Chemometric approach to evaluate the parameters affecting electrospray: application of a statistical design of experiments for the study of arginine ionization

The effects of different experimental parameters on arginine electrospray ionization have been investigated with response surface modelling design. This chemometric technique allows a study of the effects of selected experimental variables and their interactions on the response of an experiment by performing a limited number of analyses. Six variables were studied: methanol content in the liquid phase, formic acid concentration, electrospray voltage, orifice voltage, mobile phase flow rate, and sheath gas flow rate. Signal abundance and signal-to-noise ratio of the protonated molecule and the protonated dimer were measured from the electrospray mass spectra and these four responses were tested by the design. The factor that exhibits the greatest influence on MH+ abundance is shown to be the liquid flow rate whereas the formation of protonated dimer is mainly controlled by the percentage of methanol in the mobile phase. A strong synergic effect of methanol content and formic acid concentration in the liquid has also been demonstrated in the study of noise level. Moreover, the capabilities of the multicriteria optimization method have been demonstrated through a successful prediction of a set of optimal experimental conditions.     

From Multifractal Measures to Multifractal Wavelet Series

Given a positive locally finite Borel measure μ on R, a natural way to construct multifractal wavelet series is to set , where . Indeed, under suitable conditions, it is shown that the function F_μ inherits the multifractal properties of μ. The transposition of multifractal properties works with many classes of statistically selfsimilar multifractal measures, enlarging the class of processes which have self-similarity properties and controlled multifractal behaviors. Several perturbations of the wavelet coefficients and their impact on the multifractal nature of F_μ are studied. As an application, multifractal Gaussian processes associated with F_μ are created. We obtain results for the multifractal spectrum of the so-called W-cascades introduced by Arnéodo et al.     

A lower bound for the distance k-domination number of trees

A subset D of vertices of a graph G = (V, E) is a distance k-dominating set for G if the distance between every vertex of V ? D and D is at most k. The minimum size of a distance k-dominating set of G is called the distance k-domination number γ_k(G) of G. In this paper we prove that (2k + 1)γ_k(T) ≥ ¦V¦ + 2k ? kn₁ for each tree T = (V, E) with n₁ leafs, and we characterize the class of trees that satisfy the equality (2k + 1)γ_k(T) = ¦V¦ + 2k ? kn₁. Our results generalize those of Lemanska [4] for k = 1 and of Cyman, Lemanska and Raczek [1] for k = 2.     

Oxygen inducedK-shell ionization of selected elements from sulphur to bromine

K-shell X-ray production cross sections for oxygen ions on thin solid targets of 13 selected elements with atomic numbers between 16 and 35 were measured by a Si(Li) detector at incident ion energies from 7 to 24 MeV. Ionization cross sections are compared with calculations assuming Coulomb-ionization. Best agreement is found with theoretical cross sections that include corrections for binding energy and Coulomb deflection effects. Energy shifts ofK _α andK _β X-rays andK _α /K _β intensity ratios were also measured and are used to deduce information about outer shell ionization.     

Forward K1+ (892) production in K+p → π+Ks0p at 12.7 GeV/c

We have measured 618 K⁺p → π⁺K_S⁰p events at 12.7 GeV/c incident lab momentum, mass range 790 ? m_π⁺Ks⁰ ? 990 MeV and t range 0.01 ? ?t ? 0.60 (GeV/c)². The π⁺K_S⁰ mass spectrum is dominated by the K¹⁺ (892) resonance and a Breit-Wigner fit yields a mass m = 893.5 ± 1.1 MeV and a width Γ = 33.2 ± 4.1 MeV which is much narrower than measured hitherto. The t distribution of K¹⁺ (892) events shows a dip in the forward direction and an exponential fall off thereafter, consistent with dominance of helicity flip amplitudes. The spin density matrix is almost saturated by ρ₁₁ and ρ_1?1 which are very close to their maximum allowed value of $\text{1}\text{2}$ throughout the measured t range except in the very forward direction where ρ₀₀ and Re ρ₁₀ deviate from zero. Natural parity exchanges, therefore, dominate with unnatural parity exchanges being restricted to a small region in the forward direction. A Regge pole analysis of the differential cross sections of the present measurement in conjunction with previously measured total cross sections supports the f-coupled-pomeron hypothesis.     

A Mössbauer effect study of Dy impurities in the h.c.p. metal Zr

The 86.8 keV, 2⁺ → 0⁺ Mössbauer resonance of ¹⁶⁰Dy has been employed to study the paramagnetic hyperfine (hf) structure of Dy impurities in the hexagonal transition metal Zr. From the observed hf splitting it is concluded that the crystalline electric field ground state is an almost pure $\text{J}{}_{\mathrm{<mtext>z</mtext>}}\text{= ±}\text{1}\text{2}\text{Γ}{}_7$ Kramers' doublet with g_⊥ ? g_|. The quadrupole hf interaction and the effects of paramagnetic relaxation on the ME spectrum are also discussed.