Intercomparison of monochromatic source facilities for the determination of the relative spectral response of erythemal broadband filter radiometers

The relative spectral responses of erythemally weighted broadband radiometers determined at three different laboratories are compared, and the systems are described. The results of measurements of four different broadband radiometers are discussed. Although the common dynamic range of the measured relative spectral responses is approximately 10(4), the differences in the relative spectral response functions are lower than 20%. These differences are related mostly to measurement uncertainties and differences in the spectral response facilities.     

Molecular distribution of some commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs). APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e. textile manufacture. Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers. We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix. In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules [M + Na](+). The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300. Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively. In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems. Copyright 1999 John Wiley & Sons, Ltd.     

Elemental analysis of freshwater samples collected in the former USSR by inductively coupled plasma mass spectrometry

Approximately 100 freshwater samples (ground water, surface water, etc.) collected in the former USSR were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Standard water, NBS SRM 1643b, was used for quality control. By using the semi-quantitative analysis mode, analytical data and certified values (or informative values) were in agreement within ±30%. Concentrations of B, Ni, Se, Sr and Ba were found to be higher than global means. Concentration levels of Ag and Pb tended to be lower. For Be, V, Cr, Mn, Co, Cu, Zn, As, Mo, Cd, Tl, and Bi, the concentrations were almost equal to the global levels.     

Constructions of partitions of FqN into perfect q-ary codes

Given N = (q ^m − 1)/(q − 1), where q is a power of a prime, q > 2, we present two constructions of different partitions of the set F _q ^N of all q-ary length N vectors into perfect q-ary codes of length N. The lower bounds on the number of these partitions are presented.     

A combined BDF‐semismooth Newton approach for time‐dependent Bingham flow

This article is devoted to the numerical simulation of time‐dependent convective Bingham flow in cavities. Motivated by a primal‐dual regularization of the stationary model, a family of regularized time‐dependent problems is introduced. Well posedness of the regularized problems is proved, and convergence of the regularized solutions to a solution of the original multiplier system is verified. For the numerical solution of each regularized multiplier system, a fully discrete approach is studied. A stable finite element approximation in space together with a second‐order backward differentiation formula for the time discretization are proposed. The discretization scheme yields a system of Newton differentiable nonlinear equations in each time step, for which a semismooth Newton algorithm is used. We present two numerical experiments to verify the main properties of the proposed approach. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011     

Discrete breathers in nonlinear network models of proteins

We introduce a topology-based nonlinear network model of protein dynamics with the aim of investigating the interplay of spatial disorder and nonlinearity. We show that spontaneous localization of energy occurs generically and is a site-dependent process. Localized modes of nonlinear origin form spontaneously in the stiffest parts of the structure and display site-dependent activation energies. Our results provide a straightforward way for understanding the recently discovered link between protein local stiffness and enzymatic activity. They strongly suggest that nonlinear phenomena may play an important role in enzyme function, allowing for energy storage during the catalytic process.     

Parametric characterization of Gaussian beams propagating through active media

On the basis of the intensity moment formalism, within the thin-sheet approach, the beam width, the beam quality and the kurtosis parameter of a Gaussian beam propagating through active media are investigated. The analysis considers both the homogeneously and inhomogeneously broadened cases. The dependence of the above three parameters on the small-signal gain, saturation intensity and input beam size is studied. The validity of the thin-sheet approximation for the range of propagation distances and physical parameters of the system is also discussed.     

Divergence-free finite elements for the numerical solution of a hydroelastic vibration problem

In this paper, we analyze a divergence-free finite element method to solve a fluid–structure interaction spectral problem in the three-dimensional case. The unknowns of the resulting formulation are the fluid and solid displacements and the fluid pressure on the interface separating both media. The resulting mixed eigenvalue problem is approximated by using appropriate basis of the divergence-free lowest order Raviart–Thomas elements for the fluid, piecewise linear elements for the solid and piecewise constant elements for the interface pressure. It is proved that eigenvalues and eigenfunctions are correctly approximated and some numerical results are reported in order to assess the performance of the method.     

M?ssbauer study of contaminated soils by industrial activity in Paramonga city, Region Lima Provinces, Peru

In this work we characterize soils from the Paramonga city, Region Lima Provinces in Peru, which are contaminated by residual chemicals (Br, As and Sr) from sugar and paper industry in the city. Four samples were collected, labelled as S1, S2, S3 and S4 and analized by X-ray diffraction (XRD), energy-dispersive X-ray fluorescence (EDXRF) and M?ssbauer spectroscopy. For all the samples, the chemical analysis by EDXRF revealed the presence of Fe, Mn, Cu, Zn, K, Br, Sr. The XRD detected the presence of quartz as principal phase and copper sulfide and potassium magnesium as secondary phases. The M?ssbauer spectra at room temperature (RT) for all the samples exhibit sextets which reveal the presence of an iron oxide or hydroxide. The fitting M?ssbauer for both samples S1 and S4 have three doublets corresponding to iron in paramagnetic phases and a magnetic component of around 35.50?T corresponding to goethite, α-FeOOH. Sample S2 have two magnetic phases with internal fields of 37?T and 34.6?T which correspond to the goethite and other incorporated element in the structure. The sample S3 have three magnetic fields of H1?=?36.8?T, H2?=?33.6?T and H3?=?34.8?T which correspond to hydroxide iron, pyrrhotite and goethite respectively.