Opening Switch Research on a Plasma Focus VI.

DTIC Science & Technology

1988-02-26

Sausage Instability in the Plasma Focus In this section the classical Kruskal- Schwarzschild 3 theory for the sausage mode is applied to the pinch phase...on 1) the shape of the pinch, 2) axial flow of plasma, and 3) self-generated magnetic fields are also presented. The Kruskal- Schwarzschild Theory The...classical mhd theory for the m=O mode in a plasma supported by a magnetic field against gravity; this is the well-known Kruskal- Schwarzschild

Theory of Electromagnetic Surface Waves in Plasma with Smooth Boundaries

NASA Astrophysics Data System (ADS)

Kuzelev, M. V.

2018-05-01

A theory of nonpotential surface waves in plasma with smooth boundaries is developed. The complex frequencies of surface waves for plasma systems of different geometries and different profiles of the plasma density are calculated. Expressions for the rates of collisionless damping of surface waves due to their resonance interaction with local plasma waves of continuous spectrum are obtained. The influence of collisions in plasma is also considered.

The big contradiction between the perturbation theory and the chaotic state. A detailed mathematical analysis indicates when the plasma is stable or unstable

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

Xaplanteris, C. L., E-mail: cxaplanteris@yahoo.com; Xaplanteris, S. C.

2016-05-15

In the present manuscript enough observations and interpretations of three issues of Plasma Physics are presented. The first issue is linked to the common experimental confirmation of plasma waves which appear to be repeated in a standard way while there are also cases where plasma waves change to an unstable state or even to chaotic state. The second issue is associated with a mathematical analysis of the movement of a charged particle using the perturbation theory; which could be used as a guide for new researchers on similar issues. Finally, the suitability and applicability of the perturbation theory or themore » chaotic theory is presented. Although this study could be conducted on many plasma phenomena (e.g. plasma diffusion) or plasma quantities (e.g. plasma conductivity), here it was decided this study to be conducted on plasma waves and particularly on drift waves. This was because of the significance of waves on the plasmatic state and especially their negative impact on the thermonuclear fusion, but also due to the long-time experience of the plasma laboratory of Demokritos on drift waves.« less

A Van der Waals-like theory of plasma double layers

NASA Technical Reports Server (NTRS)

Katz, Ira; Davis, V. A.

1989-01-01

A theory describing plasma double layers in terms of multiple roots of the charge density expression is presented. The theory presented uses the fact that equilibrium plasmas shield small potential perturbations linearly; for high potentials, the shielding decreases. The approach is analogous to Van der Waals' theory of simple fluids in which inclusion of approximate expressions for both excluded volume and long range attractive forces sufficiently describes the first-order liquid-gas phase transition.

On a theory of surface waves in a smoothly inhomogeneous plasma in an external magnetic field

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

Kuzelev, M. V., E-mail: kuzelev@mail.ru; Orlikovskaya, N. G.

2016-12-15

A theory of surface waves in a magnetoactive plasma with smooth boundaries has been developed. A dispersion equation for surface waves has been derived for a linear law of density change at the plasma boundary. The frequencies of surface waves and their collisionless damping rates have been determined. A generalization to an arbitrary density profile at the plasma boundary is given. The collisions have been taken into account, and the application of the Landau rule in the theory of surface wave damping in a spatially inhomogeneous magnetoactive collisional plasma has been clarified.

Constructing Knowledge via a Peer Interaction in a CAS Environment with Tasks Designed from a Task-Technique-Theory Perspective

ERIC Educational Resources Information Center

Hitt, Fernando; Kieran, Carolyn

2009-01-01

Our research project aimed at understanding the complexity of the construction of knowledge in a CAS environment. Basing our work on the French instrumental approach, in particular the Task-Technique-Theory (T-T-T) theoretical frame as adapted from Chevallard's Anthropological Theory of Didactics, we were mindful that a careful task design process…

Charging of nonspherical macroparticles in a plasma

NASA Astrophysics Data System (ADS)

Holgate, J. T.; Coppins, M.

2016-03-01

The current theories of macroparticle charging in a plasma are limited to spheres, and are unsuitable for the multitude of nonspherical objects existing in astrophysical, atmospheric, laboratory, and fusion plasmas. This paper extends the most widely used spherical charging theory, orbit motion limited theory, to spheroids and, as such, provides a comprehensive study of the charging of nonspherical objects in a plasma. The spherical charging theory is shown to be a reasonable approximation for a considerable range of spheroids. However, the electric potential of highly elongated spheroids can be almost twice the spherical value. Furthermore, the total charge on the spheroids increases by a significantly larger factor than their potential.

Gender, Legitimation, and Identity Verification in Groups

ERIC Educational Resources Information Center

Burke, Peter J.; Stets, Jan E.; Cerven, Christine

2007-01-01

Drawing upon identity theory, expectation states theory, and legitimation theory, we examine how the task leader identity in task-oriented groups is more likely to be verified for persons with high status characteristics. We hypothesize that identity verification will be accomplished more readily for male group members and legitimated task leaders…

Interference between a fast-paced spatial puzzle task and verbal memory demands.

PubMed

Epling, Samantha L; Blakely, Megan J; Russell, Paul N; Helton, William S

2017-06-01

Research continues to provide evidence that people are poor multi-taskers. Cognitive resource theory is a common explanation for the inability to efficiently perform multiple tasks at the same time. This theory proposes that one's limited supply of cognitive resources can be utilized faster than it is replenished, which results in a performance decline, particularly when these limited resources must be allocated among multiple tasks. Researchers have proposed both domain-specific, for example, spatial versus verbal processing resources, and domain general cognitive resources. In the present research, we investigated whether a spatial puzzle task performed simultaneously with a verbal recall task would impair performance in either task or both tasks, compared to performance on the tasks individually. As hypothesized, a reduction in word recall was found when dual-tasking, though performance on the puzzle task did not significantly differ between the single- and dual-task conditions. This is consistent, in part, with both a general resource theory and a Multiple Resource Theory, but further work is required to better understand the cognitive processing system. The employment of the recall task in the dual-task paradigm with a variety of secondary tasks will help to continue mapping out the specificity (or lack thereof) of cognitive resources utilized in various mental and physical tasks.

The role of perceptual load in inattentional blindness.

PubMed

Cartwright-Finch, Ula; Lavie, Nilli

2007-03-01

Perceptual load theory offers a resolution to the long-standing early vs. late selection debate over whether task-irrelevant stimuli are perceived, suggesting that irrelevant perception depends upon the perceptual load of task-relevant processing. However, previous evidence for this theory has relied on RTs and neuroimaging. Here we tested the effects of load on conscious perception using the "inattentional blindness" paradigm. As predicted by load theory, awareness of a task-irrelevant stimulus was significantly reduced by higher perceptual load (with increased numbers of search items, or a harder discrimination vs. detection task). These results demonstrate that conscious perception of task-irrelevant stimuli critically depends upon the level of task-relevant perceptual load rather than intentions or expectations, thus enhancing the resolution to the early vs. late selection debate offered by the perceptual load theory.

Hemispheric asymmetry and theory of mind: is there an association?

PubMed

Herzig, Daniela A; Sullivan, Sarah; Evans, Jonathan; Corcoran, Rhiannon; Mohr, Christine

2012-01-01

In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations. Healthy participants (n=129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance. Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only). The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of "overinterpreting" the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

Tsallis non-extensive statistics and solar wind plasma complexity

NASA Astrophysics Data System (ADS)

Pavlos, G. P.; Iliopoulos, A. C.; Zastenker, G. N.; Zelenyi, L. M.; Karakatsanis, L. P.; Riazantseva, M. O.; Xenakis, M. N.; Pavlos, E. G.

2015-03-01

This article presents novel results revealing non-equilibrium phase transition processes in the solar wind plasma during a strong shock event, which took place on 26th September 2011. Solar wind plasma is a typical case of stochastic spatiotemporal distribution of physical state variables such as force fields (B → , E →) and matter fields (particle and current densities or bulk plasma distributions). This study shows clearly the non-extensive and non-Gaussian character of the solar wind plasma and the existence of multi-scale strong correlations from the microscopic to the macroscopic level. It also underlines the inefficiency of classical magneto-hydro-dynamic (MHD) or plasma statistical theories, based on the classical central limit theorem (CLT), to explain the complexity of the solar wind dynamics, since these theories include smooth and differentiable spatial-temporal functions (MHD theory) or Gaussian statistics (Boltzmann-Maxwell statistical mechanics). On the contrary, the results of this study indicate the presence of non-Gaussian non-extensive statistics with heavy tails probability distribution functions, which are related to the q-extension of CLT. Finally, the results of this study can be understood in the framework of modern theoretical concepts such as non-extensive statistical mechanics (Tsallis, 2009), fractal topology (Zelenyi and Milovanov, 2004), turbulence theory (Frisch, 1996), strange dynamics (Zaslavsky, 2002), percolation theory (Milovanov, 1997), anomalous diffusion theory and anomalous transport theory (Milovanov, 2001), fractional dynamics (Tarasov, 2013) and non-equilibrium phase transition theory (Chang, 1992).

The director task: A test of Theory-of-Mind use or selective attention?

PubMed

Rubio-Fernández, Paula

2017-08-01

Over two decades, the director task has increasingly been employed as a test of the use of Theory of Mind in communication, first in psycholinguistics and more recently in social cognition research. A new version of this task was designed to test two independent hypotheses. First, optimal performance in the director task, as established by the standard metrics of interference, is possible by using selective attention alone, and not necessarily Theory of Mind. Second, pragmatic measures of Theory-of-Mind use can reveal that people actively represent the director's mental states, contrary to recent claims that they only use domain-general cognitive processes to perform this task. The results of this study support both hypotheses and provide a new interactive paradigm to reliably test Theory-of-Mind use in referential communication.

Performance of children and adolescents with Asperger syndrome or high-functioning autism on advanced theory of mind tasks.

PubMed

Kaland, Nils; Callesen, Kirsten; Møller-Nielsen, Annette; Mortensen, Erik Lykke; Smith, Lars

2008-07-01

Although a number of advanced theory of mind tasks have been developed, there is a dearth of information on whether performances on different tasks are associated. The present study examined the performance of 21 children and adolescents with diagnoses of Asperger syndrome (AS) and 20 typically developing controls on three advanced theory of mind tasks: The Eyes Task, the Strange Stories, and the Stories from Everyday Life. The participants in the clinical group demonstrated lower performance than the controls on all the three tasks. The pattern of findings, however, indicates that these tasks may share different information-processing requirements in addition to tapping different mentalizing abilities.

Hollow cathodes as electron emitting plasma contactors Theory and computer modeling

NASA Technical Reports Server (NTRS)

Davis, V. A.; Katz, I.; Mandell, M. J.; Parks, D. E.

1987-01-01

Several researchers have suggested using hollow cathodes as plasma contactors for electrodynamic tethers, particularly to prevent the Shuttle Orbiter from charging to large negative potentials. Previous studies have shown that fluid models with anomalous scattering can describe the electron transport in hollow cathode generated plasmas. An improved theory of the hollow cathode plasmas is developed and computational results using the theory are compared with laboratory experiments. Numerical predictions for a hollow cathode plasma source of the type considered for use on the Shuttle are presented, as are three-dimensional NASCAP/LEO calculations of the emitted ion trajectories and the resulting potentials in the vicinity of the Orbiter. The computer calculations show that the hollow cathode plasma source makes vastly superior contact with the ionospheric plasma compared with either an electron gun or passive ion collection by the Orbiter.

Viscous plasma evolution from gravity using anti-de sitter/conformal-field-theory correspondence.

PubMed

Janik, Romuald A

2007-01-12

We analyze the anti-de Sitter/conformal-field-theory dual geometry of an expanding boost-invariant plasma. We show that the requirement of nonsingularity of the dual geometry for leading and subasymptotic times predicts, without any further assumptions about gauge theory dynamics, hydrodynamic expansion of the plasma with viscosity coefficient exactly matching the one obtained earlier in the static case by Policastro, Son, and Starinets.

CLASS Challenging Tasks: Using Cognitive Load Theory to Inform the Design of Challenging Mathematical Tasks

ERIC Educational Resources Information Center

Russo, James; Hopkins, Sarah

2017-01-01

This paper outlines a seven-step process for developing problem-solving tasks informed by cognitive load theory. Through an example of a task developed for Year 2 students, we show how this approach can be used to produce challenging mathematical tasks that aim to optimise cognitive load for each student.

JOURNAL SCOPE GUIDELINES: Paper classification scheme

NASA Astrophysics Data System (ADS)

2005-06-01

This scheme is used to clarify the journal's scope and enable authors and readers to more easily locate the appropriate section for their work. For each of the sections listed in the scope statement we suggest some more detailed subject areas which help define that subject area. These lists are by no means exhaustive and are intended only as a guide to the type of papers we envisage appearing in each section. We acknowledge that no classification scheme can be perfect and that there are some papers which might be placed in more than one section. We are happy to provide further advice on paper classification to authors upon request (please email jphysa@iop.org). 1. Statistical physics numerical and computational methods statistical mechanics, phase transitions and critical phenomena quantum condensed matter theory Bose-Einstein condensation strongly correlated electron systems exactly solvable models in statistical mechanics lattice models, random walks and combinatorics field-theoretical models in statistical mechanics disordered systems, spin glasses and neural networks nonequilibrium systems network theory 2. Chaotic and complex systems nonlinear dynamics and classical chaos fractals and multifractals quantum chaos classical and quantum transport cellular automata granular systems and self-organization pattern formation biophysical models 3. Mathematical physics combinatorics algebraic structures and number theory matrix theory classical and quantum groups, symmetry and representation theory Lie algebras, special functions and orthogonal polynomials ordinary and partial differential equations difference and functional equations integrable systems soliton theory functional analysis and operator theory inverse problems geometry, differential geometry and topology numerical approximation and analysis geometric integration computational methods 4. Quantum mechanics and quantum information theory coherent states eigenvalue problems supersymmetric quantum mechanics scattering theory relativistic quantum mechanics semiclassical approximations foundations of quantum mechanics and measurement theory entanglement and quantum nonlocality geometric phases and quantum tomography quantum tunnelling decoherence and open systems quantum cryptography, communication and computation theoretical quantum optics 5. Classical and quantum field theory quantum field theory gauge and conformal field theory quantum electrodynamics and quantum chromodynamics Casimir effect integrable field theory random matrix theory applications in field theory string theory and its developments classical field theory and electromagnetism metamaterials 6. Fluid and plasma theory turbulence fundamental plasma physics kinetic theory magnetohydrodynamics and multifluid descriptions strongly coupled plasmas one-component plasmas non-neutral plasmas astrophysical and dusty plasmas

The Neutralization of Ion-Rocket Beams

NASA Technical Reports Server (NTRS)

Kaufman, Harold R.

1961-01-01

The experimental ion-beam behavior obtained without neutralizers is compared with both simple collision theory and plasma-wave theory. This comparison indicates that plasma waves play an important part in beam behavior, although the present state of plasma-wave theory does not permit more than a qualitative comparison. The theories of immersed-emitter and electron-trap neutralizer operation are discussed; and, to the extent permitted by experimental data, the theory is compared with experimental results. Experimental data are lacking completely at the present time for operation in space. The results that might be expected in space and the means of simulating such operation in Earth-bound facilities, however, are discussed.

Different Ways to Cue a Coherent Memory System: A Theory for Episodic, Semantic, and Procedural Tasks.

ERIC Educational Resources Information Center

Humphreys, Michael S.; And Others

1989-01-01

An associative theory of memory is proposed to serve as a counterexample to claims that dissociations among episodic, semantic, and procedural memory tasks necessitate separate memory systems. The theory is based on task analyses of matching (recognition and familiarity judgments), retrieval (cued recall), and production (free association). (TJH)

Children's understanding of idioms and theory of mind development.

PubMed

Caillies, Stéphanie; Le Sourn-Bissaoui, Sandrine

2008-09-01

The aim of this study was to test the hypothesis according to which theory of mind competence was a prerequisite to ambiguous idioms understanding. We hypothesized that the child needs to understand that the literal interpretation could be a false world representation, a false belief, and that the speaker's intention is to mean something else, to correctly process idiomatic expressions. Two kinds of ambiguous idioms were of interest: decomposable and nondecomposable expressions (Titone & Connine, 1999). An experiment was designed to assess the figurative developmental changes that occur with theory of mind competence. Five-, 6- and 7-year-old children performed five theory of mind tasks (an appearance-reality task, three false-belief tasks and a second-order false-belief task) and listened to decomposable and nondecomposable idiomatic expressions inserted in context, before performing a multiple choice task. Results indicated that only nondecomposable idiomatic expression was predicted from the theory of mind scores, and particularly from the second-order competences. Results are discussed with respect to theory of mind and verbal competences.

Study on longitudinal dispersion relation in one-dimensional relativistic plasma: Linear theory and Vlasov simulation

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

Zhang, H.; Wu, S. Z.; Zhou, C. T.

2013-09-15

The dispersion relation of one-dimensional longitudinal plasma waves in relativistic homogeneous plasmas is investigated with both linear theory and Vlasov simulation in this paper. From the Vlasov-Poisson equations, the linear dispersion relation is derived for the proper one-dimensional Jüttner distribution. Numerically obtained linear dispersion relation as well as an approximate formula for plasma wave frequency in the long wavelength limit is given. The dispersion of longitudinal wave is also simulated with a relativistic Vlasov code. The real and imaginary parts of dispersion relation are well studied by varying wave number and plasma temperature. Simulation results are in agreement with establishedmore » linear theory.« less

Theory of mind in Alzheimer disease: Evidence of authentic impairment during social interaction.

PubMed

Moreau, Noémie; Rauzy, Stéphane; Viallet, François; Champagne-Lavau, Maud

2016-03-01

The present study aimed to investigate theory of mind (the ability to infer others' mental states) deficit in 20 patients with mild Alzheimer's disease and 20 healthy controls, with 2 theory of mind tasks, 1 of them being a real interactive task. Previous results concerning preserved or altered theory of mind abilities in Alzheimer's disease have been inconsistent and relationships with other cognitive dysfunctions (notably episodic memory and executive functions) are still unclear. The first task we used was a false belief paradigm as frequently used in literature whereas the second task, a referential communication task, assessed theory of mind in a real situation of interaction. Participants also underwent neuropsychological evaluation to investigate potential relationships between theory of mind and memory deficits. The results showed that Alzheimer patients presented a genuine and significant theory of mind deficit compared to control participants characterized notably by difficulties to attribute knowledge to an interlocutor in a real social interaction. These results further confirm that theory of mind is altered in early stages of Alzheimer dementia which is consistent with previous works. More specifically, this study is the first to objectivize this impairment in social interaction. (c) 2016 APA, all rights reserved).

Issues in Turbulence Simulation for Experimental Comparison

NASA Astrophysics Data System (ADS)

Ross, D. W.; Bravenec, R. V.; Dorland, W.; Beer, M. A.; Hammett, G. W.

1999-11-01

Studies of the sensitivity of fluctuation spectra and transport fluxes to local plasma parameters and gradients(D. W. Ross et al.), Bull. Am. Phys. Soc. 43, 1760 (1998); D. W. Ross et al., Transport Task Force Workshop, Portland, Oregon, (1999). are continued using nonlinear gyrofluid simulation(M. A. Beer et al.), Phys. Plasmas 2, 2687 (1995). on the T3E at NERSC. Parameters that are characteristic of discharges in DIII-D and Alcator C-Mod are employed. In the previous work, the gradients of Z_eff, n_e, and Te were varied within the experimental uncertainty. Amplitudes and fluxes are quite sensitive to dZ_eff/dr. Here, these studies are continued and extended to variation of other parameters, including T_e/T_i, and dT_i/dr, which are important for ion temperature gradient modes. The role of electric field shear is discussed. Implications for comparison with experiment, including transient perturbations, are discussed, with the goal of quantifying the accuracy of profile data needed to verify the turbulence theory.

Linear tearing mode stability equations for a low collisionality toroidal plasma

NASA Astrophysics Data System (ADS)

Connor, J. W.; Hastie, R. J.; Helander, P.

2009-01-01

Tearing mode stability is normally analysed using MHD or two-fluid Braginskii plasma models. However for present, or future, large hot tokamaks like JET or ITER the collisionality is such as to place them in the banana regime. Here we develop a linear stability theory for the resonant layer physics appropriate to such a regime. The outcome is a set of 'fluid' equations whose coefficients encapsulate all neoclassical physics: the neoclassical Ohm's law, enhanced ion inertia, cross-field transport of particles, heat and momentum all play a role. While earlier treatments have also addressed this type of neoclassical physics we differ in incorporating the more physically relevant 'semi-collisional fluid' regime previously considered in cylindrical geometry; semi-collisional effects tend to screen the resonant surface from the perturbed magnetic field, preventing reconnection. Furthermore we also include thermal physics, which may modify the results. While this electron description is of wide relevance and validity, the fluid treatment of the ions requires the ion banana orbit width to be less than the semi-collisional electron layer. This limits the application of the present theory to low magnetic shear—however, this is highly relevant to the sawtooth instability—or to colder ions. The outcome of the calculation is a set of one-dimensional radial differential equations of rather high order. However, various simplifications that reduce the computational task of solving these are discussed. In the collisional regime, when the set reduces to a single second-order differential equation, the theory extends previous work by Hahm et al (1988 Phys. Fluids 31 3709) to include diamagnetic-type effects arising from plasma gradients, both in Ohm's law and the ion inertia term of the vorticity equation. The more relevant semi-collisional regime pertaining to JET or ITER, is described by a pair of second-order differential equations, extending the cylindrical equations of Drake et al (1983 Phys. Fluids 26 2509) to toroidal geometry.

U.C. Davis high energy particle physics research: Technical progress report -- 1990

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

NONE

Summaries of progress made for this period is given for each of the following areas: (1) Task A--Experiment, H1 detector at DESY; (2) Task C--Experiment, AMY detector at KEK; (3) Task D--Experiment, fixed target detectors at Fermilab; (4) Task F--Experiment, PEP detector at SLAC and pixel detector; (5) Task B--Theory, particle physics; and (6) Task E--Theory, particle physics.

Theory of relativistic radiation reflection from plasmas

NASA Astrophysics Data System (ADS)

Gonoskov, Arkady

2018-01-01

We consider the reflection of relativistically strong radiation from plasma and identify the physical origin of the electrons' tendency to form a thin sheet, which maintains its localisation throughout its motion. Thereby, we justify the principle of relativistic electronic spring (RES) proposed in [Gonoskov et al., Phys. Rev. E 84, 046403 (2011)]. Using the RES principle, we derive a closed set of differential equations that describe the reflection of radiation with arbitrary variation of polarization and intensity from plasma with an arbitrary density profile for an arbitrary angle of incidence. We confirm with ab initio PIC simulations that the developed theory accurately describes laser-plasma interactions in the regime where the reflection of relativistically strong radiation is accompanied by significant, repeated relocation of plasma electrons. In particular, the theory can be applied for the studies of plasma heating and coherent and incoherent emissions in the RES regime of high-intensity laser-plasma interaction.

Trapped nonneutral plasmas, liquids, and crystals (the thermal equilibrium states)

NASA Astrophysics Data System (ADS)

Dubin, Daniel H.; O'neil, T. M.

1999-01-01

Plasmas consisting exclusively of particles with a single sign of charge (e.g., pure electron plasmas and pure ion plasmas) can be confined by static electric and magnetic fields (in a Penning trap) and also be in a state of global thermal equilibrium. This important property distinguishes these totally unneutralized plasmas from neutral and quasineutral plasmas. This paper reviews the conditions for, and the structure of, the thermal equilibrium states. Both theory and experiment are discussed, but the emphasis is decidedly on theory. It is a huge advantage to be able to use thermal equilibrium statistical mechanics to describe the plasma state. Such a description is easily obtained and complete, including for example the details of the plasma shape and microscopic order. Pure electron and pure ion plasmas are routinely confined for hours and even days, and thermal equilibrium states are observed. These plasmas can be cooled to the cryogenic temperature range, where liquid and crystal-like states are realized. The authors discuss the structure of the correlated states separately for three plasma sizes: large plasmas, in which the free energy is dominated by the bulk plasma; mesoscale plasmas, in which the free energy is strongly influenced by the surface; and Coulomb clusters, in which the number of particles is so small that the canonical ensemble is not a good approximation for the microcanonical ensemble. All three cases have been studied through numerical simulations, analytic theory, and experiment. In addition to describing the structure of the thermal equilibrium states, the authors develop a thermodynamic theory of the trapped plasma system. Thermodynamic inequalities and Maxwell relations provide useful bounds on and general relationships between partial derivatives of the various thermodynamic variables.

Electromagnetic fluctuations in magnetized plasmas. I. The rigorous relativistic kinetic theory

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

Schlickeiser, R., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu; Yoon, P. H., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu; School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701

2015-07-15

Using the system of the Klimontovich and Maxwell equations, the general linear fluctuation theory for magnetized plasmas is developed. General expressions for the electromagnetic fluctuation spectra (electric and magnetic fields) from uncorrelated plasma particles in plasmas with a uniform magnetic field are derived, which are covariantly correct within the theory of special relativity. The general fluctuation spectra hold for plasmas of arbitrary composition, arbitrary momentum dependences of the plasma particle distribution functions, and arbitrary orientations of the wave vector with respect to the uniform magnetic field. Moreover, no restrictions on the values of the real and the imaginary parts ofmore » the frequency are made. The derived fluctuation spectra apply to both non-collective fluctuations and collective plasma eigenmodes in magnetized plasmas. In the latter case, kinetic equations for the components of fluctuating electric and magnetic fields in magnetized plasmas are derived that include the effect of spontaneous emission and absorption. In the limiting case of an unmagnetized plasmas, the general fluctuation spectra correctly reduce to the unmagnetized fluctuation spectra derived before.« less

Theory of Mind and Central Coherence in Adults with High-Functioning Autism or Asperger Syndrome

ERIC Educational Resources Information Center

Beaumont, Renae; Newcombe, Peter

2006-01-01

The study investigated theory of mind and central coherence abilities in adults with high-functioning autism (HFA) or Asperger syndrome (AS) using naturalistic tasks. Twenty adults with HFA/AS correctly answered significantly fewer theory of mind questions than 20 controls on a forced-choice response task. On a narrative task, there were no…

Measuring theory of mind across middle childhood: Reliability and validity of the Silent Films and Strange Stories tasks.

PubMed

Devine, Rory T; Hughes, Claire

2016-09-01

Recent years have seen a growth of research on the development of children's ability to reason about others' mental states (or "theory of mind") beyond the narrow confines of the preschool period. The overall aim of this study was to investigate the psychometric properties of a task battery composed of items from Happé's Strange Stories task and Devine and Hughes' Silent Film task. A sample of 460 ethnically and socially diverse children (211 boys) between 7 and 13years of age completed the task battery at two time points separated by 1month. The Strange Stories and Silent Film tasks were strongly correlated even when verbal ability and narrative comprehension were taken into account, and all items loaded onto a single theory-of-mind latent factor. The theory-of-mind latent factor provided reliable estimates of performance across a wide range of theory-of-mind ability and showed no evidence of differential item functioning across gender, ethnicity, or socioeconomic status. The theory-of-mind latent factor also exhibited strong 1-month test-retest reliability, and this stability did not vary as a function of child characteristics. Taken together, these findings provide evidence for the validity and reliability of the Strange Stories and Silent Film task battery as a measure of individual differences in theory of mind suitable for use across middle childhood. We consider the methodological and conceptual implications of these findings for research on theory of mind beyond the preschool years. Copyright © 2015 Elsevier Inc. All rights reserved.

A theoretical and experimental investigation of cylindrical electrostatic probes at arbitrary incidence in flowing plasma

NASA Technical Reports Server (NTRS)

Jenkins, R. V.; Jones, W. L., Jr.

1974-01-01

The theory for calculating the current collected by a negatively biased cylindrical electrostatic probe at an arbitrary angle of attack in a weakley ionized flowing plasma is presented. The theory was constructed by considering both random and directed motion simultaneous with dynamic coupling of the flow properties and of the electric field of the probe. This direct approach yielded a theory that is more general than static plasma theories modified to account for flow. Theoretical calculations are compared with experimental electrostatic probe data obtained in the free stream of an arc-heated hypersonic wind tunnel. The theoretical calculations are based on flow conditions and plasma electron densities measured by an independent microwave interferometer technique. In addition, the theory is compared with laboratory and satellite data previously published by other investigators. In each case the comparison gives good agreement.

Performance of children with autism spectrum disorder on advanced theory of mind tasks.

PubMed

Brent, Ella; Rios, Patricia; Happé, Francesca; Charman, Tony

2004-09-01

Although a number of advanced theory of mind tasks have been developed, there is sparse information on whether performance on different tasks is associated. The study examined the performance of 20 high-functioning 6- to 12-year-old children with autism spectrum disorder and 20 controls on three high-level theory of mind tasks: Strange Stories, Cartoons and the children's version of the Eyes task. The pattern of findings suggests that the three tasks may share differing, non-specific, information-processing requirements in addition to tapping any putative mentalizing ability. They may also indicate a degree of dissociation between social-cognitive and social-perceptual or affective components of the mentalizing system.

Perceptual load in sport and the heuristic value of the perceptual load paradigm in examining expertise-related perceptual-cognitive adaptations.

PubMed

Furley, Philip; Memmert, Daniel; Schmid, Simone

2013-03-01

In two experiments, we transferred perceptual load theory to the dynamic field of team sports and tested the predictions derived from the theory using a novel task and stimuli. We tested a group of college students (N = 33) and a group of expert team sport players (N = 32) on a general perceptual load task and a complex, soccer-specific perceptual load task in order to extend the understanding of the applicability of perceptual load theory and further investigate whether distractor interference may differ between the groups, as the sport-specific processing task may not exhaust the processing capacity of the expert participants. In both, the general and the specific task, the pattern of results supported perceptual load theory and demonstrates that the predictions of the theory also transfer to more complex, unstructured situations. Further, perceptual load was the only determinant of distractor processing, as we neither found expertise effects in the general perceptual load task nor the sport-specific task. We discuss the heuristic utility of using response-competition paradigms for studying both general and domain-specific perceptual-cognitive adaptations.

A general theory for ball lightning structure and light output

NASA Astrophysics Data System (ADS)

Morrow, R.

2018-03-01

A general theory for free-floating ball lightning is presented which unifies the phantom plasma ball theory involving the production of very little light, with theories for ball lightning involving light output produced by burning particles from the soil. The mechanism for the formation of plasma balls is shown to be quite general, producing very similar plasma balls independent of initial ion densities over four orders of magnitude. All that is required is an excess of positive ions in the initial ball of ions. The central plasma density after 1 s is shown to be the reciprocal of the ion neutralization coefficient for all cases, both analytically and computationally. Further, the plasma region has zero electric field in all cases. Surrounding the plasma ball is a sphere of positive ions moving away from the centre via their own space-charge field; this space-charge field, which is the same in all cases near the plasma ball, drives negative ions and negative particles towards the plasma centre. The connection with burning particle theories is the proposition that the burning particles are highly-charged which is very likely after a lightning strike. Burning negatively charged particles would be driven into the plasma ball region and trapped while any positively charged particles would be driven away. The plasma ball structure is shown to last more than 10 s and the ‘burnout time’ for a typical coal particle (as an example) has been measured at 5-10 s this is comparable with the lifetimes observed for ball lightning. The light output from a few hundred particles is estimated to be ~1 W, a typical output for ball lightning. Finally, suggestions are made for the generation of ball lightning in the laboratory.

Theory of Mind in Williams Syndrome Assessed Using a Nonverbal Task

ERIC Educational Resources Information Center

Porter, Melanie A.; Coltheart, Max; Langdon, Robyn

2008-01-01

This study examined Theory of Mind in Williams syndrome (WS) and in normal chronological age-matched and mental age-matched control groups, using a picture sequencing task. This task assesses understanding of pretence, intention and false belief, while controlling for social-script knowledge and physical cause-and-effect reasoning. The task was…

An eye movement analysis of the effect of interruption modality on primary task resumption.

PubMed

Ratwani, Raj; Trafton, J Gregory

2010-06-01

We examined the effect of interruption modality (visual or auditory) on primary task (visual) resumption to determine which modality was the least disruptive. Theories examining interruption modality have focused on specific periods of the interruption timeline. Preemption theory has focused on the switch from the primary task to the interrupting task. Multiple resource theory has focused on interrupting tasks that are to be performed concurrently with the primary task. Our focus was on examining how interruption modality influences task resumption.We leverage the memory-for-goals theory, which suggests that maintaining an associative link between environmental cues and the suspended primary task goal is important for resumption. Three interruption modality conditions were examined: auditory interruption with the primary task visible, auditory interruption with a blank screen occluding the primary task, and a visual interruption occluding the primary task. Reaction time and eye movement data were collected. The auditory condition with the primary task visible was the least disruptive. Eye movement data suggest that participants in this condition were actively maintaining an associative link between relevant environmental cues on the primary task interface and the suspended primary task goal during the interruption. These data suggest that maintaining cue association is the important factor for reducing the disruptiveness of interruptions, not interruption modality. Interruption-prone computing environments should be designed to allow for the user to have access to relevant primary task cues during an interruption to minimize disruptiveness.

Fundamentals of Plasma Physics

NASA Astrophysics Data System (ADS)

Bellan, Paul M.

2008-07-01

Preface; 1. Basic concepts; 2. The Vlasov, two-fluid, and MHD models of plasma dynamics; 3. Motion of a single plasma particle; 4. Elementary plasma waves; 5. Streaming instabilities and the Landau problem; 6. Cold plasma waves in a magnetized plasma; 7. Waves in inhomogeneous plasmas and wave energy relations; 8. Vlasov theory of warm electrostatic waves in a magnetized plasma; 9. MHD equilibria; 10. Stability of static MHD equilibria; 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation; 12. Magnetic reconnection; 13. Fokker-Planck theory of collisions; 14. Wave-particle nonlinearities; 15. Wave-wave nonlinearities; 16. Non-neutral plasmas; 17. Dusty plasmas; Appendix A. Intuitive method for vector calculus identities; Appendix B. Vector calculus in orthogonal curvilinear coordinates; Appendix C. Frequently used physical constants and formulae; Bibliography; References; Index.

Performance of Children and Adolescents with Asperger Syndrome or High-Functioning Autism on Advanced Theory of Mind Tasks

ERIC Educational Resources Information Center

Kaland, Nils; Callesen, Kirsten; Moller-Nielsen, Annette; Mortensen, Erik Lykke; Smith, Lars

2008-01-01

Although a number of advanced theory of mind tasks have been developed, there is a dearth of information on whether performances on different tasks are associated. The present study examined the performance of 21 children and adolescents with diagnoses of Asperger syndrome (AS) and 20 typically developing controls on three advanced theory of mind…

Genetic contribution to 'theory of mind' in adolescence.

PubMed

Warrier, Varun; Baron-Cohen, Simon

2018-02-22

Difficulties in 'theory of mind' (the ability to attribute mental states to oneself or others, and to make predictions about another's behaviour based on these attributions) have been observed in several psychiatric conditions. We investigate the genetic architecture of theory of mind in 4,577 13-year-olds who completed the Emotional Triangles Task (Triangles Task), a first-order test of theory of mind. We observe a small but significant female-advantage on the Triangles Task (Cohen's d = 0.19, P < 0.01), in keeping with previous work using other tests of theory of mind. Genome-wide association analyses did not identify any significant loci, and SNP heritability was non-significant. Polygenic scores for six psychiatric conditions (ADHD, anorexia, autism, bipolar disorder, depression, and schizophrenia), and empathy were not associated with scores on the Triangles Task. However, polygenic scores of cognitive aptitude, and cognitive empathy, a term synonymous with theory of mind and measured using the "Reading the Mind in the Eyes" Test, were significantly associated with scores on the Triangles Task at multiple P-value thresholds, suggesting shared genetics between different measures of theory of mind and cognition.

Task and socioemotional behaviors of physicians: a test of reciprocity and social interaction theories in analogue physician-patient encounters.

PubMed

Roberts, C A; Aruguete, M S

2000-02-01

The purpose of the present study is to assess social interaction and reciprocity theories as explanations for patient responses to a physician in a medical consultation. Social interaction theory predicts that patients mostly recognize and react to socioemotional behavior of their physicians due to a lack of understanding of physician task behaviors or a preoccupation with anxiety. Reciprocity theory predicts that patients recognize socioemotional and task behaviors of their physicians, and they respond to these behaviors in thematically similar ways. We examined these hypotheses by having subjects view one of four videotapes which varied in physician task behavior (thorough or minimum levels of explanation of etiology, symptoms, and treatment) and physician socioemotional behavior (high or low levels of concern and affection displayed verbally and non-verbally). Results supported the general proposition of social interaction theory in that high levels of socioemotional behavior of the physician increased measures of patient self-disclosure, trust, satisfaction, and likelihood of recommending the physician. Physician task behavior had no effect on patient response to the physician, a finding inconsistent with reciprocity theory.

Different Patterns of Theory of Mind Impairment in Mild Cognitive Impairment.

PubMed

Moreau, Noémie; Rauzy, Stéphane; Bonnefoi, Bernadette; Renié, Laurent; Martinez-Almoyna, Laurent; Viallet, François; Champagne-Lavau, Maud

2015-01-01

Theory of Mind refers to the ability to infer other’s mental states, their beliefs, intentions, or knowledge. To date, only two studies have reported the presence of Theory of Mind impairment in mild cognitive impairment (MCI). In the present study,we evaluated 20 MCI patients and compared them with 25 healthy control participants using two Theory of Mind tasks. The first task was a false belief paradigm as frequently used in the literature, and the second one was a referential communication task,assessing Theory of Mind in a real situation of interaction and which had never been used before in this population. The results showed that MCI patients presented difficulties inferring another person’s beliefs about reality and attributing knowledge to them in a situation of real-life interaction. Two different patterns of Theory of Mind emerged among the patients. In comparison with the control group, some MCI patients demonstrated impairment only in the interaction task and presented isolated episodicmemory impairment, while others were impaired in both Theory of Mind tasks and presented cognitive impairment impacting both episodic memory and executive functioning. Theory of Mind is thus altered in the very early stages of cognitive impairment even in real social interaction, which could impact precociously relationships in daily life.

Book review: Modern Plasma Physics, Vol. I: Physical Kinetics of Turbulent Plasmas, by Patrick H. Diamond, Sanae-I. Itoh and Kimitaka Itoh, Cambridge University Press, Cambridge (UK), 2010, IX, 417 p., ISBN 978-0-521-86920-1 (Hardback)

NASA Astrophysics Data System (ADS)

Somov, B. V.

If you want to learn not only the most fundamental things about the physics of turbulent plasmas but also the current state of the problem including the most recent results in theoretical and experimental investigations - and certainly many physicists and astrophysicists do - this series of three excellent monographs is just for you. The first volume "Physical Kinetics of Turbulent Plasmas" develops the kinetic theory of turbulence through a focus on quasi-particle models and dynamics. It discusses the concepts and theoretical methods for describing weak and strong fluid and phase space turbulence in plasma systems far from equilibrium. The core material includes fluctuation theory, self-similar cascades and transport, mean field theory, resonance broadening and nonlinear wave-particle interaction, wave-wave interaction and wave turbulence, strong turbulence theory and renormalization. The book gives readers a deep understanding of the fields under consideration and builds a foundation for future applications to multi-scale processes of self-organization in tokamaks and other confined plasmas. In spite of a short pedagogical introduction, the book is addressed mainly to well prepared readers with a serious background in plasma physics, to researchers and advanced graduate students in nonlinear plasma physics, controlled fusions and related fields such as cosmic plasma physics

Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

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

Purohit, Gunjan, E-mail: gunjan75@gmail.com; Rawat, Priyanka; Chauhan, Prashant

This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled lasermore » beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate.« less

Domain-General Contributions to Social Reasoning: Theory of Mind and Deontic Reasoning Re-Explored

ERIC Educational Resources Information Center

McKinnon, Margaret C.; Moscovitch, Morris

2007-01-01

Using older adults and dual-task interference, we examined performance on two social reasoning tasks: theory of mind (ToM) tasks and versions of the deontic selection task involving social contracts and hazardous conditions. In line with performance accounts of social reasoning (Leslie, Friedman, & German, 2004), evidence from both aging and the…

Processing deficits in monitoring analog and digital displays: Implications for attentional theory and mental-state estimation research

NASA Technical Reports Server (NTRS)

Payne, David G.; Gunther, Virginia A. L.

1988-01-01

Subjects performed short term memory tasks, involving both spatial and verbal components, and a visual monitoring task involving either analog or digital display formats. These two tasks (memory vs. monitoring) were performed both singly and in conjunction. Contrary to expectations derived from multiple resource theories of attentional processes, there was no evidence that when the two tasks involved the same cognitive codes (i.e., either both spatial or both verbal/linguistics) there was more of a dual task performance decrement than when the two tasks employed different cognitive codes/processes. These results are discussed in terms of their implications for theories of attentional processes and also for research in mental state estimation.

Mode conversion in cold low-density plasma with a sheared magnetic field

DOE PAGES

Dodin, I. Y.; Ruiz, D. E.; Kubo, S.

2017-12-19

Here, a theory is proposed that describes mutual conversion of two electromagnetic modes in cold low-density plasma, specifically, in the high-frequency limit where the ion response is negligible. In contrast to the classic (Landau–Zener-type) theory of mode conversion, the region of resonant coupling in low-density plasma is not necessarily narrow, so the coupling matrix cannot be approximated with its first-order Taylor expansion; also, the initial conditions are set up differently. For the case of strong magnetic shear, a simple method is identified for preparing a two-mode wave such that it transforms into a single-mode wave upon entering high-density plasma. Themore » theory can be used for reduced modeling of wave-power input in fusion plasmas. In particular, applications are envisioned in stellarator research, where the mutual conversion of two electromagnetic modes near the plasma edge is a known issue.« less

Mode conversion in cold low-density plasma with a sheared magnetic field

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

Dodin, I. Y.; Ruiz, D. E.; Kubo, S.

Here, a theory is proposed that describes mutual conversion of two electromagnetic modes in cold low-density plasma, specifically, in the high-frequency limit where the ion response is negligible. In contrast to the classic (Landau–Zener-type) theory of mode conversion, the region of resonant coupling in low-density plasma is not necessarily narrow, so the coupling matrix cannot be approximated with its first-order Taylor expansion; also, the initial conditions are set up differently. For the case of strong magnetic shear, a simple method is identified for preparing a two-mode wave such that it transforms into a single-mode wave upon entering high-density plasma. Themore » theory can be used for reduced modeling of wave-power input in fusion plasmas. In particular, applications are envisioned in stellarator research, where the mutual conversion of two electromagnetic modes near the plasma edge is a known issue.« less

Fusion plasma theory project summaries

NASA Astrophysics Data System (ADS)

1993-10-01

This Project Summary book is a published compilation consisting of short descriptions of each project supported by the Fusion Plasma Theory and Computing Group of the Advanced Physics and Technology Division of the Department of Energy, Office of Fusion Energy. The summaries contained in this volume were written by the individual contractors with minimal editing by the Office of Fusion Energy. Previous summaries were published in February of 1982 and December of 1987. The Plasma Theory program is responsible for the development of concepts and models that describe and predict the behavior of a magnetically confined plasma. Emphasis is given to the modelling and understanding of the processes controlling transport of energy and particles in a toroidal plasma and supporting the design of the International Thermonuclear Experimental Reactor (ITER). A tokamak transport initiative was begun in 1989 to improve understanding of how energy and particles are lost from the plasma by mechanisms that transport them across field lines. The Plasma Theory program has actively participated in this initiative. Recently, increased attention has been given to issues of importance to the proposed Tokamak Physics Experiment (TPX). Particular attention has been paid to containment and thermalization of fast alpha particles produced in a burning fusion plasma as well as control of sawteeth, current drive, impurity control, and design of improved auxiliary heating. In addition, general models of plasma behavior are developed from physics features common to different confinement geometries. This work uses both analytical and numerical techniques. The Fusion Theory program supports research projects at U.S. government laboratories, universities and industrial contractors. Its support of theoretical work at universities contributes to the office of Fusion Energy mission of training scientific manpower for the U.S. Fusion Energy Program.

Static assignment of complex stochastic tasks using stochastic majorization

NASA Technical Reports Server (NTRS)

Nicol, David; Simha, Rahul; Towsley, Don

1992-01-01

We consider the problem of statically assigning many tasks to a (smaller) system of homogeneous processors, where a task's structure is modeled as a branching process, and all tasks are assumed to have identical behavior. We show how the theory of majorization can be used to obtain a partial order among possible task assignments. Our results show that if the vector of numbers of tasks assigned to each processor under one mapping is majorized by that of another mapping, then the former mapping is better than the latter with respect to a large number of objective functions. In particular, we show how measurements of finishing time, resource utilization, and reliability are all captured by the theory. We also show how the theory may be applied to the problem of partitioning a pool of processors for distribution among parallelizable tasks.

Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics - Revisiting Perturbative Hybrid Kinetic-MHD Theory.

PubMed

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

2016-05-10

It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle's Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas.

Theory of magnetic reconnection in solar and astrophysical plasmas.

PubMed

Pontin, David I

2012-07-13

Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this paper, we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex three-dimensional magnetic fields and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the magnetohydrodynamic framework where a number of new three-dimensional reconnection regimes have been identified. We discuss evidence from observations and simulations of Solar System plasmas that support this theory and summarize some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas.

Quark-gluon plasma (Selected Topics)

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

Zakharov, V. I., E-mail: vzakharov@itep.ru

Introductory lectures to the theory of (strongly interacting) quark-gluon plasma given at the Winter School of Physics of ITEP (Moscow, February 2010). We emphasize theoretical issues highlighted by the discovery of the low viscosity of the plasma. The topics include relativistic hydrodynamics, manifestations of chiral anomaly in hydrodynamics, superfluidity, relativistic superfluid hydrodynamics, effective stringy scalars, holographic models of Yang-Mills theories.

A Workbench for Discovering Task-Specific Theories of Learning

DTIC Science & Technology

1989-03-03

mind (the cognitive architecture) will not be of much use to educators who wish to perform a cognitive task analysis of their subject matter before...analysis packages that can be added to a cognitive architecture, thus creating a ’workbench’ for performing cognitive task analysis . Such tools becomes...learning theories have been. Keywords: Cognitive task analysis , Instructional design, Cognitive modelling, Learning.

The organization of verbs of knowing: evidence for cultural commonality and variation in theory of mind.

PubMed

Schwanenflugel, P J; Martin, M; Takahashi, T

1999-09-01

Cross-cultural commonality and variation in folk theories of knowing were studied by examining the organization of verbs of knowing in German and Japanese adults. German and Japanese adults performed one of two tasks: a similarity judgment task and an attribute rating task. Organizational structure was assessed for the similarity judgment task using multidimensional scaling and additive similarity tree analyses. The attribute rating task was used to describe the characteristics that organized the dimensions and clusters emerging from the scaling solutions. The folk theory of mind displayed was an information processing model with constructive components, although the constructive aspects were more salient for the Germans than for the Japanese.

How "fun/importance" fit affects performance: relating implicit theories to instructions.

PubMed

Bianco, Amy T; Higgins, E Tory; Klem, Adena

2003-09-01

People experience a regulatory fit when they employ means of goal pursuit that fit their regulatory orientation, and this fit increases motivation that can enhance performance. The present studies extend previous research on regulatory fit to the classic motivational variables of fun and importance. They also examine for the first time the effect on performance of the fit between individuals' implicit theories about a task's fun or importance and their strategic engagement of the task as fun or important as induced by task instructions. In all three studies, task performance was better when the external task instructions "fit" rather than did not fit participants' implicit theory for the task. The implications of these findings for understanding the motivational effects of fun and importance are discussed.

Observation of plasma toroidal-momentum dissipation by neoclassical toroidal viscosity.

PubMed

Zhu, W; Sabbagh, S A; Bell, R E; Bialek, J M; Bell, M G; LeBlanc, B P; Kaye, S M; Levinton, F M; Menard, J E; Shaing, K C; Sontag, A C; Yuh, H

2006-06-09

Dissipation of plasma toroidal angular momentum is observed in the National Spherical Torus Experiment due to applied nonaxisymmetric magnetic fields and their plasma-induced increase by resonant field amplification and resistive wall mode destabilization. The measured decrease of the plasma toroidal angular momentum profile is compared to calculations of nonresonant drag torque based on the theory of neoclassical toroidal viscosity. Quantitative agreement between experiment and theory is found when the effect of toroidally trapped particles is included.

A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

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

You, Setthivoine

Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficientmore » with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.« less

Bernstein modes in a non-neutral plasma column

NASA Astrophysics Data System (ADS)

Walsh, Daniel; Dubin, Daniel H. E.

2018-05-01

This paper presents theory and numerical calculations of electrostatic Bernstein modes in an inhomogeneous cylindrical plasma column. These modes rely on finite Larmor radius effects to propagate radially across the column until they are reflected when their frequency matches the upper hybrid frequency. This reflection sets up an internal normal mode on the column and also mode-couples to the electrostatic surface cyclotron wave (which allows the normal mode to be excited and observed using external electrodes). Numerical results predicting the mode spectra, using a novel linear Vlasov code on a cylindrical grid, are presented and compared to an analytical Wentzel Kramers Brillouin (WKB) theory. A previous version of the theory [D. H. E. Dubin, Phys. Plasmas 20(4), 042120 (2013)] expanded the plasma response in powers of 1/B, approximating the local upper hybrid frequency, and consequently, its frequency predictions are spuriously shifted with respect to the numerical results presented here. A new version of the WKB theory avoids this approximation using the exact cold fluid plasma response and does a better job of reproducing the numerical frequency spectrum. The effect of multiple ion species on the mode spectrum is also considered, to make contact with experiments that observe cyclotron modes in a multi-species pure ion plasma [M. Affolter et al., Phys. Plasmas 22(5), 055701 (2015)].

Ideal magnetohydrodynamic theory for localized interchange modes in toroidal anisotropic plasmas

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

Shi, Tonghui, E-mail: thshi@ipp.ac.cn; Wan, B. N.; Sun, Y.

2016-08-15

Ideal magnetohydrodynamic theory for localized interchange modes is developed for toroidal plasmas with anisotropic pressure. The work extends the existing theories of Johnson and Hastie [Phys. Fluids 31, 1609 (1988)], etc., to the low n mode case, where n is the toroidal mode number. Also, the plasma compressibility is included, so that the coupling of the parallel motion to perpendicular one, i.e., the so-called apparent mass effect, is investigated in the anisotropic pressure case. The singular layer equation is obtained, and the generalized Mercier's criterion is derived.

Particle and momentum confinement in tokamak plasmas with unbalanced neutral beam injection and strong rotation

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

Malik, M.A.

1988-01-01

There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such asmore » INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism.« less

Collision time measurements in a sonoluminescing microplasma with a large plasma parameter.

PubMed

Bataller, A; Kappus, B; Camara, C; Putterman, S

2014-07-11

The plasma which forms inside of a micron-sized sonoluminescing bubble in water for under a nanosecond has been probed with 3 ns long laser pulses. A comparison of the response to 532 and 1064 nm light indicates that the plasma number density is about 2×10(21)  cm(-3) and that transport properties are dominated by strong screening and correlation effects. The spherical shape, well-defined atomic density, and blackbody temperature make the sonoluminescing plasma a test bed for theories of strongly coupled plasmas. The plasma in this experiment distinguishes between competing theories of strong, intermediate, and weak effective screening.

Collision Time Measurements in a Sonoluminescing Microplasma with a Large Plasma Parameter

NASA Astrophysics Data System (ADS)

Bataller, A.; Kappus, B.; Camara, C.; Putterman, S.

2014-07-01

The plasma which forms inside of a micron-sized sonoluminescing bubble in water for under a nanosecond has been probed with 3 ns long laser pulses. A comparison of the response to 532 and 1064 nm light indicates that the plasma number density is about 2×1021 cm-3 and that transport properties are dominated by strong screening and correlation effects. The spherical shape, well-defined atomic density, and blackbody temperature make the sonoluminescing plasma a test bed for theories of strongly coupled plasmas. The plasma in this experiment distinguishes between competing theories of strong, intermediate, and weak effective screening.

RELATIVISTIC CYCLOTRON INSTABILITY IN ANISOTROPIC PLASMAS

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

López, Rodrigo A.; Moya, Pablo S.; Muñoz, Víctor

2016-11-20

A sufficiently large temperature anisotropy can sometimes drive various types of electromagnetic plasma micro-instabilities, which can play an important role in the dynamics of relativistic pair plasmas in space, astrophysics, and laboratory environments. Here, we provide a detailed description of the cyclotron instability of parallel propagating electromagnetic waves in relativistic pair plasmas on the basis of a relativistic anisotropic distribution function. Using plasma kinetic theory and particle-in-cell simulations, we study the influence of the relativistic temperature and the temperature anisotropy on the collective and noncollective modes of these plasmas. Growth rates and dispersion curves from the linear theory show amore » good agreement with simulations results.« less

Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling.

PubMed

Lee, Hyo-Chang; Chung, Chin-Wook

2015-10-20

Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling

PubMed Central

Lee, Hyo-Chang; Chung, Chin-Wook

2015-01-01

Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics. PMID:26482650

Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics – Revisiting Perturbative Hybrid Kinetic-MHD Theory

PubMed Central

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

2016-01-01

It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle’s Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas. PMID:27160346

Effects of Coulomb Coupling on the Stopping Power of Plasmas

NASA Astrophysics Data System (ADS)

Bernstein, David; Daligault, Jerome; Baalrud, Scott

2017-10-01

Stopping power of charged particles in plasma is important for a detailed understanding of particle and energy transport in plasmas, such as those found in fusion applications. Although stopping power is rather well understood for weakly coupled plasmas, this is less the case for strongly coupled plasmas. In order to shed light on the effects of strong Coulomb coupling, we have conducted detailed molecular dynamics simulations of the stopping power of a One-Component Plasma (OCP) across a wide range of conditions. The OCP allows first-principle computations that are not possible with more complex models, enabling rigorous tests of analytical theories. The molecular dynamics simulations were compared to two analytical theories that attempt to extend traditional weakly-coupled theories into the strong coupling regime. The first is based on the binary approximation, which accounts for strong coupling via an effective scattering cross section derived from the effective potential theory. The second is based on the dielectric function formulation with the inclusion of a local field corrections. Work supported by LANL LDRD project 20150520ER and ir Force Office of Scientific Research under Award Number FA9550-16-1-0221.

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

Rutherfoord, John; Toussaint, Doug; Sarcevic, Ina

The following pages describe the high energy physics program at the University of Arizona which was funded by DOE grant DE-FG03-95ER40906, for the period 1 February 1995 to 31 January 2004. In this report, emphasis was placed on more recent accomplishments. This grant was divided into two tasks, a theory task (Task A) and an experimental task (Task B but called Task C early in the grant period) with separate budgets. Faculty supported by this grant, for at least part of this period, include, for the theory task, Adrian Patrascioiu (now deceased), Ina Sarcevic, and Douglas Toussaint., and, for themore » experimental task, Elliott Cheu, Geoffrey Forden, Kenneth Johns, John Rutherfoord, Michael Shupe, and Erich Varnes. Grant monitors from the Germantown DOE office, overseeing our grant, changed over the years. Dr. Marvin Gettner covered the first years and then he retired from the DOE. Dr. Patrick Rapp worked with us for just a few years and then left for a position at the University of Puerto Rico. Dr. Kathleen Turner took his place and continues as our grant monitor. The next section of this report covers the activities of the theory task (Task A) and the last section the activities of the experimental task (Task B).« less

Executive function in middle childhood and the relationship with theory of mind.

