Synthesis of photosensitive and thermosetting poly(phenylene ether) based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol‐co‐2,6‐dimethyl‐phenol] and a photoacid generator

A chemically amplified photosensitive and thermosetting polymer based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol (15 mol %)‐co‐2,6‐dimethylphenol (85 mol %)] ( 3c ) and a photoacid generator [(5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile] was developed. Poly[2,6‐bis(3‐methyl‐2‐butenyl)phenol]‐co‐2,6‐dimethylphenol)] ( 3 ) with high molecular weights (number‐average molecular weight ～ 24,000) was prepared by the oxidative coupling copolymerization of 2,6‐di(3‐methyl‐2‐butenyl)phenol with 2,6‐dimethylphenol in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen. The structures of 3 were characterized with IR, ¹H NMR, and ¹³C NMR spectroscopy. 3 was crosslinked by a thermal treatment at 300 °C for 1 h under N₂. The 5% weight loss temperatures and glass‐transition temperatures of the cured copolymers reached around 420 °C in nitrogen and 300 °C, respectively. The average refractive index of the cured copolymer ( 3c ) film was 1.5452, from which the dielectric constant at 1 MHz was estimated to be 2.6. The resist showed a sensitivity of 35 mJ cm^?2 and a contrast of 1.6 when it was exposed to 436‐nm light, postexposure‐baked at 145 °C for 5 min, and developed with toluene at 25 °C. A fine negative image featuring 8‐μm line‐and‐space patterns was obtained on a film exposed to 100 mJ cm^?2 with 436‐nm light in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 149–156, 2005     

Integration of a Proposed All-Optical Analog-to-Digital Converter using Self-Frequency Shifting in Fiber and a Pulse-Shaping Technique

Integration of a proposed all-optical analog-to-digital (A/D) converter is described. To realize a high-speed and highthroughput system, optical A/D conversion has attracted much attention. A/D conversion generally consists of three processes of sampling, quantization and coding. Whereas an optical sampling technique has already been realized, there have been few investigations on the optical quantization and optical coding technique. We previously proposed an alloptical A/D converter which realizes both optical quantization and optical coding. In this paper, we integrate the proposed all-optical A/D converter to improve its performance and stability. We verify the operation of the integrated all-optical A/D converter composed of a short high nonlinear fiber, arrayed waveguide gratings and variable optical attenuators.     

Diode-pumped, chirped-pulse Yb:S-FAP regenerative amplifier for laser-Compton X-ray generation

We present a diode-pumped, chirped-pulse Yb:S-FAP regenerative amplifier. This regenerative amplifier was developed as a first amplifier in an all-solid-state Yb:S-FAP laser system for laser-Compton X-ray generation. The amplifier delivers pulse energies above 24 mJ at a repetition rate of 50 Hz. Pulse compression reduces pulse widths to approximately 2.0 ps.     

Thermotropic liquid‐crystalline polymers containing five‐membered heterocyclic groups. X. Relationships between structures of semirigid polyesters based on three disubstituted 2,5‐diphenyl‐1,3,4‐thiadiazoles and thermotropic liquid‐crystalline and optical properties

Thermotropic liquid‐crystalline (LC) semirigid polyesters based on three terphenyl analogues of 1,3,4‐thiadiazole (2,5‐diphenyl‐1,3,4‐thiadiazole)s (DPTD) linking undecamethyleneoxy chain at different substituted positions were synthesized from three disubstituted (4,4′‐, 3,4′‐, and 3,3′‐) dioxydiundecanols of DPTD and four diesters, and the relationships between polymer structures and LC and optical properties were investigated. DSC measurements, texture observations, and wide‐angle X‐ray analyses revealed that the polymers composed of DPTD moiety having a more linear molecular structure and 1,4‐phenylene unit or short aliphatic chain tend to exhibit LC smectic C and/or A phases. The following observations were made: (1) the emergence of smectic C and/or A phases in all the polymers on the basis of 4,4′‐disubstituted DPTD, (2) formation of enantiotropic smectic C and/or A phases in the polymers containing a 1,4‐phenylene unit in the main chain, (3) formation of a more stable smectic C phase in the polymers having a short aliphatic [(CH₂)₄] chain, and (4) a decrease of the mesomorphic property of the polyesters in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD. Solution and solid‐state ultraviolet–visible and photoluminescent spectra indicated that all the polyesters display maximum absorbances and blue emissions arising from the DPTD moiety, whose peak maxima were shifted to lower wavelengths in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD as well as the aforementioned LC property. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2676–2687, 2003     

