Beam dynamics of 20 MeV MIRRORCLE-type tabletop storage ring

An experimental study on beam dynamics in MIRRORCLE-20, a tabletop storage ring of 15 cm orbit radius, was performed. Measurement of the infrared (IR) synchrotron light is the tool of this study. The IR emission is enhanced by a circular optics, named photon storage ring (PhSR), placed around the electron orbit, and is collected by a magic mirror associated with two plane mirrors in the storage ring. The measured average IR power in mid-IR region (λ < 50 μm) is ～59 mW. The observed stored beam current is about 1.2 A at maximum, which represents a record for a storage ring. The observed beam size is about 74 × 3 mm². We conclude that this very long beam size is due to the large betatron oscillation of 2/3 resonance injection.     

Effects of RE2O3 (RE = Tm, Sc, Yb) addition on the superconducting properties of ErBa2Cu3Oy

We investigated the effects of added Tm₂O₃, Sc₂O₃, and Yb₂O₃ on the superconducting properties of sintered Er123 samples. Tm₂O₃ addition caused the least T_c degradation, exhibiting a T_c above 90 K even for 17 vol% addition. Samples with added Sc₂O₃ maintained a T_c at above 90 K up to an addition of 7.2 vol%, while Yb₂O₃-containing samples showed a monotonic decrease in T_c with increased vol% of added Yb₂O₃. Tm₂O₃-containing samples exhibited a slight increase in J_c(0.1 T)/J_c(0) and had constant J_c values even for 17 vol% addition. XRD and SEM results indicate that the Tm₂O₃ is very stable in the superconducting matrix.     

Vinylcyclopropanation of olefins via 3-methoxy-1-propenylrhodium(I)

New cyclization reactions forming vinylcyclopropanes were developed wherein an alkenylrhodium(I) possessing a methoxy group at the allylic position as a potential leaving group acts as an allylic carbene equivalent. By this protocol, a vinylcyclopropane was installed in a complex cyclic structure in a single operation via successive multiple carbon-carbon bond formations.     

Phosphorus-containing hybrid calixphyrins: promising mixed-donor ligands for visible and efficient palladium catalysts

Phosphorus-sulfur-containing hybrid calixphyrins were prepared by the BF3-promoted dehydrative condensation between sigma4-2,5-bis[(pyrrol-2-yl)methyl]phosphole and 2,5-bis[hydroxy(phenyl)methyl]thiophene. X-ray crystallographic analysis of the Pd-P,N2,S-hybrid calixphyrin complex revealed that the Pd center was coordinated by the four heteroatoms to adopt a distorted square planar geometry. The Pd complex, displaying a characteristic reddish purple color in solution, catalyzed the Heck reaction of bromoarenes with n-butyl acrylate with high efficiency at elevated temperatures.     

Molecular motions of alpha-cyclodextrin on a dodecyl chain studied by molecular dynamics simulations

Motions of an alpha-cyclodextrin (alpha-CD) molecule on a dodecyl chain adopting the all-trans conformation were investigated in the presence of water by molecular dynamics simulations with CVFF force fields, where the trimethylammonium group of dodecyltrimethylammonium bromide (DTAB) is protruded outside the secondary hydroxyl rim of alpha-CD (the secondary-in structure). The alpha-CD molecule shuttled rapidly on the chain without decomplexation. This rapid motion is consistent with the NMR data. The plane formed by 6 O4 atoms of alpha-CD is most populated between the C6 and C7 atoms of DTAB. This structure is very close to that estimated by NMR. The alpha-CD molecule underwent a restricted rotation in a range of 60 degrees with regard to the plane of the dodecyl chain: this plane at the most population is middle between the two diagonal lines of the normal hexagon formed by 6 O4 atoms of alpha-CD. The published NMR data were reanalyzed in terms of the rotation angle, and a slightly better structure was obtained. The distortion of the alpha-CD cavity from the normal hexagon was decreased upon complex formation with DTAB. The deviation of the center of alpha-CD from the center of the dodecyl chain predicted by molecular dynamics simulations is consistent with the NMR data. The secondary-in structure is energetically more stable than the primary-in structure, as calculated by molecular mechanics with CVFF and Amber force fields. This result is consistent with the NMR data. Molecular dynamics simulations were also carried out for the primary-in structure. Some of the results are close to those of the secondary-in structure.     