PubMed

Wilson, Jennifer; Andrews, Glenda; Hogan, Christy; Wang, Si; Shum, David H K

2018-01-01

A group of 126 typically developing children (aged 5-12 years) completed three cool executive function tasks (spatial working memory, stop signal, intra-extra dimensional shift), two hot executive function tasks (gambling, delay of gratification), one advanced theory of mind task (strange stories with high versus low affective tone), and a vocabulary test. Older children performed better than younger children, consistent with the protracted development of hot and cool executive functions and theory of mind. Multiple regression analyses showed that hot and cool executive functions were correlated but they predicted theory of mind in different ways.

A test of two theories for the low-frequency cutoffs of nonthermal continuum radiation

NASA Technical Reports Server (NTRS)

Shaw, R. R.; Gurnett, D. A.

1980-01-01

A discussion and analysis of two theories that differently identify the low-frequency cutoffs of nonthermal continuum radiation are presented. The cold plasma theory and an alternate one proposed by Jones (1976) are compared experimentally with the use of continuum radiation data obtained in the outer magnetosphere by the Imp 6 and ISEE 1 spacecraft. It is found that the characteristics of this specific radiation are consistent with those expected of ordinary and extraordinary mode waves described by the cold plasma theory and it is shown that the cutoff frequencies occur at the local plasma frequency and R = 0 cutoff frequency as proposed by the same theory. The inconsistencies which were found between the Jones theory (1976) and observation are presented, and in addition no evidence is found for a component of continuum radiation propagating in the Z mode in the outer magnetosphere.

Quasilinear theory of plasma turbulence. Origins, ideas, and evolution of the method

NASA Astrophysics Data System (ADS)

Bakunin, O. G.

2018-01-01

The quasilinear method of describing weak plasma turbulence is one of the most important elements of current plasma physics research. Today, this method is not only a tool for solving individual problems but a full-fledged theory of general physical interest. The author's objective is to show how the early ideas of describing the wave-particle interactions in a plasma have evolved as a result of the rapid expansion of the research interests of turbulence and turbulent transport theorists.

Nonspecificity and theory of mind: new evidence from a nonverbal false-sign task and children with autism spectrum disorders.

PubMed

Iao, Lai-Sang; Leekam, Susan R

2014-06-01

Understanding of false belief has long been considered to be a crucial aspect of "theory of mind" that can be explained by a domain-specific mechanism. We argue against this claim using new evidence from a nonverbal false representation task (false-sign task) with typically developing children and children with autism spectrum disorders (ASD). Experiments 1 and 2 showed that typically developing children (mean age=62.67months) were equivalent in their performance across nonverbal and verbal forms of both the false-belief and false-sign tasks. Results for these two misrepresentation tasks differed from the results of an outdated representation task ("false"-photograph task). Experiment 3 showed that children with ASD had difficulties with the false representation tasks, and this could not be explained by executive functioning or language impairments. These findings support the view that children with ASD might not have a specific theory-of-mind deficit. Copyright © 2013 Elsevier Inc. All rights reserved.

Children exhibit different performance patterns in explicit and implicit theory of mind tasks.

PubMed

Oktay-Gür, Nese; Schulz, Alexandra; Rakoczy, Hannes

2018-04-01

Three studies tested scope and limits of children's implicit and explicit theory of mind. In Studies 1 and 2, three- to six-year-olds (N = 84) were presented with closely matched explicit false belief tasks that differed in whether or not they required an understanding of aspectuality. Results revealed that children performed equally well in the different tasks, and performance was strongly correlated. Study 3 tested two-year-olds (N = 81) in implicit interactive versions of these tasks and found evidence for dis-unity: children performed competently only in those tasks that did not require an understanding of aspectuality. Taken together, the present findings suggest that early implicit and later explicit theory of mind tasks may tap different forms of cognitive capacities. Copyright © 2018 Elsevier B.V. All rights reserved.

Neural activity in the hippocampus during conflict resolution.

PubMed

Sakimoto, Yuya; Okada, Kana; Hattori, Minoru; Takeda, Kozue; Sakata, Shogo

2013-01-15

This study examined configural association theory and conflict resolution models in relation to hippocampal neural activity during positive patterning tasks. According to configural association theory, the hippocampus is important for responses to compound stimuli in positive patterning tasks. In contrast, according to the conflict resolution model, the hippocampus is important for responses to single stimuli in positive patterning tasks. We hypothesized that if configural association theory is applicable, and not the conflict resolution model, the hippocampal theta power should be increased when compound stimuli are presented. If, on the other hand, the conflict resolution model is applicable, but not configural association theory, then the hippocampal theta power should be increased when single stimuli are presented. If both models are valid and applicable in the positive patterning task, we predict that the hippocampal theta power should be increased by presentation of both compound and single stimuli during the positive patterning task. To examine our hypotheses, we measured hippocampal theta power in rats during a positive patterning task. The results showed that hippocampal theta power increased during the presentation of a single stimulus, but did not increase during the presentation of a compound stimulus. This finding suggests that the conflict resolution model is more applicable than the configural association theory for describing neural activity during positive patterning tasks. Copyright © 2012 Elsevier B.V. All rights reserved.

Revisited comparison of thermal instability theory with MARFE density limit experiment in TEXTOR.

NASA Astrophysics Data System (ADS)

Kelly, Frederick

2006-03-01

Density limit shots in TEXTOR [Tokamak EXperiment for Technology Oriented Research] that ended in MARFE [Multifaceted Asymmetric Radiation From the Edge] are analyzed by several thermal instability theories^1-7 with convective effects included. ^1W. M. Stacey, Phys. Plasmas 3, 2673 (1996); Phys. Plasmas 3, 3032 (1996); Phys. Plasmas 4, 134 (1997); Phys. Plasmas 4, 242 (1997). ^2W. M. Stacey, Plasma Phys. Contr. Fusion 39, 1245 (1997). ^3W. M. Stacey, Fusion Technol. 36, 38 (1999).^ ^4W. M. Stacey, Phys. Plasmas 7, 3464 (2000). ^5F. A. Kelly, W. M. Stacey, J. Rapp and M. Brix, Phys. Plasmas 8, 3382 (2001). ^6M. Z. Tokar and F. A. Kelly, Phys. Plasmas 10, 4378 (2003). ^7M. Z. Tokar, F. A. Kelly and X. Loozen, Phys. Plasmas 12, 052510 (2005).

Performance on verbal and low-verbal false belief tasks: evidence from children with Williams syndrome.

PubMed

Van Herwegen, Jo; Dimitriou, Dagmara; Rundblad, Gabriella

2013-01-01

Previous studies that have investigated the relationship between performance on theory of mind (ToM) tasks and verbal abilities in individuals with Williams syndrome (WS) have reported contradictory findings with some showing that language abilities aid performance on ToM tasks while others have found that participants with WS fail these tasks because of their verbal demands. The current study investigated this relationship again comparing performance on a classical change-location task to two newly developed low-verbal tasks, one change-location task and one unexpected content task. Thirty children with WS (aged 5-17;01 years) and 30 typically developing (TD) children (aged between 2;10 years and 9;09 years), who were matched for vocabulary comprehension scores were included in the study. Although performance in the WS group was significantly poorer compared to the TD group on all three tasks, performance was not predicted by their receptive vocabulary or grammatical ability scores. In addition, ToM abilities in both groups depended on the cognitive demands of the task at hand. This finding shows that performance on ToM tasks in WS is not necessarily hindered by their delayed language abilities but rather by the task administered. This could potentially affect the diagnosis of developmental disorders, such as Autism Spectrum Disorders, and comparison of ToM abilities across developmental disorders. Readers of this article should be able to (1) describe the current state of theory of mind research in Williams syndrome, (2) identify which cognitive abilities might explain performance on theory of mind tasks in both typically developing children and in children with Williams syndrome, and (3) interpret the importance of task demands when assessing children's theory of mind abilities. Copyright © 2013 Elsevier Inc. All rights reserved.

I. WORKING MEMORY CAPACITY IN CONTEXT: MODELING DYNAMIC PROCESSES OF BEHAVIOR, MEMORY, AND DEVELOPMENT.

PubMed

Simmering, Vanessa R

2016-09-01

Working memory is a vital cognitive skill that underlies a broad range of behaviors. Higher cognitive functions are reliably predicted by working memory measures from two domains: children's performance on complex span tasks, and infants' performance in looking paradigms. Despite the similar predictive power across these research areas, theories of working memory development have not connected these different task types and developmental periods. The current project takes a first step toward bridging this gap by presenting a process-oriented theory, focusing on two tasks designed to assess visual working memory capacity in infants (the change-preference task) versus children and adults (the change detection task). Previous studies have shown inconsistent results, with capacity estimates increasing from one to four items during infancy, but only two to three items during early childhood. A probable source of this discrepancy is the different task structures used with each age group, but prior theories were not sufficiently specific to explain how performance relates across tasks. The current theory focuses on cognitive dynamics, that is, how memory representations are formed, maintained, and used within specific task contexts over development. This theory was formalized in a computational model to generate three predictions: 1) capacity estimates in the change-preference task should continue to increase beyond infancy; 2) capacity estimates should be higher in the change-preference versus change detection task when tested within individuals; and 3) performance should correlate across tasks because both rely on the same underlying memory system. I also tested a fourth prediction, that development across tasks could be explained through increasing real-time stability, realized computationally as strengthening connectivity within the model. Results confirmed these predictions, supporting the cognitive dynamics account of performance and developmental changes in real-time stability. The monograph concludes with implications for understanding memory, behavior, and development in a broader range of cognitive development. © 2016 The Society for Research in Child Development, Inc.

The Link between Preschoolers' Executive Function and Theory of Mind and the Role of Epistemic States

ERIC Educational Resources Information Center

Henning, Anne; Spinath, Frank M.; Aschersleben, Gisa

2011-01-01

The aim of this study was to assess the specific relation between 3- to 6-year-olds' performance on a task measuring executive function (EF), the Dimensional Change Card Sort task (DCCS), and different developmental attainments in their theory of mind (ToM) by employing a battery of scaled ToM tasks that were comparable in task format and task…

Expectancy-value theory in persistence of learning effects in schizophrenia: role of task value and perceived competency.

PubMed

Choi, Jimmy; Fiszdon, Joanna M; Medalia, Alice

2010-09-01

Expectancy-value theory, a widely accepted model of motivation, posits that expectations of success on a learning task and the individual value placed on the task are central determinants of motivation to learn. This is supported by research in healthy controls suggesting that beliefs of self-and-content mastery can be so influential they can predict the degree of improvement on challenging cognitive tasks even more so than general cognitive ability. We examined components of expectancy-value theory (perceived competency and task value), along with baseline arithmetic performance and neuropsychological performance, as possible predictors of learning outcome in a sample of 70 outpatients with schizophrenia randomized to 1 of 2 different arithmetic learning conditions and followed up after 3 months. Results indicated that as with nonpsychiatric samples, perceived self-competency for the learning task was significantly related to perceptions of task value attributed to the learning task. Baseline expectations of success predicted persistence of learning on the task at 3-month follow-up, even after accounting for variance attributable to different arithmetic instruction, baseline arithmetic ability, attention, and self-reports of task interest and task value. We also found that expectation of success is a malleable construct, with posttraining improvements persisting at follow-up. These findings support the notion that expectancy-value theory is operative in schizophrenia. Thus, similar to the nonpsychiatric population, treatment benefits may be enhanced and better maintained if remediation programs also focus on perceptions of self-competency for the training tasks. Treatment issues related to instilling self-efficacy in cognitive recovery programs are discussed.

Ionospheres of the terrestrial planets

NASA Astrophysics Data System (ADS)

Schunk, R. W.; Nagy, A. F.

1980-11-01

The theory and observations relating to the ionospheres of the terrestrial planets Venus, the earth, and Mars are reviewed. Emphasis is placed on comparing the basic differences and similarities between the planetary ionospheres. The review covers the plasma and electric-magnetic field environments that surround the planets, the theory leading to the creation and transport of ionization in the ionospheres, the relevant observations, and the most recent model calculations. The theory section includes a discussion of ambipolar diffusion in a partially ionized plasma, diffusion in a fully ionized plasma, supersonic plasma flow, photochemistry, and heating and cooling processes. The sections on observations and model calculations cover the neutral atmosphere composition, the ion composition, the electron density, and the electron, ion, and neutral temperatures.

Research on radiation characteristic of plasma antenna through FDTD method.

PubMed

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

Children's Judgements concerning "Easy" Partitioning. Tasks as Related to a Theory of Partitioning.

ERIC Educational Resources Information Center

Pothier, Yvonne; Sawada, Daiyo

By varying task conditions and constraints on subjects, this study attempted to extend and refine a developmental theory of partitioning as a foundational process undergirding children's construction of a rational number. Subjects were 31 preponderantly higher-grade pupils enrolled at an elementary school in Nova Scotia, Canada. Two tasks were…

Quechua Children's Theory of Mind.

ERIC Educational Resources Information Center

McCormick, Penelope G.; Olson, David R.

Three different theory of mind tasks were conducted with 4- to 8-year-old Quechua peasant children in the Peruvian Andes. The study investigated the ways in which children in preliterate cultures think and the possibility that they think differently than children in literate cultures. The tasks included: (1) a false-belief task, which tested the…

Spatial and temporal task characteristics as stress: a test of the dynamic adaptability theory of stress, workload, and performance.

PubMed

Szalma, James L; Teo, Grace W L

2012-03-01

The goal for this study was to test assertions of the dynamic adaptability theory of stress, which proposes two fundamental task dimensions, information rate (temporal properties of a task) and information structure (spatial properties of a task). The theory predicts adaptive stability across stress magnitudes, with progressive and precipitous changes in adaptive response manifesting first as increases in perceived workload and stress and then as performance failure. Information structure was manipulated by varying the number of displays to be monitored (1, 2, 4 or 8 displays). Information rate was manipulated by varying stimulus presentation rate (8, 12, 16, or 20 events/min). A signal detection task was used in which critical signals were pairs of digits that differed by 0 or 1. Performance accuracy declined and workload and stress increased as a function of increased task demand, with a precipitous decline in accuracy at the highest demand levels. However, the form of performance change as well as the pattern of relationships between speed and accuracy and between performance and workload/stress indicates that some aspects of the theory need revision. Implications of the results for the theory and for future research are discussed. Copyright © 2011 Elsevier B.V. All rights reserved.

Reduction of the ionization energy for 1s-electrons in dense aluminum plasmas

NASA Astrophysics Data System (ADS)

Lin, C.; Reinholz, H.; Röpke, G.

2017-02-01

The properties of a bound multi-electron system immersed in a plasma environment are strongly modified by the surrounding plasma. In particular, the modification of the ionization energy is described by the electronic self-energy within the framework of the quantum statistical theory. We present the energy shift of the eigenstates and the lowering of the continuum edge of free electrons in a plasma. The reduction of the ionization potential is determined by their difference. This ionization potential depression for the 1s-levels in dense aluminum plasmas is calculated. Comparisons with other theories and the experimental data are shown for aluminum plasma at solid density 2.7 g/cm3.

Stopping power of dense plasmas: The collisional method and limitations of the dielectric formalism.

PubMed

Clauser, C F; Arista, N R

2018-02-01

We present a study of the stopping power of plasmas using two main approaches: the collisional (scattering theory) and the dielectric formalisms. In the former case, we use a semiclassical method based on quantum scattering theory. In the latter case, we use the full description given by the extension of the Lindhard dielectric function for plasmas of all degeneracies. We compare these two theories and show that the dielectric formalism has limitations when it is used for slow heavy ions or atoms in dense plasmas. We present a study of these limitations and show the regimes where the dielectric formalism can be used, with appropriate corrections to include the usual quantum and classical limits. On the other hand, the semiclassical method shows the correct behavior for all plasma conditions and projectile velocity and charge. We consider different models for the ion charge distributions, including bare and dressed ions as well as neutral atoms.

Theory of void formation in dusty plasmas

NASA Astrophysics Data System (ADS)

Hu, Zuquan; Chen, Yinhua; Zheng, Xiang; Huang, Feng; Shi, Gei-fen; Yu, M. Y.

2009-06-01

A fluid theory of void formation in dusty plasmas taking into account ionization is proposed. It is shown that if the ionization rate is larger than a threshold, an initial steady-state dust-density distribution can evolve into a stable distribution containing a void. As the ionization rate is further increased, the time required for void formation decreases. The void size first increases, but then decreases. However, for still larger ionization rates, the dusty region of the plasma becomes ringlike, including the convection term in dust momentum equation. The results are in agreement with existing experiments and theories.

Theory of Thomson scattering in inhomogeneous plasmas

NASA Astrophysics Data System (ADS)

Belyi, V. V.

2018-05-01

A self-consistent kinetic theory of Thomson scattering of an electromagnetic field by a nonuniform plasma is derived. We show that not only the imaginary part, but also the time and space derivatives of the real part of the dielectric susceptibility determine the amplitude and the width of the Thomson scattering spectral lines. As a result of inhomogeneity, these properties become asymmetric with respect to inversion of the sign of the frequency. Our theory provides a method of a remote probing and measurement of electron density gradients in plasma; this is based on the demonstrated asymmetry of the Thomson scattering lines.

Atmospheric Plasma Depainting

DTIC Science & Technology

2014-11-19

Atmospheric Plasma Depainting Peter Yancey Atmospheric Plasma Solutions, Inc. Report Documentation Page Form ApprovedOMB No. 0704-0188...00-00-2014 4. TITLE AND SUBTITLE Atmospheric Plasma Depainting 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Atmospheric Plasma Solutions, Inc,11301

Poloidal velocity of impurity ions in neoclassical theory

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

Wong, S. K.; Chan, V. S.; Solomon, W. M.

A formula for the poloidal velocity of impurity ions in a two-species plasma is derived from neoclassical theory in the banana regime, with corrections from the boundary layer separating the trapped and transiting ions. The formula is applicable to plasmas with toroidal rotations that can approach the thermal speeds of the ions. Using the formula to determine the poloidal velocity of C{sup +6} ions in a recently reported experiment [W. M. Solomon et al., Phys. Plasmas 13, 056116 (2006)] leads to agreement in the direction of the central region when it is otherwise from theories without strong toroidal rotations. Comparisonsmore » among these theories are made, demonstrating the degree of uncertainty of theoretical predictions.« less

Self-consistent formation of electron $\\kappa$ distribution: 1. Theory

NASA Astrophysics Data System (ADS)

Yoon, Peter H.; Rhee, Tongnyeol; Ryu, Chang-Mo

2006-09-01

Since the early days of plasma physics research suprathermal electrons were observed to be generated during beam-plasma laboratory experiments. Energetic electrons, often modeled by κ distributions, are also ubiquitously observed in space. Various particle acceleration mechanisms have been proposed to explain such a feature, but all previous theories rely on either qualitative analytical method or on non-self-consistent approaches. This paper discusses the self-consistent acceleration of electrons to suprathermal energies by weak turbulence processes which involve the Langmuir/ion-sound turbulence and the beam-plasma interaction. It is discussed that the spontaneous scatttering process, which is absent in the purely collisionless theory, is singularly responsible for the generation of κ distributions. The conclusion is that purely collisionless Vlasov theory cannot produce suprathermal population.

Why would I help my coworker? Exploring asymmetric task dependence and the self-determination theory internalization process.

PubMed

Poile, Christopher

2017-09-01

Research on power suggests asymmetric task dependence (sending work resources to a coworker and receiving little in return) should create a power imbalance and promote selfishness. In contrast, work design theory suggests asymmetry can lead to felt responsibility, but this link has not been tested and its theory remains underdeveloped. Drawing on self-determination theory (SDT), this article argues that work design characteristics can encourage the SDT internalization process-the transformation of external reasons for behavior into internal reasons. Two experiments demonstrate asymmetry encourages felt responsibility for the dependent's task, which helps explain the amount of help provided to the dependent. The author proposes felt responsibility indicates the extent to which an external task has been internalized as a self-directed motivation. This article clarifies how task dependence is different from power and develops an important and understudied aspect of SDT: how work design characteristics are transformed into internalized motivations. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Testing neoclassical and turbulent effects on poloidal rotation in the core of DIII-D

DOE PAGES

Chrystal, Colin; Burrell, Keith H.; Grierson, Brian A.; ...

2014-07-09

Experimental tests of ion poloidal rotation theories have been performed on DIII-D using a novel impurity poloidal rotation diagnostic. These tests show significant disagreements with theoretical predictions in various conditions, including L-mode plasmas with internal transport barriers (ITB), H-mode plasmas, and QH-mode plasmas. The theories tested include standard neoclassical theory, turbulence driven Reynolds stress, and fast-ion friction on the thermal ions. Poloidal rotation is observed to spin up at the formation of an ITB and makes a significant contribution to the measurement of themore » $$\\vec{E}$$ × $$\\vec{B}$$ shear that forms the ITB. In ITB cases, neoclassical theory agrees quantitatively with the experimental measurements only in the steep gradient region. Significant quantitative disagreement with neoclassical predictions is seen in the cores of ITB, QH-, and H-mode plasmas, demonstrating that neoclassical theory is an incomplete description of poloidal rotation. The addition of turbulence driven Reynolds stress does not remedy this disagreement; linear stability calculations and Doppler backscattering measurements show that disagreement increases as turbulence levels decline. Furthermore, the effect of fast-ion friction, by itself, does not lead to improved agreement; in QH-mode plasmas, neoclassical predictions are closest to experimental results in plasmas with the largest fast ion friction. Finally, predictions from a new model that combines all three effects show somewhat better agreement in the H-mode case, but discrepancies well outside the experimental error bars remain.« less

Toward a domain theory in English as a second language.

PubMed

Strong-Krause, Diane

2009-01-01

This paper demonstrates how domain theory development is enhanced by using both theoretical data and empirical data. The study explored the domain of speaking English as a second language (ESL) comparing hypothetical data on speaking tasks provided by an experienced teacher and by a certified ACTFL oral proficiency interview rater with observed data from scores on a computer-delivered speaking exam. While the hypothetical data and observed data showed similar patterns in task difficulty in general, some tasks were identified as being much easier or harder than expected. These differences raise questions not only about test task design but also about the theoretical underpinnings of the domain. The results of the study suggest that this approach, where theory and data are examined together, will improve test design as well as benefit domain theory development.

A perspective on the contributions of Ronald C. Davidson to plasma physics

NASA Astrophysics Data System (ADS)

Wurtele, Jonathan S.

2016-10-01

Starting in the 1960s and continuing for half a century, Ronald C. Davidson made fundamental theoretical contributions to a wide range of areas of pure and applied plasma physics. Davidson was one of the founders of nonneutral plasma physics and a pioneer in developing and applying kinetic theory and nonlinear stability theorems to collective interaction processes and nonlinear dynamics of nonneutral plasmas and intense charged particle beams. His textbooks on nonneutral plasmas are the classic references for the field and educated generations of graduate students. Davidson was a strong advocate for applying the ideas of plasma theory to develop techniques that benefit other branches of science. For example, one of the major derivative fields enabled by nonneutral plasmas is the study of antimatter plasmas and the synthesis of antihydrogen. This talk will review a few highlights of Ronald Davidson's impact on plasma physics and related fields of science.

Electrostatic Debye layer formed at a plasma-liquid interface

NASA Astrophysics Data System (ADS)

Rumbach, Paul; Clarke, Jean Pierre; Go, David B.

2017-05-01

We construct an analytic model for the electrostatic Debye layer formed at a plasma-liquid interface by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model for the plasma sheath. The model predicts a nonlinear scaling between the plasma current density and the solution ionic strength, and we confirmed this behavior with measurements using a liquid-anode plasma. Plots of the measured current density as a function of ionic strength collapse the data and curve fits yield a plasma electron density of ˜1019m-3 and an electric field of ˜104V /m on the liquid side of the interface. Because our theory is based firmly on fundamental physics, we believe it can be widely applied to many emerging technologies involving the interaction of low-temperature, nonequilibrium plasma with aqueous media, including plasma medicine and various plasma chemical synthesis techniques.

Density functional theory calculations of continuum lowering in strongly coupled plasmas.

PubMed

Vinko, S M; Ciricosta, O; Wark, J S

2014-03-24

An accurate description of the ionization potential depression of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here we present a method to study the structure and position of the continuum of highly ionized dense plasmas using finite-temperature density functional theory in combination with excited-state projector augmented-wave potentials. The method is applied to aluminium plasmas created by intense X-ray irradiation, and shows excellent agreement with recently obtained experimental results. We find that the continuum lowering for ions in dense plasmas at intermediate temperatures is larger than predicted by standard plasma models and explain this effect through the electronic structure of the valence states in these strong-coupling conditions.

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

Ivanov, A. A., E-mail: aai@a5.kiam.ru; Martynov, A. A., E-mail: martynov@a5.kiam.ru; Medvedev, S. Yu., E-mail: medvedev@a5.kiam.ru

In the MHD tokamak plasma theory, the plasma pressure is usually assumed to be isotropic. However, plasma heating by neutral beam injection and RF heating can lead to a strong anisotropy of plasma parameters and rotation of the plasma. The development of MHD equilibrium theory taking into account the plasma inertia and anisotropic pressure began a long time ago, but until now it has not been consistently applied in computational codes for engineering calculations of the plasma equilibrium and evolution in tokamak. This paper contains a detailed derivation of the axisymmetric plasma equilibrium equation in the most general form (withmore » arbitrary rotation and anisotropic pressure) and description of the specialized version of the SPIDER code. The original method of calculation of the equilibrium with an anisotropic pressure and a prescribed rotational transform profile is proposed. Examples of calculations and discussion of the results are also presented.« less

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

Ruzic, David

The Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS) project was able to establish the experimental conditions necessary for flowing liquid metal surfaces in order to be utilized as surfaces facing fusion relevant energetic plasma flux. The work has also addressed additional developments along with progressing along the timeline detailed in the proposal. A no-cost extension was requested to conduct other relevant experiment- specifically regarding the characterization droplet ejection during energetic plasma flux impact. A specially designed trench module, which could accommodate trenches with different aspect ratios was fabricated and installed in the TELS setup and plasma gun experiments were performed. Droplet ejectionmore » was characterized using high speed image acquisition and also surface mounted probes were used to characterize the plasma. The Gantt chart below had been provided with the original proposal, indicating the tasks to be performed in the third year of funding. These tasks are listed above in the progress report outline, and their progress status is detailed below.« less

BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas

NASA Astrophysics Data System (ADS)

Porkolab, Miklos

1998-11-01

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is somewhat more detailed in certain topics than, and complementary in many fusion research relevant areas to, Stix's book. (I am restricting these comments to the homogeneous plasma theory only, since the author promises a second volume on wave propagation in inhomogeneous plasmas.) This book is also much more of a theorist's approach to waves in plasmas, with the aim of developing the subject within the logical framework of kinetic theory. This may indeed be pleasing to the expert and to the specialist, but may be too difficult to the graduate student as an `introduction' to the subject (which the author explicitly states in the Preface). On the other hand, it may be entirely appropriate for a second course on plasma waves, after the student has mastered fluid theory and an introductory kinetic treatment of waves in a hot magnetized `Vlasov' plasma. For teaching purposes, my personal preference is to review the cold plasma wave treatment using the unified Stix formalism and notation (which the author wisely adopts in the present book, but only in Chapter 5). Such an approach allows one to deal with CMA diagrams early on, as well as to provide a framework to discuss electromagnetic wave propagation and accessibility in inhomogeneous plasmas (for which the cold plasma wave treatment is perfectly adequate). Such an approach does lack some of the rigour, however, that the author achieves with the present approach. As the author correctly shows, the fluid theory treatment of waves follows logically from kinetic theory in the cold plasma limit. I only question the pedagogical value of this approach. Otherwise, I welcome this addition to the literature, for it gives the teacher of the subject a valuable reference where the inquisitive student will be able to read up on and satisfy himself about the practicality and reliability of the Vlasov theory in a hot magnetized and collisionless plasma. The book has excellent treatments of several new topics not included in previous textbooks, for example, the relativistic theory of plasma wave propagation, so important in electron cyclotron heating of magnetically confined fusion plasmas, a discussion of current drive theory and there is a welcome introduction to parametric instabilities in the final chapter. There are some things that make the readability of the book somewhat difficult. In the early parts, certain advanced concepts are introduced without much motivation or explanation, although the author is trying to be helpful by providing a list of relevant references at the end of each chapter. Here the teacher's role will be critical. Again, a certain amount of previous knowledge of the subject would prove to be invaluable to the student. The main content of the book is included in 11 chapters. Use is made of CGS Gaussian units, a favourite of plasma theorists. As the author states, these are still widely used in advanced plasma theory, and the student is well advised to become familiar with this system of units (as well as the SI system for applications). To help the reader in the Introduction, the author defines various expressions often used in plasma physics in practical units (frequencies in hertz, lengths in centimetres, temperatures in kiloelectronvolts and magnetic fields in teslas). Chapter 2 is entitled `Plasma Electrodynamics' and it introduces the Maxwell-Vlasov set of equations, as well as the important fundamentals of wave propagation, such as polarization, dispersion and the dielectric tensor, and energy relations. In Chapter 3, `Elementary Plasma Kinetic Theory', the author derives the Vlasov equation and the Fokker-Planck equation from the BBGKY hierarchy. This is a somewhat unusual chapter in a book on plasma waves, but I welcome it since it demonstrates the author's desire to be complete and rigorous in justifying the use of the collisionless Vlasov equation for `high frequency' wave propagation phenomena. Incidentally, it is interesting that while the author derives the Fokker-Planck equation at great length, it is used only to derive the fluid and MHD equations, but not for estimating Coulomb collisional damping of specific waves in later chapters. Chapter 4 gives the derivation of the hot plasma dielectric tensor. There is an extensive and excellent discussion of the relativistic formulation of the dielectric tensor, which is of fundamental importance to practising fusion physicists (for example) involved in ECR heating of high temperature plasmas. Various temperature limits are taken in Chapters 5, 6 and 7, and the author discusses the infinite number of waves in the cold plasma limit (Chapter 5), in the hot plasma limit (Chapter 6) and in the electrostatic limit (Chapter 7). In my opinion, these chapters represent the `meat' of the book. Chapter 7 includes a detailed treatment of electrostatic waves in a hot plasma, including Bernstein waves and their damping at high harmonics. This is a difficult topic, and the extensive treatment presented here is hard to find in other texts. The author also includes a discussion of two stream instabilities here, together with the Nyquist-Penrose criterion for instability. Chapter 8 discusses linear wave-particle interactions, including damping of electromagnetic waves, RF current drive and RF heating. Chapter 9 is called `Collisionless Stochasticity' and institutes an introduction to the subject as well as applications to the heating of ions by high harmonic, lower hybrid waves. Chapter 10 is another key part of the book, on the quasilinear theory of heating and current drive. It deals with the practical aspects of RF heating and current drive in magnetically confined fusion plasmas, and is a `must read' for researchers dealing with RF heating and related transport. Chapter 11 attempts to deal with non-linear effects in the presence of high power RF waves in plasmas. First, the author deals with the difficult subject of mode coupling theory, but, owing to its complexity, the formulation is never reduced to practical applications. Only the `dipole approximation' section can be used to make practical estimates of non-linear effects during RF heating. There are some shortcomings of this book that need to be mentioned here. There are some typographical errors, including spelling errors. The labelling on the figures is often hard to read due to their poor quality and small size. The figures themselves are often too small and are overloaded with curves (e.g., Figs 18.1, 18.2, 21.3, 28.13). The author must have spent a significant effort in producing these curves, and they deserve a better presentation, especially if they are to be used by students. Ease of readability is important for a textbook intended for students and researchers alike. It is hoped that such shortcomings will be improved in future editions, as well as in Volume II, which is to follow. To summarize, this book presents an up to date major contribution to the field of plasma waves and is a `must' on the shelves of active researchers as well as advanced graduate students. Under the guidance of a knowledgeable teacher, the book may be used as a text, with appropriate omissions of certain sections for a one semester course in plasma waves. Alternatively for those who have mastered the fundamentals of wave propagation in plasmas, the book could be used as a basis for an advanced seminar course. I am looking forward with anticipation to Volume II, Waves in Inhomogeneous Plasmas, by Marco Brambilla, one of the eminent plasma wave theorists of our generation.

Accelerator and Fusion Research Division. Annual report, October 1978-September 1979

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

Not Available

1980-03-01

Topics covered include: Super HILAC and Bevalac operations; high intensity uranium beams line item; advanced high charge state ion source; 184-inch synchrocyclotron; VENUS project; positron-electron project; high field superconducting accelerator magnets; beam cooling; accelerator theory; induction linac drivers; RF linacs and storage rings; theory; neutral beam systems development; experimental atomic physics; neutral beam plasma research; plasma theory; and the Tormac project. (GHT)

Resolving task rule incongruence during task switching by competitor rule suppression.

PubMed

Meiran, Nachshon; Hsieh, Shulan; Dimov, Eduard

2010-07-01

Task switching requires maintaining readiness to execute any task of a given set of tasks. However, when tasks switch, the readiness to execute the now-irrelevant task generates interference, as seen in the task rule incongruence effect. Overcoming such interference requires fine-tuned inhibition that impairs task readiness only minimally. In an experiment involving 2 object classification tasks and 2 location classification tasks, the authors show that irrelevant task rules that generate response conflicts are inhibited. This competitor rule suppression (CRS) is seen in response slowing in subsequent trials, when the competing rules become relevant. CRS is shown to operate on specific rules without affecting similar rules. CRS and backward inhibition, which is another inhibitory phenomenon, produced additive effects on reaction time, suggesting their mutual independence. Implications for current formal theories of task switching as well as for conflict monitoring theories are discussed. (c) 2010 APA, all rights reserved

Understanding disruptions in tokamaksa)

NASA Astrophysics Data System (ADS)

Zakharov, Leonid E.; Galkin, Sergei A.; Gerasimov, Sergei N.; contributors, JET-EFDA

2012-05-01

This paper describes progress achieved since 2007 in understanding disruptions in tokamaks, when the effect of plasma current sharing with the wall was introduced into theory. As a result, the toroidal asymmetry of the plasma current measurements during vertical disruption event (VDE) on the Joint European Torus was explained. A new kind of plasma equilibria and mode coupling was introduced into theory, which can explain the duration of the external kink 1/1 mode during VDE. The paper presents first results of numerical simulations using a free boundary plasma model, relevant to disruptions.

Alterations in theory of mind in patients with schizophrenia and non-psychotic relatives.

PubMed

Janssen, I; Krabbendam, L; Jolles, J; van Os, Jim

2003-08-01

It has been proposed that alterations in theory of mind underlie specific symptoms of psychosis. The present study examined whether alterations in theory of mind reflect a trait that can be detected in non-psychotic relatives of patients with schizophrenia. Participants were 43 patients with schizophrenia or schizoaffective disorder, 41 first-degree non-psychotic relatives and 43 controls from the general population. Theory of mind was assessed using a hinting task and a false-belief task. There was a significant association between schizophrenia risk and failure on the hinting task (OR linear trend = 2.01, 95% CI: 1.22-3.31), with relatives having intermediate values between patients and controls. Adjustment for IQ and neuropsychological factors reduced the association by small amounts. The association between schizophrenia risk and failure on the false-belief tasks was not significant. Changes in theory of mind are associated with schizophrenia liability. General cognitive ability and neuropsychological measures seem to mediate only part of this association.

The Accidental Transgressor: Morally Relevant Theory of Mind

PubMed Central

Killen, Melanie; Mulvey, Kelly Lynn; Richardson, Cameron; Jampol, Noah

2014-01-01

To test young children’s false belief theory of mind in a morally relevant context, two experiments were conducted. In Experiment 1, children (N = 162) at 3.5, 5.5, and 7.5 years of age were administered 3 tasks: prototypic moral transgression task, false belief theory of mind task (ToM), and an “accidental transgressor” task, which measured a morally relevant false belief theory of mind (MoToM). Children who did not pass false belief ToM were more likely to attribute negative intentions to an accidental transgressor than children who passed false belief ToM, and to use moral reasons when blaming the accidental transgressor. In Experiment 2, children (N = 46) who did not pass false belief ToM viewed it as more acceptable to punish the accidental transgressor than did participants who passed false belief ToM. Findings are discussed in light of research on the emergence of moral judgment and theory of mind. PMID:21377148

Tunable polarization plasma channel undulator for narrow bandwidth photon emission

DOE PAGES

Rykovanov, S. G.; Wang, J. W.; Kharin, V. Yu.; ...

2016-09-09

The theory of a plasma undulator excited by a short intense laser pulse in a parabolic plasma channel is presented. The undulator fields are generated either by the laser pulse incident off-axis and/or under the angle with respect to the channel axis. Linear plasma theory is used to derive the wakefield structure. It is shown that the electrons injected into the plasma wakefields experience betatron motion and undulator oscillations. Optimal electron beam injection conditions are derived for minimizing the amplitude of the betatron motion, producing narrow-bandwidth undulator radiation. Polarization control is readily achieved by varying the laser pulse injection conditions.

Situational theory of leadership.

PubMed

Waller, D J; Smith, S R; Warnock, J T

1989-11-01

The situational theory of leadership and the LEAD instruments for determining leadership style are explained, and the application of the situational leadership theory to the process of planning for and implementing organizational change is described. Early studies of leadership style identified two basic leadership styles: the task-oriented autocratic style and the relationship-oriented democratic style. Subsequent research found that most leaders exhibited one of four combinations of task and relationship behaviors. The situational leadership theory holds that the difference between the effectiveness and ineffectiveness of the four leadership styles is the appropriateness of the leader's behavior to the particular situation in which it is used. The task maturity of the individual or group being led must also be accounted for; follower readiness is defined in terms of the capacity to set high but attainable goals, willingness or ability to accept responsibility, and possession of the necessary education or experience for a specific task. A person's leadership style, range, and adaptability can be determined from the LEADSelf and LEADOther questionnaires. By applying the principles of the situational leadership theory and adapting their managerial styles to specific tasks and levels of follower maturity, the authors were successful in implementing 24-hour pharmacokinetic dosing services provided by staff pharmacists with little previous experience in clinical services. The situational leadership model enables a leader to identify a task, set goals, determine the task maturity of the individual or group, select an appropriate leadership style, and modify the style as change occurs. Pharmacy managers can use this model when implementing clinical pharmacy services.

Effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in reversed field pinch plasmas

NASA Astrophysics Data System (ADS)

Guo, S. C.; Chu, M. S.

2002-11-01

The effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in the reversed field pinch (RFP) plasmas are studied. Most RFP machines are equipped with one or more metal shells outside of the vacuum vessel. These shells have finite resistivities. The eddy currents induced in each of the shells contribute to the braking electromagnetic (EM) torque which slows down the plasma rotation. In this work we study the electromagnetic torque acting on the plasma (tearing) modes produced by a system of resistive shells. These shells may consist of several nested thin shells or several thin shells enclosed within a thick shell. The dynamics of the plasma mode is investigated by balancing the EM torque from the resistive shells with the plasma viscous torque. Both the steady state theory and the time-dependent theory are developed. The steady state theory is shown to provide an accurate account of the resultant EM torque if (dω/dt)ω-2≪1 and the time scale of interest is much longer than the response (L/R) time of the shell. Otherwise, the transient theory should be adopted. As applications, the steady state theory is used to evaluate the changes of the EM torque response from the resistive shells in two variants of two RFP machines: (1) modification from Reversed Field Experiment (RFX) [Gnesotto et al., Fusion Eng. Des. 25, 335 (1995)] to the modified RFX: both of them are equipped with one thin shell plus one thick shell; (2) modification from Extrap T2 to Extrap T2R [Brunsell et al., Plasma Phys. Controlled Fusion 43, 1457 (2001)]: both of them are equipped with two thin shells. The transient theory has been applied numerically to study the time evolution of the EM torque during the unlocking of a locked tearing mode in the modified RFX.

Determination of deuterium–tritium critical burn-up parameter by four temperature theory

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

Nazirzadeh, M.; Ghasemizad, A.; Khanbabei, B.

Conditions for thermonuclear burn-up of an equimolar mixture of deuterium-tritium in non-equilibrium plasma have been investigated by four temperature theory. The photon distribution shape significantly affects the nature of thermonuclear burn. In three temperature model, the photon distribution is Planckian but in four temperature theory the photon distribution has a pure Planck form below a certain cut-off energy and then for photon energy above this cut-off energy makes a transition to Bose-Einstein distribution with a finite chemical potential. The objective was to develop four temperature theory in a plasma to calculate the critical burn up parameter which depends upon initialmore » density, the plasma components initial temperatures, and hot spot size. All the obtained results from four temperature theory model are compared with 3 temperature model. It is shown that the values of critical burn-up parameter calculated by four temperature theory are smaller than those of three temperature model.« less

Analysis of plasmas generated by fission fragments. [nuclear pumped lasers and helium plasma

NASA Technical Reports Server (NTRS)

Deese, J. E.; Hassan, H. A.

1977-01-01

A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.

Reliability and validity of advanced theory-of-mind measures in middle childhood and adolescence.

PubMed

Hayward, Elizabeth O; Homer, Bruce D

2017-09-01

Although theory-of-mind (ToM) development is well documented for early childhood, there is increasing research investigating changes in ToM reasoning in middle childhood and adolescence. However, the psychometric properties of most advanced ToM measures for use with older children and adolescents have not been firmly established. We report on the reliability and validity of widely used, conventional measures of advanced ToM with this age group. Notable issues with both reliability and validity of several of the measures were evident in the findings. With regard to construct validity, results do not reveal a clear empirical commonality between tasks, and, after accounting for comprehension, developmental trends were evident in only one of the tasks investigated. Statement of contribution What is already known on this subject? Second-order false belief tasks have acceptable internal consistency. The Eyes Test has poor internal consistency. Validity of advanced theory-of-mind tasks is often based on the ability to distinguish clinical from typical groups. What does this study add? This study examines internal consistency across six widely used advanced theory-of-mind tasks. It investigates validity of tasks based on comprehension of items by typically developing individuals. It further assesses construct validity, or commonality between tasks. © 2017 The British Psychological Society.

Selective social learning in infancy: looking for mechanisms.

PubMed

Crivello, Cristina; Phillips, Sara; Poulin-Dubois, Diane

2018-05-01

Although there is mounting evidence that selective social learning begins in infancy, the psychological mechanisms underlying this ability are currently a controversial issue. The purpose of this study is to investigate whether theory of mind abilities and statistical learning skills are related to infants' selective social learning. Seventy-seven 18-month-olds were first exposed to a reliable or an unreliable speaker and then completed a word learning task, two theory of mind tasks, and a statistical learning task. If domain-general abilities are linked to selective social learning, then infants who demonstrate superior performance on the statistical learning task should perform better on the selective learning task, that is, should be less likely to learn words from an unreliable speaker. Alternatively, if domain-specific abilities are involved, then superior performance on theory of mind tasks should be related to selective learning performance. Findings revealed that, as expected, infants were more likely to learn a novel word from a reliable speaker. Importantly, infants who passed a theory of mind task assessing knowledge attribution were significantly less likely to learn a novel word from an unreliable speaker compared to infants who failed this task. No such effect was observed for the other tasks. These results suggest that infants who possess superior social-cognitive abilities are more apt to reject an unreliable speaker as informant. A video abstract of this article can be viewed at: https://youtu.be/zuuCniHYzqo. © 2017 John Wiley & Sons Ltd.

Intergenerational Transmission of Theory-of-Mind

ERIC Educational Resources Information Center

Sabbagh, Mark A.; Seamans, Elizabeth L.

2008-01-01

We examined whether individual differences in children's performance on a scaled battery of theory-of-mind tasks was predicted by parents' performance on an adult theory-of-mind task. Forty-six 3-year-old children and their parents participated in this study when children were aged 2;11 to 4;0. Thirty dyads returned 6 months later for a second…

I can do that: the impact of implicit theories on leadership role model effectiveness.

PubMed

Hoyt, Crystal L; Burnette, Jeni L; Innella, Audrey N

2012-02-01

This research investigates the role of implicit theories in influencing the effectiveness of successful role models in the leadership domain. Across two studies, the authors test the prediction that incremental theorists ("leaders are made") compared to entity theorists ("leaders are born") will respond more positively to being presented with a role model before undertaking a leadership task. In Study 1, measuring people's naturally occurring implicit theories of leadership, the authors showed that after being primed with a role model, incremental theorists reported greater leadership confidence and less anxious-depressed affect than entity theorists following the leadership task. In Study 2, the authors demonstrated the causal role of implicit theories by manipulating participants' theory of leadership ability. They replicated the findings from Study 1 and demonstrated that identification with the role model mediated the relationship between implicit theories and both confidence and affect. In addition, incremental theorists outperformed entity theorists on the leadership task.

Silent films and strange stories: theory of mind, gender, and social experiences in middle childhood.

PubMed

Devine, Rory T; Hughes, Claire

2013-01-01

In this study of two hundred and thirty 8- to 13-year-olds, a new "Silent Films" task is introduced, designed to address the dearth of research on theory of mind in older children by providing a film-based analogue of F. G. E. Happé's (1994) Strange Stories task. Confirmatory factor analysis showed that all items from both tasks loaded onto a single theory-of-mind latent factor. With effects of verbal ability and family affluence controlled, theory-of-mind latent factor scores increased significantly with age, indicating that mentalizing skills continue to develop through middle childhood. Girls outperformed boys on the theory-of-mind latent factor, and the correlates of individual differences in theory of mind were gender specific: Low scores were related to loneliness in girls and to peer rejection in boys. © 2012 The Authors. Child Development © 2012 Society for Research in Child Development, Inc.

Neuropsychological correlates of theory of mind in patients with early Parkinson's disease.

PubMed

Santangelo, Gabriella; Vitale, Carmine; Trojano, Luigi; Errico, Domenico; Amboni, Marianna; Barbarulo, Anna Maria; Grossi, Dario; Barone, Paolo

2012-01-01

The theory of mind is the ability to attribute mental states to oneself and others and to understand that others have beliefs, desires and intentions different from one's own. The aim of the study was to explore the neuropsychological correlates of theory of mind in patients affected by early Parkinson's disease (PD). Thirty-three PD patients and 33 age-, sex-, and education-matched control subjects underwent the Frontal Assessment Battery, as well as tasks assessing "cognitive" and "affective" theory of mind, and memory abilities; questionnaires evaluating behavioral disorders and quality of life were also administrated. Although the 2 groups did not differ on neuropsychological tasks, PD patients' performance on tasks assessing cognitive and affective theory of mind was significantly worse than controls. Moreover, PD patients had more behavioral disorders and worse quality of life than controls. After covarying for behavioral and quality of life scores, the differences between patients and controls on theory of mind tasks remained significant. "Cognitive" theory of mind was associated with Frontal Assessment Battery score and 2 domains of quality of life scale, whereas "affective" theory of mind scores correlated only with behavioral scales such as the Frontal Behavioral Inventory and Apathy Evaluation Scale. The results demonstrate that both affective and cognitive aspects of theory of mind are simultaneously impaired in early PD and suggest that deficits in the 2 subcomponents of theory of mind may be linked to dysfunction of different frontosubcortical circuitries in early PD. Copyright © 2011 Movement Disorder Society.

Waves and instabilities in plasmas

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

Chen, L.

1987-01-01

The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations.

Decision theory and the evaluation of risks and benefits of clinical trials.

PubMed

Bernabe, Rosemarie D C; van Thiel, Ghislaine J M W; Raaijmakers, Jan A M; van Delden, Johannes J M

2012-12-01

Research ethics committees (RECs) are tasked to assess the risks and the benefits of a clinical trial. In previous studies, it was shown that RECs find this task difficult, if not impossible, to do. The current approaches to benefit-risk assessment (i.e. Component Analysis and the Net Risk Test) confound the various risk-benefit tasks, and as such, make balancing impossible. In this article, we show that decision theory, specifically through the expected utility theory and multiattribute utility theory, enable for an explicit and ethically weighted risk-benefit evaluation. This makes a balanced ethical justification possible, and thus a more rationally defensible decision making. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Role of Control Functions in Mentalizing: Dual-Task Studies of Theory of Mind and Executive Function

ERIC Educational Resources Information Center

Bull, Rebecca; Phillips, Louise H.; Conway, Claire A.

2008-01-01

Conflicting evidence has arisen from correlational studies regarding the role of executive control functions in Theory of Mind. The current study used dual-task manipulations of executive functions (inhibition, updating and switching) to investigate the role of these control functions in mental state and non-mental state tasks. The "Eyes"…

One Task, Divergent Solutions: High- versus Low-Status Sources and Social Comparison Guide Adaptation in a Computer-Supported Socio-Cognitive Conflict Task

ERIC Educational Resources Information Center

Baumeister, Antonia E.; Engelmann, Tanja; Hesse, Friedrich W.

2017-01-01

This experimental study extends conflict elaboration theory (1) by revealing social influence dynamics for a knowledge-rich computer-supported socio-cognitive conflict task not investigated in the context of this theory before and (2) by showing the impact of individual differences in social comparison orientation. Students in two conditions…

Cost of Purchased Versus Produced Plasma from Donor Recruitment Through Transfusion.

PubMed

Prioli, Katherine M; Pizzi, Laura T; Karp, Julie Katz; Galanis, Taki; Herman, Jay H

2016-10-01

Plasma is used to treat acquired coagulopathy or thrombotic thrombocytopenic purpura, or to reverse warfarin effect. Scant data are available, however, about its costs. To estimate total costs of plasma from production through administration, from the perspective of a US hospital blood donor center (BDC). Six sequential decision analytic models were constructed and informed by primary and secondary data on time, tasks, personnel, and supplies for donation, processing, and administration. Expected values of the models were summed to yield the BDC's total cost of producing, preparing, and transfusing plasma. Costs ($US 2015) are reported for a typical patient using three units of plasma. Models assume plasma was obtained from whole blood donation and transfused in an inpatient setting. Univariate sensitivity analyses were performed to test the impact of changing inputs for personnel costs and adverse event (AE) rates and costs. BDC production cost of plasma was $91.24/patient ($30.41/unit), a $30.16/patient savings versus purchased plasma. Administration and monitoring costs totaled $194.64/patient. Sensitivity analyses indicated that modifying BDC personnel costs during donation and processing has little impact on total plasma costs. However, the probability and cost of transfusion-associated circulatory overload (TACO) have a significant impact on costs. Plasma produced by our BDC may be less costly than purchased plasma. Though plasma processes have multiple tasks involving staff time, these are not the largest cost driver. Major plasma-related AEs are uncommon, but are the biggest driver of total plasma costs.

Parental investment theory and gender differences in the evolution of inhibition mechanisms.

PubMed

Bjorklund, D F; Kipp, K

1996-09-01

Based on the tenets of parental investment theory, the authors postulate that there was greater pressure to inhibit potentially maladaptive emotional, social, and sexual responses on prehistoric women than men in some contexts, resulting in enhanced inhibitory abilities in women in some domains. They reviewed studies whose researchers examined gender differences on social, behavioral, and cognitive tasks involving inhibition and found gender differences favoring female humans most consistent for social tasks (e.g., control of emotions), somewhat less pronounced for behavioral tasks (e.g., delay of gratification), and weak and inconsistent for cognitive tasks (e.g., conceptual tempo). This pattern was interrupted as being consistent with the position that gender differences in inhibition are relatively domain specific in nature, with women demonstrating greater abilities on tasks related to reproduction and childrearing, which is consistent with parental investment theory.

Threaded cognition: an integrated theory of concurrent multitasking.

PubMed

Salvucci, Dario D; Taatgen, Niels A

2008-01-01

The authors propose the idea of threaded cognition, an integrated theory of concurrent multitasking--that is, performing 2 or more tasks at once. Threaded cognition posits that streams of thought can be represented as threads of processing coordinated by a serial procedural resource and executed across other available resources (e.g., perceptual and motor resources). The theory specifies a parsimonious mechanism that allows for concurrent execution, resource acquisition, and resolution of resource conflicts, without the need for specialized executive processes. By instantiating this mechanism as a computational model, threaded cognition provides explicit predictions of how multitasking behavior can result in interference, or lack thereof, for a given set of tasks. The authors illustrate the theory in model simulations of several representative domains ranging from simple laboratory tasks such as dual-choice tasks to complex real-world domains such as driving and driver distraction. (c) 2008 APA, all rights reserved

Similar Brain Activation during False Belief Tasks in a Large Sample of Adults with and without Autism

PubMed Central

Dufour, Nicholas; Redcay, Elizabeth; Young, Liane; Mavros, Penelope L.; Moran, Joseph M.; Triantafyllou, Christina; Gabrieli, John D. E.; Saxe, Rebecca

2013-01-01

Reading about another person’s beliefs engages ‘Theory of Mind’ processes and elicits highly reliable brain activation across individuals and experimental paradigms. Using functional magnetic resonance imaging, we examined activation during a story task designed to elicit Theory of Mind processing in a very large sample of neurotypical (N = 462) individuals, and a group of high-functioning individuals with autism spectrum disorders (N = 31), using both region-of-interest and whole-brain analyses. This large sample allowed us to investigate group differences in brain activation to Theory of Mind tasks with unusually high sensitivity. There were no differences between neurotypical participants and those diagnosed with autism spectrum disorder. These results imply that the social cognitive impairments typical of autism spectrum disorder can occur without measurable changes in the size, location or response magnitude of activity during explicit Theory of Mind tasks administered to adults. PMID:24073267

Similar brain activation during false belief tasks in a large sample of adults with and without autism.

PubMed

Dufour, Nicholas; Redcay, Elizabeth; Young, Liane; Mavros, Penelope L; Moran, Joseph M; Triantafyllou, Christina; Gabrieli, John D E; Saxe, Rebecca

2013-01-01

Reading about another person's beliefs engages 'Theory of Mind' processes and elicits highly reliable brain activation across individuals and experimental paradigms. Using functional magnetic resonance imaging, we examined activation during a story task designed to elicit Theory of Mind processing in a very large sample of neurotypical (N = 462) individuals, and a group of high-functioning individuals with autism spectrum disorders (N = 31), using both region-of-interest and whole-brain analyses. This large sample allowed us to investigate group differences in brain activation to Theory of Mind tasks with unusually high sensitivity. There were no differences between neurotypical participants and those diagnosed with autism spectrum disorder. These results imply that the social cognitive impairments typical of autism spectrum disorder can occur without measurable changes in the size, location or response magnitude of activity during explicit Theory of Mind tasks administered to adults.

Theory of mind and central coherence in adults with high-functioning autism or Asperger syndrome.

PubMed

Beaumont, Renae; Newcombe, Peter

2006-07-01

The study investigated theory of mind and central coherence abilities in adults with high-functioning autism (HFA) or Asperger syndrome (AS) using naturalistic tasks. Twenty adults with HFA/AS correctly answered significantly fewer theory of mind questions than 20 controls on a forced-choice response task. On a narrative task, there were no differences in the proportion of mental state words between the two groups, although the participants with HFA/AS were less inclined to provide explanations for characters' mental states. No between-group differences existed on the central coherence questions of the forced-choice response task, and the participants with HFA/AS included an equivalent proportion of explanations for non-mental state phenomena in their narratives as did controls. These results support the theory of mind deficit account of autism spectrum disorders, and suggest that difficulties in mental state attribution cannot be exclusively attributed to weak central coherence.

