scholarly journals Comparison between measurements of the poloidal distribution of magnetic fluctuations and predictions of theoretical models during TAE activity

1997 ◽  
Vol 37 (10) ◽  
pp. 1411-1417 ◽  
Author(s):  
W.W Heidbrink ◽  
A Jaun ◽  
H.A Holties
Keyword(s):  
Theoretical Models ◽  
Magnetic Fluctuations

scholarly journals Properties of Hall-MHD Turbulence at Sub-Ion Scales: Spectral Transfer Analysis

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1632
Author(s):  
Emanuele Papini ◽  
Petr Hellinger ◽  
Andrea Verdini ◽  
Simone Landi ◽  
Luca Franci ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Transfer Rate ◽  
Space Plasma ◽  
Theoretical Models ◽  
Magnetic Fluctuations ◽  
Energy Transfer Rate ◽  
Mhd Turbulence ◽  
Developed Turbulence ◽  
First Time ◽  
Hall Mhd

We present results of a multiscale study of Hall-magnetohydrodynamic (MHD) turbulence, carried out on a dataset of compressible nonlinear 2D Hall-MHD numerical simulations of decaying Alfvénic turbulence. For the first time, we identify two distinct regimes of fully developed turbulence. In the first one, the power spectrum of the turbulent magnetic fluctuations at sub-ion scales exhibits a power law with a slope of ∼−2.9, typically observed both in solar wind and in magnetosheath turbulence. The second regime, instead, shows a slope of −7/3, in agreement with classical theoretical models of Hall-MHD turbulence. A spectral-transfer analysis reveals that the latter regime occurs when the energy transfer rate at sub-ion scales is dominated by the Hall term, whereas in the former regime, the governing process is the dissipation (and the system exhibits large intermittency). Results of this work are relevant to the space plasma community, as they may potentially reconcile predictions from theoretical models with results from numerical simulations and spacecraft observations.

scholarly journals High-frequency Magnetic Fluctuations in Space Plasmas and the Role of Electron Landau Damping

2022 ◽  
Vol 924 (2) ◽  
pp. L26
Author(s):  
Vincenzo Carbone ◽  
Daniele Telloni ◽  
Fabio Lepreti ◽  
Antonio Vecchio
Keyword(s):  
High Frequency ◽  
Interplanetary Space ◽  
Magnetic Energy ◽  
Low Frequency ◽  
Theoretical Models ◽  
Landau Damping ◽  
Magnetic Fluctuations ◽  
Frequency Plasma ◽  
New Framework

Abstract While low-frequency plasma fluctuations in the interplanetary space have been successfully described in the framework of classical turbulence, high-frequency fluctuations still represent a challenge for theoretical models. At these scales, kinetic plasma processes are at work, but although some of them have been identified in spacecraft measurements, their global effects on observable quantities are sometimes not fully understood. In this paper we present a new framework to the aim of describing the observed magnetic energy spectrum and directly identify in the data the presence of Landau damping as the main collisionless dissipative process in the solar wind.

Doppler observations of associated ionospheric and magnetic fluctuations

1969 ◽  
Vol 47 (15) ◽  
pp. 1585-1600 ◽  
Author(s):  
G. M. Boyd ◽  
H. J. Duffus
Keyword(s):  
Theoretical Models ◽  
Magnetic Fluctuations ◽  
Radio Waves ◽  
Geomagnetic Disturbances ◽  
Neutral Gas ◽  
Doppler Shifts ◽  
F Region ◽  
Cross Correlations ◽  
The Many ◽  
Hydromagnetic Waves

Observations of ionospheric motions associated with magnetic micropulsations were conducted during a three-year period.Current theoretical models of the interaction indicate that observable Doppler shifts of high-frequency radio waves coherently reflected from the ionosphere should accompany all reasonably large geomagnetic disturbances, and vice versa, but this is not observed. Detailed studies of particular classes of events were therefore undertaken, involving spectral analyses, cross correlations, diurnal and seasonal occurrence statistics, and studies of associations with various types of ionospheric and magnetic records.Certain classes of magnetic pulsation events are found to be directly associated with F-region motions. Of the many possible mechanisms which may be responsible for these associations, two stand out as prime candidates: (i) hydromagnetic waves and (ii) neutral-gas waves modulating ionospheric electrojets. At mid-latitudes during quiet-sun years, the direct effects of precipitation of charged particles appear to be of much less importance.

