Characterisation and mechanical testing of hydrothermally treated HA/ZrO2 composites

Hydrothermal treatment is traditionally employed to improve the sinterability of powder compacts by reducing porosity and increasing apparent density. The effect of hydrothermal treatment on green powder compacts has been assessed in order to better understand how treatment may affect the sinterability of the bodies. Laboratory synthesised nano sized hydroxyapatite (HA) and a commercial zirconia (ZrO₂) powder have been ball milled together to create composite mixtures containing 0–5 wt% ZrO₂ loadings. Disc shaped bodies have been formed using uniaxial and subsequent isostatic pressure. The resultant coherent samples were subjected to hydrothermal treatment at either 120 or 250°C for 10 h in order to assess the effect of this processing technique on the physical, mechanical and microstructural properties of the green composites. ZrO₂ loadings up to 3 wt% increased apparent density from 90 to 92%, whereas increased loading to 5 wt% increased flexural strength, from 6 to 9 MPa. Increasing the hydrothermal treatment temperature increased open porosity, from ~44 to ~48% and reduced biaxial flexural strengths of the treated bodies compared to those of their room temperature isostatically pressed counterparts (~10 to ~6 MPa).     

Aerobic Oxidation of Alcohols under Mild Conditions Catalyzed by Novel Polymer‐Incarcerated,Carbon‐Stabilized Gold Nanoclusters

Polymer‐incarcerated, carbon‐stabilized gold nanoclusters were found to be highly active in heterogeneous catalysis for the oxidation of secondary alcohols using molecular oxygen in aqueous medium. After optimization of catalyst preparation methods, highly loaded and highly effective catalysts were obtained, and a broad range of secondary alcohols could be oxidized by using these catalysts under mild conditions. The catalysts could be recovered and reused several times without significant loss of activity. Moreover, kinetics of the oxidation reaction with (±)‐1‐phenylethanol was investigated.     

织构对Cu-Al-Mn系形状记忆合金内耗的影响

In-situ observations on α/γ phase transformation were made to study the effects of grain boundary microstructures on the formation of a new phase and the migration of α/γ interphase boundary in an iron4. 2%Cr alloy. It was found that triple junctions with more random boundaries could be the primary nucleation sites for a new phase, while triple junctions with low angle or low ∑ coincidence boundaries did not play any role as preferential sites. The migration of α/γ interphase boundary during heating over the transformation temperature range showed the two stage behaviour characterized by a stage with a migration velocity of 0. 33-0. 75 mm/s and secondly by a stage with 3. 7-7. 6 mm/s. It was also found that abnormal grain growth and a high density of ∑3 coincidence boundaries could occur in a phase with bcc structure after cycling of α/γ phase transformation. A new mechanism of nucleation and growth of a new phase in α/γ phase transformation is proposed on the basis of roles of plane-matching interphase boundaries, as previously discussed on the origin of anisotropy of grain growth due to the migration of {110} plane-matching boundaries in Fe-3z%Si alloy. The most recent theoretical work on the distribution of plane-matching boundaries in solids with different crystal structures was found to be useful for the understanding of nucleation and growth during α/γ phase transformation.     

The reason for the preferential use of finger millet (Eleusine coracana) in eastern African brewing

Finger millet (Eleusine coracana) is a cereal that is widely used as an ingredient for alcoholic beverages in Eastern Africa. However, the reason for its preferred use in brewing over other types of cereal is still unknown. In this study, we aim to clarify the reason for selective use of finger millet in Eastern African brewing, through a field survey and laboratory experiments. The field survey was conducted in a rural village of Tanzania, named Bupigu. In the village, finger millet was used to prepare four types of foods: ugali (stiff porridge), uji (thin porridge), togwa (saccharified beverage) and pombe (alcoholic beverage). Among them, pombe brewing was the principal method of utilization. In addition, the survey showed that the villagers recognize that finger millet is responsible for the strong taste of pombe. Furthermore, the laboratory experiment showed that the α‐amylase activity of finger millet is higher than that of other cereals cultivated in Eastern Africa, suggesting that finger millet is a preferable ingredient for enhancing the efficiency of ethanol production. In conclusion, this study demonstrated that the high amylase activity, which led to high ethanol concentrations in the alcoholic beverages, is a preferable characteristic of the finger millet.     

