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421.
Superoxide radical (O2-) has been proposed to be an important participant in oxidation-reduction reactions of metal ions in natural waters. Here, we studied the reaction of nanomolar Mn(II) with O2- in seawater and simulated freshwater, using chemiluminescence detection of O2- to quantify the effect of Mn(II) on the decay kinetics of O2-. With 3-24 nM added [Mn(II)] and <0.7 nM [O2-], we observed effective second-order rate constants for the reaction of Mn(II) with O2- of 6×10(6) to 1×10(7) M(-1)·s(-1) in various seawater samples. In simulated freshwater (pH 8.6), the effective rate constant of Mn(II) reaction with O2- was somewhat lower, 1.6×10(6) M(-1)·s(-1). With higher initial [O2-], in excess of added [Mn(II)], catalytic decay of O2- by Mn was observed, implying that a Mn(II/III) redox cycle occurred. Our results show that reactions with nanomolar Mn(II) could be an important sink of O2- in natural waters. In addition, reaction of Mn(II) with superoxide could maintain a significant fraction of dissolved Mn in the +III oxidation state. 相似文献
422.
Georg Schramm Jens Langner Frank Hofheinz Jan Petr Bettina Beuthien-Baumann Ivan Platzek Jörg Steinbach Jörg Kotzerke Jörg van den Hoff 《Magma (New York, N.Y.)》2013,26(1):115-126
Objective
Evaluation of the quantitative accuracy of MR-based attenuation correction (MRAC) in the Philips Ingenuity TF whole-body PET/MR.Materials and methods
In 13 patients, PET emission data from the PET/MR were reconstructed using two different methods for attenuation correction. In the first reconstruction, the vendor-provided standard MRAC was used. In the second reconstruction, a coregistered transmission-based attenuation map from a second immediately preceding investigation with a stand-alone Siemens ECAT EXACT HR+ PET scanner was used (TRAC). The two attenuation maps were compared regarding occurrence of segmentation artifacts in the MRAC procedure. Standard uptake values (SUVs) of multiple VOIs (liver, cerebellum, hot focal structures at various locations in the trunk) were compared between both reconstructed data sets. Furthermore, a voxel-wise intensity correlation analysis of both data sets in the lung and trunk was performed.Results
VOI averaged SUV differences between MRAC and TRAC were as follows (relative differences, mean ± standard deviation): (+12 ± 6) % cerebellum, (?4 ± 9) % liver, (?2 ± 11) % hot focal structures. The fitted slopes of the voxel-wise correlations in the lung and trunk were 0.87 ± 0.17 and 0.95 ± 0.10 with averaged adjusted R 2 values of 0.96 and 0.98, respectively. These figures include two instances with partially erroneous lung segmentation due to artifacts in the underlying MR images.Conclusion
The MR-based attenuation correction implemented on the Philips Ingenuity PET/MR provides reasonable quantitative accuracy. On average, deviations from TRAC-based results are small (on the order of 10 % or below) across the trunk, but due to interindividual variability of the segmentation quality, deviations of more than 20 % can occur. Future improvement of the segmentation quality would help to increase the quantitation accuracy further and to reduce the inter-subject variability. 相似文献423.
424.
Moderne Deckensysteme müssen neben den statisch‐konstruktiven Anforderungen einer Vielzahl weiterer Entwurfsaspekte genügen, um am Markt bestehen zu können. Nachfolgend werden nach einer Einführung die verschiedenen marktgängigen Deckensysteme beschrieben. Im Weiteren werden neuere Entwicklungen von Deckensystemen insbesondere hinsichtlich der Multifunktionalität und der Nachhaltigkeit aufgezeigt. Steel floor structural systems. In addition to static and structural requirements, modern floor systems must meet a variety of other design issues, in order to survive on the market. After an introduction, various commercially available floor systems are described. In addition, recent developments of floor systems are presented, particularly concerning multi‐functionality and sustainability issues. 相似文献
425.
426.