Analytical Electron Microscopy of Surface-Modified Ceramics

1985 ◽  
Vol 43 ◽  
pp. 276-279
Author(s):  
P. S. Sklad
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Theoretical Models ◽  
Ceramic Materials ◽  
Solute Concentration ◽  
Second Phase ◽  
Analytical Electron ◽  
Implantation Techniques ◽  
Lattice Damage ◽  
Surface Modified

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.

On the Relationship Between General Auditory Sensitivity and Speech Perception: An Examination of Pitch and Lexical Tone Perception in 4- to 6-Year-Old Children

2020 ◽  
Vol 63 (2) ◽  
pp. 487-498
Author(s):  
Puisan Wong ◽  
Man Wai Cheng
Keyword(s):  
Speech Perception ◽  
Theoretical Models ◽  
Developmental Trajectory ◽  
Auditory Sensitivity ◽  
Pitch Discrimination ◽  
Lexical Tone ◽  
Perceptual Training ◽  
Lexical Tones ◽  
Tone Perception ◽  
Tone Discrimination

Purpose Theoretical models and substantial research have proposed that general auditory sensitivity is a developmental foundation for speech perception and language acquisition. Nonetheless, controversies exist about the effectiveness of general auditory training in improving speech and language skills. This research investigated the relationships among general auditory sensitivity, phonemic speech perception, and word-level speech perception via the examination of pitch and lexical tone perception in children. Method Forty-eight typically developing 4- to 6-year-old Cantonese-speaking children were tested on the discrimination of the pitch patterns of lexical tones in synthetic stimuli, discrimination of naturally produced lexical tones, and identification of lexical tone in familiar words. Results The findings revealed that accurate lexical tone discrimination and identification did not necessarily entail the accurate discrimination of nonlinguistic stimuli that followed the pitch levels and pitch shapes of lexical tones. Although pitch discrimination and tone discrimination abilities were strongly correlated, accuracy in pitch discrimination was lower than that in tone discrimination, and nonspeech pitch discrimination ability did not precede linguistic tone discrimination in the developmental trajectory. Conclusions Contradicting the theoretical models, the findings of this study suggest that general auditory sensitivity and speech perception may not be causally or hierarchically related. The finding that accuracy in pitch discrimination is lower than that in tone discrimination suggests that comparable nonlinguistic auditory perceptual ability may not be necessary for accurate speech perception and language learning. The results cast doubt on the use of nonlinguistic auditory perceptual training to improve children's speech, language, and literacy abilities.

Positive Arousal Enhances the Consolidation of Item Memory

2015 ◽  
Vol 74 (2) ◽  
pp. 91-104 ◽  
Author(s):  
Bo Wang
Keyword(s):  
Episodic Memory ◽  
Memory Consolidation ◽  
Source Memory ◽  
Emotional Arousal ◽  
Theoretical Models ◽  
Memory Test ◽  
Learning Phase ◽  
Item Memory ◽  
Memory Tests ◽  
Immediate Memory

Emotional arousal induced after learning has been shown to modulate memory consolidation. However, it is unclear whether the effect of postlearning arousal can extend to different aspects of memory. This study examined the effect of postlearning positive arousal on both item memory and source memory. Participants learned a list of neutral words and took an immediate memory test. Then they watched a positive or a neutral videoclip and took delayed memory tests after either 25 minutes or 1 week had elapsed after the learning phase. In both delay conditions, positive arousal enhanced consolidation of item memory as measured by overall recognition. Furthermore, positive arousal enhanced consolidation of familiarity but not recollection. However, positive arousal appeared to have no effect on consolidation of source memory. These findings have implications for building theoretical models of the effect of emotional arousal on consolidation of episodic memory and for applying postlearning emotional arousal as a technique of memory intervention.

