A Field-Theoretic Approach to the Wiener Sausage
NASA Astrophysics Data System (ADS)
Nekovar, S.; Pruessner, G.
2016-05-01
The Wiener Sausage, the volume traced out by a sphere attached to a Brownian particle, is a classical problem in statistics and mathematical physics. Initially motivated by a range of field-theoretic, technical questions, we present a single loop renormalised perturbation theory of a stochastic process closely related to the Wiener Sausage, which, however, proves to be exact for the exponents and some amplitudes. The field-theoretic approach is particularly elegant and very enjoyable to see at work on such a classic problem. While we recover a number of known, classical results, the field-theoretic techniques deployed provide a particularly versatile framework, which allows easy calculation with different boundary conditions even of higher momenta and more complicated correlation functions. At the same time, we provide a highly instructive, non-trivial example for some of the technical particularities of the field-theoretic description of stochastic processes, such as excluded volume, lack of translational invariance and immobile particles. The aim of the present work is not to improve upon the well-established results for the Wiener Sausage, but to provide a field-theoretic approach to it, in order to gain a better understanding of the field-theoretic obstacles to overcome.
A field theoretical approach to the quasi-continuum method
NASA Astrophysics Data System (ADS)
Iyer, Mrinal; Gavini, Vikram
2011-08-01
The quasi-continuum method has provided many insights into the behavior of lattice defects in the past decade. However, recent numerical analysis suggests that the approximations introduced in various formulations of the quasi-continuum method lead to inconsistencies—namely, appearance of ghost forces or residual forces, non-conservative nature of approximate forces, etc.—which affect the numerical accuracy and stability of the method. In this work, we identify the source of these errors to be the incompatibility of using quadrature rules, which is a local notion, on a non-local representation of energy. We eliminate these errors by first reformulating the extended interatomic interactions into a local variational problem that describes the energy of a system via potential fields. We subsequently introduce the quasi-continuum reduction of these potential fields using an adaptive finite-element discretization of the formulation. We demonstrate that the present formulation resolves the inconsistencies present in previous formulations of the quasi-continuum method, and show using numerical examples the remarkable improvement in the accuracy of solutions. Further, this field theoretic formulation of quasi-continuum method makes mathematical analysis of the method more amenable using functional analysis and homogenization theories.
Quantum noise in the mirror-field system: A field theoretic approach
Hsiang, Jen-Tsung; Wu, Tai-Hung; Lee, Da-Shin; King, Sun-Kun; Wu, Chun-Hsien
2013-02-15
We revisit the quantum noise problem in the mirror-field system by a field-theoretic approach. Here a perfectly reflecting mirror is illuminated by a single-mode coherent state of the massless scalar field. The associated radiation pressure is described by a surface integral of the stress-tensor of the field. The read-out field is measured by a monopole detector, from which the effective distance between the detector and mirror can be obtained. In the slow-motion limit of the mirror, this field-theoretic approach allows to identify various sources of quantum noise that all in all leads to uncertainty of the read-out measurement. In addition to well-known sources from shot noise and radiation pressure fluctuations, a new source of noise is found from field fluctuations modified by the mirror's displacement. Correlation between different sources of noise can be established in the read-out measurement as the consequence of interference between the incident field and the field reflected off the mirror. In the case of negative correlation, we found that the uncertainty can be lowered than the value predicted by the standard quantum limit. Since the particle-number approach is often used in quantum optics, we compared results obtained by both approaches and examine its validity. We also derive a Langevin equation that describes the stochastic dynamics of the mirror. The underlying fluctuation-dissipation relation is briefly mentioned. Finally we discuss the backreaction induced by the radiation pressure. It will alter the mean displacement of the mirror, but we argue this backreaction can be ignored for a slowly moving mirror. - Highlights: Black-Right-Pointing-Pointer The quantum noise problem in the mirror-field system is re-visited by a field-theoretic approach. Black-Right-Pointing-Pointer Other than the shot noise and radiation pressure noise, we show there are new sources of noise and correlation between them. Black-Right-Pointing-Pointer The noise correlations can
Field-theoretical approach to a dense polymer with an ideal binary mixture of clustering centers.
Fantoni, Riccardo; Müller-Nedebock, Kristian K
2011-07-01
We propose a field-theoretical approach to a polymer system immersed in an ideal mixture of clustering centers. The system contains several species of these clustering centers with different functionality, each of which connects a fixed number segments of the chain to each other. The field theory is solved using the saddle point approximation and evaluated for dense polymer melts using the random phase approximation. We find a short-ranged effective intersegment interaction with strength dependent on the average segment density and discuss the structure factor within this approximation. We also determine the fractions of linkers of the different functionalities.
NASA Astrophysics Data System (ADS)
Taghian, Toloo; Sheikh, Abdul; Narmoneva, Daria; Kogan, Andrei
2015-03-01
Application of external electric field (EF) as a non-pharmacological, non-invasive tool to control cell function is of great therapeutic interest. We developed a theoretical-experimental approach to investigate the biophysical mechanisms of EF interaction with cells in electrode-free physiologically-relevant configuration. Our numerical results demonstrated that EF frequency is the major parameter to control cell response to EF. Non-oscillating or low-frequency EF leads to charge accumulation on the cell surface membrane that may mediate membrane initiated cell responses. In contrast, high-frequency EF penetrates the cell membrane and reaches cell cytoplasm, where it may directly activate intracellular responses. The theoretical predictions were confirmed in our experimental studies of the effects of applied EF on vascular cell function. Results show that non-oscillating EF increases vascular endothelial growth factor (VEGF) expression while field polarity controls cell adhesion rate. High-frequency, but not low frequency, EF provides differential regulation of cytoplasmic focal adhesion kinase and VEGF expression depending on the substrate, with increased expression in cells cultured on RGD-rich synthetic hydrogels, and decreased expression for matrigel culture. The authors acknowledge the financial support from the NSF (DMR-1206784 & DMR-0804199 to AK); the NIH (1R21 DK078814-01A1 to DN) and the University of Cincinnati (Interdisciplinary Faculty Research Support Grant to DN and AK).
Plimak, L.I.; Fleischhauer, M.; Olsen, M.K.; Collett, M.J.
2003-01-01
We present an introduction to phase-space techniques (PST) based on a quantum-field-theoretical (QFT) approach. In addition to bridging the gap between PST and QFT, our approach results in a number of generalizations of the PST. First, for problems where the usual PST do not result in a genuine Fokker-Planck equation (even after phase-space doubling) and hence fail to produce a stochastic differential equation (SDE), we show how the system in question may be approximated via stochastic difference equations (S{delta}E). Second, we show that introducing sources into the SDE's (or S{delta}E's) generalizes them to a full quantum nonlinear stochastic response problem (thus generalizing Kubo's linear reaction theory to a quantum nonlinear stochastic response theory). Third, we establish general relations linking quantum response properties of the system in question to averages of operator products ordered in a way different from time normal. This extends PST to a much wider assemblage of operator products than are usually considered in phase-space approaches. In all cases, our approach yields a very simple and straightforward way of deriving stochastic equations in phase space.
Margins of freedom: a field-theoretic approach to class-based health dispositions and practices.
Burnett, Patrick John; Veenstra, Gerry
2017-03-23
Pierre Bourdieu's theory of practice situates social practices in the relational interplay between experiential mental phenomena (habitus), resources (capitals) and objective social structures (fields). When applied to class-based practices in particular, the overarching field of power within which social classes are potentially made manifest is the primary field of interest. Applying relational statistical techniques to original survey data from Toronto and Vancouver, Canada, we investigated whether smoking, engaging in physical activity and consuming fruit and vegetables are dispersed in a three-dimensional field of power shaped by economic and cultural capitals and cultural dispositions and practices. We find that aesthetic dispositions and flexibility of developing and established dispositions are associated with positioning in the Canadian field of power and embedded in the logics of the health practices dispersed in the field. From this field-theoretic perspective, behavioural change requires the disruption of existing relations of harmony between the habitus of agents, the fields within which the practices are enacted and the capitals that inform and enforce the mores and regularities of the fields. The three-dimensional model can be explored at: http://relational-health.ca/margins-freedom.
Field Theory in Organizational Psychology: An Analysis of Theoretical Approaches in Leadership.
ERIC Educational Resources Information Center
Garcia, Joseph E.
This literature review examines Kurt Lewin's influence in leadership psychology. Characteristics of field theory are described in detail and utilized in analyzing leadership research, including the trait approach, leader behavior studies, contingency theory, path-goal theory, and leader decision theory. Important trends in leadership research are…
Theoretical Approaches to Nanoparticles
NASA Astrophysics Data System (ADS)
Kempa, Krzysztof
Nanoparticles can be viewed as wave resonators. Involved waves are, for example, carrier waves, plasmon waves, polariton waves, etc. A few examples of successful theoretical treatments that follow this approach are given. In one, an effective medium theory of a nanoparticle composite is presented. In another, plasmon polaritonic solutions allow to extend concepts of radio technology, such as an antenna and a coaxial transmission line, to the visible frequency range.
Field theoretic approach to dynamical orbital localization in ab initio molecular dynamics
NASA Astrophysics Data System (ADS)
Thomas, Jordan W.; Iftimie, Radu; Tuckerman, Mark E.
2004-03-01
Techniques from gauge-field theory are employed to derive an alternative formulation of the Car-Parrinello ab initio molecular-dynamics method that allows maximally localized Wannier orbitals to be generated dynamically as the calculation proceeds. In particular, the Car-Parrinello Lagrangian is mapped onto an SU(n) non-Abelian gauge-field theory and the fictitious kinetic energy in the Car-Parrinello Lagrangian is modified to yield a fully gauge-invariant form. The Dirac gauge-fixing method is then employed to derive a set of equations of motion that automatically maintain orbital locality by restricting the orbitals to remain in the “Wannier gauge.” An approximate algorithm for integrating the equations of motion that is stable and maintains orbital locality is then developed based on the exact equations of motion. It is shown in a realistic application (64 water molecules plus one hydrogen-chloride molecule in a periodic box) that orbital locality can be maintained with only a modest increase in CPU time. The ability to keep orbitals localized in an ab initio molecular-dynamics calculation is a crucial ingredient in the development of emerging linear scaling approaches.
NASA Astrophysics Data System (ADS)
Freire, Hermann; Corrêa, Eberth
2012-02-01
We apply a functional implementation of the field-theoretical renormalization group (RG) method up to two loops to the single-impurity Anderson model. To achieve this, we follow a RG strategy similar to that proposed by Vojta et al. (in Phys. Rev. Lett. 85:4940, 2000), which consists of defining a soft ultraviolet regulator in the space of Matsubara frequencies for the renormalized Green's function. Then we proceed to derive analytically and solve numerically integro-differential flow equations for the effective couplings and the quasiparticle weight of the present model, which fully treat the interplay of particle-particle and particle-hole parquet diagrams and the effect of the two-loop self-energy feedback into them. We show that our results correctly reproduce accurate numerical renormalization group data for weak to slightly moderate interactions. These results are in excellent agreement with other functional Wilsonian RG works available in the literature. Since the field-theoretical RG method turns out to be easier to implement at higher loops than the Wilsonian approach, higher-order calculations within the present approach could improve further the results for this model at stronger couplings. We argue that the present RG scheme could thus offer a possible alternative to other functional RG methods to describe electronic correlations within this model.
Thematic Approach to Theoretical Speculations in the Field of Educational Administration
ERIC Educational Resources Information Center
Park, Jae
2015-01-01
The purpose of this article is a critical reflection on the field of educational administration and its varied and often conflicting epistemologies. It is argued that the field of educational administration is a community of diverse epistemologies. Although epistemological heterogeneity has been persistently vilified by both theorists and…
A field-theoretic approach to the May-Leonard cyclic population dynamics model
NASA Astrophysics Data System (ADS)
Serrao, Shannon; Täuber, Uwe
Spatially extended stochastic population dynamics models with cyclic predation interactions display intriguing time evolution and spontaneous structure formation. We study a version of the May-Leonard cyclic competition model in d dimensions with diffusive particle propagation. We use the second-quantized Doi-Peliti formalism and ensuing coherent-state path integral representation to construct its continuum representation and explore its collective dynamics. Expanding the resulting action about the mean-field species concentrations enables us to compute the diagonalized harmonic propagators and hence 'masses', i.e., relaxation rates and eigenfrequencies of the fundamental modes. Furthermore, operating near the Hopf bifurcation point, we identify the validity range for the necessary time scale separation that allows us to project out the purely relaxing eigenmode. The remaining oscillating fields obey the complex Ginzburg-Landau equation, which is consistent with spiral pattern formation.
Understanding the edge effect in TASEP with mean-field theoretic approaches
NASA Astrophysics Data System (ADS)
Dong, J. J.; Zia, R. K. P.; Schmittmann, B.
2009-01-01
We study a totally asymmetric simple exclusion process (TASEP) with one defect site, hopping rate q < 1, near the system boundary. Regarding our system as a pair of uniform TASEP's coupled through the defect, we study various methods to match a finite TASEP and an infinite one across a common boundary. Several approximation schemes are investigated. Utilizing the finite segment mean-field (FSMF) method, we set up a framework for computing the steady state current J as a function of the entry rate α and q. For the case where the defect is located at the entry site, we obtain an analytical expression for J(α, q) which is in good agreement with Monte Carlo simulation results. When the defect is located deeper in the bulk, we refined the scheme of MacDonald et al (1968 Biopolymers 6 1) and find reasonably good fits to the density profiles before the defect site. We discuss the strengths and limitations of each method, as well as possible avenues for further studies.
Field-theoretical Renormalization-Group approach to critical dynamics of crosslinked polymer blends
NASA Astrophysics Data System (ADS)
Benhamou, M.; Chahid, M.
2008-09-01
We consider a crosslinked polymer blend that may undergo a microphase separation. When the temperature is changed from an initial value towards a final one very close to the spinodal point, the mixture is out equilibrium. The aim is the study of dynamics at a given time t , before the system reaches its final equilibrium state. The dynamics is investigated through the structure factor, S(q, t) , which is a function of the wave vector q , temperature T , time t , and reticulation dose D . To determine the phase behavior of this dynamic structure factor, we start from a generalized Langevin equation (model C) solved by the time composition fluctuation. Beside the standard de Gennes Hamiltonian, this equation incorporates a Gaussian local noise, ζ . First, by averaging over ζ , we get an effective Hamiltonian. Second, we renormalize this dynamic field theory and write a Renormalization-Group equation for the dynamic structure factor. Third, solving this equation yields the behavior of S(q, t) , in space of relevant parameters. As result, S(q, t) depends on three kinds of lengths, which are the wavelength q-1, a time length scale R(t) thicksim t1/z , and the mesh size ξ* . The scale R(t) is interpreted as the size of growing microdomains at time t . When R(t) becomes of the order of ξ* , the dynamics is stopped. The final time, t * , then scales as t * thicksim ξ{ast z} , with the dynamic exponent z = 6 - η . Here, η is the usual Ising critical exponent. Since the final size of microdomains ξ* is very small (few nanometers), the dynamics is of short time. Finally, all these results we obtained from renormalization theory are compared to those we stated in some recent work using a scaling argument.
NASA Astrophysics Data System (ADS)
Oda, Tomohito; Kashima, Kenji; Imura, Jun-Ichi; Miyazaki, Shuji; Morita, Hiroshi
In this paper, stationary iterative methods for large-scale Toeplitz-type systems are investigated from a control theoretic point of view. We utilize spatially invariant structure of Toeplitz matrices, to avoid the curse of dimensionality arising in analysis and design of the convergence properties. Nonlinearities in the system are theoretically handled within the small gain and stability analysis for Lur'e systems. This theory enables us to achieve the desired global convergence of the proposed numerical scheme. We also evaluate the efficacy of the proposed method through an application to magnetic field analysis.
Cooper, F.
1997-09-22
This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.
Håkansson, Andreas; Magnusson, Emma; Bergenståhl, Björn; Nilsson, Lars
2012-08-31
Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.
Classical and quantum field-theoretical approach to the non-linear q-Klein-Gordon equation
NASA Astrophysics Data System (ADS)
Plastino, A.; Rocca, M. C.
2016-11-01
In the wake of efforts made Nobre and Rego-Monteiro in EPL, 97 (2012) 41001 and J. Math. Phys., 54 (2913) 103302, we extend them here by developing the conventional Lagrangian treatment of a classical field theory (FT) to the q-Klein-Gordon equation advanced in Phys. Rev. Lett., 106 (2011) 140601 and J. Math. Phys., 54 (2913) 103302 by the same authors, and the quantum theory corresponding to q=\\frac {3} {2} . This makes it possible to generate a putative conjecture regarding black matter. Our theory reduces to the usual FT for q→ 1 .
A gauge-theoretic approach to gravity
Krasnov, Kirill
2012-01-01
Einstein's general relativity (GR) is a dynamical theory of the space–time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang–Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach. PMID:22792040
A gauge-theoretic approach to gravity.
Krasnov, Kirill
2012-08-08
Einstein's general relativity (GR) is a dynamical theory of the space-time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang-Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach.
Unification of theoretical approaches for epidemic spreading on complex networks.
Wang, Wei; Tang, Ming; Eugene Stanley, H; Braunstein, Lidia A
2017-03-01
Models of epidemic spreading on complex networks have attracted great attention among researchers in physics, mathematics, and epidemiology due to their success in predicting and controlling scenarios of epidemic spreading in real-world scenarios. To understand the interplay between epidemic spreading and the topology of a contact network, several outstanding theoretical approaches have been developed. An accurate theoretical approach describing the spreading dynamics must take both the network topology and dynamical correlations into consideration at the expense of increasing the complexity of the equations. In this short survey we unify the most widely used theoretical approaches for epidemic spreading on complex networks in terms of increasing complexity, including the mean-field, the heterogeneous mean-field, the quench mean-field, dynamical message-passing, link percolation, and pairwise approximation. We build connections among these approaches to provide new insights into developing an accurate theoretical approach to spreading dynamics on complex networks.
Unification of theoretical approaches for epidemic spreading on complex networks
NASA Astrophysics Data System (ADS)
Wang, Wei; Tang, Ming; Stanley, H. Eugene; Braunstein, Lidia A.
2017-03-01
Models of epidemic spreading on complex networks have attracted great attention among researchers in physics, mathematics, and epidemiology due to their success in predicting and controlling scenarios of epidemic spreading in real-world scenarios. To understand the interplay between epidemic spreading and the topology of a contact network, several outstanding theoretical approaches have been developed. An accurate theoretical approach describing the spreading dynamics must take both the network topology and dynamical correlations into consideration at the expense of increasing the complexity of the equations. In this short survey we unify the most widely used theoretical approaches for epidemic spreading on complex networks in terms of increasing complexity, including the mean-field, the heterogeneous mean-field, the quench mean-field, dynamical message-passing, link percolation, and pairwise approximation. We build connections among these approaches to provide new insights into developing an accurate theoretical approach to spreading dynamics on complex networks.
New Theoretical Approaches for Human-Computer Interaction.
ERIC Educational Resources Information Center
Rogers, Yvonne
2004-01-01
Presents a critique of recent theoretical developments in the field of human-computer interaction (HCI) together with an overview of HCI practice. This chapter discusses why theoretically based approaches have had little impact on the practice of interaction design and suggests mechanisms to enable designers and researchers to better articulate…
Rethinking Theoretical Approaches to Stigma
Martin, Jack K; Lang, Annie; Olafsdottir, Sigrun
2008-01-01
A resurgence of research and policy efforts on stigma both facilitates and forces a reconsideration of the levels and types of factors that shape reactions to persons with conditions that engender prejudice and discrimination. Focusing on the case of mental illness but drawing from theories and studies of stigma across the social sciences, we propose a framework that brings together theoretical insights from micro, meso and macro level research: Framework Integrating Normative Influences on Stigma (FINIS) starts with Goffman’s notion that understanding stigma requires a language of social relationships, but acknowledges that individuals do not come to social interaction devoid of affect and motivation. Further, all social interactions take place in a context in which organizations, media and larger cultures structure normative expectations which create the possibility of marking “difference”. Labelling theory, social network theory, the limited capacity model of media influence, the social psychology of prejudice and discrimination, and theories of the welfare state all contribute to an understanding of the complex web of expectations shaping stigma. FINIS offers the potential to build a broad-based scientific foundation based on understanding the effects of stigma on the lives of persons with mental illness, the resources devoted to the organizations and families who care for them, and policies and programs designed to combat stigma. We end by discussing the clear implications this framework holds for stigma reduction, even in the face of conflicting results. PMID:18436358
Solar and stellar activity - The theoretical approach
NASA Astrophysics Data System (ADS)
Belvedere, G.
1985-10-01
The unified approach to understanding solar and stellar activity is examined. Stellar activity observations have stimulated theoretical work, mostly within the framework of the alpha-omega dynamo theory. A number of uncertainties and intrinsic limits in dynamo theory do still exist, and these are discussed together with alternative or complementary suggestions. The relevance is stressed of nonlinear problems in dynamo theory - magnetoconvection, growth and stability of flux tubes against magnetic buoyancy, hydromagnetic global dynamos - to improve the understanding of both small and large scale interaction of rotation, turbulent convection and magnetic fields, and the transition from the linear to the nonlinear regime. Recent dynamo models of stellar activity are critically reviewed regarding the dependence of activity indexes and cycles on rotation rate and spectral type. Open problems to be solved by future work are outlined.
A theoretical approach to measuring pilot workload
NASA Technical Reports Server (NTRS)
Kantowitz, B. H.
1984-01-01
Theoretical assumptions used by researchers in the area of attention, with emphasis upon errors and inconsistent assumptions used by some researchers were studied. Two GAT experiments, two laboratory studies and one field experiment were conducted.
Speaking of Gender Identity: Theoretical Approaches.
ERIC Educational Resources Information Center
Freedman, Susan A.
Various definitions of gender identity have ranged from recognition of one's biological sex to an individual's sense of masculinity or femininity. For the purpose of this paper, which examines some of the theoretical approaches to the subject, gender identity will be defined as "the degree to which individuals are 'aware' of and accept their…
New Theoretical Approach Integrated Education and Technology
ERIC Educational Resources Information Center
Ding, Gang
2010-01-01
The paper focuses on exploring new theoretical approach in education with development of online learning technology, from e-learning to u-learning and virtual reality technology, and points out possibilities such as constructing a new teaching ecological system, ubiquitous educational awareness with ubiquitous technology, and changing the…
Game Theoretic Approaches to Protect Cyberspace
2010-04-20
Theoretic Approaches to Protect Cyberspace 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-09-1-0752 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ...Sajjan Shiva, Dipankar Dasgupta, Qishi Wu 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME( S ...PERFORMING ORGANIZATION REPORT NUMBER CS-10-001 9. SPONSORING / MONITORING AGENCY NAME( S ) AND ADDRESS(ES) Office of Naval Research 875 North
Spinning fluids: A group theoretical approach
NASA Astrophysics Data System (ADS)
Capasso, Dario; Sarkar, Debajyoti
2014-04-01
The aim of this article is to introduce a Lagrangian formulation of relativistic non-Abelian spinning fluids in group theory language. The corresponding Mathisson-Papapetrou equation for spinning fluids in terms of the reduction limit of the de Sitter group has been proposed. The equation we find correctly boils down to the one for nonspinning fluids. Two alternative approaches based on a group theoretical formulation of particle dynamics are also explored.
Sound velocity estimation: A system theoretic approach
Candy, J.V.; Sullivan, E.J.
1993-07-30
A system-theoretic approach is proposed to investigate the feasibility of reconstructing a sound velocity profile (SVP) from acoustical hydrophone measurements. This problem is based on a state-space representation of the normal-mode propagation model. It is shown that this representation can be utilized to investigate the so-called observability of the SVP from noisy measurement data. A model-based processor is developed to extract this information and it is shown that even in cases where limited SVP information is available, the SVP can be estimated using this approach.
A decision theoretical approach for diffusion promotion
NASA Astrophysics Data System (ADS)
Ding, Fei; Liu, Yun
2009-09-01
In order to maximize cost efficiency from scarce marketing resources, marketers are facing the problem of which group of consumers to target for promotions. We propose to use a decision theoretical approach to model this strategic situation. According to one promotion model that we develop, marketers balance between probabilities of successful persuasion and the expected profits on a diffusion scale, before making their decisions. In the other promotion model, the cost for identifying influence information is considered, and marketers are allowed to ignore individual heterogeneity. We apply the proposed approach to two threshold influence models, evaluate the utility of each promotion action, and provide discussions about the best strategy. Our results show that efforts for targeting influentials or easily influenced people might be redundant under some conditions.
An information theoretic approach to pedigree reconstruction.
Almudevar, Anthony
2016-02-01
Network structure is a dominant feature of many biological systems, both at the cellular level and within natural populations. Advances in genotype and gene expression screening made over the last few decades have permitted the reconstruction of these networks. However, resolution to a single model estimate will generally not be possible, leaving open the question of the appropriate method of formal statistical inference. The nonstandard structure of the problem precludes most traditional statistical methodologies. Alternatively, a Bayesian approach provides a natural methodology for formal inference. Construction of a posterior density on the space of network structures allows formal inference regarding features of network structure using specific marginal posterior distributions. An information theoretic approach to this problem will be described, based on the Minimum Description Length principle. This leads to a Bayesian inference model based on the information content of data rather than on more commonly used probabilistic models. The approach is applied to the problem of pedigree reconstruction based on genotypic data. Using this application, it is shown how the MDL approach is able to provide a truly objective control for model complexity. A two-cohort model is used for a simulation study. The MDL approach is compared to COLONY-2, a well known pedigree reconstruction application. The study highlights the problem of genotyping error modeling. COLONY-2 requires prior error rate estimates, and its accuracy proves to be highly sensitive to these estimates. In contrast, the MDL approach does not require prior error rate estimates, and is able to accurately adjust for genotyping error across the range of models considered.
A graph theoretic approach to scene matching
NASA Technical Reports Server (NTRS)
Ranganath, Heggere S.; Chipman, Laure J.
1991-01-01
The ability to match two scenes is a fundamental requirement in a variety of computer vision tasks. A graph theoretic approach to inexact scene matching is presented which is useful in dealing with problems due to imperfect image segmentation. A scene is described by a set of graphs, with nodes representing objects and arcs representing relationships between objects. Each node has a set of values representing the relations between pairs of objects, such as angle, adjacency, or distance. With this method of scene representation, the task in scene matching is to match two sets of graphs. Because of segmentation errors, variations in camera angle, illumination, and other conditions, an exact match between the sets of observed and stored graphs is usually not possible. In the developed approach, the problem is represented as an association graph, in which each node represents a possible mapping of an observed region to a stored object, and each arc represents the compatibility of two mappings. Nodes and arcs have weights indicating the merit or a region-object mapping and the degree of compatibility between two mappings. A match between the two graphs corresponds to a clique, or fully connected subgraph, in the association graph. The task is to find the clique that represents the best match. Fuzzy relaxation is used to update the node weights using the contextual information contained in the arcs and neighboring nodes. This simplifies the evaluation of cliques. A method of handling oversegmentation and undersegmentation problems is also presented. The approach is tested with a set of realistic images which exhibit many types of sementation errors.
Approaching nanoscale oxides: models and theoretical methods.
Bromley, Stefan T; Moreira, Ibério de P R; Neyman, Konstantin M; Illas, Francesc
2009-09-01
This tutorial review deals with the rapidly developing area of modelling oxide materials at the nanoscale. Top-down and bottom-up modelling approaches and currently used theoretical methods are discussed with the help of a selection of case studies. We show that the critical oxide nanoparticle size required to be beyond the scale where every atom counts to where structural and chemical properties are essentially bulk-like (the scalable regime) strongly depends on the structural and chemical parameters of the material under consideration. This oxide-dependent behaviour with respect to size has fundamental implications with respect to their modelling. Strongly ionic materials such as MgO and CeO(2), for example, start to exhibit scalable-to-bulk crystallite-like characteristics for nanoparticles consisting of about 100 ions. For such systems there exists an overlap in nanoparticle size where both top-down and bottom-up theoretical techniques can be applied and the main problem is the choice of the most suitable computational method. However, for more covalent systems such TiO(2) or SiO(2) the onset of the scalable regime is still unclear and for intermediate sized nanoparticles there exists a gap where neither bottom-up nor top-down modelling are fully adequate. In such difficult cases new efforts to design adequate models are required. Further exacerbating these fundamental methodological concerns are oxide nanosystems exhibiting complex electronic and magnetic behaviour. Due to the need for a simultaneous accurate treatment of the atomistic, electronic and spin degrees of freedom for such systems, the top-down vs. bottom-up separation is still large, and only few studies currently exist.
Information-theoretic approach to interactive learning
NASA Astrophysics Data System (ADS)
Still, S.
2009-01-01
The principles of statistical mechanics and information theory play an important role in learning and have inspired both theory and the design of numerous machine learning algorithms. The new aspect in this paper is a focus on integrating feedback from the learner. A quantitative approach to interactive learning and adaptive behavior is proposed, integrating model- and decision-making into one theoretical framework. This paper follows simple principles by requiring that the observer's world model and action policy should result in maximal predictive power at minimal complexity. Classes of optimal action policies and of optimal models are derived from an objective function that reflects this trade-off between prediction and complexity. The resulting optimal models then summarize, at different levels of abstraction, the process's causal organization in the presence of the learner's actions. A fundamental consequence of the proposed principle is that the learner's optimal action policies balance exploration and control as an emerging property. Interestingly, the explorative component is present in the absence of policy randomness, i.e. in the optimal deterministic behavior. This is a direct result of requiring maximal predictive power in the presence of feedback.
Potential theoretic methods for far field sound radiation calculations
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.
1995-01-01
In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.
Theoretical and observational analysis of spacecraft fields
NASA Technical Reports Server (NTRS)
Neubauer, F. M.; Schatten, K. H.
1972-01-01
In order to investigate the nondipolar contributions of spacecraft magnetic fields a simple magnetic field model is proposed. This model consists of randomly oriented dipoles in a given volume. Two sets of formulas are presented which give the rms-multipole field components, for isotropic orientations of the dipoles at given positions and for isotropic orientations of the dipoles distributed uniformly throughout a cube or sphere. The statistical results for an 8 cu m cube together with individual examples computed numerically show the following features: Beyond about 2 to 3 m distance from the center of the cube, the field is dominated by an equivalent dipole. The magnitude of the magnetic moment of the dipolar part is approximated by an expression for equal magnetic moments or generally by the Pythagorean sum of the dipole moments. The radial component is generally greater than either of the transverse components for the dipole portion as well as for the nondipolar field contributions.
Child Language Acquisition: Contrasting Theoretical Approaches
ERIC Educational Resources Information Center
Ambridge, Ben; Lieven, Elena V. M.
2011-01-01
Is children's language acquisition based on innate linguistic structures or built from cognitive and communicative skills? This book summarises the major theoretical debates in all of the core domains of child language acquisition research (phonology, word-learning, inflectional morphology, syntax and binding) and includes a complete introduction…
Preferences for Three Theoretically Derived Counseling Approaches
ERIC Educational Resources Information Center
Holen, Michael C.; Kinsey, William M.
1975-01-01
This study examined differences in potential-client preference and believed effectiveness for counseling approaches. Analyses of responses to randomly ordered same-client, same-problem tapes of each approach indicated that the behavioral approach was significantly more highly preferred and believed more effective than either the client-centered or…
Experimental and theoretical approaches to conscious processing.
Dehaene, Stanislas; Changeux, Jean-Pierre
2011-04-28
Recent experimental studies and theoretical models have begun to address the challenge of establishing a causal link between subjective conscious experience and measurable neuronal activity. The present review focuses on the well-delimited issue of how an external or internal piece of information goes beyond nonconscious processing and gains access to conscious processing, a transition characterized by the existence of a reportable subjective experience. Converging neuroimaging and neurophysiological data, acquired during minimal experimental contrasts between conscious and nonconscious processing, point to objective neural measures of conscious access: late amplification of relevant sensory activity, long-distance cortico-cortical synchronization at beta and gamma frequencies, and "ignition" of a large-scale prefronto-parietal network. We compare these findings to current theoretical models of conscious processing, including the Global Neuronal Workspace (GNW) model according to which conscious access occurs when incoming information is made globally available to multiple brain systems through a network of neurons with long-range axons densely distributed in prefrontal, parieto-temporal, and cingulate cortices. The clinical implications of these results for general anesthesia, coma, vegetative state, and schizophrenia are discussed.
Planar dipolar polymer brush: field theoretical investigations
NASA Astrophysics Data System (ADS)
Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby
2015-03-01
Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.
Efficient field-theoretic simulation of polymer solutions
Villet, Michael C.; Fredrickson, Glenn H.
2014-12-14
We present several developments that facilitate the efficient field-theoretic simulation of polymers by complex Langevin sampling. A regularization scheme using finite Gaussian excluded volume interactions is used to derive a polymer solution model that appears free of ultraviolet divergences and hence is well-suited for lattice-discretized field theoretic simulation. We show that such models can exhibit ultraviolet sensitivity, a numerical pathology that dramatically increases sampling error in the continuum lattice limit, and further show that this pathology can be eliminated by appropriate model reformulation by variable transformation. We present an exponential time differencing algorithm for integrating complex Langevin equations for field theoretic simulation, and show that the algorithm exhibits excellent accuracy and stability properties for our regularized polymer model. These developments collectively enable substantially more efficient field-theoretic simulation of polymers, and illustrate the importance of simultaneously addressing analytical and numerical pathologies when implementing such computations.
Efficient field-theoretic simulation of polymer solutions.
Villet, Michael C; Fredrickson, Glenn H
2014-12-14
We present several developments that facilitate the efficient field-theoretic simulation of polymers by complex Langevin sampling. A regularization scheme using finite Gaussian excluded volume interactions is used to derive a polymer solution model that appears free of ultraviolet divergences and hence is well-suited for lattice-discretized field theoretic simulation. We show that such models can exhibit ultraviolet sensitivity, a numerical pathology that dramatically increases sampling error in the continuum lattice limit, and further show that this pathology can be eliminated by appropriate model reformulation by variable transformation. We present an exponential time differencing algorithm for integrating complex Langevin equations for field theoretic simulation, and show that the algorithm exhibits excellent accuracy and stability properties for our regularized polymer model. These developments collectively enable substantially more efficient field-theoretic simulation of polymers, and illustrate the importance of simultaneously addressing analytical and numerical pathologies when implementing such computations.
An Interpolation Theoretic Approach to Control
1994-04-11
Control 3 2.1 Causal Analytic Mappinp ....................................... 3 2.2 Causal Optimisation Problem .................................... 3...will discuss below a new approach for the approximation of Riemann mappings (conformal equivalences from simply connected sub-domains of the complex...multivariable distributed systems. (This is the most general HOO- optimisation problem.) The procedure seems to be numerically robust as evidenced by its
Understanding bimolecular machines: Theoretical and experimental approaches
NASA Astrophysics Data System (ADS)
Goler, Adam Scott
This dissertation concerns the study of two classes of molecular machines from a physical perspective: enzymes and membrane proteins. Though the functions of these classes of proteins are different, they each represent important test-beds from which new understanding can be developed by the application of different techniques. HIV1 Reverse Transcriptase is an enzyme that performs multiple functions, including reverse transcription of RNA into an RNA/DNA duplex, RNA degradation by the RNaseH domain, and synthesis of dsDNA. These functions allow for the incorporation of the retroviral genes into the host genome. Its catalytic cycle requires repeated large-scale conformational changes fundamental to its mechanism. Motivated by experimental work, these motions were studied theoretically by the application of normal mode analysis. It was observed that the lowest order modes correlate with largest amplitude (low-frequency) motion, which are most likely to be catalytically relevant. Comparisons between normal modes obtained via an elastic network model to those calculated from the essential dynamics of a series of all-atom molecular dynamics simulations show the self-consistency between these calculations. That similar conformational motions are seen between independent theoretical methods reinforces the importance of large-scale subdomain motion for the biochemical action of DNA polymerases in general. Moreover, it was observed that the major subunits of HIV1 Reverse Transcriptase interact quasi-harmonically. The 5HT3A Serotonin receptor and P2X1 receptor, by contrast, are trans-membrane proteins that function as ligand gated ion channels. Such proteins feature a central pore, which allows for the transit of ions necessary for cellular function across a membrane. The pore is opened by the ligation of binding sites on the extracellular portion of different protein subunits. In an attempt to resolve the individual subunits of these membrane proteins beyond the diffraction
Human body surface area: a theoretical approach.
Wang, Jianfeng; Hihara, Eiji
2004-04-01
Knowledge of the human body surface area has important applications in medical practice, garment design, and other engineering sizing. Therefore, it is not surprising that several expressions correlating body surface area with direct measurements of body mass and length have been reported in the literature. In the present study, based on the assumption that the exterior shape of the human body is the result of convex and concave deformations from a basic cylinder, we derive a theoretical equation minimizing body surface area (BSA) at a fixed volume (V): BSA=(9pi VL)(0.5), where L is the reference length of the body. Assuming a body density value of 1,000 kg.m(-3), the equation becomes BSA=(BM.BH/35.37)(0.5), where BSA is in square meters, BM is the body mass in kilograms, and BH is the body height in meters. BSA values calculated by means of this equation fall within +/-7% of the values obtained by means of the equations available in the literature, in the range of BSA from children to adults. It is also suggested that the above equation, which is obtained by minimizing the outer body surface at a fixed volume, implies a fundamental relation set by the geometrical constraints governing the growth and the development of the human body.
A graph theoretical approach to data fusion
Žurauskienė, Justina; Kirk, Paul D.W.; Stumpf, Michael P.H.
2016-01-01
The rapid development of high throughput experimental techniques has resulted in a growing diversity of genomic datasets being produced and requiring analysis. Therefore, it is increasingly being recognized that we can gain deeper understanding about underlying biology by combining the insights obtained from multiple, diverse datasets. Thus we propose a novel scalable computational approach to unsupervised data fusion. Our technique exploits network representations of the data to identify similarities among the datasets. We may work within the Bayesian formalism, using Bayesian nonparametric approaches to model each dataset; or (for fast, approximate, and massive scale data fusion) can naturally switch to more heuristic modeling techniques. An advantage of the proposed approach is that each dataset can initially be modeled independently (in parallel), before applying a fast post-processing step to perform data integration. This allows us to incorporate new experimental data in an online fashion, without having to rerun all of the analysis. We first demonstrate the applicability of our tool on artificial data, and then on examples from the literature, which include yeast cell cycle, breast cancer and sporadic inclusion body myositis datasets. PMID:26992203
A graph theoretical approach to data fusion.
Žurauskienė, Justina; Kirk, Paul D W; Stumpf, Michael P H
2016-04-01
The rapid development of high throughput experimental techniques has resulted in a growing diversity of genomic datasets being produced and requiring analysis. Therefore, it is increasingly being recognized that we can gain deeper understanding about underlying biology by combining the insights obtained from multiple, diverse datasets. Thus we propose a novel scalable computational approach to unsupervised data fusion. Our technique exploits network representations of the data to identify similarities among the datasets. We may work within the Bayesian formalism, using Bayesian nonparametric approaches to model each dataset; or (for fast, approximate, and massive scale data fusion) can naturally switch to more heuristic modeling techniques. An advantage of the proposed approach is that each dataset can initially be modeled independently (in parallel), before applying a fast post-processing step to perform data integration. This allows us to incorporate new experimental data in an online fashion, without having to rerun all of the analysis. We first demonstrate the applicability of our tool on artificial data, and then on examples from the literature, which include yeast cell cycle, breast cancer and sporadic inclusion body myositis datasets.
Information theoretic approaches to multidimensional neural computations
NASA Astrophysics Data System (ADS)
Fitzgerald, Jeffrey D.
Many systems in nature process information by transforming inputs from their environments into observable output states. These systems are often difficult to study because they are performing computations on multidimensional inputs with many degrees of freedom using highly nonlinear functions. The work presented in this dissertation deals with some of the issues involved with characterizing real-world input/output systems and understanding the properties of idealized systems using information theoretic methods. Using the principle of maximum entropy, a family of models are created that are consistent with certain measurable correlations from an input/output dataset but are maximally unbiased in all other respects, thereby eliminating all unjustified assumptions about the computation. In certain cases, including spiking neurons, we show that these models also minimize the mutual information. This property gives one the advantage of being able to identify the relevant input/output statistics by calculating their information content. We argue that these maximum entropy models provide a much needed quantitative framework for characterizing and understanding sensory processing neurons that are selective for multiple stimulus features. To demonstrate their usefulness, these ideas are applied to neural recordings from macaque retina and thalamus. These neurons, which primarily respond to two stimulus features, are shown to be well described using only first and second order statistics, indicating that their firing rates encode information about stimulus correlations. In addition to modeling multi-feature computations in the relevant feature space, we also show that maximum entropy models are capable of discovering the relevant feature space themselves. This technique overcomes the disadvantages of two commonly used dimensionality reduction methods and is explored using several simulated neurons, as well as retinal and thalamic recordings. Finally, we ask how neurons in a
Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo
2016-01-14
A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and
Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo
2016-01-14
A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and
Jamming in Mobile Networks: A Game-Theoretic Approach
2013-03-01
general treatment of multiplayer differential games was presented by Starr and Ho [16], Leitmann [36], Vaisbord and Zhukovskiy [65], Zhukovskiy and...REPORT Jamming in mobile networks: A game -theoretic approach. 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: In this paper, we address the problem of...model the intrusion as a pursuit-evasion game between a mobile jammer and a team of agents. First, we consider a differential game -theoretic approach
Biosensor commercialization strategy - a theoretical approach.
Lin, Chin-Tsai; Wang, Su-Man
2005-01-01
Biosensors are analytical devices, which use biological interactions to provide either qualitative or quantitative results. They are extensively employed in many fields such as clinical diagnosis and biomedicine, military applications, anti-terrorism, farm, garden and veterinary analysis, process control, fermentation control and analysis, pharmaceutical and drug analysis, food and drink production and analysis, pollution control and monitoring, microbiology, bacterial and viral analysis, mining, and industrial and toxic gases. The biosensor market has significantly increased and will be mushrooming in the next decade. The total biosensor market is estimated to be 10.8 billion dollars by 2007. The emerging biosensor market presents both opportunities and obstacles to start-up biosensor entrepreneurs. The major challenge and threat for these entrepreneurs is how to predict the biosensor market and how to convert promising biosensor technology into commercialized biosensors. By adopting a simple commercialization strategy framework, we identify two key elements of biosensor commercialization strategy: excludability and complementary asset. We further divide biosensor commercialization environments into four distinct sub-environments: the Attacker's Advantage, Reputation-Based Idea Trading, Greenfield Competition and Ideas Factories. This paper explains how the interaction between these two key elements shapes biosensor commercialization strategy and biosensor industry dynamics. This paper also discusses alternative commercialization strategies for each specific commercialization environment and how to choose from these alternatives. The analysis of this study further provides a good reference for start-up biosensor entrepreneurs to formulate effective biosensor commercialization strategy.
Theoretical approaches to lightness and perception.
Gilchrist, Alan
2015-01-01
a better account of illusions and failures of constancy. Evidence for and against these approaches is reviewed.
Dramaturgical and Music-Theoretical Approaches to Improvisation Pedagogy
ERIC Educational Resources Information Center
Huovinen, Erkki; Tenkanen, Atte; Kuusinen, Vesa-Pekka
2011-01-01
The aim of this article is to assess the relative merits of two approaches to teaching musical improvisation: a music-theoretical approach, focusing on chords and scales, and a "dramaturgical" one, emphasizing questions of balance, variation and tension. Adult students of music pedagogy, with limited previous experience in improvisation,…
Game theoretic approach for cooperative feature extraction in camera networks
NASA Astrophysics Data System (ADS)
Redondi, Alessandro E. C.; Baroffio, Luca; Cesana, Matteo; Tagliasacchi, Marco
2016-07-01
Visual sensor networks (VSNs) consist of several camera nodes with wireless communication capabilities that can perform visual analysis tasks such as object identification, recognition, and tracking. Often, VSN deployments result in many camera nodes with overlapping fields of view. In the past, such redundancy has been exploited in two different ways: (1) to improve the accuracy/quality of the visual analysis task by exploiting multiview information or (2) to reduce the energy consumed for performing the visual task, by applying temporal scheduling techniques among the cameras. We propose a game theoretic framework based on the Nash bargaining solution to bridge the gap between the two aforementioned approaches. The key tenet of the proposed framework is for cameras to reduce the consumed energy in the analysis process by exploiting the redundancy in the reciprocal fields of view. Experimental results in both simulated and real-life scenarios confirm that the proposed scheme is able to increase the network lifetime, with a negligible loss in terms of visual analysis accuracy.
A perturbation-theoretic approach to Lagrangian flow networks
NASA Astrophysics Data System (ADS)
Fujiwara, Naoya; Kirchen, Kathrin; Donges, Jonathan F.; Donner, Reik V.
2017-03-01
Complex network approaches have been successfully applied for studying transport processes in complex systems ranging from road, railway, or airline infrastructures over industrial manufacturing to fluid dynamics. Here, we utilize a generic framework for describing the dynamics of geophysical flows such as ocean currents or atmospheric wind fields in terms of Lagrangian flow networks. In this approach, information on the passive advection of particles is transformed into a Markov chain based on transition probabilities of particles between the volume elements of a given partition of space for a fixed time step. We employ perturbation-theoretic methods to investigate the effects of modifications of transport processes in the underlying flow for three different problem classes: efficient absorption (corresponding to particle trapping or leaking), constant input of particles (with additional source terms modeling, e.g., localized contamination), and shifts of the steady state under probability mass conservation (as arising if the background flow is perturbed itself). Our results demonstrate that in all three cases, changes to the steady state solution can be analytically expressed in terms of the eigensystem of the unperturbed flow and the perturbation itself. These results are potentially relevant for developing more efficient strategies for coping with contaminations of fluid or gaseous media such as ocean and atmosphere by oil spills, radioactive substances, non-reactive chemicals, or volcanic aerosols.
An integrated theoretical and practical approach for teaching hydrogeology
NASA Astrophysics Data System (ADS)
Bonomi, Tullia; Fumagalli, Letizia; Cavallin, Angelo
2013-04-01
their limitations; C) by an evaluation process whose results contribute to the final examination, so that the students are evaluated on the basis of their ability to discuss theoretical subjects and/or projects and to resolving exercises and case studies either by hand calculations or by modelling. The applied hydrogeology examination is an example of the evaluation process. It involves development of a plan to resolve a real hydrogeological issue, such as the design of a hydraulic barrier for a landfill, the design of a well field to meet the supply requirements of a muncipality, or the control of possible seepage from a contaminated site close to to sensitive discharge features such as wells, springs, rivers. The students are allowed to work on computers for three consecutive mornings for a total 15 hours, and in the end are required to produce a technical report and a hydrogeological model. Obviously their solutions are neither unique nor completely optimized (just as in the real world), but the comparisons and debates among the students are important portals to learning and improvement. A second example: the groundwater pollution and remediation examination is based on the discussion of a remediation project elaborated in stages during the course, with the addition of increasing complex types of data and information. The students have one hour a week, during the course, to submit to the teacher their analysis of the problem and possible solutions. In ten years of experience all students have considered this method of examination a challenge, and found it engaging and helpful, even if unusual, at least in Italy. The University of Milano Bicocca has recently drilled a piezometric well both to monitor the flow of groundwater and to allow students to perform aquifer tests and to conduct standard groundwater sampling procedure, without any longer needing to rely on outside private donors for access to a field site. The overall approach, which includes, lectures
Approach to Mars Field Geology
NASA Technical Reports Server (NTRS)
Muehlberger, William; Rice, James W.; Parker, Timothy; Lipps, Jere H.; Hoffman, Paul; Burchfiel, Clark; Brasier, Martin
1998-01-01
The goals of field study on Mars are nothing less than to understand the processes and history of the planet at whatever level of detail is necessary. A manned mission gives us an unprecedented opportunity to use the immense power of the human mind to comprehend Mars in extraordinary detail. To take advantage of this opportunity, it is important to examine how we should approach the field study of Mars. In this effort, we are guided by over 200 years of field exploration experience on Earth as well as six manned missions exploring the Moon.
Theoretical Approaches to Disability Content in Social Work Education.
ERIC Educational Resources Information Center
Gilson, Stephen French; DePoy, Elizabeth
2002-01-01
Analyzes disability theory and content in the social work curriculum and advances a theoretically expansive approach to disability that is consistent with social work's commitment to diversity and the elimination of oppression. Suggests shifting disability content from an emphasis on individual deficiency toward addressing disability as the…
The Feminist Supervision Scale: A Rational/Theoretical Approach
ERIC Educational Resources Information Center
Szymanski, Dawn M.
2003-01-01
This article reports the development and psychometric properties of the Feminist Supervision Scale (FSS), a new scale designed to assess feminist supervision practices in clinical supervision. This 32-item measure was developed using a rational/theoretical approach of test construction and includes four subscales: (a) collaborative relationships,…
A queer-theoretical approach to community health psychology.
Easpaig, Bróna R Nic Giolla; Fryer, David M; Linn, Seònaid E; Humphrey, Rhianna H
2014-01-01
Queer-theoretical resources offer ways of productively rethinking how central concepts such as 'person-context', 'identity' and 'difference' may be understood for community health psychologists. This would require going beyond consideration of the problems with which queer theory is popularly associated to cautiously engage with the aspects of this work relevant to the promotion of collective practice and engaging with processes of marginalisation. In this article, we will draw upon and illustrate the queer-theoretical concepts of 'performativity' and 'cultural intelligibility' before moving towards a preliminary mapping of what a queer-informed approach to community health psychology might involve.
Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use
NASA Astrophysics Data System (ADS)
Knoepfel, Heinz E.
2000-06-01
A unique resource for physicists and engineers working with magnetic fields An understanding of magnetic phenomena is essential for anyone working on the practical application of electromagnetic theory. Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use provides physicists and engineers with a thorough treatment of the magnetic aspects of classical electromagnetic theory, focusing on key issues and problems arising in the generation and application of magnetic fields. From magnetic potentials and diffusion phenomena to magnetohydrodynamics and properties of matter-topics are carefully selected for their relevance to the theoretical framework as well as current technologies. Outstanding in its organization, clarity, and scope, Magnetic Fields: Examines a wide range of practical problems, from magnetomechanical devices to magnetic acceleration mechanisms Opens each chapter with reference to pertinent engineering examples Provides sufficient detail enabling readers to follow the derivation of the results Discusses solution methods and their application to different problems Includes more than 300 graphs, 40 tables, 2,000 numbered formulas, and extensive references to the professional literature Reviews the essential mathematics in the appendices
Aircraft Control Strategies by Game Theoretic Approach against Wind Shear
NASA Astrophysics Data System (ADS)
Yamaguchi, Masahiro; Umemura, Akira
The safety problem of aircraft that encounters wind shear during the final approach flight phase is addressed using a game theoretic approach. The game consists of two players, an aircraft and wind shear. The control scheme is composed of non-cooperative game between players. In the game, aircraft tries to fly to avoid crashing to ground and down burst attempts to force the aircraft to crash. A new control strategy based on nonlinear receding horizon control is applied to the game. It is shown by simulation that this control strategy is effective against wind shear.
Field-theoretic simulations of random copolymers with structural rigidity.
Mao, Shifan; MacPherson, Quinn; Qin, Jian; Spakowitz, Andrew J
2017-04-12
Copolymers play an important role in a range of soft-materials applications and biological phenomena. Prevalent works on block copolymer phase behavior use flexible chain models and incorporate interactions using a mean-field approximation. However, when phase separation takes place on length scales comparable to a few monomers, the structural rigidity of the monomers becomes important. In addition, concentration fluctuations become significant at short length scales, rendering the mean-field approximation invalid. In this work, we use simulation to address the role of finite monomer rigidity and concentration fluctuations in microphase segregation of random copolymers. Using a field-theoretic Monte-Carlo simulation of semiflexible polymers with random chemical sequences, we generate phase diagrams for random copolymers. We find that the melt morphology of random copolymers strongly depends on chain flexibility and chemical sequence correlation. Chemically anti-correlated copolymers undergo first-order phase transitions to local lamellar structures. With increasing degree of chemical correlation, this first-order phase transition is softened, and melts form microphases with irregular shaped domains. Our simulations in the homogeneous phase exhibit agreement with the density-density correlation from mean-field theory. However, conditions near a phase transition result in deviations between simulation and mean-field theory for the density-density correlation and the critical wavemode. Chain rigidity and sequence randomness lead to frustration in the segregated phase, introducing heterogeneity in the resulting morphologies.
New theoretical and experimental approaches on maternal motivation in mammals.
Olazábal, Daniel E; Pereira, Mariana; Agrati, Daniella; Ferreira, Annabel; Fleming, Alison S; González-Mariscal, Gabriela; Lévy, Frederic; Lucion, Aldo B; Morrell, Joan I; Numan, Michael; Uriarte, Natalia
2013-09-01
Maternal behavior is expressed in different modalities, physiological conditions, and contexts. It is the result of a highly motivated brain, that allows the female to flexibily adapt her caring activities to different situations and social demands. To understand how mothers coordinate maternal and other motivated behaviors we discuss the limitations of current theoretical approaches to study maternal motivation (e.g. distinction between appetitive and consummatory behaviors), and propose a different approach (i.e. motorically active vs. passive motivations) and a distinction between maternal motivated state and maternal motivated behaviors. We review the evidence supporting dopamine mediation of maternal motivation and describe how different phases of the dopaminergic response - basal, tonic, and phasic release in the nucleus accumbens - relate to increased salience, invigorating behavior, and behavioral switching. The existing and new experimental paradigms to investigate maternal motivation, and its coexpression and coordination with other social or non-social motivations are also analyzed. An example of how specificity of motivational systems (e.g. maternal and sexual behavior at postpartum estrus) could be processed at the neural level is also provided. This revision offers new theoretical and experimental approaches to address the fundamental question of how mothers flexibly adapt and coordinate the different components of maternal behavior with other motivated behaviors, also critical for the survival of the species.
Theoretical Approach to Electroresistance in Ferroelectric Tunnel Junctions
NASA Astrophysics Data System (ADS)
Chang, Sou-Chi; Naeemi, Azad; Nikonov, Dmitri E.; Gruverman, Alexei
2017-02-01
In this paper, a theoretical approach comprising the nonequilibrium Green's function method for electronic transport and the Landau-Khalatnikov equation for electric polarization dynamics is presented to describe polarization-dependent tunneling electroresistance (TER) in ferroelectric tunnel junctions. Using appropriate contact, interface, and ferroelectric parameters, the measured current-voltage characteristic curves in both inorganic (Co /BaTi O3/La0.67Sr0.33 MnO3 ) and organic (Au /PVDF /W ) ferroelectric tunnel junctions can be well described by the proposed approach. Furthermore, under this theoretical framework, the controversy of opposite TER signs observed experimentally by different groups in Co /BaTi O3/La0.67Sr0.33 MnO3 systems is addressed by considering the interface termination effects using the effective contact ratio defined through the effective screening length and dielectric response at the metal-ferroelectric interfaces. Finally, our approach is extended to investigate the role of a CoOx buffer layer at the Co /BaTi O3 interface in a ferroelectric tunnel memristor. It is shown that in order to have a significant memristor behavior not only the interface oxygen vacancies but also the CoOx layer thickness may vary with the applied bias.
ELECTRON HOLOGRAPHY OF ELECTROMAGNETIC FIELDS - RECENT THEORETICAL ADVANCES.
BELEGGIA,M.; POZZI, G.; TONOMURA, A.
2007-01-01
It has been shown in this work that the Fourier space approach can be fruitfully applied to the calculation of the fields and the associated electron optical phase shift of several magnetic and electrostatic structures, like superconducting vortices in conventional and high-T{sub c} superconductors, reverse biased p-n junctions, magnetic domains and nanoparticles. In all these cases, this novel approach has led to unexpected but extremely interesting results, very often expressed in analytical form, which allow the quantitative and reliable interpretation of the experimental data collected by means of electron holography or of more conventional Lorentz microscopy techniques. Moreover, it is worth recalling that whenever long-range electromagnetic fields are involved, a physical model of the object under investigation is necessary in order to take into account correctly the perturbation of the reference wave induced by the tail of the field protruding into the vacuum. For these reasons, we believe that the Fourier space approach for phase computations we have introduced and discussed in this chapter will represent an invaluable tool for the investigation of electromagnetic fields at the meso- and nano-scale.
Considering children and health literacy: a theoretical approach.
