Measurement of Lamb wave polarization using a one-dimensional scanning laser vibrometer (L)

A single head scanning laser Doppler vibrometer is used for the estimation of the polarization of the first symmetric (S(0)) and antisymmetric (A(0)) Lamb wave modes. The measurements at two known incidence angles are performed in order to resolve the two components of motion. Filtering in the frequency/wavenumber domain of the response recorded along a scan line separates the contributions from each mode and allows the evaluation of the corresponding elliptical trajectories of particle motion. Comparison between measured and analytically estimated trajectories validates the measurement technique and suggests its application for the development of material characterization and diagnostics tools.     

An assessment of the impact of construction work on fine particulate matter in the University of Jordan: A PIXE study

Aerosol sampling was carried out prior to and during an active construction work at the University of Jordan in Amman, Jordan. Elemental characterization for 60 PM_2.5 samples was performed by particle-induced X-ray emission (PIXE) technique at the LABEC laboratory of INFN in Florence, Italy. Twenty three elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, Ba, and Pb) were detected, and their concentrations were assessed during three sampling periods, namely, “No Construction,” “Pouring Concrete,” and “Bleaching.” The results showed higher concentrations of soil-related elements and lower concentrations of anthropogenic-related elements during construction periods compared with their concentrations before construction. Soil-related elements showed very low enrichment factor (EF) and high correlation coefficients during all sampling periods. Anthropogenic-related elements were very much enriched and correlated only during the first sampling period “No Construction.”     

A globally convergent descent method for nonsmooth variational inequalities

We propose a descent method via gap functions for solving nonsmooth variational inequalities with a locally Lipschitz operator. Assuming monotone operator (not necessarily strongly monotone) and bounded domain, we show that the method with an Armijo-type line search is globally convergent. Finally, we report some numerical experiments. This work has been supported by the National Research Program PRIN/2005017083 “Innovative Problems and Methods in Nonlinear Optimization”.     

Studies on comblike polymers. X. Characterization of comblike polyesters by 13C NMR spectroscopy

The ¹³C NMR spectra of aromatic comblike polyesters obtained from 1,2-icosanediol and isomeric phthalic acids are reported and discussed. The analysis shows that the most informative spectral regions are those of the carbonyl and quaternary carbon resonances, whose peak multiplicities have been interpreted in terms of dyad and triad sequences. The results indicate that the extent of structural characterization possible for the polymers examined is dependent on the type of isomerism of the aromatic acid involved.     

Optically active alternating copolymers of maleic anhydride and alkylvinylethers

Maleic anhydride (MAn) was copolymerized in benzene solution at 60° using AIBN with some optically active alkylvinylethers (RVE) having an asymmetric carbon atom at the α, β, γ or δ position with respect to the oxygen atom [R = (S)-1-methylpropyl, (R)-1-methylbutyl, (S)-2-methylbutyl, (S)-3-methylpentyl, (S)-4-methylhexyl, (S)-1-methylheptyl and (S)-3,7-dimethyloctyl]. Chemical compositions and solubilities of the polymeric products as well as optical rotation properties and spectroscopic measurements (i.r. and NMR) confirmed the formation of copolymers with a predominantly alternating structure. Two Cotton effects of low but definite intensity attributable to $\text{n → π}{}^1$ electronic transitions of carbonyl groups of anhydride moieties were observed between 200 and 250 nm. Failure to achieve complete cleavage of chiral side chains does not enable us to attribute the induced optical activity of anhydride moieties either to the asymmetric carbon atom present in the side chain or to the tertiary chiral centres present in the main chain or both.     

Far-infrared absorption by collisionally interacting nitrogen and methane molecules

Quantum line shape calculations of the rototranslational enhancement spectra of nitrogen-methane gaseous mixtures are reported. The calculations are based on a recent theoretical dipole function for interacting N(2) and CH(4) molecules, which accounts for the long-range induction mechanisms: multipolar inductions and dispersion force-induced dipoles. Multipolar induction alone was often found to approximate the actual dipole surfaces of pairs of interacting linear molecules reasonably well. However, in the case of the N(2)-CH(4) pair, the absorption spectra calculated with such a dipole function still show a substantial intensity defect at the high frequencies (>250 cm(-1)) when compared to existing measurements at temperatures from 126 to 297 K, much as was previously reported.     

Solvent gradient operation of simulated moving beds. 2. Langmuir isotherms

Simulated Moving Bed separations of enantiomers or fine chemicals are usually carried out in the isocratic mode, i.e. by applying the same operating conditions (temperature, pressure, mobile phase composition, pH) in the whole SMB unit. However, it has been recently recognized that by properly modulating operating conditions in the SMB sections. i.e. Sections 1-4 normally, separation performance in terms of productivity and solvent consumption can be significantly improved. In this work, we study solvent gradient SMB (SG-SMB) operation, where the concentration of a modifier in the main solvent constituting the mobile phase is adjusted along the SMB unit, so as to have weaker retention of the species to be separated in the first two sections, and stronger retention in Sections 3 and 4. Overload chromatographic conditions are considered, where the adsorption behavior is characterized by a nonlinear competitive adsorption isotherm, e.g. a binary Langmuir isotherm. Design criteria to achieve complete separation are developed in the frame of the equilibrium theory of chromatography. The theoretical findings are discussed in view of typical effects of the modifier concentration on retention times and solubility of the species to be separated, and an overall assessment of the SG-SMB technology is attempted.