Moral judgment as information processing: an integrative review

PubMed Central

Guglielmo, Steve

2015-01-01

How do humans make moral judgments about others’ behavior? This article reviews dominant models of moral judgment, organizing them within an overarching framework of information processing. This framework poses two distinct questions: (1) What input information guides moral judgments? and (2) What psychological processes generate these judgments? Information Models address the first question, identifying critical information elements (including causality, intentionality, and mental states) that shape moral judgments. A subclass of Biased Information Models holds that perceptions of these information elements are themselves driven by prior moral judgments. Processing Models address the second question, and existing models have focused on the relative contribution of intuitive versus deliberative processes. This review organizes existing moral judgment models within this framework and critically evaluates them on empirical and theoretical grounds; it then outlines a general integrative model grounded in information processing, and concludes with conceptual and methodological suggestions for future research. The information-processing framework provides a useful theoretical lens through which to organize extant and future work in the rapidly growing field of moral judgment. PMID:26579022

Game-Theoretic Models of Information Overload in Social Networks

NASA Astrophysics Data System (ADS)

Borgs, Christian; Chayes, Jennifer; Karrer, Brian; Meeder, Brendan; Ravi, R.; Reagans, Ray; Sayedi, Amin

We study the effect of information overload on user engagement in an asymmetric social network like Twitter. We introduce simple game-theoretic models that capture rate competition between celebrities producing updates in such networks where users non-strategically choose a subset of celebrities to follow based on the utility derived from high quality updates as well as disutility derived from having to wade through too many updates. Our two variants model the two behaviors of users dropping some potential connections (followership model) or leaving the network altogether (engagement model). We show that under a simple formulation of celebrity rate competition, there is no pure strategy Nash equilibrium under the first model. We then identify special cases in both models when pure rate equilibria exist for the celebrities: For the followership model, we show existence of a pure rate equilibrium when there is a global ranking of the celebrities in terms of the quality of their updates to users. This result also generalizes to the case when there is a partial order consistent with all the linear orders of the celebrities based on their qualities to the users. Furthermore, these equilibria can be computed in polynomial time. For the engagement model, pure rate equilibria exist when all users are interested in the same number of celebrities, or when they are interested in at most two. Finally, we also give a finite though inefficient procedure to determine if pure equilibria exist in the general case of the followership model.

How absent negativity relates to affect and motivation: an integrative relief model.

PubMed

Deutsch, Roland; Smith, Kevin J M; Kordts-Freudinger, Robert; Reichardt, Regina

2015-01-01

The present paper concerns the motivational underpinnings and behavioral correlates of the prevention or stopping of negative stimulation - a situation referred to as relief. Relief is of great theoretical and applied interest. Theoretically, it is tied to theories linking affect, emotion, and motivational systems. Importantly, these theories make different predictions regarding the association between relief and motivational systems. Moreover, relief is a prototypical antecedent of counterfactual emotions, which involve specific cognitive processes compared to factual or mere anticipatory emotions. Practically, relief may be an important motivator of addictive and phobic behaviors, self destructive behaviors, and social influence. In the present paper, we will first provide a review of conflicting conceptualizations of relief. We will then present an integrative relief model (IRMO) that aims at resolving existing theoretical conflicts. We then review evidence relevant to distinctive predictions regarding the moderating role of various procedural features of relief situations. We conclude that our integrated model results in a better understanding of existing evidence on the affective and motivational underpinnings of relief, but that further evidence is needed to come to a more comprehensive evaluation of the viability of IRMO.

Conceptual Models, Choices, and Benchmarks for Building Quality Work Cultures.

ERIC Educational Resources Information Center

Acker-Hocevar, Michele

1996-01-01

The two models in Florida's Educational Quality Benchmark System represent a new way of thinking about developing schools' work culture. The Quality Performance System Model identifies nine dimensions of work within a quality system. The Change Process Model provides a theoretical framework for changing existing beliefs, attitudes, and behaviors…

Light Scattering from Rough Surfaces. Appendix. Angular Correlation of Speckle Patterns. Draft

DTIC Science & Technology

1994-06-01

For his demonstrations of the various experimental techniques, I owe thanks to Andrew Sant. Also, on behalf of all students writing (and written) up ...less controllable, radar set up . 1.1.1 Theoretical Models This section will present some of the theoretical models which exist for determining the...centre of a turntable set up to spin at :300 revolutions per minute. While the turntable is stationary, photoresist is applied to the centre of the

Size effects in non-linear heat conduction with flux-limited behaviors

NASA Astrophysics Data System (ADS)

Li, Shu-Nan; Cao, Bing-Yang

2017-11-01

Size effects are discussed for several non-linear heat conduction models with flux-limited behaviors, including the phonon hydrodynamic, Lagrange multiplier, hierarchy moment, nonlinear phonon hydrodynamic, tempered diffusion, thermon gas and generalized nonlinear models. For the phonon hydrodynamic, Lagrange multiplier and tempered diffusion models, heat flux will not exist in problems with sufficiently small scale. The existence of heat flux needs the sizes of heat conduction larger than their corresponding critical sizes, which are determined by the physical properties and boundary temperatures. The critical sizes can be regarded as the theoretical limits of the applicable ranges for these non-linear heat conduction models with flux-limited behaviors. For sufficiently small scale heat conduction, the phonon hydrodynamic and Lagrange multiplier models can also predict the theoretical possibility of violating the second law and multiplicity. Comparisons are also made between these non-Fourier models and non-linear Fourier heat conduction in the type of fast diffusion, which can also predict flux-limited behaviors.

Transactors, Transformers and Beyond. A Multi-Method Development of a Theoretical Typology of Leadership.

ERIC Educational Resources Information Center

Pearce, Craig L.; Sims, Henry P., Jr.; Cox, Jonathan F.; Ball, Gail; Schnell, Eugene; Smith, Ken A.; Trevino, Linda

2003-01-01

To extend the transactional-transformational model of leadership, four theoretical behavioral types of leadership were developed based on literature review and data from studies of executive behavior (n=253) and subordinate attitudes (n=208). Confirmatory factor analysis of a third data set (n=702) support the existence of four leadership types:…

Measuring cognition in teams: a cross-domain review.

PubMed

Wildman, Jessica L; Salas, Eduardo; Scott, Charles P R

2014-08-01

The purpose of this article is twofold: to provide a critical cross-domain evaluation of team cognition measurement options and to provide novice researchers with practical guidance when selecting a measurement method. A vast selection of measurement approaches exist for measuring team cognition constructs including team mental models, transactive memory systems, team situation awareness, strategic consensus, and cognitive processes. Empirical studies and theoretical articles were reviewed to identify all of the existing approaches for measuring team cognition. These approaches were evaluated based on theoretical perspective assumed, constructs studied, resources required, level of obtrusiveness, internal consistency reliability, and predictive validity. The evaluations suggest that all existing methods are viable options from the point of view of reliability and validity, and that there are potential opportunities for cross-domain use. For example, methods traditionally used only to measure mental models may be useful for examining transactive memory and situation awareness. The selection of team cognition measures requires researchers to answer several key questions regarding the theoretical nature of team cognition and the practical feasibility of each method. We provide novice researchers with guidance regarding how to begin the search for a team cognition measure and suggest several new ideas regarding future measurement research. We provide (1) a broad overview and evaluation of existing team cognition measurement methods, (2) suggestions for new uses of those methods across research domains, and (3) critical guidance for novice researchers looking to measure team cognition.

Spectrum analysis of radar life signal in the three kinds of theoretical models

NASA Astrophysics Data System (ADS)

Yang, X. F.; Ma, J. F.; Wang, D.

2017-02-01

In the single frequency continuous wave radar life detection system, based on the Doppler effect, the theory model of radar life signal is expressed by the real function, and there is a phenomenon that can't be confirmed by the experiment. When the phase generated by the distance between the measured object and the radar measuring head is л of integer times, the main frequency spectrum of life signal (respiration and heartbeat) is not existed in radar life signal. If this phase is л/2 of odd times, the main frequency spectrum of breath and heartbeat frequency is the strongest. In this paper, we use the Doppler effect as the basic theory, using three different mathematical expressions——real function, complex exponential function and Bessel's function expansion form. They are used to establish the theoretical model of radar life signal. Simulation analysis revealed that the Bessel expansion form theoretical model solve the problem of real function form. Compared with the theoretical model of the complex exponential function, the derived spectral line is greatly reduced in the theoretical model of Bessel expansion form, which is more consistent with the actual situation.

Elastic solitons in delaminated bars: splitting leads to fission

NASA Astrophysics Data System (ADS)

Samsonov, A. M.; Dreiden, G. V.; Khusnutdinova, K. R.; Semenova, I. V.

2008-06-01

Recent theoretical and successful experimental studies confirmed existence and demonstrated main properties of bulk strain solitary waves in nonlinearly elastic solid wave guides. Our current research is devoted to nonlinear wave processes in layered elastic wave guides with inhomogeneities modelling delamination. We present first theoretical and experimental results showing the influence of delamination on the parameters of the longitudinal strain solitary wave.

Reserves in load capacity assessment of existing bridges

NASA Astrophysics Data System (ADS)

Žitný, Jan; Ryjáček, Pavel

2017-09-01

High percentage of all railway bridges in the Czech Republic is made of structural steel. Majority of these bridges is designed according to historical codes and according to the deterioration, they have to be assessed if they satisfy the needs of modern railway traffic. The load capacity assessment of existing bridges according to Eurocodes is however often too conservative and especially, braking and acceleration forces cause huge problems to structural elements of the bridge superstructure. The aim of this paper is to review the different approaches for the determination of braking and acceleration forces. Both, current and historical theoretical models and in-situ measurements are considered. The research of several local European state norms superior to Eurocode for assessment of existing railway bridges shows the big diversity of used local approaches and the conservativeness of Eurocode. This paper should also work as an overview for designers dealing with load capacity assessment, revealing the reserves for existing bridges. Based on these different approaches, theoretical models and data obtained from the measurements, the method for determination of braking and acceleration forces on the basis of real traffic data should be proposed.

A Theoretical Approach to the Long-Hazleton Process of Public Relations Model.

ERIC Educational Resources Information Center

Myers, Scott A.

One way to implement theory into existing public relations classes is to utilize the Process of Public Relations model developed by L. W. Long and V. Hazleton. The use of the model in the classroom is important because the model stresses the interdependence between the public relations practitioner and the organization. The model begins by…

Stochastic Simulation of Actin Dynamics Reveals the Role of Annealing and Fragmentation

PubMed Central

Fass, Joseph; Pak, Chi; Bamburg, James; Mogilner, Alex

2008-01-01

Recent observations of F-actin dynamics call for theoretical models to interpret and understand the quantitative data. A number of existing models rely on simplifications and do not take into account F-actin fragmentation and annealing. We use Gillespie’s algorithm for stochastic simulations of the F-actin dynamics including fragmentation and annealing. The simulations vividly illustrate that fragmentation and annealing have little influence on the shape of the polymerization curve and on nucleotide profiles within filaments but drastically affect the F-actin length distribution, making it exponential. We find that recent surprising measurements of high length diffusivity at the critical concentration cannot be explained by fragmentation and annealing events unless both fragmentation rates and frequency of undetected fragmentation and annealing events are greater than previously thought. The simulations compare well with experimentally measured actin polymerization data and lend additional support to a number of existing theoretical models. PMID:18279896

Surface electromagnetic waves in Fibonacci superlattices: Theoretical and experimental results

NASA Astrophysics Data System (ADS)

El Hassouani, Y.; Aynaou, H.; El Boudouti, E. H.; Djafari-Rouhani, B.; Akjouj, A.; Velasco, V. R.

2006-07-01

We study theoretically and experimentally the existence and behavior of the localized surface modes in one-dimensional (1D) quasiperiodic photonic band gap structures. These structures are made of segments and loops arranged according to a Fibonacci sequence. The experiments are carried out by using coaxial cables in the frequency region of a few tens of MHz. We consider 1D periodic structures (superlattice) where each cell is a well-defined Fibonacci generation. In these structures, we generalize a theoretical rule on the surface modes, namely when one considers two semi-infinite superlattices obtained by the cleavage of an infinite superlattice, it exists exactly one surface mode in each gap. This mode is localized on the surface either of one or the other semi-infinite superlattice. We discuss the existence of various types of surface modes and their spatial localization. The experimental observation of these modes is carried out by measuring the transmission through a guide along which a finite superlattice (i.e., constituted of a finite number of quasiperiodic cells) is grafted vertically. The surface modes appear as maxima of the transmission spectrum. These experiments are in good agreement with the theoretical model based on the formalism of the Green function.

How absent negativity relates to affect and motivation: an integrative relief model

PubMed Central

Deutsch, Roland; Smith, Kevin J. M.; Kordts-Freudinger, Robert; Reichardt, Regina

2015-01-01

The present paper concerns the motivational underpinnings and behavioral correlates of the prevention or stopping of negative stimulation – a situation referred to as relief. Relief is of great theoretical and applied interest. Theoretically, it is tied to theories linking affect, emotion, and motivational systems. Importantly, these theories make different predictions regarding the association between relief and motivational systems. Moreover, relief is a prototypical antecedent of counterfactual emotions, which involve specific cognitive processes compared to factual or mere anticipatory emotions. Practically, relief may be an important motivator of addictive and phobic behaviors, self destructive behaviors, and social influence. In the present paper, we will first provide a review of conflicting conceptualizations of relief. We will then present an integrative relief model (IRMO) that aims at resolving existing theoretical conflicts. We then review evidence relevant to distinctive predictions regarding the moderating role of various procedural features of relief situations. We conclude that our integrated model results in a better understanding of existing evidence on the affective and motivational underpinnings of relief, but that further evidence is needed to come to a more comprehensive evaluation of the viability of IRMO. PMID:25806008

Changing Models for Researching Pedagogy with Information and Communications Technologies

ERIC Educational Resources Information Center

Webb, M.

2013-01-01

This paper examines changing models of pedagogy by drawing on recent research with teachers and their students as well as theoretical developments. In relation to a participatory view of learning, the paper reviews existing pedagogical models that take little account of the use of information and communications technologies as well as those that…

A Theory Based Model of Interpersonal Leadership: An Integration of the Literature

ERIC Educational Resources Information Center

Lamm, Kevan W.; Carter, Hannah S.; Lamm, Alexa J.

2016-01-01

Although the term interpersonal leadership has been well established within the literature, there remains a dearth of theoretically derived models that specifically address the comprehensive nature of the underlying leader behaviors and activities. The intent of the present article is to attempt to synthesize the existent leadership models,…

Models of Sexual and Relational Orientation: A Critical Review and Synthesis

ERIC Educational Resources Information Center

Moe, Jeffry L.; Reicherzer, Stacee; Dupuy, Paula J.

2011-01-01

Many frameworks exist to explain and describe the phenomenon of same-sex sexuality as it applies to human development. This conceptual article provides a critical overview and synthesis of previous models to serve as a theoretical bridge for the suggested multiple continua model of sexual and relational orientations. Recommendations for how…

Bifurcation analysis of a discrete SIS model with bilinear incidence depending on new infection.

PubMed

Cao, Hui; Zhou, Yicang; Ma, Zhien

2013-01-01

A discrete SIS epidemic model with the bilinear incidence depending on the new infection is formulated and studied. The condition for the global stability of the disease free equilibrium is obtained. The existence of the endemic equilibrium and its stability are investigated. More attention is paid to the existence of the saddle-node bifurcation, the flip bifurcation, and the Hopf bifurcation. Sufficient conditions for those bifurcations have been obtained. Numerical simulations are conducted to demonstrate our theoretical results and the complexity of the model.

Brain activity and cognition: a connection from thermodynamics and information theory.

PubMed

Collell, Guillem; Fauquet, Jordi

2015-01-01

The connection between brain and mind is an important scientific and philosophical question that we are still far from completely understanding. A crucial point to our work is noticing that thermodynamics provides a convenient framework to model brain activity, whereas cognition can be modeled in information-theoretical terms. In fact, several models have been proposed so far from both approaches. A second critical remark is the existence of deep theoretical connections between thermodynamics and information theory. In fact, some well-known authors claim that the laws of thermodynamics are nothing but principles in information theory. Unlike in physics or chemistry, a formalization of the relationship between information and energy is currently lacking in neuroscience. In this paper we propose a framework to connect physical brain and cognitive models by means of the theoretical connections between information theory and thermodynamics. Ultimately, this article aims at providing further insight on the formal relationship between cognition and neural activity.

A University-Industry Cooperation Model for Small and Medium Enterprises: The Case of Chengdu KEDA Optoelectronic Technology Ltd.

ERIC Educational Resources Information Center

Peng, Shanzhong; Ferreira, Fernando A. F.; Zheng, He

2017-01-01

In this study, we develop a firm-dominated incremental cooperation model. Following the critical review of current literature and various cooperation models, we identified a number of strengths and shortcomings that form the basis for our framework. The objective of our theoretical model is to contribute to overcome the existing gap within…

Toward an Integrated Gender-Linked Model of Aggression Subtypes in Early and Middle Childhood

ERIC Educational Resources Information Center

Ostrov, Jamie M.; Godleski, Stephanie A.

2010-01-01

An integrative model is proposed for understanding the development of physical and relational aggression in early and middle childhood. The central goal was to posit a new theoretical framework that expands on existing social-cognitive and gender schema models (i.e., Social Information-Processing Model of Children's Adjustment [N. R. Crick & K. A.…

Factors Influencing the Performance of Dynamic Decision Network for INQPRO

ERIC Educational Resources Information Center

Ting, Choo-Yee; Phon-Amnuaisuk, Somnuk

2009-01-01

There has been an increasing interest in employing decision-theoretic framework for learner modeling and provision of pedagogical support in Intelligent Tutoring Systems (ITSs). Much of the existing learner modeling research work focuses on identifying appropriate learner properties. Little attention, however, has been given to leverage Dynamic…

Assessing Mediational Models: Testing and Interval Estimation for Indirect Effects

ERIC Educational Resources Information Center

Biesanz, Jeremy C.; Falk, Carl F.; Savalei, Victoria

2010-01-01

Theoretical models specifying indirect or mediated effects are common in the social sciences. An indirect effect exists when an independent variable's influence on the dependent variable is mediated through an intervening variable. Classic approaches to assessing such mediational hypotheses (Baron & Kenny, 1986; Sobel, 1982) have in recent years…

A SCREENING MODEL FOR SIMULATING DNAPL FLOW AND TRANSPORT IN POROUS MEDIA: THEORETICAL DEVELOPMENT

EPA Science Inventory

There exists a need for a simple tool that will allow us to analyze a DNAPL contamination scenario from free-product release to transport of soluble constituents to downgradient receptor wells. The objective of this manuscript is to present the conceptual model and formulate the ...

Large scale surface flow generation in driven suspensions of magnetic microparticles: Experiment, theoretical model and simulations

NASA Astrophysics Data System (ADS)

Belkin, Maxim; Snezhko, Alexey; Aranson, Igor

2007-03-01

Nontrivially ordered dynamic self-assembled snake-like structures are formed in an ensemble of magnetic microparticles suspended over a fluid surface and energized by an external alternating magnetic field. Formation and existence of such structures is always accompanied by flows which form vortices. These large-scale vortices can be very fast and are crucial for snake formation/destruction. We introduce theoretical model based on Ginzburg-Landau equation for parametrically excited surface waves coupled to conservation law for particle density and Navier-Stokes equation for water flows. The developed model successfully describes snake generation, accounts for flows and reproduces most experimental results observed.

Communication: Electron ionization of DNA bases.

PubMed

Rahman, M A; Krishnakumar, E

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.

Rockfall travel distances theoretical distributions

NASA Astrophysics Data System (ADS)

Jaboyedoff, Michel; Derron, Marc-Henri; Pedrazzini, Andrea

2017-04-01

The probability of propagation of rockfalls is a key part of hazard assessment, because it permits to extrapolate the probability of propagation of rockfall either based on partial data or simply theoretically. The propagation can be assumed frictional which permits to describe on average the propagation by a line of kinetic energy which corresponds to the loss of energy along the path. But loss of energy can also be assumed as a multiplicative process or a purely random process. The distributions of the rockfall block stop points can be deduced from such simple models, they lead to Gaussian, Inverse-Gaussian, Log-normal or exponential negative distributions. The theoretical background is presented, and the comparisons of some of these models with existing data indicate that these assumptions are relevant. The results are either based on theoretical considerations or by fitting results. They are potentially very useful for rockfall hazard zoning and risk assessment. This approach will need further investigations.

Calculating CO2 uptake for existing concrete structures during and after service life.

PubMed

Andersson, Ronny; Fridh, Katja; Stripple, Håkan; Häglund, Martin

2013-10-15

This paper presents a model that can calculate the uptake of CO2 in all existing concrete structures, including its uptake after service life. This is important for the calculation of the total CO2 uptake in the society and its time dependence. The model uses the well-documented cement use and knowledge of how the investments are distributed throughout the building sector to estimate the stock of concrete applications in a country. The depth of carbonation of these applications is estimated using two models, one theoretical and one based on field measurements. The maximum theoretical uptake potential is defined as the amount of CO2 that is emitted during calcination at the production of Portland cement, but the model can also, with some adjustments, be used for the other cement types. The model has been applied on data from Sweden and the results show a CO2 uptake in 2011 in all existing structures of about 300,000 tonnes, which corresponds to about 17% of the total emissions (calcination and fuel) from the production of new cement for use in Sweden in the same year. The study also shows that in the years 2030 and 2050, an increase in the uptake in crushed concrete, from 12,000 tonnes today to 200,000 and 500,000 tonnes of CO2, respectively, could be possible if the waste handling is redesigned.

Sustained sensorimotor control as intermittent decisions about prediction errors: computational framework and application to ground vehicle steering.

PubMed

Markkula, Gustav; Boer, Erwin; Romano, Richard; Merat, Natasha

2018-06-01

A conceptual and computational framework is proposed for modelling of human sensorimotor control and is exemplified for the sensorimotor task of steering a car. The framework emphasises control intermittency and extends on existing models by suggesting that the nervous system implements intermittent control using a combination of (1) motor primitives, (2) prediction of sensory outcomes of motor actions, and (3) evidence accumulation of prediction errors. It is shown that approximate but useful sensory predictions in the intermittent control context can be constructed without detailed forward models, as a superposition of simple prediction primitives, resembling neurobiologically observed corollary discharges. The proposed mathematical framework allows straightforward extension to intermittent behaviour from existing one-dimensional continuous models in the linear control and ecological psychology traditions. Empirical data from a driving simulator are used in model-fitting analyses to test some of the framework's main theoretical predictions: it is shown that human steering control, in routine lane-keeping and in a demanding near-limit task, is better described as a sequence of discrete stepwise control adjustments, than as continuous control. Results on the possible roles of sensory prediction in control adjustment amplitudes, and of evidence accumulation mechanisms in control onset timing, show trends that match the theoretical predictions; these warrant further investigation. The results for the accumulation-based model align with other recent literature, in a possibly converging case against the type of threshold mechanisms that are often assumed in existing models of intermittent control.

Predicting fire spread in Arizona's oak chaparral

Treesearch

A. W. Lindenmuth; James R. Davis

1973-01-01

Five existing fire models, both experimental and theoretical, did not adequately predict rate-of-spread (ROS) when tested on single- and multiclump fires in oak chaparral in Arizona. A statistical model developed using essentially the same input variables but weighted differently accounted for 81 percent ofthe variation in ROS. A chemical coefficient that accounts for...

Classifying Correlation Matrices into Relatively Homogeneous Subgroups: A Cluster Analytic Approach

ERIC Educational Resources Information Center

Cheung, Mike W.-L.; Chan, Wai

2005-01-01

Researchers are becoming interested in combining meta-analytic techniques and structural equation modeling to test theoretical models from a pool of studies. Most existing procedures are based on the assumption that all correlation matrices are homogeneous. Few studies have addressed what the next step should be when studies being analyzed are…

Reproducing (Dis)advantage: The Role of Family-Based, School-Based, and Cumulative-Based Processes

ERIC Educational Resources Information Center

Conner, Sonya

2012-01-01

Pierre Bourdieu's theory of cultural and social reproduction (Bourdieu 1973; Bourdieu and Passeron 1977) offers a model that can be used to explain the existence of persistent educational stratification in the United States, which contributes to perpetuation of social inequality, more generally. This theoretical model purports three…

Formal Models of Word Recognition. Final Report.

ERIC Educational Resources Information Center

Travers, Jeffrey R.

Existing mathematical models of word recognition are reviewed and a new theory is proposed in this research. The new theory integrates earlier proposals within a single framework, sacrificing none of the predictive power of the earlier proposals, but offering a gain in theoretical economy. The theory holds that word recognition is accomplished by…

An Alternative Theoretical Model: Examining Psychosocial Identity Development of International Students in the United States

ERIC Educational Resources Information Center

Kim, Eunyoung

2012-01-01

Despite the plethora of college student identity development research, very little attention has been paid to the identity formation of international students. Rather than adopting existing identity theories in college student development, this exploratory qualitative study proposes a new psychosocial identity development model for international…

Psychofamilial Correlates of School Disorders.

ERIC Educational Resources Information Center

Ehrlich, Marc I.

A child's school disorder can, and most often does, exist within the complexity of the family's transactional patterns and must be dealt with in this context. To do so, a conceptual model of family dynamics is needed. Minuchin (1979) offers a theoretical framework to help structure such a model. He and his colleagues identified five common…

Whither Causal Models in the Neuroscience of ADHD?

ERIC Educational Resources Information Center

Coghill, Dave; Nigg, Joel; Rothenberger, Aribert; Sonuga-Barke, Edmund; Tannock, Rosemary

2005-01-01

In this paper we examine the current status of the science of ADHD from a theoretical point of view. While the field has reached the point at which a number of causal models have been proposed, it remains some distance away from demonstrating the viability of such models empirically. We identify a number of existing barriers and make proposals as…

Flow through a very porous obstacle in a shallow channel.

PubMed

Creed, M J; Draper, S; Nishino, T; Borthwick, A G L

2017-04-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence.

The structural, connectomic and network covariance of the human brain.

PubMed

Irimia, Andrei; Van Horn, John D

2013-02-01

Though it is widely appreciated that complex structural, functional and morphological relationships exist between distinct areas of the human cerebral cortex, the extent to which such relationships coincide remains insufficiently appreciated. Here we determine the extent to which correlations between brain regions are modulated by either structural, connectomic or network-theoretic properties using a structural neuroimaging data set of magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) volumes acquired from N=110 healthy human adults. To identify the linear relationships between all available pairs of regions, we use canonical correlation analysis to test whether a statistically significant correlation exists between each pair of cortical parcels as quantified via structural, connectomic or network-theoretic measures. In addition to this, we investigate (1) how each group of canonical variables (whether structural, connectomic or network-theoretic) contributes to the overall correlation and, additionally, (2) whether each individual variable makes a significant contribution to the test of the omnibus null hypothesis according to which no correlation between regions exists across subjects. We find that, although region-to-region correlations are extensively modulated by structural and connectomic measures, there are appreciable differences in how these two groups of measures drive inter-regional correlation patterns. Additionally, our results indicate that the network-theoretic properties of the cortex are strong modulators of region-to-region covariance. Our findings are useful for understanding the structural and connectomic relationship between various parts of the brain, and can inform theoretical and computational models of cortical information processing. Published by Elsevier Inc.

Assessment of credit risk based on fuzzy relations

NASA Astrophysics Data System (ADS)

Tsabadze, Teimuraz

2017-06-01

The purpose of this paper is to develop a new approach for an assessment of the credit risk to corporate borrowers. There are different models for borrowers' risk assessment. These models are divided into two groups: statistical and theoretical. When assessing the credit risk for corporate borrowers, statistical model is unacceptable due to the lack of sufficiently large history of defaults. At the same time, we cannot use some theoretical models due to the lack of stock exchange. In those cases, when studying a particular borrower given that statistical base does not exist, the decision-making process is always of expert nature. The paper describes a new approach that may be used in group decision-making. An example of the application of the proposed approach is given.

Communication: Electron ionization of DNA bases

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

Rahman, M. A.; Krishnakumar, E., E-mail: ekkumar@tifr.res.in

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve themore » existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.« less

Theoretical investigation of aberrations upon ametropic human eyes

NASA Astrophysics Data System (ADS)

Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Baker, Kevin

2003-11-01

The human eye aberrations are important for visual acuity and ophthalmic diagnostics and surgical procedures. Reported monochromatic aberration data of the normal 20/20 human eyes are scarce. There exist even fewer reports of the relation between ametropic conditions and aberrations. We theoretically investigate the monochromatic and chromatic aberrations of human eyes for refractive errors of -10 to +10 diopters. Schematic human eye models are employed using optical design software for axial, index, and refractive types of ametropia.

Poly(ethylene oxide) Chains Are Not ``Hydrophilic'' When They Exist As Polymer Brush Chains

NASA Astrophysics Data System (ADS)

Lee, Hoyoung; Kim, Dae Hwan; Witte, Kevin N.; Ohn, Kimberly; Choi, Je; Kim, Kyungil; Meron, Mati; Lin, Binhua; Akgun, Bulent; Satija, Sushil; Won, You-Yeon

2012-02-01

By using a combined experimental and theoretical approach, a model poly(ethylene oxide) (PEO) brush system, prepared by spreading a poly(ethylene oxide)-poly(n-butyl acrylate) (PEO-PnBA) amphiphilic diblock copolymer onto an air-water interface, was investigated. The polymer segment density profiles of the PEO brush in the direction normal to the air-water interface under various grafting density conditions were determined from combined X-ray and neutron reflectivity data. In order to achieve a theoretically sound analysis of the reflectivity data, we developed a new data analysis method that uses the self-consistent field theoretical modeling as a tool for predicting expected reflectivity results for comparison with the experimental data. Using this new data analysis method, we discovered that the effective Flory-Huggins interaction parameter of the PEO brush chains is significantly greater than that corresponding to the theta condition, suggesting that contrary to what is more commonly observed for PEO in normal situations, the PEO chains are actually not ``hydrophilic'' when they exist as polymer brush chains, because of the many body interactions forced to be effective in the brush situation.

Electrical flicker-noise generated by filling and emptying of impurity states in injectors of quantum-cascade lasers

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

Yamanishi, Masamichi, E-mail: masamiya@crl.hpk.co.jp; Hirohata, Tooru; Hayashi, Syohei

2014-11-14

Free running line-widths (>100 kHz), much broader than intrinsic line-widths ∼100 Hz, of existing quantum-cascade lasers are governed by strong flicker frequency-noise originating from electrical flicker noise. Understanding of microscopic origins of the electrical flicker noises in quantum-cascade lasers is crucially important for the reduction of strength of flicker frequency-noise without assistances of any type of feedback schemes. In this article, an ad hoc model that is based on fluctuating charge-dipoles induced by electron trappings and de-trappings at indispensable impurity states in injector super-lattices of a quantum-cascade laser is proposed, developing theoretical framework based on the model. The validity of the presentmore » model is evaluated by comparing theoretical voltage-noise power spectral densities based on the model with experimental ones obtained by using mid-infrared quantum-cascade lasers with designed impurity-positioning. The obtained experimental results on flicker noises, in comparison with the theoretical ones, shed light on physical mechanisms, such as the inherent one due to impurity states in their injectors and extrinsic ones due to surface states on the ridge-walls and due to residual deep traps, for electrical flicker-noise generation in existing mid-infrared quantum-cascade lasers. It is shown theoretically that quasi-delta doping of impurities in their injectors leads to strong suppression of electrical flicker noise by minimization of the dipole length at a certain temperature, for instance ∼300 K and, in turn, is expected to result in substantial narrowing of the free running line-width down below 10 kHz.« less

Brain activity and cognition: a connection from thermodynamics and information theory

PubMed Central

Collell, Guillem; Fauquet, Jordi

2015-01-01

The connection between brain and mind is an important scientific and philosophical question that we are still far from completely understanding. A crucial point to our work is noticing that thermodynamics provides a convenient framework to model brain activity, whereas cognition can be modeled in information-theoretical terms. In fact, several models have been proposed so far from both approaches. A second critical remark is the existence of deep theoretical connections between thermodynamics and information theory. In fact, some well-known authors claim that the laws of thermodynamics are nothing but principles in information theory. Unlike in physics or chemistry, a formalization of the relationship between information and energy is currently lacking in neuroscience. In this paper we propose a framework to connect physical brain and cognitive models by means of the theoretical connections between information theory and thermodynamics. Ultimately, this article aims at providing further insight on the formal relationship between cognition and neural activity. PMID:26136709

The MIKS (Member Integrated Knowledge System) Model: A Visualization of the Individual Organizational Member's Role When a Knowledge Management System Is Utilized in the Learning Organization

ERIC Educational Resources Information Center

Grobmeier, Cynthia

2007-01-01

Relating knowledge management (KM) case studies in various organizational contexts to existing theoretical constructs of learning organizations, a new model, the MIKS (Member Integrated Knowledge System) Model is proposed to include the role of the individual in the process. Their degree of motivation as well as communication and learning…

A Unified Framework for Analyzing and Designing for Stationary Arterial Networks

DOT National Transportation Integrated Search

2017-05-17

This research aims to develop a unified theoretical and simulation framework for analyzing and designing signals for stationary arterial networks. Existing traffic flow models used in design and analysis of signal control strategies are either too si...

Models, Their Application, and Scientific Anticipation: Ludwig Boltzmann's Work as Tacit Knowing

ERIC Educational Resources Information Center

Schmitt, Richard Henry

2011-01-01

Ludwig Boltzmann's work in theoretical physics exhibits an approach to the construction of theory that he transmitted to the succeeding generation by example. It involved the construction of clear models, allowed more than one, and was not based solely on the existing facts, with the intent of examining and criticizing the assumptions that made…

The Attributive Theory of Quality: A Model for Quality Measurement in Higher Education.

ERIC Educational Resources Information Center

Afshar, Arash

A theoretical basis for defining and measuring the quality of institutions of higher education, namely for accreditation purposes, is developed. The theory, the Attributive Theory of Quality, is illustrated using a calculation model that is based on general systems theory. The theory postulates that quality only exists in relation to the…

The Dubious Benefits of Multi-Level Modeling

ERIC Educational Resources Information Center

Gorard, Stephen

2007-01-01

This paper presents an argument against the wider adoption of complex forms of data analysis, using multi-level modeling (MLM) as an extended case study. MLM was devised to overcome some deficiencies in existing datasets, such as the bias caused by clustering. The paper suggests that MLM has an unclear theoretical and empirical basis, has not led…

Self-Regulation, Coregulation, and Socially Shared Regulation: Exploring Perspectives of Social in Self-Regulated Learning Theory

ERIC Educational Resources Information Center

Hadwin, Allyson; Oshige, Mika

2011-01-01

Background/Context: Models of self-regulated learning (SRL) have increasingly acknowledged aspects of social context influence in its process; however, great diversity exists in the theoretical positioning of "social" in these models. Purpose/Objective/Research Question/Focus of Study: The purpose of this review article is to introduce and…

Modeling relationships between landscape-level attributes and snorkel counts of chinook salmon and steelhead parr in Idaho

Treesearch

William L. Thompson; Danny C. Lee

2000-01-01

Knowledge of environmental factors impacting anadromous salmonids in their freshwater habitats, particularly at large spatial scales, may be important for restoring them to previously recorded levels in the northwestern United States. Consequently, we used existing data sets and an information-theoretic approach to model landscape-level attributes and snorkel count...

An investigation of interface transferring mechanism of surface-bonded fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Wu, Rujun; Fu, Kunkun; Chen, Tian

2017-08-01

Surface-bonded fiber Bragg grating sensor has been widely used in measuring strain in materials. The existence of fiber Bragg grating sensor affects strain distribution of the host material, which may result in a decrease in strain measurement accuracy. To improve the measurement accuracy, a theoretical model of strain transfer from the host material to optical fiber was developed, incorporating the influence of the fiber Bragg grating sensor. Subsequently, theoretical predictions were validated by comparing with data from finite element analysis and the existing experiment [F. Ansari and Y. Libo, J. Eng. Mech. 124(4), 385-394 (1998)]. Finally, the effect of parameters of fiber Bragg grating sensors on the average strain transfer rate was discussed.

Developing rural palliative care: validating a conceptual model.

PubMed

Kelley, Mary Lou; Williams, Allison; DeMiglio, Lily; Mettam, Hilary

2011-01-01

The purpose of this research was to validate a conceptual model for developing palliative care in rural communities. This model articulates how local rural healthcare providers develop palliative care services according to four sequential phases. The model has roots in concepts of community capacity development, evolves from collaborative, generalist rural practice, and utilizes existing health services infrastructure. It addresses how rural providers manage challenges, specifically those related to: lack of resources, minimal community understanding of palliative care, health professionals' resistance, the bureaucracy of the health system, and the obstacles of providing services in rural environments. Seven semi-structured focus groups were conducted with interdisciplinary health providers in 7 rural communities in two Canadian provinces. Using a constant comparative analysis approach, focus group data were analyzed by examining participants' statements in relation to the model and comparing emerging themes in the development of rural palliative care to the elements of the model. The data validated the conceptual model as the model was able to theoretically predict and explain the experiences of the 7 rural communities that participated in the study. New emerging themes from the data elaborated existing elements in the model and informed the requirement for minor revisions. The model was validated and slightly revised, as suggested by the data. The model was confirmed as being a useful theoretical tool for conceptualizing the development of rural palliative care that is applicable in diverse rural communities.

Design and Characterization of a Microfabricated Hydrogen Clearance Blood Flow Sensor

PubMed Central

Walton, Lindsay R.; Edwards, Martin A.; McCarty, Gregory S.; Wightman, R. Mark

2016-01-01

Background Modern cerebral blood flow (CBF) detection favors the use of either optical technologies that are limited to cortical brain regions, or expensive magnetic resonance. Decades ago, inhalation gas clearance was the choice method of quantifying CBF, but this suffered from poor temporal resolution. Electrolytic H2 clearance (EHC) generates and collects gas in situ at an electrode pair, which improves temporal resolution, but the probe size has prohibited meaningful subcortical use. New Method We microfabricated EHC electrodes to an order of magnitude smaller than those existing, on the scale of 100 µm, to permit use deep within the brain. Results Novel EHC probes were fabricated. The devices offered exceptional signal-to-noise, achieved high collection efficiencies (40 – 50%) in vitro, and agreed with theoretical modeling. An in vitro chemical reaction model was used to confirm that our devices detected flow rates higher than those expected physiologically. Computational modeling that incorporated realistic noise levels demonstrated devices would be sensitive to physiological CBF rates. Comparison with Existing Method The reduced size of our arrays makes them suitable for subcortical EHC measurements, as opposed to the larger, existing EHC electrodes that would cause substantial tissue damage. Our array can collect multiple CBF measurements per minute, and can thus resolve physiological changes occurring on a shorter timescale than existing gas clearance measurements. Conclusion We present and characterize microfabricated EHC electrodes and an accompanying theoretical model to interpret acquired data. Microfabrication allows for the high-throughput production of reproducible devices that are capable of monitoring deep brain CBF with sub-minute resolution. PMID:27102042

Comparison of analytical and experimental subsonic steady and unsteady pressure distributions for a high-aspect-ratio-supercritical wing model with oscillating control surfaces

NASA Technical Reports Server (NTRS)

Mccain, W. E.

1982-01-01

The results of a comparative study using the unsteady aerodynamic lifting surface theory, known as the Doublet Lattice method, and experimental subsonic steady- and unsteady-pressure measurements, are presented for a high-aspect-ratio supercritical wing model. Comparisons of pressure distributions due to wing angle of attack and control-surface deflections were made. In general, good correlation existed between experimental and theoretical data over most of the wing planform. The more significant deviations found between experimental and theoretical data were in the vicinity of control surfaces for both static and oscillatory control-surface deflections.

Modelling body weight, dieting and obesity traps

NASA Astrophysics Data System (ADS)

Barbieri, Paolo Nicola

2017-02-01

This paper presents a theoretical investigation into why losing weight is so difficult even in the absence of rational addiction, time-inconsistent preferences or bounded rationality. We add to the existing literature by focusing on the role that individual metabolism has on weight loss. The results from the theoretical model provide multiple steady states and a threshold revealing a situation of "obesity traps" that the individual must surpass in order to successfully lose weight. Any weight-loss efforts that the individual undertakes have to surpass such threshold in order to result in permanent weight loss, otherwise the individual will gradually regain weight and converge to his or her previous body weight.

Theoretical and material studies on thin-film electroluminescent devices

NASA Technical Reports Server (NTRS)

Summers, C. J.; Brennan, K. F.

1986-01-01

A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed.

Estimation of whole lemon mass transfer parameters during hot air drying using different modelling methods

NASA Astrophysics Data System (ADS)

Torki-Harchegani, Mehdi; Ghanbarian, Davoud; Sadeghi, Morteza

2015-08-01

To design new dryers or improve existing drying equipments, accurate values of mass transfer parameters is of great importance. In this study, an experimental and theoretical investigation of drying whole lemons was carried out. The whole lemons were dried in a convective hot air dryer at different air temperatures (50, 60 and 75 °C) and a constant air velocity (1 m s-1). In theoretical consideration, three moisture transfer models including Dincer and Dost model, Bi- G correlation approach and conventional solution of Fick's second law of diffusion were used to determine moisture transfer parameters and predict dimensionless moisture content curves. The predicted results were then compared with the experimental data and the higher degree of prediction accuracy was achieved by the Dincer and Dost model.

Shifting attention from objective risk factors to patients' self-assessed health resources: a clinical model for general practice.

PubMed

Hollnagel, H; Malterud, K

1995-12-01

The study was designed to present and apply theoretical and empirical knowledge for the construction of a clinical model intended to shift the attention of the general practitioner from objective risk factors to self-assessed health resources in male and female patients. Review, discussion and analysis of selected theoretical models about personal health resources involving assessing existing theories according to their emphasis concerning self-assessed vs. doctor-assessed health resources, specific health resources vs. life and coping in general, abstract vs. clinically applicable theory, gender perspective explicitly included or not. Relevant theoretical models on health and coping (salutogenesis, coping and social support, control/demand, locus of control, health belief model, quality of life), and the perspective of the underprivileged Other (critical theory, feminist standpoint theory, the patient-centred clinical method) were presented and assessed. Components from Antonovsky's salutogenetic perspective and McWhinney's patient-centred clinical method, supported by gender perspectives, were integrated to a clinical model which is presented. General practitioners are recommended to shift their attention from objective risk factors to self-assessed health resources by means of the clinical model. The relevance and feasibility of the model should be explored in empirical research.

Stratification established by peeling detrainment from gravity currents: laboratory experiments and models

NASA Astrophysics Data System (ADS)

Hogg, Charlie; Dalziel, Stuart; Huppert, Herbert; Imberger, Jorg; Department of Applied Mathematics; Theoretical Physics Team; CentreWater Research Team

2014-11-01

Dense gravity currents feed fluid into confined basins in lakes, the oceans and many industrial applications. Existing models of the circulation and mixing in such basins are often based on the currents entraining ambient fluid. However, recent observations have suggested that uni-directional entrainment into a gravity current does not fully describe the mixing in such currents. Laboratory experiments were carried out which visualised peeling detrainment from the gravity current occurring when the ambient fluid was stratified. A theoretical model of the observed peeling detrainment was developed to predict the stratification in the basin. This new model gives a better approximation of the stratification observed in the experiments than the pre-existing entraining model. The model can now be developed such that it integrates into operational models of lakes.

Towards a feminist empowerment model of forgiveness psychotherapy.

PubMed

McKay, Kevin M; Hill, Melanie S; Freedman, Suzanne R; Enright, Robert D

2007-03-01

In recent years Enright and Fitzgibbon's (2000) process model of forgiveness therapy has received substantial theoretical and empirical attention. However, both the process model of forgiveness therapy and the social-cognitive developmental model on which it is based have received criticism from feminist theorists. The current paper considers feminist criticisms of forgiveness therapy and uses a feminist lens to identify potential areas for growth. Specifically, Worell and Remer's (2003) model of synthesizing feminist ideals into existing theory was consulted, areas of bias within the forgiveness model of psychotherapy were identified, and strategies for restructuring areas of potential bias were introduced. Further, the authors consider unique aspects of forgiveness therapy that can potentially strengthen existing models of feminist therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved).

Flow through a very porous obstacle in a shallow channel

PubMed Central

Draper, S.; Nishino, T.; Borthwick, A. G. L.

2017-01-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence. PMID:28484321

Mathematical Analysis of an Epidemic System in the Presence of Optimal Control and Population Dispersal

NASA Astrophysics Data System (ADS)

Nandi, Swapan Kumar; Jana, Soovoojeet; Mandal, Manotosh; Kar, T. K.

In this paper, we proposed and analyzed a susceptible-infected-recovered (SIR) type epidemic model to investigate the effect of transport-related infectious diseases namely tuberculosis, measles, rubella, influenza, sexually transmitted diseases, etc. The existence and stability criteria of both the diseases include free equilibrium point and endemic equilibrium point which are established and the threshold parametric condition for which the system passes through a transcritical bifurcation is also obtained. Optimal control strategy for control parameters is formulated and solved both theoretically and numerically. Lastly, we not only illustrate our theoretical results through graphical illustrations but also computer simulation is used to show that our model would be a good model to study the SARS epidemic in 2003.

Poisson's spot and Gouy phase

NASA Astrophysics Data System (ADS)

da Paz, I. G.; Soldati, Rodolfo; Cabral, L. A.; de Oliveira, J. G. G.; Sampaio, Marcos

2016-12-01

Recently there have been experimental results on Poisson spot matter-wave interferometry followed by theoretical models describing the relative importance of the wave and particle behaviors for the phenomenon. We propose an analytical theoretical model for Poisson's spot with matter waves based on the Babinet principle, in which we use the results for free propagation and single-slit diffraction. We take into account effects of loss of coherence and finite detection area using the propagator for a quantum particle interacting with an environment. We observe that the matter-wave Gouy phase plays a role in the existence of the central peak and thus corroborates the predominantly wavelike character of the Poisson's spot. Our model shows remarkable agreement with the experimental data for deuterium (D2) molecules.

A brief review on relaxor ferroelectrics and selected issues in lead-free relaxors

NASA Astrophysics Data System (ADS)

Ahn, Chang Won; Hong, Chang-Hyo; Choi, Byung-Yul; Kim, Hwang-Pill; Han, Hyoung-Su; Hwang, Younghun; Jo, Wook; Wang, Ke; Li, Jing-Feng; Lee, Jae-Shin; Kim, Ill Won

2016-06-01

Relaxor ferroelectricity is one of the most widely investigated but the least understood material classes in the condensed matter physics. This is largely due to the lack of experimental tools that decisively confirm the existing theoretical models. In spite of the diversity in the models, they share the core idea that the observed features in relaxors are closely related to localized chemical heterogeneity. Given this, this review attempts to overview the existing models of importance chronologically, from the diffuse phase transition model to the random-field model and to show how the core idea has been reflected in them to better shape our insight into the nature of relaxor-related phenomena. Then, the discussion will be directed to how the models of a common consensus, developed with the so-called canonical relaxors such as Pb(Mg1/3Nb2/3)O3 (PMN) and (Pb, La)(Zr, Ti)O3 (PLZT), are compatible with phenomenological explanations for the recently identified relaxors such as (Bi1/2Na1/2)TiO3 (BNT)-based lead-free ferroelectrics. This review will be finalized with a discussion on the theoretical aspects of recently introduced 0-3 and 2-2 ferroelectric/relaxor composites as a practical tool for strain engineering.

Theoretical and experimental investigation of architected core materials incorporating negative stiffness elements

NASA Astrophysics Data System (ADS)

Chang, Chia-Ming; Keefe, Andrew; Carter, William B.; Henry, Christopher P.; McKnight, Geoff P.

2014-04-01

Structural assemblies incorporating negative stiffness elements have been shown to provide both tunable damping properties and simultaneous high stiffness and damping over prescribed displacement regions. In this paper we explore the design space for negative stiffness based assemblies using analytical modeling combined with finite element analysis. A simplified spring model demonstrates the effects of element stiffness, geometry, and preloads on the damping and stiffness performance. Simplified analytical models were validated for realistic structural implementations through finite element analysis. A series of complementary experiments was conducted to compare with modeling and determine the effects of each element on the system response. The measured damping performance follows the theoretical predictions obtained by analytical modeling. We applied these concepts to a novel sandwich core structure that exhibited combined stiffness and damping properties 8 times greater than existing foam core technologies.

Socio-Economic Factors Affecting Adoption of Modern Information and Communication Technology by Farmers in India: Analysis Using Multivariate Probit Model

ERIC Educational Resources Information Center

Mittal, Surabhi; Mehar, Mamta

2016-01-01

Purpose: The paper analyzes factors that affect the likelihood of adoption of different agriculture-related information sources by farmers. Design/Methodology/Approach: The paper links the theoretical understanding of the existing multiple sources of information that farmers use, with the empirical model to analyze the factors that affect the…

Dynamics of an advertising competition model with sales promotion

NASA Astrophysics Data System (ADS)

Jiang, Hui; Feng, Zhaosheng; Jiang, Guirong

2017-01-01

In this paper, an advertising competition model with sales promotion is constructed and investigated. Conditions of the existence and stability of period-T solutions are obtained by means of the discrete map. Flip bifurcation is analyzed by using the center manifold theory and three sales promotion strategies are discussed. Example and numerical simulations are illustrated which agree well with our theoretical analysis.

Analytical Investigation and Improvement of Performance of a Proton Exchange Membrane (Pem) Fuel Cell in Mobile Applications

NASA Astrophysics Data System (ADS)

Khazaee, I.

2015-05-01

In this study, the performance of a proton exchange membrane fuel cell in mobile applications is investigated analytically. At present the main use and advantages of fuel cells impact particularly strongly on mobile applications such as vehicles, mobile computers and mobile telephones. Some external parameters such as the cell temperature (Tcell ) , operating pressure of gases (P) and air stoichiometry (λair ) affect the performance and voltage losses in the PEM fuel cell. Because of the existence of many theoretical, empirical and semi-empirical models of the PEM fuel cell, it is necessary to compare the accuracy of these models. But theoretical models that are obtained from thermodynamic and electrochemical approach, are very exact but complex, so it would be easier to use the empirical and smi-empirical models in order to forecast the fuel cell system performance in many applications such as mobile applications. The main purpose of this study is to obtain the semi-empirical relation of a PEM fuel cell with the least voltage losses. Also, the results are compared with the existing experimental results in the literature and a good agreement is seen.

Noninformative prior in the quantum statistical model of pure states

NASA Astrophysics Data System (ADS)

Tanaka, Fuyuhiko

2012-06-01

In the present paper, we consider a suitable definition of a noninformative prior on the quantum statistical model of pure states. While the full pure-states model is invariant under unitary rotation and admits the Haar measure, restricted models, which we often see in quantum channel estimation and quantum process tomography, have less symmetry and no compelling rationale for any choice. We adopt a game-theoretic approach that is applicable to classical Bayesian statistics and yields a noninformative prior for a general class of probability distributions. We define the quantum detection game and show that there exist noninformative priors for a general class of a pure-states model. Theoretically, it gives one of the ways that we represent ignorance on the given quantum system with partial information. Practically, our method proposes a default distribution on the model in order to use the Bayesian technique in the quantum-state tomography with a small sample.

Consistency of Cluster Analysis for Cognitive Diagnosis: The Reduced Reparameterized Unified Model and the General Diagnostic Model.

PubMed

Chiu, Chia-Yi; Köhn, Hans-Friedrich

2016-09-01

The asymptotic classification theory of cognitive diagnosis (ACTCD) provided the theoretical foundation for using clustering methods that do not rely on a parametric statistical model for assigning examinees to proficiency classes. Like general diagnostic classification models, clustering methods can be useful in situations where the true diagnostic classification model (DCM) underlying the data is unknown and possibly misspecified, or the items of a test conform to a mix of multiple DCMs. Clustering methods can also be an option when fitting advanced and complex DCMs encounters computational difficulties. These can range from the use of excessive CPU times to plain computational infeasibility. However, the propositions of the ACTCD have only been proven for the Deterministic Input Noisy Output "AND" gate (DINA) model and the Deterministic Input Noisy Output "OR" gate (DINO) model. For other DCMs, there does not exist a theoretical justification to use clustering for assigning examinees to proficiency classes. But if clustering is to be used legitimately, then the ACTCD must cover a larger number of DCMs than just the DINA model and the DINO model. Thus, the purpose of this article is to prove the theoretical propositions of the ACTCD for two other important DCMs, the Reduced Reparameterized Unified Model and the General Diagnostic Model.

Conceptualising paediatric health disparities: a metanarrative systematic review and unified conceptual framework.

PubMed

Ridgeway, Jennifer L; Wang, Zhen; Finney Rutten, Lila J; van Ryn, Michelle; Griffin, Joan M; Murad, M Hassan; Asiedu, Gladys B; Egginton, Jason S; Beebe, Timothy J

2017-08-04

There exists a paucity of work in the development and testing of theoretical models specific to childhood health disparities even though they have been linked to the prevalence of adult health disparities including high rates of chronic disease. We conducted a systematic review and thematic analysis of existing models of health disparities specific to children to inform development of a unified conceptual framework. We systematically reviewed articles reporting theoretical or explanatory models of disparities on a range of outcomes related to child health. We searched Ovid Medline In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus (database inception to 9 July 2015). A metanarrative approach guided the analysis process. A total of 48 studies presenting 48 models were included. This systematic review found multiple models but no consensus on one approach. However, we did discover a fair amount of overlap, such that the 48 models reviewed converged into the unified conceptual framework. The majority of models included factors in three domains: individual characteristics and behaviours (88%), healthcare providers and systems (63%), and environment/community (56%), . Only 38% of models included factors in the health and public policies domain. A disease-agnostic unified conceptual framework may inform integration of existing knowledge of child health disparities and guide future research. This multilevel framework can focus attention among clinical, basic and social science research on the relationships between policy, social factors, health systems and the physical environment that impact children's health outcomes. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Modeling of information diffusion in Twitter-like social networks under information overload.

PubMed

Li, Pei; Li, Wei; Wang, Hui; Zhang, Xin

2014-01-01

Due to the existence of information overload in social networks, it becomes increasingly difficult for users to find useful information according to their interests. This paper takes Twitter-like social networks into account and proposes models to characterize the process of information diffusion under information overload. Users are classified into different types according to their in-degrees and out-degrees, and user behaviors are generalized into two categories: generating and forwarding. View scope is introduced to model the user information-processing capability under information overload, and the average number of times a message appears in view scopes after it is generated by a given type user is adopted to characterize the information diffusion efficiency, which is calculated theoretically. To verify the accuracy of theoretical analysis results, we conduct simulations and provide the simulation results, which are consistent with the theoretical analysis results perfectly. These results are of importance to understand the diffusion dynamics in social networks, and this analysis framework can be extended to consider more realistic situations.

Affectionate Touch to Promote Relational, Psychological, and Physical Well-Being in Adulthood: A Theoretical Model and Review of the Research.

PubMed

Jakubiak, Brittany K; Feeney, Brooke C

2017-08-01

Throughout the life span, individuals engage in affectionate touch with close others. Touch receipt promotes well-being in infancy, but the impacts of touch in adult close relationships have been largely unexplored. In this article, we propose that affectionate touch receipt promotes relational, psychological, and physical well-being in adulthood, and we present a theoretical mechanistic model to explain why affectionate touch may promote these outcomes. The model includes pathways through which touch could affect well-being by reducing stress and by promoting well-being independent of stress. Specifically, two immediate outcomes of affectionate touch receipt-relational-cognitive changes and neurobiological changes-are described as important mechanisms underlying the effects of affectionate touch on well-being. We also review and evaluate the existing research linking affectionate touch to well-being in adulthood and propose an agenda to advance research in this area. This theoretical perspective provides a foundation for future work on touch in adult close relationships.

Modeling of Information Diffusion in Twitter-Like Social Networks under Information Overload

PubMed Central

Li, Wei

2014-01-01

Due to the existence of information overload in social networks, it becomes increasingly difficult for users to find useful information according to their interests. This paper takes Twitter-like social networks into account and proposes models to characterize the process of information diffusion under information overload. Users are classified into different types according to their in-degrees and out-degrees, and user behaviors are generalized into two categories: generating and forwarding. View scope is introduced to model the user information-processing capability under information overload, and the average number of times a message appears in view scopes after it is generated by a given type user is adopted to characterize the information diffusion efficiency, which is calculated theoretically. To verify the accuracy of theoretical analysis results, we conduct simulations and provide the simulation results, which are consistent with the theoretical analysis results perfectly. These results are of importance to understand the diffusion dynamics in social networks, and this analysis framework can be extended to consider more realistic situations. PMID:24795541

A Mathematical Model for the Middle Ear Ventilation

NASA Astrophysics Data System (ADS)

Molnárka, G.; Miletics, E. M.; Fücsek, M.

