scholarly journals Influence of Dispersive Long-range Interactions on Properties of Vapour–liquid Equilibria and Interfaces of Binary Lennard-Jones Mixtures

2021 ◽  
Author(s):  
Simon Stephan ◽  
Hans Hasse
Keyword(s):  
Lateral Direction ◽  
Contact Processes ◽  
Lennard Jones ◽  
Flat Substrate ◽  
Long Range Interactions ◽  
Minor Part ◽  
Dynamics Simulations ◽  
A Minor ◽  
Work Done ◽  
Fluid Interaction

Liquid lubricants play an important role in contact processes; for example, they reduce friction and cool the contact zone. To gain better understanding of the influence of lubrication on the nanoscale, both dry and lubricated scratching processes in a model system are compared in the present work using molecular dynamics simulations. The entire range between total dewetting and total wetting is investigated by tuning the solid–fluid interaction energy. The investigated scratching process consists of three sequential movements: A cylindrical indenter penetrates an initially flat substrate, then scratches in the lateral direction, and is finally retracted out of the contact with the substrate. The indenter is fully submersed in the fluid in the lubricated cases. The substrate, the indenter, and the fluid are described by suitably parametrized Lennard–Jones model potentials. The presence of the lubricant is found to have a significant influence on the friction and on the energy balance of the process. The thermodynamic properties of the lubricant are evaluated in detail. A correlation of the simulation results for the profiles of the temperature, density, and pressure of the fluid in the vicinity of the chip is developed. The work done by the indenter is found to mainly dissipate and thereby heat up the substrate and eventually the fluid. Only a minor part of the work causes plastic deformation of the substrate.

scholarly journals The Influence of Lubrication and the Solid-fluid Interaction on Thermodynamic Properties in a Nanoscopic Scratching Process

2021 ◽  
Author(s):  
Simon Stephan ◽  
Maximilian Dyga ◽  
Herbert Urbassek ◽  
Hans Hasse
Keyword(s):  
Thermodynamic Properties ◽  
Lateral Direction ◽  
Contact Processes ◽  
Lennard Jones ◽  
Flat Substrate ◽  
Minor Part ◽  
Dynamics Simulations ◽  
A Minor ◽  
Work Done ◽  
Fluid Interaction

Liquid lubricants play an important role in contact processes; for example, they reduce friction and cool the contact zone. To gain better understanding of the influence of lubrication on the nanoscale, both dry and lubricated scratching processes in a model system are compared in the present work using molecular dynamics simulations. The entire range between total dewetting and total wetting is investigated by tuning the solid–fluid interaction energy. The investigated scratching process consists of three sequential movements: A cylindrical indenter penetrates an initially flat substrate, then scratches in the lateral direction, and is finally retracted out of the contact with the substrate. The indenter is fully submersed in the fluid in the lubricated cases. The substrate, the indenter, and the fluid are described by suitably parametrized Lennard–Jones model potentials. The presence of the lubricant is found to have a significant influence on the friction and on the energy balance of the process. The thermodynamic properties of the lubricant are evaluated in detail. A correlation of the simulation results for the profiles of the temperature, density, and pressure of the fluid in the vicinity of the chip is developed. The work done by the indenter is found to mainly dissipate and thereby heat up the substrate and eventually the fluid. Only a minor part of the work causes plastic deformation of the substrate.

Viewpoint

1978 ◽  
Vol 3 (4) ◽  
pp. 2-4 ◽  
Author(s):  
David L. Cheetham
Keyword(s):  
Information Seeking ◽  
Educational Institution ◽  
Open Approach ◽  
Stock Selection ◽  
Recent Conference ◽  
Eyes Open ◽  
Minor Part ◽  
Information Work ◽  
A Minor ◽  
Work Done

At the recent conference on ‘user education’ it struck me that there was a tendency in librarianship as a whole to see courses of instruction in isolation and to look upon this work done by the librarian as the sole teaching that he or she does. I come from an average Polytechnic and run fairly conventional, even orthodox, formal courses on library use linked with a rather bureaucratic compulsory library tutoring system for dissertations.Seen in isolation such courses can be given an exaggerated importance when they are, in fact, only a minor part of the process. Supporting and acting as a vital example to such tuition is everything from an initial orientation tour through to information work, to literature guides, to stock selection and relegation policies, indeed the whole library. The long term objective of a Polytechnic Library must be about introducing and promoting an ‘eyes open’ approach to information-seeking in the real world beyond the educational institution. The question that should be asked is, “Is the Polytechnic Library as a whole conceived in such a way as to be as relevant as possible to its prime objective of educating its users — or is it there because-it is there?”

