Structure–charge transfer property relationship in self-assembled discotic liquid-crystalline donor–acceptor dyad and triad thin films

Dynamics of the photo-induced charge transfer are correlated with the structural properties of self-assembled discotic donor–acceptor dyad and triad films.

Comparative transcriptome analysis of Nile tilapia (Oreochromis niloticus) in response to alkalinity stress

To identify genes of potential importance to alkalinity tolerance, RNA sequencing (RNA-Seq) was performed to survey gill transcriptome profiles from freshwater (FW) and alkaline water (AW) exposed Nile tilapia (Oreochromis niloticus). A total of 22,724,036 (AW)/16,461,040 (FW) single-end reads were generated in which 20,304,348 (AW)/14,681,290 (FW) reads (90.0/89.72%) were aligned to the reference genome. Differential expression analysis revealed 302 up-regulated and 193 down-regulated genes between AW- and FW-exposed fish. These differentially expressed genes were enriched in several Gene Ontology (GO) terms related to "stress response", "heme binding", and "carbonate dehydratase activity". Meanwhile, significant KEGG pathways were enriched in energy metabolism, including nitrogen and sulfur metabolism. These results demonstrate the response of Nile tilapia exposed to alkaline-water and might provide valuable information to further understand the molecular mechanisms of adaptation of fish to alkaline environments.

Borondifluoride complexes of hemicurcuminoids as bio-inspired push-pull dyes for bioimaging

Hemicurcuminoids are based on half of the π-conjugated backbone of curcuminoids. The synthesis of a series of such systems and their borondifluoride complexes is described. The electrochemical and photophysical properties of difluorodioxaborine species were investigated as a function of the nature of electron donor and acceptor groups appended at either terminal positions of the molecular backbone. The emissive character of these dipolar dyes was attributed to an intraligand charge transfer process, leading to fluorescence emission that is strongly dependent on solvent polarity. Quasi-quantitative quenching of fluorescence in high polarity solvents was attributed to photoinduced electron transfer. These dyes were shown to behave as versatile fluorophores. Indeed, they display efficient two-photon excited fluorescence emission leading to high two-photon brightness values. Furthermore, they form nanoparticles in water whose fluorescence emission quantum yield is less than that of the dye in solution, owing to aggregation-induced fluorescence quenching. When cos7 living cells were exposed to these weakly-emitting nanoparticles, one- and two-photon excited fluorescence spectra showed a strong emission within the cytoplasm that originated from the individual molecules. Dye uptake thus involved a disaggregation mechanism at the cell membrane which restored fluorescence emission. This off-on fluorescence switching allows a selective optical monitoring of those molecules that do enter the cell, which offers improved sensitivity and selectivity of detection for bioimaging purposes.

Electro-optic switching in metamaterial by liquid crystal

Electro-optic switching of reflection and refraction is experimentally demonstrated in metasurface liquid crystal cell. Negative metasurface is fabricated by focused-ion-beam milling, and twisted nematic cells are constructed with complementary double-split ring resonator and V-shape slot antenna metasurface. By application of an external voltage, electro-optic switchings are achieved in reflection and refraction. It has a strong implication for applications in spatial light modulation and wavelength division multiplexer/demultiplexer in a near-IR spectral range.

Resveratrol could reverse the expression of SIRT1 and MMP-1 in vitro

Intervertebral disc degeneration is the main cause of lumbago disease, in which the extracellular matrix structure and moisture in the nucleus pulposus is lost continuously. In this study, we aimed to detect differential expression of silence mating type information regulation 2 homolog 1 (SIRT1) and matrix metalloproteinase-1 (MMP-1) in human intervertebral disc nucleus pulposus cells and to explore the effects of SIRT1 and MMP-1 on the development of the intervertebral disc degeneration. Intervertebral disc nucleus pulposus specimens from 41 patients who underwent lumbar protrusion resection at HuiZhou Municipal Central Hospital, during the period from October 2011 to December 2013, were studied in comparison with 23 control cases from patients who underwent fractured lumbar resection. In degenerated human intervertebral disc nucleus pulposus cells, the expression of SIRT1 is decreased and MMP-1 is increased compared with that of the control cells. Resveratrol could reverse these effects, thereby increasing the expression of SIRT1 (0.87 ± 0.07 vs 0.54 ± 0.04), Coll2α1 (0.90 ± 0.08 vs 0.38 ± 0.01), and aggrecan (0.69 ± 0.07 vs 0.42 ± 0.05) and decreasing the expression of MMP-1 (0.61 ± 0.03 vs 0.93 ± 0.08). These results suggest that resveratrol could possibly reverse the process of intervertebral disc degeneration and thus could be applied as a potential drug for the disease.