Research on Radiation Characteristic of Plasma Antenna through FDTD Method

PubMed Central

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic. PMID:25114961

Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder

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

Galatà, A., E-mail: alessio.galata@lnl.infn.it; Patti, G.; Celona, L.

2016-02-15

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which themore » selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.« less

Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder

NASA Astrophysics Data System (ADS)

Galatà, A.; Patti, G.; Celona, L.; Mascali, D.; Neri, L.; Torrisi, G.

2016-02-01

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.

Energetic particle-driven compressional Alfvén eigenmodes and prospects for ion cyclotron emission studies in fusion plasmas

DOE PAGES

Gorelenkov, N. N.

2016-10-01

As a fundamental plasma oscillation the compressional Alfvén waves (CAW) are interesting for plasma scientists both academically and in applications for fusion plasmas. They are believed to be responsible for the ion cyclotron emission (ICE) observed in many tokamaks. The theory of CAW and ICE was significantly advanced at the end of 20th century in particular motivated by first DT experiments on TFTR and subsequent JET DT experimental studies. More recently, ICE theory was advanced by ST (or spherical torus) experiments with the detailed theoretical and experimental studies of the properties of each instability signal. There the instability responsible formore » ICE signals previously indistinguishable in high aspect ratio tokamaks became the subjects of experimental studies. We discuss further the prospects of ICE theory and its applications for future burning plasma (BP) experiments such as the ITER tokamak-reactor prototype being build in France where neutrons and gamma rays escaping the plasma create extremely challenging conditions for fusion alpha particle diagnostics.a« less

Vibrational Modes of Oblate Clouds of Charge

NASA Astrophysics Data System (ADS)

Jenkins, Thomas; Spencer, Ross L.

2000-10-01

When a nonneutral plasma confined in a Penning trap is allowed time to expand, its shape at global thermal equilibrium is that of a thin oblate spheroid [D. L. Paulson et al., Phys. Plasmas 5, 345 (1998)]. Oscillations similar to those of a drumhead can be externally induced in such a plasma. Although a theory developed by Dubin predicts the frequencies of the various normal modes of oscillation [Phys. Rev. Lett. 66, 2076 (1991)], this theory assumes that the plasma has zero temperature and is confined by an ideal quadrupole electric field. Neither of these conditions is strictly true in experiments [C. S. Weimer et al., Phys. Rev. A 49, 3842 (1994)] where physical properties of the plasma are deduced from measurements of these frequencies, causing the measurements and ideal theory to differ by about 20%. We reformulate the problem of the normal oscillatory modes as a principal-value integral eigenvalue equation, including finite-temperature and non-ideal confinement effects. The equation is solved numerically to obtain the plasma's normal mode frequencies and shapes; reasonable agreement with experiment is obtained.

Space plasma branch at NRL

NASA Astrophysics Data System (ADS)

The Naval Research Laboratory (Washington, D.C.) formed the Space Plasma Branch within its Plasma Physics Division on July 1. Vithal Patel, former Program Director of Magnetospheric Physics, National Science Foundation, also joined NRL on the same date as Associate Superintendent of the Plasma Physics Division. Barret Ripin is head of the newly organized branch. The Space Plasma branch will do basic and applied space plasma research using a multidisciplinary approach. It consolidates traditional rocket and satellite space experiments, space plasma theory and computation, with laboratory space-related experiments. About 40 research scientists, postdoctoral fellows, engineers, and technicians are divided among its five sections. The Theory and Computation sections are led by Joseph Huba and Joel Fedder, the Space Experiments section is led by Paul Rodriguez, and the Pharos Laser Facility and Laser Experiments sections are headed by Charles Manka and Jacob Grun.

Task performance in astronomical adaptive optics

NASA Astrophysics Data System (ADS)

Barrett, Harrison H.; Myers, Kyle J.; Devaney, Nicholas; Dainty, J. C.; Caucci, Luca

2006-06-01

In objective or task-based assessment of image quality, figures of merit are defined by the performance of some specific observer on some task of scientific interest. This methodology is well established in medical imaging but is just beginning to be applied in astronomy. In this paper we survey the theory needed to understand the performance of ideal or ideal-linear (Hotelling) observers on detection tasks with adaptive-optical data. The theory is illustrated by discussing its application to detection of exoplanets from a sequence of short-exposure images.

Final Scientific/Technical Report: Correlations and Fluctuations in Weakly Collisional Plasma

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

Skiff, Frederick

Plasma is a state of matter that exhibits a very rich range of phenomena. To begin with, plasma is both electrical and mechanical - bringing together theories of particle motion and the electromagnetic field. Furthermore, and especially important for this project, a weakly-collisional plasma, such as is found in high-temperature (fusion energy) experiments on earth and the majority of contexts in space and astrophysics, has many moving parts. For example, sitting in earth’s atmosphere we are immersed in a mechanical wave field (sound), a possibly turbulent fluid motion (wind), and an electromagnetic vector wave field with two polarizations (light). Thismore » is already enough to produce a rich range of possibilities. In plasma, the electromagnetic field is coupled to the mechanical motion of the medium because it is ionized. Furthermore, a weakly-collisional plasma supports an infinite number of mechanically independent fluids. Thus, plasmas support an infinite number of independent electromechanical waves. Much has been done to describe plasmas with "reduced models" of various kinds. The goal of this project was to both explore the validity of reduced plasma models that are in use, and to propose and validate new models of plasma motion. The primary means to his end was laboratory experiments employing both electrical probes and laser spectroscopy. Laser spectroscopy enables many techniques which can separate the spectrum of independent fluid motions in the ion phase-space. The choice was to focus on low frequency electrostatic waves because the electron motion is relatively simple, the experiments can be on a spatial scale of a few meters, and all the relevant parameters can be measured with a few lasers systems. No study of this kind had previously been undertaken for the study of plasmas. The validation of theories required that the experimental descriptions be compared with theory and simulation in detail. It was found that even multi-fluid theories leave out a large part of the complexity of plasma motion. Reduced descriptions were found to fail under most circumstances. A new technique was developed that enabled a measurement of the phase-space resolved ion correlation function for the first time. The wide range of plasma dynamics possible became clear through this technique. It was found that collisionless (Vlasov) theory has a large field of application even when the plasma is weakly-collisional. A new approach, the kinetic wave expansion, was proposed, tested and found to be very useful for describing electrostatic ion waves. This project demonstrated a new way of looking at the "degrees-of-freedom" of plasmas and provided significant validation tests of fluid and kinetic plasma descriptions.« less

Langmuir-Probe Measurements in Flowing-Afterglow Plasmas

NASA Technical Reports Server (NTRS)

Johnsen, R.; Shunko, E. V.; Gougousi, T.; Golde, M. F.

1994-01-01

The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing- afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

Laboratory Investigation of Space and Planetary Dust Grains

NASA Technical Reports Server (NTRS)

Spann, James

2005-01-01

Dust in space is ubiquitous and impacts diverse observed phenomena in various ways. Understanding the dominant mechanisms that control dust grain properties and its impact on surrounding environments is basic to improving our understanding observed processes at work in space. There is a substantial body of work on the theory and modeling of dust in space and dusty plasmas. To substantiate and validate theory and models, laboratory investigations and space borne observations have been conducted. Laboratory investigations are largely confined to an assembly of dust grains immersed in a plasma environment. Frequently the behaviors of these complex dusty plasmas in the laboratory have raised more questions than verified theories. Space borne observations have helped us characterize planetary environments. The complex behavior of dust grains in space indicates the need to understand the microphysics of individual grains immersed in a plasma or space environment.

The Relation between Acquisition of a Theory of Mind and the Capacity to Hold in Mind.

ERIC Educational Resources Information Center

Gordon, Anne C. L.; Olson, David R.

1998-01-01

Tested hypothesized relationship between development of a theory of mind and increasing computational resources in 3- to 5-year olds. Found that the correlations between performance on theory of mind tasks and dual processing tasks were as high as r=.64, suggesting that changes in working memory capacity allow the expression of, and arguably the…

The relationship between vocabulary, grammar, and false belief task performance in children with autistic spectrum disorders and children with moderate learning difficulties.

PubMed

Fisher, Naomi; Happé, Francesca; Dunn, Judy

2005-04-01

The aim of this study was to examine the relationship between language and theory of mind in children with autistic spectrum disorders (ASD) and children with moderate learning difficulties (MLD). Previous studies have found a strong association between language and theory of mind in a range of groups, but mostly have not included measures of both grammar and vocabulary; including these enables us to speculate about the causal direction of the relationship. Fifty-eight children with ASD and 118 children with MLD were given standardised assessments of vocabulary and grammar, along with standard theory of mind tasks. The relationship between language and theory of mind was more evident in children with ASD than in those with MLD, and grammar was a particularly strong predictor of theory of mind performance in children with ASD. Children with MLD performed better on false belief (FB) tasks than did children with ASD, and their performance was more predictable across the different theory of mind tasks. Language, in particular grammar, and theory of mind appear to be more strongly related in children with ASD than in those with MLD. We speculate that this relationship may be causal, with some grammatical understanding being a precursor of theory of mind. The implications of these findings are discussed in relation to possible routes for compensatory strategies for mentalising in children with ASD.

The hierarchy of task decision and response selection: a task-switching event related potentials study.

PubMed

Braverman, Ami; Berger, Andrea; Meiran, Nachshon

2014-07-01

According to "hierarchical" multi-step theories, response selection is preceded by a decision regarding which task rule should be executed. Other theories assume a "flat" single-step architecture in which task information and stimulus information are simultaneously considered. Using task switching, the authors independently manipulated two kinds of conflict: task conflict (with information that potentially triggers the relevant or the competing task rule/identity) and response conflict (with information that potentially triggers the relevant or the competing response code/motor response). Event related potentials indicated that the task conflict effect began before the response conflict effect and carried on in parallel with it. These results are more in line with the hierarchical view. Copyright © 2014 Elsevier Inc. All rights reserved.

Language and Theory of Mind in Autism Spectrum Disorder: The Relationship between Complement Syntax and False Belief Task Performance

ERIC Educational Resources Information Center

Lind, Sophie E.; Bowler, Dermot M.

2009-01-01

This study aimed to test the hypothesis that children with autism spectrum disorder (ASD) use their knowledge of complement syntax as a means of "hacking out" solutions to false belief tasks, despite lacking a representational theory of mind (ToM). Participants completed a "memory for complements" task, a measure of receptive vocabulary, and…

Silent Films and Strange Stories: Theory of Mind, Gender, and Social Experiences in Middle Childhood

ERIC Educational Resources Information Center

Devine, Rory T.; Hughes, Claire

2013-01-01

In this study of two hundred and thirty 8- to 13-year-olds, a new "Silent Films" task is introduced, designed to address the dearth of research on theory of mind in older children by providing a film-based analogue of F. G. E. Happe's (1994) Strange Stories task. Confirmatory factor analysis showed that all items from both tasks loaded…

Tracking speakers' false beliefs: is theory of mind available earlier for word learning?

PubMed

Houston-Price, Carmel; Goddard, Kate; Séclier, Catherine; Grant, Sally C; Reid, Caitlin J B; Boyden, Laura E; Williams, Rhiannon

2011-07-01

Happé and Loth (2002) describe word learning as a 'privileged domain' in the development of a theory of mind. We test this claim in a series of experiments based on the Sally-Anne paradigm. Three- and 4-year-old children's ability to represent others' false beliefs was investigated in tasks that required the child either to predict the actions of a protagonist in a story or to learn the meaning of a new word used by the protagonist. Experiment 1 replicated previous findings of better performance in a false belief word-learning task compared to a false belief action-prediction task. However, systematic manipulation of the task parameters in Experiments 2 and 3 revealed that this performance discrepancy disappeared when tasks were equated in their 'referential pull' (Perner, Rendl & Garnham, 2007). We conclude that the notion of a precocious theory of mind for word learning is not required to explain dissociations in performance on false belief tasks. © 2010 Blackwell Publishing Ltd.

Effects of anxiety on task switching: evidence from the mixed antisaccade task.

PubMed

Ansari, Tahereh L; Derakshan, Nazanin; Richards, Anne

2008-09-01

According to the attentional control theory of anxiety (Eysenck, Derakshan, Santos, & Calvo, 2007), anxiety impairs performance on cognitive tasks that involve the shifting function of working memory. This hypothesis was tested using a mixed antisaccade paradigm, in which participants performed single-task and mixed-task versions of the paradigm. The single task involved the completion of separate blocks of anti- and prosaccade trials, whereas in the mixed task, participants completed anti- and prosaccade trials in a random order within blocks. Analysis of switch costs showed that high-anxious individuals did not exhibit the commonly reported paradoxical improvement in saccade latency, whereas low-anxious individuals did. The findings are discussed within the framework of attentional control theory.

Metacognitive development of deaf children: lessons from the appearance-reality and false belief tasks.

PubMed

Courtin, Cyril; Melot, Anne-Marie

2005-01-01

'Theory of mind' development is now an important research field in deaf studies. Past research with the classic false belief task has consistently reported a delay in theory of mind development in deaf children born of hearing parents, while performance of second-generation deaf children is more problematic with some contradictory results. The present paper is aimed at testing the metacognitive abilities of deaf children on two tasks: the appearance-reality paradigm designed by Flavell, Flavell and Green (1983) and the classic false belief inference task (Wimmer & Perner, 1983; Hogrefe, Wimmer & Perner, 1986). Twenty-eight second-generation deaf children, 60 deaf children of hearing parents and 36 hearing children, aged 5 to 7, were tested and compared on three appearance-reality and three false belief items. Results show that early exposure to language, be it signed or oral, facilitates performance on the two theory of mind tasks. In addition, native signers equal hearing children in the appearance-reality task while surpassing them on the false belief one. The differences of performance patterns in the two tasks are discussed in terms of linguistic and metarepresentational development.

Task complexity, posture, age, sex: which is the main factor influencing manual laterality in captive Cercocebus torquatus torquatus?

PubMed

Laurence, Agathe; Wallez, Catherine; Blois-Heulin, Catherine

2011-09-01

Behavioural asymmetries reflect brain asymmetry in nonhuman primates (NHP) as in humans. By investigating manual laterality, researchers can study the evolution of brain hemisphere specialisation. Three dominant theories aim to establish an evolutionary scenario. The most recent theory relates different levels of manual laterality to task complexity. Our investigation aimed to evaluate the importance of two extrinsic factors (posture and the need for manual coordination) and two intrinsic factors (age and sex) on the expression of manual laterality by red-capped mangabeys. We observed 19 captive-born mangabeys, in spontaneous situations and under experimental conditions (seven experimental tasks varying in complexity). No directionality was observed in hand preference at the group level whatever the task. But our data revealed an effect of task complexity: more subjects were lateralised than not lateralised for the bipedal task and for the three most complex tasks. Finally, we evidenced an age and a sex effect. We compare our results with data for several other primate species and discuss them in the light of different manual laterality theories.

CONFERENCE DESCRIPTION Theory of Fusion Plasmas: Varenna-Lausanne International Workshop

NASA Astrophysics Data System (ADS)

Garbet, X.; Sauter, O.

2010-12-01

The Joint Varenna-Lausanne international workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favourable for informal and in-depth discussions. Invited and contributed papers present state-of-the-art research in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always welcomes a fruitful mix of experienced researchers and students, to allow a better understanding of the key theoretical physics models and applications. Theoretical issues related to burning plasmas Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive Macroinstabilities Plasma-Edge Physics and Divertors Fast particles instabilities Further details: http://Varenna-Lausanne.epfl.ch The conference is organized by: Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Association EURATOM - Confédération Suisse 'Piero Caldirola' International Centre for the Promotion of Science and International School of Plasma Physics Istituto di Fisica del Plasma del CNR, Milano Editors: X Garbet (CEA, Cadarache, France) and O Sauter (CRPP-EPFL, Lausanne, Switzerland)

BOOK REVIEW: Introduction to Plasma Physics: With Space and Laboratory Applications

NASA Astrophysics Data System (ADS)

Browning, P. K.

2005-07-01

A new textbook on plasma physics must be very welcome, as this will encourage the teaching of courses on the subject. This book is written by two experts in their fields, and is aimed at advanced undergraduate and postgraduate courses. There are of course many other plasma physics textbooks available. The niche which this particular book fills is really defined by its subtitle: that is, `with space and laboratory applications'. This differs from most other books which tend to emphasise either space or fusion applications (but not both) or to concentrate only on general theory. Essentially, the emphasis here is on fundamental plasma physics theory, but applications are given from time to time. For example, after developing Alfvén wave theory, observations of Alfvén waves in the solar wind and in the Jovian magnetosphere are presented; whilst ion acoustic cylcotron waves are illustrated by data from a laboratory Q machine. It is fair to say that examples from space seem to predominate. Nevertheless, the approach of including a broad range of applications is very good from an educational point of view, and this should help to train a generation of students with a grasp of fundamental plasma physics who can work in a variety of research fields. The subject coverage of the book is fairly conventional and there are no great surprises. It begins, inevitably, with a discussion of plasma parameters (Debye length etc) and of single particle motions. Both kinetic theory and magnetohydrodynamics are introduced. Waves are quite extensively discussed in several chapters, including both cold and hot plasmas, magnetised and unmagnetised. Nonlinear effects—a large subject!—are briefly discussed. A final chapter deals with collisions in fully ionised plasmas. The choice of contents of a textbook is always something of a matter of personal choice. It is easy to complain about what has been left out, and everyone has their own favourite topics. With that caveat, I would question whether the rather heavy emphasis on waves is optimal. Newcomers to plasma physics could be left with the impression that plasma physics is mainly a collection of dispersion relations. On the other hand, there is almost no mention of two fluid theory, surely an important subject. Topics relevant to fusion edge plasmas, a subject of growing research interest, are not mentioned at all (for example, sheath theory; also partially ionised plasmas, which are also of course very relevant in space applications). And I am surprised that the discussion of MHD stability does not even mention the kink instability, which is of primary importance both in fusion and solar plasmas. The book is clearly set out and easy to read. Diagrams are clear and helpful. Derivations are properly explained, without leaving too many missing steps. From the point of view of a textbook, it is useful that not too much mathematical knowledge is assumed; for example, when it is needed, the theory of Laplace transforms is explained. A nice feature—very important for a text book—is the presence of end-of-chapter problems. These will be very useful for both students and teachers! It is also good that each chapter has a comprehensive list of references, which might be used to direct more advanced students to the up-to-date scientific literature, as well as suggestions for further reading. Although the primary emphasis is on standard, `classical' plasma physics, a good attempt is made to present more recent aspects of the subject. For example, after presenting the standard theory of particle orbits—which usefully includes a discussion of Hamiltonian theory as well as guiding centre theory—there is an introduction to the topic of chaotic orbits. Such material is important from an educational point of view, so that from the very beginning students are made aware that plasma physics is a living subject. Overall, this is a very useful addition to the literature. I would recommend it for adoption as a course text for those teaching courses in plasma physics. It would also be a useful book for reference or self study for those working in the field, particularly new postgraduate students.

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

Morgan, O.B. Jr.; Berry, L.A.; Sheffield, J.

This annual report on fusion energy discusses the progress on work in the following main topics: toroidal confinement experiments; atomic physics and plasma diagnostics development; plasma theory and computing; plasma-materials interactions; plasma technology; superconducting magnet development; fusion engineering design center; materials research and development; and neutron transport. (LSP)

Spatial cognition in autism spectrum disorders: superior, impaired, or just intact?

PubMed

Edgin, Jamie O; Pennington, Bruce F

2005-12-01

The profile of spatial ability is of interest across autism spectrum disorders (ASD) because of reported spatial strengths in ASD and due to the recent association of Asperger's syndrome with Nonverbal Learning Disability. Spatial functions were examined in relation to two cognitive theories in autism: the central coherence and executive function (EF) theories. Performance on spatial tasks, EFs, and global/local processing was compared in children with ASD and controls. While the ASD group had faster reaction times on the Embedded Figures task, spatial performance was intact, but not superior, on other tasks. There was no evidence for impairments in EF or in processing global/local information, therefore contradicting these two theories. The implications of these results for these two theories are discussed.

Social motivation and implicit theory of mind in children with autism spectrum disorder.

PubMed

Burnside, Kimberly; Wright, Kristyn; Poulin-Dubois, Diane

2017-11-01

According to the social motivation theory of autism, children who develop Autism Spectrum Disorder (ASD) have early deficits in social motivation, which is expressed by decreased attention to social information. These deficits are said to lead to impaired socio-cognitive development, such as theory of mind (ToM). There is little research focused on the relation between social motivation and ToM in this population. The goal of the present study was to investigate the link between one aspect of social motivation, social orienting, and ToM in preschoolers with ASD. It was expected that, in contrast to typically developing (TD) children, children with ASD would show impaired performance on tasks measuring social orienting and ToM. It was also expected that children's performance on the social orienting tasks would be correlated with their performance on the ToM task. A total of 17 children with ASD and 16 TD children participated in this study. Participants completed two social orienting tasks, a face preference task and a biological motion preference task, as well an implicit false belief task. Results reveal that TD children, but not children with ASD, exhibited social preference as measured by a preference for faces and biological motion. Furthermore, children with ASD tended to perform worse on the ToM task compared to their TD counterparts. Performance on the social motivation tasks and the ToM task tended to be related but only for the TD children. These findings suggest that ToM is multifaceted and that motivational deficits might have downstream effects even on implicit ToM. Autism Res 2017, 10: 1834-1844. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. The goal of the present study was to examine the link between poor attention to social information and mindreading abilities in children with autism spectrum disorder (ASD). Results demonstrated that children with ASD tended to perform worse than neurotypical children on both social orienting and theory of mind tasks. Preference for human faces and motion tended to be related but only for the neurotypical children. These findings provide partial support for the social motivation theory. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Theories of Motivation--Borrowing the Best.

ERIC Educational Resources Information Center

Terpstra, David E.

1979-01-01

Five theories of motivation are discussed: Maslow's Need Hierarchy, Herzberg's dual-factor or motivation-hygiene theory, goal setting or task motivation, expectancy/valence-theory (also known as instrumentality theory, valence-instrumentality-expectancy theory, or expectancy theory), and reinforcement. (JH)

PREFACE: 1982 International Conference on Plasma Physics

NASA Astrophysics Data System (ADS)

Wilhelmsson, Hans

1982-01-01

Invited Papers: The Physics of Hot Plasmas During the last decade a dramatic evolution of plasma physics has occurred. Not only have gigantic fusion plasma machines been planned, and are now being built, and elaborate spaceships and antenna systems been constructed to explore remote parts of the cosmos; new observations have revealed fascinating structures in space, ranging from pulsar plasmas under extreme conditions in very strong magnetic fields to large-scale magnetic field and electric current systems in cosmic plasmas. X-rays from very distant sources as well as radio-waves from the plasma in the magnetosphere and in the Aurora have recently been studied with new observational techniques. Ingenious laboratory experiments are continuously being carried out to exploit new fundamental processes in plasmas. These are of great interest for the basic understanding of plasmas and also have immediate consequences for applications, like plasma heating and diagnostics. The theoretical description of new plasma phenomena, and of the plasma state in general poses challenging problems, particularly in situations where high concentration of energy is located in the plasmas. Nonlinear wave analysis and turbulence theory have accordingly been extensively developed to describe in particular the collective plasma phenomena. New concepts have been envisaged like plasma solitons, which may be thought of as excitations of local concentrations of longitudinal plasma waves which turn out to be particularly stable. More and more sophisticated structures of nonlinear nature are being revealed by means of high capacity computer facilities. Simulation experiments allow for studies of chaotic behaviour of plasma particles. Related fields of activity form new trends in the development of plasma theory. The programme of the 1982 International Conference on Plasma Physics, which was held in Göteborg, Sweden, stressed the role of the Physics of Hot Plasmas. Studies of such plasmas are essential, not only for fusion energy development, but also for astro- and space research. Plasmas in different situations often have important features in common. Results obtained under various conditions, in the laboratory or in space, should therefore be compared and interrelated. The Göteborg conference emphasized more than the previous one, which was held in Nagoya, Japan, the astro- and space aspects, but there were still more contributions from the fusion and laboratory research. The fundamental plasma theory part was, however, the most extensive one in the programme. At the conference there were seventy invited talks, including six comprehensive talks addressed to all participants. The remaining sixtyfour invited talks were topical talks. Besides, we had received about 450 contributed papers. About 300 of them were given as posters, and most of the remaining ones were presented as orals. The set of one page abstracts of these contributed papers as well as the titles of the invited talks were collected in two volumes, which were sent to all participants a month before the conference. Another set, the four page papers, which had been carefully prepared by the authors for photoreproduction to one page papers, were published in a volume of proceedings of some 460 pages available at the conference. When trying to classify the contributions, it turned out that they fell naturally into four main categories, namely: General Theory Space and Astro Plasmas Fusion Laboratory Plasmas For practical reasons we had to divide the Abstracts into two Volumes, the first one including categories (1) and (2), and the second one the two remaining categories (3) and (4). In publishing the invited talks from the conference we had to handle a great number of extensive papers. It turned out to be natural to have also the invited papers published in two parts, as two separate numbers of Physica Scripta, the first one devoted to (1) General Theory, and (2) Space and Astro Plasmas, whereas the second one to (3) Fusion and (4) Laboratory Plasmas. The 1982 International Conference on Plasma Physics was organized by Chalmers University of Technology. It gathered about 500 participants from 40 countries. Large delegations came from the USA, France, West Germany, Japan, the USSR, and India, the number of participants from these countries ranging from 100 to 20. Sweden had about 50 participating scientists. There were a total of about 20 from the other Scandinavian countries. The principal sponsor of the conference was IUPAP, the International Union of Pure and Applied Physics. The conference also had a number of co-sponsors like IAU, the International Astronomical Union, URSI, the International Union of Radio Science, EPS, the European Physical Society, and EURATOM-FUSION. The conference was supported by Swedish Industry and Swedish Research Boards. The previous ICPP, held in Nagoya two years ago, was the first attempt to combine two types of conferences: the Plasma Theory Conference, first held in Kiev in the Soviet Union in 1971, and the Waves and Instabilities Congress, held for the first time in Innsbruck, Austria in 1973. As a consequence of the success of the Nagoya conference it was decided by the International Organizing Committee of the ICPP that the 1982 conference should also be of the combined type. The 1982 ICPP in Göteborg was thus a Joint Conference of the Fifth Kiev International Conference in Plasma Theory and the Fifth International Congress on Waves and Instabilities in Plasmas. During the conference in Göteborg the International Organizing Committee had a meeting and it was decided that also the next International Conference on Plasma Physics will be of the combined type. It will be held in Lausanne, Switzerland in 1984. The International Organizing Committee on the 1982 International Conference on Plasma Physics comprised about 40 plasma physics scientists from all over the world, who represented various sections of plasma physics. I would like to thank the active members of the IOC for an efficient and friendly co-operation in deciding about the program of invited speakers and for discussions on the general structure of the conference. Our most cordial thanks are extended to the invited speakers for coming to the conference to deliver such excellent talks and to provide us in good time for printing with so beautifully prepared manuscripts. Symposium on Plasma Theory: Preface Several satellite meetings were arranged following the 1982 International Conference on Plasma Physics in Göteborg. Among them a Symposium on Plasma Theory was held at Aspenäsgården outside Göteborg during three days, June 16-18, 1982. The purpose of the symposium was to discuss problems of current interest in plasma theory with applications to space and astrophysical plasmas as well as to fusion plasmas. A total of fifteen talks were given during the three days, and some very lively discussions arose, notably in the area of plasma turbulence. There were around 30 invited scientists present, about one third from the United States, one third from the Soviet Union, and the rest from England, Japan, and various other countries. This volume of Physica Scripta (2B, 506-595) includes some of the talks which were given at Aspenäsgården. Several of the authors of contributed papers to the 1982 International Conference on Plasma Physics were encouraged to write extended versions of their contributions, and these are also included in this number, as are furthermore some papers, which were prepared during prolonged stays of visiting scientists at our institute in connection with the 1982 ICPP. It is expected that the collection of papers thus assembled will give a general picture of the activities accompanying the main conference and that it will elucidate some trends in the development of plasma theory.

Bayesian Techniques for Plasma Theory to Bridge the Gap Between Space and Lab Plasmas

NASA Astrophysics Data System (ADS)

Crabtree, Chris; Ganguli, Gurudas; Tejero, Erik

2017-10-01

We will show how Bayesian techniques provide a general data analysis methodology that is better suited to investigate phenomena that require a nonlinear theory for an explanation. We will provide short examples of how Bayesian techniques have been successfully used in the radiation belts to provide precise nonlinear spectral estimates of whistler mode chorus and how these techniques have been verified in laboratory plasmas. We will demonstrate how Bayesian techniques allow for the direct competition of different physical theories with data acting as the necessary arbitrator. This work is supported by the Naval Research Laboratory base program and by the National Aeronautics and Space Administration under Grant No. NNH15AZ90I.

Non-Markovian Effects in Turbulent Diffusion in Magnetized Plasmas

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

Zagorodny, Anatoly; Weiland, Jan

2009-10-08

The derivation of the kinetic equations for inhomogeneous plasma in an external magnetic field is presented. The Fokker-Planck-type equations with the non-Markovian kinetic coefficients are proposed. In the time-local limit (small correlation times with respect to the distribution function relaxation time) the relations obtained recover the results known from the appropriate quasilinear theory and the Dupree-Weinstock theory of plasma turbulence. The equations proposed are used to describe zonal flow generation and to estimate the diffusion coefficient for saturated turbulence.

Incoherent scatter radar observations of the ionosphere

NASA Technical Reports Server (NTRS)

Hagfors, Tor

1989-01-01

Incoherent scatter radar (ISR) has become the most powerful means of studying the ionosphere from the ground. Many of the ideas and methods underlying the troposphere and stratosphere (ST) radars have been taken over from ISR. Whereas the theory of refractive index fluctuations in the lower atmosphere, depending as it does on turbulence, is poorly understood, the theory of the refractivity fluctuations in the ionosphere, which depend on thermal fluctuations, is known in great detail. The underlying theory is one of the most successful theories in plasma physics, and allows for many detailed investigations of a number of parameters such as electron density, electron temperature, ion temperature, electron mean velocity, and ion mean velocity as well as parameters pertaining to composition, neutral density and others. Here, the author reviews the fundamental processes involved in the scattering from a plasma undergoing thermal or near thermal fluctuations in density. The fundamental scattering properties of the plasma to the physical parameters characterizing them from first principles. He does not discuss the observation process itself, as the observational principles are quite similar whether they are applied to a neutral gas or a fluctuating plasma.

Theory of mind deficit in adult patients with congenital heart disease.

PubMed

Chiavarino, Claudia; Bianchino, Claudia; Brach-Prever, Silvia; Riggi, Chiara; Palumbo, Luigi; Bara, Bruno G; Bosco, Francesca M

2015-10-01

This article provides the first assessment of theory of mind, that is, the ability to reason about mental states, in adult patients with congenital heart disease. Patients with congenital heart disease and matched healthy controls were administered classical theory of mind tasks and a semi-structured interview which provides a multidimensional evaluation of theory of mind (Theory of Mind Assessment Scale). The patients with congenital heart disease performed worse than the controls on the Theory of Mind Assessment Scale, whereas they did as well as the control group on the classical theory-of-mind tasks. These findings provide the first evidence that adults with congenital heart disease may display specific impairments in theory of mind. © The Author(s) 2013.

Flow theory – goal orientation theory: positive experience is related to athlete’s goal orientation

PubMed Central

Stavrou, Nektarios A. M.; Psychountaki, Maria; Georgiadis, Emmanouil; Karteroliotis, Konstantinos; Zervas, Yannis

2015-01-01

The main purpose of this study was to examine the relationship between flow experience and goal orientation theory, as well as, the differences in flow experience based on the orthogonal model of goal orientation theory. Two hundred and seventy eight athletes completed the Task and Ego Orientation Sport Questionnaire based on how they usually feel. The challenge and skills ratings were completed 1 h before the competition, based on how they felt at the exact time of answering. In the following, the Flow State Scale-2 was completed up to 30 min after the competition they just participated, along with the challenge-skill ratings, based on how athletes felt during the competition. The results indicated that the athletes’ task orientation may be an important factor for attaining flow in competitive sport, feeling more skillful and estimating the upcoming competition as challenging, while low ego and low task oriented athletes lack these elements, which are important for them to get into flow. Additionally, not the level of task and ego orientation per se, but the balance between athletes’ goal orientation preferences seems important for the formation of flow experience, indicating that high task – high ego and high task – low ego athletes are experiencing the most positive mental state. PMID:26500577

Components of working memory and visual selective attention.

PubMed

Burnham, Bryan R; Sabia, Matthew; Langan, Catherine

2014-02-01

Load theory (Lavie, N., Hirst, A., De Fockert, J. W., & Viding, E. [2004]. Load theory of selective attention and cognitive control. Journal of Experimental Psychology: General, 133, 339-354.) proposes that control of attention depends on the amount and type of load that is imposed by current processing. Specifically, perceptual load should lead to efficient distractor rejection, whereas working memory load (dual-task coordination) should hinder distractor rejection. Studies support load theory's prediction that working memory load will lead to larger distractor effects; however, these studies used secondary tasks that required only verbal working memory and the central executive. The present study examined which other working memory components (visual, spatial, and phonological) influence visual selective attention. Subjects completed an attentional capture task alone (single-task) or while engaged in a working memory task (dual-task). Results showed that along with the central executive, visual and spatial working memory influenced selective attention, but phonological working memory did not. Specifically, attentional capture was larger when visual or spatial working memory was loaded, but phonological working memory load did not affect attentional capture. The results are consistent with load theory and suggest specific components of working memory influence visual selective attention. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1983-09-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody selfconsistently into the theory a contact theorem, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. The interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1984-12-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody self-consistently into the theory a “contact theorem”, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. It is also shown that the interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Magnetospheric Multiscale Observation of Plasma Velocity-Space Cascade: Hermite Representation and Theory.

PubMed

Servidio, S; Chasapis, A; Matthaeus, W H; Perrone, D; Valentini, F; Parashar, T N; Veltri, P; Gershman, D; Russell, C T; Giles, B; Fuselier, S A; Phan, T D; Burch, J

2017-11-17

Plasma turbulence is investigated using unprecedented high-resolution ion velocity distribution measurements by the Magnetospheric Multiscale mission (MMS) in the Earth's magnetosheath. This novel observation of a highly structured particle distribution suggests a cascadelike process in velocity space. Complex velocity space structure is investigated using a three-dimensional Hermite transform, revealing, for the first time in observational data, a power-law distribution of moments. In analogy to hydrodynamics, a Kolmogorov approach leads directly to a range of predictions for this phase-space transport. The scaling theory is found to be in agreement with observations. The combined use of state-of-the-art MMS data sets, novel implementation of a Hermite transform method, and scaling theory of the velocity cascade opens new pathways to the understanding of plasma turbulence and the crucial velocity space features that lead to dissipation in plasmas.

Theory of plasma confinement in non-axisymmetric magnetic fields.

PubMed

Helander, Per

2014-08-01

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Can theory of mind deficits be measured reliably in people with mild and moderate Alzheimer's dementia?

PubMed

Choong, Caroline Sm; Doody, Gillian A

2013-01-01

Patients suffering from Alzheimer's dementia develop difficulties in social functioning. This has led to an interest in the study of "theory of mind" in this population. However, difficulty has arisen because the associated cognitive demands of traditional short story theory of mind assessments result in failure per se in this population, making it challenging to test pure theory of mind ability. Simplified, traditional 1st and 2nd order theory of mind short story tasks and a battery of alternative theory of mind cartoon jokes and control slapstick cartoon jokes, without memory components, were administered to 16 participants with mild-moderate Alzheimer's dementia, and 11 age-matched healthy controls. No significant differences were detected between participants with Alzheimer's dementia and controls on the 1st or 2nd order traditional short story theory of mind tasks (p = 0.155 and p = 0.154 respectively). However, in the cartoon joke tasks there were significant differences in performance between the Alzheimer participants and the control group, this was evident for both theory of mind cartoons and the control 'slapstick' jokes. It remains very difficult to assess theory of mind as an isolated phenomenon in populations with global cognitive impairment, such as Alzheimer's dementia, as the tasks used to assess this cognition invariably depend on other cognitive functions. Although a limitation of this study is the small sample size, the results suggest that there is no measurable specific theory of mind deficit in people with Alzheimer's dementia, and that the use of theory of mind representational models to measure social cognitive ability may not be appropriate in this population.

An integrative, experience-based theory of attentional control.

PubMed

Wilder, Matthew H; Mozer, Michael C; Wickens, Christopher D

2011-02-09

Although diverse, theories of visual attention generally share the notion that attention is controlled by some combination of three distinct strategies: (1) exogenous cuing from locally contrasting primitive visual features, such as abrupt onsets or color singletons (e.g., L. Itti, C. Koch, & E. Neiber, 1998), (2) endogenous gain modulation of exogenous activations, used to guide attention to task-relevant features (e.g., V. Navalpakkam & L. Itti, 2007; J. Wolfe, 1994, 2007), and (3) endogenous prediction of likely locations of interest, based on task and scene gist (e.g., A. Torralba, A. Oliva, M. Castelhano, & J. Henderson, 2006). However, little work has been done to synthesize these disparate theories. In this work, we propose a unifying conceptualization in which attention is controlled along two dimensions: the degree of task focus and the contextual scale of operation. Previously proposed strategies-and their combinations-can be viewed as instances of this one mechanism. Thus, this theory serves not as a replacement for existing models but as a means of bringing them into a coherent framework. We present an implementation of this theory and demonstrate its applicability to a wide range of attentional phenomena. The model accounts for key results in visual search with synthetic images and makes reasonable predictions for human eye movements in search tasks involving real-world images. In addition, the theory offers an unusual perspective on attention that places a fundamental emphasis on the role of experience and task-related knowledge.

Circadian rhythms in human performance and mood under constant conditions

NASA Technical Reports Server (NTRS)

Monk, T. H.; Buysse, D. J.; Reynolds, C. F. 3rd; Berga, S. L.; Jarrett, D. B.; Begley, A. E.; Kupfer, D. J.

1997-01-01

This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well-being. Seventeen healthy young adults were studied under 36 h of 'unmasking' conditions (constant wakeful bedrest, temporal isolation, homogenized 'meals') during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well-being) were obtained followed by one of two performance batteries. On odd-numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even-numbered hours, performance (% hits, response speed) was measured at a 25-30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7). In conclusion: (1) between-task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.

Attention theory and training research

NASA Technical Reports Server (NTRS)

Connelly, James G., Jr.; Wickens, Christopher D.; Lintern, Gavan; Harwood, Kelly

1987-01-01

This study used elements of attention theory as a methodological basis to decompose a complex training task in order to improve training efficiency. The complex task was a microcomputer flight simulation where subjects were required to control the stability of their own helicopter while acquiring and engaging enemy helicopers in a threat enviroment. Subjects were divided into whole-task, part-task, and part/open loop adaptive task groups in a transfer of training paradigm. The effect of reducing mental workload at the early stages of learning was examined with respect to the degree that subordinate elements of the complex task could be automated through practice of consistent, learnable stimulus-response relationships. Results revealed trends suggesting the benefit of isolating consistently mapped sub-tasks for part-task training and the presence of a time-sharing skill over and above the skill required for the separate subtasks.

Is the compressibility positive or negative in a strongly-coupled dusty plasma?

NASA Astrophysics Data System (ADS)

Goree, John; Ruhunusiri, W. D. Suranga

2014-10-01

In dusty plasmas, dust particles are often strongly coupled with a large Coulomb coupling parameter Γ, while the electrons and ions that share the same volume are weakly coupled. In most substances, compressibility β must be positive; otherwise there would be an explosive instability. In a multicomponent plasma, however, one could entertain the idea that β for a single strongly coupled component could be negative, provided that the restoring force from charge separation overwhelms the destabilizing effect. Indeed, the compressibility for a strongly-coupled dust component is assumed to be negative in three theories we identified in the literature for dust acoustic waves. These theories use a multi-fluid model, with an OCP (one component plasma) or Yukawa-OCP approach for the dust fluid. We performed dusty plasma experiments designed to determine the value of the inverse compressibility β-1, and in particular its sign. We fit an experimentally measured dispersion relation to theory, with β-1 as a free parameter, taking into account the systematic errors in the experiment and model. We find that β-1 is either positive, or it has a negligibly small negative value, which is not in agreement with the assumptions of the OCP-based theories. Supported by NSF and NASA.

The effect of topiramate plasma concentration on linguistic behavior, verbal recall and working memory.

PubMed

Marino, S E; Pakhomov, S V S; Han, S; Anderson, K L; Ding, M; Eberly, L E; Loring, D W; Hawkins-Taylor, C; Rarick, J O; Leppik, I E; Cibula, J E; Birnbaum, A K

2012-07-01

This is the first study of the effect of topiramate on linguistic behavior and verbal recall using a computational linguistics system for automated language and speech analysis to detect and quantify drug-induced changes in speech recorded during discourse-level tasks. Healthy volunteers were administered a single, 100-mg oral dose of topiramate in two double-blind, randomized, placebo-controlled, crossover studies. Subjects' topiramate plasma levels ranged from 0.23 to 2.81 μg/mL. We found a significant association between topiramate levels and impairment on measures of verbal fluency elicited during a picture description task, correct number of words recalled on a paragraph recall test, and reaction time recorded during a working memory task. Using the tools of clinical pharmacology and computational linguistics, we elucidated the relationship between the determinants of a drug's disposition as reflected in plasma concentrations and their impact on cognitive functioning as reflected in spoken language discourse. Copyright © 2012 Elsevier Inc. All rights reserved.

Plasma Disks and Rings with ``High'' Magnetic Energy Densities

NASA Astrophysics Data System (ADS)

Coppi, B.; Rousseau, F.

2006-04-01

The nonlinear theory of rotating axisymmetric thin structures in which the magnetic field energy density is comparable with the thermal plasma energy density is formulated. The only flow velocity included in the theory is the velocity of rotation around a central object whose gravity is dominant. The periodic sequence, in the radial direction, of pairs of opposite current channels that can form is shown to lead to relatively large plasma density and pressure modulations, while the relevant magnetic surfaces can acquire a ``crystal structure.'' A new class of equilibria consisting of a series of plasma rings is identified, in the regimes where the plasma pressure is comparable to the magnetic pressure associated with the fields produced by the internal currents. The possible relevance of this result to the formation of dusty plasma rings is pointed out.

A fluid description of plasma double-layers

NASA Technical Reports Server (NTRS)

Levine, J. S.; Crawford, F. W.

1979-01-01

The space-charge double-layer that forms between two plasmas with different densities and thermal energies was investigated using three progressively realistic models which are treated by fluid theory, and take into account four species of particles: electrons and ions reflected by the double-layer, and electrons and ions transmitted through it. The two plasmas are assumed to be cold, and the self-consistent potential, electric field and space-charge distributions within the double-layer are determined. The effects of thermal velocities are taken into account for the reflected particles, and the modifications to the cold plasma solutions are established. Further modifications due to thermal velocities of the transmitted particles are examined. The applicability of a one dimensional fluid description, rather than plasma kinetic theory, is discussed. Theoretical predictions are compared with double layer potentials and lengths deduced from laboratory and space plasma experiments.

Electrostatic fluctuations in collisional plasmas

NASA Astrophysics Data System (ADS)

Rozmus, W.; Brantov, A.; Fortmann-Grote, C.; Bychenkov, V. Yu.; Glenzer, S.

2017-10-01

We present a theory of electrostatic fluctuations in two-component plasmas where electrons and ions are described by Maxwellian distribution functions at unequal temperatures. Based on the exact solution of the Landau kinetic equation, that includes electron-electron, electron-ion, and ion-ion collision integrals, the dynamic form factor, S (k ⃗,ω ) , is derived for weakly coupled plasmas. The collective plasma responses at ion-acoustic, Langmuir, and entropy mode resonances are described for arbitrary wave numbers and frequencies in the entire range of plasma collisionality. The collisionless limit of S (k ⃗,ω ) and the strong-collision result based on the fluctuation-dissipation theorem and classical transport at Te=Ti are recovered and discussed. Results of several Thomson scattering experiments in the broad range of plasma parameters are described and discussed by means of our theory for S (k ⃗,ω ) .

Microscopic nonlinear relativistic quantum theory of absorption of powerful x-ray radiation in plasma.

PubMed

Avetissian, H K; Ghazaryan, A G; Matevosyan, H H; Mkrtchian, G F

2015-10-01

The microscopic quantum theory of plasma nonlinear interaction with the coherent shortwave electromagnetic radiation of arbitrary intensity is developed. The Liouville-von Neumann equation for the density matrix is solved analytically considering a wave field exactly and a scattering potential of plasma ions as a perturbation. With the help of this solution we calculate the nonlinear inverse-bremsstrahlung absorption rate for a grand canonical ensemble of electrons. The latter is studied in Maxwellian, as well as in degenerate quantum plasma for x-ray lasers at superhigh intensities and it is shown that one can achieve the efficient absorption coefficient in these cases.

Theory of beam plasma discharge

NASA Technical Reports Server (NTRS)

Papadopoulos, K.

1982-01-01

The general theory of beam plasma discharge (BPD) is discussed in relation to space and laboratory beam injection situations. An important concept introduced is that even when beam plasma instabilities are excited, there are two regime of BPD with radically different observational properties. They are described here as BPD with either classical or anomalous energy depositions. For high pressures or low altitudes, the classical is expected to dominate. For high altitudes and laboratory experiments, where the axial system size is less than lambda sub en, no BPD will be triggered unless the unstable waves are near the ambient plasma frequency and their amplitudes at saturation are large enough to create suprathermal tails by collapsing.

Theory of mind in dogs: is the perspective-taking task a good test?

PubMed

Roberts, William A; Macpherson, Krista

2011-12-01

Udell, Dorey, and Wynne (in press) have reported an experiment in which wolves, shelter dogs, and pet dogs all showed a significant preference for begging from a person who faced them (seer) over a person whose back was turned to them (blind experimenter). On tests with the blind person's eyes covered with a bucket, a book, or a camera, pet dogs showed more preference for the seer than did wolves and shelter dogs. We agree with the authors' position that most of these findings are best explained by preexperimental learning experienced by the subjects. We argue, however, that the perspective-taking task is not a good test of the domestication theory or of the theory of mind in dogs. The problem we see is that use of the perspective-taking task, combined with preexperimental learning in all the subjects, strongly biases the outcome in favor of a behavioral learning interpretation. Tasks less influenced by preexperimental training would provide less confounded tests of domestication and theory of mind.

On selecting evidence to test hypotheses: A theory of selection tasks.

PubMed

Ragni, Marco; Kola, Ilir; Johnson-Laird, Philip N

2018-05-21

How individuals choose evidence to test hypotheses is a long-standing puzzle. According to an algorithmic theory that we present, it is based on dual processes: individuals' intuitions depending on mental models of the hypothesis yield selections of evidence matching instances of the hypothesis, but their deliberations yield selections of potential counterexamples to the hypothesis. The results of 228 experiments using Wason's selection task corroborated the theory's predictions. Participants made dependent choices of items of evidence: the selections in 99 experiments were significantly more redundant (using Shannon's measure) than those of 10,000 simulations of each experiment based on independent selections. Participants tended to select evidence corresponding to instances of hypotheses, or to its counterexamples, or to both. Given certain contents, instructions, or framings of the task, they were more likely to select potential counterexamples to the hypothesis. When participants received feedback about their selections in the "repeated" selection task, they switched from selections of instances of the hypothesis to selection of potential counterexamples. These results eliminated most of the 15 alternative theories of selecting evidence. In a meta-analysis, the model theory yielded a better fit of the results of 228 experiments than the one remaining theory based on reasoning rather than meaning. We discuss the implications of the model theory for hypothesis testing and for a well-known paradox of confirmation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Taxonomic Approaches to Enlisted Occupational Classification. Volume II,

DTIC Science & Technology

1979-12-01

various media and about the social implications of the more pervasive of these, there is little of communication theory that is useful to those who...Folley’s theory is a system of interrelated definitions, constructs, and hypotheses relating task attributes to training requirements. D. C. Berliner...requirement approach, the task characteristics approach, and a third approach based on information theory . During the third project year, two of the

Diffusion of Magnetized Binary Ionic Mixtures at Ultracold Plasma Conditions

NASA Astrophysics Data System (ADS)

Vidal, Keith R.; Baalrud, Scott D.

2017-10-01

Ultracold plasma experiments offer an accessible means to test transport theories for strongly coupled systems. Application of an external magnetic field might further increase their utility by inhibiting heating mechanisms of ions and electrons and increasing the temperature at which strong coupling effects are observed. We present results focused on developing and validating a transport theory to describe binary ionic mixtures across a wide range of coupling and magnetization strengths relevant to ultracold plasma experiments. The transport theory is an extension of the Effective Potential Theory (EPT), which has been shown to accurately model correlation effects at these conditions, to include magnetization. We focus on diffusion as it can be measured in ultracold plasma experiments. Using EPT within the framework of the Chapman-Enskog expansion, the parallel and perpendicular self and interdiffusion coefficients for binary ionic mixtures with varying mass ratios are calculated and are compared to molecular dynamics simulations. The theory is found to accurately extend Braginskii-like transport to stronger coupling, but to break down when the magnetization strength becomes large enough that the typical gyroradius is smaller than the interaction scale length. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-16-1-0221.

Vlasov dynamics of periodically driven systems

NASA Astrophysics Data System (ADS)

Banerjee, Soumyadip; Shah, Kushal

2018-04-01

Analytical solutions of the Vlasov equation for periodically driven systems are of importance in several areas of plasma physics and dynamical systems and are usually approximated using ponderomotive theory. In this paper, we derive the plasma distribution function predicted by ponderomotive theory using Hamiltonian averaging theory and compare it with solutions obtained by the method of characteristics. Our results show that though ponderomotive theory is relatively much easier to use, its predictions are very restrictive and are likely to be very different from the actual distribution function of the system. We also analyse all possible initial conditions which lead to periodic solutions of the Vlasov equation for periodically driven systems and conjecture that the irreducible polynomial corresponding to the initial condition must only have squares of the spatial and momentum coordinate. The resulting distribution function for other initial conditions is aperiodic and can lead to complex relaxation processes within the plasma.

Experimental validation of Mueller-Stokes theory and investigation of the influence of the Cotton-Mouton effect on polarimetry in a magnetized fusion plasma

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

Zhang, J.; Peebles, W. A.; Crocker, N. A.

Mueller-Stokes theory can be used to calculate the polarization evolution of an electromagnetic (EM) wave as it propagates through a magnetized plasma. Historically, the theory has been used to interpret polarimeter signals from systems operating on fusion plasmas. These interpretations have mostly employed approximations of Mueller-Stokes theory in regimes where either the Faraday rotation (FR) or the Cotton-Mouton (CM) effect is dominant. The current paper presents the first systematic comparison of polarimeter measurements with the predictions of full Mueller-Stokes theory where conditions transition smoothly from a FR-dominant (i.e., weak CM effect) plasma to one where the CM effect plays amore » significant role. A synthetic diagnostic code, based on Mueller-Stokes theory accurately reproduces the trends evident in the experimentally measured polarimeter phase over this entire operating range, thereby validating Mueller-Stokes theory. The synthetic diagnostic code is then used to investigate the influence of the CM effect on polarimetry measurements. As expected, the measurements are well approximated by the FR effect when the CM effect is predicted to be weak. However, the code shows that as the CM effect increases, it can compete with the FR effect in rotating the polarization of the EM-wave. This results in a reduced polarimeter response to the FR effect, just as observed in the experiment. The code also shows if sufficiently large, the CM effect can even reverse the handedness of a wave launched with circular polarization. This helps to understand the surprising experimental observations that the sensitivity to the FR effect can be nearly eliminated at high enough B{sub T} (2.0 T). The results also suggest that the CM effect on the plasma midplane can be exploited to potentially measure magnetic shear in tokamak plasmas. These results establish increased confidence in the use of such a synthetic diagnostic code to guide future polarimetry design and interpret the resultant experimental data.« less

Language and theory of mind in autism spectrum disorder: the relationship between complement syntax and false belief task performance.

PubMed

Lind, Sophie E; Bowler, Dermot M

2009-06-01

This study aimed to test the hypothesis that children with autism spectrum disorder (ASD) use their knowledge of complement syntax as a means of "hacking out" solutions to false belief tasks, despite lacking a representational theory of mind (ToM). Participants completed a "memory for complements" task, a measure of receptive vocabulary, and traditional location change and unexpected contents false belief tasks. Consistent with predictions, the correlation between complement syntax score and location change task performance was significantly stronger within the ASD group than within the comparison group. However, contrary to predictions, complement syntax score was not significantly correlated with unexpected contents task performance within either group. Possible explanations for this pattern of results are considered.

Theory-of-mind understanding and theory-of-mind use in unaffected first-degree relatives of schizophrenia and bipolar disorder.

PubMed

Wang, Yong-Guang; Roberts, David L; Liang, Yan; Shi, Jian-Fei; Wang, Kai

2015-12-15

We assessed theory of mind (ToM) in unaffected first-degree relatives (FDR) of patients with schizophrenia (SC) and bipolar disorder (BD) compared to healthy controls with a revised computerized referential communication task. Results showed that FDR of SC performed worse than FDR of BD and controls on a task requiring ToM-use, but not on a task requiring ToM-understanding. This indicates that deficient ToM-use, rather than ToM-understanding impairments, may represent a potential candidate endophenotype for schizophrenia. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Levels of Conceptual Development in Melodic Permutation Concepts Based on Piaget's Theory

ERIC Educational Resources Information Center

Larn, Ronald L.

1973-01-01

Article considered different ways in which subjects at different age levels solved a musical task involving melodic permutation. The differences in responses to the musical task between age groups were judged to be compatible with Piaget's theory of cognitive development. (Author/RK)

The Mochi project: a field theory approach to plasma dynamics and self-organization

NASA Astrophysics Data System (ADS)

You, Setthivoine; von der Linden, Jens; Lavine, Eric Sander; Card, Alexander; Carroll, Evan

2016-10-01

The Mochi project is designed to study the interaction between plasma flows and magnetic fields from the point-of-view of canonical flux tubes. The Mochi Labjet experiment is being commissioned after achieving first plasma. Analytical and numerical tools are being developed to visualize canonical flux tubes. One analytical tool described here is a field theory approach to plasma dynamics and self-organization. A redefinition of the Lagrangian of a multi-particle system in fields reformulates the single-particle, kinetic, and fluid equations governing fluid and plasma dynamics as a single set of generalized Maxwell's equations and Ohm's law for canonical force-fields. The Lagrangian includes new terms representing the coupling between the motion of particle distributions, between distributions and electromagnetic fields, with relativistic contributions. The formulation shows that the concepts of self-organization and canonical helicity transport are applicable across single-particle, kinetic, and fluid regimes, at classical and relativistic scales. The theory gives the basis for comparing canonical helicity change to energy change in general systems. This work is supported by by US DOE Grant DE-SC0010340.

Performance of a permanent-magnet helicon source at 27 and 13 MHz

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

Chen, Francis F.

