Agricultural Use of Groundwater and Management Initiatives in the Maghreb: Challenges and Opportunities for Sustainable Aquifer Exploitation

International audienceThe rapid development of groundwater use for irrigation in the Maghreb has resulted in significant agricultural growth, but in many regions, such development has become unsustainable because of aquifer overexploitation or water and soil salinization. The paper examines groundwater use and management in Morocco, Algeria and Tunisia based on a study of national institutional and policy mechanisms and nine local case studies. Farmers address the problem of decreasing borehole flow-rates (or water salinization) either by constantly investing more in order to continue to have sufficient quantities of fresh water for their crops, or by adjusting their cropping systems to adapt to this decrease. Legal frameworks have laid management foundations, but they only have a limited impact. Concomitantly, some collective initiatives have been conceived at local level. In the cases considered, jointly used instruments have made it possible to limit increases in withdrawals and to facilitate water enhancement, without, however, restoring the resource-use balance. The design and implementation of strategies for sustainable aquifer exploitation require the building of coalitions of actors, which should include organizations responsible for water resources, those involved in agriculture, but also - and especially - farmers

Usage agricole des eaux souterraines et initiatives de gestion au Maghreb : Défis et opportunités pour un usage durable des aquifères

Le développement rapide de l'usage des eaux souterraines pour l'irrigation au Maghreb a permis une croissance agricole considérable, mais dans de nombreuses régions un tel développement devient non durable, du fait de la surexploitation des aquifères ou de la salinisation des eaux et des sols. Le document analyse l'usage et la gestion des eaux souterraines de l'eau au Maroc, en Algérie et en Tunisie, à partir d'une étude des dispositifs institutionnels et politiques au niveau national et de 9 cas d'étude locaux. Sur les cas d'étude, les agriculteurs font face à la baisse des débits de leur forage (ou la salinisation des eaux) soit en investissant toujours plus pour continuer de disposer d'eau douce en quantité suffisante, soit en modifiant leurs systèmes de cultures pour s'adapter à cette baisse. Des cadres légaux posent les fondements d'une gestion, mais ils n'ont qu'un impact limité. Parallèlement, certaines initiatives collectives ont été conçues au niveau local. Sur les cas étudiés, des instruments utilisés de façon conjointe ont permis de limiter l'augmentation des prélèvements et de mieux valoriser l'eau, sans pour autant permettre de rétablir un équilibre entre ressources et usages. La conception et la mise en œuvre de stratégies d'usage durable des aquifères nécessitent le développement de coalitions d'acteurs, qui devront inclure les organisations en charge de la ressource en eau, celles de l'agriculture, mais aussi et surtout les agriculteurs

Assessing the enhancement performance of a novel aptasensor for osteopontin detection

Dupla diplomação com a Université Libre de TunisCancer diseases are associated with the presence of a wide range of protein biomarkers. Aptasensor arrays may enable early multiple-detection of these biomarkers which can make important improvements in the lives of cancer patients. Clinical researches suggest that osteopontin, an overexpressed protein by tumor cells may be used as a diagnostic biomarker for several types of cancer. In this perspective, the objective of this dissertation was to evaluate the performance of a previously selected aptamer (C10K7) to detect osteopontin using cyclic voltammetry. The electrochemical detection of osteopontin was assessed using different screen-printed gold electrodes with the selected aptamer immobilized, being determined the detection and quantification limits. The specificity of the DNA aptasensor to other proteins was also studied using thrombin, lysozyme and bovine serum albumin which were evaluated by a previous research as possible interferents. The preliminary work carried out showed that this new aptamer allowed achieving a detection limit of 1.3 nM and a quantification limit of 4.0 nM for osteopontin. Considering that the reported range of plasma osteopontin concentrations in patients with either metastatic or recurrent breast cancer is up to 290 ng/mL (~ 4.46 nM) which is higher than the detection and quantification limits found and which suggest that the proposed aptasensor could be applied in both osteopontin detection and quantification. On the other hand, with the studied aptamer, the detection and quantification limits were lower than those reported in the literature for cyclic voltammetry, which were of 2.6 nM for a DNA aptamer (designated as C10K2) and 3.7 nM for an RNA aptamer (called OPN-R3). The repeatability assays showed a coefficient of variation equal to 7% which demonstrate the closeness of the agreement between the results. The evaluation of the specificity of the DNA aptasensor towards osteopontin showed little or almost no interference to other proteins. However, the interference study showed that the C10K7 aptamer was more prone to interferences from lysozyme and bovine serum albumin than the C10K2 aptamer, previously studied by the research team but showed a lower interference from thrombin. These results highlight the promising capability of the new DNA aptamer (C10K7) to be used in the development of an electrochemical aptasensor for the osteopontin detection, which could be foreseen as a diagnosis and therapy monitoring tool. Nevertheless, these preliminary satisfactory results need to be further checked, namely by the evaluation of its performance for the detection of human osteopontin in biological fluids like blood or plasma.O cancro é uma doença à qual se pode associar a presença de diversas proteínas nos fluidos biológicos de pacientes com essa patologia, as quais podem ser usadas como biomarcadores. Aptasensores baseados em diferentes aptâmeros selecionados para biomarcadores específicos podem permitir a sua deteção num estágio precoce da doença, contribuindo para melhorar a vida dos pacientes com cancro. Estudos clínicos sugerem que a osteopontina, é uma proteína sobre-expressa por células tumorais, podendo ser utilizada como biomarcador no diagnóstico de vários tipos de cancro. O objetivo do presente trabalho foi avaliar o desempenho de um aptâmero previamente selecionado (C10K7) para detectar osteopontina recorrendo à técnica de voltametria cíclica. O estudo realizado permitiu verificar que este novo aptasensor possui um limite de deteção de 1.3 nM e um limite de quantificação de 4.0 nM. Estes valores permitem antever a aplicabilidade prática deste dispositivo como uma ferramenta de deteção de osteopontina uma vez que as concentrações reportadas em plasma de pacientes com o cancro são da ordem dos 4.46 nM (290 ng/mL). Por outro lado, convém referir que o novo aptasensor apresenta limites de detecção e de quantificação inferiores aos descritos na literatura para outros aptasensores baseados em aptâmeros de RNA (OPN-R3) e DNA (C10K2), nomeadamente 3.7 nM e 2.6 nM, também estabelecidos por voltametria cíclica. Os ensaios de repetibilidade realizados mostraram que o aptasensor desenvolvido apresentava um desempenho satisfatório (coeficientes de variação inferiores a 7%). Por fim, o novo aptasensor mostrou-se bastante específico relativamente à osteopontina, molécula alvo, com reduzida interferência por parte de outras protéinas tipo (lisozima, albumina bovina e trombina). Os resultados obtidos sãp bastante promissores indicando o novo aptasensor de DNA (C10K7) uma possível ferramenta de diagnóstico e/ou monitorização da evolução do cancro. No entanto, o desempenho satisfatório descrito terá de ser validado na deteção de osteopontina humano em líquidos biológicos como o sangue ou o plasma.This work was partially financially supported by Associate Laboratory LSRE-LCM - UID/EQU/50020/2019 and by the strategic project PEst-OE/AGR/UI0690/2014 –CIMO funded by national funds through FCT/MCTES (PIDDAC). Professor António Peres, supervisor of this work, is member of CIMO and of the Associate Laboratory LSRE-LCM

