Chemical erosion and sputtering of solid surfaces with liquid cluster ions

The sputtering phenomena of solid surfaces such as Si(111) and SiO₂ surfaces were investigated using ethanol and water cluster ion beams. To be compared with Ar monomer ion irradiation, the sputtering yield of Si surfaces was approximately 100 times higher for ethanol cluster ion irradiation and approximately 10 times higher for water cluster ion irradiation. Furthermore, for the ethanol cluster ion irradiation, chemical erosion such as silicon hydride and hydro-carbide reaction occurred on the Si surface, which resulted in the high-rate sputtering of the surface. On the other hand, for the water cluster ion irradiation, oxidation occurred on the Si surface, and physical sputtering was performed on the surface. Based on these results, chemical reaction at a nano-scale area on the Si(111) surfaces was discussed from the thermodynamic approach, and the impact of cluster ions on the surface exhibited high temperature such as a few tens of thousands degrees, which resulted in the enhancement of the chemical reaction. Thus, liquid cluster ion irradiation exhibited unique erosion and sputtering even at room temperature, which were not obtained by a conventional wet process.     

Aerosol Generation by a Spray-Drying Technique Under Coulomb Explosion and Rapid Evaporation for the Preparation of Aerosol Particles for Inhalation Tests

In this study, nanosized (<100 nm) aerosol particles with high mass concentrations for inhalation tests were generated by a spray-drying technique with combining Coulomb explosion and rapid evaporation of the droplets. Under typical spray-drying conditions, aerosol particles with average diameter of 50–150 nm were prepared from a suspension of NiO nanoparticles with a primary diameter of 15–30 nm. Under the Coulomb explosion method, the sprayed droplets were charged by being mixed with unipolar ions to break up the droplets, which resulted in the generation of smaller aerosol particles with diameters of 15–30 nm and high number concentrations. Under the rapid evaporation method, the droplets were heated immediately after being sprayed to avoid inertial impaction on the flow path due to shrinkage of the droplet, which increased the mass concentration of the aerosol particles. The combination of the Coulomb explosion and rapid evaporation of droplets resulted in the generation of aerosol particles with sizes less than 100 nm and mass concentrations greater than 1 mg/m³; these values are often necessary for inhalation tests. The aerosols generated under the combined method exhibited good long-term stability for inhalation tests. The techniques developed in this study were also applied to other metal oxide nanoparticle materials and to fibrous multiwalled carbon nanotubes.

Copyright 2014 American Association for Aerosol Research     

Construction of a subnanosecond time-resolved, high-resolution ultraviolet resonance Raman measurement system and its application to reveal the dynamic structures of proteins

A subnanosecond time-resolved ultraviolet (UV) resonance Raman system has been developed to study protein structural dynamics. The system is based on a 1 kHz Nd:YLF-pumped Ti:Sapphire regenerative amplifier with harmonic generation that can deliver visible (412, 440, 458, and 488 nm) and UV (206, 220, 229, and 244 nm) pulses. A subnanosecond (0.2 ns) tunable near-infrared pulse from a custom-made Ti:Sapphire oscillator is used to seed the regenerative amplifier. A narrow linewidth of the subnanosecond pulse offers the advantage of high resolution of UV resonance Raman spectra, which is critical to obtain site-specific information on protein structures. By combination with a 1 m single spectrograph equipped with a 3600 grooves/mm holographic grating and a custom-made prism prefilter, the present system achieves excellent spectral (<10 cm(-1)) and frequency (approximately 1 cm(-1)) resolutions with a relatively high temporal resolution (<0.5 ns). We also report the application of this system to two heme proteins, hemoglobin A and CooA, with the 440 nm pump and 220 nm probe wavelengths. For hemoglobin A, a structural change during the transition to the earliest intermediate upon CO photodissociation is successfully observed, specifically, nanosecond cleavage of the A-E interhelical hydrogen bonds within each subunit at Trpalpha14 and Trpbeta15 residues. For CooA, on the other hand, rapid structural distortion (<0.5 ns) by CO photodissociation and nanosecond structural relaxation following CO geminate recombination are observed through the Raman bands of Phe and Trp residues located near the heme. These results demonstrate the high potential of this instrument to detect local protein motions subsequent to photoreactions in their active sites.     

