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11.
The ratio of N4+ to N3+ formed in the radiolysis of gaseous nitrogen has been measured to be 4.7 ± 0.4 using a time-resolved atmospheric pressure ionization mass spectrometer. The limit of error has been evaluated from the ion mass discrimination of the apparatus. 相似文献
12.
On-line sample preconcentration by a dynamic pH junction in conjunction with multiplexed capillary electrophoresis (CE) and UV detection represents a sensitive and high-throughput format for future metabolomic research, such as purine analysis. The optimization of purine focusing can be rapidly assessed by systematically altering the sample matrix properties, such as the buffer co-ion, pH and ionic strength using a 96-capillary array format. This method permits focusing of large sample injection volumes, resulting in over a 50-fold improvement in the concentration sensitivity. The limit of detection (S/N = 3) for purine metabolites was less than 8.0 x 10(-8) M under optimum conditions when using UV absorbance. Dynamic pH junction multiplexed CE demonstrated excellent linearity over a hundred-fold concentration range, as well as low inter-capillary precision in terms of normalized migration times and peak areas. The potential for clinically relevant high-throughput analyses of micromolar amounts of purine metabolites in urine was also demonstrated. 相似文献
13.
14.
Takuji Hirahara Takaaki Sugimura Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1970,8(10):2827-2837
Diphenylsulfone (DPSO2) was found to react with an equimolar amount of potassium in tetrahydrofuran (THF), dimethoxyethane (DME), or diglyme (DG) at reflux or an elevated temperature to yield a reddish-black solution, giving an electron spin resonance (ESR) signal. The signal was attributed to the formation of relatively labile DPSO2 anion radical. The apparent effects of solvents on the reactivity of DPSO2 with potassium depended on the polarities and the solvation powers: benzene ? toluene ? dioxane ? tetrahydrofuran < monoglyme < diglyme. The monopotassium complex was found to react further with another molecular amount of the metal to yield a dark blue solution giving no ESR signal. The monopotassium complex initiated the polymerization of acrylonitrile (AN). It did not, however, initiate the polymerization of methyl methacrylate (MMA), styrene (St), or isoprene (IP). The active species of the monopotassium complex that initiated the polymerization of AN was found from analyses of the reaction products and the infrared spectrum of oily oligomer of AN obtained by the complex to be potassium benzenesulfinate. The dipotassium complex was found to initiate the polymerization of MMA, St, IP and AN. The active species of the dipotassium complex that initiated the polymerization of MMA, St, or IP was found from analyses of the reaction products and the infrared spectrum of the oily oligomer of MMA obtained by the complex to be phenyl potassium. 相似文献
15.
Yoshitsugu Kojima Takaaki Matsuoka Norio Sato Hideroh Takahashi 《Journal of polymer science. Part A, Polymer chemistry》1995,33(17):2935-2940
New conjugated oligomers were prepared by reacting phenylacetylene under high pressure of 0.11 to 0.92 GPa at 100–200°C for 0–5 h. The number-average molecular weight M?n, the weight-average molecular weight M?w, and the oligomer yield increased with pressure, tem-perature, and time. The average molecular weight of the oligomer showed the maximum value (M?n: 830, M?w: 2400) under 0.92 GPa, the maximum pressure, where phenylacetylene was oligomerized at a constant temperature. The structure of the oligomer was investigated from ESR, infrared, UV–VIS, field desorption mass (FDMS) spectra, and 13C NMR spec-trum. Analysis of the FDMS spectrum revealed that the molecular weight of the oligomer was multiple of the monomer. 13C NMR spectrum of the oligomer showed the absence of sp-carbon (? C?). We found that the oligomer had a cyclic structure. The cyclic oligomers of pentamer or more were new compounds. © 1995 John Wiley & Sons, Inc. 相似文献
16.
We demonstrate band gap control of CdTe nanocrystals by selective surface modification using alkanethiol molecules. Both absorption and emission wavelengths can be tuned simply by mixing a dispersion of the nanocrystals with alkanethiol at room temperature, resulting in blue shifts in the optical spectra during reaction. The degree of blue shift depends on both the concentration of alkanethiols and the reaction time, thereby providing kinetic control over the emission peak wavelength of the nanocrystals in mild conditions. The observed spectral changes are suggested to be caused by a decrease in the size of the CdTe core through formation of CdTe1-x(SC10)x shells because of specific exchange of Te with alkanethiolates. The results reported herein provide a new band gap engineering scheme for semiconductor nanocrystals and offer opportunities for the design of ligand-stabilized semiconductor nanocrystals with tunable composition and optical properties. 相似文献
17.
We estimated the energy barriers of proton transfers in the systems of (CF3SO3/H/SO3CF3)− and (CF3SO3/H/H2O/SO3CF3)− as models of a water-swollen Nafion membrane by an ab initio density functional quantum calculation method with consideration of the hydration effect. As a result, the proton transfer between the SO sites, which is accompanied by one water molecule, was found to be one of the proton-transfer mechanisms in the water-swollen Nafion membrane; that is, the surface diffusion mechanism was found to be important for the proton transfer in that membrane. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1905–1914, 2004 相似文献
18.
Ryo Satoh Takaaki Goto Seon Hwa Lee Tomoyuki Oe 《Analytical and bioanalytical chemistry》2013,405(25):8001-8010
19.
Yoshihiro Shigemasa Takaaki Ueda Hiroyuki Saimoto 《Journal of carbohydrate chemistry》2013,32(4):669-673
Abstract The formose reactions2 in N,N-dimethylformamide (DMF) catalyzed by 2-(dimethylamino)ethanol and thiamine hydrochloride, have been found to give rise to dihydroxyacetone and DL-glycero-tetrulose selectively at 1.1 M and 3.0 M of formaldehyde concentration, respectively. In our consecutive study on the formose reaction in DMF, it has been fortunately found that the distribution of products is able to be controlled by the amount of water added to the reaction mixture. We describe herein the first example of the favored formation of DL-2-C-hydroxymethyl-3-pentu-lose (GP-191) in the formose reaction using DMF-H2O solvent, and it's isolation and structure elucidation. 相似文献
20.
Prof. Dr. Tsutomu Ishi-i Honoka Tanaka Rihoko Kichise Christopher Davin Takaaki Matsuda Dr. Naoya Aizawa Dr. In Seob Park Prof. Dr. Takuma Yasuda Taisuke Matsumoto 《化学:亚洲杂志》2021,16(15):2136-2145
The regulation of multicolor fluorescence changes in mechanochromic fluorescence (MCF) remains a challenging task. Herein, we report the regulation of MCF using a donor-acceptor structure. Two crystal polymorphs, BTD-pCHO(O) and BTD-pCHO(R) produced by the introduction of formyl groups to an MCF dye, respond to a mechanical stimulus, allowing a three-color fluorescence change. Specifically, the orange-colored fluorescence of the metastable BTD-pCHO(O) polymorph changed to a deep-red color in the amorphous-like state to finally give a red color in the stable BTD-pCHO(R) polymorph. This change occurred by mechanical grinding followed by vapor fuming. The two different crystal packing patterns were selectively regulated by the electronic effect of the introduced functional groups. The two types of selectively formed crystals in BTD(F)-pCHO bearing fluorine atoms, and BTD(OMe)-pCHO bearing methoxy groups, respond to mechanical grinding, allowing for the regulation of multicolor MCL from a three-color change to two different types of two-color changes. 相似文献