Improving the surface brightness-color relation for early-type stars using optical interferometry

The aim of this work is to improve the SBC relation for early-type stars in the $-1 \leq V-K \leq 0$ color domain, using optical interferometry. Observations of eight B- and A-type stars were secured with the VEGA/CHARA instrument in the visible. The derived uniform disk angular diameters were converted into limb darkened angular diameters and included in a larger sample of 24 stars, already observed by interferometry, in order to derive a revised empirical relation for O, B, A spectral type stars with a V-K color index ranging from -1 to 0. We also took the opportunity to check the consistency of the SBC relation up to $V-K \simeq 4$ using 100 additional measurements. We determined the uniform disk angular diameter for the eight following stars: $\gamma$ Ori, $\zeta$ Per, $8$ Cyg, $\iota$ Her, $\lambda$ Aql, $\zeta$ Peg, $\gamma$ Lyr, and $\delta$ Cyg with V-K color ranging from -0.70 to 0.02 and typical precision of about $1.5\%$. Using our total sample of 132 stars with $V-K$ colors index ranging from about $-1$ to $4$, we provide a revised SBC relation. For late-type stars ($0 \leq V-K \leq 4$), the results are consistent with previous studies. For early-type stars ($-1 \leq V-K \leq 0$), our new VEGA/CHARA measurements combined with a careful selection of the stars (rejecting stars with environment or stars with a strong variability), allows us to reach an unprecedented precision of about 0.16 magnitude or $\simeq 7\%$ in terms of angular diameter.Comment: 13 pages, 5 figures, accepted for publication in A&

Caractérisation interférométrique de la relation brillance de surface-couleur des binaires à éclipse et étalonnage des échelles de distance dans l'univers