The Role of Distress Disclosure Tendencies in the Experience and Expression of Laboratory-Induced Sadness

2017 ◽  
Vol 38 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Jeffrey H. Kahn ◽  
Daniel W. Cox ◽  
A. Myfanwy Bakker ◽  
Julia I. O’Loughlin ◽  
Agnieszka M. Kotlarczyk
Keyword(s):  
Individual Differences ◽  
Emotional Reactivity ◽  
Subjective Experience ◽  
Negative Emotion ◽  
Theoretical Models ◽  
Laboratory Research ◽  
Emotion Words ◽  
Distress Disclosure ◽  
Computerized Text Analysis

Abstract. The benefits of talking with others about unpleasant emotions have been thoroughly investigated, but individual differences in distress disclosure tendencies have not been adequately integrated within theoretical models of emotion. The purpose of this laboratory research was to determine whether distress disclosure tendencies stem from differences in emotional reactivity or differences in emotion regulation. After completing measures of distress disclosure tendencies, social desirability, and positive and negative affect, 84 participants (74% women) were video recorded while viewing a sadness-inducing film clip. Participants completed post-film measures of affect and were then interviewed about their reactions to the film; these interviews were audio recorded for later coding and computerized text analysis. Distress disclosure tendencies were not predictive of the subjective experience of emotion, but they were positively related to facial expressions of sadness and happiness. Distress disclosure tendencies also predicted judges’ ratings of the verbal disclosure of emotion during the interview, but self-reported disclosure and use of positive and negative emotion words were not associated with distress disclosure tendencies. The authors present implications of this research for integrating individual differences in distress disclosure with models of emotion.

Convergent and Predictive Validity of Implicit and Explicit Anxiety Measures as a Function of Specificity Similarity and Content Similarity

2008 ◽  
Vol 24 (4) ◽  
pp. 254-262 ◽  
Author(s):  
Tobias Gschwendner ◽  
Wilhelm Hofmann ◽  
Manfred Schmitt
Keyword(s):  
Implicit Association Test ◽  
Theoretical Models ◽  
Implicit Measures ◽  
Speech Anxiety ◽  
Behavioral Indicators ◽  
General Anxiety ◽  
Anxious Behavior ◽  
Content Similarity ◽  
Implicit And Explicit ◽  
Validation Strategy

In the present study we applied a validation strategy for implicit measures like the IAT, which complements multitrait-multimethod (MTMM) analyses. As the measurement method (implicit vs. explicit) and underlying representation format (associative vs. propositional) are often confounded, the validation of implicit measures has to go beyond MTMM analysis and requires substantive theoretical models. In the present study (N = 133), we employed such a model ( Hofmann, Gschwendner, Nosek, & Schmitt, 2005 ) and investigated two moderator constructs in the realm of anxiety: specificity similarity and content similarity. In the first session, different general and specific anxiety measures were administered, among them an Implicit Association Test (IAT) general anxiety, an IAT-spider anxiety, and an IAT that assesses speech anxiety. In the second session, participants had to deliver a speech and behavioral indicators of speech anxiety were measured. Results showed that (a) implicit and explicit anxiety measures correlated significantly only on the same specification level and if they measured the same content, and (b) specific anxiety measures best predicted concrete anxious behavior. These results are discussed regarding the validation of implicit measures.

Does CBT for Psychosis Have an Impact on Delusions by Improving Reasoning Biases and Negative Self-Schemas?

2018 ◽  
Vol 226 (3) ◽  
pp. 152-163 ◽  
Author(s):  
Stephanie Mehl ◽  
Björn Schlier ◽  
Tania M. Lincoln
Keyword(s):  
Behavioral Therapy ◽  
Theoretical Models ◽  
Self Esteem ◽  
Secondary Outcome ◽  
Intervention Effect ◽  
Produce Change ◽  
Attribution Biases ◽  
Carry Over ◽  
Implicit And Explicit ◽  
Reasoning Biases

Abstract. Cognitive-behavioral therapy for psychosis (CBTp) builds on theoretical models that postulate reasoning biases and negative self-schemas to be involved in the formation and maintenance of delusions. However, it is unclear whether CBTp induces change in delusions by improving these proposed causal mechanisms. This study reports on a mediation analysis of a CBTp effectiveness trial in which delusions were a secondary outcome. Patients with psychosis were randomized to individualized CBTp (n = 36) or a waiting list condition (WL; n = 34). Reasoning biases (jumping to conclusions, theory of mind, attribution biases) and self-schemas (implicit and explicit self-esteem; self-schemas related to different domains) were assessed pre- and post-therapy/WL. The results reveal an intervention effect on two of four measures of delusions and on implicit self-esteem. Nevertheless, the intervention effect on delusions was not mediated by implicit self-esteem. Changes in explicit self-schemas and reasoning biases did also not mediate the intervention effects on delusions. More focused interventions may be required to produce change in reasoning and self-schemas that have the potential to carry over to delusions.

Sign in / Sign up

Export Citation Format

Share Document