Bayesian Analysis for Binomial Models with Generalized Beta Prior Distributions.
ERIC Educational Resources Information Center
Chen, James J.; Novick, Melvin, R.
1984-01-01
The Libby-Novick class of three-parameter generalized beta distributions is shown to provide a rich class of prior distributions for the binomial model that removes some restrictions of the standard beta class. A numerical example indicates the desirability of using these wider classes of densities for binomial models. (Author/BW)
A Generalized QMRA Beta-Poisson Dose-Response Model.
Xie, Gang; Roiko, Anne; Stratton, Helen; Lemckert, Charles; Dunn, Peter K; Mengersen, Kerrie
2016-10-01
Quantitative microbial risk assessment (QMRA) is widely accepted for characterizing the microbial risks associated with food, water, and wastewater. Single-hit dose-response models are the most commonly used dose-response models in QMRA. Denoting PI(d) as the probability of infection at a given mean dose d, a three-parameter generalized QMRA beta-Poisson dose-response model, PI(d|α,β,r*), is proposed in which the minimum number of organisms required for causing infection, Kmin , is not fixed, but a random variable following a geometric distribution with parameter 0
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 motivate…
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 motivate…
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…
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
Generalized Beta Mixtures of Gaussians.
Armagan, Artin; Dunson, David B; Clyde, Merlise
2011-01-01
In recent years, a rich variety of shrinkage priors have been proposed that have great promise in addressing massive regression problems. In general, these new priors can be expressed as scale mixtures of normals, but have more complex forms and better properties than traditional Cauchy and double exponential priors. We first propose a new class of normal scale mixtures through a novel generalized beta distribution that encompasses many interesting priors as special cases. This encompassing framework should prove useful in comparing competing priors, considering properties and revealing close connections. We then develop a class of variational Bayes approximations through the new hierarchy presented that will scale more efficiently to the types of truly massive data sets that are now encountered routinely.
Constraints on general SU(2)/sub L/ x SU(2)/sub R/ x U(1) electroweak models from nuclear beta decay
Herczeg, P.
1986-01-01
The implications of beta-decay experiments for more general versions of SU(2)/sub L/ x SU(2)/sub R/ x U(1) models are analyzed, including the most general one which allows for CP-violation, unequal left- and right-handed quark mixing angles, and mixing in the leptonic sector. For each scenario, the constraints on the pertinent parameters from beta-decay measurements are compared with the constraints provided on them by other data.
Multivariate Generalized Beta Distributions with Applications to Utility Assessment.
ERIC Educational Resources Information Center
Libby, David L.; Novick, Melvin R.
1982-01-01
Two multivariate probability distributions, a generalized beta distribution and a generalized F distribution, are derived. Formulas for the moments of these distributions are given and an example of the bivariate generalized beta is presented. (Author/JKS)
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…
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…
Nakatsuji, Hidefumi; Nishikado, Hiroshi; Ueno, Kanako; Tanabe, Yoo
2009-10-01
An (E)- and (Z)-stereocomplementary preparative method for alpha,beta-disubstituted alpha,beta-unsaturated esters is performed via three general and robust reaction sequences: (i) Ti-Claisen condensation (formylation) of esters to give alpha-formyl esters (12 examples, 60-99%), (ii) (E)- and (Z)-stereocomplementary enol p-toluenesulfonylation (tosylation) using TsCl-N-methylimidazole (NMI)-Et(3)N and LiOH (24 examples, 82-99%), and (iii) stereoretentive Suzuki-Miyaura cross-coupling (18 examples, 64-96%).
Fundamental processes in the interacting boson model: 0{nu}{beta}{beta} decay
Iachello, F.; Barea, J.
2011-05-06
A program to calculate nuclear matrix elements for fundamental processes in the interacting boson model has been initiated. Results for the nuclear matrix elements in neutrinoless double beta decay 0{nu}{beta}{beta} are presented.
Modeling the beta diversity of coral reefs.
Harborne, Alastair R; Mumby, Peter J; Zychaluk, Kamila; Hedley, John D; Blackwell, Paul G
2006-11-01
Quantifying the beta diversity (species replacement along spatiotemporal gradients) of ecosystems is important for understanding and conserving patterns of biodiversity. However, virtually all studies of beta diversity focus on one-dimensional transects orientated along a specific environmental gradient that is defined a priori. By ignoring a second spatial dimension and the associated changes in species composition and environmental gradients, this approach may provide limited insight into the full pattern of beta diversity. Here, we use remotely sensed imagery to quantify beta diversity continuously, in two dimensions, and at multiple scales across an entire tropical marine seascape. We then show that beta diversity can be modeled (0.852 > or = r2 > or = 0.590) at spatial scales between 0.5 and 5.0 km2, using the environmental variables of mean and variance of depth and wave exposure. Beta diversity, quantified within a "window" of a given size, is positively correlated to the range of environmental conditions within that window. For example, beta diversity increases with increasing variance of depth. By analyzing such relationships across seascapes, this study provides a framework for a range of disparate coral reef literature including studies of zonation, diversity, and disturbance. Using supporting evidence from soft-bottom communities, we hypothesize that depth will be an important variable for modeling beta diversity in a range of marine systems. We discuss the implications of our results for the design of marine reserves.
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.…
ERIC Educational Resources Information Center
Miles, David T.; Robinson, Roger E.
The General Teaching Model is a procedural guide for the design, implementation, evaluation, and improvement of instruction. The Model is considered applicable to all levels of education, all subject matters, and any length of instructional unit. It consists of four components: 1) instructional objectives, 2) pre-assessment, 3) instructional…
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.
Size-biased distributions in the generalized beta distribution family, with applications to forestry
Mark J. Ducey; Jeffrey H. Gove
2015-01-01
Size-biased distributions arise in many forestry applications, as well as other environmental, econometric, and biomedical sampling problems. We examine the size-biased versions of the generalized beta of the first kind, generalized beta of the second kind and generalized gamma distributions. These distributions include, as special cases, the Dagum (Burr Type III),...
Generalized simplicial chiral models
NASA Astrophysics Data System (ADS)
Alimohammadi, Masoud
2000-02-01
Using the auxiliary field representation of the simplicial chiral models on a ( d-1)-dimensional simplex, the simplicial chiral models are generalized through replacing the term Tr (AA †) in the Lagrangian of these models by an arbitrary class function of AA †; V(AA †) . This is the same method used in defining the generalized two-dimensional Yang-Mills theories (gYM 2) from ordinary YM 2. We call these models the "generalized simplicial chiral models". Using the results of the one-link integral over a U( N) matrix, the large- N saddle-point equations for eigenvalue density function ρ( z) in the weak ( β> βc) and strong ( β< βc) regions are computed. In d=2, where the model is in some sense related to the gYM 2 theory, the saddle-point equations are solved for ρ( z) in the two regions, and the explicit value of critical point βc is calculated for V(B)= Tr B n(B=AA †) . For V(B)= Tr B 2, Tr B 3, and Tr B4, the critical behaviour of the model at d=2 is studied, and by calculating the internal energy, it is shown that these models have a third order phase transition.
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
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.
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.
Meta-analysis of studies with bivariate binary outcomes: a marginal beta-binomial model approach.
Chen, Yong; Hong, Chuan; Ning, Yang; Su, Xiao
2016-01-15
When conducting a meta-analysis of studies with bivariate binary outcomes, challenges arise when the within-study correlation and between-study heterogeneity should be taken into account. In this paper, we propose a marginal beta-binomial model for the meta-analysis of studies with binary outcomes. This model is based on the composite likelihood approach and has several attractive features compared with the existing models such as bivariate generalized linear mixed model (Chu and Cole, 2006) and Sarmanov beta-binomial model (Chen et al., 2012). The advantages of the proposed marginal model include modeling the probabilities in the original scale, not requiring any transformation of probabilities or any link function, having closed-form expression of likelihood function, and no constraints on the correlation parameter. More importantly, because the marginal beta-binomial model is only based on the marginal distributions, it does not suffer from potential misspecification of the joint distribution of bivariate study-specific probabilities. Such misspecification is difficult to detect and can lead to biased inference using currents methods. We compare the performance of the marginal beta-binomial model with the bivariate generalized linear mixed model and the Sarmanov beta-binomial model by simulation studies. Interestingly, the results show that the marginal beta-binomial model performs better than the Sarmanov beta-binomial model, whether or not the true model is Sarmanov beta-binomial, and the marginal beta-binomial model is more robust than the bivariate generalized linear mixed model under model misspecifications. Two meta-analyses of diagnostic accuracy studies and a meta-analysis of case-control studies are conducted for illustration. Copyright © 2015 John Wiley & Sons, Ltd.
Generalized Nonlinear Yule Models
NASA Astrophysics Data System (ADS)
Lansky, Petr; Polito, Federico; Sacerdote, Laura
2016-11-01
With the aim of considering models related to random graphs growth exhibiting persistent memory, we propose a fractional nonlinear modification of the classical Yule model often studied in the context of macroevolution. Here the model is analyzed and interpreted in the framework of the development of networks such as the World Wide Web. Nonlinearity is introduced by replacing the linear birth process governing the growth of the in-links of each specific webpage with a fractional nonlinear birth process with completely general birth rates. Among the main results we derive the explicit distribution of the number of in-links of a webpage chosen uniformly at random recognizing the contribution to the asymptotics and the finite time correction. The mean value of the latter distribution is also calculated explicitly in the most general case. Furthermore, in order to show the usefulness of our results, we particularize them in the case of specific birth rates giving rise to a saturating behaviour, a property that is often observed in nature. The further specialization to the non-fractional case allows us to extend the Yule model accounting for a nonlinear growth.
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…
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…
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…
String Field Equations from Generalized Sigma Model
Bardakci, K.; Bernardo, L.M.
1997-01-29
We propose 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. We apply it to the tachyon, massless and first massive level, and show that the resulting field equations reproduce the correct spectrum of a left-right symmetric closed bosonic string.
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
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…
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.
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.
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.
Theories and models for 1/f(beta) noise in human movement science.
Torre, Kjerstin; Wagenmakers, Eric-Jan
2009-06-01
Human motor behavior is often characterized by long-range, slowly decaying serial correlations or 1/f(beta) noise. Despite its prevalence, the role of the 1/f(beta) phenomenon in human movement research has been rather modest and unclear. The goal of this paper is to outline a research agenda in which the study of 1/f(beta) noise can contribute to scientific progress. In the first section of this article we discuss two popular perspectives on 1/f(beta) noise: the nomothetic perspective that seeks general explanations, and the mechanistic perspective that seeks domain-specific models. We believe that if 1/f(beta) noise is to have an impact on the field of movement science, researchers should develop and test domain-specific mechanistic models of human motor behavior. In the second section we illustrate our claim by showing how a mechanistic model of 1/f(beta) noise can be successfully integrated with currently established models for rhythmic self-paced, synchronized, and bimanual tapping. This model synthesis results in a unified account of the observed long-range serial correlations across a range of different tasks.
Structural transitions in model beta-sheet tapes.
Bellesia, Giovanni; Fedorov, Maxim V; Timoshenko, Edward G
2008-05-21
We present a molecular-scale simulation study of the structural transitions between helicoidal, helical, and tubular geometries in supramolecular beta-sheet tapes. Such geometries have been observed in different self-assembled amyloid systems (based on either natural or synthetic peptides) for which the beta-sheet tapes represent the simplest fibrillar aggregates. A coarse-grained model for the beta-sheet tapes is proposed, with chiral degrees of freedom and asymmetrical chemical properties, which provides a quantitative characterization of the structural transitions. A quantitative connection is established between the molecular properties and the elastic parameters of the supramolecular tapes.
Model of Break-Bone Fever via Beta-Derivatives
Atangana, Abdon; Oukouomi Noutchie, Suares Clovis
2014-01-01
Using the new derivative called beta-derivative, we modelled the well-known infectious disease called break-bone fever or the dengue fever. We presented the endemic equilibrium points under certain conditions of the physical parameters included in the model. We made use of an iteration method to solve the extended model. To show the efficiency of the method used, we have presented in detail the stability and the convergence of the method for solving the system (2). We presented the uniqueness of the special solution of system (2) and finally the numerical simulations were presented for various values of beta. PMID:25295263
In vivo modeling of beta-glucan degradation in contrasting barley (Hordeum vulgare L.) genotypes.
Gianinetti, Alberto; Ferrari, Barbara; Frigeri, Paolo; Stanca, Antonio Michele
2007-04-18
An important determinative of malt quality is the malt beta-glucan content, which in turn depends on the initial barley beta-glucan content as well as the beta-glucan depolymerization by beta-glucanase (EC 3.2.1.73) during malting. Another enzyme, named beta-glucan solubilase, has been suggested to act prior to beta-glucanase; its existence, however, has not been unequivocally proven. We monitored changes in beta-glucan levels and in the development of beta-glucan-degrading enzymes during malting of five lots of contrasting barley genotypes. Two models of in vivo kinetics for beta-glucan degradation were then compared as follows: (i) a biphasic model based on the sequential action of beta-glucan solubilase and beta-glucanase and (ii) a monophasic model assuming that all beta-glucans are depolymerized by beta-glucanase without the previous intervention of another enzyme. Confirmatory regression analysis was used to test the fit of the models to the observed data. Our results show that beta-glucan degradation is mostly monophasic, although some enzyme other than beta-glucanase seems to be required for the early solubilization of a small fraction of insoluble beta-glucans (on average, 7% of total beta-glucans). Furthermore, the genotype-dependent kinetic rate constant (indicating beta-glucan degradability), in addition to beta-glucanase activity, is suggested to play a major role in malting quality.
Models of primary generalized epilepsy.
Hosford, D A
1995-04-01
The most important recent development in primary generalized epilepsy has been the use of in-vitro and in-vivo models to delineate the neuronal populations and intrinsic mechanisms, which generate the synchronized thalamocortical burst-firing of absence seizures. Candidate molecular mechanisms, which may be critically involved in the pathogenesis of absence seizures in selected animal models, include the following: altered biophysical properties of T-type calcium channels in the genetic absence epilepsy rat of Strasbourg (GAERS) model; increased numbers of gamma-aminobutyric acid, B subtype receptors in the lethargic mouse (lh/lh mouse) model; and changes in the subunit composition of gamma-aminobutyric acid, A subtype receptors in the GAERS model. Regarding generalized convulsive seizures, neuronal populations within the inferior and superior colliculi appear to regulate seizures in the genetic epilepsy-prone rat (GEPR) model, and subpopulations within the substantia nigra pars reticulata (SNR) appear to regulate seizures in the fluorothyl model. Deficiencies in the function of GABAergic and noradrenergic receptors may underlie generalized convulsive seizures in the GEPR model.
Zhao, L.; Brown, B.A. )
1993-06-01
We examine the validity of the [ital pn] quasiparticle RPA ([ital pn]QRPA) as a model for calculating [beta][sup +] and 2[nu][beta][beta] Gamow-Teller decays by making a comparison of the [ital pn]QRPA with a large-basis shell-model calculation within the 0[ital f]1[ital p] shell. We employ [ital A]=46 nuclei (those with six valence nucleons) for this comparison. Our comparison includes the decay matrix elements summed over final states, the strength distributions, and, for the first time, the coherent transition matrix elements (CTME). The [ital pn]QRPA overestimates the total [beta][sup +] and 2[nu][beta][beta] matrix elements. There are large differences in the shape of the spectra as well as in the CTME between the [ital pn]QRPA and shell-model results. Empirical improvements for the [ital pn]QRPA are discussed.
Generalized Ordinary Differential Equation Models.
Miao, Hongyu; Wu, Hulin; Xue, Hongqi
2014-10-01
Existing estimation methods for ordinary differential equation (ODE) models are not applicable to discrete data. The generalized ODE (GODE) model is therefore proposed and investigated for the first time. We develop the likelihood-based parameter estimation and inference methods for GODE models. We propose robust computing algorithms and rigorously investigate the asymptotic properties of the proposed estimator by considering both measurement errors and numerical errors in solving ODEs. The simulation study and application of our methods to an influenza viral dynamics study suggest that the proposed methods have a superior performance in terms of accuracy over the existing ODE model estimation approach and the extended smoothing-based (ESB) method.
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…
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.
Quantitative analysis of cyclic beta-turn models.
Perczel, A.; Fasman, G. D.
1992-01-01
The beta-turn is a frequently found structural unit in the conformation of globular proteins. Although the circular dichroism (CD) spectra of the alpha-helix and beta-pleated sheet are well defined, there remains some ambiguity concerning the pure component CD spectra of the different types of beta-turns. Recently, it has been reported (Hollósi, M., Kövér, K.E., Holly, S., Radics, L., & Fasman, G.D., 1987, Biopolymers 26, 1527-1572; Perczel, A., Hollósi, M., Foxman, B.M., & Fasman, G.D., 1991a, J. Am. Chem. Soc. 113, 9772-9784) that some pseudohexapeptides (e.g., the cyclo[(delta)Ava-Gly-Pro-Aaa-Gly] where Aaa = Ser, Ser(OtBu), or Gly) in many solvents adopt a conformational mixture of type I and the type II beta-turns, although the X-ray-determined conformation was an ideal type I beta-turn. In addition to these pseudohexapeptides, conformational analysis was also carried out on three pseudotetrapeptides and three pseudooctapeptides. The target of the conformation analysis reported herein was to determine whether the ring stress of the above beta-turn models has an influence on their conformational properties. Quantitative nuclear Overhauser effect (NOE) measurements yielded interproton distances. The conformational average distances so obtained were interpreted utilizing molecular dynamics (MD) simulations to yield the conformational percentages. These conformational ratios were correlated with the conformational weights obtained by quantitative CD analysis of the same compounds. The pure component CD curves of type I and type II beta-turns were also obtained, using a recently developed algorithm (Perczel, A., Tusnády, G., Hollósi, M., & Fasman, G.D., 1991b, Protein Eng. 4(6), 669-679). For the first time the results of a CD deconvolution, based on the CD spectra of 14 beta-turn models, were assigned by quantitative NOE results. The NOE experiments confirmed the ratios of the component curves found for the two major beta-turns by CD analysis. These results
Quantitative analysis of cyclic beta-turn models.
Perczel, A; Fasman, G D
1992-03-01
The beta-turn is a frequently found structural unit in the conformation of globular proteins. Although the circular dichroism (CD) spectra of the alpha-helix and beta-pleated sheet are well defined, there remains some ambiguity concerning the pure component CD spectra of the different types of beta-turns. Recently, it has been reported (Hollósi, M., Kövér, K.E., Holly, S., Radics, L., & Fasman, G.D., 1987, Biopolymers 26, 1527-1572; Perczel, A., Hollósi, M., Foxman, B.M., & Fasman, G.D., 1991a, J. Am. Chem. Soc. 113, 9772-9784) that some pseudohexapeptides (e.g., the cyclo[(delta)Ava-Gly-Pro-Aaa-Gly] where Aaa = Ser, Ser(OtBu), or Gly) in many solvents adopt a conformational mixture of type I and the type II beta-turns, although the X-ray-determined conformation was an ideal type I beta-turn. In addition to these pseudohexapeptides, conformational analysis was also carried out on three pseudotetrapeptides and three pseudooctapeptides. The target of the conformation analysis reported herein was to determine whether the ring stress of the above beta-turn models has an influence on their conformational properties. Quantitative nuclear Overhauser effect (NOE) measurements yielded interproton distances. The conformational average distances so obtained were interpreted utilizing molecular dynamics (MD) simulations to yield the conformational percentages. These conformational ratios were correlated with the conformational weights obtained by quantitative CD analysis of the same compounds. The pure component CD curves of type I and type II beta-turns were also obtained, using a recently developed algorithm (Perczel, A., Tusnády, G., Hollósi, M., & Fasman, G.D., 1991b, Protein Eng. 4(6), 669-679). For the first time the results of a CD deconvolution, based on the CD spectra of 14 beta-turn models, were assigned by quantitative NOE results. The NOE experiments confirmed the ratios of the component curves found for the two major beta-turns by CD analysis. These results
Fermions as generalized Ising models
NASA Astrophysics Data System (ADS)
Wetterich, C.
2017-04-01
We establish a general map between Grassmann functionals for fermions and probability or weight distributions for Ising spins. The equivalence between the two formulations is based on identical transfer matrices and expectation values of products of observables. The map preserves locality properties and can be realized for arbitrary dimensions. We present a simple example where a quantum field theory for free massless Dirac fermions in two-dimensional Minkowski space is represented by an asymmetric Ising model on a euclidean square lattice.
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.
Generalized waste package containment model
Liebetrau, A.M.; Apted, M.J.
1985-02-01
The US Department of Energy (DOE) is developing a performance assessment strategy to demonstrate compliance with standards and technical requirements of the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC) for the permanent disposal of high-level nuclear wastes in geologic repositories. One aspect of this strategy is the development of a unified performance model of the entire geologic repository system. Details of a generalized waste package containment (WPC) model and its relationship with other components of an overall repository model are presented in this paper. The WPC model provides stochastically determined estimates of the distributions of times-to-failure of the barriers of a waste package by various corrosion mechanisms and degradation processes. The model consists of a series of modules which employ various combinations of stochastic (probabilistic) and mechanistic process models, and which are individually designed to reflect the current state of knowledge. The WPC model is designed not only to take account of various site-specific conditions and processes, but also to deal with a wide range of site, repository, and waste package configurations. 11 refs., 3 figs., 2 tabs.
General O-glycosylation of 2-furfuryl alcohol using beta-glucuronidase.
Martin, Brett D; Welsh, Eric R; Mastrangelo, Jonathan C; Aggarwal, Renu
2002-10-20
beta-Glucuronidase from bovine liver is able to catalyze transfer of several carbohydrates to furfuryl alcohol, an acid-sensitive diene, with transfer yields as high as 84%. Carbohydrates that were transferred in yields of 30% or higher include gluco-, galacto-, xylo-, and fucopyranose. Small variations in the configuration of the substrate hydroxyls lead to large variations in the catalytic behavior of the enzyme in terms of both the initial reaction velocities and the final ratios of transfer-to-hydrolysis. The high transfer yields and surprising nonspecificity towards carbohydrate suggest that the enzyme may be a versatile tool for the general O-glycosylation of dienic alcohols.
Estimating Litter Decomposition Rate in Single-Pool Models Using Nonlinear Beta Regression
Laliberté, Etienne; Adair, E. Carol; Hobbie, Sarah E.
2012-01-01
Litter decomposition rate (k) is typically estimated from proportional litter mass loss data using models that assume constant, normally distributed errors. However, such data often show non-normal errors with reduced variance near bounds (0 or 1), potentially leading to biased k estimates. We compared the performance of nonlinear regression using the beta distribution, which is well-suited to bounded data and this type of heteroscedasticity, to standard nonlinear regression (normal errors) on simulated and real litter decomposition data. Although the beta model often provided better fits to the simulated data (based on the corrected Akaike Information Criterion, AICc), standard nonlinear regression was robust to violation of homoscedasticity and gave equally or more accurate k estimates as nonlinear beta regression. Our simulation results also suggest that k estimates will be most accurate when study length captures mid to late stage decomposition (50–80% mass loss) and the number of measurements through time is ≥5. Regression method and data transformation choices had the smallest impact on k estimates during mid and late stage decomposition. Estimates of k were more variable among methods and generally less accurate during early and end stage decomposition. With real data, neither model was predominately best; in most cases the models were indistinguishable based on AICc, and gave similar k estimates. However, when decomposition rates were high, normal and beta model k estimates often diverged substantially. Therefore, we recommend a pragmatic approach where both models are compared and the best is selected for a given data set. Alternatively, both models may be used via model averaging to develop weighted parameter estimates. We provide code to perform nonlinear beta regression with freely available software. PMID:23049771
Modeling the mechanism of CLN025 beta-hairpin formation.
McKiernan, Keri A; Husic, Brooke E; Pande, Vijay S
2017-09-14
Beta-hairpins are substructures found in proteins that can lend insight into more complex systems. Furthermore, the folding of beta-hairpins is a valuable test case for benchmarking experimental and theoretical methods. Here, we simulate the folding of CLN025, a miniprotein with a beta-hairpin structure, at its experimental melting temperature using a range of state-of-the-art protein force fields. We construct Markov state models in order to examine the thermodynamics, kinetics, mechanism, and rate-determining step of folding. Mechanistically, we find the folding process is rate-limited by the formation of the turn region hydrogen bonds, which occurs following the downhill hydrophobic collapse of the extended denatured protein. These results are presented in the context of established and contradictory theories of the beta-hairpin folding process. Furthermore, our analysis suggests that the AMBER-FB15 force field, at this temperature, best describes the characteristics of the full experimental CLN025 conformational ensemble, while the AMBER ff99SB-ILDN and CHARMM22* force fields display a tendency to overstabilize the native state.
Modeling the mechanism of CLN025 beta-hairpin formation
NASA Astrophysics Data System (ADS)
McKiernan, Keri A.; Husic, Brooke E.; Pande, Vijay S.
2017-09-01
Beta-hairpins are substructures found in proteins that can lend insight into more complex systems. Furthermore, the folding of beta-hairpins is a valuable test case for benchmarking experimental and theoretical methods. Here, we simulate the folding of CLN025, a miniprotein with a beta-hairpin structure, at its experimental melting temperature using a range of state-of-the-art protein force fields. We construct Markov state models in order to examine the thermodynamics, kinetics, mechanism, and rate-determining step of folding. Mechanistically, we find the folding process is rate-limited by the formation of the turn region hydrogen bonds, which occurs following the downhill hydrophobic collapse of the extended denatured protein. These results are presented in the context of established and contradictory theories of the beta-hairpin folding process. Furthermore, our analysis suggests that the AMBER-FB15 force field, at this temperature, best describes the characteristics of the full experimental CLN025 conformational ensemble, while the AMBER ff99SB-ILDN and CHARMM22* force fields display a tendency to overstabilize the native state.
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.
USDA-ARS?s Scientific Manuscript database
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/...
Ingelido, Anna Maria; Abballe, Annalisa; Marra, Valentina; Valentini, Silvia; Ferro, Annamaria; Porpora, Maria Grazia; Barbieri, Pietro Gino; De Felip, Elena
2009-01-01
Because of its persistence and toxicological profile, beta-hexachlorocyclohexane (beta-HCH) has been proposed for inclusion in the Stockholm Convention on persistent organic pollutants (POPs). Although the use of technical HCH, which is the primary source of beta-HCH in the environment, has been banned in the EU in 1978 and progressively at a global level, beta-HCH is still detectable in the general environment worldwide. Human exposure mostly occurs via food and may be of concern in areas where illegal use and/or improper disposal of stockpiles occurred and locally grown food is consumed. Exposure of the Italian general population to beta-HCH has been poorly characterised. Lack of human biomonitoring data severely hinders the ability to interpret potential increases in exposure related to situations of environmental risk. We carried out a human biomonitoring study aimed to provide baseline information on background exposure of the Italian general population to this pollutant. For this purpose, we analysed 116 serum samples from groups of subjects of both sex from the general population residing in three Italian towns at different latitudes. Serum concentrations of beta-HCH resulted to be comprised between 1.64 and 300 ng/g fat, with a median value of 18.0 ng/g fat and a 90th percentile of 65.9 ng/g fat. The serum concentrations detected are in line with those detected in most Western European countries.
Guidelines for Use of the Approximate Beta-Poisson Dose-Response Model.
Xie, Gang; Roiko, Anne; Stratton, Helen; Lemckert, Charles; Dunn, Peter K; Mengersen, Kerrie
2016-10-05
For dose-response analysis in quantitative microbial risk assessment (QMRA), the exact beta-Poisson model is a two-parameter mechanistic dose-response model with parameters α>0 and β>0, which involves the Kummer confluent hypergeometric function. Evaluation of a hypergeometric function is a computational challenge. Denoting PI(d) as the probability of infection at a given mean dose d, the widely used dose-response model PI(d)=1-(1+dβ)-α is an approximate formula for the exact beta-Poisson model. Notwithstanding the required conditions α<β and β>1, issues related to the validity and approximation accuracy of this approximate formula have remained largely ignored in practice, partly because these conditions are too general to provide clear guidance. Consequently, this study proposes a probability measure Pr(0 < r < 1 | α̂, β̂) as a validity measure (r is a random variable that follows a gamma distribution; α̂ and β̂ are the maximum likelihood estimates of α and β in the approximate model); and the constraint conditions β̂>(22α̂)0.50 for 0.02<α̂<2 as a rule of thumb to ensure an accurate approximation (e.g., Pr(0 < r < 1 | α̂, β̂) >0.99) . This validity measure and rule of thumb were validated by application to all the completed beta-Poisson models (related to 85 data sets) from the QMRA community portal (QMRA Wiki). The results showed that the higher the probability Pr(0 < r < 1 | α̂, β̂), the better the approximation. The results further showed that, among the total 85 models examined, 68 models were identified as valid approximate model applications, which all had a near perfect match to the corresponding exact beta-Poisson model dose-response curve.
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.
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.
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
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.
Shell model analysis of the neutrinoless double-{beta} decay of {sup 48}Ca
Horoi, Mihai; Stoica, Sabin
2010-02-15
The neutrinoless double-{beta} (0{nu}{beta}{beta}) decay process could provide crucial information to determine the absolute scale of neutrino masses, and it is the only one that can establish whether a neutrino is a Dirac or a Majorana particle. A key ingredient for extracting the absolute neutrino masses from 0{nu}{beta}{beta} decay experiments is a precise knowledge of the nuclear matrix elements (NMEs) describing the half-life of this process. We developed a shell model approach for computing the 0{nu}{beta}{beta} decay NME, and we used it to analyze the 0{nu}{beta}{beta} mode of {sup 48}Ca. The dependence of the NME on the short-range correlation parameters, on the average energy of the intermediate states, on the finite-size cutoff parameters, and on the effective interaction used for many-body calculations is discussed.
The nature and structure of correlations among Big Five ratings: the halo-alpha-beta model.
Anusic, Ivana; Schimmack, Ulrich; Pinkus, Rebecca T; Lockwood, Penelope
2009-12-01
In light of consistently observed correlations among Big Five ratings, the authors developed and tested a model that combined E. L. Thorndike's (1920) general evaluative bias (halo) model and J. M. Digman's (1997) higher order personality factors (alpha and beta) model. With 4 multitrait-multimethod analyses, Study 1 revealed moderate convergent validity for alpha and beta across raters, whereas halo was mainly a unique factor for each rater. In Study 2, the authors showed that the halo factor was highly correlated with a validated measure of evaluative biases in self-ratings. Study 3 showed that halo is more strongly correlated with self-ratings of self-esteem than self-ratings of the Big Five, which suggests that halo is not a mere rating bias but actually reflects overly positive self-evaluations. Finally, Study 4 demonstrated that the halo bias in Big Five ratings is stable over short retest intervals. Taken together, the results suggest that the halo-alpha-beta model integrates the main findings in structural analyses of Big Five correlations. Accordingly, halo bias in self-ratings is a reliable and stable bias in individuals' perceptions of their own attributes. Implications of the present findings for the assessment of Big Five personality traits in monomethod studies are discussed.
Generalized complex geometry, generalized branes and the Hitchin sigma model
NASA Astrophysics Data System (ADS)
Zucchini, Roberto
2005-03-01
Hitchin's generalized complex geometry has been shown to be relevant in compactifications of superstring theory with fluxes and is expected to lead to a deeper understanding of mirror symmetry. Gualtieri's notion of generalized complex submanifold seems to be a natural candidate for the description of branes in this context. Recently, we introduced a Batalin-Vilkovisky field theoretic realization of generalized complex geometry, the Hitchin sigma model, extending the well known Poisson sigma model. In this paper, exploiting Gualtieri's formalism, we incorporate branes into the model. A detailed study of the boundary conditions obeyed by the world sheet fields is provided. Finally, it is found that, when branes are present, the classical Batalin-Vilkovisky cohomology contains an extra sector that is related non trivially to a novel cohomology associated with the branes as generalized complex submanifolds.
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.
You, Tony J; Maxwell, David S; Kogan, Timothy P; Chen, Qi; Li, Jian; Kassir, Jamal; Holland, George W; Dixon, Richard A F
2002-01-01
It is well established that integrin alpha 4 beta 1 binds to the vascular cell adhesion molecule (VCAM) and fibronectin and plays an important role in signal transduction. Blocking the binding of VCAM to alpha 4 beta 1 is thought to be a way of controlling a number of disease processes. To better understand how various inhibitors might block the interaction of VCAM and fibronectin with alpha 4 beta 1, we began constructing a structure model for the integrin alpha 4 beta 1 complex. As the first step, we have built a homology model of the beta 1 subunit based on the I domain of the integrin CD11B subunit. The model, including a bound Mg(2+) ion, was optimized through a specially designed relaxation scheme involving restrained minimization and dynamics steps. The native ligand VCAM and two highly active small molecules (TBC772 and TBC3486) shown to inhibit binding of CS-1 and VCAM to alpha 4 beta 1 were docked into the active site of the refined model. Results from the binding analysis fit well with a pharmacophore model that was independently derived from active analog studies. A critical examination of residues in the binding site and analysis of docked ligands that are both potent and selective led to the proposal of a mechanism for beta 1/beta 7 ligand binding selectivity. PMID:11751331
Blatov, Vladislav A; Ilyushin, Gregory D; Proserpio, Davide M
2010-02-15
A novel method for the computational description of intermetallics as an assembly of nanoclusters was improved and applied to extremely complicated crystal structures of beta, beta'-Mg(2)Al(3) polymorphs. Using the TOPOS program package that implements the method, we separated two types of two-shell primary nanoclusters A, A1, A2, and B consisting of 57-63 atoms that completely compose the structures of the polymorphs. The nanocluster model interprets structural disordering in beta-Mg(2)Al(3): the disordered atoms form the inner shell of the nanocluster A, while the outer shells of all nanoclusters are preserved. The self-assembly of the beta, beta'-Mg(2)Al(3) crystal structures was considered within the hierarchical scheme: 0D primary polyhedral clusters (coordination polyhedra) --> 0D two-shell primary nanoclusters A, A1, A2, or B --> 0D supracluster-precursor AB(2) --> 1D primary chain --> 2D microlayer --> 3D microframework. The self-assembly scheme proves the similarity of beta, beta'-Mg(2)Al(3) to other extremely complicated Samson's phases, NaCd(2) and ZrZn(22); the spatial arrangement of the centers of nanoclusters in these structures as well as the topology of the corresponding network conform to the Laves phase MgCu(2). Using the TOPOS procedure of searching for finite fragments in infinite nets we found that nanocluster B is a typical fragment of intermetallic compounds: it exists in intermetallics belonging to 42 Pearson classes. The nanocluster A was found only in two Pearson classes: cF464 and hP238, while the nanoclusters A1 and A2 occur in beta'-Mg(2)Al(3) only. Thus, the nanoclusters A, A1, and A2 can be considered as "determinants" of the corresponding structures.
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
Neuroprotective effects of thymosin beta4 in experimental models of excitotoxicity.
Popoli, Patrizia; Pepponi, Rita; Martire, Alberto; Armida, Monica; Pèzzola, Antonella; Galluzzo, Mariangela; Domenici, M Rosaria; Potenza, Rosa Luisa; Tebano, M Teresa; Mollinari, Cristiana; Merlo, Daniela; Garaci, Enrico
2007-09-01
The aim of this study was to evaluate the possible neuroprotective effects of thymosin beta(4) in different models of excitotoxicity. The application of thymosin beta(4) significantly attenuated glutamate-induced toxicity both in primary cultures of cortical neurons and in rat hippocampal slices. In in vivo experiments, the intracerebroventricular administration of thymosin beta(4) significantly reduced hippocampal neuronal loss induced by kainic acid. These results show that thymosin beta(4) induced a protective effect in models of excitotoxicity. The mechanisms underlying such an effect, as well as the real neuroprotective potential of thymosin beta(4), are worthy of further investigations.
Standard Model and Beyond with Neutron Beta Decay Experiments
NASA Astrophysics Data System (ADS)
Liu, Jianglai
2010-11-01
The underlying charge-current weak interaction of the neutron beta decay connects together the Fermi constant GF, CKM matrix element Vud, the nucleon axial weak coupling constant gA, and the free neutron life time τn. Consequently, the combination of direct measurements of these provides stringent constraints to the Standard Model. At present, GF and Vud have been measured to a precision of 5 ppm and 225 ppm, respectively, whereas the data in gA and τn are less precise, and both exhibit significant inconsistency among measurements. With polarized neutrons, gA can be determined by measuring the angular correlation of the decay electrons with the neutron spin (so-called β-asymmetry). In the past, β-asymmetry have been measured in the cold neutron beam experiments, yielding a range of results much wider than the reported uncertainties. A new β-asymmetry measurement, UCNA (Ultracold Neutron Asymmetry), has been developed using the solid deuterium pulse spallation ultracold neutron (UCN) source at the Los Alamos Neutron Science Center, where UCN are transported in a guide system, fully polarized, then loaded into a decay trap within a solenoidal beta spectrometer. Utilizing UCN give this experiment very different systematics compared to cold neutron experiments. In this talk, I will give a brief review of the neutron beta decay measurements on the angular correlations as well as the life time. The main focus of this talk will be on the UCNA experiment. I will discuss the experimental techniques, and present the new results from the data in 2008 and 2009. The implication of the new results, combined with the world data on β-asymmetry, Vud, and τn, will also be discussed.
