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Background/Aims: Coronavirus disease 2019 (COVID-19) is associated with acute respiratory syndrome. The mechanisms underlying the different degrees of pneumonia severity in patients with COVID-19 remain elusive. This study provides evidence that COVID-19 is associated with eosinophil-mediated inflammation.Methods: We performed a retrospective case series of three patients with laboratory and radiologically confirmed COVID-19 pneumonia admitted to Chosun University Hospital. Demographic and clinical data on inflammatory cell lung infiltration and cytokine levels in patients with COVID-19 were collected.Results: Cytological analysis of sputum, tracheal aspirates, and bronchoalveolar lavage fluid (BALF) samples from all three patients revealed massive infiltration of polymorphonuclear cells (PMNs), such as eosinophils and neutrophils. All sputum and BALF specimens contained high levels of eosinophil cationic proteins. The infiltration of PMNs into the lungs, together with elevated levels of natural killer T (NKT) cells in BALF and peripheral blood samples from patients with severe pneumonia in the acute phase was confirmed by flow cytometry.Conclusions: These results suggest that the lungs of COVID-19 patients can exhibit eosinophil-mediated inflammation, together with an elevated NKT cell response, which is associated with COVID-19 pneumonia.

In this work, we demonstrated a phonon-polariton in the terahertz (THz) frequency range, generated in a crystallized lead halide perovskite film coated on metamaterials. When the metamaterial resonance was in tune with the phonon resonance of the perovskite film, Rabi splitting occurred due to the strong coupling between the resonances. The Rabi splitting energy was about 1.1 meV, which is larger than the metamaterial and phonon resonance line widths; the interaction potential estimation confirmed that the strong coupling regime was reached successfully. We were able to tune the polaritonic branches by varying the metamaterial resonance, thereby obtaining the dispersion curve with a clear anticrossing behavior. Additionally, we performed

Serologic and molecular surveillance of serum collected from 152 suspected scrub typhus patients in Myanmar revealed Orientia tsutsugamushi of genotypic heterogeneity. In addition, potential co-infection with severe fever with thrombocytopenia syndrome virus was observed in 5 (3.3%) patients. Both scrub typhus and severe fever with thrombocytopenia syndrome are endemic in Myanmar.

Cholesteric liquid crystals (CLCs) form self-assembled helical structures of rodlike molecules. From its periodic helical structure, the CLC exhibits a structural color by selectively reflecting circularly polarized light of the same handedness as the helix. Here, without external stimuli of electric fields, temperature, and light, we show tuning of spectral position, width, viewing angle, and diffusivity of its reflection color in a CLC by employing amorphous and nanostructured perfluoropolymer (called CYTOP) films as alignment layers. This CLC combined with perfluoropolymer films provides new possibilities in various photonic applications such as active components of photonic sensors, reflective displays, and tunable lasers.

Despite a clear association of patient’s age with COVID-19 severity, there has been conflicting data on the association of viral load with disease severity. Here, we investigated the association of viral load dynamics with patient’s age and severity of COVID-19 using a set of respiratory specimens longitudinally collected (mean: 4.8 times/patient) from 64 patients with broad distribution of clinical severity and age during acute phase. Higher viral burden was positively associated with inflammatory responses, as assessed by IL-6, C-reactive protein, and lactate dehydrogenase levels in patients’ plasma collected on the same day, primarily in the younger cohort (≤59 years old) and in mild cases of all ages, whereas these were barely detectable in elderly patients (≥60 years old) with critical disease. In addition, viral load dynamics in elderly patients were not significantly different between mild and critical cases, even though more enhanced inflammation was consistently observed in the elderly group when compared to the younger group during the acute phase of infection. The positive correlation of viral load with disease severity in younger patients may explain the increased therapeutic responsiveness to current antiviral drugs and neutralizing antibody therapies in younger patients compared to elderly patients. More careful intervention against aging-associated inflammation might be required to mitigate severe disease progression and reduce fatality in COVID-19 patients more than 60 years old.

