Formal and convergent solutions of singular partial differential equations

We consider the problem of the existence of convergent series solutions for partial differential operators of the form . We give first conditions for P such that the linear equation Pu=f has an analytic solution, then we solve nonlinear equations of the form Pu=F(x,u). For applications we treat also cases with parameters and give a proof of a theorem of S. Kaplan [5]. In the last section we consider a case where small denominators occur.     

Recherches sur la structure électronique et les caractéristiques des différentes formes tautomères de la purine

Résumé Les caractéristiques électroniques (énergie, charges , géométrie, moment dipolaire, énergie de transition) des quatre formes tautomères de la purine et des phényl-8 N(1)H et N(3)H purines ont été déterminées par la méthode LCAO améliorée. La forme 9 est trouvée la plus stable à l'état isolé. Une interprétation nouvelle des bandes d'absorption est proposée.

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Researches on the electronic structure and the characteristics of various tautomer forms of Purine

The electronic characteristics (energy, charge , geometry, dipole moment, transition energy) of the four tautomeric forms of the purine and of the phenyl-8 N(1)H and N(3)H purines have been determined by the improved LCAO method. The form 9 is considered as the most stable at the isolated state. A new interpretation of the absorption bands is proposed.

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Zusammenfassung Die elektronischen Charakteristiken (Energie, Ladung , Geometrie, Dipolmoment, Übergangsenergie) der vier Tautomerformen des Purins und der Phenyl-8 N(1)H und N(3)H Purine sind durch die verbesserte LCAO-Methode bestimmt worden. Die Form 9 ist, zum isolierten Stand, als am meisten beständig zu betrachten. Eine neue Erklärung der Absorptionsbänder ist vorgeschlagen.

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Les auteurs remercient le Professeur B. Pullmann (Paris) de l'intérêt qu'il a porté à ce travail, ainsi que Madame H. Feilchenfeld (Jérusalem) pour les résultats inédits qu'elle a bien voulu leur communiquer.     

Thermal investigation of PEG 4000 — oxazepam binary system

A thermal study using DSC and Hot Stage Microscopy (HSM) was carried out to investigate the interaction in solid state of the binary system PEG 4000 — oxazepam, and to establish their phase diagram. The eutectic composition, which melting occurs at lower temperature as compared with the pure components, has been determined. The results obtained by DSC and HSM have indicated that PEG 4000 — oxazepam mixtures displays no obvious incompatibilities, and that the system shows a typical eutectic behaviour. However because of the closeness of the melting of PEG 4000 to the eutectic temperature, it was difficult to determine precisely the eutectic composition and temperature on the basis of DSC measurements alone. The use of heats of fusion corresponding to physical mixtures allowed an estimation of the eutectic composition at 6% w/w oxazepam. Additional information of temperature (57.6C) and composition (5–10% w/w oxazepam) of the eutectic was obtained by HSM using the contact method. This low melting temperature in this range of compositions offers advantages in terms of drug stability and easy manufacture.     

Effect of film thickness on the electro-reduction of molecular oxygen on electropolymerized cobalt tetra-aminophthalocyanine films

We studied the electrocatalytic activity of cobalt tetra-aminophthalocyanine (CoTAPc) for the reduction of molecular oxygen (O₂) on adsorbed monomeric and on electropolymerized films of different thicknesses on glassy carbon (GC) electrode. The polymeric films, denoted poly-CoTAPc, were first characterized by electrochemical impedance spectroscopy and it appears that the types of phenomena revealed to be occurring depend less on the film thickness in basic than in acid media. For O₂ reduction, the results showed that poly-CoTAPc is more active than the monomeric CoTAPc adsorbed on GC. Indeed, rotating ring-disk electrode data showed that polymeric CoTAPc promotes the four-electron reduction of O₂ to water in parallel to a two-electron reduction to give peroxide. On monomeric and thin films of poly-CoTAPc, a two-electron reduction mechanism predominates. In basic media the activity increases very slightly with thickness, whereas in acid media this increase is more pronounced. This parallels the observed behavior revealed by electrochemical impedance spectroscopy.     