The α-tocopherol transfer protein (TTP) plays an important role in the regulation of plasma α-tocopherol concentrations. We
hypothesized that hepatic TTP levels would be modulated by dietary vitamin E supplementation and/or by oxidative stress. Mice
were fed either a High E (1150 mg RRR-α-tocopheryl acetate/kg diet) or a Low E (11.5 mg/kg diet) diet for 2 wk. High E increased plasma and liver α-tocopherol
concentrations approximately 8- and 40-fold, respectively, compared with Low E-fed mice, whereas hepatic TTP increased approximately
20%. Hepatic TTP concentrations were unaffected by fasting (24 h) in mice fed either diet. To induce oxidative stress, chow-fed
mice were exposed for 3 d to environmental tobacco smoke (ETS) for 6 h/d (total suspended particulate, 57.4±1.8 mg/m3). ETS
exposure, while resulting in pulmonary and systemic oxidative stress, had no effect on hepatic α-tocopherol concentrations
or hepatic TTP. Overall, changes in hepatic TTP concentrations were minimal in response to dietary vitamin E levels or ETS-related
oxidative stress. Thus, hepatic TTP concentrations may be at sufficient levels such that they are unaffected by either modulations
of dietary vitamin E or by the conditions of environmentally related oxidative stress used in the present studies.
The first and second investigators contributed equally to this work. 相似文献
427.
428.
von Helversen Bettina; Wilke Andreas; Johnson Tim; Schmid Gabriele; Klapp Burghard 《Canadian Metallurgical Quarterly》2011,120(4):962
Previous research reported conflicting results concerning the influence of depression on cognitive task performance. Whereas some studies reported that depression enhances performance, other studies reported negative or null effects. These discrepant findings appear to result from task variation, as well as the severity and treatment status of participant depression. To better understand these moderating factors, we study the performance of individuals—in a complex sequential decision task similar to the secretary problem—who are nondepressed, depressed, and recovering from a major depressive episode. We find that depressed individuals perform better than do nondepressed individuals. Formal modeling of participants' decision strategies suggested that acutely depressed participants had higher thresholds for accepting options and made better choices than either healthy participants or those recovering from depression. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
429.
Ilario Ferrocino Kalliopi Rantsiou Ryan McClure Tanja Kostic Rafael Soares Correa de Souza Lene Lange Jamie FitzGerald Aicha Kriaa Paul Cotter Emmanuelle Maguin Bettina Schelkle Michael Schloter Gabriele Berg Angela Sessitsch Luca Cocolin The MicrobiomeSupport Consortium 《Comprehensive Reviews in Food Science and Food Safety》2023,22(2):1082-1103
430.
Uwe Kucklnder Krystina Kuna Bettina Schneider Alois Steigel B. Mayer 《Advanced Synthesis \u0026amp; Catalysis》1993,335(4):345-350
Addition of α-Ketoenamines to 2-Acetyl-p-benzoquinone Addition of 2-morpholino-2-cyclohex-1-en-one 2 to 2-acetyl-quinone 1 yields benzo[c][4 H]chromen-4,7,10-trion 4 which is unstable and rearranges to 5. 4 is converted to 3-(2,5-dihydroxy-phenyl)-2-morpholino-2-cyclohex-1-en-on 3 thermically and to dibenzo[b,d]furan-4-on 7 acid catalyzed. The structure of 7 is secured by independent synthesis. Dibenzo[b,d]furan-4-on 14 is the product of reaction from 2-(p-toluidino)-2-cyclohex-1-en-on 9 and 1 with benzo[c][4 H]chromen-4,7,10-trion 10 as intermediate. By proton catalysis 5-acetyl-6-hydroxy-carbazol-1-on 13 and 4-oxo-cyclohexa[c]isochinolinium hydrochlorid 15 is obtained from 10 . 1 H-cyclopenta[d]furan-3-on 17 is formed by addition of 2-(p-toluidino)-2-cyclopent-1-en-on 16 to 1 . It is rearranged by proton catalysis to 3-oxo-1 H-cyclopenta[c]isochinolinium salt 18 . Reaction of cyclopentan-1,2-dione and 1 yields 3 aH-cyclopenta[c]isochromen-3,6,9-trion 20 , rearranging to 1 H-cyclopenta[b]benzo[d]furan-3-on 21 . The stereochemistry of adducts is discussed in connection with the course of the reaction, spectroscopical evidence, molecular modelling and calculation of HOMO/LUMO and AO-coefficients. 相似文献