Improvement of Machining Accuracy of 5-Axis Control Ultraprecision Machining by Means of Laminarization and Mirror Surface Finishing

Air bearings are often used in ultraprecision machine tools requiring high accuracy. With increasing the high accuracy for machine tools, it is required to pay attention to microvibration with nanometer order. The fluctuation in compressed air applied to air bearings causes the air turbulence, which results in the microvibration. The study presents the laminarization by the optimal design of piping and air bearing surfaces as well as mirror surface finishing, so that the laminarization can be realized to suppress the microvibration. From experimental results, it is found that the surface roughness of workpieces can be drastically improved by using a revised ultraprecision machining center.     

Effects of Instant Coffee Consumption on Oxidative DNA Damage, DNA Repair, and Redox System in Mouse Liver

ABSTRACT:  To examine the effects of instant coffee consumption on cancer risk, we analyzed the oxidative DNA damage levels and the DNA repair and redox systems in the livers of coffee-fed mice. Three-week-old male ICR mice were fed with/without 0.1% (w/v) instant coffee solution. At 2, 4, and 8 mo, the levels of 8-hydroxydeoxyguanosine (8-OH-dG), a major form of oxidative DNA damage, and the expression of mouse 8-OH-dG repair-associated genes and redox system-associated genes, the SOD activity, and the LPO level were analyzed. Simultaneously, half of the mice were fed a low vitamin (LV) diet (autoclaved diet) to disturb the defense system against oxidative stresses. As a result, the 8-OH-dG level was increased in the livers of LV diet (+ water)-fed mice for 8 mo, in comparison to those of the 0 M control mice and normal diet (+ water)-fed mice. However, no significant differences between water drinking and coffee drinking were observed, in terms of the 8-OH-dG level. In addition, the 8-OH-dG repair-associated gene expression, the SOD activity, and the LPO level also showed no significant differences between water drinking and coffee drinking in all mouse groups. On the other hand, among the redox system-associated genes, only the expression of  GPx1  was changed. These results suggest that instant coffee consumption has little, if any, effect on the risk of liver cancer due to oxidative stresses.     

Microbial community analysis of food-spoilage bacteria in commercial custard creams using culture-dependent and independent methods

Custard cream is made from highly nutritive raw materials such as milk and sugar and is easily spoiled by the multiplication of specific microbial contaminants or residents. However, this spoilage microbial community has not been studied. We determined the spoilage microbiota in commercial custard creams using culture-dependent and independent methods. Using the culture-dependent analysis with various agar media, 185 bacterial colonies and 43 eukaryal colonies were isolated from 7 commercial custard cream products. All bacterial isolates were morphologically, physiologically, and genetically identified as bacilli, staphylococci, lactic acid bacteria, and psychrotrophic gram-negative rods. Using culture-independent molecular analysis, the PCR-denaturing gradient gel electrophoresis technique, spoilage of the commercial custard creams was found to be caused by bacilli, staphylococci, lactic acid bacteria, psychrotrophic gram-negative rods, Anoxybacillus sp., Caurobacter sp., and Streptococcus sp. bacteria. The detected spoilage bacteria were the same species as previously detected in spoiled milk products and shown in other reports, suggesting that spoilage bacteria in a raw material easily grow in processed foods made from milk. We determined the spoilage microbial communities in commercial custard creams, and these are the first data concerning spoilage microbiota in nonfermented processed foods using a culture-independent analysis. Our study will be useful for the manufacture and safe preservation of dairy products because the first step toward safe food preservation by food manufacturers is to understand the spoilage microbiota in a target food to select optimal preservatives and to reduce the use of food additives.     

Experimental study on titanium heat exchanger used in a gas fired water heater for latent heat recovery

In general, latent heat recovery is usually accompanied by the corrosion of the heat exchanger, which is caused by the strongly acidic condensate when the temperature of the flue gas is lowered below the acid dew point. The present study has been conducted to investigate the heat and mass transfer characteristics in a titanium heat exchanger with excellent corrosion resistance used for waste heat recovery with the condensation arranged in a gas fired water heater. In addition, the thermal efficiency of the gas fired water heater was evaluated based on the net calorific value at the maximum rated output during latent heat recovery from the exhaust flue gas. Parametric studies were conducted for the flue gas flow rate, inlet temperature and mass flow rate of the supplied water, respectively. Different arrangements of the tubes of the heat exchanger including in-line and staggered configurations were investigated. The experimental results indicate that the thermal efficiency of the gas fired water heater with a latent heat recovery (LHR) heat exchanger was enhanced by about 10% compared with conventional instantaneous water heaters, i.e., water heaters without heat recovery. In addition, in terms of the Nusselt number and the Sherwood number, the heat and mass transfer performance of the staggered tube bank type were approximately 50% and 10% higher than that on the in-line tube bank type when the Reynolds number of the flue gas was 10³.     

