Precise electrical transport measurements by using bridgman type pressure cell at low temperature

金沢大学理工研究域環境デザイン学系We report a technique for the precise measurement of the electrical resisivity under high pressure at low temperature by using Bridgman anvils made of tungsten carbide. Quasi-hydrostatic pressure is generated up to ∼15 GPa in the relatively large working space which allows the use of large specimens and simple experimental procedures rather than using a standard diamond anvil cell. The application is demonstrated by the measurements of the electrical resistivity of lead in order to describe the effect of pressure on the superconducting transition. © 2010 IOP Publishing Ltd

New bridge circuit-type detector to measure precise resistance change of strain gauge at low temperature and magnetic field

We report a new highly accurate and versatile bridge-circuit-type detector that has a simple structure and demonstrates a low degree of error for measurements of thermal expansion and magnetostriction by the strain gauge method. As an example, a commercial physical property measurement system (PPMS) is combined with a compact bridge-circuit box. Thermal expansion and magnetostriction are calculated from the resistance of the bridge and bridge voltage, measured by the operation of a standard PPMS resistivity option. The performance of the new detector is demonstrated by measuring the temperature and magnetic field dependences of the strain to obtain the thermal expansion coefficient and magnetostriction of the single crystals of rare-earth compounds RAl2 (R = Dy, Tb). © 2016 The Japan Society of Applied Physics

AC magnetic susceptibility studies of single crystalline CeNiGe2 under high pressure

金沢大学大学院自然科学研究科環境計画The magnetic susceptibility of CeNiGe2 single crystal has been measured under high pressure up to 2.0 GPa. Although two anomalies are observed at TN1=4.0 K and at TN2=3.0 K at ambient pressure, TN2 disappears above 0.13 GPa, while TN1 still remains near 2.0 K up to 2.0 GPa. On the other hand, the peak height of the susceptibility curve decreases with increasing pressure, which may suggest that the correlation between conduction and f-electrons is strengthened by pressure. The Kondo temperature TK is estimated from the maximum of χc–T curve. TK is remarkably enhanced by applying pressure

Unconventional drop in the electrical resistance of chromium metal thin films at low temperature

We studied the electrical resistance of single-crystal and polycrystalline chromium films. The ρ(T)ρ(T) curve of single-crystal films decrease with decreasing temperature and show humps at around 300 K consistent with the bulk chromium being an itinerant antiferromagnet. In the polycrystalline films, on the other hand, the ρ(T)ρ(T) curves deviate from those of the bulk chromium. Moreover, we observed sudden decrease in the resistance around 1.5 K. Although previous studies suggested that chromium films become superconductive (Schmidt et al. (1972) [12]), it is difficult to conclude whether a superconducting transition occurs because the electrical resistivity is not zero in all films. No anomaly was detected by resistance measurements around room temperature, and the sudden decrease in the resistance at low temperature may be attributed to the suppression of antiferromagnetic interaction by thinning down the chromium element.Embargo Period 24 month

Methanotrophic community composition based on pmoA genes in dissolved methane recovery and biological oxidation closed downflow hanging sponge reactors

Dissolved methane in the effluent of anaerobic wastewater treatment processes is unrecovered and released into the atmosphere as methane, a greenhouse gas. To prevent methane emissions from effluent, a post-treatment system consisting of two closed downflow hanging sponge (DHS) reactors for the recovery and biological oxidation of dissolved methane was developed. More than 99% of the dissolved methane was completely eliminated using this system under ambient temperatures for 1 year. In this study, the methanotrophic community composition of the two closed DHS reactors was investigated. The performance of the closed DHS reactor was evaluated at different heights of the reactor in summer and winter. The clone libraries and T-RFLP analyses based on the pmoA gene revealed that type I and type II methanotrophs were present in the closed DHS reactors. Furthermore, type I methanotrophs showed wide diversity and contained uncultured phylogenetic clusters of methanotrophs (FWs and LWs), while type II methanotrophs were dominated by Methylocystis- and Methylosarcina-related clusters. The relative abundance of type II methanotrophs increased during winter. The type I methanotroph population dynamically changed with height of the reactor. These results demonstrate the important role of methanotrophs in removal of dissolved methane from upflow anaerobic sludge blanket effluent treating sewage. © 2017 Elsevier B.V.Embargo Period 12 month

Quinolizidines. XXVIII. Racemic and chiral syntheses of ochromianine, an indoloquinolizidine alkaloid from Neisosperma miana

A full account is given of the first racemic and chiral syntheses of 11-methoxydihydrocorynantheol [(-)-1], a candidate structure for the Neisosperma alkaloid ochromianine. Coupling of (±)-trans-6-ethoxy-3-ethyl-2,3,4,5-tetrahydro-4-pyridineacetic acid ethyl ester [(±)-6] with 2-chloro-1-(6-methoxy-1H-indol-3-yl)ethanone (4) in the presence of KBr produced the lactam ketone (±)-7,which was then converted into the lactam (±)-9 through the oxazolium salt (±)-8. Bischler-Napieralski cyclization of (±)-9 followed by catalytic hydrogenation gave the tetracyclic ester (±)-11. On reduction with LiAlH_4,(±)-11 yielded the racemic target (±)-1. A parallel synthetic route starting from (+)-6 and 4 afforded the chiral target (-)-1 via (+)-7,8,(+)-9,and (-)-11. Identity of synthetic (-)-1 with ochromianine unequivocally established the structure and absolute stereochemistry of this alkaloid

Crystal Structure of the Caged Magnetic Compound DyFe2Zn20 at Low Temperature Magnetic Ordering State

We have carried out X-ray powder diffraction and thermal expansion measurements of the caged magnetic compound DyFe2Zn20. Even though a strong magnetic anisotropy exists in the magnetization and magnetic susceptibility due to strong exchange interaction between Fe and Dy, almost all X-ray powder diffraction peaks at 14 K correspond to Bragg reflections of the cubic structural models not only at room temperature paramagnetic state but also at low temperature magnetic ordering state. Although the temperature change of the lattice constant is isotropic, an anomalous behavior was observed in the thermal expansion coefficient around 15 K, while the anomaly around TC = 53 K is not clear. The results indicate that the volume change is not caused by the ferromagnetic interaction between Fe and Dy but by the exchange interaction between two Dy ions. © 2015 The Authors. Published by Elsevier B.V

Dissolved methane oxidation and competition for oxygen in down-flow hanging sponge reactor for post-treatment of anaerobic wastewater treatment

Post-treatment of anaerobic wastewater was undertaken to biologically oxidize dissolved methane, with the aim of preventing methane emission. The performance of dissolved methane oxidation and competition for oxygen among methane, ammonium, organic matter, and sulfide oxidizing bacteria were investigated using a lab-scale closed-type down-flow hanging sponge (OHS) reactor. Under the oxygen abundant condition of a hydraulic retention time of 2 h and volumetric air supply rate of 12.95 m(3)-air m(-3) day(-1), greater than 90% oxidation of dissolved methane, ammonium, sulfide, and organic matter was achieved. With reduction in the air supply rate, ammonium oxidation first ceased, after which methane oxidation deteriorated. Sulfide oxidation was disrupted in the final step, indicating that COD and sulfide oxidation occurred prior to methane oxidation. A microbial community analysis revealed that peculiar methanotrophic communities dominating the Methylocaldum species were formed in the DHS reactor operation. (C) 2011 Elsevier Ltd. All rights reserved