, Jiajian; Abel, Tom; Mo, Houjun; Sheth, Ravi; /Pennsylvania U.

    2006-01-11

    We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular {Lambda}CDM model, our analysis suggests that more than 99% of the mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than 10{sup 10}M{sub {circle_dot}} at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure.

  5. An excursion-set model for the structure of giant molecular clouds and the interstellar medium

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2012-07-01

    The interstellar medium (ISM) is governed by supersonic turbulence on a range of scales. We use this simple fact to develop a rigorous excursion-set model for the formation, structure and time evolution of dense gas structures [e.g. giant molecular clouds (GMCs), massive clumps and cores]. Supersonic turbulence drives the density distribution in non-self-gravitating regions to a lognormal with dispersion increasing with Mach number. We generalize this to include scales ≳h (the disc scale-height), and use it to construct the statistical properties of the density field smoothed on a scale R. We then compare conditions for self-gravitating collapse including thermal, turbulent and rotational (disc shear) support (reducing to the Jeans/Toomre criterion on small/large scales). We show that this becomes a well-defined barrier crossing problem. As such, an exact 'bound object mass function' can be derived, from scales of the sonic length to well above the disc Jeans mass. This agrees remarkably well with observed GMC mass functions in the Milky Way and other galaxies, with the only inputs being the total mass and size of the galaxies (to normalize the model). This explains the cut-off of the mass function and its power-law slope (close to, but slightly shallower than, -2). The model also predicts the linewidth-size and size-mass relations of clouds and the dependence of residuals from these relations on mean surface density/pressure, in excellent agreement with observations. We use this to predict the spatial correlation function/clustering of clouds and, by extension, star clusters; these also agree well with observations. We predict the size/mass function of 'bubbles' or 'holes' in the ISM, and show that this can account for the observed H I hole distribution without requiring any local feedback/heating sources. We generalize the model to construct time-dependent 'merger/fragmentation trees' which can be used to follow cloud evolution and construct semi

  6. Non-Gaussianity and Excursion Set Theory: Halo Bias

    SciTech Connect

    Adshead, Peter; Baxter, Eric J.; Dodelson, Scott; Lidz, Adam

    2012-09-01

    We study the impact of primordial non-Gaussianity generated during inflation on the bias of halos using excursion set theory. We recapture the familiar result that the bias scales as $k^{-2}$ on large scales for local type non-Gaussianity but explicitly identify the approximations that go into this conclusion and the corrections to it. We solve the more complicated problem of non-spherical halos, for which the collapse threshold is scale dependent.

  7. Halo bias in the excursion set approach with correlated steps

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Sheth, Ravi K.

    2012-01-01

    In the excursion set approach, halo abundances and clustering are closely related. This relation is exploited in many modern methods which seek to constrain cosmological parameters on the basis of the observed spatial distribution of clusters. However, to obtain analytic expressions for these quantities, most excursion-set-based predictions ignore the fact that, although different k modes in the initial Gaussian field are uncorrelated, this is not true in real space: the values of the density field at a given spatial position, when smoothed on different real-space scales, are correlated in a non-trivial way. We show that when the excursion set approach is extended to include such correlations, then one must be careful to account for the fact that the associated prediction for halo bias is explicitly a real-space quantity. Therefore, care must be taken while comparing the predictions of this approach with measurements in simulations, which are typically made in Fourier space. We show how to correct for this effect, and demonstrate that ignorance of this effect in recent analyses of halo bias has led to incorrect conclusions and biased constraints.

  8. Scale-dependent halo bias in the excursion set approach

    NASA Astrophysics Data System (ADS)

    Musso, Marcello; Paranjape, Aseem; Sheth, Ravi K.

    2012-12-01

    If one accounts for correlations between scales, then non-local, k-dependent halo bias is part and parcel of the excursion set approach, and hence of halo model predictions for galaxy bias. We present an analysis that distinguishes between a number of different effects, each of which contributes to scale-dependent bias in real space. We show how to isolate these effects and remove the scale dependence, order by order, by cross-correlating the halo field with suitably transformed versions of the mass field. These transformations may be thought of as simple one-point, two-scale measurements that allow one to estimate quantities which are usually constrained using n-point statistics. As part of our analysis, we present a simple analytic approximation for the first-crossing distribution of walks with correlated steps which are constrained to pass through a specified point, and demonstrate its accuracy. Although we concentrate on non-linear, non-local bias with respect to a Gaussian random field, we show how to generalize our analysis to more general fields.

  9. Excursion sets and non-Gaussian void statistics

    NASA Astrophysics Data System (ADS)

    D'Amico, Guido; Musso, Marcello; Noreña, Jorge; Paranjape, Aseem

    2011-01-01

    Primordial non-Gaussianity (NG) affects the large scale structure (LSS) of the Universe by leaving an imprint on the distribution of matter at late times. Much attention has been focused on using the distribution of collapsed objects (i.e. dark matter halos and the galaxies and galaxy clusters that reside in them) to probe primordial NG. An equally interesting and complementary probe however is the abundance of extended underdense regions or voids in the LSS. The calculation of the abundance of voids using the excursion set formalism in the presence of primordial NG is subject to the same technical issues as the one for halos, which were discussed e.g. in Ref. [G. D’Amico, M. Musso, J. Noreña, and A. Paranjape, arXiv:1005.1203.]. However, unlike the excursion set problem for halos which involved random walks in the presence of one barrier δc, the void excursion set problem involves two barriers δv and δc. This leads to a new complication introduced by what is called the “void-in-cloud” effect discussed in the literature, which is unique to the case of voids. We explore a path integral approach which allows us to carefully account for all these issues, leading to a rigorous derivation of the effects of primordial NG on void abundances. The void-in-cloud issue, in particular, makes the calculation conceptually rather different from the one for halos. However, we show that its final effect can be described by a simple yet accurate approximation. Our final void abundance function is valid on larger scales than the expressions of other authors, while being broadly in agreement with those expressions on smaller scales.

  10. Excursion sets and non-Gaussian void statistics

    SciTech Connect

    D'Amico, Guido; Musso, Marcello; Paranjape, Aseem; Norena, Jorge

    2011-01-15

    Primordial non-Gaussianity (NG) affects the large scale structure (LSS) of the Universe by leaving an imprint on the distribution of matter at late times. Much attention has been focused on using the distribution of collapsed objects (i.e. dark matter halos and the galaxies and galaxy clusters that reside in them) to probe primordial NG. An equally interesting and complementary probe however is the abundance of extended underdense regions or voids in the LSS. The calculation of the abundance of voids using the excursion set formalism in the presence of primordial NG is subject to the same technical issues as the one for halos, which were discussed e.g. in Ref. [51][G. D'Amico, M. Musso, J. Norena, and A. Paranjape, arXiv:1005.1203.]. However, unlike the excursion set problem for halos which involved random walks in the presence of one barrier {delta}{sub c}, the void excursion set problem involves two barriers {delta}{sub v} and {delta}{sub c}. This leads to a new complication introduced by what is called the 'void-in-cloud' effect discussed in the literature, which is unique to the case of voids. We explore a path integral approach which allows us to carefully account for all these issues, leading to a rigorous derivation of the effects of primordial NG on void abundances. The void-in-cloud issue, in particular, makes the calculation conceptually rather different from the one for halos. However, we show that its final effect can be described by a simple yet accurate approximation. Our final void abundance function is valid on larger scales than the expressions of other authors, while being broadly in agreement with those expressions on smaller scales.

  11. The excursion set approach in non-Gaussian random fields

    NASA Astrophysics Data System (ADS)

    Musso, Marcello; Sheth, Ravi K.

    2014-04-01

    Insight into a number of interesting questions in cosmology can be obtained by studying the first crossing distributions of physically motivated barriers by random walks with correlated steps: higher mass objects are associated with walks that cross the barrier in fewer steps. We write the first crossing distribution as a formal series, ordered by the number of times a walk upcrosses the barrier. Since the fraction of walks with many upcrossings is negligible if the walk has not taken many steps, the leading order term in this series is the most relevant for understanding the massive objects of most interest in cosmology. For walks associated with Gaussian random fields, this first term only requires knowledge of the bivariate distribution of the walk height and slope, and provides an excellent approximation to the first crossing distribution for all barriers and smoothing filters of current interest. We show that this simplicity survives when extending the approach to the case of non-Gaussian random fields. For non-Gaussian fields which are obtained by deterministic transformations of a Gaussian, the first crossing distribution is simply related to that for Gaussian walks crossing a suitably rescaled barrier. Our analysis shows that this is a useful way to think of the generic case as well. Although our study is motivated by the possibility that the primordial fluctuation field was non-Gaussian, our results are general. In particular, they do not assume the non-Gaussianity is small, so they may be viewed as the solution to an excursion set analysis of the late-time, non-linear fluctuation field rather than the initial one. They are also useful for models in which the barrier height is determined by quantities other than the initial density, since most other physically motivated variables (such as the shear) are usually stochastic and non-Gaussian. We use the Lognormal transformation to illustrate some of our arguments.

  12. STATISTICS OF DARK MATTER HALOS FROM THE EXCURSION SET APPROACH

    SciTech Connect

    Lapi, A.; Salucci, P.; Danese, L.

    2013-08-01

    We exploit the excursion set approach in integral formulation to derive novel, accurate analytic approximations of the unconditional and conditional first crossing distributions for random walks with uncorrelated steps and general shapes of the moving barrier; we find the corresponding approximations of the unconditional and conditional halo mass functions for cold dark matter (DM) power spectra to represent very well the outcomes of state-of-the-art cosmological N-body simulations. In addition, we apply these results to derive, and confront with simulations, other quantities of interest in halo statistics, including the rates of halo formation and creation, the average halo growth history, and the halo bias. Finally, we discuss how our approach and main results change when considering random walks with correlated instead of uncorrelated steps, and warm instead of cold DM power spectra.

  13. Testing the self-consistency of the excursion set approach to predicting the dark matter halo mass function.

    PubMed

    Achitouv, I; Rasera, Y; Sheth, R K; Corasaniti, P S

    2013-12-01

    The excursion set approach provides a framework for predicting how the abundance of dark matter halos depends on the initial conditions. A key ingredient of this formalism is the specification of a critical overdensity threshold (barrier) which protohalos must exceed if they are to form virialized halos at a later time. However, to make its predictions, the excursion set approach explicitly averages over all positions in the initial field, rather than the special ones around which halos form, so it is not clear that the barrier has physical motivation or meaning. In this Letter we show that once the statistical assumptions which underlie the excursion set approach are considered a drifting diffusing barrier model does provide a good self-consistent description both of halo abundance as well as of the initial overdensities of the protohalo patches. PMID:24476252

  14. THE HALO MASS FUNCTION FROM EXCURSION SET THEORY. II. THE DIFFUSING BARRIER

    SciTech Connect

    Maggiore, Michele; Riotto, Antonio

    2010-07-01

    In excursion set theory, the computation of the halo mass function is mapped into a first-passage time process in the presence of a barrier, which in the spherical collapse model is a constant and in the ellipsoidal collapse model is a fixed function of the variance of the smoothed density field. However, N-body simulations show that dark matter halos grow through a mixture of smooth accretion, violent encounters, and fragmentations, and modeling halo collapse as spherical, or even as ellipsoidal, is a significant oversimplification. In addition, the very definition of what is a dark matter halo, both in N-body simulations and observationally, is a difficult problem. We propose that some of the physical complications inherent to a realistic description of halo formation can be included in the excursion set theory framework, at least at an effective level, by taking into account that the critical value for collapse is not a fixed constant {delta}{sub c}, as in the spherical collapse model, nor a fixed function of the variance {sigma} of the smoothed density field, as in the ellipsoidal collapse model, but rather is itself a stochastic variable, whose scatter reflects a number of complicated aspects of the underlying dynamics. Solving the first-passage time problem in the presence of a diffusing barrier we find that the exponential factor in the Press-Schechter mass function changes from exp{l_brace}-{delta}{sup 2}{sub c}/2{sigma}{sup 2{r_brace}} to exp{l_brace}-a{delta}{sup 2}{sub c}/2{sigma}{sup 2{r_brace}}, where a = 1/(1 + D{sub B}) and D{sub B} is the diffusion coefficient of the barrier. The numerical value of D{sub B} , and therefore the corresponding value of a, depends among other things on the algorithm used for identifying halos. We discuss the physical origin of the stochasticity of the barrier and, from recent N-body simulations that studied the properties of the collapse barrier, we deduce a value D{sub B} {approx_equal} 0.25. Our model then predicts a

  15. Statistics of dark matter halos in the excursion set peak framework

    SciTech Connect

    Lapi, A.; Danese, L. E-mail: danese@sissa.it

    2014-07-01

    We derive approximated, yet very accurate analytical expressions for the abundance and clustering properties of dark matter halos in the excursion set peak framework; the latter relies on the standard excursion set approach, but also includes the effects of a realistic filtering of the density field, a mass-dependent threshold for collapse, and the prescription from peak theory that halos tend to form around density maxima. We find that our approximations work excellently for diverse power spectra, collapse thresholds and density filters. Moreover, when adopting a cold dark matter power spectra, a tophat filtering and a mass-dependent collapse threshold (supplemented with conceivable scatter), our approximated halo mass function and halo bias represent very well the outcomes of cosmological N-body simulations.

  16. Large field excursions from a few site relaxion model

    NASA Astrophysics Data System (ADS)

    Fonseca, N.; de Lima, L.; Machado, C. S.; Matheus, R. D.

    2016-07-01

    Relaxion models are an interesting new avenue to explain the radiative stability of the Standard Model scalar sector. They require very large field excursions, which are difficult to generate in a consistent UV completion and to reconcile with the compact field space of the relaxion. We propose an N -site model which naturally generates the large decay constant needed to address these issues. Our model offers distinct advantages with respect to previous proposals: the construction involves non-Abelian fields, allowing for controlled high-energy behavior and more model building possibilities, both in particle physics and inflationary models, and also admits a continuum limit when the number of sites is large, which may be interpreted as a warped extra dimension.

  17. Dark-matter halo assembly bias: Environmental dependence in the non-Markovian excursion-set theory

    SciTech Connect

    Zhang, Jun; Ma, Chung-Pei; Riotto, Antonio

    2014-02-10

    In the standard excursion-set model for the growth of structure, the statistical properties of halos are governed by the halo mass and are independent of the larger-scale environment in which the halos reside. Numerical simulations, however, have found the spatial distributions of halos to depend not only on their mass but also on the details of their assembly history and environment. Here we present a theoretical framework for incorporating this 'assembly bias' into the excursion-set model. Our derivations are based on modifications of the path-integral approach of Maggiore and Riotto that models halo formation as a non-Markovian random-walk process. The perturbed density field is assumed to evolve stochastically with the smoothing scale and exhibits correlated walks in the presence of a density barrier. We write down conditional probabilities for multiple barrier crossings and derive from them analytic expressions for descendant and progenitor halo mass functions and halo merger rates as a function of both halo mass and the linear overdensity δ {sub e} of the larger-scale environment of the halo. Our results predict a higher halo merger rate and higher progenitor halo mass function in regions of higher overdensity, consistent with the behavior seen in N-body simulations.

  18. Constrained simulations and excursion sets: understanding the risks and benefits of `genetically modified' haloes

    NASA Astrophysics Data System (ADS)

    Porciani, Cristiano

    2016-09-01

    Constrained realisations of Gaussian random fields are used in cosmology to design special initial conditions for numerical simulations. We review this approach and its application to density peaks providing several worked-out examples. We then critically discuss the recent proposal to use constrained realisations to modify the linear density field within and around the Lagrangian patches that form dark-matter haloes. The ambitious concept is to forge `genetically modified' haloes with some desired properties after the non-linear evolution. We demonstrate that the original implementation of this method is not exact but approximate because it tacitly assumes that protohaloes sample a set of random points with a fixed mean overdensity. We show that carrying out a full genetic modification is a formidable and daunting task requiring a mathematical understanding of what determines the biased locations of protohaloes in the linear density field. We discuss approximate solutions based on educated guesses regarding the nature of protohaloes. We illustrate how the excursion-set method can be adapted to predict the non-linear evolution of the modified patches and thus fine tune the constraints that are necessary to obtain preselected halo properties. This technique allows us to explore the freedom around the original algorithm for genetic modification. We find that the quantity which is most sensitive to changes is the halo mass-accretion rate at the mass scale on which the constraints are set. Finally we discuss constraints based on the protohalo angular momenta.

  19. A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations

    NASA Astrophysics Data System (ADS)

    Brown, M. C.; Korte, M.

    2016-05-01

    We explore simple excursion scenarios by imposing changes on the axial dipole component of the Holocene geomagnetic field model CALS10k.2 and investigate implications for our understanding of palaeomagnetic observations of excursions. Our findings indicate that globally observed directions of fully opposing polarity are only possible when the axial dipole reverses: linearly decaying the axial dipole to zero and then reestablishing it with the same sign produces a global intensity minimum, but does not produce fully reversed directions globally. Reversing the axial dipole term increases the intensity of the geomagnetic field observed at Earth's surface across the mid-point of the excursion, which results in a double-dip intensity structure during the excursion. Only a limited number of palaeomagnetic records of excursions contain such a double-dip intensity structure. Rather, the maximum directional change is coeval with a geomagnetic field intensity minimum.

  20. Non-Gaussian halo abundances in the excursion set approach with correlated steps

    NASA Astrophysics Data System (ADS)

    Musso, Marcello; Paranjape, Aseem

    2012-02-01

    We study the effects of primordial non-Gaussianity on the large-scale structure in the excursion set approach, accounting for correlations between steps of the random walks in the smoothed initial density field. These correlations are induced by realistic smoothing filters (as opposed to a filter that is sharp in k-space), but have been ignored by many analyses to date. We present analytical arguments - building on existing results for Gaussian initial conditions - which suggest that the effect of the filter at large smoothing scales is remarkably simple, and is in fact identical to what happens in the Gaussian case: the non-Gaussian walks behave as if they were smooth and deterministic, or 'completely correlated'. As a result, the first crossing distribution (which determines e.g. halo abundances) follows from the single-scale statistics of the non-Gaussian density field - the so-called 'cloud-in-cloud' problem does not exist for completely correlated walks. Also, the answer from single-scale statistics is simply one half that for sharp-k walks. We explicitly test these arguments using Monte Carlo simulations of non-Gaussian walks, showing that the resulting first crossing distributions, and in particular the factor 1/2 argument, are remarkably insensitive to variations in the power spectrum and the defining non-Gaussian process. We also use our Monte Carlo walks to test some of the existing prescriptions for the non-Gaussian first crossing distribution. Since the factor 1/2 holds for both Gaussian and non-Gaussian initial conditions, it provides a theoretical motivation (the first, to our knowledge) for the common practice of analytically prescribing a ratio of non-Gaussian to Gaussian halo abundances.

  1. Halo abundances and counts-in-cells: the excursion set approach with correlated steps

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Lam, Tsz Yan; Sheth, Ravi K.

    2012-02-01

    The excursion set approach has been used to make predictions for a number of interesting quantities in studies of non-linear hierarchical clustering. These include the halo mass function, halo merger rates, halo formation times and masses, halo clustering, analogous quantities for voids and the distribution of dark matter counts in randomly placed cells. The approach assumes that all these quantities can be mapped to problems involving the first-crossing distribution of a suitably chosen barrier by random walks. Most analytic expressions for these distributions ignore the fact that, although different k-modes in the initial Gaussian field are uncorrelated, this is not true in real space: the values of the density field at a given spatial position, when smoothed on different real-space scales, are correlated in a non-trivial way. As a result, the problem is to estimate first crossing distribution by random walks having correlated rather than uncorrelated steps. In 1990, Peacock & Heavens presented a simple approximation for the first crossing distribution of a single barrier of constant height by walks with correlated steps. We show that their approximation can be thought of as a correction to the distribution associated with what we call smooth completely correlated walks. We then use this insight to extend their approach to treat moving barriers, as well as walks that are constrained to pass through a certain point before crossing the barrier. For the latter, we show that a simple rescaling, inspired by bivariate Gaussian statistics, of the unconditional first crossing distribution, accurately describes the conditional distribution, independent of the choice of analytical prescription for the former. In all cases, comparison with Monte Carlo solutions of the problem shows reasonably good agreement. This represents the first explicit demonstration of the accuracy of an analytic treatment of all these aspects of the correlated steps problem. While our main focus is

  2. Model-based control rescues boiler from steam-temperature excursions

    SciTech Connect

    Hanson, K.; Werre, J.; Chloupek, J.; Richerson, J.

    1995-05-01

    This article describes how, after operators of a lignite-fired boiler wrestled for years to control its main steam temperature, a switch to model-based control resolved the problem. Decoupling of control loops was essential. Montana Dakota Utilities (MDU) is the operator of the Coyote station, a 450-MW unit located at Beulah, ND, in the heart of lignite country. Owners of the plant are MDU, Northern Municipal Power Agency, Northwestern Public Service Co., and Otter Tail Power Co. The unit, a Babcock and Wilcox Co. (Barberton, Ohio) drum-boiler design, came on line in 1981. It burns lignite with a heating value of 6,900 Btu/lb using 12 cyclones. Because of unique boiler characteristics and controls implementation using several different control systems, the Coyote station had experienced significant steam-temperature excursions over the years.

  3. Development of a Bayesian Belief Network Runway Incursion and Excursion Model

    NASA Technical Reports Server (NTRS)

    Green, Lawrence L.

    2014-01-01

    In a previous work, a statistical analysis of runway incursion (RI) event data was conducted to ascertain the relevance of this data to the top ten Technical Challenges (TC) of the National Aeronautics and Space Administration (NASA) Aviation Safety Program (AvSP). The study revealed connections to several of the AvSP top ten TC and identified numerous primary causes and contributing factors of RI events. The statistical analysis served as the basis for developing a system-level Bayesian Belief Network (BBN) model for RI events, also previously reported. Through literature searches and data analysis, this RI event network has now been extended to also model runway excursion (RE) events. These RI and RE event networks have been further modified and vetted by a Subject Matter Expert (SME) panel. The combined system-level BBN model will allow NASA to generically model the causes of RI and RE events and to assess the effectiveness of technology products being developed under NASA funding. These products are intended to reduce the frequency of runway safety incidents/accidents, and to improve runway safety in general. The development and structure of the BBN for both RI and RE events are documented in this paper.

  4. Impact of Atmosphere-sea Exchange on the Isotopic Expression of Carbon Excursions: Observations and Modeling of OAE-1a

    NASA Astrophysics Data System (ADS)

    Finkelstein, D. B.; Pratt, L. M.; Brassell, S. C.; Montañez, I. P.

    2005-12-01

    Negative carbon isotope excursions are a recurring phenomenon in earth history (e.g., Permo-Triassic boundary, Jurassic and Cretaceous oceanic anoxic events, and the Paleocene-Eocene Thermal Maximum) variously attributed to destabilization of methane clathrates, a decrease in primary productivity, intensified volcanism, and more recently to widespread peat fires. Each forcing mechanism invoked accounts for both the magnitude of the negative isotopic shift and the reservoir required to drive the shift as observed at one to several locales. Studies rarely consider the effect of latitudinal temperature changes on the excursion. Here, we explore the early Aptian oceanic anoxic event as an example of a negative isotopic shift whose magnitude varies with paleolatitude in terrestrial settings. It increases (from -2.0 to -8.2 ‰) with paleolatitude (5° to 33°N) and is greater than that expected for changes in plant C isotope discrimination driven by environmental stresses (~3 ‰). Conceptually, an isotopic shift of terrestrial vegetation across paleolatitudes represents a response to its forcing mechanism and temperature. A closed system carbon cycle model constructed of five reservoirs (atmosphere, vegetation, soil, and shallow and deep oceans), and five fluxes (productivity, respiration, litter fall, atmosphere-ocean exchange, and surface-deep ocean exchange) was employed is assessment of a negative isotopic shift at 2x pre-industrial atmospheric levels (P.A.L.) for pCO2 keeping all variables constant with the exception of temperature. The model was run at 5°C increments from 5° to 40°C to simulate the effect of temperature gradients on isotopic shifts at variable latitudes, with the appropriate temperature dependent fractionations for atmosphere - sea exchange. The magnitude of the negative isotopic shift at each temperature was calculated for both terrestrial and marine organic matter. In terrestrial vegetation it changed from -4 to -5.8 ‰ with decreasing

  5. Flow excursion time scales in the advanced neutron source reactor

    SciTech Connect

    Sulfredge, C.D.

    1995-04-01

    Flow excursion transients give rise to a key thermal limit for the proposed Advanced Neutron Source (ANS) reactor because its core involves many parallel flow channels with a common pressure drop. Since one can envision certain accident scenarios in which the thermal limits set by flow excursion correlations might be exceeded for brief intervals, a key objective is to determine how long a flow excursion would take to bring about a system failure that could lead to fuel damage. The anticipated time scale for flow excursions has been examined by subdividing the process into its component phenomena: bubble nucleation and growth, deceleration of the resulting two-phase flow, and finally overcoming thermal inertia to heat up the reactor fuel plates. Models were developed to estimate the time required for each individual stage. Accident scenarios involving sudden reduction in core flow or core exit pressure have been examined, and the models compared with RELAP5 output for the ANS geometry. For a high-performance reactor like the ANS, flow excursion time scales were predicted to be in the millisecond range, so that even very brief transients might lead to fuel damage. These results should prove useful whenever one must determine the time involved in any portion of a flow excursion transient.

  6. Design of a full scale model fuel assembly for full power production reactor flow excursion experiments

    SciTech Connect

    Nash, C.A. ); Blake, J.E.; Rush, G.C. )

    1990-01-01

    A novel full scale production reactor fuel assembly model was designed and built to study thermal-hydraulic effects of postulated Savannah River Site (SRS) nuclear reactor accidents. The electrically heated model was constructed to simulate the unique annular concentric tube geometry of fuel assemblies in SRS nuclear production reactors. Several major design challenges were overcome in order to produce the prototypic geometry and thermal-hydraulic conditions. The two concentric heater tubes (total power over 6 MW and maximum heat flux of 3.5 MW/m{sup 2}) (1.1E+6 BTU/(ft{sup 2}hr)) were designed to closely simulate the thermal characteristics of SRS uranium-aluminum nuclear fuel. The paper discusses the design of the model fuel assembly, which met requirements of maintaining prototypic geometric and hydraulic characteristics, and approximate thermal similarity. The model had a cosine axial power profile and the electrical resistance was compatible with the existing power supply. The model fuel assembly was equipped with a set of instruments useful for code analysis, and durable enough to survive a number of LOCA transients. These instruments were sufficiently responsive to record the response of the fuel assembly to the imposed transient.

  7. Design of a full scale model fuel assembly for full power production reactor flow excursion experiments

    SciTech Connect

    Nash, C.A.; Blake, J.E.; Rush, G.C.

    1990-12-31

    A novel full scale production reactor fuel assembly model was designed and built to study thermal-hydraulic effects of postulated Savannah River Site (SRS) nuclear reactor accidents. The electrically heated model was constructed to simulate the unique annular concentric tube geometry of fuel assemblies in SRS nuclear production reactors. Several major design challenges were overcome in order to produce the prototypic geometry and thermal-hydraulic conditions. The two concentric heater tubes (total power over 6 MW and maximum heat flux of 3.5 MW/m{sup 2}) (1.1E+6 BTU/(ft{sup 2}hr)) were designed to closely simulate the thermal characteristics of SRS uranium-aluminum nuclear fuel. The paper discusses the design of the model fuel assembly, which met requirements of maintaining prototypic geometric and hydraulic characteristics, and approximate thermal similarity. The model had a cosine axial power profile and the electrical resistance was compatible with the existing power supply. The model fuel assembly was equipped with a set of instruments useful for code analysis, and durable enough to survive a number of LOCA transients. These instruments were sufficiently responsive to record the response of the fuel assembly to the imposed transient.

  8. Mono Lake Excursion Reviewed

    NASA Astrophysics Data System (ADS)

    Liddicoat, J. C.; Coe, R. S.

    2007-05-01

    The Mono Lake Excursion as recorded in the Mono Basin, CA, has an older part that is about negative 30 degrees inclination and about 300 degrees declination during low relative field intensity. Those paleomagnetic directions are closely followed by greater than 80 degrees positive inclination and east declination of about 100 degrees during higher relative field intensity. A path of the Virtual Geomagnetic Poles (VGPs) for the older part followed from old to young forms a large clockwise loop that reaches 35 degrees N latitude and is centered at about 35 degrees E longitude. That loop is followed by a smaller one that is counterclockwise and centered at about 70 degrees N latitude and 270 degrees E longitude (Denham & Cox, 1971; Denham, 1974; Liddicoat & Coe, 1979). The Mono Lake Excursion outside the Mono Basin in western North America is recorded as nearly the full excursion at Summer Lake, OR (Negrini et al., 1984), and as the younger portion of steep positive inclination/east declination in the Lahontan Basin, NV. The overall relative field intensity during the Mono Lake Excursion in the Lahontan Basin mirrors very closely the relative field intensity in the Mono Basin (Liddicoat, 1992, 1996; Coe & Liddicoat, 1994). Using 14C and 40Ar/39Ar dates (Kent et al., 2002) and paleoclimate and relative paleointensity records (Zimmerman et al., 2006) for the Mono Lake Excursion in the Mono Basin, it has been proposed that the Mono Lake Excursion might be older than originally believed and instead be the Laschamp Excursion at about 40,000 yrs B.P. (Guillou et al., 2004). On the contrary, we favor a younger age for the Mono Lake Excursion, about 32,000 yrs B.P., using the relative paleointensity in the Mono Basin and Lahontan Basin and 14C dates from the Lahontan Basin (Benson et al., 2002). The age of about 32,000 yrs B.P. is also in accord with the age (32,000- 34,000 yrs B.P.) reported by Channell (2006) for the Mono Lake Excursion at ODP Site 919 in the Irminger Basin

  9. A diagenetic control on the Early Triassic Smithian-Spathian carbon isotopic excursions recorded in the marine settings of the Thaynes Group (Utah, USA).

    PubMed

    Thomazo, C; Vennin, E; Brayard, A; Bour, I; Mathieu, O; Elmeknassi, S; Olivier, N; Escarguel, G; Bylund, K G; Jenks, J; Stephen, D A; Fara, E

    2016-05-01

    In the aftermath of the end-Permian mass extinction, Early Triassic sediments record some of the largest Phanerozoic carbon isotopic excursions. Among them, a global Smithian-negative carbonate carbon isotope excursion has been identified, followed by an abrupt increase across the Smithian-Spathian boundary (SSB; ~250.8 Myr ago). This chemostratigraphic evolution is associated with palaeontological evidence that indicate a major collapse of terrestrial and marine ecosystems during the Late Smithian. It is commonly assumed that Smithian and Spathian isotopic variations are intimately linked to major perturbations in the exogenic carbon reservoir. We present paired carbon isotopes measurements from the Thaynes Group (Utah, USA) to evaluate the extent to which the Early Triassic isotopic perturbations reflect changes in the exogenic carbon cycle. The δ(13) Ccarb variations obtained here reproduce the known Smithian δ(13) Ccarb -negative excursion. However, the δ(13) C signal of the bulk organic matter is invariant across the SSB and variations in the δ(34) S signal of sedimentary sulphides are interpreted here to reflect the intensity of sediment remobilization. We argue that Middle to Late Smithian δ(13) Ccarb signal in the shallow marine environments of the Thaynes Group does not reflect secular evolution of the exogenic carbon cycle but rather physicochemical conditions at the sediment-water interface leading to authigenic carbonate formation during early diagenetic processes. PMID:26842810

  10. Penrose tilings as model sets

    NASA Astrophysics Data System (ADS)

    Shutov, A. V.; Maleev, A. V.

    2015-11-01

    The Baake construction, based on generating a set of vertices of Penrose tilings as a model set, is refined. An algorithm and a corresponding computer program for constructing an uncountable set of locally indistinguishable Penrose tilings are developed proceeding from this refined construction. Based on an analysis of the parameters of tiling vertices, 62 versions of rhomb combinations at the tiling center are determined. The combinatorial structure of Penrose tiling worms is established. A concept of flip transformations of tilings is introduced that makes it possible to construct Penrose tilings that cannot be implemented in the Baake construction.

  11. The Iceland Basin excursion: Age, duration, and excursion field geometry

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.

