The inhibition effect of two commercial compounds on interface steel/natural softened water

The protection against the corrosion of the carbon steel in aqueous environment by commercial inhibitors, based of nitrite and alkanolamine, has been studied by electrochemical impedance spectroscopy (EIS) and several analytic methods. An inhibitor’s efficiency has been determined with the two compounds on polished surface in presence of softened water. The results show that the two inhibitors act by the formation of protective layer on interface steel/electrolyte but the efficiency is more important in the case of the nitrite compound thanks to the formation of film with thickness estimated by Atomic force microscopy (AFM) at 0.8 μm after 102 days of immersion. In the case of the nitrites, the inhibitor film is a porous layer, weak conductor and presents a considerable increase of the charge transfer resistance with time. This is a result of an interest protection of the surface against corrosion. The low frequencies limit (L _LF) reaches about 150 kOhm cm² after 59 days of immersion. In the case of the alkanolamine, XPS (X-Rray Spectroscopy) show that the film formed is richer of Fe ions but is offered a considerable protection of the interface, its thickness is about 0.26 μm and L _LF reaches about 35.5 kOhm cm² after 61 days of immersion. The influence of surface state is discussed in this paper, in fact on raw surface steel, no inhibitor efficiency is observed. A few protections are given with a crude surface in contact with water softened in presence of the nitrite compound.     

Adsorption mechanism of non‐toxic organic inhibitors on steel in solutions at pH 8 determined by electrochemical quartz crystal microbalance measurements

The adsorption on steel of two compounds, ascorbic acid salts (SA) and 1‐hydroxyethylidene,1‐diphosphonic acid salts (SHEDP), used alone or simultaneously, was studied using an electrochemical quartz crystal microbalance (EQCM). These products are considered to be non‐toxic organic corrosion inhibitors. SA adsorption was greater at cathodic potentials than at the corrosion potential, while SHEDP adsorbed better at the corrosion potential. The effectiveness of these two inhibitors is discussed in relation to the polarization curves. Several hypotheses are discussed to explain the adsorption mechanism in the presence of the two compounds used either alone or together.     

Composite short-side-chain PFSA electrolyte membranes containing selectively modified halloysite nanotubes (HNTs)

Aquivion membrane displays improved properties as compared to Nafion membrane, partly due to shorter side chains. However, some improvements are still necessary for proton exchange membrane fuel cell to operate at low relative humidity. To overcome this drawback, the addition of clay nanoparticle into the Aquivion matrix can be considered. In this study, different composite membranes have been prepared mixing short-side-chain PFSA (perfluorosulfonic acid) Aquivion and selectively modified halloysite nanotubes for PEMFC low relative humidity operation. Halloysites were grafted with fluorinated groups, sulfonated groups, or perfluoro-sulfonated groups on inner or outer surface of the tubes. The obtained composite membranes showed improved properties, especially higher water uptake associated with reduced swelling and better mechanical strength compared to pristine Aquivion membrane and commercially available Nafion HP used as reference. The best performance in this study was obtained with Aquivion loaded with 5 wt% of pretreated perfluoro-sulfonated halloysite. The composite membrane, referred to as Aq/pHNT-SF5, displayed the largest water uptake and proton conductivity among the panel of membranes tested. The chemical stability was not affected by the presence of halloysite in the Aquivion matrix.

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Dietary intake in the urban and rural populations of the Cap-Bon

The correlation between cytogenetic and histopathological findings were analysed in 189 meningiomas. The tumors were classified according to increasing degrees of anaplasia. We observed normal karyotype or only monosomy 22 in grade 1 (benign) tumors, while in grade 3 (anaplastic) only 1.5% of karyotypes were normal. Grade 2 (atypical) and 3 (anaplastic) tumors showed complex structural abnormalities. Loss of chromosome 14 were only found in grade 3. In cases with complex structural rearrangements, fluorescence in situ hybridization technique (FISH) has been realized and permitted a best identification of abnormalities. In our series, five patients recurred. They presented chromosomal abnormalities. These complex karyotypes in recurrent meningiomas might indicate aggressive tumor characteristics. Our results indicate histolopathological and cytogenetics correlations might represent a prognostic factor in meningiomas.     

