Well dispersed fractal aggregates as filler in polymer-silica nanocomposites: long range effects in rheology

We are presenting a new method of processing polystyrene-silica nanocomposites, which results in a very well-defined dispersion of small primary aggregates (assembly of 15 nanoparticles of 10 nm diameter) in the matrix. The process is based on a high boiling point solvent, in which the nanoparticles are well dispersed, and controlled evaporation. The filler's fine network structure is determined over a wide range of sizes, using a combination of Small Angle Neutron Scattering (SANS) and Transmission Electronic Microscopy (TEM). The mechanical response of the nanocomposite material is investigated both for small (ARES oscillatory shear and Dynamical Mechanical Analysis) and large deformations (uniaxial traction), as a function of the concentration of the particles. We can investigate the structure-property correlations for the two main reinforcement effects: the filler network contribution, and a filler-polymer matrix effect. Above a silica volume fraction threshold, we see a divergence of the modulus correlated to the build up of a connected network. Below the threshold, we obtain a new additional elastic contribution of much longer terminal time than the matrix. Since aggregates are separated by at least 60 nm, this new filler-matrix contribution cannot be described solely with the concept of glassy layer (2nm)

Integrating precision cancer medicine into healthcare—policy, practice, and research challenges

Abstract Precision medicine (PM) can be defined as a predictive, preventive, personalized, and participatory healthcare service delivery model. Recent developments in molecular biology and information technology make PM a reality today through the use of massive amounts of genetic, ‘omics’, clinical, environmental, and lifestyle data. With cancer being one of the most prominent public health threats in developed countries, both the research community and governments have been investing significant time, money, and efforts in precision cancer medicine (PCM). Although PCM research is extremely promising, a number of hurdles still remain on the road to an optimal integration of standardized and evidence-based use of PCM in healthcare systems. Indeed, PCM raises a number of technical, organizational, ethical, legal, social, and economic challenges that have to be taken into account in the development of an appropriate health policy framework. Here, we highlight some of the more salient issues regarding the standards needed for integration of PCM into healthcare systems, and we identify fields where more research is needed before policy can be implemented. Key challenges include, but are not limited to, the creation of new standards for the collection, analysis, and sharing of samples and data from cancer patients, and the creation of new clinical trial designs with renewed endpoints. We believe that these issues need to be addressed as a matter of priority by public health policymakers in the coming years for a better integration of PCM into healthcare

Adsorption of toluene and toluene–water vapor mixture on almond shell based activated carbons

The aim of work is to study the adsorption of a common volatile organic compound such as toluene using activated carbons prepared by chemical activation with phosphoric acid of a lignocellulosic precursor, almond shell, under different conditions. The Impregnation ratio, temperature and time of activation were modified to obtain activated carbons with different characteristics. Regarding the characteristics of the activated carbons, the effects of porous structure and surface chemistry on the toluene adsorption capacity from toluene isotherms have been analysed. Results show that the control of properties of the activated carbons, particularly porous structure, highly dependent on the preparation conditions, plays a decisive role on the toluene adsorption capacity of the activated carbons. Concerning the experiments of toluene adsorption conducted in dynamic mode, activated carbons prepared at low temperatures of activation show higher breakthrough times than those obtained for activated carbons prepared at higher activation temperatures. The amount of toluene adsorbed in presence of water vapor in the gas stream lead to a decrease ranging from 33 to 46 % except for carbons prepared at higher temperatures activated that show only a slight decrease in the amount of toluene adsorbed. Activated carbons can be regenerated with soft heat treatment showing a slight decrease in the adsorption capacity. The high toluene adsorption capacities as well as the high breakthrough times obtained in presence of water vapor make these activated carbons suitable for commercial applicationsSpanish Ministry of Environment (contracts 439/2006/3-11.2 and B030/2007/2-11.2)Peer reviewe

Proceso para la obtención de tamices moleculares de carbón

La presente invención describe un proceso en el que un precursor de carbón adecuado, como por ejemplo fibras de carbón, fibras de carbón activadas, carbones activos etc. se someten a un calentamiento en un horno microondas en condiciones de temperaturas elevadas y atmósfera inerte. Las particulares características de este calentamiento en microondas producen cambios en la textura porosa de los precursores en forma tal que los transforma en materiales que pueden ser denominados tamices moleculares de carbón. Los tamices moleculares así obtenidos presentan una selectividad para la separación de mezclas O2/N2, CO2/CH4, comparable a la de otros tamices moleculares de carbón obtenidos mediante otros métodos más complejos y costosos que el aquí descrito.Peer reviewe

Cerium oxidation during leaching of CeYSiAlO glass

ACEThe chemical stability of a CeYSiAlO glass was examined after leaching with bidistilled water (autoclave: T=90$^\circ$) during 1 month. The initial $S/V$ ratio was approximately 0.06 cm$^{−1}$ and the pH was free to drift during the experiments (initial pH $\simeq$ 5.5). The leached samples were analyzed using scanning electron microscopy coupled with energy disperse X-ray spectrometer, X-ray photoelectron spectrometry and X-ray diffraction. Dissolution kinetics were also followed by inductively coupled plasma mass spectrometry and spectrophotometry analyses of the liquid medium. The results indicate that Ce is oxidized during leaching which results in the formation of a thick amorphous Ce(IV)-containing layer, possibly CeO$_2$ with Y and probably −OH (and/or H$_2$O) species. It is hypothesized that the low solubility of Ce(IV) oxide (and/or hydroxide) is mainly responsible for the formation of this layer, thus, preventing the release of Y and Ce and to a lesser extent of Si and Al after a few days of leaching

New acrylic monolithic carbon molecular sieves for O2/N2 and CO2/CH4 separations

8 pages, 5 figures, 4 tables.-- Available online Dec 20, 2005.The modification of activated carbon fibres prepared from a commercial textile acrylic fibre into materials with monolithic shape using phenolic resin as binder was studied. The molecular sieving properties for the gas separations CO2/CH4 and O2/N2 were evaluated from the gas uptake volume and selectivity at 100 s contact time taken from the kinetic adsorption curves of the individual gases. The pseudo-first order rate constant was also determined by the application of the LDF model. The samples produced show high CO2 and O2 rates of adsorption, in the range 3–35 × 10−3 s−1, and in most cases null or very low adsorption of CH4 and N2 which make them very promising samples to use in PSA systems, or similar. Although the selectivity was very high, the adsorption capacity was low in certain cases. However, the gas uptake in two samples reached 23 cm3 g−1 for CO2 and 5 cm3 g−1 for O2, which can be considered very good. The materials were heat-treated using a microwave furnace, which is a novel and more economic method, when compared with conventional furnaces, to improve the molecular sieves properties.The authors are grateful to the Fundação para a Ciência e a Tecnologia (Portugal), the European Regional Development Fund (FEDER) and Scientific and Technological Cooperation Program GRICES/CSIC (2004/5_4.1.1) for financial support.Peer reviewe