Effects of chemical structure and morphology of graphene-related materials (GRMs) on melt processing and properties of GRM/polyamide-6 nanocomposites

In this work, different graphene-related materials (GRMs) and polyamide-6 (PA6) were melt compounded by twin screw extrusion. The GRMs prepared were graphene nanoplatelets (GNPs), graphene oxide (GO), reduced graphene oxide (rGO) and silane functionalised reduced graphene oxide (f-rGO). The GRMs had comparable lateral size (20-30μm), but different thickness and surface chemistry which resulted in different behaviour in processing of melt flow, maximum loading in the PA6 matrix (15%wt for GNPs, 10%wt for GO, 2%wt for rGO and 2.5%wt for f-rGO) as well as mechanical properties. A second extrusion phase produced formulations with lower concentration of GRMs. In the case of f-rGO/PA6, the melt flow index increased by over 76% at 0.5%wt loading compared with the pure PA6 resin, facilitating processing and dispersion of the flakes within the matrix and increasing the elastic modulus and tensile strength by 39%. However, high filler content above 10% has been achieved only for GNPs improving the elastic modulus by 50% at 15%wt

ITQ's in Chile: Measuring the Economic Benefits of Reform

In 2001 an individual (operationally transferable) quota system was introduced for all the most important industrial fisheries in Chile. This system was put in place after years of declining stocks and over investment. In this paper we describe this reform and estimate related allocative efficiency benefits for the most important industrial fishery in the country, the southern pelagic fishery. Benefits were estimated using a bioeconomic model and Monte Carlo techniques. This approach allows benefits to be estimated using more realistic counterfactual scenarios than just comparing the fishery before and after the reform. Estimated discounted net benefits reach US$123 to US$366 million in the period 2001 to 2020. Fleet size fell from 148 active boats in 2000 to 65 in 2002 as a direct consequence of the reform. Among the interesting features of the recent Chilean experience is the way the political economy of the reform was facilitated by the prior introduction of de facto individual quotas within the framework of fishery research activities. When the authorities closed the southern pelagic fishery because of biological problems between 1997 and 2000, they organized ‘experimental’ fishing expeditions in which participant boats were given the right to fish a certain amount of resources per expedition. This pseudo quota system allowed fishermen to experience directly the benefits of individual quotas and that was instrumental to the political agreement leading to the reform. This successful gradual approach may be of interest to other countries planning to introduce individual quotas. Finally, it is important to note that the Chilean southern industrial pelagic fishery has average catches of over 1.4 million tons a year, making it one of the largest fisheries in the world to be regulated by individual quotas.Bioeconomic model, pelagic fisheries, individual transferable quotas

Layer-by-Layer Assembly of Efficient Flame Retardant Coatings Based On High Aspect Ratio Graphene Oxide and Chitosan Capable of Preventing Ignition of PU Foam

The layer-by-layer (LbL) technique is adopted for the construction of multilayers encompassing chitosan and graphene oxide (GO) platelets capable of improving the flame retardant properties open cell PU foams. The LbL assembly follows a linear growth regime as evaluated by infrared spectroscopy and yields a multilayer structure where GO platelets are embedded within a chitosan continuous matrix. 3 and 6 bi-layers (BL) can efficiently coat the complex 3D structure of the foam and substantially improve its flame retardant properties. 3BL only add 10% to the original mass and can suppress the melt dripping during flammability and reduce both the peak of heat release rate by 54% and the total smoke released by 59% in forced combustion tests. Unprecedented among other LbL assemblies employed for FR purposes, the deposition 6BL is capable of slowing down the release of combustible volatile to the limits of non-ignitability thus preventing ignition in half of the specimens during cone calorimetry tests. This has been ascribed to the formation of a protective coating where the thermally stable char produced by chitosan serves as a continuous matrix embedding GO platelets, which control volatile release while mechanically sustaining the PU foam structure

MCDM Farm System Analysis for Public Management of Irrigated Agriculture

In this paper we present a methodology within the multi-criteria paradigm to assist policy decision-making on water management for irrigation. In order to predict farmers' response to policy changes a separate multi-attribute utility function for each homogeneous group, attained applying cluster analysis, is elicited. The results of several empirical applications of this methodology suggest an improvement of the ability to simulate farmers' decision-making process compared to other approaches. Once the utility functions are obtained the policy maker can evaluate the differential impacts on each cluster and the overall impacts in the area of study (i.e. a river basin) by aggregation. On the empirical side, the authors present some studies for different policy instruments including water pricing, water markets, modernization of irrigation systems and a combination of them.multi-attribute utility theory, water management, irrigation, policy analysis, Agricultural and Food Policy, Q25, Q15, C61,

