Geochemistry, mineral paragenesis and geothermal conditions of oreforming fluids from the Ain El Bey Cu–Fe deposit: potential occurrence of native gold and precious metal traces (North African orogenic belt, Northern Tunisia)

The Ain El Bey abandoned mine, in North-West Tunisia, fits into the geodynamic context of the European and African plate boundary. Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization related to various hydrothermal fluid circulations. Petromineralogical studies indicate a rich mineral paragenesis with a minimum of seven mineralization phases and, at least, six pyrite generations. As is also the case for galena and native silver, native gold is observed for the first time as inclusion in quartz which opens up, thus, new perspectives for prospecting and evaluating the potential for noble metals associated with the mineralization. Scanning Electron Microscope--Energy Dispersive Spectroscopy and Transmission electron microscopy analyses show, in addition, a large incorporation of trace elements, including Ag and Au, in mineral structures such as fahlores(tetrahedrite-tennantite) and chalcopyrite ones. The mineral/mineral associations, used as geothermometers, gave estimated temperatures for the mineralizing fluids varying from 254 to 330 ℃ for phase Ⅲ, from 254 to 350 ℃ for phase Ⅳ, and from 200 to 300 ℃ for phases Ⅴ and Ⅵ. The seventh and last identified mineralization phase, marked by a deposit of native gold, reflects a drop in the mineralizing fluid’s temperature(< 200 ℃) compatible with boiling conditions. Such results open up perspectives for the development of precious metal research and the revaluation of the Cu–Fe ore deposit at the Ain El Bey abandoned mine, as well as at the surrounding areas fitting in the geodynamic framework of the Africa-Europe plate boundary.

Variations of Natural Soil Salinity in an Arid Environment Using Underground Watertable Effects on Salinization of Soils in Irrigated Perimeters in South Tunisia

In arid and semi-arid regions, salinity is a serious and chronic problem for agriculture. The aim of this study is to evaluate the hydromorphical and salinity risks, and to evaluate the relationship and the possible interfering between the water table and the soil on the oasis of Gabes. The topic is very important, especially for nations around the oceans in arid and semi-arid regions. The effect of the gypsum alkalinity in the soil salinity has investigated. The chemical characteristic of used water irrigation (salinity saturation) and their impact factor in the productivity area. Moreover, in this study the program of examination need to put fifteen piesometres by CRAD (Regional Commissariat of Agriculture Development) in the city of Gabes to controlling the variation of water levels in the superficial water table and their change chemical quality. The experimental measure of this program needs a yearly observation and investigation during April and May to evaluate the hydromorphical and salinity risks on the oasis of Gabes. The relationship and the possible interfering between the water table and the soil has evaluate in such condition.

Constrained to the Oasienne Production and Strategies of a Sustainable Development （Case of the Oasis of El Mahassen, Southwestern of Tunisia）

In the absence of all industrial activity, the oasienne agriculture represents the only advantageous economic speculation of the region. However, the agricultural soils support largest constraints, which are the salinization, the hydromorphy, and the exaggerated division of the parcels by successive inheritance what can provoke a decline and a reduction of the productivity. The sampling and the analysis of the irrigation water shows a net rise of the waters salinity, of the order of 5.25 g/L. The topographic measures made during this work serve to detect zones favorable to the accumulation of the salt layers. The object of this note is to treat these constraints differently by means of an empiric survey, all trying to establish some adequate recommendations.

Photoelectrochemical activity of ZnO:Ag/rGO photo-anodes synthesized by two-steps sol-gel method

This work investigated the influence of silver plasmon and reduced graphene oxide(r GO)on the photoelectrochemical performance(PEC)of Zn O thin films synthesized by the sol-gel method.The physicochemical properties of the obtained photo-anodes were systematically studied by using several characterization techniques.The x-ray diffraction analysis showed that all samples presented hexagonal wurtzite structure with a polycrystalline nature.Raman and energy dispersive x-ray(EDX)studies confirmed the existence of both Ag and r GO in Zn O:Ag/r GO thin films.The estimated grain size obtained from scanning electron microscopy(SEM)analysis decreased with Ag doping,then increased to a maximum value after r GO addition.The UV-vis transmission spectra of the as-prepared Zn O:Ag and Zn O:Ag/r GO thin films have shown a reduction in the visible range with a redshift at the absorption edges.The bandgaps were estimated to be around 3.17 e V,2.7 e V,and 2.52 e V for Zn O,Zn O:Ag,and Zn O:Ag/r GO,respectively.Moreover,the electrical measurements revealed that the charge exchange processes were enhanced at the Zn O:Ag/r GO/electrolyte interface,accompanied by an increase in the(PEC)performance compared to Zn O and Zn O:Ag photo-anodes.Consequently,the photocurrent density of Zn O:Ag/r GO(0.2 m A·cm^(-2)) was around 4 and 2.22 times higher than photo-anodes based on undoped Zn O(0.05 m A·cm^(-2)) and Zn O:Ag(0.09 m A·cm^(-2)),respectively.Finally,from the flat band potential and donor density,deduced from the Mott-Schottky,it was clear that all the samples were n-type semiconductors with the highest carrier density for the Zn O:Ag/r GO photo-anode.

