Capacitance in carbon pores of 0.7 to 15 nm: a regular pattern

The study of 28 porous carbons shows that the specific capacitance in the electrolyte (C(2)H(5))(4)NBF(4)/acetonitrile is relatively constant between 0.7 and 15 nm (0.094 ± 0.011 F m(-2)). The increase in pores below 1 nm and the lower values between 1 and 2 nm reported earlier are not observed in the present work.     

Influence of PVP in magnetic properties of NiSn nanoparticles prepared by polyol method

The influence of PVP on the magnetic properties of NiSn nanoparticles prepared by polyol method has been studied. NiSn nanoparticles exhibit superparamagnetic behavior although there is a ferromagnetic contribution due to particles agglomerated below the blocking temperature. The particle size is controlled by the addiction of PVP in varying amounts. The addition of PVP also favours the particles isolation, narrow the particle size distribution and decrease the interparticle interaction strength increasing the superparamagnetic contribution.     

The formation of chlorine-induced alterations in daguerreotype image particles: a high resolution SEM-EDS study

The daguerreotype image, composed of nanosized silver–mercury or silver–mercury–gold amalgam particles formed on a polished silver substrate, is particularly sensitive to deterioration by chlorine-containing compounds resulting in the formation of AgCl that generates redeposited silver upon exposure to UV and visible lights. In the present study, alterations caused by chlorides on daguerreotype test samples prepared following 19th century recipes were studied. The dependence of variations in the production steps of daguerreotypes, such as multiple sensitization and gilding, on the impact of the exposure to chlorine were analyzed by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) and atomic force microscopy (AFM), complemented by X-ray fluorescence (XRF) and Raman spectroscopy. It was observed that AgCl nucleates on the image particles and in the substrate defects, regardless of the particle density or the sensitization process. In gilded samples, Au was observed over the image particles and the polished silver substrate as a tightly packed grainy layer, which conformably follows the polishing irregularities. For the first time it is shown that Au preferentially accumulates on top of the image particles. This gold layer does not protect the image from chlorine-induced deterioration.     

The influence of low-temperature oxidation of active carbons by nitric acid on their physicochemical properties

The influence of oxidation by nitric acid on the character of oxygen-containing functional surface groups and porous structure of active carbons is considered. Adsorption properties of the initial and oxidized carbons are studied using adsorption isotherms of vapor of n-hexane and polar substances (water and methanol).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1132–1137, May, 1996.     

Mesoscopic self-collimation and slow light in all-positive index layered photonic crystals

We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows us to combine slow-light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air.     

A Goal Programming Model for Rescheduling of Generation Power in Deregulated Markets

In deregulated electrical systems, production schedule for power plants is the result of an auction process. In the Spanish case, this schedule includes two main concepts: energy production (to be actually produced) and secondary reserve (to maintain available). The generation company faces the problem of converting energy schedule into a power schedule, respecting the reserve schedule as well as technical constraints, and trying to accomplish different goals: to minimise the production costs, to obtain smooth shapes for the power schedules and to optimise eventual compensation in schedules. A weighted goal mixed integer programming model with a real-size application to deal with this problem is presented.     

Fourier transform infrared spectroscopic study of surface acidity by pyridine adsorption on Mo/ZrO2-SiO2(Al2O3) catalysts

Acidity of the oxidic molybdenum catalysts supported on mixed ZrO2-SiO2 and ZrO2-Al2O3 carriers was investigated by Fourier transform infrared spectroscopy of pyridine adsorption. Deposition of molybdenum on ZrO2-SiO2 and ZrO2-Al2O3 supports leads to formation of surface Br?nsted acid sites. The number of the Br?nsted and Lewis acid sites in supported-molybdenum catalysts depends on both the ZrO2 content and the type of the support. With increasing ZrO2 content, the Lewis acid sites increase for both series of catalysts. The Br?nsted acid sites are higher for Mo/ZrO2-SiO2 samples compared to those for Mo/ZrO2-Al2O3 and also increase with zirconia.