Trace pollutants analysis in soil by a time-resolved laser-induced breakdown spectroscopy technique

The results of a joint experiment of IFAM-Pisa and ENEA-Frascati for the detection of traces of pollutants in soil by a time-resolved laser-induced spectroscopy technique are reported. Using samples of soil with known pollutants' concentration [Geochemical Exploration Reference (GXR) silicate from US Geological Survey], we were able to estimate the sensitivity of this Laser-Induced Breakdown Spectroscopy (LIBS) technique to be of the order of some parts per million for a vast class of metallic pollutants, including extremely dangerous soil pollutants such as copper, lead and chromium.ENEA guest with HC&M fellowship     

Optimality conditions and duality theory for minimizing sums of the largest eigenvalues of symmetric matrices

The sum of the largest eigenvalues of a symmetric matrix is a nonsmooth convex function of the matrix elements. Max characterizations for this sum are established, giving a concise characterization of the subdifferential in terms of a dual matrix. This leads to a very useful characterization of the generalized gradient of the following convex composite function: the sum of the largest eigenvalues of a smooth symmetric matrix-valued function of a set of real parameters. The dual matrix provides the information required to either verify first-order optimality conditions at a point or to generate a descent direction for the eigenvalue sum from that point, splitting a multiple eigenvalue if necessary. Connections with the classical literature on sums of eigenvalues and eigenvalue perturbation theory are discussed. Sums of the largest eigenvalues in the absolute value sense are also addressed.This paper is dedicated to Phil Wolfe on the occasion of his 65th birthday.The work of this author was supported by the National Science Foundation under grants CCR-8802408 and CCR-9101640.The work of this author was supported in part during a visit to Argonne National Laboratory by the Applied Mathematical Sciences subprogram of the Office of Energy Research of the U.S. Department of Energy under contract W-31-109-Eng-38, and in part during a visit to the Courant Institute by the U.S. Department of Energy under Contract DEFG0288ER25053.     

Cyclic voltammetric studies of certain industrially potential iron chelate catalysts

 For the analysis of infrared spectroscopic bands and complex patterns partial cross correlation functions of a sample spectrum with reference spectra are calculated. The chosen ranges of the spectra are based on empirical knowledge of infrared spectrum structure correlations. The normalised maxima of the partial cross correlation functions are interpreted as fuzzy truth values and are combined by fuzzy logical operators. By application of that procedure larger common substructures will be derived from the reference spectra than by a maximum common substructure search based on the complete spectra. Received: 30 October 1996/Revised: 24 February 1997/Accepted: 26 February 1997     

High-accuracy measurer of complex reflection coefficient of SHF transmission lines

We describe a new method of constructing a device for simultaneous measurement of the relative amplitude and phase difference of microwave signals, using complex phase manipulation of input signals. It is shown that systematic errors of measurement are significantly lower in the proposed amplitude and phase meter. Root-mean-square values are obtained for a system with nonideal elements. A block diagram of the device is presented and its principal characteristics are described. Institute of Radiophysics and Electronics, Armenian Academy of Sciences, Erevan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1182–1188, September, 1997.     

Aliasing Effects and Sampling Theorems of Spherical Random Fields when Sampled on a Finite Grid

Aliasing effects are investigated for spherical random fields sampled on a finite grid. Using the spherical harmonics expansion, it is shown that for a band-limited spherical random field its trend and spectrum can be uniquely reconstructed from the sampled field if the sampling points are judiciously designed. Analytical expressions are also obtained for aliasing errors in the trend and the spectrum when the field is not band-limited.     

Intravascular and Intracellular Hepatic Relaxivities of Superparamagnetic Particles: An Isolated and Perfused Organ Pharmacokinetics Study

The relative contributions of intravascular and intracellular compartments to the proton transverse relaxation of the isolated and excised rat liver were determined during the phagocytosis of superparamagnetic particles. The evolution of the proton transverse magnetization of the organ perfused with increasing doses of starch-coated magnetic microspheres was followed up using a Carr–Purcell–Meiboom–Gill sequence with various echo times. From the multiexponential fit of the echo train, the amplitudes and the relaxation ratesR₂of the liver tissue were obtained. The results clearly indicate that shortly after contrast medium administration, an internalization takes place which can be followed by the rapid and biphasic evolution of the transverse relaxation rate of the water protons. A very fast decaying component looking like an initial loss of the magnetization is observed together with an increase of the relaxation rate of the remaining water tissue. This regime is strongly dependent on both the echo time and the iron concentration, a behavior characteristic of the agglomeration of magnetic particles. The examination of the liver tissues by electron microscopy shows that this clustering arises in cytoplasmic vacuoles.     

The effect of Fe and Ru substitution on the superconductivity in MgCNi3

We report the effects of partial substitutions of the VIIIa elements: Fe (3d) and Ru (4d) in the intermetallic perovskite superconductor MgCNi₃. In both the MgCNi_3−xRu_x and MgCNi_3−xFe_x systems, the superconducting critical temperature (T_C) decreases monotonically as x is increased. T_C decreases more slowly in the case of Ru, suggesting that the 3d electrons in Fe are magnetically pair breaking. This is supported by the normal state magnetic susceptibility measurements (χ), which shows that χ increases with Fe and decreases with Ru doping. No ferromagnetism is observed in either system.     

Synthesis of functional polymers—Vinylidene fluoride based fluorinated copolymers and terpolymers bearing bromoaromatic side‐group

The radical co‐ and terpolymerization of 4‐[(α,β,β‐trifluorovinyl)oxy]bromo benzene (TFVOBB) with 1,1‐difluoroethylene (or vinylidene fluoride, VDF, or VF₂), hexafluoropropene (HFP), perfluoromethyl vinyl ether (PMVE), and chlorotrifluroroethylene (CTFE) is presented. Although TFVOBB could be thermocyclodimerized, it could not homopolymerize under radical initiation. TFVOBB could be copolymerized in solution under a radical initiator with VDF or CTFE comonomers, while its copolymerization with HFP or PMVE were unsuccessful. The terpolymerization of TFVOBB with VDF and HFP, or VDF and PMVE, or VDF and CTFE also led to original fluorinated terpolymers bearing bromoaromatic side‐groups. The conditions of co‐ and terpolymerization were optimized in terms of the nature of the radical initiators, and of the nature of solvents (fluorinated or nonhalogenated). Various monomer concentrations in the co‐ and terpolymers were assessed by ¹⁹F and ¹H‐NMR spectroscopy. The thermal and physico chemical properties were also studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5077–5097, 2004