Nonlinear resonances and self-excited oscillations of a rotor caused by radial clearance and collision

This paper investigates oscillations in a flexible rotor system with radial clearance between an outer ring of the bearing and a casing by experiments and numerical simulations. The mathematical model considers the collisions of the bearing with the casing. The following phenomena are found: (1) Nonlinear resonances of subharmonic, super-subharmonic and combination oscillation occur. (2) Self-excited oscillation of a forward whirling mode occurs in a wide range above the major critical speed. (3) Entrainment phenomena from self-excited oscillation to nonlinear forced oscillation occur at these nonlinear resonance ranges. Moreover, this study analyzes periodic solutions of the mathematical model by the Harmonic Balance Method (HBM). As the results, the nonlinear resonances of subharmonic oscillation and its entrainment phenomenon can be explained theoretically by investigating the stability of the periodic solutions. The influence of the static force and the bearing damping on these oscillation are also clarified.     

Discovery of Hexagonal Structured Pd–B Nanocrystals

We report on hexagonal close-packed (hcp) palladium (Pd)–boron (B) nanocrystals (NCs) by heavy B doping into face-centered cubic (fcc) Pd NCs. Scanning transmission electron microscopy–electron energy loss spectroscopy and synchrotron powder X-ray diffraction measurements demonstrated that the B atoms are homogeneously distributed inside the hcp Pd lattice. The large paramagnetic susceptibility of Pd is significantly suppressed in Pd–B NCs in good agreement with the reduction of density of states at Fermi energy suggested by X-ray absorption near-edge structure and theoretical calculations.     

Test compounds for detecting the silanol effect on the elution of ionized amines in reversed‐phase LC

The effectiveness of several basic compounds for testing silica‐based stationary phases was reviewed by applying them to recent columns for reversed‐phase HPLC. Most octadecylsilylated (C18) stationary phases, prepared as a base‐deactivated material from high‐purity silica gel with endcapping, provided excellent peak shape and column efficiency for the bases including benzylamine and amitriptyline that once caused problems and were subsequently employed for testing silanol activities. However, a cyclic tertiary amine, dextrometorphan, was eluted as an acceptable peak from only a few columns at neutral pH. Such a more sensitive probe is expected to contribute to further improvement of the stationary phase for reversed‐phase HPLC.     

Determination of Ubiquinone in Blood by High-Performance Liquid Chromatography with Post-Column Fluorescence Derivatization Using 2-Cyanoacetamide

It was shown that ubiquinone (CoQ₁₀) and ubiquinol (CoQ₁₀H₂) produce fluorescence products under alkaline conditions when reacted with 2-cyanoacetamide. The reaction mixture from CoQ₁₀ gave fluorescence with excitation and emission maximum wavelengths at 442 nm and 549 nm, respectively. This reaction was considered to proceed via Craven’s reaction. Moreover, 2-cyanoacetamide was shown to be a useful reagent for high-performance liquid chromatography (HPLC) with post-column fluorescence derivatization of CoQ₁₀ and CoQ₁₀H₂ in blood. CoQ₁₀ showed a linear response in the range of 0.32–1276 ng, and the detection limit (S/N = 3) was 0.16 ng. Moreover, the sample pretreatment by deproteinization and extraction of CoQ₁₀ and CoQ₁₀H₂ from plasma using 1-propanol with potassium formate was effective for excellent separation of CoQ₁₀ and CoQ₁₀H₂ from other fluorescent substances in the blood. This simple and rapid pretreatment was considered to minimize the oxidation of CoQ₁₀H₂. On the other hand, CoQ₁₀ and CoQ₁₀H₂ in plasma samples obtained by finger prick were detected, as in venous blood obtained by venipuncture. Our method involving the simple and rapid collection of plasma by finger prick and sample pretreatment is thought to be applicable for the determination of CoQ₁₀H₂/total CoQ₁₀ ratio as a biomarker of oxidative stress.     