    2014-12-01

    Iceland Basin geomagnetic excursion coincided with the marine isotope stage (MIS) 6/7 boundary. The age and duration of the excursion, at seven North Atlantic sites with sufficient isotope data, are estimated by matching marine isotope stage (MIS) 7a-7c to a calibrated template. Two criteria for defining the excursion, virtual geomagnetic pole (VGP) latitudes <0° and <40°N, yield excursion durations of 1-4 and 2-5 kyr, respectively. The midpoints of the excursion are in the 189-192 ka range, with a mean of ˜190.2 ka. Although component magnetization directions are generally well defined, rapid changes in field direction during a time of low field intensity are not adequately recorded. During the excursion, VGPs transit southward over Africa and the South Atlantic, reach high southern latitudes at the culmination of the excursion, with partial recovery in relative paleointensity (RPI), and then track northward through the western Pacific. The high southern latitude VGPs, and the recovery in RPI, imply that the Earth's main axial dipole reversed polarity during the excursion, if only for ˜1 kyr; implying that excursions can be manifested globally and are important in millennial-scale stratigraphy. VGP clustering in the South Atlantic and NW Pacific roughly coincide with maxima in the vertical-downward component of the modern nondipole (ND) field determined at the Earth's surface, which implies that the ND field became dominant as the geocentric dipole field weakened during the excursion, and also that the ND field configuration is long-lived on multimillennial timescales.

  12. Bounded excursion stable gravastars and black holes

    SciTech Connect

    Rocha, P; Da Silva, M F; Wang, Anzhong; Santos, N O E-mail: yasuda@on.br E-mail: mfasnic@gmail.com E-mail: anzhong_wang@baylor.edu

    2008-06-15

    Dynamical models of prototype gravastars were constructed in order to study their stability. The models are the Visser-Wiltshire three-layer gravastars, in which an infinitely thin spherical shell of stiff fluid divides the whole spacetime into two regions, where the internal region is de Sitter, and the external one is Schwarzschild. It is found that in some cases the models represent the 'bounded excursion' stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes occurs. In the phase space, the region for the 'bounded excursion' gravastars is very small in comparison to that of black holes, but not empty. Therefore, although the possibility of the existence of gravastars cannot be excluded from such dynamical models, our results indicate that, even if gravastars do indeed exist, that does not exclude the possibility of the existence of black holes.

  13. An Excursion in Applied Mathematics.

    ERIC Educational Resources Information Center

    von Kaenel, Pierre A.

    1981-01-01

    An excursion in applied mathematics is detailed in a lesson deemed well-suited for the high school student or undergraduate. The problem focuses on an experimental missile guidance system simulated in the laboratory. (MP)

  14. Compliant bipedal model with the center of pressure excursion associated with oscillatory behavior of the center of mass reproduces the human gait dynamics.

    PubMed

    Jung, Chang Keun; Park, Sukyung

    2014-01-01

    Although the compliant bipedal model could reproduce qualitative ground reaction force (GRF) of human walking, the model with a fixed pivot showed overestimations in stance leg rotation and the ratio of horizontal to vertical GRF. The human walking data showed a continuous forward progression of the center of pressure (CoP) during the stance phase and the suspension of the CoP near the forefoot before the onset of step transition. To better describe human gait dynamics with a minimal expense of model complexity, we proposed a compliant bipedal model with the accelerated pivot which associated the CoP excursion with the oscillatory behavior of the center of mass (CoM) with the existing simulation parameter and leg stiffness. Owing to the pivot acceleration defined to emulate human CoP profile, the arrival of the CoP at the limit of the stance foot over the single stance duration initiated the step-to-step transition. The proposed model showed an improved match of walking data. As the forward motion of CoM during single stance was partly accounted by forward pivot translation, the previously overestimated rotation of the stance leg was reduced and the corresponding horizontal GRF became closer to human data. The walking solutions of the model ranged over higher speed ranges (~1.7 m/s) than those of the fixed pivoted compliant bipedal model (~1.5m/s) and exhibited other gait parameters, such as touchdown angle, step length and step frequency, comparable to the experimental observations. The good matches between the model and experimental GRF data imply that the continuous pivot acceleration associated with CoM oscillatory behavior could serve as a useful framework of bipedal model. PMID:24161797

  15. Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments

    NASA Astrophysics Data System (ADS)

    Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B.

    2012-10-01

    Investigated sediment cores from the southeastern Black Sea provide a high-resolution record from mid latitudes of the Laschamp geomagnetic polarity excursion. Age constraints are provided by 16 AMS 14C ages, identification of the Campanian Ignimbrite tephra (39.28±0.11 ka), and by detailed tuning of sedimentologic parameters of the Black Sea sediments to the oxygen isotope record from the Greenland NGRIP ice core. According to the derived age model, virtual geomagnetic pole (VGP) positions during the Laschamp excursion persisted in Antarctica for an estimated 440 yr, making the Laschamp excursion a short-lived event with fully reversed polarity directions. The reversed phase, centred at 41.0 ka, is associated with a significant field intensity recovery to 20% of the preceding strong field maximum at ˜50 ka. Recorded field reversals of the Laschamp excursion, lasting only an estimated ˜250 yr, are characterized by low relative paleointensities (5% relative to 50 ka). The central, fully reversed phase of the Laschamp excursion is bracketed by VGP excursions to the Sargasso Sea (˜41.9 ka) and to the Labrador Sea (˜39.6 ka). Paleomagnetic results from the Black Sea are in excellent agreement with VGP data from the French type locality which facilitates the chronological ordering of the non-superposed lavas that crop out at Laschamp-Olby. In addition, VGPs between 34 and 35 ka reach low northerly to equatorial latitudes during a clockwise loop, inferred to be the Mono lake excursion.

  16. Identification and dating of the Mono Lake excursion in lava flows from the Canary islands.

    NASA Astrophysics Data System (ADS)

    Guillou, Hervé; Laj, Carlo; Carracedo, Juan-Carlos; Kissel, Catherine; Nomade, Sebastien; Perez-Torrado, Francisco; Wandres, Camille

    2010-05-01

    The Mono Lake geomagnetic excursion was defined from the study of lacustrine sections from Western North America [Denham, 1974; Liddicoat et al., 1979]. The proposed age for this excursion reported in the literature changed in time since the first observation and a debate was even very recently opened about the reliability of the dating at the original section at Wilson Creek. In ice cores, a peak in the production of cosmogenic isotopes is clearly observed about 7 ka after the peak associated to the Laschamp excursion. This younger peak, attributed to the Mono Lake occurs between the millennial climatic cycles 7 and 6 (Dansgaard-Oeschger cycles), around 34 kyr in the most recent Greenland ice age model. In addition, in other places, this excursion is described by an intensity low with only very rarely an associated directional shift, questioning the global character of this excursion. We present a coupled paleomagnetic and dating investigation conducted on four different lavas from the island of Tenerife (Spain) on the basis of preliminary K/Ar dating. From a paleomagnetic point of view, one of these sites is characterized by a direction largely deviated from the one calculated on the basis of an axial geocentric dipole field. The paleointensity values, determined using Thellier and Thellier method and the PICRIT03 set of criteria, is very low, about 8 µT. Two other sites are slightly deviated from the GAD value, in particular with lower inclinations. Paleointensity determinations from these lavas do not yet have a statistical significance and need to be completed but the first results indicate a value around 20 µT. Finally, the last site has a direction consistent with the GAD values and no reliable paleointensity determinations could be obtained so far. The preliminary K/Ar dating are now completed by Ar/Ar dating and their combination yield an average age of about 32 ka ± 2 ka for the four outcrops, not statistically distinguishable one from another. This

  17. Geomagnetic excursions and climate change

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.

    1983-01-01

    Rampino argues that although Kent (1982) demonstrated that the intensity of natural remanent magnetism (NRM) in deep-sea sediments is sensitive to changes in sediment type, and hence is not an accurate indicator of the true strength of the geomagnetic field, it does not offer an alternative explanation for the proposed connections between excursions, climate, and orbital parameters. Kent replies by illustrating some of the problems associated with geomagnetic excursions by considering the record of proposed excursions in a single critical core. The large departure from an axial dipole field direction seen in a part of the sample is probably due to a distorted record; the drawing and storage of the sample, which is described, could easily have led to disturbance and distortion of the record.

  18. Sampling plan optimization for detection of lithography and etch CD process excursions

    NASA Astrophysics Data System (ADS)

    Elliott, Richard C.; Nurani, Raman K.; Lee, Sung Jin; Ortiz, Luis G.; Preil, Moshe E.; Shanthikumar, J. G.; Riley, Trina; Goodwin, Greg A.

    2000-06-01

    Effective sample planning requires a careful combination of statistical analysis and lithography engineering. In this paper, we present a complete sample planning methodology including baseline process characterization, determination of the dominant excursion mechanisms, and selection of sampling plans and control procedures to effectively detect the yield- limiting excursions with a minimum of added cost. We discuss the results of our novel method in identifying critical dimension (CD) process excursions and present several examples of poly gate Photo and Etch CD excursion signatures. Using these results in a Sample Planning model, we determine the optimal sample plan and statistical process control (SPC) chart metrics and limits for detecting these excursions. The key observations are that there are many different yield- limiting excursion signatures in photo and etch, and that a given photo excursion signature turns into a different excursion signature at etch with different yield and performance impact. In particular, field-to-field variance excursions are shown to have a significant impact on yield. We show how current sampling plan and monitoring schemes miss these excursions and suggest an improved procedure for effective detection of CD process excursions.

  19. Excursions in technology policy

    NASA Technical Reports Server (NTRS)

    Archibald, Robert B.

    1995-01-01

    This technical report presents a summary of three distinct projects: (1) Measuring economic benefits; (2) Evaluating the SBIR program; and (3) A model for evaluating changes in support for science and technology. the first project deals with the Technology Applications Group (TAG) at NASA Langley Research Center. The mission of TAG is to assist firms interested in commercializing technologies. TAG is a relatively new group as is the emphasis on technology commercialization for NASA. One problem faced by TAG and similar groups at other centers is measuring their effectiveness. The first project this summer, a paper entitled, 'Measuring the Economic Benefits of Technology Transfer from a National Laboratory: A Primer,' focused on this measurement problem. We found that the existing studies of the impact of technology transfer on the economy were conceptually flawed. The 'primer' outlines the appropriate theoretical framework for measuring the economic benefits of technology transfer. The second project discusses, one of the programs of TAG, the Small Business Innovation Research (SBIR) program. This program has led to over 400 contracts with Small Business since its inception in 1985. The program has never been evaluated. Crucial questions such as those about the extent of commercial successes from the contracts need to be answered. This summer we designed and implemented a performance evaluation survey instrument. The analysis of the data will take place in the fall. The discussion of the third project focuses on a model for evaluating changes in support for science and technology. At present several powerful forces are combining to change the environment for science and technology policy. The end of the cold war eliminated the rationale for federal support for many projects. The new- found Congressional conviction to balance the budget without tax increases combined with demographic changes which automatically increase spending for some politically popular programs

  20. Excursion detection using leveling data

    NASA Astrophysics Data System (ADS)

    Kim, MinGyu; Ju, Jaewuk; Habets, Boris; Erley, Georg; Bellmann, Enrico; Kim, Seop

    2016-03-01

    Wafer leveling data are usually used inside the exposure tool for ensuring good focus, then discarded. This paper describes the implementation of a monitoring and analysis solution to download these data automatically, together with the correction profiles applied by the scanner. The resulting height maps and focus residuals form the basis for monitoring metrics tailored to catching tool and process drifts and excursions in a high-volume manufacturing (HVM) environment. In this paper, we present four six cases to highlight the potential of the method: wafer edge monitoring, chuck drift monitoring, correlations between focus residuals and overlay errors, and pre-process monitoring by chuck fingerprint removal.

  1. Rough set models of Physarum machines

    NASA Astrophysics Data System (ADS)

    Pancerz, Krzysztof; Schumann, Andrew

    2015-04-01

    In this paper, we consider transition system models of behaviour of Physarum machines in terms of rough set theory. A Physarum machine, a biological computing device implemented in the plasmodium of Physarum polycephalum (true slime mould), is a natural transition system. In the behaviour of Physarum machines, one can notice some ambiguity in Physarum motions that influences exact anticipation of states of machines in time. To model this ambiguity, we propose to use rough set models created over transition systems. Rough sets are an appropriate tool to deal with rough (ambiguous, imprecise) concepts in the universe of discourse.

  2. Buoyancy-driven flow excursions in fuel assemblies. Revision 1

    SciTech Connect

    Laurinat, J.E.; Paul, P.K.; Menna, J.D.

    1995-07-01

    A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating heavy water moderator downward through channels in cylindrical fuel tubes. Powers were limited to safeguard against a flow excursion in one or more of these parallel channels. During full-power operation, limits safeguarded against a boiling flow excursion. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increases beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of the limiting power for previous long-term reactor operations.

  3. Buoyancy-driven flow excursions in fuel assemblies

    SciTech Connect

    Laurinat, J.E.; Paul, P.K.; Menna, J.D.

    1995-09-01

    A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating heavy water moderator downward through channels in cylindrical fuel tubes. Powers were limited to safeguard against a flow excursion in one of more of these parallel channels. During-full-power operation, limits safeguarded against a boiling flow excursion. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increased beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of the limiting power for previous long-term reactor operations.

  4. Global geomagnetic field mapping - from secular variation to geomagnetic excursions

    NASA Astrophysics Data System (ADS)

    Panovska, Sanja; Constable, Catherine

    2015-04-01

    The main source of the geomagnetic field is a self-sustaining dynamo produced by fluid motions in Earth's liquid outer core. We study the spatial and temporal changes in the internal magnetic field by mapping the time-varying geomagnetic field over the past 100 thousand years. This is accomplished using a new global data set of paleomagnetic records drawn from high accumulation rate sediments and from volcanic rocks spanning the past 100 thousand years (Late Pleistocene). Sediment data comprises 105 declination, 117 inclination and 150 relative paleointensity (RPI) records, mainly concentrated in northern mid-latitudes, although some are available in the southern hemisphere. Northern Atlantic and Western Pacific are regions with high concentrations of data. The number of available volcanic/archeomagnetic data is comparitively small on the global scale, especially in the Southern hemisphere. Temporal distributions show that the number of data increases toward more recent times with a good coverage for the past 50 ka. Laschamp excursion (41 ka BP) is well represented for both directional and intensity data. The significant increase in data compared to previous compilations results in an improvement over current geomagnetic field models covering these timescales. Robust aspects of individual sediment records are successfully captured by smoothing spline modeling allowing an estimate of random uncertainties present in the records. This reveals a wide range of fidelities across the sediment magnetic records. Median uncertainties are: 17° for declination (range, 1° to 113°), 6° for inclination (1° to 50°) and 0.4 for standardized relative paleointensity (0.02 to 1.4). The median temporal resolution of the records defined by the smoothing time is 400 years (range, 50 years to about 14 kyr). Using these data, a global, time-varying, geomagnetic field model is constructed covering the past 100 thousand years. The modeling directly uses relative forms of sediment

  5. An investigation of the dynamic relationship between navicular drop and first metatarsophalangeal joint dorsal excursion

    PubMed Central

    Griffin, Nicole L; Miller, Charlotte; Schmitt, Daniel; D'Août, Kristiaan

    2013-01-01

    The modern human foot is a complex biomechanical structure that must act both as a shock absorber and as a propulsive strut during the stance phase of gait. Understanding the ways in which foot segments interact can illuminate the mechanics of foot function in healthy and pathological humans. It has been proposed that increased values of medial longitudinal arch deformation can limit metatarsophalangeal joint excursion via tension in the plantar aponeurosis. However, this model has not been tested directly in a dynamic setting. In this study, we tested the hypothesis that during the stance phase, subtalar pronation (stretching of the plantar aponeurosis and subsequent lowering of the medial longitudinal arch) will negatively affect the amount of first metatarsophalangeal joint excursion occurring at push-off. Vertical descent of the navicular (a proxy for subtalar pronation) and first metatarsophalangeal joint dorsal excursion were measured during steady locomotion over a flat substrate on a novel sample consisting of asymptomatic adult males and females, many of whom are habitually unshod. Least-squares regression analyses indicated that, contrary to the hypothesis, navicular drop did not explain a significant amount of variation in first metatarsophalangeal joint dorsal excursion. These results suggest that, in an asymptomatic subject, the plantar aponeurosis and the associated foot bones can function effectively within the normal range of subtalar pronation that takes place during walking gait. From a clinical standpoint, this study highlights the need for investigating the in vivo kinematic relationship between subtalar pronation and metatarsophalangeal joint dorsiflexion in symptomatic populations, and also the need to explore other factors that may affect the kinematics of asymptomatic feet. PMID:23600634

  6. Spin foam models as energetic causal sets

    NASA Astrophysics Data System (ADS)

    Cortês, Marina; Smolin, Lee

    2016-04-01

    Energetic causal sets are causal sets endowed by a flow of energy-momentum between causally related events. These incorporate a novel mechanism for the emergence of space-time from causal relations [M. Cortês and L. Smolin, Phys. Rev. D 90, 084007 (2014); Phys. Rev. D 90, 044035 (2014)]. Here we construct a spin foam model which is also an energetic causal set model. This model is closely related to the model introduced in parallel by Wolfgang Wieland in [Classical Quantum Gravity 32, 015016 (2015)]. What makes a spin foam model also an energetic causal set is Wieland's identification of new degrees of freedom analogous to momenta, conserved at events (or four-simplices), whose norms are not mass, but the volume of tetrahedra. This realizes the torsion constraints, which are missing in previous spin foam models, and are needed to relate the connection dynamics to those of the metric, as in general relativity. This identification makes it possible to apply the new mechanism for the emergence of space-time to a spin foam model. Our formulation also makes use of Markopoulou's causal formulation of spin foams [arXiv:gr-qc/9704013]. These are generated by evolving spin networks with dual Pachner moves. This endows the spin foam history with causal structure given by a partial ordering of the events which are dual to four-simplices.

  7. Framing Learning Conditions in Geography Excursions

    ERIC Educational Resources Information Center

    Jonasson, Mikael

    2011-01-01

    The aim of this paper is to investigate and frame some learning conditions involved in the practice of geographical excursions. The empirical material from this study comes from several excursions made by students in human geography and an ethnomethodological approach through participant observation is used. The study is informed by theories from…

  8. Does the Shuram δ13C excursion record Ediacaran oxygenation?

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Maloof, A. C.; Schoene, B.; Higgins, J. A.

    2013-12-01

    The most negative carbon isotope excursion in Earth history is found in carbonate rocks of the Ediacaran Period (635-542 Ma). Known colloquially as the the 'Shuram' excursion, workers have long noted its tantalizing, broad concordance with the rise of abundant macro-scale fossils in the rock record, variously interpreted as animals, giant protists, macro-algae and lichen, and known as the 'Ediacaran Biota.' Thus, the Shuram excursion has been interpreted by many in the context of a dramatically changing redox state of the Ediacaran oceans - e.g., a result of methane cycling in a low O2 atmosphere, the final destruction of a large pool of recalcitrant dissolved organic carbon (DOC), and the step-wise oxidation of the Ediacaran oceans. More recently, diagenetic interpretations of the Shuram excursion - e.g. sedimentary in-growth of very δ13C depleted authigenic carbonates, meteoric alteration of Ediacaran carbonates, late-stage burial diagenesis - have challenged the various Ediacaran redox models. A rigorous geologic context is required to discriminate between these explanatory models, and determine whether the Shuram excursion can be used to evaluate terminal Neoproterozoic oxygenation. Here, we present chemo-stratigraphic data (δ13C, δ18O, δ44/42Ca and redox sensitive trace element abundances) from 12 measured sections of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia that require a syn-depositional age for the extraordinary range of δ13C values (-12 to +4‰) observed in the formation. In some locations, the Wonoka Fm. is ~700 meters (m) of mixed shelf limestones and siliclastics that record the full 16 ‰ δ13C excursion in a remarkably consistent fashion across 100s of square kilometers of basin area. Fabric-altering diagenesis, where present, occurs at the sub-meter vertical scale, only results in sub-permil offsets in δ13C and cannot be used to explain the full δ13C excursion. In other places, the Wonoka Fm. is host to deep (1 km

  9. Soybean canopy reflectance modeling data sets

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Biehl, L. L.; Daughtry, C. S. T.

    1984-01-01

    Numerous mathematical models of the interaction of radiation with vegetation canopies have been developed over the last two decades. However, data with which to exercise and validate these models are scarce. During three days in the summer of 1980, experiments are conducted with the objective of gaining insight about the effects of solar illumination and view angles on soybean canopy reflectance. In concert with these experiment, extensive measurements of the soybean canopies are obtained. This document is a compilation of the bidirectional reflectance factors, agronomic, characteristics, canopy geometry, and leaf, stem, and pod optical properties of the soybean canopies. These data sets should be suitable for use with most vegetation canopy reflectance models.

  10. Compensation for large thorax excursions in EIT imaging.

    PubMed

    Schullcke, B; Krueger-Ziolek, S; Gong, B; Mueller-Lisse, U; Moeller, K

    2016-09-01

    Besides the application of EIT in the intensive care unit it has recently also been used in spontaneously breathing patients suffering from asthma bronchiole, cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD). In these cases large thorax excursions during deep inspiration, e.g. during lung function testing, lead to artifacts in the reconstructed images. In this paper we introduce a new approach to compensate for image artifacts resulting from excursion induced changes in boundary voltages. It is shown in a simulation study that boundary voltage change due to thorax excursion on a homogeneous model can be used to modify the measured voltages and thus reduce the impact of thorax excursion on the reconstructed images. The applicability of the method on human subjects is demonstrated utilizing a motion-tracking-system. The proposed technique leads to fewer artifacts in the reconstructed images and improves image quality without substantial increase in computational effort, making the approach suitable for real-time imaging of lung ventilation. This might help to establish EIT as a supplemental tool for lung function tests in spontaneously breathing patients to support clinicians in diagnosis and monitoring of disease progression. PMID:27531053

  11. Human risk factors associated with pilots in runway excursions.

    PubMed

    Chang, Yu-Hern; Yang, Hui-Hua; Hsiao, Yu-Jung

    2016-09-01

    A breakdown analysis of civil aviation accidents worldwide indicates that the occurrence of runway excursions represents the largest portion among all aviation occurrence categories. This study examines the human risk factors associated with pilots in runway excursions, by applying a SHELLO model to categorize the human risk factors and to evaluate the importance based on the opinions of 145 airline pilots. This study integrates aviation management level expert opinions on relative weighting and improvement-achievability in order to develop four kinds of priority risk management strategies for airline pilots to reduce runway excursions. The empirical study based on experts' evaluation suggests that the most important dimension is the liveware/pilot's core ability. From the perspective of front-line pilots, the most important risk factors are the environment, wet/containment runways, and weather issues like rain/thunderstorms. Finally, this study develops practical strategies for helping management authorities to improve major operational and managerial weaknesses so as to reduce the human risks related to runway excursions. PMID:27344128

  12. Deep Reconstruction Models for Image Set Classification.

    PubMed

    Hayat, Munawar; Bennamoun, Mohammed; An, Senjian

    2015-04-01

    Image set classification finds its applications in a number of real-life scenarios such as classification from surveillance videos, multi-view camera networks and personal albums. Compared with single image based classification, it offers more promises and has therefore attracted significant research attention in recent years. Unlike many existing methods which assume images of a set to lie on a certain geometric surface, this paper introduces a deep learning framework which makes no such prior assumptions and can automatically discover the underlying geometric structure. Specifically, a Template Deep Reconstruction Model (TDRM) is defined whose parameters are initialized by performing unsupervised pre-training in a layer-wise fashion using Gaussian Restricted Boltzmann Machines (GRBMs). The initialized TDRM is then separately trained for images of each class and class-specific DRMs are learnt. Based on the minimum reconstruction errors from the learnt class-specific models, three different voting strategies are devised for classification. Extensive experiments are performed to demonstrate the efficacy of the proposed framework for the tasks of face and object recognition from image sets. Experimental results show that the proposed method consistently outperforms the existing state of the art methods. PMID:26353289

  13. Bayesian nonparametric models for ranked set sampling.

    PubMed

    Gemayel, Nader; Stasny, Elizabeth A; Wolfe, Douglas A

    2015-04-01

    Ranked set sampling (RSS) is a data collection technique that combines measurement with judgment ranking for statistical inference. This paper lays out a formal and natural Bayesian framework for RSS that is analogous to its frequentist justification, and that does not require the assumption of perfect ranking or use of any imperfect ranking models. Prior beliefs about the judgment order statistic distributions and their interdependence are embodied by a nonparametric prior distribution. Posterior inference is carried out by means of Markov chain Monte Carlo techniques, and yields estimators of the judgment order statistic distributions (and of functionals of those distributions). PMID:25326663

  14. Scaling properties of excursions in heartbeat dynamics

    NASA Astrophysics Data System (ADS)

    Reyes-Ramírez, I.; Guzmán-Vargas, L.

    2010-02-01

    In this work we study the excursions, defined as the number of beats to return to a local mean value, in heartbeat interval time series from healthy subjects and patients with congestive heart failure (CHF). First, we apply the segmentation procedure proposed by Bernaola-Galván et al. (Phys. Rev. Lett., 87 (2001) 168105), to nonstationary heartbeat time series to identify stationary segments with a local mean value. Next, we identify local excursions around the local mean value and construct the distributions to analyze the time organization and memory in the excursions sequences from the whole time series. We find that the cumulative distributions of excursions are consistent with a stretched exponential function given by g(x)~e-aτb, with a=1.09±0.15 (mean value±SD) and b=0.91±0.11 for healthy subjects and a=1.31±0.23 and b=0.77±0.13 for CHF patients. The cumulative conditional probability G(τ|τ0) is considered to evaluate if τ depends on a given interval τ0, that is, to evaluate the memory effect in excursion sequences. We find that the memory in excursions sequences under healthy conditions is characterized by the presence of clusters related to the fact that large excursions are more likely to be followed by large ones whereas for CHF data we do not observe this behavior. The presence of correlations in healthy data is confirmed by means of the detrended fluctuation analysis (DFA) while for CHF records the scaling exponent is characterized by a crossover, indicating that for short scales the sequences resemble uncorrelated noise.

  15. Gravitational Lens Modeling with Basis Sets

    NASA Astrophysics Data System (ADS)

    Birrer, Simon; Amara, Adam; Refregier, Alexandre

    2015-11-01

    We present a strong lensing modeling technique based on versatile basis sets for the lens and source planes. Our method uses high performance Monte Carlo algorithms, allows for an adaptive build up of complexity, and bridges the gap between parametric and pixel based reconstruction methods. We apply our method to a Hubble Space Telescope image of the strong lens system RX J1131-1231 and show that our method finds a reliable solution and is able to detect substructure in the lens and source planes simultaneously. Using mock data, we show that our method is sensitive to sub-clumps with masses four orders of magnitude smaller than the main lens, which corresponds to about {10}8{M}⊙ , without prior knowledge of the position and mass of the sub-clump. The modeling approach is flexible and maximizes automation to facilitate the analysis of the large number of strong lensing systems expected in upcoming wide field surveys. The resulting search for dark sub-clumps in these systems, without mass-to-light priors, offers promise for probing physics beyond the standard model in the dark matter sector.

  16. On the bound of first excursion probability

    NASA Technical Reports Server (NTRS)

    Yang, J. N.

    1969-01-01

    Method has been developed to improve the lower bound of the first excursion probability that can apply to the problem with either constant or time-dependent barriers. The method requires knowledge of the joint density function of the random process at two arbitrary instants.

  17. Multiple Palaeoproterozoic carbon burial episodes and excursions

    NASA Astrophysics Data System (ADS)

    Martin, A. P.; Prave, A. R.; Condon, D. J.; Lepland, A.; Fallick, A. E.; Romashkin, A. E.; Medvedev, P. V.; Rychanchik, D. V.

    2015-08-01

    Organic-rich rocks (averaging 2-5% total organic carbon) and positive carbonate-carbon isotope excursions (δ13C > + 5 ‰ and locally much higher, i.e. the Lomagundi-Jatuli Event) are hallmark features of Palaeoproterozoic successions and are assumed to archive a global event of unique environmental conditions following the c. 2.3 Ga Great Oxidation Event. Here we combine new and published geochronology that shows that the main Palaeoproterozoic carbon burial episodes (CBEs) preserved in Russia, Gabon and Australia were temporally discrete depositional events between c. 2.10 and 1.85 Ga. In northwest Russia we can also show that timing of the termination of the Lomagundi-Jatuli Event may have differed by up to 50 Ma between localities, and that Ni mineralisation occurred at c. 1920 Ma. Further, CBEs have traits in common with Mesozoic Oceanic Anoxic Events (OAEs); both are exceptionally organic-rich relative to encasing strata, associated with contemporaneous igneous activity and marked by organic carbon isotope profiles that exhibit a stepped decrease followed by a stabilisation period and recovery. Although CBE strata are thicker and of greater duration than OAEs (100 s of metres versus metres, ∼106 years versus ∼105 years), their shared characteristics hint at a commonality of cause(s) and feedbacks. This suggests that CBEs represent processes that can be either basin-specific or global in nature and a combination of circumstances that are not unique to the Palaeoproterozoic. Our findings urge circumspection and re-consideration of models that assume CBEs are a Deep Time singularity.

  18. High-resolution palaeomagnetic records of the Laschamp geomagnetic excursion from the Blake Ridge

    NASA Astrophysics Data System (ADS)

    Mac Niocaill, C.; Bourne, M. D.; Thomas, A. L.; Henderson, G. M.

    2013-05-01

    Geomagnetic excursions are brief (1000s of years) deviations in geomagnetic field behaviour from that expected during 'normal secular' variation. The Laschamp excursion (~41 ka) was a global deviation in geomagnetic field behaviour. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity. Accurate dating of excursions and determinations of their durations from multiple locations is vital to our understanding to global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172) Relatively high sedimentation rates (~30-40 cm kyr-1) at these locations allow the determination of transitional field behaviour during the excursion. Despite their advantages, sedimentary records can be limited by the potential for unrecognized variations in sedimentation rates between widely spaced age-constrained boundaries. Rather than assuming a constant sedimentation rate between assigned age tie-points, we employ measurements of the concentration of 230Thxs in the sediment. 230Thxs is a constant flux proxy and may be used to assess variations in the sedimentation rates through the core sections of interest. Following this approach, we present a new age model for Site 1061 that allows us to better determine the temporal behaviour of the Laschamp excursion with greater accuracy and known uncertainty. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. The excursion is characterised by rapid transitions (less than 200 years) between a stable normal polarity and a partially-reversed, polarity. Peaks in inclination either side of the directional excursion indicate periods of time when the local field is dominated by vertical

  19. ODP Site 1063 (Bermuda Rise) revisited: Oxygen isotopes, excursions and paleointensity in the Brunhes Chron

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.; Hodell, D. A.; Curtis, J. H.

    2012-02-01

    An age model for the Brunhes Chron of Ocean Drilling Program (ODP) Site 1063 (Bermuda Rise) is constructed by tandem correlation of oxygen isotope and relative paleointensity data to calibrated reference templates. Four intervals in the Brunhes Chron where paleomagnetic inclinations are negative for both u-channel samples and discrete samples are correlated to the following magnetic excursions with Site 1063 ages in brackets: Laschamp (41 ka), Blake (116 ka), Iceland Basin (190 ka), Pringle Falls (239 ka). These ages are consistent with current age estimates for three of these excursions, but not for "Pringle Falls" which has an apparent age older than a recently published estimate by ˜28 kyr. For each of these excursions (termed Category 1 excursions), virtual geomagnetic poles (VGPs) reach high southerly latitudes implying paired polarity reversals of the Earth's main dipole field, that apparently occurred in a brief time span (<2 kyr in each case), several times shorter than the apparent duration of regular polarity transitions. In addition, several intervals of low paleomagnetic inclination (low and negative in one case) are observed both in u-channel and discrete samples at ˜318 ka (MIS 9), ˜412 ka (MIS 11) and in the 500-600 ka interval (MIS 14-15). These "Category 2" excursions may constitute inadequately recorded (Category 1) excursions, or high amplitude secular variation.

  20. Systematic Behavior of the Non-dipole Magnetic Field during the 32 ka Mono Lake Excursion

    NASA Astrophysics Data System (ADS)

    Negrini, R. M.; McCuan, D.; Cassata, W. S.; Channell, J. E.; Verosub, K. L.; Liddicoat, J. C.; Knott, J. R.; Coe, R. S.; Benson, L. V.; Sarna-Wojcicki, A.; Lund, S.; Horton, R.; Lopez, J.

