Contamination levels of PCDDs, PCDFs and Co-PCBs in commercial baby foods in Japan

To examine dioxin contamination in commercial baby foods in Japan, congener analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) were performed on 102 varieties of baby foods obtained from supermarkets in 2001-2002. The toxic equivalent quantity (TEQ) levels for dioxins in samples ranged from < 0.001 to 0.135 pg-TEQ/g wet weight when undetected or trace levels of congeners were taken as zero. Among 102 samples tested, 26 samples exceeded 0.010 pg-TEQ/g. The highest TEQ value was for "sardine, vegetables" (0.135 pg-TEQ/g), followed by "Japanese radish (daikon), sardine" (0.080 pg-TEQ/g). Thus, dioxins were detected at low levels in baby foods containing animal products such as fishes and/or dairy products.     

Isolation of the YAP1 homologue of Candida utilis and its use as an efficient selection marker

The industrially important yeast Candida utilis is widely used in the production of food and medical materials, but its practical host-vector system has not been well developed. In order to construct a food-grade host-vector system, we isolated the YAP1 homologue, CuYAP1, of C. utilis IAM4264 and evaluated its use as a selection marker in transformation. A DNA probe was obtained by PCR using degenerate primers and the CuYAP1-encoding 438 amino acid protein was isolated by hybridization. Although the amino acid identity of Yap1 and CuYap1 was 28.7% as a whole, the characteristic bZip region and two cysteine-rich domains (CRDs) showed a higher homology. CuYAP1 was inserted in a CuGAP1 expression cassette of the C. utilis ARS vector pRI177, and C. utilis AHU3053 was transformed with this plasmid. A number of transformant colonies grew in the presence of cycloheximide, which indicated that CuGAP1-CuYAP1 is an effective selection marker. The transformant also showed higher resistance to other agents, including cadmium and fluconazole. The overexpression of CuYAP1 in S. cerevisiae also resulted in increased resistance to various types of drugs.     

Bounds on the parallel evaluation of arithmetic expressions using associativity and commutativity

Summary We show that any arithmetic expression with n operands and parentheses nested to depth d can be evaluated in at most 1+2d+ [log₂ n] steps, assuming that only associativity and commutativity are used to transform the expression. We also show that at most [n–2d/2] processors are needed to achieve this bound.This work was supported in part by NSF Grant GJ 36936. An earlier version of this paper was presented at the Seventh Annual Princeton Conference on Information Sciences and Systems, March 1973.     

Heat capacity of metallic uranium and thorium from 80 to 1000 k

The heat capacities of metallic uranium and thorium from 80 to 1000 K have been determined by laser-flash calorimetry. The results on uranium agree very well with those in the literature over the temperature range investigated. The results on thorium are several percent lower than the heat-capacity values hitherto reported, while the enthalpy data at high temperatures in the literature are in good agreement with the present results. Shomate's analysis showed that the present results are the most consistent through the temperature range from 80 to 1000 K. On this, a revised table of thermodynamic functions of thorium from 80 to 1000 K is presented. The excess heat capacity on thorium has been found to be not appreciable up to 1000 K, in contrast with the large excess heat capacity above 300 K for uranium.     

Structure and mechanical properties of nanocrystalline Ag/MgO composites

Nanocrystalline Ag/MgO composites were prepared by the ultrafine-powder-compaction method. The structure was investigated for the first time by high-resolution electron microscopy. Nanometre-sized Ag grains and MgO grains in the composites bonded directly without any intermediate phase layer. Certain preferred orientation relationships were observed between the Ag and MgO grains. The nanocrystalline Ag/MgO composites retained their grain size during annealing up to 873 K. Vickers microhardness measurements were performed on the as-compacted and annealed specimens. Generation and propagation of cracks were less active in the nanocrystalline Ag/MgO composites than in a single-phase nanocrystalline MgO. The Vickers microhardness of the nanocrystalline Ag/MgO composites remained up to 1073 K. Hot-pressing deformation tests showed that the nanocrystalline Ag/MgO composites deformed plastically at 1073 K.     

Motion control of electric vehicles and prospects of supercapacitors

Novel motion control techniques for electric vehicles (EVs) on the basis of the quick torque generation in these vehicles have been developed at the Hori Laboratory. Because EVs are powered by electric motors, they have three major advantages: (i) motor torque generation is quick and accurate, (ii) a motor can be attached to each wheel, and (iii) motor torque can be estimated precisely. These advantages enable us to (i) easily realize high-performance antilock braking systems and traction control systems with minor feedback control of each wheel, (ii) control chassis motion, for example, direct yaw control, and (iii) estimate road surface condition. We have developed test vehicles and confirmed the effectiveness of the proposed methods. Recently, we have manufactured small EVs that are powered only by supercapacitors. Supercapacitors have long operating life, large current density, and are environmental friendly. Furthermore, their energy level can be estimated from their terminal voltage. Because EVs powered by supercapacitors can run for more than 20 min by charging only for 30 s, recharging EVs will not be a major problem. In the future, EVs will be recharged via contactless power transfer. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Phenotyping and genotyping of antibiotic-resistant Escherichia coli isolated from a natural river basin

Scientists have become increasingly concerned about the occurrence of antibacterial resistance in the environment. In this study, Escherichia coli resistant to one or more antibiotics among nine antibiotics was screened from Wenyu River Basin in Beijing, China, with mean frequency of 48.7 +/- 8.7% of 388 isolates in summer and 47 +/- 6% of 236 isolates in winter. The mean multiantibiotic resistance (MAR) index in summer was 0.11 +/- 0.03, slightly lower than that (0.14 +/- 0.04) in winter. Most frequent resistance appeared for sulfonamides, tetracycline, and ampicillin. The distribution of 20 tetracycline, three sulfonamide, and three beta-lactam resistance genes was assessed in the resistant isolates. While 97% of the ampicillin (AMP) resistant mechanism could be explained by the resistance gene TEM, 90% of the tetracycline (TC) and 96% of the sulfonamide (SXT) resistances could be explained by tet(A), tet(B), tet(M), and their combinations and sul(I), sul(II), sul(III), and their combinations, respectively. tet(M), a tetracycline-resistant gene originally detected in Gram-positive bacteria, and its combinations with tet(A) or tet(B) were first detected in E. coli isolated from a natural river basin, suggesting that tet(M) in E. coli might have been transferred from other bacterial species through horizontal gene transfer, which was supported by the fact that no tet(M) was detected in the isolates of human and chicken sources, except for only one isolate from swine. The source of sulfonamide-resistant E. coli in the river was supposed to be mainly from humans, based on a comparison of the sulfonamide resistance genotypes in animals and humans.