Despite the worldwide effect of the Coronavirus disease 2019 (COVID-19) pandemic, the underlying mechanisms of fatal viral pneumonia remain elusive. Here, we show that critical COVID-19 is associated with enhanced eosinophil-mediated inflammation when compared to non-critical cases. In addition, we confirm increased Th2-biased adaptive immune responses, accompanying overt complement activation, in the critical group. Moreover, enhanced antibody responses and complement activation is associated with disease pathogenesis as evidenced by formation of immune complexes and membrane attack complexes in airways and vasculature of lung biopsies from six fatal cases, as well as by enhanced hallmark gene set signatures of FcγR signaling and complement activation in myeloid cells of respiratory specimens from critical COVID-19 patients. These results suggest that SARS-CoV-2 infection may drive specific innate immune responses, including eosinophil-mediated inflammation, and subsequent pulmonary pathogenesis via enhanced Th2-biased immune responses, which might be crucial drivers of critical disease in COVID-19 patients., Graphical Abstract, Kim et al. find that critical COVID-19 is associated with enhanced eosinophil-mediated inflammation when compared to non-critical cases. Increased Th2-biased immune responses, accompanying overt complement activation, are seen in the critical group. These findings suggest that enhanced eosinophil-mediated inflammation and dysregulated humoral responses might be drivers of severe COVID-19.

Despite the worldwide effect of the Coronavirus disease 2019 (COVID-19) pandemic, the underlying mechanisms of fatal viral pneumonia remain elusive. Here, we conducted kinetic profiling of respiratory leukocytes and associated inflammatory mediators to show that severe COVID-19 is associated with delayed but enhanced eosinophilic inflammation when compared to mild cases. In addition, we confirmed increased Th2-biased adaptive immune responses, accompanying overt complement activation, in the severe group. Moreover, enhanced antibody responses and complement activation was associated with disease pathogenesis as evidenced by formation of immune complexes and membrane attack complexes in airways and vasculature of lung biopsies from a fatal case, as well as by enhanced hallmark gene set signatures of FcgR signaling and complement activation in myeloid cells of respiratory specimens from severe COVID-19 patients. We also observed expression of viral antigen in lung epithelial and endothelial cells without producing viruses during late stage of COVID-19, indicating abortive viral infection which may further fuel antibody responses and aggravate immune-complex-mediated inflammation. These results suggest that SARS-CoV-2 infection may drive scripted specific innate immune responses, including eosinophilic inflammation, and subsequent pulmonary pathogenesis via enhanced Th2-biased immune responses, which might be crucial drivers of severe pneumonia in COVID-19 patients.

Cholesteric liquid crystals (CLCs) with periodical helical structures of nematic molecules are chiral photonic crystals that exhibit photonic band gaps for circularly polarized lights with same handedness as CLC helices. We investigated optical characteristics of CLCs on nanoimprinted CYTOP films. Here, nanoimprinted CYTOP films are used as alignment layers to control orientations of cholesteric helices because of its strongly hydrophobic surface with low polarity and low polarizability. The CLCs on the nanoimprinted films showed not specular but diffusive reflections at the specific spectral region. This nanostructured CYTOP film can provide new possibility to engineer optical characteristics of the CLCs.

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)1 and often results in fatal pneumonia.2,3 Despite the worldwide effect of the COVID-19 pandemic, the underlying mechanisms of the fatal viral pneumonia remain elusive. Here, we investigated respiratory specimens, including broncholoalveolar lavage fluids (BALFs) and bloods collected from three confirmed cases of COVID-19 patients with varying degrees of disease severity. Surprisingly, over 35% of cells from BALFs obtained from two pneumonic patients was comprised of eosinophils, while 20% was comprised of lymphocytes. Cytological analysis of sputa and tracheal aspirates from all three patients also revealed that more than 90% of total cells were eosinophils. Infiltration of CD16+/CD24+ polymorphonuclear cells into lungs, together with elevated NKT cells in BALFs and peripheral blood samples, in patients with severe pneumonia was confirmed by flow cytometry. Moreover, rapid and profound IgE responses against the N protein of SARS-CoV-2 was only detected in plasma from a patient suffering from more severe and prolonged pneumonia. A significant reduction in oxygen demand with improved chest imaging was observed in two severe COVID-19 patients after treatment with a steroid, methylprednisolone. The present study provides evidence that acute eosinophilic pneumonia4 is associated with COVID-19.

