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

Distributed Testing of Excluded Subgraphs

We study property testing in the context of distributed computing, under the classical CONGEST model. It is known that testing whether a graph is triangle-free can be done in a constant number of rounds, where the constant depends on how far the input graph is from being triangle-free. We show that, for every connected 4-node graph H, testing whether a graph is H-free can be done in a constant number of rounds too. The constant also depends on how far the input graph is from being H-free, and the dependence is identical to the one in the case of testing triangles. Hence, in particular, testing whether a graph is K_4-free, and testing whether a graph is C_4-free can be done in a constant number of rounds (where K_k denotes the k-node clique, and C_k denotes the k-node cycle). On the other hand, we show that testing K_k-freeness and C_k-freeness for k>4 appear to be much harder. Specifically, we investigate two natural types of generic algorithms for testing H-freeness, called DFS tester and BFS tester. The latter captures the previously known algorithm to test the presence of triangles, while the former captures our generic algorithm to test the presence of a 4-node graph pattern H. We prove that both DFS and BFS testers fail to test K_k-freeness and C_k-freeness in a constant number of rounds for k>4

Estabilización de aceite de oliva virgen extra ecológico con antioxidantes naturales de hojas de Artemisia absinthium obtenidos por maceración y extracción asistida por ultrasonido

Olive oil is the most popular product derived from Olea europaea L. due to its organoleptic characteristics and its beneficial effects on human health. Nowadays, there is a growing interest in olive oil enrichment with medicinal plants. In this regard, Artemisia absinthium L. is an edible source of antioxidants. The aim of the present study was to improve the oxidative stability and the nutritional value of Organic Tunisian Chetoui Olive oil by its enrichment with the phenolic compounds in Artemisia absinthium. The enrichment carried out by maceration and ultrasound-assisted extraction did not affect the organic criteria of olive oil. The comparative study, performed during one year of storage, showed that ultrasound-assisted extraction led to the lowest final peroxide and extinction coefficient values. At the end of storage, this method increased oleic acid content and biophenol contents. Furthermore, the anti-radical activities of enriched samples were higher than the control.El aceite de oliva es el producto derivado de Olea europaea L. muy popular debido a sus características organolépticas y sus efectos beneficiosos para la salud humana. En la actualidad existe un interés creciente por enriquecer el aceite de oliva con plantas medicinales. En este sentido, Artemisia absinthium L. es una fuente comestible de antioxidantes. El objetivo del presente estudio fue la mejora de la estabilidad oxidativa y el valor nutricional del aceite de oliva Chetoui tunecino orgánico mediante su enriquecimiento con compuestos fenólicos de Artemisia absinthium. El enriquecimiento realizado por maceración y extracción asistida por ultrasonidos no afectó a los criterios ecológicos del aceite de oliva. El estudio comparativo, realizado durante un año de almacenamiento, mostró que la extracción asistida por ultrasonidos condujo a los valores finales de peróxido y coeficientes de extinción más bajos. Al final del almacenamiento, este método aumentó el contenido de ácido oleico y de biofenoles. Además, las actividades antirradicales de las muestras enriquecidas fueron mayores que las del control

First-principles calculations of X-ray absorption spectra at the K-edge of 3d transition metals: an electronic structure analysis of the pre-edge

International audienceWe first present an extended introduction of the various methods used to extract electronic and structural information from the K pre-edge X-ray absorption spectra of 3d transition metal ions. The K pre-edge structure is then modelled for a selection of 3d transition metal compounds and analyzed using first-principles calculations based on the density functional theory (DFT) in the local density approximation (LDA). The selected compounds under study are presented in an ascending order of electronic structure complexity, starting with the Ti K-edge of rutile and anatase, and finishing with the Fe K-edge of the cyanomet-myoglobin. In most cases, the calculations are compared to polarized experimental spectra. It is shown that DFT-LDA methods enable us to reproduce satisfactorily the experimental features and to understand the nature of the electronic transitions involved in the pre-edge region. The limiting aspects of such methods in modelling the core-hole electron interaction and the 3d electron-electron repulsion are also pointed out

Annealing effect on physical properties of evaporated molybdenum oxide thin films for ethanol sensing

This paper deals with some physical investigations on molybdenum oxide thin films growing on glass substrates by the thermal evaporation method. These films have been subjected to an annealing process under vacuum, air and oxygen at various temperatures 673, 723 and 773 K. First, the physical properties of these layers were analyzed by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM) and optical measurements. These techniques have been used to investigate the oxygen index in MoOx properties during the heat treatment. Second, from the reflectance and transmittance optical measurements, it was found that the direct band gap energy value increased from 3.16 to 3.90 eV. Finally, the heat treatments reveal that the oxygen index varies in such molybdenum oxides showing noticeably sensitivity toward ethanol gas

Physical Layer Security for Visible Light Communication Systems:A Survey

Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies

Measurements-Based Channel Models for Indoor LiFi Systems

Light-fidelity (LiFi) is a fully-networked bidirectional optical wireless communication (OWC) that is considered a promising solution for high-speed indoor connectivity. Unlike in conventional radio frequency wireless systems, the OWC channel is not isotropic, meaning that the device orientation affects the channel gain significantly. However, due to the lack of proper channel models for LiFi systems, many studies have assumed that the receiver is vertically upward and randomly located within the coverage area, which is not a realistic assumption from a practical point of view. In this paper, novel realistic and measurement-based channel models for indoor LiFi systems are proposed. Precisely, the statistics of the channel gain are derived for the case of randomly oriented stationary and mobile LiFi receivers. For stationary users, two channel models are proposed, namely, the modified truncated Laplace (MTL) model and the modified Beta (MB) model. For LiFi users, two channel models are proposed, namely, the sum of modified truncated Gaussian (SMTG) model and the sum of modified Beta (SMB) model. Based on the derived models, the impact of random orientation and spatial distribution of LiFi users is investigated, where we show that the aforementioned factors can strongly affect the channel gain and system performance