Giant spin Hall effect in perpendicularly spin-polarized FePt/Au devices

Conversion of charge current into pure spin current and vice versa in non-magnetic semiconductors or metals, which are called the direct and inverse spin Hall effects (SHEs), provide a new functionality of materials for future spin-electronic architectures. Thus, the realization of a large SHE in a device with a simple and practical geometry is a crucial issue for its applications. Here, we present a multi-terminal device with a Au Hall cross and an FePt perpendicular spin injector to detect giant direct and inverse SHEs at room temperature. Perpendicularly magnetized FePt injects or detects perpendicularly polarized spin current without magnetic field, enabling the unambiguous identification of SHEs. The unprecedentedly large spin Hall resistance of up to 2.9 mOmega is attributed to the large spin Hall angle in Au through the skew scattering mechanism and the highly efficient spin injection due to the well-matched spin resistances of the chosen materials.     

Structural studies of copper sulfide films: effect of ambient atmosphere

We examined the structural properties of copper sulfide films as a function of the sulfurization time of 70-nm-thick Cu films. Copper sulfide films with various phases such as mixed metallic Cu-chalcocite, chalcocite, roxbyite, and covellite phases were formed with increasing sulfurization time. To evaluate the structural stability of various films, all the films were exposed to the ambient atmosphere for the same amount of time. Although the phase structure and stoichiometry of the films were maintained at a greater depth, the near-surface region of the films was oxidized and covered with overlayers of oxide, hydroxide, and/or sulfate species due to the exposure and reaction with the ambient atmosphere. The oxygen uptake and its reactivity with the copper sulfide film surfaces were enhanced with increasing sulfur content of the films. In addition, the type of divalent state of copper formed on the film surfaces depended on the phase structure, composition, and stoichiometry of the films.     

Molecular evidence that the rate-limiting step for the biosynthesis of arachidonic acid in <Emphasis Type="Italic">Mortierella alpina</Emphasis> is at the level of an elongase

The oil-producing fungus Mortierella alpina 1S-4 is an industrial strain for arachidonic acid (AA) production. To determine its physiological properties and to clarify the biosynthetic pathways for PUFA, heterologous and homologous gene expression systems were established in this fungus. The first trial was performed with an enhanced green fluorescent protein gene to assess the transformation efficiency for heterologous gene expression. As a result, strong fluorescence was observed in the spores of the obtained transformant, suggesting that the foreign gene was inherited by the spores. The next trial was performed with a homologous PUFA elongase (GLELOp) gene, this enzyme having been reported to catalyze the elongation of GLA (18∶3n−6) to dihomo-γ-linolenic acid (20∶−6), and to be the rate-limiting step of AA production. The FA composition of the transformant was different from that of the host strain: The GLA content was decreased whereas that of AA was increased. These data support the hypothesis that the GLELOp enzyme plays an important role in PUFA synthesis, and may indicate how to control PUFA biosynthesis.     

Performance of the improved version of monte Carlo code A3MCNP for large-scale shielding problems

A3MCNP (Automatic Adjoint Accelerated MCNP) is a revised version of the MCNP Monte Carlo code, which automatically prepares variance reduction parameters for the CADIS (Consistent Adjoint Driven Importance Sampling) methodology. Using a deterministic 'importance' (or adjoint) function, CADIS performs source and transport biasing within the weight-window technique. The current version of A3MCNP uses the three-dimensional (3-D) Sn transport TORT code to determine a 3-D importance function distribution. Based on simulation of several real-life problems, it is demonstrated that A3MCNP provides precise calculation results with a remarkably short computation time by using the proper and objective variance reduction parameters. However, since the first version of A3MCNP provided only a point source configuration option for large-scale shielding problems, such as spent-fuel transport casks, a large amount of memory may be necessary to store enough points to properly represent the source. Hence, we have developed an improved version of A3MCNP (referred to as A3MCNPV) which has a volumetric source configuration option. This paper describes the successful use of A3MCNPV for a concrete cask neutron and gamma-ray shielding problem, and a PWR dosimetry problem.     

Synthesis of continuous silicon carbide fibre

Polycarbosilane (PC) was obtained by adding bolodiphenylsiloxane (BDPSO) as a reaction accelerator to poly(dimethylsilane) (PDMS), then the thermal decomposition and condensation at various conditions were determined. The molecular weight distribution and the reactivity with oxygen of PC differ with the quantity of BDPSO added, the reaction temperature and the reaction time. The larger the amount of BDPSO, the higher the reaction temperature and the longer the reaction time, the larger becomes the molecular weight of PC. In addition, the higher the reaction temperature, the more stable becomes PC for oxidation. The synthesized PC was spun and the fibre was heated in air at low temperature for curing. The cured fibre was then heat-treated to obtain the SiC fibre. Properties of the SiC fibre are closely related to the oxidation properties of the PC.     

Cationic oligomerization of 1-hexene catalyzed by EtAlCl2–chloroacetic acid complexes

Lower oligomers (dimer to tetramer) of 1-hexene were obtained in high yield (65 wt %) with a new cationic complex catalyst, EtAlCl₂? CCl₃CO₂H, in n-hexane at 70°C, trimer being the major product. A strong oxo acid, CF₃SO₃H, yielded very similar products under the same conditions. Characteristics of the 1-hexene oligomerization by these two catalysts were the high selectivity for dimers to tetramers and the absence of cracking of the product. In contrast, EtAlCl₂ or AlCl₃ alone led to oligomers with a higher molecular weight (～10³) and a broad molecular weight distribution, the structure of which was very complicated because of extensive cracking of products. A series of EtAlCl₂? chloroacetic acid (CCl_nH₃–nCO₂H, n = 0–3) complexes were also examined as catalysts. The yield of dimer to tetramer increased with increasing acidity of the chloroacetic acids. The mechanism of the 1-hexene oligomerization with these complex catalysts was discussed on the basis of the structure of product oligomers.     

The role of ceramic and glass science research in meeting societal challenges: Report from an NSF‐sponsored workshop

Under the sponsorship of the U.S. National Science Foundation, a workshop on emerging research opportunities in ceramic and glass science was held in September 2016. Reported here are proceedings of the workshop. The report details eight challenges identified through workshop discussions: Ceramic processing: Programmable design and assembly; The defect genome: Understanding, characterizing, and predicting defects across time and length scales; Functionalizing defects for unprecedented properties; Ceramic flatlands: Defining structure‐property relations in free‐standing, supported, and confined two‐dimensional ceramics; Ceramics in the extreme: Discovery and design strategies; Ceramics in the extreme: Behavior of multimaterial systems; Understanding and exploiting glasses and melts under extreme conditions; and Rational design of functional glasses guided by predictive modeling. It is anticipated that these challenges, once met, will promote basic understanding and ultimately enable advancements within multiple sectors, including energy, environment, manufacturing, security, and health care.     

Effect of mill diameter on the rate of initial grinding in vibration ball mills

Vibration ball milling was carried out using three kinds of mills with the same internal volume but different diameters. The variations of specific surface area produced with time were investigated at a constant vibration intensity using feldspar with an initial size range of 74 – 149 μm. As a result, it was found that the specific surface area of product was markedly influenced by the difference in mill diameter even at the same vibrating conditions. According to an empirical equation proposed in a previous paper, the rate of initial grinding was also found to vary by a factor of 1.4 to 2.0, depending upon the mill used. The dependence of the rate of grinding on mill diameter can be explained by considering an effective area of mill shell capable of colliding with balls and a motion of balls in each mill. An available suggestion for designing a mill pot was obtained from this work.