University of Gabès

) confirmed that the relaxation process is thermally activated. The normalized imaginary part of the modulus indicated that the relaxation process is dominated by the short range movement of charge carriers.

In this review, we discuss the rich chemistry of helicenes and helicenoids containing main-group elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N, and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, and emission, together with other photochemical properties and applications.

Bisphenol-A (BPA) is one of the highest volume chemicals produced worldwide, with over 6billion pounds produced and over 100t released into the atmosphere each year. Recent extensive literature has raised concerns about its possible implication in the etiology of some human chronic diseases such as diabetes, obesity, reproductive disorders, cardiovascular diseases, birth defects, chronic respiratory and kidney diseases and breast cancer. In this review, we present the highlighted evidences on the relationship between BPA exposure and human chronic diseases and we discuss its eventual mechanisms of action, especially genetic, epigenetic and endocrine disruption mechanisms with the possible involvement of oxidative stress, mitochondrial dysfunction and cell signaling.

The unique biological and physicochemical characteristics of biogenic (green-synthesized) nanomaterials (NMs) have attracted significant interest in different fields, with applications in the agrochemical, food, medication delivery, cosmetics, cellular imaging, and biomedical industries. To synthesize biogenic nanomaterials, green synthesis techniques use microorganisms, plant extracts, or proteins as bio-capping and bio-reducing agents and their role as bio-nanofactories for material synthesis at the nanoscale size. Green chemistry is environmentally benign, biocompatible, nontoxic, and economically effective. By taking into account the findings from recent investigations, we shed light on the most recent developments in the green synthesis of nanomaterials using different types of microbes and plants. Additionally, we cover different applications of green-synthesized nanomaterials in the food and textile industries, water treatment, and biomedical applications. Furthermore, we discuss the future perspectives of the green synthesis of nanomaterials to advance their production and applications.

) spinel structure. Using FTIR spectra, the elastic and thermodynamic properties were estimated. It was observed that the particle size had a pronounced effect on elastic and thermodynamic properties. Magnetic measurements were performed up to 700 K. The prepared ferrite samples present the highest Curie temperature, which decreases with increasing particle size and which is consistent with finite-size scaling. The thickness of the surface shell of about 1 nm was estimated from size-dependent magnetization measurements using the core-shell model. Besides, spin resonance, magnetostriction, temperature coefficient of resistance (TCR), and electrical resistivity properties have been scientifically studied and appear to be different according to their size. The optical properties of synthesized NZFAO nanoparticles were investigated, and the differences caused by the particle sizes are discussed on the basis of the phonon confinement effect. This effect was also inspected by the Raman analysis. Tuning of the physical properties suggests that the Ni-Zn-Al ferrite samples may be promising for multifunctional diverse applications.

