Elemental Interfaces and Displacive Phase Transformations

2008 ◽  
Vol 59 ◽  
pp. 63-68
Author(s):  
Václav Paidar
Keyword(s):  
Phase Transformations ◽  
Structural Changes ◽  
Atomic Plane ◽  
Many Body ◽  
Single Plane ◽  
Atomistic Models ◽  
Shear Type ◽  
Hcp Structure ◽  
The Many

Two basic processes, namely shear and shuffling of atomic planes can be considered as elementary mechanisms of displacive phase transformations. The atomistic models suitable to investigate the role of interfaces in the structural changes are tested. The many-body potentials are used for the description of interatomic forces. General displacements of atomic planes are examined, i.e. γ-surface type calculations extensively used for stacking fault and lattice dislocation analysis are applied to single plane shuffling and alternate shuffling of every other atomic plane producing in combination with homogeneous deformation the hcp structure. Similar approach considering shear type planar displacements leads to the Zener path between the bcc and fcc lattices. The effect of additional deformation required to obtain the close-packed atomic arrangements is analysed.

Displacive Phase Transformations

2009 ◽  
Vol 150 ◽  
pp. 159-174 ◽  
Author(s):  
Václav Paidar ◽  
Andriy Ostapovets
Keyword(s):  
Phase Transformations ◽  
Atomic Plane ◽  
Many Body ◽  
Surface Type ◽  
Single Plane ◽  
Bcc Structure ◽  
Shear Type ◽  
Structural Configurations ◽  
Hcp Structure

Shear deformation and shuffling of atomic planes are elementary mechanisms of collective atomic motion that take place during displacive phase transformations. General displacements of atomic planes are examined, i.e. -surface type calculations extensively used for the stacking faults and crystal dislocations are applied to single plane shuffling and alternate shuffling of every other atomic plane producing in combination with homogeneous deformation the hcp structure (martensitic type) from the initial bcc structure (austenitic type). Similar approach considering shear type planar displacements leads to the Zener path between the bcc and fcc lattices. The effect of additional deformation required to obtain the close-packed atomic arrangements is examined as well. Finally, the influence of volume modification on phase transitions is investigated. The energies of various structural configurations are calculated using many-body potentials for the description of interatomic forces. Such atomic models are tested to check their suitability for investigation of the role of interfaces in the displacive structural transitions.

scholarly journals Entangling Lattice-Trapped Bosons with a Free Impurity: Impact on Stationary and Dynamical Properties

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 290
Author(s):  
Maxim Pyzh ◽  
Kevin Keiler ◽  
Simeon I. Mistakidis ◽  
Peter Schmelcher
Keyword(s):  
Structural Changes ◽  
Many Body ◽  
Wide Range ◽  
Entropy Measures ◽  
Particle Level ◽  
The Many ◽  
The One ◽  
Tunneling Dynamics ◽  
The Individual ◽  
Trapped Bosons

We address the interplay of few lattice trapped bosons interacting with an impurity atom in a box potential. For the ground state, a classification is performed based on the fidelity allowing to quantify the susceptibility of the composite system to structural changes due to the intercomponent coupling. We analyze the overall response at the many-body level and contrast it to the single-particle level. By inspecting different entropy measures we capture the degree of entanglement and intraspecies correlations for a wide range of intra- and intercomponent interactions and lattice depths. We also spatially resolve the imprint of the entanglement on the one- and two-body density distributions showcasing that it accelerates the phase separation process or acts against spatial localization for repulsive and attractive intercomponent interactions, respectively. The many-body effects on the tunneling dynamics of the individual components, resulting from their counterflow, are also discussed. The tunneling period of the impurity is very sensitive to the value of the impurity-medium coupling due to its effective dressing by the few-body medium. Our work provides implications for engineering localized structures in correlated impurity settings using species selective optical potentials.

Role of the second nearest-neighbor hoppings in a disordered Bose–Hubbard Hamiltonian in the Many-Body Localization

2020 ◽  
Vol 93 (9) ◽  
Author(s):  
Edith Djoukouo Ngueyounou ◽  
Kanabet Yapara ◽  
Celsus Bouri ◽  
Hugues Merlain Tetchou Nganso ◽  
Moïse Godfroy Kwato Njock
Keyword(s):  
Nearest Neighbor ◽  
Many Body ◽  
Hubbard Hamiltonian ◽  
The Many

scholarly journals Interatomic Forces and Bonding Mechanisms in MgO Clusters

1990 ◽  
Vol 193 ◽  
Author(s):  
Nancy F. Wright ◽  
Gayle S. Painter
Keyword(s):  
Interatomic Potentials ◽  
Many Body ◽  
Restoring Force ◽  
Mechanical Study ◽  
Quantum Mechanical Study ◽  
Force Curves ◽  
The Many ◽  
Quantum Treatment ◽  
Oxygen Ratio

ABSTRACTWe report results from a first-principles local spin density quantum mechanical study of the energetics and elastic properties of a series of magnesium-oxygen clusters of various morphologies. The role of quantum effects, e.g. covalency, in the bonding character of diatomic MgO is determined by comparison of classical and quantum restoring force curves. The dependence of binding properties on geometry and metal to oxygen ratio is determined by comparison of binding energy curves for a series of clusters. Results show that while gross features of the binding curves may be represented by simple interatomic potentials, details require the many body corrections of a full quantum treatment.