An Atomistic Simulation Study of the Role of Asperities and Indentations on Heterogeneous Bubble Nucleation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Brian R. Novak ◽  
Edward J. Maginn ◽  
Mark J. McCready
Keyword(s):  
Heat Flux ◽  
Atomistic Simulation ◽  
Surface Defects ◽  
Constant Heat Flux ◽  
Bubble Nucleation ◽  
Nonequilibrium Molecular Dynamics ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
Fluid Interaction

Heterogeneous bubble nucleation was studied on surfaces having nanometer scale asperities and indentations as well as different surface-fluid interaction energies. Nonequilibrium molecular dynamics simulations at constant normal stress and either temperature or heat flux were carried out for the Lennard–Jones fluid in contact with a Lennard–Jones solid. When surface defects were of the same size or smaller than the estimated critical nucleus (the smallest nucleus whose growth is energetically favored) size of 1000–2000Å3, there was no difference between the defected surfaces and atomically smooth surfaces. On the other hand, surfaces with significantly larger indentations had nucleation rates that were about two orders of magnitude higher than the systems with small defects. Moreover, nucleation was localized in the large indentations. This localization was greatest under constant heat flux conditions and when the solid-fluid interactions were weak. The results suggest strategies for enhancing heterogeneous bubble nucleation rates as well as for controlling the location of nucleation events.

scholarly journals Photosynthetic Surges in Coffee Seedlings

1969 ◽  
Vol 43 (1) ◽  
pp. 50-55 ◽  
Author(s):  
John P. Decker ◽  
Marco A. Tió
Keyword(s):  
Dry Weight ◽  
Dark Light ◽  
Weight Increment ◽  
Minor Part ◽  
Coffee Plants ◽  
A Minor ◽  
Work Done

This paper presents the results of a study in which leaves of coffee plants were submitted to repeated light-dark-light cycles, to observe their effects on respiration and photosynthesis. The results suggest that most of the photosynthetic work done by a leaf is immediately cancelled by photorespiration and, consequently, only a minor part remains as net gain or dry-weight increment.

scholarly journals Thermal, Caloric and Transport Properties of the Lennard–Jones Truncated and Shifted Fluid in the Adsorbed Layers at Dispersive Solid Walls

2021 ◽  
Author(s):  
Martin P. Lautenschläger ◽  
Hans Hasse
Keyword(s):  
Adsorbed Layer ◽  
Jones Potential ◽  
Self Diffusion ◽  
Lennard Jones ◽  
Adsorbed Layers ◽  
Fluid Properties ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Fluid Interaction ◽  
Solid Walls

Fluid properties change when the fluid is adsorbed at a wall. The effect of the adsorption on the fluid properties was studied here by molecular simulation. There is much previous work in this field on fluids in nanochannels that are so small that the adsorbed layers on both walls interfere. In this work, the channel width was so large that the adsorbed layers did not interfere, such that information on the adsorbed layer on single walls was obtained and average values of thermodynamic properties of the fluid in that layer were determined. The studied fluid properties are: pressure p, density ρ, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, thermal conductivity λ, shear viscosity η and self-diffusion coefficient D. For the study, non-equilibrium molecular dynamics simulations were carried out. The fluid and the solid were modelled with the Lennard–Jones potential truncated and shifted at r∗c=2.5σ. The overall density of the fluid was ρ¯=0.8. The overall temperature and the solid–fluid interaction were varied. The corresponding bulk states are liquid or supercritical. The results for the fluid properties in the adsorbed layer were compared to the corresponding bulk values and the deviations are generally below 15%.

THE ROLE OF ANTHROPONYMS IN THE SEMANTIC FIELD OF ARTISTIC WORKS

2019 ◽  
Vol 2019 (29) ◽  
pp. 66-77
Author(s):  
Lidiya Derbenyova
Keyword(s):  
Literary Work ◽  
Main Theme ◽  
Semantic Field ◽  
New Meanings ◽  
Minor Part ◽  
The One ◽  
A Minor ◽  
And Storage ◽  
Horizon Of Expectations

The article explores the role of antropoetonyms in the reader’s “horizon of expectation” formation. As a kind of “text in the text”, antropoetonyms are concentrating a large amount of information on a minor part of the text, reflecting the main theme of the work. As a “text” this class of poetonyms performs a number of functions: transmission and storage of information, generation of new meanings, the function of “cultural memory”, which explains the readers’ “horizon of expectations”. In analyzing the context of the literary work we should consider the function of antropoetonyms in vertical context (the link between artistic and other texts, and the groundwork system of culture), as well as in the context of the horizontal one (times’ connection realized in the communication chain from the word to the text; the author’s intention). In this aspect, the role of antropoetonyms in the structure of the literary text is extremely significant because antropoetonyms convey an associative nature, generating a complex mechanism of allusions. It’s an open fact that they always transmit information about the preceding text and suggest a double decoding. On the one hand, the recipient decodes this information, on the other – accepts this as a sort of hidden, “secret” sense.

