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71.
Joan Orobitg Carlos Pé rez 《Transactions of the American Mathematical Society》2002,354(5):2013-2033
We study an analogue of the classical theory of weights in without assuming that the underlying measure is doubling. Then, we obtain weighted norm inequalities for the (centered) Hardy-Littlewood maximal function and corresponding weighted estimates for nonclassical Calderón-Zygmund operators. We also consider commutators of those Calderón- Zygmund operators with bounded mean oscillation functions (), extending the main result from R. Coifman, R. Rochberg, and G. Weiss, Factorization theorems for Hardy spaces in several variables, Ann. of Math. 103 (1976), 611-635. Finally, we study self-improving properties of Poincaré-B.M.O. type inequalities within this context; more precisely, we show that if is a locally integrable function satisfying for all cubes , then it is possible to deduce a higher integrability result for , assuming a certain simple geometric condition on the functional . 相似文献
72.
Tercero J Diaz C Ribas J Mahía J Maestro M 《Chemical communications (Cambridge, England)》2002,(4):364-365
The new heterodinuclear complex [Cu(Me2oxpn)Ni(NO2)(tmen)](ClO4), that exhibits strong antiferromagnetic intramolecular coupling between CuII and NiII ions (ferrimagnetic behavior), shows ferromagnetic ordering at low temperature, due likely to a small canting phenomenon; it is one of the very few compounds made from isolated molecules that lead to cooperative magnetic behavior. 相似文献
73.
Spore photoproduct (SP) lyase, which catalyzes the direct reversal of SP (5-thyminyl-5,6-dihydrothymine) to thymine monomers, is the only identified nonphotoactivatable pyrimidine dimer lyase. Unlike DNA photolyase, SP lyase does not contain a flavin cofactor and does not require light for activation. Instead, preliminary studies point to the presence of an iron-sulfur cluster in SP lyase and the requirement for S-adenosylmethionine (AdoMet) for catalytic activity, suggesting that SP lyase belongs to the growing group of iron-sulfur cluster and AdoMet-dependent radical enzymes. Here we provide evidence for the role of AdoMet as a reversible deoxyadenosyl radical generator, which initiates repair by hydrogen atom abstraction from C-6 of SP. Reaction of 6-(3)H-SP, but not methyl-(3)H-SP, with SP lyase and AdoMet results in transfer of (3)H to AdoMet, while no tritiated 5'-deoxyadenosine is observed. When 5'-tritiated AdoMet is used in the reaction with unlabeled SP, transfer of (3)H into the repaired thymine monomers is observed. These results point to the reversible generation of a 5'-deoxyadenosyl radical intermediate, which reacts directly with the DNA lesion to initiate a radical-mediated beta-scission. We also demonstrate that AdoMet is a catalytic cofactor that is not consumed during turnover. Together, these results support a novel radical-based mechanism for the repair of UV-induced DNA damage. 相似文献
74.
75.
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
76.
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
77.
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79.
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
80.
This paper describes a flow-injection (FI) method for the simultaneous determination of aniline and cyclohexylamine impurities in cyclamate products. The method consists of the derivatization of amines with 1,2-naphthoquinone-4-sulfonate under selective and non-selective conditions. Here, the selectivity is achieved by working at 20 degree C, at which only aniline reacts, whilst higher temperatures (80 degree C) lead to a non-selective reaction of the two analytes. The FI manifold is composed of two flow cells for the spectrophotometric detection of derivatives at 480 nm. Experimental conditions have been optimized by factorial design and multicriteria making approach. Quantification is accomplished by differential analysis of the analyte contributions in the double peaks generated when the sample reaches cell 1 and cell 2. Results obtained with the proposed method are in satisfactory agreement with those provided by the standard method for the analysis of cyclamate samples. 相似文献