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991.
A survey is reported on the use of additives in organic elemental analysis of compounds containing functional groups that
may compromise the combustion process. 28 substances containing the following functional groups were selected: organic fluorine,
hexafluorophosphate, tetrafluoroborate, tetraphenylborate, sulfonate, phosphine, nitrile, carbide, organometallic. Six additives
(powdered silver, silver tungstate with magnesium oxide, silica oxide, tungsten (VI) oxide with magnesium oxide, powdered
tin, cerium (IV) oxide) in various sample:additive ratios were assayed. Silver tungstate with magnesium oxide (mixture 1:1,
w/w) turned out to be most efficient for the analysis of nitrogen, carbon, hydrogen and sulfur for almost all the compounds
assayed.
Author for correspondence.
Received August 2, 2002; accepted December 12, 2002
Published online May 19, 2003 相似文献
992.
We study a continuous time growth process on (d?1) associated to the following interacting particle system: initially there is only one simple symmetric continuous time random walk of total jump rate one located at the origin; then, whenever a random walk visits a site still unvisited by any other random walk, it creates a new independent random walk starting from that site. Let us call Pd the law of such a process and S0d(t) the set of sites, visited by all walks by time t. We prove that there exists a bounded, non-empty, convex set , such that for every ε>0, Pd-a.s. eventually in t, the set Sd0(t) is within an ε neighborhood of the set [Cdt], where for we define . Moreover, for d large enough, the set Cd is not a ball under the Euclidean norm. We also show that the empirical density of particles within Sd0(t) converges weakly to a product Poisson measure of parameter one. To cite this article: A.F. Ram??rez, V. Sidoravicius, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 821–826. 相似文献
993.
994.
Knight-shift data have been obtained for a series of nonstoichiometric VSx phases with the MnP and NiAs structure types. The data demonstrate that the change in symmetry is accompanied by an abrupt change in the Knight shift indicating that the symmetry change is accompanied by a change in the character of the conduction electrons. 相似文献
995.
Alejandro Illanes 《Proceedings of the American Mathematical Society》2002,130(7):2179-2182
A topological space is said to be -contractible provided that there exists a continuous onto function such that is homotopic to a constant function. Answering a question by Sam B. Nadler, Jr., in this paper we construct a metric continuum such that its hyperspace of subcontinua is not -contractible.
996.
We report on the "molecular wiring" efficiency of glucose oxidase in organized self-assembled nanostructures comprised of enzyme layers alternating with layers of an osmium-derivatized poly(allylamine) cationic polyelectrolyte, acting as redox relays. Varying the relative position of the active enzyme layer in nanostructures alternating active enzyme and inactive apoenzyme we have demonstrated that the specific rate of bimolecular FADH(2) oxidation ("wiring efficiency") is limited by the diffusion-like electron hopping mechanism in the multilayers. 相似文献
997.
998.
Solano-Peralta A Sosa-Torres ME Flores-Alamo M El-Mkami H Smith GM Toscano RA Nakamura T 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2444-2449
For the first time, HF-EPR (94.5 GHz) spectroscopy has been used to determine crystal field parameters in chromium(III) coordination compounds. The large zero-field splitting parameters of the dark-green photochromic trans-RSSR-[CrCl(2)(cyclam)](2)ZnCl(4), 1, the red-purple trans-RSSR-[CrCl(2)(cyclam)]Cl, 2, and the red-purple trans-RSSR-[CrCl(2)(cyclam)]Cl.4H(2)O.0.5HCl, 3, where cyclam = 1,4,8,11-tetraazacyclotetradecane, have been obtained. A full analysis of EPR spectra at 94.5 GHz of diluted complexes 1, 2 and 3 at 300 K revealed that they are extremely sensitive to D and E values. The rhombic distortion was precisely determined for each compound. For 1, g= 2.01, D=-0.305 cm(-1), E= 0.041 cm(-1) and lambda=|E/D|= 0.1396; for 2, g= 2.01; D=-0.348 cm(-1), E= 0.042 cm(-1) and lambda=|E/D|= 0.1206 and for 3, g= 1.99, D=-0.320 cm(-1), E= 0.041 cm(-1) and ambda=|E/D|= 0.1281. The EPR study at 94.5 GHz at 10 K allowed us to confirm the sign of the D value for all compounds. These data indicate that at room temperature the crystal field is mainly rhombic and as the temperature decreases, the rhombicity of the D tensor increases slightly. These found differences between 1, 2 and 3 allowed us to establish the importance of the intermolecular interactions in the solid state due to different hydrogen bonding networks in their crystalline arrangement. 相似文献
999.
[reaction: see text] A [5C+2C] oxidopyrylium-cyclopropenone acetal cycloaddition followed by ring opening of the cyclopropane unit of the resulting adduct leads to highly substituted 1,5-oxa-bridged cyclooctenes containing up to four stereocenters. The protocol formally constitutes a [5C+3C] annulation process. 相似文献
1000.
Joan Feigenbaum John Hershberger Alejandro A. Schäffer 《Discrete Applied Mathematics》1985,12(2):123-138
We consider the computational complexity of recognizinf concerned cartesian product graphs. Sabidussi gives a non-algorithmic proof that the cartesian factorization is unique. He uses a tower of successively coarser equivalence relations on the edge set in which each prime factor of the graph is identified with an equivalence class in the coarsest of the relations. We first explore the structure and size of the relation at the base of the tower. Then we give a polynomial-time algorithm to compute the relations and to construct the prime factors of any connected graph. The bounds on the size of the relations are crucial to the runtime analysis of our algorithm. 相似文献