The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides Part I: Characterization of the adsorbers

The salt of the 8-hydroxyquinoline and benzilic (diphenylglycolic) acid was prepared and incorporated into active charcoal in order to have an adsorber able to concentrate actinides dispersed in natural waters before quantitative or radiochemical analysis. The formation and the characterization of this adsorber, (adsorber B), was compared with another system containing benzilic salt of the substituted quinoline, 2-methyl, 8-hydroxyquinoline, (adsorber R). The adsorption ability of the adsorbers B and R was compared with a third product (adsorber G), prepared by incorporating benzilic acid with d-glucosamine into the charcoal. In this case, d-glucosamine gives a better stability to the system, as otherwise the benzilic acid could partially be dissolved into the water system at equilibrium, during the adsorption experiments. The dissociation acid constants of all the considered components were measured, in order to have some information on the adsorption mechanism. The compound formed during the adsorption on the prepared adsorbers with uranium, thorium, and samarium were separately analyzed and identified by means of IR and NMR. The role of the components in the adsorption was evidenced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quasiclassical trajectory calculations to evaluate a kinematic constraint on internal energy in suprathreshold collision energy abstraction reactions

Experimentally observed product quantum state distributions across a wide range of abstraction reactions at suprathreshold collision energies have shown a strong bias against product internal energy. Only a fraction, sometimes quite a small fraction, of the energetically accessible product quantum states are populated. Picconatto et al. [J. Chem. Phys. 114, 1663 (2001)] noted a simple mathematical relationship between the highest-energy rovibrational states observed and the kinematics of the reaction system. They proposed a reaction model based on reaction kinematics that quantitatively explains this behavior. The model is in excellent agreement with measured quantum state distributions. The assumptions of the model invoke detailed characteristics of reactive trajectories at suprathreshold collision energies. Here we test those assumptions using quasiclassical trajectory calculations for the abstraction reactions H+HCl-->H2+Cl, D+HCl-->HD+Cl, and H+DCl-->HD+Cl. Trajectories were run on a potential-energy surface calculated with a London-Eyring-Polyani-Sato function with a localized 3-center term (LEPS-3C) previously shown to accurately reproduce experimentally observed product state distributions for the H+HCl abstraction reaction. The trajectories sample collision energies near threshold and also substantially above it. Although the trajectories demonstrate some aspects of the model, they show that it is not valid. However, the inadequacy of the proposed model does not invalidate the apparent kinematic basis of the observed energy constraint. The present results show that there must be some other molecular behavior rooted in the reaction kinematics that is the explanation and the source of the constraint.     

Electrochemical ELISA for the screening of DDT related compounds: analysis in waste waters

An electrochemical enzyme-linked immunosorbent assay (ELISA) for the detection of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DTT), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p′-DDE), 1,1-dichloro-2,2-bis-(4-chlorophenyl)ethane (p,p′-DDD) and o,p-DDT was developed. Optimization of the ELISA competition conditions, led to similar response for the p,p′-isomers. The activity of the label enzyme (horseradish peroxidase) was measured electrochemically using 3,3′,5,5′-tetramethylbenzidine as substrate. The use of purified antiserum for p,p′-DDT resulted in a sensitive assay with a detection limit of 40 pg ml⁻¹ and R.S.D. ranging from 1 to 3% intra-day and 3 to 6% inter-day. No matrix effect for waste water samples of different origin has been evidenced. The ELISA was used to detect DDTs in 20 samples after extraction in diethylether. This method appears suitable for routine screening of DDTs without sample pre-treatment other than dilution in PBS or after organic solvent extraction if high sensitivity is required.     

