Cellulose acetate/carbon nanotube composites by melt mixing

Cellulose acetate (CA) is produced from a natural polymer and presents excellent properties, finding applications in a variety of areas. Unlike cellulose, CA is melt processable and may be molded into parts and formed into fibers or films. In this context, the production of conductive CA composites that may be processable and integrated into parts to provide specific functionalities is an area of increasing interest. The present work aims to prepare electrically conductive composites based on CA and carbon nanotubes (CNTs) by melt mixing. The nanocomposites were produced with pure and pyrrolidine-functionalized nanotubes, using a batch mixer and a twin-screw extruder. The morphology of carbon nanotube dispersion, the rheological behavior and the electrical conductivity of the final composites were evaluated. Rheological percolation was achieved for the composites with 0.5 wt% of CNT—both pure and functionalized—produced by extrusion; while electrical percolation was observed only for the composites with pure CNT.The authors acknowledge the Portuguese Foundation of Science and Technology (SFRH/BD/81711/2011 and PEst-C/CTM/LA0025/2011) and n-SteP – Nanostructured Systems for Tailored Properties, with reference NORTE-07-0124-FEDER-000039, supported by the Programa Operacional Regional do Norte (ON.2).info:eu-repo/semantics/publishedVersio

The influence of melt mixing on the stability of cellulose acetate and its carbon nanotube composites

Cellulose derivatives, such as cellulose acetate (CA), are commonly used due to their ease of processing. These polymers present interesting mechanical properties and biodegradability, but low thermal stability under melt processing conditions. Composites of carbon nanotubes (CNTs) and cellulose derivatives are expected to present enhanced properties, depending on the effect of nanotubes on polymer structure and thermal properties. This work aims to investigate the influence of melt mixing on the stability of CA and its CNT composites. Composites with 0 wt%, 0.1 wt% and 0.5 wt% CNTs, as received and functionalized with pyrrolidine groups, were prepared using a batch mixer and an extruder. Chain scission of CA occurred during processing, but the effect was considerably reduced in the presence of CNTs. The incorporation of small amounts of CNTs (with or without functionalization) decreased polymer degradation by thermomechanical effects induced during polymer processing.The authors acknowledge the Portuguese Foundation for Science and Technology (SFRH/ BD/81711/2011) and n-STeP – Nanostructured systems for Tailored Properties, with reference NORTE-07-0124- FEDER-000039, supported by the Programa Operacional Regional do Norte (ON.2).info:eu-repo/semantics/publishedVersio

miR-17∼92 exerts stage-specific effects in adult V-SVZ neural stem cell lineages

Neural stem cells (NSCs) in the adult ventricular-subventricular zone (V-SVZ) generate neurons and glia throughout life. MicroRNAs are important post-transcriptional regulators frequently acting in a context-dependent manner. Here, microRNA profiling defines cohorts of miRNAs in quiescent and activated NSCs, with miR-17∼92 highly upregulated in activated NSCs and transit amplifying cells (TACs) versus quiescent NSCs. Conditional miR-17∼92 deletion in the adult V-SVZ results in stage-specific effects. In NSCs, it reduces proliferation in vitro and in vivo, whereas in TACs, it selectively shifts neurogenic OLIG2; -; DLX2; +; toward oligodendrogenic OLIG2; +; DLX2; -; TACs, due to de-repression of an oligodendrogenic program, leading to increased oligodendrogenesis in vivo. This differential regulation of TAC subpopulations highlights the importance of TAC heterogeneity. Finally, in the NSC lineage for intraventricular oligodendrocyte progenitors, miR-17∼92 deletion decreases proliferation and maturation. Together, these findings reveal multiple stage-specific functions of the miR-17∼92 cluster within different adult V-SVZ lineages

Exercise-linked improvement in age-associated loss of balance is associated with increased vestibular input to motor neurons

Age-associated loss of muscle function is exacerbated by a concomitant reduction in balance, leading to gait abnormalities and falls. Even though balance defects can be mitigated by exercise, the underlying neural mechanisms are unknown. We now have investigated components of the proprioceptive and vestibular systems in specific motor neuron pools in sedentary and trained old mice, respectively. We observed a strong age-linked deterioration in both circuits, with a mitigating effect of exercise on vestibular synapse numbers on motor neurons, closely associated with an improvement in gait and balance in old mice. Our results thus describe how the proprioceptive and vestibular systems are modulated by age and exercise, and how these changes affect their input to motor neurons. These findings not only make a strong case for exercise-based interventions in elderly individuals to improve balance, but could also lead to targeted therapeutic interventions aimed at the respective neuronal circuitry

