Thermal conductivity, relaxation and low-frequency vibrational mode anomalies in glasses: a model using the Fermi–Pasta–Ulam nonlinear Hamiltonian

2009 ◽  
Vol 367 (1901) ◽  
pp. 3173-3181 ◽  
Author(s):  
J. R. Romero-Arias ◽  
F. Salazar ◽  
G. G. Naumis ◽  
G. Fernandez-Anaya
Keyword(s):  
Thermal Conductivity ◽  
Vibrational Mode ◽  
Low Frequency ◽  
Vibrational Modes ◽  
Conductivity Relaxation ◽  
Cooling Speed ◽  
A Chain ◽  
The Relationship ◽  
Fpu Problem

We present a nonlinear model that allows exploration of the relationship between energy relaxation, thermal conductivity and the excess of low-frequency vibrational modes (LFVMs) that are present in glasses. The model is a chain of the Fermi–Pasta–Ulam (FPU) type, with nonlinear second neighbour springs added at random. We show that the time for relaxation is increased as LFVMs are removed, while the thermal conductivity diminishes. These results are important in order to understand the role of the cooling speed and thermal conductivity during glass transition. Also, the model provides evidence for the fundamental importance of LFVMs in the FPU problem.

Role of Dominance Status in Shock-Stimulated Agonistic Behavior

1971 ◽  
Vol 29 (3) ◽  
pp. 768-770 ◽  
Author(s):  
G. McA. Kimbrell ◽  
D. Chesler
Keyword(s):  
High Frequency ◽  
Agonistic Behavior ◽  
Defensive Behavior ◽  
Low Frequency ◽  
Behavior Patterns ◽  
Dominance Status ◽  
Very Low Frequency ◽  
The Relationship ◽  
Shock Situation

To clarify the relationship between dominance status and frequency of specific sub-classes of agonistic behavior in response to foot shock, 30 mice were selected on the basis of high- or low-dominance status and paired in a foot-shock situation. Dominant pairs exhibit a high frequency of defensive behavior patterns whereas submissive pairs exhibit a very low frequency of defensive patterns.

scholarly journals Linking Empowering Leadership, Psychological Empowerment, Self-Leadership, Creative Involvement and Creativity: A Sequential Mediation Model

2017 ◽  
Vol 5 (2) ◽  
pp. 67-80
Author(s):  
Ishfaq Ahmed ◽  
Muhammad Khalid Khan ◽  
Ghulam Ali Bhatti
Keyword(s):  
Psychological Empowerment ◽  
Creative Work ◽  
Mediation Model ◽  
Employee Creativity ◽  
Empowering Leadership ◽  
Mediating Role ◽  
Work Involvement ◽  
A Chain ◽  
The Relationship

This study examines the relationship between empowering leadership and employee creativity through the serial mediating role of psychological empowerment and self-leadership with creative work involvement. Applying a chain mediation approach to a sample of 314 respondents, we find that empowering leadership has a significant effect on the selected mediators (self-leadership, psychological empowerment and creative work involvement), which in turn transfer this effect to employee creativity.

scholarly journals Low-frequency vibrational modes in G-quadruplexes reveal the mechanical properties of nucleic acids

2020 ◽  
Author(s):  
M. González-Jiménez ◽  
G. Ramakrishnan ◽  
K. Wynne
Keyword(s):  
Protein Interactions ◽  
Kerr Effect ◽  
Biological Function ◽  
Low Frequency ◽  
Theoretical Models ◽  
Protein Recognition ◽  
Optical Kerr Effect ◽  
Vibrational Modes ◽  
New Perspective

AbstractLow-frequency vibrations play an essential role in biomolecular processes involving DNA such as gene expression, charge transfer, drug intercalation, and DNA–protein recognition. However, understanding of the vibrational basis of these mechanisms relies on theoretical models due to the lack of experimental evidence. Here we present the low-frequency vibrational spectra of G-quadruplexes (structures formed by four strands of DNA) and B-DNA characterized using femtosecond optical Kerr-effect spectroscopy. Contrary to expectation, we found that G-quadruplexes show several strongly underdamped delocalized phonon-like modes that have the potential to contribute to the biology of the DNA at the atomic level. In addition, G-quadruplexes present modes at a higher frequency than B-DNA demonstrating that changes in the stiffness of the molecule alter its gigahertz to terahertz vibrational profile. These results demonstrate that current theoretical models fail to predict basic properties of the vibrational modes of DNA.Statement of significanceA number of recent studies have identified thermally excited low-frequency vibrational modes as a key deciding factor in the biological function of DNA. However, the nature of these vibrational modes has never been established. Here, vibrational spectroscopy with unrivalled signal-to-noise in the gigahertz to terahertz range is used to determine the low-frequency Raman spectra of nucleotides and oligomeric DNAs carefully chosen to form G-quadruplexes, structures formed by four strands of DNA common in the genome. These G-quadruplexes exhibit an unusual group of highly-underdamped delocalized vibrational modes—not reproduced by any of the theoretical models in use—which are expected to be the thermally excited. This provides a new perspective on the role of low-frequency vibrational modes in protein interactions and allostery.