    2012-12-01

    Paleomagnetic excursions are enigmatic phenomena that reveal geodynamo behavior in its transitional state and provide important refinements in age control for the late Pleistocene, a critical time period for the study of paleoclimate and human evolution. We report here on two widely separated, unusually detailed records of the Mono Lake excursion (MLE) from sedimentary sequences dated at 32 ka. One of the records is from Summer Lake, Oregon. The vector components of this new record faithfully reproduce the principle features of the MLE as recorded at the type localities around Mono Lake, CA, though with greater detail and higher amplitude. Radiocarbon dates on bulk organics in the Summer Lake record confirm the 32 ka age of the MLE. The other record is from the marine Irminger Basin off of eastern Greenland and is based on the measurement of discrete samples rather than u-channels. The associated VGP paths of the two records strongly suggest systematic field behavior that includes three loci of nondipole flux whose relative dominance oscillates through time. The staggered sequence followed by the two paths through each flux locus further suggests that both the demise and return of the main field floods zonally during the excursion. The composite path is also compatible with the VGPs of a 32 ka set of lavas from New Zealand and, notably, it does not include VGPs associated with the 40 ka Laschamp excursion. This confirms that these two excursions are distinct events and, more specifically, shows that it is the 32 ka Mono Lake excursion that is recorded in the sediments surrounding Mono Lake rather than the ~40 ka Laschamp excursion.

  1. Isukasia area: Regional geological setting (includes excursion guide)

    NASA Technical Reports Server (NTRS)

    Nutman, A. P.; Rosing, M.

    1986-01-01

    A brief account of the geology of the Isukasis area is given and is biased toward the main theme of the itinerary for the area: What has been established about the protoliths of the early Archean rocks of the area - the Isua supracrustal belt and the Amitsoq gneisses? The area's long and complex tectonometamorphic history of events can be divided into episodes using a combination of dike chronology, isotopic, and petrological studies. The earliest dikes, the ca 3700 Ma Inaluk dikes, intrude the earliest (tonalitic) components of the Amitsoq gneisses but are themselves cut up by the injection of the younger (granitic and pegmatitic) phases of the Amitsoq gneisses of the area. The areas of low late Archean deformation, strongly deformed early Archean mafic rocks have coarse grained metamorphic segregations and are cut by virtually undeformed mid-Archean Tarssartoq (Ameralik) dikes devoid of metamorphic segregations. The shows that the area was affected by regional amphibolite facies metamorphism in the early Archean. Late Archean and Proterozoic metamorphic imprints are marked to very strong in the area. Much of the early Archean gneiss complex was already highly deformed when the mid-Archean Tarssartoq dikes were intruded.

  2. Geomagnetic excursions in the past 60 ka: Ephemeral secular variation features

    NASA Astrophysics Data System (ADS)

    Thouveny, N.; Creer, K. M.

    1992-05-01

    Geomagnetic excursions have been reported for the past 25 years in both sedimentary and igneous rocks of Brunhes age and from widespread geographic localities. They comprise sequences of paleo-magnetic directions that are anomalous in that they depart widely from the range of geomagnetic north directions recorded through historic time; they have sometimes been interpreted as records of aborted reversals of polarity of the main geomagnetic dipole. The search for "excursions" sought to provide a set of stratigraphic markers. The case of the Laschamp "excursion," described in lava flows from the Chaîne des Puys (Massif Central, France), is analyzed here through a new sequential record of paleosecular variation recovered from sedimentary cores collected in Lac du Bouchet, a maar lake about 100 km from the Laschamp site. The absence of anomalous directions indicates that this excursion lasted for only a few centuries. This constitutes a warning to stratigraphers who attempt to use excursions as marker events, and it gives an insight on the behavior of Earth's geodynamo on the scale of 102 to 103 yr.

  3. Scaling fixed-field alternating gradient accelerators with a small orbit excursion.

    PubMed

    Machida, Shinji

    2009-10-16

    A novel scaling type of fixed-field alternating gradient (FFAG) accelerator is proposed that solves the major problems of conventional scaling and nonscaling types. This scaling FFAG accelerator can achieve a much smaller orbit excursion by taking a larger field index k. A triplet focusing structure makes it possible to set the operating point in the second stability region of Hill's equation with a reasonable sensitivity to various errors. The orbit excursion is about 5 times smaller than in a conventional scaling FFAG accelerator and the beam size growth due to typical errors is at most 10%. PMID:19905700

  4. Scaling Fixed-Field Alternating Gradient Accelerators with a Small Orbit Excursion

    SciTech Connect

    Machida, Shinji

    2009-10-16

    A novel scaling type of fixed-field alternating gradient (FFAG) accelerator is proposed that solves the major problems of conventional scaling and nonscaling types. This scaling FFAG accelerator can achieve a much smaller orbit excursion by taking a larger field index k. A triplet focusing structure makes it possible to set the operating point in the second stability region of Hill's equation with a reasonable sensitivity to various errors. The orbit excursion is about 5 times smaller than in a conventional scaling FFAG accelerator and the beam size growth due to typical errors is at most 10%.

  5. Spinodal instabilities and super-Planckian excursions in natural inflation.

    PubMed

    Albrecht, Andreas; Holman, R; Richard, Benoit J

    2015-05-01

    Models such as Natural Inflation that use pseudo-Nambu-Goldstone bosons as the inflaton are attractive for many reasons. However, they typically require trans-Planckian field excursions ΔΦ>MPl, due to the need for an axion decay constant f>MPl to have both a sufficient number of e-folds and values of ns,r consistent with data. Such excursions would in general require the addition of all other higher dimension operators consistent with symmetries, thus disrupting the required flatness of the potential and rendering the theory nonpredictive. We show that in the case of Natural Inflation, the existence of spinodal instabilities (modes with tachyonic masses) can modify the inflaton equations of motion to the point that versions of the model with f

  6. Undulator Changes Due To Temperature Excursions

    SciTech Connect

    Wolf, Zachary; Levashov, Yurii; Reese, Ed; /SLAC

    2010-11-17

    The temperature of the LCLS undulators has not been controlled during storage. The effects of the temperature excursions are documented in this note. After a number of LCLS undulators were tuned, fiducialized, and placed in storage anticipating their use, a test was made to ensure that their properties had not changed. The test revealed, however, that indeed the undulators had changed. Detailed study of this problem followed. We now believe that the gap of the undulators changes permanently when the undulators go through temperature excursions. We have tested the other possible cause, transportation, and do not see gap changes. In this note, we document how the undulators have changed since they were originally tuned. The undulators were tuned and fiducialized in the Magnetic Measurement Facility (MMF). Afterward, many of them (approximately 18) were taken to building 750 for storage during summer and fall 2007. Building 750 had no temperature control. The undulator temperatures went from 20 C, used for tuning, down to approximately 11 C during the winter. In January 2008, three of the undulators were brought back to the MMF for a check. All three undulators showed similar changes. Trajectories, phases, and most undulator properties stayed the same, but the fiducialization (beam axis position relative to tooling balls on the undulator) had changed. Further investigation showed that the undulator gap was altered in a periodic way along the magnetic axis with a net average gap change causing the fiducialization change. A new storage location in building 33 was found and future undulators were placed there. A failure in the temperature control, however, caused the undulators to get too hot. Again the gap changed, but with a different periodic pattern. This note documents the measured changes in the undulators. In particular, it shows the detailed history of undulator 39 which went through both negative and positive temperature excursions.

  7. Data Mining Using Extensions of the Rough Set Model.

    ERIC Educational Resources Information Center

    Lingras, P. J.; Yao, Y. Y.

    1998-01-01

    Examines basic issues of data mining using the theory of rough sets, a recent proposal for generalizing classical set theory. Demonstrates that a generalized rough set model can be used for generating rules from incomplete databases. Discusses the importance of rule extraction from incomplete databases in data mining. (AEF)

  8. A Comparison of two Brunhes Chron Geomagnetic Excursions Recorded by Neighbouring North Atlantic Sites (ODP Sites 1062 and 1063)

    NASA Astrophysics Data System (ADS)

    Bourne, M.; Mac Niocaill, C.; Knudsen, M. F.; Thomas, A. L.; Henderson, G. M.

    2012-04-01

    A full picture of geomagnetic field behaviour during the Blake excursion is currently limited by a paucity of robust, high-resolution records of this ambiguous event. Some records seem to point towards a 'double-excursion' character whilst others fail to record the Blake excursion at all. We present here a high-resolution record of the Blake excursion obtained from Ocean Drilling Program (ODP) Site 1062 on the Blake Outer Ridge (ODP Leg 172). Palaeomagnetic measurements in three cores reveal a single excursional feature associated with a broad palaeointensity low, characterised by rapid transitions (less than 500 years) between a stable normal polarity and a fully-reversed, pseudo-stable polarity. A relatively high sedimentation rate (~10 cm kyr-1) allows the determination of transitional field behaviour during the excursion. Rather than assuming a constant sedimentation rate between assigned age tie-points, we employ measurements of 230Thxs concentrations in the sediment to assess variations in the sedimentation rates through the core sections of interest. This allows us to determine an age and duration for the two excursions with greater accuracy and known uncertainty. Our new age model gives an age of 127 ka for the midpoint of the Blake event at Site 1062. The age model also gives a duration for the directional excursion of 7.1±1.6 kyr. This duration is similar to that previously reported for the Iceland Basin Excursion (~185 ka) from the nearby Bermuda Rise (ODP Site 1063), which recorded a ~7-8 kyr event. Similarly, a high sedimentation rate (10-15 cm kyr-1) at this site allows a high-resolution reconstruction of the geomagnetic field behaviour during the Iceland Basin Excursion. The Site 1063 palaeomagnetic record suggests more complicated behaviour than that of the Blake excursion at Site 1062. Instead, transitional VGP paths are characterised by stop-and-go behaviour between VGP clusters that may be related to long-standing thermo-dynamic features of the

  9. The IIASA set of energy models: Its design and application

    NASA Astrophysics Data System (ADS)

    Basile, P. S.; Agnew, M.; Holzl, A.; Kononov, Y.; Papin, A.; Rogner, H. H.; Schrattenholzer, L.

    1980-12-01

    The models studied include an accounting framework type energy demand model, a dynamic linear programming energy supply and conversion system model, an input-output model, a macroeconomic model, and an oil trade gaming model. They are incorporated in an integrated set for long-term, global analyses. This set makes use of a highly iterative process for energy scenario projections and analyses. Each model is quite simple and straightforward in structure; a great deal of human judgement is necessary in applying the set. The models are applied to study two alternative energy scenarios for a coming fifty year period. Examples are presented revealing the wealth of information that can be obtained from multimodel techniques. Details are given for several models (equations employed, assumptions made, data used).

  10. Carbon Isotopic Excursions Associated with the Mid-Pleistocene Transition and the Mid-Brunhes Transition

    NASA Astrophysics Data System (ADS)

    Barth, A. M.; Bill, N. S.; Clark, P. U.; Pisias, N. G.

    2015-12-01

    During the last 2 Myr, the climate system experienced two major transitions in variability: the mid-Pleistocene Transition (MPT), which represents a shift from dominant low-amplitude 41-kyr frequencies to dominant high-amplitude 100-kyr frequencies, and the mid-Brunhes Transition (MBT), which represents an increase in the amplitude of the 100-kyr frequency. While the MPT and MBT are typically identified in the benthic marine δ18O stack, their expression in other components of the climate system is less clear. Pleistocene δ13C records have been used to characterize climate and ocean circulation changes in response to orbital forcing, but these studies have used either a limited number of records or stacked data sets, which have the potential to bias the variability from the large number of young records. Here we present those existing δ13C data sets (n=18) that completely span these transitions. We use empirical orthogonal functions (EOFs) on these continuous data sets rather than stacking, allowing the determination of the dominant modes of variability and characterization of the time-frequency variation during the last 2 Myr. Our results identify two substantial carbon isotopic excursions. The first is a pronounced negative excursion during the MPT (~900 ka, MIS 23) that stands out as the strongest minimum in the last 2 Myr (previously identified from five records by Raymo et al., 1997). Corresponding ɛNd data from the South Atlantic suggest a strong weakening of the Atlantic meridional overturning circulation through the MIS 23 interglacial associated with this excursion. The second is a robust positive excursion ~530 ka (MIS 13), prior to the MBT (MIS 11), which stands out as the strongest maximum in the last 2 Myr. Possible causes of these excursions will be discussed.

  11. Parameterization of Model Validating Sets for Uncertainty Bound Optimizations. Revised

    NASA Technical Reports Server (NTRS)

    Lim, K. B.; Giesy, D. P.

    2000-01-01

    Given measurement data, a nominal model and a linear fractional transformation uncertainty structure with an allowance on unknown but bounded exogenous disturbances, easily computable tests for the existence of a model validating uncertainty set are given. Under mild conditions, these tests are necessary and sufficient for the case of complex, nonrepeated, block-diagonal structure. For the more general case which includes repeated and/or real scalar uncertainties, the tests are only necessary but become sufficient if a collinearity condition is also satisfied. With the satisfaction of these tests, it is shown that a parameterization of all model validating sets of plant models is possible. The new parameterization is used as a basis for a systematic way to construct or perform uncertainty tradeoff with model validating uncertainty sets which have specific linear fractional transformation structure for use in robust control design and analysis. An illustrative example which includes a comparison of candidate model validating sets is given.

  12. A New High-Resolution Record of the Blake Geomagnetic Excursion from ODP Site 1062

    NASA Astrophysics Data System (ADS)

    Bourne, M. D.; Mac Niocaill, C.; Henderson, G. M.; Thomas, A. L.; Faurschou Knudsen, M.

    2010-12-01

    We present a high resolution record of the Blake geomagnetic excursion from Ocean Drilling Program (ODP) Site 1062 on the Blake-Bahama Outer Ridge. The excursion is recorded in three separate cores, with the high sedimentation rate (~10 cm/ka) at this location allowing the determination of transitional field behaviour during the excursion. A complex geometry is observed for the excursional geomagnetic field at the site. The directional records show an initial deviation from the expected directions across an interval of 1 m that achieves a completely reversed state, and then returns to normal polarity. A second, although less well-defined, short-lived phase of anomalous directions is observed immediately following the first event in two of the three cores. Measurements of the magnetic susceptibility show little variation through the core indicating that the concentration and grain size of the remanence carriers remain relatively constant during the studied interval. Measurements of the S-Ratio and remanence coercivity also remain constant through the sections of interest, and indicate magnetite to be the primary remanence carrier. The relatively homogeneous sediment enables the determination of two relative palaeointensity proxies by normalizing natural remanent magnetization measurements using artificially induced magnetizations (anhysteretic remanence, ARM and isothermal remanence, IRM). These records are consistent between all three cores. The relative palaeointensity proxies suggest that the Earth's magnetic field decreased substantially in intensity several tens of kyr prior to the initial event, before reaching an intensity minimum coinciding with the directional excursion maximum. A second palaeointensity minimum is also observed after the excursional event with no associated directional change. These features are consistent with global palaeointensity stacks. Our age model uses a new oxygen isotope stratigraphy. However, rather than assuming a constant

  13. Gaussian predictive process models for large spatial data sets

    PubMed Central

    Banerjee, Sudipto; Gelfand, Alan E.; Finley, Andrew O.; Sang, Huiyan

    2009-01-01

    Summary With scientific data available at geocoded locations, investigators are increasingly turning to spatial process models for carrying out statistical inference. Over the last decade, hierarchical models implemented through Markov chain Monte Carlo methods have become especially popular for spatial modelling, given their flexibility and power to fit models that would be infeasible with classical methods as well as their avoidance of possibly inappropriate asymptotics. However, fitting hierarchical spatial models often involves expensive matrix decompositions whose computational complexity increases in cubic order with the number of spatial locations, rendering such models infeasible for large spatial data sets. This computational burden is exacerbated in multivariate settings with several spatially dependent response variables. It is also aggravated when data are collected at frequent time points and spatiotemporal process models are used. With regard to this challenge, our contribution is to work with what we call predictive process models for spatial and spatiotemporal data. Every spatial (or spatiotemporal) process induces a predictive process model (in fact, arbitrarily many of them). The latter models project process realizations of the former to a lower dimensional subspace, thereby reducing the computational burden. Hence, we achieve the flexibility to accommodate non-stationary, non-Gaussian, possibly multivariate, possibly spatiotemporal processes in the context of large data sets. We discuss attractive theoretical properties of these predictive processes. We also provide a computational template encompassing these diverse settings. Finally, we illustrate the approach with simulated and real data sets. PMID:19750209

  14. Fuzzy Partition Models for Fitting a Set of Partitions.

    ERIC Educational Resources Information Center

    Gordon, A. D.; Vichi, M.

    2001-01-01

    Describes methods for fitting a fuzzy consensus partition to a set of partitions of the same set of objects. Describes and illustrates three models defining median partitions and compares these methods to an alternative approach to obtaining a consensus fuzzy partition. Discusses interesting differences in the results. (SLD)

  15. Fully Characterizing Axially Symmetric Szekeres Models with Three Data Sets

    NASA Astrophysics Data System (ADS)

    Célérier, Marie-Nöelle Mishra, Priti; Singh, Tejinder P.

    2015-01-01

    Inhomogeneous exact solutions of General Relativity with zero cosmological constant have been used in the literature to challenge the ΛCDM model. From one patch Lemaître-Tolman-Bondi (LTB) models to axially symmetric quasi-spherical Szekeres (QSS) Swiss-cheese models, some of them are able to reproduce to a good accuracy the cosmological data. It has been shown in the literature that a zero Λ LTB model with a central observer can be fully determined by two data sets. We demonstrate that an axially symmetric zero Λ QSS model with an observer located at the origin can be fully reconstructed from three data sets, number counts, luminosity distance and redshift drift. This is a first step towards a future demonstration involving five data sets and the most general Szekeres model.

  16. A Model Evaluation Data Set for the Tropical ARM Sites

    DOE Data Explorer

    Jakob, Christian

    2008-01-15

    This data set has been derived from various ARM and external data sources with the main aim of providing modelers easy access to quality controlled data for model evaluation. The data set contains highly aggregated (in time) data from a number of sources at the tropical ARM sites at Manus and Nauru. It spans the years of 1999 and 2000. The data set contains information on downward surface radiation; surface meteorology, including precipitation; atmospheric water vapor and cloud liquid water content; hydrometeor cover as a function of height; and cloud cover, cloud optical thickness and cloud top pressure information provided by the International Satellite Cloud Climatology Project (ISCCP).

  17. AVO for one- and two-fracture set models

    USGS Publications Warehouse

    Chen, H.; Brown, R.L.; Castagna, J.P.

    2005-01-01

    A theoretical comparison is made of PP and PS angle-dependent reflection coefficients at the top of two fractured-reservoir models using exact, general, anisotropic reflection coefficients. The two vertical-fracture models are taken to have the same total crack density. The primary issue investigated is determination of the fracture orientation using azimuthal AVO analysis. The first model represents a single-fracture set and the second model has an additional fracture set oblique to the first set at an angle of 60??. As expected, the PP-wave anisotropy is reduced when multiple fracture sets are present, making the determination of orientation more difficult than for the case of a single-fracture set. Long offsets are required for identification of dominant fracture orientations using PP-wave AVO. PS-wave AVO, however, is quite sensitive to fracture orientations, even at short offsets. For multiple-fracture sets, PS signals can potentially be used to determine orientations of the individual sets. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

  18. An intelligent diagnosis model based on rough set theory

    NASA Astrophysics Data System (ADS)

    Li, Ze; Huang, Hong-Xing; Zheng, Ye-Lu; Wang, Zhou-Yuan

    2013-03-01

    Along with the popularity of computer and rapid development of information technology, how to increase the accuracy of the agricultural diagnosis becomes a difficult problem of popularizing the agricultural expert system. Analyzing existing research, baseing on the knowledge acquisition technology of rough set theory, towards great sample data, we put forward a intelligent diagnosis model. Extract rough set decision table from the samples property, use decision table to categorize the inference relation, acquire property rules related to inference diagnosis, through the means of rough set knowledge reasoning algorithm to realize intelligent diagnosis. Finally, we validate this diagnosis model by experiments. Introduce the rough set theory to provide the agricultural expert system of great sample data a effective diagnosis model.

  19. Computerized reduction of elementary reaction sets for combustion modeling

    NASA Technical Reports Server (NTRS)

    Wikstrom, Carl V.

    1991-01-01

    If the entire set of elementary reactions is to be solved in the modeling of chemistry in computational fluid dynamics, a set of stiff ordinary differential equations must be integrated. Some of the reactions take place at very high rates, requiring short time steps, while others take place more slowly and make little progress in the short time step integration. The goal is to develop a procedure to automatically obtain sets of finite rate equations, consistent with a partial equilibrium assumptions, from an elementary set appropriate to local conditions. The possibility of computerized reaction reduction was demonstrated. However, the ability to use the reduced reaction set depends on the ability of the CFD approach in incorporate partial equilibrium calculations into the computer code. Therefore, the results should be tested on a code with partial equilibrium capability.

  20. Controllable set analysis for planetary landing under model uncertainties

    NASA Astrophysics Data System (ADS)

    Long, Jiateng; Gao, Ai; Cui, Pingyuan

    2015-07-01

    Controllable set analysis is a beneficial method in planetary landing mission design by feasible entry state selection in order to achieve landing accuracy and satisfy entry path constraints. In view of the severe impact of model uncertainties on planetary landing safety and accuracy, the purpose of this paper is to investigate the controllable set under uncertainties between on-board model and the real situation. Controllable set analysis under model uncertainties is composed of controllable union set (CUS) analysis and controllable intersection set (CIS) analysis. Definitions of CUS and CIS are demonstrated and computational method of them based on Gauss pseudospectral method is presented. Their applications on entry states distribution analysis under uncertainties and robustness of nominal entry state selection to uncertainties are illustrated by situations with ballistic coefficient, lift-to-drag ratio and atmospheric uncertainty in Mars entry. With analysis of CUS and CIS, the robustness of entry state selection and entry trajectory to model uncertainties can be guaranteed, thus enhancing the safety, reliability and accuracy under model uncertainties during planetary entry and landing.

  1. ODP Site 1063 (Bermuda Rise) revisited: Oxygen isotopes, excursions and paleointensity in the Brunhes Chron

    NASA Astrophysics Data System (ADS)

    Channell, J. E.; Hodell, D. A.

    2011-12-01

    An age model for the Brunhes Chron for Ocean Drilling Program (ODP) Site 1063 (Bermuda Rise) is based on the tandem correlation of oxygen isotope and relative paleointensity data to calibrated reference templates. Four intervals in the Brunhes Chron where component inclinations are negative, for both u-channel samples and discrete samples, are correlated to the following magnetic excursions with Site 1063 ages in brackets: Laschamp (41 ka), Blake (116 ka), Iceland Basin (190 ka), Pringle Falls (239 ka). These ages are consistent with current age estimates for these excursion, other than for "Pringle Falls" which has an apparent age older than current estimates by ~20-30 kyrs. For each of these excursions, virtual geomagnetic poles (VGPs) reach high southerly latitudes implying paired polarity reversals in a brief time span (<2 kyr in each case) that is several times shorter than the observed duration of long-lived polarity transitions at mid-latitudes. Several intervals of low component inclinations, that are low and negative in one case, are observed both in u-channel and discrete samples at ~318 ka (MIS 9), ~413 ka (MIS 11) and in the 500-600 ka interval (MIS14-15). These may constitute inadequately recorded excursions, or high amplitude secular variation.

  2. An experimental methodology for a fuzzy set preference model

    NASA Technical Reports Server (NTRS)

    Turksen, I. B.; Willson, Ian A.

    1992-01-01

    A flexible fuzzy set preference model first requires approximate methodologies for implementation. Fuzzy sets must be defined for each individual consumer using computer software, requiring a minimum of time and expertise on the part of the consumer. The amount of information needed in defining sets must also be established. The model itself must adapt fully to the subject's choice of attributes (vague or precise), attribute levels, and importance weights. The resulting individual-level model should be fully adapted to each consumer. The methodologies needed to develop this model will be equally useful in a new generation of intelligent systems which interact with ordinary consumers, controlling electronic devices through fuzzy expert systems or making recommendations based on a variety of inputs. The power of personal computers and their acceptance by consumers has yet to be fully utilized to create interactive knowledge systems that fully adapt their function to the user. Understanding individual consumer preferences is critical to the design of new products and the estimation of demand (market share) for existing products, which in turn is an input to management systems concerned with production and distribution. The question of what to make, for whom to make it and how much to make requires an understanding of the customer's preferences and the trade-offs that exist between alternatives. Conjoint analysis is a widely used methodology which de-composes an overall preference for an object into a combination of preferences for its constituent parts (attributes such as taste and price), which are combined using an appropriate combination function. Preferences are often expressed using linguistic terms which cannot be represented in conjoint models. Current models are also not implemented an individual level, making it difficult to reach meaningful conclusions about the cause of an individual's behavior from an aggregate model. The combination of complex aggregate

  3. Setting up virgin stress conditions in discrete element models

    PubMed Central

    Rojek, J.; Karlis, G.F.; Malinowski, L.J.; Beer, G.

    2013-01-01

    In the present work, a methodology for setting up virgin stress conditions in discrete element models is proposed. The developed algorithm is applicable to discrete or coupled discrete/continuum modeling of underground excavation employing the discrete element method (DEM). Since the DEM works with contact forces rather than stresses there is a need for the conversion of pre-excavation stresses to contact forces for the DEM model. Different possibilities of setting up virgin stress conditions in the DEM model are reviewed and critically assessed. Finally, a new method to obtain a discrete element model with contact forces equivalent to given macroscopic virgin stresses is proposed. The test examples presented show that good results may be obtained regardless of the shape of the DEM domain. PMID:27087731

  4. Setting conservation management thresholds using a novel participatory modeling approach.

    PubMed

    Addison, P F E; de Bie, K; Rumpff, L

    2015-10-01

    We devised a participatory modeling approach for setting management thresholds that show when management intervention is required to address undesirable ecosystem changes. This approach was designed to be used when management thresholds: must be set for environmental indicators in the face of multiple competing objectives; need to incorporate scientific understanding and value judgments; and will be set by participants with limited modeling experience. We applied our approach to a case study where management thresholds were set for a mat-forming brown alga, Hormosira banksii, in a protected area management context. Participants, including management staff and scientists, were involved in a workshop to test the approach, and set management thresholds to address the threat of trampling by visitors to an intertidal rocky reef. The approach involved trading off the environmental objective, to maintain the condition of intertidal reef communities, with social and economic objectives to ensure management intervention was cost-effective. Ecological scenarios, developed using scenario planning, were a key feature that provided the foundation for where to set management thresholds. The scenarios developed represented declines in percent cover of H. banksii that may occur under increased threatening processes. Participants defined 4 discrete management alternatives to address the threat of trampling and estimated the effect of these alternatives on the objectives under each ecological scenario. A weighted additive model was used to aggregate participants' consequence estimates. Model outputs (decision scores) clearly expressed uncertainty, which can be considered by decision makers and used to inform where to set management thresholds. This approach encourages a proactive form of conservation, where management thresholds and associated actions are defined a priori for ecological indicators, rather than reacting to unexpected ecosystem changes in the future. PMID:26040608

  5. The Mono Lake Excursion Recorded in Phonolitic Lavas From Tenerife (Canary Islands): Paleomagnetic Analyses and Coupled K/Ar and Ar/Ar Dating.

    NASA Astrophysics Data System (ADS)

    Kissel, C.; Guillou, H.; Laj, C. E.; Carracedo, J. C.; Nomade, S.; Perez-Torrado, F.; Wandres, C.

    2011-12-01

    Studies of geomagnetic excursions is important for the knowledge of the geodynamo, and also because they may be used as precise time markers in various geological records (sediments, lavas and ice via their impact on the production of cosmogenic isotopes). In volcanic rocks, the identification of excursions is very challenging given the sporadic nature of the volcanic eruptions. However, it is a critical step because it allows absolute paleointensity determinations to be obtained, coupled with absolute dating methods. We present here a coupled paleomagnetic/dating investigation conducted on three different lava flows from the island of Tenerife (Canary Islands; Spain) erupted during the Mono Lake excursion (MLE). Paleomagnetic analyses consist in zero field demagnetizations (AF and/or thermal) and of Thellier and Thellier experiments using the PICRIT-03 set of criteria to select reliable intensity determinations. For dating, the unspiked K-Ar and the 40Ar/39Ar methods were coupled at LSCE for two of the flows and the third flow, with lower content in radiogenic 40Ar (40Ar*) was dated only using the unspiked K-Ar method. One of the flows is characterized by a direction largely deviated from the one expected from an axial geocentric dipole (GAD) field. Its paleointensity value is very low (7.8 μT). The two other sites are characterized by inclinations slightly shallower than the GAD value and by low intensity values (about 12 and 21 μT; present value: 38μT). The three K/Ar ages combined with two 40Ar/39Ar ages range from 32.0 to 33.2 ka and they are not statistically distinguishable from one another. It therefore appears that these lavas have recorded the MLE (the only excursion in this time interval) confirming its brief duration (shorter than the minimum age uncertainties available). The mean age is younger but, within the uncertainties and depending on the age of the standard we use, consistent with the age of the 10Be peak and of the marine intensity low when

  6. The Record of Geomagnetic Excursions from a ~150 m Sediment Core: Clear Lake, Northern California

    NASA Astrophysics Data System (ADS)

    Levin, E.; Byrne, R.; Looy, C. V.; Wahl, D.; Noren, A. J.; Verosub, K. L.

    2015-12-01

    We are studying the paleomagnetic properties of a new ~150 meter drill core from Clear Lake, CA. Step-wise demagnetization of the natural remanent magnetism (NRM) yields stable directions after 20 mT, implying that the sediments are reliable recorders of geomagnetic field behavior. Several intervals of low relative paleointensity (RPI) from the core appear to be correlated with known geomagnetic excursions. At about 46 m depth, and ~33 ka according to an age model based on radiocarbon dates obtained from pollen and the Olema ash bed, a low RPI zone seems to agree with the age and duration of the Mono Lake Excursion, previously identified between 32 and 35 ka. Slightly lower in the core, at about 50 m depth and ~40 ka, noticeably low RPI values seem to be coeval with the Laschamp excursion, which has been dated at ~41 ka. A volcanic ash near the bottom of the core (141 mblf) is near the same depth as an ash identified in 1988 by Andrei Sarna-Wojcicki and others as the Loleta ash bed in a previous Clear Lake core. If the basal ash in the new core is indeed the, Loleta ash bed, then the core may date back to about 270-300 ka. Depending on the age of the lowest ash, a sequence of low RPI intervals could correlate with the Blake (120 ka), Iceland Basin (188 ka), Jamaica/Pringle Falls (211 ka), and CR0 (260 ka) excursions. Correlation of the low RPI intervals to these geomagnetic excursions will help in the development of a higher resolution chronostratigraphy for the core, resolve a long-standing controversy about a possible hiatus in the Clear Lake record, and provide information about climatically-driven changes in sedimentation.

  7. DIFFEOMORPHIC POINT SET REGISTRATION USING NON-STATIONARY MIXTURE MODELS

    PubMed Central

    Wassermann, D.; Ross, J.; Washko, G.; Westin, C-F; Estépar, R. San José

    2013-01-01

    This paper investigates a diffeomorphic point-set registration based on non-stationary mixture models. The goal is to improve the non-linear registration of anatomical structures by representing each point as a general non-stationary kernel that provides information about the shape of that point. Our framework generalizes work done by others that use stationary models. We achieve this by integrating the shape at each point when calculating the point-set similarity and transforming it according to the calculated deformation. We also restrict the non-rigid transform to the space of symmetric diffeomorphisms. Our algorithm is validated in synthetic and human datasets in two different applications: fiber bundle and lung airways registration. Our results shows that non-stationary mixture models are superior to Gaussian mixture models and methods that do not take into account the shape of each point. PMID:24419463

  8. Geomagnetic excursions date early hominid migration to China

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-09-01

    Global-scale geomagnetic reversals, which are periods when the direction of Earth's magnetic field flips, leave imprints in magnetic minerals present in sediments. But so do smaller-scale, even local, changes in Earth's magnetic field direction. Paleomagnetists believe that the smaller-scale events represent “failed reversals” and refer to them as “geomagnetic excursions.” Scientists use geomagnetic excursions in sedimentary basins as markers to tie together events of Earth's history across the globe.

  9. Instruction manual model 600F, data transmission test set

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Information necessary for the operation and maintenance of the Model 600F Data Transmission Test Set is presented. A description is contained of the physical and functional characteristics; pertinent installation data; instructions for operating the equipment; general and detailed principles of operation; preventive and corrective maintenance procedures; and block, logic, and component layout diagrams of the equipment and its major component assemblies.