A generalized mechanistic codon model.
Zaheri, Maryam; Dib, Linda; Salamin, Nicolas
2014-09-01
Models of codon evolution have attracted particular interest because of their unique capabilities to detect selection forces and their high fit when applied to sequence evolution. We described here a novel approach for modeling codon evolution, which is based on Kronecker product of matrices. The 61 × 61 codon substitution rate matrix is created using Kronecker product of three 4 × 4 nucleotide substitution matrices, the equilibrium frequency of codons, and the selection rate parameter. The entities of the nucleotide substitution matrices and selection rate are considered as parameters of the model, which are optimized by maximum likelihood. Our fully mechanistic model allows the instantaneous substitution matrix between codons to be fully estimated with only 19 parameters instead of 3,721, by using the biological interdependence existing between positions within codons. We illustrate the properties of our models using computer simulations and assessed its relevance by comparing the AICc measures of our model and other models of codon evolution on simulations and a large range of empirical data sets. We show that our model fits most biological data better compared with the current codon models. Furthermore, the parameters in our model can be interpreted in a similar way as the exchangeability rates found in empirical codon models. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Generalized exponential function and discrete growth models
NASA Astrophysics Data System (ADS)
Souto Martinez, Alexandre; Silva González, Rodrigo; Lauri Espíndola, Aquino
2009-07-01
Here we show that a particular one-parameter generalization of the exponential function is suitable to unify most of the popular one-species discrete population dynamic models into a simple formula. A physical interpretation is given to this new introduced parameter in the context of the continuous Richards model, which remains valid for the discrete case. From the discretization of the continuous Richards’ model (generalization of the Gompertz and Verhulst models), one obtains a generalized logistic map and we briefly study its properties. Notice, however that the physical interpretation for the introduced parameter persists valid for the discrete case. Next, we generalize the (scramble competition) θ-Ricker discrete model and analytically calculate the fixed points as well as their stabilities. In contrast to previous generalizations, from the generalized θ-Ricker model one is able to retrieve either scramble or contest models.
Taylor, Rebecca C; Pagliarello, Giuseppe
2003-06-01
The benefit of administering beta-adrenergic blocking agents perioperatively to surgical patients at high risk for myocardial ischemia has been demonstrated in several well-designed randomized controlled trials. These benefits have included a reduction in the incidence of myocardial complications and an improvement in overall survival for patients with evidence of or at risk for coronary artery disease (CAD). We designed a retrospective study at the Ottawa Civic Hospital to investigate the use of beta-blockers in the perioperative period for high-risk general surgery patients who underwent laparotomy and to explore the reasons for failure to prescribe or administer beta-blockers when indicated. All 236 general surgery patients over the age of 50 years who underwent laparotomy for major gastrointestinal surgery between Jan. 1, 2001, and Dec. 31, 2001, were assigned a cardiac risk classification using the risk stratification described by Mangano and colleagues. The perioperative prescription and administration of beta-blockers were noted as were the patient's heart rate and blood pressure parameters for the first postoperative week, in-hospital adverse cardiac events and death. Of the 143 patients classified as being at risk for CAD or having definite evidence of CAD, 87 (60.8%) did not receive beta-blockers perioperatively. Of those who did, 43 were previously on beta-blockers and 13 had them ordered preoperatively. Patients with definite CAD were significantly more likely than others to receive beta-blockers perioperatively (p < 0.001), as were patients seen by an anesthesiologist or an internist preoperatively (p < 0.001). Twenty (33%) of the 61 patients who were already taking beta-blockers preoperatively had them inappropriately discontinued postoperatively. Once prescribed by the physician, beta-blockers were administered by the nurses irrespective of nil par os status. The mean heart rate and blood pressure parameters for patients receiving beta
Concellón, José M; Rodríguez-Solla, Humberto; Simal, Carmen; Santos, David; Paz, Nieves R
2008-10-16
A method to obtain (Z)-beta,gamma-unsaturated nitriles in high or good yields and with moderate or high stereoselectivity is described. The products were achieved through the photoinduced metalation of 3-acetoxy-4-chloronitriles with SmI2. The starting compounds were readily prepared, and a mechanism is proposed to explain this stereoselective beta-elimination reaction.
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.
LLNL Ocean General Circulation Model
Wickett, M. E.; Caldeira, K.; Duffy, P.
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.
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.
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.
Miller, Clark A; Gellman, Samuel H; Abbott, Nicholas L; de Pablo, Juan J
2008-10-01
Synthetic beta-peptide oligomers have been shown to form stable folded structures analogous to those encountered in naturally occurring proteins. Literature studies have speculated that the conformational stability of beta-peptides is greater than that of alpha-peptides. Direct measurements of that stability, however, are not available. Molecular simulations are used in this work to quantify the mechanical stability of four helical beta-peptides. This is achieved by subjecting the molecules to tension. The potential of mean force associated with the resulting unfolding process is determined using both an implicit and an explicit solvent model. It is found that all four molecules exhibit a highly stable helical structure. It is also found that the energetic contributions to the potential of mean force do not change appreciably when the molecules are stretched in explicit water. In contrast, the entropic contributions decrease significantly. As the peptides unfold, a loss of intramolecular energy is compensated by the formation of additional water-peptide hydrogen bonds. These entropic effects lead in some cases to a loss of stability upon cooling the peptides, a phenomenon akin to the cold denaturing of some proteins. While the location of the free energy minimum and the structural helicity of the peptides are comparable in the implicit-solvent and explicit-water cases, it is found that, in general, the helical structure of the molecules is more stable in the implicit solvent model than in explicit water.
The stochastic general epidemic model revisited and a generalization.
Billard, L; Zhao, Z
1993-01-01
While the mathematical theory of epidemics has its origins with Ross (1911), it was not until Kryscio (1975) that explicit expressions for the state probabilities of the classical general epidemic model established by Bartlett (1949) were found. However, these formulae were of limited practical use when the population size was of even moderate size. By shifting the focus from the bivariate pair representing the number of susceptibles and infectives to that for the number of infectives and removals, one is able to obtain solutions that are considerably simpler and easier to manage than those previously derived and which are not restricted by the size of the population. The results are obtained for a generalized general epidemic process in which transition probabilities are arbitrary functions of the state space, and then applied to the classical model. An extension to time-dependent transition rates is also considered.
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.
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.
Zhu, Xiao; Koenig, Peter; Gellman, Samuel H; Yethiraj, Arun; Cui, Qiang
2008-05-01
All-atom molecular mechanical (MM) force field parameters are developed for a cyclic beta-amino acid, amino-cyclo-pentane-carboxylic acid (ACPC), using a multi-objective evolutionary algorithm. The MM model is benchmarked using several short, ACPC-containing alpha/beta-peptides in water and methanol with SCC-DFTB (self consistent charge-density functional tight binding)/MM simulations as the reference. Satisfactory agreements are found between the MM and SCC-DFTB/MM results regarding the distribution of key dihedral angles for the tetra-alpha/beta-peptide in water. For the octa-alpha/beta-peptide in methanol, the MM and SCC-DFTB/MM simulations predict the 11- and 14/15-helical form as the more stable conformation, respectively; however, the two helical forms are very close in energy (2-4 kcal/mol) at both theoretical levels, which is also the conclusion from recent NMR experiments. As the first application, the MM model is applied to an alpha/beta-pentadeca-peptide in water with both explicit and implicit solvent models. The stability of the peptide is sensitive to the starting configuration in the explicit solvent simulations due to their limited length ( approximately 10-40 ns). Multiple ( approximately 20 x 20 ns) implicit solvent simulations consistently show that the 14/15-helix is the predominant conformation of this peptide, although substantially different conformations are also accessible. The calculated nuclear Overhauser effect (NOE) values averaged over different trajectories are consistent with experimental data, which emphasizes the importance of considering conformational heterogeneity in such comparisons for highly dynamical peptides.
Vector models and generalized SYK models
NASA Astrophysics Data System (ADS)
Peng, Cheng
2017-05-01
We consider the relation between SYK-like models and vector models by studying a toy model where a tensor field is coupled with a vector field. By integrating out the tensor field, the toy model reduces to the Gross-Neveu model in 1 dimension. On the other hand, a certain perturbation can be turned on and the toy model flows to an SYK-like model at low energy. A chaotic-nonchaotic phase transition occurs as the sign of the perturbation is altered. We further study similar models that possess chaos and enhanced reparameterization symmetries.
Vector models and generalized SYK models
Peng, Cheng
2017-05-23
Here, we consider the relation between SYK-like models and vector models by studying a toy model where a tensor field is coupled with a vector field. By integrating out the tensor field, the toy model reduces to the Gross-Neveu model in 1 dimension. On the other hand, a certain perturbation can be turned on and the toy model flows to an SYK-like model at low energy. Furthermore, a chaotic-nonchaotic phase transition occurs as the sign of the perturbation is altered. We further study similar models that possess chaos and enhanced reparameterization symmetries.
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.
Extended Generalized Linear Latent and Mixed Model
ERIC Educational Resources Information Center
Segawa, Eisuke; Emery, Sherry; Curry, Susan J.
2008-01-01
The generalized linear latent and mixed modeling (GLLAMM framework) includes many models such as hierarchical and structural equation models. However, GLLAMM cannot currently accommodate some models because it does not allow some parameters to be random. GLLAMM is extended to overcome the limitation by adding a submodel that specifies 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.
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.
Schmieder, Anne H; Caruthers, Shelton D; Zhang, Huiying; Williams, Todd A; Robertson, J David; Wickline, Samuel A; Lanza, Gregory M
2008-12-01
Our objectives were 1) to characterize angiogenesis in the MDA-MB-435 xenograft mouse model with three-dimensional (3D) MR molecular imaging using alpha(5)beta(1)(RGD)- or irrelevant RGS-targeted paramagnetic nanoparticles and 2) to use MR molecular imaging to assess the antiangiogenic effectiveness of alpha(5)beta(1)(alpha(nu)beta(3))- vs. alpha(nu)beta(3)-targeted fumagillin (50 mug/kg) nanoparticles. Tumor-bearing mice were imaged with MR before and after administration of either alpha(5)beta(1)(RGD) or irrelevant RGS-paramagnetic nanoparticles. In experiment 2, mice received saline or alpha(5)beta(1)(alpha(nu)beta(3))- or alpha(nu)beta(3)-targeted fumagillin nanoparticles on days 7, 11, 15, and 19 posttumor implant. On day 22, MRI was performed using alpha(5)beta(1)(alpha(nu)beta(3))-targeted paramagnetic nanoparticles to monitor the antiangiogenic response. 3D reconstructions of alpha(5)beta(1)(RGD)-signal enhancement revealed a sparse, asymmetrical pattern of angiogenesis along the tumor periphery, which occupied <2.0% tumor surface area. alpha(5)beta(1)-targeted rhodamine nanoparticles colocalized with FITC-lectin corroborated the peripheral neovascular signal. alpha(5)beta(1)(alpha(nu)beta(3))-fumagillin nanoparticles decreased neovasculature to negligible levels relative to control; alpha(nu)beta(3)-targeted fumagillin nanoparticles were less effective (P>0.05). Reduction of angiogenesis in MDA-MB-435 tumors from low to negligible levels did not decrease tumor volume. MR molecular imaging may be useful for characterizing tumors with sparse neovasculature that are unlikely to have a reduced growth response to targeted antiangiogenic therapy.
Anisotropic Generalized Ghost Pilgrim Dark Energy Model in General Relativity
NASA Astrophysics Data System (ADS)
Santhi, M. Vijaya; Rao, V. U. M.; Aditya, Y.
2017-02-01
A spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type- I Universe filled with matter and generalized ghost pilgrim dark energy (GGPDE) has been studied in general theory of relativity. To obtain determinate solution of the field equations we have used scalar expansion proportional to the shear scalar which leads to a relation between the metric potentials. Some well-known cosmological parameters (equation of state (EoS) parameter ( ω Λ), deceleration parameter ( q) and squared speed of sound {vs2}) and planes (ω _{Λ }-dot {ω }_{Λ } and statefinder) are constructed for obtained model. The discussion and significance of these parameters is totally done through pilgrim dark energy parameter ( β) and cosmic time ( t).
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
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.
A General Model for Free Response Data
ERIC Educational Resources Information Center
Samejima, Fumiko
1972-01-01
This paper proposes a general model for free-response data collected for measuring a specified unidimensional psychological process; systematizes situations which vary with respect to the scoring level of items; and finds out general conditions for the operating characteristic of an item response category to provide a unique maximum likelihood…
Percolation on general trees and HIV modeling
NASA Astrophysics Data System (ADS)
Ahmed, E.; Agiza, H. N.
1996-12-01
Percolation on a general tree is studied. A general tree is used to model the transition from HIV infection into AIDS and to explain the large differences of the transition time from one patient to another. HIV has some autoimmune effects due to its low antigenic mutants. Fuzzy mathematics is used to explain these effects.
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.
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
Bayesian inferences for beta semiparametric-mixed models to analyze longitudinal neuroimaging data.
Wang, Xiao-Feng; Li, Yingxing
2014-07-01
Diffusion tensor imaging (DTI) is a quantitative magnetic resonance imaging technique that measures the three-dimensional diffusion of water molecules within tissue through the application of multiple diffusion gradients. This technique is rapidly increasing in popularity for studying white matter properties and structural connectivity in the living human brain. One of the major outcomes derived from the DTI process is known as fractional anisotropy, a continuous measure restricted on the interval (0,1). Motivated from a longitudinal DTI study of multiple sclerosis, we use a beta semiparametric-mixed regression model for the neuroimaging data. This work extends the generalized additive model methodology with beta distribution family and random effects. We describe two estimation methods with penalized splines, which are formalized under a Bayesian inferential perspective. The first one is carried out by Markov chain Monte Carlo (MCMC) simulations while the second one uses a relatively new technique called integrated nested Laplace approximation (INLA). Simulations and the neuroimaging data analysis show that the estimates obtained from both approaches are stable and similar, while the INLA method provides an efficient alternative to the computationally expensive MCMC method.
A generalized model for coincidence counting
Lu, Ming-Shih; Teichmann, T.
1993-12-31
A generalized model for coincidence counting has been developed based on the dual probability generating function introduced. The model accounts explicitly and simultaneously the effects of multiplication, absorption by poison and instrument detection and is applicable for a wide class of NDA including Pu in waste.
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
Citrobacter diversus ULA-27 beta-lactamases. Improved purification and general properties.
Amicosante, G; Oratore, A; Franceschini, N; Maccarrone, M; Strom, R; Galleni, M; Frère, J M
1988-01-01
Two chromosome-encoded beta-lactamases have been purified from Citrobacter diversus ULA-27. They exhibited slightly different isoelectric points (6.8 and 6.2) and very similar Mr values (congruent to 29,000). Their specificity spectrum was rather wide, since they hydrolysed some cephalosporins with kcat: values similar to those observed with the best penicillin substrates. Cloxacillin, methicillin and imipenem were hydrolysed very slowly. Hydrolysis of azthreonam could not be detected. Images Fig. 3. Fig. 4. PMID:3264152
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.
Vierling-Claassen, Dorea; Siekmeier, Peter; Stufflebeam, Steven; Kopell, Nancy
2009-01-01
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 GAD67 (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
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.
Semi-Parametric Generalized Linear Models.
1985-08-01
is nonsingular, upper triangular, and of full rank r. It is known (Dongarra et al., 1979) that G-1 FT is the Moore - Penrose inverse of L . Therefore... GENERALIZED LINEAR pq Mathematics Research Center University of Wisconsin-Madison 610 Walnut Street Madison, Wisconsin 53705 TI C August 1985 E T NOV 7 8...North Carolina 27709 -. -.. . - -.-. g / 6 O5’o UNIVERSITY OF WISCONSIN-MADISON MATHD4ATICS RESEARCH CENTER SD4I-PARAMETRIC GENERALIZED LINEAR MODELS
Interacting holographic generalized cosmic Chaplygin gas model
NASA Astrophysics Data System (ADS)
Naji, Jalil
2014-03-01
In this paper we consider a correspondence between the holographic dark energy density and interacting generalized cosmic Chaplygin gas energy density in flat FRW universe. Then, we reconstruct the potential of the scalar field which describe the generalized cosmic Chaplygin cosmology. In the special case we obtain time-dependent energy density and study cosmological parameters. We find stability condition of this model which is depend on cosmic parameter.
A Tailored Testing Model Employing the Beta Distribution and Conditional Difficulties
ERIC Educational Resources Information Center
Kalisch, Stanley J.
1974-01-01
A tailored testing model employing the beta distribution, whose mean equals the difficulty of an item and whose variance is approximately equal to the sampling variance of the item difficulty, and employing conditional item difficulties, is proposed. (Author)
Tritium beta decay, neutrino mass matrices, and interactions beyond the standard model
NASA Astrophysics Data System (ADS)
Stephenson, G. J., Jr.; Goldman, T.; McKellar, B. H. J.
2000-11-01
The interference of charge changing interactions, weaker than the V-A standard model (SM) interaction and having a different Lorentz structure, with that SM interaction, can, in principle, produce effects near the end point of the tritium beta decay spectrum which are of a different character from those produced by the purely kinematic effect of neutrino mass expected in the simplest extension of the SM. We show that the existence of more than one mass eigenstate can lead to interference effects at the end point that are stronger than those occurring over the entire spectrum. We discuss these effects both for the special case of Dirac neutrinos and the more general case of Majorana neutrinos and show that, for the present precision of the experiments, one formula should suffice to express the interference effects in all cases. Implications for ``sterile'' neutrinos are noted.
Generalized Sznajd model for opinion propagation.
Timpanaro, André M; Prado, Carmen P C
2009-08-01
In the last decade the Sznajd model has been successfully employed in modeling some properties and scale features of both proportional and majority elections. We propose a version of the Sznajd model with a generalized bounded confidence rule-a rule that limits the convincing capability of agents and that is essential to allow coexistence of opinions in the stationary state. With an appropriate choice of parameters it can be reduced to previous models. We solved this model both in a mean-field approach (for an arbitrary number of opinions) and numerically in a Barabási-Albert network (for three and four opinions), studying the transient and the possible stationary states. We built the phase portrait for the special cases of three and four opinions, defining the attractors and their basins of attraction. Through this analysis, we were able to understand and explain discrepancies between mean-field and simulation results obtained in previous works for the usual Sznajd model with bounded confidence and three opinions. Both the dynamical system approach and our generalized bounded confidence rule are quite general and we think it can be useful to the understanding of other similar models.
Lactose/beta-lactoglobulin interaction during storage of model whey powders.
Thomas, M E C; Scher, J; Desobry, S
2004-05-01
The objective of this study was to evaluate the presence or absence of interaction between lactose and beta-lactoglobulin during storage of model whey powders at different water activities (a(w)). Model whey powders were prepared by colyophilization of lactose with increasing quantities of beta-lactoglobulin. These colyophilized beta-lactoglobulin:lactose powders, assigned as BL powders, were stored from 0.11 to 0.95 a(w). The water sorption behavior of BL powders was studied gravimetrically, and the state of lactose was investigated using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Before storage, BL powders were amorphous. After storage, a loss of water was observed on moisture sorption isotherms of BL powders. It was related to the formation of lactose crystals, detected by DSC and SEM analysis, and to the structural collapse of the powders. Water loss due to lactose crystallization was shifted to higher a(w) with increasing beta-lactoglobulin content in BL powders. Moreover, kinetics of moisture sorption demonstrated that beta-lactoglobulin was also responsible for a slower crystallization process in BL powders. Then, the water sorption behavior of BL powders was very different from the behavior of the 2 compounds mixed after separate lyophilization. All these results pointed out interaction between lactose and beta-lactoglobulin, which appeared during lyophilization and still occurred during storage. This lactose/beta-lactoglobulin interaction stabilized model whey powders against lactose crystallization.
Distinct in vivo roles of caspase-8 in beta-cells in physiological and diabetes models.
Liadis, Nicole; Salmena, Leonardo; Kwan, Edwin; Tajmir, Panteha; Schroer, Stephanie A; Radziszewska, Anna; Li, Xie; Sheu, Laura; Eweida, Mohamed; Xu, Shilong; Gaisano, Herbert Y; Hakem, Razqallah; Woo, Minna
2007-09-01
Inadequate pancreatic beta-cell mass resulting from excessive beta-cell apoptosis is a key defect in type 1 and type 2 diabetes. Caspases are the major molecules involved in apoptosis; however, in vivo roles of specific caspases in diabetes are unclear. The purpose of this study is to examine the role of Caspase (Casp)8 in beta-cells in vivo. Using the Cre-loxP system, mice lacking Casp8 in beta-cells (RIPcre(+)Casp8(fl/fl) mice) were generated to address the role of Casp8 in beta-cells in physiological and diabetes models. We show that islets isolated from RIPcre(+)Casp8(fl/fl) mice were protected from Fas ligand (FasL)-and ceramide-induced cell death. Furthermore, RIPcre(+)Casp8(fl/fl) mice were protected from in vivo models of type 1 and type 2 diabetes. In addition to being the central mediator of apoptosis in diabetes models, we show that Casp8 is critical for maintenance of beta-cell mass under physiological conditions. With aging, RIPcre(+)Casp8(fl/fl) mice gradually develop hyperglycemia and a concomitant decline in beta-cell mass. Their islets display decreased expression of molecules involved in insulin/IGF-I signaling and show decreased pancreatic duodenal homeobox-1 and cAMP response element binding protein expression. At the level of individual islets, we observed increased insulin secretory capacity associated with increased expression of exocytotic proteins. Our results show distinct context-specific roles of Casp8 in physiological and disease states; Casp8 is essential for beta-cell apoptosis in type 1 and type 2 diabetes models and in regulating beta-cell mass and insulin secretion under physiological conditions.
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…
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…
Fragata, Mário; Dudekula, Subhan
2005-08-04
Electron transport through photosystem II, measured as oxygen evolution (OE), was investigated in isolated thylakoid membranes treated with beta-cyclodextrin (beta-CD, a cyclic oligosaccharide constituted of seven alpha-d-glucose residues linked by alpha-1,4 glycosidic bonds) and irradiated with white light of variable intensity. First, we found that the light-response curves of oxygen evolution are well fitted with a hyperbolic function, the shape of which is not affected by the beta-CD concentration. Second, we showed that under conditions of irradiation with white light of saturating intensity ( approximately 5000 mumol of photons/m(2).s) beta-CD enhances the oxygen evolution in the thylakoid membranes according to a sigmoid function displaying a sharp inflection point, or transition. Unexpectedely, this beta-CD effect is not observed at irradiances of less than approximately 300 mumol of photons/m(2).s. We attempted a theoretical analysis of the combined effect of irradiance and beta-CD concentration on oxygen evolution (OE(th)). For this purpose, the effect of irradiance (I) was modeled with a hyperbola (i) and the beta-CD concentration (C) contribution with a Hill equation, that is, a sigmoid function (ii). The mathematical simulations generated the following general expressions: (i) OE(th) = [OE(max)(0) G(1)(C)]I/[L(1/2)(0) G(2)(C) + I] and (ii) G(i)()(C) = 1 + p[C(n)()/(K(1/2)(n)() + C(n)())], where OE(max)(0) is the OE maximum (OE(max)) in the absence of beta-CD, L(1/2)(0) is the photon flux density giving OE(max)/2 in the absence of beta-CD, G(1)(C) or G(2)(C) is obtained from G(i)()(C) where i is 1 or 2, n is the Hill coefficient, p is a parameter to account for the beta-CD-mediated maximum OE increase, and K(1/2) is the beta-CD concentration giving half-maximal OE activity. The results of the calculations yielded the expression (iii) OE(th) = 151[1 + 3.3C(4.8)/(13.1(4.8) + C(4.8))]I/{97.5[1 + 5.2C(7.8)/(14.8(7.8) + C(7.8))] + I} which agrees well with
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.
Statefinder diagnostic for a generalized Proca model
NASA Astrophysics Data System (ADS)
Xi, Ping; Jing, Yun-Long; Lü, Wen-Dong; Zhai, Xiang-Hua
2017-09-01
In this paper, we apply the statefinder diagnostic on the cosmology in the framework of the generalized Proca theories with derivative self-interactions possessing three propagating physical degrees of freedom. We discuss the evolving trajectories of the statefinder parameters with the parameter n of this model recently fitted as n = 0.254 and n = 0.16 by use of the current observational data and find that some typical characteristic of the evolution of statefinder parameters makes the model distinguishable between n = 0.254 case and n = 0.16 case and also from other dark energy models.
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.
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.
A realistic model of neutrino masses with a large neutrinoless double beta decay rate
NASA Astrophysics Data System (ADS)
del Aguila, Francisco; Aparici, Alberto; Bhattacharya, Subhaditya; Santamaria, Arcadi; Wudka, Jose
2012-05-01
The minimal Standard Model extension with the Weinberg operator does accommodate the observed neutrino masses and mixing, but predicts a neutrinoless double beta (0 νββ) decay rate proportional to the effective electron neutrino mass, which can be then arbitrarily small within present experimental limits. However, in general 0 νββ decay can have an independent origin and be near its present experimental bound; whereas neutrino masses are generated radiatively, contributing negligibly to 0 νββ decay. We provide a realization of this scenario in a simple, well defined and testable model, with potential LHC effects and calculable neutrino masses, whose two-loop expression we derive exactly. We also discuss the connection of this model to others that have appeared in the literature, and remark on the significant differences that result from various choices of quantum number assignments and symmetry assumptions. In this type of models lepton flavor violating rates are also preferred to be relatively large, at the reach of foreseen experiments. Interestingly enough, in our model this stands for a large third mixing angle, {{si}}{{{n}}^{{2}}}{θ_{{{13}}}}{˜}}}{ > }}0.00{8} , when μ→ eee is required to lie below its present experimental limit.
NASA Astrophysics Data System (ADS)
Cho, Youngsong; Kim, Jae-Kwan; Ryu, Joonghyun; Won, Chung-In; Kim, Chong-Min; Kim, Donguk; Kim, Deok-Soo
Molecular shape is one of the most critical factors that determines molecular function. Therefore, it is frequently desirable to understand geometric characteristics of a molecule more precisely and efficiently. In this paper, we introduce the BetaMol, a molecular modeling, analysis, and visualization software based on the recent theory of the beta-complex and the quasi-triangulation that are derived from the Voronoi diagram of three-dimensional spherical atoms. The powerful features of the BetaMol are solely based on a unified, single framework of the mathematically rigorous and computationally efficient beta-complex theory. The BetaMol is implemented in the standard C++ language with OpenGL graphics library and freely available at Voronoi Diagram Research Center web site (http://voronoi.hanyang.ac.kr).
Chiriac, Anca Mirela; Wang, Youna; Schrijvers, Rik; Bousquet, Philippe Jean; Mura, Thibault; Molinari, Nicolas; Demoly, Pascal
2017-07-21
Beta-lactam antibiotics represent the main cause of allergic reactions to drugs, inducing both immediate and nonimmediate allergies. The diagnosis is well established, usually based on skin tests and drug provocation tests, but cumbersome. To design predictive models for the diagnosis of beta-lactam allergy, based on the clinical history of patients with suspicions of allergic reactions to beta-lactams. The study included a retrospective phase, in which records of patients explored for a suspicion of beta-lactam allergy (in the Allergy Unit of the University Hospital of Montpellier between September 1996 and September 2012) were used to construct predictive models based on a logistic regression and decision tree method; a prospective phase, in which we performed an external validation of the chosen models in patients with suspicion of beta-lactam allergy recruited from 3 allergy centers (Montpellier, Nîmes, Narbonne) between March and November 2013. Data related to clinical history and allergy evaluation results were retrieved and analyzed. The retrospective and prospective phases included 1991 and 200 patients, respectively, with a different prevalence of confirmed beta-lactam allergy (23.6% vs 31%, P = .02). For the logistic regression method, performances of the models were similar in both samples: sensitivity was 51% (vs 60%), specificity 75% (vs 80%), positive predictive value 40% (vs 57%), and negative predictive value 83% (vs 82%). The decision tree method reached a sensitivity of 29.5% (vs 43.5%), specificity of 96.4% (vs 94.9%), positive predictive value of 71.6% (vs 79.4%), and negative predictive value of 81.6% (vs 81.3%). Two different independent methods using clinical history predictors were unable to accurately predict beta-lactam allergy and replace a conventional allergy evaluation for suspected beta-lactam allergy. Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.
Neutrinoless double beta decay in the left-right symmetric models for linear seesaw
NASA Astrophysics Data System (ADS)
Gu, Pei-Hong
2016-09-01
In a class of left-right symmetric models for linear seesaw, a neutrinoless double beta decay induced by the left- and right-handed charged currents together will only depend on the breaking details of left-right and electroweak symmetries. This neutrinoless double beta decay can reach the experimental sensitivities if the right-handed charged gauge boson is below the 100TeV scale.
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.
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
Higher dimensional generalizations of the SYK model
NASA Astrophysics Data System (ADS)
Berkooz, Micha; Narayan, Prithvi; Rozali, Moshe; Simón, Joan
2017-01-01
We discuss a 1+1 dimensional generalization of the Sachdev-Ye-Kitaev model. The model contains N Majorana fermions at each lattice site with a nearest-neighbour hopping term. The SYK random interaction is restricted to low momentum fermions of definite chirality within each lattice site. This gives rise to an ordinary 1+1 field theory above some energy scale and a low energy SYK-like behavior. We exhibit a class of low-pass filters which give rise to a rich variety of hyperscaling behaviour in the IR. We also discuss another set of generalizations which describes probing an SYK system with an external fermion, together with the new scaling behavior they exhibit in the IR.
The ToI-beta transgenic mouse: a model to study the specific role of NF-kappaB in beta-cells.
Eldor, Roy; Baum, Ketty; Abel, Roy; Sever, Dror; Melloul, Danielle
2009-12-01
Type 1 diabetes is characterized by the infiltration of inflammatory cells into pancreatic islets of Langerhans, followed by the selective and progressive destruction of insulin-secreting beta-cells. Islet infiltrating leukocytes secrete cytokines including IL-1beta and IFN-gamma, which contribute to beta-cell death. In vitro evidence suggests that cytokine-induced activation of the transcription factor NF-kappaB is an important component of the signal triggering beta-cell apoptosis. To study the role of NF-kappaB in vivo we generated a transgenic mouse line expressing a degradation-resistant NF-kappaB protein inhibitor (DeltaNIkappaBalpha) and the luciferase gene, acting specifically in beta-cells, in an inducible and reversible manner, by using the tet-on regulation system. Using this new mouse model, termed the ToI-beta mouse (for Tet-Ondelta I kappaB in beta-cells) we have previously shown in vitro, that islets expressing the DeltaNIkappaBalpha protein were resistant to the deleterious effects of IL-1beta and IFN-gamma, as assessed by reduced NO production and beta-cell apoptosis. In vivo, a nearly complete protection against multiple low dose streptozocin-induced diabetes was observed, with reduced intra-islet lymphocytic infiltration. In the present study we demonstrate the tight regulated and reversible expression of the DeltaNIkappaBalpha transgene in the ToI-beta mouse model as well as the effect of its overexpression on glucose metabolism and insulin secretion. The results show a lack of effect of transgene induction on both in vivo glucose tolerance tests and in vitro islet insulin secretion and content. Furthermore, to prove the tight control of induction in the model, luciferase mediated light emission was only detected at constant levels in Dox-treated double transgenic mice or islets as well as in a model of islet transplantation. Upon removal of the inducing stimulus, complete reversal of both NF-kappaB inhibition and luciferase activity were
Two Simple Classes of Mastery Scores Based On the Beta-Binomial Model
ERIC Educational Resources Information Center
Huynh, Huynh
1977-01-01
A model for the setting of mastery cut scores is presented. The model, based on the beta-binomial test distribution, allows for hand calculation of cut scores. The model provides a simple way to explore the consequences of selecting a particular cut score. (Author/JKS)
Dhuique-Mayer, Claudie; Borel, Patrick; Reboul, Emmanuelle; Caporiccio, Bertrand; Besancon, Pierre; Amiot, Marie-Josèphe
2007-05-01
Beta-Cryptoxanthin (beta-CX), a provitaminic carotenoid of potential interest for health, is found principally in Citrus fruit in both free and esterified forms. Little is known about the intestinal absorption of beta-CX especially with regard to the esterified forms. The aim of this study was to evaluate the absorption of free and esterified beta-CX using simulated digestion coupled with the Caco-2 model. Bioaccessibility was investigated by measuring the transfer of carotenoids from different citrus juices into micelles using an in vitro digestion system. Then, carotenoid uptake was evaluated by adding carotenoid-rich micelles (from the in vitro digestion) or synthetic micelles (made from synthetic lipids and carotenoids purified from citrus juice) to human intestinal cells (Caco-2 TC7 clone). Our results showed that beta-cryptoxanthin esters (beta-CXE) were partially hydrolysed during the in vitro digestion. The bioaccessibility of free beta-CX measured was significantly higher (40 (SD 1.05) %) than that of beta-carotene (30 (SD 1.9) %) and beta-CXE (16 (SD 1.5) %). In the same way, the incorporation of free beta-CX (27 (SD 1.01) %) into synthetic micelles exceeded (P<0.05) that of beta-carotene (10 (SD 0.7) %) and beta-CXE (8.8 (SD 0.4) %). In the case of micelles from in vitro digestion, the uptake of beta-carotene, free beta-CX and beta-CXE forms by Caco-2 cells was 14.3 (SD 1.8), 3.9 (SD 1.3), and 0.7 (SD 0.08) % respectively. These results showed a preferential uptake by Caco-2 cells of beta-carotene and free beta-CX compared with the two esters of beta-CX.
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.
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
Influence of pH on complexing of model beta-d-glucans with zearalenone.
Yiannikouris, A; François, J; Poughon, L; Dussap, C G; Jeminet, G; Bertin, G; Jouany, J P
2004-12-01
Previous studies have shown that isolated beta-(1,3 and 1,6)-D-glucans and related alkali-extracted fractions from the cell wall of Saccharomyces cerevisiae are able to complex with zearalenone in vitro (affinity up to 50%) and thus may reduce the bioavailability of toxins in the digestive tract. The complexation mechanisms involve cooperative interaction between the two chemical entities that can be computed by Hill's model. Various linear or branched soluble or insoluble beta-D-glucans were evaluated to elucidate their roles in the adsorption mechanisms under three pH conditions (3.0, 6.0, and 8.0) found in the digestive tract. A constant quantity of each beta-D-glucans (1 mg/ml) was mixed at 39 degrees C with increasing amounts of zearalenone (2 to 100 microg/ml), and the amount of bound toxin was measured. Acidic and neutral conditions gave the highest affinity rates (64 to 77%) by beta-(1,3)-D-glucans, whereas alkaline conditions decreased adsorption except when beta-(1,6)-D-glucan side chains were branched on beta-(1,3)-D-glucans. Alkaline conditions appear to impede the active three dimensional conformation of beta-D-glucans and favor single helix and/or random coil structures. Study of the equilibrium between beta-D-glucan-bound and free toxins revealed that two types of chemical interactions occur during toxin complexation with beta-D-glucans, identified as weak chemical linkages such as hydrogen and van der Waals bonds.
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.
Pavlides, Alex; Hogan, S. John; Bogacz, Rafal
2015-01-01
In Parkinson’s disease, an increase in beta oscillations within the basal ganglia nuclei has been shown to be associated with difficulty in movement initiation. An important role in the generation of these oscillations is thought to be played by the motor cortex and by a network composed of the subthalamic nucleus (STN) and the external segment of globus pallidus (GPe). Several alternative models have been proposed to describe the mechanisms for generation of the Parkinsonian beta oscillations. However, a recent experimental study of Tachibana and colleagues yielded results which are challenging for all published computational models of beta generation. That study investigated how the presence of beta oscillations in a primate model of Parkinson’s disease is affected by blocking different connections of the STN-GPe circuit. Due to a large number of experimental conditions, the study provides strong constraints that any mechanistic model of beta generation should satisfy. In this paper we present two models consistent with the data of Tachibana et al. The first model assumes that Parkinsonian beta oscillation are generated in the cortex and the STN-GPe circuits resonates at this frequency. The second model additionally assumes that the feedback from STN-GPe circuit to cortex is important for maintaining the oscillations in the network. Predictions are made about experimental evidence that is required to differentiate between the two models, both of which are able to reproduce firing rates, oscillation frequency and effects of lesions carried out by Tachibana and colleagues. Furthermore, an analysis of the models reveals how the amplitude and frequency of the generated oscillations depend on parameters. PMID:26683341
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.
