The effect of particle proximity on the oxygen reduction rate of size-selected platinum clusters.

The diminished surface-area-normalized catalytic activity of highly dispersed Pt nanoparticles compared with bulk Pt is particularly intricate, and not yet understood. Here we report on the oxygen reduction reaction (ORR) activity of well-defined, size-selected Pt nanoclusters; a unique approach that allows precise control of both the cluster size and coverage, independently. Our investigations reveal that size-selected Pt nanoclusters can reach extraordinarily high ORR activities, especially in terms of mass-normalized activity, if deposited at high coverage on a glassy carbon substrate.

In vitro antibacterial effects of five volatile oil extracts against intramacrophage Brucella abortus 544.

Background: Brucellaabortus is a gram-negative facultative intracellular bacterium that can cause a highly contagious disease in sheep, goats, cattle and one-humped camels. It is responsible for one of the most important zoonosis in human. The aim of this study was to evaluate the role of Mentha piperita, Origanum majorana, Citrus lemon, Cinnamomum verum and Myristica fragrans essential volatile oil extracts on human macrophages infected by B.

Dispersive dielectric and conductive effects in 2D resistor-capacitor networks.

How to predict and better understand the effective properties of disordered material mixtures has been a long-standing problem in different research fields, especially in condensed matter physics. In order to address this subject and achieve a better understanding of the frequency-dependent properties of these systems, a large 2D L × L square structure of resistors and capacitors was used to calculate the immittance response of a network formed by random filling of binary conductor/insulator phases with 1000 Ω resistors and 10 nF capacitors. The effects of percolating clusters on the immittance response were studied statistically through the generation of 10 000 different random network samples at the percolation threshold.