Nanostructured Catalysts for Dry-Reforming of Methane.

The manuscript deals on the main progress achieved by global scientific research on the development of nanostructured catalysts for dry-reforming reaction. The importance to have a global vision on this topic is strictly related to the most currently and important challenges in the sustainable energy production. In fact, dry-reforming is one of the few known processes in which greenhouse gases are utilized as reactants (methane and carbon dioxide) to produce syngas. Syngas represents the basis for liquid fuel production by Fischer-Tropsch process. In this broad and current context, the catalyst development plays a pivotal role due to its great influence on efficiency, and therefore on the costs, of the whole process. Several are the aspects to consider during the catalyst design: role of metal, interaction between metal and support, role of promoters and resistance to the coke deactivation. These issues, as well as the thermodynamics of the process, are the main aspects of which this review speaks about.

CO2 Adsorption Investigation on an Innovative Nanocomposite Material with Hierarchical Porosity.

A NaX nanozeolite-geopolymer monolith, with hierarchical porosity, has been produced by a one-pot hydrothermal synthesis using metakaolin as alluminosilicate source and a sodium silicate solution as activator. Its final composition, reported in terms of oxides, is 1.3-Na2O-3.0SiO2-1Al2O3-12H2O. Its microstructural and chemical features and CO2 adsorption performance have been investigated. The microstructure of the composite is characterized by NaX zeolite nanocrystals glued by the geopolymeric binder to form a complex three-dimensional network of pores. Overall porosity resulted ~23.5%, whereas compressive strength is 16±0.7 MPa. Monolith showed BET surface area of 350 m²/g, a micropore surface area of 280 m²/g and a mesopore volume, due to the geopolymeric binder, of 0.09 cm³/g. Its CO2 adsorption capacity has been measured at the temperatures of 7, 25 and 42 °C up to 15 bar using an optimized Sievert-type (volumetric) apparatus. All the adsorption data were evaluated by Toth/Langmuir isotherm model and commercial pure NaX zeolite was used as reference. CO2 adsorption isotherms show a maximum uptake value around 21 wt% at (~7 °C) that decrease to 18 wt% at high temperature (~42 °C) passing through 19 wt% at room temperature (~25 °C). The homogeneity grade of the surface, as obtained using Toth analysis performed on the adsorption isotherm, is close to t ≅ 0.40, lower than the 0.61 obtained for pure commercial NaX zeolite, as a consequence of the binder formation. Monolith exhibits a notably higher K values and quicker saturation with respect to reference that can be ascribed to the presence of mesoporosity that provides an easier and faster transport of CO2 in the NaX nanozeolite framework. The produced composite is a potential solid adsorbent candidate in industrial process.

Inusual causa de shock cardiogénico / An unusual cause of cardiogenic shock

No disponible

Metástasis pulmonares de origen desconocido / Lung metastases of unknown primary origin

No disponible

Advances in Poly(4-aminodiphenylaniline) Nanofibers Preparation by Electrospinning Technique.

Polyaniline (PANI) nanofibers are drawing a great deal of interest from academia and industry due to their multiple applications, especially in biomedical field. PANI nanofibers were successfully electrospun for the first time by MacDiarmid and co-workers at the beginning of the millennium and since then many efforts have been addressed to improve their quality. However, traditional PANI prepared from aniline monomer shows some drawbacks, such as presence of toxic (i.e., benzidine) and inorganic (salts and metals) co-products, that complicate polymer post-treatment, and low solubility in common organic solvents, making hard its processing by electrospinning technique. Some industrial sectors, such as medical and biomedical, need to employ materials free from toxic and polluting species. In this regard, the oxidative polymerization of N-(4-aminophenyl)aniline, aniline dimer, to produce poly(4-aminodiphenylaniline), P4ADA, a kind of PANI, represents an innovative alternative to the traditional synthesis because the obtained polymer results free from carcinogenic and/or polluting co-products, and, moreover, more soluble than traditional PANI. This latter feature can be exploited to obtain P4ADA nanofibers by electrospinning technique. In this paper we report the advances obtained in the P4ADA nanofibers electrospinnig. A comparison among polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and polystyrene (PS), as the second polymer to facilitate the electrospinning process, is shown. In order to increase the conductivity of P4ADA nanofibers, two strategies were adopted and compared: selective insulating binder removal from electrospun nanofibers by a rinsing tratment, afterwards optimizing the minimum amount of binder necessary for the electrospinning process. Moreover, the effect of PEO/P4ADA weight ratio on the fibers morphology and conductivity was highlighted.

A comparison of the ethanol sensing properties of α-iron oxide nanostructures prepared via the sol-gel and electrospinning techniques.

Haematite (α-Fe2O3) nanostructures were synthesized via a Pechini sol-gel method (PSG) and an electrospinning (ES) technique. Their texture and morphology were investigated by scanning and transmission electron microscopy. α-Fe2O3 nanoparticles were obtained by the PSG method, whereas fibrous structures consisting of interconnected particles were synthesized through the ES technique. The crystallinity of the α-Fe2O3 nanostructures was also studied by means of x-ray diffraction and Raman spectroscopy. Gas-sensing devices were fabricated by printing the synthesized samples on ceramic substrates provided with interdigitated Pt electrodes. The sensors were tested towards low concentrations of ethanol in air in the temperature range (200-400 °C). The results show that the α-Fe2O3 nanostructures exhibit somewhat different gas-sensing properties and, interestingly, their sensing behaviour is strongly temperature-dependent. The availability of active sites for oxygen chemisorption and the diffusion of the analyte gas within the sensing layer structure are hypothesized to be the key factors responsible for the different sensing behaviour observed.

Electrospinning of polyaniline: effect of different raw sources.

Nanofibers of conducting polymers, as polyaniline (PANI), have received a great deal of attention by the scientific community for their potential applications (electronic, magnetic, biomedical, optical fields). Recently the electrospinning has emerged as a promising technique to produce wires and fibers of polymers with diameters ranging from 10 nm to 10 microm. PANI shows poor processability by electrospinning due to its low solubility in common solvents. However, it is possible to spin polyaniline nanofibers adding another polymer to the organic solutions, generally an insulator, necessary to increase the viscosity of the polymeric solution to be spun. Unfortunately, the presence of an insulator copolymer decreases the fibers conductivity. The key factor to obtain fibers of good quality (high conductivity and a narrow distribution of the diameters) is to reduce the amount of insulator copolymer in the spun process. Accordingly, we prepared raw PANI following different synthetic methods to be compared, aiming at the best optimized protocol in terms of easy solubility and enhanced spinning behavior of the polymers achieved. All the materials have been characterized by FT-IR and UV-VIS spectroscopies. The spun samples obtained have been characterized by SEM to evaluate the fiber morphology and complex impedance spectroscopy (EIS) in order to measure the electrical conductivity.

[The scimitar syndrome in children. Apropos of 3 cases]. / Syndrome du cimeterre de l'enfant. A propos de 3 observations.

The authors describe three new cases in children of abnormal right pulmonary venous drainage into the inferior vena cava, associated with sequestration of the right lower lobe and dextrocardia caused by right pulmonary hypoplasia with a scimitar sign. The term scimitar syndrome used in the literature is to some extent inaccurate as it is neither constant nor pathognomonic. The authors have reviewed 45 paediatric cases reported in the literature and compared the different clinical, diagnostic and therapeutic aspects with their patients. To their knowledge they report the first case in childhood with right lobar sequestration, which received its blood supply from an abnormal artery arising from the right internal mammary artery.