2008-09-01

The otitis media is one of the mostly existing illness for the children, therefore investigation of the human middle ear ventilation is an actual problem. In earlier investigations both experimental and theoretical approach one can find in ([l]-[3]). Here we give a new mathematical and computer model to simulate this ventilation process. This model able to describe the diffusion and flow processes simultaneously, therefore it gives more precise results than earlier models did. The article contains the mathematical model and some results of the simulation.

A new theoretical approach to analyze complex processes in cytoskeleton proteins.

PubMed

Li, Xin; Kolomeisky, Anatoly B

2014-03-20

Cytoskeleton proteins are filament structures that support a large number of important biological processes. These dynamic biopolymers exist in nonequilibrium conditions stimulated by hydrolysis chemical reactions in their monomers. Current theoretical methods provide a comprehensive picture of biochemical and biophysical processes in cytoskeleton proteins. However, the description is only qualitative under biologically relevant conditions because utilized theoretical mean-field models neglect correlations. We develop a new theoretical method to describe dynamic processes in cytoskeleton proteins that takes into account spatial correlations in the chemical composition of these biopolymers. Our approach is based on analysis of probabilities of different clusters of subunits. It allows us to obtain exact analytical expressions for a variety of dynamic properties of cytoskeleton filaments. By comparing theoretical predictions with Monte Carlo computer simulations, it is shown that our method provides a fully quantitative description of complex dynamic phenomena in cytoskeleton proteins under all conditions.

A common ground in clinical discussion groups: Intersubjective resonance and implicit operational theories.

PubMed

Bernardi, Ricardo

2017-10-01

Clinical discussion groups based on the Three-Level Model for Observing Patient Transformations (3-LM) enable us to reflect on the clinical common ground shared by psychoanalysts who have different theoretical frameworks. The very existence of this common ground is controversial. While analysts such as Wallerstein support it, others, like Green, think it is just a myth. In their 2005 controversy Wallerstein and Green proposed an observation procedure that might clarify this matter. This procedure bears great similarity to the one used by clinical discussion groups that apply the 3-LM. The study of numerous theoretically heterogeneous groups that use this model shows that communication is possible in crucial areas. We may thus conclude that a partial and dynamic common ground exists. At a phenomenological level, certain fragments of material produce a shared resonance that enriches clinical understanding for the whole group. Communication is also possible with regard to the conceptualization of patient changes, although some controversial issues persist at this level. Finally, at the level of theoretical explanations, divergences concerning abstract theories do not prevent a fertile interaction among 'in vivo' personal implicit theories. The latter give rise to the actual operational frameworks underlying participants' approach to clinical problems. Copyright © 2017 Institute of Psychoanalysis.

Public Management Information Systems: Theory and Prescription.

ERIC Educational Resources Information Center

Bozeman, Barry; Bretschneider, Stuart

1986-01-01

The existing theoretical framework for research in management information systems (MIS) is criticized for its lack of attention to the external environment of organizations, and a new framework is developed which better accommodates MIS in public organizations: public management information systems. Four models of publicness that reflect external…

Applied Computational Chemistry for the Blind and Visually Impaired

ERIC Educational Resources Information Center

Wedler, Henry B.; Cohen, Sarah R.; Davis, Rebecca L.; Harrison, Jason G.; Siebert, Matthew R.; Willenbring, Dan; Hamann, Christian S.; Shaw, Jared T.; Tantillo, Dean J.

2012-01-01

We describe accommodations that we have made to our applied computational-theoretical chemistry laboratory to provide access for blind and visually impaired students interested in independent investigation of structure-function relationships. Our approach utilizes tactile drawings, molecular model kits, existing software, Bash and Perl scripts…

Conceptualizing Programme Evaluation

ERIC Educational Resources Information Center

Hassan, Salochana

2013-01-01

The main thrust of this paper deals with the conceptualization of theory-driven evaluation pertaining to a tutor training programme. Conceptualization of evaluation, in this case, is an integration between a conceptualization model as well as a theoretical framework in the form of activity theory. Existing examples of frameworks of programme…

Probing dark matter physics with galaxy clusters

NASA Astrophysics Data System (ADS)

Dalal, Neal

2016-10-01

We propose a theoretical investigation of the effects of a class of dark matter (DM) self-interactions on the properties of galaxy clusters and their host dark matter halos. Recent work using HST has claimed the detection of a particular form of DM self-interaction, which can lead to observable displacements between satellite galaxies within clusters and the DM subhalos hosting them. This form of self-interaction is highly anisotropic, favoring forward scattering with low momentum transfer, unlike isotropically scattering self-interacting dark matter (SIDM) models. This class of models has not been simulated numerically, clouding the interpretation of the claimed offsets between galaxies and lensing peaks observed by HST. We propose to perform high resolution simulations of cosmological structure formation for this class of SIDM model, focusing on three observables accessible to existing HST observations of clusters. First, we will quantify the extent to which offsets between baryons and DM can arise in these models, as a function of the cross section. Secondly, we will also quantify the effects of this type of DM self-interaction on halo concentrations, to determine the range of cross-sections allowed by existing stringent constraints from HST. Finally we will compute the so-called splashback feature in clusters, specifically focusing on whether SIDM can resolve the current discrepancy between observed values of splashback radii in clusters compared to theoretical predictions for CDM. The proposed investigations will add value to all existing deep HST observations of galaxy clusters by allowing them to probe dark matter physics in three independent ways.

Theory and practice in sport psychology and motor behaviour needs to be constrained by integrative modelling of brain and behaviour.

PubMed

Keil, D; Holmes, P; Bennett, S; Davids, K; Smith, N

2000-06-01

Because of advances in technology, the non-invasive study of the human brain has enhanced the knowledge base within the neurosciences, resulting in an increased impact on the psychological study of human behaviour. We argue that application of this knowledge base should be considered in theoretical modelling within sport psychology and motor behaviour alongside existing ideas. We propose that interventions founded on current theoretical and empirical understanding in both psychology and the neurosciences may ultimately lead to greater benefits for athletes during practice and performance. As vehicles for exploring the arguments of a greater integration of psychology and neurosciences research, imagery and perception-action within the sport psychology and motor behaviour domains will serve as exemplars. Current neuroscience evidence will be discussed in relation to theoretical developments; the implications for sport scientists will be considered.

Finding myself: a theory on the maturation of spirituality and its influence on behavior during late adolescence.

PubMed

Mason, Deanna M

2014-01-01

This study employed a grounded theory research design to develop a theoretical model focused on the maturation of spirituality and its influence on behavior during late adolescence. Quantitative research studies have linked spirituality with decreased health-risk behaviors and increased health-promotion behaviors during late adolescence. Qualitative, theoretical data is proposed to discover the underlying reasons this relationship exists and increase the ability to apply this knowledge to practice. Twenty-one adolescents, age 16-21 years, were e-mail interviewed and transcripts analyzed using a conceptual lens of Blumer's symbolic interactionism. From this analysis, a theoretical model emerged with the core concept, finding myself that represents 5 core process concepts. Implications of this study illustrate that late adolescents are aware of their personal spiritual maturation as well as its influence on behavior. In addition, a distinction between the generic concept of spirituality, personal spirituality, and religion emerged.

Understanding HIV disclosure: A review and application of the Disclosure Processes Model

PubMed Central

Chaudoir, Stephenie R.; Fisher, Jeffrey D.; Simoni, Jane M.

2014-01-01

HIV disclosure is a critical component of HIV/AIDS prevention and treatment efforts, yet the field lacks a comprehensive theoretical framework with which to study how HIV-positive individuals make decisions about disclosing their serostatus and how these decisions affect them. Recent theorizing in the context of the Disclosure Processes Model has suggested that the disclosure process consists of antecedent goals, the disclosure event itself, mediating processes and outcomes, and a feedback loop. In this paper, we apply this new theoretical framework to HIV disclosure in order to review the current state of the literature, identify gaps in existing research, and highlight the implications of the framework for future work in this area. PMID:21514708

Dynamics of a Class of HIV Infection Models with Cure of Infected Cells in Eclipse Stage.

PubMed

Maziane, Mehdi; Lotfi, El Mehdi; Hattaf, Khalid; Yousfi, Noura

2015-12-01

In this paper, we propose two HIV infection models with specific nonlinear incidence rate by including a class of infected cells in the eclipse phase. The first model is described by ordinary differential equations (ODEs) and generalizes a set of previously existing models and their results. The second model extends our ODE model by taking into account the diffusion of virus. Furthermore, the global stability of both models is investigated by constructing suitable Lyapunov functionals. Finally, we check our theoretical results with numerical simulations.

Understanding sport continuation: an integration of the theories of planned behaviour and basic psychological needs.

PubMed

Gucciardi, Daniel F; Jackson, Ben

2015-01-01

Fostering individuals' long-term participation in activities that promote positive development such as organised sport is an important agenda for research and practice. We integrated the theories of planned behaviour (TPB) and basic psychological needs (BPN) to identify factors associated with young adults' continuation in organised sport over a 12-month period. Prospective study, including an online psycho-social assessment at Time 1 and an assessment of continuation in sport approximately 12 months later. Participants (N=292) aged between 17 and 21 years (M=18.03; SD=1.29) completed an online survey assessing the theories of planned behaviour and basic psychological needs constructs. Bayesian structural equation modelling (BSEM) was employed to test the hypothesised theoretical sequence, using informative priors for structural relations based on empirical and theoretical expectations. The analyses revealed support for the robustness of the hypothesised theoretical model in terms of the pattern of relations as well as the direction and strength of associations among the constructs derived from quantitative summaries of existing research and theoretical expectations. The satisfaction of basic psychological needs was associated with more positive attitudes, higher levels of perceived behavioural control, and more favourable subjective norms; positive attitudes and perceived behavioural control were associated with higher behavioural intentions; and both intentions and perceived behavioural control predicted sport continuation. This study demonstrated the utility of Bayesian structural equation modelling for testing the robustness of an integrated theoretical model, which is informed by empirical evidence from meta-analyses and theoretical expectations, for understanding sport continuation. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction.

PubMed

Verma, Shwetabh; Hesser, Juergen; Arba-Mosquera, Samuel

2017-04-01

Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser-based vision correction. The purpose of the study was to outline a rigorous simulation model for simulating shot-by-shot ablation process. The impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap, and lattice geometry were tested on ablation smoothness. Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or polymethylmethacrylate [PMMA]). The roughness in ablation was determined by the root-mean-square per square root of layer depth. Truncating the beam profile increases the roughness in ablation, Gaussian profiles theoretically result in smoother ablations, round spot geometries produce lower roughness in ablation compared to square geometry, triangular lattices theoretically produce lower roughness in ablation compared to the reticular lattice, theoretically modeled beam profiles show lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tends to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness have been found. Theoretically, the proposed model can be used for achieving smoothness with laser systems used for ablation processes at relatively low cost. This model may improve the quality of results and could be directly applied for improving postoperative surface quality.

Anatomy of point-contact Andreev reflection spectroscopy from the experimental point of view

NASA Astrophysics Data System (ADS)

Naidyuk, Yu. G.; Gloos, K.

2018-04-01

We review applications of point-contact Andreev-reflection spectroscopy to study elemental superconductors, where theoretical conditions for the smallness of the point-contact size with respect to the characteristic lengths in the superconductor can be satisfied. We discuss existing theoretical models and identify new issues that have to be solved, especially when applying this method to investigate more complex superconductors. We will also demonstrate that some aspects of point-contact Andreev-reflection spectroscopy still need to be addressed even when investigating ordinary metals.

Observation of interface carrier states in no-common-atom heterostructures ZnSe/BeTe.

PubMed

Gurevich, A S; Kochereshko, V P; Bleuse, J; Mariette, H; Waag, A; Akimoto, R

2011-09-07

The existence of intrinsic carrier interface states in heterostructures with no common atom at the interface (such as ZnSe/BeTe) is shown experimentally by ellipsometry and photoluminescence spectroscopy. These states are located on interfaces and lie inside the effective bandgap of the structure; they are characterized by a high density and a long lifetime. A tight binding model confirms theoretically the existence of these states in ZnSe/BeTe heterostructures for a ZnTe-type interface, in contrast to the case of the BeSe-type interface for which they do not exist.

Observation of interface carrier states in no-common-atom heterostructures ZnSe/BeTe

NASA Astrophysics Data System (ADS)

Gurevich, A. S.; Kochereshko, V. P.; Bleuse, J.; Mariette, H.; Waag, A.; Akimoto, R.

2011-09-01

The existence of intrinsic carrier interface states in heterostructures with no common atom at the interface (such as ZnSe/BeTe) is shown experimentally by ellipsometry and photoluminescence spectroscopy. These states are located on interfaces and lie inside the effective bandgap of the structure; they are characterized by a high density and a long lifetime. A tight binding model confirms theoretically the existence of these states in ZnSe/BeTe heterostructures for a ZnTe-type interface, in contrast to the case of the BeSe-type interface for which they do not exist.

The search for new resonances in strong symmetry breaking scenarios with the ATLAS detector

NASA Astrophysics Data System (ADS)

Davies, Merlin

Using the most recent data collected by the ATLAS detector in pp collisions delivered by the LHC at 7 and 8 TeV, this thesis shall establish severe constraints on a variety of models going beyond the Standard Model (SM) of particle physics. More particularly, two types of hypothetical particles, existing in various theoretical models shall be studied and probed. The first type will be the search for vector-like quarks (VLQ) produced in pp collisions through electroweak couplings with the u and d quarks. The quest for these particles will be made as they decay into either W(ℓnu)+jet or Z(ℓℓ)+jet. There exist theoretical arguments that establish that, under certain reasonable conditions, single production of VLQ dominates over production in pairs. The particular topology of such events enables the implementation of effective techniques to extract signal over electroweak background. The second type is the search for resonant particles decaying to WZ when the gauge bosons W and Z decay leptonically. The final states detected by ATLAS therefore contain three leptons (e, or mu) and missing transverse energy. The distribution of the invariant mass of these objects will then be examined to determine the presence or absence of new resonances that manifest themselves as localized excesses in m(WZ). Despite the fact that, at first glance, these two new types of particles have very little in common, they are in fact both closely linked to electroweak symmetry breaking. In many theoretical models, the hypothetical existence of VLQ is put forward to counteract the top quark's contribution to radiative loop corrections of the Higgs mass, a calculation which assumes that the Higgs is an elementary particle. Concurrently, other models foretelling the existence WZ resonances alternatively suggest that the Higgs is a composite particle, completely rewriting the whole Higgs sector of the SM. In this perspective, the two analyses presented in this thesis have a fundamental link with the very nature of the Higgs, thereby extending our knowledge of the origin of particle masses. Ultimately, the two analyses did not observe any significant excess in their respective signal regions, paving the way for the computations of limits on the production cross section as a function of the mass of the resonances.

Educational Management within a Young Offender Institution.

ERIC Educational Resources Information Center

Fryer, Winny; Fryer, Paul

1992-01-01

Examines educational theory and objectives within prisons and relates these to the real-time case study of the Young Offender Institution at Whatton, in Nottinghamshire, England. Measuring success and cost effectiveness is extremely difficult in the prison education field, and a significant gap exists between the theoretical model and everyday…

A Longitudinal Study of Occupational Aspirations and Attainments of Iowa Young Adults.

ERIC Educational Resources Information Center

Yoesting, Dean R.; And Others

The causal linkage between socioeconomic status, occupational and educational aspiration, and attainment was examined in this attempt to test an existing theoretical model which used socioeconomic status as a major input variable, with significant other influence as a crucial intervening variable between socioeconomic status and aspiration. The…

Cognitive Processes in University Learning: A Developmental Framework Using Structural Equation Modelling

ERIC Educational Resources Information Center

Phan, Huy P.

2011-01-01

Background: Both achievement goals and study processing strategies theories have been shown to contribute to the prediction of students' academic performance. Existing research studies (Fenollar, Roman, & Cuestas, 2007; Liem, Lau, & Nie, 2008; Simons, Dewitte, & Lens, 2004) amalgamating these two theoretical orientations in different causal models…

Minimal time spiking in various ChR2-controlled neuron models.

PubMed

Renault, Vincent; Thieullen, Michèle; Trélat, Emmanuel

2018-02-01

We use conductance based neuron models, and the mathematical modeling of optogenetics to define controlled neuron models and we address the minimal time control of these affine systems for the first spike from equilibrium. We apply tools of geometric optimal control theory to study singular extremals, and we implement a direct method to compute optimal controls. When the system is too large to theoretically investigate the existence of singular optimal controls, we observe numerically the optimal bang-bang controls.

Interactive Reliability Model for Whisker-toughened Ceramics

NASA Technical Reports Server (NTRS)

Palko, Joseph L.

1993-01-01

Wider use of ceramic matrix composites (CMC) will require the development of advanced structural analysis technologies. The use of an interactive model to predict the time-independent reliability of a component subjected to multiaxial loads is discussed. The deterministic, three-parameter Willam-Warnke failure criterion serves as the theoretical basis for the reliability model. The strength parameters defining the model are assumed to be random variables, thereby transforming the deterministic failure criterion into a probabilistic criterion. The ability of the model to account for multiaxial stress states with the same unified theory is an improvement over existing models. The new model was coupled with a public-domain finite element program through an integrated design program. This allows a design engineer to predict the probability of failure of a component. A simple structural problem is analyzed using the new model, and the results are compared to existing models.

Fermi-LAT upper limits on gamma-ray emission from colliding wind binaries

DOE PAGES

Werner, Michael; Reimer, O.; Reimer, A.; ...

2013-07-09

Here, colliding wind binaries (CWBs) are thought to give rise to a plethora of physical processes including acceleration and interaction of relativistic particles. Observation of synchrotron radiation in the radio band confirms there is a relativistic electron population in CWBs. Accordingly, CWBs have been suspected sources of high-energy γ-ray emission since the COS-B era. Theoretical models exist that characterize the underlying physical processes leading to particle acceleration and quantitatively predict the non-thermal energy emission observable at Earth. Furthermore, we strive to find evidence of γ-ray emission from a sample of seven CWB systems: WR 11, WR 70, WR 125, WRmore » 137, WR 140, WR 146, and WR 147. Theoretical modelling identified these systems as the most favourable candidates for emitting γ-rays. We make a comparison with existing γ-ray flux predictions and investigate possible constraints. We used 24 months of data from the Large Area Telescope (LAT) on-board the Fermi Gamma Ray Space Telescope to perform a dedicated likelihood analysis of CWBs in the LAT energy range. As a result, we find no evidence of γ-ray emission from any of the studied CWB systems and determine corresponding flux upper limits. For some CWBs the interplay of orbital and stellar parameters renders the Fermi-LAT data not sensitive enough to constrain the parameter space of the emission models. In the cases of WR140 and WR147, the Fermi -LAT upper limits appear to rule out some model predictions entirely and constrain theoretical models over a significant parameter space. A comparison of our findings to the CWB η Car is made.« less

Visualizing the Impact of Art: An Update and Comparison of Current Psychological Models of Art Experience

PubMed Central

Pelowski, Matthew; Markey, Patrick S.; Lauring, Jon O.; Leder, Helmut

2016-01-01

The last decade has witnessed a renaissance of empirical and psychological approaches to art study, especially regarding cognitive models of art processing experience. This new emphasis on modeling has often become the basis for our theoretical understanding of human interaction with art. Models also often define areas of focus and hypotheses for new empirical research, and are increasingly important for connecting psychological theory to discussions of the brain. However, models are often made by different researchers, with quite different emphases or visual styles. Inputs and psychological outcomes may be differently considered, or can be under-reported with regards to key functional components. Thus, we may lose the major theoretical improvements and ability for comparison that can be had with models. To begin addressing this, this paper presents a theoretical assessment, comparison, and new articulation of a selection of key contemporary cognitive or information-processing-based approaches detailing the mechanisms underlying the viewing of art. We review six major models in contemporary psychological aesthetics. We in turn present redesigns of these models using a unified visual form, in some cases making additions or creating new models where none had previously existed. We also frame these approaches in respect to their targeted outputs (e.g., emotion, appraisal, physiological reaction) and their strengths within a more general framework of early, intermediate, and later processing stages. This is used as a basis for general comparison and discussion of implications and future directions for modeling, and for theoretically understanding our engagement with visual art. PMID:27199697

Visualizing the Impact of Art: An Update and Comparison of Current Psychological Models of Art Experience.

PubMed

Pelowski, Matthew; Markey, Patrick S; Lauring, Jon O; Leder, Helmut

2016-01-01

The last decade has witnessed a renaissance of empirical and psychological approaches to art study, especially regarding cognitive models of art processing experience. This new emphasis on modeling has often become the basis for our theoretical understanding of human interaction with art. Models also often define areas of focus and hypotheses for new empirical research, and are increasingly important for connecting psychological theory to discussions of the brain. However, models are often made by different researchers, with quite different emphases or visual styles. Inputs and psychological outcomes may be differently considered, or can be under-reported with regards to key functional components. Thus, we may lose the major theoretical improvements and ability for comparison that can be had with models. To begin addressing this, this paper presents a theoretical assessment, comparison, and new articulation of a selection of key contemporary cognitive or information-processing-based approaches detailing the mechanisms underlying the viewing of art. We review six major models in contemporary psychological aesthetics. We in turn present redesigns of these models using a unified visual form, in some cases making additions or creating new models where none had previously existed. We also frame these approaches in respect to their targeted outputs (e.g., emotion, appraisal, physiological reaction) and their strengths within a more general framework of early, intermediate, and later processing stages. This is used as a basis for general comparison and discussion of implications and future directions for modeling, and for theoretically understanding our engagement with visual art.

Theory of step on leading edge of negative corona current pulse

NASA Astrophysics Data System (ADS)

Gupta, Deepak K.; Mahajan, Sangeeta; John, P. I.

2000-03-01

Theoretical models taking into account different feedback source terms (e.g., ion-impact electron emission, photo-electron emission, field emission, etc) have been proposed for the existence and explanation of the shape of negative corona current pulse, including the step on the leading edge. In the present work, a negative corona current pulse with the step on the leading edge is obtained in the presence of ion-impact electron emission feedback source only. The step on the leading edge is explained in terms of the plasma formation process and enhancement of the feedback source. Ionization wave-like movement toward the cathode is observed after the step. The conditions for the existence of current pulse, with and without the step on the leading edge, are also described. A qualitative comparison with earlier theoretical and experimental work is also included.

Bounded energy states in homogeneous turbulent shear flow - An alternative view

NASA Technical Reports Server (NTRS)

Bernard, P. S.; Speziale, C. G.

1992-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if a residual vortex stretching term is maintained in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are presented for a k-epsilon model modified to account for net vortex stretching.

The Role of Trait Emotional Intelligence in Academic Performance: Theoretical Overview and Empirical Update.

PubMed

Perera, Harsha N

2016-01-01

Considerable debate still exists among scholars over the role of trait emotional intelligence (TEI) in academic performance. The dominant theoretical position is that TEI should be orthogonal or only weakly related to achievement; yet, there are strong theoretical reasons to believe that TEI plays a key role in performance. The purpose of the current article is to provide (a) an overview of the possible theoretical mechanisms linking TEI with achievement and (b) an update on empirical research examining this relationship. To elucidate these theoretical mechanisms, the overview draws on multiple theories of emotion and regulation, including TEI theory, social-functional accounts of emotion, and expectancy-value and psychobiological model of emotion and regulation. Although these theoretical accounts variously emphasize different variables as focal constructs, when taken together, they provide a comprehensive picture of the possible mechanisms linking TEI with achievement. In this regard, the article redresses the problem of vaguely specified theoretical links currently hampering progress in the field. The article closes with a consideration of directions for future research.

Coping, acculturation, and psychological adaptation among migrants: a theoretical and empirical review and synthesis of the literature

PubMed Central

Kuo, Ben C.H.

2014-01-01

Given the continuous, dynamic demographic changes internationally due to intensive worldwide migration and globalization, the need to more fully understand how migrants adapt and cope with acculturation experiences in their new host cultural environment is imperative and timely. However, a comprehensive review of what we currently know about the relationship between coping behavior and acculturation experience for individuals undergoing cultural changes has not yet been undertaken. Hence, the current article aims to compile, review, and examine cumulative cross-cultural psychological research that sheds light on the relationships among coping, acculturation, and psychological and mental health outcomes for migrants. To this end, this present article reviews prevailing literature pertaining to: (a) the stress and coping conceptual perspective of acculturation; (b) four theoretical models of coping, acculturation and cultural adaptation; (c) differential coping pattern among diverse acculturating migrant groups; and (d) the relationship between coping variabilities and acculturation levels among migrants. In terms of theoretical understanding, this review points to the relative strengths and limitations associated with each of the four theoretical models on coping-acculturation-adaptation. These theories and the empirical studies reviewed in this article further highlight the central role of coping behaviors/strategies in the acculturation process and outcome for migrants and ethnic populations, both conceptually and functionally. Moreover, the review shows that across studies culturally preferred coping patterns exist among acculturating migrants and migrant groups and vary with migrants' acculturation levels. Implications and limitations of the existing literature for coping, acculturation, and psychological adaptation research are discussed and recommendations for future research are put forth. PMID:25750766

Hadron and Photon Production of J Particles and the Origin of J Particles

DOE R&D Accomplishments Database

Ting, S. C. C.

1975-01-01

There have been many theoretical speculations on the existence of long lived neutral particles with a mass larger than 10 GeV/c{sup 2} which play the role of weak interactions that photons play in electromagnetic interactions. There is, however, no theoretical justification, and no predictions exist, for long lived particles in the mass region 1-10 GeV/{up 2}. Even though there is no strong theoretical justification for the existence of long lived particles at low masses, there is no experimental indication that they should not exist. Until last year no high sensitivity experiment had been done in this mass region.

Psychological Pathways Linking Social Support to Health Outcomes: A Visit with the “Ghosts” of Research Past, Present, and Future

PubMed Central

Uchino, Bert N.; Bowen, Kimberly; Carlisle, McKenzie; Birmingham, Wendy

2012-01-01

Contemporary models postulate the importance of psychological mechanisms linking perceived and received social support to physical health outcomes. In this review, we examine studies that directly tested the potential psychological mechanisms responsible for links between social support and health-relevant physiological processes (1980s to 2010). Inconsistent with existing theoretical models, no evidence was found that psychological mechanisms such as depression, perceived stress, and other affective processes are directly responsible for links between support and health. We discuss the importance of considering statistical/design issues, emerging conceptual perspectives, and limitations of our existing models for future research aimed at elucidating the psychological mechanisms responsible for links between social support and physical health outcomes. PMID:22326104

Modeling spatial competition for light in plant populations with the porous medium equation.

PubMed

Beyer, Robert; Etard, Octave; Cournède, Paul-Henry; Laurent-Gengoux, Pascal

2015-02-01

We consider a plant's local leaf area index as a spatially continuous variable, subject to particular reaction-diffusion dynamics of allocation, senescence and spatial propagation. The latter notably incorporates the plant's tendency to form new leaves in bright rather than shaded locations. Applying a generalized Beer-Lambert law allows to link existing foliage to production dynamics. The approach allows for inter-individual variability and competition for light while maintaining robustness-a key weakness of comparable existing models. The analysis of the single plant case leads to a significant simplification of the system's key equation when transforming it into the well studied porous medium equation. Confronting the theoretical model to experimental data of sugar beet populations, differing in configuration density, demonstrates its accuracy.

Foundations of reusable and interoperable facet models using category theory

PubMed Central

2016-01-01

Faceted browsing has become ubiquitous with modern digital libraries and online search engines, yet the process is still difficult to abstractly model in a manner that supports the development of interoperable and reusable interfaces. We propose category theory as a theoretical foundation for faceted browsing and demonstrate how the interactive process can be mathematically abstracted. Existing efforts in facet modeling are based upon set theory, formal concept analysis, and light-weight ontologies, but in many regards, they are implementations of faceted browsing rather than a specification of the basic, underlying structures and interactions. We will demonstrate that category theory allows us to specify faceted objects and study the relationships and interactions within a faceted browsing system. Resulting implementations can then be constructed through a category-theoretic lens using these models, allowing abstract comparison and communication that naturally support interoperability and reuse. PMID:27942248

Reverse-Engineering Laboratory Astrophysics: Oxygen Inner-shell Absorption in the ISM

NASA Technical Reports Server (NTRS)

Garcia, J.; Gatuzz, E.; Kallman, T. R.; Mendoza, C.; Gorczyca, T. W.

2017-01-01

The modeling of X-ray spectra from photoionized astrophysical plasmas has been significantly improved due to recent advancements in the theoretical and numerical frameworks, as well as a consolidated and reliable atomic database of inner-shell transitions for all the relevant ions. We discuss these developments and the current state of X-ray spectral modeling in the context of oxygen cold absorption in the interstellar medium (ISM). Unconventionally, we use high-resolution astrophysical observations to accurately determine line positions, and adjust the theoretical models for a comprehensive interpretation of the observed X-ray spectra. This approach has brought to light standing discrepancies in the neutral oxygen absorption-line positions determined from observations and laboratory measurements. We give an overview of our current efforts to devise a definitive model of oxygen photoabsorption that can help to resolve the existing controversy regarding ISM atomic and molecular fractions.

Reverse-engineering laboratory astrophysics: Oxygen inner-shell absorption in the ISM

NASA Astrophysics Data System (ADS)

García, J.; Gatuzz, E.; Kallman, T. R.; Mendoza, C.; Gorczyca, T. W.

2017-03-01

The modeling of X-ray spectra from photoionized astrophysical plasmas has been significantly improved due to recent advancements in the theoretical and numerical frameworks, as well as a consolidated and reliable atomic database of inner-shell transitions for all the relevant ions. We discuss these developments and the current state of X-ray spectral modeling in the context of oxygen cold absorption in the interstellar medium (ISM). Unconventionally, we use high-resolution astrophysical observations to accurately determine line positions, and adjust the theoretical models for a comprehensive interpretation of the observed X-ray spectra. This approach has brought to light standing discrepancies in the neutral oxygen absorption-line positions determined from observations and laboratory measurements. We give an overview of our current efforts to devise a definitive model of oxygen photoabsorption that can help to resolve the existing controversy regarding ISM atomic and molecular fractions.

Broken flow symmetry explains the dynamics of small particles in deterministic lateral displacement arrays.

PubMed

Kim, Sung-Cheol; Wunsch, Benjamin H; Hu, Huan; Smith, Joshua T; Austin, Robert H; Stolovitzky, Gustavo

2017-06-27

Deterministic lateral displacement (DLD) is a technique for size fractionation of particles in continuous flow that has shown great potential for biological applications. Several theoretical models have been proposed, but experimental evidence has demonstrated that a rich class of intermediate migration behavior exists, which is not predicted. We present a unified theoretical framework to infer the path of particles in the whole array on the basis of trajectories in a unit cell. This framework explains many of the unexpected particle trajectories reported and can be used to design arrays for even nanoscale particle fractionation. We performed experiments that verify these predictions and used our model to develop a condenser array that achieves full particle separation with a single fluidic input.

Quasi-particle properties from tunneling in the v = 5/2 fractional quantum Hall state.

PubMed

Radu, Iuliana P; Miller, J B; Marcus, C M; Kastner, M A; Pfeiffer, L N; West, K W

2008-05-16

Quasi-particles with fractional charge and statistics, as well as modified Coulomb interactions, exist in a two-dimensional electron system in the fractional quantum Hall (FQH) regime. Theoretical models of the FQH state at filling fraction v = 5/2 make the further prediction that the wave function can encode the interchange of two quasi-particles, making this state relevant for topological quantum computing. We show that bias-dependent tunneling across a narrow constriction at v = 5/2 exhibits temperature scaling and, from fits to the theoretical scaling form, extract values for the effective charge and the interaction parameter of the quasi-particles. Ranges of values obtained are consistent with those predicted by certain models of the 5/2 state.

Expectancy-Value and Cognitive Process Outcomes in Mathematics Learning: A Structural Equation Analysis

ERIC Educational Resources Information Center

Phan, Huy P.

2014-01-01

Existing research has yielded evidence to indicate that the expectancy-value theoretical model predicts students' learning in various achievement contexts. Achievement values and self-efficacy expectations, for example, have been found to exert positive effects on cognitive process and academic achievement outcomes. We tested a conceptual model…

Slaves, Women, and War! Engaging Middle School Students in Historical Empathy for Enduring Understanding

ERIC Educational Resources Information Center

Endacott, Jason L.; Pelekanos, Christina

2015-01-01

Research has demonstrated the benefits of using historical empathy in history classrooms to encourage historical inquiry and understanding. This article chronicles the experiences of one middle school teacher as she integrates an updated theoretical and practical model of historical empathy into an existing instructional unit on Ancient Athens to…

System Theoretic Models for High Density VLSI Structures

DTIC Science & Technology

1989-01-01

vector is also called a stable We first present a simple example to help visualize how vector of the AMN. The set of all stable vectors is denoted these...New York: Springer- Verlag. 1978. 1980 [34] B. De Finetti. "Funtzione catatteristica di un fenomeno aleato- , [16] W A Little. "The existence of

Memory Retention in Second Language Acquisition and Instruction: Insights from Literature and Research

ERIC Educational Resources Information Center

Sanatullova-Allison , Elvira

2014-01-01

This article reviews some essential theoretical and empirical research literature that discusses the role of memory in second language acquisition and instruction. Two models of literature review--thematic and study-by-study--were used to analyze and synthesize the existing research. First, issues of memory retention in second language acquisition…

The Structure of Positive Interpersonal Relations in Small Groups.

ERIC Educational Resources Information Center

Davis, James A.; Leinhardt, Samuel

The authors sought to test Homans' proposition that small groups inevitably generate a social structure which combines subgroups (cliques) and a ranking system. We present a graph theoretical model of such a structure and prove that a necessary and sufficient condition for its existence is the absence of seven particular triad types. Expected…

An Ecological-Transactional Understanding of Community Violence: Theoretical Perspectives.

ERIC Educational Resources Information Center

Overstreet, Stacy; Mazza, James

2003-01-01

Community violence has emerged as a major risk factor for the development of mental health problems in children and adolescents. The goal of this article is to present an ecological-transactional model of community violence as a conceptual framework for understanding the existing literature and for guiding future research on community violence…

Exploring the TPACK of Taiwanese Secondary School Science Teachers Using a New Contextualized TPACK Model

ERIC Educational Resources Information Center

Jang, Syh-Jong; Tsai, Meng-Fang

2013-01-01

Technological pedagogical and content knowledge (TPACK) has been one of the steering theoretical concepts widely employed by researchers in order to examine and develop teachers' knowledge of integrating technology into teaching. Existing research on TPACK shows little about in-service secondary school science teachers' TPACK through a…

Aging and Financial Planning for Retirement: Interdisciplinary Influences Viewed through a Cross-Cultural Lens

ERIC Educational Resources Information Center

Hershey, Douglas A.; Henkens, Kene; van Dalen, Hendrik P.

2010-01-01

Current theoretical models support the existence of interactions between the individual and socio-environmental forces when it comes to the formation and enactment of life plans (Friedman & Scholnick, 1997; Shanahan & Elder, 2002). In this investigation, we examine the social, economic, and psychological forces that impact financial…

Longitudinal Examination of Optimism, Personal Self-Efficacy and Student Well-Being: A Path Analysis

ERIC Educational Resources Information Center

Phan, Huy P.

2016-01-01

The present longitudinal study, based on existing theoretical tenets, explored a conceptual model that depicted four major orientations: optimism, self-efficacy, and academic well-being. An important question for consideration, in this case, involved the testing of different untested trajectories that could explain and predict individuals'…

In Pursuit of Theoretical Ground in Behavior Change Support Systems: Analysis of Peer-to-Peer Communication in a Health-Related Online Community.

PubMed

Myneni, Sahiti; Cobb, Nathan; Cohen, Trevor

2016-02-02

Research studies involving health-related online communities have focused on examining network structure to understand mechanisms underlying behavior change. Content analysis of the messages exchanged in these communities has been limited to the "social support" perspective. However, existing behavior change theories suggest that message content plays a prominent role reflecting several sociocognitive factors that affect an individual's efforts to make a lifestyle change. An understanding of these factors is imperative to identify and harness the mechanisms of behavior change in the Health 2.0 era. The objective of this work is two-fold: (1) to harness digital communication data to capture essential meaning of communication and factors affecting a desired behavior change, and (2) to understand the applicability of existing behavior change theories to characterize peer-to-peer communication in online platforms. In this paper, we describe grounded theory-based qualitative analysis of digital communication in QuitNet, an online community promoting smoking cessation. A database of 16,492 de-identified public messages from 1456 users from March 1-April 30, 2007, was used in our study. We analyzed 795 messages using grounded theory techniques to ensure thematic saturation. This analysis enabled identification of key concepts contained in the messages exchanged by QuitNet members, allowing us to understand the sociobehavioral intricacies underlying an individual's efforts to cease smoking in a group setting. We further ascertained the relevance of the identified themes to theoretical constructs in existing behavior change theories (eg, Health Belief Model) and theoretically linked techniques of behavior change taxonomy. We identified 43 different concepts, which were then grouped under 12 themes based on analysis of 795 messages. Examples of concepts include "sleepiness," "pledge," "patch," "spouse," and "slip." Examples of themes include "traditions," "social support," "obstacles," "relapse," and "cravings." Results indicate that themes consisting of member-generated strategies such as "virtual bonfires" and "pledges" were related to the highest number of theoretical constructs from the existing behavior change theories. In addition, results indicate that the member-generated communication content supports sociocognitive constructs from more than one behavior change model, unlike the majority of the existing theory-driven interventions. With the onset of mobile phones and ubiquitous Internet connectivity, online social network data reflect the intricacies of human health behavior as experienced by health consumers in real time. This study offers methodological insights for qualitative investigations that examine the various kinds of behavioral constructs prevalent in the messages exchanged among users of online communities. Theoretically, this study establishes the manifestation of existing behavior change theories in QuitNet-like online health communities. Pragmatically, it sets the stage for real-time, data-driven sociobehavioral interventions promoting healthy lifestyle modifications by allowing us to understand the emergent user needs to sustain a desired behavior change.

Genetic Algorithms and Local Search

NASA Technical Reports Server (NTRS)

Whitley, Darrell

1996-01-01

The first part of this presentation is a tutorial level introduction to the principles of genetic search and models of simple genetic algorithms. The second half covers the combination of genetic algorithms with local search methods to produce hybrid genetic algorithms. Hybrid algorithms can be modeled within the existing theoretical framework developed for simple genetic algorithms. An application of a hybrid to geometric model matching is given. The hybrid algorithm yields results that improve on the current state-of-the-art for this problem.

Privacy-preserving periodical publishing for medical information

NASA Astrophysics Data System (ADS)

Jin, Hua; Ju, Shi-guang; Liu, Shan-cheng

2013-07-01

Existing privacy-preserving publishing models can not meet the requirement of periodical publishing for medical information whether these models are static or dynamic. This paper presents a (k,l)-anonymity model with keeping individual association and a principle based on (Epsilon)-invariance group for subsequent periodical publishing, and then, the PKIA and PSIGI algorithms are designed for them. The proposed methods can reserve more individual association with privacy-preserving and have better publishing quality. Experiments confirm our theoretical results and its practicability.

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

Tuo, Rui; Wu, C. F. Jeff

Many computer models contain unknown parameters which need to be estimated using physical observations. Furthermore, the calibration method based on Gaussian process models may lead to unreasonable estimate for imperfect computer models. In this work, we extend their study to calibration problems with stochastic physical data. We propose a novel method, called the L 2 calibration, and show its semiparametric efficiency. The conventional method of the ordinary least squares is also studied. Theoretical analysis shows that it is consistent but not efficient. Here, numerical examples show that the proposed method outperforms the existing ones.

Can We Recognize an Innovation? Perspective from an Evolving Network Model

NASA Astrophysics Data System (ADS)

Jain, Sanjay; Krishna, Sandeep

"Innovations" are central to the evolution of societies and the evolution of life. But what constitutes an innovation? We can often agree after the event, when its consequences and impact over a long term are known, whether something was an innovation, and whether it was a "big" innovation or a "minor" one. But can we recognize an innovation "on the fly" as it appears? Successful entrepreneurs often can. Is it possible to formalize that intuition? We discuss this question in the setting of a mathematical model of evolving networks. The model exhibits self-organization , growth, stasis, and collapse of a complex system with many interacting components, reminiscent of real-world phenomena. A notion of "innovation" is formulated in terms of graph-theoretic constructs and other dynamical variables of the model. A new node in the graph gives rise to an innovation, provided it links up "appropriately" with existing nodes; in this view innovation necessarily depends upon the existing context. We show that innovations, as defined by us, play a major role in the birth, growth, and destruction of organizational structures. Furthermore, innovations can be categorized in terms of their graph-theoretic structure as they appear. Different structural classes of innovation have potentially different qualitative consequences for the future evolution of the system, some minor and some major. Possible general lessons from this specific model are briefly discussed.

Endogenous fertility, altruistic behavior across generations, and social security systems.

PubMed

Prinz, A

1990-01-01

This study examines the possible link between the existence of a pay-as-you-go social security program and individual procreative behavior. When a public old-age income support system takes the place of within-family support, the theoretical literature preducts that fertility rates will decline since children are no longer perceived as important to the old age security of the parents. The author takes up this theoretical problem and examines it through three different but related issues: optimal capital accumulation, optimal population growth and the role of social institutions affecting efficient intergenerational allocations. Econometric analysis employing a steady state growth model is used. Altruism between generations is studied for effect on the standard model. The model shows that for social optimum the per capita pension is related to the growth rate of the population, therefore, for society as a whole, children are investment goods. However, given the existence of a social security system, it is in each household's best interest to have no children at all. Only a government transfer, a child allowance to parents, changes the model and fertility rates. When modified to account for "caring" the model demonstrates that altruistic behavior between generations is not symmetrical. The study concludes that a pay-as-you-go funded social security system should be supplemented by a system of child allowances or replaced by a fully funded social security system.

Modeling the Prospective Relationships of Impairment, Injury Severity, and Participation to Quality of Life Following Traumatic Brain Injury

PubMed Central

Kalpinski, Ryan J.; Williamson, Meredith L. C.; Elliott, Timothy R.; Berry, Jack W.; Underhill, Andrea T.; Fine, Philip R.

2013-01-01

Identifying reliable predictors of positive adjustment following traumatic brain injury (TBI) remains an important area of inquiry. Unfortunately, much of available research examines direct relationships between predictor variables and outcomes without attending to the contextual relationships that can exist between predictor variables. Relying on theoretical models of well-being, we examined a theoretical model of adjustment in which the capacity to engage in intentional activities would be prospectively associated with greater participation, which in turn would predict subsequent life satisfaction and perceived health assessed at a later time. Structural equation modeling of data collected from 312 individuals (226 men, 86 women) with TBI revealed that two elements of participation—mobility and occupational activities—mediated the prospective influence of functional independence and injury severity to optimal adjustment 60 months following medical discharge for TBI. The model accounted for 21% of the variance in life satisfaction and 23% of the variance in self-rated health. Results indicate that the effects of functional independence and injury severity to optimal adjustment over time may be best understood in the context of participation in meaningful, productive activities. Implications for theoretical models of well-being and for clinical interventions that promote adjustmentafter TBI are discussed. PMID:24199186

Accountability and pediatric physician-researchers: are theoretical models compatible with Canadian lived experience?

PubMed

Czoli, Christine; Da Silva, Michael; Shaul, Randi Zlotnik; d'Agincourt-Canning, Lori; Simpson, Christy; Boydell, Katherine; Rashkovan, Natalie; Vanin, Sharon

2011-10-05

Physician-researchers are bound by professional obligations stemming from both the role of the physician and the role of the researcher. Currently, the dominant models for understanding the relationship between physician-researchers' clinical duties and research duties fit into three categories: the similarity position, the difference position and the middle ground. The law may be said to offer a fourth "model" that is independent from these three categories.These models frame the expectations placed upon physician-researchers by colleagues, regulators, patients and research participants. This paper examines the extent to which the data from semi-structured interviews with 30 physician-researchers at three major pediatric hospitals in Canada reflect these traditional models. It seeks to determine the extent to which existing models align with the described lived experience of the pediatric physician-researchers interviewed.Ultimately, we find that although some physician-researchers make references to something like the weak version of the similarity position, the pediatric-researchers interviewed in this study did not describe their dual roles in a way that tightly mirrors any of the existing theoretical frameworks. We thus conclude that either physician-researchers are in need of better training regarding the nature of the accountability relationships that flow from their dual roles or that models setting out these roles and relationships must be altered to better reflect what we can reasonably expect of physician-researchers in a real-world environment. © 2011 Czoli et al; licensee BioMed Central Ltd.

Scoping review of adherence promotion theories in pelvic floor muscle training - 2011 ICS state-of-the-science seminar research paper i of iv.

PubMed

McClurg, Doreen; Frawley, Helena; Hay-Smith, Jean; Dean, Sarah; Chen, Shu-Yueh; Chiarelli, Pauline; Mair, Frances; Dumoulin, Chantale

2015-09-01

This paper, the first of four emanating from the International Continence Society's 2011 State-of-the-Science Seminar on pelvic-floor-muscle training (PFMT) adherence, aimed to summarize the literature on theoretical models to promote PFMT adherence, as identified in the research, or suggested by the seminar's expert panel, and recommends future directions for clinical practice and research. Existing literature on theories of health behavior were identified through a conventional subject search of electronic databases, reference-list checking, and input from the expert panel. A core eligibility criterion was that the study included a theoretical model to underpin adherence strategies used in an intervention to promote PFM training/exercise. A brief critique of 12 theoretical models/theories is provided and, were appropriate, their use in PFMT adherence strategies identified or examples of possible uses in future studies outlined. A better theoretical-based understanding of interventions to promote PFMT adherence through changes in health behaviors is required. The results of this scoping review and expert opinions identified several promising models. Future research should explicitly map the theories behind interventions that are thought to improve adherence in various populations (e.g., perinatal women to prevent or lessen urinary incontinence). In addition, identified behavioral theories applied to PFMT require a process whereby their impact can be evaluated. © 2015 Wiley Periodicals, Inc.

Testing a Theoretical Model of Perceived Self-Efficacy for Cancer-Related Fatigue Self-Management and Optimal Physical Functional Status

PubMed Central

Hoffman, Amy J.; von Eye, Alexander; Gift, Audrey G.; Given, Barbara A.; Given, Charles W.; Rothert, Marilyn

2009-01-01

Background Critical gaps exist in the understanding of cancer symptoms, particularly for cancer-related fatigue (CRF). Existing theories and models do not examine the key role perceived self-efficacy (PSE) plays in a person's ability to manage symptoms. Objectives To test the hypothesis that physical functional status (PFS) is predicted through patient characteristics, CRF, other symptoms, and PSE for fatigue self-management in persons with cancer. Methods This study is a secondary data analysis from the baseline observation of two randomized control trials. The combined data set includes 298 subjects who were undergoing a course of chemotherapy. Key variables included physiological and contextual patient characteristics, the severity from CRF and other symptoms, PSE, and PFS. Path analysis examined the relationships among the variables in the proposed theoretical model. Results Persons with cancer reported CRF as the most prevalent symptom among a mean of 7.4 other concurrent symptoms. The severity from CRF had a direct and indirect effect on PFS, with CRF having a direct adverse impact on PFS (t = -7.02) and an indirect adverse effect as part of the severity from the other symptoms (t = 9.69) which also adversely impacted PFS (t = -2.71). Consistent with the proposed theoretical model, PSE had a positive effect on the PFS (t = 2.87) of persons with cancer while serving as a mediator between CRF severity and PFS. Discussion Cancer-related fatigure is prevalent and related to the presence of other symptoms, and PSE for fatigue self-management is an important factor influencing CRF and PFS. A foundation is provided for future intervention studies to increase PSE to achieve optimal PFS in persons with cancer. PMID:19092553

The calculation and evaluation for n+54,56,57,58Fe reactions

NASA Astrophysics Data System (ADS)

Han, Yinlu; Xu, Yongli; Guo, Hairui; Zhang, Zhengjun; Liang, Haiying; Cai, Chonghai; Shen, Qingbiao

2017-09-01

All cross sections of neutron-induced reactions, angular distributions, double differential cross sections, angle-integrated spectra, γ-ray production cross sections and energy spectra for 54,56,57,58Fe are calculated by using theoretical models at incident neutron energies from 0.1 to 200 MeV. The present consistent theoretical calculated results are in good agreement with recent experimental data. The present evaluated data are compared with the existing experimental data and evaluated results from ENDF/B-VII, JENDL-4, JEFF-3, and the results are given in ENDF/B format.

Theoretical evidence for a first-order liquid-liquid phase transition in gallium.

PubMed

Carvajal Jara, Diego Alejandro; Fontana Michelon, Mateus; Antonelli, Alex; de Koning, Maurice

2009-06-14

We report on theoretical results that lend support to recent experimental observations suggesting the existence of a first-order liquid-liquid phase transformation (LLPT) in gallium. Using molecular dynamics simulation based on a modified embedded-atom model, we observe a transition from a high-density to a low-density liquid in the supercooled regime. The first-order character of the transition is established through the detection of the release of latent heat and our findings suggest that the LLPT terminates in a critical point that is located in the tensile-strained domain of the metastable phase diagram.

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

Sharma, Anupam Deep, E-mail: dr.anupamdeep@yahoo.com; Sinha, M. M.

Perovskite oxides find wide range of applications like oxygen sensors, catalyst support, high frequency capacitors, high temperature superconducting microwave devices, solid state oxide fuel cell (SOFC) etc. LaAlO{sub 3} is one of such type of prominent perovskite oxides and very prominent material for protonic conductions. Therefore knowledge of the thermal properties of LaAlO{sub 3} is most significant. Hence in the present study we have studied phonon density of states and specific heat of LaAlO{sub 3} in cubic structure by applying lattice dynamical theoretical model. The calculated results are interpreted with existing experimental or theoretical results.

Size-Dependent Materials Properties Toward a Universal Equation

PubMed Central

2010-01-01

Due to the lack of experimental values concerning some material properties at the nanoscale, it is interesting to evaluate this theoretically. Through a “top–down” approach, a universal equation is developed here which is particularly helpful when experiments are difficult to lead on a specific material property. It only requires the knowledge of the surface area to volume ratio of the nanomaterial, its size as well as the statistic (Fermi–Dirac or Bose–Einstein) followed by the particles involved in the considered material property. Comparison between different existing theoretical models and the proposed equation is done. PMID:20596422

Game theory and plant ecology.

PubMed

McNickle, Gordon G; Dybzinski, Ray

2013-04-01

The fixed and plastic traits possessed by a plant, which may be collectively thought of as its strategy, are commonly modelled as density-independent adaptations to its environment. However, plant strategies may also represent density- or frequency-dependent adaptations to the strategies used by neighbours. Game theory provides the tools to characterise such density- and frequency-dependent interactions. Here, we review the contributions of game theory to plant ecology. After briefly reviewing game theory from the perspective of plant ecology, we divide our review into three sections. First, game theoretical models of allocation to shoots and roots often predict investment in those organs beyond what would be optimal in the absence of competition. Second, game theoretical models of enemy defence suggest that an individual's investment in defence is not only a means of reducing its own tissue damage but also a means of deflecting enemies onto competitors. Finally, game theoretical models of trade with mutualistic partners suggest that the optimal trade may reflect competition for access to mutualistic partners among plants. In short, our review provides an accessible entrance to game theory that will help plant ecologists enrich their research with its worldview and existing predictions. © 2013 Blackwell Publishing Ltd/CNRS.

A theoretical model of speed-dependent steering torque for rolling tyres

NASA Astrophysics Data System (ADS)

Wei, Yintao; Oertel, Christian; Liu, Yahui; Li, Xuebing

2016-04-01

It is well known that the tyre steering torque is highly dependent on the tyre rolling speed. In limited cases, i.e. parking manoeuvre, the steering torque approaches the maximum. With the increasing tyre speed, the steering torque decreased rapidly. Accurate modelling of the speed-dependent behaviour for the tyre steering torque is a key factor to calibrate the electric power steering (EPS) system and tune the handling performance of vehicles. However, no satisfactory theoretical model can be found in the existing literature to explain this phenomenon. This paper proposes a new theoretical framework to model this important tyre behaviour, which includes three key factors: (1) tyre three-dimensional transient rolling kinematics with turn-slip; (2) dynamical force and moment generation; and (3) the mixed Lagrange-Euler method for contact deformation solving. A nonlinear finite-element code has been developed to implement the proposed approach. It can be found that the main mechanism for the speed-dependent steering torque is due to turn-slip-related kinematics. This paper provides a theory to explain the complex mechanism of the tyre steering torque generation, which helps to understand the speed-dependent tyre steering torque, tyre road feeling and EPS calibration.

Ferroelectric Field Effect Transistor Model Using Partitioned Ferroelectric Layer and Partial Polarization

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Ho, Fat D.

2004-01-01

A model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. The model is based on an existing model that incorporates partitioning of the ferroelectric layer to calculate the polarization within the ferroelectric material. The model incorporates several new aspects that are useful to the user. It takes into account the effect of a non-saturating gate voltage only partially polarizing the ferroelectric material based on the existing remnant polarization. The model also incorporates the decay of the remnant polarization based on the time history of the FFET. A gate pulse of a specific voltage; will not put the ferroelectric material into a single amount of polarization for that voltage, but instead vary with previous state of the material and the time since the last change to the gate voltage. The model also utilizes data from FFETs made from different types of ferroelectric materials to allow the user just to input the material being used and not recreate the entire model. The model also allows the user to input the quality of the ferroelectric material being used. The ferroelectric material quality can go from a theoretical perfect material with little loss and no decay to a less than perfect material with remnant losses and decay. This model is designed to be used by people who need to predict the external characteristics of a FFET before the time and expense of design and fabrication. It also allows the parametric evaluation of quality of the ferroelectric film on the overall performance of the transistor.

Efficient calibration for imperfect computer models

DOE PAGES

Tuo, Rui; Wu, C. F. Jeff

2015-12-01

Many computer models contain unknown parameters which need to be estimated using physical observations. Furthermore, the calibration method based on Gaussian process models may lead to unreasonable estimate for imperfect computer models. In this work, we extend their study to calibration problems with stochastic physical data. We propose a novel method, called the L 2 calibration, and show its semiparametric efficiency. The conventional method of the ordinary least squares is also studied. Theoretical analysis shows that it is consistent but not efficient. Here, numerical examples show that the proposed method outperforms the existing ones.

The Hubbard Model and Piezoresistivity

NASA Astrophysics Data System (ADS)

Celebonovic, V.; Nikolic, M. G.

2018-02-01

Piezoresistivity was discovered in the nineteenth century. Numerous applications of this phenomenon exist nowadays. The aim of the present paper is to explore the possibility of applying the Hubbard model to theoretical work on piezoresistivity. Results are encouraging, in the sense that numerical values of the strain gauge obtained by using the Hubbard model agree with results obtained by other methods. The calculation is simplified by the fact that it uses results for the electrical conductivity of 1D systems previously obtained within the Hubbard model by one of the present authors.

Dynamics of a stochastic cell-to-cell HIV-1 model with distributed delay

NASA Astrophysics Data System (ADS)

Ji, Chunyan; Liu, Qun; Jiang, Daqing

2018-02-01

In this paper, we consider a stochastic cell-to-cell HIV-1 model with distributed delay. Firstly, we show that there is a global positive solution of this model before exploring its long-time behavior. Then sufficient conditions for extinction of the disease are established. Moreover, we obtain sufficient conditions for the existence of an ergodic stationary distribution of the model by constructing a suitable stochastic Lyapunov function. The stationary distribution implies that the disease is persistent in the mean. Finally, we provide some numerical examples to illustrate theoretical results.

Verification of Gyrokinetic codes: theoretical background and applications

NASA Astrophysics Data System (ADS)

Tronko, Natalia

2016-10-01

In fusion plasmas the strong magnetic field allows the fast gyro motion to be systematically removed from the description of the dynamics, resulting in a considerable model simplification and gain of computational time. Nowadays, the gyrokinetic (GK) codes play a major role in the understanding of the development and the saturation of turbulence and in the prediction of the consequent transport. We present a new and generic theoretical framework and specific numerical applications to test the validity and the domain of applicability of existing GK codes. For a sound verification process, the underlying theoretical GK model and the numerical scheme must be considered at the same time, which makes this approach pioneering. At the analytical level, the main novelty consists in using advanced mathematical tools such as variational formulation of dynamics for systematization of basic GK code's equations to access the limits of their applicability. The indirect verification of numerical scheme is proposed via the Benchmark process. In this work, specific examples of code verification are presented for two GK codes: the multi-species electromagnetic ORB5 (PIC), and the radially global version of GENE (Eulerian). The proposed methodology can be applied to any existing GK code. We establish a hierarchy of reduced GK Vlasov-Maxwell equations using the generic variational formulation. Then, we derive and include the models implemented in ORB5 and GENE inside this hierarchy. At the computational level, detailed verification of global electromagnetic test cases based on the CYCLONE are considered, including a parametric β-scan covering the transition between the ITG to KBM and the spectral properties at the nominal β value.