2012-09-15

A small helicon source is used to create dense plasma and inject it into a large chamber. A permanent magnet is used for the dc magnetic field (B-field), making the system very simple and compact. Though theory predicts that better antenna coupling will occur at 27.12 MHz, it was found that 13.56 MHz surprisingly gives even higher density due to practical effects not included in theory. Complete density n and electron temperature T{sub e} profiles are measured at three distances below the source. The plasma inside the source is also measured with a special probe, even under the antenna. Themore » density there is lower than expected because the plasma created is immediately ejected, filling the experimental chamber. The advantage of helicons over inductively coupled plasmas (with no B-field) increases with RF power. At high B-fields, edge ionization by the Trivelpiece-Gould mode can be seen. These results are useful for design of multiple-tube, large-area helicon sources for plasma etching and deposition because problems are encountered which cannot be foreseen by theory alone.« less

Kinetic theory of two-temperature polyatomic plasmas

NASA Astrophysics Data System (ADS)

Orlac'h, Jean-Maxime; Giovangigli, Vincent; Novikova, Tatiana; Roca i Cabarrocas, Pere

2018-03-01

We investigate the kinetic theory of two-temperature plasmas for reactive polyatomic gas mixtures. The Knudsen number is taken proportional to the square root of the mass ratio between electrons and heavy-species, and thermal non-equilibrium between electrons and heavy species is allowed. The kinetic non-equilibrium framework also requires a weak coupling between electrons and internal energy modes of heavy species. The zeroth-order and first-order fluid equations are derived by using a generalized Chapman-Enskog method. Expressions for transport fluxes are obtained in terms of macroscopic variable gradients and the corresponding transport coefficients are expressed as bracket products of species perturbed distribution functions. The theory derived in this paper provides a consistent fluid model for non-thermal multicomponent plasmas.

Extended capability of the integrated transport analysis suite, TASK3D-a, for LHD experiment

NASA Astrophysics Data System (ADS)

Yokoyama, M.; Seki, R.; Suzuki, C.; Sato, M.; Emoto, M.; Murakami, S.; Osakabe, M.; Tsujimura, T. Ii.; Yoshimura, Y.; Ido, T.; Ogawa, K.; Satake, S.; Suzuki, Y.; Goto, T.; Ida, K.; Pablant, N.; Gates, D.; Warmer, F.; Vincenzi, P.; Simulation Reactor Research Project, Numerical; LHD Experiment Group

2017-12-01

The integrated transport analysis suite, TASK3D-a (Analysis), has been developed to be capable for routine whole-discharge analyses of plasmas confined in three-dimensional (3D) magnetic configurations such as the LHD. The routine dynamic energy balance analysis for NBI-heated plasmas was made possible in the first version released in September 2012. The suite has been further extended through implementing additional modules for neoclassical transport and ECH deposition for 3D configurations. A module has also been added for creating systematic data for the International Stellarator-Heliotron Confinement and Profile Database. Improvement of neutral beam injection modules for multiple-ion species plasmas and loose coupling with a large-simulation code are also highlights of recent developments.

Neural correlates of confidence during item recognition and source memory retrieval: evidence for both dual-process and strength memory theories.

PubMed

Hayes, Scott M; Buchler, Norbou; Stokes, Jared; Kragel, James; Cabeza, Roberto

2011-12-01

Although the medial-temporal lobes (MTL), PFC, and parietal cortex are considered primary nodes in the episodic memory network, there is much debate regarding the contributions of MTL, PFC, and parietal subregions to recollection versus familiarity (dual-process theory) and the feasibility of accounts on the basis of a single memory strength process (strength theory). To investigate these issues, the current fMRI study measured activity during retrieval of memories that differed quantitatively in terms of strength (high vs. low-confidence trials) and qualitatively in terms of recollection versus familiarity (source vs. item memory tasks). Support for each theory varied depending on which node of the episodic memory network was considered. Results from MTL best fit a dual-process account, as a dissociation was found between a right hippocampal region showing high-confidence activity during the source memory task and bilateral rhinal regions showing high-confidence activity during the item memory task. Within PFC, several left-lateralized regions showed greater activity for source than item memory, consistent with recollective orienting, whereas a right-lateralized ventrolateral area showed low-confidence activity in both tasks, consistent with monitoring processes. Parietal findings were generally consistent with strength theory, with dorsal areas showing low-confidence activity and ventral areas showing high-confidence activity in both tasks. This dissociation fits with an attentional account of parietal functions during episodic retrieval. The results suggest that both dual-process and strength theories are partly correct, highlighting the need for an integrated model that links to more general cognitive theories to account for observed neural activity during episodic memory retrieval.

Neural Correlates of Confidence during Item Recognition and Source Memory Retrieval: Evidence for Both Dual-process and Strength Memory Theories

PubMed Central

Hayes, Scott M.; Buchler, Norbou; Stokes, Jared; Kragel, James; Cabeza, Roberto

2012-01-01

Although the medial-temporal lobes (MTL), PFC, and parietal cortex are considered primary nodes in the episodic memory network, there is much debate regarding the contributions of MTL, PFC, and parietal subregions to recollection versus familiarity (dual-process theory) and the feasibility of accounts on the basis of a single memory strength process (strength theory). To investigate these issues, the current fMRI study measured activity during retrieval of memories that differed quantitatively in terms of strength (high vs. low-confidence trials) and qualitatively in terms of recollection versus familiarity (source vs. item memory tasks). Support for each theory varied depending on which node of the episodic memory network was considered. Results from MTL best fit a dual-process account, as a dissociation was found between a right hippocampal region showing high-confidence activity during the source memory task and bilateral rhinal regions showing high-confidence activity during the item memory task. Within PFC, several left-lateralized regions showed greater activity for source than item memory, consistent with recollective orienting, whereas a right-lateralized ventrolateral area showed low-confidence activity in both tasks, consistent with monitoring processes. Parietal findings were generally consistent with strength theory, with dorsal areas showing low-confidence activity and ventral areas showing high-confidence activity in both tasks. This dissociation fits with an attentional account of parietal functions during episodic retrieval. The results suggest that both dual-process and strength theories are partly correct, highlighting the need for an integrated model that links to more general cognitive theories to account for observed neural activity during episodic memory retrieval. PMID:21736454

The role of medial temporal lobe in retrieving spatial and nonspatial relations from episodic and semantic memory.

PubMed

Ryan, Lee; Lin, Chun-Yu; Ketcham, Katie; Nadel, Lynn

2010-01-01

This study examined the involvement of medial temporal lobe, especially the hippocampus, in processing spatial and nonspatial relations using episodic and semantic versions of a relational judgment task. Participants studied object arrays and were tested on different types of relations between pairs of objects. Three prevalent views of hippocampal function were considered. Cognitive map theory (O'Keefe and Nadel (1978) The Hippocampus as a Cognitive Map. USA: Oxford University Press) emphasizes hippocampal involvement in spatial relational tasks. Multiple trace theory (Nadel and Moscovitch (1997) Memory consolidation, retrograde amnesia and the hippocampal complex Curr Opin Neurobiol 7:217-227) emphasizes hippocampal involvement in episodic tasks. Eichenbaum and Cohen's ((2001) From Conditioning to Conscious Recollection: Memory Systems of the Brain. USA: Oxford University Press) relational theory predicts equivalent hippocampal involvement in all relational tasks within both semantic and episodic memory. The fMRI results provided partial support for all three theories, though none of them fit the data perfectly. We observed hippocampal activation during all relational tasks, with increased activation for spatial compared to nonspatial relations, and for episodic compared to semantic relations. The placement of activation along the anterior-posterior axis of the hippocampus also differentiated the conditions. We suggest a view of hippocampal function in memory that incorporates aspects of all three theories. Copyright 2009 Wiley-Liss, Inc.

Rational adaptation under task and processing constraints: implications for testing theories of cognition and action.

PubMed

Howes, Andrew; Lewis, Richard L; Vera, Alonso

2009-10-01

The authors assume that individuals adapt rationally to a utility function given constraints imposed by their cognitive architecture and the local task environment. This assumption underlies a new approach to modeling and understanding cognition-cognitively bounded rational analysis-that sharpens the predictive acuity of general, integrated theories of cognition and action. Such theories provide the necessary computational means to explain the flexible nature of human behavior but in doing so introduce extreme degrees of freedom in accounting for data. The new approach narrows the space of predicted behaviors through analysis of the payoff achieved by alternative strategies, rather than through fitting strategies and theoretical parameters to data. It extends and complements established approaches, including computational cognitive architectures, rational analysis, optimal motor control, bounded rationality, and signal detection theory. The authors illustrate the approach with a reanalysis of an existing account of psychological refractory period (PRP) dual-task performance and the development and analysis of a new theory of ordered dual-task responses. These analyses yield several novel results, including a new understanding of the role of strategic variation in existing accounts of PRP and the first predictive, quantitative account showing how the details of ordered dual-task phenomena emerge from the rational control of a cognitive system subject to the combined constraints of internal variance, motor interference, and a response selection bottleneck.

Conceptual change and preschoolers' theory of mind: evidence from load-force adaptation.

PubMed

Sabbagh, Mark A; Hopkins, Sydney F R; Benson, Jeannette E; Flanagan, J Randall

2010-01-01

Prominent theories of preschoolers' theory of mind development have included a central role for changing or adapting existing conceptual structures in response to experiences. Because of the relatively protracted timetable of theory of mind development, it has been difficult to test this assumption about the role of adaptation directly. To gain evidence that cognitive adaptation is particularly important for theory of mind development, we sought to determine whether individual differences in cognitive adaptation in a non-social domain predicted preschoolers' theory of mind development. Twenty-five preschoolers were tested on batteries of theory of mind tasks, executive functioning tasks, and on their ability to adapt their lifting behavior to smoothly lift an unexpectedly heavy object. Results showed that children who adapted their lifting behavior more rapidly performed better on theory of mind tasks than those who adapted more slowly. These findings held up when age and performance on the executive functioning battery were statistically controlled. Although preliminary, we argue that this relation is attributable to individual differences in children's domain general abilities to efficiently change existing conceptual structures in response to experience. Copyright © 2010 Elsevier Ltd. All rights reserved.

Robot-assisted surgery: an emerging platform for human neuroscience research

PubMed Central

Jarc, Anthony M.; Nisky, Ilana

2015-01-01

Classic studies in human sensorimotor control use simplified tasks to uncover fundamental control strategies employed by the nervous system. Such simple tasks are critical for isolating specific features of motor, sensory, or cognitive processes, and for inferring causality between these features and observed behavioral changes. However, it remains unclear how these theories translate to complex sensorimotor tasks or to natural behaviors. Part of the difficulty in performing such experiments has been the lack of appropriate tools for measuring complex motor skills in real-world contexts. Robot-assisted surgery (RAS) provides an opportunity to overcome these challenges by enabling unobtrusive measurements of user behavior. In addition, a continuum of tasks with varying complexity—from simple tasks such as those in classic studies to highly complex tasks such as a surgical procedure—can be studied using RAS platforms. Finally, RAS includes a diverse participant population of inexperienced users all the way to expert surgeons. In this perspective, we illustrate how the characteristics of RAS systems make them compelling platforms to extend many theories in human neuroscience, as well as, to develop new theories altogether. PMID:26089785

Theory of Mind Development in Adolescence and Early Adulthood: The Growing Complexity of Recursive Thinking Ability

PubMed Central

Valle, Annalisa; Massaro, Davide; Castelli, Ilaria; Marchetti, Antonella

2015-01-01

This study explores the development of theory of mind, operationalized as recursive thinking ability, from adolescence to early adulthood (N = 110; young adolescents = 47; adolescents = 43; young adults = 20). The construct of theory of mind has been operationalized in two different ways: as the ability to recognize the correct mental state of a character, and as the ability to attribute the correct mental state in order to predict the character’s behaviour. The Imposing Memory Task, with five recursive thinking levels, and a third-order false-belief task with three recursive thinking levels (devised for this study) have been used. The relationship among working memory, executive functions, and linguistic skills are also analysed. Results show that subjects exhibit less understanding of elevated recursive thinking levels (third, fourth, and fifth) compared to the first and second levels. Working memory is correlated with total recursive thinking, whereas performance on the linguistic comprehension task is related to third level recursive thinking in both theory of mind tasks. An effect of age on third-order false-belief task performance was also found. A key finding of the present study is that the third-order false-belief task shows significant age differences in the application of recursive thinking that involves the prediction of others’ behaviour. In contrast, such an age effect is not observed in the Imposing Memory Task. These results may support the extension of the investigation of the third order false belief after childhood. PMID:27247645

The persistence of thought: evidence for a role of working memory in the maintenance of task-unrelated thinking.

PubMed

Levinson, Daniel B; Smallwood, Jonathan; Davidson, Richard J

2012-04-01

Tasks that tax working memory (WM) have consistently been found to decrease mind wandering. These findings may indicate that maintenance of mind wandering requires WM resources, such that mind wandering cannot persist when WM resources are being consumed by a task. An alternative explanation for these findings, however, is that mind wandering persists without the support of WM but is nonetheless decreased during any demanding task because good task performance requires that attention be restricted from task-unrelated thought (TUT). The present study tested these two competing theories by investigating whether individuals with greater WM resources mind-wander more during an undemanding task, as would be predicted only by the theory that WM supports TUT. We found that individuals with higher WM capacity reported more TUT in undemanding tasks, which suggests that WM enables the maintenance of mind wandering.

Inductive plasmas for plasma processing

NASA Astrophysics Data System (ADS)

Keller, John H.

1996-05-01

With the need for high plasma density and low pressure in single wafer etching tools, a number of inductive etching systems have been and are being developed for commercial sale. This paper reviews some of the history of low-pressure inductive plasmas, gives features of inductive plasmas, limitations, corrections and presents uses for plasma processing. The theory for the skin depth, rf coil impedance and efficiency is also discussed.

A theoretical and experimental investigation of the linear and nonlinear impulse responses from a magnetoplasma column

NASA Technical Reports Server (NTRS)

Grody, N. C.

1973-01-01

Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.

Dust Acoustic Wave Excitation in a Plasma with Warm Dust

NASA Astrophysics Data System (ADS)

Rosenberg, M.; Thomas, E., Jr.; Marcus, L.; Fisher, R.; Williams, J. D.; Merlino, R. L.

2008-11-01

Measurements of the dust acoustic wave dispersion relation in dusty plasmas formed in glow discharges at the University of Iowa [1] and Auburn University [2] have shown the importance of finite dust temperature effects. The effect of dust grains with large thermal speeds was taken into account using kinetic theory of the ion-dust streaming instability [3]. The results of analytic and numerical calculations of the dispersion relation based on the kinetic theory will be presented and compared with the experimental results. [1] E. Thomas, Jr., R. Fisher, and R. L. Merlino, Phys. Plasmas 14, 123701 (2007). [2] J. D. Williams, E. Thomas Jr., and L. Marcus, Phys. Plasmas 15, 043704 (2008). [3] M. Rosenberg, E. Thomas Jr., and R. L. Merlino, Phys. Plasmas 15, 073701 (2008).

Effect of Coulomb Collisions on Low Gas Pressure Plasmas

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

Nanbu, K.; Furubayashi, T.

2006-05-05

A recent trend in material processing plasmas is the use of a low gas pressure and high plasma density. In such plasmas, Coulomb collisions among charged particles has been considered to have a significant effect on plasma structure. By use of Bobylev and Nanbu's theory [Phy. Rev. E, 61(2000), 4576], this effect on argon plasmas and oxygen plasmas generated by a capacitive discharge is examined. It is found that the effect is appreciable only for oxygen plasmas.

Impedance learning for robotic contact tasks using natural actor-critic algorithm.

PubMed

Kim, Byungchan; Park, Jooyoung; Park, Shinsuk; Kang, Sungchul

2010-04-01

Compared with their robotic counterparts, humans excel at various tasks by using their ability to adaptively modulate arm impedance parameters. This ability allows us to successfully perform contact tasks even in uncertain environments. This paper considers a learning strategy of motor skill for robotic contact tasks based on a human motor control theory and machine learning schemes. Our robot learning method employs impedance control based on the equilibrium point control theory and reinforcement learning to determine the impedance parameters for contact tasks. A recursive least-square filter-based episodic natural actor-critic algorithm is used to find the optimal impedance parameters. The effectiveness of the proposed method was tested through dynamic simulations of various contact tasks. The simulation results demonstrated that the proposed method optimizes the performance of the contact tasks in uncertain conditions of the environment.

Developmental Differences in Motor Task Integration: A Test of Pascual-Leone's Theory of Constructive Operators.

ERIC Educational Resources Information Center

Todor, John I.

1979-01-01

Assesses the ability of Pascual-Leone's Theory of Constructive Operators to predict the minimum age or maturational level at which integration of a motor task could be achieved. Subjects were 114 elementary school children ranging in age from 5 to 12. (Author/MP)

The Role of Perceptual Load in Inattentional Blindness

ERIC Educational Resources Information Center

Cartwright-Finch, Ula; Lavie, Nilli

2007-01-01

Perceptual load theory offers a resolution to the long-standing early vs. late selection debate over whether task-irrelevant stimuli are perceived, suggesting that irrelevant perception depends upon the perceptual load of task-relevant processing. However, previous evidence for this theory has relied on RTs and neuroimaging. Here we tested the…

Particle trapping: A key requisite of structure formation and stability of Vlasov–Poisson plasmas

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

Schamel, Hans, E-mail: hans.schamel@uni-bayreuth.de

2015-04-15

Particle trapping is shown to control the existence of undamped coherent structures in Vlasov–Poisson plasmas and thereby affects the onset of plasma instability beyond the realm of linear Landau theory.

Mutual information optimization for mass spectra data alignment.

PubMed

Zoppis, Italo; Gianazza, Erica; Borsani, Massimiliano; Chinello, Clizia; Mainini, Veronica; Galbusera, Carmen; Ferrarese, Carlo; Galimberti, Gloria; Sorbi, Sandro; Borroni, Barbara; Magni, Fulvio; Antoniotti, Marco; Mauri, Giancarlo

2012-01-01

"Signal" alignments play critical roles in many clinical setting. This is the case of mass spectrometry data, an important component of many types of proteomic analysis. A central problem occurs when one needs to integrate (mass spectrometry) data produced by different sources, e.g., different equipment and/or laboratories. In these cases some form of "data integration'" or "data fusion'" may be necessary in order to discard some source specific aspects and improve the ability to perform a classification task such as inferring the "disease classes'" of patients. The need for new high performance data alignments methods is therefore particularly important in these contexts. In this paper we propose an approach based both on an information theory perspective, generally used in a feature construction problem, and on the application of a mathematical programming task (i.e. the weighted bipartite matching problem). We present the results of a competitive analysis of our method against other approaches. The analysis was conducted on data from plasma/ethylenediaminetetraacetic acid (EDTA) of "control" and Alzheimer patients collected from three different hospitals. The results point to a significant performance advantage of our method with respect to the competing ones tested.

Plasma forces on microparticles on a surface: an experimental investigation

NASA Astrophysics Data System (ADS)

Heijmans, L. C. J.; Neelis, T. W. C.; van Leuken, D. P. J.; Bouchut, A.; Nijdam, S.

2017-07-01

A plasma causes a force on particles on a surface. We quantitatively measure this force by means of two different setups, which use different methods to balance the forces on these particles: one using vibrations, the other a centrifuge. From this, we deduce both the adhesion that sticks the particles to the surface, and how the application of a plasma affects the adhesion of the particles. We show that the plasma alters the force balance on 100 μ {{m}} diameter particles with a force in the order of micronewtons. We can conclude, from both additional experiments and comparison to theory, that the main plasma effect is not an electrostatic force on a charged particle; its magnitude is orders of magnitude larger than what would be expected from electrostatic theory. The plasma likely has an effect on the particle adhesion, possibly caused by evaporation of water.

Electrostatic fluctuations in collisional plasmas

DOE PAGES

Rozmus, W.; Brantov, A.; Fortmann-Grote, C.; ...

2017-10-12

Here, we present a theory of electrostatic fluctuations in two-component plasmas where electrons and ions are described by Maxwellian distribution functions at unequal temperatures. Based on the exact solution of the Landau kinetic equation, that includes electron-electron, electron-ion, and ion-ion collision integrals, the dynamic form factor, S( →k,ω), is derived for weakly coupled plasmas. The collective plasma responses at ion-acoustic, Langmuir, and entropy mode resonances are described for arbitrary wave numbers and frequencies in the entire range of plasma collisionality. The collisionless limit of S( →k,ω) and the strong-collision result based on the fluctuation-dissipation theorem and classical transport at Tmore » e = T i are recovered and discussed. Results of several Thomson scattering experiments in the broad range of plasma parameters are described and discussed by means of our theory for S( →k,ω).« less

Electrostatic fluctuations in collisional plasmas

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

Rozmus, W.; Brantov, A.; Fortmann-Grote, C.

Here, we present a theory of electrostatic fluctuations in two-component plasmas where electrons and ions are described by Maxwellian distribution functions at unequal temperatures. Based on the exact solution of the Landau kinetic equation, that includes electron-electron, electron-ion, and ion-ion collision integrals, the dynamic form factor, S( →k,ω), is derived for weakly coupled plasmas. The collective plasma responses at ion-acoustic, Langmuir, and entropy mode resonances are described for arbitrary wave numbers and frequencies in the entire range of plasma collisionality. The collisionless limit of S( →k,ω) and the strong-collision result based on the fluctuation-dissipation theorem and classical transport at Tmore » e = T i are recovered and discussed. Results of several Thomson scattering experiments in the broad range of plasma parameters are described and discussed by means of our theory for S( →k,ω).« less

Kinetic theory of a two-dimensional magnetized plasma. II - Balescu-Lenard limit.

NASA Technical Reports Server (NTRS)

Vahala, G.

1972-01-01

The kinetic theory of a two-dimensional one-species plasma in a uniform dc magnetic field is investigated in the small plasma parameter limit. The plasma consists of charged rods interacting through the logarithmic Coulomb potential. Vahala and Montgomery earlier (1971) derived a Fokker-Planck equation for this system, but it contained a divergent integral, which had to be cut off on physical grounds. This cutoff is compared to the standard cutoff introduced in the two-dimensional unmagnetized Fokker-Planck equation. In the small plasma parameter limit, it is shown that the Balescu-Lenard collision term is zero in the long time average limit if only two-body interactions are considered. The energy transfer from a test particle to an equilibrium plasma is discussed and is also shown to be zero in the long time average limit. This supports the unexpected result of zero Balescu-Lenard collision term.

Electrostatic fluctuations in collisional plasmas.

PubMed

Rozmus, W; Brantov, A; Fortmann-Grote, C; Bychenkov, V Yu; Glenzer, S

2017-10-01

We present a theory of electrostatic fluctuations in two-component plasmas where electrons and ions are described by Maxwellian distribution functions at unequal temperatures. Based on the exact solution of the Landau kinetic equation, that includes electron-electron, electron-ion, and ion-ion collision integrals, the dynamic form factor, S(k[over ⃗],ω), is derived for weakly coupled plasmas. The collective plasma responses at ion-acoustic, Langmuir, and entropy mode resonances are described for arbitrary wave numbers and frequencies in the entire range of plasma collisionality. The collisionless limit of S(k[over ⃗],ω) and the strong-collision result based on the fluctuation-dissipation theorem and classical transport at T_{e}=T_{i} are recovered and discussed. Results of several Thomson scattering experiments in the broad range of plasma parameters are described and discussed by means of our theory for S(k[over ⃗],ω).

Radio propagation through solar and other extraterrestrial ionized media

NASA Technical Reports Server (NTRS)

Smith, E. K.; Edelson, R. E.

1980-01-01

The present S- and X-band communications needs in deep space are addressed to illustrate the aspects which are affected by propagation through extraterrestrial plasmas. The magnitude, critical threshold, and frequency dependence of some eight propagation effects for an S-band propagation path passing within 4 solar radii of the Sun are described. The theory and observation of propagation in extraterrestrial plasmas are discussed and the various plasma states along a near solar propagation path are illustrated. Classical magnetoionic theory (cold anisotropic plasma) is examined for its applicability to the path in question. The characteristics of the plasma states found along the path are summarized and the errors in some of the standard approximations are indicated. Models of extraterrestrial plasmas are included. Modeling the electron density in the solar corona and solar wind, is emphasized but some cursory information on the terrestrial planets plus Jupiters is included.

Proving Properties of Rule-Based Systems

DTIC Science & Technology

1990-12-01

in these systems and enable us to use them with more confidence. Each system of rules is encoded as a set of axioms that define the system theory . The...operation of the rule language and information about the subject domain are also described in the system theory . Validation tasks, such as...the validity of the conjecture in the system theory , we have carried out the corresponding validation task. If the proof is restricted to be

How a Multidimensional View of Perceived Organizational Support Impacts Self-Efficacy and Task Understanding during Training for Boundary Spanning Tasks

DTIC Science & Technology

2008-03-01

Literature Review Chapter Overview This chapter provides an overview of recent studies and research on theory and application of self-efficacy...from the literature and how it has been used in predicting success in varying measures of performance. Self-efficacy Many psychological theories ...shown to positively affect training outcomes (Bandura, 1977, Salas & Cannon-Bowers, 2001). Theories of expectancy and self-efficacy suggest 10

"I Won't Trust You if I Think You're Trying to Deceive Me": Relations between Selective Trust, Theory of Mind, and Imitation in Early Childhood

ERIC Educational Resources Information Center

DiYanni, Cara; Nini, Deniela; Rheel, Whitney; Livelli, Alicia

2012-01-01

This study explores connections between 3-, 4-, and 5-year-olds' performance in theory-of-mind tasks, their performance on an assessment of selective trust, and their decisions to (not) imitate the questionable tool choices of an adult model. The prediction was that all the tasks would be related, with improvements in theory of mind and selective…

The effects of interaction with the device described by procedural text on recall, true/false, and task performance.

PubMed

Diehl, V A; Mills, C B

1995-11-01

In two experiments, subjects interacted to different extents with relevant devices while reading two complex multistep procedural texts and were then tested with task performance time, true/false, and recall measures. While reading, subjects performed the task (read and do), saw the experimenter perform the task (read and see experimenter do), imagined doing the task (read and imagine), looked at the device while reading (read and see), or only read (read only). Van Dijk and Kintsch's (1983) text representation theory led to the prediction that exposure to the task device (in the read-and-do, read-and-see, and read-and-see-experimenter-do conditions) would lead to the development of a stronger situation model and therefore faster task performance, whereas the read-only and read-and-see conditions would lead to a better textbase, and therefore better performance on the true/false and recall tasks. Paivio's (1991) dual coding theory led to the opposite prediction for recall. The results supported the text representation theory with task performance and recall. The read-and-see condition produced consistently good performance on the true/false measure. Amount of text study time contributed to recall performance. These findings support the notion that information available while reading leads to differential development of representations in memory, which, in turn, causes differences in performance on various measures.

Decision paths in complex tasks

NASA Technical Reports Server (NTRS)

Galanter, Eugene

1991-01-01

Complex real world action and its prediction and control has escaped analysis by the classical methods of psychological research. The reason is that psychologists have no procedures to parse complex tasks into their constituents. Where such a division can be made, based say on expert judgment, there is no natural scale to measure the positive or negative values of the components. Even if we could assign numbers to task parts, we lack rules i.e., a theory, to combine them into a total task representation. We compare here two plausible theories for the amalgamation of the value of task components. Both of these theories require a numerical representation of motivation, for motivation is the primary variable that guides choice and action in well-learned tasks. We address this problem of motivational quantification and performance prediction by developing psychophysical scales of the desireability or aversiveness of task components based on utility scaling methods (Galanter 1990). We modify methods used originally to scale sensory magnitudes (Stevens and Galanter 1957), and that have been applied recently to the measure of task 'workload' by Gopher and Braune (1984). Our modification uses utility comparison scaling techniques which avoid the unnecessary assumptions made by Gopher and Braune. Formula for the utility of complex tasks based on the theoretical models are used to predict decision and choice of alternate paths to the same goal.

The influence of time management skill on the curvilinear relationship between organizational citizenship behavior and task performance.

PubMed

Rapp, Adam A; Bachrach, Daniel G; Rapp, Tammy L

2013-07-01

In this research we integrate resource allocation and social exchange perspectives to build and test theory focusing on the moderating role of time management skill in the nonmonotonic relationship between organizational citizenship behavior (OCB) and task performance. Results from matching survey data collected from 212 employees and 41 supervisors and from task performance metrics collected several months later indicate that the curvilinear association between OCB and task performance is significantly moderated by employees' time management skill. Implications for theory and practice are discussed. PsycINFO Database Record (c) 2013 APA, all rights reserved.

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

J.A. Krommes

Fusion physics poses an extremely challenging, practically complex problem that does not yield readily to simple paradigms. Nevertheless, various of the theoretical tools and conceptual advances emphasized at the KaufmanFest 2007 have motivated and/or found application to the development of fusion-related plasma turbulence theory. A brief historical commentary is given on some aspects of that specialty, with emphasis on the role (and limitations) of Hamiltonian/symplectic approaches, variational methods, oscillation-center theory, and nonlinear dynamics. It is shown how to extract a renormalized ponderomotive force from the statistical equations of plasma turbulence, and the possibility of a renormalized K-χ theorem is discussed.more » An unusual application of quasilinear theory to the problem of plasma equilibria in the presence of stochastic magnetic fields is described. The modern problem of zonal-flow dynamics illustrates a confluence of several techniques, including (i) the application of nonlinear-dynamics methods, especially center-manifold theory, to the problem of the transition to plasma turbulence in the face of self-generated zonal flows; and (ii) the use of Hamiltonian formalism to determine the appropriate (Casimir) invariant to be used in a novel wave-kinetic analysis of systems of interacting zonal flows and drift waves. Recent progress in the theory of intermittent chaotic statistics and the generation of coherent structures from turbulence is mentioned, and an appeal is made for some new tools to cope with these interesting and difficult problems in nonlinear plasma physics. Finally, the important influence of the intellectually stimulating research environment fostered by Prof. Allan Kaufman on the author's thinking and teaching methodology is described.« less

Analysis of Plasma Detachment through Magnetic Nozzle via Canonical Field Theory

NASA Astrophysics Data System (ADS)

Takagaki, Yu

In this paper, I have investigated the mechanism of plasma detachment through magnetic nozzle via canonical field theory, especially by considering canonical vorticity flux Psisigma contour and dissipative force vector Rsigma. As one of the most recent experimental proofs of plasma detachment, Olsen et al., observed and investigated three key indications of plasma detachment. However, after solving for numerical fits with their experimental data, I found that constant ion flux lines did not actually separate from constant magnetic flux lines. Thus, their first key indication becomes incorrect now. Whereas, my analytical results are consistent with the other two key indications. At the beginning, plasma detached from canonical vorticity flux contours due to non-zero dissipative force and attached on magnetic flux lines instead. However, vector Rsigma [is asymptotically equal to] 0 force makes plasma re-attach on canonical vorticity flux contours around the plume edge region. As the most significant and notable result through my analysis, I confirmed the existence of returning plasma flow around the plume edge region.

Plasma Theory and Simulation.

DTIC Science & Technology

1978-07-01

l l) A paper t i t led “Part icle-Fluid Hybrid Codes Applied to Beam- Plasma , Ring -Plasma Instabi l i ties ” was presented at Monterey (see Section V...ic le-Fluid Hybr id Codes Applied to Beam- Plasma , Ring -Plasma Ins tab i l i t ies”. (2) A. Peiravi and C. K. Birdsall , “Self-Heating of id Therma l

Asymmetrical Switch Costs in Children

ERIC Educational Resources Information Center

Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

2006-01-01

Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

Domain-general contributions to social reasoning: theory of mind and deontic reasoning re-explored.

PubMed

McKinnon, Margaret C; Moscovitch, Morris

2007-02-01

Using older adults and dual-task interference, we examined performance on two social reasoning tasks: theory of mind (ToM) tasks and versions of the deontic selection task involving social contracts and hazardous conditions. In line with performance accounts of social reasoning, evidence from both aging and the dual-task method suggested that domain-general resources contribute to performance of these tasks. Specifically, older adults were impaired relative to younger adults on all types of social reasoning tasks tested; performance varied as a function of the demands these tasks placed on domain-general resources. Moreover, in younger adults, simultaneous performance of a working memory task interfered with younger adults' performance on both types of social reasoning tasks; here too, the magnitude of the interference effect varied with the processing demands of each task. Limits placed on social reasoning by executive functions contribute a great deal to performance, even in old age and in healthy younger adults under conditions of divided attention. The role of potentially non-modular and modular contributions to social reasoning is discussed.

Implicit theories about willpower predict the activation of a rest goal following self-control exertion.

PubMed

Job, Veronika; Bernecker, Katharina; Miketta, Stefanie; Friese, Malte

2015-10-01

Past research indicates that peoples' implicit theories about the nature of willpower moderate the ego-depletion effect. Only people who believe or were led to believe that willpower is a limited resource (limited-resource theory) showed lower self-control performance after an initial demanding task. As of yet, the underlying processes explaining this moderating effect by theories about willpower remain unknown. Here, we propose that the exertion of self-control activates the goal to preserve and replenish mental resources (rest goal) in people with a limited-resource theory. Five studies tested this hypothesis. In Study 1, individual differences in implicit theories about willpower predicted increased accessibility of a rest goal after self-control exertion. Furthermore, measured (Study 2) and manipulated (Study 3) willpower theories predicted an increased preference for rest-conducive objects. Finally, Studies 4 and 5 provide evidence that theories about willpower predict actual resting behavior: In Study 4, participants who held a limited-resource theory took a longer break following self-control exertion than participants with a nonlimited-resource theory. Longer resting time predicted decreased rest goal accessibility afterward. In Study 5, participants with an induced limited-resource theory sat longer on chairs in an ostensible product-testing task when they had engaged in a task requiring self-control beforehand. This research provides consistent support for a motivational shift toward rest after self-control exertion in people holding a limited-resource theory about willpower. (c) 2015 APA, all rights reserved).

Teaching an Old Dog an Old Trick: FREE-FIX and Free-Boundary Axisymmetric MHD Equilibrium

NASA Astrophysics Data System (ADS)

Guazzotto, Luca

2015-11-01

A common task in plasma physics research is the calculation of an axisymmetric equilibrium for tokamak modeling. The main unknown of the problem is the magnetic poloidal flux ψ. The easiest approach is to assign the shape of the plasma and only solve the equilibrium problem in the plasma / closed-field-lines region (the ``fixed-boundary approach''). Often, one may also need the vacuum fields, i.e. the equilibrium in the open-field-lines region, requiring either coil currents or ψ on some closed curve outside the plasma to be assigned (the ``free-boundary approach''). Going from one approach to the other is a textbook problem, involving the calculation of Green's functions and surface integrals in the plasma. However, no tools are readily available to perform this task. Here we present a code (FREE-FIX) to compute a boundary condition for a free-boundary equilibrium given only the corresponding fixed-boundary equilibrium. An improvement to the standard solution method, allowing for much faster calculations, is presented. Applications are discussed. PPPL fund 245139 and DOE grant G00009102.

Experimental determination of plasma detachment from the diverging magnetic nozzle of the VASIMR VX-200 Electric Thruster

NASA Astrophysics Data System (ADS)

Olsen, Christopher; Squire, Jared; Longmier, Benjamin; Ballenger, Maxwell; Cassady, Leonard; Carter, Mark; Ilin, Andrew; Cloutier, Paul; Bering, Edgar; Giambusso, Matthew; Ad Astra Rocket Company Team; Rice University Collaboration; University of Houston Collaboration

2011-10-01

Theories of magnetized plasma detachment in an expanding magnetic field have been lacking detailed experimental evidence. Recent experiments using a 200 kW class electric rocket (VX-200), run at 100 kW using argon and a peak magnetic field of 2 T, produced ion energies greater than 100 eV with a flux of 2x1022 ions/s in a 150 m3 vacuum facility. Ion-neutral charge exchange effects were reduced and the resultant data show evidence of plasma detachment in a diverging magnetic field on a scale length of 2 m. The detachment is confirmed using multiple plasma diagnostics and magnetic nozzle topologies. Spatial maps of the data are compared to simulations from a particle detachment model, ParTraj, as well as MHD detachment theory. ParTraj, when compared to experiment, is shown to be more consistent in describing the data. Unless the MHD models are modified to incorporation two-fluid effects, single fluid MHD theory is inconsistent with the observations.

A hybrid Rayleigh-Taylor-current-driven coupled instability in a magnetohydrodynamically collimated cylindrical plasma with lateral gravity

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

Zhai, Xiang, E-mail: xzhai@caltech.edu; Bellan, Paul M., E-mail: pbellan@caltech.edu

We present an MHD theory of Rayleigh-Taylor instability on the surface of a magnetically confined cylindrical plasma flux rope in a lateral external gravity field. The Rayleigh-Taylor instability is found to couple to the classic current-driven instability, resulting in a new type of hybrid instability that cannot be described by either of the two instabilities alone. The lateral gravity breaks the axisymmetry of the system and couples all azimuthal modes together. The coupled instability, produced by combination of helical magnetic field, curvature of the cylindrical geometry, and lateral gravity, is fundamentally different from the classic magnetic Rayleigh-Taylor instability occurring atmore » a two-dimensional planar interface. The theory successfully explains the lateral Rayleigh-Taylor instability observed in the Caltech plasma jet experiment [Moser and Bellan, Nature 482, 379 (2012)]. Potential applications of the theory include magnetic controlled fusion, solar emerging flux, solar prominences, coronal mass ejections, and other space and astrophysical plasma processes.« less

Whistler and Alfvén Mode Cyclotron Masers in Space

NASA Astrophysics Data System (ADS)

Trakhtengerts, V. Y.; Rycroft, M. J.

2012-10-01

Preface; 1. Introduction; 2. Basic theory of cyclotron masers (CMs); 3. Linear theory of the cyclotron instability (CI); 4. Backward wave oscillator (BWO) regime in CMs; 5. Nonlinear cyclotron wave-particle interactions for a quasi-monochromatic wave; 6. Nonlinear interaction of quasi-monochromatic whistler mode waves with gyroresonant electrons in an in homogeneous plasma; 7. Wavelet amplification in an inhomogeneous plasma; 8. Quasi-linear theory of cyclotron masers; 9. Nonstationary generation regimes, and modulation effects; 10. ELF/VLF noise-like emissions and electrons in the Earth's radiation belts; 11. Generation of discrete ELF/VLF whistler mode emissions; 12. Cyclotron instability of the proton radiation belts; 13. Cyclotron masers elsewhere in the solar system and in laboratory plasma devices; Epilogue; Glossary of terms; List of acronyms; References; Index.

Maternal history of depression is associated with enhanced theory of mind in depressed and nondepressed adult women.

PubMed

Harkness, Kate Leslie; Washburn, Dustin; Theriault, Jordan Eugene; Lee, Lisa; Sabbagh, Mark Alan

2011-08-30

Theory of mind forms the basis of social cognition and develops on a stereotyped ontogenetic timetable. Yet, there are individual differences in theory of mind that may be transmitted through genetic and/or environmental mechanisms. In the current study we examined the relation of maternal history of depression to individual differences in theory of mind in a sample of adult women. Sixty-one depressed women (23% with a positive maternal history of depression) and 30 non-depressed women (33% with a positive maternal history of depression) completed the 'Reading the Mind in the Eyes task', a test of theory of mind decoding. Women with a maternal history of depression performed better on the Eyes task than those without. Further, the younger the mother's onset of depression, the better the current probands' Eyes task performance. These results are consistent with a broader literature linking hypersensitive social cognition and depression risk. We discuss the potential clinical implications of our results. Copyright © 2011 Elsevier Ltd. All rights reserved.

What is "theory of mind"? Concepts, cognitive processes and individual differences.

PubMed

Apperly, Ian A

2012-01-01

Research on "theory of mind" has traditionally focused on a narrow participant group (preschool children) using a narrow range of experimental tasks (most notably, false-belief tasks). Recent work has greatly expanded the age range of human participants tested to include human infants, older children, and adults, has devised new tasks, and has adopted methods from cognitive psychology and neuroscience. However, theoretical work has not kept pace with these changes, with the result that studies using one kind of method or participant group often inherit assumptions about the nature of theory of mind from other research, with little regard for whether these assumptions are appropriate. I argue that three distinct approaches to thinking about theory of mind are already implicit in research practice, and that future work, whether with infants, children, or adults, will benefit from articulating these approaches more clearly and following their different implications for what theory of mind is and how it should be studied.

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, J. R.; Stahara, S. S.

1984-01-01

The observed properties of bow waves and the associated plasma flows are outlined, along with those features identified that can be described by a continuum magnetohydrodynamic flow theory as opposed to a more detailed multicomponent particle and field plasma theory. The primary objectives are to provide an account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared. A number of deficiencies, ambiguities, and suggestions for improvements are discussed, and several significant extensions of the theory required to provide comparable results for all planets, their satellites, and comets are noted.

N = 2* Yang-Mills on the Lattice

NASA Astrophysics Data System (ADS)

Joseph, Anosh

2018-03-01

The N = 2* Yang-Mills theory in four dimensions is a non-conformal theory that appears as a mass deformation of maximally supersymmetric N = 4 Yang-Mills theory. This theory also takes part in the AdS/CFT correspondence and its gravity dual is type IIB supergravity on the Pilch-Warner background. The finite temperature properties of this theory have been studied recently in the literature. It has been argued that at large N and strong coupling this theory exhibits no thermal phase transition at any nonzero temperature. The low temperature N = 2* plasma can be compared to the QCD plasma. We provide a lattice construction of N = 2* Yang-Mills on a hypercubic lattice starting from the N = 4 gauge theory. The lattice construction is local, gauge-invariant, free from fermion doubling problem and preserves a part of the supersymmetry. This nonperturbative formulation of the theory can be used to provide a highly nontrivial check of the AdS/CFT correspondence in a non-conformal theory.

Presentation-Practice-Production and Task-Based Learning in the Light of Second Language Learning Theories.

ERIC Educational Resources Information Center

Ritchie, Graeme

2003-01-01

Features of presentation-practice-production (PPP) and task-based learning (TBL) models for language teaching are discussed with reference to language learning theories. Pre-selection of target structures, use of controlled repetition, and explicit grammar instruction in a PPP lesson are given. Suggests TBL approaches afford greater learning…

Analogical Reasoning: What Develops? A Review of Research and Theory.

ERIC Educational Resources Information Center

Goswami, Usha

1991-01-01

Children's analogical reasoning has traditionally been measured by classical four-term analogy tasks or problem-solving tasks. Current theories of analogical development and the evidence on which they are based are reviewed. It is concluded that structural views of analogical development are wrong, and knowledge-based accounts of what develops are…

The Problem State: A Cognitive Bottleneck in Multitasking

ERIC Educational Resources Information Center

Borst, Jelmer P.; Taatgen, Niels A.; van Rijn, Hedderik

2010-01-01

The main challenge for theories of multitasking is to predict when and how tasks interfere. Here, we focus on interference related to the problem state, a directly accessible intermediate representation of the current state of a task. On the basis of Salvucci and Taatgen's (2008) threaded cognition theory, we predict interference if 2 or more…

Increasing and Decreasing Intrinsic Interest with Contingent Rewards: A Test of Cognitive Evaluation Theory.

ERIC Educational Resources Information Center

Enzle, Michael E.; Ross, June M.

1978-01-01

University students worked puzzles and were given a high or low value cash award, contingent on simple task completion or on attainment of a performance level, or noncontingent and unexpected. Interest in the task after reward was analyzed. Results provided substantial support for Deci's cognitive evaluation theory. (Author/SJL)

Neurodevelopmental Correlates of Theory of Mind in Preschool Children

ERIC Educational Resources Information Center

Sabbagh, Mark A.; Bowman, Lindsay C.; Evraire, Lyndsay E.; Ito, Jennie M. B.

2009-01-01

Baseline electroencephalogram (EEG) data were collected from twenty-nine 4-year-old children who also completed batteries of representational theory-of-mind (RTM) tasks and executive functioning (EF) tasks. Neural sources of children's EEG alpha (6-9 Hz) were estimated and analyzed to determine whether individual differences in regional EEG alpha…

Beliefs about willpower moderate the effect of previous day demands on next day’s expectations and effective goal striving

PubMed Central

Bernecker, Katharina; Job, Veronika

2015-01-01

Research suggests that beliefs about willpower affect self-regulation following previous self-regulatory demands (Job et al., 2010). Some people believe that their willpower is limited, meaning that after a demanding task it needs to be replenished (limited theory). By contrast, others believe that willpower is not limited and that previous self-control tasks even activate willpower (non-limited theory). We hypothesized that when people experience a demanding day their beliefs about willpower predict their expected capacity to self-regulate and their actual self-regulation on the following day. In a daily diary study (N = 157), we measured students’ daily level of demands, their expected performance in unpleasant tasks, and their effective goal striving. Results showed that following a demanding day, students with a non-limited theory had higher expectations about their progress in unpleasant tasks and were striving more efficiently for their goals than students with a limited theory. These findings suggest that beliefs about willpower affect whether demands experienced on a previous day have positive or negative consequences on people’s self-regulation. PMID:26528198

Quantum kinetic theory of the filamentation instability

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

Bret, A.; Haas, F.

2011-07-15

The quantum electromagnetic dielectric tensor for a multi-species plasma is re-derived from the gauge-invariant Wigner-Maxwell system and presented under a form very similar to the classical one. The resulting expression is then applied to a quantum kinetic theory of the electromagnetic filamentation instability. Comparison is made with the quantum fluid theory including a Bohm pressure term and with the cold classical plasma result. A number of analytical expressions are derived for the cutoff wave vector, the largest growth rate, and the most unstable wave vector.

Pain judgements of patients' relatives: examining the use of social contract theory as theoretical framework.

PubMed

Kappesser, Judith; de C Williams, Amanda C

2008-08-01

Observer underestimation of others' pain was studied using a concept from evolutionary psychology: a cheater detection mechanism from social contract theory, applied to relatives and friends of chronic pain patients. 127 participants estimated characters' pain intensity and fairness of behaviour after reading four vignettes describing characters suffering from pain. Four cues were systematically varied: the character continuing or stopping liked tasks; continuing or stopping disliked tasks; availability of medical evidence; and pain intensity as rated by characters. Results revealed that pain intensity and the two behavioural variables had an effect on pain estimates: high pain self-reports and stopping all tasks led to high pain estimates; pain was estimated to be lowest when characters stopped disliked but continued with liked tasks. This combination was also rated least fair. Results support the use of social contract theory as a theoretical framework to explore pain judgements.

The mind behind the message: Advancing theory of mind scales for typically developing children, and those with deafness, autism, or Asperger Syndrome

PubMed Central

Peterson, Candida C.; Wellman, Henry M.; Slaughter, Virginia

2013-01-01

Children aged 3 to 12 years (n=184) with typical development, deafness, autism or Asperger Syndrome took a series of theory-of-mind (ToM) tasks to confirm and extend previous developmental scaling evidence. A new sarcasm task, in the format of Wellman and Liu’s (2004) 5-step ToM scale, added a statistically reliable sixth step to the scale for all diagnostic groups. A key previous finding, divergence in task sequencing for children with autism, was confirmed. Comparisons among diagnostic groups, controlling age and language ability, showed that typical developers mastered the six ToM steps ahead of each of the three disabled groups, with implications for ToM theories. The final (sarcasm) task challenged even nondisabled 9-year-olds, demonstrating the new scale’s sensitivity to post-preschool ToM growth. PMID:22304467

The impact of verbal capacity on theory of mind in deaf and hard of hearing children.

PubMed

Levrez, Clovis; Bourdin, Beatrice; Le Driant, Barbara; D'Arc, Baudouin Forgeot; Vandromme, Luc

2012-01-01

Even when they have good language skills, many children with hearing loss lag several years behind hearing children in the ability to grasp beliefs of others. The researchers sought to determine whether this lag results from difficulty with the verbal demands of tasks or from conceptual delays. The researchers related children's performance on a nonverbal theory of mind task to their scores on verbal aptitude tests. Twelve French children (average age about 10 years) with severe to profound hearing loss and 12 French hearing children (average about 7 years) were evaluated. The children with hearing loss showed persistent difficulty with theory of mind tasks, even a nonverbal task, presenting results similar to those of hearing 6-year-olds. Also, the children with hearing loss showed a correlation between language level (lexical and morphosyntactic) and understanding of false beliefs. No such correlation was found in the hearing children.

The effect of cognitive-motor dual-task training on cognitive function and plasma amyloid β peptide 42/40 ratio in healthy elderly persons: a randomized controlled trial.

PubMed

Yokoyama, Hisayo; Okazaki, Kazunobu; Imai, Daiki; Yamashina, Yoshihiro; Takeda, Ryosuke; Naghavi, Nooshin; Ota, Akemi; Hirasawa, Yoshikazu; Miyagawa, Toshiaki

2015-05-28

Physical activity reduces the incidence and progression of cognitive impairment. Cognitive-motor dual-task training, which requires dividing attention between cognitive tasks and exercise, may improve various cognitive domains; therefore, we examined the effect of dual-task training on the executive functions and on plasma amyloid β peptide (Aβ) 42/40 ratio, a potent biomarker of Alzheimer's disease, in healthy elderly people. Twenty-seven sedentary elderly people participated in a 12-week randomized, controlled trial. The subjects assigned to the dual-task training (DT) group underwent a specific cognitive-motor dual-task training, and then the clinical outcomes, including cognitive functions by the Modified Mini-Mental State (3MS) examination and the Trail-Making Test (TMT), and the plasma Aβ 42/40 ratio following the intervention were compared with those of the control single-task training (ST) group by unpaired t-test. Among 27 participants, 25 completed the study. The total scores in the 3MS examination as well as the muscular strength of quadriceps were equally improved in both groups after the training. The specific cognitive domains, "registration & recall", "attention", "verbal fluency & understanding", and "visuospatial skills" were significantly improved only in the DT group. Higher scores in "attention", "verbal fluency & understanding", and "similarities" were found in the DT group than in the ST group at post-intervention. The absolute changes in the total (8.5 ± 1.6 vs 2.4 ± 0.9, p = 0.004, 95 % confidence interval (CI) 0.75-3.39) and in the scores of "attention" (1.9 ± 0.5 vs -0.2 ± 0.4, p = 0.004, 95 % CI 2.25-9.98) were greater in the DT group than in the ST group. We found no changes in the TMT results in either group. Plasma Aβ 42/40 ratio decreased in both groups following the training (ST group: 0.63 ± 0.13 to 0.16 ± 0.03, p = 0.001; DT group: 0.60 ± 0.12 to 0.25 ± 0.06, p = 0.044), although the pre- and post-intervention values were not different between the groups for either measure. Cognitive-motor dual-task training was more beneficial than single-task training alone in improving broader domains of cognitive functions of elderly persons, and the improvement was not directly due to modulating Aβ metabolism.

Phenomenological theory of laser-plasma interaction in ``bubble'' regime

NASA Astrophysics Data System (ADS)

Kostyukov, I.; Pukhov, A.; Kiselev, S.

2004-11-01

The electron trapping in the "bubble" regime of laser-plasma interaction as proposed by Pukhov and Meyer-ter-Vehn [A. Pukhov and J. Meyer-ter-Vehn, Appl. Phys. B 74, 355 (2002)] is studied. In this regime the laser pulse generates a solitary plasma electron cavity: the bubble. It is free from the cold plasma electrons and runs with nearly light velocity. The present work discusses the form of the bubble and the spatial distribution of electromagnetic fields within the cavity. We extend the one-dimensional electron capture theory to the three-dimensional case. It is shown that the bubble can trap plasma electrons. The trapping condition is derived and the trapping cross section is estimated. Electron motion in the self-generated electron bunch is investigated. Estimates for the maximum of electron bunch energy and the bunch density are provided.

“The Marshall Rosenbluth International Summer School – 2007: Plasma Thermonuclear Fusion and Plasma Astrophysics – 2007”

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

Stefan, Vladislav Alexander

Contents: H. Berk: Frequency Sweeping Due to Phase Space Structure Formation in Plasmas M. Campbell : The Legacy of Marshall Rosenbluth in the Development of the Laser Fusion Program in the United States J. Candy: Gyrokinetic Simulations of Fusion Plasmas P. Diamond: The Legacy of Marshall Rosenbluth in Magnetic Confinement Theory G-Y. Fu: Nonlinear Hybrid Simulations of Multiple Energetic Particle Driven Alfven Modes in Toroidal Plasmas O. Gurcan: Theory of Intrinsic Rotation and Momentum Transport V. L. Jacobs: Kinetic and Spectral Descriptions for Atomic Processes in Astrophysical and Laboratory Plasmas C. F. Kennel: Marshall Rosenbluth and Roald Sagdeev in Trieste:Themore » Birth of Modern Space Plasma N. A. Krall: The Contribution of Marshall Rosenbluth in the Development of Plasma Drift Wave and Universal Instability Theories C. S. Liu: The Legacy of Marshall Rosenbluth in Laser-Plasma Interaction Research N. Rostoker: Plasma Physics Research With Marshall Rosenbluth - My Teacher R. Z. Sagdeev: The Legacy of Marshall Rosenbluth in Plasma Physics V. Alexander Stefan A Note on the Rosenbluth Paper: Phys. Rev. Letters, 29, 565 (1972), and the Research in Parametric Plasma Theory Thereupon J. W. Van Dam: The Role of Marshall Rosenbluth in the Development of the Thermonuclear Fusion Program in the U.S.A. E. P. Velikhov: Problems in Plasma Astrophysics R. White: The Role of Marshall Rosenbluth in the Development of the Particle and MHD Interaction in Plasmas X. Xu: Edge Gyrokinetic Theory and Continuum Simulations Marshall Nicholas ROSENBLUTH (A Brief Biography) b. February 5,1927 - Albany, New York. d. September 28, 2003 - San Diego, California. M. N. Rosenbluth, a world-acclaimed scientist, is one of the ultimate authorities in plasma and thermonuclear fusion research, often indicated by the sobriquet the "Pope of Plasma Physics." His theoretical contributions have been central to the development of controlled thermonuclear fusion. In the 1950s his pioneering work in plasma instabilities, together with pioneering works of A. Sakharov, I. Tamm, L. Spitzer, Jr., L. A. Artsimovich, and others, led to the design of the TOKAMAK, the principal configuration used for contemporary magnetic fusion experiments. In addition to his research achievements, he has made significant administrative contributions as a scientific advisor in the fields of energy policy and national defense. He is the founder and the first director of The Institute for Fusion Studies at Austin, Texas. M. N. Rosenbluth has been the recipient of the E. O. Lawrence Memorial Award (1964),the Albert Einstein Award (1967),the James Clerk Maxwell prize in Plasma Physics(1976),and the Enrico Fermi Award (1986). M. N. Rosenbluth had been Science Advisor for the INSTITUTE for ADVANCED PHYSICS STUDIES (presently a division of The Stefan University) since 1989. He is the editor-in-chief of the FSRC, (Frontier Science Research Conferences) Book: "NEW IDEAS in TOKAMAK CONFINEMENT" Published by the American Institute of Physics (August 1994) in the Research Trends in Physics Series founded and edited by V. Alexander Stefan in 1989. M. N. Rosenbluth was a member of the American Academy of Arts and Sciences and the National Academy of Sciences of the USA, a Professor Emeritus at the University of California, San Diego, and a Senior Scientist at General Atomics, San Diego.« less

New evidence in theory of mind deficits in subjects with chronic schizophrenia and first episode: correlation with symptoms, neurocognition and social function.

