Étude dans le système mercure solution acide des courbes I = f(E) relatives au dépôt et à la redissolution de traces de: Cu,Tl, Cd,Zn, Ni,Co, Fe

It is possible to redissolve in acid solution traces of Cu, Tl and Zu previously deposited on mercury without oxidising the mercury; the concentrations considered arcofthc order of 100y per ml of amalgam. Under the same conditions the redissolution of traces of Fe, Ni and Co can not be carried out without oxidation of the mercury.The constiuction in 1N H₂SO₄ medium of the curves I = f(E) for the Cu, Cd and Tl ions, the current I being negligible compared with the diffusion current, shows that. a. the variations in log I as a function of the potential E of the mercury or amalgam electrode are linear. b. the position of the curve log I — log a = f(E) is independent of the activity a of the element in solution or amalgam.Our experiments also show: 1° it is necessary to introduce a température coefficient for the coefficient relative to the overpotential of hydrogen on the mercury. 2° for cadmium, at weak current densities, a single electron is put into play in the case of deposition and in that of redissolving.     

Intermittency and small scale resummation

A method of sampling fluctuations in sub-dimensional phase space of (possibly fractal) dimensionD is proposed. Applied to random cascading models of multi-particle production, it gives aD-dependent nonlinear equation for the generating function of particle multiplicities in the sub-domain, whose solutions lead to new properties, e.g. the correction effects of very small scale ressumations on the generic intermittent fluctuations of the model, the unexpected possibility of non vanishing intermittency after dimensional projection and the connection of KNO scaling violations with a structural phase transition. A phenomenological discussion of \(\bar p\) p SPS data allows one to exhibit a simple fragmentation model describing both local and global multiplicity fluctuations observed in these reactions, and compare it with theoretical gluon cascading.     

H?rtebestimmung in Wasser

Ohne Zusammenfassung     

Guanine oxidation: NMR characterization of a dehydro-guanidinohydantoin residue generated by a 2e-oxidation of d(GpT).

The Mn-TMPyP/KHSO(5) system was used to oxidize guanine contained within a dinucleoside monophosphate d(GpT). To identify the guanine oxidation product having a mass with 4 amu above the mass of guanine itself, this relatively unstable compound was reduced to a more stable one. The ESI/MS and NMR data allowed us to propose a dehydro-guanidinohydantoin structure for the (G+4) guanine oxidation product.     

Syntheses of polyfunctionalized resveratrol derivatives using Wittig and Heck protocols

Improved protocols for Wittig reaction and palladium-catalyzed Heck coupling give expedient access to a series of unprecedented polyfunctionalized artificial-resveratrol derivatives. In the modified Wittig protocol, trimethylsilyl was used as a highly valuable protective group of the phenolic functions of starting aromatic materials. A clean O-alkylation of hydroxylated stilbenes with ethylene carbonate was also conducted. Thus, Wittig reaction followed by hydroxyethylation take place one-pot with only carbon dioxide as waste. Additionally, a palladium-catalyzed Heck coupling strategy was developed by using ferrocenyl phosphane ligands, and multi-functionalized hydroxylated stilbenes were obtained without the need of any protection/deprotection sequence. Up to six functional groups are introduced by these procedures, which limit the number of reactions steps, the waste toxicity, and the use of costly reagents.     

Photolysis and Thermolysis of Platinum(IV) 2,2′‐Bipyridine Complexes Lead to Identical Platinum(II)–DNA Adducts

Two Pt^IV and two Pt^II complexes containing a 2,2′‐bipyridine ligand were treated with a short DNA oligonucleotide under light irradiation at 37 °C or in the dark at 37 and 50 °C. Photolysis and thermolysis of the Pt^IV complexes led to spontaneous reduction of the Pt^IV to the corresponding Pt^II complexes and to binding of Pt^II 2,2′‐bipyridine complexes to N7 of guanine. When the reduction product was [Pt(bpy)Cl₂], formation of bis‐oligonucleotide adducts was observed, whereas [Pt(bpy)(MeNH₂)Cl]⁺ gave monoadducts, with chloride ligands substituted in both cases. Neither in the dark nor under light irradiation was the reductive elimination process of these Pt^IV complexes accompanied by oxidative DNA damage. This work raises the question of the stability of photoactivatable Pt^IV complexes toward moderate heating conditions.     

Stability of sputter-deposited gold nanoparticles in imidazolium ionic liquids

The stability of gold nanoparticles synthesised by sputter deposition has been studied in situ in 1-butyl-3-methylimidazolium ionic liquids with bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate and dicyanamide anions with UV-VIS absorption spectroscopy and transmission electron microscopy. Besides the growth of the gold nanoparticles, two other processes were observed after sputtering, namely aggregation and sedimentation of these nanoparticles. To model the absorption spectra of the sputtered gold nanoparticles, generalized multiparticle Mie calculations were performed. These theoretical calculations confirm the increase in absorbance at longer wavelength for larger aggregates and are in agreement with the experimental observations. It was found that the kinetics of aggregation and sedimentation scale with the viscosity of the ionic liquid. Small amounts of water were found to have a large detrimental influence on the stability of the colloidal suspensions of the gold nanoparticles in ionic liquids. From the large discrepancy between the theoretical and the experimentally observed stability of the NPs, it was concluded that structural forces stabilize the gold nanoparticles. This was also borne out by AFM measurements.