排序方式: 共有52条查询结果,搜索用时 453 毫秒
31.
AM Johnston CM Scrimgeour MO Henry LL Handley 《Rapid communications in mass spectrometry : RCM》1999,13(14):1531-1534
The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Rubens R Santos Jr Alexandrina Sartori Deison S Lima Patrícia RM Souza Arlete AM Coelho-Castelo Vania LD Bonato Célio L Silva 《Journal of immune based therapies and vaccines》2009,7(1):4-12
Background
Our group previously demonstrated that a DNA plasmid encoding the mycobacterial 65-kDa heat shock protein (DNA-HSP65) displayed prophylactic and therapeutic effect in a mice model for tuberculosis. This protection was attributed to induction of a strong cellular immunity against HSP65. As specific immunity to HSP60 family has been detected in arthritis, multiple sclerosis and diabetes, the vaccination procedure with DNA-HSP65 could induce a cross-reactive immune response that could trigger or worsen these autoimmune diseases. 相似文献33.
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Inelastic scattering induces dephasing in mesoscopic systems. An analysis of previous models to simulate inelastic scattering
in such systems is presented and a relatively new model based on wave attenuation is introduced. The problem of Aharonov-Bohm
(AB) oscillations in conductance of a mesoscopic ring is studied. We show that the conductance is symmetric under flux reversal
and the visibility of AB oscillations decays to zero as a function of the incoherence parameter, signaling dephasing. Further
the wave attenuation model is applied to a fundamental problem in quantum mechanics, that of the conditional (reflection/transmission)
times spent in a given region of space by a quantum particle before scattering off from that region. 相似文献
35.
Anna Skwierawska Ewa Paluszkiewicz Monika Przyborowska Tadeusz Ossowski 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):21-26
New derivatives of 1,4,7,10-tetraazacyclododecanes have been synthesized. The coordination properties toward Co2+ of these ligands have been studied by means of spectroscopic methods. The stability constants of cobalt complexes with ligand L-1 and L-2were determined. Unusual complexes with a 2:1 (L:Co2+) stoichiometry have been found. 相似文献
36.
Baumann C Cintora MA Eichler M Lifante E Cooke M Przyborowska A Halket JM 《Rapid communications in mass spectrometry : RCM》2000,14(5):349-356
A searchable library of MS/MS spectra obtained using a quadrupole ion trap mass spectrometer and electrospray or atmospheric pressure chemical ionization is presented. The application of wideband excitation (activation) and normalized collision energy leads to highly reproducible mass spectra which are searched using the NIST algorithm. Flow injection and LC/MS/MS applications of this powerful technique in the biomedical (diastereoisomeric steroids, morphine glucuronides, isovalerylcarnitine) and environmental (pirimicarb and desmethyl-pirimicarb) areas are described. 相似文献
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Suppose that a consistent one-step numerical method of orderr is applied to a smooth system of ordinary differential equations.Given any integer m 1, the method may be shown to be of orderr + m as an approximation to a certain modified equation. Ifthe method and the system have a particular qualitative propertythen it is important to determine whether the modified equationsinherit this property. In this article, a technique is introducedfor proving that the modified equations inherit qualitativeproperties from the method and the underlying system. The techniqueuses a straightforward contradiction argument applicable toarbitrary one-step methods and does not rely on the detailedstructure of associated power series expansions. Hence the conclusionsapply, but are not restricted, to the case of Runge-Kutte methods.The new approach unifies and extends results of this type thathave been derived by other means: results are presented forintegral preservation, reversibility, inheritance of fixed points.Hamiltonian problems and volume preservation. The techniquealso applies when the system has an integral that the methodpreserves not exactly, but to order greater than r. Finally,a negative result is obtained by considering a gradient systemand gradient numerical method possessing a global property thatis not shared by the associated modified equations. 相似文献
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