Optical Properties of Laser Lines and Fluorescent Spectrum in Cholesteric Liquid Crystal Laser

We experimentally studied the comprehensive optical properties of the laser lines and fluorescent spectrum generated by a continuous tunable cholesteric liquid crystal (CLC) laser array. We found that the laser lines generated from a CLC with a right-handed circular helix were right-handed circular polarized and laser lines generated from a CLC with a left-handed circular helix were left-handed circular polarized. Inside the photonic band gap, the CLC structure with right-(left-) handed helicity suppressed the fluorescence generated with right (left) circular polarized light, and instead the suppressed right (left) circular polarized light energy moved to the outside of the photonic band gap, so we can say that the fluorescence intensity outside of the photonic band gap is enhanced with right (left) handed circular polarized light. Depending on the position of the photonic band gap, the fluorescence quantum yield value increased by up to ~15%. These enhanced fluorescence intensities at the PBG edge will evolve into lasing at the upper lasing threshold. It is particularly interesting to see that the fluorescence intensity and shape could be controlled by adjusting the external geometrical factor of the photonic band gaps. The lasing threshold of the CLC lasers was in the range of 1.5-5.3 μJ/pulse. For CLC laser device applications, it is necessary and essential to know the optical properties of the generated laser lines and of the fluorescence spectrum.

Temporal, thermal, and light stability of continuously tunable cholesteric liquid crystal laser array

Fine-structured polymerized cholesteric liquid crystal (PCLC) wedge laser devices have been realized, with high fine spatial tunability of the lasing wavelength. With resolution less than 0.3 nm in a broad spectral range, more than one hundred laser lines could be obtained in a PCLC cell without extra devices. For practical device application, we studied the stability of the device in detail over time, and in response to strong external light sources, and thermal perturbation. The PCLC wedge cells had good temporal stability for 1 year and showed good stability for strong perturbations, with the lasing wavelength shifting less than 1 nm, while the laser peak intensities decreased by up to 34%, and the high energy band edge of the photonic band gap (PBG) was red shifted 3 nm by temperature perturbation. However, when we consider the entire lasing spectrum for the PCLC cell, the 1-nm wavelength shift may not matter. Although the laser peak intensities were decreased by up to 34% in total for all of the perturbation cases, the remaining 34% laser peak intensity is considerable extent to make use. This good stability of the PCLC laser device is due to the polymerization of the CLC by UV curing. This study will be helpful for practical CLC laser device development.

A novel frameshift mutation in the cylindromatosis (CYLD) gene in a Chinese family with multiple familial trichoepithelioma

Multiple familial trichoepithelioma (MFT) (OMIM: 601606) is an autosomal dominantly inherited disorder characterized by numerous, skin-colored papules and nodules with pilar differentiation. Recently, several mutations in the cylindromatosis (CYLD) gene have been reported in MFT. In this study, a mutation analysis of the CYLD was conducted in a Chinese pedigree of typical MFT. Affected individuals were identified through probands from Shanxi Province, China. Lesional skin biopsy of the proband revealed the typical histopathological characteristics of trichoepithelioma. Individuals belonging to five consecutive generations were similarly affected, which indicated an autosomal dominant inheritance pattern. Genomic DNA was extracted from peripheral blood lymphocytes using standard phenol/chloroform extraction method. All the coding exons (4-20) and exon-intron boundaries of the CYLD gene were amplified by polymerase chain reaction (PCR). Direct sequencing of all PCR products amplified from the complete coding regions of the CYLD gene was performed to identify mutations. Sequencing of the CYLD gene was performed in a further 100 unrelated, unaffected control individuals to exclude the possibility of polymorphism. A novel heterozygous frameshift mutation c.1169_1170delCA (p.Thr390Argfs) was identified in exon 10 of the CYLD gene in the affected family members. This mutation was also detected in unaffected family members, but not in the unrelated, healthy individuals who were also analyzed. Our study expands the database on the CYLD gene mutations in MFT and should be useful in providing genetic counseling and prenatal diagnosis for families affected by MFT.

