On a numerical method for solving integro-differential equations with variable coefficients with applications in finance

NASA Astrophysics Data System (ADS)

Kudryavtsev, O.; Rodochenko, V.

2018-03-01

We propose a new general numerical method aimed to solve integro-differential equations with variable coefficients. The problem under consideration arises in finance where in the context of pricing barrier options in a wide class of stochastic volatility models with jumps. To handle the effect of the correlation between the price and the variance, we use a suitable substitution for processes. Then we construct a Markov-chain approximation for the variation process on small time intervals and apply a maturity randomization technique. The result is a system of boundary problems for integro-differential equations with constant coefficients on the line in each vertex of the chain. We solve the arising problems using a numerical Wiener-Hopf factorization method. The approximate formulae for the factors are efficiently implemented by means of the Fast Fourier Transform. Finally, we use a recurrent procedure that moves backwards in time on the variance tree. We demonstrate the convergence of the method using Monte-Carlo simulations and compare our results with the results obtained by the Wiener-Hopf method with closed-form expressions of the factors.

Multi-level adaptive finite element methods. 1: Variation problems

NASA Technical Reports Server (NTRS)

Brandt, A.

1979-01-01

A general numerical strategy for solving partial differential equations and other functional problems by cycling between coarser and finer levels of discretization is described. Optimal discretization schemes are provided together with very fast general solvers. It is described in terms of finite element discretizations of general nonlinear minimization problems. The basic processes (relaxation sweeps, fine-grid-to-coarse-grid transfers of residuals, coarse-to-fine interpolations of corrections) are directly and naturally determined by the objective functional and the sequence of approximation spaces. The natural processes, however, are not always optimal. Concrete examples are given and some new techniques are reviewed. Including the local truncation extrapolation and a multilevel procedure for inexpensively solving chains of many boundary value problems, such as those arising in the solution of time-dependent problems.

Radial Artery Coursing Behind the Biceps Brachii Tendon: Significance for the Transradial Catheterization and a Clinically Oriented Classification of the Radial Artery Variations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jelev, L., E-mail: ljelev@abv.bg; Surchev, L.

2008-09-15

In routine clinical practice the variations of the radial artery are the main reason for technical failure during transradial catheterization. If these variations are well documented, however, they do not represent a problem in the transradial approach. Therefore, we report here a rare case of the radial artery which is very strange but potentially valuable for the clinical practice: it arises at a right angle from the brachial artery and passes behind the biceps brachii tendon. Based on our findings and on an extensive literature review, we propose for the first time a clinically oriented classification of the variations ofmore » the radial artery. This classification is related to the catheterization success at the usual access site of the radial artery at the wrist.« less

A variational Bayes spatiotemporal model for electromagnetic brain mapping.

PubMed

Nathoo, F S; Babul, A; Moiseev, A; Virji-Babul, N; Beg, M F

2014-03-01

In this article, we present a new variational Bayes approach for solving the neuroelectromagnetic inverse problem arising in studies involving electroencephalography (EEG) and magnetoencephalography (MEG). This high-dimensional spatiotemporal estimation problem involves the recovery of time-varying neural activity at a large number of locations within the brain, from electromagnetic signals recorded at a relatively small number of external locations on or near the scalp. Framing this problem within the context of spatial variable selection for an underdetermined functional linear model, we propose a spatial mixture formulation where the profile of electrical activity within the brain is represented through location-specific spike-and-slab priors based on a spatial logistic specification. The prior specification accommodates spatial clustering in brain activation, while also allowing for the inclusion of auxiliary information derived from alternative imaging modalities, such as functional magnetic resonance imaging (fMRI). We develop a variational Bayes approach for computing estimates of neural source activity, and incorporate a nonparametric bootstrap for interval estimation. The proposed methodology is compared with several alternative approaches through simulation studies, and is applied to the analysis of a multimodal neuroimaging study examining the neural response to face perception using EEG, MEG, and fMRI. © 2013, The International Biometric Society.

[Ethnic origin of patients remains important].

PubMed

Stronks, Karien

2013-01-01

The ethnic diversity in medical practices is increasing rapidly. In the Netherlands, ethnic groups are predominantly defined on the basis of their geographical origin, e.g. inhabitants of Turkish, Moroccan or Surinamese origin. The prevalence of health problems and the utilisation of health care differ between ethnic groups. This ethnic variation arises, firstly, from characteristics that are inherent to these groups such as genetic profile and culture, and, secondly, from characteristics that reflect their position in Dutch society such as socio-economic position and discrimination on the other. If we could fully understand which of these specific characteristics leads to a specific pattern of health problems or health care use, the classification of patient into ethnic groups would then become redundant. As long as we do not completely understand this variation, however, ethnic origin is a good entry-point for targeting health care to groups of patients.

The Ordered Clustered Travelling Salesman Problem: A Hybrid Genetic Algorithm

PubMed Central

Ahmed, Zakir Hussain

2014-01-01

The ordered clustered travelling salesman problem is a variation of the usual travelling salesman problem in which a set of vertices (except the starting vertex) of the network is divided into some prespecified clusters. The objective is to find the least cost Hamiltonian tour in which vertices of any cluster are visited contiguously and the clusters are visited in the prespecified order. The problem is NP-hard, and it arises in practical transportation and sequencing problems. This paper develops a hybrid genetic algorithm using sequential constructive crossover, 2-opt search, and a local search for obtaining heuristic solution to the problem. The efficiency of the algorithm has been examined against two existing algorithms for some asymmetric and symmetric TSPLIB instances of various sizes. The computational results show that the proposed algorithm is very effective in terms of solution quality and computational time. Finally, we present solution to some more symmetric TSPLIB instances. PMID:24701148

Microbiological testing of Skylab foods.

NASA Technical Reports Server (NTRS)

Heidelbaugh, N. D.; Mcqueen, J. L.; Rowley, D. B.; Powers , E. M.; Bourland, C. T.

1973-01-01

Review of some of the unique food microbiology problems and problem-generating circumstances the Skylab manned space flight program involves. The situations these problems arise from include: extended storage times, variations in storage temperatures, no opportunity to resupply or change foods after launch of the Skylab Workshop, first use of frozen foods in space, first use of a food-warming device in weightlessness, relatively small size of production lots requiring statistically valid sampling plans, and use of food as an accurately controlled part in a set of sophisticated life science experiments. Consideration of all of these situations produced the need for definite microbiological tests and test limits. These tests are described along with the rationale for their selection. Reported test results show good compliance with the test limits.

Discrete and continuum links to a nonlinear coupled transport problem of interacting populations

NASA Astrophysics Data System (ADS)

Duong, M. H.; Muntean, A.; Richardson, O. M.

2017-07-01

We are interested in exploring interacting particle systems that can be seen as microscopic models for a particular structure of coupled transport flux arising when different populations are jointly evolving. The scenarios we have in mind are inspired by the dynamics of pedestrian flows in open spaces and are intimately connected to cross-diffusion and thermo-diffusion problems holding a variational structure. The tools we use include a suitable structure of the relative entropy controlling TV-norms, the construction of Lyapunov functionals and particular closed-form solutions to nonlinear transport equations, a hydrodynamics limiting procedure due to Philipowski, as well as the construction of numerical approximates to both the continuum limit problem in 2D and to the original interacting particle systems.

Density of convex intersections and applications

PubMed Central

Rautenberg, C. N.; Rösel, S.

2017-01-01

In this paper, we address density properties of intersections of convex sets in several function spaces. Using the concept of Γ-convergence, it is shown in a general framework, how these density issues naturally arise from the regularization, discretization or dualization of constrained optimization problems and from perturbed variational inequalities. A variety of density results (and counterexamples) for pointwise constraints in Sobolev spaces are presented and the corresponding regularity requirements on the upper bound are identified. The results are further discussed in the context of finite-element discretizations of sets associated with convex constraints. Finally, two applications are provided, which include elasto-plasticity and image restoration problems. PMID:28989301

High MHC diversity maintained by balancing selection in an otherwise genetically monomorphic mammal

PubMed Central

Aguilar, Andres; Roemer, Gary; Debenham, Sally; Binns, Matthew; Garcelon, David; Wayne, Robert K.

2004-01-01

The San Nicolas Island fox (Urocyon littoralis dickeyi) is genetically the most monomorphic sexually reproducing animal population yet reported and has no variation in hypervariable genetic markers. Such low levels of variation imply lower resistance to pathogens, reduced fitness, and problems in distinguishing kin from non-kin. In vertebrates, the MHC contains genes that influence disease resistance and kin recognition and may be under intense balancing selection in some populations. Hence, genetic variation at the MHC might persist despite the extreme monomorphism shown by neutral markers. We examine variation of five loci within the MHC of San Nicolas Island foxes and find remarkably high levels of variation. Further, we show by simulation that genetic monomorphism at neutral loci and high MHC variation could arise only through an extreme population bottleneck of <10 individuals, ≈10–20 generations ago, accompanied by unprecedented selection coefficients of >0.5 on MHC loci. These results support the importance of balancing selection as a mechanism to maintain variation in natural populations and expose the difficulty of using neutral markers as surrogates for variation in fitness-related loci. PMID:14990802

A parabolic variational inequality arising from the valuation of strike reset options

NASA Astrophysics Data System (ADS)

Yang, Zhou; Yi, Fahuai; Dai, Min

A strike reset option is an option that allows its holder to reset the strike price to the prevailing underlying asset price at a moment chosen by the holder. The pricing model of the option can be formulated as a one-dimensional parabolic variational inequality, or equivalently, a free boundary problem, where the free boundary just corresponds to the optimal reset strategy adopted by the holder of the option. This paper is concerned with the theoretical analysis of the model. The existence and uniqueness of the solution are established. Furthermore, we study properties of the free boundary. The monotonicity and C smoothness of the free boundary are proven in some situations.

Mitigation of Power Quality Problems in Grid-Interactive Distributed Generation System

NASA Astrophysics Data System (ADS)

Bhende, C. N.; Kalam, A.; Malla, S. G.

2016-04-01

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

UV Emissions and the Electron Density in the Auroral and Low to Mid-Latitude Daytime Ionospheres.

DTIC Science & Technology

1982-11-01

Anderson, 1982). Their concern has been with the analysis of satellite observed limb profiles for features such as 01 1356 A and N2 LBH bands. We have...two in going from solar minimum to maximum conditions. An ad- vantage of there being little relative variation among intensities is that altitude...desirable for our problem of interest since it concerns remote sensing of the ionosphere. The questions ariser as to how long the wavelength of I

Convergence analysis of a monotonic penalty method for American option pricing

NASA Astrophysics Data System (ADS)

Zhang, Kai; Yang, Xiaoqi; Teo, Kok Lay

2008-12-01

This paper is devoted to study the convergence analysis of a monotonic penalty method for pricing American options. A monotonic penalty method is first proposed to solve the complementarity problem arising from the valuation of American options, which produces a nonlinear degenerated parabolic PDE with Black-Scholes operator. Based on the variational theory, the solvability and convergence properties of this penalty approach are established in a proper infinite dimensional space. Moreover, the convergence rate of the combination of two power penalty functions is obtained.

Time domain convergence properties of Lyapunov stable penalty methods

NASA Technical Reports Server (NTRS)

Kurdila, A. J.; Sunkel, John

1991-01-01

Linear hyperbolic partial differential equations are analyzed using standard techniques to show that a sequence of solutions generated by the Liapunov stable penalty equations approaches the solution of the differential-algebraic equations governing the dynamics of multibody problems arising in linear vibrations. The analysis does not require that the system be conservative and does not impose any specific integration scheme. Variational statements are derived which bound the error in approximation by the norm of the constraint violation obtained in the approximate solutions.

Atmospheric Flux Computations in Complex Terrain

NASA Technical Reports Server (NTRS)

Smith, Paul L.; Kopp, Fred J.; Orville, Harold D.

2000-01-01

The greatest challenges in applying atmospheric water budget expressions are in determining the divergence and evapotranspiration terms. The evapotranspiration problem is ubiquitous, and critical issues of spatial and temporal resolution commonly arise in establishing the divergence term. In complex terrain, further difficulties crop up in using typical data on atmospheric profiles of water vapor and wind to estimate the divergence term. Those difficulties are the subject of this paper; considerations related to topographic variations both along and normal to the flow direction are treated.

Personality and problem-solving performance explain competitive ability in the wild.

PubMed

Cole, Ella F; Quinn, John L

2012-03-22

Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait 'exploration behaviour' and a simple cognitive trait, 'innovative problem-solving performance'. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in 'individual quality', our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies.

Approximating the Helium Wavefunction in Positronium-Helium Scattering

NASA Technical Reports Server (NTRS)

DiRienzi, Joseph; Drachman, Richard J.

2003-01-01

In the Kohn variational treatment of the positronium- hydrogen scattering problem the scattering wave function is approximated by an expansion in some appropriate basis set, but the target and projectile wave functions are known exactly. In the positronium-helium case, however, a difficulty immediately arises in that the wave function of the helium target atom is not known exactly, and there are several ways to deal with the associated eigenvalue in formulating the variational scattering equations to be solved. In this work we will use the Kohn variational principle in the static exchange approximation to d e t e e the zero-energy scattering length for the Ps-He system, using a suite of approximate target functions. The results we obtain will be compared with each other and with corresponding values found by other approximation techniques.

Existence and stability, and discrete BB and rank conditions, for general mixed-hybrid finite elements in elasticity

NASA Technical Reports Server (NTRS)

Xue, W.-M.; Atluri, S. N.

1985-01-01

In this paper, all possible forms of mixed-hybrid finite element methods that are based on multi-field variational principles are examined as to the conditions for existence, stability, and uniqueness of their solutions. The reasons as to why certain 'simplified hybrid-mixed methods' in general, and the so-called 'simplified hybrid-displacement method' in particular (based on the so-called simplified variational principles), become unstable, are discussed. A comprehensive discussion of the 'discrete' BB-conditions, and the rank conditions, of the matrices arising in mixed-hybrid methods, is given. Some recent studies aimed at the assurance of such rank conditions, and the related problem of the avoidance of spurious kinematic modes, are presented.

Boundary Concentration for Eigenvalue Problems Related to the Onset of Superconductivity

NASA Astrophysics Data System (ADS)

del Pino, Manuel; Felmer, Patricio L.; Sternberg, Peter

We examine the asymptotic behavior of the eigenvalue μ(h) and corresponding eigenfunction associated with the variational problem in the regime h>>1. Here A is any vector field with curl equal to 1. The problem arises within the Ginzburg-Landau model for superconductivity with the function μ(h) yielding the relationship between the critical temperature vs. applied magnetic field strength in the transition from normal to superconducting state in a thin mesoscopic sample with cross-section Ω 2. We first carry out a rigorous analysis of the associated problem on a half-plane and then rigorously justify some of the formal arguments of [BS], obtaining an expansion for μ while also proving that the first eigenfunction decays to zero somewhere along the sample boundary when Ω is not a disc. For interior decay, we demonstrate that the rate is exponential.

On the Formulation of Weakly Singular Displacement/Traction Integral Equations; and Their Solution by the MLPG Method

NASA Technical Reports Server (NTRS)

Atluri, Satya N.; Shen, Shengping

2002-01-01

In this paper, a very simple method is used to derive the weakly singular traction boundary integral equation based on the integral relationships for displacement gradients. The concept of the MLPG method is employed to solve the integral equations, especially those arising in solid mechanics. A moving Least Squares (MLS) interpolation is selected to approximate the trial functions in this paper. Five boundary integral Solution methods are introduced: direct solution method; displacement boundary-value problem; traction boundary-value problem; mixed boundary-value problem; and boundary variational principle. Based on the local weak form of the BIE, four different nodal-based local test functions are selected, leading to four different MLPG methods for each BIE solution method. These methods combine the advantages of the MLPG method and the boundary element method.

Triangles with Integer Dimensions

ERIC Educational Resources Information Center

Gilbertson, Nicholas J.; Rogers, Kimberly Cervello

2016-01-01

Interesting and engaging mathematics problems can come from anywhere. Sometimes great problems arise from interesting contexts. At other times, interesting problems arise from asking "what if" questions while appreciating the structure and beauty of mathematics. The intriguing problem described in this article resulted from the second…

Personality and problem-solving performance explain competitive ability in the wild

PubMed Central

Cole, Ella F.; Quinn, John L.

2012-01-01

Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait ‘exploration behaviour’ and a simple cognitive trait, ‘innovative problem-solving performance’. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in ‘individual quality’, our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies. PMID:21937498

Variational methods for direct/inverse problems of atmospheric dynamics and chemistry

NASA Astrophysics Data System (ADS)

Penenko, Vladimir; Penenko, Alexey; Tsvetova, Elena

2013-04-01

We present a variational approach for solving direct and inverse problems of atmospheric hydrodynamics and chemistry. It is important that the accurate matching of numerical schemes has to be provided in the chain of objects: direct/adjoint problems - sensitivity relations - inverse problems, including assimilation of all available measurement data. To solve the problems we have developed a new enhanced set of cost-effective algorithms. The matched description of the multi-scale processes is provided by a specific choice of the variational principle functionals for the whole set of integrated models. Then all functionals of variational principle are approximated in space and time by splitting and decomposition methods. Such approach allows us to separately consider, for example, the space-time problems of atmospheric chemistry in the frames of decomposition schemes for the integral identity sum analogs of the variational principle at each time step and in each of 3D finite-volumes. To enhance the realization efficiency, the set of chemical reactions is divided on the subsets related to the operators of production and destruction. Then the idea of the Euler's integrating factors is applied in the frames of the local adjoint problem technique [1]-[3]. The analytical solutions of such adjoint problems play the role of integrating factors for differential equations describing atmospheric chemistry. With their help, the system of differential equations is transformed to the equivalent system of integral equations. As a result we avoid the construction and inversion of preconditioning operators containing the Jacobi matrixes which arise in traditional implicit schemes for ODE solution. This is the main advantage of our schemes. At the same time step but on the different stages of the "global" splitting scheme, the system of atmospheric dynamic equations is solved. For convection - diffusion equations for all state functions in the integrated models we have developed the monotone and stable discrete-analytical numerical schemes [1]-[3] conserving the positivity of the chemical substance concentrations and possessing the properties of energy and mass balance that are postulated in the general variational principle for integrated models. All algorithms for solution of transport, diffusion and transformation problems are direct (without iterations). The work is partially supported by the Programs No 4 of Presidium RAS and No 3 of Mathematical Department of RAS, by RFBR project 11-01-00187 and Integrating projects of SD RAS No 8 and 35. Our studies are in the line with the goals of COST Action ES1004. References Penenko V., Tsvetova E. Discrete-analytical methods for the implementation of variational principles in environmental applications// Journal of computational and applied mathematics, 2009, v. 226, 319-330. Penenko A.V. Discrete-analytic schemes for solving an inverse coefficient heat conduction problem in a layered medium with gradient methods// Numerical Analysis and Applications, 2012, V. 5, pp 326-341. V. Penenko, E. Tsvetova. Variational methods for constructing the monotone approximations for atmospheric chemistry models //Numerical Analysis and Applications, 2013 (in press).

The Problems of Diagnosis and Remediation of Dyscalculia.

ERIC Educational Resources Information Center

Price, Nigel; Youe, Simon

2000-01-01

Focuses on the problems of diagnosis and remediation of dyscalculia. Explores whether there is justification for believing that specific difficulty with mathematics arises jointly with a specific language problem, or whether a specific difficulty with mathematics can arise independently of problems with language. Uses a case study to illuminate…

History-Dependent Problems with Applications to Contact Models for Elastic Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartosz, Krzysztof; Kalita, Piotr; Migórski, Stanisław

We prove an existence and uniqueness result for a class of subdifferential inclusions which involve a history-dependent operator. Then we specialize this result in the study of a class of history-dependent hemivariational inequalities. Problems of such kind arise in a large number of mathematical models which describe quasistatic processes of contact. To provide an example we consider an elastic beam in contact with a reactive obstacle. The contact is modeled with a new and nonstandard condition which involves both the subdifferential of a nonconvex and nonsmooth function and a Volterra-type integral term. We derive a variational formulation of the problemmore » which is in the form of a history-dependent hemivariational inequality for the displacement field. Then, we use our abstract result to prove its unique weak solvability. Finally, we consider a numerical approximation of the model, solve effectively the approximate problems and provide numerical simulations.« less

Image enhancement and quality measures for dietary assessment using mobile devices

NASA Astrophysics Data System (ADS)

Xu, Chang; Zhu, Fengqing; Khanna, Nitin; Boushey, Carol J.; Delp, Edward J.

2012-03-01

Measuring accurate dietary intake is considered to be an open research problem in the nutrition and health fields. We are developing a system, known as the mobile device food record (mdFR), to automatically identify and quantify foods and beverages consumed based on analyzing meal images captured with a mobile device. The mdFR makes use of a fiducial marker and other contextual information to calibrate the imaging system so that accurate amounts of food can be estimated from the scene. Food identification is a difficult problem since foods can dramatically vary in appearance. Such variations may arise not only from non-rigid deformations and intra-class variability in shape, texture, color and other visual properties, but also from changes in illumination and viewpoint. To address the color consistency problem, this paper describes illumination quality assessment methods implemented on a mobile device and three post color correction methods.

Image Enhancement and Quality Measures for Dietary Assessment Using Mobile Devices

PubMed Central

Xu, Chang; Zhu, Fengqing; Khanna, Nitin; Boushey, Carol J.; Delp, Edward J.

2016-01-01

Measuring accurate dietary intake is considered to be an open research problem in the nutrition and health fields. We are developing a system, known as the mobile device food record (mdFR), to automatically identify and quantify foods and beverages consumed based on analyzing meal images captured with a mobile device. The mdFR makes use of a fiducial marker and other contextual information to calibrate the imaging system so that accurate amounts of food can be estimated from the scene. Food identification is a difficult problem since foods can dramatically vary in appearance. Such variations may arise not only from non-rigid deformations and intra-class variability in shape, texture, color and other visual properties, but also from changes in illumination and viewpoint. To address the color consistency problem, this paper describes illumination quality assessment methods implemented on a mobile device and three post color correction methods. PMID:28572695

Guidance and control strategies for aerospace vehicles

NASA Technical Reports Server (NTRS)

Naidu, Desineni S.; Hibey, Joseph L.

1989-01-01

The optimal control problem arising in coplanar orbital transfer employing aeroassist technology and the fuel-optimal control problem arising in orbital transfer vehicles employing aeroassist technology are addressed.

Bilateral subclavian origin of the bronchial arteries combined with absence of other origins.

PubMed

Jie, Bing; Sun, Xi-Wen; Yu, Dong; Jiang, Sen

2014-08-01

There are numerous anatomical variations of the sites of origin of the bronchial arteries (BAs). A subclavian origin of a BA involves an aberrant artery that originates from the subclavian artery (SCA) or its branches. However, the aberrant artery usually originates directly from the SCA, and an SCA-origin BA arising from the branches of the SCA is rare. We herein present an extremely rare case of a right BA arising from the ipsilateral costocervical trunk, and a left BA arising from the ipsilateral thyrocervical trunk, in the absence of other origins of the BA. This anatomical variation was detected during pretherapeutic evaluation by multidetector-row computed tomography and confirmed by selective angiography. Recognition of these anatomic variations is important to surgical, diagnostic, and interventional radiologic procedures in the thorax.

Generalised solutions for fully nonlinear PDE systems and existence-uniqueness theorems

NASA Astrophysics Data System (ADS)

Katzourakis, Nikos

2017-07-01

We introduce a new theory of generalised solutions which applies to fully nonlinear PDE systems of any order and allows for merely measurable maps as solutions. This approach bypasses the standard problems arising by the application of Distributions to PDEs and is not based on either integration by parts or on the maximum principle. Instead, our starting point builds on the probabilistic representation of derivatives via limits of difference quotients in the Young measures over a toric compactification of the space of jets. After developing some basic theory, as a first application we consider the Dirichlet problem and we prove existence-uniqueness-partial regularity of solutions to fully nonlinear degenerate elliptic 2nd order systems and also existence of solutions to the ∞-Laplace system of vectorial Calculus of Variations in L∞.

Applying Graph Theory to Problems in Air Traffic Management

NASA Technical Reports Server (NTRS)

Farrahi, Amir Hossein; Goldbert, Alan; Bagasol, Leonard Neil; Jung, Jaewoo

2017-01-01

Graph theory is used to investigate three different problems arising in air traffic management. First, using a polynomial reduction from a graph partitioning problem, it is shown that both the airspace sectorization problem and its incremental counterpart, the sector combination problem are NP-hard, in general, under several simple workload models. Second, using a polynomial time reduction from maximum independent set in graphs, it is shown that for any fixed e, the problem of finding a solution to the minimum delay scheduling problem in traffic flow management that is guaranteed to be within n1-e of the optimal, where n is the number of aircraft in the problem instance, is NP-hard. Finally, a problem arising in precision arrival scheduling is formulated and solved using graph reachability. These results demonstrate that graph theory provides a powerful framework for modeling, reasoning about, and devising algorithmic solutions to diverse problems arising in air traffic management.

Applying Graph Theory to Problems in Air Traffic Management

NASA Technical Reports Server (NTRS)

Farrahi, Amir H.; Goldberg, Alan T.; Bagasol, Leonard N.; Jung, Jaewoo

2017-01-01

Graph theory is used to investigate three different problems arising in air traffic management. First, using a polynomial reduction from a graph partitioning problem, it isshown that both the airspace sectorization problem and its incremental counterpart, the sector combination problem are NP-hard, in general, under several simple workload models. Second, using a polynomial time reduction from maximum independent set in graphs, it is shown that for any fixed e, the problem of finding a solution to the minimum delay scheduling problem in traffic flow management that is guaranteed to be within n1-e of the optimal, where n is the number of aircraft in the problem instance, is NP-hard. Finally, a problem arising in precision arrival scheduling is formulated and solved using graph reachability. These results demonstrate that graph theory provides a powerful framework for modeling, reasoning about, and devising algorithmic solutions to diverse problems arising in air traffic management.

Integrated sensing platform and method for improved quantitative and selective monitoring of chemical analytes in both liquid and gas phase

DOEpatents

Blair, Dianna S.; Frye-Mason, Gregory C.; Butler, Michael A.

2000-01-01

By measuring two or more physical parameters of a thin sensing film which are altered when exposed to chemicals, more effective discrimination between chemicals can be achieved. In using more than one sensor, the sensors are preferably integrated on the same substrate so that they may measure the same thin film. Even more preferably, the sensors are provided orthogonal to one another so that they may measure the same portion of the thin film. These provisions reduce problems in discrimination arising from variations in thin films.

Simultaneous reconstruction and segmentation for dynamic SPECT imaging

NASA Astrophysics Data System (ADS)

Burger, Martin; Rossmanith, Carolin; Zhang, Xiaoqun

2016-10-01

This work deals with the reconstruction of dynamic images that incorporate characteristic dynamics in certain subregions, as arising for the kinetics of many tracers in emission tomography (SPECT, PET). We make use of a basis function approach for the unknown tracer concentration by assuming that the region of interest can be divided into subregions with spatially constant concentration curves. Applying a regularised variational framework reminiscent of the Chan-Vese model for image segmentation we simultaneously reconstruct both the labelling functions of the subregions as well as the subconcentrations within each region. Our particular focus is on applications in SPECT with the Poisson noise model, resulting in a Kullback-Leibler data fidelity in the variational approach. We present a detailed analysis of the proposed variational model and prove existence of minimisers as well as error estimates. The latter apply to a more general class of problems and generalise existing results in literature since we deal with a nonlinear forward operator and a nonquadratic data fidelity. A computational algorithm based on alternating minimisation and splitting techniques is developed for the solution of the problem and tested on appropriately designed synthetic data sets. For those we compare the results to those of standard EM reconstructions and investigate the effects of Poisson noise in the data.

Inequalities, Assessment and Computer Algebra

ERIC Educational Resources Information Center

Sangwin, Christopher J.

2015-01-01

The goal of this paper is to examine single variable real inequalities that arise as tutorial problems and to examine the extent to which current computer algebra systems (CAS) can (1) automatically solve such problems and (2) determine whether students' own answers to such problems are correct. We review how inequalities arise in contemporary…

Anomalous Posterior Intercostal Arterial Trunk Arising From the Abdominal Aorta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jie, Bing, E-mail: jbshh@163.com; Yu, Dong, E-mail: yudong-mail@126.com; Jiang, Sen, E-mail: jasfly77@vip.163.com

A common trunk of the ipsilateral posterior intercostal artery (PIA) arising from the thoracic aorta is usually an anatomical variation. However, a common trunk of bilateral posterior intercostal arterial trunk (PIAT) arising from the abdominal aorta is rare. It is important to recognize this anatomical variation of PIA when performing interventional radiological procedures. We present a rare case of an anomalous PIAT that originated from the abdominal aorta in a patient with hemoptysis caused by tuberculosis sequelae. Bilateral 4th to 11th PIAs arose from a common trunk and the trunk arising from the posterior aspect of the abdominal aorta atmore » the level of T12/L1 intervertebral space. The pathological right 4th and 5th PIAs and bronchial arteries were embolized. Hemoptysis has been controlled for 3 months.« less

An automated method for the determination of deoxyribonuclease activity as exemplified by fractionation of the components of the medicament Varidase®

PubMed Central

Locke, I. C.; Ramsey, M. P.; Hill, S. S.; Carpenter, B. G.

1993-01-01

The activity of most deoxyribonuclease enzymes can be monitored by measuring the change in absorbance at 260 nm which accompanies the breakdown of the double-stranded structure of native DNA. An automated method for determining deoxyribonuclease activity, based on such an absorbance change, which can overcome problems of inhibition arising from the presence of inorganic cations, is described. Variations in inorganic cation concentration is a particular problem when measuring the activity of chromatographic fractions eluted via a salt gradient. A comparison is made between the automated and a manual method for the assay of deoxyribonuclease active constituents, of the medicament ‘Varidase’, eluted from a Cellex-D (Bio-Rad Laboratories Ltd) anionic exchange resin using a 0.05-1.0 M sodium chloride gradient. PMID:18924962

The Effect of Normalization in Violence Video Classification Performance

NASA Astrophysics Data System (ADS)

Ali, Ashikin; Senan, Norhalina

2017-08-01

Basically, data pre-processing is an important part of data mining. Normalization is a pre-processing stage for any type of problem statement, especially in video classification. Challenging problems that arises in video classification is because of the heterogeneous content, large variations in video quality and complex semantic meanings of the concepts involved. Therefore, to regularize this problem, it is thoughtful to ensure normalization or basically involvement of thorough pre-processing stage aids the robustness of classification performance. This process is to scale all the numeric variables into certain range to make it more meaningful for further phases in available data mining techniques. Thus, this paper attempts to examine the effect of 2 normalization techniques namely Min-max normalization and Z-score in violence video classifications towards the performance of classification rate using Multi-layer perceptron (MLP) classifier. Using Min-Max Normalization range of [0,1] the result shows almost 98% of accuracy, meanwhile Min-Max Normalization range of [-1,1] accuracy is 59% and for Z-score the accuracy is 50%.

Neural net diagnostics for VLSI test

NASA Technical Reports Server (NTRS)

Lin, T.; Tseng, H.; Wu, A.; Dogan, N.; Meador, J.

1990-01-01

This paper discusses the application of neural network pattern analysis algorithms to the IC fault diagnosis problem. A fault diagnostic is a decision rule combining what is known about an ideal circuit test response with information about how it is distorted by fabrication variations and measurement noise. The rule is used to detect fault existence in fabricated circuits using real test equipment. Traditional statistical techniques may be used to achieve this goal, but they can employ unrealistic a priori assumptions about measurement data. Our approach to this problem employs an adaptive pattern analysis technique based on feedforward neural networks. During training, a feedforward network automatically captures unknown sample distributions. This is important because distributions arising from the nonlinear effects of process variation can be more complex than is typically assumed. A feedforward network is also able to extract measurement features which contribute significantly to making a correct decision. Traditional feature extraction techniques employ matrix manipulations which can be particularly costly for large measurement vectors. In this paper we discuss a software system which we are developing that uses this approach. We also provide a simple example illustrating the use of the technique for fault detection in an operational amplifier.

EPR-dosimetry of ionizing radiation

NASA Astrophysics Data System (ADS)

Popova, Mariia; Vakhnin, Dmitrii; Tyshchenko, Igor

2017-09-01

This article discusses the problems that arise during the radiation sterilization of medical products. It is propose the solution based on alanine EPR-dosimetry. The parameters of spectrometer and methods of absorbed dose calculation are given. In addition, the problems that arise during heavy particles irradiation are investigated.

Mean Field Variational Bayesian Data Assimilation

NASA Astrophysics Data System (ADS)

Vrettas, M.; Cornford, D.; Opper, M.

2012-04-01

Current data assimilation schemes propose a range of approximate solutions to the classical data assimilation problem, particularly state estimation. Broadly there are three main active research areas: ensemble Kalman filter methods which rely on statistical linearization of the model evolution equations, particle filters which provide a discrete point representation of the posterior filtering or smoothing distribution and 4DVAR methods which seek the most likely posterior smoothing solution. In this paper we present a recent extension to our variational Bayesian algorithm which seeks the most probably posterior distribution over the states, within the family of non-stationary Gaussian processes. Our original work on variational Bayesian approaches to data assimilation sought the best approximating time varying Gaussian process to the posterior smoothing distribution for stochastic dynamical systems. This approach was based on minimising the Kullback-Leibler divergence between the true posterior over paths, and our Gaussian process approximation. So long as the observation density was sufficiently high to bring the posterior smoothing density close to Gaussian the algorithm proved very effective, on lower dimensional systems. However for higher dimensional systems, the algorithm was computationally very demanding. We have been developing a mean field version of the algorithm which treats the state variables at a given time as being independent in the posterior approximation, but still accounts for their relationships between each other in the mean solution arising from the original dynamical system. In this work we present the new mean field variational Bayesian approach, illustrating its performance on a range of classical data assimilation problems. We discuss the potential and limitations of the new approach. We emphasise that the variational Bayesian approach we adopt, in contrast to other variational approaches, provides a bound on the marginal likelihood of the observations given parameters in the model which also allows inference of parameters such as observation errors, and parameters in the model and model error representation, particularly if this is written as a deterministic form with small additive noise. We stress that our approach can address very long time window and weak constraint settings. However like traditional variational approaches our Bayesian variational method has the benefit of being posed as an optimisation problem. We finish with a sketch of the future directions for our approach.

Multi-excitonic (N=1,2 and 3) quantum dots in magnetic field: Analytical mapping of correlations (exchange) by multipole expansion

NASA Astrophysics Data System (ADS)

Singh, Sunny; Kaur, Harsimran; Sharma, Shivalika; Aggarwal, Priyanka; Hazra, Ram Kuntal

2017-04-01

The understanding of the physics of exciton, bi-exciton, tri-exciton and the subsequent insight into controlling the properties of mesoscopic systems holds the key to various exotic optical, electrical and magnetic phenomena like superconductivity, Mott insulation, Quantum Hall effect etc. Many of exciton properties are similar to atomic hydrogen that attracts researchers to explore electronic structure of exciton in quantum dots, but nontriviality arises due to coulombic interactions among electrons and holes. We propose an exact integral of coulomb (exchange) correlation in terms of finitely summed Lauricella functions to examine 3-D exciton of harmonic dots confined in zero and non-zero arbitrary magnetic field. The highlight of our work is the use of exact variational solution for coloumbic interaction between the hole and the electron and evaluation of the cross terms arising out of the coupling among centre-of-mass and relative coordinates. We also have extended the size of the system to generalized N-body problem with N=3,4 for tri-exciton (e-e-h/e-h-h)

Discriminant analysis in wildlife research: Theory and applications

USGS Publications Warehouse

Williams, B.K.; Capen, D.E.

1981-01-01

Discriminant analysis, a method of analyzing grouped multivariate data, is often used in ecological investigations. It has both a predictive and an explanatory function, the former aiming at classification of individuals of unknown group membership. The goal of the latter function is to exhibit group separation by means of linear transforms, and the corresponding method is called canonical analysis. This discussion focuses on the application of canonical analysis in ecology. In order to clarify its meaning, a parametric approach is taken instead of the usual data-based formulation. For certain assumptions the data-based canonical variates are shown to result from maximum likelihood estimation, thus insuring consistency and asymptotic efficiency. The distorting effects of covariance heterogeneity are examined, as are certain difficulties which arise in interpreting the canonical functions. A 'distortion metric' is defined, by means of which distortions resulting from the canonical transformation can be assessed. Several sampling problems which arise in ecological applications are considered. It is concluded that the method may prove valuable for data exploration, but is of limited value as an inferential procedure.

Efficient Mean Field Variational Algorithm for Data Assimilation (Invited)

NASA Astrophysics Data System (ADS)

Vrettas, M. D.; Cornford, D.; Opper, M.

2013-12-01

Data assimilation algorithms combine available observations of physical systems with the assumed model dynamics in a systematic manner, to produce better estimates of initial conditions for prediction. Broadly they can be categorized in three main approaches: (a) sequential algorithms, (b) sampling methods and (c) variational algorithms which transform the density estimation problem to an optimization problem. However, given finite computational resources, only a handful of ensemble Kalman filters and 4DVar algorithms have been applied operationally to very high dimensional geophysical applications, such as weather forecasting. In this paper we present a recent extension to our variational Bayesian algorithm which seeks the ';optimal' posterior distribution over the continuous time states, within a family of non-stationary Gaussian processes. Our initial work on variational Bayesian approaches to data assimilation, unlike the well-known 4DVar method which seeks only the most probable solution, computes the best time varying Gaussian process approximation to the posterior smoothing distribution for dynamical systems that can be represented by stochastic differential equations. This approach was based on minimising the Kullback-Leibler divergence, over paths, between the true posterior and our Gaussian process approximation. Whilst the observations were informative enough to keep the posterior smoothing density close to Gaussian the algorithm proved very effective on low dimensional systems (e.g. O(10)D). However for higher dimensional systems, the high computational demands make the algorithm prohibitively expensive. To overcome the difficulties presented in the original framework and make our approach more efficient in higher dimensional systems we have been developing a new mean field version of the algorithm which treats the state variables at any given time as being independent in the posterior approximation, while still accounting for their relationships in the mean solution arising from the original system dynamics. Here we present this new mean field approach, illustrating its performance on a range of benchmark data assimilation problems whose dimensionality varies from O(10) to O(10^3)D. We emphasise that the variational Bayesian approach we adopt, unlike other variational approaches, provides a natural bound on the marginal likelihood of the observations given the model parameters which also allows for inference of (hyper-) parameters such as observational errors, parameters in the dynamical model and model error representation. We also stress that since our approach is intrinsically parallel it can be implemented very efficiently to address very long data assimilation time windows. Moreover, like most traditional variational approaches our Bayesian variational method has the benefit of being posed as an optimisation problem therefore its complexity can be tuned to the available computational resources. We finish with a sketch of possible future directions.

Implications of Spatial Data Variations for Protected Areas Management: An Example from East Africa

NASA Astrophysics Data System (ADS)

Dowhaniuk, Nicholas; Hartter, Joel; Ryan, Sadie J.

2014-09-01

Geographic information systems and remote sensing technologies have become an important tool for visualizing conservation management and developing solutions to problems associated with conservation. When multiple organizations separately develop spatial data representations of protected areas, implicit error arises due to variation between data sets. We used boundary data produced by three conservation organizations (International Union for the Conservation of Nature, World Resource Institute, and Uganda Wildlife Authority), for seven Ugandan parks, to study variation in the size represented and the location of boundaries. We found variation in the extent of overlapping total area encompassed by the three data sources, ranging from miniscule (0.4 %) differences to quite large ones (9.0 %). To underscore how protected area boundary discrepancies may have implications to protected area management, we used a landcover classification, defining crop, shrub, forest, savanna, and grassland. The total area in the different landcover classes varied most in smaller protected areas (those less than 329 km2), with forest and cropland area estimates varying up to 65 %. The discrepancies introduced by boundary errors could, in this hypothetical case, generate erroneous findings and could have a significant impact on conservation, such as local-scale management for encroachment and larger-scale assessments of deforestation.

Implications of spatial data variations for protected areas management: an example from East Africa.

PubMed

Dowhaniuk, Nicholas; Hartter, Joel; Ryan, Sadie J

2014-09-01

Geographic information systems and remote sensing technologies have become an important tool for visualizing conservation management and developing solutions to problems associated with conservation. When multiple organizations separately develop spatial data representations of protected areas, implicit error arises due to variation between data sets. We used boundary data produced by three conservation organizations (International Union for the Conservation of Nature, World Resource Institute, and Uganda Wildlife Authority), for seven Ugandan parks, to study variation in the size represented and the location of boundaries. We found variation in the extent of overlapping total area encompassed by the three data sources, ranging from miniscule (0.4 %) differences to quite large ones (9.0 %). To underscore how protected area boundary discrepancies may have implications to protected area management, we used a landcover classification, defining crop, shrub, forest, savanna, and grassland. The total area in the different landcover classes varied most in smaller protected areas (those less than 329 km(2)), with forest and cropland area estimates varying up to 65 %. The discrepancies introduced by boundary errors could, in this hypothetical case, generate erroneous findings and could have a significant impact on conservation, such as local-scale management for encroachment and larger-scale assessments of deforestation.

Body size and pubertal development explain ethnic differences in structural geometry at the femur in Asian, Hispanic and white early adolescent girls living in the US

USDA-ARS?s Scientific Manuscript database

Variation in structural geometry is present in adulthood, but when this variation arises and what influences this variation prior to adulthood remains poorly understood. Ethnicity is commonly the focus of research of skeletal integrity and appears to explain some of the variation in quantification o...

Beginning inflation in an inhomogeneous universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

East, William E.; Kleban, Matthew; Linde, Andrei

Using numerical solutions of the full Einstein field equations coupled to a scalar inflaton field in 3+1 dimensions, we study the conditions under which a universe that is initially expanding, highly inhomogeneous and dominated by gradient energy can transition to an inflationary period. If the initial scalar field variations are contained within a sufficiently flat region of the inflaton potential, and the universe is spatially flat or open on average, inflation will occur following the dilution of the gradient and kinetic energy due to expansion. This is the case even when the scale of the inhomogeneities is comparable to themore » initial Hubble length, and overdense regions collapse and form black holes, because underdense regions continue expanding, allowing inflation to eventually begin. In conclusion, this establishes that inflation can arise from highly inhomogeneous initial conditions and solve the horizon and flatness problems, at least as long as the variations in the scalar field do not include values that exceed the inflationary plateau.« less

Beginning inflation in an inhomogeneous universe

DOE PAGES

East, William E.; Kleban, Matthew; Linde, Andrei; ...

2016-09-06

Using numerical solutions of the full Einstein field equations coupled to a scalar inflaton field in 3+1 dimensions, we study the conditions under which a universe that is initially expanding, highly inhomogeneous and dominated by gradient energy can transition to an inflationary period. If the initial scalar field variations are contained within a sufficiently flat region of the inflaton potential, and the universe is spatially flat or open on average, inflation will occur following the dilution of the gradient and kinetic energy due to expansion. This is the case even when the scale of the inhomogeneities is comparable to themore » initial Hubble length, and overdense regions collapse and form black holes, because underdense regions continue expanding, allowing inflation to eventually begin. In conclusion, this establishes that inflation can arise from highly inhomogeneous initial conditions and solve the horizon and flatness problems, at least as long as the variations in the scalar field do not include values that exceed the inflationary plateau.« less

Beginning inflation in an inhomogeneous universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

East, William E.; Kleban, Matthew; Linde, Andrei

Using numerical solutions of the full Einstein field equations coupled to a scalar inflaton field in 3+1 dimensions, we study the conditions under which a universe that is initially expanding, highly inhomogeneous and dominated by gradient energy can transition to an inflationary period. If the initial scalar field variations are contained within a sufficiently flat region of the inflaton potential, and the universe is spatially flat or open on average, inflation will occur following the dilution of the gradient and kinetic energy due to expansion. This is the case even when the scale of the inhomogeneities is comparable to themore » initial Hubble length, and overdense regions collapse and form black holes, because underdense regions continue expanding, allowing inflation to eventually begin. This establishes that inflation can arise from highly inhomogeneous initial conditions and solve the horizon and flatness problems, at least as long as the variations in the scalar field do not include values that exceed the inflationary plateau.« less

Genetic differentiation among populations of marine algae

NASA Astrophysics Data System (ADS)

Innes, D. J.

1984-09-01

Most of the information for genetic differentiation among populations of marine algae is from studies on ecotypic variation. Physiological ecotypes have been described for individuals showing different responses to temperature and salinity conditions. Morphological ecotypes have also been found associated with areas differing in wave exposure or different intertidal positions. Little is known on how genetic variation is organized within and between populations of marine algae. The occurrence of ecotypic variation in some species is evidence for genetic differentiation among populations resulting from selection by the local environment. The rate of dispersal and subsequent gene flow will also affect the level of differentiation among populations. In species with low dispersal, differentiation can arise through chance founder events or random genetic drift. The few studies available have shown that species of algae exhibit a range of dispersal capabilities. This information can be useful for predicting the potential level of genetic differentiation among populations of these species. Crossing experiments with several species of algae have shown that populations separated by a considerable distance can be interfertile. In some cases individuals from these populations have been found to be morphologically distinct. Crosses have been used to study the genetic basis of this variation and are evidence for genetic differentiation among the populations sampled. Genetic variation of enzyme proteins detected by electrophoresis provides an additional method for measuring genetic variation within and between populations of marine algae. Electrophoretic methods have previously been used to study systematic problems in algae. However, there have been few attempts to use electrophoretic variation to study the genetic structure of populations of marine algae. This approach is outlined and includes some of the potential problems associated with interpreting electrophoretic data. Studies of electrophoretic variation in natural populations of Enteromorpha linza from Long island Sound are used as an example. This species was found to reproduce only asexually. Despite a dispersing spore stage, genetic differentiation was found on a microgeographic scale and was correlated with differences in the local environment of some of the populations. Similar studies on other species, and especially sexually reproducing species, will add to a growing understanding of the evolutionary genetics of marine algae.

Joint reconstruction of multiview compressed images.

PubMed

Thirumalai, Vijayaraghavan; Frossard, Pascal

2013-05-01

Distributed representation of correlated multiview images is an important problem that arises in vision sensor networks. This paper concentrates on the joint reconstruction problem where the distributively compressed images are decoded together in order to take benefit from the image correlation. We consider a scenario where the images captured at different viewpoints are encoded independently using common coding solutions (e.g., JPEG) with a balanced rate distribution among different cameras. A central decoder first estimates the inter-view image correlation from the independently compressed data. The joint reconstruction is then cast as a constrained convex optimization problem that reconstructs total-variation (TV) smooth images, which comply with the estimated correlation model. At the same time, we add constraints that force the reconstructed images to be as close as possible to their compressed versions. We show through experiments that the proposed joint reconstruction scheme outperforms independent reconstruction in terms of image quality, for a given target bit rate. In addition, the decoding performance of our algorithm compares advantageously to state-of-the-art distributed coding schemes based on motion learning and on the DISCOVER algorithm.

