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81.
An automated colorimetric procedure was developed for the determination of inorganic carbon in the range 0.3–40.0 mg l-1, and then modified to handle concentrations in the range 0.01–2.00 mg l-1. The procedure entailed conversion of carbon dioxide equilibria products to carbon dioxide. By gas dialysis, a portion of this gas was dissolved in a weakly buffered alkaline phenolphthalein solution, and inorganic carbon was determined by measuring the loss in color of the indicator. Calibrations were linear within 1% full scale. When surface water samples were processed by the subject and by alternative methods, the colorimetric carbon results were lower by approximately 1% full scale. 相似文献
82.
Thomas A. Elwood Kenneth H. Dudley Joan M. Tesarek Peter F. Rogerson Maurice M. Bursey 《Journal of mass spectrometry : JMS》1970,3(7):841-861
Several alkylhydroxynaphthoquinones and chemically related cyclic compounds were subjected to mass spectrometric investigation. Fragmentation pathways were elucidated by use of metastable ions, relative intensities of normal ions and accurate mass measurement. In these series, differences in the spectra of 1,2- and 1,4-naphthoquinones are slight. Evidence for ring expansion in ions from furans is suggested. 相似文献
83.
84.
85.
[reaction: see text] Crystal structures of the one-to-one co-crystals of C(60).perchloroazatriquinacene and C(70).perchloroazatriquinacene show that the rigid, chalice-like azatriquinacene packs between completely ordered fullerene molecules with multiple, close Cl...fullerene contacts. 相似文献
86.
In this paper we compute the line integral of a complex function on a rectifiable cycle homologous to zero obtaining a Green’s
formula with multiplicities that involves the
of the function and the index of the cycle. We consider this formula in several settings and we obtain a sharp version in
terms of the Lebesgue integrability properties of the partial derivatives of the function. This result depends on the proven
fact that the index of a rectifiable cycle is square integrable with respect to the planar Lebesgue measure.
The work of both authors is partially supported by grants 2000SGR-00059, 2001SGR 00172 of Generalitat de Catalunya and BFM
2002-04072-C02-02 of Ministerio de Ciencia y Tecnologia 相似文献
87.
Sol-Gel Synthesis of Transparent Alumina Gel and Pure Gamma Alumina by Urea Hydrolysis of Aluminum Nitrate 总被引:2,自引:0,他引:2
Maria I. F. Macêdo Carla C. Osawa Celso A. Bertran 《Journal of Sol-Gel Science and Technology》2004,30(3):135-140
-Alumina was synthesized by a sol-gel method with the aluminum ion hydrolysis control performed by urea. The initial saturated Al3+/urea solution presented urea coordinated with the aluminum ion, as shown in the 13C NMR and 27Al NMR spectra and longitudinal relaxation times, T
1, from the latter. The substitution of water molecules in the Al3+ coordination shell by urea controlled the hydrolysis process and provided an extensive nucleation during the initial steps of the aluminum hydroxide formation due to urea thermolysis at 90°C. The resulting sol, composed of Al(OH)3 nanoparticles, coalesced and became a transparent gel permeated by a solution of urea and the polycation ion [Al13O4(OH)24(H2O)12]7+. The freshly prepared gel was transformed, under heating at 300°C, directly to -alumina, characterized by FTIR, 27Al-MAS-NMR and SBET techniques, without - or -phases, as a consequence of the high degree of homogeneity of the -alumina precursor. 相似文献
88.
We provide an asymptotic formula for the number of labelled essential DAGs an and show that limnan/an=c, where an is the number of labelled DAGs and c13.65, which is interesting in the field of Bayesian networks. Furthermore, we present an asymptotic formula for the number of labelled chain graphs.Acknowledgment. I would like to thank Prof. Peter Grabner for his support and very helpful discussions, which where constitutive for this article. I am also thankful to the referees for their comments.This Research was supported by the Austrian Science Fund (FWF), START-Project Y96-MATFinal version received: January 28, 2004 相似文献
89.
Both hydrophobic and hydrophilic room-temperature ionic liquids can be separated from aqueous solutions with relatively low-pressure gaseous carbon dioxide. 相似文献
90.
Konar S Zangrando E Drew MG Mallah T Ribas J Chaudhuri NR 《Inorganic chemistry》2003,42(19):5966-5973
Three new metal-organic polymeric complexes, [Fe(N(3))(2)(bpp)(2)] (1), [Fe(N(3))(2)(bpe)] (2), and [Fe(N(3))(2)(phen)] (3) [bpp = (1,3-bis(4-pyridyl)-propane), bpe = (1,2-bis(4-pyridyl)-ethane), phen = 1,10-phenanthroline], have been synthesized and characterized by single-crystal X-ray diffraction studies and low-temperature magnetic measurements in the range 300-2 K. Complexes 1 and 2 crystallize in the monoclinic system, space group C2/c, with the following cell parameters: a = 19.355(4) A, b = 7.076(2) A, c = 22.549(4) A, beta = 119.50(3) degrees, Z = 4, and a = 10.007(14) A, b = 13.789(18) A, c = 10.377(14) A, beta = 103.50(1) degrees, Z = 4, respectively. Complex 3 crystallizes in the triclinic system, space group P(-)1, with a = 7.155(12) A, b = 10.066(14) A, c = 10.508(14) A, alpha = 109.57(1) degrees, beta = 104.57(1) degrees, gamma = 105.10(1) degrees, and Z = 2. All coordination polymers exhibit octahedral Fe(II) nodes. The structural determination of 1 reveals a parallel interpenetrated structure of 2D layers of (4,4) topology, formed by Fe(II) nodes linked through bpp ligands, while mono-coordinated azide anions are pendant from the corrugated sheet. Complex 2 has a 2D arrangement constructed through 1D double end-to-end azide bridged iron(II) chains interconnected through bpe ligands. Complex 3 shows a polymeric arrangement where the metal ions are interlinked through pairs of end-on and end-to-end azide ligands exhibiting a zigzag arrangement of metals (Fe-Fe-Fe angle of 111.18 degrees) and an intermetallic separation of 3.347 A (through the EO azide) and of 5.229 A (EE azide). Variable-temperature magnetic susceptibility data suggest that there is no magnetic interaction between the metal centers in 1, whereas in 2 there is an antiferromagnetic interaction through the end-to-end azide bridge. Complex 3 shows ferro- as well as anti-ferromagnetic interactions between the metal centers generated through the alternating end-on and end-to-end azide bridges. Complex 1 has been modeled using the D parameter (considering distorted octahedral Fe(II) geometry and with any possible J value equal to zero) and complex 2 has been modeled as a one-dimensional system with classical and/or quantum spin where we have used two possible full diagonalization processes: without and with the D parameter, considering the important distortions of the Fe(II) ions. For complex 3, the alternating coupling model impedes a mathematical solution for the modeling as classical spins. With quantum spin, the modeling has been made as in 2. 相似文献