Beneficial effect of gamma irradiation on the N-deacetylation of chitin to form chitosan

The effect of gamma irradiation on the N-deacetylation of chitin to form chitosan was studied. Chitin from crab shells was irradiated up to 20 kGy and N-deacetylated in aqueous NaOH solution (40% and 60% w/w) at 60 and 100 °C for 60 min. The degree of N-deacetylation (DD) of non-irradiated and irradiated samples was determined by IR-band ratio method. It was found that higher extent of N-deacetylation was achieved for the chitin samples irradiated up to 20 kGy doses as compared to non-irradiated chitin. The DD values of chitin, prepared from non-irradiated and 20 kGy irradiated chitins by N-deacetylation at 60 °C with 40% NaOH for 60 min, were found to be 38% and 60%, respectively. The increase in DD by irradiation was interpreted as a result of reduction in molecular weight of chitin. Low dose irradiation of chitin has provided the possibility of its N-deacetylation into chitosan at much milder reaction conditions.     

From SIR to SEAIRD: A novel data-driven modeling approach based on the Grey-box System Theory to predict the dynamics of COVID-19

Applied Intelligence - Common compartmental modeling for COVID-19 is based on a priori knowledge and numerous assumptions. Additionally, they do not systematically incorporate asymptomatic cases....     

Birefringence properties of magneto-optic rib waveguide as a function of refractive index

We report on the theoretical study of magneto optical rib waveguides with two kinds of silica type matrix doped by magnetic nanoparticles and made by sol–gel process (SiO₂/ZrO₂ film or SiO₂/TiO₂). The mode propagation and the light confinement are simulated using software based on a Film Mode Matching method. The modeling is based on geometrical adjustments of the rib waveguide. We propose from those results magneto optical waveguide geometries for optical integrated applications.     

One dimensional transient numerical study of the mass heat and charge transfer in a proton exchange membrane for PEMFC

The objective of our study is to quantify the mass water transferred by various modes: diffusion, convection and migration. For the water transfer, the principal forces considered in the model are, the convection force, the osmotic force (i.e. diffusion) and the electric force (migration). The first of these forces results from a pressure gradient, the second of a concentration gradient and the third of a protons' migration from the anode to the cathode, which has an effect on the dipole of the water molecules (resistance force to the advancement). The numerical tool used to solve the equations' system is the finite element method. The results obtained numerically considering this method are concentration profiles and concentration variation with time and membrane thickness. These results illustrate the contribution of each mass transfer mode.     

Hydroxyapatite growth on multiwall carbon nanotubes grown on titanium fibers from a titanium sheet

Nano-hydroxyapatite (HA) was grown on functionalized multiwalled carbon nanotubes (MWCNTs) deposited on TiO₂ nanofibers (NFs) that were hydrothermally grown on Ti metal sheets. The HA was electrochemically grown on the MWCNTs/TiO₂ porous layer. It was found that the HA grows on the MWCNTs/TiO₂ NFs in the form of dense coating with nanorice grain-shaped. The incorporation of MWCNTs between HA and TiO₂ NFs has led to higher adhesion strength as measured by micro-scratching test indicating the benefit of MWCNTs on the improving the bonding strength of HA layer. The obtained coatings exhibit excellent corrosion resistance in simulated body fluid. It is expected that this simple route for preparing the new HA/MWCNTs/TiO₂/Ti-layered structure might be used not only in the biomedical field, but also in catalysis and biological sensing among others.     

Static liquefaction of sandy soil: An experimental investigation into the effects of saturation and initial state

The effects of initial state of the samples and the saturation evaluated in terms of Skempton??s pore pressure B on the behavior of Chlef sand are studied in this article. For this purpose, the results of two series of drained and undrained monotonic triaxial compression tests on medium dense sand are presented. In the first test series, the influence of the specimen??s fabric and confining pressure has been studied. The tests were conducted at initial confining pressure of 50, 100, and 200?kPa. The specimens were prepared by two depositional methods that include dry funnel pluviation and wet deposition. All the samples were subjected to a monotonic loading after a consolidation phase. The results of the tests demonstrate that initial confining pressure and the specimen??s fabric have detectable effects on the behavior of the sand. In the second series of tests, the saturation influence on the resistance to the sand liquefaction has been realized on samples at an effective stress of 100?kPa for Skempton??s pore pressure coefficient varying between 13 and 90%. It was found that the increase in Skempton??s pore pressure coefficient B reduces the soil dilatancy and amplifies the phase of contractancy.