Highly resolved non-contact atomic force microscopy images of the Sn/Si(111)-([Formula: see text]) surface

The Sn/Si(111)-([Formula: see text]) surface is observed by using non-contact atomic force microscopy (NC-AFM) at room temperature. The images at relatively far tip-surface distances show four protrusions in each ([Formula: see text]) unit cell, which are similar to previously reported scanning tunnelling microscopy (STM) images. On the other hand, it is found that, at closer tip-surface distances, eight protrusions are clearly resolved, which indicates that the spatial resolution of NC-AFM is higher than that of STM as far as imaging this surface is concerned. Our high-resolution NC-AFM images are in good agreement with a recently proposed model based on 13 Sn atoms per unit cell.     

Spectrophotometric determination of trace arsenic in water samples using a nanoparticle of ethyl violet with a molybdate-iodine tetrachloride complex as a probe for molybdoarsenate

A new spectrophotometric method was developed for the determination of low ppb levels of arsenic in water. We found that Ethyl Violet with molybdate-iodine tetrachloride complex forms nanoparticles under acidic conditions, which provide a sensitive probe for molybdoarsenate. The nanoparticles form stable particles with a diameter micrometers in size in the presence of heteropolyacid, and the resulting particles give a purple color to the apparently homogeneous solution, the intensity of which depends on the arsenic concentration. The nanoparticle itself is unstable due to conversion of the dye to a colorless carbinol species under acidic conditions without heteropolyacid. Although triphenylmethane dyes have been the subject of a number of investigations, there do not appear to be any reports on the dye particles for trace determination. The calibration curve is linear up to 20 microg L-1 arsenic, and the detection limit is 0.5 microg L-1 (6.6 x 10(-9) mol L-1). The coefficient of variation for spectrophotometry at 10 microg L-1 is 5.8% (n = 8). Furthermore, it is possible to detect concentrations as low as 1 microg L-1 arsenic visually using this method. The interferences from phosphorus and silica were eliminated using an anion exchange column and sodium fluoride as a masking agent, respectively. The proposed method has been successfully applied to water samples in abandoned mine water, groundwater, and river water. There was good agreement between the results obtained by the proposed method and those by hydride generation atomic absorption spectrometry. Since this method is specific for As(V), it is applicable to the speciation of arsenic oxidation states. Our method has enormous practical potential for simple and field detection of arsenic, requiring no complex apparatus or skilled laboratory support.     

160 Gb/s-Based Field Transmission Experiments Using Polarizer-Based PMD Compensator With Optical Power Monitor

Higher bit-rate transmission is attractive for improving network resource efficiency and reducing the complexity of network management in future transmission systems. However, chromatic dispersion and polarization mode dispersion (PMD) are one of the most serious impairments. In particular, PMD should be compensated for dynamically because it changes rapidly according to environmental variations such as temperature change and mechanical vibration. Therefore, an adaptive PMD compensator is indispensable for higher bit-rate transmission systems. In this paper, we employed a simple and bit-rate independent PMD compensator based on a polarizer with an optical power monitoring scheme in 160 Gb/s-based field experiments. By using the PMD compensator, the single channel transmission of a 160 Gb/s return-to-zero differential phase-shift-keying modulation signal over an installed fiber link with buried and aerial cable routes was successfully achieved. Approximately 1 dB of Q-factor was improved by using the PMD compensator when PMD impairment was maximized. Through these experiments, the effectiveness of the PMD compensator in the higher bit-rate transmission systems was confirmed in the field environment. Furthermore, single-polarization 8times160 Gb/s wavelength division multiplexing transmission over the installed 200 km standard single mode fiber without polarization demultiplexing was successfully achieved by using the simple PMD compensator.     

Development of cutting tools with microscale and nanoscale textures to improve frictional behavior

We developed novel cutting tools that had either microscale or nanoscale textures on their surfaces. Texturing microscale or nanoscale features on a solid surface allowed us to control the tribological characteristics of the tool. The textures, which had pitches and depths ranging from several hundreds of nanometers to several tens of micrometers, were fabricated utilizing the ablation and interference phenomena of a femtosecond laser. The effect of the texture shape on the machinability of an aluminum alloy was investigated with a turning experiment applying the minimum quantity lubrication method. The texture decreased the cutting force due to the corresponding reduction in the friction on the rake face. This effect strongly depended on the direction of the texture; lower cutting forces were achieved when the texture was perpendicular to the chip flow direction rather than parallel. This effect was only observed at high cutting speeds over 420 m/min. These results indicate that the developed tools effectively improved the machinability of the alloy.     

Elemental composition of ancient Japanese bones

Excavated bones (rib) obtained from 50 sites in Japan were measured by ICP atomic emission spectrometry and atomic absorption spectrometry for concentration of 19 elements, including Al, B, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, V and Zn. One hundred and forty-one specimens were classified into five groups according to Japanese prehistoric and historic eras (Jomon, Yayoi, Kofun, Kamakura and Muromachi, and Edo). The elements, with concentrations which showed no significant change with era were Al, B and Cr. Average concentrations of Ca were in the range 2-2.5 X 10(-1) g g-1 and those of P ranged from 1.1 to 1.3 X 10(-1) g g-1, indicating a well-preserved bone mineral matrix. The Ca/P ratio (mol/mol) was lowest in the Edo group--1.48 as compared with 1.54-1.66 in the other groups. Among the elements which showed changes with era were Pb, Fe, Co and Mn, all of which showed remarkably elevated concentrations in the Edo group. In addition to this unique elemental composition of Edo bones, samples from the Kofun era showed a completely different composition from those of other periods, i.e. they had the highest concentrations of Cd, Zn and Mg, and the lowest concentrations of Cu, K, Ni and Sr. The cause of the elevated Pb concentration in Edo bones is discussed in relation to human activities which may have led to environmental Pb pollution.     