Borzekowski, Dina L G
2009-11-01
The theoretical approaches of Paulo Freire, Jean Piaget, and Lev Vygotsky frame the consideration of children and health literacy. This article includes a general discussion of literacy from the Freirian perspective. A definition of health literacy is then presented; first, the established meaning is introduced, but then a Freirian extension is proposed. Next, the theories of cognitive development by Piaget and Vygotsky are discussed, and examples related to children's health literacy are given. Finally, there is a discussion of why it is important to encourage and enable health literacy among children and adolescents.
Theoretical Description of Teaching-Learning Processes: A Multidisciplinary Approach
NASA Astrophysics Data System (ADS)
Bordogna, Clelia M.; Albano, Ezequiel V.
2001-09-01
A multidisciplinary approach based on concepts from sociology, educational psychology, statistical physics, and computational science is developed for the theoretical description of teaching-learning processes that take place in the classroom. The emerging model is consistent with well-established empirical results, such as the higher achievements reached working in collaborative groups and the influence of the structure of the group on the achievements of the individuals. Furthermore, another social learning process that takes place in massive interactions among individuals via the Internet is also investigated.
Theoretical description of teaching-learning processes: a multidisciplinary approach.
Bordogna, C M; Albano, E V
2001-09-10
A multidisciplinary approach based on concepts from sociology, educational psychology, statistical physics, and computational science is developed for the theoretical description of teaching-learning processes that take place in the classroom. The emerging model is consistent with well-established empirical results, such as the higher achievements reached working in collaborative groups and the influence of the structure of the group on the achievements of the individuals. Furthermore, another social learning process that takes place in massive interactions among individuals via the Internet is also investigated.
Computational approach for calculating bound states in quantum field theory
NASA Astrophysics Data System (ADS)
Lv, Q. Z.; Norris, S.; Brennan, R.; Stefanovich, E.; Su, Q.; Grobe, R.
2016-09-01
We propose a nonperturbative approach to calculate bound-state energies and wave functions for quantum field theoretical models. It is based on the direct diagonalization of the corresponding quantum field theoretical Hamiltonian in an effectively discretized and truncated Hilbert space. We illustrate this approach for a Yukawa-like interaction between fermions and bosons in one spatial dimension and show where it agrees with the traditional method based on the potential picture and where it deviates due to recoil and radiative corrections. This method permits us also to obtain some insight into the spatial characteristics of the distribution of the fermions in the ground state, such as the bremsstrahlung-induced widening.
Theoretical, Methodological, and Empirical Approaches to Cost Savings: A Compendium
M Weimar
1998-12-10
This publication summarizes and contains the original documentation for understanding why the U.S. Department of Energy's (DOE's) privatization approach provides cost savings and the different approaches that could be used in calculating cost savings for the Tank Waste Remediation System (TWRS) Phase I contract. The initial section summarizes the approaches in the different papers. The appendices are the individual source papers which have been reviewed by individuals outside of the Pacific Northwest National Laboratory and the TWRS Program. Appendix A provides a theoretical basis for and estimate of the level of savings that can be" obtained from a fixed-priced contract with performance risk maintained by the contractor. Appendix B provides the methodology for determining cost savings when comparing a fixed-priced contractor with a Management and Operations (M&O) contractor (cost-plus contractor). Appendix C summarizes the economic model used to calculate cost savings and provides hypothetical output from preliminary calculations. Appendix D provides the summary of the approach for the DOE-Richland Operations Office (RL) estimate of the M&O contractor to perform the same work as BNFL Inc. Appendix E contains information on cost growth and per metric ton of glass costs for high-level waste at two other DOE sites, West Valley and Savannah River. Appendix F addresses a risk allocation analysis of the BNFL proposal that indicates,that the current approach is still better than the alternative.
A bilevel game theoretic approach to optimum design of flywheels
NASA Astrophysics Data System (ADS)
Ghotbi, Ehsan; Dhingra, Anoop K.
2012-11-01
Multiobjective optimization problems arise frequently in mechanical design. One approach to solving these types of problems is to use a game theoretic formulation. This article illustrates the application of a bilevel, leader-follower model for solving an optimum design problem. In particular, the optimization problem is modelled as a Stackelberg game. The partitioning of variables between the leader and follower problem is discussed and a variable partitioning metric is introduced to compare various variable partitions. A computational procedure based on variable updating using sensitivity information is developed for exchanging information between the follower and leader problems. The proposed approach is illustrated through the design of a flywheel. The two objective functions used for the design problem include maximizing the kinetic energy stored in the flywheel while simultaneously minimizing the manufacturing cost.
Theoretical approach to photoinduced inhomogeneous anisotropy in bacteriorhodopsin films.
Acebal, P; Carretero, L; Blaya, S; Murciano, A; Fimia, A
2007-07-01
The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance was found between both sets of data. The theoretical approach shows that the values of the rate constants for solid bR films are about two or three orders of magnitude lower than those observed in solution. It can also be noted that the temperature change during the experiment had a great influence on the final values of transmittance and, consequently, on the inhomogeneous distribution along the coordinate of light propagation. The study shows that, depending on the intensity and wavelength of the pump beam, we can obtain a very inhomogeneous profile of the population densities, which implies an inhomogeneous profile of the birefringence and dichroism. Therefore, this must be taken into account in the applications described for this system.
Theoretical analysis of magnetic field interactions with aortic blood flow
Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.
1996-04-01
The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.
We need theoretical physics approaches to study living systems
NASA Astrophysics Data System (ADS)
Blagoev, Krastan B.; Shukla, Kamal; affil="3" >Herbert Levine,
2013-08-01
Living systems, as created initially by the transition from assemblies of large molecules to self-reproducing information-rich cells, have for centuries been studied via the empirical toolkit of biology. This has been a highly successful enterprise, bringing us from the vague non-scientific notions of vitalism to the modern appreciation of the biophysical and biochemical bases of life. Yet, the truly mind-boggling complexity of even the simplest self-sufficient cells, let alone the emergence of multicellular organisms, of brain and consciousness, and to ecological communities and human civilizations, calls out for a complementary approach. In this editorial, we propose that theoretical physics can play an essential role in making sense of living matter. When faced with a highly complex system, a physicist builds simplified models. Quoting Philip W Anderson's Nobel prize address, 'the art of model-building is the exclusion of real but irrelevant parts of the problem and entails hazards for the builder and the reader. The builder may leave out something genuinely relevant and the reader, armed with too sophisticated an experimental probe, may take literally a schematized model. Very often such a simplified model throws more light on the real working of nature....' In his formulation, the job of a theorist is to get at the crux of the system by ignoring details and yet to find a testable consequence of the resulting simple picture. This is rather different than the predilection of the applied mathematician who wants to include all the known details in the hope of a quantitative simulacrum of reality. These efforts may be practically useful, but do not usually lead to increased understanding. To illustrate how this works, we can look at a non-living example of complex behavior that was afforded by spatiotemporal patterning in the Belousov-Zhabotinsky reaction [1]. Physicists who worked on this system did not attempt to determine all the relevant chemical intermediates
Takahashi, Kazunori; Charles, Christine; Boswell, Rod W
2013-05-10
Cross-field diffusion and plasma expansion in a rapidly diverging magnetic nozzle are controlled while maintaining constant plasma production in a contiguously attached radio frequency plasma source. It is demonstrated that the measured electron-diamagnetic-induced axial momentum increases with increasing magnetic field strength to approach the theoretical limit derived using an ideal nozzle approximation. The measured axial momentum exerted onto the axial and radial plasma source boundaries validate the prediction from a maximum electron pressure model on the back wall and from a zero net axial momentum model on the radial wall.
GTA: a game theoretic approach to identifying cancer subnetwork markers.
Farahmand, S; Goliaei, S; Ansari-Pour, N; Razaghi-Moghadam, Z
2016-03-01
The identification of genetic markers (e.g. genes, pathways and subnetworks) for cancer has been one of the most challenging research areas in recent years. A subset of these studies attempt to analyze genome-wide expression profiles to identify markers with high reliability and reusability across independent whole-transcriptome microarray datasets. Therefore, the functional relationships of genes are integrated with their expression data. However, for a more accurate representation of the functional relationships among genes, utilization of the protein-protein interaction network (PPIN) seems to be necessary. Herein, a novel game theoretic approach (GTA) is proposed for the identification of cancer subnetwork markers by integrating genome-wide expression profiles and PPIN. The GTA method was applied to three distinct whole-transcriptome breast cancer datasets to identify the subnetwork markers associated with metastasis. To evaluate the performance of our approach, the identified subnetwork markers were compared with gene-based, pathway-based and network-based markers. We show that GTA is not only capable of identifying robust metastatic markers, it also provides a higher classification performance. In addition, based on these GTA-based subnetworks, we identified a new bonafide candidate gene for breast cancer susceptibility.
Theoretical investigation of bacteria polarizability under direct current electric fields.
Dingari, Naga Neehar; Buie, Cullen R
2014-04-22
We present a theoretical model to investigate the influence of soft polyelectrolyte layers on bacteria polarizability. We resolve soft-layer electrokinetics by considering the pH-dependent dissociation of ionogenic groups and specific interactions of ionogenic groups with the bulk electrolyte to go beyond approximating soft-layer electrokinetics as surface conduction. We model the electrokinetics around a soft particle by modified Poisson-Nernst-Planck equations (PNP) to account for the effects of ion transport in the soft layer and electric double layer. Fluid flow is modeled by modified Stokes equations accounting for soft-layer permeability. Two test cases are presented to demonstrate our model: fibrillated and unfibrillated Streptococcus salivarius bacteria. We show that electrolytic and pH conditions significantly influence the extent of soft-particle polarizability in dc fields. Comparison with an approximate analytical model based on Dukhin-Shilov theory for soft particles shows the importance of resolving soft-layer electrokinetics. Insights from this study can be useful in understanding the parameters that influence soft-particle dielectrophoresis in lab-on-a-chip devices.
Intelligent cognitive radio jamming - a game-theoretical approach
NASA Astrophysics Data System (ADS)
Dabcevic, Kresimir; Betancourt, Alejandro; Marcenaro, Lucio; Regazzoni, Carlo S.
2014-12-01
Cognitive radio (CR) promises to be a solution for the spectrum underutilization problems. However, security issues pertaining to cognitive radio technology are still an understudied topic. One of the prevailing such issues are intelligent radio frequency (RF) jamming attacks, where adversaries are able to exploit on-the-fly reconfigurability potentials and learning mechanisms of cognitive radios in order to devise and deploy advanced jamming tactics. In this paper, we use a game-theoretical approach to analyze jamming/anti-jamming behavior between cognitive radio systems. A non-zero-sum game with incomplete information on an opponent's strategy and payoff is modelled as an extension of Markov decision process (MDP). Learning algorithms based on adaptive payoff play and fictitious play are considered. A combination of frequency hopping and power alteration is deployed as an anti-jamming scheme. A real-life software-defined radio (SDR) platform is used in order to perform measurements useful for quantifying the jamming impacts, as well as to infer relevant hardware-related properties. Results of these measurements are then used as parameters for the modelled jamming/anti-jamming game and are compared to the Nash equilibrium of the game. Simulation results indicate, among other, the benefit provided to the jammer when it is employed with the spectrum sensing algorithm in proactive frequency hopping and power alteration schemes.
A novel theoretical approach to the analysis of dendritic transients.
Agmon-Snir, H
1995-01-01
A novel theoretical framework for analyzing dendritic transients is introduced. This approach, called the method of moments, is an extension of Rall's cable theory for dendrites. It provides analytic investigation of voltage attenuation, signal delay, and synchronization problems in passive dendritic trees. In this method, the various moments of a transient signal are used to characterize the properties of the transient. The strength of the signal is measured by the time integral of the signal, its characteristic time is determined by its centroid ("center of gravity"), and the width of the signal is determined by a measure similar to the standard deviation in probability theory. Using these signal properties, the method of moments provides theorems, expressions, and efficient algorithms for analyzing the voltage response in arbitrary passive trees. The method yields new insights into spatiotemporal integration, coincidence detection mechanisms, and the properties of local interactions between synaptic inputs in dendritic trees. The method can also be used for matching dendritic neuron models to experimental data and for the analysis of synaptic inputs recorded experimentally. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 10 PMID:8580308
Postionization fragmentation of rare-gas trimers revisited with new theoretical approaches
NASA Astrophysics Data System (ADS)
Janeček, Ivan; Cintavá, Silvie; Hrivňák, Daniel; Kalus, René; Fárník, Michal; Gadea, Florent Xavier
2009-09-01
A new theoretical approach is presented for the general treatment of nonadiabatic hybrid dynamics (mixing classical and quantum approach) and applied to the postionization of rare-gas trimers. There was an important disagreement between trajectory surface hopping (TSH) or mean field (MF) approaches and the experimental results; noteworthy, with the new method qualitative and almost quantitative agreement is found for the fragmentation ratios of ionic monomers and dimers. For the first time in the theory as in the experiment, the dimers prevail for argon while monomers strongly dominate for the heavier rare gases, krypton and xenon. A new compromise between MF and TSH approaches is proposed and the new method is found quite robust with results not too sensitive to various possible implementations.
A choice-semantical approach to theoretical truth.
Andreas, Holger; Schiemer, Georg
2016-08-01
A central topic in the logic of science concerns the proper semantic analysis of theoretical sentences, that is sentences containing theoretical terms. In this paper, we present a novel choice-semantical account of theoretical truth based on the epsilon-term definition of theoretical terms. Specifically, we develop two ways of specifying the truth conditions of theoretical statements in a choice functional semantics, each giving rise to a corresponding logic of such statements. In order to investigate the inferential strength of these logical systems, we provide a translation of each truth definition into a modal definition of theoretical truth. Based on this, we show that the stronger notion of choice-semantical truth captures more adequately our informal semantic understanding of scientific statements.
An Information Theoretic Approach to Distributed Inference and Learning
1992-10-01
recreate realistic dynamics of Hebbian learning in VLSI using switched capacitor circuits for delayed dendritic connections and synapses. Neural activ...words) The work has focused on developing information-theoretic on probabilistic models for neural network computation . This theoretical basis is then...25 7.5 Applications .......... .................................... 26 8 VLSI Implementation of Probabilistic Neural Networks 27 8.1 Pseudo
A graph-theoretic approach to modeling metabolic pathways
NASA Astrophysics Data System (ADS)
Gifford, Eric; Johnson, Mark; Tsai, Chun-che
1991-08-01
The metabolic pathways of medazepam, oxazepam, and diazepam were modeled using graph-theoretic transforms which are incorporable into computer-assisted metabolic analysis programs. The information, represented in the form of a graph-theoretic transform kit, which was obtained from these pathways was then used to predict the metabolites of other benzodiazepine compounds. The transform kits gave statistically significant predictions with respect to a statistical method for evaluating the performance of the transform kits.
NASA Astrophysics Data System (ADS)
Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.
2014-05-01
In the framework of the self-interaction-free time-dependent density functional theory, we have performed 3D ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the novel dynamical behavior of the sub-cycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of 1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the sub-cycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several new features of the sub-cycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra. This work was partially supported by DOE.
NASA Astrophysics Data System (ADS)
Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.
2015-05-01
In the framework of the self-interaction-free time-dependent density functional theory (TDDFT), we have performed an ab initio all-electron study of subcycle structure, dynamics, and spectra of high harmonic generation (HHG) processes of Ar atoms in the presence of extreme ultraviolet (XUV) attosecond pulses and near-infrared (NIR) laser fields. The TDDFT equations are solved accurately and efficiently via the time-dependent generalized pseudospectral (TDGPS) method. We focus on the subcycle (with respect to NIR field) temporal behavior of the level shift of the excited energy levels and related dynamics of harmonic photon emission. We observe and identify the subcycle shifts in the harmonic emission spectrum as a function of the time delay between the XUV and NIR pulses. We present and analyze the harmonic emission spectra from 3snp0, 3p0ns, 3p1nd1,3p1np1, 3p0nd0, 3p0np0, and 3p0ns excited states and the 3p04p0-virtual state as functions of the time delay. In addition, we explore the subcycle a.c. Stark shift phenomenon in NIR fields and its influence on the harmonic emission process. Our analysis reveals several novel features of the subcycle HHG dynamics and spectra as well as temporal energy level shift. This work was partially supported by DOE.
Illness and symptom perception: a theoretical approach towards an integrative measurement model.
Petersen, Sibylle; van den Berg, Robert A; Janssens, Thomas; Van den Bergh, Omer
2011-04-01
Several models have been proposed to conceptualize psychological representations of health, illness, and bodily sensations. These models differ as to the cognitive and affective components they include, whether they study the interaction of these components, and whether associations between psychological representations of bodily states and affective and behavioral reactions to these representations are considered conditional. These different conceptualizations and corresponding measurement approaches exist in parallel without resulting in synergistic effects or theoretical advancements within the field. In this paper, we review theoretical models on perception and attitudes and construct an integrative theoretical framework on psychological representation of bodily symptoms as well as more abstract representations of health and disease. The aim of this combination of approaches is to unify the strengths of different research domains in the conceptualization and measurement of mental representations of bodily states. Furthermore, the aim is to specify new, testable predictions and implications about the (conditional) relationship of these mental representations and affective and behavioral consequences. A core element in this integrative model is comparison. We review how comparison processes can change the cognitive and affective reference frame for illness and symptom perception and in turn affective and behavioral reactions. We discuss implications for measurement of illness and symptom representations as well as implications for clinical practice. Finally, we make suggestions for a research agenda to validate the proposed model as well as to address new questions derived from it.
Is there a weak mixed polarity background field? Theoretical arguments
NASA Technical Reports Server (NTRS)
Spruit, H. C.; Title, A. M.; Van Ballegooijen, A. A.
1987-01-01
A number of processes associated with the formation of active regions produce 'U-loops': fluxtubes having two ends at the photosphere but otherwise still embedded in the convection zone. The mass trapped on the field lines of such loops makes them behave in a qualitatively different way from the 'omega-loops' that form active regions. It is shown that U-loops will disperse though the convection zone and form a weak (down to a few gauss) field that covers a significant fraction of the solar surface. This field is tentatively identified with the inner-network fields observed at Kitt Peak and Big Bear. The process by which these fields escape through the surface is described; a remarkable property is that it can make active region fields apparently disappear in situ. The mixed polarity moving magnetic features near sunspots are interpreted as a locally intense form of this disappearance by escape of U-loops.
A Theoretical Design Approach for Passive Shimming of a Magic-Angle-Spinning NMR Magnet.
Li, Frank X; Voccio, John P; Sammartino, Michael; Ahn, Minchul; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu
2016-06-01
This paper presents a passive shimming design approach for a magic-angle-spinning (MAS) NMR magnet. In order to achieve a 1.5-T magic-angle field in NMR samples, we created two independent orthogonal magnetic vector fields by two separate coils: the dipole and solenoid. These two coils create a combined 1.5-T magnetic field vector directed at the magic angle (54.74° from the spinning axis). Additionally, the stringent magnetic field homogeneity requirement of the MAS magnet is the same as that of a solenoidal NMR magnet. The challenge for the magic-angle passive shimming design is to correct both the dipole and solenoid magnetic field spherical harmonics with one set of iron pieces, the so-called ferromagnetic shimming. Furthermore, the magnetization of the iron pieces is produced by both the dipole and solenoid coils. In our design approach, a matrix of 2 mm by 5 mm iron pieces with different thicknesses was attached to a thin-walled tube, 90-mm diameter and 40-mm high. Two sets of spherical harmonic coefficients were calculated for both the dipole and solenoid coil windings. By using the multiple-objective linear programming optimization technique and coordinate transformations, we have designed a passive shimming set that can theoretically reduce 22 lower-order spherical harmonics and improve the homogeneity of our MAS NMR magnet.
Determining Student Competency in Field Placements: An Emerging Theoretical Model
ERIC Educational Resources Information Center
Salm, Twyla L.; Johner, Randy; Luhanga, Florence
2016-01-01
This paper describes a qualitative case study that explores how twenty-three field advisors, representing three human service professions including education, nursing, and social work, experience the process of assessment with students who are struggling to meet minimum competencies in field placements. Five themes emerged from the analysis of…
Group theoretic approaches to nuclear and hadronic collective motion
Biedenharn, L.C.
1982-01-01
Three approaches to nuclear and hadronic collective motion are reviewed, compared and contrasted: the standard symmetry approach as typified by the Interacting Boson Model, the kinematic symmetry group approach of Gell-Mann and Tomonaga, and the recent direct construction by Buck. 50 references.
A combined experimental and theoretical approach to atomic scale characterization
Pennycook, S.J.; Chisholm, M.F.; Yan, Y.; Duscher, G.; Pantelides, S.T.
1998-02-01
Recently, the scanning transmission electron microscope has become capable of forming electron probes of atomic dimensions. Through the technique of Z-contrast imaging, it is now possible to form atomic resolution images with high compositional sensitivity from which atomic column positions can be directly determined. An incoherent image of this nature also allows atomic resolution chemical analysis to be performed, by locating the probe over particular columns or planes seen in the image while electron energy loss spectra are collected. Such data represents either an ideal starting point for first principles theoretical calculations or a test of theoretical predictions. The authors present several examples where theory and experiment together give a very complete and often surprising atomic scale view of complex materials.
Theoretical Studies of High Field Transport in III-V Semiconductors.
1980-09-01
AD-A123 947 THEORETICAL STUDIES OF HIGH FIELD TRANSPORT IN Ill-V- 1/2 SENXCONDUCTORS(U) ILLINOIS UNIV AT URBANA COORDINATED SCIENCE LAB H SHICHIJO...CATALOG NUMBER 4. TITLE (and Subtitleo S. TYPE Of REPORT & PERIOD COVERED THEORETICAL STUDIES OF HIGH FIELD TRANSPORT Technical Report IN IllI-V...Continue on reverse aide It necessary and identitfy by block number) High field transport , 3-5 semicopductors, Monte Carlo simulation 20. ABSTRACT
Game Theoretic Approach to Post-Docked Satellite Control
NASA Technical Reports Server (NTRS)
Hiramatsu, Takashi; Fitz-Coy, Norman G.
2007-01-01
This paper studies the interaction between two satellites after docking. In order to maintain the docked state with uncertainty in the motion of the target vehicle, a game theoretic controller with Stackelberg strategy to minimize the interaction between the satellites is considered. The small perturbation approximation leads to LQ differential game scheme, which is validated to address the docking interactions between a service vehicle and a target vehicle. The open-loop solution are compared with Nash strategy, and it is shown that less control efforts are obtained with Stackelberg strategy.
Bacterial cell division: experimental and theoretical approaches to the divisome.
Broughton, Claire E; Roper, David I; Van Den Berg, Hugo A; Rodger, Alison
2015-01-01
Cell division is a key event in the bacterial life cycle. It involves constriction at the midcell, so that one cell can give rise to two daughter cells. This constriction is mediated by a ring composed offibrous multimers of the protein FtsZ. However a host of additional factors is involved in the formation and dynamics of this "Z-ring" and this complicated apparatus is collectively known as the "divisome". We review the literature, with an emphasis on mathematical modelling, and show how such theoretical efforts have helped experimentalists to make sense of the at times bewildering data, and plan further experiments.
A new theoretical approach to adsorption desorption behavior of Ga on GaAs surfaces
NASA Astrophysics Data System (ADS)
Kangawa, Y.; Ito, T.; Taguchi, A.; Shiraishi, K.; Ohachi, T.
2001-11-01
We propose a new theoretical approach for studying adsorption-desorption behavior of atoms on semiconductor surfaces. The new theoretical approach based on the ab initio calculations incorporates the free energy of gas phase; therefore we can calculate how adsorption and desorption depends on growth temperature and beam equivalent pressure (BEP). The versatility of the new theoretical approach was confirmed by the calculation of Ga adsorption-desorption transition temperatures and transition BEPs on the GaAs (0 0 1) -(4×2) β2 Ga-rich surface. This new approach is feasible to predict how adsorption and desorption depend on the growth conditions.
Theoretical approaches to modeling interfacial structure and EXAFS data
Schenter, G.K.; McCarthy, M.I.; Chacon-Taylor, M.R.
1997-12-31
Understanding the molecular scale processes that control the fate and transport of contaminant metals through the subsurface is a key goal of molecular environmental research. Extended Xray Absorption Fine Structure (EXAFS) spectra is a powerful experimental technique for determining the structure of solvated metal ions at mineral interfaces. The interpretation of these data is aided by theoretical models of the interfacial chemistry and physics. Using ab initio based potential models and classical mechanics simulations, we are able to predict the structure of (M+)aq/mineral interfaces. We will discuss both the development of the ab initio based classical electrostatic potentials for modeling the interaction between molecules and surfaces and the simulation techniques used to model dynamical processes of ions at water/mineral interfaces. This information is then used as input for calculations of the corresponding EXAFS spectra as a function of temperature and surface topology. Theoretical predicted spectra for Na+(H2O)n clusters on MgO (001) will be presented, emphasizing trends in the observed EXAFS spectra with cluster size, temperature, and surface topology (flat surface, edge and corner MgO sites).
Lee, Hwee Kuan; Uddin, Mohammad Shorif; Sankaran, Shvetha; Hariharan, Srivats; Ahmed, Sohail
2009-07-06
Microscopy has become a de facto tool for biology. However, it suffers from a fundamental problem of poor contrast with increasing depth, as the illuminating light gets attenuated and scattered and hence can not penetrate through thick samples. The resulting decay of light intensity due to attenuation and scattering varies exponentially across the image. The classical space invariant deconvolution approaches alone are not suitable for the restoration of uneven illumination in microscopy images. In this paper, we present a novel physics-based field theoretical approach to solve the contrast degradation problem of light microscopy images. We have confirmed the effectiveness of our technique through simulations as well as through real field experimentations.
Unified Field Theoretical Models from Generalized Affine Geometries II
NASA Astrophysics Data System (ADS)
Cirilo-Lombardo, Diego Julio
2011-06-01
The space-time structure of the new Unified Field Theory presented in previous reference (Int. J. Theor. Phys. 49:1288-1301, 2010) is analyzed from its SL(2C) underlying structure in order to make precise the notion of minimal coupling. To this end, the framework is the language of tensors and particularly differential forms and the condition a priory of the existence of a potential for the torsion is relaxed. We shown trough exact cosmological solutions from this model, where the geometry is Euclidean R⊗ O 3˜ R⊗ SU(2), the relation between the space-time geometry and the structure of the gauge group. Precisely this relation is directly connected with the relation of the spin and torsion fields. The solution of this model is explicitly compared with our previous ones and we find that: (i) the torsion is not identified directly with the Yang Mills type strength field, (ii) there exists a compatibility condition connected with the identification of the gauge group with the geometric structure of the space-time: this fact lead the identification between derivatives of the scale factor a( τ) with the components of the torsion in order to allows the Hosoya-Ogura ansatz (namely, the alignment of the isospin with the frame geometry of the space-time), (iii) this compatibility condition precisely mark the fact that local gauge covariance, coordinate independence and arbitrary space time geometries are harmonious concepts and (iv) of two possible structures of the torsion the "tratorial" form (the only one studied here) forbids wormhole configurations, leading only, cosmological instanton space-time in eternal expansion.
Graph theoretical similarity approach to compare molecular electrostatic potentials.
Marín, Ray M; Aguirre, Nestor F; Daza, Edgar E
2008-01-01
In this work we introduce a graph theoretical method to compare MEPs, which is independent of molecular alignment. It is based on the edit distance of weighted rooted trees, which encode the geometrical and topological information of Negative Molecular Isopotential Surfaces. A meaningful chemical classification of a set of 46 molecules with different functional groups was achieved. Structure--activity relationships for the corticosteroid binding affinity (CBG) of 31 steroids by means of hierarchical clustering resulted in a clear partitioning in high, intermediate, and low activity groups, whereas the results from quantitative structure--activity relationships, obtained from a partial least-squares analysis, showed comparable or better cross-validated correlation coefficients than the ones reported for previous methods based solely in the MEP.
A Theoretical Approach to Engineering a New Enzyme
NASA Astrophysics Data System (ADS)
Anderson, Greg; Behera, Raghu N.; Gomatam, Ravi
2016-08-01
Density function theory, a subfield of quantum mechanics (QM), in combination with molecular mechanics (MM) has opened the way to engineer new artificial enzymes. Herein, we report theoretical calculations done using QM/MM to examine whether the regioselectivity and rate of chlorination of the enzyme chloroperoxidase can be improved by replacing the vanadium of this enzyme with niobium through dialysis. Our calculations show that a niobium substituted chloroperoxidase will be able to enter the initial steps of the catalytic cycle for chlorination. Although the protonation state of the niobium substituted enzyme is calculated to be different from than that of the natural vanadium substituted enzyme, our calculations show that the catalytic cycle can still proceed forward. Using natural bond orbitals, we analyse the electronic differences between the niobium substituted enzyme and the natural enzyme. We conclude by briefly examining how good of a model QM/MM provides for understanding the mechanism of catalysis of chloroperoxidase.
A theoretical approach on controlling agricultural pest by biological controls.
Mondal, Prasanta Kumar; Jana, Soovoojeet; Kar, T K
2014-03-01
In this paper we propose and analyze a prey-predator type dynamical system for pest control where prey population is treated as the pest. We consider two classes for the pest namely susceptible pest and infected pest and the predator population is the natural enemy of the pest. We also consider average delay for both the predation rate i.e. predation to the susceptible pest and infected pest. Considering a subsystem of original system in the absence of infection, we analyze the existence of all possible non-negative equilibria and their stability criteria for both the subsystem as well as the original system. We present the conditions for transcritical bifurcation and Hopf bifurcation in the disease free system. The theoretical evaluations are demonstrated through numerical simulations.
A game-theoretical approach to multimedia social networks security.
Liu, Enqiang; Liu, Zengliang; Shao, Fei; Zhang, Zhiyong
2014-01-01
The contents access and sharing in multimedia social networks (MSNs) mainly rely on access control models and mechanisms. Simple adoptions of security policies in the traditional access control model cannot effectively establish a trust relationship among parties. This paper proposed a novel two-party trust architecture (TPTA) to apply in a generic MSN scenario. According to the architecture, security policies are adopted through game-theoretic analyses and decisions. Based on formalized utilities of security policies and security rules, the choice of security policies in content access is described as a game between the content provider and the content requester. By the game method for the combination of security policies utility and its influences on each party's benefits, the Nash equilibrium is achieved, that is, an optimal and stable combination of security policies, to establish and enhance trust among stakeholders.
Exploring the joint measurability using an information-theoretic approach
NASA Astrophysics Data System (ADS)
Hsu, Li-Yi
2016-12-01
We explore the legal purity parameters for the joint measurements. Instead of direct unsharpening the measurements, we perform the quantum cloning before the sharp measurements. The necessary fuzziness in the unsharp measurements is equivalently introduced in the imperfect cloning process. Based on the information causality and the consequent noisy nonlocal computation, one can derive the information-theoretic quadratic inequalities that must be satisfied by any physical theory. On the other hand, to guarantee the classicality, the linear Bell-type inequalities deduced by these quadratic ones must be obeyed. As for the joint measurability, the purity parameters must be chosen to obey both types of inequalities. Finally, the quadratic inequalities for purity parameters in the joint measurability region are derived.
Molecular properties of Cinchona alkaloids: a theoretical approach.
Oleksyn, B J; Suszko-Purzycka, A; Dive, G; Lamotte-Brasseur, J
1992-02-01
In the present work, the conformation analysis, electrostatic potential calculations, and proton affinity evaluation are carried out for Cinchona alkaloids using theoretical molecular mechanics and quantum mechanical methods. The most probable conformation of the active erythro isomers at the receptor site seems to be that which enables the molecule to form intermolecular hydrogen bonds. In epiquinidine, the mutual orientation of O(12) and N(1) atoms favors intra- rather than intermolecular bonding, and this might be responsible for its inactivity. Comparison of the shape and size of the negative electrostatic potential areas provides a tentative explanation for the interaction of different erythro diastereoisomers with the same putative receptor, as well as for lack of such interaction in epiquinidine. The protonation energies calculated for cinchonidine and cinchonine confirm the higher basicity of the aliphatic N(1) as compared with that of the aromatic N(13) atom.
A Game-Theoretical Approach to Multimedia Social Networks Security
Liu, Enqiang; Liu, Zengliang; Shao, Fei; Zhang, Zhiyong
2014-01-01
The contents access and sharing in multimedia social networks (MSNs) mainly rely on access control models and mechanisms. Simple adoptions of security policies in the traditional access control model cannot effectively establish a trust relationship among parties. This paper proposed a novel two-party trust architecture (TPTA) to apply in a generic MSN scenario. According to the architecture, security policies are adopted through game-theoretic analyses and decisions. Based on formalized utilities of security policies and security rules, the choice of security policies in content access is described as a game between the content provider and the content requester. By the game method for the combination of security policies utility and its influences on each party's benefits, the Nash equilibrium is achieved, that is, an optimal and stable combination of security policies, to establish and enhance trust among stakeholders. PMID:24977226
Development of Warp Yarn Tension During Shedding: A Theoretical Approach
NASA Astrophysics Data System (ADS)
Ghosh, Subrata; Chary, Prabhakara; Roy, Sukumar
2015-10-01
Theoretical investigation on the process of development of warp yarn tension during weaving for tappet shedding is carried out, based on the dynamic nature of shed geometry. The path of warp yarn on a weaving machine is divided into four different zones. The tension developed in each zone is estimated for every minute rotation of the bottom shaft. A model has been developed based on the dynamic nature of shed geometry and the possible yarn flow from one zone to another. A computer program, based on the model of shedding process, is developed for predicting the warp yarn tension variation during shedding. The output of the model and the experimental values of yarn tension developed in zone-D i.e. between the back rest and the back lease rod are compared, which shows a good agreement between them. The warp yarn tension values predicted by the model in zone-D are 10-13 % lesser than the experimentally measured values. By analyzing the theoretical data of the peak value of developed yarn tension at four zones i.e. zone-A, zone-B, zone-C and zone-D, it is observed that the peak yarn tension value of A, B, C-zones are much higher than the peak tension near the back rest i.e. at zone-D. It is about twice or more than the yarn tension near the back rest. The study also reveals that the developed yarn tension peak values are different for the extreme positions of a heald. The impact of coefficient of friction on peak value of yarn tension is nominal.
Unified Theoretical Approach to Electron-Ion Recombination
NASA Astrophysics Data System (ADS)
Pradhan, Anil
1998-05-01
Electron-ion recombination occurs via the electron continuum and embedded resonances that are coupled to each other and thus unified in nature. However, theoretical methods generally separate the two as ``radiative recombination" (RR), referring to recombination through the non-resonant continuum, and ``di-electronic recombination" (DR) through the autoionizing resonances. A computationally unified scheme(S.N. Nahar and A.K. Pradhan, Phys.Rev.Lett.) 68,1488(1992); H.L. Zhang and A.K. Pradhan, Phys.Rev.Lett. 78,195(1997) is described that employs the coupled channel R-matrix method, and detailed balance (the Milne relation), to obtain photo-recombination cross sections including both the continuum and resonant recombination in an ab intio manner. In the energy region corresponding to high-n Rydberg resonances, where the background recombination (RR) is negligibly small, a precise theory of DR (R.H. Bell and M.J. Seaton, J.Phys.B) 18,1589(1985) yields DR collision strengths consistent with their threshold behaviour leading to the cross section for electron impact excitation. For highly charged ions the relativistic fine structure and the effect of radiation damping of resonances are considered. Theoretical cross sections agree well with recent experiments on ion stograge rings and the electron-beam-ion-trap (EBIT). Total electron-ion recombination rates can be obtained for practical applications. For many complex atomic systems, such as the important Iron-peak elements, the new results differ considerably from those hitherto available.
The Case Study Approach: Some Theoretical, Methodological and Applied Considerations
2013-06-01
investigate the implications of new initiatives such as total quality management and learning organisation concepts that were implemented in five...2000) to determine the extent to which total quality management and learning organisation change strategies are mutually sustaining practices. In their...study, the researchers included five Australian companies that have established practices in the total quality management field. Qualitative data
Theoretical and Methodological Approaches to Social Sciences and Knowledge Management
ERIC Educational Resources Information Center
Lopez-Varela, Asuncion, Ed.
2012-01-01
This is a unique and groundbreaking collection of questions and answers coming from higher education institutions on diverse fields and across a wide spectrum of countries and cultures. It creates routes for further innovation, collaboration amidst the Sciences (both Natural and Social), the Humanities, and the private and public sectors of…
The Acquisition of Chinese Relative Clauses: Contrasting Two Theoretical Approaches
ERIC Educational Resources Information Center
Hu, Shenai; Gavarró, Anna; Vernice, Mirta; Guasti, Maria Teresa
2016-01-01
This study examines the comprehension of relative clauses by Chinese-speaking children, and evaluates the validity of the predictions of the Dependency Locality Theory (Gibson, 1998, 2000) and the Relativized Minimality approach (Friedmann, Belletti & Rizzi, 2009). One hundred and twenty children from three to eight years of age were tested by…
[Theoretical approach to motivating people for voluntary blood donation].
Andjelić, D; Sindjidj, M; Budisin, Z
1996-01-01
The study points to the experience of a considerable number of authors and to our own experience in the use of sociopsychological theories and personal approaches to the motivation of people for voluntary blood donation. The experience in the following theories is described: personal norms and contribution of responsibility to oneself, economic theory, modelling theory, theory of reasonable action and contribution theory.
A Theoretical Approach to School-based HIV Prevention.
ERIC Educational Resources Information Center
DeMuth, Diane; Symons, Cynthia Wolford
1989-01-01
Presents examples of appropriate intervention strategies for professionals working with school-based human immunodeficiency virus (HIV) prevention among adolescents. A multidisciplinary approach is advisable because influencing adolescent sexual behavior is a complex matter. Consistent, continuous messages through multiple channels and by multiple…
Data normalization in biosurveillance: an information-theoretic approach.
Peter, William; Najmi, Amir H; Burkom, Howard
2007-10-11
An approach to identifying public health threats by characterizing syndromic surveillance data in terms of its surprisability is discussed. Surprisability in our model is measured by assigning a probability distribution to a time series, and then calculating its entropy, leading to a straightforward designation of an alert. Initial application of our method is to investigate the applicability of using suitably-normalized syndromic counts (i.e., proportions) to improve early event detection.
Oxidative dissolution of silver nanoparticles: A new theoretical approach.
Adamczyk, Zbigniew; Oćwieja, Magdalena; Mrowiec, Halina; Walas, Stanisław; Lupa, Dawid
2016-05-01
A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined.
Is DNA a metal, semiconductor or insulator? A theoretical approach
NASA Astrophysics Data System (ADS)
Rey-Gonzalez, Rafael; Fonseca-Romero, Karen; Plazas, Carlos; Grupo de Óptica e Información Cuántica Team
Over the last years, scientific interest for designing and making low dimensional electronic devices with traditional or novel materials has been increased. These experimental and theoretical researches in electronic properties at molecular scale are looking for developing efficient devices able to carry out tasks which are currently done by silicon transistors and devices. Among the new materials DNA strands are highlighted, but the experimental results have been contradictories pointing to behaviors as conductor, semiconductor or insulator. To contribute to the understanding of the origin of the disparity of the measurements, we perform a numerical calculation of the electrical conductance of DNA segments, modeled as 1D disordered finite chains. The system is described into a Tight binding model with nearest neighbor interactions and a s orbital per site. Hydration effects are included as random variations of self-energies. The electronic current as a function of applied bias is calculated using Launder formalism, where the transmission probability is determined into the transfer matrix formalism. We find a conductor-to-semiconductor-to-insulator transition as a function of the three effects taken into account: chain size, intrinsic disorder, and hydration We thank Fundación para la Promoción de la Investigación y la Tecnología, Colombia, and Dirección de Investigación de Bogotá, Universidad Nacional de Colombia, for partial financial support.
A Game Theoretic Approach to Cyber Attack Prediction
Peng Liu
2005-11-28
The area investigated by this project is cyber attack prediction. With a focus on correlation-based prediction, current attack prediction methodologies overlook the strategic nature of cyber attack-defense scenarios. As a result, current cyber attack prediction methodologies are very limited in predicting strategic behaviors of attackers in enforcing nontrivial cyber attacks such as DDoS attacks, and may result in low accuracy in correlation-based predictions. This project develops a game theoretic framework for cyber attack prediction, where an automatic game-theory-based attack prediction method is proposed. Being able to quantitatively predict the likelihood of (sequences of) attack actions, our attack prediction methodology can predict fine-grained strategic behaviors of attackers and may greatly improve the accuracy of correlation-based prediction. To our best knowledge, this project develops the first comprehensive framework for incentive-based modeling and inference of attack intent, objectives, and strategies; and this project develops the first method that can predict fine-grained strategic behaviors of attackers. The significance of this research and the benefit to the public can be demonstrated to certain extent by (a) the severe threat of cyber attacks to the critical infrastructures of the nation, including many infrastructures overseen by the Department of Energy, (b) the importance of cyber security to critical infrastructure protection, and (c) the importance of cyber attack prediction to achieving cyber security.
Exploring Job Satisfaction of Nursing Faculty: Theoretical Approaches.
Wang, Yingchen; Liesveld, Judy
2015-01-01
The Future of Nursing report identified the shortage of nursing faculty as 1 of the barriers to nursing education. In light of this, it is becoming increasingly important to understand the work-life of nursing faculty. The current research focused on job satisfaction of nursing faculty from 4 theoretical perspectives: human capital theory, which emphasizes the expected monetary and nonmonetary returns for any career choices; structural theory, which emphasizes the impact of institutional features on job satisfaction; positive extrinsic environment by self-determination theory, which asserts that a positive extrinsic environment promotes competency and effective outcomes at work; and psychological theory, which emphasizes the proposed relationship between job performance and satisfaction. In addition to the measures for human capital theory, institutional variables (from structural theory and self-determination theory), and productivity measures (from psychological theory), the authors also selected sets of variables for personal characteristics to investigate their effects on job satisfaction. The results indicated that variables related to human capital theory, especially salary, contributed the most to job satisfaction, followed by those related to institutional variables. Personal variables and productivity variables as a whole contributed as well. The only other variable with marginal significance was faculty's perception of institutional support for teaching.
A NETWORK-THEORETICAL APPROACH TO UNDERSTANDING INTERSTELLAR CHEMISTRY
Jolley, Craig C.; Douglas, Trevor
2010-10-20
Recent years have seen dramatic advances in computational models of chemical processes in the interstellar medium (ISM). Typically, these models have been used to calculate changes in chemical abundances with time; the calculated abundances can then be compared with chemical abundances derived from observations. In this study, the output from an astrochemical simulation has been used to generate directed graphs with weighted edges; these have been analyzed with the tools of network theory to uncover whole-network properties of reaction systems in dark molecular clouds. The results allow the development of a model in which global network properties can be rationalized in terms of the basic physical properties of the reaction system. The ISM network exhibits an exponential degree distribution, which is likely to be a generic feature of chemical networks involving a broad range of reaction rate constants. While species abundances span several orders of magnitude, the formation and destruction rates for most species are approximately balanced-departures from this rule indicate species (such as CO) that play a critical role in shaping the dynamics of the system. Future theoretical or observational studies focusing on individual molecular species will be able to situate them in terms of their role in the complete system or quantify the degree to which they deviate from the typical system behavior.
NASA Astrophysics Data System (ADS)
Pandey, R. S.; Kaur, Rajbir
2015-10-01
Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit non-Maxwellian high-energy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electron-cyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.
Field theoretic analysis of a class of planar microwave and optoelectronic structures
NASA Astrophysics Data System (ADS)
Hahm, Yeon-Chang
2000-11-01
With increasing operating frequencies in CMOS RF/microwave integrated circuits, the performance of on- chip interconnects is becoming significantly affected by the lossy substrate. It is the purpose of the first part of this thesis to develop a rigorous field theoretic analysis approach for efficient characterization of single and multiple coupled interconnects on silicon substrate, which is applicable over a wide range of substrate resistivities. The frequency-dependent transmission line parameters of a microstrip on silicon are determined by a new formulation based on a quasi- electrostatic and quasi-magnetostatic spectral domain approach. It is demonstrated that this new quasi-static formulation provides the complete frequency-dependent interconnect characteristics for all three major transmission line modes of operation. In particular, it is shown that in the case of heavily doped CMOS substrates, the distributed series inductance and series resistance parameters are significantly affected by the presence of longitudinal substrate currents giving rise to the substrate skin-effect. The method is further extended to multiple coupled single and multi-level interconnect structures with ground plane and multiple coupled co-planar stripline structures without ground plane. The finite conductor thickness is taken into account in terms of a stacked conductor model. The new quasi-static approach is validated by comparison with results obtained with a full-wave spectral domain method and the commercial planar full-wave electromagnetic field solver HP/Momentum®, as well as published simulation and measurement data. In the second part of this thesis, coupled planar optical interconnect structures are investigated based on a rigorous field theoretic analysis combined with an application of the normal mode theory for coupled transmission lines. A new transfer matrix description for a general optical directional coupler is presented. Based on this transfer matrix formulation
From DNA radiation damage to cell death: theoretical approaches.
Ballarini, Francesca
2010-10-05
Some representative models of radiation-induced cell death, which is a crucial endpoint in radiobiology, were reviewed. The basic assumptions were identified, their consequences on predicted cell survival were analyzed, and the advantages and drawbacks of each approach were outlined. In addition to "historical" approaches such as the Target Theory, the Linear-Quadratic model, the Theory of Dual Radiation Action and Katz' model, the more recent Local Effect Model was discussed, focusing on its application in Carbon-ion hadrontherapy. Furthermore, a mechanistic model developed at the University of Pavia and based on the relationship between cell inactivation and chromosome aberrations was presented, together with recent results; the good agreement between model predictions and literature experimental data on different radiation types (photons, protons, alpha particles, and Carbon ions) supported the idea that asymmetric chromosome aberrations like dicentrics and rings play a fundamental role for cell death. Basing on these results, a reinterpretation of the TDRA was also proposed, identifying the TDRA "sublesions" and "lesions" as clustered DNA double-strand breaks and (lethal) chromosome aberrations, respectively.
From DNA Radiation Damage to Cell Death: Theoretical Approaches
Ballarini, Francesca
2010-01-01
Some representative models of radiation-induced cell death, which is a crucial endpoint in radiobiology, were reviewed. The basic assumptions were identified, their consequences on predicted cell survival were analyzed, and the advantages and drawbacks of each approach were outlined. In addition to “historical” approaches such as the Target Theory, the Linear-Quadratic model, the Theory of Dual Radiation Action and Katz' model, the more recent Local Effect Model was discussed, focusing on its application in Carbon-ion hadrontherapy. Furthermore, a mechanistic model developed at the University of Pavia and based on the relationship between cell inactivation and chromosome aberrations was presented, together with recent results; the good agreement between model predictions and literature experimental data on different radiation types (photons, protons, alpha particles, and Carbon ions) supported the idea that asymmetric chromosome aberrations like dicentrics and rings play a fundamental role for cell death. Basing on these results, a reinterpretation of the TDRA was also proposed, identifying the TDRA “sublesions” and “lesions” as clustered DNA double-strand breaks and (lethal) chromosome aberrations, respectively. PMID:20976308
Dissipative quantum transport in macromolecules: Effective field theory approach
NASA Astrophysics Data System (ADS)
Schneider, E.; a Beccara, S.; Faccioli, P.
2013-08-01
We introduce an atomistic approach to the dissipative quantum dynamics of charged or neutral excitations propagating through macromolecular systems. Using the Feynman-Vernon path integral formalism, we analytically trace out from the density matrix the atomic coordinates and the heat bath degrees of freedom. This way we obtain an effective field theory which describes the real-time evolution of the quantum excitation and is fully consistent with the fluctuation-dissipation relation. The main advantage of the field-theoretic approach is that it allows us to avoid using the Keldysh contour formulation. This simplification makes it straightforward to derive Feynman diagrams to analytically compute the effects of the interaction of the propagating quantum excitation with the heat bath and with the molecular atomic vibrations. For illustration purposes, we apply this formalism to investigate the loss of quantum coherence of holes propagating through a poly(3-alkylthiophene) polymer.
Schrödinger Approach to Mean Field Games.
Swiecicki, Igor; Gobron, Thierry; Ullmo, Denis
2016-03-25
Mean field games (MFG) provide a theoretical frame to model socioeconomic systems. In this Letter, we study a particular class of MFG that shows strong analogies with the nonlinear Schrödinger and Gross-Pitaevskii equations introduced in physics to describe a variety of physical phenomena. Using this bridge, many results and techniques developed along the years in the latter context can be transferred to the former, which provides both a new domain of application for the nonlinear Schrödinger equation and a new and fruitful approach in the study of mean field games. Utilizing this approach, we analyze in detail a population dynamics model in which the "players" are under a strong incentive to coordinate themselves.
Theoretical approach to explore the production routes of astatine radionuclides
NASA Astrophysics Data System (ADS)
Maiti, Moumita; Lahiri, Susanta
2009-02-01
To fulfill the recent thrust of astatine radionuclides in the field of nuclear medicine, various production routes have been explored in the present work. The possible production routes of At209-211 comprise both light- and heavy-ion-induced reactions at the bombarding energy range starting from threshold to a maximum of 100 MeV. Excitation functions of those radionuclides, produced through various production routes, have been calculated by using nuclear reaction model codes TALYS, ALICE91, and PACE-II and are compared with the available measured data. Contributions of various reaction mechanisms, such as direct, pre-equilibrium, and equilibrium reactions, to the total reaction cross section have been studied using the codes. Results show that the equilibrium reaction dominates in all cases over other reaction mechanisms.
Theoretical approach to explore the production routes of astatine radionuclides
Maiti, Moumita; Lahiri, Susanta
2009-02-15
To fulfill the recent thrust of astatine radionuclides in the field of nuclear medicine, various production routes have been explored in the present work. The possible production routes of {sup 209-211}At comprise both light- and heavy-ion-induced reactions at the bombarding energy range starting from threshold to a maximum of 100 MeV. Excitation functions of those radionuclides, produced through various production routes, have been calculated by using nuclear reaction model codes TALYS, ALICE91, and PACE-II and are compared with the available measured data. Contributions of various reaction mechanisms, such as direct, pre-equilibrium, and equilibrium reactions, to the total reaction cross section have been studied using the codes. Results show that the equilibrium reaction dominates in all cases over other reaction mechanisms.
Modeling of laccase inhibition by formetanate pesticide using theoretical approaches.
Martins, Ana C V; Ribeiro, Francisco W P; Zanatta, Geancarlo; Freire, Valder N; Morais, Simone; de Lima-Neto, Pedro; Correia, Adriana N
2016-04-01
The inhibition of laccase enzymatic catalytic activity by formetanate hydrochloride (FMT) was investigated by cyclic voltammetry and by quantum chemical calculations based on density functional theory with a protein fragmentation approach. The cyclic voltammograms were obtained using a biosensor prepared by enzyme immobilization on gold electrodes modified with gold nanoparticles and 4-aminophenol as the target molecule. The decrease in the peak current in the presence of FMT was used to characterize the inhibition process. The calculations identified Asp206 as the most relevant moiety in the interaction of FMT with the laccase enzymatic ligand binding domain. The amino acid residue Cys453 was important, because the Cys453-FMT interaction energy was not affected by the dielectric constant, although it was not a very close residue. This study provides an overview of how FMT inhibits laccase catalytic activity.
Theoretical approaches to entertainment education campaigns: a subaltern critique.
Dutta, Mohan Jyoti
2006-01-01
Entertainment education (E-E) is one of the most widely discussed areas in current scholarship on international health communication. In fact, much of the health communication scholarship has been historically dominated by E-E efforts directed at subaltern spaces. This article applies a subaltern studies perspective to interrogate the location of agency of the subaltern participant in the dominant E-E discourse. Based on a critical approach to E-E, the article offers points of departure for studying health communication in subaltern spaces. Subaltern voices point toward alternative definitions of problems beyond the narrow realm of problems defined by the core actors in E-E. Finally, alternative positions are suggested for applying participatory communication in engaging with subaltern participants for problem definition and solution development.
Kinetics and thermodynamics of protein adsorption: a generalized molecular theoretical approach.
Fang, F; Szleifer, I
2001-01-01
The thermodynamics and kinetics of protein adsorption are studied using a molecular theoretical approach. The cases studied include competitive adsorption from mixtures and the effect of conformational changes upon adsorption. The kinetic theory is based on a generalized diffusion equation in which the driving force for motion is the gradient of chemical potentials of the proteins. The time-dependent chemical potentials, as well as the equilibrium behavior of the system, are obtained using a molecular mean-field theory. The theory provides, within the same theoretical formulation, the diffusion and the kinetic (activated) controlled regimes. By separation of ideal and nonideal contributions to the chemical potential, the equation of motion shows a purely diffusive part and the motion of the particles in the potential of mean force resulting from the intermolecular interactions. The theory enables the calculation of the time-dependent surface coverage of proteins, the dynamic surface tension, and the structure of the adsorbed layer in contact with the approaching proteins. For the case of competitive adsorption from a solution containing a mixture of large and small proteins, a variety of different adsorption patterns are observed depending upon the bulk composition, the strength of the interaction between the particles, and the surface and size of the proteins. It is found that the experimentally observed Vroman sequence is predicted in the case that the bulk solution is at a composition with an excess of the small protein, and that the interaction between the large protein and the surface is much larger than that of the smaller protein. The effect of surface conformational changes of the adsorbed proteins in the time-dependent adsorption is studied in detail. The theory predicts regimes of constant density and dynamic surface tension that are long lived but are only intermediates before the final approach to equilibrium. The implications of the findings to the
Out-Learning Attackers: A Game Theoretic Approach to Cyber Defense
2013-04-01
Out-Learning Attackers: A Game Theoretic Approach to Cyber Defense FA9550-09-1-0049 Musacchio, John Frazier , Greg Kreidl, Pat Regents of University of...Security Program Final Report Project Period: 2/1/09 - 11/30/12 John Musacchio, UC Santa Cruz; Greg Frazier and Pat Kreidl BAE Systems 1 Introduction This...AFRL-OSR-VA-TR-2013-0172 Out-Learning Attackers: A Game Theoretic Approach to Cyber Defense John Musacchio Regents of
NASA Astrophysics Data System (ADS)
Grimm, G. W.; Potts, A. J.
2015-12-01
The Coexistence Approach has been used infer palaeoclimates for many Eurasian fossil plant assemblage. However, the theory that underpins the method has never been examined in detail. Here we discuss acknowledged and implicit assumptions, and assess the statistical nature and pseudo-logic of the method. We also compare the Coexistence Approach theory with the active field of species distribution modelling. We argue that the assumptions will inevitably be violated to some degree and that the method has no means to identify and quantify these violations. The lack of a statistical framework makes the method highly vulnerable to the vagaries of statistical outliers and exotic elements. In addition, we find numerous logical inconsistencies, such as how climate shifts are quantified (the use of a "center value" of a coexistence interval) and the ability to reconstruct "extinct" climates from modern plant distributions. Given the problems that have surfaced in species distribution modelling, accurate and precise quantitative reconstructions of palaeoclimates (or even climate shifts) using the nearest-living-relative principle and rectilinear niches (the basis of the method) will not be possible. The Coexistence Approach can be summarised as an exercise that shoe-horns a plant fossil assemblages into coexistence and then naively assumes that this must be the climate. Given the theoretical issues, and methodological issues highlighted elsewhere, we suggest that the method be discontinued and that all past reconstructions be disregarded and revisited using less fallacious methods.
Progress in Developing a New Field-theoretical Crossover Equation-of-State
NASA Technical Reports Server (NTRS)
Rudnick, Joseph; Barmatz, M.; Zhong, Fang
2003-01-01
A new field-theoretical crossover equation-of-state model is being developed. This model of a liquid-gas critical point provides a bridge between the asymptotic equation-of-state behavior close to the transition, obtained by the Guida and Zinn-Justin parametric model [J. Phys. A: Math. Gen. 31, 8103 (1998)], and the expected mean field behavior farther away. The crossover is based on the beta function for the renormalized fourth-order coupling constant and incorporates the correct crossover exponents and critical amplitude ratios in both regimes. A crossover model is now being developed that is consistent with predictions along the critical isochore and along the coexistence curve of the minimal subtraction renormalization approach developed by Dohm and co-workers and recently applied to the O(1) universality class [Phys. Rev. E, 67, 021106 (2003)]. Experimental measurements of the heat capacity at constant volume, isothermal susceptibility, and coexistence curve near the He-3 critical point are being compared to the predictions of this model. The results of these comparisons will be presented.
Armas-Perez, Julio C.; Londono-Hurtado, Alejandro; Guzman, Orlando; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.
