ERIC Educational Resources Information Center
Cepeda-Cuervo, Edilberto; Núñez-Antón, Vicente
2013-01-01
In this article, a proposed Bayesian extension of the generalized beta spatial regression models is applied to the analysis of the quality of education in Colombia. We briefly revise the beta distribution and describe the joint modeling approach for the mean and dispersion parameters in the spatial regression models' setting. Finally, we…
ERIC Educational Resources Information Center
Campos, Jose Alejandro Gonzalez; Moraga, Paulina Saavedra; Del Pozo, Manuel Freire
2013-01-01
This paper introduces the generalized beta (GB) model as a new modeling tool in the educational assessment area and evaluation analysis, specifically. Unlike normal model, GB model allows us to capture some real characteristics of data and it is an important tool for understanding the phenomenon of learning. This paper develops a contrast with the…
Lasram, Frida Ben Rais; Hattab, Tarek; Halouani, Ghassen; Romdhane, Mohamed Salah; Le Loc'h, François
2015-01-01
Spatial patterns of beta diversity are a major focus of ecology. They can be especially valuable in conservation planning. In this study, we used a generalized dissimilarity modeling approach to analyze and predict the spatial patterns of beta diversity for commercially exploited, demersal marine species assemblages along the Tunisian coasts. For this study, we used a presence/absence dataset which included information on 174 species (invertebrates and fishes) and 9 environmental variables. We first performed the modeling analyses and assessed beta diversity using the turnover component of the Jaccard’s dissimilarity index. We then performed nonmetric multidimensional scaling to map predicted beta diversity. To delineate the biogeographical regions, we used fuzzy cluster analysis. Finally, we also identified a set of indicator species which characterized the species assemblages in each identified biogeographical region. The predicted beta diversity map revealed two patterns: an inshore-offshore gradient and a south-north latitudinal gradient. Three biogeographical regions were identified and 14 indicator species. These results constitute a first contribution of the bioregionalisation of the Tunisian waters and highlight the issues associated with current fisheries management zones and conservation strategies. Results could be useful to follow an Ecosystem Based Management approach by proposing an objective spatial partitioning of the Tunisian waters. This partitioning could be used to prioritize the adjustment of the actual fisheries management entities, identify current data gaps, inform future scientific surveys and improve current MPA network. PMID:26147371
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We found that the usual "DD+D-term" construction should be amended by an extra term, xiE^1_+ (x,xi) built from the alpha/Beta moment of the DD e(Beta,alpha) that generates GPD E(x,xi). Unlike the D-term, this function has support in the whole -1< x<1 region, and in general does not vanish at the border points |x|=xi.
Trials of the beta model for complex inheritance.
Collins, A; MacLean, C J; Morton, N E
1996-01-01
Theoretical advantages of nonparametric logarithm of odds to map polygenic diseases are supported by tests of the beta model that depends on a single logistic parameter and is the only model under which paternal and maternal transmissions to sibs of specified phenotypes are independent. Although it does not precisely describe recurrence risks in monozygous twins, the beta model has greater power to detect family resemblance or linkage than the more general delta model which describes the probability of 0, 1, or 2 alleles identical by descent (ibd) with two parameters. Available data on ibd in sibs are consistent with the beta model, but not with the equally parsimonious but less powerful gamma model that assumes a fixed probability of 1/2 for 1 allele ibd. Additivity of loci on the liability scale is not disproven. A simple equivalence extends the beta model to multipoint analysis. PMID:8799174
Beta Regression Finite Mixture Models of Polarization and Priming
ERIC Educational Resources Information Center
Smithson, Michael; Merkle, Edgar C.; Verkuilen, Jay
2011-01-01
This paper describes the application of finite-mixture general linear models based on the beta distribution to modeling response styles, polarization, anchoring, and priming effects in probability judgments. These models, in turn, enhance our capacity for explicitly testing models and theories regarding the aforementioned phenomena. The mixture…
Kenakin, T. P.
1980-01-01
1. The sensitization of guinea-pig atria and trachea to noradrenaline, isoprenaline, and salbutamol, produced by an inhibitor of neuronal (cocaine) and extraneuronal (metanephrine) uptake, was studied quantitatively. The data were compared to a theoretical model. 2. Cocaine produced near maximal sensitization to noradrenaline in guinea-pig atria (5 fold) at concentrations which produced only partial sensitization in guinea-pig trachea (4.7 fold sensitization of a maximum 11 fold). These results agreed with the model which predicts that there is a direct relationship between the amount of uptake inhibitor required to produce full sensitization and the magnitude of maximal sensitization demonstrable in the tissue. This makes extrapolation of uptake inhibition concentrations from tissue to tissue a potentially erroneous practice. 3. In normal trachea, salbutamol is 20 times more potent than noradrenaline but this difference is abolished (to 0.9 times) by cocaine (100 microM). This reduction of potency-ratio is due to the selective cocaine-induced sensitization of trachea to noradrenaline and raises a serious objection to the classification of salbutamol as a beta 2 selective agonist. 4. Metanephrine produced very little sensitization of trachea to isoprenaline. Experiments with salbutamol showed metanephrine to be a simple competitive antagonist of beta-adrenoceptors (pKb = 4.3) and that this receptor antagonism masked sensitization to isoprenaline. 5. A theoretical model indicates that an inhibitor of agonist uptake requires a remarkable degree of selectivity for the uptake mechanism (i.e. Kb for receptors 10(4) x KI for uptake sites) to demonstrate tissue sensitization to the agonist. This analysis and the data with metanephrine indicate that a sinistral shift of the concentration-response curve is a poor indicator of the importance of uptake mechanisms in an isolated tissue. 6. An alternate method to determine the importance of agonist-uptake effects on
Generalized Latent Trait Models.
ERIC Educational Resources Information Center
Moustaki, Irini; Knott, Martin
2000-01-01
Discusses a general model framework within which manifest variables with different distributions in the exponential family can be analyzed with a latent trait model. Presents a unified maximum likelihood method for estimating the parameters of the generalized latent trait model and discusses the scoring of individuals on the latent dimensions.…
Decoding {beta}-decay systematics: A global statistical model for {beta}{sup -} half-lives
Costiris, N. J.; Mavrommatis, E.; Gernoth, K. A.; Clark, J. W.
2009-10-15
Statistical modeling of nuclear data provides a novel approach to nuclear systematics complementary to established theoretical and phenomenological approaches based on quantum theory. Continuing previous studies in which global statistical modeling is pursued within the general framework of machine learning theory, we implement advances in training algorithms designed to improve generalization, in application to the problem of reproducing and predicting the half-lives of nuclear ground states that decay 100% by the {beta}{sup -} mode. More specifically, fully connected, multilayer feed-forward artificial neural network models are developed using the Levenberg-Marquardt optimization algorithm together with Bayesian regularization and cross-validation. The predictive performance of models emerging from extensive computer experiments is compared with that of traditional microscopic and phenomenological models as well as with the performance of other learning systems, including earlier neural network models as well as the support vector machines recently applied to the same problem. In discussing the results, emphasis is placed on predictions for nuclei that are far from the stability line, and especially those involved in r-process nucleosynthesis. It is found that the new statistical models can match or even surpass the predictive performance of conventional models for {beta}-decay systematics and accordingly should provide a valuable additional tool for exploring the expanding nuclear landscape.
Continuous multifractal models with zero values: a continuous \\beta -multifractal model
NASA Astrophysics Data System (ADS)
Schmitt, F. G.
2014-02-01
In this paper we propose for the first time a multiplicative continuous model for generating multifractal fields with zero values, as a continuous generalization of the intermittent lognormal \\beta -model proposed by Over and Gupta (1996). It is built using infinitely multiplicative random variables, the multiplicative analog to infinitely divisible distributions for addition. The model also needs stochastic multiplicative measures and multiplicative stochastic integrals. It possesses as a special case a continuous generalization of the classical discrete \\beta -model. Applications are numerous in many fields of applied science, including small-scale rainfall and soil science.
Generalized species sampling priors with latent Beta reinforcements
Airoldi, Edoardo M.; Costa, Thiago; Bassetti, Federico; Leisen, Fabrizio; Guindani, Michele
2014-01-01
Many popular Bayesian nonparametric priors can be characterized in terms of exchangeable species sampling sequences. However, in some applications, exchangeability may not be appropriate. We introduce a novel and probabilistically coherent family of non-exchangeable species sampling sequences characterized by a tractable predictive probability function with weights driven by a sequence of independent Beta random variables. We compare their theoretical clustering properties with those of the Dirichlet Process and the two parameters Poisson-Dirichlet process. The proposed construction provides a complete characterization of the joint process, differently from existing work. We then propose the use of such process as prior distribution in a hierarchical Bayes modeling framework, and we describe a Markov Chain Monte Carlo sampler for posterior inference. We evaluate the performance of the prior and the robustness of the resulting inference in a simulation study, providing a comparison with popular Dirichlet Processes mixtures and Hidden Markov Models. Finally, we develop an application to the detection of chromosomal aberrations in breast cancer by leveraging array CGH data. PMID:25870462
Generalized gamma frailty model.
Balakrishnan, N; Peng, Yingwei
2006-08-30
In this article, we present a frailty model using the generalized gamma distribution as the frailty distribution. It is a power generalization of the popular gamma frailty model. It also includes other frailty models such as the lognormal and Weibull frailty models as special cases. The flexibility of this frailty distribution makes it possible to detect a complex frailty distribution structure which may otherwise be missed. Due to the intractable integrals in the likelihood function and its derivatives, we propose to approximate the integrals either by Monte Carlo simulation or by a quadrature method and then determine the maximum likelihood estimates of the parameters in the model. We explore the properties of the proposed frailty model and the computation method through a simulation study. The study shows that the proposed model can potentially reduce errors in the estimation, and that it provides a viable alternative for correlated data. The merits of proposed model are demonstrated in analysing the effects of sublingual nitroglycerin and oral isosorbide dinitrate on angina pectoris of coronary heart disease patients based on the data set in Danahy et al. (sustained hemodynamic and antianginal effect of high dose oral isosorbide dinitrate. Circulation 1977; 55:381-387). PMID:16220516
Functional Generalized Additive Models.
McLean, Mathew W; Hooker, Giles; Staicu, Ana-Maria; Scheipl, Fabian; Ruppert, David
2014-01-01
We introduce the functional generalized additive model (FGAM), a novel regression model for association studies between a scalar response and a functional predictor. We model the link-transformed mean response as the integral with respect to t of F{X(t), t} where F(·,·) is an unknown regression function and X(t) is a functional covariate. Rather than having an additive model in a finite number of principal components as in Müller and Yao (2008), our model incorporates the functional predictor directly and thus our model can be viewed as the natural functional extension of generalized additive models. We estimate F(·,·) using tensor-product B-splines with roughness penalties. A pointwise quantile transformation of the functional predictor is also considered to ensure each tensor-product B-spline has observed data on its support. The methods are evaluated using simulated data and their predictive performance is compared with other competing scalar-on-function regression alternatives. We illustrate the usefulness of our approach through an application to brain tractography, where X(t) is a signal from diffusion tensor imaging at position, t, along a tract in the brain. In one example, the response is disease-status (case or control) and in a second example, it is the score on a cognitive test. R code for performing the simulations and fitting the FGAM can be found in supplemental materials available online. PMID:24729671
General composite Higgs models
NASA Astrophysics Data System (ADS)
Marzocca, David; Serone, Marco; Shu, Jing
2012-08-01
We construct a general class of pseudo-Goldstone composite Higgs models, within the minimal SO(5)/SO(4) coset structure, that are not necessarily of moose-type. We characterize the main properties these models should have in order to give rise to a Higgs mass around 125 GeV. We assume the existence of relatively light and weakly coupled spin 1 and 1/2 resonances. In absence of a symmetry principle, we introduce the Minimal Higgs Potential (MHP) hypothesis: the Higgs potential is assumed to be one-loop dominated by the SM fields and the above resonances, with a contribution that is made calculable by imposing suitable generalizations of the first and second Weinberg sum rules. We show that a 125 GeV Higgs requires light, often sub-TeV, fermion resonances. Their presence can also be important for the models to successfully pass the electroweak precision tests. Interestingly enough, the latter can also be passed by models with a heavy Higgs around 320 GeV. The composite Higgs models of the moose-type considered in the literature can be seen as particular limits of our class of models.
New model for nucleon generalized parton distributions
Radyushkin, Anatoly V.
2014-01-01
We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term, {xi} E{sub +}{sup 1} (x,{xi}) which has the DD structure {alpha}/{beta} e({beta},{alpha}, with e({beta},{alpha}) being the DD that generates GPD E(x,{xi}). We found that this function, unlike the D-term, has support in the whole -1 <= x <= 1 region. Furthermore, it does not vanish at the border points |x|={xi}.
Ocean General Circulation Models
Yoon, Jin-Ho; Ma, Po-Lun
2012-09-30
1. Definition of Subject The purpose of this text is to provide an introduction to aspects of oceanic general circulation models (OGCMs), an important component of Climate System or Earth System Model (ESM). The role of the ocean in ESMs is described in Chapter XX (EDITOR: PLEASE FIND THE COUPLED CLIMATE or EARTH SYSTEM MODELING CHAPTERS). The emerging need for understanding the Earth’s climate system and especially projecting its future evolution has encouraged scientists to explore the dynamical, physical, and biogeochemical processes in the ocean. Understanding the role of these processes in the climate system is an interesting and challenging scientific subject. For example, a research question how much extra heat or CO2 generated by anthropogenic activities can be stored in the deep ocean is not only scientifically interesting but also important in projecting future climate of the earth. Thus, OGCMs have been developed and applied to investigate the various oceanic processes and their role in the climate system.
Generalized Multilevel Structural Equation Modeling
ERIC Educational Resources Information Center
Rabe-Hesketh, Sophia; Skrondal, Anders; Pickles, Andrew
2004-01-01
A unifying framework for generalized multilevel structural equation modeling is introduced. The models in the framework, called generalized linear latent and mixed models (GLLAMM), combine features of generalized linear mixed models (GLMM) and structural equation models (SEM) and consist of a response model and a structural model for the latent…
A Beta-splitting model for evolutionary trees.
Sainudiin, Raazesh; Véber, Amandine
2016-05-01
In this article, we construct a generalization of the Blum-François Beta-splitting model for evolutionary trees, which was itself inspired by Aldous' Beta-splitting model on cladograms. The novelty of our approach allows for asymmetric shares of diversification rates (or diversification 'potential') between two sister species in an evolutionarily interpretable manner, as well as the addition of extinction to the model in a natural way. We describe the incremental evolutionary construction of a tree with n leaves by splitting or freezing extant lineages through the generating, organizing and deleting processes. We then give the probability of any (binary rooted) tree under this model with no extinction, at several resolutions: ranked planar trees giving asymmetric roles to the first and second offspring species of a given species and keeping track of the order of the speciation events occurring during the creation of the tree, unranked planar trees, ranked non-planar trees and finally (unranked non-planar) trees. We also describe a continuous-time equivalent of the generating, organizing and deleting processes where tree topology and branch lengths are jointly modelled and provide code in SageMath/Python for these algorithms. PMID:27293780
A Beta-splitting model for evolutionary trees
Sainudiin, Raazesh
2016-01-01
In this article, we construct a generalization of the Blum–François Beta-splitting model for evolutionary trees, which was itself inspired by Aldous' Beta-splitting model on cladograms. The novelty of our approach allows for asymmetric shares of diversification rates (or diversification ‘potential’) between two sister species in an evolutionarily interpretable manner, as well as the addition of extinction to the model in a natural way. We describe the incremental evolutionary construction of a tree with n leaves by splitting or freezing extant lineages through the generating, organizing and deleting processes. We then give the probability of any (binary rooted) tree under this model with no extinction, at several resolutions: ranked planar trees giving asymmetric roles to the first and second offspring species of a given species and keeping track of the order of the speciation events occurring during the creation of the tree, unranked planar trees, ranked non-planar trees and finally (unranked non-planar) trees. We also describe a continuous-time equivalent of the generating, organizing and deleting processes where tree topology and branch lengths are jointly modelled and provide code in SageMath/Python for these algorithms. PMID:27293780
The Generalized DINA Model Framework
ERIC Educational Resources Information Center
de la Torre, Jimmy
2011-01-01
The G-DINA ("generalized deterministic inputs, noisy and gate") model is a generalization of the DINA model with more relaxed assumptions. In its saturated form, the G-DINA model is equivalent to other general models for cognitive diagnosis based on alternative link functions. When appropriate constraints are applied, several commonly used…
Augmented Beta rectangular regression models: A Bayesian perspective.
Wang, Jue; Luo, Sheng
2016-01-01
Mixed effects Beta regression models based on Beta distributions have been widely used to analyze longitudinal percentage or proportional data ranging between zero and one. However, Beta distributions are not flexible to extreme outliers or excessive events around tail areas, and they do not account for the presence of the boundary values zeros and ones because these values are not in the support of the Beta distributions. To address these issues, we propose a mixed effects model using Beta rectangular distribution and augment it with the probabilities of zero and one. We conduct extensive simulation studies to assess the performance of mixed effects models based on both the Beta and Beta rectangular distributions under various scenarios. The simulation studies suggest that the regression models based on Beta rectangular distributions improve the accuracy of parameter estimates in the presence of outliers and heavy tails. The proposed models are applied to the motivating Neuroprotection Exploratory Trials in Parkinson's Disease (PD) Long-term Study-1 (LS-1 study, n = 1741), developed by The National Institute of Neurological Disorders and Stroke Exploratory Trials in Parkinson's Disease (NINDS NET-PD) network. PMID:26289406
NASA Astrophysics Data System (ADS)
Alvarez-Martinez, R.; Martinez-Mekler, G.; Cocho, G.
2011-01-01
The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes.
General Graded Response Model.
ERIC Educational Resources Information Center
Samejima, Fumiko
This paper describes the graded response model. The graded response model represents a family of mathematical models that deal with ordered polytomous categories, such as: (1) letter grading; (2) an attitude survey with "strongly disagree, disagree, agree, and strongly agree" choices; (3) partial credit given in accord with an individual's degree…
The beta distribution: A statistical model for world cloud cover
NASA Technical Reports Server (NTRS)
Falls, L. W.
1973-01-01
Much work has been performed in developing empirical global cloud cover models. This investigation was made to determine an underlying theoretical statistical distribution to represent worldwide cloud cover. The beta distribution with probability density function is given to represent the variability of this random variable. It is shown that the beta distribution possesses the versatile statistical characteristics necessary to assume the wide variety of shapes exhibited by cloud cover. A total of 160 representative empirical cloud cover distributions were investigated and the conclusion was reached that this study provides sufficient statical evidence to accept the beta probability distribution as the underlying model for world cloud cover.
NASA Technical Reports Server (NTRS)
Williams, R. M.; Ryan, M. A.; LeDuc, H.; Cortez, R. H.; Saipetch, C.; Shields, V.; Manatt, K.; Homer, M. L.
1998-01-01
This paper presents a model of the exchange current developed for porous molybdenum electrodes on sodium beta-alumina ceramics in low pressure sodium vapor, but which has general applicability to gas/porous metal electrodes on solid electrolytes.
Numerical models for high beta magnetohydrodynamic flow
Brackbill, J.U.
1987-01-01
The fundamentals of numerical magnetohydrodynamics for highly conducting, high-beta plasmas are outlined. The discussions emphasize the physical properties of the flow, and how elementary concepts in numerical analysis can be applied to the construction of finite difference approximations that capture these features. The linear and nonlinear stability of explicit and implicit differencing in time is examined, the origin and effect of numerical diffusion in the calculation of convective transport is described, and a technique for maintaining solenoidality in the magnetic field is developed. Many of the points are illustrated by numerical examples. The techniques described are applicable to the time-dependent, high-beta flows normally encountered in magnetically confined plasmas, plasma switches, and space and astrophysical plasmas. 40 refs.
Xu, R; Thomas, E A; Gazina, E V; Richards, K L; Quick, M; Wallace, R H; Harkin, L A; Heron, S E; Berkovic, S F; Scheffer, I E; Mulley, J C; Petrou, S
2007-08-10
Two novel mutations (R85C and R85H) on the extracellular immunoglobulin-like domain of the sodium channel beta1 subunit have been identified in individuals from two families with generalized epilepsy with febrile seizures plus (GEFS+). The functional consequences of these two mutations were determined by co-expression of the human brain NaV1.2 alpha subunit with wild type or mutant beta1 subunits in human embryonic kidney (HEK)-293T cells. Patch clamp studies confirmed the regulatory role of beta1 in that relative to NaV1.2 alone the NaV1.2+beta1 currents had right-shifted voltage dependence of activation, fast and slow inactivation and reduced use dependence. In addition, the NaV1.2+beta1 current entered fast inactivation slightly faster than NaV1.2 channels alone. The beta1(R85C) subunit appears to be a complete loss of function in that none of the modulating effects of the wild type beta1 were observed when it was co-expressed with NaV1.2. Interestingly, the beta1(R85H) subunit also failed to modulate fast kinetics, however, it shifted the voltage dependence of steady state slow inactivation in the same way as the wild type beta1 subunit. Immunohistochemical studies revealed cell surface expression of the wild type beta1 subunit and undetectable levels of cell surface expression for both mutants. The functional studies suggest association of the beta1(R85H) subunit with the alpha subunit where its influence is limited to modulating steady state slow inactivation. In summary, the mutant beta1 subunits essentially fail to modulate alpha subunits which could increase neuronal excitability and underlie GEFS+ pathogenesis. PMID:17629415
The general NFP hospital model.
Al-Amin, Mona
2012-01-01
Throughout the past 30 years, there has been a lot of controversy surrounding the proliferation of new forms of health care delivery organizations that challenge and compete with general NFP community hospitals. Traditionally, the health care system in the United States has been dominated by general NFP (NFP) voluntary hospitals. With the number of for-profit general hospitals, physician-owned specialty hospitals, and ambulatory surgical centers increasing, a question arises: “Why is the general NFP community hospital the dominant model?” In order to address this question, this paper reexamines the history of the hospital industry. By understanding how the “general NFP hospital” model emerged and dominated, we attempt to explain the current dominance of general NFP hospitals in the ever changing hospital industry in the United States. PMID:22324062
Misleading Betas: An Educational Example
ERIC Educational Resources Information Center
Chong, James; Halcoussis, Dennis; Phillips, G. Michael
2012-01-01
The dual-beta model is a generalization of the CAPM model. In the dual-beta model, separate beta estimates are provided for up-market and down-market days. This paper uses the historical "Anscombe quartet" results which illustrated how very different datasets can produce the same regression coefficients to motivate a discussion of the…
Populational Growth Models Proportional to Beta Densities with Allee Effect
NASA Astrophysics Data System (ADS)
Aleixo, Sandra M.; Rocha, J. Leonel; Pestana, Dinis D.
2009-05-01
We consider populations growth models with Allee effect, proportional to beta densities with shape parameters p and 2, where the dynamical complexity is related with the Malthusian parameter r. For p>2, these models exhibit a population dynamics with natural Allee effect. However, in the case of 1
models do not include this effect. In order to inforce it, we present some alternative models and investigate their dynamics, presenting some important results.
General Thermodynamic Heat Engine Models
NASA Astrophysics Data System (ADS)
Nuwayhid, R. Y.; Moukalled, F.; Denton, J. C.
2002-11-01
Heat engine models, starting from the most fundamental Carnot case, are analyzed. Two major methods of viewing the power plant as a thermodynamic heat engine are presented and studied. Realistic models are sought by introducing internal heat transport or bypass heat leak treatments. Simple treatments are presented to convey the general modeling ideas without unnecessary complications. Some new results are obtained and certain old results are commented on.
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We find that the usual "DD+D-term'' construction should be amended by an extra term, generated by GPD E(x,\\xi). Unlike the $D$-term, this function has support in the whole -1 < x< 1 region, and in general does not vanish at the border points|x|=\\xi.
Fluxon modeling of low-beta plasmas
NASA Astrophysics Data System (ADS)
Deforest, C. E.; Kankelborg, C. C.
2007-02-01
We have developed a new, quasi-Lagrangian approach for numerical modeling of magnetohydrodynamics in low to moderate β plasmas such as the solar corona. We introduce the concept of a “fluxon”, a discretized field line. Fluxon models represent the magnetic field as a skeleton of such discrete field lines, and interpolate field values from the geometry of the skeleton where needed, reversing the usual direction of the field line transform. The fluxon skeleton forms the grid for a collection of 1-D Eulerian models of plasma along individual flux tubes. Fluxon models have no numerical resistivity, because they preserve topology explicitly. Our prototype code, FLUX, is currently able to find 3-D nonlinear force-free field solutions with a specified field topology, and work is ongoing to validate and extend the code to full magnetohydrodynamics. FLUX has significant scaling advantages over conventional models: for “magnetic carpet” models, with photospheric line-tied boundary conditions, FLUX simulations scale in complexity like a conventional 2-D grid although the full 3-D field is represented. The code is free software and is available online. In this current paper we introduce fluxons and our prototype code, and describe the course of future work with the code.
Minimal modeling of the extratropical general circulation
NASA Technical Reports Server (NTRS)
O'Brien, Enda; Branscome, Lee E.
1989-01-01
The ability of low-order, two-layer models to reproduce basic features of the mid-latitude general circulation is investigated. Changes in model behavior with increased spectral resolution are examined in detail. Qualitatively correct time-mean heat and momentum balances are achieved in a beta-plane channel model which includes the first and third meridional modes. This minimal resolution also reproduces qualitatively realistic surface and upper-level winds and mean meridional circulations. Higher meridional resolution does not result in substantial changes in the latitudinal structure of the circulation. A qualitatively correct kinetic energy spectrum is produced when the resolution is high enough to include several linearly stable modes. A model with three zonal waves and the first three meridional modes has a reasonable energy spectrum and energy conversion cycle, while also satisfying heat and momentum budget requirements. This truncation reproduces the basic mechanisms and zonal circulation features that are obtained at higher resolution. The model performance improves gradually with higher resolution and is smoothly dependent on changes in external parameters.
Measuring and Modeling Xenon Uptake in Plastic Beta-Cells
NASA Astrophysics Data System (ADS)
Suarez, R.; Hayes, J. C.; Harper, W. W.; Humble, P.; Ripplinger, M. D.; Stephenson, D. E.; Williams, R. M.
2013-12-01
The precision of the stable xenon volume measurement in atmospheric monitoring radio-xenon systems is a critical parameter used to determine the activity concentration of a radio-xenon sample. Typically these types of systems use a plastic scintillating beta-cell as part of a beta-gamma detection scheme to measure the radioactivity present in the gas sample. Challenges arise when performing the stable xenon calculation during or after radioactive counting of the sample due to xenon uptake into the plastic beta-cells. Plastic beta cells can adsorb as much as 5% of the sample during counting. If quantification is performed after counting, the uptake of xenon into the plastic results in an underestimation of the xenon volume measurement. This behavior also causes what is typically known as 'memory effect' in the cell. Experiments were conducted using a small volume low pressure range thermal conductivity sensor to quantify the amount of xenon uptake into the cell over a given period of time. Understanding the xenon uptake in the cell provides a better estimate of the stable volume which improves the overall measurement capability of the system. The results from these experiments along with modeling will be presented.
Modeling of mechanical properties in alpha/beta-titanium alloys
NASA Astrophysics Data System (ADS)
Kar, Sujoy Kumar
2005-11-01
The accelerated insertion of titanium alloys in component application requires the development of predictive capabilities for various aspects of their behavior, for example, phase stability, microstructural evolution and property-microstructure relationships over a wide range of length and time scales. In this presentation some navel aspects of property-microstructure relationships and microstructural evolution in alpha/beta Ti alloys will be discussed. Neural Network (NN) Models based on a Bayesian framework have been developed to predict the mechanical properties of alpha/beta Ti alloys. The development of such rules-based model requires the population of extensive databases, which in the present case are microstructurally-based. The steps involved in database development include producing controlled variations of the microstructure using novel approaches to heat-treatments, the use of standardized stereology protocols to characterize and quantify microstructural features rapidly, and mechanical testing of the heat-treated specimens. These databases have been used to train and test NN Models for prediction of mechanical properties. In addition, these models have been used to identify the influence of individual microstructural features on the mechanical properties, consequently guiding the efforts towards development of more robust mechanistically based models. In order to understand the property-microstructure relationships, a detailed understanding of microstructure evolution is imperative. The crystallography of the microstructure developing as a result of the solid-state beta → beta+alpha transformation has been studied in detail by employing Scanning Electron Microscopy (SEM), Orientation Imaging Microscopy (in a high resolution SEM), site-specific TEM sample preparation using focused ion beam, and TEM based techniques. The influence of variant selection on the evolution of microstructure will be specifically addressed.
Smart Grid Interoperability Maturity Model Beta Version
Widergren, Steven E.; Drummond, R.; Giroti, Tony; Houseman, Doug; Knight, Mark; Levinson, Alex; longcore, Wayne; Lowe, Randy; Mater, J.; Oliver, Terry V.; Slack, Phil; Tolk, Andreas; Montgomery, Austin
2011-12-02
The GridWise Architecture Council was formed by the U.S. Department of Energy to promote and enable interoperability among the many entities that interact with the electric power system. This balanced team of industry representatives proposes principles for the development of interoperability concepts and standards. The Council provides industry guidance and tools that make it an available resource for smart grid implementations. In the spirit of advancing interoperability of an ecosystem of smart grid devices and systems, this document presents a model for evaluating the maturity of the artifacts and processes that specify the agreement of parties to collaborate across an information exchange interface. You are expected to have a solid understanding of large, complex system integration concepts and experience in dealing with software component interoperation. Those without this technical background should read the Executive Summary for a description of the purpose and contents of the document. Other documents, such as checklists, guides, and whitepapers, exist for targeted purposes and audiences. Please see the www.gridwiseac.org website for more products of the Council that may be of interest to you.
Technology Transfer Automated Retrieval System (TEKTRAN)
This chapter covers the use of wild beets in sugar beet improvement, including the basic botany of the species, its distribution; geographical locations of genetic diversity; morphology; cytology and karyotype; genome size; taxonomic position; agricultural status (model plant/weeds/invasive species/...
Virasoro irregular conformal block and beta deformed random matrix model
NASA Astrophysics Data System (ADS)
Choi, Sang Kwan; Rim, Chaiho; Zhang, Hong
2015-03-01
Virasoro irregular conformal block is presented as the expectation value of Jack-polynomials of the beta-deformed Penner-type matrix model and is compared with the inner product of Gaiotto states with arbitrary rank. It is confirmed that there are non-trivial modifications of the Gaiotto states due to the normalization of the states. The relation between the two is explicitly checked for rank 2 irregular conformal block.
RNA replication by Q beta replicase: a working model.
Brown, D; Gold, L
1996-01-01
Two classes of RNA ligands that bound to separate, high affinity nucleic acid binding sites on Q beta replicase were previously identified. RNA ligands to the two sites, referred to as site I and site II, were used to investigate the molecular mechanism of RNA replication employed by the four-subunit replicase. Replication inhibition by site I- and site II-specific ligands defined two subsets of replicatable RNAs. When provided with appropriate 3' ends, ligands to either site served as replication templates. UV crosslinking experiments revealed that site I is associated with the S1 subunit, site II with elongation factor Tu, and polymerization with the viral subunit of the holoenzyme. These results provide the framework for a three site model describing template recognition and product strand initiation by Q beta replicase. Images Fig. 2 Fig. 3 PMID:8876174
Sherman, Maxwell A; Lee, Shane; Law, Robert; Haegens, Saskia; Thorn, Catherine A; Hämäläinen, Matti S; Moore, Christopher I; Jones, Stephanie R
2016-08-16
Human neocortical 15-29-Hz beta oscillations are strong predictors of perceptual and motor performance. However, the mechanistic origin of beta in vivo is unknown, hindering understanding of its functional role. Combining human magnetoencephalography (MEG), computational modeling, and laminar recordings in animals, we present a new theory that accounts for the origin of spontaneous neocortical beta. In our MEG data, spontaneous beta activity from somatosensory and frontal cortex emerged as noncontinuous beta events typically lasting <150 ms with a stereotypical waveform. Computational modeling uniquely designed to infer the electrical currents underlying these signals showed that beta events could emerge from the integration of nearly synchronous bursts of excitatory synaptic drive targeting proximal and distal dendrites of pyramidal neurons, where the defining feature of a beta event was a strong distal drive that lasted one beta period (∼50 ms). This beta mechanism rigorously accounted for the beta event profiles; several other mechanisms did not. The spatial location of synaptic drive in the model to supragranular and infragranular layers was critical to the emergence of beta events and led to the prediction that beta events should be associated with a specific laminar current profile. Laminar recordings in somatosensory neocortex from anesthetized mice and awake monkeys supported these predictions, suggesting this beta mechanism is conserved across species and recording modalities. These findings make several predictions about optimal states for perceptual and motor performance and guide causal interventions to modulate beta for optimal function. PMID:27469163
Sherman, Maxwell A.; Lee, Shane; Law, Robert; Haegens, Saskia; Thorn, Catherine A.; Hämäläinen, Matti S.; Moore, Christopher I.; Jones, Stephanie R.
2016-01-01
Human neocortical 15–29-Hz beta oscillations are strong predictors of perceptual and motor performance. However, the mechanistic origin of beta in vivo is unknown, hindering understanding of its functional role. Combining human magnetoencephalography (MEG), computational modeling, and laminar recordings in animals, we present a new theory that accounts for the origin of spontaneous neocortical beta. In our MEG data, spontaneous beta activity from somatosensory and frontal cortex emerged as noncontinuous beta events typically lasting <150 ms with a stereotypical waveform. Computational modeling uniquely designed to infer the electrical currents underlying these signals showed that beta events could emerge from the integration of nearly synchronous bursts of excitatory synaptic drive targeting proximal and distal dendrites of pyramidal neurons, where the defining feature of a beta event was a strong distal drive that lasted one beta period (∼50 ms). This beta mechanism rigorously accounted for the beta event profiles; several other mechanisms did not. The spatial location of synaptic drive in the model to supragranular and infragranular layers was critical to the emergence of beta events and led to the prediction that beta events should be associated with a specific laminar current profile. Laminar recordings in somatosensory neocortex from anesthetized mice and awake monkeys supported these predictions, suggesting this beta mechanism is conserved across species and recording modalities. These findings make several predictions about optimal states for perceptual and motor performance and guide causal interventions to modulate beta for optimal function. PMID:27469163
Earthquake Early Warning Beta Users: Java, Modeling, and Mobile Apps
NASA Astrophysics Data System (ADS)
Strauss, J. A.; Vinci, M.; Steele, W. P.; Allen, R. M.; Hellweg, M.
2014-12-01
Earthquake Early Warning (EEW) is a system that can provide a few to tens of seconds warning prior to ground shaking at a user's location. The goal and purpose of such a system is to reduce, or minimize, the damage, costs, and casualties resulting from an earthquake. A demonstration earthquake early warning system (ShakeAlert) is undergoing testing in the United States by the UC Berkeley Seismological Laboratory, Caltech, ETH Zurich, University of Washington, the USGS, and beta users in California and the Pacific Northwest. The beta users receive earthquake information very rapidly in real-time and are providing feedback on their experiences of performance and potential uses within their organization. Beta user interactions allow the ShakeAlert team to discern: which alert delivery options are most effective, what changes would make the UserDisplay more useful in a pre-disaster situation, and most importantly, what actions users plan to take for various scenarios. Actions could include: personal safety approaches, such as drop cover, and hold on; automated processes and procedures, such as opening elevator or fire stations doors; or situational awareness. Users are beginning to determine which policy and technological changes may need to be enacted, and funding requirements to implement their automated controls. The use of models and mobile apps are beginning to augment the basic Java desktop applet. Modeling allows beta users to test their early warning responses against various scenarios without having to wait for a real event. Mobile apps are also changing the possible response landscape, providing other avenues for people to receive information. All of these combine to improve business continuity and resiliency.
Beta test of models-3 with Community Multiscale Air Quality (CMAQ) model
LeDuc, S.
1997-12-31
The Models-3 framework for advanced air quality modeling, developed by the Environmental Protection Agency, Office of Research and Development (EPA/ORD), was provided to a limited number of beta test sites during the summer of 1997. Tutorial datasets and the Community Multiscale Air Quality (CMAQ) model were also provided. Valuable feedback on framework installation, performance, functionality, intuitiveness, user friendliness resulted from the beta test. This information will be used to guide framework improvements preparatory to public release in June 1998.
Modeling the transmission of beta rays through thin foils in planar geometry.
Stanga, D; De Felice, P; Keightley, J; Capogni, M; Ionescu, E
2016-01-01
This paper is concerned with the modeling of the transmission of beta rays through thin foils in planar geometry based on the plane source concept, using Monte Carlo simulation of electron transport and least squares fitting. Applications of modeling results for calculating the efficiency of large-area beta sources, transmission coefficient of beta rays through thin foils and the beta detection efficiency of large-area detectors used in surface contamination measurements are also presented. PMID:26524407
Generalized model of island biodiversity.
Kessler, David A; Shnerb, Nadav M
2015-04-01
The dynamics of a local community of competing species with weak immigration from a static regional pool is studied. Implementing the generalized competitive Lotka-Volterra model with demographic noise, a rich dynamics with four qualitatively distinct phases is unfolded. When the overall interspecies competition is weak, the island species recapitulate the mainland species. For higher values of the competition parameter, the system still admits an equilibrium community, but now some of the mainland species are absent on the island. Further increase in competition leads to an intermittent "disordered" phase, where the dynamics is controlled by invadable combinations of species and the turnover rate is governed by the migration. Finally, the strong competition phase is glasslike, dominated by uninvadable states and noise-induced transitions. Our model contains, as a special case, the celebrated neutral island theories of Wilson-MacArthur and Hubbell. Moreover, we show that slight deviations from perfect neutrality may lead to each of the phases, as the Hubbell point appears to be quadracritical. PMID:25974525
Generalized model of island biodiversity
NASA Astrophysics Data System (ADS)
Kessler, David A.; Shnerb, Nadav M.
2015-04-01
The dynamics of a local community of competing species with weak immigration from a static regional pool is studied. Implementing the generalized competitive Lotka-Volterra model with demographic noise, a rich dynamics with four qualitatively distinct phases is unfolded. When the overall interspecies competition is weak, the island species recapitulate the mainland species. For higher values of the competition parameter, the system still admits an equilibrium community, but now some of the mainland species are absent on the island. Further increase in competition leads to an intermittent "disordered" phase, where the dynamics is controlled by invadable combinations of species and the turnover rate is governed by the migration. Finally, the strong competition phase is glasslike, dominated by uninvadable states and noise-induced transitions. Our model contains, as a special case, the celebrated neutral island theories of Wilson-MacArthur and Hubbell. Moreover, we show that slight deviations from perfect neutrality may lead to each of the phases, as the Hubbell point appears to be quadracritical.
Protoplanetary Nebula Evolution using the Beta Viscosity Model
NASA Technical Reports Server (NTRS)
Davis, Sanford S.
2003-01-01
The evolutionary dynamics of a protoplanetary disk is an important component of the planet formation process. In particular, the dynamic and thermodynamic field plays a critical role in chemical evolution, the migration of dust particles in the nebula, and the radial transport of meteoritic components. The dynamic evolution is investigated using analytical solutions of the surface density transport equations using a turbulence model based on hydrodynamic generation of turbulence. It captures the major properties of the disk including region of separation between radial inflow and-outflow and the evolution of the central plane temperature. The analytical formulas are compared with available numerical solutions based on the alpha viscosity model. The beta viscosity model, heretofore used for steady-state disks, is shown to be a useful approximation for unsteady problems.
Estimating riparian understory vegetation cover with beta regression and copula models
Eskelson, Bianca N.I.; Madsen, Lisa; Hagar, Joan C.; Temesgen, Hailemariam
2011-01-01
Understory vegetation communities are critical components of forest ecosystems. As a result, the importance of modeling understory vegetation characteristics in forested landscapes has become more apparent. Abundance measures such as shrub cover are bounded between 0 and 1, exhibit heteroscedastic error variance, and are often subject to spatial dependence. These distributional features tend to be ignored when shrub cover data are analyzed. The beta distribution has been used successfully to describe the frequency distribution of vegetation cover. Beta regression models ignoring spatial dependence (BR) and accounting for spatial dependence (BRdep) were used to estimate percent shrub cover as a function of topographic conditions and overstory vegetation structure in riparian zones in western Oregon. The BR models showed poor explanatory power (pseudo-R2 ≤ 0.34) but outperformed ordinary least-squares (OLS) and generalized least-squares (GLS) regression models with logit-transformed response in terms of mean square prediction error and absolute bias. We introduce a copula (COP) model that is based on the beta distribution and accounts for spatial dependence. A simulation study was designed to illustrate the effects of incorrectly assuming normality, equal variance, and spatial independence. It showed that BR, BRdep, and COP models provide unbiased parameter estimates, whereas OLS and GLS models result in slightly biased estimates for two of the three parameters. On the basis of the simulation study, 93–97% of the GLS, BRdep, and COP confidence intervals covered the true parameters, whereas OLS and BR only resulted in 84–88% coverage, which demonstrated the superiority of GLS, BRdep, and COP over OLS and BR models in providing standard errors for the parameter estimates in the presence of spatial dependence.
Generalized Environment for Modeling Systems
2012-02-07
GEMS is an integrated environment that allows technical analysts, modelers, researchers, etc. to integrate and deploy models and/or decision tools with associated data to the internet for direct use by customers. GEMS does not require that the model developer know how to code or script and therefore delivers this capability to a large group of technical specialists. Customers gain the benefit of being able to execute their own scenarios directly without need for technical support. GEMS is a process that leverages commercial software products with specialized codes that add connectivity and unique functions to support the overall capability. Users integrate pre-existing models with a commercial product and store parameters and input trajectories in a companion commercial database. The model is then exposed into a commercial web environment and a graphical user interface (GUI) is applied by the model developer. Users execute the model through the web based GUI and GEMS manages supply of proper inputs, execution of models, routing of data to models and display of results back to users. GEMS works in layers, the following description is from the bottom up. Modelers create models in the modeling tool of their choice such as Excel, Matlab, or Fortran. They can also use models from a library of previously wrapped legacy codes (models). Modelers integrate the models (or a single model) by wrapping and connecting the models using the Phoenix Integration tool entitled ModelCenter. Using a ModelCenter/SAS plugin (DOE copyright CW-10-08) the modeler gets data from either an SAS or SQL database and sends results back to SAS or SQL. Once the model is working properly, the ModelCenter file is saved and stored in a folder location to which a SharePoint server tool created at INL is pointed. This enables the ModelCenter model to be run from SharePoint. The modeler then goes into Microsoft SharePoint and creates a graphical user interface (GUI) using the ModelCenter WebPart (CW-12
Generalized Environment for Modeling Systems
Energy Science and Technology Software Center (ESTSC)
2012-02-07
GEMS is an integrated environment that allows technical analysts, modelers, researchers, etc. to integrate and deploy models and/or decision tools with associated data to the internet for direct use by customers. GEMS does not require that the model developer know how to code or script and therefore delivers this capability to a large group of technical specialists. Customers gain the benefit of being able to execute their own scenarios directly without need for technical support.more » GEMS is a process that leverages commercial software products with specialized codes that add connectivity and unique functions to support the overall capability. Users integrate pre-existing models with a commercial product and store parameters and input trajectories in a companion commercial database. The model is then exposed into a commercial web environment and a graphical user interface (GUI) is applied by the model developer. Users execute the model through the web based GUI and GEMS manages supply of proper inputs, execution of models, routing of data to models and display of results back to users. GEMS works in layers, the following description is from the bottom up. Modelers create models in the modeling tool of their choice such as Excel, Matlab, or Fortran. They can also use models from a library of previously wrapped legacy codes (models). Modelers integrate the models (or a single model) by wrapping and connecting the models using the Phoenix Integration tool entitled ModelCenter. Using a ModelCenter/SAS plugin (DOE copyright CW-10-08) the modeler gets data from either an SAS or SQL database and sends results back to SAS or SQL. Once the model is working properly, the ModelCenter file is saved and stored in a folder location to which a SharePoint server tool created at INL is pointed. This enables the ModelCenter model to be run from SharePoint. The modeler then goes into Microsoft SharePoint and creates a graphical user interface (GUI) using the ModelCenter Web
Trending in Probability of Collision Measurements via a Bayesian Zero-Inflated Beta Mixed Model
NASA Technical Reports Server (NTRS)
Vallejo, Jonathon; Hejduk, Matt; Stamey, James
2015-01-01
We investigate the performance of a generalized linear mixed model in predicting the Probabilities of Collision (Pc) for conjunction events. Specifically, we apply this model to the log(sub 10) transformation of these probabilities and argue that this transformation yields values that can be considered bounded in practice. Additionally, this bounded random variable, after scaling, is zero-inflated. Consequently, we model these values using the zero-inflated Beta distribution, and utilize the Bayesian paradigm and the mixed model framework to borrow information from past and current events. This provides a natural way to model the data and provides a basis for answering questions of interest, such as what is the likelihood of observing a probability of collision equal to the effective value of zero on a subsequent observation.
Shell model nuclear matrix elements for competing mechanisms contributing to double beta decay
Horoi, Mihai
2013-12-30
Recent progress in the shell model approach to the nuclear matrix elements for the double beta decay process are presented. This includes nuclear matrix elements for competing mechanisms to neutrionless double beta decay, a comparison between closure and non-closure approximation for {sup 48}Ca, and an updated shell model analysis of nuclear matrix elements for the double beta decay of {sup 136}Xe.
Using beta binomials to estimate classification uncertainty for ensemble models
2014-01-01
Background Quantitative structure-activity (QSAR) models have enormous potential for reducing drug discovery and development costs as well as the need for animal testing. Great strides have been made in estimating their overall reliability, but to fully realize that potential, researchers and regulators need to know how confident they can be in individual predictions. Results Submodels in an ensemble model which have been trained on different subsets of a shared training pool represent multiple samples of the model space, and the degree of agreement among them contains information on the reliability of ensemble predictions. For artificial neural network ensembles (ANNEs) using two different methods for determining ensemble classification – one using vote tallies and the other averaging individual network outputs – we have found that the distribution of predictions across positive vote tallies can be reasonably well-modeled as a beta binomial distribution, as can the distribution of errors. Together, these two distributions can be used to estimate the probability that a given predictive classification will be in error. Large data sets comprised of logP, Ames mutagenicity, and CYP2D6 inhibition data are used to illustrate and validate the method. The distributions of predictions and errors for the training pool accurately predicted the distribution of predictions and errors for large external validation sets, even when the number of positive and negative examples in the training pool were not balanced. Moreover, the likelihood of a given compound being prospectively misclassified as a function of the degree of consensus between networks in the ensemble could in most cases be estimated accurately from the fitted beta binomial distributions for the training pool. Conclusions Confidence in an individual predictive classification by an ensemble model can be accurately assessed by examining the distributions of predictions and errors as a function of the degree of
NASA Orbital Debris Engineering Model ORDEM2008 (Beta Version)
NASA Technical Reports Server (NTRS)
Stansbery, Eugene G.; Krisko, Paula H.
2009-01-01
This is an interim document intended to accompany the beta-release of the ORDEM2008 model. As such it provides the user with a guide for its use, a list of its capabilities, a brief summary of model development, and appendices included to educate the user as to typical runtimes for different orbit configurations. More detailed documentation will be delivered with the final product. ORDEM2008 supersedes NASA's previous model - ORDEM2000. The availability of new sensor and in situ data, the re-analysis of older data, and the development of new analytical techniques, has enabled the construction of this more comprehensive and sophisticated model. Integrated with the software is an upgraded graphical user interface (GUI), which uses project-oriented organization and provides the user with graphical representations of numerous output data products. These range from the conventional average debris size vs. flux magnitude for chosen analysis orbits, to the more complex color-contoured two-dimensional (2-D) directional flux diagrams in terms of local spacecraft pitch and yaw.
General models of multilocus evolution.
Kirkpatrick, Mark; Johnson, Toby; Barton, Nick
2002-01-01
In 1991, Barton and Turelli developed recursions to describe the evolution of multilocus systems under arbitrary forms of selection. This article generalizes their approach to allow for arbitrary modes of inheritance, including diploidy, polyploidy, sex linkage, cytoplasmic inheritance, and genomic imprinting. The framework is also extended to allow for other deterministic evolutionary forces, including migration and mutation. Exact recursions that fully describe the state of the population are presented; these are implemented in a computer algebra package (available on the Web at http://helios.bto.ed.ac.uk/evolgen). Despite the generality of our framework, it can describe evolutionary dynamics exactly by just two equations. These recursions can be further simplified using a "quasi-linkage equilibrium" (QLE) approximation. We illustrate the methods by finding the effect of natural selection, sexual selection, mutation, and migration on the genetic composition of a population. PMID:12196414
Inhomogeneous generalization of some Bianchi models
NASA Astrophysics Data System (ADS)
Carmeli, M.; Charach, Ch.
1980-02-01
Vacuum Bianchi models which can be transformed to the Einstein-Rosen metric are considered. The models are used in order to construct new inhomogeneous universes, which are generalizations of Bianchi cosmologies of types III, V and VIh. Recent generalizations of these Bianchi models, considered by Wainwright et al., are also discussed.
Duality in a maximum generalized entropy model
NASA Astrophysics Data System (ADS)
Eguchi, Shinto; Komori, Osamu; Ohara, Atsumi
2015-01-01
This paper discusses a possible generalization for the maximum entropy principle. A class of generalized entropy is introduced by that of generator functions, in which the maximum generalized distribution model is explicitly derived including q-Gaussian distributions, Wigner semicircle distributions and Pareto distributions. We define a totally geodesic subspace in the total space of all probability density functions in a framework of information geometry. The model of maximum generalized entropy distributions is shown to be totally geodesic. The duality of the model and the estimation in the maximum generalized principle is elucidated to give intrinsic understandings from the point of information geometry.
Theoretical Models of Generalized Quasispecies.
Wagner, Nathaniel; Atsmon-Raz, Yoav; Ashkenasy, Gonen
2016-01-01
Theoretical modeling of quasispecies has progressed in several directions. In this chapter, we review the works of Emmanuel Tannenbaum, who, together with Eugene Shakhnovich at Harvard University and later with colleagues and students at Ben-Gurion University in Beersheva, implemented one of the more useful approaches, by progressively setting up various formulations for the quasispecies model and solving them analytically. Our review will focus on these papers that have explored new models, assumed the relevant mathematical approximations, and proceeded to analytically solve for the steady-state solutions and run stochastic simulations . When applicable, these models were related to real-life problems and situations, including changing environments, presence of chemical mutagens, evolution of cancer and tumor cells , mutations in Escherichia coli, stem cells , chromosomal instability (CIN), propagation of antibiotic drug resistance , dynamics of bacteria with plasmids , DNA proofreading mechanisms, and more. PMID:26373410
LLNL Ocean General Circulation Model
Energy Science and Technology Software Center (ESTSC)
2005-12-29
The LLNL OGCM is a numerical ocean modeling tool for use in studying ocean circulation over a wide range of space and time scales, with primary applications to climate change and carbon cycle science.
General Pressurization Model in Simscape
NASA Technical Reports Server (NTRS)
Servin, Mario; Garcia, Vicky
2010-01-01
System integration is an essential part of the engineering design process. The Ares I Upper Stage (US) is a complex system which is made up of thousands of components assembled into subsystems including a J2-X engine, liquid hydrogen (LH2) and liquid oxygen (LO2) tanks, avionics, thrust vector control, motors, etc. System integration is the task of connecting together all of the subsystems into one large system. To ensure that all the components will "fit together" as well as safety and, quality, integration analysis is required. Integration analysis verifies that, as an integrated system, the system will behave as designed. Models that represent the actual subsystems are built for more comprehensive analysis. Matlab has been an instrument widely use by engineers to construct mathematical models of systems. Simulink, one of the tools offered by Matlab, provides multi-domain graphical environment to simulate and design time-varying systems. Simulink is a powerful tool to analyze the dynamic behavior of systems over time. Furthermore, Simscape, a tool provided by Simulink, allows users to model physical (such as mechanical, thermal and hydraulic) systems using physical networks. Using Simscape, a model representing an inflow of gas to a pressurized tank was created where the temperature and pressure of the tank are measured over time to show the behavior of the gas. By further incorporation of Simscape into model building, the full potential of this software can be discovered and it hopefully can become a more utilized tool.
Levitt, P R
1975-01-01
A population genetic approach is presented for general analysis and comparison of kin selection models of sib and half-sib altruism. Nine models are described, each assuming a particular mode of inheritance, number of female inseminations, and Mendelian dominance of the altruist gene. In each model, the selective effects of altruism are described in terms of two general fitness functions, A(beta) and S(beta), giving respectively the expected fitness of an altruist and a nonaltruist as a function of the fraction of altruists beta in a given sibship. For each model, exact conditions are reported for stability at altruist and nonaltruist fixation. Under the Table 3 axions, the stability conditions may then be partially ordered on the basis of implications holding between pairs of conditions. The partial orderings are compared with predictions of the kin selection theory of Hamilton. PMID:1060136
Levitt, P R
1975-11-01
A population genetic approach is presented for general analysis and comparison of kin selection models of sib and half-sib altruism. Nine models are described, each assuming a particular mode of inheritance, number of female inseminations, and Mendelian dominance of the altruist gene. In each model, the selective effects of altruism are described in terms of two general fitness functions, A(beta) and S(beta), giving respectively the expected fitness of an altruist and a nonaltruist as a function of the fraction of altruists beta in a given sibship. For each model, exact conditions are reported for stability at altruist and nonaltruist fixation. Under the Table 3 axions, the stability conditions may then be partially ordered on the basis of implications holding between pairs of conditions. The partial orderings are compared with predictions of the kin selection theory of Hamilton. PMID:1060136
Harkany, T; Hortobágyi, T; Sasvári, M; Kónya, C; Penke, B; Luiten, P G; Nyakas, C
1999-08-01
1. beta-Amyloid peptides (A beta s) accumulate abundantly in the Alzheimer's disease (AD) brain in areas subserving information acquisition and processing, and memory formation. A beta fragments are produced in a process of abnormal proteolytic cleavage of their precursor, the amyloid precursor protein (APP). While conflicting data exist in the literature on the roles of A beta s in the brain, and particularly in AD, recent studies have provided firm experimental evidence for the direct neurotoxic properties of A beta. 2. Sequence analysis of A beta s revealed a high degree of evolutionary conservation and inter-species homology of the A beta amino acid sequence. In contrast, synthetic A beta fragments, even if modified fluorescent or isotope-labeled derivatives, are pharmacological candidates for in vitro and in vivo modeling of their cellular actions. During the past decade, acute injection, prolonged mini-osmotic brain perfusion approaches or A beta infusions into the blood circulation were developed in order to investigate the effects of synthetic A beta s, whereas transgenic models provided insight into the distinct molecular steps of pathological APP cleavage. 3. The hippocampus, caudate putamen, amygdala and neocortex all formed primary targets of acute neurotoxicity screening, but functional consequences of A beta infusions were primarily demonstrated following either intracerebroventricular or basal forebrain (medial septum or magnocellular basal nucleus (MBN)) infusions of A beta fragments. 4. In vivo investigations confirmed that, while the active core of A beta is located within the beta(25-35) sequence, the flanking peptide regions influence not only the folding properties of the A beta fragments, but also their in vivo neurotoxic potentials. 5. It has recently been established that A beta administration deranges neuron-glia signaling, affects the glial glutamate uptake and thereby induces noxious glutamatergic stimulation of nerve cells. In fact, a
Classical integrability for beta-ensembles and general Fokker-Planck equations
Rumanov, Igor
2015-01-15
Beta-ensembles of random matrices are naturally considered as quantum integrable systems, in particular, due to their relation with conformal field theory, and more recently appeared connection with quantized Painlevé Hamiltonians. Here, we demonstrate that, at least for even integer beta, these systems are classically integrable, e.g., there are Lax pairs associated with them, which we explicitly construct. To come to the result, we show that a solution of every Fokker-Planck equation in one space (and one time) dimensions can be considered as a component of an eigenvector of a Lax pair. The explicit finding of the Lax pair depends on finding a solution of a governing system–a closed system of two nonlinear partial differential equations (PDEs) of hydrodynamic type. This result suggests that there must be a solution for all values of beta. We find the solution of this system for even integer beta in the particular case of quantum Painlevé II related to the soft edge of the spectrum for beta-ensembles. The solution is given in terms of Calogero system of β/2 particles in an additional time-dependent potential. Thus, we find another situation where quantum integrability is reduced to classical integrability.
NASA Astrophysics Data System (ADS)
Schmitt, F. G.
2014-12-01
Multiplicative cascade models, when densified (continuous scale invariance) correspond to the exponential of a linear process. Hence this cannot generate zero values. Such framework is not complete and not purely multiplicative. We present here a stochastic framework which stays in the multiplicative realm and can be used to generate zero values. The multiplicative continuous model for multifractal fields with zero values is built using infinitely multiplicative random variables, the multiplicative analog to infinitely divisible distributions for addition. It also needs stochastic multiplicative measures and multiplicative stochastic integrals. The model hence generates continuous multiplicative cascades. The model produced possesses as special case a continuous generalization of the classical discrete beta-model. Applications are numerous in many fields of applied sciences, including smallscale rainfall, soil sciences. The theory is first proposed, then simulation algorithm is presented and simulations are shown in 1D and in 2D. Figure: a continuous lognormal multifractal with zero values (512x512).
A Bayesian beta distribution model for estimating rainfall IDF curves in a changing climate
NASA Astrophysics Data System (ADS)
Lima, Carlos H. R.; Kwon, Hyun-Han; Kim, Jin-Young
2016-09-01
The estimation of intensity-duration-frequency (IDF) curves for rainfall data comprises a classical task in hydrology studies to support a variety of water resources projects, including urban drainage and the design of flood control structures. In a changing climate, however, traditional approaches based on historical records of rainfall and on the stationary assumption can be inadequate and lead to poor estimates of rainfall intensity quantiles. Climate change scenarios built on General Circulation Models offer a way to access and estimate future changes in spatial and temporal rainfall patterns at the daily scale at the utmost, which is not as fine temporal resolution as required (e.g. hours) to directly estimate IDF curves. In this paper we propose a novel methodology based on a four-parameter beta distribution to estimate IDF curves conditioned on the observed (or simulated) daily rainfall, which becomes the time-varying upper bound of the updated nonstationary beta distribution. The inference is conducted in a Bayesian framework that provides a better way to take into account the uncertainty in the model parameters when building the IDF curves. The proposed model is tested using rainfall data from four stations located in South Korea and projected climate change Representative Concentration Pathways (RCPs) scenarios 6 and 8.5 from the Met Office Hadley Centre HadGEM3-RA model. The results show that the developed model fits the historical data as good as the traditional Generalized Extreme Value (GEV) distribution but is able to produce future IDF curves that significantly differ from the historically based IDF curves. The proposed model predicts for the stations and RCPs scenarios analysed in this work an increase in the intensity of extreme rainfalls of short duration with long return periods.
Modeling the Production of Beta-Delayed Gamma Rays for the Detection of Special Nuclear Materials
Hall, J M; Pruet, J A; Brown, D A; Descalle, M; Hedstrom, G W; Prussin, S G
2005-02-14
The objective of this LDRD project was to develop one or more models for the production of {beta}-delayed {gamma} rays following neutron-induced fission of a special nuclear material (SNM) and to define a standardized formatting scheme which will allow them to be incorporated into some of the modern, general-purpose Monte Carlo transport codes currently being used to simulate inspection techniques proposed for detecting fissionable material hidden in sea-going cargo containers. In this report, we will describe a Monte Carlo model for {beta}-delayed {gamma}-ray emission following the fission of SNM that can accommodate arbitrary time-dependent fission rates and photon collection histories. The model involves direct sampling of the independent fission yield distributions of the system, the branching ratios for decay of individual fission products and spectral distributions representing photon emission from each fission product and for each decay mode. While computationally intensive, it will be shown that this model can provide reasonably detailed estimates of the spectra that would be recorded by an arbitrary spectrometer and may prove quite useful in assessing the quality of evaluated data libraries and identifying gaps in the libraries. The accuracy of the model will be illustrated by comparing calculated and experimental spectra from the decay of short-lived fission products following the reactions {sup 235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f). For general-purpose transport calculations, where a detailed consideration of the large number of individual {gamma}-ray transitions in a spectrum may not be necessary, it will be shown that a simple parameterization of the {gamma}-ray source function can be defined which provides high-quality average spectral distributions that should suffice for calculations describing photons being transported through thick attenuating media. Finally, a proposal for ENDF-compatible formats that describe each of the models and
Waninge, Rianne; Walstra, Pieter; Bastiaans, Jan; Nieuwenhuijse, Hans; Nylander, Tommy; Paulsson, Marie; Bergenståhl, Björn
2005-02-01
This study investigated the competitive adsorption between milk proteins and model milk membrane lipids at the oil-water interface and its dependence on the state of the lipid dispersion and the formation of emulsions. Both protein and membrane lipid surface load were determined using a serum depletion technique. The membrane lipid mixture used was a model milk membrane lipid system, containing dioleoylphosphatidylcholine, dioleoylphosphatidylethanolamine, milk sphingomyelin, dioleoylphosphatidylserine, and soybean phosphatidylinositol. The model composition mimics the lipid composition of natural milk fat globule membranes. The interactions were studied for two proteins, beta-lactoglobulin and beta-casein. The mixing order was varied to allow for differentiation between equilibrium structures and nonequilibrium structures. The results showed more than monolayer adsorption for most combinations. Proteins dominated at the oil-water interface in the protein-emulsified emulsion even after 48 h of exposure to a vesicular dispersion of membrane lipids. The membrane lipids dominated the oil-water interface in the case of the membrane lipid emulsified emulsion even after equilibration with a protein solution. Protein displacement with time was observed only for emulsions in which both membrane lipids and beta-casein were included during the emulsification. This study shows that kinetics controls the structures rather than the thermodynamic equilibrium, possibly resulting in structures more complex than an adsorbed monolayer. Thus, it can be expected that procedures such as the mixing order during emulsion preparation are of crucial importance to the emulsification performance. PMID:15686425
Generalized Linear Models in Family Studies
ERIC Educational Resources Information Center
Wu, Zheng
2005-01-01
Generalized linear models (GLMs), as defined by J. A. Nelder and R. W. M. Wedderburn (1972), unify a class of regression models for categorical, discrete, and continuous response variables. As an extension of classical linear models, GLMs provide a common body of theory and methodology for some seemingly unrelated models and procedures, such as…
Bilepton contributions to the neutrinoless double beta decay in the economical 3-3-1 model
Soa, D. V. Dong, P. V. Huong, T. T.; Long, H. N.