When the Mannequin Dies, Creation and Exploration of a Theoretical Framework Using a Mixed Methods Approach.

PubMed

Tripathy, Shreepada; Miller, Karen H; Berkenbosch, John W; McKinley, Tara F; Boland, Kimberly A; Brown, Seth A; Calhoun, Aaron W

2016-06-01

Controversy exists in the simulation community as to the emotional and educational ramifications of mannequin death due to learner action or inaction. No theoretical framework to guide future investigations of learner actions currently exists. The purpose of our study was to generate a model of the learner experience of mannequin death using a mixed methods approach. The study consisted of an initial focus group phase composed of 11 learners who had previously experienced mannequin death due to action or inaction on the part of learners as defined by Leighton (Clin Simul Nurs. 2009;5(2):e59-e62). Transcripts were analyzed using grounded theory to generate a list of relevant themes that were further organized into a theoretical framework. With the use of this framework, a survey was generated and distributed to additional learners who had experienced mannequin death due to action or inaction. Results were analyzed using a mixed methods approach. Forty-one clinicians completed the survey. A correlation was found between the emotional experience of mannequin death and degree of presession anxiety (P < 0.001). Debriefing was found to significantly reduce negative emotion and enhance satisfaction. Sixty-nine percent of respondents indicated that mannequin death enhanced learning. These results were used to modify our framework. Using the previous approach, we created a model of the effect of mannequin death on the educational and psychological state of learners. We offer the final model as a guide to future research regarding the learner experience of mannequin death.

Small traveling clusters in attractive and repulsive Hamiltonian mean-field models.

PubMed

Barré, Julien; Yamaguchi, Yoshiyuki Y

2009-03-01

Long-lasting small traveling clusters are studied in the Hamiltonian mean-field model by comparing between attractive and repulsive interactions. Nonlinear Landau damping theory predicts that a Gaussian momentum distribution on a spatially homogeneous background permits the existence of traveling clusters in the repulsive case, as in plasma systems, but not in the attractive case. Nevertheless, extending the analysis to a two-parameter family of momentum distributions of Fermi-Dirac type, we theoretically predict the existence of traveling clusters in the attractive case; these findings are confirmed by direct N -body numerical simulations. The parameter region with the traveling clusters is much reduced in the attractive case with respect to the repulsive case.

Refining mass formulas for astrophysical applications: A Bayesian neural network approach

NASA Astrophysics Data System (ADS)

Utama, R.; Piekarewicz, J.

2017-10-01

Background: Exotic nuclei, particularly those near the drip lines, are at the core of one of the fundamental questions driving nuclear structure and astrophysics today: What are the limits of nuclear binding? Exotic nuclei play a critical role in both informing theoretical models as well as in our understanding of the origin of the heavy elements. Purpose: Our aim is to refine existing mass models through the training of an artificial neural network that will mitigate the large model discrepancies far away from stability. Methods: The basic paradigm of our two-pronged approach is an existing mass model that captures as much as possible of the underlying physics followed by the implementation of a Bayesian neural network (BNN) refinement to account for the missing physics. Bayesian inference is employed to determine the parameters of the neural network so that model predictions may be accompanied by theoretical uncertainties. Results: Despite the undeniable quality of the mass models adopted in this work, we observe a significant improvement (of about 40%) after the BNN refinement is implemented. Indeed, in the specific case of the Duflo-Zuker mass formula, we find that the rms deviation relative to experiment is reduced from σrms=0.503 MeV to σrms=0.286 MeV. These newly refined mass tables are used to map the neutron drip lines (or rather "drip bands") and to study a few critical r -process nuclei. Conclusions: The BNN approach is highly successful in refining the predictions of existing mass models. In particular, the large discrepancy displayed by the original "bare" models in regions where experimental data are unavailable is considerably quenched after the BNN refinement. This lends credence to our approach and has motivated us to publish refined mass tables that we trust will be helpful for future astrophysical applications.

σ and κ mesons as broad dynamical resonances in one-meson-exchange model

NASA Astrophysics Data System (ADS)

Hong Xiem, Ngo Thi; Shinmura, Shoji

2014-09-01

The existences of broad scalar σ (600) and κ (700) mesons have been discussed intensively in the experimental and theoretical studies on ππ and πK scatterings. By using chiral perturbation model, J. Oller, A. Gómez and J. R. Peláez confirmed the existence of these mesons as dynamical resonances. In meson-exchange models, their existence has not been established yet. In this talk, using the quasi-potential of meson-exchange model and Lippmann-Schwinger equation, we determine the T and S-matrices, from which we could find the positions of poles in physical amplitudes in the complex E-plane. With the full treatment of meson-meson interactions (ππ - πK - πη - ηη and πK - ηK) , for the first time, the existence of the scalar σ (600) and κ (700) mesons are confirmed in one-meson-exchange model. There are two kinds of form factors in our model: the monopole and the Gaussian. Our recent results show that the poles σ and κ appear at around 410 - i 540 MeV and 650 - i 20 MeV for monopole form factors, respectively. For Gaussian form factors, the poles σ and κ, respectively, are at 360 - i 510 MeV and 649 - i 190 MeV.

Mathematical interpretation of Brownian motor model: Limit cycles and directed transport phenomena

NASA Astrophysics Data System (ADS)

Yang, Jianqiang; Ma, Hong; Zhong, Suchuang

2018-03-01

In this article, we first suggest that the attractor of Brownian motor model is one of the reasons for the directed transport phenomenon of Brownian particle. We take the classical Smoluchowski-Feynman (SF) ratchet model as an example to investigate the relationship between limit cycles and directed transport phenomenon of the Brownian particle. We study the existence and variation rule of limit cycles of SF ratchet model at changing parameters through mathematical methods. The influences of these parameters on the directed transport phenomenon of a Brownian particle are then analyzed through numerical simulations. Reasonable mathematical explanations for the directed transport phenomenon of Brownian particle in SF ratchet model are also formulated on the basis of the existence and variation rule of the limit cycles and numerical simulations. These mathematical explanations provide a theoretical basis for applying these theories in physics, biology, chemistry, and engineering.

River Inflows into Lakes: Basin Temperature Profiles Driven By Peeling Detrainment from Dense Underflows

NASA Astrophysics Data System (ADS)

Hogg, C. A. R.; Huppert, H. E.; Imberger, J.; Dalziel, S. B.

2014-12-01

Dense gravity currents from river inflows feed fluid into confined basins in lakes. Large inflows can influence temperature profiles in the basins. Existing parameterisations of the circulation and mixing of such inflows are often based on the entrainment of ambient fluid into the underflowing gravity currents. However, recent observations have suggested that uni-directional entrainment into a gravity current does not fully describe the transfer between such gravity currents and the ambient water. Laboratory experiments visualised peeling detrainment from the gravity current occurring when the ambient fluid was stratified. A theoretical model of the observed peeling detrainment was developed to predict the temperature profile in the basin. This new model gives a better approximation of the temperature profile observed in the experiments than the pre-existing entraining model. The model can now be developed such that it integrates into operational models of lake basins.

Lyapunov exponent and criticality in the Hamiltonian mean field model

NASA Astrophysics Data System (ADS)

Filho, L. H. Miranda; Amato, M. A.; Rocha Filho, T. M.

2018-03-01

We investigate the dependence of the largest Lyapunov exponent (LLE) of an N-particle self-gravitating ring model at equilibrium with respect to the number of particles and its dependence on energy. This model has a continuous phase-transition from a ferromagnetic to homogeneous phase, and we numerically confirm with large scale simulations the existence of a critical exponent associated to the LLE, although at variance with the theoretical estimate. The existence of strong chaos in the magnetized state evidenced by a positive Lyapunov exponent is explained by the coupling of individual particle oscillations to the diffusive motion of the center of mass of the system and also results in a change of the scaling of the LLE with the number of particles. We also discuss thoroughly for the model the validity and limits of the approximations made by a geometrical model for their analytic estimate.

Altruism and Indirect Reciprocity: The Interaction of Person and Situation in Prosocial Behavior

ERIC Educational Resources Information Center

Simpson, Brent; Willer, Robb

2008-01-01

A persistent puzzle in the social and biological sciences is the existence of prosocial behavior, actions that benefit others, often at a cost to oneself. Recent theoretical models and empirical studies of indirect reciprocity show that actors behave prosocially in order to develop an altruistic reputation and receive future benefits from third…

Flexoelectricity in Nanostructures: Theory, Nanofabrication and Characterization

DTIC Science & Technology

2017-09-13

public release; distribution is unlimited. Major Goals: The objective of this project is to investigate, theoretically and experimentally , the... experimental approach. Accomplishments: In this report, we investigated the thermal polarization effect where the temperature- dependent dielectric...through an analytical model, which was experimentally verified. Secondly, based on the existence of the converse flexoelectric effect in materials, BST

Web-Based Cognitive Apprenticeship Model for Improving Pre-Service Teachers' Performances and Attitudes towards Instructional Planning: Design and Field Experiment

ERIC Educational Resources Information Center

Liu, Tzu-Chien

2005-01-01

Instructional planning is an essential professional activity often used by teachers. However, some characteristics of existing university-based teacher education programs may hamper pre-service teachers' learning of instructional planning. Thus, this study adopts the cognitive apprenticeship as a theoretical foundation to construct a web-based…

Some Essential Environmental Ingredients for Sex Offender Reintegration

ERIC Educational Resources Information Center

Boer, Douglas P.

2013-01-01

Until the systematic work on the Good Lives Model (GLM) produced by Tony Ward, not a great deal of conceptual structure existed to provide sex offender treatment specialists with a theoretical underpinning for their work in helping offenders develop a better life as a way to prevent reoffending. However, the work of Ward and colleagues initially…

"Your Model Is Predictive-- but Is It Useful?" Theoretical and Empirical Considerations of a New Paradigm for Adaptive Tutoring Evaluation

ERIC Educational Resources Information Center

González-Brenes, José P.; Huang, Yun

2015-01-01

Classification evaluation metrics are often used to evaluate adaptive tutoring systems-- programs that teach and adapt to humans. Unfortunately, it is not clear how intuitive these metrics are for practitioners with little machine learning background. Moreover, our experiments suggest that existing convention for evaluating tutoring systems may…

The Cortical Organization of Lexical Knowledge: A Dual Lexicon Model of Spoken Language Processing

ERIC Educational Resources Information Center

Gow, David W., Jr.

2012-01-01

Current accounts of spoken language assume the existence of a lexicon where wordforms are stored and interact during spoken language perception, understanding and production. Despite the theoretical importance of the wordform lexicon, the exact localization and function of the lexicon in the broader context of language use is not well understood.…

The link between new and return business and quality of care: patient satisfaction.

PubMed

Greeneich, D

1993-09-01

New and return business in the service setting are linked to quality of care through patient satisfaction. This article explores the conceptual underpinnings of this concept. Moreover, a theoretical model of patient satisfaction is delineated based on existing nursing research in patient satisfaction. Implications for nursing practice, administration, education, and research are discussed.

Online Investment Education: Listening to Learners to Develop an Effective Financial Literacy Program for Farm Households

ERIC Educational Resources Information Center

O'Neill, Barbara; Porter, Nancy M.; Pankow, Debra; Schuchardt, Jane; Johnson, Jason

2010-01-01

A needs assessment was conducted for the adaptation of an existing online Cooperative Extension investment course for use by farm households. The theoretical model was Social Marketing Theory. Data about financial attitudes, practices, and learning preferences of farm households were collected through a telephone survey of 300 farm households and…

Democratic Leadership and Faculty Empowerment at the Community College: A Theoretical Model for the Department Chair.

ERIC Educational Resources Information Center

McArthur, Ronald C.

2002-01-01

Argues that community college organization at the department level presents challenging leadership issues for the newly appointed department chair. Asserts that existing culture, which looks upon the chair with some mistrust, demands chairs who behave as peers rather than military commanders. Concludes that democratic leadership is the most…

Duels with Continuous Firing,

DTIC Science & Technology

A game-theoretic model is proposed for the generalization of a discrete-fire silent duel to a silent duel with continuous firing. This zero-sum two...person game is solved in the symmetric case. It is shown that pure optimal strategies exist and hence also solve a noisy duel with continuous firing. A solution for the general non-symmetric duel is conjectured. (Author)

Choice as a Global Language in Local Practice: A Mixed Model of School Choice in Taiwan

ERIC Educational Resources Information Center

Mao, Chin-Ju

2015-01-01

This paper uses school choice policy as an example to demonstrate how local actors adopt, mediate, translate, and reformulate "choice" as neo-liberal rhetoric informing education reform. Complex processes exist between global policy about school choice and the local practice of school choice. Based on the theoretical sensibility of…

Student Financial Aid and Choice of Undergraduate Major. ASHE Annual Meeting Paper.

ERIC Educational Resources Information Center

Zito, Eileen H.

This study evaluated whether the use of educational loans has an impact upon student choice of majors. In addition, the study demonstrated that the statistical technique of two-stage least squares can be appropriately used with educational data when reciprocal causation exists in the theoretical model. It was hypothesized that, since a majority of…

Virtualizing the Word: Expanding Walter Ong's Theory of Orality and Literacy through a Culture of Virtuality

ERIC Educational Resources Information Center

Dempsey, Jennifer Camille

2014-01-01

This dissertation seeks to create a vision for virtuality culture through a theoretical expansion of Walter Ong's literacy and orality culture model. It investigates the ubiquitous and multimodal nature of the virtuality cultural phenomenon that is mediated by contemporary technology and not explained by pre-existing cultural conventions. Through…

A utility-theoretic model for QALYs and willingness to pay.

PubMed

Klose, Thomas

2003-01-01

Despite the widespread use of quality-adjusted life years (QALY) in economic evaluation studies, their utility-theoretic foundation remains unclear. A model for preferences over health, money, and time is presented in this paper. Under the usual assumptions of the original QALY-model, an additive separable presentation of the utilities in different periods exists. In contrast to the usual assumption that QALY-weights do solely depend on aspects of health-related quality of life, wealth-standardized QALY-weights might vary with the wealth level in the presented extension of the original QALY-model resulting in an inconsistent measurement of QALYs. Further assumptions are presented to make the measurement of QALYs consistent with lifetime preferences over health and money. Even under these strict assumptions, QALYs and WTP (which also can be defined in this utility-theoretic model) are not equivalent preference-based measures of the effects of health technologies on an individual level. The results suggest that the individual WTP per QALY can depend on the magnitude of the QALY-gain as well as on the disease burden, when health influences the marginal utility of wealth. Further research seems to be indicated on this structural aspect of preferences over health and wealth and to quantify its impact. Copyright 2002 John Wiley & Sons, Ltd.

Ocular Chromatic Aberrations and Their Effects on Polychromatic Retinal Image Quality

NASA Astrophysics Data System (ADS)

Zhang, Xiaoxiao

Previous studies of ocular chromatic aberrations have concentrated on chromatic difference of focus (CDF). Less is known about the chromatic difference of image position (CDP) in the peripheral retina and no experimental attempt has been made to measure the ocular chromatic difference of magnification (CDM). Consequently, theoretical modelling of human eyes is incomplete. The insufficient knowledge of ocular chromatic aberrations is partially responsible for two unsolved applied vision problems: (1) how to improve vision by correcting ocular chromatic aberration? (2) what is the impact of ocular chromatic aberration on the use of isoluminance gratings as a tool in spatial-color vision?. Using optical ray tracing methods, MTF analysis methods of image quality, and psychophysical methods, I have developed a more complete model of ocular chromatic aberrations and their effects on vision. The ocular CDM was determined psychophysically by measuring the tilt in the apparent frontal parallel plane (AFPP) induced by interocular difference in image wavelength. This experimental result was then used to verify a theoretical relationship between the ocular CDM, the ocular CDF and the entrance pupil of the eye. In the retinal image after correcting the ocular CDF with existing achromatizing methods, two forms of chromatic aberration (CDM and chromatic parallax) were examined. The CDM was predicted by theoretical ray tracing and measured with the same method used to determine ocular CDM. The chromatic parallax was predicted with a nodal ray model and measured with the two-color vernier alignment method. The influence of these two aberrations on polychromatic MTF were calculated. Using this improved model of ocular chromatic aberration, luminance artifacts in the images of isoluminance gratings were calculated. The predicted luminance artifacts were then compared with experimental data from previous investigators. The results show that: (1) A simple relationship exists between two major chromatic aberrations and the location of the pupil; (2) The ocular CDM is measurable and varies among individuals; (3) All existing methods to correct ocular chromatic aberration face another aberration, chromatic parallax, which is inherent in the methodology; (4) Ocular chromatic aberrations have the potential to contaminate psychophysical experimental results on human spatial-color vision.

One Giant Leap for Categorizers: One Small Step for Categorization Theory

PubMed Central

Smith, J. David; Ell, Shawn W.

2015-01-01

We explore humans’ rule-based category learning using analytic approaches that highlight their psychological transitions during learning. These approaches confirm that humans show qualitatively sudden psychological transitions during rule learning. These transitions contribute to the theoretical literature contrasting single vs. multiple category-learning systems, because they seem to reveal a distinctive learning process of explicit rule discovery. A complete psychology of categorization must describe this learning process, too. Yet extensive formal-modeling analyses confirm that a wide range of current (gradient-descent) models cannot reproduce these transitions, including influential rule-based models (e.g., COVIS) and exemplar models (e.g., ALCOVE). It is an important theoretical conclusion that existing models cannot explain humans’ rule-based category learning. The problem these models have is the incremental algorithm by which learning is simulated. Humans descend no gradient in rule-based tasks. Very different formal-modeling systems will be required to explain humans’ psychology in these tasks. An important next step will be to build a new generation of models that can do so. PMID:26332587

Using intervention mapping to deconstruct cognitive work hardening: a return-to-work intervention for people with depression.

PubMed

Wisenthal, Adeena; Krupa, Terry

2014-12-12

Mental health related work disability leaves are increasing at alarming rates with depression emerging as the most common mental disorder in the workforce. Treatments are available to alleviate depressive symptoms and associated functional impacts; however, they are not specifically aimed at preparing people to return to work. Cognitive work hardening (CWH) is a novel intervention that addresses this gap in the health care system. This paper presents a theoretical analysis of the components and underlying mechanisms of CWH using Intervention Mapping (IM) as a tool to deconstruct its elements. The cognitive sequelae of depression and their relevance to return-to-work (RTW) are examined together with interpersonal skills and other work-related competencies that affect work ability. IM, a tool typically used to create programs, is used to deconstruct an existing program, namely CWH, into its component parts and link them to theories and models in the literature. CWH has been deconstructed into intervention elements which are linked to program performance objectives through underlying theoretical models. In this way, linkages are made between tools and materials of the intervention and the overall program objective of 'successful RTW for people with depression'. An empirical study of the efficacy of CWH is currently underway which should provide added insight and understanding into this intervention. The application of IM to CWH illustrates the theoretical underpinnings of the treatment intervention and assists with better understanding the linkage between intervention elements and intervention objective. Applying IM to deconstruct an existing program (rather than create a program) presents an alternate application of the IM tool which can have implications for other programs in terms of enhancing understanding, grounding in theoretical foundations, communicating program design, and establishing a basis for program evaluation and improvement.

The Race for Space: Tracking Land-Cover Transformation in a Socio-ecological Landscape, South Africa

NASA Astrophysics Data System (ADS)

Coetzer, Kaera L.; Erasmus, Barend F. N.; Witkowski, Edward T. F.; Reyers, Belinda

2013-09-01

Biosphere Reserves attempt to align existing biodiversity conservation with sustainable resource use, specifically for improving socio-economic circumstances of resident communities. Typically, the Biosphere Reserve model is applied to an established landscape mosaic of existing land uses; these are often socio-ecological systems where strict environmental protection and community livelihoods are in conflict, and environmental degradation frequently accompanies "use". This raises challenges for successful implementation of the model, as the reality of the existing land-use mosaic undermines the theoretical aspirations of the Biosphere concept. This study focuses on the Kruger to Canyons Biosphere Reserve (K2C), South Africa; a socio-ecological landscape where formal conservation is juxtaposed against extensive impoverished rural communities. We focus on land-cover changes of the existing land-use mosaic (1993-2006), specifically selected land-cover classes identified as important for biodiversity conservation and local-level resource utilization. We discuss the implications of transformation for conservation, sustainable resource-use, and K2C's functioning as a "Biosphere Reserve". Spatially, changes radiated outward from the settlement expanse, with little regard for the theoretical land-use zonation of the Biosphere Reserve. Settlement growth tracked transport routes, transforming cohesive areas of communal-use rangelands. Given the interdependencies between the settlement population and local environmental resources, the Impacted Vegetation class expanded accordingly, fragmenting the Intact Vegetation class, and merging rangelands. This has serious implications for sustainability of communal harvesting areas, and further transformation of intact habitat. The distribution and magnitude of Intact Vegetation losses raise concerns around connectivity and edge effects, with long-term consequences for ecological integrity of remnant habitat, and K2C's existing network of protected areas.

Broken flow symmetry explains the dynamics of small particles in deterministic lateral displacement arrays

PubMed Central

Kim, Sung-Cheol; Wunsch, Benjamin H.; Hu, Huan; Smith, Joshua T.; Stolovitzky, Gustavo

2017-01-01

Deterministic lateral displacement (DLD) is a technique for size fractionation of particles in continuous flow that has shown great potential for biological applications. Several theoretical models have been proposed, but experimental evidence has demonstrated that a rich class of intermediate migration behavior exists, which is not predicted. We present a unified theoretical framework to infer the path of particles in the whole array on the basis of trajectories in a unit cell. This framework explains many of the unexpected particle trajectories reported and can be used to design arrays for even nanoscale particle fractionation. We performed experiments that verify these predictions and used our model to develop a condenser array that achieves full particle separation with a single fluidic input. PMID:28607075

Physics of the inner heliosphere: Mechanisms, models and observational signatures

NASA Technical Reports Server (NTRS)

Withbroe, George L.

1987-01-01

Selected problems concerned with the important physical processes that occur in the corona and solar wind acceleration region, particularly time dependent phenomena were studied. Both the physics of the phenomena and the resultant effects on observational signatures, particularly spectroscopic signatures were also studied. Phenomena under study include: wave motions, particularly Alfven and fast mode waves; the formation of standing shocks in the inner heliosphere as a result of momentum and/or heat addition to the wind; and coronal transient phenomena where momentum and/or heat are deposited in the corona to produce transient plasma heating and/or mass ejection. The development of theoretical models for the inner heliosphere, the theoretical investigation of spectroscopic plasma diagnostics for this region, and the analysis of existing skylab and other relevant data are also included.

Stability and Hopf Bifurcation in a HIV-1 System with Multitime Delays

NASA Astrophysics Data System (ADS)

Zhao, Lingyan; Liu, Haihong; Yan, Fang

In this paper, we propose a mathematical model for HIV-1 infection with three time delays. The model examines a viral-therapy for controlling infections by using an engineered virus to selectively eliminate infected cells. In our model, three time delays represent the latent period of pathogen virus, pathogen virus production period and recombinant (genetically modified) virus production period, respectively. Detailed theoretical analysis have demonstrated that the values of three delays can affect the stability of equilibrium solutions, can also lead to Hopf bifurcation and oscillated solutions of the system. Moreover, we give the conditions for the existence of stable positive equilibrium solution and Hopf bifurcation. Further, the properties of Hopf bifurcation are discussed. These theoretical results indicate that the delays play an important role in determining the dynamic behavior quantitatively. Therefore, it is a fact that delays are very important, which should not be missed in controlling HIV-1 infections.

The assumption of equilibrium in models of migration.

PubMed

Schachter, J; Althaus, P G

1993-02-01

In recent articles Evans (1990) and Harrigan and McGregor (1993) (hereafter HM) scrutinized the equilibrium model of migration presented in a 1989 paper by Schachter and Althaus. This model used standard microeconomics to analyze gross interregional migration flows based on the assumption that gross flows are in approximate equilibrium. HM criticized the model as theoretically untenable, while Evans summoned empirical as well as theoretical objections. HM claimed that equilibrium of gross migration flows could be ruled out on theoretical grounds. They argued that the absence of net migration requires that either all regions have equal populations or that unsustainable regional migration propensities must obtain. In fact some moves are inter- and other are intraregional. It does not follow, however, that the number of interregional migrants will be larger for the more populous region. Alternatively, a country could be divided into a large number of small regions that have equal populations. With uniform propensities to move, each of these analytical regions would experience in equilibrium zero net migration. Hence, the condition that net migration equal zero is entirely consistent with unequal distributions of population across regions. The criticisms of Evans were based both on flawed reasoning and on misinterpretation of the results of a number of econometric studies. His reasoning assumed that the existence of demand shifts as found by Goldfarb and Yezer (1987) and Topel (1986) invalidated the equilibrium model. The equilibrium never really obtains exactly, but economic modeling of migration properly begins with a simple equilibrium model of the system. A careful reading of the papers Evans cited in support of his position showed that in fact they affirmed rather than denied the appropriateness of equilibrium modeling. Zero net migration together with nonzero gross migration are not theoretically incompatible with regional heterogeneity of population, wages, or amenities.

Cultural evolutionary theory: How culture evolves and why it matters

PubMed Central

Creanza, Nicole; Kolodny, Oren; Feldman, Marcus W.

2017-01-01

Human cultural traits—behaviors, ideas, and technologies that can be learned from other individuals—can exhibit complex patterns of transmission and evolution, and researchers have developed theoretical models, both verbal and mathematical, to facilitate our understanding of these patterns. Many of the first quantitative models of cultural evolution were modified from existing concepts in theoretical population genetics because cultural evolution has many parallels with, as well as clear differences from, genetic evolution. Furthermore, cultural and genetic evolution can interact with one another and influence both transmission and selection. This interaction requires theoretical treatments of gene–culture coevolution and dual inheritance, in addition to purely cultural evolution. In addition, cultural evolutionary theory is a natural component of studies in demography, human ecology, and many other disciplines. Here, we review the core concepts in cultural evolutionary theory as they pertain to the extension of biology through culture, focusing on cultural evolutionary applications in population genetics, ecology, and demography. For each of these disciplines, we review the theoretical literature and highlight relevant empirical studies. We also discuss the societal implications of the study of cultural evolution and of the interactions of humans with one another and with their environment. PMID:28739941

Cultural evolutionary theory: How culture evolves and why it matters.

PubMed

Creanza, Nicole; Kolodny, Oren; Feldman, Marcus W

2017-07-24

Human cultural traits-behaviors, ideas, and technologies that can be learned from other individuals-can exhibit complex patterns of transmission and evolution, and researchers have developed theoretical models, both verbal and mathematical, to facilitate our understanding of these patterns. Many of the first quantitative models of cultural evolution were modified from existing concepts in theoretical population genetics because cultural evolution has many parallels with, as well as clear differences from, genetic evolution. Furthermore, cultural and genetic evolution can interact with one another and influence both transmission and selection. This interaction requires theoretical treatments of gene-culture coevolution and dual inheritance, in addition to purely cultural evolution. In addition, cultural evolutionary theory is a natural component of studies in demography, human ecology, and many other disciplines. Here, we review the core concepts in cultural evolutionary theory as they pertain to the extension of biology through culture, focusing on cultural evolutionary applications in population genetics, ecology, and demography. For each of these disciplines, we review the theoretical literature and highlight relevant empirical studies. We also discuss the societal implications of the study of cultural evolution and of the interactions of humans with one another and with their environment.

Making sense of shared sense-making in an inquiry-based science classroom: Toward a sociocultural theory of mind

NASA Astrophysics Data System (ADS)

Ladewski, Barbara G.

Despite considerable exploration of inquiry and reflection in the literatures of science education and teacher education/teacher professional development over the past century, few theoretical or analytical tools exist to characterize these processes within a naturalistic classroom context. In addition, little is known regarding possible developmental trajectories for inquiry or reflection---for teachers or students---as these processes develop within a classroom context over time. In the dissertation, I use a sociocultural lens to explore these issues with an eye to the ways in which teachers and students develop shared sense-making, rather than from the more traditional perspective of individual teacher activity or student learning. The study includes both theoretical and empirical components. Theoretically, I explore the elaborations of sociocultural theory needed to characterize teacher-student shared sense-making as it develops within a classroom context, and, in particular, the role of inquiry and reflection in that sense-making. I develop a sociocultural model of shared sense-making that attempts to represent the dialectic between the individual and the social, through an elaboration of existing sociocultural and psychological constructs, including Vygotsky's zone of proximal development and theory of mind. Using this model as an interpretive framework, I develop a case study that explores teacher-student shared sense-making within a middle-school science classroom across a year of scaffolded introduction to inquiry-based science instruction. The empirical study serves not only as a test case for the theoretical model, but also informs our understanding regarding possible developmental trajectories and important mechanisms supporting and constraining shared sense-making within inquiry-based science classrooms. Theoretical and empirical findings provide support for the idea that perspectival shifts---that is, shifts of point-of-view that alter relationships and proximities of elements within the interaction space---play an important role in shared sense-making. Findings further suggest that the mutually constitutive interaction of inquiry and reflection plays a key role in flexible shared sense-making. Finally, findings lend support to the idea of a dialectical relationship between human models of shared sense-making and human systems of shared sense-making; that is, the ways in which human minds are coordinated is a work in progress, shaping and shaped by human culture.

Interaction of eta mesons with nuclei.

PubMed

Kelkar, N G; Khemchandani, K P; Upadhyay, N J; Jain, B K

2013-06-01

Back in the mid-1980s, a new branch of investigation related to the interaction of eta mesons with nuclei came into existence. It started with the theoretical prediction of possible exotic states of eta mesons and nuclei bound by the strong interaction and later developed into an extensive experimental program to search for such unstable states as well as understand the underlying interaction via eta-meson producing reactions. The vast literature of experimental as well as theoretical works that studied various aspects of eta-producing reactions such as the π(+)n → ηp, pd → (3)Heη, p (6)Li → (7)Be η and γ (3)He → η X, to name a few, had but one objective in mind: to understand the eta-nucleon (ηN) and hence the η-nucleus interaction which could explain the production data and confirm the existence of some η-mesic nuclei. In spite of these efforts, there remain uncertainties in the knowledge of the ηN and hence the η-nucleus interaction. Therefore, this review is an attempt to bind together the findings in these works and draw some global and specific conclusions which can be useful for future explorations.The ηN scattering length (which represents the strength of the η-nucleon interaction) using different theoretical models and analyzing the data on η production in pion, photon and proton induced reactions was found to be spread out in a wide range, namely, 0.18 ≤ Re aηN ≤ 1.03 fm and 0.16 ≤ Rm aηN ≤ 0.49 fm. Theoretical searches of heavy η-mesic nuclei based on η-nucleus optical potentials and lighter ones based on Faddeev type few-body approaches predict the existence of several quasibound and resonant states. Although some hints of η-mesic states such as (3)(η)He and (25)(η)Mg do exist from previous experiments, the promise of clearer signals for the existence of η-mesic nuclei lies in the experiments to be performed at the J-PARC, MAMI and COSY facilities in the near future. This review is aimed at giving an overall status of these efforts.

Modeling and optimization of a typical fuel cell-heat engine hybrid system and its parametric design criteria

NASA Astrophysics Data System (ADS)

Zhao, Yingru; Chen, Jincan

A theoretical modeling approach is presented, which describes the behavior of a typical fuel cell-heat engine hybrid system in steady-state operating condition based on an existing solid oxide fuel cell model, to provide useful fundamental design characteristics as well as potential critical problems. The different sources of irreversible losses, such as the electrochemical reaction, electric resistances, finite-rate heat transfer between the fuel cell and the heat engine, and heat-leak from the fuel cell to the environment are specified and investigated. Energy and entropy analyses are used to indicate the multi-irreversible losses and to assess the work potentials of the hybrid system. Expressions for the power output and efficiency of the hybrid system are derived and the performance characteristics of the system are presented and discussed in detail. The effects of the design parameters and operating conditions on the system performance are studied numerically. It is found that there exist certain optimum criteria for some important parameters. The results obtained here may provide a theoretical basis for both the optimal design and operation of real fuel cell-heat engine hybrid systems. This new approach can be easily extended to other fuel cell hybrid systems to develop irreversible models suitable for the investigation and optimization of similar energy conversion settings and electrochemistry systems.

Three dimensional dust-acoustic solitary waves in an electron depleted dusty plasma with two-superthermal ion-temperature

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

Borhanian, J.; Shahmansouri, M.

2013-01-15

A theoretical investigation is carried out to study the existence and characteristics of propagation of dust-acoustic (DA) waves in an electron-depleted dusty plasma with two-temperature ions, which are modeled by kappa distribution functions. A three-dimensional cylindrical Kadomtsev-Petviashvili equation governing evolution of small but finite amplitude DA waves is derived by means of a reductive perturbation method. The influence of physical parameters on solitary wave structure is examined. Furthermore, the energy integral equation is used to study the existence domains of the localized structures. It is found that the present model can be employed to describe the existence of positive asmore » well as negative polarity DA solitary waves by selecting special values for parameters of the system, e.g., superthermal index of cold and/or hot ions, cold to hot ion density ratio, and hot to cold ion temperature ratio. This model may be useful to understand the excitation of nonlinear DA waves in astrophysical objects.« less

The cooling rates of pahoehoe flows: The importance of lava porosity

NASA Technical Reports Server (NTRS)

Jones, Alun C.

1993-01-01

Many theoretical models have been put forward to account for the cooling history of a lava flow; however, only limited detailed field data exist to validate these models. To accurately model the cooling of lava flows, data are required, not only on the heat loss mechanisms, but also on the surface skin development and the causes of differing cooling rates. This paper argues that the cause of such variations in the cooling rates are attributed, primarily, to the vesicle content and degassing history of the lava.

Complexity and chaos control in a discrete-time prey-predator model

NASA Astrophysics Data System (ADS)

Din, Qamar

2017-08-01

We investigate the complex behavior and chaos control in a discrete-time prey-predator model. Taking into account the Leslie-Gower prey-predator model, we propose a discrete-time prey-predator system with predator partially dependent on prey and investigate the boundedness, existence and uniqueness of positive equilibrium and bifurcation analysis of the system by using center manifold theorem and bifurcation theory. Various feedback control strategies are implemented for controlling the bifurcation and chaos in the system. Numerical simulations are provided to illustrate theoretical discussion.

Women’s Sexuality: Behaviors, Responses, and Individual Differences

PubMed Central

Andersen, Barbara L.; Cyranowski, Jill M.

2009-01-01

Classic and contemporary approaches to the assessment of female sexuality are discussed. General approaches, assessment strategies, and models of female sexuality are organized within the conceptual domains of sexual behaviors, sexual responses (desire, excitement, orgasm, and resolution), and individual differences, including general and sex-specific personality models. Where applicable, important trends and relationships are highlighted in the literature with both existing reports and previously unpublished data. The present conceptual overview highlights areas in sexual assessment and model building that are in need of further research and theoretical clarification. PMID:8543712

Novel models on fluid's variable thermo-physical properties for extensive study on convection heat and mass transfer

NASA Astrophysics Data System (ADS)

Shang, De-Yi; Zhong, Liang-Cai

2017-01-01

Our novel models for fluid's variable physical properties are improved and reported systematically in this work for enhancement of theoretical and practical value on study of convection heat and mass transfer. It consists of three models, namely (1) temperature parameter model, (2) polynomial model, and (3) weighted-sum model, respectively for treatment of temperature-dependent physical properties of gases, temperature-dependent physical properties of liquids, and concentration- and temperature-dependent physical properties of vapour-gas mixture. Two related components are proposed, and involved in each model for fluid's variable physical properties. They are basic physic property equations and theoretical similarity equations on physical property factors. The former, as the foundation of the latter, is based on the typical experimental data and physical analysis. The latter is built up by similarity analysis and mathematical derivation based on the former basic physical properties equations. These models are available for smooth simulation and treatment of fluid's variable physical properties for assurance of theoretical and practical value of study on convection of heat and mass transfer. Especially, so far, there has been lack of available study on heat and mass transfer of film condensation convection of vapour-gas mixture, and the wrong heat transfer results existed in widespread studies on the related research topics, due to ignorance of proper consideration of the concentration- and temperature-dependent physical properties of vapour-gas mixture. For resolving such difficult issues, the present novel physical property models have their special advantages.

Developing a theoretical maintenance model for disordered eating in Type 1 diabetes.

PubMed

Treasure, J; Kan, C; Stephenson, L; Warren, E; Smith, E; Heller, S; Ismail, K

2015-12-01

According to the literature, eating disorders are an increasing problem for more than a quarter of people with Type 1 diabetes and they are associated with accentuated diabetic complications. The clinical outcomes in this group when given standard eating disorder treatments are disappointing. The Medical Research Council guidelines for developing complex interventions suggest that the first step is to develop a theoretical model. To review existing literature to build a theoretical maintenance model for disordered eating in people with Type 1 diabetes. The literature in diabetes relating to models of eating disorder (Fairburn's transdiagnostic model and the dual pathway model) and food addiction was examined and assimilated. The elements common to all eating disorder models include weight/shape concern and problems with mood regulation. The predisposing traits of perfectionism, low self-esteem and low body esteem and the interpersonal difficulties from the transdiagnostic model are also relevant to diabetes. The differences include the use of insulin mismanagement to compensate for breaking eating rules and the consequential wide variations in plasma glucose that may predispose to 'food addiction'. Eating disorder symptoms elicit emotionally driven reactions and behaviours from others close to the individual affected and these are accentuated in the context of diabetes. The next stage is to test the assumptions within the maintenance model with experimental medicine studies to facilitate the development of new technologies aimed at increasing inhibitory processes and moderating environmental triggers. © 2015 The Authors. Diabetic Medicine © 2015 Diabetes UK.

Riemannian theory of Hamiltonian chaos and Lyapunov exponents

NASA Astrophysics Data System (ADS)

Casetti, Lapo; Clementi, Cecilia; Pettini, Marco

1996-12-01

A nonvanishing Lyapunov exponent λ1 provides the very definition of deterministic chaos in the solutions of a dynamical system; however, no theoretical mean of predicting its value exists. This paper copes with the problem of analytically computing the largest Lyapunov exponent λ1 for many degrees of freedom Hamiltonian systems as a function of ɛ=E/N, the energy per degree of freedom. The functional dependence λ1(ɛ) is of great interest because, among other reasons, it detects the existence of weakly and strongly chaotic regimes. This aim, the analytic computation of λ1(ɛ), is successfully reached within a theoretical framework that makes use of a geometrization of Newtonian dynamics in the language of Riemannian differential geometry. An alternative point of view about the origin of chaos in these systems is obtained independently of the standard explanation based on homoclinic intersections. Dynamical instability (chaos) is here related to curvature fluctuations of the manifolds whose geodesics are natural motions and is described by means of the Jacobi-Levi-Civita equation (JLCE) for geodesic spread. In this paper it is shown how to derive from the JLCE an effective stability equation. Under general conditions, this effective equation formally describes a stochastic oscillator; an analytic formula for the instability growth rate of its solutions is worked out and applied to the Fermi-Pasta-Ulam β model and to a chain of coupled rotators. Excellent agreement is found between the theoretical prediction and numeric values of λ1(ɛ) for both models.

In Pursuit of Theoretical Ground in Behavior Change Support Systems: Analysis of Peer-to-Peer Communication in a Health-Related Online Community

PubMed Central

Cobb, Nathan; Cohen, Trevor

2016-01-01

Background Research studies involving health-related online communities have focused on examining network structure to understand mechanisms underlying behavior change. Content analysis of the messages exchanged in these communities has been limited to the “social support” perspective. However, existing behavior change theories suggest that message content plays a prominent role reflecting several sociocognitive factors that affect an individual’s efforts to make a lifestyle change. An understanding of these factors is imperative to identify and harness the mechanisms of behavior change in the Health 2.0 era. Objective The objective of this work is two-fold: (1) to harness digital communication data to capture essential meaning of communication and factors affecting a desired behavior change, and (2) to understand the applicability of existing behavior change theories to characterize peer-to-peer communication in online platforms. Methods In this paper, we describe grounded theory–based qualitative analysis of digital communication in QuitNet, an online community promoting smoking cessation. A database of 16,492 de-identified public messages from 1456 users from March 1-April 30, 2007, was used in our study. We analyzed 795 messages using grounded theory techniques to ensure thematic saturation. This analysis enabled identification of key concepts contained in the messages exchanged by QuitNet members, allowing us to understand the sociobehavioral intricacies underlying an individual’s efforts to cease smoking in a group setting. We further ascertained the relevance of the identified themes to theoretical constructs in existing behavior change theories (eg, Health Belief Model) and theoretically linked techniques of behavior change taxonomy. Results We identified 43 different concepts, which were then grouped under 12 themes based on analysis of 795 messages. Examples of concepts include “sleepiness,” “pledge,” “patch,” “spouse,” and “slip.” Examples of themes include “traditions,” “social support,” “obstacles,” “relapse,” and “cravings.” Results indicate that themes consisting of member-generated strategies such as “virtual bonfires” and “pledges” were related to the highest number of theoretical constructs from the existing behavior change theories. In addition, results indicate that the member-generated communication content supports sociocognitive constructs from more than one behavior change model, unlike the majority of the existing theory-driven interventions. Conclusions With the onset of mobile phones and ubiquitous Internet connectivity, online social network data reflect the intricacies of human health behavior as experienced by health consumers in real time. This study offers methodological insights for qualitative investigations that examine the various kinds of behavioral constructs prevalent in the messages exchanged among users of online communities. Theoretically, this study establishes the manifestation of existing behavior change theories in QuitNet-like online health communities. Pragmatically, it sets the stage for real-time, data-driven sociobehavioral interventions promoting healthy lifestyle modifications by allowing us to understand the emergent user needs to sustain a desired behavior change. PMID:26839162

Damage Mechanics Approach to Penetration of Water-filled Surface Crevasses

NASA Astrophysics Data System (ADS)

Duddu, R.; Jimenez, S. K.; Bassis, J. N.

2017-12-01

Iceberg calving is a natural process that occurs when crevasses penetrate the entire thickness of an ice shelf or a glacier leading to the detachment (birth) of icebergs. Calving from marine-terminating glaciers and floating ice shelves accounts for nearly 50% of the mass lost from both the Greenland and Antarctic ice sheets, which can directly or indirectly contribute to sealevel rise. A widely-accepted hypothesis is that crevasses in ice form due to brittle mode I fracture under the action of tensile stresses. Existing theoretical approaches for modeling crevasse propagation based on the above hypothesis include the Nye zero stress and fracture mechanics approaches. These theoretical approaches assume idealized geometry and boundary conditions, and ignore the effects of viscous creep deformations in ice over longer time scales; however, they still produced interesting results that matched well with sparse field observations available. An alternative is to use the continuum damage mechanics approach for modeling crevasse propagation, which is more easily incorporated into numerical ice sheet models that consider realistic geometries, boundary conditions and viscous creep effects. In this presentation, we describe the damage mechanics approach to penetration of dry and water-filled surface crevasses using the principles of poromechanics and compare our results with those from existing theoretical approaches. We investigate the upper limits on crevasse penetration depth in relation to ice thickness, water depth in the surface crevasse, seawater depth at the ice terminus and ice rheology (i.e., elastic vs. viscous). Our studies on idealized glaciers show that the damage mechanics approach is consistent with the fracture mechanics approach when the seawater depth at the ice terminus is low, but is inconsistent with the theoretical approaches when the seawater depth at the ice terminus is high (i.e., near floatation). Our studies also indicate that the upper limit on surface crevasse penetration depth is minimally sensitive to ice rheology when glacier geometry changes are ignored. However, viscous flow can cause geometry changes and induce stresses (e.g., due to bending) leading to deeper crevasse penetration in numerical ice sheet models.

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

Briceno, Raul A.; Cohen, Thomas D.; Coito, S.

The last few years have been witness to a proliferation of new results concerning heavy exotic hadrons. Experimentally, many new signals have been discovered that could be pointing towards the existence of tetraquarks, pentaquarks, and other exotic configurations of quarks and gluons. Theoretically, advances in lattice field theory techniques place us at the cusp of understanding complex coupled-channel phenomena, modelling grows more sophisticated, and effective field theories are being applied to an ever greater range of situations. Consequently, it is thus an opportune time to evaluate the status of the field. In the following, a series of high priority experimentalmore » and theoretical issues concerning heavy exotic hadrons is presented.« less

Study of inelastic e-Cd and e-Zn collisions

NASA Astrophysics Data System (ADS)

Piwinski, Mariusz; Klosowski, Lukasz; Dziczek, Darek; Chwirot, Stanislaw

2016-09-01

Electron-photon coincidence experiments are well known for providing more detailed information about electron-atom collision than any other technique. The Electron Impact Coherence Parameters (EICP) values obtained in such studies deliver the most complete characterization of the inelastic collision and allow for a verification of proposed theoretical models. We present the results of Stokes and EICP parameters characterising electronic excitation of the lowest singlet P-state of cadmium and zinc atoms for various collision energies. The experiments were performed using electron-photon coincidence technique in the coherence analysis version. The obtained data are presented and compared with existing CCC and RDWA theoretical predictions.

Dynamic seismic signatures of saturated porous rocks containing two orthogonal sets of fractures: theory versus numerical simulations

NASA Astrophysics Data System (ADS)

Guo, Junxin; Rubino, J. Germán; Glubokovskikh, Stanislav; Gurevich, Boris

2018-05-01

The dispersion and attenuation of seismic waves are potentially important attributes for the non-invasive detection and characterization of fracture networks. A primary mechanism for these phenomena is wave-induced fluid flow (WIFF), which can take place between fractures and their embedding background (FB-WIFF), as well as within connected fractures (FF-WIFF). In this work, we propose a theoretical approach to quantify seismic dispersion and attenuation related to these two manifestations of WIFF in saturated porous rocks permeated by two orthogonal sets of fractures. The methodology is based on existing theoretical models for rocks with aligned fractures, and we consider three types of fracture geometries, namely, periodic planar fractures, randomly spaced planar fractures and penny-shaped cracks. Synthetic 2-D rock samples with different degrees of fracture intersections are then explored by considering both the proposed theoretical approach and a numerical upscaling procedure that provides the effective seismic properties of generic heterogeneous porous media. The results show that the theoretical predictions are in overall good agreement with the numerical simulations, in terms of both the stiffness coefficients and the anisotropic properties. For the seismic dispersion and attenuation caused by FB-WIFF, the theoretical model for penny-shaped cracks matches the numerical simulations best, whereas for representing the effects due to FF-WIFF the periodic planar fractures model turns out to be the most suitable one. The proposed theoretical approach is easy to apply and is applicable not only to 2-D but also to 3-D fracture systems. Hence, it has the potential to constitute a useful framework for the seismic characterization of fractured reservoirs, especially in the presence of intersecting fractures.

Pilot evaluation of a group therapy program for children bereaved by suicide.

PubMed

Daigle, Marc S; Labelle, Réal J

2012-01-01

Thousands of children are bereaved each year by suicide, yet there exists very little literature specifically on the psychological care, programs, and interventions available to help them. (1) To build and validate theoretical models for the Group Therapy Program for Children Bereaved by Suicide (PCBS); (2) to test these models in a preliminary evaluation. In the first part, we built theoretical models, which were then validated by scientists and clinicians. In the second part, the sessions of the PCBS were observed and rated. The participating children were tested pre- and postprogram. Positive changes were observed in the participating children in terms of basic safety, realistic understanding and useful knowledge, inappropriate behaviors, physical and psychological symptoms, child-parent and child-child communication, capacity for social and affective reinvestment, actualization of new models of self and the world, self-esteem, awareness and use of tools, cognitive, verbal, written and drawing abilities, cognitive dissonance, ambivalence, antagonism, and isolation. The changes reported in the bereaved children show that the PCBS has some efficacy.

Stopping of protons - Improved accuracy of the UCA model

NASA Astrophysics Data System (ADS)

Schiwietz, G.; Grande, P. L.

2012-02-01

Recent theoretical developments in the unitary convolution approximation (UCA) for electronic energy losses of bare and screened ions are presented. Examples are given for proton beams and rare-gas targets. For gas targets there exists a sufficient amount of experimental data on charge exchange, for pinpointing the largely unknown stopping-power contribution of electron-capture processes at low and intermediate energies.

When Do Better Schools Raise Housing Prices? Evidence from Paris Public and Private Schools. CEE DP 119

ERIC Educational Resources Information Center

Fack, Gabrielle; Grenet, Julien

2010-01-01

In France, as in many other countries, there is an ongoing debate on how residence-based assignment to schools affects both educational and residential segregation. Theoretical models (including Benabou, 1993; Fernandez and Rogerson, 1996; Epple and Romano, 2003; Rothstein, 2006) have shown that the existence of peer effects in education yields…

Research on Employment in the Rural Nonfarm Sector in Africa. African Rural Employment Paper No. 5.

ERIC Educational Resources Information Center

Liedholm, Carl

Within the context of the role of rural employment in overall economic development, the objectives were to summarize existing knowledge of the rural African nonfarm sector and to develop an analytical framework for examing utilization of labor in this sector, using a descriptive profile, a theoretical model, and a research approach to rural…

A Game-Theoretic Model of Curriculum Integration and School Leadership. Publication Series No. 4

ERIC Educational Resources Information Center

Stull, William J.

2004-01-01

Curriculum integration (CI) is an educational strategy aimed primarily at students who take significant numbers of both academic and vocational courses either as part of a formal program or on their own. Its goal is to enhance the learning of these students by breaking down the traditional barrier that exists in most schools between the two…

The Categorization-Individuation Model: An Integrative Account of the Other-Race Recognition Deficit

ERIC Educational Resources Information Center

Hugenberg, Kurt; Young, Steven G.; Bernstein, Michael J.; Sacco, Donald F.

2010-01-01

The "other-race effect" (ORE), or the finding that same-race faces are better recognized than other-race faces, is one of the best replicated phenomena in face recognition. The current article reviews existing evidence and theory and proposes a new theoretical framework for the ORE, which argues that the effect results from a confluence of social…

Imitation dynamics of vaccine decision-making behaviours based on the game theory.

PubMed

Yang, Junyuan; Martcheva, Maia; Chen, Yuming

2016-01-01

Based on game theory, we propose an age-structured model to investigate the imitation dynamics of vaccine uptake. We first obtain the existence and local stability of equilibria. We show that Hopf bifurcation can occur. We also establish the global stability of the boundary equilibria and persistence of the disease. The theoretical results are supported by numerical simulations.

Learning Outside of Classroom: Exploring the Active Part of an Informal Online English Learning Community in China

ERIC Educational Resources Information Center

Sun, Yanyan; Franklin, Teresa; Gao, Fei

2017-01-01

This study explored how the GRE Analytical Writing Section Discussion Forum, an informal online language learning community in China, functioned to support its members to improve their English writing proficiency. The Community of Inquiry (CoI) model was used as the theoretical framework to explore the existence of teaching presence, cognitive…

Theoretical Analysis of the Electron Spiral Toroid Concept

NASA Technical Reports Server (NTRS)

Cambier, Jean-Luc; Micheletti, David A.; Bushnell, Dennis M. (Technical Monitor)

2000-01-01

This report describes the analysis of the Electron Spiral Toroid (EST) concept being promoted by Electron Power Systems Inc. (EPS). The EST is described as a toroidal plasma structure composed Of ion and electron shells. It is claimed that the EST requires little or no external confinement, despite the extraordinarily large energy densities resulting from the self-generating magnetic fields. The present analysis is based upon documentation made available by EPS, a previous description of the model by the Massachusetts Institute of Technology (MIT), and direct discussions with EPS and MIT. It is found that claims of absolute stability and large energy storage capacities of the EST concept have not been substantiated. Notably, it can be demonstrated that the ion fluid is fundamentally unstable. Although various scenarios for ion confinement were subsequently suggested by EPS and MIT, none were found to be plausible. Although the experimental data does not prove the existence of EST configurations, there is undeniable experimental evidence that some type of plasma structures whose characteristics remain to be determined are observed. However, more realistic theoretical models must first be developed to explain their existence and properties before applications of interest to NASA can he assessed and developed.

Optical gain coefficients of silicon: a theoretical study

NASA Astrophysics Data System (ADS)

Tsai, Chin-Yi

2018-05-01

A theoretical model is presented and an explicit formula is derived for calculating the optical gain coefficients of indirect band-gap semiconductors. This model is based on the second-order time-dependent perturbation theory of quantum mechanics by incorporating all the eight processes of photon/phonon emission and absorption between the band edges of the conduction and valence bands. Numerical calculation results are given for Si. The calculated absorption coefficients agree well with the existing fitting formula of experiment data with two modes of phonons: optical phonons with energy of 57.73 meV and acoustic phonons with energy of 18.27 meV near (but not exactly at) the zone edge of the X-point in the dispersion relation of phonons. These closely match with existing data of 57.5 meV transverse optical (TO) phonons at the X4-point and 18.6 meV transverse acoustic (TA) phonons at the X3-point of the zone edge. The calculated results show that the material optical gain of Si will overcome free-carrier absorption if the energy separation of quasi-Fermi levels between electrons and holes exceeds 1.15 eV.

Bounded energy states in homogeneous turbulent shear flow: An alternative view

NASA Technical Reports Server (NTRS)

Bernard, Peter S.; Speziale, Charles G.

1990-01-01

The equilibrium structure of homogeneous turbulent shear flow is investigated from a theoretical standpoint. Existing turbulence models, in apparent agreement with physical and numerical experiments, predict an unbounded exponential time growth of the turbulent kinetic energy and dissipation rate; only the anisotropy tensor and turbulent time scale reach a structural equilibrium. It is shown that if vortex stretching is accounted for in the dissipation rate transport equation, then there can exist equilibrium solutions, with bounded energy states, where the turbulence production is balanced by its dissipation. Illustrative calculations are present for a k-epsilon model modified to account for vortex stretching. The calculations indicate an initial exponential time growth of the turbulent kinetic energy and dissipation rate for elapsed times that are as large as those considered in any of the previously conducted physical or numerical experiments on homogeneous shear flow. However, vortex stretching eventually takes over and forces a production-equals-dissipation equilibrium with bounded energy states. The validity of this result is further supported by an independent theoretical argument. It is concluded that the generally accepted structural equilibrium for homogeneous shear flow with unbounded component energies is in need of re-examination.

From social network (centralized vs. decentralized) to collective decision-making (unshared vs. shared consensus).

PubMed

Sueur, Cédric; Deneubourg, Jean-Louis; Petit, Odile

2012-01-01

Relationships we have with our friends, family, or colleagues influence our personal decisions, as well as decisions we make together with others. As in human beings, despotism and egalitarian societies seem to also exist in animals. While studies have shown that social networks constrain many phenomena from amoebae to primates, we still do not know how consensus emerges from the properties of social networks in many biological systems. We created artificial social networks that represent the continuum from centralized to decentralized organization and used an agent-based model to make predictions about the patterns of consensus and collective movements we observed according to the social network. These theoretical results showed that different social networks and especially contrasted ones--star network vs. equal network--led to totally different patterns. Our model showed that, by moving from a centralized network to a decentralized one, the central individual seemed to lose its leadership in the collective movement's decisions. We, therefore, showed a link between the type of social network and the resulting consensus. By comparing our theoretical data with data on five groups of primates, we confirmed that this relationship between social network and consensus also appears to exist in animal societies.

Magnon Hall effect on the Lieb lattice.

PubMed

Cao, Xiaodong; Chen, Kai; He, Dahai

2015-04-29

Ferromagnetic insulators without inversion symmetry may show magnon Hall effect (MHE) in the presence of a temperature gradient due to the existence of Dzyaloshinskii-Moriya interaction (DMI). In this theoretical study, we investigate MHE on a lattice with inversion symmetry, namely the Lieb lattice, where the DMI is introduced by adding an external electric field. We show the nontrivial topology of this model by examining the existence of edge states and computing the topological phase diagram characterized by the Chern numbers of different bands. Together with the topological phase diagram, we can further determine the sign and magnitude of the transverse thermal conductivity. The impact of the flat band possessed by this model on the thermal conductivity is discussed by computing the Berry curvature analytically.

Dynamical and statistical behavior of discrete combustion waves: a theoretical and numerical study.

PubMed

Bharath, Naine Tarun; Rashkovskiy, Sergey A; Tewari, Surya P; Gundawar, Manoj Kumar

2013-04-01

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius' macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius' microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.

