Control of Oxidation State of Eu Ions in Na2O–Al2O3–SiO2 Glasses

Glasses doped with well‐controlled Eu³⁺ and Eu²⁺ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their ⁵D₀→⁷F_j and 5d–4f electron transitions. Glasses were prepared to dope Eu³⁺ ions in a Na₂O–Al₂O₃–SiO₂ system, and the changes in the valence state of Eu³⁺ ions and the glass structure surrounding the Eu atoms during heating under H₂ atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and ²⁷Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu³⁺ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al³⁺ ions formed the AlO₄ network structure accompanied by the Na⁺ ions as charge compensators; the Eu³⁺ ions occupied the interstitial positions in the SiO₄ network structure and were not reduced even under heating in H₂ gas. On the other hand, in the glasses containing Al₂O₃ with the Al/Na ratio exceeding unity, the Eu³⁺ ions commenced to be coordinated by the AlO₄ units in addition to the SiO₄ network structure. When heated in H₂ gas, H₂ gas molecules reacted with the AlO₄ units surrounding Eu³⁺ ions to form AlO₆ units terminated with OH bonds, and reduced Eu³⁺ ions to Eu²⁺ via the extracted electrons.     

Automated Synthesis of (rac)‐, (R)‐, and (S)‐[18F]Epifluorohydrin and Their Application for Developing PET Radiotracers Containing a 3‐[18F]Fluoro‐2‐hydroxypropyl Moiety

To introduce the 3‐[¹⁸F]fluoro‐2‐hydroxypropyl moiety into positron emission tomography (PET) radiotracers, we performed automated synthesis of (rac)‐, (R)‐, and (S)‐[¹⁸F]epifluorohydrin ([¹⁸F] 1 ) by nucleophilic displacement of (rac)‐, (R)‐, or (S)‐glycidyl tosylate with ¹⁸F^? and purification by distillation. The ring‐opening reaction of (R)‐ or (S)‐[¹⁸F] 1 with phenol precursors gave enantioenriched [¹⁸F]fluoroalkylated products without racemisation. We then synthesised (rac)‐, (R)‐, and (S)‐ 2‐{5‐[4‐(3‐[¹⁸F]fluoro‐2‐hydroxypropoxy)phenyl]‐2‐oxobenzo[d]oxazol‐3(2H)‐yl}‐N‐methyl‐N‐phenylacetamide ([¹⁸F] 6 ) as novel radiotracers for the PET imaging of translocator protein (18 kDa) and showed that (R)‐ and (S)‐[¹⁸F] 6 had different radioactivity uptake in mouse bone and liver. Thus, (rac)‐, (R)‐, and (S)‐[¹⁸F] 1 are effective radiolabelling reagents and can be used to develop PET radiotracers by examining the effects of chirality on their in vitro binding affinities and in vivo behaviour.     

Isolation of Non-methylene Interrupted or Acetylenic Fatty Acids from Seed Oils Using Semi-preparative Supercritical Chromatography

Preparative scale supercritical fluid chromatography was used for isolating and purifying uncommon non-methylene interrupted or acetylenic polyunsaturated fatty acids ethyl esters from seed oils. Fractionation of Biota orientalis seed oil ethyl esters was performed by supercritical fluid chromatography to obtain juniperonic acid [(5Z,11Z,14Z,17Z)-eicosa-5,11,14,17-tetraenoic acid], a non-methylene interrupted polyunsaturated fatty acid. Fractionation of sandalwood seed oil ethyl esters yielded ximenynic acid [(E)-octadec-11-en-9-ynoic acid], an acetylenic polyunsaturated fatty acid. The effects of CO₂ flow rate, column stationary phase and particle size were explored to optimize ximenynic and juniperonic ethyl ester recovery and purity from ethyl ester mixtures using online UV/Vis detection. Particle size, followed by the stationary phase, were found to be the most important parameters to achieving good separation. Under optimized conditions, ximenynic and juniperonic ethyl ester purities greater than 99 and 95%, respectively, were achieved in a one step process without co-solvent. The isolation and recovery of juniperonic acid from biota seed oil free fatty acids was also attempted. Using free fatty acids as the feed material, the non-methylene interrupted polyunsaturated sciadonic acid was also able to be separated from other compounds including juniperonic acid under some conditions, and gave an increase in concentration of more than 17 times.     

Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing

ABSTRACT: Forming electrodes on opposite sides of an individual bismuth nanowire was attempted to prepare for Hall measurements. Although a 1-mm-long bismuth nanowire which is completely covered with a quartz template has been successfully fabricated to prevent oxidation, it is very difficult to attach Hall electrodes on the opposite sides of the nanowire due to the quartz covering. One side of the cylindrical quartz template was removed by polishing without exposure of the nanowire to the atmosphere; the thickness between the polished template surface and the nanowire was estimated to be several micrometers. Focused ion beam processing was successfully employed to expose both surfaces of the nanowire under high vacuum by removing part of the quartz template. A carbon thin film was then deposited in situ on the wire surface to fabricate an electrical contact on the bismuth nanowire sample. Furthermore, the energy dispersive X-ray analysis was performed to the area processed by focused ion beam, and the bismuth component of the nanowire was successfully detected. It was confirmed that the focused ion beam processing was applicable to attach electrodes to bismuth nanowire for Hall measurement.     

