The Photorefractive Effect in Liquid Crystals

This chapter summarizes the state of the art of research regarding photorefractive liquid crystals. Photorefractive effect is of interest because it can be used to obtain dynamic holograms, based on interference between dual laser beams within a liquid crystal to generate a refractive index grating. This technique can be employed in numerous diffraction optics applications, such as optical amplifiers, phase-conjugate wave generators, 3D displays, novelty filters, and optical tomography. The photorefractive effect in liquid crystals is especially pronounced, and both ferroelectric and nematic liquid crystals have been researched for this purpose, with the former showing special promise in practical applications. As an example, ferroelectric liquid crystals have been found to readily produce a refractive index grating in conjunction with a significant gain and a formation time of 900 ms

The whole blood transcriptional regulation landscape in 465 COVID-19 infected samples from Japan COVID-19 Task Force

「コロナ制圧タスクフォース」COVID-19患者由来の血液細胞における遺伝子発現の網羅的解析 --重症度に応じた遺伝子発現の変化には、ヒトゲノム配列の個人差が影響する--. 京都大学プレスリリース. 2022-08-23.Coronavirus disease 2019 (COVID-19) is a recently-emerged infectious disease that has caused millions of deaths, where comprehensive understanding of disease mechanisms is still unestablished. In particular, studies of gene expression dynamics and regulation landscape in COVID-19 infected individuals are limited. Here, we report on a thorough analysis of whole blood RNA-seq data from 465 genotyped samples from the Japan COVID-19 Task Force, including 359 severe and 106 non-severe COVID-19 cases. We discover 1169 putative causal expression quantitative trait loci (eQTLs) including 34 possible colocalizations with biobank fine-mapping results of hematopoietic traits in a Japanese population, 1549 putative causal splice QTLs (sQTLs; e.g. two independent sQTLs at TOR1AIP1), as well as biologically interpretable trans-eQTL examples (e.g., REST and STING1), all fine-mapped at single variant resolution. We perform differential gene expression analysis to elucidate 198 genes with increased expression in severe COVID-19 cases and enriched for innate immune-related functions. Finally, we evaluate the limited but non-zero effect of COVID-19 phenotype on eQTL discovery, and highlight the presence of COVID-19 severity-interaction eQTLs (ieQTLs; e.g., CLEC4C and MYBL2). Our study provides a comprehensive catalog of whole blood regulatory variants in Japanese, as well as a reference for transcriptional landscapes in response to COVID-19 infection

DOCK2 is involved in the host genetics and biology of severe COVID-19

「コロナ制圧タスクフォース」COVID-19疾患感受性遺伝子DOCK2の重症化機序を解明 --アジア最大のバイオレポジトリーでCOVID-19の治療標的を発見--. 京都大学プレスリリース. 2022-08-10.Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge. Here we conducted a genome-wide association study (GWAS) involving 2, 393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3, 289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target

Fabrication of a Fluorophore-Doped Cylindrical Waveguide Structure Using Elastomers for Visual Detection of Stress

A fiber-optic strain sensor that can show strain via color change and which can be viewed using human eyes has demand in the civil engineering field for alerting purposes. A previous sensor was fabricated using PMMA (Poly(methyl methacrylate)), which had the exceeding hardness to exhibit satisfactory sensor performance. In this research, an elastomer-based fiber-optic structure was fabricated to enhance the elastic response of such sensors and to enlarge the waveguide cross section. Various organic fluorophores were added to the core and cladding regions of the elastic waveguide to induce energy flow from the core to the cladding when stress is applied to the waveguide. Elastomer pairs suitable for the core and cladding were selected from among several candidate materials having high transparency. A method of dispersing fluorophores to each host elastomer and constructing an excellent core–cladding interface using the selected materials was proposed. To investigate the time-dependent changes in the fluorescence of the doped elastomer waveguide, the absorption and emission spectra were monitored after the host elastomers were cured

Photoelectron Yield Spectroscopy and Transient Photocurrent Analysis for Triphenylamine-Based Photorefractive Polymer Composites

The photocurrent for poly(4-(dimethylamino)benzyl acrylate) (PDAA) photorefractive composites with (4-(diphenylamino)phenyl)methanol (TPAOH) photoconductive plasticizers was measured to be two orders of magnitude higher than that obtained with (2,4,6-trimethylphenyl)diphenylamine (TAA) photoconductive plasticizers. In this study, to determine the reason for the large difference in the photocurrent measured for PDAA photorefractive composites containing two different photoconductive plasticizers of TPAOH and TAA, the highest occupied molecular orbital (HOMO) level identical to the ionization potential (Ip) and the width of the density of states (DOS) were evaluated using photoelectron yield spectroscopy, and the transient photocurrent was analyzed using a two-trap model. The estimated hole mobility was also rationalized using a Bässler formalism together with the energetic disorder of the width of the DOS and the positional disorder of the scattering situation for carrier hopping

Photorefractivity and photocurrent dynamics of triphenylamine-based polymer composites

Abstract The photorefractive properties of triphenylamine polymer-based composites with various composition ratios were investigated via optical diffraction, response time, asymmetric energy transfer, and transient photocurrent. The composite consisted of a photoconductive polymer of poly((4-diphenylamino)benzyl acrylate), a photoconductive plasticizer of (4-diphenylamino)phenyl)methanol, a sensitizer of [6,6]-phenyl-C61-butyric acid methyl ester, and a nonlinear optical dye of (4-(azepan-1-yl)-benzylidene)malononitrile. The photorefractive properties and related quantities were dependent on the composition, which was related to the glass transition temperature of the photorefractive polymers. The quantum efficiency (QE) of photocarrier generation was evaluated from the initial slope of the transient photocurrent. Transient photocurrents were measured and showed two unique peaks: one in the range of 10−4 to 10−3 s and the other in the range of 10−1 to 1 s. The transient photocurrents was well simulated (or reproduced) by the expanded two-trapping site model with two kinds of photocarrier generation and recombination processes and two different trapping sites. The obtained photorefractive quantity of trap density was significantly related to the photoconductive parameters of QE

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Microfluidic Separation of Redox Reactions for Coulometry Based on Metallization at the Mixed Potential

Coulometric detection of an analyte in a solution at nanoliter scale was conducted by having redox reactions proceed simultaneously on a platinum electrode. The analyte was oxidized on a part of the electrode in one flow channel and silver was deposited on an array of circular microelectrodes formed in another flow channel at a mixed potential. Coulometric determination of the deposited silver showed a steep change in the generated charge as a result of the complete oxidation of silver. The short measurement time after the start of the coulometry suppressed the increase in background charge, resulting in significant lowering of the detection limit. The lower detection limit for H₂O₂ was 30 nM (3σ). To improve selectivity and minimize the influence of coexisting interferents, the shifting of the mixed potential, application of a permselective membrane, and electrochemical elimination of the interferents were effective modifications

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)