A generalized soft water acidification model
NASA Astrophysics Data System (ADS)
Nikolaidis, Nikolaos P.; Rajaram, Harihar; Schnoor, Jerald L.; Georgakakos, Konstantine P.
1988-12-01
A generalized soft water acidification model has been developed. The enhanced trickle-down (ETD) model is driven by precipitation, evaporation, acidity, sulfate, and chloride loading time series daily input data. The hydrologic component simulates snowmelt, interflow, overland flow, groundwater flow, frozen ground processes, seepage, and evapotranspiration. Physicochemical and biological processes that affect the alkalinity or sulfate balance and are included in the formulation are cation exchange, chemical weathering, sulfate sorption, and sulfate reduction. The system of 20 ordinary differential equations is solved by using a variable time step fourth-order predictor-corrector numerical scheme. Shown here is calibration of the ETD model for two lakes in the Adirondack Park of New York. ETD is relatively simple and requires limited input data, and yet it accounts for the predominant hydrologic and biochemical processes of the ecosystem.
Generalized soft-water acidification model
Nikolaidis, N.P.; Rajaram, H.; Schnoor, J.L.; Georgakakos, K.P.
1988-01-01
A generalized soft water acidification model has been developed. The enhanced trickle-down (ETD) model is driven by precipitation, evaporation, acidity, sulfate, and chloride loading time series daily input data. The hydrologic component simulates snowmelt, interflow, overland flow, groundwater flow, frozen ground processes, seepage, and evapotranspiration. Physicochemical and biological processes that affect the alkalinity or sulfate balance and are included in the formulation are cation exchange, chemical weathering, sulfate sorption, and sulfate reduction. The system of 20 ordinary differential equations is solved by using a variable time step fourth-order predictor-corrector numerical scheme. Shown here is calibration of the ETD model for two lakes in the Adirondack Park of New York. ETD is relatively simple and requires limited input data, and yet it accounts for the predominant hydrologic and biochemical processes of the ecosystem.
Statistical modeling approach for detecting generalized synchronization
NASA Astrophysics Data System (ADS)
Schumacher, Johannes; Haslinger, Robert; Pipa, Gordon
2012-05-01
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.
Generalized model of brushless dc generator
NASA Astrophysics Data System (ADS)
Vadher, V. V.; Kettleborough, J. Gordon; Smith, I. R.; Gerges, Wahid R.
1989-07-01
A generalized model is described for a brushless dc machine consisting of a multiphase synchronous machine with a full-wave bridge rectifier connected to its output terminals. The state-variable equations for the machine are suitable for numerical integration on a digital computer, and are assembled in a form which permits investigations to be made on the effects of different numbers of armature phase windings and different winding connections. The model has been used in both steady-state and transient studies on a number of generating units, with the detailed information which is provided being beneficial to design engineers. Comparisons presented between predicted and measured results illustrate the validity of the model and the mathematical techniques adopted, and confirm that accurate information on the performance of a brushless generator may be obtained prior to manufacture.
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.
Neutrinoless Double Beta Nuclear Matrix Elements Around Mass 80 in the Nuclear Shell Model
NASA Astrophysics Data System (ADS)
Yoshinaga, Naotaka; Higashiyama, Koji; Taguchi, Daisuke; Teruya, Eri
The observation of the neutrinoless double-beta decay can determine whether the neutrino is a Majorana particle or not. In its theoretical nuclear side it is particularly important to estimate three types of nuclear matrix elements, namely, Fermi (F), Gamow-Teller (GT), and tensor (T) types matrix elements. The shell model calculations and also the pair-truncated shell model calculations are carried out to check the model dependence on nuclear matrix elements. In this work the neutrinoless double-beta decay for mass A = 82 nuclei is studied. It is found that the matrix elements are quite sensitive to the ground state wavefunctions.
Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-15
... Company (Robinson) Model R22, R22 Alpha, R22 Beta, and R22 Mariner Helicopters, and Model R44, and R44 II...). SUMMARY: This document proposes adopting a new airworthiness directive (AD) for Robinson Model R22, R22 Alpha, R22 Beta, and R22 Mariner helicopters, and Model R44 and R44 II helicopters. The AD would...
Some Aspects of Generalized Modified Gravity Models
NASA Astrophysics Data System (ADS)
Myrzakulov, R.; Sebastiani, L.; Zerbini, S.
2013-07-01
In this paper, we review some general aspects of modified gravity theories, investigating mathematical and physical properties and, more specifically, the feature of viable and realistic models able to reproduce the dark energy (DE) epoch and the early-time inflation. We will discuss the black hole (BH) solutions in generalized theories of gravity: it is of fundamental interest to understand how properties and laws of BHs in General Relativity (GR) can be addressed in the framework of modified theories. In particular, we will discuss the energy issue and the possibility to derive the First Law of thermodynamics from the field equations. Then, in the analysis of cosmological solutions, we will pay particular attention to the occurrence of finite-time future singularities and to the possibility to avoid them in F(R,G)-gravity. Furthermore, realistic models of F(R)-gravity will be analyzed in detail. A general feature occurring in matter era will be shown, namely, the high derivatives of Hubble parameter may be influenced by the high frequency oscillation of the DE and some correction term may be required in order to stabilize the theory at high redshift. The inflationary scenario is also carefully analyzed and a unified description of the universe is evolved. In the final part of the work, we will look at the last developments in modified gravity, namely, we will investigate cosmological and BH solutions in a covariant field theory of gravity and we will introduce the extended "teleparallel" F(T)-gravity theories. A nice application to the dark matter (DM) problem will be presented.
On improvements of Double Beta Decay using FQTDA Model
NASA Astrophysics Data System (ADS)
de Oliveira, L.; Samana, A. R.; Krmpotic, F.; Mariano, A. E.; Barbero, C. A.
2015-07-01
The Quasiparticle Tamm-Dancoff Approximation (QTDA) is applied to describe the nuclear double beta decay with two neutrinos. Several serious inconveniences found in the Quasiparticle Random Phase Approximation (QRPA) are not present in the QTDA, as such as the ambiguity in treating the intermediary states, and further approximations necessary for evaluation of the nuclear matrix elements (NMEs) or, the extreme sensitivity of NME with the ratio between the pn and pp + nn pairings. Some years ago, the decay 48Ca → 48Ti was discussed within the particle-hole limit of QTDA. We found some mismatch in the numerical calculations when the full QTDA was being implemented, and a new performance in the particle-hole limit of QTDA is required to guarantee the fidelity of the approximation.
Hebbes, T R; Clayton, A L; Thorne, A W; Crane-Robinson, C
1994-01-01
The distribution of core histone acetylation across the chicken beta-globin locus has been mapped in 15 day chicken embryo erythrocytes by immunoprecipitation of mononucleosomes with an antibody recognizing acetylated histones, followed by hybridization probing at several points in the locus. A continuum of acetylation was observed, covering both genes and intergenic regions. Using the same probes, the generalized sensitivity to DNase I was mapped by monitoring the disappearance of intact genomic restriction fragments from Southern transfers. Close correspondence between the 33 kb of sensitive chromatin and the extent of acetylation indicates that one role of the modification could be the generation and/or maintenance of the open conformation. The precision of acetylation mapping makes it a possible approach to the definition of chromosomal domain boundaries. Images PMID:8168481
Generalized model of the microwave auditory effect
NASA Astrophysics Data System (ADS)
Yitzhak, N. M.; Ruppin, R.; Hareuveny, R.
2009-07-01
A generalized theoretical model for evaluating the amplitudes of the sound waves generated in a spherical head model, which is irradiated by microwave pulses, is developed. The thermoelastic equation of motion is solved for a spherically symmetric heating pattern of arbitrary form. For previously treated heating patterns that are peaked at the sphere centre, the results reduce to those presented before. The generalized model is applied to the case in which the microwave absorption is concentrated near the sphere surface. It is found that, for equal average specific absorption rates, the sound intensity generated by a surface localized heating pattern is comparable to that generated by a heating pattern that is peaked at the centre. The dependence of the induced sound pressure on the shape of the microwave pulse is explored. Another theoretical extension, to the case of repeated pulses, is developed and applied to the interpretation of existing experimental data on the dependence of the human hearing effect threshold on the pulse repetition frequency.
Generalized model of the microwave auditory effect.
Yitzhak, N M; Ruppin, R; Hareuveny, R
2009-07-07
A generalized theoretical model for evaluating the amplitudes of the sound waves generated in a spherical head model, which is irradiated by microwave pulses, is developed. The thermoelastic equation of motion is solved for a spherically symmetric heating pattern of arbitrary form. For previously treated heating patterns that are peaked at the sphere centre, the results reduce to those presented before. The generalized model is applied to the case in which the microwave absorption is concentrated near the sphere surface. It is found that, for equal average specific absorption rates, the sound intensity generated by a surface localized heating pattern is comparable to that generated by a heating pattern that is peaked at the centre. The dependence of the induced sound pressure on the shape of the microwave pulse is explored. Another theoretical extension, to the case of repeated pulses, is developed and applied to the interpretation of existing experimental data on the dependence of the human hearing effect threshold on the pulse repetition frequency.
Modeling Beta-Traces for Beta-Barrels from Cryo-EM Density Maps
Si, Dong
2017-01-01
Cryo-electron microscopy (cryo-EM) has produced density maps of various resolutions. Although α-helices can be detected from density maps at 5–8 Å resolutions, β-strands are challenging to detect at such density maps due to close-spacing of β-strands. The variety of shapes of β-sheets adds the complexity of β-strands detection from density maps. We propose a new approach to model traces of β-strands for β-barrel density regions that are extracted from cryo-EM density maps. In the test containing eight β-barrels extracted from experimental cryo-EM density maps at 5.5 Å–8.25 Å resolution, StrandRoller detected about 74.26% of the amino acids in the β-strands with an overall 2.05 Å 2-way distance between the detected β-traces and the observed ones, if the best of the fifteen detection cases is considered. PMID:28164115
Modeling Beta-Traces for Beta-Barrels from Cryo-EM Density Maps.
Si, Dong; He, Jing
2017-01-01
Cryo-electron microscopy (cryo-EM) has produced density maps of various resolutions. Although α-helices can be detected from density maps at 5-8 Å resolutions, β-strands are challenging to detect at such density maps due to close-spacing of β-strands. The variety of shapes of β-sheets adds the complexity of β-strands detection from density maps. We propose a new approach to model traces of β-strands for β-barrel density regions that are extracted from cryo-EM density maps. In the test containing eight β-barrels extracted from experimental cryo-EM density maps at 5.5 Å-8.25 Å resolution, StrandRoller detected about 74.26% of the amino acids in the β-strands with an overall 2.05 Å 2-way distance between the detected β-traces and the observed ones, if the best of the fifteen detection cases is considered.
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.
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.
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).
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.
A Tailored Testing Model Employing the Beta Distribution and Conditional Difficulties.
ERIC Educational Resources Information Center
Kalisch, Stanley J.
A tailored testing model employing the beta distribution, whose mean equals the difficulty of an item and whose variance is approximately equal to the sampling variance of the item difficulty, and employing conditional item difficulties, is proposed. The model provides a procedure by which a minimum number of items of a test, consisting of a set…
An optimal control model for beta defective and gamma deteriorating inventory system
NASA Astrophysics Data System (ADS)
Dhaiban, Ali Khaleel; Baten, Md. Azizul; Aziz, Nazrina
2014-12-01
We studied the optimal control of an inventory-production system with deterioration and defective items. Our objective is to develop an optimal inventory control model with Gamma distributed deterioration and beta distributed defective item. The explicit solution of the inventory-production model is derived under continuous review policy using the Pontryagin maximum principle. The optimality conditions are derived from the dynamic of the inventory-production level. Moreover, the simulation and sensitivity analysis results are illustrated numerically in this optimal control model with different demand patterns. The results of the inventory system are analyzed against different parametric values of Beta and Gamma distributions. As a result, the optimal total production strategy is increasing with increase the value of the Beta distribution parameter and decreasing with an increase in the value of the Gamma distribution parameter.
A Model Fit Statistic for Generalized Partial Credit Model
ERIC Educational Resources Information Center
Liang, Tie; Wells, Craig S.
2009-01-01
Investigating the fit of a parametric model is an important part of the measurement process when implementing item response theory (IRT), but research examining it is limited. A general nonparametric approach for detecting model misfit, introduced by J. Douglas and A. S. Cohen (2001), has exhibited promising results for the two-parameter logistic…
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.
Snow hydrology in a general circulation model
Marshall, S. ); Roads, J.O. ); Glatzmaier, G. )
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. A 3-year GCM simulation with this 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. 52 refs., 13 figs., 5 tabs.
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.
The Generalized Quantum Episodic Memory Model.
Trueblood, Jennifer S; Hemmer, Pernille
2016-12-21
Recent evidence suggests that experienced events are often mapped to too many episodic states, including those that are logically or experimentally incompatible with one another. For example, episodic over-distribution patterns show that the probability of accepting an item under different mutually exclusive conditions violates the disjunction rule. A related example, called subadditivity, occurs when the probability of accepting an item under mutually exclusive and exhaustive instruction conditions sums to a number >1. Both the over-distribution effect and subadditivity have been widely observed in item and source-memory paradigms. These phenomena are difficult to explain using standard memory frameworks, such as signal-detection theory. A dual-trace model called the over-distribution (OD) model (Brainerd & Reyna, 2008) can explain the episodic over-distribution effect, but not subadditivity. Our goal is to develop a model that can explain both effects. In this paper, we propose the Generalized Quantum Episodic Memory (GQEM) model, which extends the Quantum Episodic Memory (QEM) model developed by Brainerd, Wang, and Reyna (2013). We test GQEM by comparing it to the OD model using data from a novel item-memory experiment and a previously published source-memory experiment (Kellen, Singmann, & Klauer, 2014) examining the over-distribution effect. Using the best-fit parameters from the over-distribution experiments, we conclude by showing that the GQEM model can also account for subadditivity. Overall these results add to a growing body of evidence suggesting that quantum probability theory is a valuable tool in modeling recognition memory.
The epistemological status of general circulation models
NASA Astrophysics Data System (ADS)
Loehle, Craig
2017-05-01
Forecasts of both likely anthropogenic effects on climate and consequent effects on nature and society are based on large, complex software tools called general circulation models (GCMs). Forecasts generated by GCMs have been used extensively in policy decisions related to climate change. However, the relation between underlying physical theories and results produced by GCMs is unclear. In the case of GCMs, many discretizations and approximations are made, and simulating Earth system processes is far from simple and currently leads to some results with unknown energy balance implications. Statistical testing of GCM forecasts for degree of agreement with data would facilitate assessment of fitness for use. If model results need to be put on an anomaly basis due to model bias, then both visual and quantitative measures of model fit depend strongly on the reference period used for normalization, making testing problematic. Epistemology is here applied to problems of statistical inference during testing, the relationship between the underlying physics and the models, the epistemic meaning of ensemble statistics, problems of spatial and temporal scale, the existence or not of an unforced null for climate fluctuations, the meaning of existing uncertainty estimates, and other issues. Rigorous reasoning entails carefully quantifying levels of uncertainty.
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.
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.
Conserved Current for General Teleparallel Models
NASA Astrophysics Data System (ADS)
Itin, Y.
The obstruction for the existence of an energy-momentum tensor for the gravitational field in GR is connected with vanishing of first order invariants in (pseudo) Riemannian geometry. This specific geometric property is not valid in alternative geometrical structures1,2. A parallelizable differentiable 4D-manifold endowed with a class of smooth coframe fields ϑa is considered. A general 3-parameter class of global Lorentz invariant teleparallel models is considered. It includes a 1-parameter subclass of models with the Schwarzschild coframe solution (generalized teleparallel equivalent of gravity) 3. By introducing the notion of a 3-parameter conjugate field strength F linear in the strength Ca = dϑa the coframe Lagrangian is rewritten in the Maxwell-Yang-Mills form L = 1/2Fa ∧ Ca. The field equation turns out to have a form d * Fa = Ta completely similar to the Maxwell field equation. By applying the Noether procedure, the source 3-form Ta is shown to be connected with the diffeomorphism invariance of the Lagrangian. Thus the source Ta of the coframe field is interpreted as the total conserved energy-momentum current of the coframe field and matter4. The energy-momentum tensor is defined as a map of the module of current 3-forms into the module of vector fields 5. Thus an energy-momentum tensor for the coframe is defined in a diffeomorphism invariant and a translational covariant way. The total energy-momentum current of a system is conserved. Thus a redistribution of the energy-momentum current between material and coframe (gravity) field is possible in principle, unlike as in the standard GR. The result is: The standard GR has a neighborhood of viable models with the same Schwarzschild solutions. These models however have a better Lagrangian behavior and produce an invariant energy-momentum tensor.
Numerical modeling of large-area beta sources constructed from anodized-aluminum foils.
Stanga, D
2012-09-01
The numerical modeling of large-area beta sources constructed from anodized-aluminum foils is described in this paper. Based on a realistic model for the activity depth distribution, theoretical lower and upper bounds for the efficiency and the transmission coefficient were calculated and used to analyze the comparison method recommended by ISO 8769 for measuring the surface emission rate. The analysis shows that this method can provide measurement results with relative standard uncertainties smaller than 3% for high energy beta emitters such as (90)Sr-(90)Y, (36)Cl and (204)Tl.
Regional Validation of General Circulation Models.
NASA Astrophysics Data System (ADS)
Santer, Benjamin David
Available from UMI in association with The British Library. Requires signed TDF. General Circulation Models (GCMs) of the atmosphere and ocean have been used for performing a variety of climate experiments. Confidence in the reliability of experimental results can only be obtained by detailed validation of model control run results. It is generally accepted that current GCMs show considerable disagreement in terms of important regional and seasonal details of their control run climatologies, but there are few objective intercomparison studies to substantiate this. This study examines the regional and seasonal details of the mean sea-level pressure (MSLP) fields simulated by three GCMs--the OSU two-layer AGCM, the OSU CGCM and the GISS nine-layer AGCM. Model validation is performed in a North American/Atlantic/European study area. Prior to statistical significance testing, the principal seasonal characteristics of the observed Azores High (AH) and Iceland Low (IL) are analysed with the aid of time-averaged MSLP maps and objective locational and intensity indices. These results are then used to test the performance of the three models in simulating center of action (COA) seasonal cycle characteristics. All three GCMs have large, systematic errors throughout the seasonal cycle in their simulation of AH/IL position and intensity, and all generate an unrealistic 'Greenland High'. The main focus of the investigation is on the statistical aspects of control run validation. Eighteen different statistics are used to test the significance of differences between observed and simulated means, variances and spatial patterns. Test statistic significance is determined using Preisendorfer and Barnett's permutation procedures. Statistics which measure the degree of spatial autocorrelation in latitudinal and longitudinal directions (and at different spatial lags) are also used to compare observed and simulated fields. Validation of the simulated seasonal cycles of MSLP indicates
Lee, Y Terry; Kim, Ki Soon; Byrnes, Colleen; de Vasconcellos, Jaira F; Noh, Seung-Jae; Rabel, Antoinette; Meier, Emily R; Miller, Jeffery L
2013-01-01
Based upon the lack of clinical samples available for research in many laboratories worldwide, a significant gap exists between basic and clinical studies of beta-thalassemia major. To bridge this gap, we developed an artificially engineered model for human beta thalassemia by knocking down beta-globin gene and protein expression in cultured CD34+ cells obtained from healthy adults. Lentiviral-mediated transduction of beta-globin shRNA (beta-KD) caused imbalanced globin chain production. Beta-globin mRNA was reduced by 90% compared to controls, while alpha-globin mRNA levels were maintained. HPLC analyses revealed a 96% reduction in HbA with only a minor increase in HbF. During the terminal phases of differentiation (culture days 14-21), beta-KD cells demonstrated increased levels of insoluble alpha-globin, as well as activated caspase-3. The majority of the beta-KD cells underwent apoptosis around the polychromatophilic stage of maturation. GDF15, a marker of ineffective erythropoiesis in humans with thalassemia, was significantly increased in the culture supernatants from the beta-KD cells. Knockdown of beta-globin expression in cultured primary human erythroblasts provides a robust ex vivo model for beta-thalassemia.
Byrnes, Colleen; de Vasconcellos, Jaira F.; Noh, Seung-Jae; Rabel, Antoinette; Meier, Emily R.; Miller, Jeffery L.
2013-01-01
Based upon the lack of clinical samples available for research in many laboratories worldwide, a significant gap exists between basic and clinical studies of beta-thalassemia major. To bridge this gap, we developed an artificially engineered model for human beta thalassemia by knocking down beta-globin gene and protein expression in cultured CD34+ cells obtained from healthy adults. Lentiviral-mediated transduction of beta-globin shRNA (beta-KD) caused imbalanced globin chain production. Beta-globin mRNA was reduced by 90% compared to controls, while alpha-globin mRNA levels were maintained. HPLC analyses revealed a 96% reduction in HbA with only a minor increase in HbF. During the terminal phases of differentiation (culture days 14–21), beta-KD cells demonstrated increased levels of insoluble alpha-globin, as well as activated caspase-3. The majority of the beta-KD cells underwent apoptosis around the polychromatophilic stage of maturation. GDF15, a marker of ineffective erythropoiesis in humans with thalassemia, was significantly increased in the culture supernatants from the beta-KD cells. Knockdown of beta-globin expression in cultured primary human erythroblasts provides a robust ex vivo model for beta-thalassemia. PMID:23861885
On the strategy of future observations and modeling of the Beta Lyr system
NASA Technical Reports Server (NTRS)
Hubeny, I.; Harmanec, P.; Shore, S. N.
1994-01-01
Beta Lyr is an enigmatic object. Despite several decades of concentrated observational and theoretical effort, our understanding of the system is still rather poor. We discuss two existing structural models of the system, the massive torus model of Wilson (1981), and the low mass accretion disk model of Hubeny & Plavec (1991). In particular, we answer recent criticism of the low mass disk model expressed by the proponents of the massive disk hypothesis. We show that although both theories have a large degree of internal consistency, there are several serious physical objections against the massive disk model. In particular, such a model requires unrealistically low viscosity (large Reynolds number). Moreover, such massive disk is likely to be dynamically unstable. Finally, we propose several observational and theoretical approaches that could lead to construction of a more physically realistic model of the Beta Lyr system.
NASA Astrophysics Data System (ADS)
Liu, Fei; Wang, Jiang; Liu, Chen; Li, Huiyan; Deng, Bin; Fietkiewicz, Chris; Loparo, Kenneth A.
2016-12-01
An increase in beta oscillations within the basal ganglia nuclei has been shown to be associated with movement disorder, such as Parkinson's disease. The motor cortex and an excitatory-inhibitory neuronal network composed of the subthalamic nucleus (STN) and the external globus pallidus (GPe) are thought to play an important role in the generation of these oscillations. In this paper, we propose a neuron mass model of the basal ganglia on the population level that reproduces the Parkinsonian oscillations in a reciprocal excitatory-inhibitory network. Moreover, it is shown that the generation and frequency of these pathological beta oscillations are varied by the coupling strength and the intrinsic characteristics of the basal ganglia. Simulation results reveal that increase of the coupling strength induces the generation of the beta oscillation, as well as enhances the oscillation frequency. However, for the intrinsic properties of each nucleus in the excitatory-inhibitory network, the STN primarily influences the generation of the beta oscillation while the GPe mainly determines its frequency. Interestingly, describing function analysis applied on this model theoretically explains the mechanism of pathological beta oscillations.
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.
Effects of beta-adrenoceptor drug stimulation on various models of gastric ulcer in rats.
Esplugues, J.; Lloris, J. M.; Martí-Bonmatí, E.; Morcillo, E. J.
1982-01-01
1. Experiments were designed to evaluate the effect of the pharmacological activation of beta-adrenoceptors on various models of gastric ulcer in the rat. 2. Pretreatment with the beta-adrenoceptor stimulant drugs, isoprenaline or salbutamol, significantly inhibited stress-induced gastric ulcers. This anti-ulcer effect was abolished by propranolol but not by atenolol, suggesting that beta 2-adrenoceptors mediate this response. 3. In the pylorus-ligation model, salbutamol inhibited lesion formation and reduced the intragastric content of hydrogen ions, histamine and pepsin although the latter was only affected with the higher dose of salbutamol. 4. Salbutamol also prevented the ulcerogenic action on the gastric mucosa of an exogenously perfused artificial gastric juice, showing that the anti-ulcer effect is not necessarily dependent on acid inhibition. 5. Salbutamol also reduced the formation of acute ulcers induced by various iatrogenic means (histamine, polymyxin B, reserpine and indomethacin). 6. Long-term treatment with salbutamol accelerated the healing of experimental chronic gastric ulcer. 7. In anaesthetized rats, salbutamol produced a dose-related increase in mucosal blood flow which may contribute to its mode of action. 8. It is concluded that beta-adrenoceptor agonists exert preventive and curative effects on gastric damage induced in the rat. This effect seems specific and mediated through beta-adrenoceptor activation. PMID:6125225
Grevel, J
1986-01-01
Models describing the time course of effects (pharmacodynamic models) of various beta blockers in man are used to explain the long duration of action of bopindolol. No matter what effect is used [reduction in exercise heart rate (RER) or isoproterenol dose ratio (DR)] human data show clearly that bopindolol is very potent compared to other beta blockers such as atenolol, metoprolol, pindolol, practolol, and propranolol. In pharmacokinetic terms, however, these drugs show no pronounced difference in their elimination half-life (ranging between 4 and 8 h). Also the site of action of the therapeutic effects (beta 1 receptors) is obviously identical for all beta blockers. Furthermore, there is no evidence to suggest that bopindolol (the prodrug) or hydrolyzed bopindolol (the active substance) is further metabolized to a slowly eliminated active metabolite. Thus, drug disposition provides no argument to explain the long-lasting effects of bopindolol as compared other beta blockers. The long duration of action of bopindolol seems to reflect an usually flat plasma concentration-response curve.
Multipath diffusion: A general numerical model
NASA Astrophysics Data System (ADS)
Lee, J. K. W.; Aldama, A. A.
1992-06-01
The effect of high-diffusivity pathways on bulk diffusion of a solute in a material has been modeled previously for simple geometries such as those in tracer diffusion experiments, but not for the geometries and boundary conditions appropriate for experiments involving bulk exchange. Using a coupled system of equations for simultaneous diffusion of a solute through two families of diffusion pathways with differing diffusivities, a general 1-D finite difference model written in FORTRAN has been developed which can be used to examine the effect of high-diffusivity paths on partial and total concentration profiles within a homogeneous isotropic sphere, infinite cylinder, and infinite slab. The partial differential equations are discretized using the θ-method/central-difference scheme, and an iterative procedure analogous to the Gauss-Seidel method is employed to solve the two systems of coupled equations. Using Fourier convergence analysis, the procedure is shown to be unconditionally convergent. Computer simulations demonstrate that a multipath diffusion mechanism can enhance significantly the bulk diffusivity of a diffusing solute species through a material. The amount of solute escaping from a material is dependent strongly on the exchange coefficients, which govern the transfer of solute from the crystal lattice to the high-diffusivity paths and vice versa. In addition, the exchange coefficients ( ϰ1, and ϰ2) seem to control not only the amount of solute that is lost, but also the shape of the concentration profile. If | K1| < | K2|, concentration profiles generally are non-Fickian in shape, typically having shallow concentration gradients near the center (radius r = 0) and steep gradients towards the outer boundary of the material ( r = R). When | K1| ⩾ | K2| a concentration profile is generated which resembles a Fickian (volume) diffusion profile with an apparent bulk diffusivity between that of the crystal lattice and that of the high-diffusivity pathways
Evaluating the double Poisson generalized linear model.
Zou, Yaotian; Geedipally, Srinivas Reddy; Lord, Dominique
2013-10-01
The objectives of this study are to: (1) examine the applicability of the double Poisson (DP) generalized linear model (GLM) for analyzing motor vehicle crash data characterized by over- and under-dispersion and (2) compare the performance of the DP GLM with the Conway-Maxwell-Poisson (COM-Poisson) GLM in terms of goodness-of-fit and theoretical soundness. The DP distribution has seldom been investigated and applied since its first introduction two decades ago. The hurdle for applying the DP is related to its normalizing constant (or multiplicative constant) which is not available in closed form. This study proposed a new method to approximate the normalizing constant of the DP with high accuracy and reliability. The DP GLM and COM-Poisson GLM were developed using two observed over-dispersed datasets and one observed under-dispersed dataset. The modeling results indicate that the DP GLM with its normalizing constant approximated by the new method can handle crash data characterized by over- and under-dispersion. Its performance is comparable to the COM-Poisson GLM in terms of goodness-of-fit (GOF), although COM-Poisson GLM provides a slightly better fit. For the over-dispersed data, the DP GLM performs similar to the NB GLM. Considering the fact that the DP GLM can be easily estimated with inexpensive computation and that it is simpler to interpret coefficients, it offers a flexible and efficient alternative for researchers to model count data.
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.
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
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
Neutrinoless double beta nuclear matrix elements around mass 80 in the nuclear shell-model
NASA Astrophysics Data System (ADS)
Yoshinaga, N.; Higashiyama, K.; Taguchi, D.; Teruya, E.
2015-05-01
The observation of the neutrinoless double-beta decay can determine whether the neutrino is a Majorana particle or not. For theoretical nuclear physics it is particularly important to estimate three types of matrix elements, namely Fermi (F), Gamow-Teller (GT), and tensor (T) matrix elements. In this paper, we carry out shell-model calculations and also pair-truncated shell-model calculations to check the model dependence in the case of mass A=82 nuclei.
Study on the C-terminal beta-hairpin of protein G in AB heteropolymer model
NASA Astrophysics Data System (ADS)
Kim, Seung-Yeon
2016-08-01
The off-lattice AB heteropolymer model, consisting of the hydrophobic (A) and hydrophilic (B) polymers, is one of popular protein models. Its energy function includes the bending energy and the van der Waals interaction energy. The properties and the energy landscape of the C-terminal beta-hairpin of protein G are studied in the off-lattice AB heteropolymer model with conformational space annealing, a powerful global optimization method.
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.
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.
Mixtures of beta distributions in models of the duration of a project affected by risk
NASA Astrophysics Data System (ADS)
Gładysz, Barbara; Kuchta, Dorota
2017-07-01
This article presents a method for timetabling a project affected by risk. The times required to carry out tasks are modelled using mixtures of beta distributions. The parameters of these beta distributions are given by experts: one corresponding to the duration of a task in stable conditions, with no risks materializing, and the other corresponding to the duration of a task in the case when risks do occur. Finally, a case study will be presented and analysed: the project of constructing a shopping mall in Poland.
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
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
General single phase wellbore flow model
Ouyang, Liang-Biao; Arbabi, S.; Aziz, K.
1997-02-05
A general wellbore flow model, which incorporates not only frictional, accelerational and gravitational pressure drops, but also the pressure drop caused by inflow, is presented in this report. The new wellbore model is readily applicable to any wellbore perforation patterns and well completions, and can be easily incorporated in reservoir simulators or analytical reservoir inflow models. Three dimensionless numbers, the accelerational to frictional pressure gradient ratio R{sub af}, the gravitational to frictional pressure gradient ratio R{sub gf}, and the inflow-directional to accelerational pressure gradient ratio R{sub da}, have been introduced to quantitatively describe the relative importance of different pressure gradient components. For fluid flow in a production well, it is expected that there may exist up to three different regions of the wellbore: the laminar flow region, the partially-developed turbulent flow region, and the fully-developed turbulent flow region. The laminar flow region is located near the well toe, the partially-turbulent flow region lies in the middle of the wellbore, while the fully-developed turbulent flow region is at the downstream end or the heel of the wellbore. Length of each region depends on fluid properties, wellbore geometry and flow rate. As the distance from the well toe increases, flow rate in the wellbore increases and the ratios R{sub af} and R{sub da} decrease. Consequently accelerational and inflow-directional pressure drops have the greatest impact in the toe region of the wellbore. Near the well heel the local wellbore flow rate becomes large and close to the total well production rate, here R{sub af} and R{sub da} are small, therefore, both the accelerational and inflow-directional pressure drops can be neglected.
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.
Modeling phosphorus trapping in wetlands using generalized additive models
NASA Astrophysics Data System (ADS)
Reckhow, Kenneth H.; Qian, Song S.
1994-11-01
In the past several years, wetlands have become increasingly used for wastewater treatment purposes. As a consequence, nutrient trapping and accumulation, particularly for phosphorus, have emerged as important environmental management issues. To predict the effectiveness of wetlands for phosphorus removal, data from a large cross-sectional study and from a single wetland over time were obtained with the objective of developing a predictive model. From the analysis of these data, it was found that phosphorus trapping is predictable using a simple function of phosphorus input and water loading. Several statistical models of phosphorus trapping were developed and evaluated using the two data sets. Particular emphasis was placed on generalized additive modeling, a graphics-oriented data-driven approach, for model diagnostic and model-building purposes. A nonlinear model was recommended, and suggestions were made for future work.
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
Gerona-Navarro, Guillermo; García-López, M Teresa; González-Muñiz, Rosario
2002-05-31
The first general approach toward the asymmetric synthesis of 4-alkyl-4-carboxy-2-azetidinones derived from amino acids is described. The stereoselective construction of the beta-lactam ring was achieved through base-mediated intramolecular cyclization of the corresponding N(alpha)-chloroacetyl derivatives bearing (+)- or (-)-10-(N,N-dicyclohexylsulfamoyl)isoborneol as chiral auxiliary (ee up to 82%).
Nonlinear Feedback in a Generalized Lorenz Model
NASA Astrophysics Data System (ADS)
Shen, B.
2013-05-01
In this study, the original Lorenz Model (LM) was generalized with two or three additional modes to examine their role in the predictability of the numerical solutions and to understand the underlying processes that improve the solution stability. Based on the number of the modes, the original and generalized LMs are referred to as the 3-dimensional (3D), 5D, and 6D LMs, respectively. As a result of the simplicity of the 5DLM with respect to the 6DLM, we were able to obtain the analytical solutions of its critical points and identify the role of the major nonlinear term in solution's stability, which have previously not been documented in the literature. The Jacobian term of the governing equations was analyzed to highlight the importance of selecting new modes for extending a nonlinear feedback loop to improve the non-linear interactions. We showed that numerical solutions in the 5DLM (6DLM) require a larger parameter r for the onset of chaos and are more predictable than those in the 3DLM, as r is between 25 and 40 (and the Prandtl number σ is 10). The improved predictability is attributable to the nonlinear negative feedback by the new modes. The role of the nonlinear (negative) feedback was further verified using a revised 3DLM with a parameterized eddy dissipative term. The finding of the improved stability in the generalized LMs with the respect to the 3DLM was confirmed with the linear stability analysis and the analysis of the Lyapunov exponents using different values of r and σ .; Phase space plots in the 3DLM (a) and 5DLM (b-d). (a) A (Y,Z) plot with r=25. It shows the Lorenz strange attractors. (b) A (Y,Z) plot with r=25. (c) A (Y,Z) plot with r=43.5 with strange attractors. (d) A (Y1, Z1) plot with r=43.5. All of the solutions are normalized by the the corresponding critical points, namely, Eq. (26) for the 3DLM and Eq. (19) for the 5DLM.