Preparation and characterization of a macroporous agarose monolith as a stationary phase in IMAC chromatography

A macroporous monolith used as stationary phase for the separation of biomolecules by immobilized metal ion affinity chromatography (IMAC), based on D5 agarose (D5) chemically modified was proposed. The characterization of physical properties was studied. Pressure drop was <0.4?MPa, being a very low value compared to other similar chromatographic supports. The adsorption/desorption process was carried out using bovine serum albumin (BSA) at pH 7.4 as a target protein. The monolith was re-used for 20 adsorption/desorption cycles and it was possible to verify that the average percentage of adsorption in all cycles was 89.65%. It was also possible to apply a model in order to obtain the kinetic adsorption constant (k_a), desorption constant (k_d) and equilibrium constant (K_e) by the proposed system. These results indicate that this system is governed by the adsorption process.     

Fine structure of tooth enamel in the yellowing human teeth: SEM and HRTEM studies

Objective : The aim of this study was to clarify an influence of the fine structure of human tooth enamel to the yellowing teeth. Materials and methods : Sound maxillary first premolars of 15–50‐year‐old females that were extracted for the orthodontic treatment were used as the test samples. The tooth enamel sections of these teeth that prepared by ion polishing were observed by scanning electron microscopy (SEM). Furthermore, the fine structure of substance filling the inter‐rod spaces was analyzed by high resolution transmission electron microscopy (HRTEM). Results : In white tooth, the inter‐rod spaces were observed at the width of about 0.1 μm, while in yellow tooth, the inter‐rod spaces were not clearly observed by SEM. HRTEM observations revealed for the first time that the inter‐rod spaces were filled with fine particles of poorly crystallized hydroxyapatite in the yellow tooth. In yellow tooth, it was considered that the color of the inner dentin was recognized due to the decrease of light scattering by filling the tooth enamel inter‐rod spaces. The generation of particles in the tooth enamel inter‐rod spaces was considered to be caused by the long‐time progression of calcification. Conclusions : These results suggested that the change in fine structure, filling in inter‐rod spaces of tooth enamel, was related to progression of calcification in the inter‐rod spaces with advancing age and one of the factors of yellowness of human tooth. Microsc. Res. Tech. 79:14–22, 2016. © 2015 Wiley Periodicals, Inc.     

Effects of Some Light Alloying Elements on the Oxidation Behavior of Fe and Ni-Cr Based Alloys During Air Plasma Spraying

The oxidation behavior of iron binary powders with addition of Si (1, 4 wt.%) and B (1, 3 wt.%) and that of a Ni-Cr based alloy powder with Si (4.3 wt.%), B (3.0 wt.%), and C (0.8 wt.%) additions during atmosphere plasma spray (APS) have been investigated. Analysis of the chemical composition and phases of oxides in the captured in-flight particles and deposited coatings was carried out. The results show that the addition of Si and B to iron effectively reduced the oxygen contents in the coatings, especially during the in-flight period at higher particles temperature. Ni-Cr based alloy powder with Si, B, and C additions reduced the oxidation of the base alloys significantly. Preferential oxidation and subsequent vaporization of Si, B, and C from the surface of the sprayed particles are believed to play a major role in controlling oxidation in the APS process.     

The effect of thickness on the steady-state creep properties of freestanding aluminum nano-films

To clarify the effects of film thickness on the creep properties of nano-films we conducted tensile creep experiments on freestanding aluminum films with thickness values in the range ～100–800 nm at room temperature. The nano-films showed typical creep behavior comprising transient, steady-state, and accelerated creep stages. The steady-state creep exponents of the 100–800 nm thick specimens were 0.84–2.7 in the stress range 30–120 MPa, which are close to the value for diffusion creep (1). Creep deformation clearly shows a thickness effect: the steady-state creep rate increases as the thickness decreases from 800 to 400 nm, shows a peak in the range 400–200 nm, and then decreases in the 200–100 nm thickness range. The creep experiments under a small stress of 1 MPa show a negative strain rate, indicating the presence of a driving force to reduce the surface area due to surface tension. The explanation for the thickness effect is as follows. Since the ratio of surface and grain boundary area to volume increases with decreasing thickness, diffusion creep along these paths is enhanced, resulting in an increase in the creep rate. As the thickness decreases to 200–100 nm, however, the surface tension effect to reduce the surface area becomes dominant, decreasing the creep rate. In addition, the creep rate of the nano-films is about two or three orders of magnitude smaller than that of the bulk material dominated by the dislocation creep mechanism.