New potential hydrocarbon source-rocks in the Lower Eocene Metlaoui Formation (Central-Northern Tunisia, Northern Africa)

New potential hydrocarbon source-rocks in the Lower EoceneMetlaoui Formation (Central-Northern Tunisia, Northern Africa)Significant quantities of organic matter accumulated and were preserved in central-northern Tunisia during theYpresian (Early Eocene). The organic geochemical characterization of the organic-rich facies of the YpresianMetlaoui Formation (Ousselat and Es-Sfeïa sections) shows their significant potential as source rocks andincreases interest in the Central-Northern Tunisia oil play. The TOC content in these rocks ranges from 0.09 to3.71% suggesting their petroleum potential, whereas their T maxfluctuates from 429 to 439°C. These values andthe predominance of the hetero compounds (NSO; 2-95%) point to low organic matter maturation. The diversematurity levels reported for these organic-rich rocks never reached the conventional oil window peak stage andresulted from their different locationswithin the basin. The HI values and the high saturate concentrations(1-91%) compared to aromatics (1-33%), as well as the predominance of short-chain n-alkanes centered at n-C18 and n-C20 are indicative of unequivocal type-II kerogen. The fluctuation of the pristane/phytane ratio(0.97-2.53) records changes of the basin redox conditions, which mainly evolved around the sub-oxic rang

Applying Sodium Profile with or without Ultrafiltration Profile Failed to Show Beneficial Effects on the Incidence of Intra- dialytic Hypotension in Susceptible Hemodilaysis Patients

Introduction: Intra-dialytic hypotension (IDH) is a common complication during hemodialysis (HD) treatment. Previous studies have reportedthat modulating dialysate sodium concentration combined or not with modulation of ultrafiltration (UF) rate may reduce the incidence of IDH. The aim of the present study was to evaluate the effect of sodium and UF profiles on the occurrence of intra-dialytic complications and dialysis quality.Methods: From a total of 64 patients, we selected 18 patients who suffered from recurrent IDH. Every patient received ten HD sessions utilizing each of the following treatments: (1) Control: constant sodium concentrationand UF rates. (2) Sodium and UF profiles: a linearly decreasing sodium concentration combined with a linearly decreasing UF rate. (3) Sodium profile:decreasing sodium concentration with constant UF rate.Results: Fourteen patients completed the study protocol. The incidence of IDH, mean inter-dialytic weight gain and the delivered dialysis dose were not different between the three treatments. However, symptomatic episodes of IDH were more commonand pre-dialysis systolic bloodpressure was higher during the second and third treatment modalities compared to controls. Isolated sodium profile was associated with more malaise and less achievement of target session duration compared to the other two treatments. Isolated sodium profile was associated withless achievement of target UF while combined sodium and UF profiles were associated with more achievement of target UF compared to controls.Conclusion: Our results indicate that sodium profile with or without UF profile does not have a beneficial effect on the incidence of IDH, achievement of target session duration or the delivered dialysis dose

Perceived risk of infection and death from COVID-19 among community members of low- and middle-income countries: A cross-sectional study [version 1; peer review: awaiting peer review]

Background: Risk perceptions of coronavirus disease 2019 (COVID-19) are considered important as they impact community health behaviors. The aim of this study was to determine the perceived risk of infection and death due to COVID-19 and to assess the factors associated with such risk perceptions among community members in low- and middle-income countries (LMICs) in Africa, Asia, and South America. Methods: An online cross-sectional study was conducted in 10 LMICs in Africa, Asia, and South America from February to May 2021. A questionnaire was utilized to assess the perceived risk of infection and death from COVID-19 and its plausible determinants. A logistic regression model was used to identify the factors associated with such risk perceptions. Results: A total of 1,646 responses were included in the analysis of the perceived risk of becoming infected and dying from COVID-19. Our data suggested that 36.4% of participants had a high perceived risk of COVID-19 infection, while only 22.4% had a perceived risk of dying from COVID-19. Being a woman, working in healthcare-related sectors, contracting pulmonary disease, knowing people in the immediate social environment who are or have been infected with COVID-19, as well as seeing or reading about individuals infected with COVID-19 on social media or TV were all associated with a higher perceived risk of becoming infected with COVID-19. In addition, being a woman, elderly, having heart disease and pulmonary disease, knowing people in the immediate social environment who are or have been infected with COVID-19, and seeing or reading about individuals infected with COVID-19 on social media or TV had a higher perceived risk of dying from COVID-19. Conclusions: The perceived risk of infection and death due to COVID-19 are relatively low among respondents; this suggests the need to conduct health campaigns to disseminate knowledge and information on the ongoing pandemic