Dynamical and statistical behavior of discrete combustion waves: A theoretical and numerical study

NASA Astrophysics Data System (ADS)

Bharath, Naine Tarun; Rashkovskiy, Sergey A.; Tewari, Surya P.; Gundawar, Manoj Kumar

2013-04-01

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius’ macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius’ microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.

Research in Theoretical High Energy Physics- Final Report

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

Okada, Nobuchika

PI Dr. Okada’s research interests are centered on phenomenological aspects of particle physics. It has been abundantly clear in recent years that an extension of the Standard Model (SM), i.e. new physics beyond the SM, is needed to explain a number of experimental observations such as the neutrino oscillation data, the existence of non-baryonic dark matter, and the observed baryon asymmetry of the Universe. In addition, the SM suffers from several theoretical/conceptual problems, such as the gauge hierarchy problem, the fermion mass hierarchy problem, and the origin of the electroweak symmetry breaking. It is believed that these problems can alsomore » be solved by new physics beyond the SM. The main purpose of the Dr. Okada’s research is a theoretical investigation of new physics opportunities from various phenomenological points of view, based on the recent progress of experiments/observations in particle physics and cosmology. There are many possibilities to go beyond the SM and many new physics models have been proposed. The major goal of the project is to understand the current status of possible new physics models and obtain the future prospects of new physics phenomena toward their discoveries.« less

Verification of Gyrokinetic codes: Theoretical background and applications

NASA Astrophysics Data System (ADS)

Tronko, Natalia; Bottino, Alberto; Görler, Tobias; Sonnendrücker, Eric; Told, Daniel; Villard, Laurent

2017-05-01

In fusion plasmas, the strong magnetic field allows the fast gyro-motion to be systematically removed from the description of the dynamics, resulting in a considerable model simplification and gain of computational time. Nowadays, the gyrokinetic (GK) codes play a major role in the understanding of the development and the saturation of turbulence and in the prediction of the subsequent transport. Naturally, these codes require thorough verification and validation. Here, we present a new and generic theoretical framework and specific numerical applications to test the faithfulness of the implemented models to theory and to verify the domain of applicability of existing GK codes. For a sound verification process, the underlying theoretical GK model and the numerical scheme must be considered at the same time, which has rarely been done and therefore makes this approach pioneering. At the analytical level, the main novelty consists in using advanced mathematical tools such as variational formulation of dynamics for systematization of basic GK code's equations to access the limits of their applicability. The verification of the numerical scheme is proposed via the benchmark effort. In this work, specific examples of code verification are presented for two GK codes: the multi-species electromagnetic ORB5 (PIC) and the radially global version of GENE (Eulerian). The proposed methodology can be applied to any existing GK code. We establish a hierarchy of reduced GK Vlasov-Maxwell equations implemented in the ORB5 and GENE codes using the Lagrangian variational formulation. At the computational level, detailed verifications of global electromagnetic test cases developed from the CYCLONE Base Case are considered, including a parametric β-scan covering the transition from ITG to KBM and the spectral properties at the nominal β value.

Classifying GRB 170817A/GW170817 in a Fermi duration-hardness plane

NASA Astrophysics Data System (ADS)

Horváth, I.; Tóth, B. G.; Hakkila, J.; Tóth, L. V.; Balázs, L. G.; Rácz, I. I.; Pintér, S.; Bagoly, Z.

2018-03-01

GRB 170817A, associated with the LIGO-Virgo GW170817 neutron-star merger event, lacks the short duration and hard spectrum of a Short gamma-ray burst (GRB) expected from long-standing classification models. Correctly identifying the class to which this burst belongs requires comparison with other GRBs detected by the Fermi GBM. The aim of our analysis is to classify Fermi GRBs and to test whether or not GRB 170817A belongs—as suggested—to the Short GRB class. The Fermi GBM catalog provides a large database with many measured variables that can be used to explore gamma-ray burst classification. We use statistical techniques to look for clustering in a sample of 1298 gamma-ray bursts described by duration and spectral hardness. Classification of the detected bursts shows that GRB 170817A most likely belongs to the Intermediate, rather than the Short GRB class. We discuss this result in light of theoretical neutron-star merger models and existing GRB classification schemes. It appears that GRB classification schemes may not yet be linked to appropriate theoretical models, and that theoretical models may not yet adequately account for known GRB class properties. We conclude that GRB 170817A may not fit into a simple phenomenological classification scheme.

Theoretical study of turbulent channel flow - Bulk properties, pressure fluctuations, and propagation of electromagnetic waves

NASA Technical Reports Server (NTRS)

Canuto, V. M.; Hartke, G. J.; Battaglia, A.; Chasnov, J.; Albrecht, G. F.

1990-01-01

In this paper, we apply two theoretical turbulence models, DIA and the recent GISS model, to study properties of a turbulent channel flow. Both models provide a turbulent kinetic energy spectral function E(k) as the solution of a non-linear equation; the two models employ the same source function but different closures. The source function is characterized by a rate n sub s (k) which is derived from the complex eigenvalues of the Orr-Sommerfeld (OS) equation in which the basic flow is taken to be of a Poiseuille type. The O-S equation is solved for a variety of Reynolds numbers corresponding to available experimental data. A physical argument is presented whereby the central line velocity characterizing the basic flow, U0 sup L, is not to be identified with the U0 appearing in the experimental Reynolds number. The theoretical results are compared with two types of experimental data: (1) turbulence bulk properties, and (2) properties that depend strongly on the structure of the turbulence spectrum at low wave numbers. The only existing analytical expression for Pi (k) cannot be used in the present case because it applies to the case of a flat plate, not a finite channel.

Synchronizing movements with the metronome: nonlinear error correction and unstable periodic orbits.

PubMed

Engbert, Ralf; Krampe, Ralf Th; Kurths, Jürgen; Kliegl, Reinhold

2002-02-01

The control of human hand movements is investigated in a simple synchronization task. We propose and analyze a stochastic model based on nonlinear error correction; a mechanism which implies the existence of unstable periodic orbits. This prediction is tested in an experiment with human subjects. We find that our experimental data are in good agreement with numerical simulations of our theoretical model. These results suggest that feedback control of the human motor systems shows nonlinear behavior. Copyright 2001 Elsevier Science (USA).

Magnetic Majorana Fermions

NASA Astrophysics Data System (ADS)

Moessner, Roderich

Condensed matter systems provide emergent mini-universes in which quasiparticles may exist which do not correspond to any experimentally detected elementary particle. Topological quantum materials have been particularly productive in this regard, with the present search focussing on Majorana fermions, known theoretically already for decades. Here, we discuss manifestations of magnetic Majorana fermions in the Kitaev model. We place particular emphasis on their fate when perturbations, such as Heisenberg terms, are added to the ideal model system, and address experimental signatures of their vestiges in phases adjacent to the spin liquid.

Computational intelligence in earth sciences and environmental applications: issues and challenges.

PubMed

Cherkassky, V; Krasnopolsky, V; Solomatine, D P; Valdes, J

2006-03-01

This paper introduces a generic theoretical framework for predictive learning, and relates it to data-driven and learning applications in earth and environmental sciences. The issues of data quality, selection of the error function, incorporation of the predictive learning methods into the existing modeling frameworks, expert knowledge, model uncertainty, and other application-domain specific problems are discussed. A brief overview of the papers in the Special Issue is provided, followed by discussion of open issues and directions for future research.

Gauge interactions theory and experiment

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

Zichichi, A.

This volume brings together physicists from around the world to report and discuss the exciting advances made recently in theoretical and experimental aspects of gauge interactions. Following a presentation of the theoretical foundations of and recent developments in gauge fields, the contrib utors fogus on supersymmetry, the derivation of Higgs particles from gauge fields, and heavy leptons. Other chapters discuss the use of quantum chromodynamics in describing basic interactions among quarks and gluons, in predicting the existence of glueballs, and in application to heavy flavor production in strong interactions. The editor, Antonino Zichichi, provides a study of the multiparticle hadronicmore » systems produced in highenergy soft (pp) interactions. Other interesting chapters deal with photon scattering at very high energies and theoretical alternatives to the electroweak model, and the volume concludes with proposals for future experimental facilities for European physics.« less

NLPIR: A Theoretical Framework for Applying Natural Language Processing to Information Retrieval.

ERIC Educational Resources Information Center

Zhou, Lina; Zhang, Dongsong

2003-01-01

Proposes a theoretical framework called NLPIR that integrates natural language processing (NLP) into information retrieval (IR) based on the assumption that there exists representation distance between queries and documents. Discusses problems in traditional keyword-based IR, including relevance, and describes some existing NLP techniques.…

Sound transmission through lightweight double-leaf partitions: theoretical modelling

NASA Astrophysics Data System (ADS)

Wang, J.; Lu, T. J.; Woodhouse, J.; Langley, R. S.; Evans, J.

2005-09-01

This paper presents theoretical modelling of the sound transmission loss through double-leaf lightweight partitions stiffened with periodically placed studs. First, by assuming that the effect of the studs can be replaced with elastic springs uniformly distributed between the sheathing panels, a simple smeared model is established. Second, periodic structure theory is used to develop a more accurate model taking account of the discrete placing of the studs. Both models treat incident sound waves in the horizontal plane only, for simplicity. The predictions of the two models are compared, to reveal the physical mechanisms determining sound transmission. The smeared model predicts relatively simple behaviour, in which the only conspicuous features are associated with coincidence effects with the two types of structural wave allowed by the partition model, and internal resonances of the air between the panels. In the periodic model, many more features are evident, associated with the structure of pass- and stop-bands for structural waves in the partition. The models are used to explain the effects of incidence angle and of the various system parameters. The predictions are compared with existing test data for steel plates with wooden stiffeners, and good agreement is obtained.

Clusters of DNA induced by ionizing radiation: formation of short DNA fragments. I. Theoretical modeling

NASA Technical Reports Server (NTRS)

Holley, W. R.; Chatterjee, A.

1996-01-01

We have developed a general theoretical model for the interaction of ionizing radiation with chromatin. Chromatin is modeled as a 30-nm-diameter solenoidal fiber comprised of 20 turns of nucleosomes, 6 nucleosomes per turn. Charged-particle tracks are modeled by partitioning the energy deposition between primary track core, resulting from glancing collisions with 100 eV or less per event, and delta rays due to knock-on collisions involving energy transfers >100 eV. A Monte Carlo simulation incorporates damages due to the following molecular mechanisms: (1) ionization of water molecules leading to the formation of OH, H, eaq, etc.; (2) OH attack on sugar molecules leading to strand breaks: (3) OH attack on bases; (4) direct ionization of the sugar molecules leading to strand breaks; (5) direct ionization of the bases. Our calculations predict significant clustering of damage both locally, over regions up to 40 bp and over regions extending to several kilobase pairs. A characteristic feature of the regional damage predicted by our model is the production of short fragments of DNA associated with multiple nearby strand breaks. The shapes of the spectra of DNA fragment lengths depend on the symmetries or approximate symmetries of the chromatin structure. Such fragments have subsequently been detected experimentally and are reported in an accompanying paper (B. Rydberg, Radiat, Res. 145, 200-209, 1996) after exposure to both high- and low-LET radiation. The overall measured yields agree well quantitatively with the theoretical predictions. Our theoretical results predict the existence of a strong peak at about 85 bp, which represents the revolution period about the nucleosome. Other peaks at multiples of about 1,000 bp correspond to the periodicity of the particular solenoid model of chromatin used in these calculations. Theoretical results in combination with experimental data on fragmentation spectra may help determine the consensus or average structure of the chromatin fibers in mammalian DNA.

Determination of wind tunnel constraint effects by a unified pressure signature method. Part 2: Application to jet-in-crossflow

NASA Technical Reports Server (NTRS)

Hackett, J. E.; Sampath, S.; Phillips, C. G.

1981-01-01

The development of an improved jet-in-crossflow model for estimating wind tunnel blockage and angle-of-attack interference is described. Experiments showed that the simpler existing models fall seriously short of representing far-field flows properly. A new, vortex-source-doublet (VSD) model was therefore developed which employs curved trajectories and experimentally-based singularity strengths. The new model is consistent with existing and new experimental data and it predicts tunnel wall (i.e. far-field) pressures properly. It is implemented as a preprocessor to the wall-pressure-signature-based tunnel interference predictor. The supporting experiments and theoretical studies revealed some new results. Comparative flow field measurements with 1-inch "free-air" and 3-inch impinging jets showed that vortex penetration into the flow, in diameters, was almost unaltered until 'hard' impingement occurred. In modeling impinging cases, a 'plume redirection' term was introduced which is apparently absent in previous models. The effects of this term were found to be very significant.

Cloud Computing Value Chains: Understanding Businesses and Value Creation in the Cloud

NASA Astrophysics Data System (ADS)

Mohammed, Ashraf Bany; Altmann, Jörn; Hwang, Junseok

Based on the promising developments in Cloud Computing technologies in recent years, commercial computing resource services (e.g. Amazon EC2) or software-as-a-service offerings (e.g. Salesforce. com) came into existence. However, the relatively weak business exploitation, participation, and adoption of other Cloud Computing services remain the main challenges. The vague value structures seem to be hindering business adoption and the creation of sustainable business models around its technology. Using an extensive analyze of existing Cloud business models, Cloud services, stakeholder relations, market configurations and value structures, this Chapter develops a reference model for value chains in the Cloud. Although this model is theoretically based on porter's value chain theory, the proposed Cloud value chain model is upgraded to fit the diversity of business service scenarios in the Cloud computing markets. Using this model, different service scenarios are explained. Our findings suggest new services, business opportunities, and policy practices for realizing more adoption and value creation paths in the Cloud.

[Impact of small-area context on health: proposing a conceptual model].

PubMed

Voigtländer, S; Mielck, A; Razum, O

2012-11-01

Recent empirical studies stress the impact of features related to the small-area context on individual health. However, so far there exists no standard explanatory model that integrates the different kinds of such features and that conceptualises their relation to individual characteristics of social inequality. A review of theoretical publications on the relationship between social position and health as well as existing conceptual models for the impact of features related to the small-area context on health was undertaken. In the present article we propose a conceptual model for the health impact of the small-area context. This model conceptualises the location of residence as one dimension of social inequality that affects health through the resources as well as stressors which are inherent in the small-area context. The proposed conceptual model offers an orientation for future empirical studies and can serve as a basis for further discussions concerning the health relevance of the small-area context. © Georg Thieme Verlag KG Stuttgart · New York.

Solute Nucleation and Growth in Supercritical Fluid Mixtures

NASA Technical Reports Server (NTRS)

Smedley, Gregory T.; Wilemski, Gerald; Rawlins, W. Terry; Joshi, Prakash; Oakes, David B.; Durgin, William W.

1996-01-01

This research effort is directed toward two primary scientific objectives: (1) to determine the gravitational effect on the measurement of nucleation and growth rates near a critical point and (2) to investigate the nucleation process in supercritical fluids to aid in the evaluation and development of existing theoretical models and practical applications. A nucleation pulse method will be employed for this investigation using a rapid expansion to a supersaturated state that is maintained for approximately 1 ms followed by a rapid recompression to a less supersaturated state that effectively terminates nucleation while permitting growth to continue. Nucleation, which occurs during the initial supersaturated state, is decoupled from growth by producing rapid pressure changes. Thermodynamic analysis, condensation modeling, apparatus design, and optical diagnostic design necessary for the initiation of a theoretical and experimental investigation of naphthalene nucleation from supercritical CO2 have been completed.

Printability of alloys for additive manufacturing

PubMed Central

Mukherjee, T.; Zuback, J. S.; De, A.; DebRoy, T.

2016-01-01

Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. The findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts. PMID:26796864

Global analysis of seasonal streamflow predictability using an ensemble prediction system and observations from 6192 small catchments worldwide

NASA Astrophysics Data System (ADS)

van Dijk, Albert I. J. M.; Peña-Arancibia, Jorge L.; Wood, Eric F.; Sheffield, Justin; Beck, Hylke E.

2013-05-01

Ideally, a seasonal streamflow forecasting system would ingest skilful climate forecasts and propagate these through calibrated hydrological models initialized with observed catchment conditions. At global scale, practical problems exist in each of these aspects. For the first time, we analyzed theoretical and actual skill in bimonthly streamflow forecasts from a global ensemble streamflow prediction (ESP) system. Forecasts were generated six times per year for 1979-2008 by an initialized hydrological model and an ensemble of 1° resolution daily climate estimates for the preceding 30 years. A post-ESP conditional sampling method was applied to 2.6% of forecasts, based on predictive relationships between precipitation and 1 of 21 climate indices prior to the forecast date. Theoretical skill was assessed against a reference run with historic forcing. Actual skill was assessed against streamflow records for 6192 small (<10,000 km2) catchments worldwide. The results show that initial catchment conditions provide the main source of skill. Post-ESP sampling enhanced skill in equatorial South America and Southeast Asia, particularly in terms of tercile probability skill, due to the persistence and influence of the El Niño Southern Oscillation. Actual skill was on average 54% of theoretical skill but considerably more for selected regions and times of year. The realized fraction of the theoretical skill probably depended primarily on the quality of precipitation estimates. Forecast skill could be predicted as the product of theoretical skill and historic model performance. Increases in seasonal forecast skill are likely to require improvement in the observation of precipitation and initial hydrological conditions.

Optimizing Biorefinery Design and Operations via Linear Programming Models

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

Talmadge, Michael; Batan, Liaw; Lamers, Patrick

The ability to assess and optimize economics of biomass resource utilization for the production of fuels, chemicals and power is essential for the ultimate success of a bioenergy industry. The team of authors, consisting of members from the National Renewable Energy Laboratory (NREL) and the Idaho National Laboratory (INL), has developed simple biorefinery linear programming (LP) models to enable the optimization of theoretical or existing biorefineries. The goal of this analysis is to demonstrate how such models can benefit the developing biorefining industry. It focuses on a theoretical multi-pathway, thermochemical biorefinery configuration and demonstrates how the biorefinery can use LPmore » models for operations planning and optimization in comparable ways to the petroleum refining industry. Using LP modeling tools developed under U.S. Department of Energy's Bioenergy Technologies Office (DOE-BETO) funded efforts, the authors investigate optimization challenges for the theoretical biorefineries such as (1) optimal feedstock slate based on available biomass and prices, (2) breakeven price analysis for available feedstocks, (3) impact analysis for changes in feedstock costs and product prices, (4) optimal biorefinery operations during unit shutdowns / turnarounds, and (5) incentives for increased processing capacity. These biorefinery examples are comparable to crude oil purchasing and operational optimization studies that petroleum refiners perform routinely using LPs and other optimization models. It is important to note that the analyses presented in this article are strictly theoretical and they are not based on current energy market prices. The pricing structure assigned for this demonstrative analysis is consistent with $4 per gallon gasoline, which clearly assumes an economic environment that would favor the construction and operation of biorefineries. The analysis approach and examples provide valuable insights into the usefulness of analysis tools for maximizing the potential benefits of biomass utilization for production of fuels, chemicals and power.« less

A clear trade-off exists between the theoretical efficiency and acceptability of dietary changes that improve nutrient adequacy during early pregnancy in French women: Combined data from simulated changes modeling and online assessment survey.

PubMed

Bianchi, Clélia M; Huneau, Jean-François; Barbillon, Pierre; Lluch, Anne; Egnell, Manon; Fouillet, Hélène; Verger, Eric O; Mariotti, François

2018-01-01

During pregnancy, the diet of a mother-to-be should be adapted to meet increases in nutrient requirements. We analyzed the theoretical efficiency and acceptability of different types of tailored dietary changes for pregnant women. The nutrient adequacy of the diet was evaluated using the PANDiet score, by comparing the nutrient intakes of 344 non-pregnant premenopausal women (18-44y) with dietary reference intakes for the first trimester of pregnancy. Simulations were performed to evaluate the theoretical efficiency of three types of ten successive tailored dietary changes in improving nutrient adequacy, with graded difficulty in implementation. The acceptability (declared intention to use in the diet) of most efficient dietary changes was evaluated during an online randomized study including 115 French pregnant women (22-41y). Modifying the amount consumed of foods (type-1) did not modify the food repertoire and resulted in the smallest theoretical efficiency (increase in the PANDiet score of 9.8±0.2 points), but changes were the most acceptable (probability of the intention to use: 0.30-0.78). Conversely, replacing food items by items from the same group or eaten at the same time (type-3) broadened the food repertoire (3.6±1.3 food subgroups added) and resulted in the greatest theoretical efficiency (+23.9±0.3) but changes were the least acceptable (0.07-0.23). Replacing food items within the same subgroup (type-2) slightly broadened the food repertoire (+8.0±1.3 foods) and resulted in moderate theoretical efficiency (+14.8±0.2) and intermediate acceptability (0.11-0.35). A clear trade-off exists between the theoretical efficiency and acceptability of dietary changes, with a graded broadening of the food repertoire.

Testing a theory of aircraft noise annoyance: a structural equation analysis.

PubMed

Kroesen, Maarten; Molin, Eric J E; van Wee, Bert

2008-06-01

Previous research has stressed the relevance of nonacoustical factors in the perception of aircraft noise. However, it is largely empirically driven and lacks a sound theoretical basis. In this paper, a theoretical model which explains noise annoyance based on the psychological stress theory is empirically tested. The model is estimated by applying structural equation modeling based on data from residents living in the vicinity of Amsterdam Airport Schiphol in The Netherlands. The model provides a good model fit and indicates that concern about the negative health effects of noise and pollution, perceived disturbance, and perceived control and coping capacity are the most important variables that explain noise annoyance. Furthermore, the model provides evidence for the existence of two reciprocal relationships between (1) perceived disturbance and noise annoyance and (2) perceived control and coping capacity and noise annoyance. Lastly, the model yielded two unexpected results. Firstly, the variables noise sensitivity and fear related to the noise source were unable to explain additional variance in the endogenous variables of the model and were therefore excluded from the model. And secondly, the size of the total effect of noise exposure on noise annoyance was relatively small. The paper concludes with some recommended directions for further research.

Gödel, Tarski, Turing and the Conundrum of Free Will

NASA Astrophysics Data System (ADS)

Nayakar, Chetan S. Mandayam; Srikanth, R.

2014-07-01

The problem of defining and locating free will (FW) in physics is studied. On the basis of logical paradoxes, we argue that FW has a metatheoretic character, like the concept of truth in Tarski's undefinability theorem. Free will exists relative to a base theory if there is freedom to deviate from the deterministic or indeterministic dynamics in the theory, with the deviations caused by parameters (representing will) in the meta-theory. By contrast, determinism and indeterminism do not require meta-theoretic considerations in their formalization, making FW a fundamentally new causal primitive. FW exists relative to the meta-theory if there is freedom for deviation, due to higher-order causes. Absolute free will, which corresponds to our intuitive introspective notion of free will, exists if this meta-theoretic hierarchy is infinite. We argue that this hierarchy corresponds to higher levels of uncomputability. In other words, at any finitely high order in the hierarchy, there are uncomputable deviations from the law at that order. Applied to the human condition, the hierarchy corresponds to deeper levels of the subconscious or unconscious mind. Possible ramifications of our model for physics, neuroscience and artificial intelligence (AI) are briefly considered.

On the existence and stability of liquid water on the surface of mars today.

PubMed

Kuznetz, L H; Gan, D C

2002-01-01

The recent discovery of high concentrations of hydrogen just below the surface of Mars' polar regions by Mars Odyssey has enlivened the debate about past or present life on Mars. The prevailing assumption prior to the discovery was that the liquid water essential for its existence is absent. That assumption was based largely on the calculation of heat and mass transfer coefficients or theoretical climate models. This research uses an experimental approach to determine the feasibility of liquid water under martian conditions, setting the stage for a more empirical approach to the question of life on Mars. Experiments were conducted in three parts: Liquid water's existence was confirmed by droplets observed under martian conditions in part 1; the evolution of frost melting on the surface of various rocks under martian conditions was observed in part 2; and the evaporation rate of water in Petri dishes under Mars-like conditions was determined and compared with the theoretical predictions of various investigators in part 3. The results led to the conclusion that liquid water can be stable for extended periods of time on the martian surface under present-day conditions.

On the existence and stability of liquid water on the surface of mars today

NASA Technical Reports Server (NTRS)

Kuznetz, L. H.; Gan, D. C.

2002-01-01

The recent discovery of high concentrations of hydrogen just below the surface of Mars' polar regions by Mars Odyssey has enlivened the debate about past or present life on Mars. The prevailing assumption prior to the discovery was that the liquid water essential for its existence is absent. That assumption was based largely on the calculation of heat and mass transfer coefficients or theoretical climate models. This research uses an experimental approach to determine the feasibility of liquid water under martian conditions, setting the stage for a more empirical approach to the question of life on Mars. Experiments were conducted in three parts: Liquid water's existence was confirmed by droplets observed under martian conditions in part 1; the evolution of frost melting on the surface of various rocks under martian conditions was observed in part 2; and the evaporation rate of water in Petri dishes under Mars-like conditions was determined and compared with the theoretical predictions of various investigators in part 3. The results led to the conclusion that liquid water can be stable for extended periods of time on the martian surface under present-day conditions.

Convoys of care: Theorizing intersections of formal and informal care

PubMed Central

Kemp, Candace L.; Ball, Mary M.; Perkins, Molly M.

2013-01-01

Although most care to frail elders is provided informally, much of this care is paired with formal care services. Yet, common approaches to conceptualizing the formal–informal intersection often are static, do not consider self-care, and typically do not account for multi-level influences. In response, we introduce the “convoy of care” model as an alternative way to conceptualize the intersection and to theorize connections between care convoy properties and caregiver and recipient outcomes. The model draws on Kahn and Antonucci's (1980) convoy model of social relations, expanding it to include both formal and informal care providers and also incorporates theoretical and conceptual threads from life course, feminist gerontology, social ecology, and symbolic interactionist perspectives. This article synthesizes theoretical and empirical knowledge and demonstrates the convoy of care model in an increasingly popular long-term care setting, assisted living. We conceptualize care convoys as dynamic, evolving, person- and family-specific, and influenced by a host of multi-level factors. Care convoys have implications for older adults’ quality of care and ability to age in place, for job satisfaction and retention among formal caregivers, and for informal caregiver burden. The model moves beyond existing conceptual work to provide a comprehensive, multi-level, multi-factor framework that can be used to inform future research, including research in other care settings, and to spark further theoretical development. PMID:23273553

On the complex relationship between energy expenditure and longevity: Reconciling the contradictory empirical results with a simple theoretical model.

PubMed

Hou, Chen; Amunugama, Kaushalya

2015-07-01

The relationship between energy expenditure and longevity has been a central theme in aging studies. Empirical studies have yielded controversial results, which cannot be reconciled by existing theories. In this paper, we present a simple theoretical model based on first principles of energy conservation and allometric scaling laws. The model takes into considerations the energy tradeoffs between life history traits and the efficiency of the energy utilization, and offers quantitative and qualitative explanations for a set of seemingly contradictory empirical results. We show that oxidative metabolism can affect cellular damage and longevity in different ways in animals with different life histories and under different experimental conditions. Qualitative data and the linearity between energy expenditure, cellular damage, and lifespan assumed in previous studies are not sufficient to understand the complexity of the relationships. Our model provides a theoretical framework for quantitative analyses and predictions. The model is supported by a variety of empirical studies, including studies on the cellular damage profile during ontogeny; the intra- and inter-specific correlations between body mass, metabolic rate, and lifespan; and the effects on lifespan of (1) diet restriction and genetic modification of growth hormone, (2) the cold and exercise stresses, and (3) manipulations of antioxidant. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

A thermal/nonthermal approach to solar flares

NASA Technical Reports Server (NTRS)

Benka, Stephen G.

1991-01-01

An approach for modeling solar flare high-energy emissions is developed in which both thermal and nonthermal particles coexist and contribute to the radiation. The thermal/nonthermal distribution function is interpreted physically by postulating the existence of DC sheets in the flare region. The currents then provide both primary plasma heating through Joule dissipation, and runaway electron acceleration. The physics of runaway acceleration is discussed. Several methods are presented for obtaining approximations to the thermal/nonthermal distribution function, both within the current sheets and outside of them. Theoretical hard x ray spectra are calculated, allowing for thermal bremsstrahlung from the heated plasma electrons impinging on the chromosphere. A simple model for hard x ray images of two-ribbon flares is presented. Theoretical microwave gyrosynchrotron spectra are calculated and analyzed, uncovering important new effects caused by the interplay of thermal and nonthermal particles. The theoretical spectra are compared with observed high resolution spectra of solar flares, and excellent agreement is found, in both hard x rays and microwaves. The future detailed application of this approach to solar flares is discussed, as are possible refinements to this theory.

The fraction of quiescent massive galaxies in the early Universe

NASA Astrophysics Data System (ADS)

Fontana, A.; Santini, P.; Grazian, A.; Pentericci, L.; Fiore, F.; Castellano, M.; Giallongo, E.; Menci, N.; Salimbeni, S.; Cristiani, S.; Nonino, M.; Vanzella, E.

2009-07-01

Aims: We attempt to compile a complete, mass-selected sample of galaxies with low specific star-formation rates, and compare their properties with theoretical model predictions. Methods: We use the f(24 μ m})/f(K) flux ratio and the SED fitting to the 0.35-8.0 μm spectral distribution, to select quiescent galaxies from z≃ 0.4 to z≃ 4 in the GOODS-MUSIC sample. Our observational selection can be translated into thresholds in specific star-formation rate dot{M}/M_*, which can be compared with theoretical predictions. Results: In the framework of the well-known global decline in quiescent galaxy fraction with redshift, we find that a non-negligible fraction {≃ 15-20% of massive galaxies with low specific star-formation rate exists up to z≃ 4, including a tail of “red and dead” galaxies with dot{M}/M_*<10-11 yr-1. Theoretical models vary to a large extent in their predictions for the fraction of galaxies with low specific star-formation rates, but are unable to provide a global match to our data.

Muon g - 2 in the aligned two Higgs doublet model

DOE PAGES

Han, Tao; Kang, Sin Kyu; Sayre, Joshua

2016-02-16

In this paper, we study the Two-Higgs-Doublet Model with the aligned Yukawa sector (A2HDM) in light of the observed excess measured in the muon anomalous magnetic moment. We take into account the existing theoretical and experimental constraints with up-to-date values and demonstrate that a phenomenologically interesting region of parameter space exists. With a detailed parameter scan, we show a much larger region of viable parameter space in this model beyond the limiting case Type X 2HDM as obtained before. It features the existence of light scalar states with masses 3 GeV ≲ m H ≲ 50 GeV, or 10 GeVmore » ≲ m A ≲ 130 GeV, with enhanced couplings to tau leptons. The charged Higgs boson is typically heavier, with 200 GeV ≲ m H+ ≲ 630 GeV. The surviving parameter space is forced into the CP-conserving limit by EDM constraints. Some Standard Model observables may be significantly modified, including a possible new decay mode of the SMlike Higgs boson to four taus. Lastly, we comment on future measurements and direct searches for those effects at the LHC as tests of the model.« less

Theory of winds in late-type evolved and pre-main-sequence stars

NASA Technical Reports Server (NTRS)

Macgregor, K. B.

1983-01-01

Recent observational results confirm that many of the physical processes which are known to occur in the Sun also occur among late-type stars in general. One such process is the continuous loss of mass from a star in the form of a wind. There now exists an abundance of either direct or circumstantial evidence which suggests that most (if not all) stars in the cool portion of the HR diagram possess winds. An attempt is made to assess the current state of theoretical understanding of mass loss from two distinctly different classes of late-type stars: the post-main-sequence giant/supergiant stars and the pre-main-sequence T Tauri stars. Toward this end, the observationally inferred properties of the wind associated with each of the two stellar classes under consideration are summarized and compared against the predictions of existing theoretical models. Although considerable progress has been made in attempting to identify the mechanisms responsible for mass loss from cool stars, many fundamental problems remain to be solved.

A theoretical framework for antigay aggression: Review of established and hypothesized effects within the context of the general aggression model⋆

PubMed Central

Parrott, Dominic J.

2008-01-01

Theory and research on antigay aggression has identified different motives that facilitate aggression based on sexual orientation. However, the individual and situational determinants of antigay aggression associated with these motivations have yet to be organized within a single theoretical framework. This limits researchers’ ability to organize existing knowledge, link that knowledge with related aggression theory, and guide the application of new findings. To address these limitations, this article argues for the use of an existing conceptual framework to guide thinking and generate new research in this area of study. Contemporary theories of antigay aggression, and empirical support for these theories, are reviewed and interpreted within the unifying framework of the general aggression model [Anderson, C.A. & Bushman, B.J. (2002). Human aggression. Annual Review of Psychology, 53, 27–51.]. It is concluded that this conceptual framework will facilitate investigation of individual and situational risk factors that may contribute to antigay aggression and guide development of individual-level intervention. PMID:18355952

Interactive social contagions and co-infections on complex networks

NASA Astrophysics Data System (ADS)

Liu, Quan-Hui; Zhong, Lin-Feng; Wang, Wei; Zhou, Tao; Eugene Stanley, H.

2018-01-01

What we are learning about the ubiquitous interactions among multiple social contagion processes on complex networks challenges existing theoretical methods. We propose an interactive social behavior spreading model, in which two behaviors sequentially spread on a complex network, one following the other. Adopting the first behavior has either a synergistic or an inhibiting effect on the spread of the second behavior. We find that the inhibiting effect of the first behavior can cause the continuous phase transition of the second behavior spreading to become discontinuous. This discontinuous phase transition of the second behavior can also become a continuous one when the effect of adopting the first behavior becomes synergistic. This synergy allows the second behavior to be more easily adopted and enlarges the co-existence region of both behaviors. We establish an edge-based compartmental method, and our theoretical predictions match well with the simulation results. Our findings provide helpful insights into better understanding the spread of interactive social behavior in human society.

Physics in one dimension: theoretical concepts for quantum many-body systems.

PubMed

Schönhammer, K

2013-01-09

Various sophisticated approximation methods exist for the description of quantum many-body systems. It was realized early on that the theoretical description can simplify considerably in one-dimensional systems and various exact solutions exist. The focus in this introductory paper is on fermionic systems and the emergence of the Luttinger liquid concept.

PubChem3D: Conformer generation

PubMed Central

2011-01-01

Background PubChem, an open archive for the biological activities of small molecules, provides search and analysis tools to assist users in locating desired information. Many of these tools focus on the notion of chemical structure similarity at some level. PubChem3D enables similarity of chemical structure 3-D conformers to augment the existing similarity of 2-D chemical structure graphs. It is also desirable to relate theoretical 3-D descriptions of chemical structures to experimental biological activity. As such, it is important to be assured that the theoretical conformer models can reproduce experimentally determined bioactive conformations. In the present study, we investigate the effects of three primary conformer generation parameters (the fragment sampling rate, the energy window size, and force field variant) upon the accuracy of theoretical conformer models, and determined optimal settings for PubChem3D conformer model generation and conformer sampling. Results Using the software package OMEGA from OpenEye Scientific Software, Inc., theoretical 3-D conformer models were generated for 25,972 small-molecule ligands, whose 3-D structures were experimentally determined. Different values for primary conformer generation parameters were systematically tested to find optimal settings. Employing a greater fragment sampling rate than the default did not improve the accuracy of the theoretical conformer model ensembles. An ever increasing energy window did increase the overall average accuracy, with rapid convergence observed at 10 kcal/mol and 15 kcal/mol for model building and torsion search, respectively; however, subsequent study showed that an energy threshold of 25 kcal/mol for torsion search resulted in slightly improved results for larger and more flexible structures. Exclusion of coulomb terms from the 94s variant of the Merck molecular force field (MMFF94s) in the torsion search stage gave more accurate conformer models at lower energy windows. Overall average accuracy of reproduction of bioactive conformations was remarkably linear with respect to both non-hydrogen atom count ("size") and effective rotor count ("flexibility"). Using these as independent variables, a regression equation was developed to predict the RMSD accuracy of a theoretical ensemble to reproduce bioactive conformations. The equation was modified to give a minimum RMSD conformer sampling value to help ensure that 90% of the sampled theoretical models should contain at least one conformer within the RMSD sampling value to a "bioactive" conformation. Conclusion Optimal parameters for conformer generation using OMEGA were explored and determined. An equation was developed that provides an RMSD sampling value to use that is based on the relative accuracy to reproduce bioactive conformations. The optimal conformer generation parameters and RMSD sampling values determined are used by the PubChem3D project to generate theoretical conformer models. PMID:21272340

A Novel Information-Theoretic Approach for Variable Clustering and Predictive Modeling Using Dirichlet Process Mixtures

PubMed Central

Chen, Yun; Yang, Hui

2016-01-01

In the era of big data, there are increasing interests on clustering variables for the minimization of data redundancy and the maximization of variable relevancy. Existing clustering methods, however, depend on nontrivial assumptions about the data structure. Note that nonlinear interdependence among variables poses significant challenges on the traditional framework of predictive modeling. In the present work, we reformulate the problem of variable clustering from an information theoretic perspective that does not require the assumption of data structure for the identification of nonlinear interdependence among variables. Specifically, we propose the use of mutual information to characterize and measure nonlinear correlation structures among variables. Further, we develop Dirichlet process (DP) models to cluster variables based on the mutual-information measures among variables. Finally, orthonormalized variables in each cluster are integrated with group elastic-net model to improve the performance of predictive modeling. Both simulation and real-world case studies showed that the proposed methodology not only effectively reveals the nonlinear interdependence structures among variables but also outperforms traditional variable clustering algorithms such as hierarchical clustering. PMID:27966581

A Novel Information-Theoretic Approach for Variable Clustering and Predictive Modeling Using Dirichlet Process Mixtures.

PubMed

Chen, Yun; Yang, Hui

2016-12-14

In the era of big data, there are increasing interests on clustering variables for the minimization of data redundancy and the maximization of variable relevancy. Existing clustering methods, however, depend on nontrivial assumptions about the data structure. Note that nonlinear interdependence among variables poses significant challenges on the traditional framework of predictive modeling. In the present work, we reformulate the problem of variable clustering from an information theoretic perspective that does not require the assumption of data structure for the identification of nonlinear interdependence among variables. Specifically, we propose the use of mutual information to characterize and measure nonlinear correlation structures among variables. Further, we develop Dirichlet process (DP) models to cluster variables based on the mutual-information measures among variables. Finally, orthonormalized variables in each cluster are integrated with group elastic-net model to improve the performance of predictive modeling. Both simulation and real-world case studies showed that the proposed methodology not only effectively reveals the nonlinear interdependence structures among variables but also outperforms traditional variable clustering algorithms such as hierarchical clustering.

Measurements of Protein Crystal Face Growth Rates

NASA Technical Reports Server (NTRS)

Gorti, S.

2014-01-01

Protein crystal growth rates will be determined for several hyperthermophile proteins.; The growth rates will be assessed using available theoretical models, including kinetic roughening.; If/when kinetic roughening supersaturations are established, determinations of protein crystal quality over a range of supersaturations will also be assessed.; The results of our ground based effort may well address the existence of a correlation between fundamental growth mechanisms and protein crystal quality.

System-theoretic Interpretation of the Mode Sensing Hypothesis

DTIC Science & Technology

2014-08-01

estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the...6. AUTHOR(S) Prof. Rafal Zbikowski Prof. Graham Taylor 5d. PROJECT NUMBER 5d. TASK NUMBER 5e. WORK UNIT NUMBER 7. PERFORMING...insect flight control has more recently been modelled. The approach that we adopt here differs from previous, related work in several fundamental

Approaches for scalable modeling and emulation of cyber systems : LDRD final report.

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

Mayo, Jackson R.; Minnich, Ronald G.; Armstrong, Robert C.

2009-09-01

The goal of this research was to combine theoretical and computational approaches to better understand the potential emergent behaviors of large-scale cyber systems, such as networks of {approx} 10{sup 6} computers. The scale and sophistication of modern computer software, hardware, and deployed networked systems have significantly exceeded the computational research community's ability to understand, model, and predict current and future behaviors. This predictive understanding, however, is critical to the development of new approaches for proactively designing new systems or enhancing existing systems with robustness to current and future cyber threats, including distributed malware such as botnets. We have developed preliminarymore » theoretical and modeling capabilities that can ultimately answer questions such as: How would we reboot the Internet if it were taken down? Can we change network protocols to make them more secure without disrupting existing Internet connectivity and traffic flow? We have begun to address these issues by developing new capabilities for understanding and modeling Internet systems at scale. Specifically, we have addressed the need for scalable network simulation by carrying out emulations of a network with {approx} 10{sup 6} virtualized operating system instances on a high-performance computing cluster - a 'virtual Internet'. We have also explored mappings between previously studied emergent behaviors of complex systems and their potential cyber counterparts. Our results provide foundational capabilities for further research toward understanding the effects of complexity in cyber systems, to allow anticipating and thwarting hackers.« less

Sulfur isotope fractionation derived from reaction-transport modeling in the Eastern Equatorial Pacific (ODP Leg 201, Site 1226)

NASA Astrophysics Data System (ADS)

Tsang, M. Y.; Wortmann, U.

2016-12-01

Recent theoretical models suggest that low cell-specific sulfate reduction rates (csSRR) in marine sediments should result in high S-isotope fractionation factors (1). Existing studies on marginal sediments show actual fractionation factors indeed approach the theoretical equilibrium fractionation of 70‰ (2,3,4). Here we apply a reaction transport model (REMAP) (5) to data from ODP Site 1226 in the abyssal plain of the Eastern Equatorial Pacific (same location as Leg 138, Site 846). Our results suggest volumetric sulfate reduction rates vary from 346 fmol/cm3/day at 3 mbsf to 0.4 fmol/cm3/day in deeper sediments. Using existing cell counts, this implies csSRR between 10-3 and 10-6 fmol/cell/day, orders of magnitudes lower than those observed in shallower marine settings (10-1 to 10-4 fmol/cell/day) (6). We show that the observed S-isotopes are best explained with a constant fractionation factor of 48‰, considerably smaller than the 70‰ predicted by theoretical models (1). We hypothesize that this is due to in-situ sulfide re-oxidation and disproportionation, promoted by high contents of sedimentary Fe(III) and Mn(IV) at Site 1226 (7). We will further explore this hypothesis in our poster. Wing B.A. & Halevy I. Proc. Natl. Acad. Sci. USA 111, 18116-18125 (2014). Wortmann U.G. Geochem. Geophys. Geosyst. 7 (2006). Rudnicki M., Elderfield H. & Spiro B. Geochim. Cosmochim. Acta 65, 777-789 (2001). Tudge A.P. & Thode H.G. Canadian J. Res. 28, 567-578 (1950). Chernyavsky B.M. & Wortmann U.G. Geochem. Geophys. Geosyst. 8 (2007). Hoehler T.M. & Jørgensen B.B. Nature Rev. Microbiol. 11, 83-94 (2013). Gurvich E.G., Levitan M.A. & Kuzmina T.G. in Proc. of the Ocean Drilling Prog., Sci. Results, N. Pisias et al., Eds. (1995), vol. 138, pp. 769-778.

Electroproduction of hyperons at low momentum transfer

NASA Astrophysics Data System (ADS)

Acha, Armando R.

A high resolution study of the H(e,e'K+)Λ,Sigma 0 reaction was performed at Hall A, TJNAF as part of the hypernuclear experiment E94-107. One important ingredient to the measurement of the hypernuclear cross section is the elementary cross section for production of hyperons, Λ and Sigma0. This reaction was studied using a hydrogen (i.e. a proton) target. Data were taken at very low Q2 (˜0.07 (GeV/c) 2) and W˜2.2 GeV. Kaons were detected along the direction of q, the momentum transferred by the incident electron (thetaCM˜6°). In addition, there are few data available regarding electroproduction of hyperons at low Q2 and thetaCM and the available theoretical models differ significantly in this kinematical region of W. The measurement of the elementary cross section was performed by scaling the Monte Carlo cross section (MCEEP) with the experimental-to-simulated yield ratio. The Monte Carlo cross section includes an experimental fit and extrapolation from the existing data for electroproduction of hyperons. Moreover, the estimated transverse component of the electroproduction cross section of H(e,e'K+)Λ was compared to the different predictions of the theoretical models and exisiting data curves for photoproductions of hyperons. None of the models fully describe the cross-section results over the entire angular range. Furthermore, measurements of the Sigma 0/Λ production ratio were performed at theta CM˜6°, where data are not available. Finally, data for the measurements of the differential cross sections and the Sigma 0/Λ production were binned in Q2, W and thetaCM to understand the dependence on these variables. These results are not only a fundamental contribution to the hypernuclear spectroscopy studies but also an important experimental measurement to constrain existing theoretical models for the elementary reaction.

A general nonlinear magnetomechanical model for ferromagnetic materials under a constant weak magnetic field

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

Shi, Pengpeng; Zheng, Xiaojing, E-mail: xjzheng@xidian.edu.cn; Jin, Ke

2016-04-14

Weak magnetic nondestructive testing (e.g., metal magnetic memory method) concerns the magnetization variation of ferromagnetic materials due to its applied load and a weak magnetic surrounding them. One key issue on these nondestructive technologies is the magnetomechanical effect for quantitative evaluation of magnetization state from stress–strain condition. A representative phenomenological model has been proposed to explain the magnetomechanical effect by Jiles in 1995. However, the Jiles' model has some deficiencies in quantification, for instance, there is a visible difference between theoretical prediction and experimental measurements on stress–magnetization curve, especially in the compression case. Based on the thermodynamic relations and themore » approach law of irreversible magnetization, a nonlinear coupled model is proposed to improve the quantitative evaluation of the magnetomechanical effect. Excellent agreement has been achieved between the predictions from the present model and previous experimental results. In comparison with Jiles' model, the prediction accuracy is improved greatly by the present model, particularly for the compression case. A detailed study has also been performed to reveal the effects of initial magnetization status, cyclic loading, and demagnetization factor on the magnetomechanical effect. Our theoretical model reveals that the stable weak magnetic signals of nondestructive testing after multiple cyclic loads are attributed to the first few cycles eliminating most of the irreversible magnetization. Remarkably, the existence of demagnetization field can weaken magnetomechanical effect, therefore, significantly reduces the testing capability. This theoretical model can be adopted to quantitatively analyze magnetic memory signals, and then can be applied in weak magnetic nondestructive testing.« less

Total electron scattering cross sections of some important biomolecules at 0.2-6.0 keV energies

NASA Astrophysics Data System (ADS)

Gurung, Meera Devi; Ariyasinghe, W. M.

2017-12-01

The total electron scattering cross sections (TCS) of five nucleic bases (adenine, cytosine, guanine, thymine and uracil), phosphoric acid, three amino acids (glycine, lysine, and L-histidine), D-glucose, alpha-D-glucose, tetrahydropyran (THP), 3-hydroxytetrahydrofuran and furan have been determined in the energy range 0.2-6.0 keV using a simple model based on the effective atomic total electron scattering cross sections (EATCS). The reliability of the model is confirmed by comparing the determined TCS with the predictions of those by existing theoretical models.

Field investigation of the drift shadow

USGS Publications Warehouse

Su, G.W.; Kneafsey, T.J.; Ghezzehei, T.A.; Cook, P.J.; Marshall, B.D.

2006-01-01

The "Drift Shadow" is defined as the relatively drier region that forms below subsurface cavities or drifts in unsaturated rock. Its existence has been predicted through analytical and numerical models of unsaturated flow. However, these theoretical predictions have not been demonstrated empirically to date. In this project we plan to test the drift shadow concept through field investigations and compare our observations to simulations. Based on modeling studies we have an identified a suitable site to perform the study at an inactive mine in a sandstone formation. Pretest modeling studies and preliminary characterization of the site are being used to develop the field scale tests.

Issues and opportunities in exotic hadrons

DOE PAGES

Briceno, Raul A.; Cohen, Thomas D.; Coito, S.; ...

2016-04-01

The last few years have been witness to a proliferation of new results concerning heavy exotic hadrons. Experimentally, many new signals have been discovered that could be pointing towards the existence of tetraquarks, pentaquarks, and other exotic configurations of quarks and gluons. Theoretically, advances in lattice field theory techniques place us at the cusp of understanding complex coupled-channel phenomena, modelling grows more sophisticated, and effective field theories are being applied to an ever greater range of situations. Consequently, it is thus an opportune time to evaluate the status of the field. In the following, a series of high priority experimentalmore » and theoretical issues concerning heavy exotic hadrons is presented.« less

Theoretical microbial ecology without species

NASA Astrophysics Data System (ADS)

Tikhonov, Mikhail

2017-09-01

Ecosystems are commonly conceptualized as networks of interacting species. However, partitioning natural diversity of organisms into discrete units is notoriously problematic and mounting experimental evidence raises the intriguing question whether this perspective is appropriate for the microbial world. Here an alternative formalism is proposed that does not require postulating the existence of species as fundamental ecological variables and provides a naturally hierarchical description of community dynamics. This formalism allows approaching the species problem from the opposite direction. While the classical models treat a world of imperfectly clustered organism types as a perturbation around well-clustered species, the presented approach allows gradually adding structure to a fully disordered background. The relevance of this theoretical construct for describing highly diverse natural ecosystems is discussed.

Human-Technology Centric In Cyber Security Maintenance For Digital Transformation Era

NASA Astrophysics Data System (ADS)

Ali, Firkhan Ali Bin Hamid; Zalisham Jali, Mohd, Dr

2018-05-01

The development of the digital transformation in the organizations has become more expanding in these present and future years. This is because of the active demand to use the ICT services among all the organizations whether in the government agencies or private sectors. While digital transformation has led manufacturers to incorporate sensors and software analytics into their offerings, the same innovation has also brought pressure to offer clients more accommodating appliance deployment options. So, their needs a well plan to implement the cyber infrastructures and equipment. The cyber security play important role to ensure that the ICT components or infrastructures execute well along the organization’s business successful. This paper will present a study of security management models to guideline the security maintenance on existing cyber infrastructures. In order to perform security model for the currently existing cyber infrastructures, combination of the some security workforces and security process of extracting the security maintenance in cyber infrastructures. In the assessment, the focused on the cyber security maintenance within security models in cyber infrastructures and presented a way for the theoretical and practical analysis based on the selected security management models. Then, the proposed model does evaluation for the analysis which can be used to obtain insights into the configuration and to specify desired and undesired configurations. The implemented cyber security maintenance within security management model in a prototype and evaluated it for practical and theoretical scenarios. Furthermore, a framework model is presented which allows the evaluation of configuration changes in the agile and dynamic cyber infrastructure environments with regard to properties like vulnerabilities or expected availability. In case of a security perspective, this evaluation can be used to monitor the security levels of the configuration over its lifetime and to indicate degradations.

A theoretical and numerical study of the flow of granular materials down an inclined plane. Final report

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

Rajagopal, K.R.

The mechanics of the flowing granular materials such as coal, agricultural products, at deal of attention as it has fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the modular materials, and theories developed which can explain the experimentally observed facts. As many models have beenmore » suggested for describing the behavior of granular materials, from both continuum and kinetic theory viewpoints, we proposed to investigate the validity and usefulness of representative models from both the continuum and kinetic theory points of view, by determining the prediction of such a theory, in a representative flow, with respect to existence, non-existence, multiplicity and stability of solutions. The continuum model to be investigated is an outgrowth of a model due to Goodman and Cowin (1971, 1972) and the kinetic theory models being those due to Jenkins and Richman (1985) and Boyle and Massoudi (1989). In this report we present detailed results regarding the same. Interestingly, we find that the predictions of all the theories, in certain parameter space associated with these models, are qualitatively similar. This ofcourse depends on the values assumed for various material parameters in the models, which as yet are unknown, as reliable experiments have not been carried out as yet for their determination.« less

Simple diffusion can support the pitchfork, the flip bifurcations, and the chaos

NASA Astrophysics Data System (ADS)

Meng, Lili; Li, Xinfu; Zhang, Guang

2017-12-01

In this paper, a discrete rational fration population model with the Dirichlet boundary conditions will be considered. According to the discrete maximum principle and the sub- and supper-solution method, the necessary and sufficient conditions of uniqueness and existence of positive steady state solutions will be obtained. In addition, the dynamical behavior of a special two patch metapopulation model is investigated by using the bifurcation method, the center manifold theory, the bifurcation diagrams and the largest Lyapunov exponent. The results show that there exist the pitchfork, the flip bifurcations, and the chaos. Clearly, these phenomena are caused by the simple diffusion. The theoretical analysis of chaos is very imortant, unfortunately, there is not any results in this hand. However, some open problems are given.

Planned residential units: New development trajectories

NASA Astrophysics Data System (ADS)

Fedchenko, Irina

2017-01-01

The paper summarizes the transformation patterns of functional, morphological, social, and administrative structures of planned residential units - district (Russia, Eastern Europe), neighborhood (USA), community (UK, Europe), as the smallest structural and planning elements of the settlements. The study is based on the author's own on-site survey of the existing and new planned residential units, as well as on the analysis of theoretical sources. The multidisciplinary analysis of the theoretical concepts and on-site survey results showed that planned residential units formed in the early twentieth century retain their social and planning importance and identity, evolve and acquire new features and forms. At the same time, according to the current regulatory and legal instruments they remain basic planning elements of urban structure in the early twenty-first century. This paper also includes experimental analysis of the theoretical concepts of planned residential units' transformation, their conceptual planning model and formation principles in the early twenty-first century.

Load-Flow in Multiphase Distribution Networks: Existence, Uniqueness, Non-Singularity, and Linear Models

DOE PAGES

Bernstein, Andrey; Wang, Cong; Dall'Anese, Emiliano; ...

2018-01-01

This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for themore » non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.« less

Moral Enhancement Should Target Self-Interest and Cognitive Capacity.

PubMed

Ahlskog, Rafael

2017-01-01

Current suggestions for capacities that should be targeted for moral enhancement has centered on traits like empathy, fairness or aggression. The literature, however, lacks a proper model for understanding the interplay and complexity of moral capacities, which limits the practicability of proposed interventions. In this paper, I integrate some existing knowledge on the nature of human moral behavior and present a formal model of prosocial motivation. The model provides two important results regarding the most friction-free route to moral enhancement. First, we should consider decreasing self-interested motivation rather than increasing prosociality directly. Second, this should be complemented with cognitive enhancement. These suggestions are tested against existing and emerging evidence on cognitive capacity, mindfulness meditation and the effects of psychedelic drugs and are found to have sufficient grounding for further theoretical and empirical exploration. Furthermore, moral effects of the latter two are hypothesized to result from a diminished sense of self with subsequent reductions in self-interest.

Search for Hidden Particles (SHiP): a new experiment proposal

NASA Astrophysics Data System (ADS)

De Lellis, G.

2015-06-01

Searches for new physics with accelerators are being performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. We propose a new experimental facility meant to search for very weakly coupled particles in the few GeV mass domain. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored from the experimental point of view. A beam dump facility, built at CERN in the north area, using 400 GeV protons is a copious factory of charmed hadrons and could be used to probe the existence of such particles. The beam dump is also an ideal source of tau neutrinos, the less known particle in the Standard Model. In particular, tau anti-neutrinos have not been observed so far. We therefore propose an experiment to search for hidden particles and study tau neutrino physics at the same time.

Load-Flow in Multiphase Distribution Networks: Existence, Uniqueness, Non-Singularity, and Linear Models

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

Bernstein, Andrey; Wang, Cong; Dall'Anese, Emiliano

This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for themore » non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.« less

Engineering Weyl Superfluid in Ultracold Fermionic Gases by One-Dimensional Optical Superlattices

NASA Astrophysics Data System (ADS)

Huang, Beibing

2018-01-01

In this paper, we theoretically demonstrate by using one-dimensional superlattices to couple two-dimensional time-reversal-breaking gapped topological superfluid models, an anomalous Weyl superfluid (WS) can be obtained. This new phase features its unique Fermi arc states (FAS) on the surfaces. In the conventional WS, FAS exist only for a part of the line connecting the projections of Weyl points and extending to the border and/or center of surface Brillouin zone. But for the anomalous WS, FAS exist for the whole line. As a proof of principle, we self-consistently at the mean-field level claim the achievement of the anomalous WS in the model with a dichromatic superlattice. In addition, inversion symmetry and band inversion in this model are analyzed to provide the unique features of identifying the anomalous WS experimentally by the momentum-resolved radio-frequency spectroscopy.

Relativistic R -matrix calculations for the electron-impact excitation of neutral molybdenum

NASA Astrophysics Data System (ADS)

Smyth, R. T.; Johnson, C. A.; Ennis, D. A.; Loch, S. D.; Ramsbottom, C. A.; Ballance, C. P.