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
Li, Wei; Xie, Shuyang; Guo, Xinbing; Gong, Xiuli; Wang, Shu; Lin, Dan; Zhang, Jingzhi; Ren, Zhaorui; Huang, Shuzhen; Zeng, Fanyi; Zeng, Yitao
2008-03-01
beta-thalassemia is one of the most common genetic diseases in the world and requires extensive therapy. Lentiviral-mediated gene therapy has been successfully exploited in the treatment of beta-thalassemia and showed promise in clinical application. Using a human beta-globin transgenic mouse line in a beta-thalassemia diseased model generated with a lentiviral-mediated approach, we investigate the stable therapeutic effect on a common thalassemia syndrome. Human beta-globin gene lentiviral vector was constr ucted, followed by subzonal microinjection into single-cell embryos of beta(IVS-2-654)-thalassemia mice to generate a transgenic line. Human beta-globin gene expression was examined with RT-PCR, Western-blotting and ELISA. The hematologic parameters and tissue pathology were investigated over time in founder mice and their off-spring. Transgenic mice with stable expression of the lentivirus carrying human beta-globin gene were obtained. A marked improvement in red blood cell indices and a dramatic reduction in red blood cell anisocytosis, poikilocytosis and target cells were observed. Nucleated cell proportion was greatly decreased in bone marrow, and splenomegaly with extramedullary hematopoiesis was ameliorated. Iron deposition in liver was also reduced. There was a two-fold increase in the survival rate of the beta(IVS-2-654) mice carrying human beta-globin transgene. Significantly, the germline integration of the lentiviral construct was obtained and stable hematologic phenotype correction was observed over the next two generations of the transgenic mice. The generation of human beta-globin transgenic mice in a beta(IVS-2-654)-thalassemia mouse mediated with lentiviral vectors provides a useful model and offers an attractive means to investigate the transgenic stable therapeutic effect in beta-thalassemia.
Appropriate model selection methods for nonstationary generalized extreme value models
NASA Astrophysics Data System (ADS)
Kim, Hanbeen; Kim, Sooyoung; Shin, Hongjoon; Heo, Jun-Haeng
2017-04-01
Several evidences of hydrologic data series being nonstationary in nature have been found to date. This has resulted in the conduct of many studies in the area of nonstationary frequency analysis. Nonstationary probability distribution models involve parameters that vary over time. Therefore, it is not a straightforward process to apply conventional goodness-of-fit tests to the selection of an appropriate nonstationary probability distribution model. Tests that are generally recommended for such a selection include the Akaike's information criterion (AIC), corrected Akaike's information criterion (AICc), Bayesian information criterion (BIC), and likelihood ratio test (LRT). In this study, the Monte Carlo simulation was performed to compare the performances of these four tests, with regard to nonstationary as well as stationary generalized extreme value (GEV) distributions. Proper model selection ratios and sample sizes were taken into account to evaluate the performances of all the four tests. The BIC demonstrated the best performance with regard to stationary GEV models. In case of nonstationary GEV models, the AIC proved to be better than the other three methods, when relatively small sample sizes were considered. With larger sample sizes, the AIC, BIC, and LRT presented the best performances for GEV models which have nonstationary location and/or scale parameters, respectively. Simulation results were then evaluated by applying all four tests to annual maximum rainfall data of selected sites, as observed by the Korea Meteorological Administration.
Jiang, Dianlu; Dinh, Kim Lien; Ruthenburg, Travis C; Zhang, Yi; Su, Lei; Land, Donald P; Zhou, Feimeng
2009-03-12
At the air/buffer solution interface the kinetics of adsorption of amyloid beta peptide, Abeta(1-42), whose bulk concentration (submicromolar) is more than 2 orders of magnitude lower than that typically used in other in vitro aggregation studies, has been studied using a Langmuir-Blodgett trough. The pressure-time curves exhibit a lag phase, wherein the surface pressure essentially remains at zero, and a rising phase, corresponding to the Abeta adsorption at the interface. The duration of the lag phase was found to be highly dependent on both the Abeta bulk concentration and the solution temperature. A large activation energy (62.2 +/- 4.1 KJ/mol) was determined and the apparent adsorption rate constant was found to be linearly dependent on the Abeta bulk concentration. Attenuated total reflection-IR spectra of the adsorbed Abeta transferred to a solid substrate and circular dichroism measurements of Abeta in the solution layer near the interface reveal that the natively unstructured Abeta in the bulk undergo a conformation change (folding) to mainly the alpha-helical structure. The results suggest that, prior to the adsorption step, an equilibrium between Abeta conformations is established within the subsurface. The kinetic equation derived from this model confirms that the overall Abeta adsorption is kinetically controlled and the apparent rate constant is proportional to the Abeta bulk concentration. This model also indicates that interfaces such as cell membranes and lipid bilayers may facilitate Abeta aggregation/ fibrillation by providing a thin hydrophobic layer adjacent to the interface for the initial A/beta conformation change (misfolding) and accumulation. Such a preconcentration effect offers a plausible explanation of the fact that Abeta fibrillation occurs in vivo at nanomolar concentrations. Another important biological implication from our work is that Abeta misfolding may occur before its adsorption onto a cell membrane. This general kinetic model
Kizilkaya, Kadir; Tempelman, Robert J
2005-01-01
We propose a general Bayesian approach to heteroskedastic error modeling for generalized linear mixed models (GLMM) in which linked functions of conditional means and residual variances are specified as separate linear combinations of fixed and random effects. We focus on the linear mixed model (LMM) analysis of birth weight (BW) and the cumulative probit mixed model (CPMM) analysis of calving ease (CE). The deviance information criterion (DIC) was demonstrated to be useful in correctly choosing between homoskedastic and heteroskedastic error GLMM for both traits when data was generated according to a mixed model specification for both location parameters and residual variances. Heteroskedastic error LMM and CPMM were fitted, respectively, to BW and CE data on 8847 Italian Piemontese first parity dams in which residual variances were modeled as functions of fixed calf sex and random herd effects. The posterior mean residual variance for male calves was over 40% greater than that for female calves for both traits. Also, the posterior means of the standard deviation of the herd-specific variance ratios (relative to a unitary baseline) were estimated to be 0.60 ± 0.09 for BW and 0.74 ± 0.14 for CE. For both traits, the heteroskedastic error LMM and CPMM were chosen over their homoskedastic error counterparts based on DIC values. PMID:15588567
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.
A new theoretical framework for modeling respiratory protection based on the beta distribution.
Klausner, Ziv; Fattal, Eyal
2014-08-01
The problem of modeling respiratory protection is well known and has been dealt with extensively in the literature. Often the efficiency of respiratory protection is quantified in terms of penetration, defined as the proportion of an ambient contaminant concentration that penetrates the respiratory protection equipment. Typically, the penetration modeling framework in the literature is based on the assumption that penetration measurements follow the lognormal distribution. However, the analysis in this study leads to the conclusion that the lognormal assumption is not always valid, making it less adequate for analyzing respiratory protection measurements. This work presents a formulation of the problem from first principles, leading to a stochastic differential equation whose solution is the probability density function of the beta distribution. The data of respiratory protection experiments were reexamined, and indeed the beta distribution was found to provide the data a better fit than the lognormal. We conclude with a suggestion for a new theoretical framework for modeling respiratory protection.
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.
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
Beta-binomial model for meta-analysis of odds ratios.
Bakbergenuly, Ilyas; Kulinskaya, Elena
2017-01-25
In meta-analysis of odds ratios (ORs), heterogeneity between the studies is usually modelled via the additive random effects model (REM). An alternative, multiplicative REM for ORs uses overdispersion. The multiplicative factor in this overdispersion model (ODM) can be interpreted as an intra-class correlation (ICC) parameter. This model naturally arises when the probabilities of an event in one or both arms of a comparative study are themselves beta-distributed, resulting in beta-binomial distributions. We propose two new estimators of the ICC for meta-analysis in this setting. One is based on the inverted Breslow-Day test, and the other on the improved gamma approximation by Kulinskaya and Dollinger (2015, p. 26) to the distribution of Cochran's Q. The performance of these and several other estimators of ICC on bias and coverage is studied by simulation. Additionally, the Mantel-Haenszel approach to estimation of ORs is extended to the beta-binomial model, and we study performance of various ICC estimators when used in the Mantel-Haenszel or the inverse-variance method to combine ORs in meta-analysis. The results of the simulations show that the improved gamma-based estimator of ICC is superior for small sample sizes, and the Breslow-Day-based estimator is the best for n⩾100. The Mantel-Haenszel-based estimator of OR is very biased and is not recommended. The inverse-variance approach is also somewhat biased for ORs≠1, but this bias is not very large in practical settings. Developed methods and R programs, provided in the Web Appendix, make the beta-binomial model a feasible alternative to the standard REM for meta-analysis of ORs. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.
Winkler, Ethan A; Bell, Robert D; Zlokovic, Berislav V
2010-08-25
Pericytes are integral members of the neurovascular unit. Using mouse models lacking endothelial-secreted platelet derived growth factor-B (PDGF-B) or platelet derived growth factor receptor beta (PDGFRβ) on pericytes, it has been demonstrated that PDGF-B/PDGFRβ interactions mediate pericyte recruitment to the vessel wall in the embryonic brain regulating the development of the cerebral microcirculation and the blood-brain barrier (BBB). Relatively little is known, however, about the roles of PDGF-B/PDGFRβ interactions and pericytes in the adult brain in part due to a lack of adequate and/or properly characterized experimental models. To address whether genetic disruption of PDGFRβ signaling would result in a pericyte-specific insult in adult mice, we studied the pattern and cellular distribution of PDGFRβ expression in the brain in adult control mice and F7 mice that express two hypomorphic Pdgfrβ alleles containing seven point mutations in the cytoplasmic domain of PDGFRβ that impair downstream PDGFRβ receptor signaling. Using dual fluorescent in situ hybridization, immunofluorescent staining for different cell types in the neurovascular unit, and a fluorescent in situ proximity ligation assay to visualize molecular PDGF-B/PDGFRβ interactions on brain tissue sections, we show for the first time that PDGFRβ is exclusively expressed in pericytes, and not in neurons, astrocytes or endothelial cells, in the adult brain of control 129S1/SvlmJ mice. PDGFRβ co-localized only with well-established pericyte markers such as Chondroitin Sulfate Proteoglycan NG2 and the xLacZ4 transgenic reporter. We next confirm pericyte-specific PDGFRβ expression in the brains of F7 mutants and show that these mice are viable in spite of substantial 40-60% reductions in regional pericyte coverage of brain capillaries. Our data show that PDGFRβ is exclusively expressed in pericytes in the adult 129S1/Sv1mJ and F7 mouse brain. Moreover, our findings suggest that genetic
2010-01-01
Background Pericytes are integral members of the neurovascular unit. Using mouse models lacking endothelial-secreted platelet derived growth factor-B (PDGF-B) or platelet derived growth factor receptor beta (PDGFRβ) on pericytes, it has been demonstrated that PDGF-B/PDGFRβ interactions mediate pericyte recruitment to the vessel wall in the embryonic brain regulating the development of the cerebral microcirculation and the blood-brain barrier (BBB). Relatively little is known, however, about the roles of PDGF-B/PDGFRβ interactions and pericytes in the adult brain in part due to a lack of adequate and/or properly characterized experimental models. To address whether genetic disruption of PDGFRβ signaling would result in a pericyte-specific insult in adult mice, we studied the pattern and cellular distribution of PDGFRβ expression in the brain in adult control mice and F7 mice that express two hypomorphic Pdgfrβ alleles containing seven point mutations in the cytoplasmic domain of PDGFRβ that impair downstream PDGFRβ receptor signaling. Results Using dual fluorescent in situ hybridization, immunofluorescent staining for different cell types in the neurovascular unit, and a fluorescent in situ proximity ligation assay to visualize molecular PDGF-B/PDGFRβ interactions on brain tissue sections, we show for the first time that PDGFRβ is exclusively expressed in pericytes, and not in neurons, astrocytes or endothelial cells, in the adult brain of control 129S1/SvlmJ mice. PDGFRβ co-localized only with well-established pericyte markers such as Chondroitin Sulfate Proteoglycan NG2 and the xLacZ4 transgenic reporter. We next confirm pericyte-specific PDGFRβ expression in the brains of F7 mutants and show that these mice are viable in spite of substantial 40-60% reductions in regional pericyte coverage of brain capillaries. Conclusions Our data show that PDGFRβ is exclusively expressed in pericytes in the adult 129S1/Sv1mJ and F7 mouse brain. Moreover, our
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.
A generalized multivariate regression model for modelling ocean wave heights
NASA Astrophysics Data System (ADS)
Wang, X. L.; Feng, Y.; Swail, V. R.
2012-04-01
In this study, a generalized multivariate linear regression model is developed to represent the relationship between 6-hourly ocean significant wave heights (Hs) and the corresponding 6-hourly mean sea level pressure (MSLP) fields. The model is calibrated using the ERA-Interim reanalysis of Hs and MSLP fields for 1981-2000, and is validated using the ERA-Interim reanalysis for 2001-2010 and ERA40 reanalysis of Hs and MSLP for 1958-2001. The performance of the fitted model is evaluated in terms of Pierce skill score, frequency bias index, and correlation skill score. Being not normally distributed, wave heights are subjected to a data adaptive Box-Cox transformation before being used in the model fitting. Also, since 6-hourly data are being modelled, lag-1 autocorrelation must be and is accounted for. The models with and without Box-Cox transformation, and with and without accounting for autocorrelation, are inter-compared in terms of their prediction skills. The fitted MSLP-Hs relationship is then used to reconstruct historical wave height climate from the 6-hourly MSLP fields taken from the Twentieth Century Reanalysis (20CR, Compo et al. 2011), and to project possible future wave height climates using CMIP5 model simulations of MSLP fields. The reconstructed and projected wave heights, both seasonal means and maxima, are subject to a trend analysis that allows for non-linear (polynomial) trends.
Top-Down Beta Rhythms Support Selective Attention via Interlaminar Interaction: A Model
Lee, Jung H.; Whittington, Miles A.; Kopell, Nancy J.
2013-01-01
Cortical rhythms have been thought to play crucial roles in our cognitive abilities. Rhythmic activity in the beta frequency band, around 20 Hz, has been reported in recent studies that focused on neural correlates of attention, indicating that top-down beta rhythms, generated in higher cognitive areas and delivered to earlier sensory areas, can support attentional gain modulation. To elucidate functional roles of beta rhythms and underlying mechanisms, we built a computational model of sensory cortical areas. Our simulation results show that top-down beta rhythms can activate ascending synaptic projections from L5 to L4 and L2/3, responsible for biased competition in superficial layers. In the simulation, slow-inhibitory interneurons are shown to resonate to the 20 Hz input and modulate the activity in superficial layers in an attention-related manner. The predicted critical roles of these cells in attentional gain provide a potential mechanism by which cholinergic drive can support selective attention. PMID:23950699
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.
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.
Modeling local item dependence with the hierarchical generalized linear model.
Jiao, Hong; Wang, Shudong; Kamata, Akihito
2005-01-01
Local item dependence (LID) can emerge when the test items are nested within common stimuli or item groups. This study proposes a three-level hierarchical generalized linear model (HGLM) to model LID when LID is due to such contextual effects. The proposed three-level HGLM was examined by analyzing simulated data sets and was compared with the Rasch-equivalent two-level HGLM that ignores such a nested structure of test items. The results demonstrated that the proposed model could capture LID and estimate its magnitude. Also, the two-level HGLM resulted in larger mean absolute differences between the true and the estimated item difficulties than those from the proposed three-level HGLM. Furthermore, it was demonstrated that the proposed three-level HGLM estimated the ability distribution variance unaffected by the LID magnitude, while the two-level HGLM with no LID consideration increasingly underestimated the ability variance as the LID magnitude increased.
Thackaberry, Evan A; Kopytek, Stephen; Sherratt, Phillip; Trouba, Kevin; McIntyre, Barry
2010-10-01
This study was conducted to assess the safety and tolerability of the alternative formulation vehicles polysorbate 80 (PS80), propylene glycol (PG), and hydroxypropyl-beta-cyclodextrin (HPβCD) in general toxicology studies in the mouse, rat, dog, and monkey. Twenty (20) mg/kg of hydroxypropyl methylcellulose (MC, control), 10 mg/kg PS80, 1000 mg/kg PG, 500 mg/kg HPβCD, or 1000 mg/kg HPβCD were administered by oral gavage to mice, rats, dogs, and cynomolgus monkeys for approximately 90 days. The effects of these formulations on clinical observations, body weight and food consumption parameters, clinical pathology, and histopathology were evaluated across all species. The suitability of formulations containing up to 20 mg/kg MC, 10 mg/kg PS80, and 1000 mg/kg PG for use in preclinical safety studies was confirmed by a lack of effects on all parameters examined. However, formulations containing HPβCD produced elevated transaminase (aspartate and alanine aminotransferase) levels in rats and mice and fecal changes (loose and soft stool) in large animals. Although the etiology and toxicological significance of the transaminase elevations in rats and mice is uncertain, this finding could represent a significant liability for a preclinical formulation because of the critical importance of these biomarkers in the risk assessment of novel therapeutic agents. Based on these data, PS80 and PG are considered to be practical alternatives to MC in preclinical toxicology studies. However, formulations containing HPβCD should be used with caution because of the elevations in rodent transaminase levels.
Modeling the inhibition of the bacteral reduction of U(VI) by beta-MnO2(s).
Liu, Chongxuan; Zachara, John M; Fredrickson, James K; Kennedy, David W; Dohnalkova, Alice
2002-04-01
Pyrolusite (beta-MnO2(s)) was used to assess the influence of a competitive electron acceptor on the kinetics of reduction of aqueous uranyl carbonate by a dissimilatory metal-reducing bacterium (DMRB), Shewanella putrefaciens strain CN32. The enzymatic reduction of U(VI) and beta-MnO2(s) and the abiotic redox reaction between beta-MnO2(s) and biogenic uraninite (UO2(s)) were independently investigated to allow for interpretation of studies of U(VI) bioreduction in the presence of beta-MnO2(s). Uranyl bioreduction to UO2(s) by CN32 with H2 as the electron donor followed Monod kinetics, with a maximum specific reduction rate of 110 M/h/10(8) cells/mL and a half-saturation constant of 370 microM. The bioreduction rate of beta-MnO2(s) by CN32 was described by a pseudo-first-order model with respect to beta-MnO2(s) surface sites, with a rate constant of 7.92 x 10(-2) h(-1)/10(8) cells/mL. Uraninite that precipitated as a result of microbial U(VI) reduction was abiotically reoxidized to U(VI) by beta-MnO2(s), with concomitant reduction to Mn(II). The oxidation of biogenic UO2(s) coupled with beta-MnO2(s) reduction was well-described by an electrochemical model. However, a simple model that coupled the bacterial reduction of U(VI) and beta-MnO2(s) with an abiotic redox reaction between UO2(s) and beta-MnO2(s) failed to describe the mass loss of U(VI) in the presence of beta-MnO2(s). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed that the particle size and spatial distribution of the biogenic UO2(s) changed dynamically in systems with, as compared to without, beta-MnO2(s)). These observations suggested that the surface properties and localization of UO2(s) in relation to the cell and beta-MnO2(s) surfaces was an important factor controlling the abiotic oxidation of UO2(s) and, thus, the overall rate and extent of U(VI) bioreduction. The coupled model that was modified to account for the "effective" contact surface area between UO2
A Bayesian modeling approach for generalized semiparametric structural equation models.
Song, Xin-Yuan; Lu, Zhao-Hua; Cai, Jing-Heng; Ip, Edward Hak-Sing
2013-10-01
In behavioral, biomedical, and psychological studies, structural equation models (SEMs) have been widely used for assessing relationships between latent variables. Regression-type structural models based on parametric functions are often used for such purposes. In many applications, however, parametric SEMs are not adequate to capture subtle patterns in the functions over the entire range of the predictor variable. A different but equally important limitation of traditional parametric SEMs is that they are not designed to handle mixed data types-continuous, count, ordered, and unordered categorical. This paper develops a generalized semiparametric SEM that is able to handle mixed data types and to simultaneously model different functional relationships among latent variables. A structural equation of the proposed SEM is formulated using a series of unspecified smooth functions. The Bayesian P-splines approach and Markov chain Monte Carlo methods are developed to estimate the smooth functions and the unknown parameters. Moreover, we examine the relative benefits of semiparametric modeling over parametric modeling using a Bayesian model-comparison statistic, called the complete deviance information criterion (DIC). The performance of the developed methodology is evaluated using a simulation study. To illustrate the method, we used a data set derived from the National Longitudinal Survey of Youth.
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
Tumor propagation model using generalized hidden Markov model
NASA Astrophysics Data System (ADS)
Park, Sun Young; Sargent, Dustin
2017-02-01
Tumor tracking and progression analysis using medical images is a crucial task for physicians to provide accurate and efficient treatment plans, and monitor treatment response. Tumor progression is tracked by manual measurement of tumor growth performed by radiologists. Several methods have been proposed to automate these measurements with segmentation, but many current algorithms are confounded by attached organs and vessels. To address this problem, we present a new generalized tumor propagation model considering time-series prior images and local anatomical features using a Hierarchical Hidden Markov model (HMM) for tumor tracking. First, we apply the multi-atlas segmentation technique to identify organs/sub-organs using pre-labeled atlases. Second, we apply a semi-automatic direct 3D segmentation method to label the initial boundary between the lesion and neighboring structures. Third, we detect vessels in the ROI surrounding the lesion. Finally, we apply the propagation model with the labeled organs and vessels to accurately segment and measure the target lesion. The algorithm has been designed in a general way to be applicable to various body parts and modalities. In this paper, we evaluate the proposed algorithm on lung and lung nodule segmentation and tracking. We report the algorithm's performance by comparing the longest diameter and nodule volumes using the FDA lung Phantom data and a clinical dataset.
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. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
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.
NASA Technical Reports Server (NTRS)
Suess, Steven T.; Gary G. A.; Nerney, S. F.
1999-01-01
Streamers are often described as regions of the corona in which the density is higher than in coronal holes because the plasma is trapped by closed loops of magnetic flux. In contrast, Magnetohydrodynamics (MHD) models of the global corona show that the plasma beta identically equal to 8(pi)p/B(exp 2) > 1 in streamers above approximately 1.2Rs heliocentric height (p=pressure, B=magnetic field strength). There are three recent contributions to this topic. The first is that heating near the cusp further drives Beta up and can result in release of new slow solar wind from the top of the streamer. The second is SOHO/UVCS observations, in combination with a potential field/source surface model of the magnetic field, show beta > 1 above 1.2Rs in a streamer observed near solar sunspot minimum. The third is a magnetic field reconstruction technique (using field deforming algorithms) which was applied both to an isolated active region (AR 7999) and to the Pneuman & Kopp global MHD model. In the active region, beta becomes larger than unity at approximately 1.2Rs. In the Pneuman & Kopp model, beta = 1.0 at the base of the streamer and rises with increasing height, becoming 15-20 at 1.6Rs and 35-55 at 1.7RS. The collective implication of these three results is that beta > 1 everywhere in streamers above approximately 1.2 Rs. Global simulations go on to show that the reason streamers do not simply explode under such high beta conditions is that they are held down by pressure from the sides due to the magnetic fields (and low beta) in adjacent coronal holes. The main role of the closed magnetic loops near the cusp is to keep the streamer from continuously leaking plasma, as otherwise happens in a magnetic pinch which is similar but has no closed loops. The purpose of this note is to summarize the results implying that beta > 1 is a general property of streamers above 1.2 Rs.
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…
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 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
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
Generalized Terminal Modeling of Electromagnetic Interference
Baisden, Andrew Carson; Boroyevich, Dushan; Wang, Fei
2010-01-01
Terminal models have been used for various applications. In this paper, a three-terminal model is proposed for electromagnetic-interference (EMI) characterization. The model starts with a power electronic system at a particular operating condition and creates a unique linearized equivalent circuit. Impedances and current/voltage sources define the noise throughout the entire EMI frequency spectrum. All parameters needed to create the model are clearly defined to ensure convergence and maximize accuracy. In addition, the accuracy of the model is confirmed up to 100 MHz for a dc-dc boost converter using both simulation and experimental validation.
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…
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.
NASA Technical Reports Server (NTRS)
Marchal, C.
1971-01-01
Motion of a space probe about a spherical center of attraction is considered, applying the general theory of relativity. Motion of a probe under the influence of the sun's oblateness is also discussed. Estimates of beta, gamma, and J20 using solar probe motion are presented. It is concluded that such measurements are possible if the unknown long-period perturbing acceleration is of the order of 10 to the -11th or -12th power m/sec. sq.
Bomarrito, L; Zisa, G; Delrosso, G; Farinelli, P; Galimberti, M
2013-09-01
We present a case of acute generalized exanthematous pustolosis (AGEP) induced by amoxicillin-clavulanate. Clinical diagnosis was confirmed by symptoms presentation and histological features (Euroscar score point compatible with definite diagnosis). Patch testing performer six months later confirmed sensitization to the culprit drug and showed positivity also to other beta-lactam antibiotics (penicillin G and cephalexin). We believe that a T cell delayed response to betalactams common ring could be involved.
NASA Technical Reports Server (NTRS)
Marchal, C.
1971-01-01
Motion of a space probe about a spherical center of attraction is considered, applying the general theory of relativity. Motion of a probe under the influence of the sun's oblateness is also discussed. Estimates of beta, gamma, and J20 using solar probe motion are presented. It is concluded that such measurements are possible if the unknown long-period perturbing acceleration is of the order of 10 to the -11th or -12th power m/sec. sq.
Particle model with generalized Poincaré symmetry
NASA Astrophysics Data System (ADS)
Smith, A.
2017-08-01
Using the techniques of nonlinear coset realization with a generalized Poincaré group, we construct a relativistic particle model, invariant under the generalized symmetries, providing a dynamical realization of the B5 algebra.
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.
Sharpening Low-Energy, Standard-Model Tests via Correlation Coefficients in Neutron {beta} Decay
Gardner, S.; Zhang, C.
2001-06-18
The correlation coefficients a , A , and B in neutron {beta} decay are proportional to the ratio of the axial-vector-to-vector weak coupling constants, g{sub A}/g{sub V} , to leading recoil order. With the advent of the next generation of neutron-decay experiments, the recoil-order corrections to these expressions become experimentally accessible, admitting a plurality of standard model (SM) tests. The measurement of both a and A , e.g., allows one to test the conserved-vector-current (CVC) hypothesis and to search for second-class currents (SCC) independently. The anticipated precision of these measurements suggests that the bounds on CVC violation and SCC from studies of nuclear {beta} decay can be qualitatively bettered.
Barz, Tilman; Löffler, Verena; Arellano-Garcia, Harvey; Wozny, Günter
2010-06-25
In this work, parameters of the steric mass-formalism SMA are optimally ascertained for a reliable determination of the adsorption isotherms of beta-lactoglobulin A and B under non-isocratic conditions. For this purpose, static batch experiments are used in contrast to the protocols based on different experimental steps, which use a chromatographic column. It is shown that parameters can already be determined for a small number of experiments by using a systematic procedure based on optimal model-based experimental design and an efficient NLP-solver. The in different works observed anti-Langmuir shape of the isotherm for small concentrations of beta-lactoglobulin A was corroborated. Moreover, we also found indications for a porosity variation with changing protein concentrations.
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).
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…
Rasch Models from Objectivity: A Generalization.
ERIC Educational Resources Information Center
Linacre, John M.
Rasch models for fundamental measurement in the psychological sciences are derived from the principle of specific objectivity, the requirement that the parameter value representing each component in a test situation be independent of the other components. The dichotomous Rasch model for two-faceted analysis, applicable to conventional…
Universality in generalized models of inflation
NASA Astrophysics Data System (ADS)
Binétruy, P.; Mabillard, J.; Pieroni, M.
2017-03-01
We discuss the cosmological evolution of a scalar field with non standard kinetic term in terms of a Renormalization Group Equation (RGE). In this framework inflation corresponds to the slow evolution in a neighborhood of a fixed point and universality classes for inflationary models naturally arise. Using some examples we show the application of the formalism. The predicted values for the speed of sound cs2 and for the amount of non-Gaussianities produced in these models are discussed. In particular, we show that it is possible to introduce models with cs2 ≠ 1 that can be in agreement with present cosmological observations.
Kong, Yi-hui; Li, Wei-min; Tian, Ying
2004-03-01
To evaluate the effects of beta(3)-adrenoreceptor (AR) agonist (BRL-37344) on the expression of beta(3)-AR in a isoproterenol (ISO)-induced heart failure (HF) rat model and to investigate the influence on the levels of beta(3)-AR in failing heart. The rats were randomly divided into four groups: I group (control group, n=10); II group (normal with BRL group, n=10); III group (HF group, n=30); IV group (HF with BRL group, n=35).II and IV groups received BRL 0.4 nmol.kg-1.min-1 through caudal vein for 10 minutes twice a week. I and III groups received saline at the same time. The measure included hemodynamics, the expression of beta3-AR in left ventricular myocytes by the techniques of immunohistochemistry, beta3-AR proteins by western blot, expression levels of beta3-AR mRNA in myocardium by reverse transcription- polymerase chain reaction (RT-PCR) and the levels of apoptotic cells with a terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling(TUNEL) kit. (1)Hemodynamic: The tendency of left ventricular end systolic pressure (PES), maximal rates of rise of ventricular pressure(dp/dtmax), maximal rates of decline of ventricular pressure (dp/dtmin) in II, III and IV groups were lower (P<0.01), time constant of left ventricular relaxation (Tc) and left ventricular end diastolic pressure (PED) were higher than those of the I group (all P<0.01). There was no difference between I and II group except PED (P<0.05). Compared with III group, PES, dp/dtmax, dp/dtmin in IV group were dramatically decline (P<0.05): Tc, PED were markedly increased (Tc P<0.05, PED P<0.01). (2)The levels of beta3-AR mRNA and beta3-AR proteins were higher in III and IV groups when compared with I and II groups. There was no difference between I and II group. IV group's levels were higher than III group's. (3)The apoptotic rates in III group and IV group were significantly higher than those in I and II group (all P<0.01). When compared with III group's apoptotic cell rate, IV
Description of the General Equilibrium Model of Ecosystem Services (GEMES)
Travis Warziniack; David Finnoff; Jenny Apriesnig
2017-01-01
This paper serves as documentation for the General Equilibrium Model of Ecosystem Services (GEMES). GEMES is a regional computable general equilibrium model that is composed of values derived from natural capital and ecosystem services. It models households, producing sectors, and governments, linked to one another through commodity and factor markets. GEMES was...
Evidence for a General Factor Model of ADHD in Adults
ERIC Educational Resources Information Center
Gibbins, Christopher; Toplak, Maggie E.; Flora, David B.; Weiss, Margaret D.; Tannock, Rosemary
2012-01-01
Objective: To examine factor structures of "Diagnostic and Statistical Manual of Mental Disorders" (4th ed.) symptoms of ADHD in adults. Method: Two sets of models were tested: (a) models with inattention and hyperactivity/impulsivity as separate but correlated latent constructs and (b) hierarchical general factor models with a general factor for…
Evidence for a General Factor Model of ADHD in Adults
ERIC Educational Resources Information Center
Gibbins, Christopher; Toplak, Maggie E.; Flora, David B.; Weiss, Margaret D.; Tannock, Rosemary
2012-01-01
Objective: To examine factor structures of "Diagnostic and Statistical Manual of Mental Disorders" (4th ed.) symptoms of ADHD in adults. Method: Two sets of models were tested: (a) models with inattention and hyperactivity/impulsivity as separate but correlated latent constructs and (b) hierarchical general factor models with a general factor for…
Violin, Jonathan D; DiPilato, Lisa M; Yildirim, Necmettin; Elston, Timothy C; Zhang, Jin; Lefkowitz, Robert J
2008-02-01
G protein-coupled receptor signaling is dynamically regulated by multiple feedback mechanisms, which rapidly attenuate signals elicited by ligand stimulation, causing desensitization. The individual contributions of these mechanisms, however, are poorly understood. Here, we use an improved fluorescent biosensor for cAMP to measure second messenger dynamics stimulated by endogenous beta(2)-adrenergic receptor (beta(2)AR) in living cells. beta(2)AR stimulation with isoproterenol results in a transient pulse of cAMP, reaching a maximal concentration of approximately 10 microm and persisting for less than 5 min. We investigated the contributions of cAMP-dependent kinase, G protein-coupled receptor kinases, and beta-arrestin to the regulation of beta(2)AR signal kinetics by using small molecule inhibitors, small interfering RNAs, and mouse embryonic fibroblasts. We found that the cAMP response is restricted in duration by two distinct mechanisms in HEK-293 cells: G protein-coupled receptor kinase (GRK6)-mediated receptor phosphorylation leading to beta-arrestin mediated receptor inactivation and cAMP-dependent kinase-mediated induction of cAMP metabolism by phosphodiesterases. A mathematical model of beta(2)AR signal kinetics, fit to these data, revealed that direct receptor inactivation by cAMP-dependent kinase is insignificant but that GRK6/beta-arrestin-mediated inactivation is rapid and profound, occurring with a half-time of 70 s. This quantitative system analysis represents an important advance toward quantifying mechanisms contributing to the physiological regulation of receptor signaling.
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.
Kloen, P; Gebhardt, M C; Perez-Atayde, A; Rosenberg, A E; Springfield, D S; Gold, L I; Mankin, H J
1997-12-15
Transforming growth factor-beta (TGF-beta) is a multipotent growth factor affecting development, homeostasis, and tissue repair. In addition, increased expression of TGF-beta has been reported in different malignancies, suggesting a role for this growth factor in tumorigenesis. Using immunohistochemistry, the expression, prevalence, and distribution of TGF-beta isoforms were evaluated in 25 high grade human osteosarcomas. The Cox proportional hazards models and Kaplan-Meier curves were calculated correlating disease free survival with TGF-beta expression. Expression of one or more TGF-beta isoforms was found in all the osteosarcomas. Immunoreactivity for TGF-beta1 and TGF-beta3 generally was stronger than for TGF-beta2. The cytoplasm of the tumor cells showed stronger staining than their surrounding extracellular stroma. Most notably, osteoclasts showed strong to intense staining for all three isoforms. In 11 of 25 specimens angiogenic activity was noted with staining of multiple small vessels in the tumor stroma. Expression of TGF-beta3, but not of TGF-beta2 or TGF-beta1, related to disease progression, such that there was a statistically significant decrease in the disease free interval as the immunoreactivity for TGF-beta3 increased. All osteosarcomas expressed TGF-beta in the cytoplasm of the tumor cells as well as in their extracellular stroma. The presence of TGF-beta in the endothelial and perivascular layers of small vessels in the tumor stroma suggests angiogenic activity of this growth factor. The expression of TGF-beta3 was correlated strongly with disease progression (P = 0.027). These data suggest that increased expression of TGF-beta isoforms, especially TGF-beta3, may play a role in osteosarcoma progression.
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.
Generalized Model of a Skeletal Muscle
NASA Astrophysics Data System (ADS)
Shil'ko, S. V.; Chernous, D. A.; Bondarenko, K. K.
2016-01-01
A new phenomenological model of a skeletal muscle consisting of a contractile and two nonlinear viscoelastic elements is proposed. The corresponding system of differential equations of the model is obtained, which allows one to derive time-dependent relations between the axial stress and the longitudinal strain in passive and activated states of the muscle. Methods for determining the viscoelastic and functional characteristics of the muscle as input parameters of the equations mentioned above are developed. These methods are based on the joint application of known experimental relations for a single muscle fiber and the results of muscle indentation in vivo on a "Miometer UT 98-01" device.
Dhanasekaran, Muralikrishnan; Holcomb, Leigh A; Hitt, Angie R; Tharakan, Binu; Porter, Jami W; Young, Keith A; Manyam, Bala V
2009-01-01
PSAPP mice expressing the 'Swedish' amyloid precursor protein and the M146L presenilin 1 mutations are a well-characterized model for spontaneous amyloid beta plaque formation. Centella asiatica has a long history of use in India as a memory enhancing drug in Ayurvedic literature. The study investigated whether Centella asiatica extract (CaE) can alter the amyloid pathology in PSAPP mice by administering CaE (2.5 or 5.0 g/kg/day) starting at 2 months of age prior to the onset of detectable amyloid deposition and continued for either 2 months or 8 months. A significant decrease in amyloid beta 1-40 and 1-42 was detectable by ELISA following an 8 month treatment with 2.5 mg/kg of CaE. A reduction in Congo Red stained fibrillar amyloid plaques was detected with the 5.0 mg/kg CaE dose and long-term treatment regimen. It was also confirmed that CaE functions as an antioxidant in vitro, scavenging free radicals, reducing lipid peroxidation and protecting against DNA damage. The data indicate that CaE can impact the amyloid cascade altering amyloid beta pathology in the brains of PSAPP mice and modulating components of the oxidative stress response that has been implicated in the neurodegenerative changes that occur with Alzheimer's disease. Copyright 2008 John Wiley & Sons, Ltd.
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
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…
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.
