Search

Abstract: The accelerating cavities used in the rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) are loaded with magnetic alloy (MA) cores. Over lengthly periods of RCS operation, significant reductions in the impedance of the cavities resulting from the buckling of the cores were observed. A series of thermal structural simulations and compressive strength tests showed that the buckling can be attributed to the low-viscosity epoxy resin impregnation of the MA core that causes the stiffening of the originally flexible MA–ribbon–wound core. Our results showed that thermal stress can be effectively reduced upon using a core that is not epoxy-impregnated. [Copyright &y& Elsevier]

Abstract: Uniform InAs quantum dots (QDs) have been realized on GaAs by molecular beam epitaxy, which can increase maximum optical gain in laser diodes without sacrificing original high-density and high optical quality characteristics. This improvement enables laser operation under higher environment temperature. In order to improve QD uniformity, we searched for a proper growth condition and sequence for suppressing In out-diffusion during QD coverage. Although the same initial InAs QD structure on GaAs was used, PL linewidth was reduced after coverage under such improved conditions. In QD lasers, higher optical gain as large as 54cm−1 at room temperature which is about 10cm−1 larger than our previous data was realized. Those improved QDs are attractive for realizing novel optical devices. [Copyright &y& Elsevier]

The study of flame–wall interactions is of crucial importance for the understanding of near wall combustion. One of the parameters directly responsible for heat exchange near the wall is the quenching distance. The results of direct measurements of the quenching distance during side-wall quenching and head-on quenching of premixed methane/air flame are presented. A laminar flame is produced at the centre of a rectangular combustion chamber. The experiments are performed using different wall materials: polished steel, steel covered with soot and ceramics. Flame interacts with a rectangular obstacle placed at the bottom of the combustion chamber. The quenching distance near the top of the obstacle and in the vicinity of its side-wall is measured using direct photography of the flame position near the quenching surface.The quenching phenomenon depends on the wall material. These circumstances must be taken into account during heat flux measurements. For ceramics, the side-wall quenching distance is less than for polished steel by a factor of 1.1–1.8 in the pressure range of 0.05–0.15 MPa. The coating of polished steel by a 15–20 μm thick soot layer decreases the quenching distance by a factor of 1.1–1.5. The head-on quenching distance for polished steel is 1.4–2.5 times less than side-wall quenching in the pressure range of 0.08–0.19 MPa.An evaluated value of the maximum heat flux to the wall during quenching is obtained from the value of quenching distance using a simple relationship. For atmospheric pressure and cold wall conditions, the peak heat flux to the polished steel surface is found to be 0.46 and 0.26 MW/m2 for the head-on and side-wall quenching, respectively. Near the ceramic surface these values are 0.8 and 0.39 MW/m2 for head-on and side-wall quenching, respectively. [Copyright &y& Elsevier]

We have performed high-throughput characterization of composition-spread La1−xCaxMnO3 (LCMO) and Nd1−xSrxMnO3 (NSMO) films, fabricated by the precursor technique, with a scanning SQUID microscope (SSM). In both films, SSM successfully observed spatial variation of magnetic field, corresponding to magnetic phase transitions with respect to chemical composition. The obtained magnetic phase diagrams basically reproduced those reported in bulk materials. However, several distinctive differences have also been noted. For instance, the region identified as a charge ordered insulator in LCMO revealed intense field, suggesting the occurrence of phase separation into ferromagnetic and non-magnetic states. These results confirm that SSM possesses sufficient analytical performance for high-throughput characterization of combinatorial magnetic libraries in composition spread form. [Copyright &y& Elsevier]

A case of infantile malignant osteopetrosis is described. The patient died from respiratory hemorrhage at 7 months of age despite treatment that included high doses of active vitamin D and administration of interferon-γ. A postmortem examination revealed the presence of many osteoclasts in the bone, which lacked ruffled borders. This observation was consistent with the histology of bone reported in Atp6i-knockout mice, which lack the gene encoding the a3 subunit of vacuolar-type H+-adenosine triphosphatase (ATPase). Sequence analysis of the TCIRG1 gene encoding the a3 subunit revealed two novel mutations: a deletion/insertion mutation in exon 9 and a T-to-C transition at the splice donor site of intron 19. The former mutation caused a frame shift and premature stop codon. The latter was associated with abnormal splicing, which was confirmed by sequencing the products amplified by reverse transcription-polymerase chain reaction (RT-PCR), using total RNA from the liver specimen as template. Although several mutations in the TCIRG1 gene in infantile malignant osteopetrosis have been reported in other populations, this is the first case of a Japanese patient with a mutation identified in this gene. These results support the important role of the subunit in the function of the proton pump. [ABSTRACT FROM AUTHOR]

Abstract: Sb-introduced highly strained GaInAs/GaAs quantum wells (QWs) were grown by solid-source molecular beam epitaxy. The Sb introduction procedure and growth temperature dependence of photoluminescence (PL) property were investigated. Sb introduction into the upper part of the QW showed poor PL property and this result indicates that the three-dimensionally grown GaInAs is not recovered by the surfactant effect of Sb. For the case of the Sb introduction into the lower part of the QW, as the Sb introduction into the whole QW the PL peak intensity and linewidth improved as well. A noticeable PL improvement was also observed with increase in the growth temperature only for the case of Sb introduction. Sb introduction widened the growth temperature window for highly strained GaInAs QWs. [Copyright &y& Elsevier]

When a slender body moving forward in open air enters into a confined region, two important unsteady aerodynamic phenomena are generated. An exiting flow is created with a direction opposite to the body movement and inside the confined region, a compression wave is formed. Generation mechanism of compression wave have been extensively studied but so far, no detailed investigation of the exiting flow has ever been reported. The experimental study presented in this paper was undertaken to gain insight into the structure and the evolution of the exit-flow. Experiments were conducted with an axisymmetric apparatus and the explored range of the moving body speed was 5–50 m/s. The study focused on the influence of the body speed and the body nose geometry on the flow. It was shown that the air ejected from the tube entrance generates an annulus jet accompanied by a vortex ring. The vortex development was clarified using laser sheet visualizations associated with unsteady pressure and velocity measurements at the tube entrance. It is constituted by four phases, the pre-vortex phase, the vortex development phase, the vortex convection phase and the vortex breakdown phase. The duration of each of these steps was found to be independent of both the studied parameters in a non-dimensional time scale. Furthermore, neither the body speed nor the nose geometry induced significant changes on the vortex ring evolution, except for extreme conditions (low body speed, VM.B.<15 m/s, and/or very long nose geometry, Lnose/DM.B.>6). The evolution of the vortex ring was compared to that of ‘classical’ vortex ring generated at a tube exit by a piston motion with large non-dimensional stroke length. Main similarities and differences were discussed in the paper. In particular, the formation number of vortex ring observed in our experiments was found to be significantly smaller. [Copyright &y& Elsevier]

As-grown epitaxial composition-spread thin films of a colossal magnetoresistive compound, La1−xSrxMnO3 (0≤x≤1), are fabricated by a combinatorial laser molecular beam epitaxy (laser MBE). High throughput characterization for studying x dependencies of structural, magnetic and electronic properties is demonstrated by the combination of a concurrent X-ray diffractometer, a scanning superconducting quantum interference device (SQUID) microscope and an infrared microscope spectrometer, respectively. [Copyright &y& Elsevier]