Electro-optic switching in phase-discontinuity complementary metasurface twisted nematic cell

Electro-optic switching of refraction is experimentally demonstrated in a phase-discontinuity complementary metasurface twisted nematic cell. The phase-discontinuity complementary metasurface is fabricated by focused-ion-beam milling, and a twisted nematic cell is constructed with complementary V-shape slot antenna metasurface. By application of an external voltage, switching is achieved between ordinary refraction and extraordinary refraction satisfying the generalized Snell's law. It has a strong implication for applications in spatial light modulation and wavelength division multiplexer/demultiplexer in a near-IR spectral range.

Polarization-independent light emission enhancement of ZnO/Ag nanograting via surface plasmon polariton excitation and cavity resonance

In this study, we observed that the photoluminescence (PL) intensity of ZnO/Ag nanogratings was significantly enhanced compared with that of a planar counterpart under illumination of both transverse magnetic (TM) and transverse electric (TE)-mode light. In the TM mode, angle-resolved reflectance spectra exhibited dispersive dips, indicating cavity resonance as well as grating-coupled surface plasmon polariton (SPP) excitation. In the TE mode, cavity resonance only was allowed, and broad dips appeared in the reflectance spectra. Strong optical field confinement in the ZnO layers, with the help of SPP and cavity modes, facilitated polarization-insensitive PL enhancement. Optical simulation results were in good agreement with the experimental results, supporting the suggested scenario.

Enhanced nonlinear optical effects due to the excitation of optical Tamm plasmon polaritons in one-dimensional photonic crystal structures

We suggest optimally designed one-dimensional metal/photonic crystal structures for the excitation of optical Tamm plasmon polaritons, which show strongly enhanced electromagnetic field intensities compared to those due to conventional surface plasmon excitations. We assume that the photonic crystal is made of weakly nonlinear optical materials and calculate the reflectance and the electromagnetic field distribution precisely, using the invariant imbedding method generalized to nonlinear media. We find field intensity enhancement factors as large as 3,000 at the metal/photonic crystal interface. We verify that due to this strong enhancement, nonlinear optical effects such as optical bistability can be observed for very small values of the incident wave power. Our results imply that using our structure, very strong surface enhanced Raman scattering signals can be achieved and optical switching devices can be operated in much lower threshold light intensities.

Microsatellite markers in Paulownia kawakamii (Scrophulariaceae) and cross-amplification in other Paulownia species

Paulownia kawakamii is a fast-growing timber tree. In this study, 21 primer sets were developed using an enriched genomic library. The genetic diversity was measured in one P. kawakamii population. The number of alleles per locus ranged from 2 to 19. The observed and expected heterozygosities varied from 0.158 to 0.842 (mean = 0.421) and from 0.376 to 0.952 (mean = 0.771), respectively. All 21 loci were also polymorphic in closely related species (P. tomentosa, P. elongata, and P. fortunei). The described markers will be useful in future population genetic studies and molecular breeding of these Paulownia species.

Reflection resonance switching in metamaterial twisted nematics cell

Electric switching of reflection resonances at near-IR spectral range is experimentally demonstrated in a reflective metamaterial twisted nematic liquid crystal cell. Reflective metamaterial composed of nano-sized double-split ring resonator aperture is fabricated by a focused ion beam milling. Two-fold rotational symmetry of double-split ring resonators allows for two orthogonal polarization-dependent reflection resonances in the reflective metamaterial. With an external voltage of 10V across 12μm cell gap, a full switching is achieved between two reflection resonances. Dynamic measurements show the time constants of switch-on and switch-off are in the order of 100ms and 10ms, respectively.

Solvent-free fluidic organic dye lasers

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green- and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Förster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors.

Fabrication of polarization-dependent reflective metamaterial by focused ion beam milling

By focused ion beam milling, we fabricated near-IR reflective metamaterials consisting of nano-aperture arrays. Optimum parameters of ion beam current and accelerating voltage in the fabrication process are obtained. Nano-apertures constituting reflective metamaterial are successfully milled, and possess a reflective resonance in the near-IR spectral range. With a double-split-ring resonator structure for the nano-aperture, the intensity reflection at resonance is rendered polarization dependent. It is found that the point group symmetry of the nano-aperture array determines the amount of anisotropy in the intensity reflection. Finite-difference time-domain simulation was adopted to identify details of nano-aperture metastructures transferred from nano-aperture patterns by the focused ion beam milling.