New potential hydrocarbon source-rocks in the Lower Eocene Metlaoui Formation (Central-Northern Tunisia, Northern Africa)

Significant quantities of organic matter accumulated and were preserved in central-northern Tunisia during the Ypresian (Early Eocene). The organic geochemical characterization of the organic-rich facies of the Ypresian Metlaoui Formation (Ousselat and Es-Sfeïa sections) shows their significant potential as source rocks and increases interest in the Central-Northern Tunisia oil play. The TOC content in these rocks ranges from 0.09 to 3.71% suggesting their petroleum potential, whereas their T max fluctuates from 429 to 439°C. These values and the predominance of the hetero compounds (NSO; 2-95%) point to low organic matter maturation. The diverse maturity levels reported for these organic-rich rocks never reached the conventional oil window peak stage and resulted from their different locations within the basin. The HI values and the high saturate concentrations (1-91%) compared to aromatics (1-33%), as well as the predominance of short-chain n-alkanes centered atn-C18 and n-C20 are indicative of unequivocal type-II kerogen. The fluctuation of the pristane/phytane ratio (0.97-2.53) records changes of the basin redox conditions, which mainly evolved around the sub-oxic range

Origin and depositional environment of palygorskite and sepiolite from the ypresian phosphatic series, Southwestern Tunisia

The Ypresianphosphatic series of the Gafsa-Metlaoui basin, southwesternTun isia, is represented by an alternation of phosphatic levels and interbedded facies, which are composed of marly-clay and silica-rich rocks. The present work aimed to clarify the genesis of palygorskite and sepiolite of the interbedded facies and to understand the depositional environment of the phosphatic series. The interbedded facies of the Stah and Jellabia mines were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Energy Dispersive X-ray microanalysis (EDX) of individual constituents and their aggregates. The data obtained indicate that samples are made up of francolite, calcite, dolomite, quartz, feldspars, and clay minerals; the latter consist of palygorskite-sepiolite minerals associated with smectite. Observations by SEM revealed the occurrence of palygorskite and sepiolite as fine and filamentous fibers with thread-like facies and coating dolomite, calcite, and a marly matrix. Such features can be considered as textural evidence of authigenic palygorskite-sepiolite. At the bottom of the Stah section, SEM observations revealed that the fine fibers are more abundant within silica-rich rocks. Silica is commonly available due to bacterial activity saturating its environment with the silicic acid required for the formationof palygorskite-sepiolite. Inthe interbedded facies of the Jellabia section, the moderate fibrous clay content and the presence of well crystallized dolomite revealed that the shallowmarine water was characterized by high-Mg and low-Si activities

Development of two sandy bay bars in a deltaic environment under action of swash waves

The article describes development of two sandy bay bars located south of Sfax. The aim of the research was to determine the rate of growth of the bay bars and to find factors responsible for the process. The research was based on analysis of aerial photographs and textural features of sediments. The results show that the length of the bars grows c. 40 m/yr on average. This is linked to supply of detritus by the Wadi Chaffer which has its delta between the analysed bay bars. Developments of the bars is symmetrical on both sides of the delta and depends also on long-shore currents flowing in opposite directions along the delta coast. The bay bars are kinds of beach ridges 2 to 3 km long and consists of fine and medium, well sorted sand. Such a sediment is under permanent action of wind and swash waves. Lagoons protected by the bay bars constitute a low-energy environment and their floors are built with fine, poorly sorted sand. It is emphasised that the morphology of the bay bars is not stable and susceptible for high anthropopression in the region

Source Rock Characterization and Petroleum Systems in North Ghadames Basin, Southern Tunisia

International audienc

Mediterranean pluvial periods and sapropel formation over the last 200 000 years

International audienc