Interaction Mechanisms Between Ar–O<Subscript>2</Subscript> Post-Discharge and Stearic Acid II: Behaviour of Thick Films

We study the interaction of thick films (~4 mm) of stearic acid (SA), a C₁₈ alkane skeleton with an acid function, with late Ar–O₂ post-discharge. Contrary to what is observed with thin films of SA (~2–3 μm) which are efficiently etched (part I), only functionalization is observed over the first 2 h of treatment with a plasma source operated in the continuous mode, whatever the temperature. The heat released by surface reactions affects non-linearly the temperature of the substrate. Pulsing the source at a frequency ranging from 0.1 to 1 kHz slows down the functionalization process but does not allow any etching of the material. On the contrary, the SA can be etched as thick films by pulsing the oxygen flow rate at a frequency below 50 mHz. By pulsing the reactive gas, the time averaged value of the [O]/[O₂] ratio is decreased, limiting the functionalization processes due to oxygen atoms, and the mean temperature is lowered, decreasing the diffusion length of O₂ (and/or possibly O₂*) species in the SA which are responsible for the scission of C–C bonds of radicals.     

Crassiflorone, a new naphthoquinone from Diospyros crassiflora (Hien)

A new naphthoquinone, 11-hydroxy-1,9-dimethyl-6H-naphtho[2′,3′:4,5]furo[3,2-c]chromene-6,7,12-trione, named crassiflorone, was isolated from the stem bark of Diospyros crassiflora together with the known compounds plumbagin, cyclocanaliculatin, gerberinol, lupeol, lupenone and betulinic acid. The structures of the compounds were established on the basis of 1D and 2D NMR spectroscopic data, as well as co-TLC with authentic samples. Some of the above compounds exhibited significant antimicrobial activity against bacteria and yeasts.     

Class A mode-locked semiconductor ring laser

We experimentally demonstrate low-repetition-rate mode-locked operation of a macroscopic semiconductor ring laser. Since antiphase periodic pulses are observed only when the two directions of operation are constrained to spatially overlap in the semiconductor medium, we interpret this regime as a result of coupling and competition between clockwise and counterclockwise emission directions. Because of its time constants and the possibility of unidirectional operation, the device could be highly suitable for the generation of temporal cavity solitons.     

Mathematical Analysis of a Transport Model with Unbounded Heat Capacities

We consider a problem of nuclear waste contamination in the basement. We derive a detailed model describing the simultaneous transport of brine, radionuclides and heat in a compressible flow through a porous medium. It leads to a nonlinear system of fully coupled partial differential equations. Using a fixed point approach, we prove existence of physically relevant weak solutions.      

Sur le polygone de Newton et les courbes algébriques planes

Sans résumé     

Importance of Outer‐Sphere and Aggregation Phenomena in the Relaxation Properties of Phosphonated Gadolinium Complexes with Potential Applications as MRI Contrast Agents

A series composed of a tetra‐, a tris‐ and a bisphosphonated ligand based on a pyridine scaffold ( L⁴ , L³ and L² , respectively) was studied within the frame of lanthanide (Ln) coordination. The stability constants of the complexes formed with lanthanide cations (Ln=La, Nd, Eu, Gd, Tb, Er and Lu) were determined by potentiometry in aqueous solutions (25.0 °C, 0.1 M NaClO₄), showing that the tetraphosphonated complexes are among the most stable Ln^III complexes reported in the literature. The complexation of L⁴ was further studied by different titration experiments using mass spectrometry and various spectroscopic techniques including UV/Vis absorption, and steady state and time‐resolved luminescence (Ln=Eu and Tb). Titration experiments confirmed the formation of highly stable [Ln L⁴ ] complexes. ³¹P NMR experiments of the Lu L⁴ complex revealed an intramolecular interconversion process which was studied at different temperatures and was rationalized by DFT modelling. The relaxivity properties of the Gd^III complexes were studied by recording their ¹H NMRD profiles at various temperatures, by temperature dependent ¹⁷O NMR experiments (Gd L⁴ ) and by pH dependent relaxivity measurements at 0.47 T (Gd L³ and Gd L² ). In addition to the high relaxivity values observed for all complexes, the results showed an important second‐sphere contribution to relaxivity and pH dependent variations associated with the formation of aggregates for Gd L² and Gd L³ . Finally, intravenous injection of Gd L⁴ to a mouse was followed by dynamic MRI imaging at 1.5 T, which showed that the complex can be immediately found in the blood stream and rapidly eliminated through the liver and in large part through the kidneys.