Effect of lattice constant of zinc oxide on antibacterial characteristics

Zinc oxide powders were heated in different atmospheres at 800 and 1400 degrees C, of which the characterization and the antibacterial activity were studied by X-ray diffractometry and the measurement of the change in electrical conductivity with bacterial growth. The diffraction peaks corresponding to zinc oxide with hexagonal type structure were detected in all samples, which shifted in low-angle side with the increase in the oxidizability of atmosphere during heat-treatment. From the results of calculating lattice constants, a0 and c0, it was found that the value of c0 in hexagonal structure increased with the increase in the oxidizability of atmosphere. On the samples heated at 1400 degrees C, the changes of the c0 value were less than those at 800 degrees C. However, no change of the a0 value showed, irrespective of atmosphere and temperature. Hydrogen peroxide that contributes to the occurrence of antibacterial activity was found to generate from all samples, and the generation amount increased with the increase of c0 value; incidently the amount in the samples heated at 1400 degrees C was less than that at 800 degrees C. The antibacterial activity of zinc oxide increased with the increase of c0 value; that is, it was found that the value of c0 in crystal structure affected the antibacterial activity of zinc oxide.     

Ultrashort pulse propagation in near-field periodic diffractive structures by use of rigorous coupled-wave analysis

We present a method for near-field analysis of ultrashort optical pulse propagation in periodic structures-including subwavelength and resonant grating structures-based on the integration of Fourier spectrum decomposition and rigorous coupled-wave analysis (RCWA). We discuss the spectral decomposition, including considerations for computational efficiency, the application of the RCWA method to compute the internal and external fields of the structure, and the synthesis of the resulting fields to obtain the time-domain solution. We apply this tool to the analysis of two photonic structures: (1) a nanostructured polarization-selective mirror that exhibits the desired broadband performance characteristics when operated at the design wavelength but yields strongly diminished polarization selectivity and modulation of the pulse envelope at an offset wave-length and (2) a two-mode coupled waveguide structure that produces from one incident pulse two transmitted pulses whose temporal separation depends on the waveguide geometry. In both examples, we apply our new modeling tool to investigate the near fields and find that near-field effects are critical in determining the performance characteristics of nanostructured devices. Furthermore, detailed observation and understanding of near-field phenomena in nanostructures may be applied to the design of novel photonic devices.     

High-Average-Power Self-Starting Mode-Locked Ti:sapphire Laser With a Broadband Semiconductor Saturable-Absorber Mirror

We present a novel high-power, self-starting mode-locked Ti:sapphire laser with a semiconductor saturable-absorber mirror as the starter element. This laser, whose slope efficiency is 22%, generates pulses with an average power as high as 1.7 W and a pulse width as short as 16 fs. The self-starting process is also investigated.     

Analysis of alcohol oxidase isozymes in gene-disrupted strains of methylotrophic yeast Pichia methanolica

A cell-free extract of methanol-grown Pichia methanolica cells was found to contain nine alcohol oxidase (AOD) isozymes by active staining of a native polyacrylamide electrophoresis gel. Our previous study revealed that AOD in P. methanolica was encoded by two genes, MOD1 and MOD2, and the results of an experiment involving Candida boidinii as an expression host suggested that the AOD isozymes observed in P. methanolica were due to random association of Mod1p and Mod2p into an active octamer [Nakagawa et al., Yeast, 15, 1223-1230 (1999)]. This study was conducted using P. methanolica MOD1- and/or MOD2-gene disrupted strains to confirm a previous hypothesis. While the cell-free extract of the wild-type strain gave nine ladder bands, the mod1delta and mod2delta strains gave a single active AOD band corresponding to the mobilities of Mod2p and Mod1p on a native electrophoresis gel, respectively. The cell-free extract of glyceorl-grown wild-type cells gave a single band corresponding to Mod1p, showing that only MOD1 is expressed in glycerol-grown cells. While the expression of both MOD1 and MOD2 was induced by methanol, this finding and our previous observations indicated that the expression of MOD1 and MOD2 was controlled by a distinct regulatory mechanism in P. methanolica.     

Switching Phenomena between Laminar and Turbulent Flows of Superfluid 4He Generated by a Vibrating Wire

We have investigated the turbulence transition of the superfluid ⁴He flow generated by a vibrating wire. For a 1.2-kHz vibrating wire, we observed intermittent switchings between laminar and turbulent flows. The switching rate decreases with increasing temperature above 100 mK, until no occurrence of the switchings at 350 mK. For a 2.4-kHz vibrating wire, we find that the switching rate is much lower than that of the 1.2-kHz vibrating wire even at low temperatures. This result indicates that a mechanism causing the switchings is influenced by the temperature and the oscillation frequency of the superfluid flow.     

Optimal periodic and random inspections with first,last and overtime policies

It has been assumed for a standby unit that periodic inspection is performed more easily to detect failures, but such a strict periodic mode would be impractical if the unit is executing some procedures without stops. From the above viewpoint, this paper first optimises a random inspection policy in accordance with random procedure times, compares it with periodic inspection and computes a modified checking cost for random inspection to determine the case where such a random inspection would be adopted. Second, this paper proposes three new inspection models in which inspections with deterministic policies are scheduled strategically while their performances need to be limited by completion times of operation procedures. These policies are called inspection first, inspection last and inspection overtime. The total expected inspection and downtime costs of each model until failure detection are obtained, and optimal policies which minimise them are derived analytically. Furthermore, the three inspection policies are compared with periodic inspection, inspection first and last are compared with each other, and a modified checking cost for inspection overtime is discussed when the policy would be better than periodic inspection.     

Residual Stress Profile Assessment by Eddy Current for Shot Peened Nickel Superalloy

Eddy current (EC) measurements have shown promise toward becoming a nondestructive method of residual stress characterization, particularly for nickel-base superalloys. However, previous studies on shot-peened materials have shown apparent discrepancies between directly measured residual stress profiles and those determined from EC data. Here, we report a study of the inter-relationship among electrical conductivity deviation, residual stress and texture of shot peened materials, in order to improve understanding of the piezoresistivity effect that is essential to the on-going efforts to make EC measurements a viable technique for residual stress assessment. Specifically, we develop a macroscopic piezoresistivity theory for polycrystalline materials influenced by texture. The theory was applied to analyze the swept high frequency eddy current data obtained from a shot peened Inconel 718 sample, which was found to exhibit shot-induced texture in the near surface region using X-ray diffraction (XRD) and orientation imaging microscopy (OIM). The residual stress profile of the peened sample was inverted from EC data using a physics model-based approach, and was found to agree with the residual stress profiles measured independently using the standard layer removal XRD technique.     

Assessment of human–machine interface design for a Chinese nuclear power plant

A nuclear power plant (NPP) is a complex system but requires high reliability. The human–machine interface (HMI) design plays very important role in reactor safety. This paper describes an assessment on HMI design of a Chinese NPP, using a software system named Dynamic Interaction Analysis Support (DIAS). DIAS can give not only quantitative indices for dynamically assessing the HMI design, but also allow modify the values of these indices by taking into account human error probability during specified emergent operation procedures. The operation procedures dealing with postulated accidents and transients recorded from a full-scale plant simulator in the training center of a Chinese NPP were selected as references. According to the results of simulation and analysis, the potential problems in the HMI design and the operation procedures were detected. Suggestions to improve the HMI design and the operation procedures were addressed.