scholarly journals Director Deformations, Geometric Frustration, and Modulated Phases in Liquid Crystals

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Jonathan V. Selinger
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Local Structure ◽  
Spontaneous Order ◽  
Annual Review ◽  
Publication Date ◽  
Unified Framework ◽  
Geometric Frustration ◽  
Modulated Phases ◽  
The Ideal

This article analyzes modulated phases in liquid crystals, from the long-established cholesteric and blue phases to the recently discovered twist-bend, splay-bend, and splay nematic phases, as well as the twist-grain-boundary (TGB) and helical nanofilament variations on smectic phases. The analysis uses the concept of four fundamental modes of director deformation: twist, bend, splay, and a fourth mode related to saddle-splay. Each mode is coupled to a specific type of molecular order: chirality, polarization perpendicular and parallel to the director, and octupolar order. When the liquid crystal develops one type of spontaneous order, the ideal local structure becomes nonuniform, with the corresponding director deformation. In general, the ideal local structure is frustrated; it cannot fill space. As a result, the liquid crystal must form a complex global phase, which may have a combination of deformation modes, and may have a periodic array of defects. Thus, the concept of an ideal local structure under geometric frustration provides a unified framework to understand the wide variety of modulated phases. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Young Children's Interactions with Objects: Play as Practice and Practice as Play

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Jeffrey J. Lockman ◽  
Catherine S. Tamis-LeMonda
Keyword(s):  
Developmental Psychology ◽  
The Self ◽  
Annual Review ◽  
Publication Date ◽  
Unified Framework ◽  
Manual Skill ◽  
Immense Potential ◽  
New Framework ◽  
Imagined Interactions ◽  
Play Development

Objects permeate human culture and saturate the imagination. This duality offers both opportunity and challenge. Here we ask how young human children learn to exploit the immense potential afforded by objects that can exist simultaneously in physical and imaginary realms. To this end, we advance a new framework that integrates the presently siloed literatures on manual skill and play development. We argue that developments in children's real and imagined use of objects are embodied, reciprocal, and intertwined. Advances in one plane of action influence and scaffold advances in the other. Consistent with this unified framework, we show how real and imagined interactions with objects are characterized by developmental parallels in how children ( a) transcend the present to encompass future points in time and space, ( b) extend beyond the self, and ( c) gradually move beyond objects’ designed functions. In addition, we highlight bidirectional influences in children's real and imagined interactions with objects: Play engenders practice and skill in using objects, but just the same, practice using objects engenders advances in play. We close by highlighting the theoretical, empirical, and translational implications of this embodied and integrated account of manual skill and play development. Expected final online publication date for the Annual Review of Developmental Psychology, Volume 3 is December 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Photonics and lasing in liquid crystal materials

2006 ◽  
Vol 364 (1847) ◽  
pp. 2747-2761 ◽  
Author(s):  
Peter Palffy-Muhoray ◽  
Wenyi Cao ◽  
Michele Moreira ◽  
Bahman Taheri ◽  
Antonio Munoz
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Photonic Band Gap ◽  
Stop Band ◽  
Soft Materials ◽  
Modulated Phases ◽  
Photonic Band Gap Materials ◽  
Liquid Crystal Elastomers ◽  
Photon States ◽  
Liquid Crystal Materials

Owing to fundamental reasons of symmetry, liquid crystals are soft materials. This softness allows long length-scales, large susceptibilities and the existence of modulated phases, which respond readily to external fields. Liquid crystals with such phases are tunable, self-assembled, photonic band gap materials; they offer exciting opportunities both in basic science and in technology. Since the density of photon states is suppressed in the stop band and is enhanced at the band edges, these materials may be used as switchable filters or as mirrorless lasers. Disordered periodic liquid crystal structures can show random lasing. We highlight recent advances in this rapidly growing area, and discuss future prospects in emerging liquid crystal materials. Liquid crystal elastomers and orientationally ordered nanoparticle assemblies are of particular interest.

scholarly journals Standardized Reference Diets for Zebrafish: Addressing Nutritional Control in Experimental Methodology

2021 ◽  
Vol 41 (1) ◽  
Author(s):  
Stephen A. Watts ◽  
Louis R. D'Abramo
Keyword(s):  
Research Community ◽  
Experimental Methodology ◽  
Biomedical Science ◽  
Specific Reference ◽  
Annual Review ◽  
Publication Date ◽  
Short Term ◽  
Specific Knowledge ◽  
Species Specific ◽  
The Ideal

The ideal of experimental methodology in animal research is the reduction or elimination of environmental variables or consistency in their application. In lab animals, diet has been recognized as a very influential response variable. Reproducibility in research using rodents required the development of a unique diet of consistent ingredient and nutrient composition to allow for cross-comparisons of lab results, spatially and temporally. These diets are commonly referred to as standard reference diets (SRDs). The established validity of published nutritional requirements combined with the cooperation of commercial partners led to species-specific reference diets commonly used by the research community. During the last several decades, zebrafish ( Danio rerio) have become a widespread alternative animal model, but specific knowledge of their nutrition is lacking. We present a short-term approach for developing an SRD for zebrafish, similar to that eventually attained for rodents over decades. Imminent development of an open-formulation, commercially produced SRD for zebrafish will notably advance translational biomedical science. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

scholarly journals Liquid Crystal Devices for Beam Steering Applications

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 247
Author(s):  
Rowan Morris ◽  
Cliff Jones ◽  
Mamatha Nagaraj
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Adaptive Optics ◽  
Beam Steering ◽  
Optical Components ◽  
Advantages And Disadvantages ◽  
Liquid Crystal Devices