Partition-based acquisition model for speed up navigated beta-probe surface imaging
NASA Astrophysics Data System (ADS)
Monge, Frédéric; Shakir, Dzhoshkun I.; Navab, Nassir; Jannin, Pierre
2016-03-01
Although gross total resection in low-grade glioma surgery leads to a better patient outcome, the in-vivo control of resection borders remains challenging. For this purpose, navigated beta-probe systems combined with 18F-based radiotracer, relying on activity distribution surface estimation, have been proposed to generate reconstructed images. The clinical relevancy has been outlined by early studies where intraoperative functional information is leveraged although inducing low spatial resolution in reconstruction. To improve reconstruction quality, multiple acquisition models have been proposed. They involve the definition of attenuation matrix for designing radiation detection physics. Yet, they require high computational power for efficient intraoperative use. To address the problem, we propose a new acquisition model called Partition Model (PM) considering an existing model where coefficients of the matrix are taken from a look-up table (LUT). Our model is based upon the division of the LUT into averaged homogeneous values for assigning attenuation coefficients. We validated our model using in vitro datasets, where tumors and peri-tumoral tissues have been simulated. We compared our acquisition model with the o_-the-shelf LUT and the raw method. Acquisition models outperformed the raw method in term of tumor contrast (7.97:1 mean T:B) but with a difficulty of real-time use. Both acquisition models reached the same detection performance with references (0.8 mean AUC and 0.77 mean NCC), where PM slightly improves the mean tumor contrast up to 10.1:1 vs 9.9:1 with the LUT model and more importantly, it reduces the mean computation time by 7.5%. Our model gives a faster solution for an intraoperative use of navigated beta-probe surface imaging system, with improved image quality.
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.
Limitations of animal models in predicting beta-lactam efficacy for endocarditis and meningitis.
Gerberding, J L; Sande, M A
1986-01-01
Animal models are important in predicting the efficacy in humans of antimicrobial agents for various disease conditions, including endocarditis and meningitis. Screening models are useful in assessing antibiotic effectiveness and toxicity; their advantages include simplicity, a reproducible course of infection, a well-defined therapeutic end point, and low cost. However, the inoculum size, the virulence of the organism, and the production of beta-lactamases can have important effects on outcome and must be considered in the interpretation of data obtained from such models. Discriminative models are those designed to mimic human disease as closely as possible with respect to infectious inoculum, host response, and course of disease. Each drug's pharmacokinetics must be carefully documented before being extrapolated to humans. Rigid criteria must be established to minimize misinterpretation of results from animal studies before conclusions from in vivo animal models are applied to human disease.
Xu, Xu Steven; Samtani, Mahesh N; Dunne, Adrian; Nandy, Partha; Vermeulen, An; De Ridder, Filip
2013-08-01
Beta regression models have been recommended for continuous bounded outcome scores that are often collected in clinical studies. Implementing beta regression in NONMEM presents difficulties since it does not provide gamma functions required by the beta distribution density function. The objective of the study was to implement mixed-effects beta regression models in NONMEM using Nemes' approximation to the gamma function and to evaluate the performance of the NONMEM implementation of mixed-effects beta regression in comparison to the commonly used SAS approach. Monte Carlo simulations were conducted to simulate continuous outcomes within an interval of (0, 70) based on a beta regression model in the context of Alzheimer's disease. Six samples per subject over a 3 years period were simulated at 0, 0.5, 1, 1.5, 2, and 3 years. One thousand trials were simulated and each trial had 250 subjects. The simulation-reestimation exercise indicated that the NONMEM implementation using Laplace and Nemes' approximations provided only slightly higher bias and relative RMSE (RRMSE) compared to the commonly used SAS approach with adaptive Gaussian quadrature and built-in gamma functions, i.e., the difference in bias and RRMSE for fixed-effect parameters, random effects on intercept, and the precision parameter were <1-3 %, while the difference in the random effects on the slope was <3-7 % under the studied simulation conditions. The mixed-effect beta regression model described the disease progression for the cognitive component of the Alzheimer's disease assessment scale from the Alzheimer's Disease Neuroimaging Initiative study. In conclusion, with Nemes' approximation of the gamma function, NONMEM provided comparable estimates to those from SAS for both fixed and random-effect parameters. In addition, the NONMEM run time for the mixed beta regression models appeared to be much shorter compared to SAS, i.e., 1-2 versus 20-40 s for the model and data used in the manuscript.
McClenaghan, Joseph; Garofalo, Andrea M.; Meneghini, Orso; ...
2017-08-03
In this study, transport modeling of a proposed ITER steady-state scenario based on DIII-D high poloidal-beta (more » $${{\\beta}_{p}}$$ ) discharges finds that ITB formation can occur with either sufficient rotation or a negative central shear q-profile. The high $${{\\beta}_{p}}$$ scenario is characterized by a large bootstrap current fraction (80%) which reduces the demands on the external current drive, and a large radius internal transport barrier which is associated with excellent normalized confinement. Modeling predictions of the electron transport in the high $${{\\beta}_{p}}$$ scenario improve as $${{q}_{95}}$$ approaches levels similar to typical existing models of ITER steady-state and the ion transport is turbulence dominated. Typical temperature and density profiles from the non-inductive high $${{\\beta}_{p}}$$ scenario on DIII-D are scaled according to 0D modeling predictions of the requirements for achieving a $Q=5$ steady-state fusion gain in ITER with 'day one' heating and current drive capabilities. Then, TGLF turbulence modeling is carried out under systematic variations of the toroidal rotation and the core q-profile. A high bootstrap fraction, high $${{\\beta}_{p}}$$ scenario is found to be near an ITB formation threshold, and either strong negative central magnetic shear or rotation in a high bootstrap fraction are found to successfully provide the turbulence suppression required to achieve $Q=5$.« less
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.
Sato, H.; Sugiyama, Y.; Sawada, Y.; Iga, T.; Hanano, M.
1987-07-01
In order to simulate the distribution and elimination of radioiodinated human beta-endorphin (/sup 125/I-beta-EP) after iv bolus injection in rats, we proposed a physiologically based pharmacokinetic model incorporating diffusional transport of /sup 125/I-beta-EP across the capillary membrane. This model assumes that the distribution of /sup 125/I-beta-EP is restricted only within the blood and the tissue interstitial fluid, and that a diffusional barrier across the capillary membrane exists in each tissue except the liver. The tissue-to-blood partition coefficients were estimated from the ratios of the concentration in tissues to that in arterial plasma at the terminal (pseudoequilibrium) phase. The total body plasma clearance (9.0 ml/min/kg) was appropriately assigned to the liver and kidney. The transcapillary diffusion clearances of /sup 125/I-beta-EP were also estimated and shown to correlate linearly with that of inulin in several tissues. Numerically solving the mass-balance differential equations as to plasma and each tissue simultaneously, simulated concentration curves of /sup 125/I-beta-EP corresponded well with the observed data. It was suggested by the simulation that the initial rapid disappearance of /sup 125/I-beta-EP from plasma after iv injection could be attributed in part to the transcapillary diffusion of the peptide.
Guariniello, Luciana Doria; Correa, Mariangela; Jasiulionis, Miriam Galvonas; Machado, Joel; Silva, José Antônio; Pesquero, João Bosco; Carneiro, Célia Regina Whitaker
2006-06-01
Alterations in transforming growth factor (TGF)-beta signalling have been frequently implicated in human cancer, and an important mechanism underlying its pro-oncogenic nature is suppression of the host antitumour immune response. Considering the immunosuppressive effect of TGF-beta, we asked whether human tumour cells, known to secrete TGF-beta in culture, would survive and grow when implanted into the peritoneal cavity of immunocompetent mice. Therefore, we developed a xenogeneic model where mice were intraperitoneally (i.p.) injected with a TGF-beta-secreting human colorectal adenocarcinoma cell line, LISP-A10. Although animals did not develop macroscopic tumours, the recovery and isolation of human tumour cells was achieved when an inflammatory environment was locally induced by the administration of complete Freund's adjuvant (CFA). This procedure significantly increased TGF-beta concentrations in the peritoneal fluid and was accompanied by impaired activation of the host-specific immune response against LISP-A10 cells. Furthermore, inflammatory lesions resembling human inflammatory pseudotumours (IPTs) were observed on the surface of i.p. organs. These lesions could be induced by either injection of LISP-A10 cells, cells-conditioned medium or recombinant TGF-beta but only after administration of CFA. In addition, host cyclooxygenase-2 and kinin receptors played an important role in the induction of TGF-beta-mediated IPT-like lesions in our experimental model.
Ego Development and a General Model for Counseling and Psychotherapy.
ERIC Educational Resources Information Center
Swensen, Clifford H.
1980-01-01
Describes a general model within which various techniques of counseling and psychotherapy may be integrated. This model is based on Lewin's formula, that is, behavior is a function of the person and the environment. (Author)
Theoretical models of Beta Cephei stars constructed with new radiative opacities
NASA Technical Reports Server (NTRS)
Stothers, R.
1976-01-01
Equilibrium models for the main-sequence and early post-main-sequence phases of evolution are constructed for stars of 10.9 and 15 solar masses with two different initial hydrogen and metals abundances. Carson's (1976) radiative opacities are used in the calculations. It is found that the models which lie off the zero-age main sequence have cooler effective temperatures than corresponding models based on other opacities and cross the observed Beta Cephei strip in the H-R diagram only during the main phase of core hydrogen burning. The stability of radial and nonradial pulsations is studied by applying linear nonadiabatic perturbations to the models. The results show that all the modes examined are stable and that the margin of stability decreases with advancing evolution. It is suggested that the closeness of the periods of the two lowest nonradial quadrupole p-modes may be responsible for the 'beat' phenomenon observed in many Beta Cephei stars, if these modes are somehow excited. Possible instability mechanisms are evaluated, particularly the ultimate ionization of CNO elements.
Fourier's Law in a Generalized Piston Model
NASA Astrophysics Data System (ADS)
Caprini, Lorenzo; Cerino, Luca; Sarracino, Alessandro; Vulpiani, Angelo
2017-07-01
A simplified, but non trivial, mechanical model -- gas of $N$ particles of mass $m$ in a box partitioned by $n$ mobile adiabatic walls of mass $M$ -- interacting with two thermal baths at different temperatures, is discussed in the framework of kinetic theory. Following an approach due to Smoluchowski, from an analysis of the collisions particles/walls, we derive the values of the main thermodynamic quantities for the stationary non-equilibrium states. The results are compared with extensive numerical simulations; in the limit of large $n$, $mN/M\\gg 1$ and $m/M \\ll 1$, we find a good approximation of Fourier's law.
A Generalized Cap Model for Geological Materials
1974-11-14
modified Drucker - Prager , Ref. [31, yield condition, denoted by f(lJ ) = 0 (1) in which J and J are the first and second invariants of the stress and...models, such as anistropy, rate dependence, and hardening of the modified Drucker - Prager portion of the yield surface (isotropic and/or kinematic... DRUCKER - PRAGER LINE 11-1 1 15 in which W, D, , D, D, W and D are material constants. The quantity R in Eqs. (15, 16) represents the ratio of the
Generalized matrix models and AGT correspondence at all genera
NASA Astrophysics Data System (ADS)
Bonelli, Giulio; Maruyoshi, Kazunobu; Tanzini, Alessandro; Yagi, Futoshi
2011-07-01
We study generalized matrix models corresponding to n-point Virasoro conformal blocks on Riemann surfaces with arbitrary genus g. Upon AGT correspondence, these describe four dimensional mathcal{N} = 2 SU(2) n+3 g-3 gauge theories with generalized quiver diagrams. We obtain the generalized matrix models from the perturbative evaluation of the Liouville correlation functions and verify the consistency of the description with respect to degenerations of the Riemann surface. Moreover, we derive the Seiberg-Witten curve for the mathcal{N} = 2 gauge theory as the spectral curve of the generalized matrix model, thus providing a check of AGT correspondence at all genera.
Modeling electrokinetics in ionic liquids: General
Wang, Chao; Bao, Jie; Pan, Wenxiao; ...
2017-04-01
Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson–Nernst–Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier–Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on amore » curved ionselective surface. Lastly, we also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less
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.
A General Model for Measurement Improvement
NASA Astrophysics Data System (ADS)
Dumke, Reiner; Yazbek, Hashem; Asfoura, Evan; Georgieva, Konstantina
The following paper describes our approach for characterizing software measurement in a holistic manner. Therefore software measurement was defined as a system including all aspects of software measurement, evaluation, estimation and exploration. First of all, we define these components of software measurement considering the different levels of each component in order to classify the different levels of the software measurement itself. First examples have shown the appropriateness of this approach for paradigm related measurement comparisons and improvements. In this paper, we extend our modelling approach and demonstrate the meaningfulness of comparing software measurement practices for different standards and process improvement approaches. These examples help for identifying essential key areas for measurement improvement as basics of quality assurance.
Shell-model calculations of beta-decay rates for s- and r-process nucleosyntheses
NASA Astrophysics Data System (ADS)
Takahashi, K.; Mathews, G. J.; Bloom, S. D.
1985-10-01
Examples of large-basis shell-model calculations of Gamow-Teller (BETA)-decay properties of specific interest in the astrophysical s- and r- processes are presented. Numerical results are given for: (1) the GT-matrix elements for the excited state decays of the unstable s-process nucleus Tc-99; and (2) the GT-strength function for the neutron-rich nucleus Cd-130, which lies on the r-process path. The results are discussed in conjunction with the astrophysics problems.
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…
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…
Large deviation approach to the generalized random energy model
NASA Astrophysics Data System (ADS)
Dorlas, T. C.; Dukes, W. M. B.
2002-05-01
The generalized random energy model is a generalization of the random energy model introduced by Derrida to mimic the ultrametric structure of the Parisi solution of the Sherrington-Kirkpatrick model of a spin glass. It was solved exactly in two special cases by Derrida and Gardner. A complete solution for the thermodynamics in the general case was given by Capocaccia et al. Here we use large deviation theory to analyse the model in a very straightforward way. We also show that the variational expression for the free energy can be evaluated easily using the Cauchy-Schwarz inequality.
A Generalized Kinetic Model for Heterogeneous Gas-Solid Reactions
Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A.
2012-08-15
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.
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.
Layered Kondo lattice model for quantum critical beta-YbAlB4.
Nevidomskyy, Andriy H; Coleman, P
2009-02-20
We analyze the magnetic and electronic properties of the quantum critical heavy fermion superconductor beta-YbAlB4, calculating the Fermi surface and the angular dependence of the extremal orbits relevant to the de Haas-van Alphen measurements. Using a combination of the realistic materials modeling and single-ion crystal field analysis, we are led to propose a layered Kondo lattice model for this system, in which two-dimensional boron layers are Kondo coupled via interlayer Yb moments in a Jz=+/-5/2 state. This model fits the measured single-ion magnetic susceptibility and predicts a substantial change in the electronic anisotropy as the system is pressure tuned through the quantum critical point.
Quasideterminant solutions of the generalized Heisenberg magnet model
NASA Astrophysics Data System (ADS)
Saleem, U.; Hassan, M.
2010-01-01
In this paper we present the Darboux transformation for the generalized Heisenberg magnet (GHM) model based on the general linear Lie group GL(n) and construct multi-soliton solutions in terms of quasideterminants. Further we relate the quasideterminant multi-soliton solutions obtained by means of Darboux transformation with those obtained by the dressing method. We also discuss the model based on the Lie group SU(n) and obtain explicit soliton solutions of the model based on SU(2).
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.
Alibardi, L
2013-03-01
The maturation of the corneous material of feathers is a special case of cornification in vertebrate epidermis and is believed to occur mainly by the accumulation of small proteins of about 100 amino acids and a central beta-pleated sheet region known as feather keratins. The present immunocytochemical study carried out using double-labeling immunogold shows that a small amount of alpha-keratins of intermediate filament type form the early keratin clumps in barb and barbule cells. These initial nuclei of formation of corneous material are rapidly coated by the deposition of large amounts of small feather keratin-associated beta-proteins (feather keratins). The latter proteins turn the keratin bundles of barb and barbule cells into a compact and apparently amorphous mass of corneous material where no sign of intermediate filaments are seen. Feather beta-proteins however form an irregular filamentous network of 2-3nm thick electron-pale filaments and produce the characteristic feather X-ray pattern due to their prevalent amount over any other protein present in feather cells. The modality of cornification in feathers is discussed in relation to the process of formation of corneous material in the skin of vertebrates in general that occurs by the association of intermediate filament proteins and keratin-associated proteins.
Tokamak disruption alarm based on a neural network model of the high- beta limit
NASA Astrophysics Data System (ADS)
Wroblewski, D.; Jahns, G. L.; Leuer, J. A.
1997-06-01
An artificial neural network, combining signals from a large number of plasma diagnostics, was used to estimate the high- beta disruption boundary in the DIII-D tokamak. It is shown that inclusion of many diagnostic measurements results in a much more accurate prediction of the disruption boundary than that provided by the traditional Troyon limit. A trained neural network constitutes a non-linear, non-parametric model of the disruption boundary. Through the analysis of the input-output sensitivities, the relative statistical significance of various diagnostic measurements (plasma parameters) for the determination of the disruption boundary is directly assessed and the number of diagnostics used by the neural network model is reduced to the necessary minimum. The neural network is trained to map the disruption boundary throughout most of the discharge. As a result, it can predict the high- beta disruption boundary on a time-scale of the order of 100 ms (much longer than the precursor growth time), which makes this approach ideally suitable for real time application in a disruption avoidance scheme. Owing to the relative simplicity of the required computations, the neural network is easily implemented in a real time system. A prototype of the neural network disruption alarm was installed within the DIII-D digital plasma control system, and its real time operation, with a typical time resolution of 10 ms, was demonstrated
Akagi, K; Nagao, T; Urushidani, T
1999-09-01
We established a beta-escin-permeabilized gland model with the use of rabbit isolated gastric glands. The glands retained an ability to secrete acid, monitored by [14C]aminopyrine accumulation, in response to cAMP, forskolin, and histamine. These responses were all inhibited by cAMP-dependent protein kinase inhibitory peptide. Myosin light-chain kinase inhibitory peptide also suppressed aminopyrine accumulation, whereas the inhibitory peptide of protein kinase C or that of calmodulin kinase II was without effect. Guanosine-5'-O-(3-thiotriphosphate) (GTPgammaS) abolished cAMP-stimulated acid secretion concomitantly, interfering with the redistribution of H+-K+-ATPase from tubulovesicles to the apical membrane. To identify the targets of GTPgammaS, effects of peptide fragments of certain GTP-binding proteins were examined. Although none of the peptides related to Rab proteins showed any effect, the inhibitory peptide of Arf protein inhibited cAMP-stimulated secretion. These results demonstrate that our new model, the beta-escin-permeabilized gland, allows the introduction of relatively large molecules, e.g., peptides, into the cell, and will be quite useful for analyzing signal transduction of parietal cell function.
Preclinical transfusion-dependent humanized mouse model of beta thalassemia major.
Huo, Yongliang; McConnell, Sean C; Ryan, Thomas M
2009-05-07
A preclinical humanized mouse model of beta thalassemia major or Cooley anemia (CA) was generated by targeted gene replacement of the mouse adult globin genes in embryonic stem cells. The mouse adult alpha and beta globin genes were replaced with adult human alpha globin genes (alpha2alpha1) and a human fetal to adult hemoglobin (Hb)-switching cassette (gamma(HPFH)deltabeta(0)), respectively. Similar to human infants with CA, fully humanized mice survived postnatally by synthesizing predominantly human fetal Hb, HbF (alpha(2)gamma(2)), with a small amount of human minor adult Hb, HbA2 (alpha(2)delta(2)). Completion of the human fetal to adult Hb switch after birth resulted in severe anemia marked by erythroid hyperplasia, ineffective erythropoiesis, hemolysis, and death. Similar to human patients, CA mice were rescued from lethal anemia by regular blood transfusion. Transfusion corrected the anemia and effectively suppressed the ineffective erythropoiesis, but led to iron overload. This preclinical humanized animal model of CA will be useful for the development of new transfusion and iron chelation regimens, the study of iron homeostasis in disease, and testing of cellular and genetic therapies for the correction of thalassemia.
Bolte, Kathrin; Rensing, Stefan A; Maier, Uwe-G
2015-02-01
Beta-oxidation of fatty acids and detoxification of reactive oxygen species are generally accepted as being fundamental functions of peroxisomes. Additionally, these pathways might have been the driving force favoring the selection of this compartment during eukaryotic evolution. Here we performed phylogenetic analyses of enzymes involved in beta-oxidation of fatty acids in Bacteria, Eukaryota, and Archaea. These imply an alpha-proteobacterial origin for three out of four enzymes. By integrating the enzymes' history into the contrasting models on the origin of eukaryotic cells, we conclude that peroxisomes most likely evolved non-symbiotically and subsequent to the acquisition of mitochondria in an archaeal host cell. © 2015 WILEY Periodicals, Inc.
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.
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.;
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.
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.
Baune, Bernhard T; Ponath, Gerald; Rothermundt, Matthias; Riess, Olaf; Funke, Harald; Berger, Klaus
2008-01-01
This study is to investigate the associations between specific polymorphisms in three cytokine genes and domains of cognitive functioning in a population based study in the elderly. In a cross-sectional study of 369 community dwelling elderly subjects we examined the relationships between the polymorphisms IL-1beta-1418C-->T, IL-6-572G-->C and TNF-alpha-308G-->A and the cognitive function domains memory, processing speed and motor function using an extensive neuropsychological test battery. Linear regression models were used in the analysis and results adjusted for multiple comparisons. A significant association between the IL-1beta-1418C-->T polymorphism and memory performance was found with carriers of the T allele (dominant model) having worse memory performance than those with the C allele. In addition, a significant association between the TNF-alpha-308G-->A polymorphism and processing speed was observed, indicating better performance for heterozygous or homozygous carriers of the A allele. These results remained significant after adjustment for known confounders of cognitive function and additional Bonferroni correction for multiple comparisons. Our study provides first results on detrimental effects of the IL-1beta-1418C-->T polymorphism on memory performance and neuroprotective effects of the TNF-alpha-308G-->A polymorphism on processing speed in elderly individuals. Further research is needed to prospectively examine changes in cognitive performance in relation to cytokine genotypes.
Hierarchical Generalized Linear Models for the Analysis of Judge Ratings
ERIC Educational Resources Information Center
Muckle, Timothy J.; Karabatsos, George
2009-01-01
It is known that the Rasch model is a special two-level hierarchical generalized linear model (HGLM). This article demonstrates that the many-faceted Rasch model (MFRM) is also a special case of the two-level HGLM, with a random intercept representing examinee ability on a test, and fixed effects for the test items, judges, and possibly other…
Critical Comments on the General Model of Instructional Communication
ERIC Educational Resources Information Center
Walton, Justin D.
2014-01-01
This essay presents a critical commentary on McCroskey et al.'s (2004) general model of instructional communication. In particular, five points are examined which make explicit and problematize the meta-theoretical assumptions of the model. Comments call attention to the limitations of the model and argue for a broader approach to…
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.
Conserved Quantities in the Generalized Heisenberg Magnet (ghm) Model
NASA Astrophysics Data System (ADS)
Mushahid, N.; Hassan, M.; Saleem, U.
2013-03-01
We study the conserved quantities of the generalized Heisenberg magnet (GHM) model. We derive the nonlocal conserved quantities of the model using the iterative procedure of Brezin et al. [Phys. Lett. B82, 442 (1979).] We show that the nonlocal conserved quantities Poisson commute with local conserved quantities of the model.
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…
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.
Ising model on the generalized Bruhat-Tits tree
NASA Astrophysics Data System (ADS)
Zinoviev, Yu. M.
1991-08-01
The partition function and the correlation functions of the Ising model on the generalized Bruhat-Tits tree are calculated. We computed also the averages of these correlation functions when the corresponding vertices are attached to the boundary of the generalized Bruhat-Tits tree.
Ising model on the generalized Bruhat-Tits tree
NASA Astrophysics Data System (ADS)
Zinoviev, Yu. M.
1990-06-01
The partition function and the correlation functions of the Ising model on the generalized Bruhat-Tits tree are calculated. We computed also the averages of these correlation functions when the corresponding vertices are attached to the boundary of the generalized Bruhat-Tits tree.
The General Linear Model and Direct Standardization: A Comparison.
ERIC Educational Resources Information Center
Little, Roderick J. A.; Pullum, Thomas W.
1979-01-01
Two methods of analyzing nonorthogonal (uneven cell sizes) cross-classified data sets are compared. The methods are direct standardization and the general linear model. The authors illustrate when direct standardization may be a desirable method of analysis. (JKS)
NASA Astrophysics Data System (ADS)
Borgohain, Happy; Das, Mrinal Kumar
2017-09-01
We have studied neutrinoless double beta decay and charged lepton flavour violation in broken μ - τ symmetric neutrino masses in a generic left-right symmetric model (LRSM). The leading order μ - τ symmetric mass matrix originates from the type I (II) seesaw mechanism, whereas the perturbations to μ - τ symmetry in order for generation of non-zero reactor mixing angle 𝜃 13, as required by latest neutrino oscillation data, originates from the type II (I) seesaw mechanism. In our work, we considered four different realizations of μ - τ symmetry, viz. Tribimaximal Mixing (TBM), Bimaximal Mixing (BM), Hexagonal Mixing (HM) and Golden Ratio Mixing (GRM). We then studied the new physics contributions to neutrinoless double beta decay (NDBD) ignoring the left-right gauge boson mixing and the heavy-light neutrino mixing within the framework of LRSM. We have considered the mass of the gauge bosons and scalars to be around TeV and studied the effects of the new physics contributions on the effective mass and the NDBD half life and compared with the current experimental limit imposed by KamLAND-Zen. We further extended our analysis by correlating the lepton flavour violation of the decay processes, ( μ → 3 e) and ( μ → e γ) with the lightest neutrino mass and atmospheric mixing angle 𝜃 23 respectively.
NASA Astrophysics Data System (ADS)
Borgohain, Happy; Das, Mrinal Kumar
2017-06-01
We have studied neutrinoless double beta decay and charged lepton flavour violation in broken μ - τ symmetric neutrino masses in a generic left-right symmetric model (LRSM). The leading order μ - τ symmetric mass matrix originates from the type I (II) seesaw mechanism, whereas the perturbations to μ - τ symmetry in order for generation of non-zero reactor mixing angle 𝜃 13, as required by latest neutrino oscillation data, originates from the type II (I) seesaw mechanism. In our work, we considered four different realizations of μ - τ symmetry, viz. Tribimaximal Mixing (TBM), Bimaximal Mixing (BM), Hexagonal Mixing (HM) and Golden Ratio Mixing (GRM). We then studied the new physics contributions to neutrinoless double beta decay (NDBD) ignoring the left-right gauge boson mixing and the heavy-light neutrino mixing within the framework of LRSM. We have considered the mass of the gauge bosons and scalars to be around TeV and studied the effects of the new physics contributions on the effective mass and the NDBD half life and compared with the current experimental limit imposed by KamLAND-Zen. We further extended our analysis by correlating the lepton flavour violation of the decay processes, (μ → 3e) and (μ → e γ) with the lightest neutrino mass and atmospheric mixing angle 𝜃 23 respectively.
NASA Astrophysics Data System (ADS)
Fallah, Haniyeh
Pancreatic beta-cells produce insulin to regularize the blood glucose level. Bursting is important in beta cells due to its relation to the release of insulin. Pernarowski model is a simple polynomial model of beta-cell activities indicating bursting oscillations in these cells. This paper presents bursting behaviors of symmetric type in this model. In addition, it is shown that the current system exhibits the phenomenon of period doubling cascades of canards which is a route to chaos. Canards are also observed symmetrically near folds of slow manifold which results in a chaotic transition between n and n + 1 spikes symmetric bursting. Furthermore, mixed-mode oscillations (MMOs) and combination of symmetric bursting together with MMOs are illustrated during the transition between symmetric bursting and continuous spiking.
African wave disturbances in a general circulation model
NASA Technical Reports Server (NTRS)
Estoque, M. A.; Jiing, J. G.; Shukla, J.
1983-01-01
Evidence is presented to show that African wave disturbances are reproduced in a general circulation simulation. The model used is the general circulation model developed by the Goddard Laboratory for Atmospheric Sciences of the National Aeronautics and Space Agency. The model was integrated in order to simulate the summer of 1974. A synoptic analysis of the simulated data over Africa for the month of July was done. The results of the analysis show that wave disturbances are generated by the model; the behavior and the structure of the simulated disturbances are similar to those observed over tropical Africa during the northern summer.
Stability of Beta Limited Thermonuclear Burn.
1980-01-28
critical value of beta is exceeded. For example, in tokamaks such a critical beta might result due to the onset of magnetohydrodynamic *instabilities. Since...generally accepted theoretical models for anoma- lous plasma loss in such devices as tokamaks are not available, we shall try to make as few...situation might result from the onset of magnetic field braiding in a tokamak ). In this case a 3 % a4 >> a 1 %,a2 (6) (Note that since the a terms are
Casadio, R; Frigimelica, E; Bossù, P; Neumann, D; Martin, M U; Tagliabue, A; Boraschi, D
2001-06-15
A preliminary model has been calculated for the activating interaction of the interleukin 1 receptor (IL-1R) accessory protein IL-1RAcP with the ligand/receptor complex IL-1beta/IL-1R(I). First, IL-1RAcP was modeled on the crystal structure of IL-1R(I) bound to IL-1beta. Then, the IL-1RAcP model was docked using specific programs to the crystal structure of the IL-1beta/IL-1R(I) complex. Two types of models were predicted, with comparable probability. Experimental data obtained with the use of IL-1beta peptides and antibodies, and with mutated IL-1beta proteins, support the BACK model, in which IL-1RAcP establishes contacts with the back of IL-1R(I) wrapped around IL-1beta.
Zhang, Dongshan; Sun, Lin; Xian, Wang; Liu, Fuyou; Ling, Guanghui; Xiao, Li; Liu, Yanhong; Peng, Youmin; Haruna, Yoshisuke; Kanwar, Yashpal S
2010-03-01
Transforming growth factor-beta (TGF-beta) has a pivotal function in the progression of renal fibrosis in a wide variety of renal diseases. Smad proteins have been identified to have an important function in regulating the expression of extracellular matrix (ECM) proteins through TGF-beta signaling pathway. Aberrant TGF-beta/Smad signaling can be modulated by stabilization of microtubules with paclitaxel. In this study, we investigated if paclitaxel can attenuate tubulointerstitial fibrosis in a rat model of unilateral ureteral obstruction (UUO). Rats in groups of six were subjected to UUO and received low-dose intraperitoneal injection of paclitaxel (0.3 mg/kg) twice a week. They were killed at day 7 and 14 after UUO or Sham operation. TGF-beta signaling cascade and status of various ECM proteins were evaluated by RT-PCR, western blotting and immunohistochemical or immunofluorescence staining. The paclitaxel treatment markedly suppressed Smad2 and Smad3 phosphorylation. This was associated with attenuated expression of integrin-linked kinase, collagens I and III, fibronectin (FN) and alpha-smooth muscle actin, and a substantial decrease in renal fibrosis in animals that underwent UUO and received paclitaxel. These data indicate that the low-dose paclitaxel ameliorates renal tubulointerstitial fibrosis by modulating TGF-beta signaling, and thus, the paclitaxel may have some therapeutic value in humans.
Dickenson, Eric R V; Summers, R Scott; Croué, Jean-Philippe; Gallard, Hervé
2008-05-01
While it is known that resorcinol- and phenol-type aromatic structures within natural organic matter (NOM) react during drinking water chlorination to form trihalomethanes (THMs), limited studies have examined aliphatic-type structures as THM and haloacetic acid (HAA) precursors. A suite of aliphatic acid model compounds were chlorinated and brominated separately in controlled laboratory-scale batch experiments. Four and two beta-dicarbonyl acid compounds were found to be important precursors for the formation of THMs (chloroform and bromoform (71-91% mol/mol)), and dihaloacetic acids (DXAAs) (dichloroacetic acid and dibromoacetic acid (5-68% mol/mol)), respectively, after 24 h at pH 8. Based upon adsorbable organic halide formation, THMs and DXAAs, and to a lesser extent mono and trihaloacetic acids, were the majority (> 80%) of the byproducts produced for most of the aliphatic beta-dicarbonyl acid compounds. Aliphatic beta-diketone-acid-type and beta-keto-acid-type structures could be possible fast- and slow-reacting THM precursors, respectively, and aliphatic beta-keto-acid-type structures are possible slow-reacting DXAA precursors. Aliphatic beta-dicarbonyl acid moieties in natural organic matter, particularly in the hydrophilic fraction, could contribute to the significant formation of THMs and DXAAs observed after chlorination of natural waters.
The DINA model as a constrained general diagnostic model: Two variants of a model equivalency.
von Davier, Matthias
2014-02-01
The 'deterministic-input noisy-AND' (DINA) model is one of the more frequently applied diagnostic classification models for binary observed responses and binary latent variables. The purpose of this paper is to show that the model is equivalent to a special case of a more general compensatory family of diagnostic models. Two equivalencies are presented. Both project the original DINA skill space and design Q-matrix using mappings into a transformed skill space as well as a transformed Q-matrix space. Both variants of the equivalency produce a compensatory model that is mathematically equivalent to the (conjunctive) DINA model. This equivalency holds for all DINA models with any type of Q-matrix, not only for trivial (simple-structure) cases. The two versions of the equivalency presented in this paper are not implied by the recently suggested log-linear cognitive diagnosis model or the generalized DINA approach. The equivalencies presented here exist independent of these recently derived models since they solely require a linear - compensatory - general diagnostic model without any skill interaction terms. Whenever it can be shown that one model can be viewed as a special case of another more general one, conclusions derived from any particular model-based estimates are drawn into question. It is widely known that multidimensional models can often be specified in multiple ways while the model-based probabilities of observed variables stay the same. This paper goes beyond this type of equivalency by showing that a conjunctive diagnostic classification model can be expressed as a constrained special case of a general compensatory diagnostic modelling framework.
Graphical tools for model selection in generalized linear models.
Murray, K; Heritier, S; Müller, S
2013-11-10
Model selection techniques have existed for many years; however, to date, simple, clear and effective methods of visualising the model building process are sparse. This article describes graphical methods that assist in the selection of models and comparison of many different selection criteria. Specifically, we describe for logistic regression, how to visualize measures of description loss and of model complexity to facilitate the model selection dilemma. We advocate the use of the bootstrap to assess the stability of selected models and to enhance our graphical tools. We demonstrate which variables are important using variable inclusion plots and show that these can be invaluable plots for the model building process. We show with two case studies how these proposed tools are useful to learn more about important variables in the data and how these tools can assist the understanding of the model building process.
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.
Comparison and Contrast of Two General Functional Regression Modeling Frameworks
Morris, Jeffrey S.
2017-01-01
In this article, Greven and Scheipl describe an impressively general framework for performing functional regression that builds upon the generalized additive modeling framework. Over the past number of years, my collaborators and I have also been developing a general framework for functional regression, functional mixed models, which shares many similarities with this framework, but has many differences as well. In this discussion, I compare and contrast these two frameworks, to hopefully illuminate characteristics of each, highlighting their respecitve strengths and weaknesses, and providing recommendations regarding the settings in which each approach might be preferable. PMID:28736502
Generalized Kähler Geometry from Supersymmetric Sigma Models
NASA Astrophysics Data System (ADS)
Bredthauer, Andreas; Lindström, Ulf; Persson, Jonas; Zabzine, Maxim
2006-09-01
We give a physical derivation of generalized Kähler geometry. Starting from a supersymmetric nonlinear sigma model, we rederive and explain the results of Gualtieri (Generalized complex geometry, DPhil thesis, Oxford University, 2004) regarding the equivalence between generalized Kähler geometry and the bi-hermitean geometry of Gates et al. (Nucl Phys B248:157, 1984). When cast in the language of supersymmetric sigma models, this relation maps precisely to that between the Lagrangian and the Hamiltonian formalisms. We also discuss topological twist in this context.
A spin foam model for general Lorentzian 4-geometries
NASA Astrophysics Data System (ADS)
Conrady, Florian; Hnybida, Jeff
2010-09-01
We derive simplicity constraints for the quantization of general Lorentzian 4-geometries. Our method is based on the correspondence between coherent states and classical bivectors and the minimization of associated uncertainties. For triangulations with spacelike triangles, this scheme agrees with the master constraint method of the model by Engle, Pereira, Rovelli and Livine (EPRL). When it is applied to general triangulations of Lorentzian geometries, we obtain new constraints that include the EPRL constraints as a special case. They imply a discrete area spectrum for both spacelike and timelike surfaces. We use these constraints to define a spin foam model for general Lorentzian 4-geometries.
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.
A potential field model using generalized sigmoid functions.
