Solvent-Induced, Highly Unusual, Triangular-Shaped Organic Polar Crystal

2020 ◽  
Vol 20 (4) ◽  
pp. 2527-2534 ◽  
Author(s):  
Jia Xu ◽  
Shan Huang ◽  
Ting Cai
Keyword(s):  
Polar Crystal

The orientation of sickle hemoglobin fibers within fascicles

1988 ◽  
Vol 46 ◽  
pp. 400-401
Author(s):  
Christopher A. Miller ◽  
Bridget Carragher ◽  
William A. McDade ◽  
Robert Josephs
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Relative Orientation ◽  
Unit Cell ◽  
Red Cell ◽  
High Ph ◽  
Sickle Hemoglobin ◽  
Polar Crystal ◽  
Helical Configuration

Highly ordered bundles of deoxyhemoglobin S (HbS) fibers, termed fascicles, are intermediates in the high pH crystallization pathway of HbS. These fibers consist of 7 Wishner-Love double strands in a helical configuration. Since each double strand has a polarity, the odd number of double strands in the fiber imparts a net polarity to the structure. HbS crystals have a unit cell containing two double strands, one of each polarity, resulting in a net polarity of zero. Therefore a rearrangement of the double strands must occur to form a non-polar crystal from the polar fibers. To determine the role of fascicles as an intermediate in the crystallization pathway it is important to understand the relative orientation of fibers within fascicles. Furthermore, an understanding of fascicle structure may have implications for the design of potential sickling inhibitors, since it is bundles of fibers which cause the red cell distortion responsible for the vaso-occlusive complications characteristic of sickle cell anemia.

Selective Area Epitaxy of InGaN/GaN Stripes, Hexagonal Rings, and Triangular Rings for Achieving Green Emission

2009 ◽  
Vol 1202 ◽  
Author(s):  
Wen Feng ◽  
Vladimir Kuryatkov ◽  
Dana Rosenbladt ◽  
Nenad Stojanovic ◽  
Mahesh Pandikunta ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Green Emission ◽  
Single Type ◽  
Selective Area Epitaxy ◽  
Polar Crystal ◽  
Selective Area ◽  
Narrow Ridge ◽  
Intensity Images ◽  
Two Peaks ◽  
Surface Morphologies

AbstractWe report selective area epitaxy of InGaN/GaN micron-scale stripes and rings on patterned (0001) AlN/sapphire. The objective is to elevate indium incorporation for achieving blue and green emission on semi-polar crystal facets. In each case, GaN structures were first produced, and the InGaN quantum wells (QWs) were subsequently grown. The pyramidal InGaN/GaN stripe along the <11-20> direction has uniform CL emission at 500 nm on the smooth {1-101} sidewall and at 550 nm on the narrow ridge. In InGaN/GaN triangular rings, the structures reveal smooth inner and outer sidewall facets falling into a single type of {1-101} planes. All these {1-101} sidewall facets demonstrate similar CL spectra which appear to be the superposition of two peaks at positions 500 nm and 460 nm. Spatially matched striations are observed in the CL intensity images and surface morphologies of the {1-101} sidewall facets. InGaN/GaN hexagonal rings are comprised of {11-22} and {21-33} facets on inner sidewalls, and {1-101} facets on outer sidewalls. Distinct CL spectra with peak wavelengths as long as 500 nm are observed for these diverse sidewall facets of the hexagonal rings.

scholarly journals Stacking-engineered ferroelectricity in bilayer boron nitride

Science ◽  
2021 ◽  
pp. eabd3230
Author(s):  
Kenji Yasuda ◽  
Xirui Wang ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
Pablo Jarillo-Herrero
Keyword(s):  
Boron Nitride ◽  
Nonvolatile Memory ◽  
Rational Design ◽  
Parent Compound ◽  
High Mobility ◽  
Building Blocks ◽  
Electric Polarization ◽  
Experimental Realization ◽  
Polar Crystal ◽  
Memory Applications