Variational data assimilation system "INM RAS - Black Sea"

NASA Astrophysics Data System (ADS)

Parmuzin, Eugene; Agoshkov, Valery; Assovskiy, Maksim; Giniatulin, Sergey; Zakharova, Natalia; Kuimov, Grigory; Fomin, Vladimir

2013-04-01

Development of Informational-Computational Systems (ICS) for Data Assimilation Procedures is one of multidisciplinary problems. To study and solve these problems one needs to apply modern results from different disciplines and recent developments in: mathematical modeling; theory of adjoint equations and optimal control; inverse problems; numerical methods theory; numerical algebra and scientific computing. The problems discussed above are studied in the Institute of Numerical Mathematics of the Russian Academy of Science (INM RAS) in ICS for Personal Computers (PC). Special problems and questions arise while effective ICS versions for PC are being developed. These problems and questions can be solved with applying modern methods of numerical mathematics and by solving "parallelism problem" using OpenMP technology and special linear algebra packages. In this work the results on the ICS development for PC-ICS "INM RAS - Black Sea" are presented. In the work the following problems and questions are discussed: practical problems that can be studied by ICS; parallelism problems and their solutions with applying of OpenMP technology and the linear algebra packages used in ICS "INM - Black Sea"; Interface of ICS. The results of ICS "INM RAS - Black Sea" testing are presented. Efficiency of technologies and methods applied are discussed. The work was supported by RFBR, grants No. 13-01-00753, 13-05-00715 and by The Ministry of education and science of Russian Federation, project 8291, project 11.519.11.1005 References: [1] V.I. Agoshkov, M.V. Assovskii, S.A. Lebedev, Numerical simulation of Black Sea hydrothermodynamics taking into account tide-forming forces. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, 5-31 [2] E.I. Parmuzin, V.I. Agoshkov, Numerical solution of the variational assimilation problem for sea surface temperature in the model of the Black Sea dynamics. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, 69-94 [3] V.B. Zalesny, N.A. Diansky, V.V. Fomin, S.N. Moshonkin, S.G. Demyshev, Numerical model of the circulation of Black Sea and Sea of Azov. Russ. J. Numer. Anal. Math. Modelling (2012) 27, No.1, 95-111 [4] V.I. Agoshkov, S.V. Giniatulin, G.V. Kuimov. OpenMP technology and linear algebra packages in the variation data assimilation systems. - Abstracts of the 1-st China-Russia Conference on Numerical Algebra with Applications in Radiactive Hydrodynamics, Beijing, China, October 16-18, 2012. [5] Zakharova N.B., Agoshkov V.I., Parmuzin E.I., The new method of ARGO buoys system observation data interpolation. Russian Journal of Numerical Analysis and Mathematical Modelling. Vol. 28, Issue 1, 2013.

Cultural Variation in Implicit Mental Illness Stigma.

PubMed

Cheon, Bobby K; Chiao, Joan Y

2012-10-01

Culture shapes how individuals perceive and respond to others with mental illness. Prior studies have suggested that Asians and Asian Americans typically endorse greater stigma of mental illness compared to Westerners (White Europeans and Americans). However, whether these differences in stigma arise from cultural variations in automatic affective reactions or deliberative concerns of the appropriateness of one's reactions to mental illness remains unknown. Here we compared implicit and explicit attitudes toward mental illness among Asian and Caucasian Americans. Asian Americans showed stronger negative implicit attitudes toward mental illness relative to Caucasian Americans, suggesting that cultural variation in stigma of mental illness can be observed even when concerns regarding the validity and appropriateness of one's attitudes toward mental illness are minimized. Asian Americans also explicitly endorsed greater desire for social distance from mental illness relative to Caucasian Americans. These findings suggest that cultural variations in mental illness stigma may arise from cultural differences in automatic reactions to mental illness, though cultural variations in deliberative processing may further shape differences in these immediate reactions to mental illness.

Removal of ring artifacts in microtomography by characterization of scintillator variations.

PubMed

Vågberg, William; Larsson, Jakob C; Hertz, Hans M

2017-09-18

Ring artifacts reduce image quality in tomography, and arise from faulty detector calibration. In microtomography, we have identified that ring artifacts can arise due to high-spatial frequency variations in the scintillator thickness. Such variations are normally removed by a flat-field correction. However, as the spectrum changes, e.g. due to beam hardening, the detector response varies non-uniformly introducing ring artifacts that persist after flat-field correction. In this paper, we present a method to correct for ring artifacts from variations in scintillator thickness by using a simple method to characterize the local scintillator response. The method addresses the actual physical cause of the ring artifacts, in contrary to many other ring artifact removal methods which rely only on image post-processing. By applying the technique to an experimental phantom tomography, we show that ring artifacts are strongly reduced compared to only making a flat-field correction.

Discretization of three-dimensional free surface flows and moving boundary problems via elliptic grid methods based on variational principles

NASA Astrophysics Data System (ADS)

Fraggedakis, D.; Papaioannou, J.; Dimakopoulos, Y.; Tsamopoulos, J.

2017-09-01

A new boundary-fitted technique to describe free surface and moving boundary problems is presented. We have extended the 2D elliptic grid generator developed by Dimakopoulos and Tsamopoulos (2003) [19] and further advanced by Chatzidai et al. (2009) [18] to 3D geometries. The set of equations arises from the fulfillment of the variational principles established by Brackbill and Saltzman (1982) [21], and refined by Christodoulou and Scriven (1992) [22]. These account for both smoothness and orthogonality of the grid lines of tessellated physical domains. The elliptic-grid equations are accompanied by new boundary constraints and conditions which are based either on the equidistribution of the nodes on boundary surfaces or on the existing 2D quasi-elliptic grid methodologies. The capabilities of the proposed algorithm are first demonstrated in tests with analytically described complex surfaces. The sequence in which these tests are presented is chosen to help the reader build up experience on the best choice of the elliptic grid parameters. Subsequently, the mesh equations are coupled with the Navier-Stokes equations, in order to reveal the full potential of the proposed methodology in free surface flows. More specifically, the problem of gas assisted injection in ducts of circular and square cross-sections is examined, where the fluid domain experiences extreme deformations. Finally, the flow-mesh solver is used to calculate the equilibrium shapes of static menisci in capillary tubes.

Thermal issues at the SSC

NASA Technical Reports Server (NTRS)

Ranganathan, Raj P.; Dao, Bui V.

1992-01-01

A variety of heat transfer problems arise in the design of the Superconducting Super Collider (SSC). One class of problems is to minimize heat leak from the ambient to the SSC rings, since the rings contain superconducting magnets maintained at a temperature of 4 K. Another arises from the need to dump the beam of protrons (traveling around the SSC rings) on to absorbers during an abort of the collider. Yet another category of problems is the cooling of equipment to dissipate the heat generated during operation. An overview of these problems and sample heat transfer results are given in this paper.

Personality and problem-solving in common mynas (Acridotheres tristis).

PubMed

Lermite, Françoise; Peneaux, Chloé; Griffin, Andrea S

2017-01-01

Animals show consistent individual differences in behaviour across time and/or contexts. Recently, it has been suggested that proactive personality types might also exhibit fast cognitive styles. The speed with which individuals sample environmental cues is one way in which correlations between personality and cognition might arise. Here, we measured a collection of behavioural traits (competitiveness, neophobia, neophilia, task-directed motivation and exploration) in common mynas (Acridotheres tristis) and measured their relationship with problem solving. We predicted that fast solving mynas would interact with (i.e. sample) the problem solving task at higher rates, but also be more competitive, less neophobic, more neophilic, and more exploratory. Mynas that were faster to solve a novel foraging problem were no more competitive around food and no more inclined to take risks. Unexpectedly, these fast-solving mynas had higher rates of interactions with the task, but also displayed lower levels of exploration. It is possible that a negative relation between problem solving and spatial exploration arose as a consequence of how inter-individual variation in exploration was quantified. We discuss the need for greater consensus on how to measure exploratory behaviour before we can advance our understanding of relationships between cognition and personality more effectively. Copyright © 2016 Elsevier B.V. All rights reserved.

PROBABILISTIC CHARACTERIZATION OF ATMOSPHERIC TRANSPORT AND DIFFUSION

EPA Science Inventory

The observed scatter of observations about air quality model predictions stems from a combination of naturally occurring stochastic variations that are impossible for any model to explicitly simulate and variations arising from limitations in our knowledge and from imperfect inpu...

"For most of us Africans, we don't just speak": a qualitative investigation into collaborative heterogeneous PBL group learning.

PubMed

Singaram, Veena S; van der Vleuten, Cees P M; Stevens, Fred; Dolmans, Diana H J M

2011-08-01

Collaborative approaches such as Problem Based Learning (PBL) may provide the opportunity to bring together diverse students but their efficacy in practice and the complications that arise due to the mixed ethnicity needs further investigation. This study explores the key advantages and problems of heterogeneous PBL groups from the students' and teachers' opinions. Focus groups were conducted with a stratified sample of second year medical students and their PBL teachers. We found that students working in heterogeneous groupings interact with students with whom they don't normally interact with, learn a lot more from each other because of their differences in language and academic preparedness and become better prepared for their future professions in multicultural societies. On the other hand we found students segregating in the tutorials along racial lines and that status factors disempowered students and subsequently their productivity. Among the challenges was also that academic and language diversity hindered student learning. In light of these the recommendations were that teachers need special diversity training to deal with heterogeneous groups and the tensions that arise. Attention should be given to create 'the right mix' for group learning in diverse student populations. The findings demonstrate that collaborative heterogeneous learning has two sides that need to be balanced. On the positive end we have the 'ideology' behind mixing diverse students and on the negative the 'practice' behind mixing students. More research is needed to explore these variations and their efficacy in more detail.

Testing a Flexible Method to Reduce False Monsoon Onsets

PubMed Central

Stiller-Reeve, Mathew Alexander; Spengler, Thomas; Chu, Pao-Shin

2014-01-01

To generate information about the monsoon onset and withdrawal we have to choose a monsoon definition and apply it to data. One problem that arises is that false monsoon onsets can hamper our analysis, which is often alleviated by smoothing the data in time or space. Another problem is that local communities or stakeholder groups may define the monsoon differently. We therefore aim to develop a technique that reduces false onsets for high-resolution gridded data, while also being flexible for different requirements that can be tailored to particular end-users. In this study, we explain how we developed our technique and demonstrate how it successfully reduces false onsets and withdrawals. The presented results yield improved information about the monsoon length and its interannual variability. Due to this improvement, we are able to extract information from higher resolution data sets. This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations. PMID:25105900

Long-term scale adaptive tracking with kernel correlation filters

NASA Astrophysics Data System (ADS)

Wang, Yueren; Zhang, Hong; Zhang, Lei; Yang, Yifan; Sun, Mingui

2018-04-01

Object tracking in video sequences has broad applications in both military and civilian domains. However, as the length of input video sequence increases, a number of problems arise, such as severe object occlusion, object appearance variation, and object out-of-view (some portion or the entire object leaves the image space). To deal with these problems and identify the object being tracked from cluttered background, we present a robust appearance model using Speeded Up Robust Features (SURF) and advanced integrated features consisting of the Felzenszwalb's Histogram of Oriented Gradients (FHOG) and color attributes. Since re-detection is essential in long-term tracking, we develop an effective object re-detection strategy based on moving area detection. We employ the popular kernel correlation filters in our algorithm design, which facilitates high-speed object tracking. Our evaluation using the CVPR2013 Object Tracking Benchmark (OTB2013) dataset illustrates that the proposed algorithm outperforms reference state-of-the-art trackers in various challenging scenarios.

On the membrane approximation in isothermal film casting

NASA Astrophysics Data System (ADS)

Hagen, Thomas

2014-08-01

In this work, a one-dimensional model for isothermal film casting is studied. Film casting is an important engineering process to manufacture thin films and sheets from a highly viscous polymer melt. The model equations account for variations in film width and film thickness, and arise from thinness and kinematic assumptions for the free liquid film. The first aspect of our study is a rigorous discussion of the existence and uniqueness of stationary solutions. This objective is approached via the argument principle, exploiting the homotopy invariance of a family of analytic functions. As our second objective, we analyze the linearization of the governing equations about stationary solutions. It is shown that solutions for the associated boundary-initial value problem are given by a strongly continuous semigroup of bounded linear operators. To reach this result, we cast the relevant Cauchy problem in a more accessible form. These transformed equations allow us insight into the regularity of the semigroup, thus yielding the validity of the spectral mapping theorem for the semigroup and the spectrally determined growth property.

Fuchsian triangle groups and Grothendieck dessins. Variations on a theme of Belyi

NASA Astrophysics Data System (ADS)

Cohen, Paula Beazley; Itzykson, Claude; Wolfart, Jürgen

1994-07-01

According to a theorem of Belyi, a smooth projective algebraic curve is defined over a number field if and only if there exists a non-constant element of its function field ramified only over 0, 1 and . The existence of such a Belyi function is equivalent to that of a representation of the curve as a possibly compactified quotient space of the Poincaré upper half plane by a subgroup of finite index in a Fuchsian triangle group. On the other hand, Fuchsian triangle groups arise in many contexts, such as in the theory of hypergeometric functions and certain triangular billiard problems, which would appear at first sight to have no relation to the Galois problems that motivated the above discovery of Belyi. In this note we review several results related to Belyi's theorem and we develop certain aspects giving examples. For preliminary accounts, see the preprint [Wo1], the conference proceedings article [BauItz] and the Comptes Rendus note [CoWo2].

On the motion of a body whose dynamical structure is variable

NASA Astrophysics Data System (ADS)

Kolbut, V. R.

1982-02-01

Abul'naga and Barkin (1980) have considered the problem of the particular solutions for the translational-rotational motion of two rigid bodies, taking into account the third harmonics in the force function of their Newtonian interaction. Attention is given to the Hamiltonian of the problem, the distinctive motion of a body whose dynamical structure is variable, and the introduction of a known function of an independent variable. The solutions may be written in the form of a series. In the stationary case the solutions are the same as those provided by Abul'naga and Barkin. The variation in the dynamical structure of a constant-mass body may occur either because of changes in the density asymmetry or through redistribution of mass within the body. This last case is relevant to the analysis of effects arising from deformation of the body. One instance of a small distortion of this kind would be the tidal deformation of the earth.

Astrobiological stoichiometry.

PubMed

Young, Patrick A; Desch, Steven J; Anbar, Ariel D; Barnes, Rory; Hinkel, Natalie R; Kopparapu, Ravikumar; Madhusudhan, Nikku; Monga, Nikhil; Pagano, Michael D; Riner, Miriam A; Scannapieco, Evan; Shim, Sang-Heon; Truitt, Amanda

2014-07-01

Chemical composition affects virtually all aspects of astrobiology, from stellar astrophysics to molecular biology. We present a synopsis of the research results presented at the "Stellar Stoichiometry" Workshop Without Walls hosted at Arizona State University April 11-12, 2013, under the auspices of the NASA Astrobiology Institute. The results focus on the measurement of chemical abundances and the effects of composition on processes from stellar to planetary scales. Of particular interest were the scientific connections between processes in these normally disparate fields. Measuring the abundances of elements in stars and giant and terrestrial planets poses substantial difficulties in technique and interpretation. One of the motivations for this conference was the fact that determinations of the abundance of a given element in a single star by different groups can differ by more than their quoted errors. The problems affecting the reliability of abundance estimations and their inherent limitations are discussed. When these problems are taken into consideration, self-consistent surveys of stellar abundances show that there is still substantial variation (factors of ∼ 2) in the ratios of common elements (e.g., C, O, Na, Al, Mg, Si, Ca) important in rock-forming minerals, atmospheres, and biology. We consider how abundance variations arise through injection of supernova nucleosynthesis products into star-forming material and through photoevaporation of protoplanetary disks. The effects of composition on stellar evolution are substantial, and coupled with planetary atmosphere models can result in predicted habitable zone extents that vary by many tens of percent. Variations in the bulk composition of planets can affect rates of radiogenic heating and substantially change the mineralogy of planetary interiors, affecting properties such as convection and energy transport.

Host population structure and treatment frequency maintain balancing selection on drug resistance

PubMed Central

Baskerville, Edward B.; Colijn, Caroline; Hanage, William; Fraser, Christophe; Lipsitch, Marc

2017-01-01

It is a truism that antimicrobial drugs select for resistance, but explaining pathogen- and population-specific variation in patterns of resistance remains an open problem. Like other common commensals, Streptococcus pneumoniae has demonstrated persistent coexistence of drug-sensitive and drug-resistant strains. Theoretically, this outcome is unlikely. We modelled the dynamics of competing strains of S. pneumoniae to investigate the impact of transmission dynamics and treatment-induced selective pressures on the probability of stable coexistence. We find that the outcome of competition is extremely sensitive to structure in the host population, although coexistence can arise from age-assortative transmission models with age-varying rates of antibiotic use. Moreover, we find that the selective pressure from antibiotics arises not so much from the rate of antibiotic use per se but from the frequency of treatment: frequent antibiotic therapy disproportionately impacts the fitness of sensitive strains. This same phenomenon explains why serotypes with longer durations of carriage tend to be more resistant. These dynamics may apply to other potentially pathogenic, microbial commensals and highlight how population structure, which is often omitted from models, can have a large impact. PMID:28835542

50 CFR 600.335 - National Standard 6-Variations and Contingencies.

Code of Federal Regulations, 2014 CFR

2014-10-01

... management terms, variations arise from biological, social, and economic occurrences, as well as from fishing... strength, stock location in time and space, environmental/habitat changes, and ecological interactions... uncertainties. Social changes could involve increases or decreases in recreational fishing, or the movement of...

50 CFR 600.335 - National Standard 6-Variations and Contingencies.

Code of Federal Regulations, 2012 CFR

2012-10-01

... management terms, variations arise from biological, social, and economic occurrences, as well as from fishing... strength, stock location in time and space, environmental/habitat changes, and ecological interactions... uncertainties. Social changes could involve increases or decreases in recreational fishing, or the movement of...

50 CFR 600.335 - National Standard 6-Variations and Contingencies.

Code of Federal Regulations, 2013 CFR

2013-10-01

... management terms, variations arise from biological, social, and economic occurrences, as well as from fishing... strength, stock location in time and space, environmental/habitat changes, and ecological interactions... uncertainties. Social changes could involve increases or decreases in recreational fishing, or the movement of...

50 CFR 600.335 - National Standard 6-Variations and Contingencies.

Code of Federal Regulations, 2010 CFR

2010-10-01

... management terms, variations arise from biological, social, and economic occurrences, as well as from fishing... strength, stock location in time and space, environmental/habitat changes, and ecological interactions... uncertainties. Social changes could involve increases or decreases in recreational fishing, or the movement of...

Marked lateral deviation of the phrenic nerve due to variant origin and course of the thyrocervical trunk: a cadaveric study.

PubMed

Ogami, Keiko; Saiki, K; Okamoto, K; Wakebe, T; Manabe, Y; Imamura, T; Tsurumoto, T

2016-05-01

Phrenic nerve impairment can often lead to serious respiratory disorders under various pathological conditions. During routine dissection of an 88-year-old Japanese male cadaver, a victim of heart failure, we recognized an extremely rare variation of the right thyrocervical trunk arising from the subclavian artery laterally to the anterior scalene muscle. In addition to that, the ipsilateral phrenic nerve was drawn and displaced remarkably laterad by this vessel. We examined all of the branches arising from subclavian arteries, phrenic nerves and diaphragm muscles. The embryological background of this arterial variation is considered. The marked displacement with prolonged strain had a potential to cause phrenic nerve impairment with an atrophic change of the diaphragm muscle. Recently many image diagnostic technologies have been developed and are often used. However, it is still possible that rare variations like this case may be overlooked and can only be recognized by intimate regional examination while keeping these rare variations in mind.

Attention problems and pathological gaming: resolving the 'chicken and egg' in a prospective analysis.

PubMed

Ferguson, Christopher J; Ceranoglu, T Atilla

2014-03-01

Pathological gaming (PG) behaviors are behaviors which interfere with other life responsibilities. Continued debate exists regarding whether symptoms of PG behaviors are a unique phenomenon or arise from other mental health problems, including attention problems. Development of attention problems and occurrence of pathological gaming in 144 adolescents were followed during a 1-year prospective analysis. Teens and their parents reported on pathological gaming behaviors, attention problems, and current grade point average, as well as several social variables. Results were analyzed using regression and path analysis. Attention problems tended to precede pathological gaming behaviors, but the inverse was not true. Attention problems but not pathological gaming predicted lower GPA 1 year later. Current results suggest that pathological gaming arises from attention problems, but not the inverse. These results suggest that pathological gaming behaviors are symptomatic of underlying attention related mental health issues, rather than a unique phenomenon.

Goethe almost died of urosepsis.

PubMed

Gross, A J; Hummel, G

1999-12-01

In the year of 1805, Goethe almost died of urosepsis. His urological problems were not diseases arising from full health but a new variation in a life accompanied by illnesses. Some sources date the first colics he experienced to the year 1795 and others say 1805. The most dramatic period in the course of his illness was in February, when he suffered from fever of such an extent that one could speak of urosepsis. Recovery took place slowly and was accompanied by minor relapses. Nothing about this is written down in his work. On the advice of his doctors, Goethe undertook a cure in Lauchstädt in July and August. The report of his consultant, Professor Johann Christian Reil, on his problems in the field of urology remained undiscovered until 1937. Professor Reil recommended treatment with thermae carolinae, aqua calcis, soap soda crystallisata, herbae subastringentes, and uva ursi, among other measures. With increasing age, Goethe's colics disappeared. The passing of a stone has never been described. Whereas Goethe hinted about medical problem other than those reported herein, the urological problems discussed in this article were left unmentioned. Nonetheless, literature that deals with Goethe's diseases is interesting from the aspect of both the history of medicine and the history of culture.

Assessing the ability of isotope-enabled General Circulation Models to simulate the variability of Iceland water vapor isotopic composition

NASA Astrophysics Data System (ADS)

Erla Sveinbjornsdottir, Arny; Steen-Larsen, Hans Christian; Jonsson, Thorsteinn; Ritter, Francois; Riser, Camilla; Messon-Delmotte, Valerie; Bonne, Jean Louis; Dahl-Jensen, Dorthe

2014-05-01

During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (Los Gatos Research analyzer) in a lighthouse on the Southwest coast of Iceland (63.83°N, 21.47°W). Despite initial significant problems with volcanic ash, high wind, and attack of sea gulls, the system has been continuously operational since the end of 2011 with limited down time. The system automatically performs calibration every 2 hours, which results in high accuracy and precision allowing for analysis of the second order parameter, d-excess, in the water vapor. We find a strong linear relationship between d-excess and local relative humidity (RH) when normalized to SST. The observed slope of approximately -45 o/oo/% is similar to theoretical predictions by Merlivat and Jouzel [1979] for smooth surface, but the calculated intercept is significant lower than predicted. Despite this good linear agreement with theoretical calculations, mismatches arise between the simulated seasonal cycle of water vapour isotopic composition using LMDZiso GCM nudged to large-scale winds from atmospheric analyses, and our data. The GCM is not able to capture seasonal variations in local RH, nor seasonal variations in d-excess. Based on daily data, the performance of LMDZiso to resolve day-to-day variability is measured based on the strength of the correlation coefficient between observations and model outputs. This correlation coefficient reaches ~0.8 for surface absolute humidity, but decreases to ~0.6 for δD and ~0.45 d-excess. Moreover, the magnitude of day-to-day humidity variations is also underestimated by LMDZiso, which can explain the underestimated magnitude of isotopic depletion. Finally, the simulated and observed d-excess vs. RH has similar slopes. We conclude that the under-estimation of d-excess variability may partly arise from the poor performance of the humidity simulations.

50 CFR 600.335 - National Standard 6-Variations and Contingencies.

Code of Federal Regulations, 2011 CFR

2011-10-01

... management terms, variations arise from biological, social, and economic occurrences, as well as from fishing... uncertainties. Social changes could involve increases or decreases in recreational fishing, or the movement of... to regulate or influence such activities; propose recommendations that the Secretary will convey to...

Eliminating Unpredictable Variation through Iterated Learning

ERIC Educational Resources Information Center

Smith, Kenny; Wonnacott, Elizabeth

2010-01-01

Human languages may be shaped not only by the (individual psychological) processes of language acquisition, but also by population-level processes arising from repeated language learning and use. One prevalent feature of natural languages is that they avoid unpredictable variation. The current work explores whether linguistic predictability might…

Current status: Animal models of nausea

NASA Technical Reports Server (NTRS)

Fox, Robert A.

1991-01-01

The advantages, and possible benefits of a valid, reliable animal model for nausea are discussed, and difficulties inherent to the development of a model are considered. A principle problem for developing models arises because nausea is a subjective sensation that can be identified only in humans. Several putative measures of nausea in animals are considered, with more detailed consideration directed to variation in cardiac rate, levels of vasopressin, and conditioned taste aversion. Demonstration that putative measures are associated with reported nausea in humans is proposed as a requirement for validating measures to be used in animal models. The necessity for a 'real-time' measure of nausea is proposed as an important factor for future research; and the need for improved understanding of the neuroanatomy underlying the emetic syndrome is discussed.

Computationally efficient method for optical simulation of solar cells and their applications

NASA Astrophysics Data System (ADS)

Semenikhin, I.; Zanuccoli, M.; Fiegna, C.; Vyurkov, V.; Sangiorgi, E.

2013-01-01

This paper presents two novel implementations of the Differential method to solve the Maxwell equations in nanostructured optoelectronic solid state devices. The first proposed implementation is based on an improved and computationally efficient T-matrix formulation that adopts multiple-precision arithmetic to tackle the numerical instability problem which arises due to evanescent modes. The second implementation adopts the iterative approach that allows to achieve low computational complexity O(N logN) or better. The proposed algorithms may work with structures with arbitrary spatial variation of the permittivity. The developed two-dimensional numerical simulator is applied to analyze the dependence of the absorption characteristics of a thin silicon slab on the morphology of the front interface and on the angle of incidence of the radiation with respect to the device surface.

Emergent Fermi Sea in A System of Interacting Bosons

NASA Astrophysics Data System (ADS)

Wu, Yinghai; Jain, Jainendra

2015-03-01

An understanding of the possible ways in which interactions can produce fundamentally new emergent many-body states is a central problem of condensed matter physics. We ask if a Fermi sea can arise in a system of bosons subject to contact interaction. Based on exact diagonalization studies and variational wave functions, we predict that such a state is likely to occur when a system of two-component bosons in two dimensions, interacting via a species independent contact interaction, is exposed to a synthetic magnetic field of strength that corresponds to a filling factor of unity. The bosons each bind a single vortex as a result of the repulsive interaction, and these fermionic bound states, namely composite fermions, form a spin-singlet Fermi sea. Financial support from the DOE under Grant No. DE-SC0005042.

Modelling of multi-vortex convection of fine alloying components in the molten pool under the laser radiation

NASA Astrophysics Data System (ADS)

Gurin, A. M.; Kovalev, O. B.

2013-06-01

The work is devoted to the mathematical modelling and numerical solution of the problems of conjugate micro-convection, which arises under the laser radiation action in the metal melt with surface-active refractory disperse components added for the modification, hardening, and doping of the treated surface. A multi-vortex structure of the melt flow has been obtained, the number of vortices in which depends on the surface tension variation, on the temperature and power of laser radiation. Special attention is paid to the numerical modelling of the behavior in the melt of the substrate of disperse admixture consisting of the tungsten carbide particles. The role of microconvection in the distribution of powder particles in the surface layer of the substrate after its cooling is shown.

Electric-field noise from carbon-adatom diffusion on a Au(110) surface: First-principles calculations and experiments

NASA Astrophysics Data System (ADS)

Kim, E.; Safavi-Naini, A.; Hite, D. A.; McKay, K. S.; Pappas, D. P.; Weck, P. F.; Sadeghpour, H. R.

2017-03-01

The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. In this work, we investigate the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by density functional theory, based on detailed scanning probe microscopy, how the carbon adatom diffusion on the gold surface changes the energy landscape and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, predicts a noise spectrum, in accordance with the measured values.

Quenching rate for a nonlocal problem arising in the micro-electro mechanical system

NASA Astrophysics Data System (ADS)

Guo, Jong-Shenq; Hu, Bei

2018-03-01

In this paper, we study the quenching rate of the solution for a nonlocal parabolic problem which arises in the study of the micro-electro mechanical system. This question is equivalent to the stabilization of the solution to the transformed problem in self-similar variables. First, some a priori estimates are provided. In order to construct a Lyapunov function, due to the lack of time monotonicity property, we then derive some very useful and challenging estimates by a delicate analysis. Finally, with this Lyapunov function, we prove that the quenching rate is self-similar which is the same as the problem without the nonlocal term, except the constant limit depends on the solution itself.

Green's formula and variational principles for cosmic-ray transport with application to rotating and shearing flows

NASA Technical Reports Server (NTRS)

Webb, G. M.; Jokipii, J. R.; Morfill, G. E.

1994-01-01

Green's theorem and Green's formula for the diffusive cosmic-ray transport equation in relativistic flows are derived. Green's formula gives the solution of the transport equation in terms of the Green's function of the adjoint transport equation, and in terms of distributed sources throughout the region R of interest, plus terms involving the particle intensity and streaming on the boundary. The adjoint transport equation describes the time-reversed particle transport. An Euler-Lagrange variational principle is then obtained for both the mean scattering frame distribution function f, and its adjoint f(dagger). Variations of the variational functional with respect to f(dagger) yield the transport equation, whereas variations of f yield the adjoint transport equation. The variational principle, when combined with Noether's theorem, yields the conservation law associated with Green's theorem. An investigation of the transport equation for steady, azimuthal, rotating flows suggests the introduction of a new independent variable H to replace the comoving frame momentum variable p'. For the case of rigid rotating flows, H is conserved and is shown to be analogous to the Hamiltonian for a bead on a rigidly rotating wire. The variable H corresponds to a balance between the centrifugal force and the particle inertia in the rotating frame. The physical interpretation of H includes a discussion of nonrelativistic and special relativistic rotating flows as well as the cases of aziuthal, differentially rotating flows about Schwarzs-child and Kerr black holes. Green's formula is then applied to the problem of the acceleration of ultra-high-energy cosmic rays by galactic rotation. The model for galactic rotation assumes an angular velocity law Omega = Omega(sub 0)(omega(sub 0)/omega), where omega denotes radial distance from the axis of rotation. Green's functions for the galactic rotation problem are used to investigate the spectrum of accelerated particles arising from monoenergetic and truncated power-law sources. We conclude that it is possible to accelerate particles beyond the knee by galactic rotation, but not in sufficient number to adequately explain the observed spectrum.

Statistical issues in reporting quality data: small samples and casemix variation.

PubMed

Zaslavsky, A M

2001-12-01

To present two key statistical issues that arise in analysis and reporting of quality data. Casemix variation is relevant to quality reporting when the units being measured have differing distributions of patient characteristics that also affect the quality outcome. When this is the case, adjustment using stratification or regression may be appropriate. Such adjustments may be controversial when the patient characteristic does not have an obvious relationship to the outcome. Stratified reporting poses problems for sample size and reporting format, but may be useful when casemix effects vary across units. Although there are no absolute standards of reliability, high reliabilities (interunit F > or = 10 or reliability > or = 0.9) are desirable for distinguishing above- and below-average units. When small or unequal sample sizes complicate reporting, precision may be improved using indirect estimation techniques that incorporate auxiliary information, and 'shrinkage' estimation can help to summarize the strength of evidence about units with small samples. With broader understanding of casemix adjustment and methods for analyzing small samples, quality data can be analysed and reported more accurately.

Site occupancy models with heterogeneous detection probabilities

USGS Publications Warehouse

Royle, J. Andrew

2006-01-01

Models for estimating the probability of occurrence of a species in the presence of imperfect detection are important in many ecological disciplines. In these ?site occupancy? models, the possibility of heterogeneity in detection probabilities among sites must be considered because variation in abundance (and other factors) among sampled sites induces variation in detection probability (p). In this article, I develop occurrence probability models that allow for heterogeneous detection probabilities by considering several common classes of mixture distributions for p. For any mixing distribution, the likelihood has the general form of a zero-inflated binomial mixture for which inference based upon integrated likelihood is straightforward. A recent paper by Link (2003, Biometrics 59, 1123?1130) demonstrates that in closed population models used for estimating population size, different classes of mixture distributions are indistinguishable from data, yet can produce very different inferences about population size. I demonstrate that this problem can also arise in models for estimating site occupancy in the presence of heterogeneous detection probabilities. The implications of this are discussed in the context of an application to avian survey data and the development of animal monitoring programs.

Golden Ratio in a Coupled-Oscillator Problem

ERIC Educational Resources Information Center

Moorman, Crystal M.; Goff, John Eric

2007-01-01

The golden ratio appears in a classical mechanics coupled-oscillator problem that many undergraduates may not solve. Once the symmetry is broken in a more standard problem, the golden ratio appears. Several student exercises arise from the problem considered in this paper.

Early Origins of Autism Comorbidity: Neuropsychiatric Traits Correlated in Childhood Are Independent in Infancy.

PubMed

Hawks, Zoë W; Marrus, Natasha; Glowinski, Anne L; Constantino, John N

2018-03-16

Previous research has suggested that behavioral comorbidity is the rule rather than the exception in autism. The present study aimed to trace the respective origins of autistic and general psychopathologic traits-and their association-to infancy. Measurements of autistic traits and early liability for general psychopathology were assessed in 314 twins at 18 months, ascertained from the general population using birth records. 222 twins were re-evaluated at 36 months. Standardized ratings of variation in social communication at 18 months were highly heritable and strongly predicted autistic trait scores at 36 months. These early indices of autistic liability were independent from contemporaneous ratings of behavior problems on the Brief Infant-Toddler Social and Emotional Assessment (which were substantially environmentally-influenced), and did not meaningfully predict internalizing or externalizing scores on the Achenbach Scales of Empirically Based Assessment at 36 months. In this general population infant twin study, variation in social communication was independent from variation in other domains of general psychopathology, and exhibited a distinct genetic structure. The commonly-observed comorbidity of specific psychiatric syndromes with autism may arise from subsequent interactions between autistic liability and independent susceptibilities to other psychopathologic traits, suggesting opportunities for preventive amelioration of outcomes of these interactions over the course of development.

Calculation of Rayleigh type sums for zeros of the equation arising in spectral problem

NASA Astrophysics Data System (ADS)

Kostin, A. B.; Sherstyukov, V. B.

2017-12-01

For zeros of the equation (arising in the oblique derivative problem) μ J n ‧ ( μ ) cos α + i n J n ( μ ) sin α = 0 , μ ∈ ℂ , with parameters n ∈ ℤ, α ∈ [-π/2, π/2] and the Bessel function Jn (μ) special summation relationships are proved. The obtained results are consistent with the theory of well-known Rayleigh sums calculating by zeros of the Bessel function.

Inhomogeneous ensembles of radical pairs in chemical compasses

PubMed Central

Procopio, Maria; Ritz, Thorsten

2016-01-01

The biophysical basis for the ability of animals to detect the geomagnetic field and to use it for finding directions remains a mystery of sensory biology. One much debated hypothesis suggests that an ensemble of specialized light-induced radical pair reactions can provide the primary signal for a magnetic compass sensor. The question arises what features of such a radical pair ensemble could be optimized by evolution so as to improve the detection of the direction of weak magnetic fields. Here, we focus on the overlooked aspect of the noise arising from inhomogeneity of copies of biomolecules in a realistic biological environment. Such inhomogeneity leads to variations of the radical pair parameters, thereby deteriorating the signal arising from an ensemble and providing a source of noise. We investigate the effect of variations in hyperfine interactions between different copies of simple radical pairs on the directional response of a compass system. We find that the choice of radical pair parameters greatly influences how strongly the directional response of an ensemble is affected by inhomogeneity. PMID:27804956

Inhomogeneous ensembles of radical pairs in chemical compasses

NASA Astrophysics Data System (ADS)

Procopio, Maria; Ritz, Thorsten

2016-11-01

The biophysical basis for the ability of animals to detect the geomagnetic field and to use it for finding directions remains a mystery of sensory biology. One much debated hypothesis suggests that an ensemble of specialized light-induced radical pair reactions can provide the primary signal for a magnetic compass sensor. The question arises what features of such a radical pair ensemble could be optimized by evolution so as to improve the detection of the direction of weak magnetic fields. Here, we focus on the overlooked aspect of the noise arising from inhomogeneity of copies of biomolecules in a realistic biological environment. Such inhomogeneity leads to variations of the radical pair parameters, thereby deteriorating the signal arising from an ensemble and providing a source of noise. We investigate the effect of variations in hyperfine interactions between different copies of simple radical pairs on the directional response of a compass system. We find that the choice of radical pair parameters greatly influences how strongly the directional response of an ensemble is affected by inhomogeneity.

The fluid dynamic approach to equidistribution methods for grid generation and adaptation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delzanno, Gian Luca; Finn, John M

2009-01-01

The equidistribution methods based on L{sub p} Monge-Kantorovich optimization [Finn and Delzanno, submitted to SISC, 2009] and on the deformation [Moser, 1965; Dacorogna and Moser, 1990, Liao and Anderson, 1992] method are analyzed primarily in the context of grid generation. It is shown that the first class of methods can be obtained from a fluid dynamic formulation based on time-dependent equations for the mass density and the momentum density, arising from a variational principle. In this context, deformation methods arise from a fluid formulation by making a specific assumption on the time evolution of the density (but with some degreemore » of freedom for the momentum density). In general, deformation methods do not arise from a variational principle. However, it is possible to prescribe an optimal deformation method, related to L{sub 1} Monge-Kantorovich optimization, by making a further assumption on the momentum density. Some applications of the L{sub p} fluid dynamic formulation to imaging are also explored.« less

Variation in the Helical Structure of Native Collagen

DTIC Science & Technology

2014-02-24

unsampled molecular transform of the sample (non-crystalline diffraction arising from the helical symmetry), these patterns also contain Bragg peaks...tissues may be treated as analogous to that from a single macromolecular crystal. Except that it arises from many fibrils within the sample , giving rise...density maps, constructed from experimentally determined phases and observed amplitudes, showed good agreement. The observed diffraction and the simulated

Common Methodological Problems in Research on the Addictions.

ERIC Educational Resources Information Center

Nathan, Peter E.; Lansky, David

1978-01-01

Identifies common problems in research on the addictions and offers suggestions for remediating these methodological problems. The addictions considered include alcoholism and drug dependencies. Problems considered are those arising from inadequate, incomplete, or biased reviews of relevant literatures and methodological shortcomings of subject…

A problem with problem solving: motivational traits, but not cognition, predict success on novel operant foraging tasks.

PubMed

van Horik, Jayden O; Madden, Joah R

2016-04-01

Rates of innovative foraging behaviours and success on problem-solving tasks are often used to assay differences in cognition, both within and across species. Yet the cognitive features of some problem-solving tasks can be unclear. As such, explanations that attribute cognitive mechanisms to individual variation in problem-solving performance have revealed conflicting results. We investigated individual consistency in problem-solving performances in captive-reared pheasant chicks, Phasianus colchicus , and addressed whether success depends on cognitive processes, such as trial-and-error associative learning, or whether performances may be driven solely via noncognitive motivational mechanisms, revealed through subjects' willingness to approach, engage with and persist in their interactions with an apparatus, or via physiological traits such as body condition. While subjects' participation and success were consistent within the same problems and across similar tasks, their performances were inconsistent across different types of task. Moreover, subjects' latencies to approach each test apparatus and their attempts to access the reward were not repeatable across trials. Successful individuals did not improve their performances with experience, nor were they consistent in their techniques in repeated presentations of a task. However, individuals that were highly motivated to enter the experimental chamber were more likely to participate. Successful individuals were also faster to approach each test apparatus and more persistent in their attempts to solve the tasks than unsuccessful individuals. Our findings therefore suggest that individual differences in problem-solving success can arise from inherent motivational differences alone and hence be achieved without inferring more complex cognitive processes.

A problem with problem solving: motivational traits, but not cognition, predict success on novel operant foraging tasks

PubMed Central

van Horik, Jayden O.; Madden, Joah R.

2016-01-01

Rates of innovative foraging behaviours and success on problem-solving tasks are often used to assay differences in cognition, both within and across species. Yet the cognitive features of some problem-solving tasks can be unclear. As such, explanations that attribute cognitive mechanisms to individual variation in problem-solving performance have revealed conflicting results. We investigated individual consistency in problem-solving performances in captive-reared pheasant chicks, Phasianus colchicus, and addressed whether success depends on cognitive processes, such as trial-and-error associative learning, or whether performances may be driven solely via noncognitive motivational mechanisms, revealed through subjects' willingness to approach, engage with and persist in their interactions with an apparatus, or via physiological traits such as body condition. While subjects' participation and success were consistent within the same problems and across similar tasks, their performances were inconsistent across different types of task. Moreover, subjects' latencies to approach each test apparatus and their attempts to access the reward were not repeatable across trials. Successful individuals did not improve their performances with experience, nor were they consistent in their techniques in repeated presentations of a task. However, individuals that were highly motivated to enter the experimental chamber were more likely to participate. Successful individuals were also faster to approach each test apparatus and more persistent in their attempts to solve the tasks than unsuccessful individuals. Our findings therefore suggest that individual differences in problem-solving success can arise from inherent motivational differences alone and hence be achieved without inferring more complex cognitive processes. PMID:27122637

Why Bioethics Needs a Disability Moral Psychology.

PubMed

Stramondo, Joseph A

2016-05-01

The deeply entrenched, sometimes heated conflict between the disability movement and the profession of bioethics is well known and well documented. Critiques of prenatal diagnosis and selective abortion are probably the most salient and most sophisticated of disability studies scholars' engagements with bioethics, but there are many other topics over which disability activists and scholars have encountered the field of bioethics in an adversarial way, including health care rationing, growth-attenuation interventions, assisted reproduction technology, and physician-assisted suicide. The tension between the analyses of the disabilities studies scholars and mainstream bioethics is not merely a conflict between two insular political groups, however; it is, rather, also an encounter between those who have experienced disability and those who have not. This paper explores that idea. I maintain that it is a mistake to think of this conflict as arising just from a difference in ideology or political commitments because it represents a much deeper difference-one rooted in variations in how human beings perceive and reason about moral problems. These are what I will refer to as variations of moral psychology. The lived experiences of disability produce variations in moral psychology that are at the heart of the moral conflict between the disability movement and mainstream bioethics. I will illustrate this point by exploring how the disability movement and mainstream bioethics come into conflict when perceiving and analyzing the moral problem of physician-assisted suicide via the lens of the principle of respect for autonomy. To reconcile its contemporary and historical conflict with the disability movement, the field of bioethics must engage with and fully consider the two groups' differences in moral perception and reasoning, not just the explicit moral and political arguments of the disability movement. © 2016 The Hastings Center.

Low thrust propulsion system effects on communication satellites.

NASA Technical Reports Server (NTRS)

Hall, D. F.; Lyon, W. C.

1972-01-01

Choice of type and placement of thrusters on spacecraft (s/c) should include consideration of their effects on other subsystems. Models are presented of the exhaust plumes of mercury, cesium, colloid, hydrazine, ammonia, and Teflon rockets. Effects arising from plume impingement on s/c surfaces, radio frequency interference, optical interference, and earth environmental contamination are discussed. Some constraints arise in the placement of mercury, cesium, and Teflon thrusters. Few problems exist with other thruster types, nor is earth contamination a problem.

The use of Lanczos's method to solve the large generalized symmetric definite eigenvalue problem

NASA Technical Reports Server (NTRS)

Jones, Mark T.; Patrick, Merrell L.

1989-01-01

The generalized eigenvalue problem, Kx = Lambda Mx, is of significant practical importance, especially in structural enginering where it arises as the vibration and buckling problem. A new algorithm, LANZ, based on Lanczos's method is developed. LANZ uses a technique called dynamic shifting to improve the efficiency and reliability of the Lanczos algorithm. A new algorithm for solving the tridiagonal matrices that arise when using Lanczos's method is described. A modification of Parlett and Scott's selective orthogonalization algorithm is proposed. Results from an implementation of LANZ on a Convex C-220 show it to be superior to a subspace iteration code.

Biological and Cultural Diversity: The Legacy of Darwin for Development.

ERIC Educational Resources Information Center

Scarr, Sandra

1993-01-01

Posits that an evolutionary perspective can unite the study of the typical development for and individual variation within a species and that environments within the normal range for a species are required for species-normal development. Individual differences in children reared in normal environments arise primarily from genetic variation and…

Learning Low-Rank Class-Specific Dictionary and Sparse Intra-Class Variant Dictionary for Face Recognition.

PubMed

Tang, Xin; Feng, Guo-Can; Li, Xiao-Xin; Cai, Jia-Xin

2015-01-01

Face recognition is challenging especially when the images from different persons are similar to each other due to variations in illumination, expression, and occlusion. If we have sufficient training images of each person which can span the facial variations of that person under testing conditions, sparse representation based classification (SRC) achieves very promising results. However, in many applications, face recognition often encounters the small sample size problem arising from the small number of available training images for each person. In this paper, we present a novel face recognition framework by utilizing low-rank and sparse error matrix decomposition, and sparse coding techniques (LRSE+SC). Firstly, the low-rank matrix recovery technique is applied to decompose the face images per class into a low-rank matrix and a sparse error matrix. The low-rank matrix of each individual is a class-specific dictionary and it captures the discriminative feature of this individual. The sparse error matrix represents the intra-class variations, such as illumination, expression changes. Secondly, we combine the low-rank part (representative basis) of each person into a supervised dictionary and integrate all the sparse error matrix of each individual into a within-individual variant dictionary which can be applied to represent the possible variations between the testing and training images. Then these two dictionaries are used to code the query image. The within-individual variant dictionary can be shared by all the subjects and only contribute to explain the lighting conditions, expressions, and occlusions of the query image rather than discrimination. At last, a reconstruction-based scheme is adopted for face recognition. Since the within-individual dictionary is introduced, LRSE+SC can handle the problem of the corrupted training data and the situation that not all subjects have enough samples for training. Experimental results show that our method achieves the state-of-the-art results on AR, FERET, FRGC and LFW databases.

Learning Low-Rank Class-Specific Dictionary and Sparse Intra-Class Variant Dictionary for Face Recognition

PubMed Central

Tang, Xin; Feng, Guo-can; Li, Xiao-xin; Cai, Jia-xin

2015-01-01

Face recognition is challenging especially when the images from different persons are similar to each other due to variations in illumination, expression, and occlusion. If we have sufficient training images of each person which can span the facial variations of that person under testing conditions, sparse representation based classification (SRC) achieves very promising results. However, in many applications, face recognition often encounters the small sample size problem arising from the small number of available training images for each person. In this paper, we present a novel face recognition framework by utilizing low-rank and sparse error matrix decomposition, and sparse coding techniques (LRSE+SC). Firstly, the low-rank matrix recovery technique is applied to decompose the face images per class into a low-rank matrix and a sparse error matrix. The low-rank matrix of each individual is a class-specific dictionary and it captures the discriminative feature of this individual. The sparse error matrix represents the intra-class variations, such as illumination, expression changes. Secondly, we combine the low-rank part (representative basis) of each person into a supervised dictionary and integrate all the sparse error matrix of each individual into a within-individual variant dictionary which can be applied to represent the possible variations between the testing and training images. Then these two dictionaries are used to code the query image. The within-individual variant dictionary can be shared by all the subjects and only contribute to explain the lighting conditions, expressions, and occlusions of the query image rather than discrimination. At last, a reconstruction-based scheme is adopted for face recognition. Since the within-individual dictionary is introduced, LRSE+SC can handle the problem of the corrupted training data and the situation that not all subjects have enough samples for training. Experimental results show that our method achieves the state-of-the-art results on AR, FERET, FRGC and LFW databases. PMID:26571112

Eigenmode computation of cavities with perturbed geometry using matrix perturbation methods applied on generalized eigenvalue problems

NASA Astrophysics Data System (ADS)

Gorgizadeh, Shahnam; Flisgen, Thomas; van Rienen, Ursula

2018-07-01

Generalized eigenvalue problems are standard problems in computational sciences. They may arise in electromagnetic fields from the discretization of the Helmholtz equation by for example the finite element method (FEM). Geometrical perturbations of the structure under concern lead to a new generalized eigenvalue problems with different system matrices. Geometrical perturbations may arise by manufacturing tolerances, harsh operating conditions or during shape optimization. Directly solving the eigenvalue problem for each perturbation is computationally costly. The perturbed eigenpairs can be approximated using eigenpair derivatives. Two common approaches for the calculation of eigenpair derivatives, namely modal superposition method and direct algebraic methods, are discussed in this paper. Based on the direct algebraic methods an iterative algorithm is developed for efficiently calculating the eigenvalues and eigenvectors of the perturbed geometry from the eigenvalues and eigenvectors of the unperturbed geometry.

The Riemann-Hilbert problem for nonsymmetric systems

NASA Astrophysics Data System (ADS)

Greenberg, W.; Zweifel, P. F.; Paveri-Fontana, S.

