Palladium Nanoclusters Uniformly Enveloped Electrochemically Activated Graphene for Highly Sensitive Hydrogen Peroxide Sensor

Nonenzymatic sensors based on a metals nanocomposite with high sensitivity, selectivity, and stability has been received considerable interest. In this study, a novel electrochemical nanocomposite sensor based on palladium nanoclusters (PdNCs) decorated electrochemically activated graphene (EAGr) was established for highly sensitive nonenzymatic H₂O₂ sensor. The PdNCs/EAGr nanocomposite was fabricated via an electrochemical activation of Gr by the potential cycling in the range of +0.6 to ?1.8 V, followed by the electrodeposition of PdNCs at ?0.4 V applied potential. The homogeneous dispersion of PdNCs/EAGr nanocomposite were characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The PdNCs/EAGr nanocomposite electrode showed higher electrocatalytic activity towards the reduction of H₂O₂ in pH 7.0 of 0.1 M PBS by significantly enhancing the reduction peak current and reduced the reduction overpotential as well as eliminated other interfering species responses. The PdNCs/EAGr electrode displayed a wide linear range for H₂O₂ reduction from 1.0 to 1100 μM with limit of detection 0.02±0.01 μM. The higher sensitivity and selectivity as well as long‐time stability and excellent reproducibility obtained, indicating the proposed sensor is an effective H₂O₂ based sensor. In addition, the analytical application of the nancomposite sensor was successfully examined for the determination of H₂O₂ in the real sample of human urine indicating that the appreciable practicality of the nonenzymatic sensor for the determination of H₂O₂ in physiological fluids.     

Sparsely synchronized neuronal oscillations

We discuss here the properties of fast global oscillations that emerge in networks of neurons firing irregularly at a low rate. We first provide a simple introduction to these sparsely synchronized oscillations, then show how they can be studied analytically in the simple setting of rate models and leaky integrate-and-fire neurons, and finally describe how various neurophysiological features can be incorporated in this framework. We end by a comparison of experimental data and theoretical results.     

Influence of CuO and sintering temperature on the microstructure and magnetic properties of Mg–Cu–Zn ferrites

The synthesis of a series of Mg–Cu–Zn ferrites with the substitution of Cu for Mg has been obtained by solid-state reaction method. Microstuctural and structural analyses were carried out using a scanning electron microscope and X-ray diffraction (XRD), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. Microstructural analyses indicate that CuO influences the microstructure of the ferrites by the formation of liquid phase during sintering. The grain size significantly increases with increasing copper content. Exaggerated grain growth is observed for the samples of x=0.25–0.35. The initial magnetic permeability (μ′) increases sharply with increasing concentration of Cu ions. This increase in μ′ is explained with the grain growth mechanism and enhanced densification of the ferrites. The resonance frequency of all the samples shifts toward the lower frequency as the permeability increases with Cu content. Sintering temperature T_s also affects the densification, grain growth and initial magnetic permeability of the samples.     

Représentation de Feynman–Kac dans des domaines temps–espace et sensibilité par rapport au domaine

We consider the solution X=(X_t)_t?0 of a time-inhomogeneous stochastic differential equation and the exit time τ by (t,X_t)_t?0 of the time–space domain $\text{D}$. We prove the differentiability of expectations of functionals of X stopped at τ, with respect to the domain $\text{D}$: these results extend those in the literature, known in particular by the analysts for the issues of shape optimization. However from the probabilistic point of view, this is not standard. To cite this article: C. Costantini et al., C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Demonstration of cell-ricin interaction by electrophoretic light scattering

Electrophoretic light scattering has been used to investigate the interaction of ricin, a vegetal toxin, with cells. This technique allowed measurements in the presence of free ligand and proved particularly useful for the study of a system with low affinity. The electrophoretic mobility of erythrocytes and oligodendrocytes was found equal to 2.08 x 10(-8) and 2.35 x 10(-8)m2s-1V-1, respectively. Upon ricin binding, these values decreased significantly. This change was related to the saturation of the binding sites. The specificity of the interaction was demonstrated by conducting the experiments in the presence of lactose. This specific inhibitor fully prevented the ricin-cell interaction.     

Synthesis and structure of 5,5-diethoxycarbonyl-1-pyrroline N-oxide (DECPO). Application to superoxide radical trapping

DECPO, a new analogue of EMPO was synthesized through a two-step synthetic pathway. Its structure and its application to trap superoxide were investigated. The ESR detection of the DECPO-OOH spin adduct is easy even at low concentration of superoxide. In comparison with DEPMPO, the trapping of superoxide with DECPO is faster and the detection of DECPO-OOH can be performed using a very low nitrone concentration (0.5 mM).     

RM values of naphthols and acetophenones in structure-activity studies

The RM values of naphthols obtained in a chromatographic system where the stationary phase consisted of a silica gel G layer impregnated with silicone oil are much more closely related to the log P values in an octanol-water system than the RM values determined on polyamide layers. Similarly, the RM values of a series of acetophenones in the silicone system are closely related to their log P values. The equations describing the structure-activity relationship indicate the importance of lipophilic character and halogen substitution in determining the hemolytic activity and the acute toxicity of compounds.