2015-07-27
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.
Armas-Pérez, Julio C.; Londono-Hurtado, Alejandro; Guzmán, Orlando; Hernández-Ortiz, Juan P.; Pablo, Juan J. de
2015-07-28
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.
Armas-Pérez, Julio C; Londono-Hurtado, Alejandro; Guzmán, Orlando; Hernández-Ortiz, Juan P; de Pablo, Juan J
2015-07-28
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.
Perov, S Iu; Bogacheva, E V
2014-01-01
Results of the theoretical (numerical) and experimental dosimetry approach for portable radio transmitters are considered. The simulation and measurement results are shown. A generic type of a portable radio transmitter operating in a very high frequency range was tested as an electromagnetic field source. The analysis of specific absorption rate distribution in the flat homogeneous phantom was carried out on the basis of a portable radio transmitter. The results have shown the admissible divergence between measurements and simulation. According to these results, the authors have come to the conclusion about using the complex dosimetry approach including experimental and numerical dosimetry.
A Theoretical Approach to Understanding Population Dynamics with Seasonal Developmental Durations
NASA Astrophysics Data System (ADS)
Lou, Yijun; Zhao, Xiao-Qiang
2017-04-01
There is a growing body of biological investigations to understand impacts of seasonally changing environmental conditions on population dynamics in various research fields such as single population growth and disease transmission. On the other side, understanding the population dynamics subject to seasonally changing weather conditions plays a fundamental role in predicting the trends of population patterns and disease transmission risks under the scenarios of climate change. With the host-macroparasite interaction as a motivating example, we propose a synthesized approach for investigating the population dynamics subject to seasonal environmental variations from theoretical point of view, where the model development, basic reproduction ratio formulation and computation, and rigorous mathematical analysis are involved. The resultant model with periodic delay presents a novel term related to the rate of change of the developmental duration, bringing new challenges to dynamics analysis. By investigating a periodic semiflow on a suitably chosen phase space, the global dynamics of a threshold type is established: all solutions either go to zero when basic reproduction ratio is less than one, or stabilize at a positive periodic state when the reproduction ratio is greater than one. The synthesized approach developed here is applicable to broader contexts of investigating biological systems with seasonal developmental durations.
NASA Astrophysics Data System (ADS)
Cheng, Jin; Hon, Yiu-Chung; Seo, Jin Keun; Yamamoto, Masahiro
2005-01-01
The Second International Conference on Inverse Problems: Recent Theoretical Developments and Numerical Approaches was held at Fudan University, Shanghai from 16-21 June 2004. The first conference in this series was held at the City University of Hong Kong in January 2002 and it was agreed to hold the conference once every two years in a Pan-Pacific Asian country. The next conference is scheduled to be held at Hokkaido University, Sapporo, Japan in July 2006. The purpose of this series of biennial conferences is to establish and develop constant international collaboration, especially among the Pan-Pacific Asian countries. In recent decades, interest in inverse problems has been flourishing all over the globe because of both the theoretical interest and practical requirements. In particular, in Asian countries, one is witnessing remarkable new trends of research in inverse problems as well as the participation of many young talents. Considering these trends, the second conference was organized with the chairperson Professor Li Tat-tsien (Fudan University), in order to provide forums for developing research cooperation and to promote activities in the field of inverse problems. Because solutions to inverse problems are needed in various applied fields, we entertained a total of 92 participants at the second conference and arranged various talks which ranged from mathematical analyses to solutions of concrete inverse problems in the real world. This volume contains 18 selected papers, all of which have undergone peer review. The 18 papers are classified as follows: Surveys: four papers give reviews of specific inverse problems. Theoretical aspects: six papers investigate the uniqueness, stability, and reconstruction schemes. Numerical methods: four papers devise new numerical methods and their applications to inverse problems. Solutions to applied inverse problems: four papers discuss concrete inverse problems such as scattering problems and inverse problems in
NASA Astrophysics Data System (ADS)
Dhavalikar, Rohan; Rinaldi, Carlos
2016-12-01
Magnetic nanoparticles in alternating magnetic fields (AMFs) transfer some of the field's energy to their surroundings in the form of heat, a property that has attracted significant attention for use in cancer treatment through hyperthermia and in developing magnetic drug carriers that can be actuated to release their cargo externally using magnetic fields. To date, most work in this field has focused on the use of AMFs that actuate heat release by nanoparticles over large regions, without the ability to select specific nanoparticle-loaded regions for heating while leaving other nanoparticle-loaded regions unaffected. In parallel, magnetic particle imaging (MPI) has emerged as a promising approach to image the distribution of magnetic nanoparticle tracers in vivo, with sub-millimeter spatial resolution. The underlying principle in MPI is the application of a selection magnetic field gradient, which defines a small region of low bias field, superimposed with an AMF (of lower frequency and amplitude than those normally used to actuate heating by the nanoparticles) to obtain a signal which is proportional to the concentration of particles in the region of low bias field. Here we extend previous models for estimating the energy dissipation rates of magnetic nanoparticles in uniform AMFs to provide theoretical predictions of how the selection magnetic field gradient used in MPI can be used to selectively actuate heating by magnetic nanoparticles in the low bias field region of the selection magnetic field gradient. Theoretical predictions are given for the spatial decay in energy dissipation rate under magnetic field gradients representative of those that can be achieved with current MPI technology. These results underscore the potential of combining MPI and higher amplitude/frequency actuation AMFs to achieve selective magnetic fluid hyperthermia (MFH) guided by MPI.
NASA Astrophysics Data System (ADS)
Grimm, Guido W.; Potts, Alastair J.
2016-03-01
The Coexistence Approach has been used to infer palaeoclimates for many Eurasian fossil plant assemblages. However, the theory that underpins the method has never been examined in detail. Here we discuss acknowledged and implicit assumptions and assess the statistical nature and pseudo-logic of the method. We also compare the Coexistence Approach theory with the active field of species distribution modelling. We argue that the assumptions will inevitably be violated to some degree and that the method lacks any substantive means to identify or quantify these violations. The absence of a statistical framework makes the method highly vulnerable to the vagaries of statistical outliers and exotic elements. In addition, we find numerous logical inconsistencies, such as how climate shifts are quantified (the use of a "centre value" of a coexistence interval) and the ability to reconstruct "extinct" climates from modern plant distributions. Given the problems that have surfaced in species distribution modelling, accurate and precise quantitative reconstructions of palaeoclimates (or even climate shifts) using the nearest-living-relative principle and rectilinear niches (the basis of the method) will not be possible. The Coexistence Approach can be summarised as an exercise that shoehorns a plant fossil assemblage into coexistence and then assumes that this must be the climate. Given the theoretical issues and methodological issues highlighted elsewhere, we suggest that the method be discontinued and that all past reconstructions be disregarded and revisited using less fallacious methods. We outline six steps for (further) validation of available and future taxon-based methods and advocate developing (semi-quantitative) methods that prioritise robustness over precision.
Liu, Q.; Jiao, Y.; Yang, Y.; Hu, Z.
1996-12-01
A theoretical analysis is presented to obtain gradient distribution of particles in centrifugal field, by which the particle distribution in gradient composite can be predicted. Particle movement in liquid is described and gradient distribution of particles in composite is calculated in a centrifugal field during the solidification. The factors which affect the particle distribution and its gradient are discussed in detail. The theoretical analysis indicated that a composite zone and a blank zone exist in gradient composite, which can be controlled to the outside or inside of the tubular composite by the density difference of particle and liquid metal. The comparison of the SiC particle distribution in Al matrix composite produced by centrifugal casting between the theory model and the experiment denotes that the theoretical analysis is reasonable.
Field evaporation of insulators and semiconductors: Theoretical insights for ZnO.
Karahka, Markus; Kreuzer, H J
2015-12-01
We look at the new challenges associated with Atom Probe Tomography of insulators and semiconductors with regard to local fields inside and on the surface of such materials. The theoretical discovery that in high fields the band gap in these materials is drastically reduced to the point where at the evaporation field strength it vanishes will be crucial in our discussion. To understand Atom Probe results on the field evaporation of insulators and semiconductors we use density functional theory on ZnO clusters to follow the structural and electronic changes during field evaporation and to obtain potential energy curves, HOMO-LUMO gaps, field distributions, desorption pathways and fragments, dielectric constants, and polarizabilities. We also examine the effects of electric field reversal on the evaporation of ZnO and compare the results with Si.
ERIC Educational Resources Information Center
Jolly, Jennifer L.
2005-01-01
The previous Historical Perspectives column focused on the foundations of gifted education and the influence that Francis Galton, Alfred Binet, and Cesare Lombroso had in shaping the field. This work seeks to extend the examination of the historical roots of gifted education by focusing on definitions and theoretical underpinnings of giftedness…
Effective Field Theory approach to heavy quark fragmentation
NASA Astrophysics Data System (ADS)
Fickinger, Michael; Fleming, Sean; Kim, Chul; Mereghetti, Emanuele
2016-11-01
Using an approach based on Soft Collinear Effective Theory (SCET) and Heavy Quark Effective Theory (HQET) we determine the b-quark fragmentation function from electron-positron annihilation data at the Z-boson peak at next-to-next-to leading order with next-to-next-to leading log resummation of DGLAP logarithms, and next-to-next-to-next-to leading log resummation of endpoint logarithms. This analysis improves, by one order, the previous extraction of the b-quark fragmentation function. We find that while the addition of the next order in the calculation does not much shift the extracted form of the fragmentation function, it does reduce theoretical errors indicating that the expansion is converging. Using an approach based on effective field theory allows us to systematically control theoretical errors. While the fits of theory to data are generally good, the fits seem to be hinting that higher order correction from HQET may be needed to explain the b-quark fragmentation function at smaller values of momentum fraction.
Effective field theory approach to heavy quark fragmentation
Fickinger, Michael; Fleming, Sean; Kim, Chul; ...
2016-11-17
Using an approach based on Soft Collinear Effective Theory (SCET) and Heavy Quark Effective Theory (HQET) we determine the b-quark fragmentation function from electron-positron annihilation data at the Z-boson peak at next-to-next-to leading order with next-to-next-to leading log resummation of DGLAP logarithms, and next-to-next-to-next-to leading log resummation of endpoint logarithms. This analysis improves, by one order, the previous extraction of the b-quark fragmentation function. We find that while the addition of the next order in the calculation does not much shift the extracted form of the fragmentation function, it does reduce theoretical errors indicating that the expansion is converging. Usingmore » an approach based on effective field theory allows us to systematically control theoretical errors. Furthermore, while the fits of theory to data are generally good, the fits seem to be hinting that higher order correction from HQET may be needed to explain the b-quark fragmentation function at smaller values of momentum fraction.« less
Effective field theory approach to heavy quark fragmentation
Fickinger, Michael; Fleming, Sean; Kim, Chul; Mereghetti, Emanuele
2016-11-17
Using an approach based on Soft Collinear Effective Theory (SCET) and Heavy Quark Effective Theory (HQET) we determine the b-quark fragmentation function from electron-positron annihilation data at the Z-boson peak at next-to-next-to leading order with next-to-next-to leading log resummation of DGLAP logarithms, and next-to-next-to-next-to leading log resummation of endpoint logarithms. This analysis improves, by one order, the previous extraction of the b-quark fragmentation function. We find that while the addition of the next order in the calculation does not much shift the extracted form of the fragmentation function, it does reduce theoretical errors indicating that the expansion is converging. Using an approach based on effective field theory allows us to systematically control theoretical errors. Furthermore, while the fits of theory to data are generally good, the fits seem to be hinting that higher order correction from HQET may be needed to explain the b-quark fragmentation function at smaller values of momentum fraction.
2011-04-30
Intelligence Base? is being proposed to approach intelligence and game options in a holistic way for the strategy and the investments. 15. SUBJECT TERMS 16...theoretical, must point to some termination in action; academics have a responsibility to make their work intelligible to practitioners. Thus we continue to... Intelligence Base” is being proposed to approach intelligence and game options in a holistic way for the strategy and the investments. Introduction The
NASA Technical Reports Server (NTRS)
Weger, R. C.; Lee, J.; Zhu, Tianri; Welch, R. M.
1992-01-01
The current controversy existing in reference to the regularity vs. clustering in cloud fields is examined by means of analysis and simulation studies based upon nearest-neighbor cumulative distribution statistics. It is shown that the Poisson representation of random point processes is superior to pseudorandom-number-generated models and that pseudorandom-number-generated models bias the observed nearest-neighbor statistics towards regularity. Interpretation of this nearest-neighbor statistics is discussed for many cases of superpositions of clustering, randomness, and regularity. A detailed analysis is carried out of cumulus cloud field spatial distributions based upon Landsat, AVHRR, and Skylab data, showing that, when both large and small clouds are included in the cloud field distributions, the cloud field always has a strong clustering signal.
Multivariate Multi-Objective Allocation in Stratified Random Sampling: A Game Theoretic Approach
Hussain, Ijaz; Shoukry, Alaa Mohamd
2016-01-01
We consider the problem of multivariate multi-objective allocation where no or limited information is available within the stratum variance. Results show that a game theoretic approach (based on weighted goal programming) can be applied to sample size allocation problems. We use simulation technique to determine payoff matrix and to solve a minimax game. PMID:27936039
Understanding Older Adults' Physical Activity Behavior: A Multi-Theoretical Approach
ERIC Educational Resources Information Center
Grodesky, Janene M.; Kosma, Maria; Solmon, Melinda A.
2006-01-01
Physical inactivity is a health issue with serious consequences for older adults. Investigating physical activity promotion within a multi-theoretical approach may increase the predictive strength of physical activity determinants and facilitate the development and implementation of effective interventions for older adults. This article examines…
Making a Traditional Study-Abroad Program Geographic: A Theoretically Informed Regional Approach
ERIC Educational Resources Information Center
Jokisch, Brad
2009-01-01
Geographers have been active in numerous focused study-abroad programs, but few have created or led language-based programs overseas. This article describes the development of a Spanish language program in Ecuador and how it was made geographic primarily through a theoretically informed regional geography course. The approach employs theoretical…
ERIC Educational Resources Information Center
Feldner, Matthew T.; Monson, Candice M.; Friedman, Matthew J.
2007-01-01
Although efforts to prevent posttraumatic stress disorder (PTSD) have met with relatively limited success, theoretically driven preventive approaches with promising efficacy are emerging. The current article critically reviews investigations of PTSD prevention programs that target persons at risk for being exposed to a traumatic event or who have…
Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field
NASA Technical Reports Server (NTRS)
Voorhies, C.
1998-01-01
The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.
Sharma, Suresh C.; Gupta, Neha
2015-12-15
A theoretical modeling for the catalyst-assisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbon-clusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations.
NASA Technical Reports Server (NTRS)
Elliott, D. G.
1977-01-01
Measurements of reaction rail currents, reaction rail voltages, and airgap magnetic fields in tests of the Linear Induction Motor Research Vehicle (LIMRV) were compared with theoretical calculations from the mesh/matrix theory. It was found that the rail currents and magnetic fields predicted by the theory are within 20 percent of the measured currents and fields at most motor locations in most of the runs, but differ by as much as a factor of two in some cases. The most consistent difference is a higher experimental than theoretical magnetic field near the entrance of the motor and a lower experimental than theoretical magnetic field near the exit. The observed differences between the theoretical and experimental magnetic fields and currents do not account for the differences of as much as 26 percent between the theoretical and experimental thrusts.
Investigation of the interfacial tension of complex coacervates using field-theoretic simulations
Kumar, Rajeev
2012-01-01
Complex coacervation, a liquid-liquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultra-low interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use field-theoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from field-theoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.
Holmström, Petter; Yuan, Jun; Qiu, Min; Thylén, Lars; Bratkovsky, Alexander M
2011-04-11
The properties of integrated-photonics directional couplers composed of near-field-coupled arrays of metal nanoparticles are analyzed theoretically. It is found that it is possible to generate very compact, submicron length, high field-confinement and functionality devices with very low switch energies. The analysis is carried out for a hypothetical lossless silver to demonstrate the potential of this type of circuits for applications in telecom and interconnects. Employing losses of real silver, standalone devices with the above properties are still feasible in optimized metal nanoparticle structures.
Xiao, Chunyan; Rubinsky, Boris
2014-12-01
An analytical model was used to explore the feasibility of sinusoidal electric field transmission across a frozen saline layer into biological tissue. The study is relevant to electroporation and permeabilization of the cell membrane by electric fields. The concept was analyzed for frequencies in the range of conventional electroporation frequencies and electric field intensity. Theoretical analysis for a variety of tissues show that the transmission of electroporation type electric fields through a layer of frozen saline into tissue is feasible and the behavior of this composite system depends on tissue type, frozen domain temperature, and frequency. Freezing could become a valuable method for adherence of electroporation electrodes to moving tissue surfaces, such as the heart in the treatment of atrial fibrillation or blood vessels for the treatment of restenosis.
Yang, L.H.
2005-10-01
In this article, the derivative control equations of the simultaneous mathematical models on the temperature field, stress field of coal and rock mass, and the seepage field of retort gases in the gasification panel were established. The finite element form of the three-fields coupling problem for gas-solid solutions by means of a six-node triangular element was deduced. The numerical analysis software for three-fields coupling was developed. Combined with the calculation example, the mechanism of the thermodynamic effect was illustrated. The impact of the heating effect on the measured value and the simulated value of the seepage field, stress field, and displacement field was discussed and analyzed at length.
Research on the Field of Education Policy: Exploring Different Levels of Approach and Abstraction
ERIC Educational Resources Information Center
Mainardes, Jefferson; Tello, César
2016-01-01
This paper, of theoretical nature, explores the levels of approach and abstraction of research in the field of education policy: description, analysis and understanding. Such categories were developed based on concepts of Bourdieu's theory and on the grounds of epistemological studies focused on education policy and meta-research. This paper…
THEORETICAL LIMITS ON MAGNETIC FIELD STRENGTHS IN LOW-MASS STARS
Browning, Matthew K.; Weber, Maria A.; Chabrier, Gilles; Massey, Angela P.
2016-02-20
Observations have suggested that some low-mass stars have larger radii than predicted by 1D structure models. Some theoretical models have invoked very strong interior magnetic fields (of order 1 MG or more) as a possible cause of such large radii. Whether fields of that strength could in principle be generated by dynamo action in these objects is unclear, and we do not address the matter directly. Instead, we examine whether such fields could remain in the interior of a low-mass object for a significant amount of time, and whether they would have any other obvious signatures. First, we estimate the timescales for the loss of strong fields by magnetic buoyancy instabilities. We consider a range of field strengths and simple morphologies, including both idealized flux tubes and smooth layers of field. We confirm some of our analytical estimates using thin flux tube magnetohydrodynamic simulations of the rise of buoyant fields in a fully convective M-dwarf. Separately, we consider the Ohmic dissipation of such fields. We find that dissipation provides a complementary constraint to buoyancy: while small-scale, fibril fields might be regenerated faster than they rise, the dissipative heating associated with such fields would in some cases greatly exceed the luminosity of the star. We show how these constraints combine to yield limits on the internal field strength and morphology in low-mass stars. In particular, we find that for stars of 0.3 solar masses, no fields in flux tubes stronger than about 800 kG are simultaneously consistent with both constraints.
Classical field approach to quantum weak measurements.
Dressel, Justin; Bliokh, Konstantin Y; Nori, Franco
2014-03-21
By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between pre- and postselection boundary conditions. The classical field is itself a weak value of the corresponding quantum field operator and satisfies equations of motion that extremize an effective action. Weak measurements perturb this effective action, producing measurable changes to the classical field dynamics. As such, weakly measured effects always correspond to an effective classical field. This general result explains why these effects appear to be robust for pre- and postselected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field.
Nuclear radii calculations in various theoretical approaches for nucleus-nucleus interactions
Merino, C.; Novikov, I. S.; Shabelski, Yu.
2009-12-15
The information about sizes and nuclear density distributions in unstable (radioactive) nuclei is usually extracted from the data on interaction of radioactive nuclear beams with a nuclear target. We show that in the case of nucleus-nucleus collisions the values of the parameters depend somewhat strongly on the considered theoretical approach and on the assumption about the parametrization of the nuclear density distribution. The obtained values of root-mean-square radii (R{sub rms}) for stable nuclei with atomic weights A=12-40 vary by approximately 0.1 fm when calculated in the optical approximation, in the rigid target approximation, and using the exact expression of the Glauber theory. We present several examples of R{sub rms} radii calculations using these three theoretical approaches and compare these results with the data obtained from electron-nucleus scattering.
A Comparison of Two Topos-Theoretic Approaches to Quantum Theory
NASA Astrophysics Data System (ADS)
Wolters, Sander A. M.
2013-01-01
The aim of this paper is to compare the two topos-theoretic approaches to quantum mechanics that may be found in the literature to date. The first approach, which we will call the contravariant approach, was originally proposed by Isham and Butterfield, and was later extended by Döring and Isham. The second approach, which we will call the covariant approach, was developed by Heunen, Landsman and Spitters. Motivated by coarse-graining and the Kochen-Specker theorem, the contravariant approach uses the topos of presheaves on a specific context category, defined as the poset of commutative von Neumann subalgebras of some given von Neumann algebra. In particular, the approach uses the spectral presheaf. The intuitionistic logic of this approach is given by the (complete) Heyting algebra of closed open subobjects of the spectral presheaf. We show that this Heyting algebra is, in a natural way, a locale in the ambient topos, and compare this locale with the internal Gelfand spectrum of the covariant approach. In the covariant approach, a non-commutative C*-algebra (in the topos Set) defines a commutative C*-algebra internal to the topos of covariant functors from the context category to the category of sets. We give an explicit description of the internal Gelfand spectrum of this commutative C*-algebra, from which it follows that the external spectrum is spatial. Using the daseinisation of self-adjoint operators from the contravariant approach, we give a new definition of the daseinisation arrow in the covariant approach and compare it with the original version. States and state-proposition pairing in both approaches are compared. We also investigate the physical interpretation of the covariant approach.
1983-03-01
but it is biased toward low income indivi- duals. The linear income system does give a reasonable redistribution plan. This plan as we know from...approved i 83 06 30 068 CCS Research Report 453 EXTREMAL AND GAME-THEORETIC CHARACTERIZATIONS OF THE PROBABILISTIC APPROACH TO INCOME REDISTRIBUTION by A...Abstract In this paper we cast the problem of income redistribution in two different ways, one as a non-linear goal programming model, and the other as a
Cheng, Zhongtao; Liu, Dong; Luo, Jing; Yang, Yongying; Zhou, Yudi; Zhang, Yupeng; Duan, Lulin; Su, Lin; Yang, Liming; Shen, Yibing; Wang, Kaiwei; Bai, Jian
2015-05-04
A field-widened Michelson interferometer (FWMI) is developed to act as the spectral discriminator in high-spectral-resolution lidar (HSRL). This realization is motivated by the wide-angle Michelson interferometer (WAMI) which has been used broadly in the atmospheric wind and temperature detection. This paper describes an independent theoretical framework about the application of the FWMI in HSRL for the first time. In the framework, the operation principles and application requirements of the FWMI are discussed in comparison with that of the WAMI. Theoretical foundations for designing this type of interferometer are introduced based on these comparisons. Moreover, a general performance estimation model for the FWMI is established, which can provide common guidelines for the performance budget and evaluation of the FWMI in the both design and operation stages. Examples incorporating many practical imperfections or conditions that may degrade the performance of the FWMI are given to illustrate the implementation of the modeling. This theoretical framework presents a complete and powerful tool for solving most of theoretical or engineering problems encountered in the FWMI application, including the designing, parameter calibration, prior performance budget, posterior performance estimation, and so on. It will be a valuable contribution to the lidar community to develop a new generation of HSRLs based on the FWMI spectroscopic filter.
Decision support models for solid waste management: Review and game-theoretic approaches
Karmperis, Athanasios C.; Aravossis, Konstantinos; Tatsiopoulos, Ilias P.; Sotirchos, Anastasios
2013-05-15
Highlights: ► The mainly used decision support frameworks for solid waste management are reviewed. ► The LCA, CBA and MCDM models are presented and their strengths, weaknesses, similarities and possible combinations are analyzed. ► The game-theoretic approach in a solid waste management context is presented. ► The waste management bargaining game is introduced as a specific decision support framework. ► Cooperative and non-cooperative game-theoretic approaches to decision support for solid waste management are discussed. - Abstract: This paper surveys decision support models that are commonly used in the solid waste management area. Most models are mainly developed within three decision support frameworks, which are the life-cycle assessment, the cost–benefit analysis and the multi-criteria decision-making. These frameworks are reviewed and their strengths and weaknesses as well as their critical issues are analyzed, while their possible combinations and extensions are also discussed. Furthermore, the paper presents how cooperative and non-cooperative game-theoretic approaches can be used for the purpose of modeling and analyzing decision-making in situations with multiple stakeholders. Specifically, since a waste management model is sustainable when considering not only environmental and economic but also social aspects, the waste management bargaining game is introduced as a specific decision support framework in which future models can be developed.
Impacts of noise on a field theoretical model of the human brain
NASA Astrophysics Data System (ADS)
Frank, T. D.; Daffertshofer, A.; Beek, P. J.; Haken, H.
1999-03-01
Salient properties of the spatio-temporal patterns in MEG recordings of human brain activity, such as macroscopic coherence of a limited number of modes and the occurrence of phase transitions, have been successfully described with the help of field theoretical models for the dendritic currents in the cortex. So far, however, these models have ignored the effects of noise which play an important role in the emergence of such properties. The present article provides a formal treatment of the effects of stochastic fluctuations in the vicinity of the phase transitions that were observed by Kelso in his so-called Julliard experiment [Fuchs et al., Phase transition in the human brain: spatial mode dynamics, Int. J. Bifurcation and Chaos 2 (1992) 917-939; H. Haken, Principles of Brain Functioning, Springer, Berlin, 1996; J.A.S. Kelso, Dynamic Patterns - The Self-organization of Brain and Behavior, MIT Press, Cambridge, 1995]. To describe and examine these effects, the field theoretical model proposed by Jirsa and Haken [A field theory of electromagnetic brain activity, Phys. Rev. Lett. 77 (1996) 960-963; A derivation of a macroscopic field theory of the brain from the quasi-microscopic neural dynamics, Physica D 99 (1997) 503-526] was extended by incorporating Gaussian white noise. The extended model describes the stochastic properties of the most dominant spatio-temporal components, including stochastic variations of the amplitudes of the extracted spatial modes. Furthermore, the model captures critical phenomena such as critical slowing down and critical fluctuations, which are derived analytically. These theoretical results are generalized by means of numerical simulations of amplitude and phase dynamics.
Quantum electron-vibrational dynamics at finite temperature: Thermo field dynamics approach.
Borrelli, Raffaele; Gelin, Maxim F
2016-12-14
Quantum electron-vibrational dynamics in molecular systems at finite temperature is described using an approach based on the thermo field dynamics theory. This formulation treats temperature effects in the Hilbert space without introducing the Liouville space. A comparison with the theoretically equivalent density matrix formulation shows the key numerical advantages of the present approach. The solution of thermo field dynamics equations with a novel technique for the propagation of tensor trains (matrix product states) is discussed. Numerical applications to model spin-boson systems show that the present approach is a promising tool for the description of quantum dynamics of complex molecular systems at finite temperature.
NASA Technical Reports Server (NTRS)
Wolf, R. A.; Kamide, Y.
1983-01-01
Advanced techniques considered by Kamide et al. (1981) seem to have the potential for providing observation-based high time resolution pictures of the global ionospheric current and electric field patterns for interesting events. However, a reliance on the proposed magnetogram-inversion schemes for the deduction of global ionospheric current and electric field patterns requires proof that reliable results are obtained. 'Theoretical' tests of the accuracy of the magnetogram inversion schemes have, therefore, been considered. The present investigation is concerned with a test, involving the developed KRM algorithm and the Rice Convection Model (RCM). The test was successful in the sense that there was overall agreement between electric fields and currents calculated by the RCM and KRM schemes.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. As a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. Asmore » a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.« less
NASA Astrophysics Data System (ADS)
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-01
We demonstrate that a nonperturbative framework for the treatment of the excitations of single-walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.
Illustrating the quantum approach with an Earth magnetic field MRI
NASA Astrophysics Data System (ADS)
Pars Benli, Kami; Dillmann, Baudouin; Louelh, Ryma; Poirier-Quinot, Marie; Darrasse, Luc
2015-05-01
Teaching imaging of magnetic resonance (MR) today is still as challenging as it has always been, because it requires admitting that we cannot express fundamental questions of quantum mechanics with straightforward language or without using extensive theory. Here we allow students to face a real MR setup based on the Earth's magnetic field. We address the applied side of teaching MR using a device that is affordable and that proves to be sufficiently robust, at universities in Orsay, France, and San Sebastian, Spain, in experimental practicals at undergraduate and graduate levels. We specifically present some of the advantages of low field for measuring R2 relaxation rates, reaching a power of separation of 1.5 μmol on Mn(II) ions between two water bottles each of half a liter. Finally we propose key approaches for the lecturers to adopt when they are asked to pass from theoretical knowledge to teachable knowhow. The outcomes are fast calibration and the MR acquisition protocols, demonstrating the reproducibility of energy transfer during the saturation pulses, and the quantitative nature of MR, with water protons and a helium-3 sample.
NASA Astrophysics Data System (ADS)
Liarte, Danilo B.; Posen, Sam; Transtrum, Mark K.; Catelani, Gianluigi; Liepe, Matthias; Sethna, James P.
2017-03-01
Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-T c materials such as Nb3Sn, NbN, and MgB2. Indeed, beyond the so-called superheating field {H}{sh}, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for {H}{sh}, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB2? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.
Structure formation with scalar field dark matter: the field approach
Magaña, Juan; Sánchez-Salcedo, F.J.; Matos, Tonatiuh; Suárez, Abril E-mail: tmatos@fis.cinvestav.mx E-mail: jsanchez@astro.unam.mx
2012-10-01
We study the formation of structure in the Universe assuming that dark matter can be described by a scalar field Φ-tilde with a potential V(Φ) = −m{sup 2}Φ-tilde {sup 2}/2+λΦ-tilde {sup 4}/4. We derive the evolution equations of the scalar field in the linear regime of perturbations. We investigate the symmetry breaking and possibly a phase transition of this scalar field in the early Universe. At low temperatures, the scalar perturbations have an oscillating growing mode and therefore, this kind of dark matter could lead to the formation of gravitational structures. In order to study the nonlinear regime, we use the spherical collapse model and show that, in the quadratic potential limit, this kind of dark matter can form virialized structures. The main difference with the traditional Cold Dark Matter paradigm is that the formation of structure in the scalar field model can occur at earlier times. Thus, if the dark matter behaves as a scalar field, large galaxies are expected to be formed already at high redshifts.
Shafii, Mohammad Ali Meidianti, Rahma Wildian, Fitriyani, Dian; Tongkukut, Seni H. J.; Arkundato, Artoto
2014-09-30
Theoretical analysis of integral neutron transport equation using collision probability (CP) method with quadratic flux approach has been carried out. In general, the solution of the neutron transport using the CP method is performed with the flat flux approach. In this research, the CP method is implemented in the cylindrical nuclear fuel cell with the spatial of mesh being conducted into non flat flux approach. It means that the neutron flux at any point in the nuclear fuel cell are considered different each other followed the distribution pattern of quadratic flux. The result is presented here in the form of quadratic flux that is better understanding of the real condition in the cell calculation and as a starting point to be applied in computational calculation.
From moral theory to penal attitudes and back: a theoretically integrated modeling approach.
de Keijser, Jan W; van der Leeden, Rien; Jackson, Janet L
2002-01-01
From a moral standpoint, we would expect the practice of punishment to reflect a solid and commonly shared legitimizing framework. Several moral legal theories explicitly aim to provide such frameworks. Based on the theories of Retributivism, Utilitarianism, and Restorative Justice, this article first sets out to develop a theoretically integrated model of penal attitudes and then explores the extent to which Dutch judges' attitudes to punishment fit the model. Results indicate that penal attitudes can be measured in a meaningful way that is consistent with an integrated approach to moral theory. The general structure of penal attitudes among Dutch judges suggests a streamlined and pragmatic approach to legal punishment that is identifiably founded on the separate concepts central to moral theories of punishment. While Restorative Justice is frequently presented as an alternative paradigm, results show it to be smoothly incorporated within the streamlined approach.
Ofenheimer, Aldo; Buchmayr, Bruno; Kolleck, Ralf
2005-08-05
The influence of strain paths (loading history) on material formability is well known in sheet forming processes. Sophisticated experimental methods are used to determine the entire shape of strain paths of forming limits for aluminum AA6016-T4 alloy. Forming limits for sheet metal in as-received condition as well as for different pre-deformation are presented. A theoretical approach based on Arrieux's intrinsic Forming Limit Stress Curve (FLSC) concept is employed to numerically predict the influence of loading history on forming severity. The detailed experimental strain paths are used in the theoretical study instead of any linear or bilinear simplified loading histories to demonstrate the predictive quality of forming limits in the state of stress.
A Maximum-Likelihood Approach to Force-Field Calibration.
Zaborowski, Bartłomiej; Jagieła, Dawid; Czaplewski, Cezary; Hałabis, Anna; Lewandowska, Agnieszka; Żmudzińska, Wioletta; Ołdziej, Stanisław; Karczyńska, Agnieszka; Omieczynski, Christian; Wirecki, Tomasz; Liwo, Adam
2015-09-28
A new approach to the calibration of the force fields is proposed, in which the force-field parameters are obtained by maximum-likelihood fitting of the calculated conformational ensembles to the experimental ensembles of training system(s). The maximum-likelihood function is composed of logarithms of the Boltzmann probabilities of the experimental conformations, calculated with the current energy function. Because the theoretical distribution is given in the form of the simulated conformations only, the contributions from all of the simulated conformations, with Gaussian weights in the distances from a given experimental conformation, are added to give the contribution to the target function from this conformation. In contrast to earlier methods for force-field calibration, the approach does not suffer from the arbitrariness of dividing the decoy set into native-like and non-native structures; however, if such a division is made instead of using Gaussian weights, application of the maximum-likelihood method results in the well-known energy-gap maximization. The computational procedure consists of cycles of decoy generation and maximum-likelihood-function optimization, which are iterated until convergence is reached. The method was tested with Gaussian distributions and then applied to the physics-based coarse-grained UNRES force field for proteins. The NMR structures of the tryptophan cage, a small α-helical protein, determined at three temperatures (T = 280, 305, and 313 K) by Hałabis et al. ( J. Phys. Chem. B 2012 , 116 , 6898 - 6907 ), were used. Multiplexed replica-exchange molecular dynamics was used to generate the decoys. The iterative procedure exhibited steady convergence. Three variants of optimization were tried: optimization of the energy-term weights alone and use of the experimental ensemble of the folded protein only at T = 280 K (run 1); optimization of the energy-term weights and use of experimental ensembles at all three temperatures (run 2
Hektner, Joel M; Brennan, Alison L; Brotherson, Sean E
2013-09-01
The Nurtured Heart Approach to parenting (NHA; Glasser & Easley, 2008) is summarized and evaluated in terms of its alignment with current theoretical perspectives and empirical evidence in family studies and developmental science. Originally conceived and promoted as a behavior management approach for parents of difficult children (i.e., with behavior disorders), NHA is increasingly offered as a valuable strategy for parents of any children, despite a lack of published empirical support. Parents using NHA are trained to minimize attention to undesired behaviors, provide positive attention and praise for compliance with rules, help children be successful by scaffolding and shaping desired behavior, and establish a set of clear rules and consequences. Many elements of the approach have strong support in the theoretical and empirical literature; however, some of the assumptions are more questionable, such as that negative child behavior can always be attributed to unintentional positive reinforcement by parents responding with negative attention. On balance, NHA appears to promote effective and validated parenting practices, but its effectiveness now needs to be tested empirically.
NASA Astrophysics Data System (ADS)
Chen, Yu; Liang, Yung C.; Samudra, Ganesh S.
2005-02-01
The performance merit of silicon unipolar power devices is best described by a trade-off relationship between specific on-state resistance (Ron,sp) and breakdown voltage (Vbr), which leads to the establishment of an ideal unipolar limit on device performance. Recently, engineering the electric field in the device drift region to break this unipolar silicon limit for superior performance has become an important research topic. The superjunction (SJ) structure achieves this by paralleling precisely matched higher doping alternate p--n layers to replace the typically low doping drift region. Alternatively, for fabrication simplicity in an oxide-bypassed (OB) structure, an oxide layer of predetermined thickness together with a polycontact is used to replace the p-column of the SJ structure to modulate the electric field. The further improved gradient OB (GOB) structure with slanted oxide sidewalls delivers a performance similar to ideal SJ devices. In this paper, detailed theoretical analyses in closed-form equations on OB and GOB devices are made for the first time to model the performance in various operating regions. The theoretical analyses were also carefully verified through two-dimensional numerical simulations.
NASA Astrophysics Data System (ADS)
Runge, Jakob; Balasis, Georgios; Papadimitriou, Constantinos; Donner, Reik; Daglis, Ioannis; Kurths, Juergen
2016-04-01
The identification of directed interdependencies between variables related to causal relationships in various geoscientific processes is necessary for an improved process-based understanding of the coupling between different variables or even systems. Especially in geomagnetism, the time-dependent coupling between solar wind and the Earth's magnetic field as well as the relationship between magnetic storms and magnetospheric substorms are of paramount importance for the development of appropriate numerical simulation models of space weather. Here we utilize an information-theoretic method of directional, multivariate causality measures using graphical models that goes beyond bivariate transfer entropy approaches and allows for the identification and statistical evaluation of linear as well as nonlinear causality between variables. In this study, we present and discuss results from an application of this method to the time series of various solar wind parameters as well as the AE and SYM-H geomagnetic activity indices.
NASA Astrophysics Data System (ADS)
Iida, Kenji; Noda, Masashi; Nobusada, Katsuyuki
2017-02-01
We have developed a theoretical approach for describing the electronic properties of hetero-interface systems under an applied electrode bias. The finite-temperature density functional theory is employed for controlling the chemical potential in their interfacial region, and thereby the electronic charge of the system is obtained. The electric field generated by the electronic charging is described as a saw-tooth-like electrostatic potential. Because of the continuum approximation of dielectrics sandwiched between electrodes, we treat dielectrics with thicknesses in a wide range from a few nanometers to more than several meters. Furthermore, the approach is implemented in our original computational program named grid-based coupled electron and electromagnetic field dynamics (GCEED), facilitating its application to nanostructures. Thus, the approach is capable of comprehensively revealing electronic structure changes in hetero-interface systems with an applied bias that are practically useful for experimental studies. We calculate the electronic structure of a SiO2-graphene-boron nitride (BN) system in which an electrode bias is applied between the graphene layer and an electrode attached on the SiO2 film. The electronic energy barrier between graphene and BN is varied with an applied bias, and the energy variation depends on the thickness of the BN film. This is because the density of states of graphene is so low that the graphene layer cannot fully screen the electric field generated by the electrodes. We have demonstrated that the electronic properties of hetero-interface systems are well controlled by the combination of the electronic charging and the generated electric field.
Iida, Kenji; Noda, Masashi; Nobusada, Katsuyuki
2017-02-28
We have developed a theoretical approach for describing the electronic properties of hetero-interface systems under an applied electrode bias. The finite-temperature density functional theory is employed for controlling the chemical potential in their interfacial region, and thereby the electronic charge of the system is obtained. The electric field generated by the electronic charging is described as a saw-tooth-like electrostatic potential. Because of the continuum approximation of dielectrics sandwiched between electrodes, we treat dielectrics with thicknesses in a wide range from a few nanometers to more than several meters. Furthermore, the approach is implemented in our original computational program named grid-based coupled electron and electromagnetic field dynamics (GCEED), facilitating its application to nanostructures. Thus, the approach is capable of comprehensively revealing electronic structure changes in hetero-interface systems with an applied bias that are practically useful for experimental studies. We calculate the electronic structure of a SiO2-graphene-boron nitride (BN) system in which an electrode bias is applied between the graphene layer and an electrode attached on the SiO2 film. The electronic energy barrier between graphene and BN is varied with an applied bias, and the energy variation depends on the thickness of the BN film. This is because the density of states of graphene is so low that the graphene layer cannot fully screen the electric field generated by the electrodes. We have demonstrated that the electronic properties of hetero-interface systems are well controlled by the combination of the electronic charging and the generated electric field.
Semiclassical and quantum field theoretic bounds for traversable Lorentzian stringy wormholes
Nandi, Kamal Kanti; Zhang Yuanzhong; Kumar, K.B. Vijaya
2004-09-15
A lower bound on the size of a Lorentzian wormhole can be obtained by semiclassically introducing the Planck cutoff on the magnitude of tidal forces (Horowitz-Ross constraint). Also, an upper bound is provided by the quantum field theoretic constraint in the form of the Ford-Roman Quantum Inequality for massless minimally coupled scalar fields. To date, however, exact static solutions belonging to this scalar field theory have not been worked out to verify these bounds. To fill this gap, we examine the wormhole features of two examples from the Einstein frame description of the vacuum low energy string theory in four dimensions which is the same as the minimally coupled scalar field theory. Analyses in this paper support the conclusion of Ford and Roman that wormholes in this theory can have sizes that are indeed only a few order of magnitudes larger than the Planck scale. It is shown that the two types of bounds are also compatible. In the process, we point out a 'wormhole' analog of naked black holes.
Suflita, Joseph M.; Duncan, Kathleen E.
2010-08-14
The Joint United States - European Union Theoretical and Practical Course on Molecular Approaches for in situ Biodegradation was held May 24 through June 7 at The University of Oklahoma. Twenty-four graduate and postgraduate students from both the United States and the European Union attended the course. Nine states and ten European countries were represented. Students were assigned living quarters and laboratory partners to maximize interactions between US and EU participants as well as to mix people with different technical backgrounds together. The students used the latest methods in molecular biology to characterize beneficial microorganisms and genes involved in the biodegradation of pollutants at a nearby landfill as well as an active hydrocarbon-producing site, part of which is undergoing bioremediation. Seminars by distinguished scientists were organized to expose the students to the breadth of the environmental field, including field assay and engineering applications, laboratory scale bioreactors, microbiology, genetics, regulation, pathway analysis, design of recombinant bacteria, and application of the associated techniques to the field. Lectures were given by various OU faculty on the principles behind the techniques to be used in the laboratory. These lectures included troubleshooting hints and encouraged questions and comments from the audience. The laboratory experiments covered chemical, microbiological, and molecular genetic analyses of soils; bioavailability of contaminants; enrichment cultures; gene probing; PCR amplification of known genes and gene families; identification of microbes based traditional and nontraditional approaches, nutritional capabilities, and 16S rRNA sequence; mRNA detection; and enzyme assays. Field trips were made to the USGS landfill field sampling site, and to the Tall Grass Prairie Preserve, a Nature Conservancy site which also featured long-term studies of bioremediation of crude oil and brine spills by one of the
Afterschool Education: Approaches to an Emerging Field.
ERIC Educational Resources Information Center
Noam, Gil G.; Biancarosa, Gina; Dechausay, Nadine
Noting that there exists little systematic and conclusive research on after-school education to guide the development of practices in this emerging field, this book contributes to the definition of after-school education by focusing on three essential aspects of such programming: (1) bridging school to after-school (2) homework, or extended…
Tractors and twistors from conformal Cartan geometry: a gauge theoretic approach II. Twistors
NASA Astrophysics Data System (ADS)
Attard, J.; François, J.
2017-04-01
Tractor and Twistor bundles provide natural conformally covariant calculi on 4D-Riemannian manifolds. They have different origins but are closely related, and usually constructed bottom–up through prolongation of defining differential equations. We propose alternative top–down gauge theoretic constructions, starting from the conformal Cartan bundle P and its vectorial E and spinorial {E associated bundles. Our key ingredient is the dressing field method of gauge symmetry reduction, which allows tractors and twistors and their associated connections to exhibit as gauge fields of a non-standard kind as far as Weyl rescaling transformation is concerned. By non-standard we mean that they implement the gauge principle of physics, but are of a different geometric nature than the well-known differential geometric objects usually underlying gauge theories. We provide the corresponding BRST treatment. In a companion paper we dealt with tractors, in the present one we address the case of twistors.
A new approach to observe toroidal magnetic fields of magnetars
NASA Astrophysics Data System (ADS)
Murakami, H.; Makishima, K.; Enoto, T.; Nakano, T.; Furuta, Y.; Nakazawa, K.
2016-06-01
Over the last decade, observational evidence has amounted that magnetars harbor enormous surface dipole magnetic fields (MFs) of B_{d} = 10^{14-15} {G}. Theoretically, we expect even stronger toroidal MFs B_{t} (e.g., Takiwaki+2009), which is observationally supported by a discovery of low-B_{d} magnetars (e.g., SGR 0418+5729; Rea+2013). Here, we will present a new approach to access B_{t} more directly. Suzaku allows us to simultaneously observe a soft thermal component and a distinct hard X-ray tail of magnetars. Extensively analyzing two magnetars, 4U 0142+61 and 1E 1547.0-5408, we found that their hard X-ray pulses suffered from slow phase modulations (Makishima+2014, 2015). This can be interpreted as a manifestation of free precession, under an axial deformation by ˜0.01%. If this effect is attributed to the magnetic stress, B_{t}˜10^{16} G is inferred. We further found that, within 6 years observation of 4U 0142+61, the modulation periods remained constant, while the amplitude gradually increased from < 0.4 to ˜1.3 sec. These results suggest the shift of the hard X-ray emission region (or direction).
NASA Astrophysics Data System (ADS)
Hawthorne, Frank C.
2012-11-01
Here, I describe a theoretical approach to the structure and chemical composition of minerals based on their bond topology. This approach allows consideration of many aspects of minerals and mineral behaviour that cannot be addressed by current theoretical methods. It consists of combining the bond topology of the structure with aspects of graph theory and bond-valence theory (both long range and short range), and using the moments approach to the electronic energy density-of-states to interpret topological aspects of crystal structures. The structure hierarchy hypothesis states that higher bond-valence polyhedra polymerize to form the (usually anionic) structural unit, the excess charge of which is balanced by the interstitial complex (usually consisting of large low-valence cations and (H2O) groups). This hypothesis may be justified within the framework of bond topology and bond-valence theory, and may be used to hierarchically classify oxysalt minerals. It is the weak interaction between the structural unit and the interstitial complex that controls the stability of the structural arrangement. The principle of correspondence of Lewis acidity-basicity states that stable structures will form when the Lewis-acid strength of the interstitial complex closely matches the Lewis-base strength of the structural unit, and allows us to examine the factors that control the chemical composition and aspects of the structural arrangements of minerals. It also provides a connection between a structure, the speciation of its constituents in aqueous solution and its mechanism of crystallization. The moments approach to the electronic energy density-of-states provides a link between the bond topology of a structure and its thermodynamic properties, as indicated by correlations between average anion coordination number and reduced enthalpy of formation from the oxides for [6]Mg{/m [4]}Si n O( m+2 n) and MgSO4(H2O) n .
Babouri, A; Hedjeidj, A; Guendouz, L
2009-04-01
This paper presents in vitro investigation of an implantable cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based on the interaction by inductive coupling through the loop formed by the pacemaker and its loads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker, which can potentially disturb its operation. The studied frequencies are 50/60 Hz and 10/25 kHz. The experimental tests were carried out on several cardiac pacemakers, single chamber, and dual chamber. The results show a window effect of the detection circuits of cardiac pacemakers for the four studied frequencies. The modelling of the test bed requires studying the effects of the induced currents generated by the application of a magnetic field. Analytical calculations and Numerical simulations were carried out. We modelled the interactions of the magnetic field with a simplified representation of pacemaker embedded in the medium. The comparison of the results in the air and in vitro enabled us to make an equivalent electric model. The results obtained in experimental and theoretical studies allowed us to validate the test bed. The method applied is valid for other medical implants such as cardiac defibrillators, implant hearing aids system...etc.
Rousochatzakis, Ioannis
2005-12-17
The field of molecular magnetism[l-6] has become a subject of intense theoretical and experimental interest and has rapidly evolved during the last years. This inter-disciplinary field concerns magnetic systems at the molecular or "nanoscopic" level, whose realization has become feasible due to recent advances in the field of chemical synthesis. The present theoretical work provides a first step towards exploiting the possibilities that are offered by probing magnetic molecules using external magnetic fields with high sweep rates. These probes, apart for providing information specific to magnetic molecules, offer the possibility of conducting a detailed study of the relaxational behavior of interacting spin systems as a result of their coupling with a "heat bath" and in particular the excitations of the host lattice. Development of a broad theoretical framework for dealing with relaxational phenomena induced by dynamical magnetic fields is indeed a worthy goal.
Qiu, Peng; Gentles, Andrew J; Plevritis, Sylvia K
2010-02-01
Information theoretic approaches are increasingly being used for reconstructing regulatory networks from microarray data. These approaches start by computing the pairwise mutual information (MI) between all gene pairs. The resulting MI matrix is then manipulated to identify regulatory relationships. A barrier to these approaches is the time-consuming step of computing the MI matrix. We present a method to reduce this computation time. We apply spectral analysis to re-order the genes, so that genes that share regulatory relationships are more likely to be placed close to each other. Then, using a "sliding window" approach with appropriate window size and step size, we compute the MI for the genes within the sliding window, and the remainder is assumed to be zero. Using both simulated data and microarray data, we demonstrate that our method does not incur performance loss in regions of high-precision and low-recall, while the computational time is significantly lowered. The proposed method can be used with any method that relies on the mutual information to reconstruct networks.
Sebai, Jihane
2016-01-01
Various organizational, functional or structural issues have led to a review of the foundations of the former health care system based on a traditional market segmentation between general practice and hospital medicine, and between health and social sectors and marked by competition between private and public sectors. The current reconfiguration of the health care system has resulted in “new” levers explained by the development of a new organizational reconfiguration of the primary health care model. Coordinated care structures (SSC) have been developed in this context by making coordination the cornerstone of relations between professionals to ensure global, continuous and quality health care. This article highlights the contributions of various theoretical approaches to the understanding of the concept of coordination in the analysis of the current specificity of health care.
a Field-Theoretical Investigation of 2-D Coulomb Systems with Short-Range Yukawa Repulsion.
NASA Astrophysics Data System (ADS)
Jargocki, Krzysztof Piotr
The two-dimensional Coulomb gas, consisting of positive and negative charges, is an important system which, on one hand, is equivalent to the vortex sector of the planar X-Y model, and, on the other, to the sine-Gordon field theory. In most treatments the charged particles are assumed to have a repulsive hard core which prevents arbitrarily close approaches. In the present work a new regularization scheme based on a soft short-range Yukawa repulsion between the Coulomb gas particles is presented. This formulation is transcribed into a local sine-Gordon-like field theory involving two Bose fields, one the original massless sine -Gordon field corresponding to the long-range Coulomb interaction and an auxiliary massive field corresponding to the short -range Yukawa repulsion. The resulting Lagrangian is not Hermitian. Using the techniques of functional integration, an effective field theory involving the Coulomb field alone is obtained by integrating out the massive field. The resulting Lagrangian is now Hermitian. Then a generalization of Peierls' inequality is used to make a variational calculation of the ground state energy of the Coulomb system. Unlike in the pure sine-Gordon case the theory has a well-defined ground state energy for (beta)q('2) > 2 (or (beta)c('2) > 8(pi)). A new method is used to derive the Kosterlitz -Thouless renormalization group equations, starting with the original sine-Gordon-like theory. The equations are identical to those found previously by other authors. A wave function renormalization is found to be necessary in addition to the normal ordering discussed by Coleman. A fermionized version of the theory is obtained, using the dictionary provided by Kogut and Susskind, which involves two Fermi fields and an electromagnetic potential. Position -space correlation functions are calculated at the critical point. The effective potential is computed in the one -loop approximation. A nonlinear field theory with derivative couplings is found to
Fedorovich, E.
1995-09-01
The paper presents an extended theoretical background for applied modeling of the atmospheric convective boundary layer within the so-called zero-order jump approach, which implies vertical homogeneity of meteorological fields in the bulk of convective boundary layer (CBL) and zero-order discontinuities of variables at the interfaces of the layer. The zero-order jump model equations for the most typical cases of CBL are derived. The models of nonsteady, horizontally homogeneous CBL with and without shear, extensively studied in the past with the aid of zero-order jump models, are shown to be particular cases of the general zero-order jump theoretical framework. The integral budgets of momentum and heat are considered for different types of dry CBL. The profiles of vertical turbulent fluxes are presented and analyzed. The general version of the equation of CBL depth growth rate (entrainment rate equation) is obtained by the integration of the turbulence kinetic energy balance equation, invoking basic assumptions of the zero-order parameterizations of the CBL vertical structure. The problems of parameterizing the turbulence vertical structure and closure of the entrainment rate equation for specific cases of CBL are discussed. A parameterization scheme for the horizontal turbulent exchange in zero-order jump models of CBL is proposed. The developed theory is generalized for the case of CBL over irregular terrain. 28 refs., 2 figs.
Model-free information-theoretic approach to infer leadership in pairs of zebrafish.
Butail, Sachit; Mwaffo, Violet; Porfiri, Maurizio
2016-04-01
Collective behavior affords several advantages to fish in avoiding predators, foraging, mating, and swimming. Although fish schools have been traditionally considered egalitarian superorganisms, a number of empirical observations suggest the emergence of leadership in gregarious groups. Detecting and classifying leader-follower relationships is central to elucidate the behavioral and physiological causes of leadership and understand its consequences. Here, we demonstrate an information-theoretic approach to infer leadership from positional data of fish swimming. In this framework, we measure social interactions between fish pairs through the mathematical construct of transfer entropy, which quantifies the predictive power of a time series to anticipate another, possibly coupled, time series. We focus on the zebrafish model organism, which is rapidly emerging as a species of choice in preclinical research for its genetic similarity to humans and reduced neurobiological complexity with respect to mammals. To overcome experimental confounds and generate test data sets on which we can thoroughly assess our approach, we adapt and calibrate a data-driven stochastic model of zebrafish motion for the simulation of a coupled dynamical system of zebrafish pairs. In this synthetic data set, the extent and direction of the coupling between the fish are systematically varied across a wide parameter range to demonstrate the accuracy and reliability of transfer entropy in inferring leadership. Our approach is expected to aid in the analysis of collective behavior, providing a data-driven perspective to understand social interactions.
Expanding Access to Large-Scale Genomic Data While Promoting Privacy: A Game Theoretic Approach.
Wan, Zhiyu; Vorobeychik, Yevgeniy; Xia, Weiyi; Clayton, Ellen Wright; Kantarcioglu, Murat; Malin, Bradley
2017-02-02
Emerging scientific endeavors are creating big data repositories of data from millions of individuals. Sharing data in a privacy-respecting manner could lead to important discoveries, but high-profile demonstrations show that links between de-identified genomic data and named persons can sometimes be reestablished. Such re-identification attacks have focused on worst-case scenarios and spurred the adoption of data-sharing practices that unnecessarily impede research. To mitigate concerns, organizations have traditionally relied upon legal deterrents, like data use agreements, and are considering suppressing or adding noise to genomic variants. In this report, we use a game theoretic lens to develop more effective, quantifiable protections for genomic data sharing. This is a fundamentally different approach because it accounts for adversarial behavior and capabilities and tailors protections to anticipated recipients with reasonable resources, not adversaries with unlimited means. We demonstrate this approach via a new public resource with genomic summary data from over 8,000 individuals-the Sequence and Phenotype Integration Exchange (SPHINX)-and show that risks can be balanced against utility more effectively than with traditional approaches. We further show the generalizability of this framework by applying it to other genomic data collection and sharing endeavors. Recognizing that such models are dependent on a variety of parameters, we perform extensive sensitivity analyses to show that our findings are robust to their fluctuations.
NASA Astrophysics Data System (ADS)
Joyce, Arthur A.; Goman, Michelle
2012-11-01
In this article we discuss two theoretical approaches to landscape studies in archaeology: the ecological and social/symbolic. We suggest that an integrated approach can provide a more effective means through which archaeologists and earth scientists can model the complex interplay between people and the environment. Our perspective views peoples' engagements with the landscape as simultaneously ecological and social, material and symbolic. To illustrate this synthetic approach we discuss our research from the highland and lowland regions of the Mexican state of Oaxaca using archaeological, ethnographic, ethnohistorical, paleoecological, and geomorphological data. In highland Oaxaca we examine the ways in which political and religious principles were embedded in the landscape as well as the social, symbolic, and material dimensions of anthropogenic landscape change during the Formative period. For the coastal lowlands, we discuss the social and ecological implications of the transition to sedentism and the effects of anthropogenic landscape change during the Formative period. We also examine the interplay between politics and land use during the Classic and Postclassic periods.