1991-12-01

A comparison of the Riemann-Hilbert problem and the Wiener-Hopf factorization problem arising in the solution of half-space singular integral equations is presented. Emphasis is on the factorization of functions lacking the reflection symmetry usual in transport theory.

Robustness-Based Design Optimization Under Data Uncertainty

NASA Technical Reports Server (NTRS)

Zaman, Kais; McDonald, Mark; Mahadevan, Sankaran; Green, Lawrence

2010-01-01

This paper proposes formulations and algorithms for design optimization under both aleatory (i.e., natural or physical variability) and epistemic uncertainty (i.e., imprecise probabilistic information), from the perspective of system robustness. The proposed formulations deal with epistemic uncertainty arising from both sparse and interval data without any assumption about the probability distributions of the random variables. A decoupled approach is proposed in this paper to un-nest the robustness-based design from the analysis of non-design epistemic variables to achieve computational efficiency. The proposed methods are illustrated for the upper stage design problem of a two-stage-to-orbit (TSTO) vehicle, where the information on the random design inputs are only available as sparse point and/or interval data. As collecting more data reduces uncertainty but increases cost, the effect of sample size on the optimality and robustness of the solution is also studied. A method is developed to determine the optimal sample size for sparse point data that leads to the solutions of the design problem that are least sensitive to variations in the input random variables.

H(infinity)/H(2)/Kalman filtering of linear dynamical systems via variational techniques with applications to target tracking

NASA Astrophysics Data System (ADS)

Rawicz, Paul Lawrence

In this thesis, the similarities between the structure of the H infinity, H2, and Kalman filters are examined. The filters used in this examination have been derived through duality to the full information controller. In addition, a direct variation of parameters derivation of the Hinfinity filter is presented for both continuous and discrete time (staler case). Direct and controller dual derivations using differential games exist in the literature and also employ variational techniques. Using a variational, rather than a differential games, viewpoint has resulted in a simple relationship between the Riccati equations that arise from the derivation and the results of the Bounded Real Lemma. This same relation has previously been found in the literature and used to relate the Riccati inequality for linear systems to the Hamilton Jacobi inequality for nonlinear systems when implementing the Hinfinity controller. The Hinfinity, H2, and Kalman filters are applied to the two-state target tracking problem. In continuous time, closed form analytic expressions for the trackers and their performance are determined. To evaluate the trackers using a neutral, realistic, criterion, the probability of target escape is developed. That is, the probability that the target position error will be such that the target is outside the radar beam width resulting in a loss of measurement. In discrete time, a numerical example, using the probability of target escape, is presented to illustrate the differences in tracker performance.

Ethical analysis in public health.

PubMed

Roberts, Marc J; Reich, Michael R

2002-03-23

Public-health regularly encounters serious ethical dilemmas, such as rationing scarce resources, influencing individuals to change their behaviour, and limiting freedom to diminish disease transmission. Yet unlike medical ethics, there is no agreed-upon framework for analysing these difficulties. We offer such a framework. It distinguishes three philosophical views, often invoked in public-health discourse: positions based on outcomes (utilitarianism), positions focused on rights and opportunities (liberalism), and views that emphasise character and virtue (communitarianism). We explore critical variations within each approach, and identify practical problems that arise in addressing the ethical dimensions of health policy. We conclude by examining challenges posed by the feminist argument of ethics-of-care and by postmodern views about the nature of ethics. Health professionals need enhanced skills in applied philosophy to improve the coherence, transparency, and quality of public deliberations over ethical issues inherent in health policy.

Recent progress and challenges in population genetics of polyploid organisms: an overview of current state-of-the-art molecular and statistical tools.

PubMed

Dufresne, France; Stift, Marc; Vergilino, Roland; Mable, Barbara K

2014-01-01

Despite the importance of polyploidy and the increasing availability of new genomic data, there remain important gaps in our knowledge of polyploid population genetics. These gaps arise from the complex nature of polyploid data (e.g. multiple alleles and loci, mixed inheritance patterns, association between ploidy and mating system variation). Furthermore, many of the standard tools for population genetics that have been developed for diploids are often not feasible for polyploids. This review aims to provide an overview of the state-of-the-art in polyploid population genetics and to identify the main areas where further development of molecular techniques and statistical theory is required. We review commonly used molecular tools (amplified fragment length polymorphism, microsatellites, Sanger sequencing, next-generation sequencing and derived technologies) and their challenges associated with their use in polyploid populations: that is, allele dosage determination, null alleles, difficulty of distinguishing orthologues from paralogues and copy number variation. In addition, we review the approaches that have been used for population genetic analysis in polyploids and their specific problems. These problems are in most cases directly associated with dosage uncertainty and the problem of inferring allele frequencies and assumptions regarding inheritance. This leads us to conclude that for advancing the field of polyploid population genetics, most priority should be given to development of new molecular approaches that allow efficient dosage determination, and to further development of analytical approaches to circumvent dosage uncertainty and to accommodate 'flexible' modes of inheritance. In addition, there is a need for more simulation-based studies that test what kinds of biases could result from both existing and novel approaches. © 2013 John Wiley & Sons Ltd.

A Comparison of Solver Performance for Complex Gastric Electrophysiology Models

PubMed Central

Sathar, Shameer; Cheng, Leo K.; Trew, Mark L.

2016-01-01

Computational techniques for solving systems of equations arising in gastric electrophysiology have not been studied for efficient solution process. We present a computationally challenging problem of simulating gastric electrophysiology in anatomically realistic stomach geometries with multiple intracellular and extracellular domains. The multiscale nature of the problem and mesh resolution required to capture geometric and functional features necessitates efficient solution methods if the problem is to be tractable. In this study, we investigated and compared several parallel preconditioners for the linear systems arising from tetrahedral discretisation of electrically isotropic and anisotropic problems, with and without stimuli. The results showed that the isotropic problem was computationally less challenging than the anisotropic problem and that the application of extracellular stimuli increased workload considerably. Preconditioning based on block Jacobi and algebraic multigrid solvers were found to have the best overall solution times and least iteration counts, respectively. The algebraic multigrid preconditioner would be expected to perform better on large problems. PMID:26736543

Transcriptional regulation of metabolism in disease: From transcription factors to epigenetics

PubMed Central

2018-01-01

Every cell in an individual has largely the same genomic sequence and yet cells in different tissues can present widely different phenotypes. This variation arises because each cell expresses a specific subset of genomic instructions. Control over which instructions, or genes, are expressed is largely controlled by transcriptional regulatory pathways. Each cell must assimilate a huge amount of environmental input, and thus it is of no surprise that transcription is regulated by many intertwining mechanisms. This large regulatory landscape means there are ample possibilities for problems to arise, which in a medical context means the development of disease states. Metabolism within the cell, and more broadly, affects and is affected by transcriptional regulation. Metabolism can therefore contribute to improper transcriptional programming, or pathogenic metabolism can be the result of transcriptional dysregulation. Here, we discuss the established and emerging mechanisms for controling transcription and how they affect metabolism in the context of pathogenesis. Cis- and trans-regulatory elements, microRNA and epigenetic mechanisms such as DNA and histone methylation, all have input into what genes are transcribed. Each has also been implicated in diseases such as metabolic syndrome, various forms of diabetes, and cancer. In this review, we discuss the current understanding of these areas and highlight some natural models that may inspire future therapeutics. PMID:29922517

Problem-Solving during Shared Reading at Kindergarten

ERIC Educational Resources Information Center

Gosen, Myrte N.; Berenst, Jan; de Glopper, Kees

2015-01-01

This paper reports on a conversation analytic study of problem-solving interactions during shared reading at three kindergartens in the Netherlands. It illustrates how teachers and pupils discuss book characters' problems that arise in the events in the picture books. A close analysis of the data demonstrates that problem-solving interactions do…

Transnational Environmental Problems--The United States, Canada, Mexico.

ERIC Educational Resources Information Center

Wilcher, Marshall E.

1983-01-01

Examines problems associated with transboundary environmental pollution, focusing on problems arising between the United States and Mexico and between the United States and Canada. Also discusses new organizational forms developed to bring transboundary issues to a higher policy-making level. (JN)

An investigation into waste charges in Ireland, with emphasis on public acceptability.

PubMed

Dunne, Louise; Convery, Frank J; Gallagher, Louise

2008-12-01

There are 34 local authorities in Ireland with legal responsibility to deal with waste arising in their jurisdictions. In 2003 the National government introduced legislation that allows local authorities to recover the costs of waste collection and disposal, and to do so by 'executive function', i.e., not requiring support or agreement by the relevant local political representatives. The year 2005 was set as the date by which implementation of a pay by weight or volume was to be introduced. The local authorities were given autonomy as to how they addressed this challenge, so we have - in theory - 34 potentially different experiences from which to learn. This paper examines the pay-as-you-throw (PAYT) waste system in Ireland as it develops in line with EU and National demands, with a view to assessing economic and environmental efficiency. All local authorities were surveyed and thirteen responded. While this only represents about 38% of the total number, it includes jurisdictions that contribute in total more than 50% of waste arising. Key figures in the policy and business community were also interviewed in order to identify how the charging schemes were implemented, and to what effect. These insights and parallel investigations are used to review the potential for problems regarding public acceptability of environmental taxes and examine the evidence for economic and environmental efficiency, as well as problem areas, using data from each of the responding local authority jurisdictions. Concentrating on the incentives and drivers across households, municipalities and private waste contractors, the variations in charging system, annual charges and landfill charges are compared where information was available. The various jurisdictions are also examined in terms of relative successes and problems encountered in the transition from fixed charge or free waste collection to PAYT systems. The Irish situation is placed in the context of the international literature on PAYT, the growing waste crisis, environmental attitudes vs. behaviours, and the acceptability of environmental taxes generally.

Fair Inference on Outcomes

PubMed Central

Nabi, Razieh; Shpitser, Ilya

2017-01-01

In this paper, we consider the problem of fair statistical inference involving outcome variables. Examples include classification and regression problems, and estimating treatment effects in randomized trials or observational data. The issue of fairness arises in such problems where some covariates or treatments are “sensitive,” in the sense of having potential of creating discrimination. In this paper, we argue that the presence of discrimination can be formalized in a sensible way as the presence of an effect of a sensitive covariate on the outcome along certain causal pathways, a view which generalizes (Pearl 2009). A fair outcome model can then be learned by solving a constrained optimization problem. We discuss a number of complications that arise in classical statistical inference due to this view and provide workarounds based on recent work in causal and semi-parametric inference.

Distinctions between fraud, bias, errors, misunderstanding, and incompetence.

PubMed

DeMets, D L

1997-12-01

Randomized clinical trials are challenging not only in their design and analysis, but in their conduct as well. Despite the best intentions and efforts, problems often arise in the conduct of trials, including errors, misunderstandings, and bias. In some instances, key players in a trial may discover that they are not able or competent to meet requirements of the study. In a few cases, fraudulent activity occurs. While none of these problems is desirable, randomized clinical trials are usually found sufficiently robust by many key individuals to produce valid results. Other problems are not tolerable. Confusion may arise among scientists, scientific and lay press, and the public about the distinctions between these areas and their implications. We shall try to define these problems and illustrate their impact through a series of examples.

A non-local free boundary problem arising in a theory of financial bubbles

PubMed Central

Berestycki, Henri; Monneau, Regis; Scheinkman, José A.

2014-01-01

We consider an evolution non-local free boundary problem that arises in the modelling of speculative bubbles. The solution of the model is the speculative component in the price of an asset. In the framework of viscosity solutions, we show the existence and uniqueness of the solution. We also show that the solution is convex in space, and establish several monotonicity properties of the solution and of the free boundary with respect to parameters of the problem. To study the free boundary, we use, in particular, the fact that the odd part of the solution solves a more standard obstacle problem. We show that the free boundary is and describe the asymptotics of the free boundary as c, the cost of transacting the asset, goes to zero. PMID:25288815

Trait plasticity, not values, best corresponds with woodland plant success in novel and manipulated habitats

Treesearch

Robert J. Warren; Jeffrey K. Lake

2012-01-01

Aims: The clustering of plants with similar leaf traits along environmental gradients may arise from adaptation as well as acclimation to heterogeneous habitat conditions. Determining the forces that shape plant leaf traits requires both linking variation in trait morphology with abiotic gradients and linking that trait variation with plant performance under varying...

Wood formation and the concept of wood quality

Treesearch

Philip R. Larson

1969-01-01

Wood has been the principal product of trees from the first hunting club or digging tool of ancient man to the rich variety of industrial and decorative uses of modern civilization. The universal practical value and aesthetic appeal of wood may be traced to the seemingly infinite variation in its characteristics. These variations arise from the structure and...

A Summary of Some Discrete-Event System Control Problems

NASA Astrophysics Data System (ADS)

Rudie, Karen

A summary of the area of control of discrete-event systems is given. In this research area, automata and formal language theory is used as a tool to model physical problems that arise in technological and industrial systems. The key ingredients to discrete-event control problems are a process that can be modeled by an automaton, events in that process that cannot be disabled or prevented from occurring, and a controlling agent that manipulates the events that can be disabled to guarantee that the process under control either generates all the strings in some prescribed language or as many strings as possible in some prescribed language. When multiple controlling agents act on a process, decentralized control problems arise. In decentralized discrete-event systems, it is presumed that the agents effecting control cannot each see all event occurrences. Partial observation leads to some problems that cannot be solved in polynomial time and some others that are not even decidable.

The Visual Effects of Intraocular Colored Filters

PubMed Central

Hammond, Billy R.

2012-01-01

Modern life is associated with a myriad of visual problems, most notably refractive conditions such as myopia. Human ingenuity has addressed such problems using strategies such as spectacle lenses or surgical correction. There are other visual problems, however, that have been present throughout our evolutionary history and are not as easily solved by simply correcting refractive error. These problems include issues like glare disability and discomfort arising from intraocular scatter, photostress with the associated transient loss in vision that arises from short intense light exposures, or the ability to see objects in the distance through a veil of atmospheric haze. One likely biological solution to these more long-standing problems has been the use of colored intraocular filters. Many species, especially diurnal, incorporate chromophores from numerous sources (e.g., often plant pigments called carotenoids) into ocular tissues to improve visual performance outdoors. This review summarizes information on the utility of such filters focusing on chromatic filtering by humans. PMID:24278692

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

Several topics arising in the finite element solution of the incompressible Navier-Stokes equations are considered. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. The role of artificial viscosity in viscous flow calculations is studied, emphasizing work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some modifications are mentioned.

Analytical-numerical solution of a nonlinear integrodifferential equation in econometrics

NASA Astrophysics Data System (ADS)

Kakhktsyan, V. M.; Khachatryan, A. Kh.

2013-07-01

A mixed problem for a nonlinear integrodifferential equation arising in econometrics is considered. An analytical-numerical method is proposed for solving the problem. Some numerical results are presented.

Decision PBL: A 4-year retrospective case study of the use of virtual patients in problem-based learning.

PubMed

Ellaway, Rachel H; Poulton, Terry; Jivram, Trupti

2015-01-01

In 2009, St George's University of London (SGUL) replaced their paper-based problem-based learning (PBL) cases with virtual patients for intermediate-level undergraduate students. This involved the development of Decision-Problem-Based Learning (D-PBL), a variation on progressive-release PBL that uses virtual patients instead of paper cases, and focuses on patient management decisions and their consequences. Using a case study method, this paper describes four years of developing and running D-PBL at SGUL from individual activities up to the ways in which D-PBL functioned as an educational system. A number of broad issues were identified: the importance of debates and decision-making in making D-PBL activities engaging and rewarding; the complexities of managing small group dynamics; the time taken to complete D-PBL activities; the changing role of the facilitator; and the erosion of the D-PBL process over time. A key point in understanding this work is the construction and execution of the D-PBL activity, as much of the value of this approach arises from the actions and interactions of students, their facilitators and the virtual patients rather than from the design of the virtual patients alone. At a systems level D-PBL needs to be periodically refreshed to retain its effectiveness.

Contextualized Mathematics Problems and Transfer of Knowledge: Establishing Problem Spaces and Boundaries

ERIC Educational Resources Information Center

McGraw, Rebecca; Patterson, Cody L.

2017-01-01

In this study, we examine how inservice secondary mathematics teachers working together on a contextualized problem negotiate issues arising from the ill-structured nature of the problem such as what assumptions one may make, what real-world considerations should be taken into account, and what constitutes a satisfactory solution. We conceptualize…

The relaxed-polar mechanism of locally optimal Cosserat rotations for an idealized nanoindentation and comparison with 3D-EBSD experiments

NASA Astrophysics Data System (ADS)

Fischle, Andreas; Neff, Patrizio; Raabe, Dierk

2017-08-01

The rotation {{polar}}(F) \\in {{SO}}(3) arises as the unique orthogonal factor of the right polar decomposition F = {{polar}}(F) U of a given invertible matrix F \\in {{GL}}^+(3). In the context of nonlinear elasticity Grioli (Boll Un Math Ital 2:252-255, 1940) discovered a geometric variational characterization of {{polar}}(F) as a unique energy-minimizing rotation. In preceding works, we have analyzed a generalization of Grioli's variational approach with weights (material parameters) μ > 0 and μ _c ≥ 0 (Grioli: μ = μ _c). The energy subject to minimization coincides with the Cosserat shear-stretch contribution arising in any geometrically nonlinear, isotropic and quadratic Cosserat continuum model formulated in the deformation gradient field F :=\

Unusual arterial pattern of the gastrointestinal tract: inferior mesenteric artery arising from the iliac artery and corkscrew external iliac.

PubMed

Nassar, Lara; Atweh, Lamya Ann; Jurjus, Abdo; Al Kutoubi, Aghiad

2012-07-01

Anatomical variations of the digestive system arteries are important due to their clinical significance. However, anomalies in the inferior mesenteric artery (IMA) are the least common compared with the celiac trunk and superior mesenteric artery. This report describes the case of a 67-year-old man with an extremely rare variant in which the IMA arises from the left common iliac artery, and the ipsilateral external iliac artery has a corkscrew pattern. These findings were depicted during computed tomography angiography of the abdomen and pelvis. This case is the first report of such a variation associated with a left external iliac artery turning into a double loop before forming the femoral artery. The embryological and clinical significance of such an anomaly are discussed.

Receptivity of flat-plate boundary layer in a non-uniform free stream (vorticity normal to the plate)

NASA Technical Reports Server (NTRS)

Kogan, M. N.

1994-01-01

Recent progress in both the linear and nonlinear aspects of stability theory has highlighted the importance of the receptivity problem. One of the most unclear aspects of receptivity study is the receptivity of boundary-layer flow normal to vortical disturbances. Some experimental and theoretical results permit the proposition that quasi-steady outer-flow vortical disturbances may trigger by-pass transition. In present work such interaction is investigated for vorticity normal to a leading edge. The interest in these types of vortical disturbances arise from theoretical work, where it was shown that small sinusoidal variations of upstream velocity along the spanwise direction can produce significant variations in the boundary-layer profile. In the experimental part of this work, such non-uniform flow was created and the laminar-turbulent transition in this flow was investigated. The experiment was carried out in a low-turbulence direct-flow wind tunnel T-361 at the Central Aerohydrodynamic Institute (TsAGI). The non-uniform flow was produced by laminar or turbulent wakes behind a wire placed normal to the plate upstream of the leading edge. The theoretical part of the work is devoted to studying the unstable disturbance evolution in a boundary layer with strongly non-uniform velocity profiles similar to that produced by outer-flow vorticity. Specifically, the Tollmien-Schlichting wave development in the boundary layer flow with spanwise variations of velocity is investigated.

Manageability, vulnerability and interaction: a qualitative analysis of acute myocardial infarction patients' conceptions of the event.

PubMed

Johansson, Ingela; Swahn, Eva; Strömberg, Anna

2007-09-01

Delay in seeking care remains a problem for many patients with myocardial infarction. There is a great deal of knowledge available about clinical factors contributing to this delay, while studies focusing on the patients' own experiences are few. Describe variations in how individuals perceived suffering symptoms of an acute myocardial infarction. A qualitative method using phenomenographic design was applied. Interviews were conducted with 15 strategically selected patients with myocardial infarction. Eight sub-categories in the pre-hospital phase were summarised into three categories: manageability, vulnerability, and interaction. To manage their situation, patients expressed a need to understand it and to have a similar situation to compare with. They also described coping with the arising threat to their lives by self-medication or denying their symptoms. Patients expressed vulnerability, with feelings of anxiety, both as triggers and barriers to seeking medical care. In interaction with others, psychosocial support and guidance from the environment, was fundamental in helping the patients to manage the situation. There were large variations in myocardial infarction patients' conceptions of the event. To improve disease management in the pre-hospital phase, the awareness of this large variation in conceptions about suffering symptoms of an myocardial infarction could be used in the dialogue between patients and health care professionals, in cardiac prevention programmes, as well as in health care education.

From the Golden Rectangle and Fibonacci to Pedagogy and Problem Posing

ERIC Educational Resources Information Center

Brown, Stephen I.

1976-01-01

Beginning with an analysis of the golden rectangle, the author shows how a series of problems for student investigation arise from queries concerning changes in conditions and analogous situations. (SD)

Problems in Recording the Electrocardiogram.

ERIC Educational Resources Information Center

Webster, John G.

The unwanted signals that arise in electrocardiography are discussed. A technical background of electrocardiography is given, along with teaching techniques that educate students of medical instrumentation to solve the problems caused by these signals. (MJH)

An Inverse Problem for a Class of Conditional Probability Measure-Dependent Evolution Equations

PubMed Central

Mirzaev, Inom; Byrne, Erin C.; Bortz, David M.

2016-01-01

We investigate the inverse problem of identifying a conditional probability measure in measure-dependent evolution equations arising in size-structured population modeling. We formulate the inverse problem as a least squares problem for the probability measure estimation. Using the Prohorov metric framework, we prove existence and consistency of the least squares estimates and outline a discretization scheme for approximating a conditional probability measure. For this scheme, we prove general method stability. The work is motivated by Partial Differential Equation (PDE) models of flocculation for which the shape of the post-fragmentation conditional probability measure greatly impacts the solution dynamics. To illustrate our methodology, we apply the theory to a particular PDE model that arises in the study of population dynamics for flocculating bacterial aggregates in suspension, and provide numerical evidence for the utility of the approach. PMID:28316360

Variational Gaussian approximation for Poisson data

NASA Astrophysics Data System (ADS)

Arridge, Simon R.; Ito, Kazufumi; Jin, Bangti; Zhang, Chen

2018-02-01

The Poisson model is frequently employed to describe count data, but in a Bayesian context it leads to an analytically intractable posterior probability distribution. In this work, we analyze a variational Gaussian approximation to the posterior distribution arising from the Poisson model with a Gaussian prior. This is achieved by seeking an optimal Gaussian distribution minimizing the Kullback-Leibler divergence from the posterior distribution to the approximation, or equivalently maximizing the lower bound for the model evidence. We derive an explicit expression for the lower bound, and show the existence and uniqueness of the optimal Gaussian approximation. The lower bound functional can be viewed as a variant of classical Tikhonov regularization that penalizes also the covariance. Then we develop an efficient alternating direction maximization algorithm for solving the optimization problem, and analyze its convergence. We discuss strategies for reducing the computational complexity via low rank structure of the forward operator and the sparsity of the covariance. Further, as an application of the lower bound, we discuss hierarchical Bayesian modeling for selecting the hyperparameter in the prior distribution, and propose a monotonically convergent algorithm for determining the hyperparameter. We present extensive numerical experiments to illustrate the Gaussian approximation and the algorithms.

A Comparison of Neuroimaging Abnormalities in Multiple Sclerosis, Major Depression and Chronic Fatigue Syndrome (Myalgic Encephalomyelitis): is There a Common Cause?

PubMed

Morris, Gerwyn; Berk, Michael; Puri, Basant K

2018-04-01

There is copious evidence of abnormalities in resting-state functional network connectivity states, grey and white matter pathology and impaired cerebral perfusion in patients afforded a diagnosis of multiple sclerosis, major depression or chronic fatigue syndrome (CFS) (myalgic encephalomyelitis). Systemic inflammation may well be a major element explaining such findings. Inter-patient and inter-illness variations in neuroimaging findings may arise at least in part from regional genetic, epigenetic and environmental variations in the functions of microglia and astrocytes. Regional differences in neuronal resistance to oxidative and inflammatory insults and in the performance of antioxidant defences in the central nervous system may also play a role. Importantly, replicated experimental findings suggest that the use of high-resolution SPECT imaging may have the capacity to differentiate patients afforded a diagnosis of CFS from those with a diagnosis of depression. Further research involving this form of neuroimaging appears warranted in an attempt to overcome the problem of aetiologically heterogeneous cohorts which probably explain conflicting findings produced by investigative teams active in this field. However, the ionising radiation and relative lack of sensitivity involved probably preclude its use as a routine diagnostic tool.

Quantification of sensitivity and resistance of breast cancer cell lines to anti-cancer drugs using GR metrics

PubMed Central

Hafner, Marc; Heiser, Laura M.; Williams, Elizabeth H.; Niepel, Mario; Wang, Nicholas J.; Korkola, James E.; Gray, Joe W.; Sorger, Peter K.

2017-01-01

Traditional means for scoring the effects of anti-cancer drugs on the growth and survival of cell lines is based on relative cell number in drug-treated and control samples and is seriously confounded by unequal division rates arising from natural biological variation and differences in culture conditions. This problem can be overcome by computing drug sensitivity on a per-division basis. The normalized growth rate inhibition (GR) approach yields per-division metrics for drug potency (GR50) and efficacy (GRmax) that are analogous to the more familiar IC50 and Emax values. In this work, we report GR-based, proliferation-corrected, drug sensitivity metrics for ~4,700 pairs of breast cancer cell lines and perturbagens. Such data are broadly useful in understanding the molecular basis of therapeutic response and resistance. Here, we use them to investigate the relationship between different measures of drug sensitivity and conclude that drug potency and efficacy exhibit high variation that is only weakly correlated. To facilitate further use of these data, computed GR curves and metrics can be browsed interactively at http://www.GRbrowser.org/. PMID:29112189

Exploiting Symmetry on Parallel Architectures.

NASA Astrophysics Data System (ADS)

Stiller, Lewis Benjamin

1995-01-01

This thesis describes techniques for the design of parallel programs that solve well-structured problems with inherent symmetry. Part I demonstrates the reduction of such problems to generalized matrix multiplication by a group-equivariant matrix. Fast techniques for this multiplication are described, including factorization, orbit decomposition, and Fourier transforms over finite groups. Our algorithms entail interaction between two symmetry groups: one arising at the software level from the problem's symmetry and the other arising at the hardware level from the processors' communication network. Part II illustrates the applicability of our symmetry -exploitation techniques by presenting a series of case studies of the design and implementation of parallel programs. First, a parallel program that solves chess endgames by factorization of an associated dihedral group-equivariant matrix is described. This code runs faster than previous serial programs, and discovered it a number of results. Second, parallel algorithms for Fourier transforms for finite groups are developed, and preliminary parallel implementations for group transforms of dihedral and of symmetric groups are described. Applications in learning, vision, pattern recognition, and statistics are proposed. Third, parallel implementations solving several computational science problems are described, including the direct n-body problem, convolutions arising from molecular biology, and some communication primitives such as broadcast and reduce. Some of our implementations ran orders of magnitude faster than previous techniques, and were used in the investigation of various physical phenomena.

Parallel block schemes for large scale least squares computations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golub, G.H.; Plemmons, R.J.; Sameh, A.

1986-04-01

Large scale least squares computations arise in a variety of scientific and engineering problems, including geodetic adjustments and surveys, medical image analysis, molecular structures, partial differential equations and substructuring methods in structural engineering. In each of these problems, matrices often arise which possess a block structure which reflects the local connection nature of the underlying physical problem. For example, such super-large nonlinear least squares computations arise in geodesy. Here the coordinates of positions are calculated by iteratively solving overdetermined systems of nonlinear equations by the Gauss-Newton method. The US National Geodetic Survey will complete this year (1986) the readjustment ofmore » the North American Datum, a problem which involves over 540 thousand unknowns and over 6.5 million observations (equations). The observation matrix for these least squares computations has a block angular form with 161 diagnonal blocks, each containing 3 to 4 thousand unknowns. In this paper parallel schemes are suggested for the orthogonal factorization of matrices in block angular form and for the associated backsubstitution phase of the least squares computations. In addition, a parallel scheme for the calculation of certain elements of the covariance matrix for such problems is described. It is shown that these algorithms are ideally suited for multiprocessors with three levels of parallelism such as the Cedar system at the University of Illinois. 20 refs., 7 figs.« less

Use of Picard and Newton iteration for solving nonlinear ground water flow equations

USGS Publications Warehouse

Mehl, S.

2006-01-01

This study examines the use of Picard and Newton iteration to solve the nonlinear, saturated ground water flow equation. Here, a simple three-node problem is used to demonstrate the convergence difficulties that can arise when solving the nonlinear, saturated ground water flow equation in both homogeneous and heterogeneous systems with and without nonlinear boundary conditions. For these cases, the characteristic types of convergence patterns are examined. Viewing these convergence patterns as orbits of an attractor in a dynamical system provides further insight. It is shown that the nonlinearity that arises from nonlinear head-dependent boundary conditions can cause more convergence difficulties than the nonlinearity that arises from flow in an unconfined aquifer. Furthermore, the effects of damping on both convergence and convergence rate are investigated. It is shown that no single strategy is effective for all problems and how understanding pitfalls and merits of several methods can be helpful in overcoming convergence difficulties. Results show that Picard iterations can be a simple and effective method for the solution of nonlinear, saturated ground water flow problems.

Institutional Resource Requirements, Management, and Accountability.

ERIC Educational Resources Information Center

Matlock, John; Humphries, Frederick S.

A detailed resource management study was conducted at Tennessee State University, and resource management problems at other higher education institutions were identified through the exchange of data and studies. Resource requirements and management problems unique to black institutions were examined, as were the problems that arise from regional…

Second Computational Aeroacoustics (CAA) Workshop on Benchmark Problems

NASA Technical Reports Server (NTRS)

Tam, C. K. W. (Editor); Hardin, J. C. (Editor)

1997-01-01

The proceedings of the Second Computational Aeroacoustics (CAA) Workshop on Benchmark Problems held at Florida State University are the subject of this report. For this workshop, problems arising in typical industrial applications of CAA were chosen. Comparisons between numerical solutions and exact solutions are presented where possible.

A New Approach to Isolating External Magnetic Field Components in Spacecraft Measurements of the Earth's Magnetic Field Using Global Positioning System observables

NASA Technical Reports Server (NTRS)

Raymond, C.; Hajj, G.

1994-01-01

We review the problem of separating components of the magnetic field arising from sources in the Earth's core and lithosphere, from those contributions arising external to the Earth, namely ionospheric and magnetospheric fields, in spacecraft measurements of the Earth's magnetic field.

Solution algorithms for nonlinear transient heat conduction analysis employing element-by-element iterative strategies

NASA Technical Reports Server (NTRS)

Winget, J. M.; Hughes, T. J. R.

1985-01-01

The particular problems investigated in the present study arise from nonlinear transient heat conduction. One of two types of nonlinearities considered is related to a material temperature dependence which is frequently needed to accurately model behavior over the range of temperature of engineering interest. The second nonlinearity is introduced by radiation boundary conditions. The finite element equations arising from the solution of nonlinear transient heat conduction problems are formulated. The finite element matrix equations are temporally discretized, and a nonlinear iterative solution algorithm is proposed. Algorithms for solving the linear problem are discussed, taking into account the form of the matrix equations, Gaussian elimination, cost, and iterative techniques. Attention is also given to approximate factorization, implementational aspects, and numerical results.

Positive Discipline A to Z: 1001 Solutions to Everyday Parenting Problems.

ERIC Educational Resources Information Center

Nelsen, Jane; And Others

This book is a parenting reference work that offers background on common disciplinary problems and parenting issues, advice on how to handle problems and issues as they arise, and insight into how to avoid disciplinary problems in the future. The book is divided into three sections: Basic Positive Discipline Parenting Tools, Positive Discipline…

Cognitive Abilities Adjustment and Parenting Practices in Preschoolers with Disruption Conduct Problems

ERIC Educational Resources Information Center

Fernandez-Parra, A.; Lopez-Rubio, S.; Mata, S.; Calero, M. D.; Vives, M. C.; Carles, R.; Navarro, E.

2013-01-01

Introduction: Conduct problems arising in infancy are one of the main reasons for which parents seek psychological assistance. Although these problems usually begin when the child has started school, in recent years a group of children has been identified who begin to manifest such problems from their earliest infancy and whose prognosis seems to…

Discrete control of linear distributed systems with application to the deformable primary mirror of a large orbiting telescope. Ph.D. Thesis - Rhode Island Univ.

NASA Technical Reports Server (NTRS)

Creedon, J. F.

1970-01-01

The results are presented of a detailed study of the discrete control of linear distributed systems with specific application to the design of a practical controller for a plant representative of a telescope primary mirror for an orbiting astronomical observatory. The problem of controlling the distributed plant is treated by employing modal techniques to represent variations in the optical figure. Distortion of the mirror surface, which arises primarily from thermal gradients, is countered by actuators working against a backing structure to apply a corrective force distribution to the controlled surface. Each displacement actuator is in series with a spring attached to the mirror by means of a pad intentionally introduced to restrict the excitation of high-order modes. Control is exerted over a finite number of the most significant modes.

Electric-field noise from carbon-adatom diffusion on a Au(110) surface: First-principles calculations and experiments

DOE PAGES

Kim, E.; Safavi-Naini, A.; Hite, D. A.; ...

2017-03-01

The decoherence of trapped-ion quantum bits due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from processes on the trap-electrode surfaces. In this work, we address the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by detailed scanned probe microscopy and density functional theory how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. Lastly, a simple model for the diffusion noise,more » which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values.« less

Model Predictive Optimal Control of a Time-Delay Distributed-Parameter Systems

NASA Technical Reports Server (NTRS)

Nguyen, Nhan

2006-01-01

This paper presents an optimal control method for a class of distributed-parameter systems governed by first order, quasilinear hyperbolic partial differential equations that arise in many physical systems. Such systems are characterized by time delays since information is transported from one state to another by wave propagation. A general closed-loop hyperbolic transport model is controlled by a boundary control embedded in a periodic boundary condition. The boundary control is subject to a nonlinear differential equation constraint that models actuator dynamics of the system. The hyperbolic equation is thus coupled with the ordinary differential equation via the boundary condition. Optimality of this coupled system is investigated using variational principles to seek an adjoint formulation of the optimal control problem. The results are then applied to implement a model predictive control design for a wind tunnel to eliminate a transport delay effect that causes a poor Mach number regulation.

A partially reflecting random walk on spheres algorithm for electrical impedance tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maire, Sylvain, E-mail: maire@univ-tln.fr; Simon, Martin, E-mail: simon@math.uni-mainz.de

2015-12-15

In this work, we develop a probabilistic estimator for the voltage-to-current map arising in electrical impedance tomography. This novel so-called partially reflecting random walk on spheres estimator enables Monte Carlo methods to compute the voltage-to-current map in an embarrassingly parallel manner, which is an important issue with regard to the corresponding inverse problem. Our method uses the well-known random walk on spheres algorithm inside subdomains where the diffusion coefficient is constant and employs replacement techniques motivated by finite difference discretization to deal with both mixed boundary conditions and interface transmission conditions. We analyze the global bias and the variance ofmore » the new estimator both theoretically and experimentally. Subsequently, the variance of the new estimator is considerably reduced via a novel control variate conditional sampling technique which yields a highly efficient hybrid forward solver coupling probabilistic and deterministic algorithms.« less

Study on leaching of pollutants from vegetable tanning residue.

PubMed

Mazumder, Debabrata; Biswas, Santosh; Bandyopadhyay, Pratip

2006-07-01

The processing of heavy leather employs the vegetable tanning method involving use of tan liquor. The solid residue of this vegetable tanning process aggravates the water pollution by means of leaching of tannin and other associatedpollutants. Tannin is a biologically resistant compound causing several problems in animal body. The present study dealt with the pollution hazard arising out of leaching of pollutants from the open dumped vegetable tanning residue by rainfall washing. The concerned pollutants were pH, Chemical Oxygen Demand (COD), tannin,sulfate and chloride concentration. To explore the possible extent of contamination of these pollutants in the leached water, two different masses (2 kg and 3 kg) of tanning residue were employed. The results of the study showed that there was a continuous release of pollutants from the vegetable tanning residue. Moreover, there was no regular variation in various pollutant concentrations in both the cases solely due to non-homogeneity of the residue.

Converting baker's waste into alcohol. Revised final progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halsey, R.; Wilson, P.B.

All types of baker's waste (including waste from candy manufacturers) can be converted into alcohol to be used as a fuel. All types of waste at any stage in process can be converted, such as: basic ingredients (including floor sweepings); dry mixes (including floor sweepings); dough at any stage; partially or fully cooked products; and day old returned products. The basic steps are the same, only the initial preparation will vary slightly. The variation will be: amount of water to be added and amount and type of nutrients (if any) to be added. The basic steps are: slurrying, liquefying tomore » put starch into liquid state, saccharifying to convert starch into fermentable sugars, fermentation to convert sugars into alcohol, and distillation to separate the alcohol from the mash. Each step is discussed in detail along with problems that may arise. Directions are given and materials (enzymes, yeast, etc.) and equipment are descibed briefly.« less

Electric-field noise from carbon-adatom diffusion on a Au(110) surface: First-principles calculations and experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, E.; Safavi-Naini, A.; Hite, D. A.

The decoherence of trapped-ion quantum bits due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from processes on the trap-electrode surfaces. In this work, we address the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by detailed scanned probe microscopy and density functional theory how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. Lastly, a simple model for the diffusion noise,more » which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values.« less

Bone Density and Dental External Apical Root Resorption

PubMed Central

Iglesias-Linares, Alejandro; Morford, Lorri Ann

2016-01-01

When orthodontic patients desire shorter treatment times with aesthetic results and long-term stability, it is important for the orthodontist to understand the potential limitations and problems that may arise during standard and/or technology-assisted accelerated treatment. Bone density plays an important role in facilitating orthodontic tooth movement (OTM), such that reductions in bone density can significantly increase movement velocity. Lifestyle, genetic background, environmental factors and disease status all can influence a patients’ overall health and bone density. In some individuals, these factors may create specific conditions that influence systemic-wide bone metabolism. Both genetic variation and the onset of a bone-related disease can influence systemic bone density and local bone density, such as is observed in the mandible and maxilla. These types of localized density changes can affect the rate of OTM and may also influence the risk of unwanted outcomes, i.e., the occurrence of dental external apical root resorption (EARR). PMID:27766484

Ensemble learning in fixed expansion layer networks for mitigating catastrophic forgetting.

PubMed

Coop, Robert; Mishtal, Aaron; Arel, Itamar

2013-10-01

Catastrophic forgetting is a well-studied attribute of most parameterized supervised learning systems. A variation of this phenomenon, in the context of feedforward neural networks, arises when nonstationary inputs lead to loss of previously learned mappings. The majority of the schemes proposed in the literature for mitigating catastrophic forgetting were not data driven and did not scale well. We introduce the fixed expansion layer (FEL) feedforward neural network, which embeds a sparsely encoding hidden layer to help mitigate forgetting of prior learned representations. In addition, we investigate a novel framework for training ensembles of FEL networks, based on exploiting an information-theoretic measure of diversity between FEL learners, to further control undesired plasticity. The proposed methodology is demonstrated on a basic classification task, clearly emphasizing its advantages over existing techniques. The architecture proposed can be enhanced to address a range of computational intelligence tasks, such as regression problems and system control.

Hierarchical spatial models of abundance and occurrence from imperfect survey data

USGS Publications Warehouse

Royle, J. Andrew; Kery, M.; Gautier, R.; Schmid, Hans

2007-01-01

Many estimation and inference problems arising from large-scale animal surveys are focused on developing an understanding of patterns in abundance or occurrence of a species based on spatially referenced count data. One fundamental challenge, then, is that it is generally not feasible to completely enumerate ('census') all individuals present in each sample unit. This observation bias may consist of several components, including spatial coverage bias (not all individuals in the Population are exposed to sampling) and detection bias (exposed individuals may go undetected). Thus, observations are biased for the state variable (abundance, occupancy) that is the object of inference. Moreover, data are often sparse for most observation locations, requiring consideration of methods for spatially aggregating or otherwise combining sparse data among sample units. The development of methods that unify spatial statistical models with models accommodating non-detection is necessary to resolve important spatial inference problems based on animal survey data. In this paper, we develop a novel hierarchical spatial model for estimation of abundance and occurrence from survey data wherein detection is imperfect. Our application is focused on spatial inference problems in the Swiss Survey of Common Breeding Birds. The observation model for the survey data is specified conditional on the unknown quadrat population size, N(s). We augment the observation model with a spatial process model for N(s), describing the spatial variation in abundance of the species. The model includes explicit sources of variation in habitat structure (forest, elevation) and latent variation in the form of a correlated spatial process. This provides a model-based framework for combining the spatially referenced samples while at the same time yielding a unified treatment of estimation problems involving both abundance and occurrence. We provide a Bayesian framework for analysis and prediction based on the integrated likelihood, and we use the model to obtain estimates of abundance and occurrence maps for the European Jay (Garrulus glandarius), a widespread, elusive, forest bird. The naive national abundance estimate ignoring imperfect detection and incomplete quadrat coverage was 77 766 territories. Accounting for imperfect detection added approximately 18 000 territories, and adjusting for coverage bias added another 131 000 territories to yield a fully corrected estimate of the national total of about 227 000 territories. This is approximately three times as high as previous estimates that assume every territory is detected in each quadrat.

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

This paper considers several topics arising in the finite element solution of the incompressible Navier-Stokes equations. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. Following this, the role of artificial viscosity in viscous flow calculations is studied, emphasizing recent work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some recent modifications are mentioned.

Responding to Adolescent Suicide.

ERIC Educational Resources Information Center

Phi Delta Kappa Educational Foundation, Bloomington, IN.

This publication is designed to help educators deal with the problems that arise after an adolescent's suicide. It recommends that teachers should be able to detect differences in students' responses to emotional problems. Following a preface and a brief review of the extent of the problem, the first chapter discusses which adolescents are…

Introducing the Hero Complex and the Mythic Iconic Pathway of Problem Gambling

ERIC Educational Resources Information Center

Nixon, Gary; Solowoniuk, Jason

2009-01-01

Early research into the motivations behind problem gambling reflected separate paradigms of thought splitting our understanding of the gambler into divergent categories. However, over the past 25 years, problem gambling is now best understood to arise from biological, environmental, social, and psychological processes, and is now encapsulated…

Esperanto and International Language Problems: A Research Bibliography.

ERIC Educational Resources Information Center

Tonkin, Humphrey R.

This bibliography is intended both for the researcher and for the occasional student of international language problems, particularly as these relate to the international language Esperanto. The book is divided into two main sections: Part One deals with problems arising from communication across national boundaries and the search for a solution…

A stochastic-geometric model of soil variation in Pleistocene patterned ground

NASA Astrophysics Data System (ADS)

Lark, Murray; Meerschman, Eef; Van Meirvenne, Marc

2013-04-01

In this paper we examine the spatial variability of soil in parent material with complex spatial structure which arises from complex non-linear geomorphic processes. We show that this variability can be better-modelled by a stochastic-geometric model than by a standard Gaussian random field. The benefits of the new model are seen in the reproduction of features of the target variable which influence processes like water movement and pollutant dispersal. Complex non-linear processes in the soil give rise to properties with non-Gaussian distributions. Even under a transformation to approximate marginal normality, such variables may have a more complex spatial structure than the Gaussian random field model of geostatistics can accommodate. In particular the extent to which extreme values of the variable are connected in spatially coherent regions may be misrepresented. As a result, for example, geostatistical simulation generally fails to reproduce the pathways for preferential flow in an environment where coarse infill of former fluvial channels or coarse alluvium of braided streams creates pathways for rapid movement of water. Multiple point geostatistics has been developed to deal with this problem. Multiple point methods proceed by sampling from a set of training images which can be assumed to reproduce the non-Gaussian behaviour of the target variable. The challenge is to identify appropriate sources of such images. In this paper we consider a mode of soil variation in which the soil varies continuously, exhibiting short-range lateral trends induced by local effects of the factors of soil formation which vary across the region of interest in an unpredictable way. The trends in soil variation are therefore only apparent locally, and the soil variation at regional scale appears random. We propose a stochastic-geometric model for this mode of soil variation called the Continuous Local Trend (CLT) model. We consider a case study of soil formed in relict patterned ground with pronounced lateral textural variations arising from the presence of infilled ice-wedges of Pleistocene origin. We show how knowledge of the pedogenetic processes in this environment, along with some simple descriptive statistics, can be used to select and fit a CLT model for the apparent electrical conductivity (ECa) of the soil. We use the model to simulate realizations of the CLT process, and compare these with realizations of a fitted Gaussian random field. We show how statistics that summarize the spatial coherence of regions with small values of ECa, which are expected to have coarse texture and so larger saturated hydraulic conductivity, are better reproduced by the CLT model than by the Gaussian random field. This suggests that the CLT model could be used to generate an unlimited supply of training images to allow multiple point geostatistical simulation or prediction of this or similar variables.

Missed Total Occlusion Due to the Occipital Artery Arising from the Internal Carotid Artery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ustunsoz, Bahri, E-mail: bustunsoz2000@yahoo.com; Gumus, Burcak; Koksal, Ali

2007-02-15

A 56-year-old man was referred for digital subtraction angiography (DSA) with an ultrasound diagnosis of right proximal internal carotid artery (ICA) stenosis for possible carotid artery stenting. DSA revealed total occlusion of the ICA and an occipital artery arising from the stump and simulating continuation of the ICA. An ascending pharyngeal artery also arose from the same occipital artery. This case is of interest because this is a rare variation besides being a cause of misdiagnosis at carotid ultrasound.

Variation, "evolution", immortality and genetic instabilities in tumour cells.

PubMed

Bignold, L P

2007-08-18

The pathological characteristics of tumour cells often include variation of their histopathological features (i.e. "degrees of de-differentiation") between cases of the same tumour type and between different foci within individual tumours. Usually, only a few cell lines from tumours are immortal. Currently, somatic mutation, replicative infidelity of DNA and aneuploidy are suggested as alternative mechanisms of genomic disturbance underlying tumours. Nevertheless, apart from Hansemann's ideas of "anaplasia" and "de-differentiation" (proposed in the 1890s), and supposed "evolutionary themes" in cancer cell biology, little has been published concerning how histopathologic variation and immortality in tumour cells might arise. This paper reviews applications of the concepts of "variation" to tumours, including concepts of "evolution" and "cellular Darwinism". It is proposed that combinations of somatic mutation, DNA replicative infidelity and aneuploidy may explain the variabilities in tumours, and provide immortality in occasional tumour cells. A possible model involves (i) an initial somatic mutation causing reduced replicative fidelity of DNA, which could be variable in intensity, and thus give rise to variations between cases; (ii) a phase of replicative infidelity of DNA causing daughter cells lines to develop various abnormalities to different degrees, and hence provide for variation between areas of the same tumour. As a last event (iii) occasional asymmetric chromosomal distributions (aneuploidy) might "refresh" the ability of a daughter cell to replicate DNA faithfully causing them to become immortal. Thus extensively mutant and variable, hyperploid, and occasionally immortal cells might arise.

