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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.
AM Cardoso SM Alexandre CM Barros AJ Correia NM Nibbering 《Rapid communications in mass spectrometry : RCM》1999,13(19):1885-1888
The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
33.
RE Tribble A Azhari HL Clark CA Gagliardi Y-W Lui AM Mukhamedzhanov A Sattaroy X Tang L Trache V Burjan J Cejpek V Kroha S Piskor J Vincour F Carstoiu 《Pramana》1999,53(3):585-594
S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which
provide the normalization of the tail of the overlap function. For example the overlap for 8B → 7Be+p defines the S-factor for 7Be (p, γ)8B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of
the technique, the 16O(3He, d)17F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited
states of 17F. The S-factors for 16O(p, γ)17F calculated from these 17F → 16O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same
technique, the 10B(7Be, 8B)9Be and 14N(7Be, 8B)13C reactions have been used to measure the asymptotic normalization coefficient for 7Be(p, γ)8B. This result provides an indirect determination of S
17(0). 相似文献
34.
Abdessadek Saib 《Mathematische Nachrichten》2013,286(17-18):1863-1885
In this paper a general theory of semi‐classical d‐orthogonal polynomials is developed. We define the semi‐classical linear functionals by means of a distributional equation , where Φ and Ψ are matrix polynomials. Several characterizations for these semi‐classical functionals are given in terms of the corresponding d‐orthogonal polynomials sequence. They involve a quasi‐orthogonality property for their derivatives and some finite‐type relations. 相似文献
35.
S. Saib N. Bouarissa P. Rodríguez-Hernández A. Muñoz 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):435-438
We present a theoretical study of the structural properties, namely
lattice constant, bulk modulus and its pressure derivative of zinc-blende
GaxIn1-xN. The calculations are performed using first-principles
calculations in the framework of the density-functional-theory
within the local density approximation under the virtual
crystal approximation. The computed values are in good
agreement with the available experimental data. The composition dependence
of the studied quantities is examined. Besides, the deviation of the alloy
lattice constant from Vegard's law is evaluated. 相似文献
36.
This paper is devoted to the study of the generalized inverse problem of the left product of a d–dimensional vector form by a polynomial. The objective is to find the regularity conditions of the vector linear form ${\mathcal{V}}$ defined by ${\mathcal{U} = \mathcal{RV}}$ , where ${\mathcal{R}}$ is a d × d matrix polynomial. In such a case, the d–OPS {Q n } n ≥ 0 corresponding to ${\mathcal{V}}$ is d–quasi– orthogonal of order l with respect to ${\mathcal{U}}$ . Secondly, we study the inverse problem: Given a d -OPS P n n ≥ 0 with respect to ${\mathcal{U}}$ , characterize the parameters ${\{a^{(i)}_{n}\}{^{dl}_{i=1}}}$ such that the sequence $${Q_{n+dl} = P_{n+dl} + \sum _{i=1}^{dl} a_{n+dl}^{(i)}P_{n+dl-i},\quad n\geq 0}$$ , is d–orthogonal with respect to some regular vector linear form ${\mathcal{V}}$ . As an immediate consequence, find the explicit relation between ${\mathcal{U}}$ and ${\mathcal{V}}$ . 相似文献
37.
Electronic properties and elastic constants of wurtzite, zinc-blende and rocksalt AlN 总被引:1,自引:0,他引:1
S. Saib 《Journal of Physics and Chemistry of Solids》2006,67(8):1888-1892
Electronic properties and elastic constants of AlN in the wurtzite, zinc-blende and rocksalt structures are investigated using an ab initio pseudopotential method based on the density-functional theory with both the local-density approximation and the generalized gradient approximation for the exchange-correlation functional. The numerically calculated results compare well with the existing experimental data. For elastic constants of rocksalt AlN our results are predictions. 相似文献
38.
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
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.