The Quest for Global Justice in Health: A Review of Global Health Law by Lawrence 0. Gostin

We are witnessing the emergence of a new world health order. Health occupies an increasingly relevant place in the global agenda. An unprecedented health transition is leading to a new model characterized by expanded international and national funding for health and the involvement of a growing pluralism of actors

The effect of rippling on the mechanical properties of graphene

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very bendable. Consequently, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient of free-standing graphene. We also observed an increase of the Young's modulus with global applied strain and with the introduction of small density defects that we attributed to the decrease of rippling. Here, we will focus on a surprising feature observed in the data: the experiments consistently indicate that only the rippling with wavelengths between 5-10nm influences the mechanics of graphene. The rippling responsible of the negative TEC and anomalous elasticity is thought to be dynamic, i.e. flexural phonons. However, flexural phonons with these wavelengths should have minor effects on the mechanics of graphene, therefore other mechanisms must be considered to address our observations. We propose static ripples as one of the key elements to correctly understand the thermomechanics of graphene and suggest that rippling arises naturally due to a competition of symmetry breaking and anharmonic fluctuations

Tug-of-War games and the infinity Laplacian with spatial dependence

In this paper we look for PDEs that arise as limits of values of Tug-of-War games when the possible movements of the game are taken in a family of sets that are not necessarily euclidean balls. In this way we ¯nd existence of viscosity solutions to the Dirichlet problem for an equation of the form ¡hD 2 v ¢ Jx(Dv); Jx(Dv)i(x) = 0, that is, an in¯nity Laplacian with spatial dependence. Here Jx(Dv(x)) is a vector that depends on the the spatial location and the gradient of the solution.Fil: Gomez, Ivana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Santa Fe. Instituto de Matemática Aplicada; Argentina;Fil: Rossi, Julio Daniel. Universidad de Buenos Aires; Argentina

Effects of Graphite Oxide Nanoparticle Size on the Functional Properties of Layer-by-Layer Coated Flexible Foams

The exploitation of self-assembled coatings comprising graphite oxide (GO) nanoplates has been recently demonstrated as a promising route to improve the fire safety of flexible polyurethane (PU) foams. However, limited knowledge has been gathered on the correlations between the physical and chemical properties of different GO grades and the performance obtained in this application. This work addresses the effects of the nanoparticle dimensions on the layer-by-layer (LbL) assembly and flame-retardant properties of GO-based coatings deposited on PU foams. To this aim, three GO bearing different lateral sizes and thicknesses were selected and LbL-assembled with chitosan (CHIT). Coating growth and morphology were evaluated by FTIR and FESEM, respectively. The resulting CHIT/GO assemblies were demonstrated to be capable of slowing down the combustion of the PU both in flammability and forced combustion tests. In addition, compressive stress/strain tests pointed out that the LbL-coated foams (22–24 kg/m3) could easily replace denser commercial PU foam (40–50 kg/m3) with weight reduction potentials in the transport field. These results are correlated with the properties of the employed GO. The production of assemblies characterized by a high density of CHIT/GO interfaces is identified as the main parameter controlling the FR efficiency and the mechanical properties of the coatings

Uso de la Biblia como estrategia pedagógica para fomentar la investigación

The present article has as aim implement the use of the bible as pedagogic strategy to promote the investigation, using a methodology of qualitative type developed from the Investigation as Pedagogic Strategy (IEP), in which the technology of the observation was applied and as I orchestrate a structured interview applied to 40 students of the degrees of 6 ° to 9 ° degree between the ages of 12-16 years performing activities such as debates, roll plays and socialization spaces. From the application it was obtained that students consider that the Bible as a pedagogical means of learning if it allows to acquire new knowledge and in a didactic way strengthening and promoting research.El presente artículo tiene como objetivo implementar el uso de la biblia como estrategia pedagógica para fomentar la investigación, utilizando una metodología de tipo cualitativo desarrollado desde la Investigación como Estrategia Pedagógica  (IEP).  El desarrollo de la investigación, incluyó como técnicas de recolección de información la observación y la entrevista en profundidad; los cuales fueron aplicados a 40 estudiantes de los grados de 6° a 9° con edades comprendidas entre los 12 y los 16 años.  Adicionalmente, se realizaron actividades como debates, roll plays y espacios de socialización. A partir de los resultados obtenidos se llegó a la conclusión de que los estudiantes consideran que la Biblia como medio pedagógico de aprendizaje que permite adquirir nuevos conocimientos de manera didáctica fortaleciendo y fomentando la investigación