Model-free information-theoretic approach to infer leadership in pairs of zebrafish
NASA Astrophysics Data System (ADS)
Butail, Sachit; Mwaffo, Violet; Porfiri, Maurizio
2016-04-01
Collective behavior affords several advantages to fish in avoiding predators, foraging, mating, and swimming. Although fish schools have been traditionally considered egalitarian superorganisms, a number of empirical observations suggest the emergence of leadership in gregarious groups. Detecting and classifying leader-follower relationships is central to elucidate the behavioral and physiological causes of leadership and understand its consequences. Here, we demonstrate an information-theoretic approach to infer leadership from positional data of fish swimming. In this framework, we measure social interactions between fish pairs through the mathematical construct of transfer entropy, which quantifies the predictive power of a time series to anticipate another, possibly coupled, time series. We focus on the zebrafish model organism, which is rapidly emerging as a species of choice in preclinical research for its genetic similarity to humans and reduced neurobiological complexity with respect to mammals. To overcome experimental confounds and generate test data sets on which we can thoroughly assess our approach, we adapt and calibrate a data-driven stochastic model of zebrafish motion for the simulation of a coupled dynamical system of zebrafish pairs. In this synthetic data set, the extent and direction of the coupling between the fish are systematically varied across a wide parameter range to demonstrate the accuracy and reliability of transfer entropy in inferring leadership. Our approach is expected to aid in the analysis of collective behavior, providing a data-driven perspective to understand social interactions.
A theoretical validation of the B-matrix spatial distribution approach to diffusion tensor imaging.
Borkowski, Karol; Kłodowski, Krzysztof; Figiel, Henryk; Krzyżak, Artur Tadeusz
2017-02-01
The recently presented B-matrix Spatial Distribution (BSD) approach is a calibration technique which derives the actual distribution of the B-matrix in space. It is claimed that taking into account the spatial variability of the B-matrix improves the accuracy of diffusion tensor imaging (DTI). The purpose of this study is to verify this approach theoretically through computer simulations. Assuming three different spatial distributions of the B-matrix, diffusion weighted signals were calculated for the six orientations of a model anisotropic phantom. Subsequently two variants of the BSD calibration were performed for each of the three cases; one with the assumption of high uniformity of the model phantom (uBSD-DTI) and the other taking into account imperfections in phantom structure (BSD-DTI). Several cases of varying degrees of phantom uniformity were analyzed and the distributions of the B-matrix obtained were used for the calculation of the diffusion tensor of a model isotropic phantom. The results were compared with standard diffusion tensor calculation. The simulations confirmed the improvement of accuracy in the determination of the diffusion tensor after the calibration. BSD-DTI improves accuracy independent of both the degree of uniformity of the phantom and the inhomogeneity of the B-matrix. In cases of a relatively good uniformity of the phantom and minor distortions in the spatial distribution of the B-matrix, the uBSD-DTI approach is sufficient.
Pant, Sanjay; Lombardi, Damiano
2015-10-01
A new approach for assessing parameter identifiability of dynamical systems in a Bayesian setting is presented. The concept of Shannon entropy is employed to measure the inherent uncertainty in the parameters. The expected reduction in this uncertainty is seen as the amount of information one expects to gain about the parameters due to the availability of noisy measurements of the dynamical system. Such expected information gain is interpreted in terms of the variance of a hypothetical measurement device that can measure the parameters directly, and is related to practical identifiability of the parameters. If the individual parameters are unidentifiable, correlation between parameter combinations is assessed through conditional mutual information to determine which sets of parameters can be identified together. The information theoretic quantities of entropy and information are evaluated numerically through a combination of Monte Carlo and k-nearest neighbour methods in a non-parametric fashion. Unlike many methods to evaluate identifiability proposed in the literature, the proposed approach takes the measurement-noise into account and is not restricted to any particular noise-structure. Whilst computationally intensive for large dynamical systems, it is easily parallelisable and is non-intrusive as it does not necessitate re-writing of the numerical solvers of the dynamical system. The application of such an approach is presented for a variety of dynamical systems--ranging from systems governed by ordinary differential equations to partial differential equations--and, where possible, validated against results previously published in the literature.
Theoretical study of spectroscopic constants and anharmonic force field of SiF2.
Li, Jing; Wang, Meishan; Yang, Chuanlu; Ma, Meizhong; Tong, Dianmin
2015-05-01
The equilibrium structure, spectroscopy constants, and anharmonic force field of SiF2 have been investigated at MP2, B3LYP, and B3PW91 levels of theory employing two basis sets cc-pVQZ and cc-pVTZ, respectively. The obtained equilibrium geometries, rotational constants, fundamental vibrational wave numbers, and centrifugal distortion constants are compared with the available experimental data or the previous theoretical values. The MP2/cc-pVQZ results of SiF2 are in excellent agreement with the available experimental data and afford a marked improvement over B3LYP/cc-pVQZ and B3PW91/cc-pVQZ in the calculation of spectroscopic constants and force constants of SiF2. The basis set enhancement beyond cc-pVQZ does not lead to a major improvement so that the cc-pVQZ basis set is sufficient for SiF2. The MP2/cc-pVQZ results may provide useful data for the spectroscopic experiment studies of SiF2. The used DFT method is also an advisable choice to study anharmonic force field of SiF2.
Transport in polymer-gel composites: theoretical methodology and response to an electric field
NASA Astrophysics Data System (ADS)
Hill, Reghan J.
2006-03-01
A theoretical model of electromigrative, diffusive and convective transport in polymer-gel composites is presented. Bulk properties are derived from the standard electrokinetic model with an impenetrable charged sphere embedded in an electrolyte-saturated Brinkman medium. Because the microstructure can be carefully controlled, these materials are promising candidates for enhanced gel-electrophoresis, chemical sensing, drug delivery, and microfluidic pumping technologies. The methodology provides solutions for situations where perturbations from equilibrium are induced by gradients of electrostatic potential, concentration and pressure. While the volume fraction of the inclusions should be small, Maxwell's well-known theory of conduction suggests that the model may also be accurate at moderate volume fractions. In this work, the theory is used to compute ion fluxes, electrical current density, and convective flow driven by an electric field applied to an homogeneous composite. The electric-field-induced (electro-osmotic) flow is a sensitive indicator of the inclusion zeta-potential and size, electrolyte concentration, and Darcy permeability of the gel, while the electrical conductivity is usually independent of the polymer gel and is relatively insensitive to characteristics of the inclusions and electrolyte.
MAGNETARS VERSUS HIGH MAGNETIC FIELD PULSARS: A THEORETICAL INTERPRETATION OF THE APPARENT DICHOTOMY
Pons, Jose A.; Perna, Rosalba
2011-11-10
Highly magnetized neutron stars (NSs) are characterized by a bewildering range of astrophysical manifestations. Here, building on our simulations of the evolution of magnetic stresses in the NS crust and its ensuing fractures, we explore in detail, for the middle-aged and old NSs, the dependence of starquake frequency and energetics on the relative strength of the poloidal (B{sub p}) and toroidal (B{sub tor}) components. We find that, for B{sub p} {approx}> 10{sup 14} G, since a strong crustal toroidal field B{sub tor} {approx} B{sub p} is quickly formed on a Hall timescale, the initial toroidal field needs to be B{sub tor} >> B{sub p} to have a clear influence on the outbursting behavior. For initial fields B{sub p} {approx}< 10{sup 14} G, it is very unlikely that a middle-aged (t {approx} 10{sup 5} years) NS shows any bursting activity. This study allows us to solve the apparent puzzle of how NSs with similar dipolar magnetic fields can behave in a remarkably different way: an outbursting 'magnetar' with a high X-ray luminosity, or a quiet, low-luminosity, 'high-B' radio pulsar. As an example, we consider the specific cases of the magnetar 1E 2259+586 and the radio pulsar PSR J1814-1744, which at present have a similar dipolar field {approx}6 Multiplication-Sign 10{sup 13} G. We determine for each object an initial magnetic field configuration that reproduces the observed timing parameters at their current age. The same two configurations also account for the differences in quiescent X-ray luminosity and for the 'magnetar/outbursting' behavior of 1E 2259+586 but not of PSR J1814-1744. We further use the theoretically predicted surface temperature distribution to compute the light curve for these objects. In the case of 1E 2259+586, for which data are available, our predicted temperature distribution gives rise to a pulse profile whose double-peaked nature and modulation level are consistent with the observations.
NASA Astrophysics Data System (ADS)
Galiana-Merino, J. J.; Rosa-Cintas, S.; Rosa-Herranz, J.; Garrido, J.; Peláez, J. A.; Martino, S.; Delgado, J.
2016-05-01
Array measurements of ambient noise have become a useful technique to estimate the surface wave dispersion curves and subsequently the subsurface elastic parameters that characterize the studied soil. One of the logistical handicaps associated with this kind of measurements is the requirement of several stations recording at the same time, which limits their applicability in the case of research groups without enough infrastructure resources. In this paper, we describe the theoretical basis of the ESAC method and we deduce how the number of stations needed to implement any array layout can be reduced to only two stations. In this way, we propose a new methodology to implement an N stations array layout by using only M stations (M < N), which will be recording in different positions of the original prearranged N stations geometry at different times. We also provide some practical guidelines to implement the proposed approach and we show different examples where the obtained results confirm the theoretical foundations. Thus, the study carried out reflects that we can use a minimum of 2 stations to deploy any array layout originally designed for higher number of sensors.
Pointwise analysis of scalar fields: A nonstandard approach
Yamashita, Hideyasu
2006-09-15
A new nonstandard-analytical approach to quantum fields is presented, which gives a mathematical foundation for manipulating pointwise-defined quantum fields. In our approach, a field operator {phi}(x) is not a standard operator-valued distribution, but a nonstandard operator-valued function. Then formal expressions containing, e.g., {phi}(x){sup 2} can be understood literally, and shown to be well defined. In the free field cases, we show that the Wightman functions are explicitly calculated with the pointwise field, without any regularization, e.g., Wick product. Our notion of pointwise fields is applied also to the path integral formalisms of scalar fields. We show that some of physicists' naive expressions of Lagrangian path integral formulas can be rigorously justified.
NASA Astrophysics Data System (ADS)
Anoufa, M.; Kiat, J. M.; Bogicevic, C.
2015-10-01
Most of the theoretical and experimental studies on the electrocaloric effect (ECE) are devoted to thin films, but they can be hardly envisaged for cooling macroscopic systems; moreover, the results obtained cannot be easily transposed for larger systems like multilayered ceramics. Therefore, efforts should also be focused on predicting, synthesizing, and characterizing interesting bulk single crystal or ceramics. In ferroelectric nanoparticles and ceramics, the core-shell structure of grains is of uttermost importance to explain the experimental results at small sizes. Moreover, it can be used to tailor physical properties, such as energy storage, by experimenting with the composition, thickness, and permittivity of the shell. Here, we report the effect of such structures on the electrocaloric effects in a variety of ferroelectric materials. The magnitude of ECE as well as its field and temperature-dependence are obtained for different types of core-shells. The optimal configuration for a maximal ECE is deduced.
NASA Astrophysics Data System (ADS)
Berrada, K.
2016-11-01
In this paper, we study the Fisher information for a quantum system consisting of two identical qubits, each of them locally interacting with a bosonic reservoir in the same environment for non-Markovian open, dissipative quantum system. Based on the influx of the information, we propose an information-theoretical approach for characterizing the time-dependent memory effect of environment and diffusion function under the effect of the physical parameters. More precisely, an interesting monotonic relation between the time derivative of quantum Fisher information (QFI) and diffusion function behavior is observed during the time evolution. The phenomenon is that the QFI, namely the precision of estimation, changes dramatically with the environment structure. The dependence of the physical parameters shows that the increasing in the temperature will damage the amount of the QFI with respect of the ratio between the reservoir cutoff frequency and the system oscillation frequency.
NASA Astrophysics Data System (ADS)
Vytelingum, Perukrishnen; Cliff, Dave; Jennings, Nicholas R.
We develop a new model to analyse the strategic behaviour of buyers and sellers in market mechanisms. In particular, we wish to understand how the different strategies they adopt affect their economic efficiency in the market and to understand the impact of these choices on the overall efficiency of the marketplace. To this end, we adopt a two-population evolutionary game theoretic approach, where we consider how the behaviours of both buyers and sellers evolve in marketplaces. In so doing, we address the shortcomings of the previous state-of-the-art analytical model that assumes that buyers and sellers have to adopt the same mixed strategy in the market. Finally, we apply our model in one of the most common market mechanisms, the Continuous Double Auction, and demonstrate how it allows us to provide new insights into the strategic interactions of such trading agents.
A Game-Theoretic Approach to Branching Time Abstract-Check-Refine Process
NASA Technical Reports Server (NTRS)
Wang, Yi; Tamai, Tetsuo
2009-01-01
Since the complexity of software systems continues to grow, most engineers face two serious problems: the state space explosion problem and the problem of how to debug systems. In this paper, we propose a game-theoretic approach to full branching time model checking on three-valued semantics. The three-valued models and logics provide successful abstraction that overcomes the state space explosion problem. The game style model checking that generates counter-examples can guide refinement or identify validated formulas, which solves the system debugging problem. Furthermore, output of our game style method will give significant information to engineers in detecting where errors have occurred and what the causes of the errors are.
Reaction dynamics of the D+ + H2 system. A comparison of theoretical approaches.
Jambrina, P G; Alvariño, J M; Aoiz, F J; Herrero, Víctor J; Sáez-Rábanos, Vicente
2010-10-21
The dynamics of the deuteron-proton exchange D(+) + H(2) → HD + H(+) reaction on its ground 1(1)A' potential energy surface has been the subject of a theoretical study for collision energies below 1.5 eV. The results obtained with three theoretical approaches: quasi-classical trajectory (QCT), statistical quasi-classical trajectory (SQCT), and accurate time-independent quantum mechanical (QM) calculations are compared in the range of collision energies from 5 meV to 0.2 eV. The QM calculations included all total angular momentum quantum numbers, J, up to J(max) ≈ 40 and all the Coriolis couplings. For higher collision energies, the comparison was restricted to the QCT and SQCT results given the enormous computational cost implied in the QM calculations. Reaction cross sections as a function of collision energy (excitation functions) for various initial rovibrational states have been determined and compared with the corresponding results for the endothermic H(+) + D(2) → HD + D(+) isotopic variant. The excitation function for the title reaction decays monotonically with collision energy as expected for an exothermic reaction without a barrier, in contrast to the behaviour observed in the mentioned H(+) + D(2) (v = 0, j ≤ 3). Reaction probabilities as a function of J (opacity functions) at several collision energies calculated with the different approaches were also examined and important differences between them were found. The effect of using the gaussian binning procedure that preserves, to a large extent, the zero point energy, as compared to the standard histogram binning in the QCT calculations, is also examined. At low collision energy, the best agreement with the accurate QM results is given by the SQCT data, although they tend to overestimate the reactivity. The deviations from the statistical behaviour of the QCT data at higher energies are remarkable. Nevertheless, on the whole, the title reaction can be deemed more statistical than the H(+) + D(2
Information-Theoretic Approaches for Evaluating Complex Adaptive Social Simulation Systems
Omitaomu, Olufemi A; Ganguly, Auroop R; Jiao, Yu
2009-01-01
In this paper, we propose information-theoretic approaches for comparing and evaluating complex agent-based models. In information theoretic terms, entropy and mutual information are two measures of system complexity. We used entropy as a measure of the regularity of the number of agents in a social class; and mutual information as a measure of information shared by two social classes. Using our approaches, we compared two analogous agent-based (AB) models developed for regional-scale social-simulation system. The first AB model, called ABM-1, is a complex AB built with 10,000 agents on a desktop environment and used aggregate data; the second AB model, ABM-2, was built with 31 million agents on a highperformance computing framework located at Oak Ridge National Laboratory, and fine-resolution data from the LandScan Global Population Database. The initializations were slightly different, with ABM-1 using samples from a probability distribution and ABM-2 using polling data from Gallop for a deterministic initialization. The geographical and temporal domain was present-day Afghanistan, and the end result was the number of agents with one of three behavioral modes (proinsurgent, neutral, and pro-government) corresponding to the population mindshare. The theories embedded in each model were identical, and the test simulations focused on a test of three leadership theories - legitimacy, coercion, and representative, and two social mobilization theories - social influence and repression. The theories are tied together using the Cobb-Douglas utility function. Based on our results, the hypothesis that performance measures can be developed to compare and contrast AB models appears to be supported. Furthermore, we observed significant bias in the two models. Even so, further tests and investigations are required not only with a wider class of theories and AB models, but also with additional observed or simulated data and more comprehensive performance measures.
Buffeteau, Thierry; Lagugné-Labarthet, François; Sourisseau, Claude
2005-06-01
In this study, the measurement of the true vibrational circular dichroism (VCD) spectrum is considered from an experimental and theoretical approach for any general anisotropic thin solid sample exhibiting linear as well as circular birefringence (LB, CB) and dichroism (LD, CD) properties. For this purpose, we have made use of a simple model alpha-helix polypeptide, namely, the poly(gamma-benzyl-L-glutamate) or PBLG, reference sample possessing a well-known VCD spectrum and giving rise to slightly oriented films by deposition onto a solid substrate. Also, we have used a different Fourier transform infrared modulation of polarization (PM-FTIR) optical setup with two-channel electronic processing in order to record the PM-VLD and PM-VCD spectra for various sample orientations in its film plane. All the corresponding general relations of the expected intensities in these experiments and the related properly designed calibration measurements were established using the Stokes-Mueller formalism; in addition, the residual birefringence of the optical setup and the transmittance anisotropy of the detector were estimated. From a comparative study of the results obtained in solution and in the solid state, we then propose a simple new experimental procedure to extract the true VCD spectrum of an oriented PBLG thin film: its consists of calculating the half-sum of two spectra recorded at theta and at theta +/- 90 degrees sample orientations. Moreover, the complete linear and circular birefringence and dichroism properties of the ordered PBLG thin film are estimated in the amide I and amide II vibrational regions. This allows us to establish for any sample orientation various theoretical simulations of the VCD spectra that agree nicely with the observed experimental results; this confirms that the measurement of LD and LB is in this case a prerequisite in simulating the true VCD spectrum of a partly oriented anisotropic sample. This validates our combined experimental and
Theoretical approaches to the steady-state statistical physics of interacting dissipative units
NASA Astrophysics Data System (ADS)
Bertin, Eric
2017-02-01
The aim of this review is to provide a concise overview of some of the generic approaches that have been developed to deal with the statistical description of large systems of interacting dissipative ‘units’. The latter notion includes, e.g. inelastic grains, active or self-propelled particles, bubbles in a foam, low-dimensional dynamical systems like driven oscillators, or even spatially extended modes like Fourier modes of the velocity field in a fluid. We first review methods based on the statistical properties of a single unit, starting with elementary mean-field approximations, either static or dynamic, that describe a unit embedded in a ‘self-consistent’ environment. We then discuss how this basic mean-field approach can be extended to account for spatial dependences, in the form of space-dependent mean-field Fokker–Planck equations, for example. We also briefly review the use of kinetic theory in the framework of the Boltzmann equation, which is an appropriate description for dilute systems. We then turn to descriptions in terms of the full N-body distribution, starting from exact solutions of one-dimensional models, using a matrix-product ansatz method when correlations are present. Since exactly solvable models are scarce, we also present some approximation methods which can be used to determine the N-body distribution in a large system of dissipative units. These methods include the Edwards approach for dense granular matter and the approximate treatment of multiparticle Langevin equations with colored noise, which models systems of self-propelled particles. Throughout this review, emphasis is put on methodological aspects of the statistical modeling and on formal similarities between different physical problems, rather than on the specific behavior of a given system.
Gelo, Omar Carlo Gioacchino; Salvatore, Sergio
2016-07-01
Notwithstanding the many methodological advances made in the field of psychotherapy research, at present a metatheoretical, school-independent framework to explain psychotherapy change processes taking into account their dynamic and complex nature is still lacking. Over the last years, several authors have suggested that a dynamic systems (DS) approach might provide such a framework. In the present paper, we review the main characteristics of a DS approach to psychotherapy. After an overview of the general principles of the DS approach, we describe the extent to which psychotherapy can be considered as a self-organizing open complex system, whose developmental change processes are described in terms of a dialectic dynamics between stability and change over time. Empirical evidence in support of this conceptualization is provided and discussed. Finally, we propose a research design strategy for the empirical investigation of psychotherapy from a DS approach, together with a research case example. We conclude that a DS approach may provide a metatheoretical, school-independent framework allowing us to constructively rethink and enhance the way we conceptualize and empirically investigate psychotherapy. (PsycINFO Database Record
Electrokinetics dependence on water-content: laboratory and field approach
NASA Astrophysics Data System (ADS)
Allègre, Vincent; Sénéchal, Pascale; Lehmann, François; Bordes, Clarisse; Jouniaux, Laurence; Sailhac, Pascal; Bano, Maksim
2010-05-01
Electrokinetics results from the coupling between the water flow and the electrical current through the electrokinetic coefficient. The Self-Potential (SP) method, which is based on this phenomenon, is currently used to investigate shallow transport in the vadose zone. Thus, the understanding of the electrokinetic coefficient behaviour in unsaturated conditions is crucial to interpret such methods. Empirical and theoretical models proposed in the literature to describe this behaviour are still discussed. Consequently, physical processes involved in the electrokinetic coefficient behaviour in unsaturated conditions need to be futher investigate. We propose here to study the electrokinetics dependence on water content through an experimental approach and the numerical solving of the Richards' equation. We show several continuous records of the electrokinetic coefficient as a function of water saturation. We found that the normalized electrokinetic coefficient behaviour in unsaturated conditions is more complex than it was previously proposed. Indeed, we first observed its increasing with decreasing water saturation. After it reaches a maximum, identified around 80 % of water saturation, it begins to decrease with decreasing saturation. It is an important result since previous works predicted a monotically decreasing of the electrokinetic coefficient with decreasing saturation. We found that the normalized value of the measured electrokinetic coefficient could be two orders of magnitude greater than the classical value in saturated conditions, Csat. We performed several experiments and tried to invert the electrokinetic coefficient data and interpret it in terms of physical processes. We also propose a field study through several geophysical methods, as electrical resistivity tomography, seismoelectrics, and GPR, in order to combine the results in terms of water-content dependence in soils.
A Study of the Mean Field Approach to Knapsack Problems.
Pi, Hong; Ohlsson, Mattias
1997-03-01
The mean field theory approach to knapsack problems is extended to multiple knapsacks and generalized assignment problems with Potts mean field equations governing the dynamics. Numerical tests against "state of the art" conventional algorithms shows good performance for the mean field approach. The inherently parallelism of the mean field equations makes them suitable for direct implementations in microchips. It is demonstrated numerically that the performance is essentially not affected when only a limited number of bits is used in the mean field equations. Also, a hybrid algorithm with linear programming and mean field components is showed to further improve the performance for the difficult homogeneous N x M knapsack problem. Copyright 1997 Elsevier Science Ltd. All Rights Reserved.
Elastic field of approaching dislocation loop in isotropic bimaterial
NASA Astrophysics Data System (ADS)
Wu, Wenwang; Xia, Re; Xu, Shucai; Qian, Guian; Zhang, Jinhuan
2015-10-01
A semi-analytical solution is developed for calculating interface traction stress (ITS) fields due to elastic modulus mismatch across the interface plane of isotropic perfectly bounded bimaterial system. Based on the semi-analytical approaches developed, ITS is used to correct the bulk elastic field of dislocation loop within infinite homogenous medium, and to produce continuous displacement and stress fields across the perfectly-bounded interface. Firstly, calculation examples of dislocation loops in Al-Cu bimaterial system are performed to demonstrate the efficiency of the developed semi-analytical approach; Then, the elastic fields of dislocation loops in twinning Cu and Cu-Nb bimaterial are analyzed; Finally, the effect of modulus mismatch across interface plane on the elastic field of bimaterial system is investigated, it is found that modulus mismatch has a drastic impact on the elastic fields of dislocation loops within bimaterial system.
CALIPERS. Planning the Systems Approach to Field Testing Educational Products.
ERIC Educational Resources Information Center
Southwest Educational Development Lab., Austin, TX.
Field testing, the last step in the developmental cycle for educational products, must ascertain whether the test product, placed in a natural environment, will actually elicit the behavioral changes it was designed to effect. A systems approach to field testing requires that certain basic areas of investigation first be established. Specific…
The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach
ERIC Educational Resources Information Center
Likar, A.; Razpet, N.
2009-01-01
The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…
An effectiveness analysis of healthcare systems using a systems theoretic approach
Chuang, Sheuwen; Inder, Kerry
2009-01-01
provides a systematic search for improving the impact of accreditation on quality of care and hence on the accreditation/performance correlation. Conclusion There is clear value in developing a theoretical systems approach to achieving quality in health care. The introduction of the systematic surveyor-based search for improvements creates an adaptive-control system to optimize health care quality. It is hoped that these outcomes will stimulate further research in the development of strategic planning using systems theoretic approach for the improvement of quality in health care. PMID:19852837
Approach to non-equilibrium behaviour in quantum field theory
Kripfganz, J.; Perlt, H.
1989-05-01
We study the real-time evolution of quantum field theoretic systems in non-equilibrium situations. Results are presented for the example of scalar /lambda//phi//sup 4/ theory. The degrees of freedom are discretized by studying the system on a torus. Short-wavelength modes are integrated out to one-loop order. The long-wavelength modes considered to be the relevant degrees of freedom are treated by semiclassical phase-space methods. /copyright/ 1989 Academic Press, Inc.
Thermal benefits of melanism in cordylid lizards: a theoretical and field test.
Clusella-Trullas, Susana; van Wyk, Johannes H; Spotila, James R
2009-08-01
The hypothesis that low skin reflectance (melanism) provides an advantage for thermoregulation under cold conditions has received mixed support in ectothermic vertebrates. We selected a model system, three allopatric closely related species of cordylid lizards that differ in skin reflectance, to test this hypothesis. Cordylus niger and Cordylus oelofseni are melanistic and inhabit peninsular and montane areas, respectively, whereas Cordylus cordylus is more widespread and inhabits low inland areas. By combining theoretical, experimental, and field data on these species, we demonstrate that the difference in body temperature (T(b)) between melanistic and non-melanistic lizards under ecologically relevant climate variation ranged from 0 degrees to 2 degrees C. Despite its small magnitude, however, the faster heating rate and higher T(b) of melanistic species relative to non-melanistic species conferred an advantage under cold conditions. Comparison of habitat thermal quality (d(e)) and thermal accuracy (d(b)) across species indicated that, in winter, melanism conferred the greatest advantage during small windows of thermal opportunity. This finding was most pronounced for C. oelofseni, which is most constrained by cold temperatures in its habitat. By contrast, due to their rock-dwelling habits, melanistic and non-melanistic species benefited from rock refugia in summer, giving similar levels of thermoregulatory effectiveness across species, regardless of skin reflectance. This study therefore demonstrates that skin reflectance variation across cordylids has significant effects on their thermal balance. Furthermore, studies investigating the role of varying skin reflectance in field populations and species should incorporate fine and broad temporal scales (daily, monthly, and seasonal), environmental variability, and cost-benefit trade-offs of thermoregulation.
Theoretical study on the shape instability of an encapsulated bubble in an ultrasound field
NASA Astrophysics Data System (ADS)
Liu, Yunqiao; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro
2012-09-01
A theoretical study on the shape instability of a slightly deformed bubble encapsulated by a viscoelastic membrane in an ultrasound field is performed. The membrane effects of the inplane stress and the bending moment are incorporated into the traction jump condition at the bubble surface. The spherical motion of the bubble is numerically obtained by solving the Rayleigh-Plesset equation with the elastic stress. The deflection therefrom is linearized and expanded with respect to the Legendre polynomial. Two amplitudes for each shape mode are introduced because the membrane has mobility not only in the radial direction but also in the tangential direction. A simple expression for the natural frequency of shape mode is derived. Stability diagrams for the higherorder shape mode are mapped out in the phase space of driving amplitude versus driving frequency. The most unstable driving frequency is found to satisfy an integer multiple relationship with twice of the higher-order natural frequency. This finding is justified by a fact that the system with a boundary layer approximation is simplified into Mathieu's equation. Liquid viscosity plays an important role in the shape stability due to the vorticity generation on the deformed membrane.
Nonrotating and rotating neutron stars in the extended field theoretical model
Dhiman, Shashi K.; Kumar, Raj; Agrawal, B. K.
2007-10-15
We study the properties of nonrotating and rotating neutron stars for a new set of equations of state (EOSs) with different high-density behavior obtained using the extended field theoretical model. The high-density behavior for these EOSs are varied by varying the {omega}-meson self-coupling and hyperon-meson couplings in such a way that the quality of fit to the bulk nuclear observables, nuclear matter incompressibility coefficient, and hyperon-nucleon potential depths remain practically unaffected. We find that the largest value for maximum mass for the nonrotating neutron star is 2.1M{sub {center_dot}}. The radius for a neutron star with canonical mass is 12.8-14.1 km, provided only those EOSs are considered for which the maximum mass is larger than 1.6M{sub {center_dot}}, the lower bound on the maximum mass measured so far. Our results for the very recently discovered fastest rotating neutron star indicate that this star is supramassive with mass 1.7M{sub {center_dot}}-2.7M{sub {center_dot}} and circumferential equatorial radius 12-19 km.
Flow field design development using the segmented cell approach
Bender, G.; Ramsey, J. C.
2002-01-01
We report on fuel cell flow-field development employing two-dimensional computational fluid dynamics (2-D CFD). Simulation of the flow distribution of a parallel channel flow-field, with a simple one-channel manifold, predicted inhomogeneous performance distribution within the cell. Further modeling, focusing on modification of the inlet and outlet flow fields, was used to predict a more homogeneous flow distribution in the flow-field. Attempts were made to verify the theoretical predictions experimentally by application of the segmented cell system. Measurements of the current distribution and CO transient response supported the 2-D CFD predictions. However, the margin of error between predicted and experimental results was considered insufficient to be of practical use. Future work will involve the evaluation of 3-D CFD to achieve the appropriate level of accuracy.
Understanding uncertainty in seagrass injury recovery: an information-theoretic approach.
Uhrin, Amy V; Kenworthy, W Judson; Fonseca, Mark S
2011-06-01
Vessel groundings cause severe, persistent gaps in seagrass beds. Varying degrees of natural recovery have been observed for grounding injuries, limiting recovery prediction capabilities, and therefore, management's ability to focus restoration efforts where natural recovery is unlikely. To improve our capacity for predicting seagrass injury recovery, we used an information-theoretic approach to evaluate the relative contribution of specific injury attributes to the natural recovery of 30 seagrass groundings in Florida Keys National Marine Sanctuary, Florida, USA. Injury recovery was defined by three response variables examined independently: (1) initiation of seagrass colonization, (2) areal contraction, and (3) sediment in-filling. We used a global model and all possible subsets for four predictor variables: (1) injury age, (2) original injury volume, (3) original injury perimeter-to-area ratio, and (4) wave energy. Successional processes were underway for many injuries with fast-growing, opportunistic seagrass species contributing most to colonization. The majority of groundings that exhibited natural seagrass colonization also exhibited areal contraction and sediment in-filling. Injuries demonstrating colonization, contraction, and in-filling were on average older and smaller, and they had larger initial perimeter-to-area ratios. Wave energy was highest for colonizing injuries. The information-theoretic approach was unable to select a single "best" model for any response variable. For colonization and contraction, injury age had the highest relative importance as a predictor variable; wave energy appeared to be associated with second-order effects, such as sediment in-filling, which in turn, facilitated seagrass colonization. For sediment in-filling, volume and perimeter-to-area ratio had similar relative importance as predictor variables with age playing a lesser role than seen for colonization and contraction. Our findings confirm that these injuries
Magnetic Hyperfine Fields in Lu_2V_2O_7: A Model Approach
NASA Astrophysics Data System (ADS)
Agzamova, Polina; Nikiforov, Anatoliy; Nazipov, Dmitriy
2016-12-01
We report a theoretical approach to the investigation of the magnetic hyperfine interaction on the ^{51}V nucleus in Lu_2V_2O_7 with the view of understanding the orbital ordering pattern in this compound. First, we have evaluated the vanadium 3d^1-level splitting (Δ ) under the crystal field with the D _{3d}-symmetry using the point charges approximation. Second, we have calculated the exchange interaction constant ( J) using the ab initio approach. It is shown that the crystal field energy is much stronger than the exchange interaction one and hence the orbital liquid state cannot occur in Lu_2V_2O_7. Finally we have analyzed the magnetic hyperfine field affecting the vanadium nucleus leaning upon these results.
Yahia, Mouna Ben; Orhan, Emmanuelle; Beltrán, Armando; Masson, Olivier; Merle-Méjean, Thérèse; Mirgorodski, Andreï; Thomas, Philippe
2008-09-04
Density functional theory was used to estimate the third-order hypersusceptibility chi (3) of the alpha-TeO2 paratellurite (as a model structure for TeO2 glass) and the same value for alpha-SiO2 cristobalite (as a model structure for glassy silica). The attempt was made to gain a physical insight into the nature of the extraordinarily high hypersusceptibility of TeO2 glass. A finite field perturbation method implemented in the CRYSTAL code with the "sawtooth" approach was employed. The chi (3) values calculated for alpha-TeO2 were found to be of the same order as that measured for TeO2 glass and much higher than the values computed for alpha-SiO2 which, in turn, were close to that of glassy silica.
NASA Astrophysics Data System (ADS)
Stoisser, C. M.; Audebert, S.
2008-05-01
In order to describe the state-of-the-art on cracked rotor related problems, the current work presents the comprehensive theoretical, numerical and experimental approach adopted by EDF for crack detection in power plant rotating machinery. The work mainly focuses on the theoretical cracked beam model developed in the past years by S. Andrieux and C. Varé and associates both numerical and experimental aspects related to the crack detection problem in either turboset or turbo pump units. The theoretical part consists of the derivation of a lumped cracked beam model from the three-dimensional formulation of the general problem of elasticity with unilateral contact conditions on the crack lips, valid for any shape and number of cracks in the beam section and extended to cracks not located in a cross-section. This leads to the assessment of the cracked beam rigidity as a function of the rotation angle, in case of pure bending load or bending plus shear load. In this way the function can be implemented in a 1D rotordynamics code. An extension of the cracked beam model taking into account the torsion behaviour is also proposed. It is based on the assumption of full adherence between crack lips, when the crack closes, and on an incremental formulation of deformation energy. An experimental validation has been carried out using different cracked samples, both in static and dynamic configurations, considering one or three elliptic cracks in the same cross-section and helix-shaped cracks. Concerning the static configuration, a good agreement between numerical and experimental results is found. It is shown to be equal to 1% maximal gap of the beam deflection. Concerning the dynamical analysis, the main well-known indicator 2× rev. bending vibration component at half critical speed is approximated at maximum by 18% near the crack position. Our experiments also allowed for the observation of the bending and torsion resonance frequency shifts determined by the extra
NASA Astrophysics Data System (ADS)
Golovin, Yuri I.; Gribanovsky, Sergey L.; Golovin, Dmitry Y.; Zhigachev, Alexander O.; Klyachko, Natalia L.; Majouga, Alexander G.; Sokolsky, Marina; Kabanov, Alexander V.
2017-02-01
In the past decade, magneto-nanomechanical approach to biochemical systems stimulation has been studied intensively. This method involves macromolecule structure local deformation via mechanical actuation of functionalized magnetic nanoparticles (f-MNPs) by non-heating low frequency (LF) alternating magnetic field (AMF). Specificity at cellular or molecular level and spatial locality in nanometer scale are its key advantages as compared to magnetic fluid hyperthermia. However, current experimental studies have weak theoretical basis. Several models of magneto-nanomechanical actuation of macromolecules and cells in non-heating uniform LF AMF are presented in the article. Single core-shell spherical, rod-like, and Janus MNPs, as well as dimers consisting of two f-MNPs with macromolecules immobilized on their surfaces are considered. AMF-induced rotational oscillations of MNPs can affect properties and functioning of macromolecules or cellular membranes attached to them via periodic deformations in nanometer scale. This could be widely used in therapy, in particular for targeted drug delivery, controlled drug release, and cancer cell killing. An aggregate composed of MNPs can affect associated macromolecules by force up to several hundreds of piconewton in the case of MNPs of tens of nanometers in diameter and LF AMF below 1 T. AMF parameters and MNP design requirements for effective in vitro and in vivo magneto-nanomechanical treatment are presented.
Network-Based Enriched Gene Subnetwork Identification: A Game-Theoretic Approach.
Razi, Abolfazl; Afghah, Fatemeh; Singh, Salendra; Varadan, Vinay
2016-01-01
Identifying subsets of genes that jointly mediate cancer etiology, progression, or therapy response remains a challenging problem due to the complexity and heterogeneity in cancer biology, a problem further exacerbated by the relatively small number of cancer samples profiled as compared with the sheer number of potential molecular factors involved. Pure data-driven methods that merely rely on multiomics data have been successful in discovering potentially functional genes but suffer from high false-positive rates and tend to report subsets of genes whose biological interrelationships are unclear. Recently, integrative data-driven models have been developed to integrate multiomics data with signaling pathway networks in order to identify pathways associated with clinical or biological phenotypes. However, these approaches suffer from an important drawback of being restricted to previously discovered pathway structures and miss novel genomic interactions as well as potential crosstalk among the pathways. In this article, we propose a novel coalition-based game-theoretic approach to overcome the challenge of identifying biologically relevant gene subnetworks associated with disease phenotypes. The algorithm starts from a set of seed genes and traverses a protein-protein interaction network to identify modulated subnetworks. The optimal set of modulated subnetworks is identified using Shapley value that accounts for both individual and collective utility of the subnetwork of genes. The algorithm is applied to two illustrative applications, including the identification of subnetworks associated with (i) disease progression risk in response to platinum-based therapy in ovarian cancer and (ii) immune infiltration in triple-negative breast cancer. The results demonstrate an improved predictive power of the proposed method when compared with state-of-the-art feature selection methods, with the added advantage of identifying novel potentially functional gene subnetworks
Hernández, Florencio E; Rizzo, Antonio
2011-04-18
Many phenomena, including life itself and its biochemical foundations are fundamentally rooted in chirality. Combinatorial methodologies for catalyst discovery and optimization remain an invaluable tool for gaining access to enantiomerically pure compounds in the development of pharmaceuticals, agrochemicals, and flavors. Some exotic metamaterials exhibiting negative refractive index at optical frequencies are based on chiral structures. Chiroptical activity is commonly quantified in terms of circular dichroism (CD) and optical rotatory dispersion (ORD). However, the linear nature of these effects limits their application in the far and near-UV region in highly absorbing and scattering biological systems. In order to surmount this barrier, in recent years we made important advancements on a novel non linear, low-scatter, long-wavelength CD approach called two-photon absorption circular dichroism (TPACD). Herein we present a descriptive analysis of the optics principles behind the experimental measurement of TPACD, i.e., the double L-scan technique, and its significance using pulsed lasers. We also make an instructive examination and discuss the reliability of our theoretical-computational approach, which uses modern analytical response theory, within a Time-Dependent Density Functional Theory (TD-DFT) approach. In order to illustrate the potential of this novel spectroscopic tool, we first present the experimental and theoretical results obtained in C(2)-symmetric, axially chiral R-(+)-1,1'-bi(2-naphthol), R-BINOL, a molecule studied at the beginning of our investigation in this field. Next, we reveal some preliminary results obtained for (R)-3,3'-diphenyl-2,2'-bi-1-naphthol, R-VANOL, and (R)-2,2'-diphenyl-3,3'-(4-biphenanthrol), R-VAPOL. This family of optically active compounds has been proven to be a suitable model for the structure-property relationship study of TPACD, because its members are highly conjugated yet photo-stable, and easily derivatized at the 5
Combination of real options and game-theoretic approach in investment analysis
NASA Astrophysics Data System (ADS)
Arasteh, Abdollah
2016-02-01
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.
A game theoretic approach to a finite-time disturbance attenuation problem
NASA Technical Reports Server (NTRS)
Rhee, Ihnseok; Speyer, Jason L.
1991-01-01
A disturbance attenuation problem over a finite-time interval is considered by a game theoretic approach where the control, restricted to a function of the measurement history, plays against adversaries composed of the process and measurement disturbances, and the initial state. A zero-sum game, formulated as a quadratic cost criterion subject to linear time-varying dynamics and measurements, is solved by a calculus of variation technique. By first maximizing the quadratic cost criterion with respect to the process disturbance and initial state, a full information game between the control and the measurement residual subject to the estimator dynamics results. The resulting solution produces an n-dimensional compensator which expresses the controller as a linear combination of the measurement history. A disturbance attenuation problem is solved based on the results of the game problem. For time-invariant systems it is shown that under certain conditions the time-varying controller becomes time-invariant on the infinite-time interval. The resulting controller satisfies an H(infinity) norm bound.
Optimal hemoglobin concentration and high altitude: a theoretical approach for Andean men at rest.
Villafuerte, Francisco C; Cárdenas, Rosa; Monge-C, Carlos
2004-05-01
The beneficial role of erythrocytosis for O2 transport has been questioned by evidence from bloodletting and hemodilution research as well as by studies suggesting the existence of an "optimal" hematocrit (Hct) or hemoglobin concentration ([Hb]) value. To assess to what extent erythrocytosis is beneficial in Andean men at high altitude, we examined and discussed optimal [Hb] using a mathematical approach by modeling the mixed (mean) venous Po2 (Pv(O2)) and arterial O2 content, considering for both the relation between [Hb] and arterial Po2. Relations of [Hb] to other physiological variables such as cardiac output and convective arterial O2 transport were also discussed, revealing the importance of Pv(O2) in this model. Our theoretical analysis suggests that increasing [Hb] allows increase and maintenance of Pv(O2) with only moderate declines in arterial Po2 as a consequence of moderate increases in altitude, reaching its maximum at the optimal [Hb] of 14.7 g/dl. Our analysis also shows that [Hb] corresponding to high arterial O2 content and O2 transport values is apparently not quite advantageous for improvement of oxygenation. Furthermore, chronic mountain sickness is discussed as an insightful example of the effects of excessive erythrocytosis at high altitude.
White, Craig R; Frappell, Peter B; Chown, Steven L
2012-09-07
The effects of body mass and temperature on metabolic rate (MR) are among the most widely examined physiological relationships. Recently, these relationships have been incorporated into the metabolic theory of ecology (MTE) that links the ecology of populations, communities and ecosystems to the MR of individual organisms. The fundamental equation of MTE derives the relation between mass and MR using first principles and predicts the temperature dependence of MR based on biochemical kinetics. It is a deliberately simple, zeroth-order approximation that represents a baseline against which variation in real biological systems can be examined. In the present study, we evaluate the fundamental equation of MTE against other more parameter-rich models for MR using an information-theoretic approach to penalize the inclusion of additional parameters. Using a comparative database of MR measurements for 1359 species, from 11 groups ranging from prokaryotes to mammals, and spanning 16 orders of magnitude in mass and a 59°C range in body temperature, we show that differences between taxa in the mass and temperature dependence of MR are sufficiently large as to be retained in the best model for MR despite the requirement for estimation of 22 more parameters than the fundamental equation of MTE.
NASA Astrophysics Data System (ADS)
Kannan, Srinivasa Ramanujam; Chandrasekar, V.
2016-05-01
Even though both the rain measuring instruments, radar and radiometer onboard the TRMM observe the same rain scenes, they both are fundamentally different instruments. Radar is an active instrument and measures backscatter component from vertical rain structure; whereas radiometer is a passive instrument that obtains integrated observation of full depth of the cloud and rain structure. Further, their spatial resolutions on ground are different. Nevertheless, both the instruments are observing the same rain scene and retrieve three dimensional rainfall products. Hence it is only natural to seek answer to the question, what type of information about radiometric observations can be directly retrieved from radar observations. While there are several ways to answer this question, an informational theoretic approach using neural networks has been described in the present work to find if radiometer observations can be predicted from radar observations. A database of TMI brightness temperature and collocated TRMM vertical attenuation corrected reflectivity factor from the year 2012 was considered. The entire database is further classified according to surface type. Separate neural networks were trained for land and ocean and the results are presented.
White, Craig R.; Frappell, Peter B.; Chown, Steven L.
2012-01-01
The effects of body mass and temperature on metabolic rate (MR) are among the most widely examined physiological relationships. Recently, these relationships have been incorporated into the metabolic theory of ecology (MTE) that links the ecology of populations, communities and ecosystems to the MR of individual organisms. The fundamental equation of MTE derives the relation between mass and MR using first principles and predicts the temperature dependence of MR based on biochemical kinetics. It is a deliberately simple, zeroth-order approximation that represents a baseline against which variation in real biological systems can be examined. In the present study, we evaluate the fundamental equation of MTE against other more parameter-rich models for MR using an information-theoretic approach to penalize the inclusion of additional parameters. Using a comparative database of MR measurements for 1359 species, from 11 groups ranging from prokaryotes to mammals, and spanning 16 orders of magnitude in mass and a 59°C range in body temperature, we show that differences between taxa in the mass and temperature dependence of MR are sufficiently large as to be retained in the best model for MR despite the requirement for estimation of 22 more parameters than the fundamental equation of MTE. PMID:22673353
GTXOP: A Game Theoretic Approach for QoS Provisioning Using Transmission Opportunity Tuning
Ghazvini, Mahdieh; Movahedinia, Naser; Jamshidi, Kamal
2013-01-01
In unsupervised contention-based networks such as EDCA mode of IEEE 802.11(e)(s), upon winning the channel, each node gets a transmission opportunity (TXOP) in which the node can transmit multiple frames consequently without releasing the channel. Adjusting TXOP can lead to better bandwidth utilization and QoS provisioning. To improve WLAN throughput performance, EDCA packet bursting can be used in 802.11e, meaning that once a station has gained an EDCA-TXOP, it can be allowed to transmit more than one frame without re-contending for the channel. Following the access to the channel, the station can send multiple frames as long as the total access time does not exceed the TXOP Limit. This mechanism can reduce the network overhead and increase the channel utilization instead. However, packet bursting may cause unfairness in addition to increasing jitter, delay and loss. To the best of the authors’ knowledge, although TXOP tuning has been investigated through different methods, it has not been considered within a game theory framework. In this study, based on the analytical models of EDCA, a game theoretic approach called GTXOP is proposed to determine TXOP dynamically (i.e. according to the dynamisms of WLAN networks and the number of nodes in the network). Using GTXOP, each node can choose its TXOP autonomously, such that in addition to QoS improvement, the overall network performance is also improved. PMID:23650539
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.
NASA Astrophysics Data System (ADS)
Praveena, R.; Sadasivam, K.
2016-05-01
Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET-PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different -OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H-atom abstraction from 4'-OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B-ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.
Freeberg, Todd M; Lucas, Jeffrey R
2012-02-01
One aim of this study was to apply information theoretical analyses to understanding the structural complexity of chick-a-dee calls of Carolina chickadees, Poecile carolinensis. A second aim of this study was to compare this structural complexity to that of the calls of black-capped chickadees, P. atricapillus, described in an earlier published report (Hailman, Ficken, & Ficken, 1985). Chick-a-dee calls were recorded from Carolina chickadees in a naturalistic observation study in eastern Tennessee. Calls were analyzed using approaches from information theory, including transition probability matrices, Zipf's rules, entropies, and information coding capacities of calls and notes of calls. As described for black-capped chickadees, calls of Carolina chickadees exhibited considerable structural complexity. Most results suggested that the call of Carolina chickadees is more structurally complex than that of black-capped chickadees. These findings add support to the growing literature on the complexity of this call system in Paridae species. Furthermore, these results point to the feasibility of detailed cross-species comparative analyses that may allow strong testing of hypotheses regarding signal evolution.
Estimation-theoretic approach to delayed decoding of predictively encoded video sequences.
Han, Jingning; Melkote, Vinay; Rose, Kenneth
2013-03-01
Current video coders employ predictive coding with motion compensation to exploit temporal redundancies in the signal. In particular, blocks along a motion trajectory are modeled as an auto-regressive (AR) process, and it is generally assumed that the prediction errors are temporally independent and approximate the innovations of this process. Thus, zero-delay encoding and decoding is considered efficient. This paper is premised on the largely ignored fact that these prediction errors are, in fact, temporally dependent due to quantization effects in the prediction loop. It presents an estimation-theoretic delayed decoding scheme, which exploits information from future frames to improve the reconstruction quality of the current frame. In contrast to the standard decoder that reproduces every block instantaneously once the corresponding quantization indices of residues are available, the proposed delayed decoder efficiently combines all accessible (including any future) information in an appropriately derived probability density function, to obtain the optimal delayed reconstruction per transform coefficient. Experiments demonstrate significant gains over the standard decoder. Requisite information about the source AR model is estimated in a spatio-temporally adaptive manner from a bit-stream conforming to the H.264/AVC standard, i.e., no side information needs to be sent to the decoder in order to employ the proposed approach, thereby compatibility with the standard syntax and existing encoders is retained.
Strategic exploration of battery waste management: A game-theoretic approach.
Kaushal, Rajendra Kumar; Nema, Arvind K; Chaudhary, Jyoti
2015-07-01
Electronic waste or e-waste is the fastest growing stream of solid waste today. It contains both toxic substances as well as valuable resources. The present study uses a non-cooperative game-theoretic approach for efficient management of e-waste, particularly batteries that contribute a major portion of any e-waste stream and further analyses the economic consequences of recycling of these obsolete, discarded batteries. Results suggest that the recycler would prefer to collect the obsolete batteries directly from the consumer rather than from the manufacturer, only if, the incentive return to the consumer is less than 33.92% of the price of the battery, the recycling fee is less than 6.46% of the price of the battery, and the price of the recycled material is more than 31.08% of the price of the battery. The manufacturer's preferred choice of charging a green tax from the consumer can be fruitful for the battery recycling chain.
Theoretical analysis of the local field potential in deep brain stimulation applications.
Lempka, Scott F; McIntyre, Cameron C
2013-01-01
Deep brain stimulation (DBS) is a common therapy for treating movement disorders, such as Parkinson's disease (PD), and provides a unique opportunity to study the neural activity of various subcortical structures in human patients. Local field potential (LFP) recordings are often performed with either intraoperative microelectrodes or DBS leads and reflect oscillatory activity within nuclei of the basal ganglia. These LFP recordings have numerous clinical implications and might someday be used to optimize DBS outcomes in closed-loop systems. However, the origin of the recorded LFP is poorly understood. Therefore, the goal of this study was to theoretically analyze LFP recordings within the context of clinical DBS applications. This goal was achieved with a detailed recording model of beta oscillations (∼20 Hz) in the subthalamic nucleus. The recording model consisted of finite element models of intraoperative microelectrodes and DBS macroelectrodes implanted in the brain along with multi-compartment cable models of STN projection neurons. Model analysis permitted systematic investigation into a number of variables that can affect the composition of the recorded LFP (e.g. electrode size, electrode impedance, recording configuration, and filtering effects of the brain, electrode-electrolyte interface, and recording electronics). The results of the study suggest that the spatial reach of the LFP can extend several millimeters. Model analysis also showed that variables such as electrode geometry and recording configuration can have a significant effect on LFP amplitude and spatial reach, while the effects of other variables, such as electrode impedance, are often negligible. The results of this study provide insight into the origin of the LFP and identify variables that need to be considered when analyzing LFP recordings in clinical DBS applications.
Theoretical Analysis of the Local Field Potential in Deep Brain Stimulation Applications
Lempka, Scott F.; McIntyre, Cameron C.
2013-01-01
Deep brain stimulation (DBS) is a common therapy for treating movement disorders, such as Parkinson’s disease (PD), and provides a unique opportunity to study the neural activity of various subcortical structures in human patients. Local field potential (LFP) recordings are often performed with either intraoperative microelectrodes or DBS leads and reflect oscillatory activity within nuclei of the basal ganglia. These LFP recordings have numerous clinical implications and might someday be used to optimize DBS outcomes in closed-loop systems. However, the origin of the recorded LFP is poorly understood. Therefore, the goal of this study was to theoretically analyze LFP recordings within the context of clinical DBS applications. This goal was achieved with a detailed recording model of beta oscillations (∼20 Hz) in the subthalamic nucleus. The recording model consisted of finite element models of intraoperative microelectrodes and DBS macroelectrodes implanted in the brain along with multi-compartment cable models of STN projection neurons. Model analysis permitted systematic investigation into a number of variables that can affect the composition of the recorded LFP (e.g. electrode size, electrode impedance, recording configuration, and filtering effects of the brain, electrode-electrolyte interface, and recording electronics). The results of the study suggest that the spatial reach of the LFP can extend several millimeters. Model analysis also showed that variables such as electrode geometry and recording configuration can have a significant effect on LFP amplitude and spatial reach, while the effects of other variables, such as electrode impedance, are often negligible. The results of this study provide insight into the origin of the LFP and identify variables that need to be considered when analyzing LFP recordings in clinical DBS applications. PMID:23555799
NASA Astrophysics Data System (ADS)
Kubo, Takayuki
2017-02-01
The theory of the superconductor-insulator-superconductor (SIS) multilayer structure for application in superconducting accelerating cavities is reviewed. The theoretical field limit, optimum layer thicknesses and material combination, and surface resistance are discussed for the SIS structure and are also reviewed for the superconductor-superconductor bilayer structure.
ERIC Educational Resources Information Center
Matsumoto, Mitsuko
2015-01-01
Some argue that the field of study of "education and conflict" has yet to be solidified since its emergence in the 1990s, partly due to the weak theory base. This article reviews the literature on the "contribution" of schooling in contemporary violent conflict, via three strands of theoretical ideas, to demonstrate the…
Subjective evaluation and electroacoustic theoretical validation of a new approach to audio upmixing
NASA Astrophysics Data System (ADS)
Usher, John S.
Audio signal processing systems for converting two-channel (stereo) recordings to four or five channels are increasingly relevant. These audio upmixers can be used with conventional stereo sound recordings and reproduced with multichannel home theatre or automotive loudspeaker audio systems to create a more engaging and natural-sounding listening experience. This dissertation discusses existing approaches to audio upmixing for recordings of musical performances and presents specific design criteria for a system to enhance spatial sound quality. A new upmixing system is proposed and evaluated according to these criteria and a theoretical model for its behavior is validated using empirical measurements. The new system removes short-term correlated components from two electronic audio signals using a pair of adaptive filters, updated according to a frequency domain implementation of the normalized-least-means-square algorithm. The major difference of the new system with all extant audio upmixers is that unsupervised time-alignment of the input signals (typically, by up to +/-10 ms) as a function of frequency (typically, using a 1024-band equalizer) is accomplished due to the non-minimum phase adaptive filter. Two new signals are created from the weighted difference of the inputs, and are then radiated with two loudspeakers behind the listener. According to the consensus in the literature on the effect of interaural correlation on auditory image formation, the self-orthogonalizing properties of the algorithm ensure minimal distortion of the frontal source imagery and natural-sounding, enveloping reverberance (ambiance) imagery. Performance evaluation of the new upmix system was accomplished in two ways: Firstly, using empirical electroacoustic measurements which validate a theoretical model of the system; and secondly, with formal listening tests which investigated auditory spatial imagery with a graphical mapping tool and a preference experiment. Both electroacoustic
Sexuality Education for Young People: A Theoretically Integrated Approach from Australia
ERIC Educational Resources Information Center
Goldman, Juliette D. G.
2010-01-01
Background: Teachers of sexuality education can often be uncertain about what theoretical basis and pedagogical strategies to use in their teaching. Sexuality educational programmes designed by teachers can often show few evident theoretical principles that have been applied in its construction. Thus, there seems to be a dearth of evidence of ways…
NASA Astrophysics Data System (ADS)
Omiste, Juan J.; González-Férez, Rosario
2016-12-01
We present a theoretical study of the mixed-field-orientation of asymmetric-top molecules in tilted static electric field and nonresonant linearly polarized laser pulse by solving the time-dependent Schrödinger equation. Within this framework, we compute the mixed-field orientation of a state-selected molecular beam of benzonitrile (C7H5N ) and compare with the experimental observations [J. L. Hansen et al., Phys. Rev. A 83, 023406 (2011), 10.1103/PhysRevA.83.023406] and with our previous time-independent descriptions [J. J. Omiste et al., Phys. Chem. Chem. Phys. 13, 18815 (2011), 10.1039/c1cp21195a]. For an excited rotational state, we investigate the field-dressed dynamics for several field configurations as those used in the mixed-field experiments. The nonadiabatic phenomena and their consequences on the rotational dynamics are analyzed in detail.