Role of the valence-band mass on the many-body optical properties of a two-dimensional electron gas

1998 ◽  
Vol 249-251 ◽  
pp. 603-606
Author(s):  
H.P van der Meulen ◽  
J Rubio ◽  
J.M Calleja ◽  
C Tejedor ◽  
F Rodriguez ◽  
...  
Keyword(s):  
Optical Properties ◽  
Valence Band ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Many Body ◽  
Two Dimensional Electron Gas ◽  
Dimensional Electron Gas ◽  
The Many

scholarly journals Mechanisms of transcriptional regulation of ecdysone response

2019 ◽  
Vol 23 (2) ◽  
pp. 212-218 ◽  
Author(s):  
M. Yu. Mazina ◽  
N. E. Vorobyeva
Keyword(s):  
Salivary Glands ◽  
Structural Changes ◽  
Gene Activation ◽  
Regulatory Elements ◽  
Cell Type Specificity ◽  
Excellent Description ◽  
The Many ◽  
General Aspects ◽  
Available Information

The mechanisms of ecdysone-dependent expression have been studied for many decades. Initially, the activation of individual genes under the influence of ecdysone was studied on the model of polythene chromosomes from salivary glands of Drosophila melanogaster. These works helped to investigate the many aspects of the Drosophila development. They also revealed plenty of valuable information regarding the fundamental mechanisms controlling the genes’ work. Many years ago, a model describing the process of gene activation by ecdysone, named after the author – Ashburner model – was proposed. This model is still considered an excellent description of the ecdysone cascade, which is implemented in the salivary glands during the formation of the Drosophila pupa. However, these days there is an opinion that the response of cells to the hormone ecdysone can develop with significant differences, depending on the type of cells. The same genes can be activated or repressed under the influence of ecdysone in different tissues. Likely, certain DNA-binding transcription factors that are involved in the ecdysonedependent response together with the EcR/Usp heterodimer are responsible for cell-type specificity. A number of transcriptional regulators involved in the ecdysone response have been described. Among them are several complexes responsible for chromatin remodeling and modification. It has been shown by various methods that ecdysone-dependent activation/repression of gene transcription develops with significant structural changes of chromatin on regulatory elements. The description of the molecular mechanism of this process, in particular, the role of individual proteins in it, as well as structural interactions between various regulatory elements is a matter of the future. This review is aimed to discuss the available information regarding the main regulators that interact with the ecdysone receptor. We provide a brief description of the regulator’s participation in the ecdysone response and links to the corresponding study. We also discuss general aspects of the mechanism of ecdysone-dependent regulation and highlight the most promising points for further research.

On Future Directions in Pathology

1982 ◽  
Vol 40 ◽  
pp. 274-277
Author(s):  
Benjamin F. Trump ◽  
Irene K. Berezesky ◽  
Raymond T. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Clinical Pathology ◽  
Future Directions ◽  
Diagnostic Pathology ◽  
The Past ◽  
Transmission Electron ◽  
Organ Systems ◽  
The Many

The role of electron microscopy and associated techniques is assured in diagnostic pathology. At the present time, most of the progress has been made on tissues examined by transmission electron microscopy (TEM) and correlated with light microscopy (LM) and by cytochemistry using both plastic and paraffin-embedded materials. As mentioned elsewhere in this symposium, this has revolutionized many fields of pathology including diagnostic, anatomic and clinical pathology. It began with the kidney; however, it has now been extended to most other organ systems and to tumor diagnosis in general. The results of the past few years tend to indicate the future directions and needs of this expanding field. Now, in addition to routine EM, pathologists have access to the many newly developed methods and instruments mentioned below which should aid considerably not only in diagnostic pathology but in investigative pathology as well.

A Transmission Electron Microscopical Investigation of Phase Transformations in TiNi

1980 ◽  
Vol 38 ◽  
pp. 340-341
Author(s):  
P. Moine ◽  
G. M. Michal ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Applied Stress ◽  
Structural Changes ◽  
Microscopical Investigation ◽  
Temperature Range ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Diffraction Effects ◽  
Microscopy Images

Premartensitic effects in near equiatomic TiNi have been pointed out by several authors(1-5). These include anomalous contrast in electron microscopy images (mottling, striations, etc. ),diffraction effects(diffuse streaks, extra reflections, etc.), a resistivity peak above Ms (temperature at which a perceptible amount of martensite is formed without applied stress). However the structural changes occuring in this temperature range are not well understood. The purpose of this study is to clarify these phenomena.

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