Application of photoelectron emission microscopy (PEEM) to extraterrestrial materials

We observed the spatially resolved X-ray absorption fine structure of meteoritic inclusion by photoelectron emission microscopy in conjunction with hard-X-ray synchrotron radiation. The cracked domain in the inclusion is identified as Cr₂FeO₄ (chromite), and its electronic structure shows identical behavior with that of synthetic chromite. The photon energy is also scanned over the extended region to obtain the radial distribution function. It finally shows almost identical behavior as synthetic chromite.     

Absolute determination method using chirality for glufosinate and bialaphos by gamma-cyclodextrin modified capillary zone electrophoresis.

A novel absolute determination method using chirality without any calibration curves or comparison standards has been proposed for phosphorus-containing amino acid-type herbicides, glufosinate (D,L-GLUF) and bialaphos (BIAL). This method is based on a change in the enantiomeric ratio after the spiking of a known amount of the enantiomers with different enantiomeric ratios to a sample. D,L-GLUF was determined by adding a known amount of L-GLUF to the sample, derivatizing them with dansyl chloride, and measuring the ratio of the peak area of the D-isomer to that of the L-isomer by means of gamma-cyclodextrin modified capillary zone electrophoresis. The accuracy and precision of the method were evaluated using a synthetic sample. The mean values obtained for D- and L-GLUF agreed with the values taken within 1.6%; also the reproducibility was as good as less than 2.8%. The determination of BIAL was achieved by determining GLUF quantitatively produced by the acid hydrolysis of BIAL. The proposed methods were applied to the analysis of commercial herbicides and the validity and usefulness were evaluated.     

Facile syntheses of homothia‐ and homoazacalixarenes

Decahomotetrathiacalix[6]arenes were conveniently prepared from the 2:2 cyclization reactions of bis(chloromethyl)phenol‐formaldehyde trimers with 1,2‐ethanedithiol in high yields. In contrast, the simi lar reactions of the trimers with 1,3‐propanedithiol instead of 1,2‐ethanedithiol gave 1:1 macrocycles, hexahomodithiacalix[3]arenes, in good yields. Homoazacalixarenes were also prepared from the analogous reactions using piperazines. These macrocycles adopt a cone‐like form as a preferable conformation in solution.     

A Tunable External Cavity Laser Diode Possessing a Stable Wavelength

In this work we describe a simple external-cavity laser diode equipped with a feedback control system, in which a high-resolution position-sensitive detector detects the slight misalignment of the light within the cavity. Our system not only provides a stable wavelength that can be tuned within a maximum scanning range of 1.87 nm, but also allows for faster scanning, through precise control of the reflection angle within the cavity. The simultaneous controls on the rotation-angle of the external mirror and the injection current enabled us to realize continuous wavelength-tuning.     

Iridium-catalyzed consecutive and enantioselective [2+2+2] cycloaddition of tetraynes and hexaynes for the construction of an axially chiral biaryl system

A chiral iridium complex catalyzed a consecutive and enantioselective [2+2+2] cycloaddition of polyynes to give axially chiral compounds. Intermolecular reaction of tetraynes, possessing aryl groups on their termini, with protected but-2-yne-1,4-diols gave C₂-symmetrical quateraryl compounds. Intramolecular reaction of hexaynes, possessing aryl or alkyl groups on their termini gave C₂-symmetrical biaryl compounds. The catalytic synthesis of a pentacene derivative with axial chiralities is also discussed.     

Synthesis of one-dimensional microporous todorokite and its catalytic activity in CO oxidation

Synthesis of an octahedral molecular sieve composed of Mn, Mg and O, known as todorokite, was studied in detail. The synthesis procedure is composed of three steps; layered birnessite synthesis, ion-exchange to buserite and final hydrothermal treatment of buserite. To obtain todorokites of different morphological properties, the aging time in the birnessite synthesis was varied. The effects of the aging time on properties of todorokites were studied by XRD, FE-SEM, TG-DTA, N₂ adsorption-desorption, FT-IR and CO-TPD. In addition, catalytic activities of various todorokites for CO oxidation were investigated and the correlation between properties and activities was discussed.     

Object plane detection and phase-amplitude imaging based on transport of intensity equation

By using transport of intensity equation (TIE), phase distribution of an object is retrieved from through-focus intensity images. This technique allows simple and robust phase imaging compared with an interferometric approach. However, it is hard to measure phase distribution when a dynamic object moves in the direction of an optical axis. To clear this problem, autofocusing TIE which is based on local statistics is proposed. The proposed technique achieves the detection of the object plane and the retrieval of a focused object phase distribution simultaneously. In this approach, an object plane is determined by the focusing techniques based on local statistics such as variance, gradient, and Laplacian of amplitude distribution, after phase distribution in an image sensor plane is retrieved by the TIE. The performance of these three statistics is evaluated in numerical and optical experiments, and a suitable focus value is determined for precise phase imaging.     

FPGA-based photon-counting phase-modulation fluorometer and a brief comparison with that operated in a pulsed-excitation mode

We have constructed a high-efficiency, photon-counting phase-modulation fluorometer (PC-PMF) using a field-programmable gate array, which is a modified version of the photon-counting fluorometer (PCF) that works in a pulsed-excitation mode (Iwata and Mizuno in Meas Sci Technol 28:075501, 2017). The common working principle for both is the simultaneous detection of the photoelectron pulse train, which covers 64 ns with a 1.0-ns resolution time (1.0 ns/channel). The signal-gathering efficiency was improved more than 100 times over that of conventional time-correlated single-photon-counting at the expense of resolution time depending on the number of channels. The system dead time for building a histogram was eliminated, markedly shortening the measurement time for fluorescent samples with moderately high quantum yields. We describe the PC-PMF and make a brief comparison with the pulsed-excitation PCF in precision, demonstrating the potential advantage of PC-PMF.     

Cosmic-ray positron from superparticle dark matter and the PAMELA anomaly

Motivated by the anomalous positron flux recently reported by the PAMELA Collaboration, we study the cosmic-ray positron produced by the pair annihilation and the decay of superparticle dark matter. We calculate the cosmic-ray positron flux and discuss implications of the PAMELA data. We show that the positron excess observed by the PAMELA can be explained with some of the superparticle dark matter.