High purity pion beam at TRIUMF

An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay π⁺→e⁺ν is also described.     

Hydrogenation and dehydrogenation processes of palladium thin films measured in situ by spectroscopic ellipsometry

The hydrogenation and dehydrogenation switching processes of Pd thin films were analyzed by measuring in situ in real time the variation in ellipsometric Ψ and Δ during hydrogenation and dehydrogenation using spectroscopic ellipsometry. The hydrogenation proceeded from the film surface and a mixture layer of metal and hydride was formed at the surface. With time elapse, the thickness of the mixture layer increased rapidly. After the whole Pd metal layer transformed to the mixture layer, the concentration of hydride in the mixture layer increased. Finally, the concentration reached 1; the whole Pd in the mixture layer was hydrogenated, and the hydrogenation of Pd was complete. On the other hand, the dehydrogenation proceeded in a way completely opposite to the hydrogenation process; the concentration of hydride in the mixture layer decreased, Pd metal layer was formed at the interface between the film and the substrate, and the whole layer returned to Pd metal. The dehydrogenation proceeds much faster than hydrogenation.     

Isolation of Solid Solution Phases in Size‐Controlled LixFePO4 at Room Temperature

State‐of‐the‐art LiFePO₄ technology has now opened the door for lithium ion batteries to take their place in large‐scale applications such as plug‐in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room‐temperature phase diagram is essential to understand the facile electrode reaction of Li_xFePO₄ (0 < x < 1), but it has not been fully understood. Here, intermediate solid solution phases close to x = 0 and x = 1 have been isolated at room temperature. Size‐dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid‐solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two‐phase equilibrium potential is largely due to the bulk solid solution, and thus support the size‐dependent miscibility gap model.     

Optical on-line running reconstruction of MR-images in the phase-scrambling Fourier-imaging technique

Recently, the use of magnetic-resonance-guided navigation to improve the safety and effectiveness of surgical procedures has shown great promise. The purpose of the present study was to develop and demonstrate an imaging strategy that allows surgeons to continue operating without delays caused by imaging. The phase-scrambling Fourier-imaging technique has two prominent characteristics: localized image reconstruction and holographic image reconstruction. The combination of these characteristics allows images to be observed even during the data-acquisition period, because the acquired signal is converted into a hologram and the image is reconstructed instantly in the coherent optical image-processing system. Experimental studies have shown that the phase-scrambling Fourier-imaging technique enables the motion of objects to be imaged more quickly than the standard fast imaging. The proposed running reconstruction strategy can be easily implemented in the well-established magnetic-resonance imaging equipment that is currently in use.     

The modification of ABS resin by introducing metal salts of unsaturated acids

Graft polymerization of methacrylic acid onto ABS resin was carried out using BPO as an initiator in THF solution. Degree of grafting increased with reaction time and reached 35% in 10 hrs. Carboxyl groups were converted to carboxylates (metal salts) by refluxing MAA-g-ABS and the metal acetate in THF. In the solid graft polymers in solid, the infrared absorption of the asymmetrical C= O vibration of the carboxylic acid shifted to lower wavenumbers with increasing metal ion concentration. The absorption peak for the carboxylate anion is shifted to higher wavenumbers with the increase of alkali metal ion concentration, however, for the Mg²⁺ salt, it is shifted to lower wavenumbers. The surface and volume resistivities of the K⁺ and Na⁺ salts of MAA-g-ABS were 9.0 × 10⁹ and 9.5 × 10⁹ at 80% neutralization, respectively, and decreased with alkali metal ion concentration. The electric resistance of Li⁺, Mg²⁺ and Zn²⁺ salts decreased only slightly. The modulus of the K⁺ salt of MAA-g-ABS decreased with neutralization, whereas in Li⁺, Mg²⁺ and Zn²⁺ salts, the modulus increased with increasing metal ion concentration.     

Alleviation of the two-cell block of ICR mouse embryos by polyaminocarboxylate metal chelators

The present study was undertaken to examine the effects of various transition metal ion chelators, both polyaminocarboxylates (including nitrilotriacetate (NTA), ethylenediaminediacetate (EDDA), ethyleneglycolbistetraacetate (EGTA), ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentaacetate (DTPA)) and non-polyaminocarboxylates (dipicolinic acid and deferoxamine), on the development in vitro of one-cell ICR strain mouse embryos to the four-cell and blastocyst stages. The order of stability constants of polyaminocarboxylates for transition metal ions such as zinc, copper and iron is as follows: NTA < or = EDDA < EGTA < EDTA < DTPA. Addition of 10 or 100 micromol polyaminocarboxylates x l(-1) to the medium significantly enhanced the development of most one-cell embryos (66-88%) beyond the two-cell stage compared with that (< 25%) in medium without polyaminocarboxylates. Although EDDA, EDTA and DTPA at 10 micromol x l(-1) induced the development of most one-cell embryos to the four-cell stage and beyond, a higher concentration (100 micromol x l(-1)) of NTA and EGTA was required to obtain a similar result. Therefore, the ability of polyaminocarboxylates to overcome the two-cell block is not correlated with their potency to chelate transition metal ions. In contrast, the non-polyaminocarboxylates dipicolinic acid and deferoxamine, at 10 and 100 micromol x l(-1), did not have the same effect. Taken together, the results indicate that the ability of polyaminocarboxylates to overcome the two-cell block in embryo development is due to some common feature or features other than the ability to chelate transition metal ions.