Development of the radical C–O coupling reaction of phenols toward the synthesis of natural products comprising a diaryl ether skeleton

Compounds comprising a diaryl ether skeleton exist among natural phenols. The diaryl ether skeleton is thought to be biosynthesized through the coupling of two or more phenols. It is an important structural feature in medicines and agrochemicals, and it is imperative to develop methods for constructing such skeletons in organic synthesis. However, by the synthesis method through the coupling of phenols, coupling occurs preferentially at the ortho-substituted carbon atom of phenols. In this study, various radical-generating reagents and conditions were investigated with the aim of developing a short-step construction method of the diaryl ether skeleton by the radical homo-coupling of two phenol molecules. In addition, cross-coupling reactions between radicals of 2,4,6-tri-tert-butylphenol and p-substituted phenol were conducted to synthesize eight C (ortho)–O coupling products. Based on the results, a computational chemical approach was employed to verify the cause of C (ortho)–O bond formation.     

Synthesis of networked polymer based on ring‐opening addition reaction of 1,3‐benzoxazine with resorcinol

A highly efficient ring‐opening addition reaction of benzoxazine at ambient temperature has been developed with 2‐methylresorcinol as a nucleophilic reagent. In this reaction, 2‐methylresorcinol reacted with two equivalent amount of benzoxazine to give the corresponding 1:2 adduct, demonstrating its potential as a bifunctional nucleophile. Based on this reaction, a new crosslinking system consisting of a polymer bearing benzoxazine moieties in the side chains and 2‐methylresorcinol as a crosslinker has been performed to obtain the corresponding networked polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Seasonal variation of tropospheric aerosol properties by direct and scattered solar radiation spectroscopy

Long-term characterization of tropospheric aerosol has been carried out at Chiba, Japan, using a compact, stand-alone spectroradiometer under clear-sky conditions between August 2007 and March 2009. The spectra of direct solar radiation, aureole, and scattered solar radiation in various directions are observed in a wavelength range between 350 and 1050 nm with an optical resolution of 10 nm. Radiative transfer calculation using the MODTRAN4 code is employed to retrieve aerosol optical parameters such as aerosol optical depth (AOD), extinction coefficient, single-scattering albedo, scattering phase function, and asymmetry parameter, as well as water vapor column amount. The retrieved value of AOD varies in the range 0.1-0.5, while the water vapor column amount changes from 0.2 to 4 g/cm², showing reasonable agreements with the concurrent measurements with a sunphotometer and a microwave radiometer, respectively. The seasonal variation of the retrieved parameters indicates the major impacts of dust particles in spring, sea salt particles in summer, and anthropogenic fine particles in winter.     

Development of a precise quantitative method for monitoring sirolimus in whole blood using LC/ESI–MS/MS

Sirolimus is used on patients after solid organ transplantation and on lymphangioleiomyomatosis (LAM) patients, and therapeutic drug monitoring is required in clinical practice. We have previously reported an accurate method for quantitative determination of sirolimus, but its sample preparation step was complicated. In this study, we developed a modified liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI–MS/MS) method for sirolimus quantification. A supported liquid extraction cartridge was used to purify sirolimus from whole blood and ion suppression was mostly prevented. The validation results met the acceptance criteria. This method was compared with the antigen conjugated magnetic immunoassay (ACMIA) and our previously reported method, using whole blood samples from LAM patients. Comparison of the Bland–Altman plots of the currently developed method and the previous method revealed no significant difference between the two methods (mean bias, −2.02%; 95% CI, −7.81–3.78). The values obtained using ACMIA were significantly higher than those obtained using the current method by 13.87% (95% CI, 6.49–21.25) owing to cross-reactivity. The degrees of cross reactivities in LAM patients and in organ transplant patients were similar, and our LC/ESI–MS/MS method precisely measured the blood concentrations of sirolimus.     

