[en] The binding of zinc by purified cellulose, xylan, methylated xylan, pectin and methylated pectin was measured in vitro. Methylated xylan and methylated pectin were prepared chemically from xylan and pectin, respectively, to block hydroxyl and carboxyl groups. Comparison of zinc binding capacities was made between xylan and methylated xylan, and between pectin and methylated pectin to assess the role of the two functional groups in binding minerals. The binding of zinc was conducted at pH 2.6, 4.0, 5.4 and 6.8 in various concentrations of ZnSO₄ solution containing ⁶⁵Zn using a dialysis system for water-soluble pectin and an incubation-centrifugation model for the other four water-insoluble fibers. The results showed that zinc binding by each fiber was pH dependent and it increased from pH 2.6 to 6.8 (p < 0.001). At pH 6.8, % Zn bound to fiber decreased as concentration of ZnSO₄ increased from 1 μM to 96 μM (p less than or equal to 0.01). mean zinc binding ratio of pectin to methylated xylan was 5.1, whereas the ratio of pectin t methylated pectin was only 1.7. This suggests that the hydroxyl group in xylan plays a more important role than the carboxyl group in pectin in the binding of zinc

[en] Nb addition to Ti₃Al has been found to be effective to improve its oxidation resistance. Recently, the beneficial effect of nitrogen in the oxidation behavior of Nb contained Ti₃Al-based alloys has been noticed. In this paper, the oxidation behavior of five alloys with different Nb content from 0 to 20 at.% exposed in room air at different temperatures (from 600 to 950 C) has been examined with the focus on the TiN formation in the oxide scale. No TiN is detected in the scales of binary Ti₃Al under all temperatures tested. On the contrary, in alloys containing Nb, TiN is identified in the scales irrespective of the oxidation temperature. The amount of TiN formation differs with different Nb content. EPMA analysis of the cross section of the scales is performed and discussion is made accordingly

[en] Surface characterization of microcomponents provides key information to help understand and predict the performance of microdevices. For example, in a microgear transmission, the surface roughness has a strong effect on the friction, running life and power consumption. In a static fluid microdevice, the liquid distribution is influenced by the surface tension and capillary force, which are primarily determined by the surface roughness. In a flowing microchannel case, surface roughness results in unsteady secondary flows. In this paper, a study is presented to characterize the surface roughness of silicon and SU-8 microcomponents. The silicon components studied are fabricated using an ICP plasma etching system manufactured by Surface Technology Systems. The sidewall roughness of the component is measured using atomic force microscopy. Repeated measurements have been conducted at different sidewall depths of the microstructure. The AFM images of the measurements are present. The measurement results show that the sidewall is smoother at the lower level than that at the upper level in a Si microstructure, and the average roughness R _a obtained throughout the depth is 151.11 nm. The UltraThick SU-8 Process (UTSP) provides another way to fabricate microstructures as thick as 1 mm with a very vertical sidewall. The roughness contour of the sidewall shows that the surface topography is similar throughout the depth. The average roughness R_a is 46.46 nm. Other surface parameters, such as R_q, R _p-p, R _pk and R_sk, are also obtained and analysed. The implication of the smooth surface roughness of SU-8 structures to their applications is discussed in terms of transmission efficiency, the changes in friction to flowing liquid in a microchannel and the changes in the surface tension and capillary effect

[en] A series of solid electrolytes Ce_1-xSm_xO_2-y (x=0∼0.6) were prepared by sol-gel method. XRD measurement showed that single-phase solid solution was formed in all investigated ranges at 160 deg. C, which is a significantly lower synthesis temperature compared to traditional solid state reaction. High temperature X-ray, ESR, and Raman scattering were used to characterize the samples. ESR measurement showed that ESR with sample irradiated by high-energy particle is an effective way to study the defect structure. These changes in the Raman spectrum are attributed to O vacancies, which are introduced into the lattice when tetravalent Ce⁴⁺ is substituted by trivalent Sm³⁺