Ren, Jing; McIsaac, Kenneth A; Patel, Rajni V; Peters, Terry M
2007-04-01
The lack of a potential field model capable of providing accurate representations of objects of arbitrary shapes is considered one major limitation in applying the artificial potential field method in many practical applications. In this correspondence, we propose a potential function based on generalized sigmoid functions. The generalized sigmoid model can be constructed from combinations of implicit primitives or from sampled surface data. The constructed potential field model can achieve an accurate analytic description of objects in two or three dimensions and requires very modest computation at run time. In this correspondence, applications of the generalized sigmoid model in path-planning tasks for mobile robots and in haptic feedback tasks are presented. The validation results in this correspondence show that the model can effectively allow the user or mobile robot to avoid penetrations of obstacles while successfully accomplishing the task.
Guisan, A.; Edwards, T.C.; 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.
Standard-Model Tests with Superallowed {beta} Decay: Nuclear Data Applied to Fundamental Physics
Hardy, J.C.
2005-05-24
The study of superallowed nuclear {beta} decay currently provides the most precise and convincing confirmation of the conservation of the vector current (CVC) and is a key component of the most demanding available test of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, a basic pillar of the Electroweak Standard Model. Experimentally, the Q-value, half-life, and branching ratio for superallowed transitions must be determined with a precision better than 0.1%. This demands metrological techniques be applied to short-lived ({approx}1 s) activities and that strict standards be employed in surveying the body of world data. The status of these fundamental studies is summarized and recent work described.
Impact of intracellular beta-amyloid in transgenic animals and cell models.
Cuello, A Claudio; Canneva, Fabio
2008-01-01
The present commentary based on cell and animal models of intracellular beta-amyloid (iAbeta) expression indicates that low levels of microscopically undetectable iAbeta could have a physiological role in the modulation of the cyclic AMP response element (CRE)-dependent gene expression and, as a consequence, a positive influence on synaptic plasticity (the 'good' Abeta?). On the other hand, high levels of iAbeta resembling the pathological and microscopically visible accumulation of this amyloid peptide, akin to that observed in Down syndrome and Alzheimer's disease, disrupt CRE-regulated gene expression, therefore compromising the protein synthesis-dependent component of long-term potentiation (the 'bad' Abeta?). Moreover, intracellular pathology would be independent and additive to the toxic effects of the extracellular Abeta burden. 2008 S. Karger AG, Basel
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.
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.
A generalized hard-sphere model for Monte Carlo simulation
NASA Technical Reports Server (NTRS)
Hassan, H. A.; Hash, David B.
1993-01-01
A new molecular model, called the generalized hard-sphere, or GHS model, is introduced. This model contains, as a special case, the variable hard-sphere model of Bird (1981) and is capable of reproducing all of the analytic viscosity coefficients available in the literature that are derived for a variety of interaction potentials incorporating attraction and repulsion. In addition, a new procedure for determining interaction potentials in a gas mixture is outlined. Expressions needed for implementing the new model in the direct simulation Monte Carlo methods are derived. This development makes it possible to employ interaction models that have the same level of complexity as used in Navier-Stokes calculations.
A generalized item response tree model for psychological assessments.
Jeon, Minjeong; De Boeck, Paul
2016-09-01
A new item response theory (IRT) model with a tree structure has been introduced for modeling item response processes with a tree structure. In this paper, we present a generalized item response tree model with a flexible parametric form, dimensionality, and choice of covariates. The utilities of the model are demonstrated with two applications in psychological assessments for investigating Likert scale item responses and for modeling omitted item responses. The proposed model is estimated with the freely available R package flirt (Jeon et al., 2014b).
Itakura, Tomohiro; Kuroki, Aya; Ishibashi, Yasuhiro; Tsuji, Daisuke; Kawashita, Eri; Higashine, Yukari; Sakuraba, Hitoshi; Yamanaka, Shoji; Itoh, Kohji
2006-08-01
Sandhoff disease (SD) is an autosomal recessive GM2 gangliosidosis caused by the defect of lysosomal beta-hexosaminidase (Hex) beta-subunit gene associated with neurosomatic manifestations. Therapeutic effects of Hex subunit gene transduction have been examined on Sandhoff disease model mice (SD mice) produced by the allelic disruption of Hexb gene encoding the murine beta-subunit. We demonstrate here that elimination of GM2 ganglioside (GM2) accumulated in the fibroblastic cell line derived from SD mice (FSD) did not occur when the HEXB gene only was transfected. In contrast, a significant increase in the HexB (betabeta homodimer) activity toward neutral substrates, including GA2 (asialo-GM2) and oligosaccharides carrying the terminal N-acetylglucosamine residues at their non-reducing ends (GlcNAc-oligosaccharides) was observed. Immunoblotting with anti-human HexA (alphabeta heterodimer) serum after native polyacrylamide gel electrophoresis (Native-PAGE) revealed that the human HEXB gene product could hardly form the chimeric HexA through associating with the murine alpha-subunit. However, co-introduction of the HEXA encoding the human alpha-subunit and HEXB genes caused significant corrective effect on the GM2 degradation by producing the human HexA. These results indicate that the recombinant human HexA could interspeciesly associate with the murine GM2 activator protein to degrade GM2 accumulated in the FSD cells. Thus, therapeutic effects of the recombinant human HexA isozyme but not human HEXB gene product could be evaluated by using the SD mice.
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…
NASA Astrophysics Data System (ADS)
Kadochnikov, V. V.; Egorov, V. V.; Shvetsov, A. V.; Kuklin, A. I.; Isaev-Ivanov, V. V.; Lebedev, D. V.
2016-01-01
The behavior of the peptide corresponding to beta domain of human alpha-lactalbumin (GYDTQAIVENNESTEYG, WT) has been simulated by the molecular dynamics method. It is shown that, within the model considered, the monomer of this peptide does not tend to form a stable secondary structure; however, simulation of the behavior of several peptide molecules revealed the occurrence of beta structures due to the formation of intermolecular hydrogen bonds. Since the aforementioned interactions involve the terminal portions of peptides, the influence of the tetrapeptide corresponding to the N-terminal portion of WT, TDYG (R), on the secondary structure has been analyzed. The model calculations show that the interaction of this peptide with WT monomer facilitates formation of beta-structures. It is suggested that peptide R may affect the quaternary structure of WT.
A generalized cholera model and epidemic-endemic analysis.
Wang, Jin; Liao, Shu
2012-01-01
The transmission of cholera involves both human-to-human and environment-to-human pathways that complicate its dynamics. In this paper, we present a new and unified deterministic model that incorporates a general incidence rate and a general formulation of the pathogen concentration to analyse the dynamics of cholera. Particularly, this work unifies many existing cholera models proposed by different authors. We conduct equilibrium analysis to carefully study the complex epidemic and endemic behaviour of the disease. Our results show that despite the incorporation of the environmental component, there exists a forward transcritical bifurcation at R (0)=1 for the combined human-environment epidemiological model under biologically reasonable conditions.
Residuals analysis of the generalized linear models for longitudinal data.
Chang, Y C
2000-05-30
The generalized estimation equation (GEE) method, one of the generalized linear models for longitudinal data, has been used widely in medical research. However, the related sensitivity analysis problem has not been explored intensively. One of the possible reasons for this was due to the correlated structure within the same subject. We showed that the conventional residuals plots for model diagnosis in longitudinal data could mislead a researcher into trusting the fitted model. A non-parametric method, named the Wald-Wolfowitz run test, was proposed to check the residuals plots both quantitatively and graphically. The rationale proposedin this paper is well illustrated with two real clinical studies in Taiwan.
A General Method for Modeling Macromolecular Shape in Solution
Harding, Stephen E.
1987-01-01
A general method for modeling macromolecular shape in solution is described involving measurements of viscosity, radius of gyration, and the second thermodynamic virial coefficient. The method, which should be relatively straightforward to apply, does not suffer from uniqueness problems, involves shape functions that are independent of hydration, and models the gross conformation of the macromolecule in solution as a general triaxial ellipsoid. The method is illustrated by application to myosin, and the relevance and applicability of ellipsoid modeling to biological structures is discussed. PMID:19431695
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
2016-11-01
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.
ERIC Educational Resources Information Center
Schluchter, Mark D.
2008-01-01
In behavioral research, interest is often in examining the degree to which the effect of an independent variable X on an outcome Y is mediated by an intermediary or mediator variable M. This article illustrates how generalized estimating equations (GEE) modeling can be used to estimate the indirect or mediated effect, defined as the amount by…
ERIC Educational Resources Information Center
Schluchter, Mark D.
2008-01-01
In behavioral research, interest is often in examining the degree to which the effect of an independent variable X on an outcome Y is mediated by an intermediary or mediator variable M. This article illustrates how generalized estimating equations (GEE) modeling can be used to estimate the indirect or mediated effect, defined as the amount by…
Khrutchinsky, A; Kutsen, S; Minenko, V; Zhukova, O; Luckyanov, N; Bouville, A; Drozdovitch, V
2009-06-01
This paper presents results of Monte Carlo modeling of the beta-radiometer device with Geiger-Mueller detector used in Belarus and Russia to measure the radioactive contamination of milk after the Chernobyl accident. This type of detector, which is not energy selective, measured the total beta-activity of the radionuclide mix. A mathematical model of the beta-radiometer device, namely DP-100, was developed, and the calibration factors for the different radionuclides that might contribute to the milk contamination were calculated. The estimated calibration factors for (131)I, (137)Cs, (134)Cs, (90)Sr, (144)Ce, and (106)Ru reasonably agree with calibration factors determined experimentally. The calculated calibration factors for (132)Te, (132)I, (133)I, (136)Cs, (89)Sr, (103)Ru, (140)Ba, (140)La, and (141)Ce had not been previously determined experimentally. The obtained results allow to derive the activity of specific radionuclides, in particular (131)I, from the results of the total beta-activity measurements in milk. Results of this study are important for the purposes of retrospective dosimetry that uses measurements of radioactivity in environmental samples performed with beta-radiometer devices.
Khrutchinsky, A.; Kutsen, S.; Minenko, V.; Zhukova, O.; Luckyanov, N.; Bouville, A.; Drozdovitch, V.
2009-01-01
This paper presents results of Monte Carlo modeling of the beta-radiometer device with Geiger-Mueller detector used in Belarus and Russia to measure the radioactive contamination of milk after the Chernobyl accident. This type of detector, which is not energy selective, measured the total beta-activity of the radionuclide mix. A mathematical model of the beta-radiometer device, namely DP-100, was developed, and the calibration factors for the different radionuclides that might contribute to the milk contamination were calculated. The estimated calibration factors for 131I, 137Cs, 134Cs, 90Sr, 144Ce, and 106Ru reasonably agree with calibration factors determined experimentally. The calculated calibration factors for 132Te, 132I, 133I, 136Cs, 103Ru, 140Ba, 140La, and 141Ce had not been previously determined experimentally. The obtained results allow to derive the activity of specific radionuclides, in particular 131I, from the results of the total beta-activity measurements in milk. Results of this study are important for the purposes of retrospective dosimetry that uses measurements of radioactivity in environmental samples performed with beta-radiometer devices. PMID:19233662
Poffenberger, Greg; Dula, Adrienne N.; Moore, Daniel J.; Powers, Alvin C.
2013-01-01
We generated a mouse model (MIP-Luc-VU-NOD) that enables non-invasive bioluminescence imaging (BLI) of beta cell loss during the progression of autoimmune diabetes and determined the relationship between BLI and disease progression. MIP-Luc-VU-NOD mice displayed insulitis and a decline in bioluminescence with age which correlated with beta cell mass, plasma insulin, and pancreatic insulin content. Bioluminescence declined gradually in female MIP-Luc-VU-NOD mice, reaching less than 50% of the initial BLI at 10 weeks of age, whereas hyperglycemia did not ensue until mice were at least 16 weeks old. Mice that did not become diabetic maintained insulin secretion and had less of a decline in bioluminescence than mice that became diabetic. Bioluminescence measurements predicted a decline in beta cell mass prior to the onset of hyperglycemia and tracked beta cell loss. This model should be useful for investigating the fundamental processes underlying autoimmune diabetes and developing new therapies targeting beta cell protection and regeneration. PMID:23483929
Song, Benbo; Scheuner, Donalyn; Ron, David; Pennathur, Subramaniam; Kaufman, Randal J
2008-10-01
The progression from insulin resistance to type 2 diabetes is caused by the failure of pancreatic beta cells to produce sufficient levels of insulin to meet the metabolic demand. Recent studies indicate that nutrient fluctuations and insulin resistance increase proinsulin synthesis in beta cells beyond the capacity for folding of nascent polypeptides within the endoplasmic reticulum (ER) lumen, thereby disrupting ER homeostasis and triggering the unfolded protein response (UPR). Chronic ER stress promotes apoptosis, at least in part through the UPR-induced transcription factor C/EBP homologous protein (CHOP). We assessed the effect of Chop deletion in multiple mouse models of type 2 diabetes and found that Chop-/- mice had improved glycemic control and expanded beta cell mass in all conditions analyzed. In both genetic and diet-induced models of insulin resistance, CHOP deficiency improved beta cell ultrastructure and promoted cell survival. In addition, we found that isolated islets from Chop-/- mice displayed increased expression of UPR and oxidative stress response genes and reduced levels of oxidative damage. These findings suggest that CHOP is a fundamental factor that links protein misfolding in the ER to oxidative stress and apoptosis in beta cells under conditions of increased insulin demand.
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…
Nakabayashi, Jun; Sasaki, Akira
2009-07-21
Cell fate in multicellular organism is regulated by the diffusible factor from surrounding cells in concentration-dependent manner. TGF-beta is a large protein family of the diffusible proteins secreted from a localized source. The signal of TGF-beta is transduced by Smad family transcription factor. Though it is well known that the stoichiometry of Smads in the transcriptional complex regulates the specificity of target genes of TGF-beta signal, little is known what the stoichiometry of Smads in the transcriptional complex is determined in TGF-beta signal transduction in concentration-dependent manner. To investigate the dynamics of Smad complex formation, we construct a two-compartment model for Smad complex formation in TGF-beta signal transduction. A simplified one-way oligomerization model, which ignores dissociation and well appropriate the full model under high expression levels of R- and Co-Smad, is constructed to analytically investigate the effect of the oligomerization of Smad. Our one-way model reveals that not only shuttling of the Smad from the cytoplasm to the nucleus but also the preferential accumulation of the heteromeric complex in oligomerization can contribute to the predominant production of the heteromeric complex of Smad including both R- and Co-Smad. It is also shown that oligomerization of Smad can contribute to the specificity of signal transduction. In endothelial cells, both Smad-1/5/8 and -2/3 pathways are activated by TGF-beta. The difference of the activity between the two pathways is amplified by trimerization but not by dimerization, suggesting possible importance of trimerization in maintaining the specificity of signal transduction.
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.
General Hubbard Model for Fermions in an Optical Lattice
NASA Astrophysics Data System (ADS)
Kestner, Jason; Duan, Luming
2009-03-01
For two-component fermions in an optical lattice, an effective general Hubbard model (GHM) with tunable on-site attraction/repulsion and occupation-dependent hopping rates emerges from very general arguments [1]. This model is quite interesting, containing as special cases both the t-J and the XXZ models. However, the experimental range of applicability and the connection between the model parameters and the actual experimental parameters must be determined explicitly. To this end, we have used a stochastic variational approach with a correlated gaussian wavefunction to numerically find the eigenstates of two atoms interacting in a 3D few-well trap. By matching the few-site spectrum of the GHM to the variational spectrum obtained, the validity of the model and the relationship between experimental and model parameters are determined. [1] L.-M. Duan, Euro. Phys. Lett. 81, 20001 (2008).
A general non-linear multilevel structural equation mixture model
Kelava, Augustin; Brandt, Holger
2014-01-01
In the past 2 decades latent variable modeling has become a standard tool in the social sciences. In the same time period, traditional linear structural equation models have been extended to include non-linear interaction and quadratic effects (e.g., Klein and Moosbrugger, 2000), and multilevel modeling (Rabe-Hesketh et al., 2004). We present a general non-linear multilevel structural equation mixture model (GNM-SEMM) that combines recent semiparametric non-linear structural equation models (Kelava and Nagengast, 2012; Kelava et al., 2014) with multilevel structural equation mixture models (Muthén and Asparouhov, 2009) for clustered and non-normally distributed data. The proposed approach allows for semiparametric relationships at the within and at the between levels. We present examples from the educational science to illustrate different submodels from the general framework. PMID:25101022
Lifetime Measurements of ^170Hf and a test of the Confined Beta Soft Rotor Model
NASA Astrophysics Data System (ADS)
Smith, M. K.; Werner, V.; Heinz, A.; Terry, J. R.; Qian, J.; Winkler, R.; Casperson, R.; Williams, E.; Berant, Z.; L"Uttke, R.; Shoraka, B.; Henning, G.
2009-10-01
Significant deviations from rigid rotor model energy level predictions have been known to occur in rare earth nuclei. Recently, it was shown these deviations may be caused by centrifugal stretching effects within the nucleus [1]. New geometrical models have been proposed that account for centrifugal stretching, such as the confined beta soft model (CBS). We present the results from a high precision lifetime experiment performed with the New Yale Plunger Device at WNSL, Yale University. The ground state band of ^170Hf was measured through the J=12^+ level using the Recoil Distance Doppler Shift method. Excited states were populated in the ^124Sn(^50Ti,γ)^170Hf fusion evaporation reaction. Using the lifetimes, the B(E2) values and the quadrupole deformation parameter are determined. Centrifugal stretching is observed as an increased deviation in energy at higher spins in 170Hf. These results are compared to theoretical predictions from the CBS rotor model. Supported by grant DE-FG02-91ER40609.[4pt] [1] Costin et al, Phys.Rev. C 79, 024307 (2009)
Cosmological perturbation theory in generalized Einstein-Aether models
NASA Astrophysics Data System (ADS)
Battye, Richard A.; Pace, Francesco; Trinh, Damien
2017-09-01
We investigate the evolution of cosmological perturbations in models of dark energy described by a timelike unit normalized vector field specified by a general function F (K ), so-called generalized Einstein-Aether models. First we study the background dynamics of such models via a designer approach in an attempt to model this theory as dark energy. We find that only one specific form of this designer approach matches Λ CDM at background order, and we also obtain a differential equation which F (K ) must satisfy for general w CDM cosmologies, where CDM refers to cold dark matter. We also present the equations of state for perturbations in generalized Einstein-Aether models, which completely parametrize these models at the level of linear perturbations. A generic feature of modified gravity models is that they introduce new degrees of freedom. By fully eliminating these we are able to express the gauge invariant entropy perturbation and the scalar, vector, and tensor anisotropic stresses in terms of the perturbed fluid variables and metric perturbations only. These can then be used to study the evolution of perturbations in the scalar, vector, and tensor sectors, and we use these to evolve the Newtonian gravitational potentials.
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.
Geometric critical exponent inequalities for general random cluster models
NASA Astrophysics Data System (ADS)
Tasaki, Hal
1987-11-01
A set of new critical exponent inequalities, d(1 -1 / δ)≥2 - η, dv(1 - 1/ δ)≥ γ, and dμ> 1, is proved for a general class of random cluster models, which includes (independent or dependent) percolations, lattice animals (with any interactions), and various stochastic cluster growth models. The inequalities imply that the critical phenomena in the models are inevitably not mean-field-like in the dimensions one, two, and three.
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.
Revisiting the classical electron model in general relativity
NASA Astrophysics Data System (ADS)
Rahaman, Farook; Jamil, Mubasher; Chakraborty, Kaushik
2011-01-01
Motivated by earlier studies (Tiwari et al. in Astrophys. Space Sci. 182:105, 1984; Herrera and Varela in Phys. Lett. 189:11, 1994), we model electron as a spherically symmetric charged perfect fluid distribution of matter. The existing model is extended assuming a matter source that is characterized by quadratic equation of state in the context of general theory of relativity. For the suitable choices of the parameters, our charged fluid models almost satisfy the physical properties of electron.
Australian and overseas models of general practice training.
Hays, Richard B; Morgan, Simon
2011-06-06
General practice training in Australia continues to evolve. It is now the responsibility of an independent organisation, is delivered by regional training providers, and comprises a structured training program. Overseas, general practice varies in its importance to health care systems, and training models differ considerably. In some cases training is mandatory, in others voluntary, but the aim is always similar--to improve the quality of care delivered to the large majority of populations that access health care through primary care. We review the current status of vocational general practice training in Australia, compare it with selected training programs in international contexts, and describe how the local model is well placed to address future challenges. Challenges include changes in population demographics, increasing comorbidity, increasing costs of technology-based health care, increasing globalisation of health, and workforce shortages. Although general practice training in Australia is strong, it can improve further by learning from other training programs to meet these challengers.
Comparison of the pn quasiparticle RPA and shell model for Gamow-Teller beta and double-beta decays
NASA Astrophysics Data System (ADS)
Zhao, Liang; Brown, B. Alex
1993-06-01
We examine the validity of the pn quasiparticle RPA (pnQRPA) as a model for calculating β+ and 2νββ Gamow-Teller decays by making a comparison of the pnQRPA with a large-basis shell-model calculation within the 0f1p shell. We employ A=46 nuclei (those with six valence nucleons) for this comparison. Our comparison includes the decay matrix elements summed over final states, the strength distributions, and, for the first time, the coherent transition matrix elements (CTME). The pnQRPA overestimates the total β+ and 2νββ matrix elements. There are large differences in the shape of the spectra as well as in the CTME between the pnQRPA and shell-model results. Empirical improvements for the pnQRPA are discussed.
NASA Astrophysics Data System (ADS)
Hecksher, Tina; Olsen, Niels Boye; Dyre, Jeppe C.
2017-04-01
This paper presents data for supercooled squalane's frequency-dependent shear modulus covering frequencies from 10 mHz to 30 kHz and temperatures from 168 K to 190 K; measurements are also reported for the glass phase down to 146 K. The data reveal a strong mechanical beta process. A model is proposed for the shear response of the metastable equilibrium liquid phase of supercooled liquids. The model is an electrical equivalent-circuit characterized by additivity of the dynamic shear compliances of the alpha and beta processes. The nontrivial parts of the alpha and beta processes are each represented by a "Cole-Cole retardation element" defined as a series connection of a capacitor and a constant-phase element, resulting in the Cole-Cole compliance function well-known from dielectrics. The model, which assumes that the high-frequency decay of the alpha shear compliance loss varies with the angular frequency as ω-1 /2, has seven parameters. Assuming time-temperature superposition for the alpha and beta processes separately, the number of parameters varying with temperature is reduced to four. The model provides a better fit to the data than an equally parametrized Havriliak-Negami type model. From the temperature dependence of the best-fit model parameters, the following conclusions are drawn: (1) the alpha relaxation time conforms to the shoving model; (2) the beta relaxation loss-peak frequency is almost temperature independent; (3) the alpha compliance magnitude, which in the model equals the inverse of the instantaneous shear modulus, is only weakly temperature dependent; (4) the beta compliance magnitude decreases by a factor of three upon cooling in the temperature range studied. The final part of the paper briefly presents measurements of the dynamic adiabatic bulk modulus covering frequencies from 10 mHz to 10 kHz in the temperature range from 172 K to 200 K. The data are qualitatively similar to the shear modulus data by having a significant beta process. A
Escayg, A; De Waard, M; Lee, D D; Bichet, D; Wolf, P; Mayer, T; Johnston, J; Baloh, R; Sander, T; Meisler, M H
2000-01-01
Inactivation of the beta4 subunit of the calcium channel in the mouse neurological mutant lethargic results in a complex neurological disorder that includes absence epilepsy and ataxia. To determine the role of the calcium-channel beta4-subunit gene CACNB4 on chromosome 2q22-23 in related human disorders, we screened for mutations in small pedigrees with familial epilepsy and ataxia. The premature-termination mutation R482X was identified in a patient with juvenile myoclonic epilepsy. The R482X protein lacks the 38 C-terminal amino acids containing part of an interaction domain for the alpha1 subunit. The missense mutation C104F was identified both in a German family with generalized epilepsy and praxis-induced seizures and in a French Canadian family with episodic ataxia. These coding mutations were not detected in 255 unaffected control individuals (510 chromosomes), and they may be considered candidate disease mutations. The results of functional tests of the truncated protein R482X in Xenopus laevis oocytes demonstrated a small decrease in the fast time constant for inactivation of the cotransfected alpha1 subunit. Further studies will be required to evaluate the in vivo consequences of these mutations. We also describe eight noncoding single-nucleotide substitutions, two of which are present at polymorphic frequency, and a previously unrecognized first intron of CACNB4 that interrupts exon 1 at codon 21. PMID:10762541
Cord Neto, G; Yunes, J A; da Silva, M J; Vettore, A L; Arruda, P; Leite, A
1995-03-01
The maize opaque 2 (o2) mutation is known to have numerous pleiotropic effects. Some polypeptides have their expression depressed while others are enhanced. The best characterized effects of the o2 mutation are those exerted on endosperm genes encoding the storage protein class of the 22 kDa alpha-zeins and the ribosome inactivating protein b-32. The Opaque 2 (O2) locus encodes a basic domain-leucine zipper DNA-binding factor, O2, which transcriptionally regulates these genes. In the maize-related grass Coix lacryma-jobi, an O2-homologous protein regulates the 25 kDa alpha-coixin family. We show in this paper that O2 transcriptionally regulates the structurally and developmentally different class of the beta-prolamins. A new O2-binding box was identified in beta-prolamin genes from maize and Coix that, together with the boxes previously identified in other endosperm expressed genes, forms a curious collection of O2 cis elements. This may have regulatory implications on the role of O2 in the mechanism that controls coordinated gene expression in the developing endosperm. Considering that the O2 locus controls at least three distinct classes of genes in maize endosperm, we propose that the O2 protein may play a more general role in maize endosperm development than previously conceived.
Modeling general AIMD congestion control throughput with slow start
NASA Astrophysics Data System (ADS)
Yu, Shengsheng; Zha, Hui; Zhou, Jingli
2005-05-01
General Additive Increase and Multiplicative Decrease (General AIMD or GAIMD) congestion control generalizes the standard TCP congestion control mechanism. In this paper, we present GAIMD-SS, an enhanced model for predicting the long-term steady-state mean throughput of the GAIMD congestion control, towards more accurate results than previous GAIMD model. We develop a three-state Markov chain for analyzing the behaviors of the GAIMD, and enhance previous works by taking into account the slow start phase and receiver's maximum window limitation. Our experiment and simulation results show that the GAIMD-SS model predicts the sending rate of GAIMD congestion control more accurately than the previous works in a wider range of packet loss rate.
T-GOWler: Discovering Generalized Process Models Within Texts.
Halioui, Ahmed; Valtchev, Petko; Diallo, Abdoulaye Baniré
2017-08-01
Contemporary workflow management systems are driven by explicit process models specifying the interdependencies between tasks. Creating these models is a challenging and time-consuming task. Existing approaches to mining concrete workflows into models tackle design aspects related to the diverging abstraction levels of the tasks. Concrete workflow logs represent tasks and cases of concrete events-partially or totally ordered-grounding hidden multilevel (abstract) semantics and contexts. Relevant generalized events could be rediscovered within these processes. We propose, in this article, an ontology-based workflow mining system to generate patterns from sequences of events that are themselves extracted from texts. Our system T-GOWler (Generalized Ontology-based WorkfLow minER within Texts) is based on two ontology-based modules: a workflow extractor and a pattern miner. To this end, it uses two different ontologies: a domain one (to support workflow extraction from texts) and a processual one (to mine generalized patterns from extracted workflows).
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.
A mathematical model of the kinetics of beta-amyloid fibril growth from the denatured state.
Pallitto, M M; Murphy, R M
2001-01-01
Spontaneous conversion of beta-amyloid peptide (Abeta) from soluble monomer to insoluble fibril may underlie the neurodegeneration associated with Alzheimer's disease. A complete description of Abeta self-association kinetics requires identification of the oligomeric species present and the pathway of association, as well as quantitation of rate constants and reaction order. Abeta was rendered monomeric and denatured by dissolution in 8 M urea, pH 10. "Refolding" and fibrillization were initiated by rapid dilution into phosphate-buffered saline, pH 7.4. The kinetics of growth were followed at three different concentrations, using size exclusion chromatography, dynamic light scattering, and static light scattering. A multi-step pathway for fibril formation and growth was postulated. This pathway included 1) rapid commitment to either stable monomer/dimer or unstable intermediate, 2) cooperative association of intermediate into a multimeric "nucleus," 3) elongation of the "nucleus" into filaments via addition of intermediate, 4) lateral aggregation of filaments into fibrils, and 5) fibril elongation via end-to-end association. Differential and algebraic equations describing this kinetic pathway were derived, and model parameters were determined by fitting the data. The utility of the model for identifying toxic Abeta oligomeric specie(s) is demonstrated. The model should prove useful for designing compounds that inhibit Abeta aggregation and/or toxicity. PMID:11509390
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; ...
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
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
2015-05-01
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.
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.
Coexistence of interacting opinions in a generalized Sznajd model.
Timpanaro, André M; Prado, Carmen P C
2011-08-01
The Sznajd model is a sociophysics model that mimics the propagation of opinions in a closed society, where the interactions favor groups of agreeing people. It is based in the Ising and Potts ferromagnetic models and, although the original model used only linear chains, it has since been adapted to general networks. This model has a very rich transient, which has been used to model several aspects of elections, but its stationary states are always consensus states. In order to model more complex behaviors, we have, in a recent work, introduced the idea of biases and prejudices to the Sznajd model by generalizing the bounded confidence rule, which is common to many continuous opinion models, to what we called confidence rules. In that work we have found that the mean field version of this model (corresponding to a complete network) allows for stationary states where noninteracting opinions survive, but never for the coexistence of interacting opinions. In the present work, we provide networks that allow for the coexistence of interacting opinions for certain confidence rules. Moreover, we show that the model does not become inactive; that is, the opinions keep changing, even in the stationary regime. This is an important result in the context of understanding how a rule that breeds local conformity is still able to sustain global diversity while avoiding a frozen stationary state. We also provide results that give some insights on how this behavior approaches the mean field behavior as the networks are changed.
Coexistence of interacting opinions in a generalized Sznajd model
NASA Astrophysics Data System (ADS)
Timpanaro, André M.; Prado, Carmen P. C.
2011-08-01
The Sznajd model is a sociophysics model that mimics the propagation of opinions in a closed society, where the interactions favor groups of agreeing people. It is based in the Ising and Potts ferromagnetic models and, although the original model used only linear chains, it has since been adapted to general networks. This model has a very rich transient, which has been used to model several aspects of elections, but its stationary states are always consensus states. In order to model more complex behaviors, we have, in a recent work, introduced the idea of biases and prejudices to the Sznajd model by generalizing the bounded confidence rule, which is common to many continuous opinion models, to what we called confidence rules. In that work we have found that the mean field version of this model (corresponding to a complete network) allows for stationary states where noninteracting opinions survive, but never for the coexistence of interacting opinions. In the present work, we provide networks that allow for the coexistence of interacting opinions for certain confidence rules. Moreover, we show that the model does not become inactive; that is, the opinions keep changing, even in the stationary regime. This is an important result in the context of understanding how a rule that breeds local conformity is still able to sustain global diversity while avoiding a frozen stationary state. We also provide results that give some insights on how this behavior approaches the mean field behavior as the networks are changed.
Baquero, Esteban E; James, William H; Choi, Soo Hyuk; Gellman, Samuel H; Zwier, Timothy S
2008-04-09
The conformational preferences and infrared and ultraviolet spectral signatures of two model beta-peptides, Ac-beta3-hPhe-beta3-hAla-NHMe (1) and Ac-beta3-hAla-beta3-hPhe-NHMe (2), have been explored under jet-cooled, isolated-molecule conditions. The mass-resolved, resonant two-photon ionization spectra of the two molecules were recorded in the region of the S0-S1 origin of the phenyl substituents (37,200-37,800 cm(-1)). UV-UV hole-burning spectroscopy was used to determine the ultraviolet spectral signatures of five conformational isomers of both 1 and 2. Transitions due to two conformers (labeled A and B) dominate the R2PI spectra of each molecule, while the other three are minor conformers (C-E) with transitions a factor of 3-5 smaller. Resonant ion-dip infrared spectroscopy was used to obtain single-conformation infrared spectra in the 3300-3700 cm(-1) region. The infrared spectra showed patterns of NH stretch transitions characteristic of the number and type of intramolecular H-bonds present in the beta-peptide backbone. For comparison with experiment, full optimizations of low-lying minima of both molecules were carried out at DFT B3LYP/6-31+G*, followed by single point MP2/6-31+G* and selected MP2/aug-cc-pVDZ calculations at the DFT optimized geometries. Calculated harmonic vibrational frequencies and infrared intensities for the amide NH stretch vibrations were used to determine the beta-peptide backbone structures for nine of the ten observed conformers. Conformers 1B, 1D, and 2A were assigned to double ring structures containing two C6 H-bonded rings (C6a/C6a), conformers 1A and 2B are C10 single H-bonded rings, conformers 1C and 2D are double ring structures composed of two C8 H-bonded rings (C8/C8), and conformers 1E and 2E are double ring/double acceptor structures in which two NH groups H-bond to the same C=O group, thereby weakening both H-bonds. Both 1E and 2E are tentatively assigned to C6/C8 double ring/double acceptor structures, although C8/C12
Generalized model for incoherent detection in confocal optical microscopy.
Hammoum, Rachid; Hamady, Sidi Ould Saad; Fontana, Marc D
2010-06-01
We develop a generalized model in order to calculate the point spread functions in both the focal and the detection planes for the electric field strengths. In these calculations, based on the generalized Jones matrices, we introduce all of the interdependent parameters that could influence the spatial resolution of a confocal optical microscope. Our proposed model is more nearly complete, since we make no approximations of the scattered electric fields. These results can be successfully applied to standard confocal optical techniques to get a better understanding for more quantitative interpretations of the probe.
Bersudsky, Yuly; Shaldubina, Alona; Kozlovsky, Nitzan; Woodgett, James R; Agam, Galila; Belmaker, R H
2008-05-01
In mice glycogen synthase kinase (GSK)-3beta heterozygote knockout status was reported to cause reduced immobility in the Porsolt forced swim test and reduced amphetamine-induced hyperactivity, behaviors that mimic the effects of lithium. GSK-3beta protein and mRNA level and activity have been reported to be reduced in the postmortem brain of schizophrenia patients and this could suggest the involvement of GSK-3beta in the etiology of schizophrenia. However, apomorphine-induced stereotyping was reported to be unchanged in GSK-3beta heterozygote (HZ) knockout (KO) mice. As such behaviors are not always robust, study in another laboratory seemed indicated. Motor activity and coordination were assessed in the rotarod test. Behavior was studied in the following tests: pilocarpine-induced seizures model for lithium action, Porsolt forced swim test, tail suspension test, elevated plus-maze, large open field, startle response and prepulse inhibition of acoustic startle response, amphetamine-induced hyperactivity, and apomorphine-induced stereotypic climbing. We could not confirm the report that GSK-3beta HZ KO mice exhibit reduced immobility in the Porsolt forced swim or reduced amphetamine-induced hyperactivity in a manner mimicking the behavioral effects of lithium. We did not find increased apomorphine-induced stereotypic climbing or disruption of prepulse inhibition, suggesting that human postmortem findings regarding GSK-3beta in schizophrenia are not mediated by changes in dopamine receptors and are not the cause of prepulse inhibition deficits in schizophrenia. These data do not support the role of GSK-3beta in schizophrenia or in the mechanism of therapeutic action of lithium. Although differences in the genetic background of the GSK-3beta HZ KOs used in the present study compared with that of the previous study could be responsible, such results could suggest that the previously reported effects of GSK-3beta knockout on behavior are not robust.
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 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
Generalized gas-solid adsorption modeling: Single-component equilibria
Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; ...
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 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.
Generalized F test and generalized deviance test in two-way ANOVA models for randomized trials.
Shen, Juan; He, Xuming
2014-01-01
We consider the problem of detecting treatment effects in a randomized trial in the presence of an additional covariate. By reexpressing a two-way analysis of variance (ANOVA) model in a logistic regression framework, we derive generalized F tests and generalized deviance tests, which provide better power in detecting common location-scale changes of treatment outcomes than the classical F test. The null distributions of the test statistics are independent of the nuisance parameters in the models, so the critical values can be easily determined by Monte Carlo methods. We use simulation studies to demonstrate how the proposed tests perform compared with the classical F test. We also use data from a clinical study to illustrate possible savings in sample sizes.