NASA Technical Reports Server (NTRS)
Alford, William J , Jr
1957-01-01
The flow-field characteristics beneath swept and unswept wings as determined by potential-flow theory are compared with the experimentally determined flow fields beneath swept and unswept wing-fuselage combinations. The potential-flow theory utilized considered both spanwise and chordwise distributions of vorticity as well as the wing-thickness effects. The perturbation velocities induced by a unit horseshoe vortex are included in tabular form. The theoretical predictions of the flow-field characteristics were qualitatively correct in all cases considered, although there were indications that the magnitudes of the downwash angles tended to be overpredicted as the tip of the swept wing was approached and that the sidewash angles ahead of the unswept wing were underpredicted. The calculated effects of compressibility indicated that significant increases in the chordwise variation of flow angles and dynamic-pressure ratios should be expected in going from low to high subsonic speeds.
Game-theoretic approach for improving cooperation in wireless multihop networks.
Ng, See-Kee; Seah, Winston K G
2010-06-01
Traditional networks are built on the assumption that network entities cooperate based on a mandatory network communication semantic to achieve desirable qualities such as efficiency and scalability. Over the years, this assumption has been eroded by the emergence of users that alter network behavior in a way to benefit themselves at the expense of others. At one extreme, a malicious user/node may eavesdrop on sensitive data or deliberately inject packets into the network to disrupt network operations. The solution to this generally lies in encryption and authentication. In contrast, a rational node acts only to achieve an outcome that he desires most. In such a case, cooperation is still achievable if the outcome is to the best interest of the node. The node misbehavior problem would be more pronounced in multihop wireless networks like mobile ad hoc and sensor networks, which are typically made up of wireless battery-powered devices that must cooperate to forward packets for one another. However, cooperation may be hard to maintain as it consumes scarce resources such as bandwidth, computational power, and battery power. This paper applies game theory to achieve collusive networking behavior in such network environments. In this paper, pricing, promiscuous listening, and mass punishments are avoided altogether. Our model builds on recent work in the field of Economics on the theory of imperfect private monitoring for the dynamic Bertrand oligopoly, and adapts it to the wireless multihop network. The model derives conditions for collusive packet forwarding, truthful routing broadcasts, and packet acknowledgments under a lossy wireless multihop environment, thus capturing many important characteristics of the network layer and link layer in one integrated analysis that has not been achieved previously. We also provide a proof of the viability of the model under a theoretical wireless environment. Finally, we show how the model can be applied to design a generic
Lin, Yu-Shi; Lin, Chung-Chih; Tsai, Yuh-Show; Ku, Tien-Chuan; Huang, Yi-Hung; Hsu, Chun-Nan
2010-01-01
Motivation: High-throughput image-based assay technologies can rapidly produce a large number of cell images for drug screening, but data analysis is still a major bottleneck that limits their utility. Quantifying a wide variety of morphological differences observed in cell images under different drug influences is still a challenging task because the result can be highly sensitive to sampling and noise. Results: We propose a graph-based approach to cell image analysis. We define graph transition energy to quantify morphological differences between image sets. A spectral graph theoretic regularization is applied to transform the feature space based on training examples of extremely different images to calibrate the quantification. Calibration is essential for a practical quantification method because we need to measure the confidence of the quantification. We applied our method to quantify the degree of partial fragmentation of mitochondria in collections of fluorescent cell images. We show that with transformation, the quantification can be more accurate and sensitive than that without transformation. We also show that our method outperforms competing methods, including neighbourhood component analysis and the multi-variate drug profiling method by Loo et al. We illustrate its utility with a study of Annonaceous acetogenins, a family of compounds with drug potential. Our result reveals that squamocin induces more fragmented mitochondria than muricin A. Availability: Mitochondrial cell images, their corresponding feature sets (SSLF and WSLF) and the source code of our proposed method are available at http://aiia.iis.sinica.edu.tw/. Contact: chunnan@iis.sinica.edu.tw Supplementary information: Supplementary data are available at Bioinformatics online. PMID:20529919
An algorithmic and information-theoretic approach to multimetric index construction
Schoolmaster, Donald R.; Grace, James B.; Schweiger, E. William; Guntenspergen, Glenn R.; Mitchell, Brian R.; Miller, Kathryn M.; Little, Amanda M.
2013-01-01
The use of multimetric indices (MMIs), such as the widely used index of biological integrity (IBI), to measure, track, summarize and infer the overall impact of human disturbance on biological communities has been steadily growing in recent years. Initially, MMIs were developed for aquatic communities using pre-selected biological metrics as indicators of system integrity. As interest in these bioassessment tools has grown, so have the types of biological systems to which they are applied. For many ecosystem types the appropriate biological metrics to use as measures of biological integrity are not known a priori. As a result, a variety of ad hoc protocols for selecting metrics empirically has developed. However, the assumptions made by proposed protocols have not be explicitly described or justified, causing many investigators to call for a clear, repeatable methodology for developing empirically derived metrics and indices that can be applied to any biological system. An issue of particular importance that has not been sufficiently addressed is the way that individual metrics combine to produce an MMI that is a sensitive composite indicator of human disturbance. In this paper, we present and demonstrate an algorithm for constructing MMIs given a set of candidate metrics and a measure of human disturbance. The algorithm uses each metric to inform a candidate MMI, and then uses information-theoretic principles to select MMIs that capture the information in the multidimensional system response from among possible MMIs. Such an approach can be used to create purely empirical (data-based) MMIs or can, optionally, be influenced by expert opinion or biological theory through the use of a weighting vector to create value-weighted MMIs. We demonstrate the algorithm with simulated data to demonstrate the predictive capacity of the final MMIs and with real data from wetlands from Acadia and Rocky Mountain National Parks. For the Acadia wetland data, the algorithm identified
The effective field theorist's approach to gravitational dynamics
NASA Astrophysics Data System (ADS)
Porto, Rafael A.
2016-05-01
We review the effective field theory (EFT) approach to gravitational dynamics. We focus on extended objects in long-wavelength backgrounds and gravitational wave emission from spinning binary systems. We conclude with an introduction to EFT methods for the study of cosmological large scale structures.
This project investigated an innovative approach for transport of inorganic species under the influence of electric fields. This process, commonly known as electrokinetics uses low-level direct current (dc) electrical potential difference across a soil mass applied through inert...
Group theoretical approach to nonlinear evolution equations of lax type III. The Boussinesq equation
NASA Astrophysics Data System (ADS)
Levi, D.; Olshanetsky, M. A.; Perelomov, A. M.; Ragnisco, O.
1980-06-01
Within the group theoretical framework recently proposed by Berezin and Perelomov, we are able to derive an abstract (operator) generalization of the classical Boussinesq equation, which possesses an infinite sequence of conserved quantities.
NASA Technical Reports Server (NTRS)
Pauley, Patricia M.; Wu, Xiaohua
1990-01-01
The response of the Barnes objective analysis scheme is studied as a function of wavenumber or wavelength. The first- and second-pass theoretical response functions for continuous two-dimensional fields are derived using Fourier transforms. The results are compared with Barnes' (1973) responses for one-dimensional waves. The continuous theoretical response for one- and two-dimensional waves is compared with the response for discrete applications using uniformly spaced observations for the case where interpolation points and observation points are coincident and for the case where interpolation points are midway between observation points. The actual response of an idealized discrete application of the Barnes scheme is examined, confirming the results of the analysis of the discrete theoretical response.
NASA Technical Reports Server (NTRS)
El-Kaddah, N.; Szekely, J.
1982-01-01
A mathematical representation for the electromagnetic force field and the fluid flow field in a coreless induction furnace is presented. The fluid flow field was represented by writing the axisymmetric turbulent Navier-Stokes equation, containing the electromagnetic body force term. The electromagnetic body force field was calculated by using a technique of mutual inductances. The kappa-epsilon model was employed for evaluating the turbulent viscosity and the resultant differential equations were solved numerically. Theoretically predicted velocity fields are in reasonably good agreement with the experimental measurements reported by Hunt and Moore; furthermore, the agreement regarding the turbulent intensities are essentially quantitative. These results indicate that the kappa-epsilon model provides a good engineering representation of the turbulent recirculating flows occurring in induction furnaces. At this stage it is not clear whether the discrepancies between measurements and the predictions, which were not very great in any case, are attributable either to the model or to the measurement techniques employed.
NASA Astrophysics Data System (ADS)
El-Kaddah, N.; Szekely, J.
A mathematical representation for the electromagnetic force field and the fluid flow field in a coreless induction furnace is presented. The fluid flow field was represented by writing the axisymmetric turbulent Navier-Stokes equation, containing the electromagnetic body force term. The electromagnetic body force field was calculated by using a technique of mutual inductances. The kappa-epsilon model was employed for evaluating the turbulent viscosity and the resultant differential equations were solved numerically. Theoretically predicted velocity fields are in reasonably good agreement with the experimental measurements reported by Hunt and Moore; furthermore, the agreement regarding the turbulent intensities are essentially quantitative. These results indicate that the kappa-epsilon model provides a good engineering representation of the turbulent recirculating flows occurring in induction furnaces. At this stage it is not clear whether the discrepancies between measurements and the predictions, which were not very great in any case, are attributable either to the model or to the measurement techniques employed.
Moving beyond the Galloway diagrams for delta classification: A graph-theoretic approach.
NASA Astrophysics Data System (ADS)
Tejedor, Alejandro; Longjas, Anthony; Caldwell, Rebecca; Edmonds, Douglas; Zaliapin, Ilya; Foufoula-Georgiou, Efi
2016-04-01
Delta channel networks self-organize to a variety of stunning and complex patterns in response to different forcings (e.g., river, tides and waves) and the physical properties of their sediment (e.g., particle size, cohesiveness). Understanding and quantifying properties of these patterns is an essential step to solve the inverse problem of inferring process from form. A recently introduced framework based on spectral graph theory allows us to assess delta channel network complexity from a topologic (channel connectivity) and dynamic (flux exchange) perspective [Tejedor et al., 2015a,b]. We demonstrate the potential of this framework, together with numerical and experimental deltas, wherein different delta properties can be varied individually, to replace the qualitative approach still in use today [Galloway, 1975; Orton and Reading, 1993]. Specifically, in this work we have examined the effect of sediment parameters (grain size, cohesiveness) on the channel structure of river dominated deltas generated by a morphodynamic model (Delft3D). Our analysis shows that deltas with coarser incoming sediment are more complex topologically (increased number of looped pathways) but simpler dynamically (reduced flux exchange between subnetworks). We capitalize on the combined approach of controlled simulation (with known drivers) and quantitative comparison by positioning field and simulated deltas in the so-called TopoDynamic space to open up a path to provide valuable information towards a refined classification and inference scheme of delta morphology. Furthermore, numerical deltas allow us to explore the delta channel structure not only in a spatially explicit manner but also temporally, since the complete temporal record of delta evolution is available
2014-01-01
Background High-throughput methods for biological measurements generate vast amounts of quantitative data, which necessitate the development of advanced approaches to data analysis to help understand the underlying mechanisms and networks. Reconstruction of biological networks from measured data of different components is a significant challenge in systems biology. Results We use an information theoretic approach to reconstruct phosphoprotein-cytokine networks in RAW 264.7 macrophage cells. Cytokines are secreted upon activation of a wide range of regulatory signals transduced by the phosphoprotein network. Identifying these components can help identify regulatory modules responsible for the inflammatory phenotype. The information theoretic approach is based on estimation of mutual information of interactions by using kernel density estimators. Mutual information provides a measure of statistical dependencies between interacting components. Using the topology of the network derived, we develop a data-driven parsimonious input–output model of the phosphoprotein-cytokine network. Conclusions We demonstrate the applicability of our information theoretic approach to reconstruction of biological networks. For the phosphoprotein-cytokine network, this approach not only captures most of the known signaling components involved in cytokine release but also predicts new signaling components involved in the release of cytokines. The results of this study are important for gaining a clear understanding of macrophage activation during the inflammation process. PMID:24964861
NASA Astrophysics Data System (ADS)
Diaz, Carlos; Llovera, Ligia; Echevarria, Lorenzo; Hernández, Florencio E.
2015-02-01
Herein, we present a simple and versatile theoretical-experimental approach to assess the tautomeric distribution on 5(6)-aminobenzimidazole (5(6)-ABZ) derivatives in solution via one-photon absorption. The method is based on the optimized weighted sum of the theoretical spectra of the corresponding tautomers. In this article we show how the choice of exchange-correlation functional (XCF) employed in the calculations becomes crucial for the success of the approach. After the systematic analysis of XCFs with different amounts of exact-exchange we found a better performance for B3LYP and PBE0. The direct test of the proposed method on omeprazole, a well-known 5(6)-benzimidazole based pharmacotherapeutic, demonstrate its broader applicability. The proposed approach is expected to find direct applications on the tautomeric analysis of other molecular systems exhibiting similar tautomeric equilibria.
Managing US-Mexico "border health": an organizational field approach.
Collins-Dogrul, Julie
2006-12-01
During World War II Mexican and US health professionals and organizations constructed a transnational organizational field to manage the border's public health problems. Despite barriers to inter-organizational cooperation, including disparate administrative structures and North-South stratification, the field's transnational approach to health on the border has continued for 60 years. Using archival data to track changes in the number and types of organizations, this article argues that the field practitioners call "border health" reconfigured during the North American Free Trade Association (NAFTA) decade from an era of loosely organized professionals to a specialized bureaucracies era. This change brought new vitality to border health, with transnational ties increasing and diversifying, but has not weakened entrenched cross-border inequalities. The organizational history of the US-Mexico border health field demonstrates how macro-politics and inter-organizational stratification shape transnational public health problems.
TIME3D-IGGCAS: A New Three-Dimension Theoretical Ionospheric Model in realistic geomagnetic fields
NASA Astrophysics Data System (ADS)
Ren, Zhipeng; Liu, Libo; Huijun Le, lake709.; Wan, Weixing
Based on the previous work, a new global three-dimension theoretical ionospheric model in realistic geomagnetic fields is developed, named Three-Dimension Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS). This new model covers the whole ionosphere and plasmasphere. It self-consistently solves the equations of mass continuity, motion and energy of electron and ions to give out the time-dependent three-dimensional structures of the main ionospheric and plasmaspheric parameters in realistic geomagnetic fields, including ion number densities of O+, H+, He+, NO+, O2+ , N2+ and electron; electron and ion temperature; and ion velocity vectors. TIME3D-IGGCAS can also self-consistently run as the module of ionosphere-plasmasphere of GCITEM-IGGCAS (Global Coupled Ionosphere-Thermosphere-Electrodynamics Model developed at Institute of Geology and Geophysics, Chinese Academy of Sciences). We carry out simulations in March Equinox and in June Solstice, and compare the simulated results with that from IRI empirical model. TIME3D-IGGCAS can well reproduce the main ionospheric features in all simulations. We also simulate the ionospheric differences between different kinds of geomagnetic fields. The results suggest that the geomagnetic field configuration obviously affect the ionospheric plasma density, and the differences between NmF2 in realistic geomagnetic fields and that in tilted dipole fields can be larger than 60%.
Anderson, Rachel M; Yancey, David F; Zhang, Liang; Chill, Samuel T; Henkelman, Graeme; Crooks, Richard M
2015-05-19
The objective of the research described in this Account is the development of high-throughput computational-based screening methods for discovery of catalyst candidates and subsequent experimental validation using appropriate catalytic nanoparticles. Dendrimer-encapsulated nanoparticles (DENs), which are well-defined 1-2 nm diameter metal nanoparticles, fulfill the role of model electrocatalysts. Effective comparison of theory and experiment requires that the theoretical and experimental models map onto one another perfectly. We use novel synthetic methods, advanced characterization techniques, and density functional theory (DFT) calculations to approach this ideal. For example, well-defined core@shell DENs can be synthesized by electrochemical underpotential deposition (UPD), and the observed deposition potentials can be compared to those calculated by DFT. Theory is also used to learn more about structure than can be determined by analytical characterization alone. For example, density functional theory molecular dynamics (DFT-MD) was used to show that the core@shell configuration of Au@Pt DENs undergoes a surface reconstruction that dramatically affects its electrocatalytic properties. A separate Pd@Pt DENs study also revealed reorganization, in this case a core-shell inversion to a Pt@Pd structure. Understanding these types of structural changes is critical to building correlations between structure and catalytic function. Indeed, the second principal focus of the work described here is correlating structure and catalytic function through the combined use of theory and experiment. For example, the Au@Pt DENs system described earlier is used for the oxygen reduction reaction (ORR) as well as for the electro-oxidation of formic acid. The surface reorganization predicted by theory enhances our understanding of the catalytic measurements. In the case of formic acid oxidation, the deformed nanoparticle structure leads to reduced CO binding energy and therefore
NASA Technical Reports Server (NTRS)
Bridges, N. T.; Laity, J. E.
2001-01-01
rocks on Mars should erode at a rate of 7.7 to 210 micrometers/yr. These rates cannot have operated over the entire history of the Pathfinder site or elsewhere on Mars, because craters, knobs, and other obstacles would be quickly worn away. More likely, rock abrasion occurs over short time periods when sand supplies are sufficient and saltation friction speeds are frequently reached. Depletion or exhaustion of sand and a decline in wind fluxes at speeds greater than that of saltation friction will then act to reduce the rate of further abrasion. We are currently engaged in a new set of wind tunnel experiments coupled with theoretical models and field studies that address rock abrasion and ventifact formation on Mars and Earth. These studies have implications for the Noachian, when sand supplies were probably more plentiful and the threshold friction speed was possibly lower because of a more dense atmosphere. Under these conditions, erosion rates from the wind could have been much greater than to day, contributing, along with probable fluvial erosion, to the Noachian landscape that is in limited preservation today.
PDF approach for turbulent scalar field: Some recent developments
NASA Technical Reports Server (NTRS)
Gao, Feng
1993-01-01
The probability density function (PDF) method has been proven a very useful approach in turbulence research. It has been particularly effective in simulating turbulent reacting flows and in studying some detailed statistical properties generated by a turbulent field There are, however, some important questions that have yet to be answered in PDF studies. Our efforts in the past year have been focused on two areas. First, a simple mixing model suitable for Monte Carlo simulations has been developed based on the mapping closure. Secondly, the mechanism of turbulent transport has been analyzed in order to understand the recently observed abnormal PDF's of turbulent temperature fields generated by linear heat sources.
Revolution in Field Science: Apollo Approach to Inaccessible Surface Exploration
NASA Astrophysics Data System (ADS)
Clark, P. E.
2010-07-01
The extraordinary challenge mission designers, scientists, and engineers, faced in planning the first human expeditions to the surface of another solar system body led to the development of a distinctive and even revolutionary approach to field work. Not only were those involved required to deal effectively with the extreme limitation in resources available for and access to a target as remote as the lunar surface; they were required to developed a rigorous approach to science activities ranging from geological field work to deploying field instruments. Principal aspects and keys to the success of the field work are discussed here, including the highly integrated, intensive, and lengthy science planning, simulation, and astronaut training; the development of a systematic scheme for description and documentation of geological sites and samples; and a flexible yet disciplined methodology for site documentation and sample collection. The capability for constant communication with a ‘backroom’ of geological experts who make requests and weigh in on surface operations was innovative and very useful in encouraging rapid dissemination of information to the greater community in general. An extensive archive of the Apollo era science activity related documents provides evidence of the principal aspects and keys to the success of the field work. The Apollo Surface Journal allows analysis of the astronaut’s performance in terms of capability for traveling on foot, documentation and sampling of field stations, and manual operation of tools and instruments, all as a function of time. The application of these analysis as ‘lessons learned’ for planning the next generation of human or robotic field science activities on the Moon and elsewhere are considered here as well.
Batista Ferrer, Harriet; Audrey, Suzanne; Trotter, Caroline; Hickman, Matthew
2015-01-01
Background Interventions to increase uptake of Human Papillomavirus (HPV) vaccination by young women may be more effective if they are underpinned by an appropriate theoretical model or framework. The aims of this review were: to describe the theoretical models or frameworks used to explain behaviours in relation to HPV vaccination of young women, and: to consider the appropriateness of the theoretical models or frameworks used for informing the development of interventions to increase uptake. Methods Primary studies were identified through a comprehensive search of databases from inception to December 2013. Results Thirty-four relevant studies were identified, of which 31 incorporated psychological health behaviour models or frameworks and three used socio-cultural models or theories. The primary studies used a variety of approaches to measure a diverse range of outcomes in relation to behaviours of professionals, parents, and young women. The majority appeared to use theory appropriately throughout. About half of the quantitative studies presented data in relation to goodness of fit tests and the proportion of the variability in the data. Conclusion Due to diverse approaches and inconsistent findings across studies, the current contribution of theory to understanding and promoting HPV vaccination uptake is difficult to assess. Ecological frameworks encourage the integration of individual and social approaches by encouraging exploration of the intrapersonal, interpersonal, organisational, community and policy levels when examining public health issues. Given the small number of studies using such approach, combined with the importance of these factors in predicting behaviour, more research in this area is warranted. PMID:26314783
Morini, Filippo; Deleuze, Michael S.; Watanabe, Noboru; Takahashi, Masahiko
2015-03-07
The influence of thermally induced nuclear dynamics (molecular vibrations) in the initial electronic ground state on the valence orbital momentum profiles of furan has been theoretically investigated using two different approaches. The first of these approaches employs the principles of Born-Oppenheimer molecular dynamics, whereas the so-called harmonic analytical quantum mechanical approach resorts to an analytical decomposition of contributions arising from quantized harmonic vibrational eigenstates. In spite of their intrinsic differences, the two approaches enable consistent insights into the electron momentum distributions inferred from new measurements employing electron momentum spectroscopy and an electron impact energy of 1.2 keV. Both approaches point out in particular an appreciable influence of a few specific molecular vibrations of A{sub 1} symmetry on the 9a{sub 1} momentum profile, which can be unravelled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Morini, Filippo; Deleuze, Michael S; Watanabe, Noboru; Takahashi, Masahiko
2015-03-07
The influence of thermally induced nuclear dynamics (molecular vibrations) in the initial electronic ground state on the valence orbital momentum profiles of furan has been theoretically investigated using two different approaches. The first of these approaches employs the principles of Born-Oppenheimer molecular dynamics, whereas the so-called harmonic analytical quantum mechanical approach resorts to an analytical decomposition of contributions arising from quantized harmonic vibrational eigenstates. In spite of their intrinsic differences, the two approaches enable consistent insights into the electron momentum distributions inferred from new measurements employing electron momentum spectroscopy and an electron impact energy of 1.2 keV. Both approaches point out in particular an appreciable influence of a few specific molecular vibrations of A1 symmetry on the 9a1 momentum profile, which can be unravelled from considerations on the symmetry characteristics of orbitals and their energy spacing.
On Theoretical Broadband Shock-Associated Noise Near-Field Cross-Spectra
NASA Technical Reports Server (NTRS)
Miller, Steven A. E.
2015-01-01
The cross-spectral acoustic analogy is used to predict auto-spectra and cross-spectra of broadband shock-associated noise in the near-field and far-field from a range of heated and unheated supersonic off-design jets. A single equivalent source model is proposed for the near-field, mid-field, and far-field terms, that contains flow-field statistics of the shock wave shear layer interactions. Flow-field statistics are modeled based upon experimental observation and computational fluid dynamics solutions. An axisymmetric assumption is used to reduce the model to a closed-form equation involving a double summation over the equivalent source at each shock wave shear layer interaction. Predictions are compared with a wide variety of measurements at numerous jet Mach numbers and temperature ratios from multiple facilities. Auto-spectral predictions of broadband shock-associated noise in the near-field and far-field capture trends observed in measurement and other prediction theories. Predictions of spatial coherence of broadband shock-associated noise accurately capture the peak coherent intensity, frequency, and spectral width.
THEORETICAL ESTIMATES OF TWO-POINT SHEAR CORRELATION FUNCTIONS USING TANGLED MAGNETIC FIELDS
Pandey, Kanhaiya L.; Sethi, Shiv K.
2012-03-20
The existence of primordial magnetic fields can induce matter perturbations with additional power at small scales as compared to the usual {Lambda}CDM model. We study its implication within the context of a two-point shear correlation function from gravitational lensing. We show that a primordial magnetic field can leave its imprints on the shear correlation function at angular scales {approx}< a few arcminutes. The results are compared with CFHTLS data, which yield some of the strongest known constraints on the parameters (strength and spectral index) of the primordial magnetic field. We also discuss the possibility of detecting sub-nano Gauss fields using future missions such as SNAP.
Approaches, field considerations and problems associated with radio tracking carnivores
Sargeant, A.B.; Amlaner, C. J.; MacDonald, D.W.
1979-01-01
The adaptation of radio tracking to ecological studies was a major technological advance affecting field investigations of animal movements and behavior. Carnivores have been the recipients of much attention with this new technology and study approaches have varied from simple to complex. Equipment performance has much improved over the years, but users still face many difficulties. The beginning of all radio tracking studies should be a precise definition of objectives. Study objectives dictate type of gear required and field procedures. Field conditions affect equipment performance and investigator ability to gather data. Radio tracking carnivores is demanding and generally requires greater time than anticipated. Problems should be expected and planned for in study design. Radio tracking can be an asset in carnivore studies but caution is needed in its application.
A conservative approach for flow field calculations on multiple grids
NASA Technical Reports Server (NTRS)
Kathong, Monchai; Tiwari, Surendra N.
1988-01-01
In the computation of flow fields about complex configurations, it is very difficult to construct body-fitted coordinate systems. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach and its applications are investigated in this study. The method follows the conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-state Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Some steady state solutions of the Euler equations are presented and discussed.
The interacting gaps model: reconciling theoretical and numerical approaches to limit-order models
NASA Astrophysics Data System (ADS)
Muchnik, Lev; Slanina, Frantisek; Solomon, Sorin
2003-12-01
We consider the emergence of power-law tails in the returns distribution of limit-order driven markets. We explain a previously observed clash between the theoretical and numerical studies of such models. We introduce a solvable model that interpolates between the previous studies and agrees with each of them in the relevant limit.
Evans, R; Ferguson, E
2014-01-01
Background and Objectives While blood donation is traditionally described as a behaviour motivated by pure altruism, the assessment of altruism in the blood donation literature has not been theoretically informed. Drawing on theories of altruism from psychology, economics and evolutionary biology, it is argued that a theoretically derived psychometric assessment of altruism is needed. Such a measure is developed in this study that can be used to help inform both our understanding of the altruistic motives of blood donors and recruitment intervention strategies. Materials and Methods A cross-sectional survey (N = 414), with a 1-month behavioural follow-up (time 2, N = 77), was designed to assess theoretically derived constructs from psychological, economic and evolutionary biological theories of altruism. Theory of planned behaviour (TPB) variables and co-operation were also assessed at time 1 and a measure of behavioural co-operation at time 2. Results Five theoretical dimensions (impure altruism, kinship, self-regarding motives, reluctant altruism and egalitarian warm glow) of altruism were identified through factor analyses. These five altruistic motives differentiated blood donors from non-donors (donors scored higher on impure altruism and reluctant altruism), showed incremental validity over TPB constructs to predict donor intention and predicted future co-operative behaviour. Conclusions These findings show that altruism in the context of blood donation is multifaceted and complex and, does not reflect pure altruism. This has implication for recruitment campaigns that focus solely on pure altruism. PMID:24117697
A group-theoretic approach to constructions of non-relativistic spin-statistics
NASA Astrophysics Data System (ADS)
Harrison, J. M.; Robbins, J. M.
2000-11-01
We give a group-theoretical generalization of Berry and Robbins' treatment of identical particles with spin. The original construction, which leads to the correct spin-statistics relation, is seen to arise from particular irreducible representations—the totally symmetric representations—of the group SU(4). Here we calculate the exchange signs and corresponding statistics for all irreducible representations of SU(4).
Recent theoretical studies of internal structure and stability of field-reversed configurations
Webster, R.B.; Lewis, H.R.; Staudenmeier, J.L.; Milroy, R.D.; Barnes, D.C.; Bishop, R.C.; Spencer, R.L.; Xu, Y.H.; Matheson, P.L.
1988-01-01
In this paper we present the results of recent examinations of the low frequency, large scale stability of the field-reversed configurations (FRC). We also examined the ability to accurately infer internal transport quantities (e.g., field null resistivity) in an FRC. 7 refs., 5 figs.
Theoretical and experimental study of a high-current vacuum arc in a uniform axial magnetic field
NASA Astrophysics Data System (ADS)
Morimiya, Osami
1992-01-01
Measurements of the electron temperature, floating potential, plasma density, and average plasma pressure in a magnetically confined high-current vacuum arc are described. A 40-mm-diam, 30-mm-long arc was initiated between OFCu copper electrodes in a uniform axial magnetic field by triggering the gap. The crest values of the arc current ranged from 3 to 20 kA. The electron temperature by Langmuir probe measurement was Te= 2.5-3.0 eV with a uniform space distribution and was independent of the arc current. The space distribution of the ion density was parabolic in the radial direction and with a zero derivative in the axial direction. The average plasma pressure by paramagnetic measurement increased with the square of the arc current. The experiment showed that the arc column could be considered as an infinitely long column in which the plasma parameters have zero axial derivatives. Theoretical analysis has been carried out under the following assumptions. An infinitely long cylindrical and fully ionized steady-state plasma in which all quantities varied in the r direction only was considered. The anisotropy factor σ∥/σ⊥ for electrical conductivities was taken into account in the theoretical analysis, where σ∥ and σ⊥ were electrical conductivities parallel to the magnetic field and perpendicular to it, respectively. The plasma parameters determined from the experiments and theoretical analysis agreed closely with each other when the factor σ∥/σ⊥ was equal to ˜2, which is the theoretical upper limit in a high magnetic field. Constant temperature characteristics independent of the arc current have been found to be clearly seen by using line radiation as the dominant power loss in the power balance equation.
Theoretical investigation of boundary contours of ground-state atoms in uniform electric fields
NASA Astrophysics Data System (ADS)
Shi, Hua; Zhao, Dong-Xia; Yang, Zhong-Zhi
2015-12-01
The boundary contours were investigated for first 54 ground-state atoms of the periodic table when they are in uniform electric fields of strengths 106, 107 and 108 V/m. The atomic characteristic boundary model in combination with an ab-initio method was employed. Some regularities of the deformation of atoms, ΔR, in above electric fields are revealed. Furthermore, atomic polarisabilities of the first 54 elements of the periodic table are shown to correlate strongly with the mean variation rate of atomic radial size divided by the strength of the electric field F, ?, which provides a predictive method of calculating atomic polarisabilities of 54 atoms.
A hypothesis-driven approach to optimize field campaigns
NASA Astrophysics Data System (ADS)
Nowak, Wolfgang; Rubin, Yoram; de Barros, Felipe P. J.
2012-06-01
Most field campaigns aim at helping in specified scientific or practical tasks, such as modeling, prediction, optimization, or management. Often these tasks involve binary decisions or seek answers to yes/no questions under uncertainty, e.g., Is a model adequate? Will contamination exceed a critical level? In this context, the information needs of hydro(geo)logical modeling should be satisfied with efficient and rational field campaigns, e.g., because budgets are limited. We propose a new framework to optimize field campaigns that defines the quest for defensible decisions as the ultimate goal. The key steps are to formulate yes/no questions under uncertainty as Bayesian hypothesis tests, and then use the expected failure probability of hypothesis testing as objective function. Our formalism is unique in that it optimizes field campaigns for maximum confidence in decisions on model choice, binary engineering or management decisions, or questions concerning compliance with environmental performance metrics. It is goal oriented, recognizing that different models, questions, or metrics deserve different treatment. We use a formal Bayesian scheme called PreDIA, which is free of linearization, and can handle arbitrary data types, scientific tasks, and sources of uncertainty (e.g., conceptual, physical, (geo)statistical, measurement errors). This reduces the bias due to possibly subjective assumptions prior to data collection and improves the chances of successful field campaigns even under conditions of model uncertainty. We illustrate our approach on two instructive examples from stochastic hydrogeology with increasing complexity.
Primordial statistical anisotropies: the effective field theory approach
Abolhasani, Ali Akbar; Akhshik, Mohammad; Emami, Razieh; Firouzjahi, Hassan E-mail: m.akhshik@ipm.ir E-mail: firouz@ipm.ir
2016-03-01
In this work we present the effective field theory of primordial statistical anisotropies generated during anisotropic inflation involving a background U(1) gauge field. Besides the usual Goldstone boson associated with the breaking of time diffeomorphism we have two additional Goldstone bosons associated with the breaking of spatial diffeomorphisms. We further identify these two new Goldstone bosons with the expected two transverse degrees of the U(1) gauge field fluctuations. Upon defining the appropriate unitary gauge, we present the most general quadratic action which respects the remnant symmetry in the unitary gauge. The interactions between various Goldstone bosons leads to statistical anisotropy in curvature perturbation power spectrum. Calculating the general results for power spectrum anisotropy, we recover the previously known results in specific models of anisotropic inflation. In addition, we present novel results for statistical anisotropy in models with non-trivial sound speed for inflaton fluctuations. Also we identify the interaction which leads to birefringence-like effects in anisotropic power spectrum in which the speed of gauge field fluctuations depends on the direction of the mode propagation and the two polarization of gauge field fluctuations contribute differently in statistical anisotropy. As another interesting application, our EFT approach naturally captures interactions generating parity violating statistical anisotropies.
NASA Astrophysics Data System (ADS)
Zuo, Wanlong; Ben, Shuai; Lv, Hang; Zhao, Lei; Guo, Jing; Liu, Xue-Shen; Xu, Haifeng; Jin, Mingxing; Ding, Dajun
2016-05-01
Nonsequential double ionization (NSDI) of carbon disulfide CS2 in strong 800-nm laser fields is studied experimentally and theoretically. A knee structure is observed in the intensity-dependent double ionization (DI) yield in linearly polarized laser fields, which exhibits a strong dependence on the laser ellipticity. The electron momentum distributions and energy trajectories after DI in both linearly and circularly polarized laser fields are investigated by employing the two-dimensional classical ensemble method. The results clearly show the evidence of NSDI in the strong-field DI of CS2 molecules. It is demonstrated that, similar to that of atoms, NSDI of CS2 molecules is produced via laser-driven electron recollision with the ion core and presents electron-electron correlations in the process. Analysis indicates that both mechanisms in atomic strong-field NSDI, i.e., recollision impact ionization and recollision excitation with subsequent ionization, may also be contributed to NSDI of CS2 in strong laser fields. Further studies are no doubt necessary for a full understanding of the underlying physical mechanism of molecular strong-field NSDI, due to the multicenter character of the molecular structure and the complex molecular excited states that could be involved in the ionization.
Theoretical model of DC electric field formation in the ionosphere stimulated by seismic activity
NASA Astrophysics Data System (ADS)
Sorokin, V. M.; Chmyrev, V. M.; Yaschenko, A. K.
2005-09-01
Seismic activity is accompanied by emanation of soil gases into the atmosphere. These gases transfer positive and negative charged aerosols. Atmospheric convection of charged aerosols forms external electric current, which works as a source of perturbation in the atmosphere ionosphere electric circuit. It is shown that DC electric field generated in the ionosphere by this current reaches up to 10 mV/m, while the long-term vertical electric field disturbances near the Earth's surface do not exceed 100 V/m. Such a limitation of the near-ground field is caused by the formation of potential barrier for charged particles at the Earth's surface in a process of their transport from soil to atmosphere. This paper presents the method for calculation of the electric field in the atmosphere and the ionosphere generated by given distribution of external electric current in the atmosphere.
NASA Astrophysics Data System (ADS)
Tan, Xi; Rumbach, Paul; Griggs, Nathaniel; Jensen, Kevin L.; Go, David B.
2016-12-01
In cold field and thermo-field emission, positive ions or adsorbates very close to the cathode surface can enhance emission current by both resonant and non-resonant processes. In this paper, resonant tunneling behavior is investigated by solving the one-dimensional Schrödinger equation in the presence of an ion, and the enhancement due to resonant processes is evaluated. Results shows that as the applied electric field increases, the resonant states move from higher to lower energies as the ion energy levels are shifted down. Conversely, as the ion position moves closer to the cathode, the resonant states shift up in energy. Further, through a simplified perturbation analysis, the general scaling of these trends can be predicted. These shifts of resonant states directly impact the emission current density, and they are especially relevant when the applied field is on the order of a few volts per nanometer (˜0.5-3 V/nm) and the ion is a few nanometers (˜0.5-3 nm) away from the cathode. Further, when the energy level for resonant emission coincides with the Fermi level of a metallic cathode, the current density is particularly enhanced. The results of this study suggest that it may be possible to control (augment/inhibit) the resonant emission current by manipulating the supply function of a cathode relative to the operating conditions of the emitter in either ion-enhanced or adsorbate-enhanced field emission, which can be applied to various plasma and electron emission technologies.
NASA Astrophysics Data System (ADS)
Agha Mohammad Ali Kermani, Mehrdad; Fatemi Ardestani, Seyed Farshad; Aliahmadi, Alireza; Barzinpour, Farnaz
2017-01-01
Influence maximization deals with identification of the most influential nodes in a social network given an influence model. In this paper, a game theoretic framework is developed that models a competitive influence maximization problem. A novel competitive influence model is additionally proposed that incorporates user heterogeneity, message content, and network structure. The proposed game-theoretic model is solved using Nash Equilibrium in a real-world dataset. It is shown that none of the well-known strategies are stable and at least one player has the incentive to deviate from the proposed strategy. Moreover, violation of Nash equilibrium strategy by each player leads to their reduced payoff. Contrary to previous works, our results demonstrate that graph topology, as well as the nodes' sociability and initial tendency measures have an effect on the determination of the influential node in the network.
Black hole state counting in loop quantum gravity: a number-theoretical approach.
Agulló, Iván; Barbero G, J Fernando; Díaz-Polo, Jacobo; Fernández-Borja, Enrique; Villaseñor, Eduardo J S
2008-05-30
We give an efficient method, combining number-theoretic and combinatorial ideas, to exactly compute black hole entropy in the framework of loop quantum gravity. Along the way we provide a complete characterization of the relevant sector of the spectrum of the area operator, including degeneracies, and explicitly determine the number of solutions to the projection constraint. We use a computer implementation of the proposed algorithm to confirm and extend previous results on the detailed structure of the black hole degeneracy spectrum.
Enhancement of figure of merit of thermoelectric materials: a new theoretical approach
NASA Astrophysics Data System (ADS)
Sofi, A. H.; Abubakr, B.; Shah, M. A.
2016-03-01
Thermoelectric materials have attained importance because of the gargantuan energy crisis the world faces today. A thermoelectric material can be used efficiently and frequently, provided, its figure of merit ZT is increased. Also, easy availability, manufacturing, and low cost are the other factors to be considered for a novel thermoelectric material. A theoretical model is proposed in this paper for the enhancement of the figure of merit of thermoelectric materials.
A Comparison of Approaches for Solving Hard Graph-Theoretic Problems
2015-04-29
are explored and consist of a parallel computing approach using Matlab, a quantum annealing approach using the D-Wave computer, and lastly using...code. To work around the computational issues, a variety of methods are explored and consist of a parallel computing approach using Matlab, a quantum ...Section 2 explores a parallel computing algorithm , Section 3 discusses mapping the problem onto the D-Wave computer and using a quan- tum annealing
A Comparison of Approaches for Solving Hard Graph-Theoretic Problems
2015-05-01
collaborative effort “Adiabatic Quantum Computing Applications Research” (14-RI-CRADA-02) between the Information Directorate and Lock- 3 Algorithm 3...using Matlab, a quantum annealing approach using the D-Wave computer, and lastly using satisfiability modulo theory (SMT) and corresponding SMT...methods are explored and consist of a parallel computing approach using Matlab, a quantum annealing approach using the D-Wave computer, and lastly using
Huang, Xinting; Yang, Dapeng; Yao, Li
2014-09-15
In this work, the laser-parameter effects on the high-order harmonic generation (HHG) spectrum and attosecond trains by mixing two-color laser field, a visible light field of 800 nm and a mid-infrared (mid-IR) laser pulses of 2400 nm, are theoretically demonstrated for the first time. Different schemes are applied to discuss the function of intensity, carrier-envelope phase (CEP) and pulse duration on the generation of an isolated attosecond pulse. As a consequence, an isolated 16as pulse is obtained by Fourier transforming an ultrabroad XUV continuum of 208 eV with the fundamental field of duration of 6 fs, 9×10(14)W/cm2 of intensity, the duration of 12 fs, the CEPs of the two driving pulses of -π and the relative strength ratio √R=0.2.
Conceptual and empirical problems with game theoretic approaches to language evolution
Watumull, Jeffrey; Hauser, Marc D.
2014-01-01
The importance of game theoretic models to evolutionary theory has been in formulating elegant equations that specify the strategies to be played and the conditions to be satisfied for particular traits to evolve. These models, in conjunction with experimental tests of their predictions, have successfully described and explained the costs and benefits of varying strategies and the dynamics for establishing equilibria in a number of evolutionary scenarios, including especially cooperation, mating, and aggression. Over the past decade or so, game theory has been applied to model the evolution of language. In contrast to the aforementioned scenarios, however, we argue that these models are problematic due to conceptual confusions and empirical difficiences. In particular, these models conflate the comptutations and representations of our language faculty (mechanism) with its utility in communication (function); model languages as having different fitness functions for which there is no evidence; depend on assumptions for the starting state of the system, thereby begging the question of how these systems evolved; and to date, have generated no empirical studies at all. Game theoretic models of language evolution have therefore failed to advance how or why language evolved, or why it has the particular representations and computations that it does. We conclude with some brief suggestions for how this situation might be ameliorated, enabling this important theoretical tool to make substantive empirical contributions. PMID:24678305
Maity, Supratim; Banerjee, Diptonil; Das, Nirmalya Sankar; Chattopadhyay, Kalyan Kumar
2016-05-01
Here a dual approach has been adopted to study the effect of both synthesis as well as annealing temperature on the electron field emission property of differently synthesized carbon nanotubes (CNTs) that include solid state chemical reaction as well as chemical vapour deposition (CVD). Experimental findings were supported by theoretical simulation. All the samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD as well as TEM study confirms the amorphous nature (aCNTs) of the samples for both the synthesis techniques which is attributed to lower synthesis temperature. Prominent morphological differences of these two types of aCNTs are clearly observed from both FESEM and TEM images. It is found that electron field emission characteristics of aCNTs synthesized by CVD shows better field emission properties as compared to aCNTs synthesized by solid state reaction. Finite element based simulation shows that temperature has prominent effect on morphology, screening effect or degree of graphitization that leads to improved field emission characteristics for the CVD synthesized aCNTs.
Snodin, A. P.; Ruffolo, D.; Matthaeus, W. H. E-mail: david.ruf@mahidol.ac.th
2013-01-01
The turbulent random walk of magnetic field lines plays an important role in the transport of plasmas and energetic particles in a wide variety of astrophysical situations, but most theoretical work has concentrated on determination of the asymptotic field line diffusion coefficient. Here we consider the evolution with distance of the field line random walk using a general ordinary differential equation (ODE), which for most cases of interest in astrophysics describes a transition from free streaming to asymptotic diffusion. By challenging theories of asymptotic diffusion to also describe the evolution, one gains insight on how accurately they describe the random walk process. Previous theoretical work has effectively involved closure of the ODE, often by assuming Corrsin's hypothesis and a Gaussian displacement distribution. Approaches that use quasilinear theory and prescribe the mean squared displacement ({Delta}x {sup 2}) according to free streaming (random ballistic decorrelation, RBD) or asymptotic diffusion (diffusive decorrelation, DD) can match computer simulation results, but only over specific parameter ranges, with no obvious 'marker' of the range of validity. Here we make use of a unified description in which the ODE determines ({Delta}x {sup 2}) self-consistently, providing a natural transition between the assumptions of RBD and DD. We find that the minimum kurtosis of the displacement distribution provides a good indicator of whether the self-consistent ODE is applicable, i.e., inaccuracy of the self-consistent ODE is associated with non-Gaussian displacement distributions.
Practical approaches to field problems of stationary combustion systems
Lee, S.W.
1997-09-01
The CANMET Energy Technology Centre (CETC) business plan dictates collaboration with industrial clients and other government agencies to promote energy efficiency, health and safety, pollution reduction and productivity enhancement. The Advanced Combustion Technologies group of CETC provides consultation to numerous organizations in combustion related areas by conducting laboratory and field investigations of fossil fuel-fired combustion equipment. CETC, with its modern research facilities and technical expertise, has taken this practical approach since the seventies and has assisted many organizations in overcoming field problems and in providing cost saving measures and improved profit margins. This paper presents a few selected research projects conducted for industrial clients in north and central America. The combustion systems investigated are mostly liquid fuel fired, with the exception of the utility boiler which was coal-fired. The key areas involved include fuel quality, fuel storage/delivery system contamination, waste derived oils, crude oil combustion, unacceptable pollutant emissions, ambient soot deposition, slagging, fouling, boiler component degradation, and particulate characterization. Some of the practical approaches taken to remedy these field problems on several combustion systems including residential, commercial and industrial scale units are discussed.
Near-field Approaches to Subcellular Tissue Abalation
NASA Astrophysics Data System (ADS)
Raghu, Deepa; Hoffmann, Joan; Gamari, Benjamin; Gomella, Andrew; Reeves, Mark
2011-03-01
We report on the development of a near-field approach to MALDI (Matrix-assisted laser desorption and Ionization). In this technique analytes embedded in an energy- absorbing matrix are ablated from the surface of a sample. In the infrared region, the matrix can be water by exciting the 3-micron vibrational mode of the water molecule. We use a 3-micron wavelength lasers, coupled with a near-field scanning microscope to ablate material from cells of different membrane stiffness. We have been able to reproducibly ablate features as small as 1 micron in diameter in cell and have characterized the power-dependence of the ablation process. We will review our findings and describe demonstrations of tissue modification by this approach at length scales smaller than a single cell. This approach has the potential to allow the identification and mapping of proteins expressed in intact cells and tissues, which is of great interest as protein expression connects genomic information with the functioning of an organism.
Phenomenological approach to a hyperkagome spin liquid: Emergent gauge fields and spinons
NASA Astrophysics Data System (ADS)
Wan, Yuan; Kim, Yong Baek
2016-12-01
A number of experiments on the hyperkagome iridate, Na4Ir3O8 , suggest existence of a gapless quantum spin liquid state at low temperature. Circumventing the slave-particle approach commonly used in theoretical analyses of frustrated magnets, we provide a more intuitive, albeit more phenomenological, construction of a quantum spin liquid state for the hyperkagome Heisenberg model. An effective monomer-dimer model on the hyperkagome lattice is proposed à la Hao and Tchernyshyov's approach cultivated from the Husimi cactus model. Employing an arrow representation for the monomer-dimer model, we obtain a compact U (1 ) gauge theory with a finite density of fermionic spinons on the hyperoctagon lattice. The resulting theory and its mean-field treatment are consistent with previous slave-particle construction of a quantum spin liquid state on the hyperkagome lattice. Our results offer novel insights into the emergence of spinon Fermi surfaces and useful predictions for future experiments.
Hill, D.W.; Sharp, J.M. Jr. . Dept. of Geological Sciences)
1993-02-01
In the Texas Gulf Coastal Plain, there is a history of oil and gas production extending over 2 to 5 decades. Concurrent with this production history, there has been unprecedented population growth accompanied by vastly increased groundwater demands. Land subsidence on both local and regional bases in this geologic province has been measured and predicted in several studies. The vast majority of these studies have addressed the problem from the standpoint of groundwater usage while only a few have considered the effects of oil and gas production. Based upon field-based computational techniques (Helm, 1984), a model has been developed to predict land subsidence caused by oil and gas production. This method is applied to the Big Hill Field in Jefferson County, Texas. Inputs include production data from a series of wells in this field and lithologic data from electric logs of these same wells. Outputs include predicted amounts of subsidence, the time frame of subsidence, and sensitivity analyses of compressibility and hydraulic conductivity estimates. Depending upon estimated compressibility, subsidence, to date, is predicted to be as high as 20 cm. Similarly, depending upon estimated vertical hydraulic conductivity, the time frame may be decades for this subsidence. These same methods can be applied to other oil/gas fields with established production histories as well as new fields when production scenarios are assumed. Where subsidence has been carefully measured above petroleum reservoir, the model may be used inversely to calculate sediment compressibilities.
NASA Astrophysics Data System (ADS)
Xin, Xu; Xiaohong, Hu; Ye, Feng; Yuanshan, Liu; Wei, Zhang; Zhi, Yang; Wei, Zhao; Yishan, Wang
2016-03-01
We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. Project supported by the National Major Scientific Instrumentation Development Program of China (Grant No. 2011YQ120022), CAS/SAFEA International Partnership Program for Creative Research Teams, China, and the National Natural Science Foundation of China (Grant No. 61275164).
NASA Technical Reports Server (NTRS)
Forman, M. A.
1975-01-01
It has been shown previously (Anath et al., 1973 and Kane, 1974) that 20 to 25% of days, the diffusion component of the cosmic-ray neutron diurnal anisotropy is directed more than 30 degrees away from the ecliptic projection of the interplanetary magnetic field averaged over the same 24 hours. A number of explanations for this deviation are discussed and it is concluded that transverse gradient drifts due to gradients perpendicular to the ecliptic are likely, that diurnal variations in the diffusion component of the neutron anisotropy may affect results from single stations and that the 24 hour mean interplanetary magnetic field may not be the field appropriate to the streaming equation at neutron monitor energies.
A thematic analysis of theoretical models for translational science in nursing: mapping the field.
Mitchell, Sandra A; Fisher, Cheryl A; Hastings, Clare E; Silverman, Leanne B; Wallen, Gwenyth R
2010-01-01
The quantity and diversity of conceptual models in translational science may complicate rather than advance the use of theory. This paper offers a comparative thematic analysis of the models available to inform knowledge development, transfer, and utilization. Literature searches identified 47 models for knowledge translation. Four thematic areas emerged: (1) evidence-based practice and knowledge transformation processes, (2) strategic change to promote adoption of new knowledge, (3) knowledge exchange and synthesis for application and inquiry, and (4) designing and interpreting dissemination research. This analysis distinguishes the contributions made by leaders and researchers at each phase in the process of discovery, development, and service delivery. It also informs the selection of models to guide activities in knowledge translation. A flexible theoretical stance is essential to simultaneously develop new knowledge and accelerate the translation of that knowledge into practice behaviors and programs of care that support optimal patient outcomes.
A Thematic Analysis of Theoretical Models for Translational Science in Nursing: Mapping the Field
Mitchell, Sandra A.; Fisher, Cheryl A.; Hastings, Clare E.; Silverman, Leanne B.; Wallen, Gwenyth R.
2010-01-01
Background The quantity and diversity of conceptual models in translational science may complicate rather than advance the use of theory. Purpose This paper offers a comparative thematic analysis of the models available to inform knowledge development, transfer, and utilization. Method Literature searches identified 47 models for knowledge translation. Four thematic areas emerged: (1) evidence-based practice and knowledge transformation processes; (2) strategic change to promote adoption of new knowledge; (3) knowledge exchange and synthesis for application and inquiry; (4) designing and interpreting dissemination research. Discussion This analysis distinguishes the contributions made by leaders and researchers at each phase in the process of discovery, development, and service delivery. It also informs the selection of models to guide activities in knowledge translation. Conclusions A flexible theoretical stance is essential to simultaneously develop new knowledge and accelerate the translation of that knowledge into practice behaviors and programs of care that support optimal patient outcomes. PMID:21074646
Mashhoon, B.; Paik, H. J.; Will, C. M.
1989-05-15
The angular momentum of the Earth produces gravitomagnetic components of the Riemann curvature tensor, which are of the order of 10/sup /minus/10/ of the Newtonian tidal terms arising from the mass of the Earth. These components could be detected in principle by sensitive superconducting gravity gradiometers currently under development. We lay out the theoretical principles of such an experiment by using the parametrized post-Newtonian formalism to derive the locally measured Riemann tensor in an orbiting proper reference frame, in a class of metric theories of gravity that includes general relativity. A gradiometer assembly consisting of three gradiometers with axes at mutually right angles measures three diagonal components of a 3/times/3 ''tidal tensor,'' related to the Riemann tensor. We find that, by choosing a particular assembly orientation relative to the orbit and taking a sum and difference of two of the three gradiometer outputs, one can isolate the gravitomagnetic relativistic effect from the large Newtonian background.
NASA Astrophysics Data System (ADS)
Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele
2017-01-01
Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show
Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele
2017-01-11
Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show
NASA Astrophysics Data System (ADS)
Asakura, Hiroyuki; Shishido, Tetsuya; Teramura, Kentaro; Tanaka, Tsunehiro
2015-04-01
The characteristic peaks (pre-edge peaks) in the La L1-edge X-ray absorption near edge structure (XANES) of various La complex oxides were analyzed by both experimental and theoretical approaches. The pre-edge peak areas are correlated with the bond angle analysis (BAA) parameter, which we proposed as an indicator of the centrosymmetry or disorder of the local configuration of the La site. The origin of the pre-edge peak and the parameterization criteria of the BAA parameter were evaluated using theoretical calculations based on molecular orbital theory and multiple scattering theory. The theoretical calculations showed that the origin of the pre-edge peak at the La L1-edge is electric dipole transition from 2s to unoccupied states generated by p-d hybridization. Medium-scale theoretical simulations of the La L1-edge XANES spectra of thousands of virtual La aqueous complex models verified that the parameterization criteria of the BAA parameter are applicable to local configuration analysis of La.
Asakura, Hiroyuki; Shishido, Tetsuya; Teramura, Kentaro; Tanaka, Tsunehiro
2015-04-28
The characteristic peaks (pre-edge peaks) in the La L1-edge X-ray absorption near edge structure (XANES) of various La complex oxides were analyzed by both experimental and theoretical approaches. The pre-edge peak areas are correlated with the bond angle analysis (BAA) parameter, which we proposed as an indicator of the centrosymmetry or disorder of the local configuration of the La site. The origin of the pre-edge peak and the parameterization criteria of the BAA parameter were evaluated using theoretical calculations based on molecular orbital theory and multiple scattering theory. The theoretical calculations showed that the origin of the pre-edge peak at the La L1-edge is electric dipole transition from 2s to unoccupied states generated by p-d hybridization. Medium-scale theoretical simulations of the La L1-edge XANES spectra of thousands of virtual La aqueous complex models verified that the parameterization criteria of the BAA parameter are applicable to local configuration analysis of La.
Field Theory Approach to Many-Body Localization
NASA Astrophysics Data System (ADS)
Altland, Alexander; Micklitz, Tobias
2017-03-01
We introduce an analytic approach to many-body localization (MBL) in random spin chains. We consider MBL within a first quantized framework where it becomes a localization phenomenon in the high-dimensional lattice defined by the Hilbert space of the clean system. Designed in analogy with the field-theory description of single particle localization, our approach describes wave package propagation on that lattice after a disorder average has been performed and the system is controlled by only a few universal parameters. We discuss the stability of an ergodic weak disorder and a localized strong disorder phase, respectively, and demonstrate that the latter is protected by mechanisms which put MBL outside the universality class of Anderson localization.
Imaging through strong turbulence with a light field approach.
Wu, Chensheng; Ko, Jonathan; Davis, Christopher C
2016-05-30
Under strong turbulence conditions, object's images can be severely distorted and become unrecognizable throughout the observing time. Conventional image restoring algorithms do not perform effectively in these circumstances due to the loss of good references on the object. We propose the use a plenoptic sensor as a light field camera to map a conventional camera image onto a cell image array in the image's sub-angular spaces. Accordingly, each cell image on the plenoptic sensor is equivalent to the image acquired by a sub-aperture of the imaging lens. The wavefront distortion over the lens aperture can be analyzed by comparing cell images in the plenoptic sensor. By using a modified "Laplacian" metric, we can identify a good cell image in a plenoptic image sequence. The good cell image corresponds with the time and sub-aperture area on the imaging lens where wavefront distortion becomes relatively and momentarily "flat". As a result, it will reveal the fundamental truths of the object that would be severely distorted on normal cameras. In this paper, we will introduce the underlying physics principles and mechanisms of our approach and experimentally demonstrate its effectiveness under strong turbulence conditions. In application, our approach can be used to provide a good reference for conventional image restoring approaches under strong turbulence conditions. This approach can also be used as an independent device to perform object recognition tasks through severe turbulence distortions.
