Polar structure of N,N′-dimethylurea crystals

1997 ◽  
Vol 27 (6) ◽  
pp. 367-369 ◽  
Author(s):  
J. Pérez-Folch ◽  
J. A. Subirana ◽  
J. Aymami
Keyword(s):  
Polar Structure

Polar structure in a ferroelectric bent-core mesogen as studied by second-harmonic generation

2002 ◽  
Vol 66 (2) ◽  
Author(s):  
Fumito Araoka ◽  
Jirakorn Thisayukta ◽  
Ken Ishikawa ◽  
Junji Watanabe ◽  
Hideo Takezoe
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Polar Structure

Design and Analysis of Junctionless FinFET with Gaussian Doped for Non-polar Structure

Silicon ◽  
2022 ◽  
Author(s):  
E. Sathish Kumar ◽  
Suresh Kumar P ◽  
N. Arun Vignesh ◽  
S. Kanithan
Keyword(s):  
Polar Structure

Mechanical Neural Growth Models

2005 ◽  
Author(s):  
Kathleen B. Allen ◽  
Bradley E. Layton
Keyword(s):  
De Novo ◽  
Mechanical Load ◽  
Growth Models ◽  
Growth Patterns ◽  
Polar Structure ◽  
Structural Support ◽  
Inner Surface ◽  
Neural Growth ◽  
Free Environment ◽  
Β Tubulin

Critical to being able to control the growth patterns of cell-based sensors is being able to understand how the cytoskeleton of the cell maintains its structure and integrity both under mechanical load and in a load-free environment. Our approach to a better understanding of cell growth is to use a computer simulation that incorporates the primary structures, microtubules, necessary for growth along with their observed behaviors and experimentally determined mechanical properties. Microtubules are the main compressive structural support elements for the axon of a neuron and are created via polymerization of α-β tubulin dimers. Our de novo simulation explores the mechanics of the forces between microtubules and the membrane. We hypothesize that axonal growth is most influenced by the location and direction of the force exerted by the microtubule on the membrane, and furthermore that the interplay of forces between microtubules and the inner surface of the cell membrane dictates the polar structure of axons. The simulation will be used to understand cytoskeletal mechanics for the purpose of engineering cells to be used as sensors.

Polar Structure Formation in Solid Solution of Strontium-Substituted Fluorapatite–Gelatin Composites: From Structural and Morphogenetic Aspects to Pyroelectric Properties

2020 ◽  
Vol 32 (19) ◽  
pp. 8619-8632
Author(s):  
Jennifer Knaus ◽  
Martin Sommer ◽  
Patrick Duchstein ◽  
Roman Gumeniuk ◽  
Lev Akselrud ◽  
...  
Keyword(s):  
Solid Solution ◽  
Structure Formation ◽  
Pyroelectric Properties ◽  
Polar Structure

scholarly journals Directed synthesis of a hybrid improper magnetoelectric multiferroic material

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tong Zhu ◽  
Fabio Orlandi ◽  
Pascal Manuel ◽  
Alexandra S. Gibbs ◽  
Weiguo Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Magnetic Moment ◽  
Ferroelectric Material ◽  
Polar Phase ◽  
Antiferromagnetic State ◽  
Exchange Reactions ◽  
Polar Structure ◽  
Directed Synthesis ◽  
Atom Displacement ◽  
Spontaneous Magnetic Moment

AbstractPreparing materials which simultaneously exhibit spontaneous magnetic and electrical polarisations is challenging as the electronic features which are typically used to stabilise each of these two polarisations in materials are contradictory. Here we show that by performing low-temperature cation-exchange reactions on a hybrid improper ferroelectric material, Li2SrTa2O7, which adopts a polar structure due to a cooperative tilting of its constituent TaO6 octahedra rather than an electronically driven atom displacement, a paramagnetic polar phase, MnSrTa2O7, can be prepared. On cooling below 43 K the Mn2+ centres in MnSrTa2O7 adopt a canted antiferromagnetic state, with a small spontaneous magnetic moment. On further cooling to 38 K there is a further transition in which the size of the ferromagnetic moment increases coincident with a decrease in magnitude of the polar distortion, consistent with a coupling between the two polarisations.

High-temperature structural evolution of hexagonal multiferroic YMnO3and YbMnO3

2007 ◽  
Vol 40 (4) ◽  
pp. 730-734 ◽  
Author(s):  
Il-Kyoung Jeong ◽  
N. Hur ◽  
Th. Proffen
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Structural Parameters ◽  
Structural Evolution ◽  
Neutron Powder Diffraction ◽  
Temperature Behaviour ◽  
Rietveld Refinements ◽  
Polar Structure ◽  
Diffraction Patterns

Neutron powder diffraction studies on the structural evolution of hexagonal multiferroic YMnO3and YbMnO3from 1000 K to 1400 K, and from 1000 K to 1350 K, respectively, are presented. The temperature evolution of diffraction patterns suggests that YMnO3undergoes a phase transition to a non-polar structure above 1200 K, while YbMnO3remains ferroelectric up to 1350 K. Detailed structural parameters were obtained as a function of temperature from Rietveld refinements. Based on this result, the distinct differences in temperature behaviour between YMnO3and YbMnO3, and the origin of the ferroelectricity in these hexagonal multiferroics are discussed.

Investigation of the Cs x Rb1−x TiOAsO4 Series. II. The Problems of Interpretation of Residual Electron Densities in a Polar Space Group

1998 ◽  
Vol 54 (5) ◽  
pp. 645-651 ◽  
Author(s):  
P. A. Thomas ◽  
M. N. Womersley
Keyword(s):  
Electron Density ◽  
Polar Space ◽  
Worst Case ◽  
Polar Structure ◽  
Space Group ◽  
Disordered Structure ◽  
Strong Inversion ◽  
Residual Electron Density ◽  
Optical Crystal ◽  
True Structure

The problems of refinements of structures in a polar space group, such as Pna21, are illustrated by the example of crystals in the Cs2x Rb2−2x Ti2O2As2O8, caesium rubidium titanyl arsenate, series, which are isostructural with the well known non-linear optical crystal KTiOPO4. It is shown in particular that errors in the data collection and/or refinement tend to contribute positive residual electron density in sites which are related by an inversion operation to the real Cs/Rb sites. This phenomenon is a consequence of the presence of two minima in least-squares space, representing here the possible coordinate sets x,y,z and x,y,−z, for a polar structure and is exacerbated in these structures by the presence of strong inversion psuedo-symmetry. It is shown that in the worst case, the positive residual electron density can be eliminated and an improved agreement to the observed data obtained by refinement of a partially micro-twinned disordered structure in which the Cs/Rb occupancy is split between the main sites and the inversion-related sites. It is argued that the true structure is micro-twinned, including partial occupancy of the additional sites.

Sign in / Sign up

Export Citation Format

Share Document