Phase diagram and oxygen annealing effect of FeTe1−xSex iron-based superconductor

Phase diagrams of as-grown and O₂-annealed FeTe_1?xSe_x determined from magnetic susceptibility measurement were obtained. For as-grown samples, the antiferromagnetic order was fully suppressed in the range region x≥0.15, and weak superconductivity appeared when x≥0.1. Beginning at x=0.5, weak superconductivity was found to evolve into bulk superconductivity. Interestingly, for O₂-annealed samples, complete suppression of magnetic order and the occurrence of bulk superconductivity were observed when x≥0.1. We found that O₂-annealing induces bulk superconductivity for FeTe_1?xSe_x. Oxygen probably plays a key role in the suppression of the magnetic order and the appearance of bulk superconductivity.     

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost.     

A symmetric oxyselenenylation of simple olefins using optically active selenobinaphthyls

Asymmetric trans-addition reactions of simple olefins have been performed by using optically active 2-selenobinaphthyls 1 , 2a–g. Introduction of an amide group at the 2′-position in the binaphthyl skeleton enhances considerably the diastereomeric excess (de) of the asymmetric methoxyselenenylation. In the case of trans-olefins, introduction of another chiral center in the amide group further enhances the de due to double stereodifferentiation between the (R)-binaphthyl skeleton and the chiral amide group introduced at the 2′-position in the binaphthyl skeleton. The use of chiral nucleophiles is also effective to enhance the de for symmetrical cis-olefins.     

Inelastic scattering of cosmic ray muons on iron nuclei and the virtual photon shadowing

Hadronic cascade showers originating from inelastic interactions of cosmic ray muons with iron nuclei have been observed in a calorimeter located between two magnetic spectrometers. The separation of those events from the electromagnetic showers has been successfully done in the ranges of the transferred energy v ≳ 50 GeV and its ratio to muon energy v/E ≳ 0,1, by utilizing the difference of their longitudinal cascade developments. The comparison of the obtained μ-Fe cross section with available μ-, e- and σ-proton data as well as μ-, e- and σ-nucleus data indicates that;

• 1 At v ˜ 100 GeV, the virtual photon cross section on iron nucleus is almost the same as the real photon one, at least Q² ≳ 0.1 GeV²/c², and is about 70% of the cross section on proton times the atomic mass number of iron, i.e. the shadowing effect is clearly seen.
• 2 Up to TeV region, this virtual photon cross section on iron does not increase significantly. contrary to the tendency of the real photon cross section on proton around 100 GeV. This suggests most likely that the shadowing still increases with energy at such high energies.

     

Self-modeling curve resolution analysis of on-line vibrational spectra of polymerisation and transesterification

This article discusses the potential of self-modeling curve resolution analysis (SMCR) for the evolution of on-line vibrational spectral data of polymerisation and transesterification. After the general introduction of the SMCR approach, representative SMCR techniques like orthogonal projection analysis (OPA) and simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) are briefly outlined. As examples the SMCR analysis of the Raman spectra of the block copolymerisation of styrene and 1,3-butadiene and that of the near-infrared (NIR) spectra of the melt-extrusion transesterification of ethylene-vinylacetate copolymer will be illustrated. In the last part of this review paper, a new powerful SMCR method that we have recently proposed is demonstrated.     

Cover Picture: Electrochemical Method for G-quartet RNA Detection of COVID-19 Based on Cyclic Ferrocenylnaphthalene Diimide (Electroanalysis 4/2023)

To develop an electrochemical detection method for COVID-19, we have investigated the interaction between RG-1, a characteristic parallel four-strand RNA component of the COVID-19 genome, and cyclic ferrocenylnaphthalene diimides carrying different linker lengths 1 and 2 , which bind to RG-1 more strongly than cyclic naphthalene diimide 3 that lacks a ferrocene moiety. In particular, the binding affinity of 1 having short one showed the highest binding affinity to RG-1, and the redox current of 1 increased in the presence of RG-1 using a glassy carbon electrode. This increasing current of 1 in the presence of c-myc as a parallel G4 DNA or single-stranded RNA was lower than that in the presence of RG-1. Several RG-1 was electrochemically detected at the nanomolar level by 1 .     

Selective SERS detection of each polycyclic aromatic hydrocarbon (PAH) in a mixture of five kinds of PAHs

This paper reports the qualitative analysis and quantitative detection of polycyclic aromatic hydrocarbon (PAH) molecules with per‐6‐deoxy‐(6‐thio)‐β‐cyclodextrin (CD‐SH) modified gold nanoparticles (AuNPs) by surface‐enhanced Raman scattering (SERS) spectroscopy. For the selective sensing of PAHs, which are environmental pollutants with very low affinity to metallic surfaces, by SERS, a stable substrate with AuNPs and CD‐SH was utilized by supramolecular interaction. Quantitative detection of each PAH was carried out by SERS on inclusion complexes with different concentrations. From the SERS spectra of a mixture of five different PAHs, we could easily distinguish each PAH by its discriminant peaks. In addition, quantitative analysis of one component in a mixture of five PAHs was also investigated. This sensing platform revealed matching relationship between the host and the guest and the host–guest interaction mechanism. The proposed approach for the selective detection of PAHs holds great potential in the detection of environmental organic pollutants. Copyright © 2010 John Wiley & Sons, Ltd.     

Fourier‐Transform Raman Spectroscopic On‐Line Monitoring of the Anionic Dispersion Block Copolymerization of Styrene and 1,3‐Butadiene

The anionic dispersion block copolymerization of styrene and 1,3‐butadiene has proved a suitable technique to synthesize block copolymers of tailor‐made blocklength under technically relevant conditions. For this purpose, however, an efficient analytical on‐line technique is required to control the concentrations of individual reactants and product. The present communication shortly outlines the potential of non‐invasive light‐fiber Fourier‐transform Raman spectroscopy in combination with a self‐modeling curve‐resolution analysis to monitor the polymerization progress and to derive concentration profiles of the two monomers and polybutadiene without prior calibration of the investigated system.