Rapid hydrogen charging on metal hydride negative electrode of Fuel Cell/Battery (FCB) systems

The characteristics of rapid gaseous H₂ charging/electrochemical discharging of the metal hydride negative electrode were investigated for the application in Fuel Cell/Battery (FCB) systems. They were evaluated with the H₂ gas absorption, followed by the subsequent electrochemical discharging in the electrolyte solution (6M KOH). Then, the cyclability of charge–discharge was also examined. It was observed that more than 70% of the theoretical capacity was charged within 10 min with 0.3 MPa and 0.5 MPa of the initial H₂ pressures. The electrochemical discharge curve showed that more than 86% of the absorbed H₂ was discharged. Furthermore, the cycled charge–discharge process indicated that the H₂ gas charge and electrochemical discharge process is an effective way to rapidly charge and activate the metal hydride without degeneration.     

Availability of MCNP & MATLAB for reconstructing the water-vapor two-phase flow pattern in neutron radiography

The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008. In this paper, we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the tube were obtained using the MCNP code without influence of γ-ray and electronic-noise. The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated. The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI. The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques. And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI.     

Developmental changes in the kinetics of glucose and urea in Holstein calves

Because weaning is the point when the nutrient composition of feed changes for the neonatal ruminant, the present experiment was conducted to assess the developmental changes in the kinetics of glucose and urea over this period, using stable isotopes of glucose and urea, at 4, 13, and 24 wk in calves. Plasma concentrations of nonesterified fatty acids, amino-N, urea-N, and insulin-like growth factor-I increased, but that of growth hormone decreased with age. The plasma glucose concentration increased at 13 wk of age and thereafter decreased at 24 wk of age. The glucose irreversible loss and recycling rates were significantly higher at 4 wk of age than at 13 and 24 wk of age. On the other hand, the irreversible loss and recycling rates of urea, as well as the urea pool size, were higher at 24 wk of age than at 4 and 13 wk. It is concluded that weaning at 6 wk is the pivotal time for the alteration of glucose kinetics. However, the aging process, but not weaning, is important for changes in the kinetics of urea in calves.     

Development of large diameter ECR plasma source

To develop ECR plasma source for industrial applications, we produced a large diameter ECR plasma and examined radial profiles of the ion saturation current as a function of pressure and power. It was found that ECR plasma uniform over 300 mm is produced for pressures higher than 1 mTorr and the electron temperature decreases with increasing pressures.     

Immobilization of lysozyme on the layered silicate RUB-15

Adsorption of lysozyme over layered silicate, denoted as RUB-15, and the modified compound RUB-15-nano have been studied. The amount of enzyme adsorbed onto RUB-15 or RUB-15-nano was smaller than that recently reported as being adsorbed onto mesoporous silicas such as MCM-41 or SBA-15. However, lysozyme adsorbed onto RUB-15-nano exhibits enzymatic activity. Lysozyme was found to be immobilized on RUB-15-nano, which was modified from the layered silicate RUB-15. RUB-15-nano may therefore be useful as an inorganic substrate to immobilize enzymes.     

Electrochemical telomerase assay with ferrocenylnaphthalene diimide as a tetraplex DNA-specific binder

Spectroscopic studies revealed that ferrocenylnaphthalene diimide (1) can bind to tetraplex DNA at high potassium ion concentration. The tetraplex DNA was stabilized by the binding of 1, and this effect was larger than that of any other tetraplex stabilizers, which are known as a telomerase inhibitor. Quantitative analysis with circular dichroism and a quartz crystal microbalance strongly suggested a 3:1 binding stoichiometry of 1 to the tetraplex DNA. The telomere sequence could be extended by telomerase with the telomerase substrate primer on the surface of an electrode as proven by an increased current signal of 1 bound to the tetraplex DNA formed on the electrode. This is the first example of electrochemical detection of telomerase activity without relying on PCR.