Co-Gradient Variation in Growth Rate and Development Time of a Broadly Distributed Butterfly

PubMed Central

Barton, Madeleine; Sunnucks, Paul; Norgate, Melanie; Murray, Neil; Kearney, Michael

2014-01-01

Widespread species often show geographic variation in thermally-sensitive traits, providing insight into how species respond to shifts in temperature through time. Such patterns may arise from phenotypic plasticity, genetic adaptation, or their interaction. In some cases, the effects of genotype and temperature may act together to reduce, or to exacerbate, phenotypic variation in fitness-related traits across varying thermal environments. We find evidence for such interactions in life-history traits of Heteronympha merope, a butterfly distributed across a broad latitudinal gradient in south-eastern Australia. We show that body size in this butterfly is negatively related to developmental temperature in the laboratory, in accordance with the temperature-size rule, but not in the field, despite very strong temperature gradients. A common garden experiment on larval thermal responses, spanning the environmental extremes of H. merope's distribution, revealed that butterflies from low latitude (warmer climate) populations have relatively fast intrinsic growth and development rates compared to those from cooler climates. These synergistic effects of genotype and temperature across the landscape (co-gradient variation) are likely to accentuate phenotypic variation in these traits, and this interaction must be accounted for when predicting how H. merope will respond to temperature change through time. These results highlight the importance of understanding how variation in life-history traits may arise in response to environmental change. Without this knowledge, we may fail to detect whether organisms are tracking environmental change, and if they are, whether it is by plasticity, adaptation or both. PMID:24743771

Errors, Error, and Text in Multidialect Setting.

ERIC Educational Resources Information Center

Candler, W. J.

1979-01-01

This article discusses the various dialects of English spoken in Liberia and analyzes the problems of Liberian students in writing compositions in English. Errors arise mainly from differences in culture and cognition, not from superficial linguistic problems. (CFM)

Serial-position effects for items and relations in short-term memory.

PubMed

Jones, Tim; Oberauer, Klaus

2013-04-01

Two experiments used immediate probed recall of words to investigate serial-position effects. Item memory was tested through probing with a semantic category. Relation memory was tested through probing with the word's spatial location of presentation. Input order and output order were deconfounded by presenting and probing items in different orders. Primacy and recency effects over input position were found for both item memory and relation memory. Both item and relation memory declined over output position. The finding of a U-shaped input position function for item memory rules out an explanation purely in terms of positional confusions (e.g., edge effects). Either these serial-position effects arise from variations in the intrinsic memory strength of the items, or they arise from variations in the strength of item-position bindings, together with retrieval by scanning.

Sea-Level Acceleration Hotspot along the Atlantic Coast of North America

NASA Astrophysics Data System (ADS)

Sallenger, A. H.; Doran, K. J.; Howd, P.

2012-12-01

Spatial variations of sea level rise (SLR) can be forced by dynamic processes arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes arising from mass re-distributions changing gravity and the earth's rotation and shape. The sea-level variations can form unique spatial patterns, yet there are very few field observations verifying predicted patterns, or fingerprints. We present evidence of SLR acceleration in a 1,000-km-long hotspot on the North American Atlantic coast north of Cape Hatteras, North Carolina to above Boston, Massachusetts. By using accelerations, or rate differences, sea level signals that are linear over sub-century records, like the relative sea level changes arising from vertical land movements of glacial isostatic adjustment, do not affect our results. For a 60-yr regression window (between 1950-1979 and 1980-2009), mean increase in the rate of SLR in the hotspot was 1.97 ± 0.64 mm/yr. (For a 40-yr window, the mean rate increase was 3.80 ± 1.06 mm/yr.) South of Cape Hatteras to Key West, Florida, rate differences for either 60 yr or 40 yr windows were not statistically different from zero (e.g. for 60 yr window: mean= 0.11 ± 0.92 mm/yr). This pattern is similar to a fingerprint of dynamic SLR established by sea-level projections in several climate model studies. Correlations were consistent with accelerated SLR associated with a slowdown of Atlantic Meridional Overturning Current.

An adaptive large neighborhood search heuristic for Two-Echelon Vehicle Routing Problems arising in city logistics

PubMed Central

Hemmelmayr, Vera C.; Cordeau, Jean-François; Crainic, Teodor Gabriel

2012-01-01

In this paper, we propose an adaptive large neighborhood search heuristic for the Two-Echelon Vehicle Routing Problem (2E-VRP) and the Location Routing Problem (LRP). The 2E-VRP arises in two-level transportation systems such as those encountered in the context of city logistics. In such systems, freight arrives at a major terminal and is shipped through intermediate satellite facilities to the final customers. The LRP can be seen as a special case of the 2E-VRP in which vehicle routing is performed only at the second level. We have developed new neighborhood search operators by exploiting the structure of the two problem classes considered and have also adapted existing operators from the literature. The operators are used in a hierarchical scheme reflecting the multi-level nature of the problem. Computational experiments conducted on several sets of instances from the literature show that our algorithm outperforms existing solution methods for the 2E-VRP and achieves excellent results on the LRP. PMID:23483764

An adaptive large neighborhood search heuristic for Two-Echelon Vehicle Routing Problems arising in city logistics.

PubMed

Hemmelmayr, Vera C; Cordeau, Jean-François; Crainic, Teodor Gabriel

2012-12-01

In this paper, we propose an adaptive large neighborhood search heuristic for the Two-Echelon Vehicle Routing Problem (2E-VRP) and the Location Routing Problem (LRP). The 2E-VRP arises in two-level transportation systems such as those encountered in the context of city logistics. In such systems, freight arrives at a major terminal and is shipped through intermediate satellite facilities to the final customers. The LRP can be seen as a special case of the 2E-VRP in which vehicle routing is performed only at the second level. We have developed new neighborhood search operators by exploiting the structure of the two problem classes considered and have also adapted existing operators from the literature. The operators are used in a hierarchical scheme reflecting the multi-level nature of the problem. Computational experiments conducted on several sets of instances from the literature show that our algorithm outperforms existing solution methods for the 2E-VRP and achieves excellent results on the LRP.

"Variation Problems" and Their Roles in the Topic of Fraction Division in Chinese Mathematics Textbook Examples

ERIC Educational Resources Information Center

Sun, Xuhua

2011-01-01

This article deals with the roles of variation problems ("one problem multiple solution" and "one problem multiple changes") as used in Chinese textbooks. It is argued that variation problems as an "indigenous" Chinese practice aim to discern and to compare the invariant feature of the relationship among concepts and…

Improving Teaching Quality and Problem Solving Ability through Contextual Teaching and Learning in Differential Equations: A Lesson Study Approach

ERIC Educational Resources Information Center

Khotimah, Rita Pramujiyanti; Masduki

2016-01-01

Differential equations is a branch of mathematics which is closely related to mathematical modeling that arises in real-world problems. Problem solving ability is an essential component to solve contextual problem of differential equations properly. The purposes of this study are to describe contextual teaching and learning (CTL) model in…

Chemistry and the Internal Combustion Engine II: Pollution Problems.

ERIC Educational Resources Information Center

Hunt, C. B.

1979-01-01

Discusses pollution problems which arise from the use of internal combustion (IC) engines in the United Kingdom (UK). The IC engine exhaust emissions, controlling IC engine pollution in the UK, and some future developments are also included. (HM)

Assessment of Sampling Approaches for Remote Sensing Image Classification in the Iranian Playa Margins

NASA Astrophysics Data System (ADS)

Kazem Alavipanah, Seyed

There are some problems in soil salinity studies based upon remotely sensed data: 1-spectral world is full of ambiguity and therefore soil reflectance can not be attributed to a single soil property such as salinity, 2) soil surface conditions as a function of time and space is a complex phenomena, 3) vegetation with a dynamic biological nature may create some problems in the study of soil salinity. Due to these problems the first question which may arise is how to overcome or minimise these problems. In this study we hypothesised that different sources of data, well established sampling plan and optimum approach could be useful. In order to choose representative training sites in the Iranian playa margins, to define the spectral and informational classes and to overcome some problems encountered in the variation within the field, the following attempts were made: 1) Principal Component Analysis (PCA) in order: a) to determine the most important variables, b) to understand the Landsat satellite images and the most informative components, 2) the photomorphic unit (PMU) consideration and interpretation; 3) study of salt accumulation and salt distribution in the soil profile, 4) use of several forms of field data, such as geologic, geomorphologic and soil information; 6) confirmation of field data and land cover types with farmers and the members of the team. The results led us to find at suitable approaches with a high and acceptable image classification accuracy and image interpretation. KEY WORDS; Photo Morphic Unit, Pprincipal Ccomponent Analysis, Soil Salinity, Field Work, Remote Sensing

Reprint of Solution of Ambrosio-Tortorelli model for image segmentation by generalized relaxation method

NASA Astrophysics Data System (ADS)

D'Ambra, Pasqua; Tartaglione, Gaetano

2015-04-01

Image segmentation addresses the problem to partition a given image into its constituent objects and then to identify the boundaries of the objects. This problem can be formulated in terms of a variational model aimed to find optimal approximations of a bounded function by piecewise-smooth functions, minimizing a given functional. The corresponding Euler-Lagrange equations are a set of two coupled elliptic partial differential equations with varying coefficients. Numerical solution of the above system often relies on alternating minimization techniques involving descent methods coupled with explicit or semi-implicit finite-difference discretization schemes, which are slowly convergent and poorly scalable with respect to image size. In this work we focus on generalized relaxation methods also coupled with multigrid linear solvers, when a finite-difference discretization is applied to the Euler-Lagrange equations of Ambrosio-Tortorelli model. We show that non-linear Gauss-Seidel, accelerated by inner linear iterations, is an effective method for large-scale image analysis as those arising from high-throughput screening platforms for stem cells targeted differentiation, where one of the main goal is segmentation of thousand of images to analyze cell colonies morphology.

Solution of Ambrosio-Tortorelli model for image segmentation by generalized relaxation method

NASA Astrophysics Data System (ADS)

D'Ambra, Pasqua; Tartaglione, Gaetano

2015-03-01

Image segmentation addresses the problem to partition a given image into its constituent objects and then to identify the boundaries of the objects. This problem can be formulated in terms of a variational model aimed to find optimal approximations of a bounded function by piecewise-smooth functions, minimizing a given functional. The corresponding Euler-Lagrange equations are a set of two coupled elliptic partial differential equations with varying coefficients. Numerical solution of the above system often relies on alternating minimization techniques involving descent methods coupled with explicit or semi-implicit finite-difference discretization schemes, which are slowly convergent and poorly scalable with respect to image size. In this work we focus on generalized relaxation methods also coupled with multigrid linear solvers, when a finite-difference discretization is applied to the Euler-Lagrange equations of Ambrosio-Tortorelli model. We show that non-linear Gauss-Seidel, accelerated by inner linear iterations, is an effective method for large-scale image analysis as those arising from high-throughput screening platforms for stem cells targeted differentiation, where one of the main goal is segmentation of thousand of images to analyze cell colonies morphology.

"Que vienen los lobos!" (Breve nota sobre el plural de los apellidos) ("May The Wolves Come:" [A Brief Note on the Plural of Surnames])

ERIC Educational Resources Information Center

Vivaldi, Gonzalo Martin

1975-01-01

This article discusses the problems that arise with the formation of plural forms of surnames in Spanish, problems both with morphology and with ambiguity. Suggestions as to how to lessen problems are made. (Text is in Spanish.) (CLK)

Hotspot of accelerated sea-level rise on the Atlantic coast of North America

USGS Publications Warehouse

Sallenger,, Asbury H.; Doran, Kara S.; Howd, Peter A.

2012-01-01

Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes, arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes, arising from mass redistributions changing gravity and the Earth's rotation and shape. These sea-level variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints. Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950–1979 and 1980–2009, SLR rate increases in this northeast hotspot were ~ 3–4 times higher than the global average. Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24–36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm. SLR superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration.

Synovial sarcoma of the neck associated with previous head and neck radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mischler, N.E.; Chuprevich, T.; Tormey, D.C.

1978-08-01

Synovial sarcoma is a rare neoplasm that uncommonly arises in the neck. Fourteen years after facial and neck radiation therapy for acne, synovial sarcoma of the neck developed in a young man. Possible radiation-induced benign and malignant neoplasms that arise in the head and neck region, either of thyroid or extrathyroid origin, remain a continuing medical problem.

Obesity: a problem of darwinian proportions?

PubMed

Watnick, Suzanne

2006-10-01

Obesity has been described as an abnormality arising from the evolution of man, who becomes fat during the time of perpetual plenty. From the perspective of "Darwinian Medicine," if famine is avoided, obesity will prevail. Problems regarding obesity arise within many disciplines, including socioeconomic environments, the educational system, science, law, and government. This article will discuss various ethical aspects of several disciplines regarding obesity, with a focus on scientific inquiry. We will discuss this within the categories: (1) chronic kidney disease predialysis, (2) dialysis, and (3) renal transplantation. This article aims to help nephrologists and their patients navigate through the ethical aspects of obesity and chronic kidney disease.

Riemann–Hilbert problem approach for two-dimensional flow inverse scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agaltsov, A. D., E-mail: agalets@gmail.com; Novikov, R. G., E-mail: novikov@cmap.polytechnique.fr; IEPT RAS, 117997 Moscow

2014-10-15

We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given.

Carbon cycle: Nitrogen's carbon bonus

NASA Astrophysics Data System (ADS)

Janssens, Ivan A.; Luyssaert, Sebastiaan

2009-05-01

Atmospheric deposition of nitrogen can, but does not always, speed up the sequestration of carbon in trees and forest soil. This complexity may arise from the spatial variations in each of the three mechanisms by which nitrogen affects carbon storage.

Influence of ocean tides on the diurnal and semidiurnal earth rotation variations from VLBI observations

NASA Astrophysics Data System (ADS)

Gubanov, V. S.; Kurdubov, S. L.

2015-05-01

The International astrogeodetic standard IERS Conventions (2010) contains a model of the diurnal and semidiurnal variations in Earth rotation parameters (ERPs), the pole coordinates and the Universal Time, arising from lunisolar tides in the world ocean. This model was constructed in the mid-1990s through a global analysis of Topex/Poseidon altimetry. The goal of this study is to try to estimate the parameters of this model by processing all the available VLBI observations on a global network of stations over the last 35 years performed within the framework of IVS (International VLBI Service) geodetic programs. The complexity of the problemlies in the fact that the sought-for corrections to the parameters of this model lie within 1 mm and, thus, are at the limit of their detectability by all currently available methods of ground-based positional measurements. This requires applying universal software packages with a high accuracy of reduction calculations and a well-developed system of controlling the simultaneous adjustment of observational data to analyze long series of VLBI observations. This study has been performed with the QUASAR software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences. Although the results obtained, on the whole, confirm a high accuracy of the basic model in the IERS Conventions (2010), statistically significant corrections that allow this model to be refined have been detected for some harmonics of the ERP variations.

Closed solutions to a differential-difference equation and an associated plate solidification problem.

PubMed

Layeni, Olawanle P; Akinola, Adegbola P; Johnson, Jesse V

2016-01-01

Two distinct and novel formalisms for deriving exact closed solutions of a class of variable-coefficient differential-difference equations arising from a plate solidification problem are introduced. Thereupon, exact closed traveling wave and similarity solutions to the plate solidification problem are obtained for some special cases of time-varying plate surface temperature.

POEMS in Newton's Aerodynamic Frustum

ERIC Educational Resources Information Center

Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

2010-01-01

The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

How Do They Solve It? An Insight into the Learner's Approach to the Mechanism of Physics Problem Solving

ERIC Educational Resources Information Center

Hegde, Balasubrahmanya; Meera, B. N.

2012-01-01

A perceived difficulty is associated with physics problem solving from a learner's viewpoint, arising out of a multitude of reasons. In this paper, we have examined the microstructure of students' thought processes during physics problem solving by combining the analysis of responses to multiple-choice questions and semistructured student…

Corrosion control and disinfection studies in spacecraft water systems. [considering Saturn 5 orbital workshop

NASA Technical Reports Server (NTRS)

Shea, T. G.

1974-01-01

Disinfection and corrosion control in the water systems of the Saturn 5 Orbital Workshop Program are considered. Within this framework, the problem areas of concern are classified into four general areas: disinfection; corrosion; membrane-associated problems of disinfectant uptake and diffusion; and taste and odor problems arising from membrane-disinfectant interaction.

Psychotherapy with Older Dying Persons.

ERIC Educational Resources Information Center

Dye, Carol J.

Psychotherapy with older dying patients can lead to problems of countertransference for the clinician. Working with dying patients requires flexibility to adapt basic therapeutics to the institutional setting. Goals of psychotherapy must be reconceptualized for dying clients. The problems of countertransference arise because clinicians themselves…

Spelling: A Visual Skill.

ERIC Educational Resources Information Center

Hendrickson, Homer

1988-01-01

Spelling problems arise due to problems with form discrimination and inadequate visualization. A child's sequence of visual development involves learning motor control and coordination, with vision directing and monitoring the movements; learning visual comparison of size, shape, directionality, and solidity; developing visual memory or recall;…

Inequalities, assessment and computer algebra

NASA Astrophysics Data System (ADS)

Sangwin, Christopher J.

2015-01-01

The goal of this paper is to examine single variable real inequalities that arise as tutorial problems and to examine the extent to which current computer algebra systems (CAS) can (1) automatically solve such problems and (2) determine whether students' own answers to such problems are correct. We review how inequalities arise in contemporary curricula. We consider the formal mathematical processes by which such inequalities are solved, and we consider the notation and syntax through which solutions are expressed. We review the extent to which current CAS can accurately solve these inequalities, and the form given to the solutions by the designers of this software. Finally, we discuss the functionality needed to deal with students' answers, i.e. to establish equivalence (or otherwise) of expressions representing unions of intervals. We find that while contemporary CAS accurately solve inequalities there is a wide variety of notation used.

An iterative Riemann solver for systems of hyperbolic conservation law s, with application to hyperelastic solid mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Gregory H.

2003-08-06

In this paper we present a general iterative method for the solution of the Riemann problem for hyperbolic systems of PDEs. The method is based on the multiple shooting method for free boundary value problems. We demonstrate the method by solving one-dimensional Riemann problems for hyperelastic solid mechanics. Even for conditions representative of routine laboratory conditions and military ballistics, dramatic differences are seen between the exact and approximate Riemann solution. The greatest discrepancy arises from misallocation of energy between compressional and thermal modes by the approximate solver, resulting in nonphysical entropy and temperature estimates. Several pathological conditions arise in commonmore » practice, and modifications to the method to handle these are discussed. These include points where genuine nonlinearity is lost, degeneracies, and eigenvector deficiencies that occur upon melting.« less

Complexity seems to open a way towards a new Aristotelian-Thomistic ontology.

PubMed

Strumia, Alberto

2007-01-01

Today's sciences seem to converge all towards very similar foundational questions. Such claims, both of epistemological and ontological nature, seem to rediscover, in a new fashion some of the most relevant topics of ancient Greek and Mediaeval philosophy of nature, logic and metaphysics, such as the problem of the relationship between the whole and its parts (non redictionism), the problems of the paradoxes arising from the attempt to conceive the entity like an univocal concept (analogy and analogia entis), the problem of the mind-body relationship and that of an adequate cognitive theory (abstraction and immaterial nature of the mind), the complexity of some physical, chemical and biological systems and global properties arising from information (matter-form theory), etc. Medicine too is involved in some of such relevant questions and cannot avoid to take them into a special account.

Identifying Unique Ethical Challenges of Indigenous Field-Workers: A Commentary on Alexander and Richman's "Ethical Dilemmas in Evaluations Using Indigenous Research Workers"

ERIC Educational Resources Information Center

Smith, Nick L.

2008-01-01

In contrast with nonindigenous workers, to what extent do unique ethical problems arise when indigenous field-workers participate in field studies? Three aspects of study design and operation are considered: data integrity issues, risk issues, and protection issues. Although many of the data quality issues that arise with the use of indigenous…

A Computer Program for Solving a Set of Conditional Maximum Likelihood Equations Arising in the Rasch Model for Questionnaires.

ERIC Educational Resources Information Center

Andersen, Erling B.

A computer program for solving the conditional likelihood equations arising in the Rasch model for questionnaires is described. The estimation method and the computational problems involved are described in a previous research report by Andersen, but a summary of those results are given in two sections of this paper. A working example is also…

Inhomogeneity of microstructure, mechanical properties, magnetism, and corrosion observed in a 12Cr18Ni10Ti fuel assembly shroud irradiated in BN-350 to 59 dpa

NASA Astrophysics Data System (ADS)

Maksimkin, O. P.; Tsay, K. V.; Garner, F. A.

2015-12-01

A hexagonal shroud containing a standard in-core fueled subassembly from the BN-350 reactor was examined after reaching 59 dpa maximum, followed by long-term storage underwater. Specimens were derived from both mid-face and rib-corner positions. It was shown that there were complex spatial variations in void swelling, mechanical properties, microhardness, radiation-induced magnetism as well as corrosion while underwater. The spatial variations arose from two major sources. The first source was variations in height associated with variations in dpa rate and irradiation temperature. The second source was shown to be spatial variations in starting microstructure arising primarily from a higher level of initial deformation and hardness in the rib-corners of the hexagonal shroud. With irradiation the differences in microhardness between the two regions disappeared, but void swelling in the rib areas was larger than at mid-face positions. The swelling enhancement at the corners is thought to arise primarily from the combined effect of temper annealing at a temperature known to remove carbon from the matrix before irradiation, and the influence of higher deformed microstructures to accelerate recrystallization, possibly with assistance from localized residual stresses. Swelling was relatively low at the bottom low-temperature end of the shroud, but increased on the upper end of the assembly, reflecting primarily a transition between a precipitation regime involving titanium carbide to one involving nickel-rich and silicon-rich G-phase.

A new normalizing algorithm for BAC CGH arrays with quality control metrics.

PubMed

Miecznikowski, Jeffrey C; Gaile, Daniel P; Liu, Song; Shepherd, Lori; Nowak, Norma

2011-01-01

The main focus in pin-tip (or print-tip) microarray analysis is determining which probes, genes, or oligonucleotides are differentially expressed. Specifically in array comparative genomic hybridization (aCGH) experiments, researchers search for chromosomal imbalances in the genome. To model this data, scientists apply statistical methods to the structure of the experiment and assume that the data consist of the signal plus random noise. In this paper we propose "SmoothArray", a new method to preprocess comparative genomic hybridization (CGH) bacterial artificial chromosome (BAC) arrays and we show the effects on a cancer dataset. As part of our R software package "aCGHplus," this freely available algorithm removes the variation due to the intensity effects, pin/print-tip, the spatial location on the microarray chip, and the relative location from the well plate. removal of this variation improves the downstream analysis and subsequent inferences made on the data. Further, we present measures to evaluate the quality of the dataset according to the arrayer pins, 384-well plates, plate rows, and plate columns. We compare our method against competing methods using several metrics to measure the biological signal. With this novel normalization algorithm and quality control measures, the user can improve their inferences on datasets and pinpoint problems that may arise in their BAC aCGH technology.

Solving LP Relaxations of Large-Scale Precedence Constrained Problems

NASA Astrophysics Data System (ADS)

Bienstock, Daniel; Zuckerberg, Mark

We describe new algorithms for solving linear programming relaxations of very large precedence constrained production scheduling problems. We present theory that motivates a new set of algorithmic ideas that can be employed on a wide range of problems; on data sets arising in the mining industry our algorithms prove effective on problems with many millions of variables and constraints, obtaining provably optimal solutions in a few minutes of computation.

NASA Aviation Safety Reporting System

NASA Technical Reports Server (NTRS)

1980-01-01

Problems in briefing of relief by air traffic controllers are discussed, including problems that arise when duty positions are changed by controllers. Altimeter reading and setting errors as factors in aviation safety are discussed, including problems associated with altitude-including instruments. A sample of reports from pilots and controllers is included, covering the topics of ATIS broadcasts an clearance readback problems. A selection of Alert Bulletins, with their responses, is included.

Projected regression method for solving Fredholm integral equations arising in the analytic continuation problem of quantum physics

NASA Astrophysics Data System (ADS)

Arsenault, Louis-François; Neuberg, Richard; Hannah, Lauren A.; Millis, Andrew J.

2017-11-01

We present a supervised machine learning approach to the inversion of Fredholm integrals of the first kind as they arise, for example, in the analytic continuation problem of quantum many-body physics. The approach provides a natural regularization for the ill-conditioned inverse of the Fredholm kernel, as well as an efficient and stable treatment of constraints. The key observation is that the stability of the forward problem permits the construction of a large database of outputs for physically meaningful inputs. Applying machine learning to this database generates a regression function of controlled complexity, which returns approximate solutions for previously unseen inputs; the approximate solutions are then projected onto the subspace of functions satisfying relevant constraints. Under standard error metrics the method performs as well or better than the Maximum Entropy method for low input noise and is substantially more robust to increased input noise. We suggest that the methodology will be similarly effective for other problems involving a formally ill-conditioned inversion of an integral operator, provided that the forward problem can be efficiently solved.

How Seductive Are Decorative Elements in Learning Materials?

ERIC Educational Resources Information Center

Rey, Gunter Daniel

2012-01-01

The seductive detail effect arises when people learn more deeply from a multimedia presentation when interesting but irrelevant adjuncts are excluded. However, previous studies about this effect are rather inconclusive and contained various methodical problems. The recent experiment attempted to overcome these methodical problems. Undergraduate…

Phantom Effects in Multilevel Compositional Analysis: Problems and Solutions

ERIC Educational Resources Information Center

Pokropek, Artur

2015-01-01

This article combines statistical and applied research perspective showing problems that might arise when measurement error in multilevel compositional effects analysis is ignored. This article focuses on data where independent variables are constructed measures. Simulation studies are conducted evaluating methods that could overcome the…

Variation in mating system among birds: ecological basis revealed by hierarchical comparative analysis of mate desertion

PubMed Central

Owens, I. P. F.; Bennett, P. M.

1997-01-01

Since most bird species are socially monogamous, variation among species in social mating systems is determined largely by variation in the frequency of mate desertion. Mate desertion is expected to occur when the benefits, in terms of additional reproductive opportunities, outweigh the costs, in terms of reduced reproductive success from the present brood. However, despite much research, the relative importance of costs and benefits in explaining mating system variation is not well understood. Here, we investigate this problem using a comparative method. We analyse changes in the frequency of mate desertion at different phylogenetic levels. Differences between orders and families in the frequency of desertion are negatively associated with changes in the potential costs of desertion, but are not associated with changes in the potential benefits of desertion. Conversely, differences among genera and species in the frequency of desertion are positively associated with increases in the potential benefits of desertion, but not with changes in the potential costs of desertion. Hence, we suggest that mate desertion in birds originates through a combination of evolutionary predisposition and ecological facilitation. In particular, ancient changes in life-history strategy determine the costs of desertion and predispose certain lineages to polygamy, while contemporary changes in the distribution of resources determine the benefits of desertion and thereby the likelihood that polygamy will be viable within these lineages. Thus, monogamy can arise via two very different evolutionary pathways. Groups such as albatrosses (Procellariidae) are constrained to social monogamy by the high cost to desertion, irrespective of the potential benefits. However, in groups such as the accentors (Prunellidae), which are predisposed to desertion, monogamy occurs only when the benefits of desertion are very limited. These conclusions emphasise the additional power which a hierarchical approach contributes to the modern comparative method.

Interannual Atmospheric Variability Simulated by a Mars GCM: Impacts on the Polar Regions

NASA Technical Reports Server (NTRS)

Bridger, Alison F. C.; Haberle, R. M.; Hollingsworth, J. L.

2003-01-01

It is often assumed that in the absence of year-to-year dust variations, Mars weather and climate are very repeatable, at least on decadal scales. Recent multi-annual simulations of a Mars GCM reveal however that significant interannual variations may occur with constant dust conditions. In particular, interannual variability (IAV) appears to be associated with the spectrum of atmospheric disturbances that arise due to baroclinic instability. One quantity that shows significant IAV is the poleward heat flux associated with these waves. These variations and their impacts on the polar heat balance will be examined here.

An MHD variational principle that admits reconnection

NASA Technical Reports Server (NTRS)

Rilee, M. L.; Sudan, R. N.; Pfirsch, D.

1997-01-01

The variational approach of Pfirsch and Sudan's averaged magnetohydrodynamics (MHD) to the stability of a line-tied current layer is summarized. The effect of line-tying on current sheets that might arise in line-tied magnetic flux tubes by estimating the growth rates of a resistive instability using a variational method. The results show that this method provides a potentially new technique to gauge the stability of nearly ideal magnetohydrodynamic systems. The primary implication for the stability of solar coronal structures is that tearing modes are probably constant at work removing magnetic shear from the solar corona.

Transformational leadership can improve workforce competencies.

PubMed

Thompson, Juliana

2012-03-01

Staffing problems can arise because of poor delegation skills or a failure by leaders to respond appropriately to economic factors and patient demographics. Training dilemmas, meanwhile, can arise because of managers' confusion about what constitutes 'training' and what constitutes 'education', and where responsibility of provision lies, with the consequence that they neglect these activities. This article uses Kouzes and Posner's (2009) transformational leadership model to show how managers can respond. Leaders who challenge budgets, consider new ways of working and engage effectively with the workforce can improve productivity and care, while those who invest in appropriate learning will have a highly trained workforce. The author explains how integration of leadership roles and management functions can lead to innovative problem solving.

Euthanasia from the perspective of hospice care.

PubMed

Gillett, G

1994-01-01

The hospice believes in the concept of a gentle and harmonious death. In most hospice settings there is also a rejection of active euthanasia. This set of two apparently conflicting principles can be defended on the basis of two arguments. The first is that doctors should not foster the intent to kill as part of their moral and clinical character. This allows proper sensitivity to the complex and difficult situation that arises in many of the most difficult terminal care situations. The second argument turns on the seduction of technological solutions to human problems and the slippery slope that may arise in the presence of a quick and convenient way of dealing with problems of death and dying.

Contact line motion over substrates with spatially non-uniform properties

NASA Astrophysics Data System (ADS)

Ajaev, Vladimir; Gatapova, Elizaveta; Kabov, Oleg

2017-11-01

We develop mathematical models of moving contact lines over flat solid surfaces with spatial variation of temperature and wetting properties under the conditions when evaporation is significant. The gas phase is assumed to be pure vapor and a lubrication-type framework is employed for describing viscous flow in the liquid. Marangoni stresses at the liquid surface arise as a result of temperature variation in the vapor phase, non-equilibrium effects during evaporation at the interface, and Kelvin effect. The relative importance of these three factors is determined. Variation of wetting properties is modeled through a two-component disjoining pressure, with the main focus on spatially periodic patterns leading to time-periodic variation of the contact line speed.

Solving Integer Programs from Dependence and Synchronization Problems

DTIC Science & Technology

1993-03-01

DEFF.NSNE Solving Integer Programs from Dependence and Synchronization Problems Jaspal Subhlok March 1993 CMU-CS-93-130 School of Computer ScienceT IC...method Is an exact and efficient way of solving integer programming problems arising in dependence and synchronization analysis of parallel programs...7/;- p Keywords: Exact dependence tesing, integer programming. parallelilzng compilers, parallel program analysis, synchronization analysis Solving

The King and Prisoner Puzzle: A Way of Introducing the Components of Logical Structures

ERIC Educational Resources Information Center

Roh, Kyeong Hah; Lee, Yong Hah; Tanner, Austin

2016-01-01

The purpose of this paper is to provide issues related to student understanding of logical components that arise when solving word problems. We designed a logic problem called the King and Prisoner Puzzle--a linguistically simple, yet logically challenging problem. In this paper, we describe various student solutions to the puzzle and discuss the…

The application of NASTRAN at Sperry Univac Holland. [analysis of engineering, modelling, and use of program system

NASA Technical Reports Server (NTRS)

Koopmans, G.

1973-01-01

Very divergent problems arising with different calculations indicate that NASTRAN is not always accessible for common use. Problems with engineering, modelling, and use of the program system are analysed and a way of solution is outlined. Related to this, some supplementary modifications are made at Sperry Univac Holland to facilitate the program for the less skilled user. The implementation of a new element also gives an insight into the use of NASTRAN at Sperry Univac Holland. As the users of Univac computers are from very different kinds of industries like shipbuilders, petrochemical industries, and building industries, the variety of problems coming from these users is very large. This variety results in experience not with one special kind of calculation nor one special kind of construction, but with a wide area of problems arising in the use of NASTRAN. These problems can roughly be divided into three different groups: (1) recognition of what is to be calculated and how, (2) construction of a model, and (3) handling the NASTRAN program. These are the basic problems for every less skilled user of NASTRAN and the Application/Research Department of Sperry Univac has to give reasonable answers to these questions.

[Errors in wound management].

PubMed

Filipović, Marinko; Novinscak, Tomislav

2014-10-01

Chronic ulcers have adverse effects on the patient quality of life and productivity, thus posing financial burden upon the healthcare system. Chronic wound healing is a complex process resulting from the interaction of the patient general health status, wound related factors, medical personnel skill and competence, and therapy related products. In clinical practice, considerable improvement has been made in the treatment of chronic wounds, which is evident in the reduced rate of the severe forms of chronic wounds in outpatient clinics. However, in spite of all the modern approaches, efforts invested by medical personnel and agents available for wound care, numerous problems are still encountered in daily practice. Most frequently, the problems arise from inappropriate education, of young personnel in particular, absence of multidisciplinary approach, and inadequate communication among the personnel directly involved in wound treatment. To perceive them more clearly, the potential problems or complications in the management of chronic wounds can be classified into the following groups: problems mostly related to the use of wound coverage and other etiology related specificities of wound treatment; problems related to incompatibility of the agents used in wound treatment; and problems arising from failure to ensure aseptic and antiseptic performance conditions.

Variational principle for the Navier-Stokes equations.

PubMed

Kerswell, R R

1999-05-01

A variational principle is presented for the Navier-Stokes equations in the case of a contained boundary-driven, homogeneous, incompressible, viscous fluid. Based upon making the fluid's total viscous dissipation over a given time interval stationary subject to the constraint of the Navier-Stokes equations, the variational problem looks overconstrained and intractable. However, introducing a nonunique velocity decomposition, u(x,t)=phi(x,t) + nu(x,t), "opens up" the variational problem so that what is presumed a single allowable point over the velocity domain u corresponding to the unique solution of the Navier-Stokes equations becomes a surface with a saddle point over the extended domain (phi,nu). Complementary or dual variational problems can then be constructed to estimate this saddle point value strictly from above as part of a minimization process or below via a maximization procedure. One of these reduced variational principles is the natural and ultimate generalization of the upper bounding problem developed by Doering and Constantin. The other corresponds to the ultimate Busse problem which now acts to lower bound the true dissipation. Crucially, these reduced variational problems require only the solution of a series of linear problems to produce bounds even though their unique intersection is conjectured to correspond to a solution of the nonlinear Navier-Stokes equations.

A temps nouveaux, solutions nouvelles: quelques propositions (New Times, New Solutions: Some Proposals).

ERIC Educational Resources Information Center

Capelle, Guy

1983-01-01

Serious problems in education in Latin America arising from political, economic, and social change periodically put in question the status, objectives, and manner of French second-language instruction. A number of solutions to general and specific pedagogical problems are proposed. (MSE)

Understanding Gender-Based Wage Discrimination: Legal Interpretation and Trends of Pay Equity in Higher Education.

ERIC Educational Resources Information Center

Luna, Gaye

1990-01-01

Traces the history of laws and litigation concerning pay equity issues, also referred to as wage equity and comparable worth. Suggests that universities and colleges identify possible problems and take voluntary corrective measures before pay-equity problems arise. (MLF)

Reflective Questions, Self-Questioning and Managing Professionally Situated Practice

ERIC Educational Resources Information Center

Malthouse, Richard; Watts, Mike; Roffey-Barentsen, Jodi

2015-01-01

Reflective self-questioning arises within the workplace when people are confronted with professional problems and situations. This paper focuses on reflective and "situated reflective" questions in terms of self-questioning and professional workplace problem solving. In our view, the situational context, entailed by the setting, social…

Expanding the scope of health information systems. Challenges and developments.

PubMed

Kuhn, K A; Wurst, S H R; Bott, O J; Giuse, D A

2006-01-01

To identify current challenges and developments in health information systems. Reports on HIS, eHealth and process support were analyzed, core problems and challenges were identified. Health information systems are extending their scope towards regional networks and health IT infrastructures. Integration, interoperability and interaction design are still today's core problems. Additional problems arise through the integration of genetic information into the health care process. There are noticeable trends towards solutions for these problems.

Can ethnography save the life of medical ethics?

PubMed

Hoffmaster, B

1992-12-01

Since its inception contemporary medical ethics has been regarded by many of its practitioners as 'applied ethics', that is, the application of philosophical theories to the moral problems that arise in health care. This 'applied ethics' model of medical ethics is, however, beset with internal and external difficulties. The internal difficulties point out that the model is intrinsically flawed. The external difficulties arise because the model does not fit work in the field. Indeed, the strengths of that work are its highly nuanced, particularized analyses of cases and issues and its appreciation of the circumstances and contexts that generate and structure these cases and issues. A shift away from a theory-driven 'applied ethics' to a more situational, contextual approach to medical ethics opens the way for ethnographic studies of moral problems in health care as well as a conception of moral theory that is more responsive to the empirical dimensions of those problems.

Communicating Scientific Findings to Lawyers, Policy-Makers, and the Public (Invited)

NASA Astrophysics Data System (ADS)

Thompson, W.; Velsko, S. P.

2013-12-01

This presentation will summarize the authors' collaborative research on inferential errors, bias and communication difficulties that have arisen in the area of WMD forensics. This research involves analysis of problems that have arisen in past national security investigations, interviews with scientists from various disciplines whose work has been used in WMD investigations, interviews with policy-makers, and psychological studies of lay understanding of forensic evidence. Implications of this research for scientists involved in nuclear explosion monitoring will be discussed. Among the issues covered will be: - Potential incompatibilities between the questions policy makers pose and the answers that experts can provide. - Common misunderstandings of scientific and statistical data. - Advantages and disadvantages of various methods for describing and characterizing the strength of scientific findings. - Problems that can arise from excessive hedging or, alternatively, insufficient qualification of scientific conclusions. - Problems that can arise from melding scientific and non-scientific evidence in forensic assessments.

[Current problems arising from not having biosafety level 4 laboratories in Japan--qualitative study of infectious disease experts].

PubMed

Yamamoto, Yuko; Horiguchi, Itsuko; Marui, Eiji

2009-09-01

No public consensus exists yet on handling Biosafety Level 4 agents and no laboratory is operational at BSL4 in Japan. A discussion that includes neighboring residents and experts should be initiated to communicate risks. In this article, we present the current situation and prioritize problems we presently face. A three-stage Delphi survey was conducted. The subjects were twenty-two persons with extensive experience and knowledge of infectious diseases. Seven projections and issues were made with regard to the problems arising from the lack of an operational BSL4 laboratory. These were tabulated by the KJ method. The top seven projections were scored, such that the top received 7 points and the last received 1 point. A total of 51 projections were obtained for the first part of the survey, 39 for the second, and 29 for the last. The projection with the highest score was that it is impossible to cope with newly emerging infectious diseases. The second was that complete diagnoses are impossible without a BSL4 laboratory. All projections and issues were divided into the following four main groups: issues for researchers and laboratory staff, clinical practice and research on BSL4 agents, domestic and global security, and Japan's international position. We clarified possible problem arising from not having BSL4 laboratories in Japan. The identification of projections by the Delphi survey in this study should be considered as one of many attempts to develop effective risk communication strategies.

Fully Coupled Nonlinear Fluid Flow and Poroelasticity in Arbitrarily Fractured Porous Media: A Hybrid-Dimensional Computational Model

NASA Astrophysics Data System (ADS)

Jin, L.; Zoback, M. D.

2017-10-01

We formulate the problem of fully coupled transient fluid flow and quasi-static poroelasticity in arbitrarily fractured, deformable porous media saturated with a single-phase compressible fluid. The fractures we consider are hydraulically highly conductive, allowing discontinuous fluid flux across them; mechanically, they act as finite-thickness shear deformation zones prior to failure (i.e., nonslipping and nonpropagating), leading to "apparent discontinuity" in strain and stress across them. Local nonlinearity arising from pressure-dependent permeability of fractures is also included. Taking advantage of typically high aspect ratio of a fracture, we do not resolve transversal variations and instead assume uniform flow velocity and simple shear strain within each fracture, rendering the coupled problem numerically more tractable. Fractures are discretized as lower dimensional zero-thickness elements tangentially conforming to unstructured matrix elements. A hybrid-dimensional, equal-low-order, two-field mixed finite element method is developed, which is free from stability issues for a drained coupled system. The fully implicit backward Euler scheme is employed for advancing the fully coupled solution in time, and the Newton-Raphson scheme is implemented for linearization. We show that the fully discretized system retains a canonical form of a fracture-free poromechanical problem; the effect of fractures is translated to the modification of some existing terms as well as the addition of several terms to the capacity, conductivity, and stiffness matrices therefore allowing the development of independent subroutines for treating fractures within a standard computational framework. Our computational model provides more realistic inputs for some fracture-dominated poromechanical problems like fluid-induced seismicity.

The Human Microbiome and the Missing Heritability Problem

PubMed Central

Sandoval-Motta, Santiago; Aldana, Maximino; Martínez-Romero, Esperanza; Frank, Alejandro

2017-01-01

The “missing heritability” problem states that genetic variants in Genome-Wide Association Studies (GWAS) cannot completely explain the heritability of complex traits. Traditionally, the heritability of a phenotype is measured through familial studies using twins, siblings and other close relatives, making assumptions on the genetic similarities between them. When this heritability is compared to the one obtained through GWAS for the same traits, a substantial gap between both measurements arise with genome wide studies reporting significantly smaller values. Several mechanisms for this “missing heritability” have been proposed, such as epigenetics, epistasis, and sequencing depth. However, none of them are able to fully account for this gap in heritability. In this paper we provide evidence that suggests that in order for the phenotypic heritability of human traits to be broadly understood and accounted for, the compositional and functional diversity of the human microbiome must be taken into account. This hypothesis is based on several observations: (A) The composition of the human microbiome is associated with many important traits, including obesity, cancer, and neurological disorders. (B) Our microbiome encodes a second genome with nearly a 100 times more genes than the human genome, and this second genome may act as a rich source of genetic variation and phenotypic plasticity. (C) Human genotypes interact with the composition and structure of our microbiome, but cannot by themselves explain microbial variation. (D) Microbial genetic composition can be strongly influenced by the host's behavior, its environment or by vertical and horizontal transmissions from other hosts. Therefore, genetic similarities assumed in familial studies may cause overestimations of heritability values. We also propose a method that allows the compositional and functional diversity of our microbiome to be incorporated to genome wide association studies. PMID:28659968

Infrared variation reduction by simultaneous background suppression and target contrast enhancement for deep convolutional neural network-based automatic target recognition

NASA Astrophysics Data System (ADS)

Kim, Sungho

2017-06-01

Automatic target recognition (ATR) is a traditionally challenging problem in military applications because of the wide range of infrared (IR) image variations and the limited number of training images. IR variations are caused by various three-dimensional target poses, noncooperative weather conditions (fog and rain), and difficult target acquisition environments. Recently, deep convolutional neural network-based approaches for RGB images (RGB-CNN) showed breakthrough performance in computer vision problems, such as object detection and classification. The direct use of RGB-CNN to the IR ATR problem fails to work because of the IR database problems (limited database size and IR image variations). An IR variation-reduced deep CNN (IVR-CNN) to cope with the problems is presented. The problem of limited IR database size is solved by a commercial thermal simulator (OKTAL-SE). The second problem of IR variations is mitigated by the proposed shifted ramp function-based intensity transformation. This can suppress the background and enhance the target contrast simultaneously. The experimental results on the synthesized IR images generated by the thermal simulator (OKTAL-SE) validated the feasibility of IVR-CNN for military ATR applications.

Addressing Cultural Diversity: Effects of a Problem-Based Intercultural Learning Unit

ERIC Educational Resources Information Center

Busse, Vera; Krause, Ulrike-Marie

2015-01-01

This article explores to what extent a problem-based learning unit in combination with cooperative learning and affectively oriented teaching methods facilitates intercultural learning. As part of the study, students reflected on critical incidents, which display misunderstandings or conflicts that arise as a result of cultural differences. In…

A Separate Reality: The Problem of Uncooperative Experiments.

ERIC Educational Resources Information Center

Lersten, Ken

The problem of the uncooperative experiment arises with the use of human subjects. Evidence shows that typical volunteer subjects have the following characteristics: better education, higher paying jobs, greater need for approval, lower authoritarianism, higher I.Q. score, and better adjustment to personal questions than nonvolunteers. Data also…

Introducing Mathematics to Information Problem-Solving Tasks: Surface or Substance?

ERIC Educational Resources Information Center

Erickson, Ander

2017-01-01

This study employs a cross-case analysis in order to explore the demands and opportunities that arise when information problem-solving tasks are introduced into college mathematics classes. Professors at three universities collaborated with me to develop statistics-related activities that required students to engage in research outside the…

Classroom Crisis Intervention through Contracting: A Moral Development Model.

ERIC Educational Resources Information Center

Smaby, Marlowe H.; Tamminen, Armas W.

1981-01-01

A counselor can arbitrate problem situations using a systematic approach to classroom intervention which includes meetings with the teacher and students. This crisis intervention model based on moral development can be more effective than reliance on guidance activities disconnected from the actual classroom settings where the problems arise.…

Lexical Frames and Reported Speech

ERIC Educational Resources Information Center

Williams, Howard

2004-01-01

This paper addresses a problem of lexical choice that arises for ESL/EFL learners in the writing of research papers, critiques, interview reports, or any other sort of discourse that requires source attribution. The problem falls naturally into two parts. One part concerns the general lack of linguistic resources typically available (for various…

RACIAL IMBALANCE AND EDUCATIONAL PLANNING.

ERIC Educational Resources Information Center

CONROY, VINCENT F.

HARVARD'S ADMINISTRATIVE CAREER PROGRAM FACED THE GROWING PROBLEM OF NEGRO ENROLLMENT IN THE PUBLIC SCHOOLS. NOTING THE FREQUENCY AND INTENSITY WITH WHICH THE PROBLEM WAS ARISING AT THE NATIONAL LEVEL, A GROUP OF LAWYERS AND EDUCATORS CONVENED TO WORK OUT THE LEGAL ASPECTS OF SCHOOL INTEGRATION. FUNDS FROM THE FORD FOUNDATION INITIATED THE…

Polyomino Problems to Confuse Computers

ERIC Educational Resources Information Center

Coffin, Stewart

2009-01-01

Computers are very good at solving certain types combinatorial problems, such as fitting sets of polyomino pieces into square or rectangular trays of a given size. However, most puzzle-solving programs now in use assume orthogonal arrangements. When one departs from the usual square grid layout, complications arise. The author--using a computer,…

Digital Maps, Matrices and Computer Algebra

ERIC Educational Resources Information Center

Knight, D. G.

2005-01-01

The way in which computer algebra systems, such as Maple, have made the study of complex problems accessible to undergraduate mathematicians with modest computational skills is illustrated by some large matrix calculations, which arise from representing the Earth's surface by digital elevation models. Such problems are often considered to lie in…

Development of a process control computer device for the adaptation of flexible wind tunnel walls

NASA Technical Reports Server (NTRS)

Barg, J.

1982-01-01

In wind tunnel tests, the problems arise of determining the wall pressure distribution, calculating the wall contour, and controlling adjustment of the walls. This report shows how these problems have been solved for the high speed wind tunnel of the Technical University of Berlin.

CONGRESS ON SCIENCE TEACHING AND ECONOMIC GROWTH.

ERIC Educational Resources Information Center

Inter-Union Commission on the Teaching of Science, Paris (France).

REPORTED ARE THE ACTIVITIES OF THE CONGRESS ORGANIZED BY THE INTER-UNION COMMISSION ON SCIENCE TEACHING (CEIS) OF THE INTERNATIONAL COUNCIL OF SCIENTIFIC UNIONS (ICSU). STUDIED WERE PROBLEMS ARISING IN SEVERAL BRANCHES OF KNOWLEDGE DUE TO BOTH INCREASED NUMBERS OF STUDENTS AND SHORTAGE OF TEACHERS. OF PARTICULAR INTEREST WERE THE PROBLEMS OF…

IMPACTS OF MATERIAL SUBSTITUTION IN AUTOMOBILE MANUFACTURE ON RESOURCE RECOVERY. VOLUME II. APPENDICES A-E

EPA Science Inventory

Probable changes in the mix of materials used to manufacture automobiles were examined to determine if economic or technical problems in recycling could arise such that the 'abandoned automobile problem' would be resurrected. Future trends in materials composition of the automobi...