We demonstrate highly efficient multi-colored semitransparent perovskite solar cells that can create high angular tolerant controllable transmissive colors up to 60°, based on phase-compensated microcavities. The efficiency of the semitransparent colors was improved by impedance matching, which was enabled by placing a dielectric functional layer on top of traditional optical microcavities, with negligible influence on color pureness. The vast majority of the visible part of solar radiation is efficiently utilized for solar energy harvesting, achieving 10.47%, 10.66%, and 11.18% of efficiency for red, green, and blue (RGB) colored solar cells, respectively, while a very small proportion of the visible solar spectrum is used for structural coloration that can be readily tuned by altering the cavity medium thickness. The approach described herein can be suitable for a variety of applications such as display systems with ultra-low power consumption, highly efficient colorful solar panels, low-power wearable electronics, and energy-efficient optoelectronics.

We report a 47.1% efficiency improvement resulting from the combination of device-architecture modification and inclusion of poly(3-hexylthiophene-2,5-diyl) nanowires (P3HT NWs) in bulk heterojunction (BHJ) active layers (ALs). Modelling of ellipsometry spectra shows substantial changes in inhomogeneity and optical constants of BHJ ALs with P3HT-NW inclusion. Furthermore, finite-difference time-domain simulation results based on actual device structures with inhomogeneous AL models indicate that enhanced light harvesting is a main contributing factor to efficiency improvement. On the contrary, P3HT-NW inclusion has no significant effect on charge carrier collection, other than suppressing occurrence of cul-de-sac in hole-transport pathways and unfavourable indene-C60 bisadduct domains near top anodes.

In this work, we report on the design principles of high-power perovskite solar cells (PSCs) for low-intensity indoor light applications, with a particular focus on the electron transport layers (ETLs). It was found that the mechanism of power generation of PSCs under low-intensity LED and halogen lights is surprisingly different compared to the 1 Sun standard test condition (STC). Although a higher power conversion efficiency (PCE) was obtained from the PSC based on mesoporous-TiO2 (m-TiO2) under STC, compared to the compact-TiO2 (c-TiO2) PSC, c-TiO2 PSCs generated higher power than m-TiO2 PSCs under low-intensity (200–1600 Lux) conditions. This result indicates that high PCE at STC cannot guarantee a reliable high-power output of PSCs under low-intensity conditions. Based on the systemic characterization of the ideality factor, charge recombination, trap density, and charge-separation, it was revealed that interfacial charge traps or defects at the electron transport layer/perovskite have a critical impact on the resulting power density of PSC under weak light conditions. Based on Suns-VOC measurements with local ideality factor analyses, it was proved that the trap states cause non-ideal behavior of PSCs under low-intensity light conditions. This is due to the additional trap states that are present at the m-TiO2/perovskite interface, as confirmed by trap-density measurements. Based on Kelvin probe force microscopy (KPFM) measurements, it was confirmed that these traps prohibit efficient charge separation at the perovskite grain boundaries when the light intensity is weak. According to these observations, it is suggested that for the fabrication of high-power PSCs under low-intensity indoor light, the interface trap density should be lower than the excess carrier density to fill the traps at the perovskite's grain boundaries. Finally, using the suggested principle, we succeeded in demonstrating high-performance PSCs by employing an organic ETL, yielding maximum power densities up to 12.36 (56.43), 28.03 (100.97), 63.79 (187.67), and 147.74 (376.85) μW/cm2 under 200, 400, 800, and 1600 Lux LED (halogen) illumination which are among the highest values for indoor low-intensity-light solar cells.

