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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
32.
A. Blondel M. Bœge E. Bravin P. Bright-Thomas T. Camporesi B. Dehning M. Heemskerk M. Hildreth M. Koratzinos E. Lançon G. Mugnai A. Müller E. Peschardt M. Placidi N. Qi G. Quast P. Renton F. Sonnemann E. Torrence A. Weber P.S. Wells J. Wenninger G. Wilkinson 《The European Physical Journal C - Particles and Fields》1999,11(4):573-585
Knowledge of the centre-of-mass energy at LEP2 is of primary importance to set the absolute energy scale for the measurement
of the W-boson mass. The beam energy above 80 GeV is derived from continuous measurements of the magnetic bending field by
16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the
beam energy is calibrated against precise measurements of the average beam energy between 41 and 55 GeV made using the resonant
depolarisation technique. The linearity of the relationship is tested by comparing the fields measured by the probes with
the total bending field measured by a flux loop. This test results in the largest contribution to the systematic uncertainty.
Several further corrections are applied to derive the centre-of-mass energies at each interaction point. In addition, the
centre-of-mass energy spread is evaluated. The beam energy has been determined with a precision of 25 MeV for the data taken
in 1997, corresponding to a relative precision of . This is small in comparison to the present uncertainty on the W mass measurement at LEP. However, the ultimate statistical
precision on the W mass with the full LEP2 data sample should be around 25 MeV, and a smaller uncertainty on the beam energy
is desirable. Prospects for improvements are outlined.
Received: 14 December 1998 / Published online: 3 November 1999 相似文献
33.
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34.
35.
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
36.
Starting from the 1974 Saclay phase-shift analysis, we construct π+ p continuum ambiguities that leave unchanged the total cross section, the differential cross section, and the polarization. We find that most of the resonant structures are stable, but that alternative solutions are possible that lack the second S31 or the G39 resonances. The second P33 resonance may be moved considerably, but not killed, while the mass and width of the three-star P31 resonance are also subject to appreciable changes. We suggest that disagreements between different groups concerning the existence of weak resonances, or concerning the masses and widths of stronger ones, may be caused by the existence of the continuum ambiguity. 相似文献
37.
For acetylene the molecular g-value was found to be positive, in contradiction with the result reported in literature. The technique used is based upon the occurrence of a transverse heat flow in a gas, due to a magnetic field. 相似文献
38.
39.
Much is known about the connection between the growth and decayof subharmonic functions. The results indicate that there isa general principle: asubharmonic function cannot decay toofast relative to its growth.Three theorems are provedwhich, together with work previously published elsewhere, givea fairly complete account of how this principle works out fora subharmonic function having extremal decay along a ray. 1991Mathematics Subject Classification: 30D20, 31A05. 相似文献
40.