Abstract. On the basis of a multi-proxy approach and a strategy combining lacustrine and marine records along a north–south transect, data collected in the central Mediterranean within the framework of a collaborative project have led to reconstruction of high-resolution and well-dated palaeohydrological records and to assessment of their spatial and temporal coherency. Contrasting patterns of palaeohydrological changes have been evidenced in the central Mediterranean: south (north) of around 40° N of latitude, the middle part of the Holocene was characterised by lake-level maxima (minima), during an interval dated to ca. 10 300–4500 cal BP to the south and 9000–4500 cal BP to the north. Available data suggest that these contrasting palaeohydrological patterns operated throughout the Holocene, both on millennial and centennial scales. Regarding precipitation seasonality, maximum humidity in the central Mediterranean during the middle part of the Holocene was characterised by humid winters and dry summers north of ca. 40° N, and humid winters and summers south of ca. 40° N. This may explain an apparent conflict between palaeoclimatic records depending on the proxies used for reconstruction as well as the synchronous expansion of tree species taxa with contrasting climatic requirements. In addition, south of ca. 40° N, the first millennium of the Holocene was characterised by very dry climatic conditions not only in the eastern, but also in the central- and the western Mediterranean zones as reflected by low lake levels and delayed reforestation. These results suggest that, in addition to the influence of the Nile discharge reinforced by the African monsoon, the deposition of Sapropel 1 has been favoured (1) by an increase in winter precipitation in the northern Mediterranean borderlands, and (2) by an increase in winter and summer precipitation in the southern Mediterranean area. The climate reversal following the Holocene climate optimum appears to have been punctuated by two major climate changes around 7500 and 4500 cal BP. In the central Mediterranean, the Holocene palaeohydrological changes developed in response to a combination of orbital, ice-sheet and solar forcing factors. The maximum humidity interval in the south-central Mediterranean started ca. 10 300 cal BP, in correlation with the decline (1) of the possible blocking effects of the North Atlantic anticyclone linked to maximum insolation, and/or (2) of the influence of the remnant ice sheets and fresh water forcing in the North Atlantic Ocean. In the north-central Mediterranean, the lake-level minimum interval began only around 9000 cal BP when the Fennoscandian ice sheet disappeared and a prevailing positive NAO-(North Atlantic Oscillation) type circulation developed in the North Atlantic area. The major palaeohydrological oscillation around 4500–4000 cal BP may be a non-linear response to the gradual decrease in insolation, with additional key seasonal and interhemispheric changes. On a centennial scale, the successive climatic events which punctuated the entire Holocene in the central Mediterranean coincided with cooling events associated with deglacial outbursts in the North Atlantic area and decreases in solar activity during the interval 11 700–7000 cal BP, and to a possible combination of NAO-type circulation and solar forcing since ca. 7000 cal BP onwards. Thus, regarding the centennial-scale climatic oscillations, the Mediterranean Basin appears to have been strongly linked to the North Atlantic area and affected by solar activity over the entire Holocene. In addition to model experiments, a better understanding of forcing factors and past atmospheric circulation patterns behind the Holocene palaeohydrological changes in the Mediterranean area will require further investigation to establish additional high-resolution and well-dated records in selected locations around the Mediterranean Basin and in adjacent regions. Special attention should be paid to greater precision in the reconstruction, on millennial and centennial timescales, of changes in the latitudinal location of the limit between the northern and southern palaeohydrological Mediterranean sectors, depending on (1) the intensity and/or characteristics of climatic periods/oscillations (e.g. Holocene thermal maximum versus Neoglacial, as well as, for instance, the 8.2 ka event versus the 4 ka event or the Little Ice Age); and (2) on varying geographical conditions from the western to the eastern Mediterranean areas (longitudinal gradients). Finally, on the basis of projects using strategically located study sites, there is a need to explore possible influences of other general atmospheric circulation patterns than NAO, such as the East Atlantic–West Russian or North Sea–Caspian patterns, in explaining the apparent complexity of palaeoclimatic (palaeohydrological) Holocene records from the Mediterranean area.

Phosphogypsum (PG: CaSO4·2H2O) is a waste product generated by the phosphate industry. World production of this waste exceeds 200 million tonnes per year. PG, discharged into the sea, watercourses or in wilderness stocks, contains toxic elements harmful to ecosystems and human health, including heavy metals and radionuclides, and there is therefore a concern regarding environmental impacts. The concentrations of these elements vary between the regions and the processes used, all of which require particular and specific follow-up after the release of PG and during its use. Phosphogypsum is used in agriculture for soil amendment or as fertilizer, as well as in the brick and cement industry, and in road construction.

This study investigates the dynamic connectedness between stock indices and the effect of economic policy uncertainty (EPU) in eight countries where COVID-19 was most widespread (China, Italy, France, Germany, Spain, Russia, the US, and the UK) by implementing the time-varying VAR (TVP-VAR) model for daily data over the period spanning from 01/01/2015 to 05/18/2020. Results showed that stock markets were highly connected during the entire period, but the dynamic spillovers reached unprecedented heights during the COVID-19 pandemic in the first quarter of 2020. Moreover, we found that the European stock markets (except Italy) transmitted more spillovers to all other stock markets than they received, primarily during the COVID-19 outbreak. Further analysis using a nonlinear framework showed that the dynamic connectedness was more pronounced for negative than for positive returns. Also, findings showed that the direction of the EPU effect on net connectedness changed during the pandemic onset, indicating that information spillovers from a given market may signal either good or bad news for other markets, depending on the prevailing economic situation. These results have important implications for individual investors, portfolio managers, policymakers, investment banks, and central banks.

Pharmaceutical products have become a necessary part of life. Several studies have demonstrated that indirect exposure of humans to pharmaceuticals through the water could cause negative effects. Raw sewage and wastewater effluents are the major sources of pharmaceuticals found in surface waters and drinking water. Therefore, it is important to consider and characterize the efficiency of pharmaceutical removal during wastewater and drinking-water treatment processes. Various treatment options have been investigated for the removal/reduction of drugs (e.g., antibiotics, NSAIDs, analgesics) using conventional or biological treatments, such as activated sludge processes or bio-filtration, respectively. The efficiency of these processes ranges from 20–90%. Comparatively, advanced wastewater treatment processes, such as reverse osmosis, ozonation and advanced oxidation technologies, can achieve higher removal rates for drugs. Pharmaceuticals and their metabolites undergo natural attenuation by adsorption and solar oxidation. Therefore, pharmaceuticals in water sources even at trace concentrations would have undergone removal through biological processes and, if applicable, combined adsorption and photocatalytic degradation wastewater treatment processes. This review provides an overview of the conventional and advanced technologies for the removal of pharmaceutical compounds from water sources. It also sheds light on the key points behind adsorption and photocatalysis.

