Bioactive peptides grafted silicone dressings: A simple and specific method

The need for bioactive dressings increases with the population aging and the prevalence of chronic diseases. In contrast, there are very few dressings on the market which are designed to display a chosen bioactivity. In this context, we investigated the surface-functionalization of silicone wound dressing with bioactive peptides. One of the challenges was to avoid multistep grafting reactions involving catalysts, solvents or toxic reagents, which are not suitable for the fabrication of medical devices at an industrial scale. In the other hand, a covalent bonding was necessary to avoid the loss of the biological effect by progressive removal of the peptide in biological fluids generated by the wound. To solve these limitations, we developed a strategy allowing an easy and direct functionalization of silicone. This strategy relies on hybrid silylated bioactive peptides, which chemoselectively react with plasma-activated silicone surfaces. We synthesized three hybrid peptides with wound healing properties, which were grafted on commercially available silicone dressings Cerederm^® and Mepitel^®. Grafted dressings were evaluated in vitro and enabled a quicker scare recovery and extracellular matrix deposition with human dermal fibroblasts. These results were confirmed by in vivo studies showing an enhanced wound-healing of the pig skin. By this simple method, we transformed inert dressing into bioactive dressing which showed properties of wound healing.     

Vortex shedding modeling using diffusive van der Pol oscillatorsModélisation du détachement tourbillonnaire avec des oscillateurs de van der Pol interagissant par diffusion

A simple model for the near wake dynamics of slender bluff bodies in cross-flow is analyzed. It is based on a continuous distribution of van der Pol oscillators arranged along the spanwise extent of the structure and interacting by diffusion. Diffusive interaction is shown to be able to model cellular vortex shedding in shear flow, the cell size being estimated analytically with respect to the model parameters. Moreover, diffusive interaction succeeds in describing qualitatively the global suppression of vortex shedding from a sinuous structure in uniform flow. To cite this article: M.L. Facchinetti et al., C. R. Mecanique 330 (2002) 451–456.     

Self-excited stick–slip oscillations of drill bitsOscillations stick–slip auto-entretenues d'un outil de forage

This Note studies the self-excited stick–slip oscillations of a rotary drilling system with a drag bit, using a discrete model which takes into consideration the axial and torsional vibration modes of the bit. Coupling between these two vibration modes takes place through a bit-rock interaction law which accounts for both frictional contact and cutting processes at the bit-rock interface. The cutting process introduces a delay in the equations of motion which is ultimately responsible for the existence of self-excited vibrations, exhibiting stick–slip oscillations under certain conditions. To cite this article: T. Richard et al., C. R. Mecanique 332 (2004).     

The role of boundary conditions in the instability of one-dimensional systems

We investigate the instability properties of one-dimensional systems of finite length that can be described by a local wave equation and a set of boundary conditions. A method to quantify the respective contributions of the local instability and of wave reflections in the global instability is proposed. This allows to differentiate instabilities that emanate from wave propagation from instabilities due to wave reflections. This is illustrated on three different systems, that exhibit three different behaviors. The first one is a model system in fluid mechanics (Ginzburg–Landau equation), the second one is the fluid-conveying pipe (Bourrières equation), the third one is the fluid-conveying pipe resting on an elastic foundation (Roth equation).     

Efficient Population Transfer in a Λ-Type Quantum System Coupled to a Gold Nanoparticle Using STIRAP Shortcuts

A theoretical investigation on the population transfer in a Λ-type quantum system near a spherical gold nanoparticle under application of two stimulated Raman adiabatic passage (STIRAP) shortcuts and efficiency comparison with conventional STIRAP. It combines the density matrix approach for system dynamics, with classical electromagnetic calculations used to obtain the modified electric field amplitudes of the applied pulses and the Purcell factor of the quantum system due to the presence of the nanoparticle. The efficiency of population transfer is investigated by varying the distance between the quantum system and the nanoparticle, the free-space decay rate of quantum states, the mutual polarization, and the Rabi frequencies of each STIRAP shortcut pulses. In all cases, at least one of the applied shortcuts is more efficient than conventional STIRAP, while in most cases both perform better. When the pump and Stokes fields of the shortcuts have radial and tangential polarizations with respect to the nanoparticle surface, respectively, high transfer efficiency is obtained for small distances of the quantum system to the nanoparticle, moderate free space decay rates and large Rabi frequencies of the fields, while when the pulse polarizations are interchanged, the transfer becomes highly efficient only at large distances.     

Deciphering the Interactions of Bioactive Compounds in Selected Traditional Medicinal Plants against Alzheimer’s Diseases via Pharmacophore Modeling,Auto-QSAR,and Molecular Docking Approaches