  10. Using Set Model for Learning Addition of Integers

    ERIC Educational Resources Information Center

    Lestari, Umi Puji; Putri, Ratu Ilma Indra; Hartono, Yusuf

    2015-01-01

    This study aims to investigate how set model can help students' understanding of addition of integers in fourth grade. The study has been carried out to 23 students and a teacher of IVC SD Iba Palembang in January 2015. This study is a design research that also promotes PMRI as the underlying design context and activity. Results showed that the…

  11. A Novel Multipurpose Model Set for Teaching General Chemistry.

    ERIC Educational Resources Information Center

    Gupta, H. O.; Parkash, Brahm

    1999-01-01

    Reports on a low-cost and unique molecular model set capable of generating a large number of structures for teaching and learning general chemistry. An important component of the kit is an 11-hole ball that gives tetrahedral, octahedral, trigonal, trigonal bipyramidal, and square planar symmetries. (WRM)

  12. The Blake geomagnetic excursion recorded in a radiometrically dated speleothem

    NASA Astrophysics Data System (ADS)

    Osete, María-Luisa; Martín-Chivelet, Javier; Rossi, Carlos; Edwards, R. Lawrence; Egli, Ramon; Muñoz-García, M. Belén; Wang, Xianfeng; Pavón-Carrasco, F. Javier; Heller, Friedrich

    2012-11-01

    One of the most important developments in geomagnetism has been the recognition of polarity excursions of the Earth's magnetic field. Accurate timing of the excursions is a key point for understanding the geodynamo process and for magnetostratigraphic correlation. One of the best-known excursions is the Blake geomagnetic episode, which occurred during marine isotope stage MIS 5, but its morphology and age remain controversial. Here we show, for the first time, the Blake excursion recorded in a stalagmite which was dated using the uranium-series disequilibrium techniques. The characteristic remanent magnetisation is carried by fine-grained magnetite. The event is documented by two reversed intervals (B1 and B2). The age of the event is estimated to be between 116.5±0.7 kyr BP and 112.0±1.9 kyr BP, slightly younger (∼3-4 kyr) than recent estimations from sedimentary records dated by astronomical tuning. Low values of relative palaeointensity during the Blake episode are estimated, but a relative maximum in the palaeofield intensity coeval with the complete reversal during the B2 interval was observed. Duration of the Blake geomagnetic excursion is 4.5 kyr, two times lower than single excursions and slightly higher than the estimated diffusion time for the inner core (∼3 kyr).

  13. A fuzzy set preference model for market share analysis

    NASA Technical Reports Server (NTRS)

    Turksen, I. B.; Willson, Ian A.

    1992-01-01

    Consumer preference models are widely used in new product design, marketing management, pricing, and market segmentation. The success of new products depends on accurate market share prediction and design decisions based on consumer preferences. The vague linguistic nature of consumer preferences and product attributes, combined with the substantial differences between individuals, creates a formidable challenge to marketing models. The most widely used methodology is conjoint analysis. Conjoint models, as currently implemented, represent linguistic preferences as ratio or interval-scaled numbers, use only numeric product attributes, and require aggregation of individuals for estimation purposes. It is not surprising that these models are costly to implement, are inflexible, and have a predictive validity that is not substantially better than chance. This affects the accuracy of market share estimates. A fuzzy set preference model can easily represent linguistic variables either in consumer preferences or product attributes with minimal measurement requirements (ordinal scales), while still estimating overall preferences suitable for market share prediction. This approach results in flexible individual-level conjoint models which can provide more accurate market share estimates from a smaller number of more meaningful consumer ratings. Fuzzy sets can be incorporated within existing preference model structures, such as a linear combination, using the techniques developed for conjoint analysis and market share estimation. The purpose of this article is to develop and fully test a fuzzy set preference model which can represent linguistic variables in individual-level models implemented in parallel with existing conjoint models. The potential improvements in market share prediction and predictive validity can substantially improve management decisions about what to make (product design), for whom to make it (market segmentation), and how much to make (market share

  14. A New High-Resolution Record of the Blake Geomagnetic Excursion from ODP Site 1062

    NASA Astrophysics Data System (ADS)

    Bourne, Mark; Mac Niocaill, Conall; Henderson, Gideon; Thomas, Alex; Knudsen, Mads

    2010-05-01

    We present a high resolution record of the Blake geomagnetic excursion from Ocean Drilling Program (ODP) Site 1062 on the Blake-Bahama Outer Ridge. The excursion is recorded in three separate cores, with the high average sedimentation rate (10 cm ka-1) at this location allowing the determination of transitional field behaviour during the excursion. A complex geometry is observed for the excursional geomagnetic field. The directional records show an initial deviation from the expected directions across an interval of 1 m that achieves a completely reversed state, and then returns to normal polarity. A second, although less well-defined, short-lived phase of anomalous directions is observed immediately following the first event in two of the three cores. Measurements of the magnetic susceptibility show little variation through the core indicating that the concentration and grain size of the remanence carriers remains relatively constant throughout the studied interval. Measurements of the S-Ratio and remanence coercivity also remain constant through the core sections of interest, and indicate magnetite to be the primary remanence carrier. The relatively homogeneous sediment enables the determination of two relative palaeointensity proxies by normalizing natural remanent magnetization measurements using artificially induced magnetizations (anhysteretic remanence, ARM and isothermal remanence, IRM). These records are consistent between all three cores. The relative palaeointensity proxies suggest that the Earth's magnetic field decreased substantially in intensity up to 70 ka prior to the initial event, before reaching an intensity minimum coinciding with the directional excursion maximum. A second palaeointensity minimum is also observed after the excursional event with no associated directional change. These features are consistent with global palaeointensity stacks. A preliminary age model based on an oxygen isotope stratigraphy, and an average sedimentation rate

  15. A compressed marine data set for geomagnetic field modeling

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Baldwin, R. T.; Ridgway, J. R.; Davis, W. Minor

    1990-01-01

    Some 13 million scalar magnetic field data points that have been collected from the world's ocean areas reside in the collection of the National Geophysical Data Center. In order to derive a suitable data set for modeling the geomagnetic field of the earth, each ship track is divided into 220 km segments. The distribution of the reduced data in position, time and local time is discussed. The along-track filtering process described has proved to be an effective method of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for field modeling. This process also provides the benefits of smoothing short-wavelength crystal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be utilized in the least squares modeling.

  16. Cardiac rehabilitation delivery model for low-resource settings

    PubMed Central

    Grace, Sherry L; Turk-Adawi, Karam I; Contractor, Aashish; Atrey, Alison; Campbell, Norm; Derman, Wayne; Melo Ghisi, Gabriela L; Oldridge, Neil; Sarkar, Bidyut K; Yeo, Tee Joo; Lopez-Jimenez, Francisco; Mendis, Shanthi; Oh, Paul; Hu, Dayi; Sarrafzadegan, Nizal

    2016-01-01

    Objective Cardiovascular disease is a global epidemic, which is largely preventable. Cardiac rehabilitation (CR) is demonstrated to be cost-effective and efficacious in high-income countries. CR could represent an important approach to mitigate the epidemic of cardiovascular disease in lower-resource settings. The purpose of this consensus statement was to review low-cost approaches to delivering the core components of CR, to propose a testable model of CR which could feasibly be delivered in middle-income countries. Methods A literature review regarding delivery of each core CR component, namely: (1) lifestyle risk factor management (ie, physical activity, diet, tobacco and mental health), (2) medical risk factor management (eg, lipid control, blood pressure control), (3) education for self-management and (4) return to work, in low-resource settings was undertaken. Recommendations were developed based on identified articles, using a modified GRADE approach where evidence in a low-resource setting was available, or consensus where evidence was not. Results Available data on cost of CR delivery in low-resource settings suggests it is not feasible to deliver CR in low-resource settings as is delivered in high-resource ones. Strategies which can be implemented to deliver all of the core CR components in low-resource settings were summarised in practice recommendations, and approaches to patient assessment proffered. It is suggested that CR be adapted by delivery by non-physician healthcare workers, in non-clinical settings. Conclusions Advocacy to achieve political commitment for broad delivery of adapted CR services in low-resource settings is needed. PMID:27181874

  17. A mesoscopic network model for permanent set in crosslinked elastomers

    SciTech Connect

    Weisgraber, T H; Gee, R H; Maiti, A; Clague, D S; Chinn, S; Maxwell, R S

    2009-01-29

    A mesoscopic computational model for polymer networks and composites is developed as a coarse-grained representation of the composite microstructure. Unlike more complex molecular dynamics simulations, the model only considers the effects of crosslinks on mechanical behavior. The elastic modulus, which depends only on the crosslink density and parameters in the bond potential, is consistent with rubber elasticity theory, and the network response satisfies the independent network hypothesis of Tobolsky. The model, when applied to a commercial filled silicone elastomer, quantitatively reproduces the experimental permanent set and stress-strain response due to changes in the crosslinked network from irradiation.

  18. Late Brunhes polarity excursions (Mono Lake, Laschamp, Iceland Basin and Pringle Falls) recorded at ODP Site 919 (Irminger Basin)

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.

    2006-04-01

    Component natural remanent magnetizations derived from u-channel and 1-cm 3 discrete samples from ODP Site 919 (Irminger Basin) indicate the existence of four intervals of negative inclinations in the upper Brunhes Chronozone. According to the age model based on planktic oxygen isotope data, these "excursional" intervals occur in sediments deposited during the following time intervals: 32-34 ka, 39-41 ka, 180-188 ka and 205-225 ka. These time intervals correspond to polarity excursions detected elsewhere, known as Mono Lake, Laschamp, Iceland Basin and Pringle Falls. The isotope-based age model is supported by the normalized remanence (paleointensity) record that can be correlated to other calibrated paleointensity records for the 0-500 ka interval, such as that from ODP Site 983. For the intervals associated with the Mono Lake and Laschamp excursions, virtual geomagnetic poles (VGPs) reach equatorial latitudes and mid-southerly latitudes, respectively. For intervals associated with the Iceland Basin and Pringle Falls excursions, repeated excursions of VGPs to high southerly latitudes indicate rapid directional swings rather than a single short-lived polarity reversal. The directional instability associated with polarity excursions is not often recorded, probably due to smoothing of the sedimentary record by the process of detrital remanence (DRM) acquisition.

  19. Experiment of nitrox saturation diving with trimix excursion.

    PubMed

    Shi, Z Y

    1998-11-01

    Depth limitations to diving operation with air as the breathing gas are well known: air density, oxygen toxicity, nitrogen narcosis and requirement for decompression. The main objectives of our experiment were to assess the decompression, counterdiffusion and performance aspect of helium-nitrogen-oxygen excursions from nitrox saturation. The experiment was carried out in a wet diving stimulator with "igloo" attached to a 2-lock living chamber. Four subjects of two teams of 2 divers were saturated at 25 msw simulated depth in a nitrogen oxygen chamber environment for 8 days, during which period they performed 32 divers-excursions to 60 or 80 msw pressure. Excursion gas mix was trimix of 14.6% oxygen, 50% helium and 35.4% nitrogen, which gave a bottom oxygen partial pressure of 1.0 bars at 60 msw and 1.3 at 80 msw. Excursions were for 70 min at 60 msw with three 10-min work periods and 40 min at 80 msw with two 10-min work periods. Work was on a bicycle ergometer at a moderate level. We calculated the excursion decompression with M-Values based on methods of Hamilton (Hamilton et al., 1990). Staged decompression took 70 min for the 60 msw excursion and 98 min for 80 msw, with stops beginning at 34 or 43 msw respectively. After the second dive day bubbles were heard mainly in one diver but in three divers overall, to Spencer Grade III some times. No symptoms were reported. Saturation decompression using the Repex procedures began at 40 msw and was uneventful: Grade II and sometimes III bubbles persisted in 2 of the four divers until 24 hr after surfacing. We conclude that excursions with mixture rich in helium can be performed effectively to as deep as 80 msw using these procedures. PMID:10052222

  20. Outpatient Assessment of Determinants of Glucose Excursions in Adolescents with Type 1 Diabetes: Proof of Concept

    PubMed Central

    Mayer-Davis, Elizabeth; Bishop, Franziska K.; Wang, Lily; Mangan, Meg; McMurray, Robert G.

    2012-01-01

    Abstract Objective Controlled inpatient studies on the effects of food, physical activity (PA), and insulin dosing on glucose excursions exist, but such outpatient data are limited. We report here outpatient data on glucose excursions and its key determinants over 5 days in 30 adolescents with type 1 diabetes (T1D) as a proof-of-principle pilot study. Subjects and Methods Subjects (20 on insulin pumps, 10 receiving multiple daily injections; 15±2 years old; diabetes duration, 8±4 years; hemoglobin A1c, 8.1±1.0%) wore a continuous glucose monitor (CGM) and an accelerometer for 5 days. Subjects continued their existing insulin regimens, and time-stamped insulin dosing data were obtained from insulin pump downloads or insulin pen digital logs. Time-stamped cell phone photographs of food pre- and post-consumption and food logs were used to augment 24-h dietary recalls for Days 1 and 3. These variables were incorporated into regression models to predict glucose excursions at 1–4 h post-breakfast. Results CGM data on both Days 1 and 3 were obtained in 57 of the possible 60 subject-days with an average of 125 daily CGM readings (out of a possible 144). PA and dietary recall data were obtained in 100% and 93% of subjects on Day 1 and 90% and 100% of subjects on Day 3, respectively. All of these variables influenced glucose excursions at 1–4 h after waking, and 56 of the 60 subject-days contributed to the modeling analysis. Conclusions Outpatient high-resolution time-stamped data on the main inputs of glucose variability in adolescents with T1D are feasible and can be modeled. Future applications include using these data for in silico modeling and for monitoring outpatient iterations of closed-loop studies, as well as to improve clinical advice regarding insulin dosing to match diet and PA behaviors. PMID:22853720

  1. Modeling uncertainty in reservoir loss functions using fuzzy sets

    NASA Astrophysics Data System (ADS)

    Teegavarapu, Ramesh S. V.; Simonovic, Slobodan P.

    1999-09-01

    Imprecision involved in the definition of reservoir loss functions is addressed using fuzzy set theory concepts. A reservoir operation problem is solved using the concepts of fuzzy mathematical programming. Membership functions from fuzzy set theory are used to represent the decision maker's preferences in the definition of shape of loss curves. These functions are assumed to be known and are used to model the uncertainties. Linear and nonlinear optimization models are developed under fuzzy environment. A new approach is presented that involves development of compromise reservoir operating policies based on the rules from the traditional optimization models and their fuzzy equivalents while considering the preferences of the decision maker. The imprecision associated with the definition of penalty and storage zones and uncertainty in the penalty coefficients are the main issues addressed through this study. The models developed are applied to the Green Reservoir, Kentucky. Simulations are performed to evaluate the operating rules generated by the models considering the uncertainties in the loss functions. Results indicate that the reservoir operating policies are sensitive to change in the shapes of loss functions.

  2. HDU Pressurized Excursion Module (PEM) Prototype Systems Integration

    NASA Technical Reports Server (NTRS)

    Gill, Tracy R.; Kennedy, Kriss; Tri, Terry; Toups, Larry; Howe, A. Scott

    2010-01-01

    The Habitat Demonstration Unit (HDU) project team constructed an analog prototype lunar surface laboratory called the Pressurized Excursion Module (PEM). The prototype unit subsystems were integrated in a short amount of time, utilizing a skunk-works approach that brought together over 20 habitation-related technologies from a variety of NASA centers. This paper describes the system integration strategies and lessons learned, that allowed the PEM to be brought from paper design to working field prototype using a multi-center team. The system integration process included establishment of design standards, negotiation of interfaces between subsystems, and scheduling fit checks and installation activities. A major tool used in integration was a coordinated effort to accurately model all the subsystems using CAD, so that conflicts were identified before physical components came together. Some of the major conclusions showed that up-front modularity that emerged as an artifact of construction, such as the eight 45 degree "pie slices" making up the module whose steel rib edges defined structural mounting and loading points, dictated much of the configurational interfaces between the major subsystems and workstations. Therefore, 'one of the lessons learned included the need to use modularity as a tool for organization in advance, and to work harder to prevent non-critical aspects of the platform from dictating the modularity that may eventually inform the fight system.

  3. Maximizing Social Model Principles in Residential Recovery Settings

    PubMed Central

    Polcin, Douglas; Mericle, Amy; Howell, Jason; Sheridan, Dave; Christensen, Jeff

    2014-01-01

    Abstract Peer support is integral to a variety of approaches to alcohol and drug problems. However, there is limited information about the best ways to facilitate it. The “social model” approach developed in California offers useful suggestions for facilitating peer support in residential recovery settings. Key principles include using 12-step or other mutual-help group strategies to create and facilitate a recovery environment, involving program participants in decision making and facility governance, using personal recovery experience as a way to help others, and emphasizing recovery as an interaction between the individual and their environment. Although limited in number, studies have shown favorable outcomes for social model programs. Knowledge about social model recovery and how to use it to facilitate peer support in residential recovery homes varies among providers. This article presents specific, practical suggestions for enhancing social model principles in ways that facilitate peer support in a range of recovery residences. PMID:25364996

  4. The Mono Lake excursion recorded in phonolitic lavas from Tenerife (Canary Islands): Paleomagnetic analyses and coupled K/Ar and Ar/Ar dating

    NASA Astrophysics Data System (ADS)

    Kissel, C.; Guillou, H.; Laj, C.; Carracedo, J. C.; Nomade, S.; Perez-Torrado, F.; Wandres, C.

    2011-08-01

    We present a coupled paleomagnetic/dating investigation conducted on three different lava flows from the island of Tenerife (Canary Islands; Spain) erupted during the Mono Lake excursion (MLE). Paleomagnetic analyses consist in zero field demagnetizations (AF and/or thermal) and of Thellier and Thellier experiments using the PICRIT-03 set of criteria to select reliable intensity determinations. One of the flows is characterized by a direction largely deviated from the one expected from an axial geocentric dipole (GAD) field. Its paleointensity value is very low (7.8 μT). The two other sites are characterized by inclinations slightly shallower than the GAD value and by low intensity values (about 12 and 21 μT; present value: 38 μT). The three K/Ar ages combined with two 40Ar/ 39Ar ages range from 32.0 to 33.2 ka and they are not statistically distinguishable from one another. It therefore appears that these lavas have recorded the MLE (the only excursion in this time interval) confirming its brief duration (shorter than the minimum age uncertainties available). The mean age is younger but, within the uncertainties, consistent with the age of the 10Be peak and of the marine intensity low when reported in the most recent ice age model. These new results are the first ones with radiometric dating produced from the northern hemisphere. Combined with existing cosmogenic, marine and volcanic paleomagnetic data, these results are discussed in terms of dating, and geometry of the earth magnetic field during the excursion.

  5. Level Set Segmentation of Lumbar Vertebrae Using Appearance Models

    NASA Astrophysics Data System (ADS)

    Fritscher, Karl; Leber, Stefan; Schmölz, Werner; Schubert, Rainer

    For the planning of surgical interventions of the spine exact knowledge about 3D shape and the local bone quality of vertebrae are of great importance in order to estimate the anchorage strength of screws or implants. As a prerequisite for quantitative analysis a method for objective and therefore automated segmentation of vertebrae is needed. In this paper a framework for the automatic segmentation of vertebrae using 3D appearance models in a level set framework is presented. In this framework model information as well as gradient information and probabilities of pixel intensities at object edges in the unseen image are used. The method is tested on 29 lumbar vertebrae leading to accurate results, which can be useful for surgical planning and further analysis of the local bone quality.

  6. Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores.

    PubMed

    Nakamura, Itsumi; Goto, Yusuke; Sato, Katsufumi

    2015-05-01

    Ocean sunfish (Mola mola) were believed to be inactive jellyfish feeders because they are often observed lying motionless at the sea surface. Recent tracking studies revealed that they are actually deep divers, but there has been no evidence of foraging in deep water. Furthermore, the surfacing behaviour of ocean sunfish was thought to be related to behavioural thermoregulation, but there was no record of sunfish body temperature. Evidence of ocean sunfish feeding in deep water was obtained using a combination of an animal-borne accelerometer and camera with a light source. Siphonophores were the most abundant prey items captured by ocean sunfish and were typically located at a depth of 50-200 m where the water temperature was <12 °C. Ocean sunfish were diurnally active, made frequently deep excursions and foraged mainly at 100-200 m depths during the day. Ocean sunfish body temperatures were measured under natural conditions. The body temperatures decreased during deep excursions and recovered during subsequent surfacing periods. Heat-budget models indicated that the whole-body heat-transfer coefficient between sunfish and the surrounding water during warming was 3-7 times greater than that during cooling. These results suggest that the main function of surfacing is the recovery of body temperature, and the fish might be able to increase heat gain from the warm surface water by physiological regulation. The thermal environment of ocean sunfish foraging depths was lower than their thermal preference (c. 16-17 °C). The behavioural and physiological thermoregulation enables the fish to increase foraging time in deep, cold water. Feeding rate during deep excursions was not related to duration or depth of the deep excursions. Cycles of deep foraging and surface warming were explained by a foraging strategy, to maximize foraging time with maintaining body temperature by vertical temperature environment. PMID:25643743

  7. Geomagnetic excursions in the Brunhes and Matuyama Chrons: Do they come in bunches?

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.

    2012-04-01

    Geomagnetic excursions, defined here as brief directional aberrations of the main dipole field outside the range of expected secular variation, remain controversial. Poorly-correlated records of apparent excursions from lavas and sediments can often be assigned to sampling artifacts, sedimentological phenomena, volcanic terrane effects, or local secular variation, rather than behavior of the main dipole field. Although records of magnetic excursions date from the 1960s, the number of Brunhes excursions in recent reviews of the subject have reached the 12-17 range, of which only about ~7 are adequately and/or consistently recorded. For the Matuyama Chron, the current inventory of excursions stands at about 10. The better quality excursion records, with reasonable age control, imply millennial-scale or even sub-millennial-scale durations. When "adequately" recorded, excursions are manifest as paired polarity reversals flanking virtual geomagnetic poles (VGPs) that reach high latitudes in the opposite hemisphere. At the young end of the excursion record, the Mono Lake (~33 ka) and Laschamp (~41 ka) excursions are well documented, although records of the former are not widely distributed. Several excursions younger than the Mono Lake excursion (at 17 ka and 25 ka) have recently been recorded in lavas and sediments, respectively. Is the 17-41 ka interval characterized by multiple excursions? Similarly, multiple excursions have been recorded in the 188-238 ka interval that encompasses records of the Iceland Basin excursion (~188 ka) and the Pringle Falls (PF) excursion. The PF excursion has been assigned ages in the 211-238 ka range. Does this mean that this interval is also characterized by several discrete excursions? The 500-600 ka interval incorporates not only the Big Lost excursion at ~565 ka, but also anomalous magnetization directions from lava flows, particularly in the West Eifel volcanics that yield mid-latitude northern-hemisphere VGPs with a range of Ar

  8. A Unified Sea Ice Thickness Data Set for Model Validation

    NASA Astrophysics Data System (ADS)

    Lindsay, R.; Wensnahan, M.

    2007-12-01

    Can we, as a community, do better at using existing ice thickness measurements to more effectively evaluate the changing nature of the Arctic ice pack and to better evaluate the performance of our models? We think we can if we work together. We are trying to create a unified ice thickness data set by combining observations from various ice thickness measurement systems. It is designed to facilitate the intercomparison of different measurements, the evaluation of the state of the ice pack, and the validation of sea ice models. Datasets that might be included are ice draft estimates from various submarine and moored upward looking sonar instruments, ice thickness estimates from airborne electromagnetic instruments, and satellite altimeter freeboard measurements. Three principles for the proposed data set are: 1) Full documentation of data sources and characteristics, 2) Spatial and temporal averaging to approximately common scales, and 3) Common data formats. We would not mix data types and we would not interpolate to locations or times not represented in the observations. The target spatial and temporal scale for the measurements would be 50 lineal km of ice and/or one month. Point measurements are not so useful in this context. Data from both hemispheres and any body of ocean water would be included. Documentation would include locations, times, measurement methods, processing, snow depth assumptions, averaging distance and time, error characteristics, data provider, and more. The cooperation and collaboration of the various data providers is essential to the success of this project and so far we have had a very gratifying response to our overtures. We would like to hear from any who have not heard from us and who have collected sea ice thickness data at the approximate target scales. With potentially thousands of individual samples, much could be learned about the measurement systems, about the changing state of the ice cover, and about ice model performance and

  9. Potential Cislunar and Interplanetary Proving Ground Excursion Trajectory Concepts

    NASA Technical Reports Server (NTRS)

    McGuire, Melissa L.; Strange, Nathan J.; Burke, Laura M.; MacDonald, Mark A.; McElrath, Timothy P.; Landau, Damon F.; Lantoine, Gregory; Hack, Kurt J.; Lopez, Pedro

    2016-01-01

    NASA has been investigating potential translunar excursion concepts to take place in the 2020s that would be used to test and demonstrate long duration life support and other systems needed for eventual Mars missions in the 2030s. These potential trajectory concepts could be conducted in the proving ground, a region of cislunar and near-Earth interplanetary space where international space agencies could cooperate to develop the technologies needed for interplanetary spaceflight. Enabled by high power Solar Electric Propulsion (SEP) technologies, the excursion trajectory concepts studied are grouped into three classes of increasing distance from the Earth and increasing technical difficulty: the first class of excursion trajectory concepts would represent a 90-120 day round trip trajectory with abort to Earth options throughout the entire length, the second class would be a 180-210 day round trip trajectory with periods in which aborts would not be available, and the third would be a 300-400 day round trip trajectory without aborts for most of the length of the trip. This paper provides a top-level summary of the trajectory and mission design of representative example missions of these three classes of excursion trajectory concepts.

  10. Super_Prompt Crit excursions in Sph Geometry

    Energy Science and Technology Software Center (ESTSC)

    2000-03-17

    AX-TNT solves (a) the coupled hydrodynamic, thermodynamical neutronic equations which describe a spherical, super prompt critical reactor system during an excursion. (b) the coupled equations of motion, and ideal gas equation of state for the detonation of a spherical charge in a gas.

  11. Nongeocentric axial dipole field behavior during the Mono Lake excursion

    NASA Astrophysics Data System (ADS)

    Negrini, Robert M.; McCuan, Daniel T.; Horton, Robert A.; Lopez, James D.; Cassata, William S.; Channell, James E. T.; Verosub, Kenneth L.; Knott, Jeffrey R.; Coe, Robert S.; Liddicoat, Joseph C.; Lund, Steven P.; Benson, Larry V.; Sarna-Wojcicki, Andrei M.

    2014-04-01

    A new record of the Mono Lake excursion (MLE) is reported from the Summer Lake Basin of Oregon, USA. Sediment magnetic properties indicate magnetite as the magnetization carrier and imply suitability of the sediments as accurate recorders of the magnetic field including relative paleointensity (RPI) variations. The magnitudes and phases of the declination, inclination, and RPI components of the new record correlate well with other coeval but lower resolution records from western North America including records from the Wilson Creek Formation exposed around Mono Lake. The virtual geomagnetic pole (VGP) path of the new record is similar to that from another high-resolution record of the MLE from Ocean Drilling Program (ODP) Site 919 in the Irminger Basin between Iceland and Greenland but different from the VGP path for the Laschamp excursion (LE), including that found lower in the ODP-919 core. Thus, the prominent excursion recorded at Mono Lake, California, is not the LE but rather one that is several thousands of years younger. The MLE VGP path contains clusters, the locations of which coincide with nonaxial dipole features found in the Holocene geomagnetic field. The clusters are occupied in the same time progression by VGPs from Summer Lake and the Irminger Basin, but the phase of occupation is offset, a behavior that suggests time-transgressive decay and return of the principal field components at the beginning and end of the MLE, respectively, leaving the nonaxial dipole features associated with the clusters dominant during the excursion.

  12. 40 CFR 63.1334 - Parameter monitoring levels and excursions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 11 2010-07-01 2010-07-01 true Parameter monitoring levels and... Parameter monitoring levels and excursions. (a) Establishment of parameter monitoring levels. The owner or operator of a control or recovery device that has one or more parameter monitoring level...

  13. 40 CFR 63.1438 - Parameter monitoring levels and excursions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... caused by an activity that violates other applicable provisions of 40 CFR part 63, subparts A, F, G, or H... 40 Protection of Environment 11 2010-07-01 2010-07-01 true Parameter monitoring levels and....1438 Parameter monitoring levels and excursions. (a) Establishment of parameter monitoring levels....

  14. 5. Photocopy of photograph. JANE MOSELEY (VESSEL 53) DURING EXCURSION, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Photocopy of photograph. JANE MOSELEY (VESSEL 53) DURING EXCURSION, DETAIL OF FORE DECK AND CABIN AREA. Date end photographer unknown. (Original in Mariners Museum, Newport News, Virginia, negative #PB 30017) - Shooters Island, Ships Graveyard, Vessel No. 53, Newark Bay, Staten Island (subdivision), Richmond County, NY

  15. Stratigraphic Correlation of an Excursion at 22 kyr in the U.S. Great Basin - the Hilina Pali Excursion?

    NASA Astrophysics Data System (ADS)

    Liddicoat, J. C.; Coe, R. S.

    2013-12-01

    An unusually large secular variation of the geomagnetic field recorded in outcrops of pluvial Lake Russell sediment about 22 kyr old in the Mono Basin, CA, can be used for precise correlation to other lacustrine sections in the western U.S., and perhaps beyond. We present new AF and thermal demagnetization results for paired samples at 2-cm intervals between ash layers 7 and 8 of Lajoie (1968) in the bank of Wilson Creek that document an excursion having an inclination as low as 16 degrees and as high as 73 degrees, while the declination swings from 15 degrees west during the low inclination to 30 east when the inclination is high, and back to average northerly declination and expected inclination. The corresponding VGPs form a narrow clockwise-trending loop centered at about 50 N, 30 E. The Mono Lake Excursion (MLE; Liddicoat and Coe, 1979) occurs 1.7 m lower in the same section. The best estimates for the ages of the two excursions are about 22 and 32 kyr, based on 14-C dates (Cassata et al., 2010). About 150 km to the north, sediments of about the same age exposed along the Truckee River that were deposited in pluvial Lake Lahontan record a similar geomagnetic signature. Moreover, both the MLE and this excursion are exhibited at the appropriate levels in a sediment core taken from Pyramid Lake, the remnant of Lake Lahontan (Benson et al., 2008). Thus, this excursion is a valuable marker for high-resolution correlation of Quaternary sediments in the western U.S., especially when paired with the MLE. It is tempting to try to identify this geomagnetic feature with others of about the same age further away. On the island of Hawaii, Coe et al. (1978) discovered a lava flow on the Hilina Pali with a calibrated 14-C age of 21 +/-1 kyr that has an inclination about 30 degrees shallower and a paleointensity 60 percent lower than today. Later Teanby et al. (2002) documented an excursion with inclinations as low as -35 degrees, recorded by around 40 successive flows with

  16. Groundwater Quality Modeling with a Small Data Set.

    PubMed

    Sakizadeh, Mohamad; Malian, Abbass; Ahmadpour, Eisa

    2016-01-01

    Seventeen groundwater quality variables collected during an 8-year period (2006 to 2013) in Andimeshk, Iran, were used to implement an artificial neural network (NN) with the purpose of constructing a water quality index (WQI). The method leading to the WQI avoids instabilities and overparameterization, two problems common when working with relatively small data sets. The groundwater quality variables used to construct the WQI were selected based on principal component analysis (PCA) by which the number of variables were decreased to six. To fulfill the goals of this study, the performance of three methods (1) bootstrap aggregation with early stopping; (2) noise injection; and (3) ensemble averaging with early stopping was compared. The criteria used for performance analysis was based on mean squared error (MSE) and coefficient of determination (R(2) ) of the test data set and the correlation coefficients between WQI targets and NN predictions. This study confirmed the importance of PCA for variable selection and dimensionality reduction to reduce the risk of overfitting. Ensemble averaging with early stopping proved to be the best performed method. Owing to its high coefficient of determination (R(2)  = 0.80) and correlation coefficient (r=0.91), we recommended ensemble averaging with early stopping as an accurate NN modeling procedure for water quality prediction in similar studies. PMID:25572437

  17. Spatial and temporal patterns of subtidal and intertidal crabs excursions

    NASA Astrophysics Data System (ADS)

    Silva, A. C. F.; Boaventura, D. M.; Thompson, R. C.; Hawkins, S. J.

