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1.
N. Ahmad C. Nanjundayya W. G. Chace M. A. Ssobolew M. M. Tschilikin A. T. Iwanowa F. Kalmanowitsch A. Kolotyrewa C. F. Cross E. J. Bevan A. Eavenson J. W. Creely J. H. Skinkle O. Viertel A. J. Hall W. N. Udalskaja D. A. Clibbens A. H. Little Karin Schulze S. M. Edelstein E. Lindemann F. Schütz W. Klauditz P. Winterfeld F. H. Guernsay L. T. Howells F. Schroeder R. Finlay G. Hasse Niederhauser H. Ris R. D. Nutting W. Lesnianski F. Fabrowicz und Coch 《Fresenius' Journal of Analytical Chemistry》1938,115(1-2):51-57
Ohne Zusammenfassung 相似文献
2.
Transition metal heteropolyanions have been used to catalyze a variety of organic oxidations but have not previously been used for O2 generation, despite sharing some structural similarities with dioxoruthenium water-oxidation catalysts. In this study, we report that the di-Ru-substituted polyoxometalate (POM) [Ru2Zn2(H2O)2(ZnW9O34)2]14- can be used to catalyze the electrochemical generation of O2. By comparing the behavior of this compound to that observed using a mono-Ru-substituted POM catalyst, we show that adjacent Ru sites are necessary to observe O2 generation. These observations suggest a reaction pathway involving two Ru-bound oxygen species combining to form O2 and are consistent with the accepted mechanism of electrochemical oxygen evolution. Finally, analysis of the observed electrode kinetics yields a Tafel slope of roughly 120 mV, which is similar to values reported previously for perovskite anodes. 相似文献
3.
A.J. Leadbetter R.M. Richardson B.A. Dasannacharya W.S. Howells 《Chemical physics letters》1976,39(3):501-504
Incoherent quasi-elastic neutron scattering spectra have been measured down to low scattering vectors (Q >) 0.14 Å?1) on magnetically aligned specimens of the nematic and smectic A phases of EABAC. Data were obtained for Q || n and Q⊥n where n denotes the direction of the unique axis) giving the diffusion coefficients D|| and D⊥ for the two phases as follows (in units of 10?7 cm2 s?1); nematic: D|| = 15.8 ± 2.0, D⊥ = 12.3 ± 0.8; smectic A: D|| = 4.3 ± 0.4, D⊥ = 4.9 ± 0.8. The anisotropy is reversed between the phases and the molecules are more mobile in the nematic phase as expected. In the smectic A experiments with Q || n an apparent inconsistency between low and high Q results is interpreted as evidence for the existence of some slow motion other than translational diffusion which requires further investigation. Preliminary measurements were made to explore the application of the “fixed window” method for determining the temperature dependence of the diffusion coefficients. 相似文献
4.
The inverse addition of trichloro-2-thienyl-lithium to hexafluorobenzene in THF or ether has given 1,4-bis(trichloro-2-thienyl) tetrafluorobenzene in addition to the tetrakis(trichloro-2-thienyl)difluorobenzene. n-Butyl-lithium with hexafluorobenzene gave mono, bis tris and tetrakis compounds whereas t-BuLi afforded only 1,4-bis(t-butyl)tetrafluorobenzene in excellent yield. Other organolithium and organomagnesium reagents gave the expected products. IR, 19F NMR and UV spectral data are presented for the several new compounds. 相似文献
5.
The use of three C18 sorbents in matrix solid phase dispersion (MSPD) for the determination of clenbuterol in bovine liver fortified at 5 ng g-1 is described. MSPD grade C18 sorbents give rise to more efficient blending and packing of the material for subsequent washing and analyte elution in comparison with a non-MSPD grade C18 sorbent. Following enzymatic deconjugation of the liver extracts, radioimmunoassay is used as the method of determination. The mean recovery of clenbuterol with all sorbents is comparable and within the range 86-96% in two intra-assay studies (n = 3). The liver extracts in each case are highly coloured. The variation in recovery is observed to be lowest with MSPD grade C18 (end-capped). This sorbent was used in further studies to evaluate the use of solid phase extraction (SPE), post MSPD, with normal phase aminopropyl or mixed mode cation exchange columns for extract purification. The mean recovery of clenbuterol (n = 4, inter-assay study) following MSPD and normal phase SPE clean-up was 95 +/- 15% and 89 +/- 9% at fortification levels of 1 and 2.5 ng g-1, respectively. 相似文献
6.