The maximum common substructure as a molecular depiction in a supervised classification context: experiments in quantitative structure/biodegradability relationships

The maximum common structure between two molecules (MCS) induces a similarity that enables one to group compounds sharing the same pattern. This text relates a study based on such a structural depiction in a context of quantitative structure/biodegradability relationships (QSBR). The similarity indices are based exclusively on the MCS. First, the results of statistical tests prove that these indices significantly group compounds of similar activity together. These first conclusions enable the elaboration of classification models using those structural similarities. In a second part, a population of classifiers relying on the maximum common structure and the k-nearest-neighbor algorithm is explored. Finally, a thorough examination of the best models is conducted.     

Dérivés de la dihydro-2,4 triazole-1,2,4 thione-3 et de l'amino-2 thiadiazole-1,3,4 à partir de nouvelles thiosemicarbazones d'esters

A new general synthesis of 4,5-disubstituted 2,4-dihydro-1,2,4-triazole-3-thiones is proposed. These heterocycles are obtained by the action of primary amines, arylhydrazines or aroylhydrazines on the thiosemicarbazones of eaters. These last compounds are prepared by action of chlorhydrates of iminoethers on thiosemicarbazide in dimethylformamide. These thiosemicarbazones react also with strong acids, acid anhydrides and chlorides; by thermolysis and they give 2-amino-1,3,4-thiadiazole derivatives. Also, two derivatives of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole have been prepared.     

Crystal structure and luminescence of compounds A3BC10O20

In this paper we describe compounds A₃BC₁₀O₂₀ (A = Sr, Ba, Pb; B = Ti, Ge, Sn; and C = Al, Ga). The crystal structure of Ba₃TiAl₁₀O₂₀ has been determined by neutron powder profile refinement. The luminescence of these compounds has been investigated. Apart from the titanate luminescence of Ba₃TiAl₁₀O₂₀, these compounds show a semiconductor type of luminescence.     

Synthesis and structure determination from powder data of the first organically templated tin(IV) phosphate: MIL-76 or Sn3(IV)O2(H2O)(HPO4)4 x [H2N-C2H4-NH2]2.5 x [H2O]2

The first organically templated tin(IV) phosphate has been isolated and its structure solved from powder X-ray diffraction data; it exhibits a one-dimensional inorganic network built up from chains of trimers of tin(IV) octahedra on which phosphate tetrahedral groups are grafted interacting with water molecules and organic moieties.     

DNA-binding of semirigid binuclear ruthenium complex delta,delta-[mu-(11,11'-bidppz)(phen)(4)ru(2)](4+): extremely slow intercalation kinetics

We here report a remarkably slow rearrangement of binding modes for a binuclear ruthenium(II) complex upon interaction with DNA. It has been previously shown that Delta,Delta-[mu-(11,11'-bidppz)(phen)4Ru2]4+ binds to DNA in one of the grooves. However, we find that this is only an initial, metastable, binding mode, which is extremely slowly reorganized into an intercalative binding geometry. The slow rearrangement and dissociation, revealed by flow linear dichroism and fluorescence spectroscopy, are concluded to be a result from the complex being threaded through the DNA, with one of the bridging aromatic dppz ligands intercalated between the base pairs of the DNA, placing one metal center in the minor groove and one in the major groove. A negative LD, a high luminescence quantum yield, and long luminescence lifetimes, similar to the intercalating complex Delta-[Ru(phen)2dppz]2+, indicate intercalation of the bidppz moiety. The unique slow dissociation of the complex in its final DNA-binding mode suggests that this class of threading, partially intercalated binuclear complexes may be interesting in the context of cancer therapy. Also, their unique optical and photophysical properties could make such complexes, either alone or scaffolded by DNA structures, of interest for the development of nanometer-sized molecular optoelectronic devices.