Anisotropic change in THz resonance of planar metamaterials by liquid crystal and carbon nanotube

THz metamaterials are employed to examine changes in the meta-resonances when two anisotropic organic materials, liquid crystal and carbon nanotubes, are placed on top of metamaterials. In both anisotropic double split-ring resonators and isotropic four-fold symmetric split-ring resonators, anisotropic interactions between the electric field and organic materials are enhanced in the vicinity of meta-resonances. In liquid crystal, meta-resonance frequency shift is observed with the magneto-optical coupling giving rise to the largest anisotropic shift. In carbon nanotube, meta-resonance absorptions, parallel and perpendicular to nanotube direction, experience different amount of broadening of Lorentzian oscillator of meta-resonance. Investigation reported here opens the application of metamaterials as a sensor for anisotropic materials.

Continuous spatial tuning of laser emissions in a full visible spectral range

In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the wedge cell with positive slope, the authors demonstrated a continuous spatial laser tuning in the near full visible spectral range, with a tuning resolution less than 1 nm by pumping with only a single 355 nm laser beam. This continuous tuning behavior is due to the fact that the concentration of pitch gradient matches the fixed helical pitch determined by the cell thickness. This characteristic continuous spatial laser tuning could be confirmed again by pumping with a 532 nm laser beam, over 90 nm in the visible spectral range. The scheme of the spatial laser tuning in the wedge cell bearing a pitch gradient enabled a route to designing small-sized optical devices that allow for a wide tunability of single-mode laser emissions.

Cryogenic temperature measurement of THz meta-resonance in symmetric metamaterial superlattice

A symmetric metamaterial superlattice is introduced accommodating a high Q-factor trapped mode. THz time-domain spectroscopy is employed to measure the transmission spectra, identifying the excitation of trapped and open-modes in the meta-resonances. A finite-difference-time- domain calculation showed that the trapped mode excitation is from the cancelation of current densities among the nearest-neighboring meta-particles. A cryogenic temperature THz measurement is carried out to examine the temperature dependence of resonance characteristics of meta-resonances. At low temperatures, the temperature-independent radiative damping is dominant for the open-mode, while the Q-factor of the trapped mode is determined by the temperature-dependent phonon scattering and temperature-independent defect scattering with the radiative damping significantly suppressed. When compared with the room temperature measurement, a 16% increase in Q-factor is observed for the trapped mode, while a 7% increase for the open-mode at the cryogenic temperature.

Continuous spatial tuning of laser emissions with tuning resolution less than 1 nm in a wedge cell of dye-doped cholesteric liquid crystals

We report the design and fabrication of a wedge structured CLC film incorporating a spatial gradient of a chiral dopant concentration. A continuous spatial laser tuning in the broad visible spectral range with tuning resolution less than 1 nm is demonstrated, which renders a CLC-based micron-sized laser an important continuously tunable laser device.

Optical switching of near infrared light transmission in metamaterial-liquid crystal cell structure

A metamaterial-liquid crystal cell structure is fabricated with the metamaterial as one of the liquid crystal alignment layers. Nano-sized double-split ring resonator in the metamaterial accommodates two distinct resonances in the near infrared regime. By adopting an azo-nematic liquid crystal in a twisted nematic liquid crystal cell structure, a photo-isomerization process is utilized to achieve an optical switching of light transmissions between two resonances. A single device of the metamaterial-liquid crystal cell structure has a potential application in the photonic switching in optical fiber telecommunications.

Polarization angle control of coherent coupling in metamaterial superlattice for closed mode excitation

A superlattice structure of planar metamaterial is fabricated, where the orientation of double-split ring resonators is altered in a periodic way. A time-domain terahertz transmission spectrum shows an enhanced Q-factor resonance appears when a closed mode is selectively excited by angular tuning of polarization direction. The polarization-angle selective resonance in metamaterial superlattice has a potential application in the selective field enhancement for spectroscopy.