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961.
The German bakery waste incident; use of a combined approach of screening and confirmation for dioxins in feed and food 总被引:1,自引:0,他引:1
During the last six years several incidents have occurred with dioxins in feed, stressing the need for rapid screening methods for these compounds. The most recent incident was the contamination of bakery waste used for animal feed due to the use of waste wood for drying of the material. In addition to Germany, the material was also shipped to the Netherlands. Levels up to 12 ng TEQ/kg have been detected, being about 15 times over the current limit of 0.75 ng TEQ/kg. In the Netherlands a combined strategy of screening with the CALUX-bioassay and the HRGC/HRMS confirmatory method was used to rapidly control the incident. Pigs were contaminated by the incident but only to a very limited extent. Despite the rather low limits for pig meat, the CALUX bioassay showed excellent performance, once again confirming the value of this assay. 相似文献
962.
Chong DP van Lenthe E Van Gisbergen S Baerends EJ 《Journal of computational chemistry》2004,25(8):1030-1036
Even-tempered Slater-type orbital basis sets were developed in 1973, based on total atomic energy optimization. Here, we revisit ET STOs and propose new sets based on past experience and recent computational studies. From preliminary atomic and molecular tests, these sets are shown to be very well balanced and to perform, at lower cost, almost as well as a very large (close to complete) basis set. 相似文献
963.
In a single condensation step, a poly-ureidophthalimide is synthesized, which folds into a chiral, helical architecture according to circular dichroism spectroscopy. 相似文献
964.
Domínguez L van Nhien AN Tomassi C Len C Postel D Marco-Contelles J 《The Journal of organic chemistry》2004,69(3):843-856
The carbanion-mediated sulfonate intramolecular cyclizations (CSIC protocols) of glyco-alpha-sulfonamidonitriles derived from readily available monosaccharides have been extensively investigated using potassium carbonate, cesium carbonate, n-BuLi, and LDA as bases. As a result, a series of enantiomerically pure spiro(4-amino-5-H-2,3-dihydroisothiazole-1,1-dioxide) derivatives have been prepared efficiently and isolated in good yield. The synthesis of these new bicyclic systems is key to accessing a novel range of aza analogues of TSAO nucleosides (ATSAOs). 相似文献
965.
Grotenbreg GM Kronemeijer M Timmer MS El Oualid F van Well RM Verdoes M Spalburg E van Hooft PA de Neeling AJ Noort D van Boom JH van der Marel GA Overkleeft HS Overhand M 《The Journal of organic chemistry》2004,69(23):7851-7859
A practical gram-scale and high-yielding synthesis of the antimicrobial peptide gramicidin S is presented. An Fmoc-based solid-phase peptide synthesis protocol is employed for the generation of the linear decapeptide precursor, which is cyclized in solution to afford the target compound. The versatility of our method is demonstrated by the construction of eight gramicidin S analogues (15a-h) having nonproteinogenic sugar amino acid residues (4-7) incorporated in the turn regions. 相似文献
966.
van Eldik R 《Inorganic chemistry》2004,43(9):2756-2758
In a recent paper by Cheng and co-workers (Sun, Y.-J.; Zang, L. Z.; Cheng, P.; Lin, H.-K.; Yan, S.-P.; Sun, W.; Liao, D.-Z.; Jiang, Z.-H.; Shen, P.-W. Inorg. Chem. 2003, 42, 508-515), kinetic evidence for inhibitor effects of specific ligands on the catalyzed dehydration of HCO3- by copper(II) complexes of the type [Tp(Ph)]CuX (X- = OH-, N3-, and NCS-) was reported. The analysis of the kinetic data is not correct, and a re-evaluation shows that the claimed catalytic activity of the studied complexes on the dehydration reaction of bicarbonate is indeed questionable. Furthermore, the apparent inhibitor effect of specific selected ligands in the Cu(II) complexes does not seem to exist at all and is based on a wrong interpretation of the kinetic data. 相似文献
967.
In this article a new method for the photolithographical deposition of temperature-sensitive hydrogels is presented. The method can be used in conjunction with standard 365 nm UV-photolithography to accurately dimension and position temperature-sensitive hydrogel microactuators in a highly parallel fashion. A number of characteristics of the hydrogels were investigated. These include: the photolithographical reproduction quality, the effect of the crosslinking density in the hydrogels on their swelling behavior, the swelling hysteresis behavior, the effect of dimensional constraints on the swelling of the hydrogels and the effect of copolymerization with an ionizable comonomer on the temperature behavior of the hydrogels. The method presents a considerable improvement in the microfabrication of temperature-sensitive hydrogel microactuators and has potential for the mass-fabrication of these interesting microactuators. 相似文献
968.
Raunkjaer M El Oualid F van der Marel GA Overkleeft HS Overhand M 《Organic letters》2004,6(18):3167-3170
[reaction: see text] Novel highly functionalized dipeptide isosters are synthesized via a diastereoselective alkyl/arylation protocol of a glucose-derived (R)-tert-butanesulfinylimine. One of these novel sugar amino acid derivatives, a D-Ala-Ser/Thr isostere, was applied in a peptide synthesis protocol to afford a cyclic tetramer. 相似文献
969.
Gert-Jan van der Heiden 《Journal of Number Theory》2004,104(2):193-209
Let K be a function field with an A-algebra structure. The ring A arises in the definition of the Drinfeld module φ over K. By E(K) we denote K together with the A-module structure induced on it by φ. For any principal prime ideal (a)⊂A, we study the question whether an element x∈E(K) which is an a-fold in E(Kν) for every place ν of K, is an a-fold in E(K). In particular, we study the group
970.
Gert-Jan van der Heiden 《Monatshefte für Mathematik》2004,143(2):115-143
As is well-known, there exists a Weil pairing for elliptic curves which is a perfect bilinear form from the m-torsion of the elliptic curve E to the m-th roots of unity. In this paper we will show how Andersons paper [1] gives rise to an analogue of this pairing for Drinfeld modules.The author was supported by NWO Grant 613.007.040. The author would like to thank G. Böckle and S. J. Edixhoven for their comments. 相似文献