Fabrication of buckypaper with tailored porosity for application in water filtration

The rapid development in membrane technologies and their use as a filtration medium have been based on the use and development of new materials to improve system performance. Carbon nanotubes (CNTs) represent a class of promising nanomaterial, exhibiting outstanding mechanical, electrical, thermal conductivity and adsorption properties. The idea of using carbon nanotubes in the separation and filtration industry has been put forward, but constructing macroscopic structures with controlled density, porosity, and morphology has been a challenge. Buckypaper (BP) is a form of CNT film that is being investigated for application in water treatment. In BPs, the CNTs are oriented randomly into non-woven or paper like structure. This arrangement helps provide a large specific area with highly porous three dimensional network structures. However, the preparation of BP membranes with controlled porosity and pore size distribution entails taking into account many processing parameters. Porosity is a key property for the use of BPs in separation applications in general. The work conducted here aims at preparing BPs with controlled porosity through the investigation of three different parameters, which impact porosity. These entail the porosity of the supporting filter membrane during the preparation of the BPs, as well as the exposure of prepared BPs to different solvents vapors and for different exposure times. The retention performance of the obtained BPs in water filtration is tested using micro-sized polymer beads. CNT-BPs were prepared using vacuum filtration. Morphology and pore size distribution were investigated using scanning electron microscopy (SEM), nitrogen gas adsorption and mercury porosimetry. Different parameters were evaluated for their effect on tailoring the porosity of BPs. Statistical analysis was used to determine the effect of the three parameters investigated, namely (1) the pore size of the membrane filter used in the preparation of BPs from CNT dispersions, (2) type of solvent vapors to which the prepared BPs are exposed, and (3) the exposure time to the solvent vapors, on the final membrane porosity. Results indicated that the type of solvent affects the pore size distribution with DMF giving more pores in the smaller pore size ranges. In addition, variation of pore size distribution of the BP membranes was observed upon varying the pore size of the membrane filter. On the other hand, no significant change was detected on changing the time exposure to the boiling solvent. One variable and one combination of variables were found to be successful in producing BPs with a lower average pore size. The findings confirm the potential of the solvent evaporation technique in tailoring the porosity of BP and membranes for filtration applications. Finally, obtained BPs were tested for water filtration applications. Polystyrene beads of size ranges 0.3 µm and 0.6 µm, were chosen as model for bacteria and colloids removal, respectively. A comparison between blank BPs and modified BPs (subjected to solvent vapor for 40 minutes and prepared on specific membrane filter) was conducted. For the 0.3 µm of polystyrene beads, the blank BP showed a retention percentage of about 71% in comparison to the modified one which had a retention percentage of about 73%. For the 0.6 µm of polystyrene beads, the blank BP showed a retention percentage of about 67%, while the modified one had a percentage of about 75%. This indicates that the modified BPs possess smaller pore sizes on average than unmodified BP

Structural Behaviour of Pre-Cast Concrete Sandwich Panel under Axial and Lateral Loading

The sandwich panel is a layered structural system composed of a low density core material bonded to and acting integrally with, a relatively thin high strength facing materials held together by shear connectors which gives different degree of composite action. In a load bearing wall the two facings act as slender columns continuously supported by shear connectors. Core material usually act as insulation material to reduce the temperature inside the building. The bending action due to eccentric load or lateral load is resisted by the tensile and compressive forces developed in outer layers while shear forces are resisted by the shear connectors. Sandwich panels are used as exterior walls in multi-unit, residential, commercial and ware house building, providing structurally and thermal efficient building element. In this study, the structural behaviour of reinforced concrete sandwich wall panels has been investigated experimentally in pre and post-cracking phase. Each panel consists of two outer reinforced concrete layers, interconnected together by different layout reinforced concrete ribs, which act as shear connectors. Three layouts of shear connectors have been selected for the study; these are continuous vertical concrete ribs and truss type layout ribs inclined at 45° and 67.5° with the vertical. Finite element method has been used in analysis for comparison with the experimental test results in the pre-cracking phase and to determine the stress distribution developed in the different components of the sandwich panel under different loading conditions. Six specimens of reinforced concrete sandwich panels (two identical specimens for each shear connector layout) each of size 1 200 x 2400 mm (width x height) have been cast in the laboratory and tested in vertical position under incremental vertical axial, lateral, and combined axial and lateral loading. The effect of different shear connector layout on the overall structural behaviour of the panel is highlighted. Moreover the composite behaviuor of the sandwich panels, the percentage of load transferred to the ribs and the crack pattern have been investigated and discussed. The structural response of the sandwich panel in term of deflections have been found equal to 35 mm, 27 mm and 22 mm for panels type A, B and C respectively. The lateral collapse load of the tested panels, have been found equal to 97 KN, 40 KN and 45 KN for panels type A, B and C respectively. From the results obtained in this study, it has been found that the sandwich panel with vertical shear connector has a better overall structural response as reflected in the integrity of the sandwich wall panel systems under the action of combined axial and lateral loads, in comparison to sandwich panels with inclined layout shear connectors

