Polyesters bearing furan moieties

Summary This paper describes a preliminary set of results concerning novel systems in which the synthesis of furanic polyesters was conducted according to a transesterification procedure. Regular linear macromolecular structures were thus obtained with molecular weights well above those previously reported for similar polyesters prepared by more conventional routes.     

Mercury and methylmercury concentrations in high altitude lakes and fish (Arctic charr) from the French Alps related to watershed characteristics

Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220 mm, a standardized age of 5 years or for individualuals did not exceed the 0.5 mg kg^− 1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes.     

Electrical and Seismic Tomography Used to Image the Structure of a Tailings Pond at the Abandoned Kettara Mine, Morocco

The Kettara site (Morocco) is an abandoned pyrrhotite ore mine in a semi-arid environment. The site contains more than 3 million tons of mine waste that were deposited on the surface without concern for environmental consequences. Tailings were stockpiled in a pond, in a dyke, and in piles over an area of approximately 16?ha and have generated acid mine drainage (AMD) for more than 29?years. Geophysical methods have been used at the Kettara mine site to determine the nature of the geological substrate of the tailings pond, the internal structure of the mine wastes, and to investigate the pollution zones associated with sulphide waste dumps. Electrical resistivity tomography (ERT) and seismic refraction data were acquired, processed, and interpreted; the results from ERT and seismic refraction were complementary. A topographical survey of the tailings disposal area was also undertaken to estimate the volume of wastes and quantify the AMD process. Two-dimensional inverse models were used to investigate the geophysical data and indicated alteration zones at depth. It was determined that the material could be classified into three categories: tailings, with low resistivity (5?C15??? m) and low velocity (500?C1,800?m/s); altered, black shales, with intermediate resistivity (20?C60??? m) and velocity (2,000?C3,500?m/s), and; materials with high resistivity and velocity (>60????m and >4,000?m/s, respectively), including unaltered shales associated with quartzite seams. The low-resistivity zone generates AMD, which migrates downward through fractures and micro-fractures. The substrate is composed of broken and altered shale, which facilitates AMD infiltration.     

Hydrothermal Synthesis and Characterization of Europium-doped Barium Titanate Nanocrystallites

Nano-Micro Letters - Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite BaTiO3...     

Dynamics of viscous slugs fall in dry capillaries

The dynamics of viscous slug fall in vertical dry capillaries is investigated by extending a published model (perfect wetting case) accounting for the film left behind the slug as it falls, and Laplace pressures at both ends of the slug in the momentum balance. The present investigation provides and uses an advancing contact-angle correlation determined based on a published theoretical work. The results are found in excellent agreement with published experimental values for falling slugs. The present model does not require any fitting parameter in the perfect wetting case, and is extended to include the non-perfect wetting case along with the unsteady-state dynamics using the quasi-steady-state approximation.     

IMC-PID-fractional-order-filter controllers design for integer order systems

One of the reasons of the great success of standard PID controllers is the presence of simple tuning rules, of the automatic tuning feature and of tables that simplify significantly their design. For the fractional order case, some tuning rules have been proposed in the literature. However, they are not general because they are valid only for some model cases. In this paper, a new approach is investigated. The fractional property is not especially imposed by the controller structure but by the closed loop reference model. The resulting controller is fractional but it has a very interesting structure for its implementation. Indeed, the controller can be decomposed into two transfer functions: an integer transfer function which is generally an integer PID controller and a simple fractional filter.     

Quantification des matières en suspension et valorisation des sédiments de dragage à l’échelle d’un bassin semi-aride: Cas du barrage du K’sob (Algérie)

Due to the semi-arid climate, scarcity of vegetation, the presence of a sometimes steep slope, Algeria is vulnerable to soil erosion that threatens its socio-economic development. In the watershed of K’sob, transport of suspended sediment by rivers is a disturbing phenomenon due to siltation to 80 % of the dam at the outlet. Data of suspended sediment concentrations are closely related to liquid discharge (Q). Models of solid discharge (Q_s) according to the equation Q_s = aQ^b were used to perform qualitative and quantitative analysis of suspended sediment. Different scales of analysis helped identify and explain conclusively seasonal models. Sediment production is very high in the fall. In the spring, despite the increase in discharge, it is less significant. In summer, during a period of disappearance of vegetation cover, highly loaded floods are sometimes observed. Currently, millions of cubic meters of sediments are dredged each year. This large volume is an economic, environmental and ecological problem. To remedy this, an experimental study of manufacturing brick has been proposed with 65 % of sediment, 25 % of dune sand used as an additive and 10 % water. The shrinkage is minimal for a solid brick fabricated to 800 °C during 6 h of cooking. The mechanical tests carried out on the brick exhibit acceptable values of compression strength, mass density and water absorption. The study of the evolution of these parameters for different pressing intensities (13.2–20–30 and 40 kN) at different ages (4, 14, 21, and 28 days) shows that the solid brick acquires its resistance only after 21 days.     

Les glissements de terrain du quartier Bélouizdad, Constantine, Algérie

In Constantine, Belouizdad district landslides are extensive (Fig. 1). They occur along a hillside largely urbanized, and cover over 30 hectares. Dozens of houses were destroyed. The formations raised by these movements correspond to the alternating of thick Miocene clays and conglomerates. These contain several aquifers. The study of these landslides is conducted on the basis of recognition by deep boreholes equipped with piezometers and inclinometers. The inclinometric measurements have revealed failure surfaces sometimes deep (20 to 30 m) and north displacement, towards the Rhumel wadi. The use of a stability calculation software “Talren” shows on the one hand, the high sensitivity of unstable Miocene formations in the presence of water and on the other hand, a significant revival of the safety factor by reducing the pore pressure. The recommended solutions are therefore a lowering of underground water levels. Two techniques are recommended : deep drainage trench or galleries combined with radiating drainage holes.