PubMed

Mazza, Monica; Pollice, Rocco; Pacitti, Francesca; Pino, Maria Chiara; Mariano, Melania; Tripaldi, Simona; Casacchia, Massimo; Roncone, Rita

2012-01-01

Currently substantial evidence exists about Theory of Mind (ToM) impairment in subjects affected by chronic and first episode schizophrenia. In particular, in order to enhance the validity of our construct, we used in this study classical false beliefs tasks and advanced theory of mind tasks, together with the application of structural equation model, in order to ex-amine whether we are using ToM tasks with good psychometric properties. The main goal of the present study was to examine ToM deficits in a large sample including subjects suffering from chronic schizophrenia, first episode of schizophrenia and nor-mal controls, by observing in the same task the relationship with symptomatological gravity, neurocognition and social function.Materials and methods. A sample of 178 patients with chronic schizophrenia, a sample of 49 subjects with a first episode of psychosis and 484 healthy controls participated to this study. Measures of social cognition included task of false belief and advanced theory of mind task. No significant differences were found on ToM tasks between subjects affected by chronic and first episode schizophrenia. Social cognition showed in both groups a strong correlation with negative symptoms and social function, but did not evidence any relationship with neurocognition. CONCLUSION; ToM deficits exist in subjects suffering from chronic and first episode schizophrenia. These impairments do not seem to be a consequence of illness condition, they are likely to be state-independent and appear to be the most important cognitive mediator of social functioning in both groups.

Understanding the allocation of attention when faced with varying perceptual load in partial report: a computational approach.

PubMed

Kyllingsbæk, Søren; Sy, Jocelyn L; Giesbrecht, Barry

2011-05-01

The allocation of visual processing capacity is a key topic in studies and theories of visual attention. The load theory of Lavie (1995) proposes that allocation happens in two steps where processing resources are first allocated to task-relevant stimuli and secondly remaining capacity 'spills over' to task-irrelevant distractors. In contrast, the Theory of Visual Attention (TVA) proposed by Bundesen (1990) assumes that allocation happens in a single step where processing capacity is allocated to all stimuli, both task-relevant and task-irrelevant, in proportion to their relative attentional weight. Here we present data from two partial report experiments where we varied the number and discriminability of the task-irrelevant stimuli (Experiment 1) and perceptual load (Experiment 2). The TVA fitted the data of the two experiments well thus favoring the simple explanation with a single step of capacity allocation. We also show that the effects of varying perceptual load can only be explained by a combined effect of allocation of processing capacity as well as limits in visual working memory. Finally, we link the results to processing capacity understood at the neural level based on the neural theory of visual attention by Bundesen et al. (2005). Copyright © 2010 Elsevier Ltd. All rights reserved.

The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks: A Systematic Review With Meta-analysis.

PubMed

Lopes, Thiago Jambo Alves; Simic, Milena; Myer, Gregory D; Ford, Kevin R; Hewett, Timothy E; Pappas, Evangelos

2018-05-01

Anterior cruciate ligament (ACL) tear is a common injury in sports and often occurs during landing from a jump. To synthesize the evidence on the effects of injury prevention programs (IPPs) on landing biomechanics as they relate to the ligament, quadriceps, trunk, and leg dominance theories associated with ACL injury risk. Meta-analysis. Six electronic databases were searched for studies that investigated the effect of IPPs on landing task biomechanics. Prospective studies that reported landing biomechanics at baseline and post-IPP were included. Results from trunk, hip, and knee kinematics and kinetics related to the ACL injury theories were extracted, and meta-analyses were performed when possible. The criteria were met by 28 studies with a total of 466 participants. Most studies evaluated young females, bilateral landing tasks, and recreational athletes, while most variables were related to the ligament and quadriceps dominance theories. An important predictor of ACL injury, peak knee abduction moment, decreased ( P = .01) after the IPPs while other variables related to the ligament dominance theory did not change. Regarding the quadriceps dominance theory, after the IPPs, angles of hip flexion at initial contact ( P = .009), peak hip flexion ( P = .002), and peak knee flexion ( P = .007) increased, while knee flexion at initial contact did not change ( P = .18). Moreover, peak knee flexion moment decreased ( P = .005) and peak vertical ground-reaction force did not change ( P = .10). The exercises used in IPPs might have the potential to improve landing task biomechanics related to the quadriceps dominance theory, especially increasing peak knee and hip flexion angles. Importantly, peak knee abduction moment decreased, which indicates that IPPs influence a desired movement strategy to help athletes overcome dangerous ligament dominance loads arising from lack of frontal plane control during dynamic tasks. The lack of findings for some biomechanical variables suggests that future IPPs may be enhanced by targeting participants' baseline profile deficits, highlighting the need to deliver an individualized and task-specific IPP.

Compound risk judgment in tasks with both idiosyncratic and systematic risk: The "Robust Beauty" of additive probability integration.

PubMed

Sundh, Joakim; Juslin, Peter

2018-02-01

In this study, we explore how people integrate risks of assets in a simulated financial market into a judgment of the conjunctive risk that all assets decrease in value, both when assets are independent and when there is a systematic risk present affecting all assets. Simulations indicate that while mental calculation according to naïve application of probability theory is best when the assets are independent, additive or exemplar-based algorithms perform better when systematic risk is high. Considering that people tend to intuitively approach compound probability tasks using additive heuristics, we expected the participants to find it easiest to master tasks with high systematic risk - the most complex tasks from the standpoint of probability theory - while they should shift to probability theory or exemplar memory with independence between the assets. The results from 3 experiments confirm that participants shift between strategies depending on the task, starting off with the default of additive integration. In contrast to results in similar multiple cue judgment tasks, there is little evidence for use of exemplar memory. The additive heuristics also appear to be surprisingly context-sensitive, with limited generalization across formally very similar tasks. Copyright © 2017 Elsevier B.V. All rights reserved.

Relativistic transport theory for a two-temperature magnetized plasma

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

Metens, T.; Balescu, R.

1990-09-01

The relativistic kinetic theory of linear transport is worked out within the framework of a new moment method. A complete analytical study of the transport in a two-temperature inhomogeneous magnetized fusion plasma is given. The transport relations and coefficients are derived from the kinetic equation with the full relativistic Beliaev--Budker collision operator and the impact of relativistic effects on the confinement are investigated.

Gyrotropic Guiding-Center Fluid Theory for Turbulent Inhomogeneous Magnetized Plasma

DTIC Science & Technology

2006-01-01

this paper, a new fluid theory is given in the guiding-center and gyrotropic approximation which is derivable from the Vlasov-Maxwell equations . The... equations can be solved (1) by using measurements of the low-order velocity moments to specify the initial and boundary conditions. 15. SUBJECT TERMS...Vlasov-Maxwell equations Fokker-Planck operator guiding-center Inhomogeneous, gyrotropic, magnetized plasma 16. SECURITY CLASSIFICATION OF: 17

Effect of hydrodynamic interactions on the diffusion of integral membrane proteins: diffusion in plasma membranes.

PubMed Central

Bussell, S J; Koch, D L; Hammer, D A

1995-01-01

Tracer diffusion coefficients of integral membrane proteins (IMPs) in intact plasma membranes are often much lower than those found in blebbed, organelle, and reconstituted membranes. We calculate the contribution of hydrodynamic interactions to the tracer, gradient, and rotational diffusion of IMPs in plasma membranes. Because of the presence of immobile IMPs, Brinkman's equation governs the hydrodynamics in plasma membranes. Solutions of Brinkman's equation enable the calculation of short-time diffusion coefficients of IMPs. There is a large reduction in particle mobilities when a fraction of them is immobile, and as the fraction increases, the mobilities of the mobile particles continue to decrease. Combination of the hydrodynamic mobilities with Monte Carlo simulation results, which incorporate excluded area effects, enable the calculation of long-time diffusion coefficients. We use our calculations to analyze results for tracer diffusivities in several different systems. In erythrocytes, we find that the hydrodynamic theory, when combined with excluded area effects, closes the gap between existing theory and experiment for the mobility of band 3, with the remaining discrepancy likely due to direct obstruction of band 3 lateral mobility by the spectrin network. In lymphocytes, the combined hydrodynamic-excluded area theory provides a plausible explanation for the reduced mobility of sIg molecules induced by binding concanavalin A-coated platelets. However, the theory does not explain all reported cases of "anchorage modulation" in all cell types in which receptor mobilities are reduced after binding by concanavalin A-coated platelets. The hydrodynamic theory provides an explanation of why protein lateral mobilities are restricted in plasma membranes and why, in many systems, deletion of the cytoplasmic tail of a receptor has little effect on diffusion rates. However, much more data are needed to test the theory definitively. We also predict that gradient and tracer diffusivities are the same to leading order. Finally, we have calculated rotational diffusion coefficients in plasma membranes. They decrease less rapidly than translational diffusion coefficients with increasing protein immobilization, and the results agree qualitatively with the limited experimental data available. PMID:7612825

Time-dependent behavior in a transport-barrier model for the quasi-single helcity state

NASA Astrophysics Data System (ADS)

Terry, P. W.; Whelan, G. G.

2014-09-01

Time-dependent behavior that follows from a recent theory of the quasi-single-helicity (QSH) state of the reversed field pinch is considered. The theory (Kim and Terry 2012 Phys. Plasmas 19 122304) treats QSH as a core fluctuation structure tied to a tearing mode of the same helicity, and shows that strong magnetic and velocity shears in the structure suppress the nonlinear interaction with other fluctuations. By summing the multiple helicity fluctuation energies over wavenumber, we reduce the theory to a predator-prey model. The suppression of the nonlinear interaction is governed by the single helicity energy, which, for fixed radial structure, controls the magnetic and velocity shearing rates. It is also controlled by plasma current which, in the theory, sets the shearing threshold for suppression. The model shows a limit cycle oscillation in which the system toggles between QSH and multiple helicity states, with the single helicity phase becoming increasingly long-lived relative to the multiple helicity phase as plasma current increases.

Why Does Working Memory Capacity Predict Variation in Reading Comprehension? On the Influence of Mind Wandering and Executive Attention

PubMed Central

McVay, Jennifer C.; Kane, Michael J.

2012-01-01

Some people are better readers than others, and this variation in comprehension ability is predicted by measures of working memory capacity (WMC). The primary goal of this study was to investigate the mediating role of mind wandering experiences in the association between WMC and normal individual differences in reading comprehension, as predicted by the executive-attention theory of WMC (e.g., Engle & Kane, 2004). We used a latent-variable, structural-equation-model approach, testing skilled adult readers on three WMC span tasks, seven varied reading comprehension tasks, and three attention-control tasks. Mind wandering was assessed using experimenter-scheduled thought probes during four different tasks (two reading, two attention-control tasks). The results support the executive-attention theory of WMC. Mind wandering across the four tasks loaded onto a single latent factor, reflecting a stable individual difference. Most importantly, mind wandering was a significant mediator in the relationship between WMC and reading comprehension, suggesting that the WMC-comprehension correlation is driven, in part, by attention control over intruding thoughts. We discuss implications for theories of WMC, attention control, and reading comprehension. PMID:21875246

Executive function is necessary for perspective selection, not Level-1 visual perspective calculation: evidence from a dual-task study of adults.

PubMed

Qureshi, Adam W; Apperly, Ian A; Samson, Dana

2010-11-01

Previous research suggests that perspective-taking and other "theory of mind" processes may be cognitively demanding for adult participants, and may be disrupted by concurrent performance of a secondary task. In the current study, a Level-1 visual perspective task was administered to 32 adults using a dual-task paradigm in which the secondary task tapped executive function. Results suggested that the secondary task did not affect the calculation of perspective, but did affect the selection of the relevant (Self or Other) perspective for a given trial. This is the first direct evidence of a cognitively efficient process for "theory of mind" in adults that operates independently of executive function. The contrast between this and previous findings points to a distinction between simple perspective-taking and the more complex and cognitively demanding abilities more typically examined in studies of "theory of mind". It is suggested that these findings may provide a parsimonious explanation of the success of infants on 'indirect' measures of perspective-taking that do not explicitly require selection of the relevant perspective. Copyright © 2010 Elsevier B.V. All rights reserved.

Probability Theory Plus Noise: Descriptive Estimation and Inferential Judgment.

PubMed

Costello, Fintan; Watts, Paul

2018-01-01

We describe a computational model of two central aspects of people's probabilistic reasoning: descriptive probability estimation and inferential probability judgment. This model assumes that people's reasoning follows standard frequentist probability theory, but it is subject to random noise. This random noise has a regressive effect in descriptive probability estimation, moving probability estimates away from normative probabilities and toward the center of the probability scale. This random noise has an anti-regressive effect in inferential judgement, however. These regressive and anti-regressive effects explain various reliable and systematic biases seen in people's descriptive probability estimation and inferential probability judgment. This model predicts that these contrary effects will tend to cancel out in tasks that involve both descriptive estimation and inferential judgement, leading to unbiased responses in those tasks. We test this model by applying it to one such task, described by Gallistel et al. ). Participants' median responses in this task were unbiased, agreeing with normative probability theory over the full range of responses. Our model captures the pattern of unbiased responses in this task, while simultaneously explaining systematic biases away from normatively correct probabilities seen in other tasks. Copyright © 2018 Cognitive Science Society, Inc.

Task-Induced Development of Hinting Behaviors in Online Task-Oriented L2 Interaction

ERIC Educational Resources Information Center

Balaman, Ufuk

2018-01-01

Technology-mediated task settings are rich interactional domains in which second language (L2) learners manage a multitude of interactional resources for task accomplishment. The affordances of these settings have been repeatedly addressed in computer-assisted language learning (CALL) literature mainly based on theory-informed task design…

Making sense of theory of mind and paranoia: the psychometric properties and reasoning requirements of a false belief sequencing task.

PubMed

Corcoran, Rhiannon; Bentall, Richard P; Rowse, Georgina; Moore, Rosanne; Cummins, Sinead; Blackwood, Nigel; Howard, Robert; Shryane, Nick M

2011-11-01

INTRODUCTION. This study used Item-Response Theory (IRT) to model the psychometric properties of a false belief picture sequencing task. Consistent with the mental time travel hypothesis of paranoia, we anticipated that performance on this deductive theory of mind (ToM) task would not be associated with the presence of persecutory delusions but would be related to other clinical, cognitive, and demographic factors. METHOD. A large (N=237) and diverse clinical and nonclinical sample differing in levels of depression and paranoid ideation performed 2 ToM tasks: the false belief sequencing task and a ToM stories task that was used to assess the validity of the false belief sequencing task as a measure of ToM. RESULTS. A unidimensional IRT model was found to fit the data well. Latent ToM ability as measured by the false belief sequencing task was negatively related with age and positively with IQ. In contrast to the ToM stories measure, there was no association between clinical diagnosis or symptoms and false belief picture sequencing after controlling for age and IQ. CONCLUSIONS. In line with mental time travel hypothesis of paranoia (Corcoran, 2010 ), performance on this deductive nonverbal ToM task is not related to the presence of paranoid symptoms. This measure is best suited for assessing ToM functioning where participants' performance falls just short of the average latent ToM ability. Furthermore, it is sensitive to the effects of increasing age and decreasing IQ.

Theory and observations of high frequency Alfvén eigenmodes in low aspect ratio plasmas

NASA Astrophysics Data System (ADS)

Gorelenkov, N. N.; Fredrickson, E.; Belova, E.; Cheng, C. Z.; Gates, D.; Kaye, S.; White, R.

2003-04-01

New observations of sub-cyclotron frequency instability in low aspect ratio plasmas in national spherical torus experiments are reported. The frequencies of observed instabilities correlate with the characteristic Alfvén velocity of the plasma. A theory of localized compressional Alfvén eigenmodes (CAE) and global shear Alfvén eigenmodes (GAE) in low aspect ratio plasmas is presented to explain the observed high frequency instabilities. CAEs/GAEs are driven by the velocity space gradient of energetic super-Alfvénic beam ions via Doppler shifted cyclotron resonances. One of the main damping mechanisms of GAEs, the continuum damping, is treated perturbatively within the framework of ideal MHD. Properties of these cyclotron instability ions are presented.

Study of self-focusing of Non Gaussian laser beam in a plasma with density variation using moment theory approach

NASA Astrophysics Data System (ADS)

Pathak, Nidhi; Kaur, Sukhdeep; Singh, Sukhmander

2018-05-01

In this paper, self-focusing/defocusing effects have been studied by taking into account the combined effect of ponder-motive and relativistic non linearity during the laser plasma interaction with density variation. The formulation is based on the numerical analysis of second order nonlinear differential equation for appropriate set of laser and plasma parameters by employing moment theory approach. We found that self-focusing increases with increasing the laser intensity and density variation. The results obtained are valuable in high harmonic generation, inertial confinement fusion and charge particle acceleration.

The Exploration of Hot Nuclear Matter

NASA Astrophysics Data System (ADS)

Jacak, Barbara V.; Müller, Berndt

2012-07-01

When nuclear matter is heated beyond 2 trillion degrees, it becomes a strongly coupled plasma of quarks and gluons. Experiments using highly energetic collisions between heavy nuclei have revealed that this new state of matter is a nearly ideal, highly opaque liquid. A description based on string theory and black holes in five dimensions has made the quark-gluon plasma an archetypical strongly coupled quantum system. Open questions about the structure and theory of the quark-gluon plasma are under active investigation. Many of the insights are also relevant to ultracold fermionic atoms and strongly correlated condensed matter.

Lenard-Balescu calculations and classical molecular dynamics simulations of electrical and thermal conductivities of hydrogen plasmas

DOE PAGES

Whitley, Heather D.; Scullard, Christian R.; Benedict, Lorin X.; ...

2014-12-04

Here, we present a discussion of kinetic theory treatments of linear electrical and thermal transport in hydrogen plasmas, for a regime of interest to inertial confinement fusion applications. In order to assess the accuracy of one of the more involved of these approaches, classical Lenard-Balescu theory, we perform classical molecular dynamics simulations of hydrogen plasmas using 2-body quantum statistical potentials and compute both electrical and thermal conductivity from out particle trajectories using the Kubo approach. Our classical Lenard-Balescu results employing the identical statistical potentials agree well with the simulations.

Testing the domain-specificity of a theory of mind deficit in brain-injured patients: evidence for consistent performance on non-verbal, "reality-unknown" false belief and false photograph tasks.

PubMed

Apperly, Ian A; Samson, Dana; Chiavarino, Claudia; Bickerton, Wai-Ling; Humphreys, Glyn W

2007-05-01

To test the domain-specificity of "theory of mind" abilities we compared the performance of a case-series of 11 brain-lesioned patients on a recently developed test of false belief reasoning () and on a matched false photograph task, which did not require belief reasoning and which addressed problems with existing false photograph methods. A strikingly similar pattern of performance was shown across the false belief and false photograph tests. Patients who were selectively impaired on false belief tasks were also impaired on false photograph tasks; patients spared on false belief tasks also showed preserved performance with false photographs. In some cases the impairment on false belief and false photograph tasks coincided with good performance on control tasks matched for executive demands. We discuss whether the patients have a domain-specific deficit in reasoning about representations common to both false belief and false photograph tasks.

Particle in cell simulation of instabilities in space and astrophysical plasmas

NASA Astrophysics Data System (ADS)

Tonge, John William

Several plasma instabilities relevant to space physics are investigated using the parallel PIC plasma simulation code P3arsec. This thesis addresses electrostatic micro-instabilities relevant to ion ring distributions, proceeds to electromagnetic micro-instabilities pertinent to streaming plasmas, and then to the stability of a plasma held in the field of a current rod. The physical relevance of each of these instabilities is discussed, a phenomenological description is given, and analytic and simulation results are presented and compared. Instability of a magnetized plasma with a portion of the ions in a velocity ring distribution around the magnetic field is investigated using simulation and analytic theory. The physics of this distribution is relevant to solar flares, x-ray emission by comets, and pulsars. Physical parameters, including the mass ratio, are near those of a solar flare in the simulation. The simulation and analytic results show agreement in the linear regime. In the nonlinear stage the simulation shows highly accelerated electrons in agreement with the observed spectrum of x-rays emitted by solar flares. A mildly relativistic streaming electron positron plasma with no ambient magnetic field is known to be unstable to electrostatic (two-stream/beam instability) and purely electromagnetic (Weibel) modes. This instability is relevant to highly energetic interstellar phenomena, including pulsars, supernova remnants, and the early universe. It is also important for experiments in which relativistic beams penetrate a background plasma, as in fast ignitor scenarios. Cold analytic theory is presented and compared to simulations. There is good agreement in the regime where cold theory applies. The simulation and theory shows that to properly characterize the instability, directions parallel and perpendicular to propagation of the beams must be considered. A residual magnetic field is observed which may be of astro-physical significance. The stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while the current rod is much easier to analyze theoretically and realize in simulations. The stability properties of a plasma confined in a dipole field are important for understanding a variety of space phenomena and the Levitated Dipole eXperiment (LDX). Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles ∝ r-10/3. The simulations also show that the density profile will be stationary as long as density ∝ r -2 even though the temperature profile may not be stable.

Thermal barrier coating life prediction model development

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.; Mcknight, R. L.; Cook, T. S.; Hartle, M. S.

1988-01-01

This report describes work performed to determine the predominat modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consisted of a low pressure plasma sprayed NiCrAlY bond coat, an air plasma sprayed ZrO2-Y2O3 top coat, and a Rene' 80 substrate. The work was divided into 3 technical tasks. The primary failure mode to be addressed was loss of the zirconia layer through spalling. Experiments showed that oxidation of the bond coat is a significant contributor to coating failure. It was evident from the test results that the species of oxide scale initially formed on the bond coat plays a role in coating degradation and failure. It was also shown that elevated temperature creep of the bond coat plays a role in coating failure. An empirical model was developed for predicting the test life of specimens with selected coating, specimen, and test condition variations. In the second task, a coating life prediction model was developed based on the data from Task 1 experiments, results from thermomechanical experiments performed as part of Task 2, and finite element analyses of the TBC system during thermal cycles. The third and final task attempted to verify the validity of the model developed in Task 2. This was done by using the model to predict the test lives of several coating variations and specimen geometries, then comparing these predicted lives to experimentally determined test lives. It was found that the model correctly predicts trends, but that additional refinement is needed to accurately predict coating life.

Free recall and outdoor running: cognitive and physical demand interference.

PubMed

Epling, Samantha L; Blakely, Megan J; Russell, Paul N; Helton, William S

2016-10-01

Cognitive resource theory is a proposed explanation for people's limited ability to perform multiple tasks simultaneously. Reallocation of a restricted supply of cognitive resources to two or more tasks may be detrimental to performance on one or both tasks. Many professionals in high-risk fields, such as those engaged in firefighting, military, and search and rescue missions, face simultaneous mental and physical demands, yet little is known about the resources required to move over the natural terrain these operators may encounter. In the present research, we investigated whether interference was found between outdoor running and a word recall task. As hypothesized, a reduction in word recall was observed in the dual task compared to a recall-alone task; however, the distance run was not significantly different between the dual task and the run-alone task. Subjective reports of workload, task focus, and being "spent" (measures calculated from responses on a questionnaire) were greatest in the dual task. These results support the cognitive resource theory and have important theoretical and practical implications. Further research is required to better understand the type and extent of cognitive resources required by such physical tasks and the potential interference with simultaneous mental tasks.

Quark soup al dente: applied superstring theory

NASA Astrophysics Data System (ADS)

Myers, R. C.; Vázquez, S. E.

2008-06-01

In recent years, experiments have discovered an exotic new state of matter known as the strongly coupled quark gluon plasma (sQGP). At present, it seems that standard theoretical tools, such as perturbation theory and lattice gauge theory, are poorly suited to understand this new phase. However, recent progress in superstring theory has provided us with a theoretical laboratory for studying very similar systems of strongly interacting hot non-Abelian plasmas. This surprising new perspective extracts the fluid properties of the sQGP from physical processes in a black hole spacetime. Hence we may find the answers to difficult particle physics questions about the sQGP from straightforward calculations in classical general relativity.

Propagation velocities of laser-produced plasmas from copper wire targets and water droplets

NASA Technical Reports Server (NTRS)

Song, Kyo-Dong; Alexander, Dennis R.

1994-01-01

Experiments were performed to determine the plasma propagation velocities resulting from KrF laser irradiation of copper wire target (75 microns diameter) and water droplets (75 microns diameter) at irradiance levels ranging from 25 to 150 GW/sq cm. Plasma propagation velocities were measured using a streak camera system oriented orthogonally to the high-energy laser propagation axis. Plasma velocities were studied as a function of position in the focused beam. Results show that both the shape of the plasma formation and material removal from the copper wire are different and depend on whether the targets are focused or slightly defocused (approximately = 0.5 mm movement in the beam axis). Plasma formation and its position relative to the target is an important factor in determining the practical focal point during high-energy laser interaction with materials. At irradiance of 100 GW/sq cm, the air plasma has two weak-velocity components which propagate toward and away from the incident laser while a strong-velocity component propagates away from the laser beam as a detonation wave. Comparison of the measured breakdown velocities (in the range of 2.22-2.27 x 10(exp 5) m/s) for air and the value calculated by the nonlinear breakdown wave theory at irradiance of 100 GW/sq cm showed a quantitative agreement within approximately 50% while the linear theory and Gaussian pulse theory failed. The detonation wave velocities of plasma generated from water droplets and copper wire targets for different focused cases were measured and analyzed theoretically. The propagation velocities of laser-induced plasma liquid droplets obtained by previous research are compared with current work.

Nonlinear, relativistic Langmuir waves in astrophysical magnetospheres

NASA Technical Reports Server (NTRS)

Chian, Abraham C.-L.

1987-01-01

Large amplitude, electrostatic plasma waves are relevant to physical processes occurring in the astrophysical magnetospheres wherein charged particles are accelerated to relativistic energies by strong waves emitted by pulsars, quasars, or radio galaxies. The nonlinear, relativistic theory of traveling Langmuir waves in a cold plasma is reviewed. The cases of streaming electron plasma, electronic plasma, and two-streams are discussed.

Student Musicians' Self- and Task-Theories of Musical Performance: The Influence of Primary Genre Affiliation

ERIC Educational Resources Information Center

Hewitt, Allan

2009-01-01

One hundred and sixty-five undergraduate music students studying in Scotland completed a 30-statement Q-sort to describe their self- and task-theories of musical performance. Statements reflected the importance of effort, confidence, technical ability, significant others and luck/chance in determining a successful performance. The Q-sorts were…

Positive and Negative Effects of Family Involvement on Work-Related Burnout

ERIC Educational Resources Information Center

ten Brummelhuis, Lieke L.; van der Lippe, Tanja; Kluwer, Esther S.; Flap, Henk

2008-01-01

We aimed to explain the influence of family involvement on feelings of burnout among employees who combine work and family tasks. As proxies for family involvement, we used the family structure (partner, number and age of children) and family tasks (e.g. hours spent on household chores). We compared conflict theory and enrichment theory, and…

Secret Keepers: Children's Theory of Mind and Their Conception of Secrecy

ERIC Educational Resources Information Center

Colwell, Malinda J.; Corson, Kimberly; Sastry, Anuradha; Wright, Holly

2016-01-01

In this mixed methods study, semi-structured interviews were conducted with 3-5-year-olds (n?=?21) in a university-sponsored preschool programme and children completed a theory of mind (ToM) task. After grouping children into pass/no pass groups for the ToM tasks, analyses using interpretive phenomenology indicated that preschool children explain…

Why does working memory capacity predict variation in reading comprehension? On the influence of mind wandering and executive attention.

PubMed

McVay, Jennifer C; Kane, Michael J

2012-05-01

Some people are better readers than others, and this variation in comprehension ability is predicted by measures of working memory capacity (WMC). The primary goal of this study was to investigate the mediating role of mind-wandering experiences in the association between WMC and normal individual differences in reading comprehension, as predicted by the executive-attention theory of WMC (e.g., Engle & Kane, 2004). We used a latent-variable, structural-equation-model approach, testing skilled adult readers on 3 WMC span tasks, 7 varied reading-comprehension tasks, and 3 attention-control tasks. Mind wandering was assessed using experimenter-scheduled thought probes during 4 different tasks (2 reading, 2 attention-control). The results support the executive-attention theory of WMC. Mind wandering across the 4 tasks loaded onto a single latent factor, reflecting a stable individual difference. Most important, mind wandering was a significant mediator in the relationship between WMC and reading comprehension, suggesting that the WMC-comprehension correlation is driven, in part, by attention control over intruding thoughts. We discuss implications for theories of WMC, attention control, and reading comprehension.

Cockpit task management: A preliminary, normative theory

NASA Technical Reports Server (NTRS)

Funk, Ken

1991-01-01

Cockpit task management (CTM) involves the initiation, monitoring, prioritizing, and allocation of resources to concurrent tasks as well as termination of multiple concurrent tasks. As aircrews have more tasks to attend to due to reduced crew sizes and the increased complexity of aircraft and the air transportation system, CTM will become a more critical factor in aviation safety. It is clear that many aviation accidents and incidents can be satisfactorily explained in terms of CTM errors, and it is likely that more accidents induced by poor CTM practice will occur in the future unless the issue is properly addressed. The first step in understanding and facilitating CTM behavior was the development of a preliminary, normative theory of CTM which identifies several important CTM functions. From this theory, some requirements for pilot-vehicle interfaces were developed which are believed to facilitate CTM. A prototype PVI was developed which improves CTM performance and currently, a research program is under way that is aimed at developing a better understanding of CTM and facilitating CTM performance through better equipment and procedures.

Non-linear Frequency Shifts, Mode Couplings, and Decay Instability of Plasma Waves

NASA Astrophysics Data System (ADS)

Affolter, Mathew; Anderegg, F.; Driscoll, C. F.; Valentini, F.

2015-11-01

We present experiments and theory for non-linear plasma wave decay to longer wavelengths, in both the oscillatory coupling and exponential decay regimes. The experiments are conducted on non-neutral plasmas in cylindrical Penning-Malmberg traps, θ-symmetric standing plasma waves have near acoustic dispersion ω (kz) ~kz - αkz2 , discretized by kz =mz (π /Lp) . Large amplitude waves exhibit non-linear frequency shifts δf / f ~A2 and Fourier harmonic content, both of which are increased as the plasma dispersion is reduced. Non-linear coupling rates are measured between large amplitude mz = 2 waves and small amplitude mz = 1 waves, which have a small detuning Δω = 2ω1 -ω2 . At small excitation amplitudes, this detuning causes the mz = 1 mode amplitude to ``bounce'' at rate Δω , with amplitude excursions ΔA1 ~ δn2 /n0 consistent with cold fluid theory and Vlasov simulations. At larger excitation amplitudes, where the non-linear coupling exceeds the dispersion, phase-locked exponential growth of the mz = 1 mode is observed, in qualitative agreement with simple 3-wave instability theory. However, significant variations are observed experimentally, and N-wave theory gives stunningly divergent predictions that depend sensitively on the dispersion-moderated harmonic content. Measurements on higher temperature Langmuir waves and the unusual ``EAW'' (KEEN) waves are being conducted to investigate the effects of wave-particle kinetics on the non-linear coupling rates. Department of Energy Grants DE-SC0002451and DE-SC0008693.

Geospace Plasma Dynamics Laboratory Annual Task Report (FY11)

DTIC Science & Technology

2012-03-01

Site Contractors: Nagendra Singh, Ph.D., Physicist , 0.5 MY Neil Grossbard, M.S., Mathematician , 0.7 MY Visitors: Publications: Articles in...PhD Project Manager Division Chief, RVB This report is published in the interest of scientific and technical...Annual Task Report (FY11) 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) 5d. PROJECT NUMBER 2311 Daniel Ober 5e. TASK NUMBER

Interaction of an electromagnetic wave with a rapidly created spatially periodic plasma

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

Kuo, S.P.; Faith, J.

1997-08-01

The interaction of electromagnetic waves with rapidly created time-varying spatially periodic plasmas is studied. The numerical results of the collisionless case show that both frequency upshifted and frequency downshifted waves are generated. Moreover, the frequency downshifted waves are trapped by the plasma when the plasma frequency is larger than the wave frequency. The trapping has the effect of dramatically enhancing the efficiency of the frequency downshift conversion process, by accumulating incident wave energy during the plasma transition period. A theory based on the wave impedance of each Floquet mode of the periodic structure is formulated, incorporating with the collisional dampingmore » of the plasma. Such a theory explains the recent experimental observations [Faith, Kuo, and Huang, Phys. Rev. E {bold 55}, 1843 (1997)] where the frequency downshifted signals were detected repetitively with considerably enhanced spectral intensities while the frequency upshifted signals were missing. {copyright} {ital 1997} {ital The American Physical Society}« less

Scaled-down particle-in-cell simulation of cathode plasma expansion in magnetically insulated coaxial diode

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

Zhu, Danni; Zhang, Jun, E-mail: zhangjun@nudt.edu.cn; Zhong, Huihuang

2016-03-15

The expansion of cathode plasma in magnetically insulated coaxial diode (MICD) is investigated in theory and particle-in-cell (PIC) simulation. The temperature and density of the cathode plasma are about several eV and 10{sup 13}–10{sup 16 }cm{sup −3}, respectively, and its expansion velocity is of the level of few cm/μs. Through hydrodynamic theory analysis, expressions of expansion velocities in axial and radial directions are obtained. The characteristics of cathode plasma expansion have been simulated through scaled-down PIC models. Simulation results indicate that the expansion velocity is dominated by the ratio of plasma density other than the static electric field. The electric fieldmore » counteracts the plasma expansion reverse of it. The axial guiding magnetic field only reduces the radial transport coefficients by a correction factor, but not the axial ones. Both the outward and inward radial expansions of a MICD are suppressed by the much stronger guiding magnetic field and even cease.« less

Collective behavior of silver plasma during pulsed laser ablation

NASA Astrophysics Data System (ADS)

Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.

2015-07-01

The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

Study of Plasma Motor Generator (PMG) tether system for orbit reboost

NASA Technical Reports Server (NTRS)

1988-01-01

A progress report is given on a system study by TRW begun in January 1987 of a 2 kW Plasma Motor Generator Tether to be used for orbit reboost. Following the completion of the initial phase in September 1987, additional tasks were agreed on and work on them begun in March 1988. These tasks fell into three categories: tests on the prototype tether fabricated during the first phase, simulations of the spacecraft and tether system after deployment using GTOSS, and a brief investigation of the impact and feasibility of increasing the system to 20 kW and hosting it on the Orbital Maneuvering Vehicle. The subcontractor, Energy Sciences Laboratory, was assigned the responsibility of performing the simulations and some mechanical tests on the prototype tether to supplement those done at TRW. A summary of the significant findings and issues from each task follows. Recommendations for future work constitutes the third section. A copy of the final briefing is in Appendix A, plus additional reports for each task and additional analysis.

Acceleration of plasma electrons by intense nonrelativistic ion and electron beams propagating in background plasma due to two-stream instability

NASA Astrophysics Data System (ADS)

Kaganovich, Igor D.

2015-11-01

In this paper we study the effects of the two-stream instability on the propagation of intense nonrelativistic ion and electron beams in background plasma. Development of the two-stream instability between the beam ions and plasma electrons leads to beam breakup, a slowing down of the beam particles, acceleration of the plasma particles, and transfer of the beam energy to the plasma particles and wave excitations. Making use of the particle-in-cell codes EDIPIC and LSP, and analytic theory we have simulated the effects of the two-stream instability on beam propagation over a wide range of beam and plasma parameters. Because of the two-stream instability the plasma electrons can be accelerated to velocities as high as twice the beam velocity. The resulting return current of the accelerated electrons may completely change the structure of the beam self - magnetic field, thereby changing its effect on the beam from focusing to defocusing. Therefore, previous theories of beam self-electromagnetic fields that did not take into account the effects of the two-stream instability must be significantly modified. This effect can be observed on the National Drift Compression Experiment-II (NDCX-II) facility by measuring the spot size of the extracted beamlet propagating through several meters of plasma. Particle-in-cell, fluid simulations, and analytical theory also reveal the rich complexity of beam- plasma interaction phenomena: intermittency and multiple regimes of the two-stream instability in dc discharges; band structure of the growth rate of the two-stream instability of an electron beam propagating in a bounded plasma and repeated acceleration of electrons in a finite system. In collaboration with E. Tokluoglu, D. Sydorenko, E. A. Startsev, J. Carlsson, and R. C. Davidson. Research supported by the U.S. Department of Energy.

Self-consistent theory for the linear and nonlinear propagation of a sinusoidal electron plasma wave. Application to stimulated Raman scattering in a non-uniform and non-stationary plasma

NASA Astrophysics Data System (ADS)

Bénisti, Didier

2018-01-01

In this paper, we address the theoretical resolution of the Vlasov-Gauss system from the linear regime to the strongly nonlinear one, when significant trapping has occurred. The electric field is that of a sinusoidal electron plasma wave (EPW) which is assumed to grow from the noise level, and to keep growing at least up to the amplitude when linear theory in no longer valid (while the wave evolution in the nonlinear regime may be arbitrary). The ions are considered as a neutralizing fluid, while the electron response to the wave is derived by matching two different techniques. We make use of a perturbation analysis similar to that introduced to prove the Kolmogorov-Arnold-Moser theorem, up to amplitudes large enough for neo-adiabatic results to be valid. Our theory is applied to the growth and saturation of the beam-plasma instability, and to the three-dimensional propagation of a driven EPW in a non-uniform and non-stationary plasma. For the latter example, we lay a special emphasis on nonlinear collisionless dissipation. We provide an explicit theoretical expression for the nonlinear Landau-like damping rate which, in some instances, is amenable to a simple analytic formula. We also insist on the irreversible evolution of the electron distribution function, which is nonlocal in the wave amplitude and phase velocity. This makes trapping an effective means of dissipation for the electrostatic energy, and also makes the wave dispersion relation nonlocal. Our theory is generalized to allow for stimulated Raman scattering, which we address up to saturation by accounting for plasma inhomogeneity and non-stationarity, nonlinear kinetic effects, and interspeckle coupling.

Tasks in Pedagogical Context: Integrating Theory and Practice. Multilingual Matters 94.

ERIC Educational Resources Information Center

Crookes, Graham, Ed.; Gass, Susan M., Ed.

These six essays discuss the use of tasks as pedagogical tools in second language instruction, particularly in the contexts of curriculum and syllabus design. The essays are: (1) "Units of Analysis in Syllabus Design: The Case for Task" (Michael H. Long and Graham Crookes); (2) "Task-Based Syllabus Design: Selecting, Grading and Sequencing Tasks"…

On the evolution of jet energy and opening angle in strongly coupled plasma

NASA Astrophysics Data System (ADS)

Chesler, Paul M.; Rajagopal, Krishna

2016-05-01

We calculate how the energy and the opening angle of jets in {N} = 4 SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet /dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet /dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say the opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that {N} = 4 SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the {N} = 4 SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. We close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.

On the evolution of jet energy and opening angle in strongly coupled plasma

DOE PAGES

Chesler, Paul M.; Rajagopal, Krishna

2016-05-17

We calculate how the energy and the opening angle of jets in N = 4SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet/dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet/dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say themore » opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that N = 4SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the N = 4SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. In conclusion, we close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.« less

Finite temperature m=0 upper-hybrid modes in a non-neutral plasma, theory and simulation.

NASA Astrophysics Data System (ADS)

Hart, Grant W.; Takeshi Nakata, M.; Spencer, Ross L.

2007-11-01

Axisymmetric upper-hybrid oscillations have been known to exist in non-neutral plasmas and FTICR/MS devices for a number of years^1,2. However, because they are electrostatic in nature and axisymmetric, they are self-shielding and therefore difficult to detect in long systems. Previous theoretical studies have assumed a zero temperature plasma. In the zero temperature limit these oscillations are not properly represented as a mode, because the frequency at a given radius depends only on the local density and is not coupled to neighboring radii, much like the zero temperature plasma oscillation. Finite temperature provides the coupling which links the oscillation into a coherent mode. We have analyzed the finite-temperature theory of these modes and find that they form an infinite set of modes with frequencies above 2̂c- 2̂p. For a constant density plasma the eigenmodes are Bessel functions. For a more general plasma the eigenmodes must be numerically calculated. We have simulated these modes in our r-θ particle-in-cell code that includes a full Lorentz-force mover^3 and find that the eigenmodes correspond well with the theory.^1 J.J. Bollinger, et al., Phys. Rev. A 48, 525 (1993).^2 S.E. Barlow, et al., Int. J. Mass Spectrom. Ion Processes 74, 97 (1986).^3 M. Takeshi Nakata, et al., Bull. Am. Phys. Soc. 51, 245 (2006).

Hydrodynamic theory of diffusion in two-temperature multicomponent plasmas

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

Ramshaw, J.D.; Chang, C.H.

Detailed numerical simulations of multicomponent plasmas require tractable expressions for species diffusion fluxes, which must be consistent with the given plasma current density J{sub q} to preserve local charge neutrality. The common situation in which J{sub q} = 0 is referred to as ambipolar diffusion. The use of formal kinetic theory in this context leads to results of formidable complexity. We derive simple tractable approximations for the diffusion fluxes in two-temperature multicomponent plasmas by means of a generalization of the hydrodynamical approach used by Maxwell, Stefan, Furry, and Williams. The resulting diffusion fluxes obey generalized Stefan-Maxwell equations that contain drivingmore » forces corresponding to ordinary, forced, pressure, and thermal diffusion. The ordinary diffusion fluxes are driven by gradients in pressure fractions rather than mole fractions. Simplifications due to the small electron mass are systematically exploited and lead to a general expression for the ambipolar electric field in the limit of infinite electrical conductivity. We present a self-consistent effective binary diffusion approximation for the diffusion fluxes. This approximation is well suited to numerical implementation and is currently in use in our LAVA computer code for simulating multicomponent thermal plasmas. Applications to date include a successful simulation of demixing effects in an argon-helium plasma jet, for which selected computational results are presented. Generalizations of the diffusion theory to finite electrical conductivity and nonzero magnetic field are currently in progress.« less

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields

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

John A. Krommes

2001-02-16

A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. Those are developed independently, then shown to be special cases of the direct-interaction approximation (DIA), which providesmore » a central focus for the article. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations, stochasticity criteria for quasilinear theory, formal aspects of resonance-broadening theory, Novikov's theorem, the treatment of weak inhomogeneity, the derivation of the Vlasov weak-turbulence wave kinetic equation from a fully renormalized description, some features of a code for solving the direct-interaction approximation and related Markovian closures, the details of the solution of the EDQNM closure for a solvable three-wave model, and the notation used in the article.« less

Task difficulty, risk, effort and comfort in a simulated driving task--Implications for Risk Allostasis Theory.

PubMed

Lewis-Evans, Ben; Rothengatter, Talib

2009-09-01

Risk Allostasis Theory states that drivers seek to maintain a feeling of risk within a preferred range [Fuller, R., 2008. What drives the driver? Surface tensions and hidden consensus. In: Keynote at the 4th International Conference on Traffic and Transport Psychology, Washington, DC, August 31-September 4, 2008]. Risk Allostasis Theory is the latest version of Task-Difficulty Homeostasis theory, and is in part based on the findings of experiments where participants were asked to rate the task difficulty, feeling of risk and chance of collision of scenes shown in digitally altered video clips [Fuller, R., McHugh, C., Pender, S., 2008b. Task difficulty and risk in the determination of driver behaviour. Revue européenne de psychologie appliqée 58, 13-21]. The focus of the current research was to expand upon the previous video based experiments using a driving simulator. This allowed participants to be in control of the vehicle rather than acting as passive observers, as well as providing additional speed cues. The results support previous findings that ratings of task difficulty and feeling of risk are related, and that they are also highly related to ratings of effort and moderately related to ratings of comfort and habit. However, the linearly increasing trend for task difficulty and feeling of risk described by the previous research was not observed: instead the findings of this experiment support a threshold effect where ratings of risk (feeling of and chance of loss of control/collision), difficulty, effort, and comfort go through a period of stability and only start to increase once a certain threshold has been crossed. It is within the period of stability where subjective experience of risk and difficulty is low, or absent, that drivers generally prefer to operate.

A Matter of Timing: Developmental Theories of Romantic Involvement and Psychosocial Adjustment

PubMed Central

Furman, Wyndol; Collibee, Charlene

2014-01-01

The present study compared two theories of the association between romantic involvement and adjustment—a social timetable theory and a developmental task theory. We examined seven waves of longitudinal data on a community based sample of 200 participants (M age Wave 1 = 15 years, 10 months). In each wave, multiple measures of substance use, externalizing symptoms, and internalizing symptoms were gathered, typically from multiple reporters. Multilevel modeling revealed that greater levels of romantic involvement in adolescence were associated with higher levels of substance use and externalizing symptoms, but became associated with lower levels in adulthood. Similarly, having a romantic partner was associated with greater levels of substance use, externalizing symptoms, and internalizing symptoms in adolescence, but was associated with lower levels in young adulthood. The findings were not consistent with a social timetable theory, which predicts that nonnormative involvement is associated with poor adjustment. Instead, the findings are consistent with a developmental task theory which predicts that precocious romantic involvement undermines development and adaptation, but when romantic involvement becomes a salient developmental task in adulthood, it is associated with positive adjustment. Discussion focuses on the processes that may underlie the changing nature of the association between romantic involvement and adjustment. PMID:24703413

No interpretation without representation: the role of domain-specific representations and inferences in the Wason selection task.

PubMed

Fiddick, L; Cosmides, L; Tooby, J

2000-10-16

The Wason selection task is a tool used to study reasoning about conditional rules. Performance on this task changes systematically when one varies its content, and these content effects have been used to argue that the human cognitive architecture contains a number of domain-specific representation and inference systems, such as social contract algorithms and hazard management systems. Recently, however, Sperber, Cara & Girotto (Sperber, D., Cara, F., & Girotto, V. (1995). Relevance theory explains the selection task. Cognition, 57, 31-95) have proposed that relevance theory can explain performance on the selection task - including all content effects - without invoking inference systems that are content-specialized. Herein, we show that relevance theory alone cannot explain a variety of content effects - effects that were predicted in advance and are parsimoniously explained by theories that invoke domain-specific algorithms for representing and making inferences about (i) social contracts and (ii) reducing risk in hazardous situations. Moreover, although Sperber et al. (1995) were able to use relevance theory to produce some new content effects in other domains, they conducted no experiments involving social exchanges or precautions, and so were unable to determine which - content-specialized algorithms or relevance effects - dominate reasoning when the two conflict. When experiments, reported herein, are constructed so that the different theories predict divergent outcomes, the results support the predictions of social contract theory and hazard management theory, indicating that these inference systems override content-general relevance factors. The fact that social contract and hazard management algorithms provide better explanations for performance in their respective domains does not mean that the content-general logical procedures posited by relevance theory do not exist, or that relevance effects never occur. It does mean, however, that one needs a principled way of explaining which effects will dominate when a set of inputs activate more than one reasoning system. We propose the principle of pre-emptive specificity - that the human cognitive architecture should be designed so that more specialized inference systems pre-empt more general ones whenever the stimuli centrally fit the input conditions of the more specialized system. This principle follows from evolutionary and computational considerations that are common to both relevance theory and the ecological rationality approach.

Is Adaptation to Task Complexity Really Beneficial for Performance?

ERIC Educational Resources Information Center

Pieschl, Stephanie; Stahl, Elmar; Murray, Tom; Bromme, Rainer

2012-01-01

Theories of self-regulated learning assume that learners flexibly adapt their learning process to external task demands and that this is positively related to performance. In this study, university students (n = 119) solved three tasks that greatly differed in complexity. Their learning processes were captured in detail by task-specific…

A new semantic vigilance task: vigilance decrement, workload, and sensitivity to dual-task costs.

PubMed

Epling, Samantha L; Russell, Paul N; Helton, William S

2016-01-01

Cognitive resource theory is a common explanation for both the performance decline in vigilance tasks, known as the vigilance decrement, and the limited ability to perform multiple tasks simultaneously. The limited supply of cognitive resources may be utilized faster than they are replenished resulting in a performance decrement, or may need to be allocated among multiple tasks with some performance cost. Researchers have proposed both domain-specific, for example spatial versus verbal processing resources, and domain general cognitive resources. One challenge in testing the domain specificity of cognitive resources in vigilance is the current lack of difficult semantic vigilance tasks which reliably produce a decrement. In the present research, we investigated whether the vigilance decrement was found in a new abbreviated semantic discrimination vigilance task, and whether there was a performance decrement in said vigilance task when paired with a word recall task, as opposed to performed individually. As hypothesized, a vigilance decrement in the semantic vigilance task was found in both the single-task and dual-task conditions, along with reduced vigilance performance in the dual-task condition and reduced word recall in the dual-task condition. This is consistent with cognitive resource theory. The abbreviated semantic vigilance task will be a useful tool for researchers interested in determining the specificity of cognitive resources utilized in vigilance tasks.

Production of organic compounds in plasmas: A comparison among electric sparks, laser-induced plasmas and UV light

NASA Technical Reports Server (NTRS)

Scattergood, T. W.; Mckay, C. P.; Borucki, W. J.; Giver, L. P.; Vanghyseghem, H.; Parris, J. E.; Miller, S. L.

1991-01-01

In order to study the production of organic compounds in plasmas (and shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple hydrocarbons were measured and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the yields of C2H6 and other hydrocarbons were much higher than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The results of these experiments demonstrate that, in addition to the well-known efficient synthesis of organic compounds in plasmas, the yields of saturated species, e.g., ethane, may be higher than predicted by theory and that LIP provide a convenient and clean way of simulating planetary lightning and impact plasmas in the laboratory.

The Relationship between Systemising and Mental Rotation and the Implications for the Extreme Male Brain Theory of Autism

ERIC Educational Resources Information Center

Brosnan, Mark; Daggar, Rajiv; Collomosse, John

2010-01-01

Within the Extreme Male Brain theory, Autism Spectrum Disorder is characterised as a deficit in empathising in conjunction with preserved or enhanced systemising. A male advantage in systemising is argued to underpin the traditional male advantage in mental rotation tasks. Mental rotation tasks can be separated into rotational and non-rotational…

Cognitive Load Theory: A Broader View on the Role of Memory in Learning and Education

ERIC Educational Resources Information Center

Paas, Fred; Ayres, Paul

2014-01-01

According to cognitive load theory (CLT), the limitations of working memory (WM) in the learning of new tasks together with its ability to cooperate with an unlimited long-term memory (LTM) for familiar tasks enable human beings to deal effectively with complex problems and acquire highly complex knowledge and skills. With regard to WM, CLT has…

Success and Failure in Dynamic Decision Environments: Understanding Treatment Strategies for Patients with a Chronic Disease

ERIC Educational Resources Information Center

Ramsey, Gregory W.

2010-01-01

This dissertation proposes and tests a theory explaining how people make decisions to achieve a goal in a specific task environment. The theory is represented as a computational model and implemented as a computer program. The task studied was primary care physicians treating patients with type 2 diabetes. Some physicians succeed in achieving…

The Role of "Local Theories": Teacher Knowledge and Its Impact on Engaging Students with Challenging Tasks

ERIC Educational Resources Information Center

Choppin, Jeffrey

2011-01-01

This study explores the extent to which a teacher elicited students' mathematical reasoning through the use of challenging tasks and the role her knowledge played in doing so. I characterised the teacher's knowledge in terms of a "local theory" of instruction, a form of pedagogical content knowledge that involves an empirically tested set of…

Rationalising the 'irrational': a think aloud study of discrete choice experiment responses.

PubMed

Ryan, Mandy; Watson, Verity; Entwistle, Vikki

2009-03-01

Stated preference methods assume respondents' preferences are consistent with utility theory, but many empirical studies report evidence of preferences that violate utility theory. This evidence is often derived from quantitative tests that occur naturally within, or are added to, stated preference tasks. In this study, we use qualitative methods to explore three axioms of utility theory: completeness, monotonicity, and continuity. We take a novel approach, adopting a 'think aloud' technique to identify violations of the axioms of utility theory and to consider how well the quantitative tests incorporated within a discrete choice experiment are able to detect these. Results indicate that quantitative tests classify respondents as being 'irrational' when qualitative statements would indicate they are 'rational'. In particular, 'non-monotonic' responses can often be explained by respondents inferring additional information beyond what is presented in the task, and individuals who appear to adopt non-compensatory decision-making strategies do so because they rate particular attributes very highly (they are not attempting to simplify the task). The results also provide evidence of 'cost-based responses': respondents assumed tests with higher costs would be of higher quality. The value of including in-depth qualitative validation techniques in the development of stated preference tasks is shown.

Suppression of Phase Mixing in Drift-Kinetic Plasma Turbulence

NASA Astrophysics Data System (ADS)

Parker, J. T.; Dellar, P. J.; Schekochihin, A. A.; Highcock, E. G.

2017-12-01

The solar wind and interstellar medium are examples of strongly magnetised, weakly collisional, astrophysical plasmas. Their turbulent fluctuations are strongly anisotropic, with small amplitudes, and frequencies much lower than the Larmor frequency. This regime is described by gyrokinetic theory, a reduced five-dimensional kinetic system describing averages over Larmor orbits. A turbulent plasma may transfer free energy, a measure of fluctuation amplitudes, from injection at large scales, typically by an instability, to dissipation at small physical scales like a turbulent fluid. Alternatively, a turbulent plasma may form fine scale structures in velocity space via phase-mixing, the mechanism that leads to Landau damping in linear plasma theory. Macroscopic plasma properties like heat and momentum transport are affected by both mechanisms. While each is understood in isolation, their interaction is not. We study this interaction using a Hankel-Hermite velocity space representation of gyrokinetic theory. The Hankel transform interacts neatly with the Bessel functions that arise from averaging over Larmor orbits, so the perpendicular velocity space is decoupled for linearized problems. The Hermite transform expresses phase mixing as nearest-neighbor coupling between parallel velocity space scales represented by Hermite mode numbers. We use this representation to study transfer mechanisms in drift-kinetic plasma turbulence, the long wavelength limit of gyrokinetic theory. We show that phase space is divided into two regions, with one transfer mechanism dominating in each. Most energy is contained in the region where the fluid-like nonlinear cascade dominates. Moreover, in that region the nonlinear cascade interferes with phase mixing by exciting an "anti phase mixing" transfer of free energy from small to large velocity space scales. This cancels out the usual phase mixing, and renders the overall behavior fluid-like. These results profoundly change our understanding of free energy flow in drift-kinetic turbulence, and, moreover, explain previously observed spectra.

Temperature gradients due to adiabatic plasma expansion in a magnetic nozzle

NASA Astrophysics Data System (ADS)

Sheehan, J. P.; Longmier, B. W.; Bering, E. A.; Olsen, C. S.; Squire, J. P.; Ballenger, M. G.; Carter, M. D.; Cassady, L. D.; Díaz, F. R. Chang; Glover, T. W.; Ilin, A. V.

2014-08-01

A mechanism for ambipolar ion acceleration in a magnetic nozzle is proposed. The plasma is adiabatic (i.e., does not exchange energy with its surroundings) in the diverging section of a magnetic nozzle so any energy lost by the electrons must be transferred to the ions via the electric field. Fluid theory indicates that the change in plasma potential is proportional to the change in average electron energy. These predictions were compared to measurements in the VX-200 experiment which has conditions conducive to ambipolar ion acceleration. A planar Langmuir probe was used to measure the plasma potential, electron density, and electron temperature for a range of mass flow rates and power levels. Axial profiles of those parameters were also measured, showing consistency with the adiabatic ambipolar fluid theory.

