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281.
282.
W. Günther K. Huber U. Kneissl H. Krieger H. Ries H. Ströher W. Wilke 《Nuclear Physics A》1981,359(2):397-407
The half-lives and yield ratios for the two 241Pu fission isomers have been measured in the 242Pu(γ, n) reaction. The observed half-life for the long-lived isomer is in agreement with previous data, and the existence of a short-lived 34 ± 7 ns isomer in 241Pu could be confirmed. The measured yield ratios are Yiso/Ypr = (9.2 ± 0.8) × 10?5 and Yiso/Ypr = (3.7 ± 0.7) × 10?5, respectively. From a statistical model analysis of the isomeric fission yield ratio, Ylongiso/Yshortiso = 2.5 ± 0.6, a spin assignment for the two isomers is attempted. Possible spin combinations are compared with single-particle shell-model calculations and with available spectroscopic data for the other even-odd Pu isotopes. 相似文献
283.
284.
Ahn KC Gee SJ Kim HJ Aronov PA Vega H Krieger RI Hammock BD 《Analytical and bioanalytical chemistry》2011,401(4):1285-1293
Pyrethroid insecticides widely used in forestry, agricultural, industrial, and residential applications have potential for
human exposure. Short sample preparation time and sensitive, economical high-throughput assays are needed for biomonitoring
studies that analyze a large number of samples. An enzyme-linked immunosorbent assay (ELISA) was used for determining 3-phenoxybenzoic
acid (3-PBA), a general urinary biomarker of exposure to some pyrethroid insecticides. A mixed-mode solid-phase extraction
reduced interferences from acid hydrolyzed urine and gave 110 ± 6% recoveries from spiked samples. The method limit of quantification
was 2 μg/L. Urine samples were collected from forestry workers that harvest pine cone seeds where pyrethroid insecticides
were applied at ten different orchards. At least four samples for each worker were collected in a 1-week period. The 3-PBA
in workers classified as high, low, or no exposure based on job analysis over all sampling days was 6.40 ± 9.60 (n = 200), 5.27 ± 5.39 (n = 52), and 3.56 ± 2.64 ng/mL (n = 34), respectively. Pair-wise comparison of the differences in least squares means of 3-PBA concentrations among groups
only showed a significant difference between high and no exposure. Although this difference was not significant when 3-PBA
excretion was normalized by creatinine excretion, the general trend was still apparent. No significant differences were observed
among days or orchards. This ELISA method using a 96-well plate was performed as a high-throughput tool for analyzing around
300 urine samples measured in triplicate to provide data for workers exposure assessment. 相似文献
285.
Daniel Krieger Prof. Dr. Jens Christoffers 《European journal of organic chemistry》2023,26(39):e202300757
δ-Butyrolactams with an exocyclic ester moiety in the δ-position were accessed by reduction of 1-azido-2-cyclopentanone carboxylates with PBu3 or Zn−AcOH. The ring transformation proceeded readily under the conditions of this reduction which is an unprecedented process. Primary amines formed by catalytic hydrogenation of α-azido-β-oxoesters with larger ring sizes or with benzannulation do not show this rearrangement under the conditions of the azide reduction. In these cases, the ring transformation to respective lactams was achieved by treatment of the α-amino-β-oxoesters with a stoichiometric amount of lithium diisopropylamide. 相似文献
286.
Semi-interpenetrating polymer networks of varying composition are prepared by crosslinking polystyrene containing a small number of maleic anhydride groups (4.8 mol% of MA units) with hexamethylene-diamine (HMDA) in the presence of linear poly(vinyl methyl ether) (PVME). Lightly crosslinked samples are homogeneous at room temperature and show a phase behaviour similar to uncrosslinked blends, i.e. lower critical solution temperature (LCST) behaviour. The influence of crosslinking on the phase behaviour has been studied by small angle light scattering (SALS) and turbidity measurements. The cloud point strongly depends on the heating rate. The presence of the network reduces the stable single phase region in agreement to theory. In systems showing spinodal decomposition, it is expected that some concentration fluctuations will grow more rapidly than others resulting in a separated phase system which shows high degree of connectivity with characteristic dimensions. Using temperature jump experiments, SALS can be used to estimate parameters of the phase separation kinetics and the characteristic dimensions of the phases. In temperature jump experiments into the spinodal region a maximum in the scattered light intensity is observed with time at a certain scattering vector. However, the semi-IPN's develop no scattering maximum. This is explained by a damping of the thermodynamical dominant wavelength in spinodal decomposition in the network. 相似文献