Ana Cuesta

The gene encoding ganglioside-induced differentiation-associated protein 1 is mutated in axonal Charcot-Marie-Tooth type 4A disease

We identified three distinct mutations and six mutant alleles in GDAP1 in three families with axonal Charcot-Marie-Tooth (CMT) neuropathy and vocal cord paresis, which were previously linked to the CMT4A locus on chromosome 8q21.1. These results establish the molecular etiology of CMT4A (MIM 214400) and suggest that it may be associated with both axonal and demyelinating phenotypes.

Oxygen plasma modification of pitch-based isotropic carbon fibres

An isotropic carbon fibre was surface-treated by microwave oxygen plasma at different conditions and characterised by scanning electron microscopy (SEM), scanning tunneling microscopy (STM), N2/CO2 adsorption, Raman spectrometry, X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). It is shown that the structure of the fibre suffers only limited alterations upon plasma treatment in such a way that the local disorder on its surface, which was already large in the fresh material, barely increases after the plasma exposure, as detected by Raman measurements. At the nanometre scale, STM images revealed a moderate increase in surface roughness. Evidence for chemical changes undergone by the fibre following the etching was provided by XPS and TPD, showing that stable oxygen functionalities were introduced by the plasma exposure, a result of practical importance for the application of this treatment not only to this type of carbon fibre, but to carbon materials in general. It was also observed that very gentle plasma exposures were generally sufficient to provide the fibre surface with a large amount of oxygen functional groups and that more intense treatments had a negative effect in this respect (i.e. they were not able to supply oxygen to the surface in larger amounts than the softer treatments did).

Effects of oxygen plasma treatment on the surface of graphitized carbon black

Sterling FT carbon black was oxidized in a cool oxygen plasma to various burn-off degrees ranging between 6 and 84%. Plasma-treated samples were characterized by nitrogen and carbon dioxide adsorption, scanning electron microscopy and contact angle measurements. Following the oxygen plasma treatment no changes in BET surface area or porosity were detected. SEM examinations evidenced an absence of fractures or other changes in the morphology of the particles, suggesting that carbon black oxidation by an oxygen plasma takes place through smooth, progressive etching of successive layers of the material. Some heterogeneity in the consumption of spheres was clear at high burn-offs. The contact angles with water decreased at low burn-offs and then remained approximately constant. The oxygen plasma treatment can be tentatively proposed as a suitable method to change carbon black surfaces from hydrophobic to hydrophilic.

Carbon reactivity in an oxygen plasma : a comparison with reactivity in molecular oxygen

Abstract Reactivity upon immersion in an oxygen plasma is studied in this paper on 46 different carbons and coals. Suitable parameters are chosen to characterize the plasma reactivity of these materials. The observed plasma reactivity trend is compared with the O 2 reactivity trend shown by the same set of materials. Differences are discussed in terms of the influence of structural, chemical and textural factors upon carbon gasification in both media. To help discern these influences, multiple regression is applied to the factors derived from a principal components analysis. In contrast with O 2 reactivity, oxygen plasma reactivity shows a more feeble dependence on structural factors and none on chemical factors. On the other hand, reactivity dependence from surface area appears to be stronger for the oxygen plasma than for O 2 . The above observations are interpreted as a corroboration of the Rideal-type mechanism proposed for the carbon–oxygen plasma reaction by Rosner and Allendorf.

Thermal behavior of fullerenes in different gas atmospheres

Abstract The reactivity of a C60 + 15% C70 fullerene mixture in various gases was studied using thermal analysis (TG/DTA) and infrared spectroscopic techniques. The thermal behavior of fullerenes was found to be complex and strongly dependent on the heating rate, overlapping of different phenomena taking place. Comparison with the behavior of a number of carbon materials showed that the reactivity of fullerenes in air is similar to that of the least ordered forms of carbon. An interesting feature is the appearance of various exothermal O2 gasification peaks as the heating rate is increased. C60 undergoes concurrent sublimation and partial decomposition during heat treatment, leaving carbonaceous residues which are partially or totally gasified depending on the reactivity of the surrounding atmosphere. Condensed solids from the sublimation process could be recovered on the cool parts of the thermobalance; mixtures richer in C60 than the starting one were obtained in Ar whereas heating in CO2 led to recovery of oxygenated fullerene derivatives. Carbonaceous residues from pyrolysis in Ar and CO2 were strong infrared absorbers and contained oxygenated (epoxy and carbonyl) functional groups.

Fullerene reactivity in an oxygen plasma

Abstract Fullerene reactivity in an oxygen plasma was measured and compared with those determined under the same conditions for a comprehensive set of 50 carbon materials. The possible reasons for the high plasma reactivity of the fullerene sample in an oxygen plasma are discussed.