2009-05-15
A new bound of the mixing angle between charged gauge bosons (the standard-model W and the bilepton Y) in the economical 3-3-1 model is given. Possible contributions of the charged bileptons to the neutrinoless double beta (({beta}{beta}){sub 0{nu}}) decay are discussed. We show that the ({beta}{beta}){sub 0{nu}} decay in this model is due to both the Majorana
NASA Astrophysics Data System (ADS)
Farfan, Eduardo Balderrama
2002-01-01
Predicting equivalent dose in the human respiratory tract is significant in the assessment of health risks associated with the inhalation of radioactive aerosols. A complete respiratory tract methodology based on the International Commission on Radiological Protection Publication 66 model was used in this research project for beta-particle and photon emitters. The conventional methodology has been to use standard values (from Reference Man) for parameters to obtain a single dose value. However, the methods used in the current study allow lung dose values to be determined as probability distributions to reflect the spread or variability in doses. To implement the methodology, a computer code, LUDUC, has been modified to include inhalation scenarios of beta-particle and photon emitters. For beta particles, a new methodology was implemented into Monte Carlo simulations to determine absorbed fractions in target tissues within the thoracic region of the respiratory tract. For photons, a new mathematical phantom of extrathoracic and thoracic regions was created based on previous studies to determine specific absorbed fractions in several tissues and organs of the human body due to inhalation of radioactive materials. The application of the methodology and developed data will be helpful in dose reconstruction and prediction efforts concerning the inhalation of short-lived radionuclides or radionuclides of Inhalation Class S. The resulting dose distributions follow a lognormal distribution shape for all scenarios examined. Applying the probabilistic computer code LUDUC to inhalation of strontium and yttrium aerosols has shown several trends, which could also be valid for many S radionuclide compounds that are beta-particle emitters. The equivalent doses are, in general, found to follow lognormal distributions. Therefore, these distributions can be described by geometric means and geometric standard deviations. Furthermore, a mathematical phantom of the extrathoracic and
Stiles, Jessica M.; Amaya, Clarissa; Rains, Steven; Diaz, Dolores; Pham, Robert; Battiste, James; Modiano, Jaime F.; Kokta, Victor; Boucheron, Laura E.; Mitchell, Dianne C.; Bryan, Brad A.
2013-01-01
Therapeutic targeting of the beta-adrenergic receptors has recently shown remarkable efficacy in the treatment of benign vascular tumors such as infantile hemangiomas. As infantile hemangiomas are reported to express high levels of beta adrenergic receptors, we examined the expression of these receptors on more aggressive vascular tumors such as hemangioendotheliomas and angiosarcomas, revealing beta 1, 2, and 3 receptors were indeed present and therefore aggressive vascular tumors may similarly show increased susceptibility to the inhibitory effects of beta blockade. Using a panel of hemangioendothelioma and angiosarcoma cell lines, we demonstrate that beta adrenergic inhibition blocks cell proliferation and induces apoptosis in a dose dependent manner. Beta blockade is selective for vascular tumor cells over normal endothelial cells and synergistically effective when combined with standard chemotherapeutic or cytotoxic agents. We demonstrate that inhibition of beta adrenergic signaling induces large scale changes in the global gene expression patterns of vascular tumors, including alterations in the expression of established cell cycle and apoptotic regulators. Using in vivo tumor models we demonstrate that beta blockade shows remarkable efficacy as a single agent in reducing the growth of angiosarcoma tumors. In summary, these experiments demonstrate the selective cytotoxicity and tumor suppressive ability of beta adrenergic inhibition on malignant vascular tumors and have laid the groundwork for a promising treatment of angiosarcomas in humans. PMID:23555867
A general consumer-resource population model
Lafferty, Kevin D.; DeLeo, Giulio; Briggs, Cheryl J.; Dobson, Andrew P.; Gross, Thilo; Kuris, Armand M.
2015-01-01
Food-web dynamics arise from predator-prey, parasite-host, and herbivore-plant interactions. Models for such interactions include up to three consumer activity states (questing, attacking, consuming) and up to four resource response states (susceptible, exposed, ingested, resistant). Articulating these states into a general model allows for dissecting, comparing, and deriving consumer-resource models. We specify this general model for 11 generic consumer strategies that group mathematically into predators, parasites, and micropredators and then derive conditions for consumer success, including a universal saturating functional response. We further show how to use this framework to create simple models with a common mathematical lineage and transparent assumptions. Underlying assumptions, missing elements, and composite parameters are revealed when classic consumer-resource models are derived from the general model.
Conformity and Dissonance in Generalized Voter Models
NASA Astrophysics Data System (ADS)
Page, Scott E.; Sander, Leonard M.; Schneider-Mizell, Casey M.
2007-09-01
We generalize the voter model to include social forces that produce conformity among voters and avoidance of cognitive dissonance of opinions within a voter. The time for both conformity and consistency (which we call the exit time) is, in general, much longer than for either process alone. We show that our generalized model can be applied quite widely: it is a form of Wright's island model of population genetics, and is related to problems in the physical sciences. We give scaling arguments, numerical simulations, and analytic estimates for the exit time for a range of relative strengths in the tendency to conform and to avoid dissonance.
Building a generalized distributed system model
NASA Technical Reports Server (NTRS)
Mukkamala, Ravi
1991-01-01
A number of topics related to building a generalized distributed system model are discussed. The effects of distributed database modeling on evaluation of transaction rollbacks, the measurement of effects of distributed database models on transaction availability measures, and a performance analysis of static locking in replicated distributed database systems are covered.
Vierling-Claassen, Dorea; Siekmeier, Peter; Stufflebeam, Steven; Kopell, Nancy
2008-05-01
The disorganized symptoms of schizophrenia, including severely disordered thought patterns, may be indicative of a problem with the construction and maintenance of cell assemblies during sensory processing and attention. The gamma and beta frequency bands (15-70 Hz) are believed relevant to such processing. This paper addresses the results of an experimental examination of the cortical response of 12 schizophrenia patients and 12 control subjects when presented with auditory click-train stimuli in the gamma/beta frequency band during measurement using magnetoencephalography (MEG), as well as earlier work by Kwon et al. These data indicate that control subjects show an increased 40-Hz response to both 20- and 40-Hz stimulation as compared with patients, whereas schizophrenic subjects show a preference for 20-Hz response to the same driving frequencies. In this work, two computational models of the auditory cortex are constructed based on postmortem studies that indicate cortical interneurons in schizophrenic subjects have decreased GAT-1 (a GABA transporter) and GAD(67) (1 of 2 enzymes responsible for GABA synthesis). The models transition from control to schizophrenic frequency response when an extended inhibitory decay time is introduced; this change captures a possible effect of these GABA alterations. Modeling gamma/beta range auditory entrainment in schizophrenia provides insight into how biophysical mechanisms can impact cognitive function. In addition, the study of dynamics that underlie auditory entrainment in schizophrenia may contribute to the understanding of how gamma and beta rhythms impact cognition in general. PMID:18287555
Tensions and Models in General Education Planning.
ERIC Educational Resources Information Center
Newton, Robert R.
2000-01-01
Asserts that general education revision committees are often unprepared for their task. Presents an analysis identifying four key issues confronting reformers--knowledge, student learning, faculty competence, and content--and describing how three models of general education (Great Books, Scholarly Discipline, and Effective Citizen) might respond…
On Keats' Generalization of the Rasch Model
ERIC Educational Resources Information Center
Colonius, Hans
1977-01-01
Parameter estimation for Keats generalization of the Rasch model that takes account of guessing behavior is investigated. It is shown that no minimal sufficient statistics for the ability parameters independent of the difficulty parameters exist. (Author/JKS)
Compactlike kinks and vortices in generalized models
Bazeia, D.; Hora, E. da; Menezes, R.; Oliveira, H. P. de; Santos, C. dos
2010-06-15
This work deals with the presence of topological defects in k-field models, where the dynamics is generalized to include higher order power in the kinetic term. We investigate kinks in (1, 1) dimensions and vortices in (2, 1) dimensions, focusing on some specific features of the solutions. In particular, we show how the kinks and vortices change to compactlike solutions, controlled by the parameter used to introduce the generalized models.
GENERALIZED VISCOPLASTIC MODELING OF DEBRIS FLOW.
Chen, Cheng-lung
1988-01-01
The earliest model developed by R. A. Bagnold was based on the concept of the 'dispersive' pressure generated by grain collisions. Some efforts have recently been made by theoreticians in non-Newtonian fluid mechanics to modify or improve Bagnold's concept or model. A viable rheological model should consist both of a rate-independent part and a rate-dependent part. A generalized viscoplastic fluid (GVF) model that has both parts as well as two major rheological properties (i. e. , the normal stress effect and soil yield criterion) is shown to be sufficiently accurate, yet practical for general use in debris-flow modeling. In fact, Bagnold's model is found to be only a particular case of the GVF model. analytical solutions for (steady) uniform debris flows in wide channels are obtained from the GVF model based on Bagnold's simplified assumption of constant grain concentration.
Simple implementation of general dark energy models
Bloomfield, Jolyon K.; Pearson, Jonathan A. E-mail: jonathan.pearson@durham.ac.uk
2014-03-01
We present a formalism for the numerical implementation of general theories of dark energy, combining the computational simplicity of the equation of state for perturbations approach with the generality of the effective field theory approach. An effective fluid description is employed, based on a general action describing single-scalar field models. The formalism is developed from first principles, and constructed keeping the goal of a simple implementation into CAMB in mind. Benefits of this approach include its straightforward implementation, the generality of the underlying theory, the fact that the evolved variables are physical quantities, and that model-independent phenomenological descriptions may be straightforwardly investigated. We hope this formulation will provide a powerful tool for the comparison of theoretical models of dark energy with observational data.
Computational modelling of movement-related beta-oscillatory dynamics in human motor cortex.
Bhatt, Mrudul B; Bowen, Stephanie; Rossiter, Holly E; Dupont-Hadwen, Joshua; Moran, Rosalyn J; Friston, Karl J; Ward, Nick S
2016-06-01
Oscillatory activity in the beta range, in human primary motor cortex (M1), shows interesting dynamics that are tied to behaviour and change systematically in disease. To investigate the pathophysiology underlying these changes, we must first understand how changes in beta activity are caused in healthy subjects. We therefore adapted a canonical (repeatable) microcircuit model used in dynamic causal modelling (DCM) previously used to model induced responses in visual cortex. We adapted this model to accommodate cytoarchitectural differences between visual and motor cortex. Using biologically plausible connections, we used Bayesian model selection to identify the best model of measured MEG data from 11 young healthy participants, performing a simple handgrip task. We found that the canonical M1 model had substantially more model evidence than the generic canonical microcircuit model when explaining measured MEG data. The canonical M1 model reproduced measured dynamics in humans at rest, in a manner consistent with equivalent studies performed in mice. Furthermore, the changes in excitability (self-inhibition) necessary to explain beta suppression during handgrip were consistent with the attenuation of sensory precision implied by predictive coding. These results establish the face validity of a model that can be used to explore the laminar interactions that underlie beta-oscillatory dynamics in humans in vivo. Our canonical M1 model may be useful for characterising the synaptic mechanisms that mediate pathophysiological beta dynamics associated with movement disorders, such as stroke or Parkinson's disease. PMID:26956910
A comparison of directed evolution approaches using the beta-glucuronidase model system.
Rowe, Lori A; Geddie, Melissa L; Alexander, Omar B; Matsumura, Ichiro
2003-09-26
Protein engineers can alter the properties of enzymes by directing their evolution in vitro. Many methods to generate molecular diversity and to identify improved clones have been developed, but experimental evolution remains as much an art as a science. We previously used DNA shuffling (sexual recombination) and a histochemical screen to direct the evolution of Escherichia coli beta-glucuronidase (GUS) variants with improved beta-galactosidase (BGAL) activity. Here, we employ the same model evolutionary system to test the efficiencies of several other techniques: recursive random mutagenesis (asexual), combinatorial cassette mutagenesis (high-frequency recombination) and a versatile high-throughput microplate screen. GUS variants with altered specificity evolved in each trial, but different combinations of mutagenesis and screening techniques effected the fixation of different beneficial mutations. The new microplate screen identified a broader set of mutations than the previously employed X-gal colony screen. Recursive random mutagenesis produced essentially asexual populations, within which beneficial mutations drove each other into extinction (clonal interference); DNA shuffling and combinatorial cassette mutagenesis led instead to the accumulation of beneficial mutations within a single allele. These results explain why recombinational approaches generally increase the efficiency of laboratory evolution. PMID:12972256
Superconformal generalizations of the Starobinsky model
Kallosh, Renata; Linde, Andrei E-mail: alinde@stanford.edu
2013-06-01
We find a way to represent the Starobinsky model in terms of a simple conformally invariant theory with spontaneous symmetry breaking. We also present a superconformal theory, which, upon spontaneous breaking of the superconformal symmetry, provides a consistent supergravity generalization of the Starobinsky model.
Maximum Likelihood Estimation in Generalized Rasch Models.
ERIC Educational Resources Information Center
de Leeuw, Jan; Verhelst, Norman
1986-01-01
Maximum likelihood procedures are presented for a general model to unify the various models and techniques that have been proposed for item analysis. Unconditional maximum likelihood estimation, proposed by Wright and Haberman, and conditional maximum likelihood estimation, proposed by Rasch and Andersen, are shown as important special cases. (JAZ)
Generalized force model of traffic dynamics
NASA Astrophysics Data System (ADS)
Helbing, Dirk; Tilch, Benno
1998-07-01
Floating car data of car-following behavior in cities were compared to existing microsimulation models, after their parameters had been calibrated to the experimental data. With these parameter values, additional simulations have been carried out, e.g., of a moving car which approaches a stopped car. It turned out that, in order to manage such kinds of situations without producing accidents, improved traffic models are needed. Good results were obtained with the proposed generalized force model.
Cosmology of generalized modified gravity models
Carroll, Sean M.; Duvvuri, Vikram; De Felice, Antonio; Easson, Damien A.; Trodden, Mark; Turner, Michael S.
2005-03-15
We consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. We investigate the far future evolution of the Universe in such models, examining the possibilities for cosmic acceleration and other ultimate destinies. The models generically possess de Sitter space as an unstable solution and exhibit an interesting set of attractor solutions which, in some cases, provide alternatives to dark energy models.
Cheng, Jin; Ju, Xiu-Lian; Chen, Xiang-Yang; Liu, Gen-Yan
2009-09-01
To further explore the mechanism of selective binding of the representative gamma-aminobutyric acid receptors (GABARs) noncompetitive antagonist (NCA) fipronil to insect over mammalian GABARs, three-dimensional models of human alpha 1 beta 2 gamma 2 and house fly beta 3 GABAR were generated by homology modeling, using the cryo-electron microscopy structure of the nicotinic acetylcholine receptor (nAChR) of Torpedo marmorata as a template. Fipronil was docked into the putative binding site of the human alpha 1 beta 2 gamma 2 and house fly beta 3 receptors by Surflex-docking, and the calculated docking energies are in agreement with experimental results. The GABA receptor antagonist fipronil exhibited higher potency with house fly beta 3 GABAR than with human alpha 1 beta 2 gamma 2 GABAR. Furthermore, analyses of Surflex-docking suggest that the H-bond interaction of fipronil with Ala2 and Thr6 in the second transmembrane segment (TM2) of these GABARs plays a relatively important role in ligand selective binding. The different subunit assemblies of human alpha 1 beta 2 gamma 2 and house fly beta 3 GABARs may result in differential selectivity for fipronil. PMID:19238461
Meadows, Laurence S; Malhotra, Jyoti; Loukas, Andrew; Thyagarajan, Veena; Kazen-Gillespie, Kristin A; Koopman, Matthew C; Kriegler, Steven; Isom, Lori L; Ragsdale, David S
2002-12-15
Generalized epilepsy with febrile seizures plus type 1 is an inherited human epileptic syndrome, associated with a cysteine-to-tryptophan (C121W) mutation in the extracellular immunoglobin domain of the auxiliary beta1 subunit of the voltage-gated sodium channel. The mutation disrupts beta1 function, but how this leads to epilepsy is not understood. In this study, we make several observations that may be relevant for understanding why this beta1 mutation results in seizures. First, using electrophysiological recordings from mammalian cell lines, coexpressing sodium channel alpha subunits and either wild-type beta1 or C121Wbeta1, we show that loss of beta1 functional modulation, caused by the C121W mutation, leads to increased sodium channel availability at hyperpolarized membrane potentials and reduced sodium channel rundown during high-frequency channel activity, compared with channels coexpressed with wild-type beta1. In contrast, neither wild-type beta1 nor C121Wbeta1 significantly affected sodium current time course or the voltage dependence of channel activation. We also show, using a Drosophila S2 cell adhesion assay, that the C121W mutation disrupts beta1-beta1 homophilic cell adhesion, suggesting that the mutation may alter the ability of beta1 to mediate protein-protein interactions critical for sodium channel localization. Finally, we demonstrate that neither functional modulation nor cell adhesion mediated by wild-type beta1 is occluded by coexpression of C121Wbeta1, arguing against the idea that the mutant beta1 acts as a dominant-negative subunit. Together, these data suggest that C121Wbeta1 causes subtle effects on channel function and subcellular distribution that bias neurons toward hyperexcitabity and epileptogenesis. PMID:12486163
Space Station Freedom Beta Gimbal Control via Sensitivity Models
NASA Technical Reports Server (NTRS)
Schoenwald, David A.; Ozguner, Umit; Graham, Ronald E.
1993-01-01
Tracking control of the Space Station Freedom solar array beta gimbals is investigated. Of particular interest is the issue of control in the presence of uncertainty in gimbal friction parameters. Sensitivity functions are incorporated into the feedback loop to desensitize the gimbal control law to parameter variations. Simulation results indicated that one such sensitivity function improves the closed-loop performance of the gimbals in the presence of unexpected friction parameter dispersions.
The effects of interferon-alpha/beta in a model of rat heart transplantation
NASA Technical Reports Server (NTRS)
Slater, A. D.; Klein, J. B.; Sonnenfeld, G.; Ogden, L. L. 2nd; Gray, L. A. Jr
1992-01-01
Interferons have multiple immunologic effects. One such effect is the activation of expression of cell surface antigens. Interferon alpha/beta enhance expression of class I but not class II histocompatibility antigens. Contradictory information has been published regarding the effect of interferon-alpha/beta administration in patients with kidney transplantation. In a model of rat heart transplantation we demonstrated that administration of interferon-alpha/beta accelerated rejection in a dose-dependent fashion in the absence of maintenance cyclosporine. Animals treated with maintenance cyclosporine had evidence of increased rejection at 20 days that was resolved completely at 45 days with cyclosporine alone.
Implicitly modelled stratigraphic surfaces using generalized interpolation
NASA Astrophysics Data System (ADS)
Hillier, Michael; de Kemp, Eric; Schetselaar, Ernst
2016-06-01
Stratigraphic surfaces implicitly modelled using a generalized interpolation approach in various geological settings is presented to demonstrate its modelling capabilities and limitations. The generalized interpolation approach provides a useful mathematical framework in modelling continuous surfaces from scattered data consisting of the following geological constraints: contact locations and planar orientations. Examples are presented to show the effectiveness of the method in generating plausible representations of geological structures in sparse data environments. One of the major advantages of implicit surface modelling has long been claimed as its ability to model geometries with arbitrary topology. It is, however, demonstrated that this is in fact a disadvantage in robustly generating geologically realistic surfaces in structurally complex domains with a known topology.
Generalized Gibbs ensemble in integrable lattice models
NASA Astrophysics Data System (ADS)
Vidmar, Lev; Rigol, Marcos
2016-06-01
The generalized Gibbs ensemble (GGE) was introduced ten years ago to describe observables in isolated integrable quantum systems after equilibration. Since then, the GGE has been demonstrated to be a powerful tool to predict the outcome of the relaxation dynamics of few-body observables in a variety of integrable models, a process we call generalized thermalization. This review discusses several fundamental aspects of the GGE and generalized thermalization in integrable systems. In particular, we focus on questions such as: which observables equilibrate to the GGE predictions and who should play the role of the bath; what conserved quantities can be used to construct the GGE; what are the differences between generalized thermalization in noninteracting systems and in interacting systems mappable to noninteracting ones; why is it that the GGE works when traditional ensembles of statistical mechanics fail. Despite a lot of interest in these questions in recent years, no definite answers have been given. We review results for the XX model and for the transverse field Ising model. For the latter model, we also report original results and show that the GGE describes spin–spin correlations over the entire system. This makes apparent that there is no need to trace out a part of the system in real space for equilibration to occur and for the GGE to apply. In the past, a spectral decomposition of the weights of various statistical ensembles revealed that generalized eigenstate thermalization occurs in the XX model (hard-core bosons). Namely, eigenstates of the Hamiltonian with similar distributions of conserved quantities have similar expectation values of few-spin observables. Here we show that generalized eigenstate thermalization also occurs in the transverse field Ising model.
Redshift propagation equations in the {beta}{sup '{ne}}0 Szekeres models
Krasinski, Andrzej; Bolejko, Krzysztof
2011-04-15
The set of differential equations obeyed by the redshift in the general {beta}{sup '{ne}}0 Szekeres spacetimes is derived. Transversal components of the ray's momentum have to be taken into account, which leads to a set of 3 coupled differential equations. It is shown that in a general Szekeres model, and in a general Lemaitre-Tolman (L-T) model, generic light rays do not have repeatable paths (RLPs): two rays sent from the same source at different times to the same observer pass through different sequences of intermediate matter particles. The only spacetimes in the Szekeres class in which all rays are RLPs are the Friedmann models. Among the proper Szekeres models, RLPs exist only in the axially symmetric subcases, and in each one the RLPs are the null geodesics that intersect each t=constant space on the symmetry axis. In the special models with a 3-dimensional symmetry group (L-T among them), the only RLPs are radial geodesics. This shows that RLPs are very special and in the real Universe should not exist. We present several numerical examples which suggest that the rate of change of positions of objects in the sky, for the studied configuration, is 10{sup -6}-10{sup -7} arc sec per year. With the current accuracy of direction measurement, this drift would become observable after approximately 10 years of monitoring. More precise future observations will be able, in principle, to detect this effect, but there are basic problems with determining the reference direction that does not change.
Jobling, Andrew Ian; Wan, Ran; Gentle, Alex; Bui, Bang Viet; McBrien, Neville Anthony
2009-03-01
A visually evoked signalling cascade, which begins in the retina, transverses the choroid, and mediates scleral remodelling, is considered to control eye growth. The ubiquitous cytokine TGF-beta has been associated with alterations in ocular growth, where alterations in scleral TGF-beta isoforms mediate the scleral remodelling that results in myopia. However, while the TGF-beta isoforms have been implicated in the scleral change during myopia development, it is unclear whether alterations in retinal and choroidal isoforms constitute part of the retinoscleral cascade. This study characterised the retinal and choroidal TGF-beta isoform profiles and TGF-beta2 activation during different stages of myopia development, as induced by form deprivation, in a mammalian model of eye growth. Using quantitative real-time PCR, the mRNA for all three mammalian isoforms of TGF-beta was detected in tree shrew retina and choroid. Distinct tissue-specific isoform profiles were observed for the retina (TGF-beta1:TGF-beta2:TGF-beta3=20:2085:1) and choroid (TGF-beta1:TGF-beta2:TGF-beta3=16:23:1), which remained constant over the development period under investigation. The active and latent pools of retinal TGF-beta2 were quantified using ELISA with the majority (>94%) of total TGF-beta2 found in the latent form. Unlike previous scleral data showing early and continuous decreases in TGF-beta isoform expression during myopia development, the levels of the three isoforms remained within normal ranges for retinal (TGF-beta1, -14 to +14%; TGF-beta2, -2 to +20%; TGF-beta3, -10 to +26%) and choroidal (TGF-beta1, -19 to +21%; TGF-beta2, -26 to +8%; TGF-beta3, -11 to +28%) tissues during myopia development (induction times of 3h, 7h, 11h, 24h, and 5 days). A 40% decrease in retinal TGF-beta2 activation was observed after 5 days of myopia development, however, there was no functional correlate of altered TGF-beta2 activity, as assessed by the retinal ERG response. Overall, these data highlight
The General Education Collaboration Model: A Model for Successful Mainstreaming.
ERIC Educational Resources Information Center
Simpson, Richard L.; Myles, Brenda Smith
1990-01-01
The General Education Collaboration Model is designed to support general educators teaching mainstreamed disabled students, through collaboration with special educators. The model is based on flexible departmentalization, program ownership, identification and development of supportive attitudes, student assessment as a measure of program…
Generalized hydrodynamics model for strongly coupled plasmas
NASA Astrophysics Data System (ADS)
Diaw, A.; Murillo, M. S.
2015-07-01
Beginning with the exact equations of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, we obtain the density, momentum, and stress tensor-moment equations. We close the moment equations with two closures, one that guarantees an equilibrium state given by density-functional theory and another that includes collisions in the relaxation of the stress tensor. The introduction of a density functional-theory closure ensures self-consistency in the equation-of-state properties of the plasma (ideal and excess pressure, electric fields, and correlations). The resulting generalized hydrodynamics thus includes all impacts of Coulomb coupling, viscous damping, and the high-frequency (viscoelastic) response. We compare our results with those of several known models, including generalized hydrodynamic theory and models obtained using the Singwi-Tosi-Land-Sjolander approximation and the quasilocalized charge approximation. We find that the viscoelastic response, including both the high-frequency elastic generalization and viscous wave damping, is important for correctly describing ion-acoustic waves. We illustrate this result by considering three very different systems: ultracold plasmas, dusty plasmas, and dense plasmas. The new model is validated by comparing its results with those of the current autocorrelation function obtained from molecular-dynamics simulations of Yukawa plasmas, and the agreement is excellent. Generalizations of this model to mixtures and quantum systems should be straightforward.
General Equilibrium Models: Improving the Microeconomics Classroom
ERIC Educational Resources Information Center
Nicholson, Walter; Westhoff, Frank
2009-01-01
General equilibrium models now play important roles in many fields of economics including tax policy, environmental regulation, international trade, and economic development. The intermediate microeconomics classroom has not kept pace with these trends, however. Microeconomics textbooks primarily focus on the insights that can be drawn from the…
Anzai, Jun; Kitamura, Masahiro; Nozaki, Takenori; Nagayasu, Toshie; Terashima, Akio; Asano, Taiji; Murakami, Shinya
2010-12-17
Research highlights: {yields} Concomitant use of FGF-2 and {beta}-TCP (an osteo-conductive scaffold) significantly promotes periodontal regeneration in the severe periodontitis model (1-wall defect model) of beagle dog. {yields} FGF-2 enhanced new bone formation via {beta}-TCP at the defects. {yields} In particular, FGF-2 dramatically regenerated new periodontal ligament and cementum formations at the defects, that is one of the most important healing outcomes during the process of periodontal regeneration. {yields} Epithelial downgrowth (undesirable wound healing) was decreased by administration of FGF-2. {yields} This manuscript indicates for the first time that concomitant use of FGF-2 and {beta}-TCP is efficacious in regenerating periodontal tissue following severe destruction of the tissue by progression of periodontitis. -- Abstract: The effects of concomitant use of fibroblast growth factor-2 (FGF-2) and beta-tricalcium phosphate ({beta}-TCP) on periodontal regeneration were investigated in the beagle dog 1-wall periodontal defect model. One-wall periodontal defects were created in the mesial portion of both sides of the mandibular first molars, and 0.3% FGF-2 plus {beta}-TCP or {beta}-TCP alone was administered. Radiographic evaluation was performed at 0, 3, and 6 weeks. At 6 weeks, the periodontium with the defect site was removed and histologically analyzed. Radiographic findings showed that co-administration of FGF-2 significantly increased bone mineral contents of the defect sites compared with {beta}-TCP alone. Histologic analysis revealed that the length of the regenerated periodontal ligament, the cementum, distance to the junctional epithelium, new bone height, and area of newly formed bone were significantly increased in the FGF-2 group. No abnormal inflammatory response or ankylosis was observed in either group. These findings indicate the efficacy of concomitant use of FGF-2 and {beta}-TCP as an osteoconductive material for periodontal
Beste, Ariana; Buchanan III, A C; Younker, Jarod M
2012-01-01
The biopolymer lignin is a potential source of valuable chemicals. The $\\beta$-5 linkage comprises $\\sim$10\\% of the linkages in lignin. Density Functional Theory (DFT) was used to calculate the $\\alpha$C-O and $\\alpha$C-$\\beta$C bond dissociation enthalpies (BDEs) for $\\beta$-5 models with varied substituents, which are important for understanding initial lignin decomposition. The $\\alpha$C-O ($\\alpha$C-$\\beta$C) BDEs were in the range of 40-44 (57-62) kcal/mol. The products resulting from either homolysis are bi-radicals with multi-determinant character in the singlet electronic state. Multiconfiguration self-consistent field (MCSCF) theory results were used to verify that unrestricted DFT and broken-symmetry DFT were sufficient to study these reactions.
Bes, D. R.; Civitarese, O.
2010-01-15
Theoretical matrix elements, for the ground-state to ground-state two-neutrino double-{beta}-decay mode (2{nu}{beta}{sup -}{beta}{sup -}gs->gs) of {sup 128,130}Te isotopes, are calculated within a formalism that describes interactions between neutrons in a superfluid phase and protons in a normal phase. The elementary degrees of freedom of the model are proton-pair modes and pairs of protons and quasineutrons. The calculation is basically a parameter-free one, because all relevant parameters are fixed from the phenomenology. A comparison with the available experimental data is presented.
Topics in conformal invariance and generalized sigma models
Bernardo, L M
1997-05-01
This thesis consists of two different parts, having in common the fact that in both, conformal invariance plays a central role. In the first part, the author derives conditions for conformal invariance, in the large N limit, and for the existence of an infinite number of commuting classical conserved quantities, in the Generalized Thirring Model. The treatment uses the bosonized version of the model. Two different approaches are used to derive conditions for conformal invariance: the background field method and the Hamiltonian method based on an operator algebra, and the agreement between them is established. The author constructs two infinite sets of non-local conserved charges, by specifying either periodic or open boundary conditions, and he finds the Poisson Bracket algebra satisfied by them. A free field representation of the algebra satisfied by the relevant dynamical variables of the model is also presented, and the structure of the stress tensor in terms of free fields (and free currents) is studied in detail. In the second part, the author proposes a new approach for deriving the string field equations from a general sigma model on the world sheet. This approach leads to an equation which combines some of the attractive features of both the renormalization group method and the covariant beta function treatment of the massless excitations. It has the advantage of being covariant under a very general set of both local and non-local transformations in the field space. The author applies it to the tachyon, massless and first massive level, and shows that the resulting field equations reproduce the correct spectrum of a left-right symmetric closed bosonic string.
Mozar, Anaïs; Lin, Hugo; Williams, Katoura; Chin, Connie; Li, Rosemary; Kondegowda, Nagesha Guthalu; Stewart, Andrew F.; Garcia-Ocaña, Adolfo; Vasavada, Rupangi Chhaya
2016-01-01
Aims/Hypothesis Finding ways to stimulate the regeneration of endogenous pancreatic beta cells is an important goal in the treatment of diabetes. Parathyroid hormone-related protein (PTHrP), the full-length (1–139) and amino-terminal (1–36) peptides, enhance beta cell function, proliferation, and survival. Therefore, we hypothesize that PTHrP(1–36) has the potential to regenerate endogenous beta cells. Methods The partial pancreatectomy (PPx) mouse model of beta cell injury was used to test this hypothesis. Male Balb/c mice underwent either sham-operation or PPx, and were subsequently injected with PTHrP(1–36) (160μg/kg) or vehicle (veh), for 7, 30, or 90 days. The four groups of mice, sham-veh, sham-PTHrP, PPx-veh, and PPx-PTHrP were assessed for PTHrP and receptor expression, and glucose and beta cell homeostasis. Results PTHrP-receptor, but not the ligand, was significantly up-regulated in islets from mice that underwent PPx compared to sham-operated mice. This suggests that exogenous PTHrP could further enhance beta cell regeneration after PPx. PTHrP did not significantly affect body weight, blood glucose, plasma insulin, or insulin sensitivity, in either sham or PPx mice. Glucose tolerance improved in the PPx-PTHrP versus PPx-veh mice only in the early stages of treatment. As hypothesized, there was a significant increase in beta cell proliferation in PPx-PTHrP mice at days 7 and 30; however, this was normalized by day 90, compared to PPx-veh mice. Enhanced beta cell proliferation translated to a marked increase in beta cell mass at day 90, in PPx-PTHrP versus PPx-veh mice. Conclusions PTHrP(1–36) significantly enhances beta cell regeneration through increased beta cell proliferation and beta cell mass after PPx. Future studies will determine the potential of PTHrP to enhance functional beta cell mass in the setting of diabetes. PMID:27391423
A More General Model for the Intrinsic Scatter in Type Ia Supernova Distance Moduli
Marriner, John; Bernstein, J.P.; Kessler, Richard; Lampeitl, Hubert; Miquel, Ramon; Mosher, Jennifer; Nichol, Robert C.; Sako, Masao; Smith, Mathew; /Cape Town U.
2011-07-01
We describe a new formalism to fit the parameters {alpha} and {beta} that are used in the SALT2 model to determine the standard magnitudes of Type Ia supernovae (SNe Ia). The new formalism describes the intrinsic scatter in SNe Ia by a covariance matrix in place of the single parameter normally used. We have applied this formalism to the Sloan Digital Sky Survey Supernova Survey (SDSS-II) data and conclude that the data are best described by {alpha} = 0.135{sup +.033} - .017 and {beta} = 3.19{sup +0.14} - 0.24, where the error is dominated by the uncertainty in the form of the intrinsic scatter matrix. Our result depends on the introduction of a more general form for the intrinsic scatter of the distance moduli of SNe Ia than is conventional, resulting in a larger value of {beta} and a larger uncertainty than the conventional approach. Although this analysis results in a larger value of {beta} and a larger error, the SDSS data differ (at a 98% confidence level) from {beta} = 4.1, the value expected for extinction by the type of dust found in the Milky Way. We have modeled the distribution of SNe Ia in terms of their color and conclude that there is strong evidence that variation in color is a significant contributor to the scatter of SNe Ia around their standard candle magnitude.
General Regression and Representation Model for Classification
Qian, Jianjun; Yang, Jian; Xu, Yong
2014-01-01
Recently, the regularized coding-based classification methods (e.g. SRC and CRC) show a great potential for pattern classification. However, most existing coding methods assume that the representation residuals are uncorrelated. In real-world applications, this assumption does not hold. In this paper, we take account of the correlations of the representation residuals and develop a general regression and representation model (GRR) for classification. GRR not only has advantages of CRC, but also takes full use of the prior information (e.g. the correlations between representation residuals and representation coefficients) and the specific information (weight matrix of image pixels) to enhance the classification performance. GRR uses the generalized Tikhonov regularization and K Nearest Neighbors to learn the prior information from the training data. Meanwhile, the specific information is obtained by using an iterative algorithm to update the feature (or image pixel) weights of the test sample. With the proposed model as a platform, we design two classifiers: basic general regression and representation classifier (B-GRR) and robust general regression and representation classifier (R-GRR). The experimental results demonstrate the performance advantages of proposed methods over state-of-the-art algorithms. PMID:25531882
Generalized Models for Rock Joint Surface Shapes
Du, Shigui; Hu, Yunjin; Hu, Xiaofei
2014-01-01
Generalized models of joint surface shapes are the foundation for mechanism studies on the mechanical effects of rock joint surface shapes. Based on extensive field investigations of rock joint surface shapes, generalized models for three level shapes named macroscopic outline, surface undulating shape, and microcosmic roughness were established through statistical analyses of 20,078 rock joint surface profiles. The relative amplitude of profile curves was used as a borderline for the division of different level shapes. The study results show that the macroscopic outline has three basic features such as planar, arc-shaped, and stepped; the surface undulating shape has three basic features such as planar, undulating, and stepped; and the microcosmic roughness has two basic features such as smooth and rough. PMID:25152901
The Application of Global Kinetic Models to HMX Beta-Delta Transition and Cookoff Processes
Wemhoff, A P; Burnham, A K; Nichols III, A L
2006-12-07
The reduction of the number of reactions in kinetic models for both the HMX beta-delta phase transition and thermal cookoff provides an attractive alternative to traditional multi-stage kinetic models due to reduced calibration effort requirements. In this study, we use the LLNL code ALE3D to provide calibrated kinetic parameters for a two-reaction bidirectional beta-delta HMX phase transition model based on Sandia Instrumented Thermal Ignition (SITI) and Scaled Thermal Explosion (STEX) temperature history curves, and a Prout-Tompkins cookoff model based on One-Dimensional Time to Explosion (ODTX) data. Results show that the two-reaction bidirectional beta-delta transition model presented here agrees as well with STEX and SITI temperature history curves as a reversible four-reaction Arrhenius model, yet requires an order of magnitude less computational effort. In addition, a single-reaction Prout-Tompkins model calibrated to ODTX data provides better agreement with ODTX data than a traditional multi-step Arrhenius model, and can contain up to 90% less chemistry-limited time steps for low-temperature ODTX simulations. Manual calibration methods for the Prout-Tompkins kinetics provide much better agreement with ODTX experimental data than parameters derived from Differential Scanning Calorimetry (DSC) measurements at atmospheric pressure. The predicted surface temperature at explosion for STEX cookoff simulations is a weak function of the cookoff model used, and a reduction of up to 15% of chemistry-limited time steps can be achieved by neglecting the beta-delta transition for this type of simulation. Finally, the inclusion of the beta-delta transition model in the overall kinetics model can affect the predicted time to explosion by 1% for the traditional multi-step Arrhenius approach, while up to 11% using a Prout-Tompkins cookoff model.
The Beta Problem: The Incompatibility of X-ray and Sunyaev-Zeldovich Model Fitting
NASA Astrophysics Data System (ADS)
Burns, Jack O.; Hallman, E.; Motl, P.; Norman, M.
2006-12-01
We describe an analysis of a large sample of numerically simulated clusters which demonstrates the effects of using X-ray fitted beta-model parameters with Sunyaev-Zeldovich effect (SZE) data. There is a fundamental incompatibility between beta-model fits to X-ray surface brightness profiles and those done with SZE profiles. Since observational SZE radial profiles are in short supply, the X-ray parameters are often used in SZE analysis. We show that this leads to biased estimates of the integrated Compton y-parameter inside r500 and the value of the Hubble constant calculated from clusters. We suggest a simple scaling of the X-ray beta-model parameters which brings these calculated quantities into close agreement with the true values.
Study of {beta}-Decay in the Proton-Neutron Interacting Boson-Fermion Model
Zuffi, L.; Brant, S.; Yoshida, N.
2006-04-26
We study {beta}-decay in odd-A nuclei together with the energy levels and other properties in the proton-neutron interacting-boson-fermion model. We also report on the preliminary results in the odd-odd nuclei in the proton-neutron interacting boson-fermion-fermion model.
Modeling the Pion Generalized Parton Distribution
NASA Astrophysics Data System (ADS)
Mezrag, C.
2016-02-01
We compute the pion Generalized Parton Distribution (GPD) in a valence dressed quarks approach. We model the Mellin moments of the GPD using Ansätze for Green functions inspired by the numerical solutions of the Dyson-Schwinger Equations (DSE) and the Bethe-Salpeter Equation (BSE). Then, the GPD is reconstructed from its Mellin moment using the Double Distribution (DD) formalism. The agreement with available experimental data is very good.
Money exchange model and a general outlook
NASA Astrophysics Data System (ADS)
Gupta, Abhijit Kar
2006-01-01
The kinetic gas theory, like the two-agent money exchange model, recently introduced in the econophysics of wealth distributions, is revisited. The emergence of a Boltzmann-Gibbs-like distribution of money into Pareto's law in the tail of the distribution is examined in terms of a 2×2 transition matrix with a general and simplified outlook. Some additional interesting results are also reported.
A general business model for marine reserves.
Sala, Enric; Costello, Christopher; Dougherty, Dawn; Heal, Geoffrey; Kelleher, Kieran; Murray, Jason H; Rosenberg, Andrew A; Sumaila, Rashid
2013-01-01
Marine reserves are an effective tool for protecting biodiversity locally, with potential economic benefits including enhancement of local fisheries, increased tourism, and maintenance of ecosystem services. However, fishing communities often fear short-term income losses associated with closures, and thus may oppose marine reserves. Here we review empirical data and develop bioeconomic models to show that the value of marine reserves (enhanced adjacent fishing + tourism) may often exceed the pre-reserve value, and that economic benefits can offset the costs in as little as five years. These results suggest the need for a new business model for creating and managing reserves, which could pay for themselves and turn a profit for stakeholder groups. Our model could be expanded to include ecosystem services and other benefits, and it provides a general framework to estimate costs and benefits of reserves and to develop such business models. PMID:23573192
A General Business Model for Marine Reserves
Sala, Enric; Costello, Christopher; Dougherty, Dawn; Heal, Geoffrey; Kelleher, Kieran; Murray, Jason H.; Rosenberg, Andrew A.; Sumaila, Rashid
2013-01-01
Marine reserves are an effective tool for protecting biodiversity locally, with potential economic benefits including enhancement of local fisheries, increased tourism, and maintenance of ecosystem services. However, fishing communities often fear short-term income losses associated with closures, and thus may oppose marine reserves. Here we review empirical data and develop bioeconomic models to show that the value of marine reserves (enhanced adjacent fishing + tourism) may often exceed the pre-reserve value, and that economic benefits can offset the costs in as little as five years. These results suggest the need for a new business model for creating and managing reserves, which could pay for themselves and turn a profit for stakeholder groups. Our model could be expanded to include ecosystem services and other benefits, and it provides a general framework to estimate costs and benefits of reserves and to develop such business models. PMID:23573192
Hobolth, Asger; Siren, Jukka
2016-04-01
We consider the diffusion approximation of the multivariate Wright-Fisher process with mutation. Analytically tractable formulas for the first-and second-order moments of the allele frequency distribution are derived, and the moments are subsequently used to better understand key population genetics parameters and modeling frameworks. In particular we investigate the behavior of the expected homozygosity (the probability that two randomly sampled genes are identical) in the transient and stationary phases, and how appropriate the Dirichlet distribution is for modeling the allele frequency distribution at different evolutionary time scales. We find that the Dirichlet distribution is adequate for the pure drift model (no mutations allowed), but the distribution is not sufficiently flexible for more general mutation models. We suggest a new hierarchical Beta distribution for the allele frequencies in the Wright-Fisher process with a mutation model on the nucleotide level that distinguishes between transitions and transversions. PMID:26612605
Formulation and Application of the Generalized Multilevel Facets Model
ERIC Educational Resources Information Center
Wang, Wen-Chung; Liu, Chih-Yu
2007-01-01
In this study, the authors develop a generalized multilevel facets model, which is not only a multilevel and two-parameter generalization of the facets model, but also a multilevel and facet generalization of the generalized partial credit model. Because the new model is formulated within a framework of nonlinear mixed models, no efforts are…
Design of the UCLA general circulation model
NASA Technical Reports Server (NTRS)
Arakawa, A.
1972-01-01
An edited version is reported of notes distributed at the Summer Workshop on the UCLA General Circulation Model in June 1971. It presents the computational schemes of the UCLA model, along with the mathematical and physical principles on which these schemes are based. Included are the finite difference schemes for the governing fluid-dynamical equations, designed to maintain the important integral constraints and dispersion characteristics of the motion. Also given are the principles of parameterization of cumulus convection by an ensemble of identical clouds. A model of the ground hydrology, involving the liquid, ice and snow states of water, is included. A short summary is given of the scheme for computing solar and infrared radiation transfers through clear and cloudy air.
Nasirpour, A; Landillon, V; Cuq, B; Scher, J; Banon, S; Desobry, S
2007-08-01
Handling and storage alter infant food powders due to lactose crystallization and interactions among components. Model infant foods were prepared by colyophilization of lactose, beta-lactoglobulin (beta-LG), and gelatinized starch. A mixture design was used to define the percentage of each mixture component to simulate a wide range of infant food powders. The kinetics of crystallization was studied by a gravimetric method (dynamic vapor sorption) at 70% relative humidity (RH). After freeze-drying, lactose was amorphous and crystallized at 70% RH. The delay before crystallization depends on the contents of beta-LG and starch in the formulations. A mathematical model was proposed to predict crystallization time (delay) at 70% RH. For the formulation containing 50% lactose, 25% beta-LG, and 25% starch, lactose was still amorphous after 42 h at 70% RH, whereas pure amorphous lactose crystallized after approximately 70 min. Calculated and experimental results of adsorbed moisture from the formulations were compared. Adsorbed water of formulation containing lactose could not be calculated from moisture sorption properties of each component at a given RH because beta-LG and gelatinized starch prevented lactose crystal growth. PMID:17638972
He, Xue Ying; Wen, Guang Yeong; Merz, George; Lin, Dawei; Yang, Ying Zi; Mehta, Penkaj; Schulz, Horst; Yang, Song Yu
2002-02-28
A full-length cDNA of mouse type 10 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD10) was cloned from brain, representing the accurate nucleotide sequence information that rendered possible an accurate deduction of the amino acid sequence of the wild-type enzyme. A comparison of sequences and three-dimensional models of this enzyme revealed that structures previously reported by other groups carry either a truncated or mutated amino-terminal sequence. Fusion of the first 11 residues of the wild-type enzyme to the green fluorescent protein directed the reporter protein into mitochondria. Thus, the N-terminus was identified as a mitochondrial targeting signal that accounts for the intracellular localization of the mouse enzyme. This enzyme is normally associated with mitochondria, not with the endoplasmic reticulum as suggested by its trivial name 'endoplasmic reticulum-associated amyloid-beta biding protein (ERAB)'. After its C-terminal region was used to raise rabbit anti-17 betaHSD10 antibodies, immunogold electron microscopy showed that an abundance of this enzyme could be found in hippocampal synaptic mitochondria of betaAPP transgenic mice, but not in normal controls. High levels of this enzyme may disrupt steroid hormone homeostasis in synapses and contribute to synapse loss in the hippocampus of the mouse Alzheimer's disease model. PMID:11869808
Generalized transformation for decorated spin models
NASA Astrophysics Data System (ADS)
Rojas, Onofre; Valverde, J. S.; de Souza, S. M.
2009-04-01
The paper discusses the transformation of decorated Ising models into an effective undecorated spin model, using the most general Hamiltonian for interacting Ising models including a long range and high order interactions. The inverse of a Vandermonde matrix with equidistant nodes [-s,s] is used to obtain an analytical expression of the transformation. This kind of transformation is very useful to obtain the partition function of decorated systems. The method presented by Fisher is also extended, in order to obtain the correlation functions of the decorated Ising models transforming into an effective undecorated Ising model. We apply this transformation to a particular mixed spin-(1/2, 1) and (1/2, 2) square lattice with only nearest site interaction. This model could be transformed into an effective uniform spin- S square lattice with nearest and next-nearest interaction, furthermore the effective Hamiltonian also includes combinations of three-body and four-body interactions; in particular we considered spin 1 and 2.
Generalized Mixture Models for Molecular Phylogenetic Estimation
Evans, Jason; Sullivan, Jack
2012-01-01
The rapidly growing availability of multigene sequence data during the past decade has enabled phylogeny estimation at phylogenomic scales. However, dealing with evolutionary process heterogeneity across the genome becomes increasingly challenging. Here we develop a mixture model approach that uses reversible jump Markov chain Monte Carlo (MCMC) estimation to permit as many distinct models as the data require. Each additional model considered may be a fully parametrized general time-reversible model or any of its special cases. Furthermore, we expand the usual proposal mechanisms for topology changes to permit hard polytomies (i.e., zero-length internal branches). This new approach is implemented in the Crux software toolkit. We demonstrate the feasibility of using reversible jump MCMC on mixture models by reexamining a well-known 44-taxon mammalian data set comprising 22 concatenated genes. We are able to reproduce the results of the original analysis (with respect to bipartition support) when we make identical assumptions, but when we allow for polytomies and/or use data-driven mixture model estimation, we infer much lower bipartition support values for several key bipartitions. PMID:21873377
Generalized Drift-Diffusion Model In Semiconductors
Mesbah, S.; Bendib-Kalache, K.; Bendib, A.
2008-09-23
A new drift-diffusion model is proposed based on the computation of the stationary nonlocal current density. The semi classical Boltzmann equation is solved keeping all the anisotropies of the distribution function with the use of the continued fractions. The conductivity is calculated in the linear approximation and for arbitrary collision frequency with respect to Kv{sub t} where K{sup -1} is the characteristic length scale of the system and V{sub t} is the thermal velocity. The nonlocal conductivity can be used to close the generalized drift-diffusion equations valid for arbitrary collisionality.
A generalized model for compact stars
NASA Astrophysics Data System (ADS)
Aziz, Abdul; Ray, Saibal; Rahaman, Farook
2016-05-01
By virtue of the maximum entropy principle, we get an Euler-Lagrange equation which is a highly nonlinear differential equation containing the mass function and its derivatives. Solving the equation by a homotopy perturbation method we derive a generalized expression for the mass which is a polynomial function of the radial distance. Using the mass function we find a partially stable configuration and its characteristics. We show that different physical features of the known compact stars, viz. Her~X-1, RXJ~1856-37, SAX J ( SS1), SAX J ( SS2), and PSR~J~1614-2230, can be explained by the present model.
General Model for Multicomponent Ablation Thermochemistry
NASA Technical Reports Server (NTRS)
Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)
1994-01-01
A previous paper (AIAA 94-2042) presented equations and numerical procedures for modeling the thermochemical ablation and pyrolysis of thermal protection materials which contain multiple surface species. This work describes modifications and enhancements to the Multicomponent Ablation Thermochemistry (MAT) theory and code for application to the general case which includes surface area constraints, rate limited surface reactions, and non-thermochemical mass loss (failure). Detailed results and comparisons with data are presented for the Shuttle Orbiter reinforced carbon-carbon oxidation protection system which contains a mixture of sodium silicate (Na2SiO3), silica (SiO2), silicon carbide (SiC), and carbon (C).
Snow Hydrology in a General Circulation Model.
NASA Astrophysics Data System (ADS)
Marshall, Susan; Roads, John O.; Glatzmaier, Gary
1994-08-01
A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas.The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snow pack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter.Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.
Snow hydrology in a general circulation model
NASA Technical Reports Server (NTRS)
Marshall, Susan; Roads, John O.; Glatzmaier, Gary
1994-01-01
A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas. The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snowpack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter. Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.
Schmid, Matthias; Wickler, Florian; Maloney, Kelly O.; Mitchell, Richard; Fenske, Nora; Mayr, Andreas
2013-01-01
Regression analysis with a bounded outcome is a common problem in applied statistics. Typical examples include regression models for percentage outcomes and the analysis of ratings that are measured on a bounded scale. In this paper, we consider beta regression, which is a generalization of logit models to situations where the response is continuous on the interval (0,1). Consequently, beta regression is a convenient tool for analyzing percentage responses. The classical approach to fit a beta regression model is to use maximum likelihood estimation with subsequent AIC-based variable selection. As an alternative to this established - yet unstable - approach, we propose a new estimation technique called boosted beta regression. With boosted beta regression estimation and variable selection can be carried out simultaneously in a highly efficient way. Additionally, both the mean and the variance of a percentage response can be modeled using flexible nonlinear covariate effects. As a consequence, the new method accounts for common problems such as overdispersion and non-binomial variance structures. PMID:23626706
Generalized mathematical models in design optimization
NASA Technical Reports Server (NTRS)
Papalambros, Panos Y.; Rao, J. R. Jagannatha
1989-01-01
The theory of optimality conditions of extremal problems can be extended to problems continuously deformed by an input vector. The connection between the sensitivity, well-posedness, stability and approximation of optimization problems is steadily emerging. The authors believe that the important realization here is that the underlying basis of all such work is still the study of point-to-set maps and of small perturbations, yet what has been identified previously as being just related to solution procedures is now being extended to study modeling itself in its own right. Many important studies related to the theoretical issues of parametric programming and large deformation in nonlinear programming have been reported in the last few years, and the challenge now seems to be in devising effective computational tools for solving these generalized design optimization models.
A More General, Quasineutral Plasma Model
NASA Astrophysics Data System (ADS)
Fernsler, Richard
2003-10-01
More than seventy-five years ago, Irving Langmuir proposed a quasineutral plasma model still widely used today. The electrostatic field is derived from the electron density using the Boltzmann approximation, while the electron density is obtained from the ion densities using quasineutrality. However, the Boltzmann approximation is not always valid and has no relationship to quasineutrality. Moreover, the solutions thus obtained are usually singular near the ion sound speed, thus necessitating an additional boundary condition known as the Bohm condition. This condition is difficult to use when multiple ion species are present, is ill posed in kinetic treatments, and does not always apply. In this talk, a more general quasineutral model is presented to circumvent these limitations.
Two-loop beta-functions of the sine-Gordon model
NASA Astrophysics Data System (ADS)
Balog, János; Hegedus, Árpád
2000-09-01
We recalculate the two-loop beta-functions in the two-dimensional sine-Gordon model in a two-parameter expansion around the asymptotically free point. Our results agree with those of Amit et al (Amit D J, Goldschmidt Y Y and Grinstein G 1980 J. Phys. A: Math. Gen. 13 585).
Modeling of turbulent supersonic H2-air combustion with a multivariate beta PDF
NASA Technical Reports Server (NTRS)
Baurle, R. A.; Hassan, H. A.
1993-01-01
Recent calculations of turbulent supersonic reacting shear flows using an assumed multivariate beta PDF (probability density function) resulted in reduced production rates and a delay in the onset of combustion. This result is not consistent with available measurements. The present research explores two possible reasons for this behavior: use of PDF's that do not yield Favre averaged quantities, and the gradient diffusion assumption. A new multivariate beta PDF involving species densities is introduced which makes it possible to compute Favre averaged mass fractions. However, using this PDF did not improve comparisons with experiment. A countergradient diffusion model is then introduced. Preliminary calculations suggest this to be the cause of the discrepancy.
Sorption of agrochemical model compounds by sorbent materials containing beta-cyclodextrin.
Wilson, Lee D; Mohamed, Mohamed H; Guo, Rui; Pratt, Dawn Y; Kwon, Jae Hyuck; Mahmud, Sarker T
2010-04-01
Polymeric sorbent materials that incorporate beta-cyclodextrin (CD) have been prepared and their sorption behavior toward two model agrochemical contaminant compounds, p-nitrophenol (PNP) and methyl chloride examined. The sorption of PNP was studied in aqueous solution using ultraviolet-visible (UV-Vis) spectroscopy, whereas the sorption of methyl chloride from the gas phase was studied using a Langmuir adsorption method. The sorption results for PNP in solution were compared between granular activated carbon (GAC), modified GAC, CD copolymers, and CD-based mesoporous silica hybrid materials. Nitrogen porosimetry at 77 K was used to estimate the surface area and pore structure properties of the sorbent materials. The sorbents displayed variable surface areas as follows: copolymers (36.2-157 m(2)/g), CD-silica materials (307-906 m(2)/g), surface modified GAC (657 m(2)/g), and granular activated carbon (approximately 10(3) m(2)/g). The sorption capacities for PNP and methyl chloride with the different sorbents are listed in descending order as follows: GAC > copolymers > surface modified GAC > CD-silica hybrid materials. In general, the differences in the sorption properties of the sorbents were related to the following: (i) surface area of the sorbent, (ii) CD content and accessibility, (iii) and the chemical nature of the sorbent material. PMID:20407992
Modeling global lightning distributions in a general circulation model
NASA Technical Reports Server (NTRS)
Price, Colin; Rind, David
1994-01-01
A general circulation model (GCM) is used to model global lightning distributions and frequencies. Both total and cloud-to-ground lightning frequencies are modeled using parameterizations that relate the depth of convective clouds to lightning frequencies. The model's simulations of lightning distributions in time and space show good agreement with available observations. The model's annual mean climatology shows a global lightning frequency of 77 flashes per second, with cloud-to-ground lightning making up 25% of the total. The maximum lightning activity in the GCM occurs during the Northern Hemisphere summer, with approximately 91% of all lightning occurring over continental and coastal regions.
Generalized Chen-Wu type cosmological model
NASA Astrophysics Data System (ADS)
John, Moncy V.; Joseph, K. Babu
2000-04-01
Recent measurements require modifications in conventional cosmology by way of introducing components other than ordinary matter into the total energy density in the universe. On the basis of some dimensional considerations in line with quantum cosmology, Chen and Wu [W. Chen and Y. Wu, Phys. Rev. D 41, 695 (1990)] have argued that an additional component, which corresponds to an effective cosmological constant Λ, must vary as a-2 in the classical era. Their decaying-Λ model assumes inflation and yields a value for q0, which is not compatible with observations. We generalize this model by arguing that the Chen-Wu ansatz is applicable to the total energy density of the universe and not to Λ alone. The resulting model, which has a coasting evolution (i.e., a~t), is devoid of the problems of horizon, flatness, monopole, cosmological constant, size, age and generation of density perturbations. However, to avoid serious contradictions with big bang nucleosynthesis, the model has to make the predictions Ωm=4/3 and ΩΛ=2/3, which in turn are at variance with current observational values.
Generalization ability of fractional polynomial models.
Lei, Yunwen; Ding, Lixin; Ding, Yiming
2014-01-01
In this paper, the problem of learning the functional dependency between input and output variables from scattered data using fractional polynomial models (FPM) is investigated. The estimation error bounds are obtained by calculating the pseudo-dimension of FPM, which is shown to be equal to that of sparse polynomial models (SPM). A linear decay of the approximation error is obtained for a class of target functions which are dense in the space of continuous functions. We derive a structural risk analogous to the Schwartz Criterion and demonstrate theoretically that the model minimizing this structural risk can achieve a favorable balance between estimation and approximation errors. An empirical model selection comparison is also performed to justify the usage of this structural risk in selecting the optimal complexity index from the data. We show that the construction of FPM can be efficiently addressed by the variable projection method. Furthermore, our empirical study implies that FPM could attain better generalization performance when compared with SPM and cubic splines. PMID:24140985
MSCALE: A General Utility for Multiscale Modeling
Woodcock, H. Lee; Miller, Benjamin T.; Hodoscek, Milan; Okur, Asim; Larkin, Joseph D.; Ponder, Jay W.; Brooks, Bernard R.
2011-01-01
The combination of theoretical models of macromolecules that exist at different spatial and temporal scales has become increasingly important for addressing complex biochemical problems. This work describes the extension of concurrent multiscale approaches, introduces a general framework for carrying out calculations, and describes its implementation into the CHARMM macromolecular modeling package. This functionality, termed MSCALE, generalizes both the additive and subtractive multiscale scheme (e.g. QM/MM ONIOM-type), and extends its support to classical force fields, coarse grained modeling (e.g. ENM, GNM, etc.), and a mixture of them all. The MSCALE scheme is completely parallelized with each subsystem running as an independent, but connected calculation. One of the most attractive features of MSCALE is the relative ease of implementation using the standard MPI communication protocol. This allows external access to the framework and facilitates the combination of functionality previously isolated in separate programs. This new facility is fully integrated with free energy perturbation methods, Hessian based methods, and the use of periodicity and symmetry, which allows the calculation of accurate pressures. We demonstrate the utility of this new technique with four examples; (1) subtractive QM/MM and QM/QM calculations; (2) multi-force field alchemical free energy perturbation; (3) integration with the SANDER module of AMBER and the TINKER package to gain access to potentials not available in CHARMM; and (4) mixed resolution (i.e. coarse grain / all-atom) normal mode analysis. The potential of this new tool is clearly established and in conclusion an interesting mathematical problem is highlighted and future improvements are proposed. PMID:21691425
Pelmont, J; Barrelle, M; Hauteville, M; Gamba, D; Romdhane, M; Dardas, A; Beguin, C
1985-09-01
A lignin model compound, named in short guaiagylglycerol beta-guaiacyl ether (GGE), contains the beta-0-4 ether linkage that is common in the chemical structure of lignin. A Pseudomonas sp. (GU5) had been isolated as an organism able to grow with GGE as the sole source of carbon and energy. When grown on vanillate, the bacteria contained a NAD+ -dependent dehydrogenase converting GGE to a 355 nm absorbing product. The enzyme, named GGE-dehydrogenase, was purified about 160-fold using gel permeation, ion exchange on DEAE-Sephadex, and dye-ligand affinity chromatography. The new protein was about 52 kDa in apparent size with but one polypeptide chain after denaturation and reduction. According to several criteria, the product of GGE oxidation (Km = 12 microM) was identified as the corresponding conjugated ketone at the alpha-carbon of the C3 side-chain. The secondary alcohol function in GGE was apparently the sole target of the enzyme action. However the conversion of GGE into ketone catalyzed by the enzyme was only partial, and did not exceed 50%, probably because only one of the alpha-enantiomers was susceptible to enzyme attack. In contrast the ketone, either made by organic synthesis or by enzymic oxidation of GGE, could be totally reduced back to GGE (Km = 13 microM at pH 8.4, 8 microM at neutral pH), with NADH as the reductant, as confirmed by UV absorption and NMR spectra. Other model compounds with no primary alcoholic function, ether linkage or phenolic group were also substrates for the enzyme, confirming the specificity of GGE-dehydrogenase for the alpha-carbon position. Conjugation of the alpha-ketone with an adjacent phenolic nucleus interfered strongly with equilibrium constants and redox potentials of the system according to pH, and the enzyme displayed widely different optima with pH over 9 when oxidizing GGE, below 7 when reducing the ketone. Equilibrium studies showed that the ketone/GGE potential was -0.37 volt at pH 8.7, -0.23 volt at pH 7 (30
Neutrinoless double beta decay in type I+II seesaw models
NASA Astrophysics Data System (ADS)
Borah, Debasish; Dasgupta, Arnab
2015-11-01
We study neutrinoless double beta decay in left-right symmetric extension of the standard model with type I and type II seesaw origin of neutrino masses. Due to the enhanced gauge symmetry as well as extended scalar sector, there are several new physics sources of neutrinoless double beta decay in this model. Ignoring the left-right gauge boson mixing and heavy-light neutrino mixing, we first compute the contributions to neutrinoless double beta decay for type I and type II dominant seesaw separately and compare with the standard light neutrino contributions. We then repeat the exercise by considering the presence of both type I and type II seesaw, having non-negligible contributions to light neutrino masses and show the difference in results from individual seesaw cases. Assuming the new gauge bosons and scalars to be around a TeV, we constrain different parameters of the model including both heavy and light neutrino masses from the requirement of keeping the new physics contribution to neutrinoless double beta decay amplitude below the upper limit set by the GERDA experiment and also satisfying bounds from lepton flavor violation, cosmology and colliders.