Luo, Zhonglin; Ding, Jiandong; Zhou, Yaoqi
2008-06-14
This paper examines the folding mechanism of an individual beta-hairpin in the presence of other hairpins by using an off-lattice model of a small triple-stranded antiparallel beta-sheet protein, Pin1 WW domain. The turn zipper model and the hydrophobic collapse model originally developed for a single beta-hairpin in literature is confirmed to be useful in describing beta-hairpins in model Pin1 WW domain. We find that the mechanism for folding a specific hairpin is independent of whether it folds first or second, but the formation process are significantly dependent on temperature. More specifically, beta1-beta2 hairpin folds via the turn zipper model at a low temperature and the hydrophobic collapse model at a high temperature, while the folding of beta2-beta3 hairpin follows the turn zipper model at both temperatures. The change in folding mechanisms is interpreted by the interplay between contact stability (enthalpy) and loop lengths (entropy), the effect of which is temperature dependent.
A general graphical user interface for automatic reliability modeling
NASA Technical Reports Server (NTRS)
Liceaga, Carlos A.; Siewiorek, Daniel P.
1991-01-01
Reported here is a general Graphical User Interface (GUI) for automatic reliability modeling of Processor Memory Switch (PMS) structures using a Markov model. This GUI is based on a hierarchy of windows. One window has graphical editing capabilities for specifying the system's communication structure, hierarchy, reconfiguration capabilities, and requirements. Other windows have field texts, popup menus, and buttons for specifying parameters and selecting actions. An example application of the GUI is given.
Bengoechea, Tasha G; Chen, Zhijiang; O'Leary, Debra A; O'Leary, Deborah; Masliah, Eliezer; Lee, Kuo-Fen
2009-05-12
Beta-amyloid (Abeta) has adverse effects on brain cells, but little is known about its effects on the peripheral nervous system in Alzheimer's disease (AD). Several lines of in vitro evidence suggest that the neurotrophin receptor p75 mediates or exacerbates Abeta-induced neurotoxicity. Here, we show that p75-deficient sympathetic neurons are more sensitive to Abeta-induced neurite growth inhibition. To investigate the role of p75 in the sympathetic nervous system of AD, p75 mutant mice were crossed with a mouse line of AD model. The majority of p75-deficient AD mice died by 3 weeks of age. The lethality is associated with severe defects in sympathetic innervation to multiple organs. When 1 copy of the BACE1 gene encoding a protein essential in Abeta production was deleted in p75-deficient AD mice, sympathetic innervation was significantly restored. These results suggest that p75 is neuroprotective for the sympathetic nervous system in a mouse model of AD.
Benchmarking the thermodynamic analysis of water molecules around a model beta sheet.
Huggins, David J
2012-06-05
Water molecules play a vital role in biological and engineered systems by controlling intermolecular interactions in the aqueous phase. Inhomogeneous fluid solvation theory provides a method to quantify solvent thermodynamics from molecular dynamics or Monte Carlo simulations and provides an insight into intermolecular interactions. In this study, simulations of TIP4P-2005 and TIP5P-Ewald water molecules around a model beta sheet are used to investigate the orientational correlations and predicted thermodynamic properties of water molecules at a protein surface. This allows the method to be benchmarked and provides information about the effect of a protein on the thermodynamics of nearby water molecules. The results show that the enthalpy converges with relatively little sampling, but the entropy and thus the free energy require considerably more sampling to converge. The two water models yield a very similar pattern of hydration sites, and these hydration sites have very similar thermodynamic properties, despite notable differences in their orientational preferences. The results also predict that a protein surface affects the free energy of water molecules to a distance of approximately 4.0 Å, which is in line with previous work. In addition, all hydration sites have a favorable free energy with respect to bulk water, but only when the water-water entropy term is included. A new technique for calculating this term is presented and its use is expected to be very important in accurately calculating solvent thermodynamics for quantitative application.
Benchmarking the Thermodynamic Analysis of Water Molecules Around a Model Beta Sheet
Huggins, David J.
2016-01-01
Water molecules play a vital role in biological and engineered systems by controlling intermolecular interactions in the aqueous phase. Inhomogeneous fluid solvation theory provides a method to quantify solvent thermodynamics from molecular dynamics or Monte Carlo simulations and provides an insight into intermolecular interactions. In this study, simulations of TIP4P-2005 and TIP5P-Ewald water molecules around a model beta sheet are used to investigate the orientational correlations and predicted thermodynamic properties of water molecules at a protein surface. This allows the method to be benchmarked and provides information about the effect of a protein on the thermodynamics of nearby water molecules. The results show that the enthalpy converges with relatively little sampling, but the entropy and thus the free energy require considerably more sampling to converge. The two water models yield a very similar pattern of hydration sites and these hydration sites have very similar thermodynamic properties, despite notable differences in their orientational preferences. The results also show that a protein surface affects the free energy of water molecules to a distance of approximately 4.0 Å, which is in line with previous work. In addition, all hydration sites have a favourable free energy with respect to bulk water, but only when the water-water entropy term is included. A new technique for calculating this term is presented and its use is expected to be very important in accurately calculating solvent thermodynamics for quantitative application. PMID:22457119
Modeling Pseudomonas syringae ice-nucleation protein as a beta-helical protein.
Graether, S P; Jia, Z
2001-01-01
Antifreeze proteins (AFPs) inhibit the growth of ice, whereas ice-nucleation proteins (INPs) promote its formation. Although the structures of several AFPs are known, the structure of INP has been modeled thus far because of the difficulty in determining membrane protein structures. Here, we present a novel model of an INP structure from Pseudomonas syringae based on comparison with two newly determined insect AFP structures. The results suggest that both this class of AFPs and INPs may have a similar beta-helical fold and that they could interact with water through the repetitive TXT motif. By theoretical arguments, we show that the distinguishing feature between an ice inhibitor and an ice nucleator lies in the size of the ice-interacting surface. For INPs, the larger surface area acts as a template that is larger than the critical ice embryo surface area required for growth. In contrast, AFPs are small enough so that they bind to ice and inhibit further growth without acting as a nucleator. PMID:11222281
Amyloid beta-HSP60 peptide conjugate vaccine treats a mouse model of Alzheimer's disease.
Nemirovsky, Anna; Fisher, Yair; Baron, Rona; Cohen, Irun R; Monsonego, Alon
2011-05-23
Active vaccination with amyloid beta peptide (Aβ) to induce beneficial antibodies was found to be effective in mouse models of Alzheimer's disease (AD), but human vaccination trials led to adverse effects, apparently caused by exuberant T-cell reactivity. Here, we sought to develop a safer active vaccine for AD with reduced T-cell activation. We treated a mouse model of AD carrying the HLA-DR DRB1*1501 allele, with the Aβ B-cell epitope (Aβ 1-15) conjugated to the self-HSP60 peptide p458. Immunization with the conjugate led to the induction of Aβ-specific antibodies associated with a significant reduction of cerebral amyloid burden and of the accompanying inflammatory response in the brain; only a mild T-cell response specific to the HSP peptide but not to the Aβ peptide was found. This type of vaccination, evoking a gradual increase in antibody titers accompanied by a mild T-cell response is likely due to the unique adjuvant and T-cell stimulating properties of the self-HSP peptide used in the conjugate and might provide a safer approach to effective AD vaccination. Copyright © 2011 Elsevier Ltd. All rights reserved.
Photometric Stereo for General BRDFs via Reflection Sparsity Modeling.
Han, Tian-Qi; Shen, Hui-Liang
2015-12-01
This paper proposes a pixelwise photometric stereo method for object surfaces with general bidirectional reflectance distribution functions (BRDFs) via appropriate reflection modeling. The modeling is based on three general characteristics of reflection components, i.e., the smooth variation of diffuse reflection, the concentration of specular reflection, and the low-intensity nature of shadow. A graph, whose nodes are light directions, is introduced to model these characteristics. In the graph, the neighborhood of nodes is determined by finding the light sources with close directions. The smoothness of the diffuse component is termed as the summation of local variations under all light sources. The specular reflection is modeled by group sparsity, and the shadow is determined via weighted l1 -norm modeling. The optimization problem, which incorporates these three modeling terms, is cast as a second-order cone programming problem. The proposed method is evaluated on both synthetic and real-world scenes with both isotropic and anisotropic materials. The experimental results show that the method is effective for object surfaces with general BRDFs and outperforms the state-of-the-arts.
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.
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 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.
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…
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 generalized ingrowth model for the northeastern United States
Linda S. Gribko; Donald E. Hilt; Mary Ann Fajvan
1995-01-01
Ingrowth, the number of trees that periodically grow into the smallest inventoried diameter class, has long been recognized as a basic element of multicohort or, uneven-aged, stand development. However, very little information is available to aid forest managers in the estimation of ingrowth. The purpose of this study was to develop a generalized ingrowth model for the...
Institutional Quality and Generalized Trust: A Nonrecursive Causal Model
ERIC Educational Resources Information Center
Robbins, Blaine G.
2012-01-01
This paper investigates the association between institutional quality and generalized trust. Despite the importance of the topic, little quantitative empirical evidence exists to support either unidirectional or bidirectional causality for the reason that cross-sectional studies rarely model the reciprocal relationship between institutional…
A Generalized Life Cycle Cost Model for Electronic Equipment.
The purpose of the study is to develop a generalized life cycle cost model that can be employed by analysts of the Systems/Cost Analysis Office (S...Division. The Life Cycle Cost Handbook included in this document was developed to provide a consistent set of definitions for cost information to be
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)
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…
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…
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…
Institutional Quality and Generalized Trust: A Nonrecursive Causal Model
ERIC Educational Resources Information Center
Robbins, Blaine G.
2012-01-01
This paper investigates the association between institutional quality and generalized trust. Despite the importance of the topic, little quantitative empirical evidence exists to support either unidirectional or bidirectional causality for the reason that cross-sectional studies rarely model the reciprocal relationship between institutional…
Cellulose hydrolysis in evolving substrate morphologies I: A general modeling formalism.
Zhou, Wen; Schüttler, Heinz-Bernd; Hao, Zhiqian; Xu, Ying
2009-10-01
We develop a general framework for a realistic rate equation modeling of cellulose hydrolysis using non-complexed cellulase. Our proposed formalism, for the first time, takes into account explicitly the time evolution of the random substrate morphology resulting from the hydrolytic cellulose chain fragmentation and solubilization. This is achieved by integrating novel geometrical concepts to quantitatively capture the time-dependent random morphology, together with the enzymatic chain fragmentation, into a coupled morphology-plus-kinetics rate equation approach. In addition, an innovative site number representation, based on tracking available numbers of beta(1,4) glucosidic bonds, of different "site" types, exposed to attacks by different enzyme types, is presented. This site number representation results in an ordinary differential equation (ODE) system, with a substantially reduced ODE system size, compared to earlier chain fragmentation kinetics approaches. This formalism enables us to quantitatively simulate both the hydrolytically evolving random substrate morphology and the profound, and heretofore neglected, morphology effects on the hydrolysis kinetics. By incorporating the evolving morphology on an equal footing with the hydrolytic chain fragmentation, our formalism provides a framework for the realistic modeling of the entire solubilization process, beyond the short-time limit and through near-complete hydrolytic conversion. As part I of two companion papers, the present paper focuses on the development of the general modelling formalism. Results and testable experimental predictions from detailed numerical simulations are presented in part II.
Fyfe, J C; Kurzhals, R L; Lassaline, M E; Henthorn, P S; Alur, P R; Wang, P; Wolfe, J H; Giger, U; Haskins, M E; Patterson, D F; Sun, H; Jain, S; Yuhki, N
1999-06-01
A family of domestic cats was found that exhibited clinical and biochemical abnormalities consistent with mucopolysaccharidosis VII, an autosomal recessive lysosomal storage disorder caused by beta-glucuronidase deficiency. beta-Glucuronidase activity was undetectable in affected cat fibroblasts and restored by retroviral gene transfer of rat beta-glucuronidase cDNA. beta-Glucuronidase mRNA was normal in affected cat testis by Northern blot analysis. Normal feline beta-glucuronidase cDNA was cloned and characterized, and amplified from affected cat fibroblasts by reverse transcription coupled polymerase chain reaction. There was a G-to-A transition in the affected cat cDNA that predicted an E351K substitution, destroyed a BssSI site, and eliminated GUSB enzymatic activity in expression studies. Multiple species comparison and the crystal structure of human beta-glucuronidase indicated that E351 is a highly conserved residue most likely essential in maintenance of the enzyme's conformation. BssSI digestion of polymerase chain reaction products amplified from genomic DNA indicated that affected cats were homozygous and cats with half-normal beta-glucuronidase activity were heterozygous for the missense mutation. Carriers identified in this manner produced affected kittens in prospective breedings, and a feline MPS VII breeding colony has been established.
Song, Wei; Wei, Guanghong; Mousseau, Normand; Derreumaux, Philippe
2008-04-10
Although a wide variety of proteins can assemble into amyloid fibrils, the structure of the early oligomeric species on the aggregation pathways remains unknown at an atomic level of detail. In this paper we report, using molecular dynamics simulations with the OPEP coarse-grained force field, the free energy landscape of a tetramer and a heptamer of the beta2-microglobulin NHVTLSQ peptide. On the basis of a total of more than 17 ns trajectories started from various states, we find that both species are in equilibrium between amorphous and well-ordered aggregates with cross-beta-structure, a perpendicular bilayer beta-sheet, and, for the heptamer, six- or seven-stranded closed and open beta-barrels. Moreover, analysis of the heptamer trajectories shows that the perpendicular bilayer beta-sheet is one possible precursor of the beta-barrel, but that this barrel can also be formed from a twisted monolayer beta-sheet with successive addition of chains. Comparison with previous aggregation simulations and the fact that nature constructs transmembrane beta-sheet proteins with pores open the possibility that beta-barrels with small inner diameters may represent a common intermediate during the early steps of aggregation.
NASA Technical Reports Server (NTRS)
Schotland, R. M.; Warren, A. J.; Funariu, O. M.
1991-01-01
The second year's results of the BETA project research are presented. The program is divided into two areas, aerosol modification and climatology in the trade wind region and the climatology of BETA (CO2) on remote mountain top locations. Limited data is available on the aerosol climatology of the marine free troposphere (MFT) in the trade wind region. In order to study the effects of cumulus convection on the MFT values of BETA, a cloud model was developed to simulate the evolution of a typical Pacific trade wind cumulus cloud. The stages involved in this development are outlined. The assembly of the major optical components of the lidar was made. Tests were run of the spectral bandwidth of the Synrad laser when a portion of the beam is mixed with a component which has traveled 450 meters corresponding to a delay of 1.5 microsecs. The bandwidth of the beat signal was measured to be 3 KHz. The data processing system based on a parallel processing filter bank analyzer using true time squaring detectors at each filter was completed.
Fujii, Michihiro; Homma, Taira; Ooshima, Kazuhisa; Taniguchi, Masayuki
1991-12-31
A kinetic model representing the synergistic action of the three components that compose cellulose on hydrolysis of solid cellulose particles is proposed. The model consists of three simultaneous differential equations: one representing the action of the endoenzyme, another representing the action of the exoenzyme, and the third representing the action of the {Beta}-glucosidase. A simultaneous solution of these three equations expresses the synergism. The experimental data fit the theory well.
Federal Register 2010, 2011, 2012, 2013, 2014
2010-11-24
...This amendment adopts a new airworthiness directive (AD) for Robinson Model R22, R22 Alpha, R22 Beta, and R22 Mariner helicopters, and Model R44 and R44 II helicopters. This AD requires visually inspecting each tail rotor (T/R) control pedal bearing block support (support) for a crack, measuring the thickness of each support, installing support safety tabs on certain supports, and replacing......
Analysis of snow feedbacks in 14 general circulation models
NASA Technical Reports Server (NTRS)
Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Chalita, S.; Colman, R.; Dazlich, D. A.; Del Genio, A. D.; Keup, E.; Lacis, A.; Le Treut, H.
1994-01-01
Snow feedbacks produced by 14 atmospheric general circulation models have been analyzed through idealized numerical experiments. Included in the analysis is an investigation of the surface energy budgets of the models. Negative or weak positive snow feedbacks occurred in some of the models, while others produced strong positive snow feedbacks. These feedbacks are due not only to melting snow, but also to increases in boundary temperature, changes in air temperature, changes in water vapor, and changes in cloudiness. As a result, the net response of each model is quite complex. We analyze in detail the responses of one model with a strong positive snow feedback and another with a weak negative snow feedback. Some of the models include a temperature dependence of the snow albedo, and this has significantly affected the results.
Hobbs, Brian P; Sargent, Daniel J; Carlin, Bradley P
2012-08-28
Assessing between-study variability in the context of conventional random-effects meta-analysis is notoriously difficult when incorporating data from only a small number of historical studies. In order to borrow strength, historical and current data are often assumed to be fully homogeneous, but this can have drastic consequences for power and Type I error if the historical information is biased. In this paper, we propose empirical and fully Bayesian modifications of the commensurate prior model (Hobbs et al., 2011) extending Pocock (1976), and evaluate their frequentist and Bayesian properties for incorporating patient-level historical data using general and generalized linear mixed regression models. Our proposed commensurate prior models lead to preposterior admissible estimators that facilitate alternative bias-variance trade-offs than those offered by pre-existing methodologies for incorporating historical data from a small number of historical studies. We also provide a sample analysis of a colon cancer trial comparing time-to-disease progression using a Weibull regression model.
Hobbs, Brian P.; Sargent, Daniel J.; Carlin, Bradley P.
2014-01-01
Assessing between-study variability in the context of conventional random-effects meta-analysis is notoriously difficult when incorporating data from only a small number of historical studies. In order to borrow strength, historical and current data are often assumed to be fully homogeneous, but this can have drastic consequences for power and Type I error if the historical information is biased. In this paper, we propose empirical and fully Bayesian modifications of the commensurate prior model (Hobbs et al., 2011) extending Pocock (1976), and evaluate their frequentist and Bayesian properties for incorporating patient-level historical data using general and generalized linear mixed regression models. Our proposed commensurate prior models lead to preposterior admissible estimators that facilitate alternative bias-variance trade-offs than those offered by pre-existing methodologies for incorporating historical data from a small number of historical studies. We also provide a sample analysis of a colon cancer trial comparing time-to-disease progression using a Weibull regression model. PMID:24795786
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.
Ghatak, Supratim; Raha, Sanghamitra
2015-04-10
Role of beta catenin in Huntington's disease (HD) is not clear. Previous studies on HD reported varied levels of beta catenin. In the present study we showed that beta catenin is post transcriptionally down-regulated in mutant huntingtin knock-in cell model STHdhQ111/Q111. This in turn leads to decreased level of wnt/beta catenin responsive genes. We observed that Gsk3beta or Gsk3beta (phospho Ser 9) is unaltered in HD and this down-regulation of beta catenin is independent of proteasomal degradation. Finally, we showed that the overexpression of miR-214 leads to the down-regulation of beta catenin at protein level only and reduces its transcriptional activity. We concluded that, miR-214 contributes to the processes that result in proteasome independent post transcriptional down-regulation of beta catenin in STHdhQ111/Q111, probably through inhibition of protein synthesis from beta catenin mRNA.
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.
A general kinetic model for the hydrothermal liquefaction of microalgae.
Valdez, Peter J; Tocco, Vincent J; Savage, Phillip E
2014-07-01
We developed a general kinetic model for hydrothermal liquefaction (HTL) of microalgae. The model, which allows the protein, lipid, and carbohydrate fractions of the cell to react at different rates, successfully correlated experimental data for the hydrothermal liquefaction of Chlorella protothecoides, Scenedesmus sp., and Nannochloropsis sp. The model can faithfully account for the influence of time and temperature on the gravimetric yields of gas, solid, biocrude, and aqueous-phase products from isothermal HTL of a 15 wt% slurry. Examination of the rate constants shows that lipids and proteins are the major contributors to the biocrude, while other algal cell constituents contribute very little to the biocrude.
Generalized Born-Infeld-like models for kinks and branes
NASA Astrophysics Data System (ADS)
Bazeia, D.; Marques, M. A.; Menezes, R.
2017-04-01
In this work we deal with a non-canonical scalar field in the two-dimensional spacetime. We search for a generalized model that is twin of the standard model, supporting the same defect structure with the same energy density. We also study the stability of the defect solution under small fluctuations, which is governed by a Sturm-Liouville equation, and show how to make it stable. The model is then modified and used in the five-dimensional spacetime to construct a thick brane that engenders the first-order framework and preserves the twinlike behavior, under tensorial fluctuations of the metric in its gravitational sector.
[Modification and its application of generalized Schumacher model].
Hong, Wei; Wu, Chengzhen; Yan, Shujun
2004-02-01
Based on the concrete analysis on growth equations presented by others, a modified Schumacher growth equation was proposed as, which included Gompertz function, Schumacher equation and generalized Schumacher equation, and had stronger self-adaptability and practicality. The analytic character and adaptability of the modified Schumacher equation were analyzed. According to the genetic algorithms method, this model was used to fit the growth data of endangered plant of Tsuga longibracteata and Platycladus orientalis. The results showed that the modified Schumacher equation was not only better than Schumacher equation and generalized Schumacher equation significantly, but also better than classical Logistic model and Li's self-adaptive model. So it could be used to study the dynamics simulation for tree growth and dynamics law for population growth.
Concurrent approaches to Generalized Parton Distribution modeling: the pion's case
NASA Astrophysics Data System (ADS)
Chouika, N.; Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.
2017-03-01
The concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energy-momentum structure of hadrons by quarks and gluons. Forthcoming measurements with unprecedented accuracy at Jefferson Lab and at CERN will challenge our quantitative description of the three-dimensional structure of hadrons. To fully exploit these future measurements, new tools and models are currently being developed. We explain the difficulties of Generalized Parton Distribution modeling, and present some recent progresses. In particular we describe the symmetry-preserving Dyson-Schwinger and Bethe-Salpeter framework. We also discuss various equivalent parameterizations and sketch how to combine them to obtain models satisfying a priori all required theoretical constraints. At last we explain why these developments naturally fit in a versatile software framework, named PARTONS, dedicated to the theory and phenomenology of GPDs.
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.
Towards a generalized energy prediction model for machine tools.
Bhinge, Raunak; Park, Jinkyoo; Law, Kincho H; Dornfeld, David A; Helu, Moneer; Rachuri, Sudarsan
2017-04-01
Energy prediction of machine tools can deliver many advantages to a manufacturing enterprise, ranging from energy-efficient process planning to machine tool monitoring. Physics-based, energy prediction models have been proposed in the past to understand the energy usage pattern of a machine tool. However, uncertainties in both the machine and the operating environment make it difficult to predict the energy consumption of the target machine reliably. Taking advantage of the opportunity to collect extensive, contextual, energy-consumption data, we discuss a data-driven approach to develop an energy prediction model of a machine tool in this paper. First, we present a methodology that can efficiently and effectively collect and process data extracted from a machine tool and its sensors. We then present a data-driven model that can be used to predict the energy consumption of the machine tool for machining a generic part. Specifically, we use Gaussian Process (GP) Regression, a non-parametric machine-learning technique, to develop the prediction model. The energy prediction model is then generalized over multiple process parameters and operations. Finally, we apply this generalized model with a method to assess uncertainty intervals to predict the energy consumed to machine any part using a Mori Seiki NVD1500 machine tool. Furthermore, the same model can be used during process planning to optimize the energy-efficiency of a machining process.
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 parallel coupled oceanic-atmospheric general circulation model
NASA Astrophysics Data System (ADS)
Wehner, Michael F.; Bourgeois, Al J.; Eltgroth, Peter G.; Duffy, Phillip B.; Dannevik, William P.
1994-12-01
The Climate Systems Modeling group at Lawrence Liwermore National Laboratory (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.
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.
Hassan, Wail M; Merin, David A; Fonte, Virginia; Link, Christopher D
2009-08-01
Multiple neurodegenerative diseases are causally linked to aggregation-prone proteins. Cellular mechanisms involving protein turnover may be key defense mechanisms against aggregating protein disorders. We have used a transgenic Caenorhabditis elegans Alzheimer's disease model to identify cellular responses to proteotoxicity resulting from expression of the human beta amyloid peptide (Abeta). We show up-regulation of aip-1 in Abeta-expressing animals. Mammalian homologues of AIP-1 have been shown to associate with, and regulate the function of, the 26S proteasome, leading us to hypothesize that induction of AIP-1 may be a protective cellular response directed toward modulating proteasomal function in response to toxic protein aggregation. Using our transgenic model, we show that overexpression of AIP-1 protected against, while RNAi knockdown of AIP-1 exacerbated, Abeta toxicity. AIP-1 overexpression also reduced accumulation of Abeta in this model, which is consistent with AIP-1 enhancing protein degradation. Transgenic expression of one of the two human aip-1 homologues (AIRAPL), but not the other (AIRAP), suppressed Abeta toxicity in C. elegans, which advocates the biological relevance of the data to human biology. Interestingly, AIRAPL and AIP-1 contain a predicted farnesylation site, which is absent from AIRAP. This farnesylation site was shown by others to be essential for an AIP-1 prolongevity function. Consistent with this, we show that an AIP-1 mutant lacking the predicted farnesylation site failed to protect against Abeta toxicity. Our results implicate AIP-1 in the regulation of protein turnover and protection against Abeta toxicity and point at AIRAPL as the functional mammalian homologue of AIP-1.
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.
Gene therapy by allele selection in a mouse model of beta-thalassemia.
Eckardt, Sigrid; Leu, N Adrian; Yanchik, Ashley; Hatada, Seigo; Kyba, Michael; McLaughlin, K John
2011-02-01
To be of therapeutic use, autologous stem cells derived from patients with inherited genetic disorders require genetic modification via gene repair or insertion. Here, we present proof of principle that, for diseases associated with dominant alleles (gain-of-function or haploinsufficient loss-of-function), disease allele–free ES cells can be derived from afflicted individuals without genome manipulation. This approach capitalizes on the derivation of uniparental cells, such as parthenogenetic (PG) ES cell lines from disease allele–free gametes. Diploid mammalian uniparental embryos with only maternally (oocyte-) or paternally (sperm-)derived genomes fail early in development due to the nonequivalence of parental genomes caused by genomic imprinting. However, these uniparental embryos develop to the blastocyst stage, allowing the derivation of ES cell lines. Using a mouse model for dominant beta-thalassemia, we developed disease allele–free PG ES cell lines from the oocytes of affected animals. Phenotype correction was obtained in donor-genotype recipients after transplantation of in vitro hematopoietic ES cell derivatives. This genetic correction strategy without gene targeting is potentially applicable to any dominant disease. It could also be the sole approach for larger or more complex mutations that cannot be corrected by homologous recombination.
Dhakal, S; Manandhar, S; Shrestha, B; Dhakal, R; Pudasaini, M
2012-06-01
A study was conducted to analyze the status of the multidrug resistant (MDR) isolates producing Extended Spectrum of beta-lactamase (ESBL) among the uropathogens infecting children less than 15 years from November 2010 to April 2011 in the Bacteriology laboratory, Kathmandu Model Hospital. Urine samples received in the laboratory were processed for routine culture. The antimicrobial susceptibility of bacterial isolates was determined following Clinical and Laboratory Standard Institute (CLSI) recommended Kirby-Bauer Disc Diffusion method. The defining criterion in this study for an isolate to be multidrug resistant was resistance to two or more drugs of different structural classes. Isolates were confirmed for ESBL-production by performing the Inhibitor Potentiated Disk Diffusion (IPDD) Test/ Combined Disk Assay for ESBL confirmation. Out of 252 urine samples received in the laboratory, 59(23.41%) showed significant growth of which 54.23% (32/59) were MDR isolates. Additionally, 25 isolates (21 Escherichia coli and 3 Citrobacter freundii and single Enterobacter aerogenes) among them were ESBL producers. Among the first line drugs used against gram negative isolates, Nitrofurantoin was drug of choice; meanwhile among the second line drugs Cefoperazone/Sulbactum was drug of choice, whereas, Cephotaxime, Ciprofloxacin, Norfloxacin and Gentamicin were the drug of choice for Gram positive isolates. Significant association was found between ESBL production and spectrum of drug resistance (p < 0.05).
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.
Holmberg, Hanna; Wahlberg, Jeanette; Vaarala, Outi; Ludvigsson, Johnny
2007-01-01
Breast-feeding has been suggested to have a protective effect against the development of type 1 diabetes. In the present study, we investigated the relation between duration of breast-feeding and beta-cell autoantibodies in 5-year-old non-diabetic children who participated in a prospective population-based follow-up study (the All Babies in Southeast Sweden study). Autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA) and the protein tryosine phosphatase-like IA-2 (IA-2A) were measured by radiobinding assays. A short duration of total breast-feeding was associated with an increased risk of GADA and/or IAA above the ninety-fifth percentile at 5 years of age (OR 2.09, 95% CI 1.45, 3.02; P<0.000) as well as with an increased risk of IAA above the ninety-fifth percentile at this age (OR 2.89, 95% CI 1.81, 4.62, P<0.000). A short duration of exclusive breast-feeding was associated with an increased risk of GADA, IAA and/or IA-2A above the ninety-ninth percentile (OR 2.01, 95% CI 1.08, 3.73; P=0.028) as well as with an increased risk of IA-2A above the ninety-ninth percentile (OR 3.50, 95% CI 1.38, 8.92, P=0.009) at 5 years of age. An early introduction of formula was associated with an increased risk of GADA, IAA and/or IA-2A above the ninety-ninth percentile (OR 1.84, 95% CI 1.01, 3.37; P=0.047) at 5 years of age. The positive association between a short duration of both total and exclusive breast-feeding, as well as an early introduction of formula, and positivity for beta-cell autoantibodies in children from the general population suggest that breast-feeding modifies the risk of beta-cell autoimmunity, even years after finishing breast-feeding.
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.
UWB microwave breast cancer detection: generalized models and performance prediction.
Chen, Yifan; Gunawan, Erry; Kim, Yongmin; Low, Kay Soon; Soh, Cheong Boon; Thi, Lin Lin
2006-01-01
This paper presents a generic framework for the modeling of ultra-wideband (UWB) signal propagation in human breast, which facilitates system-level simulations and provides performance prediction. The clutter associated with the breast tissue heterogeneity is modeled through several key parameters depending on the tissue compositions. Subsequently, important channel properties such as the backscatter energy and the probability density function of time-of-arrival are derived. The modified Hermite polynomials, which fit well into the real pulse shapes, are then used to model the UWB signals. Armed with the channel/signal model preliminaries, three metrics are proposed, namely, the mean clutter response, the clean tumor response, and the worst-case clutter response. The generalized model provides a parsimonious way to study the effects of tissue structures, pulse templates, and array setup on the performance of a specified UWB imaging system. Numerical examples are used to demonstrate the usefulness of the proposed approach.
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.
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.
Harrison, Xavier A
2015-01-01
Overdispersion is a common feature of models of biological data, but researchers often fail to model the excess variation driving the overdispersion, resulting in biased parameter estimates and standard errors. Quantifying and modeling overdispersion when it is present is therefore critical for robust biological inference. One means to account for overdispersion is to add an observation-level random effect (OLRE) to a model, where each data point receives a unique level of a random effect that can absorb the extra-parametric variation in the data. Although some studies have investigated the utility of OLRE to model overdispersion in Poisson count data, studies doing so for Binomial proportion data are scarce. Here I use a simulation approach to investigate the ability of both OLRE models and Beta-Binomial models to recover unbiased parameter estimates in mixed effects models of Binomial data under various degrees of overdispersion. In addition, as ecologists often fit random intercept terms to models when the random effect sample size is low (<5 levels), I investigate the performance of both model types under a range of random effect sample sizes when overdispersion is present. Simulation results revealed that the efficacy of OLRE depends on the process that generated the overdispersion; OLRE failed to cope with overdispersion generated from a Beta-Binomial mixture model, leading to biased slope and intercept estimates, but performed well for overdispersion generated by adding random noise to the linear predictor. Comparison of parameter estimates from an OLRE model with those from its corresponding Beta-Binomial model readily identified when OLRE were performing poorly due to disagreement between effect sizes, and this strategy should be employed whenever OLRE are used for Binomial data to assess their reliability. Beta-Binomial models performed well across all contexts, but showed a tendency to underestimate effect sizes when modelling non-Beta-Binomial data
Gustafson, W G; Feinberg, B A; McFarland, J T
1986-06-15
We have determined reduction potentials for porcine mitochondrial general fatty acyl-CoA dehydrogenase (GAD) and electron transfer flavoprotein (ETF) using an anaerobic spectroelectrochemical titration method. Computer simulation techniques were used to analyze the absorbance data. Nernst plots of the simulated data gave E'0, 7.1, quinone/semiquinone = -0.014 V and E'0, 7.1, semiquinone/hydroquinone = -0.036 V for ETF and E'0, 7.1, quinone/semiquinone = -0.155 V and E'0, 7.1, semiquinone/hydroquinone = -0.122 V for GAD. Using these techniques we have also determined a conditional reduction potential of -0.156 V for the chromophore producing fatty acyl-CoA substrate beta-2-furylpropionyl-CoA. From this value and our previous determination of the equilibrium constant for the transhydrogenation reaction between beta-2-furylpropionyl-CoA and the oxidized substrate crotonyl-CoA (Keq = 10.4), we have determined a reduction potential of -0.126 V for the butyryl-CoA/crotonyl-CoA couple. In light of the structural similarity between butyryl-CoA and octanoyl-CoA, the optimal substrate for GAD, the reduction potential for octanoyl-CoA should be similar to that for butyryl-CoA; i.e. fatty acyl-CoA substrates and GAD are essentially isopotential. The ability of octanoyl-CoA to reduce GAD quantitatively (Keq = 9.0) poses a dilemma in light of the nearly equal reduction potentials. We postulate that the stable charge-transfer complex formed between enzyme and optimal product is significantly lower in energy than enzyme and product and thus is responsible for pulling the reaction toward completion.
A generalized flow path model for water distribution optimization
NASA Astrophysics Data System (ADS)
Hsu, N.; Cheng, W.; Yeh, W. W.
2008-12-01
A generalized flow path model is developed for optimizing a water distribution system. The model simultaneously describes a water distribution system in two parts: (1) the water delivery relationships between suppliers and receivers and (2) the physical water delivery system. In the first part, the model considers waters from different suppliers as multiple commodities. This helps the model to clearly describe water deliveries by identifying the relationships between suppliers and receivers. The second part characterizes a physical water distribution network by all possible flow paths. The advantages of the proposed model are that: (1) it is a generalized methodology to optimize water distribution, delivery scheduling, water trade, water transfer, and water exchange under existing reservoir operation rules, contracts, and agreements; (2) it can consider water as multiple commodities if needed; and (3) no simplifications are made for either the physical system or the delivery relationships. The model can be used as a tool for decision making for scheduling optimization. The model optimizes not only the suppliers to each receiver but also their associated flow paths for supplying water. This characteristic leads to the optimum solution that contains the optimal scheduling results and detailed information of water distribution in the physical system. That is, the water right owner, water quantity and its associated flow path of each delivery action are represented explicitly in the results rather than merely an optimized total flow quantity in each arc of a distribution network. The proposed model is first verified by a hypothetical water distribution system. Then, the model is applied to the water distribution system of the Tou-Qian River Basin in northern Taiwan. The results show that the flow path model has the ability to optimize the quantity of each water delivery, the associated flow paths of the delivery, and the strategies of water transfer while considering
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
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.
Schmidt, Philip J; Pintar, Katarina D M; Fazil, Aamir M; Topp, Edward
2013-09-01
Dose-response models are the essential link between exposure assessment and computed risk values in quantitative microbial risk assessment, yet the uncertainty that is inherent to computed risks because the dose-response model parameters are estimated using limited epidemiological data is rarely quantified. Second-order risk characterization approaches incorporating uncertainty in dose-response model parameters can provide more complete information to decisionmakers by separating variability and uncertainty to quantify the uncertainty in computed risks. Therefore, the objective of this work is to develop procedures to sample from posterior distributions describing uncertainty in the parameters of exponential and beta-Poisson dose-response models using Bayes's theorem and Markov Chain Monte Carlo (in OpenBUGS). The theoretical origins of the beta-Poisson dose-response model are used to identify a decomposed version of the model that enables Bayesian analysis without the need to evaluate Kummer confluent hypergeometric functions. Herein, it is also established that the beta distribution in the beta-Poisson dose-response model cannot address variation among individual pathogens, criteria to validate use of the conventional approximation to the beta-Poisson model are proposed, and simple algorithms to evaluate actual beta-Poisson probabilities of infection are investigated. The developed MCMC procedures are applied to analysis of a case study data set, and it is demonstrated that an important region of the posterior distribution of the beta-Poisson dose-response model parameters is attributable to the absence of low-dose data. This region includes beta-Poisson models for which the conventional approximation is especially invalid and in which many beta distributions have an extreme shape with questionable plausibility.
