Comparisons between stellar models and reliability of the theoretical models

2010 ◽  
pp. 27-36
Author(s):  
Yveline Lebreton ◽  
Josefina Montalbán
Keyword(s):  
Theoretical Models ◽  
Stellar Models

scholarly journals Properties of two star clusters of the LMC: NGC 2164, NGC 1850

1991 ◽  
Vol 148 ◽  
pp. 219-221
Author(s):  
A. Vallenari ◽  
C. Chiosi ◽  
G. Bertelli ◽  
G. Meylan ◽  
S. Ortolani
Keyword(s):  
Star Clusters ◽  
Theoretical Models ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Luminosity Functions ◽  
Stellar Models ◽  
Convective Overshoot

We present the photometry of two clusters NGC 2164 and NGC 1850 located in the Large Magellanic Cloud (LMC). The ages are determined taking into account the presence either of convective overshoot or of semiconvection in the stellar models. The experimental luminosity functions are compared with the theoretical models.

scholarly journals Abundances of the elements in the halo stars, interaction between observation and theory

1997 ◽  
Vol 189 ◽  
pp. 185-192
Author(s):  
M. Spite
Keyword(s):  
Rayleigh Scattering ◽  
Theoretical Models ◽  
Very Old ◽  
Electronic Pressure ◽  
Halo Stars ◽  
Mean Temperature ◽  
The Galaxy ◽  
The Sixties ◽  
Stellar Models ◽  
The Continuum

The halo stars are very old stars formed at the beginning of the evolution of the Galaxy. Their main characteristic is that their atmosphere is very metal-poor since at the time of their birth, the matter of the Galaxy had been enriched by only a few number of supernovae. The first very metal deficient stars have been studied in the sixties: Baschek (1959), Aller and Greenstein(1960) Wallerstein et al. (1963). The stellar models used in these first studies were rather crude: the atmosphere of the stars was represented by only one layer with a mean temperature and a mean electronic pressure, the continuum opacity was supposed to be due to H− and included in addition only the contribution by Rayleigh scattering. Later rescaled solar models were used and finally, at the end of the seventies, grids of theoretical models more and more sophisticated became available.

scholarly journals Luminosity Calibrations with Hipparcos: Theoretical Point of View

2002 ◽  
Vol 12 ◽  
pp. 669-672
Author(s):  
Yveline Lebreton
Keyword(s):  
Chemical Composition ◽  
Theoretical Models ◽  
Calibration Procedure ◽  
Point Of View ◽  
Chemical Compositions ◽  
Theoretical Point ◽  
Observational Material ◽  
Stellar Models ◽  
Stellar Temperatures

AbstractHipparcos provided us with valuable observational material that can be used to anchor more firmly the Galactic and extragalactic distance scales. A calibration which is applicable to all stars must allow for differences in chemical composition and other properties, which may require the use of theoretical models. I discuss some difficulties encountered in the calibration procedure that are related (1) to the determinations of stellar temperatures, luminosities and chemical compositions, (2) to remaining weaknesses of theoretical stellar models, and (3) to the transformations of the model outputs from the (Mbol,Teff) plane into any colour-magnitude or colour-colour diagram.

scholarly journals Stellar Seismology

1990 ◽  
Vol 121 ◽  
pp. 357-370
Author(s):  
Werner Däppen
Keyword(s):  
Theoretical Models ◽  
Acoustic Oscillation ◽  
Mode Identification ◽  
Stellar Ages ◽  
Stellar Models ◽  
Stellar Oscillation ◽  
Stellar Seismology ◽  
Oscillation Frequencies ◽  
Near Future

AbstractStellar acoustic oscillation frequencies will likely be accurately observed in the near future, in analogy to the well-known solar five-minute oscillation frequencies. Of course, we will never expect the wealth of solar data, which is a result of spatial resolution. We will therefore not be able to solve the inverse problem, that is to probe physical quantities as functions of depth, and the low number of anticipated observed frequencies will make an unambiguous mode identification difficult. Despite this restriction to the forward problem, however, observed stellar oscillation frequencies will become valuable constraints for the determination of stellar parameters. One should not forget that the present knowledge of stellar ages and compositions relies on the calibration of theoretical models (matching effective temperature and luminosity). Additional observational constraints will improve these calibrations, even if the theoretical models themselves are not questioned. We hope, however, that the observation of stellar oscillation frequencies will also lead to improvements in the physics of stellar models, in analogy to the solar case. Again, of course, stellar seismologists will be less ambitious than helioseismologists, since there are more open parameters in stellar models. However, stellar observations will allow tests of models with different age and composition.

Comparisons between stellar models and reliability of the theoretical models

2010 ◽  
Vol 328 (1-2) ◽  
pp. 29-38 ◽  
Author(s):  
Yveline Lebreton ◽  
Josefina Montalbán
Keyword(s):  
Theoretical Models ◽  
Stellar Models

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.

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