A data transmission protocol for reliable and energy-efficient data transmission in a wireless sensor-actuator network

In a wireless sensor-actuator network, sensor nodes gather information on the physical world and can deliver messages with sensed values to only nearby nodes due to weak radio. Thus, messages sent by nodes might be lost due to not only collision but also noise. Messages are forwarded by sensor nodes to an actuator node. In the redundant data transmission (RT) protocol, a sensor node sends a message with not only its sensed value but also sensed values received from other sensor nodes. Even if a message with a sensed value v is lost, an actuator node can receive the value v from a message sent by another sensor node. In addition, we have to reduce the energy consumption of a sensor node. A sensor node mainly consumes the energy to send and receive messages. Even if an event occurs, only some number of sensor nodes sensing the event send the sensed values to reduce the total energy consumption. We discuss an energy-efficient data transmission protocol. We evaluate the RT protocol compared with the CSMA protocol in terms of how much sensing data a node can receive in presence of messages loss. We evaluate the RT protocol in terms of how many number of sensed values an actuator node can receive in presence of message loss. We show that about 72% of sensed values can be delivered to an actuator node even if 95% of messages are lost due to noise and collision.     

Proposal for a Compact Resonant-Coupling-Type Polarization Splitter Based on Photonic Crystal Waveguide With Absolute Photonic Bandgap

We propose a resonant-coupling-type polarization splitter based on a photonic crystal structure with absolute photonic bandgap. The scalar finite-element method was used to calculate resonant frequencies of the cavity and frequency dependences of the polarization splitter. This device supports single-mode operation for both transverse-electric and transverse-magnetic waves. We show that miniaturization of the proposed polarization splitter can be realized by utilizing resonant coupling.     

Phase equilibrium modelling of natural gas hydrate formation conditions using LSSVM approach

The formation of gas hydrates in industries and chemical plants, especially in natural gas production and transmission, is an important factor that can lead to operational and economic risks. Hence, if the hydrate conditions are well addressed, it is possible overcome hydrate-related problems. To that end, evolving an accurate and simple-to-apply approach for estimating gas hydrate formation is vitally important. In this contribution, the least square support vector machine (LSSVM) approach has been developed based on Katz chart data points to estimate natural gas hydrate formation temperature as function of the pressure and gas gravity. In addition, a genetic algorithm has been employed to optimize hyper parameters of the LSSVM. Moreover, the present model has been compared with five popular correlations and was concluded that the LSSVM approach has fewer deviations than these correlations so to estimate hydrate formation temperature. According to statistical analyses, the obtained values of MSE and R² were 0.278634 and 0.9973, respectively. This predictive tool is simple to apply and has great potential for estimating natural gas hydrate formation temperature and can be of immense value for engineers who deal with the natural gas utilities.     

Selective retrieval of microparticles in microchambers using electrolytically generated bubbles for cell array applications

This paper describes a method for the selective retrieval of microparticles using bubbles generated by electrolysis. Microparticles (polystyrene beads, mouse embryos, and cell spheroids) were arrayed in microchambers fabricated in SU-8 on the surface of an electrode consisting of indium tin oxide (ITO) patterned on glass. Bubbles were selectively generated in a target microchamber by applying a voltage to electrodes positioned in the microchamber. As a result, we successfully retrieved microparticles (100 μm in diameter) positioned in the microchambers. This method is gentle enough to maintain cellular viability, and therefore, it will be a powerful tool for the quantitative analysis of cells in an arrayed system.     

Experimental investigation of solid–liquid mixtures freezing behavior in flow channels

The penetration and freezing of hot-core material mixtures through flow channels during core disruptive accidents (CDAs) within a sodium-cooled fast reactor is one of the major concerns confronting safety designers of the next-generation reactors. The main objective of this study is to investigate those fundamental characteristics of penetration and solidification involved in channeling molten metal and solid particle mixtures over cold structures. In this study, a low-melting-point alloy (viz., Bi–Sn–In alloy) and mixtures with solid particles (of copper and bronze) were used as a simulant melt, while L-shape metal (of stainless steel and brass) and stainless steel fuel pin bundle were used as cooling structures. Two series of basic experiments were performed to study the effect solid particles have on penetration and cooling behavior under various thermal conditions of melt by varying solid particle volume fraction, structure temperature and structural geometry. Melt flows and distributions were recorded using a digital video camera and subsequently analyzed. The melt penetration length into the flow channel and the proportion of melt adhesion on structural surfaces were measured. Results indicate that penetration length becomes shorter for molten-metal/solid particle mixtures (mixed melts) compared with pure molten metal (pure melt) as well as decreases with increasing solid particles volume fraction of the melt. The present study will contribute to a better understanding of the basic thermal-hydraulic phenomena of melt freezing in the presence of solid particles and to provide an experimental database for validation and improvement of the models of fast reactor safety analysis codes.