Electrical field induced phase-matched second harmonic generation in low Tg polymer waveguides

Second-harmonic generation in the guided waveguide configuration is very attractive because a high fundamental power density can be coupled over long propagation length therefore remarkably high conversion efficiencies can be expected compared to bulk materials.¹ Organic SHG devices in optical waveguides have not been developed extensively because of the difficulty encountered in phase-matching. To avoid this problem, the use of an artificial periodic structure, Cerenkov radiation, and non-colinear light path geometry have already been demonstrated. Recently, we reported an electric field-induced dynamic phase-matching in a guided wave configuration using a main-chain polymer in which the effective phase-matching thickness can be controlled by an applied electric field.² This technique is able to increase the waveguide dimension tolerances of phase-matching condition. In the case of a main-chain polymer, the thermal optic effects due to the heating prevent to satisfy the optimum phase-matching conditions, which causes a reduction in the conversion efficiency of devices. In order to overcome this problem, we have synthesized novel low glass transition temperature (Tg) nonlinear optical (NLO) polymers. In this presentation, we will discuss an electric field-induced dynamic phase-matching of a multilayer waveguide at room temperature using a low Tg NLO polymer which can increase both the waveguide dimension tolerances and overlap integral. Using this technique, efficient phase-matched SHG was generated from p-nitroaniline grafted NLO materials. The dimension tolerance of waveguides under an electric field will be described.     

One-step synthesis of 2,6-naphthalenedicarboxylic acid from naphthalene using cyclodextrin as catalyst

The one-step synthesis of 2,6-naphthalenedicarboxylic acid from naphthalene with carbon tetrachloride, copper powder and aqueous alkali has been achieved under mild conditions by the use of β-cyclodextrin as catalyst, producing 2,6-naphthalenedicarboxylic acid in 65 mol-% yield with 79% selectivity.     

Organoruthenium-catalyzed chemical protein synthesis to elucidate the functions of epigenetic modifications on heterochromatin factors

The application of organometallic compounds for protein science has received attention. Recently, total chemical protein synthesis using transition metal complexes has been developed to produce various proteins bearing site-specific posttranslational modifications (PTMs). However, in general, significant amounts of metal complexes were required to achieve chemical reactions of proteins bearing a large number of nucleophilic functional groups. Moreover, syntheses of medium-size proteins (>20 kDa) were plagued by time-consuming procedures due to cumbersome purification and isolation steps, which prevented access to variously decorated proteins. Here, we report a one-pot multiple peptide ligation strategy assisted by an air-tolerant organoruthenium catalyst that showed more than 50-fold activity over previous palladium complexes, leading to rapid and quantitative deprotection on a protein with a catalytic amount (20 mol%) of the metal complex even in the presence of excess thiol moieties. Utilizing the organoruthenium catalyst, heterochromatin factors above 20 kDa, such as linker histone H1.2 and heterochromatin protein 1α (HP1α), bearing site-specific PTMs including phosphorylation, ubiquitination, citrullination, and acetylation have been synthesized. The biochemical assays using synthetic proteins revealed that the citrullination at R53 in H1.2 resulted in the reduced electrostatic interaction with DNA and the reduced binding affinity to nucleosomes. Furthermore, we identified a key phosphorylation region in HP1α to control its DNA-binding ability. The ruthenium chemistry developed here will facilitate the preparation of a variety of biologically and medically significant proteins containing PTMs and non-natural amino acids.

Chemical protein synthesis assisted by an organoruthenium catalyst streamlined the production of heterochromatin factors bearing various patterns of epigenetic modifications, and their biological significance was elucidated.     

Octonionic Yang–Mills instanton on quaternionic line bundle of Spin(7) holonomy

The total space of the spinor bundle on the four-dimensional sphere S⁴ is a quaternionic line bundle that admits a metric of Spin(7) holonomy. We consider octonionic Yang–Mills instanton on this eight-dimensional gravitational instanton. This is a higher dimensional generalization of (anti-) self-dual instanton on the Eguchi-Hanson space. We propose an ansatz for Spin(7) Yang–Mills field and derive a system of non-linear ordinary differential equations. The solutions are classified according to the asymptotic behavior at infinity. We give a complete solution when the gauge group is reduced to a product of SU(2) subalgebras in Spin(7). The existence of more general Spin(7) valued solutions can be seen by making an asymptotic expansion.     

Simultaneous Measurement of Wind and Aerosol Backscattering in the Troposphere by High Spectral Resolution Lidar with Iodine Filter

We propose a high spectral resolution lidar system which is capable of measuring aerosol backscattering and line-of-sight wind velocity in the troposphere. An iodine vapor filter is used to separate the aerosol and Rayleigh scattering components as well as to discriminate the Doppler shift frequency. The performance of the lidar system is estimated with reasonable parameters. The error of horizontal wind velocity below an altitude of 6 km is less than 0.5 m/s, and accuracy of the aerosol backscattering coefficient is better than 40% below 10 km. This system is particularly suitable for the study of aerosol transportation in the troposphere.     

Collapse of quantized Hall resistance and breakdown of dissipationless state in the integer quantum Hall effect: filling factor dependence

Magnetic field dependence of critical current for collapse of quantized Hall resistance I_cr(collapse) and critical current for breakdown of dissipationless state I_cr(breakdown) have been measured near the filling factor ν=4 of Landau levels in a GaAs/AlGaAs heterostructure Hall bar. The difference I_cr(breakdown)−I_cr(collapse) decreases against the increase and the decrease in ν from 4 and the critical behavior disappears outside of the region 3.85<ν<4.15.     

Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g^–1 of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.     

Generation of a methylbismuth species and its electrothermal vaporization for the determination of bismuth by inductively coupled plasma mass spectrometry

Inorganic bismuth(III) was converted to a methylbismuth species, possibly trimethylbismuth, by a thermochemical reaction with methyllithium. It instantly vaporized and was then introduced into the ICP ion source to detect the ²⁰⁹Bi signal. Utilizing an exchangeable small sample cuvette placed on the tungsten boat furnace for the reaction was very favorable from the viewpoints of easy handling, no memory effect, and maintenance of furnace conditions. In this manner, the analyte was vaporized at quite a low temperature (150 °C). The detection limit (3σ) was 0.13 pg of bismuth and the precision in relative standard deviation for 5.0 pg of bismuth was determined to be 3.8% (n = 7). Received: 6 June 1999 / Revised: 31 August 1999 / /Accepted: 23 September 1999     

Thin-film poly-Si solar cells on glass substrate fabricated at low temperature

The performances of thin-film poly-Si solar cells with a thickness of less than 5 μm on a glass substrate have been investigated. The cell of glass/back reflector/n-i-p type Si/ITO is well characterized by the structure of naturally surface texture and enhanced absorption with a back reflector (STAR), where the active i-type poly-Si layer was fabricated by plasma chemical vapor deposition (CVD) at low temperature. The cell with a thickness of 2.0 μm demonstrated an intrinsic efficiency of 10.7% (aperture 10.1%), an open-circuit voltage of 0.539 V and a short-current density of 25.8 mA/cm² as independently confirmed by Japan Quality Assurance. No light-induced degradation is observed. The optical and transport properties of poly-Si cells are summarized. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 7 July 1999