Status and research programs of the multinuclide accelerator mass spectrometry system at the University of Tsukuba

We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12 MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of ¹⁴C, ²⁶Al, ³⁶Cl and ¹²⁹I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of ³⁶Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the ³⁶Cl/Cl ratio is lower than 1 × 10^?15 with a halite sample. We have measured over 500 samples in 1 year, including samples for earth and environmental sciences and nuclear safety research.     

Occurrence and determination of a herbicide benthiocarb in rivers and agricultural drainages

The occurrence and determination of a herbicide, benthiocarb, 4-chlorobenzyl N,N-diethylthiolcarbamate (Saturn^®) in rivers and agricultural drainages was investigated. Benthiocarb residues were detected in water samples when it has been applied to rice paddies, after rice seedling transplantation, in concentrations of between 10.00 and 0.11 μg/l. These residues entered into rivers and agricultural drainages as a result of overflows from rice paddies. However, benthiocarb residues could not be found in water samples after the termination of its application to rice paddies, suggesting that the applied benthiocarb might be degraded by microbial and physico-chemical actions such as photochemical reactions occurring on the soil surface. Benthiocarb residue levels were higher in longer rivers than in agricultural drainage. The contribution of rainfall to the benthiocarb concentrations was shown. Benthiocarb in water was extracted with n-hexane and identified by a gas chromatography using a flame photometric detector (sulphur filter 394 nm) and a combined gas chromatography-mass spectrometry-computer system. The minimum detectable amount of benthiocarb in water sample by gas chromatography was 0.56 ng and about 100 ng of benthiocarb could be identified by a gas chromatography-mass spectrometry-computer system.     

Behaviour of HCH (1,2,3,4,5,6-hexachlorocyclohexane) residue in the aquatic environment

The monthly variation in HCH (1,2,3,4,5,6-hexachlorocyclohexane) residue levels in surface waters was investigated. The logarithms of monthly HCH concentrations described the wave, and the equation of the wave was calculated by the least squares method. The waves indicated maximum concentrations in summer and minimum concentrations in winter at each sampling site. The maximum concentration of HCH in each year decreased gradually. The amplitude of the wave at the reservoir was the smallest among sampling sites. The slope of the wave at the downstream sampling site was smaller than that at the upper stream. Maximum concentration of total HCH at each sampling site in 1985 is estimated from the equations; the concentrations at the upper streams will be about a thousandth or a hundredth of that at the downstreams. Also, the equations for β-and γ-HCH were calculated, and indicated that β-HCH was more persistent than γ-HCH in surface water. The ratio of β-HCH to total HCH in surface water is estimated to be about 60% in 1985.     

Microbial conversion of glycerol into glycolipid biosurfactants, mannosylerythritol lipids, by a basidiomycete yeast, Pseudozyma antarctica JCM 10317(T)

Microbial conversion of glycerol into functional bio-based materials was investigated, aiming to facilitate the utilization of waste glycerol. A basidiomycete yeast, Pseudozyma antarctica JCM 10317, efficiently produced mannosylerythritol lipids (MELs) as glycolipid biosurfactants from glycerol. The amount of MEL yield reached 16.3 g l(-1) by intermittent feeding of glycerol.     

Identification of the gene PaEMT1 for biosynthesis of mannosylerythritol lipids in the basidiomycetous yeast Pseudozyma antarctica

The yeast Pseudozyma antarctica produces a large amount of glycolipid biosurfactants known as mannosylerythritol lipids (MELs), which show not only excellent surface‐active properties but also versatile biochemical actions. To investigate the biosynthesis of MELs in the yeast, we recently reported expressed sequence tag (EST) analysis and estimated genes expressing under MEL production conditions. Among the genes, a contiguous sequence of 938 bp, PA_004, showed high sequence identity to the gene emt1, encoding an erythritol/mannose transferase of Ustilago maydis, which is essential for MEL biosynthesis. The predicted translation product of the extended PA_004 containing the two introns and a stop codon was aligned with Emt1 of U. maydis. The predicted amino acid sequence shared high identity (72%) with Emt1 of U. maydis, although the amino‐terminal was incomplete. To identify the gene as PaEMT1 encoding an erythritol/mannose transferase of P. antarctica, the gene‐disrupted strain was developed by the method for targeted gene disruption, using hygromycin B resistance as the selection marker. The obtained ΔPaEMT1 strain failed to produce MELs, while its growth was the same as that of the parental strain. The additional mannosylerythritol into culture allowed ΔPaEMT1 strain to form MELs regardless of the carbon source supplied, indicating a defect of the erythritol/mannose transferase activity. Furthermore, we found that MEL formation is associated with the morphology and low‐temperature tolerance of the yeast. Copyright © 2010 John Wiley & Sons, Ltd.     

Capturing Expert Knowledge for Supporting Design and Manufacturing of Injection Molds

Knowledge based approach is effective for renovating design and manufacturing processes. The objective of this paper is to investigate roles and usages of expert engineering knowledge in high-quality manufacturing, and to study a practical knowledge capturing method for realizing engineering support tools. An engineer oriented interface for a capturing method is proposed, and a flexible representation framework is studied for various types of expert knowledge. An integrated knowledge-based system has been developed for mold design support. The results have been evaluated by design and manufacturing of molds for cellular phones, and have shown substantial reduction of lead time for mold production.     

Efficient preparation of liposomes encapsulating food materials using lecithins by a mechanochemical method

In order to evaluate to the feasibility of using lecithins for nanocapsules including functional food materials, liposomes were prepared from different commercially available lecithins (SLP-WHITE, SLP-PC70 and PL30S) by the Bangham method, and their physicochemical properties were examined by using a confocal laser scanning microscopy (CLSM) and the measurements of trapping efficiency. There was little difference in the trapping efficiency among the three types of liposomes. In all cases, the trapping efficiency clearly increased with an increase of the lecithin concentration up to 10 wt % , and the maximum efficiency reached at approximately 15%. CLSM observation showed the particle size of liposomes prepared from SLP-WHITE is significantly smaller than that prepared from other lecithins. In addition, liposomal solution prepared from SLP-WHITE remained well dispersed for at least 30 days, while two other liposomal solutions showed a phase separation due to aggregation and/or fusion of liposomes. These results indicated that SLP-WHITE is the most appropriate for the preparation of stable liposomes with well dispersed among the lecithins tested. SLP-WHITE liposomes were then prepared by the mechanochemical method using a homogenizer and microfluidizer, aiming at improving the preparation efficiency and liposome stability. The particle size of the prepared SLP-WHITE liposomes decreased with increasing inlet pressure and the number of processed cycles, and reached between 73 and 123 nm based on the measurement using dynamic light scattering. Moreover, freeze-fracture transmission electron microscopy revealed that the prepared liposomes are small unilamellar vesicles (SUV) with a diameter of approximately 100 nm. The extract of Curcuma longa Linn. (Ukon), which contains curcumins as a functional food material, was then subjected to the mechanochemical method with SLP-WHITE to give liposomes including the functional materials. Interestingly, the trapping efficiency of the liposomes for curcumins was found to reach over 85%. From these results, the present mechanochemical method is very likely to allow us to efficiently prepare stable and functional liposomes from the low-cost lecithin. The method may thus have a potential for manufacturing practical nanocapsules, which serves as a novel carrier of functional food materials.