Substituted tren-capped porphyrins: probing the influence of copper in synthetic models of cytochrome c oxidase

Tris(2-aminoethylamine) (tren)-capped porphyrins bearing electron donating or withdrawing groups on the amino functions of their tripod have been synthesised and the catalytic activity of each complex was carefully studied both as the iron and the iron-copper complexes: only one of our iron-copper complexes was shown to be active and selective towards the reduction of dioxygen to water.     

Comparative Study of Three Models for Moisture Transfer in Hygroscopic Materials

Transport in Porous Media - Prediction of moisture transfer within material using a classic diffusive model may lack accuracy, since numerical simulations underestimate the adsorption process when...     

D-term inflation, cosmic strings, and consistency with cosmic microwave background measurements

Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings; however, it can still be compatible with cosmic microwave background (CMB) measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained.     

Evidence by spectroscopic ellipsometry of optical property change in pulsed laser deposited NiO films when heated in air at Neel temperature

A spectroscopic ellipsometry (SE) study of Nickel oxide (NiO) films, an anti-ferromagnetic insulator, deposited by pulsed laser ablation technique (PLD) on quartz substrate has been undertaken in the region of its Neel temperature (TN=523 K), when its structure changes from rock-salt to a rhombohedral one, owing to a slight contraction along the 111 direction. The films were grown under optimal conditions in a MECA 2000 process chamber so as to reduce surface roughness to a minimum as shown by Atomic Force Microscope (AFM) and SE characterization. The optical properties have been investigated as a function of temperature in an ultra high vacuum (UHV) process chamber (in situ) and in air, under standard atmospheric conditions (ex situ). We report in this study a change in the ellipsometric parameters of NiO in the visible spectral range from 550 nm to 700 nm when the film is heated in air in the region of TN differently from that observed in ultrahigh vacuum. On the contrary, as expected, SmFeO₃ studied under the same conditions in the same temperature range in air shows no such change in ellipsometric parameters in this spectral region which corresponds to the spectral signature of NiO. Results are discussed in terms of spectral lines involving vibrational states of NiO molecule, when transitions occur between its electronic ground state X^3- and the excited states [16.0]³₀^- and [16.0]³₁^-. These results suggest that NiO ought to be classed as a charge-transfer insulator rather than a Mott–Hubbard one. PACS 07.60.Ds; 78.20.Ci; 81.15Fg     

Simulations of NMR experiments employing static and/or radio-frequency field gradients: application to slice selection by the inhomogeneous radio-frequency field of a standard coil

A general computer program has been developed in order to simulate any nuclear magnetic resonance (NMR) experiment. It includes, in addition to the action of radio-frequency (rf) pulses and of gradients of both the static and the rf magnetic fields, the effects of inhomogeneity of the latter. It has been used here for devising a slice selection procedure on the basis of the inhomogeneity of the rf field delivered by a standard coil (e.g., a saddle-shaped coil). Two sequences have been investigated, a DANTE-like pulse train and a very simple one (named S²P for slice selection with 2π pulses), (2π - τ) _n , where 2π corresponds to the flip angle of the region to be selected, whereas τ has to be chosen according to the relaxation time values;n, the number of cycles, must be sufficiently large, its actual value being uncritical. Simulations show that performances (in terms of selectivity) of both sequences are comparable, while experimental verifications favor S²P for its robustness and for the absence of any signal loss.     

Cobalt-Catalyzed 1,4-Aryl Migration/Desulfonylation Cascade: Synthesis of α-Aryl Amides

A cobalt-catalyzed 1,4-aryl migration/disulfonylation cascade applied to α-bromo N-sulfonyl amides was developed. The reaction was highly chemoselective, allowing the preparation of α-aryl amides possessing a variety of functional groups. The method was used as the key step to synthesize an alkaloid, (±)-deoxyeseroline. Mechanistic investigations suggest a radical process.     

Electrolytic Cell Design to Simulate the Electrochemical Skin Response

Small fiber peripheral neuropathy is an early complication of diabetes. Electric skin response to some stimulus, as electrochemical skin conductance ECS, is a promising route in the early follow‐up of such diseases. It is related to sweat gland innervations and their permeability to chlorides and protons; it is non‐invasive, quantitative and reproducible. In routine clinical use, it could allow to better adapt the treatments and improve the adhesion for preventing pathological progress, thus reducing colossal healthcare costs. To optimize the measurements and understand the electrochemical behavior of electrodes, an original electrolytic cell was designed in lab scale. Thereby, an electrolyte is chosen to mimic sweat composition. For achieving currents range of ESC in vivo measurements, the original idea was to play on electrolyte viscosity by adding sucrose. In this paper, the novel electrolytic lab cell is presented with its limiting kinetics processes. A model of chloride migration to the anode and global electric model dedicated to the cell are proposed. Cell parameters are thoroughly studied, e. g. the resistance, which is equivalent to the inverse of ESC, by exploiting the models and through in vitro experiments, with protocols focusing on reproducibility. This original approach establishes, inter alia, an important result: the resistance is accurately retrieved using linear voltammetry, whereas single voltage measurement fails notably and is, therefore, unsatisfactory.