Propagation of an ultrashort, intense laser pulse in a relativistic plasma

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

Ritchie, B.; Decker, C.D.

1997-12-31

A Maxwell-relativistic fluid model is developed for the propagation of an ultrashort, intense laser pulse through an underdense plasma. The separability of plasma and optical frequencies ({omega}{sub p} and {omega} respectively) for small {omega}{sub p}/{omega} is not assumed; thus the validity of multiple-scales theory (MST) can be tested. The theory is valid when {omega}{sub p}/{omega} is of order unity or for cases in which {omega}{sub p}/{omega} {much_lt} 1 but strongly relativistic motion causes higher-order plasma harmonics to be generated which overlap the region of the first-order laser harmonic, such that MST would not expected to be valid although its principalmore » validity criterion {omega}{sub p}/{omega} {much_lt} 1 holds.« less

Theory and Simulations of Solar System Plasmas

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.

2011-01-01

"Theory and simulations of solar system plasmas" aims to highlight results from microscopic to global scales, achieved by theoretical investigations and numerical simulations of the plasma dynamics in the solar system. The theoretical approach must allow evidencing the universality of the phenomena being considered, whatever the region is where their role is studied; at the Sun, in the solar corona, in the interplanetary space or in planetary magnetospheres. All possible theoretical issues concerning plasma dynamics are welcome, especially those using numerical models and simulations, since these tools are mandatory whenever analytical treatments fail, in particular when complex nonlinear phenomena are at work. Comparative studies for ongoing missions like Cassini, Cluster, Demeter, Stereo, Wind, SDO, Hinode, as well as those preparing future missions and proposals, like, e.g., MMS and Solar Orbiter, are especially encouraged.

Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

NASA Technical Reports Server (NTRS)

Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

1990-01-01

The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

Two-tone nonlinear electrostatic waves in the quantum electron–hole plasma of semiconductors

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

Dubinov, A. E., E-mail: dubinov-ae@yandex.ru; Kitayev, I. N.

2017-01-15

Longitudinal electrostatic waves in the quantum electron–hole plasma of semiconductors are considered taking into account the degeneracy of electrons and holes and the exchange interaction. It is found in the framework of linear theory that the dispersion curve of longitudinal waves has two branches: plasmon and acoustic. An expression for the critical cutoff frequency for plasma oscillations and an expression for the speed of sound for acoustic vibrations are derived. It is shown that the plasma wave always exists in the form of a superposition of two components, characterized by different periods and wavelengths. Two nonlinear solutions are obtained withinmore » nonlinear theory: one in the form of a simple superposition of two tones and the other in the form of beats.« less

An integrated theory of attention and decision making in visual signal detection.

PubMed

Smith, Philip L; Ratcliff, Roger

2009-04-01

The simplest attentional task, detecting a cued stimulus in an otherwise empty visual field, produces complex patterns of performance. Attentional cues interact with backward masks and with spatial uncertainty, and there is a dissociation in the effects of these variables on accuracy and on response time. A computational theory of performance in this task is described. The theory links visual encoding, masking, spatial attention, visual short-term memory (VSTM), and perceptual decision making in an integrated dynamic framework. The theory assumes that decisions are made by a diffusion process driven by a neurally plausible, shunting VSTM. The VSTM trace encodes the transient outputs of early visual filters in a durable form that is preserved for the time needed to make a decision. Attention increases the efficiency of VSTM encoding, either by increasing the rate of trace formation or by reducing the delay before trace formation begins. The theory provides a detailed, quantitative account of attentional effects in spatial cuing tasks at the level of response accuracy and the response time distributions. (c) 2009 APA, all rights reserved

Effects of visual and verbal interference tasks on olfactory memory: the role of task complexity.

PubMed

Annett, J M; Leslie, J C

1996-08-01

Recent studies have demonstrated that visual and verbal suppression tasks interfere with olfactory memory in a manner which is partially consistent with a dual coding interpretation. However, it has been suggested that total task complexity rather than modality specificity of the suppression tasks might account for the observed pattern of results. This study addressed the issue of whether or not the level of difficulty and complexity of suppression tasks could explain the apparent modality effects noted in earlier experiments. A total of 608 participants were each allocated to one of 19 experimental conditions involving interference tasks which varied suppression type (visual or verbal), nature of complexity (single, double or mixed) and level of difficulty (easy, optimal or difficult) and presented with 13 target odours. Either recognition of the odours or free recall of the odour names was tested on one occasion, either within 15 minutes of presentation or one week later. Both recognition and recall performance showed an overall effect for suppression nature, suppression level and time of testing with no effect for suppression type. The results lend only limited support to Paivio's (1986) dual coding theory, but have a number of characteristics which suggest that an adequate account of olfactory memory may be broadly similar to current theories of face and object recognition. All of these phenomena might be dealt with by an appropriately modified version of dual coding theory.

Introduction to Plasma Physics

NASA Astrophysics Data System (ADS)

Gurnett, Donald A.; Bhattacharjee, Amitava

2017-03-01

Preface; 1. Introduction; 2. Characteristic parameters of a plasma; 3. Single particle motions; 4. Waves in a cold plasma; 5. Kinetic theory and the moment equations; 6. Magnetohydrodynamics; 7. MHD equilibria and stability; 8. Discontinuities and shock waves; 9. Electrostatic waves in a hot unmagnetized plasma; 10. Waves in a hot magnetized plasma; 11. Nonlinear effects; 12. Collisional processes; Appendix A. Symbols; Appendix B. Useful trigonometric identities; Appendix C. Vector differential operators; Appendix D. Vector calculus identities; Index.

Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

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

Coffer, J.; Encalada, N.; Huang, M.

We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

Kinetic theory of Jeans instability of a dusty plasma.

PubMed

Pandey, B P; Lakhina, G S; Krishan, V

1999-12-01

A kinetic theory of the Jeans instability of a dusty plasma has been developed in the present work. The effect of grain charge fluctuations due to the attachment of electrons and ions to the grain surface has been considered in the framework of Krook's collisional model. We demonstrate that the grain charge fluctuations alter the growth rate of the gravitational collapse of the dusty plasma. The Jeans length has been derived under limiting cases, and its dependence on the attachment frequency is shown. In the absence of gravity, we see that the damping rate of the dust acoustic mode is proportional to the electron-dust collision frequency.

Hypnotic suggestibility, cognitive inhibition, and dissociation.

PubMed

Dienes, Zoltán; Brown, Elizabeth; Hutton, Sam; Kirsch, Irving; Mazzoni, Giuliana; Wright, Daniel B

2009-12-01

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.

Defining and measuring pilot mental workload

NASA Technical Reports Server (NTRS)

Kantowitz, Barry H.

1988-01-01

A theory is sought that is general enough to help the researcher deal with a wide range of situations involving pilot mental stress. A limited capacity theory of attention forms the basis for the theory. Mental workload is then defined as an intervening variable, similar to attention, that modulates or indexes the tuning between the demands of the environment and the capacity of the organism. Two methods for measuring pilot mental workload are endorsed: (1) objective measures based on secondary tasks; and (2) psychophysiological measures, which have not yet been perfected but which will become more useful as theoretical models are refined. Secondary-task research is illustrated by simulator studies in which flying performance has been shown not to be adversely affected by adding a complex choice-reaction secondary task.

The concept of collision strength and its applications

NASA Astrophysics Data System (ADS)

Chang, Yongbin

Collision strength, the measure of strength for a binary collision, hasn't been defined clearly. In practice, many physical arguments have been employed for the purpose and taken for granted. A scattering angle has been widely and intensively used as a measure of collision strength in plasma physics for years. The result of this is complication and unnecessary approximation in deriving some of the basic kinetic equations and in calculating some of the basic physical terms. The Boltzmann equation has a five-fold integral collision term that is complicated. Chandrasekhar and Spitzer's approaches to the linear Fokker-Planck coefficients have several approximations. An effective variable-change technique has been developed in this dissertation as an alternative to scattering angle as the measure of collision strength. By introducing the square of the reduced impulse or its equivalencies as a collision strength variable, many plasma calculations have been simplified. The five-fold linear Boltzmann collision integral and linearized Boltzmann collision integral are simplified to three-fold integrals. The arbitrary order linear Fokker-Planck coefficients are calculated and expressed in a uniform expression. The new theory provides a simple and exact method for describing the equilibrium plasma collision rate, and a precise calculation of the equilibrium relaxation time. It generalizes bimolecular collision reaction rate theory to a reaction rate theory for plasmas. A simple formula of high precision with wide temperature range has been developed for electron impact ionization rates for carbon atoms and ions. The universality of the concept of collision strength is emphasized. This dissertation will show how Arrhenius' chemical reaction rate theory and Thomson's ionization theory can be unified as one single theory under the concept of collision strength, and how many important physical terms in different disciplines, such as activation energy in chemical reaction theory, ionization energy in Thomson's ionization theory, and the Coulomb logarithm in plasma physics, can be unified into a single one---the threshold value of collision strength. The collision strength, which is a measure of a transfer of momentum in units of energy, can be used to reconcile the differences between Descartes' opinion and Leibnitz's opinion about the "true" measure of a force. Like Newton's second law, which provides an instantaneous measure of a force, collision strength, as a cumulative measure of a force, can be regarded as part of a law of force in general.

geometric optics and WKB method for electromagnetic wave propagation in an inhomogeneous plasma near cutoff

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

Light, Max Eugene

This report outlines the theory underlying electromagnetic (EM) wave propagation in an unmagnetized, inhomogeneous plasma. The inhomogeneity is given by a spatially nonuniform plasma electron density n e(r), which will modify the wave propagation in the direction of the gradient rn e(r).

The mind behind the message: advancing theory-of-mind scales for typically developing children, and those with deafness, autism, or Asperger syndrome.

PubMed

Peterson, Candida C; Wellman, Henry M; Slaughter, Virginia

2012-01-01

Children aged 3-12 years (n = 184) with typical development, deafness, autism, or Asperger syndrome took a series of theory-of-mind (ToM) tasks to confirm and extend previous developmental scaling evidence. A new sarcasm task, in the format of H. M. Wellman and D. Liu's (2004) 5-step ToM Scale, added a statistically reliable 6th step to the scale for all diagnostic groups. A key previous finding, divergence in task sequencing for children with autism, was confirmed. Comparisons among diagnostic groups, controlling age, and language ability, showed that typical developers mastered the 6 ToM steps ahead of each of the 3 disabled groups, with implications for ToM theories. The final (sarcasm) task challenged even nondisabled 9-year-olds, demonstrating the new scale's sensitivity to post-preschool ToM growth. © 2012 The Authors. Child Development © 2012 Society for Research in Child Development, Inc.

Understanding of thought bubbles as mental representations in children with autism: implications for theory of mind.

PubMed

Kerr, Sharyn; Durkin, Kevin

2004-12-01

Standard false belief tasks indicate that normally developing children do not fully develop a theory of mind until the age of 4 years and that children with autism have an impaired theory of mind. Recent evidence, however, suggests that children as young as 3 years of age understand that thought bubbles depict mental representations and that these can be false. Twelve normally developing children and 11 children with autism were tested on a standard false belief task and a number of tasks that employed thought bubbles to represent mental states. While the majority of normally developing children and children with autism failed the standard false belief task, they understood that (i) thought bubbles represent thought, (ii) thought bubbles can be used to infer an unknown reality, (iii) thoughts can be different, and (iv) thoughts can be false. These results indicate that autistic children with a relatively low verbal mental age may be capable of understanding mental representations.

Task- and self-related pathways to deep learning: the mediating role of achievement goals, classroom attentiveness, and group participation.

PubMed

Lau, Shun; Liem, Arief Darmanegara; Nie, Youyan

2008-12-01

The expectancy-value and achievement goal theories are arguably the two most dominant theories of achievement motivation in the contemporary literature. However, very few studies have examined how the constructs derived from both theories are related to deep learning. Moreover, although there is evidence demonstrating the links between achievement goals and deep learning, little research has examined the mediating processes involved. The aims of this research were to: (a) investigate the role of task- and self-related beliefs (task value and self-efficacy) as well as achievement goals in predicting deep learning in mathematics and (b) examine how classroom attentiveness and group participation mediated the relations between achievement goals and deep learning. The sample comprised 1,476 Grade-9 students from 39 schools in Singapore. Students' self-efficacy, task value, achievement goals, classroom attentiveness, group participation, and deep learning in mathematics were assessed by a self-reported questionnaire administered on-line. Structural equation modelling was performed to test the hypothesized model linking these variables. Task value was predictive of task-related achievement goals whereas self-efficacy was predictive of task-approach, performance-approach, and performance-avoidance goals. Achievement goals were found to fully mediate the relations between task value and self-efficacy on the one hand, and classroom attentiveness, group participation, and deep learning on the other. Classroom attentiveness and group participation partially mediated the relations between achievement goal adoption and deep learning. The findings suggest that (a) task- and self-related pathways are two possible routes through which students could be motivated to learn and (b) like task-approach goals, performance-approach goals could lead to adaptive processes and outcomes.

A resource-control account of sustained attention: evidence from mind-wandering and vigilance paradigms.

PubMed

Thomson, David R; Besner, Derek; Smilek, Daniel

2015-01-01

Staying attentive is challenging enough when carrying out everyday tasks, such as reading or sitting through a lecture, and failures to do so can be frustrating and inconvenient. However, such lapses may even be life threatening, for example, if a pilot fails to monitor an oil-pressure gauge or if a long-haul truck driver fails to notice a car in his or her blind spot. Here, we explore two explanations of sustained-attention lapses. By one account, task monotony leads to an increasing preoccupation with internal thought (i.e., mind wandering). By another, task demands result in the depletion of information-processing resources that are needed to perform the task. A review of the sustained-attention literature suggests that neither theory, on its own, adequately explains the full range of findings. We propose a novel framework to explain why attention lapses as a function of time-on-task by combining aspects of two different theories of mind wandering: attentional resource (Smallwood & Schooler, 2006) and control failure (McVay & Kane, 2010). We then use our "resource-control" theory to explain performance decrements in sustained-attention tasks. We end by making some explicit predictions regarding mind wandering in general and sustained-attention performance in particular. © The Author(s) 2014.

Ability Beliefs, Task Value, and Performance as a Function of Race in a Dart-Throwing Task

ERIC Educational Resources Information Center

Gao, Zan; Kosma, Maria; Harrison, Louis, Jr.

2009-01-01

This study examines differences in self-efficacy, expectancy-related beliefs, task value, and performance in a dart-throwing task as a function of race among diverse college students using the expectancy-value model and self-efficacy theory. It also examines the predictive contributions of these beliefs on task performance within each racial…

Mission Oriented Support and Theory (MOST) for MMS—the Goddard Space Flight Center/University of California Los Angeles Interdisciplinary Science Program

NASA Astrophysics Data System (ADS)

Goldstein, Melvyn L.; Ashour-Abdalla, Maha; Viñas, Adolfo F.; Dorelli, John; Wendel, Deirdre; Klimas, Alex; Hwang, Kyoung-Joo; El-Alaoui, Mostafa; Walker, Raymond J.; Pan, Qingjiang; Liang, Haoming

2016-03-01

The MOST IDS team was tasked with focusing on two general areas: The first was to participate with the Fast Plasma Investigation (FPI) team in the development of virtual detectors that model the instrument responses of the MMS FPI sensors. The virtual instruments can be "flown through" both simulation data (from magnetohydrodynamic, hybrid, and kinetic simulations) and Cluster and THEMIS spacecraft data. The goal is to determine signatures of magnetic reconnection expected during the MMS mission. Such signatures can serve as triggers for selection of burst mode downloads. The chapter contributed by the FPI team covers that effort in detail and, therefore, most of that work has not been included here. The second area of emphasis, and the one detailed in this chapter, was to build on past and present knowledge of magnetic reconnection and its physical signatures. Below we describe intensive analyses of Cluster and THEMIS data together with theoretical models and simulations that delineate the plasma signatures that surround sites of reconnection, including the effects of turbulence as well as the detailed kinetic signatures that indicate proximity to reconnection sites. In particular, we point out that particles are energized in several regions, not only at the actual site of reconnection.

Mission Oriented Support and Theory (MOST) for MMS -- The Goddard Space Flight Center/University of California Los Angeles Interdisciplinary Science Program

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.; Ashour-Abdalla, Maha; F. Vinas, Adolfo; Dorelli, John; Wendel, Deirdre; Klimas, Alex; Hwang, Kyoung-Joo; El-Alaoui, Mostafa; Walker, Raymond J.; Pan, Qingjiang;

Task-relevant perceptual features can define categories in visual memory too.

PubMed

Antonelli, Karla B; Williams, Carrick C

2017-11-01

Although Konkle, Brady, Alvarez, and Oliva (2010, Journal of Experimental Psychology: General, 139(3), 558) claim that visual long-term memory (VLTM) is organized on underlying conceptual, not perceptual, information, visual memory results from visual search tasks are not well explained by this theory. We hypothesized that when viewing an object, any task-relevant visual information is critical to the organizational structure of VLTM. In two experiments, we examined the organization of VLTM by measuring the amount of retroactive interference created by objects possessing different combinations of task-relevant features. Based on task instructions, only the conceptual category was task relevant or both the conceptual category and a perceptual object feature were task relevant. Findings indicated that when made task relevant, perceptual object feature information, along with conceptual category information, could affect memory organization for objects in VLTM. However, when perceptual object feature information was task irrelevant, it did not contribute to memory organization; instead, memory defaulted to being organized around conceptual category information. These findings support the theory that a task-defined organizational structure is created in VLTM based on the relevance of particular object features and information.

Debye sheath mechanism at laser plasma interaction and generalization to nuclear forces and quark-gluon plasma

NASA Astrophysics Data System (ADS)

Osman, Frederick; Ghahramani, Nader; Hora, Heinrich

2005-10-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation, and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension in plasmas, and led to the internal dynamic electric fields in all inhomogeneous plasmas. The surface tension causes stabilization by short length surface wave smoothing the expanding plasma plume and to stabilization against the Rayleigh Taylor instability. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature resulted in the first quantum theory of surface tension of metals in agreement with measurements. Taking the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well-known nuclear density, and the Debye lengths equal to the Hofstadter decay of the nuclear surface. Increasing the nuclear density by a factor of 10 leads to a change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark gluon plasma. Expansion of this higher density at the big bang or in super-nova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range, however with the limit to about uranium. A relation for the magic numbers leads to a quark structure of nuclear shells that can be understood as a duality property of nuclei with respect to nucleons and quarks

Some Implications of Cognitive Theory for Instructional Design.

ERIC Educational Resources Information Center

Winn, William

1990-01-01

Examines some of the recent developments in cognitive theory and explores their implications for instructional design. Topics discussed include a shift from emphasis on behavioral theory to cognitive theory; task analysis; instructional objectives; learner characteristics; instructional strategies; metacognition; and the dynamic nature of…

Persistence: A Key Factor in Human Performance at Work.

ERIC Educational Resources Information Center

Blair, Daniel V.; Price, Donna J.

1998-01-01

Reviews the construct of persistence as it relates to achievement motivation at work. Topics include foundational concepts of persistence; achievement motivation theory; a human motivation model; goal-setting theory; self-efficacy theory; expectancy theory; task assignments; confidence; and perceived value. (LRW)

Edge-to-center plasma density ratios in two-dimensional plasma discharges

NASA Astrophysics Data System (ADS)

Lucken, R.; Croes, V.; Lafleur, T.; Raimbault, J.-L.; Bourdon, A.; Chabert, P.

2018-03-01

Edge-to-center plasma density ratios—so-called h factors—are important parameters for global models of plasma discharges as they are used to calculate the plasma losses at the reactor walls. There are well-established theories for h factors in the one-dimensional (1D) case. The purpose of this paper is to establish h factors in two-dimensional (2D) systems, with guidance from a 2D particle-in-cell (PIC) simulation. We derive analytical solutions of a 2D fluid theory that includes the effect of ion inertia, but assumes a constant (independent of space) ion collision frequency (using an average ion velocity) across the discharge. Predicted h factors from this 2D fluid theory have the same order of magnitude and the same trends as the PIC simulations when the average ion velocity used in the collision frequency is set equal to the ion thermal velocity. The best agreement is obtained when the average ion velocity varies with pressure (but remains independent of space), going from half the Bohm velocity at low pressure, to the thermal velocity at high pressure. The analysis also shows that a simple correction of the widely-used 1D heuristic formula may be proposed to accurately incorporate 2D effects.

Effect of correlations on the polarizability of the one component plasma

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

Carini, P.R.

Correlational effects on the dynamical polarizability ..cap alpha..(k,..omega..) of the one component plasma (OCP) are investigated in both the weak (..gamma.. < 1) and strong (..gamma.. < 1) coupling regions (..gamma.. is the plasma parameter, ..gamma.. = k/sup 3//4..pi..n where k/sup -1/ is the Debye length and n is the number density. In the weak coupling region a numerical solution is presented over a wide range of frequencies of the complete first order (in ..gamma..) correction to the dynamical polarizability which fully accounts for dynamical screening effects and is exact in the long wavelength and weak coupling limits (k ..-->..more » 0, ..gamma.. ..-->.. 0). This complete result is compared with a similar numerical solution for the dynamical polarizability obtained from the Golden-Kalman (GK) dynamical theory for strongly coupled plasmas. Contrary to previous results reported in the literature it was found that both theories predict the change in the dispersion of the long wavelength plasmons due to finite ..gamma.. effects to be that the slope of the plasmon dispersion curve decreases from its Bohm-Gross value as the plasma parameter increases from 0. In the strong coupling region two hydrodynamical model solutions of the GK dynamical theory for the polarizability are presented.« less

Linking Task Analysis with Student Learning.

ERIC Educational Resources Information Center

Sherman, Thomas M.; Wildman, Terry M.

An examination of task analysis from several perspectives in order to identify some of its purposes and advantages reveals that, as the interest in learning theory has shifted from a predominately behavioral perspective to a more cognitive orientation, the purpose of task analysis has also shifted. Formerly the purpose of task analysis was to aid…

Dilution: A Theoretical Burden or Just Load? A Reply to Tsal and Benoni (2010)

ERIC Educational Resources Information Center

Lavie, Nilli; Torralbo, Ana

2010-01-01

Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and…

The Influence of Content on Adult L2 Learners' Task Motivation: An Interest Theory Perspective

ERIC Educational Resources Information Center

Poupore, Glen

2014-01-01

This study investigates the influence of content-related conditions on adult second language learners' task motivation during interactive tasks. It also aims to identify what is referred to as interestingness conditions within task content, that is, elements that are intrinsically interesting to most individuals. The investigation was conducted…

The fate of task-irrelevant visual motion: perceptual load versus feature-based attention.

PubMed

Taya, Shuichiro; Adams, Wendy J; Graf, Erich W; Lavie, Nilli

2009-11-18

We tested contrasting predictions derived from perceptual load theory and from recent feature-based selection accounts. Observers viewed moving, colored stimuli and performed low or high load tasks associated with one stimulus feature, either color or motion. The resultant motion aftereffect (MAE) was used to evaluate attentional allocation. We found that task-irrelevant visual features received less attention than co-localized task-relevant features of the same objects. Moreover, when color and motion features were co-localized yet perceived to belong to two distinct surfaces, feature-based selection was further increased at the expense of object-based co-selection. Load theory predicts that the MAE for task-irrelevant motion would be reduced with a higher load color task. However, this was not seen for co-localized features; perceptual load only modulated the MAE for task-irrelevant motion when this was spatially separated from the attended color location. Our results suggest that perceptual load effects are mediated by spatial selection and do not generalize to the feature domain. Feature-based selection operates to suppress processing of task-irrelevant, co-localized features, irrespective of perceptual load.

Plasticity in older adults' theory of mind performance: the impact of motivation.

PubMed

Zhang, Xin; Lecce, Serena; Ceccato, Irene; Cavallini, Elena; Zhang, Linfang; Chen, Tianyong

2017-09-08

Recently, motivation has been found to attenuate the age-related decline in Theory of Mind (ToM) performance (i.e. faux pas recognition). However, whether or not this effect could be generalized to other ToM tasks is still unknown. In the present study, we investigated whether and how motivation could enhance older adults' performance and reduce age differences in ToM tasks (Faux Pas vs. Animation task) that differ in familiarity. Following a previous paradigm, 171 Chinese adults (87 younger adults and 84 older adults) were recruited, and we experimentally manipulated the level of perceived closeness between participants and the experimenter before administering the ToM tasks in order to enhance participants' motivation. Results showed that, for the Faux Pas task, we replicated previous findings such that older adults under the enhanced motivation conditions performed equally well as younger adults. Conversely, for the Animation task, younger adults outperformed older adults, regardless of motivation. These results indicate that motivation can enhance older adults' performance in ToM tasks, however, this beneficial effect cannot be generalized across ToM tasks.

Plasma homovanillic acid in the prodromal phase of schizophrenia.

PubMed

Sumiyoshi, T; Kurachi, M; Kurokawa, K; Yotsutsuji, T; Uehara, T; Itoh, H; Saitoh, O

2000-03-01

Plasma levels of homovanillic acid (pHVA) have been used as a peripheral measure of central dopaminergic activity. Despite a large body of studies investigating pHVA in schizophrenia, little is known about pHVA in patients in the prodromal phase of the illness. Plasma HVA levels of 12 male outpatients meeting DSM-III-R criteria for the prodromal phase of schizophrenia at the time of blood sampling (who later developed psychotic symptoms) were compared with those of 12 normal male healthy volunteers. Task amounts in the Kraepelin arithmetic test at the time of blood sampling were compared between the prodromal patients and normal controls and were correlated with pHVA levels. The prodromal patients had significantly higher pHVA levels compared with normal control subjects. The mean amount of the arithmetic task for the prodromal patients was significantly less than that for controls. In the patient group, a significant negative correlation was observed between pHVA levels and the task amounts. Data from the present study indicate the presence of dopaminergic dysfunction in the prodromal stage of schizophrenia that is associated with neuropsychological impairment. Increased pHVA levels in the prodromal patients may have implications for early detection of schizophrenia.

Pellet Injection in ITER with ∇B-induced Drift Effect using TASK/TR and HPI2 Codes

NASA Astrophysics Data System (ADS)

Kongkurd, R.; Wisitsorasak, A.

2017-09-01

The impact of pellet injection in International Thermonuclear Experimental Reactor (ITER) are investigated using integrated predictive modeling codes TASK/TR and HPI2 . In the core, the plasma profiles are predicted by the TASK/TR code in which the core transport models consist of a combination of the MMM95 anomalous transport model and NCLASS neoclassical transport. The pellet ablation in the plasma is described using neutral gas shielding (NGS) model with inclusion of the ∇B-induced \\overrightarrow{E}× \\overrightarrow{B} drift of the ionized ablated pellet particles. It is found that the high-field-side injection can deposit the pellet mass deeper than the injection from the low-field-side due to the advantage of the ∇B-induced drift. When pellets with deuterium-tritium mixing ratio of unity are launched with speed of 200 m/s, radius of 3 mm and injected at frequency of 2 Hz, the line average density and the plasma stored energy are increased by 80% and 25% respectively. The pellet material is mostly deposited at the normalized minor radius of 0.5 from the edge.

Comparison of dust charging between orbital-motion-limited theory and particle-in-cell simulations

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

Delzanno, Gian Luca, E-mail: delzanno@lanl.gov; Tang, Xian-Zhu, E-mail: xtang@lanl.gov

The Orbital-Motion-Limited (OML) theory has been modified to predict the dust charge and the results were contrasted with the Whipple approximation [X. Z. Tang and G. L. Delzanno, Phys. Plasmas 21, 123708 (2014)]. To further establish its regime of applicability, in this paper, the OML predictions (for a non-electron-emitting, spherical dust grain at rest in a collisionless, unmagnetized plasma) are compared with particle-in-cell simulations that retain the absorption radius effect. It is found that for large dust grain radius r{sub d} relative to the plasma Debye length λ{sub D}, the revised OML theory remains a very good approximation as, formore » the parameters considered (r{sub d}/λ{sub D} ≤ 10, equal electron and ion temperatures), it yields the dust charge to within 20% accuracy. This is a substantial improvement over the Whipple approximation. The dust collected currents and energy fluxes, which remain the same in the revised and standard OML theories, are accurate to within 15%–30%.« less

Theory of mind in Williams syndrome assessed using a nonverbal task.

PubMed

Porter, Melanie A; Coltheart, Max; Langdon, Robyn

2008-05-01

This study examined Theory of Mind in Williams syndrome (WS) and in normal chronological age-matched and mental age-matched control groups, using a picture sequencing task. This task assesses understanding of pretence, intention and false belief, while controlling for social-script knowledge and physical cause-and-effect reasoning. The task was selected because it is entirely non-verbal, so that the WS individuals could not rely on their good verbal skills when performing the task. Results indicated a specific deficit in understanding of false belief within the WS group. There was also evidence of heterogeneity in the WS group, with the false belief impairment restricted to only a particular subgroup of WS individuals identified originally by Porter, M., & Coltheart, M. (2005). Cognitive heterogeneity in Williams syndrome. Developmental Neuropsychology, 27(2), 275-306.

A Systematic Review of the Evidence for Impaired Cognitive Theory of Mind in Maltreated Children

PubMed Central

Benarous, Xavier; Guilé, Jean-Marc; Consoli, Angèle; Cohen, David

2015-01-01

Compared to the large number of studies exploring difficulties in emotion recognition in maltreated children, few (N = 12) have explored the cognitive aspect of theory of mind (ToM), i.e., the ability to understand others’ thoughts and intentions. A systematic review of these studies shows inconsistent results regarding cognitive ToM tasks. Youths with a history of maltreatment are more likely to fail at false-belief tasks (N = 2). However, results are less conclusive regarding other tasks (perspective-taking tasks, N = 4; and hostile attribution tasks, N = 7). Additionally, only one study controlled for potential psychopathology. Measures of psychopathology and other cognitive abilities, in addition to ToM, are required to establish a specific association between maltreatment and the cognitive dimension of ToM. PMID:26283975

A Systematic Review of the Evidence for Impaired Cognitive Theory of Mind in Maltreated Children.

PubMed

Benarous, Xavier; Guilé, Jean-Marc; Consoli, Angèle; Cohen, David

2015-01-01

Compared to the large number of studies exploring difficulties in emotion recognition in maltreated children, few (N = 12) have explored the cognitive aspect of theory of mind (ToM), i.e., the ability to understand others' thoughts and intentions. A systematic review of these studies shows inconsistent results regarding cognitive ToM tasks. Youths with a history of maltreatment are more likely to fail at false-belief tasks (N = 2). However, results are less conclusive regarding other tasks (perspective-taking tasks, N = 4; and hostile attribution tasks, N = 7). Additionally, only one study controlled for potential psychopathology. Measures of psychopathology and other cognitive abilities, in addition to ToM, are required to establish a specific association between maltreatment and the cognitive dimension of ToM.

Mirrors, masks, and motivation: implicit and explicit self-focused attention influence effort-related cardiovascular reactivity.

PubMed

Silvia, Paul J

2012-07-01

Using motivational intensity theory as a framework, three experiments examined how implicit self-focus (manipulated with masked first-name priming) and explicit self-focus (manipulated with a large mirror) influence effort-related cardiovascular activity, particularly systolic blood pressure reactivity. Theories of self-focused attention suggest that both implicit and explicit self-focus bring about self-evaluation and thus make meeting a goal more important. For a "do your best" task of unfixed difficulty, implicit and explicit self-focus both increased effort (Experiment 1) compared to a control condition. For a task that varied in difficulty, implicit and explicit self-focus promoted more effort as the task became increasingly hard (Experiments 2 and 3). Taken together, the findings suggest that implicit and explicit self-processes share a similar motivational architecture. The discussion explores the value of integrating motivational intensity theory with self-awareness theory and considers the emerging interest in implicit aspects of effort regulation. Copyright © 2012 Elsevier B.V. All rights reserved.

Implications of contamination and surface area ratios for Langmuir probe diagnostics on CubeSats

NASA Astrophysics Data System (ADS)

Suresh, P.; Swenson, C.

2009-12-01

Theories describing the current collected by a biased probe under various conditions are necessary for such observation to be used to accurately determine plasma properties. Langmuir probes are routinely used on spacecraft to measure plasma parameters such as density, temperature, and vehicle charging. The collected current is a function of the potential between the surrounding plasma and probe surface. There have been both observations of and concepts for unaccounted variations of this potential which limit the application of Langmuir probe theory for determining plasma properties. These variations occur due to spatial variations of the work function across the probe surface due to non-uniformity of the crystalline surface properties and surface contamination of the probe. Currently we do not have theoretical expressions which consider these factors as first principles in their derivation. In the event of these surface potential variations, the analysis of the plasma using the currently available theories of the Langmuir probe yield erroneous results. We present a theory which models the current as a function of the surface potential variations. Another consideration for Langmuir probes on CubeSats is the ratio of the probe area to the return current collection area. If the area ratio is unfavorable this can also lead to erroneous results in the interpretation of observations. A mathematical formulation of the current collected by the probe for contaminated surfaces is presented and compared with data from a Langmuir probe flown on a sounding rocket mission. The implications of using Langmuir probes on CubeSats given the engineering limitations of probe cleanliness and area ratios are reviewed.

The Different Role of Working Memory in Open-Ended versus Closed-Ended Creative Problem Solving: A Dual-Process Theory Account

ERIC Educational Resources Information Center

Lin, Wei-Lun; Lien, Yunn-Wen

2013-01-01

This study examined how working memory plays different roles in open-ended versus closed-ended creative problem-solving processes, as represented by divergent thinking tests and insight problem-solving tasks. With respect to the analysis of different task demands and the framework of dual-process theories, the hypothesis was that the idea…

Child-Bearing Decision Making Among Women Previously Treated for Breast Cancer

DTIC Science & Technology

1997-04-01

this kind of study is an essential preliminary step to developing meaningful theory-driven psychosocial research on the issues of childbearing among...than older women with the disease and may experience unique vulnerability factors. Adult developmental theory ( Erikson , 1963; Levinson, Darrow, Klein...variety of developmental tasks characterize different stages of the adult life cycle. Several significant tasks for younger women are likely to be

I Can Talk You into It: Theory of Mind and Persuasion Behavior in Young Children

ERIC Educational Resources Information Center

Slaughter, Virginia; Peterson, Candida C.; Moore, Chris

2013-01-01

We investigated links between persuasive behavior and theory of mind (ToM) understanding using a novel naturalistic peer persuasion task in which children were invited to convince an interactive puppet to eat raw broccoli or brush his teeth. Sixty-three 3- to 8-year-olds (M age = 6 years, 6 months) took part in the persuasion task and were also…

Impaired Performance on See-Know Tasks amongst Children with Autism: Evidence of Specific Difficulties with Theory of Mind or Domain-General Task Factors?

ERIC Educational Resources Information Center

Lind, Sophie E.; Bowler, Dermot M.

2010-01-01

It is widely assumed that children with autism have a diminished understanding of the perception-knowledge relationship, as a specific manifestation of a theory of mind (ToM) impairment. However, such a conclusion may not be justified on the basis of previous studies, which have suffered from significant methodological weaknesses. The current…

The Relationship between Theory of Mind and Executive Function in a Sample of Children from Mainland China

ERIC Educational Resources Information Center

Yang, Juan; Zhou, Shijie; Yao, Shuqiao; Su, Linyan; McWhinnie, Chad

2009-01-01

To explore the relationship between theory of mind (ToM) and executive function (EF) in a sample of individuals from mainland China, 20 children with autism spectrum disorders (ASD), 26 children with Attention Deficit Hyperactivity Disorder (ADHD), and 30 normal control subjects were compared on two batteries of ToM tasks and EF tasks. Children…

Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders.

PubMed

Kana, Rajesh K; Libero, Lauren E; Moore, Marie S

2011-12-01

Recent findings of neurological functioning in autism spectrum disorder (ASD) point to altered brain connectivity as a key feature of its pathophysiology. The cortical underconnectivity theory of ASD (Just et al., 2004) provides an integrated framework for addressing these new findings. This theory suggests that weaker functional connections among brain areas in those with ASD hamper their ability to accomplish complex cognitive and social tasks successfully. We will discuss this theory, but will modify the term underconnectivity to 'disrupted cortical connectivity' to capture patterns of both under- and over-connectivity in the brain. In this paper, we will review the existing literature on ASD to marshal supporting evidence for hypotheses formulated on the disrupted cortical connectivity theory. These hypotheses are: 1) underconnectivity in ASD is manifested mainly in long-distance cortical as well as subcortical connections rather than in short-distance cortical connections; 2) underconnectivity in ASD is manifested only in complex cognitive and social functions and not in low-level sensory and perceptual tasks; 3) functional underconnectivity in ASD may be the result of underlying anatomical abnormalities, such as problems in the integrity of white matter; 4) the ASD brain adapts to underconnectivity through compensatory strategies such as overconnectivity mainly in frontal and in posterior brain areas. This may be manifested as deficits in tasks that require frontal-parietal integration. While overconnectivity can be tested by examining the cortical minicolumn organization, long-distance underconnectivity can be tested by cognitively demanding tasks; and 5) functional underconnectivity in brain areas in ASD will be seen not only during complex tasks but also during task-free resting states. We will also discuss some empirical predictions that can be tested in future studies, such as: 1) how disrupted connectivity relates to cognitive impairments in skills such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD. Published by Elsevier B.V.

Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders

NASA Astrophysics Data System (ADS)

Kana, Rajesh K.; Libero, Lauren E.; Moore, Marie S.

2011-12-01

Recent findings of neurological functioning in autism spectrum disorder (ASD) point to altered brain connectivity as a key feature of its pathophysiology. The cortical underconnectivity theory of ASD (Just et al., 2004) provides an integrated framework for addressing these new findings. This theory suggests that weaker functional connections among brain areas in those with ASD hamper their ability to accomplish complex cognitive and social tasks successfully. We will discuss this theory, but will modify the term underconnectivity to ‘disrupted cortical connectivity’ to capture patterns of both under- and over-connectivity in the brain. In this paper, we will review the existing literature on ASD to marshal supporting evidence for hypotheses formulated on the disrupted cortical connectivity theory. These hypotheses are: 1) underconnectivity in ASD is manifested mainly in long-distance cortical as well as subcortical connections rather than in short-distance cortical connections; 2) underconnectivity in ASD is manifested only in complex cognitive and social functions and not in low-level sensory and perceptual tasks; 3) functional underconnectivity in ASD may be the result of underlying anatomical abnormalities, such as problems in the integrity of white matter; 4) the ASD brain adapts to underconnectivity through compensatory strategies such as overconnectivity mainly in frontal and in posterior brain areas. This may be manifested as deficits in tasks that require frontal-parietal integration. While overconnectivity can be tested by examining the cortical minicolumn organization, long-distance underconnectivity can be tested by cognitively demanding tasks; and 5) functional underconnectivity in brain areas in ASD will be seen not only during complex tasks but also during task-free resting states. We will also discuss some empirical predictions that can be tested in future studies, such as: 1) how disrupted connectivity relates to cognitive impairments in skills such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD.

Confinement of plasma along shaped open magnetic fields from the centrifugal force of supersonic plasma rotation.

PubMed

Teodorescu, C; Young, W C; Swan, G W S; Ellis, R F; Hassam, A B; Romero-Talamas, C A

2010-08-20

Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic E × B rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

The role of local theories: teacher knowledge and its impact on engaging students with challenging tasks

NASA Astrophysics Data System (ADS)

Choppin, Jeffrey

2011-03-01

This study explores the extent to which a teacher elicited students' mathematical reasoning through the use of challenging tasks and the role her knowledge played in doing so. I characterised the teacher's knowledge in terms of a local theory of instruction, a form of pedagogical content knowledge that involves an empirically tested set of conjectures situated within a mathematical domain. Video data were collected and analysed and used to stimulate the teacher's reflection on her enactments of an instructional sequence. The teacher, chosen for how she consistently elicited student reasoning, showed evidence of possessing a local theory in that she articulated the ways student thinking developed over time, the processes by which that thinking developed, and the resources that facilitated the development of student thinking. Her knowledge informed how she revised and enacted challenging tasks in ways that elicited and refined student thinking around integer addition and subtraction. Furthermore, her knowledge and practices emphasised the progressive formalisation of students' ideas as a key learning process. A key implication of this study is that teachers are able to develop robust knowledge from enacting challenging tasks, knowledge that organises how they elicit and refine student reasoning from those tasks.

Left inferior-parietal lobe activity in perspective tasks: identity statements

PubMed Central

Arora, Aditi; Weiss, Benjamin; Schurz, Matthias; Aichhorn, Markus; Wieshofer, Rebecca C.; Perner, Josef

2015-01-01

We investigate the theory that the left inferior parietal lobe (IPL) is closely associated with tracking potential differences of perspective. Developmental studies find that perspective tasks are mastered at around 4 years of age. Our first study, meta-analyses of brain imaging studies shows that perspective tasks specifically activate a region in the left IPL and precuneus. These tasks include processing of false belief, visual perspective, and episodic memory. We test the location specificity theory in our second study with an unusual and novel kind of perspective task: identity statements. According to Frege's classical logical analysis, identity statements require appreciation of modes of presentation (perspectives). We show that identity statements, e.g., “the tour guide is also the driver” activate the left IPL in contrast to a control statements, “the tour guide has an apprentice.” This activation overlaps with the activations found in the meta-analysis. This finding is confirmed in a third study with different types of statements and different comparisons. All studies support the theory that the left IPL has as one of its overarching functions the tracking of perspective differences. We discuss how this function relates to the bottom-up attention function proposed for the bilateral IPL. PMID:26175677

Missing a trick: Auditory load modulates conscious awareness in audition.

PubMed

Fairnie, Jake; Moore, Brian C J; Remington, Anna

2016-07-01

In the visual domain there is considerable evidence supporting the Load Theory of Attention and Cognitive Control, which holds that conscious perception of background stimuli depends on the level of perceptual load involved in a primary task. However, literature on the applicability of this theory to the auditory domain is limited and, in many cases, inconsistent. Here we present a novel "auditory search task" that allows systematic investigation of the impact of auditory load on auditory conscious perception. An array of simultaneous, spatially separated sounds was presented to participants. On half the trials, a critical stimulus was presented concurrently with the array. Participants were asked to detect which of 2 possible targets was present in the array (primary task), and whether the critical stimulus was present or absent (secondary task). Increasing the auditory load of the primary task (raising the number of sounds in the array) consistently reduced the ability to detect the critical stimulus. This indicates that, at least in certain situations, load theory applies in the auditory domain. The implications of this finding are discussed both with respect to our understanding of typical audition and for populations with altered auditory processing. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

To branch out or stay focused? Affective shifts differentially predict organizational citizenship behavior and task performance.

PubMed

Yang, Liu-Qin; Simon, Lauren S; Wang, Lei; Zheng, Xiaoming

2016-06-01

We draw from personality systems interaction (PSI) theory (Kuhl, 2000) and regulatory focus theory (Higgins, 1997) to examine how dynamic positive and negative affective processes interact to predict both task and contextual performance. Using a twice-daily diary design over the course of a 3-week period, results from multilevel regression analysis revealed that distinct patterns of change in positive and negative affect optimally predicted contextual and task performance among a sample of 71 employees at a medium-sized technology company. Specifically, within persons, increases (upshifts) in positive affect over the course of a workday better predicted the subsequent day's organizational citizenship behavior (OCB) when such increases were coupled with decreases (downshifts) in negative affect. The optimal pattern of change in positive and negative affect differed, however, in predicting task performance. That is, upshifts in positive affect over the course of the workday better predicted the subsequent day's task performance when such upshifts were accompanied by upshifts in negative affect. The contribution of our findings to PSI theory and the broader affective and motivation regulation literatures, along with practical implications, are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Toward a New Theory for Selecting Instructional Visuals.

ERIC Educational Resources Information Center

Croft, Richard S.; Burton, John K.

This paper provides a rationale for the selection of illustrations and visual aids for the classroom. The theories that describe the processing of visuals are dual coding theory and cue summation theory. Concept attainment theory offers a basis for selecting which cues are relevant for any learning task which includes a component of identification…

Influence of mean radial electric field on particle transport induced by RMPs in tokamak plasmas

NASA Astrophysics Data System (ADS)

Chen, Dunqiang; Xu, Yingfeng; Wang, Shaojie

2018-06-01

The quasi-linear theory of the particle diffusion coefficient including the finite Larmor radius effect and the mean radial electric field ( E r without shear) in a stochastic magnetic field is derived. The theory has been verified by comparing with test particle simulations and previous theory. It is found that E r can shift the wave-particle resonance position. The Er-shift effect mainly modifies the ion diffusion coefficients and leads to the modification of ion particle flux. By using the ambipolar condition, we obtained the balanced flux at the edge of a tokamak plasma and found good agreement with recent experimental observations.

Nonlinear mode coupling theory of the lower-hybrid-drift instability

NASA Technical Reports Server (NTRS)

Drake, J. F.; Guzdar, P. N.; Hassam, A. B.; Huba, J. D.

1984-01-01

A nonlinear mode coupling theory of the lower-hybrid-drift instability is presented. A two-dimensional nonlinear wave equation is derived which describes lower-hybrid drift wave turbulence in the plane transverse to B (k.B = 0), and which is valid for finite beta, collisional and collisionless plasmas. The instability saturates by transferring energy from growing, long wavelength modes to damped, short wavelength modes. Detailed numerical results are presented which compare favorably to both recent computer simulations and experimental observations. Applications of this theory to space plasmas, the earth's magnetotail and the equatorial F region ionosphere, are discussed. Previously announced in STAR as N84-17734

Hindsight Bias and Developing Theories of Mind

PubMed Central

Bernstein, Daniel M.; Atance, Cristina; Meltzoff, Andrew N.; Loftus, Geoffrey R.

2013-01-01

Although hindsight bias (the “I knew it all along” phenomenon) has been documented in adults, its development has not been investigated. This is despite the fact that hindsight bias errors closely resemble the errors children make on theory of mind (ToM) tasks. Two main goals of the present work were to (a) create a battery of hindsight tasks for preschoolers, and (b) assess the relation between children’s performance on these and ToM tasks. In two experiments involving 144 preschoolers, 3-, 4-, and 5-year olds exhibited strong hindsight bias. Performance on hindsight and ToM tasks was significantly correlated independent of age, language ability, and inhibitory control. These findings contribute to a more comprehensive account of perspective taking across the lifespan. PMID:17650144

Theory of type 3b solar radio bursts. [plasma interaction and electron beams

NASA Technical Reports Server (NTRS)

Smith, R. A.; Delanoee, J.

1975-01-01

During the initial space-time evolution of an electron beam injected into the corona, the strong beam-plasma interaction occurs at the head of the beam, leading to the amplification of a quasi-monochromatic large-amplitude plasma wave that stabilizes by trapping the beam particles. Oscillation of the trapped particles in the wave troughs amplifies sideband electrostatic waves. The sidebands and the main wave subsequently decay to observable transverse electromagnetic waves through the parametric decay instability. This process gives rise to the elementary striation bursts. Owing to velocity dispersion in the beam and the density gradient of the corona, the entire process may repeat at a finite number of discrete plasma levels, producing chains of elementary bursts. All the properties of the type IIIb bursts are accounted for in the context of the theory.

Excitation and trapping of lower hybrid waves in striations

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

Borisov, N.; Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation; Honary, F.

2008-12-15

The theory of lower hybrid (LH) waves trapped in striations in warm ionospheric plasma in the three-dimensional case is presented. A specific mechanism of trapping associated with the linear transformation of waves is discussed. It is shown analytically that such trapping can take place in elongated plasma depletions with the frequencies below and above the lower hybrid resonance frequency of the ambient plasma. The theory is applied mainly to striations generated artificially in ionospheric modification experiments and partly to natural plasma depletions in the auroral upper ionosphere. Typical amplitudes and transverse scales of the trapped LH waves excited in ionosphericmore » modification experiments are estimated. It is shown that such waves possibly can be detected by backscattering at oblique sounding in very high frequency (VHF) and ultra high frequency (UHF) ranges.« less

Cooking strongly coupled plasmas

NASA Astrophysics Data System (ADS)

Clérouin, Jean

2015-09-01

We present the orbital-free method for dense plasmas which allows for efficient variable ionisation molecular dynamics. This approach is a literal application of density functional theory where the use of orbitals is bypassed by a semi-classical estimation of the electron kinetic energy through the Thomas-Fermi theory. Thanks to a coherent definition of ionisation, we evidence a particular regime in which the static structure no longer depends on the temperature: the Γ-plateau. With the help of the well-known Thomas-Fermi scaling laws, we derive the conditions required to obtain a plasma at a given value of the coupling parameter and deduce useful fits. Static and dynamical properties are predicted as well as a a simple equation of state valid on the Γ-plateau. We show that the one component plasma model can be helpful to describe the correlations in real systems.

Energetic particle-driven compressional Alfvén eigenmodes and prospects for ion cyclotron emission studies in fusion plasmas

NASA Astrophysics Data System (ADS)

Gorelenkov, N. N.

2016-10-01

As a fundamental plasma oscillation the compressional Alfvén waves (CAWs) are interesting for plasma scientists both academically and in applications for fusion plasmas. They are believed to be responsible for the ion cyclotron emission (ICE) observed in many tokamaks. The theory of CAW and ICE was significantly advanced at the end of 20th century in particular motivated by first DT experiments on TFTR and subsequent JET DT experimental studies. More recently, ICE theory was advanced by ST (or spherical torus) experiments with the detailed theoretical and experimental studies of the properties of each instability signal. There the instability responsible for ICE signals previously indistinguishable in high aspect ratio tokamaks became the subjects of experimental studies. We discuss further the prospects of ICE theory and its applications for future burning plasma experiments such as the ITER tokamak-reactor prototype being build in France where neutrons and gamma rays escaping the plasma create extremely challenging conditions for fusion alpha particle diagnostics. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

A generic testbed for the design of plasma spectrometer control software with application to the THOR-CSW solar wind instrument

NASA Astrophysics Data System (ADS)

De Keyser, Johan; Lavraud, Benoit; Neefs, Eddy; Berkenbosch, Sophie; Beeckman, Bram; Maggiolo, Romain; Gamby, Emmanuel; Fedorov, Andrei; Baruah, Rituparna; Wong, King-Wah; Amoros, Carine; Mathon, Romain; Génot, Vincent; Marcucci, Federica; Brienza, Daniele

2017-04-01

Modern plasma spectrometers require intelligent software that is able to exploit their capabilities to the fullest. While the low-level control of the instrument and basic tasks such as performing the basic measurement, temperature control, and production of housekeeping data are to be done by software that is executed on an FPGA and/or processor inside the instrument, higher level tasks such as control of measurement sequences, on-board moment calculation, beam tracking decisions, and data compression, may be performed by the instrument or in the payload data processing unit. Such design decisions, as well as an assessment of the workload on the different processing components, require early prototyping. We have developed a generic simulation testbed for the design of plasma spectrometer control software that allows an early evaluation of the level of resources that is needed at each level. Early prototyping can pinpoint bottlenecks in the design allowing timely remediation. We have applied this tool to the THOR Cold Solar Wind (CSW) plasma spectrometer. Some examples illustrating the usefulness of the tool are given.

Optimal Design of Magnetic ComponentsinPlasma Cutting Power Supply

NASA Astrophysics Data System (ADS)

Jiang, J. F.; Zhu, B. R.; Zhao, W. N.; Yang, X. J.; Tang, H. J.

2017-10-01

Phase-shifted transformer and DC reactor are usually needed in chopper plasma cutting power supply. Because of high power rate, the loss of magnetic components may reach to several kilowatts, which seriously affects the conversion efficiency. Therefore, it is necessary to research and design low loss magnetic components by means of efficient magnetic materials and optimal design methods. The main task in this paper is to compare the core loss of different magnetic material, to analyze the influence of transformer structure, winding arrangement and wire structure on the characteristics of magnetic component. Then another task is to select suitable magnetic material, structure and wire in order to reduce the loss and volume of magnetic components. Based on the above outcome, the optimization design process of transformer and dc reactor are proposed in chopper plasma cutting power supply with a lot of solutions. These solutions are analyzed and compared before the determination of the optimal solution in order to reduce the volume and power loss of the two magnetic components and improve the conversion efficiency of plasma cutting power supply.

Corrigendum

NASA Astrophysics Data System (ADS)

Lemons, Don S.; Gary, S. Peter; Winske, D.

1980-02-01

It has been called to our attention that our paper on the nonlinear evolution of a temperature anisotropic plasma (T > T¶) in the absence of an external magnetic field (Lemons, Winske & Gary 1979) did not make reference to several relevant and previously published works. Specifically, the linear theory of this unstable plasma has been explored by Kalman, Montes & Quemada (1968), the quasi-linear theory by Smith (1969) and Montes, Coste & Diener (1970) while additional thermodynamic considerations were given by Montes & Peyraud (1972). We regret this oversight.

Ring formation in self-focusing of electromagnetic beams in plasmas

NASA Astrophysics Data System (ADS)

Faisal, M.; Mishra, S. K.; Verma, M. P.; Sodha, M. S.

2007-10-01

This article presents a paraxial theory of ring formation as an initially Gaussian beam propagates in a nonlinear plasma, characterized by significant collisional or ponderomotive nonlinearity. Regions in the axial irradiance-(beamwidth)-2 space, for which the ring formation occurs and the paraxial theory is valid, have been characterized; for typical points in these regions the dependence of the beam width parameter and the radial distribution of irradiance on the distance has been specifically investigated and discussed.

Analysis of Plasma Communication Schemes for Hypersonic Vehicles: Final Report

DTIC Science & Technology

2009-02-01

repel the more mobile species. In this way quasi -neutrality can be maintained in the plasma. The potential drops near the conducting surfaces are of... potential VM cannot be determined from a quasi - neutral diffusion theory and depends on the details of sheath physics at electrode surfaces. In the...the mid potential VM, which cannot be determined by simple quasi -neutral fluid theory, is in general a function of L. This L dependence, which

Influence of emissivity on behavior of metallic dust particles in plasmas

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

Tanaka, Y.; Smirnov, R. D.; Pigarov, A. Yu.

Influence of thermal radiation emissivity on the lifetime of a dust particle in plasmas is investigated for different fusion relevant metals (Li, Be, Mo, and W). The thermal radiation is one of main cooling mechanisms of the dust in plasmas especially for dust with evaporation temperature higher than 2500 K. In this paper, the temperature- and radius-dependent emissivity of dust particles is calculated using Mie theory and temperature-dependent optical constants for the above metallic materials. The lifetime of a dust particle in uniform plasmas is estimated with the calculated emissivity using the dust transport code DUSTT[A. Pigarov et al., Physicsmore » of Plasmas 12, 122508 (2005)], considering other dust cooling and destruction processes such as physical and chemical sputtering, melting and evaporation, electron emission etc. The use of temperature-dependent emissivity calculated with Mie theory provides a longer lifetime of the refractory metal dust particle compared with that obtained using conventional emissivity constants in the literature. The dynamics of heavy metal dust particles are also presented using the calculated emissivity in a tokamak plasma.« less

Analyzing Web pages visual scanpaths: between and within tasks variability.