Background Polycyclic aromatic hydrocarbons (PAHs) produced by incomplete combustion have negative effects on human health due to their carcinogenicity and teratogenicity. Indoor sources of PAHs include tobacco smoke, heating sources, and cooking. This study evaluated the relationship between human PAH exposure and residence characteristics. Method This study was based on the second Korean National Environmental Health Survey (2012–2014). Non-smoking housewives were included in the analyses (n = 1269). The concentrations of urinary PAH metabolites (2-naphthol, 2-hydroxyfluorene, 1-hydroxyphenanthrene, and 1-hydroxypyrene) were adjusted by urine creatinine level. The geometric mean concentrations of urinary PAH metabolites by residential factors were examined. Logistic regression models were used to evaluate associations between residential variables and PAH exposures. Results The adjusted geometric mean concentrations of urinary 2-hydroxyfluorene and 1-hydroxyphenanthrene were significantly higher in the group residing within 100 m of a major road (p 100 m from a major road. In logistic regression analyses, the odds ratio (OR) for exceeding the third quartile of urinary 1-hydroxypyrene concentration was significantly higher in the group using coal or wood fuel for residential heating than in the group using gas (OR = 2.745, 95% confidence interval [CI] = 1.295–5.819). The detached house group had a significantly higher OR for 1-hydroxyphenanthrene compared with the apartment group (OR = 1.515, 95% CI = 1.023–2.243). Conclusion Our study shows the evidence of associations between some urinary PAH metabolite levels (1-hydroxyphenanthrene and 1-hydroxypyrene) and residence characteristics. Additional studies are needed to clarify these associations.

Structural colors from cholesteric liquid crystals (CLCs) are manipulated by changing the only surface anchoring energy of an alignment layer. This behavior comes from the fact that weak surface energy of the perfluoropolymer induces the tilting of the cholesteric helix. Such deformed CLC structures with durability are successfully demonstrated without any external field applications and additional solidification processes. In addition, electrical tunings of structural colors from the deformed CLCs occur at very low operating voltages, compared to those of conventional CLC structures. On the basis of easy and simple fabrication, high durability, electrical tunability at low operating voltages, and the unique optical characteristics, the new deformed CLC structure could lead to extension in applications of CLCs, including multifunctional sensors, displays, and lasers.

With poly(3-hexylthiophene) (P3HT) nanowire (NW) inclusion in active layers (ALs), organic solar cells (OSCs) based on P3HT donor and indene-C60 bisadduct (ICBA) acceptor showed power conversion efficiency (PCE) improvements for both bulk heterojunction (BHJ)- and bilayer (BL)-structure AL devices. The PCE increase was approximately 14 % for both types of P3HT:ICBA OSCs. However, improvements in short-circuit current density (Jsc ) were about 4.4 and 6.4 % for BHJ- and BL-type AL devices, respectively. A systematic study showed that the addition of P3HT NWs did not result in enhanced internal quantum efficiencies for either type of device. However, the difference in light-harvesting efficiency was important in accounting for Jsc variations. Interestingly, there was no correlation between Jsc and PCE variations, whereas the open-circuit voltage (Voc ) and fill factor (FF) showed correlations with the PCE. The variation in FF is discussed in terms of Voc and equivalent-circuit parameters based on a nonideal diode model.

The prospective application of luminescence to imaging devices is shown using a combination of color-tunable and patternable mechanoluminescent materials. A white light source is demonstrated by using an alternative color tuning method, induced under high vibration conditions. As the implementation is fairly straightforward, it is expected that the present results will find a number of potential uses in current industrial applications.

In CH3NH3PbI3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI2. This was mainly due to the inferior morphology of pure perovskite film without PbI2, inevitably produced when the remaining PbI2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI2, but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon absorption and longer carrier lifetime, leading to superior photocurrent generation with higher power conversion efficiency. Furthermore, this process was further applicable to prepare mixed phase pure perovskite crystal without PbI2 impurity, and we showed that the additional merits such as extended absorption to longer wavelength, increased carrier lifetime and reduced carrier recombination could be secured.

Despite the ongoing spread of MERS, there is limited knowledge of the factors affecting its severity and outcomes. We analyzed clinical data and specimens from fourteen MERS patients treated in a hospital who collectively represent a wide spectrum of disease severity, ranging from mild febrile illness to fatal pneumonia, and classified the patients into four groups based on severity and mortality. Comparative and kinetic analyses revealed that high viral loads, weak antibody responses, and lymphopenia accompanying thrombocytopenia were associated with disease mortality, whereas persistent and gradual increases in lymphocyte responses might be required for effective immunity against MERS-CoV infection. Leukocytosis, primarily due to increased neutrophils and monocytes, was generally observed in more severe and fatal cases. The blood levels of cytokines such as IL-10, IL-15, TGF-β, and EGF were either positively or negatively correlated with disease mortality. Robust induction of various chemokines with differential kinetics was more prominent in patients that recovered from pneumonia than in patients with mild febrile illness or deceased patients. The correlation of the virological and immunological responses with disease severity and mortality, as well as their responses to current antiviral therapy, may have prognostic significance during the early phase of MERS.