Dayan, Franck E; Singh, Nidhi; McCurdy, Christopher R; Godfrey, Colette A; Larsen, Lesley; Weavers, Rex T; Van Klink, John W; Perry, Nigel B
2009-06-24
p-Hydroxyphenylpyruvate dioxygenase (HPPD) is the target site of beta-triketone herbicides in current use. Nineteen beta-triketones and analogues, including the naturally occurring leptospermone and grandiflorone, were synthesized and tested as inhibitors of purified Arabidopsis thaliana HPPD. The most active compound was a beta-triketone with a C(9) alkyl side chain, not reported as natural, which inhibited HPPD with an I(50) of 19 +/- 1 nM. This is significantly more active than sulcotrione, which had an I(50) of 250 +/- 21 nM in this assay system. The most active naturally occurring beta-triketone was grandiflorone, which had an I(50) of 750 +/- 70 nM. This compound is of potential interest as a natural herbicide because it can be extracted with good yield and purity from some Leptospermum shrubs. Analogues without the 1,3-diketone group needed to interact with Fe(2+) at the HPPD active site were inactive (I(50)s > 50 microM), as were analogues with prenyl or ethyl groups on the triketone ring. Modeling of the binding of the triketones to HPPD, three-dimensional QSAR analysis using CoMFA (comparative molecular field analysis), and evaluation of the hydrophobic contribution with HINT (hydropathic interactions) provided a structural basis to describe the ligand/receptor interactions.
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.
Net diffusivity in ocean general circulation models with nonuniform grids
NASA Technical Reports Server (NTRS)
Yin, F. L.; Fung, I. Y.
1991-01-01
The numerical vertical diffusivity K(num), embedded in a numerical ocean general circulation model with nonuniform vertical grid, is estimated. It is shown that in a downwelling region, K(num) is negative for a grid with grid size increasing with depth. When the grid size increment, or the downward vertical velocity, is large, K(num) may exceed the vertical diffusivity specified and may result in a negative effective vertical diffusivity. Therefore care needs to be taken to specify the vertical diffusivity in a numerical model with nonuniform grid, and a lower bound is generally imposed in order to avoid an unphysical negative value. Some possible effects of the negative effective diffusivity are discussed.
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.
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.
Expression of TGF-beta 1, -beta 2 and -beta 3 in localized and systemic scleroderma.
Querfeld, C; Eckes, B; Huerkamp, C; Krieg, T; Sollberg, S
1999-09-01
Scleroderma is a generalized or localized disorder which leads to fibrosis of the affected organs. TGF-beta has been implicated as a causal agent in its pathogenesis. In mammals, TGF-beta comprises a family of three members, beta 1, beta 2 and beta 3. Since cutaneous wound healing is thought to result either in formation of a scar or in scar-free tissue regeneration, depending on the relative amounts of the beta 3 isoform, the expression of all three isoforms was studied in skin biopsies of patients with either localized or systemic scleroderma. mRNA for all three isoforms was detected in inflammatory skin areas of both disease forms, but never in sclerotic or healthy skin. Immunohistochemical analysis confirmed expression of beta1 and beta 2 proteins in inflammatory skin of patients, whereas beta 3 protein appeared to be present in the subepidermal area and also found throughout the dermis of patients and healthy dermis as well.
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
EPA`s emissions models for general nonroad sources
Fieber, J.; Rosenbaum, A.; Vranka, R.; Kleinhesselink, D.
1996-12-31
Under the sponsorship of the US EPA`s Office of Mobile Sources, SAI has developed a computer model for nonroad mobile sources. Although data and methodologies continue to be revisited, the alpha version of the model has been completed and is currently under review at EPA. The model contains modules for estimating equipment populations, activity, emission factors, and total emissions. It adjusts these estimates to predict total emissions for the calendar year and at a level of detail specified by the user (e.g., average annual estimates at a national level, hourly estimates for a specific county). The EPA`s nonroad model provides estimates for the following general classes of nonroad equipment: General Nonroad Sources: (1) Lawn and garden equipment; (2) Airport service equipment; (3) Recreational; (4) Light Commercial; (5) Industrial; (6) Construction; (7) Agricultural; and (8) Logging. Special Nonroad Sources: (1) Locomotives; (2) Aircraft; and (3) Marine Vessels. With the exception of locomotives, aircraft, and marine vessels, the methodologies used within the model are quite similar for all these source groupings. Information for specific equipment types (e.g., 15-25 horsepower, gasoline 2-stroke engine commercial turf equipment) will also be provided if the user requests this level of detail. Written in FORTRAN and designed for personal computers (though it can be ported to workstations), this new emissions tool includes an interface to improve its ease of use and flexibility. We present here some of the features of the model and provide an overview of the internal methods used for the equipment groups listed under general nonroad sources.
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.
Fire risk analysis: general conceptual framework for describing models.
Hall, J R; Sekizawa, A
1991-02-01
A general conceptual framework has been developed as an aid to discussions of alternative approaches to fire risk analysis. The purpose is to show how each alternative seeks to address a few common concerns. Basic concepts and key elements--notably scenario structures, appropriate probability functions, and security and outcome measures--are defined and discussed, as are types of modeling approaches. A number of diverse examples are then presented using the framework to illustrate its value in making comparisons.
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.
A note on the discrete approach for generalized continuum models
NASA Astrophysics Data System (ADS)
Kalampakas, Antonios; Aifantis, Elias C.
2014-12-01
Generalized continuum theories for materials and processes have been introduced in order to account in a phenomenological manner for microstructural effects. Their drawback mainly rests in the determination of the extra phenomenological coefficients through experiments and simulations. It is shown here that a graphical representation of the local topology describing deformation models can be used to deduce restrictions on the phenomenological coefficients of the gradient elasticity continuum theories.
Baroclinic Rossby Wave Signature in a General Circulation Ocean Model.
1983-06-01
northwest with a wavelength cf 300 km. For other laritudes of the North acific Ocean , Price and Maqaard (1980) determined that first mode baroclinic Rossby...role in the latitude belt 40-50N in the North acific 10 -. - !o Ocean . Magaard (1983) ir. a paper discussing bariclin _c Rossty wave energetics...HD-AI132 219 BAROCLINIC ROSSBY WAVE SIGNATURE IN A GENERAL CIRCULATION OCEAN MODEL(U) NAVAL POSTGRADUATE SCHOOLU MONTEREY CA A H RUTSCH JUN 83
Electromagnetic axial anomaly in a generalized linear sigma model
NASA Astrophysics Data System (ADS)
Fariborz, Amir H.; Jora, Renata
2017-06-01
We construct the electromagnetic anomaly effective term for a generalized linear sigma model with two chiral nonets, one with a quark-antiquark structure, the other one with a four-quark content. We compute in the leading order of this framework the decays into two photons of six pseudoscalars: π0(137 ), π0(1300 ), η (547 ), η (958 ), η (1295 ) and η (1760 ). Our results agree well with the available experimental data.
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.
A Moist Idealized Test Case for Atmospheric General Circulation Models
NASA Astrophysics Data System (ADS)
Thatcher, D.; Jablonowski, C.; Zarzycki, C.
2013-12-01
The vast array of dynamical and physical processes within atmospheric general circulation models (GCMs) makes it difficult to correctly distinguish the sources of error within a model. Therefore, simplified test cases are important in testing the accuracy of individual model components, such as the fluid flow component in the dynamical core. Typically, dynamical cores are coupled to complex subgrid-scale physical parameterization packages, and the nonlinear interactions mask the causes and effects of atmospheric phenomena. Idealized tests are a computationally efficient method for analyzing the underlying numerical techniques of dynamical cores. The newly proposed test case is based on the widely-used Held and Suarez (1994) (HS) test for dry dynamical cores. The latter replaces the full physical parameterization package with a Newtonian temperature relaxation and Rayleigh damping of low-level winds on a flat planet. However, the impact of moisture, a crucial physics-dynamics coupling process, is missing from the HS test. Here we present a moist variant of the HS test case to create a test case of intermediate complexity with idealized moisture feedbacks. It uses simplified physical processes to model large-scale condensation, boundary layer turbulence, and surface fluxes of horizontal momentum, latent heat, and sensible heat between the atmosphere and an ocean-covered planet (Reed and Jablonowski, 2012). We apply this test to four dynamical cores within NCAR's Community Atmosphere Model version 5.3, including the Finite Volume, Eulerian spectral transform, semi-Lagrangian spectral transform, and Spectral Element dynamical cores. We analyze the kinetic energy spectra, general circulation, and precipitation of this new moist idealized test case across all four dynamical cores. Simulations of the moist idealized test case are compared to aqua-planet experiments with complex physical parameterizations. The moist idealized test case successfully reproduces many features
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.
Interactive data exploration and particle tracking for general circulation models
NASA Technical Reports Server (NTRS)
Rosenbaum, R. I.; Peskin, R. L.; Walther, S. S.; Zinn, H. P.
1995-01-01
The SCENE environment for interactive visualization of complex data sets is discussed. This environment is used to create tools for graphical exploration of atmospheric flow models. These tools may be extended by the user in a seamless manner, so that no programming is required. A module for accurately tracing field lines and particle trajectories in SCENE is presented. This is used to examine the flowfield qualitatively with streamlines and pathlines and to identify critical points in the velocity field. The paper also describes a visualization tool for general circulation models on which the primary features of the environment are demonstrated.
A general model for the textural evolution of lunar soil
NASA Technical Reports Server (NTRS)
Lindsay, J. F.
1974-01-01
The investigation reported is concerned with the qualitative expansion of an earlier model developed by Lindsay (1971, 1972, 1973). Questions regarding the maturity of lunar soils are examined. A multivariate model related to textural maturity is considered, taking into account mean and standard deviations, the asymmetry of the grain size curve, the kurtosis anomaly, and pyroclastic materials. It is concluded that the mean grain size and the standard deviation of the lunar soil can be used as general indicators of the textural maturity of the soil anywhere on the lunar surface.
Anastay, M; Lagier, E; Blanc, V; Chardon, H
2013-04-01
The global epidemiology of extended spectrum betalactamases (ESBL) producing Enterobacteriaceae has evolved in recent years with the emergence of a new type of ESBL: CTX-M, mainly in Escherichia coli. These CTX-M type producing Enterobacteriaceae are responsible for both nosocomial and, more recently, community infections, including urinary tract infections. The aim of our work is to study ESBL producing Enterobacteriaceae evolution between 1999 and 2007 in the population from the Centre Hospitalier du Pays-d'Aix (CHPA), a general hospital from South of France. ESBL producing strains of Enterobacteriaceae isolated in odd years between 1999 and 2007 from clinical isolates of all origins have been phenotypically identified and their ESBL genotyped. Molecular and epidemiological data from our hospital health-care associated infection committee were analyzed. Two hundred and sixty-two ESBL producing isolates were studied. Within ESBL producing Enterobacteriaceae, Enterobacter aerogenes was predominant in 1999 (48.7% of isolates), and decreased to 18.8% of isolates in 2007. On the other hand, E. coli, which represented 10.5% of ESBL isolates in 1999, grew up to 37.5% of the isolates in 2007. ESBL prevalence in E. coli increased during this period from 0.3 to 2.5%. Simultaneously, ESBL, predominantly TEM-24 in 1999, were replaced by CTX-M in 2007, among which CTX-M-15 is predominant (88% of CTX-M). Our study confirms a major change in ESBL epidemiology in CHPA, with the emergence of CTX-M type ESBL, mainly CTX-M 15, and an increase of ESBL prevalence in E. coli. Copyright © 2012 Elsevier Masson SAS. All rights reserved.
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.
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
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. 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. 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. 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.
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
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.
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 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.
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.
A film-rupture model of hydrogen-induced, slow crack growth in alpha-beta titanium
NASA Technical Reports Server (NTRS)
Nelson, H. G.
1975-01-01
The appearance of the terrace like fracture morphology of gaseous hydrogen induced crack growth in acicular alpha-beta titanium alloys is discussed as a function of specimen configuration, magnitude of applied stress intensity, test temperature, and hydrogen pressure. Although the overall appearance of the terrace structure remained essentially unchanged, a distinguishable variation is found in the size of the individual terrace steps, and step size is found to be inversely dependent upon the rate of hydrogen induced slow crack growth. Additionally, this inverse relationship is independent of all the variables investigated. These observations are quantitatively discussed in terms of the formation and growth of a thin hydride film along the alpha-beta boundaries and a qualitative model for hydrogen induced slow crack growth is presented, based on the film-rupture model of stress corrosion cracking.
He, M; Varoglu, M; Sherman, D H
2000-05-01
A three-dimensional model of the Streptomyces coelicolor actinorhodin beta-ketoacyl synthase (Act KS) was constructed based on the X-ray crystal structure of the related Escherichia coli fatty acid synthase condensing enzyme beta-ketoacyl synthase II, revealing a similar catalytic active site organization in these two enzymes. The model was assessed by site-directed mutagenesis of five conserved amino acid residues in Act KS that are in close proximity to the Cys169 active site. Three substitutions completely abrogated polyketide biosynthesis, while two replacements resulted in significant reduction in polyketide production. (3)H-cerulenin labeling of the various Act KS mutant proteins demonstrated that none of the amino acid replacements affected the formation of the active site nucleophile.
A general mixture model for sediment laden flows
NASA Astrophysics Data System (ADS)
Liang, Lixin; Yu, Xiping; Bombardelli, Fabián
2017-09-01
A mixture model for general description of sediment-laden flows is developed based on an Eulerian-Eulerian two-phase flow theory, with the aim at gaining computational speed in the prediction, but preserving the accuracy of the complete two-fluid model. The basic equations of the model include the mass and momentum conservation equations for the sediment-water mixture, and the mass conservation equation for sediment. However, a newly-obtained expression for the slip velocity between phases allows for the computation of the sediment motion, without the need of solving the momentum equation for sediment. The turbulent motion is represented for both the fluid and the particulate phases. A modified k-ε model is used to describe the fluid turbulence while an algebraic model is adopted for turbulent motion of particles. A two-dimensional finite difference method based on the SMAC scheme was used to numerically solve the mathematical model. The model is validated through simulations of fluid and suspended sediment motion in steady open-channel flows, both in equilibrium and non-equilibrium states, as well as in oscillatory flows. The computed sediment concentrations, horizontal velocity and turbulent kinetic energy of the mixture are all shown to be in good agreement with available experimental data, and importantly, this is done at a fraction of the computational efforts required by the complete two-fluid model.
Predicting the Probability of Lightning Occurrence with Generalized Additive Models
NASA Astrophysics Data System (ADS)
Fabsic, Peter; Mayr, Georg; Simon, Thorsten; Zeileis, Achim
2017-04-01
This study investigates the predictability of lightning in complex terrain. The main objective is to estimate the probability of lightning occurrence in the Alpine region during summertime afternoons (12-18 UTC) at a spatial resolution of 64 × 64 km2. Lightning observations are obtained from the ALDIS lightning detection network. The probability of lightning occurrence is estimated using generalized additive models (GAM). GAMs provide a flexible modelling framework to estimate the relationship between covariates and the observations. The covariates, besides spatial and temporal effects, include numerous meteorological fields from the ECMWF ensemble system. The optimal model is chosen based on a forward selection procedure with out-of-sample mean squared error as a performance criterion. Our investigation shows that convective precipitation and mid-layer stability are the most influential meteorological predictors. Both exhibit intuitive, non-linear trends: higher values of convective precipitation indicate higher probability of lightning, and large values of the mid-layer stability measure imply low lightning potential. The performance of the model was evaluated against a climatology model containing both spatial and temporal effects. Taking the climatology model as a reference forecast, our model attains a Brier Skill Score of approximately 46%. The model's performance can be further enhanced by incorporating the information about lightning activity from the previous time step, which yields a Brier Skill Score of 48%. These scores show that the method is able to extract valuable information from the ensemble to produce reliable spatial forecasts of the lightning potential in the Alps.
Planetary-Scale Flow on a Two-Layer Beta-Plane Channel Model with Topography
NASA Astrophysics Data System (ADS)
Shin, Won-Tae Kwon
A two-layer low-order spectral model on a beta-plane channel with topographic, thermal and frictional forcing is designed as a compromise to resolve the relative importance and interaction of several relevant processes. The model is truncated at three zonal modes and three meridional modes. Topography forces the largest scale; the intermediate scale may be destabilized by zonal thermal forcing; the smallest scale permits barotropic scale-interaction and a rudimentary energy cascade. Multiple steady states of the simple one zonal mode and one wave mode (the 1 x 1 model) have been found. There are seven possible steady states: a zonally symmetric state, a topographically resonant state, and five baroclinic and equivalent barotropic wave states. New results emphasize relevance of the barotropic and baroclinic zonal flows; most significantly, multiple steady states exist only for a restricted range of zonal wind and vertical shear in the vicinity of the topographically resonant values. The time-dependent behavior for the 3 x 3 model is classified into six different types: zonally symmetric, steady wave state, steady propagating (Rossby wave), periodic, quasi-periodic and chaotic solutions. The regimes of the solutions for three parameters (thermal forcing, topography and friction) are investigated. The amplitude of zonal flow in wave solutions is weaker with moderate topography and is stronger with larger friction, smaller thermal forcing and higher topography or no topography. The characteristics of solutions are related to the strength of the resultant zonal flow with small or moderate topography. When the intermediate scale wave with largest meridional scale (MODE 12) is baroclinically unstable, this wave maintains the topographic wave ridge upstream of the mountain through the wave-wave interaction and also maintains other waves through form-drag; then, other modes are maintained by various mechanisms. When the topographic wave (MODE 11) becomes unstable with
Wall, Clifton; Boersma, Bendiks Jan; Moin, Parviz
2000-10-01
The assumed beta distribution model for the subgrid-scale probability density function (PDF) of the mixture fraction in large eddy simulation of nonpremixed, turbulent combustion is tested, a priori, for a reacting jet having significant heat release (density ratio of 5). The assumed beta distribution is tested as a model for both the subgrid-scale PDF and the subgrid-scale Favre PDF of the mixture fraction. The beta model is successful in approximating both types of PDF but is slightly more accurate in approximating the normal (non-Favre) PDF. To estimate the subgrid-scale variance of mixture fraction, which is required by the beta model, both a scale similarity model and a dynamic model are used. Predictions using the dynamic model are found to be more accurate. The beta model is used to predict the filtered value of a function chosen to resemble the reaction rate. When no model is used, errors in the predicted value are of the same order as the actual value. The beta model is found to reduce this error by about a factor of two, providing a significant improvement. (c) 2000 American Institute of Physics.
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.
Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities
Mikaelian, K O
2008-06-10
We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh-Taylor and Richtmyer-Meshkov instabilities. We examine single interfaces of the type A/B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A/B/A configurations like air/SF{sub 6}/air gas-curtain experiments. We first consider conventional shock tubes that have a 'fixed' boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a 'free' boundary--a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction towards the interface(s). Complex acceleration histories are achieved, relevant for Inertial Confinement Fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities, and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other, and remain to be verified experimentally.
Consensus-based training and assessment model for general surgery.
Szasz, P; Louridas, M; de Montbrun, S; Harris, K A; Grantcharov, T P
2016-05-01
Surgical education is becoming competency-based with the implementation of in-training milestones. Training guidelines should reflect these changes and determine the specific procedures for such milestone assessments. This study aimed to develop a consensus view regarding operative procedures and tasks considered appropriate for junior and senior trainees, and the procedures that can be used as technical milestone assessments for trainee progression in general surgery. A Delphi process was followed where questionnaires were distributed to all 17 Canadian general surgery programme directors. Items were ranked on a 5-point Likert scale, with consensus defined as Cronbach's α of at least 0·70. Items rated 4 or above on the 5-point Likert scale by 80 per cent of the programme directors were included in the models. Two Delphi rounds were completed, with 14 programme directors taking part in round one and 11 in round two. The overall consensus was high (Cronbach's α = 0·98). The training model included 101 unique procedures and tasks, 24 specific to junior trainees, 68 specific to senior trainees, and nine appropriate to all. The assessment model included four procedures. A system of operative procedures and tasks for junior- and senior-level trainees has been developed along with an assessment model for trainee progression. These can be used as milestones in competency-based assessments. © 2016 BJS Society Ltd Published by John Wiley & Sons Ltd.
Generalized linear mixed model for segregation distortion analysis.
Zhan, Haimao; Xu, Shizhong
2011-11-11
Segregation distortion is a phenomenon that the observed genotypic frequencies of a locus fall outside the expected Mendelian segregation ratio. The main cause of segregation distortion is viability selection on linked marker loci. These viability selection loci can be mapped using genome-wide marker information. We developed a generalized linear mixed model (GLMM) under the liability model to jointly map all viability selection loci of the genome. Using a hierarchical generalized linear mixed model, we can handle the number of loci several times larger than the sample size. We used a dataset from an F(2) mouse family derived from the cross of two inbred lines to test the model and detected a major segregation distortion locus contributing 75% of the variance of the underlying liability. Replicated simulation experiments confirm that the power of viability locus detection is high and the false positive rate is low. Not only can the method be used to detect segregation distortion loci, but also used for mapping quantitative trait loci of disease traits using case only data in humans and selected populations in plants and animals.
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
Non-canonical generalizations of slow-roll inflation models
NASA Astrophysics Data System (ADS)
Tzirakis, Konstantinos; Kinney, William H.
2009-01-01
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.
Attitude determination error analysis - General model and specific application
NASA Technical Reports Server (NTRS)
Markley, F. Landis; Seidewitz, ED; Deutschmann, Julie
1990-01-01
This paper presents a comprehensive approach to filter and dynamics modeling for attitude determination error analysis. The discussion includes models for both batch least-squares and sequential estimators, a specific dynamic model for attitude determination error analysis of a three-axis stabilized spacecraft equipped with strapdown gyros, and the incorporation of general attitude sensor observations. An analyst using this approach to perform an error analysis chooses a subset of the spacecraft parameters to be 'solve-for' parameters, which are to be estimated, and another subset to be 'consider' parameters, which are assumed to have errors but not to be estimated. The result of the error analysis is an indication of overall uncertainties in the 'solve-for' parameters, as well as the contributions of the various error sources to these uncertainties, including those of errors in the a priori 'solve-for' estimates, of measurement noise, of dynamic noise (also known as process noise or plant noise), and of 'consider' parameter uncertainties. The analysis of attitude, star tracker alignment, and gyro bias uncertainties for the Gamma Ray Observatory spacecraft provide a specific example of the use of a general-purpose software package incorporating these models.
Bayesian generalized linear mixed modeling of Tuberculosis using informative priors.
Ojo, Oluwatobi Blessing; Lougue, Siaka; Woldegerima, Woldegebriel Assefa
2017-01-01
TB is rated as one of the world's deadliest diseases and South Africa ranks 9th out of the 22 countries with hardest hit of TB. Although many pieces of research have been carried out on this subject, this paper steps further by inculcating past knowledge into the model, using Bayesian approach with informative prior. Bayesian statistics approach is getting popular in data analyses. But, most applications of Bayesian inference technique are limited to situations of non-informative prior, where there is no solid external information about the distribution of the parameter of interest. The main aim of this study is to profile people living with TB in South Africa. In this paper, identical regression models are fitted for classical and Bayesian approach both with non-informative and informative prior, using South Africa General Household Survey (GHS) data for the year 2014. For the Bayesian model with informative prior, South Africa General Household Survey dataset for the year 2011 to 2013 are used to set up priors for the model 2014.
Bayesian generalized linear mixed modeling of Tuberculosis using informative priors
Woldegerima, Woldegebriel Assefa
2017-01-01
TB is rated as one of the world’s deadliest diseases and South Africa ranks 9th out of the 22 countries with hardest hit of TB. Although many pieces of research have been carried out on this subject, this paper steps further by inculcating past knowledge into the model, using Bayesian approach with informative prior. Bayesian statistics approach is getting popular in data analyses. But, most applications of Bayesian inference technique are limited to situations of non-informative prior, where there is no solid external information about the distribution of the parameter of interest. The main aim of this study is to profile people living with TB in South Africa. In this paper, identical regression models are fitted for classical and Bayesian approach both with non-informative and informative prior, using South Africa General Household Survey (GHS) data for the year 2014. For the Bayesian model with informative prior, South Africa General Household Survey dataset for the year 2011 to 2013 are used to set up priors for the model 2014. PMID:28257437
Generalized linear mixed model for segregation distortion analysis
2011-01-01
Background Segregation distortion is a phenomenon that the observed genotypic frequencies of a locus fall outside the expected Mendelian segregation ratio. The main cause of segregation distortion is viability selection on linked marker loci. These viability selection loci can be mapped using genome-wide marker information. Results We developed a generalized linear mixed model (GLMM) under the liability model to jointly map all viability selection loci of the genome. Using a hierarchical generalized linear mixed model, we can handle the number of loci several times larger than the sample size. We used a dataset from an F2 mouse family derived from the cross of two inbred lines to test the model and detected a major segregation distortion locus contributing 75% of the variance of the underlying liability. Replicated simulation experiments confirm that the power of viability locus detection is high and the false positive rate is low. Conclusions Not only can the method be used to detect segregation distortion loci, but also used for mapping quantitative trait loci of disease traits using case only data in humans and selected populations in plants and animals. PMID:22078575
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
Symmetry in the Generalized Rotor Model for Extremely Floppy Molecules
NASA Astrophysics Data System (ADS)
Schmiedt, Hanno; Jensen, Per; Schlemmer, Stephan
2016-06-01
Protonated methane CH_5^+ is unique: It is an extremely fluxional molecule. All attempts to assign quantum numbers to the high-resolution transitions obtained over the last 20 years have failed because molecular rotation and vibration cannot be separated in the conventional way. The first step towards a theoretical description is to include internal rotational degrees of freedom into the overall ones, which can be used to formulate a fundamentally new zero order approximation for the (now) generalized rotational states and energies. Predictions from this simple five-dimensional rotor model compare very favorably with the combination differences of protonated methane found in recent low temperature experiments. This talk will focus on symmetry aspects and implications of permutation symmetry for the generalized rotational states. Furthermore, refinements of the theory will be discussed, ranging from the generalization to even higher-dimensional rotors to explicit symmetry breaking and corresponding energy splittings. The latter includes the link to well-known theories of internal rotation dynamics and will show the general validity of the presented theory. Schmiedt, H., et al.; J. Chem. Phys. 143 (15), 154302 (2015) Wodraszka, R. et al.; J. Phys. Chem. Lett. 6, 4229-4232 (2015) Asvany, O. et al.; Science, 347, (6228), 1346-1349 (2015)
A new approach for modeling generalization gradients: a case for hierarchical models
Vanbrabant, Koen; Boddez, Yannick; Verduyn, Philippe; Mestdagh, Merijn; Hermans, Dirk; Raes, Filip
2015-01-01
A case is made for the use of hierarchical models in the analysis of generalization gradients. Hierarchical models overcome several restrictions that are imposed by repeated measures analysis-of-variance (rANOVA), the default statistical method in current generalization research. More specifically, hierarchical models allow to include continuous independent variables and overcomes problematic assumptions such as sphericity. We focus on how generalization research can benefit from this added flexibility. In a simulation study we demonstrate the dominance of hierarchical models over rANOVA. In addition, we show the lack of efficiency of the Mauchly's sphericity test in sample sizes typical for generalization research, and confirm how violations of sphericity increase the probability of type I errors. A worked example of a hierarchical model is provided, with a specific emphasis on the interpretation of parameters relevant for generalization research. PMID:26074834
A new approach for modeling generalization gradients: a case for hierarchical models.
Vanbrabant, Koen; Boddez, Yannick; Verduyn, Philippe; Mestdagh, Merijn; Hermans, Dirk; Raes, Filip
2015-01-01
A case is made for the use of hierarchical models in the analysis of generalization gradients. Hierarchical models overcome several restrictions that are imposed by repeated measures analysis-of-variance (rANOVA), the default statistical method in current generalization research. More specifically, hierarchical models allow to include continuous independent variables and overcomes problematic assumptions such as sphericity. We focus on how generalization research can benefit from this added flexibility. In a simulation study we demonstrate the dominance of hierarchical models over rANOVA. In addition, we show the lack of efficiency of the Mauchly's sphericity test in sample sizes typical for generalization research, and confirm how violations of sphericity increase the probability of type I errors. A worked example of a hierarchical model is provided, with a specific emphasis on the interpretation of parameters relevant for generalization research.
Cache Allocation in CDN: An Evolutionary Game Generalized Particle Model
NASA Astrophysics Data System (ADS)
Feng, Xiang; Lau, Francis C. M.; Gao, Daqi
Content distribution networks (CDNs) increasingly have been used to reduce the response times experienced by Internet users through placing surrogates close to the clients. This paper presents an object replacement approach based on an evolutionary game generalized particle model (G-GPM). We first propose a problem model for CDNs. The CDN model is then fit into a gravitational field. The origin servers and surrogates are regarded as two kinds of particles which are located in two force-fields. The cache allocation problem is thus transformed into the kinematics and dynamics of the particles in the annular and the round force-fields. The G-GPM approach is unique in four aspects: 1) direct viewing of individual and overall optimization; 2) parallel computing (lower time complexity); 3) multi-objective solution; and 4) being able to deal with some social interactions behaviors.
On the limitations of General Circulation Climate Models
NASA Technical Reports Server (NTRS)
Stone, Peter H.; Risbey, James S.
1990-01-01
General Circulation Models (GCMs) by definition calculate large-scale dynamical and thermodynamical processes and their associated feedbacks from first principles. This aspect of GCMs is widely believed to give them an advantage in simulating global scale climate changes as compared to simpler models which do not calculate the large-scale processes from first principles. However, it is pointed out that the meridional transports of heat simulated GCMs used in climate change experiments differ from observational analyses and from other GCMs by as much as a factor of two. It is also demonstrated that GCM simulations of the large scale transports of heat are sensitive to the (uncertain) subgrid scale parameterizations. This leads to the question whether current GCMs are in fact superior to simpler models for simulating temperature changes associated with global scale climate change.
Dimensional Reduction for the General Markov Model on Phylogenetic Trees.
Sumner, Jeremy G
2017-03-01
We present a method of dimensional reduction for the general Markov model of sequence evolution on a phylogenetic tree. We show that taking certain linear combinations of the associated random variables (site pattern counts) reduces the dimensionality of the model from exponential in the number of extant taxa, to quadratic in the number of taxa, while retaining the ability to statistically identify phylogenetic divergence events. A key feature is the identification of an invariant subspace which depends only bilinearly on the model parameters, in contrast to the usual multi-linear dependence in the full space. We discuss potential applications including the computation of split (edge) weights on phylogenetic trees from observed sequence data.
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.
Generalized self-dual Maxwell-Chern-Simons-Higgs model
NASA Astrophysics Data System (ADS)
Bazeia, D.; Casana, R.; da Hora, E.; Menezes, R.
2012-06-01
We present a consistent Bogomol’nyi-Prasad-Sommerfield (BPS) framework for a generalized Maxwell-Chern-Simons-Higgs model. The overall model, including its self-dual potential, depends on three different functions, h(|ϕ|,N), w(|ϕ|), and G(|ϕ|), which are functions of the scalar fields only. The BPS energy is proportional to the magnetic flux when w(|ϕ|) and G(|ϕ|) are related to each other by a differential constraint. We present an explicit nonstandard model and its topologically nontrivial static configurations, which are described by the usual radially symmetric profile. Finally, we note that the nonstandard results behave in a similar way as their standard counterparts, as expected, reinforcing the consistence of the overall construction.
Learning Setting-Generalized Activity Models for Smart Spaces
Cook, Diane J.
2011-01-01
The data mining and pervasive computing technologies found in smart homes offer unprecedented opportunities for providing context-aware services, including health monitoring and assistance to individuals experiencing difficulties living independently at home. In order to provide these services, smart environment algorithms need to recognize and track activities that people normally perform as part of their daily routines. However, activity recognition has typically involved gathering and labeling large amounts of data in each setting to learn a model for activities in that setting. We hypothesize that generalized models can be learned for common activities that span multiple environment settings and resident types. We describe our approach to learning these models and demonstrate the approach using eleven CASAS datasets collected in seven environments. PMID:21461133
General Study of Perturbations in Bouncing and Cyclic Models
NASA Astrophysics Data System (ADS)
Mayes, Riley; Biswas, Tirthabir; Lattyak, Colleen
2015-04-01
Perturbations are important in both understanding and evaluating the importance of bounces and turnarounds in models that predict a cyclic evolution of our Universe. Moreover, tracking these perturbations through the entirety of the cycle is important as it provides an outlet for a qualitative comparison with Cosmic Microwave Background (CMB) observations. However, tracking these perturbations through each cycle proves difficult as the physics to describe bounces and turnarounds is not well established. Therefore, we first studied general anaytical and numerical techniques in order to understand the evolution of fluctuations in simple cosmological models where physics is better understood. In our research, we first developed analytical techniques from background solutions to establish a solid foundation for describing super-Hubble fluctuations in our early Universe. These analytical solutions were developed for both bounces and turnarounds allowing us to numerically verify and then further investigate the consequences of these solutions in models such as bounce inflation and cyclic inflation.
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
Violation of positivity bounds in models of generalized parton distributions
NASA Astrophysics Data System (ADS)
Tiburzi, Brian C.; Verma, Gaurav
2017-08-01
As with parton distributions, flexible phenomenological parametrizations of generalized parton distributions (GPDs) are essential for their extraction from data. The large number of constraints imposed on GPDs make simple Lorentz covariant models viable; but, such models are often incomplete in that they employ the impulse approximation. Using the GPD of the pion as a test case, we show that the impulse approximation can lead to violation of the positivity bound required of GPDs. We focus on a particular model of the pion bound-state vertex that was recently proposed and demonstrate that satisfying the bound is not guaranteed by Lorentz covariance. Violation of the positivity bound is tied to a problematic mismatch between the behavior of the quark distribution at the end point and the crossover value of the GPD.
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.
Generalized linear mixed models for meta-analysis.
Platt, R W; Leroux, B G; Breslow, N
1999-03-30
We examine two strategies for meta-analysis of a series of 2 x 2 tables with the odds ratio modelled as a linear combination of study level covariates and random effects representing between-study variation. Penalized quasi-likelihood (PQL), an approximate inference technique for generalized linear mixed models, and a linear model fitted by weighted least squares to the observed log-odds ratios are used to estimate regression coefficients and dispersion parameters. Simulation results demonstrate that both methods perform adequate approximate inference under many conditions, but that neither method works well in the presence of highly sparse data. Under certain conditions with small cell frequencies the PQL method provides better inference.
A generalized analytical compliance model for cartwheel flexure hinges
NASA Astrophysics Data System (ADS)
Wu, Jianwei; Cai, Shuai; Cui, Jiwen; Tan, Jiubin
2015-10-01
Normal cartwheel flexure hinge (NCFH) typically consists of two flexible springs crossing at their mid points. These have been used in compliant mechanism applications owing to the large motion range of such hinges. In this paper, a novel generalized cartwheel flexure hinge (GCFH) is proposed by modifying spring number and varying the angle between two springs on the basis of the NCFH. A 6 degrees of freedom (6-DOF) compliance model of the GCFH was derived. Validity of this model was demonstrated using finite element analysis simulation and experimental results on a GCFH with 3 pairs of springs and 70° angle. According to the model, influence of distribution and shape parameters of GCFH on performance was analyzed. Characteristics such as compliance, off-axis/axis compliance ratio, motion precision, and capacity of rotation were determined. Results show that the GCFH can achieve improved performance compared to NCFH with optimized GCFH parameters.
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
A general two-cycle network model of molecular motors
NASA Astrophysics Data System (ADS)
Zhang, Yunxin
2009-09-01
Molecular motors are single macromolecules that generate forces at the piconewton range and nanometer scale. They convert chemical energy into mechanical work by moving along filamentous structures. In this paper, we study the velocity of two-head molecular motors in the framework of a mechanochemical network theory. The network model, a generalization of the recently work of Liepelt and Lipowsky [Steffen Liepelt, Reinhard Lipowsky, Kinesins network of chemomechanical motor cycles, Physical Review Letters 98 (25) (2007) 258102], is based on the discrete mechanochemical states of a molecular motor with multiple cycles. By generalizing the mathematical method developed by Fisher and Kolomeisky for a single cycle motor [Michael E. Fisher, Anatoly B. Kolomeisky, Simple mechanochemistry describes the dynamics of kinesin molecules, Proceedings of the National Academy of Sciences 98 (14) (2001) 7748-7753], we are able to obtain an explicit formula for the velocity of a molecular motor.
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