2017-10-01

A recent PISCES-B Mod experiment [Nishijima et al., J. Phys. B 43, 225701 (2010), 10.1088/0953-4075/43/22/225701] has revealed up to a factor of 5 discrepancy between measurement and the two existing theoretical models [Badnell et al., J. Phys. B 29, 3683 (1996), 10.1088/0953-4075/29/16/014; Bartschat et al., J. Phys. B 35, 2899 (2002), 10.1088/0953-4075/35/13/305], providing important diagnostics for Mo i. In the following paper we address this issue by employing a relativistic atomic structure and R -matrix scattering calculations to improve upon the available models for future applications and benchmark results against a recent Compact Toroidal Hybrid experiment [Hartwell et al., Fusion Sci. Technol. 72, 76 (2017), 10.1080/15361055.2017.1291046]. We determine the atomic structure of Mo i using grasp0, which implements the multiconfigurational Dirac-Fock method. Fine structure energies and radiative transition rates are presented and compared to existing experimental and theoretical values. The electron-impact excitation of Mo i is investigated using the relativistic R -matrix method and the parallel versions of the Dirac atomic R -matrix codes. Electron-impact excitation cross sections are presented and compared to the few available theoretical cross sections. Throughout, our emphasis is on improving the results for the z 1,2,3o5P →a S52,z 2,3,4o7P → a S73 and y 2,3,4o7P → a S73 electric dipole transitions of particular relevance for diagnostic work.

Applications of statistical physics and information theory to the analysis of DNA sequences

NASA Astrophysics Data System (ADS)

Grosse, Ivo

2000-10-01

DNA carries the genetic information of most living organisms, and the of genome projects is to uncover that genetic information. One basic task in the analysis of DNA sequences is the recognition of protein coding genes. Powerful computer programs for gene recognition have been developed, but most of them are based on statistical patterns that vary from species to species. In this thesis I address the question if there exist universal statistical patterns that are different in coding and noncoding DNA of all living species, regardless of their phylogenetic origin. In search for such species-independent patterns I study the mutual information function of genomic DNA sequences, and find that it shows persistent period-three oscillations. To understand the biological origin of the observed period-three oscillations, I compare the mutual information function of genomic DNA sequences to the mutual information function of stochastic model sequences. I find that the pseudo-exon model is able to reproduce the mutual information function of genomic DNA sequences. Moreover, I find that a generalization of the pseudo-exon model can connect the existence and the functional form of long-range correlations to the presence and the length distributions of coding and noncoding regions. Based on these theoretical studies I am able to find an information-theoretical quantity, the average mutual information (AMI), whose probability distributions are significantly different in coding and noncoding DNA, while they are almost identical in all studied species. These findings show that there exist universal statistical patterns that are different in coding and noncoding DNA of all studied species, and they suggest that the AMI may be used to identify genes in different living species, irrespective of their taxonomic origin.

Principles of assessing bacterial susceptibility to antibiotics using the agar diffusion method.

PubMed

Bonev, Boyan; Hooper, James; Parisot, Judicaël

2008-06-01

The agar diffusion assay is one method for quantifying the ability of antibiotics to inhibit bacterial growth. Interpretation of results from this assay relies on model-dependent analysis, which is based on the assumption that antibiotics diffuse freely in the solid nutrient medium. In many cases, this assumption may be incorrect, which leads to significant deviations of the predicted behaviour from the experiment and to inaccurate assessment of bacterial susceptibility to antibiotics. We sought a theoretical description of the agar diffusion assay that takes into consideration loss of antibiotic during diffusion and provides higher accuracy of the MIC determined from the assay. We propose a new theoretical framework for analysis of agar diffusion assays. MIC was determined by this technique for a number of antibiotics and analysis was carried out using both the existing free diffusion and the new dissipative diffusion models. A theory for analysis of antibiotic diffusion in solid media is described, in which we consider possible interactions of the test antibiotic with the solid medium or partial antibiotic inactivation during diffusion. This is particularly relevant to the analysis of diffusion of hydrophobic or amphipathic compounds. The model is based on a generalized diffusion equation, which includes the existing theory as a special case and contains an additional, dissipative term. Analysis of agar diffusion experiments using the new model allows significantly more accurate interpretation of experimental results and determination of MICs. The model has more general validity and is applicable to analysis of other dissipative processes, for example to antigen diffusion and to calculations of substrate load in affinity purification.

By-product mutualism and the ambiguous effects of harsher environments - A game-theoretic model.

PubMed

De Jaegher, Kris; Hoyer, Britta

2016-03-21

We construct two-player two-strategy game-theoretic models of by-product mutualism, where our focus lies on the way in which the probability of cooperation among players is affected by the degree of adversity facing the players. In our first model, cooperation consists of the production of a public good, and adversity is linked to the degree of complementarity of the players׳ efforts in producing the public good. In our second model, cooperation consists of the defense of a public, and/or a private good with by-product benefits, and adversity is measured by the number of random attacks (e.g., by a predator) facing the players. In both of these models, our analysis confirms the existence of the so-called boomerang effect, which states that in a harsh environment, the individual player has few incentives to unilaterally defect in a situation of joint cooperation. Focusing on such an effect in isolation leads to the "common-enemy" hypothesis that a larger degree of adversity increases the probability of cooperation. Yet, we also find that a sucker effect may simultaneously exist, which says that in a harsh environment, the individual player has few incentives to unilaterally cooperate in a situation of joint defection. Looked at in isolation, the sucker effect leads to the competing hypothesis that a larger degree of adversity decreases the probability of cooperation. Our analysis predicts circumstances in which the "common enemy" hypothesis prevails, and circumstances in which the competing hypothesis prevails. Copyright © 2016 Elsevier Ltd. All rights reserved.

Theoretical Investigations on the Influence of Artificially Altered Rock Mass Properties on Mechanical Excavation

NASA Astrophysics Data System (ADS)

Hartlieb, Philipp; Bock, Stefan

2018-03-01

This study presents a theoretical analysis of the influence of the rock mass rating on the cutting performance of roadheaders. Existing performance prediction models are assessed for their suitability for forecasting the influence of pre-damaging the rock mass with alternative methods like lasers or microwaves, prior to the mechanical excavation process. Finally, the RMCR model was chosen because it is the only reported model incorporating a range of rock mass properties into its calculations. The results show that even very tough rocks could be mechanically excavated if the occurrence, orientation and condition of joints are favourable for the cutting process. The calculated improvements in the cutting rate (m3/h) are up to 350% for the most favourable cases. In case of microwave irradiation of hard rocks with an UCS of 200 MPa, a reasonable improvement in the performance by 120% can be achieved with as little as an extra 0.7 kWh/m3 (= 1% more energy) compared to cutting only.

Modeling adsorption with lattice Boltzmann equation

PubMed Central

Guo, Long; Xiao, Lizhi; Shan, Xiaowen; Zhang, Xiaoling

2016-01-01

The research of adsorption theory has recently gained renewed attention due to its critical relevance to a number of trending industrial applications, hydrogen storage and shale gas exploration for instance. The existing theoretical foundation, laid mostly in the early twentieth century, was largely based on simple heuristic molecular interaction models and static interaction potential which, although being insightful in illuminating the fundamental mechanisms, are insufficient for computations with realistic adsorbent structure and adsorbate hydrodynamics, both critical for real-life applications. Here we present and validate a novel lattice Boltzmann model incorporating both adsorbate-adsorbate and adsorbate-adsorbent interactions with hydrodynamics which, for the first time, allows adsorption to be computed with real-life details. Connection with the classic Ono-Kondo lattice theory is established and various adsorption isotherms, both within and beyond the IUPAC classification are observed as a pseudo-potential is varied. This new approach not only enables an important physical to be simulated for real-life applications, but also provides an enabling theoretical framework within which the fundamentals of adsorption can be studied. PMID:27256325

Economic Game Theory to Model the Attenuation of Virulence of an Obligate Intracellular Bacterium.

PubMed

Tago, Damian; Meyer, Damien F

2016-01-01

Diseases induced by obligate intracellular pathogens have a large burden on global human and animal health. Understanding the factors involved in the virulence and fitness of these pathogens contributes to the development of control strategies against these diseases. Based on biological observations, a theoretical model using game theory is proposed to explain how obligate intracellular bacteria interact with their host. The equilibrium in such a game shows that the virulence and fitness of the bacterium is host-triggered and by changing the host's defense system to which the bacterium is confronted, an evolutionary process leads to an attenuated strain. Although, the attenuation procedure has already been conducted in practice in order to develop an attenuated vaccine (e.g., with Ehrlichia ruminantium), there was a lack of understanding of the theoretical basis behind this process. Our work provides a model to better comprehend the existence of different phenotypes and some underlying evolutionary mechanisms for the virulence of obligate intracellular bacteria.

Economic Game Theory to Model the Attenuation of Virulence of an Obligate Intracellular Bacterium

PubMed Central

Tago, Damian; Meyer, Damien F.

2016-01-01

Diseases induced by obligate intracellular pathogens have a large burden on global human and animal health. Understanding the factors involved in the virulence and fitness of these pathogens contributes to the development of control strategies against these diseases. Based on biological observations, a theoretical model using game theory is proposed to explain how obligate intracellular bacteria interact with their host. The equilibrium in such a game shows that the virulence and fitness of the bacterium is host-triggered and by changing the host's defense system to which the bacterium is confronted, an evolutionary process leads to an attenuated strain. Although, the attenuation procedure has already been conducted in practice in order to develop an attenuated vaccine (e.g., with Ehrlichia ruminantium), there was a lack of understanding of the theoretical basis behind this process. Our work provides a model to better comprehend the existence of different phenotypes and some underlying evolutionary mechanisms for the virulence of obligate intracellular bacteria. PMID:27610355

The threshold of a stochastic avian-human influenza epidemic model with psychological effect

NASA Astrophysics Data System (ADS)

Zhang, Fengrong; Zhang, Xinhong

2018-02-01

In this paper, a stochastic avian-human influenza epidemic model with psychological effect in human population and saturation effect within avian population is investigated. This model describes the transmission of avian influenza among avian population and human population in random environments. For stochastic avian-only system, persistence in the mean and extinction of the infected avian population are studied. For the avian-human influenza epidemic system, sufficient conditions for the existence of an ergodic stationary distribution are obtained. Furthermore, a threshold of this stochastic model which determines the outcome of the disease is obtained. Finally, numerical simulations are given to support the theoretical results.

The evolving concept of "patient-centeredness" in patient-physician communication research.

PubMed

Ishikawa, Hirono; Hashimoto, Hideki; Kiuchi, Takahiro

2013-11-01

Over the past few decades, the concept of "patient-centeredness" has been intensively studied in health communication research on patient-physician interaction. Despite its popularity, this concept has often been criticized for lacking a unified definition and operationalized measurement. This article reviews how health communication research on patient-physician interaction has conceptualized and operationalized patient-centered communication based on four major theoretical perspectives in sociology (i.e., functionalism, conflict theory, utilitarianism, and social constructionism), and discusses the agenda for future research in this field. Each theory addresses different aspects of the patient-physician relationship and communication from different theoretical viewpoints. Patient-centeredness is a multifaceted construct with no single theory that can sufficiently define the whole concept. Different theoretical perspectives of patient-centered communication can be selectively adopted according to the context and nature of problems in the patient-physician relationship that a particular study aims to explore. The present study may provide a useful framework: it offers an overview of the differing models of patient-centered communication and the expected roles and goals in each model; it does so toward identifying a communication model that fits the patient and the context and toward theoretically reconstructing existing measures of patient-centered communication. Furthermore, although patient-centered communication has been defined mainly from the viewpoint of physician's behaviors aimed at achieving patient-centered care, patient competence is also required for patient-centered communication. This needs to be examined in current medical practice. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology

NASA Astrophysics Data System (ADS)

Kroupa, P.

2012-06-01

The current standard model of cosmology (SMoC) requires The Dual Dwarf Galaxy Theorem to be true according to which two types of dwarf galaxies must exist: primordial dark-matter (DM) dominated (type A) dwarf galaxies, and tidal-dwarf and ram-pressure-dwarf (type B) galaxies void of DM. Type A dwarfs surround the host approximately spherically, while type B dwarfs are typically correlated in phase-space. Type B dwarfs must exist in any cosmological theory in which galaxies interact. Only one type of dwarf galaxy is observed to exist on the baryonic Tully-Fisher plot and in the radius-mass plane. The Milky Way satellite system forms a vast phase-space-correlated structure that includes globular clusters and stellar and gaseous streams. Other galaxies also have phase-space correlated satellite systems. Therefore, The Dual Dwarf Galaxy Theorem is falsified by observation and dynamically relevant cold or warm DM cannot exist. It is shown that the SMoC is incompatible with a large set of other extragalactic observations. Other theoretical solutions to cosmological observations exist. In particular, alone the empirical mass-discrepancy-acceleration correlation constitutes convincing evidence that galactic-scale dynamics must be Milgromian. Major problems with inflationary big bang cosmologies remain unresolved.

Human systems dynamics: Toward a computational model

NASA Astrophysics Data System (ADS)

Eoyang, Glenda H.

2012-09-01

A robust and reliable computational model of complex human systems dynamics could support advancements in theory and practice for social systems at all levels, from intrapersonal experience to global politics and economics. Models of human interactions have evolved from traditional, Newtonian systems assumptions, which served a variety of practical and theoretical needs of the past. Another class of models has been inspired and informed by models and methods from nonlinear dynamics, chaos, and complexity science. None of the existing models, however, is able to represent the open, high dimension, and nonlinear self-organizing dynamics of social systems. An effective model will represent interactions at multiple levels to generate emergent patterns of social and political life of individuals and groups. Existing models and modeling methods are considered and assessed against characteristic pattern-forming processes in observed and experienced phenomena of human systems. A conceptual model, CDE Model, based on the conditions for self-organizing in human systems, is explored as an alternative to existing models and methods. While the new model overcomes the limitations of previous models, it also provides an explanatory base and foundation for prospective analysis to inform real-time meaning making and action taking in response to complex conditions in the real world. An invitation is extended to readers to engage in developing a computational model that incorporates the assumptions, meta-variables, and relationships of this open, high dimension, and nonlinear conceptual model of the complex dynamics of human systems.

Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues

NASA Astrophysics Data System (ADS)

Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.

2013-08-01

This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

Community stakeholder responses to advocacy advertising

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

Miller, B.; Sinclair, J.

Focus group research was used to examine how community stakeholders, a group with local industry experience, responded to coal industry advocacy messages. The stakeholders expressed beliefs about both the advertiser and the coal industry, and while their knowledge led to critical consideration of the industry campaign, they also expressed a desire to identify with positive messages about their community. Applying a postpositivist research perspective, a new model is introduced to integrate these beliefs in terms of advertiser trust and industry accountability under the existing theoretical framework of persuasion knowledge. Agent and topic knowledge are combined in this model based onmore » responses to the industry advocacy campaign. In doing so, this study integrates a priori theory within a new context, extending the current theoretical framework to include an understanding of how community stakeholders - a common target for marketplace advocacy - interpret industry messages.« less

Response simulation and theoretical calibration of a dual-induction resistivity LWD tool

NASA Astrophysics Data System (ADS)

Xu, Wei; Ke, Shi-Zhen; Li, An-Zong; Chen, Peng; Zhu, Jun; Zhang, Wei

2014-03-01

In this paper, responses of a new dual-induction resistivity logging-while-drilling (LWD) tool in 3D inhomogeneous formation models are simulated by the vector finite element method (VFEM), the influences of the borehole, invaded zone, surrounding strata, and tool eccentricity are analyzed, and calibration loop parameters and calibration coefficients of the LWD tool are discussed. The results show that the tool has a greater depth of investigation than that of the existing electromagnetic propagation LWD tools and is more sensitive to azimuthal conductivity. Both deep and medium induction responses have linear relationships with the formation conductivity, considering optimal calibration loop parameters and calibration coefficients. Due to the different depths of investigation and resolution, deep induction and medium induction are affected differently by the formation model parameters, thereby having different correction factors. The simulation results can provide theoretical references for the research and interpretation of the dual-induction resistivity LWD tools.

Oral contraceptives and mood in women with and without premenstrual dysphoria: a theoretical model.

PubMed

Kurshan, N; Neill Epperson, C

2006-01-01

Despite numerous studies on the topic, there is no consensus to date on the effects of oral contraceptives on mood or the mechanism(s) by which they exert these effects. This review article presents a theoretical model to explain the way in which oral contraceptives may affect mood. Specifically, it is argued that progestins exert differential effects on endogenous levels of neurosteroids, thereby altering mood. After providing an overview of the effects of estrogen, progesterone, and progesterone's metabolites on cortical excitability and the role of neurosteroids in depression and premenstrual dysphoria, this article reviews the research that has been conducted on the relationship between oral contraceptives and neurosteroids. Finally, suggestions for future research are made with the dual aim of improving existing studies on the relationship between oral contraceptives and mood and further investigating the possibility that fluctuations in neurosteroid levels are responsible for the effects of oral contraceptives on mood.

Printability of alloys for additive manufacturing

DOE PAGES

Mukherjee, T.; Zuback, J. S.; De, A.; ...

2016-01-22

Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is usedmore » to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. Here, the findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.« less

Rotational and frictional dynamics of the slamming of a door

NASA Astrophysics Data System (ADS)

Klein, Pascal; Müller, Andreas; Gröber, Sebastian; Molz, Alexander; Kuhn, Jochen

2017-01-01

A theoretical and experimental investigation of the rotational dynamics, including friction, of a slamming door is presented. Based on existing work regarding different damping models for rotational and oscillatory motions, we examine different forms for the (angular) velocity dependence (ωn, n = 0, 1, 2) of the frictional force. An analytic solution is given when all three friction terms are present and several solutions for specific cases known from the literature are reproduced. The motion of a door is investigated experimentally using a smartphone, and the data are compared with the theoretical results. A laboratory experiment under more controlled conditions is conducted to gain a deeper understanding of the movement of a slammed door. Our findings provide quantitative evidence that damping models involving quadratic air drag are most appropriate for the slamming of a door. Examining this everyday example of a physical phenomenon increases student motivation, because they can relate it to their own personal experience.

Numerical detection of the Gardner transition in a mean-field glass former.

PubMed

Charbonneau, Patrick; Jin, Yuliang; Parisi, Giorgio; Rainone, Corrado; Seoane, Beatriz; Zamponi, Francesco

2015-07-01

Recent theoretical advances predict the existence, deep into the glass phase, of a novel phase transition, the so-called Gardner transition. This transition is associated with the emergence of a complex free energy landscape composed of many marginally stable sub-basins within a glass metabasin. In this study, we explore several methods to detect numerically the Gardner transition in a simple structural glass former, the infinite-range Mari-Kurchan model. The transition point is robustly located from three independent approaches: (i) the divergence of the characteristic relaxation time, (ii) the divergence of the caging susceptibility, and (iii) the abnormal tail in the probability distribution function of cage order parameters. We show that the numerical results are fully consistent with the theoretical expectation. The methods we propose may also be generalized to more realistic numerical models as well as to experimental systems.

Asymptotic behaviors of a cell-to-cell HIV-1 infection model perturbed by white noise

NASA Astrophysics Data System (ADS)

Liu, Qun

2017-02-01

In this paper, we analyze a mathematical model of cell-to-cell HIV-1 infection to CD4+ T cells perturbed by stochastic perturbations. First of all, we investigate that there exists a unique global positive solution of the system for any positive initial value. Then by using Lyapunov analysis methods, we study the asymptotic property of this solution. Moreover, we discuss whether there is a stationary distribution for this system and if it owns the ergodic property. Numerical simulations are presented to illustrate the theoretical results.

Octupole deformation in odd-odd nuclei

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

Sheline, R.K.

1988-01-01

Comparison of the experimental and theoretical ground-state spins of odd-odd nuclei in the region 220less than or equal toAless than or equal to228 generally shows agreement with a folded Yukawa octupole deformed model with epsilon/sub 3/ = 0.08 and some lack of agreement with the same model with epsilon/sub 3/ = 0. Thus in spite of limited spectroscopic information, the ground-state spins suggest the existence of octupole deformation in odd-odd nuclei in the region 220less than or equal toAless than or equal to228.

A stage structure pest management model with impulsive state feedback control

NASA Astrophysics Data System (ADS)

Pang, Guoping; Chen, Lansun; Xu, Weijian; Fu, Gang

2015-06-01

A stage structure pest management model with impulsive state feedback control is investigated. We get the sufficient condition for the existence of the order-1 periodic solution by differential equation geometry theory and successor function. Further, we obtain a new judgement method for the stability of the order-1 periodic solution of the semi-continuous systems by referencing the stability analysis for limit cycles of continuous systems, which is different from the previous method of analog of Poincarè criterion. Finally, we analyze numerically the theoretical results obtained.

Acoustoelasticity

NASA Technical Reports Server (NTRS)

Dowell, E. H.

1976-01-01

Internal sound fields are considered. Specifically, the interaction between the (acoustic) sound pressure field and the (elastic) flexible wall of an enclosure is discussed. Such problems frequently arise when the vibrating walls of a transportation vehicle induce a significant internal sound field. Cabin noise in various flight vehicles and the internal sound field in an automobile are representative examples. A mathematical model, simplified solutions, and numerical results and comparisons with representative experimental data are briefly considered. An overall conclusion is that reasonable grounds for optimism exist with respect to available theoretical models and their predictive capability.

The SHiP project at CERN

NASA Astrophysics Data System (ADS)

De Lellis, G.; SHiP Collaboration

2016-07-01

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry, which deserve an explanation that could come from the discovery of new particles. Searches for new physics with accelerators are performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. A new experimental facility at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored. A beam dump facility using 400 GeV protons is a copious factory of charmed hadrons and could be used to probe the existence of such particles. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. Indeed, tau anti-neutrinos have not been directly observed so far. We report the physics potential of such an experiment. Resistive Plate Chambers could play a role in the SHiP detector.

Theoretical modeling and experimental validation of a torsional piezoelectric vibration energy harvesting system

NASA Astrophysics Data System (ADS)

Qian, Feng; Zhou, Wanlu; Kaluvan, Suresh; Zhang, Haifeng; Zuo, Lei

2018-04-01

Vibration energy harvesting has been extensively studied in recent years to explore a continuous power source for sensor networks and low-power electronics. Torsional vibration widely exists in mechanical engineering; however, it has not yet been well exploited for energy harvesting. This paper presents a theoretical model and an experimental validation of a torsional vibration energy harvesting system comprised of a shaft and a shear mode piezoelectric transducer. The piezoelectric transducer position on the surface of the shaft is parameterized by two variables that are optimized to obtain the maximum power output. The piezoelectric transducer can work in d 15 mode (pure shear mode), coupled mode of d 31 and d 33, and coupled mode of d 33, d 31 and d 15, respectively, when attached at different angles. Approximate expressions of voltage and power are derived from the theoretical model, which gave predictions in good agreement with analytical solutions. Physical interpretations on the implicit relationship between the power output and the position parameters of the piezoelectric transducer is given based on the derived approximate expression. The optimal position and angle of the piezoelectric transducer is determined, in which case, the transducer works in the coupled mode of d 15, d 31 and d 33.

From atomistic interfaces to dendritic patterns

NASA Astrophysics Data System (ADS)

Galenko, P. K.; Alexandrov, D. V.

2018-01-01

Transport processes around phase interfaces, together with thermodynamic properties and kinetic phenomena, control the formation of dendritic patterns. Using the thermodynamic and kinetic data of phase interfaces obtained on the atomic scale, one can analyse the formation of a single dendrite and the growth of a dendritic ensemble. This is the result of recent progress in theoretical methods and computational algorithms calculated using powerful computer clusters. Great benefits can be attained from the development of micro-, meso- and macro-levels of analysis when investigating the dynamics of interfaces, interpreting experimental data and designing the macrostructure of samples. The review and research articles in this theme issue cover the spectrum of scales (from nano- to macro-length scales) in order to exhibit recently developing trends in the theoretical analysis and computational modelling of dendrite pattern formation. Atomistic modelling, the flow effect on interface dynamics, the transition from diffusion-limited to thermally controlled growth existing at a considerable driving force, two-phase (mushy) layer formation, the growth of eutectic dendrites, the formation of a secondary dendritic network due to coalescence, computational methods, including boundary integral and phase-field methods, and experimental tests for theoretical models-all these themes are highlighted in the present issue. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

A theoretical model of water and trade

NASA Astrophysics Data System (ADS)

Dang, Qian; Konar, Megan; Reimer, Jeffrey J.; Di Baldassarre, Giuliano; Lin, Xiaowen; Zeng, Ruijie

2016-03-01

Water is an essential input for agricultural production. Agriculture, in turn, is globalized through the trade of agricultural commodities. In this paper, we develop a theoretical model that emphasizes four tradeoffs involving water-use decision-making that are important yet not always considered in a consistent framework. One tradeoff focuses on competition for water among different economic sectors. A second tradeoff examines the possibility that certain types of agricultural investments can offset water use. A third tradeoff explores the possibility that the rest of the world can be a source of supply or demand for a country's water-using commodities. The fourth tradeoff concerns how variability in water supplies influences farmer decision-making. We show conditions under which trade liberalization affect water use. Two policy scenarios to reduce water use are evaluated. First, we derive a target tax that reduces water use without offsetting the gains from trade liberalization, although important tradeoffs exist between economic performance and resource use. Second, we show how subsidization of water-saving technologies can allow producers to use less water without reducing agricultural production, making such subsidization an indirect means of influencing water use decision-making. Finally, we outline conditions under which riskiness of water availability affects water use. These theoretical model results generate hypotheses that can be tested empirically in future work.

Evolutionary conceptual analysis: faith community nursing.

PubMed

Ziebarth, Deborah

2014-12-01

The aim of the study was to report an evolutionary concept analysis of faith community nursing (FCN). FCN is a source of healthcare delivery in the USA which has grown in comprehensiveness and complexity. With increasing healthcare cost and a focus on access and prevention, FCN has extended beyond the physical walls of the faith community building. Faith communities and healthcare organizations invest in FCN and standardized training programs exist. Using Rodgers' evolutionary analysis, the literature was examined for antecedents, attributes, and consequences of the concept. This design allows for understanding the historical and social nature of the concept and how it changes over time. A search of databases using the keywords FCN, faith community nurse, parish nursing, and parish nurse was done. The concept of FCN was explored using research and theoretical literature. A theoretical definition and model were developed with relevant implications. The search results netted a sample of 124 reports of research and theoretical articles from multiple disciplines: medicine, education, religion and philosophy, international health, and nursing. Theoretical definition: FCN is a method of healthcare delivery that is centered in a relationship between the nurse and client (client as person, family, group, or community). The relationship occurs in an iterative motion over time when the client seeks or is targeted for wholistic health care with the goal of optimal wholistic health functioning. Faith integrating is a continuous occurring attribute. Health promoting, disease managing, coordinating, empowering and accessing health care are other essential attributes. All essential attributes occur with intentionality in a faith community, home, health institution and other community settings with fluidity as part of a community, national, or global health initiative. A new theoretical definition and corresponding conceptual model of FCN provides a basis for future nursing knowledge and model-based applications for evidence-based practice and research.

Effect of second to first normal stress difference ratio at the die exit on neck-in phenomenon in polymeric flat film production

NASA Astrophysics Data System (ADS)

Barborik, Tomas; Zatloukal, Martin

2017-05-01

In this study, viscoelastic modeling of the extrusion film casting process, based on the lD membrane model and modified Leonov constitutive equation, was conducted and the effect of the viscoelastic stress state at the die exit (captured here via second to first normal stress difference ratio) on the unwanted neck-in phenomenon has been analyzed for wide range of Deborah numbers and materials having different level of uniaxial and planar extensional strain hardening. Relevant experimental data for LDPE and theoretical predictions based on multimode eXtended Pom-Pom model acquired from the open literature were used for the validation purposes. It was found that firstly, the predicting capabilities of both constitutive equations for given material and processing conditions are comparable even if the single mode modified Leonov model was used and secondly, the agreement between theoretical and experimental data on neck-in is fairly good. Results of the theoretical study revealed that the viscoelastic stress state at the die exit (i.e. -N2/N1 ratio) increases the level of neck-in if uniaxial extensional strain hardening, planar to uniaxial extensional viscosity ratio and Deborah number increases. It has also been revealed that there exists threshold value for Deborah number and extensional strain hardening below which the neck-in becomes independent on the die exit stress state.

Generalized Ultrametric Semilattices of Linear Signals

DTIC Science & Technology

2014-01-23

53–73, 1998. [8] John C. Eidson , Edward A. Lee, Slobodan Matic, Sanjit A. Seshia, and Jia Zou. Distributed real- time software for cyber-physical...Theoretical Computer Science, 16(1):5–24, 1981. 41 [37] Yang Zhao, Jie Liu, and Edward A. Lee. A programming model for time - synchronized distributed real...response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and

Theoretical Background and Prognostic Modeling for Benchmarking SHM Sensors for Composite Structures

DTIC Science & Technology

2010-10-01

minimum flaw size can be detected by the existing SHM based monitoring methods. Sandwich panels with foam , WebCore and honeycomb structures were...Whether it be hat stiffened, corrugated sandwich, honeycomb sandwich, or foam filled sandwich, all composite structures have one basic handicap in...based monitoring methods. Sandwich panels with foam , WebCore and honeycomb structures were considered for use in this study. Eigenmode frequency

From Social Network (Centralized vs. Decentralized) to Collective Decision-Making (Unshared vs. Shared Consensus)

PubMed Central

Sueur, Cédric; Deneubourg, Jean-Louis; Petit, Odile

2012-01-01

Relationships we have with our friends, family, or colleagues influence our personal decisions, as well as decisions we make together with others. As in human beings, despotism and egalitarian societies seem to also exist in animals. While studies have shown that social networks constrain many phenomena from amoebae to primates, we still do not know how consensus emerges from the properties of social networks in many biological systems. We created artificial social networks that represent the continuum from centralized to decentralized organization and used an agent-based model to make predictions about the patterns of consensus and collective movements we observed according to the social network. These theoretical results showed that different social networks and especially contrasted ones – star network vs. equal network - led to totally different patterns. Our model showed that, by moving from a centralized network to a decentralized one, the central individual seemed to lose its leadership in the collective movement's decisions. We, therefore, showed a link between the type of social network and the resulting consensus. By comparing our theoretical data with data on five groups of primates, we confirmed that this relationship between social network and consensus also appears to exist in animal societies. PMID:22393416

Reference Specimen for Nondestructive Evaluation: Characterization of the Oxide Layer of a Cold Shot in Inconel 600

NASA Astrophysics Data System (ADS)

Saletes, I.; Filleter, T.; Goldbaum, D.; Chromik, R. R.; Sinclair, A. N.

2015-02-01

The presence of a cold shot in an aircraft turbine blade can lead to the catastrophic failure of the blade and ultimately to the failure of the power plant. Currently, no nondestructive evaluation (NDE) method exists to detect this kind of defect. This deficiency is primarily due to the fact that the only known cold shot defects in existence are those found in failed blades. Therefore, in order to develop effective NDE methods, reference specimens are needed which mimic the embedded oxide layer that is a primary distinguishing feature of a cold shot. Here, we present a procedure to synthetically reproduce the features of a real cold shot in Inconel 600 and the precise characterization of this oxide layer as a reference specimen suitable for NDE evaluation. As a first step to develop a suitable NDE technique, high-frequency ultrasound simulations are considered. A theoretical 1-D model is developed in order to quantify the multiple reflection-transmission trajectory of the acoustic wave in the reference specimen. This paper also presents an experimental determination of the density and the Young's modulus of the Inconel 600 oxide, which are required as inputs to calculate the acoustic impedance used in the theoretical model.

Ultrathin nanosheets of CrSiTe 3. A semiconducting two-dimensional ferromagnetic material

DOE PAGES

Lin, Ming -Wei; Zhung, Houlong L.; Yan, Jiaqiang; ...

2015-11-27

Finite range ferromagnetism and antiferromagnetism in two-dimensional (2D) systems within an isotropic Heisenberg model at non-zero temperature were originally proposed to be impossible. However, recent theoretical studies using an Ising model have recently shown that 2D magnetic crystals can exhibit magnetism. Experimental verification of existing 2D magnetic crystals in this system has remained elusive. In this work we for the first time exfoliate the CrSiTe 3, a bulk ferromagnetic semiconductor, to mono- and few-layer 2D crystals onto a Si/SiO 2 substrate. The Raman spectra show the good stability and high quality of the exfoliated flakes, consistent with the computed phononmore » spectra of 2D CrSiTe 3, giving a strong evidence for the existence of 2D CrSiTe 3 crystals. When the thickness of the CrSiTe 3 crystals is reduced to few-layers, we observed a clear change in resistivity at 80~120 K, consistent with the theoretical calculations on the Curie temperature (Tc) of ~80 K for the magnetic ordering of 2D CrSiTe 3 crystals. As a result, the ferromagnetic mono- and few-layer 2D CrSiTe 3 indicated here should enable numerous applications in nano-spintronics.« less

Solving Navier-Stokes Equations with Advanced Turbulence Models on Three-Dimensional Unstructured Grids

NASA Technical Reports Server (NTRS)

Wang, Qun-Zhen; Massey, Steven J.; Abdol-Hamid, Khaled S.; Frink, Neal T.

1999-01-01

USM3D is a widely-used unstructured flow solver for simulating inviscid and viscous flows over complex geometries. The current version (version 5.0) of USM3D, however, does not have advanced turbulence models to accurately simulate complicated flows. We have implemented two modified versions of the original Jones and Launder k-epsilon two-equation turbulence model and the Girimaji algebraic Reynolds stress model in USM3D. Tests have been conducted for two flat plate boundary layer cases, a RAE2822 airfoil and an ONERA M6 wing. The results are compared with those of empirical formulae, theoretical results and the existing Spalart-Allmaras one-equation model.

Estimating standard errors in feature network models.

PubMed

Frank, Laurence E; Heiser, Willem J

2007-05-01

Feature network models are graphical structures that represent proximity data in a discrete space while using the same formalism that is the basis of least squares methods employed in multidimensional scaling. Existing methods to derive a network model from empirical data only give the best-fitting network and yield no standard errors for the parameter estimates. The additivity properties of networks make it possible to consider the model as a univariate (multiple) linear regression problem with positivity restrictions on the parameters. In the present study, both theoretical and empirical standard errors are obtained for the constrained regression parameters of a network model with known features. The performance of both types of standard error is evaluated using Monte Carlo techniques.

Searching for Physics Beyond the Standard Model and Beyond

NASA Astrophysics Data System (ADS)

Abdullah, Mohammad

The hierarchy problem, convolved with the various known puzzles in particle physics, grants us a great outlook of new physics soon to be discovered. We present multiple approaches to searching for physics beyond the standard model. First, two models with a minimal amount of theoretical guidance are analyzed using existing or simulated LHC data. Then, an extension of the Minimal Supersymmetric Standard Model (MSSM) is studied with an emphasis on the cosmological implications as well as the current and future sensitivity of colliders, direct detection and indirect detection experiments. Finally, a more complete model of the MSSM is presented through which we attempt to resolve tension with observations within the context of gauge mediated supersymmetry breaking.

Critical frontier of the triangular Ising antiferromagnet in a field

NASA Astrophysics Data System (ADS)

Qian, Xiaofeng; Wegewijs, Maarten; Blöte, Henk W.

2004-03-01

We study the critical line of the triangular Ising antiferromagnet in an external magnetic field by means of a finite-size analysis of results obtained by transfer-matrix and Monte Carlo techniques. We compare the shape of the critical line with predictions of two different theoretical scenarios. Both scenarios, while plausible, involve assumptions. The first scenario is based on the generalization of the model to a vertex model, and the assumption that the exact analytic form of the critical manifold of this vertex model is determined by the zeroes of an O(2) gauge-invariant polynomial in the vertex weights. However, it is not possible to fit the coefficients of such polynomials of orders up to 10, such as to reproduce the numerical data for the critical points. The second theoretical prediction is based on the assumption that a renormalization mapping exists of the Ising model on the Coulomb gas, and analysis of the resulting renormalization equations. It leads to a shape of the critical line that is inconsistent with the first prediction, but consistent with the numerical data.

A comparison between EGS4 and MCNP computer modeling of an in vivo X-ray fluorescence system.

PubMed

Al-Ghorabie, F H; Natto, S S; Al-Lyhiani, S H

2001-03-01

The Monte Carlo computer codes EGS4 and MCNP were used to develop a theoretical model of a 180 degrees geometry in vivo X-ray fluorescence system for the measurement of platinum concentration in head and neck tumors. The model included specification of the photon source, collimators, phantoms and detector. Theoretical results were compared and evaluated against X-ray fluorescence data obtained experimentally from an existing system developed by the Swansea In Vivo Analysis and Cancer Research Group. The EGS4 results agreed well with the MCNP results. However, agreement between the measured spectral shape obtained using the experimental X-ray fluorescence system and the simulated spectral shape obtained using the two Monte Carlo codes was relatively poor. The main reason for the disagreement between the results arises from the basic assumptions which the two codes used in their calculations. Both codes assume a "free" electron model for Compton interactions. This assumption will underestimate the results and invalidates any predicted and experimental spectra when compared with each other.

Can the REBT theory explain loneliness? Theoretical and clinical applications.

PubMed

Hyland, Philip; McGinty, Gráinne; Karatzias, Thanos; Murphy, Jamie; Vallières, Frédérique; McHugh Power, Joanna

2018-06-05

Loneliness is a common psychological experience affecting a significant minority of the general population. Loneliness may in part be related to the existence of dysfunctional cognitive evaluations. To date, however, loneliness has yet to be explicitly assessed within a cognitive-behavioural theoretical framework. The current study sought to determine the association between negative cognitions, within the context of Rational Emotive Behaviour Therapy (REBT), and the experience of loneliness. A multinational sample of university students (n = 397) completed self-report assessments of rational and irrational beliefs, and loneliness. Structural equation modelling results found that the REBT model of psychopathology, and the REBT model of psychological health, provided satisfactory representations of loneliness, explaining 36% and 23% of variance in loneliness, respectively. Several dysfunctional ("Demandingness", "Catastrophising" and "Self-Downing" beliefs) and functional ("Preferences" and "Self-Acceptance" beliefs) cognitions were directly and indirectly associated with loneliness. These results highlight that cognitions and loneliness are meaningfully related, and indicate that cognitive-behavioural models may be useful in understanding loneliness. More specifically, current results suggest that REBT may offer a viable psychotherapeutic approach to treating loneliness.

Aging and financial planning for retirement: interdisciplinary influences viewed through a cross-cultural lens.

PubMed

Hershey, Douglas A; Henkens, Kene; Van Dalen, Hendrik P

2010-01-01

Current theoretical models support the existence of interactions between the individual and socio-environmental forces when it comes to the formation and enactment of life plans (Friedman & Scholnick, 1997; Shanahan & Elder, 2002). In this investigation, we examine the social, economic, and psychological forces that impact financial planning for retirement. The collective force of these three broad sets of influences was examined from developmental and cross-cultural perspectives, among respondents from two countries with very different retirement financing systems. Participants were 419 American and 556 Dutch working adults, 25-64 years of age. Path analysis models were created to examine differences in planning associated with age and national origin. Compared to younger individuals, older respondents in both countries were more involved in nearly all aspects of the financial planning process. Differences across cultures were also observed in the social support mechanisms that underlie planning and the impact economic forces have on perceptions of saving adequacy. The discussion focuses on the value of developing interdisciplinary theoretical models of planning, and how such models can inform the development of savings-oriented intervention and public policy initiatives.

A Game-Theoretical Model to Improve Process Plant Protection from Terrorist Attacks.

PubMed

Zhang, Laobing; Reniers, Genserik

2016-12-01

The New York City 9/11 terrorist attacks urged people from academia as well as from industry to pay more attention to operational security research. The required focus in this type of research is human intention. Unlike safety-related accidents, security-related accidents have a deliberate nature, and one has to face intelligent adversaries with characteristics that traditional probabilistic risk assessment techniques are not capable of dealing with. In recent years, the mathematical tool of game theory, being capable to handle intelligent players, has been used in a variety of ways in terrorism risk assessment. In this article, we analyze the general intrusion detection system in process plants, and propose a game-theoretical model for security management in such plants. Players in our model are assumed to be rational and they play the game with complete information. Both the pure strategy and the mixed strategy solutions are explored and explained. We illustrate our model by an illustrative case, and find that in our case, no pure strategy but, instead, a mixed strategy Nash equilibrium exists. © 2016 Society for Risk Analysis.

A step forward in the study of the electroerosion by optical methods

NASA Astrophysics Data System (ADS)

Aparicio, R.; Gale, M. F. Ruiz; Hogert, E. N.; Landau, M. R.; Gaggioli, y. N. G.

2003-05-01

This work develops two theoretical models of surfaces to explain the behavior of the light scattered by samples that suffers some alteration. In a first model, it is evaluated the mean intensity scattered by the sample, analyzing the different curves obtained as function of the eroded/total surface ratio. The theoretical results are compared with those obtained experimentally. It can be seen that there exists a strong relation between the electroerosion level and the light scattered by the sample. A second model analyzes a surface with random changes in its roughness. A translucent surface with its roughness changing in a controlled way is studied. Then, the correlation coefficient variation as function of the roughness variation is determined by the transmission speckle correlation method. The obtained experimental values are compared with those obtained with this model. In summary, it can be shown that the first- and second-order statistics properties of the transmitted or reflected light by a sample with a variable topography can be taken account as a parameter to analyze these morphologic changes.

Characterising an implementation intervention in terms of behaviour change techniques and theory: the 'Sepsis Six' clinical care bundle.

PubMed

Steinmo, Siri; Fuller, Christopher; Stone, Sheldon P; Michie, Susan

2015-08-08

Sepsis is a major cause of death from infection, with a mortality rate of 36 %. This can be halved by implementing the 'Sepsis Six' evidence-based care bundle within 1 h of presentation. A UK audit has shown that median implementation rates are 27-47 % and interventions to improve this have demonstrated minimal effects. In order to develop more effective implementation interventions, it is helpful to obtain detailed characterisations of current interventions and to draw on behavioural theory to identify mechanisms of change. The aim of this study was to illustrate this process by using the Behaviour Change Wheel; Behaviour Change Technique (BCT) Taxonomy; Capability, Opportunity, Motivation model of behaviour; and Theoretical Domains Framework to characterise the content and theoretical mechanisms of action of an existing intervention to implement Sepsis Six. Data came from documentary, interview and observational analyses of intervention delivery in several wards of a UK hospital. A broad description of the intervention was created using the Template for Intervention Description and Replication framework. Content was specified in terms of (i) component BCTs using the BCT Taxonomy and (ii) intervention functions using the Behaviour Change Wheel. Mechanisms of action were specified using the Capability, Opportunity, Motivation model and the Theoretical Domains Framework. The intervention consisted of 19 BCTs, with eight identified using all three data sources. The BCTs were delivered via seven functions of the Behaviour Change Wheel, with four ('education', 'enablement', 'training' and 'environmental restructuring') supported by the three data sources. The most frequent mechanisms of action were reflective motivation (especially 'beliefs about consequences' and 'beliefs about capabilities') and psychological capability (especially 'knowledge'). The intervention consisted of a wide range of BCTs targeting a wide range of mechanisms of action. This study demonstrates the utility of the Behaviour Change Wheel, the BCT Taxonomy and the Theoretical Domains Framework, tools recognised for providing guidance for intervention design, for characterising an existing intervention to implement evidence-based care.

Inversion of Surface-wave Dispersion Curves due to Low-velocity-layer Models

NASA Astrophysics Data System (ADS)

Shen, C.; Xia, J.; Mi, B.

2016-12-01

A successful inversion relies on exact forward modeling methods. It is a key step to accurately calculate multi-mode dispersion curves of a given model in high-frequency surface-wave (Rayleigh wave and Love wave) methods. For normal models (shear (S)-wave velocity increasing with depth), their theoretical dispersion curves completely match the dispersion spectrum that is generated based on wave equation. For models containing a low-velocity-layer, however, phase velocities calculated by existing forward-modeling algorithms (e.g. Thomson-Haskell algorithm, Knopoff algorithm, fast vector-transfer algorithm and so on) fail to be consistent with the dispersion spectrum at a high frequency range. They will approach a value that close to the surface-wave velocity of the low-velocity-layer under the surface layer, rather than that of the surface layer when their corresponding wavelengths are short enough. This phenomenon conflicts with the characteristics of surface waves, which results in an erroneous inverted model. By comparing the theoretical dispersion curves with simulated dispersion energy, we proposed a direct and essential solution to accurately compute surface-wave phase velocities due to low-velocity-layer models. Based on the proposed forward modeling technique, we can achieve correct inversion for these types of models. Several synthetic data proved the effectiveness of our method.

The Integrated Behavioural Model for Water, Sanitation, and Hygiene: a systematic review of behavioural models and a framework for designing and evaluating behaviour change interventions in infrastructure-restricted settings.

PubMed

Dreibelbis, Robert; Winch, Peter J; Leontsini, Elli; Hulland, Kristyna R S; Ram, Pavani K; Unicomb, Leanne; Luby, Stephen P

2013-10-26

Promotion and provision of low-cost technologies that enable improved water, sanitation, and hygiene (WASH) practices are seen as viable solutions for reducing high rates of morbidity and mortality due to enteric illnesses in low-income countries. A number of theoretical models, explanatory frameworks, and decision-making models have emerged which attempt to guide behaviour change interventions related to WASH. The design and evaluation of such interventions would benefit from a synthesis of this body of theory informing WASH behaviour change and maintenance. We completed a systematic review of existing models and frameworks through a search of related articles available in PubMed and in the grey literature. Information on the organization of behavioural determinants was extracted from the references that fulfilled the selection criteria and synthesized. Results from this synthesis were combined with other relevant literature, and from feedback through concurrent formative and pilot research conducted in the context of two cluster-randomized trials on the efficacy of WASH behaviour change interventions to inform the development of a framework to guide the development and evaluation of WASH interventions: the Integrated Behavioural Model for Water, Sanitation, and Hygiene (IBM-WASH). We identified 15 WASH-specific theoretical models, behaviour change frameworks, or programmatic models, of which 9 addressed our review questions. Existing models under-represented the potential role of technology in influencing behavioural outcomes, focused on individual-level behavioural determinants, and had largely ignored the role of the physical and natural environment. IBM-WASH attempts to correct this by acknowledging three dimensions (Contextual Factors, Psychosocial Factors, and Technology Factors) that operate on five-levels (structural, community, household, individual, and habitual). A number of WASH-specific models and frameworks exist, yet with some limitations. The IBM-WASH model aims to provide both a conceptual and practical tool for improving our understanding and evaluation of the multi-level multi-dimensional factors that influence water, sanitation, and hygiene practices in infrastructure-constrained settings. We outline future applications of our proposed model as well as future research priorities needed to advance our understanding of the sustained adoption of water, sanitation, and hygiene technologies and practices.

The Integrated Behavioural Model for Water, Sanitation, and Hygiene: a systematic review of behavioural models and a framework for designing and evaluating behaviour change interventions in infrastructure-restricted settings

PubMed Central

2013-01-01

Background Promotion and provision of low-cost technologies that enable improved water, sanitation, and hygiene (WASH) practices are seen as viable solutions for reducing high rates of morbidity and mortality due to enteric illnesses in low-income countries. A number of theoretical models, explanatory frameworks, and decision-making models have emerged which attempt to guide behaviour change interventions related to WASH. The design and evaluation of such interventions would benefit from a synthesis of this body of theory informing WASH behaviour change and maintenance. Methods We completed a systematic review of existing models and frameworks through a search of related articles available in PubMed and in the grey literature. Information on the organization of behavioural determinants was extracted from the references that fulfilled the selection criteria and synthesized. Results from this synthesis were combined with other relevant literature, and from feedback through concurrent formative and pilot research conducted in the context of two cluster-randomized trials on the efficacy of WASH behaviour change interventions to inform the development of a framework to guide the development and evaluation of WASH interventions: the Integrated Behavioural Model for Water, Sanitation, and Hygiene (IBM-WASH). Results We identified 15 WASH-specific theoretical models, behaviour change frameworks, or programmatic models, of which 9 addressed our review questions. Existing models under-represented the potential role of technology in influencing behavioural outcomes, focused on individual-level behavioural determinants, and had largely ignored the role of the physical and natural environment. IBM-WASH attempts to correct this by acknowledging three dimensions (Contextual Factors, Psychosocial Factors, and Technology Factors) that operate on five-levels (structural, community, household, individual, and habitual). Conclusions A number of WASH-specific models and frameworks exist, yet with some limitations. The IBM-WASH model aims to provide both a conceptual and practical tool for improving our understanding and evaluation of the multi-level multi-dimensional factors that influence water, sanitation, and hygiene practices in infrastructure-constrained settings. We outline future applications of our proposed model as well as future research priorities needed to advance our understanding of the sustained adoption of water, sanitation, and hygiene technologies and practices. PMID:24160869

Force-induced bone growth and adaptation: A system theoretical approach to understanding bone mechanotransduction

NASA Astrophysics Data System (ADS)

Maldonado, Solvey; Findeisen, Rolf

2010-06-01

The modeling, analysis, and design of treatment therapies for bone disorders based on the paradigm of force-induced bone growth and adaptation is a challenging task. Mathematical models provide, in comparison to clinical, medical and biological approaches an structured alternative framework to understand the concurrent effects of the multiple factors involved in bone remodeling. By now, there are few mathematical models describing the appearing complex interactions. However, the resulting models are complex and difficult to analyze, due to the strong nonlinearities appearing in the equations, the wide range of variability of the states, and the uncertainties in parameters. In this work, we focus on analyzing the effects of changes in model structure and parameters/inputs variations on the overall steady state behavior using systems theoretical methods. Based on an briefly reviewed existing model that describes force-induced bone adaptation, the main objective of this work is to analyze the stationary behavior and to identify plausible treatment targets for remodeling related bone disorders. Identifying plausible targets can help in the development of optimal treatments combining both physical activity and drug-medication. Such treatments help to improve/maintain/restore bone strength, which deteriorates under bone disorder conditions, such as estrogen deficiency.

Coupled three-layer model for turbulent flow over large-scale roughness: On the hydrodynamics of boulder-bed streams

NASA Astrophysics Data System (ADS)

Pan, Wen-hao; Liu, Shi-he; Huang, Li

2018-02-01

This study developed a three-layer velocity model for turbulent flow over large-scale roughness. Through theoretical analysis, this model coupled both surface and subsurface flow. Flume experiments with flat cobble bed were conducted to examine the theoretical model. Results show that both the turbulent flow field and the total flow characteristics are quite different from that in the low gradient flow over microscale roughness. The velocity profile in a shallow stream converges to the logarithmic law away from the bed, while inflecting over the roughness layer to the non-zero subsurface flow. The velocity fluctuations close to a cobble bed are different from that of a sand bed, and it indicates no sufficiently large peak velocity. The total flow energy loss deviates significantly from the 1/7 power law equation when the relative flow depth is shallow. Both the coupled model and experiments indicate non-negligible subsurface flow that accounts for a considerable proportion of the total flow. By including the subsurface flow, the coupled model is able to predict a wider range of velocity profiles and total flow energy loss coefficients when compared with existing equations.

Evidence - competence - discourse: the theoretical framework of the multi-centre clinical ethics support project METAP.

PubMed

Reiter-Theil, Stella; Mertz, Marcel; Schürmann, Jan; Stingelin Giles, Nicola; Meyer-Zehnder, Barbara

2011-09-01

In this paper we assume that 'theory' is important for Clinical Ethics Support Services (CESS). We will argue that the underlying implicit theory should be reflected. Moreover, we suggest that the theoretical components on which any clinical ethics support (CES) relies should be explicitly articulated in order to enhance the quality of CES. A theoretical framework appropriate for CES will be necessarily complex and should include ethical (both descriptive and normative), metaethical and organizational components. The various forms of CES that exist in North-America and in Europe show their underlying theory more or less explicitly, with most of them referring to some kind of theoretical components including 'how-to' questions (methodology), organizational issues (implementation), problem analysis (phenomenology or typology of problems), and related ethical issues such as end-of-life decisions (major ethical topics). In order to illustrate and explain the theoretical framework that we are suggesting for our own CES project METAP, we will outline this project which has been established in a multi-centre context in several healthcare institutions. We conceptualize three 'pillars' as the major components of our theoretical framework: (1) evidence, (2) competence, and (3) discourse. As a whole, the framework is aimed at developing a foundation of our CES project METAP. We conclude that this specific integration of theoretical components is a promising model for the fruitful further development of CES. © 2011 Blackwell Publishing Ltd.

The SHiP physics program

NASA Astrophysics Data System (ADS)

De Lellis, Giovanni

2018-05-01

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry of the Universe, which deserve an explanation that could come from the discovery of new particles. The SHiP experiment at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. Indeed, tau anti-neutrinos have not been directly observed so far. We report the physics potential of such an experiment including the tau neutrino magnetic moment.

A Fractal Study on the Effective Thermal Conductivity of Porous Media

NASA Astrophysics Data System (ADS)

Qin, X.; Cai, J.; Wei, W.

2017-12-01

Thermal conduction in porous media has steadily received attention in science and engineering, for instance, exploiting and utilizing the geothermal energy, developing the oil-gas resource, ground water flow in hydrothermal systems and investigating the potential host nuclear wastes, etc. The thermal conductivity is strongly influenced by the microstructure features of porous media. In this work, based on the fractal characteristics of the grains, a theoretical model of effective thermal conductivity is proposed for saturated and unsaturated porous media. It is found that the proposed effective thermal conductivity solution is a function of geometrical parameters of porous media, such as the porosity, fractal dimension of granular matrix and the thermal conductivity of the grains and pore fluid. The model predictions are compared with existing experimental data and the results show that they are in good agreement with existing experimental data. The proposed model may provide a better understanding of the physical mechanisms of thermal transfer in porous media than conventional models.

The impact of galaxy formation on satellite kinematics and redshift-space distortions

NASA Astrophysics Data System (ADS)

Orsi, Álvaro A.; Angulo, Raúl E.

2018-04-01

Galaxy surveys aim to map the large-scale structure of the Universe and use redshift-space distortions to constrain deviations from general relativity and probe the existence of massive neutrinos. However, the amount of information that can be extracted is limited by the accuracy of theoretical models used to analyse the data. Here, by using the L-Galaxies semi-analytical model run over the Millennium-XXL N-body simulation, we assess the impact of galaxy formation on satellite kinematics and the theoretical modelling of redshift-space distortions. We show that different galaxy selection criteria lead to noticeable differences in the radial distributions and velocity structure of satellite galaxies. Specifically, whereas samples of stellar mass selected galaxies feature satellites that roughly follow the dark matter, emission line satellite galaxies are located preferentially in the outskirts of haloes and display net infall velocities. We demonstrate that capturing these differences is crucial for modelling the multipoles of the correlation function in redshift space, even on large scales. In particular, we show how modelling small-scale velocities with a single Gaussian distribution leads to a poor description of the measured clustering. In contrast, we propose a parametrization that is flexible enough to model the satellite kinematics and that leads to an accurate description of the correlation function down to sub-Mpc scales. We anticipate that our model will be a necessary ingredient in improved theoretical descriptions of redshift-space distortions, which together could result in significantly tighter cosmological constraints and a more optimal exploitation of future large data sets.

A biphasic approach for the study of lift generation in soft porous media

NASA Astrophysics Data System (ADS)

Wu, Qianhong; Santhanam, Sridhar; Nathan, Rungun; Wang, Qiuyun

2017-04-01

Lift generation in highly compressible porous media under rapid compression continues to be an important topic in porous media flow. Although significant progress has been made, how to model different lifting forces during the compression process remains unclear. This is mainly because the input parameters of the existing theoretical studies, including the Darcy permeability of the porous media and the viscous damping coefficient of its solid phase, were manually adjusted so as to match the experimental data. In the current paper, we report a biphasic approach to experimentally and theoretically treat this limitation. Synthetic fibrous porous materials, whose permeability were precisely measured, were subsequently exposed to sudden impacts using a porous-walled cylinder-piston apparatus. The obtained time-dependent compression of the porous media, along with the permeability data, was applied in two different theoretical models to predict the pore pressure generation, a plug flow model and a consolidation model [Q. Wu et al., J. Fluid Mech. 542, 281 (2005a)]. Comparison between the theory and the experiments on the pore pressure distribution proved the validity of the consolidation model. Furthermore, a viscoelastic model, containing a nonlinear spring in conjunction with a linear viscoelastic generalized Maxwell mechanical module, was developed to characterize the solid phase lifting force. The model matched the experimental data very well. The paper presented herein, as one of the series studies on this topic, provides an important biphasic approach to characterize different forces that contribute to the lift generation in a soft porous medium under rapid compression.

Expanding Panjabi's stability model to express movement: a theoretical model.