    2014-01-01

    Highly mobile predators such as fish and crabs are known to migrate from the subtidal zone to forage in the intertidal zone at high-tide. The extent and variation of these habitat linking movements along the vertical shore gradient have not been examined before for several species simultaneously, hence not accounting for species interactions. Here, the foraging excursions of Carcinus maenas (L.), Necora puber (Linnaeus, 1767) and Cancer pagurus (Linnaeus, 1758) were assessed in a one-year mark-recapture study on two replicated rocky shores in southwest U.K. A comparison between the abundance of individuals present on the shore at high-tide with those present in refuges exposed at low-tide indicated considerable intertidal migration by all species, showing strong linkage between subtidal and intertidal habitats. Estimates of population size based on recapture of marked individuals indicated that an average of ~ 4000 individuals combined for the three crab species, can be present on the shore during one tidal cycle. There was also a high fidelity of individuals and species to particular shore levels. Underlying mechanisms for these spatial patterns such as prey availability and agonistic interactions are discussed. Survival rates were estimated using the Cormack-Jolly-Seber model from multi-recapture analysis and found to be considerably high with a minimum of 30% for all species. Growth rates were found to vary intraspecifically with size and between seasons. Understanding the temporal and spatial variations in predation pressure by crabs on rocky shores is dependent on knowing who, when and how many of these commercially important crab species depend on intertidal foraging. Previous studies have shown that the diet of these species is strongly based on intertidal prey including key species such as limpets; hence intertidal crab migration could be associated with considerable impacts on intertidal assemblages.

  18. The Latitudinal Excursion of Coronal Magnetic Field Lines in Response to Differential Rotation: MHD Simulations

    NASA Technical Reports Server (NTRS)

    Lionello, Roberto; Linker, Jon A.; Mikic, Zoran; Riley, Pete

    2006-01-01

    Solar energetic particles, which are believed to originate from corotating interacting regions (CIRS) at low heliographic latitude, were observed by the Ulysses spacecraft even as it passed over the Sun's poles. One interpretation of this result is that high-latitude field lines intercepted by Ulysses connect to low-latitude CIRs at much larger heliocentric distances. The Fisk model explains the latitudinal excursion of magnetic field lines in the solar corona and heliosphere as the inevitable consequence of the interaction of a tilted dipole in a differentially rotating photosphere with rigidly rotating coronal holes. We use a time-dependent three-dimensional magnetohydrodynamic (MHD) algorithm to follow the evolution of a simple model of the solar corona in response to the differential rotation of the photospheric magnetic flux. We examine the changes of the coronal-hole boundaries, the redistribution of the line-of-sight magnetic field, and the precession of field lines in the corona. Our results confirm the basic idea of the Fisk model, that differential rotation leads to changes in the heliographic latitude of magnetic field lines. However, the latitudinal excursion of magnetic field lines in this simple "tilted dipole" model is too small to explain the Ulysses observations. Although coronal holes in our model rotate more rigidly than do photospheric features (in general agreement with observations), they do not rotate strictly rigidly as assumed by Fisk. This basic difference between our model and Fisk's will be explored in the future by considering more realistic magnetic flux distributions, as observed during Ulysses polar excursions.

  19. Hierarchical set of models to estimate soil thermal diffusivity

    NASA Astrophysics Data System (ADS)

    Arkhangelskaya, Tatiana; Lukyashchenko, Ksenia

    2016-04-01

    Soil thermal properties significantly affect the land-atmosphere heat exchange rates. Intra-soil heat fluxes depend both on temperature gradients and soil thermal conductivity. Soil temperature changes due to energy fluxes are determined by soil specific heat. Thermal diffusivity is equal to thermal conductivity divided by volumetric specific heat and reflects both the soil ability to transfer heat and its ability to change temperature when heat is supplied or withdrawn. The higher soil thermal diffusivity is, the thicker is the soil/ground layer in which diurnal and seasonal temperature fluctuations are registered and the smaller are the temperature fluctuations at the soil surface. Thermal diffusivity vs. moisture dependencies for loams, sands and clays of the East European Plain were obtained using the unsteady-state method. Thermal diffusivity of different soils differed greatly, and for a given soil it could vary by 2, 3 or even 5 times depending on soil moisture. The shapes of thermal diffusivity vs. moisture dependencies were different: peak curves were typical for sandy soils and sigmoid curves were typical for loamy and especially for compacted soils. The lowest thermal diffusivities and the smallest range of their variability with soil moisture were obtained for clays with high humus content. Hierarchical set of models will be presented, allowing an estimate of soil thermal diffusivity from available data on soil texture, moisture, bulk density and organic carbon. When developing these models the first step was to parameterize the experimental thermal diffusivity vs. moisture dependencies with a 4-parameter function; the next step was to obtain regression formulas to estimate the function parameters from available data on basic soil properties; the last step was to evaluate the accuracy of suggested models using independent data on soil thermal diffusivity. The simplest models were based on soil bulk density and organic carbon data and provided different

  20. A Diagnostic Scoring Model for Leptospirosis in Resource Limited Settings

    PubMed Central

    Rajapakse, Senaka; Weeratunga, Praveen; Niloofa, Roshan; Fernando, Narmada; de Silva, Nipun Lakshitha; Rodrigo, Chaturaka; Maduranga, Sachith; Nandasiri, Nuwanthi; Premawansa, Sunil; Karunanayake, Lilani; de Silva, H. Janaka; Handunnetti, Shiroma

    2016-01-01

    Background Leptospirosis is a zoonotic infection with significant morbidity and mortality. The clinical presentation of leptospirosis is known to mimic the clinical profile of other prevalent tropical fevers. Laboratory confirmation of leptospirosis is based on the reference standard microscopic agglutination test (MAT), direct demonstration of the organism, and isolation by culture and DNA detection by polymerase chain reaction (PCR) amplification. However these methods of confirmation are not widely available in resource limited settings where the infection is prevalent, and reliance is placed on clinical features for provisional diagnosis. In this prospective study, we attempted to develop a model for diagnosis of leptospirosis, based on clinical features and standard laboratory test results. Methods The diagnostic score was developed based on data from a prospective multicentre study in two hospitals in the Western Province of Sri Lanka. All patients presenting to these hospitals with a suspected diagnosis of leptospirosis, based on the WHO surveillance criteria, were recruited. Confirmed disease was defined as positive genus specific MAT (Leptospira biflexa). A derivation cohort and a validation cohort were randomly selected from available data. Clinical and laboratory manifestations associated with confirmed leptospirosis in the derivation cohort were selected for construction of a multivariate regression model with correlation matrices, and adjusted odds ratios were extracted for significant variables. The odds ratios thus derived were subsequently utilized in the criteria model, and sensitivity and specificity examined with ROC curves. Results A total of 592 patients were included in the final analysis with 450 (180 confirmed leptospirosis) in the derivation cohort and 142 (52 confirmed leptospirosis) in the validation cohort. The variables in the final model were: history of exposure to a possible source of leptospirosis (adjusted OR = 2.827; 95% CI = 1

  1. A Whale of an Interest in Sea Creatures: The Learning Potential of Excursions

    ERIC Educational Resources Information Center

    Hedges, Helen

    2004-01-01

    Excursions, or field trips, are a common component of early childhood programs, seen as a means of enriching the curriculum by providing experiences with people, places, and things in the community. Although excursions have been used as a framework for research on children's memory development, research on the efficacy of excursions in terms of…

  2. Improving a Lecture-Size Molecular Model Set by Repurposing Used Whiteboard Markers

    ERIC Educational Resources Information Center

    Dragojlovic, Veljko

    2015-01-01

    Preparation of an inexpensive model set from whiteboard markers and either HGS molecular model set or atoms made of wood is described. The model set is relatively easy to prepare and is sufficiently large to be suitable as an instructor set for use in lectures.

  3. Geomagnetic excursion captured by multiple volcanoes in a monogenetic field

    NASA Astrophysics Data System (ADS)

    Cassidy, John

    2006-11-01

    Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within a period of only 50-100 years or less. These temporally linked volcanoes are widespread throughout the field and appear not to be structurally related. However, the general paradigm for the reawakening of monogenetic fields is that only a single new volcano or group of closely spaced vents is created, typically at intervals of several hundred years or more. Therefore, the results presented show that for any monogenetic field the impact of renewed eruptive activity may be significantly under-estimated, especially for potentially affected population centres and the siting of sensitive facilities.

  4. Final report for the flow excursion follow-on testing

    SciTech Connect

    Nash, C.A.; Walters, T.W.

    1992-08-05

    The purpose of the Mark 22 Flow Excursion Follow-On testing was to investigate the theory that approximately 15% of the flow bypassed the primary flow channels in previous testing, whereas the design called for only a 3% bypass. The results of the follow-on tests clearly confirmed this theory. The testing was performed in two phases. During the first phase, characterization tests performed during the earlier test program were repeated.

  5. Age of the Mono Lake excursion and associated tephra

    USGS Publications Warehouse

    Benson, L.; Liddicoat, J.; Smoot, J.; Sarna-Wojcicki, A.; Negrini, R.; Lund, S.

    2003-01-01

    The Mono Lake excursion (MLE) is an important time marker that has been found in lake and marine sediments across much of the Northern Hemisphere. Dating of this event at its type locality, the Mono Basin of California, has yielded controversial results with the most recent effort concluding that the MLE may actually be the Laschamp excursion (Earth Planet. Sci. Lett. 197 (2002) 151). We show that a volcanic tephra (Ash #15) that occurs near the midpoint of the MLE has a date (not corrected for reservoir effect) of 28,620 ?? 300 14C yr BP (??? 32,400 GISP2 yr BP) in the Pyramid Lake Basin of Nevada. Given the location of Ash #15 and the duration of the MLE in the Mono Basin, the event occurred between 31,500 and 33,300 GISP2 yr BP, an age range consistent with the position and age of the uppermost of two paleointensity minima in the NAPIS-75 stack that has been associated with the MLE (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009). The lower paleointensity minimum in the NAPIS-75 stack is considered to be the Laschamp excursion (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009).

  6. Age of the Mono Lake excursion and associated tephra

    NASA Astrophysics Data System (ADS)

    Benson, Larry; Liddicoat, Joseph; Smoot, Joseph; Sarna-Wojcicki, Andrei; Negrini, Robert; Lund, Steve

    2003-02-01

    The Mono Lake excursion (MLE) is an important time marker that has been found in lake and marine sediments across much of the Northern Hemisphere. Dating of this event at its type locality, the Mono Basin of California, has yielded controversial results with the most recent effort concluding that the MLE may actually be the Laschamp excursion (Earth Planet. Sci. Lett. 197 (2002) 151). We show that a volcanic tephra (Ash ♯15) that occurs near the midpoint of the MLE has a date (not corrected for reservoir effect) of 28,620±300 14C yr BP (˜32,400 GISP2 yr BP) in the Pyramid Lake Basin of Nevada. Given the location of Ash ♯15 and the duration of the MLE in the Mono Basin, the event occurred between 31,500 and 33,300 GISP2 yr BP, an age range consistent with the position and age of the uppermost of two paleointensity minima in the NAPIS-75 stack that has been associated with the MLE (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009). The lower paleointensity minimum in the NAPIS-75 stack is considered to be the Laschamp excursion (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009).

  7. Models of Music Therapy Intervention in School Settings

    ERIC Educational Resources Information Center

    Wilson, Brian L., Ed.

    2002-01-01

    This completely revised 2nd edition edited by Brian L. Wilson, addresses both theoretical issues and practical applications of music therapy in educational settings. 17 chapters written by a variety of authors, each dealing with a different setting or issue. A valuable resource for demonstrating the efficacy of music therapy to school…

  8. High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge

    NASA Astrophysics Data System (ADS)

    Bourne, Mark D.; Mac Niocaill, Conall; Thomas, Alex L.; Henderson, Gideon M.

    2013-12-01

    Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during `normal secular' variation. The Laschamp excursion at ˜41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity associated with this excursion. Accurate dating of excursions, and determination of their durations from multiple locations, is vital to our understanding of global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites, 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172). High sedimentation rates (˜30-40 cm kyr-1) at these locations allow determination of transitional field behaviour during the excursion. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. We determine the age and duration of the Laschamp excursion using a stratigraphy linked to the δ18O record from the Greenland ice cores. This chronology dates the Laschamp excursion at the Blake Ridge to 41.3 ka. The excursion is characterized by rapid transitions (less than 200 yr) between stable normal polarity and a partially reversed polarity state. The palaeointensity record is in good agreement between the two sites, revealing two prominent minima. The first minimum is associated with the Laschamp excursion at 41 ka and the second corresponds to the Mono Lake excursion at ˜35.5 ka. We determine that the directional excursion during the Laschamp at this location was no longer than ˜400 yr, occurring within a palaeointensity minimum that lasted 2000 yr. The Laschamp excursion at this location is much shorter in duration than the Blake and Iceland Basin excursions.

  9. Influences to System and Superiority of Model Parameters in Dynamic Setting AGC

    NASA Astrophysics Data System (ADS)

    Xu, LI; Hao-yu, Zhang; Jin, Zhang; Jian-fei, Guo; Cui-hong, Liu; Ping-wen, Cheng

    Dynamic setting AGC is based on the improvement of the BISRA-AGC model. Based on the control algorithms and control models of dynamic setting AGC, the influences of the model parameters to system performance were analyzed using the GUI in MATLAB. At the same time, the superiority and limitation of the dynamic setting AGC were analyzed.

  10. Attachment Disorders: A Proposed Model for the School Setting.

    ERIC Educational Resources Information Center

    Parker, Kandis Cooke

    This paper explores the literature on attachment disorders in order to discover if the school setting can be an appropriate treatment option for children with mild attachment disorders, and in order to investigate how counselors can implement this treatment option. The introduction discusses the effects of recent changes in family structure on…

  11. Judgmental Standard Setting Using a Cognitive Components Model.

    ERIC Educational Resources Information Center

    McGinty, Dixie; Neel, John H.

    A new standard setting approach is introduced, called the cognitive components approach. Like the Angoff method, the cognitive components method generates minimum pass levels (MPLs) for each item. In both approaches, the item MPLs are summed for each judge, then averaged across judges to yield the standard. In the cognitive components approach,…

  12. Modeling mania in preclinical settings: A comprehensive review.

    PubMed

    Sharma, Ajaykumar N; Fries, Gabriel R; Galvez, Juan F; Valvassori, Samira S; Soares, Jair C; Carvalho, André F; Quevedo, Joao

    2016-04-01

    The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise. PMID:26545487

  13. Linear and Nonlinear Models of Agenda Setting in Television.

    ERIC Educational Resources Information Center

    Brosius, Hans-Bernd; Kepplinger, Hans Mathias

    1992-01-01

    A content analysis of major German television news shows and 53 weekly surveys on 16 issues were used to compare linear and nonlinear models as ways to describe the relationship between media coverage and the public agenda. Results indicate that nonlinear models are in some cases superior to linear models in terms of explained variance. (34…

  14. First-excursion probability in non-stationary random vibration.

    NASA Technical Reports Server (NTRS)

    Yang, J.-N.

    1973-01-01

    The first-excursion probability of a non-stationary Gaussian process with zero mean has been studied. Within the framework of the point process approach, a variety of analytical approximations applicable to stationary random processes is extended herein to non-stationary random processes. The extension is possible owing to a recent definition of non-stationary envelope processes proposed by the author. With the aid of numerical examples, merits of each approximation are examined by comparing with the results of simulation. It is found that under non-stationary excitations with short duration, the Markov approximation is the best among all the approximations discussed in this paper.

  15. Isolating causes of yield excursions with decision tress and commonality

    NASA Astrophysics Data System (ADS)

    Waksman, Peter

    2002-07-01

    The use of Decision Trees to analyze data is discussed as an approach to solving problems of Yield excursions in semiconductor manufacturing. The relation to equipment commonality is discussed along with some of the pitfalls of incautious use of general probability estimates. The paper introduces a Mixing Diagram to help visualize commonality issues, it introduces work around methods for resolving ambiguities in the commonality, it reviews Decision Trees algorithms, and it ends with a discussion of current limitations of the method along with recommendations for future research.

  16. A geometric level set model for ultrasounds analysis

    SciTech Connect

    Sarti, A.; Malladi, R.

    1999-10-01

    We propose a partial differential equation (PDE) for filtering and segmentation of echocardiographic images based on a geometric-driven scheme. The method allows edge-preserving image smoothing and a semi-automatic segmentation of the heart chambers, that regularizes the shapes and improves edge fidelity especially in presence of distinct gaps in the edge map as is common in ultrasound imagery. A numerical scheme for solving the proposed PDE is borrowed from level set methods. Results on human in vivo acquired 2D, 2D+time,3D, 3D+time echocardiographic images are shown.

  17. Modeling a set of heavy oil aqueous pyrolysis experiments

    SciTech Connect

    Thorsness, C.B.; Reynolds, J.G.

    1996-11-01

    Aqueous pyrolysis experiments, aimed at mild upgrading of heavy oil, were analyzed using various computer models. The primary focus of the analysis was the pressure history of the closed autoclave reactors obtained during the heating of the autoclave to desired reaction temperatures. The models used included a means of estimating nonideal behavior of primary components with regard to vapor liquid equilibrium. The modeling indicated that to match measured autoclave pressures, which often were well below the vapor pressure of water at a given temperature, it was necessary to incorporate water solubility in the oil phase and an activity model for the water in the oil phase which reduced its fugacity below that of pure water. Analysis also indicated that the mild to moderate upgrading of the oil which occurred in experiments that reached 400{degrees}C or more using a FE(III) 2-ethylhexanoate could be reasonably well characterized by a simple first order rate constant of 1.7xl0{sup 8} exp(-20000/T)s{sup {minus}l}. Both gas production and API gravity increase were characterized by this rate constant. Models were able to match the complete pressure history of the autoclave experiments fairly well with relatively simple equilibria models. However, a consistent lower than measured buildup in pressure at peak temperatures was noted in the model calculations. This phenomena was tentatively attributed to an increase in the amount of water entering the vapor phase caused by a change in its activity in the oil phase.

  18. Flexor tendon excursion and load during passive and active simulated motion: a cadaver study.

    PubMed

    Sapienza, A; Yoon, H K; Karia, R; Lee, S K

    2013-11-01

    The aim of this study was to quantify the amount of tendon excursion and load experienced during simulated active and passive rehabilitation exercises. Six cadaver specimens were utilized to examine tendon excursion and load. Lateral fluoroscopic images were used to measure the excursions of metal markers placed in the flexor digitorum superficialis and profundus tendons of the index, middle, and ring fingers. Measurements were performed during ten different passive and active simulated motions. Mean tendon forces were higher in all active versus passive movements. Blocking movements placed the highest loads on the flexor tendons. Active motion resulted in higher tendon excursion than did passive motion. Simulated hook position resulted in the highest total tendon excursion and the highest inter-tendinous excursion. This knowledge may help optimize the management of the post-operative exercise therapy regimen. PMID:23221181

  19. Analysis of energy balance models using the ERBE data set

    NASA Technical Reports Server (NTRS)

    Graves, Charles E.; North, Gerald R.

    1991-01-01

    A review of Energy Balance Models is presented. Results from the Outgoing Longwave Radiation parameterization are discussed. The albedo parameterizations and the consequences of the new parameterizations are examined.

  20. Writing Models: Strategies for Writing Composition in Inclusive Settings.

    ERIC Educational Resources Information Center

    Staal, Laura A.

    2001-01-01

    Considers how expressive written language is considered one of the most difficult areas of academic achievement for children, especially those with learning disabilities. Discusses two narrative writing models: the story frame and the story pyramid. (SG)

  1. Self-reversal and apparent magnetic excursions in Arctic sediments

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.; Xuan, C.

    2009-06-01

    The Arctic oceans have been fertile ground for the recording of apparent excursions of the geomagnetic field, implying that the high latitude field had unusual characteristics at least over the last 1-2 Myrs. Alternating field demagnetization of the natural remanent magnetization (NRM) of Core HLY0503-6JPC from the Mendeleev Ridge (Arctic Ocean) implies the presence of primary magnetizations with negative inclination apparently recording excursions in sediments deposited during the Brunhes Chron. Thermal demagnetization, on the other hand, indicates the presence of multiple (often anti-parallel) magnetization components with negative inclination components having blocking temperatures predominantly, but not entirely, below ~ 350 °C. Thermo-magnetic tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the negative inclination components are carried by titanomaghemite, presumably formed by seafloor oxidation of titanomagnetite. The titanomaghemite apparently carries a chemical remanent magnetization (CRM) that is partially self-reversed relative to the detrital remanent magnetization (DRM) carried by the host titanomagnetite. The partial self-reversal could have been accomplished by ionic ordering during oxidation, thereby changing the balance of the magnetic moments in the ferrimagnetic sublattices.

  2. Geolab in NASA's First Generation Pressurized Excursion Module: Operational Concepts

    NASA Technical Reports Server (NTRS)

    Evans, C. A.; Bell, M. S.; Calway, M. J.

    2010-01-01

    We are building a prototype laboratory for preliminary examination of geological samples to be integrated into a first generation Habitat Demonstration Unit-1/Pressurized Excursion Module (HDU1-PEM) in 2010. The laboratory GeoLab will be equipped with a glovebox for handling samples, and a suite of instruments for collecting preliminary data to help characterize those samples. The GeoLab and the HDU1-PEM will be tested for the first time as part of the 2010 Desert Research and Technology Studies (DRATS), NASAs annual field exercise designed to test analog mission technologies. The HDU1-PEM and GeoLab will participate in joint operations in northern Arizona with two Lunar Electric Rovers (LER) and the DRATS science team. Historically, science participation in DRATS exercises has supported the technology demonstrations with geological traverse activities that are consistent with preliminary concepts for lunar surface science Extravehicular Activities (EVAs). Next years HDU1-PEM demonstration is a starting point to guide the development of requirements for the Lunar Surface Systems Program and test initial operational concepts for an early lunar excursion habitat that would follow geological traverses along with the LER. For the GeoLab, these objectives are specifically applied to enable future geological surface science activities. The goal of our GeoLab is to enhance geological science returns with the infrastructure that supports preliminary examination, early analytical characterization of key samples, insight into special considerations for curation, and data for prioritization of lunar samples for return to Earth.

  3. Comparison of Diaphragmatic Breathing Exercise, Volume and Flow Incentive Spirometry, on Diaphragm Excursion and Pulmonary Function in Patients Undergoing Laparoscopic Surgery: A Randomized Controlled Trial.

    PubMed

    Alaparthi, Gopala Krishna; Augustine, Alfred Joseph; Anand, R; Mahale, Ajith

    2016-01-01

    Objective. To evaluate the effects of diaphragmatic breathing exercises and flow and volume-oriented incentive spirometry on pulmonary function and diaphragm excursion in patients undergoing laparoscopic abdominal surgery. Methodology. We selected 260 patients posted for laparoscopic abdominal surgery and they were block randomization as follows: 65 patients performed diaphragmatic breathing exercises, 65 patients performed flow incentive spirometry, 65 patients performed volume incentive spirometry, and 65 patients participated as a control group. All of them underwent evaluation of pulmonary function with measurement of Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), Peak Expiratory Flow Rate (PEFR), and diaphragm excursion measurement by ultrasonography before the operation and on the first and second postoperative days. With the level of significance set at p < 0.05. Results. Pulmonary function and diaphragm excursion showed a significant decrease on the first postoperative day in all four groups (p < 0.001) but was evident more in the control group than in the experimental groups. On the second postoperative day pulmonary function (Forced Vital Capacity) and diaphragm excursion were found to be better preserved in volume incentive spirometry and diaphragmatic breathing exercise group than in the flow incentive spirometry group and the control group. Pulmonary function (Forced Vital Capacity) and diaphragm excursion showed statistically significant differences between volume incentive spirometry and diaphragmatic breathing exercise group (p < 0.05) as compared to that flow incentive spirometry group and the control group. Conclusion. Volume incentive spirometry and diaphragmatic breathing exercise can be recommended as an intervention for all patients pre- and postoperatively, over flow-oriented incentive spirometry for the generation and sustenance of pulmonary function and diaphragm excursion in the management of laparoscopic

  4. Comparison of Diaphragmatic Breathing Exercise, Volume and Flow Incentive Spirometry, on Diaphragm Excursion and Pulmonary Function in Patients Undergoing Laparoscopic Surgery: A Randomized Controlled Trial

    PubMed Central

    Anand, R.

    2016-01-01

    Objective. To evaluate the effects of diaphragmatic breathing exercises and flow and volume-oriented incentive spirometry on pulmonary function and diaphragm excursion in patients undergoing laparoscopic abdominal surgery. Methodology. We selected 260 patients posted for laparoscopic abdominal surgery and they were block randomization as follows: 65 patients performed diaphragmatic breathing exercises, 65 patients performed flow incentive spirometry, 65 patients performed volume incentive spirometry, and 65 patients participated as a control group. All of them underwent evaluation of pulmonary function with measurement of Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), Peak Expiratory Flow Rate (PEFR), and diaphragm excursion measurement by ultrasonography before the operation and on the first and second postoperative days. With the level of significance set at p < 0.05. Results. Pulmonary function and diaphragm excursion showed a significant decrease on the first postoperative day in all four groups (p < 0.001) but was evident more in the control group than in the experimental groups. On the second postoperative day pulmonary function (Forced Vital Capacity) and diaphragm excursion were found to be better preserved in volume incentive spirometry and diaphragmatic breathing exercise group than in the flow incentive spirometry group and the control group. Pulmonary function (Forced Vital Capacity) and diaphragm excursion showed statistically significant differences between volume incentive spirometry and diaphragmatic breathing exercise group (p < 0.05) as compared to that flow incentive spirometry group and the control group. Conclusion. Volume incentive spirometry and diaphragmatic breathing exercise can be recommended as an intervention for all patients pre- and postoperatively, over flow-oriented incentive spirometry for the generation and sustenance of pulmonary function and diaphragm excursion in the management of laparoscopic

  5. Non-deterministic fatigue life analysis using convex set models

    NASA Astrophysics Data System (ADS)

    Sun, WenCai; Yang, ZiChun; Li, KunFeng

    2013-04-01

    The non-probabilistic approach to fatigue life analysis was studied using the convex models—interval, ellipsoidal and multi-convex models. The lower and upper bounds of the fatigue life were obtained by using the second-order Taylor series and Lagrange multiplier method. The solving process for derivatives of the implicit life function was presented. Moreover, a median ellipsoidal model was proposed which can take into account the sample blind zone and almost impossibility of concurrence of some small probability events. The Monte Carlo method for multi-convex model was presented, an important alternative when the analytical method does not work. A project example was given. The feasibility and rationality of the presented approach were verified. It is also revealed that the proposed method is conservative compared to the traditional probabilistic method, but it is a useful complement when it is difficult to obtain the accurate probability densities of parameters.

  6. Regional Dimensions of the Triple Helix Model: Setting the Context

    ERIC Educational Resources Information Center

    Todeva, Emanuela; Danson, Mike

    2016-01-01

    This paper introduces the rationale for the special issue and its contributions, which bridge the literature on regional development and the Triple Helix model. The concept of the Triple Helix at the sub-national, and specifically regional, level is established and examined, with special regard to regional economic development founded on…

  7. Leader Succession: A Model and Review for School Settings.

    ERIC Educational Resources Information Center

    Miskel, Cecil; Cosgrove, Dorothy

    Recent research casts doubt on the commonly held notions that administrators affect student learning through instructional leadership and that changing administrators will improve school performance. To help construct a model for examining the process of leader succession that specifies a number of major school process and outcome variables…

  8. Control and Synchronization of Julia Sets in the Forced Brusselator Model

    NASA Astrophysics Data System (ADS)

    Sun, Weihua; Zhang, Yongping

    The forced Brusselator model is investigated from the fractal viewpoint. A Julia set of the discrete version of the Brusselator model is introduced and control of the Julia set is presented by using feedback control. In order to discuss the relations of two different Julia sets, a coupled item is designed to realize the synchronization of two Julia sets with different parameters, which provides a method to discuss the relation and the changing of two different Julia sets, one Julia set can be changed to be the other. Numerical simulations are used to verify the effectiveness of these methods.

  9. [Setting up of a modelling workshop in an Alzheimer's unit].

    PubMed

    Guérin-Billard, Anne; Deray, Céline; Denis, Amael; Guillon, Emmanuelle

    2012-01-01

    Modelling is an original and creative form of therapy and above all one which is accessible when the limits of cognitive care have been reached. Salt dough is a malleable, sensitive and multi-sensory mediator which is forgiving of errors. Without the use of any known technique or objective as a reference, this activity avoids any notion of failure. This workshop is an area for expression and care and the mediation is interesting for its therapeutic potential. PMID:22519136

  10. Buried-euxenic-basin model sets Tarim basin potential

    SciTech Connect

    Hsu, K.J. )

    1994-11-28

    The Tarim basin is the largest of the three large sedimentary basins of Northwest China. The North and Southwest depressions of Tarim are underlain by thick sediments and very thin crust. The maximum sediment thickness is more than 15 km. Of the several oil fields of Tarim, the three major fields were discovered during the last decade, on the north flank of the North depression and on the Central Tarim Uplift. The major targets of Tarim, according to the buried-euxenic-basin model, should be upper Paleozoic and lower Mesozoic reservoirs trapping oil and gas condensates from lower Paleozoic source beds. The paper describes the basin and gives a historical perspective of exploration activities and discoveries. It then explains how this basin can be interpreted by the buried-euxenic-basin model. The buried-euxenic-basin model postulates four stages of geologic evolution: (1) Sinian and early Paleozoic platform sedimentation on relic arcs and deep-marine sedimentation in back-arc basins in Xinjiang; (2) Late Paleozoic foreland-basin sedimentation in north Tarim; (3) Mesozoic and Paleogene continental deposition, subsidence under sedimentary load; and (4) Neogene pull-apart basin, wrench faulting and extension.

  11. A Move to an Innovative Games Teaching Model: Style E Tactical (SET)

    ERIC Educational Resources Information Center

    Nathan, Sanmuga; Haynes, John

    2013-01-01

    This paper reports on the development and testing of a hybrid model of teaching games--The Style "E" Tactical (SET) Model. The SET is a combination of two pedagogical approaches: Mosston and Ashworth's Teaching Styles and Bunker and Thorpe's Teaching Games for Understanding (TGfU). To test the efficacy of this new model, the…

  12. Causal Inference and Model Selection in Complex Settings

    NASA Astrophysics Data System (ADS)

    Zhao, Shandong

    Propensity score methods have become a part of the standard toolkit for applied researchers who wish to ascertain causal effects from observational data. While they were originally developed for binary treatments, several researchers have proposed generalizations of the propensity score methodology for non-binary treatment regimes. In this article, we firstly review three main methods that generalize propensity scores in this direction, namely, inverse propensity weighting (IPW), the propensity function (P-FUNCTION), and the generalized propensity score (GPS), along with recent extensions of the GPS that aim to improve its robustness. We compare the assumptions, theoretical properties, and empirical performance of these methods. We propose three new methods that provide robust causal estimation based on the P-FUNCTION and GPS. While our proposed P-FUNCTION-based estimator preforms well, we generally advise caution in that all available methods can be biased by model misspecification and extrapolation. In a related line of research, we consider adjustment for posttreatment covariates in causal inference. Even in a randomized experiment, observations might have different compliance performance under treatment and control assignment. This posttreatment covariate cannot be adjusted using standard statistical methods. We review the principal stratification framework which allows for modeling this effect as part of its Bayesian hierarchical models. We generalize the current model to add the possibility of adjusting for pretreatment covariates. We also propose a new estimator of the average treatment effect over the entire population. In a third line of research, we discuss the spectral line detection problem in high energy astrophysics. We carefully review how this problem can be statistically formulated as a precise hypothesis test with point null hypothesis, why a usual likelihood ratio test does not apply for problem of this nature, and a doable fix to correctly

  13. Implicit level set algorithms for modelling hydraulic fracture propagation.

    PubMed

    Peirce, A

    2016-10-13

    Hydraulic fractures are tensile cracks that propagate in pre-stressed solid media due to the injection of a viscous fluid. Developing numerical schemes to model the propagation of these fractures is particularly challenging due to the degenerate, hypersingular nature of the coupled integro-partial differential equations. These equations typically involve a singular free boundary whose velocity can only be determined by evaluating a distinguished limit. This review paper describes a class of numerical schemes that have been developed to use the multiscale asymptotic behaviour typically encountered near the fracture boundary as multiple physical processes compete to determine the evolution of the fracture. The fundamental concepts of locating the free boundary using the tip asymptotics and imposing the tip asymptotic behaviour in a weak form are illustrated in two quite different formulations of the governing equations. These formulations are the displacement discontinuity boundary integral method and the extended finite-element method. Practical issues are also discussed, including new models for proppant transport able to capture 'tip screen-out'; efficient numerical schemes to solve the coupled nonlinear equations; and fast methods to solve resulting linear systems. Numerical examples are provided to illustrate the performance of the numerical schemes. We conclude the paper with open questions for further research. This article is part of the themed issue 'Energy and the subsurface'. PMID:27597787

  14. High-resolution palaeomagnetic records of the Laschamp geomagnetic excursion from ODP Sites 1061 and 1062

    NASA Astrophysics Data System (ADS)

    Bourne, M. D.; Henderson, G. M.; Thomas, A. L.; Mac Niocaill, C.