This study presents the electrical properties, complex impedance analysis and dielectrical behavior of La0.5Ca0.5-xAgxMnO3 manganites with compositions below the concentration limit of silver solubility in perovskites (0 ≤ x ≤ 0.2). Transport measurements indicate that all the samples have a semiconductor-like behavior. The metal-semiconductor transition is not observed across the whole temperature range explored [80 K-700 K]. At a specific temperature, a saturation region was marked in the σ (T) curves. We obtained a maximum σdc value at ambient temperature with the introduction of 20% Ag content. Two hopping models were applied to study the conduction mechanism. We found that activation energy (Ea) related to ac-conductivity is lower than the Ea implicated in dc-conductivity. Complex impedance analysis confirms the contribution of grain boundary to conductivity and permits the attribution of grain boundary capacitance evolution to the temperature dependence of the barrier layer width. From the temperature dependence of the average normalized change (ANC), we deduce the temperature at which the available density of trapped charge states vanishes. Such a temperature is close to the temperature at which the saturation region appears in σ(T) curves. Moreover, complex impedance analysis (CIA) indicates the presence of electrical relaxation in materials. It is noteworthy that relaxation species such as defects may be responsible for electrical conduction. The dielectric behavior of La0.5Ca0.5-xAgxMnO3 manganites has a Debye-like relaxation with a sharp decrease in the real part of permittivity at a frequency where the imaginary part of permittivity (ε'') and tg δ plots versus frequency demonstrate a relaxation peak. The Debye-like relaxation is explained by Maxwell-Wagner (MW) polarization. Experimental results are found to be in good agreement with the Smit and Wijn theory.

emissions and from labor to economic growth and population density. A detailed policy prescription is provided based on the findings.

When integrating the Internet of Things (IoT) with Unmanned Aerial Vehicles (UAVs) occurred, tens of applications including smart agriculture have emerged to offer innovative solutions to modernize the farming sector. This paper aims to present a low-cost platform for comprehensive environmental parameter monitoring using flying IoT. This platform is deployed and tested in a real scenario on a farm in Medenine, Tunisia, in the period of March 2020 to March 2021. The experimental work fulfills the requirements of automated and real-time monitoring of the environmental parameters using both under- and aboveground sensors. These IoT sensors are on a farm collecting vast amounts of environmental data, where it is sent to ground gateways every 1 h, after which the obtained data is collected and transmitted by a drone to the cloud for storage and analysis every 12 h. This low-cost platform can help farmers, governmental, or manufacturers to predict environmental data over the geographically large farm field, which leads to enhancement in crop productivity and farm management in a cost-effective, and timely manner. Obtained experimental results infer that automated and human-made sets of actions can be applied and/or suggested, due to the innovative integration between IoT sensors with the drone. These smart actions help in precision agriculture, which, in turn, intensely boost crop productivity, saving natural resources.

The performance of a microporous activated carbon prepared chemically from olive stones for removing Cu(II), Cd(II) and Pb(II) from single and binary aqueous solutions was investigated via the batch technique. The activated carbon sample was characterized using N 2 adsorption–desorption isotherms, SEM, XRD, FTIR, and Boehm titration. The effect of initial pH and contact time were studied. Adsorption kinetic rates were found to be fast and kinetic experimental data fitted very well the pseudo-second-order equation. The adsorption isotherms fit the Redlich–Peterson model very well and maximum adsorption amounts of single metal ions solutions follow the trend Pb(II) > Cd(II) > Cu(II). The adsorption behavior of binary solution systems shows a relatively high affinity to Cu(II) at the activated carbon surface of the mixture with Cd(II) or Pb(II). An antagonistic competitive adsorption phenomenon was observed. Desorption experiments indicated that about 59.5% of Cu(II) and 23% of Cd(II) were desorbed using a diluted sulfuric acid solution.