scholarly journals Tunable, synchronized frequency down-conversion in magnetic lattices with defects

2018 ◽  
Vol 376 (2127) ◽  
pp. 20170137 ◽  
Author(s):  
Marc Serra-Garcia ◽  
Miguel Molerón ◽  
Chiara Daraio
Keyword(s):  
Energy Transfer ◽  
Frequency Conversion ◽  
Low Frequency ◽  
Multiple Sources ◽  
Localized Modes ◽  
Nonlinear Energy Transfer ◽  
Nonlinear Mechanical ◽  
Mechanical Analogue ◽  
A Chain

We study frequency conversion in nonlinear mechanical lattices, focusing on a chain of magnets as a model system. We show that, by inserting mass defects at suitable locations, we can introduce localized vibrational modes that nonlinearly couple to extended lattice modes. The nonlinear interaction introduces an energy transfer from the high-frequency localized modes to a low-frequency extended mode. This system is capable of autonomously converting energy between highly tunable input and output frequencies, which need not be related by integer harmonic or subharmonic ratios. It is also capable of obtaining energy from multiple sources at different frequencies with a tunable output phase, due to the defect synchronization provided by the extended mode. Our lattice is a purely mechanical analogue of an opto-mechanical system, where the localized modes play the role of the electromagnetic field and the extended mode plays the role of the mechanical degree of freedom. This article is part of the theme issue ‘Nonlinear energy transfer in dynamical and acoustical systems’.

Thermal Conductivity of Polymer/Carbon Nanotube Composites

2012 ◽  
Vol 714 ◽  
pp. 99-113 ◽  
Author(s):  
Manel Haddadi ◽  
Boudjemaa Agoudjil ◽  
Abderrahim Boudenne
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Processing Method ◽  
Nanotube Composites ◽  
Important Field ◽  
Carbon Nanotube Composites ◽  
Equivalent Property ◽  
New Generation ◽  
The Relationship

As one of the most important field of current nanoscience, the polymer nanocomposites is a promising and efficient way for new generation materials with high performances and multifunctionalities. The incorporating of nanofillers in a polymer matrix may improve mechanical, thermal, electrical or dielectric properties of the composites. The current paper focuses on the thermal conductivity of polymer/carbon nanotube composites. These last, are considered to be ideal candidates for the development of nanocomposite materials. Clarifying the role of the factors, influencing the properties of the composites, enable us to choose the suitable processing method for obtaining the composites and to improve the different properties of these systems. This article reviews the dependence of thermal conductivity of carbon nanotubes on the tube size and the effect of interface on the equivalent property. The relationship between the thermal conductivity and the nanostructure of composites are discussed.

scholarly journals The Relationship Between Lexical and Phonological Development in French-Speaking Children: A Longitudinal Study

2020 ◽  
Vol 63 (6) ◽  
pp. 1807-1821
Author(s):  
Margaret M. Kehoe ◽  
Tamara Patrucco-Nanchen ◽  
Margaret Friend ◽  
Pascal Zesiger
Keyword(s):  
Word Length ◽  
Low Frequency ◽  
Neighborhood Density ◽  
Phonological Development ◽  
Expressive Vocabulary ◽  
Vocabulary Size ◽  
French Speaking ◽  
Age Range ◽  
The Relationship

Purpose This study examines the influence of lexical and phonological factors on expressive lexicon size in 40 French-speaking children tested longitudinally from 22 to 48 months. The factors include those based on the lexical and phonological properties of words in the children's lexicons (phonetic complexity, word length, neighborhood density [ND], and word frequency [WF]) as well as variables measuring phonological production (percent consonants correct and phonetic inventory size). Specifically, we investigate the relative influence of these factors at individual ages, namely, 22, 29, 36, and 48 months, and which factors measured at 22 and 29 months influence lexicon size at 36 and 48 months. Method Children were selected based on parent-reported vocabulary size. We included children with low, medium, and high vocabulary scores. The children's lexicons were coded in terms of phonetic complexity, word length, ND, and WF, and their phonological production skills were based on measures of percent consonants correct and phonetic inventory size extracted from spontaneous speech samples at 29, 36, and 48 months. In the case of ND and WF, we focused on one- and two-syllable nouns. Results Across the age range, the most important factor that explained variance in lexicon size was the WF of nouns. Children who selected low-frequency nouns had larger vocabularies across all ages (22–48 months). The WF of two-syllable nouns and phonological production measured at 29 months influenced lexicon size at 36 months, whereas the WF (of one- and two-syllable words) influenced lexicon size at 48 months. Conclusions The findings support the role of WF and phonological production in explaining expressive vocabulary development. Children enlarge their vocabularies by adding nouns of increasingly lower frequency. Phonological production plays a role in accounting for vocabulary size up until the age of 36 months. Supplemental Material https://doi.org/10.23641/asha.12291074

scholarly journals Effect of Psychological Capital of Volunteers on Volunteering Behavior: The Chained Mediation Role of Perceived Social Support and Volunteer Motivation