Highly Efficient and Selective Oxidation of Ethanol to Acetaldehyde by a Hybrid Photocatalyst Consisting of SnO2 Nanorod and Rutile TiO2 with Heteroepitaxial Junction

Single-crystal SnO₂ nanorods were grown on rutile TiO₂ with a heteroepitaxial relation of SnO₂{001}/TiO₂{001} (SnO₂-NR#TiO₂) by a hydrothermal reaction. Resulting compressive lattice strain in the SnO₂-NR near the interface induces a continuous increase in the a-axis length extending over 60 nm to relax towards the [001] direction from the root to the tip. UV-light irradiation of the robust SnO₂-NR#TiO₂ stably progresses the selective oxidation of ethanol to acetaldehyde with an external quantum yield of 25.6 % at excitation wavelength (λ_ex)=365 nm under ambient temperature and pressure. Spectroscopic analyses and density functional theory simulation results suggested that the extremely high photocatalytic activity stems from the smooth interfacial electron transfer from TiO₂ to SnO₂-NR through the high-quality junction and subsequent efficient charge separation due to the lattice strain-induced unidirectional potential gradient of the conduction band minimum in the SnO₂-NR.     

Spectra of Periodic Schrödinger Operators on the Degenerate Zigzag Nanotube with δ Type Vertex Conditions

In this paper, we consider the Schrödinger operators with a periodic potential and the δ type vertex conditions on a metric graph, which is called the degenerate zigzag nanotube, and discuss those spectrum. We demonstrate that the spectrum has the band structure. Moreover, we give the asymptotics of the band edges.     

Hybrids of Copolymers of Fluorene and C60‐Carrying‐Carbazole with Semiconducting Single‐Walled Carbon Nanotubes

Three different copolymers of C₆₀‐carrying‐carbazole and fluorene units with different copolymer composition ratios were designed and synthesized. On the basis of photoluminescence, atomic force microscopy, and Vis‐NIR and Raman spectroscopic analysis, we found that these copolymers solubilize only semiconducting single‐walled carbon nanotubes (sem‐SWNTs) to form copolymer/sem‐SWNT hybrids, in which energy transfer from the copolymer/C₆₀ moieties to the SWNTs was revealed. By comparing two possible hybrid structures with molecular‐mechanics simulations, the greatest stabilization was found when the C₆₀ moieties lay on the sem‐SWNT surfaces.     

Photoluminescence enhancement induced from silver nanoparticles in Tb3+ -doped glass ceramics

We experimentally verify that surface plasmon (SP) enhances the photoluminescence (PL) of visible light from Tb3+ -doped 60SiO2 -20Al2O3 -20CaF2 :0.3Tb 3+ , 20Yb 3+ glass ceramics by using electron beam lithography to fabricate silver nanoparticles on the surface of the glass ceramics. Numerical calculation for the SP enhancement spectroscopy is achieved by using the finite-difference time-domain algorithm. A PL enhancement of Tb3+ by as much as 1.6 times is observed. The PL enhancement is mainly due to the coupling of excitation from 7 F 6 to 5 D 4 transition dipole of Tb 3+ ion with SP mode induced from the silver nanoparticles.     

Lepton number violation at the LHC with leptoquark and diquark

We investigate a model in which tiny neutrino masses are generated at the two-loop level by using scalar leptoquark and diquark multiplets. The diquark can be singly produced at the LHC, and it can decay into a pair of leptoquarks through the lepton number violating interaction. Subsequent decays of the two leptoquarks can provide a clear signature of the lepton number violation, namely two QCD jets and a pair of same-signed charged leptons without missing energy. We show that the signal process is not suppressed while neutrino masses are appropriately suppressed.     

MIXED MODES INTERLAMINAR FRACTURE TOUGHNESS OF CFRP LAMINATES TOUGHENED WITH CNF INTERLAYER

In the present paper, the influence of carbon nanofiber on interlaminar fracture toughness of CFRP investigated using MMB(Mixed Mode Bending) tests. Vapor grown carbon fiber VGCF and VGCF-S, and multi-walled carbon nanotube MWNT-7 has been employed for the toughener of the interlayer on the CFRP laminates. In order to evaluate the fracture toughness and mixed mode ratio of it, double cantilever beam (DCB) tests, end notched fracture (ENF) tests and mixed mode bending (MMB) tests have been carried out. Boundary element analysis was applied to the CFRP model to compute the interlaminar fracture toughness, where extrapolation method was used to determine the fracture toughness and mixed mode ratio. The interlaminar fracture toughness and mixed mode ratio can be extrapolated by stress distribution in the vicinity of the crack tip of the CFRP laminate. It was found that the interlaminar fracture toughness of the CFRP laminates was improved inserting the interlayer made by carbon nanofiber especially in the region where shear mode deformation is dominant.