Controlled exchange of metallic cations by polypyrrole-based resins

in Synthetic Metals (2001), 118(1-3), 45-55

Binding and release of various cations by polarization of polypyrrole based exchange-resins has been studied. The reversibility of the process has been investigated by electrochemical and nuclear ... [more ▼]

Binding and release of various cations by polarization of polypyrrole based exchange-resins has been studied. The reversibility of the process has been investigated by electrochemical and nuclear techniques. It clearly depends on both the exchanged-cation and the sulfonated doping-ion. The selectivity of the process has also been analyzed by binding experiments from a mixture of two cations. [less ▲]

New system for complexation of uranyl ions from liquid wastes of low-level activity: Polypyrrole doped with complexing polyanions

in Journal of Applied Polymer Science (2000), 77(6), 1230-1239

Polymer composites consisting of polypyrrole doped by uranyl complexing polyanions [i.e., poly(2-acrylamidoglycolic acid) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid)] were electrochemically ... [more ▼]

Polymer composites consisting of polypyrrole doped by uranyl complexing polyanions [i.e., poly(2-acrylamidoglycolic acid) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid)] were electrochemically synthesized. Bulk material and thin layers strongly adhering to inert supporting electrodes were prepared. These composites were used to precipitate uranyl ions from simulated radioactive wastes. Among different experimental techniques used for the analysis of uranium immobilized in the composites, the Rutherford backscattering of cu particles proved efficient in thin layers. Leaching tests confirmed the persistence of the uranium complexation in the solid composites. [less ▲]

Is the external beam PIXE method suitable for determining ancient silver artifact fineness?

in Nuclear Instruments & Methods in Physics Research Section B (2000), 161

In archeometry, the non-destructive characteristic of an analytical method is always very attractive. For most of techniques, besides the need of sampling, difficulties can originate from the shape and ... [more ▼]

In archeometry, the non-destructive characteristic of an analytical method is always very attractive. For most of techniques, besides the need of sampling, difficulties can originate from the shape and the size of the silver artifacts to be analyzed. The external PIXE method should be an answer to this problem but several questions are arising from the implementation of the technique to such a material. The aim of this paper is to specify the experimental procedure as to take into account several parameters, which could induce dramatic errors. Among them it can be pointed out the superficial enrichment in silver, arising from the dissolution of copper and copper oxide, the surface roughness effects, the great importance of the stability of the geometric conditions. The accuracy and the precision of the method are considered within the scope of the results obtained in ancient times by the cupellation with ashbone cupels. In addition. the process involved to obtain silver alloys has been studied in order to define its influence on the real fineness of the objects. (C) 2000 Elsevier Science B.V. All rights reserved. [less ▲]

Controlled exchange of metallic cations by a polypyrrole-based resin

in Journal de Chimie Physique et de Physico-Chimie Biologique (1998), 95(6), 1475-1478

This work shows that the binding and the release of Cs+, Ba2+, La3+ and Th4+ cations can be controlled by the application of a potential to a polypyπole doped with polystyrene sulfonate exchange-resin ... [more ▼]

This work shows that the binding and the release of Cs+, Ba2+, La3+ and Th4+ cations can be controlled by the application of a potential to a polypyπole doped with polystyrene sulfonate exchange-resin. Radiometric and nuclear techniques were carried out to characterize the reversibility of the process in relation with the exchanged-cation charge. [less ▲]

Quantification by PIXE of metallic sites in proteins separated by electrophoresis

in Nuclear Instruments & Methods in Physics Research Section B (1998), 137

Electrophoresis on polyacrylamide gel (PAGE) is widely used in life sciences to determine the molecular weight of proteins in solution by separating them into different bands. By coupling electrophoresis ... [more ▼]

Electrophoresis on polyacrylamide gel (PAGE) is widely used in life sciences to determine the molecular weight of proteins in solution by separating them into different bands. By coupling electrophoresis and Particle Induced W-ray Emission (PIXE), the nature and the quantity of metals contained in proteins can be investigated. After the electrophoresis, the gel is dried and each track is scanned with a 2.5 MeV proton beam which induces X-ray emission. Analysis of these spectra allows the determination of the metals contained in an electrophoretic band. The metal content in each band is obtained by comparing the characteristic X-ray peak area with those obtained with polyacrylamide gels doped with the same metal. Finally, the relative concentration of each protein is determined by densitometry in order to compute the protein/metal ratio. An example of metallic site determination is presented. This procedure seems to be a very useful multielementary method for the determination of the metal amounts inside proteins after their separation by electrophoresis. Furthermore it allows to check if metals remain bound to proteins. (C) 1998 Elsevier Science B.V. [less ▲]