PubMed

Hoffman, J; Gabel, P

2013-06-01

Novel theoretical models of movement have historically inspired the creation of new methods for the application of human movement. The landmark theoretical model of spinal stability by Panjabi in 1992 led to the creation of an exercise approach to spinal stability. This approach however was later challenged, most significantly due to a lack of favourable clinical effect. The concepts explored in this paper address and consider the deficiencies of Panjabi's model then propose an evolution and expansion from a special model of stability to a general one of movement. It is proposed that two body-wide symbiotic elements are present within all movement systems, stability and mobility. The justification for this is derived from the observable clinical environment. It is clinically recognised that these two elements are present and identifiable throughout the body in different joints and muscles, and the neural conduction system. In order to generalise the Panjabi model of stability to include and illustrate movement, a matching parallel mobility system with the same subsystems was conceptually created. In this expanded theoretical model, the new mobility system is placed beside the existing stability system and subsystems. The ability of both stability and mobility systems to work in harmony will subsequently determine the quality of movement. Conversely, malfunction of either system, or their subsystems, will deleteriously affect all other subsystems and consequently overall movement quality. For this reason, in the rehabilitation exercise environment, focus should be placed on the simultaneous involvement of both the stability and mobility systems. It is suggested that the individual's relevant functional harmonious movements should be challenged at the highest possible level without pain or discomfort. It is anticipated that this conceptual expansion of the theoretical model of stability to one with the symbiotic inclusion of mobility, will provide new understandings on human movement. The use of this model may provide a universal system for body movement analysis and understanding musculoskeletal disorders. In turn, this may lead to a simple categorisation system alluding to the functional face-value of a wide range of commonly used passive, active or combined musculoskeletal interventions. Further research is required to investigate the mechanisms that enable or interfere with harmonious body movements. Such work may then potentially lead to new and evolved evidence based interventions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Coarse-Graining Polymer Field Theory for Fast and Accurate Simulations of Directed Self-Assembly

NASA Astrophysics Data System (ADS)

Liu, Jimmy; Delaney, Kris; Fredrickson, Glenn

To design effective manufacturing processes using polymer directed self-assembly (DSA), the semiconductor industry benefits greatly from having a complete picture of stable and defective polymer configurations. Field-theoretic simulations are an effective way to study these configurations and predict defect populations. Self-consistent field theory (SCFT) is a particularly successful theory for studies of DSA. Although other models exist that are faster to simulate, these models are phenomenological or derived through asymptotic approximations, often leading to a loss of accuracy relative to SCFT. In this study, we employ our recently-developed method to produce an accurate coarse-grained field theory for diblock copolymers. The method uses a force- and stress-matching strategy to map output from SCFT simulations into parameters for an optimized phase field model. This optimized phase field model is just as fast as existing phenomenological phase field models, but makes more accurate predictions of polymer self-assembly, both in bulk and in confined systems. We study the performance of this model under various conditions, including its predictions of domain spacing, morphology and defect formation energies. Samsung Electronics.

Work gets unfair for the depressed: cross-lagged relations between organizational justice perceptions and depressive symptoms.

PubMed

Lang, Jessica; Bliese, Paul D; Lang, Jonas W B; Adler, Amy B

2011-05-01

The organizational justice literature has consistently documented substantial correlations between organizational justice and employee depression. Existing theoretical literature suggests this relationship occurs because perceptions of organizational (in)justice lead to subsequent psychological health problems. Building on recent research on the affective nature of justice perceptions, in the present research we broaden this perspective by arguing there are also theoretical arguments for a reverse effect whereby psychological health problems influence perceptions of organizational justice. To contrast both theoretical perspectives, we test longitudinal lagged effects between organizational justice perceptions (i.e., distributive justice, interactional justice, interpersonal justice, informational justice, and procedural justice) and employee depressive symptoms using structural equation modeling. Analyses of 3 samples from different military contexts (N₁ = 625, N₂ = 134, N₃ = 550) revealed evidence of depressive symptoms leading to subsequent organizational justice perceptions. In contrast, the opposite effects of organizational justice perceptions on depressive symptoms were not significant for any of the justice dimensions. The findings have broad implications for theoretical perspectives on psychological health and organizational justice perceptions.

Scoring the correlation of genes by their shared properties using OScal, an improved overlap quantification model.

PubMed

Liu, Hui; Liu, Wei; Lin, Ying; Liu, Teng; Ma, Zhaowu; Li, Mo; Zhang, Hong-Mei; Kenneth Wang, Qing; Guo, An-Yuan

2015-05-27

Scoring the correlation between two genes by their shared properties is a common and basic work in biological study. A prospective way to score this correlation is to quantify the overlap between the two sets of homogeneous properties of the two genes. However the proper model has not been decided, here we focused on studying the quantification of overlap and proposed a more effective model after theoretically compared 7 existing models. We defined three characteristic parameters (d, R, r) of an overlap, which highlight essential differences among the 7 models and grouped them into two classes. Then the pros and cons of the two groups of model were fully examined by their solution space in the (d, R, r) coordinate system. Finally we proposed a new model called OScal (Overlap Score calculator), which was modified on Poisson distribution (one of 7 models) to avoid its disadvantages. Tested in assessing gene relation using different data, OScal performs better than existing models. In addition, OScal is a basic mathematic model, with very low computation cost and few restrictive conditions, so it can be used in a wide-range of research areas to measure the overlap or similarity of two entities.

Core Competencies for Shared Decision Making Training Programs: Insights From an International, Interdisciplinary Working Group

PubMed Central

Légaré, France; Moumjid-Ferdjaoui, Nora; Drolet, Renée; Stacey, Dawn; Härter, Martin; Bastian, Hilda; Beaulieu, Marie-Dominique; Borduas, Francine; Charles, Cathy; Coulter, Angela; Desroches, Sophie; Friedrich, Gwendolyn; Gafni, Amiram; Graham, Ian D.; Labrecque, Michel; LeBlanc, Annie; Légaré, Jean; Politi, Mary; Sargeant, Joan; Thomson, Richard

2014-01-01

Shared decision making is now making inroads in health care professionals’ continuing education curriculum, but there is no consensus on what core competencies are required by clinicians for effectively involving patients in health-related decisions. Ready-made programs for training clinicians in shared decision making are in high demand, but existing programs vary widely in their theoretical foundations, length, and content. An international, interdisciplinary group of 25 individuals met in 2012 to discuss theoretical approaches to making health-related decisions, compare notes on existing programs, take stock of stakeholders concerns, and deliberate on core competencies. This article summarizes the results of those discussions. Some participants believed that existing models already provide a sufficient conceptual basis for developing and implementing shared decision making competency-based training programs on a wide scale. Others argued that this would be premature as there is still no consensus on the definition of shared decision making or sufficient evidence to recommend specific competencies for implementing shared decision making. However, all participants agreed that there were 2 broad types of competencies that clinicians need for implementing shared decision making: relational competencies and risk communication competencies. Further multidisciplinary research could broaden and deepen our understanding of core competencies for shared decision making training. PMID:24347105

Variations in the offence actions of deliberate firesetters: a cross-national analysis.

PubMed

Fritzon, Katarina; Doley, Rebekah; Hollows, Kerrilee

2014-10-01

Since Canter and Fritzon first introduced their "4D" classification system for arson, many studies have replicated the model with samples of arsonists from around the world. However, scholars have reported differences in the offence actions of arsonists across samples. No study as yet has attempted to statically examine the relevance of these differences. Using multidimensional scaling procedures and two-way chi-square contingency analyses, this study examined whether cross-national differences in arson variables existed between Australian and British arsonists. The results indicated that differences did exist and, furthermore, that differences reflected the environmental characteristics of the country from which each sample was drawn. These findings have important theoretical and clinical implications, particularly for the utility of the "4D" model as an investigatory tool and for the wider arson profiling literature. © The Author(s) 2013.

Dark matter and cosmological nucleosynthesis

NASA Technical Reports Server (NTRS)

Schramm, D. N.

1986-01-01

Existing dark matter problems, i.e., dynamics, galaxy formation and inflation, are considered, along with a model which proposes dark baryons as the bulk of missing matter in a fractal universe. It is shown that no combination of dark, nonbaryonic matter can either provide a cosmological density parameter value near unity or, as in the case of high energy neutrinos, allow formation of condensed matter at epochs when quasars already existed. The possibility that correlations among galactic clusters are scale-free is discussed. Such a distribution of matter would yield a fractal of 1.2, close to a one-dimensional universe. Biasing, cosmic superstrings, and percolated explosions and hot dark matter are theoretical approaches that would satisfy the D = 1.2 fractal model of the large-scale structure of the universe and which would also allow sufficient dark matter in halos to close the universe.

Qualitative dynamical analysis of chaotic plasma perturbations model

NASA Astrophysics Data System (ADS)

Elsadany, A. A.; Elsonbaty, Amr; Agiza, H. N.

2018-06-01

In this work, an analytical framework to understand nonlinear dynamics of plasma perturbations model is introduced. In particular, we analyze the model presented by Constantinescu et al. [20] which consists of three coupled ODEs and contains three parameters. The basic dynamical properties of the system are first investigated by the ways of bifurcation diagrams, phase portraits and Lyapunov exponents. Then, the normal form technique and perturbation methods are applied so as to the different types of bifurcations that exist in the model are investigated. It is proved that pitcfork, Bogdanov-Takens, Andronov-Hopf bifurcations, degenerate Hopf and homoclinic bifurcation can occur in phase space of the model. Also, the model can exhibit quasiperiodicity and chaotic behavior. Numerical simulations confirm our theoretical analytical results.

Fragmentation dynamics of ionized neon trimer inside helium nanodroplets: a theoretical study.

PubMed

Bonhommeau, David; Viel, Alexandra; Halberstadt, Nadine

2004-06-22

We report a theoretical study of the fragmentation dynamics of Ne(3) (+) inside helium nanodroplets, following vertical ionization of the neutral neon trimer. The motion of the neon atoms is treated classically, while transitions between the electronic states of the ionic cluster are treated quantum mechanically. A diatomics-in-molecules description of the potential energy surfaces is used, in a minimal basis set consisting of three effective p orbitals on each neon atom for the missing electron. The helium environment is modeled by a friction force acting on the neon atoms when their speed exceeds the Landau velocity. A reasonable range of values for the corresponding friction coefficient is obtained by comparison with existing experimental measurements. (c) 2004 American Institute of Physics.

Tight finite-key analysis for quantum cryptography

PubMed Central

Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato

2012-01-01

Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies. PMID:22252558

Tight finite-key analysis for quantum cryptography.

PubMed

Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato

2012-01-17

Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies.

Long Chain Saturated and Unsaturated Carboxylic Acids: Filling a Large Gap of Knowledge in Their Enthalpies of Formation.

PubMed

Rogers, Donald W; Zavitsas, Andreas A

2017-01-06

Despite their abundance in nature and their importance in biology, medicine, nutrition, and in industry, gas phase enthalpies of formation of many long chain saturated and unsaturated fatty acids and of dicarboxylic acids are either unavailable or have been estimated with large uncertainties. Available experimental values for stearic acid show a spread of 68 kJ mol -1 . This work fills the knowledge gap by obtaining reliable values by quantum theoretical calculations using G4 model chemistry. Compounds with up to 20 carbon atoms are treated. The theoretical results are in excellent agreement with well established experimental values when such values exist, and they provide a large number of previously unavailable values.

Critical thinking as a self-regulatory process component in teaching and learning.

PubMed

Phan, Huy P

2010-05-01

This article presents a theoretically grounded model of critical thinking and self-regulation in the context of teaching and learning. Critical thinking, deriving from an educational psychology perspective is a complex process of reflection that helps individuals become more analytical in their thinking and professional development. My conceptualisation in this discussion paper argues that both theoretical orientations (critical thinking and self-regulation) operate in a dynamic interactive system of teaching and learning. My argument, based on existing research evidence, suggests two important points: (i) critical thinking acts as another cognitive strategy of self-regulation that learners use in their learning, and (ii) critical thinking may be a product of various antecedents such as different self-regulatory strategies.

Hamiltonian flow over saddles for exploring molecular phase space structures

NASA Astrophysics Data System (ADS)

Farantos, Stavros C.

2018-03-01

Despite using potential energy surfaces, multivariable functions on molecular configuration space, to comprehend chemical dynamics for decades, the real happenings in molecules occur in phase space, in which the states of a classical dynamical system are completely determined by the coordinates and their conjugate momenta. Theoretical and numerical results are presented, employing alanine dipeptide as a model system, to support the view that geometrical structures in phase space dictate the dynamics of molecules, the fingerprints of which are traced by following the Hamiltonian flow above saddles. By properly selecting initial conditions in alanine dipeptide, we have found internally free rotor trajectories the existence of which can only be justified in a phase space perspective. This article is part of the theme issue `Modern theoretical chemistry'.

Can thermal instabilities drive galactic precipitation and explain observed circumgalactic structure?

NASA Astrophysics Data System (ADS)

Silvia, Devin

2015-10-01

Understanding the complex nature of the circumgalactic medium (CGM) has been a target of numerous research efforts, both observationally and theoretically. While significant progress has been made in probing the structure and thermodynamic state of the CGM through the detection of metal line absorption systems using the Hubble Space Telescope (HST), a complete picture of the physical mechanisms that produce the observed properties does not yet exist. Recent theoretical work has suggested that a delicate balance between radiative cooling and thermal feedback detemines whether or not the CGM is capable of sustaining a stable, multiphase medium that would allow cool clouds to precipitate out of the galactic halo. This new theoretical framework may provide the explanation for many observational results. In this project, we will detemine whether or not this elegant and simple precipitation model can be supported by physics-rich numerical simulations of isolated galaxies. We will use our simulations to gain a deeper understanding of the precipitation model and explore the ionization and temperature stucture of the CGM. Our analysis will include the comparison of realistic synthetic spectra to those produced by HST, using the newly-developed Trident software package.

Chaos in nuclei: Theory and experiment

NASA Astrophysics Data System (ADS)

Muñoz, L.; Molina, R. A.; Gómez, J. M. G.

2018-05-01

During the last three decades the quest for chaos in nuclei has been quite intensive, both with theoretical calculations using nuclear models and with detailed analyses of experimental data. In this paper we outline the concept and characteristics of quantum chaos in two different approaches, the random matrix theory fluctuations and the time series fluctuations. Then we discuss the theoretical and experimental evidence of chaos in nuclei. Theoretical calculations, especially shell-model calculations, have shown a strongly chaotic behavior of bound states in regions of high level density. The analysis of experimental data has shown a strongly chaotic behavior of nuclear resonances just above the one-nucleon emission threshold. For bound states, combining experimental data of a large number of nuclei, a tendency towards chaotic motion is observed in spherical nuclei, while deformed nuclei exhibit a more regular behavior associated to the collective motion. On the other hand, it had never been possible to observe chaos in the experimental bound energy levels of any single nucleus. However, the complete experimental spectrum of the first 151 states up to excitation energies of 6.20 MeV in the 208Pb nucleus have been recently identified and the analysis of its spectral fluctuations clearly shows the existence of chaotic motion.

Theoretical ecology without species

NASA Astrophysics Data System (ADS)

Tikhonov, Mikhail

The sequencing-driven revolution in microbial ecology demonstrated that discrete ``species'' are an inadequate description of the vast majority of life on our planet. Developing a novel theoretical language that, unlike classical ecology, would not require postulating the existence of species, is a challenge of tremendous medical and environmental significance, and an exciting direction for theoretical physics. Here, it is proposed that community dynamics can be described in a naturally hierarchical way in terms of population fluctuation eigenmodes. The approach is applied to a simple model of division of labor in a multi-species community. In one regime, effective species with a core and accessory genome are shown to naturally appear as emergent concepts. However, the same model allows a transition into a regime where the species formalism becomes inadequate, but the eigenmode description remains well-defined. Treating a community as a black box that expresses enzymes in response to resources reveals mathematically exact parallels between a community and a single coherent organism with its own fitness function. This coherence is a generic consequence of division of labor, requires no cooperative interactions, and can be expected to be widespread in microbial ecosystems. Harvard Center of Mathematical Sciences and Applications;John A. Paulson School of Engineering and Applied Sciences.

Theoretical approaches of online social network interventions and implications for behavioral change: a systematic review.

PubMed

Arguel, Amaël; Perez-Concha, Oscar; Li, Simon Y W; Lau, Annie Y S

2018-02-01

The aim of this review was to identify general theoretical frameworks used in online social network interventions for behavioral change. To address this research question, a PRISMA-compliant systematic review was conducted. A systematic review (PROSPERO registration number CRD42014007555) was conducted using 3 electronic databases (PsycINFO, Pubmed, and Embase). Four reviewers screened 1788 abstracts. 15 studies were selected according to the eligibility criteria. Randomized controlled trials and controlled studies were assessed using Cochrane Collaboration's "risk-of-bias" tool, and narrative synthesis. Five eligible articles used the social cognitive theory as a framework to develop interventions targeting behavioral change. Other theoretical frameworks were related to the dynamics of social networks, intention models, and community engagement theories. Only one of the studies selected in the review mentioned a well-known theory from the field of health psychology. Conclusions were that guidelines are lacking in the design of online social network interventions for behavioral change. Existing theories and models from health psychology that are traditionally used for in situ behavioral change should be considered when designing online social network interventions in a health care setting. © 2016 John Wiley & Sons, Ltd.

Theoretical Conversions of Different Hardness and Tensile Strength for Ductile Materials Based on Stress-Strain Curves

NASA Astrophysics Data System (ADS)

Chen, Hui; Cai, Li-Xun

2018-04-01

Based on the power-law stress-strain relation and equivalent energy principle, theoretical equations for converting between Brinell hardness (HB), Rockwell hardness (HR), and Vickers hardness (HV) were established. Combining the pre-existing relation between the tensile strength ( σ b ) and Hollomon parameters ( K, N), theoretical conversions between hardness (HB/HR/HV) and tensile strength ( σ b ) were obtained as well. In addition, to confirm the pre-existing σ b -( K, N) relation, a large number of uniaxial tensile tests were conducted in various ductile materials. Finally, to verify the theoretical conversions, plenty of statistical data listed in ASTM and ISO standards were adopted to test the robustness of the converting equations with various hardness and tensile strength. The results show that both hardness conversions and hardness-strength conversions calculated from the theoretical equations accord well with the standard data.

Mass transport in micellar surfactant solutions: 2. Theoretical modeling of adsorption at a quiescent interface.

PubMed

Danov, K D; Kralchevsky, P A; Denkov, N D; Ananthapadmanabhan, K P; Lips, A

2006-01-31

Here, we apply the detailed theoretical model of micellar kinetics from part 1 of this study to the case of surfactant adsorption at a quiescent interface, i.e., to the relaxation of surface tension and adsorption after a small initial perturbation. Our goal is to understand why for some surfactant solutions the surface tension relaxes as inverse-square-root of time, 1/t(1/2), but two different expressions for the characteristic relaxation time are applicable to different cases. In addition, our aim is to clarify why for other surfactant solutions the surface tension relaxes exponentially. For this goal, we carried out a computer modeling of the adsorption process, based on the general system of equations derived in part 1. This analysis reveals the existence of four different consecutive relaxation regimes (stages) for a given micellar solution: two exponential regimes and two inverse-square-root regimes, following one after another in alternating order. Experimentally, depending on the specific surfactant and method, one usually registers only one of these regimes. Therefore, to interpret properly the data, one has to identify which of these four kinetic regimes is observed in the given experiment. Our numerical results for the relaxation of the surface tension, micelle concentration and aggregation number are presented in the form of kinetic diagrams, which reveal the stages of the relaxation process. At low micelle concentrations, "rudimentary" kinetic diagrams could be observed, which are characterized by merging of some stages. Thus, the theoretical modeling reveals a general and physically rich picture of the adsorption process. To facilitate the interpretation of experimental data, we have derived convenient theoretical expressions for the time dependence of surface tension and adsorption in each of the four regimes.

Conceptualizing Telehealth in Nursing Practice: Advancing a Conceptual Model to Fill a Virtual Gap.

PubMed

Nagel, Daniel A; Penner, Jamie L

2016-03-01

Increasingly nurses use various telehealth technologies to deliver health care services; however, there has been a lag in research and generation of empirical knowledge to support nursing practice in this expanding field. One challenge to generating knowledge is a gap in development of a comprehensive conceptual model or theoretical framework to illustrate relationships of concepts and phenomena inherent to adoption of a broad range of telehealth technologies to holistic nursing practice. A review of the literature revealed eight published conceptual models, theoretical frameworks, or similar entities applicable to nursing practice. Many of these models focus exclusively on use of telephones and four were generated from qualitative studies, but none comprehensively reflect complexities of bridging nursing process and elements of nursing practice into use of telehealth. The purpose of this article is to present a review of existing conceptual models and frameworks, discuss predominant themes and features of these models, and present a comprehensive conceptual model for telehealth nursing practice synthesized from this literature for consideration and further development. This conceptual model illustrates characteristics of, and relationships between, dimensions of telehealth practice to guide research and knowledge development in provision of holistic person-centered care delivery to individuals by nurses through telehealth technologies. © The Author(s) 2015.

Entropic and Electrostatic Effects on the Folding Free Energy of a Surface-Attached Biomolecule: An Experimental and Theoretical Study

PubMed Central

Watkins, Herschel M.; Vallée-Bélisle, Alexis; Ricci, Francesco; Makarov, Dmitrii E.; Plaxco, Kevin W.

2012-01-01

Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged –but otherwise apparently inert– surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxyl-alkane-coated gold surface. We find that, whereas surface attachment is destabilizing at low ionic strength it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate. PMID:22239220

Reconciling Experiment and Theory in the Use of Aryl-Extended Calix[4]pyrrole Receptors for the Experimental Quantification of Chloride–π Interactions in Solution

PubMed Central

Bauzá, Antonio; Quiñonero, David; Frontera, Antonio; Ballester, Pablo

2015-01-01

In this manuscript we consider from a theoretical point of view the recently reported experimental quantification of anion–π interactions (the attractive force between electron deficient aromatic rings and anions) in solution using aryl extended calix[4]pyrrole receptors as model systems. Experimentally, two series of calix[4]pyrrole receptors functionalized, respectively, with two and four aryl rings at the meso positions, were used to assess the strength of chloride–π interactions in acetonitrile solution. As a result of these studies the contribution of each individual chloride–π interaction was quantified to be very small (<1 kcal/mol). This result is in contrast with the values derived from most theoretical calculations. Herein we report a theoretical study using high-level density functional theory (DFT) calculations that provides a plausible explanation for the observed disagreement between theory and experiment. The study reveals the existence of molecular interactions between solvent molecules and the aromatic walls of the receptors that strongly modulate the chloride–π interaction. In addition, the obtained theoretical results also suggest that the chloride-calix[4]pyrrole complex used as reference to dissect experimentally the contribution of the chloride–π interactions to the total binding energy for both the two and four-wall aryl-extended calix[4]pyrrole model systems is probably not ideal. PMID:25913375

Evolutionary Game Theory in Growing Populations

NASA Astrophysics Data System (ADS)

Melbinger, Anna; Cremer, Jonas; Frey, Erwin

2010-10-01

Existing theoretical models of evolution focus on the relative fitness advantages of different mutants in a population while the dynamic behavior of the population size is mostly left unconsidered. We present here a generic stochastic model which combines the growth dynamics of the population and its internal evolution. Our model thereby accounts for the fact that both evolutionary and growth dynamics are based on individual reproduction events and hence are highly coupled and stochastic in nature. We exemplify our approach by studying the dilemma of cooperation in growing populations and show that genuinely stochastic events can ease the dilemma by leading to a transient but robust increase in cooperation.

Modeling the state dependent impulse control for computer virus propagation under media coverage

NASA Astrophysics Data System (ADS)

Liang, Xiyin; Pei, Yongzhen; Lv, Yunfei

2018-02-01

A state dependent impulsive control model is proposed to model the spread of computer virus incorporating media coverage. By the successor function, the sufficient conditions for the existence and uniqueness of order-1 periodic solution are presented first. Secondly, for two classes of periodic solutions, the geometric property of successor function and the analogue of the Poincaré criterion are employed to obtain the stability results. These results show that the number of the infective computers is under the threshold all the time. Finally, the theoretic and numerical analysis show that media coverage can delay the spread of computer virus.

FIELD INVESTIGATIONS OF THE DRIFT SHADOW

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

G. W. Su, T. J. Kneafsey, T. A. Ghezzehei, B. D. Marshall, and P. J. Cook

The ''Drift Shadow'' is defined as the relatively drier region that forms below subsurface cavities or drifts in unsaturated rock. Its existence has been predicted through analytical and numerical models of unsaturated flow. However, these theoretical predictions have not been demonstrated empirically to date. In this project they plan to test the drift shadow concept through field investigations and compare our observations to simulations. Based on modeling studies they have an identified suitable site to perform the study at an inactive mine in a sandstone formation. Pretest modeling studies and preliminary characterization of the site are being used to developmore » the field scale tests.« less

[Masculinity and femininity scales: current state of the art].

PubMed

Fernández, Juan; Quiroga, María A; Del Olmo, Isabel; Rodríguez, Antonio

2007-08-01

A theoretical and empirical review of masculinity and femininity scales was carried out after 30 years of their existence. Hypotheses to be tested were: (a) muldimensionality versus bidimensionality; (b) inadequate percentage of variance accounted for (less than 50%); (c) inconsistency between factor structure and the dualistic model. 618, 200 and 287 students took part in each of the three studies that were carried out. Factorial analyses (PAF) were performed. Results support multidimensionality, unsatisfactory percentage of variance accounted for, and lack of congruence between obtained factors and the dualistic model. All these data were analysed within the context of the twofold sex and gender reality model.

Quantification of the electrical anisotropy in the pro­cess of numerical modelling for hydrogeological characterization

NASA Astrophysics Data System (ADS)

Gernez, S.; Bouchedda, A.; Gloaguen, E.; Paradis, D.

2017-12-01

In order to understand groundwater flow and contaminant transport in the subsurface, it is important to characterize accurately its permeability. Hydrogeophysics, which involves the use of geophysical data to infer the hydraulic properties of the subsurface, is a relatively new geoscience field that is promising to improve hydrogeological characterization. Amongst existing geophysical methods, Electrical Resistivity Tomography (ERT), that can cover a large continuous underground surface or volume, has been widely applied. The inversed electrical resistivities obtained are related to the permeabilities by different means and the resistivity anisotropy should theoretically be a proxy to the permeability anisotropy. However, the existing hydrogeophysical inversion tools usually do not take into account anisotropy. In this paper, we present an anisotropic forward- and inverse-problem 2.5D finite-differences electrical study, which allows to produce improved anisotropic permeability characterization models. We first detail the theoretical basis of the anisotropic ERT, which introduces a resistivity tensor in place of a scalar, and its numerical implementation. After that, we build a synthetic case presenting a simple but representative geological structure in two horizontal homogeneous and anisotropic beds: the numerical forward modelling shows a difference of less than 1% with the analytical solution; the inverse modelling is able to reproduce the initial structure well, with resistivity values close to the initial synthetic model (see attached figure). We show that by using both surface and single-borehole arrays, we overcome the equivalence principle making sure that a unique solution arises. The latter cannot be obtained when considering the media isotropic as typically assumed with existing inversion tools. Finally, we discuss the consequences of the integration of anisotropy in the data-integrated characterization of the permeability. We show that it has a significant influence on the electrical inversion results and then on the hydrogeological characterization. It suggests that anisotropy should be taken into account in any characterization study when its presence is presumed or known in order to produce a model closer to the true hydraulic state of the ground.

Fluid mechanics of Windkessel effect.

PubMed

Mei, C C; Zhang, J; Jing, H X

2018-01-08

We describe a mechanistic model of Windkessel phenomenon based on the linear dynamics of fluid-structure interactions. The phenomenon has its origin in an old-fashioned fire-fighting equipment where an air chamber serves to transform the intermittent influx from a pump to a more steady stream out of the hose. A similar mechanism exists in the cardiovascular system where blood injected intermittantly from the heart becomes rather smooth after passing through an elastic aorta. In existing haeodynamics literature, this mechanism is explained on the basis of electric circuit analogy with empirical impedances. We present a mechanistic theory based on the principles of fluid/structure interactions. Using a simple one-dimensional model, wave motion in the elastic aorta is coupled to the viscous flow in the rigid peripheral artery. Explicit formulas are derived that exhibit the role of material properties such as the blood density, viscosity, wall elasticity, and radii and lengths of the vessels. The current two-element model in haemodynamics is shown to be the limit of short aorta and low injection frequency and the impedance coefficients are derived theoretically. Numerical results for different aorta lengths and radii are discussed to demonstrate their effects on the time variations of blood pressure, wall shear stress, and discharge. Graphical Abstract A mechanistic analysis of Windkessel Effect is described which confirms theoretically the well-known feature that intermittent influx becomes continuous outflow. The theory depends only on the density and viscosity of the blood, the elasticity and dimensions of the vessel. Empirical impedence parameters are avoided.

A theoretical framework for the associations between identity and psychopathology.

PubMed

Klimstra, Theo A; Denissen, Jaap J A

2017-11-01

Identity research largely emerged from clinical observations. Decades of empirical work advanced the field in refining existing approaches and adding new approaches. Furthermore, the existence of linkages of identity with psychopathology is now well established. Unfortunately, both the directionality of effects between identity aspects and psychopathology symptoms, and the mechanisms underlying associations are unclear. In the present paper, we present a new framework to inspire hypothesis-driven empirical research to overcome this limitation. The framework has a basic resemblance to theoretical models for the study of personality and psychopathology, so we provide examples of how these might apply to the study of identity. Next, we explain that unique features of identity may come into play in individuals suffering from psychopathology that are mostly related to the content of one's identity. These include pros and cons of identifying with one's diagnostic label. Finally, inspired by Hermans' dialogical self theory and principles derived from Piaget's, Swann's and Kelly's work, we delineate a framework with identity at the core of an individual multidimensional space. In this space, psychopathology symptoms have a known distance (representing relevance) to one's identity, and individual multidimensional spaces are connected to those of other individuals in one's social network. We discuss methodological (quantitative and qualitative, idiographic and nomothetic) and statistical procedures (multilevel models and network models) to test the framework. Resulting evidence can boost the field of identity research in demonstrating its high practical relevance for the emergence and conservation of psychopathology. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Theorizing a model information pathway to mitigate the menstrual taboo.

PubMed

Yagnik, Arpan

2017-12-13

The impact of menstruation on the society is directly seen in the educational opportunities, quality of life and professional endeavors of females. However, lack of menstrual hygiene management has indirect implication on the balance and development of the society and nation. This study is set in the Indian context. The researcher identifies actors with a potential of mitigating menstrual taboo and then theorizes an optimal information pathway to mitigate menstrual taboo. Diffusion of innovation, framing and agenda setting theories contribute as frameworks in the creation of an optimal pathway to dissolve the menstrual taboo. The actors identified in this model are scholars, health activists, students, NGOs, media, government, corporations and villages or communities. The determinants for the direction and the order of the pathway to diffuse knowledge and confidence among these actors are the ultimate goal and sustainability of the model, strengths and weaknesses of actors, and actors' extent of influence. Considering the absence of an existing alternate, this model pathway provides a solid framework purely from a theoretical perspective. Theoretically, this model pathway is possible, practical and optimal. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Theoretical results on fractionally integrated exponential generalized autoregressive conditional heteroskedastic processes

NASA Astrophysics Data System (ADS)

Lopes, Sílvia R. C.; Prass, Taiane S.

2014-05-01

Here we present a theoretical study on the main properties of Fractionally Integrated Exponential Generalized Autoregressive Conditional Heteroskedastic (FIEGARCH) processes. We analyze the conditions for the existence, the invertibility, the stationarity and the ergodicity of these processes. We prove that, if { is a FIEGARCH(p,d,q) process then, under mild conditions, { is an ARFIMA(q,d,0) with correlated innovations, that is, an autoregressive fractionally integrated moving average process. The convergence order for the polynomial coefficients that describes the volatility is presented and results related to the spectral representation and to the covariance structure of both processes { and { are discussed. Expressions for the kurtosis and the asymmetry measures for any stationary FIEGARCH(p,d,q) process are also derived. The h-step ahead forecast for the processes {, { and { are given with their respective mean square error of forecast. The work also presents a Monte Carlo simulation study showing how to generate, estimate and forecast based on six different FIEGARCH models. The forecasting performance of six models belonging to the class of autoregressive conditional heteroskedastic models (namely, ARCH-type models) and radial basis models is compared through an empirical application to Brazilian stock market exchange index.

Modeling of vortex generated sound in solid propellant rocket motors

NASA Technical Reports Server (NTRS)

Flandro, G. A.

1980-01-01

There is considerable evidence based on both full scale firings and cold flow simulations that hydrodynamically unstable shear flows in solid propellant rocket motors can lead to acoustic pressure fluctuations of significant amplitude. Although a comprehensive theoretical understanding of this problem does not yet exist, procedures were explored for generating useful analytical models describing the vortex shedding phenomenon and the mechanisms of coupling to the acoustic field in a rocket combustion chamber. Since combustion stability prediction procedures cannot be successful without incorporation of all acoustic gains and losses, it is clear that a vortex driving model comparable in quality to the analytical models currently employed to represent linear combustion instability must be formulated.

Piezoelectric Polymers

NASA Technical Reports Server (NTRS)

Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

FIBER OPTICS: Polarization phase nonreciprocity in all-fiber ring interferometers

NASA Astrophysics Data System (ADS)

Andreev, A. Ts; Vasilev, V. D.; Kozlov, V. A.; Kuznetsov, A. V.; Senatorov, A. A.; Shubochkin, R. L.

1993-08-01

The polarization phase nonreciprocity in all-fiber ring interferometers based on single-mode optical fibers was studied experimentally. The results confirm existing theoretical models. Experimentally, it was possible to use fiber ring interferometers to measure the extinction coefficients of optical fiber polarizers. The largest extinction coefficients found for optical-fiber polarizers were 84 dB (for the wavelength 0.82 μm) and 86 dB (1.3 μm).

Steady state magnetic field configurations for the earth's magnetotail

NASA Technical Reports Server (NTRS)

Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.

1989-01-01

A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

Robustness and Vulnerability of Networks with Dynamical Dependency Groups.

PubMed

Bai, Ya-Nan; Huang, Ning; Wang, Lei; Wu, Zhi-Xi

2016-11-28

The dependency property and self-recovery of failure nodes both have great effects on the robustness of networks during the cascading process. Existing investigations focused mainly on the failure mechanism of static dependency groups without considering the time-dependency of interdependent nodes and the recovery mechanism in reality. In this study, we present an evolving network model consisting of failure mechanisms and a recovery mechanism to explore network robustness, where the dependency relations among nodes vary over time. Based on generating function techniques, we provide an analytical framework for random networks with arbitrary degree distribution. In particular, we theoretically find that an abrupt percolation transition exists corresponding to the dynamical dependency groups for a wide range of topologies after initial random removal. Moreover, when the abrupt transition point is above the failure threshold of dependency groups, the evolving network with the larger dependency groups is more vulnerable; when below it, the larger dependency groups make the network more robust. Numerical simulations employing the Erdős-Rényi network and Barabási-Albert scale free network are performed to validate our theoretical results.

The effect of testing versus restudy on retention: a meta-analytic review of the testing effect.

PubMed

Rowland, Christopher A

2014-11-01

Engaging in a test over previously studied information can serve as a potent learning event, a phenomenon referred to as the testing effect. Despite a surge of research in the past decade, existing theories have not yet provided a cohesive account of testing phenomena. The present study uses meta-analysis to examine the effects of testing versus restudy on retention. Key results indicate support for the role of effortful processing as a contributor to the testing effect, with initial recall tests yielding larger testing benefits than recognition tests. Limited support was found for existing theoretical accounts attributing the testing effect to enhanced semantic elaboration, indicating that consideration of alternative mechanisms is warranted in explaining testing effects. Future theoretical accounts of the testing effect may benefit from consideration of episodic and contextually derived contributions to retention resulting from memory retrieval. Additionally, the bifurcation model of the testing effect is considered as a viable framework from which to characterize the patterns of results present across the literature. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

Stomatal regulation based on competition for water, stochastic rainfall, and xylem hydraulic vulnerability - a new theoretical model

NASA Astrophysics Data System (ADS)

Lu, Y.; Duursma, R.; Farrior, C.; Medlyn, B. E.

2016-12-01

Stomata control the exchange of soil water for atmospheric CO2, which is one of the most important resource trade-offs for plants. This trade-off has been studied a lot but not in the context of competition. Based on the theory of evolutionarily stable strategy, we search for the uninvadable (or the ESS) response of stomatal conductance to soil water content under stochastic rainfall, with which the dominant plant population should never be invaded by any rare mutants in the water competition due to a higher fitness. In this study, we define the fitness as the difference between the long-term average photosynthetic carbon gain and a carbon cost of stomatal opening. This cost has traditionally been considered an unknown constant. Here we extend this framework by assuming it as the energy required for xylem embolism refilling. With regard to the refilling process, we explore 2 questions 1) to what extent the embolized xylem vessels can be repaired via refilling; and 2) whether this refilling is immediate or has a time delay following the formation of xylem embolism. We compare various assumptions in a total of 5 scenarios and find that the ESS exists only if the xylem damage can be repaired completely. Then, with this ESS, we estimate annual vegetation photosynthesis and water consumption and compare them with empirical results. In conclusion, this study provides a different insight from the existing empirical and mechanistic models as well as the theoretical models based on the optimization theory. In addition, as the model result is a simple quantitative relation between stomatal conductance and soil water content, it can be easily incorporated into other vegetation function models.

Improvements to Nuclear Data and Its Uncertainties by Theoretical Modeling

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

Danon, Yaron; Nazarewicz, Witold; Talou, Patrick

2013-02-18

This project addresses three important gaps in existing evaluated nuclear data libraries that represent a significant hindrance against highly advanced modeling and simulation capabilities for the Advanced Fuel Cycle Initiative (AFCI). This project will: Develop advanced theoretical tools to compute prompt fission neutrons and gamma-ray characteristics well beyond average spectra and multiplicity, and produce new evaluated files of U and Pu isotopes, along with some minor actinides; Perform state-of-the-art fission cross-section modeling and calculations using global and microscopic model input parameters, leading to truly predictive fission cross-sections capabilities. Consistent calculations for a suite of Pu isotopes will be performed; Implementmore » innovative data assimilation tools, which will reflect the nuclear data evaluation process much more accurately, and lead to a new generation of uncertainty quantification files. New covariance matrices will be obtained for Pu isotopes and compared to existing ones. The deployment of a fleet of safe and efficient advanced reactors that minimize radiotoxic waste and are proliferation-resistant is a clear and ambitious goal of AFCI. While in the past the design, construction and operation of a reactor were supported through empirical trials, this new phase in nuclear energy production is expected to rely heavily on advanced modeling and simulation capabilities. To be truly successful, a program for advanced simulations of innovative reactors will have to develop advanced multi-physics capabilities, to be run on massively parallel super- computers, and to incorporate adequate and precise underlying physics. And all these areas have to be developed simultaneously to achieve those ambitious goals. Of particular interest are reliable fission cross-section uncertainty estimates (including important correlations) and evaluations of prompt fission neutrons and gamma-ray spectra and uncertainties.« less

Testing Software Development Project Productivity Model

NASA Astrophysics Data System (ADS)

Lipkin, Ilya

Software development is an increasingly influential factor in today's business environment, and a major issue affecting software development is how an organization estimates projects. If the organization underestimates cost, schedule, and quality requirements, the end results will not meet customer needs. On the other hand, if the organization overestimates these criteria, resources that could have been used more profitably will be wasted. There is no accurate model or measure available that can guide an organization in a quest for software development, with existing estimation models often underestimating software development efforts as much as 500 to 600 percent. To address this issue, existing models usually are calibrated using local data with a small sample size, with resulting estimates not offering improved cost analysis. This study presents a conceptual model for accurately estimating software development, based on an extensive literature review and theoretical analysis based on Sociotechnical Systems (STS) theory. The conceptual model serves as a solution to bridge organizational and technological factors and is validated using an empirical dataset provided by the DoD. Practical implications of this study allow for practitioners to concentrate on specific constructs of interest that provide the best value for the least amount of time. This study outlines key contributing constructs that are unique for Software Size E-SLOC, Man-hours Spent, and Quality of the Product, those constructs having the largest contribution to project productivity. This study discusses customer characteristics and provides a framework for a simplified project analysis for source selection evaluation and audit task reviews for the customers and suppliers. Theoretical contributions of this study provide an initial theory-based hypothesized project productivity model that can be used as a generic overall model across several application domains such as IT, Command and Control, Simulation and etc... This research validates findings from previous work concerning software project productivity and leverages said results in this study. The hypothesized project productivity model provides statistical support and validation of expert opinions used by practitioners in the field of software project estimation.

On Allometry Relations

NASA Astrophysics Data System (ADS)

West, Damien; West, Bruce J.

2012-07-01

There are a substantial number of empirical relations that began with the identification of a pattern in data; were shown to have a terse power-law description; were interpreted using existing theory; reached the level of "law" and given a name; only to be subsequently fade away when it proved impossible to connect the "law" with a larger body of theory and/or data. Various forms of allometry relations (ARs) have followed this path. The ARs in biology are nearly two hundred years old and those in ecology, geophysics, physiology and other areas of investigation are not that much younger. In general if X is a measure of the size of a complex host network and Y is a property of a complex subnetwork embedded within the host network a theoretical AR exists between the two when Y = aXb. We emphasize that the reductionistic models of AR interpret X and Y as dynamic variables, albeit the ARs themselves are explicitly time independent even though in some cases the parameter values change over time. On the other hand, the phenomenological models of AR are based on the statistical analysis of data and interpret X and Y as averages to yield the empirical AR: = ab. Modern explanations of AR begin with the application of fractal geometry and fractal statistics to scaling phenomena. The detailed application of fractal geometry to the explanation of theoretical ARs in living networks is slightly more than a decade old and although well received it has not been universally accepted. An alternate perspective is given by the empirical AR that is derived using linear regression analysis of fluctuating data sets. We emphasize that the theoretical and empirical ARs are not the same and review theories "explaining" AR from both the reductionist and statistical fractal perspectives. The probability calculus is used to systematically incorporate both views into a single modeling strategy. We conclude that the empirical AR is entailed by the scaling behavior of the probability density, which is derived using the probability calculus.

Cross-Milieu Terrorist Collaboration: Using Game Theory to Assess the Risk of a Novel Threat.

PubMed

Ackerman, Gary A; Zhuang, Jun; Weerasuriya, Sitara

2017-02-01

This article uses a game-theoretic approach to analyze the risk of cross-milieu terrorist collaboration-the possibility that, despite marked ideological differences, extremist groups from very different milieus might align to a degree where operational collaboration against Western societies becomes possible. Based upon theoretical insights drawn from a variety of literatures, a bargaining model is constructed that reflects the various benefits and costs for terrorists' collaboration across ideological milieus. Analyzed in both sequential and simultaneous decision-making contexts and through numerical simulations, the model confirms several theoretical arguments. The most important of these is that although likely to be quite rare, successful collaboration across terrorist milieus is indeed feasible in certain circumstances. The model also highlights several structural elements that might play a larger role than previously recognized in the collaboration decision, including that the prospect of nonmaterial gains (amplification of terror and reputational boost) plays at least as important a role in the decision to collaborate as potential increased capabilities does. Numerical simulation further suggests that prospects for successful collaboration over most scenarios (including operational) increase when a large, effective Islamist terrorist organization initiates collaboration with a smaller right-wing group, as compared with the other scenarios considered. Although the small number of historical cases precludes robust statistical validation, the simulation results are supported by existing empirical evidence of collaboration between Islamists and right- or left-wing extremists. The game-theoretic approach, therefore, provides guidance regarding the circumstances under which such an unholy alliance of violent actors is likely to succeed. © 2016 Society for Risk Analysis.

Agent-Centric Approach for Cybersecurity Decision-Support with Partial Observability

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

Tipireddy, Ramakrishna; Chatterjee, Samrat; Paulson, Patrick R.

Generating automated cyber resilience policies for real-world settings is a challenging research problem that must account for uncertainties in system state over time and dynamics between attackers and defenders. In addition to understanding attacker and defender motives and tools, and identifying “relevant” system and attack data, it is also critical to develop rigorous mathematical formulations representing the defender’s decision-support problem under uncertainty. Game-theoretic approaches involving cyber resource allocation optimization with Markov decision processes (MDP) have been previously proposed in the literature. Moreover, advancements in reinforcement learning approaches have motivated the development of partially observable stochastic games (POSGs) in various multi-agentmore » problem domains with partial information. Recent advances in cyber-system state space modeling have also generated interest in potential applicability of POSGs for cybersecurity. However, as is the case in strategic card games such as poker, research challenges using game-theoretic approaches for practical cyber defense applications include: 1) solving for equilibrium and designing efficient algorithms for large-scale, general problems; 2) establishing mathematical guarantees that equilibrium exists; 3) handling possible existence of multiple equilibria; and 4) exploitation of opponent weaknesses. Inspired by advances in solving strategic card games while acknowledging practical challenges associated with the use of game-theoretic approaches in cyber settings, this paper proposes an agent-centric approach for cybersecurity decision-support with partial system state observability.« less

Exploring excitonic signal in optical conductivity of ZnO through first-order electron-hole vertex correction

NASA Astrophysics Data System (ADS)

Khoirunnisa, Humaira; Aziz Majidi, Muhammad

2018-04-01

The emergence of exitonic signal in the optical response of a wide band-gap semiconductor has been a common knowledge in physics. There have been numerous experimental studies exploring the important role of excitons on influencing both the transport and optical properties of the materials. Despite the existence of much information on excitonic effects, there has not been much literature that explores detailed theoretical explanation on how the exitonic signal appears and how it evolves with temperature. Here, we propose a theoretical study on the optical conductivity of ZnO, a well-known wide band-gap semiconductor that we choose as a case study. ZnO has been known to exhibit excitonic states in its optical spectra in the energy range of ∼3.13-3.41 eV, with a high exciton binding energy of ∼60 meV. An experimental study on ZnO in 2014 revealed such a signal in its optical conductivity spectrum. We present a theoretical investigation on the appearance of excitonic signal in optical conductivity of ZnO. We model the wurtzite ZnO within an 8-band k.p approximation. We calculate the optical conductivity by incorporating the first-order vertex correction derived from the Feynman diagrams. Our calculation up to the first-order correction spectrum qualitatively confirms the existence of excitons in wurtzite ZnO.

Application of natural analog studies to exploration for ore deposits

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

Gustafson, D.L.

1995-09-01

Natural analogs are viewed as similarities in nature and are routinely utilized by exploration geologists in their search for economic mineral deposits. Ore deposit modeling is undertaken by geologists to direct their exploration activities toward favorable geologic environments and, therefore, successful programs. Two types of modeling are presented: (i) empirical model development based on the study of known ore deposit characteristics, and (ii) concept model development based on theoretical considerations and field observations that suggest a new deposit type, not known to exist in nature, may exist and justifies an exploration program. Key elements that are important in empirical modelmore » development are described, and examples of successful applications of these natural analogs to exploration are presented. A classical example of successful concept model development, the discovery of the McLaughlin gold mine in California, is presented. The utilization of natural analogs is an important facet of mineral exploration. Natural analogs guide explorationists in their search for new discoveries, increase the probability of success, and may decrease overall exploration expenditure.« less

Bulk flow strength of forsterite?enstatite composites as a function of forsterite content

NASA Astrophysics Data System (ADS)

Ji, Shaocheng; Wang, Zichao; Wirth, Richard

2001-11-01

Creep experiments have been conducted to investigate the effect of varying forsterite content ( VFo) on the bulk flow strength of dry forsterite-enstatite (Fo-En) aggregates in order to evaluate the applicability of existing theoretical models to two-phase rocks, as well as to understand the rheology of polyphase systems in general. The experiments were performed at temperatures of 1423-1593 K, stresses of 18-100 MPa, oxygen fugacities of 10 -14-10 -2.5 MPa and 0.1 MPa total pressure. The fine-grained (Fo: 10-17 μm; En: 14-31 μm) composites of various Fo volume fractions ( VFo=0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) were synthesized by isostatically hot-pressing in a gas-medium apparatus at 1523 and 350 MPa. Our experiments show that flow strength contrasts between Fo and En are in the range of 3-8 at the given experimental conditions, with Fo as the stronger phase. The measured stress exponent ( n) and activation energy ( Q) values of the Fo-En composites fall between those of the end-members. The n values show a nearly linear increase from 1.3 to 2.0, while the Q values display a non-linear increase from 472 to 584 kJ/mol with En volume fraction from 0 to 1.0. There is no clear dependence of creep rates on oxygen fugacity for the Fo-En composites. The mechanical data and TEM microstructural observations suggest no change in deformation mechanism of each phase when in the composites, compared to when in a single-phase aggregate, the En deformed mainly by dislocation creep while the Fo deformed by dislocation-accommodated diffusion creep for our grain sizes and experimental conditions. Comparisons between the measured composite strengths and various theoretical models indicate that none of the existing theoretical models can give a precise predication over the entire VFo range from 0 to 1. However, the theoretical models based on weak-phase supported structures (WPS) yield a good prediction for the flow strengths of the composites with VFo<0.4, while those based on strong-phase supported structures (SPS) are better for the composites with VFo>0.6. No model gives a good prediction for the bulk strength of two-phase composites in the transitional regime ( VFo=0.4-0.6). Applications of the WPS- and SPS-based models in the transitional regime result in under- and over-estimations for the composite flow strength, respectively. Thus, the effect of rock microstructure should be taken into consideration in modeling the bulk flow strengths of the crust and upper mantle using laboratory-determined flow laws of single-phase aggregates.

Ion-acoustic and electron-acoustic type nonlinear waves in dusty plasmas

NASA Astrophysics Data System (ADS)

Volosevich, A.-V.; Meister, C.-V.

2003-04-01

In the present work, two three-dimensional nonlinear theoretical models of electrostatic solitary waves are investigated within the frame of magnetohydrodynamics. Both times, a multi-component plasma is considered, which consists of hot electrons with a rather flexible distribution function, hot ions with Boltzmann-type distribution, and (negatively as well as positively charged) dust. Additionally, cold ion beams are taken into account in the model to study ion-acoustic structures (IAS), and cold electron beams are included into the model to investigate electron-acoustic structures (EAS). The numerical results of the considered theoretical models allow to make the following conclusions: 1) Electrostatic structures with negative potential (of rarefaction type) are formed both in the IAS model and in the EAS model, but structures with negative potential (of compressional type) are formed in the IAS model only. 2) The intervals of various plasma parameters (velocities of ion and electron beams, temperatures, densities of the plasma components, ions' masses), for which the existence of IAS and EAS solitary waves and structures is possible, are calculated. 3) Further, the parameters of the electrostatic structures (wave amplitudes, scales along and perpendicular to the magnetic field, velocities) are estimated. 4) The application of the present numerical simulation for multi-component plasmas to various astrophysical systems under different physical conditions is discussed.

Use of a Computer-Mediated Delphi Process to Validate a Mass Casualty Conceptual Model

PubMed Central

CULLEY, JOAN M.

2012-01-01

Since the original work on the Delphi technique, multiple versions have been developed and used in research and industry; however, very little empirical research has been conducted that evaluates the efficacy of using online computer, Internet, and e-mail applications to facilitate a Delphi method that can be used to validate theoretical models. The purpose of this research was to develop computer, Internet, and e-mail applications to facilitate a modified Delphi technique through which experts provide validation for a proposed conceptual model that describes the information needs for a mass-casualty continuum of care. Extant literature and existing theoretical models provided the basis for model development. Two rounds of the Delphi process were needed to satisfy the criteria for consensus and/or stability related to the constructs, relationships, and indicators in the model. The majority of experts rated the online processes favorably (mean of 6.1 on a seven-point scale). Using online Internet and computer applications to facilitate a modified Delphi process offers much promise for future research involving model building or validation. The online Delphi process provided an effective methodology for identifying and describing the complex series of events and contextual factors that influence the way we respond to disasters. PMID:21076283

Use of a computer-mediated Delphi process to validate a mass casualty conceptual model.

PubMed

Culley, Joan M

2011-05-01

Since the original work on the Delphi technique, multiple versions have been developed and used in research and industry; however, very little empirical research has been conducted that evaluates the efficacy of using online computer, Internet, and e-mail applications to facilitate a Delphi method that can be used to validate theoretical models. The purpose of this research was to develop computer, Internet, and e-mail applications to facilitate a modified Delphi technique through which experts provide validation for a proposed conceptual model that describes the information needs for a mass-casualty continuum of care. Extant literature and existing theoretical models provided the basis for model development. Two rounds of the Delphi process were needed to satisfy the criteria for consensus and/or stability related to the constructs, relationships, and indicators in the model. The majority of experts rated the online processes favorably (mean of 6.1 on a seven-point scale). Using online Internet and computer applications to facilitate a modified Delphi process offers much promise for future research involving model building or validation. The online Delphi process provided an effective methodology for identifying and describing the complex series of events and contextual factors that influence the way we respond to disasters.

Implementation of Advanced Two Equation Turbulence Models in the USM3D Unstructured Flow Solver

NASA Technical Reports Server (NTRS)

Wang, Qun-Zhen; Massey, Steven J.; Abdol-Hamid, Khaled S.

2000-01-01

USM3D is a widely-used unstructured flow solver for simulating inviscid and viscous flows over complex geometries. The current version (version 5.0) of USM3D, however, does not have advanced turbulence models to accurately simulate complicated flow. We have implemented two modified versions of the original Jones and Launder k-epsilon "two-equation" turbulence model and the Girimaji algebraic Reynolds stress model in USM3D. Tests have been conducted for three flat plate boundary layer cases, a RAE2822 airfoil and an ONERA M6 wing. The results are compared with those from direct numerical simulation, empirical formulae, theoretical results, and the existing Spalart-Allmaras one-equation model.

A Theoretical Investigation of Composite Overwrapped Pressure Vessel (COPV) Mechanics Applied to NASA Full Scale Tests

NASA Technical Reports Server (NTRS)

Thesken, John C.; Murthy, Pappu L. N.; Phoenix, S. L.; Greene, N.; Palko, Joseph L.; Eldridge, Jeffrey; Sutter, James; Saulsberry, R.; Beeson, H.

2009-01-01

A theoretical investigation of the factors controlling the stress rupture life of the National Aeronautics and Space Administration's (NASA) composite overwrapped pressure vessels (COPVs) continues. Kevlar (DuPont) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of a load sharing liner, the manufacturing induced residual stresses and the complex mechanical response, the state of actual fiber stress in flight hardware and test articles is not clearly known. This paper is a companion to a previously reported experimental investigation and develops a theoretical framework necessary to design full-scale pathfinder experiments and accurately interpret the experimentally observed deformation and failure mechanisms leading up to static burst in COPVs. The fundamental mechanical response of COPVs is described using linear elasticity and thin shell theory and discussed in comparison to existing experimental observations. These comparisons reveal discrepancies between physical data and the current analytical results and suggest that the vessel s residual stress state and the spatial stress distribution as a function of pressure may be completely different from predictions based upon existing linear elastic analyses. The 3D elasticity of transversely isotropic spherical shells demonstrates that an overly compliant transverse stiffness relative to membrane stiffness can account for some of this by shifting a thin shell problem well into the realm of thick shell response. The use of calibration procedures are demonstrated as calibrated thin shell model results and finite element results are shown to be in good agreement with the experimental results. The successes reported here have lead to continuing work with full scale testing of larger NASA COPV hardware.

Stability analysis of an implicitly defined labor market model

NASA Astrophysics Data System (ADS)

Mendes, Diana A.; Mendes, Vivaldo M.

2008-06-01

Until very recently, the pervasive existence of models exhibiting well-defined backward dynamics but ill-defined forward dynamics in economics and finance has apparently posed no serious obstacles to the analysis of their dynamics and stability, despite the problems that may arise from possible erroneous conclusions regarding theoretical considerations and policy prescriptions from such models. A large number of papers have dealt with this problem in the past by assuming the existence of symmetry between forward and backward dynamics, even in the case when the map cannot be invertible either forward or backwards. However, this procedure has been seriously questioned over the last few years in a series of papers dealing with implicit difference equations and inverse limit spaces. This paper explores the search and matching labor market model developed by Bhattacharya and Bunzel [J. Bhattacharya, H. Bunzel, Chaotic Planning Solution in the Textbook Model of Equilibrium Labor Market Search and Matching, Mimeo, Iowa State University, 2002; J. Bhattacharya, H. Bunzel, Economics Bulletin 5 (19) (2003) 1-10], with the following objectives in mind: (i) to show that chaotic dynamics may still be present in the model for acceptable parameter values, (ii) to clarify some open questions related with the admissible dynamics in the forward looking setting, by providing a rigorous proof of the existence of cyclic and chaotic dynamics through the application of tools from symbolic dynamics and inverse limit theory.