A cholesteric liquid crystal (CLC) is a self-assembled photonic crystal formed by rodlike molecules, including chiral molecules, that arrange themselves in a helical fashion. The CLC has a single photonic bandgap and an associated one-colour reflection band for circularly polarized light with the same handedness as the CLC helix (selective reflection). These optical characteristics, particularly the circular polarization of the reflected light, are attractive for applications in reflective colour displays without using a backlight, for use as polarizers or colour filters and for mirrorless lasing. Recently, we showed by numerical simulation that simultaneous multicolour reflection is possible by introducing fibonaccian phase defects. Here, we design and fabricate a CLC system consisting of thin isotropic films and of polymeric CLC films, and demonstrate experimentally simultaneous red, green and blue reflections (multiple photonic bandgaps) using the single-pitched polymeric CLC films. The experimental reflection spectra are well simulated by calculations. The presented system can extend applications of CLCs to a wide-band region and could give rise to new photonic devices, in which white or multicolour light is manipulated.

We fabricated a hybrid structure composed of a dye-doped low-molecular-weight cholesteric liquid crystal (low CLC) sandwiched between polymer cholesteric liquid crystal (PCLC) films with the same handedness as the low CLC, and studied its lasing characteristics. Defect-mode lasing was observed with a threshold reduced by a factor of 3 compared with that in a simple dye-doped low CLC cell. Experimental and simulated results for the transmittance, emission, and photonic density-of-states spectra are also discussed.

An electrostatically self-assembled monolayer, composed of a pair of layers of anionic molecules and cationic polymers with a hemicyanine pendent group, was fabricated onto a thin silver film. By use of the attenuated total internal reflection technique, surface plasmon resonance and reflection modulation spectra were measured to determine the electro-optic coefficients of the monolayer. In order to take into account the dielectric property of each layer, a five-layer model is adopted in obtaining the electro-optic coefficients. From the temperature dependence measurement of reflection modulation signal, the hyperpolarizabilities of the hemicyanine pendent chromophore in benzenoid and quinoid forms are obtained.

Multilayer thin films consisting of alternate layer-pairs of cationic macrocycles (tetra-copperphthalocyanine) and anionic macromolecules (polyethylenimine) were fabricated on thin silver film using alternate electrostatic self-assembly technique. The optical properties of the film were characterized by uv-vis absorption spectra and attenuated total reflection measurements. From the data analysis based on the multilayer reflection theory, it was shown that the ultra thin films were successfully fabricated by self-assembly technique with the mean layer-pairs thickness of 25 A. Moreover, especially for tetra-copperphthalocyanine layer, we obtained the anisotropy in dielectric constants with respect to the surface normal, indicating anisotropic orientation of the tetra-copperphthalocyanine molecules on the polyethylenimine layer.

The operation characteristics of nominal bilayer (BL) organic solar cells (OSCs), the active layers (ALs) of which consisted of sequentially casted bottom P3HT donor and top ICBA acceptor layers, resembled those of OSCs with bulk heterojunction (BHJ) ALs. Optical analysis and device simulations showed that such resemblance can be attributed to a similarity in the micromorphology of ALs; as-deposited BL-type ALs transformed spontaneously into BHJ-type ALs. The inclusion of P3HT nanowires (NWs) in the donor layers resulted in different AL micromorphology and consequently a larger power conversion efficiency. Separate assessment of the exciton generation and charge–carrier transport and/or extraction showed that the contribution of P3HT NWs was more prominent in optical effects. Transformation of sequentially casted P3HT and ICBA layers into a bulk heterojunction layer accounts for good agreement between measured and simulated J–V curves.