Effect of coagulation of nodes in an evolving complex network

We propose a new type of stochastic network evolution model based on annihilation, creation, and coagulation of nodes, together with the preferential attachment rule. The system reaches a unique quasistatistically steady state in which the distribution of links follows a power law, lifetime of nodes follows an exponential distribution, and the mean number of links grows exponentially with time. The master equation of the model is solved analytically by applying Smoluchowski's coagulation equation for aerosols. The results indicate that coagulation of nodes in complex networks and mean field analysis of aerosols are similar in both the growth dynamics with irreversible processes and in the steady state statistics. We confirm that the basic properties of the model are consistent with the empirical results of a business transaction network having about 1×10(6) firms.     

Cathodoluminescence microcharacterization of forsterite in the chondrule experimentally grown under super cooling

Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450–525 nm (2.76–2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as ～10 mm/s or higher from a supercooled melt.     

Sweep-free brillouin optical time domain analysis using two individual laser sources

We propose a sweep-free measurement technique for distributed Brillouin frequency shift in optical fibers applicable to distributed strain/temperature monitoring systems, using two sets of pump-probe lights generated by two individual laser sources. This technique utilizes the Brillouin gain ratio measured at both the upper and lower side slopes of two different Brillouin spectra induced by two pump lights with different wavelengths. The proposed method offers high-speed measurement due to the combination of the frequency-sweep-free operation and the polarization-insensitive measurement scheme without polarization scramblers. A measurement accuracy of 17.3 ??? with a spatial resolution of 5m over 2.6 km sensing length and a capability of kHz sampling rate are experimentally demonstrated.     

Flow waves of hierarchical pattern formation induced by chemical waves: The birth, growth and death of hydrodynamic structures

We introduce a short review of chemically driven convection together with a series of our experiments on hydrodynamic instabilities induced by chemical waves excited in the batch reactor of a Belousov-Zhabotinsky reaction. Several unresolved phenomena are picked out and possible mechanisms are discussed extensively. Interesting features of these phenomena can be summarized as being caused by the ‘global and dynamic hydrodynamic pattern induced by chemical waves’. These chemically induced global pattern of hydrodynamic phenomena may not be simply explained by the reaction-diffusion-convection model based on Marangoni instability (surface tension-driven convection), which produces only a localized structure of the convection pattern. Observed flow waves show global and dynamic patterns of convection that generate a functional structure associated with hierarchical patterns appearing in the reaction-diffusion-convection system. In particular, we clarify the existence of a continuous stream of hydrodynamic flow with growing amplitude and its rotating direction. We find that the flow does not stabilize to a motionless state until the system has self-collapsed. This new picture of the flow waves requires a revision of the reaction-diffusion-convection model. The established flow structure can be regarded as a mixing and/or transport process to supply the substrate from the peripheral region to the centre of the chemical waves to sustain the reaction. This characteristic may be a function of the hierarchical structure. A new mechanism for the viscous-elastic feature of the gas-liquid interface is discussed in order to understand these curious phenomena of interest.     

Space-selective phase separation inside a glass by controlling compositional distribution with femtosecond-laser irradiation

Space-selective phase separation was induced inside Na₂O–SiO₂ glasses by changing the glass composition locally from a miscible composition to an immiscible one via femtosecond-laser irradiation at a high repetition rate. The formation of a nanoscale co-continuous structure due to phase separation was confirmed by scanning electron microscopy after heat treatment, polishing until the laser-modified area was exposed, and subsequent etching. The configuration of the structure could be controlled by changing the heat-treatment time.