Evaluation of quinazolin-4-piperidine sulfamides as inhibitors of human NPP1 : relevance in the treatment of pathologic mineralization of valve interstitial cells

Le rétrécissement valvulaire aortique calcifié (RAC) est le trouble valvulaire le plus fréquent chez les personnes âgées des pays développés. La seule option de traitement possible le remplacement de la valve aortique. L'identification du rôle de l’enzyme ecto-nucleotidase NPP1 dans le processus de calcification suggère que cette enzyme pourrait être une cible potentielle pour le développement d'un inhibiteur pharmacologique contre la calcification de la valve aortique. Jusqu’à présent, les composés qui ont été développés en tant qu'inhibiteurs de NPP1 manquent de puissance et de spécificité. Dans la présente étude, nous avons démontré que les dérivés de sulfonamides quinazolin-4-pipéridine sont des inhibiteurs puissants, spécifiques, et non-compétitifs de NPP1. In vitro, dans des cellules isolées de valve aortique nous avons fourni des preuves que l’inhibition de NPP1 par ces dérivés bloque la minéralisation, l’apoptose et la transition ostéogénique des cellules interstitielles de valve aortique.Calcific aortic valve disease (CAVD) is the most common valvular disorder in the elderly population in the developed counties with the only valid treatment option today remains the aortic valve repair or replacement. The identification of the role of an ectonucleotidase enzyme NPP1 in the process of calcification shed new light into the development of a pharmacological inhibitor that may prevent the calcification of the aortic valve. By far, the compounds that have been developed as inhibitors of NPP1 lack potency and specificity. In the current study, we showed that the quinazolin-4-piperidin sulfamide derivatives to be a potent, specific, and non-competitive inhibitors of NPP1. We also provided evidence that by inhibiting NPP1 enzyme activity these derivatives are able to prevent phosphate-induced mineralization of valve interstitial cells (VICs), the main cellular component of the aortic valve, by preventing both apoptosis and osteoblastic transitions of VICs

Using of Activated Jurdiga for Bleaching of Sunflower Edible Oils

Bleaching process is cost intensive process for the refining vegetable oils and this is due to the consumption of bleaching earth which is imported from abroad which contributes in raising the total operating cost of the process. The objective of this study is to investigate the possibility of using activated jurdiga to bleach edible oils to meet the local demand and lower production cost. Jurdiga was brought from Um-Shoka area in Sennar State, Sudan. The chemical composition of jurdiga was determined. The analysis of jurdiga revealed high total sodium carbonate equal to 24 % and sodium bicarbonate equal to 20%. Jurdiga was crushed and was activated by 5%, 5%, 10% and 20% of concentrated   () . The bleaching efficiency of the produced activated jurdiga for bleaching of sunflower oil was investigated by adding various dosages of 1.5, 2.5, 3.5 and 4.5 grams of activated Jurdiga at temperatures of 80℃, 100℃ and 120℃ and compared with commercial fuller earth. The conditions that gave best results for the sulfuric acid activation and bleaching test was found to be 10% acid concentration, 4.5 grams of activated jurdiga at 120℃ for 70 gram of oil. The bleaching efficiency of the activated jurdiga was 70 %. This result is compararable with commercial fuller earth which has 90% bleaching efficiency.  Key words: Bleaching, Fuller earth, Activation, Jurdiga, Edible oils

Understanding Progressive Training Through the Framework of Randomized Coordinate Descent

We propose a Randomized Progressive Training algorithm (RPT) -- a stochastic proxy for the well-known Progressive Training method (PT) (Karras et al., 2017). Originally designed to train GANs (Goodfellow et al., 2014), PT was proposed as a heuristic, with no convergence analysis even for the simplest objective functions. On the contrary, to the best of our knowledge, RPT is the first PT-type algorithm with rigorous and sound theoretical guarantees for general smooth objective functions. We cast our method into the established framework of Randomized Coordinate Descent (RCD) (Nesterov, 2012; Richt\'arik & Tak\'a\v{c}, 2014), for which (as a by-product of our investigations) we also propose a novel, simple and general convergence analysis encapsulating strongly-convex, convex and nonconvex objectives. We then use this framework to establish a convergence theory for RPT. Finally, we validate the effectiveness of our method through extensive computational experiments