Application du contrôle optimal à l'amélioration des trithérapies

Highly Active Anti-Retroviral Therapies (HAART) have proven to be extremely effective in improving and prolonging the patient's life. Though, a concern arises since a long term drug intake induces many strong sides effects and reduces reactivity of the virus to any therapy. The purpose of the paper is to use numerical analysis and optimization tools to suggest improved therapies to handle HIV infection. The evolution of the infection is modelled by an ordinary differential equation system which includes both immune response and multi-drug effects. For a fixed time, one looks for a two drugs control strategy based on Pontryagine's minimum principle with an objective function which takes into account three contributions: the viral load, the transient evolution of infection and the quantities of drug used. Simulations are carried out using an indirect optimization method along with Runge–Kutta adaptative stepsize algorithm. Numerical solutions to the optimality system are obtained and related histories are shown. The possibility of Scheduled Treatment Interruption is also examined.     

O2 diffusion in SiO2: triplet versus singlet

We address the diffusion of the oxygen molecule in SiO2, using first-principles spin-polarized total-energy calculations. We find that the potential energy surfaces for the singlet and triplet states are very different in certain regions, and that the O2 molecule preserves its spin-triplet ground state not only at its most stable interstitial position inside the solid but also throughout its diffusion pathway. Therefore, the singlet state is not a good approximation to describe the behavior of O2 inside SiO2, and spin-polarization effects are fundamental to understand the properties of this system.     

A theoretical study of Fe adsorption along Bi-nanolines on the H/Si(0 0 1) surface

We have investigated the energetic stability and equilibrium geometry of the adsorption of transition metal Fe atoms near the self-organized Bi lines on hydrogen passivated Si(0 0 1) surface. Our total energy results show that there is an attractive interaction between Fe adatoms along the Bi-nanolines. For the energetically most stable configuration, the Fe adatoms are seven-fold coordinated, occupying the subsurface interstitial sites aside the Bi-nanolines. With increased coverage, Fe atoms are predicted to form two parallel lines, symmetrically on both sides of the Bi line. Within our local spin-density functional calculations, we find that for the most stable geometries the Fe adatoms exhibit an antiferromagnetic coupling.     

Oxygen-sensitive layers for optical fibre devices

The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, luminescent metal complex Ru(5-odap) ₃ ²⁺ (where 5-odap stands for 5-octadecanamide-1,10-phenanthroline), are reported and compared to those of the well-known tris(1,10-phenanthroline) analogue. An array of silicone membranes, containing Ru(5-odap) ₃ ²⁺ or Ru(₂p) ₃ ²⁺ (where ₂p stands for 4,7-diphenyl-1,10-phenanthroline) as solid-supported luminescent indicators, have been fabricated. Their (non-linear) response to oxygen was evaluated with fibre-optics as a function of their adsorbent nature (silica gel, glass, reverse-phase silica, styrene/divinyl benzene copolymer, or none), surface coverage by the deposited metal complex, and loading of dyed support into the sensitive layer. The largest oxygen sensitivity (I ₀/I ca. 6 for a partial pressure of 130 Torr) is achieved with the highest amount of silica gel- or glass-supported Ru(₂p) ₃ ²⁺ and the highest membrane loading. Ru(5-odap) ₃ ²⁺ dissolved directly into silicone yields a linear dose/response plot, but with a small slope (I ₀ /I ca. 1.4 for a partial pressure of 720 Torr). These results are discussed in terms of dynamic surface quenching between the co-adsorbed indicator and oxygen molecules.     

