Amphiphilic maleic acid-containing alternating copolymers—1. Dissociation behavior and compositions

The dissociation of the two adjacent carboxylic acids in maleic acid-containing copolymers is expected to differ from those of poly(acrylic acid) and poly(methacrylic acid) where the acids are separated by two carbons on the backbone. In this work, we have employed potentiometric titration and NMR spectroscopy to characterize the dissociation behavior and chemical compositions of several water-soluble maleic acid-containing copolymers. A distinct two-step process corresponding to the dissociation of the two adjacent carboxylic acids is observed in aqueous CaCl₂ (0.02 N) solution for copolymers of maleic acid and isobutylene, diisobutylene, and styrene. Such a two-step ionization process is less recognizable, however, for the copolymers of maleic acid and linear alkenes ranging from n-hexene to n-octadecene. Nevertheless, the compositions of all copolymers, including the extent of neutralization and the ratio of the comonomer moieties, are estimated from the titration curves. The chemical composition derived from potentiometry and NMR spectroscopy for all copolymers are approximately 1 : 1 (maleic acid : comonomer). With the exception of the hydrophobically modified copolymer of isobutylene-maleic acid, no obvious conformational transition was observed over the whole range of ionization for these hydrophobic maleic acid-containing copolymers. This is related to the aggregated state of these copolymers in aqueous media. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3571–3583, 2004     

Determination of boron, fluorine and some medium Z elements in diet samples

As part of the study on “Reference Asian Man” project, dried food from different Asian countries, in powdered form, was analyzed applying different techniques. Boron was determined by measuring prompt alphas in ¹¹B(p,α)⁸Be reaction with 800 keV protons. Coulomb excitation was used for F and Na determination based on ¹⁹F(p,p'γ)¹⁹F (γ -rays: 110 and 197 keV) and ²³Na(p,p'γ)²³Na (γ -ray: 440 keV) reactions with 2.3 MeV protons. The elements Sc, Co, Zn, Rb, Ag and Ce were determined by neutron activation analysis. The elements Ca, Mn, Fe, Ni, Cu, Zn, Sr and Mo were determined by X-ray fluorescence technique. This revised version was published online in August 2006 with corrections to the Cover Date.     

Biotransformation of Implanted Coral in Some Animals Studied by Neutron Activation Analysis

In vivo behavior of biomaterial is dependent on the site of implantation. Characterization by atomic element transfers versus the implantation duration is a quantitative approach to the phenomenon. Here, bioactive coral is implanted in ovine, porcine and rabbit thighbones and not in sheep jawbones as previously reported. Biopsies extracted between 1 and 24 weeks are analysed by fast neutron activation. Mineral composition of the coral is greatly modified: Ca, P, Mg and Sr concentrations become comparable to those of mature bone some months after the implantation. Results suggest a bioactive resorption followed by apatite formation.     

Synthesis and photochemistry of a two-position Ru(terpy)(phen)(L)2+ scorpionate complex

A dissymmetric 1,10-phenanthroline chelate (N-phen-S) bearing two polyether chains terminated by two monodentate ligands of the benzonitrile (N) and dialkylesulfoxide (S) types was synthesized, characterized, and coordinated to ruthenium. The corresponding Ru(terpy)(N-phen-S)2+ complexes (terpy = 4'-(3,5-ditertiobutylphenyl)-2,2';6',2' '-terpyridine) were fully characterized as being two coordination isomers of the scorpionate type with one of the two tails occupying the sixth position on the coordination sphere. Photoexpulsion of the coordinated tail led to opening of the ruthena-macrocycle and subsequent rearrangement of the bidentate chelate. This rearrangement consisted of a 90 degrees rotation of the phenanthroline around the ruthenium atom. Selective irradiation of one isomer in a mixture of the two was undertaken using band-pass filters; this resulted in an enrichment of the nonirradiated isomer in the mixture. Thermal back-coordination of the tail was investigated in the dark. It took place quantitatively from the corresponding ruthenium chloride complex by trapping of the anion with silver salts.     

Charge radii and magnetic moments of odd- A 183-189Pb isotopes

Unexpected features of the BaBar data on e ⁺ e ^- $ \rightarrow$ B $ \overline{{B}}$ cross-sections (B stands for baryon) are discussed. These data have been collected, with unprecedented accuracy, by means of the initial-state radiation technique, which is particularly suitable in giving good acceptance and energy resolution at threshold. A striking feature observed in the BaBar data is the non-vanishing cross-section at threshold for all these processes. This is the expectation due to the Coulomb enhancement factor acting on a charged fermion pair. In the case of e ⁺ e ^- $ \rightarrow$ p $ \overline{{p}}$ it is found that Coulomb final-state interactions largely dominate the cross-section and the form factor is | G ^p(4M ² _p)| ～ 1 , which could be a general feature for baryons. In the case of neutral baryons an interpretation of the non-vanishing cross-section at threshold is suggested, based on quark electromagnetic interaction and taking into account the asymmetry between attractive and repulsive Coulomb factors. Besides strange baryon cross-sections are compared to U -spin invariance predictions.     

From ruthenium(II) to iridium(III): 15 years of triads based on bis-terpyridine complexes

In order to mimic the photosynthetic reaction centre and better understand photoinduced electron transfer processes, a family of compounds has been studied for the past 15 years. These are transition metal complexes, M(tpy)(2) where tpy is a 2,2':6',2" terpyridine based ligand, bearing on one side a donor group and on the other side an acceptor group. The resulting triad molecules or their two-component reference compounds (donor-M(tpy)(2) and M(tpy)(2-acceptor) can contain Ru, Os, Rh or Ir as the metal centre and both visible-light non absorbing groups and porphyrins as donor and acceptor groups. This tutorial review will briefly present the different systems studied and the reasons that led to the preparation of new systems with improved performances.