Three planar CH3NH3PbI3 (MAPbI3) solar cells having the same structure except a hole-extraction layer (HEL) showed distinctive difference in operation characteristics. Analysis of frequency-dependent capacitance and dielectric-loss spectra of the three MAPbI3 devices showed two types of recombination-loss channels with different time constants that we attributed respectively to interface and bulk defects. Discrepancy in defect formation among the three devices with a HEL of PEDOT:PSS, NiOx, or Cu-doped NiOx was not surprising because grain-size distribution and crystalline quality of MAPbI3 can be affected by surface energy and morphology of underlying HELs. We were able to quantify interface and bulk defects in these MAPbI3solar cells based on systematic and simultaneous simulations of capacitance and dielectric-loss spectra, and current–voltage characteristics by using the device simulator SCAPS. Defect density reduction is essential for efficient planar solar cells. Defect density in MAPbI3 layers, with respect to which an open-cell voltage and a fill factor vary, can be investigated by using capacitance–frequency spectra.

We demonstrated widely tunable lasing with lowered threshold in a liquid crystal (LC) laser by introducing a nanostructured indium-tin-oxide (ITO) film with two dimensional (2D) periodicity and two kinds of organic dyes in the nematic LC host. From a wedge-shaped distributed feedback (DFB) resonator, thickness of a LC layer and effective refractive indices of guided laser modes are modulated by changing the pumping position spatially, and the lasing emission is tuned by 26 nm. This LC DFB laser with wide spectral tunability and low threshold provides various approaches for practical applications in laser technology. (C) 2016 Optical Society of America

We introduce quasi-periodic Fibonaccian phase defects into single-pitched cholesteric liquid crystalline systems. Numerical simulations of reflection spectra from the proposed systems demonstrate simultaneous red, green, and blue reflections or multiple photonic band gaps. Fundamental optical properties are discussed as functions of phase jump (orientational defect angles), unit lengths and the orders of Fibonacci systems.

The authors have demonstrated the enhancement of linearly polarized lasing emission intensity using a structure made by a simple fabrication process. The enhanced lasing is achieved using a nanoimprinted distributed feedback structure together with spin-coated polymeric liquid crystals. The backward linearly TE-polarized lasing emission is transformed to left-handed circularly polarized light (L-CPL) by employing a dye-doped polymeric nematic liquid crystal (PNLC) film as a (−1/4)λ[=(3/4)λ] plate. The L-CPL is effectively reflected by a L-polymeric cholesteric liquid crystal film as a reflector and transformed back to TE-polarized light by the PNLC film; as a result one-directional emission intensity is enhanced.

We have demonstrated polarization-tunable electroluminescence (EL) from organic light-emitting diodes (OLEDs) using a combination of polymeric cholesteric liquid crystal (PCLC) and nematic liquid crystal (NLC). By electrically controlling NLC alignment, the proposed EL device shows a continuous polarization tunability including two circular (right and left) and two linear polarizations without loss of light. This simple polarization-tunable EL device is based on photonic-device concept using spin-coatable PCLC. Hence, there is no limitation for choosing emissive materials with high internal efficiency. Also, its polarization tunability will be available in various optical devices and can extend OLED application to photonic technologies.

The authors have observed highly circularly polarized electroluminescence from organic light-emitting diodes (OLEDs) using wide-band reflector consisting of three-layered left-handed polymeric cholesteric liquid crystal (PCLC) films. By simply attaching the wide-band reflective PCLC reflector to a conventional OLED, the authors obtained a high degree of circular polarization, i.e., the ratio of brightness between right- and left-handed circularly polarized electroluminescences is over 10 over the whole emission band.

The authors have demonstrated defect mode lasing emission from a spin-coated double-layered dye-doped polymeric cholesteric liquid crystal (PCLC) films with a thin rubbed isotropic layer in between. The rubbed layer acts not only as an alignment layer for the second PCLC layer but also as an isotropic defect layer breaking periodicity of PCLC films. All the processes can be achieved in a wet process. Because of the process, the present polymeric solid-state laser is available as a freestanding thin film of only 5.5μm in thickness and an almost limitless large area, which enable one to use it as a disposable laser chip of any shapes.

