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Through a systematic experimental analysis, the impact characterization of carbon-aramid hybrid composites, typically used in the automotive sports field, has been performed. CFRP laminates object of this study have been produced by adding a hybrid foil obtained using a fabric of twill type, so-called carbon-kevlar. In order to highlight the effects of hybridisation, that is, the different properties of kevlar fibre with respect to carbon, a comparative analysis was also carried out considering a CFRP laminate with the same lay-up. The analysis of the experimental results obtained through preliminary tensile tests and subsequent low-velocity drop-weight impact tests integrated with x-ray tomography, showed that although the hybrid composite has a lower static strength than the simple CFRP, it has an increase in impact strength of up to 50%, combined with an appreciable increase in maximum impact force and mainly in resistance to surface damage.

Data la crescente attenzione nei confronti dell’ambiente, le sempre più restrittive norme in materia di salvaguardia ambientale e di riciclo dei materiali hanno portato ad un notevole interesse dei ricercatori verso i biocompositi, materiali costituiti da rinforzi di origine naturale e matrici a basso impatto ambientale. Nonostante molteplici studi siano stati indirizzati a tali materiali innovativi, allo stato attuale poche ricerche hanno riguardato l’analisi della tenacità alla frattura di laminati biocompositi. Il presente lavoro propone pertanto uno studio sperimentale del comportamento alla frattura translaminare in modo I di laminati biocompositi in fibre di agave e matrice epossidica green, valutando in particolare l’effetto della variazione percentuale volumetrica del rinforzo e della sequenza di impacchettamento (unidirezionali, cross-ply, angle-ply ecc.). Le prove di resistenza alla frattura a trazione in modo I sono state eseguite su campioni con configurazione Compact Tension (CT) al fine di determinare sia il fattore critico di intensificazione delle tensioni, sia la Critical Strain Energy Release Rate (CSERR). In particolare, i diversi provini CT sono stati ottenuti attraverso laminazione manuale e successivo processo di compression-moulding, a partire da tessuti unidirezionali di tipo stitched appositamente prodotti in laboratorio. Al fine di individuare il metodo ottimale per una accurata valutazione sperimentale della CSERR, sono stati confrontati i risultati ottenuti con diversi metodi tra cui l’Area Method ed il Compliance Calibration The recent attention toward the environmental protection, as well as to the restrictive regulations in term of material recycling, have led to a noticeable interest of the scientific research for biocomposites, i.e. materials constituted by natural fibers and eco-friendly matrix. Although various research works have been focused on such innovative materials, only a few articles have been devoted to the their fracture strenght (thoughness). The present work regards the experimental study of the translaminar fracture behavior (in mode I) of biocomposite laminates constituted by green epoxy matrix reinforced by optimized agave sisalana fibers, varying the main influence parameters as the fiber concentration and the lay-up (unidirectional, cross-ply, angle-ply etc.). The fracture tests in mode I, have been performed by using Compact Tension (CT) specimens, in order to determine both the critical Stress Intensity Factor (SIFc) and the so called Critical Strain Energy Release Rate (CSERR). In more detail, several CT specimens have been manufactured by hand lay-up and successive compression-moulding process whose parameters have been optimized in previous study of the same authors. To this aim proper stitched fabrics have been previously manufactured in laboratory. In order to detect the optimal method for an accurate experimental analysis of the CSERR, the results provided by the Area Method and the Compliance Calibration, have been compared.

In order to comply with the recent regulations in terms of environmental protection, biocomposites reinforced with natural fibers are increasingly used in the automotive sector, for the replacement of synthetic materials in semi-structural applications as panels, filling material, coating, dashboards, etc. The good mechanical performances of these materials, mixed with low weight and low cost, also make it possible to minimize the weight of the vehicle, and therefore consumption, but also the relative production costs. These are composites with random short fiber appreciated for their good stiffness, generally well above that of the matrix alone. Due to the peculiar "transverse" damage phenomena, often also influenced by debonding and pull-out phenomena related to the limited fiber-matrix adhesion, the mechanical, static and fatigue resistance of these materials is instead generally comparable to that of the matrix alone. This prevents their use in more mechanically demanding applications. For this reason, several chemical treatments on the fibers have been proposed in the literature by various authors, although still not fully satisfactory results have been obtained in terms of improving resistance. Taking into account the positive effects of the nanotubes on the fatigue resistance of structural polymeric adhesives and polymer matrix composites reinforced with synthetic fibers, in this work the effects of nanotubes on the fatigue resistance of biocomposites reinforced with agave fibers are analyzed, the fibers are obtained with a special compression molding process. The tests carried out on green epoxy matrix biocomposites in which nanotubes with different concentrations in volume were previously dispersed, showed that the static strenght is significantly influenced by the presence of nanotubes, although more appreciable improvements are found in the fatigue performance.