2021 ◽  
Vol 12 ◽  
Author(s):  
Li ping Xu ◽  
Jin bao Liao ◽  
Yu shen Wu ◽  
Hong da Kuang
Keyword(s):  
Social Support ◽  
Psychological Capital ◽  
Perceived Social Support ◽  
Volunteer Motivation ◽  
Voluntary Service ◽  
Mediating Role ◽  
Service Information ◽  
A Chain ◽  
The Relationship

This study explored the role of perceived social support and voluntary motivation in the effect of psychological capital of volunteers on volunteering behavior. A sample of 1,165 volunteers who were registered in the China Voluntary Service Information System was investigated using a self-reported questionnaire, showing that the psychological capital, perceived social support, voluntary motivation, and volunteering behavior of the volunteers were significantly and positively related to each other. The psychological capital of the volunteers affected volunteering behavior not only directly, but also indirectly through the mediating role of voluntary motivation. Moreover, perceived social support and voluntary motivation also played a chain role in the relationship between the psychological capital and volunteering behavior of the volunteers. Therefore, increasing the psychological capital of the volunteers should promote their perceived social support and inspire voluntary motivation, in turn affecting their volunteering behavior.

scholarly journals Chemical equilibria of thermal associations

1941 ◽  
Vol 178 (974) ◽  
pp. 370-379 ◽  
Keyword(s):  
Equilibrium Constants ◽  
Low Frequency ◽  
Energy Difference ◽  
Vibrational Modes ◽  
Initial State ◽  
Final State ◽  
Chemical Equilibria ◽  
Chemical Constitution ◽  
The Relationship ◽  
Vibrational Contribution

The equilibrium constant, K , of an association can be represented by K = ωp'e -ΔE' 0 /RT or by K = ωpe -ΔE 0 /RT , where ΔE 0 is the energy difference between the product, at rest, and the two reactants both at rest and at infinite separation, and ΔE' 0 is deduced from the heat change under the assumption that the vibrational heat capacity of the initial state agrees with that of the final state of the reaction; the factor ω as defined by the above equations is the contribution of the rigid molecules, and can be calculated by taking into account the mass and the shape of the various participants of an equilibrium and the parameters p and p' are the contributions of the internal vibrations of the reactants and of the product molecules. In this paper the non-exponential ω factors and the energy changes, ΔE' 0 , relating to five gaseous thermal associations are computed and by substituting these quantities and the experimental equilibrium constants in the second equation mentioned above the vibrational contributions p' could be deduced. In one equilibrium it was also possible to estimate the energy change, ΔE 0 , and the vibrational contribution, p , and the relationship between the parameters p' and p is discussed. Further, an attempt is made to give a qualitative explanation for the dependence of the p' values on the chemical constitution of the participants of the various equilibria and it is pointed out that all the vibrational contributions are larger than unity, partly because the number of the vibrational modes increases on association, and partly because the reactants are stiffer than the associated molecules in which spectroscopically inactive vibrational modes of relatively low frequency can occur.

scholarly journals Schadenfreude and General Anti-Social Behaviours: The Role of Violent Content Preferences and Life Satisfaction

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Edgar Demeter ◽  
◽  
Dana Rad ◽  
Evelina Balas ◽  
◽  
...  
Keyword(s):  
Life Satisfaction ◽  
Satisfaction With Life ◽  
Antisocial Behaviour ◽  
Satisfaction With Life Scale ◽  
Meaningful Information ◽  
Violent Content ◽  
Life Scale ◽  
A Chain ◽  
The Relationship

In a digitally developed civilization access to different kinds of content and information can be easily acquired. From all the available content, some individuals chose and prefer to consume aggressive or violent content. In this light, the scope of this investigation is to determine the connection between the level of Violent Content Preferences (VC) and the levels of General Antisocial Behaviour (AS) and Schadenfreude (SCH) and the relationship between the intensity of life satisfaction (LS) and the intensity of Violent Content Preferences (VC), General Antisocial Behaviour (AS) and Schadenfreude (SCH). The present investigation is part of a chain of studies with reference to violent behaviours and cognitions. In this study, a number of 81 students (M = 27.57 SD = 9.25) from Arad, Romania, Aurel Vlaicu University, were investigated. VC and SCH were measured with the explorative affirmations, AS scores were obtained with the help of the How I Think Questionnaire (HIT) and LS was calculated with the help of the Satisfaction with life scale (SWLS). The obtained data ilustrates that VC is positively associated with AS an SCH, furthermore, AS is positively related with SCH, and LS was negatively associated with VC, AS and SCH. These outcomes point out the requirement to take into consideration the content we consume in regard to one’s satisfaction with life and can offer literature meaningful information in regards to the prevention or reduction of anti-social tendencies or cognitions.

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