This article aims to determine the phenolic, tocopherol contents, and antioxidant capacities from fruits (juices, peels, and seed oils) of 6 Tunisian pomegranate ecotypes. Total anthocyanins were determined by a differential pH method. Hydrolyzable tannins were determined with potassium iodate. The tocopherol (α-tocopherol, γ-tocopherol, and δ-tocopherol) contents were, respectively, 165.77, 107.38, and 27.29 mg/100 g from dry seed. Four phenolic compounds were identified and quantified in pomegranate peel and pulp using the high-performance liquid chromatography/ultraviolet method: 2 hydroxybenzoic acids (gallic and ellagic acids) and 2 hydroxycinnamic acids (caffeic and p-coumaric acids). Juice, peel, and seed oil antioxidants were confirmed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) methods. The highest values were recorded in peels with 25.63 mmol trolox equivalent/100 g and 22.08 mmol TE/100 g for FRAP and ORAC assay, respectively. Results showed that the antioxidant potency of pomegranate extracts was correlated with their phenolic compound content. In particular, the highest correlation was reported in peels. High correlations were also found between peel hydroxybenzoic acids and FRAP ORAC antioxidant capacities. Identified tocopherols seem to contribute in major part to the antioxidant activity of seed oil. The results implied that bioactive compounds from the peel might be potential resources for the development of antioxidant function dietary food.

The purpose of this paper is to determine those factors that influence the adoption of internet banking services inTunisia. A theoretical model is provided that conceptualizes and links different factors influencing the adoptionof internet banking. A total of 253 respondents in Tunisia were sampled for responding: 95 were internet bankusers, 158 were internet bank non users. Factor analyses and regression technique are employed to study therelationship. The results of the model tested clearly that use of internet banking in Tunisia is influenced moststrongly by convenience, risk, security and prior internet knowledge. Only information on online banking did notaffect intention to use internet banking service in Tunisia. The results also propose that demographic factorsimpact significantly internet banking behaviour, specifically, occupation and instruction. Finally, this papersuggests that an understanding the factors affecting intention to use internet banking is very important to thepractitioners who plan and promote new forms of banking in the current competitive market.

SummaryThe effects of drought on several major morphological and anatomical features of leaves were investigated in an attempt to explain the origin of the difference in drought resistance between two olive (Olea europaea L.) cultivars, (‘Chemlali’ and ‘Meski’) previously demonstrated to be drought-resistant and drought-sensitive, respectively. Under water deficit conditions, ‘Chemlali’ maintained higher rates of photosynthetic assimilation and lower rates of transpiration compared to ‘Meski’. In the present study, we found cultivar-dependent differences in leaf morpho-anatomical adaptations to drought stress. When subjected to water stress, the leaves of‘Chemlali’ increased the thickness of their upper palisade and spongy parenchyma by 17% and 22%, respectively, compared with only 9% and 13% in the case of ‘Meski’. A thicker palisade parenchyma could contain larger numbers of CO2-fixation sites, while a thicker spongy parenchyma could result in easier diffusion of CO2 to these sites. Furthermore, stomatal density (SD) in ‘Chemlali’ leaves increased by 25%(vs. 7% for ‘Meski’ leaves) during drought treatment, which could also enhance the external supply of CO2. Other morpho-structural traits implicated in the control of water loss were enhanced morein ‘Chemlali’ than in ‘Meski’ leaves. Under conditions of lower water availability, leaf size decreased by 24% in ‘Chemlali’ (vs. 15% in ‘Meski’), trichome density (TD) increased by 25% (while remaining unchanged in ‘Meski’), and the thickness of the upper and lower epidermis increased by 32% and 25%, respectively (while remaining unchanged in ‘Meski’). The above morpho-anatomical adaptations should improve the water-use efficiency of the tree. These differential changes in leaf morphology and anatomy can explain, at least in part, the difference in drought resistance between the two cultivars. In particular, the upper palisade parenchyma, the spongy parenchyma, SD, and TD could be considered key structural features of leaves that govern the ability of a tree to withstand water stress. They could therefore be used as criteria to select olive cultivars that are more resistant to drought.

In this work, effects of some experimental parameters (supporting electrolyte, initial pH, and current density) on aluminum corrosion and anodic dissolution of aluminum during electrocoagulation process were investigated. Potentiodynamic polarization tests, impedance spectroscopy measurements and potentisotatic current density transients were used to evaluate corrosion parameters and verify effects of supporting electrolyte and initial pH on aluminum corrosion. The presence of NaCl and Na2SO4 shifted the corrosion potential toward more cathodic potentials, indicating that corrosion of aluminum is catalyzed by the presence NaCl and Na2SO4. On the contrary, the presence of NaH2PO4 increased the corrosion potential, which indicates that the presence of NaH2PO4 inhibits the corrosion of aluminum. Galvanostatic electrolyses demonstrated that measured concentrations of aluminum exceeded theoretical values calculated using Faraday’s Law. The excess in dissolved aluminum produced during galvanostatic electrolyses is primary due to the chemical dissolution of aluminum, which is more significant at highly alkaline conditions. A final pH of value around pH 9 was observed in the presence of NaCl for pH values in the range pH 4–11 which can be explained by buffering effects of aluminum hydroxides.

