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1.
In this note we consider asymptotic results for self-intersections of closed geodesics on surfaces for which the angle of the intersection occurs in a given arc. We do this by extending Bonahon's definition of intersection forms for surfaces.
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4.
Michael Sharp 《Analytica chimica acta》1976,85(1):17-30
The primary redox reactions for solid-state ion-selective electrodes prepared from electronically semiconducting salts of 7,7,8,8-tetracyanoquinodimethane (tcnq) can be identified by considering the redox properties of their constituent ions or molecules. Three different processes involving the couples, Mn+/M0, 2tcnqo/(tcnq-)2 and (tcnq-)2/2tcnq2- are possible depending on salt composition. Ionic product values determined by potentiometric and atomic absorption methods are in excellent agreement for several such salts; Ks(K2tcnq2)=5.8±1.2·10-11(pot.), 1.7±1·10-11 (a.a.s.); Ks(Cdtcnq2) = 3.0±0.5·10-9 (pot.), 2.9±0.3·10-9(a.a.s.); Ks(Pbtcnq2) = 1.3±0.3·10-10 (pot.), 0.96±0.2·10-10(a.a.s.); and indicate that the lower activity limit for electrode response is controlled by the solubility of the sensor material itself. Comparisons of predicted and observed standard electrode potentials provide quantitative support for an ion-exchange mechanism of interference. The behaviour of electrodes prepared from Cu2tcnq2 (copper(I)) and Cutcnq2 (copper(II)) is explained on the basis of an interference mechanism and considerations of solid-state equilibria. 相似文献
5.
Derivatization of a variety of peptides by a method known to enhance anhydride formation is demonstrated by mass spectrometry to yield ions that have elemental composition and fragmentation properties identical to [b(n-1) + OH + H]+ ions formed by gas-phase rearrangement and fragmentation. The [b(n-1) + OH + H]+ ions formed by gas-phase rearrangement and fragmentation and the solution-phase [b(n-1) + OH + H]+ ion structural analogs formed by derivatization chemistry show two different forms of dissociation using multiple-collision CAD in a quadrupole ion trap and unimolecular decomposition in a TOF-TOF; one group yields identical product ions as a truncated form of the peptide with a free C-terminal carboxylic acid and fragments at the same activation energy; the other group fragments differently from the truncated peptide, being more resistant to fragmentation than the truncated peptide and yielding primarily the [b(n-2) + OH + H]+ product ion. Nonergodic electron capture dissociation MS/MS suggests that any structural differences between the specific-fragmenting [b(n-1) + OH + H]+ ions and the truncated peptide is at the C-terminus of the peptide. The specific-fragmentation can be readily observed by MS(n) experiments to occur in an iterative fashion, suggesting that the C-terminal structure of the original [b(n-1) + OH + H]+ ion is maintained after subsequent rearrangement and fragmentation events in peptides which fragment specifically. A mechanism for the formation of specific-fragmenting and nonspecific-fragmenting [b(n-1) + OH + H]+ ions is proposed. 相似文献
6.
An improved experimental arrangement for the determination of kinetic data relating to polarographic reductions is described. The significant feature is the constant-temperature reference electrode; its construction and use in this context are described. A comparison is made of the more realistic results obtained by these means, with those obtained with a more conventional cell where the temperature of the reference electrode is varied with that of the working solution. 相似文献
7.
The SHS route is based on the well-known thermite reaction, in which a strongly exothermic reaction can sustain itself and propagate in the form of a combustion wave until the reactants have been completely consumed. The successful application of the method to the synthesis of superconducting ceramics of stoichiometry RBa2Cu3Oy (R=Y, Er, Yb) is reported. The 123 phase was obtained when pellets of R2O3, BaO2 and Cu metal in the correct proportions were dropped into a heater held at 800°C in an oxygen atmosphere and left there for only 10 minutes. Thermal methods (DSC and DTA) are excellent techniques with which to investigate the dependence of the reaction on heating rate, atmosphere and starting composition. 相似文献
8.
A miniaturized liquid chromatographic system with electrochemical detection (LC-ED) was developed and applied to the analysis of dopamine and its metabolites in dialysate samples collected from the rat brain in vivo. An existing LC-ED system was down-scaled using a 1 mm I.D. small-bore column operated at a reduced flow-rate and with an injection volume of 1 microliter. With the small-bore system the limit of detection for dopamine of ca. 0.06 pg was almost 50 times less than with the conventional system, which represents a two-fold improvement in concentration sensitivity. Miniaturization was accomplished with negligible loss in resolution by using a conventional commercial amperometric detector with minor modifications. The results indicate that a number of useful advantages could be realized by the combination of this small-bore LC-ED system and the in vivo brain dialysis method. 相似文献
9.
The effect of sample mass, heating rate and partial pressure of carbon dioxide on TG, DTG and DTA curves for the decomposition of some common carbonates has been investigated. These variables gave a marked effect, similar in magnitude for both DTG and DTA. The effect of sample mass, or depth of undiluted sample, is shown to be due to an increase in the partial pressure of carbon dioxide within the reacting powder. This effect is most pronounced in nitrogen but is much reduced in carbon dioxide. Inert diluents have little effect on the curves since they do not increase the partial pressure of CO2. The first stage of the decomposition of dolomite (CaMg(CO3)2) varies with increasing partial pressure of carbon dioxide in an anomalous manner and hence the effects of these procedural variables (except heating rate) are not similar to those observed for magnesite (MgCO3) and calcite (CaCO3). The second stage is, however, strongly dependent on these variables and behaves in a manner that would be predicted for a sample of calcite diluted with magnesite. 相似文献
10.
N. Kukhtarev G. Dovgalenko J. Shultz G. Salamo E. J. Sharp B. A. Wechsler M. B. Klein 《Applied Physics A: Materials Science & Processing》1993,56(4):303-305
We report the first measurement of the photo-galvanic circular current antisymmetric tensor component in BaTiO3: Co. The measurement gives a value of this coefficient, for extraordinary beam amplification, of 4×10–9 A/W using a nonstationary measurement technique at a wavelength of 0.632 m.Professor N. Kukhtarev is on leave from the Institute of Physics in the Ukraine and is supported by the NSFDr. G. Dovgalenko is on leave from the IRPA Rotor-Control research laboratory of the Ukraine and is supported by the University of Arkansas 相似文献