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991.
Nobuhiro Matsumoto Kaeko Takada Takuya Shimosaka 《Accreditation and quality assurance》2016,21(5):335-339
A reference gas mixture of nitrous oxide (N2O) in nitrogen, filled in a 10-L high-pressure aluminum alloy gas cylinder, has been developed as a certified reference material for emission measurement of exhaust gases from automobiles. As an example of certified values, mole fraction of N2O is 302.36 μmol/mol. An electronic mass comparator with a home-made automatic cylinder exchanger, gas-filling equipment, and a gas chromatograph with a thermal conductivity detector have been used for the production of this CRM. The gas chromatographic analysis has of sufficient precision. The mole fraction of N2O has good long-term stability for 10 years and is independent of inner pressure in the gas cylinder. As these results, a relative expanded uncertainty (coverage factor is 2) of the certified value has become 0.28 %. This sufficiently small uncertainty of the N2O mole fraction will be advantageous in the calibration of analytical instruments for emission gas analysis. 相似文献
992.
We consider the error analysis of Lagrange interpolation on triangles and tetrahedrons. For Lagrange interpolation of order one, Babu?ka and Aziz showed that squeezing a right isosceles triangle perpendicularly does not deteriorate the optimal approximation order. We extend their technique and result to higher-order Lagrange interpolation on both triangles and tetrahedrons. To this end, we make use of difference quotients of functions with two or three variables. Then, the error estimates on squeezed triangles and tetrahedrons are proved by a method that is a straightforward extension of the original one given by Babu?ka-Aziz. 相似文献
993.
Cover Picture: An Unusual Chimeric Diterpene Synthase from Emericella variecolor and Its Functional Conversion into a Sesterterpene Synthase by Domain Swapping (Angew. Chem. Int. Ed. 5/2016) 下载免费PDF全文
994.
Nakanishi T Yamakawa N Asahi T Osaka T Ohtani B Uosaki K 《Journal of the American Chemical Society》2002,124(5):740-741
Self-assembled monolayer of atropisomeric compound, 1,1'-binaphthalene-2,2'-dithiol (BNSH), provides a field for chiral discrimination. The two-dimensional chiral arrangement with screw-like units, each of which is composed of three BNSH molecules, plays an important role in the enantioselectivity of adsorption of phenylalanine, as revealed by a quartz crystal microbalance technique. 相似文献
995.
Takuya Washio 《Tetrahedron》2007,63(48):12037-12046
Catalytic asymmetric syntheses of (−)-centrolobine and (−)-de-O-methylcentrolobine have been achieved, incorporating a hetero-Diels-Alder (HDA) reaction between 4-aryl-2-silyloxy-1,3-butadienes and phenylpropargyl aldehyde derivatives as a key step. The HDA reaction using dirhodium(II) tetrakis[(R)-3-(benzene-fused-phthalimido)-2-piperidinonate], Rh2(R-BPTPI)4, as a chiral Lewis acid catalyst provides exclusively cis-2,6-disubstituted tetrahydropyran-4-ones in up to 93% ee. 相似文献
996.
Nitrogen electrode reaction has been investigated in a LiBr-KBr-CsBr melt containing Li3N. The reaction N3- --> 1/2N2 + 3e- is confirmed by quantitative analysis of anodically evolved gas. The Nernst relation holds for the rest potential of Ni electrodes at a nitrogen gas pressure, pN2, of 0.05-1.0 atm and an anion fraction of the N3- ions, xN3-, of 0.003-0.010 (anion fraction). Then, the standard formal potential of the N2/N3- couple, , is evaluated to be 0.251 +/- 0.009 V versus Li+/Li (pN2 = 1 atm, xN3- = 1) at 673 K. The dependence of on the temperature (570-730 K) gives a linear relation, whose slope is (-0.930 +/- 0.117) x 10(-3) V K(-1). Thermodynamic quantities for the formation of Li3N in the melt are also estimated. 相似文献
997.
M. Kawano J. Falandysz T. Wakimoto 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(2):235-237
Instrumental neutron activation analysis was performed to measure the levels of extractable organohalogens (EOX) in the organisms from the Antarctic marine ecosystem. The results show that EOX (EOCl, EOBr and EOI) were found in all the samples analyzed. The highest concentration was determined in the ascidian sample. The concentration order of EOX was mainly EOCl>EOBr>EOI with the exception of nemertine, ascidian, fish and adelie penguin samples. The concentrations of man-made organochlorines (DDTs and CHLs) were analyzed by GC-MS, and the results were compared with the concentrations of EOX determined in the same samples. The results show that the contribution of known man-made organochlorines in EOCl was less than 3%. This means that a large amount of unknown organochlorine compounds is present in Antarctic marine organisms. 相似文献
998.
Kokubo K Koizumi T Harada K Mochizuki E Oshima T 《The Journal of organic chemistry》2005,70(19):7776-7779
[reactions: see text] We investigated the site selectivity switch in BF3-catalyzed dual skeletal rearrangements of cyclobutene-fused diarylhomobenzoquinones by changing the stoichiometric amount of acid concentration. From the lower to the higher equivalency of BF3 x Et2O, the branching product ratios (path A/path B) obeyed nonlinear sigmoid curves against the equivalency of BF3 x Et2O. The observed selectivity profiles were simulated to elucidate factors that govern thermodynamic aspects (binding affinity K of each carbonyl function with acid) and kinetic aspects (rate constants k for the cyclobutene-ring cleavage). 相似文献
999.
An efficient one-pot synthesis of 1,2,3-triazole-fused isoindoles from o-alkynylbenzaldehydes and trimethylsilyl azide (TMSN3) is reported. The reaction proceeds through the formation of a diazide intermediate and a subsequent intramolecular azide-alkyne cycloaddition, providing a novel access to a variety of 8-azido-8H-[1,2,3]triazolo[5,1-a]isoindoles in high yields. 相似文献
1000.
Aoki Nobuyuki Shimosaka Takuya Aoyagi Reiji Kaifuku Yuichiro 《Accreditation and quality assurance》2018,23(4):199-210
Accreditation and Quality Assurance - A reliable method for the quantification of formaldehyde (HCHO) amount fractions is required, because the results of comparisons between individual techniques... 相似文献