Photoinduced circular anisotropy has been demonstrated in thin films of a main-chain polymeric liquid crystal (PLC) system doped with photochromic $\mathsf{W}$-shaped molecules containing two azobenzene groups by irradiating with circularly polarized light (CPL). Reversible photoinduced circular dichroism (CD) was observed with sign relevant to the handedness of the CPL. The experimentally observed CD spectra were analyzed using the DeVoe polarizability model associated with the coupled oscillator method. We also propose a mechanism for the photoinduced circular anisotropy in our system; nucleating the $\mathsf{W}$-shaped molecules with preferential twisted conformation by CPL irradiation, and triggering the local formation of a chiral structure in the $\mathsf{W}$-shaped-molecule-doped main-chain PLC medium.

Second harmonic generation circular dichroism (SHG CD) measurements are performed on the B4 phase of a bent-core molecular system. Numerical analysis of SHG CD incorporating magnetic-dipole as well as electric-dipole interaction shows that the B4 phase is in a twist-grain-boundary structure with the helical axis along the bent direction of the molecules. The result is extremely important in the sense that achiral molecules are spontaneously optically resolved, i.e., deracemization, the chiral domains of which give rise to huge chiral nonlinear optical effect.

By adopting classical models of molecular chirality, contributions of the coupled-oscillator and helix natures to the chiral surface second-order susceptibilities are identified through introduction of a molecular orientational distribution. Experimentally, surface orientational distribution functions at interfaces of an isotropic chiral chitosan polymer film are determined from second harmonic generation measurement. The largest chiral component of surface nonlinear optical susceptibility is from the electric-magnetic coupling with dominant contribution from the helix nature of chitosan.

A cholesteric liquid crystal cell was fabricated possessing 1-D photonic bandgap structure. From the measurement of the linear absorption spectrum of the cell, a bandgap was identified, centered at 1.08 eV (1143 nm) with the gap width of 0.1 eV (100 nm). Based on the linear absorption spectra, the dispersion of the principal refractive indices along the parallel and perpendicular directions of the molecule was determined as 1.631 and 1.476 at the wavelength of 1064 nm through Berreman matrix method. A Q-switched Nd:YAG laser (1064 nm) was employed to investigate the nonlinear optical changes of photonic bandgap. As the laser intensity was increased to 320 MW/cm2, the transmittance decreased from 0.51 to 0.47, corresponding to an 8% change. The nonlinear transmittance change was analyzed numerically by Berreman matrix method with the incorporation of Kerr nonlinearity in the optical response of the molecules forming cholesteric liquid crystal. The changes in the refractive indices along the parallel and perpendicular directions were 3.46 and 1.51 X 10-10 (cm2/W). The changes in the position and width of bandgap were 0.02 eV and 0.03 eV at the laser intensity of 320 MW/cm2.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Scrub typhus is an acute, febrile illness caused by Orientia tsutsugamushi infection and it is one of the main causes of acute febrile illness in the Asian-Pacific region. The incidence of scrub typhus has been significantly increased in Korea during last 10 years. Although early diagnosis and proper antibiotic treatment are important to prevent severe complications, the clinical discrimination of scrub typhus from other undifferentiated fevers, such as leptospirosis or dengue fever, is often very difficult. In addition, an effective vaccine has not yet been developed. As a novel diagnostic and vaccine target for scrub typhus, we described surface cell antigen (sca) family genes encoding autotransporter proteins found in the genome of O. tsutsugamushi. The molecular characteristics and recent findings on the bacterial genes were introduced in this letter.

We investigated nanostructured indium-tin-oxide (ITO) films fabricated by all-solution processing of ITO nanoparticles and a nanoimprint lithography technique. The nanostructured ITO film with one-dimensional periodicity has low sheet resistance of ~200 Ω/sq, high optical transparency of ~80%, and specific transmission spectra due to light diffractions. By using this ITO film as a transparent electrode and an alignment layer of nematic liquid crystals (LCs), we successfully demonstrate the electro-optic performance of LC devices. This functional transparent electrode can give rise to new photonic devices with nanostructures.

The role of a strong dye absorption in determining the photonic bandgap (PBG) shape of a three-dimensional dyed photonic crystal, fabricated from dyed polystyrene nanospheres, is investigated. When the dye absorption peaks fall on the PBG spectral position, the PBG has a distorted shape, narrow top, and wide bottom. Theoretical analysis shows that the characteristic PBG shape results from two superimposed contributions with distinct origins, i.e., a Bragg reflection and a high reflection associated with the strong dye absorption.