Ocean general circulation models for parallel architectures
Smith, R.D.
1993-05-01
The authors report continuing work in developing ocean general circulation models for parallel architectures. In earlier work, they began with the widely-used Bryan-Cox ocean model, but reformulated the barotropic equations (which describe the vertically integrated flow) to solve for the surface-pressure field rather than the volume-transport streamfunction as in the original model. This had the advantage of being more easily parallelized and allowed for a more realistic representation of coastal and bottom topography. Both streamfunction and surface-pressure formulations use a rigid-lid approximation to eliminate fast surface waves. They have now replaced the rigid-lid with a free surface, and solve the barotropic equations implicitly to overcome the timestep restriction associated with the fast waves. This method has several advantages, including: (1) a better physical representation of the barotropic mode, and (2) a better-conditioned operator matrix, which leads to much faster convergence in the conjugate-gradient solver. They have also extended the model to allow use of arbitrary orthogonal curvilinear coordinates for the horizontal grid. The original model uses a standard polar grid that has a singularity at each pole, making it difficult to include the Arctic basin, which plays an important role in global ocean circulation. They can now include the Arctic (while still using an explicit time-integration scheme without high-latitude filtering) by using a distorted grid with a displaced pole for the North Atlantic - Arctic region of the ocean. The computer code, written in Fortran 90 and developed on the Connection Machine, has been substantially restructured so that all communication occurs in low-level stencil routines. The idea is that the stencil routines may be rewritten to optimize communication costs on a particular architecture, while the remainder of the code is for the most part machine-independent, involving only the simplest Fortran 90 constructs.
GPU Developments for General Circulation Models
NASA Astrophysics Data System (ADS)
Appleyard, Jeremy; Posey, Stan; Ponder, Carl; Eaton, Joe
2014-05-01
Current trends in high performance computing (HPC) are moving towards the use of graphics processing units (GPUs) to achieve speedups through the extraction of fine-grain parallelism of application software. GPUs have been developed exclusively for computational tasks as massively-parallel co-processors to the CPU, and during 2013 an extensive set of new HPC architectural features were developed in a 4th generation of NVIDIA GPUs that provide further opportunities for GPU acceleration of general circulation models used in climate science and numerical weather prediction. Today computational efficiency and simulation turnaround time continue to be important factors behind scientific decisions to develop models at higher resolutions and deploy increased use of ensembles. This presentation will examine the current state of GPU parallel developments for stencil based numerical operations typical of dynamical cores, and introduce new GPU-based implicit iterative schemes with GPU parallel preconditioning and linear solvers based on ILU, Krylov methods, and multigrid. Several GCMs show substantial gain in parallel efficiency from second-level fine-grain parallelism under first-level distributed memory parallel through a hybrid parallel implementation. Examples are provided relevant to science-scale HPC practice of CPU-GPU system configurations based on model resolution requirements of a particular simulation. Performance results compare use of the latest conventional CPUs with and without GPU acceleration. Finally a forward looking discussion is provided on the roadmap of GPU hardware, software, tools, and programmability for GCM development.
Generalized Measure of Entropy, Mathai's Distributional Pathway Model, and Tsallis Statistics
NASA Astrophysics Data System (ADS)
Mathai, A. M.; Haubold, H. J.
2006-11-01
mathai@math.mcgill.ca The well-known pathway model of Mathai (2005) mainly deals with the rectangular matrix-variate case. In this paper the scalar version is shown to be associated with a large number of probability models used in physics. Different families of densities are discussed, which are all connected through the pathway parameter α, generating a distributional pathway. The idea is to switch from one functional form to another through this parameter and it is shown that basically one can proceed from the generalized type-1 beta family to generalized type-2 beta family to generalized gamma family when the real variable is positive and a wider set of families when the variable can take negative values also. For simplicity, only the real scalar case is discussed here but corresponding families are available when the variable is in the complex domain. A large number of densities used in physics are shown to be special cases of or associated with the pathway model, including Maxwell-Boltzmann, Fermi-Dirac, and Bose- Einstein distributions. It is also shown that the pathway model is available by maximizing a generalized measure of entropy, leading to an entropic pathway. Particular cases of the pathway model are shown to cover Tsallis statistics (Tsallis, 1988) and the superstatistics introduced by Beck and Cohen (2003).
Spatiotemporal representation of 3D hand trajectory based on beta-elliptic models.
Boubaker, Houcine; Rezzoug, Nasser; Kherallah, Monji; Gorce, Philippe; Alimi, Adel M
2015-01-01
The aim of this paper was to model the hand trajectory during grasping by an extension in 3D of the 2D written language beta-elliptic model. The interest of this model is that it takes into account both geometric and velocity information. The method relies on the decomposition of the task space trajectories in elementary bricks. The latter is characterized by a velocity profile modelled with beta functions and a geometry modelled with elliptic shapes. A data base of grasping movements has been constructed and the errors of reconstruction were assessed (distance and curvature) considering two variations of the beta-elliptic model ('quarter ellipse' and 'two tangents points' method). The results showed that the method based on two tangent points outperforms the quarter ellipse method with average and maximum relative errors of 2.73% and 8.62%, respectively, and a maximum curvature error of 9.26% for the former. This modelling approach can find interesting application to characterize the improvement due to a rehabilitation or teaching process by a quantitative measurement of hand trajectory parameters. PMID:25199025
A Simple General Model of Evolutionary Dynamics
NASA Astrophysics Data System (ADS)
Thurner, Stefan
Evolution is a process in which some variations that emerge within a population (of, e.g., biological species or industrial goods) get selected, survive, and proliferate, whereas others vanish. Survival probability, proliferation, or production rates are associated with the "fitness" of a particular variation. We argue that the notion of fitness is an a posteriori concept in the sense that one can assign higher fitness to species or goods that survive but one can generally not derive or predict fitness per se. Whereas proliferation rates can be measured, fitness landscapes, that is, the inter-dependence of proliferation rates, cannot. For this reason we think that in a physical theory of evolution such notions should be avoided. Here we review a recent quantitative formulation of evolutionary dynamics that provides a framework for the co-evolution of species and their fitness landscapes (Thurner et al., 2010, Physica A 389, 747; Thurner et al., 2010, New J. Phys. 12, 075029; Klimek et al., 2009, Phys. Rev. E 82, 011901 (2010). The corresponding model leads to a generic evolutionary dynamics characterized by phases of relative stability in terms of diversity, followed by phases of massive restructuring. These dynamical modes can be interpreted as punctuated equilibria in biology, or Schumpeterian business cycles (Schumpeter, 1939, Business Cycles, McGraw-Hill, London) in economics. We show that phase transitions that separate phases of high and low diversity can be approximated surprisingly well by mean-field methods. We demonstrate that the mathematical framework is suited to understand systemic properties of evolutionary systems, such as their proneness to collapse, or their potential for diversification. The framework suggests that evolutionary processes are naturally linked to self-organized criticality and to properties of production matrices, such as their eigenvalue spectra. Even though the model is phrased in general terms it is also practical in the sense
NASA Astrophysics Data System (ADS)
Khosravi Tanak, A.; Mohtashami Borzadaran, G. R.; Ahmadi, J.
2015-11-01
In economics and social sciences, the inequality measures such as Gini index, Pietra index etc., are commonly used to measure the statistical dispersion. There is a generalization of Gini index which includes it as special case. In this paper, we use principle of maximum entropy to approximate the model of income distribution with a given mean and generalized Gini index. Many distributions have been used as descriptive models for the distribution of income. The most widely known of these models are the generalized beta of second kind and its subclass distributions. The obtained maximum entropy distributions are fitted to the US family total money income in 2009, 2011 and 2013 and their relative performances with respect to generalized beta of second kind family are compared.
A Beta Item Response Model for Continuous Bounded Responses
ERIC Educational Resources Information Center
Noel, Yvonnick; Dauvier, Bruno
2007-01-01
An item response model is proposed for the analysis of continuous response formats in an item response theory (IRT) framework. With such formats, respondents are asked to report their response as a mark on a fixed-length graphical segment whose ends are labeled with extreme responses. An interpolation process is proposed as the response mechanism…
Jupiter Thermospheric General Circulation Model (jtgcm)
NASA Astrophysics Data System (ADS)
Majeed, T.; Waite, J. H.; Bougher, S. W.; Gladstone, G. R.
Recent observations of infrared and FUV auroral emissions from Jupiter have shown the presence of high-speed (> 2km/s) winds in the jovian thermosphere. The Galileo probe measurements of the altitude profile of equatorial temperature exhibit wave-like oscillations at all altitudes from 1029 to 133 km above the 1-bar level. A number of recent studies interpret these oscillations as being due to upward propagating gravity waves. The transport of significant auroral energy and species to equatorial latitudes by the thermospheric winds has also been proposed to explain the measured temper- ature structure observed by the Galileo probe. We examine this hypothesis using a fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) that has been developed and exercised to address global scale temperature, wind, and neutral-ion specie distributions. It was developed from a suitable adaptation of the NCAR Ther- mosphere Ionosphere General Circulation Model (TIGCM). New code was developed to parameterize the estimated auroral and equatorial heating and ionization distribu- tions learned from Galileo, HST, ROSAT, and Voyager data. Asymmetric auroral ovals are specified separately for the north and south poles. The lower boundary is set at 20 µb in order to capture the bulk of the hydrocarbon cooling due to C2H2 and CH4 at the base of the thermosphere. The upper boundary is set at 10-4 nb, sufficiently high enough to capture most auroral heating processes and winds. An ion-drag scheme is incorporated based on the formulation described by Roble and Ridley [1987]. A con- vection electric field is estimated and corresponding ion drifts are generated using the formulation of Evitar and Barbosa [1984]. These prescriptions provide a means to test the general impact of ion drag and Joule heating on the JTGCM neutral winds. The JTGCM has been fully spun-up (closely approaching steady state) and exercised for various cases to simulate 3-component neutral winds, and corresponding
Detecting contaminated birthdates using generalized additive models
2014-01-01
Background Erroneous patient birthdates are common in health databases. Detection of these errors usually involves manual verification, which can be resource intensive and impractical. By identifying a frequent manifestation of birthdate errors, this paper presents a principled and statistically driven procedure to identify erroneous patient birthdates. Results Generalized additive models (GAM) enabled explicit incorporation of known demographic trends and birth patterns. With false positive rates controlled, the method identified birthdate contamination with high accuracy. In the health data set used, of the 58 actual incorrect birthdates manually identified by the domain expert, the GAM-based method identified 51, with 8 false positives (resulting in a positive predictive value of 86.0% (51/59) and a false negative rate of 12.0% (7/58)). These results outperformed linear time-series models. Conclusions The GAM-based method is an effective approach to identify systemic birthdate errors, a common data quality issue in both clinical and administrative databases, with high accuracy. PMID:24923281
Lightning Climatology with a Generalized Additive Model
NASA Astrophysics Data System (ADS)
Simon, Thorsten; Mayr, Georg; Umlauf, Nikolaus; Zeileis, Achim
2016-04-01
This study present a lightning climatology on a 1km x 1km grid estimated via generalized additive models (GAM). GAMs provide a framework to account for non-linear effects in time and space and for non-linear spatial-temporal interaction terms simultaneously. The degrees of smoothness of the non-linear effects is selected automatically in our approach. Furthermore, the influence of topography is captured in the model by including a non-linear term. To illustrate our approach we use lightning data from the ALDIS networks and selected a region in Southeastern Austria, where complex terrain extends from 200 an 3800 m asl and summertime lightning activity is high compared to other parts of the Eastern Alps. The temporal effect in the GAM shows a rapid increase in lightning activity in early July and a slow decay in activity afterwards. The estimated spatial effect is not very smooth and requires approximately 225 effective degrees of freedom. It reveals that lightning is more likely in the Eastern and Southern part of the region of interest. This spatial effect only accounts for variability not already explained by the topography. The topography effect shows lightning to be more likely at higher altitudes. The effect describing the spatio-temporal interactions takes approximately 200 degrees of freedom, and reveals local deviations of the climatology.
Generalized Reduced Order Modeling of Aeroservoelastic Systems
NASA Astrophysics Data System (ADS)
Gariffo, James Michael
Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well as moving shock waves, can only be captured through high-fidelity CFD analysis. With modern computing power, it is realtively straightforward to determine the flutter boundary for a single structural configuration at a single flight condition, but problems of larger scope remain quite costly. Some such problems include characterizing a vehicle's flutter boundary over its full flight envelope, optimizing its structural weight subject to aeroelastic constraints, and designing control laws for flutter suppression. For all of these applications, reduced-order models (ROMs) offer substantial computational savings. ROM techniques in general have existed for decades, and the methodology presented in this dissertation builds on successful previous techniques to create a powerful new scheme for modeling aeroelastic systems, and predicting and interpolating their transonic flutter boundaries. In this method, linear ASE state-space models are constructed from modal structural and actuator models coupled to state-space models of the linearized aerodynamic forces through feedback loops. Flutter predictions can be made from these models through simple eigenvalue analysis of their state-transition matrices for an appropriate set of dynamic pressures. Moreover, this analysis returns the frequency and damping trend of every aeroelastic branch. In contrast, determining the critical dynamic pressure by direct time-marching CFD requires a separate run for every dynamic pressure being analyzed simply to obtain the trend for the critical branch. The present ROM methodology also includes a new model interpolation technique that greatly enhances the benefits of these ROMs. This enables predictions of the dynamic behavior of the system for flight conditions where CFD analysis has not been explicitly
Remote Sensing of Alpha and Beta Sources - Modeling Summary
Dignon, J; Frank, M; Cherepy, N
2005-10-20
Evaluating the potential for optical detection of the products of interactions of energetic electrons or other particles with the background atmosphere depends on predictions of change in atmospheric concentrations of species which would generate detectable spectral signals within the range of observation. The solar blind region of the spectrum, in the ultra violet, would be the logical band for outdoor detection (see Figure 1). The chemistry relevant to these processes is composed of ion-molecule reactions involving the initially created N{sub 2}{sup +} and O{sub 2}{sup +} ions, and their subsequent interactions with ambient trace atmospheric constituents. Effective modeling of the atmospheric chemical system acted upon by energetic particles requires knowledge of the dominant mechanism that exchange charge and associate it with atmospheric constituents, kinetic parameters of the individual processes (see e.g. Brasseur and Solomon, 1995), and a solver for the coupled differential equations that is accurate for the very stiff set of time constants involved. The LLNL box model, VOLVO, simulates the diel cycle of trace constituent photochemistry for any point on the globe over the wide range of time scales present using a stiff Gear-type ODE solver, i.e. LSODE. It has been applied to problems such as tropospheric and stratospheric nitrogen oxides, stratospheric ozone production and loss, and tropospheric hydrocarbon oxidation. For this study we have included the appropriate ion flux.
Wade, Cian; Brown, Peter
2016-01-01
Beta oscillations are a dominant feature of the sensorimotor system. A transient and prominent increase in beta oscillations is consistently observed across the sensorimotor cortical-basal ganglia network after cessation of voluntary movement: the post-movement beta synchronization (PMBS). Current theories about the function of the PMBS have been focused on either the closure of motor response or the processing of sensory afferance. Computational models of sensorimotor control have emphasized the importance of the integration between feedforward estimation and sensory feedback, and therefore the putative motor and sensory functions of beta oscillations may reciprocally interact with each other and in fact be indissociable. Here we show that the amplitude of sensorimotor PMBS is modulated by the history of visual feedback of task-relevant errors, and negatively correlated with the trial-to-trial exploratory adjustment in a sensorimotor adaptation task in young healthy human subjects. The PMBS also negatively correlated with the uncertainty associated with the feedforward estimation, which was recursively updated in light of new sensory feedback, as identified by a Bayesian learning model. These results reconcile the two opposing motor and sensory views of the function of PMBS, and suggest a unifying theory in which PMBS indexes the confidence in internal feedforward estimation in Bayesian sensorimotor integration. Its amplitude simultaneously reflects cortical sensory processing and signals the need for maintenance or adaptation of the motor output, and if necessary, exploration to identify an altered sensorimotor transformation. SIGNIFICANCE STATEMENT For optimal sensorimotor control, sensory feedback and feedforward estimation of a movement's sensory consequences should be weighted by the inverse of their corresponding uncertainties, which require recursive updating in a dynamic environment. We show that post-movement beta activity (13–30 Hz) over sensorimotor
Sakurai, A.; Takeda, K.; Ain, K.; Ceccarelli, P.; Nakai, A.; Seino, S.; Bell, G.I.; Refetoff, S.; DeGroot, L.J. )
1989-11-01
The syndrome of generalized resistance to thyroid hormone is characterized by elevated circulating levels of thyroid hormone in the presence of an overall eumetabolic state and failure to respond normally to triiodothyronine. The authors have evaluated a family with inherited generalized resistance to thyroid hormone for abnormalities in the thyroid hormone nuclear receptors. A single guanine {yields} cytosine replacement in the codon for amino acid 340 resulted in a glycine {yields} arginine substitution in the hormone-binding domain of one of two alleles of the patient's thyroid hormone nuclear receptor {beta} gene. In vitro translation products of this mutant human thyroid hormone nuclear receptor {beta} gene did not bind triiodothyronine. Thus, generalized resistance to thyroid hormone can result from expression of an abnormal thyroid hormone nuclear receptor molecule.
NASA Astrophysics Data System (ADS)
Rudy, Ashley C. A.; Lamoureux, Scott F.; Treitz, Paul; van Ewijk, Karin Y.
2016-07-01
To effectively assess and mitigate risk of permafrost disturbance, disturbance-prone areas can be predicted through the application of susceptibility models. In this study we developed regional susceptibility models for permafrost disturbances using a field disturbance inventory to test the transferability of the model to a broader region in the Canadian High Arctic. Resulting maps of susceptibility were then used to explore the effect of terrain variables on the occurrence of disturbances within this region. To account for a large range of landscape characteristics, the model was calibrated using two locations: Sabine Peninsula, Melville Island, NU, and Fosheim Peninsula, Ellesmere Island, NU. Spatial patterns of disturbance were predicted with a generalized linear model (GLM) and generalized additive model (GAM), each calibrated using disturbed and randomized undisturbed locations from both locations and GIS-derived terrain predictor variables including slope, potential incoming solar radiation, wetness index, topographic position index, elevation, and distance to water. Each model was validated for the Sabine and Fosheim Peninsulas using independent data sets while the transferability of the model to an independent site was assessed at Cape Bounty, Melville Island, NU. The regional GLM and GAM validated well for both calibration sites (Sabine and Fosheim) with the area under the receiver operating curves (AUROC) > 0.79. Both models were applied directly to Cape Bounty without calibration and validated equally with AUROC's of 0.76; however, each model predicted disturbed and undisturbed samples differently. Additionally, the sensitivity of the transferred model was assessed using data sets with different sample sizes. Results indicated that models based on larger sample sizes transferred more consistently and captured the variability within the terrain attributes in the respective study areas. Terrain attributes associated with the initiation of disturbances were
Modeling beta-adrenergic control of cardiac myocyte contractility in silico
NASA Technical Reports Server (NTRS)
Saucerman, Jeffrey J.; Brunton, Laurence L.; Michailova, Anushka P.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)
2003-01-01
The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.
Beta-cryptoxanthin as a source of vitamin A.
Burri, Betty J
2015-07-01
Beta-cryptoxanthin is a common carotenoid that is found in fruit, and in human blood and tissues. Foods that are rich in beta-cryptoxanthin include tangerines, persimmons and oranges. Beta-cryptoxanthin has several functions that are important for human health, including roles in antioxidant defense and cell-to-cell communication. Most importantly, beta-cryptoxanthin is a precursor of vitamin A, which is an essential nutrient needed for eyesight, growth, development and immune response. We evaluate the evidence for beta-cryptoxanthin as a vitamin A-forming carotenoid in this paper. Observational, in vitro, animal model and human studies suggest that beta-cryptoxanthin has greater bioavailability from its common food sources than do alpha- and beta-carotene from theirs. Although beta-cryptoxanthin appears to be a poorer substrate for beta-carotene 15,15' oxygenase than is beta-carotene, animal model and human studies suggest that the comparatively high bioavailability of beta-cryptoxanthin from foods makes beta-cryptoxanthin-rich foods equivalent to beta-carotene-rich foods as sources of vitamin A. These results mean that beta-cryptoxanthin-rich foods are probably better sources of vitamin A, and more important for human health in general, than previously assumed. PMID:25270992
Bali, Moez; Jansen, Michaela; Akabas, Myles H
2009-03-11
The molecular basis of general anesthetic interactions with GABA(A) receptors is uncertain. An accurate homology model would facilitate studies of anesthetic action. Construction of a GABA(A) model based on the 4 A resolution acetylcholine receptor structure is complicated by alignment uncertainty between the acetylcholine and GABA(A) receptor M3 and M4 transmembrane segments. Using disulfide crosslinking we previously established the orientation of M2 and M3 within a single GABA(A) subunit. The resultant model predicts that the betaM3 residue beta2M286, implicated in anesthetic binding, faces the adjacent alpha1-M1 segment and not into the beta2 subunit interior as some models have suggested. To assess the proximity of beta2M286 to the alpha1-M1 segment we expressed beta2M286C and gamma2 with 10 consecutive alpha1-M1 cysteine (Cys) mutants, alpha1I223C to alpha1L232C, in and flanking the extracellular end of alpha1-M1. In activated states, beta2M286C formed disulfide bonds with alpha1Y225C and alpha1Q229C based on electrophysiological assays and dimers on Western blots, but not with other alpha1-M1 mutants. beta2F289, one helical turn below beta2M286, formed disulfide bonds with alpha1I228C, alpha1Q229C and alpha1L232C in activated states. The intervening residues, beta2G287C and beta2C288, did not form disulfide bonds with alpha1-M1 Cys mutants. We conclude that the beta2-M3 residues beta2M286 and beta2F289 face the intersubunit interface in close proximity to alpha1-M1 and that channel gating induces a structural rearrangement in the transmembrane subunit interface that reduces the betaM3 to alphaM1 separation by approximately 7 A. This supports the hypothesis that some intravenous anesthetics bind in the betaM3-alphaM1 subunit interface consistent with azi-etomidate photoaffinity labeling. PMID:19279245
Infrared spectroscopy of pyrrole-2-carboxaldehyde and its dimer: a planar beta-sheet peptide model?
Rice, Corey A; Dauster, Ingo; Suhm, Martin A
2007-04-01
Intermolecular interactions relevant for antiparallel beta-sheet formation between peptide strands are studied by Fourier transform infrared spectroscopy of the low temperature, vacuum-isolated model compound pyrrole-2-carboxaldehyde and its dimer in the N-H and C=O stretching range. Comparison to quantum chemical predictions shows that even for some triple-zeta quality basis sets, hybrid density functionals and Møller-Plesset perturbation calculations fail to provide a consistent and fully satisfactory description of hydrogen bond induced frequency shifts and intensity ratios in the double-harmonic approximation. The latter approach even shows problems in reproducing the planar structure of the dimer and the correct sign of the C=O stretching shift for standard basis sets. The effect of matrix isolation is modeled by condensing layers of Ar atoms on the isolated monomer and dimer. The dimer structure is discussed in the context of the peptide beta-sheet motif. PMID:17430038
Building Restoration Operations Optimization Model Beta Version 1.0
2007-05-31
The Building Restoration Operations Optimization Model (BROOM), developed by Sandia National Laboratories, is a software product designed to aid in the restoration of large facilities contaminated by a biological material. BROOMs integrated data collection, data management, and visualization software improves the efficiency of cleanup operations, minimizes facility downtime, and provides a transparent basis for reopening the facility. Secure remote access to building floor plans Floor plan drawings and knowledge of the HVAC system are critical to the design and implementation of effective sampling plans. In large facilities, access to these data may be complicated by the sheer abundance and disorganized state they are often stored in. BROOM avoids potentially costly delays by providing a means of organizing and storing mechanical and floor plan drawings in a secure remote database that is easily accessed. Sampling design tools BROOM provides an array of tools to answer the question of where to sample and how many samples to take. In addition to simple judgmental and random sampling plans, the software includes two sophisticated methods of adaptively developing a sampling strategy. Both tools strive to choose sampling locations that best satisfy a specified objective (i.e. minimizing kriging variance) but use numerically different strategies to do so. Surface samples are collected early in the restoration process to characterize the extent of contamination and then again later to verify that the facility is safe to reenter. BROOM supports sample collection using a ruggedized PDA equipped with a barcode scanner and laser range finder. The PDA displays building floor drawings, sampling plans, and electronic forms for data entry. Barcodes are placed on sample containers for the purpose of tracking the specimen and linking acquisition data (i.e. location, surface type, texture) to laboratory results. Sample location is determined by activating the integrated laser
Building Restoration Operations Optimization Model Beta Version 1.0
Energy Science and Technology Software Center (ESTSC)
2007-05-31
The Building Restoration Operations Optimization Model (BROOM), developed by Sandia National Laboratories, is a software product designed to aid in the restoration of large facilities contaminated by a biological material. BROOMs integrated data collection, data management, and visualization software improves the efficiency of cleanup operations, minimizes facility downtime, and provides a transparent basis for reopening the facility. Secure remote access to building floor plans Floor plan drawings and knowledge of the HVAC system are criticalmore » to the design and implementation of effective sampling plans. In large facilities, access to these data may be complicated by the sheer abundance and disorganized state they are often stored in. BROOM avoids potentially costly delays by providing a means of organizing and storing mechanical and floor plan drawings in a secure remote database that is easily accessed. Sampling design tools BROOM provides an array of tools to answer the question of where to sample and how many samples to take. In addition to simple judgmental and random sampling plans, the software includes two sophisticated methods of adaptively developing a sampling strategy. Both tools strive to choose sampling locations that best satisfy a specified objective (i.e. minimizing kriging variance) but use numerically different strategies to do so. Surface samples are collected early in the restoration process to characterize the extent of contamination and then again later to verify that the facility is safe to reenter. BROOM supports sample collection using a ruggedized PDA equipped with a barcode scanner and laser range finder. The PDA displays building floor drawings, sampling plans, and electronic forms for data entry. Barcodes are placed on sample containers for the purpose of tracking the specimen and linking acquisition data (i.e. location, surface type, texture) to laboratory results. Sample location is determined by activating the integrated
Application of Improved Radiation Modeling to General Circulation Models
Michael J Iacono
2011-04-07
This research has accomplished its primary objectives of developing accurate and efficient radiation codes, validating them with measurements and higher resolution models, and providing these advancements to the global modeling community to enhance the treatment of cloud and radiative processes in weather and climate prediction models. A critical component of this research has been the development of the longwave and shortwave broadband radiative transfer code for general circulation model (GCM) applications, RRTMG, which is based on the single-column reference code, RRTM, also developed at AER. RRTMG is a rigorously tested radiation model that retains a considerable level of accuracy relative to higher resolution models and measurements despite the performance enhancements that have made it possible to apply this radiation code successfully to global dynamical models. This model includes the radiative effects of all significant atmospheric gases, and it treats the absorption and scattering from liquid and ice clouds and aerosols. RRTMG also includes a statistical technique for representing small-scale cloud variability, such as cloud fraction and the vertical overlap of clouds, which has been shown to improve cloud radiative forcing in global models. This development approach has provided a direct link from observations to the enhanced radiative transfer provided by RRTMG for application to GCMs. Recent comparison of existing climate model radiation codes with high resolution models has documented the improved radiative forcing capability provided by RRTMG, especially at the surface, relative to other GCM radiation models. Due to its high accuracy, its connection to observations, and its computational efficiency, RRTMG has been implemented operationally in many national and international dynamical models to provide validated radiative transfer for improving weather forecasts and enhancing the prediction of global climate change.
Revising a statistical cloud scheme for general circulation models
NASA Astrophysics Data System (ADS)
Schemann, Vera; Stevens, Bjorn; Grützun, Verena; Quaas, Johannes
2013-04-01
Cloud cover is an important factor for global climate simulations (e.g. for radiation). But in a global climate model with a typical resolution around 100 km clouds can not be resolved. The parameterization of cloud cover still is a major reason for uncertainties in climate change simulations. The aim of this study is to revise a statistical cloud scheme with special focus on the representation of low level clouds in the trade wind region. The development is based on the assumed PDF (probability density function) scheme of Tompkins 2002, which is part of the global climate model ECHAM6. The assumed PDF approach is based on the assumption of a certain PDF family and the determination of a certain member by further assumptions or constraints. For the scheme used in this study a beta distribution is assumed and two prognostic equations are added. Besides the original prognostic equations for a shape parameter and the distribution width, adjusted equations for the higher moments variance and skewness are introduced. This change leads to an easier physical interpretation. The source and sink terms due to the physical processes of convection, turbulence and microphysics play an important role in describing the total water PDF and with this the cloud fraction in one grid box. A better understanding of these terms and their effect on the cloud fraction and their vertical distribution is essential for the evaluation and development of the statistical cloud scheme. One known problem of the scheme is the underestimation of subgrid-scale variance of total water (Quaas 2012, Weber 2011). The aim of this study is to improve the representation of subgrid-scale variability by introducing and evaluating different source terms. For this several runs with the ECHAM6 model and modified cloud schemes are performed and analyzed. The focus is placed on the trade wind region to get a better understanding of the important processes for an improved representation of shallow cumuli
Radiation protection in inhomogeneous beta-gamma fields and modelling of hand phantoms with MCNPX.
Blunck, Ch; Becker, F; Hegenbart, L; Heide, B; Schimmelpfeng, J; Urban, M
2009-02-01
The usage of beta-radiation sources in various nuclear medicine therapies is increasing. Consequently, enhanced radiation protection measures are required, as medical staff more frequently handle high-activity sources required for therapy. Inhomogeneous radiation fields make it difficult to determine absorbed dose reliably. Routine monitoring with dosimeters does not guarantee any accurate determination of the local skin dose (LSD). In general, correction factors are used to correct for the measured dose and the maximum absorbed dose received. However, strong underestimations of the maximum exposure are possible depending on the individual handling the process and the reliability of dose measurements. Simulations can be used as a tool for a better understanding of the maximum possible exposure depending on the individual-related handling. While measurements reveal the overall dose during the entire irradiation time of the dosimeter, simulations help to analyse sequences of action. Hence, simulations allow for tracking the points of highest absorbed dose received during the handling process. In this respect, simulations were performed using the MCNPX software. In order to investigate the LSD, two hand phantoms were used, a model based on geometrical elements and a voxel hand. A typical situation of radiosynoviorthesis, i.e. handling a syringe filled with (90)Y, was simulated. The results of the simulations show that the annual dose limit may be exceeded within minutes at the position of maximum absorbed dose received and that finger-ring dosimeters measure significantly different doses depending on their wearing position. It is of essential importance to wear the dosimeter properly and to use suitable correction factors with respect to the individual. Simulations are a suitable tool for ensuring reliable dose determination and may help to derive recommendations regarding radiation protection measures. PMID:19395711
Comparison of the Beta and the Hidden Markov Models of Trust in Dynamic Environments
NASA Astrophysics Data System (ADS)
Moe, Marie E. G.; Helvik, Bjarne E.; Knapskog, Svein J.
Computational trust and reputation models are used to aid the decision-making process in complex dynamic environments, where we are unable to obtain perfect information about the interaction partners. In this paper we present a comparison of our proposed hidden Markov trust model to the Beta reputation system. The hidden Markov trust model takes the time between observations into account, it also distinguishes between system states and uses methods previously applied to intrusion detection for the prediction of which state an agent is in. We show that the hidden Markov trust model performs better when it comes to the detection of changes in behavior of agents, due to its larger richness in model features. This means that our trust model may be more realistic in dynamic environments. However, the increased model complexity also leads to bigger challenges in estimating parameter values for the model. We also show that the hidden Markov trust model can be parameterized so that it responds similarly to the Beta reputation system.
McCutchan, E. A. Bonatsos, D. Zamfir, N. V.
2007-08-15
The parameter-independent (up to overall scale factors) predictions of the X(5)-{beta}{sup 2},X(5)-{beta}{sup 4}, and X(3) models, which are variants of the X(5) critical point symmetry developed within the framework of the geometric collective model, are compared to two-parameter calculations in the framework of the interacting boson approximation (IBA) model. The results show that these geometric models coincide with IBA parameters consistent with the phase/shape transition region of the IBA for boson numbers of physical interest (close to 10). {sup 186}Pt and {sup 172}Os are identified as good examples of X(3), while {sup 146}Ce, {sup 174}Os, and {sup 158}Er, {sup 176}Os are identified as good examples of X(5)-{beta}{sub 2} and X(5)-{beta}{sup 4} behavior, respectively.
Gennclus: New Models for General Nonhierarchical Clustering Analysis.
ERIC Educational Resources Information Center
Desarbo, Wayne S.
1982-01-01
A general class of nonhierarchical clustering models and associated algorithms for fitting them are presented. These models generalize the Shepard-Arabie Additive clusters model. Two applications are given and extensions to three-way models, nonmetric analyses, and other model specifications are provided. (Author/JKS)
A Continuous Correlated Beta Process Model for Genetic Ancestry in Admixed Populations
Gompert, Zachariah
2016-01-01
Admixture and recombination create populations and genomes with genetic ancestry from multiple source populations. Analyses of genetic ancestry in admixed populations are relevant for trait and disease mapping, studies of speciation, and conservation efforts. Consequently, many methods have been developed to infer genome-average ancestry and to deconvolute ancestry into continuous local ancestry blocks or tracts within individuals. Current methods for local ancestry inference perform well when admixture occurred recently or hybridization is ongoing, or when admixture occurred in the distant past such that local ancestry blocks have fixed in the admixed population. However, methods to infer local ancestry frequencies in isolated admixed populations still segregating for ancestry do not exist. In the current paper, I develop and test a continuous correlated beta process model to fill this analytical gap. The method explicitly models autocorrelations in ancestry frequencies at the population-level and uses discriminant analysis of SNP windows to take advantage of ancestry blocks within individuals. Analyses of simulated data sets show that the method is generally accurate such that ancestry frequency estimates exhibited low root-mean-square error and were highly correlated with the true values, particularly when large (±10 or ±20) SNP windows were used. Along these lines, the proposed method outperformed post hoc inference of ancestry frequencies from a traditional hidden Markov model (i.e., the linkage model in structure), particularly when admixture occurred more distantly in the past with little on-going gene flow or was followed by natural selection. The reliability and utility of the method was further assessed by analyzing genetic ancestry in an admixed human population (Uyghur) and three populations from a hybrid zone between Mus domesticus and M. musculus. Considerable variation in ancestry frequencies was detected within and among chromosomes in the Uyghur
Osinski, Bolesław L; Kay, Leslie M
2016-08-01
Odors evoke gamma (40-100 Hz) and beta (20-30 Hz) oscillations in the local field potential (LFP) of the mammalian olfactory bulb (OB). Gamma (and possibly beta) oscillations arise from interactions in the dendrodendritic microcircuit between excitatory mitral cells (MCs) and inhibitory granule cells (GCs). When cortical descending inputs to the OB are blocked, beta oscillations are extinguished whereas gamma oscillations become larger. Much of this centrifugal input targets inhibitory interneurons in the GC layer and regulates the excitability of GCs, which suggests a causal link between the emergence of beta oscillations and GC excitability. We investigate the effect that GC excitability has on network oscillations in a computational model of the MC-GC dendrodendritic network with Ca(2+)-dependent graded inhibition. Results from our model suggest that when GC excitability is low, the graded inhibitory current mediated by NMDA channels and voltage-dependent Ca(2+) channels (VDCCs) is also low, allowing MC populations to fire in the gamma frequency range. When GC excitability is increased, the activation of NMDA receptors and other VDCCs is also increased, allowing the slow decay time constants of these channels to sustain beta-frequency oscillations. Our model argues that Ca(2+) flow through VDCCs alone could sustain beta oscillations and that the switch between gamma and beta oscillations can be triggered by an increase in the excitability state of a subpopulation of GCs. PMID:27121582
Scott, B.R.
1995-12-01
Individuals who work at nuclear reactor facilities can be at risk for deterministic effects in the skin from exposure to discrete {Beta}- and {gamma}-emitting ({Beta}{gamma}E) sources (e.g., {Beta}{gamma}E hot particles) on the skin or clothing. Deterministic effects are non-cancer effects that have a threshold and increase in severity as dose increases (e.g., ulcer in skin). Hot {Beta}{gamma}E particles are {sup 60}Co- or nuclear fuel-derived particles with diameters > 10 {mu}m and < 3 mm and contain at least 3.7 kBq (0.1 {mu}Ci) of radioactivity. For such {Beta}{gamma}E sources on the skin, it is the beta component of the dose that is most important. To develop exposure limitation systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for evaluating the risk of deterministic effects of localized {Beta} irradiation of the skin. The purpose of this study was to develop dose-rate and irradiated-area dependent, response-surface models for evaluating risks of significant deterministic effects of localized irradiation of the skin by discrete {Beta}{gamma}E sources and to use modeling results to recommend approaches to limiting occupational exposure to such sources. The significance of the research results as follows: (1) response-surface models are now available for evaluating the risk of specific deterministic effects of localized irradiation of the skin; (2) modeling results have been used to recommend approaches to limiting occupational exposure of workers to {Beta} radiation from {Beta}{gamma}E sources on the skin or on clothing; and (3) the generic irradiated-volume, weighting-factor approach to limiting exposure can be applied to other organs including the eye, the ear, and organs of the respiratory or gastrointestinal tract and can be used for both deterministic and stochastic effects.
Towards a General Model of Temporal Discounting
ERIC Educational Resources Information Center
van den Bos, Wouter; McClure, Samuel M.
2013-01-01
Psychological models of temporal discounting have now successfully displaced classical economic theory due to the simple fact that many common behavior patterns, such as impulsivity, were unexplainable with classic models. However, the now dominant hyperbolic model of discounting is itself becoming increasingly strained. Numerous factors have…
A Generalized Deduction of the Ideal-Solution Model
ERIC Educational Resources Information Center
Leo, Teresa J.; Perez-del-Notario, Pedro; Raso, Miguel A.
2006-01-01
A new general procedure for deriving the Gibbs energy of mixing is developed through general thermodynamic considerations, and the ideal-solution model is obtained as a special particular case of the general one. The deduction of the Gibbs energy of mixing for the ideal-solution model is a rational one and viewed suitable for advanced students who…
Elizur, Arnon; Ben-Abraham, Ron; Manisterski, Yossi; Barak, Asher; Efrati, Ori; Lotan, Danny; Barzilay, Zohar; Paret, Gideon
2003-11-01
Tracheal epinephrine (adrenaline) has been associated with two major deletorious side effects: increased heart rate (HR) and an initial decrease of blood pressure (BP). This prospective randomized animal study compared the haemodynamic responses to tracheally administered epinephrine or norepinephrine (nor adrenaline) alone versus each after pretreatment with propranolol for ameliorating those two untoward effects associated with epinephrine administration. Five anaesthetized mongrel dogs underwent 25 experiments of tracheal epinephrine or norepinephrine (0.02 mg/kg diluted with normal saline to 5 ml total volume) with or without an I/V non-selective beta-blocker (propranolol 0.1 mg/kg) pretreatment, and served as their own controls. Tracheal epinephrine alone produced a rise in both diastolic and mean arterial BP and an increase of HR. Tracheal norepinephrine alone produced the largest increase of diastolic and mean BP but this change was associated with a significant tachycardia (from 37 to 72/m, P<0.001). While both epinephrine or norepinephrine after pretreatment with propranolol produced a significant increase in both diastolic (from 106 to 166 mmHg and from 118 to 169 mmHg, respectively) (P<0.01) and mean BP (from 122 to 183 mmHg and from 133 to 188 mmHg, respectively) (P<0.01), only propranolol-pretreated tracheal epinephrine yielded a significant decrease in HR (from 52 to 33/m, P=0.002). Pretreatment with a beta-blocker protected against the deleterious tachycardia associated with epinephrine or norepinephrine and, by doing so, may improve the myocardial oxygen supply-and-demand balance. At the same time, the pretreatment augmented the relatively mild diastolic BP increase associated with the beta-adrenergic effect of epinephrine. PMID:14625119
A Mechanistic Beta-Binomial Probability Model for mRNA Sequencing Data
Smith, Gregory R.; Birtwistle, Marc R.
2016-01-01
A main application for mRNA sequencing (mRNAseq) is determining lists of differentially-expressed genes (DEGs) between two or more conditions. Several software packages exist to produce DEGs from mRNAseq data, but they typically yield different DEGs, sometimes markedly so. The underlying probability model used to describe mRNAseq data is central to deriving DEGs, and not surprisingly most softwares use different models and assumptions to analyze mRNAseq data. Here, we propose a mechanistic justification to model mRNAseq as a binomial process, with data from technical replicates given by a binomial distribution, and data from biological replicates well-described by a beta-binomial distribution. We demonstrate good agreement of this model with two large datasets. We show that an emergent feature of the beta-binomial distribution, given parameter regimes typical for mRNAseq experiments, is the well-known quadratic polynomial scaling of variance with the mean. The so-called dispersion parameter controls this scaling, and our analysis suggests that the dispersion parameter is a continually decreasing function of the mean, as opposed to current approaches that impose an asymptotic value to the dispersion parameter at moderate mean read counts. We show how this leads to current approaches overestimating variance for moderately to highly expressed genes, which inflates false negative rates. Describing mRNAseq data with a beta-binomial distribution thus may be preferred since its parameters are relatable to the mechanistic underpinnings of the technique and may improve the consistency of DEG analysis across softwares, particularly for moderately to highly expressed genes. PMID:27326762
A Mechanistic Beta-Binomial Probability Model for mRNA Sequencing Data.
Smith, Gregory R; Birtwistle, Marc R
2016-01-01
A main application for mRNA sequencing (mRNAseq) is determining lists of differentially-expressed genes (DEGs) between two or more conditions. Several software packages exist to produce DEGs from mRNAseq data, but they typically yield different DEGs, sometimes markedly so. The underlying probability model used to describe mRNAseq data is central to deriving DEGs, and not surprisingly most softwares use different models and assumptions to analyze mRNAseq data. Here, we propose a mechanistic justification to model mRNAseq as a binomial process, with data from technical replicates given by a binomial distribution, and data from biological replicates well-described by a beta-binomial distribution. We demonstrate good agreement of this model with two large datasets. We show that an emergent feature of the beta-binomial distribution, given parameter regimes typical for mRNAseq experiments, is the well-known quadratic polynomial scaling of variance with the mean. The so-called dispersion parameter controls this scaling, and our analysis suggests that the dispersion parameter is a continually decreasing function of the mean, as opposed to current approaches that impose an asymptotic value to the dispersion parameter at moderate mean read counts. We show how this leads to current approaches overestimating variance for moderately to highly expressed genes, which inflates false negative rates. Describing mRNAseq data with a beta-binomial distribution thus may be preferred since its parameters are relatable to the mechanistic underpinnings of the technique and may improve the consistency of DEG analysis across softwares, particularly for moderately to highly expressed genes. PMID:27326762
The Beta-Geometric Model Applied to Fecundability in a Sample of Married Women
NASA Astrophysics Data System (ADS)
Adekanmbi, D. B.; Bamiduro, T. A.
2006-10-01
The time required to achieve pregnancy among married couples termed fecundability has been proposed to follow a beta-geometric distribution. The accuracy of the method used in estimating the parameters of the model has an implication on the goodness of fit of the model. In this study, the parameters of the model are estimated using the Method of Moments and Newton-Raphson estimation procedure. The goodness of fit of the model was considered, using estimates from the two methods of estimation, as well as the asymptotic relative efficiency of the estimates. A noticeable improvement in the fit of the model to the data on time to conception was observed, when the parameters are estimated by Newton-Raphson procedure, and thereby estimating reasonable expectations of fecundability for married female population in the country.
Modeling of Antarctic sea ice in a general circulation model
Wu, Xingren; Budd, W.F.; Simmonds, I.
1997-04-01
A dynamic-thermodynamic sea ice model is developed and coupled with the Melbourne University general circulation model to simulate the seasonal cycle of the Antarctic sea ice distributions The model is efficient, rapid to compute, and useful for a range of climate studies. The thermodynamic part of the sea ice model is similar to that developed by Parkinson and Washington, the dynamics contain a simplified ice rheology that resists compression. The thermodynamics is based on energy conservation at the top surface of the ice/snow, the ice/water interface, and the open water area to determine the ice formation, accretion, and ablation. A lead parameterization is introduced with an effective partitioning scheme for freezing between and under the ice floes. The dynamic calculation determines the motion of ice, which is forced with the atmospheric wind, taking account of ice resistance and rafting. The simulated sea ice distribution compares reasonably well with observations. The seasonal cycle of ice extent is well simulated in phase as well as in magnitude. Simulated sea ice thickness and concentration are also in good agreement with observations over most regions and serve to indicate the importance of advection and ocean drift in the determination of the sea ice distribution. 64 refs., 15 figs., 2 tabs.
ERIC Educational Resources Information Center
Tsai, Tien-Lung; Shau, Wen-Yi; Hu, Fu-Chang
2006-01-01
This article generalizes linear path analysis (PA) and simultaneous equations models (SiEM) to deal with mixed responses of different types in a recursive or triangular system. An efficient instrumental variable (IV) method for estimating the structural coefficients of a 2-equation partially recursive generalized path analysis (GPA) model and…
Specification of the Model 3 General Lexicon.
ERIC Educational Resources Information Center
Rhode, Mary
The Model 3 communication skills lexicon consists of three lists of words developed by the Southwest Regional Laboratory (SWRL) for use in communication skills instruction in K-6. This report documents the procedures followed in the specification and generation of the second component of the Model 3 communication skills lexicon, the general…
Stratospheric General Circulation with Chemistry Model (SGCCM)
NASA Technical Reports Server (NTRS)
Rood, Richard B.; Douglass, Anne R.; Geller, Marvin A.; Kaye, Jack A.; Nielsen, J. Eric; Rosenfield, Joan E.; Stolarski, Richard S.
1990-01-01
In the past two years constituent transport and chemistry experiments have been performed using both simple single constituent models and more complex reservoir species models. Winds for these experiments have been taken from the data assimilation effort, Stratospheric Data Analysis System (STRATAN).
Flavor constraints on two-Higgs-doublet models with general diagonal Yukawa couplings
Mahmoudi, F.
2010-02-01
We consider constraints from flavor physics on two-Higgs-doublet models (2HDM) with general, flavor-diagonal, Yukawa couplings. Analyzing the charged Higgs contribution to different observables, we find that b{yields}s{gamma} transitions and {Delta}M{sub B{sub d}} restrict the coupling {lambda}{sub tt} of the top quark (corresponding to cot{beta} in models with a Z{sub 2} symmetry) to |{lambda}{sub tt}|<1 for m{sub H}{sup +} < or approx. 500 GeV. Stringent constraints from B meson decays are obtained also on the other third generation couplings {lambda}{sub bb} and {lambda}{sub {tau}{tau},} but with stronger dependence on m{sub H}{sup +}. For the second generation, we obtain constraints on combinations of {lambda}{sub ss}, {lambda}{sub cc}, and {lambda}{sub {mu}{mu}}from leptonic K and D{sub s} decays. The limits on the general couplings are translated to the common 2HDM types I-IV with a Z{sub 2} symmetry, and presented on the (m{sub H}{sup +},tan{beta}) plane. The flavor constraints are most excluding in the type II model which lacks a decoupling limit in tan{beta}. We obtain a lower limit m{sub H}{sup +} > or approx. 300 GeV in models of type II and III, while no lower bound on m{sub H}{sup +} is found for types I and IV.
Fractal generalization of Thomas-Fermi model
NASA Astrophysics Data System (ADS)
Rekhviashvili, S. Sh.; Sokurov, A. A.
2016-05-01
The Thomas-Fermi model is developed for a multielectron neutral atom at an arbitrary metric dimension of the electron cloud. It has been shown that the electron cloud with the reduced dimension should be located in the close vicinity of the nucleus. At a metric dimension of the electron cloud of 2, the differential equation of the model admits an analytical solution. In this case, the screening parameter does not depend on the charge of the nucleus.
Duality and Stationary Distributions of the "Immediate Exchange Model" and Its Generalizations
NASA Astrophysics Data System (ADS)
van Ginkel, Bart; Redig, Frank; Sau, Federico
2016-04-01
We study the "Immediate Exchange Model", a wealth distribution model introduced in Heinsalu and Patriarca (Eur Phys J B 87:170, 2014). We prove that the model has a discrete dual, where the duality functions are natural polynomials associated to the Gamma distribution with shape parameter 2 and are exactly those connecting the Brownian Energy Process (with parameter 2) and the corresponding Symmetric Inclusion Process in Carinci et al. (J Stat Phys 152:657-697, 2013) and Giardinà et al. (J Stat Phys 135(1):25-55, 2009). As a consequence, we recover invariance of products of Gamma distributions with shape parameter 2, and obtain ergodicity results. Next we show similar properties for a more general model, where the exchange fraction is Beta(s, t) distributed, and product measures with text{ Gamma }(s+t) marginals are invariant. We also show that the discrete dual model itself is self-dual and has the original continuous model as its scaling limit. We show that the self-duality is linked with an underlying SU(1, 1) symmetry, reminiscent of the one found before for the Symmetric Inclusion Process and related processes.
Lincomycin protects mice from septic shock in beta-glucan-indomethacin model.
Nameda, Sachiko; Miura, Noriko N; Adachi, Yoshiyuki; Ohno, Naohito
2007-12-01
We have developed a septic shock model in mice by sequential administration of beta-glucan, a biological response modifier, and indomethacin (IND), a nonsteroidal anti-inflammatory drug. Lethality was significantly related to the translocation of gut flora to various organs and mal-adjustment of the cytokine network. In the present study, we have examined the effect of antibiotics on this model to further clarify meanings of microbial flora. Schizophyllan (SPG), antitumor beta-glucan for clinical use, obtained from the culture filtrate of Schizophyllum commune, was used to induce sepsis. Lincomycin (LCM), imipenem (IPM), cilastatine (CS), and ampicillin (ABPC) were used for antibiotics treatment. The survival rate of SPG/IND-treated mice was significantly increased by administering LCM or ABPC/IPM/CS, and the effect was more significant by LCM. In in vitro spleen cell culture, LCM decreased proinflammatory cytokine production. Moreover, prednisolone, immune suppresser treatment improved survival of SPG/IND-treated mice. These findings suggest that LCM is an effective antibiotic in this endogenous septic model by modulating gut microbial flora and, at least a part, by regulating cytokine production of leukocytes. PMID:18057718
Generalized random sign and alert delay models for imperfect maintenance.
Dijoux, Yann; Gaudoin, Olivier
2014-04-01
This paper considers the modelling of the process of Corrective and condition-based Preventive Maintenance, for complex repairable systems. In order to take into account the dependency between both types of maintenance and the possibility of imperfect maintenance, Generalized Competing Risks models have been introduced in "Doyen and Gaudoin (J Appl Probab 43:825-839, 2006)". In this paper, we study two classes of these models, the Generalized Random Sign and Generalized Alert Delay models. A Generalized Competing Risks model can be built as a generalization of a particular Usual Competing Risks model, either by using a virtual age framework or not. The models properties are studied and their parameterizations are discussed. Finally, simulation results and an application to real data are presented. PMID:23460491
A general simulation model for Stirling cycles
Schulz, S.; Schwendig, F.
1996-01-01
A mathematical model for the calculation of the Stirling cycle and of similar processes is presented. The model comprises a method to reproduce schematically any kind of process configuration, including free piston engines. The differential balance equations describing the process are solved by a stable integration algorithm. Heat transfer and pressure loss are calculated by using new correlations, which consider the special conditions of the periodic compression/expansion respectively of the oscillating flow. A comparison between experimental data achieved by means of a test apparatus and calculated data shows a good agreement.
Generalized Hertz model for bimodal nanomechanical mapping
Kocuń, Marta; Meinhold, Waiman; Walters, Deron; Proksch, Roger
2016-01-01
Summary Bimodal atomic force microscopy uses a cantilever that is simultaneously driven at two of its eigenmodes (resonant modes). Parameters associated with both resonances can be measured and used to extract quantitative nanomechanical information about the sample surface. Driving the first eigenmode at a large amplitude and a higher eigenmode at a small amplitude simultaneously provides four independent observables that are sensitive to the tip–sample nanomechanical interaction parameters. To demonstrate this, a generalized theoretical framework for extracting nanomechanical sample properties from bimodal experiments is presented based on Hertzian contact mechanics. Three modes of operation for measuring cantilever parameters are considered: amplitude, phase, and frequency modulation. The experimental equivalence of all three modes is demonstrated on measurements of the second eigenmode parameters. The contact mechanics theory is then extended to power-law tip shape geometries, which is applied to analyze the experimental data and extract a shape and size of the tip interacting with a polystyrene surface. PMID:27547614
Generalized Hertz model for bimodal nanomechanical mapping.
Labuda, Aleksander; Kocuń, Marta; Meinhold, Waiman; Walters, Deron; Proksch, Roger
2016-01-01
Bimodal atomic force microscopy uses a cantilever that is simultaneously driven at two of its eigenmodes (resonant modes). Parameters associated with both resonances can be measured and used to extract quantitative nanomechanical information about the sample surface. Driving the first eigenmode at a large amplitude and a higher eigenmode at a small amplitude simultaneously provides four independent observables that are sensitive to the tip-sample nanomechanical interaction parameters. To demonstrate this, a generalized theoretical framework for extracting nanomechanical sample properties from bimodal experiments is presented based on Hertzian contact mechanics. Three modes of operation for measuring cantilever parameters are considered: amplitude, phase, and frequency modulation. The experimental equivalence of all three modes is demonstrated on measurements of the second eigenmode parameters. The contact mechanics theory is then extended to power-law tip shape geometries, which is applied to analyze the experimental data and extract a shape and size of the tip interacting with a polystyrene surface. PMID:27547614
Invariance Properties for General Diagnostic Classification Models
ERIC Educational Resources Information Center
Bradshaw, Laine P.; Madison, Matthew J.
2016-01-01
In item response theory (IRT), the invariance property states that item parameter estimates are independent of the examinee sample, and examinee ability estimates are independent of the test items. While this property has long been established and understood by the measurement community for IRT models, the same cannot be said for diagnostic…
Generalized IRT Models for Extreme Response Style
ERIC Educational Resources Information Center
Jin, Kuan-Yu; Wang, Wen-Chung
2014-01-01
Extreme response style (ERS) is a systematic tendency for a person to endorse extreme options (e.g., strongly disagree, strongly agree) on Likert-type or rating-scale items. In this study, we develop a new class of item response theory (IRT) models to account for ERS so that the target latent trait is free from the response style and the tendency…
A General Model for Shallow Magmatic Intrusions
NASA Astrophysics Data System (ADS)
Thorey, C.; Michaut, C.
2015-12-01
Shallow magmatic intrusions make room for themselves by upward bending of the elastic overburden. Previous studies have shown that the bending of the overlying layer first controls the dynamics. Then, when the radius reaches a few times the flexural wavelength of the overburden, it transitions to a gravity current regime. This model predicts the appropriate geometry for both terrestrial laccoliths and large mafic sills. However, it underestimates the absolute dimensions of these magmatic intrusions; in particular, it requires abnormally high viscosity to reconcile both observations and predictions. To get some insights into the effective flow viscosity, we develop a model that account for the cooling of such elastic-plated gravity currents. We show that the coupling between the temperature field and the flow itself leads to the formation of a highly viscous region at the tip that slows down the spreading in both regimes. The intrusions are predicted to be thicker and their dimensions, especially in the bending regime, are now consistent with observations. By introducing the potentially complex structure of the overburden, we also show that the topography largely contributes to constrain the final intrusion morphology. For instance, in the case of an intrusion centered below a circular depression, the model predicts that the lithostatic increase at the crater rim prevents the magma from spreading laterally and enhances the thickening of the intrusion. This model has already proven successful in reproducing the deformations observed on potential intrusion centered below lunar impact craters. Caldera complexes often exhibit ground deformations that might be associated to the formation of shallow magmatic intrusions. InSAR imaging and GPS measurements now provide efficient tools to monitor these deformations. We conclude this study by examining the ability of the model to reproduce the deformation observed in several caldera complexes.
Takagawa, Shinsuke; Lakos, Gabriella; Mori, Yasuji; Yamamoto, Toshiyuki; Nishioka, Kiyoshi; Varga, John
2003-07-01
Transforming growth factor-beta is responsible for triggering a cascade of events leading to fibrosis in scleroderma. The Smads are intracellular signal transducers recently shown to mediate fibroblast activation and other profibrotic responses elicited by transforming growth factor-betain vitro. To understand better the involvement of Smads in the pathogenesis of fibrosis, we examined Smad expression and activation in situ in a murine model of scleroderma. Bleomycin injections induced striking dermal infiltration with macrophages by 3 d, and progressive fibrosis by 2 wk. Infiltrating macrophages and resident fibroblasts expressed Smad3, the positive mediator for transforming growth factor-beta responses. Importantly, in bleomycin-injected skin, fibroblasts showed predominantly nuclear localization of Smad3 and intense staining for phospho-Smad2/3. Furthermore, phosphorylated Smad2/3 in fibroblasts was detected even after the resolution of inflammation. Expression of Smad7, the endogenous inhibitor of transforming growth factor-beta/Smad signaling, was strongly induced in dermal cells by transforming growth factor-beta, but not by bleomycin injections. Collectively, these results indicate that bleomycin-induced murine scleroderma is associated with rapid and sustained induction of transforming growth factor-beta/Smad signaling in resident dermal fibroblasts. Despite apparent activation of the intracellular transforming growth factor-beta signaling pathway in the lesional dermis, the expression of transforming growth factor-beta-inducible Smad7 was not upregulated. In light of the critical function of Smad7 as an endogenous inhibitor of Smad signaling that restricts the duration and magnitude of transforming growth factor-beta responses, and as a mediator of apoptosis, relative Smad7 deficiency observed in the present studies may account for sustained activation of transforming growth factor-beta/Smad signaling in lesional tissues. These findings raise the
Shell-Model Calculations of Two-Nucleon Tansfer Related to Double Beta Decay
NASA Astrophysics Data System (ADS)
Brown, Alex
2013-10-01
I will discuss theoretical results for two-nucleon transfer cross sections for nuclei in the regions of 48Ca, 76Ge and 136Xe of interest for testing the wavefuntions used for the nuclear matrix elements in double-beta decay. Various reaction models are used. A simple cluster transfer model gives relative cross sections. Thompson's code Fresco with direct and sequential transfer is used for absolute cross sections. Wavefunctions are obtained in large-basis proton-neutron coupled model spaces with the code NuShellX with realistic effecive Hamiltonians such as those used for the recent results for 136Xe [M. Horoi and B. A. Brown, Phys. Rev. Lett. 110, 222502 (2013)]. I acknowledge support from NSF grant PHY-1068217.
Reduced Order Modeling in General Relativity
NASA Astrophysics Data System (ADS)
Tiglio, Manuel
2014-03-01
Reduced Order Modeling is an emerging yet fast developing filed in gravitational wave physics. The main goals are to enable fast modeling and parameter estimation of any detected signal, along with rapid matched filtering detecting. I will focus on the first two. Some accomplishments include being able to replace, with essentially no lost of physical accuracy, the original models with surrogate ones (which are not effective ones, that is, they do not simplify the physics but go on a very different track, exploiting the particulars of the waveform family under consideration and state of the art dimensional reduction techniques) which are very fast to evaluate. For example, for EOB models they are at least around 3 orders of magnitude faster than solving the original equations, with physically equivalent results. For numerical simulations the speedup is at least 11 orders of magnitude. For parameter estimation our current numbers are about bringing ~100 days for a single SPA inspiral binary neutron star Bayesian parameter estimation analysis to under a day. More recently, it has been shown that the full precessing problem for, say, 200 cycles, can be represented, through some new ideas, by a remarkably compact set of carefully chosen reduced basis waveforms (~10-100, depending on the accuracy requirements). I will highlight what I personally believe are the challenges to face next in this subarea of GW physics and where efforts should be directed. This talk will summarize work in collaboration with: Harbir Antil (GMU), Jonathan Blackman (Caltech), Priscila Canizares (IoA, Cambridge, UK), Sarah Caudill (UWM), Jonathan Gair (IoA. Cambridge. UK), Scott Field (UMD), Chad R. Galley (Caltech), Frank Herrmann (Germany), Han Hestahven (EPFL, Switzerland), Jason Kaye (Brown, Stanford & Courant). Evan Ochsner (UWM), Ricardo Nochetto (UMD), Vivien Raymond (LIGO, Caltech), Rory Smith (LIGO, Caltech) Bela Ssilagyi (Caltech) and MT (UMD & Caltech).