Experimental and Theoretical Investigations of Flow Fields and Heat Transfer in Modern Gas Turbines.
1981-12-31
34 NASA CR-2729, July 1977. 2 Thompson, J.F., Thames, F.C. and Mastin, C.W., "TOMCAT-- A Code for Numerical Generation of Boundary Fitted Curvilinear Coordinate Systems on Fields Containing Any Number of Arbitrary Two - Dimensional Bodies ." J
Zou, Yong; Wang, Changzhen; Peng, Ruiyun; Wang, Lifeng; Hu, Xiangjun
2015-04-01
A change of the transmembrane voltage is considered to cause biophysical and biochemical responses in cells. The present study focuses on the cellular transmembrane voltage (Δφ) induced by external fields. We detail analytical equations for the transmembrane voltage induced by external high-frequency (above the relaxation frequency of the cell membrane) fields on cells of a spherical shape in suspensions and layers. At direct current (DC) and low frequencies, the cell membrane was assumed to be non-conductive under physiologic conditions. However, with increasing frequency, the permittivity of the cytoplasm/extracellular medium and conductivity of the membrane must be accounted for. Our main work is to extend application of the analytical solution of Δφ to the high-frequency range. We first introduce the transmembrane voltage generated by DC and low-frequency exposures on a single cell. Then, we focus on cell suspensions exposed to high-frequency fields. Using the effective medium theory and the reasonable assumption, the approximate analytical solution of Δφ on cells in suspensions and layers can be derived. Phenomenological effective medium theory equations cannot be used to calculate the local electric field of cell suspensions, so we raised a possible solution based on the Bergman theory.
1983-01-01
with increasing electric field. This paradoxical result is caused by the high scattering rates to the X and L minima. Note also that even in the most...the average energy of electrons in a semiconductor. (In metals, it is the 106 Fermi energy.) In order to meaningfully define the distribution func
Theoretical Developments in Decision Field Theory: Comment on Tsetsos, Usher, and Chater (2010)
ERIC Educational Resources Information Center
Hotaling, Jared M.; Busemeyer, Jerome R.; Li, Jiyun
2010-01-01
Tsetsos, Usher, and Chater (2010) presented several criticisms of decision field theory (DFT) involving its distance function, instability under externally controlled stopping times, and lack of robustness to various multialternative choice scenarios. Here, we counter those claims with a specification of a distance function based on the…
Nuclear Magnetic Moment of {sup 210}Fr: A Combined Theoretical and Experimental Approach
Gomez, E.; Aubin, S.; Sprouse, G. D.; Orozco, L. A.; Iskrenova-Tchoukova, E.; Safronova, M. S.
2008-05-02
We measure the hyperfine splitting of the 9S{sub 1/2} level of {sup 210}Fr, and find a magnetic dipole hyperfine constant A=622.25(36) MHz. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of 4.38(5){mu}{sub N} for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.
Experimental and theoretical approach of nanocrystalline TiO2 with antifungal activity
NASA Astrophysics Data System (ADS)
Longo, Valeria M.; Picon, Francini C.; Zamperini, Camila; Albuquerque, Anderson R.; Sambrano, Julio R.; Vergani, Carlos E.; Machado, Ana L.; Andrés, Juan; Hernandes, Antônio C.; Varela, José A.; Longo, Elson
2013-07-01
Using a solvothermal method for this research we synthesized nanocrystalline titanium dioxide (nc-TiO2) anatase particles with a mean diameter of 5.4 nm and evaluated their potential antifungal effect against planktonic cells of Candida albicans without UV radiation. To complement experimental data, we analyzed structural and electronic properties of both the bulk and the (1 0 1) surface of anatase by first-principles calculations. Based on experimental and theoretical results, a reactive O2H and OH species formation mechanism was proposed to explain the key factor which facilitates the antifungal activity.
NASA Astrophysics Data System (ADS)
Odio, Oscar F.; Martínez, Ariel; Martínez, Ricardo; Crespo-Otero, Rachel; Montero-Cabrera, Luis A.
2011-01-01
The acrylamide polymerization in presence of diosgenin has been investigated by experimental and theoretical methods. NMR spectroscopy shows the absence of copolymerization. Viscosimetric and dilatometric experiments support the occurrence of transfer reactions that retard the polymerization. The mechanism was studied at the MPWB1K/6-31G(d,p)//B3LYP/6-31G(d,p) level of theory. Transfer, homopropagation, copolymerization and reinitiation reactions were considered either in gas or solution phase. According to results, the retardation seems to be originated by the formation of an allylic radical in the ring B of diosgenin that reinitiates acrylamide polymerization at slow rate.
Bhatia, Sangeeta; Egri-Nagy, Attila; Francis, Andrew R
2015-11-01
Establishing a distance between genomes is a significant problem in computational genomics, because its solution can be used to establish evolutionary relationships including phylogeny. The "double cut and join" (DCJ) model of chromosomal rearrangement proposed by Yancopoulos et al. (Bioinformatics 21:3340-3346, 2005) has received attention as it can model inversions, translocations, fusion and fission on a multichromosomal genome that may contain both linear and circular chromosomes. In this paper, we realize the DCJ operator as a group action on the space of multichromosomal genomes. We study this group action, deriving some properties of the group and finding group-theoretic analogues for the key results in the DCJ theory.
Field theoretical model of multilayered Josephson junction and dynamics of Josephson vortices
NASA Astrophysics Data System (ADS)
Fujimori, Toshiaki; Iida, Hideaki; Nitta, Muneto
2016-09-01
Multilayered Josephson junctions are modeled in the context of a field theory, and dynamics of Josephson vortices trapped inside insulators are studied. Starting from a theory consisting of complex and real scalar fields coupled to a U(1) gauge field which admit parallel N -1 domain-wall solutions, Josephson couplings are introduced weakly between the complex scalar fields. The N -1 domain walls behave as insulators separating N superconductors, where one of the complex scalar fields has a gap. We construct the effective Lagrangian on the domain walls, which reduces to a coupled sine-Gordon model for well-separated walls and contains more interactions for walls at short distance. We then construct sine-Gordon solitons emerging in an effective theory in which we identify Josephson vortices carrying singly quantized magnetic fluxes. When two neighboring superconductors tend to have the same phase, the ground state does not change with the positions of domain walls (the width of superconductors). On the other hand, when two neighboring superconductors tend to have π -phase differences, the ground state has a phase transition depending on the positions of domain walls; when the two walls are close to each other (one superconductor is thin), frustration occurs because of the coupling between the two superconductors besides the thin superconductor. Focusing on the case of three superconductors separated by two insulators, we find for the former case that the interaction between two Josephson vortices on different insulators changes its nature, i.e., attractive or repulsive, depending on the positions of the domain walls. In the latter case, there emerges fractional Josephson vortices when two degenerate ground states appear due to spontaneous charge-symmetry breaking, and the number of the Josephson vortices varies with the position of the domain walls. Our predictions should be verified in multilayered Josephson junctions.
A wave field synthesis approach to reproduction of spatially correlated sound fields.
Berry, Alain; Dia, Rokhiya; Robin, Olivier
2012-02-01
This article discusses an open-loop wave field synthesis (WFS) approach for the reproduction of spatially correlated sound fields. The main application concerns laboratory reproduction of turbulent boundary layer wall pressure on aircraft fuselages and measurement of their sound transmission loss. The problem configuration involves reconstruction of random sound pressure distributions on a planar reproduction surface using a planar array of reproduction monopoles parallel to the reproduction plane. In this paper, the WFS formulation is extended to sound fields with imposed time and spatial correlation properties (or equivalently imposed cross-spectral density in the frequency and wave number domains). Numerical examples are presented for the reproduction of a propagating plane wave, diffuse acoustic field and wall pressure in subsonic or supersonic turbulent boundary layers. The reproduction accuracy is examined in terms of the size of the source plane and reproduction plane, their separation, and the number of reproduction sources required per acoustic wavelength. While the reproduction approach cannot reconstruct sub-wavelength correlation scales of subsonic turbulent boundary layers, it effectively reconstructs correlation scales larger than the acoustic wavelength, making it appropriate for diffuse acoustic field and supersonic turbulent layers.
ERIC Educational Resources Information Center
Toner, John A.; And Others
1994-01-01
The Program for Organizational Interdisciplinary Self-Education teaches group self-education skills such as team development, management, and maintenance. Training includes defining and negotiating team member roles, case study approach, group simulations, and problem solving. (SK)
NASA Astrophysics Data System (ADS)
Mathammal, R.; Sudha, N.; Shankar, R.; Rajaboopathi, M.; Janagi, S.; Prabavathi, B.
2017-03-01
This report discusses crystal structure, molecular arrangements, vibrational analysis, UV-Vis-NIR spectrum, fluorescence emission and second harmonic generation (SHG) efficiency of piperazinium L-tartrate (PPZ2+·Tart2-) crystals with the support of theoretical analysis. A good optical quality PPZ2+·Tart2- crystals were grown from slow evaporation of aqueous solution. The PPZ2+·Tart2- crystal belongs to monoclinic system with non-centrosymmetric space group P21. The charge transfer from donor to acceptor moieties and corresponding changes in the bond lengths and bond angles have been observed. The observed functional group vibrations in the experimental FTIR and the Raman spectrum were assigned and compared with theoretical wavenumbers of PPZ2+·Tart2-.The electron distribution on the donor and acceptor in PPZ2+·Tart2- has been clearly visualised using molecular electrostatic potential map. Compared with L-tartaric acid, red shift was observed in absorption and fluorescence spectrum. The low value of dielectric constant and dielectric loss at the higher frequency and its high second harmonic efficiency suggest PPZ2+·Tart2- crystal is less defect free and suitable for NLO applications.
2017-01-01
It is now recognized that nucleation and growth of crystals can occur not only by the addition of solvated ions but also by accretion of nanoparticles, in a process called nonclassical crystallization. The theoretical framework of such processes has only started to be described, partly due to the lack of kinetic or thermodynamic data. Here, we study the growth of magnetite nanoparticles from primary particles—nanometer-sized amorphous iron-rich precursors—in aqueous solution at different temperatures. We propose a theoretical framework to describe the growth of the nanoparticles and model both a diffusion-limited and a reaction-limited pathway to determine which of these best describes the rate-limiting step of the process. We show that, based on the measured iron concentration and the related calculated concentration of primary particles at the steady state, magnetite growth is likely a reaction-limited process, and within the framework of our model, we propose a phase diagram to summarize the observations.
NASA Astrophysics Data System (ADS)
Claret, A.
2016-04-01
Aims: Recent observations of very fast rotating stars show systematic deviations from the von Zeipel theorem and pose a challenge to the theory of gravity-darkening exponents (β1). In this paper, we present a new insight into the problem of temperature distribution over distorted stellar surfaces to try to reduce these discrepancies. Methods: We use a variant of the numerical method based on the triangles strategy, which we previously introduced, to evaluate the gravity-darkening exponents. The novelty of the present method is that the theoretical β1 is now computed as a function of the optical depth, that is, β1 ≡ β1(τ). The stellar evolutionary models, which are necessary to obtain the physical conditions of the stellar envelopes/atmospheres inherent to the numerical method, are computed via the code GRANADA. Results: When the resulting theoretical β1(τ) are compared with the best accurate data of very fast rotators, a good agreement for the six systems is simultaneously achieved. In addition, we derive an equation that relates the locus of constant convective efficiency in the Hertzsprung-Russell (HR) diagram with gravity-darkening exponents.
Armas-Pérez, Julio C; Hernández-Ortiz, Juan P; de Pablo, Juan J
2015-12-28
A theoretically informed Monte Carlo method is proposed for Monte Carlo simulation of liquid crystals on the basis of theoretical representations in terms of coarse-grained free energy functionals. The free energy functional is described in the framework of the Landau-de Gennes formalism. A piecewise finite element discretization is used to approximate the alignment field, thereby providing an excellent geometrical representation of curved interfaces and accurate integration of the free energy. The method is suitable for situations where the free energy functional includes highly non-linear terms, including chirality or high-order deformation modes. The validity of the method is established by comparing the results of Monte Carlo simulations to traditional Ginzburg-Landau minimizations of the free energy using a finite difference scheme, and its usefulness is demonstrated in the context of simulations of chiral liquid crystal droplets with and without nanoparticle inclusions.
Iida, Kenji; Noda, Masashi; Nobusada, Katsuyuki
2014-09-28
We propose a theoretical approach for optical response in electrochemical systems. The fundamental equation to be solved is based on a time-dependent density functional theory in real-time and real-space in combination with its finite temperature formula treating an electrode potential. Solvation effects are evaluated by a dielectric continuum theory. The approach allows us to treat optical response in electrochemical systems at the atomistic level of theory. We have applied the method to surface-enhanced Raman scattering (SERS) of 4-mercaptopyridine on an Ag electrode surface. It is shown that the SERS intensity has a peak as a function of the electrode potential. Furthermore, the real-space computational approach facilitates visualization of variation of the SERS intensity depending on an electrode potential.
Cold collisions of ground-state calcium atoms in a laser field: A theoretical study
Bussery-Honvault, Beatrice; Launay, Jean-Michel; Moszynski, Robert
2003-09-01
State-of-the-art ab initio techniques have been applied to compute the potential-energy curves for the ground X {sup 1}{sigma}{sub g}{sup +} and excited {sup 1}{pi}{sub g}(4s3d) states of the calcium dimer in the Born-Oppenheimer approximation. The weakly bound ground state was calculated by symmetry-adapted perturbation theory, while the strongly bound excited state was computed using a combination of the linear-response theory within the coupled-cluster singles and doubles framework for the core-valence electronic correlation and of the full configuration interaction for the valence-valence correlation. The ground-state potential has been corrected by considering the relativistic terms resulting from the first-order many-electron Breit theory, and the retardation corrections. The magnetic electronic transition dipole moment governing the {sup 1}{pi}{sub g}(leftarrow){sup 1}{sigma}{sub g}{sup +} transitions has been obtained as the first residue of the polarization propagator computed with the coupled-cluster method restricted to single and double excitations. The computed energies and transition moments have been analytically fitted and used in the dynamical calculations of the rovibrational energy levels, ground-state scattering length, photoassociation intensities at ultralow temperatures, and spontaneous emission coefficients from the {sup 1}{pi}{sub g}(4s3d) to the X {sup 1}{sigma}{sub g}{sup +} state. The spectroscopic constants of the theoretical ground-state potential are in a good agreement with the experimental values derived from the Fourier-transform spectra [O. Allard et al., Eur. Phys. J. D (to be published)]. The theoretical s-wave scattering length for the ground state is a=44 bohrs, suggesting that it should be possible to obtain a stable Bose-Einstein condensate of calcium atoms. Finally, the computed photoassociation intensities and spontaneous emission coefficients suggest that it should be possible to obtain cold calcium molecules by
Zhang, Y; Joines, W T; Jirtle, R L; Samulski, T V
1993-08-01
The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory. This more detailed model yields better agreement with the measured field patterns, reducing the rms discrepancy by a factor of about 6 (from approximately 23 to 4%) in the central region of interest where the SEM is within 25% of the maximum. We conclude that accurate modeling of source current distributions is important for determining SEM distributions associated with such heating devices.
Theoretical study of electrolyte gate AlGaN /GaN field effect transistors
NASA Astrophysics Data System (ADS)
Bayer, M.; Uhl, C.; Vogl, P.
2005-02-01
We predict the sensitivity of solution gate AlGaN /GaN field effect transistors to pH values of the electrolyte and to charged adsorbates at the semiconductor-electrolyte interface. Invoking the site-binding model for the chemical reactions at the oxidic semiconductor-electrolyte interface and taking into account the large polarization fields within the nitride heterostructure, the spatial charge and potential distribution have been calculated self-consistently both in the semiconductor and the electrolyte. In addition, the source-drain current is calculated and its sensitivity to the electrolyte's pH value is studied systematically. Comparison with experiment shows good agreement. A significantly enhanced resolution is predicted for AlGaN /GaN structures of N-face polarity.
NASA Astrophysics Data System (ADS)
Amorós, Jaume; de Haro, Jaume
2016-12-01
The PLANCK collaboration has determined, or greatly constrained, values for the spectral parameters of the CMB radiation, namely the spectral index n s , its running α s , the running of the running β s , using a growing body of measurements of CMB anisotropies by the Planck satellite and other missions. These values do not follow the hierarchy of sizes predicted by single field, slow roll inflationary theory, and are thus difficult to fit for such inflation models. In this work we present first a study of 49 single field, slow roll inflationary potentials in which we assess the likelyhood of these models fitting the spectral parameters to their currently most accurate determination given by the PLANCK collaboration. We check numerically with a MATLAB program the spectral parameters that each model can yield for a very broad, comprehensive list of possible parameter and field values. The comparison of spectral parameter values supported by the models with their determinations by the PLANCK collaboration leads to the conclusion that the data provided by PLANCK2015 TT+lowP and PLANCK2015 TT,TE,EE+lowP taking into account the running of the running disfavours 40 of the 49 models with confidence level at least 92.8 %. Next, we discuss the reliability of the current computations of these spectral parameters. We identify a bias in the method of determination of the spectral parameters by least residue parameter fitting (using MCMC or any other scheme) currently used to reconstruct the power spectrum of scalar perturbations. This bias can explain the observed contradiction between theory and observations. Its removal is computationally costly, but necessary in order to compare the forecasts of single field, slow roll theories with observations.
NASA Astrophysics Data System (ADS)
Tran, Si Bui Quang; Byun, Doyoung
2009-11-01
The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Furthermore, the analytical simulation about the oscillation of an anchored edge hemispherical meniscus located on a conductive flat plate under a uniform ac electric field is presented. The mutual interaction between the electric field and the hydrodynamics is iteratively solved. As a result, the simulation can calculate the meniscus shapes, contours of voltage outside the meniscus and the velocity profile of liquid inside the meniscus during the period of the oscillation according to the applied frequency. Based on the present theory, one can predict the oscillation mode with a certain applied frequency. The present theory can also be applied to investigate the oscillation of a free conductive drop in a uniform ac electric field.
Theoretical investigation of single dopant in core/shell nanocrystal in magnetic field
NASA Astrophysics Data System (ADS)
Talbi, A.; Feddi, E.; Oukerroum, A.; Assaid, E.; Dujardin, F.; Addou, M.
2015-09-01
The control of single dopant or "solitary dopant" in semiconductors constitute a challenge to achieve new range of tunable optoelectronic devices. Knowing that the properties of doped monocrystals are very sensitive to different external perturbations, the aim of this study is to understand the effect of a magnetic field on the ground state energy of an off-center ionized donor in a core/shell quantum dot (CSQD). The binding energies with and without an applied magnetic field are determined by the Ritz variational method taking into account the electron-impurity correlation in the trial wave function deduced from the second-order perturbation. It has been found that the external magnetic field affects strongly the binding energy, and its effect varies as a function of the core radius and the shell thickness. We have shown the existence of a threshold ratio (a / b) crit which represents the limit between the tridimensional and the spherical surface confinement. In addition our analysis demonstrates the important influence of the position of ionized donor in the shell material.
Tulczyjew’s approach for particles in gauge fields
NASA Astrophysics Data System (ADS)
Meng, Guowu
2015-04-01
In mid-1970s Tulczyjew discovered an approach to classical mechanics which brings the Hamiltonian formalism and the Lagrangian formalism under a common geometric roof: the dynamics of a particle with configuration space X is determined by a Lagrangian submanifold D of T{{T}*}X (the total tangent space of {{T}*}X), and the description of D by its Hamiltonian H: {{T}*}X\\to {R} (resp. its Lagrangian L: TX\\to {R}) yields the Hamilton (resp. Euler-Lagrange) equation. It is reported here that Tulczyjew’s approach also works for the dynamics of (charged) particles in gauge fields, in which the role of the total cotangent space {{T}*}X is played by Sternberg phase spaces. In particular, it is shown that, for a particle in a gauge field, the equation of motion can be locally presented as the Euler-Lagrange equation for a Lagrangian which is the sum of the ordinary Lagrangian L(q,\\dot{q}), the Lorentz term, and an extra new term which vanishes whenever the gauge group is abelian. A charge quantization condition is also derived, generalizing Dirac’s charge quantization condition from U(1) gauge group to any compact connected gauge group.
al-Ghorabie, F H
2000-03-01
A Monte Carlo model has been developed using the MCNP code to aid the design of a flattening filter, to improve field uniformity of a superficial x-ray machine. The machine is operating at 90 kV and filtered with a 1.1 mm aluminium filter. In the theoretical simulation the original flat filter was replaced by a varying thickness filter to improve the uniformity across field sizes 20, 5 and 2 cm diameter as well as hardening the beam. Simulation results showed that flatness of the beam profile was improved for the 20 cm field size from +/- 7.3% to +/- 1.1% across the anode/cathode direction and from +/- 7.7% to +/- 3.2% in the anode/cathode direction. For the 5 cm field size the improvement was from +/- 4.6% to +/- 3.1% and from +/- 5.5% to +/- 3.4%, and for the 2 cm field size from +/- 3.1% to +/- 2.4% and from +/- 10.2% to +/- 9.5%, in the same directions, respectively. Beam quality simulations were made and the original half-value layer was reduced from 2.21 +/- 0.09 mm aluminium to 2.04 +/- 0.09 mm aluminium. The study demonstrated that it was possible to build a filter capable of flattening the beam profile for different sized applicators without significantly changing the penetrating ability of the beam.
NASA Astrophysics Data System (ADS)
Frank, Till; Beek, Peter
It is argued that perception-action systems should be considered as spatially extended systems on account of (i) the presence of spatially distributed synchronized brain activity during the performance of perceptual-motor tasks, and (ii) the failure of conventional zero-dimensional theoretical approaches to deal with multistable perception-action systems and hysteresis in the presence of noise. It is shown that in spatially extended systems self-organization can arise due to the emergence of mean field attractors. This mean field approach is exemplified for a particular class of perception-action systems, namely, rhythmic movements. In addition, clinical implications of the mean field approach and the notion of spatially extended perception-action systems are briefly discussed in the context of psychotherapy and Parkinson's disease.
NASA Astrophysics Data System (ADS)
Shelkovsky, V. S.; Stepanian, S. G.; Galetich, I. K.; Kosevich, M. V.; Adamowicz, L.
2002-09-01
A combined experimental-theoretical approach to modeling of building blocks of recognition complexes formed by nucleic acid bases and the amino-acids side-chain amino group is reviewed. The approach includes the temperature dependent field-ionization mass spectrometry and ab initio quantum chemical calculations. The mass spectrometric technique allows determination of interaction enthalpies of biomolecules in the gas phase, and the results it produces are directly comparable to the results obtained through theoretical modeling. In our works we have analyzed both thermodynamic and structural aspects of the recognition complexes of four canonical nucleic acid bases and acrylamide, which models the side chain of asparagine and glutamine. It has been shown that all bases can interact with amide group of the amino acids via their Watson-Crick sites when being incorporated into a single strand DNA or RNA. Stability of the complexes studied, expressed as -Δ H (kJ mole^{-1}) decreases as: m^9Gua (-59.5) > m^1Cyt (-57.0) > m^9Ade (-52.0) gg m^1Ura (-40.6). We have determined that in the double stranded DNA only purine bases can be recognized.
A theoretical approach to study the melting temperature of metallic nanowires
NASA Astrophysics Data System (ADS)
Arora, Neha; Joshi, Deepika P.
2016-05-01
The physical properties of any material change with the change of its size from bulk range to nano range. A theoretical study to account for the size and shape effect on melting temperature of metallic nanowires has been done. We have studied zinc(Zn), indium (In),lead (Pb) and tin (Sn) nanowires with three different cross sectional shapes like regular triangular, square and regular hexagonal. Variation of melting temperature with the size and shape is graphically represented with the available experimental data. It was found that melting temperature of the nanowires decreases with decrement in the size of nanowire, due to surface effect and at very small size the most probable shape also varies with material
Role of word-of-mouth for programs of voluntary vaccination: A game-theoretic approach.
Bhattacharyya, Samit; Bauch, Chris T; Breban, Romulus
2015-11-01
We propose a model describing the synergetic feedback between word-of-mouth (WoM) and epidemic dynamics controlled by voluntary vaccination. The key feature consists in combining a game-theoretic model for the spread of WoM and a compartmental model describing VSIR disease dynamics in the presence of a program of voluntary vaccination. We evaluate and compare two scenarios for determinants of behavior, depending on what WoM disseminates: (1) vaccine advertising, which may occur whether or not an epidemic is ongoing and (2) epidemic status, notably disease prevalence. Understanding the synergy between the two strategies could be particularly important for designing voluntary vaccination campaigns. We find that, in the initial phase of an epidemic, vaccination uptake is determined more by vaccine advertising than the epidemic status. As the epidemic progresses, epidemic status becomes increasingly important for vaccination uptake, considerably accelerating vaccination uptake toward a stable vaccination coverage.
Formation of Virtual Organizations in Grids: A Game-Theoretic Approach
NASA Astrophysics Data System (ADS)
Carroll, Thomas E.; Grosu, Daniel
The execution of large scale grid applications requires the use of several computational resources owned by various Grid Service Providers (GSPs). GSPs must form Virtual Organizations (VOs) to be able to provide the composite resource to these applications. We consider grids as self-organizing systems composed of autonomous, self-interested GSPs that will organize themselves into VOs with every GSP having the objective of maximizing its profit. We formulate the resource composition among GSPs as a coalition formation problem and propose a game-theoretic framework based on cooperation structures to model it. Using this framework, we design a resource management system that supports the VO formation among GSPs in a grid computing system.
NASA Astrophysics Data System (ADS)
Pandey, Akash; Arockiarajan, A.
2017-03-01
Macro fiber composite (MFC) is extensively used in vibration control and actuation applications due to its high flexibility and enhanced coupling coefficients. During these applications, MFCs are subjected to the continuous cyclic electrical loading, which may lead to the degradation in its actuation performance. In order to predict the life cycle of MFCs, an experimental setup has been devised and experiments are performed under cyclic loading condition. Efforts involved in the experiments are huge in terms of time and cost. Hence, an attempt has been made to develop a theoretical model to predict the fatigue behavior of MFCs. A nonlinear finite element method has been formulated based on Kirchhoff plate theory wherein the fatigue failure criterion based on strain energy is embedded. Simulated results based on the proposed model is compared with experimental observation and are in good agreement with each other. Variation in the life cycle of MFCs are also studied for different operating temperatures as well as structural/geometric configurations.
Sone, Daichi; Matsuda, Hiroshi; Ota, Miho; Maikusa, Norihide; Kimura, Yukio; Sumida, Kaoru; Yokoyama, Kota; Imabayashi, Etsuko; Watanabe, Masako; Watanabe, Yutaka; Okazaki, Mitsutoshi; Sato, Noriko
2016-09-01
Graph theory is an emerging method to investigate brain networks. Altered cerebral blood flow (CBF) has frequently been reported in temporal lobe epilepsy (TLE), but graph theoretical findings of CBF are poorly understood. Here, we explored graph theoretical networks of CBF in TLE using arterial spin labeling imaging. We recruited patients with TLE and unilateral hippocampal sclerosis (HS) (19 patients with left TLE, and 21 with right TLE) and 20 gender- and age-matched healthy control subjects. We obtained all participants' CBF maps using pseudo-continuous arterial spin labeling and analyzed them using the Graph Analysis Toolbox (GAT) software program. As a result, compared to the controls, the patients with left TLE showed a significantly low clustering coefficient (p=0.024), local efficiency (p=0.001), global efficiency (p=0.010), and high transitivity (p=0.015), whereas the patients with right TLE showed significantly high assortativity (p=0.046) and transitivity (p=0.011). The group with right TLE also had high characteristic path length values (p=0.085), low global efficiency (p=0.078), and low resilience to targeted attack (p=0.101) at a trend level. Lower normalized clustering coefficient (p=0.081) in the left TLE and higher normalized characteristic path length (p=0.089) in the right TLE were found also at a trend level. Both the patients with left and right TLE showed significantly decreased clustering in similar areas, i.e., the cingulate gyri, precuneus, and occipital lobe. Our findings revealed differing left-right network metrics in which an inefficient CBF network in left TLE and vulnerability to irritation in right TLE are suggested. The left-right common finding of regional decreased clustering might reflect impaired default-mode networks in TLE.
Hamiltonian truncation approach to quenches in the Ising field theory
NASA Astrophysics Data System (ADS)
Rakovszky, T.; Mestyán, M.; Collura, M.; Kormos, M.; Takács, G.
2016-10-01
In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1 + 1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.
Bindu, G; Semenov, S
2013-01-01
This paper describes an efficient two-dimensional fused image reconstruction approach for Microwave Tomography (MWT). Finite Difference Time Domain (FDTD) models were created for a viable MWT experimental system having the transceivers modelled using thin wire approximation with resistive voltage sources. Born Iterative and Distorted Born Iterative methods have been employed for image reconstruction with the extremity imaging being done using a differential imaging technique. The forward solver in the imaging algorithm employs the FDTD method of solving the time domain Maxwell's equations with the regularisation parameter computed using a stochastic approach. The algorithm is tested with 10% noise inclusion and successful image reconstruction has been shown implying its robustness.
Dispersion coefficients from a field-theoretic renormalization of fluid mechanics.
Deem, M W; Park, J M
2001-10-22
We consider subtle correlations in the scattering of fluid by randomly placed obstacles, which have been suggested to lead to a diverging dispersion coefficient at long times for high Péclet numbers, in contrast to finite mean-field predictions. We develop a new master equation description of the fluid mechanics that incorporates the physically relevant fluctuations, and we treat those fluctuations by a renormalization group procedure. We find a finite dispersion coefficient at low volume fraction of disorder and high Péclet numbers.
NASA Technical Reports Server (NTRS)
Ziebell, L. F.; Wu, C. S.; Yoon, Peter H.
1991-01-01
A theory of generation of radio waves observed by ground-based facilities in the frequency range 150-700 kHz is discussed. This work is a continuation of an earlier discussion (Wu et al., 1989) in which it was proposed that the trapped electrons along the auroral field lines can lead to a cyclotron instability which amplifies the whistler waves observed at ground level. The objective of the present study is to investigate the propagation effect on the wave amplification and to examine whether the proposed mechanism is indeed viable.
A theoretical relation between Dst and the solar wind merging electric field
NASA Technical Reports Server (NTRS)
Siscoe, G.; Crooker, N.
1974-01-01
Using a model in which magnetic merging near the nose of the magnetosphere results in energy transfer from the solar wind by means of a tangential force on the geomagnetic tail, a linear relation between the time rate of change of Dst, representing energy transfer to the magnetosphere, and the merging electric field is developed, with the proportionality factor an explicit function of magnetospheric parameters. The linear relation is in agreement with a recent empirical result; and, using the empirical numerical coefficient, it is found that the distance from the earth to the neutral line in the tail during substorms is in the range from 10 to 30 earth radii.
Devereux, Mike; Gresh, Nohad; Piquemal, Jean-Philip; Meuwly, Markus
2014-08-05
A supervised, semiautomated approach to force field parameter fitting is described and applied to the SIBFA polarizable force field. The I-NoLLS interactive, nonlinear least squares fitting program is used as an engine for parameter refinement while keeping parameter values within a physical range. Interactive fitting is shown to avoid many of the stability problems that frequently afflict highly correlated, nonlinear fitting problems occurring in force field parametrizations. The method is used to obtain parameters for the H2O, formamide, and imidazole molecular fragments and their complexes with the Mg(2+) cation. Reference data obtained from ab initio calculations using an auc-cc-pVTZ basis set exploit advances in modern computer hardware to provide a more accurate parametrization of SIBFA than has previously been available.
A New Approach to Reduce Number of Split Fields in Large Field IMRT
Lee, Chen-Chiao; Wu, Andrew; Garg, Madhur; Mutyala, Subhakar; Kalnicki, Shalom; Sayed, Gary; Mah, Dennis
2011-04-01
Intensity-modulated radiation therapy (IMRT) has been applied for treatments of primary head with neck nodes, lung with supraclavicular nodes, and high-risk prostate cancer with pelvis wall nodes, all of which require large fields. However, the design of the Varian multileaf collimator requires fields >14 cm in width to be split into 2 or more carriage movements. With the split-field technique, both the number of monitor units (MUs) and total treatment time are significantly increased. Although many different approaches have been investigated to reduce the MU, including introducing new leaf segmentation algorithms, none have resulted in widespread success. In addition, for most clinics, writing such algorithms is not a feasible solution, particularly with commercial treatment planning systems. We introduce a new approach that can minimize the number of split fields and reduce the total MUs, thereby reducing treatment time. The technique is demonstrated on the Eclipse planning system V7.3, but could be generalized to any other system.
A new approach to reduce number of split fields in large field IMRT.
Lee, Chen-Chiao; Wu, Andrew; Garg, Madhur; Mutyala, Subhakar; Kalnicki, Shalom; Sayed, Gary; Mah, Dennis
2011-01-01
Intensity-modulated radiation therapy (IMRT) has been applied for treatments of primary head with neck nodes, lung with supraclavicular nodes, and high-risk prostate cancer with pelvis wall nodes, all of which require large fields. However, the design of the Varian multileaf collimator requires fields >14 cm in width to be split into 2 or more carriage movements. With the split-field technique, both the number of monitor units (MUs) and total treatment time are significantly increased. Although many different approaches have been investigated to reduce the MU, including introducing new leaf segmentation algorithms, none have resulted in widespread success. In addition, for most clinics, writing such algorithms is not a feasible solution, particularly with commercial treatment planning systems. We introduce a new approach that can minimize the number of split fields and reduce the total MUs, thereby reducing treatment time. The technique is demonstrated on the Eclipse planning system V7.3, but could be generalized to any other system.
Analytical Psychology: A Review of a Theoretical Approach and Its Application to Counseling.
ERIC Educational Resources Information Center
Ziff, Katherine K.
Analytical psychology is a field supported by training centers, specially trained analysts, and a growing body of literature. While it receives much recognition, it remains mostly outside the mainstream of counseling and counselor education. This document presents a brief history of analytical psychology and how it has been revisited and renamed…
About some of the theoretical approaches used in double-beta decay calculations
Civitarese, O.
2007-10-12
The calculations of nuclear matrix elements, corresponding to nuclear double beta decay transitions, rely upon several approximations. The impact of these approximations upon final estimations of the nuclear matrix elements is illustrated. We pay attention to mean field (symmetry violations) and to approximate diagonalizations (pn-QRPA, renormalized pn-QRPA and fully renormalized pn-QRPA)
About some of the theoretical approaches used in double-beta decay calculations
NASA Astrophysics Data System (ADS)
Civitarese, O.
2007-10-01
The calculations of nuclear matrix elements, corresponding to nuclear double beta decay transitions, rely upon several approximations. The impact of these approximations upon final estimations of the nuclear matrix elements is illustrated. We pay attention to mean field (symmetry violations) and to approximate diagonalizations (pn-QRPA, renormalized pn-QRPA and fully renormalized pn-QRPA).
Theoretical development of Monte Carlo codes for modeling cumulus cloud fields
NASA Technical Reports Server (NTRS)
Welch, R. M.
1984-01-01
Reflected fluxes are calculated for stratocumulus cloud fields as a function of skycover, cloud aspect ratio, and cloud shape. Cloud liquid water volume is held invariant as cloud shape is varied so that the results can be utilized more effectively by general circulation models and climate models. On the basis of required accuracy in the Earth Radiation Budget Experiment program, an order of magnitude value of 10 W/sq m is used to estimate significant differences between plane parallel and broken cloudiness. This limit is exceeded for cloud covers between 10% and 90%, indicating that plane paralel calculations are not satisfactory at most values of cloud cover. The choice of cloud shape also leads to large differences in reflected fluxes. These differences are traced to the anisotropic intensity pattern out the cloud sides, to the size and shape of the holes between clouds, and to variations in cloud area as viewed from the solar direction. An empirical relationship for effective cloud cover is given at solar zenith angle of theta = 60 deg. This relationship allows for the relatively accurate (delta F = 10 - 15 W/sq m.) computation of broken cloud field reflected fluxes from plane parallel calculations.
Thought and Creation in Contemporary Education: Theoretical Approaches and Practical Suggestions
ERIC Educational Resources Information Center
Cupertino, Christina; Arantes, Denise R. B.; Melcher, Mariangela F.
2016-01-01
This article discusses the role of creation and thought in contemporary life, education and, in particular, gifted education. Beginning with traditional approaches to creativity, some implications of diverse ways of understanding these two human activities in education are discussed, and reflections upon ways in which the particular concepts of…
A Theoretical Framework for Media Law Courses (Approaches to Teaching Freedom of Expression).
ERIC Educational Resources Information Center
Helle, Steven
1991-01-01
Suggests that most students prefer teachers have a theme that provides coherence and cohesiveness to media law courses. Explains how libertarian and neoliberal themes can guide learning and enumerates some of the principles of the two theories. Identifies drawbacks of the case analysis approach to such courses. (SG)
NASA Astrophysics Data System (ADS)
Gladysiewicz, M.; Janicki, L.; Misiewicz, J.; Sobanska, M.; Klosek, K.; Zytkiewicz, Z. R.; Kudrawiec, R.
2016-09-01
Polarization engineering of GaN-based heterostructures opens a way to develop advanced transistor heterostructures, although measurement of the electric field in such heterostructures is not a simple task. In this work, contactless electroreflectance (CER) spectroscopy has been applied to measure the electric field in GaN-based heterostructures. For a set of GaN(d = 0, 5, 15, and 30 nm)/AlGaN(20 nm)/GaN(buffer) heterostructures a decrease of electric field in the GaN(cap) layer from 0.66 MV cm-1 to 0.27 MV cm-1 and an increase of the electric field in the AlGaN layer from 0.57 MV cm-1 to 0.99 MV cm-1 have been observed with the increase in the GaN(cap) thickness from 5-30 nm. For a set of GaN(20 nm)/AlGaN(d = 10, 20, 30, and 40 nm)/GaN(buffer) heterostructures a decrease of the electric field in the AlGaN layer from 1.77 MV cm-1 to 0.64 MV cm-1 and an increase of the electric field in the GaN layer from 0.57 MV cm-1 to 0.99 MV cm-1 were observed with the increase in the AlGaN thickness from 10-40 nm. To determine the distribution of the electric field in these heterostructures the Schrödinger and Poisson equations are solved in a self-consistent manner and matched with experimental data. It is shown that the built-in electric field in the GaN(cap) and AlGaN layers obtained from measurements does not reach values of electric field resulting only from polarization effects. The measured electric fields are smaller due to a screening of polarization effects by free carriers, which are inhomogeneously distributed across the heterostructure and accumulate at interfaces. The results clearly demonstrate that CER measurements supported by theoretical calculations are able to determine the electric field distribution in GaN-based heterostructures quantitatively, which is very important for polarization engineering in this material system.
Gustafsson, Mats G. L.
2005-01-01
Contrary to the well known diffraction limit, the fluorescence microscope is in principle capable of unlimited resolution. The necessary elements are spatially structured illumination light and a nonlinear dependence of the fluorescence emission rate on the illumination intensity. As an example of this concept, this article experimentally demonstrates saturated structured-illumination microscopy, a recently proposed method in which the nonlinearity arises from saturation of the excited state. This method can be used in a simple, wide-field (nonscanning) microscope, uses only a single, inexpensive laser, and requires no unusual photophysical properties of the fluorophore. The practical resolving power is determined by the signal-to-noise ratio, which in turn is limited by photobleaching. Experimental results show that a 2D point resolution of <50 nm is possible on sufficiently bright and photostable samples. PMID:16141335
Field-theoretic methods in strongly-coupled models of general gauge mediation
NASA Astrophysics Data System (ADS)
Fortin, Jean-François; Stergiou, Andreas
2013-08-01
An often-exploited feature of the operator product expansion (OPE) is that it incorporates a splitting of ultraviolet and infrared physics. In this paper we use this feature of the OPE to perform simple, approximate computations of soft masses in gauge-mediated supersymmetry breaking. The approximation amounts to truncating the OPEs for hidden-sector current-current operator products. Our method yields visible-sector superpartner spectra in terms of vacuum expectation values of a few hidden-sector IR elementary fields. We manage to obtain reasonable approximations to soft masses, even when the hidden sector is strongly coupled. We demonstrate our techniques in several examples, including a new framework where supersymmetry breaking arises both from a hidden sector and dynamically. Our results suggest that strongly-coupled models of supersymmetry breaking are naturally split.
Bounds on the coupling parameters in field theoretical models of nuclear physics
NASA Astrophysics Data System (ADS)
Mannel, T.; Ohl, T.; Manakos, P.
1990-09-01
We investigate a simple meson-nucleon field theory in relativistic random phase approximation. To avoid perturbative expansions, the relativistic random phase approximation is cast into an exactly soluble model invented by Zachariasen. To make the model well defined, it is necessary to cut off nucleon-antinucleon states with invariant mass >λ. This is achieved by introducing form factors in a consistent way. Still the elimination of unphysical ghost states implies a bound on the square of the coupling constant, which is discussed as a function of the cut off. We find that the coupling used to fit low energy properties requires a strong suppression of N-bar N-states. These results do not depend on the renormalization scheme.
NASA Astrophysics Data System (ADS)
Zhou, Xuefeng; Liu, Ruifeng; Pulay, Peter
1993-07-01
The structures and force field of 1,3,5,7-cyclooctatetraene (COT) have been studied using ab initio theory at the SCF level with the 4-21G basis set. The quadratic force field of the D2 d structure obtained by systematic scaling of the ab initio force constants successfully reproduces the observed frequencies of COT and COT- d8 with a mean deviation of less than 10 cm -1 for non-CH stretching modes. On the basis of the calculated results, assignments of the fundamental vibrations are examined. The normal mode υ 5 is reassigned to a weak band at 758 cm -1 in the Raman spectrum of COT and to a weak band at 591 cm -1 in the Raman spectrum of COT- d8. The calculations favor the assignment of υ 26 given by Lippincott et al. [J. Am. Chem. Soc. 73, 3370 (1951)] over the revised assignment of Perec [Spectrochim. Acta 47A, 799 (1991)]. The calculations also furnish reliable prediction for the inactive A2 fundamentals of COT and COT- d8. The fundamental frequencies and IR and Raman intensities of 13CC 7H 8, which constitutes about 9% of COT in natural abundance, are also calculated. Only ν 10 (calculated at 908 cm -1) of the formal inactive A2 modes has appreciable Raman intensity (0.23 Å 4/amu). A spectral feature due to this fundametal is identified in the liquid Raman spectrum of Tabacik and Blaise [C. R. Acad. Sci. Ser. II 303, 539 (1986)] as a weak peak at 908 cm -1.
Maximum entropy image reconstruction - A practical non-information-theoretic approach
NASA Astrophysics Data System (ADS)
Nityananda, R.; Narayan, R.
1982-12-01
An alternative motivation for the maximum entropy method (MEM) is given and its practical implementation discussed. The need for nonlinear restoration methods in general is considered, arguing in favor of nonclassical techniques such as MEM. Earlier work on MEM is summarized and the present approach is introduced. The whole family of restoration methods based on maximizing the integral of some function of the brightness is addressed. Criteria for the choice of the function are given and their properties are discussed. A parameter for measuring the resolution of the restored map is identified, and a scheme for controlling it by adding a constant to the zero-spacing correlation is introduced. Numerical schemes for implementing MEM are discussed and restorations obtained with various choices of the brightness function are compared. Data noise is discussed, showing that the standard least squares approach leads to a bias in the restoration.
Theoretical aspects of self-assembly of proteins: A Kirkwood-Buff-theory approach
NASA Astrophysics Data System (ADS)
Ben-Naim, Arieh
2013-06-01
A new approach to the problem of self-assembly of proteins induced by temperature, pressure, or changes in solute concentration is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. In this article we focus on the pressure and solute effects on the association-dissociation equilibrium. We examine the role of both hydrophobic and hydrophilic effects. We argue that the latter are more important than the former. The solute effect, on the other hand, depends on the preferential solvation of the monomer and the aggregate with respect to solvent and co-solvent molecules. An experimental approach based on model compounds to study these effects is suggested.
Optimal Surface Segmentation in Volumetric Images—A Graph-Theoretic Approach
Li, Kang; Wu, Xiaodong; Chen, Danny Z.; Sonka, Milan
2008-01-01
Efficient segmentation of globally optimal surfaces representing object boundaries in volumetric data sets is important and challenging in many medical image analysis applications. We have developed an optimal surface detection method capable of simultaneously detecting multiple interacting surfaces, in which the optimality is controlled by the cost functions designed for individual surfaces and by several geometric constraints defining the surface smoothness and interrelations. The method solves the surface segmentation problem by transforming it into computing a minimum s-t cut in a derived arc-weighted directed graph. The proposed algorithm has a low-order polynomial time complexity and is computationally efficient. It has been extensively validated on more than 300 computer-synthetic volumetric images, 72 CT-scanned data sets of different-sized plexiglas tubes, and tens of medical images spanning various imaging modalities. In all cases, the approach yielded highly accurate results. Our approach can be readily extended to higher-dimensional image segmentation. PMID:16402624
Modern approaches for the theoretical description of multiparticle scattering and nuclear reactions
Kukulin, V. I.; Rubtsova, O. A.
2012-11-15
A review of novel approaches to solution of multiparticle scattering problems in the area above three-body breakup together with the review of new computational technologies which provide very effective and ultrafast realization of the novel approaches with ordinary PC are given. The novel direction presented here is based on two key points: a new formulation of the quantum scattering theory in a discrete Hilbert space of stationary wave packets and the massive-parallel solution of the resulted matrix equations with usage of ultrafast graphic processors (the so called GPU-computations). For the reader's convenience, a short review of the modern GPU calculations for the medicine, physics, military applications etc. is presented.
Simultaneous CO2 and SO2 capture by using ionic liquids: a theoretical approach.
García, Gregorio; Atilhan, Mert; Aparicio, Santiago
2017-02-15
Density functional theory (DFT) methods were used to analyze the mechanism of interaction between acidic gases and ionic liquids based on the 1-ethyl-3-methylimidazolium cation coupled with five different anions. Single ion pairs and ionic clusters containing six ion pairs were used to model the interactions of the ionic liquids with acidic gas molecules. The properties of the systems were analyzed based on geometric properties, interaction energies and Bader's theory. The cluster approach gives a more accurate representation of the behavior of ions and gases in the bulk liquid phase, and despite computational challenges, the cluster approach allows us to quantify interactions beyond short range ones used in the single ion pair-acidic gas model commonly applied in the literature. The results reported herein point out efficient simultaneous capturing of both gases especially for ionic liquids containing the acetate anion.
Planning additional drilling campaign using two-space genetic algorithm: A game theoretical approach
NASA Astrophysics Data System (ADS)
Kumral, Mustafa; Ozer, Umit
2013-03-01
Grade and tonnage are the most important technical uncertainties in mining ventures because of the use of estimations/simulations, which are mostly generated from drill data. Open pit mines are planned and designed on the basis of the blocks representing the entire orebody. Each block has different estimation/simulation variance reflecting uncertainty to some extent. The estimation/simulation realizations are submitted to mine production scheduling process. However, the use of a block model with varying estimation/simulation variances will lead to serious risk in the scheduling. In the medium of multiple simulations, the dispersion variances of blocks can be thought to regard technical uncertainties. However, the dispersion variance cannot handle uncertainty associated with varying estimation/simulation variances of blocks. This paper proposes an approach that generates the configuration of the best additional drilling campaign to generate more homogenous estimation/simulation variances of blocks. In other words, the objective is to find the best drilling configuration in such a way as to minimize grade uncertainty under budget constraint. Uncertainty measure of the optimization process in this paper is interpolation variance, which considers data locations and grades. The problem is expressed as a minmax problem, which focuses on finding the best worst-case performance i.e., minimizing interpolation variance of the block generating maximum interpolation variance. Since the optimization model requires computing the interpolation variances of blocks being simulated/estimated in each iteration, the problem cannot be solved by standard optimization tools. This motivates to use two-space genetic algorithm (GA) approach to solve the problem. The technique has two spaces: feasible drill hole configuration with minimization of interpolation variance and drill hole simulations with maximization of interpolation variance. Two-space interacts to find a minmax solution
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
An information theoretic approach to use high-fidelity codes to calibrate low-fidelity codes
NASA Astrophysics Data System (ADS)
Lewis, Allison; Smith, Ralph; Williams, Brian; Figueroa, Victor
2016-11-01
For many simulation models, it can be prohibitively expensive or physically infeasible to obtain a complete set of experimental data to calibrate model parameters. In such cases, one can alternatively employ validated higher-fidelity codes to generate simulated data, which can be used to calibrate the lower-fidelity code. In this paper, we employ an information-theoretic framework to determine the reduction in parameter uncertainty that is obtained by evaluating the high-fidelity code at a specific set of design conditions. These conditions are chosen sequentially, based on the amount of information that they contribute to the low-fidelity model parameters. The goal is to employ Bayesian experimental design techniques to minimize the number of high-fidelity code evaluations required to accurately calibrate the low-fidelity model. We illustrate the performance of this framework using heat and diffusion examples, a 1-D kinetic neutron diffusion equation, and a particle transport model, and include initial results from the integration of the high-fidelity thermal-hydraulics code Hydra-TH with a low-fidelity exponential model for the friction correlation factor.
Hagemann, Ian S; O'Neill, Patrick K; Erill, Ivan; Pfeifer, John D
2015-09-01
The information-theoretic concept of Shannon entropy can be used to quantify the information provided by a diagnostic test. We hypothesized that in tumor types with stereotyped mutational profiles, the results of NGS testing would yield lower average information than in tumors with more diverse mutations. To test this hypothesis, we estimated the entropy of NGS testing in various cancer types, using results obtained from clinical sequencing. A set of 238 tumors were subjected to clinical targeted NGS across all exons of 27 genes. There were 120 actionable variants in 109 cases, occurring in the genes KRAS, EGFR, PTEN, PIK3CA, KIT, BRAF, NRAS, IDH1, and JAK2. Sequencing results for each tumor were modeled as a dichotomized genotype (actionable mutation detected or not detected) for each of the 27 genes. Based upon the entropy of these genotypes, sequencing was most informative for colorectal cancer (3.235 bits of information/case) followed by high grade glioma (2.938 bits), lung cancer (2.197 bits), pancreatic cancer (1.339 bits), and sarcoma/STTs (1.289 bits). In the most informative cancer types, the information content of NGS was similar to surgical pathology examination (modeled at approximately 2-3 bits). Entropy provides a novel measure of utility for laboratory testing in general and for NGS in particular. This metric is, however, purely analytical and does not capture the relative clinical significance of the identified variants, which may also differ across tumor types.
Information Theoretic Approaches to Rapid Discovery of Relationships in Large Climate Data Sets
NASA Technical Reports Server (NTRS)
Knuth, Kevin H.; Rossow, William B.; Clancy, Daniel (Technical Monitor)
2002-01-01
Mutual information as the asymptotic Bayesian measure of independence is an excellent starting point for investigating the existence of possible relationships among climate-relevant variables in large data sets, As mutual information is a nonlinear function of of its arguments, it is not beholden to the assumption of a linear relationship between the variables in question and can reveal features missed in linear correlation analyses. However, as mutual information is symmetric in its arguments, it only has the ability to reveal the probability that two variables are related. it provides no information as to how they are related; specifically, causal interactions or a relation based on a common cause cannot be detected. For this reason we also investigate the utility of a related quantity called the transfer entropy. The transfer entropy can be written as a difference between mutual informations and has the capability to reveal whether and how the variables are causally related. The application of these information theoretic measures is rested on some familiar examples using data from the International Satellite Cloud Climatology Project (ISCCP) to identify relation between global cloud cover and other variables, including equatorial pacific sea surface temperature (SST), over seasonal and El Nino Southern Oscillation (ENSO) cycles.
NASA Astrophysics Data System (ADS)
Taormina, R.; Galelli, S.; Karakaya, G.; Ahipasaoglu, S. D.
2016-11-01
This work investigates the uncertainty associated to the presence of multiple subsets of predictors yielding data-driven models with the same, or similar, predictive accuracy. To handle this uncertainty effectively, we introduce a novel input variable selection algorithm, called Wrapper for Quasi Equally Informative Subset Selection (W-QEISS), specifically conceived to identify all alternate subsets of predictors in a given dataset. The search process is based on a four-objective optimization problem that minimizes the number of selected predictors, maximizes the predictive accuracy of a data-driven model and optimizes two information theoretic metrics of relevance and redundancy, which guarantee that the selected subsets are highly informative and with little intra-subset similarity. The algorithm is first tested on two synthetic test problems and then demonstrated on a real-world streamflow prediction problem in the Yampa River catchment (US). Results show that complex hydro-meteorological datasets are characterized by a large number of alternate subsets of predictors, which provides useful insights on the underlying physical processes. Furthermore, the presence of multiple subsets of predictors-and associated models-helps find a better trade-off between different measures of predictive accuracy commonly adopted for hydrological modelling problems.
An information-theoretic approach to curiosity-driven reinforcement learning.
Still, Susanne; Precup, Doina
2012-09-01
We provide a fresh look at the problem of exploration in reinforcement learning, drawing on ideas from information theory. First, we show that Boltzmann-style exploration, one of the main exploration methods used in reinforcement learning, is optimal from an information-theoretic point of view, in that it optimally trades expected return for the coding cost of the policy. Second, we address the problem of curiosity-driven learning. We propose that, in addition to maximizing the expected return, a learner should choose a policy that also maximizes the learner's predictive power. This makes the world both interesting and exploitable. Optimal policies then have the form of Boltzmann-style exploration with a bonus, containing a novel exploration-exploitation trade-off which emerges naturally from the proposed optimization principle. Importantly, this exploration-exploitation trade-off persists in the optimal deterministic policy, i.e., when there is no exploration due to randomness. As a result, exploration is understood as an emerging behavior that optimizes information gain, rather than being modeled as pure randomization of action choices.
NASA Astrophysics Data System (ADS)
Shen, Yang; Zhou, Jianhua; Liu, Tianran; Tao, Yuting; Jiang, Ruibin; Liu, Mingxuan; Xiao, Guohui; Zhu, Jinhao; Zhou, Zhang-Kai; Wang, Xuehua; Jin, Chongjun; Wang, Jianfang
2013-08-01
Localized surface plasmon resonance (LSPR)-based sensing has found wide applications in medical diagnosis, food safety regulation and environmental monitoring. Compared with commercial propagating surface plasmon resonance (PSPR)-based sensors, LSPR ones are simple, cost-effective and suitable for measuring local refractive index changes. However, the figure of merit (FOM) values of LSPR sensors are generally 1-2 orders of magnitude smaller than those of PSPR ones, preventing the widespread use of LSPR sensors. Here we describe an array of submicrometer gold mushrooms with a FOM reaching ~108, which is comparable to the theoretically predicted upper limit for standard PSPR sensors. Such a high FOM arises from the interference between Wood’s anomaly and the LSPRs. We further demonstrate the array as a biosensor for detecting cytochrome c and alpha-fetoprotein, with their detection limits down to 200 pM and 15 ng ml-1, respectively, suggesting that the array is a promising candidate for label-free biomedical sensing.
Pescosolido, Bernice A; Martin, Jack K; Lang, Annie; Olafsdottir, Sigrun
2008-08-01
A resurgence of research and policy efforts on stigma both facilitates and forces a reconsideration of the levels and types of factors that shape reactions to persons with conditions that engender prejudice and discrimination. Focusing on the case of mental illness but drawing from theories and studies of stigma across the social sciences, we propose a framework that brings together theoretical insights from micro, meso and macro level research: Framework Integrating Normative Influences on Stigma (FINIS) starts with Goffman's notion that understanding stigma requires a language of social relationships, but acknowledges that individuals do not come to social interaction devoid of affect and motivation. Further, all social interactions take place in a context in which organizations, media and larger cultures structure normative expectations which create the possibility of marking "difference". Labelling theory, social network theory, the limited capacity model of media influence, the social psychology of prejudice and discrimination, and theories of the welfare state all contribute to an understanding of the complex web of expectations shaping stigma. FINIS offers the potential to build a broad-based scientific foundation based on understanding the effects of stigma on the lives of persons with mental illness, the resources devoted to the organizations and families who care for them, and policies and programs designed to combat stigma. We end by discussing the clear implications this framework holds for stigma reduction, even in the face of conflicting results.
In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.
Zhang, Weiping; Xu, Shutao; Han, Xiuwen; Bao, Xinhe
2012-01-07
In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references).
Theoretical approaches to bird migration. The white stork as a case study
NASA Astrophysics Data System (ADS)
Kölzsch, A.; Blasius, B.
