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501.
Ion exchange membranes (IEMs) are used in a variety of analytical devices, including suppressors, eluent generators and other components used in ion chromatography. Such membranes are flexible and undergo substantial dimensional changes on hydration. Presently the push to miniaturization continues; a resurgent interest in open tubular ion chromatography requires microscale adaptation of these components. Incorporating IEMs in microscale devices is difficult. Although both macroporous and microporous ion exchange materials have been made for use as chromatographic packing, ion exchange material used as membranes are porous only on a molecular scale. Because such pores have vicinal ion exchange sites, ions of the same charge sign as those of the fixed sites are excluded from the IEMs. Monolithic polymers, including ion exchangers derived therefrom, are presently extensively used. When used in a separation column, such a monolithic structure contains an extensively connected porous network. We show here that by controlling the amount of porogen added during the synthesis of monolithic polymers derived from ethylene dimethacrylate – glycidyl methacrylate, which are converted to an anion exchanger by treatment with trimethylamine, it is possible to obtain rigid ion exchange polymers that behave like IEMs and allow only one charge type of ions to pass through, i.e., are permselective. We demonstrate successful open tubular cation chromatography suppressor performance. 相似文献
502.
Syntheses of the first Cu(NH(3))(2)(FOX)(2) and various Cu(amine)(2)(FOX)(2) (methyl, propyl, and dimethyl amine) complexes were achieved by using metathetical reactions which add a new chapter to the metal chemistry of FOX-7 (1,1-diamino-2,2-dintroethene). The crystal structures of Cu(NH(3))(2)(FOX)(2) and Cu(C(3)H(7)NH(2))(2)(FOX)(2) which show square planar geometry at copper aid in the understanding of the bonding modes in FOX-7 copper complexes which is supported by natural bond orbital (NBO) calculations. Water-free K-FOX was also structured. 相似文献
503.
We report the low-threshold operation of a nanosecond β-BaB2O4 optical parametric oscillator (OPO) pumped by the third harmonic of a Q-switched Nd:YAG laser. Using cylindrical focusing of the pump beam, a threshold pulse energy of 0.5 mJ is obtained at the signal wavelength of 560 nm, which is about sixteen times lower than that of a spherical focusing configuration. The importance of diffraction loss in the design of tightly focused OPOs is discussed in terms of a simple extension of the conventional OPO model. 相似文献
504.
Collective neutrino flavor transformations deep inside a supernova are sensitive to the neutrino mass hierarchy even at extremely small values of theta_(13). Exploiting this effect, we show that comparison of the antineutrino signals from a galactic supernova in two megaton class water Cherenkov detectors, one of which is shadowed by Earth, will enable us to distinguish between the hierarchies if sin(2)theta_(13) < or approximately 10(-5), where long baseline neutrino experiments would be ineffectual. 相似文献
505.
Hinde DJ Thomas RG du Rietz R Diaz-Torres A Dasgupta M Brown ML Evers M Gasques LR Rafiei R Rodriguez MD 《Physical review letters》2008,100(20):202701
Forming the same heavy compound nucleus with different isotopes of the projectile and target elements allows nuclear structure effects in the entrance channel (resulting in static deformation) and in the dinuclear system to be disentangled. Using three isotopes of Ti and W, forming 232Cm, with measurement spanning the capture barrier energies, alignment of the heavy prolate deformed nucleus is shown to be the main reason for the broadening of the mass distribution of the quasifission fragments as the beam energy is reduced. The complex, consistently evolving mass-angle correlations that are observed carry more information than the integrated mass or angular distributions, and should severely test models of quasifission. 相似文献
506.
Narrow-band laser performance of alcohol solutions of pyrromethene 567 (PM567) and rhodamine 6G (RH6G) dye was investigated
using a home-made GIG-configured dye laser, excited by the second-harmonic radiation (at 532 nm) of a pulsed Nd:YAG laser.
Higher laser efficiency was observed with PM567 dye (∼23% peak) in comparison to the commonly used RH6G dye (16.5%), in spite
of much lower fluorescence quantum efficiency of the PM567 (0.83) vis-à-vis RH6G (0.98) dye solutions in ethanol. First principle-based electronic structure calculations were performed on PM567 dye
in the ground (S
0) and excited states (S
1) using density functional theory to elucidate the structure and photophysical properties of the dye. 相似文献