Simplified flocculation model for inorganic and polymer flocculants

Simulation of the flocculation process using both inorganic and polymer flocculants is very difficult because there are many factors that influence the process. In this study, a model that enables the visual understanding of the qualitative trends of the flocculation system using both inorganic and polymer flocculants is proposed. It is a simplified one-dimensional model that expresses flocculation under various additive manners of the flocculant. Various kinds of thought experiments as well as experimental runs with model flocculants were carried out based on the model; the results demonstrate that the model can express many empirical qualitative trends of flocculation.     

Defect sizing of small inclined cracks on a free surface using multi-tip waves

The most effective method of ultrasonic defect sizing is recognized to be the tip echo method. However, tip waves have very weak intensities, and require skill and experience by the operator. Recently, low noise fully digital flaw detectors have been developed, which make it easy to capture several tip echoes simultaneously. Experiments were carried out using a fully digital detector for the reflection by an artificial inclined crack of 1.5 mm height on a free surface, and numerical simulations were also performed to distinguish each tip echo. Crack height, inclination angle, and crack width were estimated using the tip echo distances of the experimental data from one side. The results show good agreement with actual values. The method is stable for changes in probe position. An experiment on fatigue cracks was also performed. Automatic inspection will be possible using the results of this method in the near future. Many tip waves are generated by the deflection of ultrasound from crack tips and corners, and the evaluation of defect size can be accomplished by full use of the tip waves.     

Development of a digital control system for high-performance pneumatic servo valve

Pneumatic servo systems are used in many fields, such as pneumatic robot systems or vibration isolation systems. To improve the controllability of the pneumatic servo system, a higher performance servo valve is needed.In the present paper, a pneumatic spool type servo valve having an air bearing and a high-resolution position sensor was developed. We attempted to achieve high-frequency, high-accuracy flow rate control by digitization of the controller. We present herein a control algorithm for digital control of this valve.The characteristics of this valve were measured and the natural frequency of the valve was clarified to be up to 300 Hz. The spool position accuracy and the dynamic characteristics of the developed servo valve are greatly improved compared to existing valves.     

Effects of antibacterial agents, levofloxacin and clarithromycin, on aquatic organisms.

Contamination of surface waters by pharmaceutical chemicals is an emerging environmental problem. This study evaluated the toxic effects of the antibacterial agents levofloxacin (LVFX) and clarithromycin (CAM), which are widely used in Japan, on aquatic organisms. Ecotoxicity tests using a bacterium, alga and crustacean were conducted. Microtox test using a marine fluorescent bacterium showed that LVFX and CAM have no acute toxicity to the bacterium. From the results of the Daphnia immobilisation test, LVFX and CAM did not show acute toxicity to the crustacean. Meanwhile, an algal growth inhibition test revealed that LVFX and CAM have high toxicity to the microalga. The phytotoxicity of CAM was about 100-fold higher than that of LVFX from a comparison of EC50 (median effective concentration) value. From the Daphnia reproduction test, LVFX and CAM also showed chronic toxicity to the crustacean. Concentrations of LVFX and CAM in the aquatic environment were compared with PNEC (predicted no effect concentration) to evaluate the ecological risk. As a result, the ecological risk of LVFX is considered to be low, but that of CAM is higher, suggesting that CAM discharged into an aquatic environment after therapeutic use may affect organisms in the aquatic environment.     

Synthesis of Tn, sialyl Tn and HIV-1-derived peptide antigen conjugates having a lipid A analog as an immunoadjuvant for synthetic vaccines

Conjugates (3-5) of Tn, sialyl Tn and HIV-1-derived peptide antigen with a N-tetradecanoyl L-serine-beta-alanine-containing D-glucosamine derivative, structurally related to lipid A, as an immunoadjuvant for the development of totally synthetic vaccines against cancers or HIV were synthesized. The mitogenic activity of compounds 3, 4 and 5 was stronger than that of lipid A analogs (1, 2).     

Effect of weld tip geometry on ultrasonic welding of A6061 aluminium alloy

The authors ultrasonically welded A6061 aluminium alloy sheet using two types of weld tips with different contact face geometries, and investigated the effect of the weld tip on the performance and interface structure of the welds. One type of tip has a cylindrical contact face without knurl, which is called a C-tip in this study. The other type of tip has a flat contact face with knurl, which is a called K-tip in this study. The following main results were obtained.

The strength of the joints welded using the C-tip was higher than that welded using the K-tip and the fluctuation in joint strength with the C-tip was smaller. The C-tip could stably produce the higher strength joint. Using the K-tip, the knurl indentations were made on the workpiece surface due to the pyramidal projections on the weld tip, and the indentation size expanded with welding time, resulting in the deterioration of the joint property. On the other hand, the indentation made on a workpiece surface by using the C-tip showed a distinctive shape like an ellipse, elongated perpendicular to the ultrasonic vibration, and the indentation grew with welding time.