Treatment of hypersaline-containing wastewater with salt-tolerant microorganisms

Two salt-tolerant bacteria were isolated from soil samples to treat a high-salt-content wastewater from a pickled plum production plant. The strains, which were identified as Staphylococcus sp. and Bacillus cereus, grew well in a medium containing 0 to 15% NaCl. When wastewater in a flask was treated with the strains for 72 h, the COD removal was about 70%, and this was increased to about 90% when they were used in a pilot plant (working volume 1 m3) in a batch culture carried out for 7 d. The Staphylococcus sp. and Bacillus cereus strains occupied almost all of the pilot plant, in which they were present in a ratio of 3:1 (at 23-27 degrees C).     

In hydrolyzed cow's milk Helicobacter pylori becomes nonculturable and the growth of Salmonella typhi and Escherichia coli is inhibited

ABSTRACT:  The colony forming unit (CFU) of H. pylori is reduced rapidly in lipase hydrolyzed cow's milk and a similar reduction was found in a physiological saline solution when it was supplemented with soluble C4 to C10 fatty acids of milk fat composition. Slight CFU decreases were observed for E. coli and S. typhi in hydrolyzed milk buffered to pH 3, while the counts in milk and physiological saline solution at pH 3 stayed almost unchanged for 24 h. E. coli proliferated in glucose-peptone medium, better at pH 4.7 than at pH 3. On the other hand, supplementation of the medium with soluble fatty acids of milk composition completely inhibited growth for 32 h. Supplementation of the medium with fatty acids reduced the growth of S. typhi to approximately 1/20 at pH 4.7. Therefore, milk hydrolyzed by gastric lipase may damage H. pylori , producing a nonculturable state. With E . coli and S . typhi , hydrolyzed milk does not induce inactivation to a nonculturable state but inhibits their proliferation potently. The latter is considered to be a state prior to VBNC (viable but nonculturable). However, the antibiotic effect will disappear when the fatty acids are absorbed by the intestine.     

Characterisation of the antioxidant activity of flavonoids

Inhibition of the superoxide anion (O₂⁻) generation catalysed by xanthine oxidase using certain flavonoids was examined to determine their antioxidant effects. All of the flavonoids and their glycosides, except for kaempferol-3-glucoside, considerably and markedly inhibited O₂⁻ generation. Flavonoids also inhibited uric acid formation, whereas their glycosides did not. The flavonoids and their glycosides with scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical had more than one conjugated en-diol group and exhibited more potent inhibition of the O₂⁻ generation than the uric acid formation catalysed by xanthine oxidase. The results show that the inhibition of O₂⁻ generation with flavonoids without any conjugated en-diol group was due to competitive inhibition of uric acid formation, while the inhibition with flavonoids having more than one conjugated en-diol group was due to the reduced form of the enzyme.     

Experimental Risk Estimation for Offshore Software Outsourcing

It is necessary to estimate the risk for strategic decision of offshore software outsourcing projects. In this paper we propose an experimental risk estimation method based on questionnaire for externalizing the know‐how of experienced project managers. Introducing three parts of questionnaire contents, this paper describes the estimation method and presents the implementation procedure. Focusing on five client companies, this paper reports five types of risk estimation methods considering the bias of respondents with different backgrounds, and discusses the Recall, Precision together with Accuracy of these estimation methods. This paper also applies the t‐test and vector analysis to study the bias in vendor countries, software types, as well as client companies. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Attention-based neural network with Generalized Mean Pooling for cross-view geo-localization between UAV and satellite

Artificial Life and Robotics - Cross-view geo-localization is finding images containing the same geographic target in multi-views. For example, given a query image from UAV view, a proposed...