PubMed

Drusch, Gautier; Bastien, J M Christian

2012-01-01

In this paper, we propose a new method for comparing scanpaths in a bottom-up approach, and a test of the scanpath theory. To do so, we conducted a laboratory experiment in which 113 participants were invited to accomplish a set of tasks on two different websites. For each site, they had to perform two tasks that had to be repeated ounce. The data were analyzed using a procedure similar to the one used by Duchowski et al. [8]. The first step was to automatically identify, then label, AOIs with the mean-shift clustering procedure [19]. Then, scanpaths were compared two by two with a modified version of the string-edit method, which take into account the order of AOIs visualizations [2]. Our results show that scanpaths variability between tasks but within participants seems to be lower than the variability within task for a given participant. In other words participants seem to be more coherent when they perform different tasks, than when they repeat the same tasks. In addition, participants view more of the same AOI when they perform a different task on the same Web page than when they repeated the same task. These results are quite different from what predicts the scanpath theory.

Transferring control demands across incidental learning tasks – stronger sequence usage in serial reaction task after shortcut option in letter string checking

PubMed Central

Gaschler, Robert; Marewski, Julian N.; Wenke, Dorit; Frensch, Peter A.

2014-01-01

After incidentally learning about a hidden regularity, participants can either continue to solve the task as instructed or, alternatively, apply a shortcut. Past research suggests that the amount of conflict implied by adopting a shortcut seems to bias the decision for vs. against continuing instruction-coherent task processing. We explored whether this decision might transfer from one incidental learning task to the next. Theories that conceptualize strategy change in incidental learning as a learning-plus-decision phenomenon suggest that high demands to adhere to instruction-coherent task processing in Task 1 will impede shortcut usage in Task 2, whereas low control demands will foster it. We sequentially applied two established incidental learning tasks differing in stimuli, responses and hidden regularity (the alphabet verification task followed by the serial reaction task, SRT). While some participants experienced a complete redundancy in the task material of the alphabet verification task (low demands to adhere to instructions), for others the redundancy was only partial. Thus, shortcut application would have led to errors (high demands to follow instructions). The low control demand condition showed the strongest usage of the fixed and repeating sequence of responses in the SRT. The transfer results are in line with the learning-plus-decision view of strategy change in incidental learning, rather than with resource theories of self-control. PMID:25506336

Color instabilities in the quark-gluon plasma

NASA Astrophysics Data System (ADS)

Mrówczyński, Stanisław; Schenke, Björn; Strickland, Michael

2017-04-01

When the quark-gluon plasma (QGP) - a system of deconfined quarks and gluons - is in a nonequilibrium state, it is usually unstable with respect to color collective modes. The instabilities, which are expected to strongly influence dynamics of the QGP produced in relativistic heavy-ion collisions, are extensively discussed under the assumption that the plasma is weakly coupled. We begin by presenting the theoretical approaches to study the QGP, which include: field theory methods based on the Keldysh-Schwinger formalism, classical and quantum kinetic theories, and fluid techniques. The dispersion equations, which give the spectrum of plasma collective excitations, are analyzed in detail. Particular attention is paid to a momentum distribution of plasma constituents which is obtained by deforming an isotropic momentum distribution. Mechanisms of chromoelectric and chromomagnetic instabilities are explained in terms of elementary physics. The Nyquist analysis, which allows one to determine the number of solutions of a dispersion equation without explicitly solving it, and stability criteria are also discussed. We then review various numerical approaches - purely classical or quantum - to simulate the temporal evolution of an unstable quark-gluon plasma. The dynamical role of instabilities in the processes of plasma equilibration is analyzed.

Color instabilities in the quark–gluon plasma

DOE PAGES

Mrówczyński, Stanisław; Schenke, Björn; Strickland, Michael

2017-04-09

When the quark–gluon plasma (QGP) – a system of deconfined quarks and gluons – is in a nonequilibrium state, it is usually unstable with respect to color collective modes. The instabilities, which are expected to strongly influence dynamics of the QGP produced in relativistic heavy-ion collisions, are extensively discussed under the assumption that the plasma is weakly coupled. Here, we begin by presenting the theoretical approaches to study the QGP, which include: field theory methods based on the Keldysh–Schwinger formalism, classical and quantum kinetic theories, and fluid techniques. The dispersion equations, which give the spectrum of plasma collective excitations, aremore » analyzed in detail. We pay particular attention to a momentum distribution of plasma constituents which is obtained by deforming an isotropic momentum distribution. Mechanisms of chromoelectric and chromomagnetic instabilities are explained in terms of elementary physics. The Nyquist analysis, which allows one to determine the number of solutions of a dispersion equation without explicitly solving it, and stability criteria are also discussed. We then review various numerical approaches – purely classical or quantum – to simulate the temporal evolution of an unstable quark–gluon plasma. The dynamical role of instabilities in the processes of plasma equilibration is analyzed.« less

Coupling Fluid and Kineitc Effects in Space Weather: an interdisciplinary task

NASA Astrophysics Data System (ADS)

Lapenta, Giovanni; González-Herrero, Diego; Boella, Elisabetta; Siddi, Lorenzo; Cazzola, Emanuele

2017-04-01

Two agents are key to space weather: electromagentic fields and energetic particles. Magnetic fields carried by plasmas in the solar wind interact with the Earth magnetosphere and solar energetic particles produced by solar events or in cosmic rays affect the space environment. Describing both is challenging. Magnetized plasmas are most effectively described by magneto-hydrodynamics, MHD, a fluid theory based on describing some fields defined in space: electromagnetic fields, density, velocity and temperature of the plasma. High energy particles, instead need a more detailed approach , kinetic theory, where statistical distributions of particles are governed by the Boltzmann equation. While fluid models are based on the ordinary space and time, kinetic models require a six dimensional space, called phase space, besides time. The two methods are not separated, the processes leading to the production of energetic particles are the same that involve space plasamas and fields. Arriving at a single self-consistent model has been the goal of the Swiff project funded by the EC in FP7 and it is now a key goal of the ongoing DEEP-ER project. We present a new approach developed with the goal of extending the reach of kinetic models to the fluid scales. Kinetic models are a higher order description and all fluid effects are included in them. However, the cost in terms of computing power is much higher and it has been so far prohibitively expensive to treat space weather events fully kinetically. We have now designed a new method capable of reducing that cost by several orders of magnitude making it possible for kinetic models to study space weather events [1,2]. We will report the new methodology and show its application to space weather mdeling. [1] Giovanni Lapenta,Exactly Energy Conserving Semi-Implicit Particle in Cell Formulation, to appear, JCP, arXiv:1602.06326 [2] Giovanni Lapenta, Diego Gonzalez-Herrero, Elisabetta Boella, Multiple scale kinetic simulations with the energy conserving semi implicit particle in cell (PIC) method, submitted JPP, arXiv:1612.08289

Meson thermalization by baryon injection in D4/D6 model

NASA Astrophysics Data System (ADS)

Rezaei, Z.

2016-12-01

We study meson thermalization in a strongly coupled plasma of quarks and gluons using AdS/CFT duality technique. Four dimensional large-Nc QCD is considered as a theory governing this quark-gluon plasma (QGP) and D4/D6-brane model is chosen to be its holographic dual theory. In order to investigate meson thermalization, we consider a time-dependent change of baryon number chemical potential. Thermalization in gauge theory side corresponds to horizon formation on the probe flavor brane in the gravity side. The gravitational dual theory is compactified on a circle that the inverse of its radius is proportional to energy scale of dual gauge theory. It is seen that increase of this energy scale results in thermalization time dilation. In addition we study the effect of magnetic field on meson thermalization. It will be seen that magnetic field also prolongs thermalization process by making mesons more stable.

New Equation of State Models for Hydrodynamic Applications

NASA Astrophysics Data System (ADS)

Young, David A.; Barbee, Troy W., III; Rogers, Forrest J.

1997-07-01

Accurate models of the equation of state of matter at high pressures and temperatures are increasingly required for hydrodynamic simulations. We have developed two new approaches to accurate EOS modeling: 1) ab initio phonons from electron band structure theory for condensed matter and 2) the ACTEX dense plasma model for ultrahigh pressure shocks. We have studied the diamond and high pressure phases of carbon with the ab initio model and find good agreement between theory and experiment for shock Hugoniots, isotherms, and isobars. The theory also predicts a comprehensive phase diagram for carbon. For ultrahigh pressure shock states, we have studied the comparison of ACTEX theory with experiments for deuterium, beryllium, polystyrene, water, aluminum, and silicon dioxide. The agreement is good, showing that complex multispecies plasmas are treated adequately by the theory. These models will be useful in improving the numerical EOS tables used by hydrodynamic codes.

A perception-action strategy for hummingbirds.

PubMed

Delafield-Butt, Jonathan; Galler, Andreas; Schögler, Benjaman; Lee, David N

2010-01-01

Many human and animal tasks are thought to be controlled with the tau informational variable. It is widely accepted that controlling the rate of change of tau (tau) during decelerative tasks, such as when braking or landing, is one common perceptual control strategy. However, many tasks require accelerating before decelerating to a goal, such as reaching. An advancement of tau theory shows how a single action formula may be used to control the full action unit from initiation to peak velocity, and to rest at the goal, with the same perceptual tau information as before and accounting for the same decelerative kinematics as before. Here, we test the theory against data from high-speed video of a hummingbird flying to its flower feeder. We find that the theory accounts for 97% of the variance in the data, and thus supports it.

Are There Detrimental Effects From Proficiency-Based Training in Fundamentals of Laparoscopic Surgery Among Novices? An Exploration of Goal Theory.

PubMed

Stoller, Jeremy; Joseph, Jeremy; Parodi, Nicholas; Gardner, Aimee

2016-01-01

Goal theory states that novices may experience unintended, detrimental learning effects, with decreased performance, when given performance goals on complex tasks. In these situations, it may be more appropriate to give novices learning goals to help avoid these negative consequences. The purpose of this study was to see whether this tenant of goal theory applied to novices learning 2 tasks of fundamentals of laparoscopic surgery (FLS). Medical and physician assistant students were randomized to a performance goals group and a learning goals group. The performance goals consisted of the published proficiency standards of FLS. Both groups were pretested on perception of surgery, self-efficacy, and general affect. Each group underwent a practice session for the peg transfer task. They were tested and scored per the published standards of FLS. The participants completed NASA Task Load Index, task complexity, and postaffect questionnaires related to the peg transfer task. This was repeated with the suture with intracorporeal knot task. Posttest perception of surgery and self-efficacy questionnaires were completed. In total, 48 students participated in the study: 23 in the performance goals group and 25 in the learning goals group. Most of the participants (n = 40) were first-year medical and physician assistant students. There were no significant differences between the groups in perception of surgery, affect, goal commitment, subjective task complexity, subjective workload, and self-efficacy. There were no differences between the groups concerning overall FLS score for both the peg transfer and suturing tasks. Both groups exhibited significant increases in self-efficacy and perception of surgery (p < 0.05). FLS skills can be given to novice learners without concern for detrimental effects as might be expected by other work on goal theory. Given that performance was the same for both groups, surgical educators may have multiple pathways to educational success when incorporating goals into training programs for basic surgical skills. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Modification of electromagnetic fields and plasma resistance by thermal effects in helicon plasmas

NASA Astrophysics Data System (ADS)

Kabir, M.; Niknam, A. R.

2017-05-01

The effects of the thermal motion of charged particles on physical characteristics of collisional helicon plasmas are investigated. First, the dielectric permittivity tensor of a helicon plasma is obtained by considering the thermal and collisional effects in the kinetic theory. Then, the electromagnetic wave and plasma resistance equations are presented and solved in a helicon plasma source with a Nagoya type III antenna. It is shown that by increasing the temperature of plasma electrons, the effective collision frequency is increased, and consequently, the peaks of resistance profiles are lowered and broadened.

Do motivational incentives reduce the inhibition deficit in ADHD?

PubMed

Shanahan, Michelle A; Pennington, Bruce F; Willcutt, Erik W

2008-01-01

The primary goal of this study was to test three competing theories of ADHD: the inhibition theory, the motivational theory, and a dual deficit theory. Previous studies have produced conflicting findings about the effects of incentives on executive processes in ADHD. In the present study of 25 children with ADHD and 30 typically developing controls, motivation was manipulated within the Stop Task. Stop signal reaction time was examined, as well as reaction time, its variability, and the number of errors in the primary choice reaction time task. Overall, the pattern of results supported the inhibition theory over the motivational or dual deficit hypotheses, as main effects of group were found for most key variables (ADHD group was worse), whereas the group by reward interaction predicted by the motivational and dual deficit accounts was not found. Hence, as predicted by the inhibition theory, children with ADHD performed worse than controls irrespective of incentives.

Twenty years of load theory-Where are we now, and where should we go next?

PubMed

Murphy, Gillian; Groeger, John A; Greene, Ciara M

2016-10-01

Selective attention allows us to ignore what is task-irrelevant and focus on what is task-relevant. The cognitive and neural mechanisms that underlie this process are key topics of investigation in cognitive psychology. One of the more prominent theories of attention is perceptual load theory, which suggests that the efficiency of selective attention is dependent on both perceptual and cognitive load. It is now more than 20 years since the proposal of load theory, and it is a good time to evaluate the evidence in support of this influential model. The present article supplements and extends previous reviews (Lavie, Trends in Cognitive Sciences, 9, 75-82. doi: 10.1016/j.tics.2004.12.004 , 2005, Current Directions in Psychological Science, 19, 143-148. doi: 10.1177/0963721410370295 , 2010) by examining more recent research in what appears to be a rapidly expanding area. The article comprises five parts, examining (1) evidence for the effects of perceptual load on attention, (2) cognitive load, (3) individual differences under load, (4) alternative theories and criticisms, and (5) the future of load theory. We argue that the key next step for load theory will be the application of the model to real-world tasks. The potential benefits of applied attention research are numerous, and there is tentative evidence that applied research would provide strong support for the theory itself, as well as real-world benefits related to activities in which attention is crucial, such as driving and education.

Dissociation of Short-Term Forgetting from the Passage of Time

ERIC Educational Resources Information Center

White, K. Geoffrey

2012-01-01

In many theories, forgetting is closely linked to the passage of time. In the present experiments, recall in a short-term memory task was less accurate when the retention interval included a difficult arithmetic addition task, compared with an easy task. In a novel condition, the interfering task was switched from hard to easy partway through the…

On the Geometrical Optics Approach in the Theory of Freely-Localized Microwave Gas Breakdown

NASA Astrophysics Data System (ADS)

Shapiro, Michael; Schaub, Samuel; Hummelt, Jason; Temkin, Richard; Semenov, Vladimir

2015-11-01

Large filamentary arrays of high pressure gas microwave breakdown have been experimentally studied at MIT using a 110 GHz, 1.5 MW pulsed gyrotron. The experiments have been modeled by other groups using numerical codes. The plasma density distribution in the filaments can be as well analytically calculated using the geometrical optics approach neglecting plasma diffusion. The field outside the filament is a solution of an inverse electromagnetic problem. The solutions are found for the cylindrical and spherical filaments and for the multi-layered planar filaments with a finite plasma density at the boundaries. We present new results of this theory showing a variety of filaments with complex shapes. The solutions for plasma density distribution are found with a zero plasma density at the boundary of the filament. Therefore, to solve the inverse problem within the geometrical optics approximation, it can be assumed that there is no reflection from the filament. The results of this research are useful for modeling future MIT experiments.

The Kelvin-Helmholtz instability of boundary-layer plasmas in the kinetic regime

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

Steinbusch, Benedikt, E-mail: b.steinbusch@fz-juelich.de; Gibbon, Paul, E-mail: p.gibbon@fz-juelich.de; Department of Mathematics, Centre for Mathematical Plasma Astrophysics, Katholieke Universiteit Leuven

2016-05-15

The dynamics of the Kelvin-Helmholtz instability are investigated in the kinetic, high-frequency regime with a novel, two-dimensional, mesh-free tree code. In contrast to earlier studies which focused on specially prepared equilibrium configurations in order to compare with fluid theory, a more naturally occurring plasma-vacuum boundary layer is considered here with relevance to both space plasma and linear plasma devices. Quantitative comparisons of the linear phase are made between the fluid and kinetic models. After establishing the validity of this technique via comparison to linear theory and conventional particle-in-cell simulation for classical benchmark problems, a quantitative analysis of the more complexmore » magnetized plasma-vacuum layer is presented and discussed. It is found that in this scenario, the finite Larmor orbits of the ions result in significant departures from the effective shear velocity and width underlying the instability growth, leading to generally slower development and stronger nonlinear coupling between fast growing short-wavelength modes and longer wavelengths.« less

A two-dimensional theory of plasma contactor clouds used in the ionosphere with an electrodynamic tether

NASA Technical Reports Server (NTRS)

Hastings, D. E.; Gatsonis, N. A.; Rivas, D. A.

1988-01-01

Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether then a miltiple tether array will be more efficient than a single tether.

Non-Markovian renormalization of kinetic coefficients for drift-type turbulence in magnetized plasmas

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

Zagorodny, A.; Weiland, J.

2009-05-15

The problem of derivation of the kinetic equations for inhomogeneous plasma in an external magnetic field is considered. The Fokker-Planck-type equations with the non-Markovian kinetic coefficients are proposed. In the time-local limit (small correlation times with respect to the distribution function relaxation time) the relations obtained recover the results known from the appropriate quasilinear theory and the Dupree-Weinstock theory of plasma turbulence. Kinetic calculations of the dielectric response function are also performed with regard to the influence of turbulent fields on particle motion. The equations proposed are used to describe zonal flow generation and to estimate the diffusion coefficient formore » saturated turbulence.« less

Spatially modulated phase in the holographic description of quark-gluon plasma.

PubMed

Ooguri, Hirosi; Park, Chang-Soon

2011-02-11

We present a string theory construction of a gravity dual of a spatially modulated phase. Our earlier work shows that the Chern-Simons term in the five-dimensional Maxwell theory destabilizes the Reissner-Nordström black holes in anti-de Sitter space if the Chern-Simons coupling is sufficiently high. In this Letter, we show that a similar instability is realized on the world volume of 8-branes in the Sakai-Sugimoto model in the quark-gluon plasma phase. Our result suggests a new spatially modulated phase in quark-gluon plasma when the baryon density is above 0.8Nf  fm(-3) at temperature 150 MeV.

Metriplectic Gyrokinetics and Discretization Methods for the Landau Collision Integral

NASA Astrophysics Data System (ADS)

Hirvijoki, Eero; Burby, Joshua W.; Kraus, Michael

2017-10-01

We present two important results for the kinetic theory and numerical simulation of warm plasmas: 1) We provide a metriplectic formulation of collisional electrostatic gyrokinetics that is fully consistent with the First and Second Laws of Thermodynamics. 2) We provide a metriplectic temporal and velocity-space discretization for the particle phase-space Landau collision integral that satisfies the conservation of energy, momentum, and particle densities to machine precision, as well as guarantees the existence of numerical H-theorem. The properties are demonstrated algebraically. These two result have important implications: 1) Numerical methods addressing the Vlasov-Maxwell-Landau system of equations, or its reduced gyrokinetic versions, should start from a metriplectic formulation to preserve the fundamental physical principles also at the discrete level. 2) The plasma physics community should search for a metriplectic reduction theory that would serve a similar purpose as the existing Lagrangian and Hamiltonian reduction theories do in gyrokinetics. The discovery of metriplectic formulation of collisional electrostatic gyrokinetics is strong evidence in favor of such theory and, if uncovered, the theory would be invaluable in constructing reduced plasma models. Supported by U.S. DOE Contract Nos. DE-AC02-09-CH11466 (EH) and DE-AC05-06OR23100 (JWB) and by European Union's Horizon 2020 research and innovation Grant No. 708124 (MK).

Space plasma simulations; Proceedings of the Second International School for Space Simulations, Kapaa, HI, February 4-15, 1985. Parts 1 & 2

NASA Technical Reports Server (NTRS)

Ashour-Abdalla, M. (Editor); Dutton, D. A. (Editor)

1985-01-01

Space plasma simulations, observations, and theories are discussed. Papers are presented on the capabilities of various types of simulation codes and simulation models. Consideration is given to plasma waves in the earth's magnetotail, outer planet magnetosphere, geospace, and the auroral and polar cap regions. Topics discussed include space plasma turbulent dissipation, the kinetics of plasma waves, wave-particle interactions, whistler mode propagation, global energy regulation, and auroral arc formation.

Plasma Dispersion Function for the Kappa Distribution

NASA Technical Reports Server (NTRS)

Podesta, John J.

2004-01-01

The plasma dispersion function is computed for a homogeneous isotropic plasma in which the particle velocities are distributed according to a Kappa distribution. An ordinary differential equation is derived for the plasma dispersion function and it is shown that the solution can be written in terms of Gauss' hypergeometric function. Using the extensive theory of the hypergeometric function, various mathematical properties of the plasma dispersion function are derived including symmetry relations, series expansions, integral representations, and closed form expressions for integer and half-integer values of K.

Formation of Dense Plasma around a Small Meteoroid: Kinetic Theory and its Implications

NASA Astrophysics Data System (ADS)

Dimant, Y. S.; Oppenheim, M. M.; Marshall, R.

2016-12-01

Every second, millions of small meteoroids hit the Earth from space, the vast majority too small to observe visually. Radars easily detect the plasma generated during meteoroid ablation and use this data to characterize the meteoroids and the atmosphere in which they disintegrate. Reflections of radar pulses from this plasma produce a signal called a head echo. We have developed a first-principle kinetic theory to describe the behavior of meteoric particles ablated from a fast-moving meteoroid and partially ionized through collisions with the atmosphere. This theory produces analytic expressions describing the ion and neutral density and velocity distributions. This analytical model will allow more accurate quantitative interpretations of head echo radar measurements. These, in turn, will improve our ability to infer meteoroid and atmospheric properties. Figure shows the theoretically predicted spatial distribution of the near-meteoroid plasma. This distribution is axially symmetric with respect to the path of the meteoroid. The plasma density within a collisional mean-free-path length drops in proportion to 1/R where R is the distance from the meteoroid center. Beyond this distance and behind the meteoroid, the density transitions to ∝ 1/R². This behavior makes the near-meteoroid plasma overdense to the propagating radar wave in all cases at locations sufficiently close to the meteoroid. Using the FDTD model of Marshall and Close [2015], we use this plasma density distribution to calculate the radar cross section (RCS) from head echoes. Consistent with the results of Marshall and Close [2015], we find that the RCS is given by the cross-section area of the meteor plasma inside which the plasma is overdense - the "overdense area" - as viewed from the radar. Since the distribution derived here is specified by two parameters, this result suggests that the meteor plasma distribution can be specified with two measurements of RCS at different frequencies, as was done by Close et al [2004]. The specification of the meteor plasma distribution then leads to an improved estimate of the parent meteoroid mass, a critical parameter for understanding the global meteoroid flux and deposition in the atmosphere. Work is supported by NSF Grant AGS-1244842.

Information Memory Processing and Retrieval: The Use of Information Theory to Study Primacy and Recency Characteristics of Ninth Grade Science Students Processing Learning Tasks.

ERIC Educational Resources Information Center

Dunlop, David L.

Reported is another study related to the Project on an Information Memory Model. This study involved using information theory to investigate the concepts of primacy and recency as they were exhibited by ninth-grade science students while processing a biological sorting problem and an immediate, abstract recall task. Two hundred randomly selected…

Effects of Stress on Judgment and Decision Making in Dynamic Tasks

DTIC Science & Technology

1991-06-01

their normal working conditions, (2) to ascertain whether the results from lens model theory and research in static tasks generalize to these...8217 normal work environment. A further generalization from lens model theory is that those precursors (secondary cues) that are more conceptual in...potential microburst cases. Although this sample of cases is admittedly smaller than desirable, many hours of technical work were required to remove

Modelling the Factors that Affect Individuals' Utilisation of Online Learning Systems: An Empirical Study Combining the Task Technology Fit Model with the Theory of Planned Behaviour

ERIC Educational Resources Information Center

Yu, Tai-Kuei; Yu, Tai-Yi

2010-01-01

Understanding learners' behaviour, perceptions and influence in terms of learner performance is crucial to predict the use of electronic learning systems. By integrating the task-technology fit (TTF) model and the theory of planned behaviour (TPB), this paper investigates the online learning utilisation of Taiwanese students. This paper provides a…

Multitasking as a choice: a perspective.

PubMed

Broeker, Laura; Liepelt, Roman; Poljac, Edita; Künzell, Stefan; Ewolds, Harald; de Oliveira, Rita F; Raab, Markus

2018-01-01

Performance decrements in multitasking have been explained by limitations in cognitive capacity, either modelled as static structural bottlenecks or as the scarcity of overall cognitive resources that prevent humans, or at least restrict them, from processing two tasks at the same time. However, recent research has shown that individual differences, flexible resource allocation, and prioritization of tasks cannot be fully explained by these accounts. We argue that understanding human multitasking as a choice and examining multitasking performance from the perspective of judgment and decision-making (JDM), may complement current dual-task theories. We outline two prominent theories from the area of JDM, namely Simple Heuristics and the Decision Field Theory, and adapt these theories to multitasking research. Here, we explain how computational modelling techniques and decision-making parameters used in JDM may provide a benefit to understanding multitasking costs and argue that these techniques and parameters have the potential to predict multitasking behavior in general, and also individual differences in behavior. Finally, we present the one-reason choice metaphor to explain a flexible use of limited capacity as well as changes in serial and parallel task processing. Based on this newly combined approach, we outline a concrete interdisciplinary future research program that we think will help to further develop multitasking research.

Plasma Desorption Mass Spectrometry: Coming of Age.

ERIC Educational Resources Information Center

Cotter, Robert J.

1988-01-01

Discusses the history and development of Plasma Desorption Mass Spectrometry to determine molecular weights and structures of proteins and polymers. Outlines theory, instrumentation, and sample preparation commonly used. Gives several examples of resulting spectra. (ML)

Distraction and mind-wandering under load.

PubMed

Forster, Sophie

2013-01-01

Attention research over the last several decades has provided rich insights into the determinants of distraction, including distractor characteristics, task features, and individual differences. Load Theory represented a particularly important breakthrough, highlighting the critical role of the level and nature of task-load in determining both the efficiency of distractor rejection and the stage of processing at which this occurs. However, until recently studies of distraction were restricted to those measuring rather specific forms of distraction by external stimuli which I argue that, although intended to be irrelevant, were in fact task-relevant. In daily life, attention may be distracted by a wide range of stimuli, which may often be entirely unrelated to any task being performed, and may include not only external stimuli but also internally generated stimuli such as task-unrelated thoughts. This review outlines recent research examining these more general, entirely task-irrelevant, forms of distraction within the framework of Load Theory. I discuss the relation between different forms of distraction, and the universality of load effects across different distractor types and individuals.

Context processing in adolescents with autism spectrum disorder: How complex could it be?

PubMed

Ben-Yosef, Dekel; Anaki, David; Golan, Ofer

2017-03-01

The ability of individuals with Autism Spectrum Disorder (ASD) to process context has long been debated: According to the Weak Central Coherence theory, ASD is characterized by poor global processing, and consequently-poor context processing. In contrast, the Social Cognition theory argues individuals with ASD will present difficulties only in social context processing. The complexity theory of autism suggests context processing in ASD will depend on task complexity. The current study examined this controversy through two priming tasks, one presenting human stimuli (facial expressions) and the other presenting non-human stimuli (animal faces). Both tasks presented visual targets, preceded by congruent, incongruent, or neutral auditory primes. Local and global processing were examined by presenting the visual targets in three spatial frequency conditions: High frequency, low frequency, and broadband. Tasks were administered to 16 adolescents with high functioning ASD and 16 matched typically developing adolescents. Reaction time and accuracy were measured for each task in each condition. Results indicated that individuals with ASD processed context for both human and non-human stimuli, except in one condition, in which human stimuli had to be processed globally (i.e., target presented in low frequency). The task demands presented in this condition, and the performance deficit shown in the ASD group as a result, could be understood in terms of cognitive overload. These findings provide support for the complexity theory of autism and extend it. Our results also demonstrate how associative priming could support intact context processing of human and non-human stimuli in individuals with ASD. Autism Res 2017, 10: 520-530. © 2016 International Society for Autism Research, Wiley Periodicals, Inc. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Individual Differences at High Perceptual Load: The Relation between Trait Anxiety and Selective Attention

PubMed Central

Sadeh, Naomi; Bredemeier, Keith

2010-01-01

Attentional control theory (Eysenck et al., 2007) posits that taxing attentional resources impairs performance efficiency in anxious individuals. This theory, however, does not explicitly address if or how the relation between anxiety and attentional control depends upon the perceptual demands of the task at hand. Consequently, the present study examined the relation between trait anxiety and task performance using a perceptual load task (Maylor & Lavie, 1998). Sixty-eight male college students completed a visual search task that indexed processing of irrelevant distractors systematically across four levels of perceptual load. Results indicated that anxiety was related to difficulty suppressing the behavioral effects of irrelevant distractors (i.e., decreased reaction time efficiency) under high, but not low, perceptual loads. In contrast, anxiety was not associated with error rates on the task. These findings are consistent with the prediction that anxiety is associated with impairments in performance efficiency under conditions that tax attentional resources. PMID:21547776

[Determinants of task preferences when performance is indicative of individual characteristics: self-assessment motivation and self-verification motivation].

PubMed

Numazaki, M; Kudo, E

1995-04-01

The present study was conducted to examine determinants of information-gathering behavior with regard to one's own characteristics. Four tasks with different self-congruent and incongruent diagnosticity were presented to subjects. As self-assessment theory predicted, high diagnostic tasks were preferred to low tasks. And as self-verification theory predicted, self-congruent diagnosticity had a stronger effect on task preference than self-incongruent diagnosticity. In addition, subjects who perceived the relevant characteristics important inclined to choose self-assessment behavior more than who did not. Also, subjects who were certain of their self-concept inclined to choose self-verification behavior more than who were not. These results suggest that both self-assessment and self-verification motivations play important roles in information-gathering behavior regarding one's characteristics, and strength of the motivations is determined by the importance of relevant characteristics or the certainty of self-concept.

Individual differences at high perceptual load: the relation between trait anxiety and selective attention.

PubMed

Sadeh, Naomi; Bredemeier, Keith

2011-06-01

Attentional control theory (Eysenck et al., 2007) posits that taxing attentional resources impairs performance efficiency in anxious individuals. This theory, however, does not explicitly address if or how the relation between anxiety and attentional control depends upon the perceptual demands of the task at hand. Consequently, the present study examined the relation between trait anxiety and task performance using a perceptual load task (Maylor & Lavie, 1998). Sixty-eight male college students completed a visual search task that indexed processing of irrelevant distractors systematically across four levels of perceptual load. Results indicated that anxiety was related to difficulty suppressing the behavioural effects of irrelevant distractors (i.e., decreased reaction time efficiency) under high, but not low, perceptual loads. In contrast, anxiety was not associated with error rates on the task. These findings are consistent with the prediction that anxiety is associated with impairments in performance efficiency under conditions that tax attentional resources.

Prototype-Incorporated Emotional Neural Network.

PubMed

Oyedotun, Oyebade K; Khashman, Adnan

2017-08-15

Artificial neural networks (ANNs) aim to simulate the biological neural activities. Interestingly, many ''engineering'' prospects in ANN have relied on motivations from cognition and psychology studies. So far, two important learning theories that have been subject of active research are the prototype and adaptive learning theories. The learning rules employed for ANNs can be related to adaptive learning theory, where several examples of the different classes in a task are supplied to the network for adjusting internal parameters. Conversely, the prototype-learning theory uses prototypes (representative examples); usually, one prototype per class of the different classes contained in the task. These prototypes are supplied for systematic matching with new examples so that class association can be achieved. In this paper, we propose and implement a novel neural network algorithm based on modifying the emotional neural network (EmNN) model to unify the prototype- and adaptive-learning theories. We refer to our new model as ``prototype-incorporated EmNN''. Furthermore, we apply the proposed model to two real-life challenging tasks, namely, static hand-gesture recognition and face recognition, and compare the result to those obtained using the popular back-propagation neural network (BPNN), emotional BPNN (EmNN), deep networks, an exemplar classification model, and k-nearest neighbor.

Functional heterogeneity of conflict, error, task-switching, and unexpectedness effects within medial prefrontal cortex.

PubMed

Nee, Derek Evan; Kastner, Sabine; Brown, Joshua W

2011-01-01

The last decade has seen considerable discussion regarding a theoretical account of medial prefrontal cortex (mPFC) function with particular focus on the anterior cingulate cortex. The proposed theories have included conflict detection, error likelihood prediction, volatility monitoring, and several distinct theories of error detection. Arguments for and against particular theories often treat mPFC as functionally homogeneous, or at least nearly so, despite some evidence for distinct functional subregions. Here we used functional magnetic resonance imaging (fMRI) to simultaneously contrast multiple effects of error, conflict, and task-switching that have been individually construed in support of various theories. We found overlapping yet functionally distinct subregions of mPFC, with activations related to dominant error, conflict, and task-switching effects successively found along a rostral-ventral to caudal-dorsal gradient within medial prefrontal cortex. Activations in the rostral cingulate zone (RCZ) were strongly correlated with the unexpectedness of outcomes suggesting a role in outcome prediction and preparing control systems to deal with anticipated outcomes. The results as a whole support a resolution of some ongoing debates in that distinct theories may each pertain to corresponding distinct yet overlapping subregions of mPFC. Copyright © 2010 Elsevier Inc. All rights reserved.

When Injury Clouds Understanding of Others: Theory of Mind after Mild TBI in Preschool Children.

PubMed

Bellerose, Jenny; Bernier, Annie; Beaudoin, Cindy; Gravel, Jocelyn; Beauchamp, Miriam H

2015-08-01

There is evidence to suggest that social skills, such as the ability to understand the perspective of others (theory of mind), may be affected by childhood traumatic brain injuries; however, studies to date have only considered moderate and severe traumatic brain injury (TBI). This study aimed to assess theory of mind after early, mild TBI (mTBI). Fifty-one children who sustained mTBI between 18 and 60 months were evaluated 6 months post-injury on emotion and desires reasoning and false-belief understanding tasks. Their results were compared to that of 50 typically developing children. The two groups did not differ on baseline characteristics, except for pre- and post-injury externalizing behavior. The mTBI group obtained poorer scores relative to controls on both the emotion and desires task and the false-belief understanding task, even after controlling for pre-injury externalizing behavior. No correlations were found between TBI injury characteristics and theory of mind. This is the first evidence that mTBI in preschool children is associated with theory of mind difficulties. Reduced perspective taking abilities could be linked with the social impairments that have been shown to arise following TBI.

Toward a Unified Componential Theory of Human Reasoning. Technical Report No. 4.

ERIC Educational Resources Information Center

Sternberg, Robert J.

The unified theory described in this paper characterizes human reasoning as an information processing system with a hierarchical sequence of components and subtheories that account for performance on successively narrower tasks. Both deductive and inductive theories are subsumed in the unified componential theory, including transitive chain theory…

Prospective memory in context: Moving through a familiar space.

PubMed

Smith, Rebekah E; Hunt, R Reed; Murray, Amy E

2017-02-01

Successful completion of delayed intentions is a common but important aspect of daily behavior. Such behavior requires not only memory for the intended action but also recognition of the opportunity to perform that action, known collectively as prospective memory. The fact that prospective memory tasks occur in the midst of other activities is captured in laboratory tasks by embedding the prospective memory task in an ongoing activity. In many cases the requirement to perform the prospective memory task results in a reduction in ongoing performance relative to when the ongoing task is performed alone. This is referred to as the cost to the ongoing task and reflects the allocation of attentional resources to the prospective memory task. The current study examined the pattern of cost across the ongoing task when the ongoing task provided contextual information that in turn allowed participants to anticipate when target events would occur within the ongoing task. The availability of contextual information reduced ongoing task response times overall, with an increase in response times closer to the target locations (Experiments 1-3). The fourth study, drawing on the Event Segmentation Theory, provided support for the proposal made by the Preparatory Attentional and Memory Processes theory of prospective memory that decisions about the allocation of attention to the prospective memory task are more likely to be made at points of transition. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The combination of perception of other individuals and exogenous manipulation of arousal enhances social facilitation as an aftereffect: re-examination of Zajonc's drive theory.

PubMed

Ukezono, Masatoshi; Nakashima, Satoshi F; Sudo, Ryunosuke; Yamazaki, Akira; Takano, Yuji

2015-01-01

Zajonc's drive theory postulates that arousal enhanced through the perception of the presence of other individuals plays a crucial role in social facilitation (Zajonc, 1965). Here, we conducted two experiments to examine whether the elevation of arousal through a stepping exercise performed in front of others as an exogenous factor causes social facilitation of a cognitive task in a condition where the presence of others does not elevate the arousal level. In the main experiment, as an "aftereffect of social stimulus," we manipulated the presence or absence of others and arousal enhancement before participants conducted the primary cognitive task. The results showed that the strongest social facilitation was induced by the combination of the perception of others and arousal enhancement. In a supplementary experiment, we manipulated these factors by adding the presence of another person during the task. The results showed that the effect of the presence of the other during the primary task is enough on its own to produce facilitation of task performance regardless of the arousal enhancement as an aftereffect of social stimulus. Our study therefore extends the framework of Zajonc's drive theory in that the combination of the perception of others and enhanced arousal as an "aftereffect" was found to induce social facilitation especially when participants did not experience the presence of others while conducting the primary task.

Better without (lateral) frontal cortex? Insight problems solved by frontal patients.

PubMed

Reverberi, Carlo; Toraldo, Alessio; D'Agostini, Serena; Skrap, Miran

2005-12-01

A recently proposed theory on frontal lobe functions claims that the prefrontal cortex, particularly its dorso-lateral aspect, is crucial in defining a set of responses suitable for a particular task, and biasing these for selection. This activity is carried out for virtually any kind of non-routine tasks, without distinction of content. The aim of this study is to test the prediction of Frith's 'sculpting the response space' hypothesis by means of an 'insight' problem-solving task, namely the matchstick arithmetic task. Starting from Knoblich et al.'s interpretation for the failure of healthy controls to solve the matchstick problem, and Frith's theory on the role of dorsolateral frontal cortex, we derived the counterintuitive prediction that patients with focal damage to the lateral frontal cortex should perform better than a group of healthy participants on this rather difficult task. We administered the matchstick task to 35 patients (aged 26-65 years) with a single focal brain lesion as determined by a CT or an MRI scan, and to 23 healthy participants (aged 34-62 years). The findings seemed in line with theoretical predictions. While only 43% of healthy participants could solve the most difficult matchstick problems ('type C'), 82% of lateral frontal patients did so (Fisher's exact test, P < 0.05). In conclusion, the combination of Frith's and Knoblich et al.'s theories was corroborated.

Reasoning about Probabilistic Security Using Task-PIOAs

NASA Astrophysics Data System (ADS)

Jaggard, Aaron D.; Meadows, Catherine; Mislove, Michael; Segala, Roberto

Task-structured probabilistic input/output automata (Task-PIOAs) are concurrent probabilistic automata that, among other things, have been used to provide a formal framework for the universal composability paradigms of protocol security. One of their advantages is that that they allow one to distinguish high-level nondeterminism that can affect the outcome of the protocol, from low-level choices, which can't. We present an alternative approach to analyzing the structure of Task-PIOAs that relies on ordered sets. We focus on two of the components that are required to define and apply Task-PIOAs: discrete probability theory and automata theory. We believe our development gives insight into the structure of Task-PIOAs and how they can be utilized to model crypto-protocols. We illustrate our approach with an example from anonymity, an area that has not previously been addressed using Task-PIOAs. We model Chaum's Dining Cryptographers Protocol at a level that does not require cryptographic primitives in the analysis. We show via this example how our approach can leverage a proof of security in the case a principal behaves deterministically to prove security when that principal behaves probabilistically.

Kinetic theory of twisted waves: Application to space plasmas having superthermal population of species

NASA Astrophysics Data System (ADS)

Arshad, Kashif; Poedts, Stefaan; Lazar, Marian

2017-04-01

Nowadays electromagnetic (EM) fields have various applications in fundamental research, communication, and home appliances. Even though, there are still some subtle features of electromagnetic field known to us a century ago, yet to be utilized. It is because of the technical complexities to sense three dimensional electromagnetic field. An important characteristic of electromagnetic field is its orbital angular momentum (OAM). The angular momentum consists of two distinct parts; intrinsic part associated with the wave polarization or spin, and the extrinsic part associated with the orbital angular momentum (OAM). The orbital angular momentum (OAM) is inherited by helically phased light or helical (twisted) electric field. The investigations of Allen on lasers carrying orbital angular momentum (OAM), has initiated a new scientific and technological advancement in various growing fields, such as microscopy and imaging, atomic and nano-particle manipulation, ultra-fast optical communications, quantum computing, ionospheric radar facility to observe 3D plasma dynamics in ionosphere, photonic crystal fibre, OAM entanglement of two photons, twisted gravitational waves, ultra-intense twisted laser pulses and astrophysics. Recently, the plasma modes are also investigated with orbital angular momentum. The production of electron vortex beams and its applications are indicated by Verbeeck et al. The magnetic tornadoes (rotating magnetic field structures) exhibit three types of morphology i.e., spiral, ring and split. Leyser pumped helical radio beam carrying OAM into the Ionospheric plasma under High Frequency Active Auroral Research Program (HAARP) and characteristic ring shaped morphology is obtained by the optical emission spectrum of pumped plasma turbulence. The scattering phenomenon like (stimulated Raman and Brillouin backscattering) is observed to be responsible for the interaction between electrostatic and electromagnetic waves through orbital angular momentum. The ring shape morphology of a beam with orbital angular momentum (OAM) is ideal for the observation of solar corona around the sun where the intensity of the beam is minimum at the center, in solar experiments, and Earth's ionosphere. The twisted plasma modes carrying OAM are mostly studied either by the fluid theory or Maxwellian distributed Kinetic Theory. But most of the space plasmas and some laboratory plasmas have non-thermal distributions due to super-thermal population of the plasma particles. Therefore the Kinetic Theory of twisted plasma modes carrying OAM are recently studied using non-thermal (kappa) distribution of the super-thermal particles in the presence of the helical electric field and significant change in the damping rates are observed by tuning appropriate parameters.

Proceedings of the International Conference on High-Power Particle Beams (12th) Held in Haifa, Israel on June 7-12, 1998. Volume 1

DTIC Science & Technology

1998-06-12

Bucharest, Romania 257 TO THE THEORY OF A PLASMA FILLED ION DIODE L.I. Rudakov, RRC Kurchatov Institute, Moscow, Russia, A.S. Chuvatin, Ecole...B. Moosman, S.J. Stephanakis, Naval Research Laboratory, Washington DC, USA 306 -XVII- PLASMA EVOLUTION OF A POS: COMPARISON OF THEORY AND...POSs. INTRODUCTION The POS is a critical component of the multi-module DECADE generator.’ At present, maximum bremsstrahlung is produced on DECADE Module

Appendix—Models and theory for urea metabolism

PubMed Central

Charlwood, P. A.

1965-01-01

1. Theories have been developed to try to interpret the effects of finite time of equilibration between plasma and body water, and the mechanism of renal function, on the variations of activity and specific activity of urea in plasma and urine after initial injection. 2. The magnitudes of errors likely to arise through approximations made in estimating the pool of body urea etc. have been derived. 3. Experimental results do not fit exactly with extreme models postulated, but are usually intermediate. PMID:14340104

Fundamentals of Aerodynamic-Flow and Combustion Control by Plasmas

DTIC Science & Technology

2010-05-14

d’un Générateur de Plasma Volumique avec Allumage sur le Banc Mercato” Report n°RT 1/11982/ONERA/ DMAE . [3] N.B. Anikin, E.N. Kukaev, S...based on the multichannel quantum defect theory (MQDT)[5], taking into account the ro-vibrational structure of the ion and of the neutral system. A...editor), "Molecular Applications of Quantum Defect Theory", IOP (1996) 6. S. Morisset et al, Phys. Rev. A 76, 042702 (2007) 7. A. Wolf et al

The SMART Theory and Modeling Team: An Integrated Element of Mission Development and Science Analysis

NASA Technical Reports Server (NTRS)

Hesse, Michael; Birn, J.; Denton, Richard E.; Drake, J.; Gombosi, T.; Hoshino, M.; Matthaeus, B.; Sibeck, D.

2005-01-01

When targeting physical understanding of space plasmas, our focus is gradually shifting away from discovery-type investigations to missions and studies that address our basic understanding of processes we know to be important. For these studies, theory and models provide physical predictions that need to be verified or falsified by empirical evidence. Within this paradigm, a tight integration between theory, modeling, and space flight mission design and execution is essential. NASA's Magnetospheric MultiScale (MMS) mission is a pathfinder in this new era of space research. The prime objective of MMS is to understand magnetic reconnection, arguably the most fundamental of plasma processes. In particular, MMS targets the microphysical processes, which permit magnetic reconnection to operate in the collisionless plasmas that permeate space and astrophysical systems. More specifically, MMS will provide closure to such elemental questions as how particles become demagnetized in the reconnection diffusion region, which effects determine the reconnection rate, and how reconnection is coupled to environmental conditions such as magnetic shear angles. Solutions to these problems have remained elusive in past and present spacecraft missions primarily due to instrumental limitations - yet they are fundamental to the large-scale dynamics of collisionless plasmas. Owing to the lack of measurements, most of our present knowledge of these processes is based on results from modern theory and modeling studies of the reconnection process. Proper design and execution of a mission targeting magnetic reconnection should include this knowledge and have to ensure that all relevant scales and effects can be resolved by mission measurements. The SMART mission has responded to this need through a tight integration between instrument and theory and modeling teams. Input from theory and modeling is fed into all aspects of science mission design, and theory and modeling activities are tailored to SMART needs during mission development and science analysis. In this presentation, we will present an overview of SMART theory and modeling team activities. In particular, we will provide examples of science objectives derived from state-of-the art models, and of recent research results that continue to be utilized in SMART mission development.

A practical guide for the identification of membrane and plasma membrane proteins in human embryonic stem cells and human embryonal carcinoma cells.

PubMed

Dormeyer, Wilma; van Hoof, Dennis; Mummery, Christine L; Krijgsveld, Jeroen; Heck, Albert J R

2008-10-01

The identification of (plasma) membrane proteins in cells can provide valuable insights into the regulation of their biological processes. Pluripotent cells such as human embryonic stem cells and embryonal carcinoma cells are capable of unlimited self-renewal and share many of the biological mechanisms that regulate proliferation and differentiation. The comparison of their membrane proteomes will help unravel the biological principles of pluripotency, and the identification of biomarker proteins in their plasma membranes is considered a crucial step to fully exploit pluripotent cells for therapeutic purposes. For these tasks, membrane proteomics is the method of choice, but as indicated by the scarce identification of membrane and plasma membrane proteins in global proteomic surveys it is not an easy task. In this minireview, we first describe the general challenges of membrane proteomics. We then review current sample preparation steps and discuss protocols that we found particularly beneficial for the identification of large numbers of (plasma) membrane proteins in human tumour- and embryo-derived stem cells. Our optimized assembled protocol led to the identification of a large number of membrane proteins. However, as the composition of cells and membranes is highly variable we still recommend adapting the sample preparation protocol for each individual system.

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

Chesler, Paul M.; Rajagopal, Krishna

We calculate how the energy and the opening angle of jets in N = 4SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet/dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet/dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say themore » opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that N = 4SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the N = 4SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. In conclusion, we close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.« less

Sixth-Grade Students' Engagement in Academic Tasks

ERIC Educational Resources Information Center

Parsons, Seth A.; Malloy, Jacquelynn A.; Parsons, Allison Ward; Peters-Burton, Erin E.; Burrowbridge, Sarah Cohen

2018-01-01

Student engagement is important for teachers and researchers because it is associated with student achievement. Guided by self-determination theory, this year-long case study used observations and interviews to examine six students' behavioral, affective, and cognitive engagement in integrated literacy and social studies tasks. Task differences…

Anticipatory Eye Movements in Interleaving Templates of Human Behavior

NASA Technical Reports Server (NTRS)

Matessa, Michael

2004-01-01

Performance modeling has been made easier by architectures which package psychological theory for reuse at useful levels of abstraction. CPM-GOMS uses templates of behavior to package at a task level (e.g., mouse move-click, typing) predictions of lower-level cognitive, perceptual, and motor resource use. CPM-GOMS also has a theory for interleaving resource use between templates. One example of interleaving is anticipatory eye movements. This paper describes the use of ACT-Stitch, a framework for translating CPM-GOMS templates and interleaving theory into ACT-R, to model anticipatory eye movements in skilled behavior. The anticipatory eye movements explain performance in a well-practiced perceptual/motor task, and the interleaving theory is supported with results from an eye-tracking experiment.

Task 2: Flight prototype system design report, pulsed plasma solid propellant microthruster for the Synchronous Meteorological Satellite

NASA Technical Reports Server (NTRS)

Guman, W. J. (Editor)

1972-01-01

Design details are presented of the solid propellant pulsed plasma microthruster which was analyzed during the Task 1 effort. The design details presented show that the inherent functional simplicity underlying the flight proven LES-6 design can be maintained in the SMS systems design even with minimum weight constraints imposed. A 1293 hour uninterrupted vacuum test with the engineering thermal model, simulating an 18.8 to 33 g environment of the propellant, its feed system and electrode assembly, revealed that program thruster performance requirements could be met. This latter g environment is a more severe environment than will be ever encountered in the SMS spacecraft.

Simulator test to study hot-flow problems related to a gas cooled reactor

NASA Technical Reports Server (NTRS)

Poole, J. W.; Freeman, M. P.; Doak, K. W.; Thorpe, M. L.

1973-01-01

An advance study of materials, fuel injection, and hot flow problems related to the gas core nuclear rocket is reported. The first task was to test a previously constructed induction heated plasma GCNR simulator above 300 kW. A number of tests are reported operating in the range of 300 kW at 10,000 cps. A second simulator was designed but not constructed for cold-hot visualization studies using louvered walls. A third task was a paper investigation of practical uranium feed systems, including a detailed discussion of related problems. The last assignment resulted in two designs for plasma nozzle test devices that could be operated at 200 atm on hydrogen.

A pre-registered naturalistic observation of within domain mental fatigue and domain-general depletion of self-control

PubMed Central

Harlow, Iain; Inzlicht, Michael

2017-01-01

Self-control is often believed to operate as if it were a finite, domain-general resource. However, recent attempts to demonstrate this under transparent conditions have failed to yield positive results. In the current study, we monitor two groups of students (N1 = 8,867, N2 = 8,754) over separate 17-week intervals with 24-hour coverage, as they engage in voluntary learning and self-testing using an online program. We use daily behavior to assess whether time-of-day effects support domain-general theories of self-control. Additionally, we assess whether mental fatigue emerges within task during prolonged persistent effort. Results reveal within-task fatigue emerges within an hour on-task. However, there is a negligible effect on ability throughout the day. Additionally, time-of-day has no detrimental effect on motivation; rather there is a strong tendency to increase learning time at night. Results are consistent with theories indicating people lose motivation within a specific task, but at odds with theories that argue for a domain-general self-control resource. PMID:28931013

Computer-mediated communication: task performance and satisfaction.

PubMed

Simon, Andrew F

2006-06-01

The author assessed satisfaction and performance on 3 tasks (idea generation, intellective, judgment) among 75 dyads (N = 150) working through 1 of 3 modes of communication (instant messaging, videoconferencing, face to face). The author based predictions on the Media Naturalness Theory (N. Kock, 2001, 2002) and on findings from past researchers (e.g., D. M. DeRosa, C. Smith, & D. A. Hantula, in press) of the interaction between tasks and media. The present author did not identify task performance differences, although satisfaction with the medium was lower among those dyads communicating through an instant-messaging system than among those interacting face to face or through videoconferencing. The findings support the Media Naturalness Theory. The author discussed them in relation to the participants' frequent use of instant messaging and their familiarity with new communication media.

Ab initio approach to the ion stopping power at the plasma-solid interface

NASA Astrophysics Data System (ADS)

Bonitz, Michael; Schlünzen, Niclas; Wulff, Lasse; Joost, Jan-Philip; Balzer, Karsten

2016-10-01

The energy loss of ions in solids is of key relevance for many applications of plasmas, ranging from plasma technology to fusion. Standard approaches are based on density functional theory or SRIM simulations, however, the applicability range and accuracy of these results are difficult to assess, in particular, for low energies. Here we present an independent approach that is based on ab initio nonequilibrium Green functions theory, e.g. that allows to incorporate electronic correlations effects of the solid. We present the first application of this method to low-temperature plasmas, concentrating on proton and alpha-particle stopping in a graphene layer. In addition to the stopping power we present time-dependent results for the local electron density, the spectral function and the photoemission spectrum that is directly accessible in optical, UV or x-ray diagnostics. http://www.itap.uni-kiel.de/theo-physik/bonitz/.

UCLA IGPP Space Plasma Simulation Group

NASA Technical Reports Server (NTRS)

1998-01-01

During the past 10 years the UCLA IGPP Space Plasma Simulation Group has pursued its theoretical effort to develop a Mission Oriented Theory (MOT) for the International Solar Terrestrial Physics (ISTP) program. This effort has been based on a combination of approaches: analytical theory, large scale kinetic (LSK) calculations, global magnetohydrodynamic (MHD) simulations and self-consistent plasma kinetic (SCK) simulations. These models have been used to formulate a global interpretation of local measurements made by the ISTP spacecraft. The regions of applications of the MOT cover most of the magnetosphere: the solar wind, the low- and high-latitude magnetospheric boundary, the near-Earth and distant magnetotail, and the auroral region. Most recent investigations include: plasma processes in the electron foreshock, response of the magnetospheric cusp, particle entry in the magnetosphere, sources of observed distribution functions in the magnetotail, transport of oxygen ions, self-consistent evolution of the magnetotail, substorm studies, effects of explosive reconnection, and auroral acceleration simulations.

Physical Processes in the MAGO/MFT Systems

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

Garanin, Sergey F; Reinovsky, Robert E.

2015-03-23

The Monograph is devoted to theoretical discussion of the physical effects, which are most significant for the alternative approach to the problem of controlled thermonuclear fusion (CTF): the MAGO/MTF approach. The book includes the description of the approach, its difference from the major CTF systems—magnetic confinement and inertial confinement systems. General physical methods of the processes simulation in this approach are considered, including plasma transport phenomena and radiation, and the theory of transverse collisionless shock waves, the surface discharges theory, important for such kind of research. Different flows and magneto-hydrodynamic plasma instabilities occurring in the frames of this approach aremore » also considered. In virtue of the general physical essence of the considered phenomena the presented results are applicable to a wide range of plasma physics and hydrodynamics processes. The book is intended for the plasma physics and hydrodynamics specialists, post-graduate students, and senior students-physicists.« less

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

Komppula, J., E-mail: jani.komppula@jyu.fi; Tarvainen, O.

A theoretical framework for power dissipation in low temperature plasmas in corona equilibrium is developed. The framework is based on fundamental conservation laws and reaction cross sections and is only weakly sensitive to plasma parameters, e.g., electron temperature and density. The theory is applied to low temperature atomic and molecular hydrogen laboratory plasmas for which the plasma heating power dissipation to photon emission, ionization, and chemical potential is calculated. The calculated photon emission is compared to recent experimental results.

Plasma waves

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

Vandenplas, P.E.