On the Inclusion of Difference Equation Problems and Z Transform Methods in Sophomore Differential Equation Classes

ERIC Educational Resources Information Center

Savoye, Philippe

2009-01-01

In recent years, I started covering difference equations and z transform methods in my introductory differential equations course. This allowed my students to extend the "classical" methods for (ordinary differential equation) ODE's to discrete time problems arising in many applications.

Ethical considerations in revision rhinoplasty.

PubMed

Wayne, Ivan

2012-08-01

The problems that arise when reviewing another surgeon's work, the financial aspects of revision surgery, and the controversies that present in marketing and advertising will be explored. The technological advances of computer imaging and the Internet have introduced new problems that require our additional consideration. Copyright © 2012 by Thieme Medical Publishers, Inc.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses.

PubMed

Eberhard, Monika J B; Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-09-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. Copyright © 2015 the American Physiological Society.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses

PubMed Central

Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-01-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. PMID:26041833

The legacy of Charles Marlatt and efforts to limit plant pest invasions

Treesearch

Andrew M. Liebhold; Robert L. Griffin

2016-01-01

The problem of invasions by non-native plant pests has come to dominate the field of applied entomology. Most of the damaging insect pests of agriculture and forestry are non-native (Sailer 1978, Aukema et al. 2010) and this is a problem being faced around the world. This problem did not arise overnight; instead, there has been a steady accumulation of non-native...

WhichP450: a multi-class categorical model to predict the major metabolising CYP450 isoform for a compound

NASA Astrophysics Data System (ADS)

Hunt, Peter A.; Segall, Matthew D.; Tyzack, Jonathan D.

2018-02-01

In the development of novel pharmaceuticals, the knowledge of how many, and which, Cytochrome P450 isoforms are involved in the phase I metabolism of a compound is important. Potential problems can arise if a compound is metabolised predominantly by a single isoform in terms of drug-drug interactions or genetic polymorphisms that would lead to variations in exposure in the general population. Combined with models of regioselectivities of metabolism by each isoform, such a model would also aid in the prediction of the metabolites likely to be formed by P450-mediated metabolism. We describe the generation of a multi-class random forest model to predict which, out of a list of the seven leading Cytochrome P450 isoforms, would be the major metabolising isoforms for a novel compound. The model has a 76% success rate with a top-1 criterion and an 88% success rate for a top-2 criterion and shows significant enrichment over randomised models.

Modelling toolkit for simulation of maglev devices

NASA Astrophysics Data System (ADS)

Peña-Roche, J.; Badía-Majós, A.

2017-01-01

A stand-alone App1 has been developed, focused on obtaining information about relevant engineering properties of magnetic levitation systems. Our modelling toolkit provides real time simulations of 2D magneto-mechanical quantities for superconductor (SC)/permanent magnet structures. The source code is open and may be customised for a variety of configurations. Ultimately, it relies on the variational statement of the critical state model for the superconducting component and has been verified against experimental data for YBaCuO/NdFeB assemblies. On a quantitative basis, the values of the arising forces, induced superconducting currents, as well as a plot of the magnetic field lines are displayed upon selection of an arbitrary trajectory of the magnet in the vicinity of the SC. The stability issues related to the cooling process, as well as the maximum attainable forces for a given material and geometry are immediately observed. Due to the complexity of the problem, a strategy based on cluster computing, database compression, and real-time post-processing on the device has been implemented.

Disability Benefit Generosity and Labor Force Withdrawal*

PubMed Central

Mullen, Kathleen J.; Staubli, Stefan

2016-01-01

A key component for estimating the optimal size and structure of disability insurance (DI) programs is the elasticity of DI claiming with respect to benefit generosity. Yet, in many countries, including the United States, all workers face identical benefit schedules, which are a function of one’s labor market history, making it difficult to separate the effect of the benefit level from the effect of unobserved preferences for work on individuals’ claiming decisions. To circumvent this problem, we exploit exogenous variation in DI benefits in Austria arising from several reforms to its DI and old age pension system in the 1990s and 2000s. We use comprehensive administrative social security records data on the universe of Austrian workers to compute benefit levels under six different regimes, allowing us to identify and precisely estimate the elasticity of DI claiming with respect to benefit generosity. We find that, over this time period, a one percent increase in potential DI benefits was associated with a 1.2 percent increase in DI claiming. PMID:28216797

Is diagnosing exposed dentine a suitable tool for grading erosive loss?

PubMed Central

Ganss, Carolina

2008-01-01

Quantifying tooth wear in general and erosion in particular mostly is made by distinguishing between lesions restricted to enamel and lesions reaching the underlying dentine. Various scores for grading have been used, but in all systems, higher scores are given in cases of exposed dentine, thus, indicating a more severe stage of the condition. Clinical diagnosis of exposed dentine is made by assessing changes in colour or optical properties of the hard tissues. This paper aims to review the literature and discuss critically problems arising form this approach. It appears that classifying the severity of erosion by the area or depth of exposed dentine is difficult and poorly reproducible, and taking into account the variation of enamel thickness, the amount of tissue lost often is not related simply to the area of exposed dentine. There has still been very little longitudinal investigation of the significance of exposed dentine as a prognostic indicator. Further work and discussion is needed to reevaluate the explanative power of current grading procedures. PMID:18228063

Individual differences in posttraumatic distress: problems with the DSM-IV model.

PubMed

Bowman, M L

1999-02-01

To evaluate the evidence concerning the role of threatening life events in accounting for clinically significant posttraumatic stress responses. Research was examined to review the epidemiology, evidence of dose-response relations, and individual difference factors in accounting for variations in conditions, including posttraumatic stress disorder, after exposure to threatening events. The evidence is significantly discrepant from the clinical Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) model. Greater distress arises from individual differences than from event characteristics. Important individual differences that interact with threat exposures include trait negative affectivity (neuroticism); beliefs about emotions, the self, the world, and the sources and consequences of danger; and prevent acts, disorders, and intelligence. Reasons for the discrepancies between the evidence and the current model of posttraumatic distress are proposed. In accounting for responses to threatening life events, the relatively minor contribution of event qualities compared with individual differences has significant treatment implications. Treatment approaches assuming that toxic event exposure creates a posttraumatic disorder fail to consider individual differences that could improve treatment efficacy.

Noether's Theorem and its Inverse of Birkhoffian System in Event Space Based on Herglotz Variational Problem

NASA Astrophysics Data System (ADS)

Tian, X.; Zhang, Y.

2018-03-01

Herglotz variational principle, in which the functional is defined by a differential equation, generalizes the classical ones defining the functional by an integral. The principle gives a variational principle description of nonconservative systems even when the Lagrangian is independent of time. This paper focuses on studying the Noether's theorem and its inverse of a Birkhoffian system in event space based on the Herglotz variational problem. Firstly, according to the Herglotz variational principle of a Birkhoffian system, the principle of a Birkhoffian system in event space is established. Secondly, its parametric equations and two basic formulae for the variation of Pfaff-Herglotz action of a Birkhoffian system in event space are obtained. Furthermore, the definition and criteria of Noether symmetry of the Birkhoffian system in event space based on the Herglotz variational problem are given. Then, according to the relationship between the Noether symmetry and conserved quantity, the Noether's theorem is derived. Under classical conditions, Noether's theorem of a Birkhoffian system in event space based on the Herglotz variational problem reduces to the classical ones. In addition, Noether's inverse theorem of the Birkhoffian system in event space based on the Herglotz variational problem is also obtained. In the end of the paper, an example is given to illustrate the application of the results.

The distribution of intra-genomically variable dinoflagellate symbionts at Lord Howe Island, Australia

NASA Astrophysics Data System (ADS)

Wilkinson, Shaun P.; Pontasch, Stefanie; Fisher, Paul L.; Davy, Simon K.

2016-06-01

The symbiotic dinoflagellates of corals and other marine invertebrates ( Symbiodinium) are essential to the development of shallow-water coral reefs. This genus contains considerable genetic diversity and a corresponding range of physiological and ecological traits. Most genetic variation arises through the accumulation of somatic mutations that arise during asexual reproduction. Yet growing evidence suggests that occasional sexual reproductive events also occur within, and perhaps between, Symbiodinium lineages, further contributing to the pool of genetic variation available for evolutionary adaptation. Intra-genomic variation can therefore arise from both sexual and asexual reproductive processes, making it difficult to discern its underlying causes and consequences. We used quantitative PCR targeting the ITS2 locus to estimate proportions of genetically homogeneous symbionts and intra-genomically variable Symbiodinium (IGV Symbiodinium) in the reef-building coral Pocillopora damicornis at Lord Howe Island, Australia. We then sampled colonies through time and at a variety of spatial scales to find out whether the distribution of these symbionts followed patterns consistent with niche partitioning. Estimated ratios of homogeneous to IGV Symbiodinium varied between colonies within sites (metres to tens of metres) and between sites separated by hundreds to thousands of metres, but remained stable within colonies through time. Symbiont ratios followed a temperature gradient, with the local thermal maximum emerging as a negative predictor for the estimated proportional abundance of IGV Symbiodinium. While this pattern may result from fine-scale spatial population structure, it is consistent with an increased susceptibility to thermal stress, suggesting that the evolutionary processes that generate IGV (such as inter-lineage recombination and the accumulation of somatic mutations at the ITS2 locus) may have important implications for the fitness of the symbiont and that of the coral host.

Mechanical property assessment of tissue-mimicking phantoms using remote palpation and optical read-out for amplitude of vibration and refractive index modulation.

PubMed

Usha Devi, C; Bharat Chandran, R S; Vasu, R Mohan; Sood, Ajay K

2007-01-01

A coherent light beam is used to interrogate the focal region within a tissue-mimicking phantom insonified by an ultrasound transducer. The ultrasound-tagged photons exiting from the object carry with them information on local optical path length fluctuations caused by refractive index variations and medium vibration. Through estimation of the force distribution in the focal region of the ultrasound transducer, and solving the forward elastography problem for amplitude of vibration of tissue particles, we observe that the amplitude is directed along the axis of the transducer. It is shown that the focal region interrogated by photons launched along the transducer axis carries phase fluctuations owing to both refractive index variations and particle vibration, whereas the photons launched perpendicular to the transducer axis carry phase fluctuations arising mainly from the refractive index variations, with only smaller contribution from vibration of particles. Monte-Carlo simulations and experiments done on tissue-mimicking phantoms prove that as the storage modulus of the phantom is increased, the detected modulation depth in autocorrelation is reduced, significantly for axial photons and only marginally for the transverse-directed photons. It is observed that the depth of modulation is reduced to a significantly lower and constant value as the storage modulus of the medium is increased. This constant value is found to be the same for both axial and transverse optical interrogation. This proves that the residual modulation depth is owing to refractive index fluctuations alone, which can be subtracted from the overall measured modulation depth, paving the way for a possible quantitative reconstruction of storage modulus. Moreover, since the transverse-directed photons are not significantly affected by storage modulus variations, for a quantitatively accurate read-out of absorption coefficient variation, the interrogating light should be perpendicular to the focusing ultrasound transducer axis.

Guidelines to classification and nomenclature of Arabian felsic plutonic rocks

USGS Publications Warehouse

Ramsay, C.R.; Stoeser, D.B.; Drysdall, A.R.

1986-01-01

Well-defined procedures for classifying the felsic plutonic rocks of the Arabian Shield on the basis of petrographic, chemical and lithostratigraphic criteria and mineral-resource potential have been adopted and developed in the Saudi Arabian Deputy Ministry for Mineral Resources over the past decade. A number of problems with conventional classification schemes have been identified and resolved; others, notably those arising from difficulties in identifying precise mineral compositions, continue to present difficulties. The petrographic nomenclature used is essentially that recommended by the International Union of Geological Sciences. Problems that have arisen include the definition of: (1) rocks with sodic, zoned or perthitic feldspar, (2) trondhjemites, and (3) alkali granites. Chemical classification has been largely based on relative molar amounts of alumina, lime and alkalis, and the use of conventional variation diagrams, but pilot studies utilizing univariate and multivariate statistical techniques have been made. The classification used in Saudi Arabia for stratigraphic purposes is a hierarchy of formation-rank units, suites and super-suites as defined in the Saudi Arabian stratigraphic code. For genetic and petrological studies, a grouping as 'associations' of similar and genetically related lithologies is commonly used. In order to indicate mineral-resource potential, the felsic plutons are classed as common, precursor, specialized or mineralized, in order of increasing exploration significance. ?? 1986.

New convergence results for the scaled gradient projection method

NASA Astrophysics Data System (ADS)

Bonettini, S.; Prato, M.

2015-09-01

The aim of this paper is to deepen the convergence analysis of the scaled gradient projection (SGP) method, proposed by Bonettini et al in a recent paper for constrained smooth optimization. The main feature of SGP is the presence of a variable scaling matrix multiplying the gradient, which may change at each iteration. In the last few years, extensive numerical experimentation showed that SGP equipped with a suitable choice of the scaling matrix is a very effective tool for solving large scale variational problems arising in image and signal processing. In spite of the very reliable numerical results observed, only a weak convergence theorem is provided establishing that any limit point of the sequence generated by SGP is stationary. Here, under the only assumption that the objective function is convex and that a solution exists, we prove that the sequence generated by SGP converges to a minimum point, if the scaling matrices sequence satisfies a simple and implementable condition. Moreover, assuming that the gradient of the objective function is Lipschitz continuous, we are also able to prove the {O}(1/k) convergence rate with respect to the objective function values. Finally, we present the results of a numerical experience on some relevant image restoration problems, showing that the proposed scaling matrix selection rule performs well also from the computational point of view.

Multiple shooting algorithms for jump-discontinuous problems in optimal control and estimation

NASA Technical Reports Server (NTRS)

Mook, D. J.; Lew, Jiann-Shiun

1991-01-01

Multiple shooting algorithms are developed for jump-discontinuous two-point boundary value problems arising in optimal control and optimal estimation. Examples illustrating the origin of such problems are given to motivate the development of the solution algorithms. The algorithms convert the necessary conditions, consisting of differential equations and transversality conditions, into algebraic equations. The solution of the algebraic equations provides exact solutions for linear problems. The existence and uniqueness of the solution are proved.

Program Aids Visualization Of Data

NASA Technical Reports Server (NTRS)

Truong, L. V.

1995-01-01

Living Color Frame System (LCFS) computer program developed to solve some problems that arise in connection with generation of real-time graphical displays of numerical data and of statuses of systems. Need for program like LCFS arises because computer graphics often applied for better understanding and interpretation of data under observation and these graphics become more complicated when animation required during run time. Eliminates need for custom graphical-display software for application programs. Written in Turbo C++.

Family stressors, home demands and responsibilities, coping resources, social connectedness, and Thai older adult health problems: examining gender variations.

PubMed

Krishnakumar, Ambika; Narine, Lutchmie; Soonthorndhada, Amara; Thianlai, Kanchana

2015-03-01

To examine gender variations in the linkages among family stressors, home demands and responsibilities, coping resources, social connectedness, and older adult health problems. Data were collected from 3,800 elderly participants (1,654 men and 2,146 women) residing in Kanchanaburi province, Thailand. Findings indicated gender variations in the levels of these constructs and in the mediational pathways. Thai women indicated greater health problems than men. Emotional empathy was the central variable that linked financial strain, home demands and responsibilities, and older adult health problems through social connectedness. Financial strain (and negative life events for women) was associated with lowered coping self-efficacy and increased health problems. The model indicated greater strength in predicting female health problems. Findings support gender variations in the relationships between ecological factors and older adult health problems. © The Author(s) 2014.

Environmental Hazards of Nuclear Wastes

ERIC Educational Resources Information Center

Micklin, Philip P.

1974-01-01

Present methods for storage of radioactive wastes produced at nuclear power facilities are described. Problems arising from present waste management are discussed and potential solutions explored. (JP)

Stochastic species abundance models involving special copulas

NASA Astrophysics Data System (ADS)

Huillet, Thierry E.

2018-01-01

Copulas offer a very general tool to describe the dependence structure of random variables supported by the hypercube. Inspired by problems of species abundances in Biology, we study three distinct toy models where copulas play a key role. In a first one, a Marshall-Olkin copula arises in a species extinction model with catastrophe. In a second one, a quasi-copula problem arises in a flagged species abundance model. In a third model, we study completely random species abundance models in the hypercube as those, not of product type, with uniform margins and singular. These can be understood from a singular copula supported by an inflated simplex. An exchangeable singular Dirichlet copula is also introduced, together with its induced completely random species abundance vector.

[Specific problems posed by carbohydrate utilization in the rainbow trout].

PubMed

Bergot, F

1979-01-01

Carbohydrate incorporation in trout diets arises problems both at digestive and metabolic levels. Digestive utilization of carbohydrate closely depends on their molecular weight. In addition, in the case of complex carbohydrates (starches), different factors such as the level of incorporation, the amount consumed and the physical state of starch influence the digestibility. The measurement of digestibility in itself is confronted with methodological difficulties. The way the feces are collected can affect the digestion coefficient. Dietary carbohydrates actually serve as a source of energy. Nevertheless, above a certain level in the diet, intolerance phenomena may appear. The question that arises now is to establish the optimal part that carbohydrates can take in the metabolizable energy of a given diet.

Variation of desiccation tolerance and longevity in fern spores

USDA-ARS?s Scientific Manuscript database

This work contributes to the understanding of plant cell responses to water stress when applied at different intensity and duration. Fern spores are used to explore survival at relative humidity (RH) < 85% because their unicellular nature eliminates complexities that may arise in multicellular orga...

Colour Vision: Understanding #TheDress.

PubMed

Brainard, David H; Hurlbert, Anya C

2015-06-29

A widely-viewed image of a dress elicits striking individual variation in colour perception. Experiments with multiple variants of the image suggest that the individual differences may arise through the action of visual mechanisms that normally stabilise object colour. Copyright © 2015 Elsevier Ltd. All rights reserved.

Integrative pipeline for profiling DNA copy number and inferring tumor phylogeny.

PubMed

Urrutia, Eugene; Chen, Hao; Zhou, Zilu; Zhang, Nancy R; Jiang, Yuchao

2018-06-15

Copy number variation is an important and abundant source of variation in the human genome, which has been associated with a number of diseases, especially cancer. Massively parallel next-generation sequencing allows copy number profiling with fine resolution. Such efforts, however, have met with mixed successes, with setbacks arising partly from the lack of reliable analytical methods to meet the diverse and unique challenges arising from the myriad experimental designs and study goals in genetic studies. In cancer genomics, detection of somatic copy number changes and profiling of allele-specific copy number (ASCN) are complicated by experimental biases and artifacts as well as normal cell contamination and cancer subclone admixture. Furthermore, careful statistical modeling is warranted to reconstruct tumor phylogeny by both somatic ASCN changes and single nucleotide variants. Here we describe a flexible computational pipeline, MARATHON, which integrates multiple related statistical software for copy number profiling and downstream analyses in disease genetic studies. MARATHON is publicly available at https://github.com/yuchaojiang/MARATHON. Supplementary data are available at Bioinformatics online.

On Raviart-Thomas and VMS formulations for flow in heterogeneous materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Daniel Zack

It is well known that the continuous Galerkin method (in its standard form) is not locally conservative, yet many stabilized methods are constructed by augmenting the standard Galerkin weak form. In particular, the Variational Multiscale (VMS) method has achieved popularity for combating numerical instabilities that arise for mixed formulations that do not otherwise satisfy the LBB condition. Among alternative methods that satisfy local and global conservation, many employ Raviart-Thomas function spaces. The lowest order Raviart-Thomas finite element formulation (RT0) consists of evaluating fluxes over the midpoint of element edges and constant pressures within the element. Although the RT0 element posesmore » many advantages, it has only been shown viable for triangular or tetrahedral elements (quadrilateral variants of this method do not pass the patch test). In the context of heterogenous materials, both of these methods have been used to model the mixed form of the Darcy equation. This work aims, in a comparative fashion, to evaluate the strengths and weaknesses of either approach for modeling Darcy flow for problems with highly varying material permeabilities and predominantly open flow boundary conditions. Such problems include carbon sequestration and enhanced oil recovery simulations for which the far-field boundary is typically described with some type of pressure boundary condition. We intend to show the degree to which the VMS formulation violates local mass conservation for these types of problems and compare the performance of the VMS and RT0 methods at boundaries between disparate permeabilities.« less

Scalable implicit incompressible resistive MHD with stabilized FE and fully-coupled Newton–Krylov-AMG

DOE PAGES

Shadid, J. N.; Pawlowski, R. P.; Cyr, E. C.; ...

2016-02-10

Here, we discuss that the computational solution of the governing balance equations for mass, momentum, heat transfer and magnetic induction for resistive magnetohydrodynamics (MHD) systems can be extremely challenging. These difficulties arise from both the strong nonlinear, nonsymmetric coupling of fluid and electromagnetic phenomena, as well as the significant range of time- and length-scales that the interactions of these physical mechanisms produce. This paper explores the development of a scalable, fully-implicit stabilized unstructured finite element (FE) capability for 3D incompressible resistive MHD. The discussion considers the development of a stabilized FE formulation in context of the variational multiscale (VMS) method,more » and describes the scalable implicit time integration and direct-to-steady-state solution capability. The nonlinear solver strategy employs Newton–Krylov methods, which are preconditioned using fully-coupled algebraic multilevel preconditioners. These preconditioners are shown to enable a robust, scalable and efficient solution approach for the large-scale sparse linear systems generated by the Newton linearization. Verification results demonstrate the expected order-of-accuracy for the stabilized FE discretization. The approach is tested on a variety of prototype problems, that include MHD duct flows, an unstable hydromagnetic Kelvin–Helmholtz shear layer, and a 3D island coalescence problem used to model magnetic reconnection. Initial results that explore the scaling of the solution methods are also presented on up to 128K processors for problems with up to 1.8B unknowns on a CrayXK7.« less

On a variational approach to some parameter estimation problems

NASA Technical Reports Server (NTRS)

Banks, H. T.

1985-01-01

Examples (1-D seismic, large flexible structures, bioturbation, nonlinear population dispersal) in which a variation setting can provide a convenient framework for convergence and stability arguments in parameter estimation problems are considered. Some of these examples are 1-D seismic, large flexible structures, bioturbation, and nonlinear population dispersal. Arguments for convergence and stability via a variational approach of least squares formulations of parameter estimation problems for partial differential equations is one aspect of the problem considered.

Optimization-based mesh correction with volume and convexity constraints

DOE PAGES

D'Elia, Marta; Ridzal, Denis; Peterson, Kara J.; ...

2016-02-24

In this study, we consider the problem of finding a mesh such that 1) it is the closest, with respect to a suitable metric, to a given source mesh having the same connectivity, and 2) the volumes of its cells match a set of prescribed positive values that are not necessarily equal to the cell volumes in the source mesh. This volume correction problem arises in important simulation contexts, such as satisfying a discrete geometric conservation law and solving transport equations by incremental remapping or similar semi-Lagrangian transport schemes. In this paper we formulate volume correction as a constrained optimizationmore » problem in which the distance to the source mesh defines an optimization objective, while the prescribed cell volumes, mesh validity and/or cell convexity specify the constraints. We solve this problem numerically using a sequential quadratic programming (SQP) method whose performance scales with the mesh size. To achieve scalable performance we develop a specialized multigrid-based preconditioner for optimality systems that arise in the application of the SQP method to the volume correction problem. Numerical examples illustrate the importance of volume correction, and showcase the accuracy, robustness and scalability of our approach.« less

New Old Inflation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dvali, Gia

2003-10-03

We propose a new class of inflationary solutions to the standard cosmological problems (horizon, flatness, monopole,...), based on a modification of old inflation. These models do not require a potential which satisfies the normal inflationary slow-roll conditions. Our universe arises from a single tunneling event as the inflaton leaves the false vacuum. Subsequent dynamics (arising from either the oscillations of the inflaton field or thermal effects) keep a second field trapped in a false minimum, resulting in an evanescent period of inflation (with roughly 50 e-foldings) inside the bubble. This easily allows the bubble to grow sufficiently large to containmore » our present horizon volume. Reheating is accomplished when the inflaton driving the last stage of inflation rolls down to the true vacuum, and adiabatic density perturbations arise from moduli-dependent Yukawa couplings of the inflaton to matter fields. Our scenario has several robust predictions, including virtual absence of gravity waves, a possible absence of tilt in scalar perturbations, and a higher degree of non-Gaussianity than other models. It also naturally incorporates a solution to the cosmological moduli problem.« less

Quality Problem-Based Learning Experiences for Students: Design Deliberations among Teachers from Diverse Disciplines.

ERIC Educational Resources Information Center

Butler, Susan McAleenan

This qualitative study, investigating the claims, concerns, and issues arising within the design stages of problem-based learning (PBL) curriculum units, was conducted during two masters-level classes during the summer of 1999. A hermeneutic dialectic discourse among veteran teachers (who were novice PBL curriculum designers) was facilitated by…

Peculiarities of Students of Pedagogical Specialties Training in Preventive Work with Juveniles Delinquents

ERIC Educational Resources Information Center

Moskalenko, Maxim R.; Dorozhkin, Evgenij M.; Ozhiganova, Maria V.; Murzinova, Yana A.; Syssa, Daria O.

2016-01-01

The relevance of the problem under investigation is due to the high significance of preventive work with juvenile delinquents to society. The article aims to study the problems arising while developing students' competencies in professional activities for the prevention of the infringing behavior of juvenile delinquents, as well as the…

A Solution to the Mysteries of Morality

ERIC Educational Resources Information Center

DeScioli, Peter; Kurzban, Robert

2013-01-01

We propose that moral condemnation functions to guide bystanders to choose the same side as other bystanders in disputes. Humans interact in dense social networks, and this poses a problem for bystanders when conflicts arise: which side, if any, to support. Choosing sides is a difficult strategic problem because the outcome of a conflict…

Transfer of Learning Transformed

ERIC Educational Resources Information Center

Larsen-Freeman, Diane

2013-01-01

Instruction is motivated by the assumption that students can transfer their learning, or apply what they have learned in school to another setting. A common problem arises when the expected transfer does not take place, what has been referred to as the inert knowledge problem. More than an academic inconvenience, the failure to transfer is a major…

The Plasticity of Adolescent Cognitions: Data from a Novel Cognitive Bias Modification Training Task

ERIC Educational Resources Information Center

Lau, Jennifer Y. F.; Molyneaux, Emma; Telman, Machteld D.; Belli, Stefano

2011-01-01

Many adult anxiety problems emerge in adolescence. Investigating how adolescent anxiety arises and abates is critical for understanding and preventing adult psychiatric problems. Drawing threat interpretations from ambiguous material is linked to adolescent anxiety but little research has clarified the causal nature of this relationship. Work in…

Coorientational Accuracy during Regional Development of Energy Resources: Problems in Agency-Public Communication.

ERIC Educational Resources Information Center

Bowes, John E.; Stamm, Keith R.

This paper presents a progress report from a research program aimed at elucidating communication problems which arise among citizens and government agencies during the development of regional environmental policy. The eventual objective of the program is to develop a paradigm for evaluative research in communication that will provide for the…

Anger/Frustration, Task Persistence, and Conduct Problems in Childhood: A Behavioral Genetic Analysis

ERIC Educational Resources Information Center

Deater-Deckard, Kirby; Petrill, Stephen A.; Thompson, Lee A.

2007-01-01

Background: Individual differences in conduct problems arise in part from proneness to anger/frustration and poor self-regulation of behavior. However, the genetic and environmental etiology of these connections is not known. Method: Using a twin design, we examined genetic and environmental covariation underlying the well-documented correlations…

Zones of Intervention: Teaching and Learning at All Places and at All Times

ERIC Educational Resources Information Center

Taylor, Jonathan E.; McKissac, Jonathan C.

2014-01-01

This article identifies four distinct zones in which workplace problems can be addressed through education and training. These zones enable educators to address workplace learning more widely and broadly. Very often, problems arising in the workplace are dealt with through training in the classroom, but other options exist. The theoretical…

An inverse problem for a semilinear parabolic equation arising from cardiac electrophysiology

NASA Astrophysics Data System (ADS)

Beretta, Elena; Cavaterra, Cecilia; Cerutti, M. Cristina; Manzoni, Andrea; Ratti, Luca

2017-10-01

In this paper we develop theoretical analysis and numerical reconstruction techniques for the solution of an inverse boundary value problem dealing with the nonlinear, time-dependent monodomain equation, which models the evolution of the electric potential in the myocardial tissue. The goal is the detection of an inhomogeneity \

Community-University Research Partnerships: Devising a Model for Ethical Engagement

ERIC Educational Resources Information Center

Silka, Linda; Renault-Caragianes, Paulette

2006-01-01

Profound changes taking place in communities and in universities are bringing researchers and community members new opportunities for joint research endeavors and new problems that must be resolved. In such partnerships, questions about shared decision making--about the ethics of collaboration--arise at every stage: Who decides which problems are…

Sparse Measurement Systems: Applications, Analysis, Algorithms and Design

ERIC Educational Resources Information Center

Narayanaswamy, Balakrishnan

2011-01-01

This thesis deals with "large-scale" detection problems that arise in many real world applications such as sensor networks, mapping with mobile robots and group testing for biological screening and drug discovery. These are problems where the values of a large number of inputs need to be inferred from noisy observations and where the…

The Changing Demographics of the Hispanic Family.

ERIC Educational Resources Information Center

McKay, Emily Gantz

Hispanics will become the largest United States minority population sometime early in the next century. A problem that arises with attempts to provide Hispanic people with better opportunities is the lack of adequate data on Hispanic socioeconomic status. Those data which do exist focus on problems of the individual, yet one of the greatest…

Projected Issues in the Practice of Educational Administration: The English Context.

ERIC Educational Resources Information Center

Browning, Peter

Current and incipient problems in educational administration in England can be grouped into two areas: those resulting from reorganization and those arising from social and political factors. Many problems faced by educational administrators result from school reorganization that is a result of an increase in the number of comprehensive schools.…

Focal-Plane Alignment Sensing

DTIC Science & Technology

1993-02-01

amplification induced by the inverse filter. The problem of noise amplification that arises in conventional image deblurring problems has often been... noise sensitivity, and strategies for selecting a regularization parameter have been developed. The probability of convergence to within a prescribed...Strategies in Image Deblurring .................. 12 2.2.2 CLS Parameter Selection ........................... 14 2.2.3 Wiener Parameter Selection

Damage Control: Closing Problematic Sequences in Hearing-Impaired Interaction

ERIC Educational Resources Information Center

Skelt, Louise

2007-01-01

When a problem of understanding arises for a hearing-impaired recipient in the course of a conversation, and is detected, repairing that problem is only one of several possible courses of action for participants. Another possibility is the collaborative closing of the part of the conversation which has proved problematic for understanding, to…

A New Homotopy Perturbation Scheme for Solving Singular Boundary Value Problems Arising in Various Physical Models

NASA Astrophysics Data System (ADS)

Roul, Pradip; Warbhe, Ujwal

2017-08-01

The classical homotopy perturbation method proposed by J. H. He, Comput. Methods Appl. Mech. Eng. 178, 257 (1999) is useful for obtaining the approximate solutions for a wide class of nonlinear problems in terms of series with easily calculable components. However, in some cases, it has been found that this method results in slowly convergent series. To overcome the shortcoming, we present a new reliable algorithm called the domain decomposition homotopy perturbation method (DDHPM) to solve a class of singular two-point boundary value problems with Neumann and Robin-type boundary conditions arising in various physical models. Five numerical examples are presented to demonstrate the accuracy and applicability of our method, including thermal explosion, oxygen-diffusion in a spherical cell and heat conduction through a solid with heat generation. A comparison is made between the proposed technique and other existing seminumerical or numerical techniques. Numerical results reveal that only two or three iterations lead to high accuracy of the solution and this newly improved technique introduces a powerful improvement for solving nonlinear singular boundary value problems (SBVPs).

The geometry of discombinations and its applications to semi-inverse problems in anelasticity

PubMed Central

Yavari, Arash; Goriely, Alain

2014-01-01

The geometrical formulation of continuum mechanics provides us with a powerful approach to understand and solve problems in anelasticity where an elastic deformation is combined with a non-elastic component arising from defects, thermal stresses, growth effects or other effects leading to residual stresses. The central idea is to assume that the material manifold, prescribing the reference configuration for a body, has an intrinsic, non-Euclidean, geometrical structure. Residual stresses then naturally arise when this configuration is mapped into Euclidean space. Here, we consider the problem of discombinations (a new term that we introduce in this paper), that is, a combined distribution of fields of dislocations, disclinations and point defects. Given a discombination, we compute the geometrical characteristics of the material manifold (curvature, torsion, non-metricity), its Cartan's moving frames and structural equations. This identification provides a powerful algorithm to solve semi-inverse problems with non-elastic components. As an example, we calculate the residual stress field of a cylindrically symmetric distribution of discombinations in an infinite circular cylindrical bar made of an incompressible hyperelastic isotropic elastic solid. PMID:25197257

On multiple crack identification by ultrasonic scanning

NASA Astrophysics Data System (ADS)

Brigante, M.; Sumbatyan, M. A.

2018-04-01

The present work develops an approach which reduces operator equations arising in the engineering problems to the problem of minimizing the discrepancy functional. For this minimization, an algorithm of random global search is proposed, which is allied to some genetic algorithms. The efficiency of the method is demonstrated by the solving problem of simultaneous identification of several linear cracks forming an array in an elastic medium by using the circular Ultrasonic scanning.

A bicriteria heuristic for an elective surgery scheduling problem.

PubMed

Marques, Inês; Captivo, M Eugénia; Vaz Pato, Margarida

2015-09-01

Resource rationalization and reduction of waiting lists for surgery are two main guidelines for hospital units outlined in the Portuguese National Health Plan. This work is dedicated to an elective surgery scheduling problem arising in a Lisbon public hospital. In order to increase the surgical suite's efficiency and to reduce the waiting lists for surgery, two objectives are considered: maximize surgical suite occupation and maximize the number of surgeries scheduled. This elective surgery scheduling problem consists of assigning an intervention date, an operating room and a starting time for elective surgeries selected from the hospital waiting list. Accordingly, a bicriteria surgery scheduling problem arising in the hospital under study is presented. To search for efficient solutions of the bicriteria optimization problem, the minimization of a weighted Chebyshev distance to a reference point is used. A constructive and improvement heuristic procedure specially designed to address the objectives of the problem is developed and results of computational experiments obtained with empirical data from the hospital are presented. This study shows that by using the bicriteria approach presented here it is possible to build surgical plans with very good performance levels. This method can be used within an interactive approach with the decision maker. It can also be easily adapted to other hospitals with similar scheduling conditions.

Retrospectively reported month-to-month variation in sleeping problems of people naturally exposed to high-amplitude annual variation in daylength and/or temperature.

PubMed

Putilov, Arcady A

2017-01-01

Compared to literature on seasonal variation in mood and well-being, reports on seasonality of trouble sleeping are scarce and contradictive. To extend geography of such reports on example of people naturally exposed to high-amplitude annual variation in daylength and/or temperature. Participants were the residents of Turkmenia, West Siberia, South and North Yakutia, Chukotka, and Alaska. Health and sleep-wake adaptabilities, month-to-month variation in sleeping problems, well-being and behaviors were self-assessed. More than a half of 2398 respondents acknowledged seasonality of sleeping problems. Four of the assessed sleeping problems demonstrated three different patterns of seasonal variation. Rate of the problems significantly increased in winter months with long nights and cold days (daytime sleepiness and difficulties falling and staying asleep) as well as in summer months with either long days (premature awakening and difficulties falling and staying asleep) or hot nights and days (all 4 sleeping problems). Individual differences between respondents in pattern and level of seasonality of sleeping problems were significantly associated with differences in several other domains of individual variation, such as gender, age, ethnicity, physical health, morning-evening preference, sleep quality, and adaptability of the sleep-wake cycle. These results have practical relevance to understanding of the roles playing by natural environmental factors in seasonality of sleeping problems as well as to research on prevalence of sleep disorders and methods of their prevention and treatment in regions with large seasonal differences in temperature and daylength.

Colon cancer: a civilization disorder.

PubMed

Watson, Alastair J M; Collins, Paul D

2011-01-01

Colorectal cancer arises in individuals with acquired or inherited genetic predisposition who are exposed to a range of risk factors. Many of these risk factors are associated with affluent Western societies. More than 95% of colorectal cancers are sporadic, arising in individuals without a significant hereditary risk. Geographic variation in the incidence of colorectal cancer is considerable with a higher incidence observed in the West. Environmental factors contribute substantially to this variation. A number of these risk factors are associated with a Western lifestyle and could be considered a product of 'civilization'. Recently, smoking has been recognized as a risk factor. Energy consumption also influences colorectal cancer risk, with obesity increasing risk and exercise reducing risk. However, the strongest contribution to environmental risk for colorectal cancer is dietary. Consumption of fat, alcohol and red meat is associated with an increased risk. Fresh fruit and vegetables and dietary fibre may be protective. Much has been learnt recently about the molecular pathogenesis of colorectal cancer. Colorectal cancer always arises in the context of genomic instability. There is inactivation of the tumour suppressor genes adenomatous polyposis coli, p53, transforming growth factor-β, activation of oncogene pathways including K-ras, and activation of the cyclooxygenase-2, epidermal growth factor receptor and vascular endothelial growth factor pathways. The mechanisms by which some environmental factors modify the mutation risk in these pathways have been described. Copyright © 2011 S. Karger AG, Basel.

Contraceptive services for adolescents in Latin America: facts, problems and perspectives.

PubMed

Pons, J E

1999-12-01

This review presents facts about sexual and contraceptive behavior of Latin American adolescents, analyzes barriers to contraception, and summarizes present perspectives. Between 13 and 30% of Latin American adolescent women live in union before their 20th birthday and between 46 and 63% have had sexual relations. The prevalence of contraceptive use among adolescents at risk of pregnancy remains very low. The pill is the best known contraceptive method. When sexual activity becomes a permanent practice, contraceptive use increases but remains low. Barriers to contraception can be identified as: (1) arising from adolescents themselves (moral objections, alleged medical reasons, lack of confidence in adults and in the health system, promiscuity; (2) arising from the sexual partner (partner's opposition, masculine irresponsibility); (3) arising from adults (moral objections, fear of sex education, adult control and power of decision-making); (4) arising from the health system (inappropriateness of services, regulatory barriers, gender inequality); (5) arising from health professionals (medical barriers to contraceptive use, discomfort with sexual matters); (6) arising from the educational system (educational failure, teachers' reluctance); and (7) arising from other social agents (religious opposition, media ambivalent messages, fund restraints). There have been improvements in recent years, including the achievements of groups working for and with adolescents, and the support from distinguished personalities.

Customer-centered problem solving.

PubMed

Samelson, Q B

1999-11-01

If there is no single best way to attract new customers and retain current customers, there is surely an easy way to lose them: fail to solve the problems that arise in nearly every buyer-supplier relationship, or solve them in an unsatisfactory manner. Yet, all too frequently, companies do just that. Either we deny that a problem exists, we exert all our efforts to pin the blame elsewhere, or we "Band-Aid" the problem instead of fixing it, almost guaranteeing that we will face it again and again.

Robust Consumption-Investment Problem on Infinite Horizon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zawisza, Dariusz, E-mail: dariusz.zawisza@im.uj.edu.pl

In our paper we consider an infinite horizon consumption-investment problem under a model misspecification in a general stochastic factor model. We formulate the problem as a stochastic game and finally characterize the saddle point and the value function of that game using an ODE of semilinear type, for which we provide a proof of an existence and uniqueness theorem for its solution. Such equation is interested on its own right, since it generalizes many other equations arising in various infinite horizon optimization problems.

Bethe-Salpeter Eigenvalue Solver Package (BSEPACK) v0.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

SHAO, MEIYEU; YANG, CHAO

2017-04-25

The BSEPACK contains a set of subroutines for solving the Bethe-Salpeter Eigenvalue (BSE) problem. This type of problem arises in this study of optical excitation of nanoscale materials. The BSE problem is a structured non-Hermitian eigenvalue problem. The BSEPACK software can be used to compute all or subset of eigenpairs of a BSE Hamiltonian. It can also be used to compute the optical absorption spectrum without computing BSE eigenvalues and eigenvectors explicitly. The package makes use of the ScaLAPACK, LAPACK and BLAS.

The Soccer-Ball Problem

NASA Astrophysics Data System (ADS)

Hossenfelder, Sabine

2014-07-01

The idea that Lorentz-symmetry in momentum space could be modified but still remain observer-independent has received quite some attention in the recent years. This modified Lorentz-symmetry, which has been argued to arise in Loop Quantum Gravity, is being used as a phenomenological model to test possibly observable effects of quantum gravity. The most pressing problem in these models is the treatment of multi-particle states, known as the 'soccer-ball problem'. This article briefly reviews the problem and the status of existing solution attempts.

School Politics and Conflict in Racially Isolated Schools.

ERIC Educational Resources Information Center

Michel, George J.

1991-01-01

Compares areas and levels of political conflict in racially isolated school districts by surveying six superintendents from racially isolated African-American schools and six superintendents from racially isolated white schools. Similar issues arise at every conflict level with small variations among issues between African-American and white…

Venus Clouds: A dirty hydrochloric acid model

NASA Technical Reports Server (NTRS)

Hapke, B.

1971-01-01

The spectral and polarization data for Venus are consistent with micron-sized, aerosol cloud particles of hydrochloric acid containing soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The ultraviolet features could arise from variations in the Fe-HCl concentration in the cloud particles.

Insensitivity of the octahedral spherical hohlraum to power imbalance, pointing accuracy, and assemblage accuracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huo, Wen Yi; Zhao, Yiqing; Zheng, Wudi

2014-11-15

The random radiation asymmetry in the octahedral spherical hohlraum [K. Lan et al., Phys. Plasmas 21, 0 10704 (2014)] arising from the power imbalance, pointing accuracy of laser quads, and the assemblage accuracy of capsule is investigated by using the 3-dimensional view factor model. From our study, for the spherical hohlraum, the random radiation asymmetry arising from the power imbalance of the laser quads is about half of that in the cylindrical hohlraum; the random asymmetry arising from the pointing error is about one order lower than that in the cylindrical hohlraum; and the random asymmetry arising from the assemblage errormore » of capsule is about one third of that in the cylindrical hohlraum. Moreover, the random radiation asymmetry in the spherical hohlraum is also less than the amount in the elliptical hohlraum. The results indicate that the spherical hohlraum is more insensitive to the random variations than the cylindrical hohlraum and the elliptical hohlraum. Hence, the spherical hohlraum can relax the requirements to the power imbalance and pointing accuracy of laser facility and the assemblage accuracy of capsule.« less

Cardiac emergencies and problems of the critical care patient.

PubMed

Marr, Celia M

2004-04-01

Cardiac disease and dysfunction can occur as a primary disorder(ie, with pathology situated in one or more of the cardiac structures) or can be classified as a secondary problem when it occurs in patients with another primary problem that has affected the heart either directly or indirectly. Primary cardiac problems are encountered in horses presented to emergency clinics; however,this occurs much less frequently in equine critical patients than cardiac problems arising secondary to other conditions. Nevertheless,if primary or secondary cardiac problems are not identified and addressed, they certainly contribute to the morbidity and mortality of critical care patients.

Low frequency acoustic and electromagnetic scattering

NASA Technical Reports Server (NTRS)

Hariharan, S. I.; Maccamy, R. C.

1986-01-01

This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k/2/ log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.

The inverse problem of the calculus of variations for discrete systems

NASA Astrophysics Data System (ADS)

Barbero-Liñán, María; Farré Puiggalí, Marta; Ferraro, Sebastián; Martín de Diego, David

2018-05-01

We develop a geometric version of the inverse problem of the calculus of variations for discrete mechanics and constrained discrete mechanics. The geometric approach consists of using suitable Lagrangian and isotropic submanifolds. We also provide a transition between the discrete and the continuous problems and propose variationality as an interesting geometric property to take into account in the design and computer simulation of numerical integrators for constrained systems. For instance, nonholonomic mechanics is generally non variational but some special cases admit an alternative variational description. We apply some standard nonholonomic integrators to such an example to study which ones conserve this property.

Estimating alarm thresholds and the number of components in mixture distributions

NASA Astrophysics Data System (ADS)

Burr, Tom; Hamada, Michael S.

2012-09-01

Mixtures of probability distributions arise in many nuclear assay and forensic applications, including nuclear weapon detection, neutron multiplicity counting, and in solution monitoring (SM) for nuclear safeguards. SM data is increasingly used to enhance nuclear safeguards in aqueous reprocessing facilities having plutonium in solution form in many tanks. This paper provides background for mixture probability distributions and then focuses on mixtures arising in SM data. SM data can be analyzed by evaluating transfer-mode residuals defined as tank-to-tank transfer differences, and wait-mode residuals defined as changes during non-transfer modes. A previous paper investigated impacts on transfer-mode and wait-mode residuals of event marking errors which arise when the estimated start and/or stop times of tank events such as transfers are somewhat different from the true start and/or stop times. Event marking errors contribute to non-Gaussian behavior and larger variation than predicted on the basis of individual tank calibration studies. This paper illustrates evidence for mixture probability distributions arising from such event marking errors and from effects such as condensation or evaporation during non-transfer modes, and pump carryover during transfer modes. A quantitative assessment of the sample size required to adequately characterize a mixture probability distribution arising in any context is included.

Common and separate origins of the left and right inferior phrenic artery with a review of the literature.

PubMed

Terayama, H; Yi, S-Q; Tanaka, O; Kanazawa, T; Suyama, K; Kosemura, N; Tetsu, S; Yamazaki, H; Sakamoto, R; Kawakami, S; Suzuki, T; Sakabe, K

2017-01-01

In a 94-year-old male cadaver, upon which routine dissection was being conducted, a rare variation was found in the gastrophrenic trunk (GPT), the common trunk of the left gastric artery (LGA), right inferior phrenic artery (RIPA), and left inferior phrenic artery (LIPA); the GPT arises from the abdominal aorta. A hepatosplenic trunk accompanied the variation. In this variation, the RIPA first branched from the GPT and then to the LIPA and LGA. Variations in the common trunk of the LIPA and RIPA in the GPT are common, but to our knowledge, a variation (separate inferior phrenic artery in the GPT) similar to our findings has not been previously reported. We discuss the incidence and developmental and clinical significance of this variation with a detailed review of the literature. Knowledge of such a case has important clinical significance for invasive and non-invasive arterial procedures. Therefore, different variations concerning the LGA and inferior phrenic artery should be considered during surgical and non-surgical evaluations.

Applying Deep Learning in Medical Images: The Case of Bone Age Estimation.

PubMed

Lee, Jang Hyung; Kim, Kwang Gi

2018-01-01

A diagnostic need often arises to estimate bone age from X-ray images of the hand of a subject during the growth period. Together with measured physical height, such information may be used as indicators for the height growth prognosis of the subject. We present a way to apply the deep learning technique to medical image analysis using hand bone age estimation as an example. Age estimation was formulated as a regression problem with hand X-ray images as input and estimated age as output. A set of hand X-ray images was used to form a training set with which a regression model was trained. An image preprocessing procedure is described which reduces image variations across data instances that are unrelated to age-wise variation. The use of Caffe, a deep learning tool is demonstrated. A rather simple deep learning network was adopted and trained for tutorial purpose. A test set distinct from the training set was formed to assess the validity of the approach. The measured mean absolute difference value was 18.9 months, and the concordance correlation coefficient was 0.78. It is shown that the proposed deep learning-based neural network can be used to estimate a subject's age from hand X-ray images, which eliminates the need for tedious atlas look-ups in clinical environments and should improve the time and cost efficiency of the estimation process.

