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排序方式: 共有465条查询结果,搜索用时 15 毫秒
31.
Yukari Tsumura Susumu Ishimitsu Isao Saito Hiroshi Sakai Yukari Kobayashi Yasuhide Tonogai 《Food Additives & Contaminants》2001,18(5):449-460
Plasticizers in duplicate diet samples obtained over 1 week were analysed in order to estimate daily intake. The phthalate esters were as follows: diethyl, dipropyl, dibutyl, dipentyl, dihexyl, butylbenzyl, dicyclohexyl, di(2-ethylhexyl), dioctyl, diisooctyl (mixture of isomers) and diisononyl (mixture). Di(2-ethylhexyl) adipate was also determined. Homogenized samples of composite meals were extracted with acetonitrile, lipids were removed by extraction into n-hexane and the acetonitrile layer was cleaned using FlorisilR and R Bondesil PSA dual layer column. Phthalates were determined by GC/MS (SIM). Phthalate recovery from the fortified food mixture by this method was 62.5-140.8%. Quality assurance as assessed by three laboratories indicated coefficient of variance in the levels of detected phthalates in same lot samples as below 10%. Detection limits were 0.1-23ng/g for each phthalate. One-week duplicate diet samples provided by three hospitals in three remote prefectures of Japan were analysed as individual meals. In all 63 samples, DEHP was present at the highest level among all phthalates in the range 10-4400ng/g. The intake of plasticizers estimated from all samples was 519 µ g DEHP/day, 86 µ g DEHA/day, 65 µ g DINP/day, and 4.7 µ g BBP/day. Calculated DEHP in 2-day samples out of 21 days exceeded EU TDI for a person of 50kg body weight (1850 µ g per day). Disposable PVC gloves used during the preparation of meals were suspected as the source of the high DEHP content. One-day intake of the other phthalates and DEHA was below 7% of TDI in all cases. High concentrations of DEHP (5990ng/g) was found in baby food used in quality assurance work. The source of contamination was the PVC-tube used during production and was effectively reduced by replacing the tube by one made of stainless steel. 相似文献
32.
Photocatalytic activities of CdS crystallites embedded in TiO2 gel as a stable semiconducting matrix 总被引:2,自引:0,他引:2
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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Thanks to rapid progress in microelectronics technology, a new, nomadic lifestyle has become widespread these days. People, regardless of location, enjoy greater connectivity through communication networks and intelligent electronic terminals. This nomadic lifestyle will become even more common as technology frees people from the constraints of time and location. The cool chip, characterized by high performance and low power consumption, will play a key role in inaugurating the Nomadic Age. Rather than describe its technical details, we take a broader, more historic view of the cool chip's impact. More than a necessary innovation, cool chips' increased portability and reduced power consumption will play a key role in building a better future society 相似文献
35.
H. Rotzinger J. Adams S. R. Bandler J. Beyer H. Eguchi E. Figueroa-Feliciano W. Hsieh G. M. Seidel T. Stevenson 《Journal of Low Temperature Physics》2008,151(1-2):351-356
We have been developing array technology for fabricating magnetic calorimeters for X-ray astronomy. The magnetization change
in each pixel of the paramagnetic sensor material due to the heat input of an absorbed X-ray is sensed by a meander shaped
coil. With this geometry it is possible to obtain excellent energy sensitivity, low magnetic cross-talk and large format arrays
fabricated on wafers that are separate from the SQUID read-out. A magnetic bias field for each pixel is generated by the use
of a persistent current that is stored. We report on the results from our prototype arrays, which are coupled to low noise
DC-SQUIDs. The first test results are presented and the sensitivity is compared with calculations. 相似文献
36.
Hiroshi Inoue Koshi Sekizawa Koichi Eguchi Hiromichi Arai 《Journal of the American Ceramic Society》1997,80(3):584-588
A coating of barium hexaaluminate (Ba0.75 Al11.0 O17.25 ) on an α-SiC substrate and the thermal stability of the formed film were investigated for a high-temperature catalytic application. The film prepared by sol coating consisted of BaAl2 Si2 O8 and α-Al2 O3 phases and always contained many cracks or exfoliations after heating at 1200C. A hexaaluminate porous film was successfully formed by slurry coating without void formation at the interface between the film and the substrate and exfoliation due to the formation of the intermediate layer after heating at 1200°C. The microstructure of the film remained unchanged, even after heating at 1300°C. 相似文献
37.
Mechanism‐Based Trapping of the Quinonoid Intermediate by Using the K276R Mutant of PLP‐Dependent 3‐Aminobenzoate Synthase PctV in the Biosynthesis of Pactamycin 下载免费PDF全文
Akane Hirayama Dr. Akimasa Miyanaga Prof. Dr. Fumitaka Kudo Prof. Dr. Tadashi Eguchi 《Chembiochem : a European journal of chemical biology》2015,16(17):2484-2490
Mutational analysis of the pyridoxal 5′‐phosphate (PLP)‐dependent enzyme PctV was carried out to elucidate the multi‐step reaction mechanism for the formation of 3‐aminobenzoate (3‐ABA) from 3‐dehydroshikimate (3‐DSA). Introduction of mutation K276R led to the accumulation of a quinonoid intermediate with an absorption maximum at 580 nm after the reaction of pyridoxamine 5′‐phosphate (PMP) with 3‐DSA. The chemical structure of this intermediate was supported by X‐ray crystallographic analysis of the complex formed between the K276R mutant and the quinonoid intermediate. These results clearly show that a quinonoid intermediate is involved in the formation of 3‐ABA. They also indicate that Lys276 (in the active site of PctV) plays multiple roles, including acid/base catalysis during the dehydration reaction of the quinonoid intermediate. 相似文献
38.
Fumitaka Kudo Dr. Atsushi Motegi Kazutoshi Mizoue Dr. Tadashi Eguchi Prof. Dr. 《Chembiochem : a European journal of chemical biology》2010,11(11):1574-1582
FD‐891 is a 16‐membered cytotoxic antibiotic macrolide that is especially active against human leukemia such as HL‐60 and Jurkat cells. We identified the FD‐891 biosynthetic (gfs) gene cluster from the producer Streptomyces graminofaciens A‐8890 by using typical modular type I polyketide synthase (PKS) genes as probes. The gfs gene cluster contained five typical modular type I PKS genes (gfsA, B, C, D, and E), a cytochrome P450 gene (gfsF), a methyltransferase gene (gfsG), and a regulator gene (gfsR). The gene organization of PKSs agreed well with the basic polyketide skeleton of FD‐891 including the oxidation states and α‐alkyl substituent determined by the substrate specificities of the acyltransferase (AT) domains. To clarify the involvement of the gfs genes in the FD‐891 biosynthesis, the P450 gfsF gene was inactivated; this resulted in the loss of FD‐891 production. Instead, the gfsF gene‐disrupted mutant accumulated a novel FD‐891 analogue 25‐O‐methyl‐FD‐892, which lacked the epoxide and the hydroxyl group of FD‐891. Furthermore, the recombinant GfsF enzyme coexpressed with putidaredoxin and putidaredoxin reductase converted 25‐O‐methyl‐FD‐892 into FD‐891. In the course of the GfsF reaction, 10‐deoxy‐FD‐891 was isolated as an enzymatic reaction intermediate, which was also converted into FD‐891 by GfsF. Therefore, it was clearly found that the cytochrome P450 GfsF catalyzes epoxidation and hydroxylation in a stepwise manner in the FD‐891 biosynthesis. These results clearly confirmed that the identified gfs genes are responsible for the biosynthesis of FD‐891 in S. graminofaciens. 相似文献
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