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931.
932.
Martin G.H. Gustavsson Christian Forssén Ann Marie Mårtensson Pendrill 《Hyperfine Interactions》2000,127(1-4):347-352
Measurements of the hyperfine structure in the highly charged hydrogen like systems 203Tl80+ and 205Tl80+ are underway at the Super EBIT at LLNL. This work considers the effects of the nuclear magnetization distribution on the
hyperfine structure. The difference in energy splitting due to hyperfine structure for 203Tl and 205Tl, respectively, is found to be 0.031 04(1) eV, which corresponds to a transition wavelength difference of 3.640(1) nm.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
933.
Development of a multiresidue method for the determination of multiclass pesticides in soil using GC
Jeong‐Heui Choi A. M. Abd El‐Aty M. E. Assayed Woo Jung Choi Kwang Sik Yoon Seong‐Soo Han Hee Kweon Kim Byung Jun Park Kap Soon Kim Sang Don Kim Hun Geun Choi Jae‐Han Shim 《Biomedical chromatography : BMC》2010,24(8):893-901
The principal objective of the present study was to develop a multiresidue analytical method for 62 pesticides in a soil matrix. Soil samples were fortified with known quantities of pesticides at two different concentration levels (0.1 and 0.01 μg/g) and the analytes were extracted via a liquid–solid extraction method. The pesticides were separated on an HP5 capillary column and were detected by gas chromatography coupled to an electron capture detector (GC‐ECD). The method was validated, considering its good linearities (r2 = 0.978–0.999), specificity and recovery characteristics. Recoveries were found between 70.3 and 113.4% for all pesticides except edifenphos (67.5%) and dichlobenil (69.5%) spiked at a 0.1 μg/mL concentration level and 74.5–117% except ethalfluralin (63.3%) and dichlobenil (51.9%) spiked at a concentration of 0.01 μg/mL. The developed method could be utilized as a simple and cost‐effective method for the routine analysis of 62 pesticides in soil samples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
934.
935.
936.
Zeinu Mussa Belew Michal Poborsky Hussam Hassan Nour-Eldin Barbara Ann Halkier 《Current Opinion in Green and Sustainable Chemistry》2022
Transport engineering strategies use altered expression of transporter proteins to change metabolite distribution within an organism. The production of plant specialized metabolites in microbial cell factories encounters a set of challenges that could benefit from the implementation of transport engineering technology. The range of challenges includes premature pathway termination due to secretion of intermediates, feedback inhibition due to inefficient export of final products, low yields in bioconversion processes due to inefficient import of precursors, and poor connectivity between subcellular compartments expressing different parts of complex biosynthetic pathways. We highlight the latest examples of transport engineering in microbial cell factories producing plant specialized metabolites, identify the current knowledge gap, and propose future research for advancing the field. 相似文献
937.
Stefanie?Platz Ann?Liza?Piberger Julia?Budnowski Corinna?Herz Monika?Schreiner Michael?Blaut Andrea?Hartwig Evelyn?Lamy Laura?Hanske Sascha?RohnEmail author 《Analytical and bioanalytical chemistry》2015,407(7):1819-1829
The food-related isothiocyanate sulforaphane (SFN), a hydrolysis product of the secondary plant metabolite glucoraphanin, has been revealed to have cancer-preventive activity in experimental animals. However, these studies have often provided inconsistent results with regard to bioavailability, bioaccessibility, and outcome. This might be because the endogenous biotransformation of SFN metabolites to the structurally related erucin (ERN) metabolites has often not been taken into account. In this work, a fully validated liquid chromatography tandem mass spectrometry (LC–MS–MS) method was developed for the simultaneous determination of SFN and ERN metabolites in a variety of biological matrices. To reveal the importance of the biotransformation pathway, matrices including plasma, urine, liver, and kidney samples from mice and cell lysates derived from colon-cancer cell lines were included in this study. The LC–MS–MS method provides limits of detection from 1 nmol L?1 to 25 nmol L?1 and a mean recovery of 99 %. The intra and interday imprecision values are in the range 1–10 % and 2–13 %, respectively. Using LC–MS–MS, SFN and ERN metabolites were quantified in different matrices. The assay was successfully used to determine the biotransformation in all biological samples mentioned above. For a comprehensive analysis and evaluation of the potential health effects of SFN, it is necessary to consider all metabolites, including those formed by biotransformation of SFN to ERN and vice versa. Therefore, a sensitive and robust LC–MS–MS method was validated for the simultaneous quantification of mercapturic-acid-pathway metabolites of SFN and ERN. 相似文献
938.
Of the many types of catalysis involving two or more catalysts, synergistic catalysis is of great interest because novel reactions or reaction pathways may be discovered when there is synergy between the catalysts. Herein, we describe a synergistic cascade catalysis, in which immobilized Au/Pd bimetallic nanoparticles and Lewis acids work in tandem to achieve the N-alkylation of primary amides to secondary amides with alcohols via hydrogen autotransfer. When Au/Pd nanoparticles were used with metal triflates, a significant rate acceleration was observed, and the desired secondary amides were obtained in excellent yields. The metal triflate is thought to not only facilitate the addition of primary amides to aldehydes generated in situ, but also enhance the returning of hydrogen from nanoparticles to hydrogen-accepting intermediates. This resulted in a more rapid turnover of the nanoparticle catalyst, and ultimately translated into an increase in the overall rate of the reaction. The two catalysts in this co-catalytic system work in a synergistic and cascade fashion, resulting in an efficient hydrogen autotransfer process. 相似文献
939.
Henk Don 《Random Structures and Algorithms》2015,47(4):710-730
We study the critical probability pc(M) in two‐dimensional M‐adic fractal percolation. To find lower bounds, we compare fractal percolation with site percolation. Fundamentally new is the construction of a computable increasing sequence that converges to pc(M). We prove that and . For the upper bounds, we introduce an iterative random process on a finite alphabet , which is easier to analyze than the original process. We show that and . © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 710–730, 2015 相似文献
940.
Michael S. BonoJr. Ann M. Anderson Mary K. Carroll 《Journal of Sol-Gel Science and Technology》2010,53(2):216-226
Alumina aerogels with surface areas from 460 to 840 m2/g and bulk densities from 0.025 to 0.079 g/cm3 were successfully fabricated using variations of an aluminum isopropoxide-based recipe developed by Armor and Carlson and
the rapid supercritical extraction (RSCE) process developed at Union College. By utilizing the Union College RSCE method,
it is possible to convert an alumina aerogel precursor mixture into aerogel monoliths in as little as 7.5 h. This process
is safer than methanol extraction in an autoclave and faster and simpler than liquid CO2 solvent exchange and extraction. By increasing the concentration of aqueous HNO3 used in the precursor mixture, we were able to fabricate aerogels with significantly increased surface area, decreased bulk
density, and altered microstructure. We attribute the observed variation in these aerogel properties at a given HNO3 concentration to environmental factors such as humidity. The ability to more easily fabricate alumina aerogels with desirable
properties will assist in making them a viable option for catalytic and other applications. 相似文献