A series of neutron diffraction experiments has been carried out on solutions of NiCl2, NaCl and BaCl2 in heavy water. Both the concentration of the solute and the degree of isotopic enrichment were varied in order to investigate whether the multiple-pattern method, which has been used previously to determine the partial structure factors for simple liquids, can be applied to aqueous solutions. It is concluded that the multiple-pattern method is feasible. Some general comments on the structural information contained in the single-pattern data are made. 相似文献
7.
Swenson J Schwartz GA Bergman R Howells WS 《The European physical journal. E, Soft matter》2003,12(1):179-183
The dynamics of propylene glycol (PG) and its oligomers 7-PG and PPG, with
(about 70 monomers), confined in a Na-vermiculite clay have been investigated by quasi-elastic neutron scattering and dielectric spectroscopy. The liquids are confined to a single molecular layer between the clay platelets, thus giving a true 2D liquid. The results show that the average relaxation time
, deduced from neutron scattering at a momentum transfer Q of about
, is in perfect agreement with the dielectric
-relaxation time, although neutron scattering does not only probe the main (
-) relaxation, but all motions of hydrogens on the experimental time scale. At room temperature
is proportional to Q
2, indicating that the relaxations are mainly due to ordinary translational diffusion. The most unexpected finding is that
(or the dielectric
-relaxation time) is almost unaffected by the 2D confinement, in contrast to the dielectrically active normal mode of PPG which is substantially slower in the confinement. Only the 7-mer has a significantly slower segmental translational diffusion in the clay. The results suggest that the interactions to the clay surfaces are weak and that the present 2D confinement has a very small influence on the time scale of all our observed relaxation processes, except the normal-mode relaxation.Received: 1 January 2003, Published online: 8 October 2003PACS:
61.25.Em Molecular liquids - 68.35.Ja Surface and interface dynamics and vibrations - 61.12.-q Neutron diffraction and scattering 相似文献
8.
9.
Background
Tone languages such as Thai and Mandarin Chinese use differences in fundamental frequency (F0, pitch) to distinguish lexical meaning. Previous behavioral studies have shown that native speakers of a non-tone language have difficulty discriminating among tone contrasts and are sensitive to different F0 dimensions than speakers of a tone language. The aim of the present ERP study was to investigate the effect of language background and training on the non-attentive processing of lexical tones. EEG was recorded from 12 adult native speakers of Mandarin Chinese, 12 native speakers of American English, and 11 Thai speakers while they were watching a movie and were presented with multiple tokens of low-falling, mid-level and high-rising Thai lexical tones. High-rising or low-falling tokens were presented as deviants among mid-level standard tokens, and vice versa. EEG data and data from a behavioral discrimination task were collected before and after a two-day perceptual categorization training task.Results
Behavioral discrimination improved after training in both the Chinese and the English groups. Low-falling tone deviants versus standards elicited a mismatch negativity (MMN) in all language groups. Before, but not after training, the English speakers showed a larger MMN compared to the Chinese, even though English speakers performed worst in the behavioral tasks. The MMN was followed by a late negativity, which became smaller with improved discrimination. The High-rising deviants versus standards elicited a late negativity, which was left-lateralized only in the English and Chinese groups.Conclusion
Results showed that native speakers of English, Chinese and Thai recruited largely similar mechanisms when non-attentively processing Thai lexical tones. However, native Thai speakers differed from the Chinese and English speakers with respect to the processing of late F0 contour differences (high-rising versus mid-level tones). In addition, native speakers of a non-tone language (English) were initially more sensitive to F0 onset differences (low-falling versus mid-level contrast), which was suppressed as a result of training. This result converges with results from previous behavioral studies and supports the view that attentive as well as non-attentive processing of F0 contrasts is affected by language background, but is malleable even in adult learners. 相似文献10.
RD Harris WS Baker Van Stipdonk MJ RM Crooks EA Schweikert 《Rapid communications in mass spectrometry : RCM》1999,13(14):1374-1380
A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. 相似文献