Topological Superconductivity in Cu(x)Bi(2)Se(3)

A topological superconductor (TSC) is characterized by the topologically protected gapless surface state that is essentially an Andreev bound state consisting of Majorana fermions. While a TSC has not yet been discovered, the doped topological insulator Cu(x)Bi(2)Se(3), which superconducts below ～3 K, has been predicted to possess a topological superconducting state. We report that the point-contact spectra on the cleaved surface of superconducting Cu(x)Bi(2)Se(3) present a zero-bias conductance peak (ZBCP) which signifies unconventional superconductivity. Theoretical considerations of all possible superconducting states help us conclude that this ZBCP is due to Majorana fermions and gives evidence for a topological superconductivity in Cu(x)Bi(2)Se(3). In addition, we found an unusual pseudogap that develops below ～20 K and coexists with the topological superconducting state.     

Directed transport and complex dynamics of vortices in a Josephson junction network driven by modulated currents

Directed transport of vortices in a Josephson junction network (JJN) with structural disorder is studied using a numerical simulation. Using spatiotemporal modulation of driving currents, the directed transport of vortices occurs even in the presence of disorder under certain conditions. From the analyses of the current–voltage and local voltage characteristics, it is found that the collective motion of vortices has an importance for the occurrence of directed transport.     

Determination of the rate constants of the reactions of NO3 radical with CF3I and I(2P3/2)

The rate constant of the reaction of NO₃ radical with CF₃I was determined by a relative rate method using a Fourier transform infrared (FTIR) spectrometer smog chamber with a long path length gas cell. As a result, the upper limit of the rate constant was determined to be <2.2 × 10^?18 cm³ molecule^?1 s^?1 in 100 Torr of total pressure at 298 K, which suggests that CF₃I emitted into the atmosphere accumulates during night. The rate constant of the reaction of NO₃ with I(²P_3/2) was also measured using time‐resolved cavity ring‐down spectroscopy. The rate constant showed no pressure dependence in the range of 100–500 Torr of total pressure at 298 K and was determined to be (3.9 ± 1.0) × 10^?11 cm³ molecule^?1 s^?1. The present result is different from the previous ones and is about half of that reported most recently. From this rate constant, it is likely that the reaction of NO₃ radical with I(²P_3/2) does not have a much influence on the loss of I(²P_3/2) and the formation cycle of IO radical in the atmosphere. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 649–660, 2012     

Ein metrischer Raum,der eine Verallgemeinerung des Finslerschen Raumes ist

Ohne Zusammenfassung     

Synthesis and healing properties of poly(arylether sulfone)–poly(alkylthioether) multiblock copolymers containing disulfide bonds

Thermoplastic elastomers composed of soft and hard segments are important elastic and processable synthetic polymers. The microphase‐separated soft domains show low glass transition temperature and possess sufficient chain mobility at room temperature. In this study, we report the synthesis and healing properties of multiblock copolymers containing disulfide bonds as dynamic covalent bonds. The multiblock copolymers composed of poly(arylether sulfone) and poly(alkylthioether) segments were synthesized by oxidative coupling polymerization of the corresponding thiol‐terminated oligomers. Atomic force microscopy phase images, differential scanning calorimetry, and dynamic mechanical analysis curves indicated the microphase‐separated morphology of the multiblock copolymer. Self‐healing properties of the polymer were evaluated by changes in the elongation at break of the cut/adhered samples. The elongation recovery increased with UV irradiation time, and the multiblock copolymer showed a 93% recovery after UV irradiation for 5 h. The healing efficiency induced by UV irradiation, determined by subtracting the recovery without UV irradiation, was calculated to be 51%. According to the UV spectra and solubility changes after UV irradiation, the main healing factor in this study was the crosslinking reactions caused by thiyl radicals generated from UV irradiation instead of disulfide exchange reactions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3545–3553