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871.
872.
Flow analysis preconcentration of Mg and Zn using emulsions for flame atomic absorption spectrometry
T. Yokoyama Takashi Watarai Takeo Uehara Koh-ichi Mizuoka Kenji Kohara Masato Kido Michio Zenki 《Analytical and bioanalytical chemistry》1997,357(7):860-863
A preconcentration method combining Water/ Oil/Water (W/O/W) emulsions with flow injection manifolds has been developed for
determinations of Mg and Zn. The system consists of a mixing coil filled with Span 80 as a surfactant, palmitic acid or di(2-ethylhexyl)
phosphate as an extractant, kerosene as a solvent in the oil phase, and HCl in the inner aqueous phase to form W/O emulsions,
an extraction coil for the sample solution to form W/O/W emulsions, a phase separator to waste the outer aqueous phase, a
dry bath to demulsify W/O emulsions with 2-ethylhexanol, a phase separator to waste the oil phase, and an air pump to deliver
the concentrated sample solution to the flame atomic absorption spectrophotometer. This method proved to be excellent regarding
the reproducibility, the rapidity, and the small quantity of sample, compared with the W/O/W emulsions method without the
flow injection manifolds. The signal of flame atomic absorption spectrometry (FAAS) after preconcentration of Mg by this method
was 2.4 times as large as that before preconcentration. Also, this method suppressed some interferences. The system was applied
to FAAS determinations of Mg and Zn in duralumin alloys and Zn in commercial reagents.
Received: 20 March 1996/Revised: 13 July 1996/Accepted: 20 July 1996 相似文献
873.
Masato Mikawa Naoko Seki Shoji Nagaoka Hiroyoshi Kawakami 《Journal of Polymer Science.Polymer Physics》2007,45(19):2739-2746
In this article, we have reported the influence of alcohol as a casting solution on the structure and the gas permeability of asymmetric polyimide membranes made by dry–wet phase inversion. The apparent skin layer thickness of the asymmetric membrane decreased with an increase in molecular weight of the alcohol, and the thicknesses of the membranes made from methanol, ethanol, propanol, and butanol were 250, 120, 61, and 31 nm, respectively. We found that χ12 as an interaction parameter of solvent–nonsolvent had a significant influence on the phase inversion occurring in the coagulant medium. On the other hand, the gas permeance and the gas selectivity in the asymmetric membranes increased with the increasing molecular weight of the alcohol. We believe that a more packed structure formed in the asymmetric polyimide membrane with a thinner surface skin layer is also responsible for the thickness‐dependence of the gas selectivity obtained in this study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2739–2746, 2007 相似文献
874.
Daisuke Nagai Masato Sato Bungo Ochiai Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(14):4281-4289
A matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectroscopy analysis of polythiourethanes obtained by the cationic ring‐opening polymerization of a six‐membered cyclic thiourethane [3‐benzyltetrahydro‐1,3‐oxazine‐2‐thione (BTOT)] is described. A MALDI‐TOF mass spectrum of a polymer obtained by the polymerization of BTOT with boron trifluoride etherate (BF3OEt2) as the initiator in nitrobenzene at 50 °C for 24 h followed by an end‐capping reaction with diethyldithiocarbamic acid diethylammonium salt showed a series of well‐resolved signals that were assignable to polythiourethanes possessing an amino group at the initiating end and a diethyldithiocarbamate group at the terminating end. In comparison with the MALDI‐TOF mass spectra of polymers obtained by polymerization with trifluoromethanesulfonic acid or methyl trifluoromethanesulfonate, the plausible initiating species in the polymerization with BF3OEt2 was estimated to be a proton, which successively eliminated carbonyl sulfide to produce a secondary amine group at the initiating end. The secondary amine group in the obtained telechelic polymer was converted to a tertiary amine group by a reaction with benzyl bromide in the presence of triethylamine, and this was confirmed by MALDI‐TOF mass spectroscopy. Furthermore, a telechelic polymer with a pyrrole end group was successfully synthesized by the end‐capping reaction of the growing species in the polymerization of BTOT with sodium 1‐pyrrolecarbodithioate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4281–4289, 2006 相似文献
875.
The stability of internally heated inclined plane parallel shear flows is examined numerically for the case of finite value of the Prandtl number, Pr. The transition in a vertical channel has already been studied for 0?Pr?100 with or without the application of an external pressure gradient, where the secondary flow takes the form of travelling waves (TWs) that are spanwise-independent (see works of Nagata and Generalis). In this work, in contrast to work already reported (J. Heat Trans. T. ASME 124 (2002) 635–642), we examine transition where the secondary flow takes the form of longitudinal rolls (LRs), which are independent of the steamwise direction, for Pr=7 and for a specific value of the angle of inclination of the fluid layer without the application of an external pressure gradient. We find possible bifurcation points of the secondary flow by performing a linear stability analysis that determines the neutral curve, where the basic flow, which can have two inflection points, loses stability. The linear stability of the secondary flow against three-dimensional perturbations is also examined numerically for the same value of the angle of inclination by employing Floquet theory. We identify possible bifurcation points for the tertiary flow and show that the bifurcation can be either monotone or oscillatory. To cite this article: M. Nagata, S. Generalis, C. R. Mecanique 332 (2004). 相似文献
876.
