Three-dimensional core analysis on a super fast reactor with negative local void reactivity

Keeping negative void reactivity throughout the cycle life is one of the most important requirements for the design of a supercritical water-cooled fast reactor (super fast reactor). Previous conceptual design has negative overall void reactivity. But the local void reactivity, which is defined as the reactivity change when the coolant of one fuel assembly disappears, also needs to be kept negative throughout the cycle life because the super fast reactor is designed with closed fuel assemblies. The mechanism of the local void reactivity is theoretically analyzed from the neutrons balance point of view. Three-dimensional neutronics/thermal-hydraulic coupling calculation is employed to analyze the characteristics of the super fast reactor including the local void reactivity. Some configurations of the core are optimized to decrease the local void reactivity. A reference core is successfully designed with keeping both overall and local void reactivity negative. The maximum local void reactivity is less than −30 pcm.     

Total elemental composition analysis of soil samples using the PIXE technique

The determination of major and trace element contents in soils was developed by acid digestion method combined with particle-induced X-ray emission spectrometry (PIXE). The digestion of soils was achieved by using nitric acid (HNO₃), hydrochloric acid HCl and hydrogen peroxide (H₂O₂) with repeated additions. A 20 μL aliquot from the digested samples was evaporated on the Nuclepore Track-Etch Membrane and irradiated by the 2.5 MeV proton beam from the single-end type Van de Graaff accelerator. The accuracy of this methodology was estimated based on series of measurements done for a reference material of soil CRM 023-050. The proposed experimental procedure was shown to have good reproducibility of the experimental results. The corresponding limits of detection (LODs) for Na, Mg, Al, P, S, Cl, K, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Mo and Cd were estimated. Other soil characteristics such as total carbon (TC) and nitrogen (TN) content, pH and electrical conductivity (EC) were also measured.     

Development of a microchip-based bioassay system using cultured cells

We developed a novel bioassay system using a glass microchip and cultured cells. A microchamber for cell culture and microchannels for reactions and detection were fabricated on a Pyrex glass substrate by photolithography and wet etching techniques. Cell culture, chemical and enzymatic reactions, and detection were integrated into the microchip. To keep different temperatures locally in three areas of the microchip, we designed and fabricated a temperature control device. Nitric oxide released from macrophage-like cells stimulated by lipopolysaccharide was successfully monitored with the microchip, the temperature control device, and a thermal lens microscope. The total assay time was reduced from 24 to 4 h, and detection limit of NO was improved from 1 x 10(-6) to 7 x 10(-8) M compared with conventional methods. Moreover, the system could monitor a time course of the release, which is difficult to measure by conventional batch methods. We conclude that this system is promising for a rapid bioassay system with very small consumption of cells.     

Condensation and evaporation heat transfer of R410A inside internally grooved horizontal tubes

Heat transfer coefficient and pressure drop were measured for condensation and evaporation of R410A and HCFC22 inside internally grooved tubes. The experiments were performed for a conventional spiral groove tube of 8.01 mm o.d. and 7.30 mm mean i.d., and a herring-born groove tube of 8.00 mm o.d. and 7.24 mm mean i.d. To measure the local heat transfer coefficients and pressure drop, the test section was subdivided into four small sections having 2 m working length. The ranges of refrigerant mass flow density was from 200 to 340 kg/(m² s) for both condensation and evaporation of R410A and HCFC22, and the vapour pressure was 2.41 MPa for condensation and 1.09 MPa for the evaporation of R410A. The obtained heat transfer data for R410A and HCFC22 indicate that the values of the local heat transfer coefficients of the herring-bone grooved tube are about twice as large as those of spiral one for condensation and are slightly larger than those of spiral one for the evaporation. The measured local pressure drop in both condensation and evaporation is well correlated with the empirical equation proposed by the authors.     

Paralytic shellfish poison (PSP) profiles and toxification of short-necked clams fed with the toxic dinoflagellate Alexandrium tamarense

