Practical selection of emission lines of He I to determine the photon absorption rate

A combination of helium line intensities and a collisional radiative model has been used to measure electron density and temperature. However, radiation trapping of resonance lines may disturb the measurements due to disturbances in the population distribution of helium atoms. In this study, we show that the principal contribution of radiation trapping in helium plasma can be evaluated by additionally measuring one or two specific line intensities from the singlet state. The inclusion of the effects of radiation trapping sufficiently compensates for anomalous increases in the electron density and temperature, and consequently yields proper values. An experiment was performed in the divertor simulator NAGDIS-II, and the method's validity was confirmed by comparing the spectroscopically obtained results and the values from the electrostatic probe method.     

Evaluation of retained products of conception using pulsed continuous arterial spin-labeling MRI: clinical feasibility and initial results

Objectives

We evaluated the vascularity of retained products of conception (RPOC) using arterial spin-labeling magnetic resonance imaging (ASL-MRI) to clarify the clinical feasibility of this approach.

Materials and methods

A pulsed-continuous ASL sequence with echo-planar imaging (EPI) acquisitions was used. Ten consecutive patients with RPOC were enrolled. All ASL images were evaluated visually and semiquantitatively and compared with the findings of Doppler ultrasound (US) and dynamic contrast-enhanced MRI (DCE-MRI).

Results

The technical success rate was 93.7% (15/16 scans). One failed case was excluded from the analysis. Six patients showed quite high signals over RPOC, while three patients showed no abnormal signals. Doppler US alone failed to detect the hypervascular area in two cases, and ASL-MRI alone failed in three. A significant linear correlation was found between semiquantitative values of ASL-MRI and DCE-MRI. All six patients showing high signals on ASL-MRI underwent follow-up MRI after therapy. High signals in five patients decreased visually and semiquantitatively, while one patient showed signal increases.

Conclusion

Evaluation of RPOC using ASL-MRI was clinically feasible and response to therapy could be evaluated. However, the clinical advantages over conventional imaging remain unclear and need to be evaluated.

     

Sorption behavior of thorium onto granite and its constituent minerals

The sorption behavior of thorium (Th) onto granite and its major constituent minerals, feldspar, quartz and mica were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. Distribution coefficients (K_d) decreased with increased carbonate concentrations and showed the minimal value at around pH 10. This sorption tendency was seen for all the rock and mineral samples, and it was due to the formation of aqueous hydroxo–carbonate complexes of Th in the solutions. The order of sorbability for Th was mica > feldspar > quartz ≈ granite. The sorption behaviors of Th were analyzed by the non-electrostatic surface complexation model with the Visual Minteq computer program. The K_d for granite were calculated by component additivity approaches. The model calculations were able to explain the experimental results reasonably well. It was shown that the sorption behavior of Th onto granite can be explained by the complexation with the surface sites of mainly biotite and feldspar.     

An atomistic study of grain boundary stability and crystal rearrangement using molecular dynamics techniques

The stability of grain boundaries (GBs) and the dynamic behavior of atoms in the boundary region are investigated from an atomistic standpoint. Symmetric and non-symmetric GBs are constructed using an fcc configuration, and the GB energy is calculated as a function of the misorientation angles using a Lennard-Jones-type interatomic potential. Several specific angles are revealed to exhibit cusp-shaped low values. The effect of atomic relaxation at the GB is then simulated, showing a decrease in the GB energy. Changes in the morphology of a grain embedded in a bulk single crystal are also simulated. Using both a square-grain and a circular-grain model, the following results are obtained. In models with small misorientation angles, the grain changes orientation and the GB vanishes. When the orientations are initially stable, no change in the grain is observed. However, in models with non-stable orientations, local stabilization occurs by a rearrangement of the atoms around the GB, and the shape of the grain is transformed. Finally, a similar simulation is carried out at a high temperature, and this reveals that grain contraction occurs even in models that are stable at a low temperature, and that the grain eventually disappears.     

