EDTA as a corrosion inhibitor for Al in 0.5 M HCl: adsorption, thermodynamic and theoretical study

In this study; EDTA is used in very small amount (10-10 M) as an inhibitor for the Al corrosion in 0.5 M HCl. Thermodynamic and adsorption parameters are calculated. The result shows that, in this range of concentrations, EDTA is chemisorbed at the Al surface, forming a stable complex with Al and give inhibition efficiency up to 89 %. For more con-centration, unstable complex is formed and acceleration of corrosion occurs. The adsorp-tion fit well to Langmuir, Temkin isotherms and El-awady model. Density functional theory (DFT) is used to study the geometrical optimizations of EDTA. From the obtained optimized structure, The highest occupied molecular orbital (EHOMO), the lowest unoccupied molecular orbital (ELUMO and their energy difference (ΔE), the total energy (TE), electronegativity (χ), dipole moment (μ), global hardness (η), global softness (σ), electron affinity (A), ionization potential (I), the fraction of electrons transferred (ΔN) and were determined using B3LYP/6-31G(d,p) basis set

Parametrizacija funkcije raspodjele elektronske energije u tinjavom izboju u RF elektromagnetskom polju

A set of twenty four plasma glow discharge experiments using radio-frequency electromagnetic fields were carried out. The discharge pressure was 27 Pa. Dried air was used as the discharge gas. Axial radio-frequency fields between 0.6-1.2 MHz were applied. Four different values of the RF field intensity were used. For each case, the plasma Langmuir probe characteristics were measured. A computational method was used to extract the electron energy distribution function in each case. Values of the plasma density and plasma temperature were obtained directly from the fits. They compare well with values obtained using the conventional logarithmic method. The Maxwellian behaviour of the distribution function was established to hold in many but not in all cases.Izveli smo 24 mjerenja u plazmi u tinjavom izboju pod djelovanjem radiofrekventnog (RF) elektromagnetskog polja. Tlak u izboju bio je 27 Pa. Izbojni plin bio je suhi zrak. Rabili smo osna RF polja u području 0.6 do 1.2 MHz. Primijenili smo četiri jakosti RF polja. U svakom mjerenju odredili smo značajku Langmuirove probe. Računalnom smo metodom izveli funkciju elektronske raspodjele energije za svako mjerenje. Izravno iz prilagodbi izveli smo vrijednosti gustoć i temperature plazme. Te se vrijednosti dobro uspoređuu s vrijednostima dobivenim uobičajenom logaritamskom prilagodbom. Maxwellova funkcija raspodjele se pokazuje dobrom u mnogim, ali ne svim slučajevima

Nitrogen availability and economic returns of various crop rotations with forage and annual crops

Non-Peer Reviewe

A Logarithmic Formula to Describe the Relationship between the Increased Radiosensitivity at Low Doses and the Survival at 2 Gray

Objectives: Intrinsic radiosensitivity at doses used in radiotherapy is linked to hypersensitivity (HRS) and increased radio resistance (IRR) at low doses. The aim of this study was to explore this relationship. Methods: Survival curves for 18 human tumour cell lines were analysed, using two models to fit the data points in order to extract the necessary parameters relevant for this study. Results: The IRR ratio αs/αr versus the survival at 2 gray (Gy) can be described by a logarithmic relation which leads to a series of straight lines. Conclusion: The relationship obtained implies that there is a direct link between HRS/IRR and survival at clinically relevant doses of 2 Gy

Nitrogen availability and economic returns of various crop rotations with forage and annual crops

Non-Peer Reviewe

Les arbres de Tunis peuvent-ils devenir un patrimoine urbain ? Pour qui ? Pourquoi ?