As a part of our studies on paralytic shellfish poison (PSP) accumulation kinetics in bivalves, short-necked clam Tapes japonia was experimentally contaminated with PSP by being fed with the toxic dinoflagellate Alexandrium tamarense for 2, 4, 6, 8 and 10 days, and the processes of PSP accumulation and bioconversion were investigated: the toxicity level was determined by mouse bioassay and toxin components were identified by high-performance liquid chromatography (HPLC). The strain of A. tamarense used in this study possessed a specific toxicity of 186.7 +/- 81 (mean +/- S.D., n = 5) x 10(-6) MU/cell. Total toxin concentration of this strain was 140.4 +/- 61 (mean S.D., n = 5) fmol/cell. The toxicity level of short-necked clams increased almost in parallel with the abundance of A. tamarense, reaching 1.8, 3.2, 3.8, 3.5 and 4.6 MU/g meat for 2, 4, 6, 8 and 10 days of feeding, respectively. The accumulation rates of PSP toxins, which are the ratio of the total amount of toxins accumulated in the bivalves to the estimated intake in each feeding experiment, were 7.5, 8.1, 5.7, 4.2 and 4.4% for 2, 4, 6, 8 and 10 days, respectively. At the end of each exposure period, many undigested algal cells were found in pseudofeces under microscopic observation. There was a remarkable difference in the relative proportions of the predominant toxin components between A. tamarense and short-necked clams. The most notable difference was the change in the relative amounts of C2 (carbamoyl-N-sulfo-11beta-hydroxysaxitoxin sulfate), GTX1 and GTX 4 during the first two days. In the toxic bivalves, the amount of C2, which is dominant in A. tamarense, decreased to below half a percent after being ingested. Subsequently, the amount of GTX1 in the shellfish meat reached 50.1 mol%, while that of GTX4 decreased to about half of that in A. tamarense. As for the configuration of 11-hydroxysulfate, PSP components in A. tamarense exist almost exclusively as beta-epimers (GTX3, GTX4, C2 and C4), accounting for 72.8 mol% of the total. This contrasts with the case of the short-necked clams, where the beta-epimers represented 25.8, 33.8, 30.8, 36.8 and 28.5 mol% of the total after 2, 4, 6, 8 and 10 days, respectively. PSP components seemed to be converted rapidly at an early stage of the feeding of A. tamarense.     

Propagation of Weak Pressure Waves against Two Parallel Subsonic Streams

In this paper, the characteristics of a pressure wave propagating against two parallel subsonic streams in a constant-area straight duct are investigated by one-dimensional analysis, two-dimensional numerical simulation, and experiments. Computations have been carried out by the two-dimensional Euler Equations using the Chakravarthy-Osher-type TVD scheme. Optical observations by the schlieren method as well as wall pressure measurements have been performed to clarify both the structure and the propagation velocity of pressure waves. The results show that the pressure wave propagating against the streams changes into a bifurcated pressure wave and the bifurcation occurs in the low speed streams. It is also found that the propagation velocity of the pressure wave obtained by the analysis and computation agrees well with the present experimental data.     

A preliminary analysis of item‐selection behavior of Japanese female university students examining a 2D virtual fashion web site

E‐commerce is spreading into various fields in our daily lives as a result of the growth of interactive Internet communication technologies. Two‐dimensional computer graphics (2D CG) image presentations, which are simple and inexpensive, can be displayed directly on apparel e‐commerce sites. This study uses sequential pattern mining to analyze the item‐selection behavior of Japanese female university students examining a 2D virtual fashion Web site. It is found that most users did not initially examine their favorite category items; instead, they examined the commonly viewed items first, and then examined various other fashion items before making their final selection. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Improvement of carbon monoxide analysis in fish meat

Carbon monoxide (CO) treatment of fish meat of tuna, yellowtail, tilapia etc. is not allowed in Japan, since it can maintain the red color for a longer period than the microbiological shelf life of fish meat. The official method for quantification of CO has a problem, in that a part of the CO is lost during the preparation of the fish sample. To solve this problem, we modified the official method in this study. We also applied this modified method to survey the contents of CO in tuna, yellowtail, young yellowtail, and tilapia. As a result, the modified method was found to be more suitable for CO quantification than the official method. An inter-laboratory study by 4 laboratories confirmed that the CO content of many samples of tilapia exceeded the regulation value, apparently due to the higher recovery of CO, compared to the official method. Therefore, it was suggested that the regulation value in the case of tilapia should be changed if this method is introduced as an official method.     

Thermal processing enhances anti‐radical activity and reduces pro‐oxidant activity in water‐soluble fraction of selected Allium vegetables

Both the pro‐ and antioxidant activities were found in water‐soluble components contained in onion, leek and garlic samples, and effects of thermal treatment on such activities were investigated. Raw vegetable extracts were prepared by squeezing vegetable homogenates followed by centrifugation at 4 °C. The extracts were subjected to thermal treatment at 75 or 100 °C for 30 and 60 min. The water‐soluble extracts were assayed for antiradical activity using both a chemical and a cellular system. Heating onion and leek extracts at 100 °C for 60 min, and garlic extract at 100 °C for 30 min, yielded strong antioxidant components that are able to scavenge free radicals, in either system, significantly. Measuring total phenolic content by the Folin–Ciocalteu method, we observed that thermal treatment significantly decreased the phenolic contents in leek and garlic extract. In addition, we estimated pro‐oxidant activities in the vegetable extracts, using reactive oxygen species (ROS)‐sensitive 2′,7′‐dichlorofluorescin diacetate; we found that extracts of raw alliums have strong ROS activity, and that thermal treatment destroyed most of the ROS activity present in the raw extracts. These findings indicate that thermal processing enhanced the nutritional value of alliums by increasing the total antioxidant activity, and reducing the pro‐oxidant elements. Copyright © 2007 Society of Chemical Industry