Method for Evaluating Potential Maximum Shear Strain for a Fine Metal Wire in Torsion Testing

Experimental Techniques - The torsion number of drawn fine high carbon steel wires was measured through torsion testing. The angles between the scratches on the tested wire surface and its...     

An atomic force microscope study of vanadium-benzene sandwich clusters soft-landed on self-assembled monolayers

Multiple-decker vanadium-benzene sandwich clusters V_n(benzene)_n+1 produced by a laser-vaporization synthesis method were soft-landed onto self-assembled monolayers of alkanethiol (C₁₈H-SAM) and fluorinated alkanethiol (C₁₀F-SAM) at 200 K. Noncontact atomic force microscopy has been used to examine the resulting adsorption states of the clusters landed on the SAMs at room temperature. For each SAM substrate, the aggregates of the deposited clusters were observed at the vacancy islands and near the steps of the SAM surface. The result indicates that, at room temperature, the clusters landed on the SAM substrate thermally diffuse on the surface to form columnar-shape islands around the defect sites of the SAM surface.     

Search for the invisible decay of neutrons with KamLAND

The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the -shell energy level of (12)C nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n--> 3v or nn--> 2v. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n--> inv) > 5.8 x 10(29) years and tau (nn--> inv) > 1.4 x 10(30) years at 90% C.L. These results represent an improvement of factors of approximately 3 and >10(4) and over previous experiments.     

Synthesis and NMR Spectroscopic Elucidation of Four Diastereoisomers of Oxygenated Bisabolane Side Chain

Four possible stereoisomers of a model compound of highly O‐bearing bisabolane sesquiterpenes were synthesized and their NMR spectra were compared. Starting from isopulegol, allylic oxidation and Grignard reaction afforded a mixture of alcohols at C(8), which was separated. After metathesis reaction, both α‐ and β‐epoxides were obtained via non‐stereoselective epoxidation, while VO(OⁱPr)₃‐catalyzed epoxidation afforded a single diastereoisomer selectively. NMR Spectra of twelve synthesized compounds, four stereoisomers of acetates, isobutyrates, and tiglates, were measured. A difference between C(8α)‐ and C(8β)‐acyloxy isomers was observed in the δ‐values of H? C(8) in CDCl₃. Within the 8β‐acyloxy compounds, the α‐ and the β‐epoxides were distinguished by either the J‐value of H? C(8) or the chemical shift of CH₂(9). Within the 8α‐acyloxy compounds, two epoxide isomers were distinguished by the J‐value of H? C(10) in C₆D₆ or in CD₃OD.     

CIDEP in radical-singlet molecular oxygen system

Net absorptive CIDEP generation has been demonstrated on singlet molecular oxygen and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxyl (OTEMPO) radical system in benzene. CIDEP generation was reasonably explained in terms of the radical-triplet pair mechanism of triplet molecular oxygen-OTEMPO pair with doublet precursor. Several excited molecule-OTEMPO systems have been investigated if this CIDEP generation contributes to their CIDEP spectra. Surprisingly strong CIDEP was produced even in the presence of trace amount of dissolved oxygen, which suggests the importance of complete degassing for CIDEP studies in general systems.     

Vibrationally assisted diffusion of H2O and D2O on Pd(1 1 1)

The adsorption and diffusion of isolated H₂O and D₂O molecules on Pd(1 1 1) were studied using scanning tunneling microscopy at low temperature (∼40 K). At low tunneling voltage the diffusion is thermally activated. The diffusion rate is enhanced by several orders of magnitude when the tunneling electron has enough energy to excite the vibrational “scissor” mode of the molecule. An isotope effect was observed in the threshold voltage for electron-assisted diffusion of H₂O and D₂O.     

Rooted tree analysis of the order conditions of row-type scheme for stochastic differential equations

Numerical schemes for initial value problems of stochastic differential equations (SDEs) are considered so as to derive the order conditions of ROW-type schemes in the weak sense. Rooted tree analysis, the well-known useful technique for the counterpart of the ordinary differential equation case, is extended to be applicable to the SDE case. In our analysis, the roots are bi-colored corresponding to the ordinary and stochastic differential terms, whereas the vertices have four kinds of label corresponding to the terms derived from the ROW-schemes. The analysis brings a transparent way for the weak order conditions of the scheme. An example is given for illustration.     

Structural analysis of polyelectrolyte film absorbing metal ion by SAXS utilizing with X-ray anomalous dispersion effect

A distribution of Cu ions in polyelectrolyte film (Nafion) is directly observed with a small-angle X-ray scattering (SAXS) method utilizing an X-ray anomalous dispersion effect. A partial structure factor of the Cu ions, GAA(q), can be derived from the SAXS profiles obtained by scanning the incident X-ray energy around the Cu K absorption edge. GAA(q) has two peaks, indicating that the Cu ions hierarchically distribute in Nafion film. In addition, a standard SAXS also shows that Nafion film has a hierarchical structure. These results mean that the Cu ions locate in the domain where the hydrophilic bases aggregate.     

Electronic properties of Si and Ge atoms doped in clusters: In(n)Si(m) and In(n)Ge(m)

Electronic properties of silicon and germanium atom doped indium clusters, In(n)Si(m) and In(n)Ge(m), were investigated by photoionization spectroscopy of the neutrals and photoelectron spectroscopy of the anions. Size dependence of ionization energy and electron affinity for In(n)Si(1) and In(n)Ge(1) exhibit pronounced even-odd alternation at cluster sizes of n = 10-16, as compared to those for pure In(n) clusters. This result shows that symmetry lowering with the doped atom of Si or Ge results in undegeneration of electronic states in the 1d shell formed by monovalent In atoms.