2008-04-01
Birds are often considered to be one of the best studied groups of organisms. However, only a few investigations have been devoted to a theoretical analysis of avian migration patterns in time and space. This paper is meant to be a first step into this direction. We start by presenting different types of observational data sets that are available and discuss their advantages and disadvantages for use in quantitative analysis of bird movement and migration. Based on ring recovery and satellite telemetry data we perform a statistical analysis of the migratory patterns of the white stork Ciconia ciconia. We find that standard methods from random walk theory can be applied, but have to be carefully interpreted and possibly modified to analyse migration movement data which are dominated by seasonal drift. Our analysis reveals two different modes of movement fast, directed migration and slow, undirected resting. Furthermore, we present a conceptional network model of avian migration. In our model a number of discrete breeding, resting and wintering habitats are linked by migration in the form of seasonally driven transition probabilities that are described by a unimodal circular function of time. Our study emphasises the need for more rigorous quantitative data analysis and mathematical modelling to gain a better understanding of the dynamic processes of avian migration.
Laser cooling of MgCl and MgBr in theoretical approach
Wan, Mingjie; Shao, Juxiang; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou; Gao, Yufeng
2015-07-14
Ab initio calculations for three low-lying electronic states (X{sup 2}Σ{sup +}, A{sup 2}Π, and 2{sup 2}Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f{sub 00} for A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) states for rapid laser cooling are also obtained. The proposed laser drives A{sup 2}Π{sub 3/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) transition by using three wavelengths (main pump laser λ{sub 00}; two repumping lasers λ{sub 10} and λ{sub 21}). These results indicate the probability of laser cooling MgCl and MgBr molecules.
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.
Theoretical approach to obtaining dynamic characteristics of noncontacting spiral-grooved seals
NASA Technical Reports Server (NTRS)
Iwatsubo, Takuzo; Yang, Bo-Suk; Ibaraki, Ryuji
1987-01-01
The dynamic characteristics of spiral-grooved seals are theoretically obtained by using the Navier-Stokes equation. First, with the inertia term of the fluid considered, the flow and pressure in the steady state are obtained for the directions parallel to and perpendicular to the groove. Next, the dynamic character is obtained by analyzing the steady state and by analyzing the labyrinth seal. As a result, the following conclusions were drawn: (1) As the land width becomes shorter or the helix angle decreases, the cross-coupling stiffness, direct and cross-coupling damping, and add mass coefficients decrease; (2) As the axial Reynolds number increases, the stiffness and damping coefficients increase. But the add mass coefficient is not influenced by the axial Reynolds number; (3) The rotational Reynolds number influences greatly the direct and cross-coupling stiffness and direct damping coefficients; and (4) As the journal rotating frequency increases, the leakage flow decreases. Therefore zero net leakage flow is possible at a particular rotating frequency.
Fawzy, Manal; Nasr, Mahmoud; Helmi, Shacker; Nagy, Heba
2016-11-01
Biomass of Oryza sativa (OS) was tested for the removal of Cd(II) ions from synthetic and real wastewater samples. Batch experiments were conducted to investigate the effects of operating parameters on Cd(II) biosorption. Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to examine the surface characteristics of the Cd(II)-loaded biomass. The maximum removal efficiency of Cd(II) was 89.4% at optimum pH 6.0, biosorbent dose 10.0 g L(-1), initial Cd(II) 50 mg L(-1), and biosorbent particle size 0.5 mm. The applicability of Langmuir and Freundlich isotherms to the sorbent system implied the existence of both monolayer and heterogeneous surface conditions. Kinetic studies revealed that the adsorption process of Cd(II) followed the pseudo-second-order model (r2: 0.99). On the theoretical side, an adaptive neuro-fuzzy inference system (ANFIS) was applied to select the operating parameter that mostly influences the Cd(II) biosorption process. Results from ANFIS indicated that pH was the most influential parameter affecting Cd(II) removal efficiency, indicating that the biomass of OS was strongly pH sensitive. Finally, the biomass was confirmed to adsorb Cd(II) from real wastewater samples with removal efficiency close to 100%. However, feasibility studies of such systems on a large-scale application remain to be investigated.
Amić, Ana; Marković, Zoran; Marković, Jasmina M Dimitrić; Jeremić, Svetlana; Lučić, Bono; Amić, Dragan
2016-12-01
Free radical scavenging and inhibitory potency against cyclooxygenase-2 (COX-2) by two abundant colon metabolites of polyphenols, i.e., 3-hydroxyphenylacetic acid (3-HPAA) and 4-hydroxyphenylpropionic acid (4-HPPA) were theoretically studied. Different free radical scavenging mechanisms are investigated in water and pentyl ethanoate as a solvent. By considering electronic properties of scavenged free radicals, hydrogen atom transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms are found to be thermodynamically probable and competitive processes in both media. The Gibbs free energy change for reaction of inactivation of free radicals indicates 3-HPAA and 4-HPPA as potent scavengers. Their reactivity toward free radicals was predicted to decrease as follows: hydroxyl>alkoxyls>phenoxyl≈peroxyls>superoxide. Shown free radical scavenging potency of 3-HPAA and 4-HPPA along with their high μM concentration produced by microbial colon degradation of polyphenols could enable at least in situ inactivation of free radicals. Docking analysis with structural forms of 3-HPAA and 4-HPPA indicates dianionic ligands as potent inhibitors of COX-2, an inducible enzyme involved in colon carcinogenesis. Obtained results suggest that suppressing levels of free radicals and COX-2 could be achieved by 3-HPAA and 4-HPPA indicating that these compounds may contribute to reduced risk of colon cancer development.
NASA Astrophysics Data System (ADS)
Fujita, H.; Fujita, N.
2002-01-01
Grain size in polycrystalline materials was changed from larger than phi 10 mum to smaller than phi 10 nm, and the effects of both grain size and strain rate on the strength has been investigated from a view point of heterogeneous deformation. Grains of phi10 nm or less in size were obtained by crystallization of amorphous alloys. The experimental results are summarized as follows: (a) Heterogeneous deformation is effectively suppressed when grain size decreases smaller than about phi0.1 mum. As a result, the strength remarkably increases in this grain size range, and takes the maximum value when grains of phi10 nm in size are homogeneously formed, (b) When grain size becomes smaller than phi10 nm, those ultrafine grains are embedded into the amorphous matrix, and the strength decreases with increasing volume fraction of amorphous phase. (c) Heterogeneous deformation is also effectively suppressed by increasing strain rate in general as well as decreasing grain size. The maximum strength obtained experimentally is compared with the theoretical strengths estimated under various conditions.
AQM controller design for networks supporting TCP vegas: a control theoretical approach.
Bigdeli, Nooshin; Haeri, Mohammad
2008-01-01
In this paper, a mathematical model and control theoretical framework for designing AQM controllers in networks supporting TCP Vegas is introduced. We have emphasized on a modified TCP Vegas algorithm that can respond to congestion signals through explicit congestion notification (ECN). The overall nonlinear delayed differential equations of the dynamics model of closed loop system have been derived based on TCP Vegas model. The model is then linearized to derive a transfer function representation between the packet marking probability and the bottleneck router queue length as the input and output of the modified TCP Vegas/AQM system. The model properties have been then examined especially for the case of single bottleneck homogeneous network which is closely investigated. Finally an AQM controller based on Coefficient Diagram Method (CDM) has been designed for the system and its performance has been compared with some other AQM controllers. CDM is a new indirect pole placement method that considers the speed, stability and robustness of the closed loop system in terms of time domain specifications. In order for synthesizing the simulation scenarios, our campus router traffic has been studied experimentally for a sample period of one hour and the corresponding parameters has been extracted. The simulation results are representative of good performance of developed TCP Vegas/AQM structure for different simulated scenarios.
A theoretical approach to assess microbial risks due to failures in drinking water systems.
Westrell, T; Bergstedt, O; Stenström, T A; Ashbolt, N J
2003-06-01
A failure in treatment or in the distribution network of a surface water-works could have serious consequences due to the variable raw water quality in combination with an extended distribution. The aim of this study was to examine the theoretical impact of incidents in the drinking water system on the annual risk of infection in a population served by a large water treatment plant in Sweden. Reported incidents in the system were examined and a microbial risk assessment that included three pathogens, Cryptosporidium parvum, rotavirus and Campylobacter jejuni, was performed. The main risk incidents in water treatment were associated with sub-optimal particle removal or disinfection malfunction. Incidents in the distribution network included cross-connections and microbial pollution of reservoirs and local networks. The majority of the annual infections were likely to be due to pathogens passing treatment during normal operation and not due to failures, thus adding to the endemic rate. Among the model organisms, rotavirus caused the largest number of infections. Decentralised water treatment with membranes was also considered in which failures upstream fine-pored membranes would have little impact as long as the membranes were kept intact.
A theoretical treatment of two approaches to SBS mitigation with two-tone amplification.
Dajani, Iyad; Zeringue, Clint; Bronder, T J; Shay, Thomas; Gavrielides, Athanasios; Robin, Craig
2008-09-01
A technique that employs two seed signals for the purpose of mitigating stimulated Brillouin scattering (SBS) effects in narrow-linewidth Yb-doped fiber amplifiers is investigated theoretically by constructing a self-consistent model that incorporates the laser gain, SBS, and four-wave mixing (FWM). The model reduces to solving a two-point boundary problem consisting of an 8x8 system of coupled nonlinear differential equations. Optimal operating conditions are determined by examining the interplay between the wavelength separation and power ratio of the two seeds. Two variants of this 'two-tone' amplification are considered. In one case the wavelength separation is precisely twice the Brillouin shift, while the other case considers a greater wavelength separation. For the former case, a two-fold increase in total output power over a broad range of seed power ratios centered about a ratio of approximately 2 is obtained, but with fairly large FWM. For the latter case, this model predicts an approximately 100% increase in output power (at SBS threshold with no signs of FWM) for a 'two-tone' amplifier with seed signals at 1064nm and 1068nm, compared to a conventional fiber amplifier with a single 1068nm seed. More significantly for this case, it is found that at a wavelength separation greater than 10nm, it is possible to appreciably enhance the power output of one of the laser frequencies.
Solubility of caffeine from green tea in supercritical CO2: a theoretical and empirical approach.
Gadkari, Pravin Vasantrao; Balaraman, Manohar
2015-12-01
Decaffeination of fresh green tea was carried out with supercritical CO2 in the presence of ethanol as co-solvent. The solubility of caffeine in supercritical CO2 varied from 44.19 × 10(-6) to 149.55 × 10(-6) (mole fraction) over a pressure and temperature range of 15 to 35 MPa and 313 to 333 K, respectively. The maximum solubility of caffeine was obtained at 25 MPa and 323 K. Experimental solubility data were correlated with the theoretical equation of state models Peng-Robinson (PR), Soave Redlich-Kwong (SRK), and Redlich-Kwong (RK). The RK model had regressed experimental data with 15.52 % average absolute relative deviation (AARD). In contrast, Gordillo empirical model regressed the best to experimental data with only 0.96 % AARD. Under supercritical conditions, solubility of caffeine in tea matrix was lower than the solubility of pure caffeine. Further, solubility of caffeine in supercritical CO2 was compared with solubility of pure caffeine in conventional solvents and a maximum solubility 90 × 10(-3) mol fraction was obtained with chloroform.
NASA Astrophysics Data System (ADS)
Chen, Yun; Yang, Hui
2016-12-01
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.
An information theoretic approach for generating an aircraft avoidance Markov Decision Process
NASA Astrophysics Data System (ADS)
Weinert, Andrew J.
Developing a collision avoidance system that can meet safety standards required of commercial aviation is challenging. A dynamic programming approach to collision avoidance has been developed to optimize and generate logics that are robust to the complex dynamics of the national airspace. The current approach represents the aircraft avoidance problem as Markov Decision Processes and independently optimizes a horizontal and vertical maneuver avoidance logics. This is a result of the current memory requirements for each logic, simply combining the logics will result in a significantly larger representation. The "curse of dimensionality" makes it computationally inefficient and unfeasible to optimize this larger representation. However, existing and future collision avoidance systems have mostly defined the decision process by hand. In response, a simulation-based framework was built to better understand how each potential state quantifies the aircraft avoidance problem with regards to safety and operational components. The framework leverages recent advances in signals processing and database, while enabling the highest fidelity analysis of Monte Carlo aircraft encounter simulations to date. This framework enabled the calculation of how well each state of the decision process quantifies the collision risk and the associated memory requirements. Using this analysis, a collision avoidance logic that leverages both horizontal and vertical actions was built and optimized using this simulation based approach.
Field Theoretical Approach to the Formation of Junctions of Cosmic Strings
Salmi, Petja
2007-11-20
Superstring theory predicts the potential formation of string networks with junctions. Kinematic constraints for junction formation were derived in [1], based on Nambu-Goto action. Here we test these constraints numerically within the framework of Abelian-Higgs model and report on good agreement with the analytical predictions.
Kinematic constraints on formation of bound states of cosmic strings: Field theoretical approach
Salmi, P.; Achucarro, A.; Copeland, E. J.; Kibble, T. W. B.; Putter, R. de; Steer, D. A.
2008-02-15
Superstring theory predicts the potential formation of string networks with bound states ending in junctions. Kinematic constraints for junction formation have been derived within the Nambu-Goto thin string approximation. Here we test these constraints numerically in the framework of the Abelian-Higgs model in the Type-I regime and report on good agreement with the analytical predictions. We also demonstrate that strings can effectively pass through each other when they meet at speeds slightly above the critical velocity permitting bound-state formation. This is due to reconnection effects that are beyond the scope of the Nambu-Goto approximation.
Field-Theoretical Approach to Many-Body Perturbation Theory: Combining MBPT and QED
Lindgren, Ingvar; Salomonson, Sten; Hedendahl, Daniel
2007-12-26
Many-Body Perturbation Theory (MBPT) is today highly developed. The electron correlation of atomic and molecular systems can be evaluated to essentially all orders of perturbation theory--also relativistically (RMBPT)--by means of techniques of Coupled-Cluster type. When high accuracy is needed, effects beyond RMBPT will enter, i.e., effects of retarded Breit interaction and of radiative effects (Lamb shift), effects normally referred to as QED effects. These effects can be evaluated by means of special techniques, like S-matrix formulation, which cannot simultaneously treat electron correlation. It would for many applications be desirable to have access to a numerical technique, where effects of electron correlation and of QED could be treated on the same footing. Such a technique is presently being developed and gradually implemented at our laboratory. Some numerical results will be given.
Field Structure of a Quasisoliton Approaching the Critical Point
NASA Astrophysics Data System (ADS)
Gorshkov, K. A.; Soustova, I. A.; Ermoshkin, A. V.
2016-03-01
Within the framework of an approximate approach based on the representation of the Gardnerequation solitons as compound structures (different-polarity kinks), the non-quasistationary evolution of such solitary waves, which is stipulated by the variable quadratic-nonlinearity parameter α. The structure of the composite soliton is studied in cases that are critical for the quasistationary description where the predicted increase in the solitary-wave scales becomes unbounded on finite spatio-temporal intervals. The dependence of the spatial scales of the quasisoliton-field distribution on the quadratic-nonlinearity coefficient near the critical point for the power-law time dependence α(t) is studied in detail. The obtained solution is compared with the results of direct numerical simulation of the Gardner equation with variable coefficients.
NASA Astrophysics Data System (ADS)
Marvian, Iman; Spekkens, Robert
2011-03-01
Information theory provides a novel approach to study of the consequences of symmetry of dynamics which goes far beyond the traditional conservation laws and Noether's theorem. The conservation laws are not applicable to the dissipative and open systems. In fact, as we will show, even in the case of closed system dynamics if the state of system is not pure the conservation laws do not capture all the consequences of symmetry. Using information theoretic approach to this problem we introduce new quantities called asymmetry monotones, that if the system is closed they are constant of motion and otherwise, if the system is open, they are always non-increasing. We also explain how different results in quantum information theory can have non-trivial consequences about the symmetric dynamics of quantum systems. I.M. is supported by Mike and Ophelia Lazaridis scholarship.
NASA Astrophysics Data System (ADS)
Boulon, G.; Guyot, Y.; Ito, M.; Bensalah, A.; Goutaudier, C.; Panczer, G.; Gâcon, J. C.
2004-01-01
A spectroscopic characterization was carried out to identify crystal-field levels for magnetic-dipole transitions of Yb3+ ions located in the Y3+ dodecahedral S4 crystallographic site in YLiF4 (YLF) crystals which were grown either by the Czochralski technique or by the laser heated pedestal growth (LHPG) technique. The concentration dependence of the measured decay time of the 2F5/2 excited level of Yb3+ was analysed in order to understand relevant concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to trace rare-earth impurities (Er3+, Tm3+) has been observed over the visible region and interpreted by a limited-diffusion process within the Yb3+ doping ion subsystem to the impurities. The principal parameters useful for a theoretical approach for potential laser applications of Yb3+-doped YLiF4 crystals have also been given.
Erdogdu, Y; Saglam, S; Gulluoglu, M T
2015-07-05
Fourier-Transform-Infrared, Fourier-Transform-Raman and Nuclear Magnetic Rezonans spectra of 1-(p-tolylsulfonyl) pyrrole molecule have been recorded. In the powder form, vibrational spectra of 1-(p-tolylsulfonyl) pyrrol molecule were investigated in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The conformational analysis, geometrical structure, molecular electrostatic potential map, HOMO-LUMO and vibrational spectroscopic properties of the isolated 1-(p-tolylsulfonyl) pyrrole molecule have also been carried out at the Molecular Mechanic and Density Functional Theory approaches. Density Functional Theory results have been associated with Scaled Quantum Mechanics Force Field for fitting between the theoretical and the experimental frequencies.
Theoretical and Applied Research in the Field of Higher Geodesy Conducted in Rzeszow
NASA Astrophysics Data System (ADS)
Kadaj, Roman; Świętoń, Tomasz
2016-06-01
Important qualitative changes were taking place in polish geodesy in last few years. It was related to application of new techniques and technologies and to introduction of European reference frames in Poland. New reference stations network ASG-EUPOS, together with Internet services which helps in precise positioning was created. It allows to fast setting up precise hybrid networks. New, accurate satellite networks became the basis of new definitions in the field of reference systems. Simultaneously arise the need of new software, which enables to execute the geodetic works in new technical conditions. Authors had an opportunity to participate in mentioned undertakings, also under the aegis of GUGiK, by creation of methods, algorithms and necessary software tools. In this way the automatic postprocessing module (APPS) in POZGEO service, a part of ASG-EUPOS system came into being. It is an entirely polish product which works in Trimble environment. Universal software for transformation between PLETRF89, PL-ETRF2000, PULKOWO'42 reference systems as well as defined coordinate systems was created (TRANSPOL v. 2.06) and published as open product. An essential functional element of the program is the quasi-geoid model PL-geoid-2011, which has been elaborated by adjustment (calibration) of the global quasi-geoid model EGM2008 to 570 geodetic points (satellite-leveling points). Those and other studies are briefly described in this paper.
The field-theoretic description of dynamics of interfaces in disordered media
NASA Astrophysics Data System (ADS)
Stepanow, S.
The time evolution of an interface in a disordered media is described by using the propagator method. The method enables one to represent the perturbation expansions of different quantities characterizing the interface by means of diagrams which are familiar from the field theory. By the analysis of the divergences in the vicinity of the critical dimension dc = 4 we found that the regularization of the theory demands the renormalization of the mobility and all moments of the disorder correlator excepting the zero one. The renormalization group (RG) calculations of the average velocity of the interface, the roughness, and the functional RG equation of the disorder correlator are presented to order = 4 - d. The latter coincides with the result obtained by D. S. Fisher in the equilibrium case. The RG equations have a pole at the value of the driving force, which coincides with the value of the threshold below which the interface becomes pinned as predicted by Bruinsma and Aeppli. The behavior of the mobility in the vicinity of the pole is discussed.
Almeida e Sousa, Luis; Reutzel-Edens, Susan M; Stephenson, Gregory A; Taylor, Lynne S
2015-02-02
The supersaturation potential of poorly water-soluble compounds is of interest in the context of solubility enhancing formulations for enhanced bioavailability. In this regard, the amorphous "solubility", i.e., the maximum increase in solution concentration that can be obtained relative to the crystalline form, is an important parameter, albeit a very difficult one to evaluate experimentally. The goal of the current study was to develop new approaches to determine the amorphous "solubility" and to compare the experimental values to theoretical predictions. A group of six diverse model compounds was evaluated using the solvent exchange method to generate an amorphous phase in situ, determining the concentration at which the amorphous material was formed. The theoretical estimation of the amorphous "solubility" was based on the thermal properties of the crystalline and amorphous phases, the crystalline solubility, and the estimated concentration of water in the water-saturated amorphous phase. The formation of an amorphous precipitate could be captured transiently for all six compounds and hence the amorphous "solubility" determined experimentally. A comparison of the experimental amorphous "solubility" values to those calculated theoretically showed excellent agreement, in particular when the theoretical estimate method treated the precipitated phase as a supercooled liquid, and took into account heat capacity differences between the two forms. The maximum supersaturation ratio in water was found to be highly compound dependent, varying between 4 for ibuprofen and 54 for sorafenib. This information may be useful to predict improvements in biological exposure for poorly water-soluble compounds formulated as amorphous solid dispersions or other formulations that rely on supersaturation.
Perez-Davis, M.E.; Gaier, J.R.
1994-09-01
In the foreseeable future, an expedition may be undertaken to explore the planet Mars. Some of the power source options being considered for such a mission are photovoltaics, regenerative fuel cells and nuclear reactors. In addition to electrical power requirements, environmental conditions en route to Mars, in the planetary orbit and on the Martian surface must be simulated and studied in order to anticipate and solve potential problems. Space power systems components such as photovoltaic arrays, radiators, and solar concentrators may be vulnerable to degradation in the Martian environment. Natural characteristics of Mars which may pose a threat to surface power systems include high velocity winds, dust, ultraviolet radiation, large daily variations in temperature, reaction to components of the soil, atmosphere and atmospheric condensates as well as synergistic combinations. Most of the current knowledge of the characteristics of the Martian atmosphere and soil composition was obtained from the Viking 1 and 2 missions in 1976. This paper presents a theoretical study used to assess the effects of the Martian atmospheric conditions on the power systems components. A computer program written at NASA Lewis Research Center in 1961 to 1962 for combustion research that uses a free-energy minimization technique was used to calculate chemical equilibrium for assigned thermodynamic states of temperature and pressure. The power system component materials selected for this study include: Silicon dioxide, silicon, carbon, copper, and titanium. Combinations of environments and materials considered in this study include: (1) Mars atmosphere with power surface material, (2) Mars atmosphere and dust component with power surface material, (3) Mars atmosphere and hydrogen peroxide or superoxide with power system material.
Information theoretical approach to discovering solar wind drivers of the outer radiation belt
NASA Astrophysics Data System (ADS)
Wing, Simon; Johnson, Jay R.; Camporeale, Enrico; Reeves, Geoffrey D.
2016-10-01
The solar wind-magnetosphere system is nonlinear. The solar wind drivers of geosynchronous electrons with energy range of 1.8-3.5 MeV are investigated using mutual information, conditional mutual information (CMI), and transfer entropy (TE). These information theoretical tools can establish linear and nonlinear relationships as well as information transfer. The information transfer from solar wind velocity (Vsw) to geosynchronous MeV electron flux (Je) peaks with a lag time of 2 days. As previously reported, Je is anticorrelated with solar wind density (nsw) with a lag of 1 day. However, this lag time and anticorrelation can be attributed at least partly to the Je(t + 2 days) correlation with Vsw(t) and nsw(t + 1 day) anticorrelation with Vsw(t). Analyses of solar wind driving of the magnetosphere need to consider the large lag times, up to 3 days, in the (Vsw, nsw) anticorrelation. Using CMI to remove the effects of Vsw, the response of Je to nsw is 30% smaller and has a lag time < 24 h, suggesting that the MeV electron loss mechanism due to nsw or solar wind dynamic pressure has to start operating in < 24 h. nsw transfers about 36% as much information as Vsw (the primary driver) to Je. Nonstationarity in the system dynamics is investigated using windowed TE. When the data are ordered according to transfer entropy value, it is possible to understand details of the triangle distribution that has been identified between Je(t + 2 days) versus Vsw(t).
NASA Astrophysics Data System (ADS)
Fuchs, G. W.; Cuppen, H. M.; Ioppolo, S.; Romanzin, C.; Bisschop, S. E.; Andersson, S.; van Dishoeck, E. F.; Linnartz, H.
2009-10-01
Context: Hydrogenation reactions of CO in inter- and circumstellar ices are regarded as an important starting point in the formation of more complex species. Previous laboratory measurements by two groups of the hydrogenation of CO ices provided controversial results about the formation rate of methanol. Aims: Our aim is to resolve this controversy by an independent investigation of the reaction scheme for a range of H-atom fluxes and different ice temperatures and thicknesses. To fully understand the laboratory data, the results are interpreted theoretically by means of continuous-time, random-walk Monte Carlo simulations. Methods: Reaction rates are determined by using a state-of-the-art ultra high vacuum experimental setup to bombard an interstellar CO ice analog with H atoms at room temperature. The reaction of CO + H into H2CO and subsequently CH3OH is monitored by a Fourier transform infrared spectrometer in a reflection absorption mode. In addition, after each completed measurement, a temperature programmed desorption experiment is performed to identify the produced species according to their mass spectra and to determine their abundance. Different H-atom fluxes, morphologies, and ice thicknesses are tested. The experimental results are interpreted using Monte Carlo simulations. This technique takes into account the layered structure of CO ice. Results: The formation of both formaldehyde and methanol via CO hydrogenation is confirmed at low temperature (T = 12{-}20 K). We confirm that the discrepancy between the two Japanese studies is caused mainly by a difference in the applied hydrogen atom flux, as proposed by Hidaka and coworkers. The production rate of formaldehyde is found to decrease and the penetration column to increase with temperature. Temperature-dependent reaction barriers and diffusion rates are inferred using a Monte Carlo physical chemical model. The model is extended to interstellar conditions to compare with observational H2CO/CH3OH data.
Alvarez-Puebla, R A; Valenzuela-Calahorro, C; Garrido, J J
2006-04-01
The ubiquitous presence of humic substances (HS), combined with their ability to provide multiple sites for chemical reaction, makes them relevant to numerous biogeochemical processes such as mineral weathering, nutrient bioavailability, and contaminant transport. The reactivity of HS depends on their functional group chemistry and microstructure, which are in turn influenced by the composition of the surrounding media. In order to help towards an understanding of structure conformations and aggregation process of HS in soils and waters and to get a better knowledge of these kinds of materials, a fulvic acid (FA) has been modelled as a function of its ionic state under different conditions. Our proposed theoretical model based on the Temple-Northeastern-Birmingham (TNB) monomer fits well with experimental observations on the solubility (dipolar moment) and electronic and vibrational spectra of FAs. The presence of water molecules has a great stabilization effect on the electrostatic energy; this effect is greater as ionized rate increases. In vacuum, the non-ionized aggregated species are more stable than monomers because of the increase in their interaction due to H-bonding and non-bonding forces. When the molecules are ionized, no aggregation process takes place. In solution, the FA concentration is a critical factor for the aggregation. The system containing two FA molecules probably did not form aggregates because its equivalent concentration was too low. When the concentration was increased, the system gave rise to the formation of aggregates. The ionic state is another critical factor in the aggregation process. The ionized FA has a higher electric negative charge, which increases the energetic barriers and inhibits the approximation of FA caused by the Brownian movement.
Linear game non-contextuality and Bell inequalities—a graph-theoretic approach
NASA Astrophysics Data System (ADS)
Rosicka, M.; Ramanathan, R.; Gnaciński, P.; Horodecki, K.; Horodecki, M.; Horodecki, P.; Severini, S.
2016-04-01
We study the classical and quantum values of a class of one- and two-party unique games, that generalizes the well-known XOR games to the case of non-binary outcomes. In the bipartite case the generalized XOR (XOR-d) games we study are a subclass of the well-known linear games. We introduce a ‘constraint graph’ associated to such a game, with the constraints defining the game represented by an edge-coloring of the graph. We use the graph-theoretic characterization to relate the task of finding equivalent games to the notion of signed graphs and switching equivalence from graph theory. We relate the problem of computing the classical value of single-party anti-correlation XOR games to finding the edge bipartization number of a graph, which is known to be MaxSNP hard, and connect the computation of the classical value of XOR-d games to the identification of specific cycles in the graph. We construct an orthogonality graph of the game from the constraint graph and study its Lovász theta number as a general upper bound on the quantum value even in the case of single-party contextual XOR-d games. XOR-d games possess appealing properties for use in device-independent applications such as randomness of the local correlated outcomes in the optimal quantum strategy. We study the possibility of obtaining quantum algebraic violation of these games, and show that no finite XOR-d game possesses the property of pseudo-telepathy leaving the frequently used chained Bell inequalities as the natural candidates for such applications. We also show this lack of pseudo-telepathy for multi-party XOR-type inequalities involving two-body correlation functions.
Predicting peptide vaccine candidates against H1N1 influenza virus through theoretical approaches.
Bello, Martiniano; Campos-Rodriguez, Rafael; Rojas-Hernandez, Saul; Contis-Montes de Oca, Arturo; Correa-Basurto, José
2015-05-01
Identification of potential epitopes that might activate the immune system has been facilitated by the employment of algorithms that use experimental data as templates. However, in order to prove the affinity and the map of interactions between the receptor (major histocompatibility complex, MHC, or T-cell receptor) and the potential epitope, further computational studies are required. Docking and molecular dynamics (MDs) simulations have been an effective source of generating structural information at molecular level in immunology. Herein, in order to provide a detailed understanding of the origins of epitope recognition and to select the best peptide candidate to develop an epitope-based vaccine, docking and MDs simulations in combination with MMGBSA free energy calculations and per-residue free energy decomposition were performed, taking as starting complexes those formed between four designed epitopes (P1-P4) from hemagglutinin (HA) of the H1N1 influenza virus and MHC-II anchored in POPC membrane. Our results revealed that the energetic contributions of individual amino acids within the pMHC-II complexes are mainly dictated by van der Waals interactions and the nonpolar part of solvation energy, whereas the electrostatic interactions corresponding to hydrogen bonds and salt bridges determine the binding specificity, being the most favorable interactions formed between p4 and MHC-II. Then, P1-P4 epitopes were synthesized and tested experimentally to compare theoretical and experimental results. Experimental results show that P4 elicited the highest strong humoral immune response to HA of the H1N1 and may induce antibodies that are cross-reactive to other influenza subtypes, suggesting that it could be a good candidate for the development of a peptide-based vaccine.
Sreenivasan, Karthik; Zhuang, Xiaowei; Banks, Sarah J; Mishra, Virendra; Yang, Zhengshi; Deshpande, Gopikrishna; Cordes, Dietmar
2017-03-01
Previous studies investigating the differences in olfactory processing and judgments between trained sommeliers and controls have shown increased activations in brain regions involving higher level cognitive processes in sommeliers. However, there is little information about the influence of expertise on causal connectivity and topological properties of the connectivity networks between these regions. Therefore, the current study focuses on addressing these questions in a functional magnetic resonance imaging (fMRI) study of olfactory perception in Master Sommeliers. fMRI data were acquired from Master Sommeliers and control participants during different olfactory and nonolfactory tasks. Mean time series were extracted from 90 different regions of interest (ROIs; based on Automated Anatomical Labeling atlas). The underlying neuronal variables were extracted using blind hemodynamic deconvolution and then input into a dynamic multivariate autoregressive model to obtain connectivity between every pair of ROIs as a function of time. These connectivity values were then statistically compared to obtain paths that were significantly different between the two groups. The obtained connectivity matrices were further studied using graph theoretical methods. In sommeliers, significantly greater connectivity was observed in connections involving the precuneus, caudate, putamen, and several frontal and temporal regions. The controls showed increased connectivity from the left hippocampus to the frontal regions. Furthermore, the sommeliers exhibited significantly higher small-world topology than the controls. These findings are significant, given that learning about neuroplasticity in adulthood in these regions may then have added clinical importance in diseases such as Alzheimer's and Parkinson's where early neurodegeneration is isolated to regions important in smell.
NASA Technical Reports Server (NTRS)
Perez-Davis, Marla E.; Gaier, James R.
1990-01-01
In the foreseeable future, an expedition may be undertaken to explore the planet Mars. Some of the power source options being considered for such a mission are photovoltaics, regenerative fuel cells and nuclear reactors. In addition to electrical power requirements, environmental conditions en route to Mars, in the planetary orbit and on the Martian surface must be simulated and studied in order to anticipate and solve potential problems. Space power systems components such as photovoltaic arrays, radiators, and solar concentrators may be vulnerable to degradation in the Martian environment. Natural characteristics of Mars which may pose a threat to surface power systems include high velocity winds, dust, ultraviolet radiation, large daily variation in temperature, reaction to components of the soil, atmosphere and atmospheric condensates as well as synergistic combinations. Most of the current knowledge of the characteristics of the Martian atmosphere and soil composition was obtained from the Viking 1 and 2 missions in 1976. A theoretical study is presented which was used to assess the effects of the Martian atmospheric conditions on the power systems components. A computer program written at NASA-Lewis for combustion research that uses a free energy minimization technique was used to calculate chemical equilibrium for assigned thermodynamic states of temperature and pressure. The power system component materials selected for this study include: silicon dioxide, silicon, carbon, copper, and titanium. Combinations of environments and materials considered include: (1) Mars atmosphere with power surface material, (2) Mars atmosphere and dust component with power surface material, and (3) Mars atmosphere and hydrogen peroxide or superoxide or superoxide with power system material. The chemical equilibrium calculations were performed at a composition ratio (oxidant to reactant) of 100. The temperature for the silicon dioxide material and silicon, which simulate
An improved theoretical approach to the empirical corrections of density functional theory
NASA Astrophysics Data System (ADS)
Lii, Jenn-Huei; Hu, Ching-Han
2012-02-01
An empirical correction to density functional theory (DFT) has been developed in this study. The approach, called correlation corrected atomization-dispersion (CCAZD), involves short- and long-range terms. Short-range correction consists of bond ( 1,2-) and angle ( 1,3-) interactions, which remedies the deficiency of DFT in describing the proto-branching stabilization effects. Long-range correction includes a Buckingham potential function aiming to account for the dispersion interactions. The empirical corrections of DFT were parameterized to reproduce reported Δ H f values of the training set containing alkane, alcohol and ether molecules. The Δ H f of the training set molecules predicted by the CCAZD method combined with two different DFT methods, B3LYP and MPWB1K, with a 6-31G* basis set agreed well with the experimental data. For 106 alkane, alcohol and ether compounds, the average absolute deviations (AADs) in Δ H f were 0.45 and 0.51 kcal/mol for B3LYP- and MPWB1K-CCAZD, respectively. Calculations of isomerization energies, rotational barriers and conformational energies further validated the CCAZD approach. The isomerization energies improved significantly with the CCAZD treatment. The AADs for 22 energies of isomerization reactions were decreased from 3.55 and 2.44 to 0.55 and 0.82 kcal/mol for B3LYP and MPWB1K, respectively. This study also provided predictions of MM4, G3, CBS-QB3 and B2PLYP-D for comparison. The final test of the CCAZD approach on the calculation of the cellobiose analog potential surface also showed promising results. This study demonstrated that DFT calculations with CCAZD empirical corrections achieved very good agreement with reported values for various chemical reactions with a small basis set as 6-31G*.
Costa, Dominique; Garrain, Pierre-Alain; Baaden, Marc
2013-04-01
Interactions between biomolecules and inorganic surfaces play an important role in natural environments and in industry, including a wide variety of conditions: marine environment, ship hulls (fouling), water treatment, heat exchange, membrane separation, soils, mineral particles at the earth's surface, hospitals (hygiene), art and buildings (degradation and biocorrosion), paper industry (fouling) and more. To better control the first steps leading to adsorption of a biomolecule on an inorganic surface, it is mandatory to understand the adsorption mechanisms of biomolecules of several sizes at the atomic scale, that is, the nature of the chemical interaction between the biomolecule and the surface and the resulting biomolecule conformations once adsorbed at the surface. This remains a challenging and unsolved problem. Here, we review the state of art in experimental and theoretical approaches. We focus on metallic biomaterial surfaces such as TiO(2) and stainless steel, mentioning some remarkable results on hydroxyapatite. Experimental techniques include atomic force microscopy, surface plasmon resonance, quartz crystal microbalance, X-ray photoelectron spectroscopy, fluorescence microscopy, polarization modulation infrared reflection absorption spectroscopy, sum frequency generation and time of flight secondary ion mass spectroscopy. Theoretical models range from detailed quantum mechanical representations to classical forcefield-based approaches.
Chomiak, Taylor; Hu, Bin
2009-01-01
Background The biological process underlying axonal myelination is complex and often prone to injury and disease. The ratio of the inner axonal diameter to the total outer diameter or g-ratio is widely utilized as a functional and structural index of optimal axonal myelination. Based on the speed of fiber conduction, Rushton was the first to derive a theoretical estimate of the optimal g-ratio of 0.6 [1]. This theoretical limit nicely explains the experimental data for myelinated axons obtained for some peripheral fibers but appears significantly lower than that found for CNS fibers. This is, however, hardly surprising given that in the CNS, axonal myelination must achieve multiple goals including reducing conduction delays, promoting conduction fidelity, lowering energy costs, and saving space. Methodology/Principal Findings In this study we explore the notion that a balanced set-point can be achieved at a functional level as the micro-structure of individual axons becomes optimized, particularly for the central system where axons tend to be smaller and their myelin sheath thinner. We used an intuitive yet novel theoretical approach based on the fundamental biophysical properties describing axonal structure and function to show that an optimal g-ratio can be defined for the central nervous system (≈0.77). Furthermore, by reducing the influence of volume constraints on structural design by about 40%, this approach can also predict the g-ratio observed in some peripheral fibers (≈0.6). Conclusions/Significance These results support the notion of optimization theory in nervous system design and construction and may also help explain why the central and peripheral systems have evolved different g-ratios as a result of volume constraints. PMID:19915661
Cost Allocation of Multiagency Water Resource Projects: Game Theoretic Approaches and Case Study
NASA Astrophysics Data System (ADS)
Lejano, Raul P.; Davos, Climis A.
1995-05-01
Water resource projects are often jointly carried out by a number of communities and agencies. Participation in a joint project depends on how costs are allocated among the participants and how cost shares compare with the cost of independent projects. Cooperative N-person game theory offers approaches which yield cost allocations that satisfy rationality conditions favoring participation. A new solution concept, the normalized nucleolus, is discussed and applied to a water reuse project in southern California. Results obtained with the normalized nucleolus are compared with those derived with more traditional solution concepts, namely, the nucleolus and the Shapley value.
Spectral Synthesis via Mean Field approach to Independent Component Analysis
NASA Astrophysics Data System (ADS)
Hu, Ning; Su, Shan-Shan; Kong, Xu
2016-03-01
We apply a new statistical analysis technique, the Mean Field approach to Independent Component Analysis (MF-ICA) in a Bayseian framework, to galaxy spectral analysis. This algorithm can compress a stellar spectral library into a few Independent Components (ICs), and the galaxy spectrum can be reconstructed by these ICs. Compared to other algorithms which decompose a galaxy spectrum into a combination of several simple stellar populations, the MF-ICA approach offers a large improvement in efficiency. To check the reliability of this spectral analysis method, three different methods are used: (1) parameter recovery for simulated galaxies, (2) comparison with parameters estimated by other methods, and (3) consistency test of parameters derived with galaxies from the Sloan Digital Sky Survey. We find that our MF-ICA method can not only fit the observed galaxy spectra efficiently, but can also accurately recover the physical parameters of galaxies. We also apply our spectral analysis method to the DEEP2 spectroscopic data, and find it can provide excellent fitting results for low signal-to-noise spectra.
Li, Lingfeng; Wang, Yonghuan; Chen, Chilai; Wang, Xiaozhi; Luo, Jikui
2015-06-01
High-field asymmetric ion mobility spectrometry (FAIMS) has become an efficient technique for separation and characterization of gas-phase ions at ambient pressure, which utilizes the mobility differences of ions at high and low fields. Micro FAIMS devices made by micro-electromechanical system technology have small gaps of the channels, high electric field and good installation precision, as thus they have received great attentions. However, the disadvantage of relatively low resolution limits their applications in some areas. In this study, theoretical analysis and experimental exploration were carried out to overcome the disadvantage. Multiple scans, characteristic decline curves of ion transmission and pattern recognitions were proposed to improve the performance of the microchip-based FAIMS. The results showed that although micro FAIMS instruments as a standalone chemical analyzer suffer from low resolution, by using one or more of the methods proposed, they can identify chemicals precisely and provide quantitative analysis with low detection limit in some applications. Copyright © 2015 John Wiley & Sons, Ltd.
Theoretical aspects of pressure and solute denaturation of proteins: A Kirkwood-buff-theory approach
NASA Astrophysics Data System (ADS)
Ben-Naim, Arieh
2012-12-01
A new approach to the problem of pressure-denaturation (PD) and solute-denaturation (SD) of proteins is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. It is found that both problems have one factor in common; the excluded volumes of the folded and the unfolded forms with respect to the solvent molecules. It is shown that solvent-induced effects operating on hydrophilic groups along the protein are probably the main reason for PD. On the other hand, the SD depends on the preferential solvation of the folded and the unfolded forms with respect to solvent and co-solvent molecules.
Theoretical linear approach to the combined man-manipulator system in manual control of an aircraft
NASA Technical Reports Server (NTRS)
Brauser, K.
1981-01-01
An approach to the calculation of the dynamic characteristics of the combined man manipulator system in manual aircraft control was derived from a model of the neuromuscular system. This model combines the neuromuscular properties of man with the physical properties of the manipulator system which is introduced as pilot manipulator model into the manual aircraft control. The assumption of man as a quasilinear and time invariant control operator adapted to operating states, depending on the flight phases, of the control system gives rise to interesting solutions of the frequency domain transfer functions of both the man manipulator system and the closed loop pilot aircraft control system. It is shown that it is necessary to introduce the complete precision pilot manipulator model into the closed loop pilot aircraft transfer function in order to understand the well known handling quality criteria, and to derive these criteria directly from human operator properties.
Arefin, Ahmed Shamsul; Vimieiro, Renato; Riveros, Carlos; Craig, Hugh; Moscato, Pablo
2014-01-01
In this paper we analyse the word frequency profiles of a set of works from the Shakespearean era to uncover patterns of relationship between them, highlighting the connections within authorial canons. We used a text corpus comprising 256 plays and poems from the 16th and 17th centuries, with 17 works of uncertain authorship. Our clustering approach is based on the Jensen-Shannon divergence and a graph partitioning algorithm, and our results show that authors' characteristic styles are very powerful factors in explaining the variation of word use, frequently transcending cross-cutting factors like the differences between tragedy and comedy, early and late works, and plays and poems. Our method also provides an empirical guide to the authorship of plays and poems where this is unknown or disputed. PMID:25347727
Morris, K R; Griesser, U J; Eckhardt, C J; Stowell, J G
2001-05-16
Processing-induced transformations (PITs) during pharmaceutical manufacturing are well known but difficult to predict and often difficult to control. This review of the concepts of transformations is couched in terms of the issues associated with identifying rate-controlling events from the materials side and the processing side. Specifically, the approach is reconciling the characteristic time scale of the structural change(s) in the material with the time scale of the processing-induced stress. This is definitely a model (or rather a melding of a group of existing theories) in development. This overview is a 'snapshot' of the authors' attempts to identify the categories of existing theories needed to encompass all of the relevant events for each possible PIT. The ultimate goal is to establish a framework of concepts and theories for consideration, discussion, and modeling of PITs as well as to locate much of the relevant literature in the framework.
A billiard-theoretic approach to elementary one-dimensional elastic collisions
NASA Astrophysics Data System (ADS)
Redner, S.
2004-12-01
A simple relation is developed between the elastic collisions of freely moving particles in one dimension and a corresponding billiard system. For two particles with masses m1 and m2 on the half-line x>0 that approach an elastic barrier at x=0, the corresponding billiard system is an infinite wedge. The collision history of the two particles can be easily inferred from the corresponding billiard trajectory. This connection explains the classic demonstrations of the "dime on the superball" and the "baseball on the basketball" that are a staple in elementary physics courses. It also is shown that three elastic particles on an infinite line and three particles on a finite ring correspond, respectively, to the motion of a billiard ball in an infinite wedge and on a triangular billiard table. It is shown how to determine the angles of these two sets in terms of the particle masses.
The spatial distribution of X-ray selected AGN in the Chandra deep fields: a theoretical perspective
NASA Astrophysics Data System (ADS)
Marulli, Federico; Bonoli, Silvia; Branchini, Enzo; Gilli, Roberto; Moscardini, Lauro; Springel, Volker
2009-07-01
We study the spatial distribution of X-ray selected active galactic nuclei (AGN) in the framework of hierarchical coevolution of supermassive black holes and their host galaxies and dark matter haloes. To this end, we have applied the theoretical model developed by Croton et al., De Lucia & Blaizot and Marulli et al. to the output of the Millennium Run and obtained hundreds of realizations of past light cones from which we have extracted realistic mock AGN catalogues that mimic the Chandra deep fields. We find that the model AGN number counts are in fair agreement with observations both in the soft and in the hard X-ray bands, except at fluxes <~10-15ergcm-2s-1, where the model systematically overestimates the observations. However, a large fraction of these faint objects are typically excluded from the spectroscopic AGN samples of the Chandra fields. We find that the spatial two-point correlation function predicted by the model is well described by a power-law relation out to 20h-1Mpc, in close agreement with observations. Our model matches the correlation length r0 of AGN in the Chandra Deep Field-North but underestimates it in the Chandra Deep Field-South. When fixing the slope to γ = 1.4, as in Gilli et al., the statistical significance of the mismatch is 2σ-2.5σ, suggesting that the predicted cosmic variance, which dominates the error budget, may not account for the different correlation length of the AGN in the two fields. However, the overall mismatch between the model and the observed correlation function decreases when both r0 and γ are allowed to vary, suggesting that more realistic AGN models and a full account of all observational errors may significantly reduce the tension between AGN clustering in the two fields. While our results are robust to changes in the model prescriptions for the AGN light curves, the luminosity dependence of the clustering is sensitive to the different light-curve models adopted. However, irrespective of the model
NASA Astrophysics Data System (ADS)
Yang, Fan; Fang, Dai-Ning; Liu, Bin
2012-01-01
An oxidation kinetics model is developed to account for the effects of the oxidation interface curvature and the oxidation-induced volume change or Pilling-Bedworth ratio. For the oxidation of Fe-Cr-Al-Y alloy fiber, the predictions agree well with experimental results. By considering the influence of the oxidation interface curvature on oxidation rates, the evolution of fluctuant oxidation interface is predicted. We also developed the phase field method (PFM) to simulate the evolution of the interface roughness. Both the theoretical model and the PFM results show that the interface will become smooth during high temperature oxidation. Stress distribution and evolution are calculated by PFM, which indicates that the stress level decreases as the interface morphology evolves.
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-28
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a “quantum dot”), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1–014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1–245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green’s function formalism, as well as by analysis of frontier molecular orbitals’ behavior.
NASA Astrophysics Data System (ADS)
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-01
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a "quantum dot"), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1-014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1-245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green's function formalism, as well as by analysis of frontier molecular orbitals' behavior.
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-28
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a "quantum dot"), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1-014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1-245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green's function formalism, as well as by analysis of frontier molecular orbitals' behavior.
NASA Astrophysics Data System (ADS)
Daher, Walid; Pistre, Séverin; Kneppers, Angeline; Bakalowicz, Michel; Najem, Wajdi
2011-10-01
SummaryManaged Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20-25% of the world's potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers. Accordingly, the present work presents a conceptual methodology for Aquifer Rechargeability Assessment in Karst - referred to as ARAK. The methodology was developed noting that artificial recharge in karst aquifers is considered an improbable challenge to solve since karst conduits may drain off recharge water without any significant storage, or recharge water may not be able to infiltrate. The aim of the ARAK method is to determine the ability of a given karst aquifer to be artificially recharged and managed, and the best sites for implementing artificial recharge from the surface. ARAK is based on multi-criteria indexation analysis modeled on karst vulnerability assessment methods. ARAK depends on four independent criteria, i.e. Epikarst, Rock, Infiltration and Karst. After dividing the karst domain into grids, these criteria are indexed using geological and topographic maps refined by field observations. ARAK applies a linear formula that computes the intrinsic rechargeability index based on the indexed map for every criterion, coupled with its attributed weighting rate. This index indicates the aptitude for recharging a given karst aquifer, as determined by studying its probability first on a regional scale for the whole karst aquifer, and then by characterizing the most favorable sites. Subsequently, for the selected sites, a technical and economic feasibility factor is applied, weighted
Tomkeviciene, Ausra; Grazulevicius, Juozas V; Volyniuk, Dmytro; Jankauskas, Vygintas; Sini, Gjergji
2014-07-21
Synthesis and properties of fluorene and carbazole derivatives having three electrophores per molecule with different architectures are reported. The synthesized compounds possess high thermal stabilities with 5% weight loss temperatures exceeding 350 °C. They form glasses with glass transition temperatures ranging from 60 to 68 °C. Cyclovoltammetric experiments revealed the high electrochemical stability of the fluorene trimer. In contrast, 2- and 2,7-fluorenyl substituted carbazole derivatives show irreversible oxidation in the CV experiments. The electron photoemission spectra of the films of the synthesized compounds revealed ionization potentials of 5.65-5.89 eV. Hole drift mobilities in the amorphous layers of the synthesized compounds reach 10(-2) cm(2) V(-1) s(-1) at high electric fields, as established by a xerographic time-of-flight technique. DFT calculations show that HOMO and LUMO orbitals of the compounds are very similar in energy and shape. The similar hole mobilities observed for the three compounds are discussed in the frame of the Marcus theory. An important influence of the alkyl groups on the ionization potentials and on the hole mobilities was also observed and its origin is discussed.
Szczerbinska, Barbara
2016-02-22
For last five years Center for Theoretical Underground Physics and Related Areas (CETUP*) serves as a collaboration point for scientists from around the world interested in theoretical and experimental aspects of underground science. The mission of CETUP* is to promote an organized research in physics, astrophysics, geoscience, geomicrobiology and other fields related to the underground science and provide a stimulating environment for creative thinking and open communication between researches of varying ages and nationalities in dynamic atmosphere of intense scientific interactions. Scientists invited to participate in the program will not only provide theoretical support to the underground science, but they will also examine core questions of the 21st century including: What is dark matter? How well do we know the neutrino parameters?, How have neutrinos shaped the evolution of the universe?, How were the heavy elements made?, What are the fundamental underlying symmetries of the Universe? Is there a Grand Unified Theory of the Universe? How do supernovae explode? Studies of Neutrino Physics and Dark Matter are of high interest to particle and nuclear physicists, astrophysicists and cosmologists. Ongoing and proposed Neutrino and Dark Matter experiments are expected to unveil the answers to fundamental questions about the Universe. This year summer program was focused exactly on these subjects bringing together experts in dark matter, neutrino physics, particle physics, nuclear physics and astrophysics and cosmology. CETUP*2015 consisted of 5 week long program (June 14 – July 18, 2015) covering various theoretical and experimental aspects in these research areas. The two week long session on Dark Matter physics (June 14 – June 26) was followed by two week long program on Neutrino physics (July 6 – July 18). The international conference entitled IXth International Conference on Interconnection Between Particle Physics and Cosmology (PPC) was hosted at CETUP
Surface enhanced Raman spectroscopic studies on aspirin : An experimental and theoretical approach
NASA Astrophysics Data System (ADS)
Premkumar, R.; Premkumar, S.; Rekha, T. N.; Parameswari, A.; Mathavan, T.; Benial, A. Milton Franklin
2016-05-01
Surface enhanced Raman scattering (SERS) studies on aspirin molecule adsorbed on silver nanoparticles (AgNPs) were investigated by experimental and density functional theory approach. The AgNPs were synthesized by the solution-combustion method and characterized by the X-ray diffraction and high resolution-transmission electron microscopy techniques. The averaged particle size of synthesized AgNPs was calculated as ˜55 nm. The normal Raman spectrum (nRs) and SERS spectrum of the aspirin were recorded. The molecular structure of the aspirin and aspirin adsorbed on silver cluster were optimized by the DFT/ B3PW91 method with LanL2DZ basis set. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation. The calculated nRs and SERS frequencies were correlated well with the observed frequencies. The flat-on orientation was predicted from the nRs and SERS spectra, when the aspirin adsorbed on the AgNPs. Hence, the present studies lead to the understanding of adsorption process of aspirin on the AgNPs, which paves the way for biomedical applications.
Dezfoli, Amir Reza Ansari; Hwang, Weng-Sing; Huang, Wei-Chin; Tsai, Tsung-Wen
2017-01-30
There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements.
NASA Astrophysics Data System (ADS)
Hancer, Mehmet; Arkaz, Harun
2015-11-01
Although there are many viable approaches to induce hydrophobicity, a superhydrophobic surface could only be fabricated by combination of surface chemistry modification and roughness enhancement. In this study, surface roughness was obtained by 12 nm SiO2 nanoparticles (NPs) which were chemically modified using a self-assembled monolayer of perfluorodecyltrichlorosilane. The SiO2 NPs which were rendered hydrophobic, then successfully dispersed into a poly silicon (silsesquioxane) matrix at varying concentrations from 0.5 to 4%. The NPs dispersed polymer suspension was then spray coated on to glass and aluminum coupons in order to achieve polymer thin film nanocomposites. The results were revealed a superhydrophobic surface with a water contact angle exceeding 178° with low hysteresis and bouncing water droplet behavior. Furthermore the composite film reliability (hot-humid and ice build-up) was tested in an environmental control chamber by precisely adjusting both temperature (85 °C) and relative humidity (85 RH). Taber abrasion testing was applied in order to gain insights into the abrasion resistance of nanocomposite film. Finally, ice formation was simulated at -20 °C on the superhydrophobic nanocomposite film coated substrates.
Novel information theoretic and Bayesian approach to fMRI data analysis
NASA Astrophysics Data System (ADS)
Reddy, Chandan K.; Terrazas, Alejandro
2003-05-01
Functional Magnetic Resonance Imaging (fMRI) is a powerful technique for studying the working of the human brain. This overall goals of the project are to devlop a novel method for the analysis of fMRI data in order to discover the activation of a network of regions involving most likely the hippocampus, parietal cortex and cerebellum as a person is navigating in a virtual environment. Spatially sensitive voxels are extracted by selecting voxels that have high mutual information. Each of these extracted voxels is then used to create a response curve for the stimulus of interest, in this case spatial location. Following the voxel extraction stage, the set of extracted voxel time series would be treated as a population and used to predict the location of the subject at any randomly selected time in the experiment. The population of voxels essentially "votes" with their current activity. The approach used for prediction is the Bayesian reconstruction method. The ability to predict the location of a subject in the virtual environment based on brain signals will be useful in developing a physiological understanding of spatial cognition in virtual environments.
Irons, Jessica; McKone, Elinor; Dumbleton, Rachael; Barnes, Nick; He, Xuming; Provis, Jan; Ivanovici, Callin; Kwa, Alisa
2014-02-17
Damage to central vision, of which age-related macular degeneration (AMD) is the most common cause, leaves patients with only blurred peripheral vision. Previous approaches to improving face recognition in AMD have employed image manipulations designed to enhance early-stage visual processing (e.g., magnification, increased HSF contrast). Here, we argue that further improvement may be possible by targeting known properties of mid- and/or high-level face processing. We enhance identity-related shape information in the face by caricaturing each individual away from an average face. We simulate early- through late-stage AMD-blur by filtering spatial frequencies to mimic the amount of blurring perceived at approximately 10° through 30° into the periphery (assuming a face seen premagnified on a tablet computer). We report caricature advantages for all blur levels, for face viewpoints from front view to semiprofile, and in tasks involving perceiving differences in facial identity between pairs of people, remembering previously learned faces, and rejecting new faces as unknown. Results provide a proof of concept that caricaturing may assist in improving face recognition in AMD and other disorders of central vision.
NASA Astrophysics Data System (ADS)
Tejedor, A.; Foufoula-Georgiou, E.; Longjas, A.; Zaliapin, I. V.
2014-12-01
River deltas are intricate landscapes with complex channel networks that self-organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external factors causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying river delta topology and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in quantifying the complexity of the delta network topology, computing its steady state fluxes, and identifying upstream (contributing) and downstream (nourishment) areas from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way of systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.