2D ferroelectrics with robust polarization down to atomic thicknesses provide building blocks for functional heterostructures. Experimental realization remains challenging because of the requirement of a layered polar crystal. Here, we demonstrate a rational design approach to engineering 2D ferroelectrics from a non-ferroelectric parent compound via employing van der Waals assembly. Parallel-stacked bilayer boron nitride exhibits out-of-plane electric polarization that reverses depending on the stacking order. The polarization switching is probed via the resistance of an adjacently stacked graphene sheet. Twisting the boron nitride sheets by a small angle changes the dynamics of switching thanks to the formation of moiré ferroelectricity with staggered polarization. The ferroelectricity persists to room temperature while keeping the high mobility of graphene, paving the way for potential ultrathin nonvolatile memory applications.

Nonlinear Lock-In Infrared Microscopy: A Complementary Investigation Technique for the Analysis of Functional Electroceramic Components

2015 ◽  
Vol 21 (5) ◽  
pp. 1145-1152 ◽  
Author(s):  
Michael Hofstätter ◽  
Nadine Raidl ◽  
Bernhard Sartory ◽  
Peter Supancic
Keyword(s):  
Electrical Properties ◽  
Electron Backscatter Diffraction ◽  
Barrier Properties ◽  
Infrared Microscopy ◽  
Polar Crystal ◽  
Dependent Behavior ◽  
Electroceramic Material ◽  
Lock In ◽  
Backscatter Diffraction ◽  
Micrometer Scale

AbstractUsing lock-in infrared microscopy as a tool for current detection on the micrometer scale in AC-driven specimens in combination with iterative grinding procedure allows preparation of current dominating microstructure regions on well-polished surfaces. This technique is applied successfully on varistor components based on specially doped ZnO-based varistor ceramics. This peculiar electroceramic material exhibits exceptional high nonlinear current–voltage (I-V) characteristics, described by a power law according I~Vα, caused by double Schottky barriers at the grain boundaries. As a novelty the thermographic response is used to evaluate local electrical properties, namely the nonlinearity coefficient α, on basis of higher order harmonics with respect to the basic electrical driving AC-frequency.To correlate the observed electrical properties to the microstructure, the polar crystal orientation of the relevant ZnO grains is determined by combining electron backscatter diffraction and orientation-dependent patterns as a result of a chemical etching procedure. These findings support a modified new model for describing the grain boundary controlled current flow in a varistor microstructure including orientation-dependent barrier properties. Hence, the experimentally observed current direction-dependent behavior can be described consistently.

scholarly journals On the dynamics of polarons in the strong-coupling limit

2017 ◽  
Vol 29 (10) ◽  
pp. 1750030 ◽  
Author(s):  
Marcel Griesemer
Keyword(s):  
Strong Coupling ◽  
Longitudinal Optical ◽  
Strong Coupling Limit ◽  
Poisson System ◽  
Phonon Modes ◽  
Polar Crystal ◽  
Effective Dynamics ◽  
Optical Modes ◽  
Non Local ◽  
With Memory

The polaron model of H. Fröhlich describes an electron coupled to the quantized longitudinal optical modes of a polar crystal. In the strong-coupling limit, one expects that the phonon modes may be treated classically, which leads to a coupled Schrödinger–Poisson system with memory. For the effective dynamics of the electron, this amounts to a nonlinear and non-local Schrödinger equation. We use the Dirac–Frenkel variational principle to derive the Schrödinger–Poisson system from the Fröhlich model and we present new results on the accuracy of their solutions for describing the motion of Fröhlich polarons in the strong-coupling limit. Our main result extends to [Formula: see text]-polaron systems.

The Influence of the Phonon Dispersion and a Magnetic Field on the Self-Trapping Energy of the Polaron in a Polar Crystal

2015 ◽  
Vol 21 (1) ◽  
pp. 64-68
Author(s):  
冀文慧 JI Wen-hui ◽  
杨洪涛 YANG Hong-tao ◽  
呼和满都拉 HUHEMANDULA ◽  
胡文弢 HU Wen-tao
Keyword(s):  
Magnetic Field ◽  
Phonon Dispersion ◽  
The Self ◽  
Polar Crystal ◽  
Self Trapping
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