Use of a variable incidence angle PIXE arrangement for studying pigment multilayers

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (1998), 139(1-4), 196-201

Particle induced X-ray emission (PIXE) method is used in the field of archeometry and specially to investigate pigment colored multilayers. The tilting of the sample with respect to the incident proton ... [more ▼]

Particle induced X-ray emission (PIXE) method is used in the field of archeometry and specially to investigate pigment colored multilayers. The tilting of the sample with respect to the incident proton beam direction allows to modify the relative contribution of each layer to the fluorescence signal. The experimental results coupled to computer simulations lead to semi-quantitative information about the thickness, the position and the composition of the successive layers. (C) 1998 Elsevier Science B.V. [less ▲]

Use of the alpha parameter method to calculate matrix corrections for infinitely thick targets (TTPIXE) with two different incident beam energies

in Nuclear Instruments & Methods in Physics Research Section B (1997), 129(1), 92-100

The alpha parameter correction method for calculating matrix effects in PIXE data does not require a priori knowledge of the major element composition of the matrix but implies the determination of a so ... [more ▼]

The alpha parameter correction method for calculating matrix effects in PIXE data does not require a priori knowledge of the major element composition of the matrix but implies the determination of a so-called alpha parameter linking two independent phenomena: X-ray absorption and proton energy loss. The method extrapolated to the infinitely thick targets (TTPIXE) has been previously studied using two PIXE measurements in two different geometric configurations. The present Study deals with the possibility of using pairs of PIXE measurements at two different energies to obtain the alpha corresponding to thick samples (TTPIXE). The experimental conditions and error minimization problems are discussed. General tables allowing an easy use of the method are presented. [less ▲]

A computer controlled PIGE setup for the analysis of thin samples

in Nuclear Instruments & Methods in Physics Research Section B (1996), 113(1-4), 407-410

A computer controlled PIGE setup has been improved by adding a beam energy disperser which whips out most of the structure of the proton excitation functions and allows better analysis of thin samples.

CARAIB - A global model of terrestrial biological productivity

in Global Biogeochemical Cycles (1994), 8(3), 255-270

CARAIB, a mechanistic model of carbon assimilation in the biosphere estimates the net primary productivity (NPP) of the continental vegetation on a grid of 1 degrees x 1 degrees in latitude and longitude ... [more ▼]

CARAIB, a mechanistic model of carbon assimilation in the biosphere estimates the net primary productivity (NPP) of the continental vegetation on a grid of 1 degrees x 1 degrees in latitude and longitude. The model considers the annual and diurnal cycles. It is based on the coupling of the three following submodels; a leaf assimilation model including estimates of stomatal conductance and leaf respiration, a canopy model describing principally the radiative transfer through the foliage, and a wood respiration model. Present-day climate and vegetation characteristics allow the discrimination between ecotypes. In particular, specific information on vegetation distribution and properties is successfully used at four levels; the leaf physiological level, the plant level, the ecosystem level, and the global level. The productivity determined by the CARAIB model is compared with local measurements and empirical estimates showing a good agreement with a global value of 65 Gt C yr(-1). The sensitivity of the model to the diurnal cycle and to the abundance of C-4 species is also tested. The productivity slightly decreases (10%) when the diurnal cycle of the temperature is neglected. By contrast, neglecting the diurnal cycle of solar irradiance produces unrealistically high values of NPP. Even if the importance of this increase would presumably be reduced by the coupling of CARAIB with a nutrient cycle model, this test emphasizes the key role of the diurnal cycle in a mechanistic model of the NPP. Uncertainties on the abundance and spatial distribution of C-4 plants may cause errors in the NPP estimates, however, as demonstrated by two sensitivity tests, these errors are certainly lower than 10% at the global scale as shown by two tests. [less ▲]

On Relativistic Scalar and Vector-Mesons with Harmonic Oscillator-Like Interactions

in Zeitschrift Fur Physik C-Particles and Fields (1992), 56(3), 421-425

Relativistic descriptions for spin 0 and 1 particles of nonzero restmasses are known for a long time as the so-called Kemmer or Sakata-Taketani formulations. Through harmonic oscillatorlike interactions ... [more ▼]

Relativistic descriptions for spin 0 and 1 particles of nonzero restmasses are known for a long time as the so-called Kemmer or Sakata-Taketani formulations. Through harmonic oscillatorlike interactions, we study the nonrelativistic limit of the corresponding wave equations in connection with expected spin-orbit terms. Typical Foldy-Wouthuysen developments are included in these approaches with exact results up to required orders for interacting vector mesons only. [less ▲]