Neurodegenerative diseases, for example Alzheimer’s, are perceived as driven by hereditary, cellular, and multifaceted biochemical actions. Numerous plant products, for example flavonoids, are documented in studies for having the ability to pass the blood-brain barrier and moderate the development of such illnesses. Computer-aided drug design (CADD) has achieved importance in the drug discovery world; innovative developments in the aspects of structure identification and characterization, bio-computational science, and molecular biology have added to the preparation of new medications towards these ailments. In this study we evaluated nine flavonoid compounds identified from three medicinal plants, namely T. diversifolia, B. sapida, and I. gabonensis for their inhibitory role on acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and monoamine oxidase (MAO) activity, using pharmacophore modeling, auto-QSAR prediction, and molecular studies, in comparison with standard drugs. The results indicated that the pharmacophore models produced from structures of AChE, BChE and MAO could identify the active compounds, with a recuperation rate of the actives found near 100% in the complete ranked decoy database. Moreso, the robustness of the virtual screening method was accessed by well-established methods including enrichment factor (EF), receiver operating characteristic curve (ROC), Boltzmann-enhanced discrimination of receiver operating characteristic (BEDROC), and area under accumulation curve (AUAC). Most notably, the compounds’ pIC₅₀ values were predicted by a machine learning-based model generated by the AutoQSAR algorithm. The generated model was validated to affirm its predictive model. The best models achieved for AChE, BChE and MAO were models kpls_radial_17 (R² = 0.86 and Q² = 0.73), pls_38 (R² = 0.77 and Q² = 0.72), kpls_desc_44 (R² = 0.81 and Q² = 0.81) and these externally validated models were utilized to predict the bioactivities of the lead compounds. The binding affinity results of the ligands against the three selected targets revealed that luteolin displayed the highest affinity score of −9.60 kcal/mol, closely followed by apigenin and ellagic acid with docking scores of −9.60 and −9.53 kcal/mol, respectively. The least binding affinity was attained by gallic acid (−6.30 kcal/mol). The docking scores of our standards were −10.40 and −7.93 kcal/mol for donepezil and galanthamine, respectively. The toxicity prediction revealed that none of the flavonoids presented toxicity and they all had good absorption parameters for the analyzed targets. Hence, these compounds can be considered as likely leads for drug improvement against the same.     

Changes in Light Energy Utilization in Photosystem II and Reactive Oxygen Species Generation in Potato Leaves by the Pinworm Tuta absoluta

We evaluated photosystem II (PSII) functionality in potato plants (Solanum tuberosum L.) before and after a 15 min feeding by the leaf miner Tuta absoluta using chlorophyll a fluorescence imaging analysis combined with reactive oxygen species (ROS) detection. Fifteen minutes after feeding, we observed at the feeding zone and at the whole leaf a decrease in the effective quantum yield of photosystem II (PSII) photochemistry (Φ_PSII). While at the feeding zone the quantum yield of regulated non-photochemical energy loss in PSII (Φ_NPQ) did not change, at the whole leaf level there was a significant increase. As a result, at the feeding zone a significant increase in the quantum yield of non-regulated energy loss in PSII (Φ_NO) occurred, but there was no change at the whole leaf level compared to that before feeding, indicating no change in singlet oxygen (¹O₂) formation. The decreased Φ_PSII after feeding was due to a decreased fraction of open reaction centers (q_p), since the efficiency of open PSII reaction centers to utilize the light energy (Fv′/Fm′) did not differ before and after feeding. The decreased fraction of open reaction centers resulted in increased excess excitation energy (EXC) at the feeding zone and at the whole leaf level, while hydrogen peroxide (H₂O₂) production was detected only at the feeding zone. Although the whole leaf PSII efficiency decreased compared to that before feeding, the maximum efficiency of PSII photochemistry (Fv/Fm), and the efficiency of the water-splitting complex on the donor side of PSII (Fv/Fo), did not differ to that before feeding, thus they cannot be considered as sensitive parameters to monitor biotic stress effects. Chlorophyll fluorescence imaging analysis proved to be a good indicator to monitor even short-term impacts of insect herbivory on photosynthetic function, and among the studied parameters, the reduction status of the plastoquinone pool (q_p) was the most sensitive and suitable indicator to probe photosynthetic function under biotic stress.     

Electrochemical Determination of Neomycin and Norfloxacin at a Novel Polymer Nanocomposite Electrode in Aqueous Solution

Organic compounds such as antibiotics that are not effectively removed by modern-day treatment technology are a growing threat to water quality and health. The emergence of antibiotics in the aquatic environment is a matter of concern as they may induce bacterial resistance, a major threat to health-care management and an increasing economic crisis. The current methods that are used to detect antibiotics are expensive and time consuming due to the sample preparation necessary for the determination of low concentrations of antibiotics in water and the instruments used. Electrochemical sensors and biosensors are simple systems, with high selectivity and sensitivity for individual measurements and low cost. In this study, we present a novel polyamic acid/graphene oxide electrode that was prepared for electrochemical screening of selected antibiotic residues in aqueous solution. Polyamic acid and graphene oxide were synthesized independently and characterized using microscopic, spectroscopic, and voltammetric approaches. A polyamic acid/graphene oxide/screen-sprinted carbon electrode was prepared in situ by electrochemical deposition of polyamic acid/graphene (0.03?mg/mL 50:50 mass ratio) on screen-printed carbon electrodes using five cycles between ?1000 and 1000?mV at 50?mV/s. The polyamic acid/graphene oxide/screen-printed carbon electrode provided limits of detection of 0.034?µM for norfloxacin and 1.07?µM for neomycin. Recovery studies on synthetic urine showed good inter-day and intra-day coefficients of variation (n?=?3).     

On a generalization of the Selberg formula

In this paper, we prove a theorem related to the asymptotic formula for ψk(x;q,a) which is used to count numbers up to x with at most k distinct prime factors (or k-almost primes) in a given arithmetic progression . This theorem not only gives the asymptotic formula for ψk(x;q,a) (or Selberg formula), but has played an essential role, recently, in obtaining a lower bound for the variance of distribution of almost primes in arithmetic progressions.