Chiral Domain Structure in Superfluid 3He-A Studied by Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Kasai, J.; Okamoto, Y.; Nishioka, K.; Takagi, T.; Sasaki, Y.

2018-05-01

The existence of a spatially varying texture in superfluid 3He is a direct manifestation of the complex macroscopic wave function. The real space shape of the texture, namely, a macroscopic wave function, has been studied extensively with the help of theoretical modeling but has never been directly observed experimentally with spatial resolution. We have succeeded in visualizing the texture by a specialized magnetic resonance imaging. With this new technology, we have discovered that the macroscopic chiral domains, of which sizes are as large as 1 mm, and corresponding chiral domain walls exist rather stably in 3He - A film at temperatures far below the transition temperature.

Spreading dynamics of a SIQRS epidemic model on scale-free networks

NASA Astrophysics Data System (ADS)

Li, Tao; Wang, Yuanmei; Guan, Zhi-Hong

2014-03-01

In order to investigate the influence of heterogeneity of the underlying networks and quarantine strategy on epidemic spreading, a SIQRS epidemic model on the scale-free networks is presented. Using the mean field theory the spreading dynamics of the virus is analyzed. The spreading critical threshold and equilibria are derived. Theoretical results indicate that the critical threshold value is significantly dependent on the topology of the underlying networks and quarantine rate. The existence of equilibria is determined by threshold value. The stability of disease-free equilibrium and the permanence of the disease are proved. Numerical simulations confirmed the analytical results.

Theoretical investigation of microstructure evolution and deformation of zirconium under neutron irradiation

DOE PAGES

Barashev, A. V.; Golubov, S. I.; Stoller, R. E.

2015-06-01

We studied the radiation growth of zirconium using a reaction–diffusion model which takes into account intra-cascade clustering of self-interstitial atoms and one-dimensional diffusion of interstitial clusters. The observed dose dependence of strain rates is accounted for by accumulation of sessile dislocation loops during irradiation. Moreover, the computational model developed and fitted to available experimental data is applied to study deformation of Zr single crystals under irradiation up to hundred dpa. Finally, the effect of cold work and the reasons for negative prismatic strains and co-existence of vacancy and interstitial loops are elucidated.

[The heavy ion irradiation influence on the thermodynamic parameters of liquids in human body].

PubMed

Vlasenko, T S; Bulavin, L A; Sysoev, V M

2014-01-01

In this manuscript a theoretical model describing the influence of the heavy ion radiotherapy on the liquid matter in the human body is suggested. Based on the fundamental equations of Bogoliubov chain the effective temperatures in the case of constant particles fluent are found in the context of single component model. An existence of such temperatures allows the use of equilibrium thermodynamics formalism to nonequilibrium stationary state. The obtained results provide the possibility of predicting the liquid matter structural changes in the biological systems in the area influenced by the heavy ion beams.

Twisting, supercoiling and stretching in protein bound DNA

NASA Astrophysics Data System (ADS)

Lam, Pui-Man; Zhen, Yi

2018-04-01

We have calculated theoretical results for the torque and slope of the twisted DNA, with various proteins bound on it, using the Neukirch-Marko model, in the regime where plectonemes exist. We found that the torque in the protein bound DNA decreases compared to that in the bare DNA. This is caused by the decrease in the free energy g(f) , and hence the smaller persistence lengths, in the case of protein bound DNA. We hope our results will encourage experimental investigations of supercoiling in protein bound DNA, which can provide further tests of the Neukirch-Marko model.

Modeling X-Ray Photoionized Plasmas: Ion Storage Ring Measurements of Low Temperature Dielectronic Recombination Rate Coefficients for L-Shell Iron

NASA Technical Reports Server (NTRS)

Savin, D. W.; Badnell, N. R.; Bartsch, T.; Brandau, C.; Chen, M. H.; Grieser, M.; Gwinner, G.; Hoffknecht, A.; Kahn, S. M.; Linkemann, J.

2000-01-01

Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated a laboratory program to produce reliable low temperature DR rates. Here, we present some of our recent results and discuss some of their astrophysical implications.

A Game Theoretical Model for Location of Terror Response Facilities under Capacitated Resources

PubMed Central

Kang, Qi; Xu, Weisheng; Wu, Qidi

2013-01-01

This paper is concerned with the effect of capacity constraints on the locations of terror response facilities. We assume that the state has limited resources, and multiple facilities may be involved in the response until the demand is satisfied consequently. We formulate a leader-follower game model between the state and the terrorist and prove the existence and uniqueness of the Nash equilibrium. An integer linear programming is proposed to obtain the equilibrium results when the facility number is fixed. The problem is demonstrated by a case study of the 19 districts of Shanghai, China. PMID:24459446

The theoretical and experimental study of a material structure evolution in gigacyclic fatigue regime

NASA Astrophysics Data System (ADS)

Plekhov, Oleg; Naimark, Oleg; Narykova, Maria; Kadomtsev, Andrey; Betekhtin, Vladimir

2015-10-01

The work is devoted to the study of the metal structure evolution under gigacyclic fatigue (VHCF) regime. The study of the mechanical properties of the samples (Armco iron) with different state of life time existing was carried out on the base of the acoustic resonance method. The damage accumulation (porosity of the samples) was studied by the hydrostatic weighing method. A statistical model of damage accumulation was proposed in order to describe the damage accumulation process. The model describes the influence of the sample surface on the location of fatigue crack initiation.

Data Retention and Anonymity Services

NASA Astrophysics Data System (ADS)

Berthold, Stefan; Böhme, Rainer; Köpsell, Stefan

The recently introduced legislation on data retention to aid prosecuting cyber-related crime in Europe also affects the achievable security of systems for anonymous communication on the Internet. We argue that data retention requires a review of existing security evaluations against a new class of realistic adversary models. In particular, we present theoretical results and first empirical evidence for intersection attacks by law enforcement authorities. The reference architecture for our study is the anonymity service AN.ON, from which we also collect empirical data. Our adversary model reflects an interpretation of the current implementation of the EC Directive on Data Retention in Germany.

Adopting epidemic model to optimize medication and surgical intervention of excess weight

NASA Astrophysics Data System (ADS)

Sun, Ruoyan

2017-01-01

We combined an epidemic model with an objective function to minimize the weighted sum of people with excess weight and the cost of a medication and surgical intervention in the population. The epidemic model is consisted of ordinary differential equations to describe three subpopulation groups based on weight. We introduced an intervention using medication and surgery to deal with excess weight. An objective function is constructed taking into consideration the cost of the intervention as well as the weight distribution of the population. Using empirical data, we show that fixed participation rate reduces the size of obese population but increases the size for overweight. An optimal participation rate exists and decreases with respect to time. Both theoretical analysis and empirical example confirm the existence of an optimal participation rate, u*. Under u*, the weighted sum of overweight (S) and obese (O) population as well as the cost of the program is minimized. This article highlights the existence of an optimal participation rate that minimizes the number of people with excess weight and the cost of the intervention. The time-varying optimal participation rate could contribute to designing future public health interventions of excess weight.

A theoretical signal processing framework for linear diffusion MRI: Implications for parameter estimation and experiment design.

PubMed

Varadarajan, Divya; Haldar, Justin P

2017-11-01

The data measured in diffusion MRI can be modeled as the Fourier transform of the Ensemble Average Propagator (EAP), a probability distribution that summarizes the molecular diffusion behavior of the spins within each voxel. This Fourier relationship is potentially advantageous because of the extensive theory that has been developed to characterize the sampling requirements, accuracy, and stability of linear Fourier reconstruction methods. However, existing diffusion MRI data sampling and signal estimation methods have largely been developed and tuned without the benefit of such theory, instead relying on approximations, intuition, and extensive empirical evaluation. This paper aims to address this discrepancy by introducing a novel theoretical signal processing framework for diffusion MRI. The new framework can be used to characterize arbitrary linear diffusion estimation methods with arbitrary q-space sampling, and can be used to theoretically evaluate and compare the accuracy, resolution, and noise-resilience of different data acquisition and parameter estimation techniques. The framework is based on the EAP, and makes very limited modeling assumptions. As a result, the approach can even provide new insight into the behavior of model-based linear diffusion estimation methods in contexts where the modeling assumptions are inaccurate. The practical usefulness of the proposed framework is illustrated using both simulated and real diffusion MRI data in applications such as choosing between different parameter estimation methods and choosing between different q-space sampling schemes. Copyright © 2017 Elsevier Inc. All rights reserved.

A continuous-wave ultrasound system for displacement amplitude and phase measurement.

PubMed

Finneran, James J; Hastings, Mardi C

2004-06-01

A noninvasive, continuous-wave ultrasonic technique was developed to measure the displacement amplitude and phase of mechanical structures. The measurement system was based on a method developed by Rogers and Hastings ["Noninvasive vibration measurement system and method for measuring amplitude of vibration of tissue in an object being investigated," U.S. Patent No. 4,819,643 (1989)] and expanded to include phase measurement. A low-frequency sound source was used to generate harmonic vibrations in a target of interest. The target was simultaneously insonified by a low-power, continuous-wave ultrasonic source. Reflected ultrasound was phase modulated by the target motion and detected with a separate ultrasonic transducer. The target displacement amplitude was obtained directly from the received ultrasound frequency spectrum by comparing the carrier and sideband amplitudes. Phase information was obtained by demodulating the received signal using a double-balanced mixer and low-pass filter. A theoretical model for the ultrasonic receiver field is also presented. This model coupled existing models for focused piston radiators and for pulse-echo ultrasonic fields. Experimental measurements of the resulting receiver fields compared favorably with theoretical predictions.

Combination of real options and game-theoretic approach in investment analysis

NASA Astrophysics Data System (ADS)

Arasteh, Abdollah

2016-09-01

Investments in technology create a large amount of capital investments by major companies. Assessing such investment projects is identified as critical to the efficient assignment of resources. Viewing investment projects as real options, this paper expands a method for assessing technology investment decisions in the linkage existence of uncertainty and competition. It combines the game-theoretic models of strategic market interactions with a real options approach. Several key characteristics underlie the model. First, our study shows how investment strategies rely on competitive interactions. Under the force of competition, firms hurry to exercise their options early. The resulting "hurry equilibrium" destroys the option value of waiting and involves violent investment behavior. Second, we get best investment policies and critical investment entrances. This suggests that integrating will be unavoidable in some information product markets. The model creates some new intuitions into the forces that shape market behavior as noticed in the information technology industry. It can be used to specify best investment policies for technology innovations and adoptions, multistage R&D, and investment projects in information technology.

Attention to change: A multilevel theory on the process of emergent continuous organizational change.

PubMed

Wee, Elijah X M; Taylor, M Susan

2018-01-01

Increasingly, continuous organizational change is viewed as the new reality for organizations and their members. However, this model of organizational change, which is usually characterized by ongoing, cumulative, and substantive change from the bottom up, remains underexplored in the literature. Taking a multilevel approach, the authors develop a theoretical model to explain the mechanisms behind the amplification and accumulation of valuable, ongoing work-unit level changes over time, which then become substantial changes at the organizational level. Drawing on the concept of emergence, they first focus on the cognitive search mechanisms of work-unit members and managers to illustrate how work-unit level routine changes may be amplified to the organization through 2 unique processes: composition and compilation emergence. The authors then discuss the managers' role in creating a sense of coherence and meaning for the accumulation of these emergent changes over time. They conclude this research by discussing the theoretical implications of their model for the existing literature of organizational change. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

A simplified memory network model based on pattern formations

NASA Astrophysics Data System (ADS)

Xu, Kesheng; Zhang, Xiyun; Wang, Chaoqing; Liu, Zonghua

2014-12-01

Many experiments have evidenced the transition with different time scales from short-term memory (STM) to long-term memory (LTM) in mammalian brains, while its theoretical understanding is still under debate. To understand its underlying mechanism, it has recently been shown that it is possible to have a long-period rhythmic synchronous firing in a scale-free network, provided the existence of both the high-degree hubs and the loops formed by low-degree nodes. We here present a simplified memory network model to show that the self-sustained synchronous firing can be observed even without these two necessary conditions. This simplified network consists of two loops of coupled excitable neurons with different synaptic conductance and with one node being the sensory neuron to receive an external stimulus signal. This model can be further used to show how the diversity of firing patterns can be selectively formed by varying the signal frequency, duration of the stimulus and network topology, which corresponds to the patterns of STM and LTM with different time scales. A theoretical analysis is presented to explain the underlying mechanism of firing patterns.

Spectral Entropies as Information-Theoretic Tools for Complex Network Comparison

NASA Astrophysics Data System (ADS)

De Domenico, Manlio; Biamonte, Jacob

2016-10-01

Any physical system can be viewed from the perspective that information is implicitly represented in its state. However, the quantification of this information when it comes to complex networks has remained largely elusive. In this work, we use techniques inspired by quantum statistical mechanics to define an entropy measure for complex networks and to develop a set of information-theoretic tools, based on network spectral properties, such as Rényi q entropy, generalized Kullback-Leibler and Jensen-Shannon divergences, the latter allowing us to define a natural distance measure between complex networks. First, we show that by minimizing the Kullback-Leibler divergence between an observed network and a parametric network model, inference of model parameter(s) by means of maximum-likelihood estimation can be achieved and model selection can be performed with appropriate information criteria. Second, we show that the information-theoretic metric quantifies the distance between pairs of networks and we can use it, for instance, to cluster the layers of a multilayer system. By applying this framework to networks corresponding to sites of the human microbiome, we perform hierarchical cluster analysis and recover with high accuracy existing community-based associations. Our results imply that spectral-based statistical inference in complex networks results in demonstrably superior performance as well as a conceptual backbone, filling a gap towards a network information theory.

Quantum-mechanical predictions of electron-induced ionization cross sections of DNA components

NASA Astrophysics Data System (ADS)

Champion, Christophe

2013-05-01

Ionization of biomolecules remains still today rarely investigated on both the experimental and the theoretical sides. In this context, the present work appears as one of the first quantum mechanical approaches providing a multi-differential description of the electron-induced ionization process of the main DNA components for impact energies ranging from the target ionization threshold up to about 10 keV. The cross section calculations are here performed within the 1st Born approximation framework in which the ejected electron is described by a Coulomb wave whereas the incident and the scattered electrons are both described by a plane wave. The biological targets of interest, namely, the DNA nucleobases and the sugar-phosphate backbone, are here described by means of the GAUSSIAN 09 system using the restricted Hartree-Fock method with geometry optimization. The theoretical predictions also obtained have shown a reasonable agreement with the experimental total ionization cross sections while huge discrepancies have been pointed out with existing theoretical models, mainly developed within a semi-classical framework.

Sharing methodology: a worked example of theoretical integration with qualitative data to clarify practical understanding of learning and generate new theoretical development.

PubMed

Yardley, Sarah; Brosnan, Caragh; Richardson, Jane

2013-01-01

Theoretical integration is a necessary element of study design if clarification of experiential learning is to be achieved. There are few published examples demonstrating how this can be achieved. This methodological article provides a worked example of research methodology that achieved clarification of authentic early experiences (AEEs) through a bi-directional approach to theory and data. Bi-directional refers to our simultaneous use of theory to guide and interrogate empirical data and the use of empirical data to refine theory. We explain the five steps of our methodological approach: (1) understanding the context; (2) critique on existing applications of socio-cultural models to inform study design; (3) data generation; (4) analysis and interpretation and (5) theoretical development through a novel application of Metis. These steps resulted in understanding of how and why different outcomes arose from students participating in AEE. Our approach offers a mechanism for clarification without which evidence-based effective ways to maximise constructive learning cannot be developed. In our example it also contributed to greater theoretical understanding of the influence of social interactions. By sharing this example of research undertaken to develop both theory and educational practice we hope to assist others seeking to conduct similar research.

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

El-Atwani, O.; Norris, S. A.; Ludwig, K.

In this study, several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends onmore » several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.« less

The SHIP facility at CERN

NASA Astrophysics Data System (ADS)

De Lellis, Giovanni

2016-04-01

Searches for new physics with accelerators are being performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. A new experimental facility meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored from the experimental point of view. A beam dump facility, built at CERN in the north area, using 400 GeV protons is a copious factory of charmed hadrons and could be used to probe the existence of such particles. The beam dump is also an ideal source of tau neutrinos, the less known particle in the Standard Model. In particular, tau anti-neutrinos have not been directly observed so far. We report the physics potential of such an experiment and outline the performances of a detector operating at the same facility for the search for the τ → μμμ decay.

Optical Pattern Formation in Spatially Bunched Atoms: A Self-Consistent Model and Experiment

NASA Astrophysics Data System (ADS)

Schmittberger, Bonnie L.; Gauthier, Daniel J.

2014-05-01

The nonlinear optics and optomechanical physics communities use different theoretical models to describe how optical fields interact with a sample of atoms. There does not yet exist a model that is valid for finite atomic temperatures but that also produces the zero temperature results that are generally assumed in optomechanical systems. We present a self-consistent model that is valid for all atomic temperatures and accounts for the back-action of the atoms on the optical fields. Our model provides new insights into the competing effects of the bunching-induced nonlinearity and the saturable nonlinearity. We show that it is crucial to keep the fifth and seventh-order nonlinearities that arise when there exists atomic bunching, even at very low optical field intensities. We go on to apply this model to the results of our experimental system where we observe spontaneous, multimode, transverse optical pattern formation at ultra-low light levels. We show that our model accurately predicts our experimentally observed threshold for optical pattern formation, which is the lowest threshold ever reported for pattern formation. We gratefully acknowledge the financial support of the NSF through Grant #PHY-1206040.

A design procedure for fan inflow control structures

NASA Technical Reports Server (NTRS)

Gedge, M. R.

1980-01-01

Significant differences exist in the noise generated by engine in flight and engines operating on the test stand. It was observed that these differences can be reduced by use of an inflow control structure (ICS) in the static test configuration. The results of the second phase of a three phase program are described and the results of a test program conducted to assess and modify various theoretical models, leading to the development of an ICS design system is summarized.

Technology diffusion and environmental regulation: Evidence from electric power plants under the Clean Air Act

NASA Astrophysics Data System (ADS)

Frey, Elaine F.

Even though environmental policy can greatly affect the path of technology diffusion, the economics literature contains limited empirical evidence of this relationship. My research will contribute to the available evidence by providing insight into the technology adoption decisions of electric generating firms. Since policies are often evaluated based on the incentives they provide to promote adoption of new technologies, it is important that policy makers understand the relationship between technological diffusion and regulation structure to make informed decisions. Lessons learned from this study can be used to guide future policies such as those directed to mitigate climate change. I first explore the diffusion of scrubbers, a sulfur dioxide (SO 2) abatement technology, in response to federal market-based regulations and state command-and-control regulations. I develop a simple theoretical model to describe the adoption decisions of scrubbers and use a survival model to empirically test the theoretical model. I find that power plants with strict command-and-control regulations have a high probability of installing a scrubber. These findings suggest that although market-based regulations have encouraged diffusion, many scrubbers have been installed because of state regulatory pressure. Although tradable permit systems are thought to give firms more flexibility in choosing abatement technologies, I show that interactions between a permit system and pre-existing command-and-control regulations can limit that flexibility. In a separate analysis, I explore the diffusion of combined cycle (CC) generating units, which are natural gas-fired generating units that are cleaner and more efficient than alternative generating units. I model the decision to consider adoption of a CC generating unit and the extent to which the technology is adopted in response to environmental regulations imposed on new sources of pollutants. To accomplish this, I use a zero-inflated Poisson model and focus on both the decision to adopt a CC unit at an existing power plant as well as the firm-level decision to adopt a CC unit in either a new or an existing power plant. Evidence from this empirical investigation shows that environmental regulation has a significant effect on both the decision to consider adoption as well as the extent of adoption.

Compensating for Electrode Polarization in Dielectric Spectroscopy Studies of Colloidal Suspensions: Theoretical Assessment of Existing Methods

PubMed Central

Chassagne, Claire; Dubois, Emmanuelle; Jiménez, María L.; van der Ploeg, J. P. M; van Turnhout, Jan

2016-01-01

Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed. PMID:27486575

Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures

NASA Astrophysics Data System (ADS)

Kalinin, Sergei V.; Kim, Yunseok; Fong, Dillon D.; Morozovska, Anna N.

2018-03-01

For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase per se necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this review, we summarize recent studies of surface-screening phenomena in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. We also note that the need for ionic screening renders polarization switching a coupled physical–electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this. ).

Rate and time dependent behavior of structural adhesives. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Renieri, M. P.; Herakovich, C. T.; Brinson, H. F.

1976-01-01

Studies on two adhesives (Metlbond 1113 and 1113-2) identified as having applications in the bonding of composite materials are presented. Constitutive equations capable of describing changes in material behavior with strain rate are derived from various theoretical approaches. It is shown that certain unique relationships exist between these approaches. It is also shown that the constitutive equation derived from mechanical models can be used for creep and relaxation loading. A creep to failure phenomenon is shown to exist and is correlated with a delayed yield equation proposed by Crochet. Loading-unloading results are presented and are shown to correlate well with the proposed form of the loading-unloading equations for the modified Bingham model. Experimental results obtained for relaxation tests above and below the glass transition temperature are presented. It is shown that the adhesives obey the time-temperature superposition principle.

Theory-Guided Selection of Discrimination Measures for Racial/Ethnic Health Disparities Research among Older Adults

PubMed Central

Thrasher, Angela D.; Clay, Olivio J.; Ford, Chandra L.; Stewart, Anita L.

2013-01-01

Objectives Discrimination may contribute to health disparities among older adults. Existing measures of perceived discrimination have provided important insights but may have limitations when used in studies of older adults. This paper illustrates the process of assessing the appropriateness of existing measures for theory-based research on perceived discrimination and health. Methods First we describe three theoretical frameworks that are relevant to the study of perceived discrimination and health – stress-process models, life course models, and the Public Health Critical Race praxis. We then review four widely-used measures of discrimination, comparing their content and describing how well they address key aspects of each theory, and discussing potential areas of modification. Discussion Using theory to guide measure selection can help improve understanding of how perceived discrimination may contribute to racial/ethnic health disparities among older adults. PMID:22451527

Experimental measurement and calculation of losses in planar radial magnetic bearings

NASA Technical Reports Server (NTRS)

Kasarda, M. E. F.; Allaire, P. E.; Hope, R. W.; Humphris, R. R.

1994-01-01

The loss mechanisms associated with magnetic bearings have yet to be adequately characterized or modeled analytically and thus pose a problem for the designer of magnetic bearings. This problem is particularly important for aerospace applications where low power consumption of components is critical. Also, losses are expected to be large for high speed operation. The iron losses in magnetic bearings can be divided into eddy current losses and hysteresis losses. While theoretical models for these losses exist for transformer and electric motor applications, they have not been verified for magnetic bearings. This paper presents the results from a low speed experimental test rig and compares them to calculated values from existing theory. Experimental data was taken over a range of 90 to 2,800 rpm for several bias currents and two different pole configurations. With certain assumptions agreement between measured and calculated power losses was within 16 percent for a number of test configurations.

Education And Gender Bias in the Sex Ratio At Birth: Evidence From India

PubMed Central

ECHÁVARRI, REBECA A.; EZCURRA, ROBERTO

2010-01-01

This article investigates the possible existence of a nonlinear link between female disadvantage in natality and education. To this end, we devise a theoretical model based on the key role of social interaction in explaining people’s acquisition of preferences, which justifies the existence of a nonmonotonic relationship between female disadvantage in natality and education. The empirical validity of the proposed model is examined for the case of India, using district-level data. In this context, our econometric analysis pays particular attention to the role of spatial dependence to avoid any potential problems of misspecification. The results confirm that the relationship between the sex ratio at birth and education in India follows an inverted U-shape. This finding is robust to the inclusion of additional explanatory variables in the analysis, and to the choice of the spatial weight matrix used to quantify the spatial interdependence between the sample districts. PMID:20355693

From Coexpression to Coregulation: An Approach to Inferring Transcriptional Regulation Among Gene Classes from Large-Scale Expression Data

NASA Technical Reports Server (NTRS)

Mjolsness, Eric; Castano, Rebecca; Mann, Tobias; Wold, Barbara

2000-01-01

We provide preliminary evidence that existing algorithms for inferring small-scale gene regulation networks from gene expression data can be adapted to large-scale gene expression data coming from hybridization microarrays. The essential steps are (I) clustering many genes by their expression time-course data into a minimal set of clusters of co-expressed genes, (2) theoretically modeling the various conditions under which the time-courses are measured using a continuous-time analog recurrent neural network for the cluster mean time-courses, (3) fitting such a regulatory model to the cluster mean time courses by simulated annealing with weight decay, and (4) analysing several such fits for commonalities in the circuit parameter sets including the connection matrices. This procedure can be used to assess the adequacy of existing and future gene expression time-course data sets for determining transcriptional regulatory relationships such as coregulation.

Education and gender bias in the sex ratio at birth: evidence from India.

PubMed

Echávarri, Rebeca A; Ezcurra, Roberto

2010-02-01

This article investigates the possible existence of a nonlinear link between female disadvantage in natality and education. To this end, we devise a theoretical model based on the key role of social interaction in explaining people's acquisition of preferences, which justifies the existence of a nonmonotonic relationship between female disadvantage in natality and education. The empirical validity of the proposed model is examined for the case of India, using district-level data. In this context, our econometric analysis pays particular attention to the role of spatial dependence to avoid any potential problems of misspecification. The results confirm that the relationship between the sex ratio at birth and education in India follows an inverted U-shape. This finding is robust to the inclusion of additional explanatory variables in the analysis, and to the choice of the spatial weight matrix used to quantify the spatial interdependence between the sample districts.

The relative age effect in sport: a developmental systems model.

PubMed

Wattie, Nick; Schorer, Jörg; Baker, Joseph

2015-01-01

The policies that dictate the participation structure of many youth sport systems involve the use of a set selection date (e.g. 31 December), which invariably produces relative age differences between those within the selection year (e.g. 1 January to 31 December). Those born early in the selection year (e.g. January) are relatively older—by as much as 12 months minus 1 day—than those born later in the selection year (e.g. December). Research in the area of sport has identified a number of significant developmental effects associated with such relative age differences. However, a theoretical framework that describes the breadth and complexity of relative age effects (RAEs) in sport does not exist in the literature. This paper reviews and summarizes the existing literature on relative age in sport, and proposes a constraints-based developmental systems model for RAEs in sport.

Theoretical survey on positronium formation and ionisation in positron atom scattering

NASA Technical Reports Server (NTRS)

Basu, Madhumita; Ghosh, A. S.

1990-01-01

The recent theoretical studies are surveyed and reported on the formation of exotic atoms in positron-hydrogen, positron-helium and positron-lithium scattering specially at intermediate energy region. The ionizations of these targets by positron impact was also considered. Theoretical predictions for both the processes are compared with existing measured values.

Technology dependence and health-related quality of life: a model.

PubMed

Marden, Susan F

2005-04-01

This paper presents a new theoretical model to explain people's diverse responses to therapeutic health technology by characterizing the relationship between technology dependence and health-related quality of life (HRQL). Technology dependence has been defined as reliance on a variety of devices, drugs and procedures to alleviate or remedy acute or chronic health problems. Health professionals must ensure that these technologies result in positive outcomes for those who must rely on them, while minimizing the potential for unintended consequences. Little research exists to inform health professionals about how dependency on therapeutic technology may affect patient-reported outcomes such as HRQL. Organizing frameworks to focus such research are also limited. Generated from the synthesis of three theoretical frameworks and empirical research, the model proposes that attitudes towards technology dependence affect HRQL through a person's illness representations or commonsense beliefs about their illness. Symptom distress, illness history, age and gender also influence the technology dependence and HRQL relationship. Five concepts form the major components of the model: a) attitudes towards technology dependence, b) illness representation, c) symptom distress, d) HRQL and e) illness history. The model is proposed as a guide for clinical nursing research into the impact of a wide variety of therapeutic health care interventions on HRQL. Empirical validation of the model is needed to test its generality.

A comprehensive scenario of the thermodynamic anomalies of water using the TIP4P/2005 model

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

González, Miguel A.; Department of Chemistry, Imperial College London, London SW7 2AZ; Valeriani, Chantal

2016-08-07

The striking behavior of water has deserved it to be referred to as an “anomalous” liquid. The water anomalies are greatly amplified in metastable (supercooled and/or stretched) regions. This makes difficult a complete experimental description since, beyond certain limits, the metastable phase necessarily transforms into the stable one. Theoretical interpretation of the water anomalies could then be based on simulation results of well validated water models. But the analysis of the simulations has not yet reached a consensus. In particular, one of the most popular theoretical scenarios—involving the existence of a liquid-liquid critical point (LLCP)—is disputed by several authors. Inmore » this work, we propose to use a number of exact thermodynamic relations which may shed light on this issue. Interestingly, these relations may be tested in a region of the phase diagram which is outside the LLCP thus avoiding the problems associated to the coexistence region. The central property connected to other water anomalies is the locus of temperatures at which the density along isobars attain a maximum (TMD line) or a minimum (TmD). We have performed computer simulations to evaluate the TMD and TmD for a successful water model, namely, TIP4P/2005. We have also evaluated the vapor-liquid (VL) spinodal in the region of large negative pressures. The shape of these curves and their connection to the extrema of some response functions, in particular the isothermal compressibility and heat capacity at constant pressure, provides very useful information which may help to elucidate the validity of the theoretical proposals. In this way, we are able to present for the first time a comprehensive scenario of the thermodynamic water anomalies for TIP4P/2005 and their relation to the vapor-liquid spinodal. The overall picture shows a remarkable similarity with the corresponding one for the ST2 water model, for which the existence of a LLCP has been demonstrated in recent years. It also provides a hint as to where the long-sought for extrema in response functions might become accessible to experiments.« less

A comprehensive scenario of the thermodynamic anomalies of water using the TIP4P/2005 model.

PubMed

González, Miguel A; Valeriani, Chantal; Caupin, Frédéric; Abascal, José L F

2016-08-07

The striking behavior of water has deserved it to be referred to as an "anomalous" liquid. The water anomalies are greatly amplified in metastable (supercooled and/or stretched) regions. This makes difficult a complete experimental description since, beyond certain limits, the metastable phase necessarily transforms into the stable one. Theoretical interpretation of the water anomalies could then be based on simulation results of well validated water models. But the analysis of the simulations has not yet reached a consensus. In particular, one of the most popular theoretical scenarios-involving the existence of a liquid-liquid critical point (LLCP)-is disputed by several authors. In this work, we propose to use a number of exact thermodynamic relations which may shed light on this issue. Interestingly, these relations may be tested in a region of the phase diagram which is outside the LLCP thus avoiding the problems associated to the coexistence region. The central property connected to other water anomalies is the locus of temperatures at which the density along isobars attain a maximum (TMD line) or a minimum (TmD). We have performed computer simulations to evaluate the TMD and TmD for a successful water model, namely, TIP4P/2005. We have also evaluated the vapor-liquid (VL) spinodal in the region of large negative pressures. The shape of these curves and their connection to the extrema of some response functions, in particular the isothermal compressibility and heat capacity at constant pressure, provides very useful information which may help to elucidate the validity of the theoretical proposals. In this way, we are able to present for the first time a comprehensive scenario of the thermodynamic water anomalies for TIP4P/2005 and their relation to the vapor-liquid spinodal. The overall picture shows a remarkable similarity with the corresponding one for the ST2 water model, for which the existence of a LLCP has been demonstrated in recent years. It also provides a hint as to where the long-sought for extrema in response functions might become accessible to experiments.

When the customer shouldn't be king: antecedents and consequences of sexual harassment by clients and customers.

PubMed

Gettman, Hilary J; Gelfand, Michele J

2007-05-01

Much of the work in today's service industries requires women to deal with people outside of their organizations, namely, customers and clients, yet research on sexual harassment has focused almost exclusively on sexual harassment within organizations. Because the threat of harassment also operates at the boundaries of organizations, our existing models based solely on harassment inside organizations may be too restricted to adequately explain the harassment experiences of women in today's economy. To address this, the authors introduce a theoretical model of the antecedents and consequences of sexual harassment by clients and customers (CSH) and describe 2 field studies conducted to test components of the model. In Study 1, they developed a model of antecedents and consequences of CSH and illustrated that certain contextual factors (client power and gender composition of the client base) affect levels of CSH and that CSH is related to a number of job and psychological outcomes among professional women. Study 2 revealed that CSH is related to lower job satisfaction among nonprofessional women, above and beyond that which is accounted for by internal sexual harassment. Theoretical and practical implications are discussed. 2007 APA, all rights reserved

Predicting the dynamics of bacterial growth inhibition by ribosome-targeting antibiotics

NASA Astrophysics Data System (ADS)

Greulich, Philip; Doležal, Jakub; Scott, Matthew; Evans, Martin R.; Allen, Rosalind J.

2017-12-01

Understanding how antibiotics inhibit bacteria can help to reduce antibiotic use and hence avoid antimicrobial resistance—yet few theoretical models exist for bacterial growth inhibition by a clinically relevant antibiotic treatment regimen. In particular, in the clinic, antibiotic treatment is time-dependent. Here, we use a theoretical model, previously applied to steady-state bacterial growth, to predict the dynamical response of a bacterial cell to a time-dependent dose of ribosome-targeting antibiotic. Our results depend strongly on whether the antibiotic shows reversible transport and/or low-affinity ribosome binding (‘low-affinity antibiotic’) or, in contrast, irreversible transport and/or high affinity ribosome binding (‘high-affinity antibiotic’). For low-affinity antibiotics, our model predicts that growth inhibition depends on the duration of the antibiotic pulse, and can show a transient period of very fast growth following removal of the antibiotic. For high-affinity antibiotics, growth inhibition depends on peak dosage rather than dose duration, and the model predicts a pronounced post-antibiotic effect, due to hysteresis, in which growth can be suppressed for long times after the antibiotic dose has ended. These predictions are experimentally testable and may be of clinical significance.

Majorization Minimization by Coordinate Descent for Concave Penalized Generalized Linear Models

PubMed Central

Jiang, Dingfeng; Huang, Jian

2013-01-01

Recent studies have demonstrated theoretical attractiveness of a class of concave penalties in variable selection, including the smoothly clipped absolute deviation and minimax concave penalties. The computation of the concave penalized solutions in high-dimensional models, however, is a difficult task. We propose a majorization minimization by coordinate descent (MMCD) algorithm for computing the concave penalized solutions in generalized linear models. In contrast to the existing algorithms that use local quadratic or local linear approximation to the penalty function, the MMCD seeks to majorize the negative log-likelihood by a quadratic loss, but does not use any approximation to the penalty. This strategy makes it possible to avoid the computation of a scaling factor in each update of the solutions, which improves the efficiency of coordinate descent. Under certain regularity conditions, we establish theoretical convergence property of the MMCD. We implement this algorithm for a penalized logistic regression model using the SCAD and MCP penalties. Simulation studies and a data example demonstrate that the MMCD works sufficiently fast for the penalized logistic regression in high-dimensional settings where the number of covariates is much larger than the sample size. PMID:25309048

Food insecurity: A concept analysis

PubMed Central

Schroeder, Krista; Smaldone, Arlene

2015-01-01

Aim To report an analysis of the concept of food insecurity, in order to 1) propose a theoretical model of food insecurity useful to nursing and 2) discuss its implications for nursing practice, nursing research, and health promotion. Background Forty eight million Americans are food insecure. As food insecurity is associated with multiple negative health effects, nursing intervention is warranted. Design Concept Analysis Data sources A literature search was conducted in May 2014 in Scopus and MEDLINE using the exploded term “food insecur*.” No year limit was placed. Government websites and popular media were searched to ensure a full understanding of the concept. Review Methods Iterative analysis, using the Walker and Avant method Results Food insecurity is defined by uncertain ability or inability to procure food, inability to procure enough food, being unable to live a healthy life, and feeling unsatisfied. A proposed theoretical model of food insecurity, adapted from the Socio-Ecological Model, identifies three layers of food insecurity (individual, community, society), with potential for nursing impact at each level. Conclusion Nurses must work to fight food insecurity. There exists a potential for nursing impact that is currently unrealized. Nursing impact can be guided by a new conceptual model, Food Insecurity within the Nursing Paradigm. PMID:25612146

Predicting the dynamics of bacterial growth inhibition by ribosome-targeting antibiotics

PubMed Central

Greulich, Philip; Doležal, Jakub; Scott, Matthew; Evans, Martin R; Allen, Rosalind J

2017-01-01

Understanding how antibiotics inhibit bacteria can help to reduce antibiotic use and hence avoid antimicrobial resistance—yet few theoretical models exist for bacterial growth inhibition by a clinically relevant antibiotic treatment regimen. In particular, in the clinic, antibiotic treatment is time-dependent. Here, we use a theoretical model, previously applied to steady-state bacterial growth, to predict the dynamical response of a bacterial cell to a time-dependent dose of ribosome-targeting antibiotic. Our results depend strongly on whether the antibiotic shows reversible transport and/or low-affinity ribosome binding (‘low-affinity antibiotic’) or, in contrast, irreversible transport and/or high affinity ribosome binding (‘high-affinity antibiotic’). For low-affinity antibiotics, our model predicts that growth inhibition depends on the duration of the antibiotic pulse, and can show a transient period of very fast growth following removal of the antibiotic. For high-affinity antibiotics, growth inhibition depends on peak dosage rather than dose duration, and the model predicts a pronounced post-antibiotic effect, due to hysteresis, in which growth can be suppressed for long times after the antibiotic dose has ended. These predictions are experimentally testable and may be of clinical significance. PMID:28714461

Metabolic pathway analysis and kinetic studies for production of nattokinase in Bacillus subtilis.

PubMed

Unrean, Pornkamol; Nguyen, Nhung H A

2013-01-01

We have constructed a reaction network model of Bacillus subtilis. The model was analyzed using a pathway analysis tool called elementary mode analysis (EMA). The analysis tool was used to study the network capabilities and the possible effects of altered culturing conditions on the production of a fibrinolytic enzyme, nattokinase (NK) by B. subtilis. Based on all existing metabolic pathways, the maximum theoretical yield for NK synthesis in B. subtilis under different substrates and oxygen availability was predicted and the optimal culturing condition for NK production was identified. To confirm model predictions, experiments were conducted by testing these culture conditions for their influence on NK activity. The optimal culturing conditions were then applied to batch fermentation, resulting in high NK activity. The EMA approach was also applied for engineering B. subtilis metabolism towards the most efficient pathway for NK synthesis by identifying target genes for deletion and overexpression that enable the cell to produce NK at the maximum theoretical yield. The consistency between experiments and model predictions proves the feasibility of EMA being used to rationally design culture conditions and genetic manipulations for the efficient production of desired products.

Molecular Theory of Detonation Initiation: Insight from First Principles Modeling of the Decomposition Mechanisms of Organic Nitro Energetic Materials.

PubMed

Tsyshevsky, Roman V; Sharia, Onise; Kuklja, Maija M

2016-02-19

This review presents a concept, which assumes that thermal decomposition processes play a major role in defining the sensitivity of organic energetic materials to detonation initiation. As a science and engineering community we are still far away from having a comprehensive molecular detonation initiation theory in a widely agreed upon form. However, recent advances in experimental and theoretical methods allow for a constructive and rigorous approach to design and test the theory or at least some of its fundamental building blocks. In this review, we analyzed a set of select experimental and theoretical articles, which were augmented by our own first principles modeling and simulations, to reveal new trends in energetic materials and to refine known existing correlations between their structures, properties, and functions. Our consideration is intentionally limited to the processes of thermally stimulated chemical reactions at the earliest stage of decomposition of molecules and materials containing defects.

Ontological addiction theory: Attachment to me, mine, and I.

PubMed

Van Gordon, William; Shonin, Edo; Diouri, Sofiane; Garcia-Campayo, Javier; Kotera, Yasuhiro; Griffiths, Mark D

2018-06-07

Background Ontological addiction theory (OAT) is a novel metaphysical model of psychopathology and posits that human beings are prone to forming implausible beliefs concerning the way they think they exist, and that these beliefs can become addictive leading to functional impairments and mental illness. The theoretical underpinnings of OAT derive from the Buddhist philosophical perspective that all phenomena, including the self, do not manifest inherently or independently. Aims and methods This paper outlines the theoretical foundations of OAT along with indicative supportive empirical evidence from studies evaluating meditation awareness training as well as studies investigating non-attachment, emptiness, compassion, and loving-kindness. Results OAT provides a novel perspective on addiction, the factors that underlie mental illness, and how beliefs concerning selfhood are shaped and reified. Conclusion In addition to continuing to test the underlying assumptions of OAT, future empirical research needs to determine how ontological addiction fits with extant theories of self, reality, and suffering, as well with more established models of addiction.

Molecular Theory of Detonation Initiation: Insight from First Principles Modeling of the Decomposition Mechanisms of Organic Nitro Energetic Materials

DOE PAGES

Tsyshevsky, Roman; Sharia, Onise; Kuklja, Maija

2016-02-19

Our review presents a concept, which assumes that thermal decomposition processes play a major role in defining the sensitivity of organic energetic materials to detonation initiation. As a science and engineering community we are still far away from having a comprehensive molecular detonation initiation theory in a widely agreed upon form. However, recent advances in experimental and theoretical methods allow for a constructive and rigorous approach to design and test the theory or at least some of its fundamental building blocks. In this review, we analyzed a set of select experimental and theoretical articles, which were augmented by our ownmore » first principles modeling and simulations, to reveal new trends in energetic materials and to refine known existing correlations between their structures, properties, and functions. Lastly, our consideration is intentionally limited to the processes of thermally stimulated chemical reactions at the earliest stage of decomposition of molecules and materials containing defects.« less

Developing a Theoretical Framework Using a Nursing Perspective to Investigate Perceived Health in the "Sandwich Generation" Group.

PubMed

Oulevey Bachmann, Annie; Danuser, Brigitta; Morin, Diane

2015-10-01

Coexisting workloads from professional, household and family, and caregiving activities for frail parents expose middle-aged individuals, the so-called "Sandwich Generation", to potential health risks. Current trends suggest that this situation will continue or increase. Thus SG health promotion has become a nursing concern. Most existing research considers coexisting workloads a priori pathogenic. Most studies have examined the association of one, versus two, of these three activities with health. Few studies have used a nursing perspective. This article presents the development of a framework based on a nursing model. We integrated Siegrist's Effort-Reward Imbalance middle-range theory into "Neuman Systems Model". The latter was chosen for its salutogenic orientation, its attention to preventive nursing interventions and the opportunity it provides to simultaneously consider positive and negative perceptions of SG health and SG coexisting workloads. Finally, it facilitated a theoretical identification of health protective factors. © The Author(s) 2015.

A constrained registration problem based on Ciarlet-Geymonat stored energy

NASA Astrophysics Data System (ADS)

Derfoul, Ratiba; Le Guyader, Carole

2014-03-01

In this paper, we address the issue of designing a theoretically well-motivated registration model capable of handling large deformations and including geometrical constraints, namely landmark points to be matched, in a variational framework. The theory of linear elasticity being unsuitable in this case, since assuming small strains and the validity of Hooke's law, the introduced functional is based on nonlinear elasticity principles. More precisely, the shapes to be matched are viewed as Ciarlet-Geymonat materials. We demonstrate the existence of minimizers of the related functional minimization problem and prove a convergence result when the number of geometric constraints increases. We then describe and analyze a numerical method of resolution based on the introduction of an associated decoupled problem under inequality constraint in which an auxiliary variable simulates the Jacobian matrix of the deformation field. A theoretical result of 􀀀-convergence is established. We then provide preliminary 2D results of the proposed matching model for the registration of mouse brain gene expression data to a neuroanatomical mouse atlas.

Resolving Supercritical Orion Cores

NASA Astrophysics Data System (ADS)

Li, Di; Chapman, N.; Goldsmith, P.; Velusamy, T.

2009-01-01

The theoretical framework for high mass star formation (HMSF) is unclear. Observations reveal a seeming dichotomy between high- and low-mass star formation, with HMSF occurring only in Giant Molecular Clouds (GMC), mostly in clusters, and with higher star formation efficiencies than low-mass star formation. One crucial constraint to any theoretical model is the dynamical state of massive cores, in particular, whether a massive core is in supercritical collapse. Based on the mass-size relation of dust emission, we select likely unstable targets from a sample of massive cores (Li et al. 2007 ApJ 655, 351) in the nearest GMC, Orion. We have obtained N2H+ (1-0) maps using CARMA with resolution ( 2.5", 0.006 pc) significantly better than existing observations. We present observational and modeling results for ORI22. By revealing the dynamic structure down to Jeans scale, CARMA data confirms the dominance of gravity over turbulence in this cores. This work was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Distance measurement based on light field geometry and ray tracing.

PubMed

Chen, Yanqin; Jin, Xin; Dai, Qionghai

2017-01-09

In this paper, we propose a geometric optical model to measure the distances of object planes in a light field image. The proposed geometric optical model is composed of two sub-models based on ray tracing: object space model and image space model. The two theoretic sub-models are derived on account of on-axis point light sources. In object space model, light rays propagate into the main lens and refract inside it following the refraction theorem. In image space model, light rays exit from emission positions on the main lens and subsequently impinge on the image sensor with different imaging diameters. The relationships between imaging diameters of objects and their corresponding emission positions on the main lens are investigated through utilizing refocusing and similar triangle principle. By combining the two sub-models together and tracing light rays back to the object space, the relationships between objects' imaging diameters and corresponding distances of object planes are figured out. The performance of the proposed geometric optical model is compared with existing approaches using different configurations of hand-held plenoptic 1.0 cameras and real experiments are conducted using a preliminary imaging system. Results demonstrate that the proposed model can outperform existing approaches in terms of accuracy and exhibits good performance at general imaging range.

Temperature Induced Syllable Breaking Unveils Nonlinearly Interacting Timescales in Birdsong Motor Pathway

PubMed Central

Goldin, Matías A.; Alonso, Leandro M.; Alliende, Jorge A.; Goller, Franz; Mindlin, Gabriel B.

2013-01-01

The nature of telencephalic control over premotor and motor circuits is debated. Hypotheses range from complete usurping of downstream circuitry to highly interactive mechanisms of control. We show theoretically and experimentally, that telencephalic song motor control in canaries is consistent with a highly interactive strategy. As predicted from a theoretical model of respiratory control, mild cooling of a forebrain nucleus (HVC) led to song stretching, but further cooling caused progressive restructuring of song, consistent with the hypothesis that respiratory gestures are subharmonic responses to a timescale present in the output of HVC. This interaction between a life-sustaining motor function (respiration) and telencephalic song motor control suggests a more general mechanism of how nonlinear integration of evolutionarily new brain structures into existing circuitry gives rise to diverse, new behavior. PMID:23818988

Virtual-pulse time integral methodology: A new explicit approach for computational dynamics - Theoretical developments for general nonlinear structural dynamics

NASA Technical Reports Server (NTRS)

Chen, Xiaoqin; Tamma, Kumar K.; Sha, Desong

1993-01-01

The present paper describes a new explicit virtual-pulse time integral methodology for nonlinear structural dynamics problems. The purpose of the paper is to provide the theoretical basis of the methodology and to demonstrate applicability of the proposed formulations to nonlinear dynamic structures. Different from the existing numerical methods such as direct time integrations or mode superposition techniques, the proposed methodology offers new perspectives and methodology of development, and possesses several unique and attractive computational characteristics. The methodology is tested and compared with the implicit Newmark method (trapezoidal rule) through a nonlinear softening and hardening spring dynamic models. The numerical results indicate that the proposed explicit virtual-pulse time integral methodology is an excellent alternative for solving general nonlinear dynamic problems.

Dark matter candidates

NASA Technical Reports Server (NTRS)

Turner, Michael S.

1989-01-01

The types of particles which may provide the nonluminous mass required by big-bang cosmological models are listed and briefly characterized. The observational evidence for the existence of dark matter (outweighing the luminous component by at least a factor of 10) is reviewed; the theoretical arguments favoring mainly nonbaryonic dark matter are summarized; and particular attention is given to weakly interacting massive particles (WIMPs) remaining as relics from the early universe. The WIMPs are classified as thermal relics (heavy stable neutrinos and lighter neutralinos), asymmetric relics (including baryons), nonthermal relics (superheavy magnetic monopoles, axions, and soliton stars), and truly exotic relics (relativistic debris or vacuum energy). Explanations for the current apparent baryon/exotica ratio of about 0.1 in different theoretical scenarios are considered, and the problems of experimental and/or observational dark-matter detection are examined.

Temperature induced syllable breaking unveils nonlinearly interacting timescales in birdsong motor pathway.

PubMed

Goldin, Matías A; Alonso, Leandro M; Alliende, Jorge A; Goller, Franz; Mindlin, Gabriel B

2013-01-01

The nature of telencephalic control over premotor and motor circuits is debated. Hypotheses range from complete usurping of downstream circuitry to highly interactive mechanisms of control. We show theoretically and experimentally, that telencephalic song motor control in canaries is consistent with a highly interactive strategy. As predicted from a theoretical model of respiratory control, mild cooling of a forebrain nucleus (HVC) led to song stretching, but further cooling caused progressive restructuring of song, consistent with the hypothesis that respiratory gestures are subharmonic responses to a timescale present in the output of HVC. This interaction between a life-sustaining motor function (respiration) and telencephalic song motor control suggests a more general mechanism of how nonlinear integration of evolutionarily new brain structures into existing circuitry gives rise to diverse, new behavior.

Anomalous hydrodynamics kicks neutron stars

DOE PAGES

Kaminski, Matthias; Uhlemann, Christoph F.; Bleicher, Marcus; ...

2016-06-28

Observations show that, at the beginning of their existence, neutron stars are accelerated briskly to velocities of up to a thousand kilometers per second. We argue that this remarkable effect can be explained as a manifestation of quantum anomalies on astrophysical scales. To theoretically describe the early stage in the life of neutron stars we use hydrodynamics as a systematic effective-field-theory framework. Within this framework, anomalies of the Standard Model of particle physics as underlying microscopic theory imply the presence of a particular set of transport terms, whose form is completely fixed by theoretical consistency. Here, the resulting chiral transportmore » effects in proto-neutron stars enhance neutrino emission along the internal magnetic field, and the recoil can explain the order of magnitude of the observed kick velocities.« less

Game Theoretic Modeling of Water Resources Allocation Under Hydro-Climatic Uncertainty

NASA Astrophysics Data System (ADS)

Brown, C.; Lall, U.; Siegfried, T.

2005-12-01

Typical hydrologic and economic modeling approaches rely on assumptions of climate stationarity and economic conditions of ideal markets and rational decision-makers. In this study, we incorporate hydroclimatic variability with a game theoretic approach to simulate and evaluate common water allocation paradigms. Game Theory may be particularly appropriate for modeling water allocation decisions. First, a game theoretic approach allows economic analysis in situations where price theory doesn't apply, which is typically the case in water resources where markets are thin, players are few, and rules of exchange are highly constrained by legal or cultural traditions. Previous studies confirm that game theory is applicable to water resources decision problems, yet applications and modeling based on these principles is only rarely observed in the literature. Second, there are numerous existing theoretical and empirical studies of specific games and human behavior that may be applied in the development of predictive water allocation models. With this framework, one can evaluate alternative orderings and rules regarding the fraction of available water that one is allowed to appropriate. Specific attributes of the players involved in water resources management complicate the determination of solutions to game theory models. While an analytical approach will be useful for providing general insights, the variety of preference structures of individual players in a realistic water scenario will likely require a simulation approach. We propose a simulation approach incorporating the rationality, self-interest and equilibrium concepts of game theory with an agent-based modeling framework that allows the distinct properties of each player to be expressed and allows the performance of the system to manifest the integrative effect of these factors. Underlying this framework, we apply a realistic representation of spatio-temporal hydrologic variability and incorporate the impact of decision-making a priori to hydrologic realizations and those made a posteriori on alternative allocation mechanisms. Outcomes are evaluated in terms of water productivity, net social benefit and equity. The performance of hydro-climate prediction modeling in each allocation mechanism will be assessed. Finally, year-to-year system performance and feedback pathways are explored. In this way, the system can be adaptively managed toward equitable and efficient water use.

Modelling energy production by small hydro power plants in collective irrigation networks of Calabria (Southern Italy)

NASA Astrophysics Data System (ADS)

Zema, Demetrio Antonio; Nicotra, Angelo; Tamburino, Vincenzo; Marcello Zimbone, Santo

2017-04-01

The availability of geodetic heads and considerable water flows in collective irrigation networks suggests the possibility of recovery potential energy using small hydro power plants (SHPP) at sustainable costs. This is the case of many Water Users Associations (WUA) in Calabria (Southern Italy), where it could theoretically be possible to recovery electrical energy out of the irrigation season. However, very few Calabrian WUAs have currently built SHPP in their irrigation networks and thus in this region the potential energy is practically fully lost. A previous study (Zema et al., 2016) proposed an original and simple model to site turbines and size their power output as well as to evaluate profits of SHPP in collective irrigation networks. Applying this model at regional scale, this paper estimates the theoretical energy production and the economic performances of SHPP installed in collective irrigation networks of Calabrian WUAs. In more detail, based on digital terrain models processed by GIS and few parameters of the water networks, for each SHPP the model provides: (i) the electrical power output; (iii) the optimal water discharge; (ii) costs, revenues and profits. Moreover, the map of the theoretical energy production by SHPP in collective irrigation networks of Calabria was drawn. The total network length of the 103 water networks surveyed is equal to 414 km and the total geodetic head is 3157 m, of which 63% is lost due to hydraulic losses. Thus, a total power output of 19.4 MW could theoretically be installed. This would provide an annual energy production of 103 GWh, considering SHPPs in operation only out of the irrigation season. The single irrigation networks have a power output in the range 0.7 kW - 6.4 MW. However, the lowest SHPPs (that is, turbines with power output under 5 kW) have been neglected, because the annual profit is very low (on average less than 6%, Zema et al., 2016). On average each irrigation network provides an annual revenue from electrical energy sale of about 103000 €. Even though this revenue may appear quite low, it represents an important share of the annual WUA income. For the entire region, the total revenues from recovery energy in collective irrigation networks through SHPPs have been estimated in about 12 million Euros; investment and operating costs have been evaluated by parametric equations and the total profit theoretically available for each WUA has been quantified. This study has shown the economic opportunity of integrating SHPP in existing collecting irrigation networks of WUAs, in view of providing additional economic resources for users and enhancing the exploitation of a renewable energy source. REFERENCE Zema D.A., Nicotra A., Tamburino V., Zimbone S.M. 2016. A simple method to evaluate the technical and economic feasibility of micro hydro power plants in existing irrigation systems. Renewable Energy 85, 498-506. DOI: 10.1016/j.renene.2015.06.066.

Scale-dependent feedbacks between patch size and plant reproduction in desert grassland

USGS Publications Warehouse

Svejcar, Lauren N.; Bestelmeyer, Brandon T.; Duniway, Michael C.; James, Darren K.

2015-01-01

Theoretical models suggest that scale-dependent feedbacks between plant reproductive success and plant patch size govern transitions from highly to sparsely vegetated states in drylands, yet there is scant empirical evidence for these mechanisms. Scale-dependent feedback models suggest that an optimal patch size exists for growth and reproduction of plants and that a threshold patch organization exists below which positive feedbacks between vegetation and resources can break down, leading to critical transitions. We examined the relationship between patch size and plant reproduction using an experiment in a Chihuahuan Desert grassland. We tested the hypothesis that reproductive effort and success of a dominant grass (Bouteloua eriopoda) would vary predictably with patch size. We found that focal plants in medium-sized patches featured higher rates of grass reproductive success than when plants occupied either large patch interiors or small patches. These patterns support the existence of scale-dependent feedbacks in Chihuahuan Desert grasslands and indicate an optimal patch size for reproductive effort and success in B. eriopoda. We discuss the implications of these results for detecting ecological thresholds in desert grasslands.

Theory on the Coupled Stochastic Dynamics of Transcription and Splice-Site Recognition

PubMed Central

Murugan, Rajamanickam; Kreiman, Gabriel

2012-01-01

Eukaryotic genes are typically split into exons that need to be spliced together to form the mature mRNA. The splicing process depends on the dynamics and interactions among transcription by the RNA polymerase II complex (RNAPII) and the spliceosomal complex consisting of multiple small nuclear ribonucleo proteins (snRNPs). Here we propose a biophysically plausible initial theory of splicing that aims to explain the effects of the stochastic dynamics of snRNPs on the splicing patterns of eukaryotic genes. We consider two different ways to model the dynamics of snRNPs: pure three-dimensional diffusion and a combination of three- and one-dimensional diffusion along the emerging pre-mRNA. Our theoretical analysis shows that there exists an optimum position of the splice sites on the growing pre-mRNA at which the time required for snRNPs to find the 5′ donor site is minimized. The minimization of the overall search time is achieved mainly via the increase in non-specific interactions between the snRNPs and the growing pre-mRNA. The theory further predicts that there exists an optimum transcript length that maximizes the probabilities for exons to interact with the snRNPs. We evaluate these theoretical predictions by considering human and mouse exon microarray data as well as RNAseq data from multiple different tissues. We observe that there is a broad optimum position of splice sites on the growing pre-mRNA and an optimum transcript length, which are roughly consistent with the theoretical predictions. The theoretical and experimental analyses suggest that there is a strong interaction between the dynamics of RNAPII and the stochastic nature of snRNP search for 5′ donor splicing sites. PMID:23133354

Epidemic spreading in time-varying community networks.

