No abstract

Ultraviolet light-emitting diodes (UV-LEDs) offer high flexibility in the reactor design for water disinfection. To specify the key design factors affecting the performance of a reactor, we examined how the arrangement of UV-LEDs in a cylindrical reactor affects the inactivation efficiency of Escherichia coli and coliphage Qβ. A ring-shaped UV-LED apparatus, composed of two units containing ten 285-nm UV-LEDs each, were attached to a quartz cylinder, and microbial suspensions flowed through the cylinder for single pass at altered flow rates. The distance between the two units, L, was altered to examine its effects on inactivation efficiencies. Over 4 log inactivation of E. coli was achieved at 800 mL min regardless of the L values, suggesting that the apparatus has a high potential to disinfect water. The inactivation at L = 20 mm was significantly higher than that at L = 0 in all cases tested (ANOVA, P < 0.05), while this was not true when L was extended to 40 and 60 mm. Therefore, a separate arrangement of UV-LEDs at a certain distance can improve the efficiency, and the distance matters to enhance the performance. This study involves a design concept on how to arrange UV-LEDs in a water disinfection apparatus.

In this study, we carry out high temperature glancing angle deposition (HT-GLAD) of Fe and Al on a heated substrate with trench patterns. When vapor is incident perpendicular to the trench direction, nanowhiskers grow only on the surface exposed to the vapor and not inside the trenches. When vapor is incident at a deposition angle larger than 80° on the sidewall of the trench and not on the substrate surface, nanowhiskers grow only on the sidewall because the condition of deposition at a high temperature and a large deposition angle is satisfied only for the sidewall. Thus, we succeed in the selective growth of nanowhiskers by controlling the geometrical deposition conditions. Further, we also discuss the effect of the local deposition geometry on the growth process.Geometrically selective growth by HT-GLAD is expected to be useful for growing nanowhiskers on nano-and microstructured substrates.

We report a new GaN etching technique with high anisotropy involving a thermal decomposition reaction in a low-pressure H 2 environment. A GaN microridge stripe structure (5 µm in width and 1.2 µm in height) with extremely smooth sidewalls was fabricated at 1,050°C and a H 2 pressure of 10 Pa for 15 min using a SiO 2 mask. The activation energy of the vertical etching was calculated to be 62-77 kcal/mol. In the GaN nanoridge stripe structure, the side etching under the SiO 2 mask was less than 5 nm in depth and showed top width and height of >40 and >180 nm, respectively. The sidewall was extremely smooth and tilted by >15°from the m-plane along the a-axis, while being slightly rough and tilted by >30°from the aplane along the m-axis. The fn n02g (n ¼ 4; 5; 6; 7) planes were relatively stable in this etching technique.

We demonstrate high temperature glancing deposition (HT-GLAD) of metals on the heated substrate. It has been found that Al, Ag, Au, Fe nano-whiskers grow on the substrate of Si, SiO2, and glass substrates. The robustness in the selection of materials suggests that the HT-GLAD is a universal method to grow nano-whiskers of various metals. We also demonstrate the selective growth of the nano-whiskers on the substrate with micro-trench patterns. The metal nano-whiskers are useful for the nano electromechanical devices and vacuum microelectronics.