Electrostatic effects on ionization equilibria: An MNDO study of proton and hydrogen transfer reactions of 4-fluorobutylamine

1990 ◽  
Vol 55 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Zdeněk Friedl ◽  
Stanislav Böhm
Keyword(s):  
Hydrogen Transfer ◽  
Substituent Effects ◽  
Radical Cations ◽  
Transfer Reactions ◽  
Protonated Forms ◽  
Minor Part ◽  
Bond Strengths ◽  
Ionization Equilibria ◽  
A Minor ◽  
Gas Phase Basicities

The relative enthalpies of proton transfer δ ΔH0and homolytic bond strengths δDH0(B-H+) were calculated by the MNDO method for the sp and ap conformers of 4-flurobutylamine. The data obtained, along with the experimental gas phase basicities, are compared with the values predicted by the electrostatic theory. It is shown that the substituent polar effects FD on the basicities of amines are predominantly due to interactions in their protonated forms (X-B-H+) and/or radical-cations (X-B+.), those in the neutral species (X-B) playing a minor part. A contribution, which is considerably more significant in the sp conformer than in the ap conformer, arises probably also from substituent effects on the homolytic bond strength DH0(B-H+.

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

scholarly journals Sweet taste of heavy water

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Natalie Ben Abu ◽  
Philip E. Mason ◽  
Hadar Klein ◽  
Nitzan Dubovski ◽  
Yaron Ben Shoshan-Galeczki ◽  
...  
Keyword(s):  
Heavy Water ◽  
Calcium Release ◽  
Homology Modelling ◽  
Taste Receptor ◽  
Chemical Properties ◽  
Sweet Taste ◽  
Minor Effect ◽  
Dynamics Simulations ◽  
A Minor ◽  
Physical And Chemical

AbstractHydrogen to deuterium isotopic substitution has only a minor effect on physical and chemical properties of water and, as such, is not supposed to influence its neutral taste. Here we conclusively demonstrate that humans are, nevertheless, able to distinguish D2O from H2O by taste. Indeed, highly purified heavy water has a distinctly sweeter taste than same-purity normal water and can add to perceived sweetness of sweeteners. In contrast, mice do not prefer D2O over H2O, indicating that they are not likely to perceive heavy water as sweet. HEK 293T cells transfected with the TAS1R2/TAS1R3 heterodimer and chimeric G-proteins are activated by D2O but not by H2O. Lactisole, which is a known sweetness inhibitor acting via the TAS1R3 monomer of the TAS1R2/TAS1R3, suppresses the sweetness of D2O in human sensory tests, as well as the calcium release elicited by D2O in sweet taste receptor-expressing cells. The present multifaceted experimental study, complemented by homology modelling and molecular dynamics simulations, resolves a long-standing controversy about the taste of heavy water, shows that its sweet taste is mediated by the human TAS1R2/TAS1R3 taste receptor, and opens way to future studies of the detailed mechanism of action.

scholarly journals Pervasive cooperative mutational effects on multiple catalytic enzyme traits emerge via long-range conformational dynamics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Carlos G. Acevedo-Rocha ◽  
Aitao Li ◽  
Lorenzo D’Amore ◽  
Sabrina Hoebenreich ◽  
Joaquin Sanchis ◽  
...  
Keyword(s):  
Long Range ◽  
Fitness Landscape ◽  
Conformational Dynamics ◽  
P450 Monooxygenase ◽  
Access Channel ◽  
Long Range Interactions ◽  
Limited Protein ◽  
Dynamics Simulations ◽  
The Relationship ◽  
Single Enzyme

AbstractMultidimensional fitness landscapes provide insights into the molecular basis of laboratory and natural evolution. To date, such efforts usually focus on limited protein families and a single enzyme trait, with little concern about the relationship between protein epistasis and conformational dynamics. Here, we report a multiparametric fitness landscape for a cytochrome P450 monooxygenase that was engineered for the regio- and stereoselective hydroxylation of a steroid. We develop a computational program to automatically quantify non-additive effects among all possible mutational pathways, finding pervasive cooperative signs and magnitude epistasis on multiple catalytic traits. By using quantum mechanics and molecular dynamics simulations, we show that these effects are modulated by long-range interactions in loops, helices and β-strands that gate the substrate access channel allowing for optimal catalysis. Our work highlights the importance of conformational dynamics on epistasis in an enzyme involved in secondary metabolism and offers insights for engineering P450s.

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