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One-dimensional gas chromatography (1D-GC) stationary phases are generally classified according to their relative polarity into non-polar, semi-polar, and polar columns. In comprehensive two-dimensional gas chromatography (GC*GC), it is the polarity difference between the two tandem-assembled stationary phases that determines the selectivity of the column ensemble. This polarity difference is called orthogonality, and GC*GC column sets can be broadly categorized into four groups based on the direction of the serial coupling between the primary and secondary columns. A significant portion of the GC*GC column sets in use today are operated in forward-orthogonality mode, which means that the secondary column is more polar than the primary column. A growing number of reported GC*GC applications operate in reversed-orthogonality configurations, where the secondary column is less polar than the primary column. Very few examples exist of non-orthogonal column sets because of the fact that there is limited additional selectivity that the secondary column can offer over the separation that has already been achieved in the primary column when the two phases are either identical or close in polarity. The fourth group of GC*GC column sets, called hybrid orthogonality, involves the coupling of stationary phases with peculiar selectivity differences that manifest themselves in the bi-dimensional separation plots. In this work, we are presenting a normalized approach to GC*GC column set characterization that is based on the use of a reference mixture of standards called the Century Mix. The Century Mix contains 100 chemical probes of different functionalities that span a reasonable range of volatilities and polarities to capture the selectivity profile of any GC*GC column set. The Century Mix also contains important chemical probes that are used for 1D-GC column characterization (such as the Grab mix and the Rohrschneider/McReynolds compounds) to make some connections between the 1D-GC building block columns and the GC*GC column sets. We finally also outline some other important metrics of comparison that should be taken into consideration to assess the overall performance of a GC*GC system., THE GOAL OF ANY chromatographic method is the full separation of all analytes of interest in the shortest period of time possible, with good peakshape attributes. Therefore, column selection is [...]

The graphite is an allotropic form of the element carbon consisting of layers of hexagonally arranged carbon atoms in a planar condensed ring system. Coke particles used for conventional synthetic graphite products are long and narrow. These particles produce a preferred structural orientation in the product after the conventional uniaxial pressing or extrusion with high anisotropy. With a properly election of raw materials and process is possible reduce the anisotropy to obtain isotropic graphite. Repsol-YPF has produced a binderless polyaromatic mesophase from petroleum pitch, which has shown to be very appropriated as raw material for production of high strength isotropic graphite with high performance and low cost. This graphite have offered thermal, mechanical, chemical and wear properties higher than conventional graphite. The isotropic graphite obtained is suitable for making pistons, valves, turbojoints and other automotives components. The pistons design with this isotropic graphite has been developed for an automotive petrol engine. Piston prototypes were manufactured and tested in engines at full power and at full torque. This paper analysed the physical, mechanical and fracture properties of the isotropic graphite obtained.El grafito es una forma alotrópica del carbono, consistente en capas de átomos de carbono cristalizados en anillos hexagonales planos. Las partículas de coque utilizadas para sintetizar el grafito convencional son largas y estrechas, lo que da lugar a una estructura orientada de alta anisotropía tras un proceso de compactación o extrusión. Con una adecuada selección de materias primas y procesos de conformado es posible reducir dicha anisotropía, hasta eliminarla en la obtención del grafito isotrópico. La empresa Repsol-YPF, S.A., ha desarrollado un proceso para la fabricación de una mesofase poliaromática extraída por carbonización de residuos del refino del petróleo, a partir de la cual se obtiene un grafito isotrópico de altas prestaciones y bajo costo. Este grafito presenta propiedades térmicas, mecánicas, químicas y tribológicas muy superiores al grafito convencional; habiéndose propuesto su utilización para la fabricación de pistones, válvulas, cierres de bombas de agua y otros componentes en motores de automoción. Se han desarrollado pistones diseñados con este grafito isotrópico para un motor de gasolina. Estos pistones prototipo han sido fabricados y ensayados en motores a plena potencia y plena carga. En este trabajo se analizan las propiedades físicas, mecánicas y el comportamiento a fractura de este grafito isotrópico.

Dynamic Visual Acuity (DVA) can be measured from two types of equivalently considered movement referred to as drifting-motion and displacement-motion. Displacement motion can be best described as the horizontal displacement of a stimulus, thus implying pursuit eye movements, and involves moving the stimulus from the fixation point of gaze towards the periphery. The drifting motion of a Gabor patch, for example, avoids pursuit eye movements, since the gaze is fixed in a point of the patch. Our data shows that in both types of movement visual acuity (VA), expressed in terms of spatial frequency, diminished as the velocity of the target increased. However, the slope of the regression equation indicated that this impairment is more than two-fold in the case of drifting-motion when compared to displacement motion. As the greater impairment took place when pursuit eye movements did not exist, our data suggests that these two types of motions correct differently for retinal slip. Retinal slip appears to be less efficiently compensated for in the case of drifting motion having adverse consequences on VA, while retinal slip has a higher tolerance in the case of displacement motion exhibited by the performance in VA. (Contains 5 figures.)