The existence results and Tikhonov regularization method for generalized mixed variational inequalities in Banach spaces

NASA Astrophysics Data System (ADS)

Wang, Min

2017-06-01

This paper aims to establish the Tikhonov regularization method for generalized mixed variational inequalities in Banach spaces. For this purpose, we firstly prove a very general existence result for generalized mixed variational inequalities, provided that the mapping involved has the so-called mixed variational inequality property and satisfies a rather weak coercivity condition. Finally, we establish the Tikhonov regularization method for generalized mixed variational inequalities. Our findings extended the results for the generalized variational inequality problem (for short, GVIP( F, K)) in R^n spaces (He in Abstr Appl Anal, 2012) to the generalized mixed variational inequality problem (for short, GMVIP(F,φ , K)) in reflexive Banach spaces. On the other hand, we generalized the corresponding results for the generalized mixed variational inequality problem (for short, GMVIP(F,φ ,K)) in R^n spaces (Fu and He in J Sichuan Norm Univ (Nat Sci) 37:12-17, 2014) to reflexive Banach spaces.

Ion Monitoring

DOEpatents

Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore

2003-11-18

The apparatus and method provide a technique for significantly reducing capacitance effects in detector electrodes arising due to movement of the instrument relative to the item/location being monitored in ion detection based techniques. The capacitance variations are rendered less significant by placing an electrically conducting element between the detector electrodes and the monitored location/item. Improved sensitivity and reduced noise signals arise as a result. The technique also provides apparatus and method suitable for monitoring elongate items which are unsuited to complete enclosure in one go within a chamber. The items are monitored part by part as the pass through the instrument, so increasing the range of items or locations which can be successfully monitored.

Testing whether macroevolution follows microevolution: Are colour differences among swans (Cygnus) attributable to variation at the MC1R locus?

PubMed Central

2008-01-01

Background The MC1R (melanocortin-1 receptor) locus underlies intraspecific variation in melanin-based dark plumage coloration in several unrelated birds with plumage polymorphisms. There is far less evidence for functional variants of MC1R being involved in interspecific variation, in which spurious genotype-phenotype associations arising through population history are a far greater problem than in intraspecific studies. We investigated the relationship between MC1R variation and plumage coloration in swans (Cygnus), which show extreme variation in melanic plumage phenotypes among species (white to black). Results The two species with melanic plumage, C. atratus and C. melanocoryphus (black and black-necked swans respectively), both have amino acid changes at important functional sites in MC1R that are consistent with increased MC1R activity and melanism. Reconstruction of MC1R evolution over a newly generated independent molecular phylogeny of Cygnus and related genera shows that these putative melanizing mutations were independently derived in the two melanic lineages. However, interpretation is complicated by the fact that one of the outgroup genera, Coscoroba, also has a putative melanizing mutation at MC1R that has arisen independently but has nearly pure white plumage. Epistasis at other loci seems the most likely explanation for this discrepancy. Unexpectedly, the phylogeny shows that the genus Cygnus may not be monophyletic, with C. melanocoryphus placed as a sister group to true geese (Anser), but further data will be needed to confirm this. Conclusion Our study highlights the difficulty of extrapolating from intraspecific studies to understand the genetic basis of interspecific adaptive phenotypic evolution, even with a gene whose structure-function relationships are as well understood as MC1R as confounding variation make clear genotype/phenotype associations difficult at the macroevolutionary scale. However, the identification of substitutions in the black and black-necked swan that are known to be associated with melanic phenotypes, suggests Cygnus may be another example where there appears to be convergent evolution at MC1R. This study therefore provides a novel example where previously described intraspecific genotype/phenotype associations occur at the macroevolutionary level. PMID:18789136

Testing whether macroevolution follows microevolution: are colour differences among swans (Cygnus) attributable to variation at the MCIR locus?

PubMed

Pointer, Marie A; Mundy, Nicholas I

2008-09-12

The MC1R (melanocortin-1 receptor) locus underlies intraspecific variation in melanin-based dark plumage coloration in several unrelated birds with plumage polymorphisms. There is far less evidence for functional variants of MC1R being involved in interspecific variation, in which spurious genotype-phenotype associations arising through population history are a far greater problem than in intraspecific studies. We investigated the relationship between MC1R variation and plumage coloration in swans (Cygnus), which show extreme variation in melanic plumage phenotypes among species (white to black). The two species with melanic plumage, C. atratus and C. melanocoryphus (black and black-necked swans respectively), both have amino acid changes at important functional sites in MC1R that are consistent with increased MC1R activity and melanism. Reconstruction of MC1R evolution over a newly generated independent molecular phylogeny of Cygnus and related genera shows that these putative melanizing mutations were independently derived in the two melanic lineages. However, interpretation is complicated by the fact that one of the outgroup genera, Coscoroba, also has a putative melanizing mutation at MC1R that has arisen independently but has nearly pure white plumage. Epistasis at other loci seems the most likely explanation for this discrepancy. Unexpectedly, the phylogeny shows that the genus Cygnus may not be monophyletic, with C. melanocoryphus placed as a sister group to true geese (Anser), but further data will be needed to confirm this. Our study highlights the difficulty of extrapolating from intraspecific studies to understand the genetic basis of interspecific adaptive phenotypic evolution, even with a gene whose structure-function relationships are as well understood as MC1R as confounding variation make clear genotype/phenotype associations difficult at the macroevolutionary scale. However, the identification of substitutions in the black and black-necked swan that are known to be associated with melanic phenotypes, suggests Cygnus may be another example where there appears to be convergent evolution at MC1R. This study therefore provides a novel example where previously described intraspecific genotype/phenotype associations occur at the macroevolutionary level.

Working Mothers

MedlinePlus

... valued and supported by family, friends, and coworkers. Conflicts Problems can arise if a woman does not ... is earning more money than the other. Such conflicts can strain the marriage and may make the ...

Administrators in Wonderland: Leadership through the New Sciences.

ERIC Educational Resources Information Center

Slowinski, Joseph

Recent theories associated with physical reality have increasingly been adapted as social-science paradigms. Chaos Theory and Perceptual Control Theory (PCT) are two advances that are applicable to the educational administration field. According to Edward Lorenz's Chaos Theory, profound changes in outcome can arise from small variations of input.…

Assessing the Quality of Expertise Differences in the Comprehension of Medical Visualizations

ERIC Educational Resources Information Center

Gegenfurtner, Andreas; Siewiorek, Anna; Lehtinen, Erno; Saljo, Roger

2013-01-01

Understanding how best to assess expertise, the situational variations of expertise, and distinctive qualities of expertise that arises from particular workplace experiences, presents an important challenge. Certainly, at this time, there is much interest in identifying standard occupational measures and competences, which are not well aligned…

21 CFR 862.1660 - Quality control material (assayed and unassayed).

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Quality control material (assayed and unassayed... Test Systems § 862.1660 Quality control material (assayed and unassayed). (a) Identification. A quality... that may arise from reagent or analytical instrument variation. A quality control material (assayed and...

Charleshenge--An Archeo-Astronomy Exercise for the Elementary Astronomy Lab.

ERIC Educational Resources Information Center

Dukes, Robert J. Jr.

1982-01-01

Techniques have been described for using celestial spheres as data-generating devices. Descibes a variation, capitalizing on students' interest in activities related to Stonehenge. Following a movie, students determine whether or not astronomical alignments found at Stonehenge and related structures could arise by chance. Local buildings are used.…

Manpower Planning, Rate of Return Analysis, and the University Medical Schools: The Case of Australia

ERIC Educational Resources Information Center

Davis, Denis J.

1977-01-01

Some of the errors in educational planning that arise from manpower forecasts are examined using the Australian doctors manpower plan, 1975-91 as an illustration. The large variation in results that can occur through the substitution of alternatively feasible coefficients is shown. (Editor/LBH)

The Complexity of One-Step Equations

ERIC Educational Resources Information Center

Ngu, Bing

2014-01-01

An analysis of one-step equations from a cognitive load theory perspective uncovers variation within one-step equations. The complexity of one-step equations arises from the element interactivity across the operational and relational lines. The higher the number of operational and relational lines, the greater the complexity of the equations.…

Hepatic gene expression analysis between low and high growing hybrid striped bass

USDA-ARS?s Scientific Manuscript database

Hybrid striped bass (HSB), produced from a cross between white bass (Morone chrysops) and striped bass (Morone saxatilis) represent a significant market for US aquaculture. One of the major constraints to an increase in production and profitability of producers arises from the variation in growth o...

Switchgrass Compositional Variations Arising from Spatial Distribution and Legume Intercropping

USDA-ARS?s Scientific Manuscript database

Switchgrass (Panicum virgatum) is a high–yielding, second-generation feedstock that can be grown on marginal land with minimal inputs. Due to the high genetic diversity within and among cultivars of this species, there may be a great amount of genotype x environment-induced differences among seconda...

Development of a coupled expert system for the spacecraft attitude control problem

NASA Technical Reports Server (NTRS)

Kawamura, K.; Beale, G.; Schaffer, J.; Hsieh, B.-J.; Padalkar, S.; Rodriguezmoscoso, J.; Vinz, F.; Fernandez, K.

1987-01-01

A majority of the current expert systems focus on the symbolic-oriented logic and inference mechanisms of artificial intelligence (AI). Common rule-based systems employ empirical associations and are not well suited to deal with problems often arising in engineering. Described is a prototype expert system which combines both symbolic and numeric computing. The expert system's configuration is presented and its application to a spacecraft attitude control problem is discussed.

Variational estimate method for solving autonomous ordinary differential equations

NASA Astrophysics Data System (ADS)

Mungkasi, Sudi

2018-04-01

In this paper, we propose a method for solving first-order autonomous ordinary differential equation problems using a variational estimate formulation. The variational estimate is constructed with a Lagrange multiplier which is chosen optimally, so that the formulation leads to an accurate solution to the problem. The variational estimate is an integral form, which can be computed using a computer software. As the variational estimate is an explicit formula, the solution is easy to compute. This is a great advantage of the variational estimate formulation.

Evaluation of emerging factors blocking filtration of high-adjunct-ratio wort.

PubMed

Ma, Ting; Zhu, Linjiang; Zheng, Feiyun; Li, Yongxian; Li, Qi

2014-08-20

Corn starch has become a common adjunct for beer brewing in Chinese breweries. However, with increasing ratio of corn starch, problems like poor wort filtration performance arise, which will decrease production capacity of breweries. To solve this problem, factors affecting wort filtration were evaluated, such as the size of corn starch particle, special yellow floats formed during liquefaction of corn starch, and residual substance after liquefaction. The effects of different enzyme preparations including β-amylase and β-glucanase on filtration rate were also evaluated. The results indicate that the emerging yellow floats do not severely block filtration, while the fine and uniform-shape corn starch particle and its incompletely hydrolyzed residue after liquefaction are responsible for filtration blocking. Application of β-amylase preparation increased the filtration rate of liquefied corn starch. This study is useful for our insight into the filtration blocking problem arising in the process of high-adjunct-ratio beer brewing and also provides a feasible solution using enzyme preparations.

Eigenvalue problems for Beltrami fields arising in a three-dimensional toroidal magnetohydrodynamic equilibrium problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hudson, S. R.; Hole, M. J.; Dewar, R. L.

2007-05-15

A generalized energy principle for finite-pressure, toroidal magnetohydrodynamic (MHD) equilibria in general three-dimensional configurations is proposed. The full set of ideal-MHD constraints is applied only on a discrete set of toroidal magnetic surfaces (invariant tori), which act as barriers against leakage of magnetic flux, helicity, and pressure through chaotic field-line transport. It is argued that a necessary condition for such invariant tori to exist is that they have fixed, irrational rotational transforms. In the toroidal domains bounded by these surfaces, full Taylor relaxation is assumed, thus leading to Beltrami fields {nabla}xB={lambda}B, where {lambda} is constant within each domain. Two distinctmore » eigenvalue problems for {lambda} arise in this formulation, depending on whether fluxes and helicity are fixed, or boundary rotational transforms. These are studied in cylindrical geometry and in a three-dimensional toroidal region of annular cross section. In the latter case, an application of a residue criterion is used to determine the threshold for connected chaos.« less

A stabilized element-based finite volume method for poroelastic problems

NASA Astrophysics Data System (ADS)

Honório, Hermínio T.; Maliska, Clovis R.; Ferronato, Massimiliano; Janna, Carlo

2018-07-01

The coupled equations of Biot's poroelasticity, consisting of stress equilibrium and fluid mass balance in deforming porous media, are numerically solved. The governing partial differential equations are discretized by an Element-based Finite Volume Method (EbFVM), which can be used in three dimensional unstructured grids composed of elements of different types. One of the difficulties for solving these equations is the numerical pressure instability that can arise when undrained conditions take place. In this paper, a stabilization technique is developed to overcome this problem by employing an interpolation function for displacements that considers also the pressure gradient effect. The interpolation function is obtained by the so-called Physical Influence Scheme (PIS), typically employed for solving incompressible fluid flows governed by the Navier-Stokes equations. Classical problems with analytical solutions, as well as three-dimensional realistic cases are addressed. The results reveal that the proposed stabilization technique is able to eliminate the spurious pressure instabilities arising under undrained conditions at a low computational cost.

αAMG based on Weighted Matching for Systems of Elliptic PDEs Arising From Displacement and Mixed Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Ambra, P.; Vassilevski, P. S.

2014-05-30

Adaptive Algebraic Multigrid (or Multilevel) Methods (αAMG) are introduced to improve robustness and efficiency of classical algebraic multigrid methods in dealing with problems where no a-priori knowledge or assumptions on the near-null kernel of the underlined matrix are available. Recently we proposed an adaptive (bootstrap) AMG method, αAMG, aimed to obtain a composite solver with a desired convergence rate. Each new multigrid component relies on a current (general) smooth vector and exploits pairwise aggregation based on weighted matching in a matrix graph to define a new automatic, general-purpose coarsening process, which we refer to as “the compatible weighted matching”. Inmore » this work, we present results that broaden the applicability of our method to different finite element discretizations of elliptic PDEs. In particular, we consider systems arising from displacement methods in linear elasticity problems and saddle-point systems that appear in the application of the mixed method to Darcy problems.« less

Theory of signs and statistical approach to big data in assessing the relevance of clinical biomarkers of inflammation and oxidative stress.

PubMed

Ghezzi, Pietro; Davies, Kevin; Delaney, Aidan; Floridi, Luciano

2018-03-06

Biomarkers are widely used not only as prognostic or diagnostic indicators, or as surrogate markers of disease in clinical trials, but also to formulate theories of pathogenesis. We identify two problems in the use of biomarkers in mechanistic studies. The first problem arises in the case of multifactorial diseases, where different combinations of multiple causes result in patient heterogeneity. The second problem arises when a pathogenic mediator is difficult to measure. This is the case of the oxidative stress (OS) theory of disease, where the causal components are reactive oxygen species (ROS) that have very short half-lives. In this case, it is usual to measure the traces left by the reaction of ROS with biological molecules, rather than the ROS themselves. Borrowing from the philosophical theories of signs, we look at the different facets of biomarkers and discuss their different value and meaning in multifactorial diseases and system medicine to inform their use in patient stratification in personalized medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Zhaojun; Yang, Chao

What is common among electronic structure calculation, design of MEMS devices, vibrational analysis of high speed railways, and simulation of the electromagnetic field of a particle accelerator? The answer: they all require solving large scale nonlinear eigenvalue problems. In fact, these are just a handful of examples in which solving nonlinear eigenvalue problems accurately and efficiently is becoming increasingly important. Recognizing the importance of this class of problems, an invited minisymposium dedicated to nonlinear eigenvalue problems was held at the 2005 SIAM Annual Meeting. The purpose of the minisymposium was to bring together numerical analysts and application scientists to showcasemore » some of the cutting edge results from both communities and to discuss the challenges they are still facing. The minisymposium consisted of eight talks divided into two sessions. The first three talks focused on a type of nonlinear eigenvalue problem arising from electronic structure calculations. In this type of problem, the matrix Hamiltonian H depends, in a non-trivial way, on the set of eigenvectors X to be computed. The invariant subspace spanned by these eigenvectors also minimizes a total energy function that is highly nonlinear with respect to X on a manifold defined by a set of orthonormality constraints. In other applications, the nonlinearity of the matrix eigenvalue problem is restricted to the dependency of the matrix on the eigenvalues to be computed. These problems are often called polynomial or rational eigenvalue problems In the second session, Christian Mehl from Technical University of Berlin described numerical techniques for solving a special type of polynomial eigenvalue problem arising from vibration analysis of rail tracks excited by high-speed trains.« less

Generalized vector calculus on convex domain

NASA Astrophysics Data System (ADS)

Agrawal, Om P.; Xu, Yufeng

2015-06-01

In this paper, we apply recently proposed generalized integral and differential operators to develop generalized vector calculus and generalized variational calculus for problems defined over a convex domain. In particular, we present some generalization of Green's and Gauss divergence theorems involving some new operators, and apply these theorems to generalized variational calculus. For fractional power kernels, the formulation leads to fractional vector calculus and fractional variational calculus for problems defined over a convex domain. In special cases, when certain parameters take integer values, we obtain formulations for integer order problems. Two examples are presented to demonstrate applications of the generalized variational calculus which utilize the generalized vector calculus developed in the paper. The first example leads to a generalized partial differential equation and the second example leads to a generalized eigenvalue problem, both in two dimensional convex domains. We solve the generalized partial differential equation by using polynomial approximation. A special case of the second example is a generalized isoperimetric problem. We find an approximate solution to this problem. Many physical problems containing integer order integrals and derivatives are defined over arbitrary domains. We speculate that future problems containing fractional and generalized integrals and derivatives in fractional mechanics will be defined over arbitrary domains, and therefore, a general variational calculus incorporating a general vector calculus will be needed for these problems. This research is our first attempt in that direction.

A genetic algorithm used for solving one optimization problem

NASA Astrophysics Data System (ADS)

Shipacheva, E. N.; Petunin, A. A.; Berezin, I. M.

2017-12-01

A problem of minimizing the length of the blank run for a cutting tool during cutting of sheet materials into shaped blanks is discussed. This problem arises during the preparation of control programs for computerized numerical control (CNC) machines. A discrete model of the problem is analogous in setting to the generalized travelling salesman problem with limitations in the form of precursor conditions determined by the technological features of cutting. A certain variant of a genetic algorithm for solving this problem is described. The effect of the parameters of the developed algorithm on the solution result for the problem with limitations is investigated.

Composite solvers for linear saddle point problems arising from the incompressible Stokes equations with highly heterogeneous viscosity structure

NASA Astrophysics Data System (ADS)

Sanan, P.; Schnepp, S. M.; May, D.; Schenk, O.

2014-12-01

Geophysical applications require efficient forward models for non-linear Stokes flow on high resolution spatio-temporal domains. The bottleneck in applying the forward model is solving the linearized, discretized Stokes problem which takes the form of a large, indefinite (saddle point) linear system. Due to the heterogeniety of the effective viscosity in the elliptic operator, devising effective preconditioners for saddle point problems has proven challenging and highly problem-dependent. Nevertheless, at least three approaches show promise for preconditioning these difficult systems in an algorithmically scalable way using multigrid and/or domain decomposition techniques. The first is to work with a hierarchy of coarser or smaller saddle point problems. The second is to use the Schur complement method to decouple and sequentially solve for the pressure and velocity. The third is to use the Schur decomposition to devise preconditioners for the full operator. These involve sub-solves resembling inexact versions of the sequential solve. The choice of approach and sub-methods depends crucially on the motivating physics, the discretization, and available computational resources. Here we examine the performance trade-offs for preconditioning strategies applied to idealized models of mantle convection and lithospheric dynamics, characterized by large viscosity gradients. Due to the arbitrary topological structure of the viscosity field in geodynamical simulations, we utilize low order, inf-sup stable mixed finite element spatial discretizations which are suitable when sharp viscosity variations occur in element interiors. Particular attention is paid to possibilities within the decoupled and approximate Schur complement factorization-based monolithic approaches to leverage recently-developed flexible, communication-avoiding, and communication-hiding Krylov subspace methods in combination with `heavy' smoothers, which require solutions of large per-node sub-problems, well-suited to solution on hybrid computational clusters. To manage the combinatorial explosion of solver options (which include hybridizations of all the approaches mentioned above), we leverage the modularity of the PETSc library.

System noise analysis of the dumbbell tethered satellite for gravity-gradient measurements

NASA Technical Reports Server (NTRS)

Colombo, G.

1979-01-01

An analysis of the dumbbell gravity gradiometer concept for measuring short wavelength variations in the earth's gravity gradient is presented. Variations in the gradient are recorded by measuring tension variations in a vertically stabilized satellite consisting of heavy masses connected by a long wire or rod. Tension noise arises from the excitation of various mechanical oscillations of the system. The principal noise sources that were identified are fluctuations in atmospheric drag heating and drag force resulting from density variations and winds. Approximate analytical expressions are presented for the tension noise as a function of the system design parameters for various possible configurations. Computer simulations using numerical integration were performed to study the tension noise for several sample cases. Three designs consistent with Shuttle launch capabilities are discussed.

The role of the reflection coefficient in precision measurement of ultrasonic attenuation

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1984-01-01

Ultrasonic attenuation measurements using contact, pulse-echo techniques are sensitive to surface roughness and couplant thickness variations. This can reduce considerable inaccuracies in the measurement of the attenuation coefficient for broadband pulses. Inaccuracies arise from variations in the reflection coefficient at the buffer-couplant-sample interface. The reflection coefficient is examined as a function of the surface roughness and corresponding couplant thickness variations. Interrelations with ultrasonic frequency are illustrated. Reliable attenuation measurements are obtained only when the frequency dependence of the reflection coefficient is incorporated in signal analysis. Data are given for nickel 200 samples and a silicon nitride ceramic bar having surface roughness variations in the 0.3 to 3.0 microns range for signal bandwidths in the 50 to 100 MHz range.

A Cognitive Map of Human Performance Technology: A Study of Domain Expertise.

ERIC Educational Resources Information Center

Villachica, Steven W.; Lohr, Linda L.; Summers, Laura; Lowell, Nate; Roberts, Stephanie; Javeri, Manisha; Hunt, Erin; Mahoney, Chris; Conn, Cyndie

Most representations of academic disciplines have been created when experts depict or report what they know; however, there are potential problems that can arise when practitioners rely on expert self-report. One way to avoid potential problems associated with expert self-report is to employ cognitive task analysis methods. The Pathfinder Scaling…

Development and Evaluation of an Interactive Mobile Learning Environment with Shared Display Groupware

ERIC Educational Resources Information Center

Yang, Jie Chi; Lin, Yi Lung

2010-01-01

When using mobile devices in support of learning activities, students gain mobility, but problems arise when group members share information. The small size of the mobile device screen becomes problematic when it is being used by two or more students to share and exchange information. This problem affects interactions among group members. To…

Administrative Problem-Solving for Writing Programs and Writing Centers: Scenarios in Effective Program Management.

ERIC Educational Resources Information Center

Myers-Breslin, Linda

Addressing the issues and problems faced by writing program administrators (WPAs) and writing center directors (WCDs), and how they can most effectively resolve the political, pedagogical, and financial questions that arise, this book presents essays from experienced WPAs and WCDs at a wide variety of institutions that offer scenarios and case…

Succession Planning in England: New Leaders and New Forms of Leadership

ERIC Educational Resources Information Center

Bush, Tony

2011-01-01

There are concerns about the supply of head teachers in many countries. In England, this problem arises from demographic changes and the perceived difficulty of the job. The National College responded to this problem by initiating a Succession Planning programme. This article reports the main findings from the external evaluation of the programme…

Effects of Inequality and Poverty vs. Teachers and Schooling on America's Youth

ERIC Educational Resources Information Center

Berliner, David C.

2013-01-01

Background/Context: This paper arises out of frustration with the results of school reforms carried out over the past few decades. These efforts have failed. They need to be abandoned. In their place must come recognition that income inequality causes many social problems, including problems associated with education. Sadly, compared to all other…

Practical Solutions to Practically Every Problem: The Early Childhood Teacher's Manual. Revised Edition.

ERIC Educational Resources Information Center

Saifer, Steffen

Based on sound developmentally appropriate theory, this revised guide is designed to help early childhood teachers deal with common problems that arise in all aspects of their work. Following an introduction and a list of the 20 most important principles for successful preschool teaching, the guide is divided into nine parts. Part 1 addresses…

Co-Rumination Cultivates Anxiety: A Genetically Informed Study of Friend Influence during Early Adolescence

ERIC Educational Resources Information Center

Dirghangi, Shrija; Kahn, Gilly; Laursen, Brett; Brendgen, Mara; Vitaro, Frank; Dionne, Ginette; Boivin, Michel

2015-01-01

This study tested 2 related hypotheses. The first holds that high co-rumination anticipates heightened internalizing problems. The second holds that positive relationships with friends exacerbate the risk for internalizing problems arising from co-rumination. A sample of MZ twins followed from birth (194 girls and 170 boys) completed (a)…

Symmetry of the Adiabatic Condition in the Piston Problem

ERIC Educational Resources Information Center

Anacleto, Joaquim; Ferreira, J. M.

2011-01-01

This study addresses a controversial issue in the adiabatic piston problem, namely that of the piston being adiabatic when it is fixed but no longer so when it can move freely. It is shown that this apparent contradiction arises from the usual definition of adiabatic condition. The issue is addressed here by requiring the adiabatic condition to be…

The Perceived Benefits and Problems Associated with Teaching Activities Undertaken by Doctoral Students

ERIC Educational Resources Information Center

Jordan, Katy; Howe, Christine

2018-01-01

Postgraduate students involved in delivering undergraduate teaching while working toward a research degree are known as graduate teaching assistants (GTAs). This study focused upon the problems and benefits arising from this dual role as researchers and teachers, as perceived by GTAs at the University of Cambridge. To this end, GTAs at Cambridge…

Practical Solutions to Practically Every Problem: The Early Childhood Teacher's Manual.

ERIC Educational Resources Information Center

Saifer, Steffen

This book is designed to help early childhood teachers deal with common problems that arise in all aspects of their work. Part one addresses daily dilemmas such as schedule planning, meal and nap times, art, and outdoor play. Part two covers classroom concerns such as the physical environment, curriculum, individual student needs, field trips,…

Measuring forest evapotranspiration--theory and problems

Treesearch

Anthony C. Federer; Anthony C. Federer

1970-01-01

A satisfactory general method of measuring forest evapotranspiration has yet to be developed. Many procedures have been tried, but only the soil-water budget method and the micrometeorological methods offer any degree of success. This paper is a discussion of these procedures and the problems that arise in applying them. It is designed as a reference for scientists and...

Reflections on the surface energy imbalance problem

Treesearch

Ray Leuning; Eva van Gorsela; William J. Massman; Peter R. Isaac

2012-01-01

The 'energy imbalance problem' in micrometeorology arises because at most flux measurement sites the sum of eddy fluxes of sensible and latent heat (H + λE) is less than the available energy (A). Either eddy fluxes are underestimated or A is overestimated. Reasons for the imbalance are: (1) a failure to satisfy the fundamental assumption of one-...

Who Is Listening? An Examination of Gender Effects and Employment Choice in Sustainability Education in an Undergraduate Business School

ERIC Educational Resources Information Center

Weaven, Scott; Griffin, Deborah; McPhail, Ruth; Smith, Calvin

2013-01-01

Whilst universities acknowledge the importance of sustainability education, numerous problems exist in relation to the nature, delivery and outcomes of sustainability instruction. Many of these problems arise due to a lack of understanding about students' perception towards, and knowledge about business sustainability. This article examines…

Estimation of coefficients and boundary parameters in hyperbolic systems

NASA Technical Reports Server (NTRS)

Banks, H. T.; Murphy, K. A.

1984-01-01

Semi-discrete Galerkin approximation schemes are considered in connection with inverse problems for the estimation of spatially varying coefficients and boundary condition parameters in second order hyperbolic systems typical of those arising in 1-D surface seismic problems. Spline based algorithms are proposed for which theoretical convergence results along with a representative sample of numerical findings are given.

A homotopy analysis method for the nonlinear partial differential equations arising in engineering

NASA Astrophysics Data System (ADS)

Hariharan, G.

2017-05-01

In this article, we have established the homotopy analysis method (HAM) for solving a few partial differential equations arising in engineering. This technique provides the solutions in rapid convergence series with computable terms for the problems with high degree of nonlinear terms appearing in the governing differential equations. The convergence analysis of the proposed method is also discussed. Finally, we have given some illustrative examples to demonstrate the validity and applicability of the proposed method.

An Electromagnetically-Controlled Precision Orbital Tracking Vehicle (POTV)

DTIC Science & Technology

1992-12-01

assume that C > B > A. Then 0 1(t) is purely sinusoidal. tk2 (t) is also sinusoidal because the forcing function z(t) is sinusoidal. 03 (t) is more...an unpredictable -manner. The problem arises from the rank deficiency of the G input matrix as shown below. Remember we have shown already that its...rank can never exceed five because rows two, four, and six are linearly dependent. The rank deficiency arises from the "translational part" of the input

Hausdorff dimension of certain sets arising in Engel expansions

NASA Astrophysics Data System (ADS)

Fang, Lulu; Wu, Min

2018-05-01

The present paper is concerned with the Hausdorff dimension of certain sets arising in Engel expansions. In particular, the Hausdorff dimension of the set is completely determined, where A n (x) can stand for the digit, gap and ratio between two consecutive digits in the Engel expansion of x and ϕ is a positive function defined on natural numbers. These results significantly extend the existing results of Galambos’ open problems on the Hausdorff dimension of sets related to the growth rate of digits.

Changes in hemoglobin-oxygen affinity with shape variations of red blood cells

NASA Astrophysics Data System (ADS)

Chowdhury, Aniket; Dasgupta, Raktim; Majumder, Shovan K.

2017-10-01

Shape variations of red blood cells (RBCs) are known to occur upon exposure to various drugs or under diseased conditions. The commonly observed discocytic RBCs can be transformed to echinocytic or stomatocytic shape under such conditions. Raman spectra of the three major shape variations, namely discocyte, echinocyte, and stomatocyte, of RBCs were studied while subjecting the cells to oxygenated and deoxygenated conditions. Analysis of the recorded spectra suggests an increased level of hemoglobin (Hb)-oxygen affinity for the echinocytes. Also, some level of Hb degradation could be noticed for the deoxygenated echinocytes. The effects may arise from a reduced level of intracellular adenosine triphosphate in echinocytic cells and an increased fraction of submembrane Hb.

Present-day secular variations in the zonal harmonics of earth's geopotential

NASA Technical Reports Server (NTRS)

Mitrovica, J. X.; Peltier, W. R.

1993-01-01

The mathematical formulation required for predicting secular variation in the geopotential is developed for the case of a spherically symmetric, self-gravitating, viscoelastic earth model and an arbitrary surface load which can include a gravitational self-consistent ocean loading component. The theory is specifically applied to predict the present-day secular variation in the zonal harmonics of the geopotenial arising from the surface mass loading associated with the late Pleistocene glacial cycles. A procedure is outlined in which predictions of the present-day geopotential signal due to the late Pleistocene glacial cycles may be used to derive bounds on the net present-day mass flux from the Antarctic and Greenland ice sheets to the local oceans.

Genetic variation in adaptability and pleiotropy in budding yeast

PubMed Central

Mitchell, James Kameron; Bloom, Joshua S; Kruglyak, Leonid

2017-01-01

Evolution can favor organisms that are more adaptable, provided that genetic variation in adaptability exists. Here, we quantify this variation among 230 offspring of a cross between diverged yeast strains. We measure the adaptability of each offspring genotype, defined as its average rate of adaptation in a specific environmental condition, and analyze the heritability, predictability, and genetic basis of this trait. We find that initial genotype strongly affects adaptability and can alter the genetic basis of future evolution. Initial genotype also affects the pleiotropic consequences of adaptation for fitness in a different environment. This genetic variation in adaptability and pleiotropy is largely determined by initial fitness, according to a rule of declining adaptability with increasing initial fitness, but several individual QTLs also have a significant idiosyncratic role. Our results demonstrate that both adaptability and pleiotropy are complex traits, with extensive heritable differences arising from naturally occurring variation. PMID:28826486

Genetic variation in adaptability and pleiotropy in budding yeast.

PubMed

Jerison, Elizabeth R; Kryazhimskiy, Sergey; Mitchell, James Kameron; Bloom, Joshua S; Kruglyak, Leonid; Desai, Michael M

2017-08-17

Evolution can favor organisms that are more adaptable, provided that genetic variation in adaptability exists. Here, we quantify this variation among 230 offspring of a cross between diverged yeast strains. We measure the adaptability of each offspring genotype, defined as its average rate of adaptation in a specific environmental condition, and analyze the heritability, predictability, and genetic basis of this trait. We find that initial genotype strongly affects adaptability and can alter the genetic basis of future evolution. Initial genotype also affects the pleiotropic consequences of adaptation for fitness in a different environment. This genetic variation in adaptability and pleiotropy is largely determined by initial fitness, according to a rule of declining adaptability with increasing initial fitness, but several individual QTLs also have a significant idiosyncratic role. Our results demonstrate that both adaptability and pleiotropy are complex traits, with extensive heritable differences arising from naturally occurring variation.

Artificial mismatch hybridization

DOEpatents

Guo, Zhen; Smith, Lloyd M.

1998-01-01

An improved nucleic acid hybridization process is provided which employs a modified oligonucleotide and improves the ability to discriminate a control nucleic acid target from a variant nucleic acid target containing a sequence variation. The modified probe contains at least one artificial mismatch relative to the control nucleic acid target in addition to any mismatch(es) arising from the sequence variation. The invention has direct and advantageous application to numerous existing hybridization methods, including, applications that employ, for example, the Polymerase Chain Reaction, allele-specific nucleic acid sequencing methods, and diagnostic hybridization methods.

Combination of rare right arterial variation with anomalous origins of the vertebral artery, aberrant subclavian artery and persistent trigeminal artery. A case report.

PubMed

Ishihara, H; San Millán Ruíz, D; Abdo, G; Asakura, F; Yilmaz, H; Lovblad, K O; Rüfenacht, D A

2011-09-01

A 32-year-old woman hospitalized for subarachnoid hemorrhage showed rare arterial variation on the right side with anomalous origins of the vertebral artery, aberrant subclavian artery and persistent trigeminal artery. Angiography showed the right vertebral artery to originate from the right common carotid artery, the right subclavian artery to arise separately from the descending aorta, and persistent trigeminal artery on the right side. The possible embryonic mechanism of this previously unreported variant combination is discussed.

Calculation of TIR Canopy Hot Spot and Implications for Earth Radiation Budget

NASA Technical Reports Server (NTRS)

Smith, J. A.; Ballard, J. R., Jr.

2000-01-01

Using a 3-D model for thermal infrared exitance and the Lowtran 7 atmospheric radiative transfer model, we compute the variation in brightness temperature with view direction and, in particular, the canopy thermal hot spot. We then perform a sensitivity analysis of surface energy balance components for a nominal case using a simple SVAT model given the uncertainty in canopy temperature arising from the thermal hot spot effect. Canopy thermal hot spot variations of two degrees C lead to differences of plus or minus 24% in the midday available energy.

Numerical solutions of acoustic wave propagation problems using Euler computations

NASA Technical Reports Server (NTRS)

Hariharan, S. I.

1984-01-01

This paper reports solution procedures for problems arising from the study of engine inlet wave propagation. The first problem is the study of sound waves radiated from cylindrical inlets. The second one is a quasi-one-dimensional problem to study the effect of nonlinearities and the third one is the study of nonlinearities in two dimensions. In all three problems Euler computations are done with a fourth-order explicit scheme. For the first problem results are shown in agreement with experimental data and for the second problem comparisons are made with an existing asymptotic theory. The third problem is part of an ongoing work and preliminary results are presented for this case.

Variational Principles for Buckling of Microtubules Modeled as Nonlocal Orthotropic Shells

PubMed Central

2014-01-01

A variational principle for microtubules subject to a buckling load is derived by semi-inverse method. The microtubule is modeled as an orthotropic shell with the constitutive equations based on nonlocal elastic theory and the effect of filament network taken into account as an elastic surrounding. Microtubules can carry large compressive forces by virtue of the mechanical coupling between the microtubules and the surrounding elastic filament network. The equations governing the buckling of the microtubule are given by a system of three partial differential equations. The problem studied in the present work involves the derivation of the variational formulation for microtubule buckling. The Rayleigh quotient for the buckling load as well as the natural and geometric boundary conditions of the problem is obtained from this variational formulation. It is observed that the boundary conditions are coupled as a result of nonlocal formulation. It is noted that the analytic solution of the buckling problem for microtubules is usually a difficult task. The variational formulation of the problem provides the basis for a number of approximate and numerical methods of solutions and furthermore variational principles can provide physical insight into the problem. PMID:25214886

Optimal control of a harmonic oscillator: Economic interpretations

NASA Astrophysics Data System (ADS)

Janová, Jitka; Hampel, David

2013-10-01

Optimal control is a popular technique for modelling and solving the dynamic decision problems in economics. A standard interpretation of the criteria function and Lagrange multipliers in the profit maximization problem is well known. On a particular example, we aim to a deeper understanding of the possible economic interpretations of further mathematical and solution features of the optimal control problem: we focus on the solution of the optimal control problem for harmonic oscillator serving as a model for Phillips business cycle. We discuss the economic interpretations of arising mathematical objects with respect to well known reasoning for these in other problems.

Space shuttle safety - A hybrid vehicle breeds new problems.

NASA Technical Reports Server (NTRS)

Pinkel, I. I.

1971-01-01

Discussion of a few novel problems raised by the design and flight plan of the space shuttle and by the dangerous cargos it might carry. Among the problems cited are those connected with the inspection of the bearings of the propellant turbopumps, particularly those of the hydrogen pump, for evidence of spalling, as well as problems arising in the inspection of the high-temperature parts of the combustor and turbine section of the airbreathing turbofan for shuttle booster and orbiter, and problems resulting from the possibility of fire hazard due to spontaneous ignition of fuel vapor in the fuel tank vapor space.

Applied mathematical problems in modern electromagnetics

NASA Astrophysics Data System (ADS)

Kriegsman, Gregory

1994-05-01

We have primarily investigated two classes of electromagnetic problems. The first contains the quantitative description of microwave heating of dispersive and conductive materials. Such problems arise, for example, when biological tissue are exposed, accidentally or purposefully, to microwave radiation. Other instances occur in ceramic processing, such as sintering and microwave assisted chemical vapor infiltration and other industrial drying processes, such as the curing of paints and concrete. The second class characterizes the scattering of microwaves by complex targets which possess two or more disparate length and/or time scales. Spatially complex scatterers arise in a variety of applications, such as large gratings and slowly changing guiding structures. The former are useful in developing microstrip energy couplers while the later can be used to model anatomical subsystems (e.g., the open guiding structure composed of two legs and the adjoining lower torso). Temporally complex targets occur in applications involving dispersive media whose relaxation times differ by orders of magnitude from thermal and/or electromagnetic time scales. For both cases the mathematical description of the problems gives rise to complicated ill-conditioned boundary value problems, whose accurate solutions require a blend of both asymptotic techniques, such as multiscale methods and matched asymptotic expansions, and numerical methods incorporating radiation boundary conditions, such as finite differences and finite elements.

Gardner's Two Children Problems and Variations: Puzzles with Conditional Probability and Sample Spaces

ERIC Educational Resources Information Center

Taylor, Wendy; Stacey, Kaye

2014-01-01

This article presents "The Two Children Problem," published by Martin Gardner, who wrote a famous and widely-read math puzzle column in the magazine "Scientific American," and a problem presented by puzzler Gary Foshee. This paper explains the paradox of Problems 2 and 3 and many other variations of the theme. Then the authors…

Singular optimal control and the identically non-regular problem in the calculus of variations

NASA Technical Reports Server (NTRS)

Menon, P. K. A.; Kelley, H. J.; Cliff, E. M.

1985-01-01

A small but interesting class of optimal control problems featuring a scalar control appearing linearly is equivalent to the class of identically nonregular problems in the Calculus of Variations. It is shown that a condition due to Mancill (1950) is equivalent to the generalized Legendre-Clebsch condition for this narrow class of problems.

Regularization by Functions of Bounded Variation and Applications to Image Enhancement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casas, E.; Kunisch, K.; Pola, C.

1999-09-15

Optimization problems regularized by bounded variation seminorms are analyzed. The optimality system is obtained and finite-dimensional approximations of bounded variation function spaces as well as of the optimization problems are studied. It is demonstrated that the choice of the vector norm in the definition of the bounded variation seminorm is of special importance for approximating subspaces consisting of piecewise constant functions. Algorithms based on a primal-dual framework that exploit the structure of these nondifferentiable optimization problems are proposed. Numerical examples are given for denoising of blocky images with very high noise.

Non-formal learning and tacit knowledge in professional work.

PubMed

Eraut, M

2000-03-01

This paper explores the conceptual and methodological problems arising from several empirical investigations of professional education and learning in the workplace. 1. To clarify the multiple meanings accorded to terms such as 'non-formal learning', 'implicit learning' and 'tacit knowledge', their theoretical assumptions and the range of phenomena to which they refer. 2. To discuss their implications for professional practice. A largely theoretical analysis of issues and phenomena arising from empirical investigations. The author's typology of non-formal learning distinguishes between implicit learning, reactive on-the-spot learning and deliberative learning. The significance of the last is commonly overemphasized. The problematic nature of tacit knowledge is discussed with respect to both detecting it and representing it. Three types of tacit knowledge are discussed: tacit understanding of people and situations, routinized actions and the tacit rules that underpin intuitive decision-making. They come together when professional performance involves sequences of routinized action punctuated by rapid intuitive decisions based on tacit understanding of the situation. Four types of process are involved--reading the situation, making decisions, overt activity and metacognition--and three modes of cognition--intuitive, analytic and deliberative. The balance between these modes depends on time, experience and complexity. Where rapid action dominates, periods of deliberation are needed to maintain critical control. Finally the role of both formal and informal social knowledge is discussed; and it is argued that situated learning often leads not to local conformity but to greater individual variation as people's careers take them through a series of different contexts. This abstract necessarily simplifies a more complex analysis in the paper itself.

Solar array stepping problems in satellites and solutions

NASA Astrophysics Data System (ADS)

Maharana, P. K.; Goel, P. S.

1992-01-01

The dynamics problems arising due to stepping motion of the solar arrays of spacecraft are studied. To overcome these problems, design improvements in the drive logic based on the phase plane analysis are suggested. The improved designs are applied to the Solar Array Drive Assembly (SADA) of IRS-1B and INSAT-2A satellites. In addition, an alternate torquing strategy for very successful slewing of the arrays, and with minimum excitation of flexible modes, is proposed.

Efficient Preconditioning for the p-Version Finite Element Method in Two Dimensions

DTIC Science & Technology

1989-10-01

paper, we study fast parallel preconditioners for systems of equations arising from the p-version finite element method. The p-version finite element...computations and the solution of a relatively small global auxiliary problem. We study two different methods. In the first (Section 3), the global...20], will be studied in the next section. Problem (3.12) is obviously much more easily solved than the original problem ,nd the procedure is highly

Multiobjective optimization approach: thermal food processing.

PubMed

Abakarov, A; Sushkov, Y; Almonacid, S; Simpson, R

2009-01-01

The objective of this study was to utilize a multiobjective optimization technique for the thermal sterilization of packaged foods. The multiobjective optimization approach used in this study is based on the optimization of well-known aggregating functions by an adaptive random search algorithm. The applicability of the proposed approach was illustrated by solving widely used multiobjective test problems taken from the literature. The numerical results obtained for the multiobjective test problems and for the thermal processing problem show that the proposed approach can be effectively used for solving multiobjective optimization problems arising in the food engineering field.

Steiner trees and spanning trees in six-pin soap films

NASA Astrophysics Data System (ADS)

Dutta, Prasun; Khastgir, S. Pratik; Roy, Anushree

2010-02-01

The problem of finding minimum (local as well as absolute) path lengths joining given points (or terminals) on a plane is known as the Steiner problem. The Steiner problem arises in finding the minimum total road length joining several towns and cities. We study the Steiner tree problem using six-pin soap films. Experimentally, we observe spanning trees as well as Steiner trees partly by varying the pin diameter. We propose a possibly exact expression for the length of a spanning tree or a Steiner tree, which fails mysteriously in certain cases.

Algorithms for bilevel optimization

NASA Technical Reports Server (NTRS)

Alexandrov, Natalia; Dennis, J. E., Jr.

1994-01-01

General multilevel nonlinear optimization problems arise in design of complex systems and can be used as a means of regularization for multi-criteria optimization problems. Here, for clarity in displaying our ideas, we restrict ourselves to general bi-level optimization problems, and we present two solution approaches. Both approaches use a trust-region globalization strategy, and they can be easily extended to handle the general multilevel problem. We make no convexity assumptions, but we do assume that the problem has a nondegenerate feasible set. We consider necessary optimality conditions for the bi-level problem formulations and discuss results that can be extended to obtain multilevel optimization formulations with constraints at each level.

Managing auricular haematoma to prevent 'cauliflower ear'.

PubMed

Summers, Anthony

2012-09-01

This article describes the typical signs of auricular haematoma, how people who have the condition should be treated in emergency departments and the problems that can arise if they are managed inappropriately.

L{sup {infinity}} Variational Problems with Running Costs and Constraints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aronsson, G., E-mail: gunnar.aronsson@liu.se; Barron, E. N., E-mail: enbarron@math.luc.edu

2012-02-15

Various approaches are used to derive the Aronsson-Euler equations for L{sup {infinity}} calculus of variations problems with constraints. The problems considered involve holonomic, nonholonomic, isoperimetric, and isosupremic constraints on the minimizer. In addition, we derive the Aronsson-Euler equation for the basic L{sup {infinity}} problem with a running cost and then consider properties of an absolute minimizer. Many open problems are introduced for further study.

Building Language Through Conflict Resolution: Discussing Problems Enriches Language While Leading to Solutions

ERIC Educational Resources Information Center

Church, Ellen Booth

2005-01-01

This brief article describes how classroom group time can be "talk central" for children to discuss problems, imagine solutions, even role-play hypothetical situations. It is often in the safety and support of the large group that children develop the tools they need to learn how to resolve the inevitable conflicts that arise throughout life.…

An Improved Memetic Algorithm for Break Scheduling

NASA Astrophysics Data System (ADS)

Widl, Magdalena; Musliu, Nysret

In this paper we consider solving a complex real life break scheduling problem. This problem of high practical relevance arises in many working areas, e.g. in air traffic control and other fields where supervision personnel is working. The objective is to assign breaks to employees such that various constraints reflecting legal demands or ergonomic criteria are satisfied and staffing requirement violations are minimised.

A New Method for Calibrating Perceptual Salience across Dimensions in Infants: The Case of Color vs. Luminance

ERIC Educational Resources Information Center

Kaldy, Zsuzsa; Blaser, Erik A.; Leslie, Alan M.

2006-01-01

We report a new method for calibrating differences in perceptual salience across feature dimensions, in infants. The problem of inter-dimensional salience arises in many areas of infant studies, but a general method for addressing the problem has not previously been described. Our method is based on a preferential looking paradigm, adapted to…

Improving Productivity in the Work Force: Implications for Research and Development in Vocational Education. Occasional Paper No. 72.

ERIC Educational Resources Information Center

Sullivan, Dennis J.

Declining productivity is a major problem in the American economy. Gains in productivity, and finally, actual rates of productivity, have been declining since the late 1960s. Specific problems arising as a result of this decline in productivity are the inflationary pressures that we face as a nation, the increased regulatory environment under…

Collection and curation of IDPs in the stratosphere and below. Part 2: The Greenland and Antarctic ice sheets

NASA Technical Reports Server (NTRS)

Maurette, Michel; Hammer, C.; Harvey, R.; Immel, G.; Kurat, G.; Taylor, S.

1994-01-01

In a companion paper, Zolensky discusses interplanetary dust particles (IDP's) collected in the stratosphere. Here, we describe the recovery of much larger unmelted to partially melted IDP's from the Greenland and Antarctica ice sheet, and discuss problems arising in their collection and curation, as well as future prospects for tackling these problems.

A Jubilant Connection: General Jubal Early's Troops and the Golden Ratio

ERIC Educational Resources Information Center

Bolte, Linda A.; Noon, Tim R., Jr.