1996-03-01

This paper presents a summary of important parts of `Plasma waves` by J.F. Denisse and J.L.Delcroix, Interscience-Wiley, 1963, itself a translation of `Theorie des Ondes dans les Plasmas`, Dunod, 1959. We shall, however, use S.I. units instead of cgs ones and adopt where necessary more modern notations. A rather complete overview of the complexity of waves in a hot magnetized plasma is given. The effects of collisions have been mostly neglected. 1 fig.

Dealing with Prospective Memory Demands While Performing an Ongoing Task: Shared Processing, Increased On-Task Focus, or Both?

ERIC Educational Resources Information Center

Rummel, Jan; Smeekens, Bridget A.; Kane, Michael J.

2017-01-01

Prospective memory (PM) is the cognitive ability to remember to fulfill intended action plans at the appropriate future moment. Current theories assume that PM fulfillment draws on attentional processes. Accordingly, pending PM intentions interfere with other ongoing tasks to the extent to which both tasks rely on the same processes. How do people…

Developmental Continuity in Theory of Mind: Speed and Accuracy of Belief-Desire Reasoning in Children and Adults

ERIC Educational Resources Information Center

Apperly, Ian A.; Warren, Frances; Andrews, Benjamin J.; Grant, Jay; Todd, Sophie

2011-01-01

On belief-desire reasoning tasks, children first pass tasks involving true belief before those involving false belief, and tasks involving positive desire before those involving negative desire. The current study examined belief-desire reasoning in participants old enough to pass all such tasks. Eighty-three 6- to 11-year-olds and 20 adult…

Effects of Task Familiarity on Stress Responses of Repressors and Sensitizers

ERIC Educational Resources Information Center

Pagano, Don F.

1973-01-01

R.S. Lazarus's theory of coping was used to investigate appraisal and reappraisal of threat in repressors and sensitizers. Two indexes of stress, self-report ratings of affect and palmar skin conductance, were measured prior to performance on a reaction time task, after one-third of the task was completed and after two-thirds of the task was…

Mental Imagery and Idiom Understanding in Adults: Examining Dual Coding Theory

ERIC Educational Resources Information Center

Hung, Pei-Fang

2010-01-01

This study examined idiom understanding in 120 neurologically healthy adults, ages 20-29 (20s Group), 40-49 (40s Group), 60-69 (60s Group), and 80-89 (80s Group) years old. Each participant was administered a familiarity task, definition explanation task, mental imagery task, and forced-choice comprehension task. Twenty idioms, 10 transparent and…

Working together versus working autonomously: a new power-dependence perspective on the individual-level of analysis.

PubMed

de Jong, Simon B

2014-01-01

Recent studies have indicated that it is important to investigate the interaction between task interdependence and task autonomy because this interaction can affect team effectiveness. However, only a limited number of studies have been conducted and those studies focused solely on the team level of analysis. Moreover, there has also been a dearth of theoretical development. Therefore, this study develops and tests an alternative theoretical perspective in an attempt to understand if, and if so why, this interaction is important at the individual level of analysis. Based on interdependence theory and power-dependence theory, we expected that highly task-interdependent individuals who reported high task autonomy would be more powerful and better performers. In contrast, we expected that similarly high task-interdependent individuals who reported less task autonomy would be less powerful and would be weaker performers. These expectations were supported by multi-level and bootstrapping analyses performed on a multi-source dataset (self-, peer-, manager-ratings) comprised of 182 employees drawn from 37 teams. More specifically, the interaction between task interdependence and task autonomy was γ =.128, p <.05 for power and γ =.166, p <.05 for individual performance. The 95% bootstrap interval ranged from .0038 to .0686.

Perseveration effects in detection tasks with correlated decision intervals. [applied to pilot collision avoidance

NASA Technical Reports Server (NTRS)

Gai, E. G.; Curry, R. E.

1978-01-01

An investigation of the behavior of the human decisionmaker is described for a task related to the problem of a pilot using a traffic situation display to avoid collisions. This sequential signal detection task is characterized by highly correlated signals with time varying strength. Experimental results are presented and the behavior of the observers is analyzed using the theory of Markov processes and classical signal detection theory. Mathematical models are developed which describe the main result of the experiment: that correlation in sequential signals induced perseveration in the observer response and a strong tendency to repeat their previous decision, even when they were wrong.

Increased Attentional Focus Modulates Eye Movements in a Mixed Antisaccade Task for Younger and Older Adults

PubMed Central

Wang, Jingxin; Tian, Jing; Wang, Rong; Benson, Valerie

2013-01-01

We examined performance in the antisaccade task for younger and older adults by comparing latencies and errors in what we defined as high attentional focus (mixed antisaccades and prosaccades in the same block) and low attentional focus (antisaccades and prosaccades in separate blocks) conditions. Shorter saccade latencies for correctly executed eye movements were observed for both groups in mixed, compared to blocked, antisaccade tasks, but antisaccade error rates were higher for older participants across both conditions. The results are discussed in relation to the inhibitory hypothesis, the goal neglect theory and attentional control theory. PMID:23620767

Testing the Domain-Specificity of a Theory of Mind Deficit in Brain-Injured Patients: Evidence for Consistent Performance on Non-Verbal, ''Reality-Unknown'' False Belief and False Photograph Tasks

ERIC Educational Resources Information Center

Apperly, Ian A.; Samson, Dana; Chiavarino, Claudia; Bickerton, Wai-Ling; Humphreys, Glyn W.

2007-01-01

To test the domain-specificity of ''theory of mind'' abilities we compared the performance of a case-series of 11 brain-lesioned patients on a recently developed test of false belief reasoning (Apperly, Samson, Chiavarino, & Humphreys, 2004) and on a matched false photograph task, which did not require belief reasoning and which addressed problems…

Finite-Length Diocotron Modes in a Non-neutral Plasma Column

NASA Astrophysics Data System (ADS)

Walsh, Daniel; Dubin, Daniel

2017-10-01

Diocotron modes are 2D distortions of a non-neutral plasma column that propagate azimuthally via E × B drifts. While the infinite-length theory of diocotron modes is well-understood for arbitrary azimuthal mode number l, the finite-length mode frequency is less developed (with some exceptions), and is naturally of relevance to experiments. In this poster, we present an approach to address finite length effects, such as temperature dependence of the mode frequency. We use a bounce-averaged solution to the Vlasov Equation, in which the Vlasov Equation is solved using action-angle variables of the unperturbed Hamiltonian. We write the distribution function as a Fourier series in the bounce-angle variable ψ, keeping only the bounce-averaged term. We demonstrate a numerical solution to this equation for a realistic plasma with a finite Debye Length, compare to the existing l = 1 theory, and discuss possible extensions of the existing theory to l ≠ 1 . Supported by NSF/DOE Partnership Grants PHY1414570 and DESC0002451.

Density-functional calculations of transport properties in the nondegenerate limit and the role of electron-electron scattering

DOE PAGES

Desjarlais, Michael P.; Scullard, Christian R.; Benedict, Lorin X.; ...

2017-03-13

We compute electrical and thermal conductivities of hydrogen plasmas in the non-degenerate regime using Kohn-Sham Density Functional Theory (DFT) and an application of the Kubo- Greenwood response formula, and demonstrate that for thermal conductivity, the mean-field treatment of the electron-electron (e-e) interaction therein is insufficient to reproduce the weak-coupling limit obtained by plasma kinetic theories. An explicit e-e scattering correction to the DFT is posited by appealing to Matthiessen's Rule and the results of our computations of conductivities with the quantum Lenard-Balescu (QLB) equation. Further motivation of our correction is provided by an argument arising from the Zubarev quantum kineticmore » theory approach. Significant emphasis is placed on our efforts to produce properly converged results for plasma transport using Kohn-Sham DFT, so that an accurate assessment of the importance and efficacy of our e-e scattering corrections to the thermal conductivity can be made.« less

Differential drift of plasma clouds in the magnetosphere: an update

NASA Astrophysics Data System (ADS)

Lemaire, J. F.

2001-07-01

First, Brice's (Journal of Geophysical Research 72 (1967) 5193) original theory for the formation of the plasmapause is recalled. Next, the motivation for writing a modification to this early theory is pointed out. The key aspects of Brice's manuscript are outlined and discussed. The mechanism of interchange driven by gravitational forces, centrifugal effects and kinetic pressure is considered in the cases when the integrated Pedersen conductivity is (i) negligibly small (as in Chandrasekhar's, Plasma Physics, University of Chicago Press, Chicago, 1960, 217 pp. and Longmire's, Elementary Plasma Physics, Wiley Interscience, New York, 1963, 296 pp., textbooks), (ii) infinitely large (as in many magnetospheric convection models), or (iii) has a finite value of the order of 0.2 mho, as in the Earth's ionosphere. Updates of this theory of interchange resulting from the existence of weak double layers, from quasi-interchange, or from the effects of an additional population of energetic ring-current particles forming the extended tail of the velocity distribution function, have also been reexamined.

Second-order dissipative hydrodynamics for plasma with chiral asymmetry and vorticity

NASA Astrophysics Data System (ADS)

Gorbar, E. V.; Rybalka, D. O.; Shovkovy, I. A.

2017-05-01

By making use of the chiral kinetic theory in the relaxation-time approximation, we derive an Israel-Stewart type formulation of the hydrodynamic equations for a chiral relativistic plasma made of neutral particles (e.g., neutrinos). The effects of chiral asymmetry are captured by including an additional continuity equation for the axial charge, as well as the leading-order quantum corrections due to the spin of particles. In a formulation of the chiral kinetic theory used, we introduce a symmetric form of the energy-momentum tensor that is suitable for the description of a weakly nonuniform chiral plasma. By construction, the energy and momentum are conserved to the same leading order in the Planck constant as the kinetic equation itself. By making use of such a chiral kinetic theory and the Chapman-Enskog approach, we obtain a set of second-order dissipative hydrodynamic equations. The effects of the fluid vorticity and velocity fluctuations on the dispersion relations of chiral vortical waves are analyzed.

Advanced Thermionic Technology Program

NASA Technical Reports Server (NTRS)

1977-01-01

Topics include surface studies (surface theory, basic surface experiments, and activation chamber experiments); plasma studies (converter theory and enhanced mode conversion experiments); and component development (low temperature conversion experiments, high efficiency conversion experiments, and hot shell development).

Prospective Memory and Task Interference in a Continuous Monitoring Dynamic Display Task

ERIC Educational Resources Information Center

Loft, Shayne; Remington, Roger W.

2010-01-01

Theories and methods from the prospective memory literature were used to anticipate how individuals would maintain and retrieve intentions in a continuous monitoring dynamic display task. Participants accepted aircraft into sectors and detected aircraft conflicts during an air traffic control simulation. They were sometimes required to substitute…

Isolating the Neural Mechanisms of Interference During Continuous Multisensory Dual-task Performance

DTIC Science & Technology

2014-01-01

sion accuracy in each task, the signal detection theory sensitivity measure of d0 was used (Macmillan & Creelman , 1991; Green & Swets, 1966). First...J. (1998). Sources of dual-task interference: Evidence from human electrophysiology. Psychological Science, 9, 223–227. Macmillan, N. A., & Creelman

The arcing rate for a High Voltage Solar Array - Theory, experiment and predictions

NASA Technical Reports Server (NTRS)

Hastings, Daniel E.; Cho, Mengu; Kuninaka, Hitoshi

1992-01-01

All solar arrays have biased surfaces which can be exposed to the space environment. It has been observed that when the array bias is less than a few hundred volts negative then the exposed conductive surfaces may undergo arcing in the space plasma. A theory for arcing is developed on these high voltage solar arrays which ascribes the arcing to electric field runaway at the interface of the plasma, conductor and solar cell dielectric. Experiments were conducted in the laboratory for the High Voltage Solar Array (HVSA) experiment which will fly on the Japanese Space Flyer Unit (SFU) in 1994. The theory was compared in detail to the experiment and shown to give a reasonable explanation for the data. The combined theory and ground experiments were then used to develop predictions for the SFU flight.

Arcing rates for High Voltage Solar Arrays - Theory, experiment, and predictions

NASA Technical Reports Server (NTRS)

Hastings, Daniel E.; Cho, Mengu; Kuninaka, Hitoshi

1992-01-01

All solar arrays have biased surfaces that can be exposed to the space environment. It has been observed that when the array bias is less than a few hundred volts negative, then the exposed conductive surfaces may undergo arcing in the space plasma. A theory for arcing is developed on these high voltage solar arrays that ascribes the arcing to electric field runaway at the interface of the plasma, conductor, and solar cell dielectric. Experiments were conducted in the laboratory for the High Voltage Solar Array experiment that will fly on the Japanese Space Flyer Unit (SFU) in 1994. The theory was compared in detail with the experiment and shown to give a reasonable explanation for the data. The combined theory and ground experiments were then used to develop predictions for the SFU flight.

Purposeful Program Theory: Effective Use of Theories of Change and Logic Models

ERIC Educational Resources Information Center

Funnell, Sue C.; Rogers, Patricia J.

2011-01-01

Between good intentions and great results lies a program theory--not just a list of tasks but a vision of what needs to happen, and how. Now widely used in government and not-for-profit organizations, program theory provides a coherent picture of how change occurs and how to improve performance. "Purposeful Program Theory" shows how to develop,…

Theory of mind: a new perspective on the puzzle of belief ascription.

PubMed

Airenti, Gabriella

2015-01-01

The concept of theory of mind (ToM) has considerably changed since its first proposal. The aim of first human studies was to understand how young children acquire the representation of others' mental states, in particular beliefs, and how they distinguish them from their own and from reality. The False Belief Task was designed to prove the acquisition of this capacity. According to children's performance in this test the acquisition of ToM has been attested at around 4 years of age. In last years it has been shown that using spontaneous response tasks also 15-month-old-children could attribute to an agent a false belief about the location of an object. These results have generated the puzzle of belief-ascription: Why do 3-year-old children fail the classical false belief tasks whereas much younger children show the correct expectation in the spontaneous response tasks? In this paper I shall argue that (i) infants and young children, when confronted with the two forms of false belief tasks do not face the same problem and (ii) behind the two testing situations there are different ways to understand theory of mind. I shall propose that what appears in infants is the natural human disposition to intersubjectivity.

Physical processes associated with current collection by plasma contactors

NASA Technical Reports Server (NTRS)

Katz, Ira; Davis, Victoria A.

1990-01-01

Recent flight data confirms laboratory observations that the release of neutral gas increases plasma sheath currents. Plasma contactors are devices which release a partially ionized gas in order to enhance the current flow between a spacecraft and the space plasma. Ionization of the expellant gas and the formation of a double layer between the anode plasma and the space plasma are the dominant physical processes. A theory is presented of the interaction between the contactor plasma and the background plasma. The conditions for formation of a double layer between the two plasmas are derived. Double layer formation is shown to be a consequence of the nonlinear response of the plasmas to changes in potential. Numerical calculations based upon this model are compared with laboratory measurements of current collection by hollow cathode-based plasma contactors.

Taking-On: A Grounded Theory of Addressing Barriers in Task Completion

ERIC Educational Resources Information Center

Austinson, Julie Ann

2011-01-01

This study of taking-on was conducted using classical grounded theory methodology (Glaser, 1978, 1992, 1998, 2001, 2005; Glaser & Strauss, 1967). Classical grounded theory is inductive, empirical, and naturalistic; it does not utilize manipulation or constrained time frames. Classical grounded theory is a systemic research method used to generate…

Building a Practically Useful Theory of Goal Setting and Task Motivation.

ERIC Educational Resources Information Center

Locke, Edwin A.; Latham, Gary P.

2002-01-01

Summarizes 35 years of empirical research on goal-setting theory, describing core findings of the theory, mechanisms by which goals operate, moderators of goal effects, the relation of goals and satisfaction, and the role of goals as mediators of incentives. Explains the external validity and practical significance of goal setting theory,…

Eysenck's Theory of Personality and the Role of Background Music in Cognitive Task Performance: A Mini-Review of Conflicting Findings and a New Perspective.

PubMed

Küssner, Mats B

2017-01-01

The question of whether background music is able to enhance cognitive task performance is of interest to scholars, educators, and stakeholders in business alike. Studies have shown that background music can have beneficial, detrimental or no effects on cognitive task performance. Extraversion-and its postulated underlying cause, cortical arousal-is regarded as an important factor influencing the outcome of such studies. According to Eysenck's theory of personality, extraverts' cortical arousal at rest is lower compared to that of introverts. Scholars have thus hypothesized that extraverts should benefit from background music in cognitive tasks, whereas introverts' performance should decline with music in the background. Reviewing studies that have considered extraversion as a mediator of the effect of background music on cognitive task performance, it is demonstrated that there is as much evidence in favor as there is against Eysenck's theory of personality. Further, revisiting Eysenck's concept of cortical arousal-which has traditionally been assessed by activity in the EEG alpha band-and reviewing literature on the link between extraversion and cortical arousal, it is revealed that there is conflicting evidence. Due to Eysenck's focus on alpha power, scholars have largely neglected higher frequency bands in the EEG signal as indicators of cortical arousal. Based on recent findings, it is suggested that beta power might not only be an indicator of alertness and attention but also a predictor of cognitive task performance. In conclusion, it is proposed that focused music listening prior to cognitive tasks might be a more efficient way to boost performance than listening to background music during cognitive tasks.

Eysenck's Theory of Personality and the Role of Background Music in Cognitive Task Performance: A Mini-Review of Conflicting Findings and a New Perspective

PubMed Central

Küssner, Mats B.

2017-01-01

The question of whether background music is able to enhance cognitive task performance is of interest to scholars, educators, and stakeholders in business alike. Studies have shown that background music can have beneficial, detrimental or no effects on cognitive task performance. Extraversion—and its postulated underlying cause, cortical arousal—is regarded as an important factor influencing the outcome of such studies. According to Eysenck's theory of personality, extraverts' cortical arousal at rest is lower compared to that of introverts. Scholars have thus hypothesized that extraverts should benefit from background music in cognitive tasks, whereas introverts' performance should decline with music in the background. Reviewing studies that have considered extraversion as a mediator of the effect of background music on cognitive task performance, it is demonstrated that there is as much evidence in favor as there is against Eysenck's theory of personality. Further, revisiting Eysenck's concept of cortical arousal—which has traditionally been assessed by activity in the EEG alpha band—and reviewing literature on the link between extraversion and cortical arousal, it is revealed that there is conflicting evidence. Due to Eysenck's focus on alpha power, scholars have largely neglected higher frequency bands in the EEG signal as indicators of cortical arousal. Based on recent findings, it is suggested that beta power might not only be an indicator of alertness and attention but also a predictor of cognitive task performance. In conclusion, it is proposed that focused music listening prior to cognitive tasks might be a more efficient way to boost performance than listening to background music during cognitive tasks. PMID:29184523

EDITORIAL: Interrelationship between plasma phenomena in the laboratory and in space

NASA Astrophysics Data System (ADS)

Koepke, Mark

2008-07-01

The premise of investigating basic plasma phenomena relevant to space is that an alliance exists between both basic plasma physicists, using theory, computer modelling and laboratory experiments, and space science experimenters, using different instruments, either flown on different spacecraft in various orbits or stationed on the ground. The intent of this special issue on interrelated phenomena in laboratory and space plasmas is to promote the interpretation of scientific results in a broader context by sharing data, methods, knowledge, perspectives, and reasoning within this alliance. The desired outcomes are practical theories, predictive models, and credible interpretations based on the findings and expertise available. Laboratory-experiment papers that explicitly address a specific space mission or a specific manifestation of a space-plasma phenomenon, space-observation papers that explicitly address a specific laboratory experiment or a specific laboratory result, and theory or modelling papers that explicitly address a connection between both laboratory and space investigations were encouraged. Attention was given to the utility of the references for readers who seek further background, examples, and details. With the advent of instrumented spacecraft, the observation of waves (fluctuations), wind (flows), and weather (dynamics) in space plasmas was approached within the framework provided by theory with intuition provided by the laboratory experiments. Ideas on parallel electric field, magnetic topology, inhomogeneity, and anisotropy have been refined substantially by laboratory experiments. Satellite and rocket observations, theory and simulations, and laboratory experiments have contributed to the revelation of a complex set of processes affecting the accelerations of electrons and ions in the geospace plasma. The processes range from meso-scale of several thousands of kilometers to micro-scale of a few meters to kilometers. Papers included in this special issue serve to synthesise our current understanding of processes related to the coupling and feedback at disparate scales. Categories of topics included here are (1) ionospheric physics and (2) Alfvén-wave physics, both of which are related to the particle acceleration responsible for auroral displays, (3) whistler-mode triggering mechanism, which is relevant to radiation-belt dynamics, (4) plasmoid encountering a barrier, which has applications throughout the realm of space and astrophysical plasmas, and (5) laboratory investigations of the entire magnetosphere or the plasma surrounding the magnetosphere. The papers are ordered from processes that take place nearest the Earth to processes that take place at increasing distances from Earth. Many advances in understanding space plasma phenomena have been linked to insight derived from theoretical modeling and/or laboratory experiments. Observations from space-borne instruments are typically interpreted using theoretical models developed to predict the properties and dynamics of space and astrophysical plasmas. The usefulness of customized laboratory experiments for providing confirmation of theory by identifying, isolating, and studying physical phenomena efficiently, quickly, and economically has been demonstrated in the past. The benefits of laboratory experiments to investigating space-plasma physics are their reproducibility, controllability, diagnosability, reconfigurability, and affordability compared to a satellite mission or rocket campaign. Certainly, the plasma being investigated in a laboratory device is quite different from that being measured by a spaceborne instrument; nevertheless, laboratory experiments discover unexpected phenomena, benchmark theoretical models, develop physical insight, establish observational signatures, and pioneer diagnostic techniques. Explicit reference to such beneficial laboratory contributions is occasionally left out of the citations in the space-physics literature in favor of theory-paper counterparts and, thus, the scientific support that laboratory results can provide to the development of space-relevant theoretical models is often under-recognized. It is unrealistic to expect the dimensional parameters corresponding to space plasma to be matchable in the laboratory. However, a laboratory experiment is considered well designed if the subset of parameters relevant to a specific process shares the same phenomenological regime as the subset of analogous space parameters, even if less important parameters are mismatched. Regime boundaries are assigned by normalizing a dimensional parameter to an appropriate reference or scale value to make it dimensionless and noting the values at which transitions occur in the physical behavior or approximations. An example of matching regimes for cold-plasma waves is finding a 45° diagonal line on the log--log CMA diagram along which lie both a laboratory-observed wave and a space-observed wave. In such a circumstance, a space plasma and a lab plasma will support the same kind of modes if the dimensionless parameters are scaled properly (Bellan 2006 Fundamentals of Plasma Physics (Cambridge: Cambridge University Press) p 227). The plasma source, configuration geometry, and boundary conditions associated with a specific laboratory experiment are characteristic elements that affect the plasma and plasma processes that are being investigated. Space plasma is not exempt from an analogous set of constraining factors that likewise influence the phenomena that occur. Typically, each morphologically distinct region of space has associated with it plasma that is unique by virtue of the various mechanisms responsible for the plasma's presence there, as if the plasma were produced by a unique source. Boundary effects that typically constrain the possible parameter values to lie within one or more restricted ranges are inescapable in laboratory plasma. The goal of a laboratory experiment is to examine the relevant physics within these ranges and extrapolate the results to space conditions that may or may not be subject to any restrictions on the values of the plasma parameters. The interrelationship between laboratory and space plasma experiments has been cultivated at a low level and the potential scientific benefit in this area has yet to be realized. The few but excellent examples of joint papers, joint experiments, and directly relevant cross-disciplinary citations are a direct result of the emphasis placed on this interrelationship two decades ago. Building on this special issue Plasma Physics and Controlled Fusion plans to create a dedicated webpage to highlight papers directly relevant to this field published either in the recent past or in the future. It is hoped that this resource will appeal to the readership in the laboratory-experiment and space-plasma communities and improve the cross-fertilization between them.

Simulation and analysis of chemical release in the ionosphere

NASA Astrophysics Data System (ADS)

Gao, Jing-Fan; Guo, Li-Xin; Xu, Zheng-Wen; Zhao, Hai-Sheng; Feng, Jie

2018-05-01

Ionospheric inhomogeneous plasma produced by single point chemical release has simple space-time structure, and cannot impact radio wave frequencies higher than Very High Frequency (VHF) band. In order to produce more complicated ionospheric plasma perturbation structure and trigger instabilities phenomena, multiple-point chemical release scheme is presented in this paper. The effects of chemical release on low latitude ionospheric plasma are estimated by linear instability growth rate theory that high growth rate represents high irregularities, ionospheric scintillation occurrence probability and high scintillation intension in scintillation duration. The amplitude scintillations and the phase scintillations of 150 MHz, 400 MHz, and 1000 MHz are calculated based on the theory of multiple phase screen (MPS), when they propagate through the disturbed area.

Transport Simulations of DIII-D Discharges with Impurity Injection

NASA Astrophysics Data System (ADS)

Mandrekas, J.; Stacey, W. M.; Murakami, M.

2001-10-01

Several recent DIII-D discharges with external impurity injection into L-mode plasmas are analyzed with a coupled main plasma and multi-charge state 1frac 12-D impurity transport code. These discharges exhibit various degrees of confinement improvement, which has been attributed to the synergistic effects of impurity induced enhancement of the E×B shearing rate and reduction of the drift wave turbulence growth rate (M. Murakami, et. al., Nucl. Fusion 41) (2001) 317.. Impurity transport is described by empirical and neoclassical transport models. Both the standard neoclassical theory as well as an enhanced theory which takes into account the effects of external momentum input and radial momentum transport (W.M. Stacey, Phys. Plasmas 8) (2001) 158. have been considered.

Coherent emission mechanisms in astrophysical plasmas

NASA Astrophysics Data System (ADS)

Melrose, D. B.

2017-12-01

Three known examples of coherent emission in radio astronomical sources are reviewed: plasma emission, electron cyclotron maser emission (ECME) and pulsar radio emission. Plasma emission is a multi-stage mechanism with the first stage being generation of Langmuir waves through a streaming instability, and subsequent stages involving partial conversion of the Langmuir turbulence into escaping radiation at the fundamental (F) and second harmonic (H) of the plasma frequency. The early development and subsequent refinements of the theory, motivated by application to solar radio bursts, are reviewed. The driver of the instability is faster electrons outpacing slower electrons, resulting in a positive gradient ({d}f(v_allel )/{d}v_allel >0) at the front of the beam. Despite many successes of the theory, there is no widely accepted explanation for type I bursts and various radio continua. The earliest models for ECME were purely theoretical, and the theory was later adapted and applied to Jupiter (DAM), the Earth (AKR), solar spike bursts and flare stars. ECME strongly favors the x mode, whereas plasma emission favors the o mode. Two drivers for ECME are a ring feature (implying {d}f(v)/{d}v>0) and a loss-cone feature. Loss-cone-driven ECME was initially favored for all applications. The now favored driver for AKR is the ring-feature in a horseshoe distribution, which results from acceleration by a parallel electric on converging magnetic field lines. The driver in DAM and solar and stellar applications is uncertain. The pulsar radio emission mechanism remains an enigma. Ingredients needed in discussing possible mechanisms are reviewed: general properties of pulsars, pulsar electrodynamics, the properties of pulsar plasma and wave dispersion in such plasma. Four specific emission mechanisms (curvature emission, linear acceleration emission, relativistic plasma emission and anomalous Doppler emission) are discussed and it is argued that all encounter difficulties. Coherent radio emission from extensive air showers in the Earth's atmosphere is reviewed briefly. The difference in theoretical approach from astrophysical theories is pointed out and discussed. Fine structures in DAM and in pulsar radio emission are discussed, and it is suggested that trapping in a large-amplitude wave, as in a model for discrete VLF emission, provides a plausible explanation. A possible direct measure of coherence is pointed out.

A Four–Component Model of Age–Related Memory Change

PubMed Central

Healey, M. Karl; Kahana, Michael J.

2015-01-01

We develop a novel, computationally explicit, theory of age–related memory change within the framework of the context maintenance and retrieval (CMR2) model of memory search. We introduce a set of benchmark findings from the free recall and recognition tasks that includes aspects of memory performance that show both age-related stability and decline. We test aging theories by lesioning the corresponding mechanisms in a model fit to younger adult free recall data. When effects are considered in isolation, many theories provide an adequate account, but when all effects are considered simultaneously, the existing theories fail. We develop a novel theory by fitting the full model (i.e., allowing all parameters to vary) to individual participants and comparing the distributions of parameter values for older and younger adults. This theory implicates four components: 1) the ability to sustain attention across an encoding episode, 2) the ability to retrieve contextual representations for use as retrieval cues, 3) the ability to monitor retrievals and reject intrusions, and 4) the level of noise in retrieval competitions. We extend CMR2 to simulate a recognition memory task using the same mechanisms the free recall model uses to reject intrusions. Without fitting any additional parameters, the four–component theory that accounts for age differences in free recall predicts the magnitude of age differences in recognition memory accuracy. Confirming a prediction of the model, free recall intrusion rates correlate positively with recognition false alarm rates. Thus we provide a four–component theory of a complex pattern of age differences across two key laboratory tasks. PMID:26501233

MHD instabilities in astrophysical plasmas: very different from MHD instabilities in tokamaks!

NASA Astrophysics Data System (ADS)

Goedbloed, J. P.

2018-01-01

The extensive studies of MHD instabilities in thermonuclear magnetic confinement experiments, in particular of the tokamak as the most promising candidate for a future energy producing machine, have led to an ‘intuitive’ description based on the energy principle that is very misleading for most astrophysical plasmas. The ‘intuitive’ picture almost directly singles out the dominant stabilizing field line bending energy of the Alfvén waves and, consequently, concentrates on expansion schemes that minimize that contribution. This happens when the wave vector {{k}}0 of the perturbations, on average, is perpendicular to the magnetic field {B}. Hence, all macroscopic instabilities of tokamaks (kinks, interchanges, ballooning modes, ELMs, neoclassical tearing modes, etc) are characterized by satisfying the condition {{k}}0 \\perp {B}, or nearly so. In contrast, some of the major macroscopic instabilities of astrophysical plasmas (the Parker instability and the magneto-rotational instability) occur when precisely the opposite condition is satisfied: {{k}}0 \\parallel {B}. How do those instabilities escape from the dominance of the stabilizing Alfvén wave? The answer to that question involves, foremost, the recognition that MHD spectral theory of waves and instabilities of laboratory plasmas could be developed to such great depth since those plasmas are assumed to be in static equilibrium. This assumption is invalid for astrophysical plasmas where rotational and gravitational accelerations produce equilibria that are at best stationary, and the associated spectral theory is widely, and incorrectly, believed to be non-self adjoint. These complications are addressed, and cured, in the theory of the Spectral Web, recently developed by the author. Using this method, an extensive survey of instabilities of astrophysical plasmas demonstrates how the Alfvén wave is pushed into insignificance under these conditions to give rise to a host of instabilities that do not occur in laboratory plasmas.

Charging and shielding of a non-spherical dust grain in a plasma

NASA Astrophysics Data System (ADS)

Zhao, L.; Delzanno, G.

2013-12-01

The interaction of objects with a plasma is a classic problem of plasma physics. Originally, it was investigated in the framework of probe theory but more recently its interest has grown in connection with space and complex or dusty plasmas. It is customary to assume that the dust grains are spherical, and theories such as the Orbital Motion Limited (OML) theory are usually applied to calculate the dust charge. However, in nature dust grains have a variety of sizes and shapes. It is therefore natural to ask about the influence of the dust shape on the charging and shielding process. In order to answer this question, we study the charging and shielding of a non-spherical dust grain immersed in a Maxwellian plasma at rest. We consider prolate ellipsoids, varying parametrically the aspect ratio while keeping the surface area constant. The study is conducted with CPIC [1], a newly developed Particle-In-Cell code in curvilinear geometry that conforms to objects of arbitrary shape. For a plasma with temperature ratio equal to unity and for a dust grain with characteristic size of the order of the Debye length, it is shown that the floating potential has a very weak dependence on the geometry, while the charge on the grain increases by a factor of three when the aspect ratio changes from one (a sphere) to hundred (a needle-like ellipsoid). These results are consistent with the higher capacitance of ellipsoidal dust grains, but also indicate that the screening length depends on the geometry. Scaling studies of the dependence of the charging time and screening length on the aspect ratio and plasma conditions are presented, including theoretical considerations to support the numerical results. [1] G.L. Delzanno, et al, ';CPIC: a curvilinear Particle-In-Cell code for plasma-material interaction studies', under review.

Laser plasma at low air pressure

NASA Astrophysics Data System (ADS)

Vas'kovskii, Iu. M.; Moiseev, V. N.; Rovinskii, R. E.; Tsenina, I. S.

1993-01-01

The ambient-pressure dependences of the dynamic and optical characteristics of a laser plasma generated by CO2-laser irradiation of an obstacle are investigated experimentally. The change of the sample's surface roughness after irradiation is investigated as a function of air pressure. It is concluded that the transition from the air plasma to the erosion plasma takes place at an air pressure of about 1 mm Hg. The results confirm the existing theory of plasma formation near the surface of an obstacle under the CO2-laser pulse effect in air.

Electromagnetic fluctuation spectra of collective oscillations in magnetized Maxwellian plasmas for parallel wave vectors

NASA Astrophysics Data System (ADS)

Vafin, S.; Schlickeiser, R.; Yoon, P. H.

2016-05-01

The general electromagnetic fluctuation theory for magnetized plasmas is used to calculate the steady-state wave number spectra and total electromagnetic field strength of low-frequency collective weakly damped eigenmodes with parallel wavevectors in a Maxwellian electron-proton plasma. These result from the equilibrium of spontaneous emission and collisionless damping, and they represent the minimum electromagnetic fluctuations guaranteed in quiet thermal space plasmas, including the interstellar and interplanetary medium. Depending on the plasma beta, the ratio of |δB |/B0 can be as high as 10-12 .

A geometric theory of waves and its applications to plasma physics.

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

Ruiz, Daniel

Waves play an essential role in many aspects of plasma dynamics. For example, they are indispensable in plasma manipulation and diagnostics. Although the physics of waves is well understood in the context of relatively simple problems, difficulties arise when studying waves that propagate in inhomogeneous or nonlinear media. This thesis presents a new systematic wave theory based on phase-space variational principles. In this dissertation, waves are treated as geometric objects of a variational theory rather than formal solutions of specific PDEs. This approach simplifies calculations, highlights the underlying wave symmetries, and leads to improved modeling of wave dynamics. Specifically, thismore » dissertation presents two important breakthroughs that were obtained in the general theory of waves. The first main contribution of the present dissertation is an extension of the theory of geometrical optics (GO) in order to include polarization effects. Even when diffraction is ignored, the GO ray equations are not entirely accurate. This occurs because GO treats wave rays as classical particles described by their position and momentum coordinates. However, vector waves have another degree of freedom, their polarization. As a result, wave rays can behave as particles with spin and show polarization dynamics, such as polarization precession and polarization-driven bending of ray trajectories. In this thesis, the theory of GO is reformulated as a first-principle Lagrangian wave theory that governs both mentioned polarization phenomena simultaneously. The theory was applied successfully to several systems of interest, such as relativistic spin-$1/2$ particles and radio-frequency waves propagating in magnetized plasmas. The second main contribution of this thesis is the development of a phase-space method to study basic properties of nonlinear wave--wave interactions. Specifically, a general theory is proposed that describes the ponderomotive refraction that a wave can experience when interacting with another wave. It is also shown that phase-space methods can be useful to study problems in the field of wave turbulence, such as the nonlinear interaction of high-frequency waves with large-scale structures. Overall, the results obtained can serve as a basis for future studies on more complex nonlinear wave--wave interactions, such as modulational instabilities in general wave ensembles or wave turbulence.« less

EFFECT OF CORRELATIONS ON THE TRANSPORT COEFFICIENTS OF A PLASMA (in French)

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

Balescu, R.; de Gottal, Ph.

1961-01-01

A closed formula is obtained for the long-lived corre1ations in an inhomogeneous plasma; it is expressed in terms of the one particle distribution function. This forms an appropriate starting point for a rigorous theory of transport phenomena in plasmas, including the effect of molecular corrclations. An expressson is obtained for the thermal conductivity. (auth)

Progress of plasma wakefield self-modulation experiments at FACET

NASA Astrophysics Data System (ADS)

Adli, E.; Berglyd Olsen, V. K.; Lindstrøm, C. A.; Muggli, P.; Reimann, O.; Vieira, J. M.; Amorim, L. D.; Clarke, C. I.; Gessner, S. J.; Green, S. Z.; Hogan, M. J.; Litos, M. D.; O`Shea, B. D.; Yakimenko, V.; Clayton, C.; Marsh, K. A.; Mori, W. B.; Joshi, C.; Vafaei-Najafabadi, N.; Williams, O.

2016-09-01

Simulations and theory predict that long electron and positron beams may under favorable conditions self-modulate in plasmas. We report on the progress of experiments studying the self-modulation instability in plasma wakefield experiments at FACET. The experimental results obtained so far, while not being fully conclusive, appear to be consistent with the presence of the self-modulation instability.

Scaling of theory-of-mind tasks.

PubMed

Wellman, Henry M; Liu, David

2004-01-01

Two studies address the sequence of understandings evident in preschoolers' developing theory of mind. The first, preliminary study provides a meta-analysis of research comparing different types of mental state understandings (e.g., desires vs. beliefs, ignorance vs. false belief). The second, primary study tests a theory-of-mind scale for preschoolers. In this study 75 children (aged 2 years, 11 months to 6 years, 6 months) were tested on 7 tasks tapping different aspects of understanding persons' mental states. Responses formed a consistent developmental progression, where for most children if they passed a later item they passed all earlier items as well, as confirmed by Guttman and Rasch measurement model analyses.

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

Mrówczyński, Stanisław; Schenke, Björn; Strickland, Michael

When the quark–gluon plasma (QGP) – a system of deconfined quarks and gluons – is in a nonequilibrium state, it is usually unstable with respect to color collective modes. The instabilities, which are expected to strongly influence dynamics of the QGP produced in relativistic heavy-ion collisions, are extensively discussed under the assumption that the plasma is weakly coupled. Here, we begin by presenting the theoretical approaches to study the QGP, which include: field theory methods based on the Keldysh–Schwinger formalism, classical and quantum kinetic theories, and fluid techniques. The dispersion equations, which give the spectrum of plasma collective excitations, aremore » analyzed in detail. We pay particular attention to a momentum distribution of plasma constituents which is obtained by deforming an isotropic momentum distribution. Mechanisms of chromoelectric and chromomagnetic instabilities are explained in terms of elementary physics. The Nyquist analysis, which allows one to determine the number of solutions of a dispersion equation without explicitly solving it, and stability criteria are also discussed. We then review various numerical approaches – purely classical or quantum – to simulate the temporal evolution of an unstable quark–gluon plasma. The dynamical role of instabilities in the processes of plasma equilibration is analyzed.« less

Scale-free crystallization of two-dimensional complex plasmas: Domain analysis using Minkowski tensors

NASA Astrophysics Data System (ADS)

Böbel, A.; Knapek, C. A.; Räth, C.

2018-05-01

Experiments of the recrystallization processes in two-dimensional complex plasmas are analyzed to rigorously test a recently developed scale-free phase transition theory. The "fractal-domain-structure" (FDS) theory is based on the kinetic theory of Frenkel. It assumes the formation of homogeneous domains, separated by defect lines, during crystallization and a fractal relationship between domain area and boundary length. For the defect number fraction and system energy a scale-free power-law relation is predicted. The long-range scaling behavior of the bond-order correlation function shows clearly that the complex plasma phase transitions are not of the Kosterlitz, Thouless, Halperin, Nelson, and Young type. Previous preliminary results obtained by counting the number of dislocations and applying a bond-order metric for structural analysis are reproduced. These findings are supplemented by extending the use of the bond-order metric to measure the defect number fraction and furthermore applying state-of-the-art analysis methods, allowing a systematic testing of the FDS theory with unprecedented scrutiny: A morphological analysis of lattice structure is performed via Minkowski tensor methods. Minkowski tensors form a complete family of additive, motion covariant and continuous morphological measures that are sensitive to nonlinear properties. The FDS theory is rigorously confirmed and predictions of the theory are reproduced extremely well. The predicted scale-free power-law relation between defect fraction number and system energy is verified for one more order of magnitude at high energies compared to the inherently discontinuous bond-order metric. It is found that the fractal relation between crystalline domain area and circumference is independent of the experiment, the particular Minkowski tensor method, and the particular choice of parameters. Thus, the fractal relationship seems to be inherent to two-dimensional phase transitions in complex plasmas. Minkowski tensor analysis turns out to be a powerful tool for investigations of crystallization processes. It is capable of revealing nonlinear local topological properties, however, still provides easily interpretable results founded on a solid mathematical framework.

[Welding arc temperature field measurements based on Boltzmann spectrometry].

PubMed

Si, Hong; Hua, Xue-Ming; Zhang, Wang; Li, Fang; Xiao, Xiao

2012-09-01

Arc plasma, as non-uniform plasma, has complicated energy and mass transport processes in its internal, so plasma temperature measurement is of great significance. Compared with absolute spectral line intensity method and standard temperature method, Boltzmann plot measuring is more accurate and convenient. Based on the Boltzmann theory, the present paper calculates the temperature distribution of the plasma and analyzes the principle of lines selection by real time scanning the space of the TIG are measurements.

Evaluating Prototype Tasks and Alternative Rating Schemes for a New ESL Writing Test through G-Theory

ERIC Educational Resources Information Center

Lee, Yong-Won; Kantor, Robert

2007-01-01

Possible integrated and independent tasks were pilot tested for the writing section of a new generation of the TOEFL[R] (Test of English as a Foreign Language[TM]). This study examines the impact of various rating designs and of the number of tasks and raters on the reliability of writing scores based on integrated and independent tasks from the…

How Do Alternative Ways of Responding Influence 3- and 4-Year-Olds' Performance on Tests of Executive Function and Theory of Mind?

ERIC Educational Resources Information Center

Carroll, Daniel J.; Riggs, Kevin J.; Apperly, Ian A.; Graham, Kate; Geoghegan, Ceara

2012-01-01

A total of 69 preschool children were tested on measures of false belief understanding (the Unexpected Transfer task), inhibitory control (the Grass/Snow task), and strategic reasoning (the Windows task). For each task, children indicated their response either by pointing with their index finger or by using a nonstandard response mode (pointing…

EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience

NASA Astrophysics Data System (ADS)

Ongena, Jef

2012-07-01

The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only supported but also contributed very substantially to this initiative. Without their dedication this issue would not have been possible in its present form. A special word of thanks to Marie-Line Mayoral and Joelle Mailloux for their precious help and very active support in running the JET Task Force Heating over the last years. Without Joelle and Marie-Line itwould have been a much more daunting task to prepare JET operations, monitor progress during the experiments and edit the papers that are compiled here.

Representing metarepresentations: is there theory of mind-specific cognition?

PubMed

Egeth, Marc; Kurzban, Robert

2009-03-01

What cognitive mechanisms underlie Theory of Mind? Some infer domain-specific Theory of Mind cognition based the pattern of children diagnosed with autism failing the False Belief test but passing the False Photograph test. However, we argue that the False Belief test entails various task demands the False Photograph task does not, including the necessity to represent a higher-order representation (a metarepresentation), thus confounding the inference of domain-specificity. Instead, a general difficulty that affects representations of metarepresentations might account for the seeming domain-specific failure. Here we find that False-Belief failing False-Photograph passing children fail the Meta Photograph test, a new photograph-domain test that requires subjects to represent a metarepresentation. We conclude that people who fail the False Belief test but pass the False Photograph test do not necessarily have a content-specific Theory of Mind deficit. Instead, the general ability to represent representations and metarepresentations might underlie Theory of Mind.

System-wide versus component-specific trust using multiple aids.

PubMed

Keller, David; Rice, Stephen

2010-01-01

Previous research in operator trust toward automated aids has focused primarily on single aids. The current study focuses on how operator trust is affected by the presence of multiple aids. Two competing theories of multiple-trust are presented. A component-specific trust theory predicts that operators will differentially place their trust in automated aids that vary in reliability. A system-wide trust theory predicts that operators will treat multiple imperfect aids as one "system" and merge their trust across aids despite differences in the aids' reliability. A simulated flight task was used to test these theories, whereby operators performed a pursuit tracking task while concurrently monitoring multiple system gauges that were augmented with perfect or imperfect automated aids. The data revealed that a system-wide trust theory best predicted the data; operators merged their trust across both aids, behaving toward a perfectly reliable aid in the same manner as they did towards unreliable aids.

Research briefing on contemporary problems in plasma science

NASA Technical Reports Server (NTRS)

1991-01-01

An overview is presented of the broad perspective of all plasma science. Detailed discussions are given of scientific opportunities in various subdisciplines of plasma science. The first subdiscipline to be discussed is the area where the contemporary applications of plasma science are the most widespread, low temperature plasma science. Opportunities for new research and technology development that have emerged as byproducts of research in magnetic and inertial fusion are then highlighted. Then follows a discussion of new opportunities in ultrafast plasma science opened up by recent developments in laser and particle beam technology. Next, research that uses smaller scale facilities is discussed, first discussing non-neutral plasmas, and then the area of basic plasma experiments. Discussions of analytic theory and computational plasma physics and of space and astrophysical plasma physics are then presented.

The Mind behind the Message: Advancing Theory-of-Mind Scales for Typically Developing Children, and Those with Deafness, Autism, or Asperger Syndrome

ERIC Educational Resources Information Center

Peterson, Candida C.; Wellman, Henry M.; Slaughter, Virginia

2012-01-01

Children aged 3-2 years (n = 184) with typical development, deafness, autism, or Asperger syndrome took a series of theory-of-mind (ToM) tasks to confirm and extend previous developmental scaling evidence. A new sarcasm task, in the format of H. M. Wellman and D. Liu's (2004) 5-step ToM Scale, added a statistically reliable 6th step to the scale…

A two-phase model of resource allocation in visual working memory.

PubMed

Ye, Chaoxiong; Hu, Zhonghua; Li, Hong; Ristaniemi, Tapani; Liu, Qiang; Liu, Taosheng

2017-10-01

Two broad theories of visual working memory (VWM) storage have emerged from current research, a discrete slot-based theory and a continuous resource theory. However, neither the discrete slot-based theory or continuous resource theory clearly stipulates how the mental commodity for VWM (discrete slot or continuous resource) is allocated. Allocation may be based on the number of items via stimulus-driven factors, or it may be based on task demands via voluntary control. Previous studies have obtained conflicting results regarding the automaticity versus controllability of such allocation. In the current study, we propose a two-phase allocation model, in which the mental commodity could be allocated only by stimulus-driven factors in the early consolidation phase. However, when there is sufficient time to complete the early phase, allocation can enter the late consolidation phase, where it can be flexibly and voluntarily controlled according to task demands. In an orientation recall task, we instructed participants to store either fewer items at high-precision or more items at low-precision. In 3 experiments, we systematically manipulated memory set size and exposure duration. We did not find an effect of task demands when the set size was high and exposure duration was short. However, when we either decreased the set size or increased the exposure duration, we found a trade-off between the number and precision of VWM representations. These results can be explained by a two-phase model, which can also account for previous conflicting findings in the literature. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Gas Tungsten Arc Welding and Plasma Arc Cutting. Teacher Edition [and] Student Edition [and] Student Workbook. Second Edition.

ERIC Educational Resources Information Center

Harper, Eddie; Knapp, John

This packet of instructional materials for a gas tungsten arc welding (GTAW) and plasma arc cutting course is comprised of a teacher edition, student edition, and student workbook. The teacher edition consists of introductory pages and teacher pages. Introductory pages include training and competency profile, state duty/task crosswalk,…

A training study of theory of mind and executive function in children with autistic spectrum disorders.

PubMed

Fisher, Naomi; Happé, Francesca

2005-12-01

This study investigated the relationship between theory of mind and executive functioning in children with autistic spectrum disorders through a training study. Ten children were trained on theory of mind, whilst ten were trained in executive function. Seven children were assigned to a control group, receiving no intervention. Training programmes were administered individually, lasting for 25 minutes per day for 5-10 days. Children were tested before training, after training and at a two-month follow-up. Significant improvements were seen in performance on theory of mind tasks in both trained groups, whilst the control group showed no improvement. No improvement on the executive function tasks was seen in any of the groups. The implications of these findings are discussed.

The subtle interplay of elastic and inelastic collisions in the thermalization of the quark–gluon plasma

DOE PAGES

Blaizot, Jean-Paul; Liao, Jinfeng; Mehtar-Tani, Yacine

2016-12-01

We analyze the interplay of elastic and inelastic collisions in the thermalization of the quark-gluon plasma, using kinetic theory. Our main focus is the dynamics and equilibration of long wavelength modes.

Waves in Space Plasmas (WISP)

NASA Technical Reports Server (NTRS)

Calvert, Wynne

1994-01-01

Activities under this project have included participation in the Waves in Space Plasmas (WISP) program, a study of the data processing requirements for WISP, and theoretical studies of radio sounding, ducting, and magnetoionic theory. An analysis of radio sounding in the magnetosphere was prepared.

Theory of mind selectively predicts preschoolers’ knowledge-based selective word learning

PubMed Central

Brosseau-Liard, Patricia; Penney, Danielle; Poulin-Dubois, Diane

2015-01-01

Children can selectively attend to various attributes of a model, such as past accuracy or physical strength, to guide their social learning. There is a debate regarding whether a relation exists between theory-of-mind skills and selective learning. We hypothesized that high performance on theory-of-mind tasks would predict preference for learning new words from accurate informants (an epistemic attribute), but not from physically strong informants (a non-epistemic attribute). Three- and 4-year-olds (N = 65) completed two selective learning tasks, and their theory of mind abilities were assessed. As expected, performance on a theory-of-mind battery predicted children’s preference to learn from more accurate informants but not from physically stronger informants. Results thus suggest that preschoolers with more advanced theory of mind have a better understanding of knowledge and apply that understanding to guide their selection of informants. This work has important implications for research on children’s developing social cognition and early learning. PMID:26211504

Theory of mind selectively predicts preschoolers' knowledge-based selective word learning.

PubMed

Brosseau-Liard, Patricia; Penney, Danielle; Poulin-Dubois, Diane

2015-11-01

Children can selectively attend to various attributes of a model, such as past accuracy or physical strength, to guide their social learning. There is a debate regarding whether a relation exists between theory-of-mind skills and selective learning. We hypothesized that high performance on theory-of-mind tasks would predict preference for learning new words from accurate informants (an epistemic attribute), but not from physically strong informants (a non-epistemic attribute). Three- and 4-year-olds (N = 65) completed two selective learning tasks, and their theory-of-mind abilities were assessed. As expected, performance on a theory-of-mind battery predicted children's preference to learn from more accurate informants but not from physically stronger informants. Results thus suggest that preschoolers with more advanced theory of mind have a better understanding of knowledge and apply that understanding to guide their selection of informants. This work has important implications for research on children's developing social cognition and early learning. © 2015 The British Psychological Society.

New social tasks for cognitive psychology; or, new cognitive tasks for social psychology.

PubMed

Wettersten, John

2014-01-01

To elucidate how differing theories of rationality lead to differing practices, their social rules must be analyzed. This is true not merely in science but also in society at large. This analysis of social thinking requires both the identification of innate cognitive social psychological processes and explanations of their relations with differing rules of rational practice. These new tasks can enable social psychologists to contribute to the study of how social situations facilitate or inhibit rational practice and enable cognitive psychologists to improve social psychological theory. In contrast to dominant current research strategies, social and cognitive psychologists can integrate social studies of rational practices and their consequences with studies of underlying cognitive psychological processes. In this article I do not attempt to carry out these tasks but rather point to both their lack of recognition and their importance.

The combination of perception of other individuals and exogenous manipulation of arousal enhances social facilitation as an aftereffect: re-examination of Zajonc’s drive theory

PubMed Central

Ukezono, Masatoshi; Nakashima, Satoshi F.; Sudo, Ryunosuke; Yamazaki, Akira; Takano, Yuji

2015-01-01

Zajonc’s drive theory postulates that arousal enhanced through the perception of the presence of other individuals plays a crucial role in social facilitation (Zajonc, 1965). Here, we conducted two experiments to examine whether the elevation of arousal through a stepping exercise performed in front of others as an exogenous factor causes social facilitation of a cognitive task in a condition where the presence of others does not elevate the arousal level. In the main experiment, as an “aftereffect of social stimulus,” we manipulated the presence or absence of others and arousal enhancement before participants conducted the primary cognitive task. The results showed that the strongest social facilitation was induced by the combination of the perception of others and arousal enhancement. In a supplementary experiment, we manipulated these factors by adding the presence of another person during the task. The results showed that the effect of the presence of the other during the primary task is enough on its own to produce facilitation of task performance regardless of the arousal enhancement as an aftereffect of social stimulus. Our study therefore extends the framework of Zajonc’s drive theory in that the combination of the perception of others and enhanced arousal as an “aftereffect” was found to induce social facilitation especially when participants did not experience the presence of others while conducting the primary task. PMID:25999906

Theory of Mind and social reserve: Alternative hypothesis of progressive Theory of Mind decay during different stages of Alzheimer's disease.

PubMed

Fliss, Rafika; Le Gall, Didier; Etcharry-Bouyx, Frédérique; Chauviré, Valérie; Desgranges, Béatrice; Allain, Philippe

2016-01-01

Although Theory of Mind (ToM) is thought to be impaired in Alzheimer's disease (AD), it remains unclear whether this impairment is linked to the level of task complexity, the heterogeneity of the studied patients, or the implication of executive dysfunctions. To elucidate this point, 42 AD patients, divided into two subgroups [moderate AD (mAD) patients (n = 19) and early AD (eAD) patients (n = 23)], and 23 matched healthy older subjects (HO) were enrolled. All participants were given (1) a false-belief task (cognitive ToM), (2) a revised version of the "Reading the Mind in the Eyes" test (affective ToM), and (3) a composite task designed to assess ToM abilities with minimal cognitive demands. Participants were also given executive tasks assessing inhibition, shifting, and updating processes. We observed a significant impairment of cognitive and composite ToM abilities in eAD patients compared with mAD patients. There was no impairment of affective ToM. Stepwise regression revealed that measures of global efficiency and executive functions (EFs) were the best predictors of progressive decay of ToM scores. These results indicate that cognitive aspects of ToM are more sensitive to AD progression than affective tasks. They also show that ToM abilities are more affected by dementia severity than by task complexity. One explanation of our results is the presence of compensatory mechanisms (social reserve) in AD.

Calculating the jet quenching parameter in the plasma of noncommutative Yang-Mills theory from gauge/gravity duality

NASA Astrophysics Data System (ADS)

Chakraborty, Somdeb; Roy, Shibaji

2012-02-01

A particular decoupling limit of the nonextremal (D1, D3) brane bound state system of type IIB string theory is known to give the gravity dual of space-space noncommutative Yang-Mills theory at finite temperature. We use a string probe in this background to compute the jet quenching parameter in a strongly coupled plasma of hot noncommutative Yang-Mills theory in (3+1) dimensions from gauge/gravity duality. We give expressions for the jet quenching parameter for both small and large noncommutativity. For small noncommutativity, we find that the value of the jet quenching parameter gets reduced from its commutative value. The reduction is enhanced with temperature as T7 for fixed noncommutativity and fixed ’t Hooft coupling. We also give an estimate of the correction due to noncommutativity at the present collider energies like in RHIC or in LHC and find it too small to be detected. We further generalize the results for noncommutative Yang-Mills theories in diverse dimensions.