Incurred environmental risks and potential contamination sources in an abandoned mine site

The mineralogical characterization of Fedj Lahdoum mine wastes measured by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) showed the presence of the following sulfide minerals: galena (PbS), sphalerite (ZnS), pyrite (FeS2), cerussite (PbCO3) and smithsonite (ZnCO3). The wastes were stored in tailing ponds. The results showed that the concentration of metals from tailings were up to 10 460 mg.kg-1 for total Zn, 2 100 mg.kg-1 for total Pb and 62.08 mg.kg-1 for total Cd. The tailings have presented a fine unconsolidated texture that accelerated the dispersion of the particles rich in heavy metals. Geochemical analysis of soil has revealed high total contents of Pb, Zn and Cd, respectively: 3 646, 3 236 and 17 mg.kg-1. Chemical analysis of cultivated and wild plants species inside the district contain high grades in heavy metals: 708.56 mg Zn. kg-1; 16.24 mg Pb.kg-1 (Thymus vulgaris (L)); 500.44 mg Zn. kg-1, 12.44 mg Pb. kg-1 (Laurus nobilis (L)); 128.33 mg Zn. kg-1 and 22.53 mg Pb.kg-1 (Ficus (L)) and 106.73 mgZn.kg-1 (pimento). The high levels detected in soil and plants have exceeded the Tunisian and Canadian standards. These results showed that the abandoned site was contaminated by the presence of tailing dumps which were exposed to significant water and/or wind erosion. To solve this problem, we proposed an environmental desulphurization by froth flotation.Keywords: Heavy metals, mine tailings, abandoned mining-district, plant contamination

Impact du déversement direct des eaux usées et de drainage dans la nappe libre de l'Oued Souf et son influence sur la qualité des eaux souterraines.

Ces vingt dernières années la région de l'Oued Souf souffre du phénomène de la remontée des eaux de la nappe libre, qui inonde les « ghouts » et les maisons, entrainant de graves problèmes sociaux, agriculturaux et environnementaux. Le réseau d'assainissement qui ne couvre qu'une partie de la ville d'El-Oued rend la situation plus dramatique. Jusqu'a la fin de l'année 2010 une zone, située au Nord-Est de la ville d'El-Oued, a été aménagée pour que les eaux de drainage (système pour rabattre la nappe) et les eaux usées soient déversées directement sans aucun traitement préalable. L'objectif de cette étude est de déterminer l'extension du déversement dans la nappe libre de l'Oued Souf, surtout des eaux usées, et d'évaluer les risques de pollution des eaux souterraines de la nappe libre, plus particulièrement dans la zone de rejet. Six campagnes de mesures hydrochimiques ont été faites : trois durant l'année 2007 (avril, juin et septembre), deux durant l'année 2010 Ganvier et avril) et une en mai 2012 âpres l'arrêt de rejet. L'analyse des échantillons et leur interprétation ont permis l'établissement d'une carte de l'indice de pollution organique. Cette dernière a montre que le terrain a un pouvoir autoépuratoir élève ce qui réduit considérablement les effets de la pollution d'origine organique. Cette tendance est confirmée par les valeurs de la dispersivité longitudinale αL faibles, déterminées au niveau de la zone de rejet. Pour ce qui est des teneurs de certains éléments majeurs naturels (Na+, Ca++, SO4-, Cl-...), celles-ci restent élevées et posent un sérieux problème d'aptitude de ces eaux à l'Irrigation.Mots clés: Nappe libre - Remonte des eaux - Eaux usées - Pollution organique - Oued Souf More than twenty years the region of Oued Soufis suffering from the rising of the water table in the unconfined aquifer, causing flooding of "ghouts" and damaging houses, which induces serious social, agricultural and environmental problems. The sewerage system that covers only a part of the city ofEl-Oued makes the situation more dramatic. Until the end of 2010, the drainage water and wastewater are discharged directly without any preliminary treatment in an area located north-eastern of El-Oued city. Nowadays a wastewater treatment plant was constructed and this area is not more used. The purpose of this study is to determine the extension of the contaminated area by discharged wastewater in the unconfined aquifer and to assess the risk of pollution of groundwater, particularly in the discharging zone. Three hydrochemical surveys were conducted in the discharging area and in its vicinity during 2007 (april, june and september), two during 2010 Ganuary and april) and one in may 2012. The interpretation of analysed samples shows that the pollution has a very short extension and the soil has an important self purifying role that reduces the effects of organic pollution that is shown in the established map of index of organic pollution. The low value of longitudinal dispersivity αL of the soil, evaluated in the discharging area, confirms this trend. We note that the content of some major natural elements such as (Na+, Ca++, SO4-, Cl-...) is high and the use of the groundwater is not advised for irrigation.Keywords: Unconfined aquifer- Rising water level - Wastewater- Organic pollution - Oued Sou

The role of the lateral prefrontal cortex and anterior cingulate in stimulus–response association reversals