A New Theoretical Approach Based on the Maxwell Model to Obtain Rheological Properties of Solidifying Alloys and Its Validation

This paper proposes a new method for obtaining the rheological properties of solidifying alloys in the brittle temperature range (BTR). In that range, alloys show not only rheological, but also brittle behavior. Conventional methods to obtain rheological properties require steady state stress with ductility. Therefore, rheological properties of BTR alloys are unobtainable, or are otherwise including the effects of microscopic damage. The method proposed in this paper uses the stress–strain relation derived from the Maxwell model assuming that strain hardening is negligible in solid-liquid coexistence states. By removing the plastic strain term, the creep strain rate in Norton’s law is derived by the total strain rate and stress rate without the steady state stress condition. Consequently, the stress exponent n and material constant A of Norton’s law can be obtained even for alloys in the BTR. We applied this method to both tensile process before crack initiation and stress relaxation process. According to the Maxwell model, couples of the properties (n and A) obtained in both processes must be equal. Therefore, the difference can validate the obtained properties. From tensile and stress relaxation tests, we obtained the properties of solidifying Al-5 wt pct Mg alloy. We validated results by examining the difference. This report is the first to provide a method to obtain the rheological properties of BTR alloy without damage.     

Low-loss high-silica single-mode channel waveguides

Low-loss high-silica single-mode channel optical waveguides of 0.1 dB/cm have been fabricated on crystal silicon substrates with fibre coupling losses of less than 0.05 dB by flame hydrolysis deposition and reactive ion etching. Directional couplers have also been fabricated with excess loss of 0.5 dB by this waveguide fabrication technique.     

Chlorophyll fluorescence imaging of individual algal cells: effects of herbicide on Spirogyra distenta at different growth stages

Serious environmental degradation of aquatic ecosystems has been caused by eutrophication and by pollutants such as herbicides. Therefore, measurement of in situ algal photosynthetic activity is important for environmental monitoring. With ordinary nonimaging fluorometers, algal chlorophyll fluorescence can be measured easily, but heterogeneity within samples cannot be detected. Effects of a herbicide preparation containing 3-(3,4-dichlorophenyl)-1,1 -dimethylurea (DCMU) on photosynthetic activity at different growth stages of Spirogyra distenta were investigated by using a computer-aided microscopic imaging system for chlorophyll afluorescence. Photosystem II photochemical yield (phiPSII) images were used to diagnose photosynthetic activity of spiral filate chloroplasts in algal cells. The herbicide treatment caused a stronger decline in phiPSII values in younger than in mature algae cells. This result indicated that heterogeneity within algal samples should be considered when algae are used for environmental monitoring. Thus, measurement of chlorophyll fluorescence from young and mature chloroplasts with a microscopic imaging system makes it possible to improve the sensitivity for monitoring the environmental degradation of aquatic ecosystems.     

Polarization sensitivity of a silica waveguide thermooptic phaseshifter for planar lightwave circuits

A thermooptic (TO) phase shifter, which consists of a thin-film heater loaded on a silica-based single-mode waveguide on a Si substrate, was found to exhibit a sli1h,t polarization dependence of about 3.1% between the TE and TM modes. This dependence, which is caused by anisotropic stress concentration due to local heating, was successfully reduced by forming stress-releasing grooves on either side of the heater     

Novel broad-band optical switch using silica-based planar lightwavecircuit

Novel wavelength-insensitive thermooptic switches which use silica-based planar lightwave circuits are proposed and successfully demonstrated. The fabricated switch has an extinction ratio of more than 17 dB over a 1.25-1.65 μm wavelength range