    2012-12-01

    The Laschamp geomagnetic excursion (~41 ka) was a brief global deviation in geomagnetic field behaviour from that expected during normal secular variation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172) and compare this record with previously published records of the Blake and Iceland Basin Excursions. Relatively high sedimentation rates (>10 cm kyr-1) at these locations allow the determination of transitional field behaviour during the excursion. Rather than assuming a constant sedimentation rate between assigned age tie-points, we employ measurements of 230Thxs concentration in the sediment to assess variations in the sedimentation rates through the core sections of interest. This allows us to better determine the temporal behaviour of the Laschamp excursion with greater accuracy and known uncertainty. The Laschamp excursion at this location appears to be much shorter in duration than the Blake and Iceland Basin excursions. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. The excursion is characterised by rapid transitions (less than 500 years) between a stable normal polarity and a partially-reversed, polarity. Peaks in inclination either side of the directional excursion indicate periods of time when the local field is dominated by vertical flux patches. Similar behaviour has been observed in records of the Iceland Basin Excursion from the same region. The palaeointensity record is in good agreement between the two sites. The palaeointensity record shows two minima, where the second dip in intensity is associated with a more limited directional deviation. Similar

  15. Polarity and Excursion Transitions: Can they be Adequately Recorded in High-Sedimentation-Rate Marine Sediments?

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.

    2014-12-01

    Polarity transitions and magnetic excursions have durations of a few thousand years, or less. Transition/excursion records in volcanic sequences are, at best, partial snap-shots of the transition/excursion field. Records from high-sedimentation-rate marine sediments may be more continuous but they are always smoothed by progressive acquisition of detrital remanent magnetization (DRM), and by sampling/measurement limitations. North Atlantic records of the Matuyama-Brunhes (M-B) polarity transition are compared with records of the Iceland Basin excursion (190 ka). Virtual geomagnetic polar (VGP) paths are used to map characteristic magnetization directions during the transition/excursion. Relative paleointensity (RPI) proxies indicate partial recovery of field intensity during the transition/excursion, with RPI minima coinciding with abrupt VGP shifts at the onset and end of the transition/excursion. Discrepancies in VGP paths among holes at the same site, among sites, and a comparison of u-channel and discrete sample measurements, reveal limitations in resolution of the transition/excursion fields. During the M-B polarity transition, VGP clusters appear in the NW Pacific, NE Asia and in the South Atlantic. Similarities in VGP clustering for the M-B boundary and the Iceland Basin excursion imply that the polarity transition and excursion fields had common characteristics. Similarities with the modern non-axial dipole (NAD) field imply that polarity transitions and excursions involve the demise of the Earth's axial dipole relative to the NAD field, and that the NAD field has long-lasting features locked in place by the lowermost mantle.

  16. Multiple High-Frequency Carbon Isotope Excursions Across the Precambrian-Cambrian Boundary: Implications for Correlations and Environmental Change

    NASA Astrophysics Data System (ADS)

    Smith, E. F.; Macdonald, F. A.; Schrag, D. P.; Laakso, T.

    2014-12-01

    The GSSP Precambrian-Cambrian boundary in Newfoundland is defined by the first appearance datum (FAD) of Treptichnus pedum, which is considered to be roughly coincident with the FAD of small shelly fossils (SSFs) and a large negative carbon isotope excursion. An association between the FAD of T. pedum and a negative carbon isotope excursion has previously been documented in Northwest Canada (Narbonne et al., 1994) and Death Valley (Corsetti and Hagadorn, 2000), and since then has been used as an chronostratigraphic marker of the boundary, particularly in siliciclastic poor sections that do not preserve T. pedum. Here we present new high-resolution carbon isotope (δ13C ) chemostratigraphy from multiple sections in western Mongolia and the western United States that span the Ediacaran-Cambrian transition. High-resolution sampling (0.2-1 m) reveals that instead of one large negative excursion, there are multiple, high-frequency negative excursions with an overall negative trend during the latest Ediacaran. These data help to more precisely calibrate changes in the carbon cycle across the boundary as well as to highlight the potential problem of identifying the boundary with just a few negative δ13C values. We then use a simple carbon isotope box model to explore relationships between phosphorous delivery to the ocean, oxygenation, alkalinity, and turnovers in carbonate secreting organisms. Corsetti, F.A., and Hagadorn, J.W., 2000, Precambrian-Cambrian transition: Death Valley, United States: Geology, v. 28, no. 4, p. 299-302. Narbonne, G.M., Kaufman, A.J., and Knoll, A.H., 1994, Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: Implications for Neoproterozoic correlations and the early evolution of animals: Geological Society of America Bulletin, v. 106, no. 10, p. 1281-1292.

  17. The Earth climate and life evolution response to cosmic radiation enhancement arising from reversals and excursions of geomagnetic field

    NASA Astrophysics Data System (ADS)

    Kuznetsova, N.

    Climate abrupt warming as well as biologic evolutionary events in respect to fauna and human evolution are shown to originate during reversals and excursions of geomagnetic field when the geomagnetic field loses a lot in its module value and consequently in its protective characteristics making galactic cosmic rays GCR and solar protons penetration into the Earth atmosphere possible Usually preceded by climate cooling and populations reduction reversals and excursions stimulate evolutionary genetic mutations generated by intense radiation and climate abrupt warming resulted from destruction of stratospheric aerosols by GCR Favorable environment conditions on new features and species origin For example it was Gauss-Matuyama reversal 2 3 Myr to make for Hominid evolutionary mutations and for distinctly new species Homo erectus origin The evolutionary events and climate shifts appear explicable on the context of the fundamentally new model of the geomagnetic field generation based on hypothesis of the hot Earth and the theory of the Earth magnetic poles drift throughout reversals and excursions theory

  18. Geolab 2010 Hardware in NASA's Pressurized Excursion Module

    NASA Technical Reports Server (NTRS)

    Calaway, M. J.; Evans, C. A.; Bell, M. S.

    2010-01-01

    NASA is designing and building the Habitat Demonstration Unit - 1 in a Pressurized Excursion Module (HDU1- PEM) configuration for analog testing at NASA s annual Desert Research and Technology Studies (DRATS) near Flagstaff, Arizona in late summer 2010. The HDU1-PEM design is based on NASA Constellation program s Lunar Scenario 12.1 (nicknamed "Lunabago"). This scenario uses Lunar Electric Rovers (LER) and a PEM for long-distance lunar exploration. The 2010 HDU version 1.0 will be an unpressurized PEM that contains a GeoLab in one of the eight PEM sections. The GeoLab is designed to facilitate sample curation protocol development including such activities as preliminary examination, sample archiving, and high grading of astromaterials for return to Earth. Geolab operations will be integrated with the DRATS science traverses and operations.

  19. Evolution of Autocatalytic Sets in Computational Models of Chemical Reaction Networks

    NASA Astrophysics Data System (ADS)

    Hordijk, Wim

    2016-06-01

    Several computational models of chemical reaction networks have been presented in the literature in the past, showing the appearance and (potential) evolution of autocatalytic sets. However, the notion of autocatalytic sets has been defined differently in different modeling contexts, each one having some shortcoming or limitation. Here, we review four such models and definitions, and then formally describe and analyze them in the context of a mathematical framework for studying autocatalytic sets known as RAF theory. The main results are that: (1) RAF theory can capture the various previous definitions of autocatalytic sets and is therefore more complete and general, (2) the formal framework can be used to efficiently detect and analyze autocatalytic sets in all of these different computational models, (3) autocatalytic (RAF) sets are indeed likely to appear and evolve in such models, and (4) this could have important implications for a possible metabolism-first scenario for the origin of life.

  20. Evolution of Autocatalytic Sets in Computational Models of Chemical Reaction Networks.

    PubMed

    Hordijk, Wim

    2016-06-01

    Several computational models of chemical reaction networks have been presented in the literature in the past, showing the appearance and (potential) evolution of autocatalytic sets. However, the notion of autocatalytic sets has been defined differently in different modeling contexts, each one having some shortcoming or limitation. Here, we review four such models and definitions, and then formally describe and analyze them in the context of a mathematical framework for studying autocatalytic sets known as RAF theory. The main results are that: (1) RAF theory can capture the various previous definitions of autocatalytic sets and is therefore more complete and general, (2) the formal framework can be used to efficiently detect and analyze autocatalytic sets in all of these different computational models, (3) autocatalytic (RAF) sets are indeed likely to appear and evolve in such models, and (4) this could have important implications for a possible metabolism-first scenario for the origin of life. PMID:26499126

  1. Model Developments for Development of Improved Emissions Scenarios: Developing Purchasing-Power Parity Models, Analyzing Uncertainty, and Developing Data Sets for Gridded Integrated Assessment Models

    SciTech Connect

    Yang, Zili; Nordhaus, William

    2009-03-19

    In the duration of this project, we finished the main tasks set up in the initial proposal. These tasks include: setting up the basic platform in GAMS language for the new RICE 2007 model; testing various model structure of RICE 2007; incorporating PPP data set in the new RICE model; developing gridded data set for IA modeling.

  2. Trunk-Rotation Differences at Maximal Reach of the Star Excursion Balance Test in Participants With Chronic Ankle Instability

    PubMed Central

    de la Motte, Sarah; Arnold, Brent L.; Ross, Scott E.

    2015-01-01

    Context: Functional reach on the Star Excursion Balance Test is decreased in participants with chronic ankle instability (CAI). However, comprehensive 3-dimensional kinematics associated with these deficits have not been reported. Objective: To determine if lower extremity kinematics differed in CAI participants during anteromedial, medial, and posteromedial reach on the Star Excursion Balance Test. Design: Case-control study. Setting: Sports medicine research laboratory. Patients or Other Participants: Twenty CAI participants (age = 24.15 ± 3.84 years, height = 168.95 ± 11.57 cm, mass = 68.95 ± 16.29 kg) and 20 uninjured participants (age = 25.65 ± 5.58 years, height = 170.14 ± 8.75 cm, mass = 69.89 ± 10.51 kg) with no history of ankle sprain. We operationally defined CAI as repeated episodes of ankle “giving way” or “rolling over” or both, regardless of neuromuscular deficits or pathologic laxity. All CAI participants scored ≤26 on the Cumberland Ankle Instability Tool. Intervention(s): Star Excursion Balance Test reaches in the anteromedial, medial, and posteromedial directions. The CAI participants used the unstable side as the stance leg. Control participants were sex, height, mass, and side matched to the CAI group. The 3-dimensional kinematics were assessed with a motion-capture system. Main Outcome Measure(s): Group differences on normalized reach distance, trunk, pelvis, and hip-, knee-, and ankle-joint angles at maximum Star Excursion Balance Test reach. Results: No reach-distance differences were detected between CAI and uninjured participants in any of the 3 reach directions. With anteromedial reach, trunk rotation (t1,38 = 3.06, P = .004), pelvic rotation (t1,38 = 3.17, P = .003), and hip flexion (t1,38 = 2.40, P = .002) were greater in CAI participants. With medial reach, trunk flexion (t1,38 = 6.39, P = .05) was greater than for uninjured participants. No differences were seen with posteromedial reach. Conclusions: We did not detect

  3. Place-Responsive Pedagogy: Learning from Teachers' Experiences of Excursions in Nature

    ERIC Educational Resources Information Center

    Mannion, Greg; Fenwick, Ashley; Lynch, Jonathan

    2013-01-01

    The nature-based excursion has been a significant teaching strategy in environmental education for decades. This article draws upon empirical data from a collaborative research project where teachers were encouraged to visit natural areas to provide an understanding of their roles and experiences of planning and enacting excursions. The analysis…

  4. An Exploration of the Value of an Educational Excursion for Pre-Service Teachers

    ERIC Educational Resources Information Center

    de Beer, Josef; Petersen, Nadine; Dubar-Krige, Helen

    2012-01-01

    This paper addresses the question: What is the value of an educational excursion for first year students enrolled in a 4 year pre-service professional teacher education degree at the University of Johannesburg in South Africa? The excursion is an integral part of a first year module that focuses on the personal and professional development of…

  5. Assessing the Reliability of Ultrasound Imaging to Examine Radial Nerve Excursion.

    PubMed

    Kasehagen, Ben; Ellis, Richard; Mawston, Grant; Allen, Scott; Hing, Wayne

    2016-07-01

    Ultrasound imaging allows cost effective in vivo analysis for quantifying peripheral nerve excursion. This study used ultrasound imaging to quantify longitudinal radial nerve excursion during various active and passive wrist movements in healthy participants. Frame-by-frame cross-correlation software allowed calculation of nerve excursion from video sequences. The reliability of ultrasound measurement of longitudinal radial nerve excursion was moderate to high (intraclass correlation coefficient range = 0.63-0.86, standard error of measurement 0.19-0.48). Radial nerve excursion ranged from 0.41 to 4.03 mm induced by wrist flexion and 0.28 to 2.91 mm induced by wrist ulnar deviation. No significant difference was seen in radial nerve excursion during either wrist movement (p > 0.05). Wrist movements performed in forearm supination produced larger overall nerve excursion (1.41 ± 0.32 mm) compared with those performed in forearm pronation (1.06 ± 0.31 mm) (p < 0.01). Real-time ultrasound is a reliable, cost-effective, in vivo method for analysis of radial nerve excursion. PMID:27087692

  6. Be a Healthy Role Model for Children: 10 Tips for Setting Good Examples

    MedlinePlus

    ... tips Nutrition Education Series be a healthy role model for children 10 tips for setting good examples ... replacement foods. 10 be a good food role model Try new foods yourself. Describe its taste, texture, ...

  7. Development of an Optimum Tracer Set for Apportioning Emissions of Individual Power Plants Using Highly Time-Resolved Measurements and Advanced Receptor Modeling

    SciTech Connect

    John Ondov; Gregory Beachley

    2007-07-05

    In previous studies, 11 elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) were determined in 30-minute aerosol samples collected with the University of Maryland Semicontinuous Elements in Aerosol Sampler (SEAS; Kidwell and Ondov, 2001, 2004; SEAS-II) in several locations in which air quality is influenced by emissions from coal- or oil-fired power plants. At this time resolution, plumes from stationary high temperature combustion sources are readily detected as large excursions in ambient concentrations of elements emitted by these sources (Pancras et al. ). Moreover, the time-series data contain intrinsic information on the lateral diffusion of the plume (e.g., {sigma}{sub y}), which Park et al. (2005 and 2006) have exploited in their Pseudo-Deterministic Receptor Model (PDRM), to calculate emission rates of SO{sub 2} and 11 elements (mentioned above) from four individual coal- and oil-fired power plants in the Tampa Bay area. In the current project, we proposed that the resolving power of source apportionment methods might be improved by expanding the set of maker species and that there exist some optimum set of marker species that could be used. The ultimate goal was to determine the utility of using additional elements to better identify and isolate contributions of individual power plants to ambient levels of PM and its constituents. And, having achieved better resolution, achieve, also, better emission rate estimates. In this study, we optimized sample preparation and instrumental protocols for simultaneous analysis of 28 elements in dilute slurry samples collected with the SEAS with a new state-of-the-art Thermo-Systems, Inc., X-series II, Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), and reanalyzed the samples previously collected in Tampa during the modeling period studied by Park et al. (2005) in which emission rates from four coal- and oil-fired power plants affected air quality at the sampling site. In the original model, Park et al

  8. Video Self-Modeling Intervention in School-Based Settings: A Review.

    ERIC Educational Resources Information Center

    Hitchcock, Caryl H.; Dowrick, Peter W.; Prater, Mary Anne

    2003-01-01

    This review examined 18 studies in which video self-modeling was applied in school-based settings. These studies verify the functional control of targeted academic skills and behavior/s and support the efficacy of video self-modeling to improve student outcomes. Evidence for generalization across settings and maintenance over time is also…

  9. Ca and Mg isotope constraints on the origin of Earth's deepest δ13 C excursion

    NASA Astrophysics Data System (ADS)

    Husson, Jon M.; Higgins, John A.; Maloof, Adam C.; Schoene, Blair

    2015-07-01

    Understanding the extreme carbon isotope excursions found in carbonate rocks of the Ediacaran Period (635-541 Ma), where δ13 C of marine carbonates (δ13 Ccarb) reach their minimum (- 12 ‰) for Earth history, is one of the most vexing problems in Precambrian geology. Known colloquially as the 'Shuram' excursion, the event has been interpreted by many as a product of a profoundly different Ediacaran carbon cycle. More recently, diagenetic processes have been invoked, with the very negative δ13 C values of Ediacaran carbonates explained via meteoric alteration, late-stage burial diagenesis or growth of authigenic carbonates in the sediment column, thus challenging models which rely upon a dramatically changing redox state of the Ediacaran oceans. Here we present 257 δ 44 / 40 Ca and 131 δ26 Mg measurements, along with [Mg], [Mn] and [Sr] data, from carbonates of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia to bring new isotope systems to bear on understanding the 'Shuram' excursion. Data from four measured sections spanning the basin reveal stratigraphically coherent trends, with variability of ∼1.5‰ in δ26 Mg and ∼1.2‰ in δ 44 / 40 Ca. This Ca isotope variability dwarfs the 0.2-0.3 ‰ change seen coeval with the Permian-Triassic mass extinction, the largest recorded in the rock record, and is on par with putative changes in the δ 44 / 40 Ca value of seawater seen over the Phanerozoic Eon. Changes in both isotopic systems are too large to explain with changes in the isotopic composition of Ca and Mg in global seawater given modern budgets and residence times, and thus must be products of alternative processes. Relationships between δ 44 / 40 Ca and [Sr] and δ26 Mg and [Mg] are consistent with mineralogical control (e.g., aragonite vs. calcite, limestone vs. dolostone) on calcium and magnesium isotope variability. The most pristine samples in the Wonoka dataset, preserving Sr concentrations (in the 1000s of ppm range) and δ 44 / 40

  10. Seeking genericity in the selection of parameter sets: Impact on hydrological model efficiency

    NASA Astrophysics Data System (ADS)

    Andréassian, Vazken; Bourgin, François; Oudin, Ludovic; Mathevet, Thibault; Perrin, Charles; Lerat, Julien; Coron, Laurent; Berthet, Lionel

    2014-10-01

    This paper evaluates the use of a small number of generalist parameter sets as an alternative to classical calibration. Here parameter sets are considered generalist when they yield acceptable performance on a large number of catchments. We tested the genericity of an initial collection of 106 parameter sets sampled in the parameter space for the four-parameter GR4J rainfall-runoff model. A short list of 27 generalist parameter sets was obtained as a good compromise between model efficiency and length of the short list. A different data set was used for an independent evaluation of a calibration procedure, in which the search for an optimum parameter set is only allowed within this short list. In validation mode, the performance obtained is inferior to that of a classical calibration, but when the amount of data available for calibration is reduced, the generalist parameter sets become progressively more competitive, with better results for calibration series shorter than 1 year.

  11. A novel level set model with automated initialization and controlling parameters for medical image segmentation.

    PubMed

    Liu, Qingyi; Jiang, Mingyan; Bai, Peirui; Yang, Guang

    2016-03-01

    In this paper, a level set model without the need of generating initial contour and setting controlling parameters manually is proposed for medical image segmentation. The contribution of this paper is mainly manifested in three points. First, we propose a novel adaptive mean shift clustering method based on global image information to guide the evolution of level set. By simple threshold processing, the results of mean shift clustering can automatically and speedily generate an initial contour of level set evolution. Second, we devise several new functions to estimate the controlling parameters of the level set evolution based on the clustering results and image characteristics. Third, the reaction diffusion method is adopted to supersede the distance regularization term of RSF-level set model, which can improve the accuracy and speed of segmentation effectively with less manual intervention. Experimental results demonstrate the performance and efficiency of the proposed model for medical image segmentation. PMID:26748038

  12. Magnetic Excursion Recorded in Basalt at Newberry Volcano, Central Oregon

    NASA Astrophysics Data System (ADS)

    Champion, D. E.; Donnelly-Nolan, J. M.; Lanphere, M. A.; Ramsey, D. W.

    2004-12-01

    Paleomagnetic study of basalt flows on the north flank of Newberry Volcano has identified a major eruptive episode that occurred during a magnetic excursion. The measured direction of the basalt flows erupted during the excursion shallows from 81° to 76° inclination along a declination of ˜ 155° . The Virtual Geomagnetic Pole also shallows from 29° to 19° paleolatitude, along a paleolongitude of ˜ 250° , and is located off the west coast of Mexico. Geologic evidence combined with limited argon dating indicate that the basalt erupted from multiple sites about 80,000 years ago, probably during the time of anomalous magnetic directions recorded by ( ˜80 ka) ocean sediments in the Norwegian Sea and the North Atlantic. The westernmost flows erupted from spatter vents located a few km south of the city of Bend, and flowed north through lava tube(s) which form Stevens Cave, Horse Cave, and Redmond Cave among others. This western lobe flowed more than 50 km to the north, over NW-trending faults of the Tumalo Fault Zone that cut the adjacent and underlying basalt of Bend (40Ar/39Ar plateau age of 78±9 ka; isochron age of 77±19 ka); it is overlain by the basaltic andesite of Klawhop Butte (40Ar/39Ar plateau age of 39±6 ka). One sample of the transitional magnetic direction basalt has a K-Ar age of 77±40 ka; another sample has a 40Ar/39Ar plateau age of 92±25 ka and an isochron age of 73±24 ka. The eastern lobe erupted from vents at and near Lava Top Butte, located approximately 15 km SE of the western vents. These eastern lavas flowed through Arnold Cave and formed a broad ~10-12 km rootless shield known as the Badlands, the NE extent of which is about 30 km from Lava Top Butte. The west and east lobes each cover about 150 km2, and comprise an estimated volume of 3-5 km3. Newly acquired 10-meter DEM's and compilation of the mapping in ArcGIS will allow more precise calculation of the total area covered and the volume erupted. Chemical analyses of multiple

  13. Assessing effects of variation in global climate data sets on spatial predictions from climate envelope models

    USGS Publications Warehouse

    Romanach, Stephanie; Watling, James I.; Fletcher, Robert J., Jr.; Speroterra, Carolina; Bucklin, David N.; Brandt, Laura A.; Pearlstine, Leonard G.; Escribano, Yesenia; Mazzotti, Frank J.

    2014-01-01

    Climate change poses new challenges for natural resource managers. Predictive modeling of species–environment relationships using climate envelope models can enhance our understanding of climate change effects on biodiversity, assist in assessment of invasion risk by exotic organisms, and inform life-history understanding of individual species. While increasing interest has focused on the role of uncertainty in future conditions on model predictions, models also may be sensitive to the initial conditions on which they are trained. Although climate envelope models are usually trained using data on contemporary climate, we lack systematic comparisons of model performance and predictions across alternative climate data sets available for model training. Here, we seek to fill that gap by comparing variability in predictions between two contemporary climate data sets to variability in spatial predictions among three alternative projections of future climate. Overall, correlations between monthly temperature and precipitation variables were very high for both contemporary and future data. Model performance varied across algorithms, but not between two alternative contemporary climate data sets. Spatial predictions varied more among alternative general-circulation models describing future climate conditions than between contemporary climate data sets. However, we did find that climate envelope models with low Cohen's kappa scores made more discrepant spatial predictions between climate data sets for the contemporary period than did models with high Cohen's kappa scores. We suggest conservation planners evaluate multiple performance metrics and be aware of the importance of differences in initial conditions for spatial predictions from climate envelope models.

  14. A scoping study of water table excursions induced by seismic and volcanic events

    SciTech Connect

    Carrigan, C.R.; King, G.C.P.; Barr, G.E.

    1990-11-01

    We develop conservative models of water table response to displacements just beneath the water table simulating (1) shallow intrusion of a dike and (2) high level slip on a normal fault locked at the end. For matrix flow, we fine local water table excursions of under 10 m. in cases of isotropic permeability which includes dike inflation of 4 m and fault slips corresponding to earthquakes having a moment magnitude of 7.4. Even for enhancements of vertical permeability up to 10{sup 4}:1, excursions did not exceed 15 m which implies that pumping is strongly volume limited. We also present an analysis of upward directed flow in cracks for the case of earthquake induced pore pressure changes. For matrix properties characteristic of the Calico Hills (vitric) formation and a crack distribution bounding the potential flow capacity of published data, we estimate an upper bound of 0.25 cu m. of ground water per m. of fault length as the amount capable of being pumped to a level 250 m. above the normal water table. While the presence of even larger fractures than assumed might carry more ground water to that level an absolute upper limit of less than 50 cu. m. per m. of fault length is available to be pumped assuming a value n=0.46 for the rock porosity. For less porous rocks typical of the Topopah Spring or Tiva Canyon formations (n{approx}0.10) the upper limit may be reduced to less than 10 cu. m. per m. of fault length. This upper limit depends only upon strain, the height of pumping above the water table and the formation porosity.

  15. Two-phase electro-hydrodynamic flow modeling by a conservative level set model.

    PubMed

    Lin, Yuan

    2013-03-01

    The principles of electro-hydrodynamic (EHD) flow have been known for more than a century and have been adopted for various industrial applications, for example, fluid mixing and demixing. Analytical solutions of such EHD flow only exist in a limited number of scenarios, for example, predicting a small deformation of a single droplet in a uniform electric field. Numerical modeling of such phenomena can provide significant insights about EHDs multiphase flows. During the last decade, many numerical results have been reported to provide novel and useful tools of studying the multiphase EHD flow. Based on a conservative level set method, the proposed model is able to simulate large deformations of a droplet by a steady electric field, which is beyond the region of theoretic prediction. The model is validated for both leaky dielectrics and perfect dielectrics, and is found to be in excellent agreement with existing analytical solutions and numerical studies in the literature. Furthermore, simulations of the deformation of a water droplet in decyl alcohol in a steady electric field match better with published experimental data than the theoretical prediction for large deformations. Therefore the proposed model can serve as a practical and accurate tool for simulating two-phase EHD flow. PMID:23161380

  16. Teacher Perceptions of the Role and Value of Excursions in Years 7-10 Geography Education in Victoria, Australia

    ERIC Educational Resources Information Center

    Munday, Penny

    2008-01-01

    Excursions are extremely important to the education of students in the geography curriculum. However, personal observations demonstrated a lack of readiness to conduct excursions in secondary schools. This apprehension of the teachers in this school to implement excursions in geography education was the basis for this study. The study addresses…

  17. Normative sciatic nerve excursion during a modified straight leg raise test.

    PubMed

    Ridehalgh, Colette; Moore, Ann; Hough, Alan

    2014-02-01

    Minimal data exists on how much sciatic nerve motion occurs during straight leg raise (SLR). The purpose of this study was to report preliminary normative ranges of sciatic nerve excursion using real time ultrasound during a modified SLR. The sciatic nerve was scanned in the posterior thigh in sixteen asymptomatic participants (age range 19-68 years). Nerve excursion was measured in transverse and longitudinal planes during knee extension from 90° to 0°, with the hip flexed to 30° and 60°. The ultrasound data was analysed off-line using cross correlation software. Results demonstrated that most nerves moved superficially during knee extension, a large proportion (10/16) moved laterally. Longitudinal excursion ranged from 6.4 to 14.7 mm (mean (SD) 9.92 mm (2.2)) in 30° hip flexion, and 5.1-20.2 mm (mean (SD) 12.4 mm (4.4)) in 60° hip flexion. Mean nerve excursion was significantly greater in 60° hip flexion (p = 0.02). There is a large between-subject variation in sciatic nerve excursion during this modified SLR in asymptomatic subjects. Mean nerve excursion was found to be higher with the hip pre-positioned in greater flexion, suggesting that pre-loading may not consistently reduce excursion. PMID:24034944

  18. Two Possible but Unconfirmed Paleomagnetic Excursions in Pleistocene Lacustrine Sediments in North America and Mexico

    NASA Astrophysics Data System (ADS)

    Liddicoat, J. C.

    2011-12-01

    The paleomagnetic literature is replete with reports of investigations of continuous field behavior (secular variation) using volcanic rocks and lacustrine and marine sediments from around the globe, and some of the reports are about paleomagnetic excursions. The Laschamp Excursion in volcanic rocks in the Massif Central of France (Bonhommet and Babkine, 1967) and Mono Lake Excursion in exposed lacustrine sediment in California (Denham and Cox, 1971) are two excursions that are recognized. At other localities and for different time intervals, confirmation of some excursions in sediment has not been successful at nearby sites where the deposits are believed to be the same age. An example is in the Basin of Mexico at Tlapacoya (19.4 N, 261.2 E)(Liddicoat et al., 1979). Another excursion that has not been confirmed but might have occurred is recorded in Pleistocene Lake Bonneville sediments that are exposed in the bank of the Sevier River near Delta, Utah (39.4 N, 247.6 E). In Mexico and Utah, the excursion is in a single, fully-oriented hand sample that was prepared into consecutive, 2-cm-thick horizons. Each horizon contains six samples that were demagnetized in an alternating field, and for each Lake Bonneville horizon the scatter of directions is 4 degrees or less. Several possibilities for why the excursion at Tlapacoya could not be confirmed were presented (Liddicoat et al., 1979), leaving open the possibility that the excursion might have occurred in Mexico about 14,500 years ago. The field behavior in Utah where the sediments are older than those at Tlapacoya by several tens of thousands of years (Oviatt et al., 1994) is nearly identical to the behavior recorded at Tlapacoya. At both localities, a path of the Virtual Geomagnetic Poles during the excursion is confined to a narrow meridional zone centered at about 200 E longitude and that descends to about 15 N latitude. The difficulty of confirming the anomalous field behavior at Tlapacoya and in Utah

  19. Two Possible but Unconfirmed Palaeomagnetic Excursions in Pleistocene Lacustrine Sediments in North America and Mexico

    NASA Astrophysics Data System (ADS)

    Liddicoat, J.; Coe, R.; Oviatt, J.

    2012-04-01

    The palaeomagnetic literature is replete with reports of investigations of continuous field behaviour (secular variation) using volcanic rocks and lacustrine and marine sediments, and some of the reports are about palaeomagnetic excursions. The Laschamp Excursion in volcanic rocks in the Massif Central of France (Bonhommet and Babkine, 1967) and Mono Lake Excursion in exposed lacustrine sediment in California (Denham and Cox, 1971) are two excursions that generally are accepted as having occurred in the late Pleistocene. At other localities and for different time intervals, confirmation of some excursions in sediment has not been successful at nearby sites where the deposits are believed to be the same age. An example is in the Basin of Mexico at Tlapacoya (19.4˚ N, 261.2˚ E) in lacustrine sediments about 14,500 years old (Liddicoat et al., 1979). Another excursion that has not been confirmed but might have occurred is recorded in Lake Bonneville sediments that are exposed in the bank of the Sevier River near Delta, Utah (39.4˚ N, 247.6˚ E). In Mexico and Utah, the excursions are in a single, fully-oriented hand sample that was prepared into consecutive, 2-cm-thick horizons, each consisting of six subsamples. The subsamples were demagnetized in an alternating field to at least 60 mT or when possible because of consolidation, thermally demagnetized to 600˚ C; for each Lake Bonneville horizon, the scatter of palaeomagnetic directions is 4˚ or less. Several possibilities for why the excursion at Tlapacoya could not be confirmed were presented (Liddicoat et al., 1979), leaving open the possibility that the excursion might have occurred in Mexico. The field behaviour in Utah where the sediments are older than those at Tlapacoya by several tens of thousands of years (Oviatt et al., 1994) is nearly identical to the behaviour recorded at Tlapacoya. At both localities, a path of the Virtual Geomagnetic Poles during the excursion is confined to a narrow meridional zone

  20. Diverse Data Sets Can Yield Reliable Information through Mechanistic Modeling: Salicylic Acid Clearance

    PubMed Central

    Raymond, G. M.; Bassingthwaighte, J. B.