Surrogate oracles, generalized dependency and simpler models
NASA Technical Reports Server (NTRS)
Wilson, Larry
1990-01-01
Software reliability models require the sequence of interfailure times from the debugging process as input. It was previously illustrated that using data from replicated debugging could greatly improve reliability predictions. However, inexpensive replication of the debugging process requires the existence of a cheap, fast error detector. Laboratory experiments can be designed around a gold version which is used as an oracle or around an n-version error detector. Unfortunately, software developers can not be expected to have an oracle or to bear the expense of n-versions. A generic technique is being investigated for approximating replicated data by using the partially debugged software as a difference detector. It is believed that the failure rate of each fault has significant dependence on the presence or absence of other faults. Thus, in order to discuss a failure rate for a known fault, the presence or absence of each of the other known faults needs to be specified. Also, in simpler models which use shorter input sequences without sacrificing accuracy are of interest. In fact, a possible gain in performance is conjectured. To investigate these propositions, NASA computers running LIC (RTI) versions are used to generate data. This data will be used to label the debugging graph associated with each version. These labeled graphs will be used to test the utility of a surrogate oracle, to analyze the dependent nature of fault failure rates and to explore the feasibility of reliability models which use the data of only the most recent failures.
Emergent General Relativity and Local Translation Symmetry in Tensor Model
NASA Astrophysics Data System (ADS)
Sasakura, Naoki
2009-12-01
The tensor model is discussed as theory of dynamical fuzzy spaces and as a way to formulate gravity on fuzzy spaces. From numerical analyses, it is shown that the low-lying long-wavelength fluctuation spectra around Gaussian background solutions in the tensor model are in agreement with the geometric fluctuations on flat spaces in the general relativity. It is also shown that part of the orthogonal symmetry of the tensor model spontaneously broken by the backgrounds correspond to the local translation symmetry of the general relativity. Thus the tensor model can provide an interesting model of simultaneous emergence of space and the general relativity including the local translation symmetry.
Down syndrome as a model of DNA polymerase beta haploinsufficiency and accelerated aging.
Patterson, David; Cabelof, Diane C
2012-04-01
Down syndrome is a condition of intellectual disability characterized by accelerated aging. As with other aging syndromes, evidence accumulated over the past several decades points to a DNA repair defect inherent in Down syndrome. This evidence has led us to suggest that Down syndrome results in reduced DNA base excision repair (BER) capacity, and that this contributes to the genomic instability and the aging phenotype of Down syndrome. We propose important roles for microRNA and/or folate metabolism and oxidative stress in the dysregulation of BER in Down syndrome. Further, we suggest these pathways are involved in the leukemogenesis of Down syndrome. We have reviewed the role of BER in the processing of oxidative stress, and the impact of folate depletion on BER capacity. Further, we have reviewed the role that loss of BER, specifically DNA polymerase beta, plays in accelerating the rate of aging. Like that seen in the DNA polymerase beta heterozygous mouse, the aging phenotype of Down syndrome is subtle, unlike the aging phenotypes seen in the classical progeroid syndromes and mouse models of aging. As such, Down syndrome may provide a model for elucidating some of the basic mechanisms of aging. PMID:22019846
El-Khoury, Riyad; Kaulio, Eveliina; Lassila, Katariina A; Crowther, Damian C; Jacobs, Howard T; Rustin, Pierre
2016-07-01
Mitochondrial dysfunction has been widely associated with the pathology of Alzheimer's disease, but there is no consensus on whether it is a cause or consequence of disease, nor on the precise mechanism(s). We addressed these issues by testing the effects of expressing the alternative oxidase AOX from Ciona intestinalis, in different models of AD pathology. AOX can restore respiratory electron flow when the cytochrome segment of the mitochondrial respiratory chain is inhibited, supporting ATP synthesis, maintaining cellular redox homeostasis and mitigating excess superoxide production at respiratory complexes I and III. In human HEK293-derived cells, AOX expression decreased the production of beta-amyloid peptide resulting from antimycin inhibition of respiratory complex III. Because hydrogen peroxide was neither a direct product nor substrate of AOX, the ability of AOX to mimic antioxidants in this assay must be indirect. In addition, AOX expression was able to partially alleviate the short lifespan of Drosophila models neuronally expressing human beta-amyloid peptides, whilst abrogating the induction of markers of oxidative stress. Our findings support the idea of respiratory chain dysfunction and excess ROS production as both an early step and as a pathologically meaningful target in Alzheimer's disease pathogenesis, supporting the concept of a mitochondrial vicious cycle underlying the disease. PMID:27094492
Härkänen, Lasse; Halonen, Jari; Selander, Tuomas; Kokki, Hannu
2015-12-01
We have performed a systematic literature review and a meta-analysis investigating the effect of beta-adrenergic antagonist on perioperative pain in randomized clinical trials (RCTs). The search included the CENTRAL, CINAHL, EMBASE, and MEDLINE databases (from inception to 10 February 2015). From the retrieved full texts, we hand-searched the references and PubMed related citations. A total of 11 RCTs consisting data of 701 adult patients were eligible for this systematic review. Esmolol was evaluated in ten trials and propranolol in one. Esmolol decreased the need for rescue analgesics by 32-50%; p < 0.05 (n = 7) and the proportion of patients needing rescue analgesia from 100 to 65%; p < 0.005 (n = 1), and propranolol decreased the need for rescue analgesics by 72%; p < 0.001 (n = 1). The time to the first rescue analgesics was longer (p < 0.05) and pain ratings were lower (p < 0.05) in patients with beta-adrenergic antagonists. However, in two opioid-controlled studies, one in knee arthroscopy and another in tubal ligation patients, the proportion of patients needing rescue analgesia was two-times higher in esmolol-treated patients: 52-57 vs. 23-34%, p < 0.05. Adverse effects were rarely reported, and as reported were mostly cardiovascular alterations. In conclusion, intra-operative beta-adrenergic antagonists' administration may decrease postoperative pain and analgesic consumption when given as an adjuvant to general anesthesia. PMID:26160590
Minasov, George; Wang, Xiaojun; Shoichet, Brian K.
2010-03-08
Although TEM-1 {beta}-lactamase is among the best studied enzymes, its acylation mechanism remains controversial. To investigate this problem, the structure of TEM-1 in complex with an acylation transition-state analogue was determined at ultrahigh resolution (0.85 {angstrom}) by X-ray crystallography. The quality of the data was such as to allow for refinement to an R-factor of 9.1% and an R{sub free} of 11.2%. In the resulting structure, the electron density features were clear enough to differentiate between single and double bonds in carboxylate groups, to identify multiple conformations that are occupied by residues and loops, and to assign 70% of the protons in the protein. Unexpectedly, even at pH 8.0 where the protein was crystallized, the active site residue Glu166 is clearly protonated. This supports the hypothesis that Glu166 is the general base in the acylation half of the reaction cycle. This structure suggests that Glu166 acts through the catalytic water to activate Ser70 for nucleophilic attack on the {beta}-lactam ring of the substrate. The hydrolytic mechanism of class A {beta}-lactamases, such as TEM-1, appears to be symmetrical, as are the serine proteases. Apart from its mechanistic implications, this atomic resolution structure affords an unusually detailed view of the structure, dynamics, and hydrogen-bonding networks of TEM-1, which may be useful for the design of inhibitors against this key antibiotic resistance target.
Sauvonnet, N; Pugsley, A P
1996-10-01
Pullulanase (PulA) is a 116 kDa amylolytic lipoprotein secreted by the Gram-negative bacterium Klebsiella oxytoca via the general secretory pathway. A deletion strategy was used in an attempt to determine the nature and the location of the secretion signal(s) in PulA presumed to be necessary for its specific secretion. The starting material was a gene fusion coding for an efficiently secreted PulA-beta-lactamase hybrid protein. Successive series of exonuclease III-generated deletions were used to remove internal segments of PulA from this hybrid. A simple plate test allowed the identification of truncated hybrids that retained beta-lactamase activity and that were secreted. Two non-adjacent regions, A and B (78 and 80 amino acids, respectively), were together necessary and sufficient to promote beta-lactamase translocation across the outer membrane. Secretion of PulA itself was markedly reduced when either of these regions was deleted, and was completely abolished when both regions were eliminated. PMID:8899703
General topology meets model theory, on and
Malliaris, Maryanthe; Shelah, Saharon
2013-01-01
Cantor proved in 1874 [Cantor G (1874) J Reine Angew Math 77:258–262] that the continuum is uncountable, and Hilbert’s first problem asks whether it is the smallest uncountable cardinal. A program arose to study cardinal invariants of the continuum, which measure the size of the continuum in various ways. By Gödel [Gödel K (1939) Proc Natl Acad Sci USA 25(4):220–224] and Cohen [Cohen P (1963) Proc Natl Acad Sci USA 50(6):1143–1148], Hilbert’s first problem is independent of ZFC (Zermelo-Fraenkel set theory with the axiom of choice). Much work both before and since has been done on inequalities between these cardinal invariants, but some basic questions have remained open despite Cohen’s introduction of forcing. The oldest and perhaps most famous of these is whether “,” which was proved in a special case by Rothberger [Rothberger F (1948) Fund Math 35:29–46], building on Hausdorff [Hausdorff (1936) Fund Math 26:241–255]. In this paper we explain how our work on the structure of Keisler’s order, a large-scale classification problem in model theory, led to the solution of this problem in ZFC as well as of an a priori unrelated open question in model theory. PMID:23836659
Elbert, Donald L.; Patterson, Bruce W.; Bateman, Randall J.
2014-01-01
Amyloid beta (Aβ) peptides, and in particular Aβ42, are found in senile plaques associated with Alzheimer's disease. A compartmental model of Aβ production, exchange and irreversible loss was recently developed to explain the kinetics of isotope-labeling of Aβ peptides collected in cerebrospinal fluid (CSF) following infusion of stable isotope-labeled leucine in humans. The compartmental model allowed calculation of the rates of production, irreversible loss (or turnover) and short-term exchange of Aβ peptides. Exchange of Aβ42 was particularly pronounced in amyloid plaque-bearing participants. In the current work, we describe in much greater detail the characteristics of the compartmental model to two distinct audiences: physician-scientists and biokineticists. For physician-scientists, we describe through examples the types of questions the model can and cannot answer, as well as correct some misunderstandings of previous kinetic analyses applied to this type of isotope labeling data. For biokineticists, we perform a system identifiability analysis and a sensitivity analysis of the kinetic model to explore the global and local properties of the model. Combined, these analyses motivate simplifications from a more comprehensive physiological model to the final model that was previously presented. The analyses clearly demonstrate that the current dataset and compartmental model allow determination with confidence a single ‘turnover’ parameter, a single ‘exchange’ parameter and a single ‘delay’ parameter. When combined with CSF concentration data for the Aβ peptides, production rates may also be obtained. PMID:25497960
Elbert, Donald L; Patterson, Bruce W; Bateman, Randall J
2015-03-01
Amyloid beta (Aβ) peptides, and in particular Aβ42, are found in senile plaques associated with Alzheimer's disease. A compartmental model of Aβ production, exchange and irreversible loss was recently developed to explain the kinetics of isotope-labeling of Aβ peptides collected in cerebrospinal fluid (CSF) following infusion of stable isotope-labeled leucine in humans. The compartmental model allowed calculation of the rates of production, irreversible loss (or turnover) and short-term exchange of Aβ peptides. Exchange of Aβ42 was particularly pronounced in amyloid plaque-bearing participants. In the current work, we describe in much greater detail the characteristics of the compartmental model to two distinct audiences: physician-scientists and biokineticists. For physician-scientists, we describe through examples the types of questions the model can and cannot answer, as well as correct some misunderstandings of previous kinetic analyses applied to this type of isotope labeling data. For biokineticists, we perform a system identifiability analysis and a sensitivity analysis of the kinetic model to explore the global and local properties of the model. Combined, these analyses motivate simplifications from a more comprehensive physiological model to the final model that was previously presented. The analyses clearly demonstrate that the current dataset and compartmental model allow determination with confidence a single 'turnover' parameter, a single 'exchange' parameter and a single 'delay' parameter. When combined with CSF concentration data for the Aβ peptides, production rates may also be obtained. PMID:25497960
Building a generalized distributed system model
NASA Technical Reports Server (NTRS)
Mukkamala, R.
1992-01-01
The key elements in the second year (1991-92) of our project are: (1) implementation of the distributed system prototype; (2) successful passing of the candidacy examination and a PhD proposal acceptance by the funded student; (3) design of storage efficient schemes for replicated distributed systems; and (4) modeling of gracefully degrading reliable computing systems. In the third year of the project (1992-93), we propose to: (1) complete the testing of the prototype; (2) enhance the functionality of the modules by enabling the experimentation with more complex protocols; (3) use the prototype to verify the theoretically predicted performance of locking protocols, etc.; and (4) work on issues related to real-time distributed systems. This should result in efficient protocols for these systems.
ERIC Educational Resources Information Center
Jurow, A. Susan
2004-01-01
Generalizing or making claims that extend beyond particular situations is a central mathematical practice and a focus of classroom mathematics instruction. This study examines how aspects of generality are produced through the situated activities of a group of middle school mathematics students working on an 8-week population-modeling project. The…
Integrated modeling of high poloidal beta scenario for a next-step reactor
NASA Astrophysics Data System (ADS)
McClenaghan, J.; Garofalo, A. M.; Meneghini, O.; Smith, S. P.
2015-11-01
In order to fill the scientific and technological gaps between ITER and a nuclear fusion power plant DEMO, a next-step integrated nuclear test facility is critical. A high poloidal beta tokamak regime investigated in recent DIII-D experiments is a promising candidate for steady state operation in such a next-step device because the large bootstrap current fraction (~ 80 %) reduces the demands on the external current drive. Despite the large values of q95 ~10, the normalized fusion performance observed in the experiments meet the target for an economically attractive fusion power plant such as ARIES-ACT2. In this work, we will project the performance for a conducting and superconducting coil next-step steady state reactor using theory-based 0-D modeling and full 1.5D transport modeling. Work supported by U.S. DOE under DE-FC02-04ER54698.
Model selection in the weighted generalized estimating equations for longitudinal data with dropout.
Gosho, Masahiko
2016-05-01
We propose criteria for variable selection in the mean model and for the selection of a working correlation structure in longitudinal data with dropout missingness using weighted generalized estimating equations. The proposed criteria are based on a weighted quasi-likelihood function and a penalty term. Our simulation results show that the proposed criteria frequently select the correct model in candidate mean models. The proposed criteria also have good performance in selecting the working correlation structure for binary and normal outcomes. We illustrate our approaches using two empirical examples. In the first example, we use data from a randomized double-blind study to test the cancer-preventing effects of beta carotene. In the second example, we use longitudinal CD4 count data from a randomized double-blind study. PMID:26509243
A generalized kinetic model for heterogeneous gas-solid reactions.
Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A
2012-08-21
We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used. PMID:22920132
A generalized kinetic model for heterogeneous gas-solid reactions
NASA Astrophysics Data System (ADS)
Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A.
2012-08-01
We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used.
Biodegradation and cometabolic modeling of selected beta blockers during ammonia oxidation.
Sathyamoorthy, Sandeep; Chandran, Kartik; Ramsburg, C Andrew
2013-11-19
Accurate prediction of pharmaceutical concentrations in wastewater effluents requires that the specific biochemical processes responsible for pharmaceutical biodegradation be elucidated and integrated within any modeling framework. The fate of three selected beta blockers-atenolol, metoprolol, and sotalol-was examined during nitrification using batch experiments to develop and evaluate a new cometabolic process-based (CPB) model. CPB model parameters describe biotransformation during and after ammonia oxidation for specific biomass populations and are designed to be integrated within the Activated Sludge Models framework. Metoprolol and sotalol were not biodegraded by the nitrification enrichment culture employed herein. Biodegradation of atenolol was observed and linked to the activity of ammonia-oxidizing bacteria (AOB) and heterotrophs but not nitrite-oxidizing bacteria. Results suggest that the role of AOB in atenolol degradation may be disproportionately more significant than is otherwise suggested by their lower relative abundance in typical biological treatment processes. Atenolol was observed to competitively inhibit AOB growth in our experiments, though model simulations suggest inhibition is most relevant at atenolol concentrations greater than approximately 200 ng·L(-1). CPB model parameters were found to be relatively insensitive to biokinetic parameter selection suggesting the model approach may hold utility for describing pharmaceutical biodegradation during biological wastewater treatment. PMID:24112027
An in vivo model for the neurodegenerative effects of beta amyloid and protection by substance P.
Kowall, N W; Beal, M F; Busciglio, J; Duffy, L K; Yankner, B A
1991-01-01
Deposition of the beta-amyloid protein in senile plaques is a pathologic hallmark of Alzheimer disease (AD). Focal deposition of beta amyloid in the adult rat cerebral cortex caused profound neurodegenerative changes, including neuronal loss and degenerating neurons and neurites. Chronic induction of the Alz-50 antigen appeared in neurons around focal cortical deposits of beta amyloid. Immunoblot analysis showed that beta amyloid induced Alz-50-immunoreactive proteins in rat cerebral cortex that were very similar to the proteins induced in human cerebral cortex from patients with AD. The neuropeptide substance P prevented beta-amyloid-induced neuronal loss and expression of Alz-50 proteins when coadministered into the cerebral cortex. Systemic administration of substance P also provided protection against the effects of intracerebral beta amyloid. Thus, beta amyloid is a potent neurotoxin in the adult brain in vivo, and its effects can be blocked by substance P. Images PMID:1714596
ECOLOGICAL THEORY. A general consumer-resource population model.
Lafferty, Kevin D; DeLeo, Giulio; Briggs, Cheryl J; Dobson, Andrew P; Gross, Thilo; Kuris, Armand M
2015-08-21
Food-web dynamics arise from predator-prey, parasite-host, and herbivore-plant interactions. Models for such interactions include up to three consumer activity states (questing, attacking, consuming) and up to four resource response states (susceptible, exposed, ingested, resistant). Articulating these states into a general model allows for dissecting, comparing, and deriving consumer-resource models. We specify this general model for 11 generic consumer strategies that group mathematically into predators, parasites, and micropredators and then derive conditions for consumer success, including a universal saturating functional response. We further show how to use this framework to create simple models with a common mathematical lineage and transparent assumptions. Underlying assumptions, missing elements, and composite parameters are revealed when classic consumer-resource models are derived from the general model. PMID:26293960
Adaptive multiscale model reduction with Generalized Multiscale Finite Element Methods
NASA Astrophysics Data System (ADS)
Chung, Eric; Efendiev, Yalchin; Hou, Thomas Y.
2016-09-01
In this paper, we discuss a general multiscale model reduction framework based on multiscale finite element methods. We give a brief overview of related multiscale methods. Due to page limitations, the overview focuses on a few related methods and is not intended to be comprehensive. We present a general adaptive multiscale model reduction framework, the Generalized Multiscale Finite Element Method. Besides the method's basic outline, we discuss some important ingredients needed for the method's success. We also discuss several applications. The proposed method allows performing local model reduction in the presence of high contrast and no scale separation.
Cloud Feedback in Atmospheric General Circulation Models: An Update
NASA Technical Reports Server (NTRS)
Cess, R. D.; Zhang, M. H.; Ingram, W. J.; Potter, G. L.; Alekseev, V.; Barker, H. W.; Cohen-Solal, E.; Colman, R. A.; Dazlich, D. A.; DelGenio, A. D.; Dix, M. R.; Dymnikov, V.; Esch, M.; Fowler, L. D.; Fraser, J. R.; Galin, V.; Gates, W. L.; Hack, J. J.; Kiehl, J. T.; LeTreut, H.
1996-01-01
Six years ago, we compared the climate sensitivity of 19 atmospheric general circulation models and found a roughly threefold variation among the models; most of this variation was attributed to differences in the models' depictions of cloud feedback. In an update of this comparison, current models showed considerably smaller differences in net cloud feedback, with most producing modest values. There are, however, substantial differences in the feedback components, indicating that the models still have physical disagreements.
NASA Technical Reports Server (NTRS)
Hubbard, W. B.; Jokipii, J. R.
1977-01-01
Effects of atmospheric turbulence on stellar-occultation inversion procedures are investigated using a heuristic scattering model that is believed to reproduce the essential features of turbulence. A quantitative estimate is made of the size of the error in deducing the mean refractivity profile of a planetary atmosphere, taking into account constant as well as exponential scattering. It is shown that ordinary turbulence has no important effect on the average intensity profile in a stellar occultation but could have an important instantaneous effect. A critical examination of possible manifestations of turbulent scattering during occultations of Beta Sco by Jupiter indicates that all observed phenomena during these events can be understood in terms of scintillations produced by turbulence.
Calibrating the ECCO ocean general circulation model using Green's functions
NASA Technical Reports Server (NTRS)
Menemenlis, D.; Fu, L. L.; Lee, T.; Fukumori, I.
2002-01-01
Green's functions provide a simple, yet effective, method to test and calibrate General-Circulation-Model(GCM) parameterizations, to study and quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products.
Equating Parameter Estimates from the Generalized Graded Unfolding Model.
ERIC Educational Resources Information Center
Roberts, James S.
Three common methods for equating parameter estimates from binary item response theory models are extended to the generalized grading unfolding model (GGUM). The GGUM is an item response model in which single-peaked, nonmonotonic expected value functions are implemented for polytomous responses. GGUM parameter estimates are equated using extended…
Deformed shell model results for neutrinoless double beta decay of nuclei in A = 60 - 90 region
NASA Astrophysics Data System (ADS)
Sahu, R.; Kota, V. K. B.
2015-03-01
Nuclear transition matrix elements (NTME) for the neutrinoless double beta decay (Oνββ or OνDBD) of 70Zn, 80Se and 82Se nuclei are calculated within the framework of the deformed shell model (DSM) based on Hartree-Fock (HF) states. For 70Zn, jj44b interaction in 2p3/2, 1f5/2, 2p1/2 and 1g9/2 space with 56Ni as the core is employed. However, for 80Se and 82Se nuclei, a modified Kuo interaction with the above core and model space are employed. Most of our calculations in this region were performed with this effective interaction. However, jj44b interaction has been found to be better for 70Zn. The above model space was used in many recent shell model (SM) and interacting boson model (IBM) calculations for nuclei in this region. After ensuring that DSM gives good description of the spectroscopic properties of low-lying levels in these three nuclei considered, the NTME are calculated. The deduced half-lives with these NTME, assuming neutrino mass is 1 eV, are 1.1 × 1026, 2.3 × 1027 and 2.2 × 1024 yr for 70Zn, 80Se and 82Se, respectively.
Predictability of formation damage: An assessment study and generalized models
Civan, F.
1991-01-01
The project objective is to develop improved generalized predictive models to be used for investigation of reservoir formation damage and control for various fluid and rock conditions and to account for these effects in reservoir simulation. To accomplish its objective the proposed study will first critically study and evaluate the previous modeling efforts and the experimental studies reported in the literature. Then, generalized predictive models will be formulated by combining the previous attempts and by improving and generalizing the modeling approaches to accommodate for a wide variety of conditions encountered in actual field applications. A critical review of the previous work addressing their theoretical basis, assumptions and limitations, and the generalized and improved model developed in this study will be presented in a systematic manner in terms of a standardized definition and nomenclature for direct comparison. Case studies with the generalized model will be presented to demonstrate its capacity and validity. User friendly computer programs implementing the improved modeling approaches will also be supplied. This study will form an assessment of the presently available models and methods for evaluating and predicting formation damage and present improved models. Therefore, it will be an important reference for the petroleum industry. 1 tab.
A structural model for the nucleotide binding domains of the flavocytochrome b-245 beta-chain.
Taylor, W. R.; Jones, D. T.; Segal, A. W.
1993-01-01
NADPH is a system in phagocytic cells that generates O2- and hydrogen peroxide in the endocytic vacuole, both of which are important for killing of the engulfed microbe. Dysfunction of this oxidase results in the syndrome of chronic granulomatous disease, characterized by a profound predisposition to bacterial and fungal infections. A flavocytochrome b is the site of most of the mutations causing this syndrome. The FAD and NADPH binding sites have been located on the beta subunit of this molecule, the C-terminal half of which showed weak sequence similarity to other reductases, including the ferredoxin-NADP reductase (FNR) of known structure. This enabled us to build a model of the nucleotide binding domains of the flavocytochrome using this structure as a template. The model was built initially using a novel automatic modeling method based on distance-matrix projection and then refined using energy minimization with appropriate side-chain torsional constraints. The resulting model rationalized much of the observed sequence conservation and identified a large insertion as a potential regulatory domain. It confirms the inclusion of the neutrophil flavocytochrome b-245 (Cb-245) as a member of the FNR family of reductases and strongly supports its function as the proximal electron transporting component of the NADPH oxidase. PMID:8251942
A crystallographic model for hydrous wadsleyite (Beta-Mg2SiO4)
NASA Technical Reports Server (NTRS)
Smyth, J. R.
1994-01-01
Wadsleyite (beta-Mg2SiO4) is believed to be the most abundant phase in the Earth between depths of 400 and about 525km. Because of the unusual crystal chemistry, Smyth suggested that this phase might be a significant host for hydrogen in the transition zone. Indeed, of the nominally anhydrous phases believed to make up the upper mantle and transition zone none has been reported with a greater H content than wadsleyite. Young et al, report the synthesis of hydrous, Fe-bearing wadsleyite with up to 60,000 H per 10(exp 6) Si. Using ionic constraints and maximal subgroup symmetry, a hypothetical, ordered model for hydrous wadsleyite has been created and examined. The model has formula Mg7Si4O14(OH)2, has space group Pmmb, has an ordered vacancy into one of two non-equivalent M2 sites, and contains two different H positions, one on each of the non-equivalent O1 sites. Electrostatic calculations indicate that hydration would relieve the underbonding of O1 as well as the overbonding of the bridging oxygen, O2, so that the hydrous phase may be more stable than the anhydrous phase. This model makes several predictions that may be of significance for the mechanisms and amounts of H that may be stored in the transition zone of the Earth, and by which the model may be tested experimentally.
Adaptation of a general circulation model to ocean dynamics
NASA Technical Reports Server (NTRS)
Turner, R. E.; Rees, T. H.; Woodbury, G. E.
1976-01-01
A primitive-variable general circulation model of the ocean was formulated in which fast external gravity waves are suppressed with rigid-lid surface constraint pressires which also provide a means for simulating the effects of large-scale free-surface topography. The surface pressure method is simpler to apply than the conventional stream function models, and the resulting model can be applied to both global ocean and limited region situations. Strengths and weaknesses of the model are also presented.
Two field BPS solutions for generalized Lorentz breaking models
Souza Dutra, A. de; Hott, M.; Barone, F. A.
2006-10-15
In this work we present nonlinear models in two-dimensional space-time of two interacting scalar fields in the Lorentz and CPT violating scenarios. We discuss the soliton solutions for these models as well as the question of stability for them. This is done by generalizing a model recently published by Barreto and collaborators and also by getting new solutions for the model introduced by them.
General autocatalytic theory and simple model of financial markets
NASA Astrophysics Data System (ADS)
Thuy Anh, Chu; Lan, Nguyen Tri; Viet, Nguyen Ai
2015-06-01
The concept of autocatalytic theory has become a powerful tool in understanding evolutionary processes in complex systems. A generalization of autocatalytic theory was assumed by considering that the initial element now is being some distribution instead of a constant value as in traditional theory. This initial condition leads to that the final element might have some distribution too. A simple physics model for financial markets is proposed, using this general autocatalytic theory. Some general behaviours of evolution process and risk moment of a financial market also are investigated in framework of this simple model.
A generalized statistical model for the size distribution of wealth
NASA Astrophysics Data System (ADS)
Clementi, F.; Gallegati, M.; Kaniadakis, G.
2012-12-01
In a recent paper in this journal (Clementi et al 2009 J. Stat. Mech. P02037), we proposed a new, physically motivated, distribution function for modeling individual incomes, having its roots in the framework of the κ-generalized statistical mechanics. The performance of the κ-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the US household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature.
Guisan, A.; Edwards, T.C., Jr.; Hastie, T.
2002-01-01
An important statistical development of the last 30 years has been the advance in regression analysis provided by generalized linear models (GLMs) and generalized additive models (GAMs). Here we introduce a series of papers prepared within the framework of an international workshop entitled: Advances in GLMs/GAMs modeling: from species distribution to environmental management, held in Riederalp, Switzerland, 6-11 August 2001. We first discuss some general uses of statistical models in ecology, as well as provide a short review of several key examples of the use of GLMs and GAMs in ecological modeling efforts. We next present an overview of GLMs and GAMs, and discuss some of their related statistics used for predictor selection, model diagnostics, and evaluation. Included is a discussion of several new approaches applicable to GLMs and GAMs, such as ridge regression, an alternative to stepwise selection of predictors, and methods for the identification of interactions by a combined use of regression trees and several other approaches. We close with an overview of the papers and how we feel they advance our understanding of their application to ecological modeling. ?? 2002 Elsevier Science B.V. All rights reserved.
A generalized model via random walks for information filtering
NASA Astrophysics Data System (ADS)
Ren, Zhuo-Ming; Kong, Yixiu; Shang, Ming-Sheng; Zhang, Yi-Cheng
2016-08-01
There could exist a simple general mechanism lurking beneath collaborative filtering and interdisciplinary physics approaches which have been successfully applied to online E-commerce platforms. Motivated by this idea, we propose a generalized model employing the dynamics of the random walk in the bipartite networks. Taking into account the degree information, the proposed generalized model could deduce the collaborative filtering, interdisciplinary physics approaches and even the enormous expansion of them. Furthermore, we analyze the generalized model with single and hybrid of degree information on the process of random walk in bipartite networks, and propose a possible strategy by using the hybrid degree information for different popular objects to toward promising precision of the recommendation.
A note on 'A generalized two-sex logistic model'.
Maxin, D; Sega, L
2015-01-01
We re-visit the recently published paper on a generalization of the two-sex logistic model by Maxin and Sega [A generalized two-sex logistic model, J. Biol. Dyn. 7(1) (2013), pp. 302-318]. We show that the logistic assumption of a non-increasing birth rate can be replaced by a more general assumption of a non-increasing ratio between the female/male birth and mortality rate. In this note we indicate the changes necessary in the proofs of the theorems in [D. Maxin and L. Sega, A generalized two-sex logistic model, J. Biol. Dyn. 7(1) (2013), pp. 302--318] and discuss several situations where this new assumption is useful. PMID:25653171
Phase-field modeling of the beta to omega phase transformation in Zr–Nb alloys
Yeddu, Hemantha Kumar; Lookman, Turab
2015-05-01
A three-dimensional elastoplastic phase-field model is developed, using the Finite Element Method (FEM), for modeling the athermal beta to omega phase transformation in Zr–Nb alloys by including plastic deformation and strain hardening of the material. The microstructure evolution during athermal transformation as well as under different stress states, e.g. uni-axial tensile and compressive, bi-axial tensile and compressive, shear and tri-axial loadings, is studied. The effects of plasticity, stress states and the stress loading direction on the microstructure evolution as well as on the mechanical properties are studied. The input data corresponding to a Zr – 8 at.% Nb alloy are acquired from experimental studies as well as by using the CALPHAD method. Our simulations show that the four different omega variants grow as ellipsoidal shaped particles. Our results show that due to stress relaxation, the athermal phase transformation occurs slightly more readily in the presence of plasticity compared to that in its absence. The evolution of omega phase is different under different stress states, which leads to the differences in the mechanical properties of the material. The variant selection mechanism, i.e. formation of different variants under different stress loading directions, is also nicely captured by our model.
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; Pearson, John E.; Xu, Shang -Zhong
2015-09-08
Amyloid beta (Aβ) oligomers associated with Alzheimer’s disease (AD) form Ca2+-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca2+) homeostasis. The resultant up-regulation of intracellular Ca2+ concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca2+ permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca2+ flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individualmore » pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. As a result, we demonstrate the up-regulation of gating of various Ca2+ release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca2+ permeability transition into those with high open probability and Ca2+ permeability.« less
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; Pearson, John E.
2015-01-01
Amyloid beta (Aβ) oligomers associated with Alzheimer’s disease (AD) form Ca2+-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca2+) homeostasis. The resultant up-regulation of intracellular Ca2+ concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca2+ permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca2+ flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individual pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. Towards the end, we demonstrate the up-regulation of gating of various Ca2+ release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca2+ permeability transition into those with high open probability and Ca2+ permeability. PMID:26348728
Drift wave model for geomagnetic pulsations in a high. beta. plasma
Patel, V.L.; Ng, P.H.; Cahill, L.J. Jr.
1983-07-01
A dispersion relation for the instability of the coupled drift compressional drift mirror, and shear Alven waves in the magnetospheric plasma is analyzed by numerical method. The analysis is suitable for the storm time plasma conditions in the magnetosphere which usually has gradients in plasma density temperature, magnetic field, and anisotropy in temperature. The effect of high ..beta.. which is characteristic of storm time plasma is included in the model. For a given appropriate set of plasma parameters, and wave parameters of a mode relative wave amplitudes are calculated from the model. A comparison is made of model generated and observed relative wave amplitudes by using two sample wave events observed by Explorer 45 during the August 4--6, 1972, magnetic storm. The quantitative analysis shows good agreement between theory and observations for a gradient-driven Alvenlike instability; however, growth rates are veery small for this mode. The anisotropy-driven drift mirror instability has large growth rates but does not show correlation between theory and observations of relative wave amplitudes.
Phase-field modeling of the beta to omega phase transformation in Zr–Nb alloys
Yeddu, Hemantha Kumar; Lookman, Turab
2015-05-01
A three-dimensional elastoplastic phase-field model is developed, using the Finite Element Method (FEM), for modeling the athermal beta to omega phase transformation in Zr–Nb alloys by including plastic deformation and strain hardening of the material. The microstructure evolution during athermal transformation as well as under different stress states, e.g. uni-axial tensile and compressive, bi-axial tensile and compressive, shear and tri-axial loadings, is studied. The effects of plasticity, stress states and the stress loading direction on the microstructure evolution as well as on the mechanical properties are studied. The input data corresponding to a Zr – 8 at.% Nb alloy aremore » acquired from experimental studies as well as by using the CALPHAD method. Our simulations show that the four different omega variants grow as ellipsoidal shaped particles. Our results show that due to stress relaxation, the athermal phase transformation occurs slightly more readily in the presence of plasticity compared to that in its absence. The evolution of omega phase is different under different stress states, which leads to the differences in the mechanical properties of the material. The variant selection mechanism, i.e. formation of different variants under different stress loading directions, is also nicely captured by our model.« less
Phase-field modeling of the beta to omega phase transformation in Zr-Nb alloys
Yeddu, Hemantha Kumar; Lookman, Turab
2015-03-17
A three-dimensional elastoplastic phase-field model is developed, using the finite element method (FEM), for modeling the athermal beta to omega phase transformation in Zr–Nb alloys by including plastic deformation and strain hardening of the material. The microstructure evolution during athermal transformation as well as under different stress states, e.g. uni-axial tensile and compressive, bi-axial tensile and compressive, shear and tri-axial loadings, is studied. The effects of plasticity, stress states and the stress loading direction on the microstructure evolution as well as on the mechanical properties are studied. The input data corresponding to a Zr – 8 at% Nb alloy are acquired from experimental studies as well as by using the CALPHAD method. Our simulations show that the four different omega variants grow as ellipsoidal shaped particles. Our results show that due to stress relaxation, the athermal phase transformation occurs slightly more readily in the presence of plasticity compared to that in its absence. The evolution of omega phase is different under different stress states, which leads to the differences in the mechanical properties of the material. As a result, the variant selection mechanism, i.e. formation of different variants under different stress loading directions, is also nicely captured by our model.
Modeling of Coupled Degradation, Sorption, and Transport of 17beta-Estradiol in Undisturbed Soil
Technology Transfer Automated Retrieval System (TEKTRAN)
The presence of 17 beta-estradiol in the environment, even at part-per trillion concentrations, may raise significant concern regarding the health of aquatic organisms. Once 17 beta-estradiol is released into the environment from human and animal sources, its fate and transport is controlled by fact...
A Generalized Evaluation Model for Primary Prevention Programs.
ERIC Educational Resources Information Center
Barling, Phillip W.; Cramer, Kathryn D.
A generalized evaluation model (GEM) has been developed to evaluate primary prevention program impact. The GEM model views primary prevention dynamically; delineating four structural components (program, organization, target population, system) and four developmental stages (initiation, establishment, integration, continuation). The interaction of…
Estimability of Parameters in the Generalized Graded Unfolding Model.
ERIC Educational Resources Information Center
Roberts, James S.; Donoghue, John R.; Laughlin, James E.
The generalized graded unfolding model (GGUM) (J. Roberts, J. Donoghue, and J. Laughlin, 1998) is an item response theory model designed to analyze binary or graded responses that are based on a proximity relation. The purpose of this study was to assess conditions under which item parameter estimation accuracy increases or decreases, with special…
Analysis of Radiation Pneumonitis Risk Using a Generalized Lyman Model
Tucker, Susan L. Liu, H. Helen; Liao Zhongxing; Wei Xiong; Wang Shulian; Jin Hekun; Komaki, Ritsuko; Martel, Mary K.; Mohan, Radhe
2008-10-01
Purpose: To introduce a version of the Lyman normal-tissue complication probability (NTCP) model adapted to incorporate censored time-to-toxicity data and clinical risk factors and to apply the generalized model to analysis of radiation pneumonitis (RP) risk. Methods and Materials: Medical records and radiation treatment plans were reviewed retrospectively for 576 patients with non-small cell lung cancer treated with radiotherapy. The time to severe (Grade {>=}3) RP was computed, with event times censored at last follow-up for patients not experiencing this endpoint. The censored time-to-toxicity data were analyzed using the standard and generalized Lyman models with patient smoking status taken into account. Results: The generalized Lyman model with patient smoking status taken into account produced NTCP estimates up to 27 percentage points different from the model based on dose-volume factors alone. The generalized model also predicted that 8% of the expected cases of severe RP were unobserved because of censoring. The estimated volume parameter for lung was not significantly different from n = 1, corresponding to mean lung dose. Conclusions: NTCP models historically have been based solely on dose-volume effects and binary (yes/no) toxicity data. Our results demonstrate that inclusion of nondosimetric risk factors and censored time-to-event data can markedly affect outcome predictions made using NTCP models.
Interaction Strength and a Generalized Bak-Sneppen Evolution Model
NASA Astrophysics Data System (ADS)
Li, Wei; Cai, Xu
2002-10-01
The Bak-Sneppen evolution model is generalized in terms of a new concept and quantity: interaction strength. Based on a quantitative definition, the interaction strength describes the strength of the interaction between the nearest-neighbour individuals in the model. Self-organized criticality is observed for the generalized model with ten different values of interaction strength. The gap equation governing the self-organization is derived. It is also found that the self-organized threshold depends on the value of the interaction strength.
A Generalized Information Theoretical Model for Quantum Secret Sharing
NASA Astrophysics Data System (ADS)
Bai, Chen-Ming; Li, Zhi-Hui; Xu, Ting-Ting; Li, Yong-Ming
2016-07-01
An information theoretical model for quantum secret sharing was introduced by H. Imai et al. (Quantum Inf. Comput. 5(1), 69-80 2005), which was analyzed by quantum information theory. In this paper, we analyze this information theoretical model using the properties of the quantum access structure. By the analysis we propose a generalized model definition for the quantum secret sharing schemes. In our model, there are more quantum access structures which can be realized by our generalized quantum secret sharing schemes than those of the previous one. In addition, we also analyse two kinds of important quantum access structures to illustrate the existence and rationality for the generalized quantum secret sharing schemes and consider the security of the scheme by simple examples.
Daniels, D. L.
2002-01-01
In the canonical Wnt signaling pathway, {beta}-catenin activates target genes through its interactions with Tcf/Lef-family transcription factors and additional transcriptional coactivators. The crystal structure of ICAT, an inhibitor of {beta}-catenin-mediated transcription, bound to the armadillo repeat domain of {beta}-catenin, has been determined. ICAT contains an N-terminal helilical domain that binds to repeats 11 and 12 of {beta}-catenin, and an extended C-terminal region that binds to repeats 5-10 in a manner similar that of Tcfs and other {beta}-catenin ligands. Full-length ICAT dissociates complexes of {beta}-catenin, Lef-1, and the transcriptional coactivator p300, whereas the helical domain alone selectively blocks binding to p300. The C-terminal armadillo repeats of {beta}-catenin may be an attractive target for compounds designed to disrupt aberrant {beta}-catenin-mediated transcription associated with various cancers.
Partially Observed Mixtures of IRT Models: An Extension of the Generalized Partial-Credit Model
ERIC Educational Resources Information Center
Von Davier, Matthias; Yamamoto, Kentaro
2004-01-01
The generalized partial-credit model (GPCM) is used frequently in educational testing and in large-scale assessments for analyzing polytomous data. Special cases of the generalized partial-credit model are the partial-credit model--or Rasch model for ordinal data--and the two parameter logistic (2PL) model. This article extends the GPCM to the…
Physically-Derived Dynamical Cores in Atmospheric General Circulation Models
NASA Technical Reports Server (NTRS)
Rood, Richard B.; Lin, Shian-Kiann
1999-01-01
The algorithm chosen to represent the advection in atmospheric models is often used as the primary attribute to classify the model. Meteorological models are generally classified as spectral or grid point, with the term grid point implying discretization using finite differences. These traditional approaches have a number of shortcomings that render them non-physical. That is, they provide approximate solutions to the conservation equations that do not obey the fundamental laws of physics. The most commonly discussed shortcomings are overshoots and undershoots which manifest themselves most overtly in the constituent continuity equation. For this reason many climate models have special algorithms to model water vapor advection. This talk focuses on the development of an atmospheric general circulation model which uses a consistent physically-based advection algorithm in all aspects of the model formulation. The shallow-water model of Lin and Rood (QJRMS, 1997) is generalized to three dimensions and combined with the physics parameterizations of NCAR's Community Climate Model. The scientific motivation for the development is to increase the integrity of the underlying fluid dynamics so that the physics terms can be more effectively isolated, examined, and improved. The expected benefits of the new model are discussed and results from the initial integrations will be presented.
Physically-Derived Dynamical Cores in Atmospheric General Circulation Models
NASA Technical Reports Server (NTRS)
Rood, Richard B.; Lin, Shian-Jiann
1999-01-01
The algorithm chosen to represent the advection in atmospheric models is often used as the primary attribute to classify the model. Meteorological models are generally classified as spectral or grid point, with the term grid point implying discretization using finite differences. These traditional approaches have a number of shortcomings that render them non-physical. That is, they provide approximate solutions to the conservation equations that do not obey the fundamental laws of physics. The most commonly discussed shortcomings are overshoots and undershoots which manifest themselves most overtly in the constituent continuity equation. For this reason many climate models have special algorithms to model water vapor advection. This talk focuses on the development of an atmospheric general circulation model which uses a consistent physically-based advection algorithm in all aspects of the model formulation. The shallow-water model is generalized to three dimensions and combined with the physics parameterizations of NCAR's Community Climate Model. The scientific motivation for the development is to increase the integrity of the underlying fluid dynamics so that the physics terms can be more effectively isolated, examined, and improved. The expected benefits of the new model are discussed and results from the initial integrations will be presented.
Generalized population models and the nature of genetic drift.
Der, Ricky; Epstein, Charles L; Plotkin, Joshua B
2011-09-01
The Wright-Fisher model of allele dynamics forms the basis for most theoretical and applied research in population genetics. Our understanding of genetic drift, and its role in suppressing the deterministic forces of Darwinian selection has relied on the specific form of sampling inherent to the Wright-Fisher model and its diffusion limit. Here we introduce and analyze a broad class of forward-time population models that share the same mean and variance as the Wright-Fisher model, but may otherwise differ. The proposed class unifies and further generalizes a number of population-genetic processes of recent interest, including the Λ and Cannings processes. Even though these models all have the same variance effective population size, they encode a rich diversity of alternative forms of genetic drift, with significant consequences for allele dynamics. We characterize in detail the behavior of standard population-genetic quantities across this family of generalized models. Some quantities, such as heterozygosity, remain unchanged; but others, such as neutral absorption times and fixation probabilities under selection, deviate by orders of magnitude from the Wright-Fisher model. We show that generalized population models can produce startling phenomena that differ qualitatively from classical behavior - such as assured fixation of a new mutant despite the presence of genetic drift. We derive the forward-time continuum limits of the generalized processes, analogous to Kimura's diffusion limit of the Wright-Fisher process, and we discuss their relationships to the Kingman and non-Kingman coalescents. Finally, we demonstrate that some non-diffusive, generalized models are more likely, in certain respects, than the Wright-Fisher model itself, given empirical data from Drosophila populations. PMID:21718713
Muon capture in a general class of weak models
NASA Astrophysics Data System (ADS)
Botella, F. J.
1985-10-01
We study muon capture by 12C in a general class of weak models. There is always a parameter characteristic of the weak model that can be extracted in a nuclear-model-independent way from the average polarization Pav, the longitudinal polarization PNL and the asymmetry α in the angular distribution of recoils. For a less general class of models the asymmetry α is unnecessary. Using the experimental values of PNL and Pav we get a lower bound for the mass of the right-handed gauge boson of the left-right-symmetric model, MWR>=2.5MWL, in a nuclear-model-independent way. The dependence of this bound on the experimental values is also discussed.
Asian Summer Monsoon Intraseasonal Variability in General Circulation Models
Sperber, K R; Annamalai, H
2004-02-24
The goals of this report are: (1) Analyze boreal summer Asian monsoon intraseasonal variability general circulation models--How well do the models represent the eastward and northward propagating components of the convection and how well do the models represent the interactive control that the western tropical Pacific rainfall exerts on the rainfall over India and vice-versa? (2) Role of air-sea interactions--prescribed vs. interactive ocean; and (3) Mean monsoon vs. variability.
Generalized model for photoinduced surface structure in amorphous thin films.
Lu, Chao; Recht, Daniel; Arnold, Craig
2013-09-01
We present a generalized model to explain the spatial and temporal evolution of photoinduced surface structure in photosensitive amorphous thin films. The model describes these films as an incompressible viscous fluid driven by a photoinduced pressure originating from dipole rearrangement. This derivation requires only the polarizability, viscosity and surface tension of the system. Using values of these physical parameters, we check the validity of the model by fitting to experimental data of As2S3 and demonstrating good agreement. PMID:25166680
Generalization of Richardson-Gaudin models to rank-2 algebras
Errea, B; Lerma, S; Dukelsky, J; Dimitrova, S S; Pittel, S; Van Isacker, P; Gueorguiev, V G
2006-07-20
A generalization of Richardson-Gaudin models to the rank-2 SO(5) and SO(3,2) algebras is used to describe systems of two kinds of fermions or bosons interacting through a pairing force. They are applied to the proton-neutron neutron isovector pairing model and to the Interacting Boson Model 2, in the transition from vibration to gamma-soft nuclei, respectively. In both cases, the integrals of motion and their eigenvalues are obtained.
Banerjee, Atrayee; Lee, Jin-Hyung; Ramaiah, Shashi K
2008-12-01
Previous studies from our laboratory have reported that osteopontin (OPN) mediated higher hepatic neutrophil infiltration makes female rats more susceptible to alcoholic steatohepatitis (ASH) than their male counterparts. The objective of the current work was to investigate the patho-mechanism by which OPN attracts the hepatic neutrophils in ASH. We hypothesized that OPN-mediated hepatic neutrophil infiltration is a result of signaling by N-terminal integrin binding motif (SLAYGLR) of OPN through its receptor {alpha}{sub 9}{beta}{sub 1} (VLA9) and {alpha}{sub 4}{beta}{sub 1} (VLA4) integrins on neutrophils. Compared to the males, females in the ASH group exhibited higher expression of {alpha}{sub 4}{beta}{sub 1} and {alpha}{sub 9}{beta}{sub 1} protein and mRNA and a significant decrease in the expression of these integrins was observed in rats treated with neutralizing OPN antibody. Immunoprecipitation experiments suggested the binding of OPN to {alpha}{sub 4}{beta}{sub 1} and {alpha}{sub 9}{beta}{sub 1} integrins. OPN-mediated neutrophil infiltration was also confirmed using Boyden chamber assays, and antibodies directed against {alpha}{sub 4} and {beta}{sub 1} integrins was found to significantly inhibit neutrophilic migration in vitro. In conclusion, these data suggest that SLAYGLR-mediated {alpha}{sub 4}{beta}{sub 1} and {alpha}{sub 9}{beta}{sub 1} integrin signaling may be responsible for higher hepatic neutrophil infiltration and higher liver injury in the rat ASH model.
Modeling the brain morphology distribution in the general aging population
NASA Astrophysics Data System (ADS)
Huizinga, W.; Poot, D. H. J.; Roshchupkin, G.; Bron, E. E.; Ikram, M. A.; Vernooij, M. W.; Rueckert, D.; Niessen, W. J.; Klein, S.
2016-03-01
Both normal aging and neurodegenerative diseases such as Alzheimer's disease cause morphological changes of the brain. To better distinguish between normal and abnormal cases, it is necessary to model changes in brain morphology owing to normal aging. To this end, we developed a method for analyzing and visualizing these changes for the entire brain morphology distribution in the general aging population. The method is applied to 1000 subjects from a large population imaging study in the elderly, from which 900 were used to train the model and 100 were used for testing. The results of the 100 test subjects show that the model generalizes to subjects outside the model population. Smooth percentile curves showing the brain morphology changes as a function of age and spatiotemporal atlases derived from the model population are publicly available via an interactive web application at agingbrain.bigr.nl.
Inflationary weak anisotropic model with general dissipation coefficient
NASA Astrophysics Data System (ADS)
Sharif, M.; Saleem, Rabia
2016-03-01
This paper explores the dynamics of warm intermediate and logamediate inflationary models during weak dissipative regime with a general form of dissipative coefficient. We analyze these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate solution of inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio under slow-roll approximation. We constrain the model parameters using recent data and conclude that anisotropic inflationary universe model with generalized dissipation coefficient remains compatible with WMAP9, Planck and BICEP2 data. Finally, we have checked the effects of bulk viscous pressure on this considered model and found that it remains compatible with recent data only for intermediate case.
A general diagnostic model applied to language testing data.
von Davier, Matthias
2008-11-01
Probabilistic models with one or more latent variables are designed to report on a corresponding number of skills or cognitive attributes. Multidimensional skill profiles offer additional information beyond what a single test score can provide, if the reported skills can be identified and distinguished reliably. Many recent approaches to skill profile models are limited to dichotomous data and have made use of computationally intensive estimation methods such as Markov chain Monte Carlo, since standard maximum likelihood (ML) estimation techniques were deemed infeasible. This paper presents a general diagnostic model (GDM) that can be estimated with standard ML techniques and applies to polytomous response variables as well as to skills with two or more proficiency levels. The paper uses one member of a larger class of diagnostic models, a compensatory diagnostic model for dichotomous and partial credit data. Many well-known models, such as univariate and multivariate versions of the Rasch model and the two-parameter logistic item response theory model, the generalized partial credit model, as well as a variety of skill profile models, are special cases of this GDM. In addition to an introduction to this model, the paper presents a parameter recovery study using simulated data and an application to real data from the field test for TOEFL Internet-based testing. PMID:17535481
Flood analysis using generalized logistic models in partial duration series
NASA Astrophysics Data System (ADS)
Bhunya, P. K.; Singh, R. D.; Berndtsson, R.; Panda, S. N.
2012-02-01
SummaryAs a generalization of the commonly assumed Poisson distribution (PD) used to estimate the annual number of peaks over threshold in partial duration series (PDS) model, the negative binomial (NB) distribution is proposed in this study. Instead of generalized pareto distribution (GPD) and exponential distribution (ED) models popularly applied to predict the probability of the exceedances of peak over threshold, the performance of the general logistic distribution (GLD) models is analyzed. Two different models for analyzing extreme hydrologic events are compared, based on, PDS and annual maximum series (AMS), respectively. The performance of the two models in terms of uncertainty of T-year event estimator [ q( T)] is evaluated in the cases of estimation with the method of moments (MOMs), maximum likelihood (ML), and probability weighted moments (PWMs). The annual maximum distribution corresponding to a PDS model with Poisson distributed count of peaks above threshold and GLD for flood exceedances was found to be an extreme value type I (EV1) distribution. The comparison between PDS and AMS is made using ratio of variance of the T-year event estimates, which is derived analytically after checking the reliability of the expressions with Monte Carlo simulations. The results reveal that the AMS/NB-GLD and PDS/GLD models using PWM estimation method give least variance of flood estimates with the PDS model giving marginally better results. From the overall results, it was observed that the Poisson distribution performs better, where the difference between mean ( μ) and variance of counts of threshold exceedances is small otherwise the NB distribution is found to be efficient when used in combination with generalized logistic distribution in the PDS model, and this is more prominent for μ < 1.4. Hence, in such cases when the PDS data have a mean less than this, the AMS/NB-GLD and PDS/GLD should be a better model for q( T) estimation as compared to PDS/ED.
A general relativistic model for free-fall absolute gravimeters
NASA Astrophysics Data System (ADS)
Tan, Yu-Jie; Shao, Cheng-Gang; Li, Jia; Hu, Zhong-Kun
2016-04-01
Although the relativistic manifestations of gravitational fields in gravimetry were first studied 40 years ago, the relativistic effects combined with free-fall absolute gravimeters have rarely been considered. In light of this, we present a general relativistic model for free-fall absolute gravimeters in a local-Fermi coordinates system, where we focus on effects related to the measuring devices: relativistic transverse Doppler effects, gravitational redshift effects and Earth’s rotation effects. Based on this model, a general relativistic expression of the measured gravity acceleration is obtained.
Brant, S.; Yoshida, N.; Zuffi, L.
2006-08-15
The interacting boson-fermion-fermion model approach to {beta} decay is applied to the decay from the even-even {sup 124}Ba to the odd-odd {sup 124}Cs nucleus. The theoretical results for energy levels, electromagnetic properties and {beta} decay rates are compared with experimental data for {sup 124}Cs. The calculated {beta}-decay rates demonstrate that the interacting boson approximation can be applied in the description of {beta} decays from even-even to odd-odd nuclei.
THE INITIAL MASS FUNCTION MODELED BY A LEFT TRUNCATED BETA DISTRIBUTION
Zaninetti, Lorenzo
2013-03-10
The initial mass function for stars is usually fitted by three straight lines, which means it has seven parameters. The presence of brown dwarfs (BDs) increases the number of straight lines to four and the number of parameters to nine. Another common fitting function is the lognormal distribution, which is characterized by two parameters. This paper is devoted to demonstrating the advantage of introducing a left truncated beta probability density function, which is characterized by four parameters. The constant of normalization, the mean, the mode, and the distribution function are calculated for the left truncated beta distribution. The normal beta distribution that results from convolving independent normally distributed and beta distributed components is also derived. The chi-square test and the Kolmogorov-Smirnov test are performed on a first sample of stars and BDs that belongs to the massive young cluster NGC 6611, and on a second sample that represents the masses of the stars of the cluster NGC 2362.
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; Pearson, John E.; Xu, Shang -Zhong
2015-09-08
Amyloid beta (Aβ) oligomers associated with Alzheimer’s disease (AD) form Ca^{2+}-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca^{2+}) homeostasis. The resultant up-regulation of intracellular Ca^{2+} concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca^{2+} permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca^{2+} flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individual pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. As a result, we demonstrate the up-regulation of gating of various Ca^{2+} release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca^{2+} permeability transition into those with high open probability and Ca^{2+} permeability.
The Sherman-Rinzel-Keizer model for bursting electrical activity in the pancreatic. beta. -cell
Pernarowski, M.; Kevorkian, J. . Dept. of Applied Mathematics); Miura, R.M. )
1990-03-01
Pancreatic {beta}-cells exhibit periodic bursting electrical activity (BEA) consisting of active and silent phases. The Sherman-Rinzel-Keizer (SRK) model of this phenomenon consists of three coupled first-order nonlinear differential equations which describe the dynamics of the membrane potential, the activation parameter for the voltage-gated potassium channel, and the intracellular calcium concentration. These equations are nondimensionalized and transformed into a Lienard differential equation coupled to a single first-order differential equation for the slowly changing nondimensional calcium concentration. Leading-order perturbation problems are derived for the silent and active phases of the BEA on slow and fast time scales. Numerical solutions of these leading-order problems are compared with those for the exact equation in their respective regions. The leading-order solution in the active phase has a limit cycle behavior with a slowly varying frequency. It is observed that the damping term'' in the Lienard equation is small numerically. 26 refs., 6 figs., 2 tabs.
Younker, Jarod M; Beste, Ariana; Buchanan III, A C
2011-01-01
The biopolymer lignin is a potential source of valuable chemicals. Phenethyl phenyl ether (PPE) is representative of the dominant $\\beta$-O-4 ether linkage. Density functional theory (DFT) is used to calculate the Boltzmann-weighted carbon-oxygen and carbon-carbon bond dissociation enthalpies (BDEs) of substituted PPE. These values are important in order to understand lignin decomposition. Exclusion of all conformers that have distributions of less than 5\\% at 298 K impacts the BDE by less than 1 kcal mol$^{-1}$. We find that aliphatic hydroxyl/methylhydroxyl substituents introduce only small changes to the BDEs (0-3 kcal mol$^{-1}$). Substitution on the phenyl ring at the $ortho$ position substantially lowers the C-O BDE, except in combination with the hydroxyl/methylhydroxyl substituents, where the effect of methoxy substitution is reduced by hydrogen bonding. Hydrogen bonding between the aliphatic substituents and the ether oxygen in the PPE derivatives has a significant influence on the BDE. CCSD(T)-calculated BDEs and hydrogen bond strengths of $ortho$-substituted anisoles when compared with M06-2X values confirm that the latter method is sufficient to describe the molecules studied and provide an important benchmark for lignin model compounds.
Anti-beta-2 glycoprotein I epitope specificity: from experimental models to diagnostic tools.
Meroni, P L
2016-07-01
Beta-2 glycoprotein I (β2GPI) is the main antigenic target for anti-phospholipid antibodies (aPL), the serological markers of anti-phospholipid syndrome (APS). Conformational changes of the molecule seem to be essential for exposing the cryptic epitope for aPL binding and to trigger pathogenic pathways. There is increasing evidence that a conformational epitope located in the Domain I (DI) of the molecule is the main epitope targeted by human autoantibodies. The pathogenic role of the DI epitope has been recently supported by in vivo models and by immuno-histopathological findings in APS patients. Antibodies targeting β2GPI-DI are more frequently detected in patients with full-blown APS compared to asymptomatic aPL carriers or patients with infectious diseases who have antibodies directed against the whole molecule. Anti-DI antibodies are positively correlated with medium to high titres of aPL, with the presence of lupus anticoagulant and thrombotic and pregnancy manifestations, enabling identification of patients at higher risk of clinical events. However, some APS patients develop antibodies reacting against β2GPI epitopes other than DI, suggesting that other anti-β2GPI antibody subsets may be clinically relevant. Although preliminary results suggest that anti-DI antibodies can be detected by different assays in a comparable manner, further prospective studies are needed to support their use in the clinical setting and their predictive value. PMID:27252268
Generalized memory associativity in a network model for the neuroses
NASA Astrophysics Data System (ADS)
Wedemann, Roseli S.; Donangelo, Raul; de Carvalho, Luís A. V.
2009-03-01
We review concepts introduced in earlier work, where a neural network mechanism describes some mental processes in neurotic pathology and psychoanalytic working-through, as associative memory functioning, according to the findings of Freud. We developed a complex network model, where modules corresponding to sensorial and symbolic memories interact, representing unconscious and conscious mental processes. The model illustrates Freud's idea that consciousness is related to symbolic and linguistic memory activity in the brain. We have introduced a generalization of the Boltzmann machine to model memory associativity. Model behavior is illustrated with simulations and some of its properties are analyzed with methods from statistical mechanics.
Generalized memory associativity in a network model for the neuroses.
Wedemann, Roseli S; Donangelo, Raul; de Carvalho, Luís A V
2009-03-01
We review concepts introduced in earlier work, where a neural network mechanism describes some mental processes in neurotic pathology and psychoanalytic working-through, as associative memory functioning, according to the findings of Freud. We developed a complex network model, where modules corresponding to sensorial and symbolic memories interact, representing unconscious and conscious mental processes. The model illustrates Freud's idea that consciousness is related to symbolic and linguistic memory activity in the brain. We have introduced a generalization of the Boltzmann machine to model memory associativity. Model behavior is illustrated with simulations and some of its properties are analyzed with methods from statistical mechanics. PMID:19335020
Generalized gas-solid adsorption modeling: Single-component equilibria
Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.
2015-01-07
Over the last several decades, modeling of gas–solid adsorption at equilibrium has generally been accomplished through the use of isotherms such as the Freundlich, Langmuir, Tóth, and other similar models. While these models are relatively easy to adapt for describing experimental data, their simplicity limits their generality to be used with many different sets of data. This limitation forces engineers and scientists to test each different model in order to evaluate which one can best describe their data. Additionally, the parameters of these models all have a different physical interpretation, which may have an effect on how they can bemore » further extended into kinetic, thermodynamic, and/or mass transfer models for engineering applications. Therefore, it is paramount to adopt not only a more general isotherm model, but also a concise methodology to reliably optimize for and obtain the parameters of that model. A model of particular interest is the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm. The GSTA isotherm has enormous flexibility, which could potentially be used to describe a variety of different adsorption systems, but utilizing this model can be fairly difficult due to that flexibility. To circumvent this complication, a comprehensive methodology and computer code has been developed that can perform a full equilibrium analysis of adsorption data for any gas-solid system using the GSTA model. The code has been developed in C/C++ and utilizes a Levenberg–Marquardt’s algorithm to handle the non-linear optimization of the model parameters. Since the GSTA model has an adjustable number of parameters, the code iteratively goes through all number of plausible parameters for each data set and then returns the best solution based on a set of scrutiny criteria. Data sets at different temperatures are analyzed serially and then linear correlations with temperature are made for the parameters of the model. The end result is a full set
Generalized gas-solid adsorption modeling: Single-component equilibria
Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.