Many complex tasks require us to flexibly switch between behavioral rules, associations, and strategies. The prefrontal cerebral cortex is thought to be critical to the performance of such behaviors, although the relative contribution of different components of this structure and associated subcortical regions are not fully understood. We used functional magnetic resonance imaging to measure brain activity during a simple task which required repeated reversals of a rule linking a colored cue and a left/right motor response. Each trial comprised three discrete events separated by variable delay periods. A colored cue instructed which response was to be executed, followed by a go signal which told the subject to execute the response and a feedback instruction which indicated whether to ‘‘hold’’ or ‘‘f lip’’ the rule linking the colored cue and response. The design allowed us to determine which brain regions were recruited by the specific demands of preparing a rule contingent motor response, executing such a response, evaluating the significance of the feedback, and reconfiguring stimulus–response (SR) associations. The results indicate that an increase in neural activity occurs within the anterior cingulate gyrus under conditions in which SR associations are labile. In contrast, lateral frontal regions are activated by unlikely/unexpected perceptual events regardless of their significance for behavior. A network of subcortical structures, including the mediodorsal nucleus of the thalamus and striatum were the only regions showing activity that was exclusively correlated with the neurocognitive demands of reversing SR associations. We conclude that lateral frontal regions act to evaluate the behavioral significance of perceptual events, whereas medial frontal–thalamic circuits are involved in monitoring and reconfiguring SR associations when necessary

Parametric Representation of Noncommutative Field Theory

In this paper we investigate the Schwinger parametric representation for the Feynman amplitudes of the recently discovered renormalizable $\phi^4_4$ quantum field theory on the Moyal non commutative ${\mathbb R^4}$ space. This representation involves new {\it hyperbolic} polynomials which are the non-commutative analogs of the usual "Kirchoff" or "Symanzik" polynomials of commutative field theory, but contain richer topological information.Comment: 31 pages,10 figure

Bilateral redundancy gain and callosal integrity in a man with callosal lipoma: a diffusion-tensor imaging study

We investigated whether abnormalities in the structural organisation of the corpus callosum in the presence of curvilinear lipoma are associated with increased facilitation of response time to bilateral stimuli, an effect known as the redundancy gain. A patient (A.J.) with a curvilinear lipoma of the corpus callosum, his genetically-identical twin, and age-matched control participants made speeded responses to luminant stimuli. Structural organisation of callosal regions was assessed with diffusion-tensor imaging. A.J. was found to have reduced structural integrity in the splenium of the corpus callosum and produced a large redundancy gain suggestive of neural summation

Generalized Plasmonic Modelling of the Effect of Refractive Index on Laser-Induced Periodic Nanostructures

Laser-induced periodic surface structures (LIPSS) have been studied theoretically employing generalized plasmonic modelling on several dielectric materials such as SiO2, Al2O3, ZnO, AlAs and diamond exposed to 800 nm wavelength multi-pulse femtosecond laser irradiation. The study of the optical properties of the materials during laser irradiation reveals a formation of a metallic like pseudo-material on the irradiated layer during excitation. A study of the grating periodicity of the nanostructures shows that the materials having a high refraction index allow LIPSS formation with a wide range of grating periodicities. Results also show High Spatial Frequency LIPSS formation with periodicities 3 to 8 times lower than the laser wavelength

A Physicist's Proof of the Lagrange-Good Multivariable Inversion Formula

We provide yet another proof of the classical Lagrange-Good multivariable inversion formula using techniques of quantum field theory.Comment: 9 pages, 3 diagram

Analyticity of The Ground State Energy For Massless Nelson Models

We show that the ground state energy of the translationally invariant Nelson model, describing a particle coupled to a relativistic field of massless bosons, is an analytic function of the coupling constant and the total momentum. We derive an explicit expression for the ground state energy which is used to determine the effective mass.Comment: 33 pages, 1 figure, added a section on the calculation of the effective mas

Casimir invariants for the complete family of quasi-simple orthogonal algebras

A complete choice of generators of the center of the enveloping algebras of real quasi-simple Lie algebras of orthogonal type, for arbitrary dimension, is obtained in a unified setting. The results simultaneously include the well known polynomial invariants of the pseudo-orthogonal algebras $so(p,q)$, as well as the Casimirs for many non-simple algebras such as the inhomogeneous $iso(p,q)$, the Newton-Hooke and Galilei type, etc., which are obtained by contraction(s) starting from the simple algebras $so(p,q)$. The dimension of the center of the enveloping algebra of a quasi-simple orthogonal algebra turns out to be the same as for the simple $so(p,q)$ algebras from which they come by contraction. The structure of the higher order invariants is given in a convenient "pyramidal" manner, in terms of certain sets of "Pauli-Lubanski" elements in the enveloping algebras. As an example showing this approach at work, the scheme is applied to recovering the Casimirs for the (3+1) kinematical algebras. Some prospects on the relevance of these results for the study of expansions are also given.Comment: 19 pages, LaTe