2012-01-01

The golden ratio, one of the most beautiful numbers in all of mathematics, arises in some surprising places. At first glance, we might expect that a General checking his troops' progress would be nothing more than a basic distance-rate-time problem. However, further exploration reveals a multi-faceted problem, one in which the ratio of rates…

Language Problems and the Final Act. Esperanto Documents, New Series No. 11A.

ERIC Educational Resources Information Center

Universal Esperanto Association, Rotterdam (Netherlands).

The Final Act of the Conference on Security and Co-operation in Europe, linguistic problems in the way of cooperation, language differences and the potential for discriminatory practice, and the need for a new linguistic order are discussed. It is suggested that misunderstandings arising from differences of language reduce the ability of the 35…

An Investigation of Starting Point Preferences in Human Performance on Traveling Salesman Problems

ERIC Educational Resources Information Center

MacGregor, James N.

2014-01-01

Previous studies have shown that people start traveling sales problem tours significantly more often from boundary than from interior nodes. There are a number of possible reasons for such a tendency: first, it may arise as a direct result of the processes involved in tour construction; second, boundary points may be perceptually more salient than…

Demographic controls of aboveground forest biomass across North America.

PubMed

Vanderwel, Mark C; Zeng, Hongcheng; Caspersen, John P; Kunstler, Georges; Lichstein, Jeremy W

2016-04-01

Ecologists have limited understanding of how geographic variation in forest biomass arises from differences in growth and mortality at continental to global scales. Using forest inventories from across North America, we partitioned continental-scale variation in biomass growth and mortality rates of 49 tree species groups into (1) species-independent spatial effects and (2) inherent differences in demographic performance among species. Spatial factors that were separable from species composition explained 83% and 51% of the respective variation in growth and mortality. Moderate additional variation in mortality (26%) was attributable to differences in species composition. Age-dependent biomass models showed that variation in forest biomass can be explained primarily by spatial gradients in growth that were unrelated to species composition. Species-dependent patterns of mortality explained additional variation in biomass, with forests supporting less biomass when dominated by species that are highly susceptible to competition (e.g. Populus spp.) or to biotic disturbances (e.g. Abies balsamea). © 2016 John Wiley & Sons Ltd/CNRS.

Total variation regularization of the 3-D gravity inverse problem using a randomized generalized singular value decomposition

NASA Astrophysics Data System (ADS)

Vatankhah, Saeed; Renaut, Rosemary A.; Ardestani, Vahid E.

2018-04-01

We present a fast algorithm for the total variation regularization of the 3-D gravity inverse problem. Through imposition of the total variation regularization, subsurface structures presenting with sharp discontinuities are preserved better than when using a conventional minimum-structure inversion. The associated problem formulation for the regularization is nonlinear but can be solved using an iteratively reweighted least-squares algorithm. For small-scale problems the regularized least-squares problem at each iteration can be solved using the generalized singular value decomposition. This is not feasible for large-scale, or even moderate-scale, problems. Instead we introduce the use of a randomized generalized singular value decomposition in order to reduce the dimensions of the problem and provide an effective and efficient solution technique. For further efficiency an alternating direction algorithm is used to implement the total variation weighting operator within the iteratively reweighted least-squares algorithm. Presented results for synthetic examples demonstrate that the novel randomized decomposition provides good accuracy for reduced computational and memory demands as compared to use of classical approaches.

Problem-based learning: Using students' questions to drive knowledge construction

NASA Astrophysics Data System (ADS)

Chin, Christine; Chia, Li-Gek

2004-09-01

This study employed problem-based learning for project work in a year 9 biology class. The purpose of the study was to investigate (a) students' inspirations for their self-generated problems and questions, (b) the kinds of questions that students asked individually and collaboratively, and (c) how students' questions guided them in knowledge construction. Data sources included observation and field notes, students' written documents, audiotapes and videotapes of students working in groups, and student interviews. Sources of inspiration for students' problems and questions included cultural beliefs and folklore; wonderment about information propagated by advertisements and the media; curiosity arising from personal encounters, family members' concerns, or observations of others; and issues arising from previous lessons in the school curriculum. Questions asked individually pertained to validation of common beliefs and misconceptions, basic information, explanations, and imagined scenarios. The findings regarding questions asked collaboratively are presented as two assertions. Assertion 1 maintained that students' course of learning were driven by their questions. Assertion 2 was that the ability to ask the right'' questions and the extent to which these could be answered, were important in sustaining students' interest in the project. Implications of the findings for instructional practice are discussed.

The Doubting System 1: Evidence for automatic substitution sensitivity.

PubMed

Johnson, Eric D; Tubau, Elisabet; De Neys, Wim

2016-02-01

A long prevailing view of human reasoning suggests severe limits on our ability to adhere to simple logical or mathematical prescriptions. A key position assumes these failures arise from insufficient monitoring of rapidly produced intuitions. These faulty intuitions are thought to arise from a proposed substitution process, by which reasoners unknowingly interpret more difficult questions as easier ones. Recent work, however, suggests that reasoners are not blind to this substitution process, but in fact detect that their erroneous responses are not warranted. Using the popular bat-and-ball problem, we investigated whether this substitution sensitivity arises out of an automatic System 1 process or whether it depends on the operation of an executive resource demanding System 2 process. Results showed that accuracy on the bat-and-ball problem clearly declined under cognitive load. However, both reduced response confidence and increased response latencies indicated that biased reasoners remained sensitive to their faulty responses under load. Results suggest that a crucial substitution monitoring process is not only successfully engaged, but that it automatically operates as an autonomous System 1 process. By signaling its doubt along with a biased intuition, it appears System 1 is "smarter" than traditionally assumed.

Tropical Warm Pool Surface Heat Budgets and Temperature: Contrasts Between 1997-98 El Nino and 1998-99 La Nina

NASA Technical Reports Server (NTRS)

Chou, Shu-Hsien; Chou, Ming-Dah; Chan, Pui-King; Lin, Po-Hsiung; Wang, Kung-Hwa

2003-01-01

Seasonal and interannual variations of the net surface heating F(sub NET) and sea surface temperature tendency (T(sub s)/dt) in the tropical eastern Indian and western Pacific Oceans are studied. The surface heat fluxes are derived from the Special Sensor Microwave/Imager and Japanese Geostationary Meteorological Satellite radiance measurements for the period October 1997-September 2000. It is found that the magnitude of solar heating is lager than that of evaporative cooling, but the spatial variation of the latter is significantly large than the former. As a result, the spatial variations of seasonal and interannual variability of F(sub NET), follow closely that of evaporative cooling. Seasonal variations of F(sub NET) and T(sub s)/dt are significantly correlated, except for the equatorial western Pacific. The high correlation is primarily attributable to high correlation between seasonal cycles of solar heating and T(sub s)/dt. The change of F(sub NET) between 1997-98 El Nino and 1998-99 La Nina is significantly larger in the tropical eastern Indian Ocean than tropical western Pacific. For the former region, the reduced evaporative cooling arising from weakened winds during the El Nino is generally associated with enhanced solar heating due to decreased cloudiness, and thus increases the interannual variability of F(sub NET). For the latter region, the reduced evaporative cooling due to weakened winds is generally associated with but exceeds the reduced solar heating arising from increased cloudiness, and vise versa. Thus the interannual variability of F(sub NET) is reduced due to this offsetting effect. Interannual variations of F(sub NET) and T(sub s)/dt have very low correlation. This is most likely related to interannual variability of ocean dynamics, which includes the variations of solar radiation penetrating through oceanic mixed layer, upwelling of cold thermocline water, Indonesian throughflow for transporting heat from the Pacific to Indian Ocean, and interhemispheric transport in the Indian Ocean.

The Effect of Recreation Goals on Conflict Perception: The Case of Water Skiers and Fishermen.

ERIC Educational Resources Information Center

Gramann, James H.; Burdge, Rabel J.

Variations in psychological goals for recreation participation are explored, both between and within activity categories, and related to differences in conflict perception. Support for a "goal interference" model of conflict is found. According to this model, when recreation goals are incompatible, behaviors arising out of one set of…

Local reduction of certain wave operators to one-dimensional form

NASA Technical Reports Server (NTRS)

Roe, Philip

1994-01-01

It is noted that certain common linear wave operators have the property that linear variation of the initial data gives rise to one-dimensional evolution in a plane defined by time and some direction in space. The analysis is given For operators arising in acoustics, electromagnetics, elastodynamics, and an abstract system.

NUCLEATION AND THE AUDIO-LINGUAL APPROACH.

ERIC Educational Resources Information Center

BELASCO, SIMON

IN THE PRE-NUCLEATION STAGE, THE STUDENT IS CONCERNED WITH STORING, OR INTERNALIZING, THREE KINDS OF LANGUAGE PATTERNS--(1) ONE REPRESENTING THE SOUND STRUCTURE, (2) ANOTHER INVOLVING A PORTION OF THE SYNTACTIC STRUCTURE, AND (3) A THIRD--CALLED SANDHI VARIATION--ARISING FROM THE ACCIDENTAL CO-OCCURRENCE OF CERTAIN SOUNDS MAKING UP THE ELEMENTS OF…

Nutrient loads exported from managed catchments reveal emergent biogeochemical stationarity

NASA Astrophysics Data System (ADS)

Basu, Nandita B.; Destouni, Georgia; Jawitz, James W.; Thompson, Sally E.; Loukinova, Natalia V.; Darracq, Amélie; Zanardo, Stefano; Yaeger, Mary; Sivapalan, Murugesu; Rinaldo, Andrea; Rao, P. Suresh C.

2010-12-01

Complexity of heterogeneous catchments poses challenges in predicting biogeochemical responses to human alterations and stochastic hydro-climatic drivers. Human interferences and climate change may have contributed to the demise of hydrologic stationarity, but our synthesis of a large body of observational data suggests that anthropogenic impacts have also resulted in the emergence of effective biogeochemical stationarity in managed catchments. Long-term monitoring data from the Mississippi-Atchafalaya River Basin (MARB) and the Baltic Sea Drainage Basin (BSDB) reveal that inter-annual variations in loads (LT) for total-N (TN) and total-P (TP), exported from a catchment are dominantly controlled by discharge (QT) leading inevitably to temporal invariance of the annual, flow-weighted concentration, $\\overline{Cf = (LT/QT). Emergence of this consistent pattern across diverse managed catchments is attributed to the anthropogenic legacy of accumulated nutrient sources generating memory, similar to ubiquitously present sources for geogenic constituents that also exhibit a linear LT-QT relationship. These responses are characteristic of transport-limited systems. In contrast, in the absence of legacy sources in less-managed catchments, $\\overline{Cf values were highly variable and supply limited. We offer a theoretical explanation for the observed patterns at the event scale, and extend it to consider the stochastic nature of rainfall/flow patterns at annual scales. Our analysis suggests that: (1) expected inter-annual variations in LT can be robustly predicted given discharge variations arising from hydro-climatic or anthropogenic forcing, and (2) water-quality problems in receiving inland and coastal waters would persist until the accumulated storages of nutrients have been substantially depleted. The finding has notable implications on catchment management to mitigate adverse water-quality impacts, and on acceleration of global biogeochemical cycles.

Understanding Forces: What's the Problem?

ERIC Educational Resources Information Center

Kibble, Bob

2006-01-01

Misconceptions about forces are very common and seem to arise from everyday experience and use of words. Ways to improve students' understanding of forces, as used in recent a IOP CD-Rom, are discussed here.

A Hidden Surface Algorithm for Computer Generated Halftone Pictures

DTIC Science & Technology

converting data describing three-dimensional objects into data that can be used to generate two-dimensional halftone images. It deals with some problems that arise in black and white, and color shading.

Variational algorithms for nonlinear smoothing applications

NASA Technical Reports Server (NTRS)

Bach, R. E., Jr.

1977-01-01

A variational approach is presented for solving a nonlinear, fixed-interval smoothing problem with application to offline processing of noisy data for trajectory reconstruction and parameter estimation. The nonlinear problem is solved as a sequence of linear two-point boundary value problems. Second-order convergence properties are demonstrated. Algorithms for both continuous and discrete versions of the problem are given, and example solutions are provided.

Precession of a two-layer Earth: contributions of the core and elasticity

NASA Astrophysics Data System (ADS)

Baenas, Tomás; Ferrándiz, José M.; Escapa, Alberto; Getino, Juan; Navarro, Juan F.

2016-04-01

The Earth's internal structure contributes to the precession rate in a small but non-negligible amount, given the current accuracy goals demanded by IAG/GGOS to the reference frames, namely 30 μas and 3 μas/yr. These contributions come from a variety of sources. One of those not yet accounted for in current IAU models is associated to the crossed effects of certain nutation-rising terms of a two-layer Earth model; intuitively, it gathers an 'indirect' effect of the core via the NDFW, or FCN, resonance as well as a 'direct' effect arising from terms that account for energy variations depending on the elasticity of the core. Similar order of magnitude reaches the direct effect of the departure of the Earth's rheology from linear elasticity. To compute those effects we work out the problem in a unified way within the Hamiltonian framework developed by Getino and Ferrándiz (2001). It allows a consistent treatment of the problem since all the perturbations are derived from the same tide generating expansion and the crossing effects are rigorously obtained through Hori's canonical perturbation method. The problem admits an asymptotic analytical solution. The Hamiltonian is constructed by considering a two-layer Earth model made up of an anelastic mantle and a fluid core, perturbed by the gravitational action of the Moon and the Sun. The former effects reach some tens of μas/yr in the longitude rate, hence above the target accuracy level. We outline their influence in the estimation of the Earth's dynamical ellipticity, a main parameter factorizing both precession and nutation.

Ethical challenges in conducting clinical research in lung cancer

PubMed Central

Tod, Angela M.

2016-01-01

The article examines ethical challenges that arise with clinical lung cancer research focusing on design, recruitment, conduct and dissemination. Design: problems related to equipoise can arise in lung cancer studies. Equipoise is an ethics precondition for RCTs and exists where there is insufficient evidence to decide which of two or more treatments is best. Difficulties arise in deciding what level of uncertainty constitutes equipoise and who should be in equipoise, for example, patients might not be even where clinicians are. Patient and public involvement (PPI) can reduce but not remove the problems. Recruitment: (I) lung cancer studies can be complex, making it difficult to obtain good quality consent. Some techniques can help, such as continuous consent. But researchers should not expect consent to be the sole protection for participants’ welfare. This protection is primarily done elsewhere in the research process, for example, in ethics review; (II) the problem of desperate volunteers: some patients only consent to a trial because it gives them a 50/50 option of the treatment they want and can be disappointed or upset if randomised to the other arm. This is not necessarily unfair, given clinical equipoise. However, it should be avoided where possible, for example, by using alternative trial designs; (III) the so-called problem of therapeutic misconception: this is the idea that patients are mistaken if they enter trials believing this to be in their clinical best interest. We argue the problem is misconceived and relates only to certain health systems. Conduct: lung cancer trials face standard ethical challenges with regard to trial conduct. PPI could be used in decisions about criteria for stopping rules. Dissemination: as in other trial areas, it is important that all results, including negative ones, are reported. We argue also that the role of PPI with regard to dissemination is currently under-developed. PMID:27413698

Laboratory issues: use of nutritional biomarkers.

PubMed

Blanck, Heidi Michels; Bowman, Barbara A; Cooper, Gerald R; Myers, Gary L; Miller, Dayton T

2003-03-01

Biomarkers of nutritional status provide alternative measures of dietary intake. Like the error and variation associated with dietary intake measures, the magnitude and impact of both biological (preanalytical) and laboratory (analytical) variability need to be considered when one is using biomarkers. When choosing a biomarker, it is important to understand how it relates to nutritional intake and the specific time frame of exposure it reflects as well as how it is affected by sampling and laboratory procedures. Biological sources of variation that arise from genetic and disease states of an individual affect biomarkers, but they are also affected by nonbiological sources of variation arising from specimen collection and storage, seasonality, time of day, contamination, stability and laboratory quality assurance. When choosing a laboratory for biomarker assessment, researchers should try to make sure random and systematic error is minimized by inclusion of certain techniques such as blinding of laboratory staff to disease status and including external pooled standards to which laboratory staff are blinded. In addition analytic quality control should be ensured by use of internal standards or certified materials over the entire range of possible values to control method accuracy. One must consider the effect of random laboratory error on measurement precision and also understand the method's limit of detection and the laboratory cutpoints. Choosing appropriate cutpoints and reducing error is extremely important in nutritional epidemiology where weak associations are frequent. As part of this review, serum lipids are included as an example of a biomarker whereby collaborative efforts have been put forth to both understand biological sources of variation and standardize laboratory results.

Local population density and group composition influence the signal-preference relationship in Enchenopa treehoppers (Hemiptera: Membracidae).

PubMed

Fowler-Finn, K D; Cruz, D C; Rodríguez, R L

2017-01-01

Many animals exhibit social plasticity - changes in phenotype or behaviour in response to experience with conspecifics that change how evolutionary processes like sexual selection play out. Here, we asked whether social plasticity arising from variation in local population density in male advertisement signals and female mate preferences influences the form of sexual selection. We manipulated local density and determined whether this changed how the distribution of male signals overlapped with female preferences - the signal preference relationship. We specifically look at the shape of female mate preference functions, which, when compared to signal distributions, provide hypotheses about the form of sexual selection. We used Enchenopa binotata treehoppers, a group of plant-feeding insects that exhibit natural variation in local densities across individual host plants, populations, species and years. We measured male signal frequency and female preference functions across the density treatments. We found that male signals varied across local social groups, but not according to local density. By contrast, female preferences varied with local density - favouring higher signal frequencies in denser environments. Thus, local density changes the signal-preference relationship and, consequently, the expected form of sexual selection. We found no influence of sex ratio on the signal-preference relationship. Our findings suggest that plasticity arising from variation in local group density and composition can alter the form of sexual selection with potentially important consequences both for the maintenance of variation and for speciation. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Mate-finding as an overlooked critical determinant of dispersal variation in sexually-reproducing animals.

PubMed

Gilroy, James J; Lockwood, Julie L

2012-01-01

Dispersal is a critically important process in ecology, but robust predictive models of animal dispersal remain elusive. We identify a potentially ubiquitous component of variation in animal dispersal that has been largely overlooked until now: the influence of mate encounters on settlement probability. We use an individual-based model to simulate dispersal in sexually-reproducing organisms that follow a simple set of movement rules based on conspecific encounters, within an environment lacking spatial habitat heterogeneity. We show that dispersal distances vary dramatically with fluctuations in population density in such a model, even in the absence of variation in dispersive traits between individuals. In a simple random-walk model with promiscuous mating, dispersal distributions become increasingly 'fat-tailed' at low population densities due to the increasing scarcity of mates. Similar variation arises in models incorporating territoriality. In a model with polygynous mating, we show that patterns of sex-biased dispersal can even be reversed across a gradient of population density, despite underlying dispersal mechanisms remaining unchanged. We show that some widespread dispersal patterns found in nature (e.g. fat tailed distributions) can arise as a result of demographic variability in the absence of heterogeneity in dispersive traits across the population. This implies that models in which individual dispersal distances are considered to be fixed traits might be unrealistic, as dispersal distances vary widely under a single dispersal mechanism when settlement is influenced by mate encounters. Mechanistic models offer a promising means of advancing our understanding of dispersal in sexually-reproducing organisms.

Analytic Energy Gradients for Variational Two-Electron Reduced-Density-Matrix-Driven Complete Active Space Self-Consistent Field Theory.

PubMed

Maradzike, Elvis; Gidofalvi, Gergely; Turney, Justin M; Schaefer, Henry F; DePrince, A Eugene

2017-09-12

Analytic energy gradients are presented for a variational two-electron reduced-density-matrix (2-RDM)-driven complete active space self-consistent field (CASSCF) method. The active-space 2-RDM is determined using a semidefinite programing (SDP) algorithm built upon an augmented Lagrangian formalism. Expressions for analytic gradients are simplified by the fact that the Lagrangian is stationary with respect to variations in both the primal and the dual solutions to the SDP problem. Orbital response contributions to the gradient are identical to those that arise in conventional CASSCF methods in which the electronic structure of the active space is described by a full configuration interaction (CI) wave function. We explore the relative performance of variational 2-RDM (v2RDM)- and CI-driven CASSCF for the equilibrium geometries of 20 small molecules. When enforcing two-particle N-representability conditions, full-valence v2RDM-CASSCF-optimized bond lengths display a mean unsigned error of 0.0060 Å and a maximum unsigned error of 0.0265 Å, relative to those obtained from full-valence CI-CASSCF. When enforcing partial three-particle N-representability conditions, the mean and maximum unsigned errors are reduced to only 0.0006 and 0.0054 Å, respectively. For these same molecules, full-valence v2RDM-CASSCF bond lengths computed in the cc-pVQZ basis set deviate from experimentally determined ones on average by 0.017 and 0.011 Å when enforcing two- and three-particle conditions, respectively, whereas CI-CASSCF displays an average deviation of 0.010 Å. The v2RDM-CASSCF approach with two-particle conditions is also applied to the equilibrium geometry of pentacene; optimized bond lengths deviate from those derived from experiment, on average, by 0.015 Å when using a cc-pVDZ basis set and a (22e,22o) active space.

Total variation-based neutron computed tomography

NASA Astrophysics Data System (ADS)

Barnard, Richard C.; Bilheux, Hassina; Toops, Todd; Nafziger, Eric; Finney, Charles; Splitter, Derek; Archibald, Rick

2018-05-01

We perform the neutron computed tomography reconstruction problem via an inverse problem formulation with a total variation penalty. In the case of highly under-resolved angular measurements, the total variation penalty suppresses high-frequency artifacts which appear in filtered back projections. In order to efficiently compute solutions for this problem, we implement a variation of the split Bregman algorithm; due to the error-forgetting nature of the algorithm, the computational cost of updating can be significantly reduced via very inexact approximate linear solvers. We present the effectiveness of the algorithm in the significantly low-angular sampling case using synthetic test problems as well as data obtained from a high flux neutron source. The algorithm removes artifacts and can even roughly capture small features when an extremely low number of angles are used.

Impulse position control algorithms for nonlinear systems

NASA Astrophysics Data System (ADS)

Sesekin, A. N.; Nepp, A. N.

2015-11-01

The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of such regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.

Merging information in geophysics: the triumvirat of geology, geophysics, and petrophysics

NASA Astrophysics Data System (ADS)

Revil, A.

2016-12-01

We know that geophysical inversion is non-unique and that many classical regularization techniques are unphysical. Despite this, we like to use them because of their simplicity and because geophysicists are often afraid to bias the inverse problem by introducing too much prior information (in a broad sense). It is also clear that geophysics is done on geological objects that are not random structures. Spending some time with a geologist in the field, before organizing a field geophysical campaign, is always an instructive experience. Finally, the measured properties are connected to physicochemical and textural parameters of the porous media and the interfaces between the various phases of a porous body. .Some fundamental parameters may control the geophysical observtions or their time variations. If we want to improve our geophysical tomograms, we need to be risk-takers and acknowledge, or rather embrqce, the cross-fertilization arising by coupling geology, geophysics, and ptrophysics. In this presentation, I will discuss various techniques to do so. They will include non-stationary geostatistical descriptors, facies deformation, cross-coupled petrophysical properties using petrophysical clustering, and image-guided inversion. I will show various applications to a number of relevant cases in hydrogeophysics. From these applications, it may become clear that there are many ways to address inverse or time-lapse inverse problems and geophysicists have to be pragmatic regarding the methods used depending on the degree of available prior information.

Literature Review on Dynamic Cellular Manufacturing System

NASA Astrophysics Data System (ADS)

Nouri Houshyar, A.; Leman, Z.; Pakzad Moghadam, H.; Ariffin, M. K. A. M.; Ismail, N.; Iranmanesh, H.

2014-06-01

In previous decades, manufacturers faced a lot of challenges because of globalization and high competition in markets. These problems arise from shortening product life cycle, rapid variation in demand of products, and also rapid changes in manufcaturing technologies. Nowadays most manufacturing companies expend considerable attention for improving flexibility and responsiveness in order to overcome these kinds of problems and also meet customer's needs. By considering the trend toward the shorter product life cycle, the manufacturing environment is towards manufacturing a wide variety of parts in small batches [1]. One of the major techniques which are applied for improving manufacturing competitiveness is Cellular Manufacturing System (CMS). CMS is type of manufacturing system which tries to combine flexibility of job shop and also productivity of flow shop. In addition, Dynamic cellular manufacturing system which considers different time periods for the manufacturing system becomes an important topic and attracts a lot of attention to itself. Therefore, this paper made attempt to have a brief review on this issue and focused on all published paper on this subject. Although, this topic gains a lot of attention to itself during these years, none of previous researchers focused on reviewing the literature of that which can be helpful and useful for other researchers who intend to do the research on this topic. Therefore, this paper is the first study which has focused and reviewed the literature of dynamic cellular manufacturing system.

Finite Dimensional Approximations for Continuum Multiscale Problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berlyand, Leonid

2017-01-24

The completed research project concerns the development of novel computational techniques for modeling nonlinear multiscale physical and biological phenomena. Specifically, it addresses the theoretical development and applications of the homogenization theory (coarse graining) approach to calculation of the effective properties of highly heterogenous biological and bio-inspired materials with many spatial scales and nonlinear behavior. This theory studies properties of strongly heterogeneous media in problems arising in materials science, geoscience, biology, etc. Modeling of such media raises fundamental mathematical questions, primarily in partial differential equations (PDEs) and calculus of variations, the subject of the PI’s research. The focus of completed researchmore » was on mathematical models of biological and bio-inspired materials with the common theme of multiscale analysis and coarse grain computational techniques. Biological and bio-inspired materials offer the unique ability to create environmentally clean functional materials used for energy conversion and storage. These materials are intrinsically complex, with hierarchical organization occurring on many nested length and time scales. The potential to rationally design and tailor the properties of these materials for broad energy applications has been hampered by the lack of computational techniques, which are able to bridge from the molecular to the macroscopic scale. The project addressed the challenge of computational treatments of such complex materials by the development of a synergistic approach that combines innovative multiscale modeling/analysis techniques with high performance computing.« less

Multigrid solution strategies for adaptive meshing problems

NASA Technical Reports Server (NTRS)

Mavriplis, Dimitri J.

1995-01-01

This paper discusses the issues which arise when combining multigrid strategies with adaptive meshing techniques for solving steady-state problems on unstructured meshes. A basic strategy is described, and demonstrated by solving several inviscid and viscous flow cases. Potential inefficiencies in this basic strategy are exposed, and various alternate approaches are discussed, some of which are demonstrated with an example. Although each particular approach exhibits certain advantages, all methods have particular drawbacks, and the formulation of a completely optimal strategy is considered to be an open problem.

Using process groups to implement failure detection in asynchronous environments

NASA Technical Reports Server (NTRS)

Ricciardi, Aleta M.; Birman, Kenneth P.

1991-01-01

Agreement on the membership of a group of processes in a distributed system is a basic problem that arises in a wide range of applications. Such groups occur when a set of processes cooperate to perform some task, share memory, monitor one another, subdivide a computation, and so forth. The group membership problems is discussed as it relates to failure detection in asynchronous, distributed systems. A rigorous, formal specification for group membership is presented under this interpretation. A solution is then presented for this problem.

Compact scheme for systems of equations applied to fundamental problems of mechanics of continua

NASA Technical Reports Server (NTRS)

Klimkowski, Jerzy Z.

1990-01-01

Compact scheme formulation was used in the treatment of boundary conditions for a system of coupled diffusion and Poisson equations. Models and practical solutions of specific engineering problems arising in solid mechanics, chemical engineering, heat transfer and fuid mechanics are described and analyzed for efficiency and accuracy. Only 2-D cases are discussed and a new method of numerical treatment of boundary conditions common in the fundamental problems of mechanics of continua is presented.

Method of Reproduction of the Luminous Flux of the LED Light Sources by a Spherical Photometer

NASA Astrophysics Data System (ADS)

Huriev, M.; Neyezhmakov, P.

2018-02-01

In connection with transition to energy-efficient temporally stable light-emitting diodes (LEDs) lighting, a problem of ensuring the traceability of results of measurement of characteristics of light sources arises. The problem is related to existing measurement standards of luminous flux based on spherical photometers optimized for the reference incandescent lamps with a relative spectral characteristic different from the spectrum of the LEDs. We propose a method for reproduction of the luminous flux, which solves this problem.

Singularities of the quad curl problem

NASA Astrophysics Data System (ADS)

Nicaise, Serge

2018-04-01

We consider the quad curl problem in smooth and non smooth domains of the space. We first give an augmented variational formulation equivalent to the one from [25] if the datum is divergence free. We describe the singularities of the variational space which correspond to the ones of the Maxwell system with perfectly conducting boundary conditions. The edge and corner singularities of the solution of the corresponding boundary value problem with smooth data are also characterized. We finally obtain some regularity results of the variational solution.

Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

NASA Astrophysics Data System (ADS)

Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Aappelbe, B.; Chittenden, J.; Walsh, C.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Marshall, F.; Michel, T.; Stoeckl, C.; Sangster, T. C.; Zylstra, A.

2016-10-01

Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by engineering features (such as stalks, fill tubes, tents, or capsule imperfections) or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation we report on an OMEGA experiment with intentionally asymmetric drive, designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The results provide insight into the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

Laser induced fluorescence in nanosecond repetitively pulsed discharges for CO2 conversion

NASA Astrophysics Data System (ADS)

Martini, L. M.; Gatti, N.; Dilecce, G.; Scotoni, M.; Tosi, P.

2018-01-01

A CO2 nanosecond repetitively pulsed discharge (NRP) is a harsh environment for laser induced fluorescence (LIF) diagnostics. The difficulties arise from it being a strongly collisional system in which the gas composition, pressure and temperature, have quick and strong variations. The relevant diagnostic problems are described and illustrated through the application of LIF to the measurement of the OH radical in three different discharge configurations, with gas mixtures containing CO2 + H2O. These range from a dielectric barrier NRP with He buffer gas, a less hostile case in which absolute OH density measurement is possible, to an NRP in CO2+H2O, where the full set of drawbacks is at work. In the last case, the OH density measurement is not possible with laser pulses and detector time resolution in the ns time scale. Nevertheless, it is shown that with a proper knowledge of the collisional rate constants involved in the LIF process, a collisional energy transfer-LIF methodology is still applicable to deduce the gas composition from the analysis of LIF spectra.

Phase transitions in Pareto optimal complex networks

NASA Astrophysics Data System (ADS)

Seoane, Luís F.; Solé, Ricard

2015-09-01

The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.

Mapped grid methods for long-range molecules and cold collisions

NASA Astrophysics Data System (ADS)

Willner, K.; Dulieu, O.; Masnou-Seeuws, F.

2004-01-01

The paper discusses ways of improving the accuracy of numerical calculations for vibrational levels of diatomic molecules close to the dissociation limit or for ultracold collisions, in the framework of a grid representation. In order to avoid the implementation of very large grids, Kokoouline et al. [J. Chem. Phys. 110, 9865 (1999)] have proposed a mapping procedure through introduction of an adaptive coordinate x subjected to the variation of the local de Broglie wavelength as a function of the internuclear distance R. Some unphysical levels ("ghosts") then appear in the vibrational series computed via a mapped Fourier grid representation. In the present work the choice of the basis set is reexamined, and two alternative expansions are discussed: Sine functions and Hardy functions. It is shown that use of a basis set with fixed nodes at both grid ends is efficient to eliminate "ghost" solutions. It is further shown that the Hamiltonian matrix in the sine basis can be calculated very accurately by using an auxiliary basis of cosine functions, overcoming the problems arising from numerical calculation of the Jacobian J(x) of the R→x coordinate transformation.

Dynamics of a Nonlocal Dispersal Model with a Nonlocal Reaction Term

NASA Astrophysics Data System (ADS)

Ma, Li; Guo, Shangjiang; Chen, Ting

In this paper, we study a class of nonlocal dispersal problem with a nonlocal term arising in population dynamics: ut = 𝒟u + u λ ‑ f(u) ‑∫ΩK(x,y)g(u(y))dy,in Ω × (0, +∞), u(x, 0) = u0(x) ≥ 0, in Ω,u = 0, in ℝN\\Ω × (0, +∞), where Ω ⊂ ℝN (N ≥ 1) is a bounded domain, λ ∈ ℝ, 𝒟u(x,t) =∫ΩJ(x ‑ y)[u(y,t) ‑ u(x,t)]dy represents the nonlocal dispersal operator with continuous and non-negative dispersal kernel. The kernel K ∈ C(Ω¯ ×Ω¯) is assumed to be non-negative and is allowed to have a degeneracy in a smooth subdomain Ω0 of Ω. When K is either positive or vanishes in a subdomain, we respectively investigate the existence, multiplicity and asymptotical stability of positive steady states under the local/global variation of parameter by means of sub-supersolution method, Lyapunov-Schmidt reduction, and bifurcation theory.

High-Dimensional Heteroscedastic Regression with an Application to eQTL Data Analysis

PubMed Central

Daye, Z. John; Chen, Jinbo; Li, Hongzhe

2011-01-01

Summary We consider the problem of high-dimensional regression under non-constant error variances. Despite being a common phenomenon in biological applications, heteroscedasticity has, so far, been largely ignored in high-dimensional analysis of genomic data sets. We propose a new methodology that allows non-constant error variances for high-dimensional estimation and model selection. Our method incorporates heteroscedasticity by simultaneously modeling both the mean and variance components via a novel doubly regularized approach. Extensive Monte Carlo simulations indicate that our proposed procedure can result in better estimation and variable selection than existing methods when heteroscedasticity arises from the presence of predictors explaining error variances and outliers. Further, we demonstrate the presence of heteroscedasticity in and apply our method to an expression quantitative trait loci (eQTLs) study of 112 yeast segregants. The new procedure can automatically account for heteroscedasticity in identifying the eQTLs that are associated with gene expression variations and lead to smaller prediction errors. These results demonstrate the importance of considering heteroscedasticity in eQTL data analysis. PMID:22547833

Nationwide Benthic Macroinvertebrate Assemblage Multimetric Indices: Identifying Inconsistencies and Limitations in Reporting Stream Impairment Status, USA

NASA Astrophysics Data System (ADS)

Lau, J. K.; Lauer, T. E.

2015-07-01

The objective of this study was to identify the current status of stream water-quality assessment and reporting methods for four states in the Ohio River basin (Indiana, Ohio, Tennessee, and Virginia), as required by the 305(b) section of the United States (US) Clean Water Act. Specifically, we clarified the discrepancies that exist among stream-impairment status classified by benthic macroinvertebrate multimetric indices (MMIs) and depicted using Geographic Information Systems shapefiles. In addition, we provided guidance in solving some of the comparability problems that arise when developing state-specific MMIs and depicting stream-impairment status using Geographic Information Systems technology. The MMI variation among states and differences in shapefile formats resulted in a nationwide dataset, which cannot be directly compared. Incorporating the changes suggested in this study allow for a uniform assessment and reporting method nationwide. Successful implementation of these changes would strengthen the US Environmental Protection Agency efforts to identify impaired streams and sources of those impairments without the limitations of state-by-state .developed assessment methods.

Interpretations of cigarette advertisement warning labels by Philadelphia Puerto Ricans.

PubMed

Morris, Nancy; Gilpin, Dawn R; Lenos, Melissa; Hobbs, Renee

2011-09-01

This study examined Philadelphia Puerto Ricans' interpretations of the Surgeon General's warnings that appear on cigarette packaging and in advertisements. In-home family focus groups in which participants were asked to comment on magazine cigarette advertisements showed a great variety of interpretations of the legally mandated warning labels. These findings (a) corroborate and add to research in public health and communications regarding the possibility of wide variations in message interpretations and (b) support the call for public health messages to be carefully tested for effectiveness among different social groups. The article's focus on Puerto Ricans addresses the problem of misleading conclusions that can arise from aggregating all Latino subpopulations into one group. The use of a naturalistic setting to examine interpretations of messages about smoking departs from the experimental methods typically used for such research and provides new evidence that even a seemingly straightforward message can be interpreted in multiple ways. Understanding and addressing differences in message interpretation can guide public health campaigns aimed at reducing health disparities. Copyright © Taylor & Francis Group, LLC

On Flexible Tubes Conveying Fluid: Geometric Nonlinear Theory, Stability and Dynamics

NASA Astrophysics Data System (ADS)

Gay-Balmaz, François; Putkaradze, Vakhtang

2015-08-01

We derive a fully three-dimensional, geometrically exact theory for flexible tubes conveying fluid. The theory also incorporates the change of the cross section available to the fluid motion during the dynamics. Our approach is based on the symmetry-reduced, exact geometric description for elastic rods, coupled with the fluid transport and subject to the volume conservation constraint for the fluid. We first derive the equations of motion directly, by using an Euler-Poincaré variational principle. We then justify this derivation with a more general theory elucidating the interesting mathematical concepts appearing in this problem, such as partial left (elastic) and right (fluid) invariance of the system, with the added holonomic constraint (volume). We analyze the fully nonlinear behavior of the model when the axis of the tube remains straight. We then proceed to the linear stability analysis and show that our theory introduces important corrections to previously derived results, both in the consistency at all wavelength and in the effects arising from the dynamical change of the cross section. Finally, we derive and analyze several analytical, fully nonlinear solutions of traveling wave type in two dimensions.

Viscous Moment, Mechanism of Slow Slip, and Subduction Megathrust Viscosity

NASA Astrophysics Data System (ADS)

Fagereng, A.

2015-12-01

Slow slip events (SSEs) represent transient slip velocities slower than earthquakes but faster than steady, average plate motion. SSEs repeating at the same location have characteristic slip magnitude and duration. Contrary to earthquakes, however, average slip relates to neither duration nor area. Variations in duration, slip, and slip rate can instead be tied to variations in effective viscosity, calculated from a viscous definition of moment. In this paradigm, the observation that deep slow slip events are slower and longer, implies a higher effective viscosity than in shallower, colder SSEs. Observed variations in effective viscosity and slip rate can be interpreted in terms of differences in driving stress and shear zone width, and likely arise in anastomosing shear zones containing a heterogeneous mixture of materials.

Ethnic Variation in Depressive Symptoms in a Community Sample in Hawai‘i

PubMed Central

Kanazawa, Asako; White, Patricia M.; Hampson, Sarah E.

2008-01-01

A modified CES-D was administered to a community sample of 176 European Americans (EA), 209 Native Hawaiians (NH), and 357 Japanese Americans (JA), yielding measures of depression, positive affect, depressed affect, somatic disturbance and disturbed interpersonal relations. Positive affect was lower in JA relative to EA, consistent with findings among Native Japanese, a pattern attributed to cultural variation in emotion regulation. NH reported lower positive affect than EA, accompanied by elevated negative affect and somatic disturbance, suggesting generally higher levels of depressive symptoms. The three ethnic groups varied in mental healthcare usage with differing associations between depressive symptoms and experiences of stressful life events. Taken together, these results suggest ethnic variation in depressive symptoms may arise from differing cultural beliefs. PMID:17227175

Spectral Structure of Temperature Variations in the Midlatitude Mesopause Region

NASA Astrophysics Data System (ADS)

Perminov, V. I.; Semenov, A. I.; Medvedeva, I. V.; Pertsev, N. N.; Sukhodoev, V. A.

2018-01-01

Long-term series of midnight temperature in the mesopause region have been obtained from spectral observations of hydroxyl airglow emission (OH(6-2) λ840 nm band) at the Tory station (52° N, 103° E) in 2008-2016 and Zvenigorod (56° N, 37° E) station in 2000-2016. On their basis, the Lomb-Scargle spectra of the variations in the period range from 12 days to 11 years have been determined. Estimates of the amplitudes of statistically significant temperature fluctuations are made. The dominant oscillations are the first and second harmonics of the annual variation, the amplitudes of which are 23-24 K and 4-7 K, respectively. The remaining variations, the number of which was 16 for the Tory and 22 for Zvenigorod stations, have small amplitudes (0.5-3 K). Oscillations with combinational frequencies, which arise from modulation of the annual variation harmonics, are observed in a structure of the variation spectra in addition to interannual oscillations (periods from 2 to 11 years) and harmonics of the annual variation (up to its tenth harmonic).

Abstract generalized vector quasi-equilibrium problems in noncompact Hadamard manifolds.

PubMed

Lu, Haishu; Wang, Zhihua

2017-01-01

This paper deals with the abstract generalized vector quasi-equilibrium problem in noncompact Hadamard manifolds. We prove the existence of solutions to the abstract generalized vector quasi-equilibrium problem under suitable conditions and provide applications to an abstract vector quasi-equilibrium problem, a generalized scalar equilibrium problem, a scalar equilibrium problem, and a perturbed saddle point problem. Finally, as an application of the existence of solutions to the generalized scalar equilibrium problem, we obtain a weakly mixed variational inequality and two mixed variational inequalities. The results presented in this paper unify and generalize many known results in the literature.

An Artificial Neural Network Controller for Intelligent Transportation Systems Applications

DOT National Transportation Integrated Search

1996-01-01

An Autonomous Intelligent Cruise Control (AICC) has been designed using a feedforward artificial neural network, as an example for utilizing artificial neural networks for nonlinear control problems arising in intelligent transportation systems appli...

Humane Ethics in Veterinary Education

ERIC Educational Resources Information Center

Fox, M. W.

1978-01-01

This discussion focuses on the problem faced by biomedical students who are learning objective, factual information and techniques without being given the opportunity to consider the many ethical dilemmas and moral questions that will arise after graduation. (LBH)

Reflections on psychoanalytic treatment of Lubavitch Chassidim couples: working with a culturally divergent population.

PubMed

Schulman, Martin A; Kaplan, Ricki S

2014-08-01

Chassidic Jews create separate developmental lines for males and females beginning at three years of age. Since early marriages are encouraged and there is minimal contact between the sexes prior to marriage, problems inevitably arise in relationships. This article discusses both newlywed and long-term married Lubavitch Chassidim in couples treatment with secular analysts, parameters necessary for successful treatment, and countertransferences that arise. It is part of an ongoing series of publications based on the authors' decade-long psychoanalytic work with this population.

New challenges of the ARISE project

NASA Astrophysics Data System (ADS)

Blanc, Elisabeth

2015-04-01

It has been robustly demonstrated that variations in the circulation of the middle atmosphere influence weather and climate throughout the troposphere all the way to the Earth's surface. A key part of the coupling between the troposphere and stratosphere occurs through the propagation and breaking of planetary-scale Rossby waves and gravity waves. Limited observation of the middle atmosphere and these waves in particular limits the ability to faithfully reproduce the dynamics of the middle atmosphere in numerical weather prediction and climate models. The ARISE project combines for the first time international networks with complementary technologies such as infrasound, lidar and airglow. This joint network provided advanced data products that started to be used as benchmarks for weather forecast models. The ARISE network also allows enhanced and detailed monitoring of other extreme events in the Earth system such as erupting volcanoes, magnetic storms, tornadoes and tropical thunderstorms. In order to improve the ability of the network to monitor atmospheric dynamics, ARISE proposes to extend i) the existing network coverage in Africa and the high latitudes, ii) the altitude range in the stratosphere and mesosphere, iii) the observation duration using routine observation modes, and to use complementary existing infrastructures and innovative instrumentations. Data will be collected over the long term to improve weather forecasting to monthly or seasonal timescales, to monitor atmospheric extreme events and climate change. ARISE focuses on the link between models and observations for future assimilation of data by operational weather forecasting models. Among the applications, ARISE2 proposes infrasound remote volcano monitoring to provide notifications to civil aviation.

Racial/ethnic differences in perceived reasons for mental health treatment in US adolescents with major depression.

PubMed

Cummings, Janet R; Case, Brady G; Ji, Xu; Chae, David H; Druss, Benjamin G

2014-09-01

Racial/ethnic differences in the course of treatment for a major depressive episode (MDE) among adolescents may arise, in part, from variation in the perceived rationale for treatment. We examined racial/ethnic differences in the perceived reasons for receiving mental health (MH) treatment among adolescents with an MDE. A total of 2,789 adolescent participants who experienced an MDE and received MH treatment in the past year were drawn from the 2005 to 2008 National Survey on Drug Use and Health. Adolescents reported the settings in which they received care and reasons for their most recent visit to each setting. Distributions of specific depressive symptoms were compared across racial/ethnic groups. Racial/ethnic differences in endorsing each of 11 possible reasons for receiving treatment were examined using weighted probit regressions adjusted for sociodemographic characteristics, health and mental health status, treatment setting, and survey year. Despite similar depressive symptom profiles, Hispanic adolescents were more likely than whites to endorse "breaking rules" or getting into physical fights as reasons for MH treatment. Black adolescents were more likely than white adolescents to endorse "problems at school" but less likely to endorse "felt very afraid or tense" or "eating problems" as reasons for treatment. Asian adolescents were more likely to endorse "problems with people other than friends or family" but less likely than whites to endorse "suicidal thoughts/attempt" and "felt depressed" as reasons for treatment. Racial/ethnic minority participants were more likely than white participants to endorse externalizing or interpersonal problems and less likely to endorse internalizing problems as reasons for MH treatment. Understanding racial/ethnic differences in the patient's perceived treatment rationale can offer opportunities to enhance outcomes for depression among diverse populations. Copyright © 2014 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

Interest Subsidies on Student Loans: A Better Class of Drain. CEE DP 114

ERIC Educational Resources Information Center

Barr, Nicholas; Johnston, Alison

2010-01-01

The British system of student loans has a zero real rate of interest, less than it costs the government to borrow the money. This paper discusses the problems that arise from interest subsidies in the UK system of student loans; systems in other countries, for example Australia and New Zealand, face similar problems. The topic appears to be narrow…

Two Problems with Table Saws

ERIC Educational Resources Information Center

Vautaw, William R.

2008-01-01

We solve two problems that arise when constructing picture frames using only a table saw. First, to cut a cove running the length of a board (given the width of the cove and the angle the cove makes with the face of the board) we calculate the height of the blade and the angle the board should be turned as it is passed over the blade. Second, to…

Elucidation of Heterogeneous Processes Controlling Boost Phase Signatures

DTIC Science & Technology

1990-09-12

three year research program to develop efficient theoretical methods to study collisional processes involved in radiative signature modeling . The...Marlboro, MD 20772 I. Statement of Problem For strategic defense, it is important to be able to effectively model radiative signaturesl arising from...Thus our computational work was on problems or models for which exact results for making comparisons were available. Our key validations were

Effect of refining variables on the properties and composition of JP-5

NASA Technical Reports Server (NTRS)

Lieberman, M.; Taylor, W. F.

1980-01-01

Potential future problem areas that could arise from changes in the composition, properties, and potential availability of JP-5 produced in the near future are identified. Potential fuel problems concerning thermal stability, lubricity, low temperature flow, combustion, and the effect of the use of specific additives on fuel properties and performance are discussed. An assessment of available crudes and refinery capabilities is given.

The forest ecosystem of southeast Alaska: 6. Forest diseases.

Treesearch

Thomas H. Laurent

1974-01-01

The disease problems of old growth are largely being taken care of by cutting. This same cutting is rapidly converting large areas of old growth to reproduction and young growth. It is in these areas of young growth that our disease problems will most probably arise. With a few exceptions the reproduction and young-growth stands appear quite healthy at this time with...

Compressed modes for variational problems in mathematics and physics

PubMed Central

Ozoliņš, Vidvuds; Lai, Rongjie; Caflisch, Russel; Osher, Stanley

2013-01-01

This article describes a general formalism for obtaining spatially localized (“sparse”) solutions to a class of problems in mathematical physics, which can be recast as variational optimization problems, such as the important case of Schrödinger’s equation in quantum mechanics. Sparsity is achieved by adding an regularization term to the variational principle, which is shown to yield solutions with compact support (“compressed modes”). Linear combinations of these modes approximate the eigenvalue spectrum and eigenfunctions in a systematically improvable manner, and the localization properties of compressed modes make them an attractive choice for use with efficient numerical algorithms that scale linearly with the problem size. PMID:24170861

Compressed modes for variational problems in mathematics and physics.