2015-01-07
Over the last several decades, modeling of gas–solid adsorption at equilibrium has generally been accomplished through the use of isotherms such as the Freundlich, Langmuir, Tóth, and other similar models. While these models are relatively easy to adapt for describing experimental data, their simplicity limits their generality to be used with many different sets of data. This limitation forces engineers and scientists to test each different model in order to evaluate which one can best describe their data. Additionally, the parameters of these models all have a different physical interpretation, which may have an effect on how they can be further extended into kinetic, thermodynamic, and/or mass transfer models for engineering applications. Therefore, it is paramount to adopt not only a more general isotherm model, but also a concise methodology to reliably optimize for and obtain the parameters of that model. A model of particular interest is the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm. The GSTA isotherm has enormous flexibility, which could potentially be used to describe a variety of different adsorption systems, but utilizing this model can be fairly difficult due to that flexibility. To circumvent this complication, a comprehensive methodology and computer code has been developed that can perform a full equilibrium analysis of adsorption data for any gas-solid system using the GSTA model. The code has been developed in C/C++ and utilizes a Levenberg–Marquardt’s algorithm to handle the non-linear optimization of the model parameters. Since the GSTA model has an adjustable number of parameters, the code iteratively goes through all number of plausible parameters for each data set and then returns the best solution based on a set of scrutiny criteria. Data sets at different temperatures are analyzed serially and then linear correlations with temperature are made for the parameters of the model. The end result is a full set of
Stage fright in musicians: a model illustrating the effect of beta blockers.
Neftel, K A; Adler, R H; Käppeli, L; Rossi, M; Dolder, M; Käser, H E; Bruggesser, H H; Vorkauf, H
1982-11-01
Stage fright was used to investigate the mode of action of beta blockers in acute anxiety and on the technical-motor performance of 22 performing string players. They received 100 mg of atenolol or placebo 6.5 hr before performing either in the presence or absence of an audience. Continuous heart rate, stage fright (especially devised rating scale), technical-motor performance (runs of fast notes, trills, vibratos), and urine catecholamine levels were assessed. Before an audience the placebo group showed a significant impairment of technical-motor performance (increase in the relative variance of repeated fast elements of movements: + 25.68%, p less than 0.01) as compared to performance with no audience present; there was a slight but not significant improvement under beta blockade (- 7.48%). Heart rate was significantly lower under beta blockade than under placebo (p less than 0.001). Urine catecholamine levels increased twice as much under beta blockade as under placebo before an audience (p less than 0.01). Beta blockade did not influence stage fright measured before performing, but reduced it (measured immediately after the concert) during the concert. We conclude that the drug was at least partially effective as shown by an improvement in technical-motor performance, and that the beneficial effects of beta blockade in stage fright only involve a peripheral site of action. PMID:6129674
Interacting holographic dark energy models: a general approach
NASA Astrophysics Data System (ADS)
Som, S.; Sil, A.
2014-08-01
Dark energy models inspired by the cosmological holographic principle are studied in homogeneous isotropic spacetime with a general choice for the dark energy density . Special choices of the parameters enable us to obtain three different holographic models, including the holographic Ricci dark energy (RDE) model. Effect of interaction between dark matter and dark energy on the dynamics of those models are investigated for different popular forms of interaction. It is found that crossing of phantom divide can be avoided in RDE models for β>0.5 irrespective of the presence of interaction. A choice of α=1 and β=2/3 leads to a varying Λ-like model introducing an IR cutoff length Λ -1/2. It is concluded that among the popular choices an interaction of the form Q∝ Hρ m suits the best in avoiding the coincidence problem in this model.
Patterns of Neutral Diversity Under General Models of Selective Sweeps
Coop, Graham; Ralph, Peter
2012-01-01
Two major sources of stochasticity in the dynamics of neutral alleles result from resampling of finite populations (genetic drift) and the random genetic background of nearby selected alleles on which the neutral alleles are found (linked selection). There is now good evidence that linked selection plays an important role in shaping polymorphism levels in a number of species. One of the best-investigated models of linked selection is the recurrent full-sweep model, in which newly arisen selected alleles fix rapidly. However, the bulk of selected alleles that sweep into the population may not be destined for rapid fixation. Here we develop a general model of recurrent selective sweeps in a coalescent framework, one that generalizes the recurrent full-sweep model to the case where selected alleles do not sweep to fixation. We show that in a large population, only the initial rapid increase of a selected allele affects the genealogy at partially linked sites, which under fairly general assumptions are unaffected by the subsequent fate of the selected allele. We also apply the theory to a simple model to investigate the impact of recurrent partial sweeps on levels of neutral diversity and find that for a given reduction in diversity, the impact of recurrent partial sweeps on the frequency spectrum at neutral sites is determined primarily by the frequencies rapidly achieved by the selected alleles. Consequently, recurrent sweeps of selected alleles to low frequencies can have a profound effect on levels of diversity but can leave the frequency spectrum relatively unperturbed. In fact, the limiting coalescent model under a high rate of sweeps to low frequency is identical to the standard neutral model. The general model of selective sweeps we describe goes some way toward providing a more flexible framework to describe genomic patterns of diversity than is currently available. PMID:22714413
Pechik, I.; Ji, Xinhua; Moult, J. |
1996-02-13
The crystal structure of the mutant deoxyhemoglobin in which the {beta}-globin Val{sup 67}(E11) has been replaced with threonine has been determined at 2.2 {angstrom} resolution. Prior to the crystal structure determination, molecular modeling indicated that the Thr{sup 67}(E11) side chain hydroxyl group in the distal {beta}-heme pocket forms a hydrogen bond with the backbone carbonyl of His{sup 63}(E7) and is within hydrogen-bonding distance of the N{sup {delta}} of His{sup 63}(E7). The mutant crystal structure indicates only small changes in conformation in the vicinity of the E11 mutation confirming the molecular modeling predictions. Comparison of the structures of the mutant {beta}-subunits and recombinant porcine myoglobin with the identical mutation indicates similar conformations of residues in the distal heme pocket, but there is no water molecule associated with either of the threonines of the {beta}-subunits. The introduction of threonine into the distal heme pocket, despite having only small perturbations in the local structure, has a marked affect on the interaction with ligands. In the oxy derivative there is a 2-fold decrease in O{sub 2} affinity, and the rate of autoxidation is increased by 2 orders of magnitude. In the CO derivative the IR spectrum shows modifications with respect to that of normal human hemoglobin, suggesting the presence of multiple CO conformers. In the nitrosyl derivative an interaction with the O{sup {gamma}} atom of Thr{sup 67}(E11) is probably responsible for the 10-fold increase in the rate of NO release from the {beta}-subunits. In the aquomet derivative there is a 6-fold decrease in the rate of hemin dissociation suggesting an interaction of the Fe-coordinated water with the O{sup {gamma}} of Thr{sup 67}(E11). 51 refs., 6 figs., 5 tabs.
Study of high-beta ballooning modes
Price, H.D.; Benjamin, N.M.P.; Kang, B.K.; Lichtenberg, A.J.; Lieberman, M.A.
1985-01-01
Ballooning instabilities are studied in the Berkeley multiple mirror experiment. Counterstreaming theta pinch and Marshall gun source hydrogen plasmas are used to achieve a high beta ( ..beta..>25%), where ..beta.. is the ratio of plasma to magnetic pressure at temperatures T/sub e/ = T/sub i/roughly-equal15 eV. Four magnetic field configurations are investigated, each at varying mirror ratios, to explore a range of drive and connection length parameters. In two of these the magnetic field is pulsed from a stable to a locally unstable configuration for initiation of ballooning activity. The other two (static) configurations are a weakly unstable local field region, and the standard linked quadrupole multiple-mirror configuration. Depending on the configuration, critical ..beta..'s are found for the onset of ballooning that vary from 5% for the most unstable configuration to greater than 25% for the standard multiple-mirror configuration. The m = 1 azimuthal mode is predominant, with some admixture of m = 2. The experimental results are compared with predictions from a magnetohydrodynamic theory. In the model the pressure is taken to be isotropic and constant along the axis, except in the diverging field regions at the device ends where the pressure falls to maintain beta constant, consistent with experimental observations. The theoretical results generally predict somewhat higher critical betas for the m = 1 mode than those observed. Estimates of the effect of finite Larmor radii, nearby conducting walls, axially nonuniform pressure profiles and resistivity, are also given.
Generalized nonlinear models for rear-end crash risk analysis.
Lao, Yunteng; Zhang, Guohui; Wang, Yinhai; Milton, John
2014-01-01
A generalized nonlinear model (GNM)-based approach for modeling highway rear-end crash risk is formulated using Washington State traffic safety data. Previous studies majorly focused on causal factor identification and crash risk modeling using Generalized linear Models (GLMs), such as Poisson regression, Logistic regression, etc. However, their basic assumption of a generalized linear relationship between the dependent variable (for example, crash rate) and independent variables (for example, contribute factors to crashes) established via a link function can be often violated in reality. Consequently, the GLM-based modeling results could provide biased findings and conclusions. In this research, a GNM-based approach is developed to utilize a nonlinear regression function to better elaborate non-monotonic relationships between the independent and dependent variables using the rear end accident data collected from 10 highway routes from 2002 through 2006. The results show for example that truck percentage and grade have a parabolic impact: they increase crash risks initially, but decrease them after the certain thresholds. Such non-monotonic relationships cannot be captured by regular GLMs which further demonstrate the flexibility of GNM-based approaches in the nonlinear relationship among data and providing more reasonable explanations. The superior GNM-based model interpretations help better understand the parabolic impacts of some specific contributing factors for selecting and evaluating rear-end crash safety improvement plans. PMID:24125803
Suggesting a General ESP Model for Adult Learners
ERIC Educational Resources Information Center
Al-Jumaily, Samir
2011-01-01
The study suggests a general model that could guarantee the cooperation between teachers and their students to overcome the difficulties encountered in ESP learning. It tries to join together different perspectives in the research of adult education, specifically in the teaching of English for Specific Purposes. It also provides some sort of trust…
Generalized universality in the massive sine-Gordon model
Nagy, S.; Sailer, K.; Nandori, I.; Polonyi, J.
2008-01-15
A nontrivial interplay of the UV and IR scaling laws, a generalization of the universality is demonstrated in the framework of the massive sine-Gordon model, as a result of a detailed study of the global behavior of the renormalization group flow and the phase structure.
Computerized Classification Testing under the Generalized Graded Unfolding Model
ERIC Educational Resources Information Center
Wang, Wen-Chung; Liu, Chen-Wei
2011-01-01
The generalized graded unfolding model (GGUM) has been recently developed to describe item responses to Likert items (agree-disagree) in attitude measurement. In this study, the authors (a) developed two item selection methods in computerized classification testing under the GGUM, the current estimate/ability confidence interval method and the cut…
A Note on Keats' Generalization of the Rasch Model
ERIC Educational Resources Information Center
White, P. O.
1976-01-01
An alternative derivation is given for a generalization of the Rasch model which incorporates a guessing parameter. The probability of a correct response to the problem is a projective transformation of the problem difficulty. The ability and difficulty parameters separate into additive components. (Author/JKS)
Strategy Generalization across Orientation Tasks: Testing a Computational Cognitive Model
ERIC Educational Resources Information Center
Gunzelmann, Glenn
2008-01-01
Humans use their spatial information processing abilities flexibly to facilitate problem solving and decision making in a variety of tasks. This article explores the question of whether a general strategy can be adapted for performing two different spatial orientation tasks by testing the predictions of a computational cognitive model. Human…
A general circulation model (GCM) parameterization of Pinatubo aerosols
Lacis, A.A.; Carlson, B.E.; Mishchenko, M.I.
1996-04-01
The June 1991 volcanic eruption of Mt. Pinatubo is the largest and best documented global climate forcing experiment in recorded history. The time development and geographical dispersion of the aerosol has been closely monitored and sampled. Based on preliminary estimates of the Pinatubo aerosol loading, general circulation model predictions of the impact on global climate have been made.
Self-Control and General Models of Choice
ERIC Educational Resources Information Center
Navarick, Douglas J.; Fantino, Edmund
1976-01-01
Given an opportunity to choose between an immediate, small reward and a delayed, large reward, pigeons may commit themselves to the large reward, but if the choice is encountered they will almost always select the immediate, small reward. This study tested a model, developed by H. Rachlin and his co-workers, concerning some general theories of…
Model 200 crane, general arrangement & clearances. Colby Steel & ...
Model 200 crane, general arrangement & clearances. Colby Steel & Engineering Company, Vancouver B.C., Seattle, New York. Two elevations and cab plan. No architect noted, drawn by Gould. Sheet A2, no 6365. Scaled not given. August 10, 1942. Proposal no. 318. - United Engineering Company Shipyard, Crane, 2900 Main Street, Alameda, Alameda County, CA
Confidence Intervals for Assessing Heterogeneity in Generalized Linear Mixed Models
ERIC Educational Resources Information Center
Wagler, Amy E.
2014-01-01
Generalized linear mixed models are frequently applied to data with clustered categorical outcomes. The effect of clustering on the response is often difficult to practically assess partly because it is reported on a scale on which comparisons with regression parameters are difficult to make. This article proposes confidence intervals for…
A General Linear Model Approach to Adjusting the Cumulative GPA.
ERIC Educational Resources Information Center
Young, John W.
A general linear model (GLM), using least-squares techniques, was used to develop a criterion measure to replace freshman year grade point average (GPA) in college admission predictive validity studies. Problems with the use of GPA include those associated with the combination of grades from different courses and disciplines into a single measure,…
Stability of a general SEIV epidemic model with time delay
NASA Astrophysics Data System (ADS)
Hikal, M. M.; El-Sheikh, M. M. A.
2013-10-01
An SEIV epidemic model with a general nonlinear incidence rate, vaccination and time delay in treatment is considered. Sufficient conditions for the time delay to keep the stability of the endemic equilibria are given. A numerical simulations is given to illustrate our results.
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)
Microstrain temperature evolution in beta-eurcryptite ceramics: Measurement and model
Bruno, Giovanni; Garlea, Vasile O; Muth, Joseph T.; Efremov, Alexander; Watkins, Thomas R; Shyam, Amit
2012-01-01
Mechanisms of microcracking and stress release in {beta}-eucryptite ceramics were investigated by applying a combination of neutron diffraction (ND), dilatometry and the Integrity Factor Model (IFM). It was observed that the macroscopic thermal expansion of solid samples closely follows the lattice thermal expansion as a function of temperature, and both are dominated by microcracks closing (during heating) and opening (during cooling). Analogous experiments on powders showed that the stresses that manifest peak shift are indeed relieved by comminution, and that the resulting lattice thermal expansion can be considered as unconstrained. By means of Rietveld refinement of the ND data, the evolution with temperature of peak width parameters linked to strain distributions along the basal, pyramidal and axial planes could also be extracted. The peak width parameters S{sub HKL} correlated well with the strains calculated by peak shift and with the model results. Furthermore, while the peak shifts showed that the powders are basically stress free, the S{sub HKL} showed a strong evolution of the peak width. Powders carry, therefore, a measurable strain distribution inside the particles, owing to the thermal expansion anisotropy of the crystallites. The IFM allowed this behavior to be rationalized, and the effect of microcracking on thermal expansion to be quantified. Experimental data allowed accurate numerical prediction of microcracking on cooling and of the evolution of microstresses. They also allowed the derivation of the material elastic modulus from bulk thermal expansion curves through the IFM concept. Ultrasound resonance measurements of the elastic modulus strongly support these theoretical predictions.
Molecular modeling and docking analysis of beta-lactamases with inhibitors: a comparative study.
Danishuddin, Mohd; Khan, Asad U
Beta-lactamases are bacterial enzymes which impart resistance against β-lactam-antibiotics. CTX-Ms are the β-lactamases that target cephalosporin antibiotics (e.g. cefotaxime and ceftazidime) while SME-1, KPC-2, IMI-1 and SFC-1 target carbapenems. Clavulanic acid, sulbactam and tazobactam are traditional β-lactamase inhibitors while LN1-255 and NXL-104 whereas novel inhibitors, inhibiting the activity of these enzymes. Studying the binding pattern of these drugs is helpful in predicting the versatile inhibitors for betalactamases. The aims of the study were: describing the mode of interaction of CTX-M (modeled from the blaCTX-M gene of this study) and the said carbapenemases with their respective target drugs and inhibitors and to perform an in silico comparison of the efficacies of traditional and novel β-lactamase-inhibitors based on fitness score. The blaCTX-M marker was PCR-amplified from plasmid DNA of E. coli strain isolated from community-acquired urinary tract infection. E. coli C600 cells (harboring cloned blaCTX-M) were found positive for extended-spectrum-β-lactamase (ESBL) production by the double-disk-synergy test. The three dimensional structures of CTX-M-15, SME-1 and IMI-1 were predicted by Swiss Model Server. The interaction between selected structures and inhibitors was performed by GOLD 5.0. On the basis of the docking score and binding pattern, we conclude that compound LN1-255 followed by tazobactam is best inhibitor against all the selected target enzymes as compared to clavulanate, sulbactam and NXL-104. Five conserved amino acids, Ser70, Ser130, Lys235, Thr236 and Gly237 were found crucial in stabilizing the complexes through hydrogen bonding and hydrophobic interactions. PMID:23202428
Hoffmann, S
1985-01-01
Fifty-eight general practitioners took throat swabs from 434 patients with sore throats. Office cultures were performed on Streptocult supplemented with bacitracin disks in an attempt to carry out primary grouping of beta-hemolytic streptococci (BHS). In 424 cases the findings were compared with those obtained in a microbiological laboratory. Streptocult showed a sensitivity of 75% and a specificity of 84% in the detection of BHS. The office-performed grouping procedure of the correctly detected BHS, however, only had a sensitivity of 65% and a specificity of 87%. Overall, as many as 45% of the patients with BHS group A were misdiagnosed. The unsatisfactory results obtained with primary grouping of BHS may be due partly to incorrect determinations of the diameter of the inhibition zone around the bacitracin disks and partly to an inappropriate choice of breakpoint. It is concluded that cultures of throat swabs on Streptocult in general practice should not be accompanied by attempts to carry out primary grouping with bacitracin disks. A laboratory investigation showed that incubation at room temperature for 48 h and at 35 degrees C for 24 h gave identical BHS positivity rates. PMID:3908467
Generalized models of unification of dark matter and dark energy
NASA Astrophysics Data System (ADS)
Čaplar, Neven; Štefančić, Hrvoje
2013-01-01
A model of unification of dark matter and dark energy based on the modeling of the speed of sound as a function of the parameter of the equation of state is introduced. It is found that the model in which the speed of sound depends on the power of the parameter of the equation of state, cs2=α(-w)γ, contains the generalized Chaplygin gas models as its subclass. An effective scalar field description of the model is obtained in a parametric form which in some cases can be translated into a closed form solution for the scalar field potential. A constraint on model parameters is obtained using the observational data on the Hubble parameter at different redshifts.
Generalized Levy-walk model for DNA nucleotide sequences
NASA Technical Reports Server (NTRS)
Buldyrev, S. V.; Goldberger, A. L.; Havlin, S.; Simons, M.; Stanley, H. E.
1993-01-01
We propose a generalized Levy walk to model fractal landscapes observed in noncoding DNA sequences. We find that this model provides a very close approximation to the empirical data and explains a number of statistical properties of genomic DNA sequences such as the distribution of strand-biased regions (those with an excess of one type of nucleotide) as well as local changes in the slope of the correlation exponent alpha. The generalized Levy-walk model simultaneously accounts for the long-range correlations in noncoding DNA sequences and for the apparently paradoxical finding of long subregions of biased random walks (length lj) within these correlated sequences. In the generalized Levy-walk model, the lj are chosen from a power-law distribution P(lj) varies as lj(-mu). The correlation exponent alpha is related to mu through alpha = 2-mu/2 if 2 < mu < 3. The model is consistent with the finding of "repetitive elements" of variable length interspersed within noncoding DNA.
Strategy generalization across orientation tasks: testing a computational cognitive model.
Gunzelmann, Glenn
2008-07-01
Humans use their spatial information processing abilities flexibly to facilitate problem solving and decision making in a variety of tasks. This article explores the question of whether a general strategy can be adapted for performing two different spatial orientation tasks by testing the predictions of a computational cognitive model. Human performance was measured on an orientation task requiring participants to identify the location of a target either on a map (find-on-map) or within an egocentric view of a space (find-in-scene). A general strategy instantiated in a computational cognitive model of the find-on-map task, based on the results from Gunzelmann and Anderson (2006), was adapted to perform both tasks and used to generate performance predictions for a new study. The qualitative fit of the model to the human data supports the view that participants were able to tailor a general strategy to the requirements of particular spatial tasks. The quantitative differences between the predictions of the model and the performance of human participants in the new experiment expose individual differences in sample populations. The model provides a means of accounting for those differences and a framework for understanding how human spatial abilities are applied to naturalistic spatial tasks that involve reasoning with maps. PMID:21635355
FLRW non-singular cosmological model in general relativity
NASA Astrophysics Data System (ADS)
Jas Pacif, Shibesh Kumar; Mishra, Bivudutta
2015-12-01
A singularity free cosmological model is obtained in a homogeneous and isotropic background with a specific form of the Hubble parameter in the presence of an interacting dark energy represented by a time-varying cosmological constant in general relativity. Different cases that arose have been extensively studied for different values of the curvature parameter. Some interesting results have been found with this form of the Hubble parameter to meet the possible negative value of the deceleration parameter ≤ft({ - \\frac{1}{3} ≤slant q < 0} \\right) as the current observations reveal. For some particular values of these parameters, the model reduces to Berman's model.
Generalization of a model of hysteresis for dynamical systems.
Piquette, Jean C; McLaughlin, Elizabeth A; Ren, Wei; Mukherjee, Binu K
2002-06-01
A previously described model of hysteresis [J. C. Piquette and S. E. Forsythe, J. Acoust. Soc. Am. 106, 3317-3327 (1999); 106, 3328-3334 (1999)] is generalized to apply to a dynamical system. The original model produces theoretical hysteresis loops that agree well with laboratory measurements acquired under quasi-static conditions. The loops are produced using three-dimensional rotation matrices. An iterative procedure, which allows the model to be applied to a dynamical system, is introduced here. It is shown that, unlike the quasi-static case, self-crossing of the loops is a realistic possibility when inertia and viscous friction are taken into account. PMID:12083200
Generalized Mathematical Model Predicting the Mechanical Processing Topography
NASA Astrophysics Data System (ADS)
Leonov, S. L.; Markov, A. M.; Belov, A. B.; Sczygol, N.
2016-04-01
We propose a unified approach for the construction of mathematical models for the formation of surface topography and calculation of its roughness parameters for different methods of machining processes. The approach is based on a process of geometric copy tool in the material which superimposes plastico-elastic deformation, oscillatory occurrences in processing and random components of the profile. The unified approach makes it possible to reduce the time forcreation of simulated stochastic model for a specific type of processing and guarantee the accuracy of geometric parameters calculation of the surface. We make an application example of generalized model for calculation of roughness density distribution Ra in external sharpening.
Contribution towards statistical intercomparison of general circulation models
Sengupta, S.; Boyle, J.
1995-06-01
The Atmospheric Model Intercomparison Project (AMIP) of the World Climate Research Programme`s Working Group on Numerical Experimentation (WGNE) is an ambitious attempt to comprehensively intercompare atmospheric General Circulation Models (GCMs). The participants in AMIP simulate the global atmosphere for the decade 1979 to 1988 using, a common solar constant and Carbon Dioxide(CO{sub 2}) concentration and a common monthly averaged sea surface temperature (SST) and sea ice data set. In this work we attempt to present a statistical framework to address the difficult task of model intercomparison and verification.
Generalized Jaynes-Cummings model as a quantum search algorithm
Romanelli, A.
2009-07-15
We propose a continuous time quantum search algorithm using a generalization of the Jaynes-Cummings model. In this model the states of the atom are the elements among which the algorithm realizes the search, exciting resonances between the initial and the searched states. This algorithm behaves like Grover's algorithm; the optimal search time is proportional to the square root of the size of the search set and the probability to find the searched state oscillates periodically in time. In this frame, it is possible to reinterpret the usual Jaynes-Cummings model as a trivial case of the quantum search algorithm.
Variational Bounds for the Generalized Random Energy Model
NASA Astrophysics Data System (ADS)
Giardinà, Cristian; Starr, Shannon
2007-04-01
We compute the pressure of the random energy model (REM) and generalized random energy model (GREM) by establishing variational upper and lower bounds. For the upper bound, we generalize Guerra's "broken replica symmetry bounds," and identify the random probability cascade as the appropriate random overlap structure for the model. For the REM the lower bound is obtained, in the high temperature regime using Talagrand's concentration of measure inequality, and in the low temperature regime using convexity and the high temperature formula. The lower bound for the GREM follows from the lower bound for the REM by induction. While the argument for the lower bound is fairly standard, our proof of the upper bound is new.
Generalized model for all-optical light modulation in bacteriorhodopsin
NASA Astrophysics Data System (ADS)
Roy, Sukhdev; Singh, C. P.; Reddy, K. P. J.
2001-10-01
We present a generalized model for the photochemical cycle of bacteriorhodopsin (bR) protein molecule. Rate equations have been solved for the detailed light-induced processes in bR for its nine states: B→K↔L↔MI→MII↔N↔O↔P→Q→B. The complete steady-state intensity-induced population densities in various states of the molecule have been computed to obtain a general, exact, and analytical expression for the nonlinear absorption coefficient for multiple modulation pump laser beams. All-optical light modulation of different probe laser beam transmissions by intensity induced population changes due to one and two modulation laser beams has been analyzed. The proposed model has been shown to accurately model experimental results.
A general circulation model of a Venus-like atmosphere
NASA Astrophysics Data System (ADS)
Rossow, W. B.
1983-02-01
Heat and momentum budgets are investigated for a three-dimensional general circulation model of a Venus-like, massive and slowly rotating atmosphere which is forced with an axisymmetric radiative heating/cooling distribution. Model results confirm the suggestions of Gierasch (1975) and Rossow and Williams (1979), with a mean meridional circulation which, despite its multicellular form, interacts with quasi-barotropic eddies produced by zonal flow shear instability to yield a weak superrotation of the entire model atmosphere. This process is sufficiently general to encourage the conclusion that it will occur in all slowly rotating atmospheres. Whether it can accelerate wind speeds as large as those observed on Venus cannot presently be determined.
The generalized Nash model for river flow routing
NASA Astrophysics Data System (ADS)
Yan, Baowei; Guo, Shenglian; Liang, Ji; Sun, Huaiwei
2015-11-01
The widely used instantaneous unit hydrograph (IUH) based on the Nash cascade reservoir model was obtained under a zero initial condition, or equivalently an empty reservoir assumption. In this study, a more general case with a non-zero initial condition is considered in the derivation of the classical Nash model. A generalized Nash model (GNM) has been deduced using the Laplace transform and the principle of mathematical induction. For river flow routing, the GNM physically interprets the formation of downstream outflow, i.e. the summation of the recession flow of the initial channel storage and the response to upstream inflow. The GNM, written in a state-space representation, is able to update the state of the river system in time, and hence can be applied in real-time forecasting. Two separate case studies have been used for illustration. It is indicated that the proposed updating procedure results in improved river flow forecasts when compared with the traditional IUH method.
A parallel coupled oceanic-atmospheric general circulation model
Wehner, M.F.; Bourgeois, A.J.; Eltgroth, P.G.; Duffy, P.B.; Dannevik, W.P.
1994-12-01
The Climate Systems Modeling group at LLNL has developed a portable coupled oceanic-atmospheric general circulation model suitable for use on a variety of massively parallel (MPP) computers of the multiple instruction, multiple data (MIMD) class. The model is composed of parallel versions of the UCLA atmospheric general circulation model, the GFDL modular ocean model (MOM) and a dynamic sea ice model based on the Hiber formulation extracted from the OPYC ocean model. The strategy to achieve parallelism is twofold. One level of parallelism is accomplished by applying two dimensional domain decomposition techniques to each of the three constituent submodels. A second level of parallelism is attained by a concurrent execution of AGCM and OGCM/sea ice components on separate sets of processors. For this functional decomposition scheme, a flux coupling module has been written to calculate the heat, moisture and momentum fluxes independent of either the AGCM or the OGCM modules. The flux coupler`s other roles are to facilitate the transfer of data between subsystem components and processors via message passing techniques and to interpolate and aggregate between the possibly incommensurate meshes.
A cumulus parameterization scheme designed for nested grid meso-{beta} scale models
Weissbluth, M.J.; Cotton, W.R.
1991-12-31
A generalized cumulus parameterization based upon higher order turbulence closure has been incorporated into one dimensional simulations. The scheme consists of a level 2.5w turbulence closure scheme mated with a convective adjustment scheme. The convective adjustment scheme includes a gradient term which can be interpreted as either a subsidence term when the scheme is used in large scale models or a mesoscale compensation term when the scheme is used in mesoscale models. The scheme also includes a convective adjustment term which is interpreted as a detrainment term in large scale models. In mesoscale models, the mesoscale compensation term and the advection by the mean vertical motions combine to yield no net advection which is desirable since the convective moistening and heating is now wholly accomplished by the convective adjustment term; double counting is then explicitly eliminated. One dimensional simulations indicate satisfactory performance of the cumulus parameterization scheme for a non-entraining updraft.
A cumulus parameterization scheme designed for nested grid meso-. beta. scale models
Weissbluth, M.J.; Cotton, W.R.
1991-01-01
A generalized cumulus parameterization based upon higher order turbulence closure has been incorporated into one dimensional simulations. The scheme consists of a level 2.5w turbulence closure scheme mated with a convective adjustment scheme. The convective adjustment scheme includes a gradient term which can be interpreted as either a subsidence term when the scheme is used in large scale models or a mesoscale compensation term when the scheme is used in mesoscale models. The scheme also includes a convective adjustment term which is interpreted as a detrainment term in large scale models. In mesoscale models, the mesoscale compensation term and the advection by the mean vertical motions combine to yield no net advection which is desirable since the convective moistening and heating is now wholly accomplished by the convective adjustment term; double counting is then explicitly eliminated. One dimensional simulations indicate satisfactory performance of the cumulus parameterization scheme for a non-entraining updraft.
Generalized slave-particle method for extended Hubbard models
NASA Astrophysics Data System (ADS)
Georgescu, Alexandru B.; Ismail-Beigi, Sohrab
2015-12-01
We introduce a set of generalized slave-particle models for extended Hubbard models that treat localized electronic correlations using slave-boson decompositions. Our models automatically include two slave-particle methods of recent interest, the slave-rotor and slave-spin methods, as well as a ladder of new intermediate models where one can choose which of the electronic degrees of freedom (e.g., spin or orbital labels) are treated as correlated degrees of freedom by the slave bosons. In addition, our method removes the aberrant behavior of the slave-rotor model, where it systematically overestimates the importance of electronic correlation effects for weak interaction strength, by removing the contribution of unphysical states from the bosonic Hilbert space. The flexibility of our formalism permits one to separate and isolate the effect of correlations on the key degrees of freedom.
Rotating-fluid experiments with an atmospheric general circulation model
NASA Technical Reports Server (NTRS)
Geisler, J. E.; Pitcher, E. J.; Malone, R. C.
1983-01-01
In order to determine features of rotating fluid flow that are dependent on the geometry, rotating annulus-type experiments are carried out with a numerical model in spherical coordinates. Rather than constructing and testing a model expressly for this purpose, it is found expedient to modify an existing general circulation model of the atmosphere by removing the model physics and replacing the lower boundary with a uniform surface. A regime diagram derived from these model experiments is presented; its major features are interpreted and contrasted with the major features of rotating annulus regime diagrams. Within the wave regime, a narrow region is found where one or two zonal wave numbers are dominant. The results reveal no upper symmetric regime; wave activity at low rotation rates is thought to be maintained by barotropic rather than baroclinic processes.
Hairy black holes in the general Skyrme model
NASA Astrophysics Data System (ADS)
Adam, C.; Kichakova, O.; Shnir, Ya.; Wereszczynski, A.
2016-07-01
We study the existence of hairy black holes in the generalized Einstein-Skyrme model. It is proven that in the Bogomol'nyi-Prasad-Sommerfield model limit there are no hairy black hole solutions, although the model admits gravitating (and flat space) solitons. Furthermore, we find strong evidence that a necessary condition for the existence of black holes with Skyrmionic hair is the inclusion of the Skyrme term L4. As an example, we show that there are no hairy black holes in the L2+L6+L0 model and present a new kind of black hole solutions with compact Skyrmion hair in the L4+L6+L0 model.
A generalized gamma mixture model for ultrasonic tissue characterization.
Vegas-Sanchez-Ferrero, Gonzalo; Aja-Fernandez, Santiago; Palencia, Cesar; Martin-Fernandez, Marcos
2012-01-01
Several statistical models have been proposed in the literature to describe the behavior of speckles. Among them, the Nakagami distribution has proven to very accurately characterize the speckle behavior in tissues. However, it fails when describing the heavier tails caused by the impulsive response of a speckle. The Generalized Gamma (GG) distribution (which also generalizes the Nakagami distribution) was proposed to overcome these limitations. Despite the advantages of the distribution in terms of goodness of fitting, its main drawback is the lack of a closed-form maximum likelihood (ML) estimates. Thus, the calculation of its parameters becomes difficult and not attractive. In this work, we propose (1) a simple but robust methodology to estimate the ML parameters of GG distributions and (2) a Generalized Gama Mixture Model (GGMM). These mixture models are of great value in ultrasound imaging when the received signal is characterized by a different nature of tissues. We show that a better speckle characterization is achieved when using GG and GGMM rather than other state-of-the-art distributions and mixture models. Results showed the better performance of the GG distribution in characterizing the speckle of blood and myocardial tissue in ultrasonic images. PMID:23424602
A general health policy model: update and applications.
Kaplan, R M; Anderson, J P
1988-01-01
This article describes the development of a General Health Policy Model that can be used for program evaluation, population monitoring, clinical research, and policy analysis. An important component of the model, the Quality of Well-being scale (QWB) combines preference-weighted measures of symptoms and functioning to provide a numerical point-in-time expression of well-being, ranging from 0 for death to 1.0 for asymptomatic optimum functioning. The level of wellness at particular points in time is governed by the prognosis (transition rates or probabilities) generated by the underlying disease or injury under different treatment (control) variables. Well-years result from integrating the level of wellness, or health-related quality of life, over the life expectancy. Several issues relevant to the application of the model are discussed. It is suggested that a quality of life measure need not have separate components for social and mental health. Social health has been difficult to define; social support may be a poor criterion for resource allocation; and some evidence suggests that aspects of mental health are captured by the general measure. Although it has been suggested that measures of child health should differ from those used for adults, we argue that a separate conceptualization of child health creates new problems for policy analysis. After offering several applications of the model for the evaluation of prevention programs, we conclude that many of the advantages of general measures have been overlooked and should be given serious consideration in future studies. PMID:3384669
A Generalized Gamma Mixture Model for Ultrasonic Tissue Characterization
Palencia, Cesar; Martin-Fernandez, Marcos
2012-01-01
Several statistical models have been proposed in the literature to describe the behavior of speckles. Among them, the Nakagami distribution has proven to very accurately characterize the speckle behavior in tissues. However, it fails when describing the heavier tails caused by the impulsive response of a speckle. The Generalized Gamma (GG) distribution (which also generalizes the Nakagami distribution) was proposed to overcome these limitations. Despite the advantages of the distribution in terms of goodness of fitting, its main drawback is the lack of a closed-form maximum likelihood (ML) estimates. Thus, the calculation of its parameters becomes difficult and not attractive. In this work, we propose (1) a simple but robust methodology to estimate the ML parameters of GG distributions and (2) a Generalized Gama Mixture Model (GGMM). These mixture models are of great value in ultrasound imaging when the received signal is characterized by a different nature of tissues. We show that a better speckle characterization is achieved when using GG and GGMM rather than other state-of-the-art distributions and mixture models. Results showed the better performance of the GG distribution in characterizing the speckle of blood and myocardial tissue in ultrasonic images. PMID:23424602
A generalized conditional heteroscedastic model for temperature downscaling
NASA Astrophysics Data System (ADS)
Modarres, R.; Ouarda, T. B. M. J.
2014-11-01
This study describes a method for deriving the time varying second order moment, or heteroscedasticity, of local daily temperature and its association to large Coupled Canadian General Circulation Models predictors. This is carried out by applying a multivariate generalized autoregressive conditional heteroscedasticity (MGARCH) approach to construct the conditional variance-covariance structure between General Circulation Models (GCMs) predictors and maximum and minimum temperature time series during 1980-2000. Two MGARCH specifications namely diagonal VECH and dynamic conditional correlation (DCC) are applied and 25 GCM predictors were selected for a bivariate temperature heteroscedastic modeling. It is observed that the conditional covariance between predictors and temperature is not very strong and mostly depends on the interaction between the random process governing temporal variation of predictors and predictants. The DCC model reveals a time varying conditional correlation between GCM predictors and temperature time series. No remarkable increasing or decreasing change is observed for correlation coefficients between GCM predictors and observed temperature during 1980-2000 while weak winter-summer seasonality is clear for both conditional covariance and correlation. Furthermore, the stationarity and nonlinearity Kwiatkowski-Phillips-Schmidt-Shin (KPSS) and Brock-Dechert-Scheinkman (BDS) tests showed that GCM predictors, temperature and their conditional correlation time series are nonlinear but stationary during 1980-2000 according to BDS and KPSS test results. However, the degree of nonlinearity of temperature time series is higher than most of the GCM predictors.
Some Bianchi type generalized ghost piligrim dark energy models in general relativity
NASA Astrophysics Data System (ADS)
Santhi, M. Vijaya; Aditya, Y.; Rao, V. U. M.
2016-04-01
In this paper, we consider Bianchi type-III, V and VI0 space-times filled with generalized ghost pilgrim dark energy (GGPDE) in general relativity. Here we assume the anisotropic distribution of GGPDE by introducing skewness parameters. To get deterministic solutions, we consider the scale factor a(t)=(tnet)^{ 1/k}, so called hybrid expansion, which yields a time dependent deceleration parameter, and exhibits a transition of the Universe from early decelerated phase to the recent accelerating phase. To describe the behavior of the obtained models we construct equation of state (ω_{Λ}), squared sound speed (vs2) parameters and ω_{Λ}-dot{ω }_{Λ}, r-s planes. It is worth mentioning here that the analysis of evolution parameters supports the concept of pilgrim dark energy (PDE). Also, these models remain stable for PDE parameter β =-0.5. Moreover, the cosmological planes correspond to Λ CDM limit as well as different well-known dark energy models.
Generalized Modeling of the Human Lower Limb Assembly
NASA Astrophysics Data System (ADS)
Cofaru, Ioana; Huzu, Iulia
2014-11-01
The main reason for creating a generalized assembly of the main bones of the lower human member is to create the premises of realizing a biomechanic assisted study which could be used for the study of the high range of varieties of pathologies that exist at this level. Starting from 3D CAD models of the main bones of the lower human member, which were realized in previous researches, in this study a generalized assembly system was developed, system in which are highlighted both the situation of an healthy subject and the situation of the situation of a subject affected by axial deviations. In order to achieve these purpose reference systems were created, systems that are in accordance with the mechanical axes and the anatomic axes of the lower member, which were later generally assembled in a manner that provides an easy customization option
Thermodynamics of a general stochastic model of magnetic hysteresis
NASA Astrophysics Data System (ADS)
Clatterbuck, D. M.; Morris, J. W., Jr.
2001-03-01
The thermodynamics of a general stochastic model of magnetic hysteresis are analyzed and the implications are discussed. The idea of modeling magnetic hysteresis in terms of a single degree of freedom evolving in a random potential was first proposed by Neel and subsequently studied by a number of authors. One difficulty with these models is the need for ad-hoc assumptions about the form of the random potential. Starting with a general stochastic model with no assumptions about the potential, an analysis of the conditions of equilibrium and stability demonstrates that the potential must divide into two components. One term represents the equilibrium behavior, and the other is a random pinning term with average slope of zero. This clarifies some of the past work on hysteresis and the magnetic Barkhausen effect. The thermodynamic analysis also demonstrates that the Jiles-Atherton hysteresis model can be derived from the stochastic model using a specific form of the potential. Research supported by DOE under Contract No. DE-AC03-76SF00098.
Hyperoxia modulates TGF-beta/BMP signaling in a mouse model of bronchopulmonary dysplasia.
Alejandre-Alcázar, Miguel A; Kwapiszewska, Grazyna; Reiss, Irwin; Amarie, Oana V; Marsh, Leigh M; Sevilla-Pérez, Julia; Wygrecka, Malgorzata; Eul, Bastian; Köbrich, Silke; Hesse, Mareike; Schermuly, Ralph T; Seeger, Werner; Eickelberg, Oliver; Morty, Rory E
2007-02-01
Prematurely born infants who require oxygen therapy often develop bronchopulmonary dysplasia (BPD), a debilitating disorder characterized by pronounced alveolar hypoplasia. Hyperoxic injury is believed to disrupt critical signaling pathways that direct lung development, causing BPD. We investigated the effects of normobaric hyperoxia on transforming growth factor (TGF)-beta and bone morphogenetic protein (BMP) signaling in neonatal C57BL/6J mice exposed to 21% or 85% O(2) between postnatal days P1 and P28. Growth and respiratory compliance were significantly impaired in pups exposed to 85% O(2), and these pups also exhibited a pronounced arrest of alveolarization, accompanied by dysregulated expression and localization of both receptor (ALK-1, ALK-3, ALK-6, and the TGF-beta type II receptor) and Smad (Smads 1, 3, and 4) proteins. TGF-beta signaling was potentiated, whereas BMP signaling was impaired both in the lungs of pups exposed to 85% O(2) as well as in MLE-12 mouse lung epithelial cells and NIH/3T3 and primary lung fibroblasts cultured in 85% O(2). After exposure to 85% O(2), primary alveolar type II cells were more susceptible to TGF-beta-induced apoptosis, whereas primary pulmonary artery smooth muscle cells were unaffected. Exposure of primary lung fibroblasts to 85% O(2) significantly enhanced the TGF-beta-stimulated production of the alpha(1) subunit of type I collagen (Ialpha(1)), tissue inhibitor of metalloproteinase-1, tropoelastin, and tenascin-C. These data demonstrated that hyperoxia significantly affects TGF-beta/BMP signaling in the lung, including processes central to septation and, hence, alveolarization. The amenability of these pathways to genetic and pharmacological manipulation may provide alternative avenues for the management of BPD. PMID:17071723
Attractive Hubbard model with disorder and the generalized Anderson theorem
Kuchinskii, E. Z. Kuleeva, N. A. Sadovskii, M. V.
2015-06-15
Using the generalized DMFT+Σ approach, we study the influence of disorder on single-particle properties of the normal phase and the superconducting transition temperature in the attractive Hubbard model. A wide range of attractive potentials U is studied, from the weak coupling region, where both the instability of the normal phase and superconductivity are well described by the BCS model, to the strong-coupling region, where the superconducting transition is due to Bose-Einstein condensation (BEC) of compact Cooper pairs, formed at temperatures much higher than the superconducting transition temperature. We study two typical models of the conduction band with semi-elliptic and flat densities of states, respectively appropriate for three-dimensional and two-dimensional systems. For the semi-elliptic density of states, the disorder influence on all single-particle properties (e.g., density of states) is universal for an arbitrary strength of electronic correlations and disorder and is due to only the general disorder widening of the conduction band. In the case of a flat density of states, universality is absent in the general case, but still the disorder influence is mainly due to band widening, and the universal behavior is restored for large enough disorder. Using the combination of DMFT+Σ and Nozieres-Schmitt-Rink approximations, we study the disorder influence on the superconducting transition temperature T{sub c} for a range of characteristic values of U and disorder, including the BCS-BEC crossover region and the limit of strong-coupling. Disorder can either suppress T{sub c} (in the weak-coupling region) or significantly increase T{sub c} (in the strong-coupling region). However, in all cases, the generalized Anderson theorem is valid and all changes of the superconducting critical temperature are essentially due to only the general disorder widening of the conduction band.
Gauge invariant backreaction in general single field models of inflation
NASA Astrophysics Data System (ADS)
Marozzi, G.; Vacca, G. P.
2013-07-01
In a general single field inflationary model, we consider the effects of long wavelength scalar fluctuations on the effective expansion rate and equation of state seen by a class of free-falling observers, using a physical gauge invariant formulation. In a previous work we showed that for a free massive inflaton no backreaction is observed within some constraints. In this paper we extend the validity of our previous results to the case of an arbitrary self-interacting inflation potential, working to second order in cosmological perturbation theory and to all order in slow-roll approximation. For these general inflationary models, we also show the equivalence of the free-falling observers to the ones comoving with the inflaton field.
Generalized Kronig-Penney model for ultracold atomic quantum systems
NASA Astrophysics Data System (ADS)
Negretti, A.; Gerritsma, R.; Idziaszek, Z.; Schmidt-Kaler, F.; Calarco, T.
2014-10-01
We study the properties of a quantum particle interacting with a one-dimensional structure of equidistant scattering centers. We derive an analytical expression for the dispersion relation and for the Bloch functions in the presence of both even and odd scattering waves within the pseudopotential approximation. This generalizes the well-known solid-state physics textbook result known as the Kronig-Penney model. Our generalized model can be used to describe systems such as degenerate Fermi gases interacting with ions or with another neutral atomic species confined in an optical lattice, thus enabling the investigation of polaron or Kondo physics within a simple formalism. We focus our attention on the specific atom-ion system and compare our findings with quantum defect theory. Excellent agreement is obtained within the regime of validity of the pseudopotential approximation. This enables us to derive a Bose-Hubbard Hamiltonian for a degenerate quantum Bose gas in a linear chain of ions.
Yang-Mills generalization of the geometrical collective model
NASA Astrophysics Data System (ADS)
Rosensteel, George; Sparks, Nick
2015-04-01
The geometrical or Bohr-Mottelson model is generalized and recast as a Yang-Mills theory. The gauge symmetry determines conservation of Kelvin circulation. The circulation commutes with the Hamiltonian when it is the sum of the kinetic energy and a potential that depends only on deformation. The conventional Bohr-Mottelson model is the special case of circulation zero, and wave functions are complex-valued. In the generalization, any quantized value of the circulation is allowed, and the wave functions are vector-valued. The Yang-Mills formulation introduces a new coupling between the geometrical and intrinsic degrees of freedom. The coupling appears in the covariant derivative term of the collective kinetic energy. This kind of coupling is sometimes called ``magnetic'' because of the analogy with electrodynamics.
A Coupled General Circulation Model of the Archean Earth
NASA Astrophysics Data System (ADS)
Wolf, E. T.; Toon, O. B.
2011-12-01
We present results from a new coupled general circulation model suitable for deep paleoclimate studies. Particular interest is given to the faint young Sun paradox. The model is based on the Community Earth System Model maintained by the National Center for Atmospheric Research [1]. Prognostic atmosphere, ocean, land, ice, and hydrological cycle models are coupled. A new correlated-k radiative transfer model has been implemented allowing accurate flux calculations for anoxic atmospheres containing high concentrations of CO2 and CH4 [2, 3]. This model represents a significant improvement upon one-dimensional radiative-convective climate models used previously to study ancient climate [4]. Cloud and ice albedo feedbacks will be accurately quantified and new constraints on Archean surface temperatures will be revealed. References [1] Collins W.D. et al. "Description of the NCAR Community Atmosphere Model (CAM 3.0)." NCAR Technical Note, 2004. [2] Toon O.B., McKay, C.P., Ackerman, T.P. "Rapid Calculation of Radiative Heating Rates and Photodissociation Rates in Inhomogeneous Multiple Scattering Atmospheres." J. Geo. Res., 94(D13), 16287 - 16301, 1989. [3] Mlawer, E.J., et al. "Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave." J. Geo. Res., 102(D14), 16663 - 16682, 1997. [4] Kasting J.F., Pollack, J.B., Crisp, D. "Effects of High CO2 Levels on Surface Temperature and Atmospheric Oxidation State of the Early Earth." J. Atm. Chem., 1, 403-428, 1984.
Generalized cable equation model for myelinated nerve fiber.
Einziger, Pinchas D; Livshitz, Leonid M; Mizrahi, Joseph
2005-10-01
Herein, the well-known cable equation for nonmyelinated axon model is extended analytically for myelinated axon formulation. The myelinated membrane conductivity is represented via the Fourier series expansion. The classical cable equation is thereby modified into a linear second order ordinary differential equation with periodic coefficients, known as Hill's equation. The general internal source response, expressed via repeated convolutions, uniformly converges provided that the entire periodic membrane is passive. The solution can be interpreted as an extended source response in an equivalent nonmyelinated axon (i.e., the response is governed by the classical cable equation). The extended source consists of the original source and a novel activation function, replacing the periodic membrane in the myelinated axon model. Hill's equation is explicitly integrated for the specific choice of piecewise constant membrane conductivity profile, thereby resulting in an explicit closed form expression for the transmembrane potential in terms of trigonometric functions. The Floquet's modes are recognized as the nerve fiber activation modes, which are conventionally associated with the nonlinear Hodgkin-Huxley formulation. They can also be incorporated in our linear model, provided that the periodic membrane point-wise passivity constraint is properly modified. Indeed, the modified condition, enforcing the periodic membrane passivity constraint on the average conductivity only leads, for the first time, to the inclusion of the nerve fiber activation modes in our novel model. The validity of the generalized transmission-line and cable equation models for a myelinated nerve fiber, is verified herein through a rigorous Green's function formulation and numerical simulations for transmembrane potential induced in three-dimensional myelinated cylindrical cell. It is shown that the dominant pole contribution of the exact modal expansion is the transmembrane potential solution of our
Generalized Bogoliubov Polariton Model: An Application to Stock Exchange Market
NASA Astrophysics Data System (ADS)
Thuy Anh, Chu; Anh, Truong Thi Ngoc; Lan, Nguyen Tri; Viet, Nguyen Ai
2016-06-01
A generalized Bogoliubov method for investigation non-simple and complex systems was developed. We take two branch polariton Hamiltonian model in second quantization representation and replace the energies of quasi-particles by two distribution functions of research objects. Application to stock exchange market was taken as an example, where the changing the form of return distribution functions from Boltzmann-like to Gaussian-like was studied.
Treatment of cloud radiative effects in general circulation models
Wang, W.C.; Dudek, M.P.; Liang, X.Z.; Ding, M.
1996-04-01
We participate in the Atmospheric Radiation Measurement (ARM) program with two objectives: (1) to improve the general circulation model (GCM) cloud/radiation treatment with a focus on cloud verticle overlapping and layer cloud optical properties, and (2) to study the effects of cloud/radiation-climate interaction on GCM climate simulations. This report summarizes the project progress since the Fourth ARM Science Team meeting February 28-March 4, 1994, in Charleston, South Carolina.
Credibility analysis of risk classes by generalized linear model
NASA Astrophysics Data System (ADS)
Erdemir, Ovgucan Karadag; Sucu, Meral
2016-06-01
In this paper generalized linear model (GLM) and credibility theory which are frequently used in nonlife insurance pricing are combined for reliability analysis. Using full credibility standard, GLM is associated with limited fluctuation credibility approach. Comparison criteria such as asymptotic variance and credibility probability are used to analyze the credibility of risk classes. An application is performed by using one-year claim frequency data of a Turkish insurance company and results of credible risk classes are interpreted.
Magnetization of the Ising model on the generalized checkerboard lattice
NASA Astrophysics Data System (ADS)
Lin, K. Y.; Wu, F. Y.
1988-08-01
We consider the Ising model on the generalized checkerboard lattice. Using a recent result by Baxter and Choy, we derive exact expressions for the magnetization of nodal spins at two values of the magnetic field, H=0 and H=i1/2 πkT. Our results are given in terms of Boltzmann weights of a unit cell of the checkerboard lattice without specifying its cell structures.
NASA Astrophysics Data System (ADS)
Civitarese, O.; Suhonen, J.; Zuber, K.
2015-07-01
The minimal extension of the standard model of electroweak interactions allows for massive neutrinos, a massive right-handed boson WR, and a left-right mixing angle ζ. While an estimate of the light (electron) neutrino can be extracted from the non-observation of the neutrinoless double beta decay, the limits on the mixing angle and the mass of the righthanded (RH) boson may be extracted from a combined analysis of the double beta decay measurements (GERDA, EXO-200 and KamLAND-Zen collaborations) and ATLAS data on the two-jets two-leptons signals following the excitation of a virtual RH boson mediated by a heavy-mass neutrino. In this work we shall compare results of both types of experiments, and show that the estimates are not in tension.
NASA Technical Reports Server (NTRS)
Levasseur, A.-C.; Meier, R. R.; Tinsley, B. A.
1976-01-01
New satellite Balmer alpha measurements and solar Lyman beta flux and line profile measurements, together with new measurements of the zodiacal light intensity used in correcting both ground and satellite Balmer alpha measurements for the effects of the Fraunhofer line in the zodiacal light, have been used in a reevaluation of the long-standing discrepancy between ground-based Balmer alpha emission rates and other geocoronal hydrogen parameters. The solar Lyman beta line center flux is found to be (4.1 plus or minus 1.3) billion photons per sq cm per sec per angstrom at S(10.7) equals 110 and, together with a current hydrogen model which has 92,000 atoms per cu cm at 650 km for T(inf) equals 950 K, gives good agreement between calculated Balmer alpha emission rates and the ground-based and satellite measurements.
Modeling Uncertainties in Power System by Generalized Lambda Distribution
NASA Astrophysics Data System (ADS)
Xiao, Qing
2014-06-01
This paper employs the generalized lambda distribution (GLD) to model random variables with various probability distributions in power system. In the context of the probability weighted moment (PWM), an optimization-free method is developed to assess the parameters of GLD. By equating the first four PWMs of GLD with those of the target random variable, a polynomial equation with one unknown is derived to solve for the parameters of GLD. When employing GLD to model correlated multivariate random variables, a method of accommodating the dependency is put forward. Finally, three examples are worked to demonstrate the proposed method.
Tropical disturbances in relation to general circulation modeling
NASA Technical Reports Server (NTRS)
Estoque, M. A.
1982-01-01
The initial results of an evaluation of the performance of the Goddard Laboratory of Atmospheric Simulation general circulation model depicting the tropical atmosphere during the summer are presented. Because the results show the existence of tropical wave disturbances throughout the tropics, the characteristics of synoptic disturbances over Africa were studied and a synoptic case study of a selected disturbance in this area was conducted. It is shown that the model is able to reproduce wave type synoptic disturbances in the tropics. The findings show that, in one of the summers simulated, the disturbances are predominantly closed vortices; in another summer, the predominant disturbances are open waves.
A Generalized Hydrodynamics Model for Strongly Coupled Plasmas
NASA Astrophysics Data System (ADS)
Diaw, Abdourahmane; Murillo, Michael Sean
2015-11-01
Starting with the equations of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, we obtain the density, momentum and stress tensor-moment equations. The closure proceeds in two steps. The first that guarantees an equilibrium state is given by density functional theory. It ensures self consistency in the equation-of-state properties of the plasma. The second involves modifying the two-body distribution function to include collisions in the relaxation of the stress tensor. The resulting generalized hydrodynamics thus includes all impacts of Coulomb coupling, viscous damping, and the high-frequency response. We compare our results with those of several known models, including generalized hydrodynamic theory and models obtained using the Singwi-Tosi-Land-Sjolander approximation and the quasi-localized charge approximation. We find that the viscoelastic response, including both the high-frequency elastic generalization and viscous wave damping, is important for correctly describing ion-acoustic waves. We illustrate this result by considering three very different systems: ultracold plasmas, dusty plasmas, and dense plasmas. The new model is validated by comparing its results with those obtained from molecular-dynamics simulations of Yukawa plasmas, and the agreement is excellent. This work was supported by the Air Force Office of Scientific Research (Grant No. FA9550-12-1-0344).
General covariant xp models and the Riemann zeros
NASA Astrophysics Data System (ADS)
Sierra, Germán
2012-02-01
We study a general class of models whose classical Hamiltonians are given by H = U(x)p + V(x)/p, where x and p are the position and momentum of a particle moving in one dimension, and U and V are positive functions. This class includes the Hamiltonians HI = x(p + 1/p) and HII = (x + 1/x)(p + 1/p), which have been recently discussed in connection with the nontrivial zeros of the Riemann zeta function. We show that all these models are covariant under general coordinate transformations. This remarkable property becomes explicit in the Lagrangian formulation which describes a relativistic particle moving in a (1+1)-dimensional spacetime whose metric is constructed from the functions U and V. General covariance is maintained by quantization and we find that the spectra are closely related to the geometry of the associated spacetimes. In particular, the Hamiltonian HI corresponds to a flat spacetime, whereas its spectrum approaches the Riemann zeros on average. The latter property also holds for the model HII, whose underlying spacetime is asymptotically flat. These results suggest the existence of a Hamiltonian whose underlying spacetime encodes the prime numbers, and whose spectrum provides the Riemann zeros.
Anisotropic Mesoscale Eddy Transport in Ocean General Circulation Models
NASA Astrophysics Data System (ADS)
Reckinger, S. J.; Fox-Kemper, B.; Bachman, S.; Bryan, F.; Dennis, J.; Danabasoglu, G.
2014-12-01
Modern climate models are limited to coarse-resolution representations of large-scale ocean circulation that rely on parameterizations for mesoscale eddies. The effects of eddies are typically introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically in general circulation models. Thus, only a single parameter, namely the eddy diffusivity, is used at each spatial and temporal location to impart the influence of mesoscale eddies on the resolved flow. However, the diffusive processes that the parameterization approximates, such as shear dispersion, potential vorticity barriers, oceanic turbulence, and instabilities, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters to three: a major diffusivity, a minor diffusivity, and the principal axis of alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the newly introduced parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces global temperature and salinity biases. These effects can be improved even further by parameterizing the anisotropic transport mechanisms in the ocean.
A general linear model for MEG beamformer imaging.
Brookes, Matthew J; Gibson, Andrew M; Hall, Stephen D; Furlong, Paul L; Barnes, Gareth R; Hillebrand, Arjan; Singh, Krish D; Holliday, Ian E; Francis, Sue T; Morris, Peter G
2004-11-01
A new general linear model (GLM) beamformer method is described for processing magnetoencephalography (MEG) data. A standard nonlinear beamformer is used to determine the time course of neuronal activation for each point in a predefined source space. A Hilbert transform gives the envelope of oscillatory activity at each location in any chosen frequency band (not necessary in the case of sustained (DC) fields), enabling the general linear model to be applied and a volumetric T statistic image to be determined. The new method is illustrated by a two-source simulation (sustained field and 20 Hz) and is shown to provide accurate localization. The method is also shown to locate accurately the increasing and decreasing gamma activities to the temporal and frontal lobes, respectively, in the case of a scintillating scotoma. The new method brings the advantages of the general linear model to the analysis of MEG data and should prove useful for the localization of changing patterns of activity across all frequency ranges including DC (sustained fields). PMID:15528094
Generalized Optoelectronic Model of Series-Connected Multijunction Solar Cells
Geisz, John F.; Steiner, Myles A.; Garcia, Ivan; France, Ryan M.; McMahon, William E.; Osterwald, Carl R.; Friedman, Daniel J.
2015-11-01
The emission of light from each junction in a series-connected multijunction solar cell, we found, both complicates and elucidates the understanding of its performance under arbitrary conditions. Bringing together many recent advances in this understanding, we present a general 1-D model to describe luminescent coupling that arises from both voltage-driven electroluminescence and voltage-independent photoluminescence in nonideal junctions that include effects such as Sah-Noyce-Shockley (SNS) recombination with n ≠ 2, Auger recombination, shunt resistance, reverse-bias breakdown, series resistance, and significant dark area losses. The individual junction voltages and currents are experimentally determined from measured optical and electrical inputs and outputs of the device within the context of the model to fit parameters that describe the devices performance under arbitrary input conditions. Furthermore, our techniques to experimentally fit the model are demonstrated for a four-junction inverted metamorphic solar cell, and the predictions of the model are compared with concentrator flash measurements.
Generalized Dynamic Factor Models for Mixed-Measurement Time Series
Cui, Kai; Dunson, David B.
2013-01-01
In this article, we propose generalized Bayesian dynamic factor models for jointly modeling mixed-measurement time series. The framework allows mixed-scale measurements associated with each time series, with different measurements having different distributions in the exponential family conditionally on time-varying latent factor(s). Efficient Bayesian computational algorithms are developed for posterior inference on both the latent factors and model parameters, based on a Metropolis Hastings algorithm with adaptive proposals. The algorithm relies on a Greedy Density Kernel Approximation (GDKA) and parameter expansion with latent factor normalization. We tested the framework and algorithms in simulated studies and applied them to the analysis of intertwined credit and recovery risk for Moody’s rated firms from 1982–2008, illustrating the importance of jointly modeling mixed-measurement time series. The article has supplemental materials available online. PMID:24791133
Generalized Dynamic Factor Models for Mixed-Measurement Time Series.
Cui, Kai; Dunson, David B
2014-02-12
In this article, we propose generalized Bayesian dynamic factor models for jointly modeling mixed-measurement time series. The framework allows mixed-scale measurements associated with each time series, with different measurements having different distributions in the exponential family conditionally on time-varying latent factor(s). Efficient Bayesian computational algorithms are developed for posterior inference on both the latent factors and model parameters, based on a Metropolis Hastings algorithm with adaptive proposals. The algorithm relies on a Greedy Density Kernel Approximation (GDKA) and parameter expansion with latent factor normalization. We tested the framework and algorithms in simulated studies and applied them to the analysis of intertwined credit and recovery risk for Moody's rated firms from 1982-2008, illustrating the importance of jointly modeling mixed-measurement time series. The article has supplemental materials available online. PMID:24791133
Generalized Optoelectronic Model of Series-Connected Multijunction Solar Cells
Geisz, John F.; Steiner, Myles A.; Garcia, Ivan; France, Ryan M.; McMahon, William E.; Osterwald, Carl R.; Friedman, Daniel J.
2015-10-02
The emission of light from each junction in a series-connected multijunction solar cell, we found, both complicates and elucidates the understanding of its performance under arbitrary conditions. Bringing together many recent advances in this understanding, we present a general 1-D model to describe luminescent coupling that arises from both voltage-driven electroluminescence and voltage-independent photoluminescence in nonideal junctions that include effects such as Sah-Noyce-Shockley (SNS) recombination with n ≠ 2, Auger recombination, shunt resistance, reverse-bias breakdown, series resistance, and significant dark area losses. The individual junction voltages and currents are experimentally determined from measured optical and electrical inputs and outputs of the device within the context of the model to fit parameters that describe the devices performance under arbitrary input conditions. Furthermore, our techniques to experimentally fit the model are demonstrated for a four-junction inverted metamorphic solar cell, and the predictions of the model are compared with concentrator flash measurements.