Low temperature dissolution of yeast chitin-glucan complex and characterization of the regenerated polymer

Chitin-glucan complex (CGC) is a copolymer composed of chitin and glucan moieties extracted from the cell-walls of several yeasts and fungi. Despite its proven valuable properties, that include antibacterial, antioxidant and anticancer activity, the utilization of CGC in many applications is hindered by its insolubility in water and most solvents. In this study, NaOH/urea solvent systems were used for the first time for solubilization of CGC extracted from the yeast Komagataella pastoris. Di erent NaOH/urea ratios (6:8, 8:4 and 11:4 (w/w), respectively) were used to obtain aqueous solutions using a freeze/thaw procedure. There was an overall solubilization of 63–68%, with the highest solubilization rate obtained for the highest tested urea concentration (8 wt%). The regenerated polymer, obtained by dialysis of the alkali solutions followed by lyophilization, formed porous macrostructures characterized by a chemical composition similar to that of the starting co-polymer, although the acetylation degree decreased from 61.3% to 33.9–50.6%, indicating that chitin was converted into chitosan, yielding chitosan-glucan complex (ChGC). Consistent with this, there was a reduction of the crystallinity index and thermal degradation temperature. Given these results, this study reports a simple and green procedure to solubilize CGC and obtain aqueous ChGC solutions that can be processed as novel biomaterialsinfo:eu-repo/semantics/publishedVersio

Trazabilidad de la señal isotópica del oxígeno desde la lluvia a los espeleotemas en las cuevas de Ortigosa de Cameros (La Rioja, España)

[EN] A one-year monitoring survey has been carried out in La Paz and La Viña Caves in the Ortigosa de Cameros Cave System (NE Iberian Peninsula), in order to track the oxygen isotope signal from rainfall to speleothem calcite, assessing the ability of this signal to retain environmental information. Oxygen isotope signals of rainfall events, drip water —sampled every three months—, and speleothem calcite, precipitated over three-months, are compared. Water dripping follows precipitation events in winter, spring and summer, more closely in the near-surface drip points than in the deeper ones. In autumn, dripping is delayed with respect to rainfall, suggesting that water stays in the epikarst before dripping resumes after summer. This delay causes a deviation of the total drip water signal (average δ18O=−8.39‰ V-SMOW) from the rainfall signal (average δ18O=−7.41‰ V-SMOW). On the contrary, in winter the isotopic signal of drip water keeps the rainfall signal. Calcite isotopic signal (total average δ18O=−6.83‰ V-PDB) shows a small offset (0.62–0.75%) with respect to the signal predicted by drip water oxygen composition; this points to a limited kinetic effect in calcite precipitation, therefore calcite retains the signal of rainfall, especially in winter.[ES] Durante un año se han monitorizado las cuevas de La Paz y La Viña en el Sistema de Cuevas de Ortigosa de Cameros (NE de la Península Ibérica) para rastrear la señal isotópica del oxígeno desde la lluvia a la calcita espeleotémica, y así valorar la capacidad de esta señal para conservar información medioambiental. Se han comparado las señales isotópicas del oxígeno de los eventos de la lluvia, el agua de goteo (muestreada trimestralmente) y la calcita espeleotémica, precipitada también durante cada trimestre. El goteo en las cuevas responde a la precipitación en invierno, primavera y verano, más estrechamente en los puntos más próximos a la superficie que en los profundos. En otoño hay un retraso entre la lluvia y el goteo, lo que sugiere que el agua permanece por un tiempo en el epikarst, antes de que se reanude el goteo después del verano. Este retraso provoca que la señal isotópica del agua de goteo (media total de δ18O=−8.39‰ V-SMOW) se desvíe de la señal de la lluvia (media de δ18O=−7,41‰ V-SMOW). Por el contrario, en invierno la señal isotópica del agua de goteo es muy semejante a la de la lluvia. La composición isotópica de la calcita espeleotémica (media total de δ18O=−6,83‰ V-PDB) presenta un pequeño desfase (0,62–0,75%) respecto al valor que le correspondería por la composición isotópica del agua de goteo; esto indica que los efectos cinéticos durante la precipitación de la calcita son limitados, por lo que ésta conserva la señal de la lluvia, especialmente en invierno.This study was mainly funded by the CGL2009-10455/BTE research project of the Ministry of Science and Innovation and FEDER and the Análisis de Cuencas Sedimentarias Continentales, Geotransfer, PaleoQ y Gemorfología y Cambio Global research groups of the Aragón Government. We are most grateful to Ma Angeles, Sara y Juan for their invaluable help. We also thank to the Ortigosa de Cameros town hall for the cave access. The Government of La Rioja is acknowledged by the meteorological data from Villoslada de Cameros station. We are indebted to the referees for their valuable comments.Peer reviewe