PubMed

Ozolins, Vidvuds; Lai, Rongjie; Caflisch, Russel; Osher, Stanley

2013-11-12

This article describes a general formalism for obtaining spatially localized ("sparse") solutions to a class of problems in mathematical physics, which can be recast as variational optimization problems, such as the important case of Schrödinger's equation in quantum mechanics. Sparsity is achieved by adding an regularization term to the variational principle, which is shown to yield solutions with compact support ("compressed modes"). Linear combinations of these modes approximate the eigenvalue spectrum and eigenfunctions in a systematically improvable manner, and the localization properties of compressed modes make them an attractive choice for use with efficient numerical algorithms that scale linearly with the problem size.

Investigating the Conceptual Variation of Major Physics Textbooks

NASA Astrophysics Data System (ADS)

Stewart, John; Campbell, Richard; Clanton, Jessica

2008-04-01

The conceptual problem content of the electricity and magnetism chapters of seven major physics textbooks was investigated. The textbooks presented a total of 1600 conceptual electricity and magnetism problems. The solution to each problem was decomposed into its fundamental reasoning steps. These fundamental steps are, then, used to quantify the distribution of conceptual content among the set of topics common to the texts. The variation of the distribution of conceptual coverage within each text is studied. The variation between the major groupings of the textbooks (conceptual, algebra-based, and calculus-based) is also studied. A measure of the conceptual complexity of the problems in each text is presented.

A numerical solution of a singular boundary value problem arising in boundary layer theory.

PubMed

Hu, Jiancheng

2016-01-01

In this paper, a second-order nonlinear singular boundary value problem is presented, which is equivalent to the well-known Falkner-Skan equation. And the one-dimensional third-order boundary value problem on interval [Formula: see text] is equivalently transformed into a second-order boundary value problem on finite interval [Formula: see text]. The finite difference method is utilized to solve the singular boundary value problem, in which the amount of computational effort is significantly less than the other numerical methods. The numerical solutions obtained by the finite difference method are in agreement with those obtained by previous authors.

Crack problems involving nonhomogeneous interfacial regions in bonded materials

NASA Technical Reports Server (NTRS)

Erdogan, F.

1990-01-01

Consideration is given to two classes of fracture-related solid mechanics problems in which the model leads to some physically anomalous results. The first is the interface crack problem associated with the debonding process in which the corresponding elasticity solution predicts severe oscillations of stresses and the crack surface displacements vary near the crack tip. The second deals with crack intersecting the interface. The nature of the solutions around the crack tips arising from these problems is reviewed. The rationale for introducing a new interfacial zone model is discussed, its analytical consequences within the context of the two crack-problem classes are described, and some examples are presented.

Perspective Imagery in Synthetic Scenes used to Control and Guide Aircraft during Landing and Taxi: Some Issues and Concerns

NASA Technical Reports Server (NTRS)

Johnson, Walter W.; Kaiser, Mary K.

2003-01-01

Perspective synthetic displays that supplement, or supplant, the optical windows traditionally used for guidance and control of aircraft are accompanied by potentially significant human factors problems related to the optical geometric conformality of the display. Such geometric conformality is broken when optical features are not in the location they would be if directly viewed through a window. This often occurs when the scene is relayed or generated from a location different from the pilot s eyepoint. However, assuming no large visual/vestibular effects, a pilot cad often learn to use such a display very effectively. Important problems may arise, however, when display accuracy or consistency is compromised, and this can usually be related to geometrical discrepancies between how the synthetic visual scene behaves and how the visual scene through a window behaves. In addition to these issues, this paper examines the potentially critical problem of the disorientation that can arise when both a synthetic display and a real window are present in a flight deck, and no consistent visual interpretation is available.

Finite element analysis of time-independent superconductivity. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Schuler, James J.

1993-01-01

The development of electromagnetic (EM) finite elements based upon a generalized four-potential variational principle is presented. The use of the four-potential variational principle allows for downstream coupling of EM fields with the thermal, mechanical, and quantum effects exhibited by superconducting materials. The use of variational methods to model an EM system allows for a greater range of applications than just the superconducting problem. The four-potential variational principle can be used to solve a broader range of EM problems than any of the currently available formulations. It also reduces the number of independent variables from six to four while easily dealing with conductor/insulator interfaces. This methodology was applied to a range of EM field problems. Results from all these problems predict EM quantities exceptionally well and are consistent with the expected physical behavior.

Age-related changes in strategic variations during arithmetic problem solving: The role of executive control.

PubMed

Hinault, T; Lemaire, P

2016-01-01

In this review, we provide an overview of how age-related changes in executive control influence aging effects in arithmetic processing. More specifically, we consider the role of executive control in strategic variations with age during arithmetic problem solving. Previous studies found that age-related differences in arithmetic performance are associated with strategic variations. That is, when they accomplish arithmetic problem-solving tasks, older adults use fewer strategies than young adults, use strategies in different proportions, and select and execute strategies less efficiently. Here, we review recent evidence, suggesting that age-related changes in inhibition, cognitive flexibility, and working memory processes underlie age-related changes in strategic variations during arithmetic problem solving. We discuss both behavioral and neural mechanisms underlying age-related changes in these executive control processes. © 2016 Elsevier B.V. All rights reserved.

MPT Prediction of Aircraft-Engine Fan Noise

NASA Technical Reports Server (NTRS)

Connell, Stuart D.

2004-01-01

A collection of computer programs has been developed that implements a procedure for predicting multiple-pure-tone (MPT) noise generated by fan blades of an aircraft engine (e.g., a turbofan engine). MPT noise arises when the fan is operating with supersonic relative tip Mach No. Under this flow condition, there is a strong upstream running shock. The strength and position of this shock are very sensitive to blade geometry variations. For a fan where all the blades are identical, the primary tone observed upstream of the fan will be the blade passing frequency. If there are small variations in geometry between blades, then tones below the blade passing frequency arise MPTs. Stagger angle differences as small as 0.1 can give rise to significant MPT. It is also noted that MPT noise is more pronounced when the fan is operating in an unstarted mode. Computational results using a three-dimensional flow solver to compute the complete annulus flow with non-uniform fans indicate that MPT noise can be estimated in a relatively simple way. Hence, once the effect of a typical geometry variation of one blade in an otherwise uniform blade row is known, the effect of all the blades being different can be quickly computed via superposition. Two computer programs that were developed as part of this work are used in conjunction with a user s computational fluid dynamics (CFD) code to predict MPT spectra for a fan with a specified set of geometric variations: (1) The first program ROTBLD reads the users CFD solution files for a single blade passage via an API (Application Program Interface). There are options to replicate and perturb the geometry with typical variations stagger, camber, thickness, and pitch. The multi-passage CFD solution files are then written in the user s file format using the API. (2) The second program SUPERPOSE requires two input files: the first is the circumferential upstream pressure distribution extracted from the CFD solution on the multi-passage mesh, the second file defines the geometry variations of each blade in a complete fan. Superposition is used to predict the spectra resulting from the geometric variations.

Solving multi-leader-common-follower games.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leyffer, S.; Munson, T.; Mathematics and Computer Science

Multi-leader-common-follower games arise when modelling two or more competitive firms, the leaders, that commit to their decisions prior to another group of competitive firms, the followers, that react to the decisions made by the leaders. These problems lead in a natural way to equilibrium problems with equilibrium constraints (EPECs). We develop a characterization of the solution sets for these problems and examine a variety of nonlinear optimization and nonlinear complementarity formulations of EPECs. We distinguish two broad cases: problems where the leaders can cost-differentiate and problems with price-consistent followers. We demonstrate the practical viability of our approach by solving amore » range of medium-sized test problems.« less

Overview of Krylov subspace methods with applications to control problems

NASA Technical Reports Server (NTRS)

Saad, Youcef

1989-01-01

An overview of projection methods based on Krylov subspaces are given with emphasis on their application to solving matrix equations that arise in control problems. The main idea of Krylov subspace methods is to generate a basis of the Krylov subspace Span and seek an approximate solution the the original problem from this subspace. Thus, the original matrix problem of size N is approximated by one of dimension m typically much smaller than N. Krylov subspace methods have been very successful in solving linear systems and eigenvalue problems and are now just becoming popular for solving nonlinear equations. It is shown how they can be used to solve partial pole placement problems, Sylvester's equation, and Lyapunov's equation.

About some types of constraints in problems of routing

NASA Astrophysics Data System (ADS)

Petunin, A. A.; Polishuk, E. G.; Chentsov, A. G.; Chentsov, P. A.; Ukolov, S. S.

2016-12-01

Many routing problems arising in different applications can be interpreted as a discrete optimization problem with additional constraints. The latter include generalized travelling salesman problem (GTSP), to which task of tool routing for CNC thermal cutting machines is sometimes reduced. Technological requirements bound to thermal fields distribution during cutting process are of great importance when developing algorithms for this task solution. These requirements give rise to some specific constraints for GTSP. This paper provides a mathematical formulation for the problem of thermal fields calculating during metal sheet thermal cutting. Corresponding algorithm with its programmatic implementation is considered. The mathematical model allowing taking such constraints into account considering other routing problems is discussed either.

A modified two-layer iteration via a boundary point approach to generalized multivalued pseudomonotone mixed variational inequalities.

PubMed

Saddeek, Ali Mohamed

2017-01-01

Most mathematical models arising in stationary filtration processes as well as in the theory of soft shells can be described by single-valued or generalized multivalued pseudomonotone mixed variational inequalities with proper convex nondifferentiable functionals. Therefore, for finding the minimum norm solution of such inequalities, the current paper attempts to introduce a modified two-layer iteration via a boundary point approach and to prove its strong convergence. The results here improve and extend the corresponding recent results announced by Badriev, Zadvornov and Saddeek (Differ. Equ. 37:934-942, 2001).

The Cauchy problem for the Pavlov equation

NASA Astrophysics Data System (ADS)

Grinevich, P. G.; Santini, P. M.; Wu, D.

2015-10-01

Commutation of multidimensional vector fields leads to integrable nonlinear dispersionless PDEs that arise in various problems of mathematical physics and have been intensively studied in recent literature. This report aims to solve the scattering and inverse scattering problem for integrable dispersionless PDEs, recently introduced just at a formal level, concentrating on the prototypical example of the Pavlov equation, and to justify an existence theorem for global bounded solutions of the associated Cauchy problem with small data. An essential part of this work was made during the visit of the three authors to the Centro Internacional de Ciencias in Cuernavaca, Mexico in November-December 2012.

Decentralized control

NASA Technical Reports Server (NTRS)

Steffen, Chris

1990-01-01

An overview of the time-delay problem and the reliability problem which arise in trying to perform robotic construction operations at a remote space location are presented. The effects of the time-delay upon the control system design will be itemized. A high level overview of a decentralized method of control which is expected to perform better than the centralized approach in solving the time-delay problem is given. The lower level, decentralized, autonomous, Troter Move-Bar algorithm is also presented (Troters are coordinated independent robots). The solution of the reliability problem is connected to adding redundancy to the system. One method of adding redundancy is given.

Photovoltaic module hot spot durability design and test methods

NASA Technical Reports Server (NTRS)

Arnett, J. C.; Gonzalez, C. C.

1981-01-01

As part of the Jet Propulsion Laboratory's Low-Cost Solar Array Project, the susceptibility of fat-plate modules to hot-spot problems is investigated. Hot-spot problems arise in modules when the cells become back-biased and operate in the negative-voltage quadrant, as a result of short-circuit current mismatch, cell cracking or shadowing. The details of a qualification test for determining the capability of modules of surviving field hot-spot problems and typical results of this test are presented. In addition, recommended circuit-design techniques for improving the module and array reliability with respect to hot-spot problems are presented.

Papa Pig Just Left for Pigtown: Children's Oral and Written Picture Descriptions under Varying Instructions.

ERIC Educational Resources Information Center

De Temple, Jeanne M.; And Others

1991-01-01

Investigates the extent of variation in children's language performance in a picture description task arising from mode (oral or written) versus degree of demand for decontextualization. Finds that children manipulated the wide range of the oral form of the contextualized/decontextualized continuum more skillfully than the written form. Finds no…

A Mathematical Model of the Evolution of Individual Differences in Developmental Plasticity Arising through Parental Bet-Hedging

ERIC Educational Resources Information Center

Frankenhuis, Willem E.; Panchanathan, Karthik; Belsky, Jay

2016-01-01

Children vary in the extent to which their development is shaped by particular experiences (e.g. maltreatment, social support). This variation raises a question: Is there no single level of plasticity that maximizes biological fitness? One influential hypothesis states that when different levels of plasticity are optimal in different environmental…

Global variability in leaf respiration in relation to climate, plant functional types and leaf traits

Treesearch

Owen K. Atkin; Keith J. Bloomfield; Peter B. Reich; Mark G. Tjoelker; Gregory P. Asner; Damien Bonal; Gerhard Bonisch; Matt G. Bradford; Lucas A. Cernusak; Eric G. Cosio; Danielle Creek; Kristine Y. Crous; Tomas F. Domingues; Jeffrey S. Dukes; John J. G. Egerton; John R. Evans; Graham D. Farquhar; Nikolaos M. Fyllas; Paul P. G. Gauthier; Emanuel Gloor; Teresa E. Gimeno; Kevin L. Griffin; Rossella Guerrieri; Mary A. Heskel; Chris Huntingford; Franc_oise Yoko Ishida; Jens Kattge; Hans Lambers; Michael J. Liddell; Jon Lloyd; Christopher H. Lusk; Roberta E. Martin; Ayal P. Maksimov; Trofim C. Maximov; Yadvinder Malhi; Belinda E. Medlyn; Patrick Meir; Lina M. Mercado; Nicholas Mirotchnick; Desmond Ng; Ulo Niinemets; Odhran S. O’Sullivan; Oliver L. Phillips; Lourens Poorter; Pieter Poot; I. Colin Prentice; Norma Salinas; Lucy M. Rowland; Michael G. Ryan; Stephen Sitch; Martijn Slot; Nicholas G. Smith; Matthew H. Turnbull; Mark C. VanderWel; Fernando Valladares; Erik J. Veneklaas; Lasantha K. Weerasinghe; Christian Wirth; Ian J. Wright; Kirk R. Wythers; Jen Xiang; Shuang Xiang; Joana Zaragoza-Castells

2015-01-01

A challenge for the development of terrestrial biosphere models (TBMs) and associated land surface components of Earth system models (ESMs) is improving representation of carbon (C) exchange between terrestrial plants and the atmosphere, and incorporating biological variation arising from diversity in plant functional types (PFTs) and climate (Sitch et al.,...

An Empirical Investigation of Occupational Choice and Human Capital Accumulation at Mid-Life

ERIC Educational Resources Information Center

Xue, Yu

2010-01-01

Individual variation in labor supply can arise from more than just a choice among discrete occupation groups, especially given the joint process of wage determination and time allocation. Other factors can include differential preferences for earnings, the time length of work and other related occupational attributes. Using data from the Wisconsin…

78 FR 16341 - Self-Regulatory Organizations; Financial Industry Regulatory Authority, Inc.; Notice of Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-14

... regulatory regime applicable to the over-the-counter derivatives markets. Title VII provides the SEC and the CFTC with tools to oversee these markets.\\4\\ Under the comprehensive framework established in Title VII... Rule),\\11\\ arising from the daily mark to market of the CDS (``variation margin''). FINRA notes that...

The EEOC's New Equal Pay Act Guidelines.

ERIC Educational Resources Information Center

Greenlaw, Paul S.; Kohl, John P.

1982-01-01

Analyzes the new guidelines for enforcement of the Equal Pay Act and their implications for personnel management. Argues that there are key problem areas in the new regulations arising from considerable ambiguity and uncertainty about their interpretation. (SK)

Remain in Your Seats: Crisis Management for the Alumni Travel Director.

ERIC Educational Resources Information Center

Bonenberger, Lynne M.

1991-01-01

Three alumni travel directors offer advice on taking control when tour crises arise. The cases cited involved irresponsible tour agents, problem travelers, and on-location disasters. Both precautions and creative solutions are emphasized. (MSE)

The case of the missing third.

PubMed

Robertson, Robin

2005-01-01

How is it that form arises out of chaos? In attempting to deal with this primary question, time and again a "Missing Third" is posited that lies between extremes. The problem of the "Missing Third" can be traced through nearly the entire history of thought. The form it takes, the problems that arise from it, the solutions suggested for resolving it, are each representative of an age. This paper traces the issue from Plato and Parmenides in the 4th--5th centuries, B.C.; to Neoplatonism in the 3rd--5th centuries; to Locke and Descartes in the 17th century; on to Berkeley and Kant in the 18th century; Fechner and Wundt in the 19th century; to behaviorism and Gestalt psychology, Jung, early in the 20th century, ethology and cybernetics later in the 20th century, then culminates late in the 20th century, with chaos theory.

Is CT angiography of the pulmonary arteries indicated in patients with high clinical probability of pulmonary embolism?

PubMed

Martínez Montesinos, L; Plasencia Martínez, J M; García Santos, J M

When a diagnostic test confirms clinical suspicion, the indicated treatment can be administered. A problem arises when the diagnostic test does not confirm the initially suspected diagnosis; when the suspicion is grounded in clinically validated predictive rules and is high, the problem is even worse. This situation arises in up to 40% of patients with high suspicion for acute pulmonary embolism, raising the question of whether CT angiography of the pulmonary arteries should be done systematically. This paper reviews the literature about this issue and lays out the best evidence about the relevant recommendations for patients with high clinical suspicion of acute pulmonary embolism and negative findings on CT angiography. It also explains the probabilistic concepts derived from Bayes' theorem that can be useful for ascertaining the most appropriate approach in these patients. Copyright © 2017 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

Relative locality and the soccer ball problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amelino-Camelia, Giovanni; Freidel, Laurent; Smolin, Lee

We consider the behavior of macroscopic bodies within the framework of relative locality [G. Amelino-Camelia, L. Freidel, J. Kowalski-Glikman, and L. Smolin, arXiv:1101.0931]. This is a recent proposal for Planck scale modifications of the relativistic dynamics of particles which are described as arising from deformations in the geometry of momentum space. We consider and resolve a common objection against such proposals, which is that, even if the corrections are small for elementary particles in current experiments, they are huge when applied to composite systems such as soccer balls, planets, and stars, with energies E{sub macro} much larger than M{sub P}.more » We show that this soccer ball problem does not arise within the framework of relative locality because the nonlinear effects for the dynamics of a composite system with N elementary particles appear at most of order E{sub macro}/N{center_dot}M{sub P}.« less

Survival probability of diffusion with trapping in cellular neurobiology

NASA Astrophysics Data System (ADS)

Holcman, David; Marchewka, Avi; Schuss, Zeev

2005-09-01

The problem of diffusion with absorption and trapping sites arises in the theory of molecular signaling inside and on the membranes of biological cells. In particular, this problem arises in the case of spine-dendrite communication, where the number of calcium ions, modeled as random particles, is regulated across the spine microstructure by pumps, which play the role of killing sites, while the end of the dendritic shaft is an absorbing boundary. We develop a general mathematical framework for diffusion in the presence of absorption and killing sites and apply it to the computation of the time-dependent survival probability of ions. We also compute the ratio of the number of absorbed particles at a specific location to the number of killed particles. We show that the ratio depends on the distribution of killing sites. The biological consequence is that the position of the pumps regulates the fraction of calcium ions that reach the dendrite.

Gelfand-type problem for two-phase porous media

PubMed Central

Gordon, Peter V.; Moroz, Vitaly

2014-01-01

We consider a generalization of the Gelfand problem arising in Frank-Kamenetskii theory of thermal explosion. This generalization is a natural extension of the Gelfand problem to two-phase materials, where, in contrast to the classical Gelfand problem which uses a single temperature approach, the state of the system is described by two different temperatures. We show that similar to the classical Gelfand problem the thermal explosion occurs exclusively owing to the absence of stationary temperature distribution. We also show that the presence of interphase heat exchange delays a thermal explosion. Moreover, we prove that in the limit of infinite heat exchange between phases the problem of thermal explosion in two-phase porous media reduces to the classical Gelfand problem with renormalized constants. PMID:24611025

Hamilton's Principle and Approximate Solutions to Problems in Classical Mechanics

ERIC Educational Resources Information Center

Schlitt, D. W.

1977-01-01

Shows how to use the Ritz method for obtaining approximate solutions to problems expressed in variational form directly from the variational equation. Application of this method to classical mechanics is given. (MLH)

Variational Problems with Long-Range Interaction

NASA Astrophysics Data System (ADS)

Soave, Nicola; Tavares, Hugo; Terracini, Susanna; Zilio, Alessandro

2018-06-01

We consider a class of variational problems for densities that repel each other at a distance. Typical examples are given by the Dirichlet functional and the Rayleigh functional D(u) = \\sum_{i=1}^k \\int_{Ω} |\

The Pattern of Complaints about Australian Wind Farms Does Not Match the Establishment and Distribution of Turbines: Support for the Psychogenic, ‘Communicated Disease’ Hypothesis

PubMed Central

Chapman, Simon; St. George, Alexis; Waller, Karen; Cakic, Vince

2013-01-01

Background and Objectives With often florid allegations about health problems arising from wind turbine exposure now widespread, nocebo effects potentially confound any future investigation of turbine health impact. Historical audits of health complaints are therefore important. We test 4 hypotheses relevant to psychogenic explanations of the variable timing and distribution of health and noise complaints about wind farms in Australia. Setting All Australian wind farms (51 with 1634 turbines) operating 1993–2012. Methods Records of complaints about noise or health from residents living near 51 Australian wind farms were obtained from all wind farm companies, and corroborated with complaints in submissions to 3 government public enquiries and news media records and court affidavits. These are expressed as proportions of estimated populations residing within 5 km of wind farms. Results There are large historical and geographical variations in wind farm complaints. 33/51 (64.7%) of Australian wind farms including 18/34 (52.9%) with turbine size >1 MW have never been subject to noise or health complaints. These 33 farms have an estimated 21,633 residents within 5 km and have operated complaint-free for a cumulative 267 years. Western Australia and Tasmania have seen no complaints. 129 individuals across Australia (1 in 254 residents) appear to have ever complained, with 94 (73%) being residents near 6 wind farms targeted by anti wind farm groups. The large majority 116/129(90%) of complainants made their first complaint after 2009 when anti wind farm groups began to add health concerns to their wider opposition. In the preceding years, health or noise complaints were rare despite large and small-turbine wind farms having operated for many years. Conclusions The reported historical and geographical variations in complaints are consistent with psychogenic hypotheses that expressed health problems are “communicated diseases” with nocebo effects likely to play an important role in the aetiology of complaints. PMID:24146893

The pattern of complaints about Australian wind farms does not match the establishment and distribution of turbines: support for the psychogenic, 'communicated disease' hypothesis.

PubMed

Chapman, Simon; St George, Alexis; Waller, Karen; Cakic, Vince

2013-01-01

With often florid allegations about health problems arising from wind turbine exposure now widespread, nocebo effects potentially confound any future investigation of turbine health impact. Historical audits of health complaints are therefore important. We test 4 hypotheses relevant to psychogenic explanations of the variable timing and distribution of health and noise complaints about wind farms in Australia. All Australian wind farms (51 with 1634 turbines) operating 1993-2012. Records of complaints about noise or health from residents living near 51 Australian wind farms were obtained from all wind farm companies, and corroborated with complaints in submissions to 3 government public enquiries and news media records and court affidavits. These are expressed as proportions of estimated populations residing within 5 km of wind farms. There are large historical and geographical variations in wind farm complaints. 33/51 (64.7%) of Australian wind farms including 18/34 (52.9%) with turbine size >1 MW have never been subject to noise or health complaints. These 33 farms have an estimated 21,633 residents within 5 km and have operated complaint-free for a cumulative 267 years. Western Australia and Tasmania have seen no complaints. 129 individuals across Australia (1 in 254 residents) appear to have ever complained, with 94 (73%) being residents near 6 wind farms targeted by anti wind farm groups. The large majority 116/129(90%) of complainants made their first complaint after 2009 when anti wind farm groups began to add health concerns to their wider opposition. In the preceding years, health or noise complaints were rare despite large and small-turbine wind farms having operated for many years. The reported historical and geographical variations in complaints are consistent with psychogenic hypotheses that expressed health problems are "communicated diseases" with nocebo effects likely to play an important role in the aetiology of complaints.

River banks and channel axis curvature: Effects on the longitudinal dispersion in alluvial rivers

NASA Astrophysics Data System (ADS)

Lanzoni, Stefano; Ferdousi, Amena; Tambroni, Nicoletta

2018-03-01

The fate and transport of soluble contaminants released in natural streams are strongly dependent on the spatial variations of the flow field and of the bed topography. These variations are essentially related to the presence of the channel banks and to the planform configuration of the channel. Large velocity gradients arise near to the channel banks, where the flow depth decreases to zero. Moreover, single thread alluvial rivers are seldom straight, and usually exhibit meandering planforms and a bed topography that deviates from the plane configuration. Channel axis curvature and movable bed deformations drive secondary helical currents which enhance both cross sectional velocity gradients and transverse mixing, thus crucially influencing longitudinal dispersion. The present contribution sets up a rational framework which, assuming mild sloping banks and taking advantage of the weakly meandering character often exhibited by natural streams, leads to an analytical estimate of the contribution to longitudinal dispersion associated with spatial non-uniformities of the flow field. The resulting relationship stems from a physics-based modeling of the flow in natural rivers, and expresses the bend averaged longitudinal dispersion coefficient as a function of the relevant hydraulic and morphologic parameters. The treatment of the problem is river specific, since it relies on an explicit spatial description, although linearized, of the flow field that establishes in the investigated river. Comparison with field data available from tracer tests supports the robustness of the proposed framework, given also the complexity of the processes that affect dispersion dynamics in real streams.

Coalescent Processes with Skewed Offspring Distributions and Nonequilibrium Demography.

PubMed

Matuszewski, Sebastian; Hildebrandt, Marcel E; Achaz, Guillaume; Jensen, Jeffrey D

2018-01-01

Nonequilibrium demography impacts coalescent genealogies leaving detectable, well-studied signatures of variation. However, similar genomic footprints are also expected under models of large reproductive skew, posing a serious problem when trying to make inference. Furthermore, current approaches consider only one of the two processes at a time, neglecting any genomic signal that could arise from their simultaneous effects, preventing the possibility of jointly inferring parameters relating to both offspring distribution and population history. Here, we develop an extended Moran model with exponential population growth, and demonstrate that the underlying ancestral process converges to a time-inhomogeneous psi-coalescent. However, by applying a nonlinear change of time scale-analogous to the Kingman coalescent-we find that the ancestral process can be rescaled to its time-homogeneous analog, allowing the process to be simulated quickly and efficiently. Furthermore, we derive analytical expressions for the expected site-frequency spectrum under the time-inhomogeneous psi-coalescent, and develop an approximate-likelihood framework for the joint estimation of the coalescent and growth parameters. By means of extensive simulation, we demonstrate that both can be estimated accurately from whole-genome data. In addition, not accounting for demography can lead to serious biases in the inferred coalescent model, with broad implications for genomic studies ranging from ecology to conservation biology. Finally, we use our method to analyze sequence data from Japanese sardine populations, and find evidence of high variation in individual reproductive success, but few signs of a recent demographic expansion. Copyright © 2018 by the Genetics Society of America.

Factors predicting teachers' attitudes towards the use of ICT in teaching and learning

NASA Astrophysics Data System (ADS)

Ayub, Ahmad Fauzi Mohd; Bakar, Kamariah Abu; Ismail, Rohayati

2015-10-01

Technology has revolutionized in the field of Education. The importance of technology in schools cannot be ignored. While it is important that mathematics teachers should have positive attitudes towards adopting ICT in their teaching, various problems can arise when integrating ICT into classroom lessons. This study explored the factors that influence the attitudes of mathematic teachers in the integration of ICT in the teaching and learning process. A total of 187 mathematics teachers from the state of Selangor in Malaysia were randomly selected from a stratified cluster sample. The research examined five factors that were postulated to impact teachers' attitudes towards the integration of ICT in their lessons, viz. teachers' technology competence, school culture, access to ICT, school support, and years of classroom teaching experience. The findings showed that the teachers' attitudes towards using ICT in teaching and learning were positively correlated with the teachers' technology competence [r = .41; p < .01], ICT school culture [r = .261; p < .01], school support [r = .366; p < .01] and access to ICT resources [r = .220; p < .01]. However, a negative relationship existed between years of teaching and attitudes towards using ICT in teaching and learning [r = -0.192; p < .01]. A multiple regression analysis showed that 29.1% of the variation in teachers' attitudes towards using ICT in the classroom was explained by the variation in teachers' technology competence, school support and school culture, with the effects of teaching experience and ICT resource access being negligible.

Solar tri-diurnal variation of cosmic rays in a wide range of rigidity

NASA Technical Reports Server (NTRS)

Mori, S.; Ueno, H.; Fujii, Z.; Morishita, I.; Nagashima, K.

1985-01-01

Solar tri-diurnal variations of cosmic rays have been analyzed in a wide range of rigidity, using data from neutron monitors, and the surface and underground muon telescopes for the period 1978-1983. The rigidity spectrum of the anisotropy in space is assumed to be of power-exponential type as (P/gamma P sub o) to the gamma exp (gamma-P/P sub o). By means of the best-fit method between the observed and the expected variations, it is obtained that the spectrum has a peak at P (=gamma P sub o) approx = 90 GV, where gamma=approx 3.0 and P sub o approx. 30 GV. The phase in space of the tri-diurnal variation is also obtained as 7.0 hr (15 hr and 23 hr LT), which is quite different from that of approx. 1 hr. arising from the axisymmetric distribution of cosmic rays with respect to the IMF.

Signal, noise, and variation in neural and sensory-motor latency

PubMed Central

Lee, Joonyeol; Joshua, Mati; Medina, Javier F.; Lisberger, Stephen G.

2016-01-01

Analysis of the neural code for sensory-motor latency in smooth pursuit eye movements reveals general principles of neural variation and the specific origin of motor latency. The trial-by-trial variation in neural latency in MT comprises: a shared component expressed as neuron-neuron latency correlations; and an independent component that is local to each neuron. The independent component arises heavily from fluctuations in the underlying probability of spiking with an unexpectedly small contribution from the stochastic nature of spiking itself. The shared component causes the latency of single neuron responses in MT to be weakly predictive of the behavioral latency of pursuit. Neural latency deeper in the motor system is more strongly predictive of behavioral latency. A model reproduces both the variance of behavioral latency and the neuron-behavior latency correlations in MT if it includes realistic neural latency variation, neuron-neuron latency correlations in MT, and noisy gain control downstream from MT. PMID:26971946

Power allocation for SWIPT in K-user interference channels using game theory

NASA Astrophysics Data System (ADS)

Wen, Zhigang; Liu, Ying; Liu, Xiaoqing; Li, Shan; Chen, Xianya

2018-12-01

A simultaneous wireless information and power transfer system in interference channels of multi-users is considered. In this system, each transmitter sends one data stream to its targeted receiver, which causes interference to other receivers. Since all transmitter-receiver links want to maximize their own average transmission rate, a power allocation problem under the transmit power constraints and the energy-harvesting constraints is developed. To solve this problem, we propose a game theory framework. Then, we convert the game into a variational inequalities problem by establishing the connection between game theory and variational inequalities and solve the variational inequalities problem. Through theoretical analysis, the existence and uniqueness of Nash equilibrium are both guaranteed by the theory of variational inequalities. A distributed iterative alternating optimization water-filling algorithm is derived, which is proved to converge. Numerical results show that the proposed algorithm reaches fast convergence and achieves a higher sum rate than the unaided scheme.

Recognizing the professionals who help to solve "the population problem".

PubMed

Miro, C A

1984-12-01

It is the population professionals who belong to the "developing" world who have helped to create and expand the basic information which makes it possible to describe the demographic situation of countries and social groups more adequately. These professionals have developed, promoted, and applied analytical techniques which have enriched understanding of the components of demographic change. It is these professionals who have managed to make major contributions towards explaining the relationship between demographic and socioeconomic factors. The professionals are insisting on developing applied, theoretical, and methodological population research, the results of which will serve essentially to propose alternatives for action. This group of professionals participates daily in the training of technical staff and professionals and academics, specialists who will continue to promote the development of demography as a discipline. Finally, these professionals, through various publications, keep population topics at the center of the attention of those who are concerned with studying them. Groups of countries in Africa, Asia, and Latin America suffer, although to a different extent and in different ways, from the problems created by the rapid growth of certain cities, particularly capital cities. In addition to the problems which may arise from the operation of the specific population dynamics in different countries and between different social groups within those countries, there are those arising from the unequal distribution of agricultural land, foodstuffs, and wealth in general, those arising from the unjust organization of the international economy and from the obsolete international financial structure, and those deriving from the irrational use of resources for military spending and the manufacture and stockpiling of vast nuclear arsenals.

Reducing Teacher Turnover by Utilizing a National List of Reasons for Teacher Dissatisfaction or How to Keep Teachers from Declaring "Dear Folks, I Quit"

ERIC Educational Resources Information Center

Lopez, Angela J.

2010-01-01

Background: Teacher turnover is a national problem and has been investigated on the national level since the 1920's. This study compares the reasons teachers give for leaving teaching positions from data collected nationwide with local data. Purpose: To examine whether the same problems that arise on the local level have been identified in the…

[Problems in implementing a pain management program for rheumatoid patients and studies of its effectiveness].

PubMed

Cziske, R; Jäckel, W; Jacobi, E

1987-01-01

A pain management program is presented which enables patients to reduce pain by means of relaxation and attention-diversion, etc. The problems arising from applying a psychological training to organic diseases, and the most favourable therapist's behaviour in facing these difficulties are elucidated. Finally, controlled studies are cited showing that pain can be reduced and the emotional state improved by pain management techniques.

Error Correcting Codes I. Applications of Elementary Algebra to Information Theory. Modules and Monographs in Undergraduate Mathematics and Its Applications Project. UMAP Unit 346.

ERIC Educational Resources Information Center

Rice, Bart F.; Wilde, Carroll O.

It is noted that with the prominence of computers in today's technological society, digital communication systems have become widely used in a variety of applications. Some of the problems that arise in digital communications systems are described. This unit presents the problem of correcting errors in such systems. Error correcting codes are…

Impulse position control algorithms for nonlinear systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sesekin, A. N., E-mail: sesekin@list.ru; Institute of Mathematics and Mechanics, Ural Division of Russian Academy of Sciences, 16 S. Kovalevskaya, Ekaterinburg, 620990; Nepp, A. N., E-mail: anepp@urfu.ru

2015-11-30

The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of suchmore » regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.« less

The Social Implications of Light at Night

NASA Astrophysics Data System (ADS)

Henshaw, Colin

2015-08-01

Summary: It has been shown that Light at Night (LAN) has serious implications for both the environment and human health. What is considered here are the social implications that arise from these problems, and what needs to be done to redress these issues.Introduction: Light at Night is a serious environmental problem whose environmental and medical implications have been seriously underestimated. If no action is taken the problem will become progressively worse and may reach a point where nothing can be done about it. The issues arising from it need to be identified andappropriate action taken to mitigate these issues as far as possible. Hopefully this can be done amicably by self regulation within communities, but if this fails then stringent anti-light pollution legislation will have to be enacted. Some countries and local authorities have already begun to make faltering steps in this direction1, but so far the measures taken have been minimal and largely ineffective. Light at Night (and the light pollution resulting from it) therefore remains a problem and continues to get worse despite the measures already taken to reduce it. Domes of scattered light continue to hang above our cities, killing off our wildlife and endangering public health. Attitudes need to change and urgent measures need to be taken in order to reduce or eliminate its impact.

Combining nutrient intake from food/beverages and vitamin/mineral supplements.

PubMed

Garriguet, Didier

2010-12-01

To calculate total intake of a nutrient and estimate inadequate intake for a population, the amounts derived from food/beverages and from vitamin/mineral supplements must be combined. The two methods Statistics Canada has suggested present problems of interpretation. Data collected from 34,386 respondents to the 2004 Canadian Community Health Survey-Nutrition were used to compare four methods of combining nutrient intake from food/beverages and vitamin/mineral supplements: adding average intake from supplements to the 24-hour food/beverage recall and estimating the usual distribution in the population (Method 1); estimating usual individual intake from food? beverages and adding intake from supplements (Method 2); and dividing the population into supplement users and non-users and applying Method 1 or Method 2 and combining the estimates based on the percentages of users and non-users (Methods 3 and 4). Interpretation problems arise with Methods 1 and 2; for example, the percentage of the population with inadequate intake of vitamin C and folate equivalents falls outside the expected minimum-maximum range. These interpretation problems are not observed with Methods 3 and 4. Interpretation problems that may arise in combining food and supplement intake of a given nutrient are overcome if the population is divided into supplement users and non-users before Method 1 or Method 2 is applied.

Quantifying Intrinsic and Extrinsic Variability in Stochastic Gene Expression Models

PubMed Central

Singh, Abhyudai; Soltani, Mohammad

2013-01-01

Genetically identical cell populations exhibit considerable intercellular variation in the level of a given protein or mRNA. Both intrinsic and extrinsic sources of noise drive this variability in gene expression. More specifically, extrinsic noise is the expression variability that arises from cell-to-cell differences in cell-specific factors such as enzyme levels, cell size and cell cycle stage. In contrast, intrinsic noise is the expression variability that is not accounted for by extrinsic noise, and typically arises from the inherent stochastic nature of biochemical processes. Two-color reporter experiments are employed to decompose expression variability into its intrinsic and extrinsic noise components. Analytical formulas for intrinsic and extrinsic noise are derived for a class of stochastic gene expression models, where variations in cell-specific factors cause fluctuations in model parameters, in particular, transcription and/or translation rate fluctuations. Assuming mRNA production occurs in random bursts, transcription rate is represented by either the burst frequency (how often the bursts occur) or the burst size (number of mRNAs produced in each burst). Our analysis shows that fluctuations in the transcription burst frequency enhance extrinsic noise but do not affect the intrinsic noise. On the contrary, fluctuations in the transcription burst size or mRNA translation rate dramatically increase both intrinsic and extrinsic noise components. Interestingly, simultaneous fluctuations in transcription and translation rates arising from randomness in ATP abundance can decrease intrinsic noise measured in a two-color reporter assay. Finally, we discuss how these formulas can be combined with single-cell gene expression data from two-color reporter experiments for estimating model parameters. PMID:24391934

Quantifying intrinsic and extrinsic variability in stochastic gene expression models.

PubMed

Singh, Abhyudai; Soltani, Mohammad

2013-01-01

Genetically identical cell populations exhibit considerable intercellular variation in the level of a given protein or mRNA. Both intrinsic and extrinsic sources of noise drive this variability in gene expression. More specifically, extrinsic noise is the expression variability that arises from cell-to-cell differences in cell-specific factors such as enzyme levels, cell size and cell cycle stage. In contrast, intrinsic noise is the expression variability that is not accounted for by extrinsic noise, and typically arises from the inherent stochastic nature of biochemical processes. Two-color reporter experiments are employed to decompose expression variability into its intrinsic and extrinsic noise components. Analytical formulas for intrinsic and extrinsic noise are derived for a class of stochastic gene expression models, where variations in cell-specific factors cause fluctuations in model parameters, in particular, transcription and/or translation rate fluctuations. Assuming mRNA production occurs in random bursts, transcription rate is represented by either the burst frequency (how often the bursts occur) or the burst size (number of mRNAs produced in each burst). Our analysis shows that fluctuations in the transcription burst frequency enhance extrinsic noise but do not affect the intrinsic noise. On the contrary, fluctuations in the transcription burst size or mRNA translation rate dramatically increase both intrinsic and extrinsic noise components. Interestingly, simultaneous fluctuations in transcription and translation rates arising from randomness in ATP abundance can decrease intrinsic noise measured in a two-color reporter assay. Finally, we discuss how these formulas can be combined with single-cell gene expression data from two-color reporter experiments for estimating model parameters.

Genetic recapitulation of human pre-eclampsia risk during convergent evolution of reduced placental invasiveness in eutherian mammals

PubMed Central

Elliot, Michael G.; Crespi, Bernard J.

2015-01-01

The relationship between phenotypic variation arising through individual development and phenotypic variation arising through diversification of species has long been a central question in evolutionary biology. Among humans, reduced placental invasion into endometrial tissues is associated with diseases of pregnancy, especially pre-eclampsia, and reduced placental invasiveness has also evolved, convergently, in at least 10 lineages of eutherian mammals. We tested the hypothesis that a common genetic basis underlies both reduced placental invasion arising through a developmental process in human placental disease and reduced placental invasion found as a derived trait in the diversification of Euarchontoglires (rodents, lagomorphs, tree shrews, colugos and primates). Based on whole-genome analyses across 18 taxa, we identified 1254 genes as having evolved adaptively across all three lineages exhibiting independent evolutionary transitions towards reduced placental invasion. These genes showed strong evidence of enrichment for associations with pre-eclampsia, based on genetic-association studies, gene-expression analyses and gene ontology. We further used in silico prediction to identify a subset of 199 genes that are likely targets of natural selection during transitions in placental invasiveness and which are predicted to also underlie human placental disorders. Our results indicate that abnormal ontogenies can recapitulate major phylogenetic shifts in mammalian evolution, identify new candidate genes for involvement in pre-eclampsia, imply that study of species with less-invasive placentation will provide useful insights into the regulation of placental invasion and pre-eclampsia, and recommend a novel comparative functional-evolutionary approach to the study of genetically based human disease and mammalian diversification. PMID:25602073

Acaricide resistance mechanisms in Rhipicephalus microplus

USDA-ARS?s Scientific Manuscript database

Acaricide resistance has become widespread in countries where cattle ticks, Rhipicephalus (Boophilus) microplus, are a problem. Resistance arises through genetic changes in a cattle tick population that causes modifications to the target site, increased metabolism or sequestration of the acaricide, ...

Sixth-Graders Learning on "Spaceship Earth"

ERIC Educational Resources Information Center

Journal of Aerospace Education, 1974

1974-01-01

Describes a classroom organized as a self-contained closed spaceship which provides an opportunity for individualized learning based on student interests and a chance to wrestle with the problems that would arise on an interstellar journey in a spaceship. (BR)

Application of the Bootstrap Methods in Factor Analysis.

ERIC Educational Resources Information Center

Ichikawa, Masanori; Konishi, Sadanori

1995-01-01

A Monte Carlo experiment was conducted to investigate the performance of bootstrap methods in normal theory maximum likelihood factor analysis when the distributional assumption was satisfied or unsatisfied. Problems arising with the use of bootstrap methods are highlighted. (SLD)

The problem with multiple robots

NASA Technical Reports Server (NTRS)

Huber, Marcus J.; Kenny, Patrick G.

1994-01-01

The issues that can arise in research associated with multiple, robotic agents are discussed. Two particular multi-robot projects are presented as examples. This paper was written in the hope that it might ease the transition from single to multiple robot research.

Shelter as Workplace: A Review of Home-Based Enterprise in Developing Countries.

ERIC Educational Resources Information Center

Tipple, A. Graham

1993-01-01

Describes the most common types of home-based employment activities and looks at advantages and disadvantages of such small enterprises, their profitability, and measures that could be taken to solve problems that arise. (Author/JOW)

Working To Learn: A Holistic Approach to Young People's Education and Training.

ERIC Educational Resources Information Center

Senker, Peter; Rainbird, Helen; Evans, Karen; Hodkinson, Phil; Keep, Ewart; Maguire, Malcolm; Raffe, David; Unwin, Lorna

2000-01-01

Highlights deficiencies in current British policies on work-based learning for 16-19 year-olds. Discusses problems arising from employers' voluntary participation. Outlines a holistic approach based on the community of practice model. (SK)

Improving travel information products via robust estimation techniques : final report, March 2009.

DOT National Transportation Integrated Search

2009-03-01

Traffic-monitoring systems, such as those using loop detectors, are prone to coverage gaps, arising from sensor noise, processing errors and : transmission problems. Such gaps adversely affect the accuracy of Advanced Traveler Information Systems. Th...

Information retrieval algorithms: A survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghavan, P.

We give an overview of some algorithmic problems arising in the representation of text/image/multimedia objects in a form amenable to automated searching, and in conducting these searches efficiently. These operations are central to information retrieval and digital library systems.

Recommendations for design, construction, and maintenance of bridge approach slabs.

DOT National Transportation Integrated Search

2012-09-01

Settlement and heave related movements of bridge approach slabs relative to bridge decks create a bump in : the roadway. Several problems arise from these bumps, which include poor riding conditions, potential : vehicle damage, loss of vehicle contro...

Computational Molecular Modeling for Evaluating the Toxicity of Environmental Chemicals: Prioritizing Bioassay Requirements

EPA Science Inventory

This commentary provides an overview of the challenges that arise from applying molecular modeling tools developed and commonly used for pharmaceutical discovery to the problem of predicting the potential toxicities of environmental chemicals.

Forensic Entomology: Evaluating Uncertainty Associated With Postmortem Interval (PMI) Estimates With Ecological Models.

PubMed

Faris, A M; Wang, H-H; Tarone, A M; Grant, W E

2016-05-31

Estimates of insect age can be informative in death investigations and, when certain assumptions are met, can be useful for estimating the postmortem interval (PMI). Currently, the accuracy and precision of PMI estimates is unknown, as error can arise from sources of variation such as measurement error, environmental variation, or genetic variation. Ecological models are an abstract, mathematical representation of an ecological system that can make predictions about the dynamics of the real system. To quantify the variation associated with the pre-appearance interval (PAI), we developed an ecological model that simulates the colonization of vertebrate remains by Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae), a primary colonizer in the southern United States. The model is based on a development data set derived from a local population and represents the uncertainty in local temperature variability to address PMI estimates at local sites. After a PMI estimate is calculated for each individual, the model calculates the maximum, minimum, and mean PMI, as well as the range and standard deviation for stadia collected. The model framework presented here is one manner by which errors in PMI estimates can be addressed in court when no empirical data are available for the parameter of interest. We show that PAI is a potential important source of error and that an ecological model is one way to evaluate its impact. Such models can be re-parameterized with any development data set, PAI function, temperature regime, assumption of interest, etc., to estimate PMI and quantify uncertainty that arises from specific prediction systems. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Mortar and artillery variants classification by exploiting characteristics of the acoustic signature

NASA Astrophysics Data System (ADS)

Hohil, Myron E.; Grasing, David; Desai, Sachi; Morcos, Amir

2007-10-01

Feature extraction methods based on the discrete wavelet transform and multiresolution analysis facilitate the development of a robust classification algorithm that reliably discriminates mortar and artillery variants via acoustic signals produced during the launch/impact events. Utilizing acoustic sensors to exploit the sound waveform generated from the blast for the identification of mortar and artillery variants. Distinct characteristics arise within the different mortar variants because varying HE mortar payloads and related charges emphasize concussive and shrapnel effects upon impact employing varying magnitude explosions. The different mortar variants are characterized by variations in the resulting waveform of the event. The waveform holds various harmonic properties distinct to a given mortar/artillery variant that through advanced signal processing techniques can employed to classify a given set. The DWT and other readily available signal processing techniques will be used to extract the predominant components of these characteristics from the acoustic signatures at ranges exceeding 2km. Exploiting these techniques will help develop a feature set highly independent of range, providing discrimination based on acoustic elements of the blast wave. Highly reliable discrimination will be achieved with a feed-forward neural network classifier trained on a feature space derived from the distribution of wavelet coefficients, frequency spectrum, and higher frequency details found within different levels of the multiresolution decomposition. The process that will be described herein extends current technologies, which emphasis multi modal sensor fusion suites to provide such situational awareness. A two fold problem of energy consumption and line of sight arise with the multi modal sensor suites. The process described within will exploit the acoustic properties of the event to provide variant classification as added situational awareness to the solider.

Recent developments in the theory of protein folding: searching for the global energy minimum.

PubMed

Scheraga, H A

1996-04-16

Statistical mechanical theories and computer simulation are being used to gain an understanding of the fundamental features of protein folding. A major obstacle in the computation of protein structures is the multiple-minima problem arising from the existence of many local minima in the multidimensional energy landscape of the protein. This problem has been surmounted for small open-chain and cyclic peptides, and for regular-repeating sequences of models of fibrous proteins. Progress is being made in resolving this problem for globular proteins.