Quality of life (QOL) has been considered an important outcome measure in psychiatric research and determinants of QOL have been widely investigated. We aimed at detecting predictors of QOL at baseline and at testing the longitudinal interrelations of the baseline predictors with QOL scores at a 1-year follow-up in a sample of patients living in Residential Facilities (RFs). Logistic regression models were adopted to evaluate the association between WHOQoL-Bref scores and potential determinants of QOL. In addition, all variables significantly associated with QOL domains in the final logistic regression model were included by using the Structural Equation Modeling (SEM). We included 139 patients with a diagnosis of schizophrenia spectrum. In the final logistic regression model level of activity, social support, age, service satisfaction, spiritual well-being and symptoms' severity were identified as predictors of QOL scores at baseline. Longitudinal analyses carried out by SEM showed that 40% of QOL follow-up variability was explained by QOL at baseline, and significant indirect effects toward QOL at follow-up were found for satisfaction with services and for social support. Rehabilitation plans for people with schizophrenia living in RFs should also consider mediators of change in subjective QOL such as satisfaction with mental health services.

En la última década, los principales países productores de cereales aumentaron en forma significativa su productividad, mediante la aplicación de tecnologías que combinan fundamentalmente nuevos desarrollos genéticos con ajustes más precisos en el manejo de los cultivos. Los efectos del desarrollo y adopción de tales tecnologías han sido particularmente notables en la Argentina. El aumento de las prácticas como siembra directa, fertilización, intensificación del uso de micronutrientes, riego y aplicación de reguladores de crecimiento generan cultivos con expectativas de altos rindes. La utilización de manejos altamente tecnificados se ha reflejado en una mejora significativa en los niveles de producción de los cultivos que se practican extensivamente; sin embargo, se ha evidenciado un deterioro de los suelos en sus propiedades físicas y químicas. No siendo menos importante es el impacto en la propiedades biológicas del suelo, relacionadas con el desarrollo de la biomasa de organismos y sus actividades. El sistema de siembra directa produce cambios cuali y cuantitativos a nivel de suelo, puesto que la cobertura con rastrojos y la no remoción del suelo generan un hábitat con condiciones de humedad y temperatura respondiendo a la necesidad de mantener y/o mejorar la calidad de los recursos naturales en el proceso productivo agrícola. Su adopción, generalizada en la región bajo estudio, ha permitido mejorar el aprovechamiento del agua, proteger contra la erosión, aumentar el contenido de materia orgánica (MO), y favorecer la actividad biológica en el suelo, entre otras ventajas. Sin embargo, también son renombradas sus desventajas, tales como, la potencial amenaza de los patógenos de tipo necrotróficos. En gran parte de las regiones con agricultura templada se proyecta una expansión importante del área de cultivo bajo siembra directa, lo cual, dará continuidad al proceso de intensificación, preservando el recurso suelo y permitiendo expandir las posibilidades de cultivo en otras regiones o ecosistemas frágiles. Esta sucesión de factores provocará una serie de adaptaciones entre los grupos fúngicos competitivos, o no, que se manifiestan en efectos diversos y que a nivel ecológico revisten especial importancia. Fil: Silvestro, Luciana Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina Fil: Moreno, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina Fil: Forján, Horacio José. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Albanesi, Ada. Universidad Nacional de Santiago del Estero; Argentina Fil: Arambarri, Ana Maria. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; Argentina Fil: Dinolfo, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina Fil: Stenglein, Sebastian Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina Fil: Manso, Lucrecia. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Bongiorno, F.. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina

Fifty-seven accessions of canaryseed (47 populations and 10 cultivars) from 19 countries were evaluated for agronomic traits in four field trials sown over 3 yr in the province of Buenos Aires, Argentina. Genetic variation was found for all traits scored: grain yield and its components (grain weight, grain number per square meter, grain number per head and head number per square meter), harvest index, percent lodging, and phenological characters (emergence to heading, emergence to harvest maturity and heading to harvest maturity). Although genotype×environment interaction was observed for all traits, the additive differences between accessions were sufficient to enable promising breeding materials to be identified. Accessions superior in performance to the local Argentinean population, which in general gave values close to the overall mean of the accessions evaluated, were identified. For example, a population of Moroccan origin gave good yield associated with elevated values of the highly heritable character grain weight, rather than with the more commonly observed grain number per square meter. This population was also of relatively short stature and resistant to lodging, and, although it performed best when sown within the normal sowing date, tolerated late sowing fairly well. Other accessions were also observed with high grain weight, a useful characteristic in itself, since large grains are desirable from a quality point of view. Regarding phenology, the accessions showed a range of 160 degree days (8 calendar days in our conditions) in maturity, which, while not large in magnitude, may be of some utility in crop rotation management. Some accessions were well adapted to late sowing. Grain yield in general was strongly correlated with grain number per square meter. Principal components analysis (PCA) carried out for all characteristics provided indications of accessions combining useful characteristics and identified three components that explained approximately 70% of the phenotypic variation. Furthermore, a second PCA plus regression showed that approximately 60% of the variation in grain yield could be explained by a component associated with harvest index and grain number per square meter. Pointers were provided to possible future breeding targets.