Measuring distances separating our own Galaxy from nearby ones revolutionized our understanding of the distance scale and provided the evidence for the expansion of the universe. The distances to the Small and Large Magellanic Clouds are critical steps of the cosmic distance ladder, and they have been determined using numerous independent methods (as, RR Lyrae stars, Cepheids and "red clump" stars). The aim of my thesis work is to improve our understanding of the Surface Brightness-Color relation (SBC) using optical interferometry. For this, we use the interferometer VEGA on CHARA. This instrument operates in the visible and benefits from the baselines of the CHARA interferometer. It has a spatial resolution of 0.3 mas, which makes it an ideal tool to determine diameters of stars. At first I determined the diameter of eight OBA-type stars with an average accuracy of 1.5%. Then I combined these diameters with others collected from the literature, to determine a new SBC relation for this type of stars. In a second step, a theoretical study of the impact of the rotation on the SBC relation was made to understand the physical effects affecting the accuracy of this relation and suppress the currently existing dispersion in order to further improve the accuracy of extragalactic distances.La mesure des distances aux galaxies proches de notre Voie Lactée a révolutionné notre compréhension de l'échelle de distance et a fourni la preuve de l'expansion de l'univers. Notamment les distances aux Petit et Grand Nuages de Magellan sont deux échelons essentiels de l'échelle des distances cosmiques. De nombreuses méthodes indépendantes (comme celle des RR Lyrae, des Céphéides ou des étoiles Red clump) ont été utilisées pour déterminer ces distances. Le but de mon travail de thèse est d'améliorer notre compréhension de la relation BSC grâce à l'interférométrie optique. Pour cela, j'ai utilisé l'instrument VEGA installé sur l'interféromètre CHARA. Cet instrument fonctionne dans le visible et bénéficie de la plus longue base du monde. VEGA a une résolution spatiale de 0.3 mas, ce qui en fait un outil idéal pour une détermination précise des diamètres des étoiles. Dans un premier temps j'ai déterminé le diamètre de huit étoiles de type OBA avec une précision moyenne de 1.5%. Ensuite j'ai combiné ces diamètres avec d'autres mesures collectées dans la littérature pour ainsi donner une nouvelle relation BSC pour ce type d'étoiles. Dans un second temps, une étude théorique de l'impact de rotation sur la relation BSC a été faite pour comprendre les effets physiques influant sur la précision de cette relation de manière à compenser la dispersion existant actuellement et ce dans le but d'améliorer encore la précision sur les distances extragalactiques

Spectrally resolved interferometric observations of α Cephei and physical modeling of fast rotating stars

This is the final version of the article. Available from the publisher via the DOI in this record.Context. When a given observational quantity depends on several stellar physical parameters, it is generally very difficult to obtain observational constraints for each of them individually. Therefore, we studied under which conditions constraints for some individual parameters can be achieved for fast rotators, knowing that their geometry is modified by the rapid rotation which causes a non-uniform surface brightness distribution. Aims. We aim to study the sensitivity of interferometric observables on the position angle of the rotation axis (PA) of a rapidly rotating star, and whether other physical parameters can influence the determination of PA, and also the influence of the surface differential rotation on the determination of the β exponent in the gravity darkening law that enters the interpretation of interferometric observations, using α Cep as a test star. Methods. We used differential phases obtained from observations carried out in the Hα absorption line of α Cep with the VEGA/CHARA interferometer at high spectral resolution, R = 30 000 to study the kinematics in the atmosphere of the star. Results. We studied the influence of the gravity darkening effect (GDE) on the determination of the PA of the rotation axis of α Cep and determined its value, PA = −157-10°+17°. We conclude that the GDE has a weak influence on the dispersed phases. We showed that the surface differential rotation can have a rather strong influence on the determination of the gravity darkening exponent. A new method of determining the inclination angle of the stellar rotational axis is suggested. We conclude that differential phases obtained with spectro-interferometry carried out on the Hα line can in principle lead to an estimate of the stellar inclination angle i. However, to determine both i and the differential rotation parameter α, lines free from the Stark effect and that have collision-dominated source functions are to be preferred.VEGA is a collaboration between CHARA and OCA/LAOG/CRAL/LESIA that has been supported by the French programs PNPS and ASHRA, by INSU and by the Région PACA. The project has obviously benefitted from the strong support of the OCA and CHARA technical teams. The CHARA Array is operated with support from the National Science Foundation through grant AST-0908253, the W. M. Keck Foundation, the NASA Exoplanet Science Institute, and from Georgia State University. This work has made use of the BeSS database, operated at GEPI, Observatoire de Meudon, France: http://basebe.obspm.fr, use of the Jean-Marie Mariotti Center SearchCal service1 co-developed by FIZEAU and LAOG, and of CDS Astronomical Databases SIMBAD and VIZIER2. We are grateful to an anonymous referee for her/his valuable suggestions that helped to improve the presentation of our results

Antibacterial, antioxidant and cytotoxic activities of extracts from the thermophilic green alga, Cosmarium sp.

Unicellular green algal strains, identified as Cosmarium (Chlorophyta), were isolated from Ain-Echeffa hot spring in north Tunisia. Different extracts (methanol, hexane, acetone, acetone: methanol and water) obtained from both biomass and extracellular polysaccharides (EPS) were evaluated for their antibacterial, antioxidant and cytotoxic activities. First, extracts were tested in vitro for eventual antibacterial activities against a collection of Gram positive and negative bacteria. Most extracts (biomass and EPS) showed significant antibacterial effects, with minimum inhibitory concentrations (MIC) ranging from 28 to 85 µg/ml for biomass and 50 to 150 µg/ml for EPS. Moreover, based on the capacity of each sample to scavenge the ABTS radical cation, we revealed that the EPS aqueous extract presented a moderate antioxidant activity (24.97%). Finally, the toxicity of the biomass extracts was evaluated using the brine shrimp Artemia salina, as test organism. All extracts were identified as non-toxic (LC50 > 400 µg/ml).Key words: Cosmarium, biomass, extracellular polysaccharides (EPS), cytotoxicity, antibacterial, antioxidant