    2016-01-01

    This is a practical example of a powerful research strategy: putting together data from studies covering a diversity of conditions can yield a scientifically sound grasp of the phenomenon when the individual observations failed to provide definitive understanding. The rationale is that defining a realistic, quantitative, explanatory hypothesis for the whole set of studies, brings about a “consilience” of the often competing hypotheses considered for individual data sets. An internally consistent conjecture linking multiple data sets simultaneously provides stronger evidence on the characteristics of a system than does analysis of individual data sets limited to narrow ranges of conditions. Our example examines three very different data sets on the clearance of salicylic acid from humans: a high concentration set from aspirin overdoses; a set with medium concentrations from a research study on the influences of the route of administration and of sex on the clearance kinetics, and a set on low dose aspirin for cardiovascular health. Three models were tested: (1) a first order reaction, (2) a Michaelis-Menten (M-M) approach, and (3) an enzyme kinetic model with forward and backward reactions. The reaction rates found from model 1 were distinctly different for the three data sets, having no commonality. The M-M model 2 fitted each of the three data sets but gave a reliable estimates of the Michaelis constant only for the medium level data (Km = 24±5.4 mg/L); analyzing the three data sets together with model 2 gave Km = 18±2.6 mg/L. (Estimating parameters using larger numbers of data points in an optimization increases the degrees of freedom, constraining the range of the estimates). Using the enzyme kinetic model (3) increased the number of free parameters but nevertheless improved the goodness of fit to the combined data sets, giving tighter constraints, and a lower estimated Km = 14.6±2.9 mg/L, demonstrating that fitting diverse data sets with a single model

  1. Applicability domains for classification problems: benchmarking of distance to models for AMES mutagenicity set

    EPA Science Inventory

    For QSAR and QSPR modeling of biological and physicochemical properties, estimating the accuracy of predictions is a critical problem. The “distance to model” (DM) can be defined as a metric that defines the similarity between the training set molecules and the test set compound ...

  2. USE OF ROUGH SETS AND SPECTRAL DATA FOR BUILDING PREDICTIVE MODELS OF REACTION RATE CONSTANTS

    EPA Science Inventory

    A model for predicting the log of the rate constants for alkaline hydrolysis of organic esters has been developed with the use of gas-phase min-infrared library spectra and a rule-building software system based on the mathematical theory of rough sets. A diverse set of 41 esters ...

  3. Playing with a Concept: Teaching Job Characteristics Model with a Tinkertoy[R] Builder Set

    ERIC Educational Resources Information Center

    Smrt, Diana Lazarova; Nelson, Reed Elliot

    2013-01-01

    Using a toy construction set, we introduce to students the job characteristics model in a fun and engaging way. The activity not only describes the theoretical variables of the model but also allows students to (a) experience the dynamic interaction among these variables and (b) gain a better, hands-on understanding of the model. The exercise…

  4. A Model Process for Institutional Goals-Setting. A Module of the Needs Assessment Project.

    ERIC Educational Resources Information Center

    King, Maxwell C.; And Others

    A goals-setting model for the community/junior college that would interface with the community needs assessment model was developed, using as the survey instrument the Institutional Goals Inventory (I.G.I.) developed by the Educational Testing Service. The nine steps in the model are: Establish Committee on College Goals and Identify Goals Project…

  5. Dating the Laschamp Excursion: Why Speleothems are Valuable Tools for Constraining the Timing and Duration of Short-Lived Geomagnetic Events

    NASA Astrophysics Data System (ADS)

    Lascu, I.; Feinberg, J. M.; Dorale, J. A.; Cheng, H.; Edwards, R. L.

    2015-12-01

    Short-lived geomagnetic events are reflections of geodynamo behavior at small length scales. A rigorous documentation of the anatomy, timing, duration, and frequency of centennial-to-millennial scale geomagnetic events can be invaluable for theoretical and numerical geodynamo models, and for the understanding the finer dynamics of the Earth's core. A critical ingredient for characterizing such geomagnetic instabilities are tightly constrained age models that enable high-resolution magnetostratigraphies. Here we focus on a North American speleothem geomagnetic record of the Laschamp excursion, which was the first geomagnetic excursion recognized and described in the paleomagnetic record, and remains the most studied event of its kind. The geological significance of the Laschamp lies chiefly in the fact that it constitutes a global time-synchronous geochronological marker. The Laschamp excursion occurred around the time of the demise of Homo neanderthalensis, in conjunction with high-amplitude, rapid climatic oscillations leading into the Last Glacial Maximum, and precedes a major supervolcano eruption in the Mediterranean. Thus, the precise determination of the timing and duration of the Laschamp would help in elucidating major scientific questions situated at the intersection of geology, paleoclimatology, and anthropology. Here we present a geomagnetic record from a stalagmite collected in Crevice Cave, Missouri, which we have dated using a combination of high-precision 230Th ages and annual layer counting using confocal microscopy. We have found a maximum duration for the Laschamp that spans the interval 42,250-39,700 years BP, and an age of 41,100 ± 350 years BP for the height of the excursion. During this period relative paleointensity decreased by an order of magnitude and the virtual geomagnetic pole was located at southerly latitudes. Our chronology provides the first robust bracketing for the Laschamp excursion, and improves on previous age determinations

  6. Be a Healthy Role Model for Children: 10 Tips for Setting Good Examples

    MedlinePlus

    ... Series be a healthy role model for children 10 tips for setting good examples You are the most important influence on your child. You can do many things to help your children develop healthy eating habits ...

  7. Joint Clustering and Component Analysis of Correspondenceless Point Sets: Application to Cardiac Statistical Modeling.

    PubMed

    Gooya, Ali; Lekadir, Karim; Alba, Xenia; Swift, Andrew J; Wild, Jim M; Frangi, Alejandro F

    2015-01-01

    Construction of Statistical Shape Models (SSMs) from arbitrary point sets is a challenging problem due to significant shape variation and lack of explicit point correspondence across the training data set. In medical imaging, point sets can generally represent different shape classes that span healthy and pathological exemplars. In such cases, the constructed SSM may not generalize well, largely because the probability density function (pdf) of the point sets deviates from the underlying assumption of Gaussian statistics. To this end, we propose a generative model for unsupervised learning of the pdf of point sets as a mixture of distinctive classes. A Variational Bayesian (VB) method is proposed for making joint inferences on the labels of point sets, and the principal modes of variations in each cluster. The method provides a flexible framework to handle point sets with no explicit point-to-point correspondences. We also show that by maximizing the marginalized likelihood of the model, the optimal number of clusters of point sets can be determined. We illustrate this work in the context of understanding the anatomical phenotype of the left and right ventricles in heart. To this end, we use a database containing hearts of healthy subjects, patients with Pulmonary Hypertension (PH), and patients with Hypertrophic Cardiomyopathy (HCM). We demonstrate that our method can outperform traditional PCA in both generalization and specificity measures. PMID:26221669

  8. Robust autonomous model learning from 2D and 3D data sets.

    PubMed

    Langs, Georg; Donner, René; Peloschek, Philipp; Bischof, Horst

    2007-01-01

    In this paper we propose a weakly supervised learning algorithm for appearance models based on the minimum description length (MDL) principle. From a set of training images or volumes depicting examples of an anatomical structure, correspondences for a set of landmarks are established by group-wise registration. The approach does not require any annotation. In contrast to existing methods no assumptions about the topology of the data are made, and the topology can change throughout the data set. Instead of a continuous representation of the volumes or images, only sparse finite sets of interest points are used to represent the examples during optimization. This enables the algorithm to efficiently use distinctive points, and to handle texture variations robustly. In contrast to standard elasticity based deformation constraints the MDL criterion accounts for systematic deformations typical for training sets stemming from medical image data. Experimental results are reported for five different 2D and 3D data sets. PMID:18051152

  9. A global deglacial negative carbon isotope excursion in speleothem calcite

    NASA Astrophysics Data System (ADS)

    Breecker, D.

    2015-12-01

    δ13C values of speleothem calcite decreased globally during the last deglaciation defining a carbon isotope excursion (CIE) despite relatively constant δ13C values of carbon in the ocean-atmosphere system. The magnitude of the CIE varied with latitude, increasing poleward from ~2‰ in the tropics to as much as 7‰ at high latitudes. This recent CIE provides an interesting comparison with CIEs observed in deep time. A substantial portion of this CIE can be explained by the increase in atmospheric pCO2 that accompanied deglaciation. The dependence of C3 plant δ13C values on atmospheric pCO2 predicts a 2‰ δ13C decrease driven by the deglacial pCO2 increase. I propose that this signal was transferred to caves and thus explains nearly 100% of the CIE magnitude observed in the tropics and no less than 30% at the highest latitudes in the compilation. An atmospheric pCO2 control on speleothem δ13C values, if real, will need to be corrected for using ice core data before δ13C records can be interpreted in a paleoclimate context. The decrease in the magnitude of the equilibrium calcite-CO2 carbon isotope fractionation factor explains a maximum of 1‰ of the CIE at the highest northern latitude in the compilation, which experienced the largest deglacial warming. Much of the residual extratropical CIE was likely driven by increasing belowground respiration rates, which were presumably pronounced at high latitudes as glacial retreat exposed fresh surfaces and/or vegetation density increased. The largest increases in belowground respiration would have therefore occurred at the highest latitudes, explaining the meridional trend. This work supports the notion that increases in atmospheric pCO2 and belowground respiration rates can result in large CIEs recorded in terrestrial carbonates, which, as previously suggested, may explain the magnitude of the PETM CIE as recorded by paleosol carbonates.

  10. A Science and Technology Excursion-based Unit of Work: The Human Body.

    ERIC Educational Resources Information Center

    Terry, Laura

    2000-01-01

    Presents a unit of work based on a few systems of the human body. Stretches students' learning beyond the classroom into the local community by going on an excursion to Kalgoorlie Regional Hospital. (ASK)

  11. Developing a Suitable Model for Water Uptake for Biodegradable Polymers Using Small Training Sets

    PubMed Central

    Valenzuela, Loreto M.; Knight, Doyle D.; Kohn, Joachim

    2016-01-01

    Prediction of the dynamic properties of water uptake across polymer libraries can accelerate polymer selection for a specific application. We first built semiempirical models using Artificial Neural Networks and all water uptake data, as individual input. These models give very good correlations (R2 > 0.78 for test set) but very low accuracy on cross-validation sets (less than 19% of experimental points within experimental error). Instead, using consolidated parameters like equilibrium water uptake a good model is obtained (R2 = 0.78 for test set), with accurate predictions for 50% of tested polymers. The semiempirical model was applied to the 56-polymer library of L-tyrosine-derived polyarylates, identifying groups of polymers that are likely to satisfy design criteria for water uptake. This research demonstrates that a surrogate modeling effort can reduce the number of polymers that must be synthesized and characterized to identify an appropriate polymer that meets certain performance criteria. PMID:27200091

  12. Late Ordovician (Turinian-Chatfieldian) carbon isotope excursions and their stratigraphic and paleoceanographic significance

    USGS Publications Warehouse

    Ludvigson, Greg A.; Witzke, B.J.; Gonzalez, Luis A.; Carpenter, S.J.; Schneider, C.L.; Hasiuk, F.

    2004-01-01

    Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville-Decorah succession in which background ??13C values increase upward from about -2??? at the base to about 0??? Vienna Pee Dee belemnite (VPDB) at the top. A regional north-south ??13C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion ??13C values of up to +2.75 are reported from the Quimbys Mill excursion, and up to +2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative ??13C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events. ?? 2004 Elsevier B.V. All rights reserved.

  13. Evolving Non-Dominated Parameter Sets for Computational Models from Multiple Experiments

    NASA Astrophysics Data System (ADS)

    Lane, Peter C. R.; Gobet, Fernand

    2013-03-01

    Creating robust, reproducible and optimal computational models is a key challenge for theorists in many sciences. Psychology and cognitive science face particular challenges as large amounts of data are collected and many models are not amenable to analytical techniques for calculating parameter sets. Particular problems are to locate the full range of acceptable model parameters for a given dataset, and to confirm the consistency of model parameters across different datasets. Resolving these problems will provide a better understanding of the behaviour of computational models, and so support the development of general and robust models. In this article, we address these problems using evolutionary algorithms to develop parameters for computational models against multiple sets of experimental data; in particular, we propose the `speciated non-dominated sorting genetic algorithm' for evolving models in several theories. We discuss the problem of developing a model of categorisation using twenty-nine sets of data and models drawn from four different theories. We find that the evolutionary algorithms generate high quality models, adapted to provide a good fit to all available data.

  14. Using an Agenda Setting Model to Help Students Develop & Exercise Participatory Skills and Values

    ERIC Educational Resources Information Center

    Perry, Anthony D.; Wilkenfeld, Britt S.

    2006-01-01

    The Agenda Setting Model is a program component that can be used in courses to contribute to students' development as responsible, effective, and informed citizens. This model involves students in finding a unified voice to assert an agenda of issues that they find especially pressing. This is often the only time students experience such a…

  15. Addressing HIV in the School Setting: Application of a School Change Model

    ERIC Educational Resources Information Center

    Walsh, Audra St. John; Chenneville, Tiffany

    2013-01-01

    This paper describes best practices for responding to youth with human immunodeficiency virus (HIV) in the school setting through the application of a school change model designed by the World Health Organization. This model applies a whole school approach and includes four levels that span the continuum from universal prevention to direct…

  16. An Example of the Use of Fuzzy Set Concepts in Modeling Learning Disability.

    ERIC Educational Resources Information Center

    Horvath, Michael J.; And Others

    1980-01-01

    The way a particular clinician judges, from data, the degree to which a child is in the category "learning disabled" was modeled on the basis of clinician's statement of the traits that comprise the handicap. The model illustrates the use of fuzzy set theory. (Author/RL)

  17. Information Content in Data Sets for a Nucleated-Polymerization Model

    PubMed Central

    Banks, H.T.; Doumic, Marie; Kruse, Carola; Prigent, Stephanie; Rezaei, Human

    2015-01-01

    We illustrate the use of statistical tools (asymptotic theories of standard error quantification using appropriate statistical models, bootstrapping, model comparison techniques) in addition to sensitivity analysis that may be employed to determine the information content in data sets. We do this in the context of recent models [25] for nucleated polymerization in proteins, about which very little is known regarding the underlying mechanisms; thus the methodology we develop here may be of great help to experimentalists. We conclude that the investigated data sets will support with reasonable levels of uncertainty only the estimation of the parameters related to the early steps of the aggregation process. PMID:26046598

  18. Large field excursions and approximate discrete symmetries from a clockwork axion

    NASA Astrophysics Data System (ADS)

    Kaplan, David E.; Rattazzi, Riccardo

    2016-04-01

    We present a renormalizable theory of scalars in which the low-energy effective theory contains a pseudo-Goldstone boson with a compact field space of 2 π F and an approximate discrete shift symmetry ZQ with Q ≫1 , yet the number of fields in the theory goes as log Q . Such a model can serve as a UV completion to models of relaxions and is a new source of exponential scale separation in field theory. While the model is local in "theory space," it appears not to have a continuum generalization (i.e., it cannot be a deconstructed extra dimension). Our framework shows that super-Planckian field excursions can be mimicked while sticking to renormalizable four-dimensional quantum field theory. We show that a supersymmetric extension is straightforwardly obtained, and we illustrate possible UV completions based on a compact extra dimension, where all global symmetries arise accidentally as a consequence of gauge invariance and five-dimensional locality.

  19. Enabling Interoperation of High Performance, Scientific Computing Applications: Modeling Scientific Data with the Sets & Fields (SAF) Modeling System

    SciTech Connect

    Miller, M C; Reus, J F; Matzke, R P; Arrighi, W J; Schoof, L A; Hitt, R T; Espen, P K; Butler, D M

    2001-02-07

    This paper describes the Sets and Fields (SAF) scientific data modeling system. It is a revolutionary approach to interoperation of high performance, scientific computing applications based upon rigorous, math-oriented data modeling principles. Previous technologies have required all applications to use the same data structures and/or meshes to represent scientific data or lead to an ever expanding set of incrementally different data structures and/or meshes. SAF addresses this problem by providing a small set of mathematical building blocks--sets, relations and fields--out of which a wide variety of scientific data can be characterized. Applications literally model their data by assembling these building blocks. A short historical perspective, a conceptual model and an overview of SAF along with preliminary results from its use in a few ASCI codes are discussed.

  20. A Dual Hesitant Fuzzy Multigranulation Rough Set over Two-Universe Model for Medical Diagnoses.

    PubMed

    Zhang, Chao; Li, Deyu; Yan, Yan

    2015-01-01

    In medical science, disease diagnosis is one of the difficult tasks for medical experts who are confronted with challenges in dealing with a lot of uncertain medical information. And different medical experts might express their own thought about the medical knowledge base which slightly differs from other medical experts. Thus, to solve the problems of uncertain data analysis and group decision making in disease diagnoses, we propose a new rough set model called dual hesitant fuzzy multigranulation rough set over two universes by combining the dual hesitant fuzzy set and multigranulation rough set theories. In the framework of our study, both the definition and some basic properties of the proposed model are presented. Finally, we give a general approach which is applied to a decision making problem in disease diagnoses, and the effectiveness of the approach is demonstrated by a numerical example. PMID:26858772

  1. A Dual Hesitant Fuzzy Multigranulation Rough Set over Two-Universe Model for Medical Diagnoses

    PubMed Central

    Zhang, Chao; Li, Deyu; Yan, Yan

    2015-01-01

    In medical science, disease diagnosis is one of the difficult tasks for medical experts who are confronted with challenges in dealing with a lot of uncertain medical information. And different medical experts might express their own thought about the medical knowledge base which slightly differs from other medical experts. Thus, to solve the problems of uncertain data analysis and group decision making in disease diagnoses, we propose a new rough set model called dual hesitant fuzzy multigranulation rough set over two universes by combining the dual hesitant fuzzy set and multigranulation rough set theories. In the framework of our study, both the definition and some basic properties of the proposed model are presented. Finally, we give a general approach which is applied to a decision making problem in disease diagnoses, and the effectiveness of the approach is demonstrated by a numerical example. PMID:26858772

  2. Variational and Shape Prior-based Level Set Model for Image Segmentation

    SciTech Connect

    Diop, El Hadji S.; Jerbi, Taha; Burdin, Valerie

    2010-09-30

    A new image segmentation model based on level sets approach is presented herein. We deal with radiographic medical images where boundaries are not salient, and objects of interest have the same gray level as other structures in the image. Thus, an a priori information about the shape we look for is integrated in the level set evolution for good segmentation results. The proposed model also accounts a penalization term that forces the level set to be close to a signed distance function (SDF), which then avoids the re-initialization procedure. In addition, a variant and complete Mumford-Shah model is used in our functional; the added Hausdorff measure helps to better handle zones where boundaries are occluded or not salient. Finally, a weighted area term is added to the functional to make the level set drive rapidly to object's boundaries. The segmentation model is formulated in a variational framework, which, thanks to calculus of variations, yields to partial differential equations (PDEs) to guide the level set evolution. Results obtained on both synthetic and digital radiographs reconstruction (DRR) show that the proposed model improves on existing prior and non-prior shape based image segmentation.

  3. Test data sets for calibration of stochastic and fractional stochastic volatility models.

    PubMed

    Pospíšil, Jan; Sobotka, Tomáš

    2016-09-01

    Data for calibration and out-of-sample error testing of option pricing models are provided alongside data obtained from optimization procedures in "On calibration of stochastic and fractional stochastic volatility models" [1]. Firstly we describe testing data sets, further calibration data obtained from combined optimizers is visually depicted - interactive 3d bar plots are provided. The data is suitable for a further comparison of other optimization routines and also to benchmark different pricing models. PMID:27419200

  4. The value of multiple data set calibration versus model complexity for improving the performance of hydrological models in mountain catchments

    NASA Astrophysics Data System (ADS)

    Finger, David; Vis, Marc; Huss, Matthias; Seibert, Jan

    2015-04-01

    The assessment of snow, glacier, and rainfall runoff contribution to discharge in mountain streams is of major importance for an adequate water resource management. Such contributions can be estimated via hydrological models, provided that the modeling adequately accounts for snow and glacier melt, as well as rainfall runoff. We present a multiple data set calibration approach to estimate runoff composition using hydrological models with three levels of complexity. For this purpose, the code of the conceptual runoff model HBV-light was enhanced to allow calibration and validation of simulations against glacier mass balances, satellite-derived snow cover area and measured discharge. Three levels of complexity of the model were applied to glacierized catchments in Switzerland, ranging from 39 to 103 km2. The results indicate that all three observational data sets are reproduced adequately by the model, allowing an accurate estimation of the runoff composition in the three mountain streams. However, calibration against only runoff leads to unrealistic snow and glacier melt rates. Based on these results, we recommend using all three observational data sets in order to constrain model parameters and compute snow, glacier, and rain contributions. Finally, based on the comparison of model performance of different complexities, we postulate that the availability and use of different data sets to calibrate hydrological models might be more important than model complexity to achieve realistic estimations of runoff composition.

  5. Solving the set cover problem and the problem of exact cover by 3-sets in the Adleman-Lipton model.

    PubMed

    Chang, Weng Long; Guo, Minyi

    2003-12-01

    Adleman wrote the first paper in which it is shown that deoxyribonucleic acid (DNA) strands could be employed towards calculating solutions to an instance of the NP-complete Hamiltonian path problem (HPP). Lipton also demonstrated that Adleman's techniques could be used to solve the NP-complete satisfiability (SAT) problem (the first NP-complete problem). In this paper, it is proved how the DNA operations presented by Adleman and Lipton can be used for developing DNA algorithms to resolving the set cover problem and the problem of exact cover by 3-sets. PMID:14643494

  6. Adaptive dynamic networks as models for the immune system and autocatalytic sets

    SciTech Connect

    Farmer, J.D.; Kauffman, S.A.; Packard, N.H.; Perelson, A.S.

    1986-04-01

    A general class of network models is described that can be used to present complex adaptive systems. These models have two purposes: On a practical level they are closely based on real biological phenomena, and are intended to model detailed aspects of them. On a more general level, however, they provide a framework to address broader questions concerning evolution, pattern recognition, and other properties of living systems. This paper concentrates on the more general level, illustrating the basic concepts with two examples, a model of the immune system and a model for the spontaneous emergence of autocatalytic sets in a chemically reactive polymer soup. 10 refs., 3 figs.

  7. THE DEVELOPMENT AND USE OF A MODEL TO PREDICT SUSTAINABILITY OF CHANGE IN HEALTH CARE SETTINGS

    PubMed Central

    2011-01-01

    Innovations adopted through organizational change initiatives are often not sustained leading to diminished quality, productivity, and consumer satisfaction. Research explaining variance in the use of adopted innovations in health care settings is sparse, suggesting the need for a theoretical model to guide research and practice. In this article, we describe the development of a hybrid conjoint decision theoretic model designed to predict the sustainability of organizational change in health care settings. An initial test of the model’s predictive validity using expert scored hypothetic profiles resulted in an r-squared value of .77. The test of this model offers a theoretical base for future research on the sustainability of change in health care settings. PMID:22262947

  8. Using open building data in the development of exposure data sets for catastrophe risk modelling

    NASA Astrophysics Data System (ADS)

    Figueiredo, R.; Martina, M.

    2016-02-01

    One of the necessary components to perform catastrophe risk modelling is information on the buildings at risk, such as their spatial location, geometry, height, occupancy type and other characteristics. This is commonly referred to as the exposure model or data set. When modelling large areas, developing exposure data sets with the relevant information about every individual building is not practicable. Thus, census data at coarse spatial resolutions are often used as the starting point for the creation of such data sets, after which disaggregation to finer resolutions is carried out using different methods, based on proxies such as the population distribution. While these methods can produce acceptable results, they cannot be considered ideal. Nowadays, the availability of open data is increasing and it is possible to obtain information about buildings for some regions. Although this type of information is usually limited and, therefore, insufficient to generate an exposure data set, it can still be very useful in its elaboration. In this paper, we focus on how open building data can be used to develop a gridded exposure model by disaggregating existing census data at coarser resolutions. Furthermore, we analyse how the selection of the level of spatial resolution can impact the accuracy and precision of the model, and compare the results in terms of affected residential building areas, due to a flood event, between different models.

  9. Neural model for learning-to-learn of novel task sets in the motor domain

    PubMed Central

    Pitti, Alexandre; Braud, Raphaël; Mahé, Sylvain; Quoy, Mathias; Gaussier, Philippe

    2013-01-01

    During development, infants learn to differentiate their motor behaviors relative to various contexts by exploring and identifying the correct structures of causes and effects that they can perform; these structures of actions are called task sets or internal models. The ability to detect the structure of new actions, to learn them and to select on the fly the proper one given the current task set is one great leap in infants cognition. This behavior is an important component of the child's ability of learning-to-learn, a mechanism akin to the one of intrinsic motivation that is argued to drive cognitive development. Accordingly, we propose to model a dual system based on (1) the learning of new task sets and on (2) their evaluation relative to their uncertainty and prediction error. The architecture is designed as a two-level-based neural system for context-dependent behavior (the first system) and task exploration and exploitation (the second system). In our model, the task sets are learned separately by reinforcement learning in the first network after their evaluation and selection in the second one. We perform two different experimental setups to show the sensorimotor mapping and switching between tasks, a first one in a neural simulation for modeling cognitive tasks and a second one with an arm-robot for motor task learning and switching. We show that the interplay of several intrinsic mechanisms drive the rapid formation of the neural populations with respect to novel task sets. PMID:24155736

  10. Low-shrinkage dental restorative composite: modeling viscoelastic behavior during setting.

    PubMed

    Dauvillier, Bibi S; Feilzer, Albert J

    2005-04-01

    Much attention has been directed toward developing dental direct restorative composites that generate less shrinkage stress during setting. The aim of this study was to explore the viscoelastic behavior of a new class of low-shrinkage dental restorative composite during setting. The setting behavior of an experimental oxirane composite has been investigated by analyzing stress-strain data with two-parametric mechanical models. Experimental data were obtained from a dynamic test method, in which the setting light-activated composite was continuously subjected to sinusoidal strain cycles. The material parameters and the model's predictive capacity were analyzed with validated modeling procedures. The light-activated oxirane composite exhibited shrinkage delay and low polymerization shrinkage strain and stresses when compared with conventional light-activated composite. Noise in the stress data restricted the predictive ability of the Maxwell model to the elastic modulus development of the composite only. Evaluation tests of their potential as restorative material are required, to examine if the biocompatibility and mechanical properties after setting of oxirane composites are acceptable for dental use. PMID:15685614

  11. Adapting Existing Spatial Data Sets to New Uses: An Example from Energy Modeling

    SciTech Connect

    Johanesson, G; Stewart, J S; Barr, C; Sabeff, L B; George, R; Heimiller, D; Milbrandt, A

    2006-06-23

    Energy modeling and analysis often relies on data collected for other purposes such as census counts, atmospheric and air quality observations, and economic projections. These data are available at various spatial and temporal scales, which may be different from those needed by the energy modeling community. If the translation from the original format to the format required by the energy researcher is incorrect, then resulting models can produce misleading conclusions. This is of increasing importance, because of the fine resolution data required by models for new alternative energy sources such as wind and distributed generation. This paper addresses the matter by applying spatial statistical techniques which improve the usefulness of spatial data sets (maps) that do not initially meet the spatial and/or temporal requirements of energy models. In particular, we focus on (1) aggregation and disaggregation of spatial data, (2) imputing missing data and (3) merging spatial data sets.

  12. Influence of turbulence model parameter settings on conjugate heat transfer simulation

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Li, Yu; Zou, Zhengping; Wang, Lei; Song, Songhe

    2014-04-01

    Rationality of the parameter settings in turbulence model is an important factor affecting the accuracy of conjugate heat transfer (CHT) prediction. On the basis of a developed CHT methodology and the experimental data of Mark// cooling turbine blade, influences of the turbulence model parameter settings and the selection of turbulence models on CHT simulation are investigated. Results and comparisons with experimental data indicate that the inlet setting of the in Spalart-Allmaras model has nearly no influence on flow and heat transfer in blade surface. The inlet turbulence length scale l T in the low-Reynolds number Chien k- ɛ turbulence model and the blade surface roughness in shear stress transport (SST) k- ω SST model have relatively obvious effects on the blade surface temperature which increases with the increase of them. Both of the laminar Prandtl number and turbulent Prandtl number have slight influences on the prediction, and they only need to be constant in CHT simulation. The k- ω SST model has the best accuracy in the turbine blade CHT simulation compared with the other two models.

  13. Engaging students in research learning experiences through hydrology field excursions and projects

    NASA Astrophysics Data System (ADS)

    Ewen, T.; Seibert, J.

    2014-12-01

    One of the best ways to engage students and instill enthusiasm for hydrology is to expose them to hands-on learning. A focus on hydrology field research can be used to develop context-rich and active learning, and help solidify idealized learning where students are introduced to individual processes through textbook examples, often neglecting process interactions and an appreciation for the complexity of the system. We introduced a field course where hydrological measurement techniques are used to study processes such as snow hydrology and runoff generation, while also introducing students to field research and design of their own field project. In the field projects, students design a low-budget experiment with the aim of going through the different steps of a 'real' scientific project, from formulating the research question to presenting their results. In one of the field excursions, students make discharge measurements in several alpine streams with a salt tracer to better understand the spatial characteristics of an alpine catchment, where source waters originate and how they contribute to runoff generation. Soil moisture measurements taken by students in this field excursion were used to analyze spatial soil moisture patterns in the alpine catchment and subsequently used in a publication. Another field excursion repeats a published experiment, where preferential soil flow paths are studied using a tracer and compared to previously collected data. For each field excursion, observational data collected by the students is uploaded to an online database we developed, which also allows students to retrieve data from past excursions to further analyze and compare their data. At each of the field sites, weather stations were installed and a webviewer allows access to realtime data from data loggers, allowing students to explore how processes relate to climatic conditions. With in-house film expertise, these field excursions were also filmed and short virtual

  14. Development of optimization models for the set behavior and compressive strength of sodium activated geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Fillenwarth, Brian Albert

    As large countries such as China begin to industrialize and concerns about global warming continue to grow, there is an increasing need for more environmentally friendly building materials. One promising material known as a geopolymer can be used as a portland cement replacement and in this capacity emits around 67% less carbon dioxide. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products such as fly ash. Although the benefits of geopolymers are substantial, there are a few difficulties with designing geopolymer mixes which have hindered widespread commercialization of the material. One such difficulty is the high variability of the materials used for their synthesis. In addition to this, interrelationships between mix design variables and how these interrelationships impact the set behavior and compressive strength are not well understood. A third complicating factor with designing geopolymer mixes is that the role of calcium in these systems is not well understood. In order to overcome these barriers, this study developed predictive optimization models through the use of genetic programming with experimentally collected set times and compressive strengths of several geopolymer paste mixes. The developed set behavior models were shown to predict the correct set behavior from the mix design over 85% of the time. The strength optimization model was shown to be capable of predicting compressive strengths of geopolymer pastes from their mix design to within about 1 ksi of their actual strength. In addition to this the optimization models give valuable insight into the key factors influencing strength development as well as the key factors responsible for flash set and long set behaviors in geopolymer pastes. A method for designing geopolymer paste mixes was developed from the generated optimization models. This design method provides an invaluable tool for use in future geopolymer research as well as

  15. The identifiability analysis for setting up measuring campaigns in integrated water quality modelling

    NASA Astrophysics Data System (ADS)

    Freni, Gabriele; Mannina, Giorgio

    Identifiability analysis enables the quantification of the number of model parameters that can be assessed by calibration with respect to a data set. Such a methodology is based on the appraisal of sensitivity coefficients of the model parameters by means of Monte Carlo runs. By employing the Fisher Information Matrix, the methodology enables one to gain insights with respect to the number of model parameters that can be reliably assessed. The paper presents a study where identifiability analysis is used as a tool for setting up measuring campaigns for integrated water quality modelling. Particularly, by means of the identifiability analysis, the information about the location and the number of the monitoring stations in the integrated system required for assessing a specific group of model parameters were gained. The analysis has been applied to a real, partially urbanised, catchment containing two sewer systems, two wastewater treatment plants and a river. Several scenarios of measuring campaigns have been considered; each scenario was characterised by different monitoring station locations for the gathering of quantity and quality data. The results enabled us to assess the maximum number of model parameters quantifiable for each scenario i.e. for each data set. The methodology resulted to be a powerful tool for designing measuring campaign for integrated water quality modelling. Indeed, the crucial cross sections throughout the integrated wastewater system were detected optimizing both human and economic efforts in the gathering of field data. Further, a connection between the data set and the number of model parameters effectively assessable has been established leading to much more reliable model results.

  16. An algorithm for deriving core magnetic field models from the Swarm data set

    NASA Astrophysics Data System (ADS)

    Rother, Martin; Lesur, Vincent; Schachtschneider, Reyko

    2013-11-01

    In view of an optimal exploitation of the Swarm data set, we have prepared and tested software dedicated to the determination of accurate core magnetic field models and of the Euler angles between the magnetic sensors and the satellite reference frame. The dedicated core field model estimation is derived directly from the GFZ Reference Internal Magnetic Model (GRIMM) inversion and modeling family. The data selection techniques and the model parameterizations are similar to what were used for the derivation of the second (Lesur et al., 2010) and third versions of GRIMM, although the usage of observatory data is not planned in the framework of the application to Swarm. The regularization technique applied during the inversion process smoothes the magnetic field model in time. The algorithm to estimate the Euler angles is also derived from the CHAMP studies. The inversion scheme includes Euler angle determination with a quaternion representation for describing the rotations. It has been built to handle possible weak time variations of these angles. The modeling approach and software have been initially validated on a simple, noise-free, synthetic data set and on CHAMP vector magnetic field measurements. We present results of test runs applied to the synthetic Swarm test data set.

