Photon‐Quantitative 6π‐Electrocyclization of a Diarylbenzo[b]thiophene in Polar Medium

The high reactivity of 6π‐electrocyclization in polar solvents has remained one of the important challenges for diarylethenes because of the emergence of a twisted intramolecular charge transfer (TICT) state at the excited state in such polar media, which usually quenches the photocyclization reaction. Herein we report on the preparation and highly efficient photocyclization of 2,3‐diarylbenzo[b]thiophenes with nonsymmetric side‐aryl units in a polar solvent. While the dithiazolylbenzo[b]thiophene showed a suppressed quantum yield of 6π‐electrocyclization of 54 % in methanol, the replacement of a thiazole unit with a thiophene ring led to a photon‐quantitative 6π‐cyclization reaction. The nonsymmetrical modification into the side‐aryl units was considered to enhance the CH/π interactions between side‐aryl units to support a photoreactive conformation in methanol. The stabilization of the photochromic reactive conformation is expected to suppress the formation of the TICT state at the excited state, leading to highly efficient photoreactivity.     

Simultaneous determination of phenolic xenoestrogens by solid-phase extraction and high-performance liquid chromatography with fluorescence detection.

A highly sensitive and selective method for simultaneous determination of some hydroxyl group-containing endocrine disruptors, including bisphenol A (BPA), bisphenol B (BPB), bisphenol E (BPE), bisphenol F (BPF) and 4-nonylphenol (4-NP), was developed. The method consists of precolumn derivatization of the analytes, solid-phase extraction (SPE) and subsequent chromatographic analysis by high-performance liquid chromatography (HPLC) with fluorescence detection. 4,4'-Cyclohexylidenebisphenol (BPZ) was used as an internal standard. Derivatization was carried out using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. Parameters of the derivatization reaction (temperature, time, concentration of reagent, stability, etc.) and of the solid-phase extraction (recovery, solvent, etc.) were studied in detail. Detection limits of compounds studied in standard solutions ranged from 0.08-1.3 ppb (ng/ml). The proposed method was successfully applied to plastic samples; BPA was found in both polycarbonate and polyvinyl chloride plastics, while 4-NP was found in plastics made of polyvinyl chloride and another polymer.     

Disparity Limit for Binocular Fusion in Fovea

In the human visual system, binocular disparity limit must be limited within a certain fusional area, called “Panum's fusional area”; otherwise, unsuitable disparity could cause double vision. The previous studies on Panum's fusional area have focused only on the horizontal and vertical meridians. In order to measure this area in more directions, we determined its limits in 16 different directions from 0 to 360° at 22.5° steps in fovea. It was found that: (1) the horizontal disparity limit (about 32-40 arcmin) is larger than the vertical limit (about 19.2–25.6 arcmin); (2) Panum's fusional area is approximately symmetrical around the horizontal meridian; (3) however, it is not symmetrical around the vertical meridian; the nasalward disparity limits are obviously larger than temporalward disparity limits; (4) therefore, the form of Panum's fusional area in fovea could be suggested to be an ellipse off-centered toward the nasal side on the horizontal meridian.     

Diameter-dependent relaxation dynamics of 1D excitons in single-walled carbon nanotubes

We have studied 1D exciton relaxation dynamics in semiconducting single-walled carbon nanotubes (SWNTs) by femtosecond pump–probe experiments. The time evolution of change in transmittance ΔT/T induced by photo-excitation varies depending on the tube diameter. The decay time decreases with a decrease in the tube diameter. Pressure measurements have been conducted to explore the relaxation mechanism. The deformation potential estimated from the pressure dependence of photoluminescence spectra increases with decreasing tube diameter. This means that the exciton–phonon interaction becomes stronger in the smaller diameter tubes. The diameter dependences of decay time and deformation potential suggest that the exciton–phonon interaction plays an important role in exciton nonradiative relaxation process in semiconducting SWNTs.     

The relationship between the structures of semi-rigid homo- and copolyesters based on 5,5'-diphenyl-2,2'-bis(1,3,4-thiadiazole)s and their liquid crystalline and optical properties

New semi-rigid homo- and copolyesters composed of the quaterphenyl analogue of 2,2'-bis(1,3,4-thiadiazole) (BTD), 5,5'-diphenyl-2,2'-bis(1,3,4-thiadiazole) (DBTD), were prepared by high temprature solution polycondensation of monomers, 3,3'- and 4,4'-dioxydiundecanol derivatives of DBTD with four dimethyl esters, and their liquid crystalline (LC) and optical properties were investigated. DSC measurements, texture observations using a polarizing microscope equipped with a hot stage, and powder X-ray diffraction showed that the homopolymers containing the 4,4'-DBTD unit form more stable LC phases than those having the 3,3'-DBTD unit. The 4,4'-DBTD-containing polymers and the 3,3'-DBTD unit-poor copolymers, except for the 3,3'-DBTD unit-rich copolymers and the 3,3'-DBTD-containing homopolymers (which formed highly ordered smectic or crystal mesophases), displayed a thermotropic LC smectic C phase. Solution and solid state UV-vis and photoluminescent (PL) spectra showed that the polyesters display miximum absorbances and bluish-green or blue emission based on the DBTD unit, where the Stokes shifts were observed. The peak positions in the UV-vis and the PL spectra of homopolymers composed of the 4,4'-DBTD unit were at higher wavelengths than those in the corresponding 3,3'-DBTD-containing homopolymers, due to its more conjugated structure. In the copolymers the peak maxima were shifted to shorter wavelengths with the increase of 3,3'-DBTD content.     

Impact of aerosols on the forecast accuracy of solar irradiance calculated by a numerical weather prediction model

The impact of aerosols on the forecast accuracy of solar irradiance calculated by a fine-scale, one day-ahead, and operational numerical weather prediction model (NWP) is investigated in this study. In order to investigate the impact of aerosols only, the clear sky period is chosen, which is defined as when there are no clouds in the observation data and in the forecast data at the same time. The evaluation of the forecast accuracy of the solar irradiance is done at a single observation point that is sometimes affected by aerosol events. The analysis period is one year from April 2010 to March 2011. During the clear sky period, the root mean square errors (RMSE) of the global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI) are 40.0?W?m^?2, 84.0?Wm^?2, and 47.9?W?m^?2, respectively. During one extreme event, the RMSEs of the GHI, DNI, and DHI are 70.1?W?m^?2, 211.6?W?m^?2, and 141.7?W?m^?2, respectively. It is revealed that the extreme events were caused by aerosols such as dust or haze. In order to investigate the impact of the aerosols, the sensitivity experiments of the aerosol optical depth (AOD) for the extreme events are executed. The best result is obtained by changing the AOD to 2.5 times the original AOD. This changed AOD is consistent with the satellite observation. Thus, it is our conclusion that an accurate aerosol forecast is important for the forecast accuracy of the solar irradiance.