Crystallization and dielectric behavior of PLA and PHBV in PLA/PHBV blends and PLA/PHBV/TIO 2 nanocomposites

The morphology, crystallization behavior and mechanical properties of PLA, PHBV and their blends and nanocomposites with TiO 2 as filler were investigated. An uncommon morphological change was observed with increasing PLA content in the blends, and this complicated the isothermal crystallization kinetics analyses of the different samples. It was, for example, observed that PLA, which do not normally crystallize during the cooling of the sample, showed isothermal crystallization for certain blend compositions. TiO 2 was found to be mainly present in the PLA phase, which was also confirmed through broadband dielectric analysis. The blend composition, as well as the presence of TiO 2 nanoparticles, had an influence on the cold crystallization of the PLA. The tensile properties changed with blend and nanocomposite composition, and these changes could to a certain extent be related to the respective morphologies. Very little could be said about differences between the melting behavior of the different samples, because the PLA and PHBV melted at almost exactly the same temperature.Scopu

400 ans d'exploration botanique en zone méditerranéenne algérienne Une histoire méconnue et inachevée

Cet article fait une mise au point quasi exhaustive de l'exploration botanique en Algérie. Exploration couronnée, en 1962, par la publication de la flore de Quézel et Santa, dont la révision reste toujours d'actualité

A Study of a Bi-Phasic Flow Problem in Porous Media

Abstract In this paper, we develop a simplified formulation of the hydrocarbon system used for the petroleum reservoirs simulation.This system is a simplified model which describes a two-phase flow (oil and gas) with a mass transfer in a porous medium, that leads to the fluid compressibility.this kind of flow is modelled by a system of parabolic degenerated non linear convection-diffusion equations.Under certrain hypothesis, such as validity of Darcy's law, incompressibility of the porous medium, compressibility of the fluids, mass transfer between the oil and the gas and negligible gravity, the global pressure is formulated.This formulation allows the establishment of theoretical results on the existence and uniquness of the solution. Mathematics Subject Classification: 76D07, 76M2

Les forêts d'Algérie, de Césarée la romaine à ce jour.

D'après de nombreux auteurs, les forêts d'Algérie furent jadis luxuriantes. L'état de déliquescence dans lequel elles se retrouvent aujourd'hui, pose la problématique de ce qu'elles ont subi durant les diverses époques de l'histoire de ce pays. Peu d'écrits existent sur le sujet a constitué et en fonction des convictions politiques ou religieuses des auteurs, chaque publication s'accorde à dire que c'est telle ou telle autre période de l'histoire fort tourmentée de ce pays, qui a été déterminante. La situation géographique de celui-ci, a fait qu'il a subi, de tout temps, des invasions, et que ce sera toujours la forêt qui payera le plus lourd tribut. Actuellement, la situation est encore plus complexe, du fait de la mondialisation

Halogen-free flame-retardant compounds. Thermal decomposition and flammability behavior for alternative polyethylene grades

The effect of six halogen-free flame retardant (FR) formulations was investigated on the thermal stability of two low-density polyethylenes (LDPE) and one linear low-density polyethylene (LLDPE), by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. The relative data were combined with flammability properties and the overall performance of the FRs was correlated with the type of branching in the polyethylene grades and to their processing behavior. The thermal degradation kinetics was further determined based on the Kissinger and Coats-Redfern methods. In terms of flammability, the addition of a triazine derivative and ammonium polyphosphate at a loading of 35 wt. %. was found to be the most efficient, leading to UL 94 V0 ranking in the case of the LDPE grade produced in an autoclave reactor. - 2019 by the authors.Funding: This publication was made possible by the NPRP award [NPRP 9-161-1-030] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the author(s)

Effects of the latest drought on the alluvial aquifer of a semiarid region in northeastern Brazil

Climate change has modified global and local water cycle patterns inducing more intense and severe drought events. In the Ceará state (Northeast Brazil), a semiarid region very vulnerable to droughts, groundwater acts as a strategic reserve to ensure water security for small rural communities. Well drilling jointly with the building of dams and cisterns are the main policy performed by the public authority to cope with the droughts. This study performed a preliminary qualitative analysis to investigate the effects of dam building in the piezometric level of an alluvial aquifer in the Ceará state during the most recent drought (2012–2016). The micro-basins of the Algodão and Forquilha creek were selected as study area, in which the alluvial aquifer has been monitored by Funceme since 2010. The alluvial aquifer was extensively exploited for local agriculture before the drought (2012–2016) due to public policies of well drilling (2001–2002). During the most recent drought, the construction of new dams, coupled with reduced rainfall, compromised the recharge of the alluvial aquifer. We evaluate these effects through the groundwater level. The results revealed a continuous drawdown of groundwater in the monitored wells. Since 2017 the piezometric level started to rise, however, the graphs reveal a different behavior of the piezometric levels monitored after the latest drought, with sudden changes between the periods of recharge and drawdown of the alluvial aquifer. Field diagnostics with local stakeholders revealed how the latest drought changed the dynamics of the activities developed by the rural communities. Before the drought the aquifer supplied the local agriculture. The drought has affected the recharge of the alluvial aquifer and compromised local agriculture. Local stakeholders have adapted, and agriculture has been replaced by livestock. The heterogeneity of this environment and of its water users requires efficient management policies adapted for the local physical and socioeconomic conditions to avoid overexploitation and maintain the recharge of the alluvial aquifer. These policies at the local scale can be the identification of local actors who are willing to develop their own management of surface and groundwater resources.</p

Machine-assisted cultivation and analysis of biofilms

Biofilms are the natural form of life of the majority of microorganisms. These multispecies consortia are intensively studied not only for their effects on health and environment but also because they have an enormous potential as tools for biotechnological processes. Further exploration and exploitation of these complex systems will benefit from technical solutions that enable integrated, machine-assisted cultivation and analysis. We here introduce a microfluidic platform, where readily available microfluidic chips are connected by automated liquid handling with analysis instrumentation, such as fluorescence detection, microscopy, chromatography and optical coherence tomography. The system is operable under oxic and anoxic conditions, allowing for different gases and nutrients as feeding sources and it offers high spatiotemporal resolution in the analysis of metabolites and biofilm composition. We demonstrate the platform’s performance by monitoring the productivity of biofilms as well as the spatial organization of two bacterial species in a co-culture, which is driven by chemical gradients along the microfluidic channel