Thermally stable rigid π-allylnickel compounds, (π-CHRCR′CR2)Ni(PPhMe2)C6Cl5

The reaction of C₆Cl₅Ni(PPhMe₂)₂Cl with CHRCR′CH₂MgX (X = Br or Cl) yields π-allylnickel compounds, (π-CHRCR′CH₂)Ni(PPhMe₂)C₆Cl₅ (Ia, R = R′ = H; Ib, R = H, R′ = CH₃; Ic, R = CH₃, R′ = H), which are stable in the solid state below ca. 150°C and are fairly stable in solution in the absence of oxygen. The π-allyl group was found by PMR spectroscopy to be rigid even in the presence of an excess of PPhMe₂, P(OEt)₃ or P(OMe)₃.     

Perfectly conducting channel and universality crossover in disordered graphene nanoribbons

The band structure of graphene ribbons with zigzag edges have two valleys well separated in momentum space, related to the two Dirac points of the graphene spectrum. The propagating modes in each valley contain a single chiral mode originating from a partially flat band at the band center. This feature gives rise to a perfectly conducting channel in the disordered system, if the impurity scattering does not connect the two valleys, i.e., for long-range impurity potentials. Ribbons with short-range impurity potentials, however, through intervalley scattering display ordinary localization behavior. The two regimes belong to different universality classes: unitary for long-range impurities and orthogonal for short-range impurities.     

Simulation of electron bunch generation by an ultrashort-pulse high-intensity laser-driven wakefield

Electron acceleration due to a wakefield excited by a ultrashort-pulse intense laser propagating through a finite-length underdense plasma layer is studied by two-dimensional particle-in-cell simulation. The electron energy distribution is analyzed for moderate to high intensity. For the electron density, where the pulse length is almost half of the plasma wavelength, dramatic changes of the density structure occur with cavity and bunch formation with an increase in the laser intensity, also leading to the appearance of a fast electron component well confined in phase space. The analytical form of the fast electron energy spectrum is also presented.     

Synthesis and Optical Properties of SiO2-Coated CeO2 Nanoparticles

Silica (SiO₂)-coated ceria (CeO₂) nanoparticles were prepared using water-in-oil microemulsion. Polyoxyethylene (15) cetylether and cyclohexane were used as a surfactant and organic solvent. SiO₂-coated CeO₂ nanoparticles were obtained by hydrolysis of metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing CeO₂ precursor nanoparticles. The effects of CeO₂ sources (Ce metal salt) and CeO₂ particle-forming agents on the morphology of SiO₂–CeO₂ particles were investigated. Observation via transmission electron microscopy revealed that the type of particle-forming agent affected the nanoparticles' morphology and that CeO₂ nanoparticles were spherically coated with SiO₂ when using oxalic acid ((COOH)₂) as a particle-forming agent of CeO₂. Furthermore, the transmittance of the particles was high in the visible region (above 400 nm) and decreased in the ultraviolet region.     

On the structure of the monotone asymmetric travelling salesman polytope I: hypohamiltonian facets

The monotone asymmetric travelling salesman polytope P?ⁿ_T is defined to be the convex hull of the incidence vectors of all hamiltonian circuits and all subsets of these in a complete diagraph of order n. We prove that certain hypohamiltonian diagraphs G=(V,E), i.e. diagraphs which are not hamiltonian but such that G–υ is hamiltonian for all υ?V, induce facets x(E)?n–1 of P?ⁿ_T. This result indicates that P?ⁿ_T has very complicated facets and that it is very unlikely that an explicit complete characterization of P?ⁿ_T can ever be given.     

Measurement of the g-Factor of the 27− High-Spin Isomer State of 152Dy

The g-factor of the 27⁻ isomer state of ¹⁵²Dy has been measured using the Time-Integral Perturbed Angular Distribution (TIPAD) method. The high-spin states of ¹⁵²Dy have been populated by ¹⁴¹Pr(¹⁶O,p4n)¹⁵²Dy reaction at E = 115 MeV from the AVF cyclotron at CYRIC. The paramagnetic correction factor of Dy ions in Pr has been determined to be 4.2(5) by the Time-Differential Perturbed Angular Distribution (TDPAD) measurement of the 21⁻ state of ¹⁵²Dy. As a result, the g-factor of the 27⁻ isomer state of ¹⁵²Dy has been obtained to be +0.09(5). This shows the smaller value than the expected one of +0.39 deduced from a fully aligned configuration of π(h _11/2 ²) ⊗ ν(f _7/2 ² h _9/2 i _13/2).     

Measurements of velocity distributions with a laser doppler imaging system

A laser Doppler imaging system with a TV camera has been constructed and velocity distributions of fluid flow in cross sections of a rectangular channel have been measured. Consequently, it has been found that the system has some advantages in comparison with usual laser Doppler velocimeters, for example, the visualization of flow can be easily achieved.     

Insight into Mechanical Properties of CH3SiO3/2 Film

Young's modulus and stress-optical coefficient of self-sustained gel film of CH₃SiO_3/2 were measured. Young's modulus varied from 1.1 to 1.5 GPa, depending on the structural state of the film. It increased with an increase in the degree of polymerization that was induced by heat treatments, and also increased with subsequent exposure to the ambient condition. The stress-optical coefficient was 6.3 × 10^–12 Pa^–1 for a sample treated at 120°C. The compliance of the film seems to depend mainly on the intermolecular structure of Si–CH₃...CH₃–Si as well as hydrogen bonding due to silanols and adsorbed water.     

Theoretical study of lanthanide-based in vivo luminescent probes for detecting hydrogen peroxide

The 4f-4f emissions from lanthanide trication (Ln³⁺) complexes are widely used in bioimaging probes. The emission intensity from Ln³⁺ depends on the surroundings, and thus, the design of appropriate photo-antenna ligands is indispensable. In this study, we focus on two probes for detecting hydrogen peroxide, for which emission intensities from Tb³⁺ are enhanced chemo-selectively by the H₂O₂-mediated oxidation of ligands. To understand the mechanism, the Gibbs free energy profiles of the ground and excited states related to emission and quenching are computed by combining our approximation—called the energy shift method—and density functional theory. The different emission intensities are mainly attributed to different activation barriers for excitation energy transfer from the ligand-centered triplet (T1) to the Tb³⁺-centered excited state. Additionally, quenching from T1 to the ground state via intersystem crossing was inhibited by intramolecular hydrogen bonds only in the highly emissive Tb³⁺ complexes. © 2018 Wiley Periodicals, Inc.     

Diastereoselective hydroformylation of 2,5-cyclohexadienyl-1-carbinols with catalytic amounts of a reversibly bound directing group

A phosphinite plays a role as a reversibly bound directing group for the regio- and diastereoselective hydroformylation of 2,5-cyclohexadienyl-1-carbinols. Of the two alkene functions only one was functionalized through hydroformylation to form a synthetically attractive quaternary carbon center leaving the second alkene function for potential further functionalization.