In this study, the adsorption behavior of Cu2+, Pb2+ and Cd2+ from synthetic metal solutions using natural zeolites was studied in order to investigate the efficiency of adsorbents of heavy metals from industrial wastewater. The kinetic study indicated the suitability of the zeolite for the removal of Cu2+, Pb2+ and Cd2+ ions from synthetic wastewater; batch experiments were used to identify the effect of parameters that affect the rate of adsorption such as the adsorbent mass, the initial solution concentration, the initial solution pH, the adsorbent particle size, and the agitation speed and evaluated their impact on the removal efficiency of heavy metals from industrial wastewater using the natural zeolite. Zeolite samples with masses between 1 g and 10 g were contacted with constant volume (100 ml) of multicomponent synthetic solutions containing Cu2+, Pb2+ and Cd2+ ions. They were agitated at agitation speeds in the range of 100–300 rpm for agitation times from 1 hr to 8 hrs in a magnetic stirrer at room temperature, the pH values were monitored and adjusted regularly. Every hour, 15 ml of the samples was analyzed using the Atomic Absorption Spectroscopy. The results show that the removal efficiency of Cu2+ increase from 60% for 1 gr to 99% for 10 gr of the mass of absorbent, increase from 62% for 1% to 94% for 7 of the initial solution pH, increase from 90% for 100 rpm to 94% for 300 rpm of the agitation speed, the amount adsorbed increase from 0.5 mg/g for 100 mg/l to 2.1% for 400 mg/l of the initial solution concentration. Similar results are obtained for the two other heavy metals (Pb2+, Cd2+) and showed that the capacity of the adsorbents for the removal of heavy metals is directly proportional to the mass of absorbent, initial solution pH, agitation speed, and initial solution concentration. The highest adsorption rate of Cu2+, Pb2+ and Cd2+ ions took place in the first hours followed by a slower adsorption rate later on.

Molecular and macromolecular chiral π-conjugated diketopyrrolopyrrole (DPP)-helicene derivatives were prepared and their chiroptical properties examined experimentally and theoretically. Exciton coupling leads to red and near-infrared circularly polarized absorption and luminescence arising from the achiral DPP units in the helical environment, highlighting an interesting synergy between the chiral helicene and the organic dye.

In this work, the degradation of chloroquine (CLQ), an antiviral and antimalarial drug, using electro-Fenton oxidation was investigated. Due to the importance of hydrogen peroxide (H2O2) generation during electro-Fenton oxidation, effects of pH, current density, molecular oxygen (O2) flow rate, and anode material on H2O2 generation were evaluated. H2O2 generation was enhanced by increasing the current density up to 60 mA/cm2 and the O2 flow rate up to 80 mL/min at pH 3.0 and using carbon felt cathode and boron-doped diamond (BDD) anode. Electro-Fenton-BDD oxidation achieved the total CLQ depletion and 92% total organic carbon (TOC) removal. Electro-Fenton-BDD oxidation was more effective than electro-Fenton-Pt and anodic oxidation using Pt and BDD anodes. The efficiency of CLQ depletion by electro-Fenton-BDD oxidation raises by increasing the current density and Fe2+ dose; however it drops with the increase of pH and CLQ concentration. CLQ depletion follows a pseudo-first order kinetics in all the experiments. The identification of CLQ degradation intermediates by chromatography methods confirms the formation of 7-chloro-4-quinolinamine, oxamic, and oxalic acids. Quantitative amounts of chlorides, nitrates, and ammonium ions are released during electro-Fenton oxidation of CLQ. The high efficiency of electro-Fenton oxidation derives from the generation of hydroxyl radicals from the catalytic decomposition of H2O2 by Fe2+ in solution, and the electrogeneration of hydroxyl and sulfates radicals and other strong oxidants (persulfates) from the oxidation of the electrolyte at the surface BDD anode. Electro-Fenton oxidation has the potential to be an alternative method for treating wastewaters contaminated with CLQ and its derivatives.