Analysis of Complex Electromagnetic Structures by Hybrid FDTD/WCIP Method

This paper proposes a hybrid full-wave analysis using Finite-Difference Time-Domain (FDTD) and Wave Concept Iterative Process (WCIP) methods, developed to analyze locally arbitrarily shaped microwave structures and Multilayer Planar structure. Using the equivalence principle, the original problem can be decomposed into two sub regions and solve each sub region separately. An interpolation scheme is proposed for communicating between the FDTD fields and WCIP wave, which will not require the effort of fitting the WCIP mesh to the FDTD cells in the interface region. This method is applied to calculate the scattering parameters of arbitrary (3-D) microwave structures. Applying FDTD to 3D discontinuity and WCIP to the remaining region preserves the advantages of both WCIP flexibility and FDTD efficiency. A comparison of the results with the FDTD staircasing data verifies the accuracy of the proposed method.

Multiple Relaxation Time Lattice Boltzmann Simulation of 2D Natural Convection in a Square Cavity at High Rayleigh Numbers

Natural convection in a square cavity at high Rayleigh numbers is simulated by multiple relaxation time(MRT)lattice Boltzmann method(LBM)with a separate distribution function to solve the temperature.The Rayleigh numbers examined here range from Ra=103 to Ra=10^(8).For Rayleigh numbers below 10^(8),the flow remains stationary and transition occurs beyond Ra=2×10^(8).Unsteady results at higher Rayleigh numbers(Ra=10^(9) and Ra=10^(10))are also investigated.To the best of our knowledge,this is the first accurate study which involves the high Rayleigh numbers Ra=10^(9),10^(10).

Enhanced radiation characteristics for antipodal Vivaldi antenna using high permittivity dielectric director

In this paper,we investigate the influence of higher permittivity dielectric director on the radiation performances of an antipodal Vivaldi antenna.An elliptical dielectric director with high permittivity is inserted in an antipodal Vivaldi antenna aperture in order to ameliorate the radiation characteristics of the antenna.Due to the capacity of elevated permittivity dielectric to confine and guide energy in the desired direction,an increment of 4 dB in the gain of the antenna is obtained.This antenna,which covers an ultra-wide frequency band of 146.8%from 2.3 GHz to 15 GHz,has approximately regular radiation patterns with reduced side lobe level and narrower beamwidth.In the interest to achieve radar application necessities,the proposed antenna is exploited to develop an antenna array which consists of four connected elements.Adding dielectric directors can significantly enhance the radiations characteristics of the antenna and reduce the mutual coupling inter-elements.So using four elements with dielectric director in the antenna array can achieve the same results obtained with eight elements without directors.This can decrease the used number of elements that form the antenna array.

Bioplastic reinforced with parthenocarpic date palm fibers:Characterization and microorganisms involved in degradation

The environment suffers more and more from the accumulation of plastics made by petrochemical rows,which are non-biodegradable.That is why this study aims to develop bio-based films by incorporating fibers concentrate of parthenocarpic date(FCPD)as easily available ingredients.The FCPD based film showed enhanced thickness,water solubility,phenol content and antioxidant capacity.However,the transparency was reduced which enhanced the film opacity by the addition of FCPD.Scanning electronic microscopy(SEM)showed homogeneity between fibers and the constituents of the film.The addition of FCPD did not change the FTIR peaks in comparison with starch-based film.The hydroxyl index value and water contact angle showed that the hydrophilicity increases with the film FCPD percentage.In addition,the FCPDs have enhanced the microbial biodegradation of the developed films as showed by SEM.Quantitative PCR using specific primers for nine target microbial groups showed that fungi were the predominant agent of the biodegradation.Among bacteria,realtime PCR showed thatβ-Proteobacteria,Acidobacteria,Bacteriodetes andα-Proteobacteria groups were involved in film biodegradation.