  17. Noisy attractors and ergodic sets in models of gene regulatory networks.

    PubMed

    Ribeiro, Andre S; Kauffman, Stuart A

    2007-08-21

    We investigate the hypothesis that cell types are attractors. This hypothesis was criticized with the fact that real gene networks are noisy systems and, thus, do not have attractors [Kadanoff, L., Coppersmith, S., Aldana, M., 2002. Boolean Dynamics with Random Couplings. http://www.citebase.org/abstract?id=oai:arXiv.org:nlin/0204062]. Given the concept of "ergodic set" as a set of states from which the system, once entering, does not leave when subject to internal noise, first, using the Boolean network model, we show that if all nodes of states on attractors are subject to internal state change with a probability p due to noise, multiple ergodic sets are very unlikely. Thereafter, we show that if a fraction of those nodes are "locked" (not subject to state fluctuations caused by internal noise), multiple ergodic sets emerge. Finally, we present an example of a gene network, modelled with a realistic model of transcription and translation and gene-gene interaction, driven by a stochastic simulation algorithm with multiple time-delayed reactions, which has internal noise and that we also subject to external perturbations. We show that, in this case, two distinct ergodic sets exist and are stable within a wide range of parameters variations and, to some extent, to external perturbations. PMID:17543998

  18. The GRENE-TEA model intercomparison project (GTMIP) Stage 1 forcing data set

    NASA Astrophysics Data System (ADS)

    Sueyoshi, T.; Saito, K.; Miyazaki, S.; Mori, J.; Ise, T.; Arakida, H.; Suzuki, R.; Sato, A.; Iijima, Y.; Yabuki, H.; Ikawa, H.; Ohta, T.; Kotani, A.; Hajima, T.; Sato, H.; Yamazaki, T.; Sugimoto, A.

    2016-01-01

    Here, the authors describe the construction of a forcing data set for land surface models (including both physical and biogeochemical models; LSMs) with eight meteorological variables for the 35-year period from 1979 to 2013. The data set is intended for use in a model intercomparison study, called GTMIP, which is a part of the Japanese-funded Arctic Climate Change Research Project. In order to prepare a set of site-fitted forcing data for LSMs with realistic yet continuous entries (i.e. without missing data), four observational sites across the pan-Arctic region (Fairbanks, Tiksi, Yakutsk, and Kevo) were selected to construct a blended data set using both global reanalysis and observational data. Marked improvements were found in the diurnal cycles of surface air temperature and humidity, wind speed, and precipitation. The data sets and participation in GTMIP are open to the scientific community (doi:10.17592/001.2015093001).

  19. CUTSETS - MINIMAL CUT SET CALCULATION FOR DIGRAPH AND FAULT TREE RELIABILITY MODELS

    NASA Technical Reports Server (NTRS)

    Iverson, D. L.

    1994-01-01

    Fault tree and digraph models are frequently used for system failure analysis. Both type of models represent a failure space view of the system using AND and OR nodes in a directed graph structure. Fault trees must have a tree structure and do not allow cycles or loops in the graph. Digraphs allow any pattern of interconnection between loops in the graphs. A common operation performed on digraph and fault tree models is the calculation of minimal cut sets. A cut set is a set of basic failures that could cause a given target failure event to occur. A minimal cut set for a target event node in a fault tree or digraph is any cut set for the node with the property that if any one of the failures in the set is removed, the occurrence of the other failures in the set will not cause the target failure event. CUTSETS will identify all the minimal cut sets for a given node. The CUTSETS package contains programs that solve for minimal cut sets of fault trees and digraphs using object-oriented programming techniques. These cut set codes can be used to solve graph models for reliability analysis and identify potential single point failures in a modeled system. The fault tree minimal cut set code reads in a fault tree model input file with each node listed in a text format. In the input file the user specifies a top node of the fault tree and a maximum cut set size to be calculated. CUTSETS will find minimal sets of basic events which would cause the failure at the output of a given fault tree gate. The program can find all the minimal cut sets of a node, or minimal cut sets up to a specified size. The algorithm performs a recursive top down parse of the fault tree, starting at the specified top node, and combines the cut sets of each child node into sets of basic event failures that would cause the failure event at the output of that gate. Minimal cut set solutions can be found for all nodes in the fault tree or just for the top node. The digraph cut set code uses the same

  20. Applying the SNOMED CT Concept Model to Represent Value Sets for Head and Neck Cancer Documentation.

    PubMed

    Højen, Anne Randorff; Brønnum, Dorthe; Gøeg, Kirstine Rosenbeck; Elberg, Pia Britt

    2016-01-01

    This paper presents an analysis of the extent to which SNOMED CT is suitable for representing data within the domain of head and neck cancer. In this analysis we assess whether the concept model of SNOMED CT comply with the documentation needed within this clinical domain. Attributes from the follow-up template of the clinical quality registry for Danish Head and Neck Cancer, and their respective value sets were mapped to SNOMED CT using existing mapping guidelines. Results show that post-coordination is important to represent specific types of value sets, such as absence of findings and severities. The concept model of SNOMED CT was found suitable for representing the value sets of this material. We argue for the development of further mapping guidelines for consistent post-coordination and for initiatives that demonstrate use of this important terminological feature in actual SNOMED CT implementations. PMID:27577420

  1. Refining Sunrise/set Prediction Models by Accounting for the Effects of Refraction

    NASA Astrophysics Data System (ADS)

    Wilson, Teresa; Bartlett, Jennifer L.

    2016-01-01

    Current atmospheric models used to predict the times of sunrise and sunset have an error of one to four minutes at mid-latitudes (0° - 55° N/S). At higher latitudes, slight changes in refraction may cause significant discrepancies, including determining even whether the Sun appears to rise or set. While different components of refraction are known, how they affect predictions of sunrise/set has not yet been quantified. A better understanding of the contributions from temperature profile, pressure, humidity, and aerosols, could significantly improve the standard prediction. Because sunrise/set times and meteorological data from multiple locations will be necessary for a thorough investigation of the problem, we will collect this data using smartphones as part of a citizen science project. This analysis will lead to more complete models that will provide more accurate times for navigators and outdoorsman alike.

  2. Planting-Density Optimization Study Fortomato Fruit Set and Yield Based Onfunctional-Structural Model Greenlab

    NASA Astrophysics Data System (ADS)

    Yang, Lili; Wang, Yiming; Dong, Qiaoxue

    Quantification of tomato's fruit-sets depends on the level of competition for assimilate in different environment, and this paper presented some results of fruit yield and quality (fruit size) in response to environment (mainly respect to and planting-density and light). Some experiments had been carried out to find the relationship between growth rules of tomato and plant densities A structural-functional model GREENLAB has been developed to simulate it. The results show that increasing plant density results in an increment of biomass production on a ground area but in a reduction of single plant fresh weight. To find rules between organ sink and source relationship, calibrations Environmental conditions were introduced into the model checking the influence on Q/D over plant growth period and fruit set ratio. It is found that changing the Q/D ratio in some critical periods can be used to optimize fruit set and yield of greenhouse tomato.

  3. Data sets for snow cover monitoring and modelling from the National Snow and Ice Data Center

    NASA Astrophysics Data System (ADS)

    Holm, M.; Daniels, K.; Scott, D.; McLean, B.; Weaver, R.

    2003-04-01

    A wide range of snow cover monitoring and modelling data sets are pending or are currently available from the National Snow and Ice Data Center (NSIDC). In-situ observations support validation experiments that enhance the accuracy of remote sensing data. In addition, remote sensing data are available in near-real time, providing coarse-resolution snow monitoring capability. Time series data beginning in 1966 are valuable for modelling efforts. NSIDC holdings include SMMR and SSM/I snow cover data, MODIS snow cover extent products, in-situ and satellite data collected for NASA's recent Cold Land Processes Experiment, and soon-to-be-released ASMR-E passive microwave products. The AMSR-E and MODIS sensors are part of NASA's Earth Observing System flying on the Terra and Aqua satellites Characteristics of these NSIDC-held data sets, appropriateness of products for specific applications, and data set access and availability will be presented.

  4. Towards Precise Metadata-set for Discovering 3D Geospatial Models in Geo-portals

    NASA Astrophysics Data System (ADS)

    Zamyadi, A.; Pouliot, J.; Bédard, Y.

    2013-09-01

    Accessing 3D geospatial models, eventually at no cost and for unrestricted use, is certainly an important issue as they become popular among participatory communities, consultants, and officials. Various geo-portals, mainly established for 2D resources, have tried to provide access to existing 3D resources such as digital elevation model, LIDAR or classic topographic data. Describing the content of data, metadata is a key component of data discovery in geo-portals. An inventory of seven online geo-portals and commercial catalogues shows that the metadata referring to 3D information is very different from one geo-portal to another as well as for similar 3D resources in the same geo-portal. The inventory considered 971 data resources affiliated with elevation. 51% of them were from three geo-portals running at Canadian federal and municipal levels whose metadata resources did not consider 3D model by any definition. Regarding the remaining 49% which refer to 3D models, different definition of terms and metadata were found, resulting in confusion and misinterpretation. The overall assessment of these geo-portals clearly shows that the provided metadata do not integrate specific and common information about 3D geospatial models. Accordingly, the main objective of this research is to improve 3D geospatial model discovery in geo-portals by adding a specific metadata-set. Based on the knowledge and current practices on 3D modeling, and 3D data acquisition and management, a set of metadata is proposed to increase its suitability for 3D geospatial models. This metadata-set enables the definition of genuine classes, fields, and code-lists for a 3D metadata profile. The main structure of the proposal contains 21 metadata classes. These classes are classified in three packages as General and Complementary on contextual and structural information, and Availability on the transition from storage to delivery format. The proposed metadata set is compared with Canadian Geospatial

  5. Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) Systems Integration Strategy

    NASA Technical Reports Server (NTRS)

    Gill, Tracy; Merbitz, Jerad; Kennedy, Kriss; Tri, Terry; Toups, Larry; Howe, A. Scott

    2011-01-01

    The Habitat Demonstration Unit (HDU) project team constructed an analog prototype lunar surface laboratory called the Pressurized Excursion Module (PEM). The prototype unit subsystems were integrated in a short amount of time, utilizing a rapid prototyping approach that brought together over 20 habitation-related technologies from a variety of NASA centers. This paper describes the system integration strategies and lessons learned, that allowed the PEM to be brought from paper design to working field prototype using a multi-center team. The system integration process was based on a rapid prototyping approach. Tailored design review and test and integration processes facilitated that approach. The use of collaboration tools including electronic tools as well as documentation enabled a geographically distributed team take a paper concept to an operational prototype in approximately one year. One of the major tools used in the integration strategy was a coordinated effort to accurately model all the subsystems using computer aided design (CAD), so conflicts were identified before physical components came together. A deliberate effort was made following the deployment of the HDU PEM for field operations to collect lessons learned to facilitate process improvement and inform the design of future flight or analog versions of habitat systems. Significant items within those lessons learned were limitations with the CAD integration approach and the impact of shell design on flexibility of placing systems within the HDU shell.

  6. Relation of Phanerozoic stable isotope excursions to climate, bacterial metabolism, and major extinctions.

    PubMed

    Stanley, Steven M

    2010-11-01

    Conspicuous global stable carbon isotope excursions that are recorded in marine sedimentary rocks of Phanerozoic age and were associated with major extinctions have generally paralleled global stable oxygen isotope excursions. All of these phenomena are therefore likely to share a common origin through global climate change. Exceptional patterns for carbon isotope excursions resulted from massive carbon burial during warm intervals of widespread marine anoxic conditions. The many carbon isotope excursions that parallel those for oxygen isotopes can to a large degree be accounted for by the Q10 pattern of respiration for bacteria: As temperature changed along continental margins, where ∼90% of marine carbon burial occurs today, rates of remineralization of isotopically light carbon must have changed exponentially. This would have reduced organic carbon burial during global warming and increased it during global cooling. Also contributing to the δ(13)C excursions have been release and uptake of methane by clathrates, the positive correlation between temperature and degree of fractionation of carbon isotopes by phytoplankton at temperatures below ∼15°, and increased phytoplankton productivity during "icehouse" conditions. The Q10 pattern for bacteria and climate-related changes in clathrate volume represent positive feedbacks for climate change. PMID:21041682

  7. Relation of Phanerozoic stable isotope excursions to climate, bacterial metabolism, and major extinctions

    PubMed Central

    Stanley, Steven M.

    2010-01-01

    Conspicuous global stable carbon isotope excursions that are recorded in marine sedimentary rocks of Phanerozoic age and were associated with major extinctions have generally paralleled global stable oxygen isotope excursions. All of these phenomena are therefore likely to share a common origin through global climate change. Exceptional patterns for carbon isotope excursions resulted from massive carbon burial during warm intervals of widespread marine anoxic conditions. The many carbon isotope excursions that parallel those for oxygen isotopes can to a large degree be accounted for by the Q10 pattern of respiration for bacteria: As temperature changed along continental margins, where ∼90% of marine carbon burial occurs today, rates of remineralization of isotopically light carbon must have changed exponentially. This would have reduced organic carbon burial during global warming and increased it during global cooling. Also contributing to the δ13C excursions have been release and uptake of methane by clathrates, the positive correlation between temperature and degree of fractionation of carbon isotopes by phytoplankton at temperatures below ∼15°, and increased phytoplankton productivity during “icehouse” conditions. The Q10 pattern for bacteria and climate-related changes in clathrate volume represent positive feedbacks for climate change. PMID:21041682

  8. Paradigms, Mental Models, and Mind-Sets: Triple Barriers to Transformational Change in School Systems

    ERIC Educational Resources Information Center

    Duffy, Francis M.

    2014-01-01

    This article presents a simile for understanding the power of paradigms, mental models, and mind-sets as religion-like phenomena. The author clarifies the meaning of the three phenomena to help readers to see how the phenomena become significant sources of resistance to change. He concludes by outlining a paradigm-shifting process to assist…

  9. Technology Adoption Applied to Educational Settings: Predicting Interventionists' Use of Video-Self Modeling

    ERIC Educational Resources Information Center

    Heckman, Andrew R.

    2010-01-01

    Technology provides educators with a significant advantage in working with today's students. One particular application of technology for the purposes of academic and behavioral interventions is the use of video self-modeling (VSM). Although VSM is an evidence-based intervention, it is rarely used in educational settings. The present research…

  10. Portable and Accessible Video Modeling: Teaching a Series of Novel Skills within School and Community Settings

    ERIC Educational Resources Information Center

    Taber-Doughty, Teresa; Miller, Bridget; Shurr, Jordan; Wiles, Benjamin

    2013-01-01

    This study examined the effectiveness of self-operated video models on the skill acquisition of a series of novel tasks taught in community-based settings. In addition, the percent of independent task transitions and the duration at which four secondary students with a moderate intellectual disability transitioned between tasks was also examined.…

  11. A long-term data set for hydrologic modeling in a snow-dominated mountain catchment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An hourly modeling data set is presented for the water years 1984 through 2008 for a snow-dominated headwater catchment. Meteorological forcing data and GIS watershed characteristics are described and provided. The meteorological data are measured at two sites within the catchment, and include pre...

  12. Brain extraction from cerebral MRI volume using a hybrid level set based active contour neighborhood model

    PubMed Central

    2013-01-01

    Background The extraction of brain tissue from cerebral MRI volume is an important pre-procedure for neuroimage analyses. The authors have developed an accurate and robust brain extraction method using a hybrid level set based active contour neighborhood model. Methods The method uses a nonlinear speed function in the hybrid level set model to eliminate boundary leakage. When using the new hybrid level set model an active contour neighborhood model is applied iteratively in the neighborhood of brain boundary. A slice by slice contour initial method is proposed to obtain the neighborhood of the brain boundary. The method was applied to the internet brain MRI data provided by the Internet Brain Segmentation Repository (IBSR). Results In testing, a mean Dice similarity coefficient of 0.95±0.02 and a mean Hausdorff distance of 12.4±4.5 were obtained when performing our method across the IBSR data set (18 × 1.5 mm scans). The results obtained using our method were very similar to those produced using manual segmentation and achieved the smallest mean Hausdorff distance on the IBSR data. Conclusions An automatic method of brain extraction from cerebral MRI volume was achieved and produced competitively accurate results. PMID:23587217

  13. Video Self-Modeling: A Job Skills Intervention with Individuals with Intellectual Disability in Employment Settings

    ERIC Educational Resources Information Center

    Goh, Ailsa E.; Bambara, Linda M.

    2013-01-01

    The purpose of this study was to explore the effectiveness of video self-modeling (VSM) to teach chained job tasks to individuals with intellectual disability in community-based employment settings. Initial empirical evaluations have demonstrated that VSM when used in combination with other instructional strategies, are effective methods to teach…

  14. Brief Report: Predictors of Outcomes in the Early Start Denver Model Delivered in a Group Setting

    ERIC Educational Resources Information Center

    Vivanti, Giacomo; Dissanayake, Cheryl; Zierhut, Cynthia; Rogers, Sally J.

    2013-01-01

    There is a paucity of studies that have looked at factors associated with responsiveness to interventions in preschoolers with autism spectrum disorder (ASD). We investigated learning profiles associated with response to the Early Start Denver Model delivered in a group setting. Our preliminary results from 21 preschool children with an ASD aged…

  15. Comparison of Fuzzy Set and Convex Model Theories in Structural Design

    NASA Astrophysics Data System (ADS)

    Pantelides, Chris P.; Ganzerli, Sara

    2001-05-01

    A methodology for the treatment of uncertainty in the loads applied to a structural system using convex models is presented and is compared to the fuzzy set finite-element method. The analytical results for a beam, a truss and a frame structure indicate that the two methods based on convex model or fuzzy set theory are in good agreement for equivalent levels of uncertainty applied to linear structures. Convex model or fuzzy set theories have shown that the worst-case scenario response of all possible load combinations cannot be captured simply by load factorisation, as is the current design practice in building codes. Design problems including uncertainty with a large number of degrees of freedom, that are not computationally feasible using conventional methods described in building codes, can be solved easily using convex model or fuzzy set theory. These results can be used directly and efficiently in the analyses required for the optimal design of structural systems, thus enabling optimisation of complex structural systems with uncertainty.

  16. Goal Setting and Performance Evaluation with Different Starting Positions: The Modeling Dilemma.

    ERIC Educational Resources Information Center

    Pray, Thomas F.; Gold, Steven

    1991-01-01

    Reviews 10 computerized business simulations used to teach business policy courses, discusses problems with measuring performance, and presents a statistically based approach to assessing performance that permits individual team goal setting as part of the computer model, and allows simulated firms to start with different financial and operating…

  17. Invariance, Artifact, and the Psychological Setting of Rasch's Model: Comments on Engelhard

    ERIC Educational Resources Information Center

    Michell, Joel

    2008-01-01

    In the following, I confine my comments mainly to the issue of invariance in relation to Rasch's model for dichotomous, ability test items. "It is senseless to seek in the logical process of mathematical elaboration a psychologically significant precision that was not present in the psychological setting of the problem." (Boring, 1920)

  18. Breaking Bad News in Counseling: Applying the PEWTER Model in the School Setting

    ERIC Educational Resources Information Center

    Keefe-Cooperman, Kathleen; Brady-Amoon, Peggy

    2013-01-01

    Breaking bad news is a stressful experience for counselors and clients. In this article, the PEWTER (Prepare, Evaluate, Warning, Telling, Emotional Response, Regrouping) model (Nardi & Keefe-Cooperman, 2006) is used as a guide to facilitate the process of a difficult conversation and promote client growth in a school setting. In this…

  19. Analyzing Academic Achievement of Junior High School Students by an Improved Rough Set Model

    ERIC Educational Resources Information Center

    Pai, Ping-Feng; Lyu, Yi-Jia; Wang, Yu-Min

    2010-01-01

    Rough set theory (RST) is an emerging technique used to deal with problems in data mining and knowledge acquisition. However, the RST approach has not been widely explored in the field of academic achievement. This investigation developed an improved RST (IMRST) model, which employs linear discriminant analysis to determine a reduct of RST, and…

  20. Sensitivity of the properties of ruthenium ``blue dimer'' to method, basis set, and continuum model

    NASA Astrophysics Data System (ADS)

    Ozkanlar, Abdullah; Clark, Aurora E.

    2012-05-01

    The ruthenium "blue dimer" [(bpy)2RuIIIOH2]2O4+ is best known as the first well-defined molecular catalyst for water oxidation. It has been subject to numerous computational studies primarily employing density functional theory. However, those studies have been limited in the functionals, basis sets, and continuum models employed. The controversy in the calculated electronic structure and the reaction energetics of this catalyst highlights the necessity of benchmark calculations that explore the role of density functionals, basis sets, and continuum models upon the essential features of blue-dimer reactivity. In this paper, we report Kohn-Sham complete basis set (KS-CBS) limit extrapolations of the electronic structure of "blue dimer" using GGA (BPW91 and BP86), hybrid-GGA (B3LYP), and meta-GGA (M06-L) density functionals. The dependence of solvation free energy corrections on the different cavity types (UFF, UA0, UAHF, UAKS, Bondi, and Pauling) within polarizable and conductor-like polarizable continuum model has also been investigated. The most common basis sets of double-zeta quality are shown to yield results close to the KS-CBS limit; however, large variations are observed in the reaction energetics as a function of density functional and continuum cavity model employed.

  1. Rejoinder: Evaluating Standard Setting Methods Using Error Models Proposed by Schulz

    ERIC Educational Resources Information Center

    Reckase, Mark D.

    2006-01-01

    Schulz (2006) provides a different perspective on standard setting than that provided in Reckase (2006). He also suggests a modification to the bookmark procedure and some alternative models for errors in panelists' judgments than those provided by Reckase. This article provides a response to some of the points made by Schulz and reports some…

  2. Robust Point Sets Matching by Fusing Feature and Spatial Information Using Nonuniform Gaussian Mixture Models.

    PubMed

    Tao, Wenbing; Sun, Kun

    2015-11-01

    Most of the traditional methods that handle the point sets matching between two images are based on local feature descriptors and the succedent mismatch eliminating strategies, which usually suffers from the sparsity of the initial match set because some correct ambiguous associations are easily filtered out by the ratio test of SIFT matching due to their second ranking in feature similarity. In this paper, we propose a nonuniform Gaussian mixture model (NGMM) for point sets matching between a pair of images which combines feature with position information of the local feature points extracted from the image pair to achieve point sets matching in a GMM framework. The proposed point set matching using an NGMM is able to change the correspondence assignments throughout the matching process and has the potential to match up even ambiguous matches correctly. The proposed NGMM framework can be either used to directly find matches between two point sets obtained from two images or applied to remove outliers in a match set. When finding matches, NGMM tries to learn a nonrigid transformation between the two point sets and provide a probability for every found match to measure the reliability of the match. Then, a probability threshold can be used to get the final robust match set. When removing outliers, NGMM requires that the vector field formed by the correct matches to be coherent and the matches contradicting the coherent vector field will be regarded as mismatches to be removed. A number of comparison and evaluation experiments reveal the good performance of the proposed NGMM framework in both finding matches and discarding mismatches. PMID:26111398

  3. Quantum algorithms for spin models and simulable gate sets for quantum computation

    NASA Astrophysics Data System (ADS)

    van den Nest, M.; Dür, W.; Raussendorf, R.; Briegel, H. J.

    2009-11-01

    We present simple mappings between classical lattice models and quantum circuits, which provide a systematic formalism to obtain quantum algorithms to approximate partition functions of lattice models in certain complex-parameter regimes. We, e.g., present an efficient quantum algorithm for the six-vertex model as well as a two-dimensional Ising-type model. We show that classically simulating these (complex-parameter) spin models is as hard as simulating universal quantum computation, i.e., BQP complete (BQP denotes bounded-error quantum polynomial time). Furthermore, our mappings provide a framework to obtain efficiently simulable quantum gate sets from exactly solvable classical models. We, e.g., show that the simulability of Valiant’s match gates can be recovered by using the solvability of the free-fermion eight-vertex model.

  4. Index-based groundwater vulnerability mapping models using hydrogeological settings: A critical evaluation

    SciTech Connect

    Kumar, Prashant; Bansod, Baban K.S.; Debnath, Sanjit K.; Thakur, Praveen Kumar; Ghanshyam, C.

    2015-02-15

    Groundwater vulnerability maps are useful for decision making in land use planning and water resource management. This paper reviews the various groundwater vulnerability assessment models developed across the world. Each model has been evaluated in terms of its pros and cons and the environmental conditions of its application. The paper further discusses the validation techniques used for the generated vulnerability maps by various models. Implicit challenges associated with the development of the groundwater vulnerability assessment models have also been identified with scientific considerations to the parameter relations and their selections. - Highlights: • Various index-based groundwater vulnerability assessment models have been discussed. • A comparative analysis of the models and its applicability in different hydrogeological settings has been discussed. • Research problems of underlying vulnerability assessment models are also reported in this review paper.

  5. Using the Many-Facet Rasch Model to Evaluate Standard-Setting Judgments: Setting Performance Standards for Advanced Placement® Examinations

    ERIC Educational Resources Information Center

    Kaliski, Pamela; Wind, Stefanie A.; Engelhard, George, Jr.; Morgan, Deanna; Plake, Barbara; Reshetar, Rosemary

    2012-01-01

    The Many-Facet Rasch (MFR) Model is traditionally used to evaluate the quality of ratings on constructed response assessments; however, it can also be used to evaluate the quality of judgments from panel-based standard setting procedures. The current study illustrates the use of the MFR Model by examining the quality of ratings obtained from a…

  6. Validation of the U.S. NRC coupled code system TRITON/TRACE/PARCS with the special power excursion reactor test III (SPERT III)

    SciTech Connect

    Wang, R. C.; Xu, Y.; Downar, T.; Hudson, N.

    2012-07-01

    The Special Power Excursion Reactor Test III (SPERT III) was a series of reactivity insertion experiments conducted in the 1950's. This paper describes the validation of the U.S. NRC Coupled Code system TRITON/PARCS/TRACE to simulate reactivity insertion accidents (RIA) by using several of the SPERT III tests. The work here used the SPERT III E-core configuration tests in which the RIA was initiated by ejecting a control rod. The resulting super-prompt reactivity excursion and negative reactivity feedback produced the familiar bell shaped power increase and decrease. The energy deposition during such a power peak has important safety consequences and provides validation basis for core coupled multi-physics codes. The transients of five separate tests are used to benchmark the PARCS/TRACE coupled code. The models were thoroughly validated using the original experiment documentation. (authors)

  7. Coupled level set segmentation using a point-based statistical shape model relying on correspondence probabilities

    NASA Astrophysics Data System (ADS)

    Hufnagel, Heike; Ehrhardt, Jan; Pennec, Xavier; Schmidt-Richberg, Alexander; Handels, Heinz

    2010-03-01

    In this article, we propose a unified statistical framework for image segmentation with shape prior information. The approach combines an explicitely parameterized point-based probabilistic statistical shape model (SSM) with a segmentation contour which is implicitly represented by the zero level set of a higher dimensional surface. These two aspects are unified in a Maximum a Posteriori (MAP) estimation where the level set is evolved to converge towards the boundary of the organ to be segmented based on the image information while taking into account the prior given by the SSM information. The optimization of the energy functional obtained by the MAP formulation leads to an alternate update of the level set and an update of the fitting of the SSM. We then adapt the probabilistic SSM for multi-shape modeling and extend the approach to multiple-structure segmentation by introducing a level set function for each structure. During segmentation, the evolution of the different level set functions is coupled by the multi-shape SSM. First experimental evaluations indicate that our method is well suited for the segmentation of topologically complex, non spheric and multiple-structure shapes. We demonstrate the effectiveness of the method by experiments on kidney segmentation as well as on hip joint segmentation in CT images.

  8. Exhaustively characterizing feasible logic models of a signaling network using Answer Set Programming

    PubMed Central

    Guziolowski, Carito; Videla, Santiago; Eduati, Federica; Thiele, Sven; Cokelaer, Thomas; Siegel, Anne; Saez-Rodriguez, Julio

    2013-01-01

    Motivation: Logic modeling is a useful tool to study signal transduction across multiple pathways. Logic models can be generated by training a network containing the prior knowledge to phospho-proteomics data. The training can be performed using stochastic optimization procedures, but these are unable to guarantee a global optima or to report the complete family of feasible models. This, however, is essential to provide precise insight in the mechanisms underlaying signal transduction and generate reliable predictions. Results: We propose the use of Answer Set Programming to explore exhaustively the space of feasible logic models. Toward this end, we have developed caspo, an open-source Python package that provides a powerful platform to learn and characterize logic models by leveraging the rich modeling language and solving technologies of Answer Set Programming. We illustrate the usefulness of caspo by revisiting a model of pro-growth and inflammatory pathways in liver cells. We show that, if experimental error is taken into account, there are thousands (11 700) of models compatible with the data. Despite the large number, we can extract structural features from the models, such as links that are always (or never) present or modules that appear in a mutual exclusive fashion. To further characterize this family of models, we investigate the input–output behavior of the models. We find 91 behaviors across the 11 700 models and we suggest new experiments to discriminate among them. Our results underscore the importance of characterizing in a global and exhaustive manner the family of feasible models, with important implications for experimental design. Availability: caspo is freely available for download (license GPLv3) and as a web service at http://caspo.genouest.org/. Supplementary information: Supplementary materials are available at Bioinformatics online. Contact: santiago.videla@irisa.fr PMID:23853063

  9. Many parameter sets in a multicompartment model oscillator are robust to temperature perturbations.

    PubMed

    Caplan, Jonathan S; Williams, Alex H; Marder, Eve

    2014-04-01

    Neurons in cold-blooded animals remarkably maintain their function over a wide range of temperatures, even though the rates of many cellular processes increase twofold, threefold, or many-fold for each 10°C increase in temperature. Moreover, the kinetics of ion channels, maximal conductances, and Ca(2+) buffering each have independent temperature sensitivities, suggesting that the balance of biological parameters can be disturbed by even modest temperature changes. In stomatogastric ganglia of the crab Cancer borealis, the duty cycle of the bursting pacemaker kernel is highly robust between 7 and 23°C (Rinberg et al., 2013). We examined how this might be achieved in a detailed conductance-based model in which exponential temperature sensitivities were given by Q10 parameters. We assessed the temperature robustness of this model across 125,000 random sets of Q10 parameters. To examine how robustness might be achieved across a variable population of animals, we repeated this analysis across six sets of maximal conductance parameters that produced similar activity at 11°C. Many permissible combinations of maximal conductance and Q10 parameters were found over broad regions of parameter space and relatively few correlations among Q10s were observed across successful parameter sets. A significant portion of Q10 sets worked for at least 3 of the 6 maximal conductance sets (∼11.1%). Nonetheless, no Q10 set produced robust function across all six maximal conductance sets, suggesting that maximal conductance parameters critically contribute to temperature robustness. Overall, these results provide insight into principles of temperature robustness in neuronal oscillators. PMID:24695714

  10. Many Parameter Sets in a Multicompartment Model Oscillator Are Robust to Temperature Perturbations

    PubMed Central

    Caplan, Jonathan S.; Williams, Alex H.

    2014-01-01

    Neurons in cold-blooded animals remarkably maintain their function over a wide range of temperatures, even though the rates of many cellular processes increase twofold, threefold, or many-fold for each 10°C increase in temperature. Moreover, the kinetics of ion channels, maximal conductances, and Ca2+ buffering each have independent temperature sensitivities, suggesting that the balance of biological parameters can be disturbed by even modest temperature changes. In stomatogastric ganglia of the crab Cancer borealis, the duty cycle of the bursting pacemaker kernel is highly robust between 7 and 23°C (Rinberg et al., 2013). We examined how this might be achieved in a detailed conductance-based model in which exponential temperature sensitivities were given by Q10 parameters. We assessed the temperature robustness of this model across 125,000 random sets of Q10 parameters. To examine how robustness might be achieved across a variable population of animals, we repeated this analysis across six sets of maximal conductance parameters that produced similar activity at 11°C. Many permissible combinations of maximal conductance and Q10 parameters were found over broad regions of parameter space and relatively few correlations among Q10s were observed across successful parameter sets. A significant portion of Q10 sets worked for at least 3 of the 6 maximal conductance sets (∼11.1%). Nonetheless, no Q10 set produced robust function across all six maximal conductance sets, suggesting that maximal conductance parameters critically contribute to temperature robustness. Overall, these results provide insight into principles of temperature robustness in neuronal oscillators. PMID:24695714