Development of an advanced finite difference atmospheric general circulation model
NASA Astrophysics Data System (ADS)
Randall, D. A.
1994-11-01
The essence of this research is further development of the Colorado State University (CSU) atmospheric general circulation model (AGCM). Although the CSU AGCM is currently evolving rapidly, is also being used in a variety of 'applications' in which the results of simulation performed with the model are analyzed to gain better understanding of the climate system. In parallel, a GCM development effort is also under way at UCLA. The CSU GCM was derived from the UCLA GCM of 1982, but has evolved to the point that the two models are now really quite distinct. The key distinguishing elements of the CSU model are briefly summarized. The goal of CHAMMP is 'to accelerate the development of more accurate and useful climate prediction capabilities to forecast climate change on sub-continental and smaller scales over time periods ranging from a decade to several centuries'.
Unitarity-violation in generalized Higgs inflation models
Lerner, Rose N.; McDonald, John E-mail: j.mcdonald@lancaster.ac.uk
2012-11-01
Unitarity-violation presents a challenge for non-minimally coupled models of inflation based on weak-scale particle physics. We examine the energy scale of tree-level unitarity-violation in scattering processes for generalized models with multiple scalar fields where the inflaton is either a singlet scalar or the Higgs. In the limit that the non-minimal couplings are all equal (e.g. in the case of Higgs or other complex inflaton), the scale of tree-level unitarity-violation matches the existing result. However if the inflaton is a singlet, and if it has a larger non-minimal coupling than other scalars in the model, then this hierarchy increases the scale of tree-level unitarity-violation. A sufficiently strong hierarchy pushes the scale of tree-level unitarity-violation above the Planck scale. We also discuss models which attempt to resolve the issue of unitarity-violation in Higgs Inflation.
Integrated and spectral energetics of the GLAS general circulation model
NASA Technical Reports Server (NTRS)
Tenenbaum, J.
1982-01-01
Integrated and spectral error energetics of the GLAS General circulation model are compared with observations for periods in January 1975, 1976, and 1977. For two cases the model shows significant skill in predicting integrated energetics quantities out to two weeks, and for all three cases, the integrated monthly mean energetics show qualitative improvements over previous versions of the model in eddy kinetic energy and barotropic conversions. Fundamental difficulties remain with leakage of energy to the stratospheric level, particularly above strong initial jet streams associated in part with regions of steep terrain. The spectral error growth study represents the first comparison of general circulation model spectral energetics predictions with the corresponding observational spectra on a day by day basis. The major conclusion is that eddy kinetics energy can be correct while significant errors occur in the kinetic energy of wavenumber 3. Both the model and observations show evidence of single wavenumber dominance in eddy kinetic energy and the correlation of spectral kinetics and potential energy.
Pharmaceutical Industry and Trade Liberalization Using Computable General Equilibrium Model
Barouni, M; Ghaderi, H; Banouei, AA
2012-01-01
Background Computable general equilibrium models are known as a powerful instrument in economic analyses and widely have been used in order to evaluate trade liberalization effects. The purpose of this study was to provide the impacts of trade openness on pharmaceutical industry using CGE model. Methods: Using a computable general equilibrium model in this study, the effects of decrease in tariffs as a symbol of trade liberalization on key variables of Iranian pharmaceutical products were studied. Simulation was performed via two scenarios in this study. The first scenario was the effect of decrease in tariffs of pharmaceutical products as 10, 30, 50, and 100 on key drug variables, and the second was the effect of decrease in other sectors except pharmaceutical products on vital and economic variables of pharmaceutical products. The required data were obtained and the model parameters were calibrated according to the social accounting matrix of Iran in 2006. Results: The results associated with simulation demonstrated that the first scenario has increased import, export, drug supply to markets and household consumption, while import, export, supply of product to market, and household consumption of pharmaceutical products would averagely decrease in the second scenario. Ultimately, society welfare would improve in all scenarios. Conclusion: We presents and synthesizes the CGE model which could be used to analyze trade liberalization policy issue in developing countries (like Iran), and thus provides information that policymakers can use to improve the pharmacy economics. PMID:23641393
Palmgren, Björn; Jin, Zhe; Ma, Hongmin; Jiao, Yu; Olivius, Petri
2010-06-14
Hearing impairment can be caused by a primary lesion to the spiral ganglion neurons (SGNs) with the hair cells kept intact, for example via tumours, trauma or auditory neuropathy. To mimic these conditions in animal models various methods of inflicting damage to the inner ear have been used. However, only a few methods have a selective effect on the SGNs, which is of importance since it might be clinically more relevant to study hearing impairment with the hair cells undamaged. beta-Bungarotoxin is a venom of the Taiwan banded krait, which in vitro has been shown to induce apoptosis in neurons, leaving remaining cochlear cells intact. We wanted to create an in vivo rat model of selective damage to primary auditory neurons. Under deep anaesthesia, 41 rats received beta-Bungarotoxin or saline to the round window niche. At postoperative intervals between days 3 and 21 auditory brainstem response (ABR) measurement, immunohistochemistry, SGN quantification and cochlear surface preparation were performed. The results in the beta-Bungarotoxin-treated ears, as compared with sham-operated ears, show significantly increased ABR thresholds at all postoperative intervals, illustrating a severe to profound hearing loss at all tested frequencies (3.5, 7, 16 and 28 kHz). Quantification of the SGNs showed no obvious reduction in neuronal numbers until 14 days postoperatively. Between days 14 and 21 a significant reduction in SGN numbers was observed. Cochlear surface preparation and immunohistochemistry showed that the hair cells were intact. Our results illustrate that in vivo application of beta-Bungarotoxin to the round window niche is a feasible way of deafening rats by SGN reduction while the hair cells are kept intact. PMID:20184947
Analysing the generality of spatially predictive mosquito habitat models
Li, Li; Bian, Ling; Yakob, Laith; Zhou, Guofa; Yan, Guiyun
2013-01-01
The increasing spread of multi-drug resistant malaria in African highlands has highlighted the importance of malaria suppression through vector control. Its historical success has meant that larval control has been proposed as part of an integrated malaria vector control program. Due to high operation costs, larval control activities would benefit greatly if the locations of mosquito habitats could be identified quickly and easily, allowing for focal habitat source suppression. Several mosquito habitat models have been developed to predict the location of mosquito habitats. However, to what extent these models can be generalised across time and space to predict the distribution of dynamic mosquito habitats remains largely unexplored. This study used mosquito habitat data collected in six different time periods and four different modelling approaches to establish 24 mosquito habitat models. We systematically tested the generality of these 24 mosquito habitat models. We found that although habitat–environment relationships change temporally, a modest level of performance was attained when validating the models using data collected from different time periods. We also describe flexible approaches to the predictive modelling of mosquito habitats, that provide novel modelling architecture for future research efforts. PMID:21527240
NASA Technical Reports Server (NTRS)
Pennline, James; Mulugeta, Lealem
2013-01-01
Under the conditions of microgravity, astronauts lose bone mass at a rate of 1% to 2% a month, particularly in the lower extremities such as the proximal femur [1-3]. The most commonly used countermeasure against bone loss in microgravity has been prescribed exercise [4]. However, data has shown that existing exercise countermeasures are not as effective as desired for preventing bone loss in long duration, 4 to 6 months, spaceflight [1,3,5,6]. This spaceflight related bone loss may cause early onset of osteoporosis to place the astronauts at greater risk of fracture later in their lives. Consequently, NASA seeks to have improved understanding of the mechanisms of bone demineralization in microgravity in order to appropriately quantify this risk, and to establish appropriate countermeasures [7]. In this light, NASA's Digital Astronaut Project (DAP) is working with the NASA Bone Discipline Lead to implement well-validated computational models to help predict and assess bone loss during spaceflight, and enhance exercise countermeasure development. More specifically, computational modeling is proposed as a way to augment bone research and exercise countermeasure development to target weight-bearing skeletal sites that are most susceptible to bone loss in microgravity, and thus at higher risk for fracture. Given that hip fractures can be debilitating, the initial model development focused on the femoral neck. Future efforts will focus on including other key load bearing bone sites such as the greater trochanter, lower lumbar, proximal femur and calcaneus. The DAP has currently established an initial model (Beta Version) of bone loss due to skeletal unloading in femoral neck region. The model calculates changes in mineralized volume fraction of bone in this segment and relates it to changes in bone mineral density (vBMD) measured by Quantitative Computed Tomography (QCT). The model is governed by equations describing changes in bone volume fraction (BVF), and rates of
{beta} decay of odd-A As to Ge isotopes in the interacting boson-fermion model
Brant, S.; Yoshida, N.; Zuffi, L.
2004-11-01
The structure of odd-mass isotopes of As and Ge is described in the framework of the proton-neutron interacting boson-fermion model. The energy levels and the electromagnetic properties of {sup 69,71,73}As and {sup 69,71,73}Ge are calculated and compared with the experiment. The {beta}-decay rates from the As isotopes to the Ge isotopes are calculated. The calculated decays tend to be stronger than the observed ones. This may indicate a mixture of components outside the model space in the wave functions of actual nuclei. The effect of the higher-order terms in the decay operators seems small.
Marginally specified generalized linear mixed models: a robust approach.
Mills, J E; Field, C A; Dupuis, D J
2002-12-01
Longitudinal data modeling is complicated by the necessity to deal appropriately with the correlation between observations made on the same individual. Building on an earlier nonrobust version proposed by Heagerty (1999, Biometrics 55, 688-698), our robust marginally specified generalized linear mixed model (ROBMS-GLMM) provides an effective method for dealing with such data. This model is one of the first to allow both population-averaged and individual-specific inference. As well, it adopts the flexibility and interpretability of generalized linear mixed models for introducing dependence but builds a regression structure for the marginal mean, allowing valid application with time-dependent (exogenous) and time-independent covariates. These new estimators are obtained as solutions of a robustified likelihood equation involving Huber's least favorable distribution and a collection of weights. Huber's least favorable distribution produces estimates that are resistant to certain deviations from the random effects distributional assumptions. Innovative weighting strategies enable the ROBMS-GLMM to perform well when faced with outlying observations both in the response and covariates. We illustrate the methodology with an analysis of a prospective longitudinal study of laryngoscopic endotracheal intubation, a skill that numerous health-care professionals are expected to acquire. The principal goal of our research is to achieve robust inference in longitudinal analyses. PMID:12495126
Fermion masses and mixing in general warped extra dimensional models
NASA Astrophysics Data System (ADS)
Frank, Mariana; Hamzaoui, Cherif; Pourtolami, Nima; Toharia, Manuel
2015-06-01
We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave functions to small flavor breaking effects yield hierarchical masses and mixing as it is usual in warped models with fermions in the bulk. In the neutrino sector, the exponential wave-function factors can be flavor blind and thus insensitive to the small flavor symmetry breaking effects, directly linking their masses and mixing angles to the flavor symmetric structure of the five-dimensional neutrino Yukawa couplings. The Higgs must be localized in the bulk and the model is more successful in generalized warped scenarios where the metric background solution is different than five-dimensional anti-de Sitter (AdS5 ). We study these features in two simple frameworks, flavor complimentarity and flavor democracy, which provide specific predictions and correlations between quarks and leptons, testable as more precise data in the neutrino sector becomes available.
Modeling Time Varying Effects with Generalized and Unsynchronized Longitudinal Data
Şentürk, Damla; Dalrymple, Lorien S.; Mohammed, Sandra M.; Kaysen, George A.; Nguyen, Danh V.
2013-01-01
Summary We propose novel estimation approaches for generalized varying coefficient models that are tailored for unsynchronized, irregular and infrequent longitudinal designs/data. Unsynchronized longitudinal data refers to the time-dependent response and covariate measurements for each individual measured at distinct time points. The proposed methods are motivated by data from the Comprehensive Dialysis Study (CDS). We model the potential age-varying association between infection-related hospitalization status and the inflammatory marker, C-reactive protein (CRP), within the first two years from initiation of dialysis. Traditional longitudinal modeling cannot directly be applied to unsynchronized data and no method exists to estimate time- or age-varying effects for generalized outcomes (e.g., binary or count data) to date. In addition, through the analysis of the CDS data and simulation studies, we show that preprocessing steps, such as binning, needed to synchronize data to apply traditional modeling can lead to significant loss of information in this context. In contrast, the proposed approaches discard no observation; they exploit the fact that although there is little information in a single subject trajectory due to irregularity and infrequency, the moments of the underlying processes can be accurately and efficiently recovered by pooling information from all subjects using functional data analysis. Subject-specific mean response trajectory predictions are derived and finite sample properties of the estimators are studied. PMID:23335196
Generalized Statistical Models of Voids and Hierarchical Structure in Cosmology
NASA Astrophysics Data System (ADS)
Mekjian, Aram Z.
2007-01-01
Generalized statistical models of voids and hierarchical structure in cosmology are developed. The often quoted negative binomial model and the frequently used thermodynamic model are shown to be special cases of a more general distribution that contains a parameter a. This parameter is related to the Lévy index α and the Fisher critical exponent τ, the latter of which describes the power-law falloff of clumps of matter around a phase transition. The parameter a, exponent τ, or index α can be obtained from properties of a void scaling function. A stochastic probability variable p is introduced into a statistical model, which represents the adhesive growth of galaxy structure. The galaxy count distribution decays exponentially quickly with size for p<1/2. For p>1/2, adhesive growth can go on indefinitely, thereby forming an infinite supercluster. At p=1/2, a scale-free power-law distribution for the galaxy count distribution is present. The stochastic description also leads to consequences that have some parallels with cosmic string results, percolation theory, and phase transitions.
Non-canonical generalizations of slow-roll inflation models
Tzirakis, Konstantinos; Kinney, William H. E-mail: whkinney@buffalo.edu
2009-01-15
We consider non-canonical generalizations of two classes of single-field inflation models. First, we study the non-canonical version of ''ultra-slow roll'' inflation, which is a class of inflation models for which quantum modes do not freeze at horizon crossing, but instead evolve rapidly on superhorizon scales. Second, we consider the non-canonical generalization of the simplest ''chaotic'' inflation scenario, with a potential dominated by a quadratic (mass) term for the inflaton. We find a class of related non-canonical solutions with polynomial potentials, but with varying speed of sound. These solutions are characterized by a constant field velocity, and we dub such models isokinetic inflation. As in the canonical limit, isokinetic inflation has a slightly red-tilted power spectrum, consistent with current data. Unlike the canonical case, however, these models can have an arbitrarily small tensor/scalar ratio. Of particular interest is that isokinetic inflation is marked by a correlation between the tensor/scalar ratio and the amplitude of non-Gaussianity such that parameter regimes with small tensor/scalar ratio have large associated non-Gaussianity, which is a distinct observational signature.
Comparison of Cenozoic atmospheric general circulation model simulations
Barron, E.J.
1985-01-01
Paleocene, Eocene, Miocene and present day (with polar ice) geography are specified as the lower boundary condition in a mean annual, energy balance ocean version of the Community Climate Model (CCM), a spectral General Circulation Model of the Atmosphere developed at the National Center for Atmospheric Research. This version of the CCM has a 4.5/sup 0/ latitudinal and 7.5/sup 0/ longitudinal resolution with 9 vertical levels and includes predictions for pressure, winds, temperature, evaporation, precipitation, cloud cover, snow cover and sea ice. The model simulations indicate little geographically-induced climates changes from the Paleocene to the Miocene, but substantial differences between the Miocene and the present simulations. The simulated climate differences between the Miocene and present day include: 1) cooler present temperatures (2/sup 0/C in tropics, 15-35 C in polar latitudes) with the exception of warmer subtropical desert conditions, 2) a generally weaker present hydrologic cycle, with greater subtropical aridity, 3) strengthened present day westerly jets with a slight poleward displacement, and 4) the largest regional climate changes associated with Antarctica. The results of the climate model sensitivity experiments have considerable implications for understanding how geography influences climate.
Modeling biometric systems using the general pareto distribution (GPD)
NASA Astrophysics Data System (ADS)
Shi, Zhixin; Kiefer, Frederick; Schneider, John; Govindaraju, Venu
2008-03-01
Statistical modeling of biometric systems at the score level is extremely important. It is the foundation of the performance assessment of biometric systems including determination of confidence intervals and test sample size for simulations, and performance prediction of real world systems. Statistical modeling of multimodal biometric systems allows the development of a methodology to integrate information from multiple biometric sources. We present a novel approach for estimating the marginal biometric matching score distributions by using extreme value theory in conjunction with non-parametric methods. Extreme Value Theory (EVT) is based on the modeling of extreme events represented by data which has abnormally low or high values in the tails of the distributions. Our motivation stems from the observation that the tails of the biometric score distributions are often difficult to estimate using other methods due to lack of sufficient numbers of training samples. However, good estimates of the tails of biometric distributions are essential for defining the decision boundaries. We present EVT based novel procedures for fitting a score distribution curve. A general non-parametric method is used for fitting the majority part of the distribution curve, and a parametric EVT model - the general Pareto distribution - is used for fitting the tails of the curve. We also demonstrate the advantage of applying the EVT by experiments.
Generalized Manning Condensation Model Captures the RNA Ion Atmosphere.
Hayes, Ryan L; Noel, Jeffrey K; Mandic, Ana; Whitford, Paul C; Sanbonmatsu, Karissa Y; Mohanty, Udayan; Onuchic, José N
2015-06-26
RNA is highly sensitive to the ionic environment and typically requires Mg(2+) to form compact structures. There is a need for models capable of describing the ion atmosphere surrounding RNA with quantitative accuracy. We present a model of RNA electrostatics and apply it within coarse-grained molecular dynamics simulation. The model treats Mg(2+) ions explicitly to account for ion-ion correlations neglected by mean-field theories. Since mean-field theories capture KCl well, it is treated implicitly by a generalized Manning counterion condensation model. The model extends Manning condensation to deal with arbitrary RNA conformations, nonlimiting KCl concentrations, and the ion inaccessible volume of RNA. The model is tested against experimental measurements of the excess Mg(2+) associated with the RNA, Γ(2+), because Γ(2+) is directly related to the Mg(2+)-RNA interaction free energy. The excellent agreement with experiment demonstrates that the model captures the ionic dependence of the RNA free energy landscape. PMID:26197147
Generalized Manning Condensation Model Captures the RNA Ion Atmosphere
Hayes, Ryan L.; Noel, Jeffrey K.; Mandic, Ana; Whitford, Paul C.; Sanbonmatsu, Karissa Y.; Mohanty, Udayan; Onuchic, José N.
2016-01-01
RNA is highly sensitive to the ionic environment, and typically requires Mg2+ to form compact structures. There is a need for models capable of describing the ion atmosphere surrounding RNA with quantitative accuracy. We present a model of RNA electrostatics and apply it within coarse-grained molecular dynamics simulation. The model treats Mg2+ ions explicitly to account for ion-ion correlations neglected by mean field theories. Since mean-field theories capture KCl well, it is treated implicitly by a generalized Manning counterion condensation model. The model extends Manning condensation to deal with arbitrary RNA conformations, non-limiting KCl concentrations, and the ion inaccessible volume of RNA. The model is tested against experimental measurements of the excess Mg2+ associated with the RNA, Γ2+, because Γ2+ is directly related to the Mg2+-RNA interaction free energy. The excellent agreement with experiment demonstrates the model captures the ionic dependence of the RNA free energy landscape. PMID:26197147
Stochastic Ocean Eddy Perturbations in a Coupled General Circulation Model.
NASA Astrophysics Data System (ADS)
Howe, N.; Williams, P. D.; Gregory, J. M.; Smith, R. S.
2014-12-01
High-resolution ocean models, which are eddy permitting and resolving, require large computing resources to produce centuries worth of data. Also, some previous studies have suggested that increasing resolution does not necessarily solve the problem of unresolved scales, because it simply introduces a new set of unresolved scales. Applying stochastic parameterisations to ocean models is one solution that is expected to improve the representation of small-scale (eddy) effects without increasing run-time. Stochastic parameterisation has been shown to have an impact in atmosphere-only models and idealised ocean models, but has not previously been studied in ocean general circulation models. Here we apply simple stochastic perturbations to the ocean temperature and salinity tendencies in the low-resolution coupled climate model, FAMOUS. The stochastic perturbations are implemented according to T(t) = T(t-1) + (∆T(t) + ξ(t)), where T is temperature or salinity, ΔT is the corresponding deterministic increment in one time step, and ξ(t) is Gaussian noise. We use high-resolution HiGEM data coarse-grained to the FAMOUS grid to provide information about the magnitude and spatio-temporal correlation structure of the noise to be added to the lower resolution model. Here we present results of adding white and red noise, showing the impacts of an additive stochastic perturbation on mean climate state and variability in an AOGCM.
Acute and chronic pharmacological models of generalized absence seizures.
Cortez, Miguel A; Kostopoulos, George K; Snead, O Carter
2016-02-15
This article reviews the contribution of pharmacologically induced acute and chronic animal models to our understanding of epilepsies featuring non-convulsive generalized seizures, the typical and atypical absence seizures. Typical absences comprise about 5% of all epilepsies regardless of age and the atypical ones are even more common. Although absence epilepsy was thought to be relatively benign, children with childhood epilepsy (CAE) turn out to have a high rate of pretreatment attention deficits that persist despite seizure freedom. The phenomenon of the absence seizure has long attracted research interest because of the clear temporal relationship of the conspicuous EEG rhythm of 3 Hz generalized spike and wave discharges (GSWD) and the parallel transient "loss of consciousness" characterizing these seizures which is time-locked with the GSWD. Indeed, clinical epileptologists, basic scientists and neurophysiologists have long recognized in GSWD a unique electrographic and behavioral marker of the genetic predisposition to most types of epilepsy. Interestingly, the subject is still controversial since it has recently been proposed that both classification terms of CAE currently in use: idiopathic and primary generalized, be abandoned - a point of debate. Both issues - underlying mechanisms and focal origin of absence seizures - may be further enlightened by observations in valid animal models. PMID:26343323
A statistical modeling approach for detecting generalized synchronization
Schumacher, Johannes; Haslinger, Robert; Pipa, Gordon
2012-01-01
Detecting nonlinear correlations between time series presents a hard problem for data analysis. We present a generative statistical modeling method for detecting nonlinear generalized synchronization. Truncated Volterra series are used to approximate functional interactions. The Volterra kernels are modeled as linear combinations of basis splines, whose coefficients are estimated via l1 and l2 regularized maximum likelihood regression. The regularization manages the high number of kernel coefficients and allows feature selection strategies yielding sparse models. The method's performance is evaluated on different coupled chaotic systems in various synchronization regimes and analytical results for detecting m:n phase synchrony are presented. Experimental applicability is demonstrated by detecting nonlinear interactions between neuronal local field potentials recorded in different parts of macaque visual cortex. PMID:23004851
Unitarity bound in the most general two Higgs doublet model
NASA Astrophysics Data System (ADS)
Kanemura, Shinya; Yagyu, Kei
2015-12-01
We investigate unitarity bounds in the most general two Higgs doublet model without a discrete Z2 symmetry nor CP conservation. S-wave amplitudes for two-body elastic scatterings of Nambu-Goldstone bosons and physical Higgs bosons are calculated at high energies for all possible initial and final states (14 neutral, 8 singly-charged and 3 doubly-charged states). We obtain analytic formulae for the block-diagonalized scattering matrix by the classification of the two body scattering states using the conserved quantum numbers at high energies. Imposing the condition of perturbative unitarity to the eigenvalues of the scattering matrix, constraints on the model parameters can be obtained. We apply our results to constrain the mass range of the next-to-lightest Higgs state in the model.
Generalization of independent response model for toxic mixtures.
Haas, C N; Kersten, S P; Wright, K; Frank, M J; Cidambi, K
1997-02-01
Interaction between toxic compounds has long been known to researchers. Attempts to model this interaction have been based on two basic paradigms--termed additivity and independence (1, 2). Previous models based on these assumptions focused on measuring the interaction between the compounds and then classifying the type of interaction as synergism, antagonism, additivity or independence (3, 4). The aim of this work is to present a generalization of the independent action hypothesis that is quantitatively capable of describing deviations regardless of the underlying single component dose response models. The mathematical framework of copulas is employed. This approach is then tested against data sets with both human health and ecological risk applications. PMID:9569938
Trichotomous noise controlled signal amplification in a generalized Verhulst model
NASA Astrophysics Data System (ADS)
Mankin, Romi; Soika, Erkki; Lumi, Neeme
2014-10-01
The long-time limit of the probability distribution and statistical moments for a population size are studied by means of a stochastic growth model with generalized Verhulst self-regulation. The effect of variable environment on the carrying capacity of a population is modeled by a multiplicative three-level Markovian noise and by a time periodic deterministic component. Exact expressions for the moments of the population size have been calculated. It is shown that an interplay of a small periodic forcing and colored noise can cause large oscillations of the mean population size. The conditions for the appearance of such a phenomenon are found and illustrated by graphs. Implications of the results on models of symbiotic metapopulations are also discussed. Particularly, it is demonstrated that the effect of noise-generated amplification of an input signal gets more pronounced as the intensity of symbiotic interaction increases.
Early Warning Signals for Critical Transitions: A Generalized Modeling Approach
Lade, Steven J.; Gross, Thilo
2012-01-01
Critical transitions are sudden, often irreversible, changes that can occur in a large variety of complex systems; signals that warn of critical transitions are therefore highly desirable. We propose a new method for early warning signals that integrates multiple sources of information and data about the system through the framework of a generalized model. We demonstrate our proposed approach through several examples, including a previously published fisheries model. We regard our method as complementary to existing early warning signals, taking an approach of intermediate complexity between model-free approaches and fully parameterized simulations. One potential advantage of our approach is that, under appropriate conditions, it may reduce the amount of time series data required for a robust early warning signal. PMID:22319432
Eigen model with general fitness functions and degradation rates
NASA Astrophysics Data System (ADS)
Hu, Chin-Kun; Saakian, David B.
2006-03-01
We present an exact solution of Eigen's quasispecies model with a general degradation rate and fitness functions, including a square root decrease of fitness with increasing Hamming distance from the wild type. The found behavior of the model with a degradation rate is analogous to a viral quasi-species under attack by the immune system of the host. Our exact solutions also revise the known results of neutral networks in quasispecies theory. To explain the existence of mutants with large Hamming distances from the wild type, we propose three different modifications of the Eigen model: mutation landscape, multiple adjacent mutations, and frequency-dependent fitness in which the steady state solution shows a multi-center behavior.
NASA Astrophysics Data System (ADS)
Yang, Z.; Mohanty, B.
2013-12-01
Describing convective nonwetting phase flow in unsaturated porous media requires knowledge of relative nonwetting pahse permeability. This study was mainly conducted to formulate a general nonwetting pahse relative permeability model for porous media with lognormal pore size distribution based on Kosugi (1999) work for unsaturated relative hydraulic conductivity. The model-data comparison showed that the existing commonly used Burdine and Mualem permeability model could overestimate experimental relative nonwetting phase permeability data. The sensitivity analysis of the permeability model emphasized the importance of different pore tortuosity-connectivity value for gas and water phase. Subsequently, the suggested modified Burdine and Mualem permeability model for (alpha,beta,eta) in the general nonwetting phase permeability model should be (2.5, 2, 1) and (2, 1, 2) respectively. These two suggested models have the lowest mean root mean square error (RMSE) among the investigated permeability models. This finding could present more accurate permeability model parameterization in the multiphase subsurface flow modeling under isothermal and non-isothermal conditions.
Miller, M.H.; Grierson, I.; Unger, W.G.; Hitchings, R.A. )
1990-01-01
We studied the effect of topical dexamethasone (1%) and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit. Intraocular pressure and gross facility of aqueous outflow following surgery were not influenced by either treatment, although blebs persisted longer in the irradiated eyes. Steroids reduced clinically observable inflammation as well as the number of inflammatory cells identifiable by microscopy. Fibroblast production temporarily slowed, and ultrastructural examination demonstrated lipid-filled vacuoles and dilated mitochondria in these eyes. Also, the scar was thinner at 24 days. Beta irradiation delayed wound healing and the scar was thinner in the early postoperative stages, but the light microscopic appearance of the scar was unaltered at 59 days. Inflammation was more pronounced initially, with abundant fibrin in the wound. Recovery of the conjunctival epithelium was delayed. The delay in fibroblast recruitment and wound contraction, the thinner scar tissue, and the increased survival of the bleb are all factors that suggest that beta irradiation may be a useful adjunct to glaucoma surgery.
A model of the complex between human {beta}-microseminoprotein and CRISP-3 based on NMR data
Ghasriani, Houman; Fernlund, Per; Udby, Lene; Drakenberg, Torbjoern
2009-01-09
{beta}-Microseminoprotein (MSP), a 10 kDa seminal plasma protein, forms a tight complex with cysteine-rich secretory protein 3 (CRISP-3) from granulocytes. The 3D structure of human MSP has been determined but there is as yet no 3D structure for CRISP-3. We have now studied the complex between human MSP and CRISP-3 with multidimensional NMR. {sup 15}N-HSQC spectra show substantial differences between free and complexed hMSP. Using several 3D-NMR spectra of triply labeled hMSP in complex with a recombinant N-terminal domain of CRISP-3, most of the backbone of hMSP could be assigned. The data show that only one side of hMSP, comprising {beta}-strands 1, 4, 5, and 8 are affected by the complex formation, indicating that {beta}-strands 1 and 8 form the main binding surface. Based on this we present a tentative structure for the hMSP-CRISP-3 complex using the known crystal structure of triflin as a model of CRISP-3.
Extensive investigation of the generalized dark matter model
NASA Astrophysics Data System (ADS)
Kopp, Michael; Skordis, Constantinos; Thomas, Dan B.
2016-08-01
The cold dark matter (CDM) model, wherein the dark matter is treated as a pressureless perfect fluid, provides a good fit to galactic and cosmological data. With the advent of precision cosmology, it should be asked whether this simplest model needs to be extended, and whether doing so could improve our understanding of the properties of dark matter. One established parametrization for generalizing the CDM fluid is the generalized dark matter (GDM) model, in which dark matter is an imperfect fluid with pressure and shear viscosity that fulfill certain postulated closure equations. We investigate these closure equations and the three new parametric functions they contain: the background equation of state w , the speed of sound cs2 and the viscosity cvis2. Taking these functions to be constant parameters, we analyze an exact solution of the perturbed Einstein equations in a flat GDM-dominated universe and discuss the main effects of the three parameters on the cosmic microwave background (CMB). Our analysis suggests that the CMB alone is not able to distinguish between the GDM sound speed and viscosity parameters, but that other observables, such as the matter power spectrum, are required to break this degeneracy. In order to elucidate further the meaning of the GDM closure equations, we also consider other descriptions of imperfect fluids that have a nonperturbative definition and relate these to the GDM model. In particular, we consider scalar fields, an effective field theory (EFT) of fluids, an EFT of large-scale structure, nonequilibrium thermodynamics and tightly coupled fluids. These descriptions could be used to extend the GDM model into the nonlinear regime of structure formation, which is necessary if the wealth of data available on those scales is to be employed in constraining the model. We also derive the initial conditions for adiabatic and isocurvature perturbations in the presence of GDM and standard cosmological fluids and provide the result in a
SST dependence of convective aggregation in three General Circulation Models
NASA Astrophysics Data System (ADS)
Bony, Sandrine; Becker, Tobias; Coppin, David; Medeiros, Brian; Reed, Kevin; Stevens, Bjorn; Voigt, Aiko
2015-04-01
Studies using cloud-resolving models or simple models have shown that under certain conditions, the radiative-convective equilibrium state becomes unstable to large-scale overturning circulations, and leads to the phenomenon of self-aggregation of moist convection. Modeling and observational studies suggest that the degree of aggregation of moist convection can influence the large-scale atmospheric state (e.g. humidity, clouds) and its energy budget. The question thus arises as to what extent the aggregation of convection may rectify the Earth's climate, including the large-scale atmospheric circulation, hydrological sensitivity and climate feedbacks. We explore these issues by running three General Circulation Models (IPSL-CM5A-LR, ECHAM6, CAM5) in radiative-convective equilibrium, i.e. a non-rotating aqua-planet configuration forced by a globally-uniform insolation and sea surface temperature (SST). We show that in these conditions, all three models can predict the spontaneous emergence of a large-scale convective organization and overturning circulation, and that the equilibrium aggregation state depends on SST and cloud-radiative effects. We will explore the reasons why the equilibrium aggregation state depends on temperature, and the impact of convective aggregation on the global mean state. Robust behaviors will be highlighted, as well as inter-model differences. The implications of these results will be discussed.
A general circulation model study of atmospheric carbon monoxide
NASA Technical Reports Server (NTRS)
Pinto, J. P.; Rind, D.; Russell, G. L.; Lerner, J. A.; Hansen, J. E.; Yung, Y. L.; Hameed, S.
1983-01-01
The carbon monoxide cycle is studied by incorporating the known and hypothetical sources and sinks in a tracer model that uses the winds generated by a general circulation model. Photochemical production and loss terms, which depend on OH radical concentrations, are calculated in an interactive fashion. The computed global distribution and seasonal variations of CO are compared with observations to obtain constraints on the distribution and magnitude of the sources and sinks of CO, and on the tropospheric abundance of OH. The simplest model that accounts for available observations requires a low latitude plant source of about 1.3 x 10 to the 15th g/yr, in addition to sources from incomplete combustion of fossil fuels and oxidation of methane. The globally averaged OH concentration calculated in the model is 750,000/cu cm. Models that calculate globally averaged OH concentrations much lower than this nominal value are not consistent with the observed variability of CO. Such models are also inconsistent with measurements of CO isotopic abundances, which imply the existence of plant sources.
A Generalized ideal observer model for decoding sensory neural responses.
Purushothaman, Gopathy; Casagrande, Vivien A
2013-01-01
We show that many ideal observer models used to decode neural activity can be generalized to a conceptually and analytically simple form. This enables us to study the statistical properties of this class of ideal observer models in a unified manner. We consider in detail the problem of estimating the performance of this class of models. We formulate the problem de novo by deriving two equivalent expressions for the performance and introducing the corresponding estimators. We obtain a lower bound on the number of observations (N) required for the estimate of the model performance to lie within a specified confidence interval at a specified confidence level. We show that these estimators are unbiased and consistent, with variance approaching zero at the rate of 1/N. We find that the maximum likelihood estimator for the model performance is not guaranteed to be the minimum variance estimator even for some simple parametric forms (e.g., exponential) of the underlying probability distributions. We discuss the application of these results for designing and interpreting neurophysiological experiments that employ specific instances of this ideal observer model. PMID:24137135
Modeling SAR images with a generalization of the Rayleigh distribution.
Kuruoğlu, Ercan E; Zerubia, Josiane
2004-04-01
Synthetic aperture radar (SAR) imagery has found important applications due to its clear advantages over optical satellite imagery one of them being able to operate in various weather conditions. However, due to the physics of the radar imaging process, SAR images contain unwanted artifacts in the form of a granular look which is called speckle. The assumptions of the classical SAR image generation model lead to a Rayleigh distribution model for the histogram of the SAR image. However, some experimental data such as images of urban areas show impulsive characteristics that correspond to underlying heavy-tailed distributions, which are clearly non-Rayleigh. Some alternative distributions have been suggested such as the Weibull, log-normal, and the k-distribution which had success in varying degrees depending on the application. Recently, an alternative model namely the alpha-stable distribution has been suggested for modeling radar clutter. In this paper, we show that the amplitude distribution of the complex wave, the real and the imaginery components of which are assumed to be distributed by the alpha-stable distribution, is a generalization of the Rayleigh distribution. We demonstrate that the amplitude distribution is a mixture of Rayleighs as is the k-distribution in accordance with earlier work on modeling SAR images which showed that almost all successful SAR image models could be expressed as mixtures of Rayleighs. We also present parameter estimation techniques based on negative order moments for the new model. Finally, we test the performance of the model on urban images and compare with other models such as Rayleigh, Weibull, and the k-distribution. PMID:15376587
NASA Astrophysics Data System (ADS)
Dayanandan, Baiju; Maurya, S. K.; Gupta, Y. K.; Smitha, T. T.
2016-05-01
We present a detailed investigation of the stability of anisotropic compact star models by introducing Matese and Whitman (Phys. Rev. D 11:1270, 1980) solution in general relativity. We have particularly looked into the detailed investigation of the measurements of basic physical parameters such as radial pressure, tangential pressure, energy density, red shift, sound velocity, masses and radii are affected by unknown effects such as loss, accretion and diffusion of mass. Those give insight into the characteristics of the compact astrophysical object with anisotropic matter distribution as well as the physical reality. The results obtained for the physical feature of compact stars such as, Her. X-1, RXJ 1856-37, SAX J1808.4-3658(SS2) and SAX J1808.4-3658(SS1) are compared to the recently observed massive compact object.
Generalized semiparametric varying-coefficient models for longitudinal data
NASA Astrophysics Data System (ADS)
Qi, Li
In this dissertation, we investigate the generalized semiparametric varying-coefficient models for longitudinal data that can flexibly model three types of covariate effects: time-constant effects, time-varying effects, and covariate-varying effects, i.e., the covariate effects that depend on other possibly time-dependent exposure variables. First, we consider the model that assumes the time-varying effects are unspecified functions of time while the covariate-varying effects are parametric functions of an exposure variable specified up to a finite number of unknown parameters. The estimation procedures are developed using multivariate local linear smoothing and generalized weighted least squares estimation techniques. The asymptotic properties of the proposed estimators are established. The simulation studies show that the proposed methods have satisfactory finite sample performance. ACTG 244 clinical trial of HIV infected patients are applied to examine the effects of antiretroviral treatment switching before and after HIV developing the 215-mutation. Our analysis shows benefit of treatment switching before developing the 215-mutation. The proposed methods are also applied to the STEP study with MITT cases showing that they have broad applications in medical research.
NASA Technical Reports Server (NTRS)
1982-01-01
A focused laser doppler velocimeter (LDV) system was developed for the measurement of atmospheric backscatter (beta) from aerosols at infrared wavelengths. A Doppler signal generator was used in mapping the coherent sensitive focal volume of a focused LDV system. System calibration data was analyzed during the flight test activity scheduled for the Beta system. These analyses were performed to determine the acceptability of the Beta measurement system's performance.
Zhu, Zhengxi; Margulis-Goshen, Katrin; Magdassi, Shlomo; Talmon, Yeshayahu; Macosko, Christopher W
2010-10-01
Polyelectrolyte protected beta-carotene nanoparticles (nanosuspensions) with average diameter of <100 nm were achieved by turbulent mixing and flash nanoprecipitation (FNP). Three types of multi-amine functional polyelectrolytes, epsilon-polylysine (epsilon-PL), poly(ethylene imine) (PEI), and chitosan, were investigated to electrosterically protect the nanoparticles. Particle size and distribution were measured by dynamic light scattering (DLS); particles were imaged via scanning electron microscopy (SEM) and cryogenic transmission electron microscopy (cryo-TEM). Low pH and high polyelectrolyte molecular weight gave the smallest and most stable particles. High drug loading capacity, >80 wt%, was achieved by using either PEI or chitosan. X-ray diffraction (XRD) patterns showed that beta-carotene nanoparticles were amorphous. These findings open the way for utilization of FNP for preparation of nanoparticles with enhanced bioavailability for highly water insoluble drugs. PMID:20143406
Goto, Joy J; Tanzi, Rudolph E
2002-01-01
The clearance and degradation of extracellular A beta is critical for regulating beta-amyloid deposition, a major hallmark of brains of patients with A beta in Alzheimer's Disease. The low-density lipoprotein receptor-related protein, LRP1, is a large endocytic receptor that significantly contributes to the balance between degradation and production of A beta. An extracellular portion of the LRP, known as the cluster II region can bind to the secreted form of APP (sAPP-KPI). We show here that a GST fusion protein containing the cluster II region of LRP can be used as a 'mini-receptor' that specifically binds to sAPP-KPI from conditioned cultured medium. The binding between the GST-LRP-cluster II fusion protein and sAPP-KPI can be inhibited with the strong binding ligand of LRP1, called receptor-associated protein (RAP). Furthermore, a cell-based in vitro assay system has been developed to monitor the production of total A beta and A beta(1-42) in the presence and absence of RAP in Chinese hamster ovary (CHO) cell lines both deficient in LRP and expressing LRP. A 3-day treatment of the L2 (CHO cells deficient in LRP and overexpressing APP751) and L3 (CHO cells expressing LRP and overexpressing APP751) cell lines with RAP showed a decrease in total A beta and, interestingly, also a decrease in the ratio of A beta42/A beta(total). This cell-based model system and LRP-cluster II mini-receptor will be very useful for screening novel compounds that can reduce A beta accumulation by inhibiting binding of APP-KPI to LRP1. PMID:12212791
Mak, H.W.
1986-01-01
The antibiotic ketomycin is formed from shikimic acid via chorismic acid and prephenic acid. Phenylalanine and 2',5'-dihydrophenylalanine derived from shikimic acid are not intermediates in the biosynthesis. Degradation of ketomycin derived from (1,6-/sup 14/C)shikimic acid showed that prephenic acid is converted into ketomycin with stereospecific discrimination between the two enantiotopic edges of the ring, the pro-S-R edge giving rise to the C-2', C-3' side of the cyclohexane ring of ketomycin. The resistance of pathogenic bacteria to the action of ..beta..-lactam antibiotics is mainly ascribed to their ability to produce ..beta..-lactamase to cleave the ..beta..-lactam ring. It is essential to understand the molecular nature of ..beta..-lactamase-penicillin recognition for designing and formulating more effective ..beta..-lactam antibiotics. A biomimetic study of ..beta..-lactamase is therefore initiated. To meet the requirements of hydrophobic and serine protease characteristics of ..beta..-lactamase, ..cap alpha..-cyclodextrin is chosen as a biomimetic model for ..beta..-lactamase. The structural specificity and the chemical dynamics of ..cap alpha..-cyclodextrin-phenoxymethyl penicillin inclusion complex in solid state and in solution have been determined by IR and NMR spectroscopy. The spectral results strongly indicate that the phenyl portion of the phenoxymethyl penicillin forms a stable inclusion complex with the hydrophobic cavity of ..cap alpha..-cyclodextrin in solution as well as in the solid state. Kinetic studies followed by /sup 1/HNMR and HPLC analyses under alkaline condition have shown that the ..cap alpha..-cyclodextrin mimics the catalytic function of serine of ..beta..-lactamase in the stereospecific hydrolysis of the ..beta..-lactam ring of phenoxymethyl penicillin.
Introducing Charge Hydration Asymmetry into the Generalized Born Model.
Mukhopadhyay, Abhishek; Aguilar, Boris H; Tolokh, Igor S; Onufriev, Alexey V
2014-04-01
The effect of charge hydration asymmetry (CHA)-non-invariance of solvation free energy upon solute charge inversion-is missing from the standard linear response continuum electrostatics. The proposed charge hydration asymmetric-generalized Born (CHA-GB) approximation introduces this effect into the popular generalized Born (GB) model. The CHA is added to the GB equation via an analytical correction that quantifies the specific propensity of CHA of a given water model; the latter is determined by the charge distribution within the water model. Significant variations in CHA seen in explicit water (TIP3P, TIP4P-Ew, and TIP5P-E) free energy calculations on charge-inverted "molecular bracelets" are closely reproduced by CHA-GB, with the accuracy similar to models such as SEA and 3D-RISM that go beyond the linear response. Compared against reference explicit (TIP3P) electrostatic solvation free energies, CHA-GB shows about a 40% improvement in accuracy over the canonical GB, tested on a diverse set of 248 rigid small neutral molecules (root mean square error, rmse = 0.88 kcal/mol for CHA-GB vs 1.24 kcal/mol for GB) and 48 conformations of amino acid analogs (rmse = 0.81 kcal/mol vs 1.26 kcal/mol). CHA-GB employs a novel definition of the dielectric boundary that does not subsume the CHA effects into the intrinsic atomic radii. The strategy leads to finding a new set of intrinsic atomic radii optimized for CHA-GB; these radii show physically meaningful variation with the atom type, in contrast to the radii set optimized for GB. Compared to several popular radii sets used with the original GB model, the new radii set shows better transferability between different classes of molecules. PMID:24803871
Superconductivity in the two-dimensional generalized Hubbard model
NASA Astrophysics Data System (ADS)
Lima, L. S.
2016-08-01
We have used the Green's functions method at finite temperature and the Kubo's formalism, to calculate the electron conductivity σ(ω) in the generalized two-dimensional Hubbard model. We have obtained a behavior superconductor for the system to T > T0. The AC conductivity falls to zero in ω =ω0 , where ω0 depends on Δ, which is the gap of the system. The behavior gotten is according of with the behavior of the superconductors of high Tc where there is a changes abruptly from a Mott's insulator state to superconductor.
O(N) Generalized nonlinear sigma model and its applications
Ferrari, F. Paturej, J.; Vilgis, T. A.
2010-02-15
In this work the results of an interdisciplinary research between field theory and statistical mechanics will be presented. It is shown that the dynamics of an inextensible chain is described by a slight generalization of the O(d) nonlinear sigma model. It is checked, that in the large time limit the correct equilibrium distribution is reached. Our approach is based on path integrals, but it may be also connected to the usual description of the dynamics of a chain as a diffusion stochastic process. Some applications of our results will be discussed, like for instance the calculation of the average distance between two polymer segments.
Consolidation of data base for Army generalized missile model
NASA Technical Reports Server (NTRS)
Klenke, D. J.; Hemsch, M. J.
1980-01-01
Data from plume interaction tests, nose mounted canard configuration tests, and high angle of attack tests on the Army Generalized Missile model are consolidated in a computer program which makes them readily accessible for plotting, listing, and evaluation. The program is written in FORTRAN and will run on an ordinary minicomputer. It has the capability of retrieving any coefficient from the existing DATAMAN tapes and displaying it in tabular or plotted form. Comparisons of data taken in several wind tunnels and of data with the predictions of Program MISSILE2 are also presented.
Generalized Laplacian eigenmaps for modeling and tracking human motions.
Martinez-del-Rincon, Jesus; Lewandowski, Michal; Nebel, Jean-Christophe; Makris, Dimitrios
2014-09-01
This paper presents generalized Laplacian eigenmaps, a novel dimensionality reduction approach designed to address stylistic variations in time series. It generates compact and coherent continuous spaces whose geometry is data-driven. This paper also introduces graph-based particle filter, a novel methodology conceived for efficient tracking in low dimensional space derived from a spectral dimensionality reduction method. Its strengths are a propagation scheme, which facilitates the prediction in time and style, and a noise model coherent with the manifold, which prevents divergence, and increases robustness. Experiments show that a combination of both techniques achieves state-of-the-art performance for human pose tracking in underconstrained scenarios. PMID:25137692
A generalized methodology to characterize composite materials for pyrolysis models
NASA Astrophysics Data System (ADS)
McKinnon, Mark B.
The predictive capabilities of computational fire models have improved in recent years such that models have become an integral part of many research efforts. Models improve the understanding of the fire risk of materials and may decrease the number of expensive experiments required to assess the fire hazard of a specific material or designed space. A critical component of a predictive fire model is the pyrolysis sub-model that provides a mathematical representation of the rate of gaseous fuel production from condensed phase fuels given a heat flux incident to the material surface. The modern, comprehensive pyrolysis sub-models that are common today require the definition of many model parameters to accurately represent the physical description of materials that are ubiquitous in the built environment. Coupled with the increase in the number of parameters required to accurately represent the pyrolysis of materials is the increasing prevalence in the built environment of engineered composite materials that have never been measured or modeled. The motivation behind this project is to develop a systematic, generalized methodology to determine the requisite parameters to generate pyrolysis models with predictive capabilities for layered composite materials that are common in industrial and commercial applications. This methodology has been applied to four common composites in this work that exhibit a range of material structures and component materials. The methodology utilizes a multi-scale experimental approach in which each test is designed to isolate and determine a specific subset of the parameters required to define a material in the model. Data collected in simultaneous thermogravimetry and differential scanning calorimetry experiments were analyzed to determine the reaction kinetics, thermodynamic properties, and energetics of decomposition for each component of the composite. Data collected in microscale combustion calorimetry experiments were analyzed to
Michelliza, Sophie; Abraham, William M; Jacocks, Henry M; Schuster, Thomas; Baden, Daniel G
2007-12-17
Brevetoxins are neurotoxic compounds produced by the dinoflagellate Karenia brevis. Extensive blooms induce neurotoxic shellfish poisoning (NSP) and asthma-like symptoms in humans. beta-naphthoyl-brevetoxin, the first semisynthetic brevetoxin antagonist, has been defined as the lead compound in the investigation of the mechanisms of bronchoconstriction induced by inhaled brevetoxins and relaxation or reversal of those effects by selected derivatives. In pursuit of more potent and effective brevetoxin antagonists, a series of beta-naphthoyl-brevetoxin analogues have been synthesized. Activities were determined by competitive displacement of tritiated brevetoxin-3 from rat brain synaptosomes and by lung resistance measurements in sheep. Additionally, preliminary computational structural studies have been performed. All analogues bound to rat brain synaptosomes with affinities similar to beta-naphthoyl-brevetoxin but exhibited very different responses in sheep. The biological evaluations along with computational studies suggest that the brevetoxin binding site in rat brain synaptosome might be different from the ones in lung tissue and both steric and electrostatic factors contribute to the efficacy of brevetoxin antagonism. PMID:18000915
Laboratory modeling of multiple zonal jets on the polar beta-plane
NASA Astrophysics Data System (ADS)
Afanasyev, Y.
2011-12-01
Zonal jets observed in the oceans and atmospheres of planets are studied in a laboratory rotating tank. The fluid layer in the rotating tank has parabolic free surface and dynamically simulates the polar beta-plane where the Coriolis parameter varies quadratically with distance from the pole. Velocity and surface elevation fields are measured with an optical altimetry method (Afanasyev et al., Exps Fluids 2009). The flows are induced by a localized buoyancy source along radial direction. The baroclinic flow consisting of a field of eddies propagates away from the source due West and forms zonal jets (Fig. 1). Barotropic jets ahead of the baroclinic flow are formed by radiation of beta plumes. Inside the baroclinic flow the jets flow between the chains of eddies. Experimental evidence of so-called noodles (baroclinic instability mode with motions in the radial, North-South direction) theoretically predicted by Berloff et al. (JFM, JPO 2009) was found in our experiments. Beta plume radiation mechanism and the mechanism associated with the instability of noodles are likely to contribute to formation of jets in the baroclinic flow.
The NASA/GISS Mars general circulation model: Preliminary experiments
NASA Technical Reports Server (NTRS)
Allison, Michael; Chandler, M. A.; Delgenio, A. D.; Lacis, A.; Rind, D.; Rossow, W. B.; Travis, L. D.; Zhou, W.
1993-01-01
The NASA/GISS Mars General Circulation Model (GCM) is an adapted version of the GISS Global Climate/Middle Atmosphere Model, specifically developed for the diagnostic validation and objective analysis of measured atmospheric temperatures from the Mars Observer Pressure Modulator Infrared Radiometer (PMIRR) experiment. The GISS Mars GCM has 23 vertical layers extending from the surface to approximately 80 km altitude, representing a vertical resolution of about 0.3 scale heights. The primitive (vertically hydrostatic) equations are solved in finite difference form on the Krakawa B grid, with a horizontal resolution of 8 deg x 10 deg (latitude-longitude). The model includes a diurnal solar cycle, heat transport within a two-layer ground, and a high-order 'slopes-scheme' for the advection of heat in the upper atmosphere. The radiative transfer scheme is based on the correlated k distribution method for the treatment of nongray gaseous absorption thermal emission, and multiple scattering, including options for suspended dust. A special feature of the model of particular importance for Mars is a parameterization of gravity-wave-induced drag incorporating orographic forcing, wind shear, convection, and radiative damping. The implementation of the GISS Mars model includes global maps of topography, roughness, and albedo.
The Madden-Julian Oscillation in General Circulation Models
Sperber, K R; Gleckler, P J; Doutriaux, C; Groups, A M; Groups, C M; Slingo, J M; Inness, P M; Gualdi, S; Li, W
2003-10-27
A methodology is utilized to analyze in a standardized fashion the Madden-Julian Oscillation (MJO) in general circulation models. This is attained by projecting 20-100 day bandpass filtered outgoing longwave radiation (OLR) from the models onto the two leading empirical orthogonal functions (EOF's) of observed OLR that characterize the propagation of MJO convection from the Indian Ocean to the central Pacific Ocean. The resulting principal component time series are then screened to isolate boreal winters during which they exhibit a lead-lag relationship consistent with observations. This PC subset is used for linear regression to determine the ability of the models to simulate the observed spacetime variability of the MJO. The vast majority of models underestimate the amplitude of the MJO convective anomalies by a factor of two or more, and the eastward propagation of convection is less coherent than observed, typically. For a given family of models, coupling to an ocean leads to better organization of the large-scale convection. The low-level moisture convergence mechanism for eastward propagation is represented in limited cases, as is the vertical structure of the MJO.
Application of thermospheric general circulation models for space weather operations
NASA Astrophysics Data System (ADS)
Fuller-Rowell, T.; Minter, C.; Codrescu, M.
Solar irradiance is the dominant source of heat, ionization, and dissociation of the thermosphere, and to a large extent drives the global dynamics, and controls the neutral composition and density structure. Neutral composition is important for space weather applications because of its impact on ionospheric loss rates, and neutral density is critical for satellite drag prediction. The future for thermospheric general circulation models for space weather operations lies in their use as state propagators in data assimilation techniques. The physical models can match empirical models in accuracy provided accurate drivers are available, but their true value comes when combined with data in an optimal way. Two such applications have recently been developed. The first utilizes a Kalman filter to combine space-based observation of airglow with physical model predictions to produce global maps of neutral composition. The output of the filter will be used within the GAIM (Global Assimilation of Ionospheric Measurement) model developed under a parallel effort. The second filter uses satellite tracking and remote sensing data for specification of neutral density. Both applications rely on accurate estimates of the solar EUV and magnetospheric drivers.
General mirror pairs for gauged linear sigma models
NASA Astrophysics Data System (ADS)
Aspinwall, Paul S.; Plesser, M. Ronen
2015-11-01
We carefully analyze the conditions for an abelian gauged linear σ-model to exhibit nontrivial IR behavior described by a nonsingular superconformal field theory determining a superstring vacuum. This is done without reference to a geometric phase, by associating singular behavior to a noncompact space of (semi-)classical vacua. We find that models determined by reflexive combinatorial data are nonsingular for generic values of their parameters. This condition has the pleasant feature that the mirror of a nonsingular gauged linear σ-model is another such model, but it is clearly too strong and we provide an example of a non-reflexive mirror pair. We discuss a weaker condition inspired by considering extremal transitions, which is also mirror symmetric and which we conjecture to be sufficient. We apply these ideas to extremal transitions and to understanding the way in which both Berglund-Hübsch mirror symmetry and the Vafa-Witten mirror orbifold with discrete torsion can be seen as special cases of the general combinatorial duality of gauged linear σ-models. In the former case we encounter an example showing that our weaker condition is still not necessary.
Modeling AXAF Obstructions with the Generalized Aperture Program.
NASA Astrophysics Data System (ADS)
Nguyen, D.; Gaetz, T.; Jerius, D.; Stern, I.
The generalized aperture program is designed to simulate the effects on the incident photon stream of physical obstructions, such as thermal baffles and pre- and post-collimators. It can handle a wide variety of aperture shapes, and has provisions to allow alterations of the photons by the apertures. The philosophy behind the aperture program is that a geometrically complicated aperture may be modeled by a combination of geometrically simpler apertures. This is done by incorporating a language, lua, to lay out the apertures. User provided call-back functions enable the modeling of the interactions of the incident photon with the apertures. This approach allows for maximum flexibility, since the geometry and interactions of obstructions can be specified by the user at run time.
Dynamic regulation of erythropoiesis: A computer model of general applicability
NASA Technical Reports Server (NTRS)
Leonard, J. I.
1979-01-01
A mathematical model for the control of erythropoiesis was developed based on the balance between oxygen supply and demand at a renal oxygen detector which controls erythropoietin release and red cell production. Feedback regulation of tissue oxygen tension is accomplished by adjustments of hemoglobin levels resulting from the output of a renal-bone marrow controller. Special consideration was given to the determinants of tissue oxygenation including evaluation of the influence of blood flow, capillary diffusivity, oxygen uptake and oxygen-hemoglobin affinity. A theoretical analysis of the overall control system is presented. Computer simulations of altitude hypoxia, red cell infusion hyperoxia, and homolytic anemia demonstrate validity of the model for general human application in health and disease.
High pressure experiments with a Mars general circulation model
NASA Technical Reports Server (NTRS)
Haberle, R. M.; Pollack, J. B.; Murphy, J. R.; Schaeffer, J.; Lee, H.
1992-01-01
The interaction of three physical processes will determine the stability of the Martian polar caps as the surface pressure increases: the greenhouse effect, atmospheric heat transport, and the change in the CO2 frost point temperature. The contribution of each is readily determined in the Mars general circulation model (GCM). Therefore, we have initiated experiments with the GCM to determine how these processes interact, and how the atmosphere-polar cap system responds to increasing surface pressure. The experiments are carried out for northern winter solstice and generally assume the atmosphere to be free of dust. Each experiment starts from resting isothermal conditions and runs for 50 Mars days. Mars' current orbital parameters are used. The experiments are for surface pressures of 120, 480, and 960 mb, which represent 16, 64, and 128 times the current value. To date we have analyzed the 120 mb experiment and the results indicate the contrary to the simpler models, the polar caps actually advance instead of retreat. Other aspects of this investigation are presented.
General analysis of dark radiation in sequestered string models
NASA Astrophysics Data System (ADS)
Cicoli, Michele; Muia, Francesco
2015-12-01
We perform a general analysis of axionic dark radiation produced from the decay of the lightest modulus in the sequestered LARGE Volume Scenario. We discuss several cases depending on the form of the Kähler metric for visible sector matter fields and the mechanism responsible for achieving a de Sitter vacuum. The leading decay channels which determine dark radiation predictions are to hidden sector axions, visible sector Higgses and SUSY scalars depending on their mass. We show that in most of the parameter space of split SUSY-like models squarks and sleptons are heavier than the lightest modulus. Hence dark radiation predictions previously obtained for MSSM-like cases hold more generally also for split SUSY-like cases since the decay channel to SUSY scalars is kinematically forbidden. However the inclusion of string loop corrections to the Kähler potential gives rise to a parameter space region where the decay channel to SUSY scalars opens up, leading to a significant reduction of dark radiation production. In this case, the simplest model with a shift-symmetric Higgs sector can suppress the excess of dark radiation Δ N eff to values as small as 0 .14, in perfect agreement with current experimental bounds. Depending on the exact mass of the SUSY scalars all values in the range 0 .14 ≲ Δ N eff ≲ 1 .6 are allowed. Interestingly dark radiation overproduction can be avoided also in the absence of a Giudice-Masiero coupling.
Anisotropic mesoscale eddy transport in ocean general circulation models
NASA Astrophysics Data System (ADS)
Reckinger, Scott; Fox-Kemper, Baylor; Bachman, Scott; Bryan, Frank; Dennis, John; Danabasoglu, Gokhan
2014-11-01
In modern climate models, the effects of oceanic mesoscale eddies are introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically. However, the diffusive processes that the parameterization approximates, such as shear dispersion and potential vorticity barriers, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters from one to three: major diffusivity, minor diffusivity, and alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces temperature and salinity biases. These effects can be improved by parameterizing the oceanic anisotropic transport mechanisms.
A generalized model for the thermodynamic properties of mixtures
Lemmon, E.W.; Jacobsen, R.T.
1999-05-01
A mixture model explicit in Helmholtz energy has been developed which is capable of predicting thermodynamic properties of mixtures containing nitrogen, argon, oxygen, carbon dioxide, methane, ethane, propane, n-butane, i-butane, R-32, R-125, R-134a, and R-152a within the estimated accuracy of available experimental data. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility for real gas contribution, and the contribution from mixing. The contribution from mixing is given by a single generalized equation which is applied to all mixtures studied in this work. The independent variables are the density, temperature, and composition. The model may be used to calculate the thermodynamic properties of mixtures at various compositions including dew and bubble point properties and critical points. It incorporates accurate published equations of state for each pure fluid. The estimated accuracy of calculated properties is {+-}0.2% in density, {+-}0.1% in the speed of sound at pressures below 10 MPa, {+-}0.5% in the speed of sound for pressures above 10 MPa, and {+-}1% in heat capacities. In the region from 250 to 350 K at pressures up to 30 MPa, calculated densities are within {+-}0.1% for most gaseous phase mixtures. For binary mixtures where the critical point temperatures of the pure fluid constituents are within 100 K of each other, calculated bubble point pressures are generally accurate to within {+-}1 to 2%. For mixtures with critical points further apart, calculated bubble point pressures are generally accurate to within {+-}5 to 10%.
Yamabe, Noriko; Kang, Ki Sung; Zhu Baoting
2010-11-15
The modulating effect of estrogen on glucose homeostasis remains a controversial issue at present. In this study, we sought to determine the beneficial effect of 17{beta}-estradiol (E{sub 2}) on hyperglycemia and islet {beta}-cell functions in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were injected i.p. with STZ to induce a relatively mild diabetic condition. The rats were then treated with E{sub 2} orally at 500 {mu}g/kg body weight/day for 15 days to evaluate the modulating effect on hyperglycemia, insulin secretion, and islet {beta}-cell proliferation. E{sub 2} administration for 10 days significantly lowered plasma glucose levels, increased plasma insulin levels, and improved glucose tolerance by attenuating insulin response to oral glucose loading. These beneficial effects of E{sub 2} were accompanied by increases in islet number and volume, rate of islet cell proliferation, and the amount of insulin secreted. The growth-stimulatory effect of E{sub 2} on islet cells was linked to the functions of the estrogen receptor {alpha}. Notably, these protective effects of E{sub 2} on diabetic conditions were basically not observed when the STZ-treated rats had a more severe degree of islet damage and hyperglycemia. Taken together, we conclude that E{sub 2} can promote the regeneration of damaged pancreatic islets by stimulating {beta}-cell proliferation in diabetic rats, and this effect is accompanied by improvements in glucose tolerance and a decrease in plasma glucose levels. These findings suggest that oral administration of E{sub 2} may be beneficial in diabetic patients with an accelerated loss of islet {beta}-cells.