Liquid crystals are valuable materials for applications in beam steering devices. In this paper, an overview of the use of liquid crystals in the field of adaptive optics specifically for beam steering and lensing devices is presented. The paper introduces the properties of liquid crystals that have made them useful in this field followed by a more detailed discussion of specific liquid crystal devices that act as switchable optical components of refractive and diffractive types. The relative advantages and disadvantages of the different devices and techniques are summarised.

scholarly journals Optical Response Associated with the Orientation and Structure of Liquid Crystals with Respect to Phosphatidylcholine Concentration

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 678
Author(s):  
Yuqi Han ◽  
Yan Jiang ◽  
Wei Guo ◽  
Bing Li ◽  
Lu Zhang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Reflectance Spectrum ◽  
Optical Response ◽  
The Self ◽  
Cholesteric Liquid Crystals ◽  
Anchoring Effect ◽  
Self Assembling ◽  
Sensitization Effect ◽  
Structure Of Liquid

Based on the anchoring effect due to the self-assembling behavior of the phospholipid molecules at the interface between the liquid crystal and water phases on the orientation of liquid crystals, the optical response associated with the orientation and structure of liquid crystals with respect to the concentration of 1,2-didodecanoyl-sn-glycero-3-phosphocholine solution has been investigated. The optical response owing to changes in the orientation and structure of the mixed cholesteric liquid crystals with respect to the change in the concentration of phosphatidylcholine has been obtained. Moreover, the feasibility of using as-prepared mixed cholesteric liquid crystals to measure the phosphatidylcholine concentration has been verified. A methodology to measure the reflectance spectrum by using mixed cholesteric liquid crystals to sensitize the phosphatidylcholine concentration has been further realized. The sensitization effect of the mixed cholesteric liquid crystals on the measurement of phosphatidylcholine concentration was also verified.

scholarly journals Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 908
Author(s):  
Fabrizio Ciciulla ◽  
Annamaria Zaltron ◽  
Riccardo Zamboni ◽  
Cinzia Sada ◽  
Francesco Simoni ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Lithium Niobate ◽  
Photovoltaic Effect ◽  
Optical Control ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Threshold Behaviour ◽  
All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

scholarly journals Color Response Modification of Encapsulated Liquid Crystals Used in Rotating Disk Heat Transfer Studies

1995 ◽  
Author(s):  
Cengiz Camci ◽  
Boris Glezer
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Rotational Speed ◽  
Rotating Disk ◽  
Point Of View ◽  
Centrifugal Acceleration ◽  
Relative Shift ◽  
Color Response ◽  
Stationary Conditions

The liquid crystal thermography can be successfully used in both transient and steady-state heat transfer experiments with excellent spatial resolution and good accuracy. Although most of the past liquid crystal based heat transfer studies are reported in the stationary frame, measurements from the rotating frame of turbomachinery systems exist The main objective of the present investigation is to determine the influence of rotation on the color calibration of encapsulated liquid crystals sprayed on the flat surface of a rotating aluminum disk. The investigation is performed for a rotational speed range from 0 rpm to 7500 rpm using three different liquid crystal coatings displaying red at 30, 35 and 45° C, under stationary conditions. An immediate observation from the present study is that the color response of liquid crystals is strongly modified by the centrifugal acceleration of the rotating environment. It is consistently and repeatedly observed that the hue versus temperature curve is continuously shifted toward lower temperatures by increasing rotational speed. The relative shift of the display temperature of the green can be as high as 7°C at 7500 rpm when compared to the temperature of the green observed under stationary conditions. The present study shows that relative shift of the liquid crystal color has a well-defined functional dependency to rotational speed. The shift is linearly proportional to the centrifugal acceleration. It is interesting to note that the individual shift curves of the green for all three liquid crystal coatings collapse into a single curve when they are normalized with respect to their own stationary green values. When the color attribute is selected as “intensity” instead of “hue”, very similar shifts of the temperature corresponding to the intensity maximum value appearing around green is observed. An interpretation of the observed color shift is made from a thermodynamics energy balance point of view.

Endogenous Retroviruses Drive Resistance and Promotion of Exogenous Retroviral Homologs

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Elliott S. Chiu ◽  
Sue VandeWoude
Keyword(s):  
Immune Modulation ◽  
Viral Infections ◽  
Viral Evolution ◽  
Endogenous Retroviruses ◽  
Annual Review ◽  
Publication Date ◽  
Biological Functions ◽  
Self Tolerance ◽  
Vertebrate Hosts ◽  
Insight Into

Endogenous retroviruses (ERVs) serve as markers of ancient viral infections and provide invaluable insight into host and viral evolution. ERVs have been exapted to assist in performing basic biological functions, including placentation, immune modulation, and oncogenesis. A subset of ERVs share high nucleotide similarity to circulating horizontally transmitted exogenous retrovirus (XRV) progenitors. In these cases, ERV–XRV interactions have been documented and include ( a) recombination to result in ERV–XRV chimeras, ( b) ERV induction of immune self-tolerance to XRV antigens, ( c) ERV antigen interference with XRV receptor binding, and ( d) interactions resulting in both enhancement and restriction of XRV infections. Whereas the mechanisms governing recombination and immune self-tolerance have been partially determined, enhancement and restriction of XRV infection are virus specific and only partially understood. This review summarizes interactions between six unique ERV–XRV pairs, highlighting important ERV biological functions and potential evolutionary histories in vertebrate hosts. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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