LIGAND-DEPENDENT INTERACTION OF RUTHENIUM(II) POLYPYRIDYL COMPLEXES WITH DNA PROBED BY EMISSION SPECTROSCOPY

The nature of the interaction in buffered aqueous solution of several homo and heteroleptic ruthenium(II) polypyridyl complexes containing 2,2'-bipyridine (bpy), 2,2'-bipyrazine (bpz), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (dip), 3,4,7,8-tetramethyl-1,10-phenanthroline (tmp), 1,4,5,8-tetraazaphenanthrene (tap), and 1,4,5,8,9,12-hexaazatriphenylene (hat) with calf thymus DNA and poly(dA-dT).poly(dA-dT) (pdAT) has been investigated by steady-state spectroscopy and emission lifetime measurements. Those complexes containing two or more tap/hat ligands photo-oxidize the guanine base upon binding to DNA with efficiencies that parallel their excited state redox potentials, but display "normal" behavior (increase of both the emission intensity and lifetime) when bound to pdAT. However Ru(tap)(hat)2+2 and Ru(hat)2+3 even photooxidize the adenine base of pdAT, so that their excited states are also quenched in the presence of either polynucleotide. The electron transfer quenching mechanism has been confirmed previously by detection of the monoreduced complex in laser flash photolysis experiments in the presence of mononucleotides. Most of the complexes investigated appear to bind to DNA, at least in part via intercalation, with affinities being dependent on the nature of the largest ligand (hat shows the highest ability in heteroleptic complexes). From lifetime quenching experiments, in the presence of moderate amounts of NaCl, surface binding does not appear to be a general mode for the complexes investigated, and it has been demonstrated unequivocally only for Ru(phen)2+3. In addition, the intercalation of complexes into DNA increases as the ionic strength of the medium decreases, the DNA/Ru ratio increases, or when water is partially replaced by glycerol.     

Theoretical calculation of the electronic structure and the optical spectrum of CrF2−6

The electronic structure of the CrF^2?₆ cluster has been analyzed by solving the Hartree-Fock equations on several electronic states, at five values of R, the metal-ligand distance in the a_1g vibration. The methodology of J. W. Richardson, T. F. Soules, D. M. Vaugth, and R. R. Powell (Phys. Rev. B4, 1721 (1971)) has been used. The computed R_e is in close agreement with the observed value in alkali hexafluorochromates(IV). The nuclear potentials of the d² triplets are almost parallel to the ground state potential, giving rise to a weak R-dependence of the spin-allowed transitions and a negligible contribution of the a_1g progression to the vibrational structure of the broad bands. The absorption spectrum has been discussed in terms of the results of different SCF calculations. A new assignment is proposed that avoids most of the earlier difficulties of the spectral interpretation. The best calculated spectrum agrees with the one observed in Rb₂CrF₆ within 1.5 kK.     

Penta-coordinated transition metal macrocycles as electrocatalysts for the oxygen reduction reaction

Journal of Solid State Electrochemistry - The oxygen reduction reaction (ORR) is a highly important reaction in electrochemistry. The following short review details recent advances in novel...     

Noise in the adult emergency department of Johns Hopkins Hospital

While hospitals are generally noisy environments, nowhere is the pandemonium greater than in an emergency department, where there is constant flow of patients, doctors, nurses, and moving equipment. In this noise study we collected 24 h measurements throughout the adult emergency department of Johns Hopkins Hospital, the top ranked hospital in the U.S. for 16 years running. The equivalent sound pressure level (Leq) throughout the emergency department is about 5 dB(A) higher than that measured previously at a variety of in-patient units of the same hospital. Within the emergency department the triage area at the entrance to the department has the highest Leq, ranging from 65 to 73 dB(A). Sound levels in the emergency department are sufficiently high [on average between 61 and 69 dB(A)] to raise concerns regarding the communication of speech without errors--an important issue everywhere in a hospital and a critical issue in emergency departments because doctors and nurses frequently need to work at an urgent pace and to rely on oral communication.     

Fluorescent Optosensor for Humidity Measurements in Air

A fiber‐optic sensor for relative‐humidity (RH) monitoring in environmental samples is described based on the adiabatic photoreaction that produces an intramolecular charge‐transfer excited state, which is the basis of the sensor response. The sensitive membranes are obtained immobilizing a highly fluorescent dye, 4‐[2‐(pyrazin‐2‐yl)‐1,3‐oxazol‐5‐yl]benzenamine (pzoxba; formerly called appzox), in hydroxypropylcellulose (HPC). The composition of the sensing films was optimized to a final ratio pzoxba/HPC of 1.8⋅10⁻⁵ mol g⁻¹ with a 100‐μm membrane thickness. The optode response spans from 1.68 to 100% RH, with a detection limit of 0.56% (Table 2). Typical response times (t₉₀) to 0 – 100% relative humidity are 1 – 2 min, the relative standard deviation for repeated measurements being 0.77 – 1.8%. The optode is insensitive to typical organic vapor interferents of commercial capacitive sensors (see Table 3) as well as to molecular oxygen, an important quencher of other luminescence‐based optical sensors. The proposed optode was successfully applied and validated for continuous monitoring of the relative humidity level in environmental samples.