NASA Astrophysics Data System (ADS)
Dezfoli, Amir Reza Ansari; Hwang, Weng-Sing; Huang, Wei-Chin; Tsai, Tsung-Wen
2017-01-01
There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements.
Dezfoli, Amir Reza Ansari; Hwang, Weng-Sing; Huang, Wei-Chin; Tsai, Tsung-Wen
2017-01-01
There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements. PMID:28134347
Parent-Child Aggression Risk in Expectant Mothers and Fathers: A Multimethod Theoretical Approach.
Rodriguez, Christina M; Smith, Tamika L; Silvia, Paul J
2016-11-01
The current investigation evaluated whether cognitive processes characteristic of the Social Information Processing model predicted parent-child aggression (PCA) risk independent of personal vulnerabilities and resiliencies. This study utilized a multimethod approach, including analog tasks, with a diverse sample of 203 primiparous expectant mothers and 151 of their partners. Factors considered in this study included PCA approval attitudes, empathy, reactivity, negative child attributions, compliance expectations, and knowledge of non-physical discipline alternatives; additionally, vulnerabilities included psychopathology symptoms, domestic violence victimization, and substance use, whereas resiliencies included perceived social support, partner relationship satisfaction, and coping efficacy. For both mothers and fathers, findings supported the role of greater approval of PCA attitudes, lower empathy, more overreactivity, more negative attributions, and higher compliance expectations in relation to elevated risk of PCA. Moreover, personal vulnerabilities and resiliencies related to PCA risk for mothers; however, fathers and mothers differed on the nature of these relationships with respect to vulnerabilities as well as aspects of empathy and PCA approval attitudes. Findings provide evidence for commonalities in many of the factors investigated between mothers and fathers with some notable distinctions. Results are discussed in terms of how findings could inform prevention programs.
Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L
NASA Astrophysics Data System (ADS)
Zubelewicz, Aleksander; Oliferuk, Wiera
2016-03-01
We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading.
Efficiency/equity analysis of water-resources problems--a game theoretic approach. Doctoral thesis
Ng, E.K.
1985-01-01
Successful regional water-resources planning involves an efficiency analysis to find the optimal system that maximizes benefits minus costs, and an equity analysis to apportion project costs. Traditionally, these two problems have been treated separately. A reliable total numerization procedure is used to find the optimal system for regional water-network problems. This procedure is easy to understand and can be implemented using readily available computer software; furthermore, more engineers can use realistic cost functions or perform detailed cost analysis and, also, examine good suboptimal systems. In addition, this procedure finds the optimal system for each individual and each subgroup of individuals; hence, an equity analysis can be accomplished using the theory of the core from cooperative n-person game theory on the optimal system as well as good suboptimal systems. A rigorous procedure using core conditions and linear programming is described to unambiguously measure an individual's minimum cost and maximum cost as a basis for the equitable cost allocation. Traditional approaches for quantifying minimum cost and maximum cost assume that either a regional system involving the grand coalition is built or all the individuals will go-it-alone.
Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L
Zubelewicz, Aleksander; Oliferuk, Wiera
2016-01-01
We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading. PMID:27026209
Propagating phase interface with intermediate interfacial phase: Phase field approach
NASA Astrophysics Data System (ADS)
Momeni, Kasra; Levitas, Valery I.
2014-05-01
An advanced three-phase phase field approach (PFA) is suggested for a nonequilibrium phase interface that contains an intermediate phase, in particular, a solid-solid interface with a nanometer-sized intermediate melt (IM). A thermodynamic potential in the polar order parameters is developed that satisfies all thermodynamic equilibrium and stability conditions. The special form of the gradient energy allowed us to include the interaction of two solid-melt interfaces via an intermediate melt and obtain a well-posed problem and mesh-independent solutions. It is proved that for stationary 1D solutions to two Ginzburg-Landau equations for three phases, the local energy at each point is equal to the gradient energy. Simulations are performed for β ↔δ phase transformations (PTs) via IM in an HMX energetic material. The obtained energy IM width dependence is described by generalized force-balance models for short- and long-range interaction forces between interfaces but not far from the melting temperature. A force-balance model is developed that describes phase field results even 100 K below the melting temperature. The effects of the ratios of width and energies of solid-solid and solid-melt interfaces, temperature, and the parameter characterizing interaction of two solid-melt interfaces, on the structure, width, energy of the IM and interface velocity are determined by finite element method. Depending on parameters, the IM may appear by continuous or discontinuous barrierless disordering or via critical nucleus due to thermal fluctuations. The IM may appear during heating and persist during cooling at temperatures well below than it follows from sharp-interface approach. On the other hand, for some parameters when IM is expected, it does not form, producing an IM-free gap. The developed PFA represents a quite general three-phase model and can be extended to other physical phenomena, such as martensitic PTs, surface-induced premelting and PTs, premelting
Figueroa, R G; Valente, M
2015-09-21
The main purpose of this work is to determine the feasibility and physical characteristics of a new teletherapy device of radiation therapy based on the application of a convergent x-ray beam of energies like those used in radiotherapy providing highly concentrated dose delivery to the target. We have denominated it Convergent Beam Radio Therapy (CBRT). Analytical methods are developed first in order to determine the dosimetry characteristic of an ideal convergent photon beam in a hypothetical water phantom. Then, using the PENELOPE Monte Carlo code, a similar convergent beam that is applied to the water phantom is compared with that of the analytical method. The CBRT device (Converay(®)) is designed to adapt to the head of LINACs. The converging beam photon effect is achieved thanks to the perpendicular impact of LINAC electrons on a large thin spherical cap target where Bremsstrahlung is generated (high-energy x-rays). This way, the electrons impact upon various points of the cap (CBRT condition), aimed at the focal point. With the X radiation (Bremsstrahlung) directed forward, a system of movable collimators emits many beams from the output that make a virtually definitive convergent beam. Other Monte Carlo simulations are performed using realistic conditions. The simulations are performed for a thin target in the shape of a large, thin, spherical cap, with an r radius of around 10-30 cm and a curvature radius of approximately 70 to 100 cm, and a cubed water phantom centered in the focal point of the cap. All the interaction mechanisms of the Bremsstrahlung radiation with the phantom are taken into consideration for different energies and cap thicknesses. Also, the magnitudes of the electric and/or magnetic fields, which are necessary to divert clinical-use electron beams (0.1 to 20 MeV), are determined using electromagnetism equations with relativistic corrections. This way the above-mentioned beam is manipulated and guided for its perpendicular impact
Kim, Eunjung; Rebecca, Vito; Fedorenko, Inna V; Messina, Jane L; Mathew, Rahel; Maria-Engler, Silvya S; Basanta, David; Smalley, Keiran S M; Anderson, Alexander R A
2013-12-01
We present an integrated study to understand the key role of senescent fibroblasts in driving melanoma progression. Based on the hybrid cellular automata paradigm, we developed an in silico model of normal skin. The model focuses on key cellular and microenvironmental variables that regulate interactions among keratinocytes, melanocytes, and fibroblasts, key components of the skin. The model recapitulates normal skin structure and is robust enough to withstand physical as well as biochemical perturbations. Furthermore, the model predicted the important role of the skin microenvironment in melanoma initiation and progression. Our in vitro experiments showed that dermal fibroblasts, which are an important source of growth factors in the skin, adopt a secretory phenotype that facilitates cancer cell growth and invasion when they become senescent. Our coculture experiments showed that the senescent fibroblasts promoted the growth of nontumorigenic melanoma cells and enhanced the invasion of advanced melanoma cells. Motivated by these experimental results, we incorporated senescent fibroblasts into our model and showed that senescent fibroblasts transform the skin microenvironment and subsequently change the skin architecture by enhancing the growth and invasion of normal melanocytes. The interaction between senescent fibroblasts and the early-stage melanoma cells leads to melanoma initiation and progression. Of microenvironmental factors that senescent fibroblasts produce, proteases are shown to be one of the key contributing factors that promoted melanoma development from our simulations. Although not a direct validation, we also observed increased proteolytic activity in stromal fields adjacent to melanoma lesions in human histology. This leads us to the conclusion that senescent fibroblasts may create a prooncogenic skin microenvironment that cooperates with mutant melanocytes to drive melanoma initiation and progression and should therefore be considered as a
NASA Astrophysics Data System (ADS)
Tejedor, Alejandro; Longjas, Anthony; Zaliapin, Ilya; Foufoula-Georgiou, Efi
2015-04-01
River deltas are landforms with complex channel networks that deliver water, sediment and nutrient fluxes from rivers to oceans or inland water bodies via multiple pathways. Most of the deltas are subject to anthropogenic and natural perturbations causing topological and dynamical changes in the delta structure and function. We present a quantitative framework based on spectral graph theory within which a systematic study of the topology, transport dynamics and response to change of river deltas can be performed, as well as computation of sub-networks (from apex to shoreline outlets), and contributing/nourishing areas. We introduce metrics of topologic and dynamic complexity and define a multidimensional complexity space where each delta projects. By analysis of seven deltas of different morphodynamic and environmental settings, we report a surprising power law relationship between sub-network size and its dynamic exchange with surrounding sub-networks within the deltaic system. The exponent of the relationship is universal (predicting that a sub-network twice as large leaks out to other sub-networks only 1.3 times its total flux) and the pre-exponent depends on the topologic complexity of the delta network as a whole, i.e., the ensemble of the interacting sub-sub-networks. We also use the developed framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way for systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.
NASA Astrophysics Data System (ADS)
Tan, Xuesong Jonathan; Li, Liang; Guo, Wei
One important issue in cognitive transmission is for multiple secondary users to dynamically acquire spare spectrum from the single primary user. The existing spectrum sharing scheme adopts a deterministic Cournot game to formulate this problem, of which the solution is the Nash equilibrium. This formulation is based on two implicit assumptions. First, each secondary user is willing to fully exchange transmission parameters with all others and hence knows their complete information. Second, the unused spectrum of the primary user for spectrum sharing is always larger than the total frequency demand of all secondary users at the Nash equilibrium. However, both assumptions may not be true in general. To remedy this, the present paper considers a more realistic assumption of incomplete information, i.e., each secondary user may choose to conceal their private information for achieving higher transmission benefit. Following this assumption and given that the unused bandwidth of the primary user is large enough, we adopt a probabilistic Cournot game to formulate an opportunistic spectrum sharing scheme for maximizing the total benefit of all secondary users. Bayesian equilibrium is considered as the solution of this game. Moreover, we prove that a secondary user can improve their expected benefit by actively hiding its transmission parameters and increasing their variance. On the other hand, when the unused spectrum of the primary user is smaller than the maximal total frequency demand of all secondary users at the Bayesian equilibrium, we formulate a constrained optimization problem for the primary user to maximize its profit in spectrum sharing and revise the proposed spectrum sharing scheme to solve this problem heuristically. This provides a unified approach to overcome the aforementioned two limitations of the existing spectrum sharing scheme.
Thin-film growth dynamics with shadowing effects by a phase-field approach
NASA Astrophysics Data System (ADS)
Salvalaglio, Marco; Backofen, Rainer; Voigt, Axel
2016-12-01
Shadowing effects during the growth of nano- and microstructures are crucial for the realization of several technological applications. They are given by the shielding of the incoming material flux provided by the growing structures themselves. Their features have been deeply investigated by theoretical approaches, revealing important information to support experimental activities. However, comprehensive investigations able to follow every stage of the growth processes as a whole, particularly useful to design and understand targeted experiments, are still challenging. In this work, we study the thin-film growth dynamics by means of a diffuse interface approach accounting for both deposition with shadowing effects and surface diffusion driven by the minimization of the surface energy. In particular, we introduce the coupling between a phase-field model and the detailed calculation of the incoming material flux at the surface deposited from vacuum or vapor phase in the ballistic regime. This allows us to finely reproduce the realistic morphological evolution during the growth on nonflat substrates, also accounting for different flux distributions. A general assessment of the method, focusing on two-dimensional profiles, is provided thanks to the comparison with a sharp-interface approach for the evolution of the early stages. Then, the long-time-scale dynamics is shown in two and three dimensions, providing a general overview of the features observed during deposition on corrugated surfaces involving flattening, increasing of surface roughness with the growth of columnar structures, and voids formation.
NASA Astrophysics Data System (ADS)
Qi, Huan
Direct metal deposition (DMD), a laser-cladding based solid freeform fabrication technique, is capable of depositing multiple materials at desired composition which makes this technique a flexible method to fabricate heterogeneous components or functionally-graded structures. The inherently rapid cooling rate associated with the laser cladding process enables extended solid solubility in nonequilibrium phases, offering the possibility of tailoring new materials with advanced properties. This technical advantage opens the area of synthesizing a new class of materials designed by topology optimization method which have performance-based material properties. For better understanding of the fundamental phenomena occurring in multi-material laser cladding with coaxial powder injection, a self-consistent 3-D transient model was developed. Physical phenomena including laser-powder interaction, heat transfer, melting, solidification, mass addition, liquid metal flow, and species transportation were modeled and solved with a controlled-volume finite difference method. Level-set method was used to track the evolution of liquid free surface. The distribution of species concentration in cladding layer was obtained using a nonequilibrium partition coefficient model. Simulation results were compared with experimental observations and found to be reasonably matched. Multi-phase material microstructures which have negative coefficients of thermal expansion were studied for their DMD manufacturability. The pixel-based topology-optimal designs are boundary-smoothed by Bezier functions to facilitate toolpath design. It is found that the inevitable diffusion interface between different material-phases degrades the negative thermal expansion property of the whole microstructure. A new design method is proposed for DMD manufacturing. Experimental approaches include identification of laser beam characteristics during different laser-powder-substrate interaction conditions, an
NASA Astrophysics Data System (ADS)
Ayala, Alejandro
2016-10-01
In the past few years a wealth of high quality data has made possible to test current theoretical ideas about the properties of hadrons subject to extreme conditions of density and temperature. The relativistic heavy-ion program carried out at the CERN-SPS and under development at the BNL-RHIC and CERN-LHC has provided results that probe the evolution of collisions of hadronic matter at high energies from the initially large density to the late dilute stages. In addition, QCD on the lattice has produced results complementing these findings with first principles calculations for observables in a regime where perturbative techniques cannot describe the nature of strongly coupled systems. This work aims to review some recent developments that make use of field theoretical methods to describe the physics of hadrons at finite temperature and density. I concentrate on two of the main topics that have been explored in the last few years: (1) The search for the structure of the phase diagram and (2) analytical signals linked to the chiral symmetry restoration/deconfinement.
Gilmore, J A; Liu, J; Woods, E J; Peter, A T; Critser, J K
2000-02-01
Previous reports have left unresolved discrepancies between human sperm cryopreservation methods developed using theoretical optimization approaches and those developed empirically. This study was designed to investigate possible reasons for the discrepancies. Human spermatozoa were exposed to 1 mol/l glycerol, 1 mol/l dimethyl sulphoxide (DMSO), 1 mol/l propylene glycol (PG) or 2 mol/l ethylene glycol (EG) at 22, 11 and 0 degrees C, then returned to isosmotic media while changes in cell volume were monitored. Activation energies (E(a)) of the hydraulic conductivity (L(p)) in the presence of cryoprotective agents (CPA) (L(p)(CPA)) were 22.2 (DMSO), 11.9 (glycerol), 15.8 (PG), and 7.8 (EG) kcal/mol. The E(a) values of the membrane permeability to CPA (P(CPA)) were 12.1 (DMSO), 10.4 (glycerol), 8.6 (PG) and 8.0 (EG) kcal/mol. These data indicated that even at low temperatures, EG permeates fastest. The high L(p)(CPA) in the presence of EG and low associated E(a) would allow spermatozoa to remain closer to equilibrium with the extracellular solution during slow cooling in the presence of ice. Collectively, these data suggest that the increase of the E(a) of L(p) in the presence of CPA at low temperature is the likely reason for the observed discrepancy between theoretical predictions of spermatozoa freezing response and empirical data.
Arantes, Lucas M; Varejão, Eduardo V V; Pelizzaro-Rocha, Karin J; Cereda, Cíntia M S; de Paula, Eneida; Lourenço, Maicon P; Duarte, Hélio A; Fernandes, Sergio A
2014-05-01
The aim of this work was to study the interaction between the local anesthetic benzocaine and p-sulfonic acid calix[n]arenes using NMR and theoretical calculations and to assess the effects of complexation on cytotoxicity of benzocaine. The architectures of the complexes were proposed according to (1) H NMR data (Job plot, binding constants, and ROESY) indicating details on the insertion of benzocaine in the cavity of the calix[n]arenes. The proposed inclusion compounds were optimized using the PM3 semiempirical method, and the electronic plus nuclear repulsion energy contributions were performed at the DFT level using the PBE exchange/correlation functional and the 6-311G(d) basis set. The remarkable agreement between experimental and theoretical approaches adds support to their use in the structural characterization of the inclusion complexes. In vitro cytotoxic tests showed that complexation intensifies the intrinsic toxicity of benzocaine, possibly by increasing the water solubility of the anesthetic and favoring its partitioning inside of biomembranes.
Pietrucci, Fabio; Saitta, Antonino Marco
2015-01-01
Increasing experimental and theoretical evidence points to formamide as a possible hub in the complex network of prebiotic chemical reactions leading from simple precursors like H2, H2O, N2, NH3, CO, and CO2 to key biological molecules like proteins, nucleic acids, and sugars. We present an in-depth computational study of the formation and decomposition reaction channels of formamide by means of ab initio molecular dynamics. To this aim we introduce a new theoretical method combining the metadynamics sampling scheme with a general purpose topological formulation of collective variables able to track a wide range of different reaction mechanisms. Our approach is flexible enough to discover multiple pathways and intermediates starting from minimal insight on the systems, and it allows passing in a seamless way from reactions in gas phase to reactions in liquid phase, with the solvent active role fully taken into account. We obtain crucial new insight into the interplay of the different formamide reaction channels and into environment effects on pathways and barriers. In particular, our results indicate a similar stability of formamide and hydrogen cyanide in solution as well as their relatively facile interconversion, thus reconciling experiments and theory and, possibly, two different and competing prebiotic scenarios. Moreover, although not explicitly sought, formic acid/ammonium formate is produced as an important formamide decomposition byproduct in solution. PMID:26598679
Dark energy or modified gravity? An effective field theory approach
Bloomfield, Jolyon; Flanagan, Éanna É.; Park, Minjoon; Watson, Scott E-mail: eef3@cornell.edu E-mail: gswatson@syr.edu
2013-08-01
We take an Effective Field Theory (EFT) approach to unifying existing proposals for the origin of cosmic acceleration and its connection to cosmological observations. Building on earlier work where EFT methods were used with observations to constrain the background evolution, we extend this program to the level of the EFT of the cosmological perturbations — following the example from the EFT of Inflation. Within this framework, we construct the general theory around an assumed background which will typically be chosen to mimic ΛCDM, and identify the parameters of interest for constraining dark energy and modified gravity models with observations. We discuss the similarities to the EFT of Inflation, but we also identify a number of subtleties including the relationship between the scalar perturbations and the Goldstone boson of the spontaneously broken time translations. We present formulae that relate the parameters of the fundamental Lagrangian to the speed of sound, anisotropic shear stress, effective Newtonian constant, and Caldwell's varpi parameter, emphasizing the connection to observations. It is anticipated that this framework will be of use in constraining individual models, as well as for placing model-independent constraints on dark energy and modified gravity model building.
Reniers, Genserik; Dullaert, Wout; Karel, Soudan
2009-08-15
Every company situated within a chemical cluster faces domino effect risks, whose magnitude depends on every company's own risk management strategies and on those of all others. Preventing domino effects is therefore very important to avoid catastrophes in the chemical process industry. Given that chemical companies are interlinked by domino effect accident links, there is some likelihood that even if certain companies fully invest in domino effects prevention measures, they can nonetheless experience an external domino effect caused by an accident which occurred in another chemical enterprise of the cluster. In this article a game-theoretic approach to interpret and model behaviour of chemical plants within chemical clusters while negotiating and deciding on domino effects prevention investments is employed.
NASA Astrophysics Data System (ADS)
Golovanov, A. V.; Shapovalov, V. I.
2010-07-01
A method based on the statistical approach is proposed to calculate the light intensity for the torsional deformation of lyotropic nematic liquid crystals at violated Mauguin adiabatic approximation. Theoretical dependences of the light intensity on the magnetic field strength are obtained for two limiting cases of lyotropic nematic anchoring with bearing surfaces: infinite and low anchoring energies.
NASA Astrophysics Data System (ADS)
Kumar, Priyank; Bhatt, Nisarg K.; Vyas, Pulastya R.; Gohel, Vinod B.
2016-10-01
The thermophysical properties of rhodium are studied up to melting temperature by incorporating anharmonic effects due to lattice ions and thermally excited electrons. In order to account anharmonic effects due to lattice vibrations, we have employed mean field potential (MFP) approach and for thermally excited electrons Mermin functional. The local form of the pseudopotential with only one effective adjustable parameter rc is used to construct MFP and hence vibrational free energy due to ions - Fion. We have studied equation of state at 300 K and further, to access the applicability of present conjunction scheme, we have also estimated shock-Hugoniot and temperature along principle Hugoniot. We have carried out the study of temperature variation of several thermophysical properties like thermal expansion (βP), enthalpy (EH), specific heats at constant pressure and volume (CP and CV), specific heats due to lattice ions and thermally excited electrons ( and , isothermal and adiabatic bulk moduli (BT and Bs) and thermodynamic Gruneisen parameter (γth) in order to examine the inclusion of anharmonic effects in the present study. The computed results are compared with available experimental results measured by using different methods and previously obtained theoretical results using different theoretical philosophy. Our computed results are in good agreement with experimental findings and for some physical quantities better or comparable with other theoretical results. We conclude that local form of the pseudopotential used accounts s-p-d hybridization properly and found to be transferable at extreme environment without changing the values of the parameter. Thus, even the behavior of transition metals having complexity in electronic structure can be well understood with local pseudopotential without any modification in the potential at extreme environment. Looking to the success of present scheme (MFP + pseudopotential) we would like to extend it further for the
Geosynergetic Approach for Analyze of Rock State, Theoretical and Experimental Redlts
NASA Astrophysics Data System (ADS)
Hachay, O. A.; Khachay, A. Y.; Khachay, O. Y.
2012-04-01
releasing the system returns to the same phase trajectory attracting area. That is confirmed by detailed analyze of phase trajectories of seismic massive response before and after high energetic rock burst. In the book [5] is developed a new mathematical method for modeling of processes in local active continuum, which are energetically influenced from an outer energy source. The common cause of chaotization and stochastization of dynamical system movements are its losses of stability and exponential recession of near located phase trajectories together with its common boundedness and its common compression. The mathematical result coincides as a whole with the practical result: in the phase area the smaller attracting phase trajectories area exists where can occur an exponential recession of them, then the movement character changes and the further movement of phase points lead to return to the same attracting area. These movements can occur in resonance or spontaneous mood. The work was supported by the grant RFBR 10-05-00013. 1. Hachay, O.A., and Khachay, O.Yu. 2009. "Results of electromagnetic and seismic monitoring of the state of rock massive by use the approach of the open dynamical systems,"presented at the EGU2009 - EGU General Assembly 2009, session: Thermo- hydro- mechanical coupling in stressed rock, 19 April 19 - 24 April 2009. 2. Hachay, O.A. "Synergetic events in geological medium and nonlinear features of wave propagation," presented at the EGU2009 - EGU General Assembly 2009, session: Solid Earth geocomplexity: surface processes, morphology and natural resources over wide ranges of scale, 19 April 19 - 24 April 2009. 3. Chulichkov, A.I. 2003. Mathematical models of nonlinear dynamics. Moscow: Phismatlit, p.420. 4. Malineckiy, G.G. 2007. Mathematical base of synergetics. Moscow: LKI, p.375. 5. Naimark, Yu.I.and Landa, P.S. 2009. Stochastic and Chaotic oscillations. Moscow: Knigniy dom "LIBROKOM", p.424.
Data, Methods, and Theoretical Implications
ERIC Educational Resources Information Center
Hannagan, Rebecca J.; Schneider, Monica C.; Greenlee, Jill S.
2012-01-01
Within the subfields of political psychology and the study of gender, the introduction of new data collection efforts, methodologies, and theoretical approaches are transforming our understandings of these two fields and the places at which they intersect. In this article we present an overview of the research that was presented at a National…
Uszko, Wojciech; Diehl, Sebastian; Englund, Göran; Amarasekare, Priyanga
2017-04-01
We theoretically explore consequences of warming for predator-prey dynamics, broadening previous approaches in three ways: we include beyond-optimal temperatures, predators may have a type III functional response, and prey carrying capacity depends on explicitly modelled resources. Several robust patterns arise. The relationship between prey carrying capacity and temperature can range from near-independence to monotonically declining/increasing to hump-shaped. Predators persist in a U-shaped region in resource supply (=enrichment)-temperature space. Type II responses yield stable persistence in a U-shaped band inside this region, giving way to limit cycles with enrichment at all temperatures. In contrast, type III responses convey stability at intermediate temperatures and confine cycles to low and high temperatures. Warming-induced state shifts can be predicted from system trajectories crossing stability and persistence boundaries in enrichment-temperature space. Results of earlier studies with more restricted assumptions map onto this graph as special cases. Our approach thus provides a unifying framework for understanding warming effects on trophic dynamics.
Magnetic field of Jupiter: A generalized inverse approach
NASA Technical Reports Server (NTRS)
Connerney, J. E. P.
1981-01-01
The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model nonuniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
The BAARA (Biological AutomAted RAdiotracking) System: A New Approach in Ecological Field Studies
Řeřucha, Šimon; Bartonička, Tomáš; Jedlička, Petr; Čížek, Martin; Hlouša, Ondřej; Lučan, Radek; Horáček, Ivan
2015-01-01
Radiotracking is an important and often the only possible method to explore specific habits and the behaviour of animals, but it has proven to be very demanding and time-consuming, especially when frequent positioning of a large group is required. Our aim was to address this issue by making the process partially automated, to mitigate the demands and related costs. This paper presents a novel automated tracking system that consists of a network of automated tracking stations deployed within the target area. Each station reads the signals from telemetry transmitters, estimates the bearing and distance of the tagged animals and records their position. The station is capable of tracking a theoretically unlimited number of transmitters on different frequency channels with the period of 5–15 seconds per single channel. An ordinary transmitter that fits within the supported frequency band might be used with BAARA (Biological AutomAted RAdiotracking); an extra option is the use of a custom-programmable transmitter with configurable operational parameters, such as the precise frequency channel or the transmission parameters. This new approach to a tracking system was tested for its applicability in a series of field and laboratory tests. BAARA has been tested within fieldwork explorations of Rousettus aegyptiacus during field trips to Dakhla oasis in Egypt. The results illustrate the novel perspective which automated radiotracking opens for the study of spatial behaviour, particularly in addressing topics in the domain of population ecology. PMID:25714910
The BAARA (Biological AutomAted RAdiotracking) system: a new approach in ecological field studies.
Řeřucha, Šimon; Bartonička, Tomáš; Jedlička, Petr; Čížek, Martin; Hlouša, Ondřej; Lučan, Radek; Horáček, Ivan
2015-01-01
Radiotracking is an important and often the only possible method to explore specific habits and the behaviour of animals, but it has proven to be very demanding and time-consuming, especially when frequent positioning of a large group is required. Our aim was to address this issue by making the process partially automated, to mitigate the demands and related costs. This paper presents a novel automated tracking system that consists of a network of automated tracking stations deployed within the target area. Each station reads the signals from telemetry transmitters, estimates the bearing and distance of the tagged animals and records their position. The station is capable of tracking a theoretically unlimited number of transmitters on different frequency channels with the period of 5-15 seconds per single channel. An ordinary transmitter that fits within the supported frequency band might be used with BAARA (Biological AutomAted RAdiotracking); an extra option is the use of a custom-programmable transmitter with configurable operational parameters, such as the precise frequency channel or the transmission parameters. This new approach to a tracking system was tested for its applicability in a series of field and laboratory tests. BAARA has been tested within fieldwork explorations of Rousettus aegyptiacus during field trips to Dakhla oasis in Egypt. The results illustrate the novel perspective which automated radiotracking opens for the study of spatial behaviour, particularly in addressing topics in the domain of population ecology.
Zhuo, Ye
2011-01-01
In this thesis, we theoretically study the electromagnetic wave propagation in several passive and active optical components and devices including 2-D photonic crystals, straight and curved waveguides, organic light emitting diodes (OLEDs), and etc. Several optical designs are also presented like organic photovoltaic (OPV) cells and solar concentrators. The first part of the thesis focuses on theoretical investigation. First, the plane-wave-based transfer (scattering) matrix method (TMM) is briefly described with a short review of photonic crystals and other numerical methods to study them (Chapter 1 and 2). Next TMM, the numerical method itself is investigated in details and developed in advance to deal with more complex optical systems. In chapter 3, TMM is extended in curvilinear coordinates to study curved nanoribbon waveguides. The problem of a curved structure is transformed into an equivalent one of a straight structure with spatially dependent tensors of dielectric constant and magnetic permeability. In chapter 4, a new set of localized basis orbitals are introduced to locally represent electromagnetic field in photonic crystals as alternative to planewave basis. The second part of the thesis focuses on the design of optical devices. First, two examples of TMM applications are given. The first example is the design of metal grating structures as replacements of ITO to enhance the optical absorption in OPV cells (chapter 6). The second one is the design of the same structure as above to enhance the light extraction of OLEDs (chapter 7). Next, two design examples by ray tracing method are given, including applying a microlens array to enhance the light extraction of OLEDs (chapter 5) and an all-angle wide-wavelength design of solar concentrator (chapter 8). In summary, this dissertation has extended TMM which makes it capable of treating complex optical systems. Several optical designs by TMM and ray tracing method are also given as a full complement of this
NASA Astrophysics Data System (ADS)
Yin, W.; Peyton, A. J.; Stefani, F.; Gerbeth, G.
2009-10-01
A completely contactless flow measurement technique based on the principle of EM induction measurements—contactless inductive flow tomography (CIFT)—has been previously reported by a team based at Forschungszentrum Dresden-Rossendorf (FZD). This technique is suited to the measurement of velocity fields in high conductivity liquids, and the possible applications range from monitoring metal casting and silicon crystal growth in industry to gaining insights into the working of the geodynamo. The forward problem, i.e. calculating the induced magnetic field from a known velocity profile, can be described as a linear relationship when the magnetic Reynolds number is small. Previously, an integral equation method was used to formulate the forward problem; however, although the sensitivity matrices were calculated, they were not explicitly expressed and computation involved the solution of an ill-conditioned system of equations using a so-called deflation method. In this paper, we present the derivation of the sensitivity matrix directly from electromagnetic field theory and the results are expressed very concisely as the cross product of two field vectors. A numerical method based on a finite difference method has also been developed to verify the formulation. It is believed that this approach provides a simple yet fast route to the forward solution of CIFT. Furthermore, a method for sensor design selection based on eigenvalue analysis is presented.
Limkumnerd, Surachate
2014-03-01
Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary.
NASA Astrophysics Data System (ADS)
Limkumnerd, Surachate
2014-03-01
Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary.
Zheng, Yu; Gao, Yang; Chen, Ruijuan; Wang, Huiquan; Dong, Lei; Dou, Junrong
2016-10-01
Time-varying electromagnetic fields (EMF) can induce some physiological effects in neuronal tissues, which have been explored in many applications such as transcranial magnetic stimulation. Although transmembrane potentials and induced currents have already been the subjects of many theoretical studies, most previous works about this topic are mainly completed by utilizing Maxwell's equations, often by solving a Laplace equation. In previous studies, cells were often considered to be three-compartment models with different electroconductivities in different regions (three compartments are often intracellular regions, membrane, and extracellular regions). However, models like that did not take dynamic ion channels into consideration. Therefore, one cannot obtain concrete ionic current changes such as potassium current change or sodium current change by these models. The aim of the present work is to present a new and more detailed model for calculating transmembrane potentials and ionic currents induced by time-varying EMF. Equations used in the present paper originate from Nernst-Plank equations, which are ionic current-related equations. The main work is to calculate ionic current changes induced by EMF exposure, and then transmembrane potential changes are calculated with Hodgkin-Huxley model. Bioelectromagnetics. 37:481-492, 2016. © 2016 Wiley Periodicals, Inc.
Peng, Wenbo; Yu, Ruomeng; He, Yongning; Wang, Zhong Lin
2016-04-26
Triboelectric nanogenerator has drawn considerable attentions as a potential candidate for harvesting mechanical energies in our daily life. By utilizing the triboelectric potential generated through the coupling of contact electrification and electrostatic induction, the "tribotronics" has been introduced to tune/control the charge carrier transport behavior of silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET). Here, we perform a theoretical study of the performances of tribotronic MOSFET gated by triboelectric potential in two working modes through finite element analysis. The drain-source current dependence on contact-electrification generated triboelectric charges, gap separation distance, and externally applied bias are investigated. The in-depth physical mechanism of the tribotronic MOSFET operations is thoroughly illustrated by calculating and analyzing the charge transfer process, voltage relationship to gap separation distance, and electric potential distribution. Moreover, a tribotronic MOSFET working concept is proposed, simulated and studied for performing self-powered FET and logic operations. This work provides a deep understanding of working mechanisms and design guidance of tribotronic MOSFET for potential applications in micro/nanoelectromechanical systems (MEMS/NEMS), human-machine interface, flexible electronics, and self-powered active sensors.
Alecci, M; Collins, C M; Smith, M B; Jezzard, P
2001-08-01
The RF B(1) distribution was studied, theoretically and experimentally, in phantoms and in the head of volunteers using a 3 T MRI system equipped with a birdcage coil. Agreement between numerical simulation and experiment demonstrates that B(1) distortion at high field can be explained with 3D full-Maxwell calculations. It was found that the B(1) distribution in the transverse plane is strongly dependent on the dielectric properties of the sample. We show that this is a consequence of RF penetration effects combined with RF standing wave effects. In contrast, along the birdcage coil z-axis the B(1) distribution is determined mainly by the coil geometry. In the transverse plane, the region of B(1) uniformity (within 10% of the maximum) was 15 cm with oil, 6 cm with distilled water, 11 cm with saline, and 10 cm in the head. Along z the B(1) uniformity was 9 cm with phantoms and 7 cm in the head.
Ronald Fowler
2004-11-30
This report describes the results of the one-year project entitled ''Improved Approaches to Design of Polymer Gel Treatments in Mature Oil Fields: Field Demonstration in Dickman Field, Ness County, Kansas''. The project was a 12-month collaboration of Grand Mesa Operating Company (a small independent), TIORCO Inc. (a company focused on improved recovery technology) and the University of Kansas. The study undertook tasks to determine an optimum polymer gel treatment design in Mississippian reservoirs, demonstrate application, and evaluate the success of the program. The project investigated geologic and engineering parameters and cost-effective technologies required for design and implementation of effective polymer gel treatment programs in the Mississippian reservoir in the Midcontinent. The majority of Mississippian production in Kansas occurs at or near the top of the Mississippian section just below the regional sub-Pennsylvanian unconformity and karst surface. Dickman Field with the extremely high water cuts and low recovery factors is typical of Mississippian reservoirs. Producibility problems in these reservoirs include inadequate reservoir characterization, drilling and completion design problems, and most significantly extremely high water cuts and low recovery factors that place continued operations at or near their economic limits. Geologic, geophysical and engineering data were integrated to provide a technical foundation for candidate selection and treatment design. Data includes core, engineering data, and 3D seismic data. Based on technical and economic considerations a well was selected for gel-polymer treatment (Grand Mesa Operating Company Tilley No.2). The treatment was not successful due to the small amount of polymer that could be injected. Data from the initial well and other candidates in the demonstration area was analyzed using geologic, geophysical and engineering data. Based on the results of the treatment and the integrated reservoir
NASA Technical Reports Server (NTRS)
Everhart, Joel Lee
1988-01-01
A theoretical examination of the slotted-wall flow field is conducted to determine the appropriate wall pressure drop (or boundary condition) equation. This analysis improves the understanding of the fluid physics of these types of flow fields and helps in evaluating the uncertainties and limitations existing in previous mathematical developments. It is shown that the resulting slotted-wall boundary condition contains contributions from the airfoil-induced streamline curvature and the non-linear, quadratic, slot crossflow in addition to an often neglected linear term which results from viscous shearing in the slot. Existing and newly acquired experimental data are examined in the light of this formulation and theoretical developments.
NASA Astrophysics Data System (ADS)
Kocifaj, Miroslav
2016-09-01
The study of diffuse light of a night sky is undergoing a renaissance due to the development of inexpensive high performance computers which can significantly reduce the time needed for accurate numerical simulations. Apart from targeted field campaigns, numerical modeling appears to be one of the most attractive and powerful approaches for predicting the diffuse light of a night sky. However, computer-aided simulation of night-sky radiances over any territory and under arbitrary conditions is a complex problem that is difficult to solve. This study addresses three concepts for modeling the artificial light propagation through a turbid stratified atmosphere. Specifically, these are two-stream approximation, iterative approach to Radiative Transfer Equation (RTE) and Method of Successive Orders of Scattering (MSOS). The principles of the methods, their strengths and weaknesses are reviewed with respect to their implications for night-light modeling in different environments.
NASA Technical Reports Server (NTRS)
Sinko, P. J.; Leesman, G. D.; Amidon, G. L.
1993-01-01
A theoretical analysis for estimating the extent of intestinal peptide and peptide analogue absorption was developed on the basis of a mass balance approach that incorporates convection, permeability, and reaction. The macroscopic mass balance analysis (MMBA) was extended to include chemical and enzymatic degradation. A microscopic mass balance analysis, a numerical approach, was also developed and the results compared to the MMBA. The mass balance equations for the fraction of a drug absorbed and reacted in the tube were derived from the general steady state mass balance in a tube: [formula: see text] where M is mass, z is the length of the tube, R is the tube radius, Pw is the intestinal wall permeability, kr is the reaction rate constant, C is the concentration of drug in the volume element over which the mass balance is taken, VL is the volume of the tube, and vz is the axial velocity of drug. The theory was first applied to the oral absorption of two tripeptide analogues, cefaclor (CCL) and cefatrizine (CZN), which degrade and dimerize in the intestine. Simulations using the mass balance equations, the experimental absorption parameters, and the literature stability rate constants yielded a mean estimated extent of CCL (250-mg dose) and CZN (1000-mg dose) absorption of 89 and 51%, respectively, which was similar to the mean extent of absorption reported in humans (90 and 50%). It was proposed previously that 15% of the CCL dose spontaneously degraded systematically; however, our simulations suggest that significant CCL degradation occurs (8 to 17%) presystemically in the intestinal lumen.(ABSTRACT TRUNCATED AT 250 WORDS).
Pacheco-Blas, M. A.; Novaro, O. A.; Pacheco-Sanchez, J. H.
2010-11-07
The photochemical activation of Al atoms in cryogenic matrices to induce their reaction with methane has been experimentally studied before. Here, a theoretical study of the nonadiabatic transition probabilities for the ground ({sup 2}P:3s{sup 2}3p{sup 1}) and the lowest excited states ({sup 2}S:3s{sup 2}4s{sup 1} and {sup 2}D:3s{sup 2}3d{sup 1}) of an aluminum atom interacting with a methane molecule (CH{sub 4}) was carried out through ab initio Hartree-Fock self-consistent field calculations. This was followed by a multiconfigurational study of the correlation energy obtained by extensive variational and perturbational configuration interaction analyses using the CIPSI program. The {sup 2}D state is readily inserted into a C-H bond, this being a prelude to a sequence of avoided crossings with the initially repulsive (to CH{sub 4}) lower lying states {sup 2}P and {sup 2}S. We then use a direct extension of the Landau-Zener theory to obtain transition probabilities at each avoided crossing, allowing the formation of an HAlCH{sub 3} intermediate that eventually leads to the final pair of products H+AlCH{sub 3} and HAl+CH{sub 3}.
New dynamical mean-field dynamo theory and closure approach.
Blackman, Eric G; Field, George B
2002-12-23
We develop a new nonlinear mean field dynamo theory that couples field growth to the time evolution of the magnetic helicity and the turbulent electromotive force, E. We show that the difference between kinetic and current helicities emerges naturally as the growth driver when the time derivative of E is coupled into the theory. The solutions predict significant field growth in a kinematic phase and a saturation rate/strength that is magnetic Reynolds number dependent/independent in agreement with numerical simulations. The amplitude of early time oscillations provides a diagnostic for the closure.
Karabulut, Sedat; Namli, Hilmi; Leszczynski, Jerzy
2013-08-01
Molecular structures of stable tautomers of dimedone [5,5-dimethyl-cyclohexane-1,3-dione and 3-hydroxy-5,5-dimethylcyclohex-2-enone] were optimized and vibrational frequencies were calculated in five different organic solvents (dimethylsulfoxide, methanol, acetonitrile, dichloromethane and chloroform). Geometry optimizations and harmonic vibrational frequency calculations were performed at DFT 6-31+G(d,p), DFT 6-311++G(2d,2p), MP2 6-311++G (2d,2p) and MP2 aug-cc-pVDZ levels for both stable forms of dimedone. Experimental FT-IR spectra of dimedone have also been recorded in the same solvents. A new approach was developed in order to determine tautomers' ratio using both experimental and theoretical data in Lambert-Beer equation. Obtained results were compared with experimental results published in literature. It has been concluded that while DFT 6-31+G(d,p) method provides accurate enol ratio in DMSO, MeOH, and DCM, in order to obtain accurate results for the other solvents the MP2 aug-cc-pVDZ level calculations should be used for CH₃CN and CHCl₃ solutions.
NASA Astrophysics Data System (ADS)
Karabulut, Sedat; Namli, Hilmi; Leszczynski, Jerzy
2013-08-01
Molecular structures of stable tautomers of dimedone [5,5-dimethyl-cyclohexane-1,3-dione ( 1) and 3-hydroxy-5,5-dimethylcyclohex-2-enone ( 2)] were optimized and vibrational frequencies were calculated in five different organic solvents (dimethylsulfoxide, methanol, acetonitrile, dichloromethane and chloroform). Geometry optimizations and harmonic vibrational frequency calculations were performed at DFT 6-31+G(d,p), DFT 6-311++G(2d,2p), MP2 6-311++G (2d,2p) and MP2 aug-cc-pVDZ levels for both stable forms of dimedone. Experimental FT-IR spectra of dimedone have also been recorded in the same solvents. A new approach was developed in order to determine tautomers' ratio using both experimental and theoretical data in Lambert-Beer equation. Obtained results were compared with experimental results published in literature. It has been concluded that while DFT 6-31+G(d,p) method provides accurate enol ratio in DMSO, MeOH, and DCM, in order to obtain accurate results for the other solvents the MP2 aug-cc-pVDZ level calculations should be used for CH3CN and CHCl3 solutions.
Painter, K. J.; Hunt, G. S.; Wells, K. L.; Johansson, J. A.; Headon, D. J.
2012-01-01
In his seminal 1952 paper, ‘The Chemical Basis of Morphogenesis’, Alan Turing lays down a milestone in the application of theoretical approaches to understand complex biological processes. His deceptively simple demonstration that a system of reacting and diffusing chemicals could, under certain conditions, generate spatial patterning out of homogeneity provided an elegant solution to the problem of how one of nature's most intricate events occurs: the emergence of structure and form in the developing embryo. The molecular revolution that has taken place during the six decades following this landmark publication has now placed this generation of theoreticians and biologists in an excellent position to rigorously test the theory and, encouragingly, a number of systems have emerged that appear to conform to some of Turing's fundamental ideas. In this paper, we describe the history and more recent integration between experiment and theory in one of the key models for understanding pattern formation: the emergence of feathers and hair in the skins of birds and mammals. PMID:23919127
Fernandes, Cláudia S M; Pina, Ana Sofia; Dias, Ana M G C; Branco, Ricardo J F; Roque, Ana Cecília Afonso
2014-09-30
The green fluorescent protein (GFP) is widely employed to report on a variety of molecular phenomena, but its selective recovery is hampered by the lack of a low-cost and robust purification alternative. This work reports an integrated approach combining rational design and experimental validation toward the optimization of a small fully-synthetic ligand for GFP purification. A total of 56 affinity ligands based on a first-generation lead structure were rationally designed through molecular modeling protocols. The library of ligands was further synthesized by solid-phase combinatorial methods based on the Ugi reaction and screened against Escherichia coli extracts containing GFP. Ligands A4C2, A5C5 and A5C6 emerged as the new lead structures based on the high estimated theoretical affinity constants and the high GFP binding percentages and enrichment factors. The elution of GFP from these adsorbents was further characterized, where the best compromise between mild elution conditions, yield and purity was found for ligands A5C5 and A5C6. These were tested for purifying a model GFP-fusion protein, where ligand A5C5 yielded higher protein recovery and purity. The molecular interactions between the lead ligands and GFP were further assessed by molecular dynamics simulations, showing a wide range of potential hydrophobic and hydrogen-bond interactions.
Marc Vanderhaeghen
2007-04-01
The theoretical issues in the interpretation of the precision measurements of the nucleon-to-Delta transition by means of electromagnetic probes are highlighted. The results of these measurements are confronted with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, large-Nc relations, perturbative QCD, and QCD-inspired models. The link of the nucleon-to-Delta form factors to generalized parton distributions (GPDs) is also discussed.
NASA Technical Reports Server (NTRS)
Bebout, Leslie; Keller, R.; Miller, S.; Jahnke, L.; DeVincenzi, D. (Technical Monitor)
2002-01-01
The Ames Exobiology Culture Collection Database (AECC-DB) has been developed as a collaboration between microbial ecologists and information technology specialists. It allows for extensive web-based archiving of information regarding field samples to document microbial co-habitation of specific ecosystem micro-environments. Documentation and archiving continues as pure cultures are isolated, metabolic properties determined, and DNA extracted and sequenced. In this way metabolic properties and molecular sequences are clearly linked back to specific isolates and the location of those microbes in the ecosystem of origin. Use of this database system presents a significant advancement over traditional bookkeeping wherein there is generally little or no information regarding the environments from which microorganisms were isolated. Generally there is only a general ecosystem designation (i.e., hot-spring). However within each of these there are a myriad of microenvironments with very different properties and determining exactly where (which microenvironment) a given microbe comes from is critical in designing appropriate isolation media and interpreting physiological properties. We are currently using the database to aid in the isolation of a large number of cyanobacterial species and will present results by PI's and students demonstrating the utility of this new approach.
Phase-field approach to chemotactic driving of neutrophil morphodynamics
NASA Astrophysics Data System (ADS)
Najem, Sara; Grant, Martin
2013-09-01
To simulate the motion of neutrophils and their morphodynamics in response to chemical cues, we construct a model based on the phase-field method utilizing a description with a free-energy functional and associated dynamics which captures the basic features of the phenomenon. We additionally incorporate spatial sensing by introducing an auxiliary field which depicts the polymerization of the region of the cell facing the highest concentration of the chemical attractant.
ERIC Educational Resources Information Center
Tweeikat, Mashhour Mohammad; AL-Kaddah, Muhammad Ibrahim
2014-01-01
This paper aims at studying to what extent the female students in Child Education department at Princess Alia University College manage to apply the theoretical part in field training program. The data, which is the scope of this study, consists of 42 staff members and 36 educational supervisors responsible for the program. The two researchers…
NASA Astrophysics Data System (ADS)
D'Auria, Luca; Massa, Bruno; Cristiano, Elena; Del Gaudio, Carlo; Giudicepietro, Flora; Ricciardi, Giovanni; Ricco, Ciro
2015-11-01
We investigated the Campi Flegrei caldera using a quantitative approach to retrieve the spatial and temporal variations of the stress field. For this aim we applied a joint inversion of geodetic and seismological data to a dataset of 1,100 optical levelling measurements and 222 focal mechanisms, recorded during the bradyseismic crisis of 1982-1984. The inversion of the geodetic dataset alone, shows that the observed ground deformation is compatible with a source consisting of a planar crack, located at the centre of the caldera at a depth of about 2.56 km and a size of about 4 × 4 km. Inversion of focal mechanisms using both analytical and graphical approaches, has shown that the key features of the stress field in the area are: a nearly subvertical σ 1 and a sub-horizontal, roughly NNE-SSW trending σ 3. Unfortunately, the modelling of the stress fields based only upon the retrieved ground deformation source is not able to fully account for the stress pattern delineated by focal mechanism inversion. The introduction of an additional regional background field has been necessary. This field has been determined by minimizing the difference between observed slip vectors for each focal mechanism and the theoretical maximum shear stress deriving from both the volcanic (time-varying) and the regional (constant) field. The latter is responsible for a weak NNE-SSW extension, which is consistent with the field determined for the nearby Mt. Vesuvius volcano. The proposed approach accurately models observations and provides interesting hints to better understand the dynamics of the volcanic unrest and seismogenic processes at Campi Flegrei caldera. This procedure could be applied to other volcanoes experiencing active ground deformation and seismicity.
Methodological approaches in estimating anomalous geochemical field structure
NASA Astrophysics Data System (ADS)
Gavrilov, R.; Rudmin, M.
2015-02-01
Mathematical statistic methods were applied to analyze the core samples from vertical expendable wells in Chertovo Koryto gold ore field. The following methods were used to analyse gold in samples: assay tests and atomic absorption method (AAS), while emission spectrum semiquantative method was applied to identify traces. The analysis of geochemical association distribution in one central profile demonstrated that bulk metasomatic aureoles are characteristic of concentric zonal structure. The distribution of geochemical associations is correlated to the hydrothermal stages of mineral formation identified in this deposit. It was proved that the processed geochemical data by factor and cluster analyses provided additional information on the anomalous geochemical field structure in gold- bearing black-shale strata. Such methods are effective tools in interpretating specific features of geochemical field structures in analogous potential ore-bearing areas.
A scalar field dark energy model: Noether symmetry approach
NASA Astrophysics Data System (ADS)
Dutta, Sourav; Panja, Madan Mohan; Chakraborty, Subenoy
2016-04-01
Scalar field dark energy cosmology has been investigated in the present paper in the frame work of Einstein gravity. In the context of Friedmann-Lemaitre-Robertson-Walker space time minimally coupled scalar field with self interacting potential and non-interacting perfect fluid with barotropic equation of state (dark matter) is chosen as the matter context. By imposing Noether symmetry on the Lagrangian of the system the symmetry vector is obtained and the self interacting potential for the scalar field is determined. Then we choose a point transformation (a, φ )→ (u, v) such that one of the transformation variable (say u) is cyclic for the Lagrangian. Subsequently, using conserved charge (corresponding to the cyclic co-ordinate) and the constant of motion, solutions are obtained. Finally, the cosmological implication of the solutions in the perspective of recent observation has been examined.
Elastic properties of hybrid composites by the effective field approach
NASA Astrophysics Data System (ADS)
Kanaun, S. K.; Jeulin, D.
2001-10-01
The work is dedicated to the calculation of the overall elastic properties of matrix composite materials containing two different populations of inclusions (three phase hybrid composites). The application of the well known Mori-Tanaka method or self-consistent effective medium method to the solution of this problem gives overall elastic moduli tensors of such composites that do not have the necessary symmetry (the symmetry with respect to the first and second pairs of indices). In this work, a new version of the effective field method that takes into account specific features of the microstructure of three phase composites is developed. In this version, the field that acts on every inclusion in the composite is assumed to be different for inclusions of different populations. It is shown that the modified effective field method gives a correct symmetry of the overall elastic moduli tensors of three phase composites. The method allows us to describe the influence of the peculiarities in spatial distributions of inclusions on the overall elastic constants. The cases of media containing infinite cylindrical fibers and thin ellipsoidal disks or spherical pores are considered. Various boolean type probabilistic models of random sets of such inclusions are proposed and the elastic moduli tensors of the corresponding three phase composites are obtained and analyzed. It turns out that these tensors strongly depend on statistical properties of the random fields of inclusions. It is shown that for two phase composites, the Mori-Tanaka method is a particular case of the effective field method. In the case of three phase composites, the formulas of the Mori-Tanaka method follow from the equations of the effective field method if a general property of the symmetry of cross-correlation functions of different populations of inclusions is violated. As a result, the overall elastic moduli tensors obtained by Mori-Tanaka method lose their natural symmetry.
Analytical approach to quasiperiodic beam Coulomb field modeling
NASA Astrophysics Data System (ADS)
Rubtsova, I. D.
2016-09-01
The paper is devoted to modeling of space charge field of quasiperiodic axial- symmetric beam. Particle beam is simulated by charged disks. Two analytical Coulomb field expressions are presented, namely, Fourier-Bessel series and trigonometric polynomial. Both expressions permit the integral representation. It provides the possibility of integro-differential beam dynamics description. Consequently, when beam dynamics optimization problem is considered, it is possible to derive the analytical formula for quality functional gradient and to apply directed optimization methods. In addition, the paper presents the method of testing of space charge simulation code.
Noncompeting channel approach to pair creation in supercritical fields.
Lv, Q Z; Liu, Y; Li, Y J; Grobe, R; Su, Q
2013-11-01
The Dirac and Klein-Gordon equations are solved on a space-time grid to study the strong-field induced pair creation process for bosons and fermions from the vacuum. If the external field is sufficiently strong to induce bound states that are embedded in the negative energy continuum, a complex scaling technique of the Hamiltonian can predict the longtime behavior of the dynamics. In the case of multiple bound states this technique predicts the occurrence of a new collective time scale. The longtime behavior of the pair creation is not determined by a single (most important) channel, but collectively by the sum of all individual widths of the embedded states.
NASA Technical Reports Server (NTRS)
Albers, J. A.
1973-01-01
The theoretical and experimental internal flow characteristics of a 13.97-cm-diam inlet with centerbody retracted and extended are presented at STOL takeoff and approach operating conditions. The theoretical results were obtained from incompressible potential flow corrected for compressibility and boundary layer. Comparisons between theoretical internal surface static-pressure distributions and experimental data are presented for free-stream velocities of 0, 24, 32, and 45 m/sec for a range of inlet incidence angles from 0 to 50 deg. Surface static-pressure distributions are illustrated at circumferential locations of 0, 60, 120, and 180 deg. Surface Mach number distributions from the stagnation point to the diffuser exit are presented along with turbulent boundary-layer shape factors. In general, good agreement was found between the theoretical and experimental surface static pressure distributions.
The partially averaged field approach to cosmic ray diffusion
NASA Technical Reports Server (NTRS)
Jones, F. C.; Birmingham, T. J.; Kaiser, T. B.
1976-01-01
The kinetic equation for particles interacting with turbulent fluctuations is derived by a new nonlinear technique which successfully corrects the difficulties associated with quasilinear theory. In this new method the effects of the fluctuations are evaluated along particle orbits which themselves include the effects of a statistically averaged subset of the possible configurations of the turbulence. The new method is illustrated by calculating the pitch angle diffusion coefficient D sub Mu Mu for particles interacting with slab model magnetic turbulence, i.e., magnetic fluctuations linearly polarized transverse to a mean magnetic field. Results are compared with those of quasilinear theory and also with those of Monte Carlo calculations. The major effect of the nonlinear treatment in this illustration is the determination of D sub Mu Mu in the vicinity of 90 deg pitch angles where quasilinear theory breaks down. The spatial diffusion coefficient parallel to a mean magnetic field is evaluated using D sub Mu Mu as calculated by this technique. It is argued that the partially averaged field method is not limited to small amplitude fluctuating fields and is hence not a perturbation theory.
Understrength Air Force Officer Career Fields. A Force Management Approach
2005-01-01
communications, and computers; intelligence, surveillance, and reconnaissance CFM career field manager CGO company-grade officer CMDB Consolidated Manpower...this report were drawn from two data sources. The first is the Consolidated Manpower Data Base ( CMDB ), which is the collection of Unit Manpower
The American Legal System: A Field Study Approach.
ERIC Educational Resources Information Center
Milwaukee Public Schools, WI. Div. of Curriculum and Instruction.
The document presents an outline for a high school legal education program which emphasizes field experiences. The program is called the American Legal System Satellite Center, and is designed to provide students with experiential knowledge of the functions, procedures, and facets of law; to expose them to a wide range of law-related career…
New approaches to thermoelectric cooling effects in magnetic fields
Migliori, A.; Darling, T.W.; Freibert, F.; Trugman, S.A.; Moshopoulou, E.; Sarrao, J.L.
1997-08-01
The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the limiting performance and problems with its computation for both Peltier and Ettingshausen coolers are presented. New principles are discussed to guide the materials scientist in the search for better Ettingshausen materials, and a brief review of the subtle measurement problems is presented.