Analytical characterization of bioactive fluoropolymer ultra-thin coatings modified by copper nanoparticles

Copper–fluoropolymer (Cu-CFx) nano-composite films are deposited by dual ion-beam sputtering. The extensive analytical characterization of these layers reveals that inorganic nanoparticles composed of Cu(II) species are evenly dispersed in a branched fluoropolymer matrix. In particular, X-ray photoelectron spectroscopy has been employed to study the surface chemical composition of the material and to assess how it changes on increasing the copper loading in the composite. Transmission electron microscopy reveals that the copper nanoclusters have a mean diameter of 2–3 nm and are homogeneously in-plane distributed in the composite films. Electrothermal atomic absorption spectroscopy has been used to study the kinetics of copper release in the solutions employed for the biological tests. The Cu-CFx layers are employed as bioactive coatings capable of inhibiting the growth of target microorganisms such as Saccharomyces cerevisiae, Escherichia coli, Staphylococcus aureus, and Lysteria. The results of the analytical characterization enable a strict correlation to be established among the chemical composition of the material surface, the concentration of copper dissolved in the microorganisms broths, and the bioactivity of the nano-structured layer.     

Multifunctional polyurethane foams with thermal energy storage/release capability

Journal of Thermal Analysis and Calorimetry - In this work, polyurethane (PU) insulating panels containing different amounts of a microencapsulated paraffin with a nominal melting temperature of...     

Elemental sensitivity in soft x-ray imaging with a laser-plasma source and a color center detector

Elemental sensitivity in soft x-ray imaging of thin foils with known thickness is observed using an ultrafast laser-plasma source and a LiF crystal as detector. Measurements are well reproduced by a simple theoretical model. This technique can be exploited for high spatial resolution, wide field of view imaging in the soft x-ray region, and it is suitable for the characterization of thin objects with thicknesses ranging from hundreds down to tens of nanometers.     

O-Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed-Valence Complexes

Herein we report an efficient synthesis to prepare O-doped nanographenes derived from the π-extension of pyrene. The derivatives are highly fluorescent and feature low oxidation potentials. Using electrooxidation, crystals of cationic mixed-valence (MV) complexes were grown in which the organic salts organize into face-to-face π-stacks, a favorable solid-state arrangement for organic electronics. Variable-temperature electron paramagnetic resonance (EPR) measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar π-stacking architectures. Electric measurements of single crystals of the MV salts show a semiconducting behavior with a remarkably high conductivity at room temperature. These findings support the notion that π-extension of heteroatom-doped polycyclic aromatic hydrocarbons is an attractive approach to fabricate nanographenes with a broad spectrum of semiconducting properties and high charge mobilities.     

Effects of the menstrual cycle on the red and near-infrared optical properties of the human breast

Time-resolved reflectance and transmittance spectroscopy was applied to measure in vivo the absorption and transport scattering spectra of the female breast from 610 to 1010 nm. Three measurement configurations were used to probe different breast regions, and data were collected two or three times in each of the five phases of the menstrual cycle. The absorption spectra were best-fitted with a linear combination of the spectra of the main tissue constituents (water, lipids, oxy- and deoxyhemoglobin). This allowed us to evaluate percentage contents of water and lipids, total hemoglobin content and hemoglobin oxygen saturation. The scattering spectra were interpreted with a function derived from Mie theory, providing information on the density and average size of the tissue scatterers. Significant changes in the estimated variables were observed with measurement geometry, reflecting the heterogeneous nature of the breast, and with time, in agreement with expected physiological changes over the menstrual cycle.     

A proof of the normal form theorem for the closed terms of Girard's system F by means of computability

In this paper a proof of the normal form theorem for the closed terms of Girard's system F is given by using a computability method à la Tait. It is worth noting that most of the standard consequences of the normal form theorem can be obtained using this version of the theorem as well. From the proof-theoretical point of view the interest of the proof is that the definition of computable derivation here used does not seem to be well founded. MSC: 03F05, 03B15.     

The theory of the optogalvanic effect in metal vapour-rare gas discharges

A theory of the laser-excited optogalvanic effect in metal vapour-rare gas discharges is elaborated. The metal vapour depletion due to the ionization processes and the energy losses from the plasma caused by the ion and electron flux to the wall and the elastic and inelastic collisions between electrons and atoms are taken into account. The metal atom depletion increases if the discharge current or the intensity of the laser radiation are increased. The more complete energy balance leads to a substantially greater optogalvanic signal than obtained from previous theories. The metal atom depletion, however, appreciably decreases the optogalvanic signal except very small discharge currents.