The Source of “Fairy Rings”: 2‐Azahypoxanthine and its Metabolite Found in a Novel Purine Metabolic Pathway in Plants

Rings or arcs of fungus‐stimulated plant growth occur worldwide; these are commonly referred to as “fairy rings”. In 2010, we discovered 2‐azahypoxanthine (AHX), a compound responsible for the fairy‐ring phenomenon caused by fungus; AHX stimulated the growth of all the plants tested. Herein, we reveal the isolation and structure determination of a common metabolite of AHX in plants, 2‐aza‐8‐oxohypoxanthine (AOH). AHX is chemically synthesized from 5‐aminoimidazole‐4‐carboxamide (AICA), and AHX can be converted into AOH by xanthine oxidase. AICA is one of the members of the purine metabolic pathway in animals, plants, and microorganisms. However, further metabolism of AICA remains elusive. Based on these results and facts, we hypothesized that plants themselves produce AHX and AOH through a pathway similar to the chemical synthesis. Herein, we demonstrate the existence of endogenous AHX and AOH and a novel purine pathway to produce them in plants.     

Collective Synthesis and Biological Evaluation of Tryptophan‐Based Dimeric Diketopiperazine Alkaloids

A concise two one‐pot synthesis of WIN 64821, eurocristatine, 15,15′‐bis‐epi‐eurocristatine, ditryptophenaline, ditryptoleucine A, WIN 64745, cristatumin C, asperdimin, naseseazine A, and naseseazine B is detailed, based on a unique bioinspired dimerization reaction of tryptophan derivatives in aqueous acidic solution and a one‐pot procedure for the construction of diketopiperazine rings. Total yields of these alkaloid syntheses were from 10 up to 27 %. In addition, 1′‐(2‐phenylethylene)‐ditryptophenaline was synthesized by using three one‐pot operations. The studies detailed herein provided synthesized natural products for inhibitory activities of ubiquitin‐specific protease 7 (USP7) and foam cell formation in macrophages. The newly listed biological evaluation for tryptophan‐based dimeric diketopiperazine alkaloids discovered 15,15′‐bis‐epi‐eurocristatine, 1′‐(2‐phenylethylene)‐ditryptophenaline, and WIN 64745 as new drug candidates.     

Heterogeneous Molecular Systems for Photocatalytic CO2 Reduction with Water Oxidation

Artificial photosynthesis—reduction of CO₂ into chemicals and fuels with water oxidation in the presence of sunlight as the energy source—mimics natural photosynthesis in green plants, and is considered to have a significant part to play in future energy supply and protection of our environment. The high quantum efficiency and easy manipulation of heterogeneous molecular photosystems based on metal complexes enables them to act as promising platforms to achieve efficient conversion of solar energy. This Review describes recent developments in the heterogenization of such photocatalysts. The latest state‐of‐the‐art approaches to overcome the drawbacks of low durability and inconvenient practical application in homogeneous molecular systems are presented. The coupling of photocatalytic CO₂ reduction with water oxidation through molecular devices to mimic natural photosynthesis is also discussed.     

Measurement of tritium with plastic scintillators in large vials of a low background liquid scintillation counter: an organic waste-less method

The tritium compounds, tritiated water as a volatile compound and ³H-methionine as a non-volatile compound, were measured with two types of plastic scintillators (PSs) using a low background liquid scintillation counter (LSC). It is advantage that minimal organic waste is generated when a plastic scintillator is used for LSC measurement. The effect of large vials on counting efficiency, plasma effects with three types of plasma devices for PS-sheets, the effect of UV-light on PS-pellets, the relationship between the activity and the count rate, and the detection limits of tritium were studied with respect to the development of large-scale measurement systems.