Numerical simulation of standard dissipative materials undergoing finite strains remains an important and challenging topic in computational mechanics. The incremental variational formulation (IVF), firstly proposed by Ortiz et al. [1], provides a general variational framework which is suitable for the implementation of a broad range of constitutive laws for standard dissipative materials. The IVF recasts the inelasticity theory as an equivalent optimization problem where the incremental stress potential is minimized with respect to the internal variables. However, their implementation often requires more effort than classical formulations due to high-order tensor derivatives. In this contribution, a novel implementation of IVFs is presented to arrive at a fully automatic and robust scheme with computer accuracy using hyper-dual numbers (HDNs). The HDNs, which are originally developed by Fike [2], derive exact and automatic derivative calculations without any cumbersome choice of perturbation values. Its uncomplicated implementation for associative finite strain elasto-plasticity and its performance is illustrated by a representative numerical example. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
877.
Afshin Ebrahimi Masaaki Kitano Kazushi Iyatani Yu Horiuchi Masato Takeuchi Masaya Matsuoka Masakazu Anpo 《Research on Chemical Intermediates》2013,39(4):1593-1602
Visible light-responsive TiO2 (Vis-TiO2) thin films were successfully developed by applying a radio-frequency magnetron sputtering deposition method by controlling various sputtering parameters such as the substrate temperature, Ar gas pressure, and the target-to-substrate distance. UV–Vis, XRD and SEM investigations revealed that optical property, the crystal structure, and photocatalytic activity of Vis-TiO2 are strongly affected by the sputtering parameters during the deposition step. Vis-TiO2 was found to act as an efficient photocatalyst for the H2 and O2 evolution from water under visible light irradiation (λ ≥ 420 nm). SIMS investigations have revealed that a slight decrease in the O/Ti ratio of the TiO2 thin films plays an important role in the modification of the electronic properties of Vis-TiO2 thin films, enabling them to absorb visible light. 相似文献
878.
Tomonari Tanaka Tomonori Wada Masato Noguchi Masaki Ishihara Atsushi Kobayashi Takayuki Ohnuma 《Journal of carbohydrate chemistry》2013,32(8):634-646
A novel sugar adduct, 4,6-dimethoxy-1,3,5-triazin-2-yl β-d-glucosaminide (GlcN-β-DMT), has been prepared by the reaction of d-glucosamine (GlcN) and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-morpholinium chloride (DMT-MM). The adduct was recognized by exo-β-d-glucosaminidase (GlcNase) from Amycolatopsis orientalis and transferred the GlcN moiety, giving rise to the corresponding glucosaminides. This chemo-enzymatic process was successfully applied to d-galactosamine (GalN). GalN-β-DMT prepared directly from GalN and DMT-MM behaved as an efficient glycosyl donor for transfer of the GalN moiety catalyzed by the same enzyme. The introduction of the 4,6-dimethoxy-1,3,5-triazin-2-yl leaving group to the anomeric center significantly enhanced transglycosylating ability, resulting in the efficient glycosidase-catalyzed synthesis of glycosaminides. 相似文献
879.
Dr. Tomoyasu Hirose Dr. Yoshihiko Noguchi Yujiro Furuya Dr. Aki Ishiyama Dr. Masato Iwatsuki Dr. Kazuhiko Otoguro Prof. Dr. Satoshi Ōmura Prof. Dr. Toshiaki Sunazuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10741-10750
Herein, we describe the first asymmetric total synthesis and determination of the relative and absolute stereochemistry of naturally occurring 16‐hydroxy‐16,22‐dihydroapparicine. The key steps include 1) a novel phosphinimine‐mediated cascade reaction to construct the unique 1‐azabicyclo[4.2.2]decane core, including a pseudo‐aminal‐type moiety; 2) a highly stereospecific 1,2‐addition of 2‐acylindole or a methylketone through a Felkin–Anh transition state for the construction of a tetrasubstituted carbon center; and 3) an intramolecular chirality‐transferring Michael reaction of the ketoester, with neighboring‐group participation, to introduce a chiral center at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)‐(15S,16R)‐16‐hydroxy‐16,22‐dihydroapparicine and its intermediate against chloroquine‐resistant Plasmodium falciparum (K1 strain) parasites. 相似文献
880.
Haruo Matsuyama Nobuhiro Itoh Masato Yoshida Masahiko Iyoda 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):475-476
(S)- and (R)-β-amino acid derivatives were synthesized by the asymmetric conjugate addition of ammonia and piperidazine to t-butyl (E)-2-[(R)- and (S)-p-tolylsulfinyl]cinnamates, respectively. 相似文献