Generalized Optoelectronic Model of Series-Connected Multijunction Solar Cells
Geisz, John F.; Steiner, Myles A.; Garcia, Ivan; France, Ryan M.; McMahon, William E.; Osterwald, Carl R.; Friedman, Daniel J.
2015-10-02
The emission of light from each junction in a series-connected multijunction solar cell, we found, both complicates and elucidates the understanding of its performance under arbitrary conditions. Bringing together many recent advances in this understanding, we present a general 1-D model to describe luminescent coupling that arises from both voltage-driven electroluminescence and voltage-independent photoluminescence in nonideal junctions that include effects such as Sah-Noyce-Shockley (SNS) recombination with n ≠ 2, Auger recombination, shunt resistance, reverse-bias breakdown, series resistance, and significant dark area losses. The individual junction voltages and currents are experimentally determined from measured optical and electrical inputs and outputs ofmore » the device within the context of the model to fit parameters that describe the devices performance under arbitrary input conditions. Furthermore, our techniques to experimentally fit the model are demonstrated for a four-junction inverted metamorphic solar cell, and the predictions of the model are compared with concentrator flash measurements.« less
SIR model with general distribution function in the infectious period
NASA Astrophysics Data System (ADS)
Gomes, Marcelo F. C.; Gonçalves, Sebastián
2009-08-01
The Susceptible-Infected-Removed or SIR model, as it was formulated by Kermack and McKendrick, is the key model for epidemic dynamics. Most applications of such a basic scheme use a constant rate for the removal term. However, that assumption corresponds to the rather unrealistic exponential distribution of infectious times. On the other hand, recent approaches, like numerical simulations, frequently assume a fixed and uniform duration for the infectious state-which is unrealistic too. The extreme assumptions in those different schemes are a hurdle that can frustrate any intention of drawing comparison between results from them. In the present contribution we study the delay equations for the SIR model, comparing the solutions for many typical cases with the simulation counterpart and with the standard SIR model. Using delay equations, where each infected individual is removed at a specific time after being infected, the dynamics for the infected and susceptible agree almost exactly with the numerical implementation. Even in the general case of distributed infective periods, the agreement is excellent.
Complex Environmental Data Modelling Using Adaptive General Regression Neural Networks
NASA Astrophysics Data System (ADS)
Kanevski, Mikhail
2015-04-01
The research deals with an adaptation and application of Adaptive General Regression Neural Networks (GRNN) to high dimensional environmental data. GRNN [1,2,3] are efficient modelling tools both for spatial and temporal data and are based on nonparametric kernel methods closely related to classical Nadaraya-Watson estimator. Adaptive GRNN, using anisotropic kernels, can be also applied for features selection tasks when working with high dimensional data [1,3]. In the present research Adaptive GRNN are used to study geospatial data predictability and relevant feature selection using both simulated and real data case studies. The original raw data were either three dimensional monthly precipitation data or monthly wind speeds embedded into 13 dimensional space constructed by geographical coordinates and geo-features calculated from digital elevation model. GRNN were applied in two different ways: 1) adaptive GRNN with the resulting list of features ordered according to their relevancy; and 2) adaptive GRNN applied to evaluate all possible models N [in case of wind fields N=(2^13 -1)=8191] and rank them according to the cross-validation error. In both cases training were carried out applying leave-one-out procedure. An important result of the study is that the set of the most relevant features depends on the month (strong seasonal effect) and year. The predictabilities of precipitation and wind field patterns, estimated using the cross-validation and testing errors of raw and shuffled data, were studied in detail. The results of both approaches were qualitatively and quantitatively compared. In conclusion, Adaptive GRNN with their ability to select features and efficient modelling of complex high dimensional data can be widely used in automatic/on-line mapping and as an integrated part of environmental decision support systems. 1. Kanevski M., Pozdnoukhov A., Timonin V. Machine Learning for Spatial Environmental Data. Theory, applications and software. EPFL Press
Solitons and kinks in a general car-following model.
Kurtze, Douglas A
2013-09-01
We study a general car-following model of traffic flow on an infinitely long single-lane road, which assumes that a car's acceleration depends on time-delayed values of its own speed, the headway between it and the car ahead, and the rate of change of headway, but makes minimal assumptions about the functional form of that dependence. We present a detailed characterization of the onset of linear instability; in particular we find a specific limit on the delay time below which the marginal wave number at the onset of instability is zero, and another specific limit on the delay time above which steady flow is always unstable. Crucially, the threshold of absolute stability generally does not coincide with an inflection point of the steady-state velocity function. When the marginal perturbation at onset has wave number 0, we show that Burgers and Korteweg-de Vries (KdV) equations can be derived under the usual assumptions, and that corrections to the KdV equation "select" a single member of the one-parameter set of its one-soliton solutions by driving a slow evolution of the soliton parameter. While in previous models this selected soliton has always marked the threshold of a finite-amplitude instability of linearly stable steady flow, we find that it can alternatively be a stable, small-amplitude jam that occurs when steady flow is linearly unstable. The model reduces to the usual modified Korteweg-de Vries (mKdV) equation only in the special situation that the threshold of absolute stability coincides with an inflection point of the steady-state velocity function; in general, near the threshold of absolute stability the model reduces instead to a KdV equation in the regime of small solitons, while near an inflection point it reduces to a Hayakawa-Nakanishi equation. Like the mKdV equation, the Hayakawa-Nakanishi equation admits a continuous family of kink solutions, and the selection criterion arising from the corrections to this equation can be written down
Adaptive Error Estimation in Linearized Ocean General Circulation Models
NASA Technical Reports Server (NTRS)
Chechelnitsky, Michael Y.
1999-01-01
Data assimilation methods are routinely used in oceanography. The statistics of the model and measurement errors need to be specified a priori. This study addresses the problem of estimating model and measurement error statistics from observations. We start by testing innovation based methods of adaptive error estimation with low-dimensional models in the North Pacific (5-60 deg N, 132-252 deg E) to TOPEX/POSEIDON (TIP) sea level anomaly data, acoustic tomography data from the ATOC project, and the MIT General Circulation Model (GCM). A reduced state linear model that describes large scale internal (baroclinic) error dynamics is used. The methods are shown to be sensitive to the initial guess for the error statistics and the type of observations. A new off-line approach is developed, the covariance matching approach (CMA), where covariance matrices of model-data residuals are "matched" to their theoretical expectations using familiar least squares methods. This method uses observations directly instead of the innovations sequence and is shown to be related to the MT method and the method of Fu et al. (1993). Twin experiments using the same linearized MIT GCM suggest that altimetric data are ill-suited to the estimation of internal GCM errors, but that such estimates can in theory be obtained using acoustic data. The CMA is then applied to T/P sea level anomaly data and a linearization of a global GFDL GCM which uses two vertical modes. We show that the CMA method can be used with a global model and a global data set, and that the estimates of the error statistics are robust. We show that the fraction of the GCM-T/P residual variance explained by the model error is larger than that derived in Fukumori et al.(1999) with the method of Fu et al.(1993). Most of the model error is explained by the barotropic mode. However, we find that impact of the change in the error statistics on the data assimilation estimates is very small. This is explained by the large
The transforming growth factor-beta 3 knock-out mouse: an animal model for cleft palate.
Koo, S H; Cunningham, M C; Arabshahi, B; Gruss, J S; Grant, J H
2001-09-15
The recent report of a transforming growth factor-beta 3 (TGF-beta 3) knock-out mouse in which 100 percent of the homozygous pups have cleft palate raised the question as to the potential usefulness of these animals as a model for cleft palate research. The specific aim in this study was to carefully document the anatomy of the cleft palate in the TGF-beta 3 knock-out mice as compared with wild type controls. Special attention was paid to the levator veli palatini muscle, the tensor veli palatini muscle, and their respective innervation. Because the TGF-beta 3 knock-out is lethal in the early perinatal period and because the heterozygotes are phenotypically normal, polymerase chain reaction was required to genotype the animals before mating. Time-mated pregnancies between proven heterozygotes were then delivered by cesarean section at gestational day 18.5 to prevent maternal cannibalism of homozygote pups. All delivered pups were killed and their tails processed by polymerase chain reaction to verify genotype. The heads were then fixed and sectioned in axial, coronal, or sagittal planes. Sections were stained with hematoxylin and eosin or processed for immunohistochemistry with nerve specific protein gene product 9.5 and calcitonin gene-related peptide antibodies. Sections were analyzed in a serial fashion. Nine wild type control animals were analyzed along with nine TGF-beta 3 knock-out homozygotes. Time matings between proven heterozygotes yielded wild type pups, heterozygote pups, and homozygote knock-out pups in the expected mendelian ratios (28 percent to 46 percent to 26 percent; n = 43). The results demonstrated 100 percent clefting in the homozygous TGF-beta 3 knock-out pups. Complete clefting of the secondary palate was seen in four of nine and incomplete clefting was seen in five of nine. The levator veli palatini and tensor veli palatini muscles were demonstrated coursing parallel to the cleft margin in all cleft mice. The orientation of these muscles
Kimpimäki, T; Kulmala, P; Savola, K; Kupila, A; Korhonen, S; Simell, T; Ilonen, J; Simell, O; Knip, M
2002-10-01
The aim of this study was to evaluate the frequency and predictive value of diabetes-associated autoantibodies, such as islet cell antibodies (ICA) and autoantibodies to insulin (IAA), GAD65 (GADA), and the IA-2 molecule (IA-2A) in genetically susceptible children from the general population during the first 2 yr of life. Of 12,170 newborn infants, 1,005 with increased genetic risk of type 1 diabetes (high risk, human leukocyte antigen DQB1*02/*0302; moderate risk, DQB1*0302/x, where x = other than *02, *0301, or *0602) were monitored for ICA, IAA, GADA, and IA-2A at 3- to 6-month intervals from birth up to a minimum age of 2 yr. In addition, all 15 genetically susceptible children from the general population who had participated in regular immunological follow-up and developed clinical type 1 diabetes by the end of April 2000 were analyzed for the development of autoantibodies. Among 1,005 children, 63 (6.3%) tested positive for at least one autoantibody, 31 for ICA (3.1%), 48 for IAA (4.8%), 23 for GADA (2.3%), and 13 for IA-2A (1.3%) at least once by the age of 2 yr. Both ICA and IAA identified 95% [95% confidence interval (CI), 77.2-99.9%] of those who tested persistently positive for multiple (> or = 2) antibodies at the age of 2 yr, GADA identified 86% (CI, 65.1-97.1%), and IA-2A identified 55% (CI, 32.2-75.6%). Close to half of the antibody-positive children (29 of 63) reverted back to antibody negativity. Autoantibodies disappeared more often among those who tested positive for IAA than among those who tested positive for other autoantibodies (P < or = 0.021). Among the 15 children who developed type 1 diabetes, the disease sensitivity of ICA was 80% (CI, 51.9-95.7%), that of IAA was 93% (CI, 68.0-99.8%), that of GADA was 60% (CI, 32.3-83.7%), and that of IA-2A was 40% (CI, 16.3-67.7%). These results suggest that IAA are characterized by high sensitivity, early appearance, and high frequency of transient antibody positivity, whereas ICA detected with a
The Generalized FLaIR Model (GFM) for landslide forecasting
NASA Astrophysics Data System (ADS)
De Luca, Davide Luciano; Versace, Pasquale
2015-04-01
A new version of the hydrological model named FLaIR (Forecasting of Landslides Induced by Rainfall, Capparelli and Versace 2011) is proposed, named as GFM (Generalized FLaIR Model). Non stationary rainfall thresholds, depending on antecedent precipitation, are introduced in this new release, which allow for a better prediction of landslide occurrences. It is possible to demonstrate that GFM reproduces all the Antecedent Precipitation models (AP) proposed in technical literature as particular cases, besides Intensity-Duration schemes (ID) and more conceptual approaches, whose reconstruction with the first release of FlaIR model, which adopts only stationary thresholds, was already discussed in Capparelli and Versace (2011). GFM is extremely flexible, and the main advantage of the model is represented by the possibility of using well-established procedures for the choice of the most appropriate configuration for the selected case study, and of facilitating the comparison between several options, through the use of a mobility function. Gimigliano municipality, located in Calabria region (southern Italy) was chosen as case study, where a consistent number of landslides occurred in the past years; in particular, during the period 2008-2010 this area (like the whole Calabria region) was affected by persistent rainfall events, which induced several damages related to infrastructures and buildings. For the selected case study GFM allows to obtain significant improvements in landslide prediction; in details a substantial reduction of False Alarms is obtained with respect to application of classical ID and AP schemes. REFERENCES Capparelli G, Versace P (2011). FLaIR and SUSHI: Two mathematical models for Early Warning Systems for rainfall induced landslides. Landslides 8:67-79. doi: 10.1007/s10346-010-0228-6
A generalized model for estimating the energy density of invertebrates
James, Daniel A.; Csargo, Isak J.; Von Eschen, Aaron; Thul, Megan D.; Baker, James M.; Hayer, Cari-Ann; Howell, Jessica; Krause, Jacob; Letvin, Alex; Chipps, Steven R.
2012-01-01
Invertebrate energy density (ED) values are traditionally measured using bomb calorimetry. However, many researchers rely on a few published literature sources to obtain ED values because of time and sampling constraints on measuring ED with bomb calorimetry. Literature values often do not account for spatial or temporal variability associated with invertebrate ED. Thus, these values can be unreliable for use in models and other ecological applications. We evaluated the generality of the relationship between invertebrate ED and proportion of dry-to-wet mass (pDM). We then developed and tested a regression model to predict ED from pDM based on a taxonomically, spatially, and temporally diverse sample of invertebrates representing 28 orders in aquatic (freshwater, estuarine, and marine) and terrestrial (temperate and arid) habitats from 4 continents and 2 oceans. Samples included invertebrates collected in all seasons over the last 19 y. Evaluation of these data revealed a significant relationship between ED and pDM (r2 = 0.96, p < 0.0001), where ED (as J/g wet mass) was estimated from pDM as ED = 22,960pDM − 174.2. Model evaluation showed that nearly all (98.8%) of the variability between observed and predicted values for invertebrate ED could be attributed to residual error in the model. Regression of observed on predicted values revealed that the 97.5% joint confidence region included the intercept of 0 (−103.0 ± 707.9) and slope of 1 (1.01 ± 0.12). Use of this model requires that only dry and wet mass measurements be obtained, resulting in significant time, sample size, and cost savings compared to traditional bomb calorimetry approaches. This model should prove useful for a wide range of ecological studies because it is unaffected by taxonomic, seasonal, or spatial variability.
General Description of Fission Observables: GEF Model Code
NASA Astrophysics Data System (ADS)
Schmidt, K.-H.; Jurado, B.; Amouroux, C.; Schmitt, C.
2016-01-01
The GEF ("GEneral description of Fission observables") model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass- and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and energy spectra from neutron-induced and spontaneous fission. Derived properties of delayed neutrons and decay heat are also considered. The GEF model is based on a general approach to nuclear fission that explains a great part of the complex appearance of fission observables on the basis of fundamental laws of physics and general properties of microscopic systems and mathematical objects. The topographic theorem is used to estimate the fission-barrier heights from theoretical macroscopic saddle-point and ground-state masses and experimental ground-state masses. Motivated by the theoretically predicted early localisation of nucleonic wave functions in a necked-in shape, the properties of the relevant fragment shells are extracted. These are used to determine the depths and the widths of the fission valleys corresponding to the different fission channels and to describe the fission-fragment distributions and deformations at scission by a statistical approach. A modified composite nuclear-level-density formula is proposed. It respects some features in the superfluid regime that are in accordance with new experimental findings and with theoretical expectations. These are a constant-temperature behaviour that is consistent with a considerably increased heat capacity and an increased pairing condensation energy that is
Mizushina, Y; Kasai, N; Sugawara, F; Iida, A; Yoshida, H; Sakaguchi, K
2001-11-01
The molecular action of lithocholic acid (LCA), a selective inhibitor of mammalian DNA polymerase beta (pol beta), was investigated. We found that LCA could also strongly inhibit the activity of human DNA topoisomerase II (topo II). No other DNA metabolic enzymes tested were affected by LCA. Therefore, LCA should be classified as an inhibitor of both pol beta and topo II. Here, we report the molecular interaction of LCA with pol beta and topo II. By three-dimensional structural model analysis and by comparison with the spatial positioning of specific amino acids binding to LCA on pol beta (Lys60, Leu77, and Thr79), we obtained supplementary information that allowed us to build a structural model of topo II. Modeling analysis revealed that the LCA-interaction interface in both enzymes has a pocket comprised of three amino acids in common, which binds to the LCA molecule. In topo II, the three amino acid residues were Lys720, Leu760, and Thr791. These results suggested that the LCA binding domains of pol beta and topo II are three-dimensionally very similar. PMID:11686928
Modeling of space environment impact on nanostructured materials. General principles
NASA Astrophysics Data System (ADS)
Voronina, Ekaterina; Novikov, Lev
2016-07-01
In accordance with the resolution of ISO TC20/SC14 WG4/WG6 joint meeting, Technical Specification (TS) 'Modeling of space environment impact on nanostructured materials. General principles' which describes computer simulation methods of space environment impact on nanostructured materials is being prepared. Nanomaterials surpass traditional materials for space applications in many aspects due to their unique properties associated with nanoscale size of their constituents. This superiority in mechanical, thermal, electrical and optical properties will evidently inspire a wide range of applications in the next generation spacecraft intended for the long-term (~15-20 years) operation in near-Earth orbits and the automatic and manned interplanetary missions. Currently, ISO activity on developing standards concerning different issues of nanomaterials manufacturing and applications is high enough. Most such standards are related to production and characterization of nanostructures, however there is no ISO documents concerning nanomaterials behavior in different environmental conditions, including the space environment. The given TS deals with the peculiarities of the space environment impact on nanostructured materials (i.e. materials with structured objects which size in at least one dimension lies within 1-100 nm). The basic purpose of the document is the general description of the methodology of applying computer simulation methods which relate to different space and time scale to modeling processes occurring in nanostructured materials under the space environment impact. This document will emphasize the necessity of applying multiscale simulation approach and present the recommendations for the choice of the most appropriate methods (or a group of methods) for computer modeling of various processes that can occur in nanostructured materials under the influence of different space environment components. In addition, TS includes the description of possible
Horizontal density compensation in ocean general circulation models
NASA Astrophysics Data System (ADS)
Koch, Andrey O.; Helber, Robert W.; Richman, James G.; Barron, Charlie N.
2013-04-01
Density compensation is the condition where temperature (T) and salinity (S) gradients counteract in their effect on density. Open ocean observations with SeaSoar tows and recent glider observations in the Gulf of Mexico reported in the scientific literature suggest that horizontal gradients in the surface mixed layer tend to be strongly density compensated over a range of spatial scales while in seasonal thermocline and deeper layers T,S-fronts are only partially compensated or uncompensated. We assess the capability of ocean general circulation models (OGCM) to develop horizontal density compensation as observed in the upper ocean. The physics required to evolve the initial density compensated mixed layer toward the partially compensated conditions of the thermocline is tested. Idealistic scenarios with horizontal, partially compensated density fronts in the mixed layer are examined in submesoscale-resolved run-down simulations on Hybrid Coordinate Ocean Model (HYCOM). Simulations with no atmospheric forcing show that initial Density compensation does not change substantially experiencing only minor decrease with time simultaneously with the restratification of the mixed layer by submesoscale eddies. Submesoscale fronts tend to be more compensated than mesoscale fronts. A sensitivity analysis shows that the density compensation of submesoscale fronts is particularly sensitive to the horizontal diffusion rate. Simulations with wind forcing exhibit destruction of initial density compensation due to ageostrophic frontogenesis which is confirmed by recent glider observations in the Gulf of Mexico. The lack of the model skill to develop and maintain compensated thermohaline variability is attributed to the T, S horizontal diffusion parameterization used in HYCOM and generally in modern OGCMs: it is decoupled from vertical diffusion and T and S diffusion is horizontally identical. Our findings suggest that OGCM's skill to develop compensated thermohaline variability
Takeda, K; Balzano, S; Sakurai, A; DeGroot, L J; Refetoff, S
1991-01-01
Generalized resistance to thyroid hormone (GRTH) is a syndrome characterized by impaired tissue responsiveness to thyroid hormone. Two distinct point mutations in the hormone binding domain of the thyroid hormone receptor (TR) beta have recently been identified in two unrelated families with GRTH. One, Mf, involves a replacement of the normal glycine-345 for arginine in exon 7 and another, Mh, replaces the normal proline-453 for histidine in exon 8. To probe for the presence of the Mf and Mh defect in 19 unrelated families with GRTH, we applied separate polymerase chain reactions using allele-specific oligonucleotide primers containing the normal and each of the two mutant nucleotides at the 3'-position. A total of 24 affected subjects and 13 normal family members were studied. The mode of inheritance was dominant in 13 families, was unknown in 5 families, and was clearly recessive in 1 family in which only the consanguineous subjects were affected. Primers containing the substitutions specific for Mf and Mh amplified exons 7 and 8, respectively, only in affected members of each of the two index families. Primers containing the normal sequences amplified exons 7 and 8 of the TR beta gene in all subjects except affected members of one family. In this family with recessively inherited GRTH, neither exon could be amplified using any combinations of primers and DNA blot revealed absence of all coding exons. These results indicate a major deletion of the TR beta gene, including both DNA and hormone binding domains. Since heterozygous members of this family are not affected, the presence of a single normal allele is sufficient for normal function of the TR beta. These data also support the hypothesis that in the dominant mode of GRTH inheritance the presence of an abnormal TR beta interferes with the function of the normal TR beta. Distinct mutations are probably responsible for GRTH in unrelated families. Images PMID:1991834
Generalized continuum modeling of scale-dependent crystalline plasticity
NASA Astrophysics Data System (ADS)
Mayeur, Jason R.
The use of metallic material systems (e.g. pure metals, alloys, metal matrix composites) in a wide range of engineering applications from medical devices to electronic components to automobiles continues to motivate the development of improved constitutive models to meet increased performance demands while minimizing cost. Emerging technologies often incorporate materials in which the dominant microstructural features have characteristic dimensions reaching into the submicron and nanometer regime. Metals comprised of such fine microstructures often exhibit unique and size-dependent mechanical response, and classical approaches to constitutive model development at engineering (continuum) scales, being local in nature, are inadequate for describing such behavior. Therefore, traditional modeling frameworks must be augmented and/or reformulated to account for such phenomena. Crystal plasticity constitutive models have proven quite capable of capturing first-order microstructural effects such as grain orientation (elastic/plastic anisotropy), grain morphology, phase distribution, etc. on the deformation behavior of both single and polycrystals, yet suffer from the same limitations as other local continuum theories with regard to capturing scale-dependent mechanical response. This research is focused on the development, numerical implementation, and application of a generalized (nonlocal) theory of single crystal plasticity capable of describing the scale-dependent mechanical response of both single and polycrystalline metals that arises as a result of heterogeneous deformation. This research developed a dislocation-based theory of micropolar single crystal plasticity. The majority of nonlocal crystal plasticity theories are predicated on the connection between gradients of slip and geometrically necessary dislocations. Due to the diversity of existing nonlocal crystal plasticity theories, a review, summary, and comparison of representative model classes is presented in
Relativistic model of anisotropic charged fluid sphere in general relativity
NASA Astrophysics Data System (ADS)
Pant, Neeraj; Pradhan, N.; Bansal, Rajeev K.
2016-01-01
In this present paper, we present a class of static, spherically symmetric charged anisotropic fluid models of super dense stars in isotropic coordinates by considering a particular type of metric potential, a specific choice of electric field intensity E and pressure anisotropy factor Δ which involve parameters K (charge) and α (anisotropy) respectively. The solutions so obtained are utilized to construct the models for super-dense stars like neutron stars and strange quark stars. Our solutions are well behaved within the following ranges of different constant parameters. In the absence of pressure anisotropy and charge present model reduces to the isotropic model Pant et al. (Astrophys. Space Sci. 330:353-359, 2010). Our solution is well behaved in all respects for all values of X lying in the range 0< X ≤ 0.18, α lying in the range 0 ≤ α ≤6.6, K lying in the range 0< K ≤ 6.6 and Schwarzschild compactness parameter "u" lying in the range 0< u ≤ 0.38. Since our solution is well behaved for a wide ranges of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We have shown that corresponding to X=0.088, α=0.6 and K=4.3 for which u=0.2054 and by assuming surface density ρb = 4.6888 × 10^{14} g/cm3 the mass and radius are found to be 1.51 M_{\\varTheta} and 10.90 km respectively. Assuming surface density ρb = 2 × 10^{14} g/cm3 the mass and radius for a neutron star candidate are found to be 2.313 M_{\\varTheta} and 16.690 km respectively. Hence we obtain masses and radii that fall in the range of what is generally expected for quark stars and neutron stars.
Generalized multiplicative error models: Asymptotic inference and empirical analysis
NASA Astrophysics Data System (ADS)
Li, Qian
This dissertation consists of two parts. The first part focuses on extended Multiplicative Error Models (MEM) that include two extreme cases for nonnegative series. These extreme cases are common phenomena in high-frequency financial time series. The Location MEM(p,q) model incorporates a location parameter so that the series are required to have positive lower bounds. The estimator for the location parameter turns out to be the minimum of all the observations and is shown to be consistent. The second case captures the nontrivial fraction of zero outcomes feature in a series and combines a so-called Zero-Augmented general F distribution with linear MEM(p,q). Under certain strict stationary and moment conditions, we establish a consistency and asymptotic normality of the semiparametric estimation for these two new models. The second part of this dissertation examines the differences and similarities between trades in the home market and trades in the foreign market of cross-listed stocks. We exploit the multiplicative framework to model trading duration, volume per trade and price volatility for Canadian shares that are cross-listed in the New York Stock Exchange (NYSE) and the Toronto Stock Exchange (TSX). We explore the clustering effect, interaction between trading variables, and the time needed for price equilibrium after a perturbation for each market. The clustering effect is studied through the use of univariate MEM(1,1) on each variable, while the interactions among duration, volume and price volatility are captured by a multivariate system of MEM(p,q). After estimating these models by a standard QMLE procedure, we exploit the Impulse Response function to compute the calendar time for a perturbation in these variables to be absorbed into price variance, and use common statistical tests to identify the difference between the two markets in each aspect. These differences are of considerable interest to traders, stock exchanges and policy makers.
Arctic Storms in a Regionally Refined Atmospheric General Circulation Model
NASA Astrophysics Data System (ADS)
Roesler, E. L.; Taylor, M.; Boslough, M.; Sullivan, S.
2014-12-01
Regional refinement in an atmospheric general circulation model is a new tool in atmospheric modeling. A regional high-resolution solution can be obtained without the computational cost of running a global high-resolution simulation as global climate models have increasing ability to resolve smaller spatial scales. Previous work has shown high-resolution simulations, i.e. 1/8 degree, and variable resolution utilities have resolved more fine-scale structure and mesoscale storms in the atmosphere than their low-resolution counterparts. We will describe an experiment designed to identify and study Arctic storms at two model resolutions. We used the Community Atmosphere Model, version 5, with the Spectral Element dynamical core at 1/8-degree and 1 degree horizontal resolutions to simulate the climatological year of 1850. Storms were detected using a low-pressure minima and vorticity maxima - finding algorithm. It was found the high-resolution 1/8-degree simulation had more storms in the Northern Hemisphere than the low-resolution 1-degree simulation. A variable resolution simulation with a global low resolution of 1-degree and a high-resolution refined region of 1/8 degree over a region in the Arctic is planned. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND NO. 2014-16460A
Toward a general psychological model of tension and suspense
Lehne, Moritz; Koelsch, Stefan
2015-01-01
Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309
Generalized Fiducial Inference for Binary Logistic Item Response Models.
Liu, Yang; Hannig, Jan
2016-06-01
Generalized fiducial inference (GFI) has been proposed as an alternative to likelihood-based and Bayesian inference in mainstream statistics. Confidence intervals (CIs) can be constructed from a fiducial distribution on the parameter space in a fashion similar to those used with a Bayesian posterior distribution. However, no prior distribution needs to be specified, which renders GFI more suitable when no a priori information about model parameters is available. In the current paper, we apply GFI to a family of binary logistic item response theory models, which includes the two-parameter logistic (2PL), bifactor and exploratory item factor models as special cases. Asymptotic properties of the resulting fiducial distribution are discussed. Random draws from the fiducial distribution can be obtained by the proposed Markov chain Monte Carlo sampling algorithm. We investigate the finite-sample performance of our fiducial percentile CI and two commonly used Wald-type CIs associated with maximum likelihood (ML) estimation via Monte Carlo simulation. The use of GFI in high-dimensional exploratory item factor analysis was illustrated by the analysis of a set of the Eysenck Personality Questionnaire data. PMID:26769340
A Pacific Ocean general circulation model for satellite data assimilation
NASA Technical Reports Server (NTRS)
Chao, Y.; Halpern, D.; Mechoso, C. R.
1991-01-01
A tropical Pacific Ocean General Circulation Model (OGCM) to be used in satellite data assimilation studies is described. The transfer of the OGCM from a CYBER-205 at NOAA's Geophysical Fluid Dynamics Laboratory to a CRAY-2 at NASA's Ames Research Center is documented. Two 3-year model integrations from identical initial conditions but performed on those two computers are compared. The model simulations are very similar to each other, as expected, but the simulations performed with the higher-precision CRAY-2 is smoother than that with the lower-precision CYBER-205. The CYBER-205 and CRAY-2 use 32 and 64-bit mantissa arithmetic, respectively. The major features of the oceanic circulation in the tropical Pacific, namely the North Equatorial Current, the North Equatorial Countercurrent, the South Equatorial Current, and the Equatorial Undercurrent, are realistically produced and their seasonal cycles are described. The OGCM provides a powerful tool for study of tropical oceans and for the assimilation of satellite altimetry data.
Generalized Symbolic Execution for Model Checking and Testing
NASA Technical Reports Server (NTRS)
Khurshid, Sarfraz; Pasareanu, Corina; Visser, Willem; Kofmeyer, David (Technical Monitor)
2003-01-01
Modern software systems, which often are concurrent and manipulate complex data structures must be extremely reliable. We present a novel framework based on symbolic execution, for automated checking of such systems. We provide a two-fold generalization of traditional symbolic execution based approaches: one, we define a program instrumentation, which enables standard model checkers to perform symbolic execution; two, we give a novel symbolic execution algorithm that handles dynamically allocated structures (e.g., lists and trees), method preconditions (e.g., acyclicity of lists), data (e.g., integers and strings) and concurrency. The program instrumentation enables a model checker to automatically explore program heap configurations (using a systematic treatment of aliasing) and manipulate logical formulae on program data values (using a decision procedure). We illustrate two applications of our framework: checking correctness of multi-threaded programs that take inputs from unbounded domains with complex structure and generation of non-isomorphic test inputs that satisfy a testing criterion. Our implementation for Java uses the Java PathFinder model checker.
Toward a general psychological model of tension and suspense.
Lehne, Moritz; Koelsch, Stefan
2015-01-01
Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309
Angular momentum conservation in a simplified Venus General Circulation Model
NASA Astrophysics Data System (ADS)
Lee, C.; Richardson, M. I.
2012-11-01
Angular momentum (AM) conservation and transport are critical components of all General Circulation Model (GCM) simulations, and particularly for simulations of the Venus atmosphere. We show that a Venus GCM based upon the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS) GCM conserves angular momentum to better than 2% per 1000 Venus years (≈225,000 Earth days) of integration under the extreme conditions of a simplified Venus simulation with low surface torques. With no topography in the GCM, physical torques due to surface/atmosphere frictional interactions dominate the acceleration of an initially stationary atmosphere and provide more than four times the angular momentum of solid body co-rotation over an integration period of 100 Venus years. During the subsequent steady state period of 200 Venus years negligible mean physical torques cause variation in the total angular momentum of less than 5% and produce a stable multi-century simulation. Diffusion and damping processes within the GCM account for AM losses of less than 0.2% per 1000 Venus years. This study provides a stable comparison point for other GCMs by employing a simplified forcing scheme. The diagnostics and analysis require little or no modification to the core GCM and are sufficiently robust to allow easy model inter-comparison.
Huang, B.; Schneider, E.K.
1995-10-01
Two surface wind stress datasets for 1979-91, one based on observations and the other from an investigation of the COLA atmospheric general circulation model (AGCM) with prescribed SST, are used to drive the GFDL ocean general circulation model. These two runs are referred to as the control and COLA experiments, respectively. Simulated SST and upper-ocean heat contents (HC) in the tropical Pacific Ocean are compared with observations and between experiments. Both simulation reproduced the observed mean SST and HC fields as well as their annual cycles realistically. Major errors common to both runs are colder than observed SST in the eastern equatorial ocean and HC in the western Pacific south of the equator, with errors generally larger in the COLA experiment. New errors arising from the AGCM wind forcing include higher SST near the South American coast throughout the year and weaker HC gradients along the equator in boreal spring. The former is associated with suppressed coastal upwelling by weak along shore AGCM winds, and the latter is caused by weaker equatorial easterlies in boreal spring. The low-frequency ENSO fluctuations are also realistic for both runs. Correlations between the observed and simulated SST anomalies from the COLA simulation are as high as those from the control run in the central equatorial Pacific. A major problem in the COLA simulation is the appearance of unrealistic tropical cold anomalies during the boreal spring of mature El Nino years. These anomalies propagate along the equator from the western Pacific to the eastern coast in about three months, and temporarily eliminate the warm SST and HC anomalies in the eastern Pacific. This erroneous oceanic response in the COLA simulation is caused by a reversal of the westerly wind anomalies on the equator, associated with an unrealistic southward shift of the ITCZ in boreal spring during El Nino events. 66 refs., 16 figs.
Convex foundations for generalized MaxEnt models
NASA Astrophysics Data System (ADS)
Frongillo, Rafael; Reid, Mark D.
2014-12-01
We present an approach to maximum entropy models that highlights the convex geometry and duality of generalized exponential families (GEFs) and their connection to Bregman divergences. Using our framework, we are able to resolve a puzzling aspect of the bijection of Banerjee and coauthors between classical exponential families and what they call regular Bregman divergences. Their regularity condition rules out all but Bregman divergences generated from log-convex generators. We recover their bijection and show that a much broader class of divergences correspond to GEFs via two key observations: 1) Like classical exponential families, GEFs have a "cumulant" C whose subdifferential contains the mean: Eo˜pθ[φ(o)]∈∂C(θ) ; 2) Generalized relative entropy is a C-Bregman divergence between parameters: DF(pθ,pθ')= D C(θ,θ') , where DF becomes the KL divergence for F = -H. We also show that every incomplete market with cost function C can be expressed as a complete market, where the prices are constrained to be a GEF with cumulant C. This provides an entirely new interpretation of prediction markets, relating their design back to the principle of maximum entropy.
Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System
Yin, R.; Tao, X. M.; Xu, B. G.
2016-01-01
Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters. PMID:27079187
Dynamic generalization of Stoner{endash}Wohlfarth model
Magni, A.; Bertotti, G.; Serpico, C.; Mayergoyz, I. D.
2001-06-01
A dynamic generalization of the Stoner{endash}Wohlfarth (SW) model is presented, in which the applied field component h{sub az} parallel to the particle anisotropy axis is slowly varied, whereas the one in the perpendicular plane, h{sub a{perpendicular}}, is rotated at the angular frequency {omega}. The Landau{endash}Lifshitz{endash}Gilbert equation is solved to calculate the system response under the constraint of spatially uniform magnetization at all times. Switching under slowly varying h{sub az} is discussed. Various switching modes can occur in correspondence of different types of bifurcation present in the dynamics. In addition, it is shown that the system response can become quasiperiodic, with spontaneous magnetization oscillations at a frequency definitely lower than {omega}. {copyright} 2001 American Institute of Physics.
A Generalized Brownian Motion Model for Turbulent Relative Particle Dispersion
NASA Astrophysics Data System (ADS)
Shivamoggi, Bhimsen
2015-11-01
A generalized Brownian motion model has been applied to the turbulent relative particle dispersion problem (Shivamoggi). The fluctuating pressure forces acting on a fluid particle are taken to follow an Uhlenbeck-Ornstein process while it appears plausible to take their correlation time to have a power-law dependence on the flow Reynolds number Re. This ansatz provides an insight into the result that the Richardson-Obukhov scaling holds only in the infinite-Re limit and disappears otherwise. It provides a determination of the Richardson-Obukhov constant g as a function of Re, with an asymptotic constant value in the infinite-Re limit. This ansatz is further shown to be in quantitative agreement, in the small-Re limit, with the Batchelor-Townsend ansatz for the rate of change of the mean square interparticle separation in 3D FDT. My thanks to The Netherlands Organization for Scientific Research for Support.
Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System
NASA Astrophysics Data System (ADS)
Yin, R.; Tao, X. M.; Xu, B. G.
2016-04-01
Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters.
Optimization in generalized linear models: A case study
NASA Astrophysics Data System (ADS)
Silva, Eliana Costa e.; Correia, Aldina; Lopes, Isabel Cristina
2016-06-01
The maximum likelihood method is usually chosen to estimate the regression parameters of Generalized Linear Models (GLM) and also for hypothesis testing and goodness of fit tests. The classical method for estimating GLM parameters is the Fisher scores. In this work we propose to compute the estimates of the parameters with two alternative methods: a derivative-based optimization method, namely the BFGS method which is one of the most popular of the quasi-Newton algorithms, and the PSwarm derivative-free optimization method that combines features of a pattern search optimization method with a global Particle Swarm scheme. As a case study we use a dataset of biological parameters (phytoplankton) and chemical and environmental parameters of the water column of a Portuguese reservoir. The results show that, for this dataset, BFGS and PSwarm methods provided a better fit, than Fisher scores method, and can be good alternatives for finding the estimates for the parameters of a GLM.
Topological phase boundary in a generalized Kitaev model
NASA Astrophysics Data System (ADS)
Da-Ping, Liu
2016-05-01
We study the effects of the next-nearest-neighbor hopping and nearest-neighbor interactions on topological phases in a one-dimensional generalized Kitaev model. In the noninteracting case, we define a topological number and calculate exactly the phase diagram of the system. With addition of the next-nearest-neighbor hopping, the change of phase boundary between the topological and trivial regions can be described by an effective shift of the chemical potential. In the interacting case, we obtain the entanglement spectrum, the degeneracies of which correspond to the topological edge modes, by using the infinite time-evolving block decimation method. The results show that the interactions change the phase boundary as adding an effective chemical potential which can be explained by the change of the average number of particles. Project supported by the National Basic Research Program of China (Grant No. 2012CB921704).
Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System.
Yin, R; Tao, X M; Xu, B G
2016-01-01
Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters. PMID:27079187
Development of a hybrid cloud parameterization for general circulation models
Kao, C.Y.J.; Kristjansson, J.E.; Langley, D.L.
1995-04-01
We have developed a cloud package with state-of-the-art physical schemes that can parameterize low-level stratus or stratocumulus, penetrative cumulus, and high-level cirrus. Such parameterizations will improve cloud simulations in general circulation models (GCMs). The principal tool in this development comprises the physically based Arakawa-Schubert scheme for convective clouds and the Sundqvist scheme for layered, nonconvective clouds. The term {open_quotes}hybrid{close_quotes} addresses the fact that the generation of high-attitude layered clouds can be associated with preexisting convective clouds. Overall, the cloud parameterization package developed should better determine cloud heating and drying effects in the thermodynamic budget, realistic precipitation patterns, cloud coverage and liquid/ice water content for radiation purposes, and the cloud-induced transport and turbulent diffusion for atmospheric trace gases.
Lattice Boltzmann model for generalized nonlinear wave equations
NASA Astrophysics Data System (ADS)
Lai, Huilin; Ma, Changfeng
2011-10-01
In this paper, a lattice Boltzmann model is developed to solve a class of the nonlinear wave equations. Through selecting equilibrium distribution function and an amending function properly, the governing evolution equation can be recovered correctly according to our proposed scheme, in which the Chapman-Enskog expansion is employed. We validate the algorithm on some problems where analytic solutions are available, including the second-order telegraph equation, the nonlinear Klein-Gordon equation, and the damped, driven sine-Gordon equation. It is found that the numerical results agree well with the analytic solutions, which indicates that the present algorithm is very effective and can be used to solve more general nonlinear problems.
Accelerated failure time model under general biased sampling scheme.
Kim, Jane Paik; Sit, Tony; Ying, Zhiliang
2016-07-01
Right-censored time-to-event data are sometimes observed from a (sub)cohort of patients whose survival times can be subject to outcome-dependent sampling schemes. In this paper, we propose a unified estimation method for semiparametric accelerated failure time models under general biased estimating schemes. The proposed estimator of the regression covariates is developed upon a bias-offsetting weighting scheme and is proved to be consistent and asymptotically normally distributed. Large sample properties for the estimator are also derived. Using rank-based monotone estimating functions for the regression parameters, we find that the estimating equations can be easily solved via convex optimization. The methods are confirmed through simulations and illustrated by application to real datasets on various sampling schemes including length-bias sampling, the case-cohort design and its variants. PMID:26941240
General model of electrochemical hydrogen absorption into metals
Lasia, A.; Gregoire, D.
1995-10-01
A general model for the hydrogen adsorption and hydrogen absorption into metals has been proposed. It includes reactions of hydrogen evolution M+H{sub 2}O+e=MH{sub ads}+OH{sup {minus}}; MH{sub ads}+H{sub 2}O+e=M+H{sub 2}+OH{sup {minus}}; and 2MH{sub ads}+2M+H{sub 2}; hydrogen absorption MH{sub ads}+MH{sub abs}; and hydrogen diffusion into metal. This problem leads to a system of differential equations which was solved using the differential algebraic equations method. Solutions were obtained for constant potential and constant current charging/discharging in the case of semi-infinite and finite length diffusion for planar, spherical, and cylindrical diffusion. Numerical solutions give new information about the reaction mechanism and may be useful in the determination of the kinetics of these processes.
NASA Astrophysics Data System (ADS)
Prabu, Samikannu; Swaminathan, Meenakshisundaram; Sivakumar, Krishnamoorthy; Rajamohan, Rajaram
2015-11-01
The formation through supramolecular interaction of a host-guest inclusion complex of caffeine (CA) with nano-hydrophobic cavity beta-cyclodextrin (β-CD) is achieved by a physical mixture, a kneading method and a co-precipitation method. The formation of the inclusion complex of CA with β-CD in solution state is confirmed by UV-visible spectrophotometer, fluorescence spectrophotometer and time-resolved fluorescence spectrophotometer. The stoichiometry of the inclusion complex is 1:1; the imidazole ring and pyrimidine ring of caffeine is deeply entrapped in the beta-cyclodextrin as confirmed by spectral shifts. The Benesi-Hildebrand plot is used to calculate the binding constant of the inclusion complex of CA with β-CD at room temperature. The Gibbs free energy change of the inclusion complex process is calculated and the process is found to be spontaneous. The thermal stability of the inclusion complex of CA with β-CD is analyzed using differential scanning calorimetry. The crystal structure modification of a solid inclusion complex is confirmed by scanning electron microscopy image analysis. The formation of the inclusion complex of CA with β-CD in the solid phase is also confirmed by FT-IR and XRD. The formation of the inclusion complex between CA and β-CD, as confirmed by molecular docking studies, is in good relationship with the results obtained through different experimental methods.
A model system to study the effects of beta-carotene on radon-stimulated oncogenesis
Seifter, E.; Mendecki, J.; Dawson, H.; Goodwin, P.; Friedenthal, E.
1992-12-31
Work from our laboratory has established that, in mice, the radioprotective action of supplemental beta-carotene provides protection against several insults: low-dose, gamma-irradiation-enhanced mammary tumor appearance and death in C3H mice carrying the mammary tumor virus but not in mouse strains not carrying the virus; low-dose, whole-body, gamma-irradiation-stimulated lung metastasis of Swiss and C57 mice bearing transplants of 10{sup 4} Lewis lung tumor cells injected into the hind limb, but not causing lung tumors in mice inoculated only with a buffer carrier or the same carrier containing 10{sup 2} tumor cells. Similarly, gamma-irradiation or the radiomimetic chemical cyclophosphamide decreased the amount of viral inoculum (Moloney sarcoma virus) required to cause sarcomas at the injection site, i.e., it decreased the TD{sub 50}. We now propose long-term (20- to 30-mo) studies on the effects of exposure to radon in these systems. The second aim of this study (and major thrust of this paper) is to determine how supplemental beta-carotene might modify the effect of exposure to radon in mice subjected to the insults described.
Szaniszlo, P J; Kang, M S; Cabib, E
1985-01-01
Particulate fractions from the taxonomically diverse fungi Achlya ambisexualis, Hansenula anomala, Neurospora crassa, Cryptococcus laurentii, Schizophyllum commune, and Wangiella dermatitidis were found to catalyze the time-dependent incorporation of glucose from UDP-[14C]glucose into a water-insoluble material. The reaction was stimulated by bovine serum albumin. The product was characterized as beta(1----3)glucan on the basis of its resistance to alpha- and beta-amylase and susceptibility to beta(1----3)glucanase. With the exception of the preparation from A. ambisexualis, all others were stimulated by nucleoside triphosphates and their analogs. The best activators were GTP and guanosine 5'-(gamma-thio)triphosphate. It is concluded that the stimulation by nucleotides, previously found with the glucan synthetase of Saccharomyces cerevisiae, is a regulatory mechanism that was well conserved during fungal evolution, presumably because of its importance in controlling cell wall biosynthesis and cell growth. PMID:3156122
Sensitivity simulations of superparameterised convection in a general circulation model
NASA Astrophysics Data System (ADS)
Rybka, Harald; Tost, Holger
2015-04-01
Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation. This study presents different simulations of an adapted Earth System Model (ESM) connected to a CRM which acts as a superparameterisation. Simulations have been performed with the ECHAM/MESSy atmospheric chemistry (EMAC) model comparing conventional GCM runs (including convection and large-scale cloud parameterisations) with the improved superparameterised EMAC (SP-EMAC) modeling one year with prescribed sea surface temperatures and sea ice content. The sensitivity of atmospheric temperature, precipiation patterns, cloud amount and types is observed changing the embedded CRM represenation (orientation, width, no. of CRM cells, 2D vs. 3D). Additionally, we also evaluate the radiation balance with the new model configuration, and systematically analyse the impact of tunable parameters on the radiation budget and hydrological cycle. Furthermore, the subgrid
Hospitable archean climates simulated by a general circulation model.
Wolf, E T; Toon, O B
2013-07-01
Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model. PMID:23808659
NASA Technical Reports Server (NTRS)
Eriksson, K.; Linsky, J. L.; Simon, T.
1983-01-01
In the present chromospheric and transition region model for Beta Ceti, which is consistent with IUE spectra of the Mg II, C II, and C IV resonance lines, the Mg II h and k lines are treated in partial redistribution and the C II and C IV lines in complete redistribution. Computed line fluxes are presented for a range of models to show the range of permitted temperature structures. A comparison of the Beta Ceti model to models previously computed in a similar way for other stars shows a trend of decreasing chromospheric pressures and increasing geometric scales as single stars evolve across the transition region boundary. The present analysis also suggests that transition region pressures drastically decrease and geometric scales rapidly increase as single giant stars evolve to the right, toward the boudnary. Beta Ceti's exceptional X-ray brightness is discussed.
Digital terrain model generalization incorporating scale, semantic and cognitive constraints
NASA Astrophysics Data System (ADS)
Partsinevelos, Panagiotis; Papadogiorgaki, Maria
2014-05-01
Cartographic generalization is a well-known process accommodating spatial data compression, visualization and comprehension under various scales. In the last few years, there are several international attempts to construct tangible GIS systems, forming real 3D surfaces using a vast number of mechanical parts along a matrix formation (i.e., bars, pistons, vacuums). Usually, moving bars upon a structured grid push a stretching membrane resulting in a smooth visualization for a given surface. Most of these attempts suffer either in their cost, accuracy, resolution and/or speed. Under this perspective, the present study proposes a surface generalization process that incorporates intrinsic constrains of tangible GIS systems including robotic-motor movement and surface stretching limitations. The main objective is to provide optimized visualizations of 3D digital terrain models with minimum loss of information. That is, to minimize the number of pixels in a raster dataset used to define a DTM, while reserving the surface information. This neighborhood type of pixel relations adheres to the basics of Self Organizing Map (SOM) artificial neural networks, which are often used for information abstraction since they are indicative of intrinsic statistical features contained in the input patterns and provide concise and characteristic representations. Nevertheless, SOM remains more like a black box procedure not capable to cope with possible particularities and semantics of the application at hand. E.g. for coastal monitoring applications, the near - coast areas, surrounding mountains and lakes are more important than other features and generalization should be "biased"-stratified to fulfill this requirement. Moreover, according to the application objectives, we extend the SOM algorithm to incorporate special types of information generalization by differentiating the underlying strategy based on topologic information of the objects included in the application. The final
A generalized model of atomic processes in dense plasmas
NASA Astrophysics Data System (ADS)
Chung, Hyun-Kyung; Chen, M.; Ciricosta, O.; Vinko, S.; Wark, J.; Lee, R. W.
2015-11-01
A generalized model of atomic processes in plasmas, FLYCHK, has been developed over a decade to provide experimentalists fast and simple but reasonable predictions of atomic properties of plasmas. For a given plasma condition, it provides charge state distributions and spectroscopic properties, which have been extensively used for experimental design and data analysis and currently available through NIST web site. In recent years, highly transient and non-equilibrium plasmas have been created with X-ray free electron lasers (XFEL). As high intensity x-rays interact with matter, the inner-shell electrons are ionized and Auger electrons and photo electrons are generated. With time, electrons participate in the ionization processes and collisional ionization by these electrons dominates photoionization as electron density increases. To study highly complex XFEL produced plasmas, SCFLY, an extended version of FLYCHK code has been used. The code accepts the time-dependent history of x-ray energy and intensity to compute population distribution and ionization distribution self-consistently with electron temperature and density assuming an instantaneous equilibration. The model and its applications to XFEL experiments will be presented as well as its limitations.
DISCOVERING PATIENT PHENOTYPES USING GENERALIZED LOW RANK MODELS.
Schuler, Alejandro; Liu, Vincent; Wan, Joe; Callahan, Alison; Udell, Madeleine; Stark, David E; Shah, Nigam H
2016-01-01
The practice of medicine is predicated on discovering commonalities or distinguishing characteristics among patients to inform corresponding treatment. Given a patient grouping (hereafter referred to as a phenotype), clinicians can implement a treatment pathway accounting for the underlying cause of disease in that phenotype. Traditionally, phenotypes have been discovered by intuition, experience in practice, and advancements in basic science, but these approaches are often heuristic, labor intensive, and can take decades to produce actionable knowledge. Although our understanding of disease has progressed substantially in the past century, there are still important domains in which our phenotypes are murky, such as in behavioral health or in hospital settings. To accelerate phenotype discovery, researchers have used machine learning to find patterns in electronic health records, but have often been thwarted by missing data, sparsity, and data heterogeneity. In this study, we use a flexible framework called Generalized Low Rank Modeling (GLRM) to overcome these barriers and discover phenotypes in two sources of patient data. First, we analyze data from the 2010 Healthcare Cost and Utilization Project National Inpatient Sample (NIS), which contains upwards of 8 million hospitalization records consisting of administrative codes and demographic information. Second, we analyze a small (N=1746), local dataset documenting the clinical progression of autism spectrum disorder patients using granular features from the electronic health record, including text from physician notes. We demonstrate that low rank modeling successfully captures known and putative phenotypes in these vastly different datasets. PMID:26776181
A general method for modeling population dynamics and its applications.
Shestopaloff, Yuri K
2013-12-01
Studying populations, be it a microbe colony or mankind, is important for understanding how complex systems evolve and exist. Such knowledge also often provides insights into evolution, history and different aspects of human life. By and large, populations' prosperity and decline is about transformation of certain resources into quantity and other characteristics of populations through growth, replication, expansion and acquisition of resources. We introduce a general model of population change, applicable to different types of populations, which interconnects numerous factors influencing population dynamics, such as nutrient influx and nutrient consumption, reproduction period, reproduction rate, etc. It is also possible to take into account specific growth features of individual organisms. We considered two recently discovered distinct growth scenarios: first, when organisms do not change their grown mass regardless of nutrients availability, and the second when organisms can reduce their grown mass by several times in a nutritionally poor environment. We found that nutrient supply and reproduction period are two major factors influencing the shape of population growth curves. There is also a difference in population dynamics between these two groups. Organisms belonging to the second group are significantly more adaptive to reduction of nutrients and far more resistant to extinction. Also, such organisms have substantially more frequent and lesser in amplitude fluctuations of population quantity for the same periodic nutrient supply (compared to the first group). Proposed model allows adequately describing virtually any possible growth scenario, including complex ones with periodic and irregular nutrient supply and other changing parameters, which present approaches cannot do. PMID:24057917
A general geomorphological recession flow model for river basins
NASA Astrophysics Data System (ADS)
Biswal, Basudev; Nagesh Kumar, D.
2013-08-01
Recession flows in a basin are controlled by the temporal evolution of its active drainage network (ADN). The geomorphological recession flow model (GRFM) assumes that both the rate of flow generation per unit ADN length (q) and the speed at which ADN heads move downstream (c) remain constant during a recession event. Thereby, it connects the power law exponent of -dQ/dt versus Q (discharge at the outlet at time t) curve, α, with the structure of the drainage network, a fixed entity. In this study, we first reformulate the GRFM for Horton-Strahler networks and show that the geomorphic α (αg) is equal to D/>(D-1>), where D is the fractal dimension of the drainage network. We then propose a more general recession flow model by expressing both q and c as functions of Horton-Strahler stream order. We show that it is possible to have α =α g for a recession event even when q and c do not remain constant. The modified GRFM suggests that α is controlled by the spatial distribution of subsurface storage within the basin. By analyzing streamflow data from 39 U.S. Geological Survey basins, we show that α is having a power law relationship with recession curve peak, which indicates that the spatial distribution of subsurface storage varies across recession events.
Classification images in a very general decision model.
Murray, Richard F
2016-06-01
Most of the theory supporting our understanding of classification images relies on standard signal detection models and the use of normally distributed stimulus noise. Here I show that the most common methods of calculating classification images by averaging stimulus noise samples within stimulus-response classes of trials are much more general than has previously been demonstrated, and that they give unbiased estimates of an observer's template for a wide range of decision rules and non-Gaussian stimulus noise distributions. These results are similar to findings on reverse correlation and related methods in the neurophysiology literature, but here I formulate them in terms that are tailored to signal detection analyses of visual tasks, in order to make them more accessible and useful to visual psychophysicists. I examine 2AFC and yes-no designs. These findings make it possible to use and interpret classification images in tasks where observers' decision strategies may not conform to classic signal detection models such as the difference rule, and in tasks where the stimulus noise is non-Gaussian. PMID:27174841
Critical rotation of general-relativistic polytropic models revisited
NASA Astrophysics Data System (ADS)
Geroyannis, V.; Karageorgopoulos, V.
2013-09-01
We develop a perturbation method for computing the critical rotational parameter as a function of the equatorial radius of a rigidly rotating polytropic model in the "post-Newtonia approximation" (PNA). We treat our models as "initial value problems" (IVP) of ordinary differential equations in the complex plane. The computations are carried out by the code dcrkf54.f95 (Geroyannis and Valvi 2012 [P1]; modified Runge-Kutta-Fehlberg code of fourth and fifth order for solving initial value problems in the complex plane). Such a complex-plane treatment removes the syndromes appearing in this particular family of IVPs (see e.g. P1, Sec. 3) and allows continuation of the numerical integrations beyond the surface of the star. Thus all the required values of the Lane-Emden function(s) in the post-Newtonian approximation are calculated by interpolation (so avoiding any extrapolation). An interesting point is that, in our computations, we take into account the complete correction due to the gravitational term, and this issue is a remarkable difference compared to the classical PNA. We solve the generalized density as a function of the equatorial radius and find the critical rotational parameter. Our computations are extended to certain other physical characteristics (like mass, angular momentum, rotational kinetic energy, etc). We find that our method yields results comparable with those of other reliable methods. REFERENCE: V.S. Geroyannis and F.N. Valvi 2012, International Journal of Modern Physics C, 23, No 5, 1250038:1-15.
Generalized Radiation Boundary Conditions in Gyrotron Oscillator Modeling
NASA Astrophysics Data System (ADS)
Alberti, S.; Tran, T. M.; Brunner, S.; Braunmueller, F.; Genoud, J.; Hogge, J.-Ph.; Tran, M. Q.
2015-11-01
A numerical procedure to implement a frequency-independent generalized non-reflecting radiation boundary conditions, GNRBC, based on the Laplace Transform, is described in details and tested successfully on a simple 2 frequency test problem. In the case of non-stationary regimes occurring in gyrotron oscillators, it is shown that the reflection at frequencies significantly separated from the carrier frequency can be effectively suppressed by this method. A detailed analysis shows that this numerical approach can be consistently used only for models in which there is no assumed separation of time scales between the RF field envelope time-evolution and the electron time of flight across the interaction region. The GNRBC has been implemented in a nonlinear time-dependent self-consistent monomode model, TWANGpic, in which there is no time scale separation since the RF field envelope is updated at each integration time step of the electron motion. The illustration of the effectiveness of the GNRBC is made with TWANGpic on a gyrotron for which extensive theoretical and experimental results have been performed.
DISCOVERING PATIENT PHENOTYPES USING GENERALIZED LOW RANK MODELS
SCHULER, ALEJANDRO; LIU, VINCENT; WAN, JOE; CALLAHAN, ALISON; UDELL, MADELEINE; STARK, DAVID E.; SHAH, NIGAM H.
2016-01-01
The practice of medicine is predicated on discovering commonalities or distinguishing characteristics among patients to inform corresponding treatment. Given a patient grouping (hereafter referred to as a phenotype), clinicians can implement a treatment pathway accounting for the underlying cause of disease in that phenotype. Traditionally, phenotypes have been discovered by intuition, experience in practice, and advancements in basic science, but these approaches are often heuristic, labor intensive, and can take decades to produce actionable knowledge. Although our understanding of disease has progressed substantially in the past century, there are still important domains in which our phenotypes are murky, such as in behavioral health or in hospital settings. To accelerate phenotype discovery, researchers have used machine learning to find patterns in electronic health records, but have often been thwarted by missing data, sparsity, and data heterogeneity. In this study, we use a flexible framework called Generalized Low Rank Modeling (GLRM) to overcome these barriers and discover phenotypes in two sources of patient data. First, we analyze data from the 2010 Healthcare Cost and Utilization Project National Inpatient Sample (NIS), which contains upwards of 8 million hospitalization records consisting of administrative codes and demographic information. Second, we analyze a small (N=1746), local dataset documenting the clinical progression of autism spectrum disorder patients using granular features from the electronic health record, including text from physician notes. We demonstrate that low rank modeling successfully captures known and putative phenotypes in these vastly different datasets. PMID:26776181
Generalization of Filament Braiding Model for Amyloid Fibril Assembly
NASA Astrophysics Data System (ADS)
Pope, Maighdlin; Ionescu-Zanetti, Cristian; Khurana, Ritu; Carter, Sue
2001-03-01
Research into the formation of amyloid fibrils is motivated by their association with several prominent diseases, among these Alzheimer's Disease, Parkinson's Disease and amyloidosis. Previous work in monitering the aggregation of immunoglobulin light chains to form amyloid fibrils suggests a braided structure where filaments and protofibrils wind together to form Type I and Type II fibrils. Non-contact atomic force microscopy is used to image and explore the kinetics of several other amyloid fibril forming proteins in an effort to generalize the filament braiding model. Included in this study are insulin and the B1 domain of G. Both of these have been shown to form fibrils in vitro. Alpha-synuclein is also included in this study. It is involved in the formation of Lewy bodies in Parkinson's Disease. The fourth protein used in this comparitive study is human amylin that is the cause of a systemic amyloidosis. Results from these four proteins and their associated fibrils are compared to the Ig light chain fibril structure in an effort to show the universality of the filament braiding model.
ERIC Educational Resources Information Center
Cheong, Yuk Fai; Kamata, Akihito
2013-01-01
In this article, we discuss and illustrate two centering and anchoring options available in differential item functioning (DIF) detection studies based on the hierarchical generalized linear and generalized linear mixed modeling frameworks. We compared and contrasted the assumptions of the two options, and examined the properties of their DIF…
General solutions to poroviscoelastic model of hydrocephalic human brain tissue.
Mehrabian, Amin; Abousleiman, Younane
2011-12-21
Hydrocephalus is a well-known disorder of brain fluidic system. It is commonly associated with complexities in cerebrospinal fluid (CSF) circulation in brain. In this paper, hydrocephalus and shunting surgery which is used in its treatment are modeled. Brain tissues are considered to follow a poroviscoelastic constitutive model in order to address the effects of time dependence of mechanical properties of soft tissues and fluid flow hydraulics. Our solution draws from Biot's theory of poroelasticity, generalized to account for viscoelastic effects through the correspondence principle. Geometrically, the brain is conceived to be spherically symmetric, where the ventricles are assumed to be a hollow concentric space filled with cerebrospinal fluid. A generalized Kelvin model is considered for the rheological properties of brain tissues. The solution presented is useful in the analysis of the disorder of hydrocephalus as well as the treatment associated with it, namely, ventriclostomy surgery. The sensitivity of the solution to various factors such as aqueduct blockage level and trabeculae stiffness is thoroughly analyzed using numerical examples. Results indicate that partial aqueduct stenosis may be a cause of hydrocephalus. However, only severe occlusion of the aqueduct can cause a significant increase in the ventricle and brain's extracellular fluid pressure. Ventriculostomy shunts are commonly used as a remedy to hydrocephalus. They serve to reduce the ventricular pressure to the normal level. However, sensitivity analysis on the shunt's fluid deliverability parameter has shown that inappropriate design or selection of design shunt may cause under-drainage or over-drainage of the ventricles. Excessive drainage of CSF may increase the normal tensile stress on trabeculae. It can cause rupture of superior cerebral veins or damage to trabeculae or even brain tissues which in turn may lead to subdural hematoma, a common side-effect of the surgery. These Post
Lewis, James S.; Lepak, Alex J.; Thompson, George R.; Craig, William A.; Andes, David R.; Sabol-Dzintars, Kathryn E.