[en] This article describes the new supercritical heat transfer test facility that has been constructed at the University of Ottawa and preliminary tests for its commissioning. The facility uses CO_2 as a medium and has three test sections: a tube with an 8 mm ID, to serve as a reference for comparisons with literature, a second tube with a 22 mm ID, and a rod bundle. The facility is designed for tests in the ranges of pressure, heat flux and mass flux that correspond to normal, enhanced and deteriorated heat transfer under conditions relevant to supercritical water cooled reactor designs. Some preliminary measurements of the heat transfer coefficient under subcritical and supercritical conditions in the 8 mm tube are presented and compared to representative correlations. This article also discusses plans for heat transfer measurements in the rod bundle and measurements of turbulence properties and temperature fluctuations using hot- and cold-wire probes in the 22 mm tube. (author)

[en] A sensitive and selective method is described for the determination of neodymium in mixed rare earths using fourth-derivative spectrophotometry. The method is based on the absorption spectra of 4f electron transitions of the complex of neodymium with methyl thymol blue and cetylpyridinium chloride. The influence of various instrumental parameters and reaction conditions for maximum colour development are investigated. The calibration curve is linear over the range 0-3.5 μg ml^-1 neodymium. The relative standard deviation for determination of 1.4 μg ml^-1 neodymium (n = 7) is 1.6%. The detection limit (signal-to-noise ratio = 3) is 0.2 μ g ml^-1. (author)

[en] This paper presents a successful method to fabricate high-quality composite micro parts. The fabrication process starts with producing SU-8 aster moulds using photolithography technique, mirror replication of PDMS soft moulds, preparing composite slurry using super fine 316-L stainless steel (5 µm) and α-alumina powder (≤400 nm) in 2.5, 5, 7.5 and 10 wt%, filling the moulds, obtaining the green parts, de-binding and sintering. A new method was used in this research to homogenize the alumina particles in a stainless steel composite slurry. Stainless steel and alumina powders were dispersed separately in distilled water and dispersant. Then, the two dispersed powders were mixed together to form a homogeneous composite slurry. The process resulted in high-quality composite micro parts which retain the very details of the SU-8 master moulds. The internal structures of the green and sintered micro parts showed homogeneous distribution of alumina particles in a stainless steel matrix. The density and micro hardness of the sintered parts were also investigated in detail for different stainless steel alumina compositions

[en] We have observed the Moessbauer Faraday effect in non-stoichiometric Fe₃O₄ by using a Moessbauer polarimeter. Experimental results demonstrated that electronic hopping above the Verwey temperature between Fe²⁺-Fe³⁺ ions on the octahedral sites is a localized phenomenon only and the recoilless fractions of ⁵⁷Fe nuclei in Fe_3-vO₄ (v=0.02) are 0.71 for A sites and 0.62 for B sites, respectively. (orig.)

[en] An experimental facility supporting the Canadian Super Critical Water-cooled Reactor (SCWR) research efforts has been constructed at the University of Ottawa. Loop commissioning tests have been performed, during which a number of heat transfer phenomena were observed. The measured heat transfer coefficients are compared with predictions of available correlations. The test results demonstrated that the facility operates within design specifications. (author)

[en] Recently lane formation and phase separation have been reported for experiments with binary complex plasmas in the PK3-Plus laboratory onboard the International Space Station (ISS). Positive non-additivity of particle interactions is known to stimulate phase separation (demixing), but its effect on lane formation is unknown. In this work, we used Langevin dynamics (LD) simulation to probe the role of non-additivity interactions on lane formation. The competition between laning and demixing leads to thicker lanes. Analysis based on anisotropic scaling indices reveals a crossover from normal laning mode to a demixing-stimulated laning mode. Extensive numerical simulations enabled us to identify a critical value of the non-additivity parameter Δ for the crossover.