Using the K-tip, unbonded regions remained at the weld interface due to the concavity on the weld tip face. In the cross-sectional structure parallel to the workpiece width of the joint welded using the C-type tip, a distinctive feature was observed that the faying surface of the anvil workpiece was mixed with that of the sonotrode workpiece by intense plastic deformation and a horn-like protuberance intruding into the sonotrode workpiece was formed at the periphery of the welded area.     

X-ray absorption fine structure combined with X-ray fluorescence spectroscopy. Monitoring of vanadium sites in mesoporous titania, excited under visible light by selective detection of vanadium Kbeta5,2 fluorescence

The photocatalytic role of vanadium doped in mesoporous TiO2 has not been clarified. Valence state-sensitive V Kbeta5,2-selecting (5462.9 eV) X-ray absorption fine structure (XAFS) was used to monitor the V sites in mesoporous TiO2 for ethanol dehydration under equilibrium in situ conditions and visible light-illumination. First, the feasibility of discriminating V(IV) sites from a 1:1 physical mixture of standard V(IV) and V(V) inorganic compounds was demonstrated, by tuning the secondary fluorescence spectrometer to 5459.0 eV. The chemical shift of V Kbeta5,2 emission between V(IV) and V(V) sites was 1.0 eV. The selection of valence states V(IV) and V(V) was 100% and 80%, respectively. The redox states for ethanol dehydration over mesoporous TiO2 excited in visible light were suggested to be V(III) and V(IV). The chemical shift between valence states V(III) and V(IV) was greater (3.2 eV). On the basis of V Kbeta5,2 emission and V Kbeta5,2-selecting XAFS spectra tuned to the V Kbeta5,2 peak, we determined that the fresh mesoporous V-TiO2 catalyst has a valence state of V(IV). The vanadium sites were partially reduced by the dissociative adsorption of ethanol under visible light, but they still stay within the emission-energy ranges for standard V(IV) compounds. These partially reduced vanadium sites were reoxidized in oxygen under visible light. Finally, direct XAFS observation of photoreduced V(III) sites was attempted by tuning the fluorescence spectrometer to 5456.3 eV for partially reduced mesoporous V-TiO2. Valence state V(III) was selected for 60% of the spectrum in the mixture of V(III) (minor) and V(IV) (dominant) valence states.     

Low-temperature synthesis of binary cuprates from hydroxide precursor

Binary cuprates of Sr₂CuO₃₊ and SrCuO₂ have been synthesized at low temperatures below 500 °C under various values of partial oxygen-pressure by thermal decomposition of hydroxide precursors, Sr₂Cu(OH)₆ and SrCu(OH)₄, respectively. The tetragonal Sr₂CuO₃₊ ( 0.3) is obtained by the heat-treatment at 400 ° C and 0.2 atm. The value of appears to be independent of and unchangeable. On the other hand, the orthorhombic Sr₂CuO₃₊ ( 0) is obtained by the heat-treatment at 400 °C in flowing gas of N₂. For 0 < < 0.2 atm, a mixture of the tetragonal and orthorhombic phases is obtained. The orthorhombic SrCuO₂ is obtained by the heat-treatment at 500 ° C in flowing gas of N₂, although the tetragonal SrCuO₂, namely, the so-called infinite-layer compound is not obtained.     

Electronic structure of wurtzite- and zinc blende-GaN studied by angle-resolved photoemission

The valence band structures of both wurtzite- and zinc blende-GaN were investigated by angle-resolved photoemission spectroscopy. It was found the k dispersions of the upper valence bands show band structures corresponding to wurtzite or zinc blende structure. In wurtzite-GaN, band width of the upper valence band is 6.7 eV in good agreement with the theoretically predicted value. However, the binding energy of Ga 3d level was found to be 15.7 eV relative to the valence band maximum, which is about 2 eV higher binding energy than those predicted by local density approximation calculations. In zinc blende-GaN, some discrepancies in the binding energy of the topmost bands around the valence band maximum was observed. We discuss the cause of these discrepancies by taking into account the strain effect.     

Structural defects and electrical conductivity in nanocrystalline SiC:H films doped with boron and grown by photostimulated chemical-vapor deposition

The paramagnetic DB defects and dark conductivity σ_d in films of nanocrystalline hydrogenated silicon doped with boron and carbon (nc-SiC:H) and grown by photostimulated chemical vapor deposition are studied. It is shown that an increase in the doping level leads to a phase transition from the crystalline structure to an amorphous structure. The electrical conductivity increases as the doping level increases and attains the value of σ_d = 5.5 × 10^?2 Ω^?1 cm^?1; however, the conductivity decreases once the phase transition has occurred. The concentration of DB defects decreases steadily as the doping level increases and varies from 10¹⁹ cm^?3 (in the crystalline structure) to 9×10¹⁷ cm^?3 (in the amorphous structure).