Car-following techniques: reconsidering the role of the human factor

Keeping correct distance between vehicles is a fundamental tenet in road traffic. New road signs and markings appearing on motorways aid drivers in determining this distance. However, the ‘Nagoya experiment’ (Sugiyama et al., 2008) revealed correct distance made following safe while also eventually destabilizing traffic flow. When traffic becomes dense, most drivers keep the minimum safety distance and brake when the vehicle ahead decelerates. The resultant chain reaction along the entire line of closely following vehicles causes for no apparent reason a traffic stoppage, known as a ‘phantom’ or ‘shockwave’ jam. The car-following models of Sugiyama et al. found certain speeds, traffic densities, and inter-vehicular distances combined to congest traffic. Drawing upon these and other phenomena (e.g., wave movement in Nature), car following by Driving to keep Inertia (DI) was conceived by us as an alternative to Driving to keep Distance (DD). Three studies explored possible prevention of ‘phantom’ jams by adopting DI. Using a driving simulator, affective and behavioural measures were taken (N=113). The results comparing the efficiency of DI vs. DD are summarized. DI promoted a more stable driver trajectory, in cognitive-affective and behavioural terms, and lowered fuel consumption by about 20%

Deacetylation and Desuccinylation of the Fucose-Rich Polysaccharide Fucopol: Impact on Biopolymer Physical and Chemical Properties

FucoPol is an acylated polysaccharide with demonstrated valuable functional properties that include a shear thinning fluid behaviour, a film-forming capacity, and an emulsion forming and stabilizing capacity. In this study, the different conditions (concentration, temperature, and time) for alkaline treatment were investigated to deacylate FucoPol. Complete deacetylation and desuccinylation was achieved with 0.02 M NaOH, at 60 ºC for 15 min, with no significant impact on the biopolymer’s sugar composition, pyruvate content, and molecular mass distribution. FucoPol depyruvylation by acid hydrolysis was attempted, but it resulted in a very low polymer recovery. The effect of the ionic strength, pH, and temperature on the deacetylated/desuccinylated polysaccharide, d-FucoPol, was evaluated, as well as its emulsion and film-forming capacity. d-FucoPol aqueous solutions maintained the shear thinning behaviour characteristic of FucoPol, but the apparent viscosity decreased significantly. Moreover, contrary to FucoPol, whose solutions were not affected by the media’s ionic strength, the d-FucoPol solutions had a significantly higher apparent viscosity for a higher ionic strength. On the other hand, the d-FucoPol solutions were not affected by the pH in the range of 3.6–11.5, while FucoPol had a decreased viscosity for acidic pH values and for a pH above 10.5. Although d-FucoPol displayed an emulsification activity for olive oil similar to that of FucoPol (98 +- 0%) for an oil-to-water ratio of 2:3, the emulsions were less viscous. The d-FucoPol films were flexible, with a higher Young0s modulus (798 +- 152 MPa), a stress at the break (22.5 +- 2.5 MPa), and an elongation at the break (9.3 +- 0.7%) than FucoPol (458 +- 32 MPa, 15.5 +- 0.3 MPa and 8.1 +- 1.0%, respectively). Given these findings, d-FucoPol arises as a promising novel biopolymer, with distinctive properties that may render it useful for utilization as a suspending or emulsifier agent, and as a barrier in coatings and packaging filmsinfo:eu-repo/semantics/publishedVersio

¿Locos o malos? Una revisión del trastorno de personalidad antisocial o disocial.

Los profesionales han sido tradicionalmente pesimistas en las posibilidades terapéuticas de pacientes con personalidad antisocial. Algunos autores incluso critican la inclusión de la entidad dentro de los trastornos mentales. El artículo revisa todos estos aspectos, así como otras áreas, tales como su comorbilidad, epidemiología, etiología, pronóstico y prevención