En s’appuyant sur des observations in situ et des résultats d’entretiens avec les citadins, nous avons d’abord tenté de définir en premier lieu le statut de l’arbre de Tunis. Puis, en second lieu, nous avançons quelques hypothèses quant à la perception de l’arbre par les Tunisois. Nous avançons que la perception sociale des arbres de Tunis est construite et nourrie surtout par l’identité personnelle des habitants de la ville. Mais il faut néanmoins souligner que l’arbre contribue aussi à forger l’identité des citadins en marquant leur espace public de vie. La perception de l’arbre devient ainsi un mélange complexe de goûts personnels et de possibilités pratiques, mais surtout de traditions, de croyances religieuses et d’expériences individuelles.For our case which is Tunis, we’ve been relied on in-situ observations and results of interviews with the citizens to attempt to define; first, the status of the tree of Tunis. Then, second, we do a few assumptions about the perception of the tree by the citizens. We advance the following thesis: the social perception of the tree of Tunis is built on the personal identity of the inhabitants of the city. Nevertheless, the tree helps also to forge the identity of the urban public space by marking their life. The perception of the tree becomes a complex mix of practicality, traditions, religious beliefs and personal experiences

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact

L’arbre à Tunis : hypothèses pour une histoire de l’espace public

L’arbre fait partie du paysage urbain. Il est intégralement « enraciné » dans le cadre de vie des citadins. L’histoire de l’évolution des paysages urbains de Tunis peut être lue à travers ses arbres et leur agencement. C’est l’hypothèse principale de cette thèse. Avant la colonisation, la médina disposait de peu d’arbres dans l’espace public, car l’organisation spatiale puisait ses fondements dans la sharia (loi divine), et le premier précepte d’entre eux était le respect de l’intimité des familles. C’est pour cette raison principale que les rues restaient étroites et peu entretenues. Mais les arbres trouvaient parfois leur place à l’intérieur des demeures, dans les patios, lieux de la vie intime et familiale. Les essences que l’on retrouvait le plus souvent étaient celles qui étaient citées dans le Coran pour leurs vertus, essentiellement des agrumes et des espèces aromatiques (on obéissait aux préceptes de la loi divine jusque dans l’organisation des intérieurs). Puis, à la fin du xixe siècle, lors de l’instauration du protectorat français, la ville s’est étendue au-delà des remparts. Les grandes avenues bordées d’alignements d’arbres, de nouvelles espèces parfois taillées, ont fait leur apparition. La ville européenne s’est ouverte aux arbres et les Tunisois ont commencé à découvrir un autre monde urbain importé d’Europe. Avec l’indépendance (en 1956), la capitale gonflée par l’exode rural s’est étalée. D’un côté, les Tunisois aisés voulant accéder au mode de vie moderne ont habité de nouveaux quartiers alliant style européen (rues larges, arbres d’alignements imposants) et traditions tunisoises (grands jardins plantés d’agrumes et d’espèces aromatiques). De l’autre, des Tunisiens de la campagne fuyant une vie difficile et en quête de meilleurs revenus se sont approprié des espaces jouxtant la capitale et y ont reproduit – dans la mesure du possible – leur mode de vie rurale.The tree is part of the urban landscape. It is fully "rooted" in the context of the city life. But unlike other aspects that underpin the urban landscape, the tree, as it is perceived ; with its own symbols and meanings, belongs to the sensitive human world. The changing story of Tunis’ urban landscape of was experienced through its trees and their arrangement. This is the main hypothesis of this thesis. Before colonization, the Medina had few trees in public spaces, where the spatial organization drew its roots in the Sharia (Divine Law), and the first precept of them was the respect for families’ privacy. In this sense, the streets remained narrow and poorly maintained. But the trees were sometimes included among the dwellings ; in the patios : locations for private and family life. The most often found essences were those mentioned in the Koran for their virtues, mainly citrus and aromatic species (the precepts of divine law used to be obeyed even when it concerned the interiors’organization).Then in the late nineteenth century, during the protectorate, the city expanded beyond the walls. Wide avenues lined with rows of trees, new species sometimes trimmed, emerged. The European city opened up to trees and the Tunisois began to discover another urban world imported from Europe. With the Independence (in 1956), the capital, swollen by the rural exodus, spread. On one hand, the wealthy Tunisians, wanting access to the modern living, inhabited neighborhood which combined new European-style (large imposing avenue trees) and Tunisian traditions (large garden planted with citrus and aromatic species). On the other hand, Tunisians fleeing the country and a difficult life in search of better incomes have appropriated adjacent spaces to the capital and have reproduced, as far as possible, their rural way of life