Automated Framework for Water Looped Network Equilibrium

In this paper, a novel algorithm is proposed for balancing water looped network in steady state through a fully automated general framework of hydraulic networks regardless of their topological complexity. The model is developed by combining the following two steps, firstly a set of independent loops are identified based on a graph theoretical analysis in a looped network. Further the second step is devoted to the equilibrium process by determining the flow rate distribution within the network ducts and the pressure in the delivery nodes. The above such equilibrium process gives rise to a system of non linear algebraic equations which are solved numerically using both Hardy Cross (HC) and Newton Raphson (NR) methods. In HC method, the flow correction term is modified and a generalized expression is given to consider various possibilities of independent loops selection. Some real networks topologies that were commonly used as benchmarks, for testing various independent loops selection algorithms, are taken as case studies to apply the general automatic framework for hydraulic network analysis. Such network analysis enhances proving the applicability as well as the effectiveness of the proposed approach. Also, during the equilibrium procedure, it is proved that NR method is capable of producing accurate results and it converges more rapidly comparing to the widely used HC method. Moreover, it is demonstrated that NR’s iterative process, contrary to HC’s one, converges to reliable results even with a choice of random initial flow rates which makes a NR algorithm quite simple to implement without affecting the accuracy of the results.     

Evaluation of corrosion non toxic inhibitor adsorption for steel in near neutral solution: L(+) ascorbic acid

The force of adsorption of a non‐toxic inhibitor on iron surface was studied by electrochemical quartz crystal microbalance (EQCM). The value of standard free energy of adsorption, as calculated from Freundlich‐Langmuir (LF) adsorption, indicates that L(+)ascorbic acid physisorbes on the iron surface at corrosion potential. At cathodic potential, the quantity of energy is more important. So, there is a slightly stronger interaction between inhibitor and iron surface. This behaviour can be explained by that this inhibitor occupies better the cathodic sites. The inhibition efficiency of ascorbic acid was carried out by the fact electrochemical impedance spectroscopy data (EIS). The film adsorbed on the surface is less protective for a long time of immersion.     

Adsorption of corrosion inhibitors (SA, HEDP) using EQCM: chloride effect and synergic behavior

The adsorption of inhibitor molecules, ascorbic acid (SA), and 1-hydroxyethane-1,1-diphosphonic acid (HEDP), was studied using electrochemical quartz crystal microbalance. Adsorption on iron was studied compared with gold in the presence of chloride ions and at E _OP and cathodic potential. Each of these parameters significantly affects monolayer adsorption following the Langmuir isotherm. HEDP was adsorbed more rapidly than SA. The novelty in this study concerns the influence of chloride concentration on the inhibition efficiency. Indeed, the rate of inhibition also depends on the concentration ratio of chloride/inhibitor, which is an important factor for the practical implementation of these compounds. Adding a small quantity of chloride ions can increase adsorption rate as well as degree of coverage. Optimum behavior was noted for a HEDP/Cl⁻ ratio about 500. Passivation of the electrode to cathodic potential influenced HEDP adsorption and promoted that of SA. A low adsorption current proportional to the concentration of the inhibitor was recorded. A synergic inhibition by the two molecules was observed for a concentration relationship of 1.16. The study showed that SA was not adsorbed at the interface but its presence made a reduction in lateral tensions possible between adsorbed HEDP, leading to a better coverage.     

Image compression by vector quantization: a review focused on codebook generation

Recently, vector quantization (VQ) has received considerable attention, and has become an effective tool for image compression. It provides a high compression ratio and a simple decoding process. However, studies on the practical implementation of VQ have revealed some major difficulties such as edge integrity and codebook design efficiency. After reviewing the state-of-the-art in the field of vector quantization, we focus on iterative and non-iterative codebook generation algorithms.