Microstructural design for fabrication of strain sensor utilizing tungsten-doped amorphous carbon coatings

Tungsten-containing diamond-like carbon (W-DLC) coatings were fabricated with an aim of producing new strain sensor applications. W-DLC coatings with various metal concentrations were prepared by chemical vapor deposition and DC magnetron co-sputtering of a tungsten metal target. The electrical resistance was shown to be proportional to the value of compression and tensile strain. The expression ΔR/R = Kε, was applied to the experimental results in order to determine the gauge factor of each coating, and this gauge factor varied according to the metal concentration. Transmission electron microscope was employed for structural analyses and it was shown that the structure of the W-DLC coatings consisted of nanometer size grains dispersed into an amorphous carbon host matrix. The electrical properties of the W-DLC coatings were simulated using a model based on a composite insulator-metal cluster structure. These results were in agreement with the experimental ones, and a high gauge factor can be obtained with low metal concentration or increase in size of metal cluster.     

Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE), in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm^-2. They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor.     

Effect of Molecular Weight Distribution of Mineral Oils on Life of Thrust Ball Bearings

In order to investigate the effect of molecular weight distributions of mineral oils on bearing life, the authors carried out systematic tests using thrust ball bearings, type 51104.

Besides the general trend of increasing life with viscosity, blended oils characterized by wide-ranged molecular weight distributions exhibited longer life compared with base oils with narrow-ranged distributions corresponding to the same viscosity grade. These results were obtained by estimating states of oil film and oxide film formations, and furthermore, by measuring coefficients of friction, oil temperatures, and viscosity at the glass transition points.     

SOLVENT EXTRACTION OF COPPER (II) WITH AN ALDOXIME FROM HYDROCHLORIC AND HYDROBROMIC ACIDS

2-ethylhexanal oxime was synthesized to examine the selectivities for various metals in the extractions from hydrochloric acid. It was found to be highly selective for palladium(II) over platinum(II and IV) and other base metals including copper(II), zinc and aluminum, especially in the low concentration region of chloride ions.     

Alloy Casting by the Horizontal Ohno Continuous Casting System

Abstract

Sn-Pb alloys in the compositional range 2.5–22.5% Pb have been continuously cast using the horizontal Ohno Continuous Casting (OCC) process. The effects of alloy composition and process variables on the location and size of the liquid-solid zone were investigated and information obtained was examined in order to establish the breakout point. It was found that the liquid-solid zone existed partly or entirely within the mould during casting, depending on casting conditions. The liquid-solid zone expanded with increasing mould-cooler distance and also with decreasing mould exit temperature, whereas it remained constant with the casting speed within the range investigated. As the composition approaches the eutectic point, the L+S zone shifted into the mould, and existed entirely within the mould at 22.5% Pb. It was also found that breakout occurred when the rod temperature at the mould exit exceeded a critical temperature which can be expressed as Tc=228–2A, where Tc is the critical rod temperature in Celsius and A is wt% Pb (<22.5% Pb). It was confirmed that the mould exit temperature must be kept above the liquidus temperature of the alloy to be cast in order to obtained unidirectional or single crystal materials.     

Yield and buckling behavior of Kelvin open-cell foams subjected to uniaxial compression

This study analyzes the yield and buckling behavior of Kelvin open-cell foams subjected to uniaxial compression. A homogenization theory of the updated Lagrangian type is applied to cubic unit cells and cell aggregates in the Kelvin foam model. Macroscopic instability and microscopic bifurcation are thus incrementally examined under uniaxial compression. The analysis is performed by taking into account the non-uniformity of strut cross-sectional areas and the strain hardening-softening behavior of struts that were observed in experiments on open-cell 6101-T6 aluminum alloy foams. It is shown that macroscopic instability primarily occurs as a consequence of the strain hardening-softening behavior of struts. It is further shown that the macroscopic instability stress obtained has (3/2)th power dependence on relative density as predicted in the Gibson-Ashby relation.