PubMed

Ren, Guangming; Wang, Xingyuan

2014-06-01

The spreading processes of many infectious diseases have comparable time scale as the network evolution. Here, we present a simple networks model with time-varying community structure, and investigate susceptible-infected-susceptible epidemic spreading processes in this model. By both theoretic analysis and numerical simulations, we show that the efficiency of epidemic spreading in this model depends intensively on the mobility rate q of the individuals among communities. We also find that there exists a mobility rate threshold qc. The epidemic will survive when q > qc and die when q < qc. These results can help understanding the impacts of human travel on the epidemic spreading in complex networks with community structure.

The effect of a turbulent wake on the stagnation point. II - Heat transfer results

NASA Technical Reports Server (NTRS)

Hanford, Anthony J.; Wilson, Dennis E.

1992-01-01

A phenomenological model is proposed which relates the effects of freestream turbulence to the increase in stagnation point heat transfer. The model requires both turbulence intensity and energy spectra as inputs to the unsteady velocity at the edge of the boundary layer. The form of the edge velocity contains both a pulsation of the incoming flow and an oscillation of the streamlines. The incompressible unsteady and time-averaged boundary layer response is determined by solving the momentum and energy equations. The model allows for arbitary two-dimensional geometry, however, results are given only for a circular cylinder. The time-averaged Nusselt number is determined theoretically and compared to existing experimental data.

Exact Schwarzschild-like solution in a bumblebee gravity model

NASA Astrophysics Data System (ADS)

Casana, R.; Cavalcante, A.; Poulis, F. P.; Santos, E. B.

2018-05-01

We obtain an exact vacuum solution from the gravity sector contained in the minimal standard-model extension. The theoretical model assumes a Riemann spacetime coupled to the bumblebee field which is responsible for the spontaneous Lorentz symmetry breaking. The solution achieved in a static and spherically symmetric scenario establishes a Schwarzschild-like black hole. In order to study the effects of the spontaneous Lorentz symmetry breaking we investigate some classic tests, including the advance of perihelion, the bending of light, and Shapiro's time delay. Furthermore, we compute some upper bounds, among which the most stringent associated with existing experimental data provides a sensitivity at the 10-15 level and that for future missions at the 10-19 level.

Characterizing Perceptual Performance at Multiple Discrimination Precisions in External Noise

PubMed Central

Jeon, Seong-Taek; Lu, Zhong-Lin; Dosher, Barbara Anne

2010-01-01

Existing observer models developed for studies with the external noise paradigm are strictly only applicable to target detection or identification/discrimination of orthogonal target(s). We elaborated the perceptual template model (PTM) to account for contrast thresholds in identifying non-orthogonal targets. Full contrast psychometric functions were measured in an orientation identification task with four orientation differences across a wide range of external noise levels. We showed that observer performance can be modeled by the elaborated PTM with two templates that correspond to the two stimulus categories. Sampling efficiencies of the human observers were also estimated. The elaborated PTM provides a theoretical framework to characterize joint feature and contrast sensitivity of human observers. PMID:19884915

CP-violation phases and Majorana neutrino magnetic moments in left-right models

NASA Astrophysics Data System (ADS)

Delepine, D.; Novales-Sánchez, H.

2016-10-01

An implication of nonzero neutrino masses is the existence of neutrino magnetic moments, which arise in extensions of the Standard Model. Among the whole set of electromagnetic properties, these physical quantities have received much attention, both theoretically and experimentally. In the present paper we review the contributions to neutrino magnetic moments from new physics described by a leff-right model, with Majorana neutrinos, which might be as large as 10-11μB. These electromagnetic moments depend on Majorana phases. It turns out that, in presence of CP violation, specific sets of values of these phases can cancel up to two magnetic moments, while the remaining one must necessarily be nonzero and large.

Model Checking with Edge-Valued Decision Diagrams

NASA Technical Reports Server (NTRS)

Roux, Pierre; Siminiceanu, Radu I.

2010-01-01

We describe an algebra of Edge-Valued Decision Diagrams (EVMDDs) to encode arithmetic functions and its implementation in a model checking library. We provide efficient algorithms for manipulating EVMDDs and review the theoretical time complexity of these algorithms for all basic arithmetic and relational operators. We also demonstrate that the time complexity of the generic recursive algorithm for applying a binary operator on EVMDDs is no worse than that of Multi- Terminal Decision Diagrams. We have implemented a new symbolic model checker with the intention to represent in one formalism the best techniques available at the moment across a spectrum of existing tools. Compared to the CUDD package, our tool is several orders of magnitude faster

A practitioner's guide to persuasion: an overview of 15 selected persuasion theories, models and frameworks.

PubMed

Cameron, Kenzie A

2009-03-01

To provide a brief overview of 15 selected persuasion theories and models, and to present examples of their use in health communication research. The theories are categorized as message effects models, attitude-behavior approaches, cognitive processing theories and models, consistency theories, inoculation theory, and functional approaches. As it is often the intent of a practitioner to shape, reinforce, or change a patient's behavior, familiarity with theories of persuasion may lead to the development of novel communication approaches with existing patients. This article serves as an introductory primer to theories of persuasion with applications to health communication research. Understanding key constructs and general formulations of persuasive theories may allow practitioners to employ useful theoretical frameworks when interacting with patients.

Analysis of longwave radiation for the Earth-atmosphere system

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Venuru, C. S.; Subramanian, S. V.

1983-01-01

Accurate radiative transfer models are used to determine the upwelling atmospheric radiance and net radiative flux in the entire longwave spectral range. The validity of the quasi-random band model is established by comparing the results of this model with those of line-by-line formulations and with available theoretical and experimental results. Existing radiative transfer models and computer codes are modified to include various surface and atmospheric effects (surface reflection, nonequilibrium radiation, and cloud effects). The program is used to evaluate the radiative flux in clear atmosphere, provide sensitivity analysis of upwelling radiance in the presence of clouds, and determine the effects of various climatological parameters on the upwelling radiation and anisotropic function. Homogeneous and nonhomogeneous gas emissivities can also be evaluated under different conditions.

The SHiP experiment at CERN

NASA Astrophysics Data System (ADS)

De Lellis, G.; SHiP Collaboration

2017-04-01

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry of the Universe, which deserve an explanation that could come from the discovery of new particles. Searches for new physics with accelerators are performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. A new experiment at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. Indeed, tau anti-neutrinos have not been directly observed so far. We report the physics potential of such an experiment.

The SHiP experiment at CERN

NASA Astrophysics Data System (ADS)

Bonivento, Walter M.

2017-07-01

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry of the Universe, deserving an explanation that could come from the discovery of new particles. Searches for new physics with accelerators are performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. A new experiment at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. The neutrino detector can also search for dark matter through its scattering off the electrons. We report the physics potential of the SHiP experiment.

What do we mean by sensitivity analysis? The need for comprehensive characterization of "global" sensitivity in Earth and Environmental systems models

NASA Astrophysics Data System (ADS)

Razavi, Saman; Gupta, Hoshin V.

2015-05-01

Sensitivity analysis is an essential paradigm in Earth and Environmental Systems modeling. However, the term "sensitivity" has a clear definition, based in partial derivatives, only when specified locally around a particular point (e.g., optimal solution) in the problem space. Accordingly, no unique definition exists for "global sensitivity" across the problem space, when considering one or more model responses to different factors such as model parameters or forcings. A variety of approaches have been proposed for global sensitivity analysis, based on different philosophies and theories, and each of these formally characterizes a different "intuitive" understanding of sensitivity. These approaches focus on different properties of the model response at a fundamental level and may therefore lead to different (even conflicting) conclusions about the underlying sensitivities. Here we revisit the theoretical basis for sensitivity analysis, summarize and critically evaluate existing approaches in the literature, and demonstrate their flaws and shortcomings through conceptual examples. We also demonstrate the difficulty involved in interpreting "global" interaction effects, which may undermine the value of existing interpretive approaches. With this background, we identify several important properties of response surfaces that are associated with the understanding and interpretation of sensitivities in the context of Earth and Environmental System models. Finally, we highlight the need for a new, comprehensive framework for sensitivity analysis that effectively characterizes all of the important sensitivity-related properties of model response surfaces.

Measuring implementation behaviour of menu guidelines in the childcare setting: confirmatory factor analysis of a theoretical domains framework questionnaire (TDFQ).

PubMed

Seward, Kirsty; Wolfenden, Luke; Wiggers, John; Finch, Meghan; Wyse, Rebecca; Oldmeadow, Christopher; Presseau, Justin; Clinton-McHarg, Tara; Yoong, Sze Lin

2017-04-04

While there are number of frameworks which focus on supporting the implementation of evidence based approaches, few psychometrically valid measures exist to assess constructs within these frameworks. This study aimed to develop and psychometrically assess a scale measuring each domain of the Theoretical Domains Framework for use in assessing the implementation of dietary guidelines within a non-health care setting (childcare services). A 75 item 14-domain Theoretical Domains Framework Questionnaire (TDFQ) was developed and administered via telephone interview to 202 centre based childcare service cooks who had a role in planning the service menu. Confirmatory factor analysis (CFA) was undertaken to assess the reliability, discriminant validity and goodness of fit of the 14-domain theoretical domain framework measure. For the CFA, five iterative processes of adjustment were undertaken where 14 items were removed, resulting in a final measure consisting of 14 domains and 61 items. For the final measure: the Chi-Square goodness of fit statistic was 3447.19; the Standardized Root Mean Square Residual (SRMR) was 0.070; the Root Mean Square Error of Approximation (RMSEA) was 0.072; and the Comparative Fit Index (CFI) had a value of 0.78. While only one of the three indices support goodness of fit of the measurement model tested, a 14-domain model with 61 items showed good discriminant validity and internally consistent items. Future research should aim to assess the psychometric properties of the developed TDFQ in other community-based settings.

A computational model of self-efficacy's various effects on performance: Moving the debate forward.

PubMed

Vancouver, Jeffrey B; Purl, Justin D

2017-04-01

Self-efficacy, which is one's belief in one's capacity, has been found to both positively and negatively influence effort and performance. The reasons for these different effects have been a major topic of debate among social-cognitive and perceptual control theorists. In particular, the findings of various self-efficacy effects has been motivated by a perceptual control theory view of self-regulation that social-cognitive theorists' question. To provide more clarity to the theoretical arguments, a computational model of the multiple processes presumed to create the positive, negative, and null effects for self-efficacy is presented. Building on an existing computational model of goal choice that produces a positive effect for self-efficacy, the current article adds a symbolic processing structure used during goal striving that explains the negative self-efficacy effect observed in recent studies. Moreover, the multiple processes, operating together, allow the model to recreate the various effects found in a published study of feedback ambiguity's moderating role on the self-efficacy to performance relationship (Schmidt & DeShon, 2010). Discussion focuses on the implications of the model for the self-efficacy debate, alternative computational models, the overlap between control theory and social-cognitive theory explanations, the value of using computational models for resolving theoretical disputes, and future research and directions the model inspires. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

A Theoretical Math Model for Projecting AIS3+ Thoracic Injury for Belted Occupants in Frontal Impact.

PubMed

Laituri, Tony R; Sullivan, Donald; Sullivan, Kaye; Prasad, Priya

2004-11-01

A theoretical math model was created to assess the net effect of aging populations versus evolving system designs from the standpoint of thoracic injury potential. The model was used to project the next twenty-five years of thoracic injuries in Canada. The choice of Canada was topical because rulemaking for CMVSS 208 has been proposed recently. The study was limited to properly-belted, front-outboard, adult occupants in 11-1 o'clock frontal crashes. Moreover, only AIS3+ thoracic injury potential was considered. The research consisted of four steps. First, sub-models were developed and integrated. The sub-models were made for numerous real-world effects including population growth, crash involvement, fleet penetration of various systems (via system introduction, vehicle production, and vehicle attrition), and attendant injury risk estimation. Second, existing NASS data were used to estimate the number of AIS3+ chest-injured drivers in Canada in 2001. This served as data for model validation. Third, the projection model was correlated favorably with the 2001 field estimate. Finally, for the scenario that 2004-2030 model-year systems would perform like 2000-2003 model-year systems, a projection was made to estimate the long-term effect of eliminating designs that would not comply with the proposed CMVSS 208. The 2006-2030-projection result for this scenario: 764 occupants would benefit from the proposed regulation. This projection was considered to be conservative because future innovation was not considered, and, to date, the fleet's average chest deflections have been decreasing. The model also predicted that, through 2016, the effect of improving system performance would be more influential than the population-aging effect; thereafter, the population-aging effect would somewhat counteract the effect of improving system performance. This theoretical math model can provide insights for both designers and rule makers.

Constraint on slepton intergenerational mixing from big-bang nucleosynthesis

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

Kohri, Kazunori; Ohta, Shingo; Sato, Joe

We find constraint on intergenerational mixing of slepton from big-bang nucleosynthesis (BBN). Today, we know that there exist lepton flavor violation (LFV) from the observation of neutrino oscillation, though there do not exist LFV in the standard model of particle physics (SM). LFV in charged lepton sector (cLFV) have also been expected to exist. From theoretical point of view, the effects of long-lived stau on BBN have been investigated and it is known that the stau can solve the cosmological 7Li problem. However, in the study so far, tau flavor is exactly conserved and it contradict with the existence ofmore » cLFV. In this study, we generalize the flavor to be violated and call the stau as slepton. Even if the violation is tiny, it drastically changes the lifetime and the evolution of relic density of the slepton. Thus we analyze the effects of the long-lived slepton on BBN, and constrain the magnitude of the cLFV.« less

The application of epidemiology in aquatic animal health -opportunities and challenges.

PubMed

Peeler, Edmund J; Taylor, Nicholas G H

2011-08-11

Over recent years the growth in aquaculture, accompanied by the emergence of new and transboundary diseases, has stimulated epidemiological studies of aquatic animal diseases. Great potential exists for both observational and theoretical approaches to investigate the processes driving emergence but, to date, compared to terrestrial systems, relatively few studies exist in aquatic animals. Research using risk methods has assessed routes of introduction of aquatic animal pathogens to facilitate safe trade (e.g. import risk analyses) and support biosecurity. Epidemiological studies of risk factors for disease in aquaculture (most notably Atlantic salmon farming) have effectively supported control measures. Methods developed for terrestrial livestock diseases (e.g. risk-based surveillance) could improve the capacity of aquatic animal surveillance systems to detect disease incursions and emergence. The study of disease in wild populations presents many challenges and the judicious use of theoretical models offers some solutions. Models, parameterised from observational studies of host pathogen interactions, have been used to extrapolate estimates of impacts on the individual to the population level. These have proved effective in estimating the likely impact of parasite infections on wild salmonid populations in Switzerland and Canada (where the importance of farmed salmon as a reservoir of infection was investigated). A lack of data is often the key constraint in the application of new approaches to surveillance and modelling. The need for epidemiological approaches to protect aquatic animal health will inevitably increase in the face of the combined challenges of climate change, increasing anthropogenic pressures, limited water sources and the growth in aquaculture.

Economic Incentives for Cybersecurity: Using Economics to Design Technologies Ready for Deployment

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

Vishik, Claire; Sheldon, Frederick T; Ott, David

Cybersecurity practice lags behind cyber technology achievements. Solutions designed to address many problems may and do exist but frequently cannot be broadly deployed due to economic constraints. Whereas security economics focuses on the cost/benefit analysis and supply/demand, we believe that more sophisticated theoretical approaches, such as economic modeling, rarely utilized, would derive greater societal benefits. Unfortunately, today technologists pursuing interesting and elegant solutions have little knowledge of the feasibility for broad deployment of their results and cannot anticipate the influences of other technologies, existing infrastructure, and technology evolution, nor bring the solutions lifecycle into the equation. Additionally, potentially viable solutionsmore » are not adopted because the risk perceptions by potential providers and users far outweighs the economic incentives to support introduction/adoption of new best practices and technologies that are not well enough defined. In some cases, there is no alignment with redominant and future business models as well as regulatory and policy requirements. This paper provides an overview of the economics of security, reviewing work that helped to define economic models for the Internet economy from the 1990s. We bring forward examples of potential use of theoretical economics in defining metrics for emerging technology areas, positioning infrastructure investment, and building real-time response capability as part of software development. These diverse examples help us understand the gaps in current research. Filling these gaps will be instrumental for defining viable economic incentives, economic policies, regulations as well as early-stage technology development approaches, that can speed up commercialization and deployment of new technologies in cybersecurity.« less

Factors Influencing the Use of Learning Management System in Saudi Arabian Higher Education: A Theoretical Framework

ERIC Educational Resources Information Center

Asiri, Mohammed J. Sherbib; Mahmud, Rosnaini bt; Bakar, Kamariah Abu; Ayub, Ahmad Fauzi bin Mohd

2012-01-01

The purpose of this paper is to present the theoretical framework underlying a research on factors that influence utilization of the Jusur Learning Management System (Jusur LMS) in Saudi Arabian public universities. Development of the theoretical framework was done based on library research approach. Initially, the existing literature relevant to…

Experimental and Theoretical Investigations of Phonation Threshold Pressure as a Function of Vocal Fold Elongation

PubMed Central

Tao, Chao; Regner, Michael F.; Zhang, Yu; Jiang, Jack J.

2014-01-01

Summary The relationship between the vocal fold elongation and the phonation threshold pressure (PTP) was experimentally and theoretically investigated. The PTP values of seventeen excised canine larynges with 0% to 15% bilateral vocal fold elongations in 5% elongation steps were measured using an excised larynx phonation system. It was found that twelve larynges exhibited a monotonic relationship between PTP and elongation; in these larynges, the 0% elongation condition had the lowest PTP. Five larynges exhibited a PTP minimum at 5% elongation. To provide a theoretical explanation of these phenomena, a two-mass model was modified to simulate vibration of the elongated vocal folds. Two pairs of longitudinal springs were used to represent the longitudinal elastin in the vocal folds. This model showed that when the vocal folds were elongated, the increased longitudinal tension would increase the PTP value and the increased vocal fold length would decrease the PTP value. The antagonistic effects contributed by these two factors were found to be able to cause either a monotonic or a non-monotonic relationship between PTP and elongation, which were consistent with experimental observations. Because PTP describes the ease of phonation, this study suggests that there may exist a nonzero optimal vocal fold elongation for the greatest ease for phonation in some larynges. PMID:25530744

Understanding of flux-limited behaviors of heat transport in nonlinear regime

NASA Astrophysics Data System (ADS)

Guo, Yangyu; Jou, David; Wang, Moran

2016-01-01

The classical Fourier's law of heat transport breaks down in highly nonequilibrium situations as in nanoscale heat transport, where nonlinear effects become important. The present work is aimed at exploring the flux-limited behaviors based on a categorization of existing nonlinear heat transport models in terms of their theoretical foundations. Different saturation heat fluxes are obtained, whereas the same qualitative variation trend of heat flux versus exerted temperature gradient is got in diverse nonlinear models. The phonon hydrodynamic model is proposed to act as a standard to evaluate other heat flux limiters because of its more rigorous physical foundation. A deeper knowledge is thus achieved about the phenomenological generalized heat transport models. The present work provides deeper understanding and accurate modeling of nonlocal and nonlinear heat transport beyond the diffusive limit.

Numerical study of low-frequency discharge oscillations in a 5 kW Hall thruster

NASA Astrophysics Data System (ADS)

Le, YANG; Tianping, ZHANG; Juanjuan, CHEN; Yanhui, JIA

2018-07-01

A two-dimensional particle-in-cell plasma model is built in the R–Z plane to investigate the low-frequency plasma oscillations in the discharge channel of a 5 kW LHT-140 Hall thruster. In addition to the elastic, excitation, and ionization collisions between neutral atoms and electrons, the Coulomb collisions between electrons and electrons and between electrons and ions are analyzed. The sheath characteristic distortion is also corrected. Simulation results indicate the capability of the built model to reproduce the low-frequency oscillation with high accuracy. The oscillations of the discharge current and ion density produced by the model are consistent with the existing conclusions. The model predicts a frequency that is consistent with that calculated by the zero-dimensional theoretical model.

Inferring Markov chains: Bayesian estimation, model comparison, entropy rate, and out-of-class modeling.

PubMed

Strelioff, Christopher C; Crutchfield, James P; Hübler, Alfred W

2007-07-01

Markov chains are a natural and well understood tool for describing one-dimensional patterns in time or space. We show how to infer kth order Markov chains, for arbitrary k , from finite data by applying Bayesian methods to both parameter estimation and model-order selection. Extending existing results for multinomial models of discrete data, we connect inference to statistical mechanics through information-theoretic (type theory) techniques. We establish a direct relationship between Bayesian evidence and the partition function which allows for straightforward calculation of the expectation and variance of the conditional relative entropy and the source entropy rate. Finally, we introduce a method that uses finite data-size scaling with model-order comparison to infer the structure of out-of-class processes.

Shape modeling with family of Pearson distributions: Langmuir waves

NASA Astrophysics Data System (ADS)

Vidojevic, Sonja

2014-10-01

Two major effects of Langmuir wave electric field influence on spectral line shapes are appearance of depressions shifted from unperturbed line and an additional dynamical line broadening. More realistic and accurate models of Langmuir waves are needed to study these effects with more confidence. In this article we present distribution shapes of a high-quality data set of Langmuir waves electric field observed by the WIND satellite. Using well developed numerical techniques, the distributions of the empirical measurements are modeled by family of Pearson distributions. The results suggest that the existing theoretical models of energy conversion between an electron beam and surrounding plasma is more complex. If the processes of the Langmuir wave generation are better understood, the influence of Langmuir waves on spectral line shapes could be modeled better.

Quantum lattice model solver HΦ

NASA Astrophysics Data System (ADS)

Kawamura, Mitsuaki; Yoshimi, Kazuyoshi; Misawa, Takahiro; Yamaji, Youhei; Todo, Synge; Kawashima, Naoki

2017-08-01

HΦ [aitch-phi ] is a program package based on the Lanczos-type eigenvalue solution applicable to a broad range of quantum lattice models, i.e., arbitrary quantum lattice models with two-body interactions, including the Heisenberg model, the Kitaev model, the Hubbard model and the Kondo-lattice model. While it works well on PCs and PC-clusters, HΦ also runs efficiently on massively parallel computers, which considerably extends the tractable range of the system size. In addition, unlike most existing packages, HΦ supports finite-temperature calculations through the method of thermal pure quantum (TPQ) states. In this paper, we explain theoretical background and user-interface of HΦ. We also show the benchmark results of HΦ on supercomputers such as the K computer at RIKEN Advanced Institute for Computational Science (AICS) and SGI ICE XA (Sekirei) at the Institute for the Solid State Physics (ISSP).

Development of a Solid-Oxide Fuel Cell/Gas Turbine Hybrid System Model for Aerospace Applications

NASA Technical Reports Server (NTRS)

Freeh, Joshua E.; Pratt, Joseph W.; Brouwer, Jacob

2004-01-01

Recent interest in fuel cell-gas turbine hybrid applications for the aerospace industry has led to the need for accurate computer simulation models to aid in system design and performance evaluation. To meet this requirement, solid oxide fuel cell (SOFC) and fuel processor models have been developed and incorporated into the Numerical Propulsion Systems Simulation (NPSS) software package. The SOFC and reformer models solve systems of equations governing steady-state performance using common theoretical and semi-empirical terms. An example hybrid configuration is presented that demonstrates the new capability as well as the interaction with pre-existing gas turbine and heat exchanger models. Finally, a comparison of calculated SOFC performance with experimental data is presented to demonstrate model validity. Keywords: Solid Oxide Fuel Cell, Reformer, System Model, Aerospace, Hybrid System, NPSS

Query Language for Location-Based Services: A Model Checking Approach

NASA Astrophysics Data System (ADS)

Hoareau, Christian; Satoh, Ichiro

We present a model checking approach to the rationale, implementation, and applications of a query language for location-based services. Such query mechanisms are necessary so that users, objects, and/or services can effectively benefit from the location-awareness of their surrounding environment. The underlying data model is founded on a symbolic model of space organized in a tree structure. Once extended to a semantic model for modal logic, we regard location query processing as a model checking problem, and thus define location queries as hybrid logicbased formulas. Our approach is unique to existing research because it explores the connection between location models and query processing in ubiquitous computing systems, relies on a sound theoretical basis, and provides modal logic-based query mechanisms for expressive searches over a decentralized data structure. A prototype implementation is also presented and will be discussed.

Predicting chaos in memristive oscillator via harmonic balance method.

PubMed

Wang, Xin; Li, Chuandong; Huang, Tingwen; Duan, Shukai

2012-12-01

This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.

Measuring the concentration of ozone produced by a pulsed microwave discharge

NASA Astrophysics Data System (ADS)

Stepanov, A. N.; Iazenkov, V. V.

1991-09-01

The possibility of efficient ozone production in a pulsed microwave discharge in oxygen is investigated experimentally in the context of the problem of creation of an artificial ionization region in the earth atmosphere. The experiments were conducted in commercial oxygen at a pressure of 30 tor. It is found that there exists a certain optimal (from the standpoint of ozone production) microwave pulse duration, which depends on the experimental conditions. A theoretical model is proposed which provides a consistent explanation for the experimental results.

Nonlinear aerodynamic wing design

NASA Technical Reports Server (NTRS)

Bonner, Ellwood

1985-01-01

The applicability of new nonlinear theoretical techniques is demonstrated for supersonic wing design. The new technology was utilized to define outboard panels for an existing advanced tactical fighter model. Mach 1.6 maneuver point design and multi-operating point compromise surfaces were developed and tested. High aerodynamic efficiency was achieved at the design conditions. A corollary result was that only modest supersonic penalties were incurred to meet multiple aerodynamic requirements. The nonlinear potential analysis of a practical configuration arrangement correlated well with experimental data.

Possible complementary cosmic-ray systems: Nuclei and antinuclei

NASA Technical Reports Server (NTRS)

Buck, Warren W.; Wilson, John W.; Townsend, Lawrence W.; Norbury, John W.

1987-01-01

Arguments are presented for the possible existence of antinuclei of charge Absolute Value of Z greater than 2 and particularly galactic cosmic antinuclei. Theoretical antinucleus-nucleus optical model cross sections are calculated and presented for the first time. A brief review of the nucleon-antinucleon interaction is also presented and its connection with the antinucleus-nucleus interaction is made. The predicted cross sections are smooth and show no structure. Finally, the findings are tied together with the formation of microlesions in living tissue.

An Upgrade of the Aeroheating Software ''MINIVER''

NASA Technical Reports Server (NTRS)

Louderback, Pierce

2013-01-01

Detailed computational modeling: CFO often used to create and execute computational domains. Increasing complexity when moving from 20 to 30 geometries. Computational time increased as finer grids are used (accuracy). Strong tool, but takes time to set up and run. MINIVER: Uses theoretical and empirical correlations. Orders of magnitude faster to set up and run. Not as accurate as CFO, but gives reasonable estimations. MINIVER's Drawbacks: Rigid command-line interface. Lackluster, unorganized documentation. No central control; multiple versions exist and have diverged.

Scatter Theories and Their Application to Lunar Radar Return

NASA Technical Reports Server (NTRS)

Hayre, H. S.

1961-01-01

The research work being done under this NASA grant is divided into the following three categories: (1) An estimate of the radar return for the NASA Aerobee rocket shot at White Sands Missile Range. (WSMR) (2) Development of new scatter theories, modification and correlation of existing scatter theories, and application of the theories to moon-echo data for estimation of the surface features of the moon. (3) Acoustic modeling of the lunar surface and correlation of the theoretical with both full scale and acoustical experimental results.

Magnus force effect in optical manipulation

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

Cipparrone, Gabriella; Pagliusi, Pasquale; Istituto per i Processi Chimici e Fisici, Consiglio Nazionale delle Ricerche, Ponte P. Bucci, Cubo 33B, I-87036 Rende

2011-07-15

The effect of the Magnus force in optical micromanipulation has been observed. An ad hoc experiment has been designed based on a one-dimensional optical trap that carries angular momentum. The observed particle dynamics reveals the occurrence of this hydrodynamic force, which is neglected in the common approach. Its measured value is larger than the one predicted by the existing theoretical models for micrometric particles and low Reynolds number, showing that the Magnus force can contribute to unconventional optohydrodynamic trapping and manipulation.

Solid liquid interfacial free energies of benzene

NASA Astrophysics Data System (ADS)

Azreg-Aı¨nou, M.

2007-02-01

In this work we determine for the range of melting temperatures 284.6⩽T⩽306.7 K, corresponding to equilibrium pressures 20.6⩽P⩽102.9 MPa, the benzene solid-liquid interfacial free energy by a cognitive approach including theoretical and experimental physics, mathematics, computer algebra (MATLAB), and some results from molecular dynamics computer simulations. From a theoretical and mathematical points of view, we deal with the elaboration of an analytical expression for the internal energy derived from a unified solid-liquid-vapor equation of state and with the elaboration of an existing statistical model for the entropy drop of the melt near the solid-liquid interface. From an experimental point of view, we will use our results obtained in collaboration with colleagues concerning the supercooled liquid benzene. Of particular interest for this work is the existing center-of-mass radial distribution function of benzene at 298 K obtained by computer simulation. Crystal-orientation-independent and minimum interfacial free energies are calculated and shown to increase slightly with the above temperatures. Both crystal-orientation-independent and minimum free energies agree with existing calculations and with rare existing experimental data. Taking into account the fact that the extent of supercooling is generally admitted as a constant, we determine the limits of supercooling by which we explore the behavior of the critical nucleus radius which is shown to decrease in terms of the above temperatures. The radius of the, and the number of molecules per, critical nucleus are shown to assume the average values of 20.2 A˚ and 175 with standard deviations of 0.16 Å and 4.5, respectively.

[Qualitative analysis of the evaluation indicators and their related parameters of ametropic state].

PubMed

Ren, Zeqin

2016-01-01

To investigate the theoretical basis and practical limitations of the existing calculation formulas in the evaluation of ametropic state. The evaluation indicators and their calculation parameters of ametropia were analyzed by using the reduced schematic model eye, the paraxial imaging principle, and the dimension laws. The existing formulas resulted from the reduced object vergence of object distance and image distance relation. Regarding the two measurement indicators of the existing formulas, diopter was misused for refractive power. "Ametropia degree" was a non-standard diction. Both of them were not suitable as the evaluation indicators. The outcomes of the existing formulas and their related plus or minus sign rules showed refractive corrections instead of refractive errors proper. For refractive errors, there was no suitable evaluation indicator. In the evaluation of ametropic state, there are fundamental problems in the existing formulas resulting from the reduced object vergence. The measurement indicators and their dimensional units are confused and misused. The calculation results refer to the refractive corrections only. The evaluation indicators for ametropia need to be further discussed.

Modelling the factor structure of the Child Depression Inventory in a population of apparently healthy adolescents in Nigeria.

PubMed

Olorunju, Samson Bamidele; Akpa, Onoja Matthew; Afolabi, Rotimi Felix

2018-01-01

Childhood and adolescent depression is common and often persists into adulthood with negative implications for school performances, peer relationship and behavioural functioning. The Child Depression Inventory (CDI) has been used to assess depression among adolescents in many countries including Nigeria but it is uncertain if the theoretical structure of CDI appropriately fits the experiences of adolescents in Nigeria. This study assessed varying theoretical modelling structure of the CDI in a population of apparently healthy adolescents in Benue state, Nigeria. Data was extracted on CDI scale and demographic information from a total of 1, 963 adolescents (aged 10-19 years), who participated in a state wide study assessing adolescent psychosocial functioning. In addition to descriptive statistics and reliability tests, Exploratory Factor Analysis (EFA) and Confirmatory Factor analysis (CFA) were used to model the underlying factor structure and its adequacy. The suggested new model was compared with existing CDI models as well as the CDI's original theoretical model. A model is considered better, if it has minimum Root Mean Square Error of Approximation (RMSEA<0.05), Minimum value of Discrepancy (CMIN/DF<3.0) and Akaike information criteria. All analyses were performed at 95% confidence level, using the version 21 of AMOS and the R software. Participants were 14.7±2.1 years and mostly male (54.3%), from Monogamous homes (67.9%) and lived in urban areas (52.2%). The measure of the overall internal consistency of the 2-factor CDI was α = 0.84. The 2-factor model had the minimum RMSEA (0.044), CMIN/DF (2.87) and least AIC (1037.996) compared to the other five CDI models. The child depression inventory has a 2-factor structure in a non-clinical general population of adolescents in Nigeria. Future use of the CDI in related setting may consider the 2-factor model.

What do we mean by "older adults' persistent pain self-management"? A concept analysis.

PubMed

Stewart, Carrie; Schofield, Pat; Elliott, Alison M; Torrance, Nicola; Leveille, Suzanne

2014-02-01

No standard definition exists for the concept "persistent pain self-management" or how it should be defined in relation to older adults. Poorly defined concepts can result in misunderstandings in the clinical setting and can hinder research through difficulties identifying or measuring the concept. To ascertain attributes, referents, antecedents, and consequences of the concept older adults' persistent pain self-management and develop a theoretical definition. Rodgers evolutionary model of concept analysis was used to systematically analyze articles from the academic and grey literature (N = 45). Data were extracted using standardized extraction forms and analyzed using thematic analysis. This concept was discussed in three ways: as an intervention, in reference to everyday behaviors, and as an outcome. Five defining attributes were identified: multidimensional process, personal development, active individuals, symptom response, and symptom control. Patients' perceived need and ability to manage pain with support from others is necessary for pain self-management to occur. Numerous physical, psychological, and social health consequences were identified. A theoretical definition is discussed. Our findings have clarified existing use and understanding regarding the concept of older adults' persistent pain self-management. We have identified three areas for future development: refinement of the attributes of this concept within the context of older adults, an exploration of how providers can overcome difficulties supporting older adults' persistent pain self-management, and a clarification of the overall theoretical framework of older adults' persistent pain self-management. Wiley Periodicals, Inc.

On the methods for determining the transverse dispersion coefficient in river mixing

NASA Astrophysics Data System (ADS)

Baek, Kyong Oh; Seo, Il Won

2016-04-01

In this study, the strengths and weaknesses of existing methods for determining the dispersion coefficient in the two-dimensional river mixing model were assessed based on hydraulic and tracer data sets acquired from experiments conducted on either laboratory channels or natural rivers. From the results of this study, it can be concluded that, when the longitudinal dispersion coefficient as well as the transverse dispersion coefficients must be determined in the transient concentration situation, the two-dimensional routing procedures, 2D RP and 2D STRP, can be employed to calculate dispersion coefficients among the observation methods. For the steady concentration situation, the STRP can be applied to calculate the transverse dispersion coefficient. When the tracer data are not available, either theoretical or empirical equations by the estimation method can be used to calculate the dispersion coefficient using the geometric and hydraulic data sets. Application of the theoretical and empirical equations to the laboratory channel showed that equations by Baek and Seo [[3], 2011] predicted reasonable values while equations by Fischer [23] and Boxwall and Guymer (2003) overestimated by factors of ten to one hundred. Among existing empirical equations, those by Jeon et al. [28] and Baek and Seo [6] gave the agreeable values of the transverse dispersion coefficient for most cases of natural rivers. Further, the theoretical equation by Baek and Seo [5] has the potential to be broadly applied to both laboratory and natural channels.

Neuronal pathway finding: from neurons to initial neural networks.

PubMed

Roscigno, Cecelia I

2004-10-01

Neuronal pathway finding is crucial for structured cellular organization and development of neural circuits within the nervous system. Neuronal pathway finding within the visual system has been extensively studied and therefore is used as a model to review existing knowledge regarding concepts of this developmental process. General principles of neuron pathway finding throughout the nervous system exist. Comprehension of these concepts guides neuroscience nurses in gaining an understanding of the developmental course of action, the implications of different anomalies, as well as the theoretical basis and nursing implications of some provocative new therapies being proposed to treat neurodegenerative diseases and neurologic injuries. These therapies have limitations in light of current ethical, developmental, and delivery modes and what is known about the development of neuronal pathways.

Altruistic behavior: mapping responses in the brain

PubMed Central

Filkowski, Megan M; Cochran, R Nick; Haas, Brian W

2016-01-01

Altruism is an important social construct related to human relationships and the way many interpersonal and economic decisions are made. Recent progress in social neuroscience research shows that altruism is associated with a specific pattern of brain activity. The tendency to engage in altruistic behaviors is associated with greater activity within limbic regions such as the nucleus accumbens and anterior cingulate cortex in addition to cortical regions such as the medial prefrontal cortex and temporoparietal junction. Here, we review existing theoretical models of altruism as well as recent empirical neuroimaging research demonstrating how altruism is processed within the brain. This review not only highlights the progress in neuroscience research on altruism but also shows that there exist several open questions that remain unexplored. PMID:28580317

Building Cognition: The Construction of Computational Representations for Scientific Discovery.

PubMed

Chandrasekharan, Sanjay; Nersessian, Nancy J

2015-11-01

Novel computational representations, such as simulation models of complex systems and video games for scientific discovery (Foldit, EteRNA etc.), are dramatically changing the way discoveries emerge in science and engineering. The cognitive roles played by such computational representations in discovery are not well understood. We present a theoretical analysis of the cognitive roles such representations play, based on an ethnographic study of the building of computational models in a systems biology laboratory. Specifically, we focus on a case of model-building by an engineer that led to a remarkable discovery in basic bioscience. Accounting for such discoveries requires a distributed cognition (DC) analysis, as DC focuses on the roles played by external representations in cognitive processes. However, DC analyses by and large have not examined scientific discovery, and they mostly focus on memory offloading, particularly how the use of existing external representations changes the nature of cognitive tasks. In contrast, we study discovery processes and argue that discoveries emerge from the processes of building the computational representation. The building process integrates manipulations in imagination and in the representation, creating a coupled cognitive system of model and modeler, where the model is incorporated into the modeler's imagination. This account extends DC significantly, and we present some of the theoretical and application implications of this extended account. Copyright © 2014 Cognitive Science Society, Inc.

Information-theoretic model comparison unifies saliency metrics

PubMed Central

Kümmerer, Matthias; Wallis, Thomas S. A.; Bethge, Matthias

2015-01-01

Learning the properties of an image associated with human gaze placement is important both for understanding how biological systems explore the environment and for computer vision applications. There is a large literature on quantitative eye movement models that seeks to predict fixations from images (sometimes termed “saliency” prediction). A major problem known to the field is that existing model comparison metrics give inconsistent results, causing confusion. We argue that the primary reason for these inconsistencies is because different metrics and models use different definitions of what a “saliency map” entails. For example, some metrics expect a model to account for image-independent central fixation bias whereas others will penalize a model that does. Here we bring saliency evaluation into the domain of information by framing fixation prediction models probabilistically and calculating information gain. We jointly optimize the scale, the center bias, and spatial blurring of all models within this framework. Evaluating existing metrics on these rephrased models produces almost perfect agreement in model rankings across the metrics. Model performance is separated from center bias and spatial blurring, avoiding the confounding of these factors in model comparison. We additionally provide a method to show where and how models fail to capture information in the fixations on the pixel level. These methods are readily extended to spatiotemporal models of fixation scanpaths, and we provide a software package to facilitate their use. PMID:26655340

Radiative transfer in CO2-rich atmospheres: 1. Collisional line mixing implies a colder early Mars

NASA Astrophysics Data System (ADS)

Ozak, N.; Aharonson, O.; Halevy, I.

2016-06-01

Fast and accurate radiative transfer methods are essential for modeling CO2-rich atmospheres, relevant to the climate of early Earth and Mars, present-day Venus, and some exoplanets. Although such models already exist, their accuracy may be improved as better theoretical and experimental constraints become available. Here we develop a unidimensional radiative transfer code for CO2-rich atmospheres, using the correlated k approach and with a focus on modeling early Mars. Our model differs from existing models in that it includes the effects of CO2 collisional line mixing in the calculation of the line-by-line absorption coefficients. Inclusion of these effects results in model atmospheres that are more transparent to infrared radiation and, therefore, in colder surface temperatures at radiative-convective equilibrium, compared with results of previous studies. Inclusion of water vapor in the model atmosphere results in negligible warming due to the low atmospheric temperatures under a weaker early Sun, which translate into climatically unimportant concentrations of water vapor. Overall, the results imply that sustained warmth on early Mars would not have been possible with an atmosphere containing only CO2 and water vapor, suggesting that other components of the early Martian climate system are missing from current models or that warm conditions were not long lived.

Where (who) are collectives in collectivism? Toward conceptual clarification of individualism and collectivism.

PubMed

Brewer, Marilynn B; Chen, Ya-Ru

2007-01-01

In psychological research on cultural differences, the distinction between individualism and collectivism has received the lion's share of attention as a fundamental dimension of cultural variation. In recent years, however, these constructs have been criticized as being ill-defined and "a catchall" to represent all forms of cultural differences. The authors argue that there is a conceptual confusion about the meaning of ingroups that constitute the target of collectivism. Collectives are rarely referred to in existing measures to assess collectivism. Instead, networks of interpersonal relationships dominate the operational definition of "ingroups" in these measures. Results from a content analysis of existing scales support this observation. To clarify and expand the individualism-collectivism distinction, a theoretical framework is proposed that draws on M. B. Brewer and G. Gardner's (1996) conceptualization of individual, relational, and collective selves and their manifestation in self-representations, beliefs, and values. Analyses of data from past studies provide preliminary support for this conceptual model. The authors propose that this new theoretical framework will contribute conceptual clarity to interpretation of past research on individualism and collectivism and guide future research on these important constructs. ((c) 2007 APA, all rights reserved).

E-documentation as a process management tool for nursing care in hospitals.

PubMed

Rajkovic, Uros; Sustersic, Olga; Rajkovic, Vladislav

2009-01-01

Appropriate documentation plays a key role in process management in nursing care. It includes holistic data management based on patient's data along the clinical path with regard to nursing care. We developed an e-documentation model that follows the process method of work in nursing care. It assesses the patient's status on the basis of Henderson's theoretical model of 14 basic living activities and is aligned with internationally recognized nursing classifications. E-documentation development requires reengineering of existing documentation and facilitates process reengineering. A prototype solution of an e-nursing documentation, already being in testing process at University medical centres in Ljubljana and Maribor, will be described.

On Optimizing H. 264/AVC Rate Control by Improving R-D Model and Incorporating HVS Characteristics

NASA Astrophysics Data System (ADS)

Zhu, Zhongjie; Wang, Yuer; Bai, Yongqiang; Jiang, Gangyi

2010-12-01

The state-of-the-art JVT-G012 rate control algorithm of H.264 is improved from two aspects. First, the quadratic rate-distortion (R-D) model is modified based on both empirical observations and theoretical analysis. Second, based on the existing physiological and psychological research findings of human vision, the rate control algorithm is optimized by incorporating the main characteristics of the human visual system (HVS) such as contrast sensitivity, multichannel theory, and masking effect. Experiments are conducted, and experimental results show that the improved algorithm can simultaneously enhance the overall subjective visual quality and improve the rate control precision effectively.

A new model for fluid velocity slip on a solid surface.

PubMed

Shu, Jian-Jun; Teo, Ji Bin Melvin; Chan, Weng Kong

2016-10-12

A general adsorption model is developed to describe the interactions between near-wall fluid molecules and solid surfaces. This model serves as a framework for the theoretical modelling of boundary slip phenomena. Based on this adsorption model, a new general model for the slip velocity of fluids on solid surfaces is introduced. The slip boundary condition at a fluid-solid interface has hitherto been considered separately for gases and liquids. In this paper, we show that the slip velocity in both gases and liquids may originate from dynamical adsorption processes at the interface. A unified analytical model that is valid for both gas-solid and liquid-solid slip boundary conditions is proposed based on surface science theory. The corroboration with the experimental data extracted from the literature shows that the proposed model provides an improved prediction compared to existing analytical models for gases at higher shear rates and close agreement for liquid-solid interfaces in general.

Analysis on trust influencing factors and trust model from multiple perspectives of online Auction

NASA Astrophysics Data System (ADS)

Yu, Wang

2017-10-01

Current reputation models lack the research on online auction trading completely so they cannot entirely reflect the reputation status of users and may cause problems on operability. To evaluate the user trust in online auction correctly, a trust computing model based on multiple influencing factors is established. It aims at overcoming the efficiency of current trust computing methods and the limitations of traditional theoretical trust models. The improved model comprehensively considers the trust degree evaluation factors of three types of participants according to different participation modes of online auctioneers, to improve the accuracy, effectiveness and robustness of the trust degree. The experiments test the efficiency and the performance of our model under different scale of malicious user, under environment like eBay and Sporas model. The experimental results analysis show the model proposed in this paper makes up the deficiency of existing model and it also has better feasibility.

Modelling efforts needed to advance herpes simplex virus (HSV) vaccine development: Key findings from the World Health Organization Consultation on HSV Vaccine Impact Modelling.

PubMed

Gottlieb, Sami L; Giersing, Birgitte; Boily, Marie-Claude; Chesson, Harrell; Looker, Katharine J; Schiffer, Joshua; Spicknall, Ian; Hutubessy, Raymond; Broutet, Nathalie

2017-06-21

Development of a vaccine against herpes simplex virus (HSV) is an important goal for global sexual and reproductive health. In order to more precisely define the health and economic burden of HSV infection and the theoretical impact and cost-effectiveness of an HSV vaccine, in 2015 the World Health Organization convened an expert consultation meeting on HSV vaccine impact modelling. The experts reviewed existing model-based estimates and dynamic models of HSV infection to outline critical future modelling needs to inform development of a comprehensive business case and preferred product characteristics for an HSV vaccine. This article summarizes key findings and discussions from the meeting on modelling needs related to HSV burden, costs, and vaccine impact, essential data needs to carry out those models, and important model components and parameters. Copyright © 2017. Published by Elsevier Ltd.

Towards a Rational Model for the Triple Velocity Correlations of Turbulence

NASA Technical Reports Server (NTRS)

Younis, B. A.; Gatski, T. B.; Speziale, C. G.

1999-01-01

This paper presents a rational approach to modelling the triple velocity correlations that appear in the transport equations for the Reynolds stresses. All existing models of these correlations have largely been formulated on phenomenological grounds and are defective in one important aspect: they all neglect to allow for the dependence of these correlations on the local gradients of mean velocity. The mathematical necessity for this dependence will be demonstrated in the paper. The present contribution lies in the novel use of Group Representation Theory to determine the most general tensorial form of these correlations in terms of all the second- and third-order tensor quantities that appear in the exact equations that govern their evolution. The requisite representation did not exist in the literature and therefore had to be developed specifically for this purpose by Professor G. F. Smith. The outcome of this work is a mathematical framework for the construction of algebraic, explicit, and rational models for the triple velocity correlations that are theoretically consistent and include all the correct dependencies. Previous models are reviewed, and all are shown to be an incomplete subset of this new representation, even to lowest order.

QSAR prediction of additive and non-additive mixture toxicities of antibiotics and pesticide.

PubMed

Qin, Li-Tang; Chen, Yu-Han; Zhang, Xin; Mo, Ling-Yun; Zeng, Hong-Hu; Liang, Yan-Peng

2018-05-01

Antibiotics and pesticides may exist as a mixture in real environment. The combined effect of mixture can either be additive or non-additive (synergism and antagonism). However, no effective predictive approach exists on predicting the synergistic and antagonistic toxicities of mixtures. In this study, we developed a quantitative structure-activity relationship (QSAR) model for the toxicities (half effect concentration, EC 50 ) of 45 binary and multi-component mixtures composed of two antibiotics and four pesticides. The acute toxicities of single compound and mixtures toward Aliivibrio fischeri were tested. A genetic algorithm was used to obtain the optimized model with three theoretical descriptors. Various internal and external validation techniques indicated that the coefficient of determination of 0.9366 and root mean square error of 0.1345 for the QSAR model predicted that 45 mixture toxicities presented additive, synergistic, and antagonistic effects. Compared with the traditional concentration additive and independent action models, the QSAR model exhibited an advantage in predicting mixture toxicity. Thus, the presented approach may be able to fill the gaps in predicting non-additive toxicities of binary and multi-component mixtures. Copyright © 2018 Elsevier Ltd. All rights reserved.

Willingness-to-pay for steelhead trout fishing: Implications of two-step consumer decisions with short-run endowments

NASA Astrophysics Data System (ADS)

McKean, John R.; Johnson, Donn; Taylor, R. Garth

2010-09-01

Choice of the appropriate model of economic behavior is important for the measurement of nonmarket demand and benefits. Several travel cost demand model specifications are currently in use. Uncertainty exists over the efficacy of these approaches, and more theoretical and empirical study is warranted. Thus travel cost models with differing assumptions about labor markets and consumer behavior were applied to estimate the demand for steelhead trout sportfishing on an unimpounded reach of the Snake River near Lewiston, Idaho. We introduce a modified two-step decision model that incorporates endogenous time value using a latent index variable approach. The focus is on the importance of distinguishing between short-run and long-run consumer decision variables in a consistent manner. A modified Barnett two-step decision model was found superior to other models tested.

Further theoretical studies of modified cyclone separator as a diesel soot particulate emission arrester.

PubMed

Mukhopadhyay, N; Bose, P K

2009-10-01

Soot particulate emission reduction from diesel engine is one of the most emerging problems associated with the exhaust pollution. Diesel particulate filters (DPF) hold out the prospects of substantially reducing regulated particulate emissions but the question of the reliable regeneration of filters still remains a difficult hurdle to overcome. Many of the solutions proposed to date suffer from design complexity, cost, regeneration problem and energy demands. This study presents a computer aided theoretical analysis for controlling diesel soot particulate emission by cyclone separator--a non contact type particulate removal system considering outer vortex flow, inner vortex flow and packed ceramic fiber filter at the end of vortex finder tube. Cyclone separator with low initial cost, simple construction produces low back pressure and reasonably high collection efficiencies with reduced regeneration problems. Cyclone separator is modified by placing a continuous ceramic packed fiber filter placed at the end of the vortex finder tube. In this work, the grade efficiency model of diesel soot particulate emission is proposed considering outer vortex, inner vortex and the continuous ceramic packed fiber filter. Pressure drop model is also proposed considering the effect of the ceramic fiber filter. Proposed model gives reasonably good collection efficiency with permissible pressure drop limit of diesel engine operation. Theoretical approach is predicted for calculating the cut size diameter considering the effect of Cunningham molecular slip correction factor. The result shows good agreements with existing cyclone and DPF flow characteristics.

[Settings-based prevention of overweight in childhood and adolescents : Theoretical foundation, determinants and intervention planning].

PubMed

Quilling, Eike; Dadaczynski, Kevin; Müller, Merle

2016-11-01

Childhood and adolescent overweight can still be seen as a global public health problem. Based on our socioeconomic understanding, overweight is the result of a complex interplay of a diverse array of factors acting on different levels. Hence, in addition to individual level determinants overweight prevention should also address environmental related factors as part of a holistic and integrated setting approach. This paper aims to discuss the setting approach with regard to overweight prevention in childhood and adolescence. In addition to a summary of environmental factors and their empirical influence on the determinants of overweight, theoretical approaches and planning models of settings-based overweight prevention are discussed. While settings can be characterized as specific social-spatial subsystems (e. g. kindergarten, schools), living environments relate to complex subject-oriented environments that may include various subsystems. Direct social contexts, educational contexts and community contexts as relevant systems for young people contain different evidence-based influences that need to be taken into account in settings based overweight prevention. To support a theory-driven intervention, numerous planning models exist, which are presented here. Given the strengthening of environments for health within the prevention law, the underlying settings approach also needs further development with regard to overweigth prevention. This includes the improvement of the theoretical foundation by aligning intervention practice of planning models, which also has a positive influence on the ability to measure its success.

Flame Spread and Extinction Over a Thick Solid Fuel in Low-Velocity Opposed and Concurrent Flows

NASA Astrophysics Data System (ADS)

Zhu, Feng; Lu, Zhanbin; Wang, Shuangfeng

2016-05-01

Flame spread and extinction phenomena over a thick PMMA in purely opposed and concurrent flows are investigated by conducting systematical experiments in a narrow channel apparatus. The present tests focus on low-velocity flow regime and hence complement experimental data previously reported for high and moderate velocity regimes. In the flow velocity range tested, the opposed flame is found to spread much faster than the concurrent flame at a given flow velocity. The measured spread rates for opposed and concurrent flames can be correlated by corresponding theoretical models of flame spread, indicating that existing models capture the main mechanisms controlling the flame spread. In low-velocity gas flows, however, the experimental results are observed to deviate from theoretical predictions. This may be attributed to the neglect of radiative heat loss in the theoretical models, whereas radiation becomes important for low-intensity flame spread. Flammability limits using oxygen concentration and flow velocity as coordinates are presented for both opposed and concurrent flame spread configurations. It is found that concurrent spread has a wider flammable range than opposed case. Beyond the flammability boundary of opposed spread, there is an additional flammable area for concurrent spread, where the spreading flame is sustainable in concurrent mode only. The lowest oxygen concentration allowing concurrent flame spread in forced flow is estimated to be approximately 14 % O2, substantially below that for opposed spread (18.5 % O2).

A model of self-directed learning in internal medicine residency: a qualitative study using grounded theory.

PubMed

Sawatsky, Adam P; Ratelle, John T; Bonnes, Sara L; Egginton, Jason S; Beckman, Thomas J

2017-02-02

Existing theories of self-directed learning (SDL) have emphasized the importance of process, personal, and contextual factors. Previous medical education research has largely focused on the process of SDL. We explored the experience with and perception of SDL among internal medicine residents to gain understanding of the personal and contextual factors of SDL in graduate medical education. Using a constructivist grounded theory approach, we conducted 7 focus group interviews with 46 internal medicine residents at an academic medical center. We processed the data by using open coding and writing analytic memos. Team members organized open codes to create axial codes, which were applied to all transcripts. Guided by a previous model of SDL, we developed a theoretical model that was revised through constant comparison with new data as they were collected, and we refined the theory until it had adequate explanatory power and was appropriately grounded in the experiences of residents. We developed a theoretical model of SDL to explain the process, personal, and contextual factors affecting SDL during residency training. The process of SDL began with a trigger that uncovered a knowledge gap. Residents progressed to formulating learning objectives, using resources, applying knowledge, and evaluating learning. Personal factors included motivations, individual characteristics, and the change in approach to SDL over time. Contextual factors included the need for external guidance, the influence of residency program structure and culture, and the presence of contextual barriers. We developed a theoretical model of SDL in medical education that can be used to promote and assess resident SDL through understanding the process, person, and context of SDL.

A theoretical framework informing research about the role of stress in the pathophysiology of bipolar disorder.

PubMed

Brietzke, Elisa; Mansur, Rodrigo Barbachan; Soczynska, Joanna; Powell, Alissa M; McIntyre, Roger S

2012-10-01

The staggering illness burden associated with Bipolar Disorder (BD) invites the need for primary prevention strategies. Before preventative strategies can be considered in individuals during a pre-symptomatic period (i.e., at risk), unraveling the mechanistic steps wherein external stress is transduced and interacts with genetic vulnerability in the early stages of BD will be a critical conceptual necessity. Herein we comprehensively review extant studies reporting on stress and bipolar disorder. The overarching aim is to propose a conceptual framework to inform research about the role of stress in the pathophysiology of BD. Computerized databases i.e. PubMed, PsychInfo, Cochrane Library and Scielo were searched using the following terms: "bipolar disorder" cross-referenced with "stress", "general reaction to stress", "resilience", "resistance", "recovery" "stress-diathesis", "allostasis", and "hormesis". Data from literature indicate the existence of some theoretical models to understand the influence of stress in the pathophysiology of BD, including classical stress-diathesis model and new models such as allostasis and hormesis. In addition, molecular mechanisms involved in stress adaptation (resistance, resilience and recovery) can also be translated in research strategies to investigate the impact of stress in the pathophysiology of BD. Most studies are retrospective and/or cross sectional, do not consider the period of development, assess brain function with only one or few methodologies, and use animal models which are not always similar to human phenotypes. The interaction between stress and brain development is dynamic and complex. In this article we proposed a theoretical model for investigation about the role of stress in the pathophysiology of BD, based on the different kinds of stress adaptation response and their putative neurobiological underpinnings. Copyright © 2012 Elsevier Inc. All rights reserved.