Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. IV. Properties of SiO2–TiO2 oxide fibers from polytitanosiloxane

From polytitanosiloxanes (PTS), SiO₂–TiO₂ oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network.     

Front Cover: Enhancement of Chiroptical Responses of trans‐Bis[(β‐iminomethyl)naphthoxy]platinum(II) Complexes with Distorted Square Planar Coordination Geometry (ChemistryOpen 4/2022)

The Front Cover shows the comparison of circularly polarized luminescence (CPL) properties of square planar platinum(II) complexes with different coordination geometries. Computational studies have revealed that the distortion of the coordination geometry is key to enhancement of the chiroptical responses of these compounds. More information can be found in the Research Article by Masahiro Ikeshita et al.     

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands

A new H-bonded crystal [Ru^III(Him)₃(Im)₃] with three imidazole (Him) and three imidazolate (Im⁻) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the Ru^III complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10⁻⁵ S cm⁻¹ at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [Ru^III(Him)₃(Im)₃] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state ²H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered.     

High-Affinity Ratiometric Fluorescence Probe Based on 6-Amino-2,2′-Bipyridine Scaffold for Endogenous Zn2+ and Its Application to Living Cells

Zinc is an essential trace element involved in many biological activities; however, its functions are not fully understood. To elucidate the role of endogenous labile Zn²⁺, we developed a novel ratiometric fluorescence probe, 5-(4-methoxyphenyl)-4-(methylsulfanyl)-[2,2′-bipyridin]-6-amine (6 (rBpyZ)) based on the 6-amino-2,2′-bipyridine scaffold, which acts as both the chelating agent for Zn²⁺ and the fluorescent moiety. The methoxy group acted as an electron donor, enabling the intramolecular charge transfer state of 6 (rBpyZ), and a ratiometric fluorescence response consisting of a decrease at the emission wavelength of 438 nm and a corresponding increase at the emission wavelength of 465 nm was observed. The ratiometric probe 6 (rBpyZ) exhibited a nanomolar-level dissociation constant (K_d = 0.77 nM), a large Stokes shift (139 nm), and an excellent detection limit (0.10 nM) under physiological conditions. Moreover, fluorescence imaging using A549 human lung adenocarcinoma cells revealed that 6 (rBpyZ) had good cell membrane permeability and could clearly visualize endogenous labile Zn²⁺. These results suggest that the ratiometric fluorescence probe 6 (rBpyZ) has considerable potential as a valuable tool for understanding the role of Zn²⁺ in living systems.     

Selection of meaningless steady noise for masking of speech

This paper focuses on masking speech with meaningless steady noise as a way of realizing a comfortable sound environment. As a basis for research, meaningless steady noise at minimum sound pressure levels for masking of male or female meaningful speech is considered, based on psychological experiments using a method of adjustment. From the results, band-limited pink noise can be selected as the most effective noise for masking of speech. In the case of speech with a lower sound pressure level, the sound pressure level of the meaningless steady noise needs to be a little higher.     

Nonequilibrium Green's function approach to phonon transport in defective carbon nanotubes

We have developed a new theoretical formalism for phonon transport in nanostructures using the nonequilibrium phonon Green's function technique and have applied it to thermal conduction in defective carbon nanotubes. The universal quantization of low-temperature thermal conductance in carbon nanotubes can be observed even in the presence of local structural defects such as vacancies and Stone-Wales defects, since the long wavelength acoustic phonons are not scattered by local defects. At room temperature, however, thermal conductance is critically affected by defect scattering since incident phonons are scattered by localized phonons around the defects. We find a remarkable change from quantum to classical features for the thermal transport through defective carbon nanotubes with increasing temperature.     

Characterization of heat-assisted magnetic probe recording on CoNi/Pt multilayers

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2–7 V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260 nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments.     

Measurement of the wrong-sign decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi-, and search for CP violation

Using 281 fb-1 of data from the Belle experiment recorded at or near the (4S) resonance, we have measured the rates of the "wrong-sign" decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi- relative to those of the Cabibbo-favored decays D0 --> K- pi+ pi0 and D0 --> K- pi+ pi+ pi-. These wrong-sign decays proceed via a doubly Cabibbo-suppressed amplitude or via D0-D0 mixing; the latter has not yet been observed. We obtain R(WS)(K pi pi0) = [0.229 +/- 0.015(stat)(+0.013)(-0.009)(syst)]% and R(WS)(K3pi) = [0.320 +/- 0.018(stat)(+0.018)(0.013)(syst)]%. The CP asymmetries are measured to be -0.006 +/- 0.053 and -0.018 +/- 0.044 for the K+ pi- pi0 and K+ pi- pi+ pi- final states, respectively.