2014-01-01
Inducible clindamycin resistance in beta-hemolytic streptococci remains an underrecognized phenomenon of unknown clinical significance. We performed an evaluation of inducible clindamycin resistance using an animal model as well as retrospectively reviewing the charts of patients treated with clindamycin monotherapy who were infected with beta-hemolytic streptococci inducibly resistant to clindamycin. The neutropenic mouse thigh model of infection was used to evaluate the in vivo activity of clindamycin against beta-hemolytic streptococci, including isolates susceptible, inducibly resistant, or constitutively resistant to clindamycin. The clinical microbiology laboratory information system and pharmacy databases were cross-referenced to identify patients with infections due to inducibly clindamycin-resistant beta-hemolytic streptococci who were treated with clindamycin monotherapy. Medical records of these patients were reviewed to evaluate microbiologic and clinical outcomes. Inducible clindamycin resistance resulted in impaired killing of beta-hemolytic streptococci in the animal model. Though suppressed initially, compared to those with constitutive resistance (P = 0.0429), by 48 h, colony counts of inducibly clindamycin-resistant organisms were similar to those of constitutively resistant isolates (P = 0.1142). In addition, we identified 8 patients infected with inducibly clindamycin-resistant beta-hemolytic streptococci who experienced clinical and microbiologic failure when treated with clindamycin monotherapy. These patients either improved initially and subsequently failed or never responded to clindamycin therapy. We have demonstrated in a murine model of infection and from human cases that inducible clindamycin resistance in beta-hemolytic streptococci is clinically significant. Routine testing and reporting by clinical laboratories should be encouraged and alternative antimicrobial agents considered when these organisms are encountered in clinical care
ERIC Educational Resources Information Center
Battauz, Michela; Bellio, Ruggero
2011-01-01
This paper proposes a structural analysis for generalized linear models when some explanatory variables are measured with error and the measurement error variance is a function of the true variables. The focus is on latent variables investigated on the basis of questionnaires and estimated using item response theory models. Latent variable…
NASA Astrophysics Data System (ADS)
Darnah
2016-04-01
Poisson regression has been used if the response variable is count data that based on the Poisson distribution. The Poisson distribution assumed equal dispersion. In fact, a situation where count data are over dispersion or under dispersion so that Poisson regression inappropriate because it may underestimate the standard errors and overstate the significance of the regression parameters, and consequently, giving misleading inference about the regression parameters. This paper suggests the generalized Poisson regression model to handling over dispersion and under dispersion on the Poisson regression model. The Poisson regression model and generalized Poisson regression model will be applied the number of filariasis cases in East Java. Based regression Poisson model the factors influence of filariasis are the percentage of families who don't behave clean and healthy living and the percentage of families who don't have a healthy house. The Poisson regression model occurs over dispersion so that we using generalized Poisson regression. The best generalized Poisson regression model showing the factor influence of filariasis is percentage of families who don't have healthy house. Interpretation of result the model is each additional 1 percentage of families who don't have healthy house will add 1 people filariasis patient.
Formulation and quantization of a generalized model related to the chiral Schwinger model
NASA Astrophysics Data System (ADS)
Bracken, Paul
2009-07-01
A generalized theory which describes fermions interacting with a gauge field is investigated. In 1 + 1 dimensions such a model is equivalent to a theory in which a boson field appears in the Lagrangian density rather than a fermion field. In this form, the Lagrangian density can be diagonalized and then quantized in terms of the transformed fields. The case of the chiral Schwinger model can be obtained from the general model and the physics with respect to the operator form is discussed. It is shown how the theory can be made nonanomalous by means of a Wess-Zumino field.
Groundwater Flow Model of the General Separations Area Using PORFLOW
FLACH, GREGORY
2004-07-15
The E Area PA (McDowell-Boyer et al. 2000) includes a steady-state simulation of groundwater flow in the General Separations Area as a prerequisite for saturated zone contaminant transport analyses. The groundwater flow simulations are based on the FACT code (Hamm and Aleman2000). The FACT-based GSA model was selected during preparation of the original PA to take advantage of an existing model developed for environmental restoration applications at the SRS (Flach and Harris 1997, 1999; Flach 1999). The existing GSA/FACT model was then slightly modified for PA use, as described in the PA document. FACT is a finite-element code utilizing deformed brick elements. Material properties are defined at element centers, and state variables such as hydraulic head are located at element vertices. The PORFLOW code (Analytic and Computational Research, Inc. 2000) was selected for performing saturated zone transport simulations of source zone radionuclides and their progeny. PORFLOW utilizes control volume discretization and the nodal point integration method, with all properties and state variables being defined at the center of an interior grid cell. The groundwater flow calculation includes translating the Darcy velocity field computed by FACT into a form compatible for input to PORFLOW. The FACT velocity field is defined at element vertices, whereas PORFLOW requires flux across cell faces. For the present PA, PORFLOW cell face flux is computed in a two-step process. An initial face flux is computed from FACT as an average of the normal components of Darcy velocity at the four corners. The derived flux field approximately conserves mass, but not rigorously. Thus, the flux field is subsequently perturbed to force rigorous mass conservation on a cell-by-cell basis. The undocumented process used is non-unique and can introduce significant artifacts into the final flux field.
Bounds for Neutrinoless Double Beta Decay in SO(10) Inspired Seesaw Models
NASA Astrophysics Data System (ADS)
Buccella, F.; Falcone, D.
By requiring the lower limit for the lightest right-handed neutrino mass, obtained in the baryogenesis from leptogenesis scenario, and a Dirac neutrino mass matrix similar to the up-quark mass matrix, we predict small values for the νe mass and for the matrix element mee responsible of the neutrinoless double beta decay, mνe around 5×10-3 eV and mee smaller than 10-3 eV, respectively. The allowed range for the mass of the heaviest right-handed neutrino is centered around the value of the scale of B-L breaking in the SO(10) gauge theory with Pati-Salam intermediate symmetry.
Jupiter's thermosphere general circulation model: thermal and dynamical structures
NASA Astrophysics Data System (ADS)
Majeed, T.; Waite, J. H.; Bougher, S. W.; Gladstone, G. R.
2003-04-01
Recent observations of infrared and FUV auroral emissions from Jupiter have shown the presence of high-speed (>~2km/s) winds in the jovian thermosphere. The neutral atmospheric structure measured in-situ by the Galileo probe near the jovian equator exhibited wave-like oscillations in the temperature profile at altitudes of 133--1029~km. The derived exospheric temperature was ˜940~K. While no in-situ measurement is available for the neutral atmosphere of Jupiter's auroral region, infrared and ultraviolet spectrographic imaging results indicate auroral exospheric temperatures >1200~K. We examine this hypothesis using a fully 3-D JTGCM that has been developed and exercised to address global scale temperature, wind, and neutral-ion specie distributions. It was developed from a suitable adaptation of the NCAR Thermosphere Ionosphere General Circulation Model (TIGCM). An ion drag scheme was incorporated. A convection electric field was estimated and corresponding ion drifts were generated. These prescriptions provide a means to test the general impact of ion drag and Joule heating on the JTGCM neutral winds. The JTGCM has been fully spun-up and exercised for various cases to simulate 3-component neutral winds, and corresponding temperature and density distributions. The horizontal winds at the ionospheric heights vary from 0.5 km/s to 1.6 km/s and auroral temperatures from 1000 K to 3800 K depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo ASI data. The best fit to the data implies that the major energy source for heating the equatorial atmosphere is due to adiabatic heating induced by the downward motion of the neutral atmosphere. Further details of the JTGCM code and results for moderately strong auroral heating, ion drag, and ion drag plus Joule heating will be presented.
Ahn, Y. H.; Kang, Sin Kyu; Kim, C. S.; Nguyen, T. Phong
2010-11-01
We study how leptogenesis can be implemented in a seesaw model with S{sub 4} flavor symmetry, which leads to the neutrino tribimaximal mixing matrix and degenerate right-handed (RH) neutrino spectrum. Introducing a tiny soft S{sub 4} symmetry breaking term in the RH neutrino mass matrix, we show that the flavored resonant leptogenesis can be successfully realized, which can lower the seesaw scale much so, as to make it possible to probe in colliders. Even though such a tiny soft breaking term is essential for leptogenesis, it does not significantly affect the low-energy observables. We also investigate how the effective light neutrino mass |
Salinas, Cristian; Muzic, Raymond F. Jr.; Ernsberger, Paul; Saidel, Gerald M.
2007-01-15
Myocardial {beta} adrenergic receptor ({beta}-AR) concentration can substantially decrease in congestive heart failure and significantly increase in chronic volume overload, such as in severe aortic valve regurgitation. Positron emission tomography (PET) with an appropriate ligand-receptor model can be used for noninvasive estimation of myocardial {beta}-AR concentration in vivo. An optimal design of the experiment protocol, however, is needed for sufficiently precise estimates of {beta}-AR concentration in a heterogeneous population. Standard methods of optimal design do not account for a heterogeneous population with a wide range of {beta}-AR concentrations and other physiological parameters and consequently are inadequate. To address this, we have developed a methodology to design a robust two-injection protocol that provides reliable estimates of myocardial {beta}-AR concentration in normal and pathologic states. A two-injection protocol of the high affinity {beta}-AR antagonist [{sup 18}F]-(S)-fluorocarazolol was designed based on a computer-generated (or synthetic) population incorporating a wide range of {beta}-AR concentrations. Timing and dosage of the ligand injections were optimally designed with minimax criterion to provide the least bad {beta}-AR estimates for the worst case in the synthetic population. This robust experiment design for PET was applied to experiments with pigs before and after {beta}-AR upregulation by chemical sympathectomy. Estimates of {beta}-AR concentration were found by minimizing the difference between the model-predicted and experimental PET data. With this robust protocol, estimates of {beta}-AR concentration showed high precision in both normal and pathologic states. The increase in {beta}-AR concentration after sympathectomy predicted noninvasively with PET is consistent with the increase shown by in vitro assays in pig myocardium. A robust experiment protocol was designed for PET that yields reliable estimates of {beta
Polgár, J; Magnenat, E M; Peitsch, M C; Wells, T N; Saqi, M S; Clemetson, K J
1997-04-15
Echicetin, a heterodimeric protein from the venom of Echis carinatus, binds to platelet glycoprotein Ib (GPIb) and so inhibits platelet aggregation or agglutination induced by various platelet agonists acting via GPIb. The amino acid sequence of the beta subunit of echicetin has been reported and found to belong to the recently identified snake venom subclass of the C-type lectin protein family. Echicetin alpha and beta subunits were purified. N-terminal sequence analysis provided direct evidence that the protein purified was echicetin. The paper presents the complete amino acid sequence of the alpha subunit and computer models of the alpha and beta subunits. The sequence of alpha echicetin is highly similar to the alpha and beta chains of various heterodimeric and homodimeric C-type lectins. Neither of the fully reduced and alkylated alpha or beta subunits of echicetin inhibited the platelet agglutination induced by von Willebrand factor-ristocetin or alpha-thrombin. Earlier reports about the inhibitory activity of reduced and alkylated echicetin beta subunit might have been due to partial reduction of the protein. PMID:9163349
A General Framework for Multiphysics Modeling Based on Numerical Averaging
NASA Astrophysics Data System (ADS)
Lunati, I.; Tomin, P.
2014-12-01
In the last years, multiphysics (hybrid) modeling has attracted increasing attention as a tool to bridge the gap between pore-scale processes and a continuum description at the meter-scale (laboratory scale). This approach is particularly appealing for complex nonlinear processes, such as multiphase flow, reactive transport, density-driven instabilities, and geomechanical coupling. We present a general framework that can be applied to all these classes of problems. The method is based on ideas from the Multiscale Finite-Volume method (MsFV), which has been originally developed for Darcy-scale application. Recently, we have reformulated MsFV starting with a local-global splitting, which allows us to retain the original degree of coupling for the local problems and to use spatiotemporal adaptive strategies. The new framework is based on the simple idea that different characteristic temporal scales are inherited from different spatial scales, and the global and the local problems are solved with different temporal resolutions. The global (coarse-scale) problem is constructed based on a numerical volume-averaging paradigm and a continuum (Darcy-scale) description is obtained by introducing additional simplifications (e.g., by assuming that pressure is the only independent variable at the coarse scale, we recover an extended Darcy's law). We demonstrate that it is possible to adaptively and dynamically couple the Darcy-scale and the pore-scale descriptions of multiphase flow in a single conceptual and computational framework. Pore-scale problems are solved only in the active front region where fluid distribution changes with time. In the rest of the domain, only a coarse description is employed. This framework can be applied to other important problems such as reactive transport and crack propagation. As it is based on a numerical upscaling paradigm, our method can be used to explore the limits of validity of macroscopic models and to illuminate the meaning of
Generalized internal model robust control for active front steering intervention
NASA Astrophysics Data System (ADS)
Wu, Jian; Zhao, Youqun; Ji, Xuewu; Liu, Yahui; Zhang, Lipeng
2015-03-01
Because of the tire nonlinearity and vehicle's parameters' uncertainties, robust control methods based on the worst cases, such as H ∞, µ synthesis, have been widely used in active front steering control, however, in order to guarantee the stability of active front steering system (AFS) controller, the robust control is at the cost of performance so that the robust controller is a little conservative and has low performance for AFS control. In this paper, a generalized internal model robust control (GIMC) that can overcome the contradiction between performance and stability is used in the AFS control. In GIMC, the Youla parameterization is used in an improved way. And GIMC controller includes two sections: a high performance controller designed for the nominal vehicle model and a robust controller compensating the vehicle parameters' uncertainties and some external disturbances. Simulations of double lane change (DLC) maneuver and that of braking on split- µ road are conducted to compare the performance and stability of the GIMC control, the nominal performance PID controller and the H ∞ controller. Simulation results show that the high nominal performance PID controller will be unstable under some extreme situations because of large vehicle's parameters variations, H ∞ controller is conservative so that the performance is a little low, and only the GIMC controller overcomes the contradiction between performance and robustness, which can both ensure the stability of the AFS controller and guarantee the high performance of the AFS controller. Therefore, the GIMC method proposed for AFS can overcome some disadvantages of control methods used by current AFS system, that is, can solve the instability of PID or LQP control methods and the low performance of the standard H ∞ controller.
A generalized Brownian motion model for turbulent relative particle dispersion
NASA Astrophysics Data System (ADS)
Shivamoggi, B. K.
2016-08-01
There is speculation that the difficulty in obtaining an extended range with Richardson-Obukhov scaling in both laboratory experiments and numerical simulations is due to the finiteness of the flow Reynolds number Re in these situations. In this paper, a generalized Brownian motion model has been applied to describe the relative particle dispersion problem in more realistic turbulent flows and to shed some light on this issue. The fluctuating pressure forces acting on a fluid particle are taken to be a colored noise and follow a stationary process and are described by the Uhlenbeck-Ornstein model while it appears plausible to take their correlation time to have a power-law dependence on Re, thus introducing a bridge between the Lagrangian quantities and the Eulerian parameters for this problem. This ansatz is in qualitative agreement with the possibility of a connection speculated earlier by Corrsin [26] between the white-noise representation for the fluctuating pressure forces and the large-Re assumption in the Kolmogorov [4] theory for the 3D fully developed turbulence (FDT) as well as a similar argument of Monin and Yaglom [23] and a similar result of Sawford [13] and Borgas and Sawford [24]. It also provides an insight into the result that the Richardson-Obukhov scaling holds only in the infinite-Re limit and disappears otherwise. This ansatz further provides a determination of the Richardson-Obukhov constant g as a function of Re, with an asymptotic constant value in the infinite-Re limit. It is shown to lead to full agreement, in the small-Re limit as well, with the Batchelor-Townsend [27] scaling for the rate of change of the mean square interparticle separation in 3D FDT, hence validating its soundness further.
Spontaneous Fission Barriers Based on a Generalized Liquid Drop Model
NASA Astrophysics Data System (ADS)
Guo, Shu-Qing; Bao, Xiao-Jun; Li, Jun-Qing; Zhang, Hong-Fei
2014-05-01
The barrier against the spontaneous fission has been determined within the Generalized Liquid Drop Model (GLDM) including the mass and charge asymmetry, and the proximity energy. The shell correction of the spherical parent nucleus is calculated by using the Strutinsky method, and the empirical shape-dependent shell correction is employed during the deformation process. A quasi-molecular shape sequence has been defined to describe the whole process from one-body shape to two-body shape system, and a two-touching-ellipsoid is adopted when the superdeformed one-body system reaches the rupture point. On these bases the spontaneous fission barriers are systematically studied for nuclei from 230Th to 249Cm for different possible exiting channels with the different mass and charge asymmetries. The double, and triple bumps are found in the fission potential energy in this region, which roughly agree with the experimental results. It is found that at around Sn-like fragment the outer fission barriers are lower, while the partner of the Sn-like fragment is in the range near 108Ru where the ground-state mass is lowered by allowing axially symmetric shapes. The preferable fission channels are distinctly pronounced, which should be corresponding to the fragment mass distributions.
A general superdirectivity model for arbitrary sensor arrays
NASA Astrophysics Data System (ADS)
Wang, Yong; Yang, Yixin; He, Zhengyao; Han, Yina; Ma, Yuanliang
2015-12-01
This paper proposes a general model of superdirectivity to provide analytical and closed-form solutions for arbitrary sensor arrays. Based on the equivalence between the maximum directivity factor and the maximum array gain in the isotropic noise field, Gram-Schmidt orthogonalization is introduced and recursively transformed into a matrix form to conduct pre-whitening and matching operations that result in superdirectivity solutions. A Gram-Schmidt mode-beam decomposition and synthesis method is then presented to formally implement these solutions. Illustrative examples for different arrays are provided to demonstrate the feasibility of this method, and a reduced rank technique is used to deal with the practical array design for robust beamforming and acceptable high-order superdirectivity. Experimental results that are provided for a linear array consisting of nine hydrophones show the good performance of the technique. A superdirective beampattern with a beamwidth of 48.05° in the endfire direction is typically achieved when the inter-sensor spacing is only 0.09 λ ( λ is the wavelength), and the directivity index is up to 12 dB, which outperforms that of the conventional delay-and-sum counterpart by 6 dB.
NASA Astrophysics Data System (ADS)
Borah, Debasish; Dasgupta, Arnab
2016-07-01
We study the new physics contributions to neutrinoless double beta decay (0 νββ) half-life and lepton flavour violation (LFV) amplitude within the framework of the minimal left-right symmetric model (MLRSM). Considering all possible new physics contributions to 0 νββ and charged lepton flavour violation μ → eγ , μ → 3 e in MLRSM, we constrain the parameter space of the model from the requirement of satisfying existing experimental bounds. Assuming the breaking scale of the left-right symmetry to be O (1) TeV accessible at ongoing and near future collider experiments, we consider the most general type I+II seesaw mechanism for the origin of tiny neutrino masses. Choosing the relative contribution of the type II seesaw term allows us to calculate the right handed neutrino mass matrix as well as Dirac neutrino mass matrix as a function of the model parameters, required for the calculation of 0νββ and LFV amplitudes. We show that such a general type I+II seesaw structure results in more allowed parameter space compared to individual type I or type II seesaw cases considered in earlier works. In particular, we show that the doubly charged scalar masses M Δ are allowed to be smaller than the heaviest right handed neutrino mass M N from the present experimental bounds in these scenarios which is in contrast to earlier results with individual type I or type II seesaw showing M Δ > M N .
Daikos, G L; Panagiotakopoulou, A; Tzelepi, E; Loli, A; Tzouvelekis, L S; Miriagou, V
2007-02-01
The in-vivo activity of imipenem against VIM-1-producing Klebsiella pneumoniae (VPKP) was assessed in a thigh infection model in neutropenic mice. Animals were infected with three VPKP isolates (imipenem MICs 2, 4 and 32 mg/L, respectively) and a susceptible clinical isolate (MIC 0.125 mg/L) that did not produce any beta-lactamase with broad-spectrum activity. Bacterial density at the site of infection was determined after imipenem treatment (30 and 60 mg/kg every 2 h for 24 h). The log(10) reduction in CFU/thigh was greatest for the wild-type isolate, intermediate for the two imipenem-susceptible VPKP isolates, and lowest for the imipenem-resistant VPKP isolate. Whilst in-vivo imipenem activity appeared reduced against in-vitro susceptible VIM-1 producers compared with a VIM-1-negative control, an increased drug dosage could moderate this reduction. PMID:17328735
Analysis of the noise-induced bursting-spiking transition in a pancreatic beta-cell model.
Aguirre, Jacobo; Mosekilde, Erik; Sanjuán, Miguel A F
2004-04-01
A stochastic model of the electrophysiological behavior of the pancreatic beta cell is studied, as a paradigmatic example of a bursting biological cell embedded in a noisy environment. The analysis is focused on the distortion that a growing noise causes to the basic properties of the membrane potential signals, such as their periodic or chaotic nature, and their bursting or spiking behavior. We present effective computational tools to obtain as much information as possible from these signals, and we suggest that the methods could be applied to real time series. Finally, a universal dependence of the main characteristics of the membrane potential on the size of the considered cell cluster is presented. PMID:15169046
Magneto-static Modeling of the Mixed Plasma Beta Solar Atmosphere Based on Sunrise/IMaX Data
NASA Astrophysics Data System (ADS)
Wiegelmann, T.; Neukirch, T.; Nickeler, D. H.; Solanki, S. K.; Martínez Pillet, V.; Borrero, J. M.
2015-12-01
Our aim is to model the three-dimensional magnetic field structure of the upper solar atmosphere, including regions of non-negligible plasma beta. We use high-resolution photospheric magnetic field measurements from SUNRISE/IMaX as the boundary condition for a magneto-static magnetic field model. The high resolution of IMaX allows us to resolve the interface region between the photosphere and corona, but modeling this region is challenging for the following reasons. While the coronal magnetic field is thought to be force-free (the Lorentz force vanishes), this is not the case in the mixed plasma β environment in the photosphere and lower chromosphere. In our model, pressure gradients and gravity forces are self-consistently taken into account and compensate for the non-vanishing Lorentz force. Above a certain height (about 2 Mm) the non-magnetic forces become very weak and consequently the magnetic field becomes almost force-free. Here, we apply a linear approach where the electric current density consists of a superposition of a field-line parallel current and a current perpendicular to the Sun's gravity field. We illustrate the prospects and limitations of this approach and give an outlook for an extension toward a nonlinear model.
Triton College and General Motors: The Partnership Model.
ERIC Educational Resources Information Center
Fonte, Richard; Magnesen, Vernon
1983-01-01
The cooperative training program between Illinois's Triton College and General Motors is described. Illustrates the mutual benefits of this problem and recommends that other colleges follow suit. (NJ)
Mesozoic climates: General circulation models and the rock record
NASA Astrophysics Data System (ADS)
Sellwood, Bruce W.; Valdes, Paul J.
2006-08-01
General circulation models (GCMs) use the laws of physics and an understanding of past geography to simulate climatic responses. They are objective in character. However, they tend to require powerful computers to handle vast numbers of calculations. Nevertheless, it is now possible to compare results from different GCMs for a range of times and over a wide range of parameterisations for the past, present and future (e.g. in terms of predictions of surface air temperature, surface moisture, precipitation, etc.). GCMs are currently producing simulated climate predictions for the Mesozoic, which compare favourably with the distributions of climatically sensitive facies (e.g. coals, evaporites and palaeosols). They can be used effectively in the prediction of oceanic upwelling sites and the distribution of petroleum source rocks and phosphorites. Models also produce evaluations of other parameters that do not leave a geological record (e.g. cloud cover, snow cover) and equivocal phenomena such as storminess. Parameterisation of sub-grid scale processes is the main weakness in GCMs (e.g. land surfaces, convection, cloud behaviour) and model output for continental interiors is still too cold in winter by comparison with palaeontological data. The sedimentary and palaeontological record provides an important way that GCMs may themselves be evaluated and this is important because the same GCMs are being used currently to predict possible changes in future climate. The Mesozoic Earth was, by comparison with the present, an alien world, as we illustrate here by reference to late Triassic, late Jurassic and late Cretaceous simulations. Dense forests grew close to both poles but experienced months-long daylight in warm summers and months-long darkness in cold snowy winters. Ocean depths were warm (8 °C or more to the ocean floor) and reefs, with corals, grew 10° of latitude further north and south than at the present time. The whole Earth was warmer than now by 6 °C or
Hoffman, Kurt L; Hornig, Mady; Yaddanapudi, Kavitha; Jabado, Omar; Lipkin, W Ian
2004-02-18
A syndrome of motoric and neuropsychiatric symptoms comprising various elements, including chorea, hyperactivity, tics, emotional lability, and obsessive-compulsive symptoms, can occur in association with group A beta-hemolytic streptococcal (GABHS) infection. We tested the hypothesis that an immune response to GABHS can result in behavioral abnormalities. Female SJL/J mice were immunized and boosted with a GABHS homogenate in Freund's adjuvant, whereas controls received Freund's adjuvant alone. When sera from GABHS-immunized mice were tested for immunoreactivity to mouse brain, a subset was found to be immunoreactive to several brain regions, including deep cerebellar nuclei (DCN), globus pallidus, and thalamus. GABHS-immunized mice having serum immunoreactivity to DCN also had increased IgG deposits in DCN and exhibited increased rearing behavior in open-field and hole-board tests compared with controls and with GABHS-immunized mice lacking serum anti-DCN antibodies. Rearing and ambulatory behavior were correlated with IgG deposits in the DCN and with serum immunoreactivity to GABHS proteins in Western blot. In addition, serum from a GABHS mouse reacted with normal mouse cerebellum in nondenaturing Western blots and immunoprecipitated C4 complement protein and alpha-2-macroglobulin. These results are consistent with the hypothesis that immune response to GABHS can result in motoric and behavioral disturbances and suggest that anti-GABHS antibodies cross-reactive with brain components may play a role in their pathophysiology. PMID:14973249
Generalized Parton Distributions and their Singularities
Anatoly Radyushkin
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) Ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function $f(\\beta)/\\beta$ rather than with the usual parton density $f(\\beta)$. This results in a non-integrable singularity at $\\beta=0$ exaggerated by the fact that $f(\\beta)$'s, on their own, have a singular $\\beta^{-a}$ Regge behavior for small $\\beta$. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs $H(x,\\xi)$ that are finite and continuous at the "border point'' $x=\\xi$. Using a simple input forward distribution, we illustrate the implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the $\\beta=0$ singularities is proposed that is based on the separation of the initial single DD $f(\\beta, \\alpha)$ into the "plus'' part $[f(\\beta,\\alpha)]_{+}$ and the $D$-term. It is demonstrated that the "DD+D'' separation method allows to (re)derive GPD sum rules that relate the difference between the forward distribution $f(x)=H(x,0)$ and the border function $H(x,x)$ with the $D$-term function $D(\\alpha)$.
Generalized parton distributions and their singularities
Radyushkin, A. V.
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function f({beta})/{beta} rather than with the usual parton density f({beta}). This results in a nonintegrable singularity at {beta}=0 exaggerated by the fact that f({beta})'s, on their own, have a singular {beta}{sup -a} Regge behavior for small {beta}. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs H(x,{xi}) that are finite and continuous at the 'border point' x={xi}. Using a simple input forward distribution, we illustrate implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the {beta}=0 singularities is proposed that is based on the separation of the initial single DD f({beta},{alpha}) into the 'plus' part [f({beta},{alpha})]{sub +} and the D term. It is demonstrated that the ''DD+D'' separation method allows one to (re)derive GPD sum rules that relate the difference between the forward distribution f(x)=H(x,0) and the border function H(x,x) with the D-term function D({alpha}).
Zhao, Yong; Guo, Chengshan; Hwang, David; Lin, Brian; Dingeldein, Michael; Mihailescu, Dan; Sam, Susan; Sidhwani, Seema; Zhang, Yongkang; Jain, Sumit; Skidgel, Randal A.; Prabhakar, Bellur S.; Mazzone, Theodore; Holterman, Mark J.
2010-09-03
Research highlights: {yields} Establish a human immune-mediated type 1 diabetic model in NOD-scid IL2r{gamma}{sup null} mice. {yields} Using the irradiated diabetic NOD mouse spleen mononuclear cells as trigger. {yields} The islet {beta} cells were selectively destroyed by infiltrated human T cells. {yields} The model can facilitate translational research to find a cure for type 1 diabetes. -- Abstract: Type 1 diabetes (T1D) is caused by a T cell-mediated autoimmune response that leads to the loss of insulin-producing {beta} cells. The optimal preclinical testing of promising therapies would be aided by a humanized immune-mediated T1D model. We develop this model in NOD-scid IL2r{gamma}{sup null} mice. The selective destruction of pancreatic islet {beta} cells was mediated by human T lymphocytes after an initial trigger was supplied by the injection of irradiated spleen mononuclear cells (SMC) from diabetic nonobese diabetic (NOD) mice. This resulted in severe insulitis, a marked loss of total {beta}-cell mass, and other related phenotypes of T1D. The migration of human T cells to pancreatic islets was controlled by the {beta} cell-produced highly conserved chemokine stromal cell-derived factor 1 (SDF-1) and its receptor C-X-C chemokine receptor (CXCR) 4, as demonstrated by in vivo blocking experiments using antibody to CXCR4. The specificity of humanized T cell-mediated immune responses against islet {beta} cells was generated by the local inflammatory microenvironment in pancreatic islets including human CD4{sup +} T cell infiltration and clonal expansion, and the mouse islet {beta}-cell-derived CD1d-mediated human iNKT activation. The selective destruction of mouse islet {beta} cells by a human T cell-mediated immune response in this humanized T1D model can mimic those observed in T1D patients. This model can provide a valuable tool for translational research into T1D.
A general moment expansion method for stochastic kinetic models
NASA Astrophysics Data System (ADS)
Ale, Angelique; Kirk, Paul; Stumpf, Michael P. H.
2013-05-01
Moment approximation methods are gaining increasing attention for their use in the approximation of the stochastic kinetics of chemical reaction systems. In this paper we derive a general moment expansion method for any type of propensities and which allows expansion up to any number of moments. For some chemical reaction systems, more than two moments are necessary to describe the dynamic properties of the system, which the linear noise approximation is unable to provide. Moreover, also for systems for which the mean does not have a strong dependence on higher order moments, moment approximation methods give information about higher order moments of the underlying probability distribution. We demonstrate the method using a dimerisation reaction, Michaelis-Menten kinetics and a model of an oscillating p53 system. We show that for the dimerisation reaction and Michaelis-Menten enzyme kinetics system higher order moments have limited influence on the estimation of the mean, while for the p53 system, the solution for the mean can require several moments to converge to the average obtained from many stochastic simulations. We also find that agreement between lower order moments does not guarantee that higher moments will agree. Compared to stochastic simulations, our approach is numerically highly efficient at capturing the behaviour of stochastic systems in terms of the average and higher moments, and we provide expressions for the computational cost for different system sizes and orders of approximation. We show how the moment expansion method can be employed to efficiently quantify parameter sensitivity. Finally we investigate the effects of using too few moments on parameter estimation, and provide guidance on how to estimate if the distribution can be accurately approximated using only a few moments.
Generalized charge-screening in relativistic Thomas-Fermi model
NASA Astrophysics Data System (ADS)
Akbari-Moghanjoughi, M.
2014-10-01
In this paper, we study the charge shielding within the relativistic Thomas-Fermi model for a wide range of electron number-densities and the atomic-number of screened ions. A generalized energy-density relation is obtained using the force-balance equation and taking into account the Chandrasekhar's relativistic electron degeneracy pressure. By numerically solving a second-order nonlinear differential equation, the Thomas-Fermi screening length is investigated, and the results are compared for three distinct regimes of the solid-density, warm-dense-matter, and white-dwarfs (WDs). It is revealed that our nonlinear screening theory is compatible with the exponentially decaying Thomas-Fermi-type shielding predicted by the linear response theory. Moreover, the variation of relative Thomas-Fermi screening length shows that extremely dense quantum electron fluids are relatively poor charge shielders. Calculation of the total number of screening electrons around a nucleus shows that there is a position of maximum number of screening localized electrons around the screened nucleus, which moves closer to the point-like nucleus by increase in the plasma number density but is unaffected due to increase in the atomic-number value. It is discovered that the total number of screening electrons, ( N s ∝ r T F 3 / r d 3 where rTF and rd are the Thomas-Fermi and interparticle distance, respectively) has a distinct limit for extremely dense plasmas such as WD-cores and neutron star crusts, which is unique for all given values of the atomic-number. This is equal to saying that in an ultrarelativistic degeneracy limit of electron-ion plasma, the screening length couples with the system dimensionality and the plasma becomes spherically self-similar. Current analysis can provide useful information on the effects of relativistic correction to the charge screening for a wide range of plasma density, such as the inertial-confined plasmas and compact stellar objects.
Location-scale cumulative odds models for ordinal data: a generalized non-linear model approach.
Cox, C
1995-06-15
Proportional odds regression models for multinomial probabilities based on ordered categories have been generalized in two somewhat different directions. Models having scale as well as location parameters for adjustment of boundaries (on an unobservable, underlying continuum) between categories have been employed in the context of ROC analysis. Partial proportional odds models, having different regression adjustments for different multinomial categories, have also been proposed. This paper considers a synthesis and further generalization of these two families. With use of a number of examples, I discuss and illustrate properties of this extended family of models. Emphasis is on the computation of maximum likelihood estimates of parameters, asymptotic standard deviations, and goodness-of-fit statistics with use of non-linear regression programs in standard statistical software such as SAS. PMID:7667560
Venusian Polar Vortex reproduced in an Atmospheric General Circulation Model
NASA Astrophysics Data System (ADS)
Ando, Hiroki; Imamura, Takeshi; Takagi, Masahiro; Sugimoto, Norihiko; Kashimura, Hiroki
The Venus atmosphere has a polar vortex rotating in the retrograde direction with a period of about three days. The vortex has a warm feature surrounded by a cold collar (e.g., Taylor et al. 1980; Piccioni et al. 2006). Although the Venusian polar vortex has been reported by many observations, its mechanism is still unknown. Elson (1982, 1989) examined the structure of the polar vortex by linear calculations. However, the background zonal wind assumed in the calculations was much stronger or weaker than those retrieved in the previous measurements (e.g., Peralta et al. 2008; Kouyama et al. 2012). Lee et al. (2010) and Yamamoto and Takahashi (2012) performed numerical simulations with general circulation models (GCMs) of the Venus atmosphere and obtained vertical structure in the polar region. However, the models included artificial forcing of Kelvin and/or Rossby waves. We have developed a new Venusian GCM by modifying the Atmospheric GCM For the Earth Simulator (Sugimoto et al. 2012; 2013). The basic equations of the GCM are primitive ones in the sigma coordinate on a sphere without topography. The model resolution is T42 (i.e., about 2.8 deg x 2.8 deg grids) and L60 (Deltaz is about 2 km). Rayleigh friction (sponge layer) in the upper layer (>80 km) is applied to prevent the reflection of waves, whose effect increases gradually with height. In the model, the atmosphere is dry and forced by the solar heating and Newtonian cooling. The vertical profile of the solar heating is based on Crisp (1986), and zonally averaged distribution is used. In addition diurnal component of the solar heating, which excites the diurnal and semi-diurnal tides, is also included. Newtonian cooling relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers, and its coefficient is based on Crisp (1986). To prevent numerical instability, the biharmonic hyper-diffusion is included with 0.8 days of e-folding time
On generalized distributions and pathways
NASA Astrophysics Data System (ADS)
Mathai, A. M.; Haubold, H. J.
2008-03-01
The scalar version of the pathway model of Mathai [A.M. Mathai, Linear Alg. Appl. 396 (2005) 317] is shown to be associated with a large number of probability models used in physics. Different families of densities are listed here, which are all connected through the pathway parameter α, generating a distributional pathway. The idea is to switch from one functional form to another through this parameter and it is shown that one can proceed from the generalized type-1 beta family to generalized type-2 beta family to generalized gamma family. It is also shown that the pathway model is available by maximizing a generalized measure of entropy, leading to an entropic pathway, covering the particularly interesting cases of Tsallis statistics [C. Tsallis, J. Stat. Phys. 52 (1988) 479] and superstatistics [C. Beck, E.G.D. Cohen, Physica A 322 (2003) 267].
Multidimensional Plasma Sheath Modeling Using The Three Fluid Plasma Model in General Geometries
NASA Astrophysics Data System (ADS)
Lilly, Robert; Shumlak, Uri
2012-10-01
There has been renewed interest in the use of plasma actuators for high speed flow control applications. In the plasma actuator, current is driven through the surrounding weakly ionized plasma to impart control moments on the hypersonic vehicle. This expanded general geometry study employs the three-fluid (electrons, ions,neutrals) plasma model as it allows the capture of electron inertial effects, as well as energy and momentum transfer between the charged and neutral species. Previous investigations have typically assumed an electrostatic electric field. This work includes the full electrodynamics in general geometries. Past work utilizing the research code WARPX (Washington Approximate Riemann Problem) employed cartesian grids. In this work, the problem is expanded to general geometries with the euler fluid equations employing Braginskii closure. In addition, WARPX general geometry grids are generated from Cubit or CAD files. Comparisons are made against AFRL magnetized plasma actuator experiments.
Investigation of the effect of erythrosine B on amyloid beta peptide using molecular modeling.
Lee, Juho; Kwon, Inchan; Jang, Seung Soon; Cho, Art E
2016-04-01
Neurotoxic plaques composed of 39 to 42 residue-long amyloid beta peptides (Aβs) are copiously present in the brains of patients with Alzheimer's disease (AD). Erythrosine B (ER), a xanthene food dye, inhibits the formation of Aβ fibrils and Aβ-associated cytotoxicity in vitro. Here, in an attempt to elucidate the inhibition mechanism, we performed molecular dynamics (MD) simulations to demonstrate the conformational change of Aβ40 induced by ER molecules in atomistic detail. During the simulation, the ER bound to the surfaces of both N-terminus and C-terminus regions of Aβ40. Our result shows that ER interacts with the aromatic side chains at the N-terminus region resulting in destabilization of the inter-chain stacking of Aβ40. Moreover, the stablility of the helical structures at the residues from 13 to 16 suggests that ER disturbs conformational transition of Aβ40. At the C-terminus region, the bound ER blocks water molecules and stabilizes the α-helical structure. Regardless of the number of ER molecules used, the interruption of the formation of the salt-bridge between aspartic acid 23 and lysine 28 occurred. To further validate our analysis, binding free energies of ER at each binding site were evaluated. The finding of stronger binding energy at the N-terminus region supports an inhibition mechanism induced by stacking interaction between ER and phenylalanine. These findings could aid present and future treatment studies for AD by clarifying the inhibition mechanism of ER on the conformational transition of Aβ40 at the molecular level. Graphical Abstract Conformation of two ER molecules binding to the surface of Aβ40 peptide. The ERs and Aβ40 are represented by black and cyan color, respectively. PMID:27021211
ERIC Educational Resources Information Center
Samei, Borhan; Olney, Andrew M.; Kelly, Sean; Nystrand, Martin; D'Mello, Sidney; Blanchard, Nathan; Graesser, Art
2015-01-01
It has previously been shown that the effective use of dialogic instruction has a positive impact on student achievement. In this study, we investigate whether linguistic features used to classify properties of classroom discourse generalize across different subpopulations. Results showed that the machine learned models perform equally well when…
Documentation of the GLAS fourth order general circulation model. Volume 1: Model documentation
NASA Technical Reports Server (NTRS)
Kalnay, E.; Balgovind, R.; Chao, W.; Edelmann, J.; Pfaendtner, J.; Takacs, L.; Takano, K.
1983-01-01
The volume 1, of a 3 volume technical memoranda which contains a documentation of the GLAS Fourth Order General Circulation Model is presented. Volume 1 contains the documentation, description of the stratospheric/tropospheric extension, user's guide, climatological boundary data, and some climate simulation studies.
Chandramoorthi, Gayathri Devi; Piramanayagam, Shanmughavel; Marimuthu, Parthiban
2008-09-01
Knowledge of the three-dimensional structures of protein targets from genomic data has the potential to accelerate researches pertaining to drug discovery. Human beta(2) adrenergic receptor is a G-protein-coupled receptor with seven transmembrane helices, and is important in pharmaceutical targeting on pulmonary and cardiovascular diseases. The human beta(2) adrenergic receptor has been found to play a very important role in the pathogenesis of high altitude pulmonary edema (HAPE). In the present study, a high quality of protein 3D structure has been predicted for the human beta(2) adrenergic receptor sequence with primary accession number P07550. Homologous template protein sequence with known 3D structure was identified and the template-query protein sequence validation was done by multiple sequence alignment method. The homology model was performed through Modeller and depended on the quality of the sequence alignment by BLAST, template structure and the consolidated result performed by Gene silico meta-server. The statistical verification of the generated model was evaluated by PROCHECK which revealed that the structure modeled through Modeller to be of good quality with 84.1% of residues in the most favored region. Docking studies were carried out after modeling with two well known ligands namely Salmeterol and Nifedipine, and the fitness score revealed that Salmeterol has a higher fitness score than Nifedipine. Estimation of binding affinity by X-Score revealed that Salmeterol had -10.40 binding affinity while Nifedipine showed -9.62 binding affinity. From the present study, it can be concluded that the generated model of human beta(2) adrenergic receptor can be used for further studies related to this receptor and Salmeterol was found to have a high binding affinity with human beta(2) adrenergic receptor. PMID:18512086
Modeling of turbulent supersonic H2-air combustion with an improved joint beta PDF
NASA Technical Reports Server (NTRS)
Baurle, R. A.; Hassan, H. A.
1991-01-01
Attempts at modeling recent experiments of Cheng et al. indicated that discrepancies between theory and experiment can be a result of the form of assumed probability density function (PDF) and/or the turbulence model employed. Improvements in both the form of the assumed PDF and the turbulence model are presented. The results are again used to compare with measurements. Initial comparisons are encouraging.
Neutron Beta Decay Studies with Nab
Baessler, S.; Alarcon, R.; Alonzi, L. P.; Balascuta, S.; Barron-Palos, L.; Bowman, James David; Bychkov, M. A.; Byrne, J.; Calarco, J; Chupp, T.; Cianciolo, T. V.; Crawford, C.; Frlez, E.; Gericke, M. T.; Glück, F.; Greene, G. L.; Grzywacz, R. K.; Gudkov, V.; Harrison, D.; Hersman, F. W.; Ito, T.; Makela, M.; Martin, J.; McGaughey, P. L.; McGovern, S.; Page, S.; Penttila, Seppo I; Pocanic, Dinko; Salas-Bacci, A.; Tompkins, Z.; Wagner, D.; Wilburn, W. S.; Young, A. R.
2013-01-01
Precision measurements in neutron beta decay serve to determine the coupling constants of beta decay and allow for several stringent tests of the standard model. This paper discusses the design and the expected performance of the Nab spectrometer.
Arakawa, Akio; Konor, C.S.
1997-12-31
There are great conceptual advantages in the use of an isentropic vertical coordinate in atmospheric models. Design of such a model, however, requires to overcome computational problems due to intersection of coordinate surfaces with the earth`s surface. Under this project, the authors have completed the development of a model based on a generalized vertical coordinate, {zeta} = F({Theta}, p, p{sub s}), in which an isentropic coordinate can be combined with a terrain-following {sigma}-coordinate a smooth transition between the two. One of the key issues in developing such a model is to satisfy the consistency between the predictions of pressure and potential temperature. In the model, the consistency is satisfied by the use of an equation that determines the vertical mass flux. A procedure to properly choose {zeta} = F({Theta}, p, p{sub s}) is also developed, which guarantees that {zeta} is a monotonic function of height even when unstable stratification occurs. There are two versions of the model constructed in parallel: one is the middle-latitude {beta}-plane version and the other is the global version. Both of these versions include moisture prediction, relaxed large-scale condensation and relaxed moist-convective adjustment schemes. A well-mixed planetary boundary layer (PBL) is also added.
Modular and Stochastic Approaches to Molecular Pathway Models of ATM, TGF beta, and WNT Signaling
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.; O'Neill, Peter; Ponomarev, Artem; Carra, Claudio; Whalen, Mary; Pluth, Janice M.
2009-01-01
Deterministic pathway models that describe the biochemical interactions of a group of related proteins, their complexes, activation through kinase, etc. are often the basis for many systems biology models. Low dose radiation effects present a unique set of challenges to these models including the importance of stochastic effects due to the nature of radiation tracks and small number of molecules activated, and the search for infrequent events that contribute to cancer risks. We have been studying models of the ATM, TGF -Smad and WNT signaling pathways with the goal of applying pathway models to the investigation of low dose radiation cancer risks. Modeling challenges include introduction of stochastic models of radiation tracks, their relationships to more than one substrate species that perturb pathways, and the identification of a representative set of enzymes that act on the dominant substrates. Because several pathways are activated concurrently by radiation the development of modular pathway approach is of interest.
Tamis, Jelmer; Marang, Leonie; Jiang, Yang; van Loosdrecht, Mark C M; Kleerebezem, Robbert
2014-06-25
Polyhydroxyalkanoate (PHA) production from waste streams using microbial enrichment cultures is a promising option for cost price reduction of this biopolymer. For proper understanding and successful optimization of the process, a consistent mechanistic model for PHA conversion by microbial enrichment cultures is needed. However, there is still a lack of mechanistic expressions describing the dynamics of the feast-famine process. The scope of this article is to provide an overview of the current models, investigate points of improvement, and contribute concepts for creation of a generalized model with more predictive value for the feast-famine process. Based on experimental data available in literature we have proposed model improvements for (i) modeling mixed substrates uptake, (ii) growth in the feast phase, (iii) switching between feast and famine phase, (iv) PHA degradation and (v) modeling the accumulation phase. Finally, we provide an example of a simple uniform model. Herewith we aim to give an impulse to the establishment of a generalized model. PMID:24333144
Pentón-Rol, Giselle; Lagumersindez-Denis, Nielsen; Muzio, Luca; Bergami, Alessandra; Furlan, Roberto; Fernández-Massó, Julio R; Nazabal-Galvez, Marcelo; Llópiz-Arzuaga, Alexey; Herrera-Rolo, Tania; Veliz-Rodriguez, Tania; Polentarutti, Nadia; Marín-Prida, Javier; Raíces-Cruz, Ivette; Valenzuela-Silva, Carmen; Teixeira, Mauro Martins; Pentón-Arias, Eduardo
2016-03-01
Multiple Sclerosis (MS) therapies approved so far are unable to effectively reverse the chronic phase of the disease or improve the remyelination process. Here our aim is to evaluate the effects of C-Phycocyanin (C-Pc), a biliprotein from Spirulina platensis with anti-oxidant, anti-inflammatory and cytoprotective properties, in a chronic model of experimental autoimmune encephalomyelitis (EAE) in mice. C-Pc (2, 4 or 8 mg/kg i.p.) or IFN-beta (2000 IU, s.c.) was administered daily once a day or every other day, respectively, starting at disease onset, which differ among EAE mice between 11 and 15 days postinduction. Histological and immunohistochemistry (anti-Mac-3, anti-CD3 and anti-APP) assessments were performed in spinal cord in the postinduction time. Global gene expression in the brain was analyzed with the Illumina Mouse WG-6_V2 BeadChip microarray and the expression of particular genes, assessed by qPCR using the Fast SYBR Green RT-PCR Master Mix. Oxidative stress parameters (malondialdehyde, peroxidation potential, CAT/SOD ratio and GSH) were determined spectrophoto-metrically. Results showed that C-Pc ameliorates the clinical deterioration of animals, an effect that expresses the reduction of the inflammatory infiltrates invading the spinal cord tissue, the axonal preservation and the down-regulation of IL-17 expression in brain tissue and serum. C-Pc and IFN-beta improved the redox status in mice subjected to EAE, while microarray analysis showed that both treatments shared a common subset of differentially expressed genes, although they also differentially modulated another subset of genes. Specifically, C-Pc mainly modulated the expression of genes related to remyelination, gliogenesis and axon-glia processes. Taken together, our results indicate that C-Pc has significant therapeutic effects against EAE, mediated by the dynamic regulation of multiple biological processes. PMID:26556034
Optimal Scaling of Interaction Effects in Generalized Linear Models
ERIC Educational Resources Information Center
van Rosmalen, Joost; Koning, Alex J.; Groenen, Patrick J. F.
2009-01-01
Multiplicative interaction models, such as Goodman's (1981) RC(M) association models, can be a useful tool for analyzing the content of interaction effects. However, most models for interaction effects are suitable only for data sets with two or three predictor variables. Here, we discuss an optimal scaling model for analyzing the content of…
Cloninger, C R; Rice, J; Reich, T
1979-01-01
A general linear model of combined polygenic-cultural inheritance is described. The model allows for phenotypic assortative mating, common environment, maternal and paternal effects, and genic-cultural correlation. General formulae for phenotypic correlation between family members in extended pedigrees are given for both primary and secondary assortative mating. A FORTRAN program BETA, available upon request, is used to provide maximum likelihood estimates of the parameters from reported correlations. American data about IQ and Burks' culture index are analyzed. Both cultural and genetic components of phenotypic variance are observed to make significant and substantial contributions to familial resemblance in IQ. The correlation between the environments of DZ twins is found to equal that of singleton sibs, not that of MZ twins. Burks' culture index is found to be an imperfect measure of midparent IQ rather than an index of home environment as previously assumed. Conditions under which the parameters of the model may be uniquely and precisely estimated are discussed. Interpretation of variance components in the presence of assortative mating and genic-cultural covariance is reviewed. A conservative, but robust, approach to the use of environmental indices is described. PMID:453202
NASA Astrophysics Data System (ADS)
Kim, Tae-Jeong; Kim, Ki-Young; Shin, Dong-Hoon; Kwon, Hyun-Han
2015-04-01
It has been widely acknowledged that the appropriate simulation of natural streamflow at ungauged sites is one of the fundamental challenges to hydrology community. In particular, the key to reliable runoff simulation in ungauged basins is a reliable rainfall-runoff model and a parameter estimation. In general, parameter estimation in rainfall-runoff models is a complex issue due to an insufficient hydrologic data. This study aims to regionalize the parameters of the continuous rainfall-runoff model in conjunction with Bayesian statistical techniques to facilitate uncertainty analysis. First, this study uses the Bayesian Markov Chain Monte Carlo scheme for the Sacramento rainfall-runoff model that has been widely used around the world. The Sacramento model is calibrated against daily runoff observation, and thirteen parameters of the model are optimized as well as posterior distributor distributions for each parameter are derived. Second, we applied Bayesian generalized linear regression model to set of the parameters with basin characteristics (e.g. area and slope), to obtain a functional relationship between pairs of variables. The proposed model was validated in two gauged watersheds in accordance with the efficiency criteria such as the Nash-Sutcliffe efficiency, coefficient of efficiency, index of agreement and coefficient of correlation. The future study will be further focused on uncertainty analysis to fully incorporate propagation of the uncertainty into the regionalization framework. KEYWORDS: Ungauge, Parameter, Sacramento, Generalized linear model, Regionalization Acknowledgement This research was supported by a Grant (13SCIPA01) from Smart Civil Infrastructure Research Program funded by the Ministry of Land, Infrastructure and Transport (MOLIT) of Korea government and the Korea Agency for Infrastructure Technology Advancement (KAIA).
Generalized charge-screening in relativistic Thomas–Fermi model
Akbari-Moghanjoughi, M.
2014-10-15
In this paper, we study the charge shielding within the relativistic Thomas-Fermi model for a wide range of electron number-densities and the atomic-number of screened ions. A generalized energy-density relation is obtained using the force-balance equation and taking into account the Chandrasekhar's relativistic electron degeneracy pressure. By numerically solving a second-order nonlinear differential equation, the Thomas-Fermi screening length is investigated, and the results are compared for three distinct regimes of the solid-density, warm-dense-matter, and white-dwarfs (WDs). It is revealed that our nonlinear screening theory is compatible with the exponentially decaying Thomas-Fermi-type shielding predicted by the linear response theory. Moreover, the variation of relative Thomas-Fermi screening length shows that extremely dense quantum electron fluids are relatively poor charge shielders. Calculation of the total number of screening electrons around a nucleus shows that there is a position of maximum number of screening localized electrons around the screened nucleus, which moves closer to the point-like nucleus by increase in the plasma number density but is unaffected due to increase in the atomic-number value. It is discovered that the total number of screening electrons, (N{sub s}∝r{sub TF}{sup 3}/r{sub d}{sup 3} where r{sub TF} and r{sub d} are the Thomas-Fermi and interparticle distance, respectively) has a distinct limit for extremely dense plasmas such as WD-cores and neutron star crusts, which is unique for all given values of the atomic-number. This is equal to saying that in an ultrarelativistic degeneracy limit of electron-ion plasma, the screening length couples with the system dimensionality and the plasma becomes spherically self-similar. Current analysis can provide useful information on the effects of relativistic correction to the charge screening for a wide range of plasma density, such as the inertial-confined plasmas and compact stellar
Deiber, Julio A; Piaggio, Maria V; Peirotti, Marta B
2014-09-01
Neuronal activity loss may be due to toxicity caused by amyloid-beta peptides forming soluble oligomers. Here amyloid-beta peptides (1-42, 1-40, 1-39, 1-38, and 1-37) are characterized through the modeling of their experimental effective electrophoretic mobilities determined by a capillary zone electrophoresis method as reported in the literature. The resulting electrokinetic and hydrodynamic global properties are used to evaluate amyloid-beta peptide propensities to aggregation through pair particles interaction potentials and Brownian aggregation kinetic theories. Two background electrolytes are considered at 25°C, one for pH 9 and ionic strength I = 40 mM (aggregation is inhibited through NH4OH) the other for pH 10 and I = 100 mM (without NH4OH). Physical explanations of peptide oligomerization mechanisms are provided. The effect of hydration, electrostatic, and dispersion forces in the amyloidogenic process of amyloid-beta peptides (1-40 and 1-42) are quantitatively presented. The interplay among effective charge number, hydration, and conformation of chains is described. It is shown that amyloid-beta peptides (1-40 and 1-42) at pH 10, I = 100 mM and 25°C, may form soluble oligomers, mainly of order 2 and 4, after an incubation of 48 h, which at higher times evolve and end up in complex structures (protofibrils and fibrils) found in plaques associated with Alzheimer's disease. PMID:24975363
NASA Astrophysics Data System (ADS)
Hautekèete, N.-C.; Van Dijk, H.; Piquot, Y.; Teriokhin, A.
2009-01-01
At evolutionary equilibrium, ecological factors will determine the optimal combination of life-history trait values of an organism. This optimum can be assessed by assuming that the species maximizes some criterion of fitness such as the Malthusian coefficient or lifetime reproductive success depending on the degree of density-dependence. We investigated the impact of the amount of resources and habitat stability on a plant's age at maturity and life span by using an evolutionary optimization model in combination with empirical data. We conducted this study on sea beet, Beta vulgaris subsp. maritima, because of its large variation in life span and age at first reproduction along a latitudinal gradient including considerable ecological variation. We also compared the consequence in our evolutionary model of maximizing either the Malthusian coefficient or the lifetime reproductive success. Both the data analysis and the results of evolutionary modeling pointed to habitat disturbance and resources like length of the growing season as factors negatively related to life span and age at maturity in sea beet. Resource availability had a negative theoretical influence with the Malthusian coefficient as the chosen optimality criterion, while there was no influence in the case of lifetime reproductive success. As suggested by previous theoretical work the final conclusion on what criterion is more adequate depends on the assumptions of how in reality density-dependence restrains population growth. In our case of sea beet data R0 seems to be less appropriate than λ.
The goodness of generalized STAR in spatial dependency observations modeling
NASA Astrophysics Data System (ADS)
Mukhaiyar, Utriweni
2015-12-01
The spatial and time dependencies among observations are demanded for space time modeling. In order to estimate unobserved sites in the near future, we may apply Kriging methods to the forecast results of observed sites. Here we considered two ways of forecasting, first is by using AR model and second is by using GSTAR model. We compare both ways and observe the goodness of GSTAR model, relative to the AR model, in spatial dependence observations through some numerical studies and case study. It is obtained that GSTAR model gives the better forecasting result than AR model, which always perform overestimate values. Since the Kriging interpolation is better for linear approximation then AR model will give better interpolated observations if the site has higher real observations than other sites. This result also confirms the stationarity of GSTAR model.
Goyenechea, N; Sánchez, M; Vélaz, I; Martín, C; Martínez-Ohárriz, M C; González-Gaitano, G
2001-01-01
Fluorescence, (1)H-NMR and molecular mechanics have been used to study the inclusion complexes of nabumetone (4,6-methoxy-2-naphthyl-butan-2-one; NAB) with beta-cyclodextrin (beta-CD), randomly methylated-beta (M beta-CD) and hydroxypropyl-beta-cyclodextrins (HP beta-CD). The emission spectrum of NAB shows a maximum whose fluorescence intensity increases with the different beta-CDs growing concentrations. This phenomenon allows calculation of the stability constants at 15, 25, 37 and 45 degrees C. The thermodynamic parameters Delta H degrees and Delta S degrees for the inclusion process were obtained from the temperature dependence of the stability constants. Molecular mechanics calculations, together with proton NMR measurements, for the complex with beta-CD prove that the complex can be formed by penetration through any of the rims, with the naphthalene nucleus included and the substituents outside the cavity. The influence of NaClO(4) in the aforementioned complexes has been analysed by spectrofluorimetric measurements. It has been found that the stability constants for the complexes decrease with the salt concentration; the causes are discussed. PMID:11312537
Kagawa, Shinya; Nakano, Takayuki; Inoue, Osamu; Nishimura, Tsunehiko
2002-10-01
The effect of MK-801, a noncompetitive NMDA receptor antagonist, on both in vivo and in vitro binding of [(125)I]beta-CIT (RTI-55) was investigated in a rat model of Parkinson's disease. The binding experiments were performed 2 weeks after unilateral intranigral microinjection of 6-hydroxydopamine (6-OHDA). In the in vitro binding study, no alterations in [(125)I]beta-CIT binding in rat brain sections were observed after addition of MK-801, 0.03 microM or 3 microM, to the incubation medium. However, in vivo [(125)I]beta-CIT binding to the dopamine transporter in both nonlesioned and 6-OHDA-lesioned striatum was significantly increased by pretreatment with MK-801. In vivo [(125)I]beta-CIT binding to the serotonin (5HT) transporter in nonlesioned cerebral cortex, hypothalamus, and thalamus was also significantly increased by MK-801. However, the degree of change in the specific binding of [(125)I]beta-CIT induced by MK-801 was smaller in the lesioned cerebral cortex. Kinetic analysis, by a simplified three-compartment model with the cerebellum as the reference region, revealed that these alterations in the in vivo [(125)I]beta-CIT binding induced by MK-801 were mainly due to changes in the rate constants of in vivo binding, the input rate constant, k(3), and the output rate constant, k(4). These results indicate that the glutamatergic system significantly affects the function of dopamine transporters in the degenerated dopaminergic neurons in Parkinson's disease. PMID:12211097
Generating Dichotomous Item Scores with the Four-Parameter Beta Compound Binomial Model
ERIC Educational Resources Information Center
Monahan, Patrick O.; Lee, Won-Chan; Ankenmann, Robert D.
2007-01-01
A Monte Carlo simulation technique for generating dichotomous item scores is presented that implements (a) a psychometric model with different explicit assumptions than traditional parametric item response theory (IRT) models, and (b) item characteristic curves without restrictive assumptions concerning mathematical form. The four-parameter beta…
Pruet, J; Prussin, S; Descalle, M; Hall, J
2004-02-03
A Monte Carlo method for the estimation of {beta}-delayed {gamma}-ray spectra following fission is described that can accommodate an arbitrary time-dependent fission rate and photon collection history. The method invokes direct sampling of the independent fission yield distributions of the fissioning system, the branching ratios for decay of individual fission products and the spectral distributions for photon emission for each decay mode. Though computationally intensive, the method can provide a detailed estimate of the spectrum that would be recorded by an arbitrary spectrometer, and can prove useful in assessing the quality of evaluated data libraries, for identifying gaps in these libraries, etc. The method is illustrated by a first comparison of calculated and experimental spectra from decay of short-lived fission products following the reactions {sup 235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f). For general purpose transport calculations, where detailed consideration of the large number of individual {gamma}-ray transitions in a spectrum may be unnecessary, it is shown that an accurate and simple parameterization of a {gamma}-ray source function can be obtained. These parametrizations should provide high-quality average spectral distributions that should prove useful in calculations describing photons escaping from thick attenuating media.
NASA Astrophysics Data System (ADS)
Souza, S. R.; Carlson, B. V.; Donangelo, R.; Lynch, W. G.; Tsang, M. B.
2013-07-01
The generalized Fermi breakup model, recently demonstrated to be formally equivalent to the statistical multifragmentation model, if the contribution of excited states is included in the state densities of the former, is implemented. Because this treatment requires application of the statistical multifragmentation model repeatedly on hot fragments until they have decayed to their ground states, it becomes extremely computationally demanding, making its application to the systems of interest extremely difficult. Based on exact recursion formulas previously developed by Chase and Mekjian to calculate statistical weights very efficiently, we present an implementation which is efficient enough to allow it to be applied to large systems at high excitation energies. Comparison with the gemini++ sequential decay code and the Weisskopf-Ewing evaporation model shows that the predictions obtained with our treatment are fairly similar to those obtained with these more traditional models.
On the Bayesian Nonparametric Generalization of IRT-Type Models
ERIC Educational Resources Information Center
San Martin, Ernesto; Jara, Alejandro; Rolin, Jean-Marie; Mouchart, Michel
2011-01-01
We study the identification and consistency of Bayesian semiparametric IRT-type models, where the uncertainty on the abilities' distribution is modeled